O-rings and cylinder devices

Abstract

To provide an O-ring disposed between a columnar body and a cylindrical body having an inner peripheral surface opposed to an outer peripheral surface of the columnar body and relatively moving to the columnar body, and capable of stably partitioning a clearance without twisting in relative movement of the columnar body and the cylindrical body in comparison with an O-ring having a circular cross section in a case of partitioning the clearance formed by the columnar body and the cylindrical body into two.SOLUTION: An O-ring 40 is disposed between a columnar body 20 and a cylindrical body having an inner peripheral surface opposed to an outer peripheral surface 22 of the columnar body and relatively moving to the columnar body, and is pressed to the columnar body and the cylindrical body while being fitted to a peripheral groove 24 formed on any one of the outer peripheral surface and the inner peripheral surface, so as to partition a clearance formed by the columnar body and the cylindrical body into two. A contact surface pressure P at a bottom surface 24A of the peripheral groove has at least two peaks PK1, PK2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an O-ring and a cylinder device. [Background technology]

[0002] Patent Document 1 discloses a sealing structure that includes two members that reciprocate relative to one another and an annular sealing member made of an elastic material, and seals the gap between the two members with the sealing member, as shown in Fig. 1. Specifically, it is disclosed that this sealing structure has the following structure.

[0003] One of the two members is a housing having a shaft hole, and the other member is a shaft portion inserted into the shaft hole, with an annular groove formed on the outer peripheral surface of the shaft portion. One side surface of the annular groove is an expanding tapered surface that is inclined from the opening of the annular groove toward the bottom surface so that the width of the annular groove increases. The seal member is annular and made of an elastic material that seals the gap between the two components. The seal member is placed in the annular groove of the shaft and makes sliding contact with the housing. There are no particular restrictions on the cross-sectional shape of the seal member 1, but the specific example disclosed in Patent Document 1 uses a circular shape to effectively reduce the reaction force generated on the sliding surface.

[0004] With the above-described configuration, in this sealing structure, when the two components move back and forth relative to each other and the pressure in one space separated by the sealing component (see Figure 2) rises, the sealing component moves to the other space where the pressure is lower than that of the first space. That is, in this sealing structure, an O-ring with a circular cross section is used as the sealing component, and when the two components move relative to each other, the sealing component is intentionally moved within the width of the annular groove, thereby sealing the gap between the two components. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-167648 Summary of the Invention [Problem to be solved by the invention]

[0006] The sealing member of Patent Document 1, i.e., the O-ring with a circular cross section, moves within the width of the annular groove when two components move back and forth relative to each other. In other words, the basic design concept of this O-ring is thought to be that it rotates a set angle clockwise and counterclockwise as the two components move back and forth relative to each other, causing each annular portion to simultaneously rotate an equal angle.

[0007] However, in the sealing structure of Patent Document 1, if there is a design misalignment between the axes of two components arranged with their axes overlapping each other (e.g., misalignment of the axes as viewed from the axial direction, misalignment due to the inclination of one axis relative to the other, or misalignment due to a combination of these), each annular portion of the O-ring cannot be rotated simultaneously by the same angle. As a result, there is a risk that the O-ring will be partially twisted as the two components reciprocate relative to each other. In particular, the more frequently the two components reciprocate relative to each other and the larger the diameter (periphery) of the O-ring, the more pronounced the partial twisting of the O-ring will be. As a result, in this sealing structure, the partial twisting of the O-ring will reduce the sealing performance of the gap between the two components (gap partitioning performance).

[0008] One of the objects of the present invention is to provide an O-ring that is arranged between a cylindrical body and a cylindrical body that has an inner peripheral surface facing the outer peripheral surface of the cylindrical body and moves relatively to the cylindrical body, and that, when dividing a gap formed by the cylindrical body and the cylindrical body into two, is less likely to twist during relative movement between the cylindrical bodies and can stably divide the gap compared to an O-ring with a circular cross section. [Means for solving the problem]

[0009] The O-ring of the first aspect is An O-ring is disposed between a cylindrical body and a cylindrical body that has an inner peripheral surface facing the outer peripheral surface of the cylindrical body and moves relatively to the cylindrical body, the O-ring being fitted into a circumferential groove formed in one of the outer peripheral surface and the inner peripheral surface and being pressed against the cylindrical body and the cylindrical body, dividing a gap formed by the cylindrical body and the cylindrical body into two, The contact surface pressure at the bottom surface of the circumferential groove in the width direction of the circumferential groove is configured to have at least two peaks.

[0010] The O-ring of the second embodiment is An O-ring is disposed between a cylindrical body and a cylindrical body that has an inner peripheral surface facing the outer peripheral surface of the cylindrical body and moves relatively to the cylindrical body, the O-ring being fitted into a circumferential groove formed in one of the outer peripheral surface and the inner peripheral surface and being pressed against the cylindrical body and the cylindrical body, dividing a gap formed by the cylindrical body and the cylindrical body into two, a semicircular first ring portion, the cross section of which, when cut along a cutting line perpendicular to the circumferential direction of the cylindrical body, includes a straight line portion parallel to the axis of the cylindrical body; a second ring portion that is formed integrally with the first ring portion, that protrudes from a peripheral surface portion corresponding to the linear portion toward the opposite side of the first ring portion in the radial direction of the cylindrical body, and that has a notch formed on its outer peripheral surface that faces the bottom of the circumferential groove; Equipped with.

[0011] The O-ring of the third embodiment is In the O-ring of the second aspect, The contact surface pressure at the bottom surface of the circumferential groove in the width direction of the circumferential groove is configured to have at least two peaks.

[0012] The O-ring of the fourth aspect is In the O-ring of the third aspect, The magnitude of the contact surface pressure at the at least two peaks is equal to or greater than 50% of the magnitude of the contact surface pressure at the peak with the highest contact surface pressure.

[0013] The O-ring of the fifth aspect is In the O-ring according to any one of the second to fourth aspects, The center of the portion of the second ring portion where the notch is formed is spaced apart from the bottom of the circumferential groove.

[0014] The O-ring of the sixth aspect is In the O-ring according to any one of the second to sixth aspects, The notch has an arcuate shape.

[0015] The O-ring of the seventh aspect is In the O-ring of the sixth aspect, the cut surface of the first ring portion is semicircular, The radius of curvature of the cutout is equal to or smaller than the radius of the first ring portion.

[0016] The O-ring of the eighth aspect is In the O-ring according to any one of the first to seventh aspects, The circumferential groove is formed on the outer circumferential surface.

