Pressure detection device and valve cap assembly structure

Abstract

A pressure detection device (20) comprises a housing (22) that is fastened to one end (12) of a valve stem (11), a seal member (37) that seals between the valve stem (11) and the housing (22), and a pressing part (30) that opens the valve core (15) by pressing the shaft end (18) of the valve core (15). The housing (22) is provided with an outer wall (24) provided so as to cover the outer circumferential surface of the valve stem (11). The pressing part (30) has a contact surface (31) that comes into contact with the shaft end (18). In a state before the housing (22) is fastened to the valve stem (11), in which the one end (12) of the valve stem (11) and the housing (22) are aligned in the axial direction of the valve stem (11), the distance (d11) from the seal member (37) to the one end (12) of the valve stem (11) is shorter than the distance (d12) from the contact surface (31) to the shaft end (18).

Description

Pressure detection device and valve cap assembly structure

[0001] The present disclosure relates to a pressure detection device and an assembly structure for a valve cap.

[0002] The valve cap disclosed in Patent Document 1 is attached to a valve. The valve includes a valve stem and a valve core housed in the valve stem. A male thread is formed on the outer circumferential surface of the valve stem. The valve core includes a shaft portion. When the shaft portion is pressed, the valve core opens.

[0003] The valve cap comprises a housing, a pressing portion that presses the shaft portion, and a sealing member that seals the gap between the valve cap and the valve stem. The housing is cylindrical. A female thread is formed on the inner circumferential surface of the housing. When the valve cap is attached to the valve, the female thread of the housing and the male thread of the valve stem are engaged to fasten them together. In this state, the shaft portion is pressed by the pressing portion, opening the valve core. This allows communication between the inside of the valve stem and the inside of the housing.

[0004] Japanese Patent Application Laid-Open No. 2004-25923

[0005] When assembling the valve cap to the valve stem, the female threads and male threads are mated, and the stem is pressed by the pressing part. If the sealing member is not sealed when the valve core opens, gas may leak from between the valve stem and the valve cap.

[0006] According to a first aspect of the present disclosure, there is provided a pressure detection device that can be assembled to a valve having a valve stem and a valve core housed in it. The pressure detection device includes a housing fastened to one end of the valve stem, a pressure sensor that detects pressure inside the housing, a seal member that seals between the valve stem and the housing, and a pressing portion that presses the axial end of the valve core to open the valve core. The housing has an outer wall that covers the outer peripheral surface of the valve stem. The surface of the pressing portion that contacts the axial end is a contact surface. Before the housing is fastened to the valve stem, when the one end of the valve stem and the housing are aligned in the axial direction of the valve stem, the distance from the seal member to the one end of the valve stem is shorter than the distance from the contact surface to the axial end.

[0007] When the housing is fastened to the valve stem, the seal member comes into contact with one end of the valve stem before the contact surface comes into contact with the shaft end. This allows the seal member to seal between the valve stem and the housing before the shaft end is pressed by the pressing portion. When the valve core opens, the seal between the valve stem and the housing prevents gas from leaking when the valve core opens.

[0008] In the pressure detection device described above, the valve is a tire valve. The housing includes a wall portion that contacts the one end of the valve stem and a cylindrical inner wall that protrudes from the wall portion toward the inside of the valve stem. The seal member is provided so as to be positioned between the outer peripheral surface of the inner wall and the inner peripheral surface of the valve stem. The end of the outer wall that is away from the wall portion is an outer wall end. The distance from the outer wall end to the seal member is shorter than the distance from the outer wall end to the contact surface.

[0009] The pressure detection device further includes a holder that holds the seal member, and a spring that biases the holder toward the valve stem to slide the holder and the seal member and bring the seal member into close contact with the outer wall. When the seal member is in close contact with the outer wall, the distance from the seal member to the one end of the valve stem is shorter than the distance from the contact surface to the shaft end.

[0010] According to a second aspect of the present disclosure, there is provided an assembly structure for a valve cap to be attached to a valve having a valve stem and a valve core housed in the valve stem. The valve cap includes a housing fastened to one end of the valve stem, a seal member that seals between the valve stem and the housing, and a pressing portion that presses the axial end of the valve core to open the valve core. The housing includes an outer wall that covers the outer peripheral surface of the valve stem. The surface of the pressing portion that contacts the axial end is a contact surface. Before the housing is fastened to the valve stem, when the one end of the valve stem and the housing are aligned in the axial direction of the valve stem, the distance from the seal member to the one end of the valve stem is shorter than the distance from the contact surface to the axial end.

