JP2010071369A - Hydraulic shock absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid erroneous installation of a stopper piece, by arranging a bypass passage in a piston rod, without reducing strength of the piston rod, in a hydraulic shock absorber. <P>SOLUTION: In this hydraulic shock absorber 10, the bypass passage 51 extending in the longitudinal direction of the piston rod 13 is arranged on an outer surface of a small diameter part 13B of the piston rod 13. A shoulder part 13C of the piston rod 13 is formed in a right-angled shape. A stopper piece 80 is formed so that the shoulder part 13C of the piston rod 13 and both end surfaces 80A and 80B abutting on respective disc valves 34 are formed in a plane shape orthogonal to the axial direction of the stopper piece 80. A flow passage 82 communicating with the bypass passage 51 of the piston rod 13 and opening in an oil chamber 12A of a cylinder 12, is formed by forming a cutout in one place in the peripheral direction of the stopper piece 80. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydraulic shock absorber.

As described in Patent Document 1, as a hydraulic shock absorber, an oil liquid is accommodated in an oil chamber of a cylinder, and a piston inserted into a small diameter portion of a piston rod inserted into the cylinder is slidably fitted into the cylinder. The oil chamber is divided into upper and lower oil chambers by a piston, a flow path connecting the upper and lower oil chambers is provided in the piston, and a disk valve that opens and closes the flow path provided in the piston is connected to the large diameter portion and the small diameter portion of the piston rod. It is supported by the back by a stopper piece that is locked to the shoulder of the boundary, a bypass path that bypasses the piston and connects the upper and lower oil chambers is provided in the piston rod, and a damping force adjustment unit is provided in this bypass path is there.
Reality 4-43633

  In the hydraulic shock absorber described in Patent Document 1, a hollow portion provided in the piston rod is used as a bypass path. Accordingly, the number of processing steps for providing the hollow portion in the piston rod increases, and the strength is lowered with a small diameter piston rod (for example, a rod diameter of 12.5 mmφ).

  It is also conceivable to provide a groove-like bypass path that extends over the outer surface of the piston rod, particularly the outer surface of the small diameter portion to the shoulder portion. However, in the small piston rod, the shoulder step (for example, the large diameter portion 12.5 mmφ and the small diameter portion 8 mmφ) that supports the stopper piece on the back surface has a small size, and a groove-shaped bypass is further provided in the small size shoulder portion. This greatly reduces the load bearing area of the shoulder for the stopper piece. As a result, the support surface pressure acting on the stopper piece becomes excessive, and the sintered alloy stopper piece may be deformed, buckled, and crushed.

  Further, in the stopper piece, it is desired that no erroneous assembly due to the direction of assembly occurs when the stopper piece is assembled to the small diameter portion of the piston rod and locked to the shoulder portion of the piston rod. When a wrong assembly due to the direction of stopper piece assembly occurs, the back support state of the disk valve stopper piece becomes abnormal, and there is a risk that the disk valve may be opened or closed abnormally, resulting in poor damping force.

  Further, when the stopper piece is made of a sintered alloy, it is desired to make the sintered density uniform and to improve the flatness of the end face contacting the disk valve.

  The subject of this invention is providing a bypass path in a piston rod, and avoiding incorrect assembly of a stopper piece, without reducing the intensity | strength of a piston rod in a hydraulic buffer.

  Another object of the present invention is to improve the flatness of the end surface of the sintered alloy stopper piece that contacts the disc valve.

  According to the first aspect of the present invention, the oil liquid is accommodated in the oil chamber of the cylinder, the piston inserted into the small diameter portion of the piston rod inserted into the cylinder is slidably fitted into the cylinder, and the oil chamber of the cylinder is The piston is divided into upper and lower oil chambers, and a passage that connects the upper and lower oil chambers is provided in the piston. A disk valve that opens and closes the passage provided in the piston is engaged with the shoulder at the boundary between the large diameter portion and the small diameter portion of the piston rod. In the hydraulic shock absorber that is supported by the back by a stopper piece that is stopped, bypasses the piston and connects the upper and lower oil chambers to the piston rod, and a damping force adjusting unit is provided in the bypass passage, A bypass path extending in the longitudinal direction of the piston rod is provided on the outer surface of the small-diameter portion, the shoulder of the piston rod is formed at a right angle, and the stopper piece is connected to the shoulder of the piston rod, Both end surfaces that contact each of the disk valves are formed in a planar shape perpendicular to the axial direction of the stopper piece, and a flow path that communicates with the bypass path of the piston rod and opens into the oil chamber of the cylinder is 1 in the circumferential direction of the stopper piece. Notches are formed at some points.

