Rotary electric apparatus with noise reduction structure and manufacturing method thereof

Abstract

To provide a rotary electric apparatus with a noise reduction structure capable of dealing with a wide frequency band, and a manufacturing method thereof.SOLUTION: In a rotary electric apparatus, a stator and a rotor are installed on an inner periphery side of a cylindrical outer case, and either the stator or the rotor has en electromagnetic coil structure. A ring-shaped noise reduction structure which configures a plurality of Helmholtz resonators with different attenuation frequencies is provided on an outer periphery of the outer case. In the noise reduction structure, the plurality of Helmholtz resonators are formed by a single cylindrical substrate member and a part of the cylindrical outer case that covers the substrate member from inside. The substrate member is provided with a plurality of recessed groove rows that constitute the plurality of Helmholtz resonators corresponding to the different attenuation frequencies. Each of the recessed groove rows includes a plurality of cavities and a plurality of necks corresponding to the different attenuation frequencies, and a plurality of atmosphere communication passages, which are formed on the same surface of the substrate member. Each of the atmosphere communication passages extends in an axial direction of the rotary electric apparatus and has both ends communicating with the atmosphere.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a rotating electrical machine having a noise reduction structure and a manufacturing method thereof, and more particularly to a reduction in magnetic noise caused by electromagnetic forces in a rotating electrical machine. [Background technology]

[0002] The use of Helmholtz resonators is known as a means of reducing noise in rotating electrical machinery. For example, Patent Document 1 discloses an electric blower in which, in order to reduce noise from the electric blower, a discharge flow passage for passing a fluid is provided between an outer frame that integrally covers the blower unit and the electric motor unit and the outer periphery of the electric motor unit, and a resonance type silencer that is supported in contact with the inner periphery of the outer frame is provided in the discharge flow passage. This resonance type silencer is a sound absorbing structure in which a through hole is made in a plate and an air layer is placed behind the plate, and the air in the hole and the air layer behind it form a kind of Helmholtz resonator. Noise reduction is achieved by combining multiple resonance type silencers with different sound reduction frequencies.

[0003] Furthermore, Patent Document 2 discloses a structural laminated steel plate used as a sound-absorbing panel to be attached around an electric motor and its control device, the structural laminated steel plate having a laminated structure in which a resin plate is sandwiched between a pair of steel plates, the resin plate has a plurality of through holes, and these through holes and the pair of steel plates form a plurality of volume chambers, each of which communicates with the space on the opposite side of the steel plate via a small through hole, and the laminated structure has a Helmholtz-type resonator structure that absorbs specific frequency components of sound.

[0004] Furthermore, Patent Document 3 discloses a blower equipped with a silencer component capable of attenuating sound waves in a wide frequency band. This silencer component expands in a radial direction that intersects with the central axis, and is configured to have a plurality of grooves arranged around the central axis, each of which has a tubular portion and an enlarged portion, as Helmholtz resonance chambers, and to attenuate sound waves of a plurality of frequencies by shifting the resonance frequency by varying the shapes of these grooves. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-79199 [Patent Document 2] JP 2011-221283 A [Patent Document 3] Patent Publication No. 2022-57906 Summary of the Invention [Problem to be solved by the invention]

[0006] Rotating electrical machines such as motors are used in many fields as drive sources for various types of equipment or as generators for power sources. As living environments improve, there is also an increasing demand for reducing noise caused by these rotating electrical machines themselves. For example, in the case of a brushed DC motor, noise is mainly generated from the brushes and the motor case. The noise caused by the brushes is a sliding sound caused by contact with the commutator, while the noise in the motor case is caused by resonance sound due to electromagnetic force. Many effective solutions have been adopted for noise caused by brushes. On the other hand, there is no effective solution for noise in the motor case, and it is becoming the main noise source of the motor.

