JPH10250608A - Hydraulic power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an oil seal or the like from breakage certainly even in the case where the liquid pressure in a hydraulic cylinder rises excessively with an excessive input of turbulence. SOLUTION: A hydraulic control valve 10 of a hydraulic power steering device is structured so that a ring-shaped groove 20B is coupled with a hydraulic pump through a check valve 40, between the understream of the check valve 40 (on the side with ring-shaped groove 20B), a communication path 42 is formed to put the two members in communication with each other, and there also a relief valve 44 is installed. The relief valve 44 opens with a pressure exceeding a specified level to flow the pressure oil to the side with a return oil hole 19 in the event of a rise of the pressure on the side with the groove 20B (downstream of the check valve 40). Accordingly, even if the turbulence fed from the road surface is excessive, the pressure oil on the side with the groove 20B (downstream of the check valve 40) is relieved with opening of the relief valve 44, which prevents breakage of an oil seal of power cylinder, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydraulic power steering device applied to a vehicle such as an automobile.

[0002]

2. Description of the Related Art In a hydraulic power steering device (hydraulic power steering device) for a vehicle such as an automobile, a hydraulic cylinder for steering a steered wheel and a hydraulic pressure from a hydraulic pump are distributed and controlled based on a steering operation. And a hydraulic control valve for distributing and supplying the hydraulic cylinder to the hydraulic cylinder. A predetermined auxiliary steering force is applied to the steering force of the steering mechanism, and the steering force of the driver is reduced.

[0003] Among such hydraulic power steering devices, there has been proposed a power steering device having a check valve provided between a hydraulic pump and a hydraulic control valve (Japanese Utility Model Application Laid-Open No. 62-1224069). No.).

In the power steering apparatus disclosed in this publication, only the flow of the oil liquid from the hydraulic pump to the hydraulic control valve is permitted by the check valve. As a result, even when the rack bar is moved due to disturbance input from the road surface and kickback is likely to occur,
This can be prevented from being transmitted to the steering wheel side, and the steering feeling does not deteriorate.

[0005] However, when the disturbance input from the road surface is excessive (for example, when the vehicle rides on a curb), the hydraulic pressure in the hydraulic cylinder greatly increases, and thus, for example, the oil seal of the hydraulic cylinder is damaged. Measures were needed to prevent damage.

In this case, simply forming the components of the hydraulic steering system with high strength increases the size and weight of the device and increases the cost.

[0007]

SUMMARY OF THE INVENTION In consideration of the above facts, the present invention ensures that even if the hydraulic pressure in the hydraulic cylinder rises excessively due to excessive disturbance input from the road surface, the oil seal and the like can be reliably damaged. It is an object of the present invention to provide a hydraulic power steering device which can prevent the above problem and can provide the hydraulic power steering device with a simple structure at a low cost.

[0008]

According to a first aspect of the present invention, there is provided a hydraulic power steering apparatus having a hydraulic control valve disposed in the middle of a steering mechanism for controlling hydraulic oil from a hydraulic source. In a hydraulic power steering device controlled by a valve and distributed to a hydraulic cylinder, the hydraulic power steering device is provided in an oil passage communicating the hydraulic source and a hydraulic control valve, and is provided from the hydraulic source side to the hydraulic control valve side. A check valve allowing only the flow of pressure oil, and one end communicating with an oil passage on the side of the hydraulic control valve downstream of the check valve,
A communication path having the other end communicated with a discharge path from the hydraulic control valve; and a relief valve provided on the communication path, the valve being opened at a predetermined pressure or higher to discharge pressure oil to the discharge path. It is characterized by:

In the hydraulic power steering apparatus according to the first aspect, when the steering wheel is operated, the steered wheels are steered by the steering mechanism, and the hydraulic control valve is actuated accordingly, so that the hydraulic power is transmitted from the hydraulic power source. The pressure oil is controlled and distributed to and supplied to the hydraulic cylinder, and a steering assist force according to the steering torque is applied.

Here, a check valve is provided in an oil passage communicating the hydraulic source and the hydraulic control valve, and the check valve allows only the flow of the pressure oil from the hydraulic source to the hydraulic control valve. Therefore, even if kickback is likely to occur in the steering mechanism due to disturbance input from the road surface, this can be prevented from being transmitted to the steering wheel side, and the steering feeling does not deteriorate .