  According to a second aspect of the invention, in the first aspect of the invention, the stopper piece is made of a straight cylindrical body having the same cross section in the axial direction.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the stopper piece is made of sintered metal.

(Claim 1)
(a) Since the bypass path is provided on the outer surface of the small-diameter portion of the piston rod, the machining man-hours can be reduced and the decrease in the strength of the piston rod can be avoided as compared with the case where the bypass path is formed by the hollow portion provided in the piston rod. .

  (b) The planar end surface of the stopper piece is seated on the right-angle shoulder of the piston rod, and the flow path communicating with the bypass path provided on the outer surface of the small-diameter portion of the piston rod is not provided on the right-angle shoulder of the piston rod. Only one place was provided on the stopper piece side. Therefore, in the small piston rod, even if the shoulder step supporting the stopper piece on the back (for example, the large diameter part 12.5mmφ, the small diameter part 8mmφ) is small, the load support area of the shoulder for the stopper piece is The shoulder portion can be made larger as long as no flow path is provided. Moreover, the contact area of the stopper piece with the shoulder portion of the piston rod can be increased by the amount of the flow path provided on the stopper piece side in only one place in the circumferential direction. Thereby, the support surface pressure which acts on a stopper piece can be made small, and a deformation | transformation and buckling of a stopper piece can be prevented.

  (c) Both end faces of the stopper piece have a planar shape perpendicular to the axial direction of the stopper piece. Therefore, when the stopper piece is assembled to the small-diameter portion of the piston rod and both end faces of the stopper piece are brought into contact with the shoulder portion of the piston rod and the disc valve, the stopper piece has no direction of assembly. Even if the stopper piece is installed upside down, it will not be misassembled, the back support state by the disc valve stopper piece will not become abnormal, the disc valve will not open / close abnormally, and the damping force will be poor. It does not occur.

(Claim 2)
(d) The stopper piece can be easily formed by using a straight cylindrical body having the same cross section in the axial direction.

(Claim 3)
(e) When the stopper piece is made of a sintered alloy, both end surfaces to be pressed are flat, so that the sintered alloy can be sintered at a uniform density. When the stopper piece is made of a straight cylindrical body of sintered metal, the sintered metal can be sintered at a more uniform density. Thereby, the flat part of the end surface which contact | abuts the disk valve | bulb of a stopper piece improves.

  FIG. 1 is a schematic cross-sectional view showing a hydraulic shock absorber, FIG. 2 is a cross-sectional view showing damping force adjusting means, FIG. 3 shows the flow of oil in the hydraulic shock absorber, and FIG. (B) is a schematic diagram showing a high-frequency region of the extension side stroke, (C) is a schematic diagram showing a compression side stroke, FIG. 4 is a plan view showing a slit valve, and FIG. 5 is a plan view showing a spring. 6 shows a stopper piece, (A) is a plan view, and (B) is a sectional view taken along line BB in (A).

  As shown in FIG. 1, the damping force adjusting hydraulic shock absorber 10 is a double cylinder type composed of a double pipe in which a cylinder 12 is built in a damper tube 11, and a piston rod 13 is inserted into a cylinder 12 containing oil. The axle tube side mounting portion is provided at the lower portion of the damper tube 11 and the vehicle body side mounting portion 14 is provided at the upper portion of the piston rod 13 to constitute a vehicle suspension device.

  The hydraulic shock absorber 10 has a suspension spring 16 interposed between a lower spring seat 15 on the outer periphery of the damper tube 11 and an upper spring seat (not shown) provided on the vehicle body side mounting portion 14 at the upper end portion of the piston rod 13. To do.

