Gas compressor

Abstract

A gas compressor 100 is provided with a suction duct 2, a compressor 3, and a plurality of noise reduction portions 230 for reducing noise generated by operation of the compressor 3. The noise reduction portions 230 are provided inside the suction duct 2 and at different positions in the extending direction of the suction duct 2. One side of a rectangular cross-section of each noise reduction portion 230 has the cross-sectional length different from the length of one side of a rectangular cross-section of the suction duct 2. In each noise reduction portion 230, the cross-sectional length varies according to the wavelength of noise corresponding to a plurality of frequencies at which the sound pressure level of the noise reaches a peak. The cross-sectional length is longer than half the wavelength of each noise and shorter than one wavelength.

Description

Gas compressor

[0001] The present invention relates to a gas compressor.

[0002] Conventionally, gas compressors that take in outside air and produce compressed gas have been known. In gas compressors, gas is taken in from the outside through an outside air intake connected to a compression mechanism, and the taken-in gas is compressed. Noise generated by the operation of the compression mechanism is output to the outside of the gas compressor through the outside air intake.

[0003] Patent Document 1 discloses a technology for reducing noise in a predetermined frequency band by forming multiple passages with partitions provided in a duct connecting a compression mechanism and an outside air intake. In this case, sound-absorbing material is attached to the partitions, and the length of one side of the multiple passages is formed to be longer than half the wavelength of the noise to be absorbed but shorter than one wavelength.

[0004] Japanese Patent Application Laid-Open No. 2022-332659

[0005] However, it is not possible to reduce noise with wavelengths different from the wavelength corresponding to the cross-sectional length of the passage, and the noise suppression effect is insufficient.

[0006] A gas compressor according to one embodiment includes an intake duct having a rectangular cross section through which gas flowing in from outside passes, a filter connected to the intake duct, a compressor that compresses the gas drawn in through the filter, and a plurality of noise reduction units that reduce noise generated by operation of the compressor. The plurality of noise reduction units are provided inside the intake duct at different positions in the extension direction of the intake duct. One side of the rectangular cross section of each of the noise reduction units has a cross-sectional length that is different from the length of one side of the intake duct having the rectangular cross section. The cross-sectional length of each of the noise reduction units varies depending on the wavelengths of noise corresponding to a plurality of frequencies at which the sound pressure level of the noise peaks, and the cross-sectional length is longer than half the wavelength of the noise and shorter than one wavelength.

[0007] According to the present invention, it is possible to reduce noise in a plurality of different frequency bands.

[0008] Fig. 1 is an external perspective view of a gas compressor according to an embodiment; Fig. 2 is an external perspective view of a gas compressor according to an embodiment; Fig. 3 is a diagram schematically showing the configuration of a main part of a gas compressor according to a first embodiment; Fig. 4 is a diagram schematically showing the relationship between the frequency and sound pressure level of noise generated by a gas compression mechanism; Fig. 5 is a diagram schematically showing the configuration of a main part of a gas compressor according to a second embodiment; Fig. 6 is a diagram showing the range of cross-sectional lengths;

[0009] First Embodiment A gas compressor according to a first embodiment of the present invention will now be described in detail with reference to the drawings.

[0010] 1A and 1B are external perspective views of a gas compressor 100 according to a first embodiment. Fig. 2 is a diagram schematically illustrating the configuration of a main part of the gas compressor 100 according to the first embodiment.

[0011] Gas compressor 100 includes compressor 3, housing 201 provided with suction duct 2, and drive mechanism 21. Compressor 3 is disposed on one surface of housing 201 via a connecting flow path 5. In addition, an intake port 8 is formed on the other surface of housing 201, which takes in gas from outside gas compressor 100.

[0012] In the following description, one side of the housing 201, i.e., the side where the compressor 3 is arranged, may be referred to as the front side, and the other side of the housing 201, i.e., the side where the inlet 8 is formed, may be referred to as the rear side. For this reason, Fig. 1A is an external perspective view of the gas compressor 100 as seen from the front side, and Fig. 1B is an external perspective view of the gas compressor 100 as seen from the rear side.

[0013] <Compressor 3> Compressor 3 has an inlet 1 and a gas compression mechanism 4. Inlet 1 is connected to a connection flow path 5 of an intake duct 2, which will be described later. Gas outside gas compressor 100 flows through the intake duct 2 and is supplied to the gas compression mechanism 4 via inlet 1.

[0014] The gas compression mechanism 4 is, for example, a screw rotor compressor having a male screw rotor and a female screw rotor, and compresses gas by rotating the male screw rotor and the female screw rotor. The gas compression mechanism 4 operates when the male screw rotor and the female screw rotor are rotationally driven by a drive mechanism 21, which will be described later. The gas compressed by the gas compression mechanism 4 is discharged through the discharge port 13.

