JP2012016201A - Motor and joint member for motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor using a joint member for the motor that has excellent shaft fixing strength and can secure high coaxial accuracy.SOLUTION: A motor unit 10 comprises: a motor 1; and a speed reduction mechanism section 41. An output shaft 12 of the motor is connected to an input shaft 13 of the speed reduction mechanism section 41 by a joint 1. The joint 1 includes a drive shaft mounting hole 2 through which the output shaft 12 is inserted and a driven shaft mounting hole 3 through which the input shaft 13 is inserted. The drive shaft mounting hole 2 includes an involute serration 31 press-fitted and fixed with the output shaft 12 thereto. The involute serration 31 includes a curved inner peripheral surface 31a abutting on an outer peripheral surface 12a of the output shaft 12. The output shaft 12 is brought into pressure contact with the involute serration 31 to be fixed in a rotation prevented manner by pressure contact holding force generated between the output shaft 12 and the involute serration 31.

Description

  The present invention relates to a motor used as a drive source of an electric power steering apparatus, and more particularly to a motor that connects a motor output shaft and a driven shaft by a joint member made of sintered metal.

  In a system that uses an electric motor as a drive source, a joint member that connects between the output shaft of the motor and the driven shaft is used when the rotational torque of the motor is transmitted to the driven side. The joint member is press-fitted and fixed to the motor output shaft (shaft), and is fixed by rotation by a serration provided on the shaft side or the joint member side. When this serration is provided on the shaft side, the shaft on which the serration is formed is quenched and attached so that the shaft is bite into the insertion hole of the joint.

  On the other hand, in the case where the insertion hole of the joint is provided with serration, the joint side is hardened and set so that the peak of the serration is bitten into the shaft. FIG. 6 is an explanatory view showing a configuration of a joint of a type in which serrations are provided on the insertion hole side. As shown in FIG. 6, in the joint member 51, the serration 52 is formed in a triangular tooth shape in order to cause the shaft 52 to actively bite the serration 53. The serration 53 bites into the shaft 52 in a form of scraping the surface, and the joint member 51 and the shaft 52 are fixed.

JP 2002-369443 A Japanese Patent Laid-Open No. 2004-88901

  However, in a joint member that is fixed to the shaft so as to bite the serration, the shaft can be attached to the joint in a state where the biting of the serration is not uniform even when there is a slight misalignment. For this reason, there is a problem that the shaft and the joint are connected in a misaligned state, the coaxial accuracy between the two is lowered, and the shaft is liable to be shaken. In addition, when such shaft runout occurs, an unbalanced load is applied to the bearing that supports the driven shaft, which may increase the load on the bearing and cause problems such as noise generation and reduced life.

  Furthermore, in the conventional joint member 51, since the serration 52 is formed in a triangular tooth shape, the thickness of the serration tip 54 (see FIG. 6B) is reduced. For this reason, when torsional torque is applied, the tip 54 may be lost and the serration 53 may be damaged. In particular, in the case of a sintered metal joint member, the tip portion of the triangular tooth serration is difficult to be subjected to a compressive load during the sintering process, and the density tends to be low.

  An object of the present invention is to provide a motor using a motor joint member that is excellent in shear strength against torsional torque and that can ensure high coaxial accuracy.

  The motor of the present invention is a motor in which an output shaft and a driven shaft are connected by a sintered metal joint member, and the joint member includes a drive shaft mounting hole into which the output shaft is press-fitted and fixed, and the driven shaft. A driven shaft mounting hole into which the shaft is inserted, and the drive shaft mounting hole includes a serration portion that is pressed against an outer peripheral surface of the output shaft when the output shaft is press-fitted, and the output shaft is It is characterized in that the rotation is fixed in the drive shaft mounting hole by a pressure contact holding force generated between the serration portion and the serration portion.

  In the present invention, when the motor output shaft is press-fitted into the drive shaft mounting hole of the joint member, the serration portion provided in the drive shaft mounting hole generates a pressure contact holding force between the output shaft and the serration portion. The output shaft is fixed to the joint member by this pressure contact holding force. That is, the output shaft is not fixed in the form of serrations, but is fixed around the joint member by a pressure holding force with the joint member.

  In the motor, a serration portion having a curved inner peripheral surface that abuts on the outer peripheral surface of the output shaft may be provided in the drive shaft mounting hole. In this case, the serration portion may be formed in an involute shape.

