JP2015209000A - Hydraulic power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic power steering device in which deviation is difficult to occur between hydraulic pressure applied to a hydraulic actuator and hydraulic pressure meeting a target assist force.SOLUTION: A hydraulic power steering device includes: an electric pump 25 for supplying hydraulic fluid to a hydraulic actuator 21; a flow control valve 40 for controlling an amount of supply and discharge of the hydraulic fluid for the hydraulic actuator 21; a hydraulic sensor 36 as an example of hydraulic detection means for detecting a hydraulic pressure of the hydraulic fluid flowing from the flow control valve 40 to the hydraulic actuator 21; and a control section 50. The hydraulic power steering device includes a torque sensor 14, a steering angle sensor 15, and a vehicle speed sensor 3, which are examples of state detection means for detecting a driving state of a vehicle. The control section 50 performs feedback control of at least an opening of the flow control valve 40 and supply amount of the hydraulic fluid of the electric pump 25 on the basis of the hydraulic pressure detected by the hydraulic sensor 36 and a hydraulic pressure meeting a target assist force.

Description

  The present invention relates to a hydraulic power steering apparatus that assists a steering operation with a hydraulic actuator.

  The hydraulic power steering device disclosed in Patent Document 1 includes a hydraulic actuator that applies an assist force to the steering shaft by hydraulic pressure, and a flow rate control valve that controls the flow rate of hydraulic oil flowing through an oil passage connected to the hydraulic actuator. . In addition, this hydraulic power steering apparatus has an electric pump that controls the flow rate of hydraulic oil flowing in the discharge passage connected to the flow rate control valve.

  As an example, the control unit of the hydraulic power steering apparatus calculates a target assist force applied to the steering shaft based on the steering torque of the steering shaft and the vehicle speed, that is, the hydraulic pressure applied to the hydraulic actuator. The control unit calculates a target opening degree of the flow rate control valve according to the target assist force and a target rotational angular velocity of the motor of the electric pump. The control unit feedback-controls the opening of the flow control valve based on the actual opening and the target opening of the flow control valve. Further, the control unit feedback-controls the operation of the electric pump based on the actual rotational angular velocity and the target rotational angular velocity of the electric pump motor.

JP 2012-86791 A

  By the way, there is a difference in characteristics between devices such as an electric pump, a flow control valve, and a hydraulic actuator even if they are the same device. Also, the hydraulic oil supplied to the hydraulic actuator has a difference in characteristics depending on conditions such as temperature. For this reason, even if feedback control is performed on the operations of the flow control valve and the electric pump, there is a risk that the oil pressure corresponding to the target assist force may not be applied to the hydraulic actuator due to the difference in the characteristics of the devices and the difference in the characteristics of the hydraulic oil. There is.

  An object of the present invention is to provide a hydraulic power steering apparatus in which a difference between a hydraulic pressure applied to a hydraulic actuator and a hydraulic pressure corresponding to a target assist force hardly occurs.

  A hydraulic power steering apparatus that can achieve the above object is a hydraulic power steering apparatus that assists a steering operation by a hydraulic actuator, and includes an electric pump that supplies hydraulic oil to the hydraulic actuator, and hydraulic oil that is supplied to the hydraulic actuator. A flow rate control valve for controlling the supply / discharge amount, a hydraulic pressure detection means for detecting hydraulic pressure of hydraulic fluid flowing from the flow rate control valve to the hydraulic actuator, a state detection means for detecting a driving state of a vehicle, A control unit that calculates a target assist force based on the detection result and controls the flow rate control valve according to the target assist force, the control unit including the hydraulic pressure detected by the hydraulic pressure detection unit and the target Based on the hydraulic pressure corresponding to the assist force, the opening degree of the flow control valve and the operation of the electric pump A feedback control at least one of the supply amount.

  According to this hydraulic power steering apparatus, the control unit determines the opening of the flow control valve and the amount of hydraulic oil supplied to the electric pump based on the hydraulic pressure detected by the hydraulic pressure detection means and the hydraulic pressure corresponding to the target assist force. Since at least one of them is feedback-controlled, the actual hydraulic pressure applied to the hydraulic actuator and the hydraulic pressure corresponding to the target assisting force are unlikely to occur.

