WO2025047278A1 - Shock absorber - Google Patents

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

Shock absorber

The present invention relates to a shock absorber.

Traditionally, 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 inside of the cylinder into an extension side chamber and a compression side chamber.

In conventional shock absorbers configured in this way, 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 comes into contact with the rod guide that supports the piston rod, compressing the rebound spring, and the elastic force of the rebound spring cushions the impact when the piston rod is fully extended.

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

In response to such demands, for example, as disclosed in JP2016-534290A, a shock absorber has been developed that provides a tapered enlarged diameter section at the end of the cylinder, and provides a segment that holds a C-shaped elastic ring on the outer periphery of the piston rod, as well as a spring that urges the segment towards the piston. When the segment reaches the enlarged diameter section and the shock absorber extends further, the tapered surface causes the elastic ring to gradually shrink in diameter, allowing the upper space partitioned by the elastic ring and the segment to function as an oil lock chamber.

In a shock absorber configured in this way, the segments do not reach the expanded diameter section when the vehicle is traveling on good roads, and a low damping force is exerted when the vehicle is traveling on good roads, without impairing the ride comfort of the vehicle. However, when fully extended, a hydraulic oil lock function is exerted, generating a high damping force to cushion the impact.

JP2016-534290A

　Conventional shock absorbers are able to fully meet the above-mentioned demand for reducing the impact at the extension stroke end, but they require processing to expand the cylinder diameter, and in addition, many parts must be installed on the outer periphery of the piston rod to achieve the oil lock function, which increases the processing costs and number of parts, resulting in problems with higher manufacturing costs and difficulty.

The present invention aims to provide a shock absorber that can provide a hydraulic lock function while also being easy to manufacture and reducing manufacturing costs.

In order to achieve the above object, the shock absorber of the present invention comprises a cylinder, a piston rod inserted into the cylinder so as to be movable in the axial direction, a piston connected to the piston rod and inserted into the cylinder so as to be movable, dividing 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 towards 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 towards the piston side is restricted by the support, and a lock piece which is arranged on the outer periphery of the piston rod on the opposite side of the cushion to the piston and which is axially movable and can enter the lock chamber.

In a shock absorber configured in this manner, a case that is immovable in the axial direction is provided relative to the cylinder, and a lock piece is provided on the piston rod. This allows the lock piece to enter the lock chamber near the stroke end during extension, exerting a hydraulic locking function to suppress the extension of the shock absorber, and when extension progresses to the maximum extension, a large load is generated by the compression of the cushion, stopping the extension of the shock absorber and mitigating the impact at the maximum extension. Furthermore, with a shock absorber configured in this manner, compared to a general shock absorber, the addition of a case and lock piece allows the hydraulic locking function to be exerted during extension, so there is no need to provide a tapered enlarged portion at the end of the cylinder or add many parts such as elastic rings, segments, or springs, as in conventional shock absorbers.

FIG. 1 is a cross-sectional view of a shock absorber according to one embodiment. Fig. 2(a) is a plan view of the lock piece, Fig. 2(b) is a side view of the lock piece, and 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 separated from the lock chamber L. Fig. 3(b) is a partially enlarged cross-sectional view of the shock absorber when the lock piece starts 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 separated from the lock chamber.

The shock absorber of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the shock absorber D in 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 immovable in the axial direction 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 arranged on the outer periphery of the piston rod 2, and a lock piece 6 that is provided on the outer periphery of the piston rod 2 and can enter the lock chamber L. The shock absorber D is interposed between the vehicle body and the wheels of a vehicle (not shown) and generates a damping force during expansion and contraction to suppress vibration of the vehicle body.

The various components 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 piston 3 are inserted inside 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 in addition to hydraulic oil, water, an aqueous solution, etc. may also be filled as the liquid.

