JP7740868B2 - Control device and control method - Google Patents

Description

The present invention relates to a control device and a control method.

An electric vehicle has a motor for driving the wheels and a control unit for controlling the motor and other components (see, for example, Patent Document 1 and Patent Document 2).

In such electric vehicles, the temperature of the heat source of the component that generates heat when the motor is driven must be detected by a thermistor, and the control unit must activate a temperature protection mechanism based on the temperature of the heat source to prevent the component from exceeding a temperature that would damage it.

However, in this electric vehicle, for example, when starting uphill on a slope, if the motor is at a low angular velocity and a high current flows, the temperature detected by the thermistor may deviate from the actual temperature of the heat source, and as shown in Figure 10, the thermistor may not be able to track the actual temperature of the heat source as well. Specifically, there is a thermistor non-tracking region 101 where the frequency of the current flowing through the motor is low and a high current flows, and a thermistor tracking region 102 elsewhere. As a result, even though the actual temperature of the heat source requires the temperature protection function to be activated to suppress temperature rise, the temperature detected by the thermistor is lower than the actual temperature of the heat source, and therefore the temperature protection function by the control unit may not be executed.

Therefore, it is necessary to take into account the effects of heat conduction and ambient temperature, estimate the temperature based on a physical model of how heat sources such as transistors will break down, and more accurately execute the temperature protection function to prevent the temperature from exceeding the point at which the component containing the heat source will break down.

Japanese Patent Application Laid-Open No. 2009-113676 Japanese Patent Application Laid-Open No. 2014-168341

Various aspects of the present invention aim to provide a control device and control method that can estimate the temperature of a heat source more accurately by taking into account the effects of thermal conduction and ambient temperature, even if the temperature of the heat source that serves as the reference for executing the temperature protection function cannot be directly detected.

Various aspects of the present invention are described below.

[1] A control device that controls a current source and a power conversion unit that converts power from the current source and supplies power to a drive unit,
The control device
a control unit that controls the power conversion unit;
a temperature detection unit that detects a temperature near a heat source generated by the power conversion unit or the drive unit;
a storage unit that stores a saturation temperature information table that associates a combination of a current value flowing in the drive unit and a frequency of the current flowing in the drive unit with a saturation temperature that is a maximum temperature at which the heat of the heat source is saturated,
The control unit
Acquire a current value flowing in the drive unit and acquire a frequency of the current flowing in the drive unit;
Acquire the actual temperature detected by the temperature detection unit;
calculating a control estimated temperature using the current value, the frequency, the saturation temperature information table stored in the storage unit, and the actual temperature;
The control device controls the power supplied from the power conversion unit to the drive unit based on the control estimated temperature.
[2] The control unit
After acquiring the value of the current flowing in the drive unit and the frequency of the current flowing in the drive unit,
a step a of calculating a current saturation temperature of the heat source corresponding to a combination of the current value and the frequency by referring to the saturation temperature information table;
a step c of calculating a current estimated heat source temperature by estimating the temperature of the heat source by using the current saturation temperature and a first coefficient;
a step e) of calculating a current estimated detection unit temperature by using the current estimated heat source temperature and a second coefficient to estimate a temperature in the vicinity of the heat source;
a step f of acquiring the actual temperature detected by the temperature detection unit;
a step g of calculating a temperature difference by subtracting the actual temperature from the current estimated detection portion temperature;
a step h of calculating a temperature correction value by multiplying the temperature difference by a preset temperature correction coefficient;
a step i of calculating an estimated control temperature by adding the temperature correction value to the current estimated heat source temperature;
a step j of controlling the power supplied from the power conversion unit to the drive unit based on the control estimated temperature.
[3] The current estimated heat source temperature in the step c is
When the current saturation temperature is equal to or higher than the previous estimated heat source temperature, and when the temperature difference obtained by subtracting the previous estimated heat source temperature from the current saturation temperature is equal to or higher than the first P threshold, the first coefficient is set as a first P coefficient and calculated by the following formula 31:
When the current saturation temperature is equal to or higher than the previously estimated heat source temperature, and when the temperature difference obtained by subtracting the previously estimated heat source temperature from the current saturation temperature is less than the first P threshold, the first coefficient is set to a second P coefficient smaller than the first P coefficient, and is calculated by the following formula 32:
When the current saturation temperature is lower than the past estimated heat source temperature, and when the temperature difference obtained by subtracting the past estimated heat source temperature from the current saturation temperature is equal to or less than a first N threshold, the first coefficient is set to a first N coefficient and calculated by the following formula 33:
When the current saturation temperature is lower than the past estimated heat source temperature, and when the temperature difference obtained by subtracting the past estimated heat source temperature from the current saturation temperature is larger than the first N threshold, the first coefficient is set to a second N coefficient smaller than the first N coefficient, and is calculated by the following formula 34:
the past estimated heat source temperature is a temperature calculated a first time ago using a calculation method similar to a calculation method for the current estimated heat source temperature,
The current estimated detection portion temperature in the step e is
When the current estimated heat source temperature is higher than the previous estimated detection unit temperature, and when the temperature difference obtained by subtracting the previous estimated detection unit temperature from the current estimated heat source temperature is equal to or greater than a second P threshold, the second coefficient is set as a third P coefficient and calculated using the following formula 41:
When the current estimated heat source temperature is higher than the previous estimated detection unit temperature, and when the temperature difference obtained by subtracting the previous estimated detection unit temperature from the current estimated heat source temperature is less than the second P threshold, the second coefficient is set to a fourth P coefficient that is smaller than the third P coefficient, and is calculated using the following formula 42:
When the current estimated heat source temperature is equal to or lower than the previous estimated detection unit temperature, and when the temperature difference obtained by subtracting the previous estimated detection unit temperature from the current estimated heat source temperature is less than a second N threshold, the second coefficient is set to a third N coefficient and calculated using the following formula 43:
When the current estimated heat source temperature is equal to or lower than the previous estimated detection unit temperature, and when the temperature difference obtained by subtracting the previous estimated detection unit temperature from the current estimated heat source temperature is larger than a second N threshold, the second coefficient is set to the fourth N coefficient which is smaller than the third N coefficient, and is calculated by the following formula 44:
The control device according to the above [2], wherein the past estimated detection part temperature is a temperature calculated by a calculation method similar to a calculation method for the current estimated detection part temperature before the first time period.
Current estimated heat source temperature = First P coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 31)
Current estimated heat source temperature = Second P coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 32)
Current estimated heat source temperature = First N coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 33)
Current estimated heat source temperature = Second N coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 34)
Current estimated detector temperature = Third P coefficient × (current estimated heat source temperature − previous estimated detector temperature) + previous estimated detector temperature (Equation 41)
Current estimated detector temperature = Fourth P coefficient × (current estimated heat source temperature - previous estimated detector temperature) + previous estimated detector temperature (Equation 42)
Current estimated detector temperature = Third N coefficient × (current estimated heat source temperature − previous estimated detector temperature) + previous estimated detector temperature (Equation 43)
Current estimated detector temperature = 4th N coefficient × (current estimated heat source temperature - previous estimated detector temperature) + previous estimated detector temperature (Equation 44)

[4] The steps a, c, e, and i are repeated every first time;
The control device according to the above [2] or [3], wherein the step f, the step g, and the step h are repeated every second time period that is longer than the first time period.

[5] The control device described in any one of [2] to [4] above, characterized in that the first coefficient is a value greater than 0 and less than 1, and the second coefficient is a value greater than 0 and less than 1.

[6] The control unit
In a first case where a value of the current flowing through the drive unit is equal to or greater than a predetermined switching threshold current and a frequency of the current flowing through the drive unit is less than a predetermined switching threshold frequency, the power supplied from the power conversion unit to the drive unit is controlled based on the estimated control temperature;
On the other hand, in a second case where the current value flowing through the drive unit is less than the switching threshold current or the frequency of the current flowing through the drive unit is equal to or greater than the switching threshold frequency, the control device described in any one of [1] to [5] above is characterized in that the power supplied from the power conversion unit to the drive unit is controlled based on the actual temperature rather than the control estimated temperature.

[7] The control unit
when the first case transitions to the second case such that the frequency of the current flowing in the drive unit is less than the switching threshold frequency and the value of the current flowing in the drive unit decreases from equal to or greater than the switching threshold current to a preset hysteresis threshold current that is smaller than the switching threshold current, continuously controlling the power supplied from the power conversion unit to the drive unit based on the estimated control temperature;
On the other hand, when the frequency of the current flowing to the drive unit is less than the switching threshold frequency and the current value flowing to the drive unit transitions from less than the hysteresis threshold current to the switching threshold current, the control device described in [6] above continues to control the power supplied from the power conversion unit to the drive unit based on the actual temperature.

[8] The control unit
when the first case transitions to the second case such that the value of the current flowing in the drive unit is equal to or greater than the switching threshold current and the frequency of the current flowing in the drive unit increases from less than the switching threshold frequency to a preset hysteresis threshold frequency that is higher than the switching threshold frequency, continuously controlling the power supplied from the power conversion unit to the drive unit based on the estimated control temperature;
On the other hand, when the current value flowing in the drive unit is equal to or greater than the switching threshold current and the frequency of the current flowing in the drive unit transitions from the second case to the first case so that it decreases from equal to or greater than the hysteresis threshold frequency to the switching threshold frequency, the control device described in [6] or [7] above is characterized in that the power supplied from the power conversion unit to the drive unit is continuously controlled based on the actual temperature.

[9] In the second case,
The control unit
The control device according to any one of [6] to [8] above, characterized in that when the value of the current flowing to the drive unit is less than the hysteresis threshold current or the frequency of the current flowing to the drive unit is equal to or greater than the hysteresis threshold frequency, the control device controls the power supplied from the power conversion unit to the drive unit based on the actual temperature.

[10] The drive unit is a motor,
the power conversion unit includes a bridge circuit that generates a motor drive voltage for driving the motor from the DC voltage supplied from the current source,
the control unit controls the power conversion unit to drive the motor by supplying the motor drive voltage to the motor;
a combination of a current value flowing in the drive unit and a frequency of the current flowing in the drive unit is a combination of a phase current value of a phase current of the motor and the rotation speed of the motor when the motor is continuously driven at a predetermined rotation speed for a preset drive period,
the heat generated by the heat source in the power conversion unit or the drive unit is heat generated when the motor is driven,
the temperature detection unit is a thermistor disposed near the heat source for detecting a temperature near the heat source,
the current value flowing in the drive unit acquired by the control unit is a phase current value detected by detecting a phase current of the motor,
the frequency of the current flowing in the drive unit, which is acquired by the control unit, corresponds to the number of rotations of the motor;
The control device according to any one of [1] to [9] above.

