JPH0320640B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for absorbing surge waves generated in a hydraulic piping system.

[Prior Art] When surge waves occur in high-pressure oil pipes connected to the discharge side of a hydraulic power source such as a hydraulic pump, they cause harmful vibrations and noise in the piping system. As a device for absorbing such surge waves, there is known a device such as a spring-piston type accumulator that houses a piston and a compression spring that biases the piston inside a cylinder. A sealing material such as an O-ring is provided at the sliding portion between the piston and the cylinder to prevent oil leakage.

Surge waves generated in the hydraulic oil due to the pulsation of the hydraulic pump are transmitted to the oil chamber inside the accumulator as oil elastic compression waves (concentration waves in which volume fluctuations are transmitted as density fluctuations), and are transmitted to the oil chamber inside the accumulator. is displaced and the varying volume of oil is absorbed by the deflection of the spring.

[Problems to be Solved by the Invention] When a sealing material such as an O-ring is provided at the sliding part between the cylinder and the piston as in a conventional spring-piston type acumulator, the sealing material comes into pressure contact with the inner wall surface of the cylinder. This results in large frictional resistance. Therefore, when the pressure increase due to surge is less than the frictional force of the sealing material, the piston does not move.
Unable to absorb surge. Further, when the piston moves, hydraulic oil leaks out from the sliding portion of the piston little by little due to a so-called oil-spooling phenomenon. Furthermore, since conventional rubber sealing materials have been used, there has been a problem in that they cannot withstand long-term dynamic use.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a tank-integrated surge absorbing device which has a structure in which hydraulic oil slightly leaks from the piston sliding portion, and in which the frictional resistance generated in the sliding portion is extremely small.

[Means for Solving the Problems] In order to achieve the above object, the surge absorbing device of the present invention includes a high-pressure oil passage connecting the discharge side of a hydraulic power source and an actuated part moved by hydraulic pressure, and a A reservoir tank connected via a return oil passage, a cylinder part connected to the high pressure oil passage, a free piston that is slidably fitted into this cylinder part and receives hydraulic pressure from the high pressure oil passage, and this free piston. a spring that resists the pressure of the high pressure oil passage applied to the
Further, the sliding portion between the cylinder portion and the free piston has a small gap, and the gap in the sliding portion is open to the reservoir tank.

[Operation] The pressure of the hydraulic oil flowing through the high-pressure oil passage acts on the pressure-receiving portion of the piston, and the piston is pushed to a position where the repulsive force of the spring and the oil pressure of the high-pressure oil passage are balanced. When a surge wave occurs in this state, the piston moves according to the magnitude of the hydraulic pressure acting on the pressure receiving part, and the elastic compression wave is absorbed by the volume change of the oil.
It is possible to prevent surge waves from being transmitted to the downstream side of the high-pressure oil path. A portion of the hydraulic oil flows to the sliding portion of the piston relative to the cylinder portion, forming an oil film. This oil is collected in a reservoir tank.

[Example] A first example of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 shows a power steering device 1 used in a steering system of an automobile. This power steering device 1 includes a vane pump 3 as an example of a hydraulic power source that is rotationally driven by an engine 2. A flow control valve 4 provided on the discharge side of the vane pump 3 is connected to the engine 2.
The flow rate of hydraulic oil is controlled according to the rotation speed of the Further, a relief valve 5 is provided to limit the maximum oil pressure.

A reservoir tank 8 is connected to the suction side of the vane pump 3 via an oil feed pipe 7. Hydraulic oil 9 is stored inside the reservoir tank 8 .
The pressure inside the reservoir tank 8 is approximately atmospheric pressure.

Similar to the well-known manual steering system, a steering force transmission mechanism 12 of, for example, a rack and pinion type is provided at one end of the steering shaft 11. A steering wheel 13 is provided on the other end side of the steering shaft 11. A power cylinder 15, which is an example of an actuated part moved by hydraulic pressure, has a rack shaft 16 that passes through the power cylinder in its axial direction. The rack shaft 16 moves in the left-right direction in the drawing in conjunction with the rotation of the steering shaft 11, thereby driving a steering cage (not shown).

Inside the power cylinder 15 is the easy piston 1
7 into a first cylinder chamber 18 and a second cylinder chamber 19, each cylinder chamber 18, 1
9 are connected to a high pressure oil passage 25 and a return oil passage 26 via oil passages 21, 22 and a control valve 23, respectively. The high pressure oil passage 25 is connected to the discharge side of the flow control valve 4 via a surge absorber 30, which will be described later.

