JP5202426B2 - Shock absorber - Google Patents

Description

The present invention relates to a telescopic shock absorber used for a front fork or the like of a motorcycle.

Volume compensation of hydraulic fluid as a structure to prevent the generation of excessive reaction force when contracting the maximum while allowing the set damping force to be generated in the damper housed in the shaft core part of the front fork For example, the back pressure chamber defined on the back surface of the free piston and the outer cylinder pressure chamber of the cylinder outer cylinder portion that becomes high pressure at the time of the most contraction are cut off.

JP-A-2005-30534

In the configuration of the above-mentioned patent document, since it is necessary to provide two seals on the outer part of the free piston, the sliding resistance increases due to the friction. In addition, since the back pressure chamber defined on the back of the free piston is cut off from the outer cylinder pressure chamber, the internal pressure of the back pressure chamber increases when the temperature rises due to the cushion operation, resulting in a reaction force in the damper. May increase the ride comfort. Therefore, the hydraulic pressure in the sub tank can be blown into the outer cylinder pressure chamber while the pressure in the outer cylinder pressure chamber is not applied to the back pressure chamber of the free piston. It is desirable to do. Moreover, since the reaction force at the time of the most contraction may be required depending on the running condition, it is desirable that the interruption can be easily released in such a case. The present invention aims to realize such a demand.

In order to solve the above problems, the invention according to claim 1 relating to a shock absorber is configured such that an outer tube supported on a vehicle body side and an inner tube supported on a wheel side are relatively telescopically fitted, and these tubes are fitted. A cylindrical damper is housed inside, a piston rod constituting the damper is supported by an inner tube, a sub tank is connected to a cylinder on which a piston provided on the piston rod slides, and an outer tube is connected via the sub tank. The sub tank is provided with a free piston that can be moved according to the fluid amount fluctuation in the cylinder, and the sub tank is divided into a sub tank liquid chamber on the cylinder side and a back pressure chamber on the opposite side by the free piston. In a telescopic shock absorber,
A first blow hole is provided in the back pressure chamber, and a first check valve that allows the flow of fluid only from the back pressure chamber to the outside of the sub tank is provided in the first blow hole.

Further , a cylinder member is provided on the outer periphery of the sub tank chamber, and a space formed between the cylinder member and the sub tank chamber is defined as an intermediate pressure chamber formed between the outer tube and the cylinder and the sub tank chamber. The back pressure chamber is communicated with the first blow hole through the first check valve.
According to a second aspect of the present invention, in the second aspect of the present invention, the second blow hole that communicates the intermediate pressure chamber and the outer cylinder pressure chamber, and the first blow hole are provided and opened at a predetermined set pressure. The first check valve for flowing the fluid only from the sub tank chamber to the intermediate pressure chamber and the second blow hole provided at the predetermined set pressure and flowing the fluid only from the intermediate pressure chamber to the outer cylinder pressure chamber And a second check valve.
The invention described in claim 3, in any of the preceding claims 1 or 2, characterized in that a recess entering outwardly to the inner wall surface of the sub tank of the first blow hole vicinity.
According to a fourth aspect of the present invention, in any one of the first to third aspects, a guide rod that guides the movement of the free piston is provided, and the guide rod has an outer peripheral portion partially reduced in diameter . A narrow diameter portion is formed, and a blow hole (passage) that communicates the sub tank liquid chamber 13 and the back pressure chamber 14 is formed by the small diameter portion .
The invention described in claim 5, in any one of the claims 2-4, wherein the first and second check valve is characterized in that it is constituted by an annular elastic member.

According to the invention described in claim 1, when the free piston reaches the first blow hole when the shock absorber is contracted, the internal pressure of the back pressure chamber is increased, and the first check valve is opened. The first check valve is opened, and the fluid in the back pressure chamber is blown out of the sub tank through the first blow hole to escape. For this reason, the internal pressure of the back pressure chamber can be maintained within a predetermined value.

