JPH0348397B2 - - 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 pulsation of the hydraulic pump are transmitted to the oil chamber inside the accumulator as an elastic compressed fluid (compression waves in which changes in volume are transmitted as changes in density), 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 portion between the cylinder and the piston as in a conventional spring-piston type accumulator, 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 are used, there has been a problem in that they cannot withstand long-term dynamic use.

Like the accumulator disclosed in Utility Model Application Publication No. 56-162301 and Japanese Patent Application Publication No. 61-241591,
It is also known that an O-ring is not used between the piston and the cylinder. However, in all of the above conventional examples, since the piston and spring are arranged in series in the axial direction inside the cylinder, the axial length of the entire device is inevitably large, which is disadvantageous in terms of compactness. At the same time, the mass of the piston becomes large, which is disadvantageous in absorbing minute surge waves.

Therefore, an object of the present invention is to minimize the frictional resistance generated in the sliding portion between the cylinder and the piston.
It is an object of the present invention to provide a surge absorbing device that can be configured compactly and can effectively absorb even minute surge waves.

[Means for Solving the Problems] In order to achieve the above object, the surge absorbing device of the present invention includes a cylinder portion that communicates with a high-pressure oil passage and has a circulation hole that guides oil to the outside of the high-pressure oil passage; The cylinder part has a hollow hole into which the cylinder part is inserted, and is fitted to the outside of the cylinder part so as to be movable concentrically with the cylinder part and in the axial direction of the cylinder part, and the oil flows out from the circulation hole of the cylinder part. a cylindrical free piston having a pressure-receiving part that receives pressure; and a cylindrical free piston having a pressure-receiving part that receives the pressure of a compression coil spring that produces a repulsive force that counteracts the pressure;
A labyrinth groove is formed in the sliding portion between the inner circumferential surface of the free piston and the outer circumferential surface of the cylinder portion, and an oil film that enters the sliding portion seals the cylinder portion and the free piston from each other. The housing includes a labyrinth seal portion that lubricates the moving parts, and a housing that surrounds the compression coil spring, free piston, and cylinder portion, and is connected to an oil path that returns oil leaked from the labyrinth seal portion to the reservoir tank. There is.

[Operation] A part of the hydraulic oil flowing through the high-pressure oil passage flows into the free piston from the circulation hole in the cylinder section, so the hydraulic pressure acts on the pressure receiving section of the free piston, and the repulsive force of the compression coil spring and the above hydraulic pressure are balanced. The piston is pushed to the matching position. If 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 compressed fluid is absorbed by the volume change of the oil, causing a surge on the downstream side of the high-pressure oil path. It can prevent waves from propagating. The oil that has entered the labyrinth seal portion forms a lubricating oil film, and this oil film seals and lubricates the piston sliding portion. The oil that has flowed into the housing through the labyrinth seal is collected into the reservoir tank through the oil passage.

[Example] A first example of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 2 shows a power steering device 1 used in a steering system of an automobile as an example of a hydraulic system. 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 controls the flow rate of hydraulic oil according to the rotation speed of the engine 2. 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 accommodated 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 linkage (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 absorption device 30 is provided in a bypass oil passage 29 that connects the return oil passage 26 and the high pressure oil passage 25.
As shown in FIG.
, a cylindrical container-shaped housing 32 equipped with a main pipe section 31 connected to a high-pressure oil passage 25, a cylindrical free piston 33 housed inside this housing 32 concentrically with the housing 32, and this piston. It is configured to include a compression coil spring 34 that biases the spring 33 and the like. The free piston 33 includes a hollow hole 35 into which a cylinder portion 36 described below is inserted. The inside of the housing 32 is filled with hydraulic oil.

A cylinder portion 36 is provided inside the housing 32 and concentrically with the housing 32. This cylinder section 36 communicates with the main pipe section 31.
The piston 33 is placed on the outside of the cylinder portion 36,
It is fitted so as to be movable in the axial direction of the cylinder portion 36. A flow port 37 is provided at the tip of the cylinder portion 36 .

An end wall 38 that also serves as a spring seat is provided at the end of the housing 32. A hole 39 formed in the end wall 38 communicates with the bypass oil passage 29.

One end of the free piston 33 is closed by a pressure receiving portion 41 . A spring seat 43 having a larger diameter than the pressure receiving portion 41 is provided on the other end side of the free piston 33 . There is an oil chamber 44 inside the pressure receiving part 41. A portion of the hydraulic oil flowing through the main pipe section 31 flows into the oil chamber 44 through the flow hole 37 . Therefore, the pressure of the oil flowing through the high-pressure oil passage 25 acts on the pressure receiving portion 41 .

