JP2021014873A - Sealing device - Google Patents

Abstract

To make an external peripheral seal possess pressure resistance against air pressure.SOLUTION: A piston rod is reciprocally accommodated in an outer cylinder 21 of a hydraulic damper so as to protrude from an opening part 21a, and an oil seal 101 is attached to the opening part 21a. The oil seal 101 comprises an annular metal ring 111 though which the piston rod penetrates, and a rod seal RS and an external peripheral seal OS are fixed to the metal ring 111. The rod seal RS includes a seal lip 131 extending toward an oil chamber 42 of the hydraulic damper, and a backflow prevention lip 141 extending toward an air-A side opposite to the oil chamber 42, and respective lip ends 132, 142 are made to contact with the piston rod. The external peripheral seal OS includes two strings of lip ends 152 (152a, 152b) contacting with an internal peripheral face of the outer cylinder 21 in the oil chamber 42. The lip end 152b of the external peripheral seal OS near the air-A side has a shape which is formed by shifting a surface pressure peak to the air-A side.SELECTED DRAWING: Figure 2

Description

The present invention relates to a sealing device.

A sealing device is attached to an opening portion of a housing of a hydraulic shock absorber used for an automobile suspension or the like. The sealing device seals between the oil chamber provided in the housing and the external space to prevent oil from leaking from the oil chamber.

Patent Documents 1 and 2 disclose an air suspension in which a hydraulic shock absorber and an air spring are combined. The hydraulic shock absorber described in Patent Document 1 is a double-cylinder type, and the hydraulic shock absorber described in Patent Document 2 is a single-cylinder type.

The double-cylinder type hydraulic shock absorber has a double structure of an inner cylinder (“cylinder” in Document 1) for accommodating a piston rod and an outer cylinder, and the inner cylinder and the outer cylinder are connected by an orifice. .. When the piston rod expands and contracts, oil moves between the inner cylinder and the outer cylinder via the orifice and exerts a damping force. The hydraulic shock absorber described in Patent Document 1 is provided with an orifice (“through hole” in Document 1) in a rod guide provided on the opening end side of the inner cylinder and the outer cylinder. Therefore, the outer cylinder serves as a housing, and the sealing device (“rod seal” in Document 1) is attached to the open portion of the outer cylinder.

In a single-cylinder type hydraulic shock absorber, a piston rod is housed inside an outer cylinder (“cylinder” in Document 2), and a piston valve is attached to the tip of the piston rod. The piston valve is provided with an orifice, and oil moves in the outer cylinder through the orifice. Therefore, the outer cylinder serves as a housing, and the sealing device (“washer”, “rod seal”, and “outer peripheral seal” in Document 2) is attached to the open portion of the outer cylinder.

The air spring of the air suspension has an air chamber at the opening of the housing regardless of whether the hydraulic shock absorber is a double cylinder type or a single cylinder type, and the volume of the air chamber is changed according to the expansion and contraction of the piston rod. I try to let you. When the piston rod expands and contracts, the pressure in the air chamber fluctuates and a damping force is generated.

Jikkenhei 02-143538 JP-A-2010-151296

When the hydraulic shock absorber and the air spring are combined, the volume in the air chamber becomes smaller according to the contraction of the piston rod, and the internal pressure increases. Therefore, the sealing device attached to the housing of the hydraulic shock absorber is pressurized.

In the sealing device, for example, as described in Patent Document 2, the rod seal is fixed to the inner peripheral side of the annular metal ring (“washer” in Document 2), and the outer peripheral seal is fixed to the outer peripheral side. The rod seal of the sealing device used for the air suspension has a structure capable of receiving both the oil pressure from the inside of the housing and the air pressure from the outside of the housing. For example, in the rod seal (17) of the sealing device described in Patent Document 2, the oil pressure from the inside of the housing is received by the main seal lip (19), and the air pressure from the outside of the housing is received by the backflow prevention seal lip (18). Receive at. Patent Document 2 refers to the difference in the angle formed with the outer peripheral surface of the piston rod as a difference between the dust strip and the backflow prevention seal lip provided in the sealing device of a general hydraulic shock absorber (see paragraph [0012]). Explains that the backflow prevention seal lip can receive air pressure.

