Shock absorber

Abstract

This shock absorber (D) comprises: a cylinder (1); a piston rod (2) that is inserted into the cylinder (1) so as to be movable in the axial direction; a piston (3) that is connected to the piston rod (2) and movably inserted into the cylinder (1), and that partitions the inside of the cylinder (1) into an extension-side chamber (R1) and a compression-side chamber (R2); a case (8c) that is immovable in the axial direction relative to the cylinder (1) and forms a lock chamber (L) that faces the piston (3) in the axial direction; a support (4) mounted on the extension-side chamber (R1)-facing outer circumference of the piston rod (2); a cushion (5) which is disposed on the extension-side chamber (R1)-facing outer circumference of the piston rod (2) and is restricted from moving to the piston side by the support (4); and a lock piece (6) which is provided on the outer circumference of the piston rod (2) and on the opposite side of the cushion (5) to the piston so as to be movable in the axial direction and which can penetrate into the lock chamber (L).

Description

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[0001] The present invention relates to a shock absorber.

[0002] Conventionally, shock absorbers used in vehicles include, for example, a cylinder, a piston rod that is movably inserted into the cylinder, and a piston that is connected to the tip of the piston rod and movably inserted into the cylinder to divide the interior of the cylinder into an extension-side chamber and a compression-side chamber.

[0003] In conventional shock absorbers configured in this manner, a rebound spring is attached to the outer periphery of the piston rod, with the piston-side end supported. When the free end of the rebound spring is fully extended, it abuts against the rod guide that supports the piston rod, compressing the rebound spring, and the elastic force of the rebound spring absorbs the impact when the piston rod is fully extended.

[0004] In recent years, there has been a trend to reduce the damping force of shock absorbers when driving on good roads in order to improve the ride comfort of light and compact cars. However, as the unsprung weight has increased due to electrification and improved exterior design, there has been a demand for the use of oil locks that use hydraulic pressure that does not produce elastic rebound to cushion the impact when the shock absorber is fully extended.

[0005] To meet such demands, as disclosed in JP2016-534290A, for example, a shock absorber has been developed in which a tapered enlarged diameter section is provided at the end of the cylinder, and a segment that holds a C-shaped elastic ring on the outer periphery of the piston rod and a spring that urges the segment toward the piston are provided, so that when the segment reaches the enlarged diameter section and the shock absorber extends further, the tapered surface causes the elastic ring to gradually reduce in diameter, allowing the upper space partitioned by the elastic ring and the segment to function as an oil lock chamber.

[0006] In a shock absorber configured in this manner, the segments do not reach the enlarged diameter section when the vehicle is traveling on a good road, and a low damping force is exerted when the vehicle is traveling on a good road, so that the ride comfort of the vehicle is not impaired. However, when the shock absorber is fully extended, a hydraulic oil lock function is exerted to generate a high damping force, thereby absorbing impact.

[0007] JP2016-534290A

[0008] Conventional shock absorbers can adequately meet the above-mentioned demand for reducing impact at the extension stroke end, but they require processing to expand the cylinder diameter, and furthermore, many parts must be installed around the outer periphery of the piston rod to achieve the oil lock function, which increases processing costs and the number of parts, resulting in problems such as higher manufacturing costs and difficulty of manufacturing.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a shock absorber that can exhibit a hydraulic locking function, is easy to manufacture, and can reduce manufacturing costs.

[0010] In order to achieve the above object, the shock absorber of the present invention includes a cylinder, a piston rod inserted into the cylinder so as to be movably axially, a piston connected to the piston rod and inserted into the cylinder so as to be movably arranged inside the cylinder, dividing the inside of the cylinder into an extension-side chamber filled with liquid and a compression-side chamber, a case which is immovable in the axial direction relative to the cylinder and forms a lock chamber which opens toward the piston, a support attached to the outer periphery of the piston rod facing the extension-side chamber, a cushion which is arranged on the outer periphery of the piston rod facing the extension-side chamber and whose movement toward the piston is restricted by the support, and a lock piece which is arranged on the outer periphery of the piston rod on the side opposite the piston of the cushion so as to be movably axially arranged and which can enter the lock chamber.

[0011] In a shock absorber configured in this manner, by providing a case that is immovable in the axial direction relative to the cylinder and providing a lock piece on the piston rod, the lock piece enters the lock chamber near the stroke end during extension, thereby exerting a hydraulic locking function and suppressing extension of the shock absorber, and when extension progresses to maximum extension, a large load is generated by compression of the cushion, stopping the extension of the shock absorber and mitigating the impact at maximum extension. Furthermore, with a shock absorber configured as described above, because the addition of the case and lock piece makes it possible to exert a hydraulic locking function during extension compared to a general shock absorber, there is no need to provide a tapered expanded portion at the end of the cylinder or to add many parts such as elastic rings, segments, and springs, as in conventional shock absorbers.

[0012] Fig. 1 is a cross-sectional view of a shock absorber in one embodiment. Fig. 2(a) is a plan view of a lock piece. Fig. 2(b) is a side view of the lock piece. Fig. 2(c) is a bottom view of the lock piece. Fig. 3(a) is a partially enlarged cross-sectional view of the shock absorber in a state where the lock piece is disposed at a position spaced apart from the lock chamber L. Fig. 3(b) is a partially enlarged cross-sectional view of the shock absorber when the lock piece begins to enter the lock chamber. Fig. 3(c) is a partially enlarged cross-sectional view of the shock absorber in a state where the lock piece is disposed at a position spaced apart from the lock chamber.

