JP2015160447A - power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device which can obtain a steering feeling similar to that before a failure even if an electric power steering device is failed.SOLUTION: A power steering device 11 comprises an EPS 20 and an HPS 30. The EPS 20 has a torque sensor 21 which generates an electric signal corresponding to a torsion amount of a torsion bar 65 to which steering torque is applied, and an assist motor 22 which generates a first steering assist force on the basis of the electric signal. The HPS 30 has a hydraulic actuator 31 which generates a second steering assist force according to a flow rate of a working fluid which is supplied from a motor drive pump 33, and a control valve 32 which controls the feed and discharge of the working fluid with respect to the hydraulic actuator 31 according to the torsion amount of the torsion bar 65 which is commonly used with the torque sensor 21. The assist motor 22 is connected to a downstream side (a pinion shaft 15 engaged with a rack shaft 16) of the torsion bar 65 at a transmission route of the steering torque via a reduction gear 23.

Description

  The present invention relates to a power steering apparatus.

  2. Description of the Related Art Conventionally, a power provided with an electric steering assist device using a motor as a power source and a hydraulic steering assist device using an internal combustion engine as a power source for driving an axle of the vehicle in order to apply an assist torque to the steering system of the vehicle. There is a steering device (see, for example, Patent Document 1).

  The electric steering assist device is a column assist type, which generates an output torque by adding an assist torque by a motor to an input torque to the steering wheel, and applies the output torque to the hydraulic steering assist device. The hydraulic steering assist device is a rack and pinion type steering assist device including a rotary control valve. The control valve is operated by applying the output torque of the electric steering assist device. Through this operation, the flow path and flow rate of the hydraulic oil from the hydraulic pump to the power cylinder provided in the rack body are switched according to the twist angle of the torsion bar built in the control valve. The power cylinder generates rack propulsion force (steering assist force) by supplying hydraulic oil to a cylinder chamber for assisting right steering or assisting left operation. In addition, an electromagnetic relief valve is provided between the high-pressure channel communicating with the hydraulic pump and the low-pressure channel communicating with the reservoir tank.

  Normally, the electric steering assist device does not generate assist torque by the motor when the input torque is less than the set value. That is, the input torque becomes the output torque of the electric steering assist device as it is. Until the output torque reaches a set value, an auxiliary torque corresponding to the output torque is generated by the hydraulic steering assist device. After the output torque reaches the set value, the electromagnetic relief valve is opened and a part of the hydraulic oil is returned to the reservoir tank, so that the auxiliary torque generated by the hydraulic steering auxiliary device is limited while the electric steering is performed. Generation of auxiliary torque by the auxiliary device is started. At this time, the output torque of the electric steering assist device is a value obtained by adding the assist torque by the motor to the input torque to the steering wheel.

When the electric steering assist device or the hydraulic steering assist device fails, the steering assist is continued by the remaining normal hydraulic steering assist device or the electric steering assist device.
When the electric steering assist device fails, the set opening pressure for opening the electromagnetic relief valve is increased more than usual. Since the flow rate of hydraulic oil supplied to the power cylinder can be increased more than usual, the hydraulic steering assist device not only when the torque applied to itself is less than the set value, but also when the torque exceeds the set value. Sometimes it becomes possible to generate an auxiliary torque corresponding to the torque. That is, when the electric steering assist device fails, the shortage of the assist torque due to the failure is compensated by the steering assist force of the hydraulic steering assist device.

  When the hydraulic steering assist device fails, the electric steering assist device generates the assist torque by the motor even if the input torque to the steering wheel is less than the set value.

Japanese Patent No. 5034446 (paragraph 0076, FIG. 7)

  In the power steering device of Patent Literature 1, the control valve of the hydraulic steering assist device is operated in accordance with the output torque of the electric steering assist device. Here, the rigidity (spring constant) of the torsion bar of the control valve is set according to the output torque of the electric steering assist device. That is, the torsion bar is suitably twisted by applying an output torque when the electric steering assist device operates normally, and as a result, desired operation characteristics of the control valve can be obtained. For this reason, when the electric steering assist device fails, the same steering feel as before the failure is obtained until the input torque at the steering wheel reaches the set value. However, when trying to fully demonstrate the capability of the hydraulic steering assist device in a situation where the input torque exceeds the set value, an input torque larger than that at normal time is required because the assist torque by the motor cannot be obtained. Moreover, due to the fact that a large input torque is required, there is a possibility that the opening degree of the control valve, and hence the steering assist force by the hydraulic pressure cannot be sufficiently obtained. This leads to deterioration of the steering feel.