[11] The first coefficient is a time constant based on a first-order lag relationship of a time change in the temperature of the heat source relative to the current saturation temperature,
The control device according to the above [10], wherein the second coefficient is a time constant that is based on a first-order lag relationship of a time change in heat conduction from the heat source to the thermistor and that is different from the first coefficient.

[12] The heat source is
a transistor constituting a bridge circuit of the power conversion unit,
The thermistor is
The control device according to the above [10] or [11], wherein the control device is disposed in proximity to the transistor.

[13] The heat source is
a coil of the motor,
The thermistor is
The control device according to the above [10] or [11], characterized in that it is arranged in proximity to the coil.

[14] The control device described in any one of [10] to [13] above, characterized in that the saturation temperature is the temperature of the heat source that becomes saturated by the control unit controlling the bridge circuit of the power conversion unit so that current is continuously applied to the motor at least during the driving period.

[15] The control unit
The control device according to any one of [10] to [14], characterized in that the rotation speed of the motor is obtained based on a signal output by a Hall element provided in the motor in response to the rotation of the motor.

[16] The motor is a three-phase motor, and the bridge circuit is a three-phase bridge circuit including first to third half bridges,
The control device according to any one of [10] to [15], wherein the first to third half bridges each include a high-side transistor and a low-side transistor connected in series.

[17] The control device according to the above [16], wherein the thermistors are arranged near the high-side transistors of the first to third half bridges, respectively.

[18] The motor is a three-phase motor,
The control device according to any one of the above [10] to [17], characterized in that the temperature value of the first phase coil of the motor is substituted by an average value of the temperature detection value of a second thermistor arranged in the vicinity of the second phase coil of the motor and the temperature detection value of a third thermistor arranged in the vicinity of the third phase coil of the motor.

[19] A method for controlling a power conversion unit that converts power from a current source and supplies power to a drive unit,
preparing a saturation temperature information table that associates a combination of a current value flowing in the drive unit and a frequency of the current flowing in the drive unit with a saturation temperature that is a maximum temperature at which heat from a heat source generated in the power conversion unit or the drive unit is saturated;
Acquire a current value flowing in the drive unit and acquire a frequency of the current flowing in the drive unit;
acquire an actual temperature detected by a temperature detection unit disposed near a heat source generated by the power conversion unit or the drive unit;
calculating a control estimated temperature using the current value, the frequency, the saturation temperature information table, and the actual temperature;
a control method for controlling power supplied from the power conversion unit to the drive unit based on the control estimated temperature;
[20]
After acquiring the value of the current flowing in the drive unit and the frequency of the current flowing in the drive unit,
a step a of calculating a current saturation temperature of the heat source corresponding to a combination of the current value and the frequency by referring to the saturation temperature information table;
a step c of calculating a current estimated heat source temperature by estimating the temperature of the heat source by using the current saturation temperature and a first coefficient;
a step e) of calculating a current estimated detection unit temperature by using the current estimated heat source temperature and a second coefficient to estimate a temperature in the vicinity of the heat source;
a step f of acquiring the actual temperature detected by the temperature detection unit;
a step g of calculating a temperature difference by subtracting the actual temperature from the current estimated detection portion temperature;
a step h of calculating a temperature correction value by multiplying the temperature difference by a preset temperature correction coefficient;
a step i of calculating an estimated control temperature by adding the temperature correction value to the current estimated heat source temperature;
and controlling the power supplied from the power conversion unit to the drive unit based on the control estimated temperature.
[21]
The current estimated heat source temperature in the step c is
When the current saturation temperature is equal to or higher than the previous estimated heat source temperature, and when the temperature difference obtained by subtracting the previous estimated heat source temperature from the current saturation temperature is equal to or higher than the first P threshold, the first coefficient is set as a first P coefficient and calculated by the following formula 31:
When the current saturation temperature is equal to or higher than the previously estimated heat source temperature, and when the temperature difference obtained by subtracting the previously estimated heat source temperature from the current saturation temperature is less than the first P threshold, the first coefficient is set to a second P coefficient smaller than the first P coefficient, and is calculated by the following formula 32:
When the current saturation temperature is lower than the past estimated heat source temperature, and when the temperature difference obtained by subtracting the past estimated heat source temperature from the current saturation temperature is equal to or less than a first N threshold, the first coefficient is set to a first N coefficient and calculated by the following formula 33:
When the current saturation temperature is lower than the past estimated heat source temperature, and when the temperature difference obtained by subtracting the past estimated heat source temperature from the current saturation temperature is larger than the first N threshold, the first coefficient is set to a second N coefficient smaller than the first N coefficient, and is calculated by the following formula 34:
the past estimated heat source temperature is a temperature calculated a first time ago using a calculation method similar to a calculation method for the current estimated heat source temperature,
The current estimated detection portion temperature in the step e is
When the current estimated heat source temperature is higher than the previous estimated detection unit temperature, and when the temperature difference obtained by subtracting the previous estimated detection unit temperature from the current estimated heat source temperature is equal to or greater than a second P threshold, the second coefficient is set as a third P coefficient and calculated using the following formula 41:
When the current estimated heat source temperature is higher than the previous estimated detection unit temperature, and when the temperature difference obtained by subtracting the previous estimated detection unit temperature from the current estimated heat source temperature is less than the second P threshold, the second coefficient is set to a fourth P coefficient that is smaller than the third P coefficient, and is calculated using the following formula 42:
When the current estimated heat source temperature is equal to or lower than the previous estimated detection unit temperature, and when the temperature difference obtained by subtracting the previous estimated detection unit temperature from the current estimated heat source temperature is less than a second N threshold, the second coefficient is set to a third N coefficient and calculated using the following formula 43:
When the current estimated heat source temperature is equal to or lower than the previous estimated detection unit temperature, and when the temperature difference obtained by subtracting the previous estimated detection unit temperature from the current estimated heat source temperature is larger than a second N threshold, the second coefficient is set to the fourth N coefficient which is smaller than the third N coefficient, and is calculated by the following formula 44:
The control method according to the above [20], wherein the past estimated detector temperature is a temperature calculated by a calculation method similar to a calculation method for the current estimated detector temperature before the first time period.
Current estimated heat source temperature = First P coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 31)
Current estimated heat source temperature = Second P coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 32)
Current estimated heat source temperature = First N coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 33)
Current estimated heat source temperature = Second N coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 34)
Current estimated detector temperature = Third P coefficient × (current estimated heat source temperature − previous estimated detector temperature) + previous estimated detector temperature (Equation 41)
Current estimated detector temperature = Fourth P coefficient × (current estimated heat source temperature - previous estimated detector temperature) + previous estimated detector temperature (Equation 42)
Current estimated detector temperature = Third N coefficient × (current estimated heat source temperature − previous estimated detector temperature) + previous estimated detector temperature (Equation 43)
Current estimated detector temperature = 4th N coefficient × (current estimated heat source temperature - previous estimated detector temperature) + previous estimated detector temperature (Equation 44)

[22] The steps a, c, e, and i are repeated every first time;
The control method according to the above [20] or [21], wherein the steps f, g, and h are repeated every second time period that is longer than the first time period.

[23] The control method described in any one of [19] to [22] above, characterized in that when the current value flowing through the drive unit is less than the switching threshold current, or the frequency of the current flowing through the drive unit is equal to or greater than the switching threshold frequency, the power supplied from the power conversion unit to the drive unit is controlled based on the actual temperature rather than the control estimated temperature.

Various aspects of the present invention provide a control device and control method that can estimate the temperature of a heat source more accurately by taking into account the effects of thermal conduction and ambient temperature, even if the temperature of the heat source that serves as the reference for executing the temperature protection function cannot be directly detected.

1 is a schematic diagram illustrating a control device according to an embodiment of the present invention. 1 is a schematic diagram illustrating an electric vehicle equipped with a control device according to an aspect of the present invention. 3 is a diagram showing an example of a peripheral configuration of a power conversion unit 30c shown in FIG. 2. FIG. 10 is a diagram showing an example of the relationship between the motor current and the saturation temperature of the heat source Z when the motor is driven at a predetermined rotation speed for a predetermined drive period. FIG. This figure shows an example of the relationship between the motor current value 61, the actual thermistor temperature 62 detected by the thermistor S, the actual temperature 63 of the heat source Z, and the saturation temperature 64 of the heat source Z when the motor is driven at a predetermined rotation speed. This figure explains a method in which, when controlling the drive of a motor as a drive unit, the control unit selects the above-mentioned control estimated temperature or actual thermistor temperature as the temperature of the heat source that serves as the reference for executing the temperature protection function, in accordance with the relationship between the motor current value (phase current value) and the frequency of the current flowing through the motor. FIG. 10 is a diagram showing the relationship between the temperature of the heat source and the control of the motor to perform a temperature protection function. FIG. 8 is a diagram showing an example of the characteristics of the target limit torque 57 at the limit threshold 51 shown in FIG. 7, and is a diagram showing the relationship between the target limit torque at the limit threshold and the frequency of the current flowing to the motor 3x. FIG. 10 is a diagram showing the configuration of the periphery of a power conversion unit 30c according to a third embodiment. 10 is a diagram showing an example of the ability of the temperature detected by the thermistor to follow the temperature of the heat source when the frequency of the current flowing through the motor and the current flow change. FIG. 10 is a diagram showing the relationship between the current application time and the temperature of the heat source when the motor is driven with a constant current and the temperature of the heat source increases. FIG. 10 is a diagram showing the relationship between the power supply time and the temperature of the heat source when the temperature of the heat source decreases even when the motor is driven with a constant current. FIG.

The following describes in detail embodiments of the present invention using the accompanying drawings. However, the present invention is not limited to the following description, and those skilled in the art will readily understand that various changes in form and detail may be made without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

For example, while a control device will be described as the first embodiment, this control device can also be applied to an electric vehicle control device that drives a load on an electric vehicle, or to a device that controls a drive unit that drives a load other than a load on an electric vehicle.

(First embodiment)
<Control device>
FIG. 1 is a schematic diagram showing a control device according to one embodiment of the present invention.
The control device 1 controls a current source 2 and a power conversion unit 30 that converts power from the current source 2 and supplies the power to a drive unit 3. The control device 1 also includes a control unit 10 that controls the power conversion unit 30, a memory unit 20, and a temperature detection unit 11. The temperature detection unit 11 is a detection unit that detects the temperature near a heat source (not shown) generated by the power conversion unit 30 or the drive unit 3. This heat source is a source that generates heat in the power conversion unit 30 when converting power from the current source 2, or a source that generates heat in the drive unit 3 when converting power from the current source 2 and supplying power to the drive unit 3. In FIG. 1 , the temperature detection unit 11 is disposed near the heat source of the power conversion unit 30. The memory unit 20 stores a saturation temperature information table that associates combinations of the current value and frequency of the current flowing through the drive unit 3 with saturation temperatures, which are the maximum temperatures at which the heat of the heat source saturates. The current source 2 may be, for example, a battery, and the drive unit 3 may be, for example, a motor.

