Patent Application
20080100002
The present invention relates to a cylinder apparatus installed in a suspension system of an automobile, for example.
Examples of cylinder apparatus used in suspension systems of automobiles include a hydraulic cylinder apparatus for vehicle height control and a hydraulic shock-absorbing damper.
The seal block 4 has a split structure comprising a rod guide 11 fitted to the cylinder 1 to slidably guide the piston rod 2, a seal cap 12 fitted to the rod guide 11 with the outer periphery thereof placed in close contact with the outer tube 9, and a lock ring 13 thread-engaged with the outer tube 9 to hold the seal cap 12 and the rod guide 11 from above. The double seal 7 is disposed between the rod guide 11 and the seal cap 12. For the lock ring 13, the oil seal 8 is provided. Between the rod guide 11 and the seal cap 12, a check valve 14 is provided to allow only the flow of hydraulic fluid from the cylinder 1 into the annular chamber 10. Between the seal cap 12 and the lock ring 13, a seal member 15 is provided to cut off the annular chamber 10 from the outside.
In the cylinder apparatus arranged as stated above, the rod seal 5, which constitutes the double seal 7, is formed from a fluorine-containing resin excellent in sliding performance in view of sliding characteristics. A slight fluid leakage is allowed to occur between the rod seal 5 and the piston rod 2 in response to a rise in fluid pressure in the cylinder 1. Meanwhile, the oil seal 8 is formed from a rubber material excellent in sealing properties. The hydraulic fluid leaking out from between the rod seal 5 and the piston rod 2 is prevented from leaking to the outside by the oil seal 8.
The O-ring 6, which constitutes the double seal 7, is compressively deformed upon receiving the fluid pressure in the cylinder 1 to apply a backup force to the rod seal 5. Accordingly, when the fluid pressure in the cylinder 1 rises in excess of a certain pressure value, the O-ring 6 is strongly compressed against the seal block 4 (seal cap 12) to generate a large backup force, so that the rod seal 5 is pressed against the piston rod 2 with a strong force. As a result, the frictional resistance of the rod seal 5 increases, which impairs smooth extension and contraction (movement) of the piston rod 2 and hence degrades the ride quality. Moreover, the wear of the rod seal 5 is increased, resulting in an increased leakage of hydraulic fluid.
In a cylinder apparatus according to another related art, as shown in
The above-described countermeasure in which the projection 16 is provided suffers, however, from the following problem. Because the projection 16 is present between the rod seal 5 and the O-ring 6, the backup force from the O-ring 6 is unevenly applied to the rod seal 5, making it likely that the rod seal 5 will tilt (i.e. inclination) and hence will wear unevenly. It should be noted that in the cylinder apparatus disclosed in the above-mentioned Japanese Laid Open Publication No. 2001-254838 a circumferentially extending groove is provided on an end surface of a step portion 5a of the rod seal 5 to reduce the radial rigidity of the step portion 5a, thereby preventing inclination of the rod seal 5. However, the basic structure in which the O-ring is compressively deformed by the fluid pressure to generate a backup force remains unchanged. Therefore, there is a risk that the rod seal 5 will be inclined when an excessive fluid pressure is produced in the cylinder 1.
The present invention has been made in view of the above-described problems. An object of the present invention is to provide a cylinder apparatus in which a backup mechanism for pressing a rod seal against a piston rod is arranged to generate a backup force while suppressing the influence of fluid pressure, thereby ensuring smooth movement of the piston rod and suppressing the wear of the rod seal.
To solve the above-described problem, the present invention provides a cylinder apparatus including a cylinder, a piston, a piston rod and a seal device. The cylinder has a hydraulic fluid sealed therein. The piston is slidably fitted in the cylinder. The piston rod is connected at one end thereof to the piston in the cylinder. The other end of the piston rod extends to the outside of the cylinder. The seal device is provided at an opening end of the cylinder. The piston rod extends through the seal device to the outside of the cylinder. The seal device has a rod seal provided in sliding contact with the piston rod. The seal device further has a backup mechanism that presses the rod seal against the piston rod. The backup mechanism has a ring-shaped support plate positioned closer to the cylinder than the rod seal. The backup mechanism further has a ring-shaped resilient member joined to one surface of the ring-shaped support plate and a pressing member that causes elastic deformation of the ring-shaped resilient member to apply a backup force to the rod seal.
According to one aspect of the present invention, the pressing member may be an annular wall provided around said ring-shaped resilient member. The annular wall may be a tapered wall gradually reduced in diameter toward an outer side as viewed in an axial direction of the cylinder.
According to one aspect of the present invention, the seal device may include a seal block having a bore for receiving said piston rod and closing the opening end of the cylinder, which seal block is of a split structure comprising a plurality of divided elements. The rod seal and the backup mechanism may be provided in the seal block. The ring-shaped support plate of the backup mechanism may be clamped between the divided elements of the seal block. In this case, the annular wall may be formed on one of the divided elements of the seal block.
According to one aspect of the present invention, the cylinder apparatus may further comprise a seal member joined to an outer peripheral portion of the one surface of said ring-shaped support plate constituting said backup mechanism. The seal member contacts the seal block to prevent entry of hydraulic fluid to a rear side of the ring-shaped resilient member.
According to one aspect of the present invention, the cylinder may be housed in an outer tube, one end of which is closed, so that an annular chamber is formed between the cylinder and the outer tube. The cylinder apparatus may further comprise a check valve joined to a surface of the ring-shaped support plate opposite to the surface to which the ring-shaped resilient member is joined, which check valve is adapted to allow only flow of hydraulic fluid from the cylinder into the annular chamber.
The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.
In this embodiment, a seal block 4 that constitutes the seal device 3 includes, as shown in
Meanwhile, a backup mechanism 21 that causes a rod seal 5 slidably contacting the piston rod 2 to be pressed against the piston rod 2 includes a ring-shaped support plate 22 positioned closer to the cylinder 1 than the rod seal 5 and a ring-shaped resilient member 23 joined by baking to one (upper) surface of the ring-shaped support plate 22. The backup mechanism 21 further includes an annular wall (pressing member) 24 that is formed on the inner peripheral side of the seal cap 12. The annular wall 24 causes elastic deformation of the ring-shaped resilient member 23 to apply a backup force to the rod seal 5. The ring-shaped resilient member 23 may be formed from a rubber material, for example. The backup mechanism 21 disuses the O-ring 6 (see
More specifically, the ring-shaped support plate 22, which constitutes the backup mechanism 21, has substantially the same inner and outer diameters as those of the rod guide 11 and is concentrically superimposed over the upper surface of the rod guide 11. The ring-shaped support plate 22 is clamped at an outer peripheral portion thereof between the rod guide 11 and the seal cap 12 fitted thereonto when assembled together. The annular wall 24, which constitutes the backup mechanism 21, is a tapered wall gradually reduced in diameter toward the outer side in the axial direction of the cylinder 1. The ring-shaped resilient member 23 provided on the support plate 22 has a configuration as shown by the dashed line in
In this embodiment, the rod seal 5 has a step portion 5a. That is, only a portion of the rod seal 5 on the outer side thereof in the axial direction of the cylinder 1 (i.e. the upper portion of the rod seal 5 as viewed in
In this embodiment, a seal member 25 is joined by baking to an outer peripheral portion of the upper surface of the ring-shaped support plate 22 to seal between the support plate 22 and the seal cap 12. The seal member 25 may be formed from a rubber material, for example. The seal member 25 prevents the entry of hydraulic fluid (fluid pressure) to the rear side of the ring-shaped resilient member 23. Thus, the amount of elastic deformation of the ring-shaped resilient member 23 is mechanically determined by engagement with the annular wall 24 substantially independently of the influence of fluid pressure.
In this embodiment, a check valve 26 is joined by baking to the lower surface of the ring-shaped support plate 22. The check valve 26 has a lip portion 26a (see
The overall structure of the cylinder apparatus according to this embodiment is as shown in
A ring-shaped piston 35 is slidably fitted in the cylinder 1. The piston 35 divides the interior of the cylinder 1 into two chambers, i.e. a cylinder upper chamber 1a and a cylinder lower chamber 1b. One end portion of the piston rod 2 is connected to the piston 35 through a piston bolt 36. The piston 35 is provided with a plurality of hydraulic fluid passages 37 that communicate between the cylinder upper and lower chambers 1a and 1b. The piston 35 is further provided with disk valves 38 that generate damping forces during the extension and compression strokes, respectively. The piston rod 2 is hollow. A pump tube 39 and a hollow pump rod 40 are concentrically fitted in the hollow inside of the piston rod 2 such that the pump rod 40 extends through the pump tube 39. The lower end of the pump rod 40 extends through the piston 35 as far as the partition member 31. The hollow inside of the pump rod 40 communicates with the oil tank 33. The space between the inner surface of the piston rod 2 and the pump tube 39 is provided as an annular hydraulic fluid passage. The hydraulic fluid passage is communicated with the cylinder upper chamber 1a through a hole 41 provided in the wall of the piston rod 2.
