Sealing ring

Abstract

An annular seal ring having a cut-off section (2) is provided with: a pair of reduced sections (5, 6) in which the radial dimension of the seal ring (1) gradually decreases as the seal ring approaches the cut-off section (2); and a plurality of recesses (7) formed in at least one of the end surfaces (1C, 1D) facing the axis (x) direction, the plurality of recesses (7) being configured from a first recess (7A) disposed within a range included in the reduced sections (5, 6) and a second recess (7B) disposed within a range farther from the cutting section (2) than the first recess (7A). An inner peripheral side wall part (9B) for dividing the inner peripheral surface (1A) of the seal ring (1) and the second concave part (7B) and a communication part (91) for communicating the inner peripheral surface (1A) and the second concave part (7B) are formed between the inner peripheral surface (1A) and the second concave part (7B). An expanded communication section (74) is formed between the inner peripheral surface (1A) of the seal ring (1) and the first recess (7A), said expanded communication section (74) communicating the inner peripheral surface (1A) and the first recess (7A). The expanded communication section (74) is configured from one portion, and the circumferential dimension of the expanded communication section (74) is larger than the circumferential dimension of the communication section (91).

Description

Technical Field

[0001] The present invention relates to a sealing ring. Background Art

[0002] Generally, as a sealing ring disposed between a relatively rotating outer peripheral member and an inner peripheral member, a sealing ring formed in an annular shape by connecting both ends of a long strip-shaped member is known. As such a sealing ring, a sealing ring formed such that the radial thickness gradually decreases toward the joint portion has been proposed (for example, refer to Patent Document 1). In the sealing ring described in Patent Document 1, as described above, by reducing the thickness (radial dimension), when the sealing ring is disposed in contact with the cylindrical inner peripheral surface of the outer member or the cylindrical outer peripheral surface of the inner member, the outer peripheral surface or the inner peripheral surface of the sealing ring easily approaches a perfect cylinder, and by reducing the gap between the sealing ring and the outer member or the inner member, the sealing performance is improved.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: International Publication No. 2021-010005 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] In the case of the sealing ring described in Patent Document 1, if the radial dimension is reduced as described above, the closer to the portion where both ends of the long strip-shaped member are connected, the lower the rigidity, the easier it is to deform, and the easier it is for the sealing ring to approach a perfect cylinder. In addition, in the sealing ring described in Patent Document 1, a groove is formed in the end face on the atmospheric space side. By forming such a groove, a dynamic pressure action is generated, and an oil film is formed between this end face and the wall surface of the circumferential groove provided with the sealing ring, thereby achieving a reduction in the torque applied to the shaft (hereinafter, sometimes simply referred to as "torque").

[0008] Thus, in the case of forming a groove in the end face of the sealing ring, in order to suppress the leakage of oil from the sealed object space to the atmospheric space in a manner of cutting across the groove in the radial direction, it is necessary to provide a wall portion having a width of a certain level or more at a position adjacent to the groove in the radial direction. In a structure in which the thickness of the sealing ring itself decreases in the radial direction, if the above-described groove is formed and the wall portion is provided, the groove width in the radial direction also becomes smaller toward the joint portion. At this time, the magnitude of the above-described dynamic pressure action is proportional to the area of the formed oil film. If the radial dimension of the groove is small, the area of the oil film formed by the groove also becomes small, and the obtained dynamic pressure action becomes small, so that it may be difficult to reduce the torque. That is, it is difficult to simultaneously achieve an improvement in the sealing performance by reducing the radial dimension of the sealing ring and a reduction in the torque by utilizing the dynamic pressure action generated by the groove.

[0009] The present invention has been completed in view of the above problems, and an object thereof is to provide a sealing ring that can improve the sealing performance while reducing the torque.

