JP2010196842A - Shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shock absorber capable of surely generating high attenuating force relative to an input of vibration in a low-frequency range. <P>SOLUTION: This shock absorber D includes: a cylinder 1; a partitioning member 2 slidably inserted into the cylinder 1 to partition the inside of the cylinder 1 into two operation chambers R1 and R2; passages 2a and 2b communicating the two operation chambers R1 and R2 with each other in the partitioning member 2; a housing 4 connected to the partitioning member 2 and forming a pressure chamber R3; a free piston 9 slidably inserted into the housing 4 to partition the pressure chamber 3 into one chamber 7 communicated with one operation chamber R2 through one side flow passage 5 and the other chamber 8 communicated with the other operation chamber R1 through the other side flow passage 6; and spring elements 18 and 19 for generating energizing force for restricting displacement of the free piston 9 relative to the housing 4. A friction member 20 is provided to restrict displacement of the free piston 9 relative to the housing 4. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

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

  Conventionally, in this kind of shock absorber, a cylinder, a piston that is slidably inserted into the cylinder and 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 passage, a second passage that opens from the tip of the piston rod to the side and communicates with the upper chamber and the lower chamber, and a pressure chamber that is connected to the middle of the second passage are attached to the tip of the piston rod. And a free piston that is slidably inserted into the pressure chamber and divides 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 first passage, and the other chamber in the pressure chamber communicates with the upper chamber through the second 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、図５のボード線図に示したように、Ｆａ＝Ｋ／｛２・π・Ａ^２・（Ｃ１＋Ｃ２＋Ｃ３）｝とＦｂ＝Ｋ／｛２・π・Ａ^２・（Ｃ２＋Ｃ３）｝の２つの折れ点周波数を持ち、また、Ｆ＜Ｆａの領域においては、伝達ゲインは略Ｃ１となり、Ｆａ≦Ｆ≦Ｆｂの領域においてはＣ１からＣ１・（Ｃ２＋Ｃ３）／（Ｃ１＋Ｃ２＋Ｃ３）まで漸減するように変化して、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 during expansion and contraction of the shock absorber 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 passage are C1 is the coefficient in the other chamber, P1 is the pressure in the other chamber, C2 is the coefficient in the relationship between the pressure P1 and the flow rate Q2 of the liquid flowing into the other chamber from the upper chamber, and the pressure in the one 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 to the lower chamber is C3, the cross-sectional area that is the pressure receiving area of the free piston is A, and the displacement of the free piston with respect to the pressure chamber is X. When a transfer function of the differential pressure P with respect to the flow rate Q is obtained with K as the spring constant of the coil spring, Expression (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 characteristic of the transfer function of the differential pressure P with respect to the flow rate Q in this shock absorber is expressed as Fa = K / {2 · π · A ² as shown in the Bode diagram of FIG. (C1 + C2 + C3)} and Fb = K / {2 · π · A ² · (C2 + C3)}, and in the region of F <Fa, the transfer gain is substantially C1, and Fa ≦ In the region of F ≦ Fb, it changes so as to gradually decrease from C1 to C1 · (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 is large in the low frequency region and the transfer gain is small in the high frequency region.

  Therefore, as shown by the damping characteristic X in FIG. 6, this shock absorber generates a large damping force for low-frequency vibration input, and on the other hand, small damping for high-frequency vibration input. Because it is possible to generate force, it is possible to reliably generate high damping force in scenes where the input vibration frequency is low, such as when the vehicle is turning, and in situations where the input vibration frequency is high such that the vehicle gets over the road surface unevenness A low damping force can be reliably generated to improve the riding comfort in the vehicle (see, for example, Patent Document 1).

JP 2006-336816 A (FIG. 2)

  The above-described shock absorber is useful in that it can improve the ride comfort in the vehicle, but has the following problems.

  In the above-described shock absorber, when a higher damping force is to be obtained as in the damping characteristic Y indicated by the alternate long and short dash line in FIG. 6, the differential pressure between the one chamber and the other chamber increases even when vibrating at a low frequency. As shown by the solid line Z in FIG. 6, there is a possibility that the damping force with respect to the vibration frequency drops from the extremely low frequency range to the target damping characteristic Y as shown by the solid line Z in FIG. is there.

