JP7584183B2 - Silencers and vacuum pumps - Google Patents

Description

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. More specifically, the present invention relates to a silencer in which one or more stages of expansion chambers for silencing are formed in the exhaust flow path and which is equipped with a check valve that prevents backflow of exhaust gas flowing through the exhaust flow path, and to a vacuum exhaust device equipped with the silencer.

Mechanical equipment such as vacuum pumps can be noise sources that generate vibrations and noise due to exhaust. In order to suppress noise caused by exhaust, silencers are attached to the mechanical equipment that is the noise source. 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 a silencer and a check valve are disclosed in, for example, Patent Documents 1 and 2.

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, thereby reducing the pump exhaust noise to a predetermined level or less. The muffler also has 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, preventing backflow of gas 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.

International Publication No. 2018/220943 JP 2015-4344 A, FIG.

In a silencer equipped with a check valve, the check valve and silencer are connected in tandem to the exhaust port of the mechanical device that is the noise source, so a large amount of installation space is required. It is desirable to have a silencer with a check valve that is small and compact in configuration. 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.

In view of these points, the object of the present invention is to provide a silencer with a check valve that requires a relatively small installation space and allows the valve characteristics of the check valve to be easily changed, and a vacuum exhaust device equipped with the silencer with a check valve.

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;
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;
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.

In the muffler of the present invention, the expansion chamber for muffling, which has a predetermined volume and a large cross-sectional area, is used as a space for arranging the spherical valve body, which is a component of the check valve. In addition, 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.

According to the present invention, the spherical valve body and valve seat plate, which are components of the check valve, require less installation space. In addition, because the communication passage, which is part of the exhaust flow path in the silencer, is defined by a 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.

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.

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.

In the silencer of the present invention, the valve seat plate can be attached and detached from the upstream case by screw fastening. Since there is no need to use fastening hardware such as bolts and nuts, the valve seat plate can be easily attached and detached, which is advantageous for making the silencer smaller and more compact.

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 in the valve seat plate (the communication passage). In addition, the through hole can be used as an engagement hole for a tool used to attach and detach the valve seat plate, such as a fastening tool for screwing and fixing the valve seat plate to the upstream case.

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

1 is an explanatory diagram showing a vacuum exhaust device to which a silencer according to an embodiment of the present invention is attached; FIG. 2 is a schematic vertical cross-sectional view showing the muffler of FIG. 1 . FIG. 2 is a half-sectional perspective view showing a portion of an external case (downstream case) of the silencer of FIG. 1 . FIG. 2 is an exploded view showing the main components of the silencer of FIG. 1 . 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 the downstream end face of the communication passage forming plate, FIG. 2C is a longitudinal sectional view of the communication passage forming plate, and FIG. 2D is an end view showing the upstream end face of the communication passage forming plate. 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.

Below, 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 one example of the present invention, and is not intended to limit the present invention to the embodiment.

Figure 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. Of course, various types of dry vacuum pumps can be used, such as a screw type vacuum pump, a roots type, a claw type, or a scroll type.

The intake port 5 and exhaust port 6 of the vacuum exhaust device 1 are arranged, 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. The exhaust from the exhaust port 6 passes through the silencer 10 and is then discharged via an exhaust pipe 9 connected to the silencer 10.

2 is a schematic longitudinal section of the silencer 10, FIG. 3 is a half-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 device case 20 (upstream case) and a cylindrical external case 30 (downstream case) removably attached to the device case 20.

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

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.

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 inlet 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 in a state in which it coaxially surrounds 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.

When the external case 30 is attached to the device-side case 20, an expansion chamber 16 sealed from the outside is formed, and when the external case 30 is removed from the device-side case 20, the downstream expansion chamber 16 opens to the outside. A case connection portion between the device-side case 20 and the external case 30 is configured so that. Also, when the external case 30 is removed from the device-side case 20, the communication passage forming plate (valve seat plate) 40 can be removed from the device-side case 20.

The exhaust gas from the vacuum exhaust device 1 flows from the exhaust port 6 through the inlet 12 in the exhaust flow path 11 of the silencer 10 into the inlet 13, and 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 connecting 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 path 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 a vacuum on the upstream side even when the vacuum exhaust device 1 is not in operation.

