Silencers and vacuum pumps

Abstract

A muffler (10) with a check valve is attached to an exhaust port (6) of an evacuation device (1). A downstream check valve (60) of the muffler (10) comprises a spherical valve body (62) inserted into a downstream expansion chamber (16), and a communication-path-forming plate (valve seat plate) (40) attached between an upstream expansion chamber (14) and the downstream expansion chamber (16). The downstream expansion chamber (16) is used as a space in which the spherical valve body (62) is placed. A through hole (41) formed in the communication-path-forming plate (valve seat plate) (40) defines a communication path (15) of the upstream expansion chamber (14) and the downstream expansion chamber (16). The muffler with a check valve can be configured to be small and compact, which is advantageous for reduced size and compactness of an evacuation device such as a vacuum pump equipped with the muffler with a check valve.

Description

[Technical field]

[0001] The present invention relates to a silencer used to reduce vibrations and noise caused by exhaust gas discharged from a vacuum exhaust device incorporating a vacuum pump, etc. More specifically, the present invention relates to a silencer having one or more stages of expansion chambers for silencing in an exhaust flow path and equipped with a check valve for preventing backflow of exhaust gas flowing through the exhaust flow path, and to a vacuum exhaust device equipped with said silencer. [Background technology]

[0002] Mechanical devices such as vacuum pumps may become noise sources that generate vibrations and noise due to exhaust. In order to suppress noise caused by exhaust, silencers are attached to the mechanical devices that are noise sources. In addition, in vacuum pumps and the like, a check valve may be placed between the exhaust port and the silencer to prevent backflow of exhaust. Vacuum pumps equipped with silencers and check valves are disclosed in, for example, Patent Documents 1 and 2.

[0003] In the muffler of a vacuum pump disclosed in Patent Document 1, the gas discharged from the exhaust port is passed through a first passage, an expansion chamber (expansion chamber), and a second passage, and discharged to reduce the pump exhaust noise to a predetermined level or less. The muffler also includes a valve chamber between the exhaust port and the expansion chamber (expansion chamber) that houses a valve member capable of opening and closing the exhaust port, and prevents gas from flowing back from the muffler side into the inside of the pump body. Patent Document 2 also discloses a vacuum pump unit in which a check valve and a silencer (muffler) are attached externally to the exhaust port. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 220943 [Patent Document 2] JP 2015-4344 A, FIG. 2 Summary of the Invention [Problem to be solved by the invention]

[0005] In a silencer equipped with a check valve, the check valve and the silencer are connected in tandem to the exhaust port of the mechanical device that is the noise source, so they require a large installation space. It is desirable to make the silencer equipped with a check valve small and compact. It is also desirable to be able to easily change the characteristics of the check valve, such as the cracking pressure, according to the exhaust of the mechanical device to which it is attached, such as a vacuum pump.

[0006] In view of the above, an object of the present invention is to provide a silencer with a check valve that requires a relatively small installation space and enables the valve characteristics of the check valve to be easily changed, and a vacuum exhaust device equipped with the silencer with a check valve. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a silencer including an exhaust flow path, an expansion chamber for silencing sound formed in the middle of the exhaust flow path, and a check valve for preventing backflow of exhaust gas flowing through the exhaust flow path, The check valve is a spherical valve body inserted in the expansion chamber in a freely movable state; a valve seat plate on which a seating surface of the spherical valve body is formed; It is equipped with The valve seat plate is an upstream end surface facing an upstream flow passage portion of the exhaust flow passage; a downstream end surface facing the expansion chamber; a through hole extending from the upstream end surface to the downstream end surface; It is equipped with the through hole defines a communication passage that communicates between an upstream flow passage portion of the exhaust flow passage and the extension chamber, The seating surface is characterized in that it is formed on the downstream end surface so as to coaxially surround the through hole.

[0008] In the muffler of the present invention, the expansion chamber for muffling, which has a predetermined volume and is made larger in cross-sectional area, is used as a space for arranging the spherical valve body, which is a component of the check valve. Also, the through hole formed in the valve seat plate, on which the seating surface of the check valve is formed, is used as a communication passage that connects the upstream flow passage part in the exhaust flow passage with the expansion chamber.

