JP5822355B2 - Shock absorber - Google Patents

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.

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, since the housing which accommodates a free piston is being fixed to the front-end | tip of a piston rod with a piston, a leaf valve, etc., the full length from a piston to a housing becomes long.

  Therefore, in the case of such a shock absorber, the stroke length is shortened by the amount of installation of the housing compared to a shock absorber without a housing, and if the stroke length is to be secured, the total length of the shock absorber becomes long and the vehicle is The mounting length of the vehicle deteriorates, and when it is attempted to secure the mounting property to the vehicle, the stroke length becomes insufficient, and it is difficult to achieve both the stroke length and the mounting property to the vehicle.

  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 capable of achieving both ensuring of the stroke length and mounting on a vehicle. It is to be.

  In order to solve the above-described object, the problem solving means in the present invention includes a cylinder, a piston 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 and the compression side. Attenuation passage communicating with the chamber, a pressure chamber, and an expansion side pressure chamber that is movably inserted into the pressure chamber and communicates with the expansion side chamber via the expansion side channel and the pressure side channel In the shock absorber provided with a free piston that is partitioned into a pressure side pressure chamber that communicates with the pressure side chamber, and a spring element that generates a biasing force that suppresses displacement of the free piston with respect to the pressure chamber, the pressure chamber includes: It is provided in the cylinder shape which covers the outer periphery of the said cylinder.

  As described above, in the shock absorber according to the present invention, since the pressure chamber has a cylindrical shape covering the outer periphery of the cylinder, it is not necessary to provide the pressure chamber at the tip of the piston rod, so the stroke length of the shock absorber is sacrificed. And the overall length of the shock absorber does not increase.

  According to the shock absorber of the present invention, it is possible to achieve both ensuring of the stroke length and mountability to the vehicle.

It is a longitudinal cross-sectional view of the shock absorber in one embodiment. It is a longitudinal cross-sectional view of the buffering device in other embodiment. It is a figure which shows the characteristic (frequency damping force characteristic) of the damping force which a buffer device generate | occur | produces with respect to a vibration frequency when a piston speed exists in a high-speed area and a buffer device expands and contracts. It is a figure which shows the characteristic (speed damping force characteristic) of the damping force generate | occur | produced with respect to the piston speed of a buffering device, when a buffering device vibrates with a certain vibration frequency.

  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, Attenuation passages 3a and 3b communicating the extension side chamber R1 and the pressure side chamber R2, the pressure chamber R3, and the pressure chamber R3 are movably inserted to extend the pressure chamber R3 via the extension side channel 5. A free piston 9 partitioned into an expansion side pressure chamber 7 communicated with the side chamber R1 and a pressure side pressure chamber 8 communicated with the pressure side chamber R2 via the pressure side flow path 6, and displacement of the free piston 9 relative to the pressure chamber R3. And a spring element 10 that generates an urging force to be suppressed. The spring element 10 is interposed between a vehicle body and an axle in a vehicle to generate a damping force and 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 the upper end of the cylinder 1. Is slidably supported by an annular head member 11. A valve case 13 having a base valve 12 is fitted to the lower end of the cylinder 1.

