JPH08121524A - Shock absorber - Google Patents

Abstract

PURPOSE: To enable the application to a strut type suspension device in a vehicle in a shock absorber to respectively exhibit extremely small damping force to small displacement and proper damping force to large displacement. CONSTITUTION: A shock absorber is provided with a piston 66 to define the inside of a cylinder 26 into two chambers, a free piston 48 to define an upper chamber of the piston 66 into a first reservoir chamber 50 and a first variable pressure chamber 52 and a base case to define a lower chamber of the piston 66 into a second reservoir chamber 106 and a second variable pressure chamber 104. In order to define a gas chamber 31, a devide piston 27 is arranged under a reservoir chamber 30 communicated with the first and the second reservoir chambers 50 and 106. Mechanisms to allow a flow of fluid when differential pressure not less than prescribed pressure is generated in the first and the second variable pressure chambers 52 and 104, are arranged in the piston 66 and the base case 90.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber, and more particularly to a shock absorber suitable as a damper mechanism for a vehicle suspension device.

[0002]

2. Description of the Related Art Conventionally, a shock absorber has been known as a damper mechanism of a vehicle suspension device.
This shock absorber is provided in order to apply an appropriate damping force to the relative displacement between the wheel and the vehicle body, appropriately absorb the traveling vibration, and maintain the vehicle posture properly.

As such a shock absorber, for example, in Japanese Patent Laid-Open No. 58-221032, a large damping force is not generated while the relative speed between the wheel and the vehicle body is relatively small, and the relative speed exceeds a predetermined level. Then, a material having a characteristic that the damping force rises sharply thereafter is disclosed. According to the damping force characteristics described above, when the relative displacement between the vehicle body and the wheels is relatively small, a large damping force is not exerted, and high-frequency vibration with a small amplitude due to running of the vehicle can be flexibly absorbed and at the same time, The focus is on the fact that a relatively large damping force is exerted against vibration with a large amplitude that greatly changes the posture, and the posture of the vehicle can be appropriately maintained.

The shock absorber described in the above publication includes a piston that slides in the cylinder and a piston rod that can move relative to the piston by a predetermined distance. In the communication passage, an orifice that reduces the opening area as the pressing force acting between the piston and the piston rod increases is provided.

That is, according to the above construction, within the range in which the piston rod can move relative to the piston, the piston rod can be displaced with almost no damping force, and the amplitude input to the piston rod can be changed. When is small, a large opening area is secured in the orifice, and the damping force when the piston moves is also suppressed.

Further, when the amplitude input to the piston rod is large, a relatively large pressing force acts between the piston and the piston rod, and as a result, the opening area of the orifice in the communication passage becomes small and the piston A relatively large damping force will be exerted with the movement of the. Therefore,
According to the above configuration, the damping force characteristic described above, which is effective for flexibly absorbing the traveling vibration and maintaining the stable posture of the vehicle, is realized.

[0007]

However, in the conventional shock absorber described above, the desired damping force characteristic is realized by the smooth relative movement of the piston rod and the piston. On the other hand, in the strut type suspension device, the shock absorber itself constitutes a rigid member, and a moment for maintaining the wheel and the vehicle body in a regular positional relationship is directly applied to the tip end portion of the piston rod thereof.

Therefore, when the above-mentioned conventional shock absorber is used in the strut type suspension device, a large moment is applied to the connecting portion between the piston rod and the piston, which is disadvantageous for smooth relative movement between the two. Will occur. In this sense, the conventional shock absorber described above has a problem that when applied to a strut suspension device, a situation may occur in which a desired damping force characteristic cannot be appropriately exhibited.

The present invention has been made in view of the above points, and appropriately absorbs the traveling vibration and the vehicle attitude even when a relatively large moment is applied to the connecting portion between the piston rod and the piston. An object of the present invention is to provide a shock absorber capable of exhibiting effective damping force characteristics for maintenance.

[0010]

The above object is to provide a piston that divides the inside of a cylinder into a first chamber and a second chamber, and to hold the piston in the first chamber in a floating state. A first free piston that divides the chamber of the second chamber into a first reservoir chamber and a first variable pressure chamber, and a second reservoir chamber that is held in a floating state in the second chamber. And a second variable pressure chamber, a second free piston, a reservoir pressure adjusting mechanism that maintains the pressures of the first reservoir chamber and the second reservoir chamber at a predetermined pressure, and displacement of the piston. Accordingly, after the differential pressure between the first variable pressure chamber and the second variable pressure chamber reaches a predetermined pressure, a damping force generating mechanism that generates a predetermined damping force when the piston is further displaced is provided. Achieved by shock absorbers.

