JP2011007213A - Buffer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a buffer capable of reducing the hammering sound volume and improving the driving comfort in a vehicle.SOLUTION: The buffer includes a housing 15 forming a pressure chamber therein, a free piston 9 slidably inserted within the housing 15, a free piston 9 partitioning the pressure chamber R3 into one chamber 7 communicating with one operating chamber R2 through a flow path 5 on one side and the other chamber communicating with the other operating chamber R1 through a flow passage 6 on the other side, and a spring element for generating energizing force for suppressing the displacement of the free piston 9 relative to the housing 15. A resin-made stopper 16 is installed on either the free piston 9 or the housing 15 so as to limit the displacement of the free piston 9 in such a manner that the free piston 9 is displaced to the movement limit on one side or the other side or both sides relative to the housing 15, and brought into contact with the other side of the free piston 9 or the housing 15.

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 inside of the cylinder into an upper chamber and a lower chamber, and an upper chamber and a lower chamber provided in the piston communicate with each other. A first flow path, a second flow path that opens from the tip of the piston rod to the side to communicate the upper chamber and the lower chamber, and a pressure chamber that is connected in the middle of the second flow path, , A free piston that is slidably inserted into the pressure chamber and partitions the pressure chamber into one chamber and the other chamber, and a coil spring that biases the free piston. That is, one chamber in the pressure chamber communicates with the lower chamber through the second flow path, and the other chamber in the pressure chamber communicates with the upper chamber through the second flow path.

  In the shock absorber configured in this manner, the pressure chamber is divided into one chamber and the other chamber by a free piston, and the upper chamber and the lower chamber are not directly communicated with each other via the second flow path. However, when the free piston moves, the volume ratio of the one chamber and the other chamber changes, and the liquid in the pressure chamber enters and exits the upper and lower chambers according to the amount of movement of the free piston. It behaves as if the chamber is in communication with the second flow path.

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 upper chamber and the lower chamber when the shock absorber is expanded and contracted is P, the flow rate of the liquid flowing out from the upper chamber is Q, the differential pressure P and the flow rate Q1 of the liquid passing through the first flow path are Is a relationship between the difference between the pressure difference P and the pressure P1, and the flow rate Q2 of the liquid flowing from the upper chamber into the other chamber of the pressure chamber. The coefficient is C2, the pressure in one chamber of the pressure chamber is P2, the coefficient that is the relationship between the pressure P2 and the flow rate Q2 of the liquid flowing out from the one chamber into the lower chamber is C3, and the pressure receiving area of the free piston When the area is A, the displacement of the free piston with respect to the pressure chamber is X, the spring constant of the coil spring is K, and the transfer function of the differential pressure P with respect to the flow rate Q is obtained, the equation (1) is obtained. In formula (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 is large in the low frequency region and the transfer gain is small in the high frequency region.

  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. The vehicle can reliably generate a high damping force in a scene where the input vibration frequency is low, such as a medium, and can reliably generate a low damping force in a scene where the input vibration frequency is high such that the vehicle travels on an uneven road surface. The riding comfort can be improved (see, for example, Patent Documents 1 and 2).

JP 2006-336816 A JP 2007-78004 A

  By the way, in the said shock absorber, the step part is provided in the inner periphery of the housing, and when the free piston is displaced downward to compress the one chamber and reaches the movement limit, the step part is located on the one chamber side of the free piston. Abutting on the outer periphery of the end, the further downward displacement of the free piston with respect to the housing is restricted.

  Therefore, for example, when vibration with a large amplitude is input, the displacement of the free piston is restricted at the stroke end, so that liquid does not pass through the pressure chamber, and the shock absorber exerts a large damping force. It is possible to suppress the stretch and bottoming.

  In this way, by restricting the displacement of the free piston, it is possible to suppress expansion and bottoming, but when the free piston collides with the stepped portion, a sound is generated and the vehicle occupant feels uncomfortable. This may give a sense of anxiety and may impair the riding comfort of the vehicle.

  Therefore, the present invention was devised to improve the above-described problems, and an object of the present invention is to provide a buffer capable of reducing the volume of the hitting sound and improving the riding comfort in the vehicle. Is to provide a device.

