JP2013204628A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shock absorber capable of restraining generation of a hitting sound, capable of preventing a sudden change in damping force, and capable of improving ride comfort in a vehicle.SOLUTION: A problem solving means is a shock absorber D including a cylinder 1, a partition wall member 2 slidably inserted into the cylinder 1 and partitioning the inside of the cylinder 1 into an extension side chamber R1 and a pressing side chamber R2, passages 3a and 3b for communicating the extension side chamber R1 and the pressure side chamber R2, a housing 15 for forming a pressure chamber R3, a free piston 9 movably inserted into the housing 15 and partitioning the pressure chamber R3 into an extension side pressure chamber 7 communicated with the extension side chamber R1 via an extension side flow passage 5 and a pressing side pressure chamber 8 communicated with the pressing side chamber R2 via a pressing side flow passage 6, and spring elements 10 and 11 for generating energizing force for restraining displacement of the free piston 9 to the housing 15. The shock absorber includes a cushion C for preventing a collision between the free piston 9 and the housing 15.

Description

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

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

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

さらに、上記式（１）で示された伝達関数中のラプラス演算子ｓにｊωを代入して、周波数伝達関数Ｇ（ｊω）の絶対値を求めると、以下の式（２）が得られる。

上記各式から理解できるように、この緩衝装置における流量Ｑに対する差圧Ｐの伝達関数の周波数特性は、Ｆａ＝Ｋ／｛２・π・Ａ^２・（Ｃ１＋Ｃ２＋Ｃ３）｝とＦｂ＝Ｋ／｛２・π・Ａ^２・（Ｃ２＋Ｃ３）｝の２つの折れ点周波数を持ち、また、Ｆ＜Ｆａの領域においては、伝達ゲインは略Ｃ１となり、Ｆａ≦Ｆ≦Ｆｂの領域においてはＣ１からＣ１・（Ｃ２＋Ｃ３）／（Ｃ１＋Ｃ２＋Ｃ３）まで漸減するように変化して、Ｆ＞Ｆｂの領域においては一定となる。すなわち、流量Ｑに対する差圧Ｐの伝達関数の周波数特性は、低周波数域では伝達ゲインが大きくなり、高周波数域では伝達ゲインが小さくなる。 Here, the differential pressure between the upper chamber and the lower chamber when the shock absorber is expanded and contracted is P, the flow rate of the liquid flowing out from the upper chamber is Q, the differential pressure P and the flow rate Q1 of the liquid passing through the first flow path are Is a relationship between the difference between the pressure difference P and the pressure P1, and the flow rate Q2 of the liquid flowing from the upper chamber into the other chamber of the pressure chamber. The coefficient is C2, the pressure in one chamber of the pressure chamber is P2, the coefficient that is the relationship between the pressure P2 and the flow rate Q2 of the liquid flowing out from the one chamber into the lower chamber is C3, and the pressure receiving area of the free piston When the area is A, the displacement of the free piston with respect to the pressure chamber is X, the spring constant of the coil spring is K, and the transfer function of the differential pressure P with respect to the flow rate Q is obtained, Equation (1) is obtained. In equation (1), s represents a Laplace operator.

Furthermore, substituting jω for the Laplace operator s in the transfer function shown in the above equation (1) to obtain the absolute value of the frequency transfer function G (jω) yields the following equation (2).

As can be understood from the above equations, the frequency characteristics of the transfer function of the differential pressure P with respect to the flow rate Q in this buffer device are Fa = K / {2 · π · A ² · (C1 + C2 + C3)} and Fb = K / {2 Π · A ² · (C2 + C3)} has two breakpoint frequencies, and in the region of F <Fa, the transfer gain is substantially C1, and in the region of Fa ≦ F ≦ Fb, C1 to C1 · ( C2 + C3) / (C1 + C2 + C3), and changes so as to decrease gradually, and becomes constant in the region of F> Fb. That is, in the frequency characteristic of the transfer function of the differential pressure P with respect to the flow rate Q, the transfer gain increases in the low frequency range, and the transfer gain decreases in the high frequency range.

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

JP 2006-336816 A JP 2007-78004 A

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

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

  In this way, by restricting the displacement of the free piston, it is possible to suppress expansion and bottoming, but when the free piston collides with the stepped portion, a sound is generated and the vehicle occupant feels uncomfortable. In addition to giving anxiety, the damping force generated by the shock absorber changes abruptly because the free piston is suddenly stopped, which may impair the riding comfort of the vehicle.

  Therefore, the present invention was devised to improve the above-mentioned problems, and the object of the present invention is to suppress the occurrence of a hitting sound and to prevent a sudden change in damping force. It is an object of the present invention to provide a shock absorber capable of improving comfort.