[0017] The O-ring of the ninth aspect is In the O-ring according to any one of the second to eighth aspects, Both ends of the notch form curved surfaces.

[0018] The O-ring of the tenth aspect is In the O-ring according to any one of the second to ninth aspects, A notch different from the notch is formed in a portion of the first ring portion that contacts either the inner circumferential surface or the outer circumferential surface.

[0019] The O-ring of the eleventh aspect is In the O-ring of the tenth aspect, The shape of the other cutout is different from the shape of the cutout.

[0020] The O-ring of the twelfth embodiment is In the O-ring of the tenth or eleventh aspect, Both ends of the other cutout form curved surfaces.

[0021] The O-ring of the thirteenth aspect is In the O-ring according to any one of the first to twelfth aspects, In a cross section obtained by cutting the cylindrical body along a cutting line perpendicular to the circumferential direction, the portion on one side in the axial direction and the other side, which is all the portion other than the portion on that side, are in a line-symmetrical relationship with each other.

[0022] One aspect of the cylinder device is A cylindrical body; a cylindrical body having an inner peripheral surface facing the outer peripheral surface of the cylindrical body and moving relatively to the cylindrical body; an O-ring according to any one of the first to thirteenth aspects, which is disposed between the columnar body and the cylindrical body; Equipped with a circumferential groove into which the O-ring is fitted is formed on either the outer circumferential surface or the inner circumferential surface, The O-ring is fitted into the circumferential groove and pressurized against the columnar body and the cylindrical body, dividing the gap formed by the columnar body and the cylindrical body into two. [Effects of the Invention]

[0023] The O-ring of the first embodiment is disposed between a cylinder and a cylindrical body that has an inner peripheral surface facing the outer peripheral surface of the cylinder and moves relative to the cylinder, and when dividing the gap formed by the cylinder and the cylindrical body into two (hereinafter referred to as the case of specific operating conditions), it is less likely to twist during relative movement between the cylinder and the cylindrical body and can stably divide the gap compared to an O-ring with a circular cross section.

[0024] Under specific operating conditions, the O-ring of the second embodiment is less likely to twist during relative movement between the cylindrical body and the cylindrical member than an O-ring with a circular cross section, and can stably separate the gap.

[0025] Under specific operating conditions, the O-ring of the third embodiment is less likely to twist during relative movement between the cylindrical body and the cylindrical member, and can stably separate the gap, compared to an O-ring in which the contact surface pressure at the bottom surface of the circumferential groove in the width direction of the circumferential groove has only one peak.

[0026] The O-ring of the fourth embodiment is less likely to twist during relative movement between the cylindrical body and the cylindrical member and can stably separate the gap under specific operating conditions, compared to an O-ring in which all peak contact pressures are less than 50% of the highest peak contact pressure.

[0027] Under specific operating conditions, the O-ring of the fifth embodiment is less likely to twist during relative movement between the cylindrical body and the cylindrical body and can stably separate the gap, compared to an O-ring in which the entire center of the part where the notch is formed in the second ring part is in contact with the bottom of the circumferential groove.

[0028] Under specific operating conditions, the O-ring of the sixth embodiment is less likely to twist during relative movement between the cylindrical body and the cylindrical member, and can stably separate the gap, compared to an O-ring with a rectangular cutout shape.

[0029] Under specific operating conditions, the O-ring of the seventh embodiment is less likely to twist during relative movement between the cylindrical body and the cylindrical body and can stably separate the gap, compared to an O-ring in which the cut surface of the first ring portion is semicircular and the radius of curvature of the cutout is larger than the radius of the first ring portion.

[0030] The O-ring of the eighth embodiment is less likely to be fitted in a twisted state than an O-ring with a perfectly circular cross section when the O-ring is fitted into a circumferential groove formed on the outer surface of a cylinder by moving the O-ring from one axial side to the other of the cylinder (hereinafter referred to as the case of specific set conditions).

[0031] The O-ring of the ninth embodiment, under specific set conditions, is less likely to be fitted in a twisted state than an O-ring in which straight edges are formed on both ends of the notch.

[0032] In the O-rings of the tenth to twelfth embodiments, under specific operating conditions, the magnitude of the contact surface pressure at at least two peaks can be adjusted by the other cutouts, compared to when the cut surface of the first ring portion is semicircular.

[0033] Under certain setting conditions, the O-ring of the thirteenth embodiment can be set in the same way regardless of whether one side or the other side is fitted onto the cylindrical body first. In other words, the O-ring of the thirteenth embodiment can be set in any orientation onto the cylindrical body.

[0034] In one embodiment of the cylinder device, under certain operating conditions, malfunctions caused by the O-ring twisting during relative movement between the cylindrical body and the cylindrical body are less likely to occur than in a cylinder device equipped with an O-ring with a circular cross section. [Brief explanation of the drawings]

[0035] [Figure 1] 1 is a diagram of a cylinder device according to an embodiment of the present invention (hereinafter referred to as the present embodiment), and is a vertical cross-sectional view of the main part and its surroundings. [Figure 2] FIG. 2 is an enlarged view of the area surrounded by dashed line A in FIG. [Figure 3] 3 is a composite diagram including a partial view of FIG. 2 and a one-dimensional profile of the contact pressure applied by the O-ring to the bottom surface of the circumferential groove of the cylindrical body. [Figure 4] 1 is a cross-sectional view of an O-ring according to an embodiment of the present invention in its natural state. [Figure 5] 5A to 5C are diagrams for explaining a part of the manufacturing process of the cylinder device of the present embodiment. [Figure 6] FIG. 4 is a composite view corresponding to FIG. 3 in a comparative embodiment. [Figure 7] FIG. 2 is a view corresponding to FIG. 1 in a first modified example. [Figure 8] FIG. 4 is a composite view corresponding to FIG. 3 in a second modified example. [Figure 9] FIG. 10 is a view corresponding to FIG. 2 in a third modified example. [Figure 10] FIG. 10 is a view corresponding to FIG. 2 in a fourth modified example. [Figure 11] FIG. 10 is a view corresponding to FIG. 2 in a fifth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0036] Overview The present embodiment and several modified examples thereof will be described below. First, the present embodiment will be described. Then, several modified examples will be described. Please note that in this specification, components having equivalent functions are denoted by the same or equivalent reference numerals in each drawing referred to in different embodiments, etc.

[0037] <<Present Embodiment>> Below, (1) the function, configuration, and action of this embodiment, (2) part of the manufacturing process of the cylinder device 10 of this embodiment (see Figure 1), and (3) the effects of this embodiment will be described in the order described with reference to the drawings.