[0009] According to the present invention, the spherical valve body and the valve seat plate, which are components of the check valve, require less installation space. Also, since the communication passage, which is part of the exhaust flow path in the silencer, is defined by the through hole formed in the valve seat plate of the check valve, the number of components of the silencer with a check valve can be reduced. This allows the silencer with a check valve to be made small and compact, which is advantageous for making vacuum exhaust devices such as vacuum pumps equipped with a silencer with a check valve smaller and more compact.

[0010] The muffler of the present invention may be a muffler having a divided structure. In this case, the silencer of the present invention is a silencer case in which the exhaust flow path and the extension chamber are formed, the exhaust flow path includes an upstream flow path portion and a downstream flow path portion communicating with the upstream flow path portion via the extension chamber, The silencer case includes an upstream case and a downstream case detachably connected to the upstream case, the upstream flow path portion is formed inside the device case, The downstream flow path portion is formed inside the external case, The expansion chamber is formed inside a case connecting portion between the device case and the external case.

[0011] If the muffler has a split structure that can be split at the expansion chamber, the spherical valve body inserted in the expansion chamber and the valve seat plate attached to the upstream case can be easily replaced. In this case, for example, if different types of replacement spherical valve bodies and replacement valve seat plates are prepared, it is easy to optimize the check valve characteristics, such as cracking pressure, for the vacuum exhaust device to which it is attached.

[0012] In the silencer of the present invention, the valve seat plate can be attached and detached to the upstream case by screw fastening. Since there is no need to use fastening metal fittings such as bolts and nuts, the work of attaching and detaching the valve seat plate is simplified, which is advantageous for making the silencer smaller and more compact.

[0013] In the silencer of the present invention, it is desirable to make the shape of the through hole in the valve seat plate non-circular, such as polygonal. This makes it difficult for the spherical valve body to get stuck in the through hole (communication passage) in the valve seat plate. Also, the through hole can be used as an engagement hole for a tool used to attach and detach the valve seat plate, for example, a fastening tool for screwing and fixing the valve seat plate to the upstream case.

[0014] Next, the vacuum exhaust device of the present invention is characterized by including a silencer with a check valve having the above-mentioned configuration. By using a silencer having a small and compact configuration, it is possible to achieve a small and compact vacuum exhaust device. [Brief description of the drawings]

[0015] [Figure 1] 1 is an explanatory diagram showing a vacuum exhaust device to which a silencer according to an embodiment of the present invention is attached; [Diagram 2] FIG. 2 is a schematic vertical cross-sectional view showing the silencer of FIG. [Diagram 3] 2 is a half-sectional perspective view showing an external case (downstream case) portion of the silencer in FIG. 1. FIG. [Figure 4] FIG. 2 is an exploded view showing the main components of the silencer of FIG. 1. [Diagram 5]2A is a perspective view showing a communication passage forming plate (a valve seat plate of a check valve) attached to the silencer of FIG. 1, FIG. 2B is an end view showing its downstream end face, FIG. 2C is a longitudinal sectional view, and FIG. 2D is an end view showing its upstream end face. [Figure 6] 1A is a perspective view showing another example of a communication passage forming plate (a valve seat plate of a check valve), FIG. 1B is an end view showing the downstream end face thereof, FIG. 1C is a side view thereof, and FIG. 1D is an end view showing the upstream end face thereof. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of a vacuum exhaust device equipped with a silencer to which the present invention is applied will be described with reference to the drawings. Note that the embodiment described below shows an example of the present invention, and is not intended to limit the present invention to the embodiment.

[0017] 1 is an explanatory diagram showing a vacuum exhaust device equipped with a silencer according to an embodiment. The vacuum exhaust device 1 is equipped with two dry vacuum pumps connected in series inside a rectangular parallelepiped device housing 2. For example, the vacuum exhaust device 1 is equipped with a mechanical booster pump 3 in the front stage and a dry vacuum pump 4 in the rear stage. It goes without saying that various types of dry vacuum pumps can be used as the dry vacuum pump, such as a screw type vacuum pump, a roots type, a claw type, or a scroll type.

