Shock absorber and method for manufacturing shock absorber

Abstract

A shock absorber (D) according to the present invention comprises: an outer tube (1) that accommodates a liquid; a rod (2) that is inserted into the outer tube (1) so as to be capable of moving in the axial direction; a damping passage (3) through which the liquid passes when the outer tube (1) and the rod (2) move relative to each other; a damping valve (4) provided in the damping passage (3); a cylindrical housing (20) that protrudes from the side of the outer tube (1) and accommodates the damping valve (4) therein; a cylindrical sleeve (21) that has, at one end thereof, a crimped part (21a) formed by crimping the outer periphery of the housing (20), and accommodates the damping valve (4) therein together with the housing (20); and a coating film (P) that covers the crimped part (21a) of the sleeve (21).

Description

Shock absorber and method for manufacturing a shock absorber

[0001] The present invention relates to a shock absorber and a method for manufacturing a shock absorber.

[0002] In a shock absorber that exhibits a damping force for suppressing vibration, for example, there is one in which a damping valve capable of adjusting the damping force is attached to the side portion of an outer tube. In this shock absorber, the damping force can be adjusted up and down by adjusting the resistance given to the flow of the working oil generated when the shock absorber expands and contracts with the damping valve.

[0003] As disclosed in, for example, JP2017-57864A, when the entire damping valve is provided inside the outer tube, the outer diameter becomes large or the overall length becomes long, resulting in poor mountability on a vehicle. Therefore, the damping valve is projected radially outward from the side portion of the outer tube to shorten the axial length without sacrificing the stroke length.

[0004] JP2017-57864A

[0005] A conventional shock absorber includes a cylindrical housing that houses a damping valve, a sleeve that is cylindrical and has one end fitted to the housing, and an annular nut that is restricted from moving axially on the outer periphery of the housing and is allowed to rotate in the circumferential direction and is screwed to the outer periphery of the sleeve.

[0006] And in a conventional shock absorber, the damping valve is assembled to the sleeve in advance. While inserting the damping valve into the housing, after abutting the end portion of the sleeve against the end portion of the housing, the nut is screwed to the sleeve to connect the sleeve to the housing.

[0007] Therefore, in a conventional shock absorber, processing for forming a screw groove on the outer periphery of the sleeve is required, and a stop ring for preventing the nut from falling off from the housing of the nut and the nut is required for connecting the housing and the sleeve, so there is a problem that the manufacturing cost increases.

[0008] Furthermore, if the sleeve is connected to the housing by crimping in order to reduce manufacturing costs, a new problem arises: the plating applied to the sleeve for rust prevention is damaged and cracked by the crimping process to the housing, causing rust to form on the sleeve and making it unsuitable for long-term use.

[0009] Therefore, the present invention aims to provide a shock absorber that can withstand long-term use while reducing manufacturing costs by reducing the number of parts.

[0010] To achieve the above objective, the shock absorber of the present invention comprises an outer tube for containing liquid, a rod inserted into the outer tube so as to be movable in the axial direction, a damping passage through which the liquid passes when the outer tube and the rod move relative to each other, a damping valve provided in the damping passage, a cylindrical housing that protrudes from the side of the outer tube and houses the damping valve inside, a cylindrical sleeve having a crimped portion at one end formed by crimping the outer circumference of the housing and housing the damping valve inside together with the housing, and a coating film covering the crimped portion of the sleeve.

[0011] With a buffer configured in this way, the crimped portion, which is subjected to stress due to the crimping process on the sleeve, is covered with a coating. Therefore, even if cracks occur on the surface of the crimped portion due to the crimping process, the coating protects it and prevents rust from forming on the sleeve.

[0012] Furthermore, the present invention relates to a method for manufacturing a shock absorber comprising: an outer tube for containing liquid; a rod inserted into the outer tube so as to be movable in the axial direction; a damping passage through which the liquid passes when the outer tube and the rod move relative to each other; a damping valve provided in the damping passage; a cylindrical housing that protrudes from the side of the outer tube and houses the damping valve inside; and a cylindrical sleeve mounted on the outer circumference of the housing, the method for manufacturing a shock absorber comprising: a mounting step of fitting the sleeve to the outer circumference of the housing and crimping one end of the sleeve to mount the sleeve to the housing; and a painting step of painting the crimped portion formed by the crimping of the sleeve together with the outer tube after the mounting step.

