JP2011043245A - Shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate adjustment of damping characteristic in a shock absorber. <P>SOLUTION: The shock absorber is provided with the first passage 3 and the second passage 4 which provide fluid communication with two working chambers R1, R2, a pressure chamber R3 which is provided at the intermediate part of the second passage 4, a free piston 5 which is inserted into the pressure chamber R3, and a spring element which generates an urged force proportional to an amount of displacement to the free piston 5 and inhibits the displacement of the free piston 5. Crossover frequencies Fa, Fb in gain characteristic of frequency transfer function G(jω) of a differential pressure P between the working chambers R1, R2 with respect to a flow rate Q moving from one working chamber R1 to the other working chamber R2 and the pressure chamber R3 are to set based upon a relationship C1 between at least the differential pressure P and flow rate Q1 of the first passage 3, each of the relationships C2, C3 between the differential pressures P2, P3 between the pressure chamber R3 and each of the working chambers R1, R2 and the flow rate Q2 of the second passage 4, a spring constant K of a spring element 6, and a received area A of the free piston 5 and are configured so as to form the pressure chamber by a housing fixed to a piston rod. <P>COPYRIGHT: (C)2011,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 main passage, a sub-passage that opens from the tip of the piston rod to the side, a housing that is attached to the tip of the piston rod and communicates with the sub-passage, and a pressure chamber that is slidably inserted into the pressure chamber And a spring element that elastically supports the free piston and generates a non-linear urging force with respect to the displacement, and one chamber in the pressure chamber is connected to one working chamber via a sub-passage. The other chamber in the pressure chamber communicates with the other working chamber by opening the end of the housing.

  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. With respect to the vibration, the amount of hydraulic oil passing through the sub-passage decreases due to the decrease in the vertical movement amount of the free piston, and most of the hydraulic oil passes through the main passage and generates a large damping force (for example, Patent Document 1). reference).

  In addition, in other shock absorbers having the same configuration, since the free piston is elastically supported, the free piston is moved up and down in the opposite phase to the piston rod by the inertial force, and the free piston is located near the neutral position in the spring element. In this case, a small urging force is generated and a large urging force is generated when the free piston moves greatly from the neutral position, so that the amount of hydraulic fluid flowing into the pressure chamber for the small amplitude is increased. A small damping force is generated, and when a large amplitude vibration occurs, the amount of hydraulic fluid flowing into the pressure chamber corresponding to the amplitude is reduced to generate a large damping force (see, for example, Patent Document 2).

JP 2000-356237 A (FIG. 3) Japanese Utility Model Publication No. 7-19642 (paragraph number 0026, FIG. 1)

  By the way, in general, in a shock absorber mounted on a vehicle, a large damping force is generated to suppress rolling of the vehicle body under a situation where the vibration frequency input to the shock absorber is relatively low, such as during turning. While it is desirable to ensure a comfortable ride in the vehicle, the damping force is reduced as much as possible under circumstances where the vibration frequency input to the shock absorber in which the wheels get over the unevenness of the road surface is relatively high. It is desired to suppress vibrations from being transmitted to the vehicle body as the sprung member.

  Here, even with the idea of changing the damping force according to the magnitude of the input amplitude as in the conventional shock absorber, it is possible to cope with each situation as described above by making the change characteristic of the damping force with respect to the amplitude amount appropriate. Although it is not impossible, there is a case where it is necessary to generate a large damping force even when the vibration has a small amplitude, and it is very difficult to adjust the change characteristic of the damping force based on this idea. It is preferable to make the change in the damping force dependent on the frequency of this, and if it can be adjusted, it would be easy.

  Therefore, the present invention was devised to improve the above-described problems, and the object of the present invention is to change the damping force with respect to the input vibration frequency in the shock absorber (hereinafter simply referred to as “damping characteristics”). It is easy to adjust.