  Further, on the outer periphery of the cylinder 1, a housing pipe 14 that covers the cylinder 1 and forms a pressure chamber R <b> 3 with an annular gap between the cylinder 1 is provided. An outer cylinder 15 that covers the outer periphery of the housing pipe 14 and forms a reservoir R in an annular gap between the housing pipe 14 is provided on the outer periphery of the housing pipe 14. The upper end of the housing pipe 14 is fitted with the head member 11 and the upper end of the housing pipe 14 is closed. The lower end of the housing pipe 14 is fitted with the valve case 13 and the lower end of the housing pipe 14 is closed. Has been. Further, the upper end of the outer cylinder 15 is fitted with the above-described head member 11, the upper end of the outer cylinder 15 is closed, and the lower end of the outer cylinder 15 is closed by a cap 16. The reservoir R formed between the outer cylinder 15 and the housing pipe 14 communicates with the pressure side chamber R2 in the cylinder 1 through ports 13a and 13b provided in the valve case 13. 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 the case of this shock absorber D, since it is a single rod type shock absorber, the volume of liquid that the piston rod 4 retreats from the cylinder 1 is insufficient in the cylinder 1 during the extension operation, and the piston rod 4 is in the cylinder 1 during the contraction operation. The volume of liquid that enters the inside is excessive in the cylinder 1, but when the liquid is excessive in the cylinder 1, it is absorbed by the reservoir R, and when the liquid is insufficient in the cylinder 1, the liquid is absorbed from the reservoir R. The liquid is supplied into the cylinder 1 to perform volume compensation. In this embodiment, the reservoir R is provided to perform volume compensation. However, a sliding partition wall is slidably inserted in the cylinder 1 to provide a gas chamber in the cylinder 1, and the volume of the gas chamber is set. You may make it volume-compensate by a change. 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. The cylinder 1 is provided with an extension-side flow path 5 formed of a through hole communicating with the inside and outside in the vicinity of the upper end in FIG. A pressure-side flow path 6 made of holes is provided. An annular head member 11 is fitted to the upper ends of the cylinder 1, the housing pipe 14, and the outer cylinder 15 in FIG. 1, and an annular seal member 17 is laminated above the head member 11, and the outer cylinder 1, the head member 11 and the seal member 17 are fixed to the cylinder 1, the housing pipe 14, and the outer cylinder 15. Further, a valve case 13 is fitted to the lower ends in FIG. 1 of the cylinder 1 and the housing pipe 14, and a cap 16 is attached to the lower ends in FIG. 1 of the outer cylinder 15, and the cylinder 1 and the housing pipe 14 are It is sandwiched between the head member 11 and the valve case 13 and fixed to the outer cylinder 15. The seal member 17 seals between the outer periphery of the piston rod 4 inserted through the head member 11 and the outer cylinder 15.

  As shown in FIG. 1, the piston rod 4 has a small-diameter portion 4a formed on the lower end side thereof, and a screw portion 4b formed on the distal end side of the small-diameter portion 4a. 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 damping passages 3a and 3b for communicating the expansion side chamber R1 and the pressure side chamber R2, and the upper end of the damping passage 3a in FIG. 1 is closed by a pressure side leaf valve V1 which is a damping force generating element. Further, the lower end in FIG. 1 of the other damping passage 3b is also closed by the extension side leaf valve V2 which is a damping force generating element.

  Both the pressure side leaf valve V1 and the extension side leaf valve V2 are formed in an annular shape, and the small diameter portion 4a of the piston rod 4 is inserted on the inner peripheral side, and is screwed to the screw portion 4b from below the extension side leaf valve V2. The piston 2, the pressure side leaf valve V 1, and the extension side leaf valve V 2 are fixed to the small diameter portion 4 a of the piston rod 4 by the piston nut 18.

  The compression side leaf valve V1 is bent by the pressure difference between the compression side chamber R2 and the expansion side chamber R1 when the shock absorber D contracts, opens the damping passage 3a, and moves from the compression side chamber R2 to the expansion side chamber R1. The damping passage 3a is closed when the shock absorber D is extended, and the other extension side leaf valve V2 is opposite to the compression side leaf valve V1 when the shock absorber D is extended. And the damping passage 3b is closed during contraction. 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 damping 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 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 damping passages 3a and 3b are provided as in the shock absorber D so that the liquid can pass only when the shock absorber D is extended or contracted. Alternatively, 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.