  In order to solve the above-described object, the problem solving means in the present invention communicates a cylinder, a partition member slidably inserted into the cylinder and partitioning the cylinder into two working chambers, and the two working chambers. A passage, a housing that forms a pressure chamber, and a chamber that is slidably inserted into the housing and communicates with the one working chamber via the one-side flow path and the one-side flow path One of the free piston and the housing is provided with a shock absorber including a free piston that is divided into the other chamber communicated with the other working chamber, and a spring element that generates a biasing force that suppresses displacement of the free piston with respect to the housing. When the free piston is displaced to the limit of movement on one side, the other side, or both sides with respect to the housing, the free piston or the other side of the housing is Characterized in that a resin stopper for regulating the displacement of the free piston and.

  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 riding 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 partial expanded longitudinal cross-sectional view of the buffering device in the modification of one embodiment.

  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 partition wall that is slidably inserted into the cylinder 1 and divides the cylinder 1 into two working chambers R1 and lower chamber R2. The piston 2 as a member, the passages 3a and 3b communicating the upper chamber R1 and the lower chamber R2, the housing 15 forming the pressure chamber R3, and the pressure chamber R3 slidably inserted into the housing 15. Is connected to the lower chamber R2 which is one working chamber via the one-side flow path 5 and the other chamber 8 which is communicated to the upper chamber R1 which is the other working chamber via the other-side flow path 6. A free piston 9 that partitions, a spring element 10 that generates a biasing force that suppresses displacement of the free piston 9 with respect to the pressure chamber R3, and a free piston 9 that is mounted on the housing 15 to the lower limit of movement relative to the housing 15 When displaced -It is provided with a resin stopper 16 that abuts on the piston 9 to restrict the displacement of the free piston 9, and is interposed between the vehicle body and the axle of the vehicle to generate a damping force and suppress the vibration of the vehicle body. Is.

  The shock absorber D includes a piston rod 4 that is movably inserted into the cylinder 1. One end of the piston rod 4 is connected to the piston 2, and the upper end that is the other end is not shown. The upper end of the cylinder 1 is slidably supported by an annular head member. Note that the lower end of the cylinder 1 is sealed by a bottom member (not shown).

  The upper chamber R1, the lower chamber R2, and the pressure chamber R3 are filled with a liquid such as hydraulic oil. The lower chamber R2 is slidably contacted with the inner periphery of the cylinder 1 in the lower portion of the cylinder 1 in the figure. A sliding partition wall 13 that partitions the gas chamber G is provided.

  Note that the liquid filled in the upper chamber R1, the lower chamber R2, and the pressure chamber R3, which are the working chambers, may be liquids such as water and an aqueous solution in addition to the working oil.

  Since the shock absorber D is set to a so-called single rod type, the volume of the piston rod 4 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 13 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 13 and the gas chamber G, a reservoir is provided on the outer periphery or outside of the cylinder 1, and the piston rod 4 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.

  In the following, each part will be described in detail. As shown in FIG. 2, the piston rod 4 has a small diameter portion 4a formed at the lower end thereof and a screw portion 4b formed at the distal end side of the small diameter portion 4a. .

  The piston rod 4 is formed with the other-side flow path 6 that opens from the tip of the small diameter portion 4 a and passes through the side of the piston rod 4. In the figure, a valve that serves as a resistor is not provided in the middle of the other-side flow path 6, but a valve such as a throttle may be provided.

  The piston 2 is formed in an annular shape, and the small diameter portion 4a of the piston rod 4 is inserted on the inner peripheral side thereof. Further, the piston 2 is provided with passages 3a and 3b communicating the upper chamber R1 and the lower chamber R2, and the upper end in FIG. 1 of the passage 3a is closed by a laminated leaf valve V1 which is a damping force generating element. The lower end of the other passage 3b in FIG. 1 is also closed by a laminated leaf valve V2 that is a damping force generating element.

  The laminated leaf valves V1 and V2 are both formed in an annular shape, and the small diameter portion 4a of the piston rod 4 is inserted on the inner peripheral side, and annular valve stoppers 21 and 22 for restricting the amount of deflection of the laminated leaf valves V1 and V2. At the same time, it is stacked on the piston 2.

