JP6462341B2 - Shock absorber - Google Patents

Description

  The present invention relates to a shock absorber.

  Conventionally, this type of shock absorber is used between the vehicle body and the axle of the vehicle to suppress vehicle body vibration. For example, a cylinder and a cylinder that is slidably inserted into the cylinder are used. A piston that divides the inside into a rod side extension side chamber and a piston side pressure side chamber, a first passage that is provided in the piston and communicates with the extension side chamber and the pressure side chamber; A second passage communicating with the pressure side chamber, a housing having a pressure chamber connected to the middle of the second passage and attached to the tip of the rod, and slidably inserted into the pressure chamber to extend the pressure chamber. And a free piston that is divided into a pressure side pressure chamber and a coil spring that biases the free piston. That is, the expansion side pressure chamber is communicated with the expansion side chamber via the second passage, and the compression side pressure chamber is communicated with the compression side chamber via the second passage.

  In the shock absorber configured as described above, the pressure chamber is divided into the expansion side pressure chamber and the pressure side pressure chamber by the free piston, and the expansion side chamber and the pressure side chamber are directly communicated with each other via the second passage. However, when the free piston moves, the volume ratio between the expansion side pressure chamber and the compression side pressure chamber changes, and the liquid in the pressure chamber moves into and out of the expansion side chamber and the compression side chamber according to the amount of movement of the free piston. The extension side chamber and the pressure side chamber behave as if they are communicated with each other via the second passage.

  Here, on the basis of the pressure in the compression side chamber, the differential pressure between the expansion side chamber and the compression side chamber during the expansion operation of the shock absorber is P, the flow rate of the liquid flowing out from the expansion side chamber is Q, and the differential pressure P and the first pressure A coefficient which is a relationship with the flow rate Q1 of the liquid passing through the passage is C1, a differential pressure between the extension side chamber and the extension side pressure chamber is P1, and a flow rate Q2 of the liquid flowing into the extension side pressure chamber from the differential pressure P1 and the extension side chamber. The coefficient that is the relationship between the pressure side chamber and the pressure side pressure chamber is P2, and the coefficient that is the relationship between the pressure difference P2 and the flow rate Q2 of the liquid flowing from the pressure side pressure chamber to the pressure side chamber is C3. The transfer function of the differential pressure P with respect to the flow rate Q is obtained by assuming that the cross-sectional area, which is the pressure receiving area of the free piston, is A, the displacement of the free piston with respect to the pressure chamber is X, and the spring constant of the coil spring is K. ) Is obtained. In equation (1), s represents a Laplace operator.

さらに、上記式（１）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（２）が得られる。

Furthermore, substituting jω for the Laplace operator s in the transfer function shown in the above equation (1) to obtain the absolute value of the frequency transfer function G (jω) yields the following equation (2).

上記各式から理解できるように、この緩衝器における流量Ｑに対する差圧Ｐの伝達関数の周波数特性は、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て、Ｆ＞Ｆｂの領域においては一定となる。すなわち、流量Ｑに対する差圧Ｐの伝達関数の周波数特性は、低周波数域では伝達ゲインが大きくなり、高周波数域では伝達ゲインが小さくなる。

As can be understood from the above equations, the frequency characteristics of the transfer function of the differential pressure P with respect to the flow rate Q in this buffer are Fa = K / {2 · π · A ² · (C1 + C2 + C3)} and Fb = K / {2 Π · A ² · (C2 + C3)} has two breakpoint frequencies, and in the region of F <Fa, the transfer gain is substantially C1, and in the region of Fa ≦ F ≦ Fb, C1 to C1 · ( C2 + C3) / (C1 + C2 + C3), and changes so as to decrease gradually, and becomes constant in the region of F> Fb. That is, in the frequency characteristic of the transfer function of the differential pressure P with respect to the flow rate Q, the transfer gain increases in the low frequency range, and the transfer gain decreases in the high frequency range.

  Therefore, this shock absorber can generate a large damping force for low-frequency vibration input, and can generate a small damping force for high-frequency vibration input. In the scene where the input vibration frequency is low, it is possible to reliably generate a high damping force, and in the scene where the input vibration frequency is high such that the vehicle passes through the unevenness of the road surface, the damping force is surely generated. Riding comfort in the vehicle can be improved (see, for example, Patent Documents 1 and 2).

JP 2006-336816 A JP 2008-215459 A

  Here, in the shock absorber disclosed in Japanese Patent Application Laid-Open No. 2006-336816 and Japanese Patent Application Laid-Open No. 2008-215459, the frequency sensitive unit for obtaining the above-described damping characteristics includes a free piston, a pressure chamber, a second passage, and a coil spring. The frequency sensitive part is attached to the tip of the rod. Then, the frequency sensitive part protrudes from the piston toward the axial pressure side chamber side, and when trying to secure the stroke length of the shock absorber, the shock absorber is attached to the axle from the vehicle body side attachment part for attaching the shock absorber to the vehicle body. The length to the axle side mounting portion for mounting (hereinafter referred to as the basic length) becomes long, and the mounting property to the vehicle deteriorates.

  Accordingly, the present invention was devised in order to improve the above-described problems, and the object of the present invention is to provide a shock absorber capable of improving the mountability to a vehicle by shortening the basic length while ensuring the stroke length. Is to provide.

