JP2018179091A - Hydraulic buffer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relax attenuation force based on a flow passage area of a throttle flow passage set by a needle valve, at an initial stage of an expansion side stroke of a piston, to generate the attenuation force, with simple configuration, in a hydraulic buffer having an attenuation force regulator with the needle valve.SOLUTION: A hydraulic buffer 10 with an attenuation force regulator 30 is configured such that inside a piston rod 12, a relief flow passage 37 is formed, the relief flow passage positioned at an intermediate part of a bypass flow passage 31 in parallel with a throttle flow passage 36; and a relief valve 41 for opening/closing the relief flow passage 37 is provided in the vicinity of a pressure side oil chamber 26A with respect to the relief flow passage 37 in the bypass flow passage 31 inside the piston rod 12.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a hydraulic shock absorber.

  In automobiles, motorcycles and the like, hydraulic shock absorbers are used which suppress the change in posture of the vehicle body due to the unevenness of the road surface.

  A conventional hydraulic shock absorber generally comprises a pressure side oil chamber which is pressurized in a pressure side stroke of the piston by a piston provided on a piston rod inserted into the cylinder, and an extension of the piston. The piston is divided into an expansion-side oil chamber to be pressurized in the side stroke, and the piston includes a pressure-side flow passage for introducing oil in the pressure-side oil chamber to the expansion side oil chamber, and the pressure-side oil chamber pressurized in the pressure side stroke. The pressure side damping valve opens the pressure side flow path by oil pressure, the expansion side flow path for guiding the oil of the expansion side oil chamber to the pressure side oil chamber, and the oil pressure of the expansion side oil chamber pressurized in the expansion side stroke An expansion damping valve is provided to open the expansion channel. As a result, in the middle and high speed region where the piston speed exceeds a predetermined speed, the compression side damping valve or the expansion side damping valve is opened to secure a predetermined damping force characteristic on the compression side or the expansion side.

  Further, in the conventional hydraulic shock absorber, for example, in the hydraulic shock absorber described in Patent Document 1, a bypass flow passage for bypassing the piston and communicating the pressure side oil chamber with the expansion side oil chamber is provided inside the piston rod. And the damping force adjusting rod is passed through the inside of the piston rod, and the tip needle valve of the damping force adjusting rod advances and retracts to the throttling passage of the throttling portion fixedly disposed in the middle of the bypass passage. There is provided a damping force adjusting device which can change the setting of the flow passage area of the throttling flow passage. Thus, by rotating the adjuster connected to the upper end portion of the damping force adjusting rod, the needle valve is advanced and retracted to change the setting of the flow passage area of the throttle channel, and the throttle in the pressure side stroke or expansion side stroke The flow rate of the oil flowing through the flow path is adjusted, and the flow resistance applied to the oil flowing through the throttling flow path increases in proportion to the square of the flow rate through which the flow rate flows (the square of the piston speed). In particular, adjust the damping force at low speeds.

  Furthermore, in the hydraulic shock absorber described in Patent Document 1, on the piston rod on the back surface of the pressure side damping valve, a passage that communicates the pressure side oil chamber with the expansion side oil chamber through a bypass flow path formed inside the piston rod. And a piston member different from the piston. Further, an expansion side sub-valve is provided in a passage of a piston member different from the piston so as to communicate the pressure side oil chamber with the expansion side oil chamber through the bypass flow passage at the initial stage of the expansion side stroke of the piston. As a result, in the low speed region where the piston speed is constant, the expansion side auxiliary valve is opened to allow the oil to flow and the damping force in the low speed region is alleviated.

  That is, in the hydraulic shock absorber described in Patent Document 1, in addition to adjusting the damping force in the low speed range of the piston speed by the presence of the damping force adjusting device having the needle valve, a piston member different from the piston Due to the presence of the expansion side sub-valve provided in the passage of (1), the damping force is relaxed in the low speed region of the piston speed at the beginning of the expansion side stroke of the piston. As a result, the damping force can be reduced in the expansion side stroke of the low speed range to the medium and high speed range of the piston speed, and the road surface followability of the tire when riding on a soft ride, step or curb can be improved. .