  In the hydraulic power steering apparatus described above, it is preferable that the hydraulic pressure detection means is a hydraulic pressure sensor provided in an oil passage connecting the flow control valve and the hydraulic actuator.

In the hydraulic power steering apparatus described above, the control unit preferably executes sliding mode control as feedback control.
According to this hydraulic power steering apparatus, for example, the influence of disturbance such as a difference in hydraulic oil characteristics can be reduced as compared with the case where PID control is performed as feedback control, that is, robustness is ensured. be able to. For this reason, a shift is less likely to occur between the hydraulic pressure applied to the hydraulic actuator and the hydraulic pressure corresponding to the target assist force.

  According to this hydraulic power steering apparatus, a difference is hardly generated between the hydraulic pressure applied to the hydraulic actuator and the hydraulic pressure corresponding to the target assist force.

The schematic diagram which shows the whole structure of the hydraulic power steering device of embodiment. The block diagram which shows the control structure of the hydraulic power steering apparatus of embodiment.

The configuration of the hydraulic power steering apparatus will be described with reference to FIG.
The hydraulic power steering device includes a steering device 10 that transmits an operation of the steering wheel 1 by the driver to the steered wheels 2, an assist device 20 that generates an assist force that assists a force necessary for the operation of the steering wheel 1, and an assist. A control unit 50 that controls the apparatus 20 is included.

  The steering device 10 includes a steering shaft 11 that rotates together with the steering wheel 1, a rack and pinion mechanism 12 that converts the rotational motion of the steering shaft 11 into linear motion, and a tie rod 13 that connects the rack and pinion mechanism 12 and the steered wheels 2. Have The steering shaft 11 is provided with a torque sensor 14 that detects a steering torque acting on the shaft 11 and a steering angle sensor 15 that detects a steering angle of the shaft 11. A vehicle speed sensor 3 that detects the vehicle speed based on the rotational speed of the steered wheels 2 is disposed in the vicinity of the steered wheels 2. The torque sensor 14, the steering angle sensor 15, and the vehicle speed sensor 3 correspond to an example of “state detection means”.

  The torque sensor 14 outputs a signal corresponding to the steering torque acting on the steering shaft 11 to the control unit 50. The steering angle sensor 15 outputs a signal corresponding to the steering angle of the steering shaft 11 to the control unit 50. Further, the vehicle speed sensor 3 outputs a signal corresponding to the rotational speed of the steered wheels 2 to the control unit 50.

  The assist device 20 includes a hydraulic cylinder 21 as an example of a hydraulic actuator, an electric pump 25 that draws hydraulic oil from a storage tank 26, and a flow rate control valve 40 that controls the supply and discharge amount of hydraulic oil to and from the hydraulic cylinder 21.

  The hydraulic cylinder 21 has a steered shaft 22 that is displaced in the axial direction in accordance with the operation of the rack and pinion mechanism 12, and a housing 23 that supports the steered shaft 22 so as to be capable of reciprocating. A space inside the housing 23 is partitioned into a pair of hydraulic chambers, that is, a first hydraulic chamber 21A and a second hydraulic chamber 21B by a piston 24 formed on the steered shaft 22.

  The electric pump 25 incorporates a brushless motor (not shown) with a three-phase coil that rotates only in one direction when electric power is supplied to the drive circuit 25A. Further, an impeller is connected to the output shaft of the brushless motor, and the output oil of the storage tank 26 is sucked up and discharged toward the flow control valve 40 by rotating the output shaft of the brushless motor.

  The flow control valve 40 supplies the hydraulic oil to the first hydraulic chamber 21A while supplying / discharging the hydraulic oil to / from the hydraulic cylinder 21, while discharging the hydraulic oil from the second hydraulic chamber 21B, 2 The hydraulic oil is supplied to the hydraulic chamber 21B, while the hydraulic oil is discharged from the first hydraulic chamber 21A, and the hydraulic oil is supplied to both the first hydraulic chamber 21A and the second hydraulic chamber 21B. Switch to the neutral state where no power is supplied.

