Shock absorber

Abstract

Provided is a shock absorber which prevents air from entering a damping force adjustment mechanism. In the present invention, the radial outer side (reservoir chamber side) opening of a hole (second hole) of a common communication passage (second communication passage) by which a damping force adjustment mechanism and a reservoir chamber are in communication is configured to be lower than the liquid level height of the reservoir chamber when a shock absorber is disposed so as to be horizontal. It is therefore possible to suppress entry of air inside the reservoir chamber into the common communication passage through the hole of the common communication passage and thus suppress entry of air inside the reservoir chamber into the damping force adjustment mechanism via the common communication passage.

Description

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[0001] The present invention relates to a shock absorber that adjusts damping force by controlling the flow of hydraulic fluid relative to the stroke of a piston rod.

[0002] Patent Document 1 discloses a shock absorber (hereinafter referred to as a "conventional shock absorber") in which an extension damping force generating mechanism and a compression damping force generating mechanism are arranged at a distance along the axial direction of the cylinder.

[0003] International Publication No. 2018 / 216716

[0004] In conventional shock absorbers, one end of a passage that communicates with a damping force generation mechanism (hereinafter referred to as the "damping force adjustment mechanism") opens to a reservoir chamber at the other end, so if the shock absorber is oriented sideways with the center line of the cylinder horizontal, there is a risk that air in the reservoir chamber will enter the damping force adjustment mechanism via the passage. Therefore, after the air in the damping force adjustment mechanism is purged during the inspection process, conventional shock absorbers must be maintained in a vertical orientation with the center line vertical to prevent air from entering the damping force adjustment mechanism during transportation and assembly into the vehicle.

[0005] An object of the present invention is to provide a shock absorber in which air does not enter a damping force adjusting mechanism.

[0006] The shock absorber of the present invention is characterized by comprising: a cylinder having an outer tube and an inner tube provided inside the outer tube and containing hydraulic fluid; an annular reservoir chamber defined between the outer tube and the inner tube and containing the hydraulic fluid and a gas; a piston slidably inserted into the inner tube and dividing the inner tube into two fluid chambers; a piston rod connected to the piston at one axial side and having the other axial side protruding to the outside of the cylinder; a damping force adjustment mechanism protruding radially outward from the outer tube and capable of adjusting a damping force; a first communication passage connecting the damping force adjustment mechanism to the inside of the inner tube; and a second communication passage having a passage member one end connected to the damping force adjustment mechanism and the other end connected to the reservoir chamber at a circumferentially different position from the damping force adjustment mechanism, connecting the damping force adjustment mechanism to the reservoir chamber.

[0007] According to one embodiment of the present invention, it is possible to provide a shock absorber in which air does not enter the damping force adjusting mechanism.

[0008] Fig. 1 is a conceptual diagram of a shock absorber according to the present embodiment; Fig. 2 is an enlarged view of a main part in Fig. 1; Fig. 3 is a conceptual diagram of a shock absorber in which the center line of the cylinder is arranged horizontally, and is a cross-sectional view taken along a plane perpendicular to the axis of the cylinder that includes the center lines of a hole (second hole) and a port (first hole); Fig. 4 is a conceptual diagram of a shock absorber in which the center line of the cylinder is arranged horizontally, and is a cross-sectional view taken along a plane perpendicular to the axis of the cylinder that includes the center lines of a hole (second hole) and a port (first hole) when the lower end position of the cylinder and the lower end position of the damping force adjusting mechanism are located on the same plane.

[0009] An embodiment of the present invention will be described with reference to the accompanying drawings. In this embodiment, a bi-flow type vertical motion damper (hereinafter referred to as "shock absorber 1") that is attached between the carbody and the bogie of a railway vehicle is illustrated. However, the shock absorber 1 can also be used as a lateral motion damper or a yaw damper. FIG. 1 is a conceptual diagram of the shock absorber 1, and is a cross-sectional view of the shock absorber 1 taken along an axial plane. For convenience, the upper and lower sides in FIG. 1 will be referred to as the upper and lower sides.

