Piping device and thermostat

Abstract

This piping device includes a piping component 2 having an inner cylinder 3, a housing 1 having an outer cylinder 4 externally fitted to the inner cylinder 3, a seal chamber 13, a seal member (O-ring 6) for creating a seal between the inner cylinder 3 and the outer cylinder, and a backup ring 5 press-fitted to the outer peripheral surface of the inner cylinder 3. A step part 9, which faces the backup ring 5, is formed at a boundary between a seal wall part 8 and a press-fitting part 10 of the inner cylinder 3 into which the backup ring 5 is press-fitted.

Description

Piping equipment and thermostats

[0001] The present invention relates to a piping device and a thermostat that include a sealing member such as an O-ring and a backup ring.

[0002] Conventionally, a piping device has been known in which an O-ring seals a connection portion to prevent leakage of fluid flowing inside when connecting a cylindrical member to a connecting member having an opening (see, for example, Japanese Patent Application Laid-Open No. 2019-124175). Also, a backup ring may be used to prevent the O-ring from entering the fitting gap due to pressure, thereby impairing the sealing performance.

[0003] Japanese Patent Application Laid-Open No. 2019-124175

[0004] If the backup ring falls off when assembling the two parts, the assembling of the two parts will be difficult. To address this, it is possible to press the backup ring into one of the parts.

[0005] However, press-fitting the backup ring causes a change in the diameter of one of the components, which may enlarge the seal chamber in which the O-ring is housed, resulting in a risk of reduced sealing performance.

[0006] In view of the above, an object of the present invention is to provide a piping device that can prevent the backup ring from falling off, improve assembly ease, and maintain good sealing performance.

[0007] In order to achieve the above object, the piping device of the present invention comprises: a first part having an inner tube; a second part having an outer tube fitted onto the outside of the inner tube; a seal chamber defined by the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube; a seal member that is sandwiched between the outer peripheral surface of the inner tube and the inner peripheral surface of the outer tube and is provided in the seal chamber in a compressed state, sealing the space between the inner tube and the outer tube; and a backup ring press-fitted onto the outer periphery of the inner tube or press-fitted onto the inner periphery of the outer tube, and on the side of the inner tube or the outer tube into which the backup ring is press-fitted, there are formed a press-fit portion into which the backup ring is press-fitted, a seal wall portion facing the seal chamber, and a step portion located at the boundary between the press-fit portion and the seal wall portion and facing the backup ring.

[0008] According to the present invention, even if the press-fit portion is deformed radially due to the press-fitting of the backup ring, this deformation originates from the step portion, preventing any effect on the seal wall portion. As a result, even if the backup ring is press-fitted and fixed, the radial gap in the seal chamber can be prevented from widening, and the seal member can be properly sandwiched between the inner and outer cylinders, maintaining good sealing performance.

[0009] In the present invention, the press-fit portion may be made up of a plurality of ribs.

[0010] In this way, the press-fit load can be adjusted more easily than when the entire circumference is press-fitted.

[0011] In the present invention, the backup ring may be press-fitted onto the outer periphery of the inner cylinder.

[0012] It is easier to press fit the backup ring onto the outer periphery than onto the inner periphery, and therefore, with this configuration, assembly can be facilitated.

[0013] In the present invention, the backup ring may be provided with a plurality of ribs facing the press-fit portion.

[0014] In this way, even when it is difficult to provide ribs on the inner and outer cylinders, the press-fit load can be easily adjusted.

[0015] In the present invention, the inner or outer periphery of the backup ring facing the press-fit portion may have an oval shape.

[0016] Examples of oval shapes include elliptical, oblong, and egg-shaped shapes. For ease of explanation, an elliptical shape will be used as an example. When the surface of the backup ring that is press-fitted is the inner peripheral surface and the cross-sectional shape of this inner peripheral surface is elliptical, the minor axis of the ellipse is press-fitted, but the major axis of the ellipse is not press-fitted, thereby making it possible to keep the contact area small during press-fitting. This can also be achieved with other oval shapes such as oblong and egg-shaped. Therefore, according to the present invention, the operation of press-fitting the backup ring is easier than when two perfect circular shapes are press-fitted together.

[0017] In the present invention, the press-fit portion may have an oval cross-sectional shape.