The cylinder 1 is housed in a cylindrical outer tube 7 that is arranged on the outer periphery, and a reservoir R is formed in the annular gap between the cylinder 1 and the outer tube 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 tube 7, but the reservoir R may also be formed by a tank provided separately from the cylinder 1.

The piston rod 2 is inserted into the inner circumference of an annular rod guide 8 that fits into the upper end of the cylinder 1 in FIG. 1, with the tip end inserted into the cylinder 1, and the base end (the upper end in FIG. 1) protruding outward from the cylinder 1.

The rod guide 8 is annular and includes a small diameter section 8a that fits into the inner periphery of the upper end of the cylinder 1, a large diameter section 8b that is connected to the upper end of the small diameter section 8a in FIG. 1 and fits into the inner periphery of the outer tube 7, a cylindrical case 8c that extends downward in FIG. 1 from the outer periphery of the lower end of the small diameter section 8a, a seal housing section 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 housing section 8d and leads to the lower end of the large diameter section 8b. A cylindrical bush 9 that slides against the outer periphery of the piston rod 2 is attached to the inner periphery of the rod guide 8.

The rod guide 8 has its small diameter portion 8a fitted into the inner periphery of the upper end of the cylinder 1 and its outer periphery of the large diameter portion 8b fitted into the inner periphery of the upper end of the outer tube 7, thereby closing off the upper ends of the cylinder 1 and the outer tube 7. The case 8c is cylindrical and hangs down from the outer periphery of the lower end of the small diameter portion 8a, with an expanded inner diameter on the lower side, and opens into the extension side chamber R1 to form a lock chamber L facing the extension 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 as it approaches the bottom in FIG. 1.

The rod guide 8 closes the upper ends of the cylinder 1 and the outer tube 7 in FIG. 1, and supports the piston rod 2 inserted into the bush 9 to guide the axial movement of the piston rod 2.

Also, above the rod guide 8 in FIG. 1, an annular seal member 10 that seals between the piston rod 2 and the outer tube 7 is stacked. The seal member 10 includes a core metal 10a formed of an annular plate, an annular inner circumference seal 10b welded to the inner circumference side of the core metal 10a and in sliding contact with the outer circumference of the piston rod 2, an annular outer circumference seal 10c welded to the outer circumference of the lower end of the core metal 10a in FIG. 1 and in close contact with the inner circumference of the outer tube 7, and an annular check seal 10d welded to the lower end of the core metal 10a and housed in the seal housing portion 8d of the rod guide 8, and seated and released between the inner circumference of the rod guide 8 and the pressure relief passage 8e.

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 accommodation portion 8d, and the inner seal 10b slides against the outer periphery of the piston rod 2 while the outer periphery of the outer seal 10c adheres closely to the inner periphery of the outer tube 7. In this way, the seal member 10 seals between the piston rod 2 and the outer tube 7, preventing liquid and gas in the shock absorber D from leaking out of the shock absorber D.

In addition, when the liquid scraped off by the inner seal 10b after passing between the piston rod 2 and the bush 9 from the extension side chamber R1 accumulates in the seal accommodating portion 8d and the pressure in the seal accommodating portion 8d increases, the check seal 10d lifts off the rod guide 8 and returns the liquid in 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 the inner seal 10b does not excessively tighten the piston rod 2 due to the pressure in the seal accommodating portion 8d, preventing the piston rod 2 from moving smoothly.

The piston 3 is equipped with an extension-side passage 3a and a compression-side passage 3b that connect 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 that only allows hydraulic oil to flow 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 that only allows hydraulic oil to flow from the compression-side chamber R2 to the extension-side chamber R1.

Furthermore, a valve case 11 that is placed on the bottom of the outer tube 7 is fitted to the lower end of the cylinder 1 in FIG. 1. The valve case 11 is provided with a flange 11a that fits into the inner circumference of the outer tube 7 on the outer periphery of the lower end in FIG. 1 and abuts against the lower end of the cylinder 1, and 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 clamped between the bottom of the outer tube 7 and the crimped portion 7a formed by crimping the upper end of the outer tube 7 from the outer periphery side.

