JP2007078004A - Shock-absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shock-absorber which can improve the driving comfort in a vehicle which can certainly prevent damping force from abruptly changing in the expansion and contraction stroke. <P>SOLUTION: The shock absorber includes a cylinder 1, a partition member 2 slidably inserted inside the cylinder 1 to partition the inside of the cylinder 1 into two working chambers R1 and R2, a first passage 3 and a second passage 4 to communicate with the two working chambers R1 and R2, a pressure chamber R3 formed halfway in the second passage 4, a free piston 5 slidably inserted in the pressure chamber R3 to interrupt the communication between the working chambers R1 and R2, and a spring element 6 to generate urging power to suppress the displacement for the pressure chamber R3 of the free piston 5. The passage resistance of the second passage 4 increases depending on the displacement amount from the neutral position of the free piston 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement of a shock absorber.

  Conventionally, in this kind of shock absorber, a cylinder, a piston that is slidably inserted into the cylinder and that divides the two working chambers in the cylinder, and two working chambers provided in the piston communicate with each other. A first passage, a second passage that opens from the tip of the piston rod to the side and communicates with the two working chambers, and a pressure chamber that is connected to the middle of the second passage are attached to the intermediate portion of the piston rod. The housing includes a housing and a free piston that is slidably inserted into the pressure chamber and partitions the pressure chamber into one chamber and the other chamber. That is, one chamber in the pressure chamber communicates with one working chamber through the second passage, and the other chamber in the pressure chamber communicates with the other working chamber through the second passage.

  This shock absorber generates a relatively small damping force by exchanging hydraulic oil in the pressure chamber and one or the other working chamber by moving the free piston in the pressure chamber up and down against small amplitude vibrations. The free piston moves to the stroke end (position where it abuts against the inner wall of the pressure chamber end), and the hydraulic oil cannot pass through the second passage, and the hydraulic oil passes through the first passage and is large. A damping force is generated (see, for example, Patent Document 1).

  As described above, in the shock absorber, when the free piston reaches the stroke end, the hydraulic oil is preferentially passed through the first passage to increase the damping force. Since the damping force suddenly changes greatly when the end is reached, in order to avoid this, a cushion that protrudes toward the inner wall of the pressure chamber end is provided on the free piston so that the free piston reaches the vicinity of the stroke end. When it is displaced, the cushion is brought into contact with the inner wall so that the movement of the free piston toward the stroke end side is gradually blunted, so that the damping force gradually changes greatly.

Further, in the above proposal of the shock absorber, a plunger that penetrates into the second passage provided in the piston rod is provided in the free piston, and when the free piston moves downward, the flow passage resistance in the second passage is increased to increase the free piston. A configuration is also disclosed in which the movement of only one side to the stroke end is gradually blunted to suppress a rapid change in damping force during the extension stroke.
US2005 / 0011712A1 publication (see each figure)

  The above-described shock absorber is useful in that it can improve the ride comfort in the vehicle, but has the following problems.

  In the configuration of the above-described shock absorber, the free piston is not necessarily in the neutral position when the piston is in the neutral position, and there is a possibility that the function of suppressing a sudden change in damping force may not be exhibited when necessary. The ride comfort may be impaired.

  In general, in a shock absorber mounted on a vehicle, there is a large difference of several MPa between the pressure in one working chamber and the pressure in the other working chamber during expansion and contraction. In order to suppress a rapid change in force, it is necessary to set a large spring constant and strain amount of the cushion, and durability is also required, and a very difficult design is forced.

  Furthermore, in the case of using a plunger, the configuration of the shock absorber described above cannot suppress a sudden change in damping force during the pressure stroke, and there is no guarantee that the plunger is always inserted without being eccentric to the second passage. When the shaft is inserted eccentrically compared to the state inserted in the center of the second passage, the flow path resistance may differ by a maximum of 2.5 times. Will fluctuate each time the shock absorber expands and contracts, giving the passenger a sense of incongruity and possibly impairing the riding comfort of the vehicle.

  Therefore, the present invention was devised to improve the above-described problems, and the object of the present invention is to reliably suppress a sudden change in damping force during the expansion / contraction stroke and to improve the riding comfort in the vehicle. It is another object of the present invention to provide a shock absorber that can be easily designed and reduced in cost, and yet another object of the present invention is to provide an abrupt damping force. It is an object of the present invention to provide a shock absorber capable of stably suppressing a change.

  In order to solve the above-described object, the problem solving means in the present invention communicates a cylinder, a partition member slidably inserted into the cylinder and partitioning the cylinder into two working chambers, and the two working chambers. A first passage, a second passage, a pressure chamber provided in the middle of the second passage, a free piston that is slidably inserted into the pressure chamber and disconnects the working chambers, and a displacement of the free piston with respect to the pressure chamber. A spring element that generates an urging force to be suppressed, and the flow path resistance of the second passage increases depending on the amount of displacement from the neutral position of the free piston.

  According to the shock absorber of the present invention, even if a vibration having a high frequency and a large amplitude is input, the generated damping force does not change abruptly, so that the riding comfort in the vehicle can be improved. A situation in which the vehicle body vibrates due to a change in the damping force and the bonnet resonates to generate abnormal noise can be prevented. In this respect as well, the riding comfort in the vehicle can be improved.

  In addition, since the urging force for returning the free piston to the neutral position is acting by the spring element by the spring element, it is possible to avoid a situation in which the function of suppressing a sudden change in the damping force cannot be exhibited when necessary.

  Furthermore, when the free piston reaches the stroke end on both ends in the pressure chamber, the flow resistance of the second passage is gradually changed to increase, so that the damping force suddenly changes each time the shock absorber expands and contracts. The function to suppress does not change and does not give the passenger a sense of incongruity.

  Further, in order to achieve the function of suppressing the sudden change in the damping force, the flow resistance of the second passage is gradually changed and increased without using a cushion or a plunger, so the design is very easy. It becomes.

  The shock absorber according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram conceptually illustrating a shock absorber. FIG. 2 is a model diagram during operation of the shock absorber. FIG. 3 is a Bode diagram showing the gain characteristic of the frequency transfer function of the pressure with respect to the flow rate. FIG. 4 is a diagram showing the relationship between the attenuation coefficient, phase, and frequency. FIG. 5 is a longitudinal sectional view of a specific shock absorber in one embodiment. FIG. 6 is an enlarged longitudinal sectional view of a piston portion of a specific shock absorber in one embodiment. FIG. 7A is a diagram illustrating a cross-sectional shape of a specific orifice of a shock absorber according to a modification of the embodiment. (B) It is a figure which shows the cross-sectional shape of the orifice of the concrete shock absorber in one modification of one Embodiment. (C) It is a figure which shows the cross-sectional shape of the orifice of the concrete shock absorber in one modification of one Embodiment. FIG. 8 is an enlarged longitudinal sectional view of a free piston of a shock absorber according to another modification of the embodiment. FIG. 9 is an enlarged longitudinal sectional view of a piston portion of a shock absorber according to another modification of the embodiment. FIG. 10 is an enlarged longitudinal sectional view of a piston portion of a shock absorber according to another embodiment.