[0013] With this method of manufacturing the shock absorber, even if cracks occur on the surface of the crimped portion where stress is applied to the sleeve during the installation process, the crimped portion is painted in the subsequent painting process and protected by the paint film, thus preventing rust from forming on the sleeve.

[0014] Figure 1 is a cross-sectional view of a shock absorber in one embodiment. Figure 2 is an enlarged cross-sectional view of the damping valve portion of the shock absorber in one embodiment. Figure 3 is an enlarged cross-sectional view of the sleeve of the shock absorber in one embodiment. Figure 4(a) is a diagram illustrating the mounting process of crimping and attaching the sleeve to the housing. Figure 4(b) is a diagram illustrating the painting process of painting the outer tube, housing, and sleeve.

[0015] The shock absorber D of the present invention will be described below with reference to the figures. In one embodiment, as shown in Figures 1 and 2, the shock absorber D comprises an outer tube 1, a rod 2 inserted into the outer tube 1 so as to be movable in the axial direction, a damping passage 3 through which liquid passes when the outer tube 1 and the rod 2 move relative to each other, a damping valve 4 provided in the damping passage 3, a housing 20 that protrudes from the side of the outer tube 1 and houses the damping valve 4 inside, a cylindrical sleeve 21 that is connected to the outer circumference of the housing 20 by crimping and houses the damping valve 4 inside together with the housing 20, and a coating film P that covers the crimped portion 21a of the sleeve 21.

[0016] The following describes in detail each part of the shock absorber D. In this embodiment, in addition to the configuration described above, the shock absorber D includes a cylinder 5 housed in the outer tube 1, a piston 6 connected to the tip of the rod 2 and movably inserted into the cylinder 5, which divides the inside of the cylinder 5 into an extension chamber R1 and a compression chamber R2 filled with liquid, an intermediate cylinder 7 positioned between the cylinder 5 and the outer tube 1, and a reservoir R formed between the outer tube 1 and the intermediate cylinder 7.

[0017] The extension chamber R1 and the compression chamber R2 are filled with liquid, and the reservoir R is filled with liquid and gas. The liquid used to operate the buffer D is specifically, for example, hydraulic oil, but may also be water, an aqueous solution, or the like.

[0018] Furthermore, the cylinder 5 is housed within a bottomed cylindrical outer tube 1 positioned on its outer circumference. As previously mentioned, an intermediate cylinder 7 is inserted between the cylinder 5 and the outer tube 1. An annular gap between the cylinder 5 and the intermediate cylinder 7 forms an annular passage 10, which is part of the damping passage 3, and an annular gap between the intermediate cylinder 7 and the outer tube 1 forms a reservoir R. Near the upper end of the cylinder 5, a hole 5a is provided that communicates with the extension chamber R1 and the annular passage 10. In addition, the outer tube 1 covers the outer circumference of the cylinder 5 along its entire length, housing the entire cylinder 5 inside. The damping passage 3 and the reservoir R are filled with liquid, similar to the inside of the cylinder 5.

[0019] Furthermore, a valve case 8 is fitted to the lower ends of the cylinder 5 and the intermediate cylinder 7 in Figure 1, and a rod guide 9, which slidably supports the rod 2, is fitted to the upper ends of the cylinder 5 and the intermediate cylinder 7 in Figure 1. The cylinder 5 and the intermediate cylinder 7 are positioned concentrically in the radial direction, sandwiched between the valve case 8 and the rod guide 9. In addition, the lower ends of the cylinder 5 and the intermediate cylinder 7 are both closed by the valve case 8, and the valve case 8 separates the pressure chamber R2 inside the cylinder 5 from the reservoir R formed outside the cylinder 5 and inside the outer tube 1.

[0020] In this manner, the valve case 8 and rod guide 9, which sandwich the cylinder 5 and the intermediate cylinder 7, are inserted into the inner circumference of the outer tube 1. When the upper end of the outer tube 1 is crimped, the cylinder 5, intermediate cylinder 7, valve case 8, and rod guide 9 are clamped between the crimped portion and the bottom of the outer tube 1 and fixed inside the outer tube 1. The space between the rod guide 9 and the rod 2, and the space between the rod guide 9 and the outer tube 1 are sealed by sealing members (not shown), preventing leakage of liquid from inside the buffer D. Alternatively, instead of crimping the upper opening of the outer tube 1, a cap may be screwed onto the upper opening of the outer tube 1, and the rod guide 9, cylinder 5, intermediate cylinder 7, and valve case 8 may be clamped between this cap and the bottom of the outer tube 1, thereby fixing these components inside the outer tube 1.