  An object of the present invention is to provide a power steering device that can obtain the same steering feel as that before the failure even when the electric power steering has failed.

  A power steering apparatus that can achieve the above object includes an electric power steering and a hydraulic power steering. The electric power steering includes a torque sensor that generates an electric signal corresponding to a torsion amount of a torsion bar to which a steering torque is applied, and an electric actuator that generates a first steering assist force based on the electric signal generated by the torque sensor. And have. The hydraulic power steering includes a hydraulic actuator that generates a second steering assist force according to a flow rate of hydraulic oil supplied from a pump, and a torsion bar that shares the supply and discharge of hydraulic oil to and from the hydraulic actuator with the torque sensor. A control valve for controlling the amount of twist. The electric actuator is provided downstream of the torsion bar in a steering torque transmission path.

  According to this configuration, the first steering assist force by the electric power steering is not applied to the torsion bar. Therefore, even when the electric power steering fails, the same steering feel as before the failure can be obtained.

  In the power steering apparatus described above, the transmission path may include a pinion shaft that rotates when steering torque is transmitted through the torsion bar, and a steered shaft that moves linearly as the pinion shaft rotates. Good. At this time, it is preferable that the electric actuator is connected to the pinion shaft or the steered shaft that is downstream of the torsion bar in the transmission path.

  According to this configuration, the first steering assist force by the electric actuator is applied to the pinion shaft or the steered shaft. The first steering assist force assists the rotational motion of the pinion shaft or the linear motion of the steered shaft.

  In the power steering apparatus described above, the electric actuator may be a motor that rotates by power feeding. And the relay which opens and closes the electric power feeding path | route with respect to the said electric actuator, and the control apparatus which controls opening and closing of the said relay may be provided. At this time, it is preferable that the control device opens the relay when the electric power steering fails.

  According to this configuration, when the electric power steering fails, the power supply path to the motor is interrupted by opening the relay. Thereby, it is suppressed that a motor transfers to electric power generation mode. That is, the rotation resistance (regenerative resistance) during power generation in the motor is suppressed from acting as a braking force for steering.

  In the power steering apparatus described above, the hydraulic actuator uses the differential pressure generated in the two oil chambers to selectively switch the supply and discharge of the hydraulic oil through the control valve to provide a second steering assist for the steered shaft. It may be a hydraulic cylinder that applies force. An electric valve that opens and closes between the first supply / discharge pipe and the second supply / discharge pipe respectively connected between the control valve and the two oil chambers, and a control that controls opening and closing of the electric valve And a device. At this time, it is preferable that the control device opens the electric valve when the hydraulic power steering fails.

  According to this configuration, when the hydraulic power steering fails, the electric supply valve is opened so that the first supply / discharge pipe communicates with the second supply / discharge pipe. For example, when clogging occurs somewhere in the hydraulic oil supply path (hydraulic piping), it is conceivable that there is no escape area for hydraulic oil in one or the other oil chamber of the hydraulic cylinder. In this respect, the hydraulic oil in one or the other oil chamber can escape to the first or second supply / discharge pipe by opening the electric valve. For this reason, the hydraulic resistance resulting from the hydraulic oil in one or the other oil chamber that has lost its escape is reduced.

  According to the present invention, even if the electric power steering fails, the same steering feeling as before the failure can be obtained.

The lineblock diagram showing the outline of the power steering device in one embodiment. Sectional drawing of the control valve and torque sensor in one Embodiment. The block diagram which shows the electric constitution of the power steering apparatus in one Embodiment. The block diagram which shows the outline of the power steering apparatus in other embodiment. The block diagram which shows the outline of the engine drive pump in other embodiment.

Hereinafter, an embodiment of a power steering device for a vehicle will be described.
<Outline of power steering device>
As shown in FIG. 1, the power steering device 11 employs a rack and pinion mechanism 12 as a steering mechanism. The rack and pinion mechanism 12 converts the rotation of the pinion shaft 15 interlocked with the operation of the steering wheel 13 via the steering shaft 14 into a linear motion of the rack shaft 16 meshing with the pinion shaft 15. Wheels are connected to both ends of the rack shaft 16 via ball joints (not shown). As the rack shaft 16 moves in the direction of its own axis, the direction of the wheels (steering angle) changes.

