JP2013190011A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shock absorber capable of well maintaining the ride quality in a vehicle even if the extension/retraction speed thereof is increased to middle and high speeds.SOLUTION: A shock absorber D includes a cylinder 1, a piston 2 which is slidably inserted into the cylinder 1 and partitions the inside of the cylinder 1 into an extension-side chamber R1 and a pressing-side chamber R2, a pressure chamber R3, a free piston 9 which partitions the pressure chamber R3 into an extension-side pressure chamber 7 and a pressing-side pressure chamber 8, and a spring element 10 for pressing the free piston 9. The shock absorber further includes a valve disk 12 stacked on the piston 2. A communication port 12e allowing an extension-side port 4 to communicate with the pressing-side chamber R2 and an annular valve seat 12d surrounding the outer periphery of the communication port 12e are provided to the valve disk 12. An extension-side leaf valve EV sits on and off the annular valve seat 12d of the valve disk 12. The inner diameter of the annular valve seat 12d is set larger than a virtual circular diameter which comes into contact with the internal edge of a pressing-side port 3.

Description

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

  Conventionally, this type of shock absorber is interposed between the vehicle body and the axle of the vehicle and used for the purpose of suppressing vehicle body vibration. For example, the cylinder and the cylinder can be slid freely. A piston that is inserted and divides the inside of the cylinder into an extension side chamber on the piston rod side and a pressure side chamber on the piston side, an extension side port and a pressure side port that communicates the extension side chamber provided in the piston and the pressure side chamber, and opens and closes the extension side port An expansion-side annular leaf valve, a pressure-side annular leaf valve that opens and closes the pressure-side port, a pressure chamber, an expansion-side passage that communicates the pressure chamber with the expansion-side chamber, and a pressure-side passage that communicates the pressure chamber with the compression-side chamber A free piston that is slidably inserted into the pressure chamber and divides the pressure chamber into an expansion side pressure chamber that communicates with the expansion side chamber and a pressure side pressure chamber that communicates with the compression side chamber; and a coil spring that urges the free piston; Configured with That.

  In the shock absorber configured as described above, the pressure chamber is divided into the expansion side pressure chamber and the pressure side pressure chamber by the free piston, and the expansion side chamber and the pressure side chamber are directly connected via the expansion side flow channel and the pressure side flow channel. Although not communicated, the volume ratio of the expansion side pressure chamber to the compression side pressure chamber changes as the free piston moves, and the fluid in the pressure chamber enters and exits the extension side chamber and the compression side chamber according to the amount of movement of the free piston. Therefore, it seems that the extension side chamber and the pressure side chamber are communicated with each other through the extension side flow path and the pressure side flow path.

  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. It is possible to reliably generate a high damping force in a scene where the input vibration frequency of the vehicle is low, and to reliably generate a low damping force in a scene where the input vibration frequency is high such that the vehicle passes through the unevenness of the road surface. The riding comfort can be improved (for example, see Patent Document 1).

  Further, in the above-described shock absorber, the piston and the annular leaf valve on the extension side and the pressure side are provided by screwing the housing to the tip of the piston rod using the housing forming the pressure chamber instead of the piston nut. It is fixed to the tip of the piston rod. Thus, since a large housing is attached to the tip of the piston rod, the stroke length of the shock absorber is shortened accordingly.

  Therefore, the piston is provided with a bottom portion on which the ports on the expansion side and the compression side are provided, and a cylindrical portion on which a piston ring provided on the outer periphery of the bottom portion and in sliding contact with the inner periphery of the cylinder is mounted. Also, the axial length of the cylinder part can be lengthened to ensure a sufficient sliding length of the piston ring with respect to the cylinder, while preventing the rattle and tilt of the piston with respect to the cylinder, while the annular leaf on the extension side is inside the cylinder part. By accommodating the valve, the total length of the piston portion including the housing can be shortened, and the shortening of the stroke length of the shock absorber is kept to a minimum.

JP 2011-122676 A

  The shock absorber described above can exhibit a damping force that is sensitive to the above frequency by providing an orifice in the pressure side passage and controlling the movement of the free piston, that is, with respect to the input of low frequency vibration. Exhibits a large damping force and can exhibit a small damping force against the input of high-frequency vibrations, but the leaf valve opens when the expansion / contraction speed of the shock absorber increases to some extent, so that the expansion / contraction speed is in the medium to high speed range. In such a case, the characteristics of the leaf valve become prominent, and the effect of frequency sensitivity becomes relatively less apparent.

