JP6381417B2 - Silencer - Google Patents

Description

  The present invention relates to a silencer that is connected in the middle of a pipe in which a fluid flows in one direction and blocks propagation of acoustic noise in the fluid.

  Conventionally, as this type of silencer, there has been known one in which a ring plate and a disk are alternately arranged three or more on the same axis and the sound noise propagation path is bent several times to mute the sound. (For example, refer to Patent Document 1).

JP2013-127443A (FIG. 2)

  However, the conventional silencer described above cannot provide a sufficient silencing effect. On the other hand, when the ring plate and the disk are increased in order to increase the silencing effect, the number of times of expansion / contraction of the flow path diameter is increased correspondingly, causing a problem that the pressure loss increases.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a silencer that has a higher silencing effect and a smaller pressure loss than conventional ones.

  In order to achieve the above object, the invention of claim 1 is characterized in that a pipe-type case connected in the middle of a pipe through which a fluid flows in one direction and an inner diameter of an axially intermediate portion of the pipe-type case are expanded. The intermediate enlarged portion and the upstream small diameter portion on the upstream side thereof, and all of the fluid that is provided in the intermediate enlarged portion and goes straight from the upstream small diameter portion is prohibited from being laterally or obliquely forward or obliquely rearward. And a plurality of ring guides arranged adjacent to each other with an annular gap in the direction of the central axis, and the radial guide part, It is a silencer provided with the center member which covers the inner side opening of the said ring guide of one end side among several ring guides.

  According to a second aspect of the present invention, the radial guide portion is a cup in which one end opening of a cylindrical portion formed by laminating the plurality of ring guides in the axial direction of the pipe-shaped case with the annular gap therebetween is covered with the center member. The silencer according to claim 1, wherein the silencer has a structure, and an opening side end of the cylindrical portion is connected to a downstream opening edge of the upstream small diameter portion.

  The invention according to claim 3 is the silencer according to claim 2, wherein each of the ring guides has a tapered shape whose diameter is increased in a direction away from the upstream small diameter portion.

  Invention of Claim 4 is a silencer of Claim 2 or 3 provided with the terminal taper guide which protruded from the said center member to the opposite side of the said upstream small diameter part, and was gradually diameter-reduced toward the front. .

  According to a fifth aspect of the present invention, the pipe-shaped case is provided with a downstream small-diameter portion that is reduced in a stepped shape from a downstream end portion of the intermediate enlarged-diameter portion, and a distal end portion of the terminal taper guide is formed on the pipe-shaped case. The silencer according to claim 4, wherein the downstream small-diameter portion enters.

  According to a sixth aspect of the present invention, the center member and the plurality of ring guides are formed with bolt insertion holes through which a common bolt passes, and adjacent to the surface of the plurality of ring guides on the center member side. The silencer according to any one of claims 2 to 5, further comprising a spacer protrusion for forming the annular gap between the ring guide and the center member to be fitted.

  A seventh aspect of the present invention is the silencer according to any one of the second to sixth aspects, wherein a mesh that covers the cylindrical portion from the outside or the inside is provided.

  The invention according to claim 8 is the silencer according to any one of claims 1 to 7, wherein an inner peripheral surface of the intermediate enlarged diameter portion is covered with a sound absorbing member.

  The invention according to claim 9 is a skeleton sleeve formed by connecting a pair of support rings fitted inside the intermediate enlarged portion with a plurality of connecting bars extending in the axial direction of the intermediate enlarged portion. The sound absorbing member is a silencer according to claim 8, wherein the sound absorbing member is formed in a sheet shape and is wound around an outer periphery of the skeleton sleeve.

  According to a tenth aspect of the present invention, the pipe-shaped case is provided with a downstream small-diameter portion that is reduced in a stepped shape from a downstream end portion of the intermediate enlarged portion, and the intermediate enlarged portion and the downstream side are provided. The corner arc surface between the step surface with the small-diameter portion and the inner peripheral surface of the downstream-side small-diameter portion is provided with a corner arc surface continuous to the step surface and the inner peripheral surface. It is a silencer as described in a claim.

