Buffer and rebound spring

Abstract

To provide a buffer and a rebound spring in which a failure caused by galling between a winding end of a coil spring and a resin cushion in the rebound spring has been eliminated.SOLUTION: By insert-molding a metal wire 32 for a spring, a rebound spring 30 is applied in which a coil part 31 and cushion parts 41, 51 are integrally formed. This eliminates a resin cushion pressing process, which eliminates problems such as generation of burrs and loss of a resin cushion caused by galling between the winding end of the coil spring and the resin cushion in the resin cushion pressing process.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a shock absorber and a rebound spring applied to the shock absorber.

Background Art

[0002] Patent Document 1 discloses a rebound spring S (hereinafter referred to as "conventional rebound spring") in which resin cushions 7 and 8 are integrated with a coil spring 6 by press-fitting press-fitting portions 7b and 8b into the inner circumferences of the seat winding portions 6a and 6b of the coil spring 6.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional rebound spring, in the process of press-fitting the resin cushion into the coil spring, if the winding end of the metal coil spring and the resin cushion bite, problems such as the occurrence of burrs, incomplete press-fitting, and the resin cushion coming off may occur.

[0005] An object of the present invention is to solve the problems caused by the biting between the winding end of the coil spring and the resin cushion in the rebound spring.

Means for Solving the Problems

[0006] The shock absorber of the present invention includes a cylinder, a piston provided in the cylinder and partitioning the inside of the cylinder into a first chamber and a second chamber, a piston rod having a first end connected to the piston and a second end extending outside the cylinder, a rebound spring provided in the cylinder and into which the piston rod is inserted, and a stopper member fixed to the piston rod and restricting the axial movement of the rebound spring with respect to the piston rod. The rebound spring has a coil portion at least partially formed of a resin material, and cushion portions provided at both axial ends and integrally formed with the coil portion. The rebound spring of the present invention includes a coil portion at least partially formed of a resin material, and cushion portions provided at both axial ends and integrally formed with the coil portion. The coil portion has a single concave portion formed on one axial side and extending along the coil portion, and a single convex portion formed on the other axial side and extending along the coil portion and capable of fitting into the concave portion.

Advantages of the Invention

[0007] According to the present invention, it is possible to eliminate problems caused by chafing between the coil ends of the coil spring and the resin cushion in the rebound spring.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0009] (First Embodiment) The first embodiment of the present invention will be described with reference to the attached drawings. FIG. 1 is a cross-sectional view taken along the axial plane of a shock absorber 1 according to the first embodiment. For convenience, the vertical direction in FIG. 1 is simply referred to as the "vertical direction". The shock absorber 1 is a twin-tube hydraulic shock absorber applied to a strut type suspension device.

[0010] The shock absorber 1 has a cylinder 2 and an outer tube 3 provided on the outer periphery of the cylinder 2. The shock absorber 1 has a piston 4 fitted in the cylinder 2 and partitioning the inside of the cylinder 2 into a first chamber 2A and a second chamber 2B, and a piston rod 21 having a first end 22 connected to the piston 4 and a second end 23 extending to the outside of the cylinder 2. The shock absorber 1 has a reservoir chamber 5 formed between the cylinder 2 and the outer tube 3. Note that hydraulic oil is enclosed in the cylinder 2 as a working fluid, and hydraulic oil and gas are enclosed in the reservoir chamber 5.

[0011] The piston 4 has an extension side passage 9 and a compression side passage 10. The piston 4 is provided with a disk valve 11 that allows the flow of hydraulic oil from the first chamber 2A to the second chamber 2B in the extension side passage 9, and a disk valve 12 that allows the flow of hydraulic oil from the second chamber 2B to the first chamber 2A in the compression side passage 10. The disk valve 11 generates an extension side damping force when hydraulic oil flows through the extension side passage 9 from the first chamber 2A to the second chamber 2B. On the other hand, the disk valve 12 generates a compression side damping force when hydraulic oil flows through the compression side passage 10 from the second chamber 2B to the first chamber 2A.

