JP6114652B2 - Shock absorber - Google Patents

Description

  It is related with improvement of a shock absorber.

  In general, the shock absorber attenuates vibrations of a vehicle, equipment, structure, or the like. For example, a shock absorber D2 disclosed in Patent Document 1 shown in FIG. 2 is interposed between a bicycle body and a wheel, and is formed and operated in a cylinder 100 coupled to the vehicle body side. A working chamber (not shown) filled with liquid, a piston rod 300 connected to the wheel side to enter and exit the cylinder 100, a bladder 500 provided outside the cylinder 100 and capable of expanding and contracting, and the bladder 500 are partitioned. Resistant to the liquid reservoir chamber b3 filled with the hydraulic fluid, the pipe H communicating the hydraulic chamber and the liquid reservoir chamber b3, and the hydraulic fluid moving between the hydraulic chamber and the liquid reservoir chamber b3 through the pipe H. And a damping valve V6. In the shock absorber D2, when an impact due to road surface unevenness is input to the wheel and the piston rod 300 enters and exits the cylinder 100, the hydraulic fluid corresponding to the piston rod volume that enters and exits the cylinder 100 passes through the conduit H and passes through the cylinder 100. Since it moves between the inner working chamber and the liquid reservoir b3, the shock absorber D2 can generate a damping force due to the resistance of the damping valve V6. Furthermore, according to the above configuration, since the liquid reservoir chamber b3, the bladder 50 that partitions the liquid reservoir chamber b3, and the damping valve V6 are provided separately from the cylinder 100 outside the cylinder 100, the shock absorber D2 is provided. The mountability of the shock absorber D2 can be improved without being bulky in the longitudinal direction.

JP 2001-304325 A

  However, the structure of the conventional shock absorber D2 cannot be applied to a shock absorber provided with a relief mechanism as disclosed in, for example, Japanese Patent Laid-Open No. 2005-30534. This is because, as shown in FIG. 3, such a shock absorber D <b> 3 includes a free piston 400 slidably contacting the inner peripheral surface of the cylinder 100 on the side opposite to the piston rod and defining a liquid reservoir chamber b <b> 3 in the cylinder 100, A telescopic tube member T that is disposed on the outer periphery and forms a reservoir R between the cylinder 100 and the cylinder 100 is provided, and the hydraulic fluid in the cylinder 100 increases or the hydraulic fluid expands due to a temperature rise (not shown). When the amount of the piston rod entering the cylinder 100 increases, the free piston 400 moves backward by a predetermined amount so that the hydraulic fluid in the cylinder 100 can be discharged to the reservoir R, that is, can be relieved, and dissolved in the hydraulic fluid. Even if the gas that has been deposited is deposited, the gas can be discharged out of the cylinder 100 together with the hydraulic fluid during relief. However, if the technique of Patent Document 1 is applied and the liquid reservoir b3 and the free piston 400 that partitions the liquid reservoir b3 are moved out of the cylinder 100 and separated from the cylinder 100, the gas deposited in the cylinder 100 during relief May not be discharged, and gas may be accumulated in the cylinder 100 to reduce the damping force generation response.

  Accordingly, an object of the present invention is to provide a shock absorber capable of improving mountability by suppressing bulkiness in the longitudinal direction even when a relief mechanism is provided.

  Means for solving the above problems are a telescopic tube member comprising an outer tube and an inner tube that enters and exits the outer tube, a cylinder that stands up within the tube member, and an axial movement within the cylinder. A piston inserted into the piston, a piston rod that stands up on one side of the piston and projects out of the cylinder, a rod side chamber and a piston side chamber that are partitioned by the piston and filled with hydraulic fluid, the tube member, and the cylinder And a reservoir in which hydraulic fluid is stored, and a free piston that is inserted in the axial direction so as to be movable on the anti-piston rod side of the cylinder, and the piston-side chamber with the free piston. A first liquid reservoir chamber that is partitioned and filled with hydraulic fluid, and is provided outside the tube member. A housing, a second liquid reservoir chamber that is formed in the housing and in which hydraulic fluid is stored and can be expanded and contracted, a communication member that communicates the first liquid reservoir chamber and the second liquid reservoir chamber, and the housing A base member that is fixed and divides the first liquid reservoir chamber and the second liquid reservoir chamber; and a relief mechanism that discharges the hydraulic fluid in the piston side chamber to the reservoir when the free piston is retracted by a predetermined amount. It is.