  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 compression side chamber, and the extension side chamber. A passage communicating with the compression side chamber, a housing forming a pressure chamber therein, and an extension side pressure chamber that is movably inserted into the housing and communicates with the extension side chamber via the extension side channel And a free piston that is partitioned into a pressure side pressure chamber that communicates with the pressure side chamber via a pressure side flow path, and a shock absorber that includes a spring element that generates a biasing force that suppresses displacement of the free piston with respect to the housing. A cushion for preventing a collision between the free piston and the housing is provided.

  According to the shock absorber of the present invention, the collision between the free piston and the housing can be suppressed by the cushion, so that the occurrence of the hitting sound of both can be suppressed and the sudden change in the damping force can be prevented, and the riding comfort in the vehicle can be reduced. It is possible to improve.

It is a longitudinal cross-sectional view of the shock absorber in one embodiment. It is a partial expanded longitudinal cross-sectional view of the buffering device in the modification of one embodiment. It is a partial expanded longitudinal cross-sectional view of the buffering device in the other modification of one Embodiment. It is a partially expanded longitudinal cross-sectional view of the buffering device in another modification of one Embodiment.

  Hereinafter, the present invention will be described with reference to the drawings. As shown in FIG. 1, the shock absorber D of the present invention includes a cylinder 1, a piston 2 as a partition member that is slidably inserted into the cylinder 1 and divides the cylinder 1 into an expansion side chamber R <b> 1 and a pressure side chamber R <b> 2, The passages 3a and 3b communicating the extension side chamber R1 and the pressure side chamber R2, the housing 15 forming the pressure chamber R3, and the pressure chamber R3 are slidably inserted into the extension passage 5 through the housing 15 A free piston 9 partitioned into an extension side pressure chamber 7 communicated with the extension side chamber R1 via the pressure side and a pressure side pressure chamber 8 communicated with the pressure side chamber R2 via the pressure side flow path 6, and a pressure chamber R3 of the free piston 9 The extension-side coil spring 10 and the compression-side coil spring 11 that are spring elements that generate an urging force that suppresses the displacement of the free piston 9 and a cushion C that prevents the free piston 9 from colliding with the housing 15 are provided in the vehicle. Generates the damping force is interposed between the vehicle body and the axle is to suppress the vibration of the vehicle body.

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

  The extension side chamber R1, the pressure side chamber R2, and further the pressure chamber R3 are filled with a liquid such as hydraulic oil. In addition, since the shock absorber D is a single rod type shock absorber, in order to compensate for the volume of the piston rod 4 entering and exiting the cylinder 1, although not shown, A sliding partition that slidably contacts the circumference and divides the pressure side chamber R2 and the gas chamber is provided, or a reservoir is provided outside the cylinder 1. When the reservoir is provided outside the cylinder 1, an outer cylinder that covers the outer periphery of the cylinder 1 is provided to form the reservoir between the cylinder 1 and the outer cylinder, and a tank is provided separately from the cylinder 1, and the reservoir is provided in the tank. You may make it form. In addition, in order to increase the pressure of the pressure side chamber R2 during the contraction operation of the shock absorber D, a partition member that partitions the pressure side chamber R2 and the reservoir, and a resistance provided to a liquid flow that is provided in the partition member and travels from the pressure side chamber R2 to the reservoir A base valve for providing the above may be provided. In addition to the working oil, for example, a liquid such as water or an aqueous solution can be used as the liquid filled in the extension chamber R1, the pressure chamber R2, and the pressure chamber R3, which are the working chambers.

  In the following, each part will be described in detail. As shown in FIG. 1, the piston rod 4 has a small-diameter portion 4a formed at the lower end side and a screw portion 4c formed at the distal end side of the small-diameter portion 4a. .

  The piston rod 4 is formed with a rod inner passage 4b that opens from the tip of the small diameter portion 4a and passes through the side of the piston rod 4. The rod inner passage 4b forms a part of the extension side passage 5. doing. In the drawing, a valve serving as a resistance is not provided in the middle of the extension side flow path 5, but a valve such as a throttle may be provided.

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

  The compression side leaf valve V1 and the extension side leaf valve V2 are both formed in an annular shape, and a small diameter portion 4a of the piston rod 4 is inserted on the inner peripheral side to regulate the amount of bending of the compression side leaf valve V1 and the extension side leaf valve V2. Are laminated on the piston 2 together with the annular valve stoppers 41 and 42.

  The pressure-side leaf valve V1 is bent by the pressure difference between the pressure-side chamber R2 and the expansion-side chamber R1 when the shock absorber D is contracted, and opens the passage 3a, so that the liquid flows from the pressure-side chamber R2 to the expansion-side chamber R1 In addition to providing resistance, the passage 3a is closed when the shock absorber D extends, and the other leaf valve V2 opens the passage 3b when the shock absorber D extends, as opposed to the compression leaf valve V1. During the contraction, the passage 3b is closed. That is, the compression side leaf valve V1 is a damping force generating element that generates a compression side damping force when the shock absorber D is contracted, and the other extension side leaf valve V2 generates an extension side damping force when the shock absorber D is extended. It is a damping force generating element. Even when the passages 3a and 3b are closed by the pressure side leaf valve V1 and the extension side leaf valve V2, the extension side chamber R1 and the pressure side chamber R2 are communicated with each other by a well-known orifice (not shown). The orifice is formed, for example, by providing a notch on the outer periphery of the pressure side leaf valve V1 and the extension side leaf valve V2, or by providing a recess in the valve seat on which the pressure side leaf valve V1 and the extension side leaf valve V2 are seated.