[0010] Means for Solving the Problems

[0011] In order to achieve the above object, the sealing ring according to the present invention is an annular sealing ring having a cut portion, and includes: a pair of reducing portions whose radial dimension of the sealing ring gradually decreases as approaching the cut portion; and a plurality of concave portions formed on at least one of the surfaces facing the axial direction. The plurality of concave portions include a first concave portion disposed within a range included in the reducing portion and a second concave portion disposed within a range away from the cut portion with respect to the first concave portion. A wall portion that divides the two and a communication portion that connects the two are formed between the inner peripheral surface or the outer peripheral surface of the sealing ring and the second concave portion, and an enlarged communication portion that connects the two is formed between the inner peripheral surface or the outer peripheral surface of the sealing ring and the first concave portion. The enlarged communication portion is composed of one or more parts, and the total circumferential dimension of the enlarged communication portion is larger than the circumferential dimension of the communication portion.

[0012] In the sealing ring according to one aspect of the present invention, the enlarged communication portion connects the entire first concave portion to the inner peripheral surface or the outer peripheral surface.

[0013] In the sealing ring according to one aspect of the present invention, the plurality of concave portions are formed on both surfaces of the sealing ring facing the axial direction.

[0014] Advantageous Effects of the Invention

[0015] According to the sealing ring of the present invention, it is possible to improve the sealing performance while reducing the torque. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a cross-sectional view of a sealing structure provided with the sealing ring according to an embodiment of the present invention.

[0017] Figure 2 is a top view of the sealing ring according to an embodiment of the present invention.

[0018] Figure 3 is a perspective view of the sealing ring according to an embodiment of the present invention.

[0019] Figure 4 is a perspective view of the sealing ring according to an embodiment of the present invention.

[0020] Figure 5 is along Figure 4 Cross-sectional view taken along line B-B of.

[0021] Figure 6The top view of the seal ring related to the embodiment of the present invention is schematically enlarged and shown.

[0022] Figure 7 It is a cross-sectional view taken along Figure 2 the A-A line of

[0023] Figure 8 It is a cross-sectional view of the seal ring of Modification 1 of the present invention.

[0024] Figure 9 It is a cross-sectional view of the seal ring of Modification 2 of the present invention.

[0025] Figure 10 It is a cross-sectional view of the seal ring of Modification 3 of the present invention.

[0026] Figure 11 It is a cross-sectional view of the seal ring of Modification 4 of the present invention.

[0027] Figure 12 It is a cross-sectional view of the seal ring of Modification 5 of the present invention.

[0028] Figure 13 It is a cross-sectional view of the seal ring of Modification 6 of the present invention.

[0029] Figure 14 It is a cross-sectional view of the seal ring of Modification 7 of the present invention. Detailed Embodiments

[0030] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 It is a cross-sectional view of the sealing structure 300 provided with the seal ring 1 related to the embodiment of the present invention, Figure 2 It is the top view of the seal ring 1, Figure 3 It is the perspective view of the seal ring 1, Figure 4 It is the perspective view of the seal ring 1, Figure 5 It is along Figure 4 the B-B line of Figure 6 It is a schematically enlarged top view showing the seal ring 1, Figure 7 It is along Figure 2 the A-A line of

[0031] As Figures 1 to 7As shown, the seal ring 1 according to an embodiment of the present invention is an annular seal ring having a cut portion 2, and includes: a pair of reducing portions 5, 6, the radial dimension of the seal ring 1 gradually decreasing as it approaches the cut portion 2; and a plurality of recesses 7 formed on at least one of end faces 1C, 1D facing the axis x direction. The plurality of recesses 7 are composed of a first recess 7A disposed within the range of the reducing portions 5, 6 and a second recess 7B disposed within a range away from the cut portion 2 with respect to the first recess 7A. An inner peripheral side wall portion 9B partitioning the two and a communication portion 91 communicating the two are formed between the inner peripheral surface 1A of the seal ring 1 and the second recess 7B. An enlarged communication portion 74 communicating the two is formed between the inner peripheral surface 1A of the seal ring 1 and the first recess 7A. The enlarged communication portion 74 is composed of one part, and the circumferential dimension of the enlarged communication portion 74 is larger than the circumferential dimension of the communication portion 91.