In the sliding portion between the piston 33 and the cylinder portion 36, a plurality of annular labyrinth grooves 45 that are continuous in the circumferential direction are provided on the inner peripheral side of the piston 33 and spaced apart from each other in the axial direction, thereby creating a labyrinth seal portion 48. It consists of These annular grooves 4
The cross-sectional shape of each of the holes 5 is a v shape or a semicircular concave shape. There is a slight gap 4 between the inner circumferential surface of the piston 33 and the outer circumferential surface of the cylinder portion 36 to the extent that an oil film is formed.
6, and a part of the hydraulic oil in the oil chamber 44 can enter into this gap 46. In this case, as the labyrinth groove 45 is filled with oil, the hydraulic pressure acts evenly over the entire circumference of the piston sliding part, so the piston 33 is biased and the cylinder part 36
It can prevent you from getting hit. The above distance is set to about 1 to 10 microns depending on the viscosity of the oil.

A compression coil spring 34 provided between the spring seat 43 and the end wall 38 urges the piston 33 toward the main pipe section 31 . This coil spring 34 is
It is arranged concentrically with the housing 32 and the cylinder part 36 so as to surround the outer circumference of the piston 33. Therefore, even if the coil spring 34 is built-in, the axial dimension of the housing 32 can be made relatively compact. Moreover, this piston 33 has a hollow hole 35 for inserting the cylinder portion 36.
Since it has a small mass, it has good followability even for surge waves with a short period.

Since the spring seat 43 can be made sufficiently larger than the outer diameter of the pressure receiving part 41, the spring 34 can be used in a size that can sufficiently cope with high hydraulic oil pressure. The 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, the hydraulic oil discharged by the rotation of the vane pump 3 flows from the flow control valve 4 through the main pipe line 31 of the surge absorber 30 and the high pressure oil line 25 to the control valve 23, and returns oil. It returns to the reservoir tank 8 via the path 26. While the engine 2 is rotating, the reference oil pressure above a certain level (for example, any pressure value in the pressure range of about 50 to 120 Kgf/ ^cm2 ) is maintained in the high pressure oil path 2.
5. In the surge absorption device 30,
The pressure of the hydraulic oil flowing through the main pipe section 31 is applied to the pressure receiving section 41.
As a result, the spring 34 is compressed and the piston 33 is pushed upward in the drawing. The piston 33 stops at a reference position where the pressure of the hydraulic oil flowing through the main pipe section 31 and the reaction force of the spring 34 are balanced.

Since the pressure of the hydraulic oil is always acting on the pressure receiving part 41 of the piston 33, it passes through the labyrinth seal part 48 provided at the sliding part between the piston 33 and the cylinder part 36 and into the inside of the housing 32. Oil flows out little by little. This oil forms an oil film on the sliding portion of the piston, which not only seals the sliding portion but also functions as a lubricating oil film. Therefore, the sliding resistance of the piston 33 is significantly reduced. The oil leaking into the housing 32 is
The oil is collected into the reservoir tank 8 via the bypass oil path 29 and the return oil path 26.

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 passage 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 surge wave is absorbed by the displacement of the piston 33, the vibration is transmitted to the hydraulic oil on the low pressure side (bypass oil passage 29 side) due to the movement of the piston 33. Since the low-pressure return oil passage 26 is connected to the reservoir tank 8 at approximately atmospheric pressure, vibrations generated by surge absorption and within the return oil passage 26 are transmitted to the reservoir tank 8, and the hydraulic fluid in the tank 8 is It can be dispersed by moving the surface up and down. 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, and this surge absorbing device 30 has a double cylindrical container-shaped housing housing a cylinder part 36 as a center stud connected to a high-pressure oil passage 25. 3
2, a cylindrical free piston 33 with both ends open, a compression coil spring 34, and the like. Each of these members is made of metal to withstand high temperatures. The inside of the housing 32 is filled with hydraulic oil. 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. Diameter portion 52
There is. Further, a first spring seat 53 is provided on one end side of the cylinder portion 36 .

The cylindrical free piston 33 has a hollow hole 35, into which a cylinder portion 36 is inserted. In other words, this piston 33
is fitted concentrically with the cylinder portion 36 so as to surround the different diameter portion 52 of the cylinder portion 36 . The piston 33 is slidable in the axial direction of the cylinder portion 36, and a pressure receiving portion 41 is provided at the inner end of the piston 33. A plurality of annular labyrinth 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, and a labyrinth seal portion 48 is formed in the piston sliding portion. There is.

An annular oil chamber 44 located inside the piston 33
The inside of the cylinder portion 36, that is, the high-pressure oil passage 25 is
It communicates with A second spring seat 56 is provided on the outer periphery of the piston 33. First spring seat 53
The compression coil spring 34 provided between the second spring seat 56 and the second spring seat 56 urges the piston 33 in a direction that reduces the volume of the oil chamber 44 (leftward in FIG. 3). In the case of this embodiment as well, the piston 33, the spring 34 and the cylinder part 3 are provided inside the housing 32.
6 are housed concentrically, and the spring 34
A piston 33 and a cylinder part 36 are inserted inside the cylinder.