The valve case 11 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 hydraulic oil to flow 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 hydraulic oil to flow from the reservoir R to the compression side chamber R2.

Therefore, when shock absorber D is in an extension operation in which piston 3 moves upward in FIG. 1 relative to cylinder 1, hydraulic oil in extension side chamber R1, which is reduced by the movement of piston 3, moves through extension side damping valve 3c to the expanding compression side chamber R2, and the extension side damping valve 3c provides resistance to the flow of hydraulic oil, causing the pressure in extension side chamber R1 to rise, generating a damping force that impedes the extension operation. Also, when shock absorber D is in an extension operation, piston rod 2 retreats from within cylinder 1, and hydraulic oil equivalent to the volume of the piston rod 2 retreating from within cylinder 1 is supplied from reservoir R to cylinder 1 via extension side check valve 11e.

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

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

Next, an annular support 4 is attached to the outer periphery of the piston rod 2 facing the extension side chamber R1. The support 4 has a cylindrical portion 4a and a flange-shaped support portion 4b that is connected to 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.

The cushion 5 is annular and made of rubber or urethane foam, etc., and is fitted to the outer periphery of the piston rod 2 facing the extension side chamber R1. The cushion 5 is disposed above the support 4 of the piston rod 2 in FIG. 1, and is placed on the side of the support 4 opposite the piston in FIG. 1, and the support 4 restricts the movement of the cushion 5 toward the piston side. In this way, the cushion 5 is disposed on the outer periphery of the piston rod 2 facing the extension side chamber R1, and the support 4 restricts the movement of the cushion 5 toward the piston side. Since the cushion 5 is annular, it is easy to attach it to the piston rod 2, but it does not necessarily have to be annular, and it may be attached to the support 4 by welding or the like, as long as it is disposed on the outer periphery of the piston rod 2 and the support 4 restricts the movement of the cushion 5 toward the piston side. Furthermore, as long as the support 4 can restrict the movement of the cushion 5 toward the piston side, the structure of the support 4 can be arbitrarily changed in design, and may have a structure other than that shown in the figure.

The lock piece 6 is provided on the outer periphery of the piston rod 2, on the opposite side of the cushion 5 from the piston, at the upper side in FIG. 1, so as to be movable in the axial direction. As shown in FIGS. 1 and 2, the lock piece 6 is annular and includes a piece body 6a that is disposed on the outer periphery of the piston rod 2, and an extension part 6b that extends from the piece 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.

The piece body 6a is annular, 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 body 6a is such that it can fit into the inner periphery of the case 8c, and when the piston rod 2 displaces to the vicinity of the stroke end on the extension side during the extension operation of the shock absorber D in which the piston rod 2 retreats from inside the cylinder 1, it can enter the lock chamber L formed by the case 8c.

The axial length of the piece body 6a is longer than the overall length of the case 8c, and when the piece body 6a penetrates to 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 on the lock chamber side in FIG. 2 is an uneven surface 6a2 in the circumferential direction, so that even if 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 it is possible to prevent 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 against each other.

The inner diameter of the piece body 6a is larger than the outer diameter of the piston rod 2, and a ring-shaped throttle passage P is formed between the piece body 6a and the piston rod 2. In addition, because a clearance is provided between the piece body 6a and the piston rod 2, which is the amount of the throttle passage P, the piece body 6a can move radially relative to the piston rod 2 by the amount of the clearance.

The outer diameter of the piece body 6a is a diameter that can fit into the inner circumference of the case 8c, and the inner diameter of the piece body 6a is larger than the outer diameter of the piston rod 2, and the piece body 6a is allowed to move radially relative to the piston rod 2 by the amount of the clearance between the inner circumference of the piece body 6a and the piston rod 2, so that the piece body 6a can enter the lock chamber L even if it is eccentric with respect to the case 8c. If the piece body 6a can be inserted into the case 8c even when it is in sliding contact with the outer circumference of the piston rod 2, the throttle passage P may be formed by a groove provided along the axial direction on the outer circumference of the piece body 6a 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 along the axial direction on the inner circumference of the case 8c 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.

