JPH1113824A - Shock absorber for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To vary a spring characteristic in accordance with a running environment of a vehicle, in a shock absorber for the vehicle. SOLUTION: In the inside of a slider 22, a pressure adjusting piston 48 is arranged, a first pressure chamber 60 communicating with an upper chamber 24 and a second pressure chamber 62 communicating with an intermediate chamber 33 are formed. Springs 64, 66 energizing the pressure adjusting piston 48 to a neutral position are provided. Through holes 58, 72 communicating in the case of the pressure adjusting piston 48 displaced to a side of the upper chamber 24 by a prescribed length and through holes 56, 74 communicating in the case of the pressure adjusting piston 48 displaced to a side of the intermediate chamber 33 by a prescribed length are provided. Between the upper chamber 24 and the intermediate chamber 33, communication paths 34, 46 changing circulating resistance in accordance with a temperature of absorber oil are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Utility Model Laid-Open No. 63-147
As disclosed in Japanese Patent No. 946, a shock absorber for a vehicle is known. The above-mentioned conventional shock absorber has a piston inside an absorber shell. The interior space of the absorber shell is divided into an upper chamber and a lower chamber by a piston.

[0003] The piston is provided with a through hole communicating the upper chamber and the lower chamber. In addition, a leaf valve that closes the through hole is fixed to the piston. The conventional shock absorber includes a first leaf valve that opens when the internal pressure of the upper chamber exceeds a first threshold value compared to the internal pressure of the lower chamber, and a first leaf valve that opens when the internal pressure of the upper chamber decreases. A second leaf valve that opens when the pressure exceeds a second threshold value and becomes higher than the internal pressure of the chamber. When the first leaf valve is opened, a flow path with a small effective area is secured between the upper chamber and the lower chamber. When the second leaf valve is opened, a hydraulic passage having a large effective area is secured between the upper chamber and the lower chamber.

The magnitude of the damping force generated by the shock absorber changes according to the moving speed Vp of the piston. Specifically, the shock absorber generates a larger damping force as the moving speed Vp of the piston increases. The change that appears in the damping force with the change in the moving speed Vp of the piston becomes steeper as the effective area of the flow path connecting the upper chamber and the lower chamber is smaller. Therefore, according to the conventional shock absorber, in a region where the differential pressure between the upper chamber and the lower chamber is small, that is, in a region where the moving speed Vp of the piston is small, the damping force suddenly increases when the moving speed Vp increases. Can be raised. Further, according to the conventional shock absorber, in a region where the differential pressure between the upper chamber and the lower chamber is large, that is, in a region where the moving speed Vp of the piston is large, when the moving speed Vp increases, the damping is relatively gradual. Power can be increased.

[0005] In order to ensure the steering stability of the vehicle, it is desirable that the damping force rises quickly after the shock absorber starts to stroke at a low speed. On the other hand, in order to ensure the riding comfort of the vehicle, it is desirable that unnecessary large damping force is not generated when the shock absorber strokes at high speed. According to the above conventional shock absorber, both of these requirements can be satisfied.
Therefore, according to the above-described conventional shock absorber, both excellent steering stability and comfortable riding comfort can be realized.

[0006]

In order to ensure good steering stability and comfortable riding comfort in a vehicle, it is necessary to change the damping force characteristic of the shock absorber according to the piston displacement speed Vp as described above. In addition to being effective, it is effective to generate a spring force according to the stroke amount in the shock absorber.

That is, in order to ensure the steering stability of the vehicle, it is desirable that the suspension generate a large spring force when a slight stroke occurs in the shock absorber. On the other hand, in order to ensure the riding comfort of the vehicle, it is desirable that the suspension does not generate unnecessary large spring force when a large stroke occurs in the shock absorber.

[0008] The above-mentioned requirement is, for example, to generate a spring force proportional to the stroke amount in a small stroke region and to generate an upper limit spring force in a region where the stroke exceeds a predetermined value in a shock absorber. Can be satisfied. Therefore, if the shock absorber is provided with a spring characteristic that generates the above-described spring force, it is possible to realize an advantageous situation for achieving both steering stability and ride comfort of the vehicle.

[0009] However, the spring characteristics required of the shock absorber in order to achieve both excellent steering stability and comfortable riding comfort are not always constant. Specifically, when the vehicle is traveling on a flat road such as a paved road, that is, when traveling vibration to be absorbed by the suspension is small, a large spring force is applied to the shock absorber in order to improve steering stability. Is required. On the other hand, when the vehicle is traveling on a rough road, the shock absorber is required to have a characteristic that does not generate a large spring force in order to flexibly absorb large traveling vibrations that occur frequently. Therefore, when imparting spring characteristics to the shock absorber,
It is desirable that the spring characteristics be appropriately changed according to the traveling environment of the vehicle.

The present invention has been made in view of the above points, and has as its object to provide a shock absorber that exhibits different spring characteristics according to the running environment of a vehicle.