[0032] The seal ring 1 constitutes a sealing structure 300. In the present embodiment, the sealing structure 300 is a structure for sealing an annular gap between a power transmission shaft component in a vehicle and a housing. In addition, the sealing structure constituted by the seal ring 1 is not limited to the above, as long as it is a structure for sealing fluids such as lubricating oil and cooling water in various hydraulic devices, water pressure devices, and air pressure devices. Specific devices as objects include engines, motors, generators, pumps, compressors, power steering devices of vehicles, speed reducers, transmissions, and coolers.

[0033] The seal ring 1 is disposed between a housing 100 as an outer peripheral side component and a shaft portion 200 as an inner peripheral side component, thereby constituting the sealing structure 300. The housing 100 forms a lubricating oil space S1 as a sealing object space inside thereof, and has a wall portion 101 partitioning the lubricating oil space S1 and an external space (atmosphere) S2. A cylindrical through hole 102 is formed in the wall portion 101.

[0034] The shaft portion 200 is a power transmission shaft component of a vehicle that rotates about the axis x, is formed in a rod shape with a circular cross-section, and is inserted through the through hole 102. The outer diameter of the shaft portion 200 is smaller than the inner diameter of the through hole 102. A concave circumferential groove 201 is formed over the entire circumference in a region of the outer peripheral surface of the shaft portion 200 that faces the inner peripheral surface of the through hole 102. By being disposed in the circumferential groove 201, the seal ring 1 contacts both the through hole 102 and the shaft portion 200 disposed in the through hole 102, sealing the gap between the housing 100 and the shaft portion 200. Thereby, the seal ring 1 inhibits the leakage of lubricating oil as a sealing object from the lubricating oil space S1 to the external space S2.

[0035] Hereinafter, for ease of explanation, in the direction of the axis x, which is the rotation axis passing through the center of the shaft portion 200, an arrow a (refer to Figure 1 、 2) The direction (the direction towards the lubricating oil space S1) is taken as one side, and the arrow b in the x-axis direction (refer to Figure 1 , 2 ) direction (the direction towards the external space S2) is taken as the other side. Further, in the direction perpendicular to the axis x (hereinafter, also referred to as the "radial direction"), the direction away from the axis x ( Figure 1 the arrow c direction) is taken as the outer peripheral side, and the direction approaching the axis x ( Figure 1 the arrow d direction) is taken as the inner peripheral side.

[0036] By rotating the shaft portion 200 relative to the fixed housing 100, they rotate relative to each other. At this time, the seal ring 1 does not rotate relative to the housing 100, but slides relative to the shaft portion 200. That is, the seal ring 1 makes sliding contact with the shaft portion 200. In addition, the seal ring 1 may also rotate slightly in conjunction with the shaft portion 200.

[0037] The seal ring 1 is formed in an annular shape from a long strip-shaped elastic body. The material of the elastic body constituting the seal ring 1 can be, for example, resin materials such as polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), etc., or these materials can be used as the base polymer, and filler materials, etc. can be added for the purpose of improving sliding characteristics and strength.

[0038] The annular seal ring 1 has an inner peripheral surface 1A, an outer peripheral surface 1B, an end surface 1C on one side in the x-axis direction, and an end surface 1D on the other side in the x-axis direction. The seal ring 1 is formed in an annular shape with a cut portion 2. That is, the seal ring 1 is in a shape in which both ends 31, 32 of the long strip-shaped arc portion 3 can be joined by elastic deformation. The both ends 31, 32 have appropriate shapes such as special step cutting, step cutting, straight cutting, oblique cutting, etc. and are connected to each other.

[0039] The seal ring 1 is provided in the sealing structure 300 such that the outer peripheral surface 1B is in close contact with the inner peripheral surface of the through hole 102. In contrast, a gap 301 through which lubricating oil can pass is formed between the inner peripheral surface 1A of the seal ring 1 and the bottom surface 202 of the circumferential groove 201 of the shaft portion 200. By the lubricating oil entering the gap 301, the seal ring 1 is subjected to a pressure towards the outer peripheral side, and its outer peripheral surface 1B is pressed against the inner peripheral surface of the through hole 102. Thereby, the outer peripheral surface 1B of the seal ring 1 is approximately cylindrical, and the gap between the outer peripheral surface 1B and the inner peripheral surface of the through hole 102 becomes smaller.

[0040] In addition, the dimension of the sealing ring 1 in the x-axis direction is smaller than that of the circumferential groove 201 in the x-axis direction, and the lubricating oil space S1 is at a higher pressure than the external space S2. Therefore, a gap 302 through which lubricating oil can pass is formed between the end face 1C on the lubricating oil space S1 side and the inner surface 203 of the circumferential groove 201 facing the end face 1C, and the end face 1D on the external space S2 side and the inner surface 204 of the circumferential groove 201 facing the end face 1D are in close contact. Through the lubricating oil entering the gap 302, the sealing ring 1 is subjected to a pressure toward the external space S2 side and is pressed against the inner surface 204.

[0041] When viewed in the x-axis direction, both the inner circumferential surface 1A and the outer circumferential surface 1B of the sealing ring 1 are circular, but the centers of these circles are offset from each other. That is, the center of the inner circumferential surface 1A is offset radially toward the cut portion 2 with respect to the center of the outer circumferential surface 1B. As a result, the radial dimension of the sealing ring 1 gradually decreases as it moves from the intermediate portion (the central portion of the long strip-shaped arc portion 3) 4 located on the opposite side of the cut portion 2 in the radial direction toward the cut portion 2. That is, the sealing ring 1 has a pair of reducing portions 5, 6 whose radial dimensions gradually decrease. In the present embodiment, the entire sealing ring 1 is a pair of reducing portions 5, 6. In addition, the radial dimension (i.e., the minimum dimension) of the sealing ring 1 in the cut portion 2 may be, for example, about 0.5 to 0.8 times the radial dimension (i.e., the maximum dimension) of the sealing ring 1 in the intermediate portion 4. Alternatively, a part of the annular sealing ring 1 may be a reducing portion, and the other part may be an equal-thickness portion with a constant radial dimension. For example, the central angle of each of the pair of reducing portions may be set to 60 to 120°, and the remaining 120 to 60° may be set as the equal-thickness portion.

[0042] The end faces 1C, 1D on both sides of the sealing ring 1 in the x-axis direction have the same (i.e., symmetric) shape. The shape of the end face 1D will be described below. That is, a concave portion identical to the concave portion 7 of the end face 1D described below is formed on the end face 1C. As Figure 3 , 4 shown, the end face 1D has a plurality of concave portions 7 and flat portions 8 between adjacent two concave portions 7. That is, the flat portion 8 is the portion where the concave portion 7 is not formed and extends along a plane perpendicular to the x-axis.

[0043] The concave portion 7 has a pair of boundary portions 71 with the flat portion 8, a bottom portion 72 located at the center of the concave portion 7 in the circumferential direction around the x-axis, and an inclined portion 73 that is inclined such that the groove depth (the height difference in the x-direction between the flat portion 8 and each portion of the concave portion 7) gradually becomes deeper from the boundary portion 71 toward the bottom portion 72. The boundary portion 71 extends radially. In the present embodiment, a step is formed between the inclined portion 73 and the bottom portion 72, but they may also be smoothly connected. The bottom portion 72 extends along a plane perpendicular to the x-axis and is similar to the flat portion 8. The inclined portion 73 has an inclination in a direction such that it gradually becomes deeper (away from the inner surface 204) as it approaches the bottom portion 72 in the circumferential direction from the boundary portion 71.

[0044] The plurality of recesses 7 include Figure 3 the second recess 7B shown and Figure 4 the first recess 7A shown. The range for forming the first recess 7A is, for example, 60 to 120° on both sides from the cut portion 2, and the remaining recesses 7 may be the second recesses 7B. In addition, when the reducing portion is formed only in a part of the sealing ring 1, the range for setting the first recess may be the same as the range for forming the reducing portion, or may be a part on the cut portion side in the reducing portion. The second recess 7B is demarcated from the outer peripheral surface 1B by providing an outer peripheral side wall portion 9A on the outer peripheral side, and an inner peripheral side wall portion 9B is provided on the inner peripheral side. The inner peripheral side wall portion 9B demarcates the second recess 7B and the inner peripheral surface 1A at the inclined portion 73, and a notch-shaped communication portion 91 is formed in such a manner that the inner peripheral surface 1A and the bottom portion 72 communicate with each other. Thereby, the lubricating oil located on the inner peripheral surface 1A enters the second recess 7B through the communication portion 91, and an oil film is formed between the end surface 1D and the inner surface 204 of the shaft portion 200.

[0045] In this way, by providing the outer peripheral side wall portion 9A and the inner peripheral side wall portion 9B with respect to the second recess 7B, it is difficult for the lubricating oil to flow out of the second recess 7B. In addition, by providing the outer peripheral side wall portion 9A and the inner peripheral side wall portion 9B, the contact area between the end surface 1D and the inner surface 204 can be ensured around the second recess 7B. Thereby, it is easy to ensure the stability when the end surface 1D contacts the inner surface 204.

[0046] Since the outer peripheral side wall portion 9A and the inner peripheral side wall portion 9B, especially the outer peripheral side wall portion 9A, as described above, it is difficult for the lubricating oil to flow out of the second recess 7B. At this time, if the lubricating oil does not pass through the outer peripheral side wall portion 9A, the sealing between the lubricating oil space S1 and the external space S2 is ensured. For this purpose, the outer peripheral side wall portion 9A needs to have a thickness (radial dimension) of a certain level or more. In other words, even when the inner peripheral side wall portion 9B is not provided, as long as the outer peripheral side wall portion 9A with a thickness of a certain level or more is provided, the sealing can be ensured.

[0047] On the other hand, although the outer peripheral side wall portion 9A is provided on the outer peripheral side of the first recess 7A, the inner peripheral side wall portion 9B is not provided. That is, the whole of the first recess 7A (i.e., the bottom portion 72 and the inclined portion 73) is continuous (communicates) with the inner peripheral surface 21. Here, "continuous" means that there is no wall between two portions, that is, a corner portion is formed by these two surfaces (in the present embodiment, a corner portion is formed between the bottom portion 72 and the inner peripheral surface 1A and between the inclined portion 73 and the inner peripheral surface 1A). In this way, by the whole of the first recess 7A communicating with the inner peripheral surface 1A, an enlarged communication portion 74 is formed between the inner peripheral surface 1A of the sealing ring 1 and the first recess 7A. The circumferential dimension of the enlarged communication portion 74 is larger than the circumferential dimension of the communication portion 91.

[0048] The entirety of the first recess 7A is continuous (communicates) with the inner circumferential surface 21. Thus, the radial dimension of the first recess 7A is the size obtained by subtracting the radial dimension of the outer circumferential side wall portion 9A from the radial dimension of the end face 1D. In contrast, the radial dimension of the second recess 7B is the size obtained by subtracting the radial dimensions of both the outer circumferential side wall portion 9A and the inner circumferential side wall portion 9B from the radial dimension of the end face 1D.