  The valve case 13 includes ports 13a and 13b communicating the pressure side chamber R2 and the reservoir R, and a base valve 12 that provides resistance to the flow of liquid from the pressure side chamber R2 to the reservoir R at the lower end of the port 13a. A check valve 23 is provided at the upper end of the port 13b to allow the flow of liquid from the reservoir R to the pressure side chamber R2. When the shock absorber D contracts and compresses the pressure side chamber R2, the base valve 12 gives resistance to the flow of the liquid and discharges excess liquid in the cylinder 1 to the reservoir R. Demonstrate the damping force on the compression side in cooperation with V1. Further, when the shock absorber D is extended, the check valve 23 opens the port 13b and the liquid deficient in the cylinder 1 is supplied from the reservoir R.

  Subsequently, an annular free piston 9 slidably contacting both the outer periphery of the cylinder 1 and the inner periphery of the housing pipe 14 is inserted into the pressure chamber R3. 1 is divided into an extension side pressure chamber 7 in the upper part in FIG. 1 communicated with the extension side chamber R1 through the passage 5 and a pressure side pressure chamber 8 in the lower part in FIG. 1 in communication with the compression side chamber R2 through the pressure side flow path 6. Has been.

  An annular groove 9 a is provided on the inner periphery of the free piston 9, and a seal ring 19 that slides on the outer periphery of the cylinder 1 is mounted in the annular groove 9 a. An annular groove 9 b is also provided on the outer periphery of the free piston 9, and a seal ring 20 that is in sliding contact with the inner periphery of the housing pipe 14 is mounted in the annular groove 9 b. Since the annular grooves 9a and 9b are provided in the free piston 9 so as to be shifted in the axial direction, the annular grooves 9a and 9b are arranged in the radial direction of the free piston 9 rather than arranged in the radial direction of the free piston 9. , And the cylinder 1 and the housing pipe 14 can be inserted into a narrow space without difficulty.

  In this case, the pressure side flow path 6 is set to have a diameter capable of giving resistance to the liquid passing through the hole diameter, and functions as a throttle path. It may be made to function, or one or both of the expansion side flow path 5 and the pressure side flow path 6 may be made to function as a throttle passage depending on the attenuation characteristic to be realized.

  Further, as a spring element for applying an urging force that suppresses the displacement of the free piston 9 relative to the pressure chamber R3 to the free piston 9, it is in the extension side pressure chamber 7 and between the free piston 9 and the head member 11. The expansion side coil spring 21 is interposed, and the compression side coil spring 22 is interposed in the compression side pressure chamber 8 between the free piston 9 and the valve case 13. It is sandwiched from above and below by a spring element 10 composed of a coil spring 21 and a pressure side coil spring 22, and is elastically supported after being positioned at a predetermined neutral position in the pressure chamber R3. The neutral position does not indicate the center of the pressure chamber R3 in the axial direction, but is a position where the free piston 9 is positioned by the spring element.

  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 21 and the pressure side coil spring 22, and the expansion side pressure chamber 7 corresponds to the urging force of the extension side coil spring 21 and the pressure side coil spring 22. 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 attenuation 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 21 and the compression side coil spring 22 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 at a large value, the flow rate passing through the extension side flow channel 5 and the pressure side flow channel 6 becomes larger than that at the low frequency, and the flow rate of the attenuation passages 3a and 3b is reduced correspondingly, and the shock absorber D is generated. The damping force 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.

  In the shock absorber D of the present invention, since the pressure chamber R3 has a cylindrical shape covering the outer periphery of the cylinder 1, it is not necessary to provide the pressure chamber R3 at the tip of the piston rod 4, so that the stroke of the shock absorber D The length is not sacrificed, and the total length of the shock absorber D is not increased. Therefore, according to the shock absorber D of the present invention, it is possible to achieve both ensuring of the stroke length and mountability to the vehicle.

