JP5667488B2 - Damping valve - Google Patents

Description

  The present invention relates to an improved damping valve.

  Conventionally, this type of damping valve is embodied in, for example, a piston part of a shock absorber for a vehicle, and an annular leaf valve is stacked on an outlet end of a port provided in the piston part. Piston valves that open and close ports are known.

  In particular, in the above-described valve structure in which the port is opened and closed by the leaf valve by fixing and supporting the inner periphery of the leaf valve and bending the outer periphery, the damping force in the low speed region of the piston speed is reduced when the leaf valve deflection rigidity is reduced. On the contrary, if the flexural rigidity is increased, the damping force in the medium to high speed region of the piston speed becomes too large, and it is difficult to satisfy the riding comfort in the vehicle in all speed regions.

  In order to solve this problem, the leaf valve is slidably mounted on the outer periphery of a cylindrical piston nut attached to the tip of the piston rod without fixedly supporting the inner peripheral side of the leaf valve. Furthermore, a valve structure for energizing the leaf valve with a coil spring has been proposed.

  In the shock absorber using this valve structure, when the piston speed when the piston is extended, the leaf valve does not open and the damping force is generated only by the orifice stamped on the valve seat. Therefore, the damping characteristic is substantially the same as that of the valve structure in which the inner periphery is fixedly supported.

  On the other hand, in this valve structure, when the piston speed of the shock absorber reaches the medium to high speed region, the pressure of the hydraulic oil passing through the port acts on the leaf valve, the leaf valve is bent and opened, and the biasing force of the coil spring In contrast to this, the leaf valve lifts and retreats from the piston in the axial direction together with the main valve, and the flow passage area becomes larger than the valve structure in which the inner periphery is fixedly supported. Therefore, in the shock absorber to which this valve structure is applied, the damping force in the medium / high speed region of the piston speed does not become excessive, and the riding comfort in the vehicle can be satisfied in all speed regions during the extension operation. (For example, refer to Patent Document 1).

JP-A-9-291196 (FIG. 1)

  In the damping valve disclosed in the above-mentioned Japanese Patent Laid-Open No. 9-291196, the damping force of the shock absorber can be reduced only when the shock absorber is extended. The damping force at the time cannot be reduced, and the damping force reduction effect is not exhibited especially for shocking vibration input that pushes up the wheel generated when the vehicle travels over the unevenness on the road surface.

  Therefore, in a shock absorber equipped with a conventional damping valve, when such vibration is input to the wheel, the thrust vibration cannot be sufficiently reduced and the vibration is transmitted to the vehicle body. There is a problem that an impact called an impact shock is applied to the vehicle and the ride comfort in the vehicle cannot be sufficiently improved.

  Therefore, the present invention was devised to improve the above-described problems, and the object of the present invention is to exhibit a damping force reducing effect during the contraction operation of the shock absorber. It is to provide a damping valve that can improve the comfort.

  In order to solve the above-described problems, the problem-solving means of the present invention includes a piston that is movably inserted into a cylinder and divides the cylinder into an extension side chamber and a pressure side chamber, and the piston is provided on the piston. A damping passage communicating the side chamber and the pressure side chamber, a piston rod movably inserted into the cylinder and connected to the piston at one end, and provided on the piston rod to bypass the damping passage In a damping valve including a bypass communicating the compression side chamber with the extension side chamber and a relief valve opening the bypass by the action of the pressure side chamber, the bypass opens from one end of the piston rod facing the pressure side chamber. A valve hole extending in the axial direction of the piston rod and a lateral hole that opens from a side portion of the piston rod facing the extension side chamber and communicates with the valve hole. A half valve is provided in the middle of the valve hole and on the pressure side chamber side with respect to the opening of the horizontal hole, and in the valve hole and slides on the extension side chamber side with respect to the annular valve seat. A valve body that is movably inserted to partition a back pressure chamber in the valve hole; a biasing spring that is inserted into the back pressure chamber and biases the valve body toward the annular valve seat; and the piston And a throttle provided on the rod for communicating the back pressure chamber with the extension side chamber.