Patent No. 4663379

  In a hydraulic shock absorber having a damping force adjustment device using a needle valve described in Patent Document 1, when providing an extension side auxiliary valve as a configuration for reducing the damping force in the low speed region of the piston speed at the initial stage of the extension side stroke of the piston. It is necessary to provide a piston member different from the piston and to provide an expansion side valve in the passage of the piston member. That is, it is necessary to provide a piston member on the piston rod on the back side of the compression side damping valve on which the extension side sub valve is provided so as to be stacked in the axial direction of the piston rod. And the axial length of the piston rod is increased by the length of the piston member, as a result of which the hydraulic shock absorber becomes complicated and elongated.

  An object of the present invention is a hydraulic shock absorber having a damping force adjustment device by a needle valve, which has a compact configuration and is based on the flow passage area of the throttle passage set by the needle valve in the early stage of the expansion side stroke of the piston. It is to generate damping force.

  The invention according to claim 1 relates to a pressure side oil chamber in which an oil chamber in the cylinder is pressurized in a pressure side stroke of the piston by a piston provided on a piston rod inserted into the cylinder, and an extension side of the piston It divides into the expansion side oil chamber pressurized in a stroke, and the oil pressure of the pressure side oil chamber is introduced to the expansion side oil chamber to the piston, and the oil pressure of the pressure side oil chamber pressurized in the compression side stroke The pressure-side damping valve that bends to open the pressure-side flow path, the expansion-side flow path that guides the oil in the expansion-side oil chamber to the pressure-side oil chamber, and the oil pressure of the expansion-side oil chamber pressurized in the expansion side stroke There is provided an expansion side damping valve which bends and opens the expansion side flow path, and a bypass flow path which bypasses the piston and connects the pressure side oil chamber and the expansion side oil chamber is formed inside the piston rod. Through a damping force adjusting rod inside the piston rod, the damping force adjusting rod The tip needle valve of the present invention has a damping force adjusting device capable of advancing and retracting to the throttling channel of the throttling portion fixedly disposed in the middle part of the bypass channel to enable the setting area of the throttling channel to be changed. A hydraulic shock absorber, wherein a relief flow passage is provided inside the piston rod in parallel with the throttling flow passage and located at an intermediate portion of the bypass flow passage, and the bypass flow passage inside the piston rod A relief valve for opening and closing the relief flow path is provided near the pressure side oil chamber with respect to the relief flow path inside, and the relief valve is a relief valve by the oil pressure of the pressure side oil chamber pressurized in the pressure side stroke of the piston. The valve is closed so as to close the flow path, and the oil pressure in the expansion side oil chamber pressurized in the expansion side stroke of the piston causes the relief flow path to be opened.

  According to a second aspect of the present invention, in the first aspect, the relief valve is resiliently moved in a direction to close the relief flow passage by the action of a resilient force, and the relief valve is urged by an expansion side stroke of the piston. The relief flow path is opened by the hydraulic pressure of the expansion side oil chamber which is pressurized and resists the elastic force.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the hollow portion of the piston rod forms a vertical passage of the bypass flow passage, and the piston rod intersects the vertical passage. A drilled horizontal passage is formed to communicate with the expansion side oil chamber, the narrowed portion is fitted and fixed in the longitudinal passage, and the narrowed passage is formed by the central hole thereof. The relief flow passage is formed around the center hole portion, and the relief valve and the resilient member are provided closer to the pressure side oil chamber than the relief flow passage formed in the narrowed portion in the vertical passage. The relief valve is adapted to be sprung by the resilient body.

(Claim 1)
(a) In the expansion stroke of the piston, the relief valve is opened by the oil pressure of the expansion oil chamber pressurized and boosted in the expansion stroke. As a result, the oil of the expansion side oil chamber flowing in the bypass flow passage forming the damping force adjusting device passes through both the throttle flow passage and the relief flow passage in the bypass flow passage, and The passing flow rate is reduced by the passing flow rate to the relief flow path, and as a result, the damping force based on the flow path area of the throttle flow path set by the needle valve is alleviated and generated.

