JP2013216233A - Hydraulic power steering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic power steering system that can protect a pump drive motor and a drive circuit thereof against overheating and enhance a steering feeling.SOLUTION: A valve opening command value limit unit computes a valve opening limit value θon the basis of a detected temperature T by a temperature sensor (S1). When the absolute value |θ*| of a valve opening command value θ* is larger than the valve opening limit value θ(S2-YES), the valve opening command value limit unit determines whether the valve opening command value θ* is equal to or higher than 0 or not (S4). When the valve opening command value θ* is equal to or higher than 0 (S4-YES), the valve opening command value limit unit outputs the valve opening limit value θas the valve opening command value θ* (S5), and when the valve opening command value θ* is less than 0 (S4-NO), the valve opening command value limit unit outputs a value -θobtained by reversing a sign of the valve opening limit value θas the valve opening command value θB* (S6).

Description

  The present invention relates to a hydraulic power steering apparatus.

  2. Description of the Related Art Conventionally, a hydraulic power steering device that generates a steering assist force by supplying hydraulic oil from a hydraulic pump to a power cylinder coupled to a steering mechanism of a vehicle via a hydraulic control valve is known. In a general hydraulic power steering apparatus, a hydraulic control valve is mechanically connected to a steering member such as a steering wheel via a steering shaft, and the opening degree of the hydraulic control valve is adjusted according to the operation of the steering member. Is done.

  As a hydraulic power steering apparatus, an apparatus that controls the opening of a hydraulic control valve by an electric motor (valve driving motor) without mechanically connecting the hydraulic control valve to a steering member has been developed.

JP 2006-306239 A

  In a hydraulic power steering apparatus in which the opening of a hydraulic control valve is controlled by a valve drive motor, a drive circuit for an electric motor (pump drive motor) for driving a hydraulic pump and a valve drive motor When the ambient temperature of at least one of the drive circuits rises, it is conceivable to reduce and correct the rotational speed command value of the pump drive motor for overheat protection. However, if the rotational speed of the pump drive motor is reduced, the steering assist force decreases in the entire range of the valve opening change range of the hydraulic control valve, and thus the steering operation is felt heavy overall. For this reason, the steering feeling may be deteriorated.

  An object of the present invention is to provide a hydraulic power steering apparatus that can protect the pump drive motor and the drive circuit thereof from overheating and improve the steering feeling.

  In order to achieve the above object, a hydraulic control valve according to claim 1 is not mechanically connected to a steering member (3) to a power cylinder (16) connected to a steering mechanism (2) of a vehicle. (14) A hydraulic power steering device (1) for assisting a steering force by supplying hydraulic oil from a hydraulic pump (23) via a pump drive for driving the hydraulic pump. A motor (25), a valve drive motor (15) for controlling the opening of the hydraulic control valve, a first drive circuit (43) for the pump drive motor, and the valve drive motor A second drive circuit (42) for detecting the temperature, a temperature detecting means (38) for detecting an ambient temperature of at least one of the first drive circuit and the second drive circuit, and the hydraulic control An opening command value setting means (52) for setting an opening command value that is a command value for the opening of the valve, and an opening command for limiting the opening command value in accordance with the temperature detected by the temperature detection means. Based on the opening command value set by the value limiting means (60) and the opening command value setting means and limited by the opening command value limiting means according to the temperature detected by the temperature detecting means, And a hydraulic power steering apparatus including means (54, 55) for controlling the second drive circuit. In addition, although the alphanumeric character in parentheses represents a corresponding component in an embodiment described later, of course, the scope of the present invention is not limited to the embodiment. The same applies hereinafter.

  In the present invention, the opening command value is limited according to the temperature detected by the temperature detecting means. When the opening command value is limited, the amount of hydraulic oil supplied to the power cylinder decreases, and the steering assist force decreases. As a result, the load on the pump drive motor is reduced, so that the drive current of the pump drive motor is reduced. As a result, overheating protection of the pump drive motor and its drive circuit can be achieved.