[0011]

The above object is achieved by the present invention.
As described in the above, a first sliding body that separates the first chamber and the second chamber is provided inside the absorber shell, and a damping force is generated when the first sliding body slides inside the absorber shell. A second sliding body for further dividing the first chamber into an upper chamber and an intermediate chamber, wherein the second sliding body communicates with the upper chamber with a first pressure. Chamber, a second pressure chamber communicating with the intermediate chamber, a pressure adjustment piston separating the first pressure chamber and the second pressure chamber, and an urging force for urging the pressure adjustment piston toward a neutral position. When the member and the pressure adjustment piston displace toward the upper chamber beyond a predetermined distance from the neutral position, the second pressure chamber and the upper chamber are brought into a conductive state, and the pressure adjustment piston is set to the neutral position. Beyond the specified distance from the position to the intermediate chamber side And a conductive state control mechanism for the said intermediate chamber and said first pressure chamber and conductive when coordinating,
Further, the present invention is achieved by a vehicle shock absorber having a communication path between the upper chamber and the intermediate chamber, the communication path changing the flow resistance according to the oil temperature of the absorber oil.

In the present invention, a first pressure chamber communicates with the upper chamber. A second pressure chamber communicates with the intermediate chamber. The upper chamber and the second pressure chamber are kept in a shut-off state until a displacement exceeding a predetermined distance occurs in the pressure adjusting piston. Similarly, the intermediate chamber and the first pressure chamber are kept in a shut-off state until the displacement of the pressure adjustment piston exceeds a predetermined distance. On the other hand, a communication passage is provided between the upper chamber and the intermediate chamber. Therefore, until the pressure adjusting piston is displaced beyond a predetermined distance, the upper chamber and the intermediate chamber are in communication only through the communication passage.

When the temperature of the absorber oil is low, the communication passage generates a large flow resistance. In such a situation, when the second sliding body moves from the upper chamber toward the intermediate chamber,
The internal pressure of the intermediate chamber increases, and the absorber oil flows from the intermediate chamber into the second pressure chamber. When the absorber oil flows into the second pressure chamber from the intermediate chamber, the pressure adjusting piston is displaced toward the first pressure chamber, and the absorber oil flows out of the first pressure chamber to the upper chamber. At this time, the urging member urges the pressure adjusting piston toward the neutral position with an urging force corresponding to the displacement amount. For this reason, when the second sliding body is displaced to the intermediate chamber side under a situation where the communication path exhibits a large flow resistance, the second
The internal pressure of the pressure chamber becomes higher than the internal pressure of the first pressure chamber by a pressure substantially corresponding to the displacement amount of the pressure adjustment piston.

The above differential pressure generated between the second pressure chamber and the first pressure chamber generates an urging force for urging the second sliding body toward the upper chamber. The urging force increases as the differential pressure between the second pressure chamber and the first pressure chamber increases, that is, as the displacement amount of the pressure adjustment piston increases. The pressure adjusting piston is displaced from the neutral position by a distance corresponding to the amount of the absorber oil flowing from the intermediate chamber to the second pressure chamber and from the first pressure chamber to the upper chamber. Further, the above-described absorber oil amount is proportional to the distance that the second sliding body is displaced from the upper chamber toward the intermediate chamber. Therefore, when the sliding body is displaced from the upper chamber side to the intermediate chamber side, the force for urging the sliding body toward the upper chamber side changes according to the displacement amount of the sliding body.

If the displacement of the sliding body continues, the displacement of the pressure adjusting piston eventually exceeds a predetermined distance. When a displacement exceeding a predetermined distance occurs in the pressure adjusting piston, the second pressure chamber and the upper chamber are in a communication state. When the second pressure chamber communicates with the upper chamber, the absorber oil flows out from the second pressure chamber toward the upper chamber, and the internal pressure of the second pressure chamber decreases. For this reason, after the displacement exceeding a predetermined distance occurs in the pressure adjusting piston, even if the displacement of the sliding body continues, the second pressure chamber and the first
The pressure difference with the pressure chamber is not subsequently increased. Therefore, the force for urging the sliding body toward the upper chamber increases in accordance with the amount of displacement of the sliding body in the process of reaching the predetermined length, and after the displacement reaches the predetermined length, the force increases by a predetermined amount. It is kept at the upper limit. Thus, when the second sliding body is displaced toward the intermediate chamber, the shock absorber of the present invention generates a spring force with a non-linear characteristic with respect to the displacement amount.

When the communication passage connecting the upper chamber and the intermediate chamber generates a large flow resistance, the shock absorber according to the present invention can provide the second sliding member even when the second sliding body is displaced toward the upper chamber. As in the case where the moving body is displaced toward the intermediate chamber, a spring force is generated with non-linear characteristics with respect to the displacement amount of the sliding body. Therefore, in the shock absorber according to the present invention, when the shock absorber oil has a low temperature, when a stroke occurs in the shock absorber, a spring force is generated in a direction for blocking the stroke with a non-linear characteristic to the stroke.

The communication passage connecting the upper chamber and the intermediate chamber generates a small flow resistance when the temperature of the absorber oil is high. In a situation where the absorber oil generates a small flow resistance, a differential pressure is unlikely to be generated between the upper chamber and the intermediate chamber even if the sliding body is displaced. When the differential pressure between the upper chamber and the intermediate chamber is small, the pressure adjusting piston is maintained at a substantially neutral position even if the sliding body is displaced. In this case, when the sliding body is displaced from the upper chamber side to the intermediate chamber side, or from the intermediate chamber side to the upper chamber side, no spring force is generated in a direction to hinder the displacement. Therefore, according to the shock absorber of the present invention, when the absorber oil is at a high temperature, it does not exhibit spring characteristics.

