JP2594904Y2 - Steering force control device for power steering device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering force control device for a vehicle power steering device.

[0002]

2. Description of the Related Art Conventionally, a steering force control device for a power steering device is disclosed in Japanese Patent Application Laid-Open No. 63-188570. In the steering force control apparatus shown in FIG. 16 of the publication, as shown in FIG. 3, a pair of supply paths L ₁ , L connecting the pump 1 and the left and right oil chambers 3a, 3b of the cylinder 3 are provided.
₂ is provided with variable throttles 1R, 1L constituting a first variable throttle, and a pair of discharge passages L ₃ , L connecting left and right oil chambers 3a, 3b of the cylinder 3 and the reservoir tank 2.
₄ , variable apertures 2R and 2L constituting a second variable aperture are provided. Said pair of variable throttle 2R of the pair of discharge path L _3, L _4, upstream of 2L is variable aperture 3R, a 3L provided which constitutes the third variable restrictor, the pair of the variable throttle 3R, than 3L variable aperture 4R, a 4L are provided to the pair of supply paths L _1, L ₂ side. The pair of variable diaphragms 2R,
2L and a pair of the variable throttle 3R, communicated via the bypass passage L ₅ between the pair of discharge path L _3, L ₄ in between the 3L, to the bypass channel L _5, the diaphragm according to the vehicle speed An externally controlled variable stop 5 whose area is controlled is provided.

[0003] An externally controlled variable throttle 5 according to the vehicle speed.
When the steering wheel 11 is
For example, when the steering is turned to the right, the hydraulic oil from the pump 1 is supplied to the left chamber 3b of the cylinder 3, and
The hydraulic oil is discharged to the reservoir tank 2 while reducing the pressure in three stages by the variable throttles 4R, 3R, and 5, so that the pressure drop is reduced to a level that does not cause cavitation.

[0004]

However, when the vehicle is at a standstill and the steering wheel 11 is not turned and the steering wheel is in a neutral position, the hydraulic oil supplied from the pump 1 is supplied to the pair of flow paths L ₁ , L ₃ ; ₂ and L ₄ , and each of the four variable throttles 1 L, 4 R, 3 L,
2R; 1R, 4L, 3R, and 2L, the hydraulic oil does not easily flow, and the pressure loss increases. As a result, a load is applied to the pump 1 and power loss is increased, leading to deterioration of fuel efficiency.

In view of this, it is conceivable to increase the aperture area of the four variable apertures when the steering is neutral, but it is necessary to make the aperture area not too large. If it is too large, there will be a delay in starting the steering assist when turning the steering. It is difficult to increase the aperture areas of the four variable apertures only when the steering is not turned off so that such a delay in steering assist does not occur. Therefore, it is inevitable that the above-mentioned pressure loss occurs.

The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a power steering apparatus capable of reducing pressure loss when steering is neutral and reliably preventing cavitation. It is to provide a steering force control device.

[0007]

In order to achieve the above object, the present invention provides a pair of supply passages connecting a pump and left and right oil chambers of a cylinder, a pair of supply passages for the left and right oil chambers of the cylinder, and a reservoir tank. A first variable throttle and a second variable throttle responsive to a steering torque are provided in the pair of supply paths and the pair of discharge paths, respectively, and at least the pair of first and second variable throttles are provided. A third variable throttle responsive to the steering torque is provided upstream of the second variable throttle, and the third variable throttle starts functioning as a throttle near a point where the second variable throttle closes. In the steering force control device for a power steering device configured as described above, the steering force control device may be disposed between the pair of third variable throttles and the first or second variable throttle immediately downstream of the third variable throttle. The pair of flow paths are communicated via a bypass flow path, and The external control variable throttle provided in the bypass flow path, is provided with a respective aperture between the external control variable throttle and said pair of flow paths.

[0008]

According to the above construction, when no steering assist force is generated (when the steering is neutral), all of the variable throttles are fully opened, and the operating oil from the pump is equally divided into the pair of flow passages, and thus the reservoir is opened. It discharges to the tank and does not generate a differential pressure between the left and right oil chambers of the cylinder, and there is no flow in the bypass flow path provided with an externally controlled variable throttle. It is possible to make the flow of the hydraulic oil smoother.