The control valve 23 forms a flow path for hydraulic oil depending on the direction in which the steering shaft 11 is steered. For example, when the steering wheel 13 is rotated so that the rack shaft 16 moves to the right in the figure, the hydraulic oil sent from the high pressure oil passage 25 is sent into the first cylinder chamber 18 via one oil passage 21. In some cases, the easy shaft 16
An axial force is generated in the right direction as shown in the figure. On the contrary, easy axis 1
When the steering wheel 13 is rotated so that the shaft 6 moves to the left side in the figure, the hydraulic oil from the high pressure oil passage 25 is sent into the second cylinder chamber 19 via the other oil passage 22, thereby causing the rack shaft 16 to move to the left side in the figure.
An axial force is generated in the left direction as shown in the figure.

A surge absorber 30 is provided between the reservoir tank 8 and the high pressure oil passage 25. As shown in FIG. 2, the surge absorption device 30
A cylindrical container-shaped housing 32 connected to the housing 32 and a free piston 33 accommodated in the housing 32.
The piston 33 is configured to include a spring 34 and the like that bias the piston 33. The inside of the housing 32 is filled with hydraulic oil. Further, a cylinder portion 36 communicating with the high pressure oil passage 25 is provided at the lower end side of the housing 32 in the drawing. The upper end of the housing 32 in the figure, that is, the open end on the reservoir tank 8 side is fixed to the reservoir tank 8 and is provided with an end wall 38 that also serves as a spring seat. An opening 39 formed in the end wall 38 is open to the inside of the reservoir tank 8.

The pressure receiving part 41 of the free piston 33 is the high pressure oil passage 2
Receives the pressure of hydraulic oil flowing through 5. piston 33
A piston main portion 42 located on one end side is inserted into the cylinder portion 36 so as to be movable in the axial direction.
A spring seat 43 is provided on the other end side of the piston 33. The spring seat 43 is movable in the axial direction of the housing 32. An oil chamber 44 is provided on the pressure receiving part 41 side.

A plurality of annular grooves 45 continuous in the circumferential direction are provided in the outer peripheral portion of the piston main portion 42 and spaced apart from each other in the axial direction. The cross-sectional shape of this annular groove 45 is a v shape or a semicircular concave shape. There is a small gap 46 between the outer circumferential surface of the piston main portion 42 and the inner circumferential surface of the cylinder portion 36, which is large enough to form an oil film, and a portion of the hydraulic oil flowing through the high-pressure oil passage 25 passes through the gap 46 to the housing 32. You can move inside. In this case, since the annular groove 45 is filled with oil, the oil pressure is applied evenly over the entire circumference of the piston main portion 42, so that the piston main portion 42 can be prevented from hitting the cylinder portion 36 unevenly. In addition, the piston main part 42
The sliding portion between the piston main portion 42 and the cylinder portion 36 is removed by inserting a sliding bush having an outer diameter slightly smaller than the inside diameter of the cylinder portion 36 and having an annular groove similar to that described above. You may also allow the oil to flow through.

A compression coil spring 34 provided between the spring seat 43 and the wall end 38 biases the piston 33 toward the high pressure oil passage 25 side. The spring seat 43 is the pressure receiving part 41
Since the outer diameter of the spring 34 can be sufficiently large compared to the outer diameter of the spring 34, it is possible to use a spring 34 having a size that can sufficiently cope with high hydraulic oil pressure. spring 34
may be a coil spring of equal pitch, but preferably a coil spring of unequal pitch may be used so that as the load increases, the amount of contact between the strands increases and the spring constant increases non-linearly.

Next, the operation of the power steering device 1 including the surge absorbing device 30 having the above configuration will be explained.

When the engine 2 rotates, hydraulic oil discharged by the rotation of the vane pump 3 flows from the flow rate control valve 4 through the high pressure oil path 25 to the control valve 23 and returns to the reservoir tank 8 through the return oil path 26. While the engine 2 is rotating, a reference oil pressure of a certain level or higher (for example, any pressure value in a pressure range of about 50 to 120 Kgf/cm ² ) acts on the high-pressure oil passage 25 . In the surge absorbing device 30, the pressure of the hydraulic oil flowing through the high-pressure oil passage 25 acts on the pressure receiving part 41, so that the spring 34 is bent and the piston 33 is pressed upward in the figure. piston 3
3 stops at a reference position where the pressure of the hydraulic oil flowing through the high pressure oil path 25 and the reaction force of the spring 34 are balanced.

