JP6027462B2 - Shock absorber - Google Patents

Description

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

  Conventionally, in this type of shock absorber, 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, and an extension side chamber and a pressure side chamber provided in the piston communicate with each other. A damping passage, a housing attached to the tip of the piston rod to form a pressure chamber, a free piston that is slidably inserted into the pressure chamber and divides the pressure chamber into an expansion side pressure chamber and a pressure side pressure chamber, and free Some are configured to include a coil spring for energizing the piston, an extension side passage that communicates the extension side chamber and the extension side pressure chamber, and a pressure side passage that communicates the pressure side chamber and the pressure side pressure chamber.

  In the shock absorber configured as described above, the pressure chamber is divided into an expansion side pressure chamber and a pressure side pressure chamber by a free piston, and the extension side chamber and the pressure side chamber are directly connected to each other via the extension side passage and the pressure side passage. However, when the free piston moves, the volume ratio between the expansion side chamber and the compression side 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. In addition, the extension side chamber and the pressure side chamber behave as if they are communicated with each other via the extension side passage and the pressure side passage.

  For this reason, this shock absorber can generate a high damping force for low-frequency vibration input, and can generate a low damping force for high-frequency vibration input. It is possible to generate a high damping force in a scene where the input vibration frequency of the vehicle is low, and reliably generate a low damping force in a scene where the input vibration frequency is high such that the vehicle passes through the road surface unevenness. Comfort can be improved (for example, refer patent document 1).

In the above shock absorber, a step portion is provided on the inner periphery of the housing. When the free piston is displaced downward, that is, when it is displaced downward to reach the movement limit (stroke end), the step portion is provided. cushion member made of an elastic material abutting the annular and abuts against the free piston part being adapted to regulate the displacement of the more downward relative to the housing of the free piston, the free piston and the housing The generation of hitting sound due to a collision is prevented.

JP 2012-52630 A

  As described above, in the conventional shock absorber, it is possible to suppress the generation of hitting sound due to the collision between the free piston and the housing. However, the cushion member is simply attached to the inner periphery of the housing. This is done by restraining the outer periphery of the cushion member with the housing simply by fitting, and the degree of fixing of the cushion member to the housing depends on the elastic force of the cushion member, and if the elastic force is weak, the cushion member will rise from the housing There is a possibility that it interferes with the free piston and prevents the smooth movement of the free piston.

  Therefore, the present invention was devised in order to improve the above-mentioned problems, and the object of the present invention is to suppress the occurrence of a hitting sound due to a collision between the free piston and the housing, and to prevent the cushion member from being generated. It is an object of the present invention to provide a shock absorber that can prevent the housing from falling off.

To solve the above object, problem solving means in the present invention includes a cylinder, a piston for partitioning the slidably inserted in said cylinder expansion side chamber and the compression side chamber within the cylinder, the expansion side chamber and the a damping passage connecting the pressure side chamber, a housing defining a pressure chamber, a free piston that is inserted slidably in the pressure chamber defining the pressure chamber and the extension side pressure chamber and the compression side pressure chamber, the and the extension side passage communicating the expansion side chamber and the expansion side pressure chamber, said free with a pressure side passage communicating with the compression side chamber and the pressure side pressure chamber, the free piston is positioned at a neutral position relative to the housing A spring element that exerts an urging force that suppresses displacement from the neutral position of the piston, and a stroke end in a direction in which the free piston compresses the pressure side pressure chamber with respect to the housing. In the displaced abuts to the free piston shock absorber having a suppressing cushion member any further displacement of the free piston, the housing is a cylindrical, inner diameter large diameter portion of the free piston sliding contact When having an inner diameter smaller-diameter portion, and a stepped portion formed between the inner diameter large diameter portion and the inner diameter small-diameter portion, and a cushion fixed piece that rises from the inner peripheral side of the stepped portion, the cushion member is annular And it is contact | abutting to the said step part, It is fixing to the said housing by being hold | maintained by the said cushion fixing piece bent by the said cushion member side, It is characterized by the above-mentioned .

  Thus, since the cushion fixing piece is bent toward the cushion member and the cushion member is held by the cushion fixing piece and the cushion member is fixed to the housing, the cushion member is firmly fixed to the housing.

