JP2008118813A - Electric motor for hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor for hybrid vehicle, with which noise and vibration can be suppressed. <P>SOLUTION: Ball bearings 7 and 8 on an output gear OG-side and ball bearings 14 and 15 on an opposite side across a rotor 5 are back-combined. Thus, rigidity of a rotation axis 4 with respect to bending can be improved and a resonance frequency can be raised. When a helical gear is used for the output gear OG, large thrust force is given to the rotation axis 4. Since thrust force can be supported by the ball bearings in two rows in such a case, it is advantageous in respect of rolling contact fatigue life. Prescribed pre-load is given to the ball bearings 7, 8, 14 and 15. Thus, support rigidity is improved, play inside the bearing is removed and vibration and noise can be suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric motor, and more particularly to an electric motor suitable for use in a hybrid vehicle.

Hybrid vehicles with good fuel efficiency are attracting attention against the background of global warming and rising crude oil prices. A hybrid vehicle converts kinetic energy into electric energy during deceleration and collects it, and drives the electric motor using the collected electric energy during re-acceleration to assist the driving force of the engine (Patent Literature). 1 and 2). Therefore, it is important to increase the efficiency of the electric motor in order to improve the fuel efficiency of the vehicle. As one method for improving the efficiency of the electric motor, the high speed rotation is being studied.
JP 2004-248449 A JP-A-8-183347

  By the way, when an electric motor is rotated at a high speed, noise and vibration generated from the motor become a problem. If it is attempted to suppress noise and vibration with a shielding plate or the like, there is a risk that a countermeasure against heat may be required, or that the weight may increase. Therefore, it is strongly desired to suppress noise and vibration by the configuration of the electric motor itself.

  The present invention has been made in view of the problems of the prior art, and an object thereof is to provide an electric motor for a hybrid vehicle that can suppress noise and vibration.

The electric motor for a hybrid vehicle of the present invention is
Case and
A stator fixed to the case;
An output gear is provided on one end side, a rotor is disposed on the outer periphery, and a rotating shaft that rotates with respect to the case;
A plurality of ball bearings arranged across the rotor and rotatably supporting the rotating shaft with respect to the case;
Two ball bearings provided on the one end side are arranged via a spacer between the two,
The ball bearing on the one end side and the ball bearing on the other end side are a back surface combination and are provided with a predetermined preload.

  Generally, in an electric motor for a hybrid vehicle, if the radial resonance point (dangerous speed) of the rotating shaft is not sufficiently higher than the maximum speed of the motor, vibration and noise cannot be suppressed to an allowable range. Usually, it is said that the critical speed is preferably suppressed to 50 to 60% or less of the maximum rotational speed. However, as described above, in applications such as hybrid vehicles, it is desired to increase the maximum speed of the electric motor, and therefore it is necessary to increase the dangerous speed accordingly. For example, if the rotation shaft of the electric motor is to be rotated at 50,000 revolutions per minute, the resonance frequency (dangerous speed) needs to be 1400 Hz or higher.

  The present inventor tried to suppress vibrations by increasing the critical speed (resonance rotation speed) of the rotating shaft as the electric motor for a hybrid vehicle is rotated at a high speed. However, in order to suppress the resonance, it is directly effective to shorten the rotating shaft and reduce the weight, but this usually has a trade-off relationship with the required performance (output, torque, etc.) of the motor. In other words, since an electric motor used in a hybrid vehicle needs to have as high performance as possible, it is difficult to shorten or reduce the weight of the rotating shaft below a required dimension. Also, even if the output gear is brought closer to the rotor, it naturally has a limit in order to avoid interference with the coil end of the motor.

  Therefore, the present inventor has examined whether the critical speed can be increased by the support mode even when the same rotating shaft is used. FIG. 1 is a diagram showing a vibration mode of a rotating shaft at the time of resonance. The rotating shaft forms an output gear at one end, and a rotor is disposed on the center outer periphery. It is supported by rolling bearings at both ends of the rotor. Here, as the vibration mode, there are a tip mode in which the tip is bent as shown in FIG. 1 (a) and a rotor mode in which the rotor center portion is bent as shown in FIG. 1 (b).

  FIG. 2 is a cross-sectional view of a normal electric motor on which the present inventor has studied, and the rotating shaft SH is supported by two ball bearings BR provided on both sides of the rotor RT. In general, the position of the output gear and the weight and length of the rotor are determined by the specifications of the motor, so these cannot be freely changed. Therefore, it is examined whether the critical speed can be increased by changing the position of the bearing.