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

  A housing 15 that forms a pressure chamber R3 is screwed to the screw portion 4c of the piston rod 4 from below the extension side leaf valve V2. The housing 15 allows the piston 2, the pressure side leaf valve V1, and the extension side to extend. The side leaf valve V2 and the valve stoppers 41 and 42 are fixed to the piston rod 4. Thus, the housing 15 not only forms the pressure chamber R3 inside, but also plays a role of fixing the piston 2 to the piston rod 4.

  Next, the housing 15 will be described. The housing 15 includes a nut portion 30 having a bottomed cylindrical shape that is screwed to the screw portion 4c of the piston rod 4 and having a flange 30c on the outer periphery, and a bottomed cylindrical housing body 32, The upper end opening in FIG. 1 of the housing main body 32 is crimped toward the outer periphery of the flange 30c and attached to the outer periphery of the flange 30c, and the housing main body 32 and the nut portion 30 are integrated. 32 defines a pressure chamber R3 within the pressure side chamber R2. In addition, when integrating the nut part 30 and the housing main body 32, it is also possible to employ | adopt other methods, such as welding other than the said crimping process.

  A free piston 9 is slidably inserted into the pressure chamber R3 formed as described above, and the pressure chamber R3 includes an upper side expansion pressure chamber 7 and a lower side pressure side pressure in FIG. It is partitioned into a chamber 8.

  The nut portion 30 has a bottomed cylindrical shape, and includes a bottom portion 30a, a cylindrical portion 30b provided on the outer periphery of the bottom portion 30a, and a flange 30c provided in a flange shape on the outer periphery of the end portion of the cylindrical portion 30b. A screw portion 30d is formed on the inner periphery of the cylindrical portion 30b, and an opening 30e that opens from the side and communicates with the inside is provided in the cylindrical portion 30b. And by screwing the cylinder part 30b in this nut part 30 to the screw part 4c of the piston rod 4, the above-mentioned piston 2 and each member laminated | stacked on this can be fixed to the piston rod 4 as mentioned above. In addition, the housing 15 can be fixed to the small diameter portion 4 a of the piston rod 4. Further, a gap is formed between the bottom 30a of the nut portion 30 and the lower end of the small diameter portion 4a of the piston rod 4 in FIG. 1, and the rod internal passage 4b provided in the piston rod 4 and the opening 30e. And communicate with each other. Therefore, the extension side pressure chamber 7 is communicated with the extension side chamber R1 via the opening 30e and the in-rod passage 4b, and the extension side flow path 5 is formed by the opening 30e and the in-rod passage 4b. A part of the extension channel 5 is formed.

  The housing body 32 has a cylindrical portion 32a having a small outer diameter at the lower end in FIG. 1 and a bottom portion 32b, and has a bottomed cylindrical shape. The small diameter portion 32c of the cylindrical portion 32a opens from the side. An opening 32d leading to the inside is provided. The opening 32d faces the pressure side pressure chamber 8 defined by a free piston 9 slidably inserted into the housing body 32, and serves as a pressure side flow path 6 that communicates the pressure side pressure chamber 8 with the pressure side chamber R2. In addition to functioning, it also functions as an orifice that provides resistance to the flow of liquid flowing back and forth between the pressure side pressure chamber 8 and the pressure side chamber R2. In addition, the cross-sectional shape of the outer periphery of the small-diameter portion 32c of the cylindrical portion 32a is a shape other than a perfect circle, for example, a shape in which a part is notched or a hexagonal shape, and a tool is engaged with the small-diameter portion 32c. Thus, the housing 15 can be screwed onto the tip of the piston rod 4.

  The free piston 9 is formed in a cylindrical shape with a bottom, and includes a cylindrical portion 9a and a bottom portion 9b that closes one end of the cylindrical portion 9a. The outer periphery of the cylindrical portion 9a is connected to the cylindrical portion 32a of the housing main body 32. The pressure chamber R3 is inserted into the pressure chamber R3 in sliding contact with the inner periphery, and the pressure chamber R3 is divided into an expansion side pressure chamber 7 communicating with the expansion side chamber R1 and a pressure side pressure chamber 8 communicating with the compression side chamber R2. Yes. In this way, the free piston 9 has a bottomed cylindrical shape, so that the axial length of the cylindrical portion 9a can be secured, and the free piston 9 can be reduced in weight without impairing the slidability with respect to the housing 15, Ensuring the spring length and stroke length of the extension side coil spring 10 and the compression side coil spring 11 as the spring elements is facilitated, and the increase in the overall length of the housing 15 can be suppressed.

