JP2011259647A - Motor for electrically-driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent abnormal noise of a bearing due to caulking to improve silence of a motor.SOLUTION: A shaft 13 of a rotor 3 is rotatably supported by ball bearings 14a and 14b in a motor 1 for an electrically-driven power steering device. The bearing 14b is caulked and fixed to a housing 4 by caulking parts 42. When C is the number of the caulking parts 42, n is a positive integer number, and z is the number of balls in the ball bearing, the number of the caulking parts 42 satisfies following conditions: (1) C≠nZ, C≠n(Z±1); (2) n×(Z+1)>C>(n-1)×(Z-1), n=2; and (3) C is an even number. The number of the caulking parts 42 is set so that a highest part of waviness formed in the ball bearing in a radial direction and in a axial direction is not coincided with the caulking parts 42.

Description

  The present invention relates to an electric motor used as a drive source of an electric power steering apparatus, and more particularly to a bearing fixing structure that supports a rotating shaft of a motor.

  In an electric motor for an electric power steering device (hereinafter abbreviated as EPS), a rotating shaft (motor shaft) of the motor is rotatably supported by a bearing. FIG. 4 is an explanatory view showing a mounting state of the bearing in the EPS motor. As shown in FIG. 4, the bearing 51 is inserted and fixed in a cylindrical bearing housing portion 53 provided at the end of the motor housing 52. A shaft 54 is rotatably inserted inside the inner ring 51 a of the bearing 51. A bearing washer 55 is disposed on the left end side of the outer ring 51b of the bearing 51 in accordance with the specifications.

  The bearing 51 is restricted from moving in the thrust direction by caulking. Further, the movement in the rotational direction is restricted by the frictional force between the outer ring 51b and the inner peripheral surface of the bearing accommodating portion 53. The bearing housing portion 53 is provided with a plurality of crimping portions 56 along the circumferential direction. The caulking portion 56 is formed by plastically deforming the inner peripheral surface of the bearing accommodating portion 53 with a caulking punch 57. By this caulking portion 56, the outer ring 51 b is fixed in the bearing housing portion 53 together with the bearing washer 55.

Japanese Unexamined Patent Publication No. 2009-201255 JP 2010-41871 A

  However, since the caulking is fixed directly or indirectly through a bearing washer, the outer ring of the bearing may be slightly deformed. As is well known, the bearing is arranged between the outer and inner rings where a very high precision ball is controlled with high precision. It becomes. In particular, in EPS motors that are subjected to high loads, the caulking is firmly fixed to prevent the bearing from being detached, and the clearance inside the bearing tends to narrow due to the influence of the deflection of the rotating shaft. There was a problem that sound was easily generated. Furthermore, abnormal noise of the bearing is transmitted to the shaft as vibration of the motor, which may affect the rattling noise of the worm gear of the reduction gear, and countermeasures have been demanded.

  An object of the present invention is to improve the quietness of a motor by suppressing abnormal noise of a bearing due to caulking.

  A motor for an electric power steering apparatus according to the present invention is used as a drive source of an electric power steering apparatus, and a rotor attached to a rotating shaft, a stator disposed outside the rotor, and the rotating shaft are rotatably supported. An electric motor having a ball bearing that houses the stator and a bearing housing portion to which the ball bearing is mounted, the ball bearing extending along a circumferential direction of the ball bearing, Movement in the axial direction is restricted by caulking portions provided at a plurality of locations in the bearing accommodating portion, and the caulking portion is defined by C being the number of caulking portions, n being a positive integer, and Z being the number of balls of the ball bearing. (1) C ≠ nZ, C ≠ n (Z ± 1), (2) n × (Z + 1)> C> (n−1) × (Z−1) n = 2, and wherein (3) that C is an even number, provided conditions are satisfied the number of.