[0011] When the housing is fastened to the valve stem, the seal member comes into contact with one end of the valve stem before the contact surface comes into contact with the shaft end. This allows the seal member to seal between the valve stem and the housing before the shaft end is pressed by the pressing portion. When the valve core opens, the seal between the valve stem and the housing prevents gas from leaking when the valve core opens.

[0012] FIG. 1 is a cross-sectional view showing a pressure detection device in a state where a housing is fastened to a valve stem. FIG. 2 is a cross-sectional view showing a pressure detection device before the housing is fastened to the valve stem. FIG. 3 is a cross-sectional view showing a pressure detection device in the process of fastening the housing to the valve stem. FIG. 4 is a cross-sectional view showing a pressure detection device in a state where the housing is fastened to the valve stem. FIG. 5 is a cross-sectional view showing a pressure detection device before the housing is fastened to the valve stem. FIG. 6 is a cross-sectional view showing a pressure detection device in the process of fastening the housing to the valve stem. FIG. 7 is a cross-sectional view showing a modified example of the housing. FIG. 8 is a cross-sectional view showing a modified example of the housing.

[0013] [First embodiment] A first embodiment of an assembly structure for a pressure detection device and a valve cap will be described. As shown in Fig. 1, a pressure detection device 20 is fastened to a valve 10. The pressure detection device 20 and the valve 10 constitute a valve device. The valve 10 is a tire valve that is attached to a wheel and used to inject gas into a tire.

[0014] The valve 10 includes a cylindrical valve stem 11 and a valve core 15. The valve stem 11 is cylindrical. The valve stem 11 is made of, for example, metal. The valve stem 11 includes a first end 12 and a second end 13. The first end 12 is one end of the valve stem 11. A male thread 14 is formed on the outer circumferential surface of the valve stem 11. The male thread 14 is formed over a predetermined range from the first end 12 to the second end 13. The first end 12 of the valve stem 11 is located outside the tire when mounted on a wheel. The second end 13 of the valve stem 11 is located inside the tire when mounted on a wheel.

[0015] The valve core 15 is housed in the valve stem 11. The valve core 15 comprises a base 16, a shaft portion 17, and a valve element 19. The base 16 is a cylindrical member. The axial direction of the base 16 coincides with the axial direction of the valve stem 11. A seal is formed between the outer circumferential surface of the base 16 and the inner circumferential surface of the valve stem 11.

[0016] The shaft portion 17 passes through the base 16. The axial direction of the shaft portion 17 coincides with the axial direction of the base 16. The shaft portion 17 has a shaft end 18. The shaft end 18 is the end of the shaft portion 17 that protrudes from the base 16 toward the first end 12.

[0017] The valve element 19 is provided on a portion of the shaft portion 17 that protrudes from the base 16 toward the second end 13. The valve element 19 closes the base 16 by coming into close contact with the base 16. The valve element 19 opens the base 16 by moving away from the base 16.

[0018] The shaft 17 is provided so as to be movable in the axial direction of the base 16. The shaft 17 is biased toward the first end 12 by a spring (not shown). As a result, the valve element 19 comes into close contact with the base 16, thereby closing the base 16. When the valve element 19 comes into close contact with the base 16, the valve is in a closed state, in which gas is prohibited from passing through the valve stem 11. When the valve element 19 is separated from the base 16, the valve is in an open state, in which gas is allowed to pass through the valve stem 11. When the valve element 19 comes into close contact with the base 16, the valve core 15 opens. When the valve element 19 separates from the base 16, the valve core 15 closes.

[0019] The pressure detection device 20 includes a valve cap 21 and a sensor unit 50. <Valve Cap> The valve cap 21 includes a housing 22. The housing 22 is made of, for example, metal. The housing 22 includes a wall portion 23 and an outer wall 24 extending from the wall portion 23. The wall portion 23 is circular. The outer wall 24 is cylindrical. The wall portion 23 is an end wall provided at one end of the outer wall 24. A female thread 25 is formed on the inner circumferential surface of the outer wall 24. The outer wall 24 includes an outer wall end portion 26. The outer wall end portion 26 is the end opposite to the end where the wall portion 23 is provided. The outer wall end portion 26 is an open end having an opening that receives the valve stem 11. The valve cap 21 and the valve 10 constitute a valve device.