[0010] As shown in FIG. 1 , the shock absorber 1 has a cylinder 2 in which an outer cylinder 3 and an inner cylinder 4 are arranged coaxially. The cylinder 2 has a reservoir chamber 5 formed between the outer cylinder 3 and the inner cylinder 4. A piston 6 is slidably inserted into the inner periphery of the inner cylinder 4. The piston 6 divides the interior of the inner cylinder 4 into two liquid chambers: an upper liquid chamber 2A and a lower liquid chamber 2B. The lower end side (one axial side) of a piston rod 7 is connected to the piston 6. The upper end side (other axial side) of the piston rod 7 is inserted into a rod guide 8 attached to the upper end of the cylinder 2 and protrudes outside the cylinder 2. The rod guide 8 closes the opening on the upper end side of the cylinder 2.

[0011] The piston 6 has a relief valve 9 that opens when the pressure in the upper fluid chamber 2A of the cylinder 2 reaches a set pressure during the extension stroke, releasing the pressure in the upper fluid chamber 2A to the lower fluid chamber 2B. The piston 6 has a relief valve 10 that opens when the pressure in the lower fluid chamber 2B of the cylinder 2 reaches a set pressure during the compression stroke, releasing the pressure in the lower fluid chamber 2B to the upper fluid chamber 2A. The piston 6 also has an orifice passage 11 that constantly connects the upper fluid chamber 2A and the lower fluid chamber 2B of the cylinder 2.

[0012] An upper end 19 of the inner cylinder 4 is fitted into an annular recess 17 formed in the rod guide 8. A base valve 13 is provided at a lower end 12 of the inner cylinder 4, separating the lower fluid chamber 2B of the cylinder 2 from the reservoir chamber 5. The base valve 13 has a check valve 14 that allows only the flow of hydraulic fluid from the reservoir chamber 5 to the lower fluid chamber 2B of the cylinder 2. The base valve 13 has a relief valve 15 that opens when the pressure in the lower fluid chamber 2B of the cylinder 2 reaches a set pressure, and releases the pressure in the lower fluid chamber 2B to the reservoir chamber 5. The upper fluid chamber 2A and lower fluid chamber 2B of the cylinder 2 are filled with hydraulic fluid, and the reservoir chamber 5 is filled with hydraulic fluid and gas.

[0013] The shock absorber 1 has a damping force adjustment mechanism 30 that protrudes radially outward from the outer cylinder 3 (to the "right" in FIG. 1 ) and adjusts the damping force by controlling the flow of hydraulic fluid relative to the stroke of the piston rod 7. The damping force adjustment mechanism 30 has a housing 31 that is fixed to a base block 18 that is provided radially outward from the outer cylinder 3, and an extension-side mechanism 32 and a compression-side mechanism 33 that are housed in the housing 31. The extension-side mechanism 32 and the compression-side mechanism 33 have the same basic structure as the extension-side damping force generating mechanism and the compression-side damping force generating mechanism in a conventional shock absorber. Therefore, to simplify the description of this specification, detailed explanations of the extension-side mechanism 32 and the compression-side mechanism 33 will be omitted.

[0014] The extension-side mechanism 32 is connected to the upper fluid chamber 2A of the cylinder 2 via an extension-side communication passage 34 (first communication passage). The extension-side communication passage 34 has a passage 64 and an annular passage 66 formed in the extension-side passage member 36, and a plurality of holes 20 (only two are shown in FIG. 1 ) formed in the upper end 19 of the inner cylinder 4. The holes 20 are arranged at equal intervals around the circumference of the cylinder 2.

[0015] 1 or 2, the extension-side passage member 36 has a straight tube 38 and a separator tube 40. A radially outer end 42 of the straight tube 38 is connected to a port 46 formed in the outer cylinder 3 and the base block 18, and a radially inner end 44 is connected to a port 48 formed in the separator tube 40. A seal member 50 (O-ring) seals the radially outer end 42 of the straight tube 38 and the port 46, and a seal member 52 (O-ring) seals the radially inner end 44 of the straight tube 38 and the port 48.