[0012] The shock absorber 1 has a rod guide 13 that closes the upper end sides of the cylinder 2 and the outer tube 3. The rod guide 13 has a small-diameter portion 14 inserted into the upper end portion of the cylinder 2 and a large-diameter portion 15 inserted into the upper end portion of the outer tube 3. Note that the lower end side of the cylinder 2 of the shock absorber 1 is closed by a base valve (not shown) that partitions the second chamber 2B and the reservoir chamber 5, and the lower end side of the outer tube 3 is closed by a bottom cap (not shown).

[0013] The shock absorber 1 has a seal member 16 that slidably contacts the outer peripheral surface 24 of the piston rod 21 and seals the first chamber 2A, the reservoir chamber 5, and the outside. The seal member 16 forms a caulked portion 17 by caulking the upper end periphery of the outer tube 3 inward, so that the outer peripheral portion is sandwiched between the rod guide 13 and the caulked portion 17. A bumper cap 18 is provided at the upper end portion of the outer tube 3. The bumper cap 18 covers the outer periphery of the upper end side of the outer tube 3 and the upper end side opening (seal member 16).

[0014] The shock absorber 1 includes a rebound spring 30. The rebound spring 30 has a coil portion 31, a cushion portion 41 formed continuously at one end of the coil portion 31, and a cushion portion 51 formed continuously at the other end of the coil portion 31. The coil portion 31 has a spring metal wire 32 with a circular cross-section and a plastic resin portion 33 covering the surface of the spring metal wire 32. The resin portion 33 is made of the same resin material as the cushion portion 41 and the cushion portion 51. The rebound spring 30 is integrally formed with the coil portion 31 and the cushion portions 41 and 51 by insert molding (integral molding) of the spring metal wire 32.

[0015] As shown in FIG. 2 or FIG. 3, the inner peripheral surface 34 of the coil portion 31 (resin portion 33) is disposed on a cylindrical surface coaxial with the axis of the rebound spring 30 (hereinafter referred to as the "axis"), has a constant height in the axial direction (the "vertical direction" in FIGS. 2 and 3), and is formed by a single surface that extends in a spiral shape. The outer peripheral surface 35 of the coil portion 31 (resin portion 33) is disposed on a cylindrical surface coaxial with the axis, has a constant height in the axial direction (the same height as the inner peripheral surface 34), and is formed by a single surface that extends in a spiral shape.

[0016] The coil portion 31 (resin portion 33) is formed over the entire width at the portion facing the upper side (one side in the axial direction), and has a convex portion 36 whose cross section by a plane including the axis (hereinafter referred to as the "axial plane") is arcuate. The convex portion 36 extends in a spiral shape with the same cross-sectional shape from the end on the cushion portion 41 side to the end on the cushion portion 51 side of the coil portion 31. On the other hand, the coil portion 31 is formed over the entire width at the portion facing the lower side (the other side in the axial direction), and has a concave portion 37 whose cross section by the axial plane is arcuate. The concave portion 37 extends in a spiral shape with the same cross-sectional shape from the end on the cushion portion 41 side to the end on the cushion portion 51 side of the coil portion 31. And when the rebound spring 30 is compressed and extended and the coil portion 31 is in a state of line contact, the convex portion 36 of the coil portion 31 is fitted into the concave portion 37 facing in the axial direction.

[0017] As shown in FIG. 1, the cushion portion 41 is received by a ring-shaped stopper member 25 fixed to the piston rod 21. The stopper member 25 is fitted into an annular groove 26 formed on the outer peripheral surface 24 of the piston rod 21 at its inner peripheral edge portion, thereby preventing axial movement with respect to the piston rod 21. As shown in FIG. 2, the axial height of the cushion portion 41 is set higher than the axial height of the wire portion of the coil portion 31. The cushion portion 41 has a cylindrical portion 42 disposed coaxially with the coil portion 31.