  The flow rate control valve 40 sets the amount of hydraulic oil supplied to the first hydraulic chamber 21A and sets the hydraulic oil supply / discharge state to the second state when the hydraulic oil supply / discharge state is set to the first state. Sometimes, the assist force generated by the hydraulic cylinder 21 is controlled by adjusting the amount of hydraulic oil supplied to the second hydraulic chamber 21B. The flow control valve 40 discharges the hydraulic oil from the first hydraulic chamber 21A and the second hydraulic chamber 21B when the hydraulic oil supply / discharge state is set to the neutral state.

  Moreover, the flow control valve 40, the hydraulic cylinder 21, the storage tank 26, and the electric pump 25 described above are connected by a plurality of flow paths. The storage tank 26 and the electric pump 25 are connected by a suction passage 31, and the electric pump 25 and the flow rate control valve 40 are connected by a discharge passage 32. The flow rate control valve 40 is connected to the first hydraulic chamber 21 </ b> A of the hydraulic cylinder 21 by the first oil passage 33, and is connected to the second hydraulic chamber 21 </ b> B of the hydraulic cylinder 21 by the second oil passage 34. Further, the flow control valve 40 and the storage tank 26 are connected by a discharge path 35. The first oil passage 33 and the second oil passage 34 are provided with a hydraulic sensor 36 as an example of a hydraulic pressure detection unit that detects the hydraulic pressure of the hydraulic oil supplied to the hydraulic cylinder 21.

  The flow control valve 40 connects the first oil passage 33 to the discharge passage 32 and connects the second oil passage 34 to the discharge passage 35 when the hydraulic oil supply / discharge state to the hydraulic cylinder 21 is set to the first state. To do. Then, the amount of hydraulic fluid supplied from the first oil passage 33 to the first hydraulic chamber 21 </ b> A of the hydraulic cylinder 21 is controlled by adjusting the communication area between the first oil passage 33 and the discharge passage 32.

  On the other hand, the flow rate control valve 40 connects the first oil passage 33 to the discharge passage 35 and the second oil passage 34 to the discharge passage 32 when the hydraulic oil supply / discharge state to the hydraulic cylinder 21 is set to the second state. Connect to. Then, the amount of hydraulic oil supplied from the second oil passage 34 to the second hydraulic chamber 21 </ b> B of the hydraulic cylinder 21 is controlled by adjusting the communication area between the second oil passage 34 and the discharge passage 32.

A control configuration of the hydraulic power steering apparatus will be described with reference to FIG.
The control unit 50 includes a target assist force calculation unit 51 that calculates a target assist force AS to be applied to the steering shaft 11.

  The target assist force calculation unit 51 calculates the steering torque of the steering shaft 11 based on the output signal of the torque sensor 14. The target assist force calculation unit 51 calculates the vehicle speed based on the output signal of the vehicle speed sensor 3. The target assist force calculation unit 51 calculates the steering angle of the steering shaft 11 based on the output signal of the steering angle sensor 15. The target assist force calculator 51 calculates a target assist force AS to be applied to the steering shaft 11 based on the calculated steering torque, vehicle speed, and steering angle. For example, the target assist force calculation unit 51 calculates a larger value as the target assist force AS as the calculated steering torque value is smaller. For example, the target assist force calculation unit 51 calculates a larger value as the target assist force AS as the calculated vehicle speed is lower. For example, the target assist force calculation unit 51 calculates a larger value as the target assist force AS as the calculated steering angle is smaller.

  Further, the control unit 50 calculates the target rotational angular velocity ωm of the brushless motor of the electric pump 25 based on the target assist force AS, and the target opening θv of the flow control valve 40 based on the target assist force AS. It has the valve opening calculation part 53 which calculates.

  For example, the rotational angular velocity calculation unit 52 calculates a larger value as the target rotational angular velocity ωm as the target assist force AS is larger. As an example, the valve opening calculation unit 53 calculates a larger value as the target opening θv as the target assist force AS is larger.

  Further, the control unit 50 calculates a current command value Ip to be output to the drive circuit 25A of the electric pump 25 based on the target rotation angular velocity ωm, while calculating a current command value Iv to be output to the flow control valve 40 based on the target opening θv. A current command value calculation unit 54 for calculating is provided. As an example, the current command value calculation unit 54 calculates a larger value as the current command value Ip as the target rotational angular velocity ωm increases. For example, the current command value calculation unit 54 calculates a larger value as the current command value Iv as the target opening degree θv is larger. Note that the actual opening θr of the flow control valve 40 is input to the current command value calculation unit 54.