[0018] The absorber oil is kept at a low temperature unless the shock absorber expands and contracts so much. Also, the absorber oil becomes hot when the shock absorber repeatedly expands and contracts frequently. Therefore, the shock absorber of the present invention exhibits the above-described non-linear spring characteristics when the expansion and contraction are not repeated so much, and does not exhibit the above-mentioned spring characteristics when the expansion and contraction are repeated frequently.

[0019]

FIG. 1 is a sectional view of a shock absorber 10 according to an embodiment of the present invention. The shock absorber 10 includes an outer shell 12. An inner shell 14 is provided inside the outer shell 12. Between the outer shell 12 and the inner shell 14,
A gas chamber 16 is formed. The gas chamber 16 is filled with an inert gas having a predetermined pressure.

At the lower end of the inner shell 14, a damping force generating mechanism 18 is provided. Inside the inner shell 14, a lower chamber 20 is formed above the damping force generating mechanism 18. The inside of the inner shell 14 is filled with absorber oil. The damping force generating mechanism 18 includes a lower chamber 20.
When the absorber oil flows from the gas chamber 16 to the gas chamber 16 and when the absorber oil flows from the gas chamber 16 to the lower chamber 20, a damping force corresponding to the flow rate of the absorber oil is generated.

A sliding member 22 is provided inside the inner shell 14.
Is inserted. The sliding body 22 can slide inside the inner shell 14. An upper chamber 24 is formed on the upper part of the sliding body 22. Further, a piston rod 26 is fixed to the sliding body 22. Piston rod 26
Project above the inner shell 14 and the outer shell 12.

The shock absorber 10 according to the present embodiment is characterized by the structure of the slide 22. Hereinafter, the configuration of the sliding body 22 will be described with reference to FIG. FIG.
FIG. The sliding member 22 includes an oil passage forming portion 28,
Spring element storage section 30 and absorber piston section 3
2 is provided. An intermediate chamber 33 is formed inside the inner shell 14 between the spring element storage section 30 and the absorber piston section 32.

The oil passage forming portion 28 has a communication passage 34 for communicating the side surface of the sliding member 22 with the inside of the spring element housing portion 30. The spring element storage section 30 is formed in a tubular shape. A seal ring portion 3 is provided on a side surface of the spring element storage portion 30.
6 are formed. The seal ring portion 36 can slide along the inner wall of the inner shell 14 while ensuring sealing with the inner wall of the inner shell 14. The above-described upper chamber 24 and intermediate chamber 33 are separated by a seal ring portion 36.

A communication path forming member 38 is provided inside the spring element storage section 30. The communication path forming member 38 includes:
A shaft portion 40 and flange portions 42 and 44 are provided. The flange part 42 is fixed inside the spring element storage part 30 so as to be in contact with the upper end of the spring element storage part 30. On the other hand, the flange portion 44 is fixed to the lower end of the spring element storage portion 30 so as to seal the internal space of the spring summary storage portion 30.

The communication passage forming member 38 has a communication passage 46 penetrating the shaft portion 40 and the flange portions 42 and 44. One end of the communication passage 46 is connected to the upper chamber 24 through the communication passage 34.
Is in communication with The other end of the communication passage 46 opens to the intermediate chamber 33 below the spring element housing 30.
The diameter and length of the communication passage 46 are such that a large flow resistance occurs when the low-temperature absorber oil flows through the inside thereof, and a small flow resistance occurs when the high-temperature absorber oil flows through the inside thereof. Designed for

The shaft 40 is provided with a pressure adjusting piston 48. The pressure adjusting piston 48 can slide inside the spring element housing portion 30 along the shaft portion 40. The pressure adjusting piston 48 is provided with a seal portion 50 and guide portions 52 and 54. Also, the sealing portion 5
Through holes 56 and 58 are provided between the guide portion 52 and the seal portion 50 and between the seal portion 50 and the guide portion 54, respectively.

The seal portion 50 slides inside the spring element housing portion 30 while ensuring sealing with the inner wall of the spring element housing portion 30. A first pressure chamber 60 and a second pressure chamber 62 are formed inside the spring element housing 30. First
The pressure chamber 60 and the second pressure chamber 62 are
Eight seal portions 50. The guide portion 52 of the pressure adjusting piston 48 is provided with a vertical groove for communicating the first pressure chamber 60 and the through hole 56 on the outer peripheral side of the guide portion 52. Similarly, the second pressure chamber 62 and the through hole 58 are formed in the guide portion 54 of the pressure adjusting piston 48.
4 is provided with a vertical groove communicating with the outer peripheral side.

A first spring 64 is provided inside the first pressure chamber 60. On the other hand, a second spring 66 is provided inside the second pressure chamber 62. The pressure adjusting piston 48 is biased toward a neutral position by the first spring 64 and the second spring 66. In the spring element housing portion 30, through holes 68 and 70 are provided near the flange portion 42 and near the flange portion 44, respectively. The first pressure chamber 60 and the upper chamber 24 are always maintained in a conductive state by the through hole 68. Further, the second pressure chamber 62 and the intermediate chamber 33 are always kept in a conductive state by the through hole 70.