[0018] Examples of oval shapes include elliptical, oblong, and egg-shaped shapes. For ease of explanation, an elliptical shape will be used as an example. When the cross-sectional shape of the press-fit portion is elliptical, the press-fit occurs on the major axis side of the ellipse, but not on the minor axis side of the ellipse, thereby making it possible to keep the contact area small during press-fitting. This also applies to other oval shapes such as oblong and egg-shaped shapes. Therefore, according to the present invention, it is easier to adjust the press-fit load compared to when two perfect circular shapes are press-fitted together.

[0019] Furthermore, the piping device of the present invention may be a thermostat equipped with an on-off valve, and the on-off valve may have a valve body that contacts the tip of the inner cylinder as a valve seat and closes the inner cylinder by contacting the valve seat.

[0020] According to the present invention, an outer cylinder having a larger inner diameter than the inner cylinder is disposed around the outer periphery of the inner cylinder, sandwiching the seal member and backup ring therebetween, thereby ensuring a relatively large gap around the thermostat valve body and reducing flow resistance when the thermostat valve is open.

[0021] Fig. 1 is a perspective view, partially in cross section, showing a connection portion between a housing and a piping part of a piping device according to a first embodiment of the present invention. Fig. 2 is a perspective view showing the piping part of the first embodiment. Fig. 3 is a schematic view showing the piping device of the first embodiment. Fig. 4 is a schematic view showing a piping device of a second embodiment. Fig. 5 is a sectional view, partially in cross section, of a piping device of a third embodiment.

[0022] A piping device according to an embodiment of the present invention will be described with reference to the drawings. Referring to Fig. 1, a piping device 100 according to a first embodiment of the present invention includes a housing 1 and a piping component 2 connected to the housing 1. The piping component 2 includes an inner tube 3 at an end thereof. The housing 1 includes an outer tube 4. The inner tube 3 is inserted into the outer tube 4. In the piping device 100 according to the first embodiment, the piping component 2 corresponds to a first component of the present invention, and the housing 1 corresponds to a second component of the present invention.

[0023] The piping device 100 also includes a backup ring 5 and an O-ring 6 (sealing member) provided on the outer periphery of the inner cylinder 3 in this order from the end inserted into the housing 1. The backup ring 5 is press-fitted into the inner cylinder 3 and fixed thereto. The thickness of the first cylindrical portion 7, which is provided with a rib 10 (described later) as a press-fit portion into which the backup ring 5 of the inner cylinder 3 is press-fitted, is thinner than the thickness of the seal wall portion 8 with which the O-ring 6 of the inner cylinder 3 comes into contact. Referring to FIGS. 2 and 3 , a step portion 9 is formed on the outer periphery of the inner cylinder 3 between the first cylindrical portion 7 and the seal wall portion 8 due to the difference in thickness. Note that, in the first embodiment, the O-ring 6 is used as the sealing member, but the sealing member of the present invention is not limited to an O-ring and may be, for example, an X-packing or a U-packing.

[0024] 1 and 3, the O-ring 6 is sandwiched between the seal wall portion 8 of the inner cylinder 3 and the inner circumferential surface of the outer cylinder 4, thereby providing a seal to prevent fluid flowing through the housing 1 and the piping component 2 from leaking from the gap between the inner cylinder 3 and the outer cylinder 4. The gap between the seal wall portion 8 and the inner circumferential surface of the outer cylinder 4 is set to an appropriate gap for the O-ring 6 to maintain its sealing properties. If this gap is too wide, the O-ring 6 will not be properly crushed and appropriate sealing performance will not be achieved, and conversely, if this gap is too narrow, the O-ring 6 will be damaged and appropriate sealing performance will not be achieved.

[0025] The O-ring 6 is housed in a seal chamber 13 defined by the outer peripheral surface of the inner cylinder 3 and the inner peripheral surface of the outer cylinder 4. The seal wall portion 8 faces the seal chamber 13 and constitutes one surface of the seal chamber 13.

[0026] 2 and 3, the outer peripheral surface of the first cylindrical portion 7 is set at a height lower than the outer peripheral surface of the sealing wall portion 8, and is provided with three ribs 10 extending in the direction of the central axis of the inner cylinder 3 and formed at equal intervals in the circumferential direction. In the first embodiment, the ribs 10 correspond to the press-fit portion of the present invention.