  The hydraulic shock absorber 10 clamps a rod guide 17, a bush 18, and an oil seal 19 for the piston rod 13 inserted into the cylinder 12 between the upper end crimped portion 11 </ b> A of the damper tube 11 and the upper end portion of the cylinder 12. It is fixed.

  The damping force adjusting hydraulic shock absorber 10 includes a piston valve device 20 and a bottom valve device 40. The piston valve device 20 and the bottom valve device 40 generate a damping force by controlling the flow of oil and liquid caused by the piston 24 (described later) provided at the insertion end of the piston rod 13 into the cylinder 12 sliding on the cylinder 12. The expansion and contraction vibration of the piston rod 13 accompanying the absorption of the impact force by the suspension spring 16 is suppressed by the damping force generated by them. The piston rod 13 has a large-diameter portion 13A and a small-diameter portion 13B. The insertion end of the piston rod 13 into the cylinder 12 is a small-diameter portion 13B, and a stepped shoulder at the boundary between the large-diameter portion 13A and the small-diameter portion 13B. 13C is provided.

(Piston valve device 20)
As shown in FIG. 2, the piston valve device 20 has a stopper piece 80, a piston 24, and a valve stopper 25 inserted into the outer periphery of the small diameter portion 13B of the piston rod 13 inserted into the cylinder 12, and these are attached to the small diameter portion 13B. The valve housing 61 for the sub-extension-side damping valve 60, which is screwed to the tip screw portion 21, is clamped and fixed between the shoulder portion 13C of the piston rod 13.

  The piston 24 is slidably inserted into the cylinder 12, and is provided with an expansion side flow path 31 and a pressure side flow path 32, and an annular center of a disk valve-shaped main expansion side damping valve 33 between the piston 24 and the valve stopper 25. The annular portion of the disc-valve compression side damping valve 34 is clamped between the piston 24 and the stopper piece 80. That is, the piston valve device 20 divides the inside of the cylinder 12 into a rod side chamber 12A (upper oil chamber) and a piston side chamber 12B (lower oil chamber) by the piston 24, and the rod side chamber 12A and the piston side chamber 12B are provided in the piston 24. The main passage 31 and the main extension side damping valve 33 that opens and closes the extension side passage 31, and the pressure side passage 32 and the pressure side attenuation valve 34 that opens and closes the pressure side passage 32 communicate with each other. That is, in the hydraulic shock absorber 10, the pressure side damping valve 34 that opens and closes the pressure side flow path 32 provided in the piston 24 is supported on the back surface by the stopper piece 80 that is locked to the shoulder portion 13 </ b> C of the piston rod 13.

  Therefore, at the time of extension, the oil in the rod side chamber 12A passes through the extension side flow path 31 of the piston 24, bends and opens the main extension side damping valve 33, is guided to the piston side chamber 12B, and generates an extension side damping force. . At the time of compression, the oil in the piston side chamber 12B passes through the pressure side flow path 32 of the piston 24, bends and deforms the pressure side damping valve 34, is guided to the rod side chamber 12A, and generates a pressure side damping force.

(Bottom valve device 40)
In the hydraulic shock absorber 10, a gap between the damper tube 11 and the cylinder 12 is defined as a reservoir chamber 12C, and the interior of the reservoir chamber 12C is partitioned into an oil chamber and a gas chamber. The bottom valve device 40 includes a bottom piece 41 that partitions the piston side chamber 12B and the reservoir chamber 12C inside the cylinder 12 between the lower end portion of the cylinder 12 and the bottom portion of the damper tube 11, and the bottom portion of the damper tube 11. The space between the bottom piece 41 and the bottom piece 41 can be communicated with the reservoir chamber 12C through a flow path provided in the bottom piece 41.

  The bottom valve device 40 includes a disk valve 42 and a check valve 43 as bottom valves for opening and closing a pressure side channel 41A and an extension side channel (not shown) provided in the bottom piece 41, respectively.

