JP2012207750A - Shock absorbing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shock absorbing device which improves comfort in a vehicle even when piston speed is significantly increased.SOLUTION: The shock absorbing device D includes a cylinder 1, a partition wall member 2 which is inserted slidably in the cylinder 1 and divides the inside of the cylinder 1 into an extension side chamber R1 and a compression side chamber R2, a pressure chamber R3, a free piston 9 which divides the pressure chamber R3 into an extension side pressure chamber 7 and a compression side pressure chamber 8, and a spring element 10 which biases the free piston 9. This device is provided with a damping passage 3 which connects the extension side chamber R1 with the compression side chamber R2, an extension side sub damping passage 12, a compression side sub damping passage 13, and a switching mechanism 14.

Description

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

  Conventionally, this type of shock absorber is interposed between the vehicle body and the axle of the vehicle and used for the purpose of suppressing vehicle body vibration. For example, the cylinder and the cylinder can be slid freely. A piston that is inserted and divides the inside of the cylinder into an extension side chamber on the piston rod side and a pressure side chamber on the piston side, a first flow path that communicates the extension side chamber provided on the piston and the pressure side chamber, and opens from the tip of the piston rod to the side part And a second flow passage communicating the extension side chamber and the pressure side chamber, a housing provided with a pressure chamber connected to the middle of the second flow passage and attached to the tip of the piston rod, and slidably inserted into the pressure chamber. A free piston that divides the pressure chamber into an expansion side pressure chamber and a pressure side pressure chamber and a coil spring that urges the free piston are provided. That is, the expansion side pressure chamber is similarly communicated with the expansion side chamber via the second flow path, and the pressure side pressure chamber is communicated with the pressure side chamber via the second flow path.

  In the shock absorber configured as described above, the pressure chamber is divided into the expansion side pressure chamber and the pressure side pressure chamber by the free piston, and the expansion side chamber and the pressure side chamber communicate directly with each other via the second flow path. Although not done, the volume ratio between the expansion side pressure chamber and the compression side pressure chamber changes as the free piston moves, and the fluid in the pressure chamber enters and exits the extension 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 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、図９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, on the basis of the pressure in the compression side chamber, P is the differential pressure between the expansion side chamber and the compression side chamber when the shock absorber is expanded and contracted, Q is the flow rate of the fluid flowing out from the expansion side chamber, and the differential pressure P and the first flow path The coefficient which is the relationship with the flow rate Q1 of the fluid passing through the cylinder is C1, the differential pressure between the compression side chamber and the expansion side pressure chamber is P1, and the difference between the differential pressure P and the differential pressure P1 and the extension side chamber to the extension side pressure chamber The coefficient which is the relationship with the flow rate Q2 of the inflowing fluid is C2, the differential pressure between the pressure side chamber and the pressure side pressure chamber is P2, and the relationship between the differential pressure P2 and the flow rate Q2 of the fluid flowing out from the pressure side pressure chamber to the pressure side chamber Where C is a coefficient, and A is the cross-sectional area that is the pressure receiving area of the free piston, X is the displacement of the free piston with respect to the pressure chamber, K is the spring constant of the coil spring, and the transfer function of the differential pressure P with respect to the flow rate Q is If it calculates | requires, Formula (1) will be 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 approximately 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 increases in the low frequency range, and the transfer gain decreases in the high frequency range.

  Therefore, in this shock absorber, as shown by the damping characteristic in FIG. 10, a high damping force is generated for low frequency vibration input, while a low damping force is generated for high frequency vibration input. In a scene where the input vibration frequency is low, such as when the vehicle is turning, a high damping force can be reliably generated, and in a scene where the vehicle has a high input vibration frequency that passes through the unevenness of the road surface. Can reduce the damping force and improve the riding comfort in the vehicle (see, for example, Patent Document 1).

JP 2008-215459 A

  By the way, if the shock absorber is contracting while the vehicle body is moving upward, or if the shock absorber is extending while the vehicle body is sinking downward, the shock absorber Lowering the damping force generated by the device can suppress vehicle vibration, but conventional shock absorbers always exhibit a high damping force against low-frequency vibrations. In some cases, the vehicle body vibration may be increased and the ride comfort in the vehicle may be deteriorated.

  Accordingly, the present invention has been developed to improve the above-described problems, and an object of the present invention is to provide a shock absorber that can improve the riding comfort in a vehicle.

  In order to solve the above-described 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 cylinder into an extension side chamber and a pressure side chamber, a pressure chamber, A pressure side inserted in the pressure chamber so as to be movable in the axial direction and communicated with the pressure side chamber via the expansion side flow channel and the pressure side chamber via the pressure side flow channel. In a shock absorber comprising: a free piston that is partitioned into a pressure chamber; and a spring element that generates a biasing force that positions the free piston in a neutral position in the pressure chamber and suppresses displacement from the neutral position of the free piston. A damping passage communicating the extension side chamber and the pressure side chamber, an extension side sub-attenuation passage that allows only a flow from the extension side chamber to the pressure side chamber and is arranged in parallel with the attenuation passage, and a pressure side chamber. The pressure side sub-attenuation passage that allows only the flow toward the extension side chamber and the free piston is displaced in the direction of compressing the extension side pressure chamber from a neutral position by a predetermined extension side displacement or more. When the free piston is displaced by a predetermined displacement or more in the direction of compressing the pressure side pressure chamber from the neutral position, the extension side sub damping path is opened and the pressure side sub damping path is opened. And a switching mechanism for blocking the attenuation passage.

  According to the shock absorber of the present invention, the riding comfort in the vehicle can be improved even if the piston speed becomes very high.

It is a longitudinal cross-sectional view of the shock absorber in one embodiment. It is the figure which showed the suspension model of the vehicle to which the conventional shock absorber is applied. It is a figure which shows the correlation with the vehicle body up-down direction speed, the expansion-contraction speed of the conventional buffer, and the displacement of a free piston. 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 a figure showing the structure of the buffering device of one embodiment more concretely. It is a figure explaining the action | operation of the switching mechanism in the state which the free piston displaced to the direction which compresses an expansion side pressure chamber. It is a figure explaining the action | operation of the switching mechanism in the state which the free piston displaced to the direction which compresses a pressure side pressure chamber. 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.

  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 2 as a partition member that is slidably inserted into the cylinder 1 and partitions the cylinder 1 into an expansion side chamber R1 and a compression side chamber R2. The pressure chamber R3, the expansion side pressure chamber 7 inserted into the pressure chamber R3 so as to be movable in the axial direction, and communicated with the expansion side chamber R1 through the expansion side channel 5 and the pressure side channel 6 are connected. A free piston 9 that is divided into a pressure side pressure chamber 8 that communicates with the pressure side chamber R2 via the pressure side, and an urging force that positions the free piston 9 at the neutral position in the pressure chamber R3 and suppresses displacement from the neutral position of the free piston 9 , A damping passage 3 communicating the extension side chamber R1 and the compression side chamber R2, and only a flow from the extension side chamber R1 toward the compression side chamber R2 and allowing the extension side sub-attenuation parallel to the attenuation passage 3 Extend from passage 12 and compression side chamber R2 A compression side sub damping passage 13 which is parallel to the damping passage 3 while permitting flow only toward the chamber R1, and is configured with a switching mechanism 14. The shock absorber D 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. The expansion side chamber R1 is a chamber that is compressed when the vehicle body and the axle are separated and the shock absorber D is extended, and the compression side chamber R2 is a state where the vehicle body and the axle are close to each other and the shock absorber D is A chamber that is compressed when contracted.

  The extension side chamber R1, the pressure side chamber R2, and further the pressure chamber R3 are filled with fluid such as hydraulic fluid, and the pressure side chamber R2 is in sliding contact with the inner periphery of the cylinder 1 in the lower part of the cylinder 1 in the figure. And a gas partition wall 15 are provided. In addition to the hydraulic fluid, for example, a fluid such as water or an aqueous solution can be used as the fluid filled in the extension side chamber R1, the pressure side chamber R2, and the pressure chamber R3.

  The piston 2 is connected to one end of a piston rod 4 that is movably inserted into the cylinder 1, and the piston rod 4 protrudes outward from the upper end of the cylinder 1 in the figure. In addition, between the piston rod 4 and the cylinder 1, the inside of the cylinder 1 is in a liquid-tight state with a seal (not shown). 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 15 is expanded or contracted to be compensated by 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 4 is provided by the reservoir. Volume compensation may be performed. When the fluid filling the expansion side chamber R1, the pressure side chamber R2, and the pressure chamber R3 is a gas, the gas chamber G and the reservoir can be omitted. Further, the shock absorber D may be set to a double rod type instead of a single rod type.

  Further, the damping passage 3 allows only the flow of fluid from the expansion side chamber R1 to the compression side chamber R2, and gives resistance to the flow of the passing fluid, and the flow of fluid from the compression side chamber R2 to the expansion side chamber R1. The piston 2 is provided with a compression-side damping passage 3b that allows only the flow of fluid and allows resistance to the flow of the passing fluid.