A pump chamber 42 is formed in an upper end portion of the pump tube 39. The upper end of the pump rod 40 is provided with a check valve 43 that allows only the flow of hydraulic fluid from the oil tank 33 into the pump chamber 42 through the hollow inside of the pump rod 40. The upper end of the pump tube 39 is provided with a check valve 44 that allows only the flow of hydraulic fluid from the pump chamber 42 to the hydraulic fluid passage around the pump tube 39. It should be noted that when the length to which the piston rod 2 extends is within a standard range, the pump chamber 42 and the cylinder upper and lower chambers 1a and 1b are kept in communication with each other through a bypass passage (not shown) provided on the pump rod 40. The bypass passage is formed, for example, from a groove provided on the outer periphery of the pump rod 40 to extend axially from the pump chamber 42 to the vicinity of the piston 35. When the extending length of the piston rod 2 exceeds the standard range, the oil tank 33 and the cylinder upper and lower chambers 1a and 1b communicate with each other through a release passage (not shown) provided on the pump rod 40. For example, the release passage is formed from a hole provided on the pump rod 40 below the lower end of the above-described groove to extend diametrically through the center of the pump rod 40.
The cylinder apparatus according to this embodiment is incorporated into a suspension system as shown in
In the cylinder apparatus arranged as stated above, when the vehicle height is a standard vehicle height, the pump chamber 42 and the cylinder upper and lower chambers 1a and 1b are in communication with each other through the bypass passage. Therefore, when the piston rod 2 extends and contracts in response to vibration of the suspension system during running of the vehicle, the cylinder apparatus operates as follows.
During the extension stroke of the piston rod 2, a part of hydraulic fluid in the cylinder upper and lower chambers 1a and 1b flows into the pump chamber 42. During the compression stroke of the piston rod 2, a part of hydraulic fluid in the pump chamber 42 is discharged into the cylinder upper and lower chambers 1a and 1b. Accordingly, there is no change in the vehicle height.
When the vehicle height becomes lower than the standard vehicle height due, for example, to an increase in the carrying load of the vehicle and consequently the extending length of the piston rod 2 becomes less than the standard range, the communication between the pump chamber 42 and the cylinder upper and lower chambers 1a and 1b is cut off. Therefore, when the piston rod 2 extends and contracts in response to vibration of the suspension system during running of the vehicle, the cylinder apparatus operates as follows.
During the extension stroke of the piston rod 2, the pump rod 40 retracts (moves downward in
When the vehicle height becomes higher than the standard vehicle height due, for example, to a decrease in the carrying load of the vehicle and consequently the extending length of the piston rod 2 exceeds the standard range, the pump chamber 42 is communicated with the cylinder upper and lower chambers 1a and 1b through the bypass passage, and the pumping operation is canceled. In addition, the cylinder upper and lower chambers 1a and 1b are communicated with the hollow inside of the pump rod 40 through the release passage. Consequently, the hydraulic fluid in the cylinder upper and lower chambers 1a and 1b is returned to the oil tank 33, resulting in a decrease in the volume of hydraulic fluid in the cylinder upper and lower chambers 1a and 1b and the annular chamber (reservoir chamber) 10. Accordingly, the vehicle height lowers. When the vehicle height lowers to the standard vehicle height and consequently the extending length of the piston rod 2 falls within the standard range, the hydraulic fluid returning operation is stopped.
Thus, the vehicle height can be adjusted to a constant level independently of the carrying load and so forth by repeating the pumping operation and the hydraulic fluid returning operation utilizing vibration of the suspension system during running of the vehicle. It should be noted that when the piston rod 2 extends and contracts, the disk valves 38, which are provided on the piston 35, open and close to generate predetermined damping forces.