[0015] The gas compression mechanism 4 is not limited to a screw rotor type. The gas compression mechanism 4 may be, for example, a reciprocating type that compresses gas by the reciprocating motion of a piston, or a turbo type that compresses gas by using centrifugal force generated by the rotation of an impeller.

[0016] <Drive mechanism 21> The drive mechanism 21 has a control device 20, a motor 18, a power supply / control line 19, and a power transmission mechanism 16. The control device 20 controls the operation of the gas compression mechanism 4 by controlling the rotational drive of the motor 18. The motor 18 receives a control signal output from the control device 20 via the power supply / control line 19 and performs rotational drive in response to the control signal. The power transmission mechanism 16 is, for example, a shaft provided along the rotation axis of the motor 18, and is connected to the screw rotor of the gas compression mechanism 4. The rotation of the power transmission mechanism 16 together with the rotation of the motor 18 rotates the screw rotor connected to the power transmission mechanism 16, thereby operating the gas compression mechanism 4.

[0017] <Intake Duct 2> The intake duct 2 is provided in the housing 201. The intake duct 2 has a connecting flow path 5, a flow path 210, a dust filter 220, and a noise reduction unit 230. The flow path 210 is made of sheet metal and has a rectangular cross section. An inlet 8 is formed at one end of the flow path 210, and a connecting flow path 5 is provided at the other end. Gas taken in from outside the gas compressor 100 via the inlet 8 passes through the flow path 210 and reaches the compressor 3 via the connecting flow path 5. In other words, gas flowing in from outside passes through the intake duct 2. The inlet 8 side of the flow path 210 may be referred to as the upstream side, and the connecting flow path 5 side may be referred to as the downstream side.

[0018] In this embodiment, the flow path 210 is bent at two bent portions 211 and 212 so that the direction of gas flow is changed. Specifically, the flow path 210 is composed of a first flow path 213, a second flow path 214, and a third flow path 215. The first flow path 213 is provided downstream of the bent portion 212 and is a straight portion extending along the first direction. The third flow path 215 is provided upstream of the bent portion 211 and is a straight portion extending along the first direction. The second flow path 214 is provided between the first flow path 213 and the third flow path 215 and is a straight portion extending along the second direction. That is, the flow path 210 of the suction duct 2 has multiple bent portions 211 and 212 and multiple straight portions, namely the first flow path 213, the second flow path 214, and the third flow path 215.

[0019] The first direction is a direction intersecting the front-rear direction of the housing 201 and may also be referred to as the left-right direction. The second direction is a direction intersecting the front-rear direction and the left-right direction and may also be referred to as the up-down direction.

[0020] The gas taken in from the inlet 8 flows to the right along the third flow path 215. Thereafter, the flow direction of the gas in the flow path 210 is changed downward at the bent portion 211, and the gas flows along the second flow path 214. Then, the flow direction of the gas in the flow path 210 is changed to the left at the bent portion 212, and the gas flows through the first flow path 213.

[0021] The flow path 210 is not limited to being bent at two locations, but may be bent at three or more locations.

[0022] The dust filter 220 is housed in a space 240 formed downstream of the first flow path 213, i.e., in a position close to the connection flow path 5. The dust filter 220 is made of a porous synthetic resin such as a sponge. The dust filter 220 has a cylindrical shape. The dust filter 220 captures dust contained in the gas flowing through the flow path 210. As a result, the gas from which the dust has been removed is supplied to the compressor 3 via the connection flow path 5 and compressed by the compressor 3.

[0023] <Noise reduction section 230> The noise reduction section 230 is provided to reduce noise generated by the operation of the gas compression mechanism 4 of the compressor 3. The noise reduction section 230 has a partition plate 10 and a sound-absorbing material 11. The partition plate 10 is a plate-shaped member provided in the flow path 210. The sound-absorbing material 11 is formed from, for example, a urethane foam-based material, glass wool-based material, felt-based material, or the like. The sound-absorbing material 11 is attached to at least one of the partition plate 10 and the flow path 210. Note that the noise reduction section 230 does not necessarily have to have the sound-absorbing material 11.

[0024] Noise generated by the operation of gas compression mechanism 4 is output to both inlet 1 and compressed gas discharge port 13. Inlet 1 communicates with the outside of gas compressor 100 via connecting flow path 5, dust filter 220, space 240, flow path 210, and inlet 8. Therefore, noise output to the inlet 1 side is also output to the outside of gas compressor 100 via connecting flow path 5, dust filter 220, space 240, flow path 210, and inlet 8. Noise reduction unit 230 is provided in flow path 210, and reduces noise output to the outside of gas compressor 100.