In the present invention, the opening command value is limited when the temperature detected by the temperature detecting means rises. For this reason, the possibility that the opening command value is limited when the hydraulic control valve is in the vicinity of the neutral position is low, and therefore the steering operation does not become heavy in the vicinity of the neutral position. Thereby, a steering feeling can be improved.
The invention according to claim 2 is set by a rotational speed command value setting means (72) for setting a rotational speed command value which is a rotational speed command value of the pump driving motor, and the rotational speed command value setting means. The hydraulic power steering apparatus according to claim 1, further comprising means (75, 76) for controlling the first drive circuit based on a rotation speed command value.

FIG. 1 is a schematic diagram showing a schematic configuration of a hydraulic power steering apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing an electrical configuration of the ECU. FIG. 3 is a graph showing a setting example of the pump rotation speed command value with respect to the steering angular velocity. FIG. 4 is a graph showing an example of setting the assist torque command value with respect to the detected steering torque. FIG. 5 is a graph showing a setting example of the valve opening command value with respect to the assist torque command value. FIG. 6 is a flowchart for explaining the operation of the valve opening command value limiting unit. FIG. 7 is a graph showing a setting example of the valve opening limit value with respect to the detected temperature.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of a hydraulic power steering apparatus according to an embodiment of the present invention.
The hydraulic power steering device 1 is for applying a steering assist force to a steering mechanism 2 of a vehicle. The steering mechanism 2 is connected to a steering wheel 3 as a steering member operated by a driver for steering the vehicle, a steering shaft 4 connected to the steering wheel 3, and a tip end portion of the steering shaft 4. A pinion shaft 5 having a pinion gear 6 and a rack shaft 7 having a rack 7a meshing with the pinion gear 6 and extending in the left-right direction of the vehicle are provided.

Tie rods 8 are connected to both ends of the rack shaft 7, and the tie rods 8 are connected to knuckle arms 11 that support the left and right steered wheels 9 and 10, respectively. The knuckle arm 11 is rotatably provided around the kingpin 12.
When the steering wheel 3 is operated and the steering shaft 4 is rotated, this rotation is converted into a linear motion along the axial direction of the rack shaft 7 by the pinion gear 6 and the rack 7a. This linear motion is converted into a rotational motion around the kingpin 12 of the knuckle arm 11, whereby the left and right steered wheels 9, 10 are steered.

  A steering angle sensor 31 for detecting a steering angle θh, which is a rotation angle of the steering shaft 4, is disposed around the steering shaft 4. In this embodiment, the rudder angle sensor 31 detects the amount of rotation (rotation angle) of the steering shaft 4 in both forward and reverse directions from the neutral position of the steering shaft 4, and the amount of rotation from the neutral position to the left is detected. For example, a positive value is output, and the amount of rotation from the neutral position to the right is output as, for example, a negative value. The pinion shaft 5 is provided with a torque sensor 32 for detecting the steering torque Th.

The hydraulic power steering apparatus 1 includes a hydraulic control valve 14, a power cylinder 16 and a hydraulic pump 23. The hydraulic control valve 14 is, for example, a rotary valve, and includes a rotor housing (not shown) and a rotor (not shown) for switching the flow direction of hydraulic oil. As the hydraulic control valve 14, for example, a hydraulic control valve disclosed in Patent Document 1 may be used. The opening degree of the hydraulic control valve 14 is controlled by rotating the rotor of the hydraulic control valve 14 by an electric motor 15 (hereinafter referred to as “valve driving motor 15”). The valve drive motor 15 is composed of, for example, a three-phase brushless motor. In the vicinity of the valve driving motor 15, for detecting the rotation angle theta _B of the rotor of the valve driving motor 15, for example, the rotation angle sensor 33 made of a resolver is disposed.

  The hydraulic control valve 14 is connected to a power cylinder 16 that applies a steering assist force to the steering mechanism 2. The power cylinder 16 is coupled to the steering mechanism 2. Specifically, the power cylinder 16 has a piston 17 provided integrally with the rack shaft 7 and a pair of cylinder chambers 18 and 19 defined by the piston 17. These are connected to the hydraulic control valve 14 through corresponding oil passages 20 and 21, respectively.