  At the time of extension, the oil corresponding to the retraction volume of the piston rod 13 retreating from the cylinder 12 pushes the check valve 43 open, and enters the piston side chamber 12B from the reservoir chamber 12C via the expansion side flow path (not shown) of the bottom piece 41. To be replenished. During compression, the oil corresponding to the volume of the piston rod 13 entering the cylinder 12 is opened from the piston side chamber 12B through the pressure side flow path 41A of the bottom piece 41 by bending and deforming the disk valve 42 and pushed into the reservoir chamber 12C. Get the compression side damping force.

  In the hydraulic shock absorber 10, the piston rod 13 extends around the piston rod 13 located in the rod side chamber 12A of the cylinder 12 and on the rebound seat 46 fixed to the piston 24 side (lower side). A rebound rubber 47 that is compressed and deformed at the time of cutting (the most extended state of the hydraulic shock absorber 10) is provided.

  However, the hydraulic shock absorber 10 includes an extension side damping force adjusting device 50 for adjusting the damping force of the piston valve device 20, in this embodiment, the extension side damping force as follows.

  As shown in FIG. 2, the extension side damping force adjusting device 50 is provided with a bypass passage 51 in the piston rod 13 that bypasses the main extension side damping valve 33 and communicates the rod side chamber 12 </ b> A and the piston side chamber 12 </ b> B. A sub-extension-side damping valve 60 (damping force adjusting unit) is provided. The valve stopper 25 of the main extension side damping valve 33 inserted into the small diameter portion 13B of the piston rod 13 and the main body 61A and the collar of the valve housing 61 screwed into the tip screw portion 21 of the small diameter portion 13B of the piston rod 13 The annular central portion of the disk valve-like sub-extension-side damping valve 60 is clamped between 61B. That is, the extension side damping force adjusting device 50 opens one end of the bypass passage 51 into the rod side chamber 12A and opens the other end of the bypass passage 51 into the sub flow path 25A provided in the valve stopper 25, thereby sub-extension attenuation. The sub channel 25A is opened and closed with respect to the piston side chamber 12B by the valve 60.

  The extension side damping force adjusting device 50 is connected to the back side of the sub extension side damping valve 60 on the back side thereof through the orifice 62A of the slit valve 62 to the rod side chamber 12A (one oil chamber pressurized when extended). 63 is provided, and the back pressure chamber 63 is closed by a partition body 70 including a plurality of laminated leaf springs 71. The slit valve 62 is attached to the back surface of the sub extension side damping valve 60, and an annular central portion is sandwiched between the valve stopper 25 of the main extension side damping valve 33 and the valve housing 61. As shown in FIG. 4, the slit valve 62 includes slits on the inner periphery of the annular central portion, and each slit is an orifice 62A.

  The extension-side damping force adjusting device 50 is composed of a combined body of a main body 61A and a collar 61B in which the valve housing 61 is screwed to the tip screw portion 21 of the small diameter portion 13B of the piston rod 13, and the screw portion 21 of the main body 61A is attached to the screw portion 21. Upper and lower annular portions b and c are provided on the upper and lower sides of the outer peripheral side of the disk portion a to be screwed, and an annular stopper 65 is press-fitted to the inner periphery of the lower annular portion c of the main body 61A. The valve housing 61 is provided with a plurality of communication holes 61C at a plurality of positions in the circumferential direction of the disc portion a of the main body 61A so that the back pressure chambers 63 can be continued on both sides in the axial direction inside the valve housing 61.

  The back pressure chamber 63 is slidably provided in the valve housing 61 of the sub extension side damping valve 60 and the upper annular portion b of the main body 61A of the valve housing 61, and is attached to the back surface of the sub extension side damping valve 60 by a spring 66. A partition is formed by the backup collar 67 to be urged and a partition body 70 seated on the support surface 68 of the valve housing 61 (in this embodiment, the upper surface 68 on the outer periphery side of the stopper 65). The backup collar 67 slides up and down in a liquid-tight manner on the sealing material 67A loaded in the inner circumferential annular groove of the upper annular portion b of the main body 61A of the valve housing 61. Collide with the back of the. As shown in FIG. 5, the spring 66 includes a cross-shaped protruding portion 66A on the outer periphery of the annular central portion, and the annular central portion is located between the collar 61B of the valve housing 61 and the annular protruding step surface of the disc portion a of the main body 61A. The lower end surface of the backup collar 67 is supported on the tip end portion of the overhang portion 66A.