  Further, the pressure chamber R3 having a cylindrical shape can be realized by forming the pressure chamber R3 between the cylinder 1 and the housing pipe 14 covering the outer periphery of the cylinder 1. Furthermore, by providing an outer cylinder 15 that covers the outer periphery of the housing pipe 14 and forming the reservoir R in the annular gap between the outer cylinder 15 and the housing pipe 14, the reservoir R is also formed into a cylindrical shape. Since it is provided on the outer periphery of 1, the reservoir R does not affect the stroke length of the shock absorber D, and the length of the shock absorber D can be prevented from becoming long. An outer cylinder 15 is provided on the outer periphery of the cylinder 1, a reservoir R is provided between the cylinder 1 and the outer cylinder 15, and a housing pipe 14 is provided on the outer periphery of the outer cylinder 15, between the outer cylinder 15 and the housing pipe 14. It is also possible to provide a pressure chamber R3. However, as described above, by providing the pressure chamber R3 between the cylinder 1 and the housing pipe 14, the communication between the expansion side pressure chamber 7 and the expansion side chamber R1, the communication between the pressure side pressure chamber 8 and the pressure side chamber R2, Is advantageous in that the communication between the pressure side chamber R2 and the reservoir R is facilitated. This is because an outer cylinder 15 is provided on the outer periphery of the cylinder 1, a reservoir R is provided between the cylinder 1 and the outer cylinder 15, a housing pipe 14 is provided on the outer periphery of the outer cylinder 15, and the outer cylinder 15, the housing pipe 14, When the pressure chamber R3 is provided between them, the head member 11 and the valve case 13 need to be processed for the communication between the expansion side pressure chamber 7 and the expansion side chamber R1 and the communication between the pressure side pressure chamber 8 and the pressure side chamber R2. In addition, the arrangement and structure of the port for communicating the compression side chamber R2 and the reservoir R, and the base valve 12 and the check valve 23 to be provided in the port become complicated.

Further, in the case where the spring constant is set so as to increase when the extension side coil spring 21 and the compression side coil spring 22 are compressed by a predetermined amount, the free piston 9 is located near or below the stroke end on the upper side in FIG. In the case of displacement up to the vicinity of the stroke end, the spring constant of the extension side coil spring 21 or the compression side coil spring 22 becomes large, and the force that suppresses the movement of the free piston 9 toward the stroke end side can be increased. The displacement can be suppressed while the moving speed to the stroke end side of 9 or more is decelerated. Here, until the free piston 9 reaches the stroke end, the free piston 9 can move in the pressure chamber R3 with respect to the input of high-frequency vibration, and a relatively low damping force can be generated. When the displacement of the free piston 9 is completely stopped, the damping force reducing effect is lost and the damping force is generated with the maximum damping coefficient. However, the extension side coil spring 21 and the compression side coil spring 22 are compressed by a predetermined amount. If the spring constant is set so as to increase, if the displacement of the free piston 9 reaches the stroke end as described above, the displacement is suppressed while decelerating the moving speed of the free piston 9. Since the damping device D gradually increases the generated damping force, there is no sudden change from a low damping force to a high damping force. The damping force change of is gentle. Therefore, in this case, in the shock absorber D, even if a vibration with a large amplitude is input, the generated damping force changes gently, and the passenger does not perceive a shock due to the change in the damping force. That's it. In particular, when the vibration frequency is high, since a low damping force is generated, a sudden change in the generated damping force can be effectively mitigated. In order to increase the spring constant of the extension side coil spring 21 and the compression side coil spring 22 by a predetermined amount, for example, a portion having a narrow pitch is provided in a part of the extension side coil spring 21 and the compression side coil spring 22. When a predetermined amount is compressed, it is possible to realize that only a portion with a wide pitch is effective as a spring by closely contacting the filaments in a portion with a narrow pitch, and a portion with a large spring constant This may be realized by providing a small portion and allowing the filament of the portion having a small spring constant to be in close contact when compressed by a predetermined amount. Providing the narrow and wide portions of the extension side coil spring 21 and the compression side coil spring 22 includes laminating a narrow pitch spring and a wide pitch spring to function as a single spring. Providing the extension-side coil spring 21 and the compression-side coil spring 22 with a portion having a large spring constant and a portion with a small spring constant includes laminating a spring having a large spring constant and a spring having a small spring constant to function as one spring. . The predetermined amount, which is the amount of compression at which the spring constant increases, can be arbitrarily set. However, if the spring constant increases, the effect of reducing the damping force is reduced when high-frequency vibration is input. It is preferable to keep the spring constant from changing until the vicinity of the end is reached because the effect of reducing the damping force is not reduced.