  In the present invention, by providing the number of crimping portions in accordance with the above-described conditions, the radial and axial undulation peaks generated in the ball bearing do not overlap with the crimping portions, and the vibration of the bearing can be kept small. As a result, the noise generated by the crimping portion is also minimized, and the quietness of the motor is improved.

  In addition, another motor for an electric power steering apparatus according to the present invention is used as a drive source of the electric power steering apparatus, and includes a rotor attached to a rotating shaft, a stator disposed outside the rotor, and the rotating shaft. An electric motor comprising: a ball bearing that is rotatably supported; and a housing that houses the stator and includes a bearing housing portion to which the ball bearing is attached, wherein the ball bearing is a circumferential direction of the ball bearing. The movement in the axial direction is restricted by the caulking portions provided at a plurality of locations in the bearing housing portion, and the number of the caulking portions is determined by the radial and axial undulation peaks generated in the ball bearing. It is characterized by the number not overlapping with the part.

  In the present invention, by setting the number of crimping portions so that the radial and axial undulation peaks generated in the ball bearing do not overlap with the crimping portions, the shake of the bearing can be suppressed to a small value. As a result, the noise generated by the crimping portion is also minimized, and the quietness of the motor is improved.

  In the present invention, in the motor for an electric power steering apparatus using a ball bearing having a motor ball number C of 8, the number of the caulking portions may be set to 10, thereby using, for example, 6000 series bearings. Abnormal noise in the motor is minimized and the quietness of the motor is improved.

  According to the motor for an electric power steering apparatus of the present invention, the caulking portion that restricts the movement of the ball bearing that rotatably supports the rotor rotating shaft in the axial direction includes the number of the caulking portions as C, n is a positive integer, When Z is the number of balls of the ball bearing, (1) C ≠ nZ, C ≠ n (Z ± 1), (2) n × (Z + 1)> C> (n−1) × (Z−1) , N = 2, (3) By providing a number that satisfies the conditions of an even number of C, the runout of the bearing can be reduced. Therefore, abnormal noise generated by the crimping portion is suppressed to the minimum, and it is possible to improve the quietness of the motor.

  According to another motor for an electric power steering apparatus of the present invention, the number of caulking portions that restrict movement of the ball bearing that rotatably supports the rotor rotating shaft in the axial direction is set to a radial direction generated in the ball bearing and By setting the number of axial waviness peaks so as not to overlap with the caulking portion, it is possible to reduce the bearing runout. Therefore, abnormal noise generated by the crimping portion is suppressed to the minimum, and it is possible to improve the quietness of the motor.

It is sectional drawing of the motor for electric power steering apparatuses which is one Example of this invention. It is a table | surface which shows the relationship between the number of crimps and the order of a wave | undulation in 6000 series bearings (the number of balls: 8). It is a table | surface which shows the experimental result which actually measured the run-out in the 6000 series bearing. It is explanatory drawing which shows the attachment state of the bearing in the motor for electric power steering apparatuses.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of an EPS motor according to an embodiment of the present invention. The EPS motor 1 (hereinafter abbreviated as “motor 1”) is used, for example, as a power source of a column assist type EPS, and applies an operation assisting force to a steering shaft of an automobile. The motor 1 is a so-called brushless motor, and has an inner rotor type configuration in which a stator (stator) 2 is arranged on the outside and a rotor (rotor) 3 is arranged on the inside, as shown in FIG. The motor 1 is attached to a reduction mechanism (not shown) provided on the steering shaft, and the rotation of the motor 1 is reduced and transmitted to the steering shaft by the reduction mechanism.

  The stator 2 includes a bottomed cylindrical housing 4, a stator core 5, a stator coil 6 (hereinafter abbreviated as a coil 6) wound around the stator core 5, and a bus bar unit 7 attached to the stator core 5. . The housing 4 is formed in a bottomed cylindrical shape with iron or the like, and also serves as a motor yoke. A bracket 8 made of synthetic resin is attached to the opening of the housing 4 with a fixing screw 10. A synthetic resin insulator 11 is attached to the stator core 5, and a coil 6 is wound around the insulator 11. An end portion 6 a of the coil 6 is drawn out at one end side of the stator core 5.