Further, when a large steering assist force is required, for example, when steering is turned off, the external control variable throttle is fully closed to close the bypass passage, and the small steering torque is used to close the bypass passage. While closing the first variable throttle, the second and third variable throttles in the other flow path are also closed, and by these throttles, almost all of the hydraulic oil from the pump is supplied to one oil chamber of the cylinder. At the same time, the hydraulic oil in the other oil chamber of the cylinder is discharged to a reservoir tank. At this time, the pressure is reduced in two stages by the second and third variable throttles, so that the pressure drop at the second variable throttle is reduced to a level that does not cause cavitation.

Further, when the steering assist force is not so required during high-speed running of the vehicle, the external control variable throttle is opened to open the bypass flow passage, and the same as when the steering is turned off, the one of the flow passages is opened. The throttle areas of the first variable throttle and the second and third variable throttles in the other flow path are closed in accordance with the steering torque, and hydraulic oil from the pump is supplied to one oil chamber of the cylinder. Is discharged to the reservoir tank while being throttled by the throttle provided in the bypass flow passage and the externally controlled variable throttle. At this time, the pressure is reduced in multiple stages by a throttle provided in the bypass flow passage and an externally controlled variable throttle, so that the pressure drop at each throttle is reduced to such an extent that cavitation does not occur.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a hydraulic bridge circuit diagram schematically showing a steering force control device of a power steering device, and FIG. 2 is a longitudinal sectional view specifically showing the steering force control device.

In these figures, 1 is a pump, 2 is a reservoir tank, 3 is a cylinder, 4 is a rotary valve, and 5 is a solenoid valve which constitutes an externally controlled variable throttle.

The rotary valve 4 includes a valve body 6
And a valve shaft 7 in a valve housing 8. A valve shaft 7 is fitted to the inner periphery of the valve body 6 so as to be relatively rotatable, and a steering wheel (not shown) is connected to one end of the valve shaft 7. Further, one end of a pinion shaft 9 is connected to one end of the valve body 6, and the one end and one end of the valve shaft 7 are connected via a torsion bar 10.

The rotary valve 4 has a hydraulic bridge circuit A in which four flow paths including a pair of supply paths L ₁ and L ₂ and a pair of discharge paths L ₃ and L ₄ are connected in a ring shape. . The pump 1 is connected to a connection point between the supply paths L ₁ and L _{2, and} the reservoir tank 2 is connected to a connection point between the discharge paths L ₃ and L ₄ . Further, the supply path L ₁
Right chamber 3a of the cylinder 3 to a connection point between the discharge passage L ₄ are connected, the left chamber 3b of the supply passage L ₂ and the connection point of the discharge passage L ₃ the cylinder 3 is connected to.

The pair of supply paths L ₁ and L ₂ are provided with first variable throttles 1 R and 1 L respectively responsive to a steering torque, and the pair of discharge paths L ₃ and L ₄ are provided with a steering torque. The second variable diaphragms 2R and 2L are provided in response to the above.

A third variable throttle 3R, 3L responsive to a steering torque is provided upstream of the pair of second variable throttles 2R, 2L of the pair of discharge paths L ₃ , L ₄ .

The first variable throttles 1R, 1L and the second variable throttles 2R, 2L respond to steering torque and can be closed with a small steering torque. Further, the third variable throttles 3R, 3L start functioning as throttles near the point where the first variable throttles 1R, 1L close in response to the steering torque, and are configured to close with a large steering torque. Have been. The variable apertures 1R, 1L,
The grooves 2R, 2L, 3R, and 3L are adjacent to the respective grooves and lands that are formed on the respective peripheral surfaces of the valve body 6 and the valve shaft 7 so as to extend in the axial direction and are separated by lands. It consists of an edge. When the steering wheel 11 connected to one end of the valve shaft 7 is turned, for example, rightward with respect to the steering resistance acting on the pinion shaft 9, the torsion bar 10 is twisted and the valve The shaft 7 is relatively rotated, and the variable apertures 1R, 3R, 2R are closed, and conversely, the variable apertures 1L, 3L, 2L are opened.

The pair of third variable apertures 3R, 3L and the second variable aperture 2 immediately downstream of the third variable aperture 3
The pair of discharge passages L ₃ and L ₄ are communicated between R and 2L via a bypass passage L ₅ .