The saturation temperature information table here is a table that associates the combination of the current value and frequency of the current flowing through the drive unit 3 when the drive unit 3 is continuously driven at a predetermined frequency for a preset drive period with the saturation temperature, which is the maximum temperature at which the heat source generated when the drive unit 3 is driven becomes saturated. This saturation temperature is the temperature of the heat source that becomes saturated when the control unit 10 controls the power conversion unit 30 so that current is continuously applied to the drive unit 3 (current flows continuously) at least during the drive period.

Note that the above phrase "the combination of the current value and frequency of the current flowing through drive unit 3 when drive unit 3 is continuously driven at a predetermined frequency for a predetermined drive period" may be replaced with "the combination of the current value and frequency of the current flowing through drive unit 3 when drive unit 3 is continuously driven at a predetermined rotation speed for a predetermined drive period."

The control unit 10 acquires the value of the current flowing through the drive unit 3, acquires the frequency of the current flowing through the drive unit 3, acquires the actual temperature detected by the temperature detection unit 11, calculates an estimated control temperature using the current value, the frequency, the saturation temperature information table stored in the storage unit 20, and the actual temperature, and controls the power supplied from the power conversion unit 30 to the drive unit 3 based on the estimated control temperature. Using the saturation temperature information table makes it possible to calculate a more accurate estimated control temperature.
In detail, the control unit 10 controls the power supplied from the power conversion unit 30 to the drive unit 3 through the following steps (step a) to (step j).
(Step a) The current value flowing through the drive unit 3 is acquired, and the frequency of the current flowing through the drive unit 3 is acquired. By referring to the saturation temperature information table stored in the memory unit 20, the current saturation temperature of the heat source corresponding to the combination of the current value and the frequency is calculated.
(Step c) Using the current saturation temperature and a first coefficient, a current estimated heat source temperature is calculated by estimating the temperature of the heat source.
For example, the current estimated heat source temperature is calculated by any one of the following methods (i) to (iv).
(i) When the current saturation temperature is equal to or higher than the past estimated heat source temperature and the temperature difference obtained by subtracting the past estimated heat source temperature from the current saturation temperature is equal to or higher than the first P threshold, the current estimated heat source temperature is calculated using the following equation 31, with the first coefficient being the first P coefficient.
Current estimated heat source temperature = First P coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 31)
The past estimated heat source temperature is a temperature calculated a first time ago using the same calculation method as the current estimated heat source temperature.
(ii) When the current saturation temperature is equal to or higher than the past estimated heat source temperature and the temperature difference obtained by subtracting the past estimated heat source temperature from the current saturation temperature is less than the first P threshold, the current estimated heat source temperature is calculated using the following equation 32, with the first coefficient being set to a second P coefficient that is smaller than the first P coefficient.
Current estimated heat source temperature = Second P coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 32)
(iii) When the current saturation temperature is lower than the past estimated heat source temperature and the temperature difference obtained by subtracting the past estimated heat source temperature from the current saturation temperature is equal to or less than the first N threshold, the current estimated heat source temperature is calculated using the following equation 33, with the first coefficient being the first N coefficient.
Current estimated heat source temperature = First N coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 33)
(iv) When the current saturation temperature is lower than the past estimated heat source temperature and the temperature difference obtained by subtracting the past estimated heat source temperature from the current saturation temperature is greater than the first N threshold, the current estimated heat source temperature is calculated using the following equation 34, with the first coefficient being set to a second N coefficient smaller than the first N coefficient.
Current estimated heat source temperature = Second N coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 34)
(Step e) Using the current estimated heat source temperature and a second coefficient, a current estimated detection unit temperature is calculated, which is an estimate of the temperature in the vicinity of the heat source.
For example, the current estimated detection portion temperature is calculated by one of the following methods (i) to (iv).
(i) When the current estimated heat source temperature is higher than the past estimated detection temperature and the temperature difference obtained by subtracting the past estimated detection temperature from the current estimated heat source temperature is equal to or greater than the second P threshold, the second coefficient is set to the third P coefficient and the current estimated detection temperature is calculated using the following equation 41.
Current estimated detector temperature = Third P coefficient × (current estimated heat source temperature − previous estimated detector temperature) + previous estimated detector temperature (Equation 41)
The past estimated detector temperature is a temperature calculated the first time before using the same calculation method as the current estimated detector temperature.
(ii) When the current estimated heat source temperature is higher than the past estimated detection temperature and the temperature difference obtained by subtracting the past estimated detection temperature from the current estimated heat source temperature is less than the second P threshold, the second coefficient is set to a fourth P coefficient smaller than the third P coefficient, and the current estimated detection temperature is calculated using the following equation 42.
Current estimated detector temperature = Fourth P coefficient × (current estimated heat source temperature - previous estimated detector temperature) + previous estimated detector temperature (Equation 42)
(iii) When the current estimated heat source temperature is lower than the past estimated detection temperature and the temperature difference obtained by subtracting the past estimated detection temperature from the current estimated heat source temperature is less than a second N threshold, the second coefficient is set to a third N coefficient and the current estimated detection temperature is calculated using the following equation 43.
Current estimated detector temperature = Third N coefficient × (current estimated heat source temperature − previous estimated detector temperature) + previous estimated detector temperature (Equation 43)
(iv) When the current estimated heat source temperature is lower than the past estimated detection temperature and the temperature difference obtained by subtracting the past estimated detection temperature from the current estimated heat source temperature is greater than a second N threshold, the second coefficient is set to the fourth N coefficient, which is smaller than the third N coefficient, and the current estimated detection temperature is calculated using the following equation 44.
Current estimated detector temperature = Fourth N coefficient × (current estimated heat source temperature - previous estimated detector temperature) + previous estimated detector temperature (Equation 44)
(Step f) The actual temperature detected by the temperature detection unit 11 is acquired.
(Step g) A temperature difference is calculated by subtracting the actual temperature from the current estimated detection portion temperature.
(Step h) A temperature correction value is calculated by multiplying the temperature difference by a preset temperature correction coefficient. Details of the temperature correction coefficient will be described later.
(i) An estimated control temperature is calculated by adding the temperature correction value to the current estimated heat source temperature.
(j) The power supplied from the power conversion unit 30 to the drive unit 3 is controlled based on the control estimated temperature.

The above steps a, c, e, and i may be repeated every first time period (e.g., 10 ms), and the above steps f, g, and h may be repeated every second time period (e.g., 100 ms) that is longer than the first time period.

Second Embodiment
<Electric vehicles>
FIG. 2 is a schematic diagram illustrating an electric vehicle equipped with a control device 1a according to one aspect of the present invention.

The electric vehicle in Figure 2 is a vehicle that moves forward or backward by driving a motor 3x using power supplied from a battery 2a as a current source. Note that the motor 3x is an example of a drive unit.

This electric vehicle is an electric two-wheeled vehicle such as an electric motorcycle, and more specifically, an electric two-wheeled vehicle in which the motor 3x and a load 8 such as a wheel are mechanically connected directly without a clutch. Note that the electric vehicle according to one aspect of the present invention is not limited to two-wheeled vehicles, and may be, for example, a three- or four-wheeled electric vehicle.

As shown in FIG. 2, the electric vehicle includes a control device 1a, a power conversion unit 30c, a battery 2a, a motor 3x, an angle sensor 4, an accelerator position sensor (not shown), an assist switch 6, a meter (display unit) 7, a load 8, and a charger 9.

The following describes in detail each component of the electric vehicle shown in Figure 2.

The control device 1a controls each component of the electric vehicle, and as mentioned above, is mounted on, for example, an electric motorcycle (electric vehicle). In this case, the load 8 is the wheel of the electric motorcycle. The motor 3x is connected to the wheel of the electric motorcycle. The control device 1 can then control the power conversion unit 30c, which converts power from the battery 2a and supplies it to the motor 3x.

The control device 1a may also be configured as an ECU (Electronic Control Unit) that controls the entire electric vehicle.

As shown in FIG. 2, this control device 1a includes a control unit 10a, a memory unit 20a, and a temperature detection unit 11a. This temperature detection unit 11a is a thermistor S for detecting the temperature of the heat source Z of the power conversion unit 30c (see FIG. 3). However, as described below, the control device 1a may also include a thermistor S for detecting the temperature of the heat source Z of the motor 3x.

The battery 2a supplies power to the motor 3x that rotates the wheels of the electric vehicle. More specifically, the battery 2a supplies DC power to the power conversion unit 30c. The battery 2a is, for example, a lithium-ion battery, but may be other types of battery. The battery 2a may also include a lead battery for supplying operating voltage to the control unit 10a.

The battery 2a also includes a battery management unit (BMU). The battery management unit transmits battery information related to the voltage and state (charge rate, etc.) of the battery 2a to the control unit 10a. Note that the number of batteries 2a is not limited to one, and may be multiple. In other words, the electric vehicle may be provided with multiple batteries 2a connected in parallel or in series.

Motor 3x is a three-phase motor driven by AC power supplied from power conversion unit 30c. This motor 3x is mechanically connected to the wheel and rotates the wheel in the desired direction. In this embodiment, motor 3x is mechanically connected directly to the wheel without a clutch (including a transmission mechanism). There are no particular limitations on the type of motor 3x.

The angle sensor 4 is a sensor that detects the rotation angle of the rotor of the motor 3x. N-pole and S-pole magnets (sensor magnets) are attached alternately to the circumferential surface of the rotor (not shown).

This angle sensor 4 is composed of, for example, a Hall element, and is designed to detect changes in the magnetic field that accompany the rotation of the motor 3x.

The accelerator position sensor also detects the amount of accelerator operation of the electric vehicle (hereinafter referred to as "accelerator operation amount") and transmits it as an electrical signal to the control unit 10a. The accelerator operation amount corresponds to the throttle opening of an engine vehicle. When the user wants to accelerate, the accelerator operation amount increases, and when the user wants to decelerate, the accelerator operation amount decreases.

The accelerator position sensor also detects the amount of accelerator operation by the user of the electric vehicle (electric motorcycle) and transmits this as an electrical signal to the control unit 10a.

The assist switch 6 is a switch that is operated by the user when requesting assistance from the electric vehicle. When operated by the user, the assist switch 6 transmits an assistance request signal to the control unit 10a.

The meter (display unit) 7 is a display (e.g., a liquid crystal panel) provided on the electric vehicle, and displays various information. The meter 7 is provided, for example, on the steering wheel (not shown) of the electric vehicle. The meter 7 displays information such as the electric vehicle's traveling speed, the remaining charge of the battery 2a, the current time, the total distance traveled, and the remaining distance traveled. The remaining distance traveled indicates how far the electric vehicle can travel.