  According to the shock absorber of the present invention, even if a relief mechanism is provided, it is possible to suppress the bulkiness in the longitudinal direction and improve the mountability.

It is the front view which notched and showed the buffer which concerns on one embodiment of this invention partially. It is the front view which notched and showed the conventional shock absorber partially. It is the longitudinal cross-sectional view which showed the principal part of the other conventional shock absorber.

  A shock absorber according to an embodiment of the present invention will be described below with reference to the drawings. The same reference numerals given throughout the several drawings indicate the same or corresponding parts.

  As shown in FIG. 1, the shock absorber D1 according to the present embodiment includes a telescopic tube member T composed of an outer tube t1 and an inner tube t2 that enters and exits the outer tube t1, and stands in the tube member T. A cylinder 1 that is inserted into the cylinder 1 so as to be movable in the axial direction, a piston rod 3 that stands on one side of the piston 2 and protrudes outside the cylinder 1, and the piston 2. And a rod side chamber a1 and a piston side chamber a2 filled with the working fluid, and a reservoir R formed between the tube member T and the cylinder 1 for storing the working fluid.

  Further, the shock absorber D1 includes a free piston 4 that is inserted on the side opposite to the piston rod of the cylinder 1 so as to be movable in the axial direction, and is partitioned from the piston side chamber a2 by the free piston 4 and filled with hydraulic fluid. One liquid reservoir chamber b1, a housing 5 provided outside the tube member T, a second liquid reservoir chamber b2 formed in the housing 5 and capable of storing and expanding and contracting hydraulic fluid, and the first liquid reservoir chamber a communication member H that communicates b1 and the second liquid reservoir chamber b2, a base member 6 that is fixed to the housing 5 and divides the first liquid reservoir chamber b1 and the second liquid reservoir chamber b2, and the free member And a relief mechanism E that discharges the hydraulic fluid in the piston side chamber a2 to the reservoir R when the piston 4 moves backward by a predetermined amount.

  Further, in the present embodiment, the shock absorber D1 is used for a front fork that suspends a front wheel of a saddle-ride type vehicle such as a two-wheeled vehicle or a three-wheeled vehicle. Since the structure of the front fork is well known, it is not shown in detail, but the front fork is a pair of shock absorbers standing on both sides of the front wheel (only one shock absorber D1 is shown, and the other shock absorber is not shown). ), And a vehicle body side bracket (not shown) connected to the vehicle body frame which is a skeleton of the vehicle body, and a wheel side bracket W which connects each shock absorber to the axle of the front wheel. In the present embodiment, the present invention is embodied in one or both of a pair of shock absorbers constituting the front fork. The shock absorber according to the present invention may be used in addition to the front fork, and may be used for a rear cushion for suspending a rear wheel of a two-wheeled vehicle or for other vehicles.

  Hereinafter, one shock absorber D1 in which the present invention is embodied in the present embodiment will be described in detail. The shock absorber D1 stands on one side of the tube member T, a cylinder 1 standing in the tube member T, a piston 2 movably inserted in the cylinder 1 in the axial direction, and the piston 2. A piston rod 3 projecting out of the cylinder 1, a free piston 4 movably inserted in the axial direction on the side opposite to the piston rod of the cylinder 1, a housing 5 provided outside the tube member T, and the housing 5 And a base member 6 fixed via a base rod 7.

  As described above, the tube member T is composed of the outer tube t1 and the inner tube t2 that enters and exits the outer tube t1 and is a telescopic type, and constitutes the outer shell of the shock absorber D1. The upper opening of the tube member T is closed with the cap member C, and the lower opening of the tube member T is closed with the wheel side bracket W, and is formed between the overlapping portions of the outer tube t1 and the inner tube t2. Since the lower opening of the cylindrical gap is closed by the annular dust seal s1 and the oil seal s2, the liquid or gas stored in the tube member T is prevented from leaking to the outside air side. In the present embodiment, a vehicle body side bracket (not shown) is attached to the outer tube t1, and a wheel side bracket W is attached to the inner tube t2. When the impact due to road surface unevenness is input to the front wheel, the inner tube t2 The shock absorber D can be expanded and contracted by entering and exiting the outer tube t1. In this embodiment, the outer tube t1 is connected to the vehicle body side, and the inner tube t2 is connected to the wheel side so that the front fork is set upside down. However, the outer tube t1 is connected to the wheel side. In addition, the inner fork t2 may be connected to the vehicle body side and the front fork may be set upright.