The power steering apparatus 11 includes an EPS (electric power steering) 20 and an HPS (hydraulic power steering) 30 as components for assisting steering.
<EPS>
The EPS 20 assists steering by assisting the operation of the pinion shaft 15 (steering shaft 14). The EPS 20 includes a torque sensor 21, an assist motor 22, a speed reducer 23, and an ECU (electronic control unit) 24.

  The torque sensor 21 is provided in the middle of the steering shaft 14. The torque sensor 21 generates an electric signal Sτ corresponding to the steering torque applied to the steering shaft 14 via the steering wheel 13.

  The assist motor 22 is connected to the pinion shaft 15 via a speed reducer 23. The speed reducer 23 has a worm 23a connected to the output shaft of the assist motor 22, and a worm wheel 23b provided on the steering shaft 14 and meshing with the worm 23a. The reduction gear 23 decelerates the rotation of the assist motor 22 and transmits the decelerated rotational force to the pinion shaft 15 as a steering assist force (assist force).

  The ECU 24 detects the steering torque τ based on the electric signal Sτ generated by the torque sensor 21 and controls the assist motor 22 according to the steering torque τ. Specifically, the ECU 24 calculates a target assist force (target assist amount) based on the steering torque τ, and supplies drive power for generating the target assist force to the assist motor 22. The ECU 24 may obtain, for example, a vehicle speed (vehicle traveling speed) as information indicating the traveling state of the vehicle, and calculate the target assist force in consideration of the vehicle speed.

<HPS>
The HPS 30 assists steering by assisting the operation of the rack shaft 16. The HPS 30 includes a hydraulic actuator 31, a control valve 32, a motor drive pump 33, and an oil tank 34.

  The motor drive pump 33 is integrally provided with a pump body 33a, a pump motor 33b for driving the pump body 33a, and a pump ECU (electronic control unit) 33c for controlling the pump motor 33b. The motor drive pump 33 sucks the working oil (working fluid) stored in the oil tank 34, and discharges the sucked working oil by increasing the pressure. The hydraulic oil discharged from the motor drive pump 33 is supplied to the hydraulic actuator 31 via the control valve 32.

  The hydraulic actuator 31 has a hollow cylinder 41 and a piston 42. The cylinder 41 is also used as a housing for the rack shaft 16. A rack shaft 16 that also functions as a piston rod is inserted into the cylinder 41. Inside the cylinder 41, a piston 42 is fixed to the rack shaft 16 in a penetrating manner. The piston 42 divides the inside of the cylinder 41 into a first oil chamber 41a and a second oil chamber 41b. The piston 42 is integrated with the rack shaft 16 and slides in the cylinder 41 in the axial direction of the rack shaft 16. Further, the rack shaft 16 moves in the first direction LA or the second direction RA indicated by an arrow in FIG. 1 due to the differential pressure between the first oil chamber 41a and the second oil chamber 41b. The displacement of the rack shaft 16 due to the differential pressure acts as a steering assist force.

  The control valve 32 is provided integrally with the torque sensor 21. The torque sensor 21 is located on the steering wheel 13 side, and the control valve 32 is located on the pinion shaft 15 side. The control valve 32 is a rotary valve that switches between a hydraulic oil supply path and a hydraulic discharge path for the hydraulic actuator 31 in conjunction with the operation of the steering wheel 13, that is, the rotation of the steering shaft 14.

  More specifically, the pump port 32a of the control valve 32 is connected to the motor drive pump 33 (discharge port) via the discharge pipe 51. The first and second cylinder ports 32b and 32c of the control valve 32 are connected to the first and second oil chambers 41a and 41b through the first and second supply / discharge pipes 52 and 53, respectively. Has been. The tank port 32 d of the control valve 32 is connected to the oil tank 34 via the discharge pipe 54. The oil tank 34 is connected to a motor drive pump 33 (suction port) via a suction pipe 55. The motor drive pump 33 sucks the hydraulic oil stored in the oil tank 34 through the suction pipe 55, and discharges the hydraulic oil with the pressure of the sucked hydraulic oil increased.