  In such a situation, the characteristic of the leaf valve becomes dominant as described above. In particular, from the viewpoint of securing the stroke length of the shock absorber, the expansion-side annular leaf valve is accommodated in the cylinder portion of the piston. Therefore, the diameter of the annular leaf valve is small, and the inner diameter of the annular valve seat that surrounds the outer circumference of the extension side port and the annular leaf valve on the extension side is separated is small, so that the bending rigidity of the annular leaf valve is increased. As shown by the broken line in FIG. 5, the damping force when the expansion / contraction speed of the shock absorber is in the middle / high speed range becomes large.

  Then, when the expansion / contraction speed of the shock absorber is in the low speed range, the frequency sensitivity is good and the ride comfort in the vehicle is very good, but when the expansion speed of the shock absorber is in the medium / high speed range, the damping force is excessive. This leads to a jerky feeling, and the ride comfort in the vehicle is relatively worse than in the low speed range, and on the contrary, there is a problem that the rider is impressed that the ride comfort is bad.

  Accordingly, the present invention has been developed to solve the above-described problems, and the object of the present invention is to provide a buffer capable of maintaining a good riding comfort in a vehicle even when the expansion / contraction speed is medium to high. Is to provide a device.

  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 pressure side chamber, and the piston has the same circle. A plurality of compression side ports provided on the pressure side chamber and communicated with the extension side chamber and the compression side chamber; and provided on the inner circumference side of the piston and on the inner circumference side of the pressure side port. A plurality of expansion ports that communicate with the chamber; a pressure valve that opens and closes the compression port; an expansion leaf valve that opens and closes the expansion port; a pressure chamber; and an axial movement within the pressure chamber. A free piston that divides the pressure chamber into an extension-side pressure chamber that communicates with the extension-side chamber via an extension-side channel and a pressure-side pressure chamber that communicates with the compression-side chamber via a pressure-side channel; Of the free piston A shock absorber provided with a spring element that generates a biasing force that suppresses displacement from a standing position, and a valve disk stacked on the piston is provided, and the valve disk communicates with a downstream outlet of the extension side port. A port, an annular window that communicates the downstream outlet of the communication port to the pressure side chamber, and an annular valve seat that surrounds the outer periphery of the annular window, and the extension leaf valve is detachably seated on the annular valve seat. It is laminated on the valve disc, and the inner diameter of the annular valve seat is set to be larger than the virtual circle diameter in contact with the inner edge of each pressure side port.

  By configuring the shock absorber of the present invention in this way, an extension side leaf valve having a larger outer diameter than before can be used, and the extension side leaf valve receives pressure from the extension side chamber. Can be shifted to the outer peripheral side as compared with the conventional case, and the bending rigidity of the extension side leaf valve can be apparently lowered.

  In the shock absorber of the present invention, the damping force when the expansion / contraction speed is in the middle / high speed range can be reduced, and the riding comfort can be improved by eliminating the excessive damping force. The difference in ride comfort in the middle and high speed range is reduced.

  Therefore, according to the shock absorber of the present invention, it is possible to maintain a good riding comfort in the vehicle even when the expansion / contraction speed becomes medium to high.

It is a longitudinal cross-sectional view of the shock absorber in one embodiment. It is a top view of the piston of the buffer device in one embodiment. It is a top view of the valve disc of the buffering device in one embodiment. It is a figure explaining the change of the damping force with respect to the vibration frequency of the buffering device in one Embodiment. It is a figure explaining the damping characteristic (damping force speed characteristic) of the shock absorber in 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 that is slidably inserted into the cylinder 1, and divides the cylinder 1 into an extension side chamber R <b> 1 and a pressure side chamber R <b> 2, A plurality of compression-side ports 3 provided on the same circle and communicated with the expansion-side chamber R1 and the compression-side chamber R2, and the piston 2 on the same circle and provided on the inner peripheral side of the compression-side port 3 and extending on the expansion-side chamber R1 A plurality of expansion side ports 4 communicating with the compression side chamber R2, a pressure side valve PV for opening and closing the compression side port 3, an expansion side leaf valve EV for opening and closing the expansion side port 4, a pressure chamber R3, and a pressure chamber R3 The pressure chamber R3 is movably inserted in the axial direction into the pressure chamber R3 and communicated with the expansion side pressure chamber 7 via the expansion side flow channel 5 and the expansion side pressure chamber 7 and with the pressure side chamber R2 via the pressure side flow channel 6. A free piston 9 partitioned into a pressure side pressure chamber 8, and a free piston 9 A spring element 10 for generating the inhibit biasing force of the displacement from the neutral position, and is constituted by a valve disc 12 which is stacked on the piston 2. The shock absorber D is interposed between the vehicle body and the axle of the vehicle to generate a damping force and suppress the vibration of the vehicle body. The expansion side chamber R1 is a chamber that is compressed when the vehicle body and the axle are separated and the shock absorber D is extended, and the compression side chamber R2 is a state where the vehicle body and the axle are close to each other and the shock absorber D is A chamber that is compressed when contracted. The extension side chamber R1, the pressure side chamber R2, and further the pressure chamber R3 are filled with a fluid such as hydraulic fluid. In addition to the hydraulic fluid, for example, a fluid such as water or an aqueous solution is used as this fluid. You can also.