[0020] The housing 22 has an inner wall 28. The inner wall 28 extends from the wall portion 23 in the same direction as the outer wall 24. The inner wall 28 has an annular cross-sectional shape. The tip of the inner wall 28 is folded back so as to expand in the radial direction of the inner wall 28. The outer wall 24 and the inner wall 28 are provided so as to form concentric circles.

[0021] The housing 22 includes a pressing portion 30. The pressing portion 30 protrudes from the wall portion 23 in the same direction as the extension of the outer wall 24. The pressing portion 30 is provided inside the inner wall 28. The pressing portion 30 includes a contact surface 31. The contact surface 31 is the tip surface of the pressing portion 30.

[0022] The housing 22 includes a support portion 33 extending from the wall portion 23. The support portion 33 has an annular cross-sectional shape. The support portion 33 extends from the wall portion 23 in a direction opposite to the direction in which the outer wall 24 extends.

[0023] The housing 22 includes a pressure introducing hole 35. The pressure introducing hole 35 is a through-hole that connects the area surrounded by the outer wall 24 and the area surrounded by the support portion 33. The pressure introducing hole 35 penetrates, for example, the pressing portion 30 and the wall portion 23.

[0024] The valve cap 21 includes a seal member 37. The seal member 37 is, for example, an O-ring. The seal member 37 is cylindrical. The seal member 37 is provided to surround the inner wall 28. The seal member 37 is located between the outer peripheral surface of the inner wall 28 and the inner peripheral surface of the outer wall 24. The seal member 37 includes a seal end 38. The seal end 38 is the end of the seal member 37 opposite the wall portion 23. A distance d1 from the outer wall end 26 to the seal member 37 is shorter than a distance d2 from the outer wall end 26 to the contact surface 31. The distance d1 from the outer wall end 26 to the seal member 37 is the distance from the outer wall end 26 to the seal end 38.

[0025] The valve cap 21 includes a cover 40. The cover 40 includes a cover wall portion 41 and a peripheral cover wall 42. The cover wall portion 41 is disk-shaped. The peripheral cover wall 42 is cylindrical. The cover 40 is attached to cover the housing 22. The inner peripheral surface of the peripheral cover wall 42 faces the outer peripheral surface of the outer wall 24. The housing 22 is housed in the cover 40 such that the direction in which the outer wall 24 extends from the wall portion 23 and the direction in which the peripheral cover wall 42 extends from the cover wall portion 41 coincide with each other.

[0026] The valve cap 21 includes a cover seal member 43 that seals between the cover 40 and the housing 22. The cover seal member 43 is provided between the cover peripheral wall 42 and the outer wall 24.

[0027] <Sensor Unit> The sensor unit 50 includes a substrate 51, a pressure sensor 52, and a battery 53. The pressure sensor 52 and the battery 53 are mounted on the substrate 51. The substrate 51 is supported by the support portion 33. A transmission circuit may be mounted on the substrate 51. The transmission circuit is a circuit for transmitting the detection result of the pressure sensor 52 to a receiver. The receiver may be installed in the vehicle or may be a mobile terminal carried by the user. The detection result of the pressure sensor 52 is transmitted to the receiver by the transmission circuit, and the receiver monitors the pressure.

[0028] The pressure sensor 52 is provided in an area surrounded by the support portion 33. The pressure sensor 52 detects the pressure inside the housing 22. The battery 53 is provided between the substrate 51 and the cover wall portion 41. The battery 53 serves as a power source for the sensor unit 50. For example, the battery 53 serves as a power source for the pressure sensor 52 and the transmission circuit.

[0029] The sensor unit 50 includes a sensor seal member 54. The sensor seal member 54 is provided between the pressure sensor 52 and the wall portion 23. The sensor seal member 54 is cylindrical. The sensor seal member 54 is provided so as to surround the pressure introduction hole 35. Pressure is introduced into the pressure sensor 52 through the pressure introduction hole 35, and the pressure is detected by the pressure sensor 52. When the interior of the housing 22 and the interior of the valve stem 11 are in communication, the pressure inside the housing 22 and the pressure inside the valve stem 11 are the same. Therefore, the pressure detected by the pressure sensor 52 is the pressure inside the valve stem 11. If the valve 10 is a tire valve, the pressure sensor 52 can detect the pressure inside the tire when the valve core 15 is open.