[0011]

In the present invention, the first and second free pistons are held in a floating state in the first chamber or the second chamber, and the inside thereof is further provided with the first and second variable pressure chambers,
It is divided into the first and second reservoir chambers. The internal pressures of the first and second reservoir chambers are kept at a predetermined pressure by the reservoir pressure adjusting mechanism.

Therefore, when the piston is displaced, and as a result, the internal pressures of the first and second variable pressure chambers are increased or decreased, the first and second free pistons are
The volume of the first or second reservoir chamber is displaced in the direction of contracting or expanding without substantially any displacement resistance.
Therefore, the piston can freely slide in the cylinder until the first and second free pistons reach their displacement ends, and for such a small displacement, Almost no damping force is generated with the displacement.

On the other hand, when an external force in a direction of further increasing the displacement of the piston acts after the first and second free pistons reach their displacement ends, the first and second free pistons are subsequently processed. Since the piston cannot be displaced, the internal pressures of the first and second variable pressure chambers change, and a differential pressure is generated between them. Then, after the differential pressure reaches a predetermined pressure, when the piston is further displaced, a predetermined damping force is generated in the damping force generating mechanism. Therefore, when the piston is largely displaced beyond the extent of reaching the displacement ends of the first and second free pistons, an appropriate damping force is exerted against the large displacement. become.

Therefore, in the shock absorber according to the present invention, a small damping force is generated when the amplitude of the vibration input to the piston is small, and a large damping force is generated when the amplitude is large. Become. At this time, in the shock absorber according to the present invention, the first and second free pistons are held in the cylinder in a floating state and can be displaced without any resistance until they reach the displacement end. As a result, the above damping force characteristics are realized.

Therefore, even when the rigidity is ensured at the contact portion between the piston and the cylinder, the damping force characteristics are not impaired at all, and even when applied to a strut suspension device, it is appropriately desired. The damping force characteristic of will be exhibited.

[0016]

1 is a front sectional view showing the overall structure of a shock absorber 10 according to an embodiment of the present invention. In addition, FIGS. 2, 3, and 4 are enlarged views showing the configuration of the main part of the shock absorber 10, respectively. The configuration of the shock absorber 10 will be described below with reference to the drawings.

The shock absorber 10 has a cylindrical outer shell 12 as shown in FIG. Here, the outer shell 12 is provided with a plurality of ribs 14 at predetermined positions on the outer circumference thereof, and the coil springs (not shown) arranged around the outer circumference of the shock absorber 10 are hooked on these ribs 14. The lower seat 16 for holding the lower end of the () is provided.

A lower cap 20 having a through hole 18 in the center is welded to the lower end of the outer shell 12.
The through hole 18 is a hole used when the absorber gas is injected into the outer shell 12, and the ball 22 is press-fitted after the absorber gas is injected into a closed state.
Further, a collar 24 is welded to a lower portion of the lower cap 20 at a position to cover the press-fitted ball 22. The collar 24 is a member fixed to the wheel (not shown) side when the suspension device is configured using the shock absorber 10.

Inside the outer shell 12, a cylinder 26 having a smaller diameter than that of the outer shell 12 and a divide piston 27 slidable inside the outer shell 12 are provided. Here, the divide piston 27 is provided with an O-ring 28 on its outer circumference, and
The inner space is divided into two spaces. As a result, in the shock absorber 10, between the outer shell 12 and the cylinder 26 and in the upper part of the divide piston 27, reservoir chambers 29 and 30 filled with absorber oil, respectively, as will be described later, are provided, and the divide piston 27 is also provided. A gas chamber 31 filled with the above-mentioned absorber gas is formed in the lower portion.

A piston rod 32 fixed to the vehicle body (not shown) is inserted into the cylinder 26 at its upper end. A rod guide for slidably holding the piston rod 32 is provided near the upper end of the cylinder 26.
And a free piston or the like held in a floating state in the cylinder 26, a piston or the like fixed to the lower end portion of the piston rod 32 near the center of the cylinder 26, and a cylinder inside the cylinder 26 near the lower end of the cylinder 26. A base case or the like that is held in a floating state is provided in the.

