JPH03219133A - Hydraulic pressure buffer - Google Patents

Abstract

PURPOSE:To improve the durability of a seal and vehicle riding comfort in the case of applying a hydraulic pressure buffer to a suspension unit by holding the pressure in a seal housing constantly to the same low pressure as that in a reservoir chamber by a pressure relief passage. CONSTITUTION:An outer tube 11 is provided to form a reservoir chamber D at the outer periphery of a second cylinder tube 1b, above a base 3. The base 3 is provided with a pressing-side communicating passage I formed to allow a fluid in an upper chamber A to to flow into an outer chamber C through a damping force generating means 21 at the time of the pressing-side stroke as well as with an expanding-side communicating passage II formed to allow the fluid in the outer chamber C to flow into the reservoir chamber D through a damping force generating means 15 at the time of the expanding-side stroke. There are further provided a check passage 22b for allowing the fluid staying in the reservoir chamber D to to flow into an upper chamber A at the time of the expanding-side stroke; an oil seal 4c provided in contact with the outer peripheral surface of a piston rod 6, outside a rod insertion hole 2a through a seal housing 7; and a pressure relief passage 2e for communicating the seal housing 7 with the reservoir chamber D.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic shock absorber applied to a vehicle suspension.
It relates to an inverted type in which the cylinder tube side is connected to the vehicle body.

(Prior art) Conventionally, as an inverted type hydraulic shock absorber, for example,
The one described in Japanese Patent No. 8-97334 is known.

This conventional hydraulic shock absorber has a structure in which the inside of the cylinder tube is divided into an upper chamber and a lower chamber by a piston, and a reservoir chamber is further defined at the upper end of the upper chamber by a hose. Ta. The seal structure of the front guide portion is such that a gap between the piston rod and the rod insertion hole is sealed with one seal member.

(Problem to be Solved by the Invention) However, in such a conventional hydraulic shock absorber, the gap between the piston rod and the rod insertion hole is sealed with one seal, so the liquid In order to prevent leakage, it is necessary to increase the seal contact pressure, which increases friction and reduces the durability of the seal, and also prevents the piston rod from stroking smoothly. had the problem of making the ride uncomfortable.

The present invention has been made with a focus on such intersensitivity,
It is an object of the present invention to provide a hydraulic shock absorber that can reliably prevent liquid leakage while having low friction.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the hydraulic shock absorber of the present invention includes a first cylinder tube in which a guide member having a rod insertion hole is provided at the lower end and a base is provided at the upper end. The first cylinder tube is defined into an upper chamber and a lower chamber, a piston connected to a piston rod inserted into the first cylinder tube from a rod insertion hole, and a piston provided surrounding the first cylinder tube. , a second cylinder tube forming an outer chamber communicating with the lower chamber via a lower communication passage on the outer periphery of the first cylinder tube; and a second cylinder tube surrounding the guide member, the second cylinder tube, and the base; an outer tube that forms a reservoir chamber on the outer periphery and the upper part of the base; a compression side communication passage that is formed in the hess and allows the fluid in the upper chamber to flow to the outer chamber via a damping force generating means during the compression side stroke; an expansion-side communication path that allows the fluid to flow into the reservoir chamber via the damping force generating means;

and a check flow path that allows the fluid in the reservoir chamber to flow to the upper chamber during the extension stroke, and an oil seal that is in contact with the outer peripheral surface of the piston rod and is provided outside the rod insertion hole via the seal housing. and a pressure relief flow path communicating between the seal house sink and the server room.

(Function) The function of the hydraulic shock absorber of the present invention will be explained based on the fluid circuit diagram shown in FIG. This FIG. 1 shows the fluid flow path in the configuration of the present invention, in which a is the upper chamber, b is the lower chamber, C is the outer chamber, d is the reservoir chamber, e is the lower communication path, and f is the lower chamber. 9 is a compression side damping force generation means, h is a compression side damping force generation means, j is a growth side communication passage, and n is a check passage.

First, during the extension stroke, the volume of the lower chamber a in the first cylinder tube is reduced and the upper chamber a is enlarged.

According to this volume change, the fluid in the lower chamber flows through the lower communication passage e.
After flowing into the outer chamber C through the extension side communication path J of the base
It flows into the reservoir chamber d through the damping force generating means on the rebound side, and from there it flows through the check flow path n to the upper chamber a.
flows into.

