JP2017227201A - Silencer and supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silencer and a supercharger capable of effectively reducing noise at a specified frequency.SOLUTION: A silencer 21 is equipped with a body portion 23 which includes a cylindrical portion 27 including an introducing port of gas from the outside, and a cover portion 29 blocking one end of the cylindrical portion 27; a cover portion 25 provided on an outer peripheral side of the cylindrical portion 27 so as to cover the cylindrical portion 27; an air supply port 30 which forms a circle about a rotary axis A, and sends gas in the body portion 23 to a suction port 9 of a compressor 3; and a curved wall portion 31 which is provided in the body portion 23 and curves so as to project out in the rotary axis A direction from a periphery of the air supply port 30 toward the cover portion 29. In a range of the cover portion 29, the cover portion 25, and the curved wall portion 31, at least two kinds of sound absorption materials with different sound absorption characteristics are arranged.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a silencer and a supercharger.

  A technique for reducing noise in a compressor, a supercharger, or the like is known. In the compressor described in Patent Document 1, a cavity is formed between the central portion and the upper portion of the casing. In the central part of the casing, an opening such as a slot for communicating the cavity and the inflow channel is formed. In the compressor described in Patent Document 2, the inlet of the housing serves as a silencer, and a plurality of noise attenuation openings are formed on the inner surface of the housing along the length of the inlet. The noise attenuation opening is covered with a sound absorbing material. The intake silencer cover described in Patent Document 3 covers the intake silencer connected to the air intake port of the exhaust turbine supercharger. A sound absorbing material is provided on the inner surface of the outer peripheral plate of the intake silencer cover. The sound absorbing material is held between the inner surface of the outer peripheral plate and a porous plate that is detachably fixed to the inner surface of the outer peripheral plate.

JP 2011-94618 A International Publication No. 2006/090152 Japanese Patent Laying-Open No. 2015-151940

  Conventionally, when a sound absorbing material is used, the sound absorption volume is increased by increasing the thickness and amount of the sound absorbing material, and noise reduction is realized. On the other hand, there are cases where space is limited, and there is a limit to the amount of sound absorbing material (installation area, thickness, etc.) that can be installed.

  Noise that can be generated by a compressor or the like has some frequency characteristics. As described above, it is difficult to effectively reduce noise at a specific frequency only by increasing the amount of the sound absorbing material. An object of the present invention is to provide a silencer and a supercharger that can effectively reduce noise even when sound of a specific frequency is included.

  One aspect of the present invention is a silencer that is attached to the compressor inlet side of a turbocharger, and has a cylindrical portion that has an axis in the rotational axis direction of an impeller of the compressor and includes a gas inlet from the outside. An opening end that is provided on the outer peripheral side of the cylindrical portion so as to cover the cylindrical portion and opens on the opposite side of the compressor in the rotational axis direction. A cover part including a part, a circular shape centering on the rotation axis, an air supply port provided in the main body part at a position on the suction port side of the compressor, and a cover part provided in the main body part from the periphery of the air supply port And a curved wall portion curved so as to protrude in the direction of the rotation axis, and at least two types of sound absorbing materials having different sound absorption characteristics are disposed in the range of the lid portion, the cover portion, and the curved wall portion of the main body portion Has been.

  The silencer includes a cover portion that covers the cylindrical portion of the main body portion. When the supercharger operates, the gas is sent to the suction port of the compressor through the opening end of the cover part, the introduction port of the cylindrical part, and the air supply port. On the other hand, the sound generated with the rotation of the impeller of the compressor passes through the air supply port and is emitted to the outside while hitting the lid portion, the curved wall portion, the cover portion, or the like of the main body portion. According to this silencer, at least two types of sound absorbing materials having different sound absorbing characteristics are disposed in the range of the lid portion, the cover portion, and the curved wall portion of the main body portion. The sound absorption characteristic of the sound absorbing material indicates a sound absorption rate corresponding to the frequency. For example, a certain sound absorbing material has a high sound absorption coefficient in a high sound range or a medium high sound range, and a certain sound absorbing material has a high sound absorption coefficient in a medium sound range or a low sound range. By arranging at least two kinds of sound absorbing materials having different sound absorption characteristics, even when noise including sound of a specific frequency is generated, the noise can be effectively reduced. This specific frequency can be any frequency. For example, effective sound absorption is possible even with respect to a blade passing frequency (BPF) sound, which is a major problem in a turbocharger.