Other with the means for solving the above problems, a cylinder, a piston for partitioning the slidably inserted in the said cylinder and expansion side chamber and the compression side chamber within the cylinder, one end is connected to the piston a rod end extending out of the cylinder, and a tank attached to the outside of the cylinder, a reservoir formed within the tank to compensate for the cylinder volume change of the rod retractable volume fraction, the reservoir and the pressure side chamber A first main passage communicating the extension side chamber and the pressure side chamber, a second main passage communicating the pressure side chamber and the reservoir, and a pressure chamber formed in the tank If, Furipisu sever communication of the extension side pressure chamber and the pressure side pressure chamber with inserted movably in the pressure chamber defining the pressure chamber and the extension side pressure chamber and the compression side pressure chamber And down, and a spring element for generating a biasing force to suppress the displacement with respect to the pressure chamber of the free piston, and the extension side passage communicating with the extension side pressure chamber and the reservoir, and the compression side pressure chamber and the compression side chamber And a pressure side passage that communicates with each other.

  According to the present invention, the basic length can be shortened while securing the stroke length, and the mountability to the vehicle can be improved.

It is the front view which notched and showed the buffer which concerns on one embodiment of this invention partially. It is the figure which expanded and showed the principal part of FIG.

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

  As shown in FIG. 1, the shock absorber D according to the present embodiment is slidably inserted into the cylinder 1 and divides the cylinder 1 into an extension side chamber L1 and a pressure side chamber L2. A piston 2; a rod 6 having one end connected to the piston 2 and the other end extending outside the cylinder 1; a tank 10 attached to the outside of the cylinder 1; A reservoir T that compensates for the change in volume in the cylinder corresponding to the volume, a base member 3 that partitions the reservoir T and the compression side chamber L2, and a first main passage R1 that communicates the extension side chamber L1 and the compression side chamber L2. A second main passage R2 communicating the pressure side chamber L2 and the reservoir T, a pressure chamber L4 formed in the tank 10, and a pressure chamber L4 movably inserted into the pressure chamber L4. A free piston 4 partitioned into an extension side pressure chamber L40 and a compression side pressure chamber L41, a spring element S that generates a biasing force that suppresses displacement of the free piston 4 with respect to the pressure chamber L4, and the extension side pressure chamber L40 An expansion side passage R3 that communicates with the reservoir T, and a pressure side passage R4 that communicates the pressure side pressure chamber L41 and the pressure side chamber L2 are provided.

  In the following, the shock absorber D according to the present embodiment will be described in detail. The shock absorber D is interposed between the vehicle body and the axle of the vehicle and used for the purpose of suppressing vehicle body vibration, and is connected to the vehicle body side. A side attachment portion (not shown), an axle side attachment portion J connected to the axle side, and a shock absorber body D1 interposed between the vehicle body side attachment portion and the axle side attachment portion J.

  The shock absorber main body D1 has a cylindrical cylinder 1 arranged vertically, a piston 2 slidably inserted into the cylinder 1, and a lower end in FIG. A rod 6 whose middle and upper ends extend outside the cylinder 1, an annular head member 11 that closes the upper opening in FIG. 1 of the cylinder 1 and pivotally supports the rod 6 slidably, and a lower opening in FIG. A bottomed cylindrical bottom member 12 that closes the part, a tank 10 provided outside the cylinder 1, one end connected to the bottom member 12 and the other end connected to the tank 10, and the cylinder 1 and the tank 10 A joint pipe 13 communicating with each other, a sliding partition wall 14 slidably inserted into the tank 10, a base member 3 provided on the joint pipe 13 side of the sliding partition wall 14 in the tank 10, and a housing. A grayed 5, and a fixing rod 8 connecting the these base member 3 and the housing 5.

A vehicle body side mounting portion (not shown) is fixed to the upper end portion of the rod 6 extending outside the cylinder 1 in FIG. 1, and the axle side mounting portion J is fixed to the bottom portion of the bottom member 12. The piston 2 moves together with the rod 6 in the cylinder 1 in the axial direction, and the shock absorber D is expanded and contracted. The configuration of the shock absorber body D1 is not limited to the above, and the cylinder 1 is connected to the vehicle body side through the vehicle body side mounting member, and the rod 6 is connected to the axle side through the axle side mounting portion J. The shock absorber D may be set upside down.

  In the cylinder 1, an extension side chamber L1 on the rod 6 side defined by the piston 2 and a pressure side chamber L2 on the piston 2 side are formed, and these are filled with a liquid such as hydraulic oil. In addition, a reservoir T that is partitioned from the pressure side chamber L2 by the base member 3 is formed in the tank 10, and this reservoir T is opposite to the tank internal chamber L3 on the joint pipe 13 side by the sliding partition wall 14. The tank chamber is filled with the liquid, while the gas chamber G is filled with a compressed gas.