[0013] A shock absorber according to the present invention will be described below with reference to the drawings. As shown in Fig. 1, a shock absorber D according to one embodiment includes a cylinder 1, a piston rod 2 inserted into the cylinder 1, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 to divide the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2 filled with liquid, a case 8c that is axially immovable relative to the cylinder 1 and forms a lock chamber L axially facing the piston 3, an annular support 4 attached to the outer periphery of the piston rod 2, a cushion 5 disposed on the outer periphery of the piston rod 2, and a lock piece 6 provided on the outer periphery of the piston rod 2 and capable of entering the lock chamber L. The shock absorber D is interposed between a vehicle body and a wheel of a vehicle (not shown) and generates a damping force during extension / contraction to suppress vibration of the vehicle body.

[0014] Each part of the shock absorber D will be described in detail below. The cylinder 1 is cylindrical, and as described above, the piston rod 2 and the piston 3 are inserted inside the cylinder 1 so as to be movable in the vertical direction in FIG. 1 , which is the axial direction. The inside of the cylinder 1 is divided by the piston 3 into an extension-side chamber R1 at the top in FIG. 1 and a compression-side chamber R2 at the bottom in FIG. 1 . The extension-side chamber R1 and the compression-side chamber R2 are filled with a liquid, specifically, hydraulic oil, for example. Note that the liquid may be water, an aqueous solution, or the like, in addition to hydraulic oil.

[0015] The cylinder 1 is housed in a cylindrical outer cylinder 7 that is arranged on the outer periphery and has a bottom, and a reservoir R is formed in the annular gap between the cylinder 1 and the outer cylinder 7. In this case, the reservoir R stores hydraulic oil as a liquid and gas. The gas filled in the reservoir R is an inert gas such as nitrogen to prevent deterioration of the hydraulic oil, but other gases may also be used. In this embodiment, the reservoir R is formed between the cylinder 1 and the outer cylinder 7, but the reservoir R may also be formed by a tank provided separately from the cylinder 1.

[0016] The piston rod 2 is inserted through the inner periphery of an annular rod guide 8 that fits into the upper end of the cylinder 1 in FIG. 1, with its tip end inserted into the cylinder 1, and its base end, or upper end in FIG. 1, protrudes outward from the cylinder 1.

[0017] The rod guide 8 is annular and includes a small-diameter portion 8a that fits around the inner periphery at the top end of the cylinder 1, a large-diameter portion 8b that is continuous with the upper end of the small-diameter portion 8a in Fig. 1 and fits around the inner periphery of the outer cylinder 7, a cylindrical case 8c that extends downward in Fig. 1 from the outer periphery of the lower end of the small-diameter portion 8a, a seal receiving portion 8d that is formed by expanding the inner periphery on the atmosphere side, which is the upper end in Fig. 1, and a pressure relief passage 8e that opens from the seal receiving portion 8d and leads to the lower end of the large-diameter portion 8b. A cylindrical bushing 9 that comes into sliding contact with the outer periphery of the piston rod 2 is attached to the inner periphery of the rod guide 8.

[0018] The rod guide 8 has a small diameter portion 8a fitted into the inner periphery at the upper end of the cylinder 1 and an outer periphery of the large diameter portion 8b fitted into the inner periphery at the upper end of the outer cylinder 7, thereby closing off the upper ends of the cylinder 1 and the outer cylinder 7. The case 8c is cylindrical and hangs down from the outer periphery of the lower end of the small diameter portion 8a, with the inner diameter on the lower side expanded, and the interior is open to the expansion-side chamber R1 to form a lock chamber L facing the expansion-side chamber R1. The inner periphery of the opening at the lower end of the case 8c is provided with a tapered surface 8c1 whose inner diameter increases downward in FIG.

[0019] The rod guide 8 closes the upper ends of the cylinder 1 and the outer cylinder 7 in FIG. 1, and supports the piston rod 2 inserted into the bushing 9 to guide the movement of the piston rod 2 in the axial direction.

[0020] 1, an annular seal member 10 that seals the gap between the piston rod 2 and the outer cylinder 7 is stacked. The seal member 10 includes a core 10a formed of an annular plate, an annular inner seal 10b welded to the inner periphery of the core 10a and in sliding contact with the outer periphery of the piston rod 2, an annular outer seal 10c welded to the outer periphery of the lower end of the core 10a in FIG. 1 and in close contact with the inner periphery of the outer cylinder 7, and an annular check seal 10d welded to the lower end of the core 10a and accommodated in a seal accommodating portion 8d of the rod guide 8, and seated and releasable between the inner periphery of the rod guide 8 and the pressure relief passage 8e.

[0021] When the seal member 10 is stacked on the rod guide 8, the lower portion of the inner seal 10b and the check seal 10d are accommodated in the seal accommodating portion 8d, and the inner seal 10b comes into sliding contact with the outer periphery of the piston rod 2, while the outer periphery of the outer seal 10c comes into close contact with the inner periphery of the outer cylinder 7. In this way, the seal member 10 seals between the piston rod 2 and the outer cylinder 7, preventing liquid and gas within the shock absorber D from leaking out of the shock absorber D.