  Therefore, according to the shock absorber of the present invention, it is possible to prevent the cushion member from falling off the housing while suppressing the generation of a hitting sound due to the collision between the free piston and the housing.

It is a longitudinal cross-sectional view of the shock absorber in one embodiment. It is a figure explaining the state before bending a cushion fixing piece toward a cushion member in the buffer device of one embodiment. It is a figure explaining the plastic deformation process which bends a cushion fixing piece toward the cushion member side in the buffer device of one embodiment. It is a figure which shows the characteristic of the damping force with respect to the input frequency of a buffering device.

  Hereinafter, the present invention will be described with reference to the drawings. As shown in FIG. 1, a shock absorber D according to an embodiment of the present invention is slidably inserted into a cylinder 1 and the cylinder 1 and divides the cylinder 1 into two extension side chambers R1 and a pressure side chamber R2. The piston 2, the damping passages 4 and 5 communicating with the extension side chamber R1 and the pressure side chamber R2, the housing 6 forming the pressure chamber C, and the pressure chamber C are slidably inserted into the housing 6. A free piston 9 that partitions the expansion side pressure chamber 7 and the compression side pressure chamber 8, an expansion side passage 10 that connects the expansion side chamber R1 and the expansion side pressure chamber 7, and a compression side chamber R2 and the compression side pressure chamber 8 are communicated. The pressure side passage 11, the spring element 12 that exerts a biasing force that positions the free piston 9 in a neutral position with respect to the housing 6 and suppresses the displacement of the free piston 9 from the neutral position, and the free piston 9 with respect to the housing 6 The A cushion member 13 is provided that suppresses displacement of the free piston 9 toward the extension side pressure chamber when it is displaced from the standing position toward the extension side pressure chamber by a predetermined amount or more. It is configured.

  The shock absorber D includes a piston rod 3 that is movably inserted into the cylinder 1. One end of the piston rod 3 is connected to the piston 2, and the upper end that is the other end is not shown. The cylinder 1 is slidably supported by an annular rod guide that seals the upper end of the cylinder 1. Note that the lower end of the cylinder 1 is sealed by a bottom member (not shown).

  The extension side chamber R1, the pressure side chamber R2, and the pressure chamber C are filled with a liquid such as hydraulic fluid, and the lower side of the cylinder 1 in the drawing is in sliding contact with the inner periphery of the cylinder 1 to be the pressure side chamber R2. A sliding partition wall 17 that partitions the gas chamber G is provided. In addition to the hydraulic fluid, for example, a liquid such as water or an aqueous solution can be used as the liquid filled in the extension side chamber R1, the pressure side chamber R2, and the pressure chamber C.

  Since the shock absorber D is a single rod type in which the piston rod 3 is inserted only into the expansion side chamber R1, the volume of the piston rod 3 that goes in and out of the cylinder 1 as the shock absorber D expands and contracts is as follows. The volume of the gas in the gas chamber G expands or contracts and the sliding partition wall 17 moves in the vertical direction in FIG. For compensation of the volume by which the piston rod 3 advances and retreats to and from the cylinder 1, in addition to providing the gas chamber G in the cylinder 1, a reservoir may be provided in the cylinder 1 or outside the cylinder 1. In this case, an outer cylinder that covers the outer periphery of the cylinder 1 is provided to form a double cylinder type shock absorber that forms a reservoir between the cylinder 1 and the outer cylinder, and a tank is provided separately from the cylinder 1 A reservoir may be formed. Further, when the reservoir is provided, in order to increase the pressure of the pressure side chamber R2 during the contraction operation of the shock absorber D, a partition member that partitions the pressure side chamber R2 and the reservoir, and a partition member that is provided to the pressure side chamber R2 toward the reservoir. A base valve that provides resistance to the flow of liquid may be provided. Further, the shock absorber D may be set to a double rod type instead of a single rod type.

  Hereinafter, each part of the shock absorber D will be described in detail. The piston 2 is connected to one end 3a which is a lower end in FIG. 1 of a piston rod 3 which is movably inserted into the cylinder 1, and the piston rod 3 is an annular rod (not shown) fixed to the upper end of the cylinder 1 in the drawing. It protrudes outward through the inner circumference of the guide. The piston rod 3 and the rod guide (not shown) are sealed by a seal member (not shown), and the cylinder 1 is kept in a liquid-tight state.