  On the other hand, it is conceivable to increase the spring constant of the coil spring, but in this case, it becomes difficult for the free piston to be displaced with respect to the housing, and the damping force does not decrease even in a high frequency range, and the damping force is large. As a result, the original purpose cannot be achieved.

  Therefore, the present invention was devised to improve the above-described problems, and the object of the present invention is to reliably generate a high damping force for the input of vibration in a low frequency range. It is to provide a possible shock absorber.

  In order to solve the above-mentioned object, the problem solving means in the present invention includes a cylinder, a partition member that is slidably inserted into the cylinder and divides the inside of the cylinder into two working chambers, and two working chambers in the partition member. A passage that communicates with the partition wall, a housing that is connected to the partition member and forms a pressure chamber, and is slidably inserted into the housing to communicate the pressure chamber with one working chamber via a one-side flow path. A free piston that divides the one chamber into the other chamber that communicates with the other working chamber via the other-side flow path, and a spring element that generates a biasing force that suppresses the displacement of the free piston with respect to the pressure chamber. In the above shock absorber, friction means for suppressing displacement of the free piston with respect to the housing is provided.

  According to the shock absorber of the present invention, since the displacement of the free piston with respect to the vibration in the low frequency range is suppressed, the damping force drops from the extremely low frequency range, or the damping that is planned in the low frequency range is expected. There is no fear that power cannot be generated.

  In addition, since it is not necessary to increase the spring constant of the spring element that biases the free piston, the free piston does not become difficult to displace with respect to the housing in the high frequency range where the free piston can be displaced. The damping force can be reduced by reducing the damping force.

  That is, in this shock absorber, since the displacement of the free piston with respect to the low-frequency vibration is suppressed, the damping force is prevented from dropping with respect to the low-frequency vibration and reliably high. A damping force can be exhibited, and a low damping force is generated by displacing the free piston with respect to the housing for vibrations in a high frequency range.

  Therefore, the shock absorber can surely generate a low damping force in a scene where the input vibration frequency is high such that the vehicle gets over the unevenness of the road surface, and in a scene where the input vibration frequency is low such as when the vehicle is turning. High damping force can be generated reliably.

  Therefore, according to this shock absorber, a high damping force is generated for vibrations in the low frequency range, and a low damping force is generated for vibrations in the high frequency range, thereby improving the riding comfort in the vehicle. Can do.

  Further, the damping characteristic can be tuned only by setting the friction member, regardless of the setting of the spring element and the management of the fit between the free piston and the housing, and the tuning is greatly simplified.

It is a longitudinal cross-sectional view of the shock absorber in one embodiment. It is an expansion longitudinal cross-sectional view of the piston part of the buffer device in one embodiment. It is a Bode diagram which showed the gain characteristic of the frequency transfer function of the pressure to the flow rate. It is the figure which showed the damping characteristic with respect to the vibration frequency of a buffering device. It is the Bode diagram which showed the gain characteristic of the frequency transfer function of the pressure with respect to the flow volume of the conventional shock absorber. It is the figure which showed the damping characteristic with respect to the vibration frequency of the conventional shock absorber.

  The shock absorber according to the present invention will be described below with reference to the drawings. As shown in FIG. 1 and FIG. 2, the shock absorber D in one embodiment basically includes a cylinder 1 and two working chambers that are slidably inserted into the cylinder 1. Piston 2, which is a partition member that divides the chamber R1 and the lower chamber R2, a piston rod 15 having one end connected to the piston 2, and passages 2a and 2b that are formed in the piston 2 and communicate with the upper chamber R1 and the lower chamber R2. The housing 4 is fixed to the tip of the piston rod 15 to form a pressure chamber R3, and is slidably inserted into the housing 4 so that the pressure chamber R3 passes through the one-side flow path 5 as one working chamber. A free piston 9 that divides into one chamber 7 that communicates with the chamber R2 and another chamber 8 that communicates with the upper chamber R1 that is the other working chamber via the other-side flow path 6, and the inside of the one chamber 7 and the other chamber 8 Each housed in a free A pair of coil springs 18 and 19 that elastically support the stone 9 from both sides are configured, and the upper chamber R1, the lower chamber R2, and the pressure chamber R3 are filled with a liquid such as hydraulic oil. In the case of the shock absorber D, a sliding partition 30 that slidably contacts the inner periphery of the cylinder 1 and divides the lower chamber R2 and the gas chamber G is provided below the cylinder 1 in the figure.