  Then, the laminated leaf valve V1 is bent by the pressure difference between the lower chamber R2 and the upper chamber R1 when the shock absorber D contracts, opens the passage 3a, and moves the liquid that moves from the lower chamber R2 to the upper chamber R1. While providing resistance, the passage 3a is closed when the shock absorber D is extended, and the other laminated leaf valve V2 opens the passage 3b when the shock absorber D is extended, opposite to the laminated leaf valve V1, During the contraction, the passage 3b is closed. That is, the laminated leaf valve V1 is a damping force generating element that generates a compression side damping force when the shock absorber D is contracted, and the other laminated leaf valve V2 generates an extension side damping force when the shock absorber D is extended. It is a damping force generating element. Even when the passages 3a and 3b are closed by the laminated leaf valves V1 and V2, the upper chamber R1 and the lower chamber R2 are communicated with each other by a well-known orifice (not shown). For example, it is formed by providing a notch on the outer periphery of the laminated leaf valves V1, V2 or by providing a recess in the valve seat on which the laminated leaf valves V1, V2 are seated.

  As described above, when the passage is one-way, the passages 3a and 3b may be provided as in the shock absorber D so that the liquid passes only when the shock absorber D is extended or contracted. Also, if the passage allows bidirectional flow, only one may be provided. Furthermore, the damping force generating element can naturally adopt, for example, a configuration in which a choke and a leaf valve are arranged in parallel, or another configuration in addition to a configuration in which an orifice and a leaf valve are arranged in parallel.

  A housing 15 that forms a pressure chamber R3 is screwed onto the screw portion 4b of the piston rod 4 from below the laminated leaf valve V2. The housing 15 allows the piston 2, the laminated leaf valves V1 and V2, and A valve stopper 22 is fixed to the piston rod 4. Thus, the housing 15 not only forms the pressure chamber R3 inside, but also plays a role of fixing the piston 2 to the piston rod 4.

  Next, the housing 15 will be described. As shown in FIG. 2, the housing 15 is a cylindrical shape that is screwed into the screw portion 4 b of the piston rod 4, and includes a nut portion 30 having a flange 31 on the outer periphery, and a bottomed cylindrical housing body 32. The upper end opening in FIG. 2 of the housing main body 32 is crimped toward the outer periphery of the flange 31 and attached to the outer periphery of the flange 31, and the housing main body 32 and the nut portion 30 are integrated. The portion 30 and the housing body 32 define a pressure chamber R3 in the lower chamber R2. In addition, when integrating the nut part 30 and the housing main body 32, it is also possible to employ | adopt other methods, such as welding other than the said crimping process.

  A free piston 9 is slidably inserted into the pressure chamber R3 formed as described above, and the pressure chamber R3 is placed in the other chamber 8 on the upper side and the one chamber 7 on the lower side in FIG. It is partitioned.

  Further, the nut portion 30 includes the flange 31 as described above, and a screw portion 30a is formed on the inner periphery thereof. By screwing the screw portion 30a to the screw portion 4b of the piston rod 4, the housing 15 is attached. The piston rod 4 can be fixed to the small diameter portion 4a.

  The housing main body 32 has a cylindrical portion 32a having a small outer diameter at the lower end in FIG. 2 and a bottom portion 32b, and has a bottomed cylindrical shape. The bottom portion 32b constitutes a part of the one-side flow path 5. A fixed orifice 33 is provided. The cylindrical portion 32 a of the housing body 32 is provided with two variable orifices 34 and 35 communicating with the lower chamber R 2 and the inside of the housing body 32. In addition, the cross-sectional shape of the outer periphery at the small-diameter lower end of the cylindrical portion 32a is a shape other than a perfect circle, for example, a partially cut-out shape or a hexagonal shape, and a tool is applied to the lower end of the cylindrical portion 32a. The housing 15 can be screwed onto the tip of the piston rod 4 by being engaged.

  Further, a cylindrical stopper 16 is accommodated in the one chamber 7 which is in the housing main body 32, and this stopper 16 is made of resin and is fitted to the inner periphery of the cylindrical portion 32 a of the housing main body 32. The housing body 32 is fixed. The material of the stopper 16 may be natural resin or synthetic resin, but in this case, it is preferably soft. When the free piston 9 is displaced to the movement limit to one side which is the lower side in FIG. 2 with respect to the housing main body 32, the stopper 16 abuts on the free piston 9 and further moves to the lower side of the free piston 9. Displacement is regulated. Further, since the stopper 16 is fitted to the inner periphery of the housing main body 32, the stopper 16 does not play in the housing 15, and does not interfere with the coil spring 24 and hinder expansion and contraction of the coil spring 24.

