JPH08200501A - Seal structure of piston - Google Patents

Abstract

PURPOSE: To effectively prevent the projection of a seal ring by providing a radial displacement providing means to displace a back-up ring at least in one of the inner or outer diameter direction when the pressing force is applied from the seal ring to the back-up ring. CONSTITUTION: A seal ring 16 is arranged on the high pressure side of a back-up ring 18, and when the seal ring 16 is moved to the low pressure side, the pressing force from the seal ring 16 to the back-up ring 18 is applied thereto. A radial displacement providing means displaces the back-up ring 18 at least in one of the inner or outer diameter direction when such pressing force is applied. When the radial displacement on the back-up ring 18 is provided, both the clearance between an arrangement groove 14 and the back-up ring 18, and the clearance between a sliding surface on which the back-up ring 18 is abutted and the back-up ring 18 are reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seal structure for a piston, and in particular, secures a sealability between an inner wall of a housing and a piston sliding inside the housing by using a seal ring and a backup ring. The present invention relates to a piston seal structure.

[0002]

2. Description of the Related Art Conventionally, there has been known a structure in which a sealability between an inner wall of a housing and a piston sliding therein is ensured by using a seal ring and a backup ring. That is, when the piston slides in the housing, if only the seal ring such as the O-ring is used to secure the sealing performance, the compression chamber is not moved along with the sliding movement of the piston during the compression process of the piston. Due to the high pressure, pressure is applied to the seal ring, the seal ring protrudes between the piston and the housing, and local deterioration of the seal ring is promoted.

On the other hand, adjacent to the seal ring,
With a backup ring made of Teflon,
The amount of deformation of the seal ring when the piston performs the compression process is suppressed by the backup ring, and it is possible to avoid the situation where the seal ring sticks out between the piston and the housing as described above, and is effective in ensuring the durability of the seal part. Is.

By the way, in the seal structure as described above, the piston is fitted in the housing in a state where the seal material disposing groove is provided in one of the piston and the housing, and the seal ring and the backup ring are disposed in the disposing groove. It is realized by inserting. At this time, in order to prevent the above-mentioned protrusion of the seal ring, it is necessary that the backup ring is in contact with a surface on which the backup ring and the seal ring slide (hereinafter referred to as a sliding surface).

On the other hand, it is practically impossible to bring the backup ring into contact with both the mounting groove and the sliding surface due to various dimensional tolerances, processing accuracy limits, and the like. Therefore, when such a structure is adopted, a certain amount of clearance is allowed between the backup ring and the arrangement groove.

However, if there is a gap between the backup ring and the disposition groove, when the seal ring is pressed toward the backup ring due to the force received by the seal ring during the compression process of the piston, the inside of the gap is increased. The seal ring protrudes to the outside, which causes an undesirable situation in terms of durability of the seal ring. In this sense, a structure that allows a certain amount of clearance between the backup ring and the disposition groove is not necessarily ideal as a piston seal structure.

On the other hand, for example, actual Kaihei 2-1090
Japanese Patent Laid-Open No. 72-72 discloses a structure in which an elastic material layer is provided on the side of the arrangement groove of the backup ring to fill the gap between the backup ring and the arrangement groove. In this case, the elastic material layer can absorb various dimensional tolerances, and the backup ring can be brought into contact with both the housing and the disposition groove. Therefore, it is functionally ideal for preventing the seal ring from protruding. It is possible to form various structures.

[0008]

However, the conventional piston seal structure described above is a structure in which the backup ring is constantly pressed against the sliding surface by the restoring force of the elastic material layer. In this case, a relatively large frictional force always acts between the backup ring and the sliding surface, which causes disadvantages such as increased sliding loss and accelerated wear of the backup ring. Further, the process of forming the elastic material layer on the backup ring is not always easy in terms of production technology, and is accompanied by disadvantages such as reduced productivity and increased production cost.

The present invention has been made in view of the above points, and the gap between the backup ring and the housing or the installation groove is provided by the backup ring only when the seal ring is pressed toward the backup ring. An object of the present invention is to provide a piston seal structure capable of effectively preventing the seal ring from protruding by closing the seal ring.