[0018] The intake port 5 and exhaust port 6 of the vacuum exhaust device 1 are disposed, for example, on the housing top surface 2a of the device housing 2. An intake pipe 8 is connected to the intake port 5 via an intake port joint (not shown). A silencer 10 according to the embodiment is attached to the exhaust port 6. Exhaust air from the exhaust port 6 passes through the silencer 10 and is then discharged via an exhaust pipe 9 connected to the silencer 10.

[0019] Fig. 2 is a schematic vertical cross-sectional view showing the silencer 10, Fig. 3 is a half cross-sectional perspective view showing a portion of the external case of the silencer 10, and Fig. 4 is an exploded view showing the main components of the silencer 10. The silencer 10 is equipped with a silencer case 10A in which an exhaust flow path 11 is formed, through which the exhaust gas discharged from the exhaust port 6 flows. The silencer case 10A is composed of a cylindrical apparatus-side case 20 (upstream case) and a cylindrical external case 30 (downstream case) removably attached to the apparatus-side case 20.

[0020] In the exhaust flow path 11, an inlet 12 communicating with the exhaust port 6, an inflow path 13, an upstream expansion chamber 14, a communication path 15, a downstream expansion chamber 16, an outlet path 17, and an outlet 18 are formed along the exhaust flow direction. An upstream flow path portion (inlet 12, inflow path 13, upstream expansion chamber 14, and communication path 15) is formed inside the device side case 20. In this example, the communication path 15 is defined by a through hole formed in a communication path forming plate 40 attached inside the device side case 20. Meanwhile, a downstream expansion chamber 16 and a downstream flow path portion (outflow path 17 and outlet 18) are formed inside the external case 30.

[0021] In addition, the silencer 10 in this example is a silencer device with a check valve, and is equipped with an upstream check valve 50 that can seal the space between the inlet passage 13 and the upstream expansion chamber 14 from the upstream expansion chamber 14 side, and a downstream check valve 60 that can seal the space between the connecting passage 15 and the expansion chamber 16 from the downstream expansion chamber 16 side.

[0022] The upstream check valve 50 includes a spherical valve body 52 movably inserted into the upstream expansion chamber 14 and a seating surface 51 of the spherical valve body 52. ​​The seating surface 51 is formed on the inner peripheral surface of the device-side case 20 and coaxially surrounds the upstream communication port of the upstream expansion chamber 14 that communicates with the inflow passage 13. The downstream check valve 60 includes a spherical valve body 62 movably inserted into the downstream expansion chamber 16 and a seating surface 61 of the spherical valve body 62. The seating surface 61 is formed in the communication passage forming plate 40 so as to coaxially surround the communication passage 15. The communication passage forming plate 40 functions as a valve seat plate on which the seating surface 61 of the downstream check valve 60 is formed. In the following description, the communication passage forming plate 40 will be described as the communication passage forming plate (valve seat plate) 40.

[0023] When the external case 30 is attached to the equipment-side case 20, an expansion chamber 16 sealed from the outside is formed, and when the external case 30 is removed from the equipment-side case 20, the downstream expansion chamber 16 opens to the outside, and a case connection portion between the equipment-side case 20 and the external case 30 is configured. In addition, when the external case 30 is removed from the equipment-side case 20, the communication passage forming plate (valve seat plate) 40 can be taken out from the equipment-side case 20.

[0024] The exhaust gas from the vacuum exhaust device 1 flows from the exhaust port 6 to the inlet 12 in the exhaust flow path 11 of the silencer 10, into the inlet 13, and then flows into the upstream expansion chamber 14 through the upstream check valve 50. The upstream expansion chamber 14 has a predetermined volume with a larger flow path area than the inlet 13. The exhaust gas flows from the upstream expansion chamber 14 through the communication passage 15 with a narrowed flow path area and the downstream check valve 60 into the downstream expansion chamber 16 with a wide flow path area and a predetermined volume. The exhaust gas that flows into the downstream expansion chamber 16 is discharged from the outlet 18 through the outlet 17 with a narrowed flow path area. The exhaust gas that flows out from the outlet 18 is discharged into the exhaust pipe 9 connected to the outlet 18. By discharging the exhaust gas from the vacuum exhaust device 1 into the exhaust pipe 9 through the silencer 10 with a two-stage silencing expansion chamber structure, the vibration and noise caused by the exhaust gas are suppressed. Furthermore, the upstream check valve 50 and the downstream check valve 60 can prevent backflow of exhaust gas, making it possible to maintain the vacuum on the upstream side even when the vacuum exhaust device 1 is not in operation.

[0025] 2 to 4, the apparatus-side case 20, the external case 30, and the communication passage forming plate (valve seat plate) 40 will be described in order. First, the apparatus-side case 20 is a part integrally formed with an apparatus component 19 such as a housing component defining the housing upper surface 2a of the apparatus housing 2 of the vacuum exhaust apparatus 1, or a pump housing component of the downstream dry vacuum pump 4 disposed inside the housing, or a part fixed to the apparatus component 19. This apparatus-side case 20 includes an upstream cylindrical portion 21, an intermediate cylindrical portion 22, and a downstream cylindrical portion 23 from the upstream side to the downstream side in the exhaust flow direction.

[0026] An inflow port 12 opens at the upstream end face of the upstream cylindrical portion 21, and an inflow passage 13 is formed inside the upstream cylindrical portion 21. An upstream expansion chamber 14 having a rectangular parallelepiped shape with a predetermined volume and a larger flow passage area than the inflow passage 13 is formed inside the intermediate cylindrical portion 22. In the upstream cylindrical portion 21, a tapered seating surface 51 is formed on the inner circumferential surface between the inflow passage 13 and the upstream expansion chamber 14, the inner diameter of which gradually increases from the inflow passage 13 toward the upstream expansion chamber 14. The seating surface 51 and a spherical valve body 52 inserted in the upstream expansion chamber 14 in a freely movable state constitute an upstream check valve 50.

[0027] A screw hole 23b of a predetermined depth is formed in the downstream-side cylindrical portion 23 of the device-side case 20, opening to an end face 23a on the downstream side. That is, a female screw 26 is formed over a predetermined range from the end face 23a side on the circular inner peripheral surface of the downstream-side cylindrical portion 23. In addition, a receiving portion 27 for a communication passage forming plate 40 is formed at the bottom of the screw hole 23b by protruding the inner peripheral surface of the screw hole inward by a certain width.

[0028] 5A is a perspective view of the communication passage forming plate (valve seat plate) 40, (B) is an end view showing the downstream end face, (C) is a vertical cross-sectional view, and (D) is an end view showing the upstream end face. The communication passage forming plate (valve seat plate) 40 will be described with reference to FIG. 5. The disc-shaped valve seat plate 40 has an upstream end face 42 with a circular contour facing the upstream expansion chamber 14 of the exhaust flow path 11, a downstream end face 43 with a circular contour facing the downstream expansion chamber 16, and a circular outer peripheral surface 45 with a constant width. A through hole 41 with a circular cross section is formed in the center part of the valve seat plate 40, which extends from the upstream end face 42 to the downstream end face 43. The through hole 41 functions as a communication passage 15 that communicates the upstream expansion chamber 14 and the downstream expansion chamber 16 in the exhaust flow path 11.

[0029] A seating surface 61 of the spherical valve body 62 is formed on the downstream end surface 43 of the valve seat plate 40 so as to coaxially surround the through hole 41. The seating surface 61 is a conical concave surface whose inner diameter gradually increases from the opening edge 41a of the through hole 41 toward the downstream expansion chamber 16. When the spherical valve body 62 is pressed against the seating surface 61 of this shape from the downstream side, the through hole 41 is sealed. The spherical valve body 62 abuts against the seating surface 61, which is a conical concave surface, in a state of line contact along a circle that coaxially surrounds the through hole 41. The inner diameter and taper angle of the seating surface 61, the outer diameter and weight of the spherical valve body 62, etc. are appropriately set so that the spherical valve body 62 operates at a desired cracking pressure.

[0030] In addition, the portion of the through hole 41 that opens to the upstream end face 42 of the valve seat plate 40 has a stepped opening edge portion 41b with an elliptical contour. This prevents the spherical valve body 52 of the upstream check valve 50 inserted into the upstream expansion chamber 14 from getting stuck in the through hole 41.