Hereinafter, referring to FIGS. 2 to 4 together with FIG. 1,
The configuration around the rod guide, the free piston, the piston, the base case, and the like will be described in detail. As shown in FIG. 2, the rod guide 3 is provided at the upper end of the cylinder 26.
4 are provided. The rod guide 34 includes a small-diameter portion having substantially the same diameter as the inner diameter of the cylinder 26 and the outer shell 12
Is a member having a large diameter portion having substantially the same diameter as the inner diameter of the groove, and a groove 34a is provided on the outer periphery of the large diameter portion.

Therefore, as shown in FIG. 2, the rod guide 34
When the outer diameter of the outer shell 12 is fitted to the cylinder 26, the outer shell 12 is assembled to the outer periphery of the outer shell 12, and the outer shell 12 is caulked in accordance with the groove 34a, the outer shell 1
2 and the cylinder 26 are accurately centered. Further, the rod guide 34 is provided with a bush 36 that slidably holds the piston rod 32 at the center thereof. Therefore, the piston rod 32 can slide in the axial direction of the outer shell 12 and the cylinder 26 while being accurately centered.

An oil seal 38 is provided above the rod guide 34 to abut the outer periphery of the piston rod 32 to ensure the sealing performance of the shock absorber 10.
The oil seal 38 is fixed at a predetermined position by caulking the outer shell 12 inside. On the upper part of the outer shell 12 crimped inside as described above,
The cap 42 to which the rebound stopper 40 is fixed by welding is fixed by press fitting. Here, the rebound stopper 40 is a member that comes into contact with an abutting member (not shown) to regulate the displacement end on the compression side when the piston rod 32 is displaced by a predetermined distance in the compression direction.

At the lower part of the rod guide 34, a free piston 48 having seal rings 44 and 46 on the inner peripheral side and the outer peripheral side, respectively, is arranged. The free piston 48 includes an outer peripheral surface of the piston rod 32 and the cylinder 2
It is arranged so as to be liquid-tight and slidable with respect to the inner peripheral surface of 6, and divides the internal space of the cylinder 26 into a first reservoir chamber 50 and a first variable pressure chamber 52.

The free piston 48 is supported by conical conical springs 54 and 56 arranged above and below the free piston 48, and is held in the cylinder 26 in a floating state. Here, the upper end of the conical spring 54 is restricted by the lower end surface of the rod guide 34, while the lower end of the conical spring 56 is restricted by the spool 58 provided in the cylinder 26.

Therefore, the free piston 48 can be appropriately displaced within that range, with the upper displacement end being a position substantially in contact with the rod guide 34 and the lower displacement end being substantially in contact with the spool 58. Here, the rod guide 34 described above has a plurality of communication passages 34 b that communicate the first reservoir chamber 50 and the space near the oil seal 38.
And the space near the oil seal 38 and the reservoir chamber 2 described above.
It is provided with a plurality of communication passages 34c that communicate with the communication port 9. Therefore, the first reservoir chamber 5 formed inside the cylinder 26
0 and the reservoir chamber 29 formed between the cylinder 26 and the outer shell 12 are always in a conductive state.

Next, the structure around the piston will be described with reference to FIG. As shown in FIG. 3, the piston rod 3
At the lower end of 2, a stopper 60, a leaf seat 62, a leaf valve 64, a piston 66, a leaf valve 68, a leaf seat 70, and a stopper 72 are sequentially inserted and fixed by a nut 74. Where the piston 66
Is provided with a piston band 76 on its outer circumference, and is in a slidable state while ensuring a seal with the inner circumferential surface of the cylinder 26. Further, the piston 66 has a communication passage 66 a whose upper end is opened to a first chamber 78 above the piston 66 and whose lower end is closed by the leaf valve 68, and a second chamber 80 whose lower end is below the piston 66. Communication passage 66 that is open to the outside and whose upper end is closed by the leaf valve 64.
b.