The spring element housing section 30 is further provided with through holes 72 and 74 above and below the seal ring section 36. The through hole 72 communicates with the through hole 58 of the pressure adjustment piston 48 when the pressure adjustment piston 48 is displaced upward beyond a predetermined distance. When the through-hole 72 and the through-hole 58 communicate with each other, the upper chamber 24 and the second pressure chamber 62 are brought into conduction.
Further, the through hole 74 communicates with the through hole 56 of the pressure adjustment piston 48 when the pressure adjustment piston 48 is displaced downward beyond a predetermined distance. When the through-hole 74 and the through-hole 56 communicate with each other, the intermediate chamber 33 and the first pressure chamber 60 become conductive. Therefore, in the shock absorber 10, the upper chamber 2
When the pressure adjusting piston 48 is displaced upward or downward beyond a predetermined value, the 4 and the intermediate chamber 33 conduct through the through holes 72 and 58 or the through holes 74 and 56.

The absorber piston section 32 includes a piston 7
6 and leaf valves 78 and 80. The piston 76 is provided with ports 82 and 84 penetrating vertically. The leaf valve 78 is provided so as to cover the upper end of the port 82. On the other hand, leaf valve 8
0 is disposed so as to cover the lower end of the port 84. An orifice 85 is provided at a portion of the piston 76 in contact with the leaf valve 80.

When the piston 76 is displaced from above to below, the absorber oil flows through the port 82 from below to above the piston 76. When the piston 76 is displaced upward from below, the absorber oil flows through the orifice 85 through the port 84. The flow rate of the absorber oil flowing through the ports 82 and 84 increases as the displacement speed Vp of the piston 76 increases. The damping force Fc generated by the shock absorber 10 is mainly determined by the characteristics of the ports 82 and 84, the orifice 85, and the leaf valves 78 and 80.

Next, referring to FIG. 3 to FIG.
The function 2 will be described. FIG. 3 shows a state realized when the sliding body 40 moves upward or downward under a situation where the absorber oil is at a sufficiently high temperature. The absorber oil becomes hot when the shock absorber 10 repeatedly expands and contracts frequently, such as when the vehicle is running on a rough road. The higher the temperature of the absorber oil, the lower the viscosity. In the shock absorber 10, the flow resistance generated when the absorber oil passes through the communication passage 46 decreases as the viscosity of the absorber oil decreases.

As described above, the diameter and length of the communication passage 46 are designed such that when the absorber oil is at a high temperature, the absorber oil can be flowed without generating a large flow resistance. More specifically, the diameter and the length of the communication path 46 are determined by the upper chamber 2 when the temperature of the absorber oil increases due to the vehicle traveling on a rough road, and as a result, the viscosity of the absorber oil decreases.
The absorber oil is designed to be able to flow from 4 to the intermediate chamber 33 or from the intermediate chamber 33 to the upper chamber 20 without generating a large flow resistance.

When the communication passage 46 allows the absorber oil to flow without generating a large flow resistance, a large differential pressure is generated between the upper chamber 24 and the intermediate chamber 33 when the sliding body 40 moves upward or downward. do not do. In the shock absorber 10 of the present embodiment, the upper chamber 24 and the first pressure chamber 6
0, and the intermediate chamber 33 and the second pressure chamber 62 are always maintained in a conductive state. For this reason, when a large differential pressure does not occur between the upper chamber 24 and the intermediate chamber 33, the pressure difference is also generated between the first pressure chamber 60 and the second pressure chamber 62, that is, on both sides of the pressure adjusting piston 48. No large differential pressure occurs.

The pressure adjusting piston 48 is maintained at a substantially neutral position by the first spring 64 and the second spring 66 when a large differential pressure is not generated on both sides thereof.
Therefore, when the shock absorber oil is at a high temperature, that is, when the shock absorber 10 repeatedly expands and contracts frequently, the sliding body 22 of the shock absorber 10 moves the inner shell 14 while maintaining the pressure adjustment piston 48 at a substantially neutral position. Can slide inside.

The arrows shown by solid lines in FIG. 3 indicate the flow generated in the absorber oil when the sliding body 22 is displaced from above to below. As indicated by the arrow, when the absorber oil is at a high temperature, when the sliding body 22 is displaced from above to below, the piston 76 moves upward from below, that is, from the lower chamber 20 to the intermediate chamber. The absorber oil flows toward 33, and the absorber oil flows from the intermediate chamber 33 to the upper chamber 24 through the communication passages 46 and 34. In this case, the piston rod 26
The damping force Fc generated in the piston 76 is transmitted.

The dashed line in FIG.
2 shows a flow generated in the absorber oil when the cylinder 2 is displaced upward from below. As indicated by the arrow, when the absorber oil is at a high temperature, when the sliding body 22 is displaced upward from below, the communication passages 46 and 34 are displaced.
Flow of the absorber oil from the upper chamber 24 to the intermediate chamber 33 through the upper chamber 24 and downward from above the piston 76,
That is, a flow of the absorber oil from the intermediate chamber 33 toward the lower chamber 20 is generated. In this case, the damping force Fc generated in the piston 76 is transmitted to the piston rod 26.