  The partition body 70 is provided with a core 73 at the center of a disc-shaped plate spring 71, an auxiliary spring 72 is provided on the opposite side of the plate spring 71 in the axial direction of the core 73, and the auxiliary spring 72 is connected to the valve housing 61. The leaf spring 71 is seated on the support surface 68 of the stopper 65 by the urging force of the auxiliary spring 72, which is supported on the lower end support surface 69 provided so as to form a step on the inner periphery of the lower annular portion c of the main body 61 </ b> A. In the present embodiment, the core member 73 has small diameter portions 73B and 73C projecting on both sides in the axial direction of the bulging portion 73A, the central hole of the leaf spring 71 is loaded into the small diameter portion 73B, and the small diameter portion 73C is loaded. With the central hole of the auxiliary spring 72 loaded, the outer edge side end surface of the leaf spring 71 is placed on the support surface 68 of the stopper 65 and seated, and the outer edge side end surface of the auxiliary spring 72 is placed on the support surface 69 of the valve housing 61. Support. The leaf spring 71 of the partition wall 70 is not fixedly held on the support surface 68 of the stopper 65, but is freely slidable along the surface of the support surface 68, and the spring constant of the leaf spring 71 is set low. . The auxiliary spring 72 of the partition wall 70 is also free to slide along the support surface 69 of the valve housing 61.

  In the partition body 70, in the extension side stroke, the pressure of the rod side chamber 12 </ b> A to be pressurized receives the pressure of the back pressure chamber 63 applied from the bypass passage 51 via the orifice 62 </ b> A, the leaf spring 71 bends, and the auxiliary spring 72. Is separated from the support surface 69 of the valve housing 61, and the pressure in the back pressure chamber 63 reaches the intermediate chamber 74 between the leaf spring 71 and the auxiliary spring 72. In the extension side stroke, the leaf spring 71 of the partition wall body 70 abuts against the abutment surface 65B of the stopper 65, and the deflection of the leaf spring 71 is restricted. In the reverse pressure side stroke, the pressure of the pressurized piston side chamber 12B extends from the communication hole 65A provided in the central surface of the stopper 65 to the leaf spring 71, the auxiliary spring 72 is bent, and the leaf spring 71 is the support surface of the stopper 65. The pressure in the piston side chamber 12 </ b> B extends to the intermediate chamber 74. In the compression side stroke, the core member 73 of the partition wall body 70 abuts against the end face of the piston rod 13 and restricts the bending of the auxiliary spring 72. The partition body 70 repeats the above-described extension side stroke and pressure side stroke, causes a delay in the pressure propagation in the rod side chamber 12A in the extension side stroke, and causes a delay in the pressure propagation in the piston side chamber 12B in the compression side stroke. The spring constants of the leaf spring 71 and the auxiliary spring 72 can be set independently of each other, and the pressure propagation delay from the rod side chamber 12A to the back pressure chamber 63 is generated by reducing the number of laminated leaf springs 71 and setting the extension side weak. The pressure side of the piston side chamber 12B is slightly increased by increasing the number of laminated auxiliary springs 72 to make the pressure side strong, and the response speed of the damping force of the piston valve device 20 and the extension side damping force adjusting device 50 can be adjusted. .

  The extension side damping force adjusting device 50 regulates the stroke of the partition wall 70 by the stopper 65 and can make the stroke a minute stroke of about 0.2 to 2 mm, improving the responsiveness when switching between the extension and the compression stroke. it can. The communication hole 65A provided in the stopper 65 may be an orifice. By making the flow path area of the orifice 65A larger than the orifice 62A at the inlet of the back pressure chamber 63, the opening / closing timing of the compression side damping valve 34 is frequency-dependent in the compression side stroke without affecting the frequency dependency in the expansion side stroke. Can be adjusted.