  The piston 2 includes damping passages 4 and 5 that communicate the expansion side chamber R1 and the pressure side chamber R2, and a leaf valve V1 in which the lower end in FIG. 1 of the damping passage 4 is stacked below the piston 2 in FIG. Further, the upper end of the damping passage 5 in FIG. 1 is opened and closed by a leaf valve V2 stacked above the piston 2 in FIG. The leaf valve V1 is annular and is attached to the one end 3a of the piston rod 3 together with the piston 2, so that the liquid extends through the damping passage 4 during the extension stroke of the shock absorber D in which the piston 2 moves upward in FIG. When the fluid flows from the side chamber R1 toward the pressure side chamber R2, it bends to open the attenuation passage 4 and provide resistance to the flow of the liquid, and closes the attenuation passage 4 against a reverse flow. The damping passage 4 is set as a one-way passage that allows only the flow from the extension side chamber R1 to the compression side chamber R2. On the other hand, the leaf valve V2 is annular and is attached to the one end 3a of the piston rod 3 together with the piston 2, so that the liquid passes through the damping passage 5 in the contraction stroke of the shock absorber D in which the piston 2 moves downward in FIG. When the fluid flows from the chamber R2 toward the extension chamber R1, it bends to open the attenuation passage 5 and provides resistance to the flow of the liquid, and closes the attenuation passage 5 against the reverse flow. The damping passage 5 is set as a one-way passage that allows only the flow from the compression side chamber R2 to the extension side chamber R1. That is, the leaf valve V1 functions as an expansion-side attenuation valve that provides resistance to the flow of liquid flowing through the attenuation passage 4 during the extension stroke, and the leaf valve V2 provides resistance to the flow of liquid that flows through the attenuation passage 5 during the contraction stroke. Functions as a compression side damping valve. As described above, when a plurality of attenuation passages 4 and 5 are provided, the attenuation passage may be set to be one-way so that the liquid flows only during the extension stroke or during the contraction stroke. The passage may allow bidirectional flow and provide resistance to the flow of liquid passing therethrough. Various damping valves such as a poppet valve, an orifice, and a choke can be used as a damping valve that serves as a damping passage that gives resistance to the flow of liquid passing through the damping passage. The damping passages 4 and 5 can be provided in addition to the piston 2.

  Subsequently, in the case of this embodiment, the pressure chamber C is formed by a hollow housing 6 that is screwed into a screw portion 3b provided on the outermost outer periphery of the one end 3a of the piston rod 3. The piston 2 and the leaf valves V1 and V2 also function as a piston nut that fixes the one end 3a of the piston rod 3.

  The pressure chamber C formed in the housing 6 is a free piston 9 that is slidably inserted into the pressure chamber C. The expansion side pressure chamber 7 at the upper side in FIG. 1 and the pressure side pressure chamber at the lower side in FIG. 1, and the free piston 9 can be displaced in the vertical direction in FIG. 1 with respect to the housing 6 in the pressure chamber C.

  Specifically, the housing 6 includes a nut portion 20 that is screwed into a screw portion 3 b formed at one end 3 a of the piston rod 3, a cylindrical portion 22 that is suspended from the outer periphery of the nut portion 20, and an end portion of the cylindrical portion 22. In FIG. 1, a bottomed cylindrical housing cylinder 21 having a bottom 23 that closes the lower end is provided, and a pressure chamber C is defined in the compression side chamber R2.

  Moreover, the nut part 20 is provided with the screw cylinder 20a screwed together with the screw part 3b of the piston rod 3 on the inner periphery thereof, and a flange 20b provided on the outer periphery of the screw cylinder 20a and protruding outward.