  The free piston 9 is formed in a bottomed cylindrical shape, and is provided at the bottom portion 9b of the cylindrical body portion 9a, the bottom portion 9b closing one end of the cylindrical portion 9a, and the bottom portion 9b in FIG. And a projecting portion 9c that protrudes, an annular groove 9d formed on the outer periphery of the cylindrical portion 9a, and a hole 9e that communicates the annular groove 9d and the one chamber 7 with the inner portion facing the nut portion 30. 9 a is brought into sliding contact with the inner periphery of the housing body 32 and inserted into the pressure chamber R 3, thereby dividing the pressure chamber R 3 into one chamber 7 and the other chamber 8. In this way, the free piston 9 has a bottomed cylindrical shape, so that the axial length of the cylindrical portion 9a can be secured, and the free piston 9 can be reduced in weight without impairing the slidability with respect to the housing 15, Ensuring the spring length and stroke length of coil springs 23 and 24, which will be described later, is facilitated, and an increase in the overall length of the housing 15 can be suppressed.

  Further, in order to apply an urging force that suppresses the displacement of the free piston 9 in proportion to the amount of displacement of the free piston 9 relative to the housing 15, the flange 31 of the nut portion 30 and the free piston 9 are disposed in the other chamber 8. Coil springs 23, 24 as spring elements 10, respectively, between the inner side of the bottom portion 9 b and the inner side of the one chamber 7 and between the bottom portion 32 b of the housing body 32 and the outer side of the bottom portion 9 b of the free piston 9. The free piston 9 is sandwiched from above and below by the spring element 10 composed of the coil springs 23 and 24, and is elastically supported after being positioned at a predetermined neutral position in the pressure chamber R3. . The neutral position does not indicate the center in the axial direction of the housing main body 32 but is a position where the free piston 9 is positioned by the spring element 10.

  As the spring element 10, it is only necessary to elastically support the free piston 9, and other elements than the coil springs 23 and 24 may be employed. For example, the free piston 9 is elastically supported using an elastic body such as a disc spring. You may make it do. Moreover, when using the single spring element 10 with one end connected to the free piston 9, the other end may be fixed to the nut portion 30 or the housing body 32.

  The coil spring 23 is accommodated in the cylindrical portion 9a of the free piston 9, and the coil spring 24 is fitted to the convex portion 9c of the free piston 9 so that both the coil springs 23, 24 are adjusted. The position of the free piston 9 is prevented from being shifted by the core, so that an urging force can be applied to the free piston 9 stably.

  A slight gap is provided between the inner periphery of the cylindrical portion 9a of the free piston 9 and the coil spring 23. When the coil spring 23 is compressed and the winding diameter is expanded, the coil spring 23 The wire does not rub against the inner periphery of the cylindrical portion 9a, thereby preventing the occurrence of contamination.

  Further, as described above, the convex portion 9c has a function of centering the coil spring 24, and its height (length in the vertical direction in FIG. 2) is a height that can sufficiently prevent the coil spring 24 from climbing up. Is set to

  When the free piston 9 is elastically supported by the coil springs 23 and 29 as described above and is in the neutral position, the variable orifices 34 and 35 provided in the cylindrical portion 32a of the housing body 32 are formed in the annular groove 9d of the free piston 9. Oppositely, the one chamber 7 communicates with the lower chamber R2. Further, when the free piston 9 is displaced to the stroke end, that is, until the free piston 9 is displaced until it contacts the lower end in FIG. 2 of the nut portion 30 or the upper end in FIG. 2 of the stopper 16, the variable orifices 34, 35 are the cylindrical portions of the free piston 9. The outer periphery of 9a is completely overlapped and closed. That is, the one-side flow path 5 includes an annular groove 9d, variable orifices 34 and 35, a hole 9e, and a fixed orifice 33. Two variable orifices 34 and 35 are provided, but the number thereof is arbitrary.

  That is, in the case of this specific shock absorber D, when the amount of displacement from the neutral position of the free piston 9 becomes an arbitrary amount of displacement, the cylinders from the situation where all the openings of the variable orifices 34 and 35 face the annular groove 9d. Shifting to a situation where it starts to face the outer periphery of the portion 9a, the flow area of the variable orifices 34, 35 begins to decrease gradually, and the flow resistance in the one-side flow path 5 gradually increases. Therefore, the above-mentioned arbitrary displacement amount is set by setting the vertical width in FIG. 2 of the annular groove 9d and the opening position of the variable orifices 34, 35 on the inner peripheral side of the housing body 32. In this embodiment, as the amount of displacement of the free piston 9 increases, the flow area of the variable orifices 34 and 35 gradually decreases, and when the free piston 9 reaches the stroke ends on both the upper and lower sides, the variable orifice 34 , 35 are completely closed so as to face the cylinder portion 9 a, the flow resistance in the one-side flow path 5 is maximized, and the one chamber 7 is communicated with the lower chamber R 2 only by the fixed orifice 33.