  Hydraulic fluid discharged from the motor drive pump 33 is supplied to the control valve 32 via a discharge pipe 51. The control valve 32 supplies the first and second supply / discharge pipes with hydraulic oil supplied through the discharge pipe 51 in accordance with the direction (steering direction) and magnitude (steering resistance) of the steering torque applied to the steering wheel 13. Assign to either 52 or 53. That is, the hydraulic oil is supplied to any one of the first and second oil chambers 41a and 41b via any one of the first and second supply / discharge pipes 52 and 53.

  For example, when hydraulic oil is supplied to the first oil chamber 41a via the first supply / discharge pipe 52, the hydraulic actuator 31 generates an oil pressure corresponding to the hydraulic pressure difference generated between the first hydraulic chamber 41a and the second oil chamber 41b. The hydraulic pressure is generated and acts on the rack shaft 16 as a steering assist force. At this time, the hydraulic oil in the second oil chamber 41 b is pushed out, and the pushed-out hydraulic oil returns (circulates) to the control valve 32 via the second supply / discharge pipe 53 and further passes through the discharge pipe 54. Return to the oil tank 34. Here, since the oil pressure acts in the second direction RA (rightward in FIG. 1) via the piston 42, the rack shaft 16 moves in the second direction RA together with the piston 42. Steering is assisted by the movement of the rack shaft 16.

  The first supply / discharge pipe 52 and the second supply / discharge pipe 53 are connected by a bypass pipe 56. The bypass pipe 56 is provided with an electric valve 57. The electric valve 57 is opened and closed under the control of the ECU 24. Normally, the electric valve 57 is kept closed. By switching the electric valve 57 from the closed state to the open state, the first supply / discharge pipe 52 and the second supply / discharge pipe 53 communicate with each other.

<Torque sensor and control valve>
Next, the configuration of the torque sensor 21 and the control valve 32 will be described in detail.
As shown in FIG. 2, the torque sensor 21 and the control valve 32 are provided inside a hollow cylindrical valve housing 61. The torque sensor 21 is located on the steering wheel 13 side, and the control valve 32 is located on the pinion shaft 15 side (reduction gear 23 side).

  A cylindrical end stopper 62 is fixed to the end of the valve housing 61 on the steering wheel 13 side (upper end in the drawing) by screwing. The end (lower end in the figure) of the valve housing 61 on the side of the speed reducer 23 may be coupled to a speed reducer housing 23c in which the speed reducer 23 is accommodated, for example.

  A hollow cylindrical input shaft 63 and a hollow cylindrical output shaft 64 are provided inside the valve housing 61 so as to be rotatable about the same axis. The input shaft 63 and the output shaft 64 are connected so as to be relatively rotatable via a torsion bar 65 inserted through these. The outer end (upper end in the figure) of the input shaft 63 is connected to the steering shaft 14. The outer end (lower end in the figure) of the output shaft 64 is connected to the pinion shaft 15.

  The torsion bar 65 is twisted when a steering torque τ is applied to the steering wheel 13. When the steering wheel 13 requires an appropriate reaction force (hand response), the power steering device 11 uses the twist of the torsion bar 65 as a reaction force in order to obtain the feeling of response. In other words, the torsion bar 65 provides a feeling of response accompanying the operation of the steering wheel 13, that is, a so-called steering weight. When the road resistance is large, the torsion bar 65 is also twisted to increase the reaction force, and when the road resistance is small, the twist angle is small and the reaction force is small. The torsional rigidity (spring constant) of the torsion bar 65 is set to such a value that it can be twisted (sufficiently) by the steering torque τ by the driver.

<Control valve>
The control valve 32 has an inner valve 71 and an outer valve 72. The inner valve 71 is provided on the outer periphery of the input shaft 63. The outer valve 72 is provided between the outer periphery of the inner valve 71 and the inner periphery of the valve housing 61. The outer valve 72 is slidably rotatable with respect to the outer periphery of the inner valve 71 and the inner periphery of the valve housing 61. The outer valve 72 is coupled to the output shaft 64 in the axial direction. As a connection means between the outer valve 72 and the output shaft 64, for example, a pin 73 may be used.