  The piston 2 that partitions the extension side chamber L1 and the pressure side chamber L2 is formed in an annular shape, and is held by a nut 7 on the outer periphery of the lower end portion in FIG. 1 of the rod 6 inserted into the cylinder 1. The piston 2 is provided with a first main passage R1 that communicates the extension side chamber L1 and the pressure side chamber L2. The first main passage R1 is composed of an extension side piston passage 2a and a pressure side piston passage 2b, and the lower end of the extension side piston passage 2a in FIG. 1 is an extension side valve consisting of a leaf valve stacked below the piston 2 in FIG. The other pressure side piston passage 2b is opened and closed by a pressure side valve V2 including a leaf valve stacked on the upper side of the piston 2 in FIG. The extension side valve V1 and the pressure side valve V2 are both formed in an annular shape, and the lower end in FIG. 1 of the rod 6 is inserted on the inner peripheral side, the inner peripheral side is fixed to the rod 6 and the outer peripheral side is bent. Is laminated on the piston 2 in a permitted state.

  The expansion side valve V1 stacked on the piston 2 is bent and opened by the differential pressure between the expansion side chamber L1 and the compression side chamber L2 when the shock absorber D is extended, opens the expansion side piston passage 2a, and is compressed from the expansion side chamber L1. A resistance is given to the flow of the liquid moving to the chamber L2, and the expansion side piston passage 2a is closed during the contraction operation of the shock absorber D, and the expansion side piston passage 2a is set to be one-way. The pressure side valve V2 stacked on the piston 2 is opposite to the expansion side valve V1, and the flow of the liquid that moves from the pressure side chamber L2 to the expansion side chamber L1 by opening the pressure side piston passage 2b when the shock absorber D is contracted. The pressure side piston passage 2b is closed when the shock absorber D is extended, and the pressure side piston passage 2b is set to be one-way.

  Further, in the present embodiment, the expansion side valve V1 and the pressure side valve V2 stacked on the piston 2 have different pressure flow characteristics (pressure characteristics with respect to the flow rate), and the piston speed when the shock absorber D is expanded and contracted is high. In the same case, the resistance by the expansion side valve V1 is set larger than the resistance by the compression side valve V2, and the basic damping force of the shock absorber D is generated by the expansion side valve V1 and the compression side valve V2 stacked on the piston 2. The extension side damping force is larger than the compression side damping force.

  The number and thickness of the leaf valves constituting the extension side valve V1 and the pressure side valve V2 can be arbitrarily changed according to the desired damping characteristics. Further, the expansion side valve V1 and the pressure side valve V2 may be valves other than the leaf valve, but the leaf valve is a thin annular plate, and the axial length when assembled to the rod 6 can be shortened. By making the extension side valve V1 and the pressure side valve V2 into leaf valves, the stroke length of the shock absorber D can be easily secured.

  Subsequently, the base member 3 that partitions the in-tank working chamber L3 of the reservoir T and the compression side chamber L2 in the cylinder 1 is formed in an annular shape, and is attached to the outer periphery of the fixed rod 8 disposed in the tank 10. It is held by a nut 9. Specifically, as shown in FIG. 2, the fixed rod 8 is connected to the shaft main body 8a to which the base member 3 is attached to the outer periphery, and the lower end of the shaft main body 8a in FIG. A flange portion 8b projecting to the outer peripheral side and a screw portion 8c connected to the upper end portion of the shaft main body 8a in FIG. 2 and having a screw groove formed on the outer periphery are provided. The shaft main body 8a is a screw portion. The base 9 is inserted between the flange 8b and the flange nut 9 by screwing the flange nut 9 into the outer periphery of the screw portion 8c that is inserted from the 8c side to the inner periphery of the base member 3 and protrudes from the base member 3. The member 3 is sandwiched and fixed. The fixed rod 8 is formed with a pressure side passage R4 penetrating the fixed rod 8 in the axial direction. The pressure side passage R4 is formed inside the housing 5 via the joint pipe 13 and the bottom member 12. A pressure side chamber L41 and a pressure side chamber L2, which will be described later, are formed to communicate with each other. In addition, although the valve element used as resistance is not illustrated in this pressure side channel | path R4 in illustration, you may make it provide damping force generation elements, such as a throttle | throttle.

  The base member 3 held on the outer periphery of the shaft body 8a of the fixed rod 8 has a second main passage R2 that communicates the in-tank working chamber L3 and the pressure side chamber L2 through the inside of the joint pipe 13 and the bottom member 12. Is provided. The second main passage R2 includes an extension side base passage 3a and a pressure side base passage 3b. The lower end of the extension side base passage 3a in FIG. 2 is an extension side formed of a leaf valve stacked below the base member 3 in FIG. 2 is closed by a valve V3, and the upper end of the other pressure-side base passage 3b in FIG. 2 is opened and closed by a pressure-side valve V4 composed of leaf valves stacked on the upper side of the base member 3 in FIG. The extension side valve V3 and the pressure side valve V4 are both formed in an annular shape, and the shaft body 8a of the fixed rod 8 is inserted on the inner peripheral side. The inner peripheral side is fixed to the fixed rod 8 and the outer peripheral side is bent. Is laminated on the base member 3 in a permitted state.

  The expansion side valve V3 stacked on the base member 3 is bent and opened by the differential pressure between the compression side chamber L2 and the in-tank working chamber L3 when the shock absorber D is extended, and the expansion side base passage 3a is opened to open the inside of the tank. A resistance is given to the flow of the liquid moving from the working chamber L3 to the pressure side chamber L2, and the expansion side base passage 3a is closed during the contraction operation of the shock absorber D, and the expansion side base passage 3a is set to be one-way. doing. Also, the pressure side valve V4 stacked on the base member 3 moves from the pressure side chamber L2 to the in-tank working chamber L3 by opening the pressure side base passage 3b when the shock absorber D is contracted, contrary to the expansion side valve V3. In addition to providing resistance to the flow of liquid, the compression side base passage 3b is closed when the shock absorber D is extended, and the compression side base passage 3b is set to be one-way.