  Next, the shock absorber D1 in another embodiment shown in FIG. 2 will be described. The shock absorber D1 in this other embodiment has the same structure as that of the shock absorber D of the above-described embodiment, but includes a bypass passage 30 that connects the extension side chamber R1 and the pressure side chamber R2 around the damping passages 3a and 3b. In the middle of the bypass passage 30, an extension side relief valve 31 that allows the flow of liquid from the extension side chamber R1 to the compression side chamber R2, and a liquid that is parallel to the extension side relief valve 31 and goes from the compression side chamber R2 to the extension side chamber R1. The pressure-side relief valve 32 that allows the flow of gas is added. In the description of the shock absorber D1, since the description of the same configuration as that of the shock absorber D according to the embodiment is repeated, detailed description thereof is omitted.

  The bypass passage 30 is formed by a rod inner passage 4c that opens from the lower end in FIG. 2 facing the pressure side chamber R2 of the piston rod 4 and communicates with the extension side chamber R1 above the piston 2 in FIG. Further, the piston rod 4 is provided with a stretch stopper 40 made of an elastic body that regulates further upward movement of the piston 2 by abutting against the head member 11 at an intermediate portion, and the expansion side relief valve. 31 and the pressure side relief valve 32 are provided between the piston 2 and the extending stopper 40. When the shock absorber D1 pivotally supports the piston rod 4 with the head member 11 and the piston 2 provided at the tip of the piston rod 4 is in sliding contact with the cylinder 1, it receives a lateral force (lateral force). Furthermore, since the head member 11 and the piston 2 receive the lateral force, it is necessary to secure a certain length of the fitting between the head member 11 and the piston 2, so that the extension stopper 40 The extended position is regulated so as to ensure the minimum required fitting length of the head member 11, and the length between the extended stopper 40 and the piston 2 does not contribute to the stroke length of the shock absorber D1. Therefore, even if the extension side relief valve 31 and the pressure side relief valve 32 are provided between the piston 2 and the extension stopper 40, the stroke length of the shock absorber D1 is not affected at all. The total length of the device D1 is not increased.

  The extension side relief valve 31 is mounted on the extension side chamber R1 side above the piston 2 of the piston rod 4 and has an extension side valve disc 33 having an extension side port 33a that communicates the extension side chamber R1 with the in-rod passage 4c. The extension side valve disc 34 is laminated on the extension side valve disc 33 and opens and closes the extension side port 33a.

  The pressure side relief valve 32 is mounted on the side of the expansion side chamber that is above the piston 2 of the piston rod 4 and below the expansion side valve disk 33, and communicates the expansion side chamber R1 with the in-rod passage 4c. A pressure side valve disc 35 having a port 35a and a pressure side valve body 36 that is stacked on the pressure side valve disc 35 and opens and closes the pressure side port 35a are configured.

  Specifically, a piston rod is formed by laminating a pressure side valve body 36, a pressure side valve disk 35, an extension side valve body 34, and an extension side valve disk 33 in this order above the pressure side leaf valve V1 stacked above the piston 2 in FIG. 4, and a partition wall cylinder 37 is fitted to the outer circumferences of the expansion side valve disk 33 and the compression side valve disk 35, and a space A between the expansion side valve disk 33 and the compression side valve disk 35. Is partitioned from the extension side chamber R1. The outlet end of the rod inner passage 4c provided in the piston rod 4 is opposed to a concave portion 35b provided on the inner circumference of the pressure side valve disk 35 and communicating with the pressure side port 35a, and through the concave portion 35b and the pressure side port 35a. And communicated with the space A described above. Therefore, the space A communicates with the compression side chamber R2 through the in-rod passage 4c and also communicates with the expansion side chamber R1 through the expansion side port 33a and the compression side port 35a. In other words, in this case, the bypass path 30 is configured by the in-rod passage 4c, the space A, the extension side port 33a, the concave portion 35b, and the pressure side port 35a.