[0049] A part of the recess 7 disposed in the reducing portions 5 and 6 becomes the first recess 7A. Since the reducing portions 5 and 6 are formed, the radial dimension of the seal ring 1 is the smallest near the cutting portion 2 and the largest at the intermediate portion 4. At this time, in the first recess 7A where the inner circumferential side wall portion 9B is not provided, the radial dimension becomes larger compared to the case where the inner circumferential side wall portion 9B is provided. The range where the first recess 7A is provided is, for example, 60° to 120° from the cutting portion 2 toward both sides as described above, and it may be appropriately set so that the difference in the radial dimensions between the plurality of recesses 7 becomes smaller.

[0050] Here, as Figure 7 shown, a protruding portion 11 protruding toward the inner circumferential side is formed on the inner circumferential surface 1A of the seal ring 1. The cross section of the protruding portion 11 is rectangular, and the front end portion on the inner circumferential side has a flat shape. In addition, the base end portion of the protruding portion 11 is formed in a conical shape so as to smoothly stand up on the inner circumferential surface 1A. Half of the difference between the dimension of the seal ring 1 as a whole in the axis x direction and the dimension of the protruding portion 11 in the axis x direction is larger than the depth of the recess 7. That is, the protruding portion 11 protrudes from a position deeper than the bottom 72.

[0051] Thus, according to the seal ring 1 according to the embodiment of the present invention, the circumferential dimension of the enlarged communication portion 74 of the first recess 7A disposed in the reducing portions 5 and 6 is larger than the circumferential dimension of the communication portion 91 of the second recess 7B. Thereby, the radial dimension of the first recess 7A can be ensured. Thus, in a structure in which the sealing performance is improved by forming the reducing portions 5 and 6, even in a region where the radial dimension of the seal ring 1 becomes smaller, by ensuring the area of the oil film formed by the recess 7, hydrodynamic action is likely to occur. Thereby, by forming an oil film layer between the inner surface 204 of the circumferential groove 201 and the end face 1D, the sliding resistance is reduced and the torque can be lowered. That is, the torque can be lowered while improving the sealing performance.

[0052] In addition, by making the enlarged communication portion 74 communicate the entirety of the first recess 7A (that is, the bottom 72 and the inclined portion 73) with the inner circumferential surface 1A, it is not necessary to provide the inner circumferential side wall portion 9B with respect to the first recess 7A, and the structure can be simplified while reducing the torque.

[0053] In addition, the sealing ring 1 has a plurality of recesses on two end faces 1C and 1D in the axial direction x of the axis. Thus, regardless of which orientation the sealing ring 1 is installed on the shaft portion 200 (which of the end faces 1C and 1D faces the inner surface 204), the recesses are arranged on the surface where the oil film is formed. That is, the operator does not need to confirm the orientation of the sealing ring 1 during assembly to prevent misassembly, and dynamic pressure action can be generated as described above to reduce the torque regardless of the assembly orientation.

[0054] In addition, the present invention is not limited to the above-described embodiments, and includes other structures and the like that can achieve the object of the present invention. Deformations and the like shown below are also included in the present invention. For example, in the above-described embodiment, the recesses 7 have a bottom 72 and a pair of inclined portions 73, but the shape of the recesses is not limited thereto.

[0055] For example, as Modification Example 1, as Figure 8 shown, the recess 70A may also have a pair of boundary portions 701 that are boundaries with the flat portion 8 and a pair of inclined portions 702 whose groove depth becomes deeper as they approach each other from the pair of boundary portions 701, and the pair of inclined portions 702 are directly connected to each other. That is, a structure in which a flat (constant-depth) bottom is not formed between the pair of inclined portions 702 may also be adopted. The inclined portion 702 is formed in a planar shape.

[0056] In addition, as Modification Example 2, as Figure 9 shown, the recess 70B may also be configured to have a pair of boundary portions 701 that are boundaries with the flat portion 8, a pair of vertical portions 703 extending along the axial direction x from the boundary portions 701, and a bottom 704 connecting the deepest parts of the vertical portions 703 to each other. That is, it may not be a structure in which the depth gradually becomes deeper from the boundary portion toward the circumferential central portion of the recess.