Furthermore, if the disturbance input from the road surface is excessive (for example, when the vehicle rides on a curbstone), the hydraulic pressure in the hydraulic cylinder rises greatly, and The hydraulic pressure on the control valve side rises significantly.
Here, since the communication path is connected to the oil passage on the side of the hydraulic control valve downstream of the check valve and the relief valve is provided, the inside of the hydraulic cylinder (the downstream side of the check valve, that is, the hydraulic control valve When the fluid pressure on the side (2) rises above a predetermined value, the relief valve is opened and the pressure oil is released to the discharge path. Therefore, for example, the oil seal of the hydraulic cylinder is prevented from being damaged.

As described above, in the hydraulic power steering apparatus according to the first aspect, even if the hydraulic pressure in the hydraulic cylinder rises excessively due to an excessive disturbance input from the road surface, the oil seal and the like can be used. Breakage can be reliably prevented, and this can be provided at a low cost with a simple structure.

According to a second aspect of the present invention, in the hydraulic power steering device according to the first aspect, the communication path and the relief valve are provided in a housing of the hydraulic control valve. It is characterized by.

In the hydraulic power steering apparatus according to the second aspect, the communication path and the relief valve communicating with the oil path on the side of the hydraulic control valve downstream of the check valve are provided in the housing of the hydraulic control valve. Therefore, the size of the device can be reduced. Further, as the hydraulic source, a hydraulic pump having a pressure setting valve is generally used, but by adopting the above configuration, the pressure setting valve provided in the hydraulic pump as the hydraulic source can be eliminated. Will be possible.

[0015]

FIG. 4 shows the overall configuration of a hydraulic power steering device 60 according to an embodiment of the present invention.

The hydraulic power steering device 60 includes a hydraulic control valve 10 constituting a steering mechanism. As shown in detail in FIG. 1, the hydraulic control valve 10 has a cylindrical valve housing 12, in which a valve sleeve 14 is disposed so as to be relatively rotatable.
The valve sleeve 14 has a cylindrical shape, and is connected to a pinion shaft 15 (output shaft) via a pin 17 so as to be integrally rotatable.

A valve shaft 16 is fitted to the valve sleeve 14 so as to be relatively rotatable. The valve shaft 16 is connected to an input shaft (not shown).

A torsion bar 18 is arranged at the axis of the valve shaft 16. One end of the torsion bar 18 is connected to the input shaft, and the other end is connected to the pinion shaft 15. That is, the input shaft is connected to the pinion shaft 15 via the torsion bar 18, and when the torsion bar 18 is twisted by the turning operation of the steering, the valve sleeve 14 connected to the pinion shaft 15 and the input shaft are connected. Relative to the valve shaft 16 connected to the valve shaft 16.

On the outer peripheral surface of the valve sleeve 14, annular grooves 20A, 20B and 20C are formed at predetermined intervals in the axial direction. The central annular groove 20B is connected to a hydraulic pump 50 via a hydraulic circuit described in detail later, and the axially upper annular groove 20A is connected to, for example, a right oil chamber 54 of a power cylinder (hydraulic cylinder) 52. The annular groove 20 </ b> C on the lower side in the axial direction is connected to, for example, an oil chamber 56 on the left side of the power cylinder 52.

As shown in FIG. 3, on the inner peripheral surface of the valve sleeve 14, land portions 22 and concave grooves 24 extending in the axial direction are formed alternately along the circumferential direction. A pressure oil hole 26 for introducing the oil pressure from the hydraulic pump 50 into the hydraulic control valve 10 through the central annular groove 20 </ b> B is formed through the valve sleeve 14 in the radial direction of the land 22. Also, for example, the oil chamber 5 on the right side of the power cylinder 52
The oil suction / discharge oil hole 28 communicating with one of the annular grooves 20A for sucking and discharging the oil pressure is formed in the concave groove 24, and the other annular groove 2 for sucking and discharging the oil pressure into, for example, the left oil chamber 56 of the power cylinder 52.
A suction / discharge oil hole 30 communicating with OC is formed in the concave groove 24.