  The shock absorber D is configured as described above. Next, the operation of the shock absorber D will be described.

(A) Operation in the shock absorber D when the amount of displacement from the neutral position in the free piston 9 is within a range in which the variable orifices 34 and 35 do not begin to close. In this case, the piston speed is low, and the free piston 9 The flow path 5 can be displaced without changing the resistance.

  When the input frequency to the shock absorber D is low and high, and the input speed is low, the input amplitude increases when the input frequency is low, and the amplitude of the free piston 9 also changes the variable orifice 34. , 35 within a range not starting to close.

  When the amplitude of the free piston 9 increases within the above range, the free piston 9 is displaced, so that an urging force is exerted by the coil springs 23 and 24 to return the free piston 9 to the neutral position. In accordance with the power, a difference occurs between the pressures of the one chamber 7 and the other chamber 8 in which the volume increases and the volume decreases, and the pressure in the expansion side chamber becomes higher than that in the reduction side chamber.

  Then, the differential pressure between the one chamber 7 and the lower chamber R2 and the differential pressure between the other chamber 8 and the upper chamber R1 become small, and the flow rate passing through the one side flow path 5 and the other side flow path 6 decreases. . As the flow rate passing through the one side channel 5 and the other side channel 6 decreases, the flow rate of the passages 3a and 3b 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 upper chamber R1 to the lower chamber R2 or from the lower chamber R2 to the upper chamber R1 is small, and the movement displacement of the free piston 9 is also small. . Then, the biasing force of the coil springs 23 and 24 received by the free piston 9 is also reduced. Accordingly, the difference between the pressure in the one chamber 7 and the pressure in the other chamber 8 is reduced, and the differential pressure between the one chamber 7 and the lower chamber R2 and the differential pressure between the other chamber 8 and the upper chamber R1 are maintained large. The flow rate passing through the one-side flow channel 5 and the other-side flow channel 6 becomes larger than that at the low frequency, and accordingly, the flow rate in the passages 3a and 3b is reduced, and the damping force generated by the shock absorber D is also reduced. Become.

  Thus, the shock absorber D can generate a large damping force for vibrations in the low frequency range, and can reduce the damping force for vibrations in the high frequency range, depending on the input vibration frequency. A damping force suitable for the vehicle can be generated.

(B) Operation in shock absorber D when the amount of displacement from the neutral position of the free piston 9 is within the range of increasing the channel resistance of the one-side channel 5 In turn, the amount of displacement from the neutral position of the free piston 9 The operation of the shock absorber D when the flow resistance of the one-side flow path 5 is increased by starting to close both the variable orifices 34 and 35 will be described.

  In this case, since the degree of blockage of the variable orifices 34 and 35 proceeds according to the displacement amount of the free piston 9, the one-side passage 5 gradually decreases the passage area according to the displacement amount of the free piston 9, When the free piston 9 reaches the stroke end, the variable orifices 34 and 35 are completely closed, and the flow passage area is made the same as the flow passage area of the fixed orifice 33.

  That is, after the free piston 9 starts to close the variable orifices 38 and 39, the flow resistance of the one-side flow path 5 is gradually increased according to the amount of displacement, and when the free piston 9 reaches the stroke end, the flow resistance Is the maximum.

  Here, the free piston 9 is displaced to the stroke end when the amount of liquid flowing into and out of the one chamber 7 or the other chamber 8 is large. Specifically, when the vibration amplitude of the shock absorber D is large. It is.

  As described above, when the free piston 9 is displaced beyond the position where the variable orifices 34 and 35 start to be closed, the flow resistance of the one-side flow path 5 gradually increases. 9 is further reduced in the moving speed toward the stroke end side, and the amount of liquid movement between the upper chamber R1 and the lower chamber R2 via the pressure chamber R3 is also reduced, and accordingly, the passage passes through the passages 3a and 3b. The amount of liquid increases, and the damping force generated by the shock absorber D gradually increases regardless of the vibration frequency.