  The torsion bar 65 is twisted according to the steering torque applied to the input shaft 63 through the steering wheel 13, and the positional relationship (relative angle) in the rotational direction between the inner valve 71 and the outer valve 72 changes with the twist. . The flow path of the hydraulic oil supplied from the pump port 32a is switched between the first cylinder port 32b and the second cylinder port 32c using the change in the positional relationship. Further, a throttle is formed according to the difference between the rotation angle of the inner valve 71 and the rotation angle of the outer valve 72 (valve operating angle), so that it is supplied to the first cylinder port 32b or the second cylinder port 32c. The flow rate of hydraulic oil is adjusted.

<Torque sensor>
The torque sensor 21 is a so-called differential transformer type torque sensor, and includes a first cylinder portion 81, a second cylinder portion 82, and two coils 83 and 84. The first cylinder portion 81 is disposed on the steering wheel 13 side (the upper side in the drawing). The second cylindrical portion 82 is disposed on the speed reducer 23 side, that is, on the pinion shaft 15 side (lower side in the figure).

  The first cylinder portion 81 is fixed in a state of being fitted on the outer periphery of the input shaft 63. The outer peripheral surface of the first cylindrical portion 81 can slide and rotate with respect to the inner peripheral surface of the end stopper 62. A plurality of notches (recesses) 81a are provided at equal intervals in the circumferential direction at the end (lower end in the figure) of the first cylinder 81 on the second cylinder 82 side.

  The second cylinder part 82 is provided between the first cylinder part 81 and the outer valve 72. The second cylinder portion 82 is inserted through the outer periphery of the input shaft 63. The inner peripheral surface of the second cylindrical portion 82 can slide and rotate with respect to the outer peripheral surface of the input shaft 63, and the outer peripheral surface of the second cylindrical portion 82 can slide with respect to the inner peripheral surface of the end stopper 62. The second cylindrical portion 82 is fixed in a state in which a part thereof is fitted to the end portion of the outer valve 72 in the axial direction. The end (the lower end in the figure) on the side where the notch 81a of the first cylinder 81 is formed is inserted slightly into the second cylinder 82 in a non-contact state. A plurality of notches (concave portions) 82a are provided at equal intervals in the circumferential direction at the end portion (upper end portion in the drawing) of the second tube portion 82 on the first tube portion 81 side. Each notch 82a faces each notch 81a in the radial direction of the second cylindrical portion 82.

  The two coils 83 and 84 are provided on the outer peripheral surface of the end stopper 62 (more precisely, its small diameter portion). These coils 83 and 84 are arranged at intervals in the axial direction of the end stopper 62. The coil 83 is provided at a position corresponding to the first cylindrical portion 81, and the coil 84 is provided at a position corresponding to the notches 81a and 82a. A gap is formed between the two coils 83 and 84 and the inner peripheral surface of the valve housing 61. AC power is supplied to the coil 83.

  Now, when a steering torque is applied to the input shaft 63 through steering, the torsion bar 65 connected between the input and output shafts is twisted, whereby the first cylindrical portion 81 and the second cylindrical portion 82 are relatively rotated. With the relative rotation, the overlap amount (opposite area in the radial direction) between the notch 81a and the notch 82a changes. The induced electromotive force generated in the coil 84 changes (increases / decreases) in accordance with the change in the overlap amount. The induced electromotive force generated in the coil 84 is taken out as an electric signal Sτ corresponding to the steering torque.

  In the valve housing 61, a ring member 85 is provided at a position on the control valve 32 side of the coil 84 located on the control valve 32 side of the two coils 83 and 84. The ring member 85 is interposed between the outer peripheral surface of the end stopper 62 and the inner peripheral surface of the valve housing 61. An O-ring 86 is provided as a sealing material on the inner peripheral surface of the ring member 85 (surface that contacts the outer peripheral surface of the end stopper 62), and a sealing material is provided on the outer peripheral surface of the ring member 85 (surface that contacts the inner peripheral surface of the valve housing 61). An O-ring 87 is provided. These O-rings 86 and 87 ensure liquid tightness between the ring member 85 and the end stopper 62 and between the ring member 85 and the valve housing 61, respectively. For this reason, it is prevented that hydraulic oil contacts the coils 83 and 84. Incidentally, O-rings 88 and 89 are provided as sealing materials on the inner peripheral surface and the outer peripheral surface of the second cylindrical portion 82, respectively. These O-rings 88 and 89 ensure liquid tightness between the second cylindrical portion 82 and the input shaft 63 and between the second cylindrical portion 82 and the end stopper 62, respectively.