Since the pressure of hydraulic oil is always acting on the pressure receiving part 41 of the piston 33, the oil gradually flows from the high pressure oil passage 25 to the housing 32 on the low pressure side through the gap 46 of the sliding part between the piston 33 and the cylinder part 36. flows. Since this oil forms an oil film on the sliding portion of the piston main portion 42, the sliding resistance of the piston 33 is significantly reduced. This leaked oil is then collected into the reservoir tank 8.

When the steering wheel 13 is rotated by the driver, the hydraulic oil sent from the high pressure oil passage 25 is directed to the first cylinder chamber 18 (or the second cylinder chamber 19) depending on the steering direction of the steering shaft 11. By flowing into the shaft, the axial force of the rack shaft 16 is reduced to the right or left. The hydraulic oil pushed out from the second cylinder chamber 19 (or the first cylinder chamber 18) by the movement of the rack piston 17 is returned to the reservoir tank 8 via the control valve 23 and the return oil passage 26.

When a surge wave is generated in the high-pressure oil pipe 25 or the like due to the operation of the vane pump 3, the surge component is combined with the reference oil pressure of the hydraulic oil. Since the volume change of the hydraulic oil due to the surge wave acts on the piston pressure receiving part 41 of the surge absorber 30, the piston 33 moves in the axial direction of the cylinder part 36 from the reference position. In this way, by expanding or contracting the volume of the oil chamber 44, surge waves are absorbed while maintaining the reference pressure of the hydraulic oil.

When the sealing material is absorbed by the displacement of the piston 33, the hydraulic oil on the low pressure side (housing 32 side) is compressed by the amount of movement of the piston 33. Since the opening 39 of the housing 32 is connected to the reservoir tank 8 at approximately atmospheric pressure, the energy of vibrations generated by surge absorption is dissipated by raising and lowering the hydraulic fluid level in the reservoir tank 8. Therefore, it is possible to prevent surge waves from propagating to the control valve 23 and power cylinder 15 side. The power steering device of this embodiment equipped with this surge absorber 30 has a significantly lower pulsating pressure than a conventional product without a surge absorber, and as a result, vibration and noise in the piping system are also reduced. decreased.

FIG. 3 shows a second embodiment of the present invention. The surge absorbing device 30 of this embodiment includes a cylinder portion 36 that also serves as a main pipe connected to a high-pressure oil path 25, a cylindrical free piston 33 with both ends open, a compression coil spring 34, etc. These are provided in the reservoir tank 8. Each of these members is made of metal to withstand high temperatures. The cylinder portion 36 is formed with two portions having different outer diameters in the tube axis direction, namely a large diameter portion 50 and a small diameter portion 51, and a stepped difference is formed between the large diameter portion 50 and the small diameter portion 51. There is a diameter portion 52. Also,
A first spring seat 53 is provided at one end of the cylinder portion 36 .

The cylindrical piston 33 is fitted into the cylinder portion 36 so as to surround the different diameter portion 52 . The piston 33 is slidable in the axial direction of the cylinder portion 36. A plurality of annular grooves 45 continuous in the circumferential direction are provided on the inner circumferential surface of the sliding portion of the piston 33 relative to the cylinder portion 36, so that hydraulic oil can gradually flow through the sliding portion of the piston 33. It's getting old.

An annular oil chamber 44 located inside the piston 33
communicates with the inside of the cylinder portion 36, that is, the high pressure oil passage 25, through a hole 55 as an example of a circulation means. A second spring seat 5 is provided on the outer periphery of the piston 33.
6 is provided. Compression coil spring 3 provided between first spring seat 53 and second spring seat 56
4 urges the piston 33 in a direction that reduces the volume of the oil chamber 44 (leftward in FIG. 3).