In order to solve the above-described object, the problem solving means in the present invention includes a cylinder, a partition member that is slidably inserted into the cylinder and divides the cylinder into two working chambers, and a piston to which the partition member is fixed. A rod, a first passage and a second passage communicating with the two working chambers, a pressure chamber provided in the middle of the second passage, and a slidably inserted into the pressure chamber to disconnect the working chambers from each other; In a shock absorber including a free piston and a spring element that generates a biasing force that suppresses the displacement of the free piston in proportion to the amount of displacement of the free piston with respect to the pressure chamber, the pressure chamber is placed on the piston rod. The housing is formed by a fixed housing, and the housing includes an annular plate fixed to the outer periphery of the piston rod, and an opening end fixed to the outer periphery of the annular plate and the piston rod at the bottom. A free-end piston that is slidably in contact with the inner periphery of the cylinder member and the outer periphery of the piston rod is inserted into the pressure chamber. The pressure chamber is divided into one chamber on the piston rod side and the other chamber on the cap side, and the one chamber is a flow path that forms part of the second passage formed in the cylindrical member or the annular plate. The other chamber is communicated with the other working chamber through a flow path forming a part of the second passage formed in the piston rod, and the one working chamber is connected to the other working chamber. And the break frequency in the gain characteristic of the frequency transfer function of the differential pressure between the working chambers with respect to the flow rate moving to the pressure chamber is at least the relationship between the differential pressure and the flow rate of the first passage, the one chamber and the one Differential pressure with working chamber Based on the relationship between the flow rate of the second passage, the differential pressure between the other chamber and the other working chamber, the relationship between the flow rate of the second passage, the spring constant of the spring element, and the pressure receiving area of the free piston. Is set.

  According to the shock absorber of the present invention, the breakpoint frequency includes the relationship between the differential pressure and the flow rate of the liquid passing through the first passage, the relationship between the pressure inside the chamber and the flow rate of the liquid passing through the flow path, and the other. It is set by the relationship between the indoor pressure and the flow rate of the liquid passing through the flow path, the pressure receiving area of the free piston, and the spring constant of the spring element. The point frequency can be easily adjusted.

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

  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. Furthermore, in order to attach the housing to the piston rod, it is only necessary to fit the piston rod, and it is not necessary to apply torque to the housing, and there is no concern about deformation of the housing during the housing installation process, and the free piston is smooth. Therefore, it is possible to reliably generate a damping characteristic aimed at the shock absorber.

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. It is an expansion longitudinal cross-sectional view of the piston part of the buffering device in the modification of one Embodiment. It is an expansion longitudinal cross-sectional view of the piston part of the buffering 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 other embodiment.

  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. 7 is an enlarged longitudinal sectional view of a piston portion of a shock absorber according to a modification of the embodiment. FIG. 8 is an enlarged longitudinal sectional view of a piston portion 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 embodiment.

  As shown in FIG. 1, a shock absorber D of the present invention includes a cylinder 1 and a partition wall that is slidably inserted into the cylinder 1 and divides the cylinder 1 into two working chambers R1 and lower chamber R2. A piston 2 as a member, a first passage 3 and a second passage 4 communicating with the upper chamber R1 and the lower chamber R2, a pressure chamber R3 provided in the middle of the second passage 4, and a slide in the pressure chamber R3. A free piston 5 inserted into the upper chamber R1 and disconnecting the lower chamber R2 from each other, and a spring that generates a biasing force that suppresses the displacement of the free piston 5 in proportion to the amount of displacement of the free piston 5 relative to the pressure chamber R3. The upper chamber R1, the lower chamber R2, and the pressure chamber R3 are filled with a liquid such as hydraulic fluid, and the lower portion of the cylinder 1 in the figure is in sliding contact with the inner periphery of the cylinder 1. The sliding partition wall 7 that partitions the lower chamber R2 and the gas chamber G It has been kicked.

  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 outward 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 the piston 2 is also moved vertically 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.