[0027] The inner cylinder 3 is provided with a large diameter portion 11, which is located on the side farther away from the housing 1 than the seal wall portion 8 and has an outer diameter larger than that of the seal wall portion 8 in order to position the O-ring 6. A seal chamber 13 for the O-ring 6 is defined by the large diameter portion 11, the backup ring 5, the inner cylinder 3, and the outer cylinder 4. In the direction of the central axis of the inner cylinder 3, one movement limiting position of the O-ring 6 is defined by the large diameter portion 11, and the other movement limiting position is defined by the backup ring 5.

[0028] 1 and 3, the inner peripheral surface of the outer cylinder 4 is provided with a small diameter portion 12 that is positioned more inward of the housing 1 than the backup ring 5 and has a diameter smaller than the outer diameter of the backup ring 5. This prevents the backup ring 5 from falling off the inner cylinder 3 even if the backup ring 5 gradually moves toward the tip of the inner cylinder 3 due to vibration or the like.

[0029] The piping device 100 of the first embodiment comprises: a first part (piping part 2) having an inner cylinder 3; a second part (housing 1) having an outer cylinder 4 fitted onto the outside of the inner cylinder 3; a seal chamber 13 defined by the outer peripheral surface of the inner cylinder 3 and the inner peripheral surface of the outer cylinder 4; a seal member (O-ring 6) that is sandwiched between the outer peripheral surface of the inner cylinder 3 and the inner peripheral surface of the outer cylinder 4 and is provided in the seal chamber 13 in a compressed state, and seals the space between the inner cylinder 3 and the outer cylinder 4; and a backup ring 5 press-fitted onto the outer periphery of the inner cylinder 3. The inner cylinder 3 (either the inner cylinder 3 or the outer cylinder 4, into which the backup ring is press-fitted) is formed with a rib (press-fit portion) 10 into which the backup ring 5 is press-fitted, a seal wall portion 8 facing the seal chamber 13, and a step portion 9 located at the boundary between the rib 10 and the seal wall portion 8 and facing the backup ring 5.

[0030] According to the piping device 100 of the first embodiment, even if the first cylindrical portion 7 is deformed in the radial direction (inward in the radial direction in the first embodiment) due to the press-fitting of the backup ring 5, this deformation will originate from the step portion 9. Therefore, the influence of the deformation due to the press-fitting can be prevented from extending to the seal wall portion 8 with which the O-ring 6 is in contact. This makes it possible to maintain a constant gap between the inner cylinder 3 and the outer cylinder 4 at the seal wall portion 8, and even if the backup ring 5 is press-fitted and fixed, the O-ring 6 can be appropriately sandwiched and compressed between the inner cylinder 3 and the outer cylinder 4, thereby maintaining an appropriate seal.

[0031] The backup ring 5 may be press-fitted onto the inner periphery of the outer cylinder 4 to form a step portion on the outer cylinder 4. This embodiment will be described in the second embodiment.

[0032] The press-fit portion 10 of the piping device 100 is made up of a plurality of ribs 10 .

[0033] In this way, even if the inner cylinder 3 into which the backup ring 5 is press-fitted is made of synthetic resin, the press-fit load can be adjusted more easily than when the entire circumference is press-fitted. In other words, the press-fit load when press-fitting the backup ring 5 can be controlled to a load that makes press-fitting easier, making it easier to press-fit the backup ring 5.

[0034] In the piping device 100 , the backup ring 5 is press-fitted onto the outer periphery of the inner cylinder 3 , and the step portion 9 is formed on the outer periphery of the inner cylinder 3 .

[0035] This makes assembly easier than when the backup ring is press-fitted onto the inner periphery of the outer cylinder. For example, as a comparative example, consider a case where the inner cylinder is assembled to the outer cylinder after the backup ring is press-fitted onto the outer cylinder and the O-ring is fitted onto the inner cylinder. In this case, the inner cylinder must be inserted into the outer cylinder from below to prevent the O-ring from falling off. Therefore, in the comparative example, the inner cylinder cannot be assembled from any direction, reducing the degree of freedom in assembly.

[0036] Furthermore, in this comparative example, when the backup ring is press-fitted into the outer cylinder, if the backup ring passes through the sealing wall with which the O-ring is in contact, there is a risk that the backup ring may come into contact with the sealing wall and be damaged. To avoid this, the step may be made two-stepped so that the backup ring is less likely to come into contact with the sealing wall.