[0010]

The above-mentioned object is defined in claim 1.
In a seal structure of a piston, wherein a seal ring and a backup ring are disposed in a seal material disposition groove, the seal ring is disposed on the high pressure side of the backup ring and the seal ring is disposed. From a sealing structure of a piston provided with a radial displacement applying means for displacing the backup ring in at least one of an inner diameter direction and an outer diameter direction of the backup ring when a pressing force from the back ring to the backup ring is applied. .

Further, as described in claim 2, the above-mentioned object is, in the piston seal structure according to claim 1, the radial displacement imparting means includes a convex portion on the seal ring, and the backup. This is also achieved by a piston seal structure that is formed by providing a ring with a recess that fits into the protrusion.

[0012]

In the invention of claim 1, the seal ring is disposed on the high pressure side of the backup ring. Therefore, if the seal ring tries to move to the low pressure side, a pressing force from the seal ring to the backup ring acts.

Further, the radial displacement imparting means displaces the backup ring in at least one of an inner diameter direction and an outer diameter direction of the backup ring when the pressing force acts. Then, when such a radial displacement is applied to the backup ring, a gap between the arrangement groove and the backup ring and a gap between the sliding surface on which the backup ring should abut and the backup ring are generated. Both are reduced.

According to the second aspect of the present invention, the backup ring is provided with a recess that fits into the projection provided on the seal ring. Therefore, when a high pressure acts on the seal ring and the seal ring is pressed toward the backup ring side, the convex portion of the seal ring fitted in the concave portion has the backup ring on the inner diameter side of the concave portion. Press in the direction in which the diameter decreases, and press the outer diameter side of the recess in the direction in which the backup ring expands. Therefore, both the gap between the backup ring and the disposing groove and the gap between the bappack ring and the sliding surface on which the outer backup ring should come into contact are reduced.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing the principal part of a piston seal structure according to an embodiment of the present invention. In the figure, the piston 10 is slidably fitted in the housing 12.

Here, an annular seal material disposition groove (hereinafter simply referred to as disposition groove) 14 is provided on the outer peripheral surface of the piston 10. A seal ring 16 made of an elastic material such as rubber is provided in the mounting groove 14 on the side on which the high pressure acts.
However, a backup ring 18 made of Teflon or the like is arranged on the side where high pressure does not act.

The seal ring 16 is provided with protrusions 16a, 16b, 16c on its surface that contacts the inner wall of the housing 12, the surface that contacts the side surface of the mounting groove 14, and the surface that contacts the backup ring 18, respectively. ing. On the other hand, the backup ring 18 is provided with a concave portion 18a that fits into the convex portion 16c.

Therefore, when the seal ring 16 is pressed toward the backup ring 18, the pressing force is increased.
It is transmitted to the backup ring 18 via c and the recess 18a. At this time, since the convex portions 16c and the concave portions 18a are provided with appropriate curvatures, the pressing force transmitted as described above increases the outer diameter bu18b of the backup ring 18 and reduces the inner diameter portion 18c. Act on.

On the other hand, in consideration of the dimensional tolerances of the piston 10 and the housing 12, the backup ring 18 has its outer peripheral surface abutted against the inner wall of the housing 12 with an appropriate biasing force, and Installation groove 1
The dimensional specifications are set so that an appropriate gap is formed between the dimensional difference and the number.

Therefore, in the piston seal structure shown in FIG. 1, when the pressing force toward the backup ring 18 does not act on the seal ring 16, it acts between the backup ring 18 and the inner wall of the housing 12. The frictional force is suppressed to be relatively small.

On the other hand, when a pressing force directed to the backup ring 18 side acts on the seal ring 16, a relatively large urging force is generated between the backup ring 18 and the inner wall of the housing 12, and the seal between them is generated. Ring 16
The protrusion of the seal ring 16 is surely prevented, and the gap between the backup ring 18 and the disposition groove 14 is reduced, and the protrusion of the seal ring 16 between them is also prevented.