  Further, in the present embodiment, the extension side valve V3 and the pressure side valve V4 stacked on the base member 3 have the same pressure flow characteristics, and when the piston speed is the same, the resistance by the extension side valve V3 and the resistance by the pressure side valve V4. Are set to be the same, and an additional damping force is generated when the shock absorber D is expanded or contracted.

  The number and thickness of the leaf valves constituting the extension side valve V3 and the pressure side valve V4 can be arbitrarily changed according to the desired damping characteristics. Further, the extension side valve V3 and the pressure side valve V4 may be valves other than the leaf valve, but the leaf valve is a thin annular plate, and the axial length when assembled to the fixed rod 8 can be shortened. By making the expansion side valve V3 and the pressure side valve V4 leaf valves, the axial length of the tank 10 can be shortened.

  Returning to the flange portion 9a of the flanged nut 9 screwed into the screw portion 8c of the fixed rod 8, the opening portion 5a of the top tubular housing 5 is fixed by caulking from the opposite side of the base member 3. The housing 5 defines a pressure chamber L4 in the tank working chamber L3. In the pressure chamber L4, a free piston 4 is slidably inserted and a spring element S is provided. The pressure chamber L4 is divided by the free piston 4 into an extension side pressure chamber L40 on the upper side in FIG. 2 and a pressure side pressure chamber L41 on the lower side in FIG. The spring element S is composed of coil springs S1 and S2 arranged above and below the free piston 4 in FIG. 2, and has a free urging force that suppresses the displacement in proportion to the amount of displacement of the free piston 4 relative to the pressure chamber L4. It acts on the piston 4.

  The housing 5 that divides the pressure chamber L4 inside includes an opening 5a that is fixed to the flange portion 9a of the flanged nut 9, a cylindrical large inner diameter portion 5b that extends upward from the opening 5a in FIG. A cylindrical small inner diameter portion 5c having an inner diameter smaller than the large inner diameter portion 5b and extending upward from the large inner diameter portion 5b in FIG. 2, and a top portion 5d for closing the upper opening in FIG. 2 of the small inner diameter portion 5c. Yes. In the present embodiment, the housing 5 is composed of one component, but may be configured by combining a plurality of components. Further, the housing 5 may be attached to the joint pipe 13 side of the base member 3.

  A central portion of the top portion 5d of the housing 5 protrudes toward the inside of the housing 5, and a fixed orifice 5e that communicates the in-tank working chamber L3 and the expansion side pressure chamber L40 is provided at the central portion. . Further, the large inner diameter portion 5 b is provided with a variable orifice 5 f that communicates with the in-tank working chamber L 3 and the expansion side pressure chamber L 40 and is opened and closed by the free piston 4. That is, in the present embodiment, the expansion side passage R3 that communicates the in-tank working chamber L3 and the expansion side pressure chamber L40 of the reservoir T includes the fixed orifice 5e and the variable orifice 5f. In addition, as described above, the pressure side passage R4 formed in the fixed rod 8 communicates the pressure side pressure chamber L41 and the pressure side chamber L2 via the joint pipe 13 and the inside of the bottom member 12.

  Thus, the tank working chamber L3 and the expansion side pressure chamber L40 are communicated by the expansion side passage R3, the pressure side chamber L2 and the pressure side pressure chamber L41 are communicated by the pressure side passage R4, and the expansion side pressure chamber L40 and the pressure side pressure chamber L41 are communicated. Is changed by the displacement of the free piston 4 in the housing 5, in the shock absorber D, the flow path comprising the expansion side passage R3, the expansion side pressure chamber L40, the pressure side pressure chamber L41, and the pressure side passage R4. However, apparently, the in-tank working chamber L3 and the pressure side chamber L2 communicate with each other. That is, the in-tank working chamber L3 and the pressure side chamber L2 are communicated not only by the above-described apparent flow path but also by the second main passage R2 composed of the expansion side base passage 3a and the pressure side base passage 3b. .

  The free piston 4 that divides the expansion side pressure chamber L40 and the compression side pressure chamber L41 includes a top portion 4a and a cylindrical portion 4b extending downward from the outer peripheral portion of the top portion 4a in FIG. And is slidably inserted into the large inner diameter portion 5 b of the housing 5. In the present embodiment, since the axis of the large inner diameter portion 5b and the axis of the cylinder 1 are parallel, the width of the shock absorber D in the left-right direction in FIG. It is set that the vibration of the free piston 4 in the vertical direction with respect to the housing 5 is excited by setting the wire and the axis of the large inner diameter portion 5b to intersect, and the entire shock absorber D vibrates up and down in FIG. It may be avoided.

  Further, an annular groove 4c is formed on the outer periphery of the free piston 4 along the circumferential direction, and a hole 4d penetrating in the axial direction from the top 4a of the free piston 4 to the annular groove 4c is formed. Coil springs S1 and S2 are interposed between the top 4a of the free piston 4 and the top 5d of the housing 5, and between the top 4a of the free piston 4 and the flange 9a of the flanged nut 9, respectively. The free piston 4 is elastically supported after being positioned at a predetermined neutral position in the pressure chamber L4 by the spring element S including the coil springs S1 and S2.