In this embodiment, the extension 6b has multiple arms 6b1 that extend downward from the portion that spans from the outer periphery to 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 is the tip of each arm 6b1 that constitutes the extension 6b.

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 each other.

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 is 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 lock piece 6 can bring the inner surface of each arm 6b1 into sliding contact with the outer periphery of the support portion 4b of the support 4. Also, 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 if the piece body 6a abuts against the small diameter portion 8a, the case 8c does not interfere with the arm 6b1, so the load from the rod guide 8 does not act on the arm 6b1, but it is also possible to abut the base of the arm 6b1 against the case 8c to avoid contact between the piece body 6a and the small diameter portion 8a.

The claws 6c are provided at the lower end in FIG. 2, which is the tip of the arm 6b1, and protrude radially toward the inner peripheral surface of the arm 6b1, and the diameter of a circle inscribed with the tips of each claw 6c is smaller than the outer diameter of the support part 4b of the support 4. The claws 6c also have a tapered surface 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 FIG. 1 during assembly of the lock piece 6, the outer periphery of the upper end of the support part 4b of the support 4 in FIG. 1 eventually comes into contact with the tapered surface 6c1 of each claw 6c, and when the piston rod 2 continues to be inserted into the lock piece 6, the support part 4b of the support 4 is pressed against the tapered surface 6c1, so that the arm 6b1 is bent and the claws 6c are pushed aside radially. Then, when the support portion 4b passes over the claw 6c, the bent arm 6b1 returns to its original position by the restoring force and abuts against the outer peripheral surface of the support portion 4b, and the tip of the claw 6c faces the lower surface in FIG. 1, which is the piston side of the support portion 4b. When the lock piece 6 is placed on the outer periphery of the piston rod 2 and assembled to the support portion 4b of the support 4 in this way, the inner surface of the arm 6b1 in the extension portion 6b slides against the outer peripheral surface of the support portion 4b, and the claw 6c faces the piston side of the support portion 4b, so that the lock piece 6 can move in a direction away from the support 4 until the claw 6c abuts against the piston side of the support portion 4b without falling off the support 4. In this way, the claw 6c constitutes a restricting portion that prevents the lock piece 6 from coming off the support 4, and while allowing the lock piece 6 to move in the axial direction relative to the support 4, it prevents the lock piece 6 from coming off the support 4 and falling off when the lock piece 6 reaches the movement limit in the direction of coming off the support 4.

Also, as shown in Figure 1, the length X from the bottom end of the piece body 6a in Figure 3 to the claw 6c on the arm 6b1 is longer than the length Y from the bottom end of the support part 4b of the support 4 in Figure 1 to the top end of the cushion 5, and when the claw 6c is in contact with the support part 4b, a gap is created between the bottom end of the piece body 6a and the top end of the cushion 5 placed on the support part 4b. Therefore, without considering the compressive deformation of the cushion 5, the lock piece 6 is able to reciprocate axially relative to the piston rod 2 in the range from when the claw 6c is in contact with the support part 4b to when the piece body 6a is in contact with the cushion 5.

Furthermore, the piston side end of the piece body 6a, which is the lower end in FIG. 2, is provided with multiple grooves 6a1 from the inner circumference to the outer circumference. The grooves 6a1 are provided at a position that avoids the arm 6b1, so that even if the cushion 5 abuts against the piece body 6a, the throttle passage P is able to communicate with the outside of the lock piece 6 via the grooves 6a1.

The shock absorber D is constructed as described above, and its operation will be explained below. As mentioned above, when shock absorber D performs an expansion/contraction operation, it generates a damping force. During the expansion operation in which the piston 3 moves upward in FIG. 1 relative to the cylinder 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.