  In the invention of claim 11, the radiation guide portion is fitted to an intermediate position in the axial direction of the intermediate enlarged diameter portion, and the plurality of ring guides of the radiation guide portion respectively approach the upstream small diameter portion. And the ring guide arranged closer to the upstream small diameter portion is configured such that the maximum diameter and the minimum diameter become smaller, and the center member is the most upstream small diameter portion. The silencer according to claim 1, wherein an opening having a minimum diameter of the ring guide is covered from the upstream small diameter portion side.

  In the silencer according to the first aspect, the radiation guide portion provided in the intermediate enlarged portion of the pipe-shaped case prohibits all straight travel of the fluid passing through the upstream small diameter portion. The radiation guide portion includes a plurality of ring guides arranged adjacent to each other with an annular gap, and a center member that covers the inner opening of the ring guide on one end side of the plurality of ring guides. The fluid is dispersed in a plurality of annular gaps and guided to the side or obliquely forward or obliquely rearward and passes through the radiation guide portion. At that time, the acoustic noise propagating through the fluid is significantly attenuated by repeated reflection between the opposing surfaces on both sides of the annular gap. On the other hand, the fluid receives a pressure loss when passing through the annular gap, but the pressure loss can be kept small because a plurality of annular gaps are provided. In particular, if the fluid is a gas, the viscosity is lower than that of the liquid, so that the pressure loss due to passing through the annular gap is greatly reduced as compared with the conventional one in which the flow path diameter is repeatedly expanded and contracted. Thus, according to the present invention, it is possible to provide a silencer that has a higher silencing effect and a lower pressure loss than conventional ones.

  In the silencer according to claim 2, the radiation guide portion has a cup structure in which one end opening of a cylindrical portion formed by laminating a plurality of ring guides with an annular gap therebetween is covered with a center member, and downstream of the upstream small-diameter portion. Since the opening side end of the cylindrical portion is connected to the opening edge, the fluid flows from the upstream small diameter portion into the cylindrical portion, then passes through the annular gap, and the cylinder between the cylindrical portion and the intermediate enlarged diameter portion. Flow into the area. Thereby, acoustic noise can be absorbed also on the inner side surface of the intermediate enlarged diameter portion.

  In the silencer according to the third aspect, each ring guide has a tapered shape whose diameter is increased in the direction away from the upstream small diameter portion, so that the fluid flows obliquely forward from the annular gap, The pressure loss can be suppressed as compared with the case where the gas flows laterally or obliquely backward.

  The silencer according to the fourth aspect of the present invention is provided with the end tapered guide that protrudes from the center member opposite to the upstream small-diameter portion and is gradually reduced in diameter toward the tip, so that the turbulence of the fluid after passing through the radiation guide portion Can prevent the occurrence of excessive flow.

  In the silencer according to the fifth aspect of the invention, the downstream small-diameter portion enters the distal end portion of the end taper guide so that the fluid smoothly flows into the downstream small-diameter portion and flows into the downstream small-diameter portion from the intermediate enlarged portion. Generation of turbulent flow can be suppressed.

  In the silencer of the sixth aspect, an annular gap can be formed between adjacent ring guides or center members simply by putting the plurality of bolts through the center member and the plurality of bolt insertion holes of the plurality of ring guides.

  In the silencer according to the seventh aspect, the rectifying effect is improved by providing the mesh covering the outer side or the inner side of the cylindrical portion.

  According to the silencer of the eighth aspect, the inner peripheral surface of the intermediate enlarged diameter portion is covered with the sound absorbing member, and the noise reduction effect is enhanced. Further, as in claim 9, if the sound absorbing member is formed into a sheet shape and wound around the outer periphery of the skeleton sleeve fitted inside the intermediate enlarged diameter portion, the assembling work is facilitated.

