JP6041785B2 - Electric motor control device - Google Patents

Description

  The present invention relates to an electric motor control device that controls an electric motor.

  Conventionally, when the temperature of the winding of the motor becomes equal to or higher than a threshold temperature during operation of the motor, the motor that limits the operation of the motor in order to prevent the temperature of the winding from becoming excessively high. A control device is known (see, for example, Patent Document 1).

JP 2000-32602 A

  By the way, an electric motor including a permanent magnet in a rotor is generally used. In such an electric motor, when the rotational speed of the electric motor is low, generally, if the temperature of the winding is maintained below the allowable upper limit temperature of the winding, the temperature of the permanent magnet is generally It falls below the allowable upper limit temperature that can prevent the magnet from demagnetizing.

  On the other hand, according to various studies and experiments conducted by the inventors of the present application, when the rotational speed of the motor is high, even if the temperature of the winding is kept below the allowable upper limit temperature of the winding, the energy loss of the permanent magnet Due to an increase in the temperature of the permanent magnet, the temperature of the permanent magnet is raised to a high temperature that exceeds an allowable upper limit temperature that can prevent demagnetization of the permanent magnet, and demagnetization of the permanent magnet occurs. It turns out that there is a possibility of doing.

  However, in the electric motor control device described in Patent Document 1, this point is not taken into consideration, and thus there is a possibility that the demagnetization of the permanent magnet may occur when the rotation speed of the electric motor is high. In order to prevent this, for example, the temperature of the winding that can prevent the demagnetization of the permanent magnet from occurring even when the rotational speed of the motor is high is always set as the threshold temperature. Can be considered. However, in this case, when the rotational speed of the electric motor is low, the operation of the electric motor is restricted more than necessary.

  This invention is made in view of the above point, and provides the electric motor control apparatus which can prevent a coil | winding and a permanent magnet from heating up excessively, without restrict | limiting the operation | movement of an electric motor more than necessary. With the goal.

When the temperature of the winding of the motor exceeds a predetermined threshold temperature during the operation of the electric motor having a permanent magnet, the operation control unit for limiting the operation of the electric motor,
When the rotational speed of the electric motor is smaller than a predetermined threshold rotational speed, the threshold temperature is set to a predetermined first threshold, and when the rotational speed of the electric motor is larger than a predetermined threshold rotational speed, the threshold temperature A threshold setting unit that sets a second threshold lower than the first threshold ,
A characteristic line representing the relationship between the rotation speed of the motor and the upper limit output torque of the motor for maintaining the temperature of the winding below a predetermined allowable upper limit temperature of the winding is defined as a first winding characteristic. A characteristic line representing the relationship between the rotation speed of the motor and the upper limit output torque of the motor to maintain the temperature of the permanent magnet below a predetermined allowable upper limit temperature of the permanent magnet. When defined as a magnet characteristic line,
The threshold rotational speed is set to match the rotational speed at the intersection of the first winding characteristic line and the magnet characteristic line,
When defining the characteristic line representing the relationship between the rotation speed of the electric motor and the upper limit output torque of the electric motor to maintain the temperature of the winding below the second threshold value as the second winding characteristic line,
The first threshold is set based on a predetermined allowable upper limit temperature of the winding,
The second threshold value is smaller than the upper limit output torque of the motor in the magnet characteristic line at an arbitrary rotational speed at which the upper limit output torque of the motor in the second winding characteristic line is larger than the threshold rotation speed. It is characterized by being set to satisfy the following condition .

  In the present invention, when the rotation speed of the electric motor is larger than the threshold rotation speed, the threshold setting unit sets the threshold so that the second threshold is lower than the first threshold set when the rotation speed is lower than the threshold rotation speed. The temperature is set low.

  As a result, when the rotational speed of the motor is greater than the threshold rotational speed, the operation control unit operates the motor when the temperature of the winding of the motor exceeds a second threshold value that is lower than the first threshold value. Restrict. Thereby, it can prevent that a coil | winding and a permanent magnet heat up excessively.