  The housing cylinder 21 has a bottomed cylindrical shape as described above, and is integrated with the nut portion 20 by caulking the upper end opening in FIG. 1 toward the outer periphery of the flange 20b of the nut portion 20. . More specifically, the housing cylinder 21 includes a cylindrical portion 22 that hangs down from the flange 20b, and a bottom portion 23 that closes the end of the cylindrical portion 22, and has a bottomed cylindrical shape. The cylindrical portion 22 is formed on the nut portion side between the large-diameter portion 22a slidably contacting the free piston 9, the small-diameter portion 22b on the counter-nut portion side, and the large-diameter portion 22a and the small-diameter portion 22b. And a circular cushion fixing piece 22d rising from the inner periphery of the step 22c. In addition, when the nut portion 20 and the housing cylinder 21 are integrated, other processing directions such as welding and screwing can be adopted in addition to the caulking processing. 2 on the inner circumference of the cushion fixing piece 22d is larger than the inner diameter on the lower end side in FIG. 2, and the inner circumferential surface of the cushion fixing piece 22d is a tapered surface facing the housing cylinder 21 side. Has been.

Then, the cushion member 13 is inserted between the outer periphery of the cushion fixing piece 22d and the inner diameter large diameter portion 22a, and the cushion member 13 is brought into contact with the step portion 22c.

The cushion member 13 is formed of a material having elasticity such as rubber or synthetic resin and excellent in shock absorption at the time of contact with the free piston 9, and has a tapered inner peripheral surface whose inner diameter becomes smaller toward the lower end side. the annular base 14 you contact with the step portion 22c with having, and an annular abutment portion 15 which faces the free piston 9 continues to the in Figure 1 the upper side is anti stepped portion side of the base portion 14 Yes.

  When the free piston 9 is displaced to the stroke end in the direction in which the compression side pressure chamber 8 is compressed, the cushion member 13 collides with the free piston 9 and exerts an elastic force, so that the compression side pressure chamber beyond the free piston 9 is exerted. Slowly decelerate by suppressing displacement to the 8 side, and finally stop. The abutting portion 15 only needs to be able to prevent the collision between the free piston 9 and the housing 6, and therefore may not necessarily be annular, and may be provided intermittently in the circumferential direction with respect to the annular base 14. .

  If the abutting portions 15 are provided intermittently, it is not always necessary to provide them at regular intervals. However, the load received by the free piston 9 from the abutting portion 15 at the time of the abutting with the free piston 9 is as much as possible in the circumferential direction. In order to disperse in a well-balanced manner, it is preferable that the number of the abutting portions 15 be three or more and provided at equal intervals in the circumferential direction. Further, in this embodiment, the height level of the upper end in FIG. 1 which is the end of the abutting portion 15 facing the free piston 9 is substantially the same, and the free piston 9 is displaced to the stroke end. The entire circumference of the abutting portion 15 comes into contact with the free piston 9 almost simultaneously. However, when the abutting portion 15 is annular, the height is varied in the circumferential direction, or the height is partially increased. If it is provided intermittently, the height is made different at some or all of the abutting parts, and the abutting timing to the free piston 9 is varied to tune the effectiveness of the cushion. You may make it do.

In order to fix the cushion member 13 configured in this way to the housing 6, first, the cushion member 13 is inserted into the housing cylinder 21 from the base portion 14 side, and the base portion 14 is brought into contact with the step portion 22 c to be cushion member. 13 is disposed between the cushions fixing piece 22d and the inner diameter large diameter portion 22a. Then, the cushion member 13 is positioned by the step portion 22c, and the inner peripheral surface of the base portion 14 faces the cushion fixing piece 22d. The step portion 22 c provided in the housing 6 exhibits a function of positioning at a predetermined position in order to fix the cushion member 13 to the housing 6 in this way.

  Next, in FIG. 2 of the housing cylinder 21, a die T whose tip is smaller than the inner diameter of the cushion fixing piece 22d but whose diameter increases toward the rear end and becomes larger than the inner diameter of the cushion fixing piece 22d. It is inserted from the upper end opening and enters the cushion fixing piece 22d as shown in FIG. Then, as shown in FIG. 3, the cushion fixing piece 22d is pressed from the inner peripheral side by the die T and is plastically deformed into a state of being bent toward the cushion member 13 side.

  When the die T is removed from the cushion fixing piece 22d, the folded cushion fixing piece 22d holds the base 14 and the cushion member 13 is firmly fixed to the housing 6 as shown in FIG. . Although the cushion fixing piece 22d has an annular shape as described above, the cushion fixing piece 22d may be configured by a plurality of claws that rise from the inner peripheral side of the stepped portion 22c.