  The upper end of the cylinder 1 is sealed with a head member (not shown) that slidably supports the piston rod 15, and the lower end of the cylinder 1 is also sealed with a bottom member (not shown).

  Hereinafter, each part will be described in detail. The piston rod 15 has a small-diameter portion 15a formed on the lower end side in FIG. 2, and a screw portion 15b formed on the distal end side of the small-diameter portion 15a.

  The piston rod 15 is formed with the other-side flow path 6 that opens from the tip of the small diameter portion 15 a and passes through the side of the piston rod 15. 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 a small diameter portion 15a of the piston rod 15 is inserted on the inner peripheral side thereof. The piston 2 is provided with passages 2a and 2b communicating the upper chamber R1 and the lower chamber R2, and the upper end of the passage 2a in the figure is closed by a laminated leaf valve V1 that is a damping force generating element. The lower end of the passage 2b in the figure is also closed by a laminated leaf valve V2 which is a damping force generating element.

  The laminated leaf valves V1 and V2 are both formed in an annular shape, and a small-diameter portion 15a of the piston rod 15 is inserted on the inner peripheral side, and annular valve stoppers 16 for restricting the amount of deflection of the laminated leaf valves V1 and V2, respectively. 17 and the piston 2 are laminated together.

  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 is contracted to open the passage 2a, and the liquid flow moves from the lower chamber R2 to the upper chamber R1. In addition to providing resistance, the passage 2a is closed when the shock absorber D is extended, and the other laminated leaf valve V2 opens the passage 2b when the shock absorber D is extended, as opposed to the laminated leaf valve V1. During contraction, the passage 2b 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. As described above, when the passage is one-way, the passages 2a and 2b 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.

  A housing 4 that forms a pressure chamber R3 is screwed to the screw portion 15b of the piston rod 15 from below the valve stopper 17, and the piston 2, the laminated leaf valves V1 and V2, and the valve are formed by the housing 4. Stoppers 16 and 17 are fixed to the piston rod 15. Thus, the housing 4 not only forms the pressure chamber R3 inside, but also plays a role of fixing the piston 2 to the piston rod 15.

  The housing 4 will be described. The housing 4 includes an inner cylinder 21 with a flange 22 that is screwed into the screw portion 15 b of the piston rod 15, and a bottomed cylindrical outer cylinder 23. The upper cylinder 23 and the inner cylinder 21 are integrated by caulking the upper end opening in FIG. 2 toward the outer periphery of the flange 22, and the inner cylinder 21 and the outer cylinder 23 define a pressure chamber R3 in the lower chamber R2. It is made. In addition, when integrating the inner cylinder 21 and the outer cylinder 23, it is also possible to employ | adopt other methods, such as welding other than the said crimping process.

  The inner cylinder 21 includes the flange 22 as described above, and a screw portion 21a is formed on the inner periphery thereof. By screwing the screw portion 21a to the screw portion 15b of the piston rod 15, the housing 4 is fixed. The piston rod 15 can be fixed to the small diameter portion 15a. Therefore, if the cross-sectional shape of the outer periphery of the outer cylinder 23 is a shape other than a perfect circle, for example, a shape with a part cut away or a hexagonal shape, the operation of screwing the housing 4 to the tip of the piston rod 15 is performed. It becomes easy.

  Further, the outer cylinder 23 has a small diameter at the lower end in FIG. 1 and a step portion 23b is formed in the cylinder portion 23a, and a fixed orifice constituting a part of the one-side flow path 5 at the bottom portion 23c. 13 is provided.