  The hydraulic control valve 14 is interposed in the middle of an oil circulation path 24 that passes through a reservoir tank 22 and a hydraulic pump 23 for generating a steering assist force. The hydraulic pump 23 is composed of, for example, a gear pump, is driven by an electric motor 25 (hereinafter referred to as “pump drive motor 25”), draws hydraulic oil stored in the reservoir tank 22, and supplies it to the hydraulic control valve 14. . Excess hydraulic oil is returned from the hydraulic control valve 14 to the reservoir tank 22 via the oil circulation path 24.

The pump driving motor 25 is driven to rotate in one direction to drive the hydraulic pump 23. Specifically, the output shaft of the pump drive motor 25 is connected to the input shaft of the hydraulic pump 23, and the input shaft of the hydraulic pump 23 rotates as the output shaft of the pump drive motor 25 rotates. Thus, driving of the hydraulic pump 23 is achieved. The pump driving motor 25 is a three-phase brushless motor. In the vicinity of the pump drive motor 25, for detecting the rotation angle theta _P of the rotor of the pump drive motor 25, for example, the rotation angle sensor 34 made of a resolver is disposed.

  When the rotor of the hydraulic control valve 14 is rotated in one direction from the reference rotation angle position (neutral position) by the valve drive motor 15, the hydraulic control valve 14 passes through one of the oil passages 20 and 21. The hydraulic oil is supplied to one of the cylinder chambers 18 and 19 of the power cylinder 16 and the other hydraulic oil is returned to the reservoir tank 22. When the rotor of the hydraulic control valve 14 is rotated in the other direction from the neutral position by the valve driving motor 15, the other of the cylinder chambers 18, 19 is passed through the other of the oil passages 20, 21. Is supplied to the reservoir tank 22 and one hydraulic oil is returned to the reservoir tank 22.

  When the rotor of the hydraulic control valve 14 is in the neutral position, the hydraulic control valve 14 is in a so-called equilibrium state, and the cylinder chambers 18 and 19 of the power cylinder 16 are maintained at the same pressure when the steering is neutral. It circulates through the circulation path 24. When the rotor of the hydraulic control valve 14 is rotated by the valve drive motor 15, hydraulic oil is supplied to one of the cylinder chambers 18 and 19 of the power cylinder 16, and the piston 17 is in the vehicle width direction (the left-right direction of the vehicle). Move along. As a result, a steering assist force acts on the rack shaft 7.

  The valve driving motor 15 and the pump driving motor 25 are controlled by an ECU (Electronic Control Unit) 40. In this embodiment, the ECU 40 and the pump driving motor 25 are mounted on one substrate 100. As will be described later, the ECU 40 includes a drive circuit 42 (see FIG. 2) for the valve drive motor 15 and a drive circuit 43 (see FIG. 2) for the pump drive motor 25. The hydraulic power steering device 1 includes a temperature sensor 38 for detecting the ambient temperature of at least one of the drive circuits 42 and 43. In this embodiment, for example, a temperature sensor 38 for detecting the ambient temperature of the drive circuit 43 is disposed around the drive circuit 43 for the pump drive motor 25.

  The ECU 40 detects the steering angle θh detected by the steering angle sensor 31, the steering torque Th detected by the torque sensor 32, the output signal of the rotation angle sensor 33, the output signal of the rotation angle sensor 34, and the vehicle speed sensor 35. The vehicle speed V, the temperature T detected by the temperature sensor 38 (the ambient temperature of the drive circuit 43 for the pump drive motor 25), and the current sensor 36 for detecting the current flowing through the valve drive motor 15 (see FIG. 2). Output signal or the like is input.

FIG. 2 is a block diagram showing an electrical configuration of the ECU 40.
The ECU 40 is controlled by the microcomputer 41, is controlled by the microcomputer 41 and supplies power to the valve drive motor 15, and is controlled by the microcomputer 41 to supply power to the pump drive motor 25. And a drive circuit (inverter circuit) 43 for performing the above operation. A current sensor 36 is provided on the power supply line connecting the drive circuit 42 and the valve drive motor 15.

  The microcomputer 41 includes a CPU and a memory (such as a ROM and a RAM), and functions as a plurality of function processing units by executing a predetermined program. The plurality of function processing units include a valve drive motor control unit 50 for controlling the valve drive motor 15 and a pump drive motor control unit 70 for controlling the pump drive motor 25. .