<Electrical configuration>
Next, an electrical configuration of the power steering apparatus will be described.
As shown in FIG. 3, the torque sensor 21, the pump ECU 33 c, and the electric valve 57 are connected to the ECU 24. The assist motor 22 is connected to the ECU 24 via a motor driver (PWM inverter) 91. A relay 93 (motor terminal relay) is provided in the power supply path 92 between the motor driver 91 and the assist motor 22.

  The ECU 24 calculates a target assist amount (target assist torque) based on at least the detection result of the torque sensor 21, that is, the steering torque τ. The ECU 24 controls the driving power (current amount) supplied to the assist motor 22 by controlling the switching of the motor driver 91 based on the target assist amount. The ECU 24 controls the opening and closing of the relay 93, and normally maintains the relay 93 in a closed state. The ECU 24 also controls the opening and closing of the electric valve 57, and normally maintains the electric valve 57 in a closed state.

<Abnormality detection function>
The ECU 24 has an EPS 20 abnormality detection function.
The ECU 24 detects, for example, the following (A) or (B) state as an abnormality in the EPS 20. The ECU 24 opens (OFF) the relay 93 when an abnormality of the EPS 20 is detected.

(A) Abnormality of the torque sensor 21 (electric signal Sτ).
When the value of the electrical signal Sτ deviates from a value that can be taken at normal time, the deviated electrical signal Sτ is abnormal.

(B) The assist motor 22 is abnormal.
The ECU 24 detects a current supplied to the assist motor 22 through a current sensor (not shown). When the current value supplied to the assist motor 22 is zero even though the duty ratio of the PWM control signal for the motor driver 91 is set to 100%, an abnormality such as disconnection occurs in the assist motor 22 or its power supply path. ing.

Further, the ECU 24 detects an abnormality of the HPS 30 through the pump ECU 33c. The ECU 24 opens the electric valve 57 when an abnormality of the HPS 30 is detected.
For example, the pump ECU 33c detects the following state (C) as an abnormality of the HPS 30. The pump ECU 33c generates an abnormality signal Sp when an abnormality of HPS is detected. Based on this abnormality signal Sp, the ECU 24 detects an abnormality in the HPS 30.

(C) Abnormality of the pump body 33a.
The pump ECU 33c detects a current supplied to the pump motor 33b through a current sensor (not shown). The pump ECU 33c detects the rotation speed of the pump body 33a through a rotation speed sensor (not shown). The pump ECU 33c detects an abnormality in the pump body 33a and the like by utilizing the fact that a proportional relationship is established between the value of the current supplied to the pump motor 33b and the rotation speed of the pump body 33a. For example, when the rotation speed of the pump body 33a is small relative to the value of the current supplied to the pump motor 33b, the pump body 33a may not operate normally. There is also concern about clogging of hydraulic piping.

<Operation of power steering device>
Next, the operation of the power steering apparatus 11 will be described.
First, when both EPS 20 and HPS 30 are normal, steering may be assisted by each of EPS 20 and HPS 30. The assist amount by the EPS 20 is determined by the steering torque τ acquired through the torque sensor 21. The assist amount by the HPS 30 is determined by the difference between the rotation angle of the inner valve 71 and the rotation angle of the outer valve 72 in the control valve 32. When the EPS 20 and the HPS 30 are used in combination, the steering is assisted by the total assist amount of the assist amount by the EPS 20 and the assist amount by the HPS 30.

  For example, the pump ECU 33 c can perform the following steering assist by adjusting the discharge amount of the motor-driven pump 33 based on a command from the ECU 24. That is, from the viewpoint of energy saving, the steering is assisted by the EPS 20 as much as possible. When the assist is insufficient even with the maximum capacity of the EPS 20, the assist amount by the HPS 30 is increased according to the shortage. In addition, when the amount of assist required is small, such as when traveling at high speed, the assist may be performed only with the EPS 20 and not with the HPS 30. Through cooperation between the EPS 20 and the HPS 30, it is possible to execute more advanced assist control.

