Sealing device

Abstract

A sealing device in which diameter expansion of an inserted first back-up ring is suppressed. The sealing device includes a seal ring mounted in a rectangular mounting groove, the first back-up ring, and a second back-up ring. The first back-up ring has an end surface contacting an opposing-sealing-fluid-side side surface of the mounting groove. The second back-up ring has an end surface contacting the seal ring. A contact surface in an inner peripheral end of second back-up ring is perpendicular to the axis to contact an opposing-sealing-fluid-side side surface of the mounting groove. The inner diameter of the first back-up ring is set to be larger than the outer diameter of the contact surface portion of the second back-up ring, and the outer diameter of the first back-up ring is set to be smaller than the inner diameter of a housing.

Claims

1. A sealing device that is placed between two structures facing each other to seal in sealing fluid, the sealing device comprising: a seal ring that is mounted in a mounting groove provided on one of the two structures, and is in close contact with the other structure; a first back-up ring placed on an opposing sealing fluid side of the seal ring; and a second back-up ring placed between the seal ring and the first back-up ring, wherein the first back-up ring is made of a material that is harder than a material that the second back-up ring is made of, the mounting groove is a groove with a rectangular cross-section, the first back-up ring has a shape having an end surface in contact with an opposing-sealing-fluid-side surface of the mounting groove, a peripheral surface facing the other structure, and an inclined surface intersecting with the end surface and the peripheral surface, the second back-up ring has a shape having an end surface in contact with the seal ring, a peripheral surface facing a bottom surface of the mounting groove, and an inclined surface that is provided to correspond to the inclined surface of the first back-up ring, a contact surface that is a plane perpendicular to an axis in contact with the opposing-sealing-fluid-side surface of the mounting groove is provided in an inner peripheral end of the inclined surface of the second back-up ring, an inner diameter size of the first back-up ring is set to be larger than an outer diameter size of the contact surface of the second back-up ring, and an outer diameter size of the first back-up ring is set to be smaller than an inner diameter size of the other structure.

2. The sealing device according to claim 1, wherein the inclined surface of the first back-up ring is a surface with a concave circular cross-section, the inclined surface of the second back-up ring is a surface with a convex circular cross-section, and the end surface of the second back-up ring is a surface with a concave circular cross-section.

3. The sealing device according to claim 1, wherein the seal ring includes a cross-sectional O-ring shape.

4. The sealing device according to claim 1, wherein a gap is disposed between the peripheral surface of the first back-up ring and an inner surface of the other structure that is opposed to the peripheral surface of the first back-up ring.

5. The sealing device according to claim 1, wherein a gap is disposed between a corner of the second back-up ring and an inner surface of the other structure that is opposed to the corner of the second back-up ring, the corner being formed between the inclined surface of the second back-up ring and the end surface of the second back-up ring.

6. The sealing device according to claim 1, wherein when at least a threshold pressure acts on the seal ring, the seal ring presses the end surface of the second back-up ring to elastically expand the second back-up ring radially, and the second back-up ring presses the first back-up ring to elastically expand the first back-up ring radially so that the first back-up ring closes a gap between the peripheral surface of the first back-up ring and an inner surface of the other structure that is opposed to the peripheral surface of the first back-up ring.

7. The sealing device according to claim 1, wherein a radial gap exists between the contact surface of the second back-up ring and the end surface of the first back-up ring.

8. The sealing device according to claim 1, wherein the peripheral surface of the first back-up ring is disposed radially outward with respect to a corner of the second back-up ring formed between the inclined surface of the second back-up ring and the end surface of the second back-up ring.

9. The sealing device according to claim 1, wherein the first back-up ring is made of nylon resin and the second back-up ring is made of PTFE (polytetrafluoroethylene) resin.

10. The sealing device according to claim 1, wherein a crescent shaped gap is formed between the inclined surface of the first back-up ring and the inclined surface of the second back-up ring.

11. The sealing device according to claim 1, wherein a corner between the peripheral surface of the first back-up ring and the inclined surface of the first back-up ring includes a flat surface so that the corner is not pointed.

12. The sealing device according to claim 1, wherein a corner between the end surface of the first back-up ring and the inclined surface of the first back-up ring includes a flat surface so that the corner is not pointed.

13. Hydraulic equipment comprising the sealing device according to claim 1.

14. A direct-injection injector comprising the sealing device according to claim 1.

Description

BRIEF EXPLANATION OF THE DRAWINGS

(1) FIG. 1 is a cross-sectional diagram of main parts of a sealing device according to an embodiment of the present invention.

(2) FIG. 2 is a cross-sectional diagram of a sealing device according to a conventional example.

(3) FIGS. 3A and 3B are explanatory diagrams illustrating a mounting step of the sealing device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(4) The present invention includes the following embodiments.