  In some embodiments, the at least two types of sound absorbing materials include two of wool, a non-woven structure made of batting material, punched metal, and foamed rubber. Nonwoven structures made of wool, batting material, punching metal, and foamed rubber have different sound absorption characteristics. By combining these, effective sound absorption in a wide range is possible.

  Some embodiments include a layered structure in which any one of a lid, a cover, and a curved wall, any one of a sound absorbing material, and a perforated plate-like member that forms an air layer are stacked. In this case, a structure showing a high sound absorption rate at a specific frequency is realized by utilizing the resonance of air.

  In some embodiments, the foam rubber includes a plurality of holes extending in the thickness direction. In this case, by providing the foamed rubber including the hole, the vibration of the surface of the foamed rubber with respect to the sound wave can be adjusted by the opening of the hole. Thereby, the frequency used as sound absorption object can be adjusted.

  In some embodiments, the cross section perpendicular to the thickness direction of the hole is polygonal. In this case, the exposed area of the foamed rubber is increased by providing the foamed rubber as the sound absorbing material with a hole having a polygonal cross section. Thereby, the sound absorption performance of the foamed rubber can be exhibited in a limited space.

  The supercharger of the present invention includes any of the above silencers. According to this supercharger, noise generated in the compressor can be effectively reduced.

  According to some aspects of the present invention, even when noise including sound of a specific frequency is generated, the noise can be effectively reduced.

It is sectional drawing which shows the supercharger which concerns on 1st Embodiment of this invention. It is sectional drawing which shows notionally the flow of the gas in the supercharger of FIG. It is sectional drawing which shows notionally the discharge route of the noise in the supercharger of FIG. It is sectional drawing which shows the silencer which concerns on 2nd Embodiment. It is sectional drawing which shows the layer structure of the silencer of FIG. It is sectional drawing which shows the silencer which concerns on 3rd Embodiment. FIG. 7A is a plan view of the foamed rubber in FIG. 6, and FIG. 7B is a perspective view showing the hole of the foamed rubber in FIG. It is a figure which shows the sound absorption test result which concerns on Example 1 and a comparative example. It is a figure which shows the sound absorption test result which concerns on Example 2 and a comparative example. It is a figure which shows the sound absorption test result which concerns on Example 3 and a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

  FIG. 1 is a cross-sectional view of a supercharger 1 according to the first embodiment, including a cross section including a rotation axis A. The supercharger 1 is applied to an internal combustion engine of a ship or a vehicle, for example. As shown in FIG. 1, the supercharger 1 includes a turbine 2 and a compressor 3. The turbine 2 includes a turbine housing 4 and a turbine impeller 6 housed in the turbine housing 4. The turbine housing 4 has a scroll channel 16 extending in the circumferential direction around the turbine impeller 6. The compressor 3 includes a compressor housing 5 and a compressor impeller 7 housed in the compressor housing 5. The compressor housing 5 has a scroll passage 17 extending in the circumferential direction around the compressor impeller 7.

  The turbine impeller 6 is provided at one end of the rotating shaft 14, and the compressor impeller 7 is provided at the other end of the rotating shaft 14. A bearing housing 13 is provided between the turbine housing 4 and the compressor housing 5. The rotating shaft 14 is rotatably supported by the bearing housing 13 via a bearing 15, and the rotating shaft 14, the turbine impeller 6 and the compressor impeller 7 rotate around the rotation axis A as an integral rotating body 12.

  The turbine housing 4 is provided with an exhaust gas inlet (not shown) and an exhaust gas outlet 10. Exhaust gas discharged from an internal combustion engine (not shown) flows into the turbine housing 4 through the exhaust gas inlet, flows into the turbine impeller 6 through the scroll passage 16, and rotates the turbine impeller 6. Thereafter, the exhaust gas flows out of the turbine housing 4 through the exhaust gas outlet 10.