  (b) In the damping force adjustment device using a needle valve, as described above in (a), during the stroke on the expansion side of the piston, the damping force based on the flow passage area of the throttled flow passage set by the needle valve is relaxed. At the time of generation, a throttling portion provided at an intermediate portion of the bypass flow path is fixedly disposed, and the needle valve is advanced and retracted to the throttling flow path of the throttling portion to change the flow path area of the throttling flow path did. Therefore, when the needle valve abuts against the throttle portion and is set at a reference stroke position (reference advance / retraction position of the needle valve) at which the flow passage area (opening degree) of the throttle passage in the throttle portion is zero, the throttle portion Is fixed and does not move due to the abutment force of the needle valve, and it can be easily and correctly recognized that the needle valve has been set to its reference stroke position. Therefore, the needle valve is recognized as having a flow passage area of the throttle flow passage when the needle valve is at this reference stroke position is zero, and its advancing / retracting amount can be adjusted. The flow passage area of the passage can be easily changed with high accuracy.

  (c) Since the throttling portion for the needle valve that constitutes the damping force adjustment device in the above (a) and (b), the throttling channel, and the relief channel are provided inside the piston rod (hollow portion of the piston rod) The damping force adjustment device can be configured compactly.

  The above-mentioned damping force adjusting device provided on the inner side of the piston rod (hollow part of the piston rod) is within the installation range of the piston, compression side damping valve and expansion side damping valve provided on the piston rod in the axial direction of the piston rod. The damping force adjustment device can be compactly provided without lengthening the hydraulic shock absorber.

(Claim 2)
(d) In the expansion stroke of the piston, although the relief valve is resiliently closed in the direction to close the relief channel by the action of the elastic force, the hydraulic pressure of the expansion oil chamber pressurized and pressurized in the expansion stroke When the pressure exceeds the above-mentioned elastic force, the relief valve is opened by the oil pressure of the boosted side oil chamber. Therefore, the opening timing of the relief valve can be changed by changing the above-mentioned elastic force (replacement of the elastic body, etc.).

(Claim 3)
(e) Since the throttling portion fixedly disposed in the middle portion of the bypass flow path formed inside the piston rod forms the relief flow path together with the throttling flow path, it is positioned at the middle portion of the bypass flow path The throttling channel and the relief channel can be easily formed. It is possible to improve the processability and assembly for providing the damping force adjusting device.

FIG. 1 is an overall sectional view showing a hydraulic shock absorber. FIG. 2 is an enlarged sectional view of a main part of FIG. 3A and 3B show the throttling portion, in which FIG. 3A is a sectional view and FIG. 3B is a plan view. FIG. 4 is a cross-sectional view showing a relief valve. FIG. 5 is a schematic view showing the flow of oil in the bypass flow passage in the pressure side stroke. FIG. 6 shows the flow of oil in the bypass flow path during the expansion stroke, and (A) is a schematic view showing the flow when the piston speed is in the very low speed region, (B) is in the low speed region where the piston speed is constant or more It is a schematic diagram which shows the flow of time. FIG. 7 is a diagram showing damping force characteristics of the hydraulic shock absorber.

  As shown in FIG. 1, the hydraulic shock absorber 10 has a piston rod 12 inserted into a cylinder 11, and a suspension spring (not shown) is provided outside the cylinder 11 and the piston rod 12. The cylinder 11 is provided with an axle side attachment member (not shown), and the piston rod 12 is provided with a vehicle body side attachment member (not shown).

  The rod guide 13 is fluid-tightly fitted to the cylinder 11 via the O-ring 14. The rod guide 13 supports the piston rod 12 slidably in a fluid-tight manner on an inner diameter portion provided with the oil seal 15, the bush 16, the dust seal 17, and the like. The cylinder 11 is provided with a bump rubber stopper 18 on the outside of the rod guide 13.

  The hydraulic shock absorber 10 has a piston valve device 20 and a damping force adjustment device 30, and due to the damping force generated by the piston valve device 20 and the damping force adjustment device 30 as described later, the damping force is absorbed by the suspension spring. The expansion and contraction vibration of the cylinder 11 and the piston rod 12 is damped.

  In the piston valve device 20, as shown in FIG. 2, a pair of valve units 20A is inserted and attached to the tip of the piston rod 12 inserted into the cylinder 11, and fixed by a nut 20B. The valve unit 20A includes a valve stopper 21, a compression side damping valve 28A, a piston 23, an expansion side damping valve 28B, and a valve stopper 25. The valve unit 20A is fastened and fixed to the tip side small diameter step portion of the piston rod 13 by a nut 20B.

