WO2009063304A1

WO2009063304A1 - Shock absorber component and shock absorber

Info

Publication number: WO2009063304A1
Application number: PCT/IB2008/003060
Authority: WO
Inventors: Ichisei Kamimura
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2007-11-15
Filing date: 2008-11-14
Publication date: 2009-05-22
Anticipated expiration: 2010-05-15
Also published as: JP2009121617A

Abstract

A floating piston (20) of a shock absorber includes a partition portion (22), a cylindrical guide portion (24) that is provided on the outer periphery of the partition portion (22), and a sealing member (26) that is provided on the outer periphery of the cylindrical guide portion (24). The sealing member (26) includes a plurality of circular lip portions (26a, 26b) that radially protrude outward, and the partition portion (22) is disposed in a region between the outermost circular lip portions (26a, 26b) in the direction perpendicular to the diameter of the sealing member (26).

Description

SHOCKABSORBER COMPONENTAND SHOCKABSORBER

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a shock absorber component and a shock absorber that includes the shock absorber component. More specifically, the invention relates to a shock absorber component and a shock absorber used in a suspension system for a vehicle.

2. Description of the Related Art

[0002] There is a shock absorber that absorbs a shock using hydraulic fluid flow resistance which is produced in accordance with a movement of a piston that slides in a cylinder. In a monotube shock absorber, which is a type of the above-described shock absorber, a floating piston, which serves as a shock absorber component, is slidably provided in a cylinder in order to partition the space within the cylinder into an upper space which is used as an oil chamber and a lower space which is used as a gas chamber. The oil chamber is filled with hydraulic oil, and a piston to which a rod is connected is provided in the oil chamber. The gas chamber is filled with high-pressure gas. [0003] The floating piston moves up and down in the cylinder in accordance with an up-and-down motion of the rod. The floating piston partitions the space within the cylinder into the oil chamber and the gas chamber to prevent a pressure drop that is caused if the high-pressure gas in the gas chamber is dissolved in the hydraulic oil in the oil chamber. Therefore, in order to efficiently operate the shock absorber and stably absorb a shock, the floating piston needs to move up and down smoothly in the cylinder and provide reliable sealing between the oil chamber and the gas chamber.

[0004] In order to provide a floating piston having the above-described features, for example, Japanese Unexamined Utility Model Application Publication No. 5-52385 (JP-UM-A-5-52385) proposes a sealing device for a shock absorber that includes a floating piston to which an oil seal including a seal ring and a metal ring is attached. The seal ring includes seal lips that have substantially wedge-shaped cross section. The metal ring has a substantially L-shaped cross section, and is embedded in the seal ring. In the sealing device for a shock absorber, the seal lips are brought into line contact with the cylinder. As a result, the floating piston further smoothly moves in the cylinder and more reliable sealing between an oil chamber and a gas chamber is provided.

[0005] However, the structure of the floating piston described in JP-UM- A-5-52385 is complicated, which causes complication of the manufacturing process of the floating piston.

SUMMARY OF THE INVENTION

[0006] The invention provides a shock absorber component and a shock absorber in which a sealing portion is formed by line contact between a cylinder and a shock absorber component with a simplified structure. [0007] A first aspect of the invention relates to a shock absorber component including a partition portion, a cylindrical guide portion that is provided on the outer periphery of the partition portion, and a sealing member that is provided on the outer periphery of the cylindrical guide portion. The sealing member includes a plurality of circular lip portions that radially protrude outward; and the partition portion is disposed in a region between the outermost circular lip portions among the plurality of circular lip portions in the direction perpendicular to the diameter of the sealing member.

[0008] According to the first aspect of the invention, it is possible to form the sealing portion in a cylinder using a line contact between the cylinder and the shock absorber component with the simplified structure. [0009] The cylindrical guide portion may have an outer face that is longer than a thickness of the partition portion in the axial direction of the cylindrical guide portion, and the sealing member may be disposed on the outer face. With this structure, it is possible to achieve highly accurate line contact between the sealing member and the inner face of the cylinder. As a result, reliable sealing is provided between the sealing member and the inner face of the cylinder.

