JP2012052630A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shock absorber that prevents hitting noise between a free piston and a housing from generating to improve riding comfort of a motorcycle.SOLUTION: The shock absorber D includes: an expansion-side chamber R1 and a pressure-side chamber R2 which are disposed in a cylinder 1; the housing 6 which forms a pressure chamber C; and the free piston 9 which separates the inside of the pressure chamber C into an expansion-side pressure chamber 7 communicated to the expansion-side chamber R1 and a pressure-side pressure chamber 8 communicated to the pressure-side chamber R2. The shock absorber further includes: an expansion-side elastic body 13 which, when the free piston 9 displaces from a neutral position to a side of the expansion-side pressure chamber 7 by a predetermined displacement magnitude or larger, abuts the displacement to exert resilient force to prevent the displacement of the free piston 9; and a pressure-side elastic body 14 which, when the free piston 9 displaces from the neutral position to a side of the pressure-side pressure chamber 8 by the predetermined displacement magnitude or larger, abuts the displacement to exert the resilient force to prevent the displacement of the free piston 9.

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.

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 and the compression side chamber during expansion and contraction 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 flow rate Q1 of the liquid passing through the attenuation passage The coefficient that is the relationship is C1, the pressure in the pressure side pressure chamber is P1, and the coefficient that is the relationship between the difference between the differential pressure P and the pressure P1 and the flow rate Q2 of the liquid flowing from the extension side chamber into the extension side pressure chamber is C2. , P2 is the pressure in the expansion side pressure chamber, C3 is a coefficient that is a relationship between the pressure P2 and the flow rate Q2 of the liquid flowing out from the pressure side pressure chamber into the pressure side chamber, and A is the cross-sectional area that is the pressure receiving area of the free piston. When the displacement of the free piston with respect to the pressure chamber is X and the spring constant of the coil spring is K, the transfer function of the differential pressure P with respect to the flow rate Q is obtained as shown in Equation (1). 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 this buffer device 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, as shown in FIG. 3, this shock absorber generates a large damping force for low-frequency vibration input, while exhibiting a damping force reducing effect for high-frequency vibration input. Therefore, it is possible to reliably 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 high scenes, a low damping force can be reliably generated to improve the riding comfort in the vehicle (see, for example, Patent Documents 1 and 2).

JP 2006-336816 A JP 2007-78004 A

  By the way, when the shock absorber is used for a suspension of a two-wheeled vehicle, the weight of the two-wheeled vehicle is very light relative to the weight of the four-wheeled vehicle. In order to improve the riding comfort by reducing the damping force, it is required to set the frequency at which the damping force is reduced to a lower frequency than that of a four-wheeled vehicle. That is, in a two-wheeler application, it is required to set the breakpoint frequency Fa lower than that of a four-wheeled vehicle.

  In order to satisfy this requirement, it is conceivable to reduce the spring multiplier K of the coil spring, and by doing so, the frequency at which the damping force reduction effect begins to appear is lowered. Riding comfort can be improved.

  However, in this shock absorber, when the free piston compresses and displaces the extension-side pressure chamber and the compression-side pressure chamber and reaches its stroke end, the housing collides with the free piston, and the free piston further exceeds the housing. The displacement to the stroke end side is regulated.

  Therefore, for example, when a vibration with a large amplitude is input, the displacement of the free piston is restricted by the housing. Therefore, if the spring multiplier K is reduced as described above, As the chance of interference with the housing increases, the displacement speed of the free piston tends to increase. Then, when the free piston collides with the housing, a loud hitting sound is generated, which gives the vehicle occupant a sense of discomfort and anxiety, which may impair the riding comfort in vehicles other than the vibration surface.

  Accordingly, the present invention has been developed to improve the above-described problems, and the object of the present invention is to improve the riding comfort in a motorcycle by suppressing the occurrence of a hitting sound between the free piston and the housing. Is to provide a shock absorber.