The pump drive motor control unit 70 includes a steering angular velocity calculation unit 71, a pump rotation number command value setting unit 72, a rotation angle calculation unit 73, a rotation number calculation unit 74, a rotation number deviation calculation unit 75, and PI control. Part 76 and PWM control part 77 are included.
The steering angular velocity calculation unit 71 calculates the steering angular velocity by differentiating the output value of the steering angle sensor 31 with respect to time. The pump rotation speed command value setting unit 72 is based on the steering angular speed calculated by the steering angular speed calculation unit 71, and the rotation speed (rotation speed) command value of the hydraulic pump 23 (rotation speed command value of the pump driving motor 25) The pump rotation speed command value (motor rotation speed command value) V _P ^* is set.

Specifically, the pump rotation speed command value setting unit 72 sets the pump rotation speed command value V _P ^* on the basis of the map storing the relation between the steering angular velocity and the pump rotation speed command value V _P ^*. FIG. 3 is a graph showing a setting example of the pump rotation speed command value V _P ^* with respect to the steering angular velocity. The pump rotation speed command value V _P ^* takes a predetermined lower limit value when the steering angular velocity is 0, and is set so as to increase monotonously as the steering angular velocity increases.

Rotation angle calculating section 73, based on the output signal of the rotational angle sensor 34, calculates a rotation angle theta _P of the pump drive motor 25. Rotational speed calculator 74, based on the rotation angle theta _P of the pump drive motor 25 that is calculated by the rotation angle calculation unit 73 calculates the rotational speed of the pump drive motor 25 (rotational speed) V _P. Rotational speed deviation computing unit 75, the rotational speed V _P of the pump drive motor 25 which is calculated by the pump rotation speed command value V _P ^* and the rotation speed computing unit 74 which is set by the pump rotation speed command value setting unit 72 The deviation ΔV _P (= V _P ^* −V _P ) is calculated.

PI control unit 76 performs PI calculation on rotation speed deviation ΔV _P calculated by rotation speed deviation calculation unit 75. That is, the revolution speed deviation computing unit 75 and the PI control unit 76, the rotational speed feedback control unit that brings the rotational speed V _P of the pump drive motor 25 to the pump rotation speed command value V _P ^* is formed. PI control unit 76, by performing the PI calculation with respect to the rotational speed deviation [Delta] V _P, calculates the control voltage value to be applied to the pump drive motor 25.

PWM controller 77, based on the rotational angle theta _P of the PI controller and the calculated control voltage value by 76, the pump drive motor 25 computed by the rotation angle computation unit 63 generates a driving signal, This is supplied to the drive circuit 43. As a result, a voltage corresponding to the control voltage value calculated by the PI controller 76 is applied from the drive circuit 43 to the pump drive motor 25.
The valve drive motor control unit 50 includes an assist torque command value setting unit 51, a valve opening command value setting unit 52, a valve opening command value limiting unit 60, a rotation angle calculation unit 53, and a rotation angle deviation calculation unit. 54, a PI (proportional integration) control unit 55, a motor current calculation unit 56, a current deviation calculation unit 57, a PI control unit 58, and a PWM (Pulse Width Modulation) control unit 59.

The assist torque command value setting unit 51 is an assist torque that is a command value of assist torque to be generated by the power cylinder 16 based on the detected steering torque Th detected by the torque sensor 32 and the vehicle speed V detected by the vehicle speed sensor 35. Set the command value T _A ^* .
Specifically, the assist torque command value setting unit 51 based on the map storing the relationship between the detected steering torque and the assist torque command value for each vehicle speed, and sets the assist torque command value T _A ^*. FIG. 4 is a graph showing an example of setting the assist torque command value with respect to the detected steering torque.