In this case, while the pressure difference between the first chamber 78 and the second chamber 80 is small, both of the communication passages 66a and 66b are maintained in the closed state. In addition, the internal pressure of the first chamber 78 is
When the pressure is sufficiently higher than the internal pressure of the chamber 80 of FIG.
When the inner pressure of the second chamber 80 becomes sufficiently higher than the inner pressure of the first chamber 78 by opening the valve toward the inside and the lower side, the leaf valve 64 hits the stopper 60 as a limit, and FIG. The valve is opened toward the upper middle, and the communication passage 66a or 6 is opened.
6b becomes conductive.

By the way, the piston rod 32 has a rebound stopper plate 82,
And a rebound stopper 84. The rebound stopper 84 is made of a member having elasticity, and comes into contact with the above-mentioned free piston 48 when the piston rod 32 is displaced by a predetermined distance in the extension direction, so that the piston rod 32 is prevented.
Is a member that regulates the extension side displacement end of.

Next, the configuration around the base case will be described with reference to FIG. As shown in FIG. 4, the cylinder 26
At the lower end of the cylindrical base bracket 86, a cylindrical base bracket 86 having a small diameter portion having substantially the same diameter as the inner diameter of the cylinder 26 and a large diameter portion having substantially the same diameter as the inner diameter of the outer shell 12 is disposed. Here, the base bracket 86 has a groove 86a on the outer circumference of the large diameter portion.
The outer shell 12 is caulked to fit the groove 86a. As a result, the cylinder 26 and the outer shell 12 can be accurately centered even at the lower end.

Above the base placket 86, a base case 90 having a seal ring 88 on its outer periphery is disposed in the cylinder 26 so as to be liquid-tight and slidable. Here, the leaf valve 9 is provided above the base case 90.
2 has a leaf valve 94 and a leaf seat 9 below it.
6 and the stopper 98 are bolts and nuts 100, 10
It is fixed by 2.

The base case 90 has a communication passage 90 whose upper end opens to the second variable pressure chamber 104 above the base case 90 and whose lower end is closed by the leaf valve 94.
a and its lower end open to the second reservoir chamber 106 below the base case 90, and its upper end is the leaf valve 9
The communication passage 90b is closed by 2. in this case,
While the differential pressure between the second variable pressure chamber 104 and the second reservoir chamber 106 is small, both the communication passages 90a and 90b are maintained in the cutoff state. In addition, the internal pressure of the second transformer chamber 104 is
When the pressure is sufficiently higher than the internal pressure of the reservoir chamber 106, the leaf valve 94 opens downward in FIG. 4, and conversely, the internal pressure of the second variable pressure chamber 104 changes to the second reservoir chamber 10.
When the pressure becomes sufficiently lower than the internal pressure of 6, the leaf valve 9
2 opens upward in FIG. 4, and the communication passage 90a
Alternatively, 90b becomes conductive.

By the way, the base case 90 is supported by springs 108 and 110 arranged above and below the base case 90, and is held in a floating state in the cylinder 26. Here, the upper end of the spring 108 is regulated by the spool 112 provided in the cylinder 26, while the spring 11
The lower end of 0 is regulated by the upper end surface of the base bracket 86.

Therefore, the base case 90 can be appropriately displaced within that range, with the position that substantially abuts the spool 112 as the upper displacement end and the position that substantially abuts the base bracket 86 as the lower displacement end. it can. The base bracket 86 is a cylindrical member as described above. Further, the base bracket 86 is provided with a plurality of grooves 86b axially provided on its large diameter portion so as to communicate the upper and lower sides of the base bracket 86. Therefore, the second reservoir chamber 106 that is partitioned below the base case 90 is provided.
Is in communication with a reservoir chamber 30 formed above the divide piston 27, and this reservoir chamber 30 is
A reservoir chamber 29 formed between the cylinder 26 and the outer shell 12 is also in communication.

The first reservoir chamber 50 and the first variable pressure chamber 52 described above are provided in the first chamber 78 defined by the piston 66, and the second reservoir chamber 10 described above.
6 and the second variable pressure chamber 104 are formed in the second chamber 80 that is defined by the piston 66. Hereinafter, referring to FIGS. 5 to 10, the shock absorber 10 will be described.
The operation of will be described.