As shown in FIG. 3(b), when the piece body 6a of the lock piece 6 starts to be inserted into the lock chamber L in the case 8c, the piece body 6a fits into the case 8c, and the lock chamber L and the expansion side chamber R1 communicate only through the throttle passage P. Even if the piece body 6a is eccentric with respect to the case 8c when the piece body 6a is inserted into 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, the lock piece 6 can move radially with respect to the piston rod 2 because the annular throttle passage P is provided between the piece body 6a and the piston rod 2, so that the piece body 6a can easily enter the lock chamber L even if it is eccentric with respect to the case 8c.

When the piece body 6a is inserted into the lock chamber L and the piston rod 2 moves further upward relative to the cylinder 1, 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 flow of liquid, so the pressure in the lock chamber L rises and pushes down the lock piece 6, bringing the piece body 6a into contact with the cushion 5. Even when the cushion 5 comes into contact with the piece body 6a, the groove 6a1 is not blocked, so communication between the lock chamber L and the extension side chamber R1 is not interrupted.

Then, as the pressure rises in the lock chamber L, the piece body 6a comes into contact with the cushion 5, and the load caused by the pressure rise 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 a shock absorber D configured in this way, when the lock piece 6 enters the lock chamber L and the shock absorber D attempts to extend further, a hydraulic lock function is exerted that prevents the shock absorber D from extending due to the load caused by the pressure rise in the lock chamber L described above.

Furthermore, after the piece body 6a is inserted into the lock chamber L, as the piston rod 2 continues to move upward relative to the cylinder 1, the upper end of the piece body 6a eventually comes into contact with the lower end of the small diameter portion 8a of the rod guide 8, which is the bottom of the lock chamber L, as shown in FIG. 3(c), restricting the upward movement of the lock piece 6 relative to the case 8c and maximally compressing the lock chamber L. Then, when the shock absorber D tries to extend further, the upward movement of the lock piece 6 is restricted, so the cushion 5 is compressed and exerts 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 maximally 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 due to the compression of the cushion 5 is greater than the load due to the hydraulic lock function, and when the shock absorber D reaches its maximum extension state, it generates a large force that prevents the extension operation.

After the lock piece 6 enters 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 exits the lock chamber L. Even if the lock piece 6 enters 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 exits. Therefore, there is no excessive resistance to the downward movement of the piston rod 2 when the lock piece 6 comes out of the lock chamber L.

In this way, when the shock absorber D extends near the stroke end, it first prevents the extension operation by increasing the pressure in the lock chamber L and using the load from 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.

As described above, the shock absorber D of this embodiment includes a cylinder 1, a piston rod 2 inserted into the cylinder 1 so as to be axially movable, a piston 3 connected to the piston rod 2 and inserted into the cylinder 1 so as to be axially movable, dividing the cylinder 1 into an extension side chamber R1 filled with liquid and a compression side chamber R2, a case 8c which is immovable in the axial direction relative to the cylinder 1 and forms a lock chamber L axially opposed to the piston 3, a support 4 attached to the outer periphery of the piston rod 2 facing the extension side chamber R1, a cushion 5 which is disposed 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 a 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 axially movable and which can enter the lock chamber L.

In the shock absorber D configured in this way, a case 8c that is immovable in the axial direction is provided for the cylinder 1, and a lock piece 6 is provided for the piston rod 2. This allows the lock piece 6 to enter the lock chamber L near the stroke end during extension, exerting a hydraulic locking function to suppress the extension of the shock absorber D. When the shock absorber D is fully extended, 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 full extension.

Therefore, when driving on good roads, shock absorber D exerts a hydraulic locking function that does not generate elastic rebound near the stroke end even when the damping force is low, improving ride comfort when the vehicle body pitches during braking, while at the same time exerting a large force through cushion 5 when fully extended to suppress rebound, making it ideal for use in modern light and compact cars.