  And the 2nd channel | path 4 is a flow which connects the flow path 4a which connects the upper chamber R1 and pressure chamber R3 which are one side of a working chamber, and the lower chamber R2 and pressure chamber R3 which are the other side of a working chamber. Damping force generating elements 11 and 12 that provide resistance to the flow of liquid passing through the flow paths 4a and 4b are provided in the middle of the flow paths 4a and 4b.

  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 proportional to the amount of displacement acts from the spring element 6.

  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. At the same time 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 enters the one chamber 13 communicated with the upper chamber R1 in the pressure chamber R3 via the flow path 4a. The free piston 5 in the pressure chamber R3 is pushed downward 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 communicated with the lower chamber R2 in the other pressure chamber R3 is compressed, the liquid flows out from the other chamber 14 into the lower chamber R2 through the flow path 4b.

  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 other chamber 14 in the pressure chamber R3 via the flow path 4b, and the pressure chamber R3 The free piston 5 is pushed up against the urging force of the spring element 6 to expand the other chamber 14. Conversely, since the one chamber 13 in the other pressure chamber R3 is compressed, the liquid flows out from the one chamber 13 into the upper chamber R1 via the flow path 4a.

  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.

  The shock absorber D operates as described above, and the attenuation characteristics generated during this operation will be described 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 one chamber 13 is P1, and the pressure P1 passes through the flow path 4a that forms a part of the second passage 4 and the one in the pressure chamber R3 from the upper chamber R1. A coefficient that is a relationship with the flow rate Q2 of the liquid flowing into the chamber 13 is C2, and the pressure in the other chamber 14 is P2, and the pressure chamber passes through the flow path 4b that forms part of the second passage 4 with the pressure P2. A coefficient that is a relationship with the flow rate Q2 of the liquid flowing out from the other chamber 14 in R3 into the lower chamber R2 is C3, a cross-sectional area that is a pressure receiving area of the free piston 5 is A, and the pressure chamber R3 of the free piston 5 is relative to the pressure chamber R3. When the displacement is X and the spring constant of the spring element 6 is K, the following (1 Equation (6) is 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, | G (jω) | is multiplied by the square of the pressure receiving area B of the piston 2 to attenuate The relationship between the characteristics, phase Φ and frequency F is as shown 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 one chamber 13, and the flow path 4a. The relationship C2 between the flow rate Q2 of the liquid passing through the cylinder 14, the relationship C3 between the pressure P2 in the other chamber 14 and the flow rate Q2 of the liquid passing through the flow path 4b, and the cross-sectional area that is the pressure receiving area of the free piston 5 The damping coefficient ζ can be set by the coefficients C1, C2, C3 and the pressure receiving area B of the piston 2, and the shock absorber D can be set by the spring constant K of the spring element 6. The damping characteristics are set by the coefficients C1, C2, 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 in other coefficients C2 and C3, a part of the second passage 4 is used. Since the value is determined by the resistance given to the liquid flow of the damping force generation elements 11 and 12 provided in the flow paths 4a and 4b, respectively, the amount of change in the damping coefficient ζ with respect to the frequency F, and the breakpoint frequency Fa and 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.

  Note that any one of the damping force generation elements 11 and 12 may be eliminated by setting the coefficients C2 and C3 of the above relationships, and the passage areas of the flow paths 4a and 4b may be increased or decreased by the above settings. it can.

  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. And a spring element 55 that generates an urging force that suppresses the displacement of the free piston 50 in proportion to the upper chamber R4 formed in the piston rod 24 as a pressure chamber. 6 and a flow path 41 forming a part of a second passage communicating with one chamber 26 and a flow path forming a part of the second passage provided in the housing 30 and communicating with the lower chamber R5 and the other chamber 27 of the pressure chamber R6. 42, and the upper chamber R4, the lower chamber R5, and the pressure chamber R6 are filled with a liquid such as hydraulic oil. Even in this specific shock absorber D1, the inside of the cylinder 20 is also illustrated. A sliding partition wall 58 that slidably contacts the inner periphery of the cylinder 20 and partitions the lower chamber R5 and the gas chamber G1 is provided in the middle and lower portion.