By the way, the piston seal structure shown in FIG. 1 has a plunger pump 20 as shown in FIG.
Can be used as a seal structure. The plunger pump 20 shown in FIG. 2 has a known configuration as an ABS pump used in an antilock brake system (ABS) for vehicles.

The plunger pump 20 shown in the figure includes an eccentric cam 22 that contacts one end of the piston 10 to rotate, and a spring 24 that contacts the other end of the piston 10 to bias the piston 10 toward the eccentric cam. I have it. Here, the spring 24 is disposed in a pump chamber 28 provided in the housing 12 while being supported by the plug 26. Further, the pump chamber 28 includes a suction passage 30, a check valve 32 that allows only a flow from the reservoir tank 31 side to the pump chamber 28, and a discharge passage 34 from the pump chamber 28.
A check valve 36 that allows only the flow to

The arrangement groove 14 provided in the piston 10
The seal ring 16 and the backup ring 18 are arranged so that the seal ring 16 is located on the pump chamber 28 side and the backup ring 18 is located on the eccentric cam 22 side. In this case, when the pressing force acting on the piston 10 from the eccentric cam 20 is released, the piston 10 is displaced leftward in FIG. 2, and as a result, the volume of the pump chamber 28 is increased and the check valve 32 is expanded. Is opened and fluid is inhaled.

At this time, a negative pressure corresponding to the valve opening pressure of the check valve 32 is generated in the pump chamber 28, but since the valve opening pressure can be set to a sufficiently low pressure, the suction stroke described above is used. ,
The seal ring 16 is not overloaded. Further, in the process in which the piston 10 moves to the eccentric cam 22 side, the pressing force does not act between the seal ring 16 and the backup ring 18, and the frictional force acting between the backup ring 18 and the housing 12 is suppressed to be small. To be done.

Therefore, in the plunger pump 20, the seal ring 16 is connected to the piston 10 and the housing 12.
It does not stick out between
Also, it is possible to execute the suction stroke in which the amount of wear of the backup ring 18 is suppressed. When the eccentric cam 22 presses the piston 10 in such a situation, the piston 10 moves to the position shown in FIG.
The displacement is made to the right in the middle, and as a result, the volume of the pump chamber 28 is reduced and the fluid is discharged from the check valve 36 to the discharge passage 34.

At this time, a relatively high discharge pressure is generated in the pump chamber 28. Further, since the seal ring 16 receives a high pressure from the pump chamber 28 in the process in which the piston 10 is displaced in the direction of reducing the volume of the pump chamber 28, the seal ring 16 tends to relatively move to the backup ring 18 side. . Therefore, a relatively large pressing force acts on the recess 18a of the backup ring 18.

Therefore, in the plunger pump 20, when the discharge stroke of the fluid is started, the outer diameter portion 18b and the inner diameter portion 18c of the backup ring 18 are displaced in the outer diameter direction and the inner diameter direction of the backup ring 18, respectively, and the backup is performed. Since the backup ring closes the gap between the ring 18 and the housing 12 and the gap between the backup ring 18 and the arrangement groove 14, the seal ring 16 is surely prevented from protruding into the respective gaps.

As described above, when the piston seal structure shown in FIG. 1 is used, the backup ring 18 is not provided with an elastic material layer and the backup ring 1 is used.
It is possible to prevent the seal ring 16 from protruding without unnecessarily increasing the frictional force between the housing 8 and the housing 12. In this sense, the seal structure of this embodiment shown in FIG.
This has the advantage that a piston seal mechanism having excellent durability can be realized at low cost with excellent productivity.

In the embodiment shown in FIG. 1, the convex portion 16c of the seal ring 16 and the concave portion 18a of the backup ring 18 constitute the radial displacement imparting means. FIG. 3 is a sectional view showing a main part of a piston seal structure according to a second embodiment of the present invention. Here, in the figure, the same components as those shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

That is, in the piston seal structure shown in FIG. 3, a general D ring is used as the seal ring 40, and the backup ring 42 is provided with an inner ring 42a and an outer ring 42b.
It is characterized in that it is composed of and. Incidentally, the seal ring 40 is arranged on the high pressure side and the backup ring 42 is arranged on the low pressure side, as in the structure shown in FIG.