In the surge absorbing device 30 of FIG. 3 having the above configuration, the pressure of the hydraulic oil flowing through the high pressure oil passage 25 is
5 to act on the oil chamber 44, the piston 3
3 stops at a reference position where the pressure of the hydraulic oil and the reaction force of the spring 34 are balanced. The area of the pressure receiving portion 41 of the piston 33 is expressed by the difference between the outer diameter cross-sectional area of the large diameter portion 50 and the outer diameter cross-sectional area of the small diameter portion 51. When a surge wave occurs in the high pressure oil passage 25 etc., the volume change of the hydraulic oil will occur in the hole 5.
5 to act on the oil chamber 44, the piston 3
3 moves in the axial direction of the cylinder portion 36 from the reference position. In this way, by expanding or contracting the volume of the oil chamber 44, surge waves are absorbed while maintaining the reference pressure of the hydraulic oil.

Since high-pressure hydraulic oil pressure is constantly acting on the oil chamber 44, a portion of the hydraulic oil leaks little by little from the gap 46 between the sliding portion of the piston 33 and the cylinder portion 36. Since an oil film is formed on the sliding portion of the piston 33, the sliding resistance of the piston 33 is significantly reduced. This leaked oil is collected in the reservoir tank 8.

The surge absorbing device 30 shown in FIG. 3 described above can cause the hydraulic oil flowing in the high pressure oil passage 25 to flow into the cylinder portion 36 as a main pipe. In other words, the cylinder part 36 constitutes a part of the high-pressure oil passage, and since it is an axial flow type in which the piston 33 moves in the flow direction of the hydraulic oil, it can be constructed compactly. It also saves space.

FIG. 4 shows a third embodiment of the present invention, and a surge absorber 30 of this embodiment includes a cylinder portion 36, a free piston 36, and a spring 34 housed in a reservoir tank 8, and a high-pressure oil A passage 25 passes through the reservoir tank 8. Further, an annular groove 45 similar to that of the previous embodiment is provided in the sliding portion between the cylinder portion 36 and the piston 33, and an oil film is formed by oil flowing into the piston sliding portion. A gap 46 where the piston 33 slides is open into the reservoir tank 8. The spring 34 is provided in a compressed state between a portion 8a of the reservoir tank 8 and a spring seat 56.

Note that the hydraulic pressure source may be other than the vane pump. Moreover, it goes without saying that it can be used in hydraulic equipment other than power steering devices.

[Effects of the Invention] In the surge absorbing device of the present invention, a stable and thick lubricating oil film is formed by flowing a portion of the hydraulic oil to the sliding portion of the piston, and the sliding portion of the piston is lubricated, resulting in extremely low frictional resistance. few. Therefore, even minute surge waves can be sufficiently absorbed. Furthermore, since no sealing material such as rubber is used in the sliding portion of the piston, the piston can sufficiently withstand dynamic use over a long period of time.

The low pressure side of the piston is open into the reservoir tank, and by passing through the sliding portion of the piston, the oil that has lubricated the sliding portion can directly flow back into the reservoir tank.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic system diagram of a power steering device equipped with a surge absorber according to a first embodiment of the present invention, FIG. 2 is a sectional view of the surge absorber according to a first embodiment of the present invention, and FIG. FIG. 4 is a cross-sectional view of a surge absorber according to a second embodiment of the present invention, and FIG. 4 is a cross-sectional view of a surge absorber according to a third embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Power steering device, 3... Vane pump (hydraulic source), 8... Reservoir tank, 15... Power cylinder (operated part), 25... High pressure oil path, 26
...Return oil path, 30...Surge absorber, 33...Free piston, 34...Spring, 36...Cylinder section, 4
6... Gap.

Claims (1)

[Scope of Claims] 1. A high-pressure oil passage connecting the discharge side of a hydraulic power source and an actuated part moved by hydraulic pressure, a reservoir tank connected to the actuated part via an oil passage that returns to the actuated part, and the high-pressure A cylinder part connected to the oil passage, a free piston that is slidably fitted into the cylinder part and receives the oil pressure of the high pressure oil passage, and a spring that opposes the pressure of the high pressure oil passage applied to the free piston. ,
A hydraulic surge absorber characterized in that a sliding portion between the cylinder portion and the free piston has a small gap, and the gap in the sliding portion is open to the reservoir tank. 2. The hydraulic surge absorber according to claim 1, wherein the free piston and the spring are housed in a housing having the cylinder portion, and one open end of the housing is fixed to a reservoir tank. 3 The cylinder part, free piston, and spring are housed in the reservoir tank, and
The hydraulic surge absorption device according to claim 1, wherein the high pressure oil passage passes through a reservoir tank.