[0030] The valve cap 21 is fastened to the first end 12 of the valve stem 11. The female threads 25 formed on the inner circumferential surface of the outer wall 24 engage with the male threads 14 formed on the outer circumferential surface of the valve stem 11, thereby fastening the valve cap 21 to the valve stem 11. In this way, the valve cap 21 is assembled to the valve 10. Similarly, the pressure detection device 20 is assembled to the valve 10.

[0031] When the valve cap 21 is fastened to the first end 12 of the valve stem 11, the contact surface 31 of the pressing portion 30 contacts the axial end 18. The pressing portion 30 presses the axial end 18 in the direction from the first end 12 toward the second end 13, causing the axial portion 17 to move in the axial direction. This opens the valve core 15. The wall portion 23 is located in the axial direction of the valve stem 11. The outer wall 24 is provided to cover the outer peripheral surface of the valve stem 11. The seal member 37 is located between the inner peripheral surface of the valve stem 11 and the outer peripheral surface of the inner wall 28. The first end 12 of the valve stem 11 contacts the wall portion 23. The inner wall 28 protrudes toward the inside of the valve stem 11.

[0032] As shown in FIG. 2 , assume that the first end 12 of the valve stem 11 and the housing 22 are aligned in the axial direction of the valve stem 11 before the housing 22 is fastened to the valve stem 11. The axial direction of the valve stem 11 and the axial direction of the outer wall 24 are aligned. In this state, the distance d11 from the seal member 37 to the first end 12 of the valve stem 11 is shorter than the distance d12 from the contact surface 31 to the axial end 18. The distance d11 from the seal member 37 to the first end 12 of the valve stem 11 is the distance from the seal end 38 to the first end 12 of the valve stem 11. Before the housing 22 is fastened to the valve stem 11, the position of the axial end 18 of the valve stem 11 in the axial direction is the same as or approximately the same as the first end 12 of the valve stem 11 in the axial direction of the valve stem 11.

[0033] [Operation of First Embodiment] Before the housing 22 is fastened to the valve stem 11, the distance d11 from the seal member 37 to the first end 12 of the valve stem 11 is shorter than the distance d12 from the contact surface 31 to the axial end 18. Therefore, as shown in FIG. 3 , when the insertion amount of the valve stem 11 into the valve cap 21 is increased by engaging the female thread 25 with the male thread 14, the seal member 37 contacts the first end 12 of the valve stem 11 before the contact surface 31 contacts the axial end 18. The seal member 37 contacts the first end 12 of the valve stem 11, thereby sealing the gap between the valve stem 11 and the housing 22. When the axial end 18 is pressed by the pressing portion 30 to open the valve core 15, the gap between the valve stem 11 and the housing 22 is sealed. Therefore, the opening of the valve core 15 prevents gas from leaking between the valve stem 11 and the housing 22. If the valve 10 is a tire valve, it is possible to prevent the pressure inside the tire from decreasing due to gas leaking out.

[0034] [Effects of the First Embodiment] (1-1) Before the housing 22 is fastened to the valve stem 11, the distance d11 from the seal member 37 to the first end 12 of the valve stem 11 is shorter than the distance d12 from the contact surface 31 to the shaft end 18. The seal member 37 seals the gap between the valve stem 11 and the housing 22 before the pressing portion 30 presses the shaft end 18. When the valve core 15 opens, the gap between the valve stem 11 and the housing 22 is sealed, which prevents gas from leaking when the valve core 15 opens.

[0035] (1-2) The distance d1 from the outer wall end 26 to the seal member 37 is shorter than the distance d2 from the outer wall end 26 to the contact surface 31. When the valve 10 is a tire valve, the position of the axial end 18 of the valve stem 11 in the axial direction is the same as or approximately the same as the first end 12 of the valve stem 11 in the axial direction of the valve stem 11. In this case, by setting the distance d1 from the outer wall end 26 to the seal end 38 and the distance d2 from the outer wall end 26 to the contact surface 31 as described above, the seal member 37 can seal between the valve stem 11 and the housing 22 before the axial end 18 is pressed by the pressing portion 30.

