JP6281573B2 - Power steering device - Google Patents

Description

  The present invention relates to a power steering device used in an industrial vehicle or the like that travels by receiving power from a DC motor.

  2. Description of the Related Art Conventionally, in an industrial vehicle that travels by receiving power supply from a motor, a DC motor that is inexpensive, has a large generated torque, and is small is widely used to drive a steering device. Also, instead of the hydraulic power steering that has been widely used in the past, the Steer by Wire method of generating the voltage supplied to the DC motor that drives the steering device by detecting the steering operation with an electric signal and inputting it to the control device In recent years, electric (hydraulic) power steering has been adopted.

  As a method for controlling the DC motor of such electric power steering, pulse width modulation control (hereinafter referred to as PWM control) with low energy loss and low energy loss has been used (see, for example, Patent Document 1). More specifically, in PWM control, a pulse wave is generated by repeatedly turning on and off the applied voltage, and the ratio of the energization time in the pulse wave, in other words, the duty ratio is arbitrarily changed to change the average value of the output voltage. It is changing. That is, the energy supplied to the DC motor is controlled as a result by modulating the pulse wave.

  Here, in the Steer by Wire type electric (hydraulic) power steering, when the DC motor that drives the steering device is PWM-controlled, as shown in FIG. 6, the duty ratio is low and the rotational speed of the DC motor is low. There has been known a problem that tire rotation is uneven and it is difficult to operate a tire angle necessary for an industrial vehicle traveling in a warehouse with a narrow passage width. This problem is due to the fact that the energization time is shortened when the duty ratio is low, and the rotation of the DC motor rapidly decreases during the OFF state.

  As a method for avoiding the influence caused by the longer OFF period of the pulse wave in PWM control, a method of repeating ON-OFF at a high speed by increasing the pulse frequency is known. However, when controlling the rotor of a DC motor, since the moment of inertia is large, the rotational speed of the DC motor does not decrease even if the pulse frequency is lowered. Therefore, ON / OFF is repeated at a high speed by increasing the pulse frequency. Even if the method is adopted, the effect of eliminating the above-described problems cannot be obtained.

JP 62-34852 A

  The present invention pays attention to the above points, and in a power steering device that drives a steering device using a DC motor and controls the DC motor by PWM control, the rotation of the DC motor is performed in a state where the rotational speed of the DC motor is low. It aims at reducing the nonuniformity of.

In order to solve the above problems, a power steering apparatus according to the present invention has a configuration as described below. That is, a power steering device according to the present invention is a power steering device used in an industrial vehicle that travels by receiving power from a DC motor, and includes a rotation sensor that detects a rotation angle and an angular velocity of the steering, and the rotation sensor. A signal generator for outputting a PWM signal based on the output signal, a DC motor for realizing a Steer by Wire system that receives the PWM signal output from the signal generator and drives the steering device, and a high voltage A power source that selectively takes a first state to be supplied and a second state to supply a low voltage lower than the high voltage to supply the voltage of the PWM signal, and the DC motor based on the rotation angle and angular velocity of the steering control for determining the average value of the voltage to be supplied, duty ratio when the DC motor drives the steering device Order to maintain a constant above the second state the power when the average value of the determined voltage is below a predetermined threshold value, control of the power supply to the first state when the other, and the first state And a control device that performs control to determine a duty ratio based on the average value of the voltages in the second state and the voltage of the PWM signal and to output a signal indicating the duty ratio to the signal generation device.

  In such a case, in the region where the voltage to be supplied to the DC motor is low and the average value of the voltage to be supplied to the DC motor is low, the voltage supplied from the power source is reduced while the duty ratio is increased. Thus, by shortening the OFF period of the pulse wave and securing the average value of the voltage supplied to the DC motor, it is possible to suppress the occurrence of the above-described problems due to the longer OFF period of the pulse wave in the PWM control. In other words, uneven rotation of the DC motor can be reduced by keeping the duty ratio at a certain level or more.