On the other hand, on the outer peripheral surface of the valve shaft 16,
The land portions 32 and the concave grooves 34 extending in the axial direction are alternately formed along the circumferential direction. In the valve shaft 16, a communication oil hole 36 for guiding pressure oil to the inner peripheral space 38 of the valve shaft 16 penetrates through a concave groove 34 facing the land portion 22 where the pressure oil hole 26 of the valve sleeve 14 is not formed. Is formed.

As shown in FIG. 2, the valve shaft 16 has a return oil hole 1 for guiding pressure oil to a reservoir tank 58 (see FIG. 4) at a portion not corresponding to the valve sleeve 14.
9 are formed through.

When the torsion bar 18 is not twisted (neutral steering state), the groove 24 of the valve sleeve 14 and the land 32 of the valve shaft 16 are connected to each other in FIG. As shown in the figure, the valve sleeves 1 are opposed to each other in the circumferential direction so that the center portions in the circumferential direction are aligned.
A predetermined gap 39 is formed between the second land portion 22 and the fourth land portion 22. This gap 39 is provided in the valve shaft 1
When the valve sleeve 6 and the valve sleeve 14 rotate relative to each other, it becomes a throttle portion.

The valve housing 12 is provided with a check valve 40 which communicates with the central annular groove 20B of the valve sleeve 14. The check valve 40 is configured to allow only the flow of the pressure oil from the hydraulic pump 50 described below to the annular groove 20B. Further, between the downstream side of the check valve 40 (the side of the annular groove 20B) and the return oil hole 19,
A communication path 42 that connects the two is formed, and a relief valve 44 is provided in the communication path 42. That is, the relief valve 44 is connected to the hydraulic control valve 10 (the valve sleeve 14 and the valve shaft 16) in parallel with the check valve 40 in a hydraulic circuit. This relief valve 44
When the pressure on the side of the annular groove 20B (the pressure oil hole 26 of the valve sleeve 14) (downstream of the check valve 40) rises,
It has a function of opening the valve at a pressure equal to or higher than a predetermined pressure and flowing the pressure oil back to the oil hole 19 side.

The hydraulic control valve 10 having the above configuration is connected to a hydraulic circuit as shown in FIG. In this hydraulic circuit,
The annular groove 20B of the hydraulic control valve 10 (the pressure oil hole 26 of the valve sleeve 14) is connected to the hydraulic pump 50 via the check valve 40, and the return oil hole 19 of the hydraulic control valve 10 is connected to the reservoir tank. 58. Therefore, the oil liquid discharged from the hydraulic pump 50 is supplied to the check valve 4
0, the oil is supplied into the hydraulic control valve 10 (the valve sleeve 14 and the valve shaft 16), and is returned to the reservoir tank 58 through the return oil hole 19.

Next, the operation of the present embodiment will be described. In the hydraulic control valve 10 (hydraulic power steering device 60) having the above configuration, the pressure oil supplied from the hydraulic pump 50 is supplied to the central annular groove 20B via the check valve 40 of the hydraulic control valve 10, Further, the valve sleeve 1 is introduced into the concave groove 34 of the valve shaft 16 through the pressure oil hole 26 and is adjacent to both sides of the concave groove 34 through the gaps 39 on both sides in the circumferential direction.
4 is introduced into the groove 24. Further, the pressure oil introduced into the concave groove 24 is introduced into the concave groove 34 communicated with the communication oil hole 36 via a gap 39 on the opposite side of the concave groove 34 in the concave groove 24, 36, the inner peripheral space 38, and the return oil hole 19 return to the reservoir tank 58.

When the steering is in a neutral state,
Since the torsion bar 18 is not twisted, the opening areas of the gaps 39 located on both circumferential sides of the concave groove 34 facing the pressure oil hole 26 are equal as shown in FIG. At this time, no pressure difference occurs between the concave grooves 24 on both sides of the land portion 22 in which the pressure oil hole 26 is formed, and the pressure in the right oil chamber 54 and the pressure in the left oil chamber 56 of the power cylinder 52 are different. As a result, no assist force is generated in the power cylinder 52.

When the torsion bar 18 is twisted by rotating the steering wheel, the valve sleeve 1
A relative angular displacement occurs between the valve groove 4 and the valve shaft 16, and a difference occurs in the opening area of the gap 39 on both sides in the circumferential direction of the concave groove 34. As a result, one gap 39 (a gap on the opposite side in the rotation direction) is narrowed between the concave grooves 24 on both sides of the land portion 22 in which the pressure oil hole 26 is formed, so that a pressure difference is generated, and the power connected to these is reduced. A pressure difference also occurs between the two oil chambers of the cylinder 52, and an assist force is generated in the steering direction.