In this embodiment, the backup ring 4
The inner ring 42a and the outer ring 42b of No. 2 have an inclination in the opposing surface, respectively. Therefore, when a pressing force from the seal ring 40 toward the backup ring 42 acts, the inner ring 42a is deformed in the direction of reducing its inner diameter, and the outer ring 42b is deformed in the direction of increasing its outer diameter.

Incidentally, the inner ring 42a and the outer ring 42b are provided with a cutting portion used for assembling into the disposing groove 14 at an arbitrary portion (not shown). Therefore, the seal ring 4
When a pressing force from 0 to the backup ring 42 acts, it can be easily deformed as described above.

In this case, the high pressure does not act on the right side of the seal ring 40 in FIG.
In a situation where the protrusion of 0 is not a problem, the frictional force between the backup ring 42 and the housing 12 is not unnecessarily increased, while on the other hand, when high pressure acts on the right side of the seal ring 40, The gap between the ring 42a and the mounting groove 14 is reduced, and the outer ring 42b and the housing 12 are
The urging force acting between and is increased.

Therefore, according to the seal structure of the present embodiment as well, similar to the seal structure shown in FIG. 1, the sliding loss is reduced, the wear amount of the backup ring 42 is reduced, and the like. The protrusion can be prevented. In this embodiment, the inclined surfaces of the inner ring 42a and the outer ring 42b of the backup ring 42 constitute the radial displacement imparting means described above.

FIG. 4 is a sectional view showing the principal part of a piston seal structure according to a third embodiment of the present invention. Here, in the figure, the same components as those shown in FIGS. 1 to 3 are designated by the same reference numerals, and the description thereof will be omitted. The piston seal structure shown in FIG.
Is provided with an arrangement groove 52 having an inclined surface 52a, and the backup ring 54 is arranged in contact with the outer periphery of the inclined surface 52a.

The structure shown in FIG. 3 is that the seal ring 40 is disposed on the high pressure side of the backup ring 54 and the backup ring 54 has a cut portion at an arbitrary point (not shown). Is the same as. With this structure, when the pressing force from the seal ring 40 toward the backup ring 54 does not act, the frictional force acting between the backup ring 54 and the housing 12 is suppressed to an extremely small value.

On the other hand, when the pressing force from the seal ring 40 toward the backup ring 54 acts, the backup ring 54 is displaced along the inclined surface 52a, and as a result,
The outer diameter of the backup ring 54 expands, and the gap between the backup ring 54 and the housing 12 disappears.

Therefore, also with the seal structure of the present embodiment, as with the seal structures shown in FIG. 1 and FIG. 3, the seal ring 40 accompanying the sliding of the piston 50 is reduced while the sliding loss is reduced. It is possible to appropriately prevent the protrusion of the. In this embodiment, the inclined surface 5 of the arrangement groove 52 is
2a constitutes the above-mentioned radial displacement imparting means.

FIG. 5 is a sectional view showing the principal part of a piston seal structure according to a fourth embodiment of the present invention. Here, in the figure, the same components as those shown in FIGS. 1 to 4 are designated by the same reference numerals, and the description thereof will be omitted. That is, the seal structure of the piston shown in FIG. 5 is characterized in that the backup ring 60 is provided with the recess 60 a on the surface in contact with the seal ring 40.
Regarding the point that the seal ring 40 is arranged on the high pressure side of the backup ring 60, FIG. 1, FIG. 3 and FIG.
It is similar to the structure shown in.

In the seal structure shown in FIG. 5, when the pressing force from the seal ring 40 toward the backup ring 60 is not applied, no special load is applied to the backup ring 60. Therefore, in this case, the frictional force between the backup ring 60 and the housing 12 does not unnecessarily increase.