  Next, when an abnormality (failure) occurs in the EPS 20, the assist amount by the EPS 20 becomes zero. That is, the assist amount of the HPS 30 becomes the total assist amount as it is. Further, when an abnormality occurs in the EPS 20, the relay 93 is opened, so that the power supply path 92 to the assist motor 22 is interrupted. Thereby, the assist motor 22 shifts to the power generation mode, that is, the power generation action of the assist motor 22 is suppressed. The rotation resistance (regenerative resistance) during power generation in the assist motor 22 is suppressed from acting as a braking force for steering.

  Next, when an abnormality (failure) occurs in the HPS 30, the assist amount by the HPS 30 becomes zero. That is, the assist amount of the EPS 20 becomes the total assist amount as it is. Further, when an abnormality occurs in the HPS 30, the electric valve 57 is opened. As a result, the first supply / discharge pipe 52 and the second supply / discharge pipe 53 communicate with each other via the bypass pipe 56. For example, when the portion on the control valve 32 side of the connecting point of the bypass pipe 56 in the first or second supply / exhaust pipe 52, 53 is clogged, the first or second oil chamber 41a, It is conceivable that there is no escape space for the hydraulic oil inside 41b. In this regard, by opening the electric valve 57, the hydraulic oil inside the first or second oil chamber 41a, 41b can escape to the second or first supply / discharge pipe 53, 52 through the bypass pipe 56. . For this reason, the hydraulic resistance resulting from the hydraulic oil inside the first or second oil chamber 41a, 41b that has lost its escape is reduced.

<Operation of power steering device>
Next, the operation of the power steering device 11 will be described.
The torque sensor 21 and the control valve 32 share the same torsion bar 65. Further, in the steering torque τ transmission path (steering shaft 12 → pinion shaft 15 → rack shaft 16), the assist motor 22 is provided on the pinion shaft 15 downstream of the torsion bar 65 when the steering wheel 13 side is set upstream. ing. For this reason, the assist force by the EPS 20 (assist motor 22) is not applied to the torsion bar 65. Therefore, even when the EPS 20 has failed, the same steering feel as before the failure can be obtained. This is because the responsiveness of the steering wheel 13 depends on the torsion bar 65 whether the EPS 20 is normal or has failed.

  In addition, it is possible to improve the driver's steering feel or steering stability as compared with the case where the torque sensor 21 and the control valve 32 are separated and each has a torsion bar separately. When two torsion bars are provided in the transmission path of the steering torque τ, the torsion bars are twisted cumulatively, so that a soft steering feel can be easily obtained. For this reason, there is a concern that there is a slight lack of response when performing steady steering. As in this example, the torque sensor 21 and the control valve 32 share the same torsion bar 65, so that a firm steering feel can be obtained.

<Effect of Embodiment>
Therefore, according to the present embodiment, the following effects can be obtained.
(1) In the transmission route of the steering torque τ, the assist motor 22 is provided downstream of the torsion bar 65 when the steering wheel 13 side is upstream. For this reason, the assist force by the EPS 20 is not applied to the torsion bar 65. Therefore, even when the EPS 20 has failed, the same steering feel as before the failure can be obtained.

  (2) The torque sensor 21 and the control valve 32 share the same torsion bar 65. For this reason, it is easy to ensure a firm steering feel. Further, since a single torsion bar 65 may be provided, it contributes to a reduction in the number of parts.

  (3) Even when either one of the EPS 20 and the HPS 30 is lost, the steering assist can be continued by the other normal HPS 30 and the EPS 20. A highly independent dual system can be constructed.

  (4) When the EPS 20 or the HPS 30 fails, the following operation is performed so that the failed EPS 20 or the HPS 30 does not become a steering resistance (steering load). That is, the relay 93 is opened when the EPS 20 fails, and the electric valve 57 is opened when the HPS 30 fails. Thereby, it is possible to minimize the shortage of assist force as a whole by maximizing the assist capability of the normal HPS 30 or EPS 20.

  (5) A motor-driven pump 33 is employed as the hydraulic pressure source of the HPS 30. For this reason, the stable assist force by HPS30 is obtained. In addition, the fuel consumption is reduced and energy is saved as compared with the case where an oil pump using the rotation of the engine is employed.