However, the outer peripheral seal fixed to the outer peripheral side of the metal ring is designed to receive oil pressure exclusively, and is not configured to receive air pressure. Therefore, when the pressure in the air chamber of the air spring increases, air may be mixed into the machine of the flood control shock absorber. Improvement is required.

An object of the present invention is to provide the outer peripheral seal with pressure resistance to air pressure.

One aspect of the sealing device of the present invention is an annular metal ring arranged in an opening of a housing of a hydraulic shock absorber and penetrating a piston rod housed in the housing so as to be reciprocally movable, and fixed to the metal ring. An annular rod seal having a main lip extending toward the oil chamber of the hydraulic shock absorber and a secondary lip extending toward the air side opposite to the oil chamber, and bringing each lip end into contact with the piston rod. And an annular outer peripheral seal having at least two lip ends in the oil chamber fixed to the metal ring and in contact with the inner peripheral surface of the housing, and the lip end of the outer peripheral seal closer to the air side. Has a shape in which the surface pressure peak is closer to the air side.

Another aspect of the sealing device of the present invention is an annular metal ring, a main lip fixed to the metal ring and extending toward a space on one side of the metal ring, and a space opposite to the one side. An annular inner peripheral seal having an auxiliary lip extending toward the metal ring and positioning each lip end inward of the inner peripheral surface of the metal ring, and an annular inner peripheral seal fixed to the metal ring having a diameter larger than that of the metal ring. An annular outer peripheral seal having at least two lip ends in the space on one side thereof is provided, and the lip end of the outer peripheral seal closer to the space on the opposite side brings a surface pressure peak closer to the space on the opposite side. It has a shape.

According to the present invention, the outer peripheral seal can be provided with pressure resistance against air pressure.

The schematic diagram which shows the air suspension which uses the sealing device of this embodiment. The vertical sectional view of the sealing device of this embodiment. A vertical cross-sectional view showing an enlarged outer lip. FIG. 6A is a schematic view showing the contact pressure of the outer peripheral lip of the comparative example, (B) is the outer peripheral lip of another comparative example, and (C) is the contact pressure of the outer peripheral lip of the present embodiment when the air pressure is increased.

An embodiment will be described with reference to the drawings. This embodiment is an example of a sealing device used for an air suspension.

As schematically shown in FIG. 1, the air suspension 1 is a combination of a hydraulic shock absorber 11 and an air spring 51.

[Flood shock absorber]
The air suspension 1 of the present embodiment uses a single-cylinder type hydraulic shock absorber 11 called a de-carboxylic type.

As shown in FIG. 1, the hydraulic shock absorber 11 houses the piston rod 31 inside a metal outer cylinder 21 having a cylindrical shape with both ends open. The outer cylinder 21 is a housing for accommodating each part.

The piston rod 31 includes a metal rod 32. A disk-shaped piston 33 is fixed to one end of the rod 32, and a rod head 34 is fixed to the opposite end. The end of the piston rod 31 on the piston 33 side is housed inside the outer cylinder 21. The end of the piston rod 31 on the rod head 34 side protrudes to the outside from one opening 21a of the outer cylinder 21.

The outer peripheral surface of the piston 33 is in contact with the inner wall of the outer cylinder 21 so as to be slidable. The amount of expansion and contraction of the rod 32 from the outer cylinder 21 is changed by the piston 33 reciprocating inside the outer cylinder 21.

The internal space of the outer cylinder 21 is divided into two by the free piston 41. One of the two divided spaces is filled with oil O, and the other space is filled with gas G. The space filled with the oil O is the oil chamber 42, and the space filled with the gas G is the gas chamber 43.

The oil chamber 42 is defined by a space defined by an oil seal 101 provided in one opening of the outer cylinder 21 and a free piston 41. The oil seal 101 is an aspect of a sealing device.

The gas chamber 43 is defined by a space defined by a cap 22 and a free piston 41 that close the other opening 21b of the outer cylinder 21. The free piston 41 is in close contact with the inner wall of the outer cylinder 21, and slides along the axial direction while maintaining the posture of partitioning the internal space of the outer cylinder 21.

A rod guide 23 that guides the rod 32 through the opening is fixed to the opening on one end side of the outer cylinder 21. The rod guide 23 is arranged on the inner side of the outer cylinder 21 with respect to the oil seal 101, that is, in the oil chamber 42. The piston 33 of the piston rod 31 is also arranged in the oil chamber 42. The rod 32 is restrained from free movement by the piston 33 and the rod guide 23, and can move back and forth concentrically with the outer cylinder 21.