[0022] Note that when the liquid that has passed between the piston rod 2 and the bushing 9 from the extension-side chamber R1 and then been scraped off by the inner circumferential seal 10b accumulates in the seal accommodating portion 8d and the pressure inside the seal accommodating portion 8d increases, the check seal 10d lifts off from the rod guide 8 and returns the liquid inside the seal accommodating portion 8d to the reservoir R via the pressure relief passage 8e. This prevents the seal accommodating portion 8d from becoming high pressure, and prevents the inner circumferential seal 10b from excessively tightening the piston rod 2 due to the pressure inside the seal accommodating portion 8d, thereby preventing smooth movement of the piston rod 2.

[0023] The piston 3 is provided with an extension-side passage 3a and a compression-side passage 3b that communicate between the extension-side chamber R1 and the compression-side chamber R2, an extension-side damping valve 3c that is provided in the extension-side passage 3a and allows hydraulic oil to flow only from the extension-side chamber R1 to the compression-side chamber R2 and provides resistance to the flow of hydraulic oil, and a compression-side check valve 3d that is provided in the compression-side passage 3b and allows hydraulic oil to flow only from the compression-side chamber R2 to the extension-side chamber R1.

[0024] 1 of the cylinder 1 is fitted with a valve case 11 placed on the bottom of the outer tube 7. The valve case 11 is provided with a flange 11a on the outer periphery of the lower end in FIG. 1 that fits onto the inner periphery of the outer tube 7 and abuts against the lower end of the cylinder 1. The valve case 11 is inserted into the outer tube 7 together with the seal member 10, rod guide 8, and cylinder 1, and is fixed inside the outer tube 7 by being sandwiched between the bottom of the outer tube 7 and a crimped portion 7a formed by crimping the upper end of the outer tube 7 from the outer periphery.

[0025] The valve case 11 also separates the compression side chamber R2 from the reservoir R, and is equipped with a discharge passage 11b and a suction passage 11c that connect the compression side chamber R2 to the reservoir R, a compression side damping valve 11d that is provided in the discharge passage 11b and that only allows the flow of hydraulic oil from the compression side chamber R2 to the reservoir R and provides resistance to the flow of hydraulic oil, and an extension side check valve 11e that is provided in the suction passage 11c and that only allows the flow of hydraulic oil from the reservoir R to the compression side chamber R2.

[0026] 1 relative to the cylinder 1, hydraulic oil in the extension-side chamber R1, which is reduced in size by the movement of the piston 3, passes through the extension-side damping valve 3c and moves to the expansion-side chamber R2, and the extension-side damping valve 3c applies resistance to the flow of hydraulic oil, causing the pressure in the extension-side chamber R1 to rise, generating a damping force that hinders the extension operation. Also, during the extension operation of the shock absorber D, the piston rod 2 retracts from the cylinder 1, and hydraulic oil equivalent to the volume of the piston rod 2 retracted from the cylinder 1 is supplied from the reservoir R to the cylinder 1 via the extension-side check valve 11e.

[0027] 1 relative to the cylinder 1, the hydraulic oil in the compression-side chamber R2, which is reduced in size by the movement of the piston 3, passes through the compression-side check valve 3d and moves to the expansion-side chamber R1, and since the compression-side check valve 3d does not provide much resistance to the flow of hydraulic oil, the pressures in the expansion-side chamber R1 and the compression-side chamber R2 become approximately equal. When the shock absorber D is contracting, the piston rod 2 enters the cylinder 1, and the hydraulic oil in the cylinder 1 becomes excessive by the volume of the piston rod 2 entering the cylinder 1, so the excess hydraulic oil passes through the compression-side damping valve 11d and is discharged to the reservoir R. In this way, when the hydraulic oil is discharged from the cylinder 1 to the reservoir R, the pressures in the expansion-side chamber R1 and the compression-side chamber R2 increase approximately equally because the compression-side damping valve 11d provides resistance to the flow of hydraulic oil. Here, the pressure-receiving area receiving the pressure from the compression-side chamber R2 of the piston 3 is larger than the pressure-receiving area receiving the pressure from the extension-side chamber R1 of the piston 3 by the cross-sectional area of ​​the piston rod 2. Therefore, the force pushing up the piston 3 increases with the increase in pressure in the extension-side chamber R1 and the compression-side chamber R2, and the shock absorber D generates a damping force that hinders the contraction operation.

[0028] In this way, when shock absorber D expands or contracts due to input of vibration, it generates a damping force that impedes expansion or contraction. Furthermore, reservoir R compensates for the volume of piston rod 2 moving in or out of cylinder 1 by exchanging hydraulic oil with cylinder 1 in an amount equal to the volume of piston rod 2 moving in or out of cylinder 1 due to the expansion or contraction of shock absorber D. In the present embodiment, shock absorber D compensates for the volume of piston rod 2 moving in or out of cylinder 1 by exchanging liquid between reservoir R and cylinder 1. However, instead of providing reservoir R, an air chamber filled with gas by a free piston or bladder may be provided in cylinder 1, and the volume of piston rod 2 moving in or out of cylinder 1 may be compensated for by expanding or contracting the volume of the air chamber. Therefore, shock absorber D may be configured as a twin-cylinder shock absorber having reservoir R as in the present embodiment, or as a single-cylinder shock absorber having an air chamber in cylinder 1. Shock absorber D may also be a twin-cylinder shock absorber having an intermediate cylinder to form a passage between cylinder 1 and outer cylinder 7.