  The piston 2 includes a bottom portion 2a, a cylindrical portion 2b provided on the outer periphery of the bottom portion 2a, and an annular belt-shaped piston ring 2c that is attached to the outer periphery of the cylindrical portion 2b and slidably contacts the inner periphery of the cylinder 1. . The bottom 2a of the piston 2 is annular so that the piston rod 13 can be inserted, and the compression side port 3 and the extension side port 4 are provided along the axial direction of the piston 2 so as to penetrate the bottom 2a. ing. A plurality of compression side ports 3 are provided, all arranged on the same circle, and all the compression side ports 3 communicate with an annular window 2d provided at the end of the bottom side 2a on the extension side chamber side. Similarly, a plurality of expansion side ports 4 are provided, all of which are provided on the same circle, and the downstream outlets of all the expansion side ports 4 are annular windows 2e provided at the pressure side chamber side end of the bottom portion 2a. Leads to. An annular seat 2f covering the outer periphery of the annular window 2e is provided at the pressure side chamber side end of the bottom 2a of the piston 2. Therefore, the compression side port 3 is provided outside the above-described annular seat 2 f of the piston 2, and the other extension side port 4 is provided inside the above-described annular seat 2 f of the piston 2.

  A pressure side valve PV, which is an annular leaf valve that opens and closes the pressure side port 3, is stacked on the extension side chamber side, which is the upper side of the piston 2 in FIG. The pressure side valve PV is allowed to bend at the outer periphery, and when the outer periphery is seated on the piston 2, the pressure side port 3 is closed, and the pressure of the pressure side chamber R2 acting via the pressure side port 3 reaches the valve opening pressure and is bent. When the outer periphery is separated from the piston 2, the pressure side port 3 is opened. Therefore, the pressure side valve PV also functions as a check valve, allows only the flow of fluid from the pressure side chamber R2 to the extension side chamber R1, sets the pressure side port 3 as a one-way passage, and pressurizes the pressure side chamber R2. When the pressure side port 3 is opened under the pressure of the pressure, resistance is given to the flow of fluid passing therethrough.

  On the other hand, a valve disk 12 is laminated on the pressure side chamber side of the piston 2 which is the lower side in FIG. The valve disk 12 is cylindrical and has an outer diameter smaller than that of the main body 12a smaller than the inner diameter of the cylindrical portion 2b of the piston 2 and the main body 12a provided at the pressure side chamber side end which is the lower end of the main body 12a in FIG. A large diameter portion 12b, an annular window 12c provided at the pressure side chamber side end of the large diameter portion 12b, and an annular valve provided at the pressure side chamber side end of the large diameter portion 12b and on the outer periphery of the annular window 12c A seat 12d and a communication port 12e provided along the axial direction of the valve disk 12 through the annular window 12c and the main body 12a to the end on the side of the extension side chamber in FIG. The communication port 12e is provided in the same circular shape with respect to the valve disk 12, and all of the communication ports 12e can face the annular window 2e provided on the bottom 2a of the piston 2.

  As shown in FIGS. 2 and 3, the inner diameter of the annular valve seat 12 d of the valve disk 12 is set larger than the diameter of the virtual circle C passing through the inner edges of all the pressure side ports 3 provided in the piston 2 described above. ing. Further, one or more communication ports 12e may be provided in the valve disk 12, but in this embodiment, the flow paths of all the communication ports 12e are larger than the total flow area of all the extension ports 4. The area is set to be larger.

  In the valve disk 12 configured in this way, the outer diameter of the main body 12a is smaller than the inner diameter of the cylindrical portion 2b of the piston 2, so that the main body 12a enters the cylindrical portion 2b of the piston 2 and the bottom of the piston 2 When the valve disc 12 is laminated on the bottom 2a of the piston 2 in this way, all the communication ports 12e face the annular window 2e and lead to the downstream outlet of the extension side port 4, and the valve disc 12, the outer periphery of the communication port 12 e contacts the seat 2 f provided on the piston 2, so that the expansion side port 4 does not communicate with the compression side chamber R 2 through the gap between the piston 2 and the valve disk 12. Yes. Further, the downstream outlet of the communication port 12e communicates with the pressure side chamber R2 through the annular window 12c.