[0037] In the first embodiment, three ribs 10 are arranged at equal intervals, but the number of ribs of the present invention may be one, two, four or more. Also, the ribs do not have to be arranged at equal intervals in the circumferential direction.

[0038] In addition, the rib 10 may be omitted, in which case the first cylindrical portion 7 may be used as the press-fit portion, and the backup ring 5 may have a plurality of ribs provided opposite the first cylindrical portion (press-fit portion) 7.

[0039] In this way, the press-fit load can be easily adjusted and the backup ring 5 can be easily press-fitted without providing the ribs 10 on the inner cylinder 3. In other words, even if it is difficult to provide the ribs 10 on the inner cylinder 3 and the outer cylinder 4, the ribs provided on the backup ring 5 make it easy to adjust the press-fit load.

[0040] If the rib 10 is omitted from the inner tube 3 and the first tubular portion 7 is used as the press-fit portion, a step portion 9 can be formed at the boundary between the first tubular portion 7 and the sealing wall portion 8, thereby preventing the effects of deformation due to press-fit from extending to the sealing wall portion 8 with which the O-ring 6 is in contact, and maintaining appropriate sealing properties by the O-ring 6.

[0041] In the first embodiment, the first cylindrical portion 7 is thinner than the sealing wall portion 8. However, the piping device of the present invention may have the same thickness as long as it includes a step portion. Making the thicknesses equal in this way makes it easier to form the piping component 2 from synthetic resin.

[0042] The piping device 100 of this embodiment is not limited to automotive cooling circuits. The present invention can also be used in piping devices for other applications as long as they are equipped with O-rings and backup rings that prevent leakage from gaps between the inner and outer cylinders. While the first embodiment uses inner and outer cylinders made of synthetic resin, the piping device of the present invention can also be applied to inner and outer cylinders made of materials other than synthetic resin. For example, the inner and outer cylinders may be made of metal.

[0043] Furthermore, when the first cylindrical portion 7 is a press-fit portion, the shape of the inner periphery of the backup ring 5 that faces the press-fit portion may be oval.

[0044] Examples of oval shapes include an elliptical shape, an oval shape, and an egg shape. For ease of explanation, an elliptical shape will be used as an example. The surface of the backup ring 5 that is press-fitted is the inner peripheral surface, and when the shape of this inner peripheral surface is elliptical, the minor axis side of the ellipse is press-fitted, but the major axis side of the ellipse is not press-fitted, and the contact area during press-fitting can be kept small.

[0045] This also applies to other oval shapes such as an elliptical shape, an egg shape, etc. Therefore, by making the backup ring 5 oval as described above, the operation of press-fitting the backup ring 5 becomes easier compared to when two perfect circular shapes are press-fitted together.

[0046] For the same reason, the cross-sectional shape of the first cylindrical portion 7 serving as the press-fit portion may be oval. Note that both the first cylindrical portion 7 and the backup ring 5 serving as the press-fit portion may be oval in shape and fitted together to reduce the contact area during press-fitting, or only one of the first cylindrical portion 7 and the backup ring 5 serving as the press-fit portion may be oval in shape. Alternatively, if press-fitting is possible, both the first cylindrical portion 7 and the backup ring 5 serving as the press-fit portion may be circular in shape.

[0047] Note that when the first cylindrical portion 7 and the backup ring 5 serving as press-fit portions are both oval shaped, there is a possibility that press-fitting will not occur depending on the orientation of the oval shapes. For example, when the first cylindrical portion 7 and the backup ring 5 serving as press-fit portions have the same oval shape, press-fitting will not occur if the major axes of the two are aligned and fitted together. Therefore, if the first cylindrical portion 7 and the backup ring 5 have different shapes or if a rib is provided on one of them, the influence of orientation can be eliminated.