  Further, as a spring element for applying an urging force that suppresses the displacement of the free piston 9 relative to the housing 15 to the free piston 9, the flange 30 c of the nut portion 30 and the free piston 9 are located in the extension side pressure chamber 7. The expansion side coil spring 10 is interposed between the bottom portion 9 b and the compression side coil spring 11 is interposed between the bottom portion 32 b of the housing body 32 and the bottom portion 9 b of the free piston 9 in the compression side pressure chamber 8. The free piston 9 is sandwiched from above and below by a spring element composed of the extension side coil spring 10 and the pressure side coil spring 11, and is elastically supported after being positioned at a predetermined neutral position in the pressure chamber R3. ing. The neutral position does not indicate the center of the pressure chamber R3 in the axial direction, but is a position where the free piston 9 is positioned by the spring element.

  Further, an extension side cushion 20 is interposed between the extension side coil spring 10 and the extension side pressure chamber side surface of the bottom portion 9 b of the free piston 9, and the compression side coil spring 11 and the pressure side pressure chamber in the bottom portion 32 b of the housing body 32. A compression side cushion 21 is interposed between the side surface and the extension side cushion 20 and the compression side cushion 21 constitute a cushion C.

  The extension side cushion 20 is composed of an annular plate 20a stacked on the bottom portion 9b of the free piston 9, and a convex cushion body 20b formed of an elastic body such as rubber fixed to the inner periphery of the plate 20a. The plate 20 a is sandwiched between the extension side coil spring 10 and the free piston 9 and fixed to the side of the extension side pressure chamber at the bottom 9 b of the free piston 9. The extension side cushion 20 is accommodated without any play in the radial direction when inserted into the cylindrical portion 9 a of the free piston 9.

  When the free piston 9 moves upward in FIG. 1 and is displaced to the vicinity of the stroke end, the cushion body 20b collides with the bottom 30a of the nut portion 30, and further displacement of the free piston 9 toward the stroke end side. Is compressed according to the degree of compression, the moving speed of the free piston 9 is gradually decelerated, and the end of the cylindrical portion 9a of the free piston 9 collides with the flange 30c of the nut portion 30 of the housing 15 vigorously. To prevent the hitting sound from occurring. The extension side cushion 20 may be fixed to the bottom 30a side of the nut portion 30. Since the extension side cushion 20 can be fixed using the extension side coil spring 10, a separate fixing means is required. This is advantageous in that it does not.

  The compression side cushion 21 is fixed to the annular plate 21a stacked on the bottom 32b of the housing body 32, the holding cylinder 21b provided on the inner periphery of the plate 21a, and the inner periphery of the free piston side end of the holding cylinder 21b. It is comprised by the convex-shaped cushion body 21c formed with elastic bodies, such as rubber | gum, which the front-end | tip protrudes toward the free piston side from the holding | maintenance cylinder 21b, The said plate 21a is clamped by the compression side coil spring 11 and the housing main body 32. And fixed to the bottom 32 b of the housing body 32. When the free piston 9 moves downward in FIG. 1 and is displaced to the vicinity of the stroke end, the cushion body 21c collides with the bottom portion 9b of the free piston 9, and further displacement of the free piston 9 toward the stroke end side. 1 generates a reaction force according to the degree of compression, gradually reducing the moving speed of the free piston 9, and the outer periphery of the bottom portion 9 b of the free piston 9 in FIG. 1 on the cylindrical portion 32 a of the housing body 32 in the housing 15. The collision with the stepped portion 32e provided is prevented and the generation of hitting sound is prevented. The compression side cushion 21 may be fixed to the bottom 9b side of the free piston 9, and the compression side coil spring 11 can be used to fix the compression side cushion 21, so that no separate fixing means is required. It is advantageous.

  If the spring element is not used for fixing the cushion C as described above, it is not necessary to use a coil spring for the spring element, and it is only necessary to be able to elastically support the free piston 9. For example, the free piston 9 may be elastically supported by using an elastic body such as a disc spring as a spring element. When a single spring element whose one end is connected to the free piston 9 is used, the other end may be fixed to the nut portion 30 or the housing body 32.

  Further, in this case, the extension side cushion 20 is fixed to either the bottom portion 9b of the free piston 9 or the bottom portion 30a of the nut portion 30. Since it is provided in the cylinder part 30b, the expansion side flow path 5 is not blocked, and the compression side cushion 21 is fixed to either the bottom part 9b of the free piston 9 or the bottom part 32b of the housing body 32. Even if it collides with the other of these, since the opening 32d is provided in the cylindrical portion 32b of the housing body 21, the pressure side flow path 6 is not blocked, so that the extension side cushion 20 and the pressure side cushion 21 are opened. It will not be damaged by interfering with 30e, 32d, and the smooth displacement of the free piston 9 will not be hindered.