  As shown in FIG. 1, the shock absorber D of the present invention includes a cylinder 1, one lower chamber R <b> 2 and two other upper chambers R <b> 1 that are slidably inserted into the cylinder 1 and are two working chambers. A piston 2 that is a partition member that is partitioned into a first passage 3, a first passage 3 and a second passage 4 that communicate with the upper chamber R1 and the lower chamber R2, a pressure chamber R3 provided in the middle of the second passage 4, and the pressure chamber R3 A free piston 5 that is slidably inserted into the upper chamber R1 and the lower chamber R2, and a spring element 6 that generates a biasing force that suppresses displacement of the free piston 5 relative to the pressure chamber R3. A variable throttle 11 provided in the middle of the passage 4 is configured, and the upper chamber R1, the lower chamber R2, and further the pressure chamber R3 are filled with a liquid such as hydraulic oil, and the inside of the cylinder 1 is also illustrated. The lower chamber is in sliding contact with the inner circumference of the cylinder 1 2 and the gas chamber slides partition 7 partitioning the G is provided.

  Furthermore, the piston 2 is connected to one end of a piston rod 8 that is movably inserted into the cylinder 1, and the piston rod 8 projects from the upper end of the cylinder 1 in the figure. The piston rod 8 and the cylinder 1 are in a liquid-tight state inside the cylinder 1 with a seal (not shown).

  Therefore, when an axial force is applied to the piston rod 8 and / or the cylinder 1 from the outside, the piston rod 8 and the cylinder 1 are moved relative to each other, and accordingly, the piston 2 is also vertically moved with respect to the cylinder 1 in the figure. Will be moved to.

  Furthermore, a damping force generating element 10 such as an orifice or a leaf valve is provided in the middle of the first passage 3 so that resistance can be given to the flow of the liquid passing through the first passage 3. Yes.

  The pressure chamber R <b> 3 is partitioned into a first chamber 13 and a second chamber 14 by the free piston 5. In addition, the second passage 4 includes a one-side flow path 4a that communicates the lower chamber R2 that is one side of the working chamber and the one chamber 13, an upper chamber R1 that is the other side of the working chamber, and the other chamber 14. The variable throttle 11 is provided in the middle of the one-side channel 4a as a damping force generating element that provides resistance to the flow of the liquid passing through the one-side channel 4a. Yes.

  The free piston 5 is slidably inserted into the pressure chamber R3 and can be displaced with respect to the pressure chamber R3. Further, the free piston 5 is connected to the end of the pressure chamber R3 at one end. Is connected to the other end of the spring element 6 to be connected, whereby the free piston 5 is positioned at a predetermined position of the pressure chamber R3 and the position positioned relative to the pressure chamber R3 (hereinafter simply referred to as "neutral position"). ), An urging force corresponding to the amount of displacement acts from the spring element 6.

  Furthermore, when the free piston 5 is displaced from the neutral position, the variable throttle 11 does not change the flow path area when the free piston 5 is within an arbitrary displacement amount, and the free piston 5 is in the neutral position toward both ends of the pressure chamber R3. When the displacement exceeds the above-mentioned arbitrary displacement amount, the flow passage area is reduced according to the displacement amount, and the flow passage resistance of the one-side flow passage 4a is increased. When the variable throttle 11 is displaced to the stroke end where it comes into contact with both ends of R3, the variable throttle 11 minimizes the channel area and maximizes the channel resistance of the one-side channel 4a.

  Therefore, in this shock absorber D, the flow resistance of the second passage 4 is changed by changing the flow resistance of the one-side flow path 4a depending on the amount of displacement from the neutral position of the free piston 5. It is supposed to let you.

  When the shock absorber D is extended, that is, when the piston rod 8 is retracted from the cylinder 1, the upper chamber R1 is compressed by the piston 2 and the lower chamber R2 is expanded. As the pressure increases, the pressure in the lower chamber R2 decreases to generate a differential pressure, and the liquid in the upper chamber R1 moves into the lower chamber R2 via the first passage 3.

  At this time, since the pressure in the upper chamber R1 becomes higher than the pressure in the lower chamber R2, the liquid in the upper chamber R1 is communicated with the upper chamber R1 in the pressure chamber R3 through the other-side channel 4b. The air flows into the other chamber 14, and the free piston 5 in the pressure chamber R3 is pushed downward in the figure against the urging force of the spring element 6 to expand the other chamber 14. On the contrary, since the one chamber 13 communicated with the lower chamber R2 in the pressure chamber R3 is compressed, the liquid flows out from the one chamber 13 into the lower chamber R2 through the one-side flow path 4a.

  In turn, when the shock absorber D contracts, that is, when the piston rod 8 enters the cylinder 1, the upper chamber R1 is expanded by the piston 2 and the lower chamber R2 is compressed. As the internal pressure increases, the pressure in the upper chamber R1 decreases to generate a differential pressure, and the liquid in the lower chamber R2 moves into the upper chamber R1 via the first passage 3.

  At this time, since the pressure in the lower chamber R2 becomes higher than the pressure in the upper chamber R1, the liquid in the lower chamber R2 flows into the one chamber 13 in the pressure chamber R3 via the one-side flow path 4a. The free piston 5 in the pressure chamber R3 is pushed upward in the figure against the urging force of the spring element 6, and the one chamber 13 is expanded. On the contrary, since the other chamber 14 in the pressure chamber R3 is compressed, the liquid flows out from the other chamber 14 into the upper chamber R1 through the other channel 4b.

  It should be noted that when the shock absorber D is expanded and contracted, the volume of the piston rod 8 that retreats from the cylinder 1 that is insufficient in the cylinder 1 or the piston rod 8 that enters the cylinder 1 that is excessive in the cylinder 1. The volume of liquid is compensated by the sliding partition 7 moving up and down relative to the cylinder 1 and the gas chamber G expanding or contracting.

(A) Operation of the shock absorber D when the displacement amount from the neutral position of the free piston 5 is equal to or less than the arbitrary displacement amount The displacement amount of the free piston 5 in the pressure chamber R3 of the shock absorber D is not displaced to the arbitrary displacement amount. The operation of the shock absorber D in this case will be described below using the model diagram shown in FIG.