[0029] Next, an annular support 4 is attached to the outer periphery of the piston rod 2 that faces the extension-side chamber R1. The support 4 includes a cylindrical portion 4a and a flange-shaped support portion 4b that is continuous with the upper end of the cylindrical portion 4a in FIG. 1, and is attached to the piston rod 2 by spot welding the cylindrical portion 4a to the outer periphery of the piston rod 2, for example.

[0030] The cushion 5 is annular and made of rubber, urethane foam, or the like, and is fitted to the outer periphery of the piston rod 2 facing the extension-side chamber R1. The cushion 5 is located higher than the support 4 of the piston rod 2 in FIG. 1 , rests on the side of the support portion 4b of the support 4 opposite the piston in FIG. 1 , and its movement toward the piston is restricted by the support 4. Thus, the cushion 5 is located on the outer periphery of the piston rod 2 facing the extension-side chamber R1, and its movement toward the piston is restricted by the support 4. Because the cushion 5 is annular, it can be easily attached to the piston rod 2. However, as long as the cushion 5 is located on the outer periphery of the piston rod 2 and its movement toward the piston is restricted by the support 4, it does not necessarily have to be annular and may be attached to the support 4 by welding or the like. As long as the support 4 restricts the movement of the cushion 5 toward the piston, the design of the support 4 can be arbitrarily modified, and structures other than those shown in the drawings may be used.

[0031] The lock piece 6 is provided axially movably on the outer periphery of the piston rod 2, on the upper side in Fig. 1 which is the side opposite the piston of the cushion 5. As shown in Figs. 1 and 2, the lock piece 6 is annular and includes a piece main body 6a that is disposed on the outer periphery of the piston rod 2, and an extension part 6b that extends from the piece main body 6a and comes into sliding contact with the outer periphery of the support part 4b of the support 4. In this embodiment, the lock piece 6 is made of a hard synthetic resin, but the material is not limited to this.

[0032] The piece main body 6a is annular, and is disposed on the outer periphery of the piston rod 2 with the piston rod 2 inserted into its inner periphery, and faces the lock chamber L formed by the case 8c in the axial direction. The outer diameter of the piece main body 6a is set to a diameter that can fit into the inner periphery of the case 8c, and when the piston rod 2 is displaced to near the stroke end on the extension side during the extension operation of the shock absorber D in which the piston rod 2 retreats from the cylinder 1, it can enter the lock chamber L formed by the case 8c.

[0033] Furthermore, the axial length of the piece body 6a is longer than the overall length of the case 8c, and when the piece body 6a reaches the deepest part of the lock chamber L, it can abut against the lower end surface of the small diameter portion 8a of the rod guide 8. The upper end surface of the piece body 6a in Figure 2, which faces the lock chamber, has an uneven surface 6a2 in the circumferential direction, so that even when the piece body 6a abuts against the lower end of the small diameter portion 8a of the rod guide 8, the piece body 6a does not come into surface contact with the small diameter portion 8a, and this prevents the lock piece 6 from sticking to the small diameter portion 8a of the rod guide 8 when the piece body 6a and rod guide 8 abut.

[0034] The inner diameter of the piece body 6a is larger than the outer diameter of the piston rod 2, and an annular throttle passage P is formed between the piece body 6a and the piston rod 2. In addition, a clearance corresponding to the throttle passage P is provided between the piece body 6a and the piston rod 2, so the piece body 6a can move radially relative to the piston rod 2 by the clearance.

[0035] Furthermore, the outer diameter of the piece body 6a is set to a diameter that can fit into the inner periphery of the case 8c, and the inner diameter of the piece body 6a is set to be larger than the outer diameter of the piston rod 2, and radial movement of the piece body 6a relative to the piston rod 2 is allowed by the clearance between the inner periphery of the piece body 6a and the piston rod 2, so that even if the piece body 6a is eccentric with respect to the case 8c, the piece body 6a can enter the lock chamber L. Note that, if the piece body 6a can be inserted into the case 8c even when it is in sliding contact with the outer periphery of the piston rod 2, the throttle passage P may be formed by a groove provided in the outer periphery of the piece body 6a along the axial direction or a hole that opens from the upper end of the piece body 6a and communicates with the lower end, or the throttle passage P may be formed by a groove provided in the inner periphery of the case 8c along the axial direction or a gap between the case 8c and the piece body 6a formed by making the inner diameter of the case 8c larger than the outer diameter of the piece body 6a.

[0036] In this embodiment, the extension 6b has a plurality of arms 6b1 that extend downward from the portion that spans the outer periphery of the lower end of the piece body 6a in Fig. 2. The lock piece 6 also has claws 6c that protrude inward from the lower end in Fig. 2, which are the tips of the arms 6b1 that make up the extension 6b.

[0037] Five arms 6b1 are provided on the piece body 6a at equal intervals in the circumferential direction of the piece body 6a. The arms 6b1 extend downward from the piece body 6a in parallel to one another.