[0020] The bypass channel and L ₅ provided outside of the valve housing 8, the said bypass passage L ₅ is provided with the solenoid valve 5. The solenoid valve 5 has a configuration in which the first variable apertures 1R and 1L and the second variable apertures 2R and 2L have their aperture areas controlled independently of the vehicle speed. Between the solenoid valve 5 and the pair of discharge paths L ₃ , L ₄ , fixed throttles 12 incorporated in the valve housing 8 are provided as shown in FIG.

According to the above configuration, when the vehicle is at a standstill and the steering wheel 11 is not turned and the steering is neutral, all of the variable throttles 1R, 1L to 3R, 3L are fully open. Therefore, the operating oil from the pump 1 is equally divided into the pair of flow paths L ₁ , L ₄ ; L ₂ , L ₃ and discharged to the reservoir tank 2. Therefore, no differential pressure is generated between the left and right oil chambers 3a, 3b of the cylinder 3, so that no steering assist force is generated by the cylinder 3, and the steered wheels maintain a straight running state. Also, the external control variable throttle 5 is a fully closed state, the flow in the bypass passage L ₅ do not occur, each flow path L _1, L _4; variable throttle of the hydraulic fluid passes at L _2, L ₃ The number is smaller than before, and the flow of the hydraulic oil is smooth.

When the steering wheel 11 is turned to the right, for example, while the vehicle is stopped, the variable throttles 1R, 3R, 2R are closed according to the steering torque at that time, and the supply path L ₁ is turned on.
The variable stop 1R variable throttle 2R of the discharge passage L ₃ will be fully closed by a small steering torque, the variable throttle 3 of the discharge path L ₃
R reduces the aperture area. On the other hand, the variable aperture 1L, 3
L and 2L maintain the fully open state. Further, a bypass passage which L ₅ closed externally controlled variable throttle 5 is fully closed. For this reason,
Almost all of the hydraulic oil from the pump 1 is supplied to the left chamber 3 of the cylinder 3
b, and the hydraulic oil in the right chamber 3 a of the cylinder 3 is discharged to the reservoir tank 2. Therefore, the maximum steering assist force can be obtained with a relatively small steering torque,
As a result, a light steering feeling is obtained.

[0023] When Ri据切to the steering of the right, the pressure drop is variable aperture 3R across the discharge path L _3, is divided in the 2R, variable aperture 3R squeezing especially in the vicinity of the point where the variable throttle 2R Kiru closed , The pressure drop at the variable throttle 2R is reduced to such an extent that cavitation does not occur, and no fluid noise is generated.

When the vehicle is traveling at high speed and constant speed,
And the relatively large aperture area of the external control variable throttle 5 in accordance with the vehicle speed, the bypass flow passage L ₅ in the open position. In such a state, when the steering wheel 11 is not turned and the steering is neutral, the variable apertures 1R, 1L to 3L are set in the same manner as when the steering is neutral in the vehicle stopped state.
Since R and 3L are fully opened, the hydraulic oil from the pump 1 is equally divided into a pair of flow paths L ₁ and L ₄ ; L ₂ and L _3, and the left and right oil chambers 3 a and 3 b of the cylinder 3. No differential pressure occurs between them. Therefore, no steering assist force is generated by the cylinder 3, and the steered wheels maintain the straight traveling state.

Further, when the steering wheel 11 is turned to the right while the vehicle is running at a high speed, the variable throttles 1R, 3R and 2R are closed in accordance with the steering torque in the same manner as when the steering is turned to the right. Go, variable aperture 1L, 3
L and 2L maintain the fully open state, but the external control variable throttle 5
It was opened bypass passage L ₅ open, the bypass flow passage L
₅ through a pair of discharge passage L _3, since L ₄ are in communication, the hydraulic fluid from the pump 1 is supplied to the left chamber 3b of the cylinder 3, a portion of the hydraulic oil two fixed throttle 12 and the outer The hydraulic oil in the right chamber 3a of the cylinder 3 is also discharged to the reservoir tank 2 while being discharged to the reservoir tank 2 while being throttled by the controllable restrictor 5. Therefore, a minimum steering assist force is obtained, and a heavy steering feeling is obtained.

[0026] During the steering of right turn in a high-speed running of the vehicle, the pressure drop across the bypass channel which L ₅ 2
The three fixed throttles 12 and the externally controlled variable throttle 5 distribute the pressure, and the throttles 5 and 12 reduce the pressure in three stages. The pressure drop at each throttle is reduced to such an extent that cavitation does not occur. No fluid noise is generated.