  The cylinder 1 standing in the tube member T is formed in a cylindrical shape and is held in a state of being suspended from the cap member C, and a sub cylinder 10 into which a free piston 4 is inserted, and the sub cylinder 10. 1 and a cylinder body 11 into which the piston 2 is inserted. The sub-cylinder 10 includes a holding portion 10a in which the cylinder body 11 is screwed to the inner periphery, a sliding contact portion 10b coaxially connected to the upper side of the holding portion 10a, and an inner diameter sliding to the upper side of the sliding contact portion 10b. The enlarged diameter part 10c formed larger than the internal diameter of the contact part 10b, and the communicating hole 10d which penetrates the thickness of this enlarged diameter part 10c are provided. The upper opening of the sub cylinder 10 is closed with the cap member C, and the connecting portion between the sub cylinder 10 and the cylinder body 11 is closed with the seal s3. Further, an annular rod guide 8 through which the piston rod 3 passes is provided in the lower opening in FIG. 1 of the cylinder body 11, and the cylinder 1 and the piston rod are sealed by a seal (not shown) held by the rod guide 8. 3 is blocked.

  In the cylinder 1, a first liquid reservoir chamber b1 on the upper side in FIG. 1 and a working chamber A on the lower side in FIG. 1 are defined by a free piston 4 inserted in the sub-cylinder 10. The chamber A is divided by a piston 2 inserted into the cylinder body 11 into a lower rod side chamber a1 in FIG. 1 and an upper piston side chamber a2 in FIG. The first liquid reservoir b1, the rod side chamber a1, and the piston side chamber a2 formed in the cylinder 1 are filled with hydraulic fluid, respectively. In this embodiment, this hydraulic fluid is called hydraulic fluid. Although it consists of oil, you may consist of other liquids, such as water and aqueous solution. On the other hand, a reservoir R is formed between the tube 1 and the tube member T. The reservoir R stores the working fluid, and gas flows upward through the fluid level of the working fluid. It is enclosed.

  The free piston 4 includes a bottomed cylindrical partition wall 40 and a pair of upper and lower annular seals 41 and 42 held on the outer periphery of the partition wall 40. The upper seal 41 is always in sliding contact with the inner peripheral surface of the enlarged diameter portion 10c above the communication hole 10d of the sub cylinder 10 and closes the space between the partition wall portion 40 and the sub cylinder 10. On the other hand, the lower seal 42 normally slidably contacts the inner peripheral surface of the slidable contact portion 10b and closes the space between the partition wall portion 40 and the sub cylinder 10. When the amount of the piston rod 3 entering the cylinder 1 increases in a state where the hydraulic fluid expands due to an increase or a temperature rise, the diameter reaches the enlarged diameter portion 10c, and between the enlarged diameter portion 10c and the lower seal 42. A gap is created. Accordingly, the hydraulic fluid in the piston side chamber a2 can be moved to the reservoir R through the gap and the communication hole 10d, that is, can be relieved. That is, in the present embodiment, the relief mechanism E is formed in the enlarged diameter portion 10c that creates a gap between the free piston 4 and the free piston 4 when the free piston 4 is retracted by a predetermined amount, and the enlarged diameter portion 10c is formed in the reservoir R. The open communication hole 10d is provided. The shock absorber D1 includes the relief mechanism E, thereby suppressing an excessive increase in the cylinder internal pressure and discharging the gas deposited in the working chamber A to the outside of the cylinder 1 at the time of relief.