  The extension side coil spring 10 is accommodated in the cylindrical portion 9a of the free piston 9, and the extension side coil spring 10 is aligned to prevent positional displacement with respect to the free piston 9, thereby stably supplying the free piston 9 to the free piston 9. An energizing force can be applied. Further, by setting the outer peripheral shape of the plate 21 a of the compression side cushion 21 to a shape that matches the inner peripheral shape of the small diameter portion 32 c of the housing body 32, the compression side coil spring 11 is loosely fitted to the outer periphery of the holding cylinder 21 b of the compression side cushion 21. As a result, the pressure-side coil spring 11 can be roughly aligned, thereby preventing the displacement of the pressure-side coil spring 11 with respect to the free piston 9, and the urging force can be applied to the free piston 9 stably. .

  The operation of the shock absorber D configured as described above will be described. First, the case where the input frequency to the shock absorber D is low will be described. Considering the condition that the input speed is the same, if the input frequency is low, the free piston 9 is displaced when the amplitude of the free piston 9 is increased, so that the elongation is increased. The urging force for returning the free piston 9 to the neutral position is acted by the resultant force of the side coil spring 10 and the pressure side coil spring 11, and the expansion side pressure chamber 7 corresponds to the urging force of the extension side coil spring 10 and the pressure side coil spring 11. There is a difference in pressure between the pressure-side pressure chamber 8 and the pressure-expanding chamber, and the expansion-side chamber has a higher pressure than the decreasing-side chamber.

  Then, the differential pressure between the expansion side pressure chamber 7 and the expansion side chamber R1 and the differential pressure between the compression side pressure chamber 8 and the compression side chamber R2 become small, and the flow rate passing through the expansion side flow channel 5 and the pressure side flow channel 6 is as follows. Decrease. As the flow rate passing through the extension side flow channel 5 and the pressure side flow channel 6 decreases, the flow rate of the passages 3a and 3b increases, and the generated damping force of the shock absorber D increases.

  On the contrary, since the input amplitude is small at the time of high frequency input, the flow rate of one cycle moving from the expansion side chamber R1 to the compression side chamber R2 or from the compression side chamber R2 to the expansion side chamber R1 is small, and the displacement of the free piston 9 is also small. . Then, the urging force of the extension side coil spring 10 and the compression side coil spring 11 received by the free piston 9 is also reduced. Accordingly, the difference between the pressure in the expansion side pressure chamber 7 and the pressure in the compression side pressure chamber 8 becomes smaller, the differential pressure between the expansion side pressure chamber 7 and the expansion side chamber R1, and the differential pressure between the compression side pressure chamber 8 and the compression side chamber R2. Is maintained large, the flow rate passing through the extension side flow channel 5 and the pressure side flow channel 6 becomes larger than that at the time of low frequency, and the flow rate of the passages 3a and 3b is reduced correspondingly, and the damping generated by the shock absorber D Power will also decrease.

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

  Further, when the free piston 9 is displaced to the vicinity of the stroke end, the extension side cushion 20 or the compression side cushion 21 abuts on the free piston 9 or the housing 15 as described above, and the free piston 9 is further moved toward the stroke end side. It is possible to prevent the free piston 9 and the housing 15 from colliding with each other by suppressing the displacement while gradually reducing the moving speed, and the expansion side cushion 20 or the compression side cushion 21 is free from the free piston 9 or the housing 15. Since it functions so as to gradually decrease the moving speed of the free piston 9 toward the stroke end side, the liquid movement through the expansion side flow path 5 and the pressure side flow path 6 is gradually suppressed. Will be. Therefore, when the vibration frequency of the shock absorber D is relatively high, a relatively low damping force is generated until the shock absorber D contacts the free piston 9 or the housing 15 with the expansion side cushion 20 or the compression side cushion 21. When the expansion side cushion 20 or the compression side cushion 21 abuts on the free piston 9 or the housing 15, the damping force generated by the shock absorber D gradually increases, and the displacement of the free piston 9 is changed to the expansion side cushion 20 or the compression side cushion 21. When it is completely stopped by, the damping force is generated with the maximum damping coefficient. Therefore, the shock absorber D gradually reduces the generated damping force with respect to the input of vibration with a large amplitude such that the free piston 9 is displaced until the expansion side cushion 20 or the compression side cushion 21 abuts the free piston 9 or the housing 15. Since it is increased, there is no sudden change from a low damping force to a high damping force, and the damping force change from a low damping force to a high damping force becomes gentle. Therefore, in this shock absorber D, even if a vibration with a large amplitude is input, the generated damping force changes gently, and it is not necessary for the passenger to perceive a shock due to the change in the damping force. In particular, when the vibration frequency is high, since a low damping force is generated, a sudden change in the generated damping force can be effectively mitigated.