  Furthermore, the control unit 50 determines the rotation angle speed ωr of the brushless motor of the electric pump 25 by differentiating the rotation angle detection unit 55 that detects the actual rotation angle Sr of the brushless motor of the electric pump 25 and the rotation angle Sr. A rotation angular velocity calculation unit 56 for calculating is provided. The rotation angular velocity calculation unit 56 outputs the calculated rotation angular velocity ωr to the current command value calculation unit 54.

  The current command value calculation unit 54 has a sliding mode control unit 57 to which the target hydraulic pressure Pa applied to the hydraulic cylinder 21 corresponding to the target assist force AS and the actual hydraulic pressure Pr detected by the hydraulic sensor 36 are input. The sliding mode control unit 57 calculates a deviation ΔP between the target hydraulic pressure Pa and the hydraulic pressure Pr. Further, the sliding mode control unit 57 calculates a deviation Δω between the target rotational angular velocity ωm and the rotational angular velocity ωr. Further, the sliding mode control unit 57 calculates a deviation Δθ between the target opening θv and the opening θr. As an example of feedback control, the sliding mode control unit 57 performs sliding mode control on the current command value Ip and the current command value Iv so that the deviation ΔP, the deviation Δω, and the deviation Δθ become zero.

Next, the operation of the hydraulic power steering apparatus will be described.
The target oil pressure Pa corresponding to the target assist force AS and the oil pressure Pr detected by the oil pressure sensor 36 are input to the sliding mode control unit 57 of the current command value calculation unit 54, and the deviation ΔP between the target oil pressure Pa and the oil pressure Pr is 0. The sliding mode control is executed so that For this reason, the actual hydraulic pressure Pr applied to the hydraulic cylinder 21 and the target hydraulic pressure Pa are unlikely to shift.

The hydraulic power steering device has the following effects.
As feedback control, for example, it is possible to reduce the influence of disturbance such as a difference in characteristics of hydraulic oil as compared with the case of executing PID control, that is, to ensure robustness. For this reason, a shift is less likely to occur between the hydraulic pressure Pr applied to the hydraulic cylinder 21 and the target hydraulic pressure Pa.

In addition, you may change the said embodiment as follows. The following other embodiments can be combined with each other within a technically consistent range.
-Although sliding mode control was performed as feedback control, you may perform P control, PI control, PD control, or PID control.

The sliding mode control can be executed so that the deviation ΔP and at least one of the deviation Δω and the deviation Δθ are zero.
The target assist force calculation unit 51 may calculate the target assist force AS based on at least one output signal of the output signal of the torque sensor 14, the output signal of the vehicle speed sensor 3, and the output signal of the steering angle sensor 15. .

  DESCRIPTION OF SYMBOLS 3 ... Vehicle speed sensor (state detection means), 14 ... Torque sensor (state detection means), 15 ... Steering angle sensor (state detection means), 21 ... Hydraulic cylinder (hydraulic actuator), 25 ... Electric pump, 36 ... Hydraulic sensor ( Oil pressure detection means), 40... Flow control valve, 50.

Claims (3)

A hydraulic power steering device that assists steering operation with a hydraulic actuator,
An electric pump for supplying hydraulic oil to the hydraulic actuator;
A flow rate control valve for controlling the amount of hydraulic oil supplied to and discharged from the hydraulic actuator;
Oil pressure detecting means for detecting the oil pressure of the hydraulic fluid flowing from the flow control valve to the hydraulic actuator;
State detection means for detecting the driving state of the vehicle;
A control unit that calculates a target assist force based on a detection result of the state detection unit and controls the flow rate control valve according to the target assist force;
The controller controls at least one of the opening of the flow control valve and the amount of hydraulic oil supplied to the electric pump based on the hydraulic pressure detected by the hydraulic pressure detection means and the hydraulic pressure corresponding to the target assist force. Hydraulic power steering device with feedback control. The hydraulic power steering apparatus according to claim 1, wherein the hydraulic pressure detection means is a hydraulic pressure sensor provided in an oil passage connecting the flow control valve and the hydraulic actuator. The hydraulic power steering apparatus according to claim 1, wherein the control unit executes a sliding mode control as the feedback control.