  According to the valve structure of the present invention, the damping force reduction effect can be exhibited during the contraction operation of the shock absorber, and the riding comfort of the vehicle can be improved.

It is a longitudinal cross-sectional view of the shock absorber to which the damping valve in one embodiment was applied. It is a figure which shows the damping characteristic at the time of contraction action | operation of the buffer with which the damping valve in one Embodiment was applied. It is a longitudinal cross-sectional view of the damping valve in one modification of one embodiment. It is a figure which shows the attenuation | damping characteristic at the time of contraction action | operation of the shock absorber to which the damping valve in one modification of one Embodiment was applied. It is a perspective view of the cylindrical valve body in a variable aperture.

  The present invention will be described below based on the embodiments shown in the drawings. As shown in FIG. 1, the damping valve V in one embodiment is applied to a shock absorber D, and is movably inserted into the cylinder 1 so as to be divided into an extension side chamber R1 and a pressure side chamber R2. The piston 2 is connected to the lower end in FIG. 1 which is inserted into the cylinder 1 so as to move freely, and is provided in the piston 2 so as to communicate with the extension side chamber R1 and the compression side chamber R2. A piston rod 4 provided in the piston rod 4, a bypass 5 that bypasses the damping passage 3 and communicates the pressure side chamber R2 to the expansion side chamber R1, and a relief valve 6 that opens the bypass 5 by the action of the pressure in the pressure side chamber R2. And is configured.

  On the other hand, as shown in FIG. 1, the shock absorber D to which the damping valve V is applied is slidably inserted into the cylinder 1, the piston 2, the piston rod 4, and the cylinder 1. A free piston 7 that divides the air chamber G, a rod guide 8 that closes the upper end of the cylinder 1 in FIG. 1 and slidably supports the piston rod 4, and a bottom cap that closes the lower end of the cylinder 1 in FIG. 9 and. The extension side chamber R1 and the pressure side chamber R2 in the cylinder 1 are filled with fluid such as hydraulic oil, and the gas chamber G is filled with gas. In addition to the hydraulic oil, water or an aqueous solution may be used as the fluid. The gas filled in the air chamber G may be an inert gas such as nitrogen that hardly changes the properties of the liquid when the liquid is hydraulic oil.

  Since the shock absorber D is set to a so-called single rod type, the volume of the piston rod 4 that enters and exits the cylinder 1 as the shock absorber D expands and contracts is the volume of the gas in the air chamber G. The free piston 7 expands or contracts and is compensated by moving up and down in FIG. As described above, the shock absorber D is set to be a single cylinder type in the present embodiment, but instead of installing the free piston 7 and the air chamber G, a reservoir is provided on the outer periphery or outside of the cylinder 1 to provide the reservoir. The volume compensation of the piston rod 4 may be performed by Further, the shock absorber D may be set to a double rod type instead of a single rod type. In addition, when the fluid filled in the expansion side chamber R1 and the pressure side chamber R2 is gas, the air chamber G and the reservoir can be omitted.

  Hereinafter, each part will be described in detail. The piston rod 4 has a small-diameter portion 4a formed at the lower end side in FIG. 1 and a screw portion 4b formed at 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 a damping passage 3 and an extension side passage 10 that communicate the extension side chamber R1 and the pressure side chamber R2. Further, the piston 2 includes a valve seat 11 that surrounds the outer periphery of the upper end opening of the damping passage 3 at the upper end in FIG. 1, and a valve seat 12 that surrounds the outer periphery of the lower end opening of the extension side passage 10 at the lower end in FIG. I have.

  1 is stacked with a leaf valve 13 that opens and closes the valve seat 11 and opens and closes the upper end opening in FIG. 1 of the damping passage 3. 1 is stacked with a leaf valve 14 that opens and closes the valve seat 12 and opens and closes the lower end opening in FIG.