  That is, the piston valve device 20 is a pressure side oil chamber in which the oil chamber 26 of the hydraulic fluid in the cylinder 11 is pressurized by the pressure side stroke of the piston 23 by the piston 23 provided on the piston rod 12 inserted into the cylinder 11 26A and an expansion side oil chamber 26B pressurized in the expansion side stroke of the piston 23. The piston 23 is flexed by the hydraulic pressure of the pressure side flow passage 27A for guiding the oil of the pressure side oil chamber 26A to the expansion side oil chamber 26B and the pressure side oil chamber 26A pressurized in the pressure side stroke to open the pressure side flow passage 27A. Pressure side damping valve 28A, extension side flow path 27B for guiding the oil of extension side oil chamber 26B to pressure side oil chamber 26A, and oil pressure of extension side oil chamber 26B pressurized in the extension side stroke An expansion damping valve 28B is provided to open 27B. Each of the compression side damping valve 28A and the expansion side damping valve 28B is configured by laminating a plurality of bending plates.

  Therefore, in the piston valve device 20, the oil of the pressure side oil chamber 26A pressurized in the pressure side stroke of the piston 23 bends the pressure side damping valve 28A to open the pressure side flow passage 27A in the middle high speed region of the piston 23. As the fluid flows through the gap between the compression side damping valve 28A and the piston 23 to the expansion side oil chamber 26B, a pressure side damping force based on the flow resistance that the gap exerts on the flow of oil is generated. Further, in the middle and high speed region of the piston 23, the oil of the expansion oil chamber 26B pressurized in the expansion stroke causes the expansion damping valve 28B to flex and opens the expansion channel 27B, and this oil is an expansion damping valve When flowing through the gap between the piston 28 and the piston 23 to the pressure side oil chamber 26A, a pressure side damping force is generated based on the flow resistance that the gap exerts on the flow of oil. Thereby, predetermined damping force characteristics in the medium and high speed range are secured.

  As shown in FIG. 2, the damping force adjustment device 30 bypasses the piston 23 and connects the pressure side oil chamber 26A and the expansion side oil chamber 26B with each other by the bypass flow path 31 inside the piston rod 12. The damping force adjusting rod 33 connected to the adjuster 32 is passed through the hollow portion 12P of the piston rod 12, and the tip needle valve 34 of the damping force adjusting rod 33 is in the middle of the bypass passage 31. The flow path area (opening area) of the throttling channel 36 is made changeable by advancing and retreating to the throttling channel 36 of the throttling portion 35 fixedly disposed in the portion. The bypass passage 31 is composed of a longitudinal passage 31K and a lateral passage 31L. The longitudinal passage 31K is formed by the hollow portion 12P of the piston rod 12 and opens to the pressure side oil chamber 26A. The lateral passage 31L intersects the longitudinal passage 31K. It is drilled at 12 and opens to the expansion side oil chamber 26B.

  Here, in the damping force adjusting device 30, the adjuster 32, which is rotationally operated by a hexagonal wrench or the like, is screwed to the proximal end female thread provided in the hollow portion 12P of the piston rod 12, The damping force adjusting rod 33 and the tip needle valve 34 are inserted in series in the portion 12P, and one end face of the damping force adjusting rod 33 is butted to the end face of the adjuster 32 facing the hollow portion 12P of the piston rod 12 The end face of the tip needle valve 34 is butted to the other end face of the valve. The tip needle valve 34 receives the oil pressure generated in the oil chamber 26 of the cylinder 11 and abuts on the damping force adjusting rod 33, and the damping force adjusting rod 33 abuts on the end face of the adjuster 32. The screw displacement causes the tip needle valve 34 to advance and retract with respect to the throttle channel 36 of the throttle unit 35.

  Therefore, in the damping force adjustment device 30, in the low speed range of the piston 23, one oil of the pressure side oil chamber 26A and the expansion side oil chamber 26B pressurized in the pressure side stroke or the extension side stroke The flow resistance that the throttle channel 36 exerts on the flow of oil when it flows to the other of the pressure side oil chamber 26A and the expansion side oil chamber 26B through the throttle channel 36 of the throttle unit 35 whose channel area is already set by dynamic operation. Generate a compression side damping force or an expansion side damping force based on Thereby, predetermined damping force characteristics in the low speed range are secured.

  The opening of the hollow portion 12P facing the external space of the piston rod 12 is provided with a central hole 38H into which a hexagonal wrench for turning the adjuster 32 can be inserted, and the backward limit due to the turning operation of the adjuster 32 is restricted. A retaining collar 38 for retaining the adjuster 32 is screwed on.