  As described above, according to the shock absorber D of the present invention, by suppressing the collision between the free piston 9 and the housing 15 with the cushion C, it is possible to suppress the occurrence of both of the hitting sounds and to prevent a sudden change in the damping force. It is possible to improve the riding comfort in the vehicle.

  Further, since the occurrence of a hitting sound can be suppressed, in this shock absorber D, it is not necessary for the vehicle occupant to perceive the hitting sound, and the passenger does not feel uneasy or uncomfortable. . The cushion bodies 20b and 21c in the extension side cushion 20 and the compression side cushion 21 are made of an elastic body such as rubber. However, as described above, the free piston 9 and the housing 15 are prevented from colliding with force. If possible, it is also possible to use metal springs for the cushion bodies 20b and 21c.

  As shown in FIG. 2, the cushion C <b> 1 may be configured by a cushion rubber 22 that is a rubber member that penetrates the bottom portion 13 b of the free piston 13. Specifically, the free piston 13 is formed in a bottomed cylindrical shape, and protrudes toward the pressure side pressure chamber 8 from the cylindrical portion 13a, an annular bottom portion 13b provided at one end of the cylindrical portion 13a, and the inner periphery of the bottom portion 13b. The holding cylinder 13c is provided, and a rod-like cushion rubber 22 is inserted into the holding cylinder 13c. The cushion rubber 22 has an upper end 22a in FIG. 2 and a lower end 22b in FIG. 2 protruding outward from the holding cylinder 13c, and the body 22c is held by the holding cylinder 13c. In addition, as a method for fixing the cushion rubber 22 to the holding cylinder 13c, various fixing methods such as adhesion, fusion, and press-fitting can be employed.

  The upper end 22a of the cushion rubber 22 is hemispherical, protrudes into the extension side pressure chamber 7, and constitutes an extension side cushion facing the bottom 30a of the nut portion 30, and the lower end 22b of the cushion rubber 22 is hemispherical. The pressure side cushion protrudes into the pressure side pressure chamber 8 and faces the bottom portion 32b of the housing main body 32 to constitute a pressure side cushion.

  Even if the cushion C1 is configured in this way, when the free piston 13 is displaced to the vicinity of the upper stroke end in FIG. 2, the upper end 22a of the cushion rubber 22 as the extension side cushion is the bottom 30a of the nut portion 30 which is the housing 15. 2, the displacement of the free piston 13 is suppressed, and when the free piston 13 is displaced to the vicinity of the stroke end on the lower side in FIG. 2, the lower end 22 b of the cushion rubber 22 as the compression side cushion is the housing 15. The displacement of the free piston 13 is suppressed by abutting against the bottom 32b.

  Therefore, even in the shock absorber provided with the cushion C1, as with the shock absorber D, the collision between the free piston 13 and the housing 15 can be suppressed by the cushion C1, thereby suppressing the occurrence of both hit sounds. A sudden change in the damping force can be prevented, and the riding comfort in the vehicle can be improved.

  Further, since the occurrence of a hitting sound can be suppressed, even with this shock absorber, it is not necessary for the vehicle occupant to perceive the hitting sound, and the occupant does not feel uneasy or uncomfortable. Further, it is a rubber member that penetrates the free piston 13 to form the expansion side cushion and the compression side cushion, and the expansion side pressure chamber 7 and the pressure side pressure chamber 8 communicate with each other even though it penetrates the free piston 13. Therefore, there is no need to consider the seal, the number of parts is small and the number of assembly steps is not required, and the installation cost of the cushion C1 is low as compared with the shock absorber D of FIG.

  Further, as shown in FIG. 3, the cushion 17 may be provided by changing the structure of the housing 17. The housing 17 is configured to include a nut portion 33 having a cylindrical shape that is screwed to the screw portion 4c of the piston rod 4 and having a flange 33b on the outer periphery thereof, and a bottomed cylindrical housing main body 34. The upper end opening in FIG. 3 of the main body 34 is crimped toward the outer periphery of the flange 33b and is attached to the outer periphery of the flange 33b, so that the housing main body 34 and the nut portion 33 are integrated.

  The nut portion 33 has a cylindrical shape, and includes a cylindrical portion 33a having a screw portion 33c on the inner periphery, and a flange 33b provided in a flange shape on the outer periphery of the end portion of the cylindrical portion 33a. And this nut part 33 fixes the above-mentioned piston 2 and each member laminated | stacked on this to the piston rod 4 as mentioned above by screwing the cylinder part 33a to the screw part 4c of the piston rod 4. In addition, the housing 17 can be fixed to the small diameter portion 4a of the piston rod 4. Further, in this case, since the first elastic body 23 constituting the cushion C2 is provided at a position where there is no fear of closing the lower end in FIG. 3 of the cylindrical portion 33a of the nut portion 33, it is shown in FIG. 1 and FIG. Unlike the nut portion 30, the lower end of the cylindrical portion 33 a is not closed by the bottom portion, and in this embodiment, the nut portion 33 is not involved in the formation of the extension-side flow path 5.