  Further, since an annular gap is formed between the cylindrical portion 2b of the piston 2 and the outer periphery of the valve disk 12, the upstream side of the pressure side port 3 is not blocked. Therefore, by stacking the valve disk 12 on the bottom 2a of the piston 2, the expansion side port 4 and the communication port 12e are communicated with each other, whereby the expansion side chamber R1 and the pressure side chamber R2 are communicated. . When the communication port 12e and the expansion side port 4 communicate with each other, the annular window 2e can be omitted if the piston 2 and the valve disk 12 can be positioned in the circumferential direction. Alternatively, an annular window that communicates with all the communication ports 12e and can be opposed to all the extension ports 4 may be provided at the extension side chamber side end of the valve disc 12, or the opposite ends of the piston 2 and the valve disc 12 may be provided. Each may be provided with an annular window.

  Further, the above-described valve disc 12 is laminated with an extension side leaf valve EV which is an annular leaf valve for opening and closing the annular window 12c. The expansion-side leaf valve EV is allowed to be deflected on the outer periphery and can be separated from and seated on the annular valve seat 12d. When the seat is seated on the annular valve seat 12d, the passage formed by the expansion-side port 4 and the communication port 12e is closed. When the pressure of the extension side chamber R1 acting via the extension side port 4 and the communication port 12e reaches the valve opening pressure and bends away from the annular valve seat 12d, the passage formed by the extension side port 4 and the communication port 12e is opened. It is like that. Therefore, the extension side leaf valve EV also functions as a check valve, allows only the flow of fluid from the extension side chamber R1 to the pressure side chamber R2, sets the extension side port 4 as a one-way passage, When the expansion side port 4 is opened by receiving the pressure of the expansion side chamber R1, resistance is given to the flow of fluid passing therethrough.

  The piston rod 13 protrudes outward from the upper end of the cylinder 1 in the figure, and the inside of the cylinder 1 is in a liquid-tight state between the piston rod 13 and the cylinder 1 with a seal (not shown). As shown in the figure, in the case of the shock absorber D, a housing 17 that forms the piston 2, the valve disk 12, and the pressure chamber R3 is fixed to the tip of the piston rod 13, and is configured as a so-called single rod type shock absorber. Although not shown, an air chamber or a reservoir for compensating the volume of the piston rod 13 entering and exiting the cylinder 1 is provided. Further, the shock absorber D may be set to a double rod type instead of a single rod type. In this case, an accumulator or the like for compensating for a volume change due to a temperature change of the fluid is provided instead of a volume compensation. That's fine.

  The housing 17 that forms the pressure chamber R3 is mounted on the outer periphery of the small-diameter portion 13a at the tip of the piston rod 13 after the pressure-side valve PV, the piston 2, the valve disk 12, and the extension-side leaf valve EV are assembled. The piston 2 and the valve disc 12 are fixed to the piston rod 13 by being screwed to the portion 13a, and the compression side valve PV and the extension side leaf valve EV are attached to the piston rod 13 in a state where the outer side deflection is allowed. Fixed.

  The housing 17 has a nut portion 18 with a flange 19 screwed to the screw portion 13 b of the piston rod 13, and a bottomed cylindrical shape in which an opening is crimped on the outer periphery of the flange 19 in the nut portion 18. A cylindrical portion 20 is provided. The nut portion 18 and the cylindrical portion 20 define a pressure chamber R3 in the pressure side chamber R2. In addition, in integrating the nut part 18 and the cylinder part 20, other methods, such as welding, can also be employ | adopted besides the said caulking process. Moreover, in the shock absorber D of this embodiment, the cross-sectional shape of the outer periphery at the lower end of the cylindrical portion 20 of the housing 17 is a shape other than a circular shape, and the cylindrical portion is gripped with a tool. By rotating 20, the nut portion 18 can be easily screwed to the screw portion 13 b of the piston rod 13.

  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 divided into a chamber 8.

  Further, as described above, the nut portion 18 includes the flange 19 on the side, and a cylindrical screw portion 18a is formed on the inner periphery thereof. The screw portion 18a is screwed to the screw portion 13b of the piston rod 13. Thus, the housing 17 can be fixed to the small diameter portion 13a of the piston rod 13. In addition, by setting the cross-sectional shape of the outer periphery of the cylindrical portion 20 to a shape other than a perfect circle, for example, a shape with a part cut away or a hexagonal shape, the housing 17 can be mounted using a tool that engages with the outer periphery. The operation of screwing onto the piston rod 13 can be facilitated.