[0025] The noise reduction section 230 includes a first noise reduction section 230a provided in the first flow path 213, which is a straight portion of the flow path 210, and a second noise reduction section 230b provided in the second flow path 214, which is a straight portion. More specifically, the first noise reduction section 230a is formed by a first partition plate 10a, which is one of the partition plates 10, provided in the first flow path 213. The second noise reduction section 230b is formed by a second partition plate 10b and a third partition plate 10c, which are one of the partition plates 10, provided in the second flow path 214. That is, each of the multiple noise reduction sections 230 is provided inside the flow path 210 (i.e., the suction duct 2) at a different position in the direction in which the flow path 210 extends.

[0026] The first partition plate 10a is a plate extending in the left-right direction of the first flow path 213. The first partition plate 10a of the first noise reduction section 230a divides the first flow path 213 into a plurality of (two) regions (first divided regions DR1). One of the two first divided regions DR1 is referred to as the first region R1.

[0027] Because the first partition plate 10a extends in the direction in which the first flow passage 213 having a rectangular cross section extends, the first divided region DR1 including the first region R1 also has a rectangular cross section. Therefore, in the first region R1, the length of one side of the rectangular cross section (cross-sectional length) b1 is different from the length of one side of the rectangular cross section of the first flow passage 213 (i.e., the flow passage 210 of the suction duct 2). Note that the cross-sectional length of the first divided region DR1 other than the first region R1 may be equal to or different from the cross-sectional length b1 of the first region R1.

[0028] The second partition plate 10b and the third partition plate 10c are plate-shaped and extend in the vertical direction in which the second flow path 214 extends. The second flow path 214 is divided by the second partition plate 10b and the third partition plate 10c of the second noise reduction section 230b to form multiple (three) regions (second divided regions DR2). Of these three second divided regions DR2, one is referred to as the second region R2 and the other is referred to as the third region R3. The second region R2 is the space between the wall surface of the second flow path 214 and the second partition plate 10b. The third region R3 is the space between the second partition plate 10b and the third partition plate 10c.

[0029] Because the second partition plate 10b and the third partition plate 10c extend in the direction of the second flow path 214, which has a rectangular cross section, the second divided region DR2, including the second region R2 and the third region R3, also has a rectangular cross section. Therefore, the length of one side (cross-sectional length) b2 of the second region R2 having a rectangular cross section is different from the length of one side of the rectangular cross section of the second flow path 214 (i.e., the flow path 210 of the suction duct 2). Similarly, the length of one side (cross-sectional length) b3 of the rectangular cross section of the third region R3 is different from the length of one side of the rectangular cross section of the second flow path 214. The cross-sectional lengths b2 and b3 may be equal to or different from each other. Furthermore, the cross-sectional lengths of the second divided region DR2 other than the second region R2 and the third region R3 may be equal to at least one of the cross-sectional lengths b2 and b3, or may be different from the cross-sectional lengths b2 and b3.

[0030] The third partition plate 10c is not limited to being provided in the second flow path 214, and may be provided in the first flow path 213, or may be provided in both the first flow path 213 and the second flow path 214. That is, the third partition plate 10c may be provided in at least one of the first flow path 213 and the second flow path 214. Furthermore, the third partition plate 10c may not be provided in either the first flow path 213 or the second flow path 214. That is, the second noise reduction unit 230b may have only the second partition plate 10b that divides the second flow path 214 into two second dividing regions DR2.

[0031] As described above, the partition plate 10 causes one side of the rectangular cross section of each of the plurality of noise reduction sections 230 to have a cross-sectional length b1, b2, b3 that is different from the length of one side of the rectangular cross section of the flow path 210 of the suction duct 2. These cross-sectional lengths b1, b2, b3 are determined based on the frequency of the noise generated by the operation of the gas compression mechanism 4.

[0032] The noise generated by the gas compression mechanism 4 includes sounds of various frequencies. Some frequency bands are particularly loud, which makes the noise louder. Although these frequency bands differ depending on the gas compression method used in the gas compression mechanism 4, the ranges of these frequency bands are known.

[0033] Fig. 3 is a diagram schematically showing the relationship between the frequency and sound pressure level (noise intensity) of noise generated from the gas compression mechanism 4. In Fig. 3, the horizontal axis represents the noise frequency [Hz], and the vertical axis represents the noise value [dB], which is the sound pressure level. Fig. 3 shows a case in which peaks in the sound pressure level exist at frequencies f1, f2, f3, and f4 of the noise generated from the gas compression mechanism 4. That is, the sounds at frequencies f1, f2, f3, and f4 are louder. Note that in Fig. 3, frequencies f1, f2, f3, and f4 are representative frequencies of a frequency band in which the sounds become louder.