  Further, when the rotation speed of the motor is smaller than the threshold rotation speed, the operation control unit operates the motor more than necessary until the temperature of the winding of the motor exceeds the first threshold value that is higher than the second threshold value. Therefore, the performance of the electric motor can be utilized more effectively.

  In order to prevent the winding and permanent magnet from excessively raising the temperature (keeping the winding temperature below the allowable upper limit temperature of the winding and maintaining the permanent magnet temperature below the allowable upper limit temperature of the permanent magnet) In order to achieve both, the output torque of the motor has an upper limit output torque (hereinafter referred to as “winding upper limit torque”) on the winding characteristic line with respect to the rotation speed of the motor and a magnet characteristic with respect to the rotation speed of the motor. The upper limit output torque on the wire (hereinafter referred to as “magnet upper limit torque”) needs to be equal to or less than the smaller upper limit output torque.

  When the rotation speed of the motor is smaller than the rotation speed at the intersection of the winding characteristic line and the magnet characteristic line, the winding upper limit torque is smaller than the magnet upper limit torque, and the motor rotation speed is lower than the winding characteristic line and the magnet. When it is larger than the rotation speed at the intersection with the characteristic line, the magnet upper limit torque is smaller than the winding upper limit torque.

  Therefore, as in the above configuration, the threshold rotation speed is set so as to coincide with the rotation speed at the intersection of the winding characteristic line and the magnet characteristic line, so that the operation control unit allows the rotation speed of the motor to When the rotation speed of the motor is lower than the first threshold value set as the threshold temperature when the temperature of the winding of the motor exceeds the first threshold, the operation of the motor is restricted to prevent the winding from being excessively heated. it can. At this time, since the allowable upper limit temperature of the permanent magnet is higher than the allowable upper limit temperature of the winding, it is possible to prevent the permanent magnet from being excessively heated.

  In addition, when the rotation speed of the motor is higher than the rotation speed at the intersection, the operation control unit limits the operation of the motor when the temperature of the winding of the motor exceeds the second threshold set as the threshold temperature. Thus, it is possible to prevent the permanent magnet from being excessively heated. At this time, since the allowable upper limit temperature of the winding is higher than the allowable upper limit temperature of the permanent magnet, it is possible to prevent the winding from being excessively heated.

Furthermore , when the allowable upper limit temperature of the winding is lower than the allowable upper limit temperature of the permanent magnet, such as when the rotational speed of the motor is smaller than the threshold rotational speed, the first threshold set as the threshold temperature is Since the temperature is set based on the allowable upper limit temperature of the wire, it is possible to prevent the winding and the permanent magnet from being excessively heated.

  On the other hand, when the allowable upper limit temperature of the permanent magnet is lower than the allowable upper limit temperature of the winding, such as when the rotation speed of the motor is larger than the threshold rotation speed, the second threshold value set as the threshold temperature is Since the upper limit output torque of the motor in the two-winding characteristic line is set so as to satisfy the condition that the upper limit output torque of the motor in the magnet characteristic line is smaller, if the temperature of the winding can be prevented from excessively rising Further, it is possible to prevent the permanent magnet from being excessively heated.

In the present invention, when the threshold temperature is set to the second threshold, the threshold setting unit sets the threshold temperature to be decreased stepwise or continuously as the rotation speed of the electric motor increases. Is preferred.

  According to this configuration, when the threshold temperature is set to the second threshold (that is, when the rotation speed of the motor is higher than the threshold rotation speed), when the rotation speed of the motor is relatively low, the threshold temperature is relatively high. Compared to the case, since the motor operation is not restricted until the winding temperature of the motor reaches a relatively high temperature, it is possible to effectively prevent the motor operation from being restricted more than necessary.

The block diagram of a vehicle provided with the electric motor control apparatus of embodiment of this invention. The figure which shows the characteristic line of the electric motor shown in FIG. The flowchart which showed the process sequence of the operation control process performed by the electric motor control apparatus shown in FIG. The flowchart which showed the process sequence of the threshold value change process performed by the electric motor control apparatus shown in FIG. The flowchart which showed the process sequence of the threshold value change process performed by the electric motor control apparatus of another form. The flowchart which showed the process sequence of the threshold value change process performed by the electric motor control apparatus of another form.