  As an example of a suitable configuration of such a power steering apparatus, a first state in which the power supply supplies a high voltage and a second state in which a low voltage lower than the high voltage is selectively taken. The control device controls the power supply to be in the second state when the average value of the voltage to be supplied to the DC motor is below a predetermined threshold, and in other cases the power supply is in the first state. Is mentioned.

  As an example of a configuration that can easily realize the configuration of the power source as described in the previous stage, the power source is a combination of a plurality of power source elements, and the average value of the voltage to be supplied to the DC motor has a predetermined threshold value. One example is one in which the control device performs control for setting the power supply to the second state by reducing the number of power supply elements used when the power supply is lower than in other cases.

  According to the present invention, when a steering device is driven using a DC motor and this DC motor is controlled by PWM control, when the steering speed is low, in other words, when the rotational speed of the DC motor is low. Furthermore, by reducing the voltage of the PWM signal supplied from the power supply, the duty ratio can be kept above a certain level, and uneven rotation of the DC motor can be reduced.

1 is a schematic diagram showing a power steering apparatus according to an embodiment of the present invention. Schematic which shows the structure of the power supply which concerns on the same embodiment. The flowchart which shows the procedure of the process which the control apparatus which concerns on the same embodiment performs. The figure which shows the example of the time-dependent change of the voltage supplied to the DC motor which concerns on the same embodiment, and the rotation speed of a DC motor. Schematic which shows the power steering apparatus which concerns on other embodiment of this invention. The figure which shows the example of the time-dependent change of the voltage supplied to the DC motor of the conventional power steering apparatus, and the rotation speed of a DC motor.

  An embodiment of the present invention will be described below with reference to FIGS.

The power steering apparatus according to the present embodiment is used for an industrial vehicle that travels by receiving power supplied from a DC motor 4. As shown in FIG. 1, a rotation sensor that detects the rotation angle and angular velocity of the steering 1. 2, a signal generation device 3 that outputs a PWM signal based on a signal output from the rotation sensor 2, a DC motor 4 that receives the PWM signal output from the signal generation device 3 and drives the tire 9, A power supply 5 that supplies the voltage of the PWM signal, and a control that lowers the voltage of the PWM signal that is supplied from the power supply 5 when the average value V of the voltage to be supplied to the DC motor 4 is lower than a predetermined threshold _Vth. A control device 6 is provided, and a tire phase sensor 10 that detects the orientation of the tire 9 is provided.

  More specifically, the rotation sensor 2 detects an operation amount and an angular velocity of the steering 1, and outputs an operation amount signal indicating the operation amount and an angular velocity signal indicating the angular velocity to the control device 6.

  The signal generation device 3 receives a duty ratio signal indicating a duty ratio from the control device 6 and also receives a voltage from the power supply 5 and turns on / off the voltage at the duty ratio indicated by the duty ratio signal. Is output.

  The DC motor 4 is supplied with a voltage from the signal generator 3 and rotates the axle of the tire 9 around the vertical axis.

In the present embodiment, the power source 5 includes a first power source element 5a composed of twelve 2V battery cells, and a second power source composed of twelve 2V battery cells connected in series to the first power source element 5a. A short circuit 5c that short-circuits the element 5b, the negative electrode of the first power supply element 5a, and the negative electrode of the second power supply element 5b; and a contact between the first power supply element 5a of the short circuit 5c and the second power supply A first switch 5d that is provided between the positive electrode of the element 5b and electrically connects or disconnects between the first switch 5d and an electrical connection between both contacts of the short circuit 5c provided in the short circuit 5c. And a second switch 5e for blocking. The first and second switches 5d and 5e are turned on and off in response to a signal from the control device 6. That is, the power source 5 uses the first and second power source elements 5b in a state where the first switch 5d is connected and the second switch 5e is cut off, in other words, a 2V battery cell. The first state in which 24 are used and a high voltage V _hi , specifically a voltage of 48 V in total, is supplied, and the first switch 5d is cut off and the second switch 5e is connected in using only the first power supply element 5a, using only twelve 2V battery cells other words, the high voltage V is lower than _hi low voltage V _lo, in particular the supply voltage of the meter 24V The second state is selectively taken.