  The housing main body 34 has a cylindrical portion 34a and a bottom portion 34b that closes the lower end of the cylindrical portion 34a, and has a bottomed cylindrical shape. The cylindrical portion 34a has a large diameter portion 34c and a large diameter portion 34c from above in FIG. An intermediate portion 34d having a smaller diameter and a small diameter portion 34e having a diameter smaller than that of the intermediate portion 34d are formed in this order. In addition, a second step portion 34g is provided at the boundary between the intermediate portion 34d and the small diameter portion 34e. Furthermore, an orifice hole 34 h is provided in the bottom 34 b of the housing body 34.

  A bottomed cylindrical free piston 14 is slidably inserted into the housing 17 formed by the housing main body 34 and the nut portion 33, and the inside of the housing 17 is extended by the free piston 14. It is divided into a pressure chamber 7 and a pressure side pressure chamber 8.

  The free piston 14 has a bottomed cylindrical shape, and is provided on the housing main body 34 provided on the cylinder portion 14a, the bottom portion 14b that closes the lower end in FIG. 3 of the cylinder portion 14a, and the pressure side pressure chamber side of the bottom portion 14b. And a convex portion 14c facing the orifice hole 34h. The free piston 14 configured as described above has the outer periphery of the cylindrical portion 14 a in sliding contact with the inner periphery of the intermediate portion 34 d of the cylindrical portion 34 a of the housing body 34, and the first step portion 34 f is brought into contact with the expansion side pressure chamber 7. The second step portion 34g faces the pressure side pressure chamber 8.

  The cushion C2 is an annular elastic body, and is a first elastic body 23 interposed between the flange 33b of the nut portion 33 and the first step portion 34f of the housing main body 34, and is also an annular elastic body. The second elastic body 24 is fitted to the intermediate portion 34d and stacked on the upper end in FIG. 3 of the second step portion 34g.

  In this embodiment, the first elastic body 23 and the second elastic body 24 are both rubber rings made of annular rubber. When the free piston 14 strokes upward in FIG. 3 and collides with the upper end in FIG. 3 of the cylindrical portion 14 a of the free piston 14, the first elastic body 23 is an upper side that is further on the stroke end side of the free piston 14. 3, and when the compression of the free piston 14 ascends in FIG. 3, a repulsive force corresponding to the amount of compression is exerted to gradually reduce the speed of the free piston 14, thereby reducing the free piston 14 and the housing 17. Prevent collisions. When the free piston 14 strokes downward in FIG. 3 and collides with the outer periphery of the lower end in FIG. 3 of the bottom 14b of the free piston 14, the second elastic body 24 is the lower end of the free piston 14 on the further stroke end side. 3, and when the compression progresses as the free piston 14 descends in FIG. 3, a repulsive force corresponding to the amount of compression is exerted to gradually reduce the speed of the free piston 14, thereby reducing the free piston 14 and the housing 17. Prevent collisions.

  Therefore, even in the shock absorber provided with the cushion C2, as in the shock absorber D, the collision between the free piston 14 and the housing 17 can be suppressed by the cushion C2, thereby suppressing the occurrence of both hit sounds. A sudden change in the damping force can be prevented, and the riding comfort in the vehicle can be improved.

  In the case of this embodiment, when the free piston 14 strokes downward in FIG. 3 in which the compression side pressure chamber 8 is compressed, the convex portion 14c provided below the bottom portion 14b of the free piston 14 approaches the orifice hole 34h. Since the orifice hole 34h is gradually closed, the closer the free piston 14 is to the lower stroke end in FIG. 3, the lower the movement of the free piston 14 by the second elastic body 24 is suppressed. In addition, since it is difficult for the liquid to escape from the pressure side pressure chamber 8 compressed by the free piston 14 to the pressure side chamber R2 and the moving speed of the free piston 14 is reduced, it is possible to reliably prevent the occurrence of a hitting sound between the free piston 14 and the housing 17. can do.

  Further, since the occurrence of a hitting sound can be suppressed, even with this shock absorber, it is not necessary for the vehicle occupant to perceive the hitting sound, and the occupant does not feel uneasy or uncomfortable. The first elastic body 23 and the second elastic body 24 are formed by annularly forming a resin such as a rubber such as a square ring or an O-ring, or a synthetic resin, and as wave washers 25 and 26 as shown in FIG. Alternatively, either one of the stretch side cushion and the pressure side cushion may be a wave washer, and the other of the stretch side cushion and the pressure side cushion may be a ring made of a resin such as rubber or a synthetic resin.

  In the above-described embodiment, the housings 15 and 17 are provided in the cylinder 1, but may be provided outside the cylinder 1.

 This is the end of the description of the embodiment of the present invention, but the scope of the present invention is of course not limited to the details shown or described.