  The leaf valves 13 and 14 are both formed in an annular shape, and a piston 4 is inserted into a small diameter portion 4 a of the piston rod 4 on the inner peripheral side, stacked on the piston 2, and screwed onto a screw portion 4 b of the piston rod 4. The nut 15 is fixed to the piston rod 4 together with the piston 2 in a state where the outer side deflection is allowed.

  Each of the leaf valves 13 and 14 is configured as a laminated leaf valve in which a plurality of annular plates are stacked. The leaf valves 13 and 14 are provided with notches 13a and 14a on the outer periphery of the annular plate contacting the valve seats 11 and 12, respectively. When the valves 13 and 14 are seated on the valve seats 11 and 12, the notches 13a and 14a function as orifices. Instead of providing the orifices by providing the notches 13a and 14a on the annular plate side, recesses may be imprinted in the valve seats 11 and 12 so that they function as the orifices.

  The leaf valve 13 is bent and opened by the differential pressure between the compression side chamber R2 and the expansion side chamber R1 during the contraction operation of the shock absorber D, opens the damping passage 3, and moves from the compression side chamber R2 to the expansion side chamber R1. In addition, the damping passage 3 is closed when the shock absorber D is extended. Therefore, the damping passage 3 is set as a one-way passage that allows only the flow of fluid from the pressure side chamber R2 toward the extension side chamber R1 by the leaf valve 13. In contrast to the leaf valve 13, the other leaf valve 14 opens the expansion-side passage 10 when the shock absorber D is extended to provide resistance to the fluid passing therethrough, and closes the expansion-side passage 10 during the contraction operation. That is, the leaf valve 14 is a damping force generating element that generates an extension side damping force during the contraction operation of the shock absorber D, and the extension side passage 10 is moved from the extension side chamber R1 to the compression side chamber R2 by the leaf valve 14. It is set as a one-way passage allowing only fluid flow. In addition to the above-described leaf valves 13 and 14, for example, a configuration in which a choke and a leaf valve are arranged in parallel instead of the orifice is adopted as a valve that gives resistance to the fluid passing through the damping passage 3 and the extension side passage 10. In addition to the leaf valve, a poppet valve and other configurations can also be employed.

  The bypass 5 opens from the lower end in FIG. 1 as one end of the piston rod 4 facing the compression side chamber R2 and extends in the axial direction of the piston rod 4, and opens from the side of the piston rod 4 facing the expansion side chamber R1. And a lateral hole 5b communicating with the valve hole 5a.

  The relief valve 6 is provided in the middle of the valve hole 5a and on the pressure side chamber side of the opening of the lateral hole 5b. The relief valve 6 is provided on the lower side in FIG. 1, and the annular valve seat 16 in the valve hole 5a. A valve body 17 that is slidably inserted upward in FIG. 1, which is closer to the extension side chamber R <b> 1, and partitions the back pressure chamber P in the valve hole 5 a, and a valve body 17 that is inserted into the back pressure chamber P. Is provided with an urging spring 18 that urges the annular valve seat 16 toward the annular valve seat 16 and a throttle 19 that is provided on the piston rod 4 and communicates the back pressure chamber P to the expansion side chamber R1.

  The annular valve seat 16 is annular and is press-fitted into the valve hole 5a and fixed. The annular valve seat 16 is a separate component from the piston rod 4, but a step portion may be provided on the inner periphery of the valve hole 5a of the piston rod 4 to form the annular valve seat. In this case, a through hole is provided from the upper end of the piston rod 4 in FIG. 1 to the valve hole 5a, the valve body 17 and the urging spring 18 are inserted from the through hole side, and the upper end of the urging spring 18 is supported. The spring seat to be fixed may be fixed by press-fitting the valve hole 5a from the through hole side. The annular valve seat 16 may be fixed by a method other than press fitting.

  The valve body 17 is mounted along the circumferential direction on the outer periphery of the body portion 17a, the body portion 17a that is in sliding contact with the inner periphery of the valve hole 5a, the conical valve head 17b provided at the lower end of the body portion 17a in FIG. The two seal rings 17c are provided. Since the valve head 17b has a conical shape, it can abut against the inner periphery of the upper end of the annular valve seat 16 in FIG. 1 without any gap, and the communication between the compression side chamber R2 and the extension side chamber R1 through the bypass 5 is blocked. can do.