[0034] In this embodiment, the cross-sectional lengths b1, b2, and b3 are set so as to be able to reduce noise at specific different frequencies among the multiple frequencies f1, f2, f3, and f4. Specifically, the cross-sectional lengths b1, b2, and b3 are set using a wavelength value λ (= speed of sound ÷ frequency) calculated based on the frequency of the noise to be reduced. In other words, the cross-sectional lengths b1, b2, and b3 vary depending on the wavelength of the noise corresponding to the multiple frequencies at which the sound pressure level peaks.

[0035] When the cross-sectional lengths b1, b2, and b3 are λ / 2 or λ, the gas vibrations at the wall surfaces of the first region R1, the second region R2, and the third region R3 increase, resulting in a large transmission loss (sound absorption). Therefore, the partition plate 10 of the noise reduction section 230 is arranged so that the cross-sectional lengths b1, b2, and b3 satisfy the relationship of being longer than half the wavelength and shorter than one wavelength, respectively, with respect to the wavelengths corresponding to different peaks in sound pressure level. Therefore, the first noise reduction section 230a and the second noise reduction section 230b reduce noises of different frequencies.

[0036] In this embodiment, the first partition plate 10a defines a first region R1 having a cross-sectional length b1. The cross-sectional length b1 satisfies the relationship λ1 / 2<b1<λ1, where λ1 is the wavelength (first wavelength) corresponding to the frequency f1 shown in FIG. 3 . That is, the first noise reduction unit 230a reduces noise of the first wavelength.

[0037] The second partition plate 10b defines a second region R2 having a cross-sectional length b2. The cross-sectional length b2 satisfies the relationship λ2 / 2<b2<λ2, where λ2 is a wavelength (second wavelength) corresponding to one of frequencies f2, f3, or f4 (e.g., frequency f2) different from frequency f1 shown in FIG. 3. That is, the second noise reduction unit 230b reduces noise of the second wavelength different from the first wavelength.

[0038] The second partition plate 10b and the third partition plate 10c define a third region R3 having a cross-sectional length b3. The cross-sectional length b3 satisfies the relationship λ3 / 2<b3<λ3, where λ3 is a wavelength (third wavelength) corresponding to one of frequencies f3 and f4 (e.g., frequency f3) that is different from frequencies f1 and f2 shown in FIG. 3 . That is, the second noise reduction unit 230b reduces noise of the third wavelength that is different from the first and second wavelengths.

[0039] As described above, the cross-sectional length b3 may be equal to the cross-sectional length b2. In this case, the noise of the second wavelength is also reduced in the third region R3.

[0040] With the above-described configuration, noise reduction section 230 in flow path 210 can reduce noise having a plurality of different wavelengths corresponding to frequencies at which the sound pressure level peaks, among noise generated from gas compression mechanism 4. As a result, by selectively reducing loud noise, it is possible to lower the overall value of noise generated by gas compression mechanism 4. Furthermore, bends 211 and 212 are provided in flow path 210, and bends 211 and 212 can also reduce overall noise.

[0041] Note that the present invention is not limited to the case where the noise reduction section 230 is provided in the first flow path 213 and the second flow path 214 as described above, and may also be provided in the third flow path 215. Furthermore, the present invention is not limited to the case where the first noise reduction section 230a is provided in the first flow path 213 and the second noise reduction section 230b is provided in the second flow path 214. For example, the first noise reduction section 230a and the second noise reduction section 230b may be provided at a predetermined interval in the first flow path 213. Alternatively, the first noise reduction section 230a and the second noise reduction section 230b may be provided at a predetermined interval in the second flow path 214. Alternatively, three or more noise reduction sections 230 may be provided in the first flow path 213 or the second flow path 214, and each noise reduction section 230 may reduce noise of a different wavelength.

[0042] Furthermore, when the flow path 210 does not have bends 211, 212, the first noise reduction section 230a and the second noise reduction section 230b may be provided at a predetermined interval in the flow path 210. Furthermore, three or more noise reduction sections 230 may be provided in the flow path 210, and each noise reduction section 230 may reduce noise of a different wavelength.

[0043] <Example of Derivation of Cross-Sectional Lengths b1, b2, and b3> An example of derivation of the cross-sectional lengths b1, b2, and b3 when the gas compression mechanism 4 is of a screw rotor type will be described. The main noise generated by the screw rotor type gas compression mechanism 4 is noise based on the meshing frequency. This frequency is calculated by multiplying the male screw rotor rotation speed [rpm] by the number of teeth of the male screw rotor by 60. Noise also increases at frequencies twice, three times, and so on, of this meshing frequency, i.e., frequencies that are integer multiples of this meshing frequency. Applying this to FIG. 3 , frequencies f1, f2, f3, and f4 correspond to the meshing frequency and frequencies that are integer multiples of the meshing frequency. In this case, the magnitude of the noise is not constant but varies depending on various conditions, such as the shape of the screw rotor and the flow path.