  A free piston 9 is slidably inserted into the pressure chamber R3 formed by the inner cylinder 21 and the outer cylinder 23, and the pressure chamber R3 is slid by the other side flow path 6 by the free piston 9. The other chamber 8 communicated with the upper chamber R1 and the one chamber 7 communicated with the lower chamber R2 by the fixed orifice 13 are partitioned.

  The free piston 9 is formed in a bottomed cylindrical shape, and is provided at the bottom portion 9c of the cylindrical portion 9a, the bottom portion 9b closing one end of the cylindrical portion 9a, and the bottom portion 9b in FIG. Convex portion 9c projecting toward the outside and annular groove 9d formed on the outer periphery of the cylinder portion 9a. The inner portion is directed to the inner cylinder 21, and the cylinder portion 9a is slidably brought into contact with the inner periphery of the outer cylinder 23. Inserted into the chamber R3, the pressure chamber R3 is partitioned into one chamber 7 and the other chamber 8.

  In the annular groove 9 d of the free piston 9, a square ring 20 that is a friction member that is in sliding contact with the inner periphery of the outer cylinder 23 is mounted, and the free piston 9 is displaced with respect to the outer cylinder 23. The first chamber 7 and the other chamber 8 are restrained by a frictional force and the space between the free piston 9 and the outer cylinder 23 is sealed and the sliding gap between the free piston 9 and the outer cylinder 23 is sealed. Is refused communication. That is, in the case of this embodiment, the friction means is constituted by the square ring 20 which is the friction member described above.

  Further, in order to apply an urging force to the free piston 9 in proportion to the amount of displacement of the free piston 9 relative to the housing 4, the flange 22 of the inner cylinder 21 and the free piston 9 are located in the other chamber 8. Coil springs 18 and 19 are interposed as spring elements between the inside of the bottom portion 9b of the outer cylinder 23 and between the bottom portion 23c of the outer cylinder 23 and the outside of the bottom portion 9b of the free piston 9, respectively. The free piston 9 is sandwiched from above and below by the spring elements of these coil springs 18 and 19, and is elastically supported after being positioned at a predetermined neutral position in the pressure chamber R3.

  As the spring element, it is sufficient that the free piston 9 can be elastically supported, and other elements than the coil springs 18 and 19 may be employed. For example, the free piston 9 may be elastically supported using an elastic body such as a disc spring. It may be. 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 inner cylinder 21 or the outer cylinder 23.

  The lower end of the coil spring 18 in the drawing is fitted to the inner periphery of the deepest portion of the cylindrical portion 9 a of the free piston 9 and is positioned in the radial direction. The coil spring 19 has a convex portion 9 c of the free piston 9 on the inner periphery of the coil spring 19. By being inserted, it is centered to prevent positional displacement with respect to the free piston 9, thereby enabling an urging force to act on the free piston 9 stably.

  Note that the inner circumference of the cylindrical portion 9a of the free piston 9 is expanded in diameter compared to the deepest portion thereof, so that when the coil spring 18 is compressed and the winding diameter is expanded, the wire of the coil spring 18 is cylindrical. There is no rubbing against the inner periphery of the portion 9a, thereby preventing the occurrence of contamination.

  Further, as described above, the convex portion 9c has a function of centering the coil spring 19, and its height (length in the vertical direction in FIG. 2) is set to a height that can sufficiently prevent the coil spring 19 from climbing up. Has been.

  Subsequently, in the case of this embodiment, the above-described free piston 9 includes, in addition to the above-described configuration, an annular recess 9e provided at a position that does not interfere with the annular groove 9d on the outer periphery of the cylindrical portion 9a, and A hole 9f that passes through the thickness of the free piston 9 and communicates with the annular recess 9e and the one chamber 7 is provided.