  The cylindrical portion 20 has a bottomed cylindrical shape, and a fixed orifice 21 that constitutes a part of the pressure side flow path 6 is provided at the bottom, and the pressure side chamber R <b> 2 enters the housing 17 at the side of the cylindrical portion 20. Two variable orifices 22 and 23 communicating with each other are provided.

  On the other hand, the free piston 9 has a bottomed cylindrical shape, and is inserted into the housing 17 with the bottom portion 9a facing downward in FIG. 1 and the outer periphery of the tube portion 9b slidably contacting the inner periphery of the tube portion 20. Yes. When the free piston 9 is slidably inserted into the housing 17 as described above, the pressure chamber R3 is divided into the expansion side pressure chamber 7 and the pressure side pressure chamber 8. In addition, by accommodating the bottom portion 9a of the free piston 9 in the housing 17 facing downward in FIG. 1, interference with the screw portion 18a in the nut portion 18 of the free piston 9 can be avoided. Furthermore, in the case of this embodiment, the free piston 9 includes an annular groove 9c on the outer periphery of the cylindrical portion 9b, and a hole 9d that communicates from the bottom 9a of the free piston 9 to the annular groove 9c.

  The free piston 9 is provided with a spring element 10 that applies a biasing force that suppresses the displacement of the free piston 9 relative to the housing 17 according to the amount of displacement of the free piston 9. 1 between the flange 19 of the nut portion 18 and the upper end of the bottom portion 9a of the free piston 9 in FIG. 1 and in the compression side pressure chamber 8 and the bottom portion of the cylindrical portion 20 and the bottom portion 9a of the free piston 9. 1, coil springs 24 and 25 are interposed between the middle and lower ends, respectively. The free piston 9 is elastically supported by the coil springs 24 and 25 after being positioned at a predetermined neutral position in the pressure chamber R3. The neutral position is not limited to the position that coincides with the stroke center of the free piston 9 in the housing 17.

  The coil spring 24 is prevented from being significantly displaced in the radial direction by the inner circumference of the cylindrical portion 9b of the free piston 9, and the coil spring 25 is formed by inserting the convex portion 9e of the free piston 9 into the inner circumference. In this way, a significant displacement is prevented, so that the urging force can be applied to the free piston 9 stably. Further, since the free piston 9 has a bottomed cylindrical shape, the sliding length in the axial direction with the cylindrical portion 20 of the housing 17 can be secured while accommodating the coil spring 24, and the axial direction of the housing 17 can be secured. Shaking with respect to the cylinder part 20 can be prevented without increasing the overall length, and the sliding resistance is prevented from becoming excessive. As the spring element 10, it is only necessary that the free piston 9 can be elastically supported. Therefore, a spring other than the coil springs 24 and 25 may be employed. You may make it support. Further, 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 18 or the cylindrical portion 20.

  Further, when the upper end of the cylindrical portion 9b comes into contact with the flange 19 of the nut portion 18 in the housing 17, the free piston 9 is further restricted from moving upward in FIG. 1, and conversely, the outer periphery of the bottom portion 9a is cylindrical. When abutting against a step portion 20a provided on the inner periphery of the portion 20, further downward movement in FIG. 1 is restricted.

  The free piston 9 is provided with an annular groove 9c formed along the circumference on the outer periphery of the cylindrical portion 9b. Further, the annular groove 9c and the pressure side pressure chamber 8 pass through the thickness inside the free piston 9. Is provided with a hole 9d. Further, variable orifices 22 and 23 communicating with the pressure side chamber R2 in the cylindrical portion 20 and the inside of the housing 17 are provided. These variable orifices 22 and 23 are in a neutral position when the free piston 9 is elastically supported by the spring element 10. In some cases, the pressure-side pressure chamber 8 and the pressure-side chamber R2 are always connected to face the annular groove 9c, and the free piston 9 is displaced to the stroke end, that is, the flange 19 of the nut portion 18 or the step portion of the cylindrical portion 20 When it is displaced until it comes into contact with 20a, it is completely overlapped with the outer periphery of the cylindrical portion 9b of the free piston 9 so as to be closed. That is, in this case, the pressure side flow path 6 is constituted by the annular groove 9 c, the variable orifices 22 and 23, the hole 9 d and the fixed orifice 21. In the figure, two variable orifices 22 and 23 are provided, but the number thereof is arbitrary.