そして、上記（１）から（６）の各式を整理してラプラス変換して、流量Ｑに対する差圧Ｐの伝達関数を求めると、式（７）が得られる。なお、式（７）中、ｓはラプラス演算子を示している。

さらに、上記（７）式で示された伝達関数中のラプラス演算子ｓにｊωを代入して、周波数伝達関数Ｇ（ｊω）の絶対値を求めると、以下の式（８）が得られる。

また、その位相Φは、式（９）で計算される。

上記式（８）で、角周波数ωを２πで割ると周波数Ｆとなり、周波数伝達関数Ｇ（ｊω）の周波数Ｆに対するゲイン特性は、図３のボード線図に示したように、Ｆａ＝Ｋ／｛２・π・Ａ^２・（Ｃ１＋Ｃ２＋Ｃ３）｝とＦｂ＝Ｋ／｛２・π・Ａ^２・（Ｃ２＋Ｃ３）｝の２つの折れ点周波数を持ち、また、Ｆ＜Ｆａの領域においては、伝達ゲインは略Ｃ１となり、Ｆａ≦Ｆ≦Ｆｂの領域においてはＣ１からＣ１・（Ｃ２＋Ｃ３）／（Ｃ１＋Ｃ２＋Ｃ３）まで漸減するように変化し、Ｆ＞Ｆｂの領域においてはＣ１・（Ｃ２＋Ｃ３）／（Ｃ１＋Ｃ２＋Ｃ３）となる。 The differential pressure between the upper chamber R1 and the lower chamber R2 when the shock absorber D is expanded and contracted is P, the flow rate of the liquid flowing out from the upper chamber R1 is Q, and the differential pressure P and the flow rate of the liquid passing through the first passage 3 The coefficient that is related to Q1 is C1, the pressure in the other chamber 14 is P1, and the pressure of the liquid that passes through this pressure P1 and the other channel 4b and flows into the other chamber 14 in the pressure chamber R3 from the upper chamber R1. The coefficient that is related to the flow rate Q2 is C2, the pressure in the one chamber 13 is P2, and the pressure P2 passes through the one-side flow path 4a and flows out from the one chamber 13 in the pressure chamber R3 into the lower chamber R2. The coefficient that is the relationship with the liquid flow rate Q2 is C3, the cross-sectional area that is the pressure receiving area of the free piston 5 is A, the displacement of the free piston 5 with respect to the pressure chamber R3 is X, and the spring constant of the spring element 6 is K. Then, the following equations (1) to (6) are obtained.

Then, when the equations (1) to (6) are arranged and Laplace converted to obtain a transfer function of the differential pressure P with respect to the flow rate Q, an equation (7) is obtained. In Expression (7), s represents a Laplace operator.

Furthermore, substituting jω for the Laplace operator s in the transfer function shown in the above equation (7) to obtain the absolute value of the frequency transfer function G (jω) yields the following equation (8).

Further, the phase Φ is calculated by the equation (9).

In the above equation (8), when the angular frequency ω is divided by 2π, the frequency F is obtained. The gain characteristic of the frequency transfer function G (jω) with respect to the frequency F is expressed as Fa = K / {2 · π · A ² · (C 1 + C 2 + C 3)} and Fb = K / {2 · π · A ² · (C 2 + C 3)}, and in the region where F <Fa, the transfer gain is obtained. Becomes approximately C1 and changes so as to gradually decrease from C1 to C1 · (C2 + C3) / (C1 + C2 + C3) in the region of Fa ≦ F ≦ Fb, and C1 · (C2 + C3) / (C1 + C2 + C3) in the region of F> Fb. Become.

  Then, in order to convert the gain characteristic of the frequency transfer function G (jω) obtained from the above into the damping coefficient ζ, multiplying | G (jω) | by the square of the pressure receiving area B of the piston 2 gives the frequency The relationship between the damping characteristic, which is a change in damping force with respect to F, and the phase Φ and the frequency F is as shown in FIG. The attenuation characteristic is indicated by a solid line in FIG. 4, and the phase Φ is indicated by a broken line in FIG.

  As is apparent from FIG. 4, the shock absorber D generates a high damping force when the frequency F is lower than the break frequency Fa, and generates a low damping force when the frequency F is higher than the break frequency Fb. It can be understood that when the frequency F is greater than or equal to the breakpoint frequency Fa and less than or equal to the breakpoint frequency Fb, the damping characteristic gradually decreases.

  Therefore, the breakpoint frequencies Fa and Fb are determined from the above, the coefficient C1 of the relationship between the differential pressure P and the flow rate Q1 of the liquid passing through the first passage 3, the pressure P1 in the other chamber 14, and the other side flow. The relationship C2 between the flow rate Q2 of the liquid passing through the passage 4b, the relationship C3 between the pressure P2 in the one chamber 13 and the flow rate Q2 of the liquid passing through the one-side flow passage 4a, and the pressure receiving area of the free piston 5 The area can be set by A and the spring constant K of the spring element 6, and the damping coefficient ζ can be set by the coefficients C 1, C 2, C 3 and the pressure receiving area B of the piston 2. In this case, the damping characteristics are set by the coefficients C1, C2 and C3 of the respective relationships, the pressure receiving area A of the free piston 5 and the spring constant K of the spring element 6.

  The coefficient C1 is a value determined by the resistance that the damping force generating element 10 of the first passage 3 gives to the liquid flow. Even if the coefficient C1 is other coefficients C2 and C3, the liquid flow rate in the other channel 4b is determined. Since it is a value determined by the resistance given to the flow and the resistance given to the liquid flow of the variable throttle 11 provided in the one-side flow path 4a, the adjustment of the amount of change of the attenuation coefficient ζ with respect to the frequency F and the bending point frequency Fa , Fb can be easily adjusted.

  That is, the change of the damping force of the shock absorber D can be made to depend on the input vibration frequency, and the adjustment thereof is very easy. The shock absorber D is similar to the conventional shock absorber. Rather than adjusting the damping characteristics based on the magnitude of the amplitude, it outputs a damping characteristic that depends on the input vibration frequency, ensuring a low damping force in situations where the input vibration frequency is high, such as when a vehicle rides over road irregularities. In addition, in a scene where the input vibration frequency is low such as when the vehicle is turning, a high damping force can be reliably generated.

  In addition, since the damping characteristics can be easily adjusted, there is no need for complicated adjustment work to realize damping characteristics matched to the vehicle by groping when applying the shock absorber D to various vehicles having different standards. Its design and tuning are easy.

  Further, when the breakpoint frequency Fb value other than the breakpoint frequency Fa that takes the minimum value among the plurality of breakpoint frequencies Fa and Fb is set to be equal to or lower than the value of the unsprung resonance frequency of the vehicle, When vibration of the lower resonance frequency is input, a low damping force is always generated, so that the riding comfort in the vehicle is not impaired.

  In the region where the input vibration frequency F exceeds the breakpoint frequency Fb, the phase lag of the damping coefficient ζ tends to disappear, and the generation of the damping force follows the vibration input without delay. There is no loss of comfort.

  Further, the damping device D is configured so that the minimum bending point frequency Fa is set to be not less than the value of the sprung resonance frequency of the vehicle and not more than the value of the unsprung resonance frequency. It is possible to reliably generate a high damping force with respect to the vibration input of the vehicle, to stabilize the posture of the vehicle, and to prevent the passenger from feeling uneasy when turning the vehicle. In the lower frequency region, the phase delay of the damping coefficient ζ tends to be eliminated, and the generation of the damping force follows the vibration input without delay. Therefore, in this respect as well, the passenger does not feel uncomfortable or uneasy.