[0038] Next, the diameter of the inscribed circle inscribed on the inner surface of each arm 6b1 facing the piston rod side is equal to or slightly smaller than the outer diameter of the support portion 4b of the support 4, and larger than the outer diameter of the cushion 5. Therefore, when the lock piece 6 is assembled to the outer periphery of the piston rod 2, the inner surface of each arm 6b1 of the lock piece 6 can be brought into sliding contact with the outer periphery of the support portion 4b of the support 4. Furthermore, the length from the upper end of the piece main body 6a in FIG. 1 to the upper end of the arm 6b1 in FIG. 1 is longer than the length from the lower end in FIG. 1, which is the tip of the case 8c, to the small diameter portion 8a, which is the bottom of the lock chamber L, and the piece main body 6a can enter the lock chamber L until it abuts against the small diameter portion 8a of the rod guide 8. In the shock absorber D of this embodiment, even when the piece main body 6a abuts against the small diameter portion 8a, the case 8c does not interfere with the arm 6b1, so no load is applied to the arm 6b1 from the rod guide 8. However, it is also possible to abut the base of the arm 6b1 against the case 8c to avoid contact between the piece main body 6a and the small diameter portion 8a.

[0039] The claws 6c are provided at the lower end of the arm 6b1 in Figure 2, which is the tip of the arm 6b1, and protrude radially toward the inner peripheral surface of the arm 6b1. The diameter of a circle inscribed with the tips of the claws 6c is smaller than the outer diameter of the support portion 4b of the support 4. Furthermore, the claws 6c have tapered surfaces 6c1 on the tip side of the lower end, and are shaped to taper toward the tip. Therefore, when the lock piece 6 is inserted into the piston rod 2 from the upper end side in Figure 1 during assembly, the outer peripheral edge of the upper end of the support portion 4b of the support 4 in Figure 1 eventually abuts against the tapered surfaces 6c1 of each claw 6c. As the piston rod 2 continues to be inserted into the lock piece 6, the support portion 4b of the support 4 is pressed against the tapered surfaces 6c1, bending the arms 6b1 and pushing the claws 6c radially away. When the support portion 4b passes over the claw 6c, the bent arm 6b1 returns to its original position due to a restoring force and abuts against the outer peripheral surface of the support portion 4b, and the tip of the claw 6c faces the underside of the support portion 4b, which is the piston side surface of the support portion 4b in FIG. 1. When the lock piece 6 is disposed on the outer periphery of the piston rod 2 and assembled to the support portion 4b of the support 4 in this manner, the inner surface of the arm 6b1 of the extension portion 6b slides against the outer peripheral surface of the support portion 4b, and the claw 6c faces the piston side surface of the support portion 4b. Therefore, the lock piece 6 can move in a direction away from the support 4 until the claw 6c abuts against the piston side surface of the support portion 4b without falling off the support 4. In this way, the claw 6c forms a restricting portion that prevents the lock piece 6 from coming off the support 4, and while allowing the lock piece 6 to move axially relative to the support 4, it prevents the lock piece 6 from coming off the support 4 when it reaches its movement limit in the direction of coming off relative to the support 4.

[0040] 1, the length X from the lower end of the piece main body 6a in FIG. 3 to the claw 6c on the arm 6b1 is longer than the length Y from the lower end of the support portion 4b of the support 4 in FIG. 1 to the upper end of the cushion 5, and when the claw 6c is in contact with the support portion 4b, a gap is created between the lower end of the piece main body 6a and the upper end of the cushion 5 placed on the support portion 4b. Therefore, ignoring compressive deformation of the cushion 5, the lock piece 6 is able to reciprocate in the axial direction relative to the piston rod 2 within the range from when the claw 6c is in contact with the support portion 4b to when the piece main body 6a is in contact with the cushion 5.

[0041] Furthermore, a plurality of grooves 6a1 are provided from the inner periphery to the outer periphery at the piston side end of the piece body 6a, which is the lower end in Figure 2. The grooves 6a1 are provided at positions that avoid the arms 6b1, so that even when the cushion 5 abuts against the piece body 6a, the throttle passage P continues to communicate with the outside of the lock piece 6 via the grooves 6a1.

[0042] The shock absorber D is configured as described above, and its operation will be described below. As described above, when the shock absorber D performs an expansion / contraction operation, a damping force is generated, but during an expansion operation in which the piston 3 moves upward relative to the cylinder 1 in FIG. 1, the piston rod 2 moves upward relative to the cylinder 1, and as a result, the cushion 5 placed on the support 4 and the lock piece 6 attached to the outer periphery of the support part 4b of the support 4 also move upward and approach the case 8c in the rod guide 8.

[0043] 3(b), when the piece body 6a of the lock piece 6 begins to be inserted into the lock chamber L in the case 8c, the piece body 6a fits into the case 8c, connecting the lock chamber L and the expansion-side chamber R1 only through the throttle passage P. Note that even if the piece body 6a is eccentric with respect to the case 8c when the outer periphery of the upper end of the piece body 6a in FIG. 1 abuts against the tapered surface 8c1 provided on the inner periphery of the lower end of the case 8c, the piece body 6a can easily enter the case 8c while moving radially along the tapered surface 8c1. In this way, because the annular throttle passage P is provided between the piece body 6a and the piston rod 2, the lock piece 6 can move radially with respect to the piston rod 2, and therefore can easily enter the lock chamber L even if the piece body 6a is eccentric with respect to the case 8c.