[0038] <Function, configuration and action of the cylinder device 10 of this embodiment> Fig. 1 is a diagram of a cylinder device 10 of this embodiment, showing a longitudinal cross section of its main part and its surroundings. As shown in Fig. 1, the cylinder device 10 of this embodiment includes a cylindrical body 20, a cylindrical body 30, and an O-ring 40. As an example, the cylinder device 10 is connected to a power source (not shown), and has the function of using the driving force from the power source to reciprocate the cylindrical body 20 relative to the cylindrical body 30. Below, the cylinder device 10 will be explained by dividing it into its constituent elements.

[0039] [Cylinders and cylindrical bodies] The cylindrical body 20 is rod-shaped and, for example, is a member whose cross section is a perfect circle. The symbol O in FIG. 1 denotes the axis (axis O) of the cylindrical body 20. As shown in FIG. 1, a circumferential groove 24 into which an O-ring 40 is fitted is formed in the outer peripheral surface 22 of the cylindrical body 20. The circumferential groove 24 is formed endlessly around the entire circumferential direction of the outer peripheral surface 22. Here, the bottom (or bottom surface) of the circumferential groove 24 is referred to as bottom surface 24A. In the following description, the direction along the axis O will be simply referred to as the axial direction. The cylindrical body 20 of this embodiment has the following relationship with an O-ring 40, which will be described later. (1) The overall circumferential length of the bottom surface 24A of the circumferential groove 24 is longer than the inner circumferential length of the O-ring 40 in its natural state. In other words, the diameter of the circumferential groove 24 is larger than the inner diameter of the O-ring 40 in its natural state. (2) The width of the bottom surface 24A and the width in the axial direction of the bottom surface 24A are wider than the thickness (width in the axial direction) of the O-ring 40 in its natural state. (3) The depth of the bottom surface 24A is shallower than the radial width of the O-ring 40 in its natural state.

[0040] As shown in FIG. 1 , the cylinder 30 is a cylindrical member having an inner peripheral surface 32 facing the outer peripheral surface 22 of the cylinder 20. The cylinder 30 is disposed such that its axis overlaps the axis of the cylinder 20, and its inner peripheral surface 32 faces the outer peripheral surface 22 of the cylinder 20, while being spaced apart from the cylinder 20 (forming a gap G). Therefore, for example, the cross section of the inner peripheral surface 32 of the cylinder 30 is the same perfect circle as the outer peripheral surface 22 of the cylinder 20. The diameter of the inner peripheral surface 32 is larger than the diameter of the outer peripheral surface 22 of the cylinder 20. The distance from the inner peripheral surface 32 of the cylinder 30 to the outer peripheral surface 22 of the cylinder 20 is shorter than the width of each portion of the O-ring 40 in the circumferential direction in its natural state.

[0041] As explained above, the cylinder device 10 has the function of moving one of the cylindrical body 20 and the cylindrical body 30 back and forth relative to the other, but in this embodiment, a power source (not shown) is connected to one end portion (not shown) of the axial direction of the cylindrical body 20, so that the cylindrical body 30 moves back and forth in the axial direction.

[0042] [O-ring] Next, the O-ring 40, which is a main part of this embodiment, will be described with reference to Figs. 1 to 4. Fig. 2 is an enlarged view of the portion surrounded by dashed line A in Fig. 1. Fig. 3 is a composite diagram including a view of a portion of Fig. 2 and a one-dimensional profile of the contact surface pressure P that the O-ring 40 applies to the bottom surface 24A of the circumferential groove 24 of the cylindrical body 20. Fig. 4 is a cross-sectional view of the O-ring 40 in its natural state (a cross-sectional view obtained by cutting a portion of the circumferential direction along a cutting plane including an axis O parallel to the axial direction).

[0043] 1, the O-ring 40 of this embodiment is fitted into the circumferential groove 24 of the cylindrical body 20 and pressurized by the cylindrical body 20 and the cylindrical body 30, and has the function of dividing the gap G formed by the cylindrical body 20 and the cylindrical body into two. Here, the O-ring 40 is pressurized by the cylindrical body 20 from its inner circumferential side and by the cylindrical body 30 from its outer circumferential side because, as explained above, the distance from the inner circumferential surface 32 to the outer circumferential surface 22 is shorter than the width of each portion of the O-ring 40 in the circumferential direction in its natural state.

[0044] The O-ring 40 of this embodiment is an elastic body that elastically deforms when an external force is applied, and is made of rubber, for example. Although the O-ring 40 is an integrally formed member, please note that in the following explanation, the O-ring 40 will be divided into multiple parts for the convenience of clearly explaining the configuration of the O-ring 40. As shown in FIGS. 1 to 4 (see FIG. 4 in particular), the O-ring 40 has a first ring portion 42 and a second ring portion 44.

[0045] (First ring part) As shown in FIG. 4, the first ring portion 42 is a semicircular portion in which a cross section taken along a cutting line perpendicular to the circumferential direction of the cylindrical body 20 (a cross section taken along a cross section including the parallel axis O) includes a straight line portion SL parallel to the axis O of the cylindrical body 20. Note that although FIG. 4 shows a cross section of the O-ring 40, it is not hatched for ease of explanation. As shown in FIG. 1, the first ring portion 42 is the radially outer portion of the O-ring 40. Therefore, the first ring portion 42 contacts the inner circumferential surface 32 of the cylindrical body 30 at the radially outer portions of the cylindrical body 20 and the cylindrical body 30. It should be noted that although the cross section of the first ring portion 42 has been described as being semicircular, in this embodiment it is, for example, half of a perfect circle, that is, a semicircle.

[0046] (Second ring part) 1 and other figures, the second ring portion 44 is formed integrally with the first ring portion 42, and protrudes from a portion (circumferential surface portion) corresponding to the straight portion SL that extends over the entire circumferential direction of the first ring portion 42 toward the radially inner side of the cylindrical body 20 (the radially opposite side from the first ring portion 42 in this embodiment). Also, a notch 44A is formed in the outer peripheral surface of the second ring portion 44 (the inner peripheral surface of the O-ring 40). In this embodiment, the notch 44A faces and contacts the bottom surface 24A of the circumferential groove 24 of the cylindrical body 20. If the cross section of the second ring portion 44 is not cut out by the notch 44A, it has, as an example, a shape that is symmetrical to the first ring portion 42 with the straight line portion SL as the line of symmetry, i.e., half of a perfect circle.