(5) (1) General-use back-up ring used in a rectangular groove for a high-pressure application is provided. The back-up ring is composed of a combination of a hard back-up ring (a first back-up ring) and a soft back-up ring (a second back-up ring).

(6) (2) The soft back-up ring is mounted so that there is no gap left on the non-pressurized side. The hard back-up ring is smaller than the inner diameter of an other-side housing (the other member) so as not to interfere when the sealing device is inserted. That is, the soft back-up ring is installed so that there is no gap with a groove side surface, and there is provided the hard back-up ring of which the outer diameter is smaller than the inner diameter of the housing, which allows the hard back-up ring to be mounted in this state. In other words, the soft back-up ring is provided with a portion in parallel contact with the groove side surface, thereby does not move when attached (when inserted); therefore, the soft back-up ring does not push up the hard back-up ring, and the diameter of the hard back-up ring is not expanded.

(7) (3) The mating surfaces of the hard back-up ring and the soft back-up ring are formed into an arch. The seal ring contact side of the soft back-up ring is formed into an arch. By forming them into an arch, when subjected to high pressure after they are mounted, an O-ring (a seal ring) deforms the arch-like soft back-up ring to cause its diameter to be expanded, and pushes up the hard back-up ring, so that the sealing performance is ensured.

(8) Subsequently, an embodiment of the present invention is described with reference to the drawings.

(9) FIG. 1 shows cross-sections of main parts of a sealing device 1 according to the embodiment of the present invention. The sealing device 1 according to the embodiment is one used in a high-pressure seal portion of hydraulic equipment such as a direct-injection injector, and is configured as below.

(10) That is, the sealing device 1 is placed in an annular gap between two members facing each other, namely a shaft (one of the members) 51 and a housing (the other member) 52 to seal in sealing fluid existing on the high-pressure side H that is on the right of the drawing so that the sealing fluid does not leak to the low-pressure side (the atmosphere side) L that is on the left of the drawing. The sealing device 1 includes an O-ring 11 as a seal ring, a first back-up ring 21, and a second back-up ring 31. The O-ring 11 is mounted in an annular mounting groove 53 provided on the peripheral surface of the shaft 51, and is in close contact with the inner peripheral surface of a shaft hole of the housing 52. The first back-up ring 21 is placed on the opposing sealing fluid side (the low-pressure side L) of the O-ring 11, and is likewise mounted in the mounting groove 53. The second back-up ring 31 is placed between the O-ring 11 and the first back-up ring 21, and is likewise mounted in the mounting groove 53. Instead of the O-ring 11, a seal ring with another cross-sectional shape, such as a D-ring or an X-ring, can be used.

(11) The O-ring 11 is made of a rubbery elastic body. The first back-up ring 21 is made of, for example, nylon resin harder than the second back-up ring 31. The second back-up ring 31 is made of, for example, PTFE resin softer than the first back-up ring 21.

(12) The mounting groove 53 is formed as a rectangular groove with a rectangular cross-section because it is easy to process. Therefore, a sort of tapered shape is not formed in the groove, and the mounting groove 53 is a combination of only a bottom surface portion 53a that is a cylindrical surface and both side surface portions 53b that are a plane perpendicular to the axis.

(13) The first back-up ring 21 has an end surface portion 21a that is a plane perpendicular to the axis on the opposing sealing fluid side (the low-pressure side L) thereof in contact with the side surface portion 53b of the mounting groove 53, a peripheral surface portion 21b that is a cylindrical surface on the outer peripheral side thereof in contact with the inner peripheral surface of the shaft hole of the housing 52, and an inclined surface portion 21c that is a tapered surface intersecting with the end surface portion 21a and the peripheral surface portion 21b, and is formed to be triangular (right triangular) or substantially triangular in cross-section. The diameter size (the inner diameter size) of the inclined surface portion 21c is tapered off from the sealing fluid side (the high-pressure side H) to the opposing sealing fluid side (the low-pressure side L).

(14) The second back-up ring 31 has an end surface portion 31a on the sealing fluid side (the high-pressure side H) thereof in contact with the O-ring 11, a peripheral surface portion 31b that is a cylindrical surface on the inner peripheral side thereof in contact with the bottom surface portion 53a of the mounting groove 53, and an inclined surface portion 31c that is a tapered surface intersecting with the end surface portion 31a and the peripheral surface portion 31b, and is formed to be triangular (right triangular) or substantially triangular in cross-section. The diameter size (the outer diameter size) of the inclined surface portion 31c is tapered off from the sealing fluid side (the high-pressure side H) to the opposing sealing fluid side (the low-pressure side L).