  Further, the motor joint member of the present invention connects between the output shaft of the motor and the driven shaft driven by the motor, the drive shaft mounting hole in which the output shaft is press-fitted and fixed, and the driven shaft is inserted. A joint member for a motor having a driven shaft mounting hole, wherein the drive shaft mounting hole includes a serration portion pressed against an outer peripheral surface of the output shaft when the output shaft is press-fitted, and the output The shaft is fixed around the drive shaft mounting hole by a pressure contact holding force generated between the shaft and the serration portion.

  According to the motor of the present invention, when the output shaft is press-fitted into the drive shaft mounting hole of the joint member in the motor in which the output shaft and the driven shaft are connected by the sintered metal joint member, the output shaft A serration part that is press-contacted to the outer peripheral surface of the shaft is provided, and the output shaft is fixed around the drive shaft mounting hole by the press-contact holding force generated between the serration part and the output shaft. It is possible to fix the joint member and the output shaft by a pressure contact force rather than a form in which serrations are caused.

  By providing such a serration portion, it becomes difficult to press-fit the output shaft into the joint member in a state where there is a misalignment, and the joint member and the output shaft can be coupled with high coaxial accuracy. In addition, since the serration portion can finish the inner diameter with high accuracy as compared with the triangular tooth serration, the coaxial accuracy between the output shaft and the joint can be improved also in this respect.

  Furthermore, since the above-mentioned serration portion can increase the thickness in the circumferential direction as compared with the triangular tooth serration, the strength of the serration can be improved and the sintered density can be increased. Therefore, the serration portion can be prevented from being damaged by the torsional torque, and the reliability of the joint member can be improved.

  On the other hand, according to the joint member for a motor of the present invention, the output shaft of the motor and the driven shaft driven by the motor are connected, and the drive shaft mounting hole into which the output shaft is inserted, and the driven shaft are inserted. When the output shaft is press-fitted into the material drive shaft mounting hole in the motor joint portion having the driven shaft mounting hole, a serration portion that is pressed against the outer peripheral surface of the output shaft is provided. The serration portion and the output shaft Because the output shaft is fixed around the drive shaft mounting hole by the pressure contact holding force generated between the joint member and the output shaft. It becomes possible to do.

It is sectional drawing which shows the structure of the motor which is one Example of this invention. It is sectional drawing which shows the structure of the joint which is one Example of this invention. It is a right view of a joint. It is explanatory drawing which shows the state of the involute serration at the time of an output shaft press injection, and an output shaft. It is explanatory drawing which shows the structure of the trapezoid tooth shape serration. It is explanatory drawing which shows the structure of the conventional joint.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a motor unit using a motor according to an embodiment of the present invention. The motor unit 10 shown in FIG. 1 is used as a drive source of the electric power steering apparatus, and supplies steering assist force according to the steering angle, vehicle travel speed, and the like when the driver operates the steering wheel. The motor unit 10 includes a motor 11 and a speed reduction mechanism 41, and an output shaft 12 of the motor 11 is connected to a speed reduction mechanism 41 via a joint (joint member) 1 according to an embodiment of the present invention. Input shaft (driven shaft) 13.

  In the motor unit 10, the rotation of the motor 11 is transmitted to the input shaft 13 via the joint 1. The rotation of the input shaft 13 is appropriately decelerated in the deceleration mechanism unit 41. In the gear housing 42 of the reduction mechanism 41, the input shaft 13 is rotatably supported by bearings 43a and 43b. A worm 44 is formed on the input shaft 13 and meshes with the worm wheel 45. The worm wheel 45 is fixed to the wheel shaft 46, and the wheel shaft 46 rotates together with the worm wheel 45.

  When the motor 11 rotates, the rotation is decelerated by the decelerating mechanism 41 and output from the wheel shaft 46. The rotation of the wheel shaft 46 is transmitted to the steering column via a universal joint (not shown). The rotating operation of the steering column is converted into the reciprocating operation of the tie rods in the rack and pinion type steering gear portion, and the steered wheels are steered. Thus, the steering force is assisted by the rotational force of the motor 11, and the driver can operate the steering wheel with a small force.

  The motor 11 is a normal electromagnetic motor, and a plurality of field permanent magnets 16 are fixed to the inner surface of the cylindrical yoke 15. An armature 17 is rotatably disposed inside the field permanent magnet 16. The armature 17 includes a core 19 having a plurality of slots 18 extending in the axial direction, and a winding 20 wound around the slot 18. The armature 17 is fixed to the output shaft 12 and is rotatably supported by bearings 21a and 21b.

  A commutator 22 is provided on the left side of the armature 17 in FIG. The commutator 22 is fixed to the output shaft 12, and a brush 23 is in contact with the surface thereof. The brush 23 is held in a brush holder 24. The brush holder 24 is accommodated in the bracket 25 and is fixed to the bracket 25 with screws 26. The bracket 25 is coupled to the yoke 15 by a bolt 27.