[0048] Next, a piping device of a second embodiment shown in Fig. 4 will be described. The piping device 100 of this embodiment differs from the piping device 100 of the first embodiment in that a backup ring is press-fitted onto the inner periphery of the outer cylinder, and a press-fit portion, a seal wall portion 8, and a step portion 9 are formed on the outer cylinder 4, but the other basic configurations are the same. Therefore, components that are the same as or correspond to those of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

[0049] The piping device of the second embodiment comprises: a first part having an inner cylinder 3; a second part having an outer cylinder 4 fitted onto the outside of the inner cylinder 3; a seal chamber 13 defined by the outer peripheral surface of the inner cylinder 3 and the inner peripheral surface of the outer cylinder 4; an O-ring (sealing member) 6 that is sandwiched between the outer peripheral surface of the inner cylinder 3 and the inner peripheral surface of the outer cylinder 4 and is provided in the seal chamber 13 in a compressed state, sealing the gap between the inner cylinder 3 and the outer cylinder 4; and a backup ring 5 press-fitted onto the outer periphery of the outer cylinder 4, and the outer cylinder 4 (either the inner cylinder 3 or the outer cylinder 4, into which the backup ring 5 is press-fitted) is formed with a rib (press-fit portion) 10 into which the backup ring 5 is press-fitted, a seal wall portion 8 facing the seal chamber 13, and a step portion 9 located at the boundary between the rib 10 and the seal wall portion 8 and facing the backup ring 5.

[0050] According to the piping device of the second embodiment, even if the first cylindrical portion 7 is deformed in the radial direction (in the second embodiment, radially outward) due to the press-fitting of the backup ring 5, this deformation will originate from the step portion 9. Therefore, the influence of the deformation due to the press-fitting can be prevented from extending to the seal wall portion 8 with which the O-ring 6 is in contact. This makes it possible to maintain a constant gap between the inner cylinder 3 and the outer cylinder 4 at the seal wall portion 8, and even if the backup ring 5 is press-fitted and fixed, the O-ring 6 can be appropriately sandwiched and compressed between the inner cylinder 3 and the outer cylinder 4, thereby maintaining an appropriate seal.

[0051] In the piping device of this embodiment, the press-fit portion also comprises a plurality of ribs 10. In this way, even if the outer cylinder 4 into which the backup ring 5 is press-fitted is made of synthetic resin, the press-fit load can be more easily adjusted compared to when the entire circumference is press-fitted. In other words, the press-fit load when press-fitting the backup ring 5 can be controlled to a load that makes press-fitting easier, making it easier to press-fit the backup ring 5.

[0052] It should be noted that, in the piping device of this embodiment, the ribs 10 may also be omitted, in which case the first cylindrical portion 7 may be used as the press-fit portion, and the backup ring 5 may be provided with a plurality of ribs provided opposite the first cylindrical portion (press-fit portion) 7. In this way, even without providing the ribs 10 on the outer cylinder 4, it is possible to easily adjust the press-fit load and make it easier to press-fit the backup ring. In other words, even if it is difficult to provide the ribs 10 on the outer cylinder 4, the ribs provided on the backup ring 5 make it easy to adjust the press-fit load.

[0053] When the rib 10 is omitted from the outer tube 4 and the first tubular portion 7 is used as the press-fit portion, a step portion 9 is formed at the boundary between the first tubular portion 7 and the sealing wall portion 8, which prevents the effects of deformation due to press-fitting from reaching the sealing wall portion 8 with which the O-ring is in contact, thereby maintaining appropriate sealing performance by the O-ring 6.

[0054] In the second embodiment, the thickness of the first cylindrical portion 7 is thinner than the thickness of the seal wall portion 8, but as long as a step is formed between the press-fit portion and the seal wall portion 8, the thicknesses of the first cylindrical portion 7 and the seal wall portion 8 may be the same. In addition, when the first cylindrical portion 7 is the press-fit portion, the outer periphery of the backup ring 5 that faces the press-fit portion may be oval, and the cross section of the first cylindrical portion 7 as the press-fit portion may also be oval. The effects of doing so are as described in the first embodiment.

[0055] FIG. 5 shows a thermostat 100 ′ as a piping device 100 according to a third embodiment, which is provided with an on-off valve 20 .

[0056] The on-off valve 20 comprises a valve body 21, a valve seat 22 with which the valve body 21 can come into contact, a thermoelement body 23 fixed to the valve body 21 and containing paraffin wax, a piston 24 that can protrude from the thermoelement body 23 due to the expansion of the paraffin wax, and a spring 25 that presses the valve body 21 against the valve seat 22.