  In order to solve the above-described object, the problem solving means in the present invention communicates 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 two working chambers. A damping passage, a housing that forms 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 an expansion side chamber and an expansion side pressure chamber. The expansion side passage that communicates, the pressure side passage that communicates the pressure side chamber and the pressure side pressure chamber, and the biasing force that positions the free piston in the neutral position and suppresses the displacement from the neutral position of the free piston. In a shock absorber provided with a spring element, when the free piston is displaced from the neutral position to the extension side pressure chamber by a predetermined amount or more with respect to the housing, the free piston collides with the free piston. The extension side elastic body that exerts the elastic force to suppress the displacement of the cylinder toward the extension side pressure chamber side, and the free piston is more than the predetermined displacement amount from the neutral position to the compression side pressure chamber side with respect to the housing A compression-side elastic body is provided, which, when displaced, abuts against the free piston and exerts an elastic force that suppresses further displacement of the free piston toward the pressure-side pressure chamber.

  According to the shock absorber of the present invention, when the free piston reaches the stroke end which is the movement limit, the free piston collides with the resin stopper, and further displacement is regulated. Therefore, the volume of the hitting sound at the time of collision can be reduced. Therefore, in this shock absorber, it is not necessary for the vehicle occupant to perceive the hit sound, and the rider does not feel uneasy or uncomfortable, and the ride comfort in the vehicle can be improved.

It is a longitudinal cross-sectional view of the shock absorber in one embodiment. It is a partial expanded longitudinal cross-sectional view of the shock absorber in 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, the shock absorber D of the present invention includes a cylinder 1 and a piston that is slidably inserted into the cylinder 1 and divides the cylinder 1 into two working chambers, an extension side chamber R1 and a pressure side chamber R2. 2, damping passages 4 and 5 communicating with the extension side chamber R <b> 1 and the pressure side chamber R <b> 2, a housing 6 forming the pressure chamber C, and a slidable insertion into the housing 6 to extend the pressure chamber C. A free piston 9 that divides the side pressure chamber 7 and the pressure side pressure chamber 8, a stretch side passage 10 that communicates the stretch side chamber R1 and the stretch side pressure chamber 7, and a pressure side that communicates the pressure side chamber R2 and the pressure side pressure chamber 8 The passage 11, the spring element 12 that exerts a biasing force that positions the free piston 9 in the 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 Neutral position When it is displaced to the extension side pressure chamber 7 side by a predetermined displacement amount or more, it is engaged with the free piston 9 and exerts an elastic force that suppresses the further displacement of the free piston 9 toward the extension side pressure chamber 7 side. When the side elastic body 13 and the free piston 9 are displaced from the neutral position to the pressure side pressure chamber 8 with respect to the housing 6 by a predetermined displacement amount or more, they abut against the free piston 9 and the pressure side pressure chamber 8 beyond that of the free piston 9. And a compression-side elastic body 14 that exhibits a resilient force that suppresses displacement to the side.

  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. And a gas partition wall 15 are 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 set to a so-called single rod type, the volume of the piston rod 3 that enters and exits the cylinder 1 as the shock absorber D expands and contracts is the volume of the gas in the gas chamber G. The sliding partition 15 is compensated for by expanding or contracting and moving in the vertical direction in FIG. Thus, the shock absorber D is set to a single cylinder type, but instead of installing the sliding partition wall 15 and the gas chamber G, a reservoir is provided on the outer periphery or outside of the cylinder 1 and the piston rod 3 is provided by the reservoir. Volume compensation may be performed. 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 of a piston rod 3 that is movably inserted into the cylinder 1, and the piston rod 3 is outside through an inner circumference of an annular rod guide (not shown) fixed to the upper end of the cylinder 1 in the figure. It protrudes towards. 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 the lower end of the damping passage 4 in FIG. 1 is opened and closed by a leaf valve 17, and the upper end of the damping passage 5 in FIG. 1 is opened and closed by a leaf valve 18 as a damping valve stacked above the piston 2 in FIG. Yes. The leaf valve 17 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 expansion 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 18 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 during 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 17 functions as an expansion-side damping valve that provides resistance to the flow of liquid flowing through the attenuation passage 4 during the extension stroke, and the leaf valve 18 provides resistance to the flow of liquid flowing 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 17 and 18 also function as a piston nut that fixes the piston rod 3 to one end 3a.