(1. Configuration of motor control device and vehicle)
An electric motor control device 1 (hereinafter simply referred to as “control device 1”) and a vehicle C including the same according to an embodiment of the present invention will be described with reference to FIG.

  The vehicle C is an electric vehicle using the electric motor 2 as a drive source. The control device 1 is a control device that controls the electric motor 2. The control device 1 is constituted by an electronic control unit having a CPU, a memory, etc. (not shown). The control device 1 has functions as an operation control unit 101 and a threshold setting unit 102.

  In the electric motor 2, a rotor (not shown) is provided with a permanent magnet (not shown), and a stator (not shown) is provided with a winding (not shown) that generates a rotating magnetic field. The output shaft 2 a of the electric motor 2 is configured to rotate integrally with the rotor of the electric motor 2.

  The electric motor 2 can perform a power running operation and a regenerative operation. During the power running operation of the electric motor 2, AC power is supplied to the electric motor 2 from the inverter 7. The inverter 7 is supplied with power obtained by DC-DC conversion of the DC power output from the fuel cell stack 5 by the second converter 6. The rotation of the output shaft 2a of the electric motor 2 at this time is transmitted to the left and right drive wheels 9L and 9R via a transmission 8 (including a differential gear).

  Further, during the regenerative operation of the electric motor 2, the rotation of the left and right drive wheels 9 </ b> L and 9 </ b> R is transmitted to the output shaft 2 a via the transmission 8. At this time, the control apparatus 1 can charge the secondary battery 3 by operating the electric motor 2 as a generator to convert the electric power generated by the electric motor 2 by the inverter 7 and the first converter 4.

  Output signals from the temperature sensor 21, the rotation speed sensor 22, and the accelerator sensor 23 are input to the control device 1.

  The temperature sensor 21 is disposed in the vicinity of the stator of the electric motor 2. The temperature sensor 21 detects the temperature (hereinafter referred to as “motor temperature”) Tm of the winding of the electric motor 2 and outputs a signal representing the detected electric motor temperature Tm. The rotation speed sensor 22 is a sensor that detects the rotation speed (hereinafter referred to as “motor rotation speed”) Nm of the output shaft 2 a of the electric motor 2. The rotation speed sensor 22 outputs a signal representing the detected motor rotation speed Nm. The accelerator sensor 23 is a sensor that detects an operation amount of an accelerator pedal (not shown) of the vehicle C. The accelerator sensor 23 outputs a signal representing the detected operation amount.

  The control device 1 controls the inverter 7 so as to output the target torque τcmd determined according to the detection result of the accelerator sensor 23 from the electric motor 2 (hereinafter, such control is simply referred to as “control the electric motor 2”). To do ").

  In addition, the control device 1 operates when the electric motor temperature Tm exceeds a predetermined threshold temperature Tt (the setting of the threshold temperature Tt will be described later) during operation of the electric motor 2 (during powering operation or regenerative operation). Restricts the operation of the electric motor 2 (this process corresponds to a control process executed by the operation control unit 101). Thereby, it is preventing that the coil | winding and permanent magnet of the electric motor 2 heat up excessively.

(2. Characteristics of the motor)
The characteristics of the electric motor 2 will be described with reference to FIG. 2 (Note that Lact2, Lact3, Nt1, Nt2, and Nt3 in FIG. 2 are used in the description of another embodiment to be described later. can not touch). In FIG. 2, the horizontal axis represents the motor rotation speed Nm, and the vertical axis represents the motor torque τm. In FIG. 2, a characteristic line Lw represented by a broken line is a first winding characteristic line, and a characteristic line Lmg represented by a solid line is a magnet characteristic line.

Here, the first winding characteristic line Lw, the temperature of the windings of the motor 2, the allowable upper limit temperature of a predetermined said winding (hereinafter referred to as "winding allowable upper limit temperature") Tw _ lim below It is a characteristic line showing the relationship between the motor rotation speed Nm and the upper limit output torque of the electric motor 2 for maintaining. More specifically, the characteristic line Lw is the winding of the electric motor 2 that is reached when the electric motor 2 is continuously operated with a combination of the motor rotation speed Nm and the motor torque τm at an arbitrary point on the characteristic line Lw. temperature is a characteristic curve having the property that fits below the winding allowable upper limit temperature Tw _ lim.