  When the free piston 9 reaches the stroke end, the liquid no longer moves between the upper chamber R1 and the lower chamber R2 via the pressure chamber R3, and the liquid passes through the passage 3a until the expansion / contraction direction of the shock absorber D is changed. , 3b only, and the shock absorber D generates a damping force with the maximum damping coefficient regardless of the vibration frequency.

  When the vibration frequency of the shock absorber D is relatively high, the shock absorber D generates a relatively low damping force until the free piston 9 is displaced to a position where it begins to close the variable orifices 34 and 35. When the free piston 9 is displaced beyond the position where it begins to close the variable orifices 34 and 35, the damping force gradually increases, and when the free piston 9 reaches the stroke end, the damping force is generated with the maximum damping coefficient. To do.

  That is, in response to an input of a large amplitude vibration that causes the free piston 9 to be displaced to the stroke end, the amount of displacement from the neutral position of the free piston 9 exceeds an arbitrary amount of displacement and the free piston 9 moves to the stroke end. Since the damping device D gradually increases the generated damping force until it reaches, it does not suddenly change from a low damping force to a high damping force. That is, when the free piston 9 reaches the stroke end and the liquid cannot be exchanged between the pressure chamber R3 and the upper chamber R1 and the lower chamber R2, the magnitude of the damping force does not change suddenly. The damping force change from the damping force to the high damping force becomes 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.

  Then, when a large amplitude vibration is input to the shock absorber D and the free piston 9 reaches the stroke end which is the lower limit of movement in FIG. 2, the free piston 9 collides with the resin stopper 16. Further, since further downward displacement is regulated, the volume of the hitting sound at the time of the collision can be reduced. Therefore, in this shock absorber D, it is not necessary for the vehicle occupant to perceive the percussive sound, and the rider does not feel uneasy or uncomfortable, and the riding comfort in the vehicle can be improved. .

  Note that the stopper 40 may be provided on the free piston 9 side as shown in FIG. 3, as in the shock absorber in one modification of the embodiment. In the shock absorber of this modification, a step 32c is provided on the inner periphery of the cylindrical portion 32a of the housing body 32, and the free piston 9 is displaced to the movement limit on one side which is the lower side in FIG. Then, the stopper 40 fixed to the free piston 9 is brought into contact with the step 32c. Since the rest of the configuration is the same as that of the shock absorber D of the above-described embodiment, the description will be repeated, and only the different parts will be described by omitting the detailed description.

  The stopper 40 is interposed between the free piston 9 and the coil spring 24 and fixed to the free piston 9. The stopper 40 is provided on the outer peripheral side of the fixed portion 41 and provided on the inner periphery of the housing 15. And an abutting portion 42 that abuts against the stepped portion 32c.

  More specifically, the fixed portion 41 is attached to the outer periphery of the convex portion 9c of the free piston 9, and the inner periphery 41a is an insertion portion into which the convex portion 9c is inserted, and is positioned in the radial direction by the free piston 9. Yes. Moreover, since the fixing | fixed part 41 is urged | biased toward the free piston 9 by the coil spring 24 as mentioned above, it fixes especially to the free piston 9 without requiring the addition of another fixing means or components. Can be done.

  The abutting portion 42 includes an annular facing portion 42a that faces the stepped portion 32c, and an annular inclined portion 42b that is inclined from the outer periphery of the fixed portion 41 toward the one chamber 7 and is connected to the facing portion 42a. In this case, the notch 42c is provided in the facing portion 42a so that the communication between the hole 9e and the one chamber 7 can be maintained even if it collides with the stepped portion 32c. When the variable orifices 34 and 35 are closed, the gap formed in the outer periphery of the lower end of the free piston 9 by the stopper 40 and the housing main body 32 is not sealed, so that the displacement of the free piston 9 is not hindered. ing. Instead of providing the notch 42c in the opposed portion 42a, the inclined portion 42b may be provided with a hole, or the inclined portion 42b or the opposed portion 42a may not be formed in an annular shape to avoid sealing the gap.

  The stopper 40 configured in this way is also made of resin, and the volume of the hitting sound is reduced when it hits the stepped portion 32c. Similarly to the shock absorber D of this form, it is not necessary for the vehicle occupant to perceive the percussive sound, and the rider does not feel uneasy or uncomfortable, and the riding comfort in the vehicle can be improved.