5 to 7 are state diagrams when the piston rod 32 is displaced in the extension direction in the shock absorber 10, and are a general view of the shock absorber 10, an enlarged view of the periphery of the pre-piston 48, and a base case 90, respectively. An enlarged view of the periphery is shown. That is, when an external force acts on the piston rod 32 in the extension direction, the piston 66 is displaced upward in FIG. When the piston 66 maintains the liquid-tight state and is displaced upward in the cylinder 26, the first
The internal pressure of the variable pressure chamber 52 is about to increase, and the internal pressure of the second variable pressure chamber 104 is about to decrease.

Therefore, a thrust force acting upward acts on both the free piston 48 and the base case 90.
At this time, the first reservoir chamber 50 separated above the free piston 48 is communicated with the reservoir chamber 29 via the communication passages 34 b and 34 c formed in the rod guide 34. In addition, the second reservoir chamber 106, which is formed below the base case, communicates with the reservoir chamber 30 via the central portion of the base bracket 86.

Then, the reservoir chamber 29 and the reservoir chamber 30
Is the groove 8 formed in the base bracket 86 as described above.
They are communicated with each other via 6b, and are both controlled by the internal pressure of a gas chamber 31 defined below the divide piston 27. Therefore, the free piston 48 and the base case 9
0 can be displaced without being restricted by the internal pressures of the first reservoir chamber 50 and the second reservoir chamber 106, respectively, and when upward thrust is applied to the free piston 48 and the base case 90 as described above. Can be displaced to the upper displacement end as shown in FIGS. 6 and 7 without a great resistance.

Therefore, the shock absorber 1 of this embodiment is
At 0, the damping force generated when the piston rod 10 is displaced in the extension direction is suppressed to an extremely small value until the free piston 48 and the base case 90 reach the upper displacement end with the displacement of the piston 66. become. The cross-sectional area of the cylinder 26 is S, and the piston rod 3
2 is s, and the displacement of the piston 66 is L,
The volume change amount Δv of the first reservoir chamber 50 is Δv = (S
−s) × L. In the same case, the volume change amount ΔV of the second reservoir chamber 106 is represented by ΔV = S × L.

In this case, there is a clear difference between the volume change amounts Δv and ΔV of both, but in the present embodiment, the divide piston 27 is replaced by the cylinder 26.
By displacing the inside up and down, the difference in the volume change amount is absorbed. Therefore, in the shock absorber 10, smooth operation is always ensured despite the existence of such a difference.

By the way, as shown in FIGS. 5 to 7, when the free piston 48 and the base case 90 reach the upper displacement end and the piston 66 is further displaced in the extension direction, the displacement is free. It cannot be absorbed by the piston 48 and the base case 90, and the internal pressure of the first variable pressure chamber 52 greatly increases, and the internal pressure of the second variable pressure chamber 104 greatly decreases.

As a result, a differential pressure is generated above and below the piston 66, and when the differential pressure reaches a predetermined pressure, the leaf valve 68 opens and the communication passage 66a becomes conductive as described above. Then, when the displacement of the piston 66 progresses thereafter,
The absorber oil flows from the first variable pressure chamber 52 toward the second variable pressure chamber 104 through the communication passage 66a, and the damping force corresponding to the flow resistance of the absorber oil is transmitted to the piston rod 32. become.

By the way, in this case, the amount of absorber oil flowing out from the first variable pressure chamber 52 is determined by the volume change amount Δv of the first reservoir chamber 50 and the second reservoir chamber 1 as described above.
For the same reason as causing the imbalance with the volume change amount ΔV of 06, the amount is smaller than the volume change amount that occurs in the second variable pressure chamber 104. Therefore, when the piston 66 is displaced along with the outflow of the absorber oil from the first variable pressure chamber 52 to the second variable pressure chamber 104, the internal pressure of the second variable pressure chamber 104 increases as the displacement increases. The pressure is lower than the internal pressure of the second reservoir chamber 106 that is partitioned below the case 90.

When the differential pressure reaches a predetermined pressure, the leaf valve 92 opens as described above, and the communication passage 90b of the base case 90 becomes conductive. Therefore, when the displacement of the piston 66 progresses thereafter, the shortage of absorber oil is compensated from the second reservoir chamber 106 toward the second variable pressure chamber 104. At this time, the second
Between the variable pressure chamber 104 and the second reservoir chamber 106 of
A differential pressure is generated according to the flow resistance generated when the absorber oil flows through the communication passage 90b. Therefore, when the piston 66 is displaced, a differential pressure is generated above and below the piston 66 depending on the flow resistance in the communication passage 66a of the piston 66 and the flow resistance in the communication passage 90b of the base case 90. Thus, the damping force corresponding to the flow resistances at these two locations is transmitted to.