  Further, two variable orifices 11 and 12 communicating with the lower chamber R2 and the inside of the outer cylinder 23 are provided in the cylinder portion 23a of the outer cylinder 23. In the variable orifices 11 and 12, the free piston 9 is a coil spring 18. , 19 is always in the neutral position and is in communication with the annular recess 9e so that the one chamber 7 communicates with the lower chamber R2, and the free piston 9 is displaced to the stroke end. 1, when it is displaced until it contacts the lower end or the step portion 23b of the outer cylinder 23, it is completely overlapped with the outer periphery of the cylinder portion 9a of the free piston 9 so as to be closed. That is, in this case, the one-side flow path 5 is constituted by the annular recess 9e, the variable orifices 11 and 12, the hole 9f, and the fixed orifice 13. Two variable orifices 11 and 12 are provided, but the number thereof is arbitrary.

  In other words, in the case of the shock absorber D, when the displacement amount from the neutral position of the free piston 9 is an arbitrary displacement amount, the opening of the variable orifices 11 and 12 faces the annular recess 9e from the situation where the cylindrical portion 9a The situation starts to face the outer periphery and the flow area of the variable orifices 11 and 12 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 the figure of the annular recess 9e and the opening position of the variable orifices 11 and 12 on the inner peripheral side of the outer cylinder 23. In this embodiment, as the displacement amount of the free piston 9 increases, the flow area of the variable orifices 11 and 12 gradually decreases, and when the free piston 9 reaches the stroke end, the variable orifices 11 and 12 It is completely closed so as to face the cylinder portion 9a, and the flow resistance in the one-side flow path 5 is maximized so that the one chamber 7 is communicated with the lower chamber R2 only by the fixed orifice 13.

  The sliding partition wall 30 has a recess on the lower chamber R2 side, and when the shock absorber D is contracted to the minimum, the lower end in FIG. 1 that is the tip of the outer cylinder 23 of the housing 4 enters the recess. The loss of the stroke length due to the provision of the housing 4 at the tip of the piston rod 15 in the shock absorber D configured as a single cylinder is caused by the shape of the outer cylinder 23 and the sliding partition wall 30. It will be relieved by the recess.

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

(A) When the displacement amount from the neutral position in the free piston 9 is within a range where the variable orifices 11 and 12 do not begin to be closed. In this case, the free piston 9 is displaced without changing the resistance of the one-side flow path 5. It is possible. And in this free piston 9, the angular ring 20 which is a friction member is attached to the outer periphery, and when the differential pressure between the one chamber 7 and the other chamber 8 is small, the angular ring 20 and the outer cylinder 23 The free piston 9 tries to stay in place without being displaced with respect to the housing 4 due to the frictional force generated between the two chambers. When the differential pressure between the one chamber 7 and the other chamber 8 increases to some extent, the square ring 20 The free piston 9 is displaced with respect to the housing 4 for the first time.

  Therefore, in the state where the free piston 9 is not displaced with respect to the housing 4 and the volumes of the one chamber 7 and the other chamber 8 are not changed, the shock absorber D is configured such that the laminated leaf valves V1 and V2 of the passages 2a and 2b flow in the liquid. A damping force is generated only by the resistance applied to the.

  In the shock absorber D incorporated between the vehicle body and the axle of the vehicle, the pressure difference between the one chamber 7 and the other chamber 8 is generally reduced when the expansion speed of the shock absorber D is low. The frequency of expansion and contraction vibration of the shock absorber D is also lowered. On the other hand, when the frequency of the expansion and contraction vibration of the shock absorber D is high, the expansion and contraction speed of the shock absorber D becomes high, and the differential pressure between the one chamber 7 and the other chamber 8 becomes large.

  That is, the gain characteristics with respect to the frequency of the frequency transfer function of the differential pressure with respect to the flow rate in the shock absorber D until the pressure difference between the one chamber 7 and the other chamber 8 increases to some extent and the free piston 9 starts to move as shown in FIG. In addition, the damping characteristic in the shock absorber D indicating the gain of the damping force with respect to the vibration frequency remains constant and high as shown in FIG. Since the flow rate per unit time depends on the vibration amplitude per unit time of the shock absorber D, the frequency characteristic of the damping characteristic of FIG. 4 is obtained from the gain characteristic shown in FIG. 3 and the pressure receiving area of the piston 2. This attenuation characteristic follows the same locus as the gain characteristic of FIG.