  As described above, in the seated state where the valve body 17 is in contact with the annular valve seat 16, the relief valve 6 is closed to shut off the bypass 5, and in the state where the valve body 17 is separated from the annular valve seat 16, the relief valve 6 is closed. The valve 6 is opened to open the bypass 5.

  Further, when the valve body 17 moves upward in FIG. 1 from the closed position where the valve head 17b contacts the annular valve seat 16 and moves away from the annular valve seat 16, the valve head 17b and the annular valve seat 16 are opened. An annular gap is formed between the inner peripheral edge and the compression side chamber R2 and the extension side chamber R1. However, the valve head 17b that is attached to and detached from the annular valve seat 16 has a conical shape. The annular gap can be gradually increased by increasing the amount of displacement of the valve body 17 upward, that is, the flow passage area can be gradually increased.

  Further, by providing two seal rings 17c on the valve body 17, the space between the valve body 17 and the piston rod 4 is tightly sealed so that the front side and the back side of the valve body 17 which are the lower side in FIG. The pressure chamber P can be reliably prevented from communicating with the outer periphery of the valve body 17 and the valve body can be moved when the valve body 17 moves in the vertical direction in FIG. 17 can be prevented, the valve head 17b can be brought into contact with the annular valve seat 16 without deviation, and the valve can be reliably closed. You can show your power.

  In addition, a small-diameter convex portion 17d is provided on the rear side end, which is the upper end in FIG. 1 of the trunk portion 17a, and the convex portion 17d is fitted to the inner periphery of the coiled biasing spring 18. . The urging spring 18 is interposed between the bottom of the valve hole 5a and the valve body 17 in a compressed state, and urges the valve body 17 toward the annular valve seat 16 so that the valve body 17 is annular. Even when seated on the valve seat 16, the urging force is exerted and an initial load is applied to the valve body 17.

  The restrictor 19 provides resistance to the flow of fluid that exchanges between the back pressure chamber P and the extension side chamber R1. Therefore, when the relief valve 6 is opened and the valve body 17 moves backward in a direction away from the annular valve seat 16, the throttle 19 is opened when the fluid is pushed out from the compressed back pressure chamber P to the expansion side chamber R1. Since the pressure in the back pressure chamber P is increased, the pressure in the back pressure chamber P is restrained from retreating the valve element 17. On the contrary, when the valve body 17 moves forward in the direction of approaching from the annular valve seat 16, when the fluid is sucked into the expansion-side chamber R <b> 1 into the back-pressure chamber P to be expanded, the throttle 19 has a pressure in the back-pressure chamber P. Is reduced, the forward movement of the valve body 17 is suppressed.

  The relief valve 6 is configured as described above, and the force that presses the valve element 17 in the direction away from the annular valve seat 16 by the action of the pressure in the pressure side chamber R2 urges the valve element 17 toward the annular valve seat 16 side. When the valve body 17 is retracted against the urging force of the urging spring 18 and the force by which the back pressure chamber P presses the valve body 17 toward the annular valve seat 16 with internal pressure, the valve 5 opens and the bypass 5 is opened. To do. That is, the relief valve 6 is opened when the pressure in the pressure side chamber R2 reaches a predetermined valve opening pressure, and the bypass 5 is opened. The valve opening pressure is determined by the initial load applied to the valve body 17 by the biasing spring 18. Can be adjusted.

  Further, since the back pressure chamber P functions to suppress the movement of the valve body 17, even if the pressure in the pressure side chamber R2 fluctuates in vibration, the vibration of the valve body 17 can be suppressed, and the relief valve 6 The valve opening degree does not change in vibration, and the damping force can be exhibited stably.

  The damping valve V is configured as described above, and the operation of the damping valve V will be described below. The damping valve V exerts a damping force on the shock absorber D when the shock absorber D is contracted.