  The compressor housing 5 is provided with a suction port 9 and a discharge port (not shown). When the turbine impeller 6 rotates as described above, the compressor impeller 7 rotates via the rotating shaft 14. The rotating compressor wheel 7 sucks external air through the suction port 9, compresses it, and discharges it from the discharge port through the scroll flow path 17. The compressed air discharged from the discharge port is supplied to the aforementioned internal combustion engine.

  Further, the supercharger 1 includes a silencer 21 attached to the suction port 9 of the compressor 3. Air supplied to the compressor 3 from the outside is sucked into the suction port 9 of the compressor 3 via the silencer 21. The silencer 21 reduces the release of noise generated in the compressor impeller 7 to the outside. The silencer 21 is of a so-called “inverted type”. In FIG. 1, a cross-sectional view of the silencer 21 is shown, but the silencer 21 has a three-dimensional shape of a rotating body formed by rotating the cross section shown in FIG. 1 around the rotation axis A.

  The main body portion 23 of the silencer 21 includes a cylindrical portion 27 that has a cylindrical shape, and a circular lid portion 29 that closes one end of the cylindrical portion 27. The silencer 21 is attached to the compressor housing 5 so that the cylinder axis of the cylindrical portion 27 and the rotation axis A substantially coincide with each other. The lid part 29 does not allow air to pass therethrough. On the other hand, the cylindrical portion 27 is made of a metal plate (for example, punching metal) having a structure that allows air to pass therethrough, and air from the outside passes through the cylindrical portion 27 in the radial direction and is introduced into the main body portion 23. That is, the entire peripheral wall surface of the cylindrical portion 27 functions as an inlet for introducing air from outside in the radial direction. A filter 39 may be provided on the outer peripheral surface of the cylindrical portion 27 so as to cover the cylindrical portion 27.

  The silencer 21 includes an air supply port 30 provided in the main body 23 at a position on the suction port 9 side of the compressor 3. The air supply port 30 sends air introduced from the outside to the compressor 3 side. The air supply port 30 has a circular shape centered on the rotation axis A and is connected to the suction port 9 of the compressor 3.

  The silencer 21 includes a curved wall portion 31 that is curved so as to protrude in the direction of the rotation axis A from the periphery of the air supply port 30 toward the lid portion 29 in the main body portion 23. The curved wall portion 31 is connected to the suction port 9 to form a cylindrical inner tube portion 31a that forms the air supply port 30, and an outer portion that is provided on the radially outer side of the inner tube portion 31a and connected to the cylindrical portion 27. The cylinder part 31b and the top part 31c which connects these between the inner cylinder part 31a and the outer cylinder part 31b are included. An annular cavity is defined in the curved wall portion 31 by the inner tube portion 31a, the outer tube portion 31b, and the top portion 31c.

  The inner cylinder portion 31a is formed of a punching metal including a large number of holes. As an example, a punching metal having a hole diameter of 3 mm, a hole pitch of 4 mm, and a thickness of 0.8 mm can be used for the inner cylinder portion 31a. On the other hand, the outer cylinder part 31b has a shape corresponding to a part of a conical surface. In the outer cylinder portion 31b, the end portion on the compressor 3 side connected to the cylindrical portion 27 has a large diameter, and the diameter decreases toward the end portion on the lid portion 29 side (that is, the end portion on the top portion 31c side). ing. The outer cylinder part 31b which makes the inclined surface with respect to the rotating shaft A is formed with the punching metal containing many holes, for example. The punching metal that forms the outer cylinder portion 31b includes a large number of holes arranged radially, for example. As an example, a punching metal having a hole diameter of 3 mm, a hole pitch of 6 mm, and a thickness of 1.2 mm may be used for the outer cylinder portion 31b. In addition, the hole part is not formed in the top part 31c.