  The piston rod 24 will be described in detail below. A small diameter portion 24a is formed on the lower end side in the drawing, and a screw portion 24b is formed on the distal end side of the small diameter portion 24a.

  In the piston rod 24, a flow path 41 is formed that forms 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. In order to give resistance to the flow of the liquid passing through the channel 41, a throttle 41 a having an inner diameter smaller than the inner diameter of the channel 41 is provided. The restrictor 41a is not at the position as shown in the figure, but has a small diameter of either the opening area of the portion opening from the side of the piston rod 24 or the opening area of the portion opening from the tip of the small diameter portion 24a. You may make it give resistance to a flow.

  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 integrally formed from the outer peripheral side of the flange 32 of the inner cylinder 31, and the outer cross-sectional shape of the outer cylinder 33 is rotated around the inner cylinder 31 via the outer cylinder 33 with a tool matching the outer peripheral shape. In the illustrated case, the outer cylinder 33 has a shape in which a part of the outer periphery is notched so as to be able to be moved, but may be a shape other than a perfect circle such as a hexagon.

  As a result, the assembling process when the housing 30 is screwed to the piston rod 24 becomes very simple.

  The cap 34 is formed in a bottomed cylindrical shape 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 flow path 42 forming 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, and the flow chamber 41 is formed in the pressure chamber R6 by the free piston 50. Is divided into one chamber 26 communicated with the upper chamber R4 and the other chamber 27 communicated with the lower chamber R5 by the flow path 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 52 of the free piston 50 are used as a spring element 55 that applies a biasing force to the free piston 50 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 52 of the free piston 50. The coil springs 56 and 57 cause the free piston 50 to move inside the pressure chamber R6. Elastically supported at a predetermined 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 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.

  Now, the specific shock absorber D1 is configured as described above, but the damping characteristics thereof are the coefficients C1, C2, C3, the pressure received by the free piston 50, as described using the conceptual shock absorber D. It is set by the area A and the spring constant K of the spring element 55 (in this case, the spring constant synthesized by the coil springs 56 and 57).

  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 one of the second passages. Is determined by the resistance given to the liquid flow by the throttle 41a of the flow path 41 forming the part, and the coefficient C3 is determined by the flow of the liquid that the flow path 42 itself forming a part of the second passage passes through the flow path 42. Determined by the resistance given.

  In addition, like the flow path 42, a part of the second passage may be formed so that the flow path itself functions as a throttle valve. In this case, depending on the setting of the coefficient C3, the opening area of the flow path 42 may be increased. As long as the free piston 50 and the coil spring 56 are prevented from falling out of the housing 30, it is possible to increase the resistance to the liquid flow as much as possible. Even if there is no diaphragm 41a, the diaphragm 41a may be omitted if the setting of the coefficient C2 is satisfied.

  Further, when the user of the vehicle changes the damping characteristic by himself or by the control device, for example, a valve seat is provided somewhere in the portion of the flow path 41 that opens from the tip of the small diameter portion 24a of the piston rod 24, A poppet type valve element that can be advanced and retracted from the outside of the shock absorber D1 toward the valve seat via a control rod penetrating the piston rod 24 may be provided. By doing so, the opening area of the poppet valve can be adjusted, and the resistance given to the liquid flow in the flow path 41 can be changed. Therefore, the coefficient C2 can be made variable, and the damping characteristic of the shock absorber D1 can be arbitrarily set. It becomes possible to adjust to. 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, adjustment of the change amount of the damping coefficient ζ with respect to the frequency F and adjustment of the breakpoint frequencies Fa and Fb are easy, and the change in the damping force of the shock absorber D1 is input vibration. It can be made to depend on the frequency, and the adjustment is very easy. Even in this specific shock absorber D1, the same effect as the shock absorber D can be obtained.

  Subsequently, a shock absorber D2 in a modification of the embodiment will be described. In the shock absorber D2 of this modified example, as shown in FIG. 7, only the configuration of the shock absorber D1 and the housing are different, and there is no difference with respect to other parts, so this different part will be described. About the same site | part, the detailed description is abbreviate | omitted only to attach | subject the same code | symbol.