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 acts on the oil chamber 44 through the circulation hole 55, so the piston 33 It stops at the reference position where the reaction force is balanced. The area of the pressure receiving part 41 is expressed by the difference between the outer diameter cross-sectional area of the large diameter part 50 and the outer diameter cross-sectional area of the small diameter part 51. When a surge wave occurs in the high pressure oil passage 25 or the like, the volume change of the hydraulic oil acts on the oil chamber 44 through the flow hole 55, so the piston 33 moves in the axial direction of the cylinder portion 36 from the reference position. By expanding or contracting the volume of the oil chamber 44 in this manner, 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 oil leaks little by little into the housing 32 through the labyrinth seal portion 48 provided at the piston sliding portion. In this way, an oil film is formed on the piston sliding portion, and the piston 33
The sliding resistance is significantly reduced, and the sealing function is also demonstrated. The oil leaking into the housing 32 is
The oil is collected into the reservoir tank 8 via the bypass oil path 29 and the return oil path 26.

The in-line surge absorber 30 of the second embodiment allows the hydraulic oil flowing in the high-pressure oil passage 25 to flow through the cylinder portion 36 as a main pipe passage. Moreover, since the piston 33 is of an axial flow type that moves in the flow direction of the hydraulic oil, there is no need to connect a branch pipe for the surge absorber in a direction perpendicular to the high pressure oil passage 25, and the installation space can be reduced. Furthermore, since the piston 33, the cylinder portion 36, and the annular oil chamber 44 are arranged concentrically inside the coil spring 34, the entire device can be constructed extremely compactly.

Note that the surge absorbing device of the present invention can also be used by being directly connected to the outlet of a hydraulic pump, a safety valve such as the relief valve 5, or the control valve 23. The hydraulic power source may be other than a 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 lubricating oil film is formed by flowing part of the hydraulic oil into the labyrinth seal provided in the piston sliding part, and the piston sliding part is lubricated. frictional resistance is extremely low. Furthermore, since the piston is provided with a hollow hole into which the cylinder portion is inserted, the mass of the piston can be small. For these reasons, even minute surge waves can be sufficiently absorbed. Since the piston and cylinder part are concentrically inserted inside the coil spring, the axial length can be shortened.
It can be configured compactly. 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.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a surge absorbing device showing a first embodiment of the present invention, FIG. 2 is a hydraulic system diagram of a power steering device equipped with the surge absorbing device shown in FIG. 1, and FIG. 3 is a diagram of the present invention. FIG. 3 is a sectional view of a surge absorbing device showing a second embodiment of the invention. 1... Power steering device, 3... Vane pump (hydraulic source), 8... Reservoir tank, 15
... Power cylinder (actuated part), 25 ... High pressure oil path, 26 ... Return oil path, 29 ... Bypass oil path, 30 ... Surge absorption device, 32 ... Housing, 33 ... Free piston, 34 ... Compression coil spring, 35 ... Hollow hole, 36 ... Cylinder part,
37...Flow hole, 41...Pressure receiving part, 46...〓
Between, 48... Labyrinth seal portion, 55... Communication hole.

Claims (1)

[Claims] 1. Used in a hydraulic system having a high-pressure oil passage connecting the discharge side of a hydraulic power source and an actuated part moved by hydraulic pressure, and a return oil passage connecting the actuated part and a reservoir tank. A hydraulic surge absorption device comprising: a cylinder portion having a circulation hole that communicates with the high-pressure oil passage and guides oil to the outside of the high-pressure oil passage; and a hollow hole into which the cylinder portion is inserted. a cylindrical shape having a pressure receiving part that is fitted on the outside of the cylinder part concentrically with the cylinder part and movable in the axial direction of the cylinder part, and receives the pressure of oil flowing out from the circulation hole of the cylinder part; a compression coil spring that surrounds the outer periphery of the free piston and is provided concentrically on the outside of the free piston and generates a repulsive force that opposes the pressure of the oil acting on the pressure receiving portion of the free piston; A labyrinth groove is formed in the sliding portion between the inner circumferential surface of the free piston and the outer circumferential surface of the cylinder portion, and an oil film that enters the sliding portion seals the cylinder portion and the free piston from each other. The housing includes a labyrinth seal portion that lubricates the moving parts, and a housing that surrounds the compression coil spring, free piston, and cylinder portion and is connected to an oil path that returns oil leaked from the labyrinth seal portion to the reservoir tank. A hydraulic surge absorption device characterized by: