Cylinder device

Abstract

Cylinder device comprising: an outer tube (3) having a chamber (2A, 2B, 116, 117) with a hydraulic fluid sealed therein, the outer tube (3) having a first and a second end spaced from the first end in the axial direction of the outer tube (3), the first end being open, a piston (5) provided in the chamber (2A, 2B, 116, 117) of the outer tube (3), a piston rod (6) connected to the piston (5) and projecting from the outer tube (3) through the first end of the outer tube (3), an annular seal housing (27) provided in the outer tube (3) at a position closer to the first end, the seal housing (27) having an inner peripheral portion and an outer peripheral portion, a first outer peripheral seal (43) provided between the outer tube (3) and the outer peripheral portion of the seal housing (27), the first outer peripheral seal (43) sealing between the outer tube (3) and the seal housing (27), a second outer peripheral seal (40) provided between the outer tube (3) and the outer peripheral portion of the seal housing (27), the second outer peripheral seal (40) sealing between the outer tube (3) and the seal housing (27), an annular rod seal (33) provided on an inner peripheral portion of the seal housing (27) in sliding contact with the piston rod (6), and an annular oil seal (9) provided on a side of the seal housing (27) closer to the first end, the annular oil seal (9) being in sliding contact with the piston rod (6), wherein the piston rod (6) is sealed in two stages by the rod seal (33) and the oil seal (9), wherein the outer peripheral portion of the seal housing (27) is provided with an outer peripheral groove (37) and is secured to the outer pipe (3) by a first notched portion (38) formed by notching the outer pipe (3) from the outside into the outer peripheral groove (37) in a radial direction of the outer pipe (3), and wherein the outer peripheral portion of the seal housing (27) on a side thereof closer to the chamber (2A, 117) receives a pressure which is the same as a pressure exerted on the rod seal (33), wherein the outer peripheral portion of the seal housing (27) on an opposite side spaced from the chamber (2A, 117) receives a pressure between the rod seal (33) and the oil seal (9, 35), which pressure is reduced by the rod seal (33), wherein the first outer peripheral seal (43) is provided on a first side of the first notched portion (38) which is closer to the first end of the outer tube, wherein the second outer peripheral seal (40) is on an axially opposite second side to the first notched portion (38) which is closer to the second end of the outer tube, wherein the first outer peripheral seal (43) and the second outer peripheral seal (40) are spaced from the first notched portion (38) in the axial direction of the piston rod, wherein the first outer peripheral seal (43) is arranged to prevent the pressure between the rod seal (33) and the oil seal (9), which is reduced by the rod seal, from being applied between the first notched portion (38) of the outer tube and the outer peripheral portion of the seal housing (27), and wherein the second outer peripheral seal (40) is arranged to prevent the pressure, which is the same as the pressure exerted on the rod seal (33), from being applied between the first notched portion (38) of the outer tube and the outer peripheral portion of the seal housing (27).

Description

Field of the invention

[0001] The present invention relates to a cylinder device for use, for example, in a suspension system of an automobile.

[0002] Examples of cylinder devices include a tubular hydraulic shock absorber mounted on a suspension system of an automobile. In such a cylinder device, an open end of a cylinder may be closed using a plug structure, as disclosed in Japanese Patent Application Laid-Open No. 2004-251413. With this plug structure, after a seal housing and an oil seal are inserted into the cylinder, the open end of the cylinder is staked or caulked to prevent the seal housing and oil seal from being extracted from the cylinder. In a high-pressure cylinder device, as disclosed in Japanese Patent Application Laid-Open No. 2005-133902, a cap is threaded onto the open end of the cylinder.

[0003] The closure structure in which a cap is screwed onto the open end of the cylinder is disadvantageous in terms of manufacturability. Therefore, it is desirable to use notching or caulking to close the open end of the cylinder. However, in cylinder devices in which high hydraulic pressure acts in a gas chamber, the notched or caulked portion is subjected to large forces. Therefore, it is desirable for these cylinder devices to have further increased pressure resistance.

[0004] DE 31 28 723 A1, US 7 458 314 B2 and JP H07- 8 659 U represent further prior art. Content of the invention

[0005] Accordingly, it is an object of the present invention to provide a cylinder device having an increased pressure resistance at the open end of an outer tube constituting the cylinder device.

[0006] To solve the problem described above, the present invention provides an invention according to the independent claims. Short description of the drawings Fig. 1 is a fragmentarily enlarged vertical sectional view showing a sealing part for a piston rod, which is a main part of a cylinder device according to a first embodiment of the present invention. Fig. 2 is a fragmentarily enlarged vertical sectional view showing a sealing member for a piston rod, which is a main part of a cylinder device according to a second embodiment of the present invention. Fig. 3 is a vertical sectional view of the Fig. 1 shown cylinder device. Fig. 4 is a partially sectional view of a cylinder device according to a third embodiment of the present invention. Fig. 5 is a fragmentary enlarged view of a main part of the cylinder device according to the third embodiment of the present invention. Fig. 6 is an enlarged view of an oil seal used in the cylinder device according to the third embodiment of the present invention. Fig. 7 is an enlarged view of a dust seal employed in the cylinder device according to the third embodiment of the present invention. Fig. 8 is a fragmentary enlarged view of a main part of the cylinder device according to a fourth embodiment of the present invention. Detailed description of the invention

[0007] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0008] A cylinder device 1 according to a first embodiment of the present invention will be described with reference to Fig. 1 and Fig. 3. The cylinder device 1 according to this embodiment is installed in each of the suspension systems for the front and rear, left and right wheels of an automobile. The cylinder devices 1 mounted on the four wheels are connected to each other with a pipe through an external hydraulic circuit, allowing the cylinder devices to operate in conjunction with each other. In addition, the flow of hydraulic fluid between the cylinder devices 1 caused by changes in the posture of the vehicle body, etc., is controlled by an accumulator of the external hydraulic circuit and damping valves, thereby controlling the vibrations and posture of the vehicle body.

[0009] As in Fig. 1 and Fig. 3, the cylinder device 1 has a double-tube structure including a cylinder 2 and a circumferential cylindrical outer tube 3 provided around the outer periphery of the cylinder 2 to form an annular passage 4 therebetween. A piston 5 is slidably fitted into the cylinder 2. The cylinder 5 divides the interior of the cylinder 2 into two chambers, i.e., cylinder chambers 2A and 2B. The piston 5 is connected to one end of a piston rod 6 using a nut 7. The other end portion of the piston rod 6 slidably and fluid-tightly extends through a rod guide 8 and an oil seal 9 as a sliding seal, which are attached to the lower end of the double-tube structure including the cylinder 2 and the outer tube 3. The other end of the piston rod 6 protrudes to the exterior of the cylinder device 1.The cylinder chamber 2A and the annular passage 4 are in communication with each other through a cutout portion 12 provided on the rod guide 8.

[0010] A damping valve 13 is attached to the upper end of the cylinder 2. The damping valve 13 is secured by a through member 14 welded to the upper end of the outer tube 3. The through member 14 has a connection interface 15 extending axially therethrough. The cylinder chamber 2B communicates with the connection interface 15 through the damping valve 13. The upper end of the annular passage 4 is closed by the damping valve 13 and the through member 14. The damping valve 13 is provided with a check valve that allows the flow of hydraulic fluid from the connection interface 15 toward the cylinder chamber 2B, and is further provided with a damping mechanism comprising an orifice, a disc valve, etc., which generates a damping force by controlling the flow of hydraulic fluid from the cylinder chamber 2B to the connection interface 15.

[0011] The outer tube 3 has an opening 16 provided in an intermediate part of the side wall thereof. The opening 16 is connected to a damping force generating mechanism 17. The damping force generating mechanism 17 has a reduced-diameter circumferential cylindrical valve housing 18 at one end thereof, a damping valve 19 housed in the valve housing 18, and a connecting member 21 secured to the large-diameter open end side of the valve housing 18 using a nut 20.

[0012] The valve housing 18 has an annular connecting portion 23 projecting around a reduced-diameter opening portion 22 at one end of the valve housing 18. The valve housing 18 is connected to the outer tube 3 by abutting the connecting portion 23 against the outer peripheral surface of the outer tube 3 around the opening 16 and welding the connecting portion 23 to the side wall of the outer tube 3.

[0013] The connecting member 21 is provided with a connecting interface 24 that communicates with the interior of the valve housing 18. The damping valve 19 is provided with a check valve 25 that only allows the flow of hydraulic fluid from the connecting interface 24 toward the opening portion 22, and is further provided with a disc valve 26 having an orifice 26A that generates a damping force by controlling the flow of hydraulic fluid from the opening portion 22 toward the connecting interface 24.

[0014] Next, the structure of a sealing part S for the piston rod 6, which is a main part of this embodiment, will be described with reference to mainly Fig. 1 explained.

[0015] As in Fig. 1, the outer tube 3 comprises an annular rod guide 8, a seal housing 27, an oil seal 9, a dust seal 28 and a securing member 29 through which the piston rod extends, and which are inserted and secured in the lower end of the outer tube 3 in the above-mentioned order.

[0016] The rod guide 8 is fitted at one end thereof into the end of the cylinder 2. The rod guide 8 has a flange 8A formed on the outer periphery of an intermediate portion thereof. The flange 8A abuts against the cylinder 2 to position the rod guide 8 in the axial direction. The other end of the rod guide 8 is fitted into a recess 30 formed in the seal housing 27. One end of the rod guide 8 and a part of the flange 8A are provided with a cutout portion 12 that communicates between the cylinder chamber 2A and the annular passage 4. The rod guide 8 has a circumferential cylindrical low-friction member 31 press-fitted on the inner periphery thereof to slidably guide the piston rod 6 by the low-friction member 31.It should be noted that the low-friction member 31 is made of a metal, and the surface of the low-friction member 31 is coated with a fluorocarbon resin or the like to prevent the piston rod 6 from being damaged when the piston rod 6 slidably contacts the surface of the low-friction member 31.

[0017] The seal housing 27 has a recess 30 formed at one end thereof, which is to be equipped with the rod guide 8. The bottom of the recess 30 is formed with a sealing recess 32 having a smaller diameter than that of the recess 30. The sealing groove is formed between the sealing recess 32 and the end of the rod guide 8 pressed into the recess 30. The sealing groove is equipped with a rod seal 33 and a retaining ring 34 comprising an O-ring. The rod seal 33 seals between the seal housing 27 and the piston rod 6. The other end of the seal housing 27 is provided with a recess 36 that accommodates a sealing lip 35 of the oil seal 9. It should be noted that the rod seal 33 is a resin material with self-lubricating properties and is in sliding contact with the piston rod 6 at all times under tension.

[0018] The seal housing 27 has an outer peripheral groove 37 formed at an intermediate portion of the outer periphery thereof, which is fitted onto the outer tube 3. The seal housing 27 is secured to the outer tube 3 by a first notched or caulked portion 38 formed by notching or caulking the outer tube 3 from a radially outer side into the outer peripheral groove 37. The seal housing 27 has a seal groove 39 formed on the outer periphery thereof at a position closer to one end thereof (axially inward of the outer peripheral groove 37). The seal groove 39 is provided with an O-ring 40 serving as an outer peripheral seal to seal between the seal housing 27 and the outer tube 3. The seal housing 27 has a tapered seal surface 27A formed on the outer peripheral edge at the other end thereof.It should be noted that the seal housing 27 and the rod guide 8 may be formed as an integral structure.