  In the present embodiment, the upper end portion of the coil spring S1 in FIG. 2 is inserted into the small inner diameter portion 5c of the housing 5, and the lower end of the coil spring S1 in FIG. 2 is more than the hole 4d of the top portion 4a of the free piston 4. 2 is inserted into the annular recess 4e formed inside, and the upper end portion of the coil spring S2 in FIG. 2 is inserted into the cylindrical portion 4b of the free piston 4, and the lower end of the coil spring S2 in FIG. The coil springs S1 and S2 are prevented from being significantly misaligned because they are inserted into the annular recess 9b formed in the flange 9a. For this reason, it is possible to stably apply an urging force to the free piston 4 with the coil springs S1 and S2, and the free piston 4 causes shaft shake or the like with respect to the housing 5 to increase the sliding resistance. It is designed not to end up. Further, the free piston 4 includes a cylindrical portion 4b, and the upper and lower portions of the annular groove 4c in FIG. 2 are slidably contacting the inner peripheral surface of the large inner diameter portion 5b. It is easy to ensure, and this also suppresses the shaft shake of the free piston 4.

  Here, when the free piston 4 is in the neutral position, the annular groove 4c of the free piston 4 and the variable orifice 5f face each other, and the in-tank working chamber L3 and the expansion side pressure chamber are interposed via the variable orifice 5f, the annular groove 4c and the hole 4d. L40 communicates. However, when the free piston 4 is displaced to the stepped surface 5g formed at the boundary portion between the large inner diameter portion 5b and the small inner diameter portion 5c in the housing 5 or the stroke end contacting the flange portion 9a of the flanged nut 9, the free piston Since the sliding portion 4 and the variable orifice 5f completely overlap with each other and the communication between the in-tank working chamber L3 and the expansion side pressure chamber L40 is blocked, the variable orifice 5f is closed.

  That is, in the case of the shock absorber D, when the free piston 4 is displaced from the neutral position and the state in which all the openings of the variable orifice 5f are opposed to the annular groove 4c is changed to the situation in which the sliding portion is opposed, the displacement amount increases. Along with this, the flow passage area of the variable orifice 5f gradually decreases, and the resistance when the liquid passes through the extension side passage R3 gradually increases. Before the free piston 4 reaches the stroke end, the variable orifice 5f is completely closed so as to face the sliding portion, and the tank working chamber L3 communicates with the expansion side pressure chamber L40 only by the fixed orifice 5e. At this time, the resistance when the liquid passes through the extension side passage R3 is maximized.

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

  During the extension operation of the shock absorber D in which the rod 6 is withdrawn from the cylinder 1, the expansion side chamber L1 is compressed by the piston 2 and the compression side chamber L2 is expanded, so that the liquid for the rod withdrawal volume is insufficient in the cylinder 1, At the same time as the pressure in L1 increases, the pressure in the pressure side chamber L2 decreases, and a differential pressure is generated between the expansion side chamber L1 and the pressure side chamber L2 and between the pressure side chamber L2 and the in-tank working chamber L3. The liquid in the expansion side chamber L1 opens the expansion side valve V1 stacked on the piston 2, passes through the expansion side piston passage 2a, and moves to the compression side chamber L2. Furthermore, the expansion side valve V3 in which the liquid in the in-tank working chamber L3 is stacked on the base member 3 is opened, passes through the expansion side base passage 3a and moves to the compression side chamber L2, and the expansion side passage R3, the expansion side pressure chamber. It moves to the pressure side chamber L2 through an apparent flow path composed of L40, the pressure side pressure chamber L41 and the pressure side passage R4. At this time, since the liquid corresponding to the rod withdrawal volume flows out from the in-tank working chamber L3, the sliding partition wall 14 is pushed downward in FIG. 1 to enlarge the air chamber G, and the rod withdrawal volume integral in the air chamber G. It is possible to compensate for changes in the cylinder volume.

  On the contrary, when the shock absorber D in which the rod 6 enters the cylinder 1 is contracted, the compression side chamber L2 is compressed by the piston 2 and the expansion side chamber L1 expands, and the liquid corresponding to the rod entry volume becomes surplus in the cylinder 1. Therefore, the pressure in the compression side chamber L2 increases and simultaneously the pressure in the expansion side chamber L1 decreases, and a differential pressure is generated between the expansion side chamber L1 and the compression side chamber L2 and between the compression side chamber L2 and the in-tank working chamber L3. Arise. The liquid in the pressure side chamber L2 opens the pressure side valve V2 stacked on the piston 2, passes through the pressure side piston passage 2b, and moves to the expansion side chamber L1. Furthermore, the pressure side valve V4 in which the liquid in the pressure side chamber L2 is stacked on the base member 3 is opened, passes through the pressure side base passage 3b and moves to the tank internal working chamber L3, and the extension side passage R3, the extension side pressure chamber L40, It moves to the in-tank working chamber L3 via an apparent flow path composed of the pressure side pressure chamber L41 and the pressure side passage R4. At this time, since the liquid corresponding to the rod entry volume flows into the in-tank working chamber L3, the sliding partition wall 14 is pushed upward in FIG. 1 and the air chamber G is compressed. Compensates for cylinder volume changes.