[0036] (1-3) The first end 12 of the valve stem 11 contacts the wall portion 23. If a seal member is provided between the first end 12 of the valve stem 11 and the wall portion 23 and the gap between the valve stem 11 and the housing 22 is sealed by compressing this seal member, the axial force acting on the valve stem 11 and the housing 22 will depend on the compressive reaction force of the seal member. If the compressive reaction force of the seal member decreases, the axial force will decrease, causing gas to leak. By not providing a seal member between the first end 12 of the valve stem 11 and the wall portion 23, the axial force will not depend on the compressive reaction force. Therefore, the decrease in the compressive reaction force of the seal member can prevent the axial force from decreasing.

[0037] (1-4) The seal member 37 is an O-ring. The O-ring seals by self-sealing. Because the sealing force does not depend on the compression reaction force, the reliability of the seal member 37 can be ensured over a long period of time.

[0038] (1-5) The seal member 37 is located between the inner peripheral surface of the valve stem 11 and the outer peripheral surface of the inner wall 28. Due to frictional forces acting on the interface between the inner peripheral surface of the valve stem 11 and the seal member 37, and on the interface between the outer peripheral surface of the inner wall 28 and the seal member 37, the housing 22 is unlikely to become loose even if the axial force is reduced.

[0039] Second Embodiment A second embodiment of a pressure detection device and a valve cap assembly structure will be described. As shown in Fig. 4, a pressure detection device 60 includes a valve cap 61 and a sensor unit 50. The valve 10 to which the pressure detection device 60 is assembled has the same configuration as that of the first embodiment.

[0040] The valve cap 61 includes a housing 62. The housing 62 is cylindrical. An internal thread 63 is formed on the inner peripheral surface of the housing 62. The housing 62 is the outer wall. The valve cap 61 includes a cover 65. The cover 65 includes a cover wall portion 66 and a peripheral cover wall 67. The cover wall portion 66 is circular. The peripheral cover wall 67 is cylindrical. The cover 65 is attached so as to cover the housing 62. The inner peripheral surface of the peripheral cover wall 67 faces the outer peripheral surface of the housing 62.

[0041] The valve cap 61 includes a seal member 69. The seal member 69 is provided in an area defined by the cover 65 and the housing 62. The seal member 69 is circular. The seal member 69 includes a through-hole 70. The through-hole 70 is provided in the center of the seal member 69. The outer diameter of the seal member 69 is the same as the outer diameter of the housing 62. The seal member 69 is provided facing the housing 62. The seal member 69 is, for example, a packing. The outer peripheral surface of the seal member 69 is in close contact with the inner peripheral surface of the cover peripheral wall 67.

[0042] The valve cap 61 includes a holder 72. The holder 72 is provided in an area defined by the cover 65 and the housing 62. The holder 72 includes a main body 73 and a protrusion 75. The main body 73 is circular. The outer diameter of the main body 73 is the same as the outer diameter of the seal member 69. The protrusion 75 is cylindrical. The protrusion 75 is provided at the center of the main body 73. The tip of the protrusion 75 is folded back so as to expand in the radial direction of the protrusion 75. The main body 73 is provided overlapping the seal member 69. The protrusion 75 passes through the through-hole 70. The protrusion 75 passes through the seal member 69, allowing the holder 72 to hold the seal member 69. The holder 72 and the seal member 69 held by the holder 72 are provided to be movable in the axial direction of the cover peripheral wall 67.

[0043] The valve cap 61 includes a pressing member 77. The pressing member 77 is provided in an area defined by the cover 65 and the housing 62. The pressing member 77 includes a main body 78, a support portion 79, and a pressing portion 80. The main body 78 is disk-shaped. The support portion 79 is cylindrical. The support portion 79 extends from the outer peripheral edge of the main body 78 in the thickness direction of the main body 78. The outer diameter of the support portion 79 is smaller than the outer diameter of the holder 72.

[0044] The pressing portion 80 includes a cylindrical first portion 81 and a second portion 82 provided at the tip of the first portion 81. The first portion 81 extends in the thickness direction of the main body 78. The first portion 81 is provided at the center of the main body 78. The extending direction of the first portion 81 is opposite to the extending direction of the support portion 79. The first portion 81 includes a pressure introducing hole 83. The pressure introducing hole 83 penetrates the first portion 81. The second portion 82 closes the end of the first portion 81. The second portion 82 includes a contact surface 84. The contact surface 84 is the tip surface of the pressing portion 80. The main body 78 of the pressing member 77 is provided overlapping the main body 73 of the holder 72. The pressing portion 80 protrudes into the protruding portion 75.