[0019] The oil seal 9 serving as a sliding seal includes a disc-shaped reinforcing plate 41 and a seal lip 35, which is a lip-shaped sealing member. The seal lip 35 is fixed to the inner side of the inner peripheral portion of the reinforcing plate 41. The inner peripheral portion of the seal lip 35 is in contact with the piston rod 6. A tension spring 42 is fitted onto the outer peripheral portion of the seal lip 35. A seal member 43 serving as an outer peripheral seal is fixed to one end of the outer peripheral portion of the reinforcing plate 41. The seal member 43 is pressed against the sealing surface 27A of the seal housing 27 by the reinforcing plate 41 to seal between the seal housing 27 and the outer tube 3.The sealing lip 35 and the sealing member 43 are continuous with each other at the end face of the reinforcing plate 41 to seal between the mutually abutting portions of the reinforcing plate 41 and the seal housing 27.

[0020] The dust seal 28 includes a disc-shaped reinforcing plate 44 and a dust lip 45, which is a lip-shaped sealing member. The dust lip 45 is fixed to the outer peripheral portion of the reinforcing plate 44. The inner peripheral portion of the dust lip 45 is in sliding contact with the piston rod 6. A tension spring 46 is fitted onto the outer peripheral portion of the dust lip 45. Note that the oil seal 9 and the dust seal 28 may be formed by jointly utilizing the reinforcing plates 41 and 44 in an integral structure.

[0021] The retaining member 29 has a groove 47 formed on its outer peripheral portion, which is fitted onto the outer tube 3. The retaining member 29 is secured to the outer tube by a second notched or caulked portion 48 formed by notching or caulking the outer tube 3 from the radially outer side into the outer peripheral groove 47. The retaining member 29 secures the reinforcing plates 41 and 44 of the oil seal 9 and the dust seal 28 by pressing them toward the seal housing 27. Note that the first notched portion 38 and the second notched portion 48 may be different from each other in configuration; however, if the first and second notched portions 38 and 48 have the same configuration, they can be formed using the same notching tool.The first and second notched portions 38 and 48 need not be formed over the entire circumference of the outer tube 3, but may be provided locally at, for example, four positions on the outer tube 3. In such a case, the first and second notched portions 38 and 48 should preferably be arranged at corresponding circumferentially spaced positions from each other. Thus, the number of notched portions can be reduced without reducing the withdrawal load. Further, the first and second notched portions 38 and 48 are applied by notching or caulking the outer tube 3 from the radially outer side into a groove provided on the associated component with a notching or caulking tool on the outer circumference of the outer tube 3.

[0022] Therefore, the removal load of the seal housing 27 and the securing component 29 can be further increased.

[0023] The following is an explanation of the operation of this embodiment arranged as mentioned above.

[0024] The cylinder device 1 has a through member 14 and a piston rod 6, which are respectively connected to sprung and unsprung components of each wheel of an automobile, and an external hydraulic circuit constituting a suspension system is connected to each of the connection interfaces 15 of the through member 14 and to the connection interface 24 of the connection member 21.

[0025] During an extension stroke of the piston rod 6, the hydraulic fluid in the cylinder chamber 2A is pressurized by the sliding movement of the piston 5 in the cylinder 2 to flow toward the external hydraulic circuit through the cutout portion 12, the annular passage 4, the orifice 16, the orifice portion 22, the orifice 26A and the disc valve 26 of the damping valve 19, and the connection interface 24. On the other hand, the pressure in the cylinder chamber 2B is reduced by the sliding movement of the piston 5 in the cylinder 2. Consequently, the hydraulic fluid flows from the external hydraulic circuit connected to the connection interface 15 of the passage member 14 into the cylinder chamber 2B through the check valve of the damping valve 13. Thus, a damping force is generated by the orifice 26A and the disc valve 26 of the damping valve 19 against the impact of the piston rod 6.In addition, a resistance force provided by the external hydraulic circuit acts against the impact of the piston rod 6.

[0026] During the compression stroke of the piston rod 6, the hydraulic fluid in the cylinder chamber 2B is pressurized by the sliding movement of the piston 5 in the cylinder 2 to flow through the damping mechanism of the damping valve 13 toward the external hydraulic circuit connected to the connection interface 15 of the passage member 14. On the other hand, the pressure in the cylinder chamber 2A is reduced by the sliding movement of the piston 5 in the cylinder 2. Consequently, the hydraulic fluid flows from the external hydraulic circuit connected to the connection interface 20 through the check valve 25 of the damping valve 19, the orifice portion 22, the orifice 16, the annular passage 4, and the cutout portion 12 into the cylinder chamber 2A. Thus, a damping force is generated by the damping mechanism of the damping valve 13 against the impact of the cylinder piston 6.In addition, a resistance force provided by the external hydraulic circuit acts on the impact of the cylinder piston 6.

[0027] Regarding cylinder devices mounted on left and right wheels, for example, the corresponding connection interfaces 24 and 15 of the two cylinder devices 1 may be connected to external hydraulic circuits having accumulators to connect the cylinder chamber 2A and the cylinder chamber 2B, respectively. With this arrangement, the reaction force from the accumulators is small when the impacts of the cylinder devices 1 mounted on the left and right wheels are in the same direction (in phase), and the reaction force is large when the impacts are in different directions (antiphase). Accordingly, the system can function as a kind of stabilizer that suppresses changes in the attitude of the vehicle body when the vehicle is turned.

[0028] During the above-described operation of the cylinder device 1, the sealing member S for the piston rod 6 is subjected to a very high pressure on the order of a maximum of 35 MPa. The seal housing 27, which receives the high pressure, is supported by the first and second notched portions 38 and 48 provided at two axially spaced positions, that is, by the fit between the outer peripheral groove 37 of the seal housing 27 and the first notched portion 38 of the outer tube 3, and the fit between the outer peripheral groove 47 of the locking member 29 and the second notched portion 48 of the outer tube 3. The piston rod 6 is sealed in two stages by the rod seal 32 and the sealing lip 35 of the oil seal 9.Accordingly, the pressure acting on the seal lip 35, which is housed in the recess 36 of the seal housing 27 to serve as a second-stage seal, is reduced to approximately 4 MPa by the rod seal 33 serving as a first-stage seal. Thus, the seal lip 35 must seal the pressure reduced by the rod seal 33. Consequently, the pressure resistance of the seal part S for the piston rod 6 can be increased considerably. Compared with the cylinder device disclosed in the prior art, the cylinder device of the present invention offers the following advantages. In the prior art cylinder device, the pressure in the cylinder acts on the entire area of ​​the rod guide at the cylinder end, whereas in the cylinder device of the present invention, the pressure acting on the inner peripheral side of the seal housing 27 is reduced by the rod seal 33.Therefore, the pressure acting on the first notched portion 38 is the differential pressure between the pressure in the cylinder and the pressure reduced by the rod seal 33 serving as the first-stage seal. For example, if the pressure in the cylinder is 35 MPa and the pressure reduced by the rod seal 33 is 31 MPa, a force equivalent to 4 MPa acts on the first notched portion 38. Meanwhile, the pressure acting on the second notched portion 48 is mainly the pressure in the recess 36. Thus, the pressures acting on the first and second notched portions 38 and 48 are reduced in two stages. Accordingly, it is possible to increase the resistance to extraction in the axial direction and the pressure resistance to expansion in the radial direction.