  Although the stoppers 16 and 40 are provided on the one chamber 7 side as described above, a resin stopper is provided at the upper end of the cylindrical portion 9a of the free piston 9 in FIGS. When the upper reaches the upper movement limit, the stopper may be brought into contact with the flange 31 of the nut portion 30, or the other chamber 8 side of the flange 31 of the nut portion 30 on the inner periphery of the housing body 32. Alternatively, an annular stopper made of resin may be stacked on the end of the cylinder, and abutted with the upper end of the cylindrical portion 9a of the free piston. In this way, the resin stopper and the free piston 9 or the housing 15 are brought into contact with each other at the upper and lower movement limits of the free piston 9 in the drawing, and the free piston 9 is hit on both the upper and lower sides in the drawing. The volume of the sound may be reduced.

  The housing 15 is provided in the cylinder 1 in the above embodiment, but can be provided outside the cylinder 1.

  For convenience of explanation in the above embodiment, the one chamber 7 is connected to the lower chamber R2 of the shock absorber D, and the other chamber 8 is communicated with the upper chamber R2, but the one chamber 7 is connected to the upper chamber R1. The other chamber 8 may be connected to the lower chamber R2 while being connected.

 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 3a, 3b Channel | path 4 Piston rod 4a Small diameter part 4b in a piston rod Screw part 5 in a piston rod 5 One side flow path 6 The other side flow path 7 One chamber 8 The other chamber 9 Free piston 9a The cylinder part 9b in a free piston Bottom portion 9c in piston Piston portion 9d in free piston Annular groove 9e in free piston Hole 10 in free piston Spring element 13 Sliding partition 15 Housing 16, 40 Stopper 22 Valve stopper 23, 24 Coil spring 30 as spring element Nut portion 30a Nut portion Screw part 31 鍔 32 in the housing body
32a Cylindrical portion 32b in housing body 32b Bottom portion in housing body 32c Stepped portion 33 in housing body Fixed orifice 34, 35 Variable orifice 41 Fixed portion in stopper 42 Abutting portion 42a in stopper Abutting portion 42b in abutting portion Inclined portion in abutting portion 42c Notch D at opposite portion Damper G Gas chamber R1 Upper chamber R2 as the other working chamber Lower chamber R3 as one working chamber Pressure chambers V1, V2 Stacked leaf valve

Claims (6)

A cylinder, a partition member that is slidably inserted into the cylinder and divides the inside of the cylinder into two working chambers, a passage communicating the two working chambers, a housing that forms a pressure chamber, and a slide within the housing A free piston that is freely inserted and divides the pressure chamber into one chamber that communicates with one working chamber via one channel and the other chamber that communicates with the other working chamber via the other channel; A shock absorber including a spring element that generates an urging force that suppresses displacement of the free piston with respect to the housing. The free piston is attached to either the free piston or the housing, and the free piston is attached to one side or the other side of the housing. A resin stopper is provided to restrict the displacement of the free piston by abutting against the free piston or the other housing when displaced to the movement limit on both sides. Buffer and wherein the door. The shock absorber according to claim 1, wherein the stopper is annular and is accommodated in the housing so as to abut the free piston. The shock absorber according to claim 2, wherein the stopper is fitted and fixed to the inner periphery of the housing. The spring element includes a pair of coil springs that are accommodated in the one chamber and the other chamber and sandwich the free piston, and the stopper is interposed between the free piston and the coil spring and is fixed to the free piston. The shock absorber according to claim 1, further comprising an abutting portion that is provided on an outer peripheral side of the fixed portion and abuts on a step portion provided on an inner periphery of the housing. The shock absorber according to claim 4, wherein a convex portion is provided at an end portion of the free piston, and the stopper is provided with an insertion portion into which the convex portion is inserted into the fixed portion, and is positioned on the free piston. The housing is a cylindrical part that is fixed to the piston rod by a partition wall member that is screwed to the piston rod and is fitted to the piston rod. The housing includes a nut portion having a flange on the outer periphery, and extends from the outer periphery of the flange of the nut portion. A pressure chamber is formed by providing a bottomed cylindrical housing main body, and the pressure chamber is divided into one chamber and the other chamber by a free piston slidingly contacting the inner periphery of the housing main body. The shock absorber according to any one of claims 1 to 5.

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