[0044] When the piston rod 2 moves further upward relative to the cylinder 1 while the piece body 6a is inserted into the lock chamber L, the lock chamber L is compressed by the lock piece 6, and the liquid in the lock chamber L passes through the throttle passage P between the piece body 6a and the piston rod 2, between the piece body 6a and the cushion 5, and between the arms 6b1, 6b1, and moves to the extension-side chamber R1. The throttle passage P provides resistance to this liquid flow, so the pressure in the lock chamber L increases, pushing down the lock piece 6 and bringing the piece body 6a into contact with the cushion 5. Even when the cushion 5 contacts the piece body 6a, the groove 6a1 is not closed, and therefore communication between the lock chamber L and the extension-side chamber R1 is not interrupted.

[0045] Then, as the pressure in the lock chamber L increases, the piece body 6a and the cushion 5 come into contact, and the load caused by the pressure increase in the lock chamber L acts on the support 4 and the piston rod 2, preventing the piston rod 2 from moving upward relative to the cylinder 1. Therefore, in the shock absorber D configured in this manner, when the lock piece 6 enters the lock chamber L and the shock absorber D attempts to extend further, a hydraulic locking function is exerted that prevents the extension of the shock absorber D due to the load caused by the pressure increase in the lock chamber L described above.

[0046] Furthermore, as the piston rod 2 continues to move upward relative to the cylinder 1 after the piece body 6a is inserted into the lock chamber L, eventually, as shown in FIG. 3(c), the upper end of the piece body 6a abuts against the lower end of the small-diameter portion 8a of the rod guide 8, which is the bottom of the lock chamber L, restricting the upward movement of the lock piece 6 relative to the case 8c and fully compressing the lock chamber L. If the shock absorber D attempts to extend further, the upward movement of the lock piece 6 is restricted, and the cushion 5 compresses, exerting a resilient force that prevents the upward movement of the piston rod 2 relative to the cylinder 1. In this way, when the lock piece 6 fully compresses the lock chamber L, the shock absorber D generates a load that prevents extension due to the resilient force caused by the compression of the cushion 5. The resilient force caused by the compression of the cushion 5 is greater than the load caused by the hydraulic locking function, and the shock absorber D generates a large force when in the fully extended state, preventing extension.

[0047] After the lock piece 6 has entered the lock chamber L, when the shock absorber D contracts and the piston rod 2 moves downward relative to the cylinder 1, the piston rod 2 also moves downward relative to the lock piece 6, but when the claw 6c of the lock piece 6 abuts against the piston-side end of the support portion 4b of the support 4, the lock piece 6 also moves downward together with the piston rod 2 and retracts from the lock chamber L. Even when the lock piece 6 has entered the lock chamber L, the lock chamber L is connected to the extension-side chamber R1 via the throttle passage P, so that liquid is supplied from the extension-side chamber R1 to the lock chamber L when the lock piece 6 retracts. Therefore, excessive resistance is not applied to the downward movement of the piston rod 2 when the lock piece 6 is removed from the lock chamber L.

[0048] In this way, when the shock absorber D undergoes an extension operation and extends to near the stroke end, it first increases the pressure in the lock chamber L, preventing the extension operation by the load caused by the hydraulic lock function, and also prevents the extension operation by the elastic force of the cushion 5, which is in its fully extended state.

[0049] As described above, the shock absorber D of this embodiment includes the cylinder 1, the piston rod 2 inserted into the cylinder 1 so as to be movably axially, the piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be movably arranged, dividing the interior of the cylinder 1 into an extension-side chamber R1 and a compression-side chamber R2 filled with liquid, the case 8c which is immovable in the axial direction relative to the cylinder 1 and forms a lock chamber L axially opposing the piston 3, the support 4 attached to the outer periphery of the piston rod 2 facing the extension-side chamber R1, the cushion 5 which is arranged on the outer periphery of the piston rod 2 facing the extension-side chamber R1 and whose movement towards the piston side is restricted by the support 4, and the lock piece 6 which is provided on the outer periphery of the piston rod 2 on the opposite piston side of the cushion 5 so as to be movably axially and which can enter the lock chamber L.

[0050] In the shock absorber D configured in this manner, a case 8c that is immovable in the axial direction is provided relative to the cylinder 1, and a lock piece 6 is provided on the piston rod 2. This allows the lock piece 6 to enter the lock chamber L near the stroke end during extension, thereby exerting a hydraulic locking function and suppressing the extension of the shock absorber D. As extension progresses and the shock absorber D reaches its maximum extension, a large load is generated by the compression of the cushion 5, which stops the extension of the shock absorber D and reduces the impact at the time of maximum extension.

[0051] Therefore, when driving on good roads, shock absorber D exhibits a hydraulic locking function that does not cause elastic rebound near the stroke end even when the damping force is low, improving ride comfort when the vehicle body pitches during braking, and when fully extended, shock absorber D can exert a large force with cushion 5 to suppress rebound, making it ideal for use in recent light cars and compact cars.