  When the piston speed is in the low speed region during the contraction operation of the shock absorber D, the compression side chamber R2 is compressed and the expansion side chamber R1 is expanded by the piston 2, but the leaf valve 13 is also relief when the piston speed is low. Since the valve 6 is not opened, the fluid in the pressure side chamber R2 passes through only the notch 13a functioning as an orifice provided on the outer periphery of the leaf valve 13, and is moved to the extension side chamber R1. Therefore, the damping characteristic (damping force characteristic with respect to the piston speed) of the shock absorber D at this time is an orifice that rises so that the compression side damping force is proportional to the square of the piston speed with respect to the piston speed, as shown in FIG. It has a characteristic square characteristic, and in this low speed region, the attenuation coefficient is relatively large (section a in FIG. 2). The attenuation coefficient is grasped as the slope of the attenuation characteristic in FIG.

  Further, when the medium speed exceeds the low speed, the fluid bends the outer periphery of the leaf valve 13, passes through the gap between the leaf valve 13 and the valve seat 11, and moves from the compression side chamber R2 to the extension side chamber R1. Then, until the area of the gap between the leaf valve 13 and the valve seat 11 becomes equal to the flow passage area of the attenuation passage 3, the damping characteristic of the shock absorber D is governed by the characteristic of the leaf valve 13 (in FIG. 2). b section). When the area of the gap between the leaf valve 13 and the valve seat 11 becomes larger than the flow passage area of the attenuation passage 3, the attenuation characteristic of the shock absorber D is governed by the characteristic of the attenuation passage 3 (section c in FIG. 2). . That is, in the section “b”, the area of the gap between the leaf valve 13 and the valve seat 11 is smaller than the flow path area of the attenuation passage 3. The area of the gap between the valve seat 11 and the flow of fluid between the leaf valve 13 and the valve seat 11 is restricted, so that the damping characteristic of the shock absorber D is the characteristic of restricting the flow of fluid at the leaf valve 13, that is, The characteristic of generating a damping force proportional to the pressure increase in the pressure chamber R2 becomes dominant. On the other hand, in the section c, the piston speed is increased and the pressure in the pressure side chamber R2 is increased, so that the amount of deflection of the leaf valve 13 is increased, but the area of the gap between the leaf valve 13 and the valve seat 11 is attenuated. Since the flow passage area is larger than the flow passage area of the passage 3, the flow passage area is the smallest because it becomes the flow passage area of the attenuation passage 3 and the flow of fluid is restricted by the attenuation passage 3. The attenuation characteristic is dominated by the port characteristic that restricts the flow of fluid in the attenuation passage 3. The reason why the damping coefficient in the b section is larger than the damping coefficient in the c section is that a restoring force is applied to the leaf valve 13 to close the damping passage 3 according to the amount of deflection in the b section.

  Next, the case where the piston speed reaches the high speed region, the pressure in the pressure side chamber R2 exceeds the valve opening pressure of the relief valve 6, and the relief valve 6 opens will be described. In this case, not only the leaf valve 13 but also the relief valve 6 is opened, and the pressure side chamber R2 and the extension side chamber R1 are communicated not only by the attenuation passage 3 but also by the bypass 5, and the flow path area is increased. As a result, the pressure in the compression side chamber R2 escapes to the expansion side chamber R1 even through the bypass 5, and the pressure increase in the compression side chamber R2 is suppressed against the increase in the piston speed. As a result, the damping characteristic of the shock absorber D when the piston speed is in the high speed region is proportional to the increase in the piston speed as shown in FIG. The slope of the characteristic becomes small (d section).