  A bus bar unit 7 in which a copper bus bar 9 is insert-molded in a synthetic resin main body is attached to one end side of the stator core 5. A plurality of power feeding terminals 12 project from the bus bar 9 in the radial direction, and the power feeding terminals 12 project radially around the bus bar unit 7. On the other hand, the end of the bus bar 9 extends in the axial direction from the end face of the bus bar unit 7 to form a bus bar terminal 33. When the bus bar unit 7 is attached, the coil end 6 a is welded to the power feeding terminal 12. In the bus bar unit 7, the number of bus bars 9 corresponding to the number of phases of the motor 1 (here, three for the U phase, V phase, and W phase) is provided, and each coil 6 corresponds to that phase. It is electrically connected to the power supply terminal 12. The stator core 5 is press-fitted and fixed in the housing 4 after the bus bar unit 7 is attached.

  A rotor 3 is inserted inside the stator 2. The rotor 3 has a shaft 13 that serves as a motor rotation shaft. The shaft 13 is rotatably supported by ball bearings (hereinafter abbreviated as bearings) 14a and 14b. The rear-side bearing 14 a is press-fitted and fixed to a bearing accommodating portion 41 formed at the center of the bottom of the housing 4. The front-side bearing 14 b is fixed to the central portion of the bracket 8 by a metal bearing holder 19. A bearing housing 41 having a bottomed cylindrical shape is formed at the center of the bearing holder 19. The bearing 14b is inserted into the bearing accommodating portion 41 and fixed by caulking. A caulking portion 42 is formed in the bearing accommodating portion 41 with the same configuration as in FIG. 4. The bearing 14a is fixed in a state where movement in the axial direction is restricted by the crimping portion 42. The caulking portion 42 is provided at a plurality of locations along the circumferential direction.

  Here, in the motor 1 according to the present invention, the noise of the bearing due to the caulking is suppressed by optimizing the number of the caulking portions 42, and the quietness of the motor is improved. Generally, the vibration of the bearing depends on the number of balls of the bearing, and the number of undulations in the radial direction in one rotation of the shaft (inner ring) is nZ ± 1 (n: positive integer, Z: number of balls), shaft It is known that the number of undulation vibrations in the direction is nZ. In the conventional EPS motor, so-called 6000 series bearings using eight balls are used as the bearings, and the number of caulking portions 42 is four. That is, the number of balls is a multiple of the number of crimps. For this reason, it was inferred that the deformation part caused by caulking and the undulation pile overlap each other, and the influence of the undulation appears greatly and abnormal noise is generated.

  Therefore, the present inventors have focused on the relationship between the number of crimps and the undulation peaks (the number of bearing balls), and examined the relationship between the bearings in the 6000 series. FIG. 2 is a table showing the results. In FIG. 2, ● represents the degree of waviness due to caulking (number of caulking), 、 represents the degree of waviness in the radial direction (number of peaks), and ○ represents the degree of waviness in the axial direction (number of peaks). Note that the swell of the order exceeding the 20th order has a small shake and little influence on the motor performance, so attention is paid to the swell of the 20th order or less.

  As can be seen from FIG. 2, for example, in the case of 4-point caulking, ● and ○ overlap with the number of balls 8 or a multiple thereof, and in the case of 6-point caulking, it is a multiple (18) of the number of balls 8 ● and ◎ overlap. Thus, in the setting where ● and ◎ or ○ overlap, the deformed portion caused by caulking and the undulation mountain overlap with each other in a completely coincident manner. Therefore, a setting in which ●, ◎, and ○ overlap must be avoided to suppress abnormal noise. Analyzing the table of FIG. 2 from this point of view, the fact that ● and ◎ or ○ do not overlap at all is that the number of crimps is 5 or 10 for a bearing with 8 balls. However, when the number of caulking is 5, the arrangement of the caulking portions 42 is asymmetrical, the balance is lost, and undulation is likely to occur. Therefore, from the analysis of the table, the caulking number of 10 is optimal for the number of balls of eight.