  One end side (the right end side in FIG. 1) of the joint 1 is attached to the left end portion of the output shaft 12. On the other hand, an input shaft 13 is attached to the other end side (the left end side) of the joint 1, thereby connecting the output shaft 12 and the input shaft 13. The joint 1 is a shaft joint made of sintered metal using iron, stainless steel or the like, and is carburized and tempered. The joint 1 is attached with a gap of about 0.3 to 1 mm between the end face of the bearing 21b.

  FIG. 2 is a cross-sectional view showing the configuration of the joint 1, and FIG. 3 is a right side view of the joint 1. As shown in FIG. 2, the joint 1 is formed in a cylindrical shape, and a drive shaft mounting hole (drive shaft mounting portion) 2 is provided on one end side thereof. An involute serration (serration portion) 31 is formed on the inner peripheral surface of the drive shaft mounting hole 2. The involute serration 31 has a tooth shape formed by an involute curve, and an inner peripheral surface thereof has a curved surface shape. An output shaft 12 is press-fitted and fixed in the drive shaft mounting hole 2. On the other end side of the joint 1, a driven shaft mounting hole (driven shaft mounting portion) 3 is provided. A spline 32 is formed on the inner peripheral surface of the driven shaft mounting hole 3. An input shaft 13 is inserted and fixed in the driven shaft mounting hole 3.

  In the joint 1, the driven shaft mounting hole 3 is formed to have a larger diameter than the drive shaft mounting hole 2, the reference pitch circle diameter of the driven shaft mounting hole 3 is 10 mm, and the reference pitch circle diameter of the drive shaft mounting hole 2. Is formed to 8.5 mm. The involute serration 31 is formed with a module 0.25 and the number of teeth 34, and the spline 32 is formed with a module 0.5 and a number of teeth 20. Needless to say, these numerical values can be appropriately changed depending on the specifications of the motor and the like.

  In such a motor 11, the output shaft 12 and the input shaft 13 are connected as follows. Here, first, the joint 1 is attached to the output shaft 12 as shown in FIG. As described above, the output shaft 12 is press-fitted into the drive shaft mounting hole 2, and at this time, the involute serration 31 is pressed into contact with the output shaft 12. FIG. 4 is an explanatory diagram showing the state of the involute serration 31 and the output shaft 12 when the output shaft is press-fitted. As shown in FIG. 4, when the output shaft 12 is press-fitted into the drive shaft mounting hole 2, the inner peripheral surface 31 a of the involute serration 31 comes into pressure contact with the outer peripheral surface 12 a of the output shaft 12. By this pressure contact, the outer peripheral surface 12a of the output shaft 12 is plastically deformed, the output shaft 12 and the involute serration 31 are brought into close contact with each other, and a pressure contact holding force is generated by a frictional force therebetween. The output shaft 12 is fixed to the involute serration 31 in a surface contact state under this pressure contact holding force.

  In the joint 1, the inner peripheral surface of the drive shaft mounting hole 2 is not a triangular tooth but a curved serration. For this reason, the joint 1 is not configured to bite the serration portion into the shaft like a conventional joint, but the involute serration 31 and the output shaft 12 are fixed by the pressure holding force. That is, the output shaft 12 is not cut by serration, but is fixed in the joint 1 by the pressure holding force accompanying the plastic deformation of the output shaft 12. Therefore, unlike the conventional joint, it is difficult to press-fit the output shaft 12 into the joint 1 when there is a misalignment, and the joint 1 is attached to the output shaft 12 with high coaxial accuracy.

  Further, in the conventional triangular tooth serration, it is difficult to form the inner diameter of the serration portion, that is, the inner diameter dimension of the tip of the triangular tooth with high precision, and it is difficult to avoid a decrease in coaxiality with the press-fitted shaft. On the other hand, in the joint 1 according to the present invention, since the serration is involute, the inner diameter can be finished with high accuracy. Therefore, also in this point, the coaxial accuracy between the output shaft 12 and the joint 1 is improved. In addition, as the dimensional accuracy is improved, it is easy to adjust the press-fit load.

  Furthermore, the pressure contact portion between the involute serration 31 and the output shaft 12 has a circumferential thickness (thickness t in the left-right direction in FIG. 3) that is different from a conventional triangular tooth, so that the strength of the serration itself is improved. In addition, there is no portion that is difficult to be subjected to a compressive load during the sintering process as in the case of triangular teeth, and the sintering density can be increased. In this respect as well, the serration strength can be improved. Therefore, the involute serration 31 can be prevented from being damaged by the torsional torque, and the reliability of the joint 1 can be improved.