When the pressure of hydraulic fluid in the cylinder 1 (cylinder upper chamber 1a) rises in response to the extension and contraction of the piston rod 2, the fluid pressure may also act on the backup mechanism 21 in the seal device 3. In this regard, the ring-shaped resilient member 23, which presses the rod seal 5 against the piston rod 2, is surrounded by the ring-shaped support plate 22, which is clamped between the rod guide 11 and the seal cap 12, and the annular wall (tapered wall) 24 at the rear of the ring-shaped resilient member 23. Therefore, the fluid pressure does not act on the ring-shaped resilient member 23. Accordingly, the backup force applied to the rod seal 5 from the ring-shaped resilient member 23 is kept substantially constant independently of the influence of fluid pressure. As a result, there is no likelihood that the frictional resistance of the rod seal 5 will increase. Thus, smooth extension and contraction (movement) of the piston rod 2 can be ensured, and the wear of the rod seal 5 itself can be suppressed. Particularly, in this embodiment, the seal member 25 provided on the outer peripheral portion of the ring-shaped support plate 22 surely blocks the entry of hydraulic fluid (fluid pressure) to the rear side of the ring-shaped resilient member 23. Therefore, the backup force is kept very stable, so that the extension and contraction movement of the piston rod 2 becomes even smoother. In addition, because the ring-shaped resilient member 23 applies pressure uniformly to the rod seal 5 while being in contact with the back of the rod seal 5, inclination of the rod seal 5 no longer occurs. As a result, uneven wear of the rod seal 5 is also suppressed.
In this embodiment, the ring-shaped support plate 22, which constitutes the backup mechanism 21, is integrally provided with the check valve 26 that allows only the flow of hydraulic fluid from the cylinder 1 into the annular chamber 10 around the cylinder 1. Therefore, it is possible to reduce the number of constituent parts in comparison to the cylinder apparatus according to the related art in which the check valve 14 (
Although in the foregoing embodiment the cylinder apparatus is constructed as a vehicle height control cylinder apparatus incorporating a self-pumping mechanism, the present invention is applicable to any type of vehicle height control system. The vehicle height control cylinder apparatus may be arranged such that a hydraulic fluid supply and discharge mechanism and a damping force generating mechanism are provided outside a cylinder as disclosed in the aforementioned Japanese Laid Open Publication No. 2001-254838. In addition, the application range of the present invention is not limited to the above-described vehicle height control cylinder apparatus. The present invention is also applicable to various cylinder apparatus that require a rod seal and a backup mechanism therefor as a seal device, for example, hydraulic cylinders and hydraulic shock absorbers.
Further, although in the foregoing embodiment the ring-shaped resilient member 23 is shown to be a perfect ring-shaped member, by way of example, the configuration of the ring-shaped resilient member 23 is not necessarily limited to the described shape. The ring-shaped resilient member 23 may be of a partially discontinuous ring shape. However, in case that a partially discontinuous ring-shaped resilient member 23 is employed, an extra seal member needs to be provided at a side of the rod seal 5 closer to the cylinder 1.
In the cylinder apparatus according to the foregoing embodiment, the ring-shaped resilient member 23 is joined to the ring-shaped support plate 22, and this ring-shaped resilient member 23 is elastically deformed by the pressing member 24 to generate a backup force. Therefore, the backup force is determined by the amount of elastic deformation of the ring-shaped resilient member 23 caused by the pressing member 24. Accordingly, the force with which the rod seal 5 is pressed against the piston rod 2 is kept substantially constant independently of the change in fluid pressure in the cylinder 1. Consequently, there is no likelihood that the frictional resistance of the rod seal 5 will increase excessively. Thus, smooth extension and contraction movement of the piston rod 2 is ensured, and the wear of the rod seal 5 is suppressed. Further, because it is unnecessary to interpose an extra member between the rod seal 5 and the backup mechanism 21, the backup force can be applied uniformly to the rod seal 5. Accordingly, the inclination of the rod seal 5 is suppressed, and the uneven wear of the rod seal 5 is also suppressed.
In the cylinder apparatus according to the foregoing embodiment, the backup mechanism 21 that presses the rod seal 5 against the piston rod 2 is arranged to generate a backup force while suppressing the influence of fluid pressure. Therefore, the force with which the rod seal 5 is pressed against the piston rod 2 is kept substantially constant. Accordingly, it becomes possible to ensure smooth movement of the piston rod 2, and the wear of the rod seal 5, including uneven wear thereof, is suppressed.
Although only some exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teaching and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.
The present application claims priority under 35 U.S.C. section 119 to Japanese Patent Application No. 2006-296844, filed on Sep. 30, 2006. The entire disclosure of Japanese Patent Application No. 2006-296844 filed on Sep. 30, 2006, including specification, claims, drawings and summary is incorporated herein by reference in its entirety.
The Japanese Laid Open Publication No. 2001-254838 is incorporated herein by reference in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 296844/2006 | Oct 2006 | JP | national |