  More specifically, damping valves 16a and 16b are provided in the extension side damping passage 3a and the pressure side damping passage 3b, and the damping valves 16a and 16b are added to the flow of fluid passing through the extension side damping passage 3a and the compression side damping passage 3b. Can be given resistance. Although not shown in detail, the damping valve 16a also functions as a check valve, and the extension side damping passage 3a is set as a one-way passage that allows only the flow of fluid from the extension side chamber R1 to the compression side chamber R2. The damping valve 16b also functions as a check valve, and the pressure side damping passage 3b is set as a one-way passage that allows only the flow of fluid from the pressure side chamber R2 to the extension side chamber R1. That is, when the damping device D expands and contracts, considering a case where a damping force is generated only through the extension side damping passage 3a and the compression side damping passage 3b, the fluid passes only through the extension side damping passage 3a during the extension operation. During the contraction operation, only the fluid passes through the compression side damping passage 3b. The damping valves 16a and 16b may have, for example, a known configuration in which an orifice and a leaf valve are arranged in parallel. For example, a configuration in which a choke and a leaf valve are arranged in parallel or other configurations are adopted. If a check valve is separately provided, it is also possible to employ a valve that allows bidirectional fluid passage.

  In this embodiment, the pressure chamber R3 is formed by a hollow portion 17a connected to the lower side of the piston 2 and provided in the housing 17 facing the pressure side chamber R2, and is slid on the side wall of the hollow portion 17a. The pressure chamber R3 is moved upward and downward in FIG. 1 and the pressure side pressure chamber in the lower part of FIG. It is divided into eight. That is, the free piston 9 is slidably inserted into the housing 17 and can be displaced with respect to the housing 17 in the axial direction which is the vertical direction in FIG.

  The free piston 9 is connected to the lower end of the hollow portion 17a and connected to the other end of the spring element 10 accommodated in the pressure side pressure chamber 8, whereby the free piston 9 is connected to the pressure chamber R3. When displaced from a position positioned at a predetermined position (hereinafter simply referred to as “free piston neutral position”), an urging force proportional to the amount of displacement is applied from the spring element 10. Note that the above-described free piston neutral position is a position where the free piston 9 is positioned by the spring element 10 with respect to the pressure chamber R3, and does not necessarily have to be set at an intermediate point in the vertical direction of the hollow portion 17a.

  Note that the housing 17 is divided into an expansion side pressure chamber 7 and a compression side pressure chamber 8 up and down by a free piston 9 and the vibration direction and the movement direction of the free piston 9 are suppressed by the shock absorber D, as shown in the figure. If the entire shock absorber D vibrates in the vertical direction in FIG. 1 to avoid exciting the vertical vibration of the free piston 9 relative to the housing 17, the movement of the free piston 9 The direction can be set to a direction orthogonal to the expansion / contraction direction of the shock absorber D, that is, the left-right direction in FIG. 1, and the expansion-side pressure chamber 7 and the compression-side pressure chamber 8 can be arranged in the lateral direction in FIG.

  Further, the housing 17 is provided with a pressure-side flow path 6 that communicates the pressure-side chamber R2 and the pressure-side pressure chamber 8, and the pressure-side flow path 6 is provided with a restrictor 6a for fluid passing therethrough. It is possible to give resistance to the flow. The throttle 6a may be a variable throttle that reduces the opening area as the free piston 9 is displaced from the neutral position. In this case, the free piston 9 contacts the upper end of the housing 17 or the spring element 10. As the stroke end approaches the compression state, the displacement speed of the free piston 9 can be reduced.

  Further, the extension side chamber R1 and the extension side pressure chamber 7 are opened from the side of the piston rod 4 facing the extension side chamber R1 and communicated with each other via the extension side flow path 5 passing through the piston 2 and the housing 17. In this way, the expansion side chamber R1 and the expansion side pressure chamber 7 are communicated by the expansion side flow channel 5, and are communicated by the compression side chamber R2, the compression side pressure chamber 8, and the compression side flow channel 6, and the expansion side pressure chamber 7 and the compression side pressure chamber 8 is changed by the displacement of the free piston 9 within the housing 17, in the shock absorber D, the expansion side flow path 5, the expansion side pressure chamber 7, the pressure side pressure chamber 8, and the pressure side flow are described above. A flow path formed by the path 6 apparently communicates the expansion side chamber R1 and the compression side chamber R2, and the expansion side chamber R1 and the compression side chamber R2 are formed by the expansion side attenuation passage 3a and the compression side attenuation passage 3b constituting the attenuation passage 3. In addition, communication is also performed by the above-described apparent flow path.

  Here, as shown in FIG. 2, a suspension model in which a conventional shock absorber disclosed in Japanese Patent Laid-Open No. 2008-215459 that does not include a switching mechanism 14 is interposed between a vehicle body and an axle is considered. In FIG. 2, M2 is the sprung member in the vehicle, K2 is the suspension spring, Do is the conventional shock absorber without the switching mechanism 14, M1 is the unsprung member in the vehicle, and K1 is the tire that behaves as a spring. Is positive. When a sine wave is input to the suspension model of FIG. 2 from the lower end of the tire K1 on the road surface side, the vertical speed of the sprung member M2 serving as the vehicle body, the expansion / contraction speed of the shock absorber Do, and the displacement of the free piston are shown in FIG. As shown. Note that the displacement of the free piston is positive for the displacement that compresses the compression side pressure chamber. In FIG. 3, the solid line indicates the vertical speed of the vehicle body, the broken line indicates the expansion / contraction speed of the shock absorber Do, and the alternate long and short dash line indicates the displacement of the free piston. In the graph of FIG. 3, when the amount of displacement by which the free piston compresses the compression-side pressure chamber or the expansion-side pressure chamber from the neutral position is large, the vertical speed of the vehicle body does not match the direction of the expansion / contraction speed of the shock absorber Do. I understand that.

  More specifically, when the free piston is largely displaced from the neutral position in the direction of compressing the expansion side pressure chamber, the vertical speed of the vehicle body is generally positive and the expansion / contraction speed of the shock absorber Do is negative ( When the free piston is greatly displaced from the neutral position in the direction of compressing the pressure side pressure chamber, the vertical speed of the vehicle body is generally negative and the expansion / contraction speed of the shock absorber Do is positive. (Region y in FIG. 3).

  Therefore, the inventors reduce the damping force in the contraction direction of the shock absorber D and reduce the damping force in the extension direction when the free piston 9 is greatly displaced from the neutral position in the direction of compressing the expansion side pressure chamber. On the contrary, when the free piston 9 is greatly displaced from the neutral position in the direction of compressing the compression side pressure chamber, the damping force in the expansion direction of the shock absorber D is lowered and the damping force in the contraction direction is increased. Then, it came to know that the problem of vibrating the vehicle body with the damping force of the shock absorber D could be solved.

  Therefore, in the shock absorber D of the present invention, when the free piston 9 is largely displaced from the neutral position in the direction of compressing the expansion side pressure chamber, the damping force in the contraction direction of the shock absorber D is lowered and the damping force in the extension direction is reduced. On the contrary, when the free piston 9 is greatly displaced from the neutral position in the direction of compressing the compression side pressure chamber, the damping force in the expansion direction of the shock absorber D is lowered and the damping force in the contraction direction is increased. Further, an extension side sub-attenuation passage 12, a pressure side sub-attenuation passage 13, and a switching mechanism 14 are provided.

  In this embodiment, the extension-side sub-attenuation passage 12 and the pressure-side sub-attenuation passage 13 both lead from the extension-side chamber side end at the upper end in FIG. 1 to the pressure-side chamber side end at the lower end in FIG. The extension side chamber R1 and the compression side chamber R2 communicate with each other.

  Specifically, the extension side sub-attenuation passage 12 includes an extension side sub valve 12a in the middle. The expansion side sub-valve 12a can provide resistance to the flow of fluid passing through the expansion side sub-attenuation passage 12, and in this example, only the flow of fluid from the expansion side chamber R1 to the compression side chamber R2. The extension-side sub-attenuation passage 12 is set as a one-way passage. The resistance given to the passage fluid by the extension side sub-valve 12a may be larger or smaller than the resistance given to the passage fluid by the damping valve 16a provided in the extension side attenuation passage 3a. Since the expansion side attenuation passage 3a and the expansion side sub attenuation passage 12 are connected in parallel to the expansion side chamber R1 and the compression side chamber R2, the expansion side sub attenuation passage 12 is opened when the shock absorber D is extended. Then, the fluid passes through the expansion side sub attenuation passage 12 in addition to the expansion side attenuation passage 3a and moves from the expansion side chamber R1 to the compression side chamber R2. Therefore, the damping force generated by the shock absorber D is lower when the extension side sub-attenuation passage 12 is opened than when the fluid passes only through the extension-side attenuation passage 3a.

  The other pressure side sub-attenuation passage 13 is also provided with a pressure side sub valve 13a in the middle. The pressure side subvalve 13a can provide resistance to the flow of fluid passing through the pressure side subattenuation passage 13, and in this example, allows only the flow of fluid from the pressure side chamber R2 toward the extension side chamber R1. The pressure-side sub-attenuation passage 13 is set as a one-way passage. The resistance given to the passing fluid by the pressure side sub-valve 13a may be larger or smaller than the resistance given to the passing fluid by the damping valve 16b provided in the pressure side damping passage 3b. Since the compression side damping passage 3b and the compression side sub damping passage 13 communicate in parallel with the expansion side chamber R1 and the compression side chamber R2, when the compression device D is contracted, the compression side sub damping passage 13 is opened. The fluid passes through the compression side sub-attenuation passage 13 in addition to the compression side attenuation passage 3b and moves from the compression side chamber R2 to the expansion side chamber R1. Therefore, the damping force generated by the shock absorber D is lower when the pressure side sub-attenuation passage 13 is opened than when the fluid passes only through the pressure-side attenuation passage 3b.