[0031] 2 and 3, the external case 30 includes an upstream cylindrical portion 31 that can form the downstream expansion chamber 16 by attaching it to the device case 20, and a downstream cylindrical portion 32 in which the outflow passage 17 is formed and the outflow port 18 opens to the downstream end face. A circular mounting flange 33 is formed on the outer periphery of the downstream end of the downstream cylindrical portion 32, to which the exhaust pipe 9 can be connected.

[0032] A connecting cylindrical portion 34 coaxially protrudes from an end surface 31a of the upstream side tube portion 31 of the external case 30. The connecting cylindrical portion 34 (second cylindrical end portion) has an end surface 34a as an opening, and a male screw 35 is formed on its circular outer circumferential surface. The male screw 35 can be coaxially screwed into a screw hole 23b of the downstream side tube portion 23 (first cylindrical end portion) of the device side case 20 and fixed. In this example, the length of the upstream side tube portion 31 of the external case 30 is shorter than the depth of the screw hole 23b of the downstream side tube portion 23 of the device side case 20. The connecting passage forming plate 40 is sandwiched between the end surface 34a of the connecting cylindrical portion 34 screwed into the screw hole 23b and the annular receiving portion 27 formed at the bottom of the screw hole 23b of the device side case 20, so that the connecting passage forming plate 40 is attached to the inside of the device side case 20.

[0033] When the external case 30 is attached, the spherical valve body 52 is inserted into the upstream expansion chamber 14 of the device-side case 20. The communication passage forming plate 40 is inserted into the screw hole 23b of the downstream cylinder portion 23 of the device-side case 20 and placed on the annular receiving portion 27, and the spherical valve body 62 is inserted and placed on the seating surface 61 of the communication passage forming plate 40. Next, the communication passage forming plate 40 is sandwiched, and the connecting cylindrical portion 34 (second cylindrical end portion) of the external case 30 is screwed coaxially into the screw hole 23b of the downstream cylinder portion 23 (second cylindrical end portion) of the device-side case 20 and fixed. As a result, the internal space of the upstream cylinder portion 31 of the external case 30 is sealed from the outside, and the downstream expansion chamber 16 is formed between the inner peripheral surface of the upstream cylinder portion 31 and the downstream end surface 43 of the communication passage forming plate 40 attached to the device-side case 20. Furthermore, a downstream check valve 60 equipped with a spherical valve body 62 is incorporated inside the downstream expansion chamber 16 .

[0034] O-ring mounting grooves 44, 28 are formed on the outer circumferential edge of the upstream end face 42 of the communication passage forming plate 40 and on the end face 23a of the downstream cylindrical portion 23 of the device-side case 20, respectively. With O-rings 71, 72 mounted in the O-ring mounting grooves 44, 28, respectively, the external case 30 is screwed and fixed to the device-side case 20. This seals the screw fastening surface of the case connection portion between the device-side case 20 and the external case 30, ensuring airtightness of the exhaust flow path 11.

[0035] As described above, the silencer 10 of this embodiment uses ball valve mechanisms equipped with spherical valve bodies 52, 62 as the upstream check valve 50 and the downstream check valve 60. The upstream expansion chamber 14 and the downstream expansion chamber 16 for silencing, which have a predetermined volume by widening the flow passage cross section, are used as the arrangement space for the spherical valve bodies 52, 62. In addition, the through hole 41 formed in the communication passage forming plate (valve seat plate) 40 on which the seating surface 61 of the downstream check valve 60 is formed defines the communication passage 15 that communicates the upstream expansion chamber 14 and the downstream expansion chamber 16 in the exhaust flow passage 11. Therefore, the upstream check valve 50 and the downstream check valve 60 can be incorporated into the silencer 10 without requiring a large installation space. In addition, since the communication passage 15 is defined by the through hole 41 formed in the communication passage forming plate (valve seat plate) 40, the number of components of the silencer with a check valve can be reduced. This allows the check valve-equipped silencer to be configured small and compact, which is advantageous in making a vacuum exhaust device such as a vacuum pump to which the check valve-equipped silencer is attached small and compact.