[0047] Next, the details of the notch 44A will be described with reference to FIGS. 1 to 4, the cross-sectional shape of the notch 44A is, for example, an arc shape. As shown in FIG. 4, the radius of curvature R1 of the notch 44A is preferably equal to or smaller than the radius R2 of the first ring portion 42. In each drawing, the radius of curvature R1 of the notch 44A is smaller than the radius R2 of the first ring portion 42. In FIG. 4, point C1 is the center of an imaginary circle that includes the notch 44A as a part, and point C2 is the center of an imaginary circle that includes a curve corresponding to the outer peripheral surface of the first ring portion 42 as a part. Note that the distance R3 from point C2 to the notch 44A is shorter than the radius R2 of the first ring portion 42. However, in this embodiment, the distance R3 is set to, for example, 80% or more of the radius R2. An imaginary line passing through both ends of the notch 44A is parallel to the axis O. That is, a line connecting point C1, which is the center of the imaginary circle of the notch 44A, with point C2 is set perpendicular to the axis O. In other words, in the O-ring 40 of this embodiment, an upper axial portion 40U (the cross section of which is an example of a portion on one side in the axial direction) and a lower axial portion 40L (the cross section of which is an example of a portion on the other side in the axial direction) are symmetrical with respect to an imaginary plane VP perpendicular to the axial direction that divides them into two (see FIG. 4). That is, the upper axial portion 40U and the lower axial portion 40L are line-symmetrical with each other.

[0048] As shown in Fig. 2, the portion of the second ring portion 44 where the notch 44A is formed contacts the bottom surface 24A of the circumferential groove 24 of the cylindrical body 20 at both ends, and is spaced apart from the bottom surface 24A of the circumferential groove 24 of the cylindrical body 20 at its center. Also, as shown in Fig. 4, both ends of the notch 44A form curves (gentle, convex mountain shapes facing the axis O). That is, both ends of the notch 44A each form a curved surface 44A1.

[0049] 3, since the notch 44A has the above-described shape, the O-ring 40 is configured so that the contact surface pressure P at the bottom surface 24A of the circumferential groove 24 in the width direction (meaning the axial direction) of the circumferential groove 24 of the cylindrical body 20 has two peaks PK1 and PK2. In this embodiment, the magnitudes of the two peaks PK1 and PK2 are equal.

[0050] The above is a description of the function, configuration, and action of the cylinder device 10 of this embodiment.

[0051] <Part of the manufacturing process of the cylinder device of this embodiment> Next, a part of the manufacturing process of the cylinder device 10 (see FIG. 1) of this embodiment will be described with reference to FIG. 5. Specifically, the process of setting the O-ring 40 into the cylindrical body 20 will be described.

[0052] First, an operator deforms the O-ring 40 to a diameter larger than its natural diameter, and fits the O-ring 40 into the cylindrical body 20 from one end side (see FIG. 5(A)). Then, the O-ring 40 brings the lower end of the notch 44A formed on its inner peripheral surface into contact with the outer peripheral surface 22 of the cylindrical body 20.

[0053] Next, when the worker further moves (pushes) the O-ring 40 from one end side to the other end side of the cylindrical body 20, the O-ring 40 reaches the opening edge of the circumferential groove 24 while the lower end of the notch 44A contacts the outer peripheral surface 22 of the cylindrical body 20 (see Figure 5(B)).

[0054] Next, when the worker further moves (pushes) the O-ring 40 from one end side to the other end side of the cylindrical body 20, the O-ring 40 moves while the upper end of the notch 44A contacts the outer peripheral surface 22 of the cylindrical body 20 (see FIG. 5(C)). Then, when the upper end reaches the opening edge of the circumferential groove 24, the O-ring 40 deforms and contracts due to its own compressive stress, and fits inside the circumferential groove 24.

[0055] The above-described multiple steps complete the process of setting the O-ring 40 into the cylindrical body 20 in this embodiment. In this embodiment, the notch 44A is formed in the inner peripheral surface of the O-ring 40, and the notch 44A contacts the outer peripheral surface 22 of the cylindrical body 20 and moves in a sliding manner. Therefore, when the O-ring 40 is finally set in the circumferential groove 24, it is not twisted at each location around the entire circumference.

[0056] The above is a description of part of the manufacturing process of the cylinder device 10 of this embodiment.

[0057] <Effects of this embodiment> Next, the effects of this embodiment will be described with reference to the drawings.

[0058] [First effect] This effect is due to the fact that the O-ring 40 is formed with a notch 44A (see FIGS. 1, 2, etc.) that comes into contact with the bottom surface 24A of the circumferential groove 24 of the cylindrical body 20. This effect will be explained by comparing this embodiment with a comparative embodiment described later.

[0059] The only difference between the comparative cylinder device 10A (see FIG. 6) and the cylinder device 10 of this embodiment (see FIG. 2) is the shape of the O-ring. Specifically, the cross-sectional shape of the comparative O-ring 40A is a circle (a perfect circle). In other words, the comparative O-ring 40A has a general shape. As shown in Fig. 6, when the O-ring 40A of the comparative embodiment is sandwiched between the cylindrical body 20 and the cylindrical body 30 and pressurized, each of the arc-shaped portions AP is crushed from both sides in the opposing direction, and the O-ring 40A is deformed from its natural circular shape (indicated by the broken lines) into an elliptical shape (or flattened shape). As a result, the O-ring 40A of the comparative embodiment contacts the bottom surface 24A with a contact pressure that forms a single peak PK at one location.

[0060] Furthermore, the O-ring 40A of the comparative embodiment has the same configuration as the O-ring included in the sealing structure of the aforementioned Patent Document 1. That is, as explained in the aforementioned Patent Document 1, the O-ring 40A of the comparative embodiment is prone to movement in the direction of reciprocation of the cylindrical body 20 (in the width direction of the circumferential groove 24) as the cylindrical body 20 moves relative to the cylindrical body 20. Furthermore, as explained in the aforementioned Patent Document 1, if there is a design misalignment between the axes of the cylindrical body 20 and the cylindrical body 30, which are arranged with their axes overlapping each other (e.g., misalignment of the axes as viewed from the axial direction, misalignment due to the inclination of one axis relative to the other, or misalignment due to a combination of these), each circumferential portion of the O-ring 40A cannot be simultaneously rotated by the same angle. As a result, there is a risk of partial twisting of the O-ring 40A due to the relative reciprocation of the cylindrical body 20 and the cylindrical body 30. Particularly, the more frequently this relative reciprocation occurs and the larger the diameter (peripheral length) of the O-ring 40A, the more pronounced the partial twisting of the O-ring 40A becomes. Accordingly, in the comparative example, the sealing performance of the gap G (the performance of partitioning the gap) is reduced due to the partial twisting of the O-ring 40A.

[0061] In contrast, the O-ring 40 of this embodiment has a notch 44A formed along the entire inner circumferential surface thereof (see FIGS. 1 to 4), and the notch 44A is configured to contact the bottom surface 24A of the circumferential groove 24 (see FIGS. 1 and 2). That is, the O-ring 40 of this embodiment contacts the bottom surface 24A at two locations, on both ends of the notch 44A, in the direction of relative movement between the cylindrical body 20 and the cylindrical body 30. From another perspective, in this embodiment, the O-ring 40 contacts the bottom surface 24A in a state where the contact pressure at the bottom surface 24A forms two peaks PK1 and PK2 in the width direction of the bottom surface 24A (the direction of relative movement between the cylindrical body 20 and the cylindrical body 30). Therefore, in this embodiment, the position is more easily maintained during relative movement between the cylindrical body 20 and the cylindrical body 30 than in the comparative embodiment.

[0062] Therefore, compared to the comparative embodiment in which the cross section of the O-ring 40A is circular, the O-ring 40 of this embodiment is less likely to twist during relative movement between the cylindrical body 20 and the cylindrical body 30, and can stably separate the gap G. Also, from another perspective, compared to the O-ring 40A of the comparative embodiment in which the contact surface pressure at the bottom surface 24A of the circumferential groove 24 in the width direction of the circumferential groove 24 has only one peak, the O-ring 40 of this embodiment is less likely to twist during relative movement between the cylindrical body 20 and the cylindrical body 30, and can stably separate the gap G. Accordingly, compared to the cylinder device 10 equipped with the O-ring 40 of this embodiment equipped with the O-ring 40 of the comparative embodiment, malfunctions caused by the O-ring twisting during relative movement between the cylindrical body and the cylindrical body (for example, the creation of a gap in the gap G that was previously closed) are less likely to occur. 4, the O-ring 40 of this embodiment has an upper portion 40U and a lower portion 40L in the axial direction that are symmetrical to each other, so that balance is maintained and the posture is easily maintained during relative movement between the cylindrical body 20 and the cylindrical body 30. Due to this point, it can be said that the O-ring 40 of this embodiment significantly exhibits this effect.

[0063] [Second effect] This effect is due to the fact that the magnitudes of the contact surface pressure P at the bottom surface 24A of the circumferential groove 24 by the O-ring 40 at the two peaks PK1 and PK2 are equal to each other. If the magnitude of the contact surface pressure P at the two peaks PK1 and PK2 is significantly different (for example, if the magnitude of the contact surface pressure at the other peaks is less than 50% of the magnitude of the contact surface pressure at the peak with the highest contact surface pressure P), the distribution of the reaction force that the O-ring receives from the bottom surface 24A and the frictional forces in the movement directions that the O-ring receives from the cylindrical body 20 and the cylindrical body 30 will periodically reverse between the outward and return paths during the relative movement between the cylindrical body 20 and the cylindrical body 30. Accordingly, the O-ring 40 may be subjected to stress biased in one of the movement directions as the number of relative movements between the cylindrical body 20 and the cylindrical body 30 increases. In contrast to this, in the case of this embodiment, the magnitudes of the contact surface pressure P at the two peaks PK1 and PK2 of the O-ring 40 on the bottom surface 24A of the circumferential groove 24 are set to be equal (see FIG. 3). Therefore, in the case of this embodiment, the stress that the O-ring 40 receives is less likely to be uneven between the outward and return paths during the relative movement between the cylindrical body 20 and the cylindrical body 30. Therefore, compared to an O-ring in which the magnitude of all peak contact surface pressures P is less than 50% of the magnitude of the highest peak contact surface pressure, the O-ring 40 of this embodiment is less likely to twist during relative movement between the cylindrical body 20 and the cylindrical body 30, and can stably separate the gap G. The configuration used for comparison in the explanation of this effect is a configuration that achieves the first effect described above. In other words, it goes without saying that this comparative configuration is included in the technical scope of the present invention.

[0064] [Third effect] This effect is due to the fact that the center of the portion of the second ring portion 44 where the notch 44A is formed is separated from the bottom surface 24A of the circumferential groove 24 (see FIGS. 2 and 3, etc.). In this embodiment, the notch 44A contacts the bottom surface 24A at two points on both ends (see Figures 2, 3, etc.). Therefore, even if one of the ends of the notch 44A moves due to a force exceeding its maximum static friction force during relative movement between the cylindrical body 20 and the cylindrical body 30, the O-ring 40 will not move in the direction of relative movement between the cylindrical body 20 and the cylindrical body 30 unless the other end receives a force exceeding its maximum static friction force. If the part of the second ring portion 44 where the notch 44A is formed contacts the bottom surface 24A of the circumferential groove 24 (see the third modified example shown in Figure 9, which will be described later), this effect cannot be expected. Therefore, the O-ring 40 of this embodiment is less likely to twist during relative movement between the cylindrical body 20 and the cylindrical body 30 and can stably separate the gap G, compared to when the entire center of the part of the O-ring 40 where the cutout 44A is formed is in contact with the bottom surface 24A of the circumferential groove 24.

[0065] [Fourth Effect] This effect is due to the fact that the shape (cross-sectional shape) of the notch 44A is arc-shaped (see FIG. 4). For example, in the case of an O-ring (not shown) in which the cross-sectional shape of the cutout 44A is rectangular, it is difficult for the O-ring to deform uniformly at all locations around the circumference when it is sandwiched and pressurized between the cylindrical body 20 and the cylindrical body 30. Furthermore, in the case of such an O-ring, it is difficult for the O-ring to deform gradually or continuously when the cylindrical body 20 and the cylindrical body 30 move relative to each other. Therefore, compared to an O-ring with a rectangular cutout, the O-ring 40 of this embodiment is less likely to twist during relative movement between the cylindrical body 20 and the cylindrical body 30, and can stably separate the gap G. The configurations used for comparison in the explanation of this effect are configurations that achieve the first to third effects described above. In other words, it goes without saying that these comparative configurations are included in the technical scope of the present invention.