(B) Operation of the shock absorber D when the displacement amount from the neutral position of the free piston 5 exceeds an arbitrary displacement amount In turn, the buffering when the displacement amount from the neutral position of the free piston 5 exceeds the arbitrary displacement amount The operation of the device D will be described. In this case, the variable throttle 11 gradually reduces the flow path area according to the amount of displacement of the free piston 5, and minimizes the flow path area when the free piston 5 reaches the stroke end. That is, when the free piston 5 is displaced beyond the arbitrary displacement amount, the flow resistance of the second passage 4 is gradually increased according to the displacement amount exceeding the arbitrary displacement amount, and the free piston 5 is moved to the stroke end. Reaches the maximum flow path resistance of the second passage 4.

  Here, the free piston 5 is displaced to the stroke end when the amount of liquid flowing into and out of the one chamber 13 or the other chamber 14 is large. Specifically, when the vibration amplitude of the shock absorber D is large. It is.

  When the vibration frequency of the shock absorber D is relatively high, the shock absorber D generates a relatively low damping force until the free piston 5 is displaced to an arbitrary displacement amount. When the displacement amount exceeds an arbitrary displacement amount, the flow resistance of the second passage 4 gradually increases, so that the moving speed of the free piston 5 toward the stroke end is further reduced. Thus, the AC amount of the liquid between the upper chamber R1 and the lower chamber R2 via the pressure chamber R3 also decreases, and the amount of liquid passing through the first passage 3 increases accordingly, and the generation and attenuation of the shock absorber D The power gradually increases.

  When the free piston 5 reaches the stroke end, there is no more liquid exchange between the upper chamber R1 and the lower chamber R2 via the pressure chamber R3, and the liquid is the first until the expansion / contraction direction of the shock absorber D is changed. Only the passage 3 is passed, and the shock absorber D generates a damping force with the maximum damping coefficient.

  That is, even if high-frequency and large-amplitude vibration that causes the free piston 5 to be displaced to the stroke end is input to the shock absorber D, the amount of displacement from the neutral position of the free piston 5 exceeds an arbitrary amount of displacement. Since the damping device D gradually increases the generated damping force until the free piston 5 reaches the stroke end, the sudden damping force does not change from a low damping force to a high damping force. That is, when the free piston 5 reaches the stroke end and the liquid in the pressure chamber R3, the upper chamber R1, and the lower chamber R2 cannot exchange with each other, the magnitude of the damping force does not change suddenly, and the low damping The damping force change from force to high damping force becomes smooth. Furthermore, since the generated damping force is gradually increased when the free piston 5 reaches the stroke ends at both ends in the pressure chamber R3, the function of suppressing a sudden change in the damping force is Demonstrated in both strokes.

  Therefore, in this shock absorber D, even if vibration with a high frequency and a large amplitude is input, the generated damping force does not change abruptly, so that the riding comfort in the vehicle can be improved. It is possible to prevent a situation in which the vehicle body vibrates due to a sudden change in damping force and the bonnet resonates to generate abnormal noise. In this respect as well, the riding comfort in the vehicle can be improved.

  Further, in this shock absorber D, the urging force for returning the free piston 5 to the neutral position is acting on the free piston 5 by the spring element 6, so that the function of suppressing a sudden change in the damping force when necessary. It is possible to avoid the situation that cannot be demonstrated.

  Further, in the shock absorber D, when the free piston 5 reaches the stroke ends on both ends in the pressure chamber R3, the flow resistance of the second passage 4 is gradually changed to increase the shock absorber. The function of suppressing a sudden change in damping force does not fluctuate every time the vehicle expands and contracts, and the passenger does not feel uncomfortable.

  Furthermore, in order to achieve the function of suppressing the sudden change in the damping force, the flow resistance of the second passage 4 is gradually changed and increased without using a cushion or a plunger. It becomes easy.

  In the above description, the variable throttle 11 is provided in the one-side flow path 4a of the second passage 4, but the variable throttle is also provided in the other-side flow path 4b or the variable throttle of the one-side flow path 4a is provided. It is also possible to change the flow path resistance of the second passage 4 by providing a variable throttle only in the other side flow path 4b and changing the flow path area of the variable throttle in the other side flow path 4b. . Moreover, you may make it provide damping force generation elements, such as a fixed aperture, in the other side flow path 4b.

  Although the shock absorber D has been conceptually described above, a specific configuration of the shock absorber D will be shown and described below.

  As shown in FIGS. 5 and 6, a specific shock absorber D <b> 1 in one embodiment includes a cylinder 20 and an upper chamber R <b> 4 that is slidably inserted into the cylinder 20 and is two working chambers. The piston 21 is a partition member that is partitioned into the lower chamber R5, the first passages 22 and 23 that communicate with the upper chamber R4 and the lower chamber R5 formed in the piston 21, and the piston rod 24. The piston 21 to be fitted is fixed to the piston rod 24 and the housing 30 in which the pressure chamber R6 is formed, the free piston 50 accommodated in the pressure chamber R6, and the displacement amount of the free piston 50 with respect to the pressure chamber R6. The upper chamber R, which is formed in the piston rod 24 and the other working chamber, has an urging force that suppresses the displacement of the free piston 50 in proportion to To the other chamber 26 of the pressure chamber R6, the other-side flow passage 41 constituting a part of the second passage, and the lower chamber R5 provided in the housing 30 as one working chamber to the one chamber 27 of the pressure chamber R6. The upper chamber R4, the lower chamber R5, and the pressure chamber R6 are filled with a liquid such as hydraulic oil, and this specific shock absorber D1 is provided with a one-side flow path in the second passage that communicates. However, a sliding partition wall 58 that slidably contacts the inner periphery of the cylinder 20 and divides the lower chamber R5 and the gas chamber G1 is provided below the cylinder 20 in the drawing.

  In the following, the piston rod 24 has a small diameter portion 24a formed at the lower end side in FIG. 6 and a screw portion 24b formed at the distal end side of the small diameter portion 24a.

  In the piston rod 24, the other-side flow path 41 is formed that constitutes a part of the second passage that opens from the tip of the small diameter portion 24 a and passes through the side of the piston rod 24. Although not shown, a damping force generating element such as a throttle may be provided in the middle of the other side channel 41.

  The piston 21 is formed in an annular shape, and a small diameter portion 24a of the piston rod 24 is inserted on the inner peripheral side thereof. The piston 21 is provided with first passages 22 and 23 for communicating the upper chamber R4 and the lower chamber R5. The upper end of the first passage 22 in the figure is a laminated leaf valve V1 that is a damping force generating element. The lower end of the other first passage 23 in the figure is also closed by the laminated leaf valve V2 that is a damping force generating element.

  The laminated leaf valves V1 and V2 are both formed in an annular shape, and a small-diameter portion 24a of the piston rod 24 is inserted on the inner peripheral side, and annular valve stoppers 28, which regulate the deflection amount of the laminated leaf valves V1 and V2, respectively. 29 and the piston 21 are laminated together.