[0010] A rib may be formed in a region of the partition portion, which contacts the cylindrical guide portion. With this structure, it is possible to further increase radial rigidity of the shock absorber component, thereby maintaining highly reliable line contact between the sealing member and the inner face of the cylinder.

[0011] The partition portion may be formed integrally with the cylindrical guide portion. In this case, the structure of the shock absorber component is further simplified.

[0012] A second aspect of the invention relates to a shock absorber including: a cylinder; a piston rod that is inserted into the cylinder; a piston that is connected to the piston rod; and the shock absorber component according to the first aspect of the invention, which is movably provided in the cylinder and which partitions a space within the cylinder into a first fluid chamber and a second fluid chamber.

[0013] According to the second aspect of the invention, it is possible to operate the shock absorber more efficiently, thereby achieving good shock-absorbing performance.

[0014] According to the aspects of the invention described above, it is possible to form the sealing portion by line contact between the cylinder and the shock absorber component with the simplified structure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The foregoing and further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein: FIG. 1 is a cross-sectional view schematically showing a shock absorber including a floating piston according to a first embodiment of the invention;

FIG. 2 is a cross-sectional view schematically showing the floating piston according to the first embodiment of the invention;

FIGs. 3 A to 3 C are cross-sectional views schematically showing floating pistons that differ from each other in the position at which a partition portion is disposed; and

FIG. 4 is a cross-sectional view schematically showing a floating piston according to a second embodiment of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0016] Hereafter, example embodiments of the invention will be described in detail with reference to the attached drawings. It should be noted that the same structural elements will be denoted by the same reference numerals in the description of the drawings, and the description concerning the structural elements having the same reference numerals will be provided only once below.

[0017] (First embodiment of the invention) FIG. 1 is a cross-sectional view schematically showing a shock absorber that includes a floating piston according to a first embodiment of the invention. As shown in FIG. 1, a shock absorber 10 according to the first embodiment of the invention is a monotube shock absorber for a vehicle. The shock absorber 10 includes a cylinder 12, a piston rod 14, a piston 16, a floating piston 20, and other components.

[0018] A rod guide 18 is provided in an opening that is formed at one end of the cylinder 12. A through-hole 18a is formed at the center of the rod guide 18, and the piston rod 14 is inserted through the through-hole 18a in a manner such that the piston rod 14 is slidable in the axial direction of the cylinder 12. The piston 16 is attached to one end of the piston rod 14 in such a manner that the piston 16 is slidable in the cylinder 12. An orifice 16a is formed in the piston 16. The floating piston 20 is provided in the cylinder 12 at a. position below the piston 16 in such a manner that the floating piston 20 is movable in the cylinder 12 in the axial direction of the cylinder 12. The space within the cylinder 12 is partitioned into an oil chamber 121 and a gas chamber 122 by the floating piston 20. The oil chamber 121 functions as a first fluid chamber that is filled with hydraulic oil, and the gas chamber 122 functions as a second fluid chamber that is filled with high-pressure gas. Further, the oil chamber 121 is partitioned into an upper chamber 121a and a lower chamber 121b by the piston 16. [0019] When the piston 16 moves in the cylinder 12 in the axial direction of the cylinder 12 while the shock absorber 10 undergoes an extension stroke and a compression stroke, the hydraulic oil flows back and forth between the upper chamber 121a and the lower chamber 121b through the orifice 16a. A damping force is produced by the fluid resistance that is generated when the hydraulic oil flows in the manner described above. As a result, a shock is absorbed. The "extension stroke" means a stroke during which the piston rod 14 moves in such a manner that a portion of the piston rod 14, which is positioned outside the cylinder 12, increases. The "compression stroke" means a stroke during which the piston rod 14 moves in such a manner that a portion of the piston rod 14, which is positioned outside the cylinder 12, decreases.

[0020] During the extension stroke, the piston rod 14 moves in such a manner that a portion of the piston rod 14, which is positioned inside the upper chamber 121a, decreases, and therefore the hydraulic pressure in the lower chamber 121b drops. On the other hand, during the compression stroke, the piston rod 14 moves in such a manner that a portion of the piston rod 14, which is positioned inside the upper chamber 121a, increases, and therefore the hydraulic pressure in the lower chamber 121b increases. During the extension stroke and the compression stroke, the floating piston 20 moves in the cylinder until the floating piston 20 reaches a position at which a balance between the pressure in the upper chamber 121a and the pressure in the lower chamber 121b is achieved.