Therefore, a damping force is generated in the damping force generating means on the expansion side.

In this case, an amount of fluid corresponding to the volume of the piston rod withdrawn from the first cylinder tube is supplied to the upper chamber a from the reservoir chamber d via the check flow path n of the base. Therefore, the upper chamber a does not become under negative pressure, and cavitation does not occur.

Next, during the pressure side stroke, the volume of the lower chamber a is expanded and the upper chamber a is decreased in the cylinder tube.

According to this volume change, the fluid in the upper chamber a flows into the outer chamber C through the pressure side communication passage f and through the pressure side damping force generating means 9, and from there, a part of the circulating fluid flows into the lower communication passage e. It flows into the lower chamber through. In addition, the remaining circulating fluid (first
The amount of fluid (equivalent to the volume of the piston rod) that has entered the cylinder tube flows into the reservoir chamber d through the damping force generating means of the expansion side communication path.

Therefore, damping force is generated in series in the damping force generating means 9 on the compression side and the damping force generating means on the rebound side.

Also, during the extension stroke of the piston, if the fluid pressure in the lower chamber increases and a pressure difference is created between the cylinder tube and the outside, this differential pressure causes the fluid in the lower chamber to pass through the rod insertion hole. The fluid flows into the seal housing in a reduced pressure state, and the oil seal prevents it from flowing out to the outside of the cylinder tube. However, if the fluid pressure in the seal housing increases, the fluid in the seal housing flows into a pressure relief flow. The liquid flows out through the passage to the reservoir chamber side, thereby reducing the pressure inside the seal housing.

(Example) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, the configuration of the embodiment will be explained.

FIG. 2 is a cross-sectional view showing the hydraulic shock absorber according to the first embodiment of the present invention, in which 1a and Ib denote a first
They are a cylinder tube and a second cylinder tube.

Both the first and second cylinder tubes 1a and 1b have a cylindrical shape, and an annular external chamber C is formed between the two cylinder tubes Ia and 1b, and a guide member 2 is formed at the lower end.
However, a hess 3 is provided at the upper end, and the inside thereof is filled with fluid such as oil.

The guide member 2 includes an inner member 2b which is formed with a rod insertion hole 2a and fits into the lower end openings of both cylinder tubes la and lb, and an outer periphery of the inner member 2 which is also formed with a rod insertion hole 2a. and an outer member 2c fitted into the outer member 2c.

A piston 5 is slidably provided in the first cylinder tube 1a, and defines an upper chamber A and a lower chamber B inside the first cylinder tube 1a.

The piston 5 is inserted into the loft insertion hole 2 of the guide member 2.
It is attached to the tip of a piston rod 6 inserted into the first cylinder tube 1a from a. The piston rod 6 has its lower end connected to the axle.

The rod insertion hole 2a of the inner member 2a is provided with a pressure reducing seal 4a which is slidably in contact with the outer peripheral surface of the piston rod 6, and a guide bush 4b which slidably guides the piston rod 6 with a small gap. Furthermore, an oil seal 4c that is slidable in contact with the outer peripheral surface of the piston rod 6 is provided in the rod insertion hole 2a of the outer member 2b, and a seal house sink is provided between this oil seal and the inner member 2a. It is formed.

An outer tube 11 is provided on the outer periphery of the second cylinder tube 1b and extends above the second cylinder tube 1b. The outer tube 11 has a lower end opening screwed to the outer periphery of the outer member 2C, and an inner periphery of an upper intermediate portion fitted to the base 3, and the upper end is not shown. It is closed with a lid and can be attached to the vehicle body.

This outer tube 11 forms reservoir chambers on the outer circumference of the second cylinder tube 1b and on the upper part of the base 3, and these two reservoir chambers communicate with each other through a communication passage 3a formed on the outer circumferential surface of the base 3. and is filled with the desired amount of fluid under pressure from an enclosed gas.

Note that the seal housing sink Y and the lower part of the reservoir chamber are communicated through a pressure relief passage 2e formed in the inner member 2b, and a lower communication passage 2d formed in the inner member 2b.
The lower chamber abutment and the outer chamber C communicate with each other via.