  In FIG. 2, the result of simulating how the resonance frequency changes when the position of the ball bearing BR on the right side indicated by the solid line is the origin and the position of the ball bearing BR is shifted to the output gear OG side, As shown in FIG. FIG. 3 shows that in the rotor mode, the resonance frequency increases as the bearing position is farther from the output gear OG, and in the tip mode, the resonance frequency increases as the bearing position is closer to the output gear OG. That is, from the result shown in FIG. 3, it was found that the resonance frequency could not be sufficiently increased in both the tip mode and the rotor mode regardless of the position of the ball bearing in the example of FIG.

  Therefore, in order to increase the resonance frequency in both the tip mode and the rotor mode, the present inventor has two rows of ball bearings on the output gear side and arranges a spacer between them to make a span and to rotate the rotating shaft. I came up with support. As a result, the resonance frequency can be increased in both the tip mode and the rotor mode.

Further, in order to increase the resonance frequency in both the tip mode and the rotor mode, the present inventor predetermines a ball bearing on the output gear side and a ball bearing on the opposite side across the rotor as a back surface combination. I came up with a preload. As shown in FIG. 4, “back surface combination” means a line α connecting the contact point between the ball and the two wheels in one ball bearing and a line connecting the contact point between the ball and the other wheel in the other ball bearing in the axial cross section. β is a combination of ball bearings that intersect the ball radially outward. Since the action point distance a ₀ can be secured large, there is a feature that the rigidity against moment load is strong.

  According to the present invention, by combining the ball bearing on the output gear side and the ball bearing on the opposite side across the rotor with respect to the back bearing, the rigidity against bending of the rotating shaft can be increased, and the resonance frequency Can be raised. Furthermore, when a helical gear is used as the output gear, a large thrust force is applied to the rotating shaft. In such a case, since the thrust force can be supported by two rows of ball bearings, the point of rolling fatigue life is increased. But it is advantageous. Furthermore, by applying a predetermined preload to the ball bearing, it is possible to provide an electric motor for a hybrid vehicle that can increase support rigidity and eliminate vibrations and noise by eliminating backlash inside the bearing.

  When the ball bearing has ceramic balls, high radial rigidity can be obtained by reducing the weight of the balls.

  If the ball bearing on the one end side and the ball bearing on the other end side are different from each other in the ball PCD (pitch circle diameter), the ball diameter, or the contact angle, it suppresses the beat phenomenon of the ball revolution component vibration. , Noise can be reduced.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 5 is a cross-sectional view of the electric motor for the hybrid vehicle according to the present embodiment. In FIG. 5, a stator 3 around which a coil 2 is wound is fixed to the inner peripheral surface of a cylindrical case 1. The rotor 5 disposed on the outer periphery of the rotating shaft 4 inserted through the case 1 is positioned so as to be included in the stator 3. An output gear OG is attached to the right end of the rotating shaft 4 so as to rotate integrally.

  A large holder 6 is fixed to the right end of the case 1. The large holder 6 includes a central cylindrical portion 6b having an opening 6a and a flange portion 6c extending radially outward from the central cylindrical portion 6b. The outer rings of the angular contact ball bearings 7 and 8 are fitted in the opening 6a, and the inner rings of the angular contact ball bearings 7 and 8 are fitted on the outer peripheral surface of the rotating shaft 4 inserted through the opening 6a. Yes. The balls of the angular contact ball bearings 7 and 8 are made of ceramic. In addition, the angular contact ball bearings 7 and 8 are a parallel combination.

  An outer ring spacer 9 and an inner ring spacer 10 are arranged between the angular contact ball bearings 7 and 8, and the angular distance between the angular contact ball bearings 7 and 8 is A. A passage 6d that penetrates the inside of the large holder 6 from the outside in the radial direction to the inside is communicated with a passage 9a that is formed in the spacer 9 and branches toward the angular contact ball bearings 7 and 8 and opens. The lubricating oil can be supplied from the outside to the angular contact ball bearings 7 and 8 through the passages 6d and 9a.

  The tip of the outer ring retainer 11 screwed to the large holder 6 presses the outer ring of the angular contact ball bearing 8 inward, so that the outer ring of the angular contact ball bearing 7 is axially inward via the outer ring spacer 9. Is pushed to the bottom of the large holder 6. On the other hand, the tip of the inner screw member 12 that is screwed onto the rotating shaft 4 presses the inner ring of the angular contact ball bearing 8 inward, so that the inner ring of the angular contact ball bearing 7 passes through the inner ring spacer 10. It is pushed inward in the axial direction and is supported by the rotor 5.