  The housing 70 of the shock absorber D2 has an opening of a case member 74 having a shape in which the cap 34 and the outer tube 33 of the shock absorber D1 are integrally molded on the flange 72 of the inner cylinder 71 having the same shape as the inner cylinder 31 of the shock absorber D1. Formed by caulking and fixing the ends.

  In this case, the inner cylinder 71 is screwed into the screw portion 24b of the piston rod 24 in advance, and then the case member 74, the coil springs 55 and 56, and the free piston 50 are assembled and fixed to the inner cylinder 71. In this case, since no torque is applied to the case member 74 when the inner cylinder 71 is screwed to the screw portion 24b, the deformation of the case member 74 is prevented, and the assembling process is also performed. Is also easier.

  Therefore, since the deformation of the case member 74 is prevented, the smooth movement of the free piston 50 in the case member 74 is ensured, and this makes it possible to reliably generate the damping characteristic aimed at the shock absorber D2. .

  Further, a specific shock absorber D3 in another modification of the embodiment shown in FIG. 8 will be described. The shock absorber D3 also differs from the shock absorber D1 only in the configuration of the housing, similarly to the shock absorber D2. Since the other parts are not different, the different parts will be described, and the same parts are simply denoted by the same reference numerals, and detailed description thereof will be omitted.

  The housing 80 of the shock absorber D3 includes an inner cylinder 81 provided with a flange 82, an outer cylinder 83 whose one end is welded to the outer peripheral edge of the flange 82, a cap 34 that is caulked and fixed to the other end of the outer cylinder 83, A cylindrical sleeve 84 to be inserted on the inner peripheral side of the cylinder 83 is provided.

  A step 82a is provided on the outer peripheral edge of the lower end of the flange 82 of the inner cylinder 81, and one end of the outer cylinder 83 is fitted into the step 82a, and the outer cylinder 83 and the flange 82 are welded together. As a result, the inner cylinder 81 and the outer cylinder 83 are coupled.

  A sleeve 84 is fitted into the outer cylinder 83, the other end of the outer cylinder 83 is caulked, and the cap 34 is fixed to the other end of the outer cylinder 83. At this time, the sleeve 84 is sandwiched between the flange 82 of the inner cylinder 81 and the cap 34 to restrict the movement in the axial direction, and the outer cylinder 83 also restricts the movement in the radial direction.

  A free piston 50 similar to the shock absorber D1 is slidably inserted into the sleeve 84, and the pressure chamber R6 is partitioned into one chamber 26 and the other chamber 27.

  In the shock absorber D3 configured in this way, torque is applied to the outer cylinder 83 when the inner cylinder 81 coupled to the outer cylinder 83 is screwed to the screw portion 24b of the piston rod 24. However, even if the outer cylinder 83 is slightly deformed, there is no effect on the sleeve 84 with which the free piston 50 is slidably contacted, and the smooth movement of the free piston 50 is ensured, thereby ensuring the damping characteristic aimed at the shock absorber D2. Can be generated.

  Even if the outer cylinder 83 and the inner cylinder 81 are welded to cause welding distortion in the outer cylinder 83 or the flange 82 of the inner cylinder 81, the free piston 50 is in sliding contact with the sleeve 84. It is prevented that 50 smooth movement is inhibited.

  The shock absorber D2 and the shock absorber D3 are different from the shock absorber D1 only in the configuration of the housing, and the effects other than the advantages due to the differences are not different from those of the shock absorber D and the shock absorber D1.

  Finally, a specific shock absorber D4 in another embodiment will be described. As shown in FIG. 9, the shock absorber D4 has a housing 90 that forms a pressure chamber R9 provided on the upper chamber R7 side of the piston rod 24, so that the shock absorbers D1 and D2 in each of the above embodiments are provided. , D3.

  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 24b of the rod 24.