  The silencer 21 includes a cover portion 25 provided on the outer peripheral side of the cylindrical portion 27. The cover part 25 is formed of, for example, a cylindrical metal plate (for example, an aluminum plate). The cover portion 25 is provided on the outer peripheral side of the cylindrical portion 27 so as to cover the cylindrical portion 27, the other end of the peripheral wall 25 a (the end portion on the compressor 3 side in the rotation axis A direction), the cylindrical portion 27, And an annular end wall 25c for closing the gap between the two. The peripheral wall 25 a faces the cylindrical portion 27 in a state of being radially separated from the cylindrical portion 27. A cylindrical space having a predetermined width in the radial direction is formed between the peripheral wall 25a and the cylindrical portion 27. The peripheral wall 25a has a shape corresponding to a part of the conical surface. In the peripheral wall 25a, the end on the compressor 3 side connected to the cylindrical portion 27 has a small diameter, and the diameter increases toward the end on the open end 25b side.

  An opening end 25b that opens in an annular shape is provided at one end of the peripheral wall 25a (the end on the opposite side of the compressor 3 in the direction of the rotation axis A). The peripheral wall 25a and the end wall 25c do not transmit air. Therefore, the air from the outside passes through the open end 25b. A flange portion that extends radially inward may be formed at one end of the peripheral wall 25a. In that case, an open end 25 b is formed between the inner peripheral end of the flange portion and the outer peripheral end of the lid portion 29.

  As shown in FIG. 2, external air is taken into the silencer 21 from the open end 25b, passes through the above-described cylindrical portion 27 and the air supply port 30 in the inner cylindrical portion 31a, and the compressor 3 It is delivered to the suction port 9. A part of the air from the cylindrical portion 27 toward the air supply port 30 once flows to the lid portion 29 side in order to bypass the curved wall portion 31, and then flows toward the air supply port 30 by reversing the flow direction. become. More precisely, the curved wall portion 31 inverts the direction of the component in the direction of the rotation axis A in the flow direction for a part of the air from the cylindrical portion 27 toward the air supply port 30.

  In the silencer 21 of the present embodiment, two or more types of sound absorbing materials having different sound absorbing characteristics are arranged in the range of the lid portion 29, the cover portion 25, and the curved wall portion 31 of the main body portion 23. As shown in FIGS. 1 and 3, the silencer 21 includes a sound absorbing structure S <b> 1 provided on the lid portion 29, a sound absorbing structure S <b> 2 provided on the curved wall portion 31, and a sound absorbing structure S <b> 3 provided on the cover portion 25. With.

  Here, the sound absorption characteristic means the relationship (correlation) of the sound absorption rate with respect to the frequency. If there are two sound-absorbing materials having different relationships (correlations) of sound-absorbing rates to frequencies, the sound-absorbing characteristics of these two sound-absorbing materials are different. Even when the materials of the two sound absorbing materials are the same, the sound absorbing characteristics may be different. Even when the materials of the two sound absorbing materials are different, the sound absorbing characteristics are usually different. Hereinafter, each structure will be described.

  The sound absorbing structure S <b> 1 includes a first sound absorbing material 32 provided on the inner surface side of the lid portion 29. For example, the first sound absorbing material 32 is provided on substantially the entire surface of the lid portion 29. The first sound absorbing material 32 has a circular shape and a predetermined thickness. As the first sound absorbing material 32, wool felt is used. The thickness of the wool felt as the first sound absorbing material 32 is, for example, 10 mm. The first sound absorbing material 32 is fixed to the lid portion 29 with screws, rivets, bolts or the like. More specifically, R23M felt may be used as the wool felt. The same applies to the wool felt described below.

  The sound absorbing structure S2 includes a second sound absorbing material 33 provided on the back side of the inner cylinder portion 31a, the top portion 31c, and the outer cylinder portion 31b. For example, the second sound absorbing material 33 is provided on substantially the entire surface of the curved wall portion 31. The second sound absorbing material 33 has a predetermined thickness. As the second sound absorbing material 33, wool felt is used. The thickness of the wool felt as the first sound absorbing material 32 is, for example, 10 mm. The first sound absorbing material 32 is in close contact with the inner surfaces of the inner cylinder portion 31a, the top portion 31c, and the outer cylinder portion 31b.

  Furthermore, the sound absorbing structure S <b> 2 includes a third sound absorbing material 34 filled in an annular cavity in the curved wall portion 31. The third sound absorbing material 34 may be provided without a gap in the curved wall portion 31 (in the space surrounded by the second sound absorbing material 33), or may be provided with a slight gap. As the third sound absorbing material 34, a non-woven structure made of a batting material is used. More specifically, cinsalate (registered trademark) is used as the third sound absorbing material 34.