[0057] In addition, as Modification Example 3, as Figure 10 shown, the recess 70C may also have a pair of boundary portions 701 that are boundaries with the flat portion 8 and a pair of inclined portions 705 whose groove depth becomes deeper as they approach each other from the pair of boundary portions 701, and the pair of inclined portions 705 are directly connected to each other. That is, a structure in which a flat (constant-depth) bottom is not formed between the pair of inclined portions 705 may also be adopted. In Modification Example 3, different from Modification Example 1, the inclined portion 705 becomes a curved surface protruding to the other side in the axial direction x of the axis. That is, as the circumferential central portion of the recess 70C is approached, the change rate of the groove depth becomes larger.

[0058] In addition, as Modification Example 4, as Figure 11 shown, the recess 70D may also have a pair of boundary portions 701 that are boundaries with the flat portion 8 and a pair of stepped portions 706 whose groove depth becomes deeper in a stepped manner from the boundary portions 701. In Figure 11In the illustrated example, the stepped portion 706 has three segments (there are three portions extending in the x-axis direction), but the number of segments is not particularly limited, and two or more segments are sufficient.

[0059] In the manner where the inclined portion is connected to the boundary portion as in the above-described embodiment or Modifications 1 and 3, it is possible to reduce the angle formed between the inclined portion and the inner surface 204 of the shaft portion 200 at the boundary portion, and it is easy to obtain a hydrodynamic pressure effect. Further, in the case where the inclined portion is a convex curved surface as in Modification 3, even when some wear occurs in the seal ring, the change in the above-described formed angle is small, and it is easy to maintain the hydrodynamic pressure effect. On the other hand, in the structure where the portion extending in the axial direction is connected to the boundary portion as in Modifications 2 and 4, even when wear occurs in the seal ring, the change in the size of the concave portion is small, that is, it is easy to obtain a stable hydrodynamic pressure effect.

[0060] Further, as Modification 5, as Figure 12 shown, in addition to the outer annular portion 10 formed with the concave portion 7, the seal ring 1 may further include an inner annular portion 20 disposed on its inner peripheral side. The inner annular portion 20 has an end face 20A that recedes (away from the inner surface 204) from the flat portion 8 and a cutout portion 20B that communicates with the bottom portion 72.

[0061] Further, as Modification 6, as Figure 13 shown, the concave portion 70E may also have a pair of boundary portions 707 and 708 as boundaries with the flat portion 8, an inclined portion 709 where the groove depth gradually becomes deeper from one boundary portion 707 to the other boundary portion 708, a vertical portion 710 extending in the x-axis direction from the other boundary portion 708, and a bottom portion 711 formed between the inclined portion 709 and the vertical portion 710. Further, in Figure 13 the shown example, the outer annular portion 10 and the inner annular portion 20 are formed in the same manner as in Modification 5, but the inner annular portion 20 may not be formed. Further, in Modifications 1 to 4, the outer annular portion 10 and the inner annular portion 20 may also be formed.

[0062] Further, in the above-described embodiment, the inner peripheral side wall portion 9B is not provided in the first concave portion 7A, but as Modification 7, as Figure 14 shown, it may also be the first concave portion 7C provided with the inner peripheral side wall portion 9B. In Figure 14 the shown first concave portion 7C, a cutout portion 92 is formed in a portion of the inner peripheral side wall portion 9B that includes the boundary portion 71. Thus, the first concave portion 7C is continuous with the inner peripheral surface 1A at the boundary portion 71. That is, the communication portion 91 and the cutout portion 92 constitute an enlarged communication portion, and their total circumferential dimension is larger than the circumferential dimension of the communication portion 91. Further, when the inner peripheral side wall portion is provided with respect to the first concave portion and the cutout portion is formed in the inner peripheral side wall portion, the position of the cutout portion is not limited to the position including the boundary portion.