  In addition, when the number of teeth (the number of peaks) of the involute serration 31 is small, the contact surface becomes large and the press contact force increases, but the press-fit load also increases. Therefore, the press-fit allowance is set small to secure the press-contact holding force. While avoiding deterioration of workability. On the contrary, when the number of teeth of the involute serration 31 is large, the contact surface becomes small and the press-contact force becomes small, but the press-fit load also becomes small, so the press-fit allowance is set large to secure the fixing force. As described above, the fixing force between the joint 1 and the output shaft 12 depends exclusively on the press-fitting allowance between the two. By appropriately setting the number of teeth, the press-fitting allowance, and the press-fitting load, the involute serration 31 is tightly bound. The power can be adjusted.

  After the joint 1 is attached to the output shaft 12, the input shaft 13 is inserted into the driven shaft attachment hole 3. A spline portion 14 is formed at the tip of the input shaft 13, and the input shaft 13 is inserted into the driven shaft mounting hole 3 while engaging the spline portion 14 with the spline 32 of the driven shaft mounting hole 3. As a result, the input shaft 13 is attached to the joint 1 in a state where it is stopped, and the output shaft 12 and the input shaft 13 are connected by the joint 1. At that time, the joint 1 is attached to the output shaft 12 with high coaxial accuracy as described above, and the input shaft 13 is connected to the output shaft 12 with high coaxial accuracy. Therefore, the shake of the input shaft 13 due to the misalignment is suppressed, and the uneven load applied to the bearings 43a and 43b is also suppressed. For this reason, it is possible to suppress vibration, abnormal noise, life reduction, and the like of the motor unit 10, and to improve the quietness and durability of the motor unit 10.

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, an example in which the involute serration 31 is formed on the inner peripheral surface of the drive shaft mounting hole 2 is shown. It may be formed. Such a trapezoidal tooth-shaped serration 35 is also easy to ensure the accuracy of the inner diameter, and the strength of the tooth itself is high. Further, the inner peripheral surface of the serration can be formed in another curved shape such as a sine curve or an elliptic curve instead of the involute shape.

  On the other hand, although the example which used the joint 1 by this invention for the motor with a brush was shown in the above-mentioned Example, there is no limitation in particular in the form of the motor of this invention, It can apply also to a brushless motor etc. Moreover, there is no limitation in particular also in the use of a motor, This invention can be used also for the general motor used for other vehicle-mounted motors, such as a wiper apparatus, and household appliances. Note that the joint of the present invention can also be used for rotating electrical machines other than motors, such as generators.

1 Joint (joint member)
2 Drive shaft mounting hole 3 Driven shaft mounting hole 10 Motor unit 11 Motor 12 Output shaft 12a Outer peripheral surface 13 Input shaft (driven shaft)
14 Spline portion 15 Yoke 16 Field permanent magnet 17 Armature 18 Slot 19 Core 20 Winding 21a, 21b Bearing 22 Commutator 23 Brush 24 Brush holder 25 Bracket 26 Screw 27 Bolt 31 Involute serration
31a Inner peripheral surface 32 Spline 35 Serration 41 Reduction mechanism 42 Gear housing 43a, 43b Bearing 44 Worm 45 Worm wheel 46 Wheel shaft 51 Joint member 52 Shaft 53 Serration 54 Serration tip

Claims (4)

A motor connecting the output shaft and the driven shaft by a sintered metal joint member,
The joint member has a drive shaft mounting hole into which the output shaft is press-fitted and fixed, and a driven shaft mounting hole into which the driven shaft is inserted,
The drive shaft mounting hole includes a serration portion that is pressed against an outer peripheral surface of the output shaft when the output shaft is press-fitted,
The motor is characterized in that the output shaft is fixed and fixed in the drive shaft mounting hole by a pressure contact holding force generated between the output shaft and the serration portion.   The motor according to claim 1, wherein the serration portion has a curved inner peripheral surface that abuts on an outer peripheral surface of the output shaft.   The motor according to claim 2, wherein the serration portion is formed in an involute shape. Connected between an output shaft of a motor and a driven shaft driven by the motor, and having a drive shaft mounting hole into which the output shaft is press-fitted and a driven shaft mounting hole into which the driven shaft is inserted A joint member,
The drive shaft mounting hole includes a serration portion that is pressed against an outer peripheral surface of the output shaft when the output shaft is press-fitted,
The motor joint member, wherein the output shaft is fixed and fixed in the drive shaft mounting hole by a pressure holding force generated between the output shaft and the serration portion.

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