[0021] Next, the structure of the floating piston 20 will be described in detail. FIG. 2 is a cross-sectional view schematically showing the floating piston 20 that serves as a shock absorber component according to the first embodiment of the invention. As shown in FIG. 2, the floating piston 20 includes a partition portion 22, a cylindrical guide portion 24, and a sealing member 26.

[0022] The partition portion 22 functions as a partition that partitions the space within the cylinder 12 into the oil chamber 121 and the gas chamber 122. The partition portion 22 is made of a metal, for example, iron or aluminum, or made of an elastic body, for example, a rubber member. A rib may be formed in a region of the partition portion 22 that contacts the cylindrical guide portion 24, which will be described later in detail, in order to minimize radial deformation of the floating piston 20. When the partition portion 22 is made of an elastic body, it is especially preferable to form a rib in the aforementioned region of the partition portion 22. In this way, the radial rigidity of the floating piston 20 increases, which makes it possible to minimize radial deformation of the floating piston 20. The shape of the rib is not specifically limited. For example, the rib may be a circular rib that is provided on the entire periphery of the partition portion 22 along an inner face of the cylindrical guide portion 24.

[0023] The cylindrical guide portion 24 is provided on the outer periphery of the partition portion 22. The cylindrical guide portion 24 is made of metal, for example, iron or aluminum, and the cylindrical guide portion 24 is bonded to the partition portion 22 by means of, for example, brazing. The cylindrical guide portion 24 has an outer face 24a that extends substantially in parallel with the inner face of the cylinder 12 and is longer in the axial direction of the cylinder 12 than the thickness of the partition portion 22 (that is, longer than the length of the partition portion 22 in the axial direction of the cylinder 12). Therefore, the floating piston 20 is guided by the cylindrical guide portion 24 when the floating piston 20 moves in the cylinder 12 in the axial direction thereof. In other words, even if the floating piston 20 is inclined with respect to the axial direction of the cylinder 12, the cylindrical guide portion 24 prevents the situation in which the floating piston 20 is out of proper alignment in the cylinder 12. As a result, the floating piston 20 continuously provides reliable sealing between the gas chamber 122 and the oil chamber 121 in the cylinder 12. Further, the cylindrical guide portion 24 increases rigidity of the floating piston 20 in the axial direction of the cylinder 12.

[0024] The sealing member 26 is provided on the outer periphery of the cylindrical guide portion 24. The sealing member 26 is attached to the outer face 24a of the cylindrical guide portion 24 by means of, for example, cure adhesion. The sealing member 26 has two circular lip portions 26a and 26b that protrude outward in the radial direction of the floating piston 20, and the circular lip portions 26a and 26b contact the inner face of the cylinder 12. With this structure, the floating piston 20 is brought into line contact with the inner face of the cylinder 12, thereby forming sealing portions. The sealing portions separate the hydraulic oil in the lower chamber 121b from the gas in the gas chamber 122. The sealing member 26 is formed on the outer face 24a that extends in parallel with the inner face of the cylinder 12 and is longer in the axial direction of the cylinder 12 than the thickness of the partition portion 22. Therefore, it is possible to provide highly reliable sealing between sealing member 26 and the inner face of the cylinder 12. That is, highly accurate line contact between the sealing member 26 and the cylinder 12 is achieved. The sealing member 26 is made of plastic material, for example, rubber. [0025] The partition portion 22 is disposed in a region (indicated by an arrow A in

FIG. 2) between the circular lip portions 26a and 26b in the direction perpendicular to the diameter of the sealing member 26. More specifically, the partition portion 22 is disposed at substantially the center position between the peak portions of the circular lip portions 26a and 26b. Further, it is preferable to dispose the partition portion 22 in such a manner that the partition portion 22 passes through the center of gravity of the floating piston 20.

