JPH06147327A - Packing - Google Patents

Abstract

PURPOSE:To improve effective prevention of blow-by phenomenon and sealing performance. CONSTITUTION:A packing wherein an annular back-up ring 14 is joined onto a step part formed on the peripheral surface on the low-pressure side of a packing main body 11 housed in a packing attaching groove 20 and provided on the peripheral surface of one member between two members to be fitted and relatively moved, and provided with a lip part of a fluid seal on the high- pressure side, which is provided with a passage 15 provided with end surface grooves 17, 18 whose at least one end is opened to the other member side on both end surfaces of the back-up ring and whose other ends are communicated with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packing, and more particularly to a packing in which pressure builds up on the seal side of the packing.

[0002]

2. Description of the Related Art A rod packing provided on a rod cover of a hydraulic cylinder is well known as an example of this kind of packing. As a conventional technique of this kind, the actual Kaihei 1
There is a packing disclosed in No. 152151. The schematic configuration thereof is shown in FIGS. In the figure, the packing 1 is a sliding seal for the ram 31 of the hydraulic jack and is installed in the packing groove 33 of the cylinder cover 32.
The packing 1 has a shape in which a U packing 1a made of synthetic rubber or synthetic resin and a backup ring 4 made of synthetic resin or metal are integrated. The U packing 1a has an annular inner lip 2 that elastically contacts the ram 31 to seal it, and an annular outer lip 3 that elastically contacts the bottom surface 33a of the packing groove 33 to seal it. The backup ring 4 is provided on the low-pressure side of the inner lip 2, and a plurality of, for example, six depressurizing grooves 6 extending in the axial direction are provided on the inner peripheral surface 5 thereof at equal intervals in the circumferential direction. The pressure relief groove 6 is, for example, an arc shape having an inner diameter of 100 mm and a clearance G of about 0.1 mm, an opening width on the inner peripheral surface 5 of 3 mm, and a depth of 1 mm.

The pressure relief groove 6 is provided to prevent the blow-through phenomenon. That is, the pressure relief groove 6
In the case where the amount of oil leaked from the clearance G is small because the clearance G is small and the temperature of the pressure oil is low and the viscosity is low, the seal portion C by the inner lip 2 is not provided. Ram room side A1
Due to a minute oil leak from the space E to the space E, oil is accumulated in the space E to increase the pressure, and the force for pushing up the inner lip 2 acts to reduce the seal pressure. This decrease in the seal pressure increases the amount of oil leakage in the seal portion C, and further increases the pressure in the gap E, which eventually pushes the inner lip 2 up from the surface of the ram 31,
Sealing becomes impossible and a large amount of oil leaks, causing a so-called blow-through phenomenon. If the pressure relief groove 6 is provided, both sides of the backup ring 4 in the axial direction are communicated with each other,
The oil accumulated in the void E is released to prevent the pressure in the void E from rising, and the sealing pressure by the inner lip 2 does not decrease,
The stable sealing property can be maintained, and there is no fear of occurrence of blow-through phenomenon.

[0004]

However, the conventional packing 1 having the pressure relief groove 6 is deformed so that the void E on the inner lip 2 side disappears when pressure is applied to the ram chamber side A1. The sealing ability of the inner lip 2 is reduced. At the same time, the fluid leaking from the inner lip 2 flows out from the pressure relief groove 6 provided in the backup ring, which poses a serious problem. In particular, if the material of the backup ring is made of a hard material according to the high-pressure fluid, the flow cross-sectional area of the pressure relief groove 6 does not decrease according to the pressure, so that the fluid leakage from the pressure relief groove 6 becomes large. The present invention aims to solve the above problems.

[0005]

The means of the present invention is accommodated in a packing mounting groove provided on the peripheral surface of one member of two members which are fitted and move relative to each other, and a lip of a fluid seal is provided on the high pressure side. A packing in which an annular backup ring is joined to a step portion formed on the low-pressure side peripheral surface of a packing body having a portion, and one end is formed on both end surfaces of the backup ring and at least one end surface groove is opened to the other member side. It is characterized in that the other has a flow passage communicating with each other.

It is preferable that a sheet-shaped fluororesin layer is formed on the contact surface of the lip portion, which is in contact with the other member, excluding the end portion on the high-pressure side.

[0007]

In the packing of the present invention, the stronger the fluid pressure acts on the high-pressure side, the part of the packing body is less likely to enter the end face groove, and the flow passage cross-sectional area of the end face groove is reduced. As a result, the fluid that has leaked from the lip portion temporarily accumulates in the void, and the void is effectively prevented from being deformed so that the lip is separated from the sliding member. At the same time, if the fluid pressure accumulated in the gap approaches the working fluid pressure, it is possible to reduce the pressure by pushing apart a part of the packing body that has entered the end surface groove.
As a result, the lip portion of the seal keeps its original shape and is prevented from being deformed by pressure accumulation.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In this embodiment, the piston rod 2 of the hydraulic cylinder is used.
1 is a rod packing 22 having a packing groove 20 provided in a rod cover 22 penetrating therethrough and accommodated in the groove. The rod packing 10 is composed of a lip packing 11 and a backup ring 14. The lip packing 11 is made of nitrile rubber and is located on the high pressure side, that is, the pressure chamber 2 of the cylinder.
3 has an inner lip portion 12 and an outer lip portion 13, and a fluororesin backup ring 14 is provided on the opposite low-pressure side, that is, on the step of the inner circumference on the outside 24 side. A sheet-like layer 16 of fluororesin is provided on the inner peripheral surface of the inner lip portion 12. This fluororesin layer 1
6 is provided so as to avoid the inner peripheral surface of the high pressure side end of the inner lip portion 12 and the inner peripheral surface of the portion close to the high pressure side end surface of the backup ring 14, and the inner diameter of this portion is the rod 21 on the low pressure side.
Parallel portion 16 forming a gap E slightly away from the peripheral surface of
It is composed of a and a tapered portion 16b which is reduced toward the high pressure side.

The backup ring 14 is provided with a plurality of axial communication grooves 15 at equal intervals in the circumferential direction, and both end surfaces of the communication groove 15 are connected to both end surfaces of the backup ring 14 to reach inner holes of the backup ring. 17, 1
8 is provided. The communication groove 15 may be a communication hole penetrating in the axial direction. Each of these grooves 15, 17 and 18 has a width of about 4 mm and a depth of about 0.5 mm, and although the corners of the groove opening edge and the groove bottom corners in the groove cross-sectional shape are not shown, the radius is less than 1 mm. It is as an arc.

In the rod packing 10, the outer periphery of the outer lip portion 13 is in pressure contact with the bottom of the groove 20 in the mounted state, and the taper portion 1 of the fluororesin layer 16 of the inner lip portion 12 is attached.
The inner peripheral surface of 6b and the inner peripheral surface of the rubber portion at the end on the pressure chamber side are in pressure contact with the outer periphery of the rod 21. In this state, the pressure chamber 23
When the pressure rises, the outer lip portion 13 is further pressed to the bottom of the groove 20, and the inner lip portion 12 also has a larger pressing force on the rod 21. At the same time, a part of the packing body elastically deforms and enters the end surface groove 18, so that this flow path is narrowed. As a result, the fluid leaked from the inner lip portion 12 by a small amount is
Although the pressure is stored in the space E, when the working fluid pressure on the pressure chamber 23 side is approached, a part of the packing body that has entered the end surface groove 18 is pressed and flows out. Therefore, the blow-through phenomenon that separates the inner lip portion 12 from the rod 21 does not occur.
At the same time, the pressure in the space is lower than that in the pressure chamber 23 side, but the pressure is accumulated, so that the space E is not extremely narrowed and the inner lip portion 12 is prevented from being deformed abnormally. Further, when the rubber portion of the lip packing 11 is repeatedly pressed by the grooves 16 and 18 under pressure, it is pressed by the corner portion of the groove opening edge, but it is slightly rounded and the groove is particularly shallow. ,
It does not lead to damage. Further, when the rod 21 slides in the direction of arrow a or b, the presence of the fluororesin layer 16 has an action of reducing sliding resistance. The fluororesin layer may be omitted in some cases, and in that case, it is formed of the same material as the other rubber portions.

The above embodiment is an example in which the packing groove is provided in the inner peripheral surface of the rod cover to accommodate the packing, and the backup ring is provided in the step portion on the inner peripheral side of the packing. In the configuration in which the packing groove is provided on the outer peripheral surface to accommodate the packing, the packing has the backup ring on the step portion on the outer periphery of the packing, and the end surface groove and the communication passage are formed on the step portion surface side. If only the end surface of the cross section of FIG. 1 is quoted, 22 is a piston and 21 is a cylinder.

[0012]

Since the packing of the present invention has the end face groove which is connected to the step surface of the packing of the backup ring and has the flow passage which communicates with the other end face, when the pressure fluid acts on the packing, A part of the packing main body elastically deforms and enters the end face groove, and the flow passage formed by the end face groove can be narrowed in response to pressure. Therefore, it is possible to store the fluid leaking from the lip portion in a small amount in the gap between the backup ring and the sealing surface of the lip portion. As a result, even if a high-pressure fluid acts on the packing, it is possible to effectively prevent the sealing effect of the sealing surface from being lowered due to the lip portion coming into full contact with the facing sliding member. At the same time, it can be expected that a part of the lip portion side will be attracted to the sliding member and will not enter the gap between the backup ring and the sliding member, and the peeling damage will be effectively prevented. Furthermore, if the pressure stored in the gap approaches the working fluid pressure, the pressure can spread the main body that has entered the end face groove, so that the so-called blow-through phenomenon that backflows from the lip portion is effectively prevented. Therefore, the packing of the present invention is excellent in sealing ability, and can be expected to prevent this phenomenon at the time when the blow-through phenomenon occurs and to suppress the minimum fluid leakage to the atmosphere side.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view in a direction along an axis showing a schematic structure of an embodiment of the present invention.

FIG. 2 is a diagram showing a backup ring of the same embodiment as shown in FIG.
FIG. 3 is a schematic front view seen from the right side of FIG.

FIG. 3 is a partially enlarged sectional view in a direction along an axis showing an example of a structure of a conventional rod packing.

FIG. 4 is a schematic front view of the same packing as seen from the low pressure side (right side in FIG. 3) in the axial direction.

[Explanation of symbols]

 10 rod packing 11 lip packing 12 inner lip portion 13 outer lip portion 14 backup ring 15 axial communication groove 17 end face groove 18 end face groove 20 packing groove 21 rod 22 rod cover 23 pressure chamber side (high pressure side) 24 outside side (low pressure side) ) E void

Claims (1)

[Claims] 1. A low pressure side circumference of a packing main body, which is housed in a packing mounting groove provided on the peripheral surface of one member of the two members which are fitted and move relative to each other, and which has a lip portion of a fluid seal on the high pressure side. In a packing in which an annular backup ring is joined to a step formed on the surface, one end of each of the backup rings has an end surface groove that opens at least to the other member side, and the other has flow passages that communicate with each other. Packing characterized by.