  Subsequently, the piston 2 that divides the working chamber A into a rod-side chamber a1 and a piston-side chamber a2 is in sliding contact with the inner peripheral surface of the cylinder body 11, and the piston 2 is connected to the rod-side chamber a1 and the piston-side chamber a2. A communicating extension side and pressure side piston passage 21 (only the pressure side piston passage 21 is shown and the extension side piston passage is not shown) is formed, and the extension side damping is formed on the piston side chamber a2 side which is the upper side in FIG. A valve V1 is laminated, and a pressure side check valve V2 is laminated on the rod side chamber a1 side which is the lower side in FIG. The expansion side damping valve V1 allows the flow of the hydraulic fluid that moves from the rod side chamber a1 to the piston side chamber a2 through an expansion side piston passage (not shown) and blocks the flow in the opposite direction. Further, the expansion side damping valve V1 is set to have a high valve opening pressure, and is set so as to give a predetermined resistance to the hydraulic fluid passing through the expansion side piston passage (not shown). On the other hand, the pressure-side check valve V2 allows the flow of hydraulic fluid that moves the pressure-side piston passage 21 from the piston-side chamber a2 to the rod-side chamber a1, and blocks the flow in the opposite direction. Further, the pressure check valve V2 is set so that the valve opening pressure is low and the resistance given to the hydraulic fluid passing through the pressure side piston passage 21 is small. Note that the valve opening pressures of the extension side damping valve V1 and the pressure side check valve V2 can be arbitrarily set so that the damping characteristic of the shock absorber D1 becomes a desired characteristic.

  The piston 2 is held on the outer periphery of the upper end portion in FIG. 1 of the piston rod 3 that is formed in an annular shape and is inserted into the cylinder 1. The piston rod 3 extends outside the cylinder 1 through the rod side chamber a1 and the shaft center portion of the rod guide 8, and the lower end portion in FIG. 1 is fixed to the bottom portion of the wheel side bracket W. An annular bush (not shown) is fitted to the inner periphery of the rod guide 8, and the piston rod 8 is pivotally supported by the bush so as to be movable in the axial direction. The piston rod 3 bypasses the rod side chamber a1 and the piston side chamber a2 by bypassing the expansion side and pressure side piston passages 21 (only the pressure side piston passage 21 is shown and the expansion side piston passage 21 is not shown). A bypass passage 30 that communicates is formed, and a needle valve 31 that squeezes the bypass passage 30 to form a known orifice is inserted into the bypass passage 30. The opening amount of the bypass passage 30 can be adjusted by operating the push rod.

  Subsequently, the housing 5 provided outside the tube member T has a hollow portion. The housing 5 is partitioned by an elastically deformable bladder 50 and filled with a working fluid b2. And an air chamber G in which gas is enclosed. When the hydraulic fluid flows out from the second liquid reservoir b2, the gas chamber G expands, so that the second liquid reservoir chamber b2 is reduced, and when the hydraulic fluid flows into the second liquid reservoir b2, the gas chamber G is reduced. As a result, the second liquid reservoir chamber b2 expands. That is, in the present embodiment, the second liquid reservoir chamber b2 is partitioned from the air chamber G by the bladder 50, whereby the second liquid reservoir chamber b2 can be expanded and contracted. Note that, for example, a free piston or a bellows may be used instead of the bladder 50 in order to expand and contract the second liquid reservoir chamber b2.

  The housing 5 is connected to a communication member H made of a hose or the like for communicating the second liquid reservoir chamber b2 and the first liquid reservoir chamber b1, and between the communication member H and the second liquid reservoir chamber b2. And a base member 6 that partitions the first liquid reservoir chamber b1 and the second liquid reservoir chamber b2, a base rod 7 that holds the base member 6 at the tip, a pressure sensor 51, and an actuator 52 are attached. ing.

  The base member 6 is formed with an extension side and pressure side base member passages 60 and 61 communicating with the second liquid reservoir chamber b2 and the first liquid reservoir chamber b1, and on the first liquid reservoir chamber b1 side. 1, an extension check valve V3 is stacked on the upper side, and a pressure-side damping valve V4 is stacked on the lower side in FIG. The extension-side check valve V3 allows the flow of hydraulic fluid that moves from the second liquid reservoir chamber b2 to the first liquid reservoir chamber b1 through the extension-side base member passage 60, and blocks the flow in the opposite direction. Further, the extension check valve V3 is set so that the valve opening pressure is low and the resistance given to the working fluid passing through the base member passage 60 on the extension side is reduced. On the other hand, the pressure side damping valve V4 allows the flow of the working fluid that moves in the pressure side base member passage 61 from the first liquid reservoir chamber b1 to the second liquid reservoir chamber b2, and blocks the flow in the opposite direction. Further, the pressure side damping valve V4 is set so that the initial load is applied and the valve opening pressure is set high, and is set so as to give a predetermined resistance to the hydraulic fluid passing through the pressure side base member passage 61. Note that the valve opening pressures of the extension-side check valve V3 and the pressure-side damping valve V4 can be arbitrarily set so that the damping characteristics of the shock absorber D1 become desired characteristics.