  In other words, in the case of this shock absorber D, when the displacement amount from the neutral position of the free piston 9 becomes an arbitrary displacement amount, the opening of the variable orifices 22, 23 faces the annular groove 9c from the situation where the cylindrical portion 9b The situation starts to face the outer periphery, the flow area of the variable orifices 22 and 23 begins to decrease gradually, and the flow resistance in the pressure side flow path 6 gradually increases. Therefore, the above-mentioned arbitrary displacement amount is set by setting the vertical width in the figure of the annular groove 9c and the opening position on the inner peripheral side of the cylindrical portion 20 of the variable orifices 22 and 23. In this embodiment, the flow areas of the variable orifices 22 and 23 gradually decrease as the displacement of the free piston 9 increases, and when the free piston 9 reaches the stroke end, the variable orifices 22 and 23 It is completely closed so as to oppose the cylindrical portion 9 b, and the flow path resistance in the pressure side flow path 6 is maximized so that the pressure side pressure chamber 8 is communicated with the pressure side chamber R 2 only by the fixed orifice 21.

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

  First, the frequency sensitive characteristic realized by the free piston 9 moving in the pressure chamber R3 will be described.

  When the amount of displacement from the neutral position in the free piston 9 is within a range in which the variable orifices 22 and 23 do not begin to close, the free piston 9 can be displaced without changing the resistance of the pressure side flow path 6. . Then, when considering the condition that the piston speed is the same when the vibration frequency input to the shock absorber D is low and high, first, when the input frequency is low, the amplitude of the input vibration increases, The amplitude of the free piston 9 also increases within a range where the variable orifices 22 and 23 do not begin to close.

  When the amplitude of the free piston 9 increases in the above range, the urging force that the free piston 9 receives from the coil springs 24 and 25 increases, and when the shock absorber D extends, the pressure in the compression side pressure chamber 8 is increased by the expansion side pressure chamber. When the shock absorber D contracts, the pressure in the expansion side pressure chamber 7 is smaller than the pressure in the compression side pressure chamber 8. The coil springs 24 and 25 become smaller by the urging force.

  In this way, when the shock absorber D exhibits low frequency vibration, a differential pressure corresponding to the urging force of the coil springs 24 and 25 is generated in the expansion side pressure chamber 7 and the compression side pressure chamber 8, and therefore, the expansion side chamber R 1 and the expansion side pressure chamber 7. And the pressure difference between the pressure side chamber R2 and the pressure side pressure chamber 8 become smaller and pass through the apparent flow path consisting of the expansion side flow path 5, the pressure side flow path 6, the expansion side pressure chamber 7, and the pressure side pressure chamber 8. The flow rate is small. Since the flow rate of the compression side port 3 and the expansion side port 4 is increased by the small flow rate passing through the apparent flow path, the damping force generated by the shock absorber D is maintained high.

  On the other hand, when the input frequency to the shock absorber D is high, the amplitude of the input vibration becomes small and the amplitude of the free piston 9 becomes smaller. When the amplitude of the free piston 9 is reduced, the urging force received by the free piston 9 from the coil springs 24 and 25 is reduced, and the pressure in the extension side pressure chamber 7 is maintained regardless of whether the shock absorber D is in the expansion stroke or the contraction stroke. And the pressure in the pressure side pressure chamber 8 become substantially equal. Then, since the differential pressure between the expansion side chamber R1 and the expansion side pressure chamber 7 and the differential pressure between the compression side chamber R2 and the compression side pressure chamber 8 increase, the flow rate passing through the expansion side flow channel 5 and the pressure side flow channel 6 also increases.

  When the frequency of vibration input to the shock absorber D is low, the flow rate that passes through the apparent flow path is small, and when the input frequency is high, the flow rate that passes through the apparent flow path increases. If the speed is the same, the flow rate flowing 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 must be equal regardless of the input frequency. The flow rate passing through the expansion side leaf valve EV that opens and closes the side port 4 increases when the input frequency is low and increases the damping force. Conversely, the flow rate decreases when the input frequency is high and decreases the damping force. . Therefore, in a situation where the expansion / contraction speed of the shock absorber D is relatively low and the characteristics of the compression side valve PV and the expansion side leaf valve EV do not appear remarkably, the damping force of the shock absorber D is shown in FIG. 4 in response to the frequency. It will transition to.

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

  Next, the operation of the shock absorber D when the amount of displacement from the neutral position of the free piston 9 falls within the range in which the flow path resistance of the pressure side flow path 6 is increased will be described.

  Even if the shock absorber D is extended or contracted, the variable orifices 22 and 23 are displaced from the neutral position by the free piston 9, and the flow passage area is gradually reduced according to the amount of displacement. When either of the upper and lower stroke ends is reached, it is completely blocked, and the flow passage area becomes the same as the flow passage area of the fixed orifice 21 to be minimized.

  That is, after the free piston 9 starts to close the variable orifices 22 and 23, the flow resistance of the pressure side flow path 6 is gradually increased according to the amount of displacement, and when the free piston 9 reaches the stroke end, the flow resistance is reduced. Maximum.