  Further, since the inner peripheral surface of the cushion fixing piece 22d has a tapered surface as described above, consideration is given so that the die T can easily enter and the plastic deformation processing of the cushion fixing piece 22d does not fail. Yes.

  Further, the outer diameter of the cushion member 13 is set to a diameter that can be inserted into the inner diameter large diameter portion 22a. However, since the cushion member 13 has elasticity, it can be inserted into the inner diameter large diameter portion 22a in a reduced diameter state. In this case, the outer periphery of the cushion member 13 is restrained by the inner periphery of the housing cylinder 21 even if the abutting portion 15 is detached from the cushion fixing piece 22d and falls off the housing 6. Therefore, the cushion member 13 can be prevented from being lifted from the housing 6.

Returning, the outer peripheral cross-sectional shape of at least a part of the cylindrical part 22 of the housing cylinder 21 is a shape other than a circle so as to be gripped by a tool (not shown) and matches the tool, for example, a part is notched. The outer periphery of the cylindrical portion 22 is gripped with a tool, the housing 6 is rotated in the circumferential direction, and a predetermined tightening torque is applied to the nut portion 20 to form the screw portion 3b. It can be screwed on. Furthermore, the tubular portion 22 has an orifice hole 22e is provided which leads upward from the cushion member 13 there in the inner circumference of the inner diameter large diameter portion 22 a opened from the outer periphery, the pressure chamber C at the orifice hole 22e And the pressure side chamber R2 are communicated with each other, and an orifice hole 23a is provided in the bottom 23, and the pressure chamber C and the pressure side chamber R2 are communicated with each other through the orifice hole 23a.

  The expansion side pressure chamber 7 communicates with the expansion side chamber R1 by an expansion side passage 10 that leads from the side of the piston rod 3 facing the expansion side chamber R1 to the end of the one end 3a. The extension side passage 10 is composed of a horizontal hole 10a that opens from the side facing the extension side chamber R1 of the piston rod 3, and a vertical hole 10b that opens from the end of one end 3a and communicates with the horizontal hole 10a.

  The free piston 9 inserted into the pressure chamber C includes a slidable contact cylinder 30 that slidably contacts the inner diameter large diameter portion 22 a of the cylindrical portion 22 of the housing cylinder 21, and a mirror portion 31 that closes the lower end of the slidable contact cylinder 30. The housing 6 is divided into a pressure side pressure chamber 7 communicating with the pressure side chamber R2 and a pressure side pressure chamber 8 communicating with the pressure side chamber R2. The free piston 9 includes an annular recess 32 provided over the entire outer periphery of the sliding contact cylinder 30 and a communication hole 33 that communicates the annular recess 32 with the pressure side pressure chamber 8. 6, the pressure side chamber R2 communicates with the pressure side pressure chamber 8, and the annular recess 32 does not face the orifice hole 22e, but the sliding hole 30 does not face the orifice hole 22e. In the case of closing 22e, the communication between the pressure side chamber R2 and the pressure side pressure chamber 8 via the orifice hole 22e is cut off. The orifice hole 22e gives resistance to the flow of the liquid passing therethrough and generates a predetermined pressure loss, and generates a differential pressure between the pressure side chamber R2 and the pressure side pressure chamber 8. In addition, the orifice hole 23a provided in the bottom 23 of the housing cylinder 21 also functions as a constriction passage, which gives resistance to the flow of liquid passing therethrough and causes a predetermined pressure loss. A differential pressure is generated between the pressure side pressure chamber 8 and the pressure side pressure chamber 8. The orifice hole 23a is not closed by the free piston 9 and is always open. That is, the pressure side pressure chamber 8 is communicated with the pressure side chamber R2 via the orifice holes 22e and 23a when the orifice hole 22e is in communication, and only the orifice hole 23a when the orifice hole 22e is in a shut-off state. The pressure-side passage 11 is formed by the orifice holes 22e and 23a, the annular recess 32 and the communication hole 33.