  As described above, punching metal is used for the inner cylinder portion 31a and the outer cylinder portion 31b, but the plate member itself constituting the curved wall portion 31 is also provided as a kind of sound absorbing material. That is, the curved wall portion 31 made of a punching metal constitutes a part of the sound absorbing structure S2.

  The sound absorbing structure S3 includes a fourth sound absorbing material 36 provided on the inner surface side of the peripheral wall 25a and a pressing plate 37 provided on the inner surface side of the fourth sound absorbing material 36. The fourth sound absorbing material 36 and the pressing plate 37 are provided in the vicinity of the opening end 25b or a position reaching the opening end 25b. The fourth sound absorbing material 36 and the pressing plate 37 are provided in the vicinity of the end wall 25c or a position reaching the end wall 25c. In order to avoid interference with fastening members such as bolts for joining the peripheral wall 25a and the end wall 25c, the fourth sound absorbing material 36 and the pressing plate 37 extend to a region excluding those fastening members.

  For example, the fourth sound absorbing material 36 is provided on substantially the entire surface of the peripheral wall 25a. The fourth sound absorbing material 36 has a predetermined thickness. As the fourth sound absorbing material 36, a non-woven structure made of a batting material is used. More specifically, a thinner is used as the fourth sound absorbing material 36. The thickness of the synthate as the fourth sound absorbing material 36 is, for example, 13 mm. The fourth sound absorbing material 36 is sandwiched between the peripheral wall 25a and the pressing plate 37, and is fixed to the peripheral wall 25a with screws, rivets, bolts, or the like.

  For example, the pressing plate 37 faces substantially the entire surface of the peripheral wall 25a. The pressing plate 37 is arranged so as to be parallel to the peripheral wall 25a, but is bent at the end on the opening end 25b side and inclined radially inward. As the pressing plate 37, a punching metal is used. As an example, a punching metal having a hole diameter of 3 mm, a hole pitch of 4 mm, and a thickness of 1.0 mm may be used for the pressing plate 37. At the end where the pressing plate 37 is bent, the gap between the pressing plate 37 and the peripheral wall 25a is widened, and the thickness (the radial width) of the fourth sound absorbing material 36 is increased accordingly.

  The plate member itself constituting the pressing plate 37 is also provided as a kind of sound absorbing material. That is, the pressing plate 37 made of punching metal constitutes a part of the sound absorbing structure S3. In other words, the sound absorbing structure S3 has a three-layer structure formed by the peripheral wall 25a, the fourth sound absorbing material 36, and the pressing plate 37.

  The sound absorbing structure S3 further includes a fifth sound absorbing material 38 provided on the end wall 25c. For example, the fifth sound absorbing material 38 is provided on substantially the entire end wall 25c. The fifth sound absorbing material 38 has an annular shape and has a predetermined thickness. As the fifth sound absorbing material 38, wool felt is used. The thickness of the wool felt as the fifth sound absorbing material 38 is, for example, 4 mm. The fifth sound absorbing material 38 is fixed to the end wall 25c by, for example, adhesion.

  In the supercharger 1 to which the silencer 21 having the above-described configuration is attached, as shown in FIG. And then sent to the suction port 9 of the compressor 3. On the other hand, as shown in FIG. 3, the sound generated with the rotation of the compressor wheel 7 passes through the air supply port 30 and hits the lid portion 29, the curved wall portion 31, the cover portion 25, or the like of the main body portion 23. However, it is emitted to the outside through the open end 25b (some sounds pass through the wall such as the lid 29). According to the silencer 21, at least two types of sound absorbing materials (wool felt, synthalate, and punching metal) having different sound absorbing characteristics are arranged in the range of the lid portion 19, the cover portion 25, and the curved wall portion 31 of the main body portion 23. Has been. The sound absorption characteristic of the sound absorbing material indicates a sound absorption rate corresponding to the frequency. For example, a certain sound absorbing material has a high sound absorption coefficient in a high sound range or a medium high sound range, and a certain sound absorbing material has a high sound absorption coefficient in a medium sound range or a low sound range. By arranging at least two kinds of sound absorbing materials having different sound absorption characteristics, even when noise including sound of a specific frequency is generated, the noise can be effectively reduced.