[0052] Furthermore, with the shock absorber D configured as described above, unlike a typical shock absorber that includes the support 4 and cushion 5 and absorbs impact at full extension only by compressing the cushion 5, the addition of the case 8c and lock piece 6 enables a hydraulic locking function during extension, eliminating the need to provide a tapered expanded diameter portion at the end of the cylinder or to add many parts such as elastic rings, segments, and springs as in conventional shock absorbers. Therefore, with the shock absorber D of this embodiment, the processing required for expanding the diameter of the cylinder and the installation of many parts around the outer periphery of the piston rod 2, which were necessary in conventional shock absorbers, are no longer necessary, thereby reducing processing costs and the number of parts. As described above, the shock absorber D of this embodiment can provide a hydraulic locking function and is easy to manufacture, thereby reducing manufacturing costs.

[0053] Furthermore, the lock piece 6 in the shock absorber D of this embodiment is annular and is disposed on the outer periphery of the piston rod 2, forming an annular throttle passage P between it and the piston rod 2, and is equipped with a piece main body 6a that can enter the lock chamber L. According to the shock absorber D configured in this manner, when the piece main body 6a enters the lock chamber L, a load of a magnitude corresponding to the resistance of the throttle passage P can be generated, and the load can be adjusted by setting the flow path area of ​​the throttle passage P. In addition, the piece main body 6a can easily move in the vertical direction relative to the cushion 5 due to the clearance between the inner periphery of the piece main body 6a and the piston rod 2, so that the cushion 5 can be smoothly compressed after the lock piece 6 enters the lock chamber L.

[0054] Furthermore, the lock piece 6 in the shock absorber D of this embodiment has a piece main body 6a that can enter the lock chamber L, and an extension 6b that extends from the piece main body 6a toward the support, and the extension 6b is in sliding contact with the support 4. With the shock absorber D configured in this manner, the lock piece 6 can be centered by the support 4 and positioned radially relative to the case 8c and cushion 5, making it easy to insert the lock piece 6 into the case 8c. Note that, although the extension 6b is formed as a plurality of arms 6b1 in this embodiment, it may instead be formed as a cylinder or some other shape.

[0055] Furthermore, in the shock absorber D of this embodiment, the piece body 6a of the lock piece 6 has a circumferentially uneven surface 6a2 on the surface facing the case 8c. According to the shock absorber D configured in this manner, the upper surface of the piece body 6a facing the case in FIG. 1 has the uneven surface 6a2, so even if the piece body 6a penetrates deep into the lock chamber L and abuts against the underside of the small diameter portion 8a of the rod guide 8, which forms the bottom of the lock chamber L, the entire upper surface of the piece body 6a does not abut against the small diameter portion 8a, preventing the piece body 6a from sticking to the bottom of the lock chamber L. Therefore, when the shock absorber D is fully extended and the piece body 6a abuts against the bottom of the lock chamber L and then begins to retract, the piece body 6a can quickly retract from within the lock chamber L, preventing resistance to the retraction of the shock absorber D.

[0056] Furthermore, in the shock absorber D of this embodiment, the lock piece 6 includes a piece main body 6a that can enter the lock chamber L and an extension portion 6b that extends from the piece main body 6a toward the support side, and the extension portion 6b includes a claw (restriction portion) 6c that prevents the lock piece 6 from coming out of the support 4. According to the shock absorber D configured in this manner, after the lock piece 6 enters the lock chamber L during extension and performs the hydraulic locking function, when the extension / contraction direction switches and the shock absorber D performs the contraction operation, the claw (restriction portion) 6c of the lock piece 6 gets caught on the side surface of the piston of the support 4, and the lock piece 6 moves downward in Figure 1 relative to the case 8c together with the piston rod 2, so that the lock piece 6 does not remain in the lock chamber L and can stably perform the hydraulic locking function even when extension and contraction are repeated. The restricting portion only needs to allow the lock piece 6 to move a certain distance in the axial direction relative to the support 4, and prevent the lock piece 6 from coming out of the support 4 so that the lock piece 6, which has entered the lock chamber L when the piston rod 2 moves downward in Figure 1, can follow the movement of the piston rod 2 toward the contraction side and not be left behind in the lock chamber L. Therefore, other than the claw 6c provided on the extension portion 6b, the restricting portion may be formed by a groove provided on the outer periphery of the piston rod 2 along the axial direction and a pin provided on the extension portion 6b and inserted into the groove, or by an elongated hole provided on the extension portion 6b along the axial direction and a pin provided on the support 4 or the piston rod 2 and inserted into the elongated hole.

[0057] Furthermore, in the shock absorber D of this embodiment, when the lock piece 6 is farthest from the cushion 5 in the axial direction, a gap is formed between the lock piece 6 and the cushion 5, and the extension portion 6b is composed of multiple arms 6b1 extending at intervals in the circumferential direction from the piece main body 6a. In the shock absorber D configured in this manner, after the lock piece 6 enters the lock chamber L during extension and performs the hydraulic locking function, when the direction of extension and contraction switches and the lock piece 6 performs contraction and leaves the lock chamber L, the lock piece 6 and the cushion 5 separate, and the throttle passage P, which is on the inner periphery of the piece main body 6a and communicates with the lock chamber L, communicates with the extension-side chamber R1 via the gap between the lock piece 6 and the cushion 5 and the gap between the arms 6b1, 6b1. The extension portion 6b is made up of multiple arms 6b1, and a large gap can be formed between the arms 6b1, 6b1. In addition, the lock piece 6 and the cushion 5 are separated to form a gap. Therefore, when the lock piece 6 retreats from the lock chamber L, the resistance provided by the gap to the flow of liquid moving from the expansion-side chamber R1 to the lock chamber L can be made extremely small. As a result, no extra resistance is provided other than the resistance of the throttle passage P, and the lock piece 6 can be quickly retreated from within the lock chamber L, and no resistance is provided to the contraction operation of the shock absorber D.