  Further, in order to apply an urging force that suppresses the displacement of the free piston 9 relative to the housing 6, there is an extension side pressure chamber 7 between the flange 20 b of the nut portion 20 and the mirror portion 31 of the free piston 9. In the compression side pressure chamber 8 and between the bottom 23 and the mirror part 31 of the free piston 9, both the extension side spring 34 and the compression side spring 35, which are coil springs as the spring element 12, are compressed. It is intervened in. In this way, the free piston 9 is sandwiched from above and below by the extension side spring 34 and the compression side spring 35 and is positioned at a predetermined neutral position in the pressure chamber C. When the free piston 9 is displaced from the neutral position, the extension side spring 34 and The pressure side spring 35 exerts an urging force to return the free piston 9 to the neutral position. The neutral position does not indicate the axial center of the pressure chamber C, but a position where the free piston 9 is positioned by the spring element 12.

  In addition, as the spring element 12, it is only necessary to position the free piston 9 at the neutral position and to exert an urging force, so that other than the coil spring may be employed. For example, an elastic body such as a disc spring is used. The free piston 9 may be elastically supported. When a single spring element whose one end is connected to the free piston 9 is used, the other end may be fixed to the nut portion 20 or the bottom portion 23.

  The extension side spring 34 is loosely fitted to the inner periphery of the sliding contact cylinder 30 of the free piston 9 and is positioned at an approximate position in the radial direction. The upper end of the compression side spring 35 in FIG. 31 is loosely fitted to a protrusion 31a formed at the lower end of the member 31 and is positioned at an approximate position in the radial direction. As described above, the extension side spring 34 and the pressure side spring 35 are centered together by the free piston 9 as described above, and are prevented from being displaced with respect to the free piston 9, thereby stably attaching to the free piston 9. It is possible to apply power.

As described above, the free piston 9 is elastically supported by the extension side spring 34 and the compression side spring 35 as the spring element 12 in the housing 6, and the housing 6 is in a state where no force other than the urging force by the spring element 12 is applied. The annular recessed portion 32 is always opposed to the orifice hole 22e so that the pressure side pressure chamber 8 and the pressure side chamber R2 are communicated with each other when in the neutral position. On the other hand, when the free piston 9 is displaced from the neutral position to some extent, the outer periphery of the sliding contact cylinder 30 of the free piston 9 completely overlaps the orifice hole 22e to close it. The amount of displacement from the neutral position at which the free piston 9 begins to close the orifice hole 22e can be arbitrarily set, and the expansion side pressure chamber located above the free piston 9 in FIG. 1 starting to close the orifice hole 22e. The displacement amount from the neutral position to the 7 side and the displacement amount from the neutral position to the pressure side pressure chamber 8 side of the free piston 9 starting to close the orifice hole 22e in FIG. Also good. In this embodiment, two orifice holes 22e are provided, but the number thereof is arbitrary, and an annular recess communicated with the compression side chamber R2 is provided on the inner periphery of the cylindrical portion 22, and the outer periphery of the free piston 9 is provided. Orifice holes that communicate the pressure side and the pressure side pressure chamber 8 may be provided in the free piston 9.

  The shock absorber D is configured as described above. In the shock absorber D, the pressure chamber C is divided into the expansion side pressure chamber 7 and the pressure side pressure chamber 8 by the free piston 9, and the expansion side passage 10 and the pressure side passage are separated. 11, the expansion side chamber R1 and the compression side chamber R2 are not directly communicated with each other. However, when the free piston 9 moves, the volume ratio of the expansion side chamber R1 and the compression side chamber R2 changes, and the free piston 9 moves. Since the liquid in the pressure chamber C enters and exits the expansion side chamber R1 and the compression side chamber R2 according to the amount, the expansion side chamber R1 and the pressure side chamber R2 are apparently communicated with each other via the expansion side passage 10 and the pressure side passage 11. Act as if you are.

  In this shock absorber D, a high damping force can be generated for low frequency vibration input, while a low damping force can be generated for high frequency vibration input. A high damping force can be generated in a scene where the input vibration frequency is low, such as a medium, and a low damping force is reliably generated in a scene where the input vibration frequency is high such that the vehicle passes through the unevenness of the road surface. Riding comfort can be improved (see, for example, Patent Document 1).