  The laminated leaf valve V1 bends and opens due to the pressure difference between the lower chamber R5 and the upper chamber R4 when the shock absorber D1 contracts, opens the first passage 22, and flows the liquid from the lower chamber R5 to the upper chamber R4. The first passage 22 is closed when the shock absorber D is extended, and the other laminated leaf valve V2 is opposite to the laminated leaf valve V1 when the shock absorber D1 is extended. Is opened, and the first passage 23 is closed during contraction. That is, the laminated leaf valve V1 is an element that generates a compression-side damping force when the shock absorber D1 is contracted, and the other laminated leaf valve V2 is an element that generates an expansion-side damping force when the shock absorber D1 is extended. . As described above, if the communication between the upper chamber R4 and the lower chamber R5 is not completely interrupted when the shock absorber D1 is expanded or contracted, a plurality of first passages are provided, and each of them is liquid only when the shock absorber D1 is extended or contracted. May be configured to pass.

  A housing 30 is screwed onto the screw portion 24b of the piston rod 24 from below the valve stopper 29, and the piston 21, the laminated leaf valves V1 and V2, and the valve stoppers 28 and 29 are connected to the piston by the housing 30. It is fixed to the rod 24.

  As described above, the housing 30 plays a role of fixing the piston 21 to the piston rod 24, and a pressure chamber R6 is formed therein.

  The housing 30 will be described. The housing 30 includes an inner cylinder 31 with a flange 32 that is screwed into the screw portion 24b of the piston rod 24, an outer cylinder 33 that extends from the outer periphery of the flange 32, and an outer cylinder 33. And the cap 34 that closes the opening, and the inner cylinder 31, the outer cylinder 33, and the cap 34 form a pressure chamber R6.

  The inner cylinder 31 includes the flange 32 as described above, and a screw portion 31a is formed on the inner periphery thereof. By screwing the screw portion 31a to the screw portion 24b of the piston rod 24, the housing 30 is moved to the piston rod. 24 can be fixed to the small diameter portion 24a.

  The outer cylinder 33 is integrated with the inner cylinder 31 by caulking from the outer peripheral side of the flange 32 of the inner cylinder 31. In addition, when integrating the inner cylinder 31 and the outer cylinder 33, other methods, such as welding, can also be employ | adopted besides the said crimping process. Further, if the cross-sectional shape of the outer periphery of the outer cylinder 33 is a shape other than a perfect circle, for example, a shape with a part cut away or a hexagonal shape, the operation of screwing the housing 30 onto the tip of the piston rod 24 is performed. It becomes easy.

  The cap 34 is formed in the shape of a bottomed cylinder with a flange, and the flange portion is fixed to the lower end of the outer cylinder 33 by caulking the lower end of the outer cylinder 33 in the figure. A bypass path 42 constituting a part is provided.

  A free piston 50 is slidably inserted into the pressure chamber R6 formed by the inner cylinder 31, the outer cylinder 33, and the cap 34. The free piston 50 causes the pressure chamber R6 to flow to the other side. The other chamber 26 communicated with the upper chamber R4 by the passage 41 and the other chamber 27 communicated with the lower chamber R5 by the bypass passage 42.

  The free piston 50 is formed in a bottomed cylindrical shape, and the cylindrical portion 51 is in sliding contact with the inner periphery of the outer cylinder 33, and the bottom portion 52 is provided with a convex portion 53 protruding in the direction of the cap 34. ing.

  Furthermore, the flange 32 of the inner cylinder 31 and the bottom 51 of the free piston 50 serve as a spring element 55 that applies a biasing force that suppresses the displacement in proportion to the amount of displacement of the free piston 50 relative to the pressure chamber R6. Coil springs 56 and 57 are interposed between the inner side and between the cap 34 and the outer side of the bottom portion 52 of the free piston 50, respectively, and the free piston 50 is provided in the pressure chamber R 6 by the coil springs 56 and 57. It is elastically supported at the neutral position.

  The lower end of the coil spring 56 in the figure is fitted into the inner periphery of the deepest portion of the cylindrical portion 51 of the free piston 50 and positioned in the radial direction, and the convex portion 53 of the free piston 50 is inserted into the inner periphery of the coil spring 57. Thus, a significant positional deviation is prevented, and it is possible to stably apply an urging force to the free piston 50, and the free piston 50 causes a shaft shake or the like with respect to the outer cylinder 33, thereby causing a sliding resistance. Will not grow.

  In addition, the inner periphery of the cylinder part 51 of the free piston 50 is expanded in diameter as compared with the deepest part thereof, so that when the coil spring 56 is compressed and the winding diameter is expanded, the wire material of the coil spring 56 is cylindrical. It does not rub against the inner periphery of the part 51 and prevents the occurrence of contamination.

  Moreover, since the free piston 50 uses the cylindrical portion 51 as a sliding contact portion with respect to the inner periphery of the outer cylinder 33, it is easy to ensure the axial length of the sliding portion, and this also allows the shaft of the free piston 50 to be secured. Shake is suppressed.

  The free piston 50 is provided with an annular groove 51 a formed along the circumference on the outer periphery of the cylindrical portion 51, and further, the annular groove 51 a and the one chamber 27 communicate with each other through the thickness of the free piston 50. A hole 51b is provided.

  Further, a plurality of orifices 33a communicating with the lower chamber R5 and the inside of the outer cylinder 33 are provided on the side of the outer cylinder 33. The orifice 33a is neutral with the free piston 50 elastically supported by a spring element 55. When it is at the position, it faces at least the annular groove 51a and the free piston 50 is displaced to the stroke end, that is, when it is displaced until it contacts the lower end of the inner cylinder 31 or the flange of the cap 34, the cylindrical part of the free piston 50 The outer periphery of 51 is completely overlapped and closed.

  That is, in the case of this shock absorber D1, when the amount of displacement from the neutral position of the free piston 50 becomes an arbitrary amount of displacement, the entire opening of the orifice 33a faces the outer periphery of the cylindrical portion 51 from the situation where it faces the annular groove 51a. The flow area of the orifice 33a begins to decrease gradually after the transition to the situation where the flow begins, and the flow resistance in the one-side flow path constituted by the orifice 33a, the annular groove 51a, the hole 51b and the bypass path 42 gradually increases. To do. Therefore, the above-mentioned arbitrary amount of displacement is set by setting the vertical width of the annular groove 51a in the drawing and the opening position of the orifice 33a on the inner peripheral side of the outer cylinder 33.

  When the free piston 50 reaches the stroke end while gradually decreasing the flow path area of the orifice 33a and increasing the flow resistance, the orifice 33a is completely overlapped and closed by the cylindrical portion 51. The flow path resistance in the one-side flow path becomes the maximum, and the one chamber 27 is communicated with the lower chamber R5 only by the bypass path 42.

  When the bypass path 42 is not provided in the cap 34, the orifice 33a may be prevented from being completely closed when the free piston 50 reaches the stroke end.

  The sliding partition wall 58 is provided with a recess on the lower chamber R5 side, and allows the tip of the cap 34 of the housing 30 to enter the recess when the shock absorber D1 contracts most. The loss of the stroke length due to the provision of the housing 30 at the tip of the piston rod 24 in the cylindrical shock absorber D1 is alleviated by the shape of the cap 34 and the recess of the sliding partition wall 58.