  The expansion side valve element 34 is an annular leaf valve that is stacked on the space A side of the expansion side valve disk 33 and opens and closes the expansion side port 33a, and the pressure in the expansion side chamber R1 controls the pressure in the compression side chamber R2. When the upper valve opening pressure is reached, the valve opens and the expansion side relief valve 31 opens the bypass passage 30. Therefore, the liquid in the expansion side chamber R1 passes through not only the attenuation passage 3b but also the bypass passage 30 and passes through the pressure side chamber R2. To move to.

  The pressure side valve body 36 is an annular leaf valve that is stacked on the expansion side chamber R1 side of the pressure side valve disk 35 and opens and closes the pressure side port 35a. The pressure in the pressure side chamber R2 exceeds the pressure in the expansion side chamber R1, and the valve opening pressure is increased. Since the pressure side relief valve 32 opens the bypass passage 30, the liquid in the pressure side chamber R2 passes through not only the attenuation passage 3a but also the bypass passage 30 and moves to the extension side chamber R1. Become.

  If the extension side relief valve 31 and the pressure side relief valve 32 are provided between the piston 2 and the extension stopper 40, the stroke length of the shock absorber D is not sacrificed, and the overall length of the shock absorber D is increased. Therefore, the structures of the extension-side relief valve 31 and the pressure-side relief valve 32 are not limited to the specific structures described above.

  The operation of the shock absorber D1 in another embodiment will be described. First, when the extension-side relief valve 31 and the pressure-side relief valve 32 do not open the bypass passage 30, the operation of the shock absorber D1 is the same as that of the shock absorber D described above, and the shock absorber D1 operates against vibrations in a low frequency range. Thus, a large damping force can be generated, and the damping force can be reduced with respect to vibration in a high frequency range, and a damping force suitable for the vehicle can be generated depending on the input vibration frequency.

  On the other hand, in a scene where a sudden large-amplitude vibration is input to the shock absorber D1, when the moving speed of the piston 2 relative to the cylinder 1 reaches a high speed range regardless of the input vibration frequency, the extension side chamber R1 The flow rate of movement to the compression side chamber R2 or from the compression side chamber R2 to the expansion side chamber R1 is increased, and the resistance given to the flow of liquid passing through the pressure side flow path 6 that functions as a throttle passage is liquid in the expansion side leaf valve V1 and the pressure side leaf valve V2. The resistance is much larger than the resistance given to the flow of the liquid, and the liquid flows preferentially through the attenuation passages 3a and 3b and tries to move 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. However, in the case of the shock absorber D1 of the present embodiment, when the piston speed is high and moves upward in FIG. 2 to exhibit the extension operation, the high pressure in the extension side chamber R1 acts on the extension side relief valve 31. Then, the expansion side relief valve 31 opens and the expansion side chamber R1 and the pressure side chamber R2 communicate with each other through the bypass passage 30, and the piston speed is high and moves downward in FIG. When the operation is performed, the pressure in the pressure side chamber R2 that has become high pressure acts on the pressure side relief valve 32, and the pressure side relief valve 32 is opened so that the pressure side chamber R2 and the expansion side chamber R1 communicate with each other through the bypass passage 30. It has become.

  Therefore, when the shock absorber D1 exhibits an expansion / contraction operation at high speed, the liquid passes from the expansion side chamber R1 to the compression side chamber R2 or from the compression side chamber R2 to the expansion side chamber via the bypass passage 30 as well as the attenuation passages 3a and 3b. The damping force generated by the shock absorber D1 is reduced and does not increase to the values set by the specifications of the extension side leaf valve V1 and the compression side leaf valve V2.