  During the expansion / contraction operation, the shock absorber D is configured such that the liquid is the extension side piston passage 2a and the compression side piston passage 2b that constitute the first main passage R1, and the extension side base passage 3a and the compression side base passage that constitute the second main passage R2. A damping force due to the resistance when passing through 3b is generated. That is, the expansion side valves V1 and V3 stacked on the piston 2 and the base member 3 are damping force generating elements that generate the expansion side damping force during the expansion operation of the shock absorber D, and the compression side valves V2 and V4 are buffering. It is a damping force generating element that generates a compression side damping force when the container D is contracted. In addition to the second main passage R2, the pressure side chamber L2 and the tank working chamber L3 are connected via an apparent flow path including an extension side passage R3, an extension side pressure chamber L40, a pressure side pressure chamber L41, and a pressure side passage R4. However, the total flow rate of the liquid flowing through the second main passage R2 and the apparent flow path is the rod retracting volume integral. For this reason, when the flow rate of the liquid passing through the apparent flow path changes, the flow rate of the liquid passing through the second main passage R2 changes. The damping force of D changes.

  More specifically, when the piston speed at the time of expansion / contraction operation of the shock absorber D is the same, the amplitude of the shock absorber D at the time of low frequency vibration input is larger than the amplitude of the shock absorber D at the time of high frequency vibration input. Thus, when the frequency of the vibration input to the shock absorber D is low, the amplitude is large, so that the flow rate of the liquid flowing between the compression side chamber L2 and the tank internal chamber L3 increases in one expansion / contraction cycle. Although the displacement of the free piston 4 is increased in proportion to the flow rate, the free piston 4 is biased by the spring element S. Therefore, when the displacement of the free piston 4 increases, the spring element that the free piston 4 receives is increased. The urging force from S is also increased, and a differential pressure is generated between the pressure in the expansion side pressure chamber L40 and the pressure side pressure chamber L41, and the pressure difference between the in-tank chamber L3 and the expansion side pressure chamber L40 and the pressure side chamber are increased. The differential pressure between L2 and the pressure side pressure chamber L41 is reduced, and the flow rate passing through the apparent flow path is reduced. The flow rate of the liquid passing through the second main passage R2 is increased by the small flow rate passing through this apparent flow path, the pressure side chamber L2 is depressurized when the shock absorber D is extended, and the pressure side chamber L2 is reduced during the compression operation. Increased pressure. Therefore, the damping force generated by the shock absorber D is kept large.

  On the contrary, when the high frequency vibration is input to the shock absorber D, the amplitude is smaller than that when the low frequency vibration is input. Therefore, the flow rate of the liquid flowing between the compression side chamber L2 and the in-tank working chamber L3 is small in one expansion and contraction cycle. The moving displacement of 4 is also reduced. Accordingly, the pressure in the expansion side pressure chamber L40 and the pressure in the pressure side pressure chamber L41 become substantially the same, and the differential pressure between the in-tank working chamber L3 and the expansion side pressure chamber L40 and the differential pressure between the pressure side chamber L2 and the pressure side pressure chamber L41 are as follows. It becomes larger than when low-frequency vibration is input, and the flow rate of the liquid passing through the apparent flow path is increased as compared with when low-frequency vibration is input. The increase in the flow rate passing through this apparent flow path results in a decrease in the flow rate of the fluid passing through the second main passage R2, and when the shock absorber D is extended compared to when the low frequency vibration is input. The pressure reduction degree of the pressure side chamber L2 becomes small, and the pressure increase degree of the pressure side chamber L2 becomes small during the compression operation. Then, the damping force generated by the shock absorber D is smaller than the damping force when the low frequency vibration is input.

Here, on the basis of the pressure in the pressure side chamber L2, the differential pressure between the tank working chamber L3 and the pressure side chamber L2 during the expansion operation of the shock absorber D is P, and the flow rate of the liquid flowing out from the tank working chamber L3 is Q. The coefficient which is the relationship between the pressure difference P and the flow rate Q1 of the liquid passing through the second main passage R2 is C1, the pressure difference between the tank working chamber L3 and the expansion side pressure chamber L40 is P1, and the pressure difference P1 The coefficient which is the relationship with the flow rate Q2 of the liquid flowing into the expansion side pressure chamber L40 from the in-tank working chamber L3 is C2, and the differential pressure between the pressure side chamber L2 and the pressure side pressure chamber L41 is P2, and this differential pressure P2 and the pressure side pressure The coefficient that is the relationship with the flow rate Q2 of the liquid flowing out from the chamber L41 to the pressure side chamber L2 is C3, the cross-sectional area that is the pressure receiving area of the free piston 4 is A, and the displacement of the free piston 4 with respect to the pressure chamber L4 is X. , And the spring constant of the spring element S is K Then, the gain characteristic with respect to the frequency of the frequency transfer function of the differential pressure P with respect to the flow rate Q becomes a characteristic represented by the equation (2) as in the conventional example, and the shock absorber D has a large damping force against vibration in a low frequency range. The damping force can be reduced with respect to the vibration in the high frequency range, and the change in the damping force of the shock absorber D can be made to depend on the input vibration frequency. Even during the compression operation of the shock absorber D, a large damping force is generated for vibrations in the low frequency range and the damping force is reduced for vibrations in the high frequency range, as in the above-described expansion operation. The change of the damping force of the shock absorber D can be made to depend on the input vibration frequency. The damping characteristics of the shock absorber D are set by coefficients C1, C2, C3, the spring constant K of the spring element S, and the pressure receiving area A of the free piston 4 as in the conventional shock absorber. , C2, C3, the spring constant K, and the pressure receiving area A of the free piston 4 are set, and the presence or absence of a throttle (fixed orifice 5e or variable orifice 5f) provided in the extension side passage R3 or the pressure side passage R4 is also arbitrary.