Accordingly, the hydraulic shock absorber 10 includes the extension side damping force adjusting device 50 and operates as follows.
(1) When the piston speed of the hydraulic shock absorber 10 is in the normal low frequency range during the extension stroke, the pressure in the pressurized rod side chamber 12A is propagated through the orifice 62A as shown in FIG. When the pressure in the back pressure chamber 63 rises after the partition body 70 made of the leaf spring 71 is pushed and stroked without being delayed, the sub pressure body 63 receives the pressure in the back pressure chamber 63. The main extension side damping valve 33 is opened without generating the extension side damping valve 60 to generate a damping force. The main extension side damping valve 33 has a higher bending rigidity than the sub extension side damping valve 60 so as to improve the maneuverability during normal running, and generates a normally required damping force.

  (2) When the vehicle rides on the road surface unevenness and the piston speed enters the high frequency range in the extension side stroke, the pressure in the pressurized rod side chamber 12A is delayed by the pressure propagation by the orifice 62A as shown in FIG. Accordingly, the pressure in the back pressure chamber 63 is not increased, and the sub-extension-side damping valve 60 is easily opened to reduce the damping force.

  (3) In the pressure side stroke, as shown in FIG. 3C, the pressure side damping valve 34 is opened to generate a damping force.

The hydraulic shock absorber 10 includes the extension side damping force adjusting device 50 and has the following effects.
(a) In the low frequency range of the piston speed, the pushing stroke of the partition body 70 biased by the leaf spring 71 is small, the pressure in the back pressure chamber 63 rises quickly, and it is uncomfortable even when the extension / pressure stroke is switched. It can respond without any problems and the response speed is fast. The leaf spring 71 occupies a small space, and the spring force can be easily set by adjusting the number of stacked springs.

  The frequency characteristics of the damping force generated by the hydraulic shock absorber 10 by changing the pressure receiving area of the sub extension side damping valve 60 with respect to the back pressure chamber 63, the flow path area of the orifice 62A, or the spring constant of the leaf spring 71 of the partition wall 70 is obtained. Easy to adjust.

  (b) Since the leaf spring 71 of the partition wall 70 is free to move on the support surface 68 of the valve housing 61, the spring constant of the leaf spring 71 can be easily reduced. In the low frequency region of the piston speed, the pressure increase in the back pressure chamber 63 can be accelerated, and the response speed can be increased.

  (c) The partition body 70 is provided with a core 73 at the center of the leaf spring 71, an auxiliary spring 72 is provided on the opposite side of the leaf spring 71 in the axial direction of the core 73, and the auxiliary spring 72 is supported on the valve housing 61. The leaf spring 71 is seated on the support surface 68 of the valve housing 61 by the biasing force of the auxiliary spring 72. The leaf spring 71 of the partition wall 70 can be stably seated on the support surface 68 of the valve housing 61 by the biasing force of the auxiliary spring 72.

  (d) The main extension side damping valve 33 and the sub extension side damping valve 60 are provided, and the back pressure chamber 63 is provided on the back side of the sub extension side damping valve 60. By making the deflection rigidity of the main extension side damping valve 33 larger than the deflection rigidity of the sub extension side damping valve 60, a high damping force can be obtained by the main extension side damping valve 33 in the normal time when the piston speed is in a low frequency range. it can. When the piston speed enters the high frequency range, the sub-extension-side damping valve 60 can be easily opened and the damping force can be lowered by the above-described (a), and the feeling of slight vibration can be eliminated. That is, in the normal low frequency range, the main expansion side damping valve 33 provides a stable damping force in a wide range of piston speeds from low to high speed to ensure operability, and high-frequency micro vibrations are generated by the sub expansion side damping valve 60. It absorbs by opening and can secure riding comfort.

  Furthermore, even in a normal low frequency range, by setting the pressure receiving area of the sub extension side damping valve 60 to the back pressure chamber 63 to be small, when the damping force of the main extension side damping valve 33 is increased, the sub extension side damping valve is increased. 60 can be opened, and the upper limit of the damping force can be set (fast blow).

  Even in a normal low frequency range, by setting the pressure receiving area of the sub extension side damping valve 60 to the back pressure chamber 63 to be small, a damping force is generated by the sub extension side damping valve 60, and When the damping force increases, the main extension side damping valve 33 can be opened to set an upper limit of the damping force (high-speed blowing).

  However, the hydraulic shock absorber 10 has the following configuration in order to allow the bypass path 51 to be provided in the piston rod 13 without reducing the strength of the piston rod 13.