On the other hand, when the pressing force from the seal ring 40 toward the backup ring 60 is applied, the seal ring 40 is deformed along the recess 60a of the backup ring 60, and a part thereof is stored inside the recess 60a. At this time, the seal ring 40 is deformed so that the intermediate portion in the wall thickness direction, that is, the intermediate portion between the outer peripheral portion and the inner peripheral portion protrudes toward the backup ring 60 side, and under the influence thereof, The inner peripheral portion is relatively separated from the backup ring 60.

Further, as described above, the backup ring 60
When a part of the seal ring 40 is deformed and accommodated in the recess 60a, the pressing force from the seal ring 40 acts in the direction of expanding the recess 60a. Therefore, the backup ring 60 is deformed such that the inner peripheral portion 60b of the recess 60a is reduced in diameter and the outer peripheral portion 60c of the recess 60a is enlarged in diameter.

That is, in the seal structure shown in FIG.
When a pressing force acts from the seal ring 40 toward the backup ring 60, the outer peripheral portion and the inner peripheral portion of the seal ring 40 are deformed into a state in which it is difficult for the seal ring 40 to protrude from the inner and outer periphery of the backup ring 60, and the backup ring 60
Deforms in a direction in which the urging force with respect to the housing 12 is increased and the gap with the arrangement groove 14 is reduced.

Therefore, according to the seal structure of this embodiment, the sliding loss is reduced and the wear amount of the backup ring 60 is suppressed as in the seal structure shown in FIGS. Further, it is possible to enjoy a further excellent effect in preventing the seal ring 40 from protruding.

By the way, in the above-mentioned first to fourth embodiments, the arrangement grooves 14 and 52 are provided on the piston 10 and 50 side, but the present invention is not limited to this, and the arrangement grooves are formed on the housing 12 side. It may be provided.

[0047]

As described above, according to the first aspect of the invention, the gap between the backup ring and the disposition groove, and the backup ring and the sliding surface thereof only when the high pressure acts on the seal ring. The gap can be narrowed together.

Therefore, according to the seal structure of the piston of the present invention, the sliding resistance of the backup ring can be obtained only when the elastic material layer is not formed on the backup ring and when the seal ring is required to have the sealing ability. By increasing it, it is possible to reliably prevent the seal ring from protruding while reducing sliding loss.

According to the second aspect of the present invention, when a high pressure is applied to the seal ring, the gap between the backup ring and the mounting groove and the gap between the backup ring and its sliding surface are reduced, and the seal is sealed. It is difficult for the ring to protrude to the inside and outside of the backup ring.

Therefore, according to the piston seal structure of the present invention, the sliding loss can be reduced and the protrusion of the seal ring can be prevented more reliably as in the seal structure according to the first aspect. it can.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing a seal structure for a piston that is a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a plunger pump configured by using the seal structure of the present embodiment.

FIG. 3 is a cross-sectional view of essential parts showing a seal structure for a piston that is a second embodiment of the present invention.

FIG. 4 is a sectional view showing the principal part of a piston seal structure according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional view of essential parts showing a seal structure for a piston that is a fourth embodiment of the present invention.

[Explanation of symbols]

 10,50 Piston 12 Housing 14,52 Disposing groove 16,40 Seal ring 16a, 16b, 16c Convex portion 18, 42, 54, 60 Backup ring 18a, 60a Recess 20 Plunger pump 42a Inner ring 42b Outer ring 52a Sloping surface

Claims (2)

[Claims] 1. A seal structure for a piston, wherein a seal ring and a backup ring are disposed in a seal material disposition groove, wherein the seal ring is disposed on the high pressure side of the backup ring, and the seal ring is disposed. Of the piston, comprising a radial displacement applying means for displacing the backup ring in at least one of an inner diameter direction and an outer diameter direction of the backup ring when a pressing force from the backup ring to the backup ring is applied. Seal structure. 2. The piston seal structure according to claim 1, wherein the radial displacement imparting means is provided with a convex portion on the seal ring, and is provided with a concave portion for fitting the convex portion on the backup ring. A piston seal structure characterized by being composed of