  The specific shock absorber D1 is configured as described above. However, if the displacement amount from the neutral position in the free piston 50 is in a range that does not exceed an arbitrary displacement amount, the damping characteristic is conceptual. As described with reference to the shock absorber D, the coefficients C1, C2, C3, the pressure receiving area A of the free piston 50, and the spring constant K of the spring element 55 (in this case, the spring constant synthesized by the coil springs 56, 57). Is set.

  In this specific shock absorber D1, the coefficient C1 is determined by the resistance that the laminated leaf valves V1, V2 of the first passages 22, 23 give to the liquid flow, and the coefficient C2 is the other coefficient in the second passage. The side channel 41 is determined by the resistance given to the liquid flow, and the coefficient C3 is further decided by the resistance given by the bypass channel 42 and the orifice 33a in the one side channel in the second passage to the liquid flow.

  Note that, depending on the setting of the damping force, the bypass passage 42 itself may function as a throttle valve, or a throttle may be provided even in the other side flow passage 41.

  Further, when the user of the vehicle changes the damping characteristic by himself or by the control device, for example, the valve seat is placed somewhere in the portion of the other side passage 41 that opens from the tip of the small diameter portion 24a of the piston rod 24. It is also possible to provide a poppet type valve element that can be moved forward and backward from the outside of the shock absorber D1 via a control rod penetrating the piston rod 24. By doing so, the opening area of the poppet valve can be adjusted, and the resistance given to the liquid flow in the other channel 41 can be changed, so that the coefficient C2 can be made variable, and the damping characteristic of the shock absorber D1. Can be arbitrarily adjusted. In addition to the poppet valve, use of a spool valve, a rotary valve, or the like can be employed.

  Even in the shock absorber D1, it is easy to adjust the amount of change in the damping coefficient ζ with respect to the frequency F and the breakpoint frequencies Fa and Fb. The change in the damping force of the shock absorber D1 is used as the input vibration frequency. The adjustment can be made very easy, and even with this specific shock absorber D1, the same effects as the shock absorber D can be achieved.

  In the shock absorber D1, when the displacement amount from the neutral position in the free piston 50 exceeds an arbitrary displacement amount, the flow passage area of the orifice 33a gradually decreases, and the flow passage resistance in the one-side flow passage gradually increases. Depending on the stroke amount of the free piston 50, the damping force generated by the shock absorber D1 gradually increases.

  Therefore, even in this specific shock absorber D1, as with the shock absorber D described above, even if there is an input of vibration with a high frequency and a large amplitude, the damping force does not change abruptly and low damping The damping force change from force to high damping force becomes smooth, improving the ride comfort in the vehicle, and the damping force does not change suddenly, so that it gives unnecessary noise to the car body and generates abnormal noise Things are also avoided.

  Further, since the flow passage area of the orifice 33a is reduced by the free piston 50 without using a cushion or a plunger, the design is easy, and both the expansion and contraction of the shock absorber D1 can be performed with a simple configuration. A sudden change in the damping force during the stroke can be reliably suppressed, and the processing is easy.

  Although the shape of the orifice 33a is not limited to a circular cross section, it may be a triangle, a ginkgo leaf shape, or a square shape. In the case of a triangle shape or a ginkgo leaf shape, FIGS. 7A and 7B. As shown in FIG. 7C, when the triangular shape or the ginkgo leaf shape having the apex in the moving direction T of the free piston 50 is used, the diagonal line is the movement of the free piston 50 as shown in FIG. By keeping the direction along the direction, the rate of decrease when the flow area of the orifice is reduced by the free piston 50 can be made smoother than that of the circular orifice, and the degree of damping force change can be made even smoother. And the ride comfort in the vehicle can be further improved.

  Further, as shown in FIG. 8, if the hole 51 b formed in the thickness of the free piston 50 is formed obliquely with respect to the axis of the free piston 50, the hole of the cylindrical portion 51 of the free piston 50 is formed. Since it becomes easy to ensure the thickness of the outer peripheral side from 51b and it becomes easy to ensure the strength of the free piston 50, the free piston 50 can be downsized.

  Further, as another modification of the specific shock absorber D1 shown in FIG. 9, the orifice 51c is connected to the free piston 50 side, and the orifice 51c and the one chamber 27 are communicated with each other. The formed hole 51d may be provided, and an annular groove 33b facing the orifice 51c and a port 33c communicating the annular groove 33b and the lower chamber R5 may be provided on the outer cylinder 33 side.

  Also in this case, when the displacement amount from the neutral position exceeds the arbitrary displacement amount by the vertical movement of the free piston 50, the orifice 51c starts to face the inner peripheral surface of the outer cylinder 33 and gradually wraps on the inner peripheral surface. Then, the flow area of the orifice 51c gradually decreases as the free piston 50 moves toward the stroke end, and is finally closed.

  Therefore, even in this modified example, when the displacement amount from the neutral position in the free piston 50 exceeds an arbitrary displacement amount, the flow passage area of the orifice 51c gradually decreases, and the flow passage resistance in the one-side flow passage. Gradually increases, and the damping force generated depending on the stroke amount of the free piston 50 gradually increases.

  That is, even in this specific modification of the shock absorber D1, as with the shock absorber D described above, the damping force does not change abruptly even if there is an input of vibration with a high frequency and a large amplitude. , The damping force change from low damping force to high damping force becomes smooth, and the ride comfort in the vehicle can be improved, and the damping force does not change abruptly. Such a situation is avoided.

  Further, in this modified example, an annular groove is not provided on the free piston 50 side, but an orifice 51c that has less influence on the strength of the free piston 50 than the annular groove is provided. It becomes easy to ensure the strength and the free piston 50 can be downsized.

  Finally, a specific shock absorber D2 in another embodiment will be described. In this shock absorber D2, as shown in FIG. 10, the shock absorber D1 is different from the housing only in the configuration of the housing, and other parts are not different. Are given the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 10, in the shock absorber D2, the housing 90 forming the pressure chamber R9 is provided on the upper chamber R7 side which is one working chamber side of the piston rod 24. Different from the shock absorber D1 in the form.

  Hereinafter, a different part will be described in the same manner as in the above embodiment. The housing 90 is inserted into the small diameter portion 24a of the piston rod 24 ahead of the piston 21, the laminated leaf valves V1, V2 and the valve stoppers 28, 29, and the piston 90 The piston nut 24 is fixed to the upper chamber R7 side of the piston rod 24 by screwing the piston nut N into the screw portion 24a of the rod 24.

  The other-side flow path 71 constituting a part of the second passage that opens from the tip of the piston rod 24 is communicated with the pressure chamber R9 formed in the housing 90 at the side of the piston rod 24, In the case of this shock absorber D2, the other-side channel 71 communicates the pressure chamber R9 and the lower chamber R8, which is the other working chamber.

  The housing 90 will be described in detail. An annular plate 91 fixed to the outer periphery of the piston rod 24, an outer cylinder 92 having a lower end opening fixed to the outer periphery of the annular plate 91, and an annular closing the upper end opening of the outer cylinder 92. The pressure chamber R9 is defined by the outer cylinder 92 and the annular plates 91, 93.