[0044] For the above meshing frequency, the wavelength value λ corresponding to the meshing frequency is calculated by dividing the speed of sound [m / s] by the meshing frequency [Hz]. The cross-sectional lengths b1, b2, and b3 are determined within the range from the calculated wavelength value λ to λ / 2.

[0045] When the rotation speed of the male screw rotor is 15,000 rpm and the number of teeth is five, the meshing frequency (i.e., frequency f1 in Figure 3) is 1,250 Hz. If the speed of sound is 340 m / s, the wavelength λ is 0.272 mm. Therefore, the cross-sectional length b1 that satisfies λ / 2 < b < λ is 136 mm to 272 mm. Furthermore, the cross-sectional length b2 for a frequency twice the meshing frequency (i.e., frequency f2 in Figure 3) is in the range of 68 mm to 136 mm. For a frequency three times the meshing frequency (i.e., frequency f3 in Figure 3), the cross-sectional length b3 is in the range of 45.3 mm to 90.6 mm.

[0046] Suppose the sound pressure levels at the meshing frequency (frequency f1 in FIG. 3 ) and the triple frequency (frequency f3 in FIG. 3 ) are particularly high. In this case, the first partition plate 10a of the first noise reduction unit 230a is provided so that the cross-sectional length b1 is 204 mm. This cross-sectional length b1 of 204 mm is, for example, the median value of the range of 136 mm to 272 mm calculated for the meshing frequency as described above. Furthermore, the second partition plate 10b and the third partition plate 10c of the second noise reduction unit 230b are provided so that the cross-sectional length b3 is 68 mm. The cross-sectional length b3 of 68 mm is, for example, the median value of the range of 68 mm to 136 mm calculated for the triple frequency as described above.

[0047] The second partition plate 10b and the third partition plate 10c may be arranged so that the cross-sectional length b2 and the cross-sectional length b3 are the same value, thereby making it possible to reduce noise that can be reduced in the second region R2 also in the third region R3, thereby improving the efficiency of noise reduction.

[0048] The first embodiment described above provides at least one of the following advantageous effects. (1) The gas compressor 100 includes a plurality of noise reduction units 230 that reduce noise generated by the operation of the gas compression mechanism 4. The plurality of noise reduction units 230 are provided inside the suction duct 2 at different positions in the direction in which the suction duct 2 extends. Each of the noise reduction units 230 has a cross-sectional length b1, b2, or b3 that is different from the length of one side of the suction duct 2, which has a rectangular cross section. The cross-sectional lengths b1, b2, or b3 of each of the noise reduction units 230 vary depending on the wavelengths of noise corresponding to multiple frequencies at which the sound pressure level of the noise peaks. These cross-sectional lengths b1, b2, or b3 are longer than half the wavelength of the respective noises and shorter than one wavelength. This makes it possible to reduce noises generated by the compressor 3 that have different frequencies at which the sound pressure level peaks. As a result, it is possible to contribute to improving the quietness of the gas compressor 100.

[0049] (2) Noise reduction unit 230 includes first noise reduction unit 230a and second noise reduction unit 230b. First noise reduction unit 230a is provided in first flow path 213 of suction duct 2 and reduces noise having a first wavelength. Second noise reduction unit 230b is provided in second flow path 214, which is located at a different position from first flow path 213 of suction duct 2, and reduces noise having a second wavelength different from the first wavelength. This makes it possible to reduce noise of different specific wavelengths at different positions in suction duct 2. As a result, it is possible to reduce the overall value of noise generated by gas compressor 100 and provide gas compressor 100 with improved quietness.

[0050] (3) The first noise reduction unit 230a has a first partition plate 10a that divides the first flow path 213 into a plurality of first divided regions DR1 including a first region R1. The cross-sectional length b1 of the first region R1 is longer than half the first wavelength but shorter than the first wavelength. The second noise reduction unit 230b has a second partition plate 10b that divides the second flow path 214 into a plurality of second divided regions DR2 including a second region R2. The cross-sectional length b2 of the second region R2 is longer than half the second wavelength but shorter than the second wavelength. This allows the first noise reduction unit 230a and the second noise reduction unit 230b to reduce noises of different wavelengths with a simple configuration of providing the partition plate 10.

[0051] (4) The second noise reduction unit 230b includes a third partition plate 10c. The cross-sectional length b3 of the region (third region R3) divided by the third partition plate 10c is different from the cross-sectional lengths b1 and b2. The cross-sectional length b3 is longer than half the wavelength but shorter than one wavelength of a third wavelength, which is different from the first wavelength and the second wavelength. This allows the second noise reduction unit 230b to reduce noises with different frequencies that peak at sound pressure levels.