The shock absorber D configured as described above is different from a typical shock absorber that has a support 4 and a cushion 5 and absorbs the impact at maximum extension only by compressing the cushion 5. By adding the case 8c and the lock piece 6, the shock absorber can exert a hydraulic locking function during extension, and there is no need to provide a tapered enlarged 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, the shock absorber D of this embodiment does not require the processing required for enlarging the cylinder and the installation of many parts on the outer periphery of the piston rod 2, which were necessary in conventional shock absorbers, and therefore the processing costs can be reduced and the number of parts can be reduced. As described above, the shock absorber D of this embodiment can exert a hydraulic locking function and is easy to manufacture, reducing manufacturing costs.

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 to form an annular throttle passage P between the piston rod 2 and the lock chamber L. The shock absorber D thus configured can generate a load according to the resistance of the throttle passage P when the piece body 6a enters the lock chamber L, and the load can be adjusted by setting the flow area of the throttle passage P. In addition, the clearance between the inner periphery of the piece body 6a and the piston rod 2 allows the piece body 6a to easily move vertically relative to the cushion 5, which makes it easier to compress the cushion 5 after the lock piece 6 enters the lock chamber L.

Furthermore, the lock piece 6 in the shock absorber D of this embodiment has a piece body 6a capable of entering the lock chamber L, and an extension 6b extending from the piece body 6a towards the support, with the extension 6b in sliding contact with the support 4. With the shock absorber D configured in this way, 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 a plurality of arms 6b1 in this embodiment, it may instead be cylindrical or have some other shape.

In addition, in the shock absorber D of this embodiment, the piece body 6a of the lock piece 6 has an uneven surface 6a2 along the circumferential direction on the surface facing the case 8c. With the shock absorber D configured in this way, the upper surface of the piece body 6a facing the case in FIG. 1 is the uneven surface 6a2, so even if the piece body 6a penetrates deeply into the lock chamber L and abuts against the lower surface of the small diameter portion 8a of the rod guide 8, which forms the bottom surface of the lock chamber L, the entire upper surface of the piece body 6a does not abut against the small diameter portion 8a, so the piece body 6a is prevented from sticking to the bottom surface of the lock chamber L. Therefore, when the shock absorber D is fully extended and the piece body 6a abuts against the bottom surface of the lock chamber L and then performs a contraction operation, the piece body 6a can quickly retreat from within the lock chamber L, and there is no resistance to the contraction operation of the shock absorber D.

Furthermore, in shock absorber D of this embodiment, lock piece 6 has a piece body 6a capable of entering lock chamber L, and an extension portion 6b extending from piece body 6a toward the support side, and extension portion 6b has a claw (regulating portion) 6c that prevents it from coming out of support 4. With shock absorber D configured in this manner, after lock piece 6 enters lock chamber L during extension operation to exert its hydraulic locking function, when the extension direction switches to contraction operation, claw (regulating portion) 6c of lock piece 6 gets caught on the piston side of support 4, and lock piece 6 moves downward in Figure 1 with piston rod 2 relative to case 8c, so that lock piece 6 does not remain in lock chamber L, and hydraulic locking function can be stably exerted 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 off the support 4 so that the lock piece 6, which has entered the lock chamber L when the piston rod 2 moves downward in FIG. 1, can follow the movement of the piston rod 2 toward the contraction side so as not to be left behind in the lock chamber L. Therefore, in addition to the claw 6c provided on the extension portion 6b, the restricting portion may be composed of a groove along the axial direction provided on the outer periphery of the piston rod 2 and a pin provided on the extension portion 6b and inserted into the groove, or may be composed of an elongated hole along the axial direction provided on the extension portion 6b and a pin provided on the support 4 or the piston rod 2 and inserted into the elongated hole.