[0066] [Fifth Effect] This effect is achieved by the fact that the radius of curvature R1 of the cutout 44A is equal to or smaller than the radius R2 of the first ring portion 42 (see FIG. 4). If a notch of the same width as in the present embodiment is formed under the condition that the radius of curvature R1 of the notch 44A is larger than the radius R2 of the first ring portion 42, the depth of the notch will be shallower than in the present embodiment. That is, in the case of this comparative embodiment, the shallower the depth of the notch, i.e., the closer the cross section is to a circle, the lower the intensity of the two peaks PK1 and PK2 of the contact surface pressure P and the wider their widths. That is, compared to the present embodiment, it is more difficult to apply a strong force to a small contact area. Therefore, compared to an O-ring in which the radius of curvature R1 of the notch is larger than the radius R2 of the O-ring, the O-ring 40 of this embodiment is less likely to twist during relative movement between the cylindrical body 20 and the cylindrical body 30, and can stably separate the gap G. The configurations used for comparison in the explanation of this effect are configurations that achieve the first to fourth effects described above. In other words, it goes without saying that these comparative configurations are included in the technical scope of the present invention.

[0067] [Sixth Effect] This effect is achieved in the process of setting the O-ring 40 onto the cylindrical body 20 due to the formation of the notch 44A in the O-ring 40. For example, the O-ring 40A of the comparative embodiment (see FIG. 6) has a cross section that is a perfect circle. When an operator sets the O-ring 40A of the comparative embodiment in the circumferential groove 24 of the cylindrical body 20, the operator moves (pushes) the O-ring 40 from one end of the cylindrical body 20 to the other end, and the O-ring 40A may twist or roll while rotating due to the frictional force it receives while in contact with the outer circumferential surface 22 of the cylindrical body 20. As a result, when the O-ring 40A of the comparative embodiment is fitted into the circumferential groove 24, the O-ring 40A is set in a state that is partially twisted in the circumferential direction.

[0068] In contrast, the O-ring 40 of this embodiment has a notch 44A formed therein, as shown in FIGS. 2 to 4 . As described above with respect to part of the manufacturing process for the cylinder device 10 of this embodiment, the notch 44A contacts and slides against the outer peripheral surface 22 of the cylindrical body 20, allowing the O-ring 40 to maintain its position while moving from one end of the cylindrical body 20 to the other end and being set in the circumferential groove 24 (see FIG. 5 ). The O-ring 40 of this embodiment may also be partially twisted when an operator moves the O-ring 40 from one end of the cylindrical body 20 to the other end. However, because the O-ring 40 of this embodiment has the notch 44A, if partial twisting occurs, local stress (tensile stress) due to the notch 44A is generated. Therefore, the O-ring 40 of this embodiment is more easily able to eliminate partial twisting when set in the cylindrical body 20 than the O-ring 40A of the comparative embodiment.

[0069] Therefore, when the O-ring 40 of this embodiment is fitted into the circumferential groove 24 of the cylindrical body 20 while being moved from one side to the other in the axial direction, it is less likely to be fitted in a twisted state than the O-ring 40A of the comparative embodiment.

[0070] [Seventh Effect] This effect is due to the fact that both ends of the notch 44A in the O-ring 40 form curved surfaces 44A1 (see FIG. 4). If both ends of the notch 44A of the O-ring 40 do not form a curved surface 44A1 but form a straight edge (not shown), that is, if it does not have a so-called R-chamfered shape, there is a risk that the edge will get caught on the outer surface 22 of the cylindrical body 20 when it is set on the cylindrical body 20. However, in the O-ring 40 of this embodiment, both ends of the notch 44A form curved surfaces 44A1, so when set on the cylindrical body 20, the curved surfaces 44A1 come into contact with the outer peripheral surface 22 of the cylindrical body 20 and the O-ring 40 can easily move while sliding. Therefore, when the O-ring 40 of this embodiment is fitted into the circumferential groove 24 of the cylindrical body 20 while being moved from one side to the other in the axial direction, it is less likely to be fitted in a twisted state than an O-ring in which both ends of the notch 44A form straight edges. Note that the configurations used for comparison in the explanation of this effect are configurations that achieve the first to fifth effects described above. In other words, it goes without saying that these comparative embodiments are included in the technical scope of the present invention.

[0071] [Eighth Effect] This effect is due to the fact that the upper axial portion 40U and the lower axial portion 40L of the O-ring 40 are symmetrical with respect to an imaginary plane VP perpendicular to the axial direction that divides them into two, or, from another perspective, the upper axial portion 40U and the lower axial portion 40L are symmetrical with each other (see Figure 4). If the upper part 40U and the lower part 40L are not symmetrical to each other (not shown), it is not possible to manufacture a cylinder device (not shown) in the same set state unless one of them is fitted into the cylindrical body 20 first when setting it into the cylindrical body 20. In contrast, in the O-ring 40 of this embodiment, the upper portion 40U and the lower portion 40L are symmetrical with respect to each other, as shown in Fig. 4. Therefore, the orientation of the O-ring 40 when it is set in the cylindrical body 20 does not matter. Therefore, the O-ring 40 of this embodiment can be set in the same manner regardless of whether the upper portion 40U or the lower portion 40L is fitted into the cylindrical body 20 first.

[0072] The above is a description of the effects of this embodiment. Also, the above is a description of this embodiment.

[0073] <<Multiple Modifications>> As described above, the present invention has been described using the above-mentioned embodiment as an example, but the present invention is not limited to this embodiment. The technical scope of the present invention also includes, for example, several modified examples described below.

[0074] In the present embodiment, the O-ring 40 has been described as being made of rubber. However, as long as the O-ring 40 is capable of elastic deformation, it does not have to be made of rubber. For example, the O-ring 40 may be made of an elastomer. As long as the O-ring 40 is capable of elastic deformation when pressed by another member, it may be made of a composite material in which other materials (e.g., inorganic filler) are added to rubber or elastomer, or other elastic materials.

[0075] In this embodiment, the O-ring 40 has been described as constituting the cylinder device 10 (see FIG. 1 ) together with the columnar body 20 and the cylindrical body 30. However, if the O-ring 40 is used to separate spaces on both sides by bringing its notch 44A into contact with another member, the application including the O-ring 40 does not have to be the cylinder device 10. For example, the O-ring 40 may be used as a seal between the opening edge of a sealed container and the periphery of its opening / closing lid.

[0076] In addition, in this embodiment, it has been described that a power source (not shown) is connected to one end portion (not shown) of the cylindrical body 20 in the axial direction, and the cylindrical body 20 is configured to move back and forth in the axial direction relative to the cylindrical body 30. However, as long as either the cylindrical body 20 or the cylindrical body 30 can move back and forth relative to the other, the power source may be connected to the cylindrical body 30. Also, depending on the method of use, two power sources may be prepared and connected to the cylindrical body 20 and the cylindrical body 30, respectively, so that they move relative to each other.