The piston 33 is provided with a plurality of orifices 35. When the piston 33 moves in the oil chamber 42 together with the rod 32, the oil O passes through the orifice 35.

[Air spring]
The air spring 51 includes an air chamber 52 that defines a space on the rod head 34 side of the piston rod 31. The air chamber 52 is formed by a head cap 53, an outer shell 54, and a diaphragm 55.

The head cap 53 is a metal cap fixed to the rod head 34, and extends the sidewall 56 toward the hydraulic shock absorber 11.

The outer shell 54 is a metal annular member fixed to the sidewall 56 of the head cap 53. It has a shape that narrows the diameter from the portion fixed to the head cap 53 toward the hydraulic shock absorber 11.

The diaphragm 55 is a rubber member having a bag shape fixed to a small diameter portion of the outer shell 54. It is folded upward inward at an intermediate portion that goes downward from the portion fixed to the outer shell 54, and the end portion is fixed to the outer cylinder 21 of the hydraulic shock absorber 11.

The air spring 51 fills the air chamber 52 with air A. The volume of the air chamber 52 is changed according to the expansion and contraction of the piston rod 31, and the internal pressure is changed. The air spring 51 generates a damping force due to pressure fluctuations in the air chamber 52.

[Oil seal]
As shown in FIG. 2, in the oil seal 101, an elastic body 121 having various lips is fixed to a metal ring 111 having an annular shape. The metal ring 111 is crimped on one end side of the outer cylinder 21 of the oil seal 101, and is sandwiched and fixed between the oil seal 101 and the rod guide 23. In FIG. 2, the end portion of the outer cylinder 21 crimping the metal ring 111 of the oil seal 101 is indicated by reference numeral 24.

The elastic body 121 is formed of a rubber-like elastic material, and is divided into three types of regions having a seal lip 131 as a main lip, a backflow prevention lip 141 as a secondary lip, and an outer peripheral lip 151. The seal lip 131 and the backflow prevention lip 141 are lips that seal the rod 32 included in the piston rod 31, and constitute the rod seal RS. The outer peripheral lip 151 is a lip that seals between the outer cylinder 21 and the inner peripheral surface, and constitutes the outer peripheral seal OS.

As the material of the elastic body 121, for example, nitrile butadiene rubber (NBR), fluororubber and the like are used.

The seal lip 131 is generated by an elastic body 121 vulcanized and bonded to the inner peripheral side of the metal ring 111. The elastic body 121 that produces the seal lip 131 extends toward the oil chamber 42, which is a space on one side of the metal ring 111, and is provided with a lip end 132 at the tip end portion. Fitted to the back side of the lip end 132 is a garter spring 133. The garter spring 133 contracts in the inner diameter direction of the seal lip 131 to increase the tension of the lip end 132 with respect to the outer peripheral surface of the rod 32.

The backflow prevention lip 141 is generated by an elastic body 121 vulcanized and adhered to the inner peripheral side of the metal ring 111. The elastic body 121 that generates the backflow prevention lip 141 extends toward the air A side (air chamber 52 side) opposite to the oil chamber 42, and the lip end 142 is provided at the tip end portion.

The rod seal RS including the seal lip 131 and the backflow prevention lip 141 has an annular shape in which the lip ends 132 and 142 are positioned inward of the inner peripheral surface of the metal ring 111, respectively.

The elastic body 121 that produces the seal lip 131 wraps around the entire surface of the metal ring 111 facing the oil chamber 42 and communicates with the outer peripheral lip 151.

As shown in FIG. 3, the outer peripheral lip 151 is generated by an elastic body 121 vulcanized and adhered to the outer peripheral side of the metal ring 111. The elastic body 121 is vulcanized and adhered to one surface and the outer peripheral surface of the metal ring 111 facing the oil chamber 42. The outer peripheral surface of the elastic body 121 is obliquely extended toward the inner side of the outer cylinder 21, and lip ends 152 are provided in the diagonally extended tip region and root region, respectively. The two lip ends 152 are in close contact with the inner wall of the outer cylinder 21.