Further , since the intermediate pressure chamber is provided between the outer tube, the cylinder and the sub tank chamber, the internal pressure of the back pressure chamber can be released to the intermediate pressure chamber. Further, the intermediate pressure chamber can be easily formed by fitting the cylindrical member around the sub tank chamber, and the shock absorber can be made compact.
According to the second aspect of the present invention, when the shock absorber is contracted, the internal pressure of the outer cylinder pressure chamber is larger than the internal pressure of the subtank liquid chamber, but the intermediate pressure chamber is shut off from the outer cylinder pressure chamber, When the free piston reaches the first blow hole, it is constant without being affected by the cylinder pressure chamber, and the internal pressure of the back pressure chamber becomes larger than the set pressure of the first check valve, and the first check valve 61 is opened. Then, the first check valve is opened and the fluid in the back pressure chamber is easily blown into the intermediate pressure chamber.
Thereafter, when the shock absorber expands, the internal pressure of the outer cylinder pressure chamber becomes smaller than the internal pressure of the intermediate pressure chamber. Therefore, the valve opening condition of the second check valve 63 exceeds the predetermined valve opening pressure of the second check valve 63. Then, the second check valve is opened, and the fluid is blown from the second blow hole to the outer cylinder pressure chamber.
For this reason, the working fluid in the sub tank liquid chamber can be blown into the outer cylinder pressure chamber while preventing the pressure in the outer cylinder pressure chamber during expansion / contraction from being applied to the free piston back pressure chamber.
According to the invention described in claim 3 , when the free piston slides from the normal position and passes through the first blow hole, the sliding surface in the vicinity of the first blow hole partially becomes a recess, and the first piston In addition to the second blow hole, there is a blow hole (passage) communicating the sub tank liquid chamber and the back pressure chamber, so that the working fluid in the sub tank liquid chamber is blown into the back pressure chamber of the free piston through this recess. Can be temporarily stored.
According to the fourth aspect of the present invention, the blow hole is a narrow-diameter portion formed in the guide rod, and separately from the first and second blow holes, the blow tank communicating the sub tank liquid chamber and the back pressure chamber. Since it has a hole (passage), when the free piston slides from the normal position and comes on the small diameter part, the hydraulic fluid is blown through the small diameter part to the pressure chamber on the back of the free piston. Can be stored.
According to the invention described in claim 5 , since the first and second check valves are configured by the annular elastic members, the structure becomes simple and the shock absorber can be made compact.

1 is an overall sectional view showing a front fork, FIG. 2 is an enlarged sectional view of the lower part of FIG. 1, FIG. 3 is an enlarged sectional view of the upper part of FIG. 1, and FIG. Is an overall sectional view showing a front fork, FIG. 6 is an enlarged sectional view of the upper part of FIG. 5, FIG. 7 is a sectional view showing a sliding guide structure of a free piston, and FIG. 8 is a sectional view showing an upper cylinder tube.
Note that. In the following description, the vertical direction is based on the state shown in FIG. Moreover, the inside and outside refers to the axial center side of the front fork as the inside and the outside as the outside.

As shown in FIG. 1, the front fork is a telescopic type, and an inner tube 2, which is an axle side tube, is slidably inserted into an outer tube 1, which is a vehicle body side tube. The spring 3 is interposed, and the cylindrical damper 4 is turned upside down. The outer tube 1 is supported on the vehicle body side, and the inner tube 2 is coupled to the axle (both the vehicle body and the axle are not shown).

A main piston 6 slides in a cylinder 5 constituting the damper 4, and the inside is partitioned into an upper first liquid chamber 7 and a lower second liquid chamber 8 with the main piston 6 interposed therebetween. The main piston 6 is supported in the inner tube 2 by the tip of a piston rod 9 extending upward in the axial direction from its lower end.
A sub tank 10 is provided continuously and in communication with the upper end of the cylinder 5, and the sub tank 10 is disposed in the upper end of the outer tube 1. A sub-piston 11 and a free piston 12 are provided in the sub-tank 10 and are partitioned into a first liquid chamber 7 on the cylinder 5 side and a sub-tank liquid chamber 13 on the upper side across the sub-piston 11. The inside of the damper 4 and the outside of the damper 4 are filled with hydraulic fluid such as oil, air is enclosed inside the upper portion of the outer tube 1, and hydraulic fluid and air are mixed in the sub tank 10.

The damper 4 includes a main piston 6 and a sub piston 11, and suppresses expansion and contraction vibration of the outer tube 1 and the inner tube 2 by a damping force generated by the main piston 6 and the sub piston 11.
The sub tank liquid chamber 13 has a variable capacity by a free piston 12 that slides in the sub tank 10, and is partitioned from the upper back pressure chamber 14 by the free piston 12.
An intermediate pressure chamber 15 is provided on the outer periphery of the subtank 10, and is partitioned from the outer cylinder pressure chamber 17 by the partition pipe 16.