[0007] In the electric blower described in Patent Document 1, a predetermined number of resonance-type silencers are provided in the radial direction of the motor unit between a discharge flow passage provided on the outer periphery of the motor unit and an outer frame. Each resonance-type silencer is provided with a back air space with a thickness (length in the radial direction of the motor unit) L, and furthermore, a perforated plate on the outside of each of the resonance-type silencers is provided with a number of holes that extend in the radial direction of the motor unit and have a different radius for each resonance-type silencer. The resonance type silencer described in Patent Document 1 has a radial length that is relatively larger than the radial length of the electric motor section, resulting in an electric blower with a long radial length as a whole.

[0008] The invention described in Patent Document 2 is a sound-absorbing panel made of vibration-damping steel plates having a laminated structure in which a resin plate is sandwiched between a pair of steel plates. This sound-absorbing panel is presumably used as a sound-absorbing panel to be attached around an electric motor and its control device (see the description in paragraph 0024). Since it does not change the structure of the electric motor itself, installation space is required for the sound-absorbing panel. In addition, a small through hole provided in one of the steel plates of this sound-absorbing panel extends in the radial direction of the electric motor, which causes the radial length of the entire device including the electric motor to be longer.

[0009] The invention described in Patent Document 3 is a silencer component that expands in the radial direction and is suitable for silencing noise from a blower, but cannot be applied as is to noise from rotating electrical equipment itself caused by electromagnetic forces such as a motor case.

[0010] An object of the present invention is to provide a rotating electrical device having a noise reduction structure that can deal with a wide frequency range of noise caused by electromagnetic force generated by the rotating electrical device itself, and a manufacturing method thereof. Another object of the present invention is to provide a rotating electrical machine having a compact, inexpensive noise reduction structure that can be incorporated into the rotating electrical machine with almost no change in radial length, and a manufacturing method thereof. [Means for solving the problem]

[0011] The present invention relates to a rotating electrical machine in which a stator and a rotor are disposed on the inner periphery of a cylindrical outer case, and one of the stator and the rotor has an electromagnetic coil structure, a ring-shaped noise reduction structure that constitutes a plurality of Helmholtz resonators having different attenuation frequencies is provided on an outer periphery of the outer case; the ring-shaped noise reduction structure is a structure in which the multiple Helmholtz resonators are formed by a single cylindrical substrate member and a cover member that covers the substrate member from the inside, the substrate member is provided with a plurality of groove rows that constitute the plurality of Helmholtz resonators corresponding to the different attenuation frequencies; Each of the groove rows includes a plurality of cavities and a plurality of necks corresponding to the different attenuation frequencies, and a plurality of atmospheric communication passages, which are formed on the same surface of the base member, and each of the atmospheric communication passages extends in the axial direction of the rotating electrical machine with both ends communicating with the atmosphere.

[0012] According to the present invention, it is possible to provide a rotating electrical machine equipped with a noise reduction structure that is simple in structure and can accommodate a plurality of different frequencies. According to another feature of the present invention, the ring-shaped noise reduction structure comprises a cylindrical base member and a cover member which covers the base member from the inside, and the cover member of the ring-shaped noise reduction structure is formed by a part of the cylindrical outer case which covers the base member from the inside. According to the present invention, it is possible to provide a rotating electrical machine having a compact and inexpensive noise reduction structure without modifying the rotating electrical machine itself and with almost no change in radial length. [Brief description of the drawings]