  This specific frequency can be any frequency. For example, effective sound absorption is possible even for blade passing frequency (BPF) sound, which is a major problem in superchargers. For example, if the engine speed is 60,000 rpm and the number of blades of the compressor wheel 7 (for example, the number of long blades) is 8, the sound source frequency of the compressor 3 is about 8000 Hz (1000 Hz × 8). Can be calculated. Therefore, it is possible to efficiently reduce noise by providing a sound absorbing material or a sound absorbing structure / sound absorbing mechanism having a sound absorbing region around 8000 Hz at an appropriate location. Compared to simply increasing the number of sound absorbing materials, it is possible to reduce the noise in a small space.

  Nonwoven structures made of wool, batting material (for example, synthalate), and punching metal have different sound absorption characteristics. By combining these, effective sound absorption in a wide range is possible.

  By combining a perforated plate (punching metal) and a sound absorbing material, it is possible to cover a region where each sound absorption coefficient is low and to effectively absorb sound in a wide range.

  According to the supercharger 1 including the silencer 21, noise generated in the compressor 3 can be effectively reduced. Noise reduction is achieved while maintaining fluid performance.

  Next, the silencer 21A according to the second embodiment will be described. As shown in FIG. 4, the silencer 21 </ b> A employs a resonance structure including an air layer at a plurality of locations. Specifically, the sound absorbing structure S1A includes a plate-like spacer (plate-like member) 41 provided on the inner surface side of the lid portion 29, a first sound absorbing material 42 provided on the inner surface side of the spacer 41, and a first It includes a spacer 41 and a pressing plate 43 that presses the first sound absorbing material 42 and is provided on the inner surface side of the sound absorbing material 42. In other words, the sound absorbing structure S1A has a multilayer structure (laminated structure) in which the lid portion 29, the spacer 41, the first sound absorbing material 42, and the pressing plate 43 are overlapped. The spacer 41 includes a large number of holes. As the spacer 41, for example, a honeycomb panel having a thickness of 1.5 mm can be used. As the first sound absorbing material 42, for example, a wool felt having a thickness of 5 mm may be used. As the pressing plate 43, for example, a punching metal having a hole diameter of 3 mm, a hole pitch of 4 mm, and a thickness of 1.0 mm can be used.

  The sound absorbing structure S <b> 2 </ b> A includes a sixth sound absorbing material 48 provided on the back surface side of the inner cylindrical portion 31 a, a plate-like spacer (plate-like member) 47 provided on the back surface side of the sixth sound absorbing material 48, A pressing plate 49 provided on the back surface side and pressing the sixth sound absorbing material 48 and the spacer 47 is included. In other words, the sound absorbing structure S2A has a multilayer structure in which the inner cylindrical portion 31a, the sixth sound absorbing material 48, the spacer 47, and the pressing plate 49 are stacked. The spacer 47 includes a large number of holes. As the spacer 47, for example, a honeycomb panel having a thickness of 1.5 mm can be used. As the sixth sound absorbing material 48, for example, a wool felt having a thickness of 5 mm may be used. As the pressing plate 49, for example, a punching metal having a hole diameter of 3 mm, a hole pitch of 4 mm, and a thickness of 0.8 mm can be used. In the sound absorbing structure S2A, the second sound absorbing material 33 is provided on the back surface side of the outer cylinder portion 31b, but the second sound absorbing material 33 is not provided on the back surface side of the inner cylinder portion 31a.