Here, in the hydraulic control valve 10 (hydraulic power steering device 60), the annular groove 2 at the center of the valve sleeve 14 is used.
A check valve 40 is provided in an oil passage communicating the hydraulic pump 0B with the hydraulic pump 50. The check valve 40 allows only the flow of the hydraulic fluid from the hydraulic pump 50 to the inside of the hydraulic control valve 10 (the annular groove 20B). Is allowed, even if a kickback is likely to occur in the steering mechanism due to disturbance input from the road surface, this can be prevented from being transmitted to the steering wheel side, and the steering feeling is reduced. There is no.

Furthermore, if the disturbance input from the road surface is excessive (for example, when the vehicle rides on a curbstone), the hydraulic pressure in the power cylinder 52 rises greatly, and the downstream side of the check valve 40 That is, the hydraulic pressure on the side of the annular groove 20B greatly increases. Here, downstream of the check valve 40 (the annular groove 20B)
Is formed between the return oil hole 19 and the return oil hole 19, and a relief valve 4 is formed in the communication path 42.
When the hydraulic pressure in the power cylinder 52 (downstream of the check valve 40, ie, the side of the annular groove 20B) rises to a predetermined value or more, the relief valve 44 is opened and the reservoir 42 is The pressure oil is released to the tank 58.
Therefore, for example, the oil seal of the power cylinder 52 is prevented from being damaged.

As described above, in the hydraulic power steering device 60, even if the hydraulic pressure in the power cylinder 52 is excessively increased due to excessive disturbance input, it is possible to reliably prevent the oil seal and the like from being damaged. This can be provided at a low cost with a simple structure.

Further, in the hydraulic power steering device 60, the communication path 42 and the relief valve 44 described above correspond to the hydraulic control valve 1
Since it is provided in the valve housing 12, the size of the entire apparatus can be reduced. Also, as in the present embodiment, a hydraulic pump 50 having a pressure setting valve is generally used as a hydraulic pressure source, but by adopting the above configuration, the pressure setting valve provided in the hydraulic pump 50 is eliminated. It becomes possible to do.

[0033]

As described above, the hydraulic power steering apparatus according to the present invention can prevent damage to the oil seal and the like even when the hydraulic pressure in the hydraulic cylinder rises excessively due to excessive disturbance input. This has an excellent effect that it can be reliably prevented and can be provided at a low cost with a simple structure.

[Brief description of the drawings]

FIG. 1 is a sectional view taken along an axis of a hydraulic control valve applied to a hydraulic power steering apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing details of a communication path of a hydraulic control valve and a relief valve applied to the hydraulic power steering apparatus according to the embodiment of the present invention.

FIG. 3 is a schematic half sectional view perpendicular to an axis of a hydraulic control valve applied to the hydraulic power steering apparatus according to the embodiment of the present invention.

FIG. 4 is an overall configuration diagram of a hydraulic power steering device according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 hydraulic control valve 12 valve housing 14 valve sleeve 16 valve shaft 18 torsion bar 40 check valve 42 communication path 44 relief valve 50 hydraulic pump (hydraulic power source) 52 power cylinder (hydraulic cylinder) 60 hydraulic power steering device

Claims (2)

[Claims] 1. A hydraulic power steering device having a hydraulic control valve disposed in the middle of a steering mechanism, wherein hydraulic oil from a hydraulic source is controlled by the hydraulic control valve and distributed to a hydraulic cylinder. Provided in an oil passage communicating the hydraulic pressure source and a hydraulic control valve,
A check valve that allows only the flow of pressure oil from the hydraulic pressure source side to the hydraulic control valve side, one end of which communicates with an oil passage downstream of the check valve on the hydraulic control valve side; A communication path having an end communicating with a discharge path from the hydraulic control valve; and a relief valve provided in the communication path and opening at a predetermined pressure or higher to discharge pressure oil to the discharge path. A hydraulic power steering device characterized by the following. 2. The hydraulic power steering apparatus according to claim 1, wherein the communication path and the relief valve are provided in a housing of the hydraulic control valve.