Next, the structure of the base 3 will be explained in detail.

As shown, the base 3 is connected to the support rod 12.
Cover 8. Retainer 13. washer 14, second damping valve 15. 2nd body 76. 2nd chain valve 17. Washer 18. Retainer 19, washer 20. First damping valve 21. 1st Poday 22. 1st check valve 23.
Washer 24. The retainers 25 are sequentially attached and finally fastened with nuts 26.

An intermediate chamber E is formed between the first body 22 and the second body 16.

The first body 22 is formed with double upper annular grooves 22d and 22e on the upper surface thereof, which communicate with each other, as well as a first communication hole 22a that communicates the upper chamber A with the intermediate chamber E, and a reservoir. Check channel 22 that connects the chamber to the upper chamber A
b, a base communication path 2 that communicates between the intermediate chamber E and the outer chamber C.
2c is formed. The first communication hole 22a is narrowed by the first damping valve 21, and the first check flow path 22b is narrowed by the first check valve 23 so that only flow from the reservoir chamber to the upper chamber A is allowed. It has become.

Next, in the second body 16, annular grooves 16c and +6d are formed on the upper surface of the inner and outer double layers (g11) that communicate with each other, and a second communication hole 16a that communicates the intermediate chamber E with the reservoir chamber. A second check passage 16b is formed which communicates the reservoir chamber with the intermediate chamber E.The second communication hole 16a is narrowed by the second damping valve 15, and
The second check flow path 16b is configured such that only flow from the reservoir chamber to the intermediate chamber E is permitted by the second check valve 17.

The support rod 12 has a through hole +2a that opens into the upper chamber A at its axis, and has a first port 12b communicating with the reservoir chamber and a first port 12b communicating with the upper annular groove +6c in the radial direction. The second port 12C and the third port 12d communicating with the upper annular groove 22d are formed on the same axis.

A cylindrical adjuster 27 is provided in the through hole 12a so as to be rotatable in the circumferential direction with the top and bottom supported by thrust bushes 28 and 29, and the adjuster 2Y has a variable orifice. The vertical groove 27a is connected to the three ports +
2b, 12c, and 12d are formed in communication with each other.

Further, the adjuster 27 is connected to an external motor actuator attached to the upper end of the reservoir chamber via the control loft 30, and is rotated by the drive control of this motor actuator, and by this rotation, The opening degree of each port 12b, +2c, and L2d is changed.

As described above, in this embodiment, the base 3 defines the upper chamber A, the outer chamber C, and the reservoir chamber, and the passages formed in the base 3 define the liquid chambers A, C, and C. , D are in communication, that is, as shown in FIG. 3, the first communication hole 22a, the upper annular groove 22d, and the
2e, the intermediate chamber E, and the base communication path 2c constitute the pressure side communication path (2) in the claims.

In addition, the base communication passage 22C2 intermediate chamber E, the second communication hole 16
a, upper annular groove +6c, and 16d constitute the extension side communication path II of the claims.

Further, the first communication hole 22a, the upper annular groove 22d, the third port 12d, the vertical groove 27a, and the first port 12b constitute a pressure side bypass path ■■.

In addition, the base communication passage 22C2 intermediate chamber E, the second communication hole 16
a, upper groove] 6C1 second boat 12C1 vertical groove 27a
, and the first port 12b constitute an extension side bypass path 1■.

Further, the first check flow path 2 including the first check valve 23 constitutes the check flow path of the claims.

Next, the operation of the embodiment will be explained with reference to the circuit diagram shown in FIG.

(a) During the expansion side stroke During the expansion side stroke, the volume of the lower chamber B is reduced and the upper chamber A is expanded in the first cylinder tube 1a.

According to this volume change, the fluid in the lower chamber B is transferred to the guide member 2.
It flows into the outer chamber C through the lower communication passage 2d, and then flows into the upper chamber A through the following two routes.

The first path passes through the growth side communication path II, flows into the reservoir chamber via the second damping valve 15, and from there the first path flows into the reservoir chamber through the second damping valve 15.
The flow path passes through the check flow path 22b, opens the first check valve 23, and flows into the upper chamber A, and the second path passes through the expansion side bypass path 1■, which is parallel to the first check valve 23, and forms a variable throttle. It flows into the reservoir chamber through the second port 12c and the first boat 12b, and from there the first check channel 22
b, and open the first chain valve 23 to open the upper chamber A.
This is the route through which it flows into the country.