As described above, when the sliding body 22 is displaced when the absorber oil is at a high temperature,
Only the damping force Fc generated by the piston 76 is transmitted to the piston rod 26. When the sliding body 22 functions as described above, the shock absorber 10 exhibits the same function as a normal shock absorber. For this reason, according to the shock absorber 10, in a situation where expansion and contraction are frequently repeated, that is, when the vehicle is traveling on a rough road,
The characteristics of a normal shock absorber can be realized without exhibiting the spring characteristics.

FIG. 4 shows a state which is realized when the sliding body 22 is slightly displaced downward in a situation where the absorber oil is at a low temperature. The temperature of the absorber oil is maintained at a low temperature when the expansion and contraction of the shock absorber 10 is not repeated frequently, such as when the vehicle is traveling on a flat road. In this case, the absorber oil has a higher viscosity than when the vehicle is traveling on a rough road.

As described above, the diameter and the length of the communication passage 46 are designed so that when the absorber oil is at a low temperature, a large flow resistance is generated when the absorber oil flows through the inside. More specifically, the communication path 4
The diameter and length of 6 are designed so that the flow rate of the absorber oil flowing through the communication passage 46 is extremely small when the vehicle is traveling on a flat road.

When the communication passage 46 generates a large flow resistance as described above, a large differential pressure is generated between the upper chamber 24 and the intermediate chamber 33 when the sliding body 40 is displaced upward or downward. Therefore, when the absorber oil is at a low temperature, a large differential pressure is generated between the first pressure chamber 60 and the second pressure chamber 62, that is, on both sides of the pressure adjusting piston 48, with the displacement of the sliding body 40. Sometimes.

The arrows shown by solid lines in FIG. 4 indicate the flow generated in the absorber oil when the sliding body 22 is displaced from above to below. When the absorber oil is at a low temperature, the sliding body 22 is displaced downward from above, so that the internal pressure of the intermediate chamber 33 becomes higher than the internal pressure of the upper chamber 24. In this case, as indicated by the arrow, the absorber oil flows from the lower chamber 20 toward the intermediate chamber 33 and flows from the intermediate chamber 33 into the second pressure chamber 62.

When the absorber oil flows from the intermediate chamber 33 into the second pressure chamber 62, the internal pressure of the second pressure chamber 62 increases
The pressure becomes higher than the internal pressure of the pressure chamber 60. When a differential pressure is generated between the second pressure chamber 62 and the first pressure chamber 60 in this manner, the pressure adjusting piston 48 is displaced toward the first pressure chamber 60. As a result, when the sliding body 22 is displaced downward, a flow of the absorber oil from the first pressure chamber 60 to the upper chamber 24 is generated as shown in FIG.

When the pressure adjusting piston 48 is displaced from the neutral position to the first pressure chamber 60 side as described above, the first spring 64 and the second spring 66 bias the pressure adjusting piston 48 toward the neutral position. A force Fs is generated. The spring force Fs can be expressed by the following equation using the displacement L from the neutral position of the pressure adjustment piston 48, where K is the combined spring constant of the first spring 64 and the second spring 66.

Fs = K · L (1) By the way, the displacement amount L of the pressure adjusting piston 48 from the neutral position is the absorber oil amount V flowing from the intermediate chamber 33 into the second pressure chamber 62, It is proportional to the amount V of the absorber oil flowing out from one pressure chamber 60 to the upper chamber 24. The oil amount V is substantially proportional to the stroke S of the sliding member 22 when the temperature of the absorber oil is low and the flow rate of the absorber oil flowing through the communication passage 46 is extremely small. Therefore, the spring force Fs acting on the pressure adjusting piston 48 when the sliding body 22 is displaced by the predetermined length S under the condition that the absorber oil is at a low temperature can be expressed by the following equation using the proportionality constant α _1. .

Fs = α ₁ · S (2) When a spring force Fs is applied to the pressure adjusting piston 48 toward the neutral position, that is, toward the second pressure chamber 62, the second pressure chamber is actuated. pressure of 62, a high pressure by a predetermined pressure [Delta] P ₂₁ than the internal pressure of the first pressure chamber 60. ΔP ₂₁ is
Using the cross-sectional area Ap of the pressure adjusting piston 48, it can be expressed as the following equation.

ΔP ₂₁ = Fs / Ap = α ₁ · S / Ap (3) The above equation (3) can be expressed as the following equation using a constant β ₁ = α ₁ / Ap. ΔP ₂₁ = β ₁ · S (4) In the shock absorber 10, an internal pressure equal to the internal pressure of the first pressure chamber 60 or the second pressure chamber 62 is generated in the upper chamber 24 and the intermediate chamber 33, respectively. Therefore, according to the shock absorber 10, when the absorber oil is at a low temperature, the inner pressure of the intermediate chamber 33 is reduced by displacing the sliding body 22 downward as shown in FIG. it can be a high pressure by the pressure [Delta] P ₂₁ in proportion to the stroke S.