Further, the magnetic characteristic line Lmg, the temperature of the permanent magnets of the electric motor 2, to prevent demagnetization of the permanent magnet with a predetermined allowable upper limit temperature (hereinafter, referred to as "magnet permissible upper limit temperature") Tmg _ lim It is a characteristic line showing the relationship between the motor rotation speed Nm and the upper limit output torque of the electric motor 2 for maintaining below. More specifically, the characteristic line Lmg is a permanent magnet of the electric motor 2 that is reached when the electric motor 2 is continuously operated with a combination of the motor rotation speed Nm and the motor torque τm at an arbitrary point on the characteristic line Lmg. temperature is a characteristic curve having the property that fits below the magnet allowable upper limit temperature Tmg _ lim.

In FIG. 2, when the motor rotation speed Nm is Nt, the first winding characteristic line Lw and the magnet characteristic line Lmg intersect (hereinafter, this intersecting point is referred to as an intersection point P). Specifically, when "Nm <Nt" is the upper limit output torque of the first winding characteristic line Lw with respect to the rotational speed of the electric motor (hereinafter, referred to as "winding upper limit torque") is towards the τw _ lim, the rotational speed of the electric motor the upper limit output torque of the magnet characteristic line Lmg for (hereinafter, referred to as "magnet limit torque") lower than τmg _ lim. On the other hand, in the case of "Nm>Nt" it is, towards the magnet upper limit torque τmg _ lim is lower than the winding upper limit torque τw _ lim.

  Therefore, in the present embodiment, when the motor rotation speed Nm is higher than the rotation speed (hereinafter referred to as “threshold rotation speed”) Nt at the intersection P, the first threshold value set when the motor rotation speed Nm is lower than the threshold rotation speed Nt. The threshold temperature Tt is set low so that the second threshold T2 is lower than T1 (this process corresponds to the process executed by the threshold setting unit 102. Hereinafter, the process is referred to as “threshold change process”. ").

In the present embodiment, by setting the winding allowable upper limit temperature Tw _ lim to the first threshold value T1. The first threshold value T1 is not set to the winding allowable upper limit temperature Tw _ lim same temperature, in order to leave a margin, winding allowable upper limit temperature Tw _ slightly lower temperature than the lim (e.g., It may be set to a temperature lower by a predetermined temperature).

  Further, the second threshold T2 is the motor torque τm in the winding characteristic line representing the relationship between the motor rotation speed Nm and the allowable upper limit torque for maintaining the temperature of the winding of the motor 2 below the second threshold T2. Is set so as to satisfy the condition that it becomes smaller than the motor torque τm in the magnet characteristic line Lmg at an arbitrary rotation speed Nm of “motor rotation speed Nm> threshold rotation speed Nt”. Note that the second winding characteristic line Lwu in FIG. 2 is a characteristic line representing the relationship between the motor rotation speed Nm and the allowable upper limit torque for maintaining the temperature of the winding of the motor 2 below the second threshold T2. is there.

By the threshold value changing process is executed, the winding upper limit torque τw _ lim of the motor 2, in the enlarged view of the characteristic line Lact (Fig. 2 indicated by a broken line in FIG. 2, from the first winding characteristic line Lw (See also fine dashed lines). In particular, the winding upper limit torque τw _ lim, when "the motor rotational speed Nm <threshold rotation speed Nt" of the temperature windings of the winding motor 2 permissible upper limit temperature Tw _ lim (first threshold T1) or less The second winding for maintaining the temperature of the winding of the motor 2 at the second threshold T2 or less when “motor rotation speed Nm> threshold rotation speed Nt”. Defined according to winding characteristic line Lwu.