[0013] [Figure 1] 1 is a vertical sectional view of a brushed DC motor provided with a noise reduction structure according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of the brushed DC motor shown in FIG. [Diagram 3] FIG. 2 is an exploded perspective view showing components of the noise reduction structure shown in FIG. [Figure 4] 2A to 2C are diagrams showing a manufacturing process of the noise reduction structure shown in FIG. 1. [Figure 5A] 2 is a plan view showing a detailed configuration example of the noise reduction structure shown in FIG. 1. [Figure 5B] 5B is a cross-sectional view taken along line AA in FIG. 5A. [Figure 6A] FIG. 11 is a diagram showing noise level characteristics as an effect of one embodiment of the present invention. [Figure 6B] FIG. 11 is a diagram showing, as a comparative example, noise level characteristics in a case where the present invention is not adopted. [Figure 7]FIG. 11 is a perspective view of a substrate member of a noise reduction structure according to a second embodiment of the present invention. [Figure 8] FIG. 11 is a perspective view of a substrate member of a noise reduction structure according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention can be applied to various types of rotating electrical equipment, but an embodiment in which the present invention is applied to a brushed DC motor will be described below. FIG. 1 is a vertical cross-sectional view of a brushed DC motor equipped with a noise reduction structure according to one embodiment of the present invention, and FIG. 2 is a horizontal cross-sectional view of the same motor. Permanent magnets 14 that form a magnetic field for this DC motor 10 are arranged in an annular shape and fixed to the inner wall of a cylindrical outer case (motor case) 11. The outer case 11 and the permanent magnets 14 form a stator 13 of the DC motor 100. A rotor (armature) 15 is arranged facing the permanent magnets 14. This rotor 15 has a laminated steel plate (core) 17 formed by laminating silicon steel plates or the like, and a winding 18 wound around a salient pole formed on this laminated steel plate 17.

[0015] The laminated steel plate 17 around which the winding 18 is wound is fixed to the rotating shaft 16. One end (output side) of the rotating shaft 16 is supported by a rolling bearing 20 or the like held in a bearing holder formed in the center of the side cover 12. The other end of the rotating shaft 16 is supported by a sleeve bearing 21 of an end bracket 27. The outer case 11 of the motor and the side cover 12 may be integrally formed into a cup shape. A commutator 24 for supplying power to the windings 18 is fixed to the rotating shaft 16, and two brushes 25 held by a brush holder 26 are biased against the commutator by a coil spring.

[0016] A ring-shaped noise reduction structure 30 constituting a Helmholtz resonator is provided on the outer periphery of a cylindrical outer case (motor case) 11. The installation position of the ring-shaped noise reduction structure 30 is slightly shifted to the left of the center of the axial length of the DC motor 10. As shown in Fig. 2, the width (axial length) Ws of the ring-shaped noise reduction structure 30 is shorter than the entire axial length Wm of the outer case 11 and longer than half the axial length Wm. The axial length and installation position of the noise reduction structure 30 relative to the outer case 11 can be appropriately determined depending on the structure and characteristics of the rotating electrical equipment, the damping frequency that requires measures, etc.

[0017] Fig. 3 is an exploded perspective view showing the components of the noise reduction structure, and Fig. 4 is a diagram showing a manufacturing process of this noise reduction structure. The noise reduction structure 30 is composed of one thin plate-shaped base member 31 and one thin plate-shaped cover member 32. These base member and cover member are manufactured from, for example, a thin flat steel plate. The cover member 32 is joined at both end faces 324A, 324B to form a ring shape. The cover member may be manufactured by other methods such as drawing. The ring-shaped noise reduction structure 30 is composed of a plurality of resonance type silencers, in other words a plurality of Helmholtz resonators, with different attenuation frequencies so as to absorb a plurality of frequencies. That is, a groove array constituting a plurality of Helmholtz resonators 31A, 31B, 31C is provided on a surface 310 of a flat plate-shaped substrate member 31. Each groove array includes a cavity 311, a neck portion 312, and an atmosphere communication passage 313. Each of the Helmholtz resonators 31A, 31B, 31C is connected to a common atmosphere communication passage 313. Both ends of each atmosphere communication passage 313 communicate with the atmosphere at an end 314 of the substrate member 31. In the example shown in FIG. 3, the Helmholtz resonator 31A corresponds to a high frequency, the Helmholtz resonator 31B corresponds to an intermediate frequency, and the Helmholtz resonator 31C corresponds to a low frequency. The atmosphere communication passage 313 extends in the axial direction of the rotating electrical machine and is configured so that both ends thereof communicate with the atmosphere. The cavity 311, the neck portion 312, and the atmosphere communication passage 313 are formed, for example, by etching a flat steel plate having a thickness of 2 mm to a uniform depth of 1.5 mm. The depths of the cavity 311, neck portion 312, and atmosphere communication passage 313 formed in the thin plate-like base member 31 do not have to be uniform. In other words, it is desirable that the cavity 311, neck portion 312, and atmosphere communication passage 313 have little difference in depth in the radial direction of the DC motor 10 and ensure the necessary volume or length in the axial direction of the DC motor 10, regardless of the damping frequency, in relation to the shapes of the recessed grooves in the base member.