  When the differential pressure between the one chamber 7 and the other chamber 8 is increased to some extent and the free piston 9 starts to move, the gain characteristic with respect to the frequency of the frequency transfer function of the differential pressure with respect to the flow rate in the shock absorber D is shown in FIG. Thus, it gradually decreases and becomes constant in the high frequency range, and the damping characteristic in the shock absorber D also changes as shown in FIG.

  In the description of this embodiment, for the sake of convenience, the differential pressure between the one chamber 7 and the other chamber 8 resists the friction force generated between the square ring 20 serving as the friction member and the outer cylinder 23, thereby causing the free piston 9 to move the housing 4. With reference to the vibration frequency in the shock absorber D when the displacement is large enough to be displaced, the frequency range smaller than the reference vibration frequency is set as the low frequency range, and the frequency range above the reference vibration frequency is set as the high frequency range. However, it is possible to arbitrarily set the reference vibration frequency by appropriately setting the surface pressure and the friction coefficient of the friction member according to the weight and character of the vehicle.

  As described above, in this shock absorber D, the displacement of the free piston 9 with respect to the housing 4 is suppressed with respect to vibrations in the low frequency range, so that the damping force drops from the extremely low frequency range or the low frequency range. There is no fear that the damping force that is planned in the above cannot be generated, and the damping force becomes constant in the low frequency range, and the drop of the damping force is eliminated.

  Further, since it is not necessary to increase the spring constants of the coil springs 18 and 19 as the spring elements, the free piston 9 is not easily displaced with respect to the housing 4 in a high frequency range where the free piston 9 can be displaced. In the high frequency range, the damping force can be reduced to reduce the damping force.

  That is, in this shock absorber D, the displacement of the free piston 9 with respect to the housing 4 is suppressed with respect to vibrations in the low frequency range, so that the fall of the damping force is prevented with respect to the vibrations in the low frequency range. A high damping force can be surely exhibited, and a low damping force is generated by displacing the free piston 9 with respect to the housing 4 for vibrations in a high frequency range.

  Therefore, the shock absorber D can surely generate a low damping force in a scene where the input vibration frequency is high such that the vehicle gets over the unevenness of the road surface, and in a scene where the input vibration frequency is low such as when the vehicle is turning. Can reliably generate a high damping force.

  Therefore, according to this shock absorber D, a high damping force is generated for vibrations in the low frequency range, and a low damping force is generated for vibrations in the high frequency range, thereby improving the riding comfort in the vehicle. be able to.

  Further, if the above-described reference vibration frequency is set to be equal to or lower than the value of the unsprung resonance frequency of the vehicle, the shock absorber D always generates a low damping force when vibration of the unsprung resonance frequency is input. Therefore, the ride comfort in the vehicle is not impaired, and a high damping force can be reliably generated with respect to the vibration input of the sprung resonance frequency, the vehicle posture is stabilized, and the vehicle When turning, it is possible to prevent the passenger from feeling uneasy.

  Further, the static friction coefficient and the dynamic friction coefficient between the friction member and the outer cylinder 23 of the counterpart housing 4 are set regardless of the settings of the coil springs 18 and 19 and the management of the fit between the free piston 9 and the housing 4. Thus, the reference vibration frequency and the sliding resistance when the free piston 9 is displaced can be adjusted, so that the damping characteristic can be tuned only by setting the friction member, and the tuning is greatly simplified. Become.

  Further, in this embodiment, the friction member is a square ring 20 and seals between the free piston 9 and the outer cylinder 23, so that the one chamber 7 and the other chamber 8 are connected to the free piston 9 and the outer cylinder 23. Can be prevented from communicating through the sliding clearance between the two, and it is difficult to be affected by the dimensional tolerances of the free piston 9 and the outer cylinder 23. As a result, it is possible to prevent a situation in which the damping characteristic changes during traveling.