The outer cylinder pressure chamber 17 and the outer cylinder side liquid chamber 18 are provided inside the outer tube 1 and the inner tube 2 and outside the damper 4, and the outer cylinder pressure chamber 17 and the outer cylinder side liquid chamber 18 are connected via a free interface. And the air trapped in the outer cylinder pressure chamber 17 constitutes an air spring. These fork springs 3 and air springs generate a reaction force against the load that the vehicle receives from the road surface.

Details of each part will be described below. In FIG. 1, a hydraulic fluid lock collar 20 is fitted in a liquid tight manner on the inner periphery of the lower end portion of the inner tube 2, and the hydraulic fluid lock collar 20 is fixed in a fluid tight manner to the axle bracket 22 by a bottom bolt 21. A bottom end of the piston rod 9 is screwed to the bottom bolt 21 and is locked by a lock nut 23.
The tip of the piston rod 9 is inserted into the cylinder 5. A rod guide 24 is screwed to the lower end portion of the cylinder 5. The piston rod 9 passes through the rod guide 24 and is supported by the rod guide 24 in a liquid-tight and slidable manner.

A seal member 25 is provided between the piston rods 9 at the upper portion of the rod guide 24. The seal member 25 seals the second liquid chamber 8 in the cylinder 5, and the working fluid in the second liquid chamber 8 is transferred to the cylinder. It has a sealing function to prevent escape from 5.
In the figure, reference numeral 26 denotes a hydraulic fluid lock collar provided on the outer periphery of the rod guide 24, and reference numeral 27 denotes a rebound spring, the lower end of which is supported by the upper end of the rod guide 24. Reference numeral 28 denotes a pipe nut integrated by connecting and locking the lower end of the sub tank 10 and the upper end of the cylinder 5.

The fork spring 3 includes a spring receiver 29 provided on the outer peripheral side of the lower end portion of the hydraulic fluid lock collar 20, and a spring receiver 31 provided on a perforated spring collar 30 that is engaged with the outer periphery of the intermediate portion in the axial direction of the cylinder 5. It is intervened between.

Next, the main piston 6 will be described. In FIG. 1, the main piston 6 is supported by a piston holder 32 attached to the tip of the piston rod 9, and includes an expansion side valve 33 so that the first liquid chamber 7 and the second liquid chamber 8 can communicate with each other. The expansion side flow path 34 and the pressure side flow path 36 provided with a pressure side valve 35 to enable communication between the first liquid chamber 7 and the second liquid chamber 8 are provided.

The piston holder 32 is provided with a bypass path 37 between the first liquid chamber 7 and the second liquid chamber 8, and the area of the flow path can be adjusted by a needle 38. The needle 38 is provided at the tip of a damping force adjusting rod 38a passed through the hollow portion of the piston rod 9, and the lower end of the damping force adjusting rod 38a is coupled to an adjuster 39. The damping force can be adjusted by moving it back and forth.

Next, the sub tank 10 will be described. As shown in FIG. 2, the upper end of the sub-tank 10 is screwed to the upper end of the outer tube 1, and the upper end opening of the sub-tank 10 is closed by screwing a fork bolt 40. The upper end of a guide rod 41 that is a pipe is screwed to the fork bolt 40, the guide rod 41 hangs down in the sub-tank 10 in the axial direction, and a valve holder 42 is screwed to the lower end of the guide rod 41 . The sub piston 11 is fixed to the lower end with a nut 43 or the like.
The free piston 12 is externally fitted to the guide rod 41 above the valve holder 42 and is movable up and down along the guide rod 41 .

The sub-piston 11 is disposed relative to the main piston 6 inside the sub-tank 10, and a seal 11 a provided on the outer peripheral portion is in liquid-tight contact with the inner peripheral portion of the sub-tank 10, and the sub-tank is disposed above the first liquid chamber 7. The liquid chamber 13 is partitioned.
The sub-piston 11 is provided with a pressure-side valve 44 so that the first liquid chamber 7 and the sub-tank liquid chamber 13 can communicate with each other, and an extension-side valve 46 is provided with the first-side liquid chamber 7 and the sub-tank liquid chamber 13. And an extension channel (not shown).