  The base member 6 is held on the outer periphery of the tip of a base rod 7 that is formed in an annular shape and is fixed inside the housing 5. A bypass passage 70 is formed from the base rod 7 to the housing 5 so as to bypass the extension-side and pressure-side base member passages 60 and 61 and connect the first liquid reservoir chamber b1 and the second liquid reservoir chamber b2. Hereinafter, in order to distinguish the bypass passage 70 from the bypass passage 30 formed in the piston rod 3, the bypass passage formed in the piston rod 3 is formed from the first bypass passage 30 and the base rod 7 to the housing 5. Let the bypass passage be the second bypass passage 70. The second bypass passage 70 is provided with a valve body V5 that opens and closes the second bypass passage 70. In the present embodiment, a pressure sensor 51 that detects the pressure in the first liquid reservoir b1 and an actuator 52 that biases the valve body V5 in the closing direction are attached to the housing 5. And this actuator 52 consists of a well-known proportional solenoid, The valve opening pressure of the valve body V5 is arbitrarily set by changing the electric current supplied to the coil of the actuator 52 based on the value detected by the pressure sensor 51. Can be adjusted. For example, if the current supply amount to the actuator 52 is increased, the valve opening pressure of the valve body V5 can be increased, and conversely, if the current supply amount to the actuator 52 is decreased, the valve opening pressure of the valve body V5 is increased. Can be small.

  Hereinafter, the operation of the shock absorber D1 according to the present embodiment will be described.

  Since the extension side damping valve V1 does not open when the piston speed is in the low speed region when the shock absorber D1 is extended so that the inner tube t2 is retracted from the outer tube t1 and the piston rod 3 is retracted from the cylinder 1, the piston 2 The hydraulic fluid in the rod side chamber a1 pressurized in step passes through the first bypass passage 30 and moves to the piston side chamber a2. Further, when the shock absorber D1 is extended, the piston speed increases, and when the shock absorber D1 leaves the low speed region and reaches the medium high speed region, the expansion side damping valve V1 opens and the hydraulic fluid in the rod side chamber a1 pressurized by the piston 2 is opened. Passes through the piston passage on the extension side (not shown) and moves to the piston side chamber a2.

  When the shock absorber D1 is extended, the internal volume of the piston rod integral cylinder that has withdrawn from the cylinder 1 increases, so that the free piston 4 moves downward in FIG. 1 and the extension check valve V3 opens. The hydraulic fluid in the second liquid reservoir b2 passes through the base member passage 60 and the communication member H on the extension side and flows into the first liquid reservoir b1 so that the air chamber G is expanded.

  In the present embodiment, since the resistance by the expansion check valve V3 is set to be small, when the piston speed is in the low speed region when the shock absorber D1 is extended, the shock absorber D1 mainly has the hydraulic fluid in the first bypass. When the expansion side low-speed damping force due to the resistance of the orifice formed by the needle valve 31 when passing through the passage 30 is generated and the piston speed is in the medium-high speed region when the shock absorber D1 extends, the shock absorber D1 The expansion side medium and high speed damping force is mainly generated due to the resistance of the expansion side damping valve V1 when the hydraulic fluid passes through the expansion side piston passage (not shown).

  On the other hand, when the shock absorber D1 in which the inner tube t2 enters the outer tube t1 and the piston rod 3 enters the cylinder 1 is compressed, the compression side check valve V2 is opened and the piston side chamber a2 pressurized by the piston 2 is opened. The hydraulic fluid passes through the pressure side piston passage 21 and moves to the rod side chamber a1.

  When the shock absorber D1 is compressed, the piston rod volume integrating cylinder volume that has entered the cylinder 1 is reduced, so that the free piston 4 moves backward in FIG. When the piston speed is in the low speed region, the pressure-side damping valve V4 does not open, so that the hydraulic fluid in the first liquid reservoir b1 passes through the communication member H and the second bypass passage 70 and passes through the second liquid reservoir b2. The air chamber G is reduced. When the piston speed increases and the low-speed region is reached and the middle-high speed region is reached, the pressure-side damping valve V4 opens, and the hydraulic fluid in the first liquid reservoir b1 passes through the communication member H and the pressure-side base member passage 61. Passing through and flowing into the second liquid reservoir chamber b2, the air chamber G is reduced.