When the internal pressure of the intermediate chamber 33 becomes higher than the internal pressure of the upper chamber 24 by ΔP ₂₁ , the sliding body 22 generates the differential pressure ΔP.
To the upper chamber 24 side by the urging force corresponding to P _21, i.e., it is biased in a direction to prevent the sliding of the sliding body 22. Therefore, according to the shock absorber 10, when the absorber oil is at a low temperature, when the sliding body 22 is displaced downward, the piston rod 26 is moved according to the stroke S in a direction that hinders the displacement of the sliding body 22. Force can be applied.
Hereinafter, the urging force generated by the shock absorber 10 in accordance with the stroke S is referred to as a spring force Fk.

FIG. 5 shows a state that is realized when the sliding body 22 is displaced downward beyond a predetermined distance in a situation where the absorber oil is at a low temperature. When the displacement of the sliding body 22 in the downward direction continues when the absorber oil is at a low temperature, the pressure adjusting piston 48 eventually moves to the position shown in FIG. (Referred to as side displacement end). Through hole 5
8 communicates with the through hole 72, the second pressure chamber 62 and the upper chamber 2
4 becomes conductive.

Assuming that the stroke of the sliding body 22 required to cause the pressure adjustment piston 48 to reach the upper displacement end is _SD , the second pressure chamber is reached when the pressure adjustment piston 48 reaches the upper displacement end. The differential pressure ΔP ₂₁ generated between the pressure chamber 62 and the first pressure chamber 60 is calculated by using the above equation (4).
₂₁ = β ₁ · _SD . When the pressure adjustment piston 48 reaches the upper displacement end, the internal pressure of the second pressure chamber 62 is released to the upper chamber 24. For this reason, when the pressure adjusting piston 48 reaches the upper displacement end, the sliding member 22
Pressure ΔP ₂₁ is ΔP ₂₁ = β _1.
Maintained as _SD . Hereinafter, this differential pressure ΔP ₂₁ = β ₁ ·
It referred to as the upper limit value [Delta] P _21MAX the S _D.

As described above, according to the shock absorber 10 of the present embodiment, when the absorber oil is at a low temperature, when the sliding body 22 is displaced downward beyond the predetermined distance _SD , the second pressure chamber 62 is displaced. Pressure difference Δ between the pressure and the first pressure chamber 60
P ₂₁ , that is, the differential pressure ΔP between the lower chamber 20 and the upper chamber 24
₂₁ can always be maintained at the upper limit value ΔP _21MAX .
Therefore, according to the shock absorber 10, when the absorber oil is at a low temperature, the sliding body 22 is moved a predetermined distance _SD.
When the piston rod 26 is displaced downward beyond
In a direction to prevent the displacement of the sliding body 22 can always exert a spring force Fk corresponding to the upper limit value [Delta] P _21.

FIG. 6 shows a state realized when the sliding body 22 is slightly displaced upward in a situation where the absorber oil is at a low temperature. The solid arrows in FIG. 6 indicate flows generated in the absorber oil when the sliding body 22 is displaced from below to above. As shown by the arrow, when the absorber oil is at a low temperature, the sliding body 22
Is displaced upward from below, the absorber oil flows from the upper chamber 24 toward the first pressure chamber 60.

When the absorber oil flows from the upper chamber 24 to the first pressure chamber 60, the internal pressure of the first pressure chamber 60 becomes
The pressure becomes higher than the internal pressure of the second pressure chamber 62. When a pressure difference is generated between the first pressure chamber 60 and the second pressure chamber 62 in this manner, the pressure adjustment piston 48 is displaced toward the second pressure chamber 62. As a result, when the sliding body 22 is displaced upward, as shown in FIG. 6, the absorber oil flows from the second pressure chamber 62 toward the intermediate chamber 33, and the absorber flows downward from above the piston 76. Oil flow occurs.

When the pressure adjustment piston 48 is displaced from the neutral position toward the second pressure chamber 62 as described above, the second spring 66 and the first spring 64 bias the pressure adjustment piston 48 toward the neutral position. A force Fs is generated. The spring force Fs is calculated by using the composite spring constant K of the second spring 66 and the first spring 64 and the displacement L of the pressure adjusting piston 48 as Fs = KL (see the above equation (1)).
It can be expressed as. Further, this spring force Fs is obtained by using the stroke S of the sliding member 22 and the proportionality constant α _2, and
α ₂ · S (see the above equation (2)).

When a spring force Fs is applied to the pressure adjusting piston 40 toward the neutral position, that is, toward the first pressure chamber 60, the internal pressure of the first pressure chamber 60 is changed to the internal pressure of the second pressure chamber 62. a high pressure by a predetermined pressure [Delta] P ₁₂ compared to.
ΔP ₁₂ can be expressed as ΔP ₁₂ = Fs / Ap = α ₂ · S / Ap (see the above equation (3)) using the cross-sectional area Ap of the pressure adjustment piston 40. The differential pressure ΔP ₁₂ can be expressed as ΔP ₁₂ = β ₂ · S (see the above equation (4)) using a constant β ₂ = α ₂ / Ap.