  Thereby, when the motor rotation speed Nm is larger than the threshold rotation speed Nt, the control device 1 defines the upper limit of the motor torque τm according to the second winding characteristic line Lwu rather than the first winding characteristic line Lw. Therefore, when the electric motor temperature Tm exceeds the second threshold value T2 lower than the first threshold value T1, the operation of the electric motor 2 is restricted. Thereby, it can prevent that a coil | winding and a permanent magnet heat up excessively.

  Furthermore, when the motor rotation speed Nm is smaller than the threshold rotation speed Nt, the control device 1 defines the upper limit of the motor torque τm according to the first winding characteristic line Lw rather than the second winding characteristic line Lwu. The performance of the electric motor 2 can be utilized more effectively without restricting the operation of the electric motor 2 more than necessary until the electric motor temperature Tm exceeds the first threshold value T1 higher than the second threshold value T2.

(3. Control by motor control device)
Next, details of the operation control process and the threshold value changing process executed by the control device 1 will be described.

(3-1. Operation control processing)
The control device 1 executes an operation control process according to the flowchart shown in FIG. 3 at every predetermined control cycle.

  The control device 1 first determines the target torque τcmd of the electric motor 2 in the first step ST1. For example, the control device 1 determines the target torque τcmd with reference to a predetermined map or table based on the output signal of the accelerator sensor 23.

  The control device 1 subsequently proceeds to step ST2 and determines whether or not the motor temperature Tm is higher than the threshold temperature Tt.

  If the controller 1 determines in step ST2 that the motor temperature Tm is greater than the threshold temperature Tt, the control device 1 proceeds to step ST3 and decreases the upper limit torque that is the upper limit value of the motor torque τm. At this time, if the target torque τcmd determined in step ST1 exceeds the reduced upper limit torque, the target torque τcmd is decreased to the upper limit torque. Thereby, it can prevent that the coil | winding and permanent magnet of the electric motor 2 heat up excessively.

  Here, in the present embodiment, “reducing the upper limit torque of the motor torque τm in step ST3” corresponds to “restricting the operation of the motor” of the present invention. The operation limitation of the motor is not limited to this, and other operation control may be used as long as the operation control can prevent the temperature of the winding of the motor 2 from being raised from the current temperature. Good.

  When it is determined in step ST2 that the motor temperature Tm is not greater than the threshold temperature Tt, or when the process of step ST3 is completed, the control device 1 proceeds to step ST4. In step ST4, the control device 1 controls the electric motor 2 so that the electric motor torque τm becomes the target torque τcmd.

  When the process of step ST4 ends, the control device 1 ends this flowchart.

(3-2. Threshold change process)
The control device 1 executes the threshold value changing process according to the flowchart shown in FIG. 4 at every predetermined control cycle.

  First, in step ST101, the control device 1 determines whether or not the motor rotation speed Nm is smaller than the threshold rotation speed Nt. If the controller 1 determines in step ST101 that the motor rotation speed Nm is lower than the threshold rotation speed Nt, the control apparatus 1 proceeds to step ST102 and sets the threshold temperature Tt to the first threshold T1.

  When determining in step ST101 that the motor rotation speed Nm is not smaller than the threshold rotation speed Nt, the control device 1 proceeds to step ST103 and sets the threshold temperature Tt to the second threshold T2. When the process of step ST102 or step ST103 ends, the control device 1 ends the process of this flowchart.

(4. Modifications)
(4-1. Modified example of threshold temperature)
When the motor rotation speed Nm is higher than the threshold rotation speed Nt (in other words, when the threshold temperature Tt is set to the second threshold T2 in the present embodiment), the rotation speed of the motor 2 is relatively low. Sometimes, the threshold temperature Tt may be set so that the threshold temperature Tt is higher than when it is relatively large. Specifically, for example, when the motor rotation speed Nm is higher than the threshold rotation speed Nt, the threshold temperature Tt may be set to decrease stepwise or continuously as the motor rotation speed Nm increases.

  Thereby, when the motor rotation speed Nm is larger than the threshold rotation speed Nt, the temperature of the winding of the motor 2 is relatively high when the motor rotation speed Nm is relatively small compared to when the motor rotation speed Nm is relatively large. Since the operation of the electric motor 2 is not restricted until the temperature is reached, it is possible to effectively prevent the electric motor 2 from being restricted more than necessary.