[0045] The valve cap 61 includes a spring 86. The spring 86 is provided in an area defined by the cover 65 and the housing 62. The spring 86 is provided between the cover wall portion 66 and the holder 72. More specifically, the spring 86 is provided so as to extend between the cover wall portion 66 and the holder 72, passing between the support portion 79 and the cover peripheral wall 67. The spring 86 biases the holder 72 and the seal member 69 held by the holder 72 toward the housing 62. As a result, the spring 86 slides the holder 72 and the seal member 69, bringing the seal member 69 into close contact with the housing 62.

[0046] The sensor unit 50 has the same configuration as in the first embodiment. The substrate 51 is supported by a support portion 79. The pressure sensor 52 is provided in an area surrounded by the support portion 79. The sensor seal member 54 is provided between the main body 73 and the pressure sensor 52. The battery 53 is provided between the substrate 51 and the cover wall portion 66.

[0047] The housing 62 is fastened to the first end 12 of the valve stem 11. The female threads 63 formed on the inner circumferential surface of the housing 62 engage with the male threads 14 formed on the outer circumferential surface of the valve stem 11, thereby fastening the housing 62 to the valve stem 11. In this way, the valve cap 61 is assembled to the valve 10. The pressure detection device 60 is also assembled to the valve 10.

[0048] When the housing 62 is fastened to the valve stem 11, the first end 12 of the valve stem 11 contacts the seal member 69. The seal member 69 is pressed by the valve stem 11, causing the spring 86 to contract. This separates the seal member 69 from the housing 62. The shaft end 18 contacts the contact surface 84. The shaft end 18 is pressed by the pressing portion 80, causing the valve core 15 to open.

[0049] As shown in FIG. 5 , assume that the first end 12 of the valve stem 11 and the housing 62 are aligned in the axial direction of the valve stem 11 before the housing 62 is fastened to the valve stem 11. The axial direction of the valve stem 11 and the axial direction of the housing 62 are assumed to coincide. Before the housing 62 is fastened to the valve stem 11, the spring 86 biases the holder 72 and the seal member 69 held by the holder 72 toward the housing 62. Because the valve stem 11 is aligned with the housing 62, the spring 86 biases the holder 72 and the seal member 69 held by the holder 72 toward the valve stem 11. As a result, the seal member 69 is in close contact with the housing 62. In this state, the distance d21 from the seal member 69 to the first end 12 of the valve stem 11 is shorter than the distance d22 from the contact surface 84 to the axial end 18. Before the housing 62 is fastened to the valve stem 11 , the seal member 69 is in close contact with the housing 62 .

[0050] [Operation of Second Embodiment] Before the housing 62 is fastened to the valve stem 11, the distance d21 from the seal member 69 to the first end 12 of the valve stem 11 is shorter than the distance d22 from the contact surface 84 to the axial end 18. Therefore, as shown in FIG. 6 , when the insertion amount of the valve stem 11 into the valve cap 61 is increased by engaging the female thread 63 with the male thread 14, the seal member 69 contacts the first end 12 of the valve stem 11 before the contact surface 84 contacts the axial end 18. The seal member 69 contacts the first end 12 of the valve stem 11, thereby sealing the gap between the valve stem 11 and the housing 62. When the axial end 18 is pressed by the pressing portion 80 to open the valve core 15, the gap between the valve stem 11 and the housing 62 is sealed. Therefore, the opening of the valve core 15 prevents gas from leaking between the valve stem 11 and the housing 62.

[0051] [Effects of the Second Embodiment] (2-1) Before the housing 62 is fastened to the valve stem 11, the distance d21 from the seal member 69 to the first end 12 of the valve stem 11 is shorter than the distance d22 from the contact surface 84 to the shaft end 18. The seal member 69 seals the gap between the valve stem 11 and the housing 62 before the pressing portion 80 presses the shaft end 18. When the valve core 15 opens, the gap between the valve stem 11 and the housing 62 is sealed, which prevents gas from leaking when the valve core 15 opens.