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。

上記各式から理解できるように、この緩衝装置Ｄ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。 Here, the differential pressure between the expansion side chamber R1 and the compression side chamber R2 when the shock absorber expands and contracts is P, the flow rate of the liquid flowing out from the expansion side chamber R1 is Q, and the differential pressure P and the attenuation passages 4 and 5 pass through. The coefficient which is the relationship with the liquid flow rate Q1 is C1, the pressure in the expansion side pressure chamber 7 is P1, the difference between the differential pressure P and the pressure P1 and the liquid flowing into the expansion side pressure chamber 7 from the expansion side chamber R1. The coefficient that is the relationship with the flow rate Q2 is C2, the pressure in the pressure side pressure chamber 8 is P2, and the coefficient that is the relationship between this pressure P2 and the flow rate Q2 of the liquid flowing out from the pressure side pressure chamber 8 into the pressure side chamber R2 is C3, A is the cross-sectional area that is the pressure receiving area of the free piston 9, A is the displacement of the free piston 9 relative to the pressure chamber C, and the spring constant of the spring element 12, that is, the combined spring of the extension side spring 34 and the pressure side spring 35 The transmission of differential pressure P with respect to flow rate Q, where K is a constant When determining the function, equation (1) is obtained. In equation (1), s represents a Laplace operator.

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).

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 the shock absorber D are Fa = K / {2 · π · A ² · (C1 + C2 + C3)} and Fb = K / { 2 · π · A ² · (C2 + C3)}, the transfer gain is approximately C1 in the region of F <Fa, and C1 to C1 · in the region of Fa ≦ F ≦ Fb. It changes so as to gradually decrease to (C2 + C3) / (C1 + C2 + C3), 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, as shown in FIG. 4, this shock absorber D generates a large damping force for low-frequency vibration input, while exhibiting a damping force reduction effect for high-frequency vibration input. Therefore, it is possible to generate a high damping force in a scene where the input vibration frequency is low, such as when the vehicle is turning, and the input vibration frequency is such that the vehicle travels on an uneven road surface. In a scene with high, it is possible to reliably generate a low damping force and improve the riding comfort in the vehicle.

  When the free piston 9 is displaced from the neutral position until the orifice hole 22e is closed, the flow resistance of the pressure side passage 11 gradually increases from the start of closing the orifice hole 22e until the orifice hole 22e is completely closed. The movement speed of the piston 9 toward the stroke end side is reduced, and the apparent amount of liquid movement between the extension side chamber R1 and the pressure side chamber R2 via the pressure chamber C is reduced, and the damping passages 4, 5 are correspondingly reduced. The amount of liquid that passes through the cylinder increases, and the damping force generated by the shock absorber D gradually increases regardless of the vibration frequency. Therefore, when the displacement from the neutral position of the free piston 9 is large and closes the orifice hole 22e in this way, the displacement of the free piston 9 toward the stroke end is suppressed, and the shock absorber D is low when high-frequency vibration is input. It is prevented that the damping force is suddenly switched from a state where the damping force is generated to a high damping force, and it is not necessary for the passenger to perceive a shock due to a change in the damping force. In this embodiment, as the free piston 9 is displaced from the neutral position, the flow passage area of the compression side passage 11 is decreased to gradually increase the flow passage resistance. In addition, or Instead of this, the same effect as described above can be obtained even if the flow resistance of the extension side passage 10 is increased.

  When the shock absorber D receives an input of vibration in the extension direction with a large amplitude, and the free piston 9 is displaced from the neutral position to the pressure side pressure chamber side beyond a predetermined displacement amount, the abutting portion in the cushion member 13 15 collides with the free piston 9 to suppress further displacement of the free piston 9 to the pressure side pressure chamber side to reduce the displacement speed of the free piston 9 to the pressure side pressure chamber side. Since direct collision with the housing 6 is prevented, no hitting sound is generated.

  As described above, according to the shock absorber D of the present invention, the cushion member 13 can be installed to solve the problem of hitting sound, and the rider can not perceive the hitting sound. A feeling of anxiety or discomfort is not given, and the riding comfort in the vehicle can be improved.