[0077] In addition, in this embodiment, it has been explained that a notch 44A is formed on the inner peripheral side of the O-ring 40, and the O-ring 40 is fitted with the notch 44A facing the circumferential groove 24 formed on the outer peripheral surface 22 of the cylindrical body 20 (see Figures 1, 2, etc.). However, as in the first modified cylinder device 10B shown in Figure 7, a configuration may be adopted in which a circumferential groove 34 is provided on a cylindrical body 30 without providing a circumferential groove 24 on a cylindrical body 20, and an O-ring 40B having a notch 44B formed on the outer periphery around the entire circumference is fitted into the circumferential groove 34 of the cylindrical body 30, so that the notch 44B comes into contact with the bottom surface 34B of the circumferential groove 34.

[0078] In the present embodiment, the magnitudes of the contact surface pressure P at the two peaks PK1 and PK2 of the O-ring 40 on the bottom surface 24A of the circumferential groove 24 are set to be equal to each other (see FIG. 3). However, as in the case of O-ring 40C of cylinder device 10C of a second modified example shown in Fig. 8, the magnitude of the contact surface pressure P at two peaks PK1 and PK2 on bottom surface 24A of circumferential groove 24 may be different from each other. In this case, considering the bias in the stress that O-ring 40C receives during the forward and backward movements of cylindrical body 20 and cylindrical body 30 relative to each other, it is preferable that the magnitude of the contact surface pressure P at peak PK2 be 50% or more of the magnitude of the contact surface pressure P at peak PK1, which is the highest contact surface pressure.

[0079] In the present embodiment, the center of the portion of the second ring portion 44 (O-ring 40) where the notch 44A is formed is described as being separated from the bottom surface 24A of the circumferential groove 24 (see FIGS. 2 and 3). However, as in a cylinder device 10D of a third modified example shown in Fig. 9, the entire portion of the O-ring 40 where the notch 44A is formed may be brought into contact with the bottom surface 24A of the circumferential groove 24. In the case of this modified example, the third effect described above is not obtained, but it goes without saying that the other effects of the present embodiment are obtained. In this modified example, the notch 44A is in contact with the bottom surface 24A in its entirety, so the O-ring 40 is in contact with the bottom surface 24A at one point, but the contact pressure profile in this case is similar to the contact pressure profile in Fig. 3 as in the present embodiment. That is, in this modified example, the O-ring 40 generates a contact pressure P that has two peaks on both ends of the notch 44A in the width direction, with a gentle curve connecting them (not shown).

[0080] Furthermore, in this embodiment, the description has been given on the assumption that the number of notches 44A formed in the O-ring 40 is one (see FIGS. 3 and 4, etc.). However, the number of notches 44E in the O-ring 40E may be two or more (two is exemplified in this modification) as in a cylinder device 10E of a fourth modification shown in Fig. 10. That is, the O-ring 40E may be configured to contact the bottom surface 24A of the circumferential groove 24 with a contact surface pressure P having three or more peaks.

[0081] In addition, in this embodiment, the notch 44A is described as being formed on the inner periphery side of the O-ring 40 over the entire circumferential direction (see FIG. 1, etc.). However, as in a cylinder device 10F of a fifth modified example shown in FIG. 11, another notch 44F may be formed on the outer circumferential side (second ring portion side) of an O-ring 40F. According to this modification, the contact pressure profile of the O-ring 40 on the bottom surface 24A (see FIG. 3) can be adjusted by using the notch 44F while maintaining the shape of the notch 44A. Accordingly, the shape of the other notch 44F may be different from the shape of the notch A. Here, the cylinder device 10F of the fifth modified example shown in FIG. 11 can be said to be an invention encompassed by the following technical idea, for example. (technical thought) A cylindrical body; a cylindrical body having an inner peripheral surface facing the outer peripheral surface of the cylindrical body and moving relatively to the cylindrical body; an O-ring (O-ring 40F, for example) that is disposed between the cylindrical body and the cylindrical body, is pressed against the cylindrical body and divides a gap formed by the cylindrical body and the cylindrical body into two, the O-ring having a first notch (notch 44A, for example) formed on its inner circumferential side and a second notch (notch 44F, for example) formed on its outer circumferential side; Equipped with The O-ring is configured so that the first notch is in contact with the outer peripheral surface and the second notch is in contact with the inner peripheral surface so that one or both of a first contact pressure on the outer peripheral surface and a second contact pressure on the inner peripheral surface have at least two peaks in the relative movement direction between the columnar body and the cylindrical body. Sliding device (for example, cylinder device 10F). The cylinder device 10F of the fifth modified example shown in FIG. 11 can be said to be an invention that also includes the following other technical ideas that are further generalized versions of this technical idea. (Other technical ideas) A first wall (for example, a wall whose surface is the bottom surface 24A) a second wall (for example, a wall whose surface is an inner circumferential surface 32) that faces the first wall and moves relative to the first wall; an O-ring (e.g., O-ring 40F) that is disposed between the first wall and the second wall, is pressed against the first wall and the second wall, and divides a gap formed by the first wall and the second wall into two, the O-ring having a first notch (e.g., notch 44A) formed on its inner circumferential side and a second notch (e.g., notch 44F) formed on its outer circumferential side; Equipped with The O-ring is configured so that the first notch is in contact with the first wall and the second notch is in contact with the second wall so that one or both of a first contact pressure on the first wall and a second contact pressure on the second wall have at least two peaks in a relative movement direction between the first wall and the second wall. Sliding device (for example, cylinder device 10F).

[0082] In addition, in this embodiment, the O-ring 40 has been described assuming that it is a continuous block with no hollow portion or the like formed therein (see FIG. 4, etc.). However, as long as the formation of the notch 44A provides the aforementioned effects, the O-ring 40 does not have to be a continuous block. For example, even if a hollow portion is formed therein (not shown), it is sufficient as long as the position, size, shape, range, and other requirements of the hollow portion are met so as not to affect the effects of the notch 44A. Such a configuration can also be applied to the multiple modified examples described above.