  The silencer of claim 10 includes a corner arc surface that is continuous with the inner peripheral surface of the downstream small-diameter portion, the stepped surface of the intermediate large-diameter portion, and the downstream small-diameter portion of the pipe-shaped case. It is possible to smoothly flow into the side small-diameter portion, and to suppress the occurrence of a turbulent flow in the portion flowing from the intermediate large-diameter portion into the upstream small-diameter portion.

  According to the structure of the silencer of claim 11 and claim 11, the radiation guide portion becomes compact in the axial direction of the pipe-shaped case.

1 is a side sectional view of an ultrasonic flowmeter having a silencer according to a first embodiment of the present invention. Partially enlarged side sectional view of ultrasonic flowmeter Disassembled perspective view of radiation guide Exploded side view of radiation guide Sound absorption sleeve perspective view Disassembled perspective view of sound absorbing sleeve The exploded side view of the radiation guide part concerning a modification to the present invention The perspective view of the radiation | emission guide part which concerns on this invention

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. As shown in FIG. 1, the silencer 30 of this embodiment is provided as a part of the ultrasonic flowmeter 10. In FIG. 1, reference numeral 11 denotes a pipe-shaped case according to the present invention, which extends in a straight line and has tapered screws 12 and 12 inside both ends. Then, for example, gas pipes 90 and 90 are connected to the taper screws 12 and 12, and a commercial gas (for example, argon gas, nitrogen gas, propane gas) is formed in one direction (the direction from the left to the right in FIG. 1) on the inner side. Etc.) flows as “fluid” according to the present invention.

  The inside of the pipe-shaped case 11 has an upstream side small diameter portion 13 according to the present invention where the upstream side taper screw 12 is formed, and in order from the upstream side small diameter portion 13 toward the downstream side, the intermediate expansion is performed. A diameter portion 14 and a downstream small diameter portion 15 are formed, and the other taper screw 12 is formed on the downstream side of the downstream small diameter portion 15. Further, the downstream side small diameter portion 15 has a slightly smaller inner diameter than the upstream side small diameter portion 13, and the intermediate diameter expanded portion 14 expands stepwise with respect to the upstream side small diameter portion 13 and the downstream side small diameter portion 15. It is a diameter. Further, a corner arc surface 15 </ b> A is formed at the opening edge of the downstream small-diameter portion 15 so as to be continuous with the step surface with the intermediate enlarged-diameter portion 14 and the inner peripheral surface of the downstream small-diameter portion 15.

  The pipe-shaped case 11 is divided into first to third case components 11A, 11B, and 11C in the axial direction. The first case component 11A and the second case component 11B are fitted and coupled at an intermediate position of the intermediate enlarged portion 14, and the second case component 11B and the third case component 11C are the downstream small-diameter portion. 15 are fitted and connected at the downstream end.

  At two locations on the inner surface of the downstream small-diameter portion 15, a pair of element receiving recesses 16, 16 are formed in a recess on a straight line that obliquely intersects the axial direction. The sound wave elements 17, 17 are received and face each other. Then, similarly to a known ultrasonic flow meter, the propagation time of the ultrasonic wave from one ultrasonic element 17 to the other ultrasonic element 17 and the ultrasonic wave from the other ultrasonic element 17 to one ultrasonic element 17 are as follows. The flow rate of the fluid passing through the downstream small diameter portion 15 is measured based on the difference from the propagation time of the sound wave, and the flow rate of the fluid is detected by multiplying the flow velocity by the fluid passage area of the downstream small diameter portion 15. Yes.

  The upstream side of the ultrasonic flow meter 10 from the upstream ultrasonic element 17 is a silencer 30 according to the present invention, and a radiation guide portion 20 according to the present invention is provided in the intermediate enlarged diameter portion 14. It has been. The radiation guide part 20 has a cup structure in which one end of a cylindrical part 23 formed by laminating a plurality of ring guides 21 is covered with a center member 24. Then, the opening side end portion of the cylindrical portion 23 is connected to the downstream opening edge of the upstream small diameter portion 13, and the entire radiation guide portion 20 is intermediately expanded from the step surface between the upstream small diameter portion 13 and the intermediate large diameter portion 14. It protrudes to the diameter portion 14 side.