[0016] The separator tube 40 is formed in a cylindrical shape coaxial with the cylinder 2 and is provided on the outer periphery of the upper part of the inner tube 4. An annular passage 66 is formed between the separator tube 40 and the inner tube 4. The separator tube 40 has an inner flange-shaped fitting portion 54 that fits onto the upper end portion 19 of the inner tube 4, and an inner flange-shaped fitting portion 56 that fits onto an intermediate portion (reference numeral omitted) of the inner tube 4. The fitting portion 54 of the separator tube 40 and the inner tube 4 are sealed by a seal member 58 (O-ring), and the fitting portion 56 of the separator tube 40 and the inner tube 4 are sealed by a seal member 60 (O-ring).

[0017] As shown in Figure 1, the compression side mechanism 33 is connected to the lower fluid chamber 2B of the cylinder 2 by a compression side communication passage 35 (first communication passage). The compression side communication passage 35 has a passage 65 and an annular passage 67 formed in the compression side passage member 37, and a plurality of holes 21 (only two are shown in Figure 1) formed in the lower end 12 of the inner cylinder 4. The holes 21 are arranged at equal intervals around the circumference of the cylinder 2.

[0018] 1 or 2, the compression-side passage member 37 has a straight tube 39 and a separator tube 41. A radially outer end 43 of the straight tube 39 is connected to a port 47 formed in the outer cylinder 3 and the base block 18, and a radially inner end 45 is connected to a port 49 formed in the separator tube 41. The radially outer end 43 of the straight tube 39 and the port 47 are sealed by a seal member 51 (O-ring), and the radially inner end 45 of the straight tube 39 and the port 49 are sealed by a seal member 53 (O-ring).

[0019] The separator tube 41 is formed in a cylindrical shape coaxial with the cylinder 2 and is provided on the outer periphery of the lower end 12 of the inner tube 4. An annular passage 67 is formed between the separator tube 41 and the inner tube 4. The separator tube 41 has an inner flange-shaped fitting portion 55 that fits onto the outer periphery of the inner tube 4, and an inner flange-shaped fitting portion 57 that fits onto the lower end 12 of the inner tube 4. The fitting portion 55 of the separator tube 41 and the inner tube 4 are sealed by a seal member 59 (O-ring), and the fitting portion 57 of the separator tube 41 and the inner tube 4 are sealed by a seal member 61 (O-ring).

[0020] 1, the damping force adjusting mechanism 30 has a mechanism section communication passage 70 that connects the extension side mechanism section 32 and the compression side mechanism section 33, a common passage 71 connected to the mechanism section communication passage 70, and a common communication passage 72 (second communication passage) that connects the common passage 71 with the reservoir chamber 5 and thereby connects the extension side mechanism section 32 and the compression side mechanism section 33 with the reservoir chamber 5. The common communication passage 72 has a passage 74, an annular passage 75, and a hole 76 (second hole) formed in a common passage member 73 (passage member).

[0021] 1 or 2, the common passage member 73 has a straight tube 77 and a separator tube 78. A radially outer end 79 of the straight tube 77 is connected to a port 81 formed in the outer cylinder 3 and the base block 18, and a radially inner end 80 is connected to a port 82 (first hole) formed in the separator tube 78. The radially outer end 79 of the straight tube 77 and the port 81 are sealed by a seal member 83 (O-ring), and the radially inner end 80 of the straight tube 77 and the port 82 are sealed by a seal member 84 (O-ring).