For the detected steering torque Th, for example, the torque for steering in the left direction is a positive value, and the torque for steering in the right direction is a negative value. The assist torque command value T _A ^* is a positive value when assist torque for leftward steering is generated by the power cylinder 16, and negative when assist torque for rightward steering is generated by the power cylinder 16. The value of

^* Assist torque command value T _A takes a positive value for positive values of the detected steering torque Th, it takes a negative value for negative values of the detected steering torque Th. When the detected steering torque Th is a minute value in the range of -T1 to T1, the assist torque is set to zero. The detection in the region other than the range of the steering torque Th is -T1～T1, the assist torque command value T _A ^*, the absolute value becomes larger of the detected steering torque Th, it is set such that the absolute value becomes larger Yes. Moreover, ^* the assist torque command value T _A is as the vehicle speed V detected by the vehicle speed sensor 35 is large, it is set such that the absolute value becomes smaller. ^* Assist torque command value set by the setting unit 51 the assist torque command value T _A is given to the valve opening command value setting unit 52.

Valve opening command value setting unit 52 based on the assist torque command value setting unit assist torque command value set by the 51 T _A ^*, the opening command value of the hydraulic control valve 14 (the rotation of the valve drive motor 15 The valve opening command value (motor rotation angle command value) θ _B ^*, which is an angle command value), is set. In this embodiment, the rotation angle of the valve drive motor 15 when the rotor of the hydraulic control valve 14 is in the neutral position is 0 °. When the rotation angle of the valve drive motor 15 becomes larger than 0 °, the opening degree of the hydraulic control valve 14 is controlled so that assist torque for leftward steering is generated by the power cylinder 16. On the other hand, when the rotation angle of the valve driving motor 15 is smaller than 0 °, the opening degree of the hydraulic control valve 14 is controlled so that assist torque for rightward steering is generated by the power cylinder 16. The absolute value of the assist torque generated by the power cylinder 16 increases as the absolute value of the rotation angle of the valve driving motor 15 increases.

Valve opening command value setting unit 52 based on the map storing the relation between the assist torque command value T _A ^* and the valve opening command value theta _B ^*, sets the valve opening command value theta _B ^*. FIG. 5 is a graph showing a setting example of the valve opening command value θ _B ^* with respect to the assist torque command value T _A ^* .
Valve opening command value theta _B ^* takes a positive value for the assist torque command value T _A ^* of a positive value, a negative value for the assist torque command value T _A ^* negative values of Take. The valve opening command value θ _B ^* is set such that the absolute value of the assist torque command value T _A ^* increases as the absolute value of the assist torque command value T _A ^* increases. The valve opening command value θ _B ^* set by the valve opening command value setting unit 52 is given to the valve opening command value limiting unit 60.

The valve opening command value limiting unit 60 limits the absolute value | θ _B ^* | of the valve opening command value θ _B ^* according to the temperature T detected by the temperature sensor 38. Details of the valve opening command value limiting unit 60 will be described later.
The rotation angle calculation unit 53 calculates the rotation angle θ _B of the valve driving motor 15 based on the output signal of the rotation angle sensor 33. The rotation angle θ _B calculated by the rotation angle calculation unit 53 is given to the rotation angle deviation calculation unit 54. Rotation angle deviation computing section 54, a valve opening command value theta _B ^*, the deviation [Delta] [theta] _B of the rotation angle theta _B of the valve drive motor 15 computed by the rotation angle calculation unit 53 ₍₌ θ _B ^* '-θ _B ) is calculated. The valve opening command value θ _B ^* input to the rotation angle deviation calculating unit 54 is a value set by the valve opening command value setting unit 52 and limited by the valve opening command value limiting unit 60 as necessary. is there.

The PI control unit 55 performs PI calculation on the rotation angle deviation Δθ _B calculated by the rotation angle deviation calculation unit 54. That is, the rotation angle deviation calculating unit 54 and the PI control unit 55 constitute a rotation angle feedback control means for guiding the rotation angle θ _B of the valve driving motor 15 to the valve opening command value θ _B ^* . The PI control unit 55 calculates the current command value of the valve driving motor 15 by performing PI calculation on the rotation angle deviation Δθ _B.

  The motor current calculation unit 56 detects the motor current flowing through the valve driving motor 15 based on the output signal of the current sensor 36. The current deviation calculation unit 57 calculates a deviation between the current command value obtained by the PI control unit 55 and the motor current calculated by the motor current calculation unit 56. The PI control unit 58 performs a PI calculation on the current deviation calculated by the current deviation calculation unit 57. That is, the current deviation calculation unit 57 and the PI control unit 58 constitute current feedback control means for guiding the motor current flowing through the valve driving motor 15 to the current command value. The PI control unit 58 calculates a control voltage value to be applied to the valve driving motor 15 by performing PI calculation on the current deviation.