(4-1-1. Example in which threshold temperature is decreased stepwise)
FIG. 2 and FIG. 5 show the threshold value changing process in the case where the threshold temperature Tt is set to decrease stepwise as the motor rotation speed Nm increases when the motor rotation speed Nm is larger than the threshold rotation speed Nt. The description will be given with reference.

  First, in step ST201, the control device 1 determines whether or not the motor rotation speed Nm is smaller than a first threshold rotation speed Nt1 (corresponding to “threshold rotation speed” of the present invention). When determining in step ST201 that the motor rotation speed Nm is smaller than the first threshold rotation speed Nt1, the control device 1 proceeds to step ST202 and sets the threshold temperature Tt to the first threshold T1.

  When determining in step ST201 that the motor rotation speed Nm is not smaller than the first threshold rotation speed Nt1, the control device 1 proceeds to step ST203 and determines whether or not the motor rotation speed Nm is smaller than the second threshold rotation speed Nt2. Determine whether. Here, “first threshold rotation speed Nt1 <second threshold rotation speed Nt2”.

  When determining in step ST203 that the motor rotation speed Nm is smaller than the second threshold rotation speed Nt2, the control device 1 proceeds to step ST204 and sets the threshold temperature Tt to the third threshold T21. Here, “first threshold T1> third threshold T21”.

  When determining in step ST203 that the motor rotation speed Nm is not smaller than the second threshold rotation speed Nt2, the control device 1 proceeds to step ST205 and determines whether or not the motor rotation speed Nm is smaller than the third threshold rotation speed Nt3. Determine whether. Here, “second threshold rotational speed Nt2 <third threshold rotational speed Nt3”.

  When determining in step ST205 that the motor rotation speed Nm is smaller than the third threshold rotation speed Nt3, the control device 1 proceeds to step ST206 and sets the threshold temperature Tt to the fourth threshold T22. Here, “third threshold T21> fourth threshold T22”.

  When determining in step ST205 that the motor rotation speed Nm is not smaller than the third threshold rotation speed Nt3, the control device 1 proceeds to step ST207 and sets the threshold temperature Tt to the second threshold T2. Here, “fourth threshold T22> second threshold T2”.

  When one of steps ST202, ST204, ST206, and ST207 ends, control device 1 ends the process of this flowchart.

Determined by the control unit 1 is controlled such, the winding upper limit torque τw _ lim of the motor 2 in accordance with the characteristic line Lact2 indicated by (thin solid line than Lmg drawn with a solid line) thin solid line in FIG. 2 Is done. Thus, better when the winding upper limit torque τw _ lim of the motor 2 is determined according to the characteristic line Lact2, when compared to that determined in accordance with the characteristic line Lact, motor rotation speed Nm is within the scope of Nt1~Nt3 The performance of the electric motor 2 can be utilized more effectively without limiting the electric motor torque τm more than necessary.

(4-1-2. Example of continuously reducing threshold temperature)
FIG. 2 and FIG. 6 show the threshold value changing process in the case where the threshold temperature Tt is set to continuously decrease as the motor rotation speed Nm increases when the motor rotation speed Nm is larger than the threshold rotation speed Nt. The description will be given with reference.

  First, in step ST301, the controller 1 determines whether or not the motor rotation speed Nm is smaller than the threshold rotation speed Nt. When determining in step ST301 that the motor rotation speed Nm is smaller than the threshold rotation speed Nt, the control device 1 proceeds to step ST302 and sets the threshold temperature Tt to the first threshold T1.

  When determining in step ST301 that the motor rotation speed Nm is not smaller than the threshold rotation speed Nt, the control device 1 proceeds to step ST303 and sets the threshold temperature Tt according to the following equation (1).

Tt = T1−α · (Nm−Nt) (1)
Here, α is a positive constant and is determined in advance by experiments or the like.

  When the process of step ST302 or step ST303 ends, the control device 1 ends the process of this flowchart.