  Here, the free piston 9 is displaced to the stroke end when the amount of liquid flowing into and out of the expansion side pressure chamber 7 or the pressure side pressure chamber 8 is large. Is the case.

  When the vibration frequency input to the shock absorber D is relatively high, the shock absorber D generates a relatively low damping force until the free piston 9 is displaced to a position where it begins to close the variable orifices 22 and 23. However, when the free piston 9 is displaced beyond the position where the variable orifices 22 and 23 begin to be closed, the flow resistance of the pressure side flow path 6 gradually increases. The movement speed to the stroke end side is reduced, the amount of liquid movement through the apparent flow path is also reduced, and the amount of liquid passing through the partial pressure side port 3 and the expansion side port 4 is increased. Thus, the damping force generated by the shock absorber D gradually increases.

  When the free piston 9 reaches the stroke end, the liquid does not move through the apparent flow path any more, and the liquid is compressed side port 3 and extended side port 4 until the expansion / contraction direction of the shock absorber D is changed. Therefore, the shock sensitive device D generates a large damping force.

  Further, when the expansion / contraction speed of the shock absorber D reaches the middle / high speed range, it is difficult for the liquid to pass through the fixed orifice 21 and the variable orifices 22 and 23, and the free piston 9 does not easily move in the pressure chamber R3. Therefore, similarly to the case where the free piston 9 reaches the stroke end, it becomes difficult to exhibit the characteristics sensitive to the frequency due to the movement of the free piston 9, and the liquid gives priority to the compression side port 3 and the extension side port 4. Passing through, it becomes difficult to exhibit the characteristics sensitive to the frequency.

  In such a situation, that is, when the free piston 9 is displaced to the stroke end or when the expansion / contraction speed of the shock absorber D reaches a medium / high speed, the characteristics of the compression side valve PV and the extension side leaf valve EV become prominent. . Therefore, the damping characteristic (damping force speed characteristic) of the shock absorber D is a slanted line in FIG. 5 depending on the vibration frequency of the shock absorber D even if the speed is the same when the expansion / contraction speed of the shock absorber D is in the low speed range. Although the damping force becomes higher and lower within the range, when the expansion / contraction speed of the shock absorber D is in the middle / high speed range, the characteristics of the compression side valve PV and the extension side leaf valve EV are dominant as shown in FIG. As a result, the frequency-sensitive characteristic hardly appears.

  However, in the shock absorber D of the present invention, the valve disk 12 is laminated on the piston 2, and the communication port 12e is connected to the downstream outlet of the expansion side port 4 and the communication port 12e. An annular window 12c communicating with the downstream outlet to the pressure side chamber and an annular valve seat 12d surrounding the outer periphery of the annular window 12c are provided, and the extension side leaf valve EV is stacked on the valve disc 12 so as to be detachable from the annular valve seat 12d. Since the inner diameter of the annular valve seat 12d is set to be larger than the virtual circular diameter in contact with the inner edge of each pressure side port 3, the seat diameter (annular valve seat) of the extension side leaf valve EV to the annular valve seat 12d is set. 12d) is larger than the seat diameter when the annular leaf valve is provided on the piston 2 to surround the outer periphery of the expansion side port 4 and the expansion side leaf valve is stacked on the piston 2 as in the conventional shock absorber. The extension side leaf valve EV having a larger outer diameter than before can be used, and the point of action at which the extension side leaf valve EV receives the pressure from the extension side chamber R1 can be shifted to the outer peripheral side compared to the conventional one. The bending rigidity of the side leaf valve EV can be made apparently low.

  Therefore, the damping characteristic when the expansion / contraction speed in the conventional shock absorber is in the middle / high speed range has a high damping coefficient as shown by the broken line in FIG. 5, but according to the shock absorber D of the present invention, in FIG. As indicated by the solid line, the damping force can be exhibited with a lower damping coefficient than the conventional shock absorber.

  As described above, in the shock absorber D of the present invention, the damping force when the expansion / contraction speed is in the middle / high speed range can be reduced, and excessive damping force can be eliminated to improve riding comfort. The difference between the ride comfort in the vehicle and the ride comfort in the medium and high speed range is reduced. Therefore, according to the shock absorber D of the present invention, it is possible to maintain a good riding comfort in the vehicle even when the expansion / contraction speed becomes a medium / high speed.