[0021] The piston 6 is annular in shape and connected to the rod 2, dividing the inside of the cylinder 5 into an extension chamber R1 at the top of Figure 1 and a compression chamber R2 at the bottom of Figure 1. It is equipped with an extension damping passage 6a that resists the flow of liquid passing through it while allowing only the flow of liquid from the extension chamber R1 to the compression chamber R2, and a compression passage 6b that blocks the flow of liquid in the opposite direction while allowing only the flow of liquid from the compression chamber R2 to the extension chamber R1.

[0022] Next, as shown in Figure 1, the valve case 8 is annular and has two stepped portions on its outer circumference that are not indicated, and fits into the inner circumference of the lower end of the cylinder 5 and the inner circumference of the lower end of the intermediate cylinder 7, as well as the inner circumference of the lower end of the outer tube 1. The valve case 8 includes a pressure-side damping passage 8a that allows only the flow of liquid from the pressure-side chamber R2 to the reservoir R while providing resistance to the liquid flow, and a suction passage 8b that allows the flow of liquid from the reservoir R to the pressure-side chamber R2 while preventing the flow of liquid in the reverse direction.

[0023] As described above, the intermediate cylinder 7 covers the outer circumference of the cylinder 5 and is sandwiched between the rod guide 9 and the valve case 8, forming an annular passage 10 between it and the cylinder 5. The annular passage 10 communicates with the extension chamber R1 through a hole 5a provided in the cylinder 5, and also communicates with the reservoir R through a passage 41b formed in the valve assembly 41 of the damping valve 4. Therefore, in the shock absorber D of this embodiment, the damping passage 3 is formed by the hole 5a provided in the cylinder 5, the annular passage 10, and the passage 41b provided in the valve assembly 41.

[0024] Furthermore, the intermediate cylinder 7 is provided with a hole 7a at the bottom and a collar 7b on its outer circumference that surrounds the hole 7a and protrudes radially. The tip of the valve assembly 41 of the damping valve 4 is fitted inside the collar 7b. The space between the collar 7b and the valve assembly 41 is sealed by a seal ring 30, preventing communication between the damping passage 3 and the reservoir R through the space between the valve assembly 41 and the collar 7b. In this case, the hole 5a provided in the cylinder 5 is used to connect the annular passage 10 in the intermediate cylinder 7 with the extension chamber R1, but instead of the hole 5a, a passage may be provided in the rod guide 9 that connects the extension chamber R1 with the annular gap between the cylinder 5 and the intermediate cylinder 7, thereby connecting the annular passage 10 with the extension chamber R1.

[0025] Furthermore, the outer tube 1 is provided with a hole 1a located radially opposite to the hole 7a and collar 7b of the intermediate tube 7. A cylindrical housing 20 is mounted on the side of the outer tube 1, surrounding the hole 1a and protruding radially. The housing 20 is cylindrical in shape, with one end cut off by a cylindrical surface perpendicular to the axis, so that one end follows the outer circumference of the outer tube 1. The housing 20 is joined to the outer tube 1 by welding, with this end in contact with the outer circumference of the outer tube 1, specifically the outer circumference side of the hole 1a.

[0026] Therefore, the interior of the housing 20 is connected to the outer tube 1 through hole 1a and is directly facing hole 7a in the radial direction. In addition, an annular groove 20a is provided on the outer circumference of the other end of the housing 20.

[0027] As shown in Figure 2, the damping valve 4 comprises a valve assembly 41 and a molded coil 42 fitted to the outer circumference of the valve assembly 41. The valve assembly 41 comprises a valve case 41a fitted into the collar 7b, a passage 41b that opens from the tip of the valve case 41a and extends laterally to connect the annular passage 10 and the reservoir R, a valve body 41c provided inside the valve case 41a and in the middle of the passage 41b, a fixed iron core 41d which has a larger outer diameter than the valve case 41a and is mounted at the rear end of the valve case 41a and fitted to the inner circumference of the housing 20, a cylindrical body 41e made of a non-magnetic material attached to the right end of the fixed iron core 41d in Figure 2, a movable iron core 41f inserted into the cylindrical body 41e so as to be movable in the axial direction, and a cap 41g which closes the right end of the cylindrical body 41e in Figure 2.