[0018] As shown in FIG. 2 or FIG. 3, the outer diameter of the cylindrical portion 42 is set to be smaller than the inner diameter of the cylinder 2 and substantially the same as the outer diameter of the coil portion 31 when the rebound spring 30 is at its free length. The inner diameter of the cylindrical portion 42 is set to be smaller than the inner diameter of the coil portion 31 and larger than the outer diameter of the piston rod 21. A plurality (four in the first embodiment) of protrusions 46 are formed on the inner peripheral surface 43 of the cylindrical portion 42. The plurality of protrusions 46 have spherical surfaces and are arranged at regular intervals in the circumferential direction of the inner peripheral surface 43. The plurality of protrusions 46 are formed so as to contact the outer peripheral surface 24 (see FIG. 1) of the inserted piston rod 21.

[0019] On the end face 45 of the cylindrical portion 42 on the side facing the stopper member 25, a plurality (eight in one embodiment) of contact portions 47 are formed. The contact portion 47 has a semi-circular axial plane and extends in the radial direction (hereinafter referred to as the "radial direction") of the cylindrical portion 42 from the inner peripheral surface 43 to the outer peripheral surface 44 of the cylindrical portion 42. The plurality of contact portions 47 are arranged at regular intervals in the circumferential direction of the cylindrical portion 42. Note that an R-shaped portion (reference numeral omitted) is formed between the contact portion 47 and the end face 45 of the cylindrical portion 42 to avoid forming an edge at the boundary between the contact portion 47 and the end face 45.

[0020] As shown in FIG. 1, the cushion portion 51 is received by the rod guide 13 when the piston rod 21 is extended. The cushion portion 51 is formed in the same shape as the cushion portion 41. That is, as shown in FIG. 3, the axial height of the cushion portion 51 is set to be higher than the axial height of the wire portion of the coil portion 31. The cushion portion 51 has a cylindrical portion 52 arranged coaxially with the coil portion 31.

[0021] As shown in FIG. 3 or FIG. 4, the outer diameter of the cylindrical portion 52 is set to be smaller than the inner diameter of the cylinder 2 and substantially the same as the outer diameter of the coil portion 31 when the rebound spring 30 is at its free length. The inner diameter of the cylindrical portion 52 is set to be smaller than the inner diameter of the coil portion 31 and larger than the outer diameter of the piston rod 21 (see FIG. 1). A plurality (four in the first embodiment) of protrusions 56 are formed on the inner peripheral surface 53 of the cylindrical portion 52. The plurality of protrusions 56 have spherical surfaces and are arranged at regular intervals in the circumferential direction of the inner peripheral surface 53. The plurality of protrusions 56 are formed so as to contact the outer peripheral surface 24 (see FIG. 1) of the inserted piston rod 21.

[0022] On the end face 55 of the cylindrical portion 52 on the side facing the rod guide 13 (see FIG. 1), a plurality (eight in one embodiment) of contact portions 57 are formed. The contact portions 57 have semi-circular axial planes and extend radially from the end face 55 of the cylindrical portion 52 across the inner peripheral surface 53 to the outer peripheral surface 54. The plurality of contact portions 57 are arranged at regular intervals in the circumferential direction of the cylindrical portion 52. Note that an R-shaped portion (reference numeral omitted) is formed between the contact portion 57 and the end face 55 of the cylindrical portion 52 to avoid forming an edge at the boundary between the contact portion 57 and the end face 55.

[0023] Here, in a conventional rebound spring, in the process of press-fitting a resin cushion into a coil spring (hereinafter referred to as the "resin cushion press-fitting process"), if the wound end of the metal coil spring and the resin cushion bite into each other, problems such as the occurrence of burrs and the resin cushion coming off due to incomplete press-fitting occur.

[0024] On the other hand, in the first embodiment, by insert molding the spring wire 32, the coil portion 31 and the cushion portions 41 and 51 are integrally formed, so that the above-described resin cushion press-fitting process can be abolished. Thereby, it is possible to eliminate problems such as the occurrence of burrs and the coming-off of the resin cushion caused by the biting of the wound end of the coil spring and the resin cushion in the resin cushion press-fitting process.

