JPH0641369U - Noise suppression device for electric motor - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to suppress mechanical vibration caused by rotation of a rotor during operation of a motor by absorbing and relaxing it by a vibration absorbing device inserted in a bearing portion. [Structure] A casing 16 and a cover body 1 that rotatably support a rotor shaft 14 of a rotor 13 via a bearing 15.
7, inside the bearing portions 19, 20 formed in
Between the inner bottom surfaces 19a and 20c of the bearing 20 and the bearing 15, there is a thick plate-shaped rubber member 23, 23 having excellent oil resistance.
a and a washer 22 made of a hard material such as metal that presses the entire surface of the rubber members 23, 23a with a substantially uniform force.
To form the vibration absorbers 24 and 25, and absorb the mechanical vibrations transmitted to the bearings 19 and 20 by the vibration absorbers 24 and 25 so that the casing 16 or the like does not induce resonance vibrations. It is characterized by having done.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of a device for preventing noise generated during operation of an electric motor.

[0002]

[Prior art]

 The structure of a conventionally used electric motor will be described with reference to FIG. In the conventional electric motor Y shown in FIG. 11, 1 is a stator core around which a stator winding 2 is wound, and 3 is a rotor with a rotor shaft 4 fixedly attached to the rotor shaft 4. A bearing 5 including a ball bearing is fitted in a predetermined position. Reference numeral 6 denotes a bowl-shaped casing formed by pressing a steel plate, to which the stator core 1 having the stator winding 2 is fitted by means such as press fitting. Reference numeral 7 denotes a cover body attached to the opening a of the casing 6 into which the stator core 1 is press fitted. A cylindrical portion 6b that projects inward from the end wall 6a of the casing 6 orthogonal to the rotor shaft 4 in the axial direction of the rotor shaft 4 is integrally formed on the casing 6 by press working. The tubular portion 6b is formed to have a double wall structure including an inner wall portion 6c and an outer wall portion 6d. Further, the outer wall of the inner wall portion 6c has an end wall 9e for receiving the bearing 5. Is integrally formed with the tubular portion 6b to form the bearing portion 8. A bearing portion 10 is formed by integrally bulging a tubular portion 10a for fitting the bearing 5 at the center of the cover body 7 side, which constitutes the bearing portion 10. The end wall 10b of the tubular portion 10a has a through hole 10c through which the rotor shaft 4 penetrates. Then, the bearings 5 and 5 fitted to the rotor shaft 4 are inserted into the bearings 8 and 10 of the casing 6 and the cover body 7, and the cover body 7 is attached to the opening a of the casing 6. , Assembling the electric motor Y.

[0003]

[Problems to be solved by the device]

 When the electric motor Y having the above structure is used by being attached to, for example, a blower for a water heater, the electric motor causes mechanical vibration as the rotor rotates. This vibration generally tends to increase as the number of rotations of the rotor increases. This vibration is further promoted by the rotation of the fan of the blower, and is transmitted to the connecting portion between the cover body of the electric motor and the case of the blower, the casing of the electric motor, and so on. Resonance vibration was induced, which was a major factor in noise generation.

As a factor of the noise, when a fan is attached to the rotor shaft of an electric motor, the center of gravity of the rotor itself moves to the fan side (cover body side) depending on the weight of the fan. When the motor is operated in such a state, the center of gravity of the rotor moves to the fan side, so the end of the rotor shaft located in the bearing part on the casing side serves as a fulcrum and the fan The tip side for mounting the motor will rotate in an eccentric state like a swinging motion, off the axial center of the rotor, just like manipulating scrap wood. This phenomenon is promoted as the number of rotations of the rotor is increased, resulting in a large mechanical vibration, which is propagated along the rotor shaft to the bearing side of the casing and the cover body, causing resonance on the bottom side of the casing. It is considered that this may be the cause of noise generation by causing the resonance vibration to be transmitted to the case side of the blower that is connected to the cover body.