  The inner diameter of the annular plate 91 is a diameter that fits to the outer periphery of the small-diameter portion 24a, and the annular plate 91 is restricted from moving in the axial direction at the end step of the small-diameter portion 24a.

  In addition, the annular plate 93 is provided with a bypass passage 94 that constitutes a part of the one-side flow path in the second passage while the piston rod 24 is inserted into the axial center portion.

  In the case of this embodiment, the outer cylinder 92 and the annular plate 93 are integrally formed, the lower end opening end of the outer cylinder 92 is fitted to the outer periphery of the annular plate 91, and the lower end opening end is caulked. Thus, the outer cylinder 92 and the annular plate 91 are integrated.

  Further, a free piston 95 is slidably inserted into a pressure chamber R 9 formed by the annular plates 91 and 93 and the outer cylinder 92, and the pressure chamber R 9 is connected to the one chamber 110 by the free piston 95. The other chamber 111 is partitioned.

  The one chamber 110 is communicated with the upper chamber R7 serving as one working chamber of the shock absorber D4 through the bypass 94, and the other chamber 111 is a lower chamber serving as the other working chamber by the other channel 71. It communicates with R8.

  The free piston 95 has a cylindrical main body 96 that is smaller than the inner diameter of the outer cylinder 92 and larger than the outer diameter of the piston rod 24, and extends from one end outer periphery of the main body 96 and is in sliding contact with the inner periphery of the outer cylinder 92. A first collar 97, a first annular part 98 that rises from the end of the first collar 97 toward the main body 96 and is flush with the outer peripheral surface of the first collar 97, and the other end inner periphery of the main body 96 A second collar 99 that extends and slidably contacts the outer periphery of the piston rod 24, and a second ring that rises from the end of the second collar 99 toward the main body 96 and is flush with the inner peripheral surface of the second collar 99. Unit 100.

  A coil spring 101 that is a spring element is interposed between the first flange portion 97 and the annular plate 93, and a coil spring 102 that is also a spring element is interposed between the second flange portion 99 and the annular plate 91. Is intervening.

  Thus, by interposing the coil springs 101 and 102, the coil spring 101 is inserted into the gap between the main body 96 and the first annular portion 98, and the coil spring 102 is connected to the main body 96 and the second annular portion 100. In both cases, the radial displacement of the free piston 95 is prevented.

  Therefore, the coil springs 101 and 102 can apply a biasing force to the free piston 95 in a balanced and stable manner, and the free piston 95 slides due to shaft shake or the like with respect to the piston rod 24 or the outer cylinder 92. The resistance does not increase.

  As described above, the one chamber 110 communicates with the upper chamber R7 through the bypass passage 94 provided in the annular plate 93, and the other chamber 111 communicates with the lower chamber R8 through the other channel 71 provided in the piston rod 24. However, in the case of this embodiment, when the bypass passage 94 is provided in the annular plate 91 and the other chamber 111 communicates with the upper chamber R7, the side portion of the piston rod 24 of the other side flow passage 71 is provided. The one end 110 may be communicated with the one chamber 110 and the one chamber 110 may be communicated with the lower chamber R8.

  An annular groove 98a is provided along the circumference on the outer periphery of the first annular portion 98, which is the outer periphery of the free piston 95, and further, the annular groove passes through the inner thickness of the first annular portion 98 of the free piston 95. A hole 98b is provided to communicate between 98a and the one chamber 110.

  A plurality of orifices 92a communicating with the upper chamber R7, which is one working chamber, and the inside of the outer cylinder 92 are provided on the side of the outer cylinder 92. The orifice 92a includes a free piston 95 as a spring element. When it is elastically supported by a certain coil spring 101, 102 and is in a neutral position, it faces at least the annular groove 98a, and the free piston 95 is displaced to the stroke end, that is, free until it abuts against the annular plates 91, 93. The outer periphery of the first annular portion 98 of the piston 95 is completely overlapped and closed.

  That is, in the case of this shock absorber D2, when the displacement amount from the neutral position of the free piston 95 becomes an arbitrary displacement amount, the outer circumference of the first annular portion 98 is determined from the situation where all the openings of the orifice 92a face the annular groove 98a. The flow area of the orifice 92a begins to gradually decrease, and the one-side flow composed of the orifice 92a, the annular groove 98a, the hole 98b, and the bypass 94 is started. The flow resistance in the road gradually increases.

  When the free piston 95 reaches the stroke end while gradually decreasing the flow area of the orifice 92a and increasing the flow resistance, the orifice 92a is completely closed by the first annular portion 98, The flow path resistance in the flow path is maximized, and the one chamber 110 is communicated with the upper chamber R7 only by the bypass path 94.

  If the bypass plate 94 is not provided in the annular plate 93, the orifice 92a may be prevented from being completely closed when the free piston 95 reaches the stroke end.

  The specific shock absorber D2 is configured as described above. However, if the displacement amount from the neutral position in the free piston 95 is within a range that does not exceed an arbitrary displacement amount, the damping characteristic is conceptual. As described with reference to the shock absorber D, the coefficient C1, C2, C3, the pressure receiving area A of the free piston 95, and the spring constant K of the coil springs 101, 102 that are spring elements are set.

  Even in this specific shock absorber D2, the coefficient C1 is determined by the resistance that the laminated leaf valves V1, V2 of the first passages 22, 23 give to the liquid flow, and the coefficient C2 is the other coefficient in the second passage. The side channel 71 is determined by the resistance given to the liquid flow, and the coefficient C3 is further decided by the resistance given by the bypass channel 94 and the orifice 92a in the one side channel in the second passage to the liquid flow.

  Even in the shock absorber D2, when the displacement amount from the neutral position in the free piston 95 exceeds an arbitrary displacement amount, the flow path area of the orifice 92a gradually decreases, and the flow path in the one-side flow path The resistance gradually increases, and the damping force generated by the shock absorber D2 gradually increases depending on the stroke amount of the free piston 95.

  Therefore, even in this specific shock absorber D2, the damping force does not change abruptly even if there is an input of vibration with a high frequency and a large amplitude, similarly to the shock absorbers D and D1 described above. The damping force change from low damping force to high damping force becomes smooth, improving the riding comfort in the vehicle, and the damping force does not change abruptly. Such a situation is also avoided.

  Further, since the flow area of the orifice 92a is reduced by the free piston 95 without using a cushion or plunger, the design is easy, and both the expansion and contraction of the shock absorber D1 can be performed with a simple configuration. A sudden change in the damping force during the stroke can be reliably suppressed, and the processing is easy.

  Further, in the shock absorber D2, in order to attach the housing 90 to the piston rod 24, it is only necessary to fit the piston rod 24, and it is not necessary to apply torque to the housing 90.

  Therefore, there is no fear of deformation of the housing 90 during the mounting process of the housing 90, and the smooth movement of the free piston 95 is ensured, thereby making it possible to reliably generate the damping characteristic aimed at the shock absorber D4. Become.