  As described above, in the shock absorber D1 of the present embodiment, even if the piston speed becomes very high and the apparent movement of the liquid through the pressure chamber R3 becomes difficult, FIG. 3 and FIG. In contrast to the frequency damping force characteristic and speed damping force characteristic (damping force characteristic with respect to the piston speed of the shock absorber) indicated by the broken line in FIG. 3, as shown by the solid line in FIG. 3 and FIG. Since the force gradient can be reduced and the damping force can be reliably reduced, the damping force stays high as in the case of conventional shock absorbers, and the effect of insulating the transmission of vibration from the axle to the vehicle body is effective. The problem of disappearing can be solved, and the riding comfort in the vehicle can be improved.

  Further, when the shock absorber D1 is extended, only the expansion side relief valve 31 is opened, and when the shock absorber D1 is contracted, only the pressure side relief valve 32 is opened, so that the speed damping force characteristic when the shock absorber D1 is extended is shown. It can be adjusted by setting the expansion side valve body 34 and the expansion side port 33a, and the speed damping force characteristic when the shock absorber D1 is contracted can be adjusted by setting the compression side valve body 36 and the compression side port 35a. That is, the speed damping force characteristics at the time of expansion and contraction of the shock absorber D1 can be set independently, and the degree of tuning freedom is greatly improved.

  That is, as shown in FIG. 4, the position of the extension side fold point a of the extension side speed damping force characteristic of the shock absorber D1, the inclination after the fold point a, and the speed damping force characteristic of the shock absorber D1 on the contraction side. The position of the fold point b on the contraction side and the inclination after the fold point b can be set independently. The position of the fold point a is determined by the valve opening pressure of the expansion side valve body 34 and the inclination after the fold point a. Is designed according to the opening area and passage resistance of the expansion side port 33a, the position of the break point b is the valve opening pressure of the compression side valve body 36, and the inclination after the break point b is designed according to the opening area and passage resistance of the compression side port 35a. Can be freely set according to the intention of the person.

  As described above, since the gradient of the speed damping force characteristic in the contraction stroke of the shock absorber D1 can be reduced, the impact shock reduction effect when the wheel rides on the road surface is increased, and the gradient of the speed damping force characteristic in the extension stroke is increased. Since it can be reduced, it is possible to mitigate the impact generated when the submerged vehicle body is turned back, and the speed damping force characteristics can be freely set on both sides of the expansion and contraction. The impact shock can be reduced while firmly supporting the vehicle body when turning, and the vehicle can be provided with a supple but firm suspension.

  Note that the extension-side and compression-side velocity damping force characteristics shown in FIG. 4 are obtained when an orifice is arranged in parallel with the extension-side leaf valve V1 and the compression-side leaf valve V2. As shown in FIG. 4, the damping force characteristic when the piston speed is in the extremely low speed range by the vibration input in the low frequency range is a characteristic that rises when the liquid preferentially passes through the orifice, and the piston speed is in the low speed range. The reason why the inflection point appears in the damping force characteristic in the middle is that the expansion side leaf valve V1 and the compression side leaf valve V2 are opened, and the characteristic by the leaf valve becomes dominant.

  Although it is conceivable to reduce the damping force when the piston speed becomes high by reducing the resistance in the extension side leaf valve V1 and the compression side leaf valve V2, this is the case when the piston speed is low. However, the damping force generated with respect to the vibration in the low frequency range is also reduced, causing a deficiency in the damping force and causing the passenger to feel uneasy when turning the vehicle. However, the shock absorber D1 of the present embodiment has a problem. Thus, since the damping force when the piston speed is high can be reduced without reducing the resistance in the extension-side leaf valve V1 and the compression-side leaf valve V2, such a problem does not occur.