  The present inventors conducted an experiment to confirm this conclusion, and obtained a result as shown in the graph of FIG. As shown in FIG. 3, 10-point caulking was the best result, confirming the predictions from the previous analysis. That is, by setting so that the radial and axial undulation peaks generated in the bearing do not overlap with the caulking portion, the vibration of the bearing can be suppressed to be small, and the noise generated by the caulking portion 42 is also minimized. Can be suppressed. Further, it was also found that the odd-number caulking of 5 points and 9 points is not preferable because the primary component has particularly large fluctuation. The same analysis and experiment was performed on a 600 series bearing with 7 balls. However, the 10-point caulking where ●, ◎ and ○ do not overlap is the best, and ●, ◎ and ○ are heavy. Although it was not possible, the odd-numbered 5-point caulking had a large fluctuation.

Based on such results, the inventors have found that a very quiet motor can be provided by setting the caulking points of the EPS motor as follows.
C: number of crimps, n: positive integer, Z: number of balls (1) C ≠ nZ, C ≠ n (Z ± 1)
(2) n × (Z + 1)>C> (n−1) × (Z−1), n = 2
(3) C is an even number In this case, (1) is a setting for avoiding resonance with the order component of the waviness of the bearing. The reason why n = 2 is set in (2) is that n = 3 or more is not preferable in terms of management because the number of crimping punches increases. The reason (3) is that if C is an odd number and the caulking portion is asymmetrically arranged, a large swell of even components occurs.

  As described above, in the EPS motor of the present invention, by setting the number of the caulking portions 42 as described above, it is possible to avoid the competition between the caulking portions and the “swells” of the bearings. It is possible to minimize abnormal noise. Therefore, it is possible to provide a motor with high quietness that suppresses roller noise of the bearing. Moreover, since the number of crimps is also optimized, it is not necessary to increase the number of crimps more than necessary. For this reason, the number of crimps can be suppressed as much as possible, the quality control of the motor becomes easy, and the product quality can be improved and the product price can be reduced. Further, with the reduction of abnormal noise, the contact state in the bearing is relaxed and the life of the bearing is improved.

  Cylindrical rotor cores 15a to 15c are fixed to the shaft 13, and segment type magnets (permanent magnets) 16a to 16c are attached to the outer periphery thereof. A bottomed cylindrical magnet cover 18 is attached to the outside of the magnets 16a to 16c.

  Synthetic resin magnet holders 17a to 17c are attached to the outside of the magnets 16a to 16c. The magnets 16a to 16c are arranged on the outer circumferences of the rotor cores 15a to 15c so as to be held by the magnet holders 17a to 17c. In the motor 1, the magnets 16a to 16c are arranged in three rows in the axial direction by the magnet holders 17a to 17c.

  A rotor (resolver rotor) 22 of a resolver 21 serving as a rotation angle detection unit is attached to the end of the magnet holder 17a. On the other hand, a stator (resolver stator) 23 of the resolver 21 is press-fitted into a metal resolver holder 24 and accommodated in a bracket holder 25 made of synthetic resin. The resolver holder 24 is formed in a bottomed cylindrical shape, and is lightly press-fitted into the outer periphery of the end portion of the rib 26 provided in the center portion of the bracket 8. The bracket holder 25 is fixed to the inside of the bracket 8 by a tapping screw (not shown).