[0029] It should be noted that the sliding and sealability between the sealing lip 35 and the piston rod 6 is improved by the hydraulic fluid leaking through the rod seal 33 and stored in the recess 36. The dust lip 45 prevents contaminants from entering the sliding area of ​​the piston rod 6.

[0030] The area between the seal housing 27 and the outer tube 3 is sealed by the first notched portion 38 and the O-ring 40 and the sealing member 43 provided on the axially opposite sides of the first notched portion 38, thereby increasing the resistance to high pressure. In this regard, because the pressure in the cylinder acting on the first notched portion 38 is blocked by the O-ring 40, it is possible to suppress the increasing deformation of the first and second notched portions 38 and 48 due to the hoop stress generated by the pressure in the cylinder, and it is thereby possible to make it difficult to extract the seal housing 27. In addition, notching or caulking of the seal housing 27, which takes place near the end of the cylinder 3, can increase the deflection remaining in the cylinder 2 after the notching process.In other words, a high axial force remains in cylinder 2, so that rattling of cylinder 2 is unlikely to occur when a kickback force is applied to the wheel. Accordingly, it is possible to suppress the generation of noise from cylinder 2 during vehicle running.

[0031] Thus, the pressure resistance of the sealing member S for the piston rod 6 can be increased considerably. Note that the O-ring 40, which is one of the outer peripheral seals, may be omitted, and only the sealing member 43 is used as an outer peripheral seal, provided it is possible to obtain the required sealing and extraction resistance of the seal housing 27 against the pressure in the cylinder. In this case, the pressure in the radial direction undesirably acts from the annular passage 4 to the first notched portion 38; therefore, the pressure resistance in the radial direction cannot be increased much.However, the axial pressure acting on the first notched portion 38 is the differential pressure between the pressure in the recess 36 and the pressure in the annular passage 4 (assuming that the pressure in the recess 36 is 4 MPa and the pressure in the annular passage 4 is 35 MPa, for example, a pressure of 31 MPa acts on the first notched portion 38). The axial pressure acting on the second notched portion 48 is the pressure in the recess 36 and the pressure in the annular passage 4 corresponding to the area of ​​the sealing member 43. Therefore, the axial forces acting on the corresponding notched portions are reduced compared to the prior art. Consequently, the extraction resistance of the notched portions increases, and the pressure resistance can be increased to a considerable level.

[0032] Next, a second embodiment of the present invention will be described with reference to Fig. 2. In the following description, components and sections are included which are identical to those described in the Fig. 1 and Fig. 3 are designated by the same reference numerals as used in the first embodiment, and only those portions in which the second embodiment differs from the first embodiment will be explained in detail.

[0033] As in Fig. As shown in Fig. 2, a cylinder device 49 according to the second embodiment of the present invention is applied to a single-tube hydraulic shock absorber. In the cylinder device 49, the outer tube 3 also serves as the cylinder 2, thereby omitting the cylinder 2, and the piston 5 is slidably fitted into the outer tube 3. Further, the damping valve 13 and the connection interface 15 are omitted. The bottom of the outer tube 3 (cylinder) is closed, and a free piston (not shown) is fitted into the bottom of the outer tube 3 to form a gas chamber. The gas chamber is filled with a high-pressure gas.

[0034] Furthermore, the damping force generating mechanism 17 provided on the outer tube 3 side in the first embodiment has been omitted, but the piston 5 is instead provided with expansion and compression damping valves 50 and 51. The expansion damping valve 50 generates a damping force by controlling the flow of hydraulic fluid from the cylinder chamber 2A toward the cylinder chamber 2B. The compression damping valve 51 generates a damping force by controlling the flow of hydraulic fluid from the cylinder chamber 2B toward the cylinder chamber 2A.

[0035] The rod guide 8 is secured by being press-fitted into the recess 30 of the seal housing 27. The securing member 29 has been omitted. The reinforcing plate 44 of the dust seal 28 is secured by a notched or caulked portion 52 formed by notching or caulking the end portion of the outer tube 3 inwardly over the entire circumference thereof. Note that the notched portion 52 may be provided by partially notching or caulking the end portion of the outer tube 3 at four circumferentially spaced positions.

[0036] With the above-described structure, the cylinder device 49, which is a single-tube hydraulic shock absorber, operates as follows. During the extension stroke of the piston rod 6, the hydraulic fluid in the cylinder chamber 2A is pressurized by the sliding movement of the piston 5 in the outer tube 3 (cylinder) to flow toward the cylinder chamber 2B through the extension damping valve 50. Thus, a damping force is generated by the extension damping valve 50. During the compression stroke of the piston rod 6, the hydraulic fluid in the cylinder chamber 2B is pressurized to flow toward the cylinder chamber 2A through the compression damping valve 51. Thus, a damping force is generated by the compression damping valve 51. During the expansion and compression stroke, a volume change in the outer tube 3 (cylinder) due to the expansion and contraction of the piston rod 6 is compensated by the compression and expansion of the high-pressure gas in the gas chamber.The sealing part S for the piston rod 6 has a greatly increased pressure resistance against the pressure in the outer tube 3 (cylinder), as in the previous first embodiment.