The charger 9 also has a power plug (not shown) and a converter circuit (not shown) that converts AC power supplied via the power plug into DC power. The battery 2a is charged with the DC power converted by the converter circuit. The charger 9 is communicatively connected to the control device 1a, for example, via a communications network (such as a CAN) within the electric vehicle.

In addition, the control unit 10a is configured to input and output information from various devices connected to the control device 1a.

Specifically, the control unit 10a receives various signals output from the battery 2a, angle sensor 4, accelerator position sensor, assist switch 6, and charger 9. The control unit 10a outputs signals to be displayed on the meter 7. The control unit 10a also controls the motor 3x via the power conversion unit 30c. Details of the control unit 10a will be described later.

The memory unit 20a also stores information used by the control unit 10a (such as the various maps described below) and programs for the operation of the control unit 10a. This memory unit 20a is, for example, a non-volatile semiconductor memory, but is not limited to this. The memory unit 20a may also be incorporated as part of the control unit 10a.

In particular, the storage unit 20a is configured to store a saturation temperature information table (not shown) that associates combinations of the value of the current flowing through the motor 3x and the frequency of the current flowing through the motor 3x when the motor 3x is continuously driven at a predetermined rotation speed for a preset driving period with the saturation temperature, which is the maximum temperature at which the heat generated by the heat source Z when the motor 3x is driven is saturated.
The above "combination of the value of the current flowing through the motor 3x and the frequency of the current flowing through the motor 3x" may be replaced with "combination of the value of the phase current of the motor 3x and the rotation speed of the motor 3x."

The above-mentioned saturation temperature is the temperature of the heat source Z that becomes saturated when the control unit 10a controls the bridge circuit X of the power conversion unit 30c so that current flows continuously to the motor 3x (so that current (phase current) flows continuously) at least during the drive period described above (see Figure 4). It is believed that using such a saturation temperature is useful for estimating the temperature of the heat source.

In addition, the power conversion unit 30c converts the DC power output from the battery 2a into AC power and supplies it to the motor 3x (see Figure 3).

The power conversion unit 30c, which is an inverter device, is equipped with a three-phase bridge circuit X including first to third half bridges that generates a motor drive voltage for driving the motor 3x from the DC voltage supplied by the battery 2a. By providing this bridge circuit X, the phase and wave height of the sine wave required to drive the motor can be controlled, and heat generation can be minimized by using the motor efficiently.

The first to third half bridges each include a high-side transistor (semiconductor switches Q1, Q3, and Q5) and a low-side transistor (semiconductor switches Q2, Q4, and Q6) connected in series.

The control terminals of these semiconductor switches Q1 to Q6 are electrically connected to the control unit 10a. A smoothing capacitor C is provided between the power supply terminals 30a and 30b. The semiconductor switches Q1 to Q6 are, for example, MOSFETs or IGBTs.

As shown in Figure 3, the semiconductor switch Q1 is connected between the power supply terminal 30a, to which the positive electrode of the battery 2a is connected, and the input terminal 3a of the motor 3x.

Similarly, semiconductor switch Q3 is connected between power supply terminal 30a and input terminal 3b of motor 3x.

Semiconductor switch Q5 is connected between power supply terminal 30a and input terminal 3c of motor 3x.

Semiconductor switch Q2 is connected between the input terminal 3a of motor 3x and power supply terminal 30b to which the negative pole of battery 2a is connected.

Similarly, semiconductor switch Q4 is connected between input terminal 3b of motor 3x and power supply terminal 30b.

Semiconductor switch Q6 is connected between input terminal 3c of motor 3x and power supply terminal 30b.

Note that input terminal 3a is the U-phase input terminal of motor 3x, input terminal 3b is the V-phase input terminal of motor 3x, and input terminal 3c is the W-phase input terminal of motor 3x.

In addition, the control unit 10a controls the power conversion unit 30c to output a command torque from the motor 3x in accordance with an externally input command signal, and supplies a motor drive voltage to the motor 3x, thereby driving the motor 3x.

As mentioned above, the accelerator position sensor detects the amount of accelerator operation by the user of the electric vehicle (electric motorcycle) 100 and transmits it as an electrical signal to the control unit 10. In this case, the electrical signal output by the accelerator position sensor corresponds to the command signal.

The control unit 10a controls the on/off of the semiconductor switches Q1 to Q6 of the power conversion unit 30c according to the motor stage. This converts the DC power supplied from the battery 2a into AC power.

As mentioned above, the thermistor S is placed near the heat source Z to detect the temperature of the heat source Z (see Figure 3). As shown in Figure 3, the heat source Z is the transistors Q1 to Q6 that make up the bridge circuit X of the power conversion unit 30c.

In this embodiment, the thermistor S is placed close to transistors Q1 to Q6. Using the thermistor S simplifies circuit board design and allows the temperature to be read from changes in resistance due to temperature, making it possible to simply configure the conversion control.

In particular, as shown in FIG. 3, the thermistor S includes three thermistors S1, S2, and S3. Thermistor S1 is located near the high-side transistor Q1 of the first half-bridge. Thermistor S2 is located near the high-side transistor Q3 of the second half-bridge. Thermistor S3 is located near the high-side transistor Q5 of the third half-bridge.

In this way, the thermistors S (S1, S2, S3) are placed near the high-side transistors Q1, Q3, and Q5 of the first to third half bridges, which are believed to generate particularly large amounts of heat. This is thought to be useful for estimating the temperature of each of the high-side transistors Q1, Q3, and Q5.

<Method for estimating the heat source temperature used when implementing the temperature protection function>
An example of a method for estimating the heat source temperature used when the temperature protection function is performed by the control device 1a will be described.

Here, we consider a physical model based on the on-resistance of the transistor (heat source Z), the temperature rise due to the current of the motor 3x (driver), the heat capacity of the unit, and thermal conduction between the unit's ambient temperature.The temperature of the transistor is then estimated from the saturation temperature after time has passed until the heat of the heat source is saturated.To prevent any discrepancy between this estimated temperature and the actual temperature due to calculation errors, we use a method that uses the actual temperature (see Figure 5).
In addition, the "current of the motor 3x" above and below may be replaced with the "phase current of the motor 3x."

First, to implement the temperature protection function, the control unit 10a obtains the current value flowing through the motor 3x (detects the phase current of the motor 3x and obtains the phase current value (e.g., 100 A)), as well as the frequency of the current flowing through the motor 3x (or the rotation speed of the motor 3x (e.g., 1000 rpm)).

The control unit 10a can obtain the rotation speed of the motor 3x, for example, based on a signal output by a Hall element (not shown) provided in the motor 3x in response to the rotation of the motor 3x. It is believed that using such a Hall element will be useful in obtaining the rotation speed of the motor 3x.

Furthermore, when detecting the current (phase current), the peak current of each current (phase current) may be obtained for each of the six stages defined by the on/off combinations of the transistors Q1 to Q6 of the motor 3x during 120° conduction and 180° conduction, and the current value (phase current value) may be obtained by removing switching noise and averaging the current.

As described above, the memory unit 20a stores a saturation temperature information table that associates a combination of the current value (phase current value) flowing through the motor 3x and the frequency of the current flowing through the motor 3x (or the rotation speed of the motor 3x) when the motor 3x is continuously driven at a predetermined rotation speed for a predetermined driving period with the saturation temperature, which is the maximum temperature at which the heat from the heat source Z generated when the motor 3x is driven is saturated (see Figure 4).
The control unit 10a acquires the current value flowing in the drive unit (motor 3x), acquires the frequency of the current flowing in the motor 3x, acquires the actual temperature detected by the temperature detection unit 11a, calculates an estimated control temperature using the current value, the frequency, the saturation temperature information table, and the actual temperature, and controls the power supplied from the power conversion unit 30c to the motor 3x based on the estimated control temperature.
This is explained in detail below.

(Step a) The control unit 10a refers to the saturation temperature information table stored in the memory unit 20a and calculates the current saturation temperature (e.g., 90°C) of the heat source Z that corresponds to (is associated with) the combination of the acquired current value (phase current value; e.g., 100 A) and the acquired frequency (or rotation speed (e.g., 1000 rpm)).

In this way, the current saturation temperature of heat source Z is calculated based on the measurement data of the current current value (phase current value) and frequency (or rotation speed) by referencing a pre-set saturation temperature information table.

Next, the control unit 10a calculates the current estimated heat source temperature as the provisionally estimated temperature of the heat source Z by using a first coefficient (time constant) based on a first-order lag relationship 65 of the time change of the temperature of the heat source Z relative to the current saturation temperature, as shown in the following (Equation 3). In other words, as shown in Fig. 5, the temperature of the heat source is estimated by using a time constant (first coefficient) based on a first-order lag relationship 65 relative to the current saturation temperature.
The first coefficient is, for example, a value greater than 0 and less than 1. The first coefficient can correct the first-order lag for the current saturation temperature.

The method for calculating the current estimated heat source temperature will be described in detail below.
First, the first coefficient will be described in detail below. Fig. 11 is a diagram showing the relationship between the power supply time and the temperature of the heat source when the motor is driven with a constant current and the temperature of the heat source increases. Fig. 12 is a diagram showing the relationship between the power supply time and the temperature of the heat source when the motor is driven with a constant current and the temperature of the heat source decreases.

(Step b) The current saturation temperature is compared with the previously estimated heat source temperature (e.g., 100°C) calculated a first time (e.g., 10 ms) ago (the previous time). At this time, if the current saturation temperature is equal to or higher than the previously estimated heat source temperature (Equation a) below, it is determined that the temperature of the heat source is rising. In this case, the first coefficient is positive (P).

(Current saturation temperature - Previous estimated heat source temperature) ≧ 0 (Equation a)

The past estimated heat source temperature is a temperature calculated the first time before using a method similar to that for calculating the current estimated heat source temperature. If the past estimated heat source temperature has not been calculated, the actual thermistor temperature detected by thermistor S may be used.

When the first coefficient is positive (P) and the temperature difference between the current saturation temperature and the previously estimated heat source temperature is equal to or greater than the P slope threshold (first P threshold; for example, 20°C) (formula b), it is determined that the temperature rise of the heat source is rapid, as in (i) below. The P slope threshold is also called

(Current saturation temperature - Previous estimated heat source temperature) ≧ P gradient threshold (Equation b)

(i) In the case where the temperature of the heat source rises rapidly toward the current saturation temperature (reference numeral 71 in FIG. 11), a P coefficient (rapid) is used as the first coefficient. This P coefficient (rapid) is, for example, 0.05. This P coefficient (rapid) is also called the first P coefficient.

Furthermore, when the first coefficient is positive (P) and the temperature difference between the current saturation temperature and the previously estimated heat source temperature is less than the P slope threshold (first P threshold; for example, 20°C) (equation c) below, it is determined that the temperature rise of the heat source is gradual, as in (ii) below.