  Further, the hydraulic shock absorber 10 has a free piston 39 that defines a volume compensation chamber 39A with respect to the pressure side oil chamber 26A of the cylinder 11. The free piston 39 slides in the cylinder 11 according to the volume change of the piston rod 12 entering / exiting the cylinder 11 during the compression side stroke and the expansion side stroke of the piston 23, and the volume of the volume compensation chamber 39A increases and decreases accordingly The change absorbs the volume change of the piston rod 12. The volume compensation chamber 39A is sucked with high pressure gas such as nitrogen gas and is closed by the plug 39P.

  However, the hydraulic shock absorber 10 has the damping force adjusting device 30 by the needle valve 34, and has a compact configuration, and the throttle passage 36 set by the needle valve 34 at the beginning of the expansion stroke of the piston 23. The damping force based on the flow passage area is to be relaxed as follows.

  As shown in FIG. 2, the damping force adjusting device 30 fits and fixes the throttling portion 35 in the vertical passage 31 K of the bypass passage 31 provided in the piston rod 12. The throttling portion 35 has a collar shape as shown in FIG. 3, and the throttling channel 36 is formed by the central hole portion, and the relief channel 37 is formed around the central hole portion. The throttling channel 36 has a round hole shape penetrating on the central axis of the throttling section 35, and the relief channel 37 is provided at two positions opposite to each other on the diameter of the throttling section 35. It has a square groove-like shape.

  The relief flow channel 37 may be provided at three positions in the circumferential direction (for example, 120 degrees equal distribution) or four positions in the circumferential direction (for example, 90 degrees equal distribution) of the throttling portion 35. Further, the relief flow channel 37 is not limited to the angular groove shape, and may be, for example, a semilunar groove shape.

  The damping force adjustment device 30 further includes a relief valve 41 and a relief valve 41 in the longitudinal passage 31 K of the bypass passage 31 provided in the piston rod 12 and closer to the pressure side oil chamber 26 A than the relief passage 37 formed in the narrowed portion 35. The resilient body 42 is inserted and the relief valve 41 is resiliently urged to the side of the throttling portion 35 by the resilient body 42 and abuts against the end face of the throttling portion 35, and the relief flow path 37 of the throttling portion 35 is compressed. The oil chamber 26A can be closed. As shown in FIG. 4, the relief valve 41 has a cylindrical shape, has a uniform inner diameter, has an outer diameter at one end as a large outer diameter portion 41A, and at the other end as a small outer diameter portion 41B. The end face of one end side is abutted against the end face of the squeezed portion 35 so that the relief flow path 37 can be closed, and the coiled elastic body 42 can be idle mounted around the small outer diameter portion 41B of the relief valve 41.

  Here, the throttling portion 35 and the cylindrical spacer 43 are sequentially inserted into the hollow portion 12P opened to the pressure side oil chamber 26A of the piston rod 12, and the cylindrical cap 44 is screwed. The cap 44 presses the narrowed portion 35 via the spacer 43, and the narrowed portion 35 is fastened to the small diameter step portion of the hollow portion 12P and fixedly disposed in the middle portion of the bypass flow passage 31. Further, the relief valve 41 and the resilient member 42 are fitted inside the spacer 43, and the cap 44 compresses the resilient member 42 inserted inside the bypass flow path 31. The relief valve 41 is made to spring to the side of the throttle portion 35 by the action of the elastic force.

  That is, in the damping force adjusting device 30, the damping force adjusting device 30 is disposed in the middle of the bypass flow passage 31 in parallel with the restriction flow passage 36 of the restriction unit 35 inside the piston rod 12 (in the present embodiment, the hollow portion 12P). To form a relief channel 37. Further, a relief valve 41 for opening and closing the relief flow passage 37 is provided closer to the pressure side oil chamber 26A with respect to the relief flow passage 37 in the bypass flow passage 31 in the hollow portion 12P of the piston rod 12. The relief valve 41 is pressed toward the throttle portion 35 by the backup of the hydraulic pressure of the pressure side oil chamber 26A pressurized in the pressure side stroke of the piston 23, and is closed so as to close the relief flow path 37 (FIG. 5) . Further, the relief valve 41 is pushed toward the pressure side oil chamber 26A by the hydraulic pressure of the expansion side oil chamber 26B pressurized in the expansion side stroke of the piston 23, and the relief flow path 37 is opened. (FIGS. 6A to 6B).