[0028] In the valve assembly 41, the valve case 41a, together with the passage 41b and the valve body 41c, constitutes the valve portion of the damping valve 4. When the tip of the valve case 41a is fitted onto the collar 7b and the outer circumference of the fixed iron core 41d is fitted onto the inner circumference of the housing 20, the collar 7b closes off the valve assembly 41. The passage 41b opens from the tip of the valve case 41a and extends laterally, and is not closed off by the collar 7b even when fitted onto it, thus connecting the annular passage 10 and the reservoir R. Therefore, the annular passage 10 and the reservoir R are connected only through the passage 41b. Furthermore, since the passage 41b is connected to the extension chamber R1 through the annular passage 10 and the hole 5a of the cylinder 5, the extension chamber R1 and the reservoir R are connected by the hole 5a, the annular passage 10, and the passage 41b. Thus, in this embodiment, the damping passage 3 is formed by a hole 5a, an annular passage 10, and a passage 41b.

[0029] The valve body 41c comprises a valve element 41c1 that seats away from a valve seat (not shown) provided in the passage 41b, and a spring 41c2 that biases the valve element 41c1 in the direction of closing the valve. The valve element 41c1 is in contact with the movable core 41f so as to be able to receive a thrust force from the movable core 41f in the direction of opening the valve. Furthermore, the valve element 41c1 is designed to receive a force in the direction of opening the valve due to the pressure in the extension chamber R1 which is upstream of the passage 41b.

[0030] The valve case 41a only needs to have a structure that prevents the annular passage 10 and the reservoir R from communicating without going through the passage 41b by enclosing the passage 41b, holding the valve body 41c, and being fitted into the collar 7b. In that respect, the structure and shape of the valve case 41a can be arbitrarily modified.

[0031] Furthermore, the structure of the valve body 41c can be modified as appropriate, and the valve body 41c may be an assembly of multiple valves. In addition, although the damping valve 4 is equipped with a solenoid S to adjust the damping force, it may also be a damping valve that adjusts the damping force manually by the user without a solenoid S, or a damping valve that does not have a damping force adjustment function.

[0032] The fixed core 41d is made of a soft magnetic material and is attached to the valve case 41a. When the valve case 41a is inserted into the housing 20 and fitted into the collar 7b, the outer circumference is fitted into the housing 20 and the fixed core 41d is housed within the housing 20. The fixed core 41d also has a through hole 41d1 in its center. The fixed core 41d may be integrally and inseparably connected to the valve case 41a and constitute a single component.

[0033] The cylindrical body 41e is a cylinder made of a non-magnetic material and is fixed to the right end of the fixed core 41d in Figure 2. The movable core 41f is made of a soft magnetic material and its outer circumference is in sliding contact with the inner circumference of the cylindrical body 41e, allowing it to move axially within the cylindrical body 41e. The movable core 41f is axially opposed to the fixed core 41d and is equipped with a push rod 41f1 that is inserted into the through hole 41d1 of the fixed core 41d and contacts the valve body 41c1 in the valve body 41c. In this embodiment, the movable core 41f is equipped with a push rod 41f1, but a push rod that contacts the movable core 41f may be provided on the valve body 41c1 side, or the push rod may be omitted as long as the movable core 41f and the valve body 41c1 are in contact. The cap 41g is attached to the right end of the cylindrical body 41e in Figure 2, closing the opening of the cylindrical body 41e and preventing the movable iron core 41f from falling out of the cylindrical body 41e.

[0034] The molded coil 42 comprises a coil 42a, an annular molded resin 42b enclosing the coil 42a, and a cylindrical coupler 42d enclosing a terminal 42c that protrudes upward from the right end side of the molded resin 42b in Figure 2 and is connected to the coil 42a.

[0035] When the molded resin 42b of the molded coil 42 is fitted onto the outer circumference of the cylindrical body 41e of the valve assembly 41, the molded coil 42, the fixed core 41d, and the movable core 41f form a solenoid S.

[0036] When current is supplied to the coil 42a of the solenoid S configured in this way, the fixed core 41d is magnetized, attracting the movable core 41f, and this attractive force acts as a thrust on the valve body 41c1. The valve body 41c1, having received thrust from the solenoid S, is driven in the opening direction against the biasing force of the spring 41c2. Therefore, the larger the amount of current supplied to the coil 42a, the smaller the opening pressure when the valve body 41c opens the passage 41b. By adjusting the amount of current supplied to the coil 42a, the opening pressure of the valve body 41c can be adjusted, and the pressure in the extension chamber R1 upstream of the damping passage 3 can be adjusted. Furthermore, when the current to the coil 42a is stopped, the thrust that attracts the movable core 41f to the valve body 41c1 disappears, and it moves in the closing direction under the biasing force of the spring 41c2, blocking the passage 41b.