[0022] The separator tube 78 is formed in a cylindrical shape coaxial with the cylinder 2 and is provided on the outer periphery of the inner tube 4. An annular passage 75 is formed between the separator tube 78 and the inner tube 4. The separator tube 78 has an inner flange-shaped fitting portion 85 formed on the upper end side that fits onto the outer periphery of the inner tube 4, and an inner flange-shaped fitting portion 86 formed on the lower end side that fits onto the inner tube 4. The fitting portion 85 of the separator tube 78 and the inner tube 4 are sealed by a seal member 87 (O-ring), and the fitting portion 86 of the separator tube 78 and the inner tube 4 are sealed by a seal member 88 (O-ring).

[0023] As shown in FIG. 1 , the separator tube 78 has a boss portion 89 that protrudes radially outward. A port 82 that opens toward the damping force adjustment mechanism 30 (the "right side" in FIG. 1 ) is formed on the inner periphery (inside) of the boss portion 89. The hole 76 of the common communication passage 72 is formed in the side wall of the separator tube 78 on the opposite side to the port 82 (the "left side" in FIG. 1 ). In other words, the hole 76 (second hole) is positioned to face the port 82 (first hole) across the center line of the cylinder 2. The center line of the hole 76 (second hole) is positioned on the same straight line as the center line of the port 82 (first hole).

[0024] 1 or 2 , the separator tube 78 of the common passage member 73 has an upper end face 90 that is parallel to a plane perpendicular to the center line of the cylinder 2 (hereinafter referred to as the “axis-perpendicular plane of the cylinder 2”), and a lower end face 91 that is parallel to the axis-perpendicular plane of the cylinder 2. On the other hand, the separator tube 40 of the extension-side passage member 36 has an end face 92 that is parallel to the axis-perpendicular plane of the cylinder 2 and that is in surface contact with the upper end face 90 of the separator tube 78 of the common passage member 73.

[0025] The separator tube 41 of the compression-side passage member 37 is parallel to the plane perpendicular to the axis of the cylinder 2 and has an end surface 93 that is in surface contact with a lower end surface 91 of the separator tube 78 of the common passage member 73. The center lines of the ports 48 formed in the separator tube 40, the center lines of the ports 49 formed in the separator tube 41, and the center line of the ports 82 (first holes) formed in the separator tube 78 are all disposed on the same plane and are parallel to one another.

[0026] Next, the operation of this embodiment will be described. During the compression stroke of the piston rod 7, the hydraulic fluid in the lower fluid chamber 2B of the cylinder 2 flows into the compression mechanism 33 of the damping force adjusting mechanism 30 via the compression communication passage 35 (first communication passage), thereby generating a compression damping force. The hydraulic fluid that flows out of the compression mechanism 33 flows into the reservoir chamber 5 via the mechanism communication passage 70, the common passage 71, and the common communication passage 72 (second communication passage).

[0027] During the compression stroke, hydraulic fluid equivalent to the volume displaced by the piston 6 flows from the lower fluid chamber 2B via the compression-side communicating passage 35 (first communicating passage), the mechanism communicating passage 70, and the extension-side communicating passage 34 (first communicating passage) to the upper fluid chamber 2A of the cylinder 2. When the pressure in the lower fluid chamber 2B of the cylinder 2 reaches the valve opening pressure of the relief valve 10 of the piston 6, the relief valve 10 opens to release the pressure in the lower fluid chamber 2B to the upper fluid chamber 2A, thereby preventing an excessive pressure increase in the lower fluid chamber 2B. When the pressure in the lower fluid chamber 2B of the cylinder 2 reaches the valve opening pressure of the relief valve 15 of the base valve 13, the relief valve 15 opens to release the pressure in the lower fluid chamber 2B to the reservoir chamber 5, thereby preventing an excessive pressure increase in the lower fluid chamber 2B.

[0028] During the extension stroke of the piston rod 7, the hydraulic fluid in the upper fluid chamber 2A of the cylinder 2 flows into the extension-side mechanism 32 of the damping force adjusting mechanism 30 via the extension-side communication passage 34 (first communication passage), thereby generating an extension-side damping force. The hydraulic fluid that flows out of the extension-side mechanism 32 flows into the reservoir chamber 5 via the mechanism communication passage 70, the common passage 71, and the common communication passage 72 (second communication passage).