[0037] For example, although in the foregoing first and second embodiments, the present invention is applied to a cylinder device installed in an automobile suspension system to generate a damping force, it should be noted that the present invention is not limited thereto but can also be applied to other cylinder devices having a sealing part for a piston rod.

[0038] For example, although the oil seal 9 and the dust seal 28 are shown as individual components in the foregoing embodiments, it is possible to use a well-known seal in which oil and dust seals are integrated with each other.

[0039] A third embodiment of the present invention will be described in detail below with reference to the Fig. 4 to 7. Unlike the first and second embodiments, the third embodiment is a cylinder device that does not include a damping force generating mechanism. The cylinder device according to the third embodiment controls the protruding position of a rod by supplying or discharging a fluid into or from an upper and lower cylinder chamber. This type of cylinder device can be provided, for example, in a part of an automobile where a stabilizer is installed to change the rigidity of the stabilizer, and can also be used in general applications to control the relative position between two objects.

[0040] The cylinder device according to the third embodiment of the present invention is provided as a hydraulic cylinder device 101a in which hydraulic oil is used as a hydraulic fluid. Note that the following explanation is made assuming that the open end side of an outer tube 102 is the lower side, and the bottom side of the outer tube 102 is the upper side, as shown in the figures.

[0041] The hydraulic cylinder device 101a according to the third embodiment has, as shown in the Fig. 4 and Fig. 5, a double-pipe structure in which a rotating cylindrical outer pipe 102, one end of which is closed, is arranged around the outer periphery of a rotating cylindrical inner pipe 103. The outer pipe 102 has an opening portion 104 at the lower end thereof. An annular communication passage 109 is formed between the outer pipe 102 and the inner pipe 103. In the double-pipe structure, a rod guide 105a, a sealing member 106, and a securing member 110a are fitted at the lower end of the inner pipe 103 and into the opening portion 104 at the lower end of the outer pipe 102 so as to abut against the inner peripheral surface of the outer pipe 102. The rod guide 105a, the sealing member 106 and the securing member 110a are arranged in the order mentioned from the top side, that is, from the bottom side of the inner tube 103, so that they abut against each other.It should be noted that a fastening eye 113 is integrally provided at the upper end of the outer tube 102.

[0042] As in Fig. 4, a piston 114 is slidably fitted into the inner tube 103. The piston 114 divides the interior of the inner tube 103 to define two chambers, that is, a first cylinder chamber 116 and a second cylinder chamber 117. The piston 114 is connected to the upper end of the piston rod 115 using a nut 118. Note that the piston 114 has an annular groove provided on the outer peripheral surface of the bottom thereof. The annular groove is equipped with a sealing mechanism 135 comprising a clamp ring (O-ring) provided on the inner peripheral side of the annular groove and a resin seal ring on the outer peripheral side of the groove. The lower end portion of the piston rod 115 extends through the rod guide 105a, the sealing member 106 and the securing member 110a, and protrudes to the outside of the outer tube 102.The protruding lower end of the piston rod 115 extends through a cover fixture 120 and is connected to a fixture 121 having a semi-circular sectional configuration. Further, an expandable cover 122 is arranged to cover the end portion of the piston rod 115 protruding from the outer tube 102. The expandable cover 122 is connected at its upper end to the outer peripheral surface of the lower end of the outer tube 102, and at its lower end to the outer periphery of the cover fixture 120. Note that a rubber buffer 123 abutting against the cover fixture 120 is fitted to the lower end of the piston rod 115.

[0043] As in Fig. 4, a chamber 124 is formed in the upper end portion of the outer tube 102. The chamber 124 is in direct communication with the first cylinder chamber 116. The upper end of the chamber 124 has a substantially hemispherical configuration in which the diameter is gradually reduced upward. The side wall of the chamber 124 is formed with a first supply-discharge interface 125 communicating with the interior of the chamber 124 and is also formed with a first vent hole 126 communicating with the uppermost portion of the chamber 124 above the first supply-discharge interface 125. Note that the first vent hole 126 is provided with a first vent plug 127.Further, the side wall of the upper surface of the outer tube 102 is formed with a second supply-discharge interface 128 communicating with the communication passage 109, and is also formed with a second vent hole 129 communicating with the uppermost portion of the communication passage 109 above the second supply-discharge interface 128. Note that the second vent hole 129 is provided with a second vent plug 130.

[0044] The rod guide 105a is, as shown in Fig. 5, formed in a circumferential cylindrical shape through which the piston rod 115 extends. The rod guide 105 has an annular stepped portion 132 formed on the outer peripheral edge of the upper end thereof. The annular stepped portion 132 has an L-shaped cross-sectional configuration to be fitted onto the lower end of the inner tube 103. A passage 133 is formed between the annular stepped portion 132 and the lower end of the inner tube 103 to provide communication between the communication passage 133 and the second cylinder chamber 117. A cylinder member 138 is fitted onto the inner peripheral surface of the upper surface of the rod guide 105. The rod guide 105a has a recess 134 formed substantially in the center of the lower end surface thereof to accommodate a part of the oil seal 107 constituting the sealing member 106.The rod guide 105a further includes an annular groove provided on its inner peripheral surface. The annular groove is equipped with a retaining ring 136 comprising an O-ring. A seal ring 137 is provided inside the retaining ring 136. Furthermore, the rod guide 105 includes an annular recess 139 formed on its outer peripheral surface at the same position as the retaining ring 136 in the axial direction. The annular recess 139 has an open-side rectangular cross-sectional configuration for receiving and securing a notched or caulked portion.

[0045] The oil seal 107 as a sliding seal forming the sealing member 106 is arranged such that a diaphragm portion 141 (see Fig. 6) of the oil seal 107 abuts against the lower end surface of the rod guide 105a.