  The extension side sub-valve 12a and the pressure side sub-valve 13a may have, for example, a well-known configuration in which an orifice and a leaf valve are arranged in parallel. In addition to this configuration, for example, a configuration in which a choke and a leaf valve are arranged in parallel or other The configuration can also be adopted, and if a check valve is separately provided, it is possible to adopt a valve that allows bidirectional fluid passage.

  The switching mechanism 14 is provided in the middle of the expansion side sub-attenuation passage 12 and the compression side sub-attenuation passage 13. A switching spool 18 provided in the middle of the expansion side sub-attenuation passage 12 and the pressure side sub-attenuation passage 13, and a switching spool 18. And a connecting lever 19 that connects the free piston 9 to each other. The switching spool 18 includes an extension side position 18b that is taken when the free piston 9 is displaced by a predetermined extension side displacement or more in the direction of compressing the extension side pressure chamber 7 from the neutral position, and the free piston 9 from the neutral position to the compression side pressure chamber 8. A pressure side position 18c taken when the displacement of the free piston 9 is more than a predetermined pressure side displacement in the compression direction, and a neutral position 18a taken when the displacement from the neutral position of the free piston 9 does not reach the extension side displacement and the pressure side displacement. Further, it is configured as a 4-port 3-position switching valve.

  The switching spool 18 shuts off both the extension side sub-attenuation passage 12 and the compression side sub-attenuation passage 13 when taking the neutral position 18a, and cuts off the extension side sub-attenuation passage 12 when taking the extension side position 18b. At the same time, the compression-side sub-attenuation passage 13 is opened, and when the compression-side position 18c is adopted, the expansion-side sub-attenuation passage 12 is opened and the compression-side sub-attenuation passage 13 is blocked.

  The switching mechanism 14 shuts off the extension side sub-attenuation passage 12 and opens the pressure side sub-attenuation passage 13 when the free piston 9 is displaced from the neutral position in a direction of compressing the extension side pressure chamber 7 by a predetermined extension side displacement or more. When the free piston 9 is displaced from the neutral position in the direction of compressing the pressure side pressure chamber 8 by a predetermined pressure side displacement or more, the extension side sub-attenuation passage 12 may be opened and the pressure side sub-attenuation passage 13 may be shut off. A configuration other than the above configuration can also be adopted. For example, an on-off valve that opens and closes the expansion side sub-attenuation passage 12 and an on-off valve that opens and closes the compression side sub-attenuation passage 13 are provided independently. It may be interlocked with the piston 9. In addition, the predetermined extension side displacement and the predetermined compression side displacement described above can be arbitrarily set.

  Further, if a spring for biasing the switching spool 18 toward the free piston 9 is provided so that the connecting lever 19 always abuts on the free piston 9, the connecting lever 19 and the free piston 9 are integrally connected. In this case, since the free piston 9 and the switching spool 18 are interposed between the spring for energizing the switching spool 18 and the spring element 10, the spring and the spring element 10 are disposed. A spring element that positions the free piston 9 at the neutral position may be configured.

  Next, the basic operation of the shock absorber D will be described.

(A) Operation of the shock absorber D in a state where the displacement from the neutral position of the free piston 9 does not reach the above-described predetermined extension side displacement and compression side displacement. In this case, the switching mechanism 14 takes the neutral position 18a and extends the extension side. The sub-attenuation passage 12 and the pressure side sub-attenuation passage 13 are blocked. In this state, when the shock absorber D exhibits an expansion / contraction operation in which the piston 2 moves up and down in FIG. 1 with respect to the cylinder 1, one of the expansion side chamber R1 and the compression side chamber R2 is compressed by the piston 2, and the expansion side chamber R1 and the compression side chamber are compressed. Since the other of R2 is expanded, the pressure of the expansion side chamber R1 and the compression side chamber R2 that is compressed increases, and at the same time, the pressure of the expansion side chamber R1 and the compression side chamber R2 whose volume is expanded decreases and both A differential pressure is generated in the expansion side chamber R1 and the compression side chamber R2. The compression side fluid is the attenuation passage 3 (the expansion side attenuation passage 3a and the compression side attenuation passage 3b), and in addition to this, the expansion side passage 5 and the expansion side It moves to the expansion side of the expansion side chamber R1 and the pressure side chamber R2 via an apparent flow path consisting of the pressure chamber 7, the pressure side pressure chamber 8, and the pressure side flow path 6.

  Here, the piston speed in the expansion stroke of the shock absorber D is the same regardless of whether the vibration frequency input to the shock absorber D, that is, the vibration frequency in the expansion / contraction direction of the shock absorber D is low or high. In this case, the amplitude of the shock absorber D at the time of low frequency vibration input is larger than the amplitude of the shock absorber D at the time of high frequency vibration input. In this way, when the frequency of vibration input to the shock absorber D is low, the amplitude is large, so that the flow rate of the fluid passing through the expansion side chamber R1 and the compression side chamber R2 in one expansion / contraction cycle increases. Although the displacement of the free piston 9 increases substantially in proportion to the flow rate, the free piston 9 is biased by the spring element 10, so that when the displacement of the free piston 9 increases, the spring element received by the free piston 9 The urging force from 10 also increases, and accordingly, a differential pressure is generated between the pressure in the expansion side pressure chamber 7 and the pressure in the compression side pressure chamber 8, and the differential pressure between the expansion side chamber R1 and the expansion side pressure chamber 7 and the pressure side chamber R2 The differential pressure in the pressure side pressure chamber 8 is reduced, and the flow rate passing through the apparent flow path is reduced. Since the flow rate of the damping passage 3 is increased by the small flow rate passing through the apparent flow path, the damping force generated by the shock absorber D is maintained high.

  Conversely, when high-frequency vibration is input to the shock absorber D, the amplitude is smaller than when low-frequency vibration is input. Therefore, the flow rate of the fluid flowing between the expansion side chamber R1 and the compression side chamber R2 in one expansion / contraction cycle is small and the free piston 9 The moving displacement is also reduced. Then, the biasing force is also reduced from the spring element 10 received by the free piston 9. Accordingly, the pressure in the expansion side pressure chamber 7 and the pressure in the compression side pressure chamber 8 become substantially equal, and the differential pressure between the expansion side chamber R1 and the expansion side pressure chamber 7 and the differential pressure between the compression side chamber R2 and the compression side pressure chamber 8 are low frequency. It becomes larger than that at the time of vibration input, and the flow rate passing through the above apparent flow path is increased compared to that at the time of low frequency vibration input. As the flow rate passing through the apparent flow path increases, the flow rate of the damping passage 3 decreases, so that the damping force generated by the shock absorber D is reduced from the damping force at the time of low frequency vibration input. Lower.

  As described above, when the piston speed is low, the gain characteristic with respect to the frequency of the frequency transfer function of the differential pressure with respect to the flow rate is the characteristic as shown in FIG. In addition, the damping force characteristic of the shock absorber D indicating the gain of the damping force with respect to the input of the vibration frequency generates a high damping force for the vibration in the low frequency range as shown in FIG. The damping force can be lowered with respect to the vibration, and the change in the damping force of the shock absorber D can be made dependent on the input vibration frequency. Even in the contraction stroke of the shock absorber D, a high damping force is generated for vibrations in the low frequency range and a damping force is low for vibrations in the high frequency range, as in the above-described expansion stroke. And the change of the damping force of the shock absorber D can be made to depend on the input vibration frequency. 5 is set to a value greater than the value of the sprung resonance frequency of the vehicle and equal to or less than the value of the unsprung resonance frequency of the vehicle, and a larger value is taken. By setting the frequency Fb to be equal to or lower than the unsprung resonance frequency of the vehicle, the shock absorber D can generate a high damping force with respect to the vibration input of the sprung resonance frequency and stabilize the posture of the vehicle. When turning the vehicle, it is possible to prevent the passenger from feeling uneasy, and when vibration of the unsprung resonance frequency is input, the damping force is always reduced and a low damping force is generated. The transmission of vibration to the vehicle body side can be insulated to improve the riding comfort in the vehicle.

(B) Operation of the shock absorber D in a state where the displacement from the neutral position of the free piston 9 reaches the predetermined extension side displacement and pressure side displacement described above In this case, the piston speed of the shock absorber D is high and the amplitude is large, A large flow rate flows into the expansion side pressure chamber 7 or the compression side pressure chamber 8 and the free piston 9 is greatly displaced from the neutral position, and the stroke margin to the stroke end is reduced. Since the alternating current of the fluid in the extension side chamber R1 and the compression side chamber R2 is reduced through the flow path, the effect of reducing the damping force with respect to the input of the high frequency vibration is reduced.

  However, when the free piston 9 is displaced in this way, the switching mechanism 14 shuts off the expansion side sub-attenuation passage 12 when the free piston 9 is displaced from the neutral position in the direction of compressing the expansion side pressure chamber 7. When the compression side sub-attenuation passage 13 is opened and the free piston 9 is displaced from the neutral position in the direction of compressing the compression side pressure chamber 8, the extension side sub-attenuation passage 12 is opened and the compression side sub-attenuation passage 12 is opened. The attenuation passage 13 is blocked.

  In the state where the switching mechanism 14 blocks the expansion side sub-attenuation passage 12 and opens the compression side sub-attenuation passage 13, when the shock absorber D performs the expansion operation, the fluid in the expansion side chamber R1 is only the expansion side attenuation passage 3a. The shock absorber D generates a high damping force because it moves from the pressure side chamber R2 to the pressure side chamber R2. In this state, when the shock absorber D performs a contracting operation, the pressure side sub-attenuation passage 13 is opened, so that the fluid in the pressure side chamber R2 not only passes through the pressure side attenuation passage 3a but also the pressure side sub attenuation passage 13. Since it moves to the extension side chamber R1, the shock absorber D generates a low damping force.