As described above, in the shock absorber 10, when the piston 66 is further displaced in the extension direction after the free piston 48 and the base case 90 reach the upper displacement end, it is appropriate for the displacement. The damping force will be transmitted to the piston rod 32, and when the piston rod 32 is displaced relatively large, an appropriate damping force will be generated.

8 to 10 show the shock absorber 10.
3 is a state diagram when the piston rod 32 is displaced in the compression direction, showing an overall view of the shock absorber 10, an enlarged view of the periphery of the pre-piston 48, and an enlarged view of the periphery of the base case 90, respectively. That is, when an external force in the compression direction acts on the piston rod 32, the above-mentioned FIG.
Contrary to the situation shown in FIG. 7, until the free piston 48 and the base case 90 reach the lower displacement end, the piston 66 is displaced downward in the figure with extremely small resistance. Therefore, as long as the piston 66 is displaced in the compression direction within this range, the damping force exerted by the shock absorber 10 is suppressed to an extremely small value.

In this case, the volume variation Δv of the first reservoir chamber 50 and the volume variation Δv of the second reservoir chamber 106.
The imbalance generated in V and V is absorbed by the displacement of the divide piston 27, similarly to the case where the piston rod 32 is displaced in the extension direction. Further, when the free piston 48 and the base case 90 reach the lower displacement end as shown in FIGS. 8 to 10 and the piston 66 is further displaced in the compression direction, the internal pressure of the second variable pressure chamber 104 increases, Moreover, when the internal pressure of the first variable pressure chamber 52 decreases and the differential pressure thereof reaches a predetermined pressure, the leaf valve 64 opens and the communication passage 66b becomes conductive.

At this time, the volume change occurring in the second variable pressure chamber 104 is larger than the volume change occurring in the first variable pressure chamber 52. Therefore, as the displacement of the piston 66 increases, the second variable pressure chamber 104 increases. Has a higher pressure than the second reservoir chamber 106. Therefore, when the displacement of the piston 66 toward the compression direction continues, the leaf valve 94 opens and the communication passage 90a of the base case 90 also becomes conductive.

Therefore, after the free piston 48 and the base case 90 reach the lower displacement end, the piston 6 is further
When 6 is displaced in the compression direction, the damping force corresponding to the flow resistance in the communication passage 66b of the piston 66 and the flow resistance in the communication passage 90a of the base case 90 is transmitted to the piston rod 32. Thus, according to the shock absorber 10 of the present embodiment, the piston 66
In either direction, the damping force transmitted to the piston rod 32 can be suppressed to an extremely small value for a small displacement such that the free piston 48 and the base case 90 do not reach the displacement end. ,on the other hand,
Appropriate damping force can be transmitted to the piston rod 32 for a large displacement that continues after the free piston 48 and the base case 90 reach the displacement end.

Therefore, when the suspension device is constructed using the shock absorber 10 of the present embodiment, it is possible to flexibly absorb the vibration of high frequency and small amplitude which should be appropriately absorbed to secure a comfortable riding comfort. In addition, it is possible to realize a suspension device that can exhibit high rigidity with respect to vibration of low frequency and large amplitude, which should be ensured to maintain rigidity of the vehicle posture.

By the way, the shock absorber 10 includes the free piston 48 and the base case 90 in the cylinder 26.
The above-mentioned damping force characteristic is realized by holding it in a floating state. Therefore, even when the shock absorber 10 is applied to the strut suspension device and a relatively large moment is applied to the contact portion between the piston 66 and the cylinder 26, the damping force characteristic is not impaired.

In this sense, since the shock absorber 10 of this embodiment has a movable portion at a portion connecting the piston and the piston rod, a desired damping force characteristic is realized, so that the strut suspension device can be used. Therefore, it has an advantage that it can be applied in a wider range as compared with the conventional shock absorber, which is difficult to apply.

Further, in the shock absorber 10, the damping force when a relatively large displacement occurs is determined by the mechanism using the leaf valves 64, 68, 92, 94 which is generally used as the damping force generating mechanism of the shock absorber. Is generated. Therefore, the production thereof is easy, and a high degree of freedom regarding the adjustment of the damping force characteristic can be secured.