In the shock absorber 10, an internal pressure equal to the internal pressure of the first pressure chamber 60 or the internal pressure of the second pressure chamber 62 is generated in the intermediate chamber 33 and the upper chamber 24, respectively. Therefore, according to the shock absorber 10, when the absorber oil is at a low temperature, the sliding body 22 is displaced upward as shown in FIG. A pressure higher by the proportional pressure ΔP ₁₂ can be generated.

When the internal pressure of the upper chamber 24 is higher than the internal pressure of the intermediate chamber 33 by ΔP ₁₂ , the sliding body 22 is moved toward the lower chamber 20 by the urging force corresponding to the pressure difference ΔP ₁₂ , ie, the sliding body. 22 is urged in a direction that hinders sliding. Therefore, according to the shock absorber 10, when the absorber oil is at a low temperature, when the sliding body 22 is displaced upward, the piston rod 26 is moved in a direction that hinders the displacement of the sliding body 22 according to the stroke S thereof. A large spring force Fk can be applied.

FIG. 7 shows a state that is realized when the sliding body 22 is displaced upward beyond a predetermined distance in a situation where the absorber oil is at a low temperature. If the displacement of the sliding body 22 continues upward when the absorber oil is at a low temperature, the pressure adjusting piston 48 will eventually move to the position shown in FIG. (Referred to as side displacement end). Through hole 5
When 6 communicates with the through hole 74, the first pressure chamber 60 and the intermediate chamber 33 are brought into conduction.

[0059] When the stroke of the sliding body 22 required for the pressure regulating piston 48 to reach the lower side displacement end of the the S _U, the first pressure chamber when the pressure regulating piston 48 has reached the lower side displacement end 60 and the differential pressure [Delta] P ₁₂ that occurs between the second pressure chamber 62 can be expressed as _{ΔP 12 = β 2 · S U} . When the pressure adjustment piston 48 reaches the lower displacement end, the internal pressure of the first pressure chamber 60 is released to the intermediate chamber 33. Therefore, the pressure regulating piston 48 reaches the lower side displacement end, thereafter, the differential pressure [Delta] P ₁₂ also increases the stroke S of the slider 22 is maintained at _{ΔP 12 = β 2 · S U} . Hereinafter, the upper limit value [Delta] P of the pressure difference ΔP ₁₂ = β ₂ · S _{U
Called 12MAX} .

[0060] Thus, according to the shock absorber 10 of this embodiment, when the absorber oil is cold, when the sliding body 22 is displaced upward beyond a predetermined distance S _U, the first pressure chamber 60 Pressure Δ between the pressure chamber and the second pressure chamber 62
P ₁₂ , that is, the differential pressure ΔP ₁₂ between the upper chamber 24 and the intermediate chamber 33
_Can always be maintained at the upper limit value ΔP _12MAX . Therefore, according to the shock absorber 10, when the absorber oil is cold, when the sliding member 22 is displaced beyond a predetermined distance S _U, the piston rod 26, sliding body 2
The spring force Fk according to the upper limit value ΔP ₁₂ can always be applied in a direction that hinders the displacement of No. 2.

FIG. 8 shows a shock absorber 1 of this embodiment.
0 shows a spring characteristic realized by zero. The characteristics shown by the solid line in FIG. 8 indicate the spring characteristics realized by the shock absorber 10 when the absorber oil is at a low temperature. In addition, the characteristics indicated by the one-dot chain line in FIG. 8 indicate the spring characteristics realized in the shock absorber 10 when the absorber oil is at an intermediate temperature.

As described above, the shock absorber 10 is
When the absorber oil is at a low temperature, a spring force Fk proportional to the stroke S is generated in a region where the stroke S of the shock absorber is less than the predetermined values S _{U and} S _D , and the stroke S is reduced to the predetermined values S _{U and} S _D. An upper limit spring force F _UMAX or F _DMAX is always generated in a region exceeding the range (characteristic indicated by a solid line in FIG. 8). When the absorber oil is at a high temperature, the shock absorber 10 functions in the same manner as a normal shock absorber without generating the spring force Fk as described above. Then, when the absorber oil is at an intermediate temperature, the shock absorber 10 has an intermediate characteristic between a spring characteristic realized when the absorber oil is at a low temperature and a spring characteristic realized when the absorber oil is at a high temperature. This is achieved (the characteristic indicated by the dashed line in FIG. 8).

According to the spring characteristic shown by the solid line in FIG. 8, when the shock absorber 10 expands and contracts, the spring force Fc can be quickly raised from the initial stage of the expansion and contraction, and the region where the amount of expansion and contraction is large is obtained. Thus, it is possible to prevent the spring force Fk from becoming an unnecessarily large value. When the shock absorber 10 exhibits the above-described spring characteristics, a large spring force can be generated in the suspension of the vehicle in a direction to suppress the posture change at the stage when the posture of the vehicle slightly starts to change. Also, according to the above spring characteristics,
When the shock absorber absorbs large traveling vibration,
The ride quality of the vehicle can be prevented from being significantly deteriorated.