  On the contrary, in the state where the switching mechanism 14 opens the expansion side sub-attenuation passage 12 and blocks the compression side sub-attenuation passage 13, when the shock absorber D performs the expansion operation, the expansion side sub-attenuation passage 12 is opened. Therefore, the fluid in the extension side chamber R1 moves to the compression side chamber R2 via the extension side attenuation passage 3a and the extension side sub-attenuation passage 12, so that the shock absorber D generates a low damping force. In this state, when the shock absorber D is contracted, the pressure side sub-attenuation passage 13 is blocked, so that the fluid in the pressure side chamber R2 moves to the expansion side chamber R1 only through the pressure side attenuation passage 3b. Generates a high damping force.

  Thus, when the free piston 9 is largely displaced from the neutral position in the direction of compressing the expansion side pressure chamber, the shock absorber D lowers the damping force in the contraction direction and increases the damping force in the extension direction. In addition, when the free piston 9 is greatly displaced from the neutral position in the direction of compressing the compression side pressure chamber, the damping force in the expansion direction is lowered and the damping force in the contraction direction is increased.

  In general, in Skyhook control, the shock absorber effectively suppresses vibration of the vehicle body by causing the shock absorber to exert a force obtained by multiplying the vertical speed of the vehicle body by the Skyhook damping coefficient. Therefore, if the vertical speed of the vehicle body and the direction of the expansion / contraction speed of the shock absorber are different, the vibration generated by the shock absorber is reduced to promote the vibration of the car body. Do not. On the other hand, as can be understood from the above, the shock absorber D exhibits a low damping force in a state where the vertical speed of the vehicle body and the direction of the expansion / contraction speed are different, and the vertical speed of the vehicle body and the direction of the expansion / contraction speed. Since the high damping force is exhibited in the state where the two are in agreement, the damping force is exhibited as if the shock absorber is controlled using the skyhook control.

  In other words, the shock absorber D can behave as a skyhook damper in a state where the displacement from the neutral position of the free piston 9 reaches the above-described predetermined extension side displacement and compression side displacement, and the damping force exerted by the shock absorber D is reversed. In the situation where the vehicle is vibrated, the damping force can be lowered to suppress the vibration of the vehicle body, and the riding comfort in the vehicle can be improved.

  In addition, in this shock absorber D, which acts as a skyhook damper, it is only necessary to switch the life and death of the expansion side sub-attenuation passage 12 and the compression side sub-attenuation passage 13 by interlocking the switching mechanism 14 with the operation of the free piston 9. A sensor that detects speed and acceleration is attached to the vehicle body and the shock absorber D, a damping force adjustment valve is provided, and it is not necessary to control the damping force adjustment valve by using an expensive control device. can do.

  Further, in a situation where the shock absorber D does not need to behave as a skyhook damper, the damping force can be reduced when the input vibration frequency becomes high. The transmission of the side vibration to the vehicle body side can be insulated to improve the riding comfort in the vehicle.

  As the predetermined extension side displacement and compression side displacement from the neutral position of the free piston 9 are reduced, the damping force changes depending on the frequency described in (a) of the operation of the above-described shock absorber D. The operation as a skyhook damper (skyhook operation) described in (b) appears more preferentially than the operation (frequency sensitive operation). On the contrary, the larger the frequency, the more frequency sensitive operation than the skyhook operation. Will appear preferentially. Therefore, it is preferable that the shock absorber D exhibits an operation suitable for the vehicle by tuning the predetermined extension side displacement and compression side displacement according to the characteristics of the vehicle.

  The basic structure of the shock absorber D has been described above. Hereinafter, the shock absorber D1 with a more specific structure will be described.

  As shown in FIG. 6, the specific shock absorber D1 basically includes a cylinder 21 and a partition member that is slidably inserted into the cylinder 21 and partitions the cylinder 21 into an extension side chamber R4 and a pressure side chamber R5. A piston 22, a pressure chamber R 6, an extension side pressure chamber 27 that is inserted into the pressure chamber R 6 so as to be movable in the axial direction, and communicates with the extension side chamber R 4 via the extension side channel 25. Displacement from the neutral position of the free piston 29 by positioning the free piston 29 in the pressure chamber R6 to the neutral position and the free piston 29 that is partitioned into the pressure side pressure chamber 28 that communicates with the pressure side chamber R5 via the pressure side flow path 26 The spring element 30 that generates an urging force that suppresses the pressure, the damping passage 31 that communicates the extension side chamber R4 and the compression side chamber R5, and only the flow from the extension side chamber R4 to the pressure side chamber R5 are allowed and parallel to the damping passage 31. Ru The side sub damping passage 32, the compression side sub damping passage 33 which is parallel to the damping passage 31 while allowing only flow from the compression side chamber R5 to expansion side chamber R4, it is configured to include a switching mechanism 34. Although not shown in the drawing, similarly to the shock absorber D shown in FIG. 1, a sliding partition is provided below the cylinder 21 and a gas chamber is provided.

  Hereinafter, each part will be described in detail. The piston rod 23 has a small-diameter portion 23a formed on the lower end side in FIG. 6 and a screw portion 23b formed on the distal end side of the small-diameter portion 23a.

  The piston rod 23 is provided with a bag hole-shaped valve hole 35 that opens from the tip of the small-diameter portion 23a, and the bottom side of the valve hole 35 is formed by a communication hole 36 that opens from the side of the piston rod 23. It communicates with the extension side chamber R4.

  The piston 22 is formed in an annular shape, and a small diameter portion 23a of the piston rod 23 is inserted on the inner peripheral side thereof. Further, the piston 22 is provided with an expansion side port 31a and a compression side port 31c for communicating the expansion side chamber R4 and the pressure side chamber R5, and the lower end of the expansion side port 31a in FIG. 6 is stacked below the piston 22 in FIG. 6 is opened / closed by the expansion side valve 31b, which is a leaf valve, and the upper end in FIG. 6 of the other pressure side port 31c is also opened / closed by the pressure side valve 31d, which is a leaf valve stacked above the piston 22 in FIG.

  Both the expansion side valve 31b and the pressure side valve 31d are formed in an annular shape, the small diameter portion 23a of the piston rod 23 is inserted on the inner peripheral side, the inner peripheral side is fixed to the piston rod 23, and the outer peripheral side is allowed to bend. Are stacked on the piston 22. Note that the number and thickness of the leaf valves constituting the extension side valve 31b and the pressure side valve 31d can be arbitrarily changed according to desired damping characteristics.

  The expansion side valve 31b is a fluid that is bent and opened by the differential pressure between the expansion side chamber R4 and the compression side chamber R5 when the shock absorber D1 is extended, opens the expansion side port 31a, and moves from the expansion side chamber R4 to the compression side chamber R5. In addition, the expansion side port 31a is closed during the contraction operation of the shock absorber D1, and the expansion side port 31a is set to be one-way. The other pressure side valve 31d opens the pressure side port 31c when the shock absorber D1 is contracted, and closes the pressure side port 31c when the shock absorber D1 is contracted, and makes the pressure side port 31c one-way. It is set. That is, the expansion side valve 31b is a damping force generating element that generates an expansion side damping force during the expansion operation of the shock absorber D1, and the other compression side valve 31d generates a compression side damping force during the contraction operation of the shock absorber D. It is a damping force generating element. Therefore, in this embodiment, the attenuation passage 31 includes the expansion side port 31a, the expansion side valve 31b, the compression side port 31c, and the compression side valve 31d.

  A window 31 e is provided at the opening end of the expansion side port 31 a on the pressure side chamber side, and the window 31 e communicates with the inner periphery of the piston 22. A window 31 f is provided at the opening end of the compression side port 31 c on the extension side chamber side, and the window 31 f is also communicated with the inner periphery of the piston 22.

  Subsequently, the expansion side valve disk 37 is laminated on the lower side of the piston 22 in FIG. 6 and on the compression side chamber side which is the lower side of the expansion side valve 31b in FIG. 6, an extension side sub-valve 38 made of a leaf valve is stacked on the pressure side chamber side which is the lower side in the middle. Further, a pressure side valve disc 39 is laminated on the upper side of the piston 22 in FIG. 6 and on the extension side chamber side which is the upper side in FIG. 6 of the pressure side valve 31d, and further on the upper side of the pressure side valve disc 39 in FIG. A pressure side sub-valve 40 made of a leaf valve is stacked on the extension side chamber side.

  The extension side valve disc 37 is annular and includes an extension side subport 37a that communicates from the compression side chamber side end to the inner periphery. The outlet end of the extension side subport 37a is opened and closed by the extension side subvalve 38 described above. It has become so. The pressure side valve disc 39 is annular and includes a pressure side subport 39a that communicates from the end on the expansion side to the inner periphery. The outlet end of the pressure side subport 39a is opened and closed by the pressure side subvalve 40 described above. ing. In other words, the expansion side sub-valve 38 opens the expansion side sub-port 37a and passes through the expansion side sub-port 37a when bent by receiving the pressure of the expansion side chamber R4 without opening due to the pressure from the compression side chamber R5. A resistance is given to the flow of the fluid, and the extension side subport 37a is set to be one-way. The pressure side sub-valve 40 is not opened by the pressure from the expansion side chamber R4 but is bent by receiving the pressure in the pressure side chamber R5 so as to open the pressure side subport 39a, and the flow of fluid passing through the pressure side subport 39a. The pressure side subport 39a is set to one-way.