[0052] (5) The flow path 210 of the suction duct 2 has multiple bent portions 211, 212 and multiple straight portions, namely, the first flow path 213, the second flow path 214, and the third flow path 215. The noise reduction section 230 is provided in the straight portions (the first flow path 213 and the second flow path 214). This reduces noise not only in the noise reduction section 230 but also in the bent portions 211, 212, thereby reducing the overall noise generated by the compressor 3. Furthermore, compared to a case in which the bent portions 211, 212 are not provided and the suction duct 2 extends linearly, the housing 201 can be made smaller.

[0053] Second Embodiment A gas compressor according to a second embodiment will be described. In the following description, the same reference numerals will be used to designate components that are the same or substantially the same as those described in the first embodiment. Differences from the first embodiment will be mainly described. The second embodiment differs from the first embodiment in that the cross-sectional length is variable.

[0054] 4 is a diagram schematically illustrating the configuration of the main parts of the gas compressor 100 of the second embodiment. The noise reduction unit 330 provided in the gas compressor 100 of the second embodiment has a change unit 331 that changes the cross-sectional lengths b1 and b2, in addition to the partition plate 10 and sound-absorbing material 11 of the first embodiment. Note that the sound-absorbing material 11 does not necessarily have to be provided.

[0055] <Changer 331> The changer 331 has a drive source 332 and an actuator 333. The drive source 332 is configured by, for example, a motor or the like, and is electrically connected to the control device 20 via a power supply / control line 22. The drive source 332 rotates by drive power (current) output from the control device 20. The rotation direction of the drive source 332 is reversed depending on the direction of the supplied current.

[0056] The actuator 333 has, for example, a rotating shaft 333a, a gear 333b, and a rack portion 333c. The rotating shaft 333a rotates in response to the rotational drive of the driving source 332. The gear 333b is attached to the rotating shaft 333a. Therefore, when the rotating shaft 333a rotates in response to the rotation of the driving source 332, the gear 333b also rotates. When the rotation direction of the driving source 332 is reversed in response to the direction of the supplied current, the rotation directions of the rotating shaft 333a and the gear 333b are also reversed.

[0057] The rack portion 333c is a member having a plurality of teeth arranged along the extension direction A1, and meshes with the gear 333b. When the gear 333b is driven in accordance with the rotation of the drive source 332, the rack portion 333c converts the rotational force into a linear movement force along the extension direction A1. As a result, the rack portion 333c moves along the extension direction A1.

[0058] As will be described later, the wall surface or partition plate 10 of the flow path 210 is attached to one end of the rack portion 333c. Therefore, in response to the movement of the rack portion 333c along the extension direction A1, the wall surface or partition plate 10 of the flow path 210 can also move along the extension direction A1.

[0059] The above-described structure of the actuator 333 is merely an example. The actuator 333 is not limited to the above-described structure, and may have various structures suitable for moving the wall surface of the flow channel 210 or the partition plate 10.

[0060] As shown in FIG. 4, the noise reduction section 330 includes a first noise reduction section 330a and a second noise reduction section 330b.

[0061] <First noise reduction section 330a> The change section 331 of the first noise reduction section 330a is connected to the first partition plate 10a. More specifically, one end of the rack section 333c is connected to the first partition plate 10a. In this case, the rack section 333c and the first partition plate 10a are connected so that the extension direction A1 of the rack section 333c intersects with the left-right direction, which is the extension direction of the first flow path 213 and the first partition plate 10a.

[0062] Therefore, as the rack portion 333c moves along the extension direction A1, the first partition plate 10a also moves along the extension direction A1. That is, the first partition plate 10a moves in a direction intersecting the left-right direction in which the first flow path 213 extends. By moving the first partition plate 10a along the extension direction A1, the distance between the first partition plate 10a of the first noise reduction portion 330a and the wall surface 213a of the first flow path 213, i.e., the cross-sectional length b1, can be changed.

[0063] <Second noise reduction section 330b> The change section 331 of the second noise reduction section 330b is connected to the wall surface 214a of the second flow path 214. More specifically, one end of the rack section 333c is connected to the wall surface 214a. In this case, the rack section 333c and the wall surface 214a are connected so that the extension direction A1 of the rack section 333c intersects with the up-down direction, which is the extension direction of the second flow path 214 and the second partition plate 10b.

[0064] The wall surface 214a is separated from the wall surfaces of the adjacent first flow path 213 and third flow path 215. Therefore, as the rack portion 333c moves along the extension direction A1, the wall surface 214a also moves along the extension direction A1. In other words, the wall surface 214a moves in a direction intersecting the up-and-down direction in which the second flow path 214 extends.

[0065] A sealing member or the like may be attached to the side wall surface 214b of the wall surface 214a along the extension direction A1. This allows the boundaries between the wall surface 214a and the first flow path 213 and the third flow path 215 to be sealed by the sealing member within a movable range of the wall surface 214a along the extension direction A1, thereby making it possible to maintain the airtightness of the flow path 210.