[0037] In this embodiment, when the current to the coil 42a is stopped, the valve body 41c is closed by the spring 41c2. However, the spring 41c2 may be eliminated, and a spring may be provided that biases the valve body 41c1 and the movable iron core 41f in the direction of opening the valve. The fixed iron core may be provided on the opposite side of the movable iron core 41f from the valve, and driven in the direction of closing the valve body 41c1 when current is supplied. In this case, the opening pressure of the valve body 41c can be increased by increasing the amount of current supplied to the coil 42a, and the opening pressure of the valve body 41c can be minimized by closing the valve body 41c when the current to the coil 42a is stopped.

[0038] Next, as shown in Figure 2, the sleeve 21 is attached to the housing 20 which is mounted on the side of the outer tube 1. The sleeve 21 is cylindrical and its inner diameter is set to a diameter that can be fitted to the outer circumference of the housing 20. After being fitted to the outer circumference of the housing 20, one end, near the left end in Figure 2, is formed by crimping from the outer circumference side, and has a crimped portion 21a that is plastically deformed to fit into the annular groove 20a of the housing 20. In this way, the sleeve 21 is attached and fixed to the outer circumference of the housing 20 by the crimped portion 21a formed by the crimping process fitting into the annular groove 20a. Furthermore, the sleeve 21 has an annular cap mounting portion 21b that protrudes axially from the outer circumference of the other end, which is the right end in Figure 2, and is thinner than the left end, and an outlet hole 21c formed by a notch that opens at the other end.

[0039] As mentioned above, the sleeve 21 is equipped with a crimped portion 21a formed by crimping from the outer circumference side while one end is fitted onto the outer circumference of the housing 20. The process of forming the crimped portion 21a will be described in detail.

[0040] Before being fixed to the housing 20 by crimping, the sleeve 21 has a flange 21d at one end, the left end in Figure 3, as shown in Figure 3. For rust prevention, the entire sleeve is plated, and a metal coating of zinc, nickel-chromium, or the like is formed on the surface by the plating process.

[0041] As shown in Fig. 4(a), the sleeve 21 before caulking is fitted onto the outer periphery of the housing 20 with the flange 21d positioned to face the annular groove 20a of the housing 20. Then, the annular die 100 is brought close to the flange 21d from the right side in Fig. 4, and caulking is performed to bend the flange 21d toward the housing 20 side and fold it. Note that an annular groove 21e is provided adjacent to the flange 21d on the inner periphery of the sleeve 21 to facilitate the bending of the flange 21d by forming a fragile portion that assists in the bending of the flange 21d and to allow escape of the inner peripheral portion of the bent flange 21d. A part of the flange 21d bent by plastic deformation becomes the caulked portion 21a, fits into the annular groove 20a of the housing 20, and clamps the outer periphery of the housing 20, so that the sleeve 21 is firmly fixed to the housing 20.

[0042] When the sleeve 21 is fixed to the housing 20 by performing such caulking, a large load acts on the caulked portion 21a formed by the caulking during the caulking process, and the metal film formed by plating applied for rust prevention may crack.

[0043] Therefore, in the shock absorber D of the present embodiment, after the sleeve 21 is attached to the outer periphery of the housing 20 attached to the outer tube 1 by caulking, as shown in Fig. 4(b), a bottomed cylindrical cap 101 that prevents the adhesion of paint is placed over the outer periphery of the other end of the sleeve 21, and cationic painting is applied to the outer surface of the caulked portion 21a not covered by the outer tube 1, the housing 20, and the cap 101 of the sleeve 21. As shown in Fig. 2, a coating film P is formed on the outer surface of the caulked portion 21a as well as the outer tube 1, the housing 20, and the sleeve 21.

[0044] The height of the cap 101 is set to a height that covers the lead-out hole 21c of the sleeve 21 but does not cover the caulked portion 21a, and the cationic painting is performed so that the coating film P can cover at least the entire caulked portion 21a. In the present embodiment, the caulked portion 21a and the vicinity thereof where stress due to caulking of the sleeve 21 acts are covered by the coating film P.