  It should be noted that the number and thickness of the leaf valves constituting the extension side subvalve 38 and the pressure side subvalve 40 can be arbitrarily changed according to the desired damping characteristics.

  An annular shim 60 is interposed between the expansion side valve 31b and the expansion side valve disk 37, and an annular shim 61 is interposed between the compression side valve 31d and the compression side valve disk 39. Yes. Further, an annular shim 62 and an annular valve stopper 42 that regulates the amount of bending of the expansion side sub-valve 38 are stacked below the expansion side sub-valve 38 in FIG. The annular shim 63 and the annular valve stopper 41 that regulates the amount of bending of the compression side subval 40 are laminated. The shim 60 is annular and has an outer diameter that is smaller than the outer diameter of the expansion side valve 31b. The shim 61 is annular and has an outer diameter that is smaller than the outer diameter of the compression side valve 31d. The shim 63 is annular and has an outer diameter smaller than the outer diameter of the expansion side sub-valve 38, and the shim 63 is annular and has an outer diameter smaller than the outer diameter of the compression-side sub valve 40. These shims 60, 61, 62 and 63 may be configured by laminating a plurality of annular plates.

  The valve stopper 41, shim 63, pressure side sub valve 40, pressure side valve disk 39, shim 61, pressure side valve 31d, piston 22, expansion side valve 31b, shim 60, expansion side valve disk 37, expansion side sub valve 38, shim 62 and The valve stopper 42 is sequentially assembled to the small diameter portion 23a of the piston rod 23 described above, and a housing 43 that forms a pressure chamber R6 is screwed to the screw portion 23b from below the valve stopper 42 in FIG. By this housing 43, the valve stopper 41, shim 63, pressure side sub valve 40, pressure side valve disk 39, shim 61, pressure side valve 31d, piston 22, extension side valve 31b, shim 60, extension side valve disk 37, extension side sub valve 38, The shim 62 and the valve stopper 42 are fixed to the piston rod 23. As described above, the housing 43 not only forms the pressure chamber R <b> 6 inside, but also plays a role of fixing the piston 22 to the piston rod 23.

  As described above, when the piston 22, the pressure side valve disk 39 and the expansion side valve disk 37 are mounted on the outer periphery of the small diameter portion 23a of the piston rod 23, the expansion side port 31a of the piston 22 is connected to the window 31e and the small diameter portion of the piston rod 23. The pressure side port 31c of the piston 22 communicates with the valve hole 35 through the window 31f and the through hole 23d opened from the outer periphery of the small diameter portion 23a of the piston rod 23. The expansion side subport 37a provided on the expansion side valve disc 37 is also communicated with the valve hole 35 through the through hole 23e opened from the outer periphery of the small diameter portion 23a of the piston rod 23, and the pressure side subport 39a provided on the pressure side valve disc 39 is also a piston rod. The small-diameter portion 23a communicates with the valve hole 35 through a through-hole 23f opened from the outer periphery.

  In this embodiment, the extended side sub-attenuating passage 32 is constituted by the extended side port 31a, the through hole 23c, the through hole 23e, and the extended side sub port 37a. Further, the through hole 23 c and the through hole 23 e are communicated with each other through the valve hole 35, and thus the valve hole 35 is provided in the middle of the expansion side sub-attenuation passage 32.

  The pressure side sub-attenuation passage 33 is constituted by a pressure side port 31c, a through hole 23d, a through hole 23f, and a pressure side sub port 39a. Further, the through hole 23 d and the through hole 23 f are communicated with each other through the valve hole 35, and thus the valve hole 35 is provided in the middle of the pressure side sub-attenuation passage 33.

  The housing 43 has a nut portion 44 with a flange 45 that is screwed to the screw portion 23b of the piston rod 23, and a bottomed cylindrical shape that is integrated by crimping an opening on the outer periphery of the flange 45 in the nut portion 44. A cylindrical portion 47 is provided. The nut portion 44 and the tubular portion 47 define a pressure chamber R6 in the pressure side chamber R5. In addition, when integrating the nut part 44 and the cylinder part 47, it is also possible to employ | adopt other methods, such as welding other than the said caulking process.

  A free piston 29 is slidably inserted into the pressure chamber R6 formed as described above, and the pressure chamber R6 includes an upper pressure side pressure chamber 27 and a lower pressure side pressure in FIG. It is divided into chambers 28.

  Further, the nut portion 44 is provided with the flange 45 on the side as described above, and a cylindrical screw portion 46 is formed on the inner periphery thereof, and the screw portion 46 is screwed to the screw portion 23b of the piston rod 23. Thus, the housing 43 can be fixed to the small diameter portion 23 a of the piston rod 23. Therefore, the cross-sectional shape of the lower outer periphery in FIG. 6 of the cylindrical portion 47 is a shape other than a perfect circle, for example, a shape with a part cut away, a hexagon, etc., and a tool that engages with the outer periphery is used. The operation of screwing the housing 43 onto the piston rod 23 is facilitated.

  The cylindrical portion 47 has a bottomed cylindrical shape, and a fixed orifice 48 that constitutes a part of the pressure side flow path 26 is provided at the bottom, and the pressure side chamber R <b> 5 enters the housing 43 at the side of the cylindrical portion 47. Two variable orifices 49 and 50 communicating with each other are provided.

  On the other hand, the free piston 29 has a bottomed cylindrical shape, and is inserted into the housing 43 with the bottom portion 29a facing downward in FIG. 6 and the outer periphery of the cylindrical portion 29b being in sliding contact with the inner periphery of the cylindrical portion 47. Yes. When the free piston 29 is slidably inserted into the housing 43 as described above, the pressure chamber R <b> 6 is divided into the expansion side pressure chamber 27 and the pressure side pressure chamber 28. In addition, by accommodating the bottom part 29a of the free piston 29 in the housing 43 facing downward in FIG. 6, it is possible to avoid interference with the screw part 46 in the nut part 44 of the free piston 29. Furthermore, in the case of this embodiment, the free piston 29 includes an annular groove 29c on the outer periphery of the cylindrical portion 29b and a hole 29d that communicates from the bottom 29a of the free piston 9 to the annular groove 29c.

  The free piston 29 is provided with a spring element 30 that applies a biasing force that suppresses the displacement according to the amount of displacement of the free piston 29 with respect to the pressure chamber R6. A coil spring 51 interposed between the bottom of the cylindrical portion 47 and the bottom 29a of the free piston 29 and a coil interposed between the valve hole 35 and a switching spool 53 described later. And a spring 52. The switching spool 53 is slidably inserted into the valve hole 35, and the lower end in FIG. 6 is in contact with the bottom 29 a of the free piston 29, and the free piston 29 is coiled via the switching spool 53. 51, 52 and elastically supported after being positioned at the neutral position in the pressure chamber R6.

  As the spring element, it is sufficient if the free piston 29 can be elastically supported, and other elements than the coil springs 51 and 52 may be employed. For example, the free piston 29 is elastically supported using an elastic body such as a disc spring. You may do it. When a single spring element whose one end is connected to the free piston 29 is used, the other end may be fixed to the nut portion 44 or the cylinder portion 47. When the switching spool 53 is integrated with the free piston 29, the coil spring 52 is eliminated and the coil spring is accommodated in the expansion side pressure chamber 27 and interposed between the free piston 29 and the nut portion 44. Alternatively, the coil spring 52 may be left as it is, and another coil spring may be accommodated in the extension-side pressure chamber 27 to constitute the spring element 30 with the coil springs 51 and 52 and the other coil spring. .

  The annular groove 29c always communicates the pressure side pressure chamber 28 and the pressure side chamber R5 so as to face the variable orifices 49 and 50 when the free piston 29 is elastically supported by the spring element 30 and is in the neutral position. When the piston 29 is displaced to the stroke end, that is, until it is in contact with the flange 45 of the nut portion 44 or the stepped portion 47a provided on the inner periphery of the cylindrical portion 47, the free piston 29 is completely wrapped and closed. It is like that. That is, the pressure side flow path 26 includes an annular groove 29 c, a hole 29 d, variable orifices 49 and 50, and a fixed orifice 48. Two variable orifices 49 and 50 are provided, but the number is arbitrary.

  In other words, in the case of this specific shock absorber D1, when the amount of displacement from the neutral position of the free piston 29 increases, all the openings of the variable orifices 49 and 50 face the annular groove 29c. The situation starts to face the outer periphery, the flow area of the variable orifices 49 and 50 starts to decrease gradually, and the flow resistance in the pressure side flow path 26 gradually increases. In this embodiment, as the amount of displacement of the free piston 29 increases, the flow area of the variable orifices 49 and 50 gradually decreases, and when the free piston 29 reaches the stroke end, the variable orifices 49 and 50 It is completely closed at the outer periphery of the free piston 29, the flow path resistance in the pressure side flow path 26 is maximized, and the pressure side pressure chamber 28 is communicated with the pressure side chamber R5 only by the fixed orifice 48.

  Subsequently, the switching mechanism 34 opens from the lower end in FIG. 6 which is one end of the piston rod 23 and is provided in the middle of the extension side sub-attenuation passage 32 and the pressure side sub-attenuation passage 33. And a switching spool 53 that is slidably inserted into the shaft and is displaced in the axial direction by the displacement of the free piston 29.