The valve holder 42 includes a bypass flow path 47 that bypasses the pressure side flow path 45 and the expansion side flow path to enable communication between the first liquid chamber 7 and the sub tank liquid chamber 13. The channel area of the bypass channel 47 can be adjusted by the needle 48. The needle 48 is provided at the tip of a damping force adjusting rod 48a inserted into the guide rod 41, and the upper end of the damping force adjusting rod 48a is advanced and retracted in the axial direction by rotating the adjuster 49 screwed to the fork bolt 40. Adjust the damping force.

The free piston 12 defines a sub tank liquid chamber 13 and a back pressure chamber 14 forming a volume compensation chamber on the fork bolt 40 side.
The fork bolt 40 has an exhaust plug 55 for exhausting air that has entered the outer cylinder pressure chamber 17 and the back pressure chamber 14 from the sliding portion of the outer tube 1 and the inner tube 2 due to the expansion and contraction of the front fork. Removably screwed to the part.

A piston ring 50 as a seal member is loaded in an annular groove formed in the outer peripheral portion of the free piston 12, and the free piston 12 slides liquid-tightly on the inner periphery of the sub tank 10 through the piston ring 50. Thus, the sliding resistance can be reduced by using only one piston ring 50.

A boss 51 protruding upward is provided at the center of the upper surface of the free piston 12, and the guide rod 41 passes through the boss 51, and a hydraulic fluid seal 52 is provided on the inner peripheral surface of the boss 51. The outer periphery of the guide rod 41 is slid liquid-tightly via the hydraulic fluid seal 52.

The periphery of the boss 51 forms a spring receiving surface 53 and supports the lower end of the spring 54. The upper end of the spring 54 is supported by the fork bolt 40.
The spring 54 has a slight initial load so as to pressurize the oil even when the front fork is fully extended.

At the time of compression, the piston rod 9 entering the cylinder 5 compensates for the piston rod integral and the volume increase of the working fluid integral that has entered the cylinder 5 and entered the cylinder 5 by sliding of the free piston 12.

Given the thus configured front fork, at the time of compression results in a compression side damping force by hydraulic fluid flowing through the two Doru 48 and the compression side valve 44 in the sub-piston 11, the hydraulic fluid flowing through the compression side valve 35 in the main piston 6 The compression side damping force is generated.
At the time of extension, an extension side damping force is generated in the main piston 6 by the hydraulic fluid flowing through the needle 38 and the extension side flow path 34.
These compression side and extension side damping forces suppress the expansion and contraction vibration of the front fork.

When the front fork is compressed most, the hydraulic fluid lock collar 26 attached to the outer periphery of the rod guide 24 provided at the lower end portion of the cylinder 5 is replaced with the hydraulic fluid lock collar 17 provided at the lower end portion of the inner tube 2. By engaging and compressing the hydraulic fluid, the hydraulic fluid is locked and the bottom of the damper 4 is prevented (see FIG. 1).
When the front fork is fully extended, the lower end surface of the piston holder 32 provided on the piston rod 9 compresses and extends the rebound spring 27 supported by the rod guide 24 provided at the opening of the cylinder 5. Buffers the time (same as above).

Next, the blow structure will be described. In FIG. 2, each time the piston rod 9 makes a stroke, the main piston 6 increases the volume of the piston rod volume, and in addition, causes the working fluid in the second liquid chamber 8 attached to the outer peripheral surface of the piston rod 9 to pass through the rod guide 24 . It is brought into the cylinder 5 from the seal member 25. Due to this piston rod adhering oil, the working fluid in the first fluid chamber 7, the second fluid chamber 8 and the sub tank fluid chamber 13 inside the cylinder 5 gradually increases. For this reason, it has a blow function which discharges the fluid (working fluid and air) excessively stored in the sub tank liquid chamber 13 to the outer cylinder side liquid chamber 18. Also, it has a function of blowing hydraulic fluid from the sub tank liquid chamber 13 to the back pressure chamber 14.

In order to realize this blow function, a first blow hole 60 is provided in the upper part of the sub tank 10 so as to face the back pressure chamber 14, and the outside is normally closed by a first check valve 61. The inner wall surface of the sub tank 10 in the vicinity of the first blow hole 60 forms a concave portion 60a that protrudes outward, and when the free piston 12 moves onto the concave portion 60a, as shown in the enlarged portion of FIG. A gap is formed between the outer peripheral portion of the free piston 12 including the piston ring 50 that is the 12 seal members and the recess 60a.