[0025] In addition, when a shock absorber equipped with a conventional rebound spring is applied to a strut type suspension device, when steering occurs in response to a vehicle steering operation, the cylinder of the shock absorber fixed to the hub carrier rotates with respect to the piston rod fixed to the vehicle body, and by extension, the rod guide fixed to the cylinder of the shock absorber rotates with respect to the stopper member fixed to the piston rod of the shock absorber.

[0026] That is, in a conventional shock absorber, when steering occurs in response to a vehicle steering operation, the resin cushion on the side received by the rod guide rotates with respect to the resin cushion on the side received by the stopper member. Therefore, in a conventional shock absorber, when steering occurs in a state where the piston rod is extended and the coil spring of the rebound spring is in close contact with the wire, torsion occurs on the side of the coil spring received by the resin cushion on the rod guide side, and the diameter of the rod guide side of the coil spring increases or decreases. As a result, wire displacement occurs between the coils, which causes damage to the rebound spring.

[0027] On the other hand, in the first embodiment, when the piston rod 21 is extended and the rebound spring 30 is contracted and the coil portion 31 is in a state of close contact with the wire, the convex portion 36 formed on the surface on one end side in the axial direction of the coil portion 31 is fitted into the concave portion 37 formed on the surface on the other end side in the axial direction of the coil portion 31. Therefore, it is possible to suppress wire displacement when the coil portion 31 is in close contact with the wire, and the durability of the rebound spring 30 can be improved.

[0028] Note that the first embodiment is not limited to the above-described form, and for example, it can be configured as follows. In the first embodiment, the cushion portion 41 on one end side in the axial direction and the cushion portion 51 on the other end side in the axial direction have the same shape, but the cushion portion 41 on one end side in the axial direction and the cushion portion 51 on the other end side in the axial direction can have different shapes. For example, by setting the axial height of the cylindrical portion 42 of the cushion portion 41 and the axial height of the cylindrical portion 52 of the cushion portion 51 to different heights, the cushion portion 41 and the cushion portion 51 can be set to have different load deflection characteristics. Further, by making the contact portion 47 of the cushion portion 41 and the contact portion 57 of the cushion portion 51 have different shapes (in the first embodiment, the cross-section by the axial plane is "semicircular") or quantities (in the first embodiment, "eight"), the cushion portion 41 and the cushion portion 51 can be set to have different load deflection characteristics. In the first embodiment, the rebounding spring 30 in which the coil portion 31 and the cushion portions 41 and 51 are integrally formed by insert molding the spring metal wire 32 is applied. However, the coil portion 31 and the cushion portions 41 and 51 may be integrally molded only by the resin material without using the spring metal wire 32. In the first embodiment, the convex portion 36 is formed on the surface on one axial end side of the coil portion 31, and the concave portion 37 is formed on the surface on the other axial end side of the coil portion 31. However, the convex portion 36 may be formed on the surface on the other axial end side of the coil portion 31, and the concave portion 37 may be formed on the surface on one axial end side of the coil portion 31 to form the rebounding spring 30.

[0029] (Second Embodiment) Next, the second embodiment will be described with reference to FIG. 5. Regarding the common parts with the first embodiment, the same names and reference numerals are used, and the overlapping descriptions are omitted. Further, in the second embodiment, the spring metal wire 32 is not used in the coil portion 31, that is, an aspect in which the coil portion 31 and the cushion portions 41 and 51 are integrally molded only by the resin material is illustrated.

[0030] In the first embodiment, when the piston rod 21 is extended and the rebound spring 30 is compressed so that the coil portion 31 is in a state of being in close contact with the wire, the convex portion 36 formed on the surface on the other end side in the axial direction of the coil portion 31 is fitted into the concave portion 37 formed on the surface on one end side in the axial direction of the coil portion 31, thereby suppressing the displacement of the wire of the coil portion 31. In the first embodiment, the cross sections of the convex portion 36 and the concave portion 37 in the axial plane are formed in an arc shape.