  Furthermore, the damping force adjustment device 30 has the elastic body 42, whereby the relief valve 41 is resiliently urged in the direction to close the relief flow path 37 by backup of the elastic force of the resilient body 42, and the piston 23 is stretched. The relief valve 41 can be opened so as to open the relief flow path 37 by the hydraulic pressure of the expansion side oil chamber 26 B which is pressurized in the side stroke and resists the elastic force of the elastic body 42. The opening timing of the relief valve 41 can be changed by the resilient force of the resilient member 42. In FIG. 6A, in the very low speed region of the piston 23, the hydraulic pressure of the expansion side oil chamber 26B pressurized and pressurized in the expansion side stroke is smaller than the elastic force of the elastic body 42, and the relief valve 41 is FIG. 6 (B) shows a state in which the oil pressure in the expansion side oil chamber 26B pressurized and pressurized in the expansion side stroke is elastic at the low speed region beyond the minute low speed region of the piston 23. The relief valve 41 is in an opened state (opening amount δ).

  Accordingly, the hydraulic shock absorber 10 performs damping as follows. In the damping force characteristic diagram shown in FIG. 7, the horizontal axis represents the piston velocity V, and the vertical axis represents the damping force F.

(Pressure side stroke) (Damping force characteristic DC shown in Fig. 7)
In the low speed region of the piston speed in the early stage of the pressure side stroke, that is, in the low speed region before the pressure side damping valve 28A opens, when the oil pressure of the pressure side oil chamber 26A slightly increases, the oil of the pressure side oil chamber 26A is A predetermined pressure-side damping force in the low speed region is generated by passing through the set flow passage area of the throttle flow passage 36.

  When the piston speed exceeds a predetermined speed, the compression side damping valve 28A is opened, and in the middle and high speed range, a predetermined compression side damping force based on the presence of the needle valve 34 and the compression side damping valve 28A is generated.

  That is, by setting the flow passage area of the throttle flow passage 36 by the needle valve 34 of the throttle portion 35 and selecting the deflection characteristics of the compression side damping valve 28A, a desired compression side damping force is obtained in the low speed range Can. By setting the damping force harder, the steering stability of the vehicle is ensured, or by setting the damping force softer, the road surface following property of the tire when riding on the vehicle's soft riding comfort, steps or curbs etc. Improvements can be made.

(Stretch side stroke) (Damping force characteristic DE shown in Fig. 7)
In the very low speed region of the piston speed at the beginning of the expansion stroke, that is, in the very low speed region before the relief valve 41 opens (FIG. 6A), when the hydraulic pressure of the expansion oil chamber 26B slightly increases, the expansion oil chamber 26B Oil passes through the flow passage area of the throttle passage 36 set by the needle valve 34 of the throttle portion 35, and generates a predetermined expansion-side damping force in the very low speed region (damping force DE1 in FIG. 7).

  In a low speed region where the piston speed exceeds the predetermined speed (speed V1 in FIG. 7), when the hydraulic pressure boosted in the expansion side oil chamber 26B exceeds the elastic force of the elastic body 42 and the relief valve 41 is opened, The oil in the expansion side oil chamber 26B passes not only the throttle flow path 36 of the throttle portion 35 but also the relief flow path 37 to generate a predetermined pressure side damping force (DE2 in FIG. 7) in the low speed region. The expansion damping force (DE2) generated in the low speed region is set by the expansion damping force in the low speed region (the needle valve 34 in the damping force characteristic DF shown in FIG. 7 by the conventional hydraulic shock absorber without the relief valve 41). The damping force DF2) of FIG. 7 based on the flow passage area of the throttle flow passage 36 is reduced and relaxed.

  When the piston speed exceeds a predetermined speed (speed V2 in FIG. 7), the relief valve 41 fully opens the relief flow path 37.

  In the hydraulic shock absorber 10, the expansion damping valve 28B is also opened when the piston speed exceeds a predetermined speed, and a predetermined expansion based on the presence of the needle valve 34, the relief valve 41 and the expansion damping valve 28B in the middle high speed region. A side damping force (damping force DE3 in FIG. 7) is generated.