Therefore, according to the shock absorber 10, when the absorber oil is at a low temperature, it is possible to provide the suspension of the vehicle with characteristics suitable for achieving both good steering stability and comfortable riding comfort. it can. Absorber oil has a low temperature when the shock absorber does not repeatedly expand and contract as described above, that is, when the vehicle travels on a flat road. For this reason, according to the shock absorber 10 of the present embodiment, when the vehicle travels on a flat road, the characteristics of the suspension of the vehicle are reduced.
Characteristics suitable for achieving both good steering stability and comfortable riding comfort can be obtained.

When the shock absorber 10 does not generate the spring force Fk, a suitable characteristic can be imparted to the vehicle suspension for flexibly absorbing a large traveling vibration. Therefore, according to the shock absorber 10,
When the absorber oil is at a high temperature, it is possible to impart suitable characteristics to the suspension of the vehicle in order to secure a comfortable ride on a rough road or the like. As described above, the absorber oil becomes hot when the shock absorber repeatedly expands and contracts frequently. For this reason, according to the shock absorber 10 of the present embodiment, when the vehicle travels on a rough road, the characteristics of the suspension of the vehicle can be set to characteristics suitable for securing a comfortable ride on a rough road. it can.

The shock absorber 10 according to the present embodiment is
According to this, the spring characteristics can be continuously changed according to the temperature of the absorber oil. Therefore, according to the shock absorber 10 of the present embodiment, when the running environment of the vehicle changes, the characteristics of the suspension of the vehicle can be changed to the optimum characteristics for the changed running environment.

In the above embodiment, the spring characteristic of the shock absorber 10 is changed by utilizing the fact that the viscosity of the absorber oil changes with the temperature change of the absorber oil. The method of making the setting is not limited to this. That is, the spring characteristic of the shock absorber 10 is such that, for example, by utilizing the thermal expansion of the communication passage 46, the effective area of the communication passage 46 is larger when the absorber oil is at a higher temperature than when the absorber oil is at a lower temperature. Can also be changed. Further, the spring characteristics of the shock absorber 10 can also be realized by, for example, configuring the urging member for urging the pressure adjusting piston 48 so that the spring force Fk decreases as the temperature of the absorber oil increases. it can.

In the above embodiment, the upper chamber 24 and the intermediate chamber 33 correspond to the "first chamber" of the first aspect, and the lower chamber 20 corresponds to the "second chamber" of the first aspect. 2. The "first sliding body" according to claim 1, wherein the absorber piston portion 32 is provided.
The oil passage forming part 28 and the spring element housing part 30 are provided in the “second sliding body” of the first embodiment.
The second spring 66 and the second spring 66 correspond to the “biasing member” of the first aspect, and the through holes 56, 58, 72, and 74 correspond to the “conduction state control mechanism” of the first aspect.

[0069]

As described above, according to the first aspect of the present invention, a predetermined spring characteristic is exhibited when expansion and contraction are not repeated frequently, and the spring characteristic is exhibited when expansion and contraction is repeated frequently. It is possible to realize a shock absorber that does not exhibit. Therefore, according to the shock absorber according to the present invention, when the vehicle is traveling on a flat road, and
When the vehicle is traveling on a rough road, appropriate suspension characteristics can be respectively realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a shock absorber according to one embodiment of the present invention.

FIG. 2 is an enlarged view of a sliding body of the shock absorber of the present embodiment.

FIG. 3 is a diagram showing a state realized when the sliding body is displaced in a situation where the absorber oil is at a high temperature.

FIG. 4 is a diagram showing a state realized when the sliding body is slightly displaced downward in a situation where the absorber oil is at a low temperature.

FIG. 5 is a diagram showing a state realized when the sliding body is largely displaced downward under a situation where the absorber oil is at a low temperature.

FIG. 6 is a diagram showing a state realized when the sliding body is slightly displaced upward in a situation where the absorber oil is at a low temperature.

FIG. 7 is a diagram showing a state realized when the sliding body is largely displaced upward in a situation where the absorber oil is at a low temperature.

FIG. 8 is a diagram showing spring characteristics of the shock absorber of the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Shock absorber 20 Lower chamber 22 Sliding body 24 Upper chamber 33 Intermediate chamber 34, 46 Communication passage 48 Pressure adjusting piston 56, 58, 72, 74 Through hole 60 First pressure chamber 62 Second pressure chamber 64 First spring 66 Second spring

Claims (1)

[Claims] 1. A first chamber and a second chamber inside an absorber shell.
A shock absorber for a vehicle, comprising: a first sliding body that separates a chamber, wherein the first sliding body generates a damping force when the first sliding body slides inside the absorber shell. A second pressure body that communicates with the upper chamber; a second pressure chamber that communicates with the intermediate chamber; and a second pressure chamber that communicates with the upper chamber. A pressure adjustment piston separating the first pressure chamber and the second pressure chamber, an urging member for urging the pressure adjustment piston toward a neutral position, and the pressure adjustment piston exceeding a predetermined distance from the neutral position When the second pressure chamber and the upper chamber are in a conductive state when displaced toward the upper chamber side, and when the pressure adjustment piston is displaced toward the intermediate chamber side beyond a predetermined distance from the neutral position. Conduction between the first pressure chamber and the intermediate chamber And a communication path for changing a flow resistance in accordance with the oil temperature of the absorber oil between the upper chamber and the intermediate chamber. Absorber.