  Specifically, each ring guide 21 is, for example, a resin molded product, and has a tapered shape that is gently inclined toward the side away from the upstream small-diameter portion 13 toward the outside in the radial direction, as shown in FIG. ing. In addition, the plurality of ring guides 21 other than the ring guide 21 at the end on the upstream side small diameter portion 13 side have the same slope of the tapered surfaces 21S and 21T on both the front and back sides. The ring guide 21 at the end on the upstream small diameter portion 13 side has a tapered surface 21S on the upstream small diameter portion 13 side that is steeper than the tapered surface 21S of the other ring guide 21, and the upstream small diameter portion 21S. It is adapted to be fitted into a recess 13 </ b> D formed at the opening edge of the portion 13.

  As shown in FIG. 3, bolt insertion holes 21 </ b> A are formed through a plurality of locations in the circumferential direction of each ring guide 21 in parallel to the center axis of the ring guide 21, and the center member 24 extends from the opening edge of each bolt insertion hole 21 </ b> A. A spacer protrusion 21B protrudes on the side (opposite the upstream small diameter part 13). Further, the tip surface of each ring guide 21 is inclined so as to be able to come into surface contact with the tapered surface 21S on the upstream small-diameter portion 13 side in another ring guide 21 arranged on the downstream side of the ring guide 21. Yes.

  As shown in FIG. 4, the surface of the center member 24 on the ring guide 21 side (upstream small diameter portion 13 side) is a tapered surface 24S having the same gradient as the tapered surface 21S of the ring guide 21, and an inner opening of the tapered surface 24S. And a circular flat surface 24F that closes the surface. In addition, an annular flat surface 24B orthogonal to the axial direction of the pipe-shaped case 11 is provided on the back side of the tapered surface 24S of the center member 24, and penetrates between the annular flat surface 24B and the tapered surface 24S. A plurality of bolt insertion holes 24A corresponding to the bolt insertion holes 21A of the ring guide 21 are formed. A plurality of common bolts B are inserted from the annular flat surface 24B side into the center member 24 and bolt insertion holes 24A, 21A of the plurality of ring guides 21 and formed at the opening edge of the upstream small diameter portion 13 (not shown). It is fastened to the female screw hole. As a result, as shown in FIG. 2, the plurality of ring guides 21 and the center member 24 are held in a state of being stacked in the axial direction of the pipe-shaped case 11 with the annular gap 22 therebetween, and the center member 24 group described above. The cylindrical portion 23 is configured, and one end opening of the cylindrical portion 23 is closed by the center member 24 from the opposite side to the upstream small diameter portion 13. Further, in this state, the downstream end surface (that is, the annular flat surface 24B) of the center member 24 is located closer to the downstream small diameter portion 15 than the center in the axial direction of the intermediate expanded diameter portion 14.

  As shown in FIG. 1, a terminal taper guide 25 according to the present invention is provided on the back side of the circular flat surface 24F of the center member 24. The terminal taper guide 25 has a tapered shape with a diameter gradually reduced toward the downstream side. Further, the distal taper guide 25 forms a proximal taper portion 25A from the proximal end portion to an intermediate position that is approximately 1/3 in the axial direction, and a distal taper portion 25B extends from the intermediate position to the distal end. In addition, the gradient of the distal end taper portion 25B is gentler than the proximal end taper portion 25A. In other words, the distal tapered guide 25 has a shape in which the distal tapered portion 25B is sharper and narrower than the proximal tapered portion 25A. Then, the distal end side projects into the downstream small diameter portion 15 from the axial intermediate position of the distal tapered portion 25B.

  The cylindrical portion 23 of the radiation guide portion 20 is covered with a mesh 26 on the outside. Further, as shown in FIG. 2, the center member 24 and the ring guide 21 at the end on the upstream side small diameter portion 13 side have a slightly larger outer diameter than the other ring guide 21 groups, and the mesh 26 has a shaft. It moves in the direction so as not to leave the cylinder part 23.