[0026] FIGs. 3A to 3C are cross-sectional views schematically showing floating pistons that differ from each other in the position at which the partition portion 22 is disposed. The floating piston shown in FIG. 3A includes the partition portion 22 that is disposed at the upper end of the sealing member 26, and the floating piston shown in FIG. 3 C includes the partition portion 22 that is disposed at the lower end of the sealing member 26. In contrast, the floating piston shown in FIG. 3B includes the partition portion 22 that is disposed at substantially the center position of the cylindrical guide portion 24 in the axial direction of the cylinder 12, that is, at a position in the region between the circular lip portions 26a and 26b. The floating piston shown in FIG. 3B corresponds to the floating piston 20 according to the first embodiment of the invention.

[0027] When the floating piston is inclined with respect to the axial direction of the cylinder 12 as shown in FIGs. 3 A to 3C, a force, directed inward in the radial direction of the floating piston, is applied from the inner face of the cylinder 12 to a portion of the peak portion of the circular lip portion 26a, which is shown on the left side in the FIGs. 3A to 3C, and to a portion of the peak portion of the circular lip portion 26b, which is shown on the right side in FIGs. 3 A to 3 C. Therefore, in the floating piston that includes the partition portion 22 which is disposed at the upper end of the cylindrical guide portion 24 shown in FIG. 3A, large bending stress is applied to a portion of the sealing member 26, which is shown on the right side in FIG. 3A. In the floating piston that includes the partition portion 22 which is disposed at the lower end of the cylindrical guide portion 24 shown in FIG. 3 C, large bending stress is applied to a portion of the sealing member 26, which is shown on the left side in FIG. 3C. In contrast, in the floating piston 20 that includes the partition portion 22 which is disposed in the region between the circular lip portions 26a and 26b, bending stress that is applied to the sealing member 26 is smaller than that in each of the floating pistons shown in FIGs. 3 A and 3C. Therefore, it is possible to increase the radial rigidity of the floating piston 20 by disposing the partition portion 22 between the circular lip portions 26a and 26b. Further, this structure maintains the state where the pressing force that is applied the circular lip portion 26a is substantially equal to the pressing force that is applied to the circular lip portion 26b. Therefore, it is possible to maintain highly accurate line contact between the circular lip portions 26a and 26b and the cylinder 12. Further, it is experimentally verified that a leverage force that is generated when the floating piston 20 is inclined is reduced by disposing the partition portion 22 between the circular lip portions 26a and 26b.

[0028] According to the first embodiment of the invention described above, it is possible to form the sealing portions using the line contact between the sealing member and the cylinder with a simplified structure. Moreover, it is possible to provide a lighter and smaller floating piston, which requires a smaller installation space. Further, it is possible to manufacture the floating piston by a simple manufacturing process, and consequently, it is possible to reduce the manufacturing cost.

[0029] Further, because the sealing member is provided on the face of the cylindrical guide portion that extends in parallel with the inner face of the cylinder, highly accurate line contact between the sealing member and the inner face of the cylinder is achieved. As a result, reliable sealing is maintained between the gas chamber and the oil chamber. Accordingly, the shock absorber operates more efficiently, and therefore, good shock-absorbing performance is achieved. [0030] (Second embodiment of the invention) FIG. 4 is a cross-sectional view schematically showing a floating piston that serves as a shock absorber component according to a second embodiment of the invention. The floating piston according to the second embodiment has mostly the same structure as that of the floating piston 20 according to the first embodiment of the invention except that the partition portion and the cylindrical guide portion are formed integrally with each other.

[0031] As shown in FIG. 4, the floating piston 20 according to the second embodiment of the invention has a structure in which the partition portion 22 is formed integrally with the cylindrical guide portion 24. The partition portion 22 and the cylindrical guide portion 24 may be formed integrally with each other by, for example, press-molding using metal material, for example, iron or aluminum. The press-molded cylindrical guide portion 24 includes a folded portion 24b. With this folded portion 24b, the radial rigidity of the floating piston 20 is increased. Further, the partition portion 22 is made of metal material. Therefore, according to the second embodiment of the invention, it is possible to minimize radial deformation of the floating piston 20 without formation of a rib in the partition portion 22. However, the partition portion 22 may be provided with a rib.