  A flange 1a extending radially inward and a cylindrical portion 1b extending in the axial direction from the flange portion 1a are formed at the left end of the case 1. A hollow cylindrical bearing sleeve 13 is fitted to the inner periphery of the cylindrical portion 1b so as to be slidable in the axial direction while interposing an O-ring having a sealing function. The outer rings of the angular contact ball bearings 14 and 15 are fitted to the inner peripheral surface 13a of the bearing sleeve 13, and the inner rings of the angular contact ball bearings 14 and 15 of the rotating shaft 4 inserted through the inner peripheral surface 13a. It is fitted to the outer peripheral surface. The balls of the angular contact ball bearings 14 and 15 are made of ceramic. The angular contact ball bearings 14 and 15 are combined in parallel. However, the angular contact ball bearings 7 and 8 on the opposite side across the rotor 5 are in a combination of the rear surfaces.

  An outer ring spacer 16 and an inner ring spacer 17 are arranged between the angular contact ball bearings 14 and 15, and the angular distance between the angular contact ball bearings 14 and 15 is B. A passage 1c that penetrates the inside of the flange portion 1a and the cylindrical portion 1b of the case 1 from the radially outer side to the inner side communicates with a hole 13b that penetrates the bearing sleeve 13 in the radial direction, and the hole 13b is a spacer. 16 is communicated with a passage 16a formed toward the angular contact ball bearings 14 and 15 so as to be supplied to the angular contact ball bearings 14 and 15 from the outside through the passages 1c, 13b and 16a. It has become.

  A coil spring 18 is disposed in a bag hole 1d formed in the cylindrical portion 1b and extending in the axial direction. The left end of the coil spring 18 is in contact with a donut plate-shaped outer ring retainer 19. The outer ring retainer 19 is connected to the bearing sleeve 13. Accordingly, since the bearing sleeve 13 is urged to the left in the figure via the outer ring restraint 19 by the urging force of the coil spring 18, the angular contact ball bearings 14, 15 are integrated with each other via the outer ring spacer 16. It will be urged to the left. Accordingly, a predetermined preload is applied between the angular contact ball bearings 7 and 8 and the angular contact ball bearings 14 and 15.

  On the other hand, the tip of the inner screw member 20 that is screwed onto the rotating shaft 4 presses the inner ring of the angular contact ball bearing 14 inward, so that the inner ring of the angular contact ball bearing 14 passes through the inner ring spacer 17. It is pushed inward in the axial direction and is supported by the rotor 5.

  A resolver rotor 21 is attached to the left end of the rotating shaft 4. On the other hand, a resolver holder 22 is fixed to the flange portion 1 a of the case 1, and a resolver stator 23 attached to the inner periphery thereof is disposed at a position facing the resolver rotor 21.

A magnetic force acts between the stator 3 and the rotor 5 by the electric power supplied from the outside of the case 1 via the wiring H, whereby the rotary shaft 4 rotates with respect to the case 1. At this time, an electrical signal is output from the resolver stator 23, whereby the rotation angle of the rotary shaft 4 can be detected. Since the output gear OG is a helical gear, a thrust force is generated on the rotating shaft 4 during power transmission, and this can be supported by the angular contact ball bearings 7 and 8 on the load side of the rear combination. . Here, the maximum rotation speed of the rotating shaft 4 is 50000 min ⁻¹ and an output of about 100 KW is exhibited. The inner diameter of the ball bearing is 30 mm, and the dmN value (rotational speed min ⁻¹ × ball pitch circle diameter of the bearing) is about 2 million. The angular contact ball bearings 7, 8, 14, and 15 may be those obtained by appropriately giving a contact angle to the deep groove ball bearing.

In the present embodiment, it is possible to increase the resonance frequency in both the tip mode and the rotor mode by ensuring a large inter-ball distance A between the angular contact ball bearings 7 and 8 on the output gear OG side. Furthermore, in this embodiment, two rows of angular contact ball bearings 14 and 15 are provided on the counter-output gear OG side to increase the resonance frequency. However, by reducing the distance B between the balls, the resonance in the rotor mode is achieved. The frequency can be further increased. Instead of the two rows of angular contact ball bearings 14 and 15, a single row of angular contact ball bearings may be provided. The resonance frequency when the ball bearing arrangement is optimally designed is shown below.
1200 Hz: Example in which the rotating shaft is supported by two ball bearings 1400 Hz: Example in which the rotating shaft is supported by three ball bearing pairs (two on the output gear side and one on the non-output gear side) 1500 Hz: Four rotating shafts Example of support with two ball bearing pairs (two on the output gear side and two on the non-output gear side) (see Fig. 5)

  In order to increase the rotation speed of an electric motor, it is necessary to increase the resonance frequency sufficiently. For this purpose, it is necessary to increase the radial rigidity of the bearing. The inventor has compared and examined the radial rigidity during high-speed rotation with respect to the conventional example, Example 1, and Example 2. Each specification is shown in Table 1. FIG. 6 shows the relationship between the rotational speed and the radial stiffness, and FIG. 7 shows the relationship between the radial stiffness and the resonance frequency. FIG. 7 shows that the higher the radial rigidity, the higher the resonance frequency.