  That is, in the present embodiment, the frequency sensitive portion F1 is configured to include the free piston 4, the pressure chamber L4, the extension side passage R3, the pressure side passage R4, and the spring element S, and the frequency sensitive portion F1 is provided. As described above, the change in the damping force can be made to depend on the input vibration frequency. In the present embodiment, since the frequency sensitive part F1 is arranged in the tank 10 attached to the outside of the cylinder 1, even if the stroke length is secured in the shock absorber D provided with the frequency sensitive part F1. The basic length (the length from the vehicle body side mounting portion to the axle side mounting portion when the stroke is at the stroke reference position) M can be shortened, and the mountability to the vehicle can be improved.

  Further, in the shock absorber D according to the present embodiment, the sliding partition wall 14 that divides the in-tank working chamber L3 and the air chamber G in the reservoir T is provided with a recess 14a on the in-tank working chamber L3 side. When the container D is extended to the maximum, the upper end in FIG. 1 of the housing 5 is allowed to enter the recess 14a, and the axial length of the tank 10 is prevented from increasing.

  Further, in the shock absorber D according to the present embodiment, the pressure flow characteristics of the extension side valve V1 and the pressure side valve V2 stacked on the piston 2 are changed, and the extension side valve V3 and the pressure side valve V4 stacked on the base member 3 are changed. The extension side damping force is made larger than the compression side damping force so that the ride comfort of the vehicle is improved.

  Here, for example, as disclosed in Japanese Patent Application Laid-Open No. 2006-336816 and Japanese Patent Application Laid-Open No. 2008-215459, in a shock absorber in which a pressure chamber constituting a frequency sensitive portion is communicated with an extension side chamber and a pressure side chamber, If the extension side damping force is made larger than the compression side damping force by changing the pressure flow characteristics of the extension side valve and the pressure side valve provided in the valve, the damping force reduction effect by the frequency sensitive part may not be fully exhibited. More specifically, when the shock absorber repeatedly expands and contracts at a high frequency, the pressure in the extension side chamber tends to be higher than the pressure in the compression side chamber. For this reason, the pressure in the expansion side pressure chamber through which the pressure in the expansion side chamber propagates is higher than the pressure in the pressure side pressure chamber through which the pressure in the compression side chamber propagates, and the free piston is displaced toward the pressure side pressure chamber side. It becomes a state. If the displacement of the free piston is biased in this way, the stroke margin of the free piston toward the pressure side pressure chamber becomes small, and the damping force reducing effect by the frequency sensitive part may not be fully exhibited.

  However, in this embodiment, even if there is a difference between the extension side damping force and the compression side damping force in order to improve the riding comfort of the vehicle, the extension side valve V3 and the compression side valve V4 stacked on the base member 3 are used. By making the pressure flow characteristics of the same, the displacement of the free piston 4 can be suppressed from being biased to one of the expansion side pressure chamber L40 side and the pressure side pressure chamber L41 side. For this reason, in this embodiment, the extension side damping force is set larger than the compression side damping force, and the stroke margin of the free piston 4 can be secured even in a situation where high-frequency vibration is continuously input. The damping force reduction effect is not lost.

  Further, in the present embodiment, the rod 6 is connected to the vehicle body side, the cylinder 1 is connected to the axle side, the shock absorber D is set upright, and the frequency sensitive portion F1 is a spring of the vehicle. Located below. For this reason, it is difficult for the hitting sound when the free piston 4 reaches the stroke end to be propagated to the vehicle body side via the rod 6, and it becomes difficult for the passenger to perceive the hitting sound.

  Hereinafter, the operational effects of the shock absorber D according to the present embodiment will be described.

  In the present embodiment, the shock absorber D includes a sliding partition wall 14 that is slidably inserted into the tank 10 and partitions the reservoir T into an in-tank working chamber L3 and an air chamber G. A second main passage R2 is connected to the tank working chamber L3, and the gas chamber G is filled with compressed gas.

  According to the above configuration, since the tank working chamber L3 is pressurized in the air chamber G through the sliding partition wall 14, the liquid traveling from the tank working chamber L3 to the pressure side chamber L2 through the second main passage R2. Even if resistance is given to the flow by the expansion side valve V3, it is possible to suppress the pressure side chamber L2 from becoming negative pressure when the shock absorber D is extended. For this reason, as described above, it is easy to make the pressure flow characteristics of the expansion side valve V3 and the pressure side valve V4 laminated on the base member 3 the same.