The PWM control unit 59 generates a drive signal based on the control voltage value calculated by the PI control unit 58 and the rotation angle θ _{B of} the valve drive motor 15 calculated by the rotation angle calculation unit 53, This is supplied to the drive circuit 42. As a result, a voltage corresponding to the control voltage value calculated by the PI controller 58 is applied from the drive circuit 42 to the valve drive motor 15.
FIG. 6 is a flowchart for explaining the operation of the valve opening command value limiting unit 60. The process of FIG. 6 is repeatedly executed at every predetermined calculation cycle.

Based on the temperature T detected by the temperature sensor 38, the valve opening command value limiting unit 60 determines a limit value for the absolute value | θ _B ^* | of the valve opening command value θ _B ^* (hereinafter referred to as “valve opening limit value θ _Blim ") (step S1). For example, the valve opening command value limiting unit 60 calculates the valve opening limit value θ _Blim based on a map that stores the relationship between the detected temperature T and the valve opening limit value.

FIG. 7 is a graph showing a setting example of the valve opening limit value θ _Blim with respect to the detected temperature T. A constant valve opening limit value θ _Blim is set for a detected temperature below a certain threshold Tth. In the range exceeding the threshold value Tth, the valve opening limit value θ _Blim decreases monotonously (linearly in the example of FIG. 7) as the detected temperature increases. In the range above the predetermined upper limit temperature, the valve opening limit value θ _Blim is set to zero. In this embodiment, in the range exceeding the threshold value Tth, the valve opening limit value θ _Blim is _linearly decreased as the detected temperature increases. However, the valve opening limit value θ _Blim is decreased nonlinearly. Also good.

Next, the valve opening command value limiting unit 60 calculates the absolute value | θ _B ^* | of the valve opening command value θ _B ^* set by the valve opening command value setting unit 52 in step S1. It is determined whether or not the valve opening limit value θ _{Blim is} greater (step S2). When the absolute value | θ _B ^* | of the valve opening command value θ _B ^* is equal to or less than the valve opening limit value θ _Blim (step S2: NO), the valve opening command value limiting unit 60 The valve opening command value θ _B ^* set by the setting unit 52 is output as it is (step S3). Then, the processing in the current calculation cycle is finished.

When the absolute value | θ _B ^* | of the valve opening command value θ _B ^* is larger than the valve opening limit value θ _{Blim in} step S2 (step S2: YES), the valve opening command value limiting unit 60 It is determined whether or not the opening command value θ _B ^* is equal to or greater than 0 (step S4). When the valve opening command value θ _B ^* is equal to or greater than 0 (step S4: YES), the valve opening command value limiting unit 60 sets the valve opening command value θ _Blim as the valve opening command value θ _B ^*. Output (step S5). That is, the valve opening command value θ _B ^* set by the valve opening command value setting unit 52 is limited to the valve opening limit value θ _Blim . Then, the processing in the current calculation cycle is finished.

If it is determined in step S4 that the valve opening command value θ _B ^* is less than 0 (step S4: NO), the valve opening command value limiting unit 60 sets the valve opening command value limiting value θ _Blim to A value −θ _Blim obtained by inverting the sign is output as a valve opening command value θ _B ^* (step S6). That is, the valve opening command value θ _B ^* set by the valve opening command value setting unit 52 is limited to a value −θ _{Blim obtained} by inverting the sign of the valve opening limit value θ _Blim . Then, the processing in the current calculation cycle is finished.

In the embodiment, the absolute value of the valve opening command value θ _B ^* is limited by the valve opening limit value θ _Blim set according to the detected temperature T of the temperature sensor 38. Thereby, the drive of the valve drive motor 15 is limited. Further, when the absolute value of the valve opening command value θ _B ^* is limited, the amount of hydraulic oil supplied to the power cylinder 16 decreases, and the steering assist force decreases. As a result, the load on the pump drive motor 25 is reduced, so that the drive current of the pump drive motor 25 is reduced. As a result, the valve drive motor 15, the power element provided in the drive circuit 42 for the valve drive motor 15, the pump drive motor 25, and the power element provided in the drive circuit 43 for the pump drive motor 25. Can be prevented from being destroyed by overheating. That is, overheat protection of the ECU 40, the pump driving motor 25, and the valve driving motor 15 can be achieved.