However, the mechanical vibration generated during the operation of the electric motor is shown in, for example, the casing of the electric motor or the plate thickness of the cover body, or, for example, Japanese Utility Model Publication No. 57-31645. As described above, it can be seen that the motor is further surrounded by a case, and a vibration damping rubber is interposed between the motor and the case so that the vibration noise of the motor does not propagate to the outside. However, in the former case, the material thickness of the casing and cover body is thick, so there is a problem in the machine (press) processing and dimensional accuracy, and in addition, noise countermeasures for the motor, such as an increase in the weight of the motor, are taken. In doing so, it was difficult to solve the problems of improving productivity and reducing manufacturing costs. Also, in the latter case, the anti-vibration rubber is in complete contact with the entire front and rear surfaces of the case, so mechanical vibrations are easily transmitted, and vibrations of the electric motor cannot be sufficiently blocked, and mechanical vibrations cannot be sufficiently prevented. It is difficult to surely solve the noise problem due to vibration, but a special case and soundproof rubber surrounding the electric motor are required, so that the electric motor becomes larger and the number of parts increases and the manufacturing cost increases. There was a problem such as raising the price. Furthermore, in a commutatorless motor, the current flowing is a distorted wave, so if the rotor is rotated by this distorted wave and the number of revolutions is increased, mechanical vibration is generated by the distorted wave. This is transmitted to the rotor shaft and induces resonance vibration in the casing, causing noise.

In view of the above-mentioned various problems, the present invention causes a load member such as a blower fan attached to a rotor to rotate the load member side of the rotor in an eccentric state like a swing motion. The mechanical vibration caused by the above-mentioned phenomenon is absorbed and mitigated to prevent the resonance vibration from being induced by propagating to the casing or the like along the rotor shaft of the rotor, thereby preventing the noise caused by the mechanical vibration. It is an object of the present invention to provide a noise prevention device for an electric motor, which is designed to reduce the generation to a level that does not cause discomfort.

[0007]

[Means for Solving the Problems]

 The present invention provides a casing in which a stator core is press-fitted and fitted, and a bearing portion formed in a cover body attached to the opening end of the casing, and a flat plate-like rubber member having a large thickness and elasticity. , A flat washer having a high rigidity such as a metal or a synthetic resin that presses almost the entire surface of the rubber member with a uniform pressure is provided with a vibration absorbing / relaxing means, and the outside of the casing bottom surface having the bearing portion. Is a combination of the above-mentioned vibration absorbing / relaxing means, or a casing reinforcing layer or buffer layer made of a synthetic resin or rubber member alone, and the resonance bottom vibration easily propagates due to mechanical vibration. Since it is configured to enhance the rigidity of the and to absorb and mitigate the resonance vibration satisfactorily, its action is as follows.

[0008]

[Action]

 In the present invention, mechanical vibration generated by rotation of a load member such as a fan attached to the rotor during operation of the electric motor is transmitted through the rotor shaft of the rotor, and most of the mechanical vibration is generated by the stator core. It is propagated to the bearing portion of the fitted casing side. However, the casing-side bearings (including the cover-side bearings) have a flat rubber washer inserted through a flat washer with excellent rigidity, and a flat rubber member that absorbs Since the absorption / relaxation means or the resin reinforcement / absorption layer made of synthetic resin formed on the end wall of the casing where the bearing portion on the casing side is located is provided to absorb and moderate mechanical vibration. The mechanical vibration transmitted to the bearing portion of the casing is well absorbed by the rubber member inserted in the bearing portion, or the rigidity of the casing itself is increased by the resin reinforcement / absorption layer formed on the end wall of the casing. Since reinforcement is achieved, it is possible to remarkably suppress the induction of resonance vibration due to the mechanical vibration, so that noise caused by mechanical vibration can be easily suppressed to a level at which it does not feel uncomfortable. Can be reduced to

Further, the present invention simplifies noise prevention means by inserting a rubber member into a bearing portion such as a casing or forming a resin reinforcement / absorption layer at a place where mechanical vibration of the casing is easily propagated. In addition, since the electric motor can be configured without increasing the size, it becomes possible to efficiently and economically manufacture this seed electric motor.

【Example】

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. In FIG. 1, 11 is a stator core, around which a stator winding 12 is wound. Reference numeral 13 denotes a rotor which penetrates and is fixed to the rotor shaft 14, and bearings 15, 15a such as ball bearings are attached to the rotor shaft 14 at predetermined positions. Reference numeral 16 denotes a casing formed by pressing a steel plate into a bowl shape, in which the stator core 11 is housed by means such as press fitting. Reference numeral 17 denotes a cover body that covers the opening end a of the casing 16. The casing 16 is integrally formed with a cylindrical portion 18 that linearly protrudes inward from the end wall 16a of the bottom surface thereof. The cylindrical portion 18 is formed by the inner and outer wall portions 18a and 18b. By forming it with a heavy wall structure, the bearing portion 19 can be provided integrally with the casing 16 on the inner wall portion 18a side by the end wall 16a that prevents the bearing 15 from coming off.