[0046] Note that, although in the third embodiment, an annular recess 139 is formed on the outer peripheral surface of the rod guide 105 to receive and secure the notched or caulked portion, the annular recess 139 may be replaced by a plurality of circumferentially spaced groove portions. The annular recess 139 may be formed with a U-shaped cross-sectional configuration or a V-shaped cross-sectional configuration. Further, a plurality of axially spaced annular recesses 139 may be provided.

[0047] The sealing component 106 comprises, as in Fig. 5, Fig. 6 and Fig. 7, an oil seal 107 and a dust seal 108 through which the piston rod 115 extends are in pressure contact with the outer peripheral surface of the piston rod 115. The oil seal 107 abuts against the lower end surface of the rod guide 105, and the dust seal 108 abuts against the lower end surface of the oil seal 107. The oil seal 107 has an annular washer 140 contacting the inner wall of the opening portion 104 and has a synthetic resin baked onto the inner periphery of the washer 140. The dust seal 108 has an annular washer 144 contacting the inner wall of the opening portion 104 and a synthetic resin baked onto the inner periphery of the washer 145.

[0048] The oil seal 107 further includes a sealing part. The sealing part of the oil seal 107 is integrally formed of a diaphragm portion 141 and an outer peripheral sealing portion 142 that seals between the outer peripheral surface of the washer 140 and the inner peripheral surface of the outer tube 102. Furthermore, the oil seal 107 includes a sealing lip 143 protruding inward from the inner peripheral surface of the top thereof to press against the outer peripheral surface of the piston rod 115. A backup ring 150 is provided on the inner peripheral surface of the bottom of the oil seal 107. Note that a retaining ring 144 is provided on the outer periphery of the part of the oil seal 107 where the sealing lip 143 is formed to suppress the expansion of the sealing lip 143.

[0049] The dust seal 108 further includes a sealing part. The sealing part of the dust seal 108 is integrally formed by a diaphragm portion 146 and an outer peripheral sealing portion 147 that seals between the outer peripheral surface of the washer 145 and the inner peripheral surface of the outer tube 102. Furthermore, the dust seal 108 includes a sealing lip 148 that protrudes inward from the inner peripheral surface of the bottom thereof to press against the outer peripheral surface of the piston rod 115. Note that a retaining ring 149 is provided on the outer periphery of the part of the dust seal 108 where the sealing lip 148 is formed to suppress the expansion of the sealing lip 148.

[0050] The securing member 110a abuts against the lower end surface of the dust seal 108, that is, the diaphragm portion 146 of the dust seal 108.

[0051] As in Fig. 5, the securing member 110a is formed in a circumferential cylindrical shape. The thickness of the securing member 110a is set to substantially one-half the thickness of the rod guide 105a and substantially three times the thickness of the washer 140 of the oil seal 107 or the thickness of the washer 145 of the dust seal 108. The outer diameter of the securing member 110a coincides with the inner diameter of the outer tube 102. The inner diameter of the securing member 110a is slightly larger than the inner diameter of the washer 140 of the oil seal 107. The securing member 110a has an annular recess 151 formed at a substantially axially central portion of the outer peripheral surface thereof. The annular recess 151 has an open-sided rectangular cross-sectional configuration to receive and secure a notched or caulked portion.

[0052] Note that, although in the third embodiment, an annular recess 151 is formed on the outer peripheral surface of the securing member 110a to receive and secure a notched or caulked portion, the annular recess 151 may be replaced by a plurality of circumferentially spaced groove portions. The annular recess 151 may be formed with a U-shaped cross-sectional configuration or a V-shaped cross-sectional configuration. Further, a plurality of axially spaced annular recesses 151 may be provided.

[0053] The oil seal 107, the dust seal 108 and the securing member 110a are respectively similar to the oil seal 9, the dust seal 28 and the securing member 29 of the first embodiment.

[0054] To construct the hydraulic cylinder device 101a according to the third embodiment as shown in Fig. 4, the rod guide 105a, the oil seal 107, the dust seal 108, and the locking member 110a are fitted onto the piston rod 115, and the upper end of the piston rod 115 is secured to the piston 114 using the nut 118, thereby forming a rod assembly. Subsequently, the piston rod is inserted into the inner tube 103.

[0055] Subsequently, the rod assembly is inserted into the outer tube 102 together with the inner tube 103. After that, the inner tube 103 is axially pushed from the top, using the lower end surface of the securing member 110a as a retaining surface to eliminate kickback and prevent rattling of the inner tube 103.

[0056] Thereafter, keeping the described state, the outer circumference of the outer tube 102 is formed as shown in Fig. 5, is pressed to a position corresponding to the annular recess 139 provided on the rod guide 105 from the outside with a caulking tool (not shown), whereby this part of the peripheral wall of the outer tube 102 protrudes inward to form a projection 152 engaged with the annular recess 139 of the rod guide 105a. In this way, the rod guide 105a is secured to the outer tube 102 by caulking.Further, the outer periphery of the outer tube 102 is pressed at a position corresponding to the annular recess 151 provided on the securing member 110a from the outside with a caulking tool (not shown), whereby that part of the peripheral wall of the outer tube 102 protrudes inward to form a projection 153 engaged with the annular recess 151 of the securing member 110a, and thus caulking or securing the securing member 110a to the outer tube 102 to complete the hydraulic cylinder device 101a.

[0057] The following is an explanation of the operation of the hydraulic cylinder device 101a according to the third embodiment.

[0058] A hydraulic oil supply-discharge system (not shown) is connected to first and second supply-discharge interfaces 125 and 128. To extend the piston rod 115, hydraulic fluid is supplied from the first supply-discharge interface 125 through the chamber 124 into the first cylinder chamber 116, and at the same time, hydraulic fluid in the second cylinder chamber 117 is discharged from the second supply-discharge interface 128 through the passage 133 and the communication passage 109.

[0059] To contract the piston rod 115, hydraulic fluid is supplied from the second supply-discharge interface 128 through the communication passage 109 and the passage 133 into the second cylinder chamber 117, and at the same time, hydraulic fluid in the first cylinder chamber 116 is discharged from the first supply-discharge interface 125 through the chamber 124. Note that the piston rod 115 is locked in position by closing the first and second supply-discharge interfaces 125 and 128.