[0045] Thus, the sleeve 21 is fixed to the housing 20 with a crimped portion 21a formed by a crimping process, and the crimped portion 21a is covered with a coating film P formed by painting. Therefore, even if cracks occur in the metal film formed by plating on the crimped portion 21a due to the crimping process, it is protected by the coating film P. As a result, even if the sleeve 21 is fixed to the housing 20 by a crimping process that does not require any other parts to fix the sleeve 21 to the housing 20, rust on the crimped portion 21a of the sleeve 21 is prevented.

[0046] After fixing the sleeve 21 to the housing 20 in this manner, the pre-assembled valve assembly 41 is inserted into the space between the collar 7b of the intermediate cylinder 7 inside the outer tube 1 and the housing 20. The molded coil 42 is then fitted onto the outer circumference of the cylindrical body 41e of the valve assembly 41, while housing the molded coil 42 inside the sleeve 21, and the coupler 42d is placed inside the outlet hole 21c. Seal rings 30, 31, and 32 are provided between the outer circumference of the valve case 41a of the valve assembly 41 and the collar 7b, between the fixed iron core 41d and the housing 20, and between the outer circumference of the fixed iron core 41d, the outer circumference of the molded coil 42, and the inner circumference of the sleeve 21, respectively, to prevent leakage of liquid from inside the buffer D.

[0047] Next, a disc-shaped cap 23 is inserted into the thin-walled cap mounting portion 21b at the right end of the sleeve 21 in Figure 2, and the cap mounting portion 21b is crimped from the outer circumference to fix the cap 23 to the sleeve 21. The strength required for fastening the cap mounting portion 21b and the cap 23 is much lower than the strength required for fastening the sleeve 21 and the housing 20, so even if the cap mounting portion 21b is crimped, no cracks will occur in the metal coating formed by plating on the cap mounting portion 21b. Therefore, it is not necessary to form a coating P on the cap mounting portion 21b. A seal ring 33 is provided between the outer circumference of the cylindrical body 41e, the inner circumference of the molded coil 42, and the cap 23, preventing water, dust, etc. from entering the solenoid S through the outlet hole 21c.

[0048] When the cap 23 is fixed to the sleeve 21, the damping valve 4 is housed in the housing 20 and the sleeve 21 and is fixed to the housing 20 and the sleeve 21 so as not to fall off.

[0049] The coupler 42d of the mold coil 42 housed in the sleeve 21 is led out of the sleeve 21 through the lead-out hole 21c of the sleeve 21, but the orientation of the coupler 42d may be changed according to the specifications required for the shock absorber D. Therefore, when performing the caulking process for fixing the sleeve 21 to the housing 20, the lead-out hole 21c is positioned in accordance with the orientation of the coupler 42d of the mold coil 42 required by the specifications, the sleeve 21 is fitted to the housing 20, and the caulking process of the sleeve 21 is performed. The orientation of the lead-out hole 21c of the sleeve 21 can be freely and easily adjusted to any angle in the circumferential direction of the housing 20 when the sleeve 21 is fitted to the outer periphery of the housing 20. Therefore, the sleeve 21 can be easily joined to the housing 20 according to the orientation required for the coupler 42d.

[0050] In the present embodiment, the mold coil 42 includes the coupler 42d. However, when the coil 42a is provided with a wiring connected without the coupler 42d, the wiring may be housed in the lead-out hole 21c.

[0051] Next, the operation of the shock absorber D configured as described above will be described. First, the case where the shock absorber D extends will be described. When the piston 6 moves upward in FIG. 1 with respect to the cylinder 5 and the shock absorber D is in the extension stroke, the extension side chamber R1 is compressed and the compression side chamber R2 is expanded. The liquid in the extension side chamber R1 passes through the extension side damping passage 6a and moves to the compression side chamber R2. Since the extension side damping passage 6a gives resistance to the flow of the liquid, the pressure in the extension side chamber R1 becomes higher than the pressure in the compression side chamber R2, and the shock absorber D generates an extension side damping force that hinders the extension operation.

[0052] Here, by adjusting the amount of current supplied to coil 42a, if the opening pressure of damping valve 4 is lowered, the liquid in the extension chamber R1 will preferentially pass through damping passage 3 rather than extension damping passage 6a to move to reservoir R, and any insufficient liquid in the compression chamber R2 will be supplied from reservoir R to compression chamber R2 through suction passage 8b. Therefore, lowering the opening pressure of damping valve 4 reduces the pressure difference between the extension chamber R1 and the compression chamber R2, thus reducing the extension damping force generated by buffer D. Conversely, by adjusting the amount of current supplied to coil 42a, if the opening pressure of damping valve 4 is increased, the liquid in the extension chamber R1 will pass through extension damping passage 6a to move to compression chamber R2, but it will have difficulty passing through damping passage 3, and the pressure difference between the extension chamber R1 and the compression chamber R2 will increase. Therefore, increasing the opening pressure of the damping valve 4 increases the difference between the pressure in the extension chamber R1 and the pressure in the compression chamber R2, thereby increasing the extension damping force generated by the buffer D.