(Current saturation temperature - Previous estimated heat source temperature) < P gradient threshold (Equation c)

(ii) In the case where the temperature of the heat source rises gradually toward the current saturation temperature (reference numeral 72 in FIG. 11), a P coefficient (slow) is used as the first coefficient. This P coefficient (slow) is, for example, 0.03. This P coefficient (slow) is smaller than the P coefficient (fast), and is also called the second P coefficient.

Furthermore, if the current saturation temperature is lower than the previously estimated heat source temperature (equation d) below, it is determined that the heat source temperature is decreasing. In this case, the first coefficient is negative (N).

(Current saturation temperature - Previous estimated heat source temperature) < 0 (Equation d)

When the first coefficient is negative (N) and the temperature difference between the current saturation temperature and the previously estimated heat source temperature is less than the N gradient threshold (first N threshold; for example, -30°C) (equation e) below, it is determined that the temperature drop of the heat source is rapid, as in (iii) below.

(Current saturation temperature - Previous estimated heat source temperature) ≦ N gradient threshold (Equation e)

(iii) In the case where the temperature of the heat source drops rapidly toward the current saturation temperature (reference numeral 73 in FIG. 12), the N coefficient (rapid) is used as the first coefficient. This N coefficient (rapid) is, for example, 0.06. This N coefficient (rapid) is also called the first N coefficient.

Furthermore, when the first coefficient is negative (N) and the temperature difference between the current saturation temperature and the previously estimated heat source temperature is greater than the N gradient threshold (first N threshold; for example, −30°C) (equation f) below, it is determined that the temperature of the heat source is decreasing slowly, as in (iv) below.

(Current saturation temperature - Previous estimated heat source temperature) > N gradient threshold ... (Equation f)

(iv) In the case where the temperature of the heat source gradually decreases toward the current saturation temperature (reference numeral 74 in FIG. 12), the N coefficient (slow) is used as the first coefficient. This N coefficient (slow) is, for example, 0.04. Note that the N coefficient (slow) is smaller than the N coefficient (fast) and is also called the second N coefficient.

Based on the above determination, one of the P coefficients (steep) to N coefficients (gentle) from (i) to (iv) above is used as the first coefficient.
Since the first coefficient is a time constant, the coefficient becomes complex whether the temperature is rising or falling. However, by approximating the time constant to the above four cases, the calculation load can be reduced and the accuracy of the temperature estimation of the heat source can be improved.

(Step c) Next, as shown in the following (Equation 3), the first coefficient determined as explained above (i.e., P coefficient (rapid), P coefficient (slow), N coefficient (rapid), N coefficient (slow)) is multiplied by the difference between the current saturation temperature (e.g., 90°C) calculated using the method described above and the previously estimated heat source temperature (e.g., 100°C), and the result is added to the previously estimated heat source temperature, thereby calculating the current estimated heat source temperature (e.g., 99.6°C) as the provisionally estimated heat source temperature.

Current estimated heat source temperature = First coefficient (either P coefficient (rapid), P coefficient (slow), N coefficient (rapid), or N coefficient (slow)) × (current saturation temperature - previous estimated heat source temperature) + previous estimated heat source temperature ... (Equation 3)

In this way, the temperature of the transistor, which is heat source Z, is tentatively estimated from the current saturation temperature using the first coefficient, which is a digitized time constant.

Next, the control unit 10a calculates a current estimated thermistor temperature, which is a provisionally estimated thermistor temperature, based on the first-order lag relationship 66 of the thermal conduction time change from the heat source Z to the thermistor S, as shown in the following (Equation 4), by using a second coefficient (time constant) different from the above-mentioned first coefficient. In other words, as shown in Fig. 5, the actual thermistor temperature is estimated by using a time constant (second coefficient) based on the first-order lag relationship 66 of the thermal conduction time change from the heat source Z to thermistor S.
The current estimated thermistor temperature is also referred to as the current estimated detector temperature.
Moreover, this second coefficient is, for example, a value greater than 0 and less than 1. This second coefficient makes it possible to correct the first-order lag of the change in heat conduction from the heat source Z to the thermistor S over time.

The method for calculating the above-mentioned current estimated thermistor temperature (current estimated detection unit temperature) is explained in detail below.

First, the second coefficient will be described in detail below.
(Step d) The current estimated heat source temperature calculated using (Equation 3) is compared with the previous estimated thermistor temperature calculated a first time (e.g., 10 ms) ago (the previous time). If the current estimated heat source temperature is higher than the previous estimated thermistor temperature (Equation g), the thermistor temperature is determined to be rising. The second coefficient in this case is positive (P).

(current estimated heat source temperature - previous estimated thermistor temperature) ≧ 0 (equation g)

The previous estimated thermistor temperature is a temperature calculated the first time before using a method similar to that for calculating the current estimated thermistor temperature. If the previous estimated thermistor temperature has not been calculated, the actual thermistor temperature detected by thermistor S may be used.

When the second coefficient is positive (P) and the temperature difference between the current estimated heat source temperature and the previously estimated thermistor temperature is greater than the P slope threshold (second P threshold; for example, 20°C) (equation h) below, it is determined that the thermistor temperature rise is rapid, as in (i) below.

(Current estimated heat source temperature - Previous estimated thermistor temperature) ≧ P gradient threshold (Equation h)

(i) In the case where the temperature of the thermistor rises suddenly, the P coefficient (sudden) is used as the second coefficient. This P coefficient (sudden) is, for example, 0.03. This P coefficient (sudden) is also called the third P coefficient.

Furthermore, when the second coefficient is positive (P) and the temperature difference between the current estimated heat source temperature and the previously estimated thermistor temperature is less than the P slope threshold (second P threshold; for example, 20°C) as shown in (formula i) below, it is determined that the thermistor temperature rise is gradual as shown in (ii) below.

(Current estimated heat source temperature - Previous estimated thermistor temperature) < P gradient threshold (Equation i)

(ii) In the case where the temperature of the thermistor rises slowly, the P coefficient (slow) is used as the second coefficient. This P coefficient (slow) is, for example, 0.02. This P coefficient (slow) is smaller than the P coefficient (fast) and is also called the fourth P coefficient.

Furthermore, when the current estimated heat source temperature is lower than the previous estimated thermistor temperature (Equation j), it is determined that the thermistor temperature is decreasing. In this case, the second coefficient is negative (N).

(current estimated heat source temperature−previous estimated thermistor temperature)<0 (equation j)

When the second coefficient is negative (N) and the temperature difference between the current estimated heat source temperature and the previously estimated thermistor temperature is less than the N gradient threshold (second N threshold; for example, −10°C) (equation k) below, it is determined that the thermistor temperature has dropped rapidly, as in (iii) below.

(Current estimated heat source temperature - Previous estimated thermistor temperature) ≦ N gradient threshold (equation k)

(iii) In the case where the temperature of the thermistor drops suddenly, the N coefficient (sudden) is used as the second coefficient. This N coefficient (sudden) is, for example, 0.02. The N coefficient (sudden) is also called the third N coefficient.

Furthermore, when the second coefficient is negative (N) and the temperature difference between the current estimated heat source temperature and the previously estimated thermistor temperature is greater than the N gradient threshold (second N threshold; for example, −10°C) (equation m), it is determined that the thermistor temperature is decreasing slowly, as in (iv) below.

(Current estimated heat source temperature - Previous estimated thermistor temperature) > N gradient threshold ... (Equation m)

(iv) In the case where the temperature of the thermistor drops slowly, the N coefficient (slow) is used as the second coefficient. This N coefficient (slow) is, for example, 0.01. The N coefficient (slow) is smaller than the third N coefficient and is also called the fourth N coefficient.

Based on the above determination, one of the P coefficients (steep) to N coefficients (gentle) from (i) to (iv) above is used as the second coefficient.
Since the second coefficient is a time constant, the coefficient becomes complex whether the temperature is rising or falling. However, by approximating the time constant to the above four cases, the calculation load can be reduced and the accuracy of the temperature estimation of the heat source can be improved.

(Step e) Next, as shown in the following (Equation 4), the second coefficient determined as explained above (i.e., P coefficient (rapid), P coefficient (slow), N coefficient (rapid), N coefficient (slow)) is multiplied by the difference between the current estimated heat source temperature (e.g., 46.65°C) calculated using (Equation 3) above and the previous estimated thermistor temperature (e.g., 30°C), and the result is added to the previous estimated thermistor temperature, thereby calculating the current estimated thermistor temperature (e.g., 30.5), which is the temperature of the thermistor that has been provisionally estimated.

Current estimated thermistor temperature = Second coefficient (either P coefficient (rapid), P coefficient (slow), N coefficient (rapid), or N coefficient (slow)) x (current estimated heat source temperature - previous estimated thermistor temperature) + previous estimated thermistor temperature... (Equation 4)

In this way, the temperature of thermistor S is estimated using the second coefficient, which is a digitized version of the time constant.

(Step f) Next, the control unit 10a acquires the actual thermistor temperature (e.g., 30.9°C) detected by thermistor S.

(Step g) Next, the control unit 10a calculates the temperature difference (e.g., 0.4°C) by subtracting the actual thermistor temperature (e.g., 30.9°C) detected by thermistor S from the current estimated thermistor temperature (e.g., 30.5°C) in (Equation 4) above, as shown in (Equation 5) below.

Current estimated thermistor temperature - actual thermistor temperature = temperature difference (Equation 5)

The actual thermistor temperature is also called the actual temperature.

(Step h) Next, the control unit 10a can calculate a temperature correction value (e.g., 0.36°C) for correcting the current estimated heat source temperature (e.g., 46.65°C) of (Equation 3) above by multiplying a preset temperature correction coefficient (e.g., 0.9) by the temperature difference calculated by (Equation 5) above, as shown in the following (Equation 6).

Temperature difference × temperature correction coefficient = temperature correction value (Equation 6)

The temperature correction coefficient is a ratio at which the temperature difference due to the type of temperature detection unit (for example, thermistor) and individual variations is reflected in the estimated control temperature.

(Step i) Next, the control unit 10a calculates the estimated control temperature (e.g., 47.01°C) by adding the temperature correction value of (Equation 6) above to the current estimated heat source temperature of (Equation 3) above, as shown in the following (Equation 7).

Current estimated heat source temperature + temperature correction value = estimated control temperature (Equation 7)

The above steps (a) to (e) and (i) are repeated every first time (e.g., every 10 ms), and the above steps (f) to (h) are repeated every second time (e.g., every 100 ms). By calculating the temperature correction value for correcting the temperature error every second time, which is longer than the first time, from steps (f) to (h), the load on the control unit can be reduced while maintaining the accuracy of the estimated control temperature. Since the temperature correction value for step (h) can only be obtained every 100 ms, the same temperature correction value is used 10 times in step (i), which is performed every 10 ms.
Furthermore, the estimated control temperature obtained every first time (e.g., every 10 ms) and the current estimated heat source temperature in the calculation process are stored in the storage unit, and the temperature correction value obtained every second time (e.g., every 100 ms) and the current estimated thermistor temperature in the calculation process are stored in the storage unit. Furthermore, the current saturation temperature obtained every first time may also be stored in the storage unit, and the actual temperature obtained every second time may also be stored in the storage unit.