For convenience of explanation, of the two lip ends 152 of the outer peripheral lip 151, the one closer to the oil chamber 42 is referred to as the lip end 152a, and the one closer to the air A side (air chamber 52) is referred to as the lip end 152b.

The lip end 152a of the outer peripheral lip 151 is located in the tip region of the elastic body 121 extending obliquely from the metal ring 111. When the internal pressure of the oil chamber 42 increases, the lip end 152a is pressurized by the oil O and tends to expand to the outer diameter side. The tapered surface 153 formed on the bottom surface of the outer peripheral lip 151 also enhances the action of the lip end 152a that tends to expand toward the outer diameter side. At this time, since the lip end 152a of the outer peripheral lip 151 is in contact with the inner wall of the outer cylinder 21, it does not expand to the outer diameter side and increases the close force with respect to the inner wall of the outer cylinder 21.

The lip end 152b of the outer peripheral lip 151 is located in the root region of the elastic body 121 with respect to the metal ring 111. Therefore, the air chamber 52 is contacted and the air A is contacted. The lip end 152b has a shape in which the surface pressure peak is closer to the air A side. As an example, the lip end 152b has a triangular cross-section with the apex position closer to the air A side.

[Mounting on vehicle]
The air suspension 1 is used by fixing the side of the rod head 34 of the piston rod 31 to a vehicle body (not shown) and fixing the cap 22 to a suspension (not shown).

[Action effect]
In such a configuration, the air suspension 1 generates a damping force by both the hydraulic shock absorber 11 and the air spring 51.

In the hydraulic shock absorber 11, the rod 32 of the piston rod 31 expands and contracts according to the movement of the suspension, and the piston 33 slides in the outer cylinder 21. At this time, the volume of oil O in which the rod 32 has entered pushes down the free piston 41 and compresses the gas chamber 43. The damping force on the contraction side and the extension side of the suspension is controlled by the speed of the oil O passing through the orifice 35 provided in the piston 33.

When the input on the extension side is applied to the suspension, the rod 32 moves in the direction of being pulled out from the outer cylinder 21, so that the oil O on the side of the oil seal 101 is added by the sliding movement of the piston 33 that follows in the oil chamber 42. Be pressured. At this time, in the outer peripheral seal OS, the lip end 152a of the outer peripheral lip 151 receives a high pressure and is strongly pressed against the inner wall of the outer cylinder 21. As a result, the sealing property of the outer peripheral sealing OS is ensured.

In the air spring 51, when the rod 32 of the piston rod 31 expands and contracts according to the movement of the suspension, the volume of the air chamber 52 changes while deforming the diaphragm 55. Along with this, the pressure inside the air chamber 52 fluctuates, and the air spring 51 generates a damping force.

When the input on the contraction side is applied to the suspension, the rod 32 moves in the direction of being pushed into the outer cylinder 21, so that the internal pressure in the air chamber 52 increases. As a result, a large air pressure is applied to the lip end 152b of the outer peripheral lip 151 located on the air chamber 52 side.

4 (A) to 4 (C) are schematic views showing the state of the outer peripheral lip 151 when the air pressure is increased. As a comparative example, FIG. 4A shows a state of contact pressure of the outer peripheral lip 151C1 having only the lip end 152a without the lip end 152b. As another comparative example, FIG. 4B shows a state of contact pressure of the outer peripheral lip 151C2 whose lip end 152b has an isosceles triangle cross section. FIG. 4C shows the state of the contact pressure of the outer peripheral lip 151 of the present embodiment.

In the outer peripheral lip 151C1 of the comparative example shown in FIG. 4 (A), when the air pressure in the air chamber 52 increases, the air A is directly applied to the other lip end 152a because the lip end 152b is not provided. Be guided. At this time, since the oil pressure in the oil chamber 42 is lowered, air A may be mixed into the oil chamber 42 from between the inner wall of the outer cylinder 21 and the lip end 152a.

In the outer peripheral lip 151C2 of another comparative example shown in FIG. 4B, when the air pressure in the air chamber 52 increases, the lip end 152b in contact with the inner wall of the outer cylinder 21 blocks the air A, and the oil chamber Prevents air A from entering the 42.

In the outer peripheral lip 151 of the present embodiment shown in FIG. 4C, when the air pressure in the air chamber 52 increases, the lip end 152b in contact with the inner wall of the outer cylinder 21 blocks the air A, and the oil chamber Prevents air A from entering the 42.