[0029] During the extension stroke, hydraulic fluid equivalent to the volume displaced by the piston 6 flows from the reservoir chamber 5 through the common communication passage 72 (second communication passage), the common passage 71, the mechanism communication passage 70, and the compression-side communication passage 35 (first communication passage) to the lower fluid chamber 2B of the cylinder 2. Here, when the pressure in the upper fluid chamber 2A of the cylinder 2 reaches the valve opening pressure of the relief valve 9 of the piston 6, the relief valve 9 opens to release the pressure in the upper fluid chamber 2A to the lower fluid chamber 2B, thereby preventing an excessive pressure rise in the upper fluid chamber 2A.

[0030] 3 is a conceptual diagram of the shock absorber 1 in which the center line of the cylinder 2 is arranged horizontally, and is a cross-sectional view of the shock absorber 1 taken along a plane perpendicular to the axis of the cylinder 2 that includes the center lines of the hole 76 (second hole) and the port 82 (first hole) formed in the separator tube 78 of the common passage member 73. In FIG. 3, for convenience, the lower end position of the damping force adjusting mechanism 30 is shown lower than the lower end position of the cylinder 2 (outer cylinder 3).

[0031] 3, in this embodiment, when the lower end position of the opening 95 on the radially outer side (reservoir chamber 5 side) of the hole 76 (second hole) is located at the fluid level height H1 of the reservoir chamber 5, the upper end position of the opening 96 on the radially inner side (annular passage 75 side) of the hole 76 is set to be lower than the fluid level height H1 of the reservoir chamber 5. Note that hydraulic fluid is injected into the reservoir chamber 5 such that when the piston rod 7 is extended to its maximum length, that is, when the amount of hydraulic fluid in the reservoir chamber 5 is at its lowest, the fluid level H1 of the reservoir chamber 5 is higher than half the height H2 of the reservoir chamber 5.

[0032] In a conventional shock absorber, one end of a passage that communicates with the damping force adjustment mechanism opens to a reservoir chamber at the other end, so if the shock absorber is placed sideways (with the center line of the cylinder positioned horizontally), there is a risk that air in the reservoir chamber will enter the damping force adjustment mechanism via the passage. Therefore, after the air in the damping force adjustment mechanism is purged during the inspection process, conventional shock absorbers must be kept in a vertical position (with the center line positioned vertically) to prevent air from entering the damping force adjustment mechanism during transportation and assembly into the vehicle.

[0033] In contrast to this, in this embodiment, when the shock absorber 1 is placed sideways so that the lower end position of the damping force adjustment mechanism 30 and the lower end position of the cylinder 2 are located on the same horizontal plane, as shown in Figure 4, the opening 95 on the radially outer side (reservoir chamber 5 side) of the hole 76 (second hole) of the common communication passage 72 (second communication passage) that communicates between the damping force adjustment mechanism 30 and the reservoir chamber 5 becomes lower than the liquid level height H1 of the reservoir chamber 5.

[0034] According to this embodiment, when the shock absorber 1 is placed in a horizontal position, the hole 76 (second hole) of the common communication passage 72 (second communication passage) opens into the working fluid sealed in the reservoir chamber 5, which prevents air in the reservoir chamber 5 from entering the common communication passage 72 through the hole 76 of the common communication passage 72, and ultimately prevents air in the reservoir chamber 5 from entering the damping force adjusting mechanism 30 via the common communication passage 72. In this way, in this embodiment, there is no need to maintain the shock absorber 1 in a vertical position, which makes it easy to handle the shock absorber 1 during transportation and installation into a vehicle.

[0035] In this embodiment, the upper end face 90 of the separator tube 78 of the common passage member 73 (passage member) is in surface contact with the lower end face 92 of the separator tube 40 of the extension-side passage member 36, and the lower end face 91 of the separator tube 78 is in surface contact with the upper end face 93 of the separator tube 41 of the compression-side passage member 37.