  In this shock absorber D, even if a vibration with a high frequency and a large amplitude that causes the free piston 9 to be displaced to the stroke end is input to the shock absorber D, the free piston 9 is moved from the neutral position. If the amount of displacement exceeds an arbitrary amount of displacement, the shock absorber D gradually increases the generated damping force until the free piston 9 reaches the stroke end, so that it does not suddenly change from a low damping force to a high damping force. That is, when the free piston 9 reaches the stroke end and the liquid in the extension side chamber R1 and the pressure side chamber R2 cannot be exchanged through the pressure chamber R3, the magnitude of the damping force does not change suddenly. The damping force change from low damping force to high damping force becomes gentle. Furthermore, since the generated damping force is gradually increased when the free piston 9 reaches the stroke ends on both ends in the pressure chamber R3, the function of suppressing a sudden change in the damping force is Demonstrated in both strokes.

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

  Further, in the shock absorber D in the present embodiment, the entire flow passage area of the communication port 12e is made larger than the total flow passage area of the expansion side port 4, so that the expansion side leaf valve EV is connected to the expansion side port. Since the damping characteristic when opening 4 is determined by the flow path area of the expansion side port 4, the damping characteristic when the expansion / contraction speed of the shock absorber D is in the middle / high speed range is changed by exchanging the piston 2. be able to. Accordingly, it is possible to use the piston 2 that is widely used except for the shock absorber D using the valve disk 12, and it is not necessary to use the special piston 2, so that the practicality is improved and the cost is also reduced. Note that the above does not prevent the entire flow passage area of the communication port 12e from being made smaller than the entire flow passage area of the extension side port 4, and such a configuration can also be adopted.

  Further, the expansion side port 4 is provided along the axial direction with respect to the piston 2, and the communication port 12 e is provided along the axial direction with respect to the valve disk 12. It is not necessary to perform the process of opening the ports obliquely, and it is possible to adopt a processing method using a mold such as sintering, and the processing cost of the shock absorber D can be reduced.

Further, the piston 2 includes a bottom portion 2a where the expansion side port 4 and the compression side port 3 are provided, and a cylindrical portion 2b where a piston ring 2c provided on the outer periphery of the bottom portion 2a and slidably contacting the inner periphery of the cylinder 1 is mounted. Therefore, not only can the valve disc 12 be inserted into the cylindrical portion 2b, but also the fitting length with the cylinder 1 (the axial length of the piston ring 2c) can be ensured, and there is no backlash with respect to the cylinder 1. While preventing sticking, the overall axial length of the piston 2 and the valve disk 12 can be shortened to ensure the stroke length of the shock absorber D.

  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 2a Piston bottom part 2b Piston cylinder part 2c Piston ring 3 Pressure side port 4 Extension side port 5 Extension side flow path 7 Extension side pressure chamber 6 Pressure side flow path 8 Pressure side pressure chamber 9 Free piston 10 Spring element 12 Valve disk 12e Communication port 12c Annular window 12d Annular valve seat D Shock absorber EV Extension side leaf valve PV Pressure side valve R1 Extension side chamber R2 Pressure side chamber R3 Pressure chamber

Claims (4)

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, and is provided on the same circle on the piston and communicates with the extension side chamber and the pressure side chamber A plurality of compression-side ports, a plurality of expansion-side ports provided on the inner circumference side of the piston on the same circle and communicating with the extension-side chamber and the compression-side chamber, and the compression-side port. A pressure-side valve that opens and closes, an expansion-side leaf valve that opens and closes the expansion-side port, a pressure chamber, and the pressure chamber that is inserted in the pressure chamber so as to be movable in the axial direction. A free piston that divides into an expansion side pressure chamber that communicates with the pressure side passage and a pressure side pressure chamber that communicates with the pressure side chamber via a pressure side flow path, and an urging force that suppresses displacement from the neutral position of the free piston. With spring elements In the shock absorber,
A valve disk stacked on the piston, the communication port communicating with the downstream outlet of the extension port; an annular window communicating the downstream outlet of the communication port to the pressure side chamber; and the annular window An annular valve seat surrounding the outer periphery of the valve, and the extension leaf valve is stacked on the valve disc so as to be detachable from the annular valve seat, and the inner diameter of the annular valve seat is at the inner edge of each pressure side port. A shock absorber, wherein the shock absorber is set to have a larger diameter than a virtual circle diameter in contact with the shock absorber. 2. The shock absorber according to claim 1, wherein the entire flow passage area of the communication port is made larger than the whole flow passage area of the extension side port. The extension side port is provided along the axial direction with respect to the piston, and the communication port is provided along the axial direction with respect to the valve disk. Shock absorber. The piston includes a bottom portion on which the extension side port and the pressure side port are provided, and a cylindrical portion to which a piston ring that is provided on the outer periphery of the bottom portion and is in sliding contact with the inner periphery of the cylinder is mounted. The shock absorber according to any one of claims 1 to 3.

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