[0036] Moreover, the silencer case 10A of the silencer 10 of this example has a split structure in which the external case 30 is removably attached to the device-side case 20. When the external case 30 is removed from the device-side case 20, the downstream expansion chamber 16 portion opens, and it becomes possible to attach and detach the communication passage forming plate (valve seat plate) 40 to and from the device-side case 20, to insert and remove the spherical valve body 62 into and from the downstream expansion chamber 16, and to insert and remove the spherical valve body 52 into and from the upstream expansion chamber 14. Therefore, the characteristics of the check valve can be easily adjusted according to the noise on the vacuum exhaust device 1 side.

[0037] For example, multiple types of replacement valve seat plates with different shapes of the seating surface 61 (inner diameter, taper angle, diameter of the through hole, etc.) and multiple types of replacement spherical valve bodies with different outer diameters and weights are prepared as components of the downstream check valve 60. By selecting and using one of the replacement valve seat plates and one of the replacement spherical valve bodies as the communication passage forming plate (valve seat plate) 40 and the spherical valve body 62, respectively, depending on the mechanical device to which the silencer 10 is to be attached, a check valve according to the target pressure, etc. can be attached.

[0038] Furthermore, in this example, the communication passage forming plate 40 that defines the communication passage 15 that connects the upstream expansion chamber 14 and the downstream expansion chamber 16 is sandwiched between the external case 30 and the device side case 20. This simplifies the structure for fixing the communication passage forming plate 40 to the device side case 20, so the cost of the silencer 10 can be reduced and an increase in size can be suppressed. Also, since the communication passage forming plate 40 is a disc-shaped part with a predetermined thickness, it is effective in suppressing an increase in size of the silencer 10.

[0039] On the other hand, in the silencer 10 of this example, the silencer case 10A has a divided structure, so that the downstream expansion chamber 16 can be changed to an expansion chamber of a different volume by replacing the external case 30, and the communication passage 15 can be changed to a different flow passage diameter or flow passage length by replacing the communication passage forming plate (valve seat plate) 40, as necessary. By replacing these parts, the silencing effect of the silencer 10 can be more effectively exhibited.

[0040] For example, a plurality of types of replacement external cases are prepared, each of which has a common male thread 35 formed on the outer circumferential surface of the connecting cylindrical portion 34, but has different inner diameters and lengths of the portion forming the downstream expansion chamber 16, and different inner diameters and lengths of the outflow passage 17. In this case, the one that is most effective in reducing the noise of the mechanical device to be silenced can be selected from these replacement parts and attached to the device-side case 20.

[0041] Furthermore, in the silencer 10 of this embodiment, screw fastening is used as a mechanism for detachably fastening the external case 30 to the device case 20. Compared to a fastening mechanism that uses fastening metal fittings such as bolts and nuts, the number of parts required is reduced, and increases in the dimensions and costs of the silencer 10 can be suppressed. Also, by applying sealing tape to the threaded portion and applying a sealing agent, airtightness can be ensured.

[0042] (Another example of a valve seat plate) Fig. 6 shows a valve seat plate that can be used in place of the above-mentioned communication passage forming plate (valve seat plate) 40. Fig. 6(A) is a perspective view thereof, Fig. 6(B) is an end view showing the downstream end face thereof, Fig. 6(C) is a side view thereof, and Fig. 6(D) is an end view showing the upstream end face thereof.

[0043] 6 has the same basic configuration as the communication passage forming plate (valve seat plate) 40, and is disk-shaped overall, with a circular upstream end face 82, a circular downstream end face 83, a circular outer circumferential surface 85, a through hole 81 functioning as the communication passage 15, and a conical seating surface 86 formed in the downstream end face 83 so as to surround an opening edge 81b of the through hole 81. The upstream inner circumferential edge of the through hole 81 exposed at the upstream end face 82 is a stepped inner circumferential edge 81a with an elliptical contour.

[0044] The difference is that the circular outer peripheral surface 85 is a fastening outer peripheral surface on which a male thread 87 is formed, and the cross-sectional shape of the through hole 81 is non-circular; in the illustrated example, it is an elliptical cross-section in which the surfaces facing each other in the diametric direction are planar inner peripheral surfaces extending parallel to each other.

[0045] A male thread 87 formed on a circular outer peripheral surface 85 of the valve seat plate 80 can be screwed into a female thread 26 formed on an inner peripheral surface of the downstream-side cylindrical portion 23 of the equipment-side case 20. When attaching the valve seat plate 80, the valve seat plate 80 is inserted coaxially into the equipment-side case 20, a fastening tool is engaged with the inner peripheral surface of the through hole 81 having an oval cross section, and the valve seat plate 80 can be screwed in using the fastening tool.