  The tire phase sensor 10 detects the direction of the tire 9 and outputs a tire angle signal indicating the direction of the tire 9 to the control device 6.

  The control device 6 is known as a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  An operation amount signal and an angular velocity signal from the rotation sensor 2 and a tire angle signal from the tire phase sensor 10 are input to the input interface.

  From the output interface, a signal for turning ON / OFF the duty ratio signal and the first and second switches 5d and 5e of the power supply 5 are output to the signal generating device 3, respectively.

Thus, in the present embodiment, the average value V of the voltage to be output from the signal generating device 3 to the DC motor 4 is determined using the operation amount signal, the angular velocity signal, and the angle signal as parameters, and the duty ratio corresponding to the average value is determined. A voltage control program for performing control to output a PWM signal is incorporated. Further, in the present embodiment, when the average value V of the voltage is lower than a predetermined threshold value V _th , more specifically, 12 V, the voltage control program sets the power source 5 to the second state and lowers the voltage from the power source 5. _Vlo (= 24V) is supplied to the signal generation device 3, and in other cases, the power supply 5 is set to the first state and the high voltage V _hi (= 48V) is supplied from the power supply 5 to the signal generation device 3. Like to do. The processor controls the average value V of the voltage output from the signal generator 3 to the DC motor 4 by executing this voltage control program, and consequently controls the rotational speed of the DC motor 4.

  Hereinafter, a control procedure performed by the processor executing this voltage control program will be described below with reference to FIG. 3 which is a flowchart.

First, input of an operation amount signal, an angular velocity signal, and a tire angle signal is received (step S1), and an average value V of voltages to be output is determined using these as parameters (step S2). Then, when the determined average value V of the voltages is lower than the predetermined threshold value V _th (step S3), the power source 5 is set in the second state. That is, the voltage supplied from the power source 5 to the signal generating device 3 is set to the low voltage V _lo (24 V) (step S4). On the other hand, in other cases, the power source 5 is set to the first state. That is, the voltage supplied from the power source 5 to the signal generating device 3 is set to the high voltage V _hi (48V) (step S5). Then, the duty ratio is determined based on the average value V of the voltages and the voltage supplied from the power source 5 (step S6), and a signal indicating the duty ratio is output to the signal generating device 3.

That is, during the period when the average value V of the voltage to be output is lower than the threshold value V _th as in the period T in FIG. 4, the power supply 5 is in the second state. _Vlo, that is, 24V. In the other period, since the power supply 5 is in the second state, the voltage supplied to the signal generating device 3 is the high voltage V _hi, that is, 48V. Therefore, by performing the control of the present embodiment, the duty ratio in the period in which the average value V of the voltage to be output is lower than the threshold value V _th , in other words, the ratio of the period in which the pulse wave is ON is given to the signal generator 3. When the supplied voltage is always the high voltage V _hi , that is, when the power source 5 is always in the first state, the voltage is doubled. In other words, the OFF period of the pulse wave supplied to the signal generation device 3 is shortened.

That is, according to the present embodiment, in the region where the average value V of the voltage to be supplied to the DC motor 4 is lower than the threshold value V _th , the voltage supplied from the power source 5 is set to the low voltage V _lo while increasing the duty ratio. Thus, by shortening the OFF period of the pulse wave and securing the average value V of the voltage supplied to the DC motor 4, it is possible to suppress the occurrence of the above-described problems due to the longer OFF period of the pulse wave in PWM control. it can. In other words, uneven rotation of the DC motor 4 can be reduced by maintaining the duty ratio at a certain level or more. In other words, it is possible to suppress the occurrence of a problem that the tire angle is uneven and the tire angle required for an industrial vehicle traveling in a warehouse with a narrow passage width is difficult to operate.

In addition, the power supply 5 uses the first power supply element 5a and the second power supply element 5b to supply the high voltage _Vhi , and the first power supply element 5a alone is used to reduce the low voltage _Vlo . The second state to be supplied is selectively taken, and when the average value V of the voltage to be supplied to the DC motor 4 is lower than a predetermined threshold value V _th , the power source 5 is controlled to be in the second state. Therefore, the voltage supplied from the power supply 5 of such a power steering apparatus can be easily changed.