尚、溝Ｒ比とは、（軌道輪の溝断面の曲率半径Ｒ／玉の外径Ｄ）で表される値をいい、５０である場合にはＲ＝Ｄ／２である。

The groove R ratio is a value expressed by (the radius of curvature R of the cross section of the raceway ring / the outer diameter D of the ball), and in the case of 50, R = D / 2.

  In general, when a ball bearing rotates at high speed, the radial rigidity decreases due to the centrifugal force of the ball. In the result of FIG. 6, the radial rigidity of Example 1 is improved as compared with the conventional example. This is because if the inner ring groove R ratio is larger than the outer ring groove R ratio, the balance between the ball centrifugal force, the preload and the contact point reaction force is stabilized, and the reduction in radial rigidity during high rotation can be suppressed. Because.

  Further, in the result of FIG. 6, the radial rigidity of Example 2 is improved as compared with Example 1. This is because changing the ball material from SUJ2 to ceramic reduces the weight of the ball and reduces the influence of centrifugal force, thereby suppressing a decrease in radial rigidity during high rotation.

  In the present invention, the design of the right and left ball bearings is further changed with the rotor interposed therebetween, and the reduction of noise has also been studied. In rolling bearings, the revolution component vibration of the rolling elements always occurs. In the ball bearings on the right and left sides of the rotor, the revolution speed of the rolling elements slightly changes due to temperature changes and manufacturing variations. The vibration is canceled or strengthened, which causes a beat phenomenon. In a high-speed rotation specification such as an electric motor targeted by the present invention, an irritating beat sound is generated at a cycle of 1 to several seconds.

The revolution speed Nc of the rolling element is approximately Nc when Da: ball diameter (mm), α: contact angle (°), Dm: rolling element PCD (mm), Ni: shaft rotation speed (Hz). = (1-Da × cos α ÷ Dm) × Ni / 2
Can be expressed as Therefore, in this example, the right and left ball bearings of the rotor are designed differently so that the revolution speed Nc of the right ball bearing and the revolution speed Nc of the left ball bearing are sufficiently separated from each other. At least one of the parameters is changed. It was confirmed that when the difference between the revolution speed Nc of the right ball bearing and the revolution speed Nc of the left ball bearing is about 5 Hz or more, the annoying sound disappears.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate.

It is a figure which shows the vibration mode of the rotating shaft at the time of resonance. It is sectional drawing of the normal electric motor used as the foundation which this inventor examined. It is a figure which shows the relationship between the position of the ball bearing BR, and the resonance frequency. It is sectional drawing which shows the example of the ball bearing made into the back combination. It is sectional drawing of the electric motor concerning this Embodiment. It is a figure which shows the relationship between a rotational speed and radial rigidity. It is a figure which shows the relationship between radial rigidity and a resonant frequency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 1a Flange part 1b Cylindrical part 1c Passage 1d Bag hole 2 Coil 3 Stator 4 Rotating shaft 5 Rotor 6 Large holder 6a Opening 6b Central cylindrical part 6c Flange part 6d Passage 7, 8 Angular contact ball bearing 9 Outer ring spacer 9a Passage 10 Inner ring spacer 11 Outer ring restraint 12 Inner screw member 13 Bearing sleeve 13a Inner peripheral surface 14 Angular contact ball bearing 16 Outer ring spacer 16a Passage 17 Inner ring spacer 18 Coil spring 19 Outer ring restrainer 20 Inner screw member 21 Resolver rotor 22 Resolver holder 23 Resolver stator OG output gear

Claims (3)

Case and
A stator fixed to the case;
An output gear is provided on one end side, a rotor is disposed on the outer periphery, and a rotating shaft that rotates with respect to the case;
A plurality of ball bearings arranged across the rotor and rotatably supporting the rotating shaft with respect to the case;
Two ball bearings provided on the one end side are arranged via a spacer between the two,
The electric motor for a hybrid vehicle, wherein the ball bearing on the one end side and the ball bearing on the other end side are a combination of the back surfaces and are provided with a predetermined preload.   The electric motor for a hybrid vehicle according to claim 1, wherein the ball bearing has a ceramic ball.   3. The electric vehicle for a hybrid vehicle according to claim 1, wherein the ball bearing on the one end side and the ball bearing on the other end side are different from each other in a ball PCD, a ball diameter, or a contact angle. motor.

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