[0066] As described above, the movement of the wall surface 214a along the extension direction A1 makes it possible to change the distance between the second partition plate 10b and the wall surface 214a of the second noise reduction section 330b, i.e., the cross-sectional length b2. Note that, because the cross-sectional length b2 can be changed by moving the wall surface 214a, the second noise reduction section 330b does not need to include the second partition plate 10b and the third partition plate 10c. In other words, it is sufficient that the distance between the wall surface 214a and the wall surface 214c opposite the wall surface 214a is changed as the cross-sectional length b2 by the change unit 331.

[0067] In the above description, an example has been given in which the partition plate 10 in the first noise reduction section 330a is configured to be movable and the wall surface 214a in the second noise reduction section 330b is configured to be movable, but this is not limited to this example. Both the first noise reduction section 330a and the second noise reduction section 330b may be configured so that a portion of the wall surface of the flow path 210 is movable. Alternatively, both the first noise reduction section 330a and the second noise reduction section 330b may be configured so that the partition plate 10 is movable. Alternatively, one of the first noise reduction section 330a and the second noise reduction section 330b may not include the change section 331 and may have a configuration similar to the noise reduction section 230 of the first embodiment.

[0068] <Example of Changes to the Cross-Sectional Lengths b1 and b2> A description will be given of the ranges of the cross-sectional lengths b1 and b2 in a second embodiment when the gas compression mechanism 4 is of a screw rotor type. In the gas compression mechanism 4 of the second embodiment, the rotation speed [rpm] of the male screw rotor is variable between 18,000, 15,000, and 12,000, and the number of teeth is five.

[0069] In this case, as in the first embodiment, the wavelength value λ corresponding to the meshing frequency is calculated, and the cross-sectional lengths b1 and b2 are determined based on this wavelength value λ. When the rotation speed of the male screw rotor is 18,000 rpm, the wavelength value λ is 340 ÷ (18,000 × 5 ÷ 60) = 0.2266 m. Therefore, the cross-sectional lengths b1 and b2 are in the range of 113.6 mm to 226.6 mm, which is longer than λ / 2 but shorter than λ. When the rotation speed of the male screw rotor is 15,000 rpm, the cross-sectional lengths b1 and b2 are in the range of 136 mm to 272 mm. When the rotation speed of the male screw rotor is 12,000 rpm, the cross-sectional lengths b1 and b2 are in the range of 170 mm to 340 mm.

[0070] FIG. 5 is a diagram showing the relationship between the rotation speed of the male screw rotor and the range of the cross-sectional lengths b1 and b2 calculated as described above. In FIG. 5, the horizontal axis represents the rotation speed [rpm] of the male screw rotor, and the vertical axis represents the cross-sectional lengths b1 and b2 [mm]. In FIG. 5, the shaded range R4 represents the range of values ​​that can be set for the cross-sectional lengths b1 and b2. In other words, the change unit 331 can move the wall surface 214a or the first partition plate 10a based on the rotation speed of the gas compression mechanism 4 so that the cross-sectional lengths b1 and b2 fall within the range R4. That is, the change unit 331 changes the cross-sectional lengths b1 and b2. Specifically, as shown in FIG. 5, the change unit 331 shortens the cross-sectional lengths b1 and b2 as the rotation speed of the gas compression mechanism 4 increases.

[0071] <Operation> The operation of the control device 20 and the change unit 331 performed to change the cross-sectional lengths b1 and b2 will be described. Drive data that associates the rotation speed of the gas compression mechanism 4 with the position of the rack portion 333c in the extension direction A1 is stored in advance in a memory (not shown) of the control device 20. The drive data is created based on the relationship between the rotation speed of the gas compression mechanism 4 and the cross-sectional lengths b1 and b2 shown in FIG. 5.

[0072] Once the rotation speed of the gas compression mechanism 4 is set, the control device 20 refers to the drive data and calculates the position of the rack portion 333c in the extension direction A1. The control device 20 calculates the drive amount of the drive source 332, i.e., the direction and amount of rotation, based on the calculated position of the rack portion 333c and the current position of the rack portion 333c. The control device 20 outputs a signal indicating the calculated direction and amount of rotation to the change unit 331 as a drive signal.

[0073] Drive source 332 of change unit 331 is driven by an amount and direction of rotation corresponding to the input drive signal. As a result, rack portion 333c moves along extension direction A1, and wall surface 214a or partition plate 10b moves along extension direction A1 following the movement of rack portion 333c. As a result, cross-sectional lengths b1 and b2 are changed to lengths corresponding to the rotation speed of gas compression mechanism 4. That is, cross-sectional lengths b1 and b2 change in response to the frequency (wavelength) of noise that changes with changes in the rotation speed of gas compression mechanism 4. As a result, even if the frequency (wavelength) of noise changes with changes in the rotation speed of gas compression mechanism 4, it is possible to reduce the noise output to the outside of gas compressor 100 via flow path 210.