[0058] Furthermore, since the extension portion 6b is composed of multiple arms 6b1, as described above, when the lock piece 6 exits the lock chamber L, a gap can be formed between the arms 6b1, 6b1 that allows the passage of liquid from the extension-side chamber R1 to the lock chamber L without much resistance.

[0059] As described above, when the extension portion 6b has a plurality of arms 6b1, the various advantages described above can be enjoyed, but when the extension portion 6b is cylindrical and in sliding contact with the outer periphery of the support portion 4b of the support 4, it is sufficient if the extension portion 6b has an opening such as a hole or notch that communicates with the expansion-side chamber R1 a gap formed between the lock piece 6 and the cushion 5 when the lock piece 6 is farthest axially from the cushion 5. If an opening is provided when the extension portion 6b is cylindrical in this way, when the shock absorber D switches its extension / contraction direction to perform a contraction operation and the lock piece 6 retreats from the lock chamber L, the lock piece 6 and the cushion 5 separate, and the throttle passage P, which is on the inner periphery of the piece main body 6a and communicates with the lock chamber L, comes into communication with the expansion-side chamber R1 via the gap between the lock piece 6 and the cushion 5 and the opening provided in the extension portion 6b, and when the lock piece 6 retreats from the lock chamber L, the lock piece 6 can be quickly retreated from within the lock chamber L without providing resistance to the contraction operation of the shock absorber D. When the extension 6b is cylindrical in this way, the claws 6c may be provided annularly at the lower end of the cylinder or may be provided intermittently in the circumferential direction.

[0060] Furthermore, in the shock absorber D of this embodiment, the case 8c that forms the lock chamber L is provided on the rod guide 8, so the number of parts can be reduced compared to when another case is provided independently, and manufacturing costs can be further reduced, but the case may be a separate part from the rod guide 8, or may be fixed to the cylinder 1 or outer tube 7 independently of the rod guide 8, or may be attached to the rod guide 8 as a separate part.

[0061] The lock piece 6 may be integrated with the cushion 5 by adhesion, fusion, or the like, in which case the cushion 5 may be attached to the support 4 by gripping the outer periphery of the support 4. The lock chamber L is formed inside the case 8c of the rod guide 8, but an annular case may be provided on the inner periphery of the rod guide 8 to form the lock chamber L between the case and the cylinder 1. When the lock chamber L is provided on the outer periphery of the rod guide 8 in this way, it is sufficient that the lock piece 6 has an annular piece main body facing the lock chamber L so that it can enter the lock chamber L.

[0062] Although the preferred embodiment of the present invention has been described in detail, modifications, variations and changes can be made thereto without departing from the scope of the appended claims.

[0063] DESCRIPTION OF SYMBOLS 1: Cylinder, 2: Piston rod, 3: Piston, 4: Support, 5: Cushion, 6: Lock piece, 6a: Piece body, 6a2: Concave and recessed surface, 6b: Extension portion, 6b1: Arm, 6c: Claw (restriction portion), 8c: Case, D: Shock absorber, P: Return passage, R: Reservoir, R1: Extension side chamber, R2: Compression side chamber

Claims

1. A shock absorber comprising: a cylinder; a piston rod inserted into the cylinder so as to be axially movably; a piston connected to the piston rod and movably inserted into the cylinder, dividing the inside of the cylinder into an extension-side chamber filled with liquid and a compression-side chamber; a case forming a lock chamber that is immovable in the axial direction relative to the cylinder and opens toward the piston; a support attached to the outer periphery of the piston rod facing the extension-side chamber; a cushion arranged on the outer periphery of the piston rod facing the extension-side chamber, the movement of which toward the piston side being restricted by the support; and a lock piece arranged on the outer periphery of the piston rod on the opposite piston side of the cushion, axially movably provided and capable of entering the lock chamber.

2. A shock absorber as claimed in claim 1, wherein the lock piece is annular and arranged on the outer periphery of the piston rod to form an annular throttle passage between the piston rod and the lock piece, and has a piece body which can enter the lock chamber.

3. A shock absorber as claimed in claim 1, wherein the lock piece has a piece body capable of entering the lock chamber and an extension portion extending from the piece body towards the support, the extension portion being in sliding contact with the support.

4. A shock absorber as claimed in claim 1, wherein said lock piece has a piece body capable of entering said lock chamber and having an uneven surface on the surface facing said case.

5. A shock absorber as claimed in claim 1, wherein the lock piece has a piece body capable of entering the lock chamber and an extension portion extending from the piece body towards the support, the extension portion having a restricting portion for preventing the piece from coming off the support.

6. A shock absorber as claimed in claim 2, wherein the lock piece has an extension extending from the piece body towards the support side, and when the lock piece moves away from the cushion in the axial direction, a gap communicating with the throttle passage is formed between the lock piece and the cushion, and the extension has an opening communicating the gap with the expansion side chamber.

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