[0057] The valve seat 22 in the third embodiment is formed by the open edge of the inner cylinder 3. The valve element 21 closes the open edge of the inner cylinder 3 by the pressing force of the spring 25. A retaining portion 101 is provided inside the inner cylinder 3. The tip of the piston 24 is inserted into the retaining portion 101. This restricts the upward movement of the piston 24 relative to the inner cylinder 3 in FIG. 5 . When the temperature of the fluid flowing through the outer cylinder 4 and the housing 1 reaches a predetermined temperature or higher, the paraffin wax expands, and the thermo-element body 23 moves downward together with the valve element 21 toward the bottom in FIG. 4 against the pressing force of the spring 25. This separates the valve element 21 from the valve seat 22, which is formed by the open edge of the inner cylinder 3, and the fluid flows through the piping component 2 via the inner cylinder 3.

[0058] 5, an outer cylinder having an inner diameter 4 larger than that of the inner cylinder 3 is disposed around the outer periphery of the inner cylinder 3, with an O-ring 6 (sealing member) and a backup ring 5 sandwiched therebetween. This allows a relatively wide gap to be secured around the valve element 21 of the thermostat 100', ensuring a large flow path cross-sectional area and reducing flow path resistance when the thermostat 100' is open.

[0059] 5 , the backup ring 5 may also be press-fitted into the outer cylinder 4. However, when press-fitting the backup ring 5 into the outer cylinder 4 in the thermostat 100', there may be cases where the outer diameter of the outer cylinder 4 cannot be increased due to restrictions on peripheral parts when assembling the thermostat 100' into an automobile or the like. In this case, the inner diameter of the outer cylinder 4 must be designed to be reduced to allow for press-fitting. Therefore, it is preferable to press-fit the backup ring 5 into the inner cylinder 3.

[0060] Furthermore, in a thermostat such as that shown in Fig. 5, if the backup ring 5 is press-fitted into the outer cylinder 4 from below as shown in Fig. 4, there is a possibility that the backup ring 5 will have to withstand falling off downwards when negative pressure is applied from below in Fig. 4, relying solely on the press-fitting. This makes it more difficult to produce the thermostat 100' as a finished product. Therefore, it is preferable to press-fit the backup ring 5 into the inner cylinder 3.

[0061] Furthermore, the piping device 100 is not limited to the thermostat 100' having the on-off valve 20, but may be a piping device other than the thermostat 100'.

[0062] Although the preferred embodiments of the present invention have been described above, appropriate changes and modifications can be made without departing from the scope of the claims.

[0063] REFERENCE SIGNS LIST 1 Housing (second part) 2 Piping part (first part) 3 Inner cylinder 4 Outer cylinder 5 Backup ring 6 O-ring (sealing member) 7 First cylinder portion 8 Seal wall portion 9 Step portion 10 Rib (press-fit portion) 11 Large diameter portion 12 Small diameter portion 13 Seal chamber 20 On-off valve 21 Valve body 22 Valve seat 23 Thermoelement body 24 Piston 25 Spring 100 Piping device 100' Thermostat 101 Holding portion

Claims

1. A piping device comprising: a first component having an inner cylinder; a second component having an outer cylinder externally fitted to the inner cylinder; a seal chamber defined by an outer peripheral surface of the inner cylinder and an inner peripheral surface of the outer cylinder; a seal member provided in the seal chamber in a compressed state sandwiched between the outer peripheral surface of the inner cylinder and the inner peripheral surface of the outer cylinder for sealing between the inner cylinder and the outer cylinder; and a backup ring press-fitted onto an outer periphery of the inner cylinder or an inner periphery of the outer cylinder, wherein on one of the inner cylinder or the outer cylinder into which the backup ring is press-fitted, a press-fitting portion into which the backup ring is press-fitted, a seal wall portion facing the seal chamber, and a step portion located at a boundary between the press-fitting portion and the seal wall portion and facing the backup ring are formed.

2. The piping device according to claim 1, wherein the press-fitting portion comprises a plurality of ribs.

3. The piping device according to claim 1 or claim 2, wherein the backup ring is press-fitted onto an outer periphery of the inner cylinder.

4. The piping device according to claim 1, wherein the backup ring comprises a plurality of ribs provided to face the press-fitting portion.

5. The piping device according to claim 1, wherein a shape of an inner periphery or an outer periphery of the backup ring facing the press-fitting portion is an oval shape.

6. The piping device according to claim 1, wherein a cross-sectional shape of the press-fitting portion is an oval shape.

7. The piping device according to claim 1 is a thermostat provided with an on-off valve, wherein the on-off valve comprises a valve body that contacts the valve seat with a tip of the inner cylinder as the valve seat to close the inner cylinder.

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