[0052] (2-2) The seal member 69 is compressed by the spring 86 to seal the gap between the valve stem 11 and the housing 62. This prevents a decrease in the compression reaction force of the seal member 69, thereby preventing a decrease in the sealing force.

[0053] [Modifications] The embodiment can be modified as follows: The embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0054] In the first embodiment, the housing 22 may be configured to allow the position of the seal member 37 to be adjusted. For example, as shown in FIGS. 7 and 8 , the housing 22 may include a restriction wall 90 protruding from the wall portion 23. The restriction wall 90 is provided, for example, along the outer circumferential surface of the inner wall 28. The restriction wall 90 restricts the seal member 37 from moving toward the wall portion 23. Compared to a case in which the restriction wall 90 is not provided, the distance from the tip of the inner wall 28 to the seal member 37 can be shortened. When the housing 22 is fastened to the valve stem 11, the distance from the first end 12 of the valve stem 11 to the seal member 37 can be lengthened. That is, the seal member 37 can be inserted deep into the valve stem 11. The surface of the restriction wall 90 that contacts the seal member 37 may be flat, as shown in FIG. 7 , or tapered, as shown in FIG. 8 .

[0055] In each embodiment, the valve 10 may be different from a tire valve. For example, the valve 10 may be a charge valve. In each embodiment, the pressure sensor 52 does not have to be provided.

[0056] The term "annular" as used in the embodiments may refer to any structure that forms a loop, i.e., a continuous shape with no ends, as well as structures that have a gap, such as a C-shape, that form an overall loop shape. "Annular" shapes include, but are not limited to, circles, ellipses, and polygons with sharp or rounded corners. The term "cylindrical" as used in the embodiments may refer to a structure that forms a loop, i.e., a continuous shape with no ends. "Cylindrical" shapes include, but are not limited to, circles, ellipses, and polygons with sharp or rounded corners.

[0057] 10...valve, 11...valve stem, 12...first end, 15...valve core, 18...shaft end, 20...pressure detection device, 21...valve cap, 22...housing, 23...wall portion, 24...outer wall, 26...outer wall end, 28...inner wall, 30...pressure portion, 31...contact surface, 37...sealing member, 52...pressure sensor.

Claims

1. A pressure detection device to be assembled to a valve having a valve stem accommodating a valve core, the pressure detection device comprising: a housing fastened to one end of the valve stem; a pressure sensor that detects the pressure inside the housing; a sealing member that seals between the valve stem and the housing; and a pressing portion that presses the axial end of the valve core to open the valve core, the housing having an outer wall that covers the outer circumferential surface of the valve stem, the pressing portion having a contact surface that comes into contact with the axial end, and in a state before the housing is fastened to the valve stem and in a state where the one end of the valve stem and the housing are aligned in the axial direction of the valve stem, the distance from the sealing member to the one end of the valve stem is shorter than the distance from the contact surface to the axial end.

2. The pressure detection device of claim 1, wherein the valve is a tire valve, the housing comprises a wall portion that contacts the one end of the valve stem, and a cylindrical inner wall that protrudes from the wall portion toward the inside of the valve stem, the sealing member is positioned between the outer peripheral surface of the inner wall and the inner peripheral surface of the valve stem, the outer wall has an outer wall end portion that has an opening that receives the valve stem, and the distance from the outer wall end portion to the sealing member is shorter than the distance from the outer wall end portion to the contact surface.

3. A pressure detection device as described in claim 1, further comprising: a holder for holding the sealing member; and a spring for biasing the holder toward the valve stem, thereby sliding the holder and the sealing member and bringing the sealing member into close contact with the outer wall, wherein when the sealing member is in close contact with the outer wall, the distance from the sealing member to the one end of the valve stem is shorter than the distance from the contact surface to the shaft end.

4. An assembly structure for a valve cap to be attached to a valve having a valve stem accommodating a valve core, the valve cap comprising: a housing fastened to one end of the valve stem; a sealing member that seals between the valve stem and the housing; and a pressing portion that presses the axial end of the valve core to open the valve core, the housing having an outer wall that covers the outer circumferential surface of the valve stem, the pressing portion having a contact surface that comes into contact with the axial end, and in a state before the housing is fastened to the valve stem and in a state where the one end of the valve stem and the housing are aligned in the axial direction of the valve stem, the distance from the sealing member to the one end of the valve stem is shorter than the distance from the contact surface to the axial end.

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