  The sound absorbing structure S3A includes a plate-like spacer (plate-like member) 51 provided on the inner surface side of the peripheral wall 25a, a fourth sound absorbing material 52 provided on the inner surface side of the spacer 51, and an inner surface side of the fourth sound absorbing material 52. And a pressing plate 53 that presses the spacer 51 and the fourth sound absorbing material 52. In other words, the sound absorbing structure S3A has a multilayer structure in which the peripheral wall 25a, the spacer 51, the fourth sound absorbing material 52, and the pressing plate 53 are stacked. The spacer 51 includes a large number of holes. As the spacer 51, for example, a honeycomb panel having a thickness of 1.5 mm can be used. For example, a wool felt having a thickness of 5 mm may be used as the fourth sound absorbing material 52. As the pressing plate 53, for example, a punching metal having a hole diameter of 3 mm, a hole pitch of 4 mm, and a thickness of 1.0 mm can be used.

  In these sound absorbing structures S1A, S2A, and S3A, the sound absorbing material layer (that is, the wool felt layer) and the spacer layer (that is, the honeycomb panel layer) are regarded as a total air layer to form a resonance structure. doing. For example, as shown in FIG. 5, an air layer L having a thickness H is formed by the spacer 51 having a thickness h1 and the fourth sound absorbing material 52 having a thickness h2. The thickness h2 is larger than the thickness h1. The thickness h1 (corresponding to the thickness of the air layer L) is about 1 to 1.5 mm, and the thickness h2 is about 5 to 5.5 mm. The hole diameter and pitch of the punching metal, the thickness of the wool felt, and the thickness of the air layer L in the sound absorbing structures S1A, S2A, and S3A are the natural frequencies (natural frequencies) when the sound absorbing structure is regarded as a resonance sound absorbing mechanism based on the Helmholtz resonance frequency. Frequency) equation. The sound absorption region of this resonance structure is a mid-low range. Although the sound absorbing structure S3A has been described as an example, the sound absorbing structure S1A and the sound absorbing structure S2A can have the same configuration.

  Furthermore, in the sound absorbing structures S1A, S2A, and S3A, the fourth sound absorbing material 52 (that is, a layer of wool felt) that is a porous material is used. The sound absorption region of the porous material is a high temperature region. As described above, a structure having a high sound absorption coefficient in a high temperature range composed of a porous material and a rigid wall is combined with a structure having a high sound absorption coefficient in a mid-low sound range composed of a resonance structure and a perforated plate.

  Also with the silencer 21A, the same operations and effects as the silencer 21 described above can be achieved. Furthermore, a structure that exhibits a high sound absorption rate at a specific frequency is realized using the resonance of air.

  Next, the silencer 21B according to the third embodiment will be described. As shown in FIG. 6, in the silencer 21B, foamed rubber including a large number of holes is used. The sound absorbing structure S <b> 1 </ b> B includes a first sound absorbing material 32 provided on the inner surface side of the lid portion 29 and a foamed rubber 56 provided on the inner surface side of the first sound absorbing material 32. As the foam rubber 56, a semi-independent foam (bubble) type may be used. Although there are types of closed foam (bubbles) and continuous foam (bubbles), it is desirable to use a semi-closed foam (bubble) type. The thickness of the foam rubber 56 is, for example, about 10 mm. The foam rubber 56 is made of EPDM, for example. The hole of the foamed rubber 56 has a columnar shape, for example. The diameter of the hole is, for example, about 10 mm. More specifically, EPT SEALER (registered trademark) can be used as the foamed rubber 56. As the foam rubber 56, PORON (registered trademark) L-24 (manufactured by INOAC Corporation) may be used. The sound absorbing structure S3B includes a fourth sound absorbing material 36 provided on the inner surface side of the peripheral wall 25a and a foam rubber 57 provided on the inner surface side of the fourth sound absorbing material 36. The material, thickness, and specific example of the foam rubber 57 may be the same as those of the foam rubber 56 described above. The sound absorbing structure S2B has the same configuration as the sound absorbing structure S3 of the silencer 21.

  Also with the silencer 21B, the same operations and effects as the silencer 21 described above can be achieved. Further, by providing the foamed rubber 57 including the hole, the vibration of the surface of the foamed rubber 57 with respect to the sound wave can be adjusted by the opening of the hole. Thereby, the frequency used as sound absorption object can be adjusted.