  Furthermore, even in the other specific shock absorber D2, the ride comfort in the vehicle can be further improved by making the shape of the orifice 92a as shown in FIG. 7, and further, in FIGS. As in the modification of the shock absorber D1 shown, the hole 98b is formed obliquely with respect to the axis of the free piston 95, or an orifice is provided on the first annular portion 98 side and an annular groove is formed on the inner periphery of the outer cylinder 92 It can be provided on the side to increase the strength of the free piston 95.

  In addition, although the shock absorber in each embodiment is configured as a so-called single cylinder type shock absorber, this is a double cylinder type provided with an annular reservoir formed to cover the cylinder outside the cylinder. The shock absorber may be configured as a shock absorber, or may be configured as a shock absorber provided with a completely separate reservoir tank outside the cylinder.

  Moreover, in each embodiment, although the pressure chamber is formed in the cylinder, it can also be provided outside the cylinder.

 This is the end of the description of the embodiment of the present invention, but the scope of the present invention is of course not limited to the details shown or described.

It is the figure which showed the shock absorber conceptually. It is a model figure at the time of operation | movement of a buffering device. It is a Bode diagram which showed the gain characteristic of the frequency transfer function of the pressure to the flow rate. It is the figure which showed the relationship between an attenuation coefficient, a phase, and a frequency. It is a longitudinal cross-sectional view of the specific shock absorber in one Embodiment. It is an expansion longitudinal cross-sectional view of the piston part of the specific shock absorber in one Embodiment. (A) It is a figure which shows the cross-sectional shape of the orifice of the concrete shock absorber in one modification of one Embodiment. (B) It is a figure which shows the cross-sectional shape of the orifice of the specific shock absorber in the modification of one Embodiment. (C) It is a figure which shows the cross-sectional shape of the orifice of the concrete shock absorber in one modification of one Embodiment. It is an expansion longitudinal cross-sectional view of the free piston of the buffer device in the other modification of one Embodiment. It is an expansion longitudinal cross-sectional view of the piston part of the buffering device in another modification of one Embodiment. It is an expansion longitudinal cross-sectional view of the piston part of the buffering device in other embodiment.

Explanation of symbols

1, 20 Cylinder 2, 21 Piston 3, 22, 23 First passage 4 Second passage 4a One side flow passage 4b, 41, 71 The other side flow passage 5, 50, 95 Free piston 6, 55 Spring element 7, 58 Slide Moving partition 8, 24 Piston rod 10 Damping force generating element 11 Variable throttle 13, 26, 110 One chamber 14, 27, 111 Other chamber 30, 90 Housing 31, 71 Inner cylinder 32, 72 鍔 33, 92 Outer cylinder 33a, 51c , 92a Orifice 33c Port 34 Cap 42, 94 Bypass path 33b, 51a, 98a Annular groove 51b, 51d, 98b Hole 56, 57, 101, 102 Coil spring 91, 93 Annular plate 96 Main body 97 First collar part 98 First annular part 99 Second collar 100 Second annular part D, D1, D2 Buffer G, G1 Gas chamber R1, R4 Upper chamber R7, which is the other working chamber Upper chamber R2 as a working chamber, R5 one of the working chamber lower chamber is a lower chamber R8 other working chamber is R3, R6, R9 pressure chamber

Claims (11)

A cylinder, a partition member that is slidably inserted into the cylinder and divides the inside of the cylinder into two working chambers, a first passage and a second passage that communicate the two working chambers, and a middle portion of the second passage. A pressure chamber, a free piston that is slidably inserted into the pressure chamber and disconnects the working chambers, and a spring element that generates a biasing force that suppresses displacement of the free piston with respect to the pressure chamber. A shock absorber characterized in that the flow path resistance increases depending on the amount of displacement from the neutral position of the free piston. When the amount of displacement of the free piston from the neutral position is within an arbitrary amount of displacement, the flow path resistance of the second passage is not changed, and if the free piston is displaced beyond the amount of arbitrary displacement, the second depends on the amount of displacement. The shock absorber according to claim 1, wherein a flow path resistance of the passage is increased. The shock absorber according to claim 1 or 2, wherein the flow path resistance of the second passage is maximized when the free piston reaches the stroke end. The second passage is configured such that one of the one chamber and the other chamber defined by the free piston in the pressure chamber communicates with one working chamber and the other chamber communicates with the other working chamber. The flow path resistance of one or both of the one-side flow path and the other-side flow path increases depending on the displacement of the free piston with respect to the pressure chamber. The shock absorber according to any one of the above. A partition member that is screwed to the piston rod and fitted to the piston rod is fixed to the piston rod and includes a housing that forms a pressure chamber. The housing includes a flanged inner cylinder that is screwed to the piston rod; The outer cylinder extending from the outer periphery of the rod and a cap that closes the opening of the outer cylinder, and a free piston that slides on the inner periphery of the outer cylinder is inserted into the pressure chamber. The shock absorber according to any one of claims 1 to 4, wherein the pressure chamber is partitioned into one chamber and the other chamber. The housing includes a housing fixed to the piston rod and forming a pressure chamber. The housing includes an outer cylinder disposed on the outer periphery of the piston rod, and annular plates that are fixed to the outer periphery of the piston rod and respectively close both ends of the opening of the outer cylinder. A free piston that is slidably in contact with the inner periphery of the outer cylinder and the outer periphery of the piston rod is inserted into the pressure chamber, and the pressure chamber is divided into one chamber and the other chamber by the free piston. Item 5. The shock absorber according to any one of Items 1 to 4. The one-side flow path communicates an annular groove formed along the circumference of the free piston, a hole that passes through the thickness of the free piston and communicates the annular groove with the one chamber, and communicates the inside and outside of the outer cylinder. When the free piston is in the neutral position and communicates with one of the working chambers, it faces at least the annular groove, and when the free piston is displaced to the stroke end, it is wrapped around the outer periphery of the free piston and maximizes the flow resistance. The shock absorber according to claim 5 or 6, further comprising an orifice. The one-side flow path includes an annular groove formed along the circumference on the inner periphery of the outer cylinder, a port that communicates the annular groove and one working chamber, and a free piston wall that opens from the outer periphery of the free piston. When the free piston is in the neutral position, it is opposed to at least the annular groove, and when the free piston is displaced to the stroke end, it is wrapped around the inner periphery of the outer cylinder to maximize the flow resistance. The shock absorber according to claim 5 or 6, comprising one or more orifices. The shock absorber according to claim 7 or 8, wherein the hole is formed obliquely with respect to the axis of the free piston. The one-side flow path has a bypass passage that communicates one chamber and one working chamber without passing through the orifice, and the orifice is closed against the outer periphery of the free piston when the free piston is displaced to the stroke end. The shock absorber according to any one of claims 7 to 9. The cross-sectional shape of the orifice is a triangular shape with a top in the moving direction of the free piston or a ginkgo leaf shape, or a quadrangular shape with a diagonal line along the moving direction of the free piston. The shock absorber according to any one of the above.

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