It is advisable to return the previous estimated thermistor temperature to the actual thermistor temperature at regular intervals. The reason for this is that errors in the control estimated temperature accumulate, and as a countermeasure, the previous estimated thermistor temperature is corrected and returned before the difference with the actual temperature due to the error becomes too large. For example, the current estimated heat source temperature and current estimated thermistor temperature are calculated every 10 msec, and the current estimated heat source temperature is corrected using the actual thermistor temperature every 100 msec.

This allows the temperature of the heat source (driver circuit transistor) Z to be estimated based on the temperature detected by the thermistor, the motor current, and rotation speed, taking into account the effects of heat conduction and ambient temperature, and executes the temperature protection function described below.

As mentioned above, the estimated control temperature is estimated based on the saturation temperature of heat source Z, taking into account the first-order lag characteristics, so the temperature protection function described below can be executed more reliably before the temperature reaches a point where the transistor, which is heat source Z, will be damaged.

<How to select the heat source temperature that will be the reference for executing the temperature protection function>
6 is a diagram illustrating a method in which, when controlling the drive of a motor serving as a drive unit, the control unit selects the above-mentioned estimated control temperature or the actual thermistor temperature (actual temperature) as the reference temperature of the heat source for executing the temperature protection function in accordance with the relationship between the motor current value and the frequency of the current flowing through the motor serving as a drive unit. In other words, the control unit 10a may switch the reference temperature of the heat source for executing the temperature protection function between the above-mentioned estimated control temperature and the temperature (actual temperature) detected by the thermistor S.

In Figure 6, the reference heat source temperature for executing the temperature protection function is selected from the above-mentioned estimated control temperature or actual thermistor temperature (actual temperature) in accordance with the relationship between the motor current value and the frequency of the current flowing through the motor. However, it is also possible to select the reference heat source temperature for executing the temperature protection function from the above-mentioned estimated control temperature or actual thermistor temperature (actual temperature) in accordance with the relationship between the motor phase current value and the motor rotation speed.

In the first case where the current value of the current flowing through the motor 3x is equal to or greater than a preset switching threshold current 45 and the frequency of the current flowing through the motor 3x is less than a preset switching threshold frequency 46, the control unit 10a controls the power supplied from the power conversion unit 30c to the motor 3x based on the estimated control temperature 47. This controls the drive of the motor 3x.

In addition, the above-mentioned "first case in which the current value of the current flowing through motor 3x is equal to or greater than the predetermined switching threshold current 45 and the frequency of the current flowing through motor 3x is less than the predetermined switching threshold frequency 46" may be replaced with "first case in which the phase current value flowing through motor 3x is equal to or greater than the predetermined switching threshold current and the rotation speed of motor 3x is less than the predetermined switching threshold rotation speed."
Furthermore, the "current value of the current of the motor 3x" above and below may be replaced with the "phase current value of the phase current of the motor 3x."

In the first case above, because motor 3x is driven at a high current and low frequency, the temperature detected by thermistor S cannot adequately track the actual temperature of heat source Z. However, in such a case, the power conversion unit 30c controls the driving of motor 3x while executing the temperature protection function based on the above-mentioned estimated control temperature, which is calculated by estimating the temperature of the heat source more accurately. This prevents the power conversion unit 30c, which has a heat source, from exceeding a temperature that would damage it.

On the other hand, in a second case where the current value of the current flowing through the motor 3x is less than the switching threshold current 45 or the frequency of the current flowing through the motor 3x is equal to or greater than the switching threshold frequency 46, the control unit 10a controls the power supplied from the power conversion unit 30c to the motor 3x based on the actual thermistor temperature (actual temperature) 50 detected by the thermistor S. This controls the drive of the motor 3x.

Note that the above "second case in which the current value of the current flowing through motor 3x is less than the switching threshold current 45, or the frequency of the current flowing through motor 3x is equal to or greater than the switching threshold frequency 46" may be replaced with "second case in which the phase current value flowing through motor 3x is less than the switching threshold current, or the rotation speed of motor 3x is equal to or greater than the switching threshold rotation speed."

In the second case above, because motor 3 is driven at a low current or high frequency, the temperature detected by thermistor S can adequately track the actual temperature of heat source Z. In such a case, the power conversion unit 30c controls the driving of motor 3x while executing the temperature protection function based on the actual thermistor temperature detected by thermistor S. This prevents the power conversion unit 30c, which has a heat source, from exceeding a temperature that would damage it.

Here, as shown in Figure 6, the above-mentioned control estimated temperature and the actual thermistor temperature detected by thermistor S may be switched so as to have a hysteresis characteristic.

In detail, when the frequency of the current flowing through motor 3x is less than switching threshold frequency 46 and the current value of motor 3x decreases from greater than or equal to switching threshold current 45 to a preset hysteresis threshold current 49 that is less than switching threshold current 45, i.e., when transitioning from the first case to the second case as indicated by arrow 41, control unit 10a continues to control the driving of motor 3 using power conversion unit 30 based on the estimated control temperature (see Figure 6).

Note that the above statement "The frequency of the current flowing through motor 3x is less than the switching threshold frequency 46, and the value of the current flowing through motor 3x decreases from equal to or greater than the switching threshold current 45 to a preset hysteresis threshold current 49 that is smaller than the switching threshold current 45" may be replaced with "The rotation speed of motor 3x is less than the switching threshold rotation speed, and the phase current value of the phase current of motor 3x decreases from equal to or greater than the switching threshold current to a preset hysteresis threshold current that is smaller than the switching threshold current."

When transitioning from the first case to the second case as indicated by arrow 41, it takes time for the temperature to converge, and the temperature detected by the thermistor S may not be able to adequately track the temperature of the heat source Z. In this case, the power conversion unit 30c controls the drive of the motor 3x while executing the temperature protection function based on the estimated control temperature. This prevents the power conversion unit 30c, which has a heat source, from exceeding a temperature that would damage it.

On the other hand, when the frequency of the current flowing through motor 3x is less than switching threshold frequency 46 and the current value of motor 3x rises from less than hysteresis threshold current 49 to switching threshold current 45, i.e., when transitioning from the second case to the first case as indicated by arrow 42, the control unit 10a continues to control the driving of motor 3 using the power conversion unit 30 based on the actual thermistor temperature (actual temperature) 50 (see Figure 6).

Note that the above statement "The frequency of the current flowing through motor 3x is less than the switching threshold frequency 46, and the current value of the current through motor 3x rises from less than the hysteresis threshold current 49 to the switching threshold current 45" may be replaced with "The rotation speed of motor 3x is less than the switching threshold rotation speed, and the phase current value of the phase current through motor 3x rises from less than the hysteresis threshold current to the switching threshold current."

When transitioning from the second case to the first case as indicated by arrow 42, the temperature rise is rapid, allowing the detected temperature of the thermistor S to adequately track the temperature of the heat source Z. In this case, the power conversion unit 30c controls the drive of the motor 3x while executing the temperature protection function based on the actual thermistor temperature. This prevents the power conversion unit 30c, which has a heat source, from exceeding a temperature that would damage it.

Furthermore, when the current value of the current flowing through motor 3x is equal to or greater than switching threshold current 45 and the frequency of the current flowing through motor 3x rises from below switching threshold frequency 46 to a preset hysteresis threshold frequency 48 that is higher than switching threshold frequency 46, i.e., when transitioning from the first case to the second case as indicated by arrow 43, the control unit 10a continues to control the driving of motor 3 using the power conversion unit 30 based on the estimated control temperature (see Figure 6).

Note that the above statement "The current value of the current flowing through motor 3x is equal to or greater than the switching threshold current 45, and the frequency of the current flowing through motor 3x rises from below the switching threshold frequency 46 to a preset hysteresis threshold frequency 48 that is higher than the switching threshold frequency 46" may be replaced with "The phase current value of the phase current flowing through motor 3x is equal to or greater than the switching threshold current, and the rotation speed of motor 3x rises from below the switching threshold rotation speed to a preset hysteresis threshold rotation speed that is higher than the switching threshold rotation speed."

When transitioning from the first case to the second case as indicated by arrow 43, it takes time for the temperature to converge, and the temperature detected by the thermistor S may not be able to adequately track the temperature of the heat source Z. In this case, the power conversion unit 30c controls the drive of the motor 3x while executing the temperature protection function based on the estimated control temperature. This prevents the power conversion unit 30c, which has a heat source, from exceeding a temperature that would damage it.

On the other hand, when the current value of the current flowing through motor 3x is equal to or greater than switching threshold current 45 and the frequency of the current flowing through motor 3 decreases from above hysteresis threshold frequency 48 to switching threshold frequency 46, i.e., when transitioning from the second case to the first case as indicated by arrow 44, the control unit 10a continues to control the driving of motor 3 using the power conversion unit 30 based on the actual thermistor temperature (actual temperature) 50 (see Figure 6).

Note that the above statement "The current value of the current flowing through motor 3x is equal to or greater than the switching threshold current 45, and the frequency of the current flowing through motor 3 decreases from equal to or greater than the hysteresis threshold frequency 48 to the switching threshold frequency 46" may be replaced with "The phase current value of the phase current flowing through motor 3x is equal to or greater than the switching threshold current, and the rotation speed of motor 3x decreases from equal to or greater than the hysteresis threshold rotation speed to the switching threshold rotation speed."

When transitioning from the second case to the first case, as indicated by arrow 44, the temperature rise is rapid, allowing the temperature detected by the thermistor S to adequately track the temperature of the heat source Z. In this case, the power conversion unit 30c controls the drive of the motor 3x while executing the temperature protection function based on the actual thermistor temperature. This prevents the power conversion unit 30c, which has a heat source, from exceeding a temperature at which it would be damaged.

Furthermore, in the second case described above, if the current value of the current flowing through motor 3x is less than hysteresis threshold current 49 or the frequency of the current flowing through motor 3x is equal to or greater than hysteresis threshold frequency 48, control unit 10a controls the driving of motor 3 using power conversion unit 30 based on the actual thermistor temperature detected by thermistor S.

Note that the above phrase "when the current value of the current flowing through motor 3x is less than hysteresis threshold current 49, or when the frequency of the current flowing through motor 3x is equal to or greater than hysteresis threshold frequency 48" may be replaced with "when the phase current value of the phase current flowing through motor 3x is less than hysteresis threshold current, or when the rotation speed of motor 3x is equal to or greater than hysteresis threshold rotation speed."