[0031] On the other hand, in the second embodiment, a convex portion 61 having a cross section in the axial plane that is triangular (an isosceles triangle with an obtuse apex angle) is formed on the surface on one end side in the axial direction of the coil portion 31, and on the other hand, a concave portion 62 having a cross section in the axial plane that is triangular is formed on the surface on the other end side in the axial direction of the coil portion 31. When the coil portion 31 is in a state of being in close contact with the wire, the rebound spring 30 is configured such that the convex portion 61 formed on the surface on one end side in the axial direction of the coil portion 31 is fitted into the concave portion 62 formed on the surface on the other end side in the axial direction of the coil portion 31. In the second embodiment, the same operational effects as those of the first embodiment described above can be obtained.

[0032] (Third Embodiment) Next, the third embodiment will be described with reference to FIG. 6. Regarding the common parts with the first embodiment, the same names and reference numerals are used, and redundant explanations are omitted. Further, in the third embodiment, a spring metal wire 32 is not used for the coil portion 31, that is, an embodiment in which the coil portion 31 and the cushion portions 41 and 51 are integrally formed only of a resin material is illustrated.

[0033] In the first embodiment, the cross sections of the convex portion 36 and the concave portion 37 in the axial plane are formed in an arc shape. In contrast, in the third embodiment, a convex portion 67 with a semi-circular cross-section in the axial plane is formed on the surface 65 on one end side in the axial direction of the coil portion 31, and on the other hand, a concave portion 68 with a semi-circular cross-section in the axial plane is formed on the surface 66 on the other end side in the axial direction of the coil portion 31. When the coil portion 31 is in a state of being in close contact with the wire, the convex portion 67 formed on the surface 65 on one end side in the axial direction of the coil portion 31 is fitted into the concave portion 68 formed on the surface 66 on the other end side in the axial direction of the coil portion 31, thus constituting the rebound spring 30.

[0034] The convex portion 67 is arranged at the center in the width direction (the left-right direction in the cross-section of the convex portion 67 shown in FIG. 6) of the surface 65 on one end side of the coil portion 31. The concave portion 68 is arranged at the center in the width direction (the left-right direction in the cross-section of the concave portion 68 shown in FIG. 6) of the surface 66 on the other end side of the coil portion 31. The radial length of the convex portion 67 and the concave portion 68 is set to be longer than the axial length. Also, the radial length of the concave portion 68 is set to be slightly larger than the radial length of the convex portion 67 in order to facilitate the fitting of the convex portion 67. In the third embodiment, the same operational effects as those of the first embodiment described above can be obtained.

[0035] (Fourth Embodiment) Next, the fourth embodiment will be described with reference to FIG. 7. Regarding the common parts with the first embodiment, the same names and reference numerals are used, and redundant explanations are omitted. Also, in the fourth embodiment, a spring metal wire 32 is not used for the coil portion 31, that is, an embodiment in which the coil portion 31 and the cushion portions 41 and 51 are integrally formed only by a resin material is illustrated.

[0036] In the first embodiment, the cross-sections of the convex portion 36 and the concave portion 37 in the axial plane are formed in an arc shape. In contrast, in the fourth embodiment, a convex portion 71 with a rectangular cross-section in the axial plane is formed on the surface 65 on one end side in the axial direction of the coil portion 31, and on the other hand, a concave portion 72 with a rectangular cross-section in the axial plane is formed on the surface 66 on the other end side in the axial direction of the coil portion 31. When the coil portion 31 is in a state of being in close contact with the wire, the convex portion 71 formed on the surface 65 on one end side in the axial direction of the coil portion 31 is fitted into the concave portion 72 formed on the surface 66 on the other end side in the axial direction of the coil portion 31, thus constituting the rebound spring 30.