  A sound absorbing sleeve 29 is fitted to the inner peripheral surface of the intermediate enlarged diameter portion 14. As shown in FIG. 5, the sound absorbing sleeve 29 is formed by winding a sheet-like sound absorbing member 27 (for example, sponge) around the outer side of the skeleton sleeve 28. Further, as shown in FIG. 6, the skeleton sleeve 28 has a plurality of axially extending portions of the intermediate enlarged portion 14 extending between a pair of support rings 28 </ b> A and 28 </ b> A fitted inside the intermediate enlarged portion 14. Contact is made at the contact bar 28B. Furthermore, a plurality of locking projections 28C that protrude straight outward from the connecting bar 28B are provided at a plurality of locations in the circumferential direction of the skeleton sleeve 28, and a plurality of locking hooks are provided at one location in the circumferential direction of the skeleton sleeve 28. 28F is formed on the outer surface of one connection bar 28B. Among the skeleton sleeves 28 group, a part of the locking hooks 28F constitutes a first locking hook 28G whose tip is bent to one side around the outer periphery of the skeleton sleeve 28, and the other part of the locking hooks 28F includes The distal end portion is a second locking hook 28 </ b> H bent to the other side around the outer periphery of the skeleton sleeve 28. Then, as shown in FIG. 5, the sound absorbing member 27 is wound around the skeleton sleeve 28 with one end hooked on the first locking hook 28G, and the other end hooked on the second locking hook 28H. ing. Further, the locking projections 28C group penetrate the sound absorbing member 27 on the front and back sides. As a result, the sound absorbing member 27 is fixed to the skeleton sleeve 28 to form a sound absorbing sleeve 29.

  The description regarding the structure of the silencer 30 of this embodiment is above. Next, the effect of the silencer 30 will be described. In the silencer 30 of the present embodiment, the radiation guide part 20 provided in the intermediate enlarged diameter part 14 of the pipe-shaped case 11 prohibits all straight travel of the fluid passing through the upstream small diameter part 13. And, as shown in FIG. 2, the radiation guide portion 20 has a cup structure in which one end opening of a cylindrical portion 23 formed by laminating a plurality of ring guides 21 with an annular gap 22 is covered with a center member 24, Since the opening end of the cylindrical portion 23 is connected to the downstream opening edge of the upstream small diameter portion 13, all the fluid flows in a dispersed manner in the plurality of annular gaps 22 and passes through the radiation guide portion 20. At this time, the acoustic noise propagating through the fluid is significantly attenuated by repeated reflection between the opposing surfaces on both sides of the annular gap 22. Further, the acoustic noise that could not be silenced by the annular gap 22 is absorbed by the sound absorbing member 27 that covers the inner peripheral surface of the intermediate enlarged diameter portion 14 after passing through the annular gap 22. The acoustic noise is, for example, in the vicinity of the frequency component of the ultrasonic wave used for measurement by the ultrasonic flow meter 10 among noises generated by a noise source such as a governor or a valve disposed in the vicinity of the ultrasonic flow meter 10. The noise of the frequency.

  On the other hand, although the fluid receives a pressure loss when passing through the annular gap 22, the pressure loss can be suppressed to be small because a plurality of the annular gaps 22 are provided. In particular, the fluid of this embodiment is a gas (commercial gas), and its viscosity is lower than that of liquid. Therefore, the pressure loss caused by passing through the annular gap 22 is significantly larger than that of the conventional one in which the flow path diameter is repeatedly expanded and contracted. It is reduced. In addition, each ring guide 21 has a tapered shape whose diameter is increased in a direction away from the upstream small-diameter portion 13, so that the fluid flows obliquely forward from the annular gap 22, and the fluid flows into the annular gap. The pressure loss can be suppressed as compared with the case of flowing from 22 to the side perpendicular to the axial direction of the pipe-shaped case 11 and obliquely rearward. As a result, the silencer 30 of the present embodiment can increase the silencing effect as compared with the conventional one, and can accurately measure the flow rate in the ultrasonic flowmeter 10 and reduce the pressure loss. It is possible to prevent misfire and insufficient fuel power in the downstream gas equipment.