[0053] Next, we will explain the case when the shock absorber D contracts. When the piston 6 moves downward relative to the cylinder 5 in Figure 1, and the shock absorber D is in the contraction stroke, the compression chamber R2 is compressed and the extension chamber R1 is expanded. The liquid in the compression chamber R2 moves to the reservoir R through the compression damping passage 8a, and the compression damping passage 8a resists the flow of the liquid, while liquid is supplied from the compression chamber R2 to the extension chamber R1, whose volume is expanded by the contraction of the shock absorber D, through the compression passage 6b. As a result, the pressure in the extension chamber R1 and the pressure in the compression chamber R2 become almost equal and both rise, and the shock absorber D generates a compression damping force that hinders the contraction operation.

[0054] Here, by adjusting the amount of current supplied to coil 42a, if the opening pressure of damping valve 4 is lowered, damping valve 4 opens and connects the extension chamber R1 to reservoir R, thus lowering the pressure inside cylinder 5 and reducing the compression damping force generated by buffer D. Conversely, by adjusting the amount of current supplied to coil 42a, if the opening pressure of damping valve 4 is increased, it becomes more difficult for the liquid to pass through damping passage 3, and the pressure inside cylinder 5 increases. Therefore, if the opening pressure of damping valve 4 is increased, both the pressure in the extension chamber R1 and the pressure in the compression chamber R2 increase, and the compression damping force generated by buffer D increases.

[0055] In this manner, the shock absorber D generates a damping force when the rod 2 moves relative to the outer tube 1 in the axial direction, by the damping valve 4 providing resistance to the liquid flowing through the damping passage 3.

[0056] As described above, the shock absorber D of this embodiment comprises an outer tube 1 for containing liquid, a rod 2 inserted into the outer tube 1 so as to be movable in the axial direction, a damping passage 3 through which the liquid passes when the outer tube 1 and the rod 2 move relative to each other, a damping valve 4 provided in the damping passage 3, a cylindrical housing 20 that protrudes from the side of the outer tube 1 and houses the damping valve 4 inside, a cylindrical sleeve 21 having a crimped portion 21a at one end formed by crimping the outer circumference of the housing 20 and housing the damping valve 4 inside together with the housing 20, and a coating film P covering the crimped portion 21a of the sleeve 21.

[0057] With the shock absorber D configured in this way, the crimped portion 21a, which is subjected to stress due to the crimping process on the sleeve 21, is covered with a coating film P. Therefore, even if cracks occur on the surface of the crimped portion 21a due to the crimping process, the coating film P protects it, preventing rust from forming on the sleeve 21. Thus, with the shock absorber D of this embodiment, rust on the sleeve 21 can be prevented, allowing the sleeve 21 to be joined to the housing 20 using a crimping process with fewer parts. This reduces the number of parts and lowers manufacturing costs, while preventing rust and ensuring long-term use.

[0058] Furthermore, the damping valve 4 in the shock absorber D of this embodiment has a solenoid S, and the sleeve 21 is provided with a lead-out hole 21c on the side for a coupler 42d for supplying power to the solenoid S. With the shock absorber D configured in this way, the position of the lead-out hole 21c in the sleeve 21 before fixing can be easily made to correspond to the orientation of the coupler 42d of the solenoid S, making assembly even easier. If the solenoid S has wiring instead of a connector, the wiring may be led outward from the lead-out hole 21c.

[0059] Furthermore, the damping valve 4 in the buffer D of this embodiment comprises a valve assembly 41 that is pre-assembled and includes a valve body 41c provided in the damping passage 3, a fixed core 41d, and a movable core 41f that drives the valve body 41c, and an annular molded coil 42 that can be attached to the outer circumference of the movable core 41f in the valve assembly 41 and attracts the movable core 41f to the fixed core 41d when energized, and the sleeve 21 functions as a case for housing the molded coil 42.

[0060] With the buffer D configured in this way, the damping valve 4 can be easily assembled into the buffer D by sequentially inserting the pre-assembled valve assembly 41 and molded coil 42 into the housing 20 and the sleeve 21 fixed to the housing 20.