[0046] By making the valve seat plate 80 a screw-fixing type, the work of attaching the valve seat plate 80 to the device-side case 20 is simplified. In addition, by applying a sealant to the fastening surface or using a seal tape, it is possible to ensure airtightness of the fastening surface between the device-side case 20 and the valve seat plate 80. Of course, as shown in Figures 2 and 3, it is also possible to ensure airtightness by sandwiching a seal ring such as an O-ring.

[0047] The cross-sectional shape of the through hole 81 of the valve seat plate 80 is not limited to an oval shape as shown in the figure, and may be a non-circular shape such as a polygon. The contour shape (cross-sectional shape) of at least the opening edge of the through hole 81 may be a shape that makes it difficult for the spherical valve body 52, 62 to fit. The cross-sectional shape of the through hole 81 may be a non-circular shape such as a polygon rather than a perfect circle, so long as it provides a hook for a fastening tool. For example, by making the through hole a polygonal cross section such as a hexagon, the valve seat plate 80 can be turned using a hexagonal wrench or a flathead screwdriver, and the installation and removal of the valve seat plate 80 becomes easier.

Claims

1. A silencer including an exhaust flow path, an expansion chamber for silencing formed in the middle of the exhaust flow path, and a check valve for preventing backflow of exhaust gas flowing through the exhaust flow path, a silencer case in which the exhaust flow path and the extension chamber are formed, the exhaust flow path includes an upstream flow path portion and a downstream flow path portion communicating with the upstream flow path portion via the extension chamber, The silencer case includes an upstream case and a downstream case detachably connected to the upstream case, The upstream flow path portion is formed inside the upstream case, The downstream flow path portion is formed inside the downstream case, The expansion chamber is formed inside a case connection portion between the upstream case and the downstream case, The check valve is a spherical valve body inserted in the expansion chamber in a freely movable state; a valve seat plate on which a seating surface of the spherical valve body is formed; It is equipped with The valve seat plate is an upstream end surface facing the upstream flow passage portion of the exhaust flow passage; a downstream end surface facing the expansion chamber; a through hole extending from the upstream end surface to the downstream end surface; It is equipped with the through hole defines a communication passage that communicates between the upstream flow passage portion of the exhaust flow passage and the extension chamber, The seating surface is formed on the downstream end surface so as to coaxially surround the through hole, Furthermore, A plurality of types of replacement spherical valve bodies that are different in at least one of dimensions and weight; A plurality of types of replacement valve seat plates having different shapes and dimensions of the through hole and the seating surface; It is equipped with one of the replacement spherical valve bodies is inserted into the expansion chamber as the spherical valve body; A silencer, wherein one of the replacement valve seat plates is attached to the upstream case as the valve seat plate.

2. In claim 1, The seating surface is a conical surface whose inner diameter gradually increases from the opening edge of the through hole toward the expansion chamber.

3. (delete)

4. (delete)

5. In claim 1, the valve seat plate has a fastening outer peripheral surface on which a male screw for fastening to the upstream case is formed, The upstream case is provided with a fastening inner circumferential surface on which a female thread is formed so that the male thread can be screwed thereinto.

6. In claim 5, A silencer comprising a seal member that seals between the fastening outer peripheral surface of the valve seat plate and the fastening inner peripheral surface of the upstream case.

7. In claim 1, A silencer, wherein the through hole in the valve seat plate has a non-circular cross-sectional shape.

8. In claim 5, A silencer, wherein the through hole of the valve seat plate has a polygonal cross-sectional shape.

9. In claim 1, The exhaust flow path includes an upstream expansion chamber upstream of the expansion chamber, an upstream spherical valve body for preventing backflow of the exhaust gas is movably inserted into the upstream expansion chamber; The upstream end surface of the valve seat plate faces the upstream expansion chamber, A silencer in which an inner peripheral edge portion on an upstream end side of the through hole that opens into the upstream end face of the valve seat plate has a non-circular contour shape.

10. A vacuum exhaust system comprising the silencer according to claim 1.

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