Therefore, if the growth side bypass path IV fJ < distribution possible (
In the state shown in FIG. 2), a damping force is generated in the second damping valve 15 and both boats 12c and 12b, and in this case, there is a large amount of fluid flowing, resulting in a characteristic of low damping current. Then, the speed 2/3 power characteristic of the second damping valve 15 and the speed square characteristic of both boat ports 12c and 12b are combined in parallel, resulting in a characteristic linearly proportional to speed.

Also, based on the rotation of the adjuster 2γ, both ports 12c, +
If 2b is closed, the damping force characteristic will be that of the second damping valve 15 alone, and in this case, the fluid flow rate will be small and the speed will be a 2/3 power characteristic with high damping current.

Further, the opening area of both boats 12c and 12b can be arbitrarily changed from a fully open state to a fully open state by moving the longitudinal groove 2γa by rotating the adjuster 27, thereby increasing the damping current. can be changed to any range from a low attenuation current to a high attenuation current.

Incidentally, an amount of fluid corresponding to the volume of the piston rod 6 that has exited from the first cylinder tube 1a is supplied to the upper chamber from the reservoir chamber via the first check flow path 22b of the base. Therefore, the second; Iti, decaying valve 15
Even if the upper chamber A is made to have high damping force characteristics, the upper chamber A does not become a negative pressure, and cavitation does not occur.

Therefore, the damping force characteristics during the rebound stroke are determined by the second damping valve 1.
5 and both boats 12c, 12 constituting a variable orifice.
The characteristic of Ushidera is that it can be varied based on the characteristics of b, and that the damping force characteristics can be varied over a wide range.

(b) During the pressure side stroke During the pressure side stroke, in the first cylinder tube ] a,
The volume of the lower chamber B is expanded, and the upper chamber A is reduced.

According to this volume change, the fluid in the upper chamber A flows to the outer chamber C through the following two paths, and flows into the lower chamber B via the lower communication path 2d.

That is, - the first path is a path that passes through the pressure side communication passageway and flows into the outer chamber C via the first damping valve 21;
The path passes through the pressure-side bypass passage III parallel to that, flows into the reservoir chamber via the third port 12d and the first port +2b, flows from the reservoir chamber through the second check passage 16b, and flows into the second chain valve. 1Y is opened to flow into the intermediate chamber E, and from there further flow into the outer chamber C through the base communication passage 22c.

Furthermore, during this pressure side stroke, there is a third path through which the fluid in the upper chamber A flows into the reservoir chamber.

That is, this third path is from the upper chamber A to the first communication hole 22.
a and the upper annular grooves 22d and 22e, and flows into the intermediate chamber via the first damping valve 21. From there, it passes through the second communication hole 16a and the upper annular grooves 16c and +6d, and passes through the second damping valve 15. This is the path that flows into the reservoir chamber.

Therefore, when the pressure side bypass path III is available for circulation (the second
In the state shown in the figure), the first damping valve 21 and both boats 12
A damping force is generated at d and 12b, and in this case, there is a large amount of fluid flowing, and the characteristics are in the low damping force range. Then, the speed 2/3 power characteristic of the first damping valve 21 and the speed square characteristic of both ports 12d and 12b are combined in parallel, resulting in a characteristic linearly proportional to speed.

Also, based on the rotation of the adjuster 2a, both boats 12d and 1
2b, the fluid in the upper chamber A flows into the lower chamber B and the reservoir chamber through the first and third paths, respectively, and a damping force is generated in the first damping valve 21 and the second damping valve 15. In this case, the flow rate of fluid is small, resulting in a high damping current characteristic. Further, the opening area of both ports 12d and +2b can be arbitrarily changed from a fully closed state to a fully open state by moving the vertical groove 2a by rotating the adjuster 2. As a result, the damping current can be changed to any desired range within the range from low damping current to high damping current.

In addition, if the pressure outside (011 room C (lower room)) is lower than that of the server room, the second check valve] Y will open and the fluid in the reservoir room will flow from the middle room E to the outside room. C
supplied to Therefore, even if the first damping valve 21 has high damping force characteristics, during this pressure side stroke, the outside chamber C and the lower chamber connected thereto do not become negative pressure, and cavitation does not occur.