  In the present embodiment, in order to explain the operation of the extension-side relief valve 31 and the pressure-side relief valve 32, for the sake of convenience, the piston speed is provided with sections of low speed and high speed. The speed is a speed at which the expansion side relief valve 31 and the pressure side relief valve 32 are opened, and the boundary speeds of the low speed and the high speed may not be the same on the extension side and the contraction side. Therefore, the valve opening pressures of the extension side relief valve 31 and the pressure side relief valve 32 can be set arbitrarily.

 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 Damping channel | path 4 Piston rod 4c Rod inner channel | path 5 Stretch side flow path 7 Stretch side pressure chamber 6 Pressure side channel 8 Pressure side pressure chamber 9 Free piston 10 Spring element 14 Housing pipe 15 Outer cylinder 21 Stretch side coil Spring 22 Pressure side coil spring 30 Bypass path 31 Extension side relief valve 32 Pressure side relief valve 33 Extension side valve disk 33a Extension side port 34 Extension side valve body 35 Pressure side valve disk 35a Pressure side port 36 Pressure side valve body 40 Extension stoppers D, D1 Buffer Device R Reservoir R1 Extension side chamber R2 Pressure side chamber R3 Pressure chamber

Claims (8)

A cylinder, a piston that is slidably inserted into the cylinder and divides the cylinder into an extension side chamber and a pressure side chamber, a damping passage that communicates the extension side chamber and the pressure side chamber, a pressure chamber, and a pressure chamber A free piston that is movably inserted and divides the pressure chamber into an extension side pressure chamber that communicates with the extension side chamber via the extension side channel and a pressure side pressure chamber that communicates with the pressure side chamber via the pressure side channel; A shock absorber provided with a spring element that generates an urging force that suppresses displacement of the free piston with respect to the pressure chamber, wherein the pressure chamber is provided in a cylindrical shape covering the outer periphery of the cylinder. apparatus. The shock absorber according to claim 1, wherein the pressure chamber is formed between the cylinder and a housing pipe covering an outer periphery of the cylinder. The shock absorber according to claim 2, wherein an outer cylinder that covers an outer periphery of the housing pipe is provided, and a reservoir that communicates with the pressure side chamber is provided between the outer cylinder and the housing pipe. The spring element is housed in the expansion side pressure chamber and urges the free piston toward the compression side pressure chamber, and is accommodated in the compression side pressure chamber and the free piston is expanded on the expansion side. 4. A pressure-side coil spring biased toward the pressure chamber side, wherein the free-side piston is sandwiched by the extension-side coil spring and the pressure-side coil spring and elastically supported in a neutral position. The shock absorber according to any one of the above. 5. The shock absorber according to claim 4, wherein the extension side coil spring and the compression side coil spring are set so that a spring constant increases when compressed by a predetermined amount. A bypass path that bypasses the attenuation passage and communicates the extension side chamber and the pressure side chamber, and an extension side relief valve that allows a flow of liquid from the extension side chamber to the pressure side chamber in the middle of the bypass path; The buffer according to any one of claims 1 to 5, further comprising: a pressure side relief valve arranged in parallel with the extension side relief valve and allowing a flow of liquid from the pressure side chamber toward the extension side chamber. apparatus. A piston rod having one end connected to the piston and movably inserted into the cylinder;
Opening from the tip facing the pressure side chamber to the piston rod and providing a passage in the rod leading to the extension side chamber side than the piston to form the bypass path,
6. The shock absorber according to claim 5, wherein the extension-side relief valve and the pressure-side relief valve are provided between the piston and an extension stopper provided in the middle of the piston rod. The extension side relief valve is mounted on the extension side chamber side of the piston rod with respect to the piston, and has an extension side valve disc having an extension side port communicating the extension side chamber with the passage in the rod, and the extension side valve disc. An extension valve body that is laminated and opens and closes the extension port;
The pressure-side relief valve is mounted on the extension side chamber side of the piston rod with respect to the piston and has a pressure side valve disk having a pressure side port communicating the extension side chamber with the passage in the rod, The shock absorber according to claim 7, further comprising a pressure side valve body for opening and closing the port.

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