  Further, in the present embodiment, the second main passage R2 includes an extension side base passage 3a and a pressure side base passage 3b communicating the reservoir T and the pressure side chamber L2, and in the middle of the extension side base passage 3a, An expansion side valve V3 that opens during the expansion operation and allows the flow of fluid from the reservoir T toward the pressure side chamber L2 is provided. In the middle of the pressure side base passage 3b, the valve opens during the compression operation. A pressure side valve V4 that allows the flow of fluid from the pressure side chamber L2 toward the reservoir T is provided. The extension side valve V3 and the pressure side valve V4 have the same pressure flow characteristics.

  According to the above configuration, the resistance given to the flow of liquid from the reservoir T to the pressure side chamber L2 through the second main passage R2 and the resistance given to the flow of liquid from the pressure side chamber L2 to the reservoir T can be made the same. The bias of the free piston 4 can be suppressed and the loss of the damping force reduction effect can be prevented.

  In the present embodiment, the shock absorber D includes a cylinder 1, a piston 2 that is slidably inserted into the cylinder 1 and divides the cylinder 1 into an expansion side chamber L 1 and a compression side chamber L 2, and one end Is connected to the piston 2 and has the other end extending outside the cylinder 1, a tank 10 attached to the outside of the cylinder 1, and the cylinder formed in the tank 10 for the rod protruding and retracting volume. A reservoir T that compensates for changes in the internal volume, a base member 3 that partitions the reservoir T and the pressure side chamber L2, a first main passage R1 that communicates the extension side chamber L1 and the pressure side chamber L2, and the pressure side chamber A second main passage R2 communicating L2 and the reservoir R; a pressure chamber L4 formed in the tank 10; and a pressure chamber L4 that is movably inserted into the pressure chamber L4 to expand the pressure chamber L4 A free piston 4 partitioned into a chamber L40 and a pressure side pressure chamber L41, a spring element S that generates a biasing force that suppresses displacement of the free piston 4 with respect to the pressure chamber L4, the extension side pressure chamber L40, and the reservoir T And a pressure side passage R4 that communicates the pressure side pressure chamber L41 and the pressure side chamber L2.

  According to the above configuration, the frequency sensitive portion F1 including the free piston 4, the pressure chamber L4, the extension side passage R3, the pressure side passage R4, and the spring element S is disposed in the tank 10 disposed outside the cylinder 1. Since it is provided, even if the stroke length of the shock absorber D is secured, the basic length M of the shock absorber D can be shortened, and the mountability to the vehicle can be improved.

  Further, in the present embodiment, the first main passage R1 is formed in the piston 2, and the expansion side valve V1 and the pressure side valve V2 for opening and closing the first main passage R1 are laminated on the piston 2. The first main passage R1 communicates with the extension side chamber L1 and the pressure side chamber L2 through the outside of the cylinder 1, and the extension side valve V1 and the pressure side valve V2 for opening and closing the first main passage R1 are provided outside the cylinder 1. Also good. In this case, the basic length M of the shock absorber D can be further shortened.

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

D Buffer G Air chamber L1 Extension side chamber L2 Pressure side chamber L3 In-tank action chamber L4 Pressure chamber L40 Extension side pressure chamber L41 Pressure side pressure chamber R1 First main passage R2 Second main passage R3 Extension side passage R4 Pressure side passage S Spring element T Reservoir V3 Extension side valve V4 Pressure side valve 1 Cylinder 2 Piston 3 Base member 3a Extension side base passage 3b Pressure side base passage 4 Free piston 6 Rod 10 Tank 14 Sliding partition

Claims (3)

A cylinder,
A piston that is slidably inserted into the cylinder and divides the cylinder into an extension side chamber and a pressure side chamber;
A rod other end extending out of the cylinder with one end connected to said piston,
A tank attached to the outside of the cylinder;
A reservoir that is formed in the tank and compensates for a change in the volume of the cylinder corresponding to the volume of the rod;
A base member defining the said reservoir and the pressure side chamber,
A first main passage communicating the extension side chamber and the pressure side chamber;
A second main passage communicating the pressure side chamber and the reservoir;
A pressure chamber formed in the tank;
A free piston that is movably inserted into the pressure chamber and divides the pressure chamber into an extension side pressure chamber and a pressure side pressure chamber and disconnects the extension side pressure chamber and the pressure side pressure chamber ;
A spring element for generating the inhibit biasing force of the displacement with respect to the pressure chamber of the free piston,
An extension side passage communicating the extension side pressure chamber and the reservoir;
A shock absorber comprising a pressure side passage communicating the pressure side pressure chamber and the pressure side chamber. The second main passage includes an extension side base passage and a pressure side base passage communicating the reservoir and the pressure side chamber,
In the middle of the extension side base passage, there is provided an extension side valve that opens during the extension operation and allows the flow of fluid from the reservoir toward the pressure side chamber,
In the middle of the pressure side base passage, there is provided a pressure side valve that opens during compression operation and allows the flow of fluid from the pressure side chamber toward the reservoir,
The shock absorber according to claim 1, wherein the extension side valve and the pressure side valve have the same pressure flow characteristics. A sliding partition wall that is slidably inserted into the tank and divides the reservoir into a tank working chamber and an air chamber;
The second main passage is connected to the working chamber in the tank,
The shock absorber according to claim 1 or 2, wherein a compressed gas is sealed in the air chamber.

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