  In the present embodiment, since the resistance by the pressure check valve V2 is set to be small, when the piston speed is in the low speed region when the shock absorber D1 is compressed, the shock absorber D1 mainly contains the working fluid in the second bypass passage. When the compression side low speed damping force due to the resistance of the valve body V5 when passing through 70 is generated and the piston speed is in the middle to high speed region when the shock absorber D1 is compressed, the shock absorber D1 mainly has the hydraulic fluid on the pressure side. A compression-side medium / high-speed damping force is generated due to the resistance of the compression-side damping valve V4 when passing through the base member passage 61. The compression-side low-speed damping force can be adjusted by changing the valve opening pressure of the valve body V5 by the actuator 52 in accordance with the pressure of the first liquid reservoir chamber b1 detected by the pressure sensor 51.

  Further, when the amount of hydraulic fluid in the cylinder 1 increases or the hydraulic fluid expands due to a rise in temperature when the shock absorber D1 is compressed, if the amount of the piston rod 3 entering the cylinder 1 increases, the lower seal 42 The free piston 4 moves backward until it reaches the enlarged diameter portion 10c, and the hydraulic fluid in the piston side chamber a2 passes through the gap formed between the lower seal 42 and the sub cylinder 10 and the communication hole 10d to reach the reservoir R. Are discharged, that is, relieved. When the pressure in the piston side chamber a2 is reduced by the relief, the free piston 4 is moved forward by the pressure in the first liquid reservoir chamber b1, and the lower seal 42 is opposed to the sliding contact portion 10b. The communication between the side chamber a1 and the reservoir R is blocked.

  In the above description, the piston speed region is divided into the low speed region and the medium / high speed region, but the threshold value of each region can be arbitrarily set.

  Hereinafter, the effect of the buffer D1 which concerns on this Embodiment is demonstrated.

  In the present embodiment, the actuator 52 is composed of a proportional solenoid.

  Thus, when the actuator 52 is composed of a proportional solenoid, the damping force generated by the shock absorber D1 (in this embodiment, the compression-side low-speed damping force) can be electrically adjusted. When directly attached to the member T, the shock absorber D1 is bulky in the axial direction, and the mountability of the shock absorber D1 is deteriorated. For this reason, when the actuator 52 is composed of a proportional solenoid, the actuator 52 is attached to the housing 5 provided outside the tube member T and separated from the tube member T. It is valid. However, the damping force may be adjusted by a configuration other than the actuator 52. For example, an adjuster for manual operation may be used.

  In the present embodiment, the shock absorber D1 includes a second bypass passage (passage) 70 that communicates the first liquid reservoir chamber b1 and the second liquid reservoir chamber b2, and hydraulic fluid passes through the second bypass passage 70. And an actuator 52 capable of changing the resistance at the time, and this actuator 52 is attached to the housing 5.

  According to the above configuration, by attaching the actuator 52 to the housing 5 provided separately from the tube member T on the outer side of the tube member T, it becomes difficult to receive dimensional restrictions, so the degree of freedom of selection of the actuator 52 is improved. . However, the actuator 52 may be fixed to the tube member side, such as attached to the cap member C.

  Further, in the present embodiment, the cylinder 1 includes the sliding contact portion 10b with which the free piston 4 slides, and the sliding contact portion 10b. The cylinder 1 is formed to have an inner diameter larger than the inner diameter of the sliding contact portion 10b. 4 and a communication hole 10d that is formed in the enlarged diameter portion 10c and opens into the reservoir R. The relief mechanism E includes the enlarged diameter portion 10c, The communication hole 10d is provided.

  According to the above configuration, the configuration of the relief mechanism E can be simplified. However, the configuration of the relief mechanism E is not limited to the above, and the hydraulic fluid in the piston side chamber a2 when the free piston 4 is retracted by a predetermined amount. As long as it can be discharged into the reservoir R.

  In the present embodiment, the shock absorber D1 includes a telescopic tube member T composed of an outer tube t1 and an inner tube t2 that enters and exits the outer tube t1, and a cylinder 1 that stands up in the tube member T. A piston 2 that is inserted into the cylinder 1 so as to be movable in the axial direction, a piston rod 3 that stands on one side of the piston 2 and protrudes out of the cylinder 1, and is partitioned by the piston 2 and filled with hydraulic fluid Rod side chamber a1 and piston side chamber a2, and a reservoir R that is formed between the tube member T and the cylinder 1 and stores hydraulic fluid.