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

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3a, 3b as a partition member Passage 4 Piston rod 5 Stretch side flow path 7 Stretch side pressure chamber 6 Pressure side flow path 8 Pressure side pressure chamber 9, 13, 14 Free piston 9b Bottom part 10 in free piston As spring element Extension side coil spring 11 Pressure side coil springs 15 and 17 as spring elements Housing 20 Extension side cushion 21 Pressure side cushion 22 Rubber member 22a Upper end 22b of rubber member as extension side cushion Lower end 23 of rubber member as compression side cushion First elastic body 24 Second elastic body 25, 26 Wave washer 30, 33 Nut portion 30a Nut portion bottom portion 30b Nut portion tube portion 30c, 33b 鍔 30e Nut portion opening 32, 34 Housing body 32a, 34a Tube portion 32d in housing body Housing Openings C, C1, C2 in the body Cushion D dampener R1 expansion side chamber R2 compression side chamber R3 pressure chamber

Claims (8)

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 passage that communicates the extension side chamber and the pressure side chamber, and a housing that forms a pressure chamber therein An expansion side pressure chamber that is movably inserted into the housing and communicates the pressure chamber with the expansion side chamber via the expansion side flow channel, and a pressure side pressure chamber that communicates with the compression side chamber via the pressure side flow channel. In a shock absorber provided with a free piston partitioned into two and a spring element that generates an urging force that suppresses displacement of the free piston with respect to the housing, a cushion is provided to prevent a collision between the free piston and the housing. A shock absorber characterized by. The cushion includes an extension side cushion that prevents a collision with the housing when moving in the direction of compressing the extension side pressure chamber of the free piston, and a case of moving in the direction of compressing the compression side pressure chamber of the free piston. The shock absorber according to claim 1, further comprising a compression side cushion that prevents a collision with the housing. One end includes a piston rod that penetrates the partition member, and the housing is a bottomed cylindrical shape that is screwed to one end of the piston rod to fix the partition member to the piston rod and has a flange on the outer periphery. And a bottomed cylindrical housing main body extending from the outer periphery of the flange of the nut portion to form a pressure chamber, and a part of the extension side flow path is formed in the cylindrical portion of the nut portion. And an opening forming a part of the pressure side flow path in the cylindrical portion of the housing main body, and the extension side cushion is one of a side surface of the extension side pressure chamber of the free piston and a bottom portion of the nut portion. The free piston and the housing are prevented from colliding with each other by the abutment between the side surface of the expansion side pressure chamber of the free piston and the other bottom of the nut portion. Fixed to one of the pressure side pressure chamber side of the free piston and the bottom of the housing body, and the free piston and the housing are brought into contact with each other by the side of the pressure side pressure chamber of the free piston and the other bottom of the housing body. The shock absorber according to claim 2, wherein collision is prevented. The spring element includes an extension side coil spring interposed between the free piston and the nut portion, and a compression side coil spring interposed between the free piston and the housing body. The extension side cushion is fixed to one of the extension side pressure chamber side surface of the free piston and the bottom of the nut portion by the extension side coil spring, and the compression side cushion is fixed to the pressure side pressure chamber side surface of the free piston by the compression side coil spring. The shock absorber according to claim 3, wherein the shock absorber is fixed to one of the bottom portions of the housing body. A rubber member penetrating the free piston is provided, an extension side pressure chamber side end of the rubber member is used as the extension side cushion, and a pressure side pressure chamber side end of the rubber member is used as the compression side cushion. 2. The shock absorber according to 2. One end includes a piston rod that penetrates the partition member, and the housing is a bottomed cylindrical shape that is screwed to one end of the piston rod to fix the partition member to the piston rod and has a flange on the outer periphery. And a bottomed cylindrical housing main body extending from the outer periphery of the flange of the nut portion to form a pressure chamber, and the free piston is a bottomed cylindrical shape, and the outer periphery of the cylindrical portion is The sliding body is slidably contacted with the cylindrical portion of the housing main body and is inserted into the pressure chamber with the inside facing the expansion side pressure chamber, and the expansion side cushion is interposed between the flange of the nut portion and the cylindrical portion of the housing main body. And an annular first elastic body interposed between the first step portion provided at the portion facing the extension side pressure chamber side, and the compression side cushion is disposed in the middle of the cylindrical portion of the housing body. Facing the pressure side pressure chamber Shock absorber according to claim 2, characterized in that the the second elastic body annular laminated to the second step portion provided on the site. The shock absorber according to claim 6, wherein the first elastic body and the second elastic body are wave washers or rubber rings. The housing is provided with an orifice hole for communicating the pressure side pressure chamber and the pressure side chamber, and a convex portion facing the orifice hole is provided on the pressure side pressure chamber side of the bottom of the free piston, and the free piston has the pressure side pressure. The shock absorber according to claim 6 or 7, wherein the convex portion approaches the orifice hole when the chamber is displaced in a compressing direction.

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