On the other hand, on the cover body 17 side, a cylindrical portion 17 a for fitting the bearing 15 a is integrally formed in the center portion thereof to form the bearing portion 20, and an end wall of the bearing portion 20. A through hole 20b through which the rotor shaft 14 penetrates is formed at 20a.

Next, in the bearing portion 19 of the casing 16, as shown in FIG. 1, between the bearing 15 and the inner bottom surface 19 a of the bearing portion 19, a corrugated annular shape for urging the bearing 15 in the thrust direction is provided. A spring 21, a disk-shaped washer 22 made of synthetic resin or metal or the like with excellent rigidity, and a rubber member 23 such as nitrile rubber processed into a disk shape with a wall thickness excellent in oil resistance and elasticity. The first vibration absorbing device 24 also having a preload function is inserted therein. Further, in the bearing portion 20 of the cover body 17, between the bearing 15a and the inner bottom surface 20c of the bearing portion 20, holes b, c through which the rotor shaft 14 penetrates are formed, and the same washer 22a and the rubber member 23a are formed. A second vibration absorbing device 25 having the function of preloading is inserted.

Next, the operation of the above embodiment will be described. When assembling the electric motor, the stator core 11 around which the stator winding 12 is wound is press-fitted into the casing 16 to be housed. Subsequently, the bearings 15 and 15a are fitted to the rotor shaft 14 of the rotor 13 at predetermined positions, and then the bearing portion 19 of the casing 16 has a rubber member 23, a washer 22, and a wave 22 on its inner bottom surface 19a. A first vibration absorber 24 consisting of a mold annular spring 21 is inserted. On the other hand, in the bearing portion 20 of the cover body 17, the second vibration absorbing device 25 including the rubber member 23a and the washer 22a is inserted on the inner bottom surface 20c. In this state, the tip of the rotor shaft 14 (on the left side in FIG. 1) is passed through the through hole 20b of the inner bottom surface 20c of the bearing portion 20 of the cover body 17, and the bearing 15a is passed through the second vibration absorber 25. Bearing that is fitted in the bearing portion 20 and then the rotor 13 is inserted into the rotor insertion hole 11a of the stator core 11 and is fitted to the base end of the rotor shaft 14 (right side in FIG. 1). By fitting 15 into the bearing portion 19 of the casing 16 via the first vibration absorber 24, the opening a of the casing 16 is covered with the cover body 17, and the cover body 17 is not tightened. The assembly work of the electric motor X is completed by fastening the casing 16 with screws or the like. By assembling the electric motor X as described above, the rotor 13 is thrust by the preloading action of the first and second vibration absorbing devices 24 and 25 of the bearing portions 19 and 20 via the bearings 15 and 15a. The bearing portions 19 and 20 are rotatably supported by the bearing portions 19 and 20 via the rotor shaft 14 while being pressed and biased in the direction.

The electric motor X assembled as described above is assembled in a case of a blower, for example, by attaching a fan (not shown) for blowing to the tip of the rotor shaft 14. In this state, the electric motor X is energized to rotate the blower fan attached to the rotor shaft 14. The rotation of the fan causes mechanical vibration in the rotor 13. That is, when an unillustrated blower fan is attached to the tip of the rotor shaft 14 (on the left side in FIG. 1) and is rotated, the center of gravity of the rotor 13 depends on the weight of the fan and the rotation speed of the rotor 13. 1 moves to the bearing portion 20 side of the cover body 17 in FIG. Therefore, with the movement of the center of gravity of the rotor 13, the base end (right side in FIG. 1) side is the fulcrum, and the tip end (left side in FIG. 1) side where the fan is attached is relative to the axis of the rotor 13 itself. It will rotate like oscillating motion in an eccentric state. That is, since the center of gravity of the rotor 13 is changed by attaching a load member such as a fan to the tip of the rotor 13, both ends of the rotor shaft 14 cannot be rotated about the shaft center, and the rotor 13 cannot be rotated. With the base end of the shaft 14 (on the side of the bearing 19) as a fulcrum, the shaft 14 rotates with the tip (fan) side swinging. As a result, the rotor 13 rotates within the rotor insertion hole 11a of the stator core 11 with a small amplitude with respect to its axis, and mechanical vibration is generated.