  Further, the shock absorber D1 is a free piston 4 inserted in the axial direction so as to be movable in the axial direction on the side opposite to the piston rod of the cylinder 1, and the free piston 4 is partitioned from the piston side chamber a2 and filled with the hydraulic fluid. A liquid reservoir chamber b1, a housing 5 provided outside the tube member T, a second liquid reservoir chamber b2 that is formed in the housing 5 and stores and can be expanded and contracted, and the first liquid reservoir chamber b1. And a communication member H that communicates with the second liquid reservoir chamber b2, a base member 6 that is fixed to the housing 5 and divides the first liquid reservoir chamber b1 and the second liquid reservoir chamber b2, and the free piston. And a relief mechanism E that discharges the hydraulic fluid in the piston side chamber a2 to the reservoir R when the piston 4 is retracted by a predetermined amount.

  According to the above configuration, since the base member 6 can be separated from the cylinder 1 even if the shock absorber D1 includes the relief mechanism E, the shock absorber D1 is prevented from being bulky in the longitudinal direction, and the mountability of the shock absorber D1 is good. It becomes possible to.

  In addition, since the free piston 4 is disposed in the cylinder 1, even if the gas dissolved in the working fluid is deposited in the working chamber A, this gas can be discharged together with the working fluid at the time of relief.

  Furthermore, according to the above configuration, the hydraulic fluid contained in the rod side chamber a1, the piston side chamber a2 and the reservoir R (hereinafter referred to as hydraulic fluid for the working chamber) and the first and second liquid reservoir chambers b1 and b2 Since the stored hydraulic fluid (hereinafter referred to as the hydraulic fluid for the reservoir) is not mixed, the hydraulic fluid for the hydraulic chamber and the hydraulic fluid for the reservoir chamber should be different. Can do.

  Although preferred embodiments of the present invention have been described in detail above, it should be understood that modifications, variations and changes may be made without departing from the scope of the claims.

a1 Rod side chamber a2 Piston side chamber b1 First reservoir chamber b2 Second reservoir chamber D1 Buffer E Relief mechanism H Communication member T Tube member t1 Outer tube t2 Inner tube R Reservoir 1 Cylinder 2 Piston 3 Piston rod 4 Free piston 5 Housing 6 Base member 10b Sliding contact portion 10c Expanded diameter portion 10d Communication hole 52 Actuator 70 Second bypass passage (passage)

Claims (4)

A telescopic tube member comprising an outer tube and an inner tube that enters and exits the outer tube, a cylinder that stands up in the tube member, a piston that is movably inserted in the axial direction into the cylinder, A piston rod that stands on one side and protrudes out of the cylinder, a rod side chamber and a piston side chamber that are partitioned by the piston and filled with the working fluid, and is formed between the tube member and the cylinder so that the working fluid is formed. In a shock absorber comprising a reservoir to be stored,
A free piston that is inserted in the axial direction on the side opposite to the piston rod of the cylinder, a first liquid reservoir chamber that is partitioned from the piston side chamber by the free piston and filled with working fluid, and provided outside the tube member A housing formed therein, a second liquid reservoir chamber in which hydraulic fluid is stored and expandable and contractable, a communication member communicating the first liquid reservoir chamber and the second liquid reservoir chamber, and the housing A base member that divides the first liquid reservoir chamber and the second liquid reservoir chamber, and a relief mechanism that discharges the hydraulic fluid in the piston side chamber to the reservoir when the free piston is retracted by a predetermined amount. Shock absorber. The cylinder includes a sliding contact portion with which the free piston slides, and an enlarged diameter portion that is connected to the sliding contact portion and has an inner diameter larger than the inner diameter of the sliding contact portion so that a gap can be formed between the free piston and the cylinder. And a communication hole formed in the enlarged diameter portion and opened to the reservoir,
The shock absorber according to claim 1, wherein the relief mechanism includes the enlarged diameter portion and the communication hole.   A passage communicating the first liquid reservoir chamber and the second liquid reservoir chamber; and an actuator capable of changing a resistance when the hydraulic fluid passes through the passage. The actuator is attached to the housing. The shock absorber according to claim 1 or 2, wherein the shock absorber is provided.   The shock absorber according to any one of claims 1 to 3, wherein the actuator includes a proportional solenoid.

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