[0074] According to the second embodiment, in addition to the effects achieved by the first embodiment, the following effects are achieved: (6) The change unit 331 is provided in the suction duct 2 and changes the cross-sectional lengths b1, b2 by moving at least one of the partition plate 10, which is provided in the suction duct 2 and extends along the extension direction of the suction duct 2, and the wall surface 214a of the second flow path 214, which is part of the suction duct 2. This makes it possible to reduce noise even when the operating condition of the compressor 3 changes and the frequency at which the sound pressure level peaks changes.

[0075] (8) The change unit 331 shortens the cross-sectional lengths b1 and b2 as the rotation speed of the gas compression mechanism 4 increases. This makes it possible to obtain cross-sectional lengths suitable for reducing noise according to the rotation speed of the gas compression mechanism 4 of the compressor 3, thereby improving the quietness of the gas compressor 100.

[0076] The present invention is not limited to the above-described embodiments and modifications, and other aspects that are conceivable within the scope of the technical concept of the present invention are also included within the scope of the present invention.

[0077] 1, 8 Intake port, 2 Intake duct, 3 Compressor, 4 Gas compression mechanism, 5 Connecting flow path, 10 Partition plate, 10a First partition plate, 10b Second partition plate, 10c Third partition plate, 11 Sound absorbing material, 16 Power transmission mechanism, 18 Motor, 19, 22 Power supply / control line, 20 Control device, 21 Drive mechanism, 100 Gas compressor, 210 Flow path, 211, 212 Bent portion, 213 First flow path, 213a, 214a, 214c Wall surface, 214 Second flow path, 214b Side wall surface, 215 Third flow path, 220 Dust filter, 230, 330 Noise reduction section, 230a, 330a First noise reduction section, 230b, 330b Second noise reduction section, 331 Change section, 332 Driving source, 333 actuator, b1, b2, b3 cross-sectional length, DR1 first divided region, DR2 second divided region, R1 first region, R2 second region, R3 third region

Claims

1. A gas compressor comprising: an intake duct having a rectangular cross section through which gas flowing in from the outside passes; a filter connected to the intake duct; a compressor that compresses the gas sucked in through the filter; and a plurality of noise reduction units that reduce noise generated by the operation of the compressor, wherein the plurality of noise reduction units are provided inside the intake duct at different positions in the extension direction of the intake duct, one side of the rectangular cross section of each of the noise reduction units has a cross-sectional length that differs from the length of one side of the intake duct having the rectangular cross section, and the cross-sectional length of each of the noise reduction units varies according to the wavelengths of the noise corresponding to a plurality of frequencies at which the sound pressure level of the noise reaches its peak, and the cross-sectional length is longer than half the wavelength of the noise and shorter than one wavelength.

2. A gas compressor according to claim 1, wherein the noise reduction section comprises a first noise reduction section provided in a first flow path of the suction duct and reducing the noise of a first wavelength, and a second noise reduction section provided in a second flow path of the suction duct that is positioned differently from the first flow path and reducing the noise of a second wavelength different from the first wavelength.

3. A gas compressor according to claim 2, wherein the first noise reduction section has a first partition plate that divides the first flow path into a plurality of regions including a first region, the second noise reduction section has a second partition plate that divides the second flow path into a plurality of regions including a second region, the cross-sectional length of the first region is longer than half the first wavelength and shorter than the first wavelength, and the cross-sectional length of the second region is longer than half the second wavelength and shorter than the second wavelength.

4. A gas compressor according to claim 3, wherein at least one of the first noise reduction section and the second noise reduction section further comprises a third partition plate.

5. A gas compressor according to claim 4, wherein the region divided by the third partition plate has a third cross-sectional length different from the cross-sectional length of the first region and the cross-sectional length of the second region, and the third cross-sectional length is longer than half the wavelength and shorter than one wavelength of the third wavelength different from the first wavelength and the second wavelength.

6. A gas compressor according to claim 1, wherein the noise reduction section has a change section that changes the cross-sectional length, and the change section is provided within the suction duct and changes the cross-sectional length by moving at least one of a partition plate that extends in the direction in which the suction duct extends and a part of the wall surface of the suction duct.

7. A gas compressor according to claim 6, wherein the rotation speed of the compressor is variable, and the changer shortens the cross-sectional length as the rotation speed of the compressor increases.

8. A gas compressor according to any one of claims 1 to 7, wherein the suction duct has a plurality of bent portions and a plurality of straight portions, and the noise reduction portion is provided in the straight portions.

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