  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 covers 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 opening of the cylindrical portion 22. A bottomed cylindrical housing cylinder 21 provided with a bottom 23, and a step 22a provided on the inner periphery of the cylinder 22 by reducing the diameter of the lower side of the cylinder 22 in the housing cylinder 21. Thus, a pressure chamber C is defined in the pressure side chamber R2.

  Moreover, the nut part 20 is provided with the screw part 20a and the flange 20b which screw together with the screw part 3b of the piston rod 3 in the inner periphery. 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. . In addition, integration of the nut part 20 and the housing cylinder 21 can employ | adopt other process directions, such as welding and screwing, besides a caulking process. Further, a step portion 22a is provided on the inner periphery of the tube portion 22 of the housing tube 21 so as to face the extension side pressure chamber 7 which is the upper side in FIG. 1, and the extension side pressure chamber 7 which is directly above the step portion 22a. The inner diameter of the side is enlarged and an annular groove 22b whose side is flush with the stepped part 22a is provided. Apart from the annular groove 22b, the inner diameter directly below the crimping part 22c fixed to the nut part 20 is provided. An annular groove 22d that is expanded in diameter and faces the expansion side pressure chamber 7 is provided.

  It should be noted that the outer peripheral cross-sectional shape of at least a part of the cylindrical portion 22 of the housing cylinder 21 is a shape other than a circle so as to be gripped by a tool (not shown), and a shape corresponding to the tool, for example, a part is notched The outer periphery of the cylindrical portion 22 is gripped by a tool and the housing 6 is rotated in the circumferential direction by applying a predetermined tightening torque to the nut portion 20 to the screw portion 3b. It can be screwed. Further, a port 22e is provided on the side portion of the cylindrical portion 22, the pressure chamber C and the pressure side chamber R2 communicate with each other at the port 22e, and the port 23a is also provided at the bottom portion 23. The pressure chamber C and the pressure side chamber R2 communicate with each other at 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 constituted by 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 leads to the horizontal hole 10a.

  The free piston 9 inserted into the pressure chamber C includes a sliding contact cylinder 30 that is in sliding contact with the cylindrical portion 22 of the housing cylinder 21 and a mirror portion 31 that closes the inner periphery of the sliding contact cylinder 30. The interior is divided into an extension side pressure chamber 7 communicated with the extension side chamber R1 and a pressure side pressure chamber 8 communicated with the compression 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 port 22e and the port 22e is closed with the sliding contact cylinder 30. In this case, the communication between the pressure side chamber R2 and the pressure side pressure chamber 8 via the port 22e is cut off. The port 22e provides resistance to the flow of liquid passing therethrough to cause a predetermined pressure loss, and generates a differential pressure between the pressure side chamber R2 and the pressure side pressure chamber 8. Further, the port 23a provided at the bottom 23 of the housing cylinder 21 also functions as a throttle 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 chamber 8 and the pressure chamber 8. This port 23a is not closed by the free piston 9 and is always open. In other words, the pressure side pressure chamber 8 communicates with the pressure side chamber R2 through the ports 22e and 23a when the port 22e is in communication, and when only the port 23e is in the shut off state, the pressure side pressure chamber 8 communicates with the pressure side. The pressure side passage 11 is formed by the ports 22 e and 23 a, the annular recess 32 and the communication hole 33.

  Furthermore, in order to apply an urging force that suppresses the displacement of the free piston 9 relative to the housing 6, it is within the extension side pressure chamber 7 between the nut portion 20 and the mirror portion 31 of the free piston 9, and In the compression-side pressure chamber 8, coil springs 34 and 35 are interposed in a compressed state as the spring element 12 between the bottom 23 and the mirror portion 31 of the free piston 9. As described above, the free piston 9 is sandwiched from above and below by the spring elements 12 of the coil springs 34 and 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 coil spring 34, 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.