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, when the lock piece 6 enters the lock chamber L during the extension operation to exert its hydraulic locking function, and then the direction of extension and contraction is switched to perform a contraction operation and the lock piece 6 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 6b is made up of multiple arms 6b1, and a large gap can be formed between the arms 6b1, 6b1. The lock piece 6 and the cushion 5 are separated to form a gap, so that when the lock piece 6 leaves the lock chamber L, the resistance to the flow of liquid moving from the expansion side chamber R1 to the lock chamber L due to the gap can be minimized. Since no extra resistance is applied other than the resistance of the throttle passage P, the lock piece 6 can be quickly removed from the lock chamber L, and no resistance is applied to the contraction operation of the shock absorber D.

Also, because 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.

As described above, when the extension 6b has multiple arms 6b1, the various advantages described above can be enjoyed, but when the extension 6b is cylindrical and in sliding contact with the outer periphery of the support part 4b of the support 4, it is sufficient to provide an opening such as a hole or notch that connects the gap formed between the lock piece 6 and the cushion 5 when the lock piece 6 is most distant from the cushion 5 in the axial direction to the expansion-side chamber R1. If an opening is provided when the extension 6b is cylindrical in this way, when the shock absorber D switches its expansion/contraction direction and performs a contraction operation to cause the lock piece 6 to exit 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, is connected to the expansion-side chamber R1 via the gap between the lock piece 6 and the cushion 5 and the opening provided in the extension 6b, so that when the lock piece 6 exits the lock chamber L, the lock piece 6 can be quickly exited from within the lock chamber L, and there is no 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 bottom end of the cylinder or may be provided intermittently in the circumferential direction.

In addition, 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 a separate case is provided, and manufacturing costs can be further reduced, but the case may be a separate part from the rod guide 8, and 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.

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.

Although the preferred embodiment of the present invention has been described in detail above, modifications, variations, and changes are possible without departing from the scope of the claims.

1: Cylinder, 2: Piston rod, 3: Piston, 4: Support, 5: Cushion, 6: Lock piece, 6a: Piece body, 6a2: Concave surface, 6b: Extension part, 6b1: Arm, 6c: Claw (regulating part), 8c: Case, D: Shock absorber, P: Return passage, R: Reservoir, R1: Expansion side chamber, R2: Compression side chamber

Claims (6)

A shock absorber,
A cylinder;
A piston rod is inserted into the cylinder so as to be movable in the axial direction;
a piston connected to the piston rod and movably inserted into the cylinder to divide the inside of the cylinder into an expansion-side chamber and a compression-side chamber filled with liquid;
a case that is immovable in the axial direction relative to the cylinder and that defines a lock chamber that is open toward the piston;
A support is attached to an outer periphery of the piston rod facing the extension-side chamber;
a cushion that is disposed on an outer periphery of the piston rod facing the extension-side chamber and whose movement toward the piston side is restricted by the support;
a lock piece that is arranged on the outer periphery of the piston rod on the side of the cushion opposite to the piston and is axially movable so as to enter the lock chamber. 2. The shock absorber according to claim 1,
The lock piece is
a piece body that is annular and disposed on an outer periphery of the piston rod to form an annular throttle passage between the piece body and the piston rod, and that is capable of entering the lock chamber. 2. The shock absorber according to claim 1,
The lock piece is
A piece body capable of entering the lock chamber;
and an extension portion extending from the piece body toward a support side,
The extension portion is in sliding contact with the support. 2. The shock absorber according to claim 1,
The lock piece has a piece body that can enter the lock chamber and has an uneven surface facing the case. 2. The shock absorber according to claim 1,
The lock piece is
A piece body capable of entering the lock chamber;
and an extension portion extending from the piece body toward a support side,
The extension portion has a restricting portion that prevents the extension portion from coming off the support. 3. The shock absorber according to claim 2,
The lock piece has an extension portion extending from the piece body toward the support side,
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,
the extension portion has an opening that connects the gap to the expansion-side chamber.

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