In the above case, the detected temperature of thermistor S closely tracks the temperature of heat source Z, so the power conversion unit 30c controls the drive of motor 3x while executing the temperature protection function based on the actual thermistor temperature. This prevents the power conversion unit 30c, which has a heat source, from exceeding a temperature at which it would be damaged.

In addition, in the second case described above, even when the current value of the current flowing through the motor 3x is less than the switching threshold current 45 and the frequency of the current flowing through the motor 3x is greater than or equal to the switching threshold frequency 46, the control unit 10a may control the driving of the motor 3x using the power conversion unit 30c based on the actual thermistor temperature detected by the thermistor S.
In addition, the above-mentioned "when the current value of the current of motor 3x is less than the switching threshold current 45 and the frequency of the current flowing through motor 3 is equal to or greater than the switching threshold frequency 46" may be replaced with "when the phase current value of the phase current of motor 3x is less than the switching threshold current and the rotation speed of motor 3x is equal to or greater than the switching threshold rotation speed."

In other words, the actual thermistor temperature may be used, assuming that the detected temperature of thermistor S sufficiently tracks the temperature of heat source Z.

The control unit 10a may select the temperature to switch to depending on the rotation acceleration of the motor 3x, regardless of the temperature switching relationship shown in Figure 6.

For example, if the acceleration of motor 3 is greater than a preset reference threshold, control unit 10a may forcibly (regardless of the relationship shown in FIG. 6) control the driving of motor 3x using power conversion unit 30c based on the estimated control temperature.

As a result, regardless of the relationship shown in Figure 6, even if the temperature detected by the thermistor S cannot adequately track the temperature of the heat source Z in response to a sudden temperature rise when the rotational acceleration of the motor 3x is high, the power conversion unit 30c can control the drive of the motor 3x while executing the temperature protection function based on the above-mentioned control estimated temperature. This prevents the power conversion unit 30c, which has a heat source, from exceeding a temperature that would cause damage.

Furthermore, when the acceleration of the motor 3x is smaller than the reference threshold, in the first case, the control unit 10a controls the driving of the motor 3x using the power conversion unit 30c based on the above-mentioned estimated control temperature (based on the relationship shown in Figure 6).

If the acceleration of motor 3x is smaller than the reference threshold, in the second case, control unit 10a controls the driving of motor 3x using power conversion unit 30c based on the actual thermistor temperature detected by the thermistor S (based on the relationship shown in Figure 6).

In this way, the temperature protection function can be executed appropriately by switching between the detected temperature of the thermistor S and the estimated temperature as the heat source temperature to be applied when executing the temperature protection function, depending on the current and angular velocity of the motor 3x.

<Temperature protection function execution>
Fig. 7 is a diagram showing the relationship between the temperature of the heat source and the control of the motor for executing the temperature protection function. Fig. 8 is a diagram showing an example of the characteristics of the target limit torque 57 at the limit threshold 51 shown in Fig. 7.

As shown in Fig. 8, the target limit torque at the limit threshold and the frequency of the current flowing through the motor 3x have a quadratic function relationship. That is, when the estimated control temperature or actual thermistor temperature selected as the temperature of the heat source is equal to the limit threshold 51 shown in Fig. 7, the target limit torque 57 is set to increase as the frequency of the current flowing through the motor 3x increases, and to decrease as the frequency of the current flowing through the motor 3x decreases.
Note that the "frequency of the current flowing through the motor 3x" above and below may be replaced with the "number of rotations of the motor 3x." Also, the heat source temperatures above and below are temperatures obtained based on the detection results of the thermistor S serving as a temperature detection unit.

The memory unit 20a also stores a target limit torque table that associates the frequency of the current flowing through the motor 3x with the target limit torque 57 when the estimated control temperature or actual thermistor temperature selected as the temperature of the heat source is the limit threshold 51. Therefore, the control unit 10a can obtain the target limit torque 57 associated with the frequency of the current flowing through the motor 3x by referencing the target limit torque table stored in the memory unit 20a.

Furthermore, the target limit torque table is preferably set so that the target limit torque 57 increases as the frequency of the current flowing through the motor 3x serving as the drive unit increases, and decreases as the frequency of the current flowing through the motor 3x decreases. This ensures a minimum torque at the limit threshold 51.

Note that this "target limit torque 57 is set to increase as the frequency of the current flowing through motor 3x increases, and to decrease as the frequency of the current flowing through motor 3x decreases" may be replaced with "target limit torque 57 is set to increase as the rotation speed of motor 3x increases, and to decrease as the rotation speed of motor 3x decreases."

To execute the temperature protection function, as shown in FIG. 7, the control unit 10a controls the power conversion unit 30c to drive the motor 3x in a restricted state 53 where the control estimated temperature or actual thermistor temperature (actual temperature) selected as the heat source temperature for driving the motor 3x using the method described above in <Method for selecting the heat source temperature that serves as the reference for executing the temperature protection function> is equal to or greater than a preset limit threshold 51 and less than a preset abnormality threshold 52 that is higher than the limit threshold 51, thereby driving the motor 3x.

To explain the limit torque 54 in detail, first, the control unit 10a acquires the frequency of the current flowing through the motor 3x.
The above phrase "obtain the frequency of the current flowing through the motor 3x" may be replaced with "obtain the number of rotations of the motor 3x."

Next, the control unit 10a references the target limit torque table stored in the memory unit 20a and sets the limit torque 54 so that it is equal to or greater than the target limit torque 57 corresponding to the acquired frequency. Note that this "acquired frequency" may be replaced with the "acquired rotation speed."

This prevents the transistors Q1 to Q6, which are the heat source Z, from being damaged due to an increase in temperature, and allows the electric vehicle to continue running while reducing the torque of the motor 3x.
The limit torque 54 is set so that the estimated control temperature or the actual thermistor temperature selected as the temperature of the heat source does not exceed the abnormality threshold value 52 .

As explained above, in the restricted state 53, when the torque of the motor 3x is increased by user operation, causing a high current to flow while the motor is at a low angular velocity, and the temperature of the heat source Z generated when the motor 3x is driven rises above the restriction threshold 51 that activates the temperature protection function, the control unit 10a operates to limit the motor's output torque regardless of user operation, thereby suppressing the temperature rise.

On the other hand, in an abnormal state 55 in which the control estimated temperature or actual thermistor temperature selected as the temperature of the heat source is equal to or greater than the abnormal threshold value 52, the control unit 10a controls the power conversion unit 30c to stop the motor 3x so that the torque output from the motor 3x becomes zero, regardless of the command signal (see Figure 7).

For example, the control unit 10a may determine that an abnormal state 55, in which the control estimated temperature or actual thermistor temperature selected as the temperature of the heat source is equal to or greater than the abnormality threshold value 52, is a state in which an abnormality has occurred in the control unit 10a's system. This allows the electric vehicle to be stopped appropriately, for example, if an abnormality occurs in transistors Q1 to Q6.

Furthermore, if the estimated control temperature or actual thermistor temperature selected as the temperature of the heat source exceeds this abnormality threshold 52, the control unit 10a may, for example, stop the motor 3x and then not resume control of the motor 3x until the operation of the control unit 10a is reset.

In this abnormal state 55, the operation of the control unit 10a allows the motor 3x to be stopped appropriately if an abnormality occurs in the control unit 10a, power conversion unit 30c, etc., causing the heat source Z to reach an extremely high temperature.

In addition, in a normal state 56 in which the control estimated temperature or actual thermistor temperature selected as the temperature of the heat source is below the limit threshold 51, the control unit 10a controls the power conversion unit 30c to drive the motor 3x so as to output a command torque according to the command signal (see Figure 7).

In this normal state 56, the operation of the control unit 10a allows the motor to output a command torque in accordance with a command signal based on user operation.

<Example of operation with limited torque 54 in limited state 53>
Here, an example of an operation in which the control unit 10a calculates the limit torque 54 in the above-mentioned limited state 53 and drives the motor 3x with the limit torque 54 will be described.

First, in the restricted state 53, the control unit 10a calculates a temperature difference value, which is a parameter for the temperature difference between the heat source temperature and the restricted threshold 51, by multiplying the value obtained by subtracting the restricted threshold 51 from the control estimated temperature or actual thermistor temperature (referred to as the "heat source temperature" in the following Equation A) selected as the temperature of the heat source, by a positive adjustment coefficient, as shown in the following (Equation A).

The adjustment coefficient is set so that the heat source temperature falls within the range from the limit threshold 51 to the abnormal threshold 52 when the torque output by the motor 3x is the limit torque 54, for example.

Temperature difference value = Positive adjustment coefficient × (Heat source temperature - Limit threshold) ... (Equation A)

Next, the control unit 10a acquires the frequency of the current flowing through the motor 3x serving as the drive unit.
Next, the target limit torque table stored in the storage unit 20a is referenced to calculate the target limit torque 57 corresponding to the acquired frequency.

Next, the control unit 10a calculates a negative cut torque to be subtracted from the command torque by subtracting the current torque currently being output by the motor 3x from the target limit torque 57 and multiplying the result by the temperature difference value, as shown in the following (Equation B).

Cut torque = temperature difference value × (target limit torque - current torque) (Equation B)

Next, the control unit 10a calculates the limit torque 54 by adding a negative cut torque to the command torque (i.e., subtracting the absolute value of the cut torque from the command torque) as shown in the following (Equation C).

Limit torque = command torque + cut torque (Equation C)

Then, the control unit 10a controls the power conversion unit 30c to output the limited torque, thereby driving the motor 3x.

As a result, if the user's throttle operation increases the motor's output torque, causing a high current to flow while the motor is at a low angular velocity, and the temperature of the heat source rises above the threshold at which the temperature protection function is activated, the motor's output torque is limited regardless of the user's throttle operation, thereby suppressing the rise in the heat source temperature and allowing the electric vehicle to continue running.

(Third embodiment)
In the second embodiment described above, the heat source Z is a transistor in the bridge circuit X of the power conversion unit 30c. However, it is also possible that the heat source Z is the coil of the motor 3x. Therefore, a third embodiment in which the heat source Z is the coil of the motor 3x will be described with reference to FIG. 9. The third embodiment is similar to the second embodiment except that the heat source Z is the coil of the motor 3x.

As shown in Figure 9, heat source Z is the coils L1, L2, and L3 of motor 3x. Note that in the example of Figure 9, as in the second embodiment, transistors Q1 to Q6 of driver circuit X are also shown as heat source Z.

The thermistors S are arranged close to the coils L1, L2, and L3. That is, the first thermistor S1a is arranged close to the coil L1, which is the heat source. The second thermistor S2a is arranged close to the coil L2, which is the heat source. The third thermistor S3a is arranged close to the coil L3, which is the heat source.

In this embodiment, for example, the temperature value of the first phase coil of motor 3x may be substituted by the average value of the temperature detection value of second thermistor Sa2 located near the second phase coil of motor 3x and the temperature detection value of third thermistor Sa3 located near the third phase coil of motor 3x.