At this time, in the outer peripheral lip 151 of the present embodiment, the surface pressure peak of the lip end 152b is brought closer to the air A side. Therefore, the surface to which the air pressure is applied is steeper than that of the outer peripheral lip 151C2 of the comparative example shown in FIG. 4B in which the surface pressure peak is set at the center position of the lip end 152b. Therefore, the lip end 152b is pressed against the inner wall of the outer cylinder 21, and it is possible to reliably prevent air A from entering the oil chamber 42.

The effect of the outer peripheral lip 151 of the present embodiment becomes clearer when compared with the outer peripheral lip 151C2 of another comparative example shown in FIG. 4 (B). In the case of the outer peripheral lip 151C2 shown as a comparative example, the surface to which the air pressure is applied is gentler than that of the outer peripheral lip 151 of the present embodiment. Therefore, it is difficult to obtain the effect of pressing the lip end 152b against the inner wall of the outer cylinder 21, and as the air pressure increases, the lip end 152b tends to separate from the inner wall of the outer cylinder 21. This tendency becomes more remarkable as the position of the apex in the cross section of the lip end 152b approaches the other lip end 152a.

From the above analysis, it is clear that when the air pressure in the air chamber 52 increases, the outer peripheral lip 151 of the present embodiment can more reliably prevent the air A from being mixed into the oil chamber 42. ..

[Modification example]
At the time of implementation, various modifications and changes are possible.

For example, in the above embodiment, an example of application to the air suspension 1 using the single-cylinder type hydraulic shock absorber 11 called the de-carboxylic type has been illustrated. At the time of implementation, the hydraulic shock absorber 11 may be a double cylinder type. Further, the application to the air suspension 1 is not indispensable, and the application to the hydraulic shock absorber 11 having no air chamber 52 is also possible.

Further, the outer peripheral seal OS may have at least two lip ends 152 in the oil chamber 42, and the lip end 152 may have three or more threads.

All other transformations and changes are possible.

1 Air suspension 11 Hydraulic shock absorber 21 Outer cylinder (housing)
21a, 21b Opening 22 Cap 23 Rod Guide 31 Piston Rod 32 Rod 33 Piston 34 Rod Head 35 Orchid 41 Free Piston 42 Oil Chamber 43 Gas Chamber 51 Air Spring 52 Air Chamber 53 Head Cap 54 Outer Shell 55 Diaphragm 56 Sidewall 101 Oil Seal (sealing device)
111 Metal ring 121 Elastic body 131 Seal lip (main lip)
132 Lip end 133 Garter spring 141 Backflow prevention lip (secondary lip)
142 Lip End 151 Outer Lip 151C1 Outer Lip 151C2 Outer Lip 152 (152a, 152b) Lip End 153 Tapered Surface A Air G Gas O Oil OS Outer Seal RS Rod Seal

Claims (4)

An annular metal ring arranged in the opening of the housing of the hydraulic shock absorber and penetrating a piston rod movably housed in the housing.
It has a main lip fixed to the metal ring and extending toward the oil chamber of the hydraulic shock absorber, and a sub lip extending toward the air side opposite to the oil chamber, and each lip end is attached to the piston rod. An annular rod seal to be contacted and
An annular outer peripheral seal fixed to the metal ring and having at least two lip ends in the oil chamber in contact with the inner peripheral surface of the housing.
A sealing device having a shape in which the lip end of the outer peripheral seal closer to the air side has a surface pressure peak closer to the air side. The outer peripheral lip closer to the air side has a triangular cross-sectional shape with the apex position closer to the air side.
The sealing device according to claim 1. Used in an air suspension provided with an air chamber on the air side that is compressed according to the contraction of the piston rod.
The sealing device according to claim 1 or 2. An annular metal ring and
It has a main lip that is fixed to the metal ring and extends toward the space on one side of the metal ring, and a sub lip that extends toward the space on the opposite side of the one side, and each lip end has the metal ring. An annular inner peripheral seal located inward of the inner peripheral surface of the
An annular outer peripheral seal fixed to the metal ring and having at least two lip ends having a diameter larger than that of the metal ring in the space on one surface side.
The lip end of the outer peripheral seal, which is closer to the space on the opposite side, has a shape in which the surface pressure peak is brought closer to the space on the opposite side.

Images