[0018] 3 is a planar development view for the purpose of making the configuration of the components of the noise reduction structure 30 easier to understand, and in reality, the noise reduction structure 30 is formed in a cylindrical shape. That is, as shown in Fig. 4, the substrate member 31 provided with the groove arrays constituting the Helmholtz resonators 31A, 31B, 31C is placed on the outside of the cylindrical case (motor case) 11 to form a cylindrical body, and the ring-shaped noise reduction structure 30 is completed by fixing the two together. That is, in the present invention, the cover member 32 can also serve as a part of the case (motor case) 11. Incidentally, even if the cover member 32 is formed separately from the case 11 of the rotating electrical machine, there is almost no difference in the outer diameter of the rotating electrical machine. Therefore, depending on the application, a thin plate as shown in FIG. 3, which is separate from the case (motor case) 11, may be used as the cover member 32.

[0019] One substrate member 31 is formed into a ring shape with both end faces 314A, 314B in contact with each other. Next, this ring-shaped substrate member 31 is placed from the outside onto and fixed to a cover member 32 of a cylindrical motor in which a stator and a rotor are installed (see FIG. 4), thereby completing one ring-shaped noise reduction structure 30. The base member 31 may be any material that has the necessary strength and workability and is not expensive. For example, when a steel plate is used, the resonance type silencer may be formed on the base member by plastic processing. Alternatively, a synthetic resin material may be used and the groove array may be formed by molding. As described above, the depth of the recessed grooves of the hollow portion 311, the neck portion 312, and the atmosphere communication passage 313 may not be uniform. For example, the depth of the atmosphere communication passage 313 and the neck portion 312 may be made shallower than the hollow portion 311, and the width of the atmosphere communication passage may be made wider instead, thereby ensuring the rigidity of the outer case 11. Furthermore, the atmosphere communication passage 313 may include a curved portion in part.

[0020] As a means for fixing the ring-shaped base plate member 31 to the cover member 32, for example, an adhesive may be applied to the surface 310 of the base plate member 31, and this may be pressed against the surface (outer circumferential surface) 321 of the motor cover member 32 in which the stator and rotor are installed, thereby fixing the two together. Alternatively, fixing means or connecting means such as screws may be provided on both end surfaces 314A, 314B of the base plate member 31, and with the base plate member 31 placed over the surface 321 of the motor cover member 32, both end surfaces 314A, 314B may be tightened and joined.

[0021] The volume V of the cavity 311 and the cross-sectional area S of the neck portion 312 of each of the Helmholtz resonators 31A, 31B, and 31C are determined according to the frequency of the sound that is the target of noise reduction. Here, if the speed of sound is c, the volume of the cavity of the Helmholtz resonator is V, the cross-sectional area of ​​the neck is S, and the length of the neck is L, the resonant frequency f of the Helmholtz resonance is given by the following equation.