  Thus, in the shock absorber D to which the damping valve V of the present invention is applied, the notch 13a functioning as an orifice, the leaf valve 13 and the damping passage 3 are sufficient when the piston speed is in the low / medium speed region during the contraction operation. On the other hand, when the piston speed is in the high speed region, the pressure increase in the compression side chamber R2 is suppressed, and the compression side damping force of the shock absorber D does not become excessive. Therefore, according to the damping valve V of the present invention, the ride comfort in the vehicle can be satisfied in all speed ranges. In the damping valve V according to the present invention, for example, even if the shocking vibration that pushes up the wheel by inputting the bump on the road surface while the vehicle is running, the compression side damping force of the shock absorber D is excessive. Therefore, since the transmission of the shock vibration to the vehicle body is insulated, the impact shock can be effectively reduced. Therefore, according to the damping valve V of the present invention, the damping force reduction effect can be exhibited during the contraction operation of the shock absorber D, and the riding comfort of the vehicle can be improved.

  Further, in the damping valve V of the present invention, the bypass 5 opens from one end of the piston rod 4 and extends in the axial direction of the piston rod 4 and opens from the side of the piston rod 4 to communicate with the valve hole 5a. The relief valve 6 is composed of a lateral hole 5b, and the relief valve 6 is inserted into the back pressure chamber P, an annular valve seat 16 provided in the valve hole 5a, a valve body 17 slidably inserted into the valve hole 5a, and Since the biasing spring 18 and the throttle 19 provided in the piston rod 4 and communicating the back pressure chamber P to the expansion side chamber R1, both the bypass 5 and the relief valve 6 are provided in the piston rod 4. These do not affect the stroke length of the shock absorber D. Therefore, according to the damping valve V of the present invention, there is no inconvenience of shortening the stroke length of the shock absorber D. Therefore, the shock absorber D can be mounted on a vehicle having a limited mounting space.

  In addition to the spring constant of the urging spring 18, the retraction displacement amount of the valve element 17 after the relief valve 6 is opened can be controlled by controlling the pressure in the back pressure chamber P. The damping characteristic of the shock absorber D after the opening of 6 can be adjusted. The control of the pressure in the back pressure chamber P is performed according to the magnitude of the resistance that the throttle 19 gives to the passing fluid. Therefore, in the damping valve V of this embodiment, the damping characteristic can be tuned by setting the area so as to realize the damping characteristic aiming at the flow passage area of the throttle 19 in advance. If the damping characteristic is tuned only by the spring constant of the urging spring 18, not only the inclination of the damping coefficient after the relief valve 6 is opened but also the valve opening pressure of the relief valve 6 is changed. It is necessary to change the natural length of the biasing spring 18 or to change the total length of the interposing space of the biasing spring 18 by changing the total length of the valve body 17 or the back pressure chamber P. However, since such a change is complicated, it is easier to achieve the targeted attenuation characteristic by tuning the attenuation characteristic by providing the back pressure chamber P and the throttle 19.

  In addition, by providing the throttle 19, it is possible to suppress the receding of the valve element 17 by the pressure in the back pressure chamber P, so that the change in inclination at the inflection points of the c section and the d section of the damping characteristic becomes smooth. A sudden change in damping force can be mitigated.

  In this way, the pressure in the back pressure chamber P can be controlled by the flow passage area of the throttle 19, so that the throttle 19 as in the damping valve V1 of one modification of the embodiment shown in FIG. By providing the variable throttle 20 instead, the damping characteristic after the relief valve 6 is opened can be adjusted to a preference. In FIG. 3, the configuration of the shock absorber other than the damping valve V1 is the same, and therefore the parts other than the damping valve V1 are omitted in the drawing.

  Specifically, the variable throttle 20 is open from the side facing the expansion side chamber R1 of the piston rod 4 and communicates with the back pressure chamber P, and is freely rotatable in the circumferential direction within the back pressure chamber P. A cylindrical valve body 22 having throttle holes 23a, 23b that can be inserted and face the through hole 21, and a figure connected to the cylindrical valve body 22 and inserted into the piston rod 4 to become the other end of the piston rod 4. 3 is provided with a control rod 25 that can be rotated by a rotating operation of an adjuster 24 provided at the upper end of the center 3.