The mechanical vibration of the rotor 13 generated in the rotor insertion hole 11 a is transmitted to the bearings 19 and 20 of the casing 16 and the cover body 17 along the rotor shaft 14. In this case, the bearing portions 19 and 20 have flat washers 22 and 22a and thick rubber members 23 and 23a (a corrugated annular spring 21 is also used in the bearing portion 19 of the casing 16). The first and second vibration absorbers 24 and 25 made of are built in, and most of the vibrations can be absorbed and damped by the rubber members 23 and 23a. This is because the bearings 15 and 15a fitted to the rotor shaft 14 are urged in the thrust direction by the preloading action due to the presence of the first and second vibration absorbers 24 and 25. Is effectively absorbed by the rubber members 23 and 23a, and induction of resonance vibration or the like to the casing 16 and the cover body 17 can be suppressed as much as possible, and noise generated by driving the electric motor X can be reduced.

FIG. 7 and FIG. 9 are spectrums for comparing noise differences by performing a noise test using an electric motor X equipped with the noise prevention device of the present invention and a conventional electric motor Y having no noise prevention measures. In the figure, the horizontal axis represents the frequency (0 to 2000 Hz) in the range where humans perceive it as noise, and the vertical axis represents the noise level (0 to 60 dB). Comparing the graph values of both FIGS. 7 and 9 at the same level, in the vicinity of 400 to 1,400 Hz, the present invention shows a large noise reduction effect as compared with the conventional product, and particularly in the vicinity of 600 to 800 Hz. The sound reduction effect is exhibited. In addition, in the vibration absorbing devices 24 and 25 of the present invention, the thick rubber members 23 and 23a inserted into the bearing portions 19 and 20 contact the surfaces of the rubber members 23 and 23a through the washers 22 and 22a over almost the entire area to obtain a uniform force. Since it is pressed and urged by, the mechanical vibration transmitted to the bearing portions 19 and 20 through the rotor shaft 14 can be evenly received. As a result, as can be seen from FIGS. 7 and 9, the noise level of the present invention is lower than that of the conventional electric motor Y in the range of audible frequency as a whole, and the effect of the present invention is sufficiently exerted. I was able to figure it out. In addition, FIG. 10 shows an electric motor of the present invention in which the noise level near the rotation frequency (3,500 to 4,000 rpm), which is frequently used in the electric motor, uses the electric motor Y of the conventional structure and the vibration absorbing devices 24 and 25. When compared with X, it was found that in the example of the present invention, it was lowered by 3 to 6 dB.

FIG. 4 shows a second embodiment of the present invention. The difference from the first embodiment of FIG. 1 is that only the corrugated annular spring 21 is inserted into the bearing portion 19 of the casing 16 (cover body). A rubber member 23a and a washer 22a are inserted in the bearing portion 20 of 17 like the first embodiment, and the bearing portion 19 is surrounded by the end wall 16a outside the bearing portion 19. A thermosetting resin such as an epoxy resin is attached, and this is heated and cured at a predetermined curing temperature to form a resin reinforcement / absorption layer 30 on the end wall 16a of the bottom of the casing 16 to enhance the rigidity of the bottom of the casing 16. Thus, the electric motor X ₁ is constructed. Then, as described above, when the electric motor X ₁ is operated, mechanical vibration is generated with the rotation of the rotor 13 and is transmitted to the bearing portions 19 and 20 through the rotor shaft 14. In this case, since the cover body 17 side is provided with the vibration absorbing device 25 as in the first embodiment of FIG. 1, it is possible to prevent the resonance vibration from being attracted to the cover body 17 and to prevent the casing 16 side. In addition, since the resin reinforcement / absorption layer 30 formed on the end wall 16a near the bearing portion 19 where the mechanical vibration is transmitted enhances the rigidity near the bearing portion 19, it is transmitted to the bearing portion 19. The mechanical vibration to be generated is such that the mechanical vibration is absorbed and mitigated by the presence of the resin reinforcing / absorbing layer 30 formed on the end wall 16a without providing the first vibration absorbing device 24 on the bearing portion 19. Therefore, it is possible to remarkably reduce the induction of resonance vibration to the casing 16.