2 to 4, the device side case 20, the external side case 30, and the communication passage forming plate (valve seat plate) 40 will be described in order. First, the device side case 20 is a part integrally formed with device components 19 such as the housing components that define the housing top surface 2a of the device housing 2 of the vacuum exhaust device 1, and the pump housing components of the downstream dry vacuum pump 4 that are arranged inside the housing, or a part fixed to the device components 19. This device side case 20 comprises, from the upstream side to the downstream side in the exhaust flow direction, an upstream side tubular section 21, an intermediate tubular section 22, and a downstream side tubular section 23.

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

The downstream cylinder 23 of the device case 20 has a screw hole 23b of a predetermined depth formed on the downstream side thereof, which opens to the end face 23a. That is, a female screw 26 is formed on the circular inner peripheral surface of the downstream cylinder 23 over a predetermined range from the end face 23a side. In addition, a receiving portion 27 for the 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.

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 longitudinal 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 disk-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 of a constant width. A through hole 41 with a circular cross section is formed in the center 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.

The 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, taper angle, outer diameter, weight, etc. of the seating surface 61, the spherical valve body 62, are appropriately set so that the spherical valve body 62 operates at the desired cracking pressure.

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 becoming stuck in the through hole 41.

Referring again to Figures 2 and 3, the external case 30 comprises an upstream tubular portion 31 that can form the downstream expansion chamber 16 by attaching it to the device case 20, and a downstream tubular 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 tubular portion 32, to which the exhaust pipe 9 can be connected.

A connecting cylindrical portion 34 protrudes coaxially from the end face 31a of the upstream side tube portion 31 of the external case 30. The connecting cylindrical portion 34 (second cylindrical end portion) has an opening at its end face 34a, and a male screw 35 is formed on its circular outer circumferential surface. The male screw 35 can be coaxially screwed into the 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 face 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 inside the device side case 20.

When attaching the external case 30, 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 cylindrical 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) of the external case 30 is screwed coaxially into the screw hole 23b of the downstream cylindrical portion 23 (second cylindrical end) of the device-side case 20 and fixed. As a result, the internal space of the upstream cylindrical 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 cylindrical 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 .

O-ring mounting grooves 44, 28 are formed on the outer peripheral 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 part between the device side case 20 and the external case 30, ensuring airtightness of the exhaust flow path 11.

As described above, in the silencer 10 of this example, a ball valve mechanism equipped with spherical valve bodies 52, 62 is used as the upstream check valve 50 and the downstream check valve 60. The upstream expansion chamber 14 and downstream expansion chamber 16 for silencing, which have a predetermined volume by widening the flow path 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.

In addition, the silencer case 10A of the silencer 10 in 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 the device-side case 20, insert and remove the spherical valve body 62 into and from the downstream expansion chamber 16, and 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.

For example, multiple types of replacement valve seat plates with different seating surface 61 shapes (inner diameter, taper angle, through-hole diameter, 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.

Furthermore, in this example, the communication passage forming plate 40, which 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, reducing the cost of the silencer 10 and suppressing an increase in size. In addition, 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.

On the other hand, in the silencer 10 of this example, the silencer case 10A has a split 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 sound absorbing effect of the silencer 10 can be more effectively exerted.

For example, multiple types of replacement external cases 30 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 replacement part 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 case 20.

In addition, in the silencer 10 of this example, 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 smaller, and increases in the dimensions and costs of the silencer 10 can be suppressed. In addition, airtightness can be ensured by applying sealing tape to the threaded portion and coating it with a sealant.

(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.

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

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, and in the illustrated example, 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.

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

By fixing the valve seat plate 80 by screwing it in, 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 sealing tape, the airtightness of the fastening surface between the device-side case 20 and the valve seat plate 80 can be ensured. Of course, airtightness can also be ensured by sandwiching a seal ring such as an O-ring, as shown in Figures 2 and 3.

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 into. 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, making it easier to install and remove the valve seat plate 80.

Claims (10)

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;
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;
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;
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. 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. (delete) (delete) 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. 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. In claim 1,
A silencer, wherein the through hole in the valve seat plate has a non-circular cross-sectional shape. In claim 5,
A silencer, wherein the through hole of the valve seat plate has a polygonal cross-sectional shape. 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. A vacuum exhaust system comprising the silencer according to claim 1.

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