  That is, the setting of the flow passage area of the restricting flow passage 36 by the needle valve 34 of the restricting portion 35, the setting of the flow passage area of the relief flow passage 37 formed in the restricting portion 35, and the flexibility characteristic of the expansion side damping valve 28B Depending on the selection, the desired expansion-side damping force can be set with a high degree of freedom in the low to middle high-speed range of the piston speed. By setting the damping force harder, the steering stability of the vehicle is ensured, or by setting the damping force softer, the road surface following property of the tire when riding on the vehicle's soft riding comfort, steps or curbs etc. Improvements can be made.

  At this time, in the hydraulic shock absorber 10, the damping force based on the flow passage area of the throttle flow passage 36 set by the needle valve 34 is set in the low speed region where the piston speed exceeds the predetermined speed (speed V1 in FIG. 7). I was relieved. Therefore, in a very low speed region where the damping force is not relaxed, the steering force of the vehicle is secured by setting the damping force harder, while in a speed range after the low speed region where the damping force is relaxed, the damping force is softened. By setting the value to be, it is possible to further improve the road surface followability of the tire when the vehicle has a soft ride, a step or a curb or the like.

According to this embodiment, the following effects can be obtained.
(a) In the extension side stroke of the piston 23, the relief valve 41 is opened by the hydraulic pressure of the extension side oil chamber 26B pressurized and boosted in the extension side stroke. As a result, the oil of the expansion oil chamber 26B flowing in the bypass flow passage 31 forming the damping force adjustment device 30 passes through both the throttle flow passage 36 and the relief flow passage 37 in the bypass flow passage 31. The flow rate to the throttle flow path 36 is reduced by the flow rate to the relief flow path 37, and as a result, the damping force based on the flow area of the throttle flow path 36 set by the needle valve 34 is relaxed and generated. It becomes a thing.

  (b) In the damping force adjusting device 30 by the needle valve 34, as described above in (a), the damping based on the flow passage area of the throttle flow passage 36 set by the needle valve 34 during the expansion stroke of the piston 23. When the force is generated by being reduced, the throttling portion 35 provided in the middle portion of the bypass flow path 31 is fixed and disposed, and the needle valve 34 is advanced and retracted to the throttling flow path 36 of the throttling portion 35 The flow path area of 36 was changed. Therefore, the needle valve 34 is abutted against the throttling portion 35, and is set at a reference stroke position (reference advancing and retracting position of the needle valve 34) at which the flow area (opening degree) of the throttling flow path 36 in the throttling portion 35 is zero. At this time, the throttling portion 35 is fixedly arranged and does not move by the abutting force of the needle valve 34, so that it can be easily and correctly recognized that the needle valve 34 is set to its reference stroke position. Therefore, the needle valve 34 is recognized as having a flow passage area of the throttle flow passage 36 when the needle valve 34 is at this reference stroke position as being zero, and the amount of movement thereof can be adjusted. It is possible to change the setting of the flow passage area of the throttle flow passage 36 by the simple method 34 with high accuracy.

  (c) The throttling portion 35, the throttling channel 36, and the relief channel 37 for the needle valve 34 constituting the damping force adjusting device 30 in the above (a) and (b) Since it is provided in the hollow portion 12P, the damping force adjustment device 30 can be configured compactly.

  The above-described damping force adjusting device 30 provided on the inner side of the piston rod 12 (hollow part 12P of the piston rod 12) has the piston 23, pressure side damping valve 28A and pressure side damping valve 28A provided on the piston rod 12 in the axial direction of the piston rod 12. It can be provided within the installation range of the expansion side damping valve 28B (within the range of R shown in FIG. 2), and the damping force adjustment device 30 can be compactly provided without lengthening the hydraulic shock absorber 10.

  (d) In the expansion side stroke of the piston 23, although the relief valve 41 is elasticized in the direction to close the relief flow path 37 by the action of the elastic force, the expansion side oil pressurized and pressurized in the expansion side stroke When the hydraulic pressure in the chamber 26B exceeds the above-mentioned elastic force, the relief valve 41 is opened by the hydraulic pressure in the expansion side oil chamber 26B. Therefore, the opening timing of the relief valve 41 can be changed by the change of the elastic force (such as the replacement of the resilient member 42).

  In the hydraulic shock absorber 10, by setting the elastic force of the elastic body 42 to be weak, the relief valve 41 is opened from the beginning of the movement of the piston 23 in the expansion stroke, and the needle valve 34 is used. The damping force based on the set flow passage area of the throttle flow passage 36 may be started to be relaxed.