  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. Therefore, elements other than the coil springs 34 and 35 may be employed. For example, an elastic body such as a disc spring May be used to elastically support the free piston 9. 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 coil spring 34 is loosely fitted on 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 coil spring 35 in FIG. 1 is the mirror portion 31 of the free piston 9. Is loosely fitted to a protrusion 31a formed at the lower end of the member and positioned at an approximate position in the radial direction. As described above, the coil springs 34 and 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, whereby a biasing force is stably applied to the free piston 9. It is possible to make it.

  As described above, the free piston 9 is elastically supported by the coil springs 34 and 35 as the spring element 12 in the housing 6 and is in a neutral position in the housing 6 in a state where no force other than the urging force by the spring element 12 is applied. The annular recess 32 always faces the port 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 cylinder 31 of the free piston 9 completely overlaps the port 22e to close it. The amount of displacement from the neutral position at which the free piston 9 begins to close the port 22e can be set arbitrarily, and the side of the expansion side pressure chamber 7 that is the upper side in FIG. 1 of the free piston 9 that starts to close the port 22e. The displacement amount from the neutral position to the neutral position may be set differently from the displacement amount of the free piston 9 starting to close the port 22e from the neutral position toward the pressure side pressure chamber 8 which is the lower side in FIG. In this embodiment, two ports 22e are provided, but the number thereof is arbitrary. An annular recess communicated with the pressure side chamber R2 is provided on the inner periphery of the cylindrical portion 21, and the outer periphery side of the free piston 9 is provided. A port for communicating with the pressure side pressure chamber 8 may be provided in the free piston 9.

  In the case of the shock absorber D, the annular pressure side elastic body 14 and the extension side elastic body 13 are fitted in the annular grooves 22b and 22d provided in the cylindrical portion 22 of the housing cylinder 21, respectively.

  Specifically, the stretch-side elastic body 13 is an annular flat rubber having an inner and outer diameter that is annular and can be fitted into the annular groove 22d, and the coil spring 34 so as not to interfere with the coil spring 34. The inner diameter is set to be larger than the outer diameter, and the upper end is installed in the housing 6 so as to contact the nut portion 20. The compression-side elastic body 14 is also an annular flat rubber, and has an inner and outer diameter that is annular and can be fitted into the annular groove 22b, and is within the inner edge of the step portion 22a and protrudes from the annular groove 22b. The inner diameter of the housing 6 is set so that the lower end thereof is in contact with the stepped portion 22a.

  When the expansion side elastic body 13 is installed in the housing 6 in this way, when the free piston 9 displaces a predetermined displacement amount from the neutral position toward the expansion side pressure chamber 7 which is the upper side in FIG. It collides with the upper end of the sliding contact cylinder 30 and is compressed between the sliding contact cylinder 30 and the nut portion 20 to exert an elastic force, and the further displacement of the free piston 9 toward the extension side pressure chamber 7 side. Is suppressed by the elasticity.

  In addition, when the compression-side elastic body 14 is installed in the housing 6, when the free piston 9 displaces a predetermined amount of displacement from the neutral position toward the compression-side pressure chamber 8 which is the lower side in FIG. 30 is abutted against the lower end of the cylinder 30 and compressed between the sliding contact cylinder 30 and the step portion 22a to exert a resilience, and further displacement of the free piston 9 toward the pressure side pressure chamber 8 is caused by the resilience. It has come to be suppressed.

  The predetermined upward displacement from the neutral position of the free piston 9 when the extension side elastic body 13 starts to abut with the sliding contact cylinder 30 of the free piston 9 indicates that the compression side elastic body 14 is in sliding contact with the free piston 9. The predetermined downward displacement amount from the neutral position of the free piston 9 when starting to collide with 30 can be arbitrarily set or can be set differently. Further, the extension side elastic body 13 and the pressure side elastic body 14 need only be installed in the housing 6 so as to abut against the free piston 9, so that the installation location for the housing 6 described above is the housing 6 and the free piston. The free piston 9 should be as close to the stroke end as possible because it is better to make the stroke length of the free piston 9 as large as possible to obtain a damping force reduction effect. It is desirable to make contact with the extension side elastic body 13 and the compression side elastic body 14.