The first power supply element 5a and the second power supply element 5b of the power supply 5 are each composed of 12 2V battery cells, and the average value V of the voltage to be supplied to the DC motor 4 is below a predetermined threshold value _Vth . In this case, control is performed so that the number of cells to be used is reduced as compared with the other cases. More specifically, the average value V of the voltage to be supplied to the DC motor 4 is a predetermined threshold value V. If it is _less than _th , the power source 5 is set to the second state and only 12 battery cells are used. In other cases, the power source 5 is set to the first state and 24 battery cells are used. Therefore, the configuration of the power source 5 for easily changing the voltage can be realized.

  In addition, this embodiment is not restricted to embodiment mentioned above.

  For example, as shown in FIG. 5, a hydraulic pump 7 is driven using a DC motor 4, and hydraulic fluid is supplied from the hydraulic pump 7 to a cylinder 8 to connect an actuator (not shown) connected to the cylinder 8. Therefore, the present invention may be applied to a power steering device in which the orientation of the tire 9 is changed through the power steering device. In FIG. 5, parts corresponding to those in the above-described embodiment and FIG.

  In the above-described embodiment, the power supply selectively takes the first state and the second state, and the power supply voltage output to the signal generation device is changed in two stages. You may employ | adopt the power supply which can change the power supply voltage output to a production | generation apparatus in three steps or more. When a power supply that can change the power supply voltage in three or more stages, in other words, a power supply that can take the first, second, and third states in order from the highest supplied voltage, a predetermined first And a second threshold value on the lower voltage side than the first threshold value, and the average value of the voltage to be supplied to the DC motor is less than the predetermined first threshold value and equal to or greater than the second threshold value. The power supply is set to the second state, the power supply is set to the third state when the average value of the voltage is lower than the second threshold value, and in other cases, that is, the average value of the voltage is set to the first threshold value. When it exceeds, it is good for a control apparatus to perform control which makes the said power supply a 1st state.

  In addition, various changes may be made without departing from the spirit of the present invention.

  A power steering device used in an industrial vehicle or the like that travels by receiving power supply from a DC motor, drives the steering device using the DC motor, and controls the DC motor by PWM control. If adopted, the rotation unevenness of the DC motor can be reduced in a state where the rotational speed of the DC motor is low, and the tire angle required for industrial vehicles traveling in a warehouse with a narrow passage width can be smoothly operated. Become.

DESCRIPTION OF SYMBOLS 1 ... Steering 2 ... Rotation sensor 3 ... Signal generation device 4 ... DC motor 5 ... Control device 6 ... Power supply

Claims (2)

A power steering device used in an industrial vehicle that travels by receiving power from a DC motor,
A rotation sensor for detecting the rotation angle and angular velocity of the steering;
A signal generation device that outputs a PWM signal based on a signal output from the rotation sensor;
A DC motor for realizing a Steer by Wire system that receives a PWM signal output from this signal generation device and drives a steering device;
A power supply that selectively takes a first state for supplying a high voltage and a second state for supplying a low voltage lower than the high voltage to supply the voltage of the PWM signal;
Control for determining the average value of the voltage to be supplied to the DC motor based on the rotation angle and angular velocity of the steering, and the determined voltage in order to keep the duty ratio when the DC motor drives the steering device above a certain level . Control where the power supply is in the second state if the average value is below a predetermined threshold, otherwise the power supply is in the first state, and the average of the voltage in the first state and the second state A power steering device comprising: a control device that performs control to determine a duty ratio based on the value and the voltage of the PWM signal and to output a signal indicating the duty ratio to the signal generation device. The power supply is a combination of a plurality of power supply elements, and the number of power supply elements to be used when the average value of the voltage to be supplied to the DC motor is below a predetermined threshold is reduced compared to other cases. The power steering device according to claim 1, wherein the control device controls the power supply to be in the second state.

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