  A flow path 41 that forms a part of the second flow path 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, and this buffer. In the case of the device D4, the flow path 41 communicates the pressure chamber R9 and the lower chamber R8.

  The housing 90 will be described in detail. The annular plate 91 and a bottomed cylindrical tube member 92 whose opening end is fixed to the outer periphery of the annular plate 91 are formed. The annular chamber 91 and the cylindrical member 92 define the pressure chamber R9. It is partitioned.

  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.

  Further, a hole 93 is provided in the shaft center portion of the bottom portion of the cylindrical member 92 so that the piston rod 24 can be inserted, and the second position is provided so as to avoid the hole 93 of the shaft center portion provided in the bottom portion. There are provided flow paths 94 and 94 that form part of the flow path. Thus, a plurality of second passages may be provided depending on the setting of the coefficients C2 and C3.

  The cylindrical member 92 and the annular plate 91 are integrated by fitting the open end of the cylindrical member 92 to the outer periphery of the annular plate 91 and caulking the open end.

  Further, a free piston 95 is slidably inserted into a pressure chamber R9 formed by the annular plate 91 and the cylindrical member 92, and the pressure chamber R9 is separated from the one chamber 110 and the other chamber by the free piston 95. 111.

  The one chamber 110 communicates with the upper chamber R7 of the shock absorber D4 through the flow paths 94, 94, and the other chamber 111 communicates with the lower chamber R8 through the flow path 41.

  The free piston 95 has a cylindrical main body 96 that is smaller in diameter than the inner diameter of the cylindrical member 92 and larger in diameter than the outer peripheral 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 cylindrical member 92. A first collar 97, a first annular part 98 that rises in parallel with the main body 96 from the end of the first collar 97, and is flush with the outer peripheral surface of the first collar 97; A second flange 99 extending from the end of the piston rod 24 and coming into sliding contact with the outer periphery of the piston rod 24, rising from the end of the second flange 99 in parallel with the main body 96 and flush with the inner peripheral surface of the second flange 99. And two annular portions 100.

  A coil spring 101, which is a spring element, is interposed between the first flange portion 97 and the bottom portion of the cylindrical member 92. Further, a spring element is also interposed between the second flange portion 99 and the annular plate 91. A coil spring 102 is interposed.

  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 cylindrical member 92. The resistance does not increase.

  As described above, the one chamber 110 communicates with the upper chamber R7 through the flow paths 94 and 94 provided in the cylindrical member 92, and the other chamber 111 communicates with the lower chamber R8 through the flow path 41 provided in the piston rod 24. However, in the case of this embodiment, when the flow paths 94, 94 are provided in the annular plate 91 and the other chamber 111 communicates with the upper chamber R7, the side of the piston rod 24 of the flow path 41 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.

  If the inner diameter of the hole 93 of the cylindrical member 92 is set to a diameter that fits the outer periphery of the small diameter portion 24a, and the inner diameter of the annular plate 91 is set to a diameter that can be inserted into a portion other than the small diameter portion 24a of the piston rod 24, The housing 90 may be attached to the piston rod 24 in the upside down direction in the figure.

  Although the shock absorber D4 is configured as described above, the damping characteristics thereof are the coefficients C1, C2, and C3, the pressure receiving area A of the free piston 95, and the spring element, as described using the conceptual shock absorber D. The spring constant K (in this case, the spring constant synthesized by the coil springs 101 and 102) is set.

  In this specific shock absorber D4, 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 one of the second passages. And the coefficient C3 is determined by the resistance of the liquid passing through the flow path 41 by the throttle 41a of the flow path 41 forming a part of the second passage. Determined by resistance to flow.

  Therefore, even in the shock absorber D4, 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 D4 is input vibration. It can be made to depend on the frequency, and the adjustment is very easy. Even in this specific shock absorber D4, the same effect as the shock absorber D can be obtained.

  Further, in the shock absorber D4 configured as described above, 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.

  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.