The housing 6 is cylindrical and has a large inner diameter portion 22a in sliding contact with the free piston 9, a small inner diameter portion 22b, and a step formed between the large inner diameter portion 22a and the small inner diameter portion 22b. 22c and a cushion fixing piece 22d that rises from the inner peripheral side of the step portion 22c, the cushion member 13 is annular and is in contact with the step portion 22c, the cushion fixing piece 22d is bent toward the cushion member side, and the cushion fixing piece Since the cushion member 13 is held by 22d and the cushion member 13 is fixed to the housing 6, the cushion member 13 is firmly fixed to the housing 6. Therefore, according to the shock absorber D of the present invention, the cushion member 13 can be prevented from falling off from the housing 6 while suppressing the occurrence of hitting sound due to the collision between the free piston 9 and the housing 6.

  Further, since the cushion member 13 is prevented from falling off from the housing 6, the cushion member 13 does not interfere with the free piston 9 except for the displacement of the free piston 9 to the stroke end, thereby affecting the smooth movement of the free piston 9. And the function of the shock absorber D that reduces the damping force at high frequencies is not adversely affected.

  Further, the base portion 14 of the cushion member 13 held by the folded cushion fixing piece 22d is a tapered surface whose inner diameter is increased as the inner diameter of the cushion member 13 is further away from the stepped portion 22c. Since the gripping member follows the inner peripheral surface of the base portion 14, the cushion member 13 is not unnecessarily deformed, and an unnecessary gap is not generated between the cushion fixing piece 22 d and the base portion 14. Even if the cushion member 13 is repeatedly deformed by the collision with the free piston 9, the deterioration of the cushion member 13 can be suppressed.

  Since the cushion fixing piece 22d has an annular shape, the cushion fixing piece 22d hits the corner of the cushion member 13 as compared with the case where the cushion fixing piece 22d is constituted by a claw intermittently provided on the step portion 22c. Since the number of locations can be reduced, the deterioration of the cushion member 13 can be suppressed and the life can be extended.

 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.

  The shock absorber of the present invention can be used for vehicle vibration control.

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 Piston rods 4, 5 Damping passage 6 Housing 7 Extension side pressure chamber 8 Pressure side pressure chamber 9 Free piston 10 Extension side passage 11 Pressure side passage 12 Spring element 13 Cushion member 14 Base part 15 Contact part 22a Inner diameter large diameter part 22b Inner diameter small diameter portion 22c Stepped portion 22d Cushion fixing piece C Pressure chamber R1 Extension side chamber R2 Pressure side chamber

Claims (4)

A cylinder, a piston for partitioning the slidably inserted in said cylinder within said cylinder expansion side chamber and the compression side chamber, a damping passage connecting the said expansion side chamber and the compression side chamber, a housing defining a pressure chamber , and the extension side passage communicating with the free piston, and the expansion side chamber and the expansion side pressure chamber is slidably inserted into the pressure chamber defining the pressure chamber and the extension side pressure chamber and the compression side pressure chamber, a spring element exerting a pressure side passage communicating with the compression side chamber and the pressure side pressure chambers, to suppress biasing force of the displacement from the neutral position of the free piston with the free piston is positioned at a neutral position relative to the housing When, the free piston of the free piston to abut on the free piston when displaced to the stroke end in the direction to compress the compression side pressure chamber relative to the housing In the shock absorber having a suppressing cushion member is further displacement,
It said housing is a cylindrical, inner diameter large diameter portion of the free piston sliding contact, an inner diameter small-diameter portion, and a stepped portion formed between the inner diameter large diameter portion and the inner diameter smaller-diameter portion, the stepped portion And a cushion fixing piece that rises from the inner peripheral side of the
The said cushion member is cyclic | annular, Comprising: It contact | abuts to the said step part, It is fixed to the said housing by being hold | maintained by the said cushion fixing piece bent by the said cushion member side, It is characterized by the above-mentioned. Shock absorber. The shock absorber according to claim 1 , wherein the cushion member is housed in a compressed state on an inner periphery of the housing. The cushion member is
A base to be held by the cushion fixing piece,
And a abutment portion facing the free piston continuous to said base,
The shock absorber according to claim 1 or 2, wherein the inner peripheral surface of the base portion is a tapered surface having an inner diameter that increases as the distance from the stepped portion increases. The shock absorber according to any one of claims 1 to 3, wherein the cushion fixing piece is annular.

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