[0061] Furthermore, in the shock absorber D of this embodiment, the sleeve 21 has a flange 21d on the outer circumference of one end, and the crimped portion 21a is formed by the flange 21d bent toward the housing side by a crimping process. With the shock absorber D configured in this way, the crimped portion 21a that is fixed to the outer circumference of the housing 20 is formed by bending and folding the flange 21d with an annular die 100, so the fitting length with the housing 20 can be easily adjusted to the design by relying on the flange 21d, and the crimping process is made easier.

[0062] Furthermore, the buffer D of this embodiment comprises an outer tube 1 for containing liquid, a rod 2 inserted into the outer tube 1 so as to be movable in the axial direction, a damping passage 3 through which the liquid passes when the outer tube 1 and the rod 2 move relative to each other, a damping valve 4 provided in the damping passage 3, a cylindrical housing 20 that protrudes from the side of the outer tube 1 and houses the damping valve 4 inside, and a cylindrical sleeve 21 mounted on the outer circumference of the housing 20. The method for manufacturing the buffer D includes a mounting step of mounting the sleeve 21 to the housing 20 by crimping one end of the sleeve 21 while the sleeve 21 is fitted to the outer circumference of the housing 20, and a painting step of painting the crimped portion 21a formed by the crimping of the sleeve 21 together with the outer tube 1 after the mounting step.

[0063] According to the manufacturing method of the shock absorber D configured in this way, even if cracks occur on the surface of the crimped portion 21a where stress from the crimping process acts on the sleeve 21 during the mounting process, the crimped portion 21a is painted in the subsequent painting process and protected by the paint film P, thus preventing rust from occurring on the sleeve 21. Therefore, according to the manufacturing method of the shock absorber D of this embodiment, since rust on the sleeve 21 can be prevented, the sleeve 21 can be joined to the housing 20 using a crimping process with fewer parts, thereby reducing the number of parts and lowering manufacturing costs, while preventing rust and ensuring long-term use.

[0064] Although preferred embodiments of the present invention have been described in detail above, modifications, alterations, and changes are permitted as long as they do not deviate from the scope of the claims.

[0065] 1...Outer tube, 2...Rod, 3...Damping passage, 4...Damping valve, 20...Housing, 21...Sleeve, 21c...Outlet hole, 21d...Flange, 41...Valve assembly, 41d...Fixed core, 41f...Movable core, D...Shock absorber, P...Coating, S...Solenoid

Claims

1. A shock absorber comprising: an outer tube for containing liquid; a rod inserted into the outer tube so as to be movable in the axial direction; a damping passage through which the liquid passes when the outer tube and the rod move relative to each other; a damping valve provided in the damping passage; a cylindrical housing that protrudes from the side of the outer tube and houses the damping valve inside; a cylindrical sleeve having a crimped portion at one end formed by crimping the outer circumference of the housing, and together with the housing, houses the damping valve inside; and a coating film covering the crimped portion of the sleeve.

2. A shock absorber according to claim 1, wherein the damping valve has a solenoid, and the sleeve has a connector or wiring outlet hole on the side for supplying power to the solenoid.

3. A shock absorber according to claim 1, wherein the damping valve comprises a valve assembly that is pre-assembled and includes a valve body provided in the damping passage, a fixed core, and a movable core that drives the valve body, and an annular molded coil that can be attached to the outer circumference of the movable core in the valve assembly and causes the movable core to be attracted to the fixed core when energized, and the sleeve functions as a case for housing the molded coil.

4. A shock absorber according to claim 1, wherein the sleeve has a flange on the outer circumference of one end, and the crimping portion is formed by the flange which is bent and folded toward the housing side by a crimping process.

5. A method for manufacturing a shock absorber, comprising: an outer tube for containing liquid; a rod inserted into the outer tube so as to be movable in the axial direction; a damping passage through which the liquid passes when the outer tube and the rod move relative to each other; a damping valve provided in the damping passage; a cylindrical housing that protrudes from the side of the outer tube and houses the damping valve inside; and a cylindrical sleeve mounted on the outer circumference of the housing, the method for manufacturing a shock absorber comprising: a mounting step of fitting the sleeve to the outer circumference of the housing and crimping one end of the sleeve to mount the sleeve to the housing; and a painting step of painting the crimped portion formed by the crimping of the sleeve together with the outer tube after the mounting step.

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