  Further, the tapered end taper guide 25 is formed to project from the downstream end face of the center member 24 of the radiation guide section 20, and the corner arc surface 15 A is provided at the opening edge of the downstream small diameter section 15. The fluid smoothly flows into the downstream small-diameter portion 15 and the occurrence of a turbulent flow in the portion where the fluid flows into the upstream small-diameter portion 13 from the intermediate enlarged-diameter portion 14 can be suppressed. In particular, the disturbed flow can be effectively suppressed by causing the distal end portion of the end taper guide 25 to enter the downstream side small diameter portion 15. Furthermore, the silencer 30 also has the effect of rectifying the turbulent flow generated upstream of the radiation guide portion 20 by passing the fluid between the mutually parallel tapered surfaces 21T and 21S of the ring guide 21 group. Further, the rectifying effect can also be obtained by covering the cylindrical portion 23 composed of the ring guide 21 group with the mesh 26 from the outside.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

(1) The distal taper guide 25 of the radiation guide portion 20 of the above embodiment includes the proximal taper portion 25A and the distal taper portion 25B. However, as illustrated in FIG. 7, the distal taper guide 25C has a uniform gradient. It may be a different structure. Moreover, in the terminal taper guide 25 of the said embodiment, although the front-end | tip taper part 25B entered the downstream small diameter part 15, it does not need to enter. Furthermore, the downstream end face of the radiation guide portion 20 may be flattened or bulged into a dome shape without providing the terminal taper guide.

(2) Although the outer peripheral surface of the radiation guide unit 20 of the above embodiment is covered with the mesh 26, it may not be covered with the mesh 26.

(3) The ring guide 21 of the above embodiment has a tapered shape with a diameter increased as it is away from the upstream small diameter portion 13, but conversely, a tapered shape with a diameter gradually increased toward the upstream small diameter portion 13. Alternatively, it may be flat.

(4) In the radiation guide portion 20 of the above-described embodiment, the portion of the center member 24 that faces the upstream small diameter portion 13 side through the cylindrical portion 23 is the circular flat surface 24F, but it faces the upstream small diameter portion 13. It may be a shape that protrudes in a tapered shape or a shape that bulges into a dome shape, or a recessed surface on the back side of the terminal tapered guide 25 instead of the circular flat surface 24F may face the upstream small diameter portion 13 side. Good. Further, a sound absorbing member may be laid on the portion of the center member 24 facing the upstream side small diameter portion 13 through the cylindrical portion 23.

(5) The silencer 30 of the above embodiment is provided as a part of the ultrasonic flow meter 10, but may be separate from the ultrasonic flow meter 10.

(6) Although the radiation guide part 20 of the said embodiment was a cup structure, it may be a trumpet structure like the radiation guide part 50 shown in FIG. Specifically, each of the plurality of ring guides 51 of the radiation guide portion 50 shown in FIG. 8 has a shape that expands in a trumpet shape toward the upstream side, and is as large as the ring guide 51 arranged on the upstream side. The diameter and the minimum diameter are configured to be small. Then, the opening having the smallest diameter of the most upstream ring guide 51 is covered with the center member 52 from the upstream side, and the ring guide 51 group is fixed by the connecting members 53 extending radially from the center member 52. Further, the abutting struts 54 protrude from the plurality of connecting members 53, and the radiation guide portion 50 is piped in a state in which the abutting struts 54 are abutted against the step surfaces of the upstream small diameter portion 13 and the intermediate enlarged diameter portion 14. A ring guide 51 that is fixed to the case 11 and has the largest outer diameter is just fitted into the intermediate enlarged diameter portion 14. Even if it is such a structure, while being able to remove an acoustic noise, the radiation | emission guide part 50 becomes compact in the axial direction of the pipe-shaped case 11. FIG. In addition, you may attach to the pipe-shaped case 11 by making the upstream and downstream sides of this radiation guide part 50 reverse. That is, the radiation guide part 50 may be attached to the pipe-shaped case 11 in a state where the abutting support 54 is pushed up on the step surface between the intermediate enlarged diameter part 14 and the downstream small diameter part 15.