  The bracket holder 25 and the bracket 8 are fixed by the aforementioned tapping screw in a form in which the flange portion 24a of the resolver holder 24 is interposed therebetween. The flange portion 24a is attached between the bracket holder 25 and the bracket 8 so as to be slightly movable in the circumferential direction. After the position of the stator 23 is adjusted, the resolver holder 24 is attached to the bracket holder 25 by a resolver fixing screw 28. Fixed. As shown in FIG. 1, a metal resolver fixing nut 27 is attached to the bracket holder 25. A resolver fixing screw 28 is screwed into the resolver fixing nut 27 from the outside of the bracket 8, and the bearing holder 19 and the resolver holder 24 are fastened together with the bracket 8. Thereby, the resolver holder 24 is fixed to the inside of the bracket 8 in a state where the position in the circumferential direction is adjusted.

  A power terminal 31 is also insert-molded in the bracket 8. The power terminal 31 is provided for each of the U, V, and W phases, and one end side 31 a thereof is disposed in the opening 32. The other end 31 b of the power terminal 31 is disposed in the power connector 34. When the bracket 8 is assembled to the housing 4, the bus bar terminal 33 extending in the axial direction from the bus bar unit 7 faces the power terminal 31 in parallel. In the motor 1, after the bracket 8 is attached to the housing 4, the bus bar terminal 33 and the power terminal 31 are fixed by welding in the opening 32.

It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.
For example, in the above-described embodiment, the configuration in which the bearing 14 is caulked when the bearing is caulked is shown. However, the bearing 14b is directly caulked by the caulking portion 42 without using the bearing washer. It may be fixed.

DESCRIPTION OF SYMBOLS 1 Motor for electric power steering apparatus 2 Stator 3 Rotor 4 Housing 5 Stator core 6 Stator coil 6a Coil end 7 Bus bar unit 8 Bracket 9 Bus bar 10 Fixing screw 11 Insulator 12 Feed terminal 13 Shafts 14a, 14b Ball bearings 15a to 15c Rotor core 16a -16c Magnet 17a-17c Magnet holder 18 Magnet cover 19 Bearing holder 21 Resolver 22 Resolver rotor 23 Resolver stator 24 Resolver holder 24a Flange 25 Bracket holder 26 Rib 27 Resolver fixing nut 28 Resolver fixing screw 31 Power terminal 31a One end 31b The other end Side 32 Opening 33 Busbar terminal 34 Power connector 41 Bearing housing part 42 Caulking part 51 Bear Ring 51a inner race 51b outer race 52 motor housing 53 bearing housing 54 a shaft 55 bearing washer 56 caulking portion 57 caulking punch

Claims (3)

Used as a drive source for an electric power steering device,
A rotor attached to the rotating shaft;
A stator disposed outside the rotor;
A ball bearing that rotatably supports the rotating shaft;
An electric motor having a housing that houses the stator and has a bearing housing portion to which the ball bearing is attached,
The ball bearing is restricted from moving in the axial direction along the circumferential direction of the ball bearing by caulking portions provided at a plurality of locations in the bearing housing portion,
When the number of the crimped portions is C, n is a positive integer, and Z is the number of balls of the ball bearing,
(1) C ≠ nZ, C ≠ n (Z ± 1)
(2) n × (Z + 1)>C> (n−1) × (Z−1), n = 2
(3) A motor for an electric power steering apparatus, wherein C is provided in a number satisfying even-numbered conditions. Used as a drive source for an electric power steering device,
A rotor attached to the rotating shaft;
A stator disposed outside the rotor;
A ball bearing that rotatably supports the rotating shaft;
An electric motor having a housing that houses the stator and has a bearing housing portion to which the ball bearing is attached,
The ball bearing is restricted from moving in the axial direction along the circumferential direction of the ball bearing by caulking portions provided at a plurality of locations in the bearing housing portion,
The motor for an electric power steering apparatus, wherein the number of the crimping portions is a number that does not overlap the radial and axial undulations generated in the ball bearing with the crimping portions.   3. The motor for an electric power steering apparatus according to claim 1, wherein the number of the caulking portions is set to 10 in the motor for an electric power steering apparatus using a ball bearing having 8 balls.

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