  As shown in FIGS. 7A and 7B, the hole 57a of the foamed rubber 57 may have a polygonal shape such as a star in cross section perpendicular to the thickness direction. By providing the foamed rubber 57 with holes 57a having a polygonal cross section, the surface area of the exposed surface 57b of the foamed rubber 57 is increased. By maximizing the surface area of the exposed surface 57b, the sound absorbing performance of the foamed rubber 57 can be maximized in a limited space. Although the foam rubber 57 has been described as an example, the foam rubber 56 may be provided with a hole having a polygonal cross section such as a star shape.

  Subsequently, a comparison result of the noise level will be described with reference to FIGS. 8-10 is a figure which shows the sound-absorption test result based on Examples 1-3 and a comparative example, respectively.

  Example 1 shown in FIG. 8 has the same configuration as the silencer 21 according to the first embodiment described above. As shown in FIG. 8, noise drop (that is, reduction) that could not be obtained in the comparative example was confirmed at a plurality of frequencies. Improvement of sound absorption performance was confirmed over a wide range of 13 kHz or higher.

  Example 2 shown in FIG. 9 has the same configuration as the silencer 21A according to the second embodiment described above. As shown in FIG. 9, noise drop (that is, reduction) that could not be obtained in the comparative example was confirmed at a plurality of frequencies.

  Example 3 shown in FIG. 10 has a configuration similar to that of the silencer 21B according to the above-described third embodiment (form having a cylindrical hole). As shown in FIG. 10, noise drop (that is, reduction) that could not be obtained in the comparative example was confirmed at a plurality of frequencies.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. As the non-woven structure made of the batting material, a material other than synthetic acid may be applied. The wool is not limited to the above-mentioned wool felt, but may be other types of wool. The hole diameter and pitch of the punching metal are not limited to the specific examples described above, and can be changed as appropriate. The positional relationship between the foamed rubber and other sound absorbing material may be reversed. It is not limited to the case where the sound absorbing material is stacked on the air layer, and only the air layer may be used. A perforated plate and an air layer may be stacked. A sound absorbing material other than a non-woven structure made of wool, batting material, punching metal, or foamed rubber may be used. Only two types of sound absorbing materials having different sound absorbing characteristics may be provided, or three or more types of sound absorbing materials may be provided.

DESCRIPTION OF SYMBOLS 1 Supercharger 3 Compressor 7 Compressor impeller 9 Inlet 21 Silencer 23 Main body part 25 Cover part 25b Open end part 27 Cylindrical part (cylindrical part)
29 Lid portion 30 Air supply port 31 Curved wall portion 32 First sound absorbing material 33 Second sound absorbing material 34 Third sound absorbing material 36 Fourth sound absorbing material 38 Fifth sound absorbing material 41 Spacer (plate-like member)
47 Spacer (plate member)
51 Spacer (plate member)
56 Foam rubber 57 Foam rubber 57a Hole A Rotation axis L Air layer

Claims (6)

A silencer attached to the suction side of the turbocharger compressor,
A main body including a cylindrical portion having an axis in the direction of the rotation axis of the impeller of the compressor and including a gas introduction port from the outside, and a lid for closing one end of the cylindrical portion;
A cover part including an opening end provided on the outer peripheral side of the cylindrical part so as to cover the cylindrical part and opening on the opposite side of the compressor in the rotational axis direction;
A circular shape centering on the rotational axis, and an air supply port provided in the main body at a position on the suction port side of the compressor,
A curved wall portion provided in the main body portion and curved so as to protrude from the periphery of the air supply port toward the lid portion in the rotation axis direction;
A silencer in which at least two types of sound absorbing materials having different sound absorbing characteristics are disposed in the range of the lid portion, the cover portion, and the curved wall portion of the main body portion.   The silencer according to claim 1, wherein the at least two types of sound absorbing materials include two of wool, a non-woven structure made of a batting material, a punching metal, and foamed rubber.   3. A layered structure in which any one of the lid, the cover, and the curved wall, one of the sound absorbing materials, and a perforated plate-like member that forms an air layer is provided. The silencer described in 1.   The silencer according to claim 2, wherein the foamed rubber includes a plurality of holes extending in a thickness direction.   The silencer according to claim 4, wherein a cross section of the hole portion perpendicular to the thickness direction has a polygonal shape.   A turbocharger provided with the silencer as described in any one of Claims 1-5.

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