  Further, as the stretch-side elastic body 13 and the compression-side elastic body 14, in addition to the ring-plate-shaped rubber, an O-ring or other annular rubber can be used, not only being fitted in the annular grooves 22b and 22d, The housing 6 may be integrated with the housing 6 by bonding, welding, or fusing rubber.

  The shock absorber D is configured as described above. Next, the operation of the shock absorber D will be described. First, the operation of the shock absorber D when the amount of displacement from the neutral position of the free piston 9 is within a range where the port 22e does not begin to be closed will be described. In this case, the free piston 9 can be displaced while maintaining the communication state of the port 22e.

  When the input frequency to the shock absorber D is low and high, under the condition that the input speed is the same, when the input frequency is low, the input amplitude increases and the amplitude of the free piston 9 also increases. When the amplitude of the free piston 9 increases within a range in which the port 22e does not begin to close, the free piston 9 is displaced, so that an urging force is exerted to return the free piston 9 to the neutral position by the coil springs 34, 35. There is a difference in the pressure between the expansion side pressure chamber 7 and the compression side pressure chamber 8 of the expansion side pressure chamber 7 and the compression side pressure chamber 8 corresponding to the urging force of 34 and 35, and the expansion side chamber is on the reduction side. The pressure is higher than the chamber.

  Then, the differential pressure between the expansion side pressure chamber 7 and the expansion side chamber R1 and the differential pressure between the compression side pressure chamber 8 and the compression side chamber R2 become small, and the flow rate passing through the expansion side passage 10 and the compression side passage 11 decreases. . As the flow rate passing through the extension side passage 10 and the pressure side passage 11 decreases, the flow rate of the damping passages 4 and 5 increases, and the damping force generated by the shock absorber D increases.

  On the contrary, since the input amplitude is small at the time of high frequency input, the flow rate of one cycle moving from the compression side chamber R1 to the expansion side chamber R2 or from the compression side chamber R2 to the expansion side chamber R1 is small, and the displacement of the free piston 9 is also small. . Then, the biasing force of the coil springs 34 and 35 received by the free piston 9 is also reduced. Accordingly, the difference between the pressure in the expansion side pressure chamber 7 and the pressure in the compression side pressure chamber 8 becomes smaller, the differential pressure between the expansion side pressure chamber 7 and the expansion side chamber R1, and the differential pressure between the compression side pressure chamber 8 and the compression side chamber R2. Therefore, the flow rate passing through the expansion side passage 10 and the pressure side passage 11 becomes larger than that at the low frequency, and the flow rate of the attenuation passages 4 and 5 is reduced accordingly, and the damping force generated by the shock absorber D is also increased. Will be reduced.

  Thus, as shown in FIG. 3, the shock absorber D generates a large damping force for low-frequency vibrations and a damping force for high-frequency vibrations, as shown in FIG. A reduction effect can be exhibited and the damping force can be reduced, and a damping force depending on the input vibration frequency can be generated.

  On the other hand, the operation of the shock absorber D when the free piston 9 is displaced from the neutral position to the point where it starts to close the port 22e will be described. When the amplitude of vibration input to the shock absorber D increases, the amount of displacement of the free piston 9 from the neutral position also increases, and the free piston 9 begins to close the port 22e, and finally the port 22e is completely closed. It becomes a state.

  That is, after the free piston 9 starts to close the port 22e, the flow path resistance of the pressure side passage 11 gradually increases according to the amount of displacement, and when the free piston 9 closes the port 22e, the flow path resistance in the pressure side passage 11 is increased. Maximum.

  As described above, when the free piston 9 is displaced beyond the position where it begins to close the port 22e, the flow resistance of the pressure side passage 11 gradually increases. The moving speed to 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 liquid passing through the attenuation passages 4 and 5 correspondingly. As the amount increases, the damping force generated by the shock absorber D gradually increases regardless of the vibration frequency.

  When the free piston 9 is stroked until the port 22e is completely closed, the apparent movement of the liquid between the expansion side chamber R1 and the pressure side chamber R2 is eliminated via the pressure chamber C, and the expansion and contraction direction of the shock absorber D is eliminated. The liquid will pass only through the damping passages 4 and 5 until it turns over, and the shock absorber D generates a damping force with the maximum damping coefficient regardless of the vibration frequency.