In this sense as well, the shock absorber 10 of this embodiment is a conventional shock absorber that realizes a desired damping force characteristic by using an orifice whose opening area is changed according to the relative positional relationship between the piston and the piston rod. In comparison with the above, it has an excellent effect. By the way, in the shock absorber 10, the leaf valves 64, 68,
A mechanism for generating a damping force is provided by arranging 92 and 94, but the invention is not limited to this, and the damping force can be set using, for example, the free piston 48 and the piston 66, or the free piston 48 and the base case 90. It is also possible to realize a mechanism for generating

In the shock absorber 10 of this embodiment, the free piston 48 is the above-mentioned first free piston, the base case 90 is the above-mentioned second free piston, and the divide piston 27, the reservoir chamber 29, 30 and the gas chamber 31 realize the aforementioned reservoir pressure adjusting mechanism, and the piston 66, the base case 90, and the leaf valves 64, 68, 92, 94 realize the aforementioned damping force generating mechanism.

[0056]

As described above, according to the present invention, the relatively small displacement applied to the piston is absorbed by the displacement of the first and second free pistons. Further, when a relatively large displacement that cannot be absorbed by the displacement of the first and second free pistons is applied to the piston, an appropriate damping force corresponding to the displacement is generated.

The damping force characteristic is realized by smooth sliding of the first and second free pistons in the cylinder, and the rigidity is ensured at the contact portion between the piston and the cylinder. The damping force characteristics are not impaired. Therefore, according to the present invention, including when applied to a strut type suspension device, a small damping force is appropriately exerted when the displacement amount is small, and a large damping force is appropriately exerted when the displacement amount is large. The shock absorber can be realized.

[Brief description of drawings]

FIG. 1 is a front sectional view showing the overall configuration of a shock absorber that is an embodiment of the present invention.

FIG. 2 is an enlarged front sectional view showing a configuration around a free piston of the shock absorber according to the present embodiment.

FIG. 3 is an enlarged front sectional view showing a configuration around a piston of the shock absorber according to the present embodiment.

FIG. 4 is an enlarged front sectional view showing the configuration around the base case of the shock absorber according to the present embodiment.

FIG. 5 is a front sectional view showing the overall configuration of the shock absorber according to the present embodiment when it is extended.

FIG. 6 is an enlarged front sectional view showing a state around the free piston when the shock absorber according to the present embodiment is extended.

FIG. 7 is an enlarged front cross-sectional view showing a state around the base case when the shock absorber according to the present embodiment is extended.

FIG. 8 is a front cross-sectional view showing the overall configuration of the shock absorber according to the present embodiment at the time of compression.

FIG. 9 is an enlarged front sectional view showing a state around the free piston at the time of compression of the shock absorber according to the present embodiment.

FIG. 10 is an enlarged front cross-sectional view showing a state around the base case when the shock absorber according to the present embodiment is compressed.

[Explanation of symbols]

 10 Shock Absorber 12 Outer Shell 26 Cylinder 27 Divide Piston 29,30 Reservoir Chamber 31 Gas Chamber 32 Piston Rod 34 Rod Guide 48 Free Piston 50 First Reservoir Chamber 52 First Variable Chamber 64, 68, 92, 94 Leaf Valve 66 Piston 66a, 66b, 90a, 90b Communication passage 78 First chamber 80 Second chamber 86 Base bracket 90 Base case 104 Second transformer chamber 106 Second reservoir chamber

Claims (1)

[Claims] 1. A piston that divides the inside of a cylinder into a first chamber and a second chamber; a piston that is held in a floating state in the first chamber, and the first chamber is a first reservoir chamber. A first free piston that is separated from a first variable pressure chamber; and a second reservoir that is held in a floating state in the second chamber and that divides the second chamber into a second reservoir chamber and a second variable pressure chamber. A second free piston that is formed, a reservoir pressure adjusting mechanism that maintains the pressures of the first reservoir chamber and the second reservoir chamber at a predetermined pressure, and the first variable pressure chamber with displacement of the piston. And a damping force generating mechanism that generates a predetermined damping force when the piston further displaces after the differential pressure in the second variable pressure chamber reaches a predetermined pressure, and a shock absorber.