[0060] When hydraulic fluid is to be charged into the first and second cylinder chambers 116 and 117, air venting is performed by opening the first and second vent plugs 127 and 130. Regarding air venting, the first vent hole 126 is connected to the uppermost portion of the chamber 124, and the second vent hole 129 is connected to the uppermost portion of the communication passage 109. Therefore, air venting can be efficiently performed by attaching the hydraulic cylinder device 101a to an object to be equipped with the hydraulic cylinder device 101a with the attachment hole 113 facing upward.

[0061] Next, a hydraulic cylinder device 101c as a cylinder device according to a fourth embodiment of the present invention will be described with reference to Fig. 8 explained.

[0062] The following explanation will be given only on the points in which the hydraulic cylinder device 101c according to the fourth embodiment differs from the hydraulic cylinder device 101a according to the third embodiment.

[0063] In the hydraulic cylinder device 101c, the thickness of the securing member 110b is substantially the same as the thickness of the washer 140 of the oil seal 107 or the thickness of the washer 145 of the dust seal 108.

[0064] To construct the hydraulic cylinder device 101c according to the fourth embodiment, the rod guide 105a, the oil seal 107, the dust seal 108, and the locking member 110b are fitted onto the piston rod 115, and the upper end of the piston rod 115 is secured to the piston 114 using the nut 118, thereby forming a rod assembly. After the rod assembly is inserted into the outer tube together with the inner tube 103, the lower end surface of the locking member 110b abuts against a split-type retaining jig (not shown) installed in the opening portion 104 of the outer tube 102, and the inner tube 103 is axially pressed from the upper side.

[0065] Thereafter, while maintaining the above-described state, the outer periphery of the outer tube 102 is pressed to a position corresponding to the annular recesses 139 provided on the rod guide 105 from the outside with a caulking tool (not shown), whereby that part of the peripheral wall of the outer tube 102 protrudes inward to form a projection 152 engaged with the annular recess 139 of the rod guide 105a. Thus, the rod guide 105a is secured to the outer tube 102 by caulking.Further, the outer periphery of the outer tube 102 is pressed at a position slightly below the lower end surfaces of the securing member 110b (that is, below the end surface of the securing member 110b on a side thereof closer to an open end of the outer tube 102) from the outside with a caulking tool (not shown), whereby this part of the peripheral wall of the outer tube 102 protrudes inward to form a projection 153 engaging with the lower end surface of the securing member 110b, and thus caulking the securing member 110b to the outer tube 102. Finally, the retaining jig is removed from the opening portion 104 of the outer tube 102 and separated into two pieces before being removed from the hydraulic cylinder device 101c.The fourth embodiment can provide a pressure resistance substantially equal to that obtained with the third embodiment, but is inferior in assembly efficiency to the third embodiment in which the hydraulic cylinder device 101a also functions as a retaining template.

[0066] In the foregoing hydraulic cylinder devices 101a and 101c according to the third and fourth embodiments of the present invention, the opening portion 104 of the outer tube 102 is closed by securing the securing member 110a (110b) to the outer tube 102 by staking or caulking. Compared with the conventional technique of closing the opening portion 104 by screwing a female thread cap onto the outer periphery of the outer tube 102, the hydraulic cylinder devices 101a and 101c according to the third and fourth embodiments do not require female threading processes in component manufacturing, and can thus suppress the mixing of very fine chips or the like into the outer tube 102. Furthermore, the hydraulic cylinder devices 101a and 101c can eliminate some troublesome operations, such as tightening torque control, and thus provide increased operating efficiency.

[0067] Therefore, among the hydraulic cylinder devices 101a and 101c according to the third and fourth embodiments, the hydraulic cylinder device 101a according to the third embodiment is preferable from the perspective of pressure resistance and assembly efficiency. The hydraulic cylinder device 101c according to the fourth embodiment can be used for applications where the deformation of the outer tube 102 due to cylinder pressure is small.

[0068] Although the foregoing embodiments of the cylinder device according to the present invention have been applied to oil hydraulic cylinders, the present invention can also be applied to water hydraulic cylinders and air cylinders.

[0069] The hydraulic cylinder devices of the preceding embodiments can increase the pressure resistance at the open end of the outer tube.

[0070] Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily understand that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.