  In addition, with respect to the vibration in the frequency range where the shock absorber D produces a damping force reduction effect, the shock absorber D has a relatively low damping until the free piston 9 is displaced from the neutral position to the position where the port 22e begins to close. When the free piston 9 begins to close the port 22e, the damping force gradually increases. When the free piston 9 is further displaced toward the stroke end side and completely closes the port 22e, the maximum is generated. A damping force is generated with a damping coefficient of. In other words, the shock absorber D is exhibiting a damping force reduction effect, and even when a large amplitude vibration is input, the damping device D does not suddenly change the magnitude of the damping force. The damping force change to a high damping force can be made gentle. Therefore, in this shock absorber D, even if a vibration with a large amplitude is input, the generated damping force changes gently, and it is not necessary for the passenger to perceive a shock due to the change in the damping force. In particular, when the vibration frequency is high, since a low damping force is generated, a sudden change in the generated damping force can be effectively mitigated. 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 reduced to gradually increase the flow passage resistance. In addition to this, or Instead, the same effect as described above can be obtained by increasing the flow path resistance of the extension side passage 10. When the flow passage area of the extension side passage 10 is reduced, for example, a shaft to be inserted into the vertical hole 10b is provided in the mirror part 31 of the free piston 9, and the vertical hole 10b and the shaft are moved as the free piston 9 is displaced from the neutral position. The shape of the shaft and the vertical hole 10b may be set so that the gap between the first and second holes becomes gradually smaller. However, in the present embodiment in which the housing 6 faces the pressure side chamber R2 as described above, the port 22e is provided in the housing 6 and the port 22e is throttled by the free piston 9, so that the flow path of the pressure side passage 11 is provided. Employing a configuration that reduces the area has an advantage that the structure of the free piston 9 is simplified and dimensional management is facilitated. Further, the displacement amount (decrease starting displacement amount) from the neutral position at which the free piston 9 starts to decrease the flow passage area of the compression side passage 11 and the extension side passage 10 can be arbitrarily set.

  When the shock absorber D receives vibration of a large amplitude in the contracting direction and the free piston 9 is displaced from the neutral position to the extension side pressure chamber 7 side beyond a predetermined displacement amount, the extension side elastic body 13 is used. Abuts on the free piston 9 to suppress further displacement of the free piston 9 toward the expansion side pressure chamber 7 to reduce the displacement speed of the free piston 9 toward the expansion side pressure chamber 7 and Since the direct collision between the piston 9 and the housing 6 is prevented, no hitting sound is generated.

  Further, 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 8 side beyond the predetermined displacement amount, the pressure side elastic body 14 is free. The piston 9 collides with the piston 9 to suppress further displacement of the free piston 9 toward the pressure side pressure chamber 8 to reduce the displacement speed of the free piston 9 toward the pressure side pressure chamber 8 side. Since the direct collision with 6 is prevented, no hitting sound is generated.

  In this way, by installing the stretch-side elastic body 13 and the compression-side elastic body 14, the problem of hitting sound can be solved, so the frequency at which the damping force reduction effect of the shock absorber D appears can be lowered to be suitable for a motorcycle. Therefore, the spring multiplier of the spring element can be reduced, and the riding comfort of the two-wheeled vehicle with respect to the vibration surface can be improved.

  That is, according to the shock absorber D, not only the generation of the hitting sound between the free piston 9 and the housing 6 can be prevented, but also the riding comfort on the vibration surface of the two-wheeled vehicle can be improved, so that the total riding comfort of the two-wheeled vehicle can be improved. Can be improved.

  Further, the extension side elastic body 13 and the pressure side elastic body 14 act so as to add a resilient force to the urging force of the spring element 12 when the free piston 9 is displaced by a predetermined displacement amount or more from the neutral position. The function of suppressing the displacement of the free piston 9 can be effectively exhibited even with respect to the vibration in the frequency band in which the movement of the free piston 9 cannot be sufficiently suppressed by the aperture resistance at the port 23a. Abrupt changes in force change can be suppressed, and the displacement of the free piston 9 is allowed even after a collision with the free piston 9, so that the damping force reduction effect is not completely lost even after the collision.