[0063] In addition, in the above-described embodiment, the sealing ring 1 has a plurality of recesses on the two end faces 1C and 1D in the axial direction of the axis x. However, the recesses may be formed only on one end face, as long as the sealing ring is installed such that the end face on which the recesses are formed becomes the side where the oil film is formed.

[0064] In addition, in the above-described embodiment, in the sealing structure 300 formed between the housing 100 as the fixed outer peripheral member and the shaft portion 200 as the rotating inner peripheral member, the sealing ring 1 is provided in the circumferential groove 201 of the shaft portion 200, and the sealing ring 1 is in sliding contact with the shaft portion 200. However, the sealing ring may have other structures. That is, the sealing ring may be provided with respect to a structure in which the inner peripheral member is fixed and the outer peripheral member rotates, or a structure in which both the inner peripheral member and the outer peripheral member rotate. In addition, a groove may be formed on the inner peripheral surface of the outer peripheral member, and the sealing ring may be disposed in the groove. In addition, the sealing ring may follow either the outer peripheral member or the inner peripheral member (i.e., in sliding contact with either one), or may follow either the rotating member or the fixed member (i.e., in sliding contact with either one). In addition, depending on the arrangement of the sealing ring, it is only necessary to select which one of the inner peripheral surface and the outer peripheral surface of the sealing ring the recess is continuous with.

[0065] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the sealing ring according to the above-described embodiments of the present invention, and includes all modes included in the concept and claims of the present invention. In addition, the respective structures may be appropriately and selectively combined to achieve at least a part of the above-described problems and effects. For example, the shape, material, arrangement, dimensions, etc. of the respective components in the above-described embodiments may be appropriately changed according to the specific usage mode of the present invention.

[0066] Reference numerals:

[0067] 1…Sealing ring, 1A…Inner circumferential surface, 1B…Outer circumferential surface, 1C, 1D…End faces, 11…Protrusion, 2…Cutting portion, 3…Arc-shaped portion, 31, 32…Both ends, 4…Middle portion, 5, 6…Reduction portions, 7, 70B~70E…Recesses, 7A, 70C…First recess, 70B…Second recess, 71, 701, 707, 708…Boundary portions, 72, 704, 711…Bottoms, 73, 702, 705, 709…Inclined portions, 74…Enlarged communication portion, 8…Flat portion, 9A…Outer peripheral side wall portion, 9B…Inner peripheral side wall portion, 91…Communication portion, 92…Notch portion, 703, 710…Vertical portions, 706…Stepped portion, 10…Outer annular portion, 20…Inner annular portion, 20A…End face, 20B…Notch portion, 100…Housing, 101…Wall portion, 102…Through hole, 200…Shaft portion, 201…Circumferential groove, 202…Bottom surface, 203, 204…Inner surfaces, 300…Sealing structure, 301, 302…Clearances, S1…Lubricating oil space, S2…External space.

Claims

1. A circular sealing ring having a cut-off portion, comprising: a pair of reducing portions, the radial dimension of the sealing ring gradually decreasing as it approaches the cut-off portion; and a plurality of recesses formed on at least one of the surfaces facing the axial direction, the plurality of recesses including a first recess disposed within the range of the reducing portion and a second recess disposed within a range farther from the cut-off portion relative to the first recess, a wall portion dividing the inner peripheral surface or outer peripheral surface of the sealing ring and the second recess and a communication portion communicating the two are formed therebetween, an enlarged communication portion communicating the inner peripheral surface or outer peripheral surface of the sealing ring and the first recess is formed therebetween, the enlarged communication portion is composed of one or more parts, and the total circumferential dimension of the enlarged communication portion is larger than the circumferential dimension of the communication portion.

2. The sealing ring according to claim 1, wherein the enlarged communication portion communicates the entirety of the first recess with the inner peripheral surface or outer peripheral surface.

3. The sealing ring according to claim 1 or 2, wherein the plurality of recesses are formed on both surfaces of the sealing ring facing the axial direction.

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