In the above embodiment, when the detected temperature T of the temperature sensor 38 increases, the rotational speed command value (pump rotational speed command value V _P ^* ) of the pump driving motor 25 is not reduced, but the valve opening degree is reduced. The absolute value of the command value θ _B ^* is limited to the valve opening limit value θ _Blim . Therefore, only when the absolute value of the valve opening command value θ _B ^* set by the valve opening command value setting unit 52 is larger than the valve opening limit value θ _Blim , the absolute value of the valve opening command value θ _B ^* . There is limited, the absolute value of the valve opening command value theta _B ^* when the absolute value of the valve opening command value theta _B ^* is less than the valve opening limit value theta _Blim is not limited. Therefore, when the rotor of the hydraulic control valve 14 is in the vicinity of the neutral position, the possibility that the absolute value of the valve opening command value θ _B ^* is limited is low, and thus the steering operation does not become heavy in the vicinity of the neutral position. Thereby, a steering feeling can be improved.

As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above-described embodiment, the valve opening command value limiter 60 calculates the valve opening limit value θ _Blim based on a map that stores the relationship between the detected temperature T and the valve opening limit value. The valve opening limit value θ _Blim corresponding to the detected temperature T may be calculated based on a predetermined calculation formula.

In the above embodiment, the temperature sensor 38 for detecting the ambient temperature of the drive circuit 43 is disposed around the drive circuit 43 for the pump drive motor 25, but instead of or in addition to this, the valve drive is performed. A temperature sensor for detecting the ambient temperature of the drive circuit 42 may be disposed around the drive circuit 42 for the motor 15. When two temperature sensors, a temperature sensor for detecting the ambient temperature of the drive circuit 43 and a temperature sensor for detecting the ambient temperature of the drive circuit 42, are provided, the valve opening command value limiting unit 60 is The valve opening limit value θ _Blim may be calculated based on the detected temperature of the higher temperature of the two temperature sensors.

  In addition, various design changes can be made within the scope of matters described in the claims.

  DESCRIPTION OF SYMBOLS 1 ... Hydraulic power steering apparatus, 2 ... Steering mechanism, 3 ... Steering wheel, 14 ... Hydraulic control valve, 15 ... Valve drive motor, 16 ... Power cylinder, 23 ... Hydraulic pump, 25 ... Pump drive motor, 38 ... Temperature sensor 42, 43 ... Drive circuit 52 ... Valve opening command value setting unit 60 ... Valve opening command value limiting unit 72 ... Pump rotation speed command value setting unit 73 ... Rotation angle calculation unit 74 ... Rotation Number calculation unit, 75... Rotation speed deviation calculation unit

Claims (2)

Hydraulic power steering that assists steering force by supplying hydraulic oil from a hydraulic pump to a power cylinder coupled to a steering mechanism of a vehicle via a hydraulic control valve that is not mechanically connected to a steering member A device,
A pump driving motor for driving the hydraulic pump;
A valve drive motor for controlling the opening of the hydraulic control valve;
A first drive circuit for the pump drive motor;
A second drive circuit for the valve drive motor;
Temperature detecting means for detecting an ambient temperature of at least one of the first drive circuit and the second drive circuit;
An opening command value setting means for setting an opening command value which is a command value of the opening of the hydraulic control valve;
An opening command value limiting means for limiting the opening command value according to the temperature detected by the temperature detecting means;
The second drive circuit is controlled based on the opening command value set by the opening command value setting means and limited by the opening command value limiting means according to the temperature detected by the temperature detection means. And a hydraulic power steering device. A rotational speed command value setting means for setting a rotational speed command value that is a rotational speed command value of the pump drive motor;
The hydraulic power steering apparatus according to claim 1, further comprising means for controlling the first drive circuit based on a rotational speed command value set by the rotational speed command value setting means.

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