When the amount of hydraulic fluid in the subtank liquid chamber 13 increases, the free piston 12 moves onto the recess 60a, and a gap is formed between the outer peripheral portion of the free piston 12 and the recess 60a, the subtank liquid chamber 13 and the back pressure chamber Since 14 is communicated, the hydraulic fluid can flow from the subtank liquid chamber 13 to the back pressure chamber 14 and temporarily stored as indicated by the solid line arrow. The gap between the outer periphery of the free piston 12 and the recess 60 a forms a blow hole (passage) that communicates the sub tank liquid chamber 13 and the back pressure chamber 14 separately from the first blow hole 60 and the second blow hole 62.

The first blow hole 60 is normally disconnected by the first check valve 61 and is disconnected from the intermediate pressure chamber 15, but the internal pressure P1 of the back pressure chamber 14 is equal to the internal pressure P2 of the intermediate pressure chamber 15 and the first check. Only when the opening condition of the first check valve 61 becomes higher than the sum of the valve opening pressures P4 of the valve 61, that is, when P1> (P2 + P4), the first check valve 61 opens outward and the first blow hole 60 is opened. Is released, and a fluid composed of air or hydraulic fluid is discharged to the intermediate pressure chamber 15, thereby releasing an excessive internal pressure in the back pressure chamber 14.

When the internal pressure P1 of the back pressure chamber 14 rises due to the movement of the free piston 12 and reaches a set pressure in which the differential pressure of P1-P2 is set to a predetermined value in advance, the first check valve 61 is turned on as indicated by a virtual line. Push and open to discharge the fluid consisting of hydraulic fluid and air to the intermediate pressure chamber 15. While the differential pressure exceeds the set pressure, the fluid escapes from the first blow hole 60 to the intermediate pressure chamber 15 and the internal pressure P1 of the back pressure chamber 14 decreases, so that the internal pressure P1 of the back pressure chamber 14 can be adjusted. it can.

A second blow hole 62 is also formed in the partition pipe 16 at the lower part of the intermediate pressure chamber 15, and the second blow hole 62 is also normally closed by the second check valve 63 from the outside, and the internal pressure P 2 in the intermediate pressure chamber 15 is Only when the opening condition of the second check valve 63 becomes higher than the sum of the internal pressure P3 of the cylinder pressure chamber 17 and the opening pressure P5 of the second check valve 63, that is, when P2> (P3 + P5), the second check valve 63 is outside. The second blow hole 62 is opened and the excess fluid in the intermediate pressure chamber 15 is discharged to the outer cylinder pressure chamber 17. Of the fluid discharged to the outer cylinder pressure chamber 17, air remains in the outer cylinder pressure chamber 17, and the working fluid flows into the lower outer cylinder side liquid chamber 18.

The upper end portion of the partition pipe 16 is liquid-tightly fitted on the large diameter portion 64 formed on the upper portion of the sub tank 10 via a seal 65, and the lower end portion is also formed on the large diameter portion 66 formed on the upper side surface of the cylinder 5. As a result, the intermediate pressure chamber 15 is fitted between the partition pipe 16 and the periphery of the portion having a relatively small diameter portion of the sub tank 10 and the partition pipe 16. It is long along the axial direction.
The large-diameter portion 66 is formed at the lower end portion of the sub tank 10 slightly below the step portion 69 that changes to a small-diameter portion below the sub piston 11, and the intermediate pressure chamber 15 in this portion is located below the step portion 69. As the diameter is reduced, the capacity is increased, and the second blow hole 62 faces this portion. Further, by utilizing this capacity, the end of the partition pipe 16 is thickened to increase the rigidity, so that the second blow hole 62 can be formed and the second check valve 63 can be attached.

As shown in FIG. 3, the first check valve 61 is a ring made of an appropriate elastic member such as a rubber band. The first check valve 61 extends to the outer periphery of the sub-tank 10 where the first blow hole 60 is formed. The first blow hole 60 is closed by its external resilience and wound by external fitting, and a normally closed check valve is maintained that maintains the closed state until the internal pressure P1 in the back pressure chamber 14 overcomes this resilience. To do. In addition, since the check valve can be configured simply by externally fitting an elastic ring such as a rubber band, the structure can be simple and inexpensive.