  The hydraulic shock absorber 10 is provided with a bypass passage 51 extending in the longitudinal direction of the piston rod 13 on the outer surface of the small diameter portion 13B of the piston rod 13 and makes the shoulder portion 13C of the piston rod 13 have a right angle. The bypass passage 51 is formed in the small-diameter portion 13B of the piston rod 13 from the portion immediately below the shoulder portion 13C where the straight inner peripheral portion 81 of the stopper piece 80 is inserted, to the tip screw portion 21 where the valve stopper 25 is inserted. It extends over the range up to the top. In the small-diameter portion 13B of this embodiment, the cross section of the portion where the bypass passage 51 is provided has a D-section, and the bypass passage 51 is milled so as to be continuous in the longitudinal direction of the piston rod 13. Consists of. However, the bypass 51 may have a groove shape.

  On the other hand, as shown in FIG. 2 and FIG. 6, the stopper piece 80 is inserted from the small diameter portion 13B side of the piston rod 13 and locked to the right shoulder 13C. It is inserted over the part 13C and the small diameter part 13B. In the stopper piece 80, both end faces 80 </ b> A and 80 </ b> B that are in contact with the right-angle shoulder portion 13 </ b> C of the piston rod 13 and the compression side damping valve 34 are planar shapes orthogonal to the axial direction of the stopper piece 80. The stopper piece 80 communicates with the upper end portion of the bypass passage 51 of the small-diameter portion 13B of the piston rod 13 and has a flow path 82 opened to the rod side chamber 12A of the cylinder 12 in a straight shape at one place in the circumferential direction of the stopper piece 80. A notch is formed so as to face the peripheral portion 81. The flow path 82 of the present embodiment has a U-shaped groove extending in the axial direction of the stopper piece 80.

  In addition, the piston rod 13 of the present embodiment is provided with an annular flow path 52 that intersects with the bypass path 51 in an intermediate portion of the insertion portion of the stopper piece 80 in the small diameter portion 13B. Therefore, the bypass passage 51 provided in the small diameter portion 13B of the piston rod 13 communicates with the rod side chamber 12A of the cylinder 12 via the annular flow passage 52 of the small diameter portion 13B and the flow passage 82 of the stopper piece 80.

  Moreover, the stopper piece 80 of the present embodiment is composed of a straight cylindrical body such as a cylinder having the same cross section in the axial direction. In the stopper piece 80, the upper and lower portions sandwiching the central plane perpendicular to the axial direction at the center in the axial direction are symmetrical with respect to the central plane.

  Moreover, the stopper piece 80 of the present embodiment is made of, for example, a sintered alloy.

According to the present embodiment, the following operational effects can be obtained.
(a) Since the bypass passage 51 is provided on the outer surface of the small-diameter portion 13B of the piston rod 13, the processing man-hour is reduced as compared with the case where the bypass passage 51 is formed by the hollow portion provided in the piston rod 13. A decrease in strength can be avoided.

  (b) The planar end surface 80A of the stopper piece 80 is seated on the right-angled shoulder 13C of the piston rod 13, and the flow path 82 communicating with the bypass path 51 provided on the outer surface of the small diameter portion 13B of the piston rod 13 is defined as the piston rod 13. Without being provided on the right shoulder 13C, only one location was provided on the stopper piece 80 side. Accordingly, in the small-diameter piston rod 13, even if the step (for example, the large diameter portion 12.5 mmφ and the small diameter portion 13B8 mmφ) of the shoulder portion 13C that supports the stopper piece 80 on the back surface is small, the shoulder portion 13C for the stopper piece 80 is used. The load supporting area can be increased by the amount that the flow path 82 is not provided in the shoulder portion 13C. Moreover, the contact area of the stopper piece 80 with the shoulder portion 13C of the piston rod 13 can be increased by the amount of the flow path 82 provided on the stopper piece 80 side in only one place in the circumferential direction. Thereby, the support surface pressure which acts on the stopper piece 80 can be made small, and the deformation | transformation and buckling of the stopper piece 80 can be prevented.