  The housing 6 is provided in the cylinder 1 in the above-described embodiment. However, the housing 6 can be provided outside the cylinder 1, and a configuration in which the housing 6 is provided in the extension side chamber R1 is adopted. You can also. In addition, the operational effects obtained by installing the stretch-side elastic body 13 and the compression-side elastic body 14 can be enjoyed regardless of the presence or absence of the port 22e and the annular recess 32, and these can be eliminated. .

 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 according to the present invention can be used for vibration control of a motorcycle.

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 Piston rod 3a One end 3b of a piston rod Screw part 4 and 5 of a piston rod Damping passage 6 Housing 7 Extension side pressure chamber 8 Pressure side pressure chamber 9 Free piston 10 Extension side passage 10a Horizontal hole 10b Vertical hole 11 Pressure side passage 12 Spring Element 13 Stretch-side elastic body 14 Pressure-side elastic body 15 Sliding partition walls 17 and 18 Leaf valve 20 Nut portion 20a Screw portion 20b Fitting recess 21 Housing tube 22 Tube portion 22a Step portions 22b and 22d Annular groove 22c Caulking portion 22e Port 23 Bottom 23a Port 21a Port 23 Valve seat member 23a Annular valve seat 30 Sliding tube 31 Mirror part 32 Annular recess 33 Communication hole 34, 35 Coil spring C as spring element C Pressure chamber D Buffer device G Air chamber L Liquid chamber R1 Extension side chamber R2 Pressure side chamber

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 damping passage that communicates the two working chambers, a housing that forms a pressure chamber, and a slide in the pressure chamber A free piston that is freely inserted and divides the pressure chamber into an expansion side pressure chamber and a pressure side pressure chamber, an expansion side passage that communicates the expansion side chamber and the expansion side pressure chamber, and a pressure side chamber and a pressure side pressure chamber communicate with each other. In a shock absorber provided with a compression side passage and a spring element that positions the free piston in a neutral position with respect to the free piston housing and exerts a biasing force that suppresses displacement from the neutral position of the free piston. When it is displaced from the neutral position to the expansion side pressure chamber side by more than a predetermined amount of displacement, it will collide with the free piston and suppress the elastic force against further displacement of the free piston to the expansion side pressure chamber side. When the extension side elastic body and the free piston are displaced from the neutral position to the pressure side pressure chamber by a predetermined amount or more with respect to the housing, they collide with the free piston and the free piston is displaced further to the pressure side pressure chamber. A shock absorber provided with a compression-side elastic body that exerts an elastic force to suppress the above. One end is provided with a piston rod connected to the piston, and a housing fixes a piston fitted to the piston rod to the piston rod, a cylindrical portion hanging from the outer periphery of the nut portion, and an opening of the cylindrical portion is covered A pressure chamber is formed by including a bottomed cylindrical housing cylinder having a bottom portion and a step portion provided on an inner periphery of the cylindrical portion of the housing cylinder, and the free piston is formed by a step portion of the cylindrical portion of the housing. A sliding contact cylinder that is in sliding contact with the nut portion side; and a mirror portion that closes the inner periphery of the sliding contact cylinder; the spring element is housed in the expansion side pressure chamber and is interposed between the mirror portion and the nut portion. An extension side spring and a compression side spring that is housed in the compression side pressure chamber and interposed between the mirror part and the bottom part of the housing cylinder in the cylinder part. Free piston An expansion side elastic body that suppresses the movement to the expansion side pressure chamber side is installed in contact with the nut portion, and abuts against the pressure side pressure chamber side end of the sliding piston of the free piston to press the pressure side pressure chamber side of the free piston The shock absorber according to claim 1, wherein a compression-side elastic body that suppresses movement of the shock absorber is disposed in contact with the stepped portion. 3. The shock absorber according to claim 1, wherein when the free piston is displaced from the neutral position by a decrease start displacement amount or more, the flow passage area of one or both of the expansion side passage and the pressure side passage is reduced.

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