Claims

[1] Cylinder device comprising: an outer tube (3) having a chamber (2A, 2B, 116, 117) with a hydraulic fluid sealed therein, the outer tube (3) having a first and a second end spaced from the first end in the axial direction of the outer tube (3), the first end being open, a piston (5) provided in the chamber (2A, 2B, 116, 117) of the outer tube (3), a piston rod (6) connected to the piston (5) and projecting from the outer tube (3) through the first end of the outer tube (3), an annular seal housing (27) provided in the outer tube (3) at a position closer to the first end, the seal housing (27) having an inner peripheral portion and an outer peripheral portion, a first outer peripheral seal (43) provided between the outer tube (3) and the outer peripheral portion of the seal housing (27), the first outer peripheral seal (43) sealing between the outer tube (3) and the seal housing (27), a second outer peripheral seal (40) provided between the outer tube (3) and the outer peripheral portion of the seal housing (27), the second outer peripheral seal (40) sealing between the outer tube (3) and the seal housing (27), an annular rod seal (33) provided on an inner peripheral portion of the seal housing (27) in sliding contact with the piston rod (6), and an annular oil seal (9) provided on a side of the seal housing (27) closer to the first end, the annular oil seal (9) being in sliding contact with the piston rod (6), wherein the piston rod (6) is sealed in two stages by the rod seal (33) and the oil seal (9), wherein the outer peripheral portion of the seal housing (27) is provided with an outer peripheral groove (37) and is secured to the outer pipe (3) by a first notched portion (38) formed by notching the outer pipe (3) from the outside into the outer peripheral groove (37) in a radial direction of the outer pipe (3), and wherein the outer peripheral portion of the seal housing (27) on a side thereof closer to the chamber (2A, 117) receives a pressure which is the same as a pressure exerted on the rod seal (33), wherein the outer peripheral portion of the seal housing (27) on an opposite side spaced from the chamber (2A, 117) receives a pressure between the rod seal (33) and the oil seal (9, 35), which pressure is reduced by the rod seal (33), wherein the first outer peripheral seal (43) is provided on a first side of the first notched portion (38) which is closer to the first end of the outer tube, wherein the second outer peripheral seal (40) is on an axially opposite second side to the first notched portion (38) which is closer to the second end of the outer tube, wherein the first outer peripheral seal (43) and the second outer peripheral seal (40) are spaced from the first notched portion (38) in the axial direction of the piston rod, wherein the first outer peripheral seal (43) is arranged to prevent the pressure between the rod seal (33) and the oil seal (9), which is reduced by the rod seal, from being applied between the first notched portion (38) of the outer tube and the outer peripheral portion of the seal housing (27), and wherein the second outer peripheral seal (40) is arranged to prevent the pressure, which is the same as the pressure exerted on the rod seal (33), from being applied between the first notched portion (38) of the outer tube and the outer peripheral portion of the seal housing (27). [2] The cylinder device according to claim 1, wherein the oil seal (9) is secured to the outer tube (3) by a second notched portion (48) formed by notching the outer tube (3) from the outside. [3] A cylinder device according to claim 2, wherein the oil seal (9) is secured to the outer tube (3) by fitting an annular securing member (29) in the outer tube (3) axially outwardly of the oil seal (9) and by securing the securing member (29) to the outer tube (3) by the second notched portion (48). [4] A cylinder device according to claim 3, wherein the securing member (29) has a groove (47) provided on an outer periphery thereof, the second notched portion (48) being notched into the groove (47). [5] A cylinder device according to any one of claims 1 to 4, wherein the piston (5) has damping valves (50, 51) and the cylinder device is a single-tube hydraulic shock absorber in which the piston (5) is slidably fitted into the outer tube (3). [6] Cylinder device comprising: an outer tube (3) having a chamber (2A, 2B, 116, 117) with a hydraulic fluid sealed therein, the outer tube (3) having a first and a second end spaced from the first end in the axial direction of the outer tube (3), the first end being open, a piston (5), the cylinder device having a double-tube structure in which the outer tube (3) is provided outside a cylinder (2) slidably fitted therein with the piston (5), a piston rod (6) connected to the piston (5) and projecting from the outer tube (3) through the first end of the outer tube (3), an annular seal housing (27) provided in the outer tube (3) at a position closer to the first end, the seal housing (27) having an inner peripheral portion and an outer peripheral portion, a first outer peripheral seal (43) provided between the outer tube (3) and the outer peripheral portion of the seal housing (27), the first outer peripheral seal (43) sealing between the outer tube (3) and the seal housing (27), a second outer peripheral seal (40) provided between the outer tube (3) and the outer peripheral portion of the seal housing (27), the second outer peripheral seal (40) sealing between the outer tube (3) and the seal housing (27), an annular rod seal (33) provided on an inner peripheral portion of the seal housing (27) in sliding contact with the piston rod (6), and an annular oil seal (9) provided on a side of the seal housing (27) closer to the first end, the annular oil seal (9) being in sliding contact with the piston rod (6), wherein the piston rod (6) is sealed in two stages by the rod seal (33) and the oil seal (9), wherein the outer peripheral portion of the seal housing (27) is provided with an outer peripheral groove (37) and is secured to the outer pipe (3) by a first notched portion (38) formed by notching the outer pipe (3) from the outside into the outer peripheral groove (37) in a radial direction of the outer pipe (3), and wherein the outer peripheral portion of the seal housing (27) on a side thereof closer to the chamber (2A, 117) receives a pressure which is the same as a pressure exerted on the rod seal (33), wherein the outer peripheral portion of the seal housing (27) on an opposite side spaced from the chamber (2A, 117) receives a pressure between the rod seal (33) and the oil seal (9, 35), which pressure is reduced by the rod seal (33), wherein the first outer peripheral seal (43) is provided on a first side of the first notched portion (38) which is closer to the first end of the outer tube, wherein the second outer peripheral seal (40) is on an axially opposite second side to the first notched portion (38) which is closer to the second end of the outer tube, wherein the first outer peripheral seal (43) and the second outer peripheral seal (40) are spaced from the first notched portion (38) in the axial direction of the piston rod, wherein the first outer peripheral seal (43) is arranged to prevent the pressure between the rod seal (33) and the oil seal (9), which is reduced by the rod seal, from being applied between the first notched portion (38) of the outer tube and the outer peripheral portion of the seal housing (27), and wherein the second outer peripheral seal (40) is arranged to prevent the pressure, which is the same as the pressure exerted on the rod seal (33), from being applied between the first notched portion (38) of the outer tube and the outer peripheral portion of the seal housing (27). [7] Cylinder device according to claim 6, wherein the interior of the outer tube (3) is divided by the piston (5) into a first chamber (2B) in which the piston rod (6) is not provided, and a second chamber (2A) in which the piston rod (6) is provided, wherein an annular passage (4) is provided between the cylinder (2) and the outer tube (3), the second chamber (2A) being in communication with the annular passage (4) through a passage (12) at a position closer to the first end of the outer tube (3) without passing through the rod seal (33). [8] Cylinder device according to claim 7, wherein the first chamber (2B) is connected to an external hydraulic circuit through a first damping valve (13) and a first connection interface (15) and the first damping valve (13) is configured to control the flow of a hydraulic fluid between the first connection interface (15) and the first chamber (2B) to generate a damping force. [9] Cylinder device according to claim 7 or 8, in which a damping force generating mechanism (17) is provided on a side wall of the outer tube (3), the damping force generating mechanism (17) is connected to an external hydraulic circuit through a second connection interface (24), wherein the cylinder device further comprises a second damping valve (19) configured to control the flow of hydraulic fluid between the second connection interface (24) and the annular passage (4) to generate a damping force.

Images