[0022]

number

[0023] 5A and 5B show a detailed configuration example of the noise reduction structure 30. In FIG. The example Helmholtz resonator shown corresponds to a damping frequency of 5000 Hz. The sound velocity c is 340,000 mm / s, and the cross-sectional area S of the neck is 1 mm 2 The length of the neck, L, is 6 mm, and the volume of the cavity, V, is 19.5 mm. 3 As shown in Fig. 5A, the neck portion 312 is formed at an inclination of 30 degrees with respect to the atmosphere communication passage 313. The numerical values ​​shown in Fig. 5A indicate the length values ​​related to the groove corresponding to the damping frequency of 5000 Hz in mm. The thickness of the substrate member is 2.00 mm, the depth of the groove is 1.5 mm, and the thickness of the bottom of the groove is 0.5 mm.

[0024] Fig. 6A is a diagram showing the noise level characteristics when the Helmholtz resonators 31A, 31B, and 31C of the noise reduction structure 30 as shown in Fig. 3 are formed to correspond to attenuation frequencies of 2000 Hz, 3000 Hz, and 5000 Hz as an effect of one embodiment of the present invention. As a comparative example, Fig. 6B shows the noise level characteristics when the present invention is not adopted. 6A and 6B, it can be seen that the noise reduction structure 30 according to one embodiment of the present invention functions effectively for the frequencies of 2000 Hz, 3000 Hz, and 5000 Hz.

[0025] According to the present invention, a noise reduction structure that is simple in structure and can accommodate a wide frequency band is provided. In other words, it is not necessary to modify the motor body, and a resonance groove that can accommodate a wide frequency band can be provided by adding a part with a simple structure without substantially increasing the radial length of the entire device including the motor.

[0026] Furthermore, it is possible to provide a rotating electrical machine having a compact and inexpensive noise reduction structure, which does not require modification of the main body of the rotating electrical machine and requires almost no change in the radial length. As an example, the thickness of the base member is 2 mm, and the diameter of the outer case (motor case) 11 is 50 mm, making it possible to provide a noise reduction structure with almost no change in the radial length of the motor. The noise reduction structure 30 shown in Figs. 1 and 2 is suitable for small motors and generators, for example, small motors used as drive sources for automobile windshield wipers, sliding doors, and the like.

[0027] Next, Fig. 7 shows an example of a substrate member 31 of a noise reduction structure according to a second embodiment of the present invention. The substrate member 31 of the second embodiment has a structure in which the noise reduction structure of the first embodiment is repeated. That is, on one substrate member 31, the number of Helmholtz resonators 31A, 31B, 31C is, for example, two to three times as many in the axial direction and in the direction perpendicular thereto. This makes it possible to provide a noise reduction structure targeted at larger motors and generators, such as drive motors for electric vehicles.

[0028] Next, FIG. 8 shows an example of a substrate member 31 of a noise reduction structure according to a third embodiment of the present invention. In this third embodiment, in the base member 31 of the noise reduction structure 30, cavities 311 and neck portions 312 of different sizes corresponding to different attenuation frequencies are connected to each atmosphere communication passage 313. For example, cavities 311A ​​and 311B are connected to the atmosphere communication passage 313 in the second row from the left, and cavities 311B and 311C are connected to the atmosphere communication passage 313 in the third row. In this case as well, the atmosphere communication passage 313 is configured to extend in the axial direction of the rotating electrical machine, with both ends communicating with the atmosphere. In this way, in one substrate member 31, the cavities 311 and neck portions 312 connected to the respective atmosphere communication passages 313 may be appropriately distributed depending on the specific attenuation frequency for which measures need to be taken.

[0029] 3, 7, and 8, the Helmholtz resonators corresponding to the same attenuation frequency are arranged along the atmospheric communication passage 313. However, instead of this, Helmholtz resonators corresponding to different attenuation frequencies may be arranged along the atmospheric communication passage 313. For example, instead of the two rows of Helmholtz resonators 31A and 31C shown in FIG. 3, two sets of Helmholtz resonators may be formed along one atmospheric communication passage 313, with one Helmholtz resonator 31C arranged in the center and one Helmholtz resonator 31A arranged on each side of the central Helmholtz resonator 31C. In this way, it is desirable to change the combination of Helmholtz resonators for each attenuation frequency to form an optimal noise reduction structure on the surface 310 of the substrate member 31.