  Further, when the above-described angular ring 20 as the friction member has elasticity, the displacement of the free piston 9 relative to the housing 4 is basically caused by the frictional force with respect to the vibration in the low frequency range as described above. However, the displacement of the free piston 9 with respect to the housing 4 is allowed due to the elastic deformation of the square ring 20. Therefore, when the friction member has elasticity, the displacement of the free piston 9 with respect to the housing 4 is allowed in accordance with the elastic deformation of the friction member in the low frequency range, so that the damping force is remarkably different from the conventional shock absorber. While avoiding falling, it is possible to obtain a damping characteristic in which the damping force slightly decreases as the frequency increases with respect to vibration in the low frequency range, and the tuning range of the damping characteristic is widened, which is more suitable for a vehicle. Attenuation characteristics can be obtained.

  As described above, when it is not necessary to seal between the free piston 9 and the housing 4 with a friction member, the friction member does not necessarily have to be annular, and the friction member in this case is a square ring 20. However, the friction member may be attached to the housing 4 so as to be in sliding contact with the outer periphery of the free piston 9. Specifically, when the friction member is annular, the friction member may be mounted by providing an annular groove on the inner periphery of the outer cylinder 23 of the housing 4.

(B) Operation in the case where the displacement amount from the neutral position of the free piston 9 is within the range in which the flow passage resistance of the one-side flow passage 5 is increased. In turn, the displacement amount from the neutral position of the free piston 9 is variable orifice 11. The operation of the shock absorber D in a case where the flow resistance of the one-side flow path 5 is increased by starting to close both of the first and second flow paths 12 will be described. In the description of this operation, since the free piston 9 is displaced with respect to the housing 4, the operation of the friction member is ignored in order to simplify the description.

  In this case, the variable orifices 11 and 12 gradually reduce the flow passage area in accordance with the amount of displacement of the free piston 9, and are completely closed when the free piston 9 reaches the stroke end so that the flow passage area is fixed to the fixed orifice 13. This is the same as the flow path area.

  That is, after the free piston 9 starts to close the variable orifices 11 and 12, 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.

  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 the free piston 9 begins to close the variable orifices 11 and 12. When the piston 9 is displaced beyond the position where the variable orifices 11 and 12 begin to close, the flow resistance of the one-side flow path 5 gradually increases, so that the stroke beyond that of the free piston 9 increases. The moving speed to the end side is reduced, the amount of liquid movement between the upper chamber R1 and the lower chamber R2 via the pressure chamber R3 is also reduced, and the amount of liquid passing through the passages 2a and 2b is increased accordingly. Thus, the generated damping force of the shock absorber D gradually increases.

  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 2a until the expansion / contraction direction of the shock absorber D is changed. , 2b, the shock absorber D generates a damping force with the maximum damping coefficient.

  That is, even if a high-frequency and large-amplitude vibration that causes the free piston 9 to be displaced to the stroke end is input to the shock absorber D, the amount of displacement from the neutral position of the free piston 9 exceeds an arbitrary amount of displacement. Since the shock absorbing device D gradually increases the generated damping force until the free piston 9 reaches the stroke end, there is no sudden change from a low damping force to a high damping force. In other words, when the free piston 9 reaches the stroke end and the liquid in the pressure chamber R3 and the lower chamber R2 cannot exchange with each other, the magnitude of the damping force does not change suddenly. The change in damping force to damping force becomes gentle. Furthermore, since the generated damping force is gradually increased when the free piston 9 reaches the stroke ends on both ends in the pressure chamber R3, the function of suppressing a sudden change in the damping force is Demonstrated in both strokes.

  Therefore, in this shock absorber D, even if a vibration with a high frequency and a large amplitude is input, the generated damping force changes gently, and the passenger does not perceive a shock due to the change in the damping force. It is possible to improve the ride comfort in the vehicle, and in particular, it is possible to prevent a situation in which the vehicle body vibrates due to a sudden change in damping force and the bonnet resonates and abnormal noise is generated. Can be improved.

  Further, in this shock absorber D, since the urging force for returning the free piston 5 to the neutral position is acting on the free piston 9 by the coil springs 18 and 19, the sudden change in the damping force is suppressed when necessary. It is possible to avoid a situation where the function cannot be performed.