  (c) The stopper piece 80 has both end faces 80A and 80B in a planar shape perpendicular to the axial direction of the stopper piece 80. Accordingly, when the stopper piece 80 is assembled to the small diameter portion 13B of the piston rod 13 and both end faces 80A of the stopper piece 80 are brought into contact with the shoulder portion 13C of the piston rod 13 and the disc valve 34, the stopper piece 80 There is no direction of assembly. Even if the stopper piece 80 is assembled upside down, the assembled state does not become incorrect, the back support state of the disc valve 34 by the stopper piece 80 does not become abnormal, and the opening and closing of the disc valve 34 is abnormal. Damping force failure does not occur.

  (d) The stopper piece 80 can be easily formed by using a straight cylindrical body having the same cross section in the axial direction.

  (e) When the stopper piece 80 is made of a sintered alloy, both end faces 80A to be pressed are flat, so that the sintered alloy can be sintered at a uniform density. When the stopper piece 80 is formed of a straight cylindrical body of sintered metal, the sintered metal can be sintered at a more uniform density. As a result, the flat portion of the end surface 80A that contacts the disc valve 34 of the stopper piece 80 is improved.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention. For example, the flow path provided in the stopper piece of the present invention may be any channel that communicates with the bypass path of the piston rod and opens into the oil chamber of the cylinder, and is necessarily provided on the inner periphery of the stopper piece to form a groove shape. It is not limited to a thing, The thing drilled in a stopper piece and making a hole shape may be used.

FIG. 1 is a schematic cross-sectional view showing a hydraulic shock absorber. FIG. 2 is a cross-sectional view showing the damping force adjusting means. 3A and 3B show the flow of oil in the hydraulic shock absorber, FIG. 3A is a schematic diagram showing a low frequency region in the extension side stroke, FIG. 3B is a schematic diagram showing a high frequency region in the extension side stroke, and FIG. It is a schematic diagram which shows a process. FIG. 4 is a plan view showing the slit valve. FIG. 5 is a plan view showing the spring. 6A and 6B show the stopper piece, where FIG. 6A is a plan view and FIG. 6B is a cross-sectional view taken along line BB in FIG.

Explanation of symbols

10 Hydraulic shock absorber 12 Cylinder 12A Rod side chamber (oil chamber)
12B Piston side chamber (oil chamber)
13 Piston rod 13A Large diameter part 13B Small diameter part 13C Shoulder part 24 Piston 31 Stretch side flow path 32 Pressure side flow path 33 Stretch side damping valve (disc valve)
34 Pressure-side damping valve (disc valve)
51 Bypass path 60 Sub extension side damping valve (Damping force adjustment part)
80 Stopper piece 80A, 80B End face 82 Flow path

Claims (3)

Oil is stored in the oil chamber of the cylinder,
The piston inserted into the small diameter part of the piston rod inserted into the cylinder is slidably fitted into the cylinder,
The oil chamber of the cylinder is divided into upper and lower oil chambers by a piston, and a flow path that connects the upper and lower oil chambers is provided in the piston.
A disk valve that opens and closes the flow path provided in the piston is supported on the back by a stopper piece that is locked to the shoulder at the boundary between the large diameter portion and the small diameter portion of the piston rod,
In the hydraulic shock absorber in which a bypass path that bypasses the piston and connects the upper and lower oil chambers is provided in the piston rod, and a damping force adjustment unit is provided in the bypass path,
A bypass path extending in the longitudinal direction of the piston rod is provided on the outer surface of the small diameter portion of the piston rod, and the shoulder of the piston rod is formed at a right angle,
The stopper piece has both a shoulder surface of the piston rod and both end surfaces abutting on the disk valve in a flat shape perpendicular to the axial direction of the stopper piece, and communicates with the bypass path of the piston rod and opens into the oil chamber of the cylinder. A hydraulic shock absorber, characterized in that a flow path is cut out at one place in the circumferential direction of the stopper piece.   The hydraulic shock absorber according to claim 1, wherein the stopper piece is formed of a straight cylindrical body having the same cross section in the axial direction.   The hydraulic shock absorber according to claim 1 or 2, wherein the stopper piece is made of sintered metal.

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