Further, in an off-road vehicle or the like, since the reaction force at the time of the most contraction is required, when it is desired to communicate the back pressure chamber 14 with the intermediate pressure chamber 15 , it is easy to simply pull out an elastic ring such as a rubber band. Therefore, there is no need for special additional processing, and the specification change becomes extremely easy. However, check valves having various known structures can be used as appropriate without using such a structure. The second check valve 63 has the same structure as the first check valve 61.

Next, the operation of this embodiment will be described. When the front fork contracts, the volume of the outer cylinder pressure chamber 17 decreases with the stroke, and the internal pressure P3 increases. The free piston 12 also strokes with the hydraulic fluid corresponding to the increased volume of the piston rod 9 that enters the cylinder 5, and the internal pressure P1 of the back pressure chamber 14 rises. However, it is considered in advance that the rear pressure chamber 14 has a sufficient volume so that the internal pressure P1 does not become an excessively large damper reaction force even in the vicinity of the maximum compression, and the first check valve 61 and the second check valve 63 are used. Therefore, the pressure from the outer cylinder pressure chamber 17 side and the intermediate pressure chamber 15 is not applied. Further, in the state where the first check valve 61 and the second check valve 63 are not opened, the internal pressure P2 of the intermediate pressure chamber 15 is constant.

When the amount of hydraulic fluid in the subtank liquid chamber 13 increases and the free piston 12 moves onto the recess 60a, blow occurs and the hydraulic fluid flows from the subtank liquid chamber 13 to the back pressure chamber 14 and is temporarily stored. The Further, when the internal pressure P1 of the back pressure chamber 14 increases due to a temperature rise or hydraulic fluid that has entered from the lower part of the cylinder 5 and P1> (P2 + P4), the first check valve 61 is opened, and the intermediate pressure from the back pressure chamber 14 is increased. A fluid blow occurs in the chamber 15, and an excessive pressure is released to the intermediate pressure chamber 15. At this time, the stroke amount of the front fork is sufficient, and the internal pressure P3 of the outer cylinder pressure chamber 17 is also sufficiently high. Therefore, the second check valve 63 is not opened, and the intermediate pressure chamber 15 and the outer cylinder pressure chamber 17 remain blocked. is there.

Thereafter, when turning to elongation, the internal pressure P3 of the outer cylinder pressure chamber 17 decreases. On the other hand, the intermediate pressure chamber 15 is pressurized by the inflow of fluid from the back pressure chamber 14, and the internal pressure P2 of the intermediate pressure chamber 15 is reduced by the pressure drop of the internal pressure P3 of the outer cylinder pressure chamber 17 in the vicinity of the full extension, P2> When (P3 + P5) is reached, the second check valve 63 is opened, blow occurs from the intermediate pressure chamber 15 to the outer cylinder pressure chamber 17 through the second blow hole 62, and hydraulic fluid and air are discharged, and the intermediate pressure chamber 15 The internal pressure P2 does not become excessive. Moreover, since the second check valve 63 is provided in the lower part of the intermediate pressure chamber 15, it is easy to discharge the hydraulic fluid.

By configuring the blow structure in this way, the internal pressure of the back pressure chamber 14 can always be kept within a specified value. In addition, by providing the intermediate pressure chamber 15, the internal pressure of the back pressure chamber 14 can be appropriately maintained even when the temperature rises due to the expansion and contraction operation of the front fork (buffer).

    Next, another embodiment will be described. FIG. 4 is a view similar to FIG. 2 according to another embodiment, and FIG. In addition, the same code | symbol is used for the part which is common in previous embodiment, and duplication description is abbreviate | omitted. In this embodiment, a blow hole (passage) that communicates the sub-tank liquid chamber 13 and the back pressure chamber 14 is provided separately from the first blow hole 60 and the second blow hole 62 by the small diameter portion 70 provided in the guide rod 41. The point formed is different from the previous embodiment.