[0037] The convex portion 71 is arranged at the center in the width direction (the left-right direction in the cross-section of the convex portion 71 shown in FIG. 7) of the surface 65 on one end side of the coil portion 31. The concave portion 72 is arranged at the center in the width direction (the left-right direction in the cross-section of the concave portion 72 shown in FIG. 7) of the surface 66 on the other end side of the coil portion 31. The radial length of the convex portion 71 and the concave portion 72 is set to be longer than the axial length. Also, the radial length of the concave portion 72 is set to be slightly larger than the radial length of the convex portion 71 in order to facilitate fitting with the convex portion 71. In the fourth embodiment, the same operational effects as those of the first embodiment described above can be obtained.

[0038] (Fifth Embodiment) Next, the fifth embodiment will be described with reference to FIG. 8. Regarding the common parts with the first embodiment, the same names and reference numerals are used, and duplicate explanations are omitted. Also, in the fifth embodiment, a spring metal wire 32 is not used for the coil portion 31, that is, an embodiment in which the coil portion 31 and the cushion portions 41 and 51 are integrally formed only of a resin material is illustrated.

[0039] In the first embodiment, the cross-sections of the convex portion 36 and the concave portion 37 in the axial plane are formed in an arc shape. In contrast, in the fifth embodiment, a convex portion 75 having a triangular cross-section (an isosceles triangle with an obtuse vertex angle) in an axial plane is formed on a surface 65 on one axial end side of the coil portion 31, and on the other hand, a concave portion 76 having a triangular cross-section in an axial plane is formed on a surface 66 on the other axial end side of the coil portion 31. When the coil portion 31 is in a state of being in close contact with a wire, the convex portion 75 formed on the surface 65 on one axial end side of the coil portion 31 is fitted into the concave portion 76 formed on the surface 66 on the other axial end side of the coil portion 31, thereby constituting the rebound spring 30.

[0040] The convex portion 75 is disposed at the center in the width direction (the left-right direction in the cross-section of the convex portion 75 shown in FIG. 8) of the surface 65 on one end side of the coil portion 31. The concave portion 76 is disposed at the center in the width direction (the left-right direction in the cross-section of the concave portion 76 shown in FIG. 8) of the surface 66 on the other end side of the coil portion 31. Further, the radial length of the concave portion 76 is set to be slightly larger than the radial length of the convex portion 75 in order to facilitate fitting with the convex portion 75. In the fifth embodiment, the same operational effects as those of the first embodiment described above can be obtained.

Description of Reference Numerals

[0041] 1 shock absorber, 2 cylinder, 2A first chamber, 2B second chamber, 4 piston, 21 piston rod, 22 first end, 23 second end, 25 stopper member, 30 rebound spring, 31 coil portion, 41, 51 cushion portion

Claims

1. A cylinder, a piston provided in the cylinder and partitioning the inside of the cylinder into a first chamber and a second chamber, a piston rod having a first end connected to the piston and a second end extending outside the cylinder, a rebound spring provided in the cylinder and into which the piston rod is inserted, and a stopper member fixed to the piston rod and restricting axial movement of the rebound spring with respect to the piston rod. The rebound spring is a shock absorber having a coil portion at least partially formed of a resin material and cushion portions provided at both axial ends and integrally formed with the coil portion.

2. The shock absorber according to Claim 1, wherein the coil portion has a single recess formed on one axial side and extending along the coil portion, and a single protrusion formed on the other axial side and extending along the coil portion and engageable with the recess.

3. The shock absorber according to Claim 1, wherein the shapes of the cushion portion on one axial end side and the cushion portion on the other axial end side are different.

4. The shock absorber according to Claim 1, wherein the coil portion is composed of a metal wire for a spring and the resin material covering the surface of the wire for the spring.

5. A rebound spring having a coil portion at least partially formed of a resin material and cushion portions provided at both axial ends and integrally formed with the coil portion, wherein the coil portion has a single recess formed on one axial side and extending along the coil portion, and a single protrusion formed on the other axial side and extending along the coil portion and engageable with the recess.

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