  The switching spool 53 slidably inserted into the valve hole 35 is provided with two annular recesses 53a and 53b provided on the outer periphery along the circumferential direction, and the lower end in FIG. This lower end is brought into contact with the bottom 29 a of the free piston 29. Since the contact surface of the switching spool 53 with the free piston 29 is spherical, the bottom 29a of the free piston 29 is not damaged. Further, since the free piston 29 and the switching spool 53 are separated, the free piston 29 sliding in the axial direction within the pressure chamber R6 and the switching spool 53 sliding in the axial direction within the valve hole 35 are provided. Even if it is eccentric, it can be easily assembled, and the free piston 29 and the switching spool 53 do not generate frictional forces that interfere with the displacement of the other party.

  Further, the switching spool 53 includes an in-spool passage 53c that opens from the upper end in FIG. 6 as the other end and communicates with the outer periphery on one end side. The in-spool passage 53c always communicates with the expansion side pressure chamber 27 and communicates with the expansion side chamber R4 through the valve hole 35 and the communication hole 36 to form the expansion side flow path 25 together with the communication hole 36. ing. As shown in the figure, a valve that serves as a resistance is not provided in the middle of the extension side flow path 25, but a valve such as a throttle is provided in the middle of the spool passage 53c or the communication hole 36 so as to pass the fluid. Resistance may be given.

  Further, the switching spool 53 is interposed between the bottom of the valve hole 35 and the upper end in FIG. 6 which is the other end of the switching spool 53, and is always biased toward the free piston 29 by the coil spring 52. And is not separated from the free piston 29.

  When the displacement from the neutral position of the free piston 29 does not reach the extension side displacement and the pressure side displacement, the switching spool 53 is inserted into the through holes 23e and 23f communicating with the extension side subport 37a and the pressure side subport 39a. On the other hand, on the outer periphery, the portions other than the annular grooves 53a and 53b are made to face each other and are closed. In this state, the communication between the through hole 23c communicating with the expansion side port 31a and the through hole 23e communicating with the expansion side subport 37a is blocked by the switching spool 53, and the communication between the through hole 23d communicating with the compression side port 31c and the compression side subport 39a. The communication of the hole 23f is also blocked by the switching spool 53. Therefore, when the displacement from the neutral position of the free piston 29 does not reach the extension side displacement and the compression side displacement, even if the shock absorber D1 exhibits the expansion / contraction operation, the fluid is only in the extension side port 31a or the compression side port. Only the passage 31c passes through the extension side chamber R4 and the compression side chamber R5. Note that when the communication between the through hole 23c and the through hole 23e is cut off, the part other than the annular grooves 53a and 53b of the notch spool 53 may be opposed to the through hole 23c. The through hole 23d and the through hole 23f When the communication is cut off, the portion other than the annular grooves 53a and 53b of the notch spool 53 may be opposed to the through hole 23d.

  On the other hand, when the free piston 29 moves upward as shown in FIG. 7 and is displaced beyond the predetermined extension side displacement from the neutral position, the switching spool 53 is also moved from the state of FIG. Thus, the annular groove 53b is opposed to the through holes 23d and 23f, and the through holes 23d and 23f are communicated with each other through the annular groove 53b. In this state, the switching spool 53 blocks the through-hole 23e with the outer peripheral portion other than the annular grooves 53a and 53b opposed to the through-hole 23e. In this case, the through hole 23 d communicating with the compression side port 31 c and the through hole 23 f communicating with the compression side sub port 39 a are communicated by the switching spool 53, and the through hole 23 e communicating with the expansion side sub port 37 a is blocked by the switching spool 53. Therefore, when the free piston 29 is displaced from the neutral position to a predetermined extension side displacement or more, the extension side port 31a, the compression side sub-attenuation passage 33 and the compression side port 31c are brought into communication, and the extension side sub-attenuation passage 32 is blocked. It will be in the state. In this case, instead of closing the through hole 23e with the switching spool 53, a portion other than the annular grooves 53a and 53b of the switching spool 53 may be opposed to the through hole 23c to block it.

  As shown in FIG. 8, when the free piston 29 moves downward and is displaced beyond the predetermined pressure side displacement from the neutral position, the switching spool 53 is also moved by the coil spring 52 in FIG. As shown in FIG. 8, the annular groove 53a is opposed to the through holes 23c and 23e, and the through holes 23c and 23e are communicated with each other through the annular groove 53a. In this state, the switching spool 53 blocks the through-hole 23f with the outer periphery, except for the annular grooves 53a and 53b, facing the through-hole 23f. In this case, the through hole 23 c communicating with the expansion side port 31 a and the through hole 23 e communicating with the expansion side sub port 37 a are communicated by the switching spool 53, and the through hole 23 f communicating with the compression side sub port 39 a is blocked by the switching spool 53. Accordingly, when the free piston 29 is displaced beyond the predetermined pressure side displacement from the neutral position, the pressure side port 31c, the extension side sub-attenuation passage 32, and the extension side port 31a are brought into communication, and the pressure side sub-attenuation passage 33 is blocked. It becomes a state. In this case, instead of closing the through hole 23f with the switching spool 53, a portion other than the annular grooves 53a and 53b of the switching spool 53 may be opposed to the through hole 23d to block it.

  Note that the resistance that the extension side valve 31b, the pressure side valve 31d, the extension side subvalve 38, and the pressure side subvalve 40 provide to the passing fluid can be performed by changing the number of stacked leaf valves and the thickness. When changing the number and thickness of the leaf valves, the relative positions of the through holes 23c, 23d, 23e, and 23f and the piston 22, the expansion side valve disk 37, and the pressure side valve disk 39 change. By adjusting the thickness of 61, 62, 63 and the number of laminated annular plates, the through hole 23c communicates with the expansion side port 31a, the through hole 23d communicates with the compression side port 31c, and the through hole 23e communicates with the expansion side subport 37a. The piston 22, the extension side valve disc 37, and the pressure side valve disc 39 may be positioned with respect to the piston rod 23 to a position where the through hole 23f can communicate with the compression side subport 39a. In this embodiment, since the damping characteristics are relatively easy to set, leaf valves are used for the expansion side valve 31b, the compression side valve 31d, the expansion side subvalve 38, and the compression side subvalve 40. It is possible to adopt a valve configuration with a check valve in series, or a configuration other than a leaf valve such as a poppet valve or a needle valve, but by adopting a leaf valve, it is easy to adjust the damping characteristics, In addition, since the entire length of the valve itself in the axial direction is short, there is an advantage that the stroke length of the shock absorber D1 is secured and the mountability of the shock absorber D1 on the vehicle is improved.

  The shock absorber D1 is configured as described above. Next, the operation of the shock absorber D1 will be described.

(C) Operation of the shock absorber D1 in a state where the displacement from the neutral position of the free piston 29 does not reach the predetermined extension side displacement and compression side displacement described above First, the displacement amount of the free piston 29 from the neutral position is variable orifice 49. , 50 is defined as a variable displacement, the variable displacement is set to be less than the above-described extension side displacement and compression side displacement, and the amount of displacement from the neutral position of the free piston 29 becomes the above variable displacement. The operation when not reached will be described.

  In this case, the free piston 29 can be displaced without changing the resistance of the pressure side flow path 26. Then, when considering the condition that the piston speed is the same when the vibration frequency input to the shock absorber D1 is low and high, first, when the input frequency is low, the amplitude of the input vibration increases. The amplitude of the free piston 29 also increases within a range where the variable orifices 49 and 50 do not begin to close. Further, since the displacement amount of the switching spool 53 from the neutral position does not reach the variable displacement, only the expansion side port 31a or only the compression side port 31c is effective, and the expansion side sub-attenuation passage 32 and the pressure side sub-attenuation passage 33 are blocked. Is in a state.

  When the amplitude of the free piston 29 increases in the above range, the urging force that the free piston 29 receives from the coil springs 51 and 52 increases, and when the shock absorber D1 extends, the pressure in the compression side pressure chamber 28 is increased by the expansion side pressure. If the pressure of the coil springs 51 and 52 is smaller than the pressure in the chamber 27 and conversely, the shock absorber D1 contracts, the pressure in the expansion side pressure chamber 28 is increased in the pressure side pressure chamber 27. It becomes smaller than the pressure by the urging force of the coil springs 51 and 52.

  As described above, when the shock absorber D1 exhibits low frequency vibration, a differential pressure corresponding to the urging force of the coil springs 51 and 52 is generated in the expansion side pressure chamber 27 and the compression side pressure chamber 28. Therefore, the expansion side chamber R4 and the expansion side The differential pressure in the pressure chamber 27 and the differential pressure between the pressure side chamber R5 and the pressure side pressure chamber 28 become smaller, and an apparent flow path composed of the expansion side flow path 25, the pressure side flow path 26, the expansion side pressure chamber 27, and the pressure side pressure chamber 28. The flow rate passing through is small. Since the flow rate passing through this apparent flow path is small, the flow rates of the expansion side port 31a and the compression side port 31c, which are the attenuation passages 31, are increased, so that the damping force generated by the shock absorber D1 is maintained high.

  On the other hand, when the input frequency to the shock absorber D1 is high, the amplitude of the input vibration becomes small and the amplitude of the free piston 29 becomes smaller. When the amplitude of the free piston 29 is reduced, the urging force received by the free piston 29 from the coil springs 51 and 52 is reduced, so that the shock absorber D1 in the extension side pressure chamber 27 is in the extension stroke or the contraction stroke. The pressure and the pressure in the pressure side pressure chamber 28 are substantially equal. Then, since the differential pressure between the expansion side chamber R4 and the expansion side pressure chamber 27 and the differential pressure between the compression side chamber R5 and the compression side pressure chamber 28 increase, they pass through the expansion side flow channel 25 and the pressure side flow channel 26 which are apparent flow channels. The flow rate to be increased.