[0032] According to the second embodiment of the invention described above, the partition portion and the cylindrical guide portion of the floating piston are formed integrally with each other. Therefore, it is possible to further simplify the structure of the floating piston (more specifically, the floating piston is formed by just bonding one metal plate that constitutes the partition portion 22 and one sealing member 26 to each other by means of, for example, cure adhesion). Accordingly, it is possible to further simplify the manufacturing process of the floating piston.

[0033] While the invention has been described with reference to example embodiments thereof, it is to be understood that the invention is not limited to the described embodiments or constructions. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. For example, in the aforementioned embodiments of the invention, the floating piston includes two circular lip portions. However, the number of the circular lip portions is not limited to two. Any number of the circular lip portions may be formed as long as there are at least two circular lip portions. The number of the circular lip portions may be changed on an as-required basis in accordance with, for example, the desired sealing performance and cost. It should be noted that, if the floating piston includes three or more circular lip portions, the partition portion is disposed in a region between the outermost circular lip portions. Here, the "outermost circular lip portions" mean the uppermost circular lip portion and the lowermost circular lip portion in the axial direction of the cylinder.

[0034] Further, according to the aforementioned embodiments of the invention, the invention is applied to a monotube shock absorber. However, the invention may be applied not only to a monotube shock absorber but also any type of shock absorber as long as the shock absorber has a gas chamber that is separated from an oil chamber. For example, the invention may be applied to a twin-tube shock absorber and a triple-tube shock absorber, as long as the shock absorber has a gas chamber that is separated from an oil chamber.

Claims

CLAIMS:

1. A shock absorber component including a partition portion (22), a cylindrical guide portion (24) that is provided on an outer periphery of the partition portion, and a sealing member (26) that is provided on an outer periphery of the cylindrical guide portion, wherein: the sealing member (26) includes a plurality of circular lip portions (26a, 26b) that radially protrude outward; and the partition portion (22) is disposed in a region between the outermost circular lip portions (26a, 26b) among the plurality of circular lip portions in a direction perpendicular to a diameter of the sealing member (26).

2. The shock absorber component according to claim 1, wherein: the cylindrical guide portion (24) has an outer face that is longer than a thickness of the partition portion (22) in an axial direction of the cylindrical guide portion; and the sealing member (26) is disposed on the outer face.

3. The shock absorber component according to claim 1 or 2, wherein a rib is formed in a region of the partition portion (22), which contacts the cylindrical guide portion (24).

4. The shock absorber component according to any one of claims 1 to 3, wherein the partition portion (22) is formed integrally with the cylindrical guide portion (24).

5. The shock absorber component according to any one of claims 1 to 4, wherein: the number of the circular lip portions (26a, 26b) of the sealing member (26) is two; and the partition portion (22) is disposed between the two circular lip portions.

6. The shock absorber component according to any one of claims 1 to 5, wherein the sealing member (26) is bonded to the cylindrical guide portion (24) by means of cure adhesion.

7. The shock absorber component according to any one of claims 1 to 6, wherein the cylindrical guide portion (24) is bonded to the partition portion by means of brazing.

8. A shock absorber comprising: a cylinder (12); a piston rod (14) that is inserted into the cylinder; a piston (16) that is connected to the piston rod; and the shock absorber component according to any one of claims 1 to 4, which is movably provided in the cylinder and which partitions a space within the cylinder into a first fluid chamber (121) and a second fluid chamber (122).

9. The shock absorber according to claim 8, wherein: the first fluid chamber (121) is a liquid chamber; and the second fluid chamber (122) is a gas chamber.

10. A vehicle suspension system, comprising the shock absorber according to claim 8 or 9.

11. A shock absorber component comprising: a partition portion (22); a cylindrical guide portion (24) that is provided on an outer periphery of the partition portion; and a sealing member (26) that is provided on an outer periphery of the cylindrical guide portion, wherein the sealing member includes a plurality of circular lip portions (26a, 26b) that protrude radially outward, and the partition portion (22) is disposed in a region between the outermost circular lip portions (26a, 26b) among the plurality of circular lip portions in a direction perpendicular to a diameter of the sealing member.