FIG. 5 shows an enlarged view of the state when the free piston 12 moves on the small diameter portion 70. When the free piston 12 comes on the small diameter portion 70, the free piston 12 is provided on the inner peripheral portion of the free piston 12. Since a gap is formed between the sliding surface of the working fluid seal 52 and the small diameter portion 70, the working fluid in the sub tank fluid chamber 13 blows to the back pressure chamber 14. At this time, the hydraulic fluid in the subtank liquid chamber 13 enters the gap from the opening of the hydraulic fluid seal 52 that opens relatively large toward the subtank liquid chamber 13 as indicated by the solid line, and the hydraulic fluid passes through the gap to the back surface. It moves to the pressure chamber 14 and is temporarily stored here. In this way, since only the outer peripheral portion of the guide rod 41 is processed into a small diameter, a blow structure from the sub tank liquid chamber 13 to the back pressure chamber 14 can be easily manufactured.

Further, only one O-ring 71 is fitted in the annular groove formed in the outer peripheral portion of the free piston 12. In this way, the sliding resistance can be reduced by using the seal member alone, and the manufacturing becomes easy. The free piston 12 is integrally provided with a cylindrical wall 72 protruding into the back pressure chamber 14, and a pressure relief hole 73 is formed in a part of the cylindrical wall 72. The cylindrical wall 72 is an annular wall that surrounds the periphery of the spring 54 and protrudes along the axial direction of the sub-tank 10, and has an outer peripheral surface facing the inner peripheral surface of the sub-tank 10 with a predetermined interval. The pressure fluid in the back pressure chamber 14 is allowed to escape from the pressure release hole 73 toward the first blow hole 60 as indicated by phantom lines.

Overall sectional view showing the front fork Upper enlarged sectional view of FIG. It is a perspective view of the principal part. The same figure as FIG. 2 which concerns on another embodiment Explanatory drawing of the effect | action in another embodiment

1: outer tube, 2: inner tube, 4: damper, 5: cylinder. 6: Main piston, 9: Piston rod, 10: Sub tank, 11: Sub piston. 12: free piston, 13: sub tank liquid chamber, 14: back pressure chamber, 15: intermediate pressure chamber, 16: partition pipe, 17: outer cylinder pressure chamber, 60: first blow hole, 61: first check valve, 62 : Second blow hole, 63: Second check valve

Claims (5)

The outer tube (1) supported on the vehicle body side and the inner tube (2) supported on the wheel side are relatively telescopically fitted, and the cylindrical damper (4) is accommodated inside these tubes. The piston rod (9) constituting the damper is supported on the inner tube, and the sub tank (10) is connected to the cylinder (5) on which the piston (6) provided on the piston rod slides. A free piston (12) that is supported by the outer tube and is movable in accordance with fluctuations in the amount of liquid in the cylinder is provided in the sub tank, and the inside of the sub tank is opposite to the sub tank liquid chamber (13) on the cylinder side by the free piston. A telescopic shock absorber partitioned into a back pressure chamber (14) of
The first blow hole (60) provided on the back pressure chamber, the first blow hole, provided with the first check valve which permits a flow of fluid only to the sub-tank outside from the rear pressure chamber (61) Rutotomoni,
A cylinder member is provided on the outer periphery of the sub tank chamber, and a space formed between the cylinder member and the sub tank chamber is defined as an intermediate pressure chamber (15) formed between the outer tube and the cylinder and the sub tank chamber. A shock absorber characterized in that a chamber and the back pressure chamber are communicated with each other through the first check valve through the first blow hole . A second blow hole (62) communicating the intermediate pressure chamber (15) and the outer cylinder pressure chamber (17) ;
A first check valve (61) provided in the first blow hole, opened at a predetermined set pressure, and allowing fluid to flow only from the sub tank chamber to the intermediate pressure chamber;
A second check valve (63) is provided in the second blow hole (62) , opens at a predetermined set pressure, and flows a fluid only from the intermediate pressure chamber to the outer cylinder pressure chamber. Item 4. The shock absorber according to item 1. The shock absorber according to any one of claims 1 and 2, wherein a recess (60a) is provided on an inner wall surface of the sub tank (10) in the vicinity of the first blow hole. A guide rod (41) for guiding the movement of the free piston is provided, and the guide rod is formed with a narrow diameter portion (70) in which the outer periphery of the guide rod is partially narrowed, and the sub tank is formed by the narrow diameter portion. The shock absorber according to any one of claims 1 to 3, wherein a blow hole (passage) communicating the liquid chamber 13 and the back pressure chamber 14 is formed . The shock absorber according to any one of claims 2 to 4 , wherein the first and second check valves are constituted by annular elastic members.

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