[0027] In this embodiment, the variable aperture 3R to the discharge path L _3, but each provided a variable throttle 3L to discharge passage L _4,
The variable aperture 3R upstream of the variable throttle 1R supply channel L _1, a variable aperture 3L may be respectively provided on the upstream side of the variable throttle 1L feed path L _2.

The variable diaphragms 3R and 3L and the fixed diaphragm 1
Although two pairs are provided for each pair, two or more pairs may be provided.

Further, the fixed throttle 12 is mounted on the valve housing 8.
The hole for assembling the throttle formed in the valve housing 8 can be made simple and small in diameter.
It is preferable to use a variable aperture in place of the fixed aperture 12.

[0030]

As described above, this invention comprises a pair of supply paths connecting the pump and the left and right oil chambers of the cylinder, and a pair of discharge paths connecting the left and right oil chambers of the cylinder and the reservoir tank. A first variable throttle and a second variable throttle responsive to a steering torque are provided in the pair of supply paths and the pair of discharge paths, respectively, at least upstream of the pair of second variable throttles. A power steering device configured to provide a third variable throttle responsive to the steering torque, and to start functioning as a throttle near the point where the second variable throttle closes. In the steering force control device of
Communicating between the pair of flow paths via a bypass flow path between the pair of third variable throttles and the first or second variable throttle immediately downstream of the third variable throttle; Since an externally controlled variable throttle is provided in the bypass flow path, and the respective throttles are provided between the externally controlled variable throttle and the pair of flow paths, the supply pressure to the cylinder is determined by the steering torque and the throttle area of the externally controlled variable throttle. Can be controlled in a wide range, and a desired steering assist force can be obtained by the cylinder, so that the controllability of the steering assist force is improved.

When the vehicle is in a straight running state without generating steering assist force (when the steering is neutral).
In addition, since there is no flow in the bypass flow path provided with the externally controlled variable throttle, the number of variable throttles through which the hydraulic oil passes can be reduced as compared with the conventional case, thereby allowing the hydraulic oil to flow smoothly,
Since the pressure loss can be made smaller than before, the load on the pump can be reduced, and the fuel efficiency can be improved.

Further, when the steering is turned off, the second,
The pressure is reduced in two stages by the third variable throttle to reduce the pressure drop at the second variable throttle to a level that does not cause cavitation, and is provided in the bypass passage when the steering is turned off during high-speed running of the vehicle. The pressure is reduced in multiple stages by the provided throttle and the externally controlled variable throttle, and the pressure drop at each throttle can be reduced to such an extent that cavitation does not occur, so that the generation of fluid noise can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a hydraulic bridge circuit diagram schematically illustrating a steering force control device of a power steering device according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view specifically showing the steering force control device.

FIG. 3 is a hydraulic bridge circuit diagram corresponding to FIG. 1 and showing a steering force control device of a power steering device according to a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pump 2 Reservoir tank 3 Cylinder 5 Solenoid valve (externally controlled variable throttle) L ₁ , L ₂ supply path (flow path) L ₃ , L ₄ discharge path (flow path) L ₅ bypass flow path 1 R, 1 L First variable Aperture 2R, 2L Second variable aperture 3R, 3L Third variable aperture 12 Fixed aperture (aperture)

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B62D 5/083 B62D 6/00-6/02

Claims (1)

(57) [Scope of request for utility model registration] 1. A pair of supply paths for connecting a pump and left and right oil chambers of a cylinder, and a pair of discharge paths for connecting left and right oil chambers of the cylinder and a reservoir tank. A first variable throttle and a second variable throttle responsive to a steering torque are provided in a pair of discharge paths, respectively, and at least upstream of the pair of second variable throttles is responsive to the steering torque. A third variable throttle, wherein the third variable throttle is configured to start functioning as a throttle near a point where the second variable throttle closes; A pair of third variable throttles and the first or second variable throttle immediately downstream of the third variable throttle, communicating between the pair of flow paths via a bypass flow path; An externally controlled variable throttle is provided in the bypass passage, and the externally controlled variable throttle is provided. A steering force control device for a power steering device, wherein throttles are respectively provided between the first and second flow paths.