FIG. 8 shows a spectrum diagram of a noise test of the electric motor X ₁ manufactured according to the second embodiment of the present invention. The spectrum diagram of FIG. 8 and the noise of the conventional electric motor Y shown in FIG. Comparing the graph values at the same level with the spectrum diagram of the test, the second embodiment of the present invention, that is, by forming the resin reinforcing / absorbing layer 30 on the end wall 16a of the casing 16, Although it is not as high as that of the first embodiment, it is obvious that the sound reduction effect is obtained. In FIG. 10, it was found that even when the noise level values at the required number of revolutions were compared, the noise level values were slightly inferior to those in the first embodiment, but fell by about 2 to 4 dB.

FIGS. 5 and 6 show a modification of the first embodiment of the present invention. In FIG. 5, the bearing portions 19 and 20 of the casing 16 and the cover body 17 are respectively provided with first bearings. , The second vibration absorbing device 24, 25, and further, as described in the second embodiment of the present invention, the resin reinforcing / absorbing layer 30 is provided on the end wall 16a of the casing 16 to drive the electric motor X. _In addition, in FIG. 6, in place of the resin reinforcement / absorption layer 30 formed in FIG. 5, the same vibration isolation as the rubber members 23, 23a in the bearing portions 19, 20 is used in FIG. in which the rubber member, and to the resonant absorption layer 31 formed by equally stuck so as to surround the outside of the bearing portion 19 provided on the end wall 16a of the casing 16 constituting the motor X ₃ .

Then, as shown in FIGS. 5 and 6, the first and second vibration absorbers 24 and 25 are provided on the bearings 19 and ₂₀ of the electric motors X ₂ and X ₃ , respectively, and the casing 16 By forming the resin reinforcement / absorption layer 30 and the resonance absorption layer 31 so as to surround the bearing portion 19 on the end wall 16a of the motor 16, the electric motors X ₂ and X ₃ are provided with the bearing portion 19 of the casing 16. The outer side is completely surrounded by the resin reinforcement / absorption layer 30 or the resonance absorption layer 31 to increase the rigidity around the bearing portion 19 or to absorb and relax the resonance of the bearing portion 19. Therefore, even if mechanical vibrations from the rotor 13 are transmitted to the bearing portions 19 and 20 through the rotor shaft 14 by the driving of the electric motors X ₂ and X ₃ , these vibrations are Absorbed by vibration absorbers 24 and 25 In addition, even if the mechanical vibrations are induced into the casing 16 as resonance vibrations, these resonance vibrations can be satisfactorily improved by the resin reinforcement / absorption layer 30 and the resonance absorption layer 31 formed outside the bearing portion 19. Since it is possible to absorb and mitigate the noise, it is possible to reduce the noise caused by the mechanical vibration generated by the operation of the electric motors X ₂ and X _{3 in} the same manner as the electric motors X and X ₁ shown in FIGS. It will be possible.

[0021]

[Effect of device]

 As described above, the present invention is an electric motor that rotatably supports a rotor shaft to which a rotor is attached to a bearing portion formed on a casing and a cover body through a bearing. , A washer made of a hard material such as metal and a thick rubber member rich in oil resistance are inserted between the inner bottom surface and the bearing to form a vibration absorber, and if necessary, on the casing side. A mechanical reinforcement generated by rotating the rotor of the electric motor is provided on the outer circumference of the bearing to strengthen the rigidity of the bearing and to form a resin reinforcement / absorption layer or a resonance absorption layer to alleviate resonance vibration. When it is transmitted to the above bearing through the rotor shaft, this vibration is absorbed by the vibration absorber provided in the bearing to suppress the resonance vibration from being induced in the casing and the cover body as much as possible, and Mechanical vibration is the most transmitted The casing-side bearing, which is susceptible to vibration, is surrounded by a synthetic resin or anti-vibration rubber member as necessary to ensure that the resonance vibration is not transmitted to the casing. All mechanical vibrations generated by the operation of the motor shall be transmitted to the entire electric motor, and by doing so, it shall be possible to reliably prevent induction of resonance vibrations, etc. in the electric motor and the components of the equipment driven by this electric motor. As a result, it is possible to reduce the noise caused by the operation of the electric motor, and it is possible to reliably prevent the generation of unpleasant noise for humans from equipment using the electric motor.