  (e) Since the throttling portion 35 fixedly disposed in the middle portion of the bypass flow path 31 formed inside the piston rod 12 forms the relief flow path 37 together with the throttling flow path 36, the bypass flow path The throttling flow passage 36 and the relief flow passage 37 located in the middle part of 31 can be easily formed. The processability and the assemblability for providing the damping force adjustment device 30 can be improved.

  The embodiment of the present invention has been described in detail with reference to the drawings, but the specific configuration of the present invention is not limited to this embodiment, and even if there is a design change or the like within the scope of the present invention. Included in the present invention. For example, the hydraulic shock absorber 10 may have no resilient member 42, and the relief valve 41 may open the relief flow path 37 only by backup of the hydraulic pressure of the pressure side oil chamber 26A.

  According to the present invention, in a hydraulic shock absorber having a damping force adjustment device by a needle valve, it is compact and based on the flow passage area of the throttle passage set by the needle valve at the initial stage of the expansion side stroke of the piston. The damping force can be reduced and generated.

10 hydraulic shock absorber 11 cylinder 12 piston rod 12P hollow part 23 piston 26 oil chamber 26A pressure side oil chamber 26B expansion side oil chamber 27A pressure side flow path 27B expansion side flow path 28A pressure side damping valve 28B expansion side damping valve 30 damping force adjustment device 31 Bypass channel 31K Vertical channel 31L Horizontal channel 33 Damping force adjustment rod 34 Needle valve 35 Throttle portion 36 Throttle channel 37 Relief channel 41 Relief valve 42 Resilient body

Claims (3)

An oil chamber in the cylinder is pressurized by a pressure side stroke of the piston by a piston provided on a piston rod inserted into the cylinder, and an expansion side pressurized in an expansion side stroke of the piston Divided into oil chambers,
A pressure-side flow passage for guiding the oil of the pressure-side oil chamber to the expansion-side oil chamber, and a pressure-side damping valve that is bent by the oil pressure of the pressure-side oil chamber pressurized in the pressure side stroke to open the pressure side flow passage. An expansion-side flow passage for guiding the oil in the expansion-side oil chamber to the pressure-side oil chamber, and an expansion-side damping valve that is flexed by the hydraulic pressure of the expansion-side oil chamber pressurized in the expansion side stroke Provide
A bypass flow passage is formed on the inside of the piston rod for connecting the pressure side oil chamber and the extension side oil chamber by bypassing the piston, and a damping force adjusting rod is passed through the inside of the piston rod to produce the damping force. It has a damping force adjustment device that allows the tip end needle valve of the adjustment rod to move back and forth to the throttle channel of the throttle unit fixedly arranged in the middle part of the bypass channel so that the channel area of the throttle channel can be changed. Hydraulic shock absorber,
Inside the piston rod, a relief flow passage is formed parallel to the throttle flow passage and located at an intermediate portion of the bypass flow passage,
A relief valve for opening and closing the relief flow passage is provided on the inner side of the piston rod near the pressure side oil chamber with respect to the relief flow passage in the bypass flow passage.
The relief valve is closed so as to close the relief flow path by the oil pressure of the pressure side oil chamber pressurized in the pressure side stroke of the piston, and the expansion side oil chamber pressurized in the expansion side stroke of the piston A hydraulic shock absorber opened so as to open the relief channel by the hydraulic pressure of   The relief valve is resiliently urged in the direction to close the relief flow passage by the action of elastic force, and is pressurized in the expansion side stroke of the piston so that the hydraulic pressure of the expansion side oil chamber resists the elastic force. The hydraulic shock absorber according to claim 1, which is opened so as to open the relief flow passage. A vertical passage of the bypass flow passage is formed by the hollow portion of the piston rod, and a horizontal passage drilled in the piston rod is formed to communicate with the extension oil chamber so as to intersect the vertical passage.
The throttling portion is fitted and fixed in the longitudinal path, the throttling channel is formed by the central hole portion, and the relief channel is formed around the central hole portion.
The relief valve and the resilient member are provided closer to the pressure side oil chamber than the relief flow passage formed in the narrowed portion in the longitudinal passage, and the relief valve is resiliently resiliently moved by the resilient member. The hydraulic shock absorber according to item 1 or 2.

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