[0030] The present invention can also be applied to other rotating electrical machines that generate electromagnetic vibrations, such as brushless motors and synchronous motors, and AC generators, such as DC generators, synchronous generators, and induction generators. Furthermore, in cases where the output side of the rotating shaft of a motor is connected to a driven device such as a compressor and these are housed in a single outer case, such as in the case of a car air conditioner for an electric vehicle, the noise reduction structure of the present invention may be installed on the outer periphery of the single outer case that this rotating electrical device and the driven device are housed in. If measures against noise from the driven device are also required, a Helmholtz resonator for the attenuation frequency of the driven device may be extended in the axial direction to the outer periphery of the outer case corresponding to the outside of the driven device, and formed integrally with the noise reduction structure. [Explanation of symbols]

[0031] 10 DC motor 11 Outer case 16 Rotation Axis 17 Laminated steel plate 18 Windings 30 Noise reduction structure 31 Substrate materials 31A, 31B, 31C Helmholtz resonators 310 Surface of substrate member 311 Cavity 312 Neck 313 Atmospheric passage 314A, 314B Both end faces of the substrate member 32 Cover member 321 Surface of cover member 324A, 324B Both end faces of cover member

Claims

1. A rotating electrical machine comprising: a stator and a rotor disposed on the inner periphery of a cylindrical outer case, and one of the stator and the rotor having an electromagnetic coil structure; a ring-shaped noise reduction structure that constitutes a plurality of Helmholtz resonators having different attenuation frequencies is provided on an outer periphery of the outer case; the ring-shaped noise reduction structure is a structure in which the plurality of Helmholtz resonators are formed by a single cylindrical substrate member and a cover member that covers the substrate member from the inside, the substrate member is provided with a plurality of groove rows that constitute the plurality of Helmholtz resonators corresponding to the different attenuation frequencies; a plurality of atmosphere communication passages, each of which is formed on the same surface of the base member, and each of the atmosphere communication passages extends in the axial direction of the rotating electrical machine with both ends communicating with the atmosphere.

2. In claim 1, 2. A rotating electrical device, comprising: a cover member of the ring-shaped noise reduction structure, the cover member being formed from a part of the cylindrical outer case of the rotating electrical device, the cover member covering the base member from the inside.

3. In claim 1, a Helmholtz resonator provided on the substrate member, the Helmholtz resonators extending in an axial direction of the rotating electrical device with different lengths or shapes on the same surface of the substrate member corresponding to the different attenuation frequencies.

4. In claim 1 or 2, a plurality of resonators corresponding to different attenuation frequencies, each of the resonators corresponding to each attenuation frequency being connected to a common atmosphere communication passage;

5. In claim 1 or 2, the atmosphere communication passage extends in the axial direction of the rotary electric machine, a resonator having a different type corresponding to the different damping frequencies and connected to each of the atmosphere communication passages;

6. In claim 1 or 2, A rotating electrical machine, characterized in that the rotating electrical machine and its driven device are housed within the outer case, and the noise reduction structure is provided on an outer periphery of the outer case.

7. In claim 1 or 2, The rotating electrical machine is a DC motor, comprising: a permanent magnet disposed on the inner periphery of the cylindrical motor case; an armature having a winding and laminated steel plates disposed opposite the permanent magnet; and a brush electrically connected to the armature.

8. A method for manufacturing a rotating electrical device according to claim 1 or 2, comprising the steps of: forming the substrate member by providing a plurality of the cavities and the neck portions constituting the plurality of Helmholtz resonators, and a row of the recessed grooves corresponding to the plurality of the atmosphere communication passages, in a single flat steel plate or a single plate made of synthetic resin; A manufacturing method for a rotating electrical device, characterized in that the ring-shaped noise reduction structure is formed by covering and fixing the single substrate member from the outside to the cylindrical outer case in which the stator and rotor are installed.

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