Further, in the present invention, the vibration absorbing device provided in the bearing portion, the resin reinforcement / absorption layer for cushioning the resonance vibration formed on the outer periphery of the bearing portion of the casing, and the like are special vibration absorbing members, installation places, etc. It is possible to configure the inside of the motor or a required place on the peripheral surface thereof by using a commercially available material without increasing the size of the motor, thereby increasing the size of the motor and increasing the manufacturing cost. There is also the advantage that it can be economically manufactured with a simple structure.

Further, since the rubber member inserted in the bearing portion is pressed and urged in the thrust direction by a washer made of a hard material with a substantially uniform force over the entire surface thereof, the mechanical force transmitted to the bearing portion is increased. It is possible to satisfactorily absorb the physical vibration by the washer made of a hard material, and as a result, it is possible to satisfactorily block the resonance vibration induced in the casing and the like.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an electric motor equipped with a noise suppression device of the present invention.

FIG. 2 is a perspective view of a rubber member.

FIG. 3 is a perspective view of a rubber member.

FIG. 4 is a vertical sectional view of an electric motor according to a second embodiment of the present invention.

FIG. 5 is a vertical sectional view of an electric motor showing another embodiment of the present invention in which a reinforcing / absorbing layer of synthetic resin is provided on the outside of the casing.

FIG. 6 is a vertical cross-sectional view of an electric motor according to still another embodiment of the present invention in which a rubber member is attached to the outside of the casing to reduce the resonance vibration propagating to the casing.

FIG. 7 is a spectrum diagram showing noise of an electric motor to which the first embodiment of the present invention is applied.

FIG. 8 is a spectrum diagram showing noise of an electric motor to which a second embodiment of the present invention is applied.

FIG. 9 is a spectrum diagram showing noise in a conventional electric motor.

FIG. 10 is a diagram showing a noise level difference at a required rotation speed between a conventional electric motor and an electric motor to which the first and second embodiments of the present invention are applied.

FIG. 11 is a cross-sectional view showing a conventional electric motor in a longitudinal section.

[Explanation of symbols]

 13 rotor 14 rotor shaft 15 bearing 16 casing 16a end wall 17 cover body 18 tubular part 19 bearing part 20 bearing part 21 annular spring 22 washer 23 rubber member 24 vibration absorber 25 vibration absorber 30 resin reinforcement / absorption layer 31 Resonance absorption layer X Electric motor

Claims (4)

[Scope of utility model registration request] 1. A casing in which a stator core is press-fitted and fixed, and a cover body covering an opening of the casing,
Cylindrical bearings are integrally formed on end walls of the stator core that face each other in the axial direction, and the rotor shaft is mounted on the bearings via bearings fitted to the rotor shaft of the rotor. In a motor configured to rotatably support, a washer made of a hard material such as a metal material and a rubber member excellent in oil resistance are respectively inserted between the inner bottom surface of the bearing portion and the bearing, and further, the casing. A corrugated annular spring is inserted between the bearing and the washer in the side bearing portion, and each of the bearing portions of the casing and the cover body is equipped with a vibration absorbing device including the washer and a rubber member. Characteristic motor noise prevention device. 2. A resin reinforcing / absorbing layer surrounding the bearing portion from the outside of the casing is provided on an end wall on the casing side having a bearing portion containing the vibration absorbing device. Item 1. A noise prevention device for an electric motor according to item 1. 3. A resonance absorption layer made of a rubber member that surrounds the bearing portion from the outside of the casing is provided on an end wall on the casing side having a bearing portion containing the vibration absorbing device. The noise prevention device for an electric motor according to claim 1. 4. A casing in which a stator core is press-fitted and fixed, and a cover body covering an opening of the casing,
Each of the rotor cores is integrally formed with a cylindrical bearing portion on an end wall opposite to the axial direction of the stator core, and the rotor is mounted on the bearing portions via bearings fitted to the rotor shaft of the rotor. In a motor in which a shaft is rotatably supported, a washer made of a hard material such as a metal member and a rubber member excellent in oil resistance are inserted between the inner bottom surface and the bearing of the bearing portion of the cover body. To form a vibration absorber, further, in the bearing portion on the casing side, while inserting a corrugated annular spring between the inner bottom surface and the bearing, on the casing end wall outside the bearing portion, A noise suppressing device for an electric motor, comprising a resin reinforcing / absorbing layer integrally surrounding the bearing portion from the outside.