JP2010093943A - Electric motor with gear mechanism, and motor-driven power steering device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor with a gear mechanism preventing vibration due to torque ripples generated in the electric motor or electromagnetic vibration thereof from being transmitted to a gear shaft when the gear shaft and a rotating shaft of the electric motor are integrally formed, and simplifying the configuration and improving a ratio of reducing a shaft direction length; and to provide a power steering device using the electric motor. <P>SOLUTION: A rotating shaft portion 31a of an outer rotor 31 is supported on one end of the gear shaft 13d whose one end is rotatably supported by a motor frame 21 attached on a gear housing 13a and the other end having a gear 13c extending in the gear housing 13a, a stator 32 is disposed facing the outer rotor 31 on the motor frame 21, and a vibration buffering member 25 is disposed between the gear shaft and the rotating shaft portion of the outer rotor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention includes a gear mechanism in which a rotor is disposed at a free end of a gear shaft that is supported by a gear housing by a pair of front and rear rolling bearings and integrally formed with a gear, and a stator is disposed at a fixed portion facing the outer peripheral surface of the rotor. The present invention relates to an electric motor and an electric power steering device using the same.

As this type of electric motor with a gear mechanism and an electric power steering apparatus using the same, for example, a unit housing formed integrally with a reduction gear unit with a motor includes a first portion that mainly accommodates a worm gear mechanism and an electric motor. A configuration is proposed in which an extension portion is provided at the second end portion of the worm shaft so as to be directly connected to the adjacent first end portion of the hollow rotor. (For example, refer to Patent Document 1).
JP 2004-304877 A

  However, in the conventional example described in Patent Document 1, the worm shaft is rotatably supported by a pair of rolling bearings provided in the unit housing, and the rotor is integrally formed at the free end of the worm shaft. While having the advantage of not requiring a rolling bearing that supports the rotating shaft on the electric motor side and having a hollow rotor, the rotational inertia characteristics can be improved. There is an unresolved problem that electromagnetic vibrations cannot be insulated from being transmitted to the gear shaft.

In addition, since it has a configuration in which the stator is supported by a rolling bearing directly fixed to the unit housing, the mold of the unit housing becomes large and the configuration becomes complicated, and further, it is necessary to ensure the accuracy of the stator core fixing portion by machining. There is also an unsolved problem that the manufacturing cost increases.
Furthermore, when the unit housing is made of aluminum, there is an unsolved problem that the number of important quality control items increases because a structural design is required to secure the fixing strength due to the difference in the coefficient of linear expansion with the stator core material. is there.

Furthermore, since the electric motor is an inner rotor type, there is an unsolved problem that the reduction rate of the axial length is small and it is difficult to reduce the size.
Therefore, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and when the gear shaft and the rotating shaft of the electric motor are integrated, vibration caused by torque ripple generated in the electric motor and An electric motor with a gear mechanism that can suppress transmission of electromagnetic vibration to a gear shaft, and that can improve the reduction rate of the axial length by simplifying the configuration, and an electric power steering device using the same It is intended to provide.

  In order to achieve the above object, an electric motor with a gear mechanism according to one embodiment has a gear that is rotatably supported at one end side by a motor frame attached to the gear housing and extends into the gear housing at the other end side. A rotating shaft portion of the outer rotor is supported on the one end side of the formed gear shaft, a stator is disposed on the motor frame so as to face the outer rotor, and vibration is generated between the rotating shaft portion of the motor rotating shaft and the outer rotor. A buffer member is arranged.

Moreover, the electric motor with