[0083] As described above, the present embodiment (see Figures 1 to 4, etc.) and several variations thereof (Figures 7 to 11, etc.) have been described. However, it goes without saying that the technical scope of the present invention also includes forms in which one of these forms is combined with some of the components of other forms, forms in which one of these forms is substituted with some of the components of other forms, and other forms. [Explanation of symbols]

[0084] 10 Cylinder device 10B Cylinder device 10C Cylinder device 10D Cylinder Device 10E Cylinder device 10F Cylinder device 20 Cylinder 22 Outer surface 24 Circumferential groove 24A Bottom 30 Cylinder 32 Inner surface 40 O-rings 40B O-ring 40C O-ring 40E O-ring 40F O-ring 40L Lower part (example of the other side part) 40U Upper part (example of one side part) 42 First Ring 44 Second Ring Section 44A Notch 44A1 Curved surface 44B Notch 44E Notch 44F notch (an example of another notch) G Gap O-axis P Contact surface pressure PK1 Peak PK2 Peak R1 Radius of curvature of the notch R2 Radius of the first ring R3: Distance from the center of the imaginary circle that is part of the curve corresponding to the outer surface of the first ring part to the notch SL: A straight line parallel to the axis of a cylinder VP Virtual Plane

Claims

1. An O-ring disposed between a cylindrical body and a cylindrical body having an inner peripheral surface facing the outer peripheral surface of the cylindrical body and moving relative to the cylindrical body, the O-ring being fitted into a circumferential groove formed on either the outer peripheral surface or the inner peripheral surface and pressurized by the cylindrical body and the cylindrical body, dividing the gap formed by the cylindrical body and the cylindrical body into two, a semicircular first ring portion, the cross section of which, when cut along a cutting line perpendicular to the circumferential direction of the cylindrical body, includes a straight line portion parallel to the axis of the cylindrical body; a second ring portion that is formed integrally with the first ring portion, that protrudes from a peripheral surface portion corresponding to the linear portion toward the opposite side of the first ring portion in the radial direction of the cylindrical body, and that has a notch formed in its outer peripheral surface that faces the bottom of the circumferential groove; Equipped with a contact surface pressure at a bottom surface of the circumferential groove in a width direction of the circumferential groove has at least two peaks, The magnitude of the contact surface pressure at the at least two peaks is equal to or greater than 50% of the magnitude of the contact surface pressure at the peak with the highest contact surface pressure. O-ring.

2. An O-ring disposed between a cylindrical body and a cylindrical body having an inner peripheral surface facing the outer peripheral surface of the cylindrical body and moving relative to the cylindrical body, the O-ring being fitted into a circumferential groove formed on either the outer peripheral surface or the inner peripheral surface and pressurized by the cylindrical body and the cylindrical body, dividing the gap formed by the cylindrical body and the cylindrical body into two, a semicircular first ring portion, the cross section of which, when cut along a cutting line perpendicular to the circumferential direction of the cylindrical body, includes a straight line portion parallel to the axis of the cylindrical body; a second ring portion that is formed integrally with the first ring portion, that protrudes from a peripheral surface portion corresponding to the linear portion toward the opposite side of the first ring portion in the radial direction of the cylindrical body, and that has a notch formed in its outer peripheral surface that faces the bottom of the circumferential groove; Equipped with The shape of the notch is an arc, the cut surface of the first ring portion is semicircular, The radius of curvature of the notch is equal to or less than the radius of the first ring portion. O-ring.

3. An O-ring disposed between a cylindrical body and a cylindrical body having an inner peripheral surface facing the outer peripheral surface of the cylindrical body and moving relatively to the cylindrical body, the O-ring being fitted into a circumferential groove formed on either the outer peripheral surface or the inner peripheral surface and pressurized by the cylindrical body and the cylindrical body, dividing the gap formed by the cylindrical body and the cylindrical body into two, a semicircular first ring portion, the cross section of which, when cut along a cutting line perpendicular to the circumferential direction of the cylindrical body, includes a straight line portion parallel to the axis of the cylindrical body; a second ring portion formed integrally with the first ring portion, protruding from a peripheral surface portion corresponding to the linear portion toward the opposite side of the first ring portion in the radial direction of the cylindrical body, the second ring portion having a notch formed on its outer peripheral surface facing the bottom of the circumferential groove and having curved ends; An O-ring with

4. The contact surface pressure at the bottom surface of the circumferential groove in the width direction of the circumferential groove is configured to have at least two peaks. The O-ring according to claim 2.

5. The contact surface pressure at the bottom surface of the circumferential groove in the width direction of the circumferential groove is configured to have at least two peaks. The O-ring according to claim 3.

6. The magnitude of the contact surface pressure at the at least two peaks is equal to or greater than 50% of the magnitude of the contact surface pressure at the peak with the highest contact surface pressure. The O-ring according to claim 4.

7. The magnitude of the contact surface pressure at the at least two peaks is equal to or greater than 50% of the magnitude of the contact surface pressure at the peak with the highest contact surface pressure. The O-ring according to claim 5.

8. The center of the portion of the second ring portion where the notch is formed is spaced apart from the bottom of the circumferential groove. The O-ring according to any one of claims 1 to 7.

9. The shape of the notch is arcuate. An O-ring according to any one of claims 1, 3, 5 and 7 and claim 8 depending on any one of claims 1, 3, 5 and 7.

10. the cut surface of the first ring portion is semicircular, The radius of curvature of the notch is equal to or less than the radius of the first ring portion. The O-ring according to claim 9.

11. The circumferential groove is formed on the outer circumferential surface. The O-ring according to any one of claims 1 to 7.

12. Both ends of the notch form curved surfaces.

7. An O-ring according to any one of claims 1, 2 and 6.

13. a notch different from the notch is formed in a portion of the first ring portion that contacts either the inner circumferential surface or the outer circumferential surface; The O-ring according to any one of claims 1 to 7.

14. The shape of the other cutout is different from the shape of the cutout. The O-ring according to claim 13.

15. Both ends of the other cutout form curved surfaces. The O-ring according to claim 13.

16. In a cross section obtained by cutting the cylindrical body along a cutting line perpendicular to the circumferential direction, a portion on one side in the width direction of the circumferential groove and a portion on the other side, which is the entire portion other than the portion on the one side, are in a line-symmetrical relationship with each other. The O-ring according to any one of claims 1 to 7.

17. A cylindrical body; a cylindrical body having an inner peripheral surface facing the outer peripheral surface of the cylindrical body and moving relatively to the cylindrical body; The O-ring according to any one of claims 1 to 7, which is disposed between the columnar body and the cylindrical body; Equipped with a circumferential groove into which the O-ring is fitted is formed on either the outer circumferential surface or the inner circumferential surface, The O-ring is fitted into the circumferential groove and pressurized against the columnar body and the cylindrical body, dividing the gap formed by the columnar body and the cylindrical body into two. Cylinder device.

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