[0036] As a result, the error in the relative position in the axial direction of the cylinder 2 between the port 82 (first hole) formed in the separator tube 78, the port 48 formed in the separator tube 40, and the port 49 formed in the separator tube 41 depends on the processing error of each separator tube 78, 40, 41. In other words, the relative positions of the separator tubes 78, 40, 41 are determined with high precision.

[0037] Therefore, in this embodiment, when assembling the damping force adjustment mechanism 30 to the cylinder 2, that is, when connecting the end 79 of the straight tube 77 protruding from the cylinder 2 to the port 81 on the damping force adjustment mechanism 30 side and at the same time connecting the ends 44, 45 of the straight tubes 38, 39 protruding from the damping force adjustment mechanism 30 to the ports 48, 49 on the cylinder 2 side, it is possible to easily insert each of the straight tubes 77, 38, 39 into the corresponding ports 81, 48, 39, thereby improving the ease of assembly of the shock absorber 1.

[0038] Furthermore, when inserting the rod guide 8 into the cylinder 2 during the assembly process of the shock absorber 1, the straight tube 77 is inserted in advance into the port 82 (first hole) of the separator tube 78 attached to the outer periphery of the inner cylinder 4 and into the port 81 formed in the outer cylinder 3 and the base block 18. This ensures concentricity of the inner cylinder 4 with respect to the outer cylinder 3, making it possible to easily fit the upper end 19 of the inner cylinder 4 into the annular recess 17 formed in the rod guide 8, thereby improving the assembly ease of the shock absorber 1.

[0039] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0040] This application claims priority to Japanese Patent Application No. 2023-166111, filed September 27, 2023. The entire disclosure of Japanese Patent Application No. 2023-166111, filed September 27, 2023, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety.

[0041] REFERENCE SIGNS LIST 1 shock absorber, 2 cylinder, 2A upper fluid chamber (fluid chamber), 2B lower fluid chamber (fluid chamber), 3 outer cylinder, 4 inner cylinder, 5 reservoir chamber, 6 piston, 7 piston rod, 30 damping force adjustment mechanism, 34 extension side communication passage (first communication passage), 35 compression side communication passage (first communication passage), 72 common communication passage (second communication passage), 73 common passage member (passage member)

Claims

1. A shock absorber comprising: a cylinder having an outer tube and an inner tube provided inside the outer tube and containing hydraulic fluid; a ring-shaped reservoir chamber defined between the outer tube and the inner tube and containing the hydraulic fluid and a gas; a piston slidably inserted into the inner tube and dividing the inner tube into two fluid chambers; a piston rod having one axial side connected to the piston and the other axial side protruding to the outside of the cylinder; a damping force adjustment mechanism protruding radially outward from the outer tube and capable of adjusting a damping force; a first communication passage connecting the damping force adjustment mechanism with the inside of the inner tube; and a second communication passage having a passage member one end connected to the damping force adjustment mechanism and the other end connected to the reservoir chamber at a circumferentially different position from the damping force adjustment mechanism, connecting the damping force adjustment mechanism with the reservoir chamber.

2. A shock absorber as described in claim 1, wherein the passage member has a first hole that opens to the damping force adjustment mechanism side and a second hole that opens to the reservoir chamber side, and the second hole is provided at a position opposite to the first hole across the center line of the cylinder.

3. A shock absorber as described in claim 2, wherein the passage member has an annular passage provided on the outer periphery of the inner cylinder and communicating the first hole and the second hole, and when the center line of the cylinder is arranged horizontally and the lower end of the opening of the second hole on the reservoir chamber side is positioned at the liquid level of the working fluid in the reservoir chamber, the opening of the second hole on the annular passage side is formed at a position lower than the liquid level.

4. A shock absorber as claimed in claim 2, characterized in that the hydraulic fluid is injected so that when the centre line is positioned horizontally and the piston rod is extended to its maximum length, the fluid level in the reservoir chamber becomes higher than half the height in the reservoir chamber.

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