  When the frequency of vibration input to the shock absorber D1 is low, the flow rate passing through the apparent flow path is small, and when the input frequency is high, the flow rate passing through the apparent flow path is large, and the input If the speed is the same, the flow rate flowing from the expansion side chamber R4 to the compression side chamber R5 or from the compression side chamber R5 to the expansion side chamber R4 must be equal regardless of the input frequency, so the expansion side valve 31b and the compression side valve of the damping passage 31 The flow rate passing through 31d increases when the input frequency is low, and the damping force is high. Conversely, when the input frequency is high, the flow rate decreases and the damping force is low. Therefore, the damping characteristic of the shock absorber D1 changes as shown in FIG.

  Therefore, even in the shock absorber D1, the change in the damping force can be made to depend on the input vibration frequency, and the vehicle posture can be changed by generating a high damping force with respect to the vibration input at the sprung resonance frequency. It is possible to stabilize and prevent the passenger from feeling uneasy when turning the vehicle, and when a vibration at the unsprung resonance frequency is input, a low damping force is always generated to transmit the vibration on the axle side to the vehicle body side. Insulation can improve the ride comfort in the vehicle.

  Next, the operation when the variable displacement is set to be less than the extension side displacement and the pressure side displacement and the displacement amount from the neutral position of the free piston 29 reaches the variable displacement will be described.

  The variable orifices 49 and 50 gradually reduce the flow path area in accordance with the amount of displacement after the free piston 29 reaches a variable displacement regardless of whether the shock absorber D1 extends or contracts. That is, after the free piston 29 starts to close the variable orifices 49 and 50, the flow path resistance of the pressure side flow path 26 gradually increases in accordance with the amount of displacement.

  Here, the free piston 29 is displaced to a variable displacement when there is a large amount of fluid flowing into and out of the expansion side pressure chamber 27 or the compression side pressure chamber 28. Specifically, the amplitude of expansion and contraction of the shock absorber D1. Is the case.

  When the vibration frequency input to the shock absorber D1 is relatively high, the shock absorber D1 generates a relatively low damping force until the free piston 29 is displaced to a position where it begins to close the variable orifices 49 and 50. However, when the free piston 29 is displaced beyond the position where the variable orifices 49 and 50 begin to be closed, the flow resistance of the pressure side flow passage 26 gradually increases. The movement speed of the fluid toward the stroke end side is reduced, the amount of fluid movement through the apparent flow path is also reduced, and the amount of fluid passing through the attenuation passage 31 is increased correspondingly. The generated damping force of D1 gradually increases.

  That is, if the amount of displacement from the neutral position of the free piston 29 exceeds the variable displacement in a situation where high-frequency vibration is input to the shock absorber D1, the shock absorber D1 gradually generates damping force until the free piston 29 reaches the stroke end. Therefore, the damping force generated by the shock absorber D does not increase rapidly, and the damping force does not change suddenly. That is, when the free piston 29 reaches the stroke end and the fluid in the extension side chamber R4 and the pressure side chamber R5 cannot be exchanged via the pressure chamber R6, the height of the damping force does not change abruptly. The damping force change from the damping force to the high damping force becomes gentle. Furthermore, since the generated damping force is gradually increased when the free piston 29 reaches the stroke ends on both ends in the pressure chamber R6, the function of suppressing a sudden change in the damping force is the function of the expansion of the shock absorber D1. Demonstrated in both strokes. The variable displacement on the expansion side, which is a variable displacement in the direction of compressing the expansion side pressure chamber, from the neutral position of the free piston 29, and the compression side, which is a variable displacement, on the compression side, from the neutral position of the free piston 29, to the compression direction. The variable displacement can be arbitrarily set, and both are not necessarily equal.

  Therefore, in this shock absorber D1, even if a vibration having a high frequency and a large amplitude is input, the generated damping force changes gently, so that 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.

  As described above, when the piston speed becomes high and the flow resistance in the fixed orifice 48 and the variable orifices 49 and 50 does not become too large, the specific shock absorber D1 is the above (c). As explained, when the damping force depending on the input vibration frequency is exhibited and the amount of displacement from the neutral position of the free piston 29 exceeds the variable displacement, the damping force is gradually increased and decreased. Therefore, it is possible to suppress a change in damping force that suddenly increases the damping force.

(D) Operation of the shock absorber D1 in a state where the displacement from the neutral position of the free piston 29 reaches the above-described predetermined extension side displacement and compression side displacement In this case, the piston speed of the shock absorber D1 is high and the amplitude is large, A large flow rate flows into the extension side pressure chamber 27 or the pressure side pressure chamber 28, the free piston 29 is greatly displaced from the neutral position, and the stroke margin to the stroke end is reduced. Since the alternating current of the fluid in the extension side chamber R4 and the compression side chamber R5 is reduced through the flow path, the effect of reducing the damping force with respect to the input of the high frequency vibration is reduced.

  However, when the free piston 29 is displaced in this way, the switching mechanism 34 shuts off the expansion side sub-attenuation passage 32 when the free piston 29 is displaced from the neutral position in the direction of compressing the expansion side pressure chamber 27. Then, when the compression side sub-attenuation passage 33 is opened and the free piston 29 is displaced from the neutral position in the direction of compressing the compression side pressure chamber 28, the compression side sub-attenuation passage 33 is shut off to extend the extension side sub-attenuation. The passage 32 is opened.

  In the state in which the switching mechanism 34 opens the expansion side sub-attenuation passage 32 and blocks the compression side sub-attenuation passage 33, if the shock absorber D1 performs the expansion operation, the fluid in the expansion side chamber R4 is only the expansion side port 31a. The buffer device D1 generates a low damping force because it moves to the compression side chamber R5 via the extension side sub damping passage 32 as well. In this state, when the shock absorber D1 is contracted, the pressure side sub-attenuation passage 33 is blocked, so that the fluid in the pressure side chamber R5 moves to the expansion side chamber R4 only through the pressure side port 31c. Generates high damping force.

  On the contrary, in the state where the switching mechanism 34 blocks the expansion side sub-attenuation passage 32 and opens the compression side sub-attenuation passage 33, when the shock absorber D1 performs the expansion operation, the expansion side sub-attenuation passage 32 is blocked. Therefore, since the fluid in the extension side chamber R4 moves to the compression side chamber R5 only through the extension side port 31a, the shock absorber D1 generates a high damping force. In this state, when the shock absorber D1 is contracted, the fluid in the pressure side chamber R5 moves to the expansion side chamber R4 not only through the pressure side port 31c but also through the pressure side sub-attenuation passage 33. Therefore, the shock absorber D1 has a low damping force. Is generated.

  Thus, when the free piston 29 is greatly displaced from the neutral position in the direction in which the expansion side pressure chamber is compressed, the shock absorber D1 lowers the damping force in the contraction direction and increases the damping force in the extension direction. In addition, when the free piston 29 is greatly displaced from the neutral position in the direction of compressing the compression side pressure chamber, the damping force in the expansion direction is lowered and the damping force in the contraction direction is increased.

  That is, similarly to the shock absorber D, the shock absorber D1 can behave as a skyhook damper in a state where the displacement from the neutral position of the free piston 29 reaches the above-described predetermined extension side displacement and pressure side displacement. In a situation where the damping force exerted on the vehicle causes the vehicle body to vibrate, the damping force can be lowered to suppress the vibration of the vehicle body and improve the riding comfort in the vehicle.

  Further, with respect to the behavior as a skyhook damper, in this shock absorber D1, it is only necessary to switch the life and death of the expansion side sub-attenuation passage 32 and the compression side sub-attenuation passage 33 by interlocking the switching mechanism 34 with the operation of the free piston 29. A sensor that detects speed and acceleration is attached to the vehicle body and the shock absorber D1, a damping force adjustment valve is provided, and there is no need to control the damping force adjustment valve using an expensive control device, so a skyhook damper is realized at low cost. can do.

  Further, in a situation where the shock absorber D1 does not need to behave as a skyhook damper, the damping force can be reduced when the input vibration frequency becomes high. The transmission of the side vibration to the vehicle body side can be insulated to improve the riding comfort in the vehicle.

  As the predetermined extension side displacement and compression side displacement from the neutral position of the free piston 9 are made smaller, the damping force changes depending on the frequency described in (c) of the operation of the above-described shock absorber D. The operation (skyhook operation) as the skyhook damper described in (d) appears more preferentially than the operation (frequency sensitive operation). Conversely, the larger the frequency, the more frequency sensitive operation than the skyhook operation. Will appear preferentially. Therefore, it is preferable that the shock absorber D exhibits an operation suitable for the vehicle by tuning the predetermined extension side displacement and compression side displacement according to the characteristics of the vehicle.

  Further, the variable displacement, which is the displacement at which the displacement of the free piston 29 from the neutral position starts to close the variable orifices 49 and 50, is set to a displacement that exceeds the above-described extension side displacement and compression side displacement, and from the neutral position of the free piston 29. When the displacement amount reaches the variable displacement, the flow passage area in the pressure side flow passage 26 decreases, and the displacement of the free piston 29 is suppressed. Since the displacement of the free piston 29 is thus suppressed, the switching spool 53 opens the expansion side sub-attenuation passage 32 and blocks the pressure side sub-attenuation passage 33, or the switching spool 53 enters the pressure side sub-attenuation passage 33. The state of opening and blocking the extension side sub-attenuation passage 32 is maintained for a while, and the skyhook operation is maintained for a long time. The functioning time as a skyhook damper becomes longer, and the vibration transmission from the axle side to the vehicle body can be kept insulated.