Determined by the control unit 1 is controlled such, the winding upper limit torque τw _ lim of the motor 2 in accordance with the characteristic line Lact3 indicated by (thin broken than Lact drawn in broken lines) a thin broken line in FIG. 2 Is done. Thus, better when the winding upper limit torque τw _ lim of the motor 2 is determined according to the characteristic line Lact3, when compared to that determined in accordance with the characteristic line Lact and characteristic line Lact2, unnecessarily motor torque τm Without limiting, the performance of the electric motor 2 can be utilized more effectively.

(4-2. Other modifications)
In the present embodiment, the threshold rotation speed Nt is set to the same rotation speed as the rotation speed at the intersection point P, but is not limited thereto, and may be set to match the rotation speed at the intersection point P. Here, “to match” includes not only those set at the same rotational speed but also those set at a rotational speed close to that.

  In the present embodiment, the threshold value changing process and the operation control process are performed during the power running operation of the electric motor 2. However, the threshold value changing process and the operation control process are performed during the regenerative operation of the electric motor 2. May be.

  In the present embodiment, the motor temperature Tm or the motor rotation speed Nm is directly detected by the temperature sensor 21 or the rotation speed sensor 22, but the present invention is not limited to this. For example, for the motor temperature Tm or the motor rotation speed Nm, Alternatively, the motor temperature Tm or the motor rotation speed Nm may be estimated from the detected values of other state quantities having a certain correlation.

DESCRIPTION OF SYMBOLS 1 ... Control apparatus (electric motor control apparatus), 101 ... Operation control part, 102 ... Threshold setting part, 2 ... Electric motor, Nm ... Electric motor rotational speed (motor rotational speed), Nt ... Threshold rotational speed (threshold rotational speed, intersection) rotational speed), the temperature of the windings of the Tm ... motor temperature (motor), Tt ... threshold temperature, T1 ... first threshold, T2 ... second threshold value, .tau.m ... motor torque (the output torque of the electric motor), Tw _ lim ... winding line (allowable upper limit temperature of the windings) allowable upper limit temperature, (allowable upper limit temperature of the magnet) Tmg _ lim ... magnet allowable upper limit temperature, Lw ... first winding characteristic line, Lwu ... second winding characteristic line, Lmg ... magnet Characteristic line, P: intersection, Nt1: first threshold rotation speed (threshold rotation speed, rotation speed at the intersection).

Claims (2)

During operation of the electric motor having a permanent magnet, when the temperature of the winding of the electric motor exceeds a predetermined threshold temperature, an operation control unit that restricts the operation of the electric motor,
When the rotational speed of the electric motor is smaller than a predetermined threshold rotational speed, the threshold temperature is set to a predetermined first threshold, and when the rotational speed of the electric motor is larger than a predetermined threshold rotational speed, the threshold temperature A threshold setting unit that sets a second threshold lower than the first threshold ,
A characteristic line representing the relationship between the rotation speed of the motor and the upper limit output torque of the motor for maintaining the temperature of the winding below a predetermined allowable upper limit temperature of the winding is defined as a first winding characteristic. A characteristic line representing the relationship between the rotation speed of the motor and the upper limit output torque of the motor to maintain the temperature of the permanent magnet below a predetermined allowable upper limit temperature of the permanent magnet. When defined as a magnet characteristic line,
The threshold rotational speed is set to match the rotational speed at the intersection of the first winding characteristic line and the magnet characteristic line,
When defining the characteristic line representing the relationship between the rotation speed of the electric motor and the upper limit output torque of the electric motor to maintain the temperature of the winding below the second threshold value as the second winding characteristic line,
The first threshold is set based on a predetermined allowable upper limit temperature of the winding,
The second threshold value is smaller than the upper limit output torque of the motor in the magnet characteristic line at an arbitrary rotational speed at which the upper limit output torque of the motor in the second winding characteristic line is larger than the threshold rotation speed. An electric motor control device characterized by being set to satisfy the following condition . In the electric motor control device according to claim 1,
When the threshold temperature is set to the second threshold, the threshold setting unit sets the threshold temperature to be reduced stepwise or continuously as the rotation speed of the electric motor increases. Electric motor control device.