<Other embodiments>
In addition, you may implement the said embodiment as follows.
The EPS 20, and more precisely, the assist motor 22 and the speed reducer 23 may be installed anywhere as long as they are downstream of the torsion bar 65 in the transmission path of the steering torque τ. For example, the assist motor 22 and the speed reducer 23 may be provided downstream of the pinion shaft 15. Specifically, it is as follows.

  As shown in FIG. 4, rack teeth 16 b are also provided on a portion of the rack shaft 16 opposite to the rack teeth 16 a with which the pinion shaft 15 meshes. Then, a pinion shaft 101 that meshes with the rack teeth 16b is provided. An assist motor 22 is connected to the pinion shaft 101 via a speed reducer 23. Even if it does in this way, the effect similar to this Embodiment is acquired.

In this example, the motor drive pump 33 is employed as the hydraulic pressure source of the HPS 30, but an engine drive pump driven by the engine may be employed.
As shown in FIG. 5, for example, the engine drive pump 102 may be connected to an engine (internal combustion engine) 104 via a clutch 103. In a state where the clutch 103 is connected, the rotation of the engine 104 is transmitted to the engine drive pump 102 (more precisely, its drive shaft). The engine drive pump 102 sucks the hydraulic oil stored in the oil tank 34, and discharges it by increasing the pressure of the sucked hydraulic oil. The hydraulic oil discharged from the engine drive pump 102 is supplied to the hydraulic actuator 31 via the control valve 32.

  In this example, when the EPS 20 fails, the relay 93 is opened, and when the HPS 30 fails, the electric valve 57 is opened to reduce the steering resistance that may be caused by the failed EPS 20 or HPS 30. However, the relay 93 and the electric valve 57 are not necessarily provided. For example, only one of the relay 93 and the electric valve 57 may be provided, or both may not be provided. Even if it does in this way, the effect of (1)-(3) of this example can be acquired.

<Other technical ideas>
Next, the technical idea that can be grasped from the above embodiment will be added below.
(A) The pump is a motor-driven pump.

  (B) The pump is an engine-driven pump.

  DESCRIPTION OF SYMBOLS 11 ... Power steering apparatus, 15 ... Pinion shaft, 16 ... Rack axis | shaft (steering axis), 20 ... Electric power steering, 21 ... Torque sensor, 22 ... Assist motor (electric actuator), 24 ... ECU (control apparatus), 30 ... hydraulic power steering, 31 ... hydraulic actuator, 32 ... control valve, 33 ... motor-driven pump, 41a ... first oil chamber, 41b ... second oil chamber, 52 ... first supply / discharge pipe, 53 ... second , 57 ... electric valve, 65 ... torsion bar, 93 ... relay.

Claims (4)

Electric power having a torque sensor that generates an electric signal corresponding to the torsion amount of a torsion bar to which steering torque is applied, and an electric actuator that generates a first steering assist force based on the electric signal generated by the torque sensor Steering,
A hydraulic actuator that generates a second steering assist force according to the flow rate of hydraulic oil supplied from the pump, and a twist amount of the torsion bar that shares the hydraulic oil supply and discharge with the torque sensor. A hydraulic power steering having a control valve for controlling,
The electric actuator is a power steering device provided downstream of the torsion bar in a steering torque transmission path. The power steering apparatus according to claim 1, wherein
The transmission path includes a pinion shaft that rotates when steering torque is transmitted through the torsion bar, and a steered shaft that linearly moves with the rotation of the pinion shaft,
The power steering device, wherein the electric actuator is connected to the pinion shaft or the steered shaft that is downstream of the torsion bar in the transmission path. In the power steering device according to claim 1 or 2,
The electric actuator is a motor that rotates by feeding power,
A relay for opening and closing a power supply path to the electric actuator;
And a control device that controls opening and closing of the relay. The control device is a power steering device that opens the relay when the electric power steering fails. In the power steering device according to any one of claims 1 to 3,
The hydraulic actuator is a hydraulic cylinder that applies a second steering assist force to the steered shaft by using a differential pressure generated in two oil chambers that are selectively switched between supply and discharge of hydraulic oil through the control valve. There,
An electric valve that opens and closes between a first supply and discharge pipe and a second supply and discharge pipe respectively connected between the control valve and the two oil chambers;
And a control device that controls opening and closing of the electric valve. The control device is a power steering device that opens the electric valve when the hydraulic power steering fails.