1, 20 Cylinder 2, 21 Piston 3, 22, 23 First passage 4 Second passage 4a, 4b, 41, 42, 94 Flow path 5, 50, 95 Free piston 6, 55 Spring element 7, 58 Sliding partition 8 , 24 Piston rods 10, 11, 12 Damping force generating elements 13, 26, 110 One chamber 14, 27, 111 Other chamber 30, 70, 80, 90 Housing 31, 71, 81 Inner cylinder 32, 72, 82 鍔 33, 83 Outer cylinder 34 Cap 56, 57, 101, 102 Coil spring 74 Case member 84 Sleeve 91 Annular plate 92 Cylindrical member 93 Hole 96 Main body 97 First collar part 98 First annular part 99 Second collar part 100 Second annular part D, D1, D2, D3, D4 Buffer G, G1 Gas chamber R1, R4, R7 Upper chamber R2, R5, R8 Lower chamber R3, R6, R9 Pressure chamber

Claims (5)

A cylinder, a partition member slidably inserted into the cylinder and partitioning the inside of the cylinder into two working chambers, a piston rod to which the partition member is fixed, and a first passage and a second passage communicating the two working chambers A pressure chamber provided in the middle of the second passage, a free piston that is slidably inserted into the pressure chamber and that disconnects the working chambers, and a displacement of the free piston relative to the pressure chamber. And a spring element that generates a biasing force that suppresses the displacement of the free piston, wherein the pressure chamber is formed by a housing fixed to the piston rod, and the housing is formed on the outer periphery of the piston rod. An annular plate to be fixed, and a bottomed cylindrical cylindrical member having an opening end fixed to the outer periphery of the annular plate and having a piston rod inserted into the bottom thereof. Is inserted with a free piston slidingly contacting the inner periphery of the cylindrical member and the outer periphery of the piston rod, and the free piston divides the pressure chamber into one chamber on the piston rod side and the other chamber on the cap side. The chamber communicates with one working chamber through a flow path that forms part of the second passage formed in the cylindrical member or the annular plate, and the second chamber is formed in the piston rod. Gain of frequency transfer function of differential pressure between the working chambers with respect to the flow rate that is communicated with the other working chamber through a flow path that forms part of the passage and moves from one working chamber to the other working chamber and the pressure chamber The breakpoint frequency in the characteristics includes at least the relationship between the differential pressure and the flow rate of the first passage, the relationship between the differential pressure between the one chamber and one working chamber and the flow rate of the second passage, and the other chamber. And the other working chamber The relationship between the flow rate of the second passage pressure, buffers and wherein the set based on the pressure receiving area of the spring constant and the free piston of the spring element. 2. One of the breakpoint frequencies other than the breakpoint frequency that takes at least the minimum value among the plurality of breakpoint frequencies is set to be equal to or less than the value of the unsprung resonance frequency of the vehicle. The shock absorber described. The shock absorber according to claim 1 or 2, wherein the value of the minimum breakpoint frequency is set to be equal to or greater than the value of the sprung resonance frequency of the vehicle and equal to or less than the value of the unsprung resonance frequency. The free piston has a cylindrical main body that is smaller in diameter than the inner diameter of the cylindrical member and larger in diameter than the outer peripheral diameter of the piston rod, and a first that extends from the outer periphery of one end of the main body and slides on the inner periphery of the cylindrical member A flange portion and a second flange portion that extends from the inner periphery of the other end of the main body and is in sliding contact with the outer periphery of the piston rod, and is interposed between the first flange portion and the bottom portion of the cylindrical member. 4. The shock absorber according to claim 1, wherein the shock absorber is elastically supported by a spring element, a spring element interposed between the second flange and the annular plate. A first annular portion is provided that rises from the end of the first collar to the main body and is flush with the outer peripheral surface of the first collar, and the second rises from the end of the second collar to the main body. A second annular portion that is flush with the inner peripheral surface of the flange portion is provided, and coil springs that serve as spring elements are inserted between the main body and the first annular portion and between the main body and the second annular portion. The shock absorber according to claim 4.

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