  Further, in this shock absorber D, when the free piston 9 reaches the stroke ends on both ends in the pressure chamber R3, the flow resistance of the one-side flow path 5 is gradually changed to increase, so The function of suppressing a sudden change in damping force does not fluctuate each time the device expands and contracts, and the passenger does not feel uncomfortable.

  In addition, although the shock absorber in each embodiment is configured as a so-called single cylinder type shock absorber, this is a double cylinder type provided with an annular reservoir formed to cover the cylinder outside the cylinder. The shock absorber may be configured as a shock absorber, or may be configured as a shock absorber provided with a completely separate reservoir tank outside the cylinder.

  Furthermore, as the friction means, it is sufficient if the displacement of the free piston 9 with respect to the housing 4 can be suppressed. Therefore, a part or all of the sliding portion outer cylinder 23 of the free piston 9 and the housing 4 is roughened to suppress the displacement. The structure which suppresses the displacement with respect to the housing 4 of the free piston 9 by forming one or both of the free piston 9 and the housing 4 with a material having a particularly large friction coefficient may be employed. Even if it is in the friction member, a member other than the square ring 20 can be used as described above, and if the function as a seal is not required, it is not necessary to surround the entire outer periphery of the free piston 9. It does n’t matter. When it is expected to seal between the free piston 9 and the housing 4, a friction member that is used for sealing purposes such as an O-ring or an annular U-packing may be employed.

 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 present invention can be used, for example, for a shock absorber incorporated between a vehicle body and an axle.

1 Cylinder 2 Piston (partition wall member)
2a, 2b Passage 4 Housing 5 One side flow path 6 Other side flow path 7 One chamber 8 Other chamber 9 Free piston 9a Tube portion 9b in free piston Bottom portion 9c in free piston Protruding portion 9d in free piston Annular groove 9e in free piston Annular recess 9f in the piston Holes 11 and 12 in the free piston Variable orifice 13 Fixed orifice 15 Piston rod 15a Small diameter portion 15b in the piston rod Screw portions 16 and 17 in the piston rod Valve stoppers 18 and 19 Coil spring (spring element)
20 Square ring 21 which is a friction member 21 Inner cylinder 21a in housing 22 Threaded portion 22 in inner cylinder 23 Outer cylinder 23a in housing Outer cylinder 23a in outer cylinder 23c in outer cylinder Step 23c in outer cylinder Bottom 30 in outer cylinder Sliding partition D Buffer Device G Gas chamber R1 Upper chamber R2 as the other working chamber Lower chamber R3 as one of the working chambers 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 that communicates the two working chambers in the partition member; And a housing that is slidably inserted into the housing and communicates with the one working chamber through the one-side flow path and into the other working chamber through the other-side flow path. In a shock absorber provided with a free piston partitioned into the other chamber communicated with, and a spring element that generates a biasing force that suppresses the displacement of the free piston with respect to the housing, friction means for suppressing the displacement of the free piston with respect to the housing is provided. A shock absorber characterized by that. The friction means includes a friction member that is attached to either the outer periphery of the free piston or the inner periphery of the housing and is in sliding contact with the other of the outer periphery of the free piston or the inner periphery of the housing, and the friction member displaces the free piston with respect to the housing. The shock absorber according to claim 1, wherein the shock absorber is suppressed. The shock absorber according to claim 2, wherein the friction member is annular and seals between the free piston and the housing. The shock absorber according to claim 2 or 3, wherein the friction member has elasticity. The shock absorber according to any one of claims 2 to 4, wherein the friction member is an O-ring or a square ring. The housing includes a flanged inner cylinder that fixes to the piston rod a partition wall member that is screwed to the piston rod and is fitted to the piston rod, and a bottomed cylindrical outer cylinder that extends from the outer periphery of the flange. A pressure chamber is formed, and the pressure chamber is divided into one chamber and the other chamber by a free piston that is in sliding contact with the inner periphery of the outer cylinder. Shock absorber.

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