(15) A contact surface portion 31e that is a plane perpendicular to the axis in contact with the side surface portion 53b of the mounting groove 53 is provided in an inner peripheral end of the inclined surface portion 31c of the second back-up ring 31, and the inner diameter size d.sub.3 of the first back-up ring 21 is set to be larger than the outer diameter size d.sub.4 of the contact surface portion 31e. Therefore, since the end surface portion 21a of the first back-up ring 21 is located on the outer peripheral side of the contact surface portion 31e of the second back-up ring 31, the contact surface portion 31e of the second back-up ring 31 and the end surface portion 21a of the first back-up ring 21 enable the both back-up rings 21 and 31 to be in contact with the side surface portion 53b of the mounting groove 53 at the same time.

(16) Furthermore, the outer diameter size d.sub.5 of the first back-up ring 21 is set to be smaller than the inner diameter size d.sub.6 of the housing 52 so that the first back-up ring 21 does not interfere with an opening periphery (not shown) of the shaft hole of the housing 52 when inserted.

(17) Moreover, the inclined surface portion 21c of the first back-up ring 21 and the inclined surface portion 31c of the second back-up ring 31 are provided to correspond to each other; the inclined surface portion 21c of the first back-up ring 21 is a surface with a concave circular cross-section, and the inclined surface portion 31c of the second back-up ring 31 is a surface with a convex circular cross-section. Furthermore, the end surface portion 31a of the second back-up ring 31 is also a surface with a concave circular cross-section.

(18) In the sealing device 1 having the above-described configuration, the first back-up ring 21 is placed on the opposing sealing fluid side (the low-pressure side L) of the O-ring 11, and therefore, it is possible to prevent the O-ring 11 from protruding into a gap 54 between the shaft 51 and the housing 52 and being damaged when subjected to high pressure P; furthermore, the second back-up ring 31 is placed between the O-ring 11 and the first back-up ring 21, and therefore, it is possible to prevent the O-ring 11 from protruding into a gap 55 between the first back-up ring 21 and the housing 52 and being damaged. Accordingly, it is possible to suppress the degradation of sealing performance caused by the O-ring 11 protruding into the gap 54 or 55 and being damaged.

(19) Furthermore, the contact surface portion 31e that is a plane perpendicular to the axis in contact with the opposing-sealing-fluid-side side surface portion 53b of the mounting groove 53 is provided in the inner peripheral end of the inclined surface portion 31c of the second back-up ring 31; therefore, by bringing the contact surface portion 31e that is a plane perpendicular to the axis into contact with the side surface portion 53b of the mounting groove 53 from the beginning of the mounting in the mounting groove 53, the overall second back-up ring 31 does not move to a direction of getting close to the side surface portion 53b of the mounting groove 53.

(20) Therefore, when the sealing device 1 is inserted into a shaft hole 52a of the housing 52, the overall second back-up ring 31 does not move to the direction of getting close to the side surface portion 53b of the mounting groove 53, thus the second back-up ring 31 does not press the first back-up ring 21, which prevents the first back-up ring 21 from deformation of its outer diameter size d.sub.5 being expanded. Accordingly, there never arises a situation in which the first back-up ring 21 interferes with the opening periphery of the shaft hole 52a when inserted; therefore, it is possible to suppress the damage on the first back-up ring 21 caused by the interference.

(21) Moreover, the inclined surface portion 21c of the first back-up ring 21 is a surface with a concave circular cross-section, the inclined surface portion 31c of the second back-up ring 31 is a surface with a convex circular cross-section, and the end surface portion 31a of the second back-up ring 31 is a surface with a concave circular cross-section; therefore, if high pressure P acts on the O-ring 11, the O-ring 11 presses the end surface portion 31a with a concave circular cross-section in the second back-up ring 31, and the second back-up ring 31 is elastically deformed, which causes its outer diameter size to be expanded, thereby pressing the first back-up ring 21. The pressed first back-up ring 21 is also elastically deformed, which causes its outer diameter size d5 to be expanded, and, as a result, comes in contact with the inner surface of the housing 52, or at least reduces the radial distance to the inner surface of the housing 52. Accordingly, the first back-up ring 21 elastically deformed outward in a radial direction in this way exerts the sealing function, and therefore, it is possible to expect the sealing effect of the first back-up ring 21, and is possible to enhance the sealing performance of the sealing device 1.

DESCRIPTION OF REFERENCE NUMERALS

(22) 1 sealing device 11 seal ring 21 first back-up ring 21a, 31a end surface portion 21b, 31b peripheral surface portion 21c, 31c inclined surface portion 31 second back-up ring 31d corner 31e contact surface portion 51 shaft (one of two members) 52 housing (the other member) 52a shaft hole 53 mounting groove 53a bottom surface portion 53b side surface portion 54, 55 gap