DESCRIPTION OF SYMBOLS 11 Pipe type case 13 Upstream side small diameter part 14 Middle diameter expansion part 15 Downstream side small diameter part 15A Corner circular arc surface 20, 50 Radiation guide part 21, 51 Ring guide 21A, 24A Bolt insertion hole 21B Spacer protrusion 22 Annular gap 23 Cylindrical part 24,52 Center member 25,25C End taper guide 26 Mesh 27 Sound absorbing member 28 Skeleton sleeve 28A Support ring 28B Connection bar 30 Silencer

Claims (11)

A pipe-type case connected in the middle of a pipe that allows fluid to flow in one direction;
An intermediate enlarged portion formed by expanding the inner diameter of the intermediate portion in the axial direction of the pipe-shaped case and an upstream small diameter portion on the upstream side thereof;
A radiation guide part that is provided in the intermediate diameter expansion part and prohibits all straight advancement of the fluid that has traveled straight from the upstream small diameter part and guides it sideways or diagonally forward or diagonally backward;
The radiation guide part has an annular shape surrounding the central axis of the pipe-shaped case and is arranged adjacent to each other with an annular clearance in the direction of the central axis, and the one of the multiple ring guides on the one end side. A silencer comprising a center member that covers an inner opening of the ring guide.   The radiation guide portion has a cup structure in which one end opening of a cylindrical portion formed by laminating the ring guides in the axial direction of the pipe-shaped case with the annular gap therebetween is covered with the center member, and the upstream side The silencer according to claim 1, wherein an opening side end of the cylindrical portion is connected to a downstream opening edge of the small diameter portion.   The silencer according to claim 2, wherein each of the ring guides has a tapered shape whose diameter is increased in a direction away from the upstream small diameter portion.   4. The silencer according to claim 2, further comprising a terminal taper guide that protrudes from the center member opposite to the upstream small-diameter portion and gradually decreases in diameter toward the front.   The pipe-shaped case is provided with a downstream small diameter portion having a stepped diameter reduced from the downstream end portion of the intermediate enlarged diameter portion, and the downstream small diameter portion projects into the distal end portion of the end tapered guide. The silencer according to claim 4.   The center member and the plurality of ring guides are formed with bolt insertion holes through which a common bolt penetrates, and the ring guide or the center adjacent to the surface of the plurality of ring guides on the center member side is formed. The silencer according to any one of claims 2 to 5, further comprising a spacer protrusion for forming the annular gap with a member.   The silencer according to any one of claims 2 to 6, further comprising a mesh that covers the cylindrical portion from the outside or the inside.   The silencer according to any one of claims 1 to 7, wherein an inner peripheral surface of the intermediate enlarged diameter portion is covered with a sound absorbing member. A skeleton sleeve formed by connecting a plurality of connecting bars extending in the axial direction of the intermediate enlarged portion between a pair of support rings fitted inside the intermediate enlarged portion;
The silencer according to claim 8, wherein the sound absorbing member has a sheet shape and is wound around an outer periphery of the skeleton sleeve.   The pipe-shaped case is provided with a downstream small-diameter portion having a stepped diameter reduced from a downstream end of the intermediate large-diameter portion, and a step surface between the intermediate large-diameter portion and the downstream small-diameter portion. The silencer according to any one of claims 1 to 9, wherein a corner arc surface that is continuous with the step surface and the inner peripheral surface is provided at a corner of the downstream small-diameter portion with the inner peripheral surface. . The radiation guide portion is fitted at an intermediate position in the axial direction of the intermediate enlarged diameter portion,
The plurality of ring guides of the radiation guide part each have a shape that expands in a trumpet shape as it approaches the upstream small-diameter part and is arranged closer to the upstream small-diameter part. The minimum diameter is configured to be small,
2. The silencer according to claim 1, wherein the center member covers an opening having a minimum diameter of the ring guide closest to the upstream small-diameter portion from the upstream small-diameter portion side.