This allows the first thermistor Sa1 to be omitted.

Furthermore, in this embodiment, if necessary, the higher of the actual thermistor temperature detected by the aforementioned thermistor S and the estimated control temperature may be selected to drive the motor.

According to this embodiment, the temperature of the heat source (transistors in the power conversion unit (inverter circuit) or motor coil) can be estimated based on the temperature detected by the thermistor, the motor current, frequency, or rotation speed, taking into account the effects of thermal conduction and ambient temperature, and the temperature protection function can be executed.

REFERENCE SIGNS LIST 1 control device 2 current source 3 drive unit 10 control unit 11 temperature detection unit 20 storage unit 30 power conversion unit

Claims (9)

a control device that controls a current source and a power conversion unit that converts power from the current source and supplies the power to a drive unit,
The control device
a control unit that controls the power conversion unit;
a temperature detection unit that detects a temperature in the vicinity of a heat source generated by the power conversion unit or the drive unit;
a storage unit that stores a saturation temperature information table that associates a combination of a current value flowing in the drive unit and a frequency of the current flowing in the drive unit with a saturation temperature that is a maximum temperature at which the heat of the heat source is saturated,
The vicinity of the heat source includes a distance from the heat source to a position where the temperature due to heat generated by the heat source can be detected,
The control unit
Acquire a current value flowing in the drive unit and acquire a frequency of the current flowing in the drive unit;
Acquire the actual temperature detected by the temperature detection unit;
calculating a control estimated temperature using the current value, the frequency, the saturation temperature information table stored in the storage unit, and the actual temperature;
The power supplied from the power conversion unit to the drive unit is controlled based on the control estimated temperature,
The control unit
After acquiring the value of the current flowing in the drive unit and the frequency of the current flowing in the drive unit,
a step a of calculating a current saturation temperature of the heat source corresponding to a combination of the current value and the frequency by referring to the saturation temperature information table;
a step c of calculating a current estimated heat source temperature by estimating the temperature of the heat source by using the current saturation temperature and a first coefficient;
a step e) of calculating a current estimated detection unit temperature by estimating a temperature in the vicinity of the heat source by using the current estimated heat source temperature and a second coefficient;
a step f of acquiring the actual temperature detected by the temperature detection unit;
a step g of calculating a temperature difference by subtracting the actual temperature from the current estimated detection portion temperature;
a step h of calculating a temperature correction value by multiplying the temperature difference by a preset temperature correction coefficient;
a step i of calculating an estimated control temperature by adding the temperature correction value to the current estimated heat source temperature;
and j) controlling the power supplied from the power conversion unit to the drive unit based on the control estimated temperature. a control device that controls a current source and a power conversion unit that converts power from the current source and supplies the power to a drive unit,
The control device
a control unit that controls the power conversion unit;
a temperature detection unit that detects a temperature in the vicinity of a heat source generated by the power conversion unit;
a storage unit that stores a saturation temperature information table that associates a combination of a current value flowing in the drive unit and a frequency of the current flowing in the drive unit with a saturation temperature that is a maximum temperature at which the heat of the heat source is saturated,
The vicinity of the heat source includes a distance from the heat source to a position where the temperature due to heat generated by the heat source can be detected,
The control unit
Acquire a current value flowing in the drive unit and acquire a frequency of the current flowing in the drive unit;
Acquire the actual temperature detected by the temperature detection unit;
calculating a control estimated temperature using the current value, the frequency, the saturation temperature information table stored in the storage unit, and the actual temperature;
controlling the power supplied from the power conversion unit to the drive unit based on the control estimated temperature;
After acquiring the value of the current flowing in the drive unit and the frequency of the current flowing in the drive unit,
a step a of calculating a current saturation temperature of the heat source corresponding to a combination of the current value and the frequency by referring to the saturation temperature information table;
a step c of calculating a current estimated heat source temperature by estimating the temperature of the heat source by using the current saturation temperature and a first coefficient;
a step e) of calculating a current estimated detection unit temperature by using the current estimated heat source temperature and a second coefficient to estimate a temperature in the vicinity of the heat source;
a step f of acquiring the actual temperature detected by the temperature detection unit;
a step g of calculating a temperature difference by subtracting the actual temperature from the current estimated detection portion temperature;
a step h of calculating a temperature correction value by multiplying the temperature difference by a preset temperature correction coefficient;
a step i of calculating an estimated control temperature by adding the temperature correction value to the current estimated heat source temperature;
and j) controlling the power supplied from the power conversion unit to the drive unit based on the control estimated temperature. The current estimated heat source temperature in the step c is
When the current saturation temperature is equal to or higher than the previous estimated heat source temperature, and when the temperature difference obtained by subtracting the previous estimated heat source temperature from the current saturation temperature is equal to or higher than the first P threshold, the first coefficient is set as a first P coefficient and calculated by the following formula 31:
When the current saturation temperature is equal to or higher than the previously estimated heat source temperature, and when the temperature difference obtained by subtracting the previously estimated heat source temperature from the current saturation temperature is less than the first P threshold, the first coefficient is set to a second P coefficient smaller than the first P coefficient, and is calculated by the following formula 32:
When the current saturation temperature is lower than the past estimated heat source temperature, and when the temperature difference obtained by subtracting the past estimated heat source temperature from the current saturation temperature is equal to or less than a first N threshold, the first coefficient is set to a first N coefficient and calculated by the following formula 33:
When the current saturation temperature is lower than the past estimated heat source temperature, and when the temperature difference obtained by subtracting the past estimated heat source temperature from the current saturation temperature is larger than the first N threshold, the first coefficient is set to a second N coefficient smaller than the first N coefficient, and is calculated by the following formula 34:
the past estimated heat source temperature is a temperature calculated a first time ago using a calculation method similar to a calculation method for the current estimated heat source temperature,
The current estimated detection portion temperature in the step e is
When the current estimated heat source temperature is higher than the previous estimated detection unit temperature, and when the temperature difference obtained by subtracting the previous estimated detection unit temperature from the current estimated heat source temperature is equal to or greater than a second P threshold, the second coefficient is set as a third P coefficient and calculated using the following formula 41:
When the current estimated heat source temperature is higher than the previous estimated detection unit temperature, and when the temperature difference obtained by subtracting the previous estimated detection unit temperature from the current estimated heat source temperature is less than the second P threshold, the second coefficient is set to a fourth P coefficient that is smaller than the third P coefficient, and is calculated using the following formula 42:
When the current estimated heat source temperature is equal to or lower than the previous estimated detection unit temperature, and when the temperature difference obtained by subtracting the previous estimated detection unit temperature from the current estimated heat source temperature is less than a second N threshold, the second coefficient is set to a third N coefficient and calculated using the following formula 43:
When the current estimated heat source temperature is equal to or lower than the previous estimated detection unit temperature, and when the temperature difference obtained by subtracting the previous estimated detection unit temperature from the current estimated heat source temperature is greater than a second N threshold, the second coefficient is set to a fourth N coefficient that is smaller than the third N coefficient, and is calculated using the following formula 44:
The control device according to claim 1 or 2, wherein the past estimated temperature is a temperature calculated by a calculation method similar to a calculation method for the current estimated temperature before the first time period.
Current estimated heat source temperature = First P coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 31)
Current estimated heat source temperature = Second P coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 32)
Current estimated heat source temperature = First N coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 33)
Current estimated heat source temperature = Second N coefficient × (current saturation temperature − previous estimated heat source temperature) + previous estimated heat source temperature (Equation 34)
Current estimated detector temperature = Third P coefficient × (current estimated heat source temperature − previous estimated detector temperature) + previous estimated detector temperature (Equation 41)
Current estimated detector temperature = Fourth P coefficient × (current estimated heat source temperature - previous estimated detector temperature) + previous estimated detector temperature (Equation 42)
Current estimated detector temperature = Third N coefficient × (current estimated heat source temperature − previous estimated detector temperature) + previous estimated detector temperature (Equation 43)
Current estimated detector temperature = 4th N coefficient × (current estimated heat source temperature - previous estimated detector temperature) + previous estimated detector temperature (Equation 44) the step a, the step c, the step e, and the step i are repeated every first time;
The control device according to claim 3 , wherein the steps f, g, and h are repeated every second time period that is longer than the first time period. The control device according to any one of claims 1 to 4, wherein the first coefficient is a value greater than 0 and less than 1, and the second coefficient is a value greater than 0 and less than 1. The control unit
In a first case where a value of the current flowing through the drive unit is equal to or greater than a predetermined switching threshold current and a frequency of the current flowing through the drive unit is less than a predetermined switching threshold frequency, the power supplied from the power conversion unit to the drive unit is controlled based on the estimated control temperature;
On the other hand, in a second case where the current value flowing through the drive unit is less than the switching threshold current or the frequency of the current flowing through the drive unit is equal to or greater than the switching threshold frequency, the control device described in any one of claims 2 to 5, characterized in that the power supplied from the power conversion unit to the drive unit is controlled based on the actual temperature rather than the control estimated temperature. The control unit
when the first case transitions to the second case such that the frequency of the current flowing in the drive unit is less than the switching threshold frequency and the value of the current flowing in the drive unit decreases from equal to or greater than the switching threshold current to a preset hysteresis threshold current that is smaller than the switching threshold current, continuously controlling the power supplied from the power conversion unit to the drive unit based on the estimated control temperature;
On the other hand, when the frequency of the current flowing to the drive unit is less than the switching threshold frequency and the current value flowing to the drive unit transitions from less than the hysteresis threshold current to the switching threshold current, the control device according to claim 6 continues to control the power supplied from the power conversion unit to the drive unit based on the actual temperature. The control unit
when the first case transitions to the second case such that the value of the current flowing in the drive unit is equal to or greater than the switching threshold current and the frequency of the current flowing in the drive unit increases from less than the switching threshold frequency to a preset hysteresis threshold frequency that is higher than the switching threshold frequency, continuously controlling the power supplied from the power conversion unit to the drive unit based on the estimated control temperature;
On the other hand, when the current value flowing in the drive unit is equal to or greater than the switching threshold current and the frequency of the current flowing in the drive unit transitions from the second case to the first case so that the frequency of the current flowing in the drive unit decreases from equal to or greater than the hysteresis threshold frequency to the switching threshold frequency, the control device according to claim 6 or 7 continues to control the power supplied from the power conversion unit to the drive unit based on the actual temperature. In the second case,
The control unit
The control device according to claim 8, which cites claim 7 , further comprising: when a current value flowing through the drive unit is less than the hysteresis threshold current according to claim 7 , or when a frequency of the current flowing through the drive unit is equal to or greater than the hysteresis threshold frequency according to claim 8 , the control device controls the power supplied from the power conversion unit to the drive unit based on the actual temperature.