Therefore, the damping force characteristics of the compression side stroke are set by the first damping valve 21.
The damping force characteristic can be varied based on both ports 112d and +2b, and the damping force characteristic can be varied over a wide range.

Next, the sealing action of the rod insertion hole 2a will be explained.

When the piston 5 moves on the pressure side, the fluid pressure in the lower chamber B increases and a pressure difference is generated between the first cylinder tube 1a and the outside, but there is a pressure difference between the rod insertion hole 2a and the piston front. Since it is sealed with a vacuum seal 4a, the leakage fluid that has passed through the vacuum seal 4a will leak through this vacuum seal 4.
While the pressure is reduced at point a, the seal housing γ is moved along the entire gap between the guide bush 4b and the piston rod 6.
The oil seal 4C prevents the fluid from flowing out to the outside of the first cylinder tube 1a.

When the fluid pressure in the seal house sink Y rises due to the inflow of leaked fluid 1, the fluid in the seal house sink Y flows out to the low pressure reservoir chamber side through the pressure relief passage 2e. , the pressure inside the sea house sink is always reduced.

As described above, in this embodiment, the pressure inside the seal house sink Y is always maintained at the same low pressure as the reservoir chamber, so fluid leakage can be reliably prevented while maintaining low friction. This has the feature that the durability of the seal can be improved.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and even if there are design changes within the scope of the gist of the present invention, they are included in the present invention. It will be done.

For example, in the embodiment, the damping force variable structure is provided, but a structure in which the damping current does not change may be used.

Further, the piston may also be provided with a damping bulk.

(Effects of the Invention) As explained above, in the hydraulic shock absorber of the present invention, the pressure inside the seal house sink formed between the double seal structures by the pressure relief channel is always the same as that in the reservoir chamber. Since the hydraulic shock absorber of the present invention is maintained at a low pressure, it is possible to reliably prevent fluid leakage while maintaining low friction. When applied, the effect of improving the ride comfort of the vehicle can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the fluid flow path of the hydraulic shock absorber of the present invention, FIG. 2 is a sectional view showing the main parts of the hydraulic shock absorber of the present invention,
FIG. 3 is a circuit diagram showing the fluid flow path of the embodiment. 1a...-first cylinder tube]b...second cylinder tube 2...guide member 2a...-rod insertion port 2b...-inner member 2d...lower communication passage 2e...pressure relief flow Path 3...Base 4a...-Reducing seal 4c...Oil seal 5...Piston 6...Piston rod a...-Seal housing sink 11...Outer tube 15...-Second damping valve (Damping force generating means) 21...
・First damping valve (damping force generating means) 22b...first
Check flow path A...-Upper chamber B...Lower chamber C...Outer chamber D...Reservoir chamber■...-Pressure side communication path 11...-Elongation side communication path Patent Atsukunisia Co., Ltd. Figure 1 Figure 3

Claims (1)

[Scope of Claims] 1) a first cylinder tube having a guide member having a rod insertion hole at the lower end and a base at the upper end; the inside of the first cylinder tube is defined into an upper chamber and a lower chamber;
A piston connected to a piston rod inserted into the first cylinder tube from the rod insertion hole, and an outer side provided around the first cylinder tube and communicating with the lower chamber via a lower communication passage on the outer periphery of the first cylinder tube. a second cylinder tube that forms a chamber; an outer tube that is provided surrounding the guide member, the second cylinder tube, and the base and forms a reservoir chamber on the outer periphery of the second cylinder tube and the upper part of the base; a pressure-side communication passage that allows fluid in the upper chamber to flow to the outer chamber via the damping force generating means during the pressure-side stroke;
an extension side communication path that allows fluid in the outer chamber to flow to the reservoir chamber via the damping force generating means during the extension stroke; and a check flow path that allows fluid in the reservoir chamber to flow to the upper chamber during the extension stroke; and the piston rod. an oil seal provided outside the rod insertion hole through a seal housing and in contact with the outer peripheral surface of the oil seal; and a pressure relief passage communicating the seal housing and the reservoir chamber. Hydraulic shock absorber.