  In addition, the shock absorber D1 includes a piston rod 23 that is movably inserted into the cylinder 21 and to which a piston 22 as a partition member is fixed at one end, and the pressure chamber R6 is fixed to one end of the piston rod 23. The switching mechanism 34 is formed by a housing 43 that is opened from one end of the piston rod 23 and is provided in the middle of the extension side sub-attenuation passage 32 and the pressure side sub-attenuation passage 33, and slides into the valve hole 35. Since the switching spool 53 that is movably inserted and is displaced in the axial direction by the displacement of the free piston 29 is provided, the switching mechanism 34 can be incorporated in the piston rod 23, thereby making the shock absorber D1 compact. can do.

  Further, the shock absorber D1 includes an expansion side sub disk 37a and an expansion side valve disposed in the compression side chamber R5, including an expansion side sub port 37a in which the expansion side sub damping passage 32 communicates with the expansion side chamber R4 via the switching mechanism 34. An expansion side sub-valve 38 that is stacked on the disk 37 and opens and closes the expansion side sub-port 37a. The compression side sub-attenuation passage 33 includes a pressure side sub-port 39a that communicates with the compression side chamber R5 via the switching mechanism 34. Since the pressure-side valve disk 39 and the pressure-side subvalve 40 stacked on the pressure-side valve disk 39 to open and close the pressure-side subport 39a are provided, the resistance and pressure-side subflow applied to the fluid flow passing through the expansion-side sub-attenuation passage 32 are provided. The resistance given to the flow of the fluid passing through the damping passage 33 can be set separately, and the extension side sub damping passage 32 and the pressure side sub damping passage 33 are opened. In time, it is possible to occupy different damping force during elongation operation and at the time of the contraction operation.

  Further, in this shock absorber D1, the damping passage 31 is provided in the piston 22 as the partition member, and the expansion side port 31a and the pressure side port 31c communicating the expansion side chamber R4 and the pressure side chamber R5, and the pressure side chamber R5 side of the piston 22 And the expansion side valve 31b that opens and closes the expansion side port 31a and the compression side valve 31d that is stacked on the expansion side chamber R5 side of the piston 22 and opens and closes the compression side port 31c. When the compression side sub-attenuation passage 33 is blocked, the damping force during the extension operation and the contraction operation can be made different.

  Further, in this shock absorber D1, the piston rod 23 is provided with a communication hole 36 for communicating the valve hole 35 to the expansion side chamber R4, and the switching spool 53 is in contact with the free piston 29 at one end and opened from the other end. In addition, a spool passage 53c that communicates with the extension side pressure chamber 27 is provided, and the extension side passage 25 is formed including the spool passage 53c and the communication hole 36. Therefore, the extension passage 25 is connected to the piston rod 23 and the switching spool 53. Compared with the case where the extension side passage 25 is provided elsewhere, the shock absorber D1 can be made compact, and a throttle valve or the like is not provided in the spool passage 53c. Even if the pressure in the expansion side pressure chamber 27 acts on the upper and lower ends in FIG. 6 which are both ends of the switching spool 53, the switching spool 53 is not urged in the vertical direction by the pressure. It does not affect the displacement of emissions 29.

  In the shock absorber D1, the piston 22, the expansion side valve 31b, and the compression side valve 31d as the partition members are all annular, and the expansion side valve disc 37 is annular, and the compression side chamber of the expansion side valve 31b. Stacked on the R5 side, the expansion side sub-valve 38 is annular and stacked on the pressure side chamber R5 side of the expansion side valve disc 37, and the compression side valve disc 39 is annular and stacked on the expansion side chamber R4 side of the compression side valve 31d. The pressure side sub-valve 40 is annular and is laminated on the expansion side chamber side of the pressure side valve disk 39, and the piston 22, the expansion side valve 31b, the pressure side valve 31d, the expansion side valve disk 37, the expansion side sub valve 38, and the pressure side valve disk 39. The pressure side sub-valve 40 is attached to the outer periphery of one end of the piston rod 23 and fixed to the piston rod 23 by the housing 43. Therefore, the extension side sub-attenuation passage 32 and the pressure side sub-attenuation passage 33 can be formed by simply assembling the above-described members to the piston rod 23 in order, and the fixing can be performed by the housing 43. It becomes easy. Further, since the expansion side valve 31b, the expansion side sub valve 38, the pressure side valve 31d and the pressure side sub valve 40 do not face each other, they do not interfere with each other, and each bending is not hindered, so that a stable damping force is exhibited. can do.

  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.

1, 21 Cylinder 2, 22 Piston 3.31 as partition member Damping passage 4, 23 Piston rod 5, 25 Stretch side flow path 7, 27 Stretch side pressure chamber 6, 26 Pressure side flow path 8, 28 Pressure side pressure chamber 9, 29 Free piston 10, 30 Spring element 12, 32 Extension side sub damping passage 12a, 38 Extension side sub valve 13, 33 Pressure side sub damping passage 13a, 40 Pressure side sub valve 14, 34 Switching mechanism 17, 43 Housing 31a Extension side port 31c Pressure side port 31b Extension side valve 31d Pressure side valve 35 Valve hole 36 Communication hole 37 Extension side valve disk 37a Extension side subport 39 Pressure side valve disk 39a Pressure side subport 53 Switching spool 53c Passage in spool D, D1 Shock absorber R1, R4 Extension side chamber R2, R5 Pressure side Chamber R3, R6 Pressure chamber

Claims (7)

A cylinder, a partition member that is slidably inserted into the cylinder, partitions the inside of the cylinder into an extension side chamber and a pressure side chamber, a pressure chamber, and is inserted into the pressure chamber so as to be movable in the axial direction. A free piston that divides into an extension pressure chamber that communicates with the extension side chamber via an extension side flow channel and a pressure side pressure chamber that communicates with the pressure side chamber via a pressure side channel; And a spring element that generates a biasing force that suppresses displacement from the neutral position of the free piston.
A damping passage communicating the extension side chamber and the pressure side chamber;
An extension side sub-attenuation passage that allows only a flow from the extension side chamber to the compression side chamber and is arranged in parallel with the attenuation passage;
A pressure side sub-attenuation passage that allows only a flow from the pressure side chamber to the extension side chamber and is arranged in parallel with the attenuation passage;
When the free piston is displaced more than a predetermined extension side displacement from the neutral position in the direction of compressing the extension side pressure chamber, the extension side sub-attenuation passage is shut off and the compression side sub-attenuation passage is opened, and the free piston is moved from the neutral position to the above-mentioned position. A shock absorber comprising: a switching mechanism that opens the expansion-side sub-attenuation passage and shuts off the compression-side sub-attenuation passage when the compression-side pressure chamber is displaced by a predetermined displacement or more in the compression direction. A piston rod that is movably inserted into the cylinder and to which the partition member is fixed at one end;
The pressure chamber is formed by a housing fixed to one end of the piston rod;
The switching mechanism includes a valve hole that is opened from one end of the piston rod and is provided in the middle of the extension side sub-attenuation passage and the pressure side sub-attenuation passage, and is slidably inserted into the valve hole, A switching spool that is displaced in the axial direction by displacement,
2. The shock absorber according to claim 1, wherein the switching spool switches between opening and closing of the extension side sub-attenuation passage and the pressure side sub-attenuation passage. The extension side sub-attenuation passage includes an extension side subport communicated with the extension side chamber via the switching mechanism, and is stacked on the extension side valve disc disposed in the compression side chamber and the extension side valve disc so as to be stacked on the extension side. It has an extension side sub valve that opens and closes the sub port,
The pressure side sub-attenuation passage includes a pressure side subport communicating with the pressure side chamber via the switching mechanism, and is stacked on the pressure side valve disk disposed in the extension side chamber and the pressure side valve disk to open and close the pressure side subport. The shock absorber according to claim 1, further comprising a sub valve. The attenuation passage is provided in the partition member and is stacked on the extension side port and the compression side port for communicating the extension side chamber and the compression side chamber, and on the compression side chamber side of the partition member, and extends and closes the extension side port. The shock absorber according to any one of claims 1 to 3, further comprising: a side valve; and a pressure side valve that is stacked on the extension side chamber side of the partition member and opens and closes the pressure side port. The piston rod is provided with a communication hole that communicates the valve hole to the expansion side chamber, and the switching spool has a passage in the spool that contacts one end of the free piston and opens from the other end to the expansion side pressure chamber. 5. The shock absorber according to claim 2, wherein the extension-side flow path is formed to include the passage in the spool and the communication hole. The partition member, the extension side valve, and the pressure side valve are both annular,
The extension side valve disc is annular and laminated on the pressure side chamber side of the extension side valve,
The extension side sub-valve is annular and is laminated on the compression side chamber side of the extension side valve disc,
The pressure side valve disc is annular and laminated on the extension side chamber side of the pressure side valve,
The pressure side subvalve is annular and is laminated on the extension side chamber side of the pressure side valve disc,
The partition member, the extension side valve, the pressure side valve, the extension side valve disc, the extension side sub-valve, the pressure side valve disc and the pressure side sub-valve are attached to the outer periphery of one end of the piston rod, and the piston rod is attached by the housing. The shock absorber according to claim 4, wherein the shock absorber is fixed to the shock absorber. The shock absorber according to any one of claims 1 to 6, wherein the switching mechanism blocks the extension side sub-attenuation passage and the pressure side sub-attenuation passage when the free piston is in a neutral position.

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