  In this example, the cylindrical valve body 22 includes two throttle holes 23a and 23b that communicate with the inside and outside of the cylindrical valve body 22 and have different opening areas, and have the outer periphery slidably contact the inner periphery of the valve hole 5a. Yes. The throttle holes 23 a and 23 b are provided on the same circumference of the cylindrical main body 22, and the cylindrical valve body 22 is rotated in the circumferential direction so that one of the throttle holes 23 a and 23 b faces the through hole 21. Can be done. Moreover, in this example, the cylindrical valve body 22 is formed into a crested cylindrical shape, and the cylindrical valve body 22 is valved by interposing an urging spring 18 between the top portion 22a and the valve body 17. Pressed against the bottom of the hole 5a and positioned in the axial direction in the back pressure chamber P, the cylindrical valve body 22 is displaced in the axial direction, so that the throttle holes 23a and 23b cannot be opposed to the through hole 21. Care is taken so that there is nothing.

  The control rod 25 is rotatably inserted into a control rod insertion hole 4c that opens from the bottom of the valve hole 5a provided in the piston rod 4 and communicates with the other end that is the upper end. The control rod 25 has one end connected to the tubular valve body 22 and the other end connected to an adjuster 24 that is rotatably attached to the upper end that is the other end of the piston rod 4 in the circumferential direction. Therefore, the cylindrical valve element 22 can be rotated in the back pressure chamber P in the circumferential direction via the control rod 25 by the rotation operation of the adjuster 24.

  Therefore, in the damping valve V1 of this embodiment, the adjuster 24 is rotated so that the throttle hole 23a having a large opening area is opposed to the through hole 21, and the throttle hole 23b having a small opening area is passed through. Compared with the case where it opposes the hole 21, the pressure of the back pressure chamber P with respect to the retraction of the valve body 17 when the throttle hole 23 a is opposed is when the valve body 17 is retracted from the annular valve seat 16. The degree of increase is small. Therefore, as shown in FIG. 4, after the relief valve 6 is opened, the damping characteristic e (solid line in the figure) of the shock absorber D when the throttle hole 23a is opposed to the through hole 21 is the same as the throttle hole 23b. The damping coefficient is smaller than the damping characteristic f (broken line in the figure) of the shock absorber D when facing the through hole 21. When the outer periphery of the cylindrical valve body 22 and between the throttle holes 23a, 23b are opposed to the through hole 21, the back pressure chamber P is isolated from the expansion side chamber R1, so that the valve body 17 is in a locked state. Thus, the bypass 5 is maintained in the cut-off state. In this case, the damping characteristic of the shock absorber D has the largest damping force as shown by the one-dot chain line in FIG.

  When the valve body 17 is displaced backward from the annular valve seat 16 to some extent, the lower end in FIG. 2 of the cylindrical valve body 22 is brought into contact with the valve body 17 to restrict further backward displacement of the valve body 17. You can also In this case, if the valve element 17 is retracted until it contacts the cylindrical valve element 22, it cannot be retracted any further, so the attenuation coefficient is increased after the e section or the f section of the attenuation characteristic (the inclination of the attenuation characteristic increases). ) A section can be provided.

  Thus, by providing the variable throttle 20, the damping coefficient in the damping characteristic after the relief valve 6 is opened can be easily adjusted, and the damping characteristic that suits the user's preference can be easily realized. . In addition, in the place mentioned above, the two throttle holes 23a and 23b are provided in the cylindrical valve body 22, and the damping characteristic of the shock absorber D includes the case where the through hole 21 is closed as shown in FIG. However, it may be possible to switch to four or more stages by increasing the number of apertures installed, or, for example, as shown in FIG. A long throttle hole 23c in the circumferential direction in which the axial length gradually changes along the circumferential direction is provided in the cylindrical valve body 22, and by rotating the cylindrical valve body 22, the through hole 21 and the throttle hole 23c It is possible to gradually change the overlapping area, and to change the attenuation characteristics of the shock absorber D steplessly. The through hole provided in the piston rod 4 is a long hole in the piston rod 4 whose axial length gradually changes along the circumferential direction, and the throttle hole provided in the cylindrical valve body 22 is an arbitrary position of the long hole. The area where the through hole overlaps with the throttle hole may be changed.

  Note that the adjuster 24 may be operated manually by the user, or may be rotated by an actuator. When the actuator is rotated, the actuator is controlled in accordance with the vehicle body posture. A control device may be provided.

  In addition, the valve body 17 of the relief valve 6 includes the conical valve head 17b as described above. However, the present invention is not limited to this. The valve head may be inserted into the valve body, and the bypass 5 may be opened through the valve body by retreating from the annular valve seat 16. Although it is possible to employ a valve that maximizes the flow path area when the relief valve 6 is opened, the flow path area gradually increases in accordance with the distance from the annular valve seat 16 of the valve element 17. By adopting an increasing valve body, it is possible to prevent an extreme inflection point from being generated in the damping characteristic, and to improve the riding comfort in the vehicle.

  In the present embodiment, in order to explain the change of the damping characteristic, the piston speed is provided with sections of low speed, medium speed, and high speed, but the speed of the boundary between these sections is arbitrarily set. The valve opening pressure of the relief valve 6 may be set according to the setting of this section. In other words, when shifting the medium speed and high speed sections to a higher piston speed, the valve opening pressure of the relief valve 6 may be increased. When shifting to a lower speed, the valve opening pressure of the relief valve 6 may be increased. Should be lowered accordingly. Further, when shifting the low speed and medium speed categories to a higher piston speed, the valve opening pressure of the leaf valve 13 may be increased, and when shifting to a lower speed, the valve opening pressure of the leaf valve 13 may be increased. Should be lowered accordingly.

  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.

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston 3 Damping passage 4 Piston rod 5 Bypass 5a Valve hole 5b Side hole 6 Relief valve 16 Annular valve seat 17 Valve body 17c Seal ring 17b Valve head 18 Energizing spring 19 Restriction 21 Through-hole 22 Cylindrical valve body 23a, 23b, 23c Restriction hole 25 Control rod P Back pressure chamber R1 Extension side chamber R2 Pressure side chamber

Claims (5)

A piston that is movably inserted into the cylinder and divides the cylinder into an extension side chamber and a pressure side chamber; a damping passage that is provided in the piston and communicates the extension side chamber and the pressure side chamber; and A piston rod that is movably inserted and connected to the piston at one end; a bypass that is provided in the piston rod and bypasses the damping passage and communicates the pressure side chamber to the extension side chamber; and a pressure in the pressure side chamber In the damping valve having a relief valve that opens the bypass by the action of
The bypass opens from one end of the piston rod facing the pressure side chamber and extends in the axial direction of the piston rod, and the horizontal hole opens from the side of the piston rod facing the extension side chamber and communicates with the valve hole And
The relief valve includes an annular valve seat provided in the middle of the valve hole and closer to the pressure side chamber than the opening of the lateral hole, and a slide in the valve hole to the extension side chamber side from the annular valve seat. A valve body that is movably inserted to partition a back pressure chamber in the valve hole; a biasing spring that is inserted into the back pressure chamber and biases the valve body toward the annular valve seat; and the piston A damping valve comprising a throttle provided on a rod and communicating the back pressure chamber with the extension side chamber. The damping valve according to claim 1, wherein two seal rings that are in sliding contact with the inner periphery of the valve hole are mounted on the outer periphery of the valve body. The damping valve according to claim 1, wherein the throttle can change a resistance given to a flow of the passing fluid. The throttle is open from a side facing the extension side chamber of the piston rod and communicates with the back pressure chamber, and is inserted into the back pressure chamber in a circumferential direction so as to be able to face the through hole. A cylindrical valve body having a throttle hole, and a control rod connected to the cylindrical valve body, inserted into the piston rod, and rotatable from the outside of the other end of the piston rod. The damping valve according to any one of claims 1 to 3. The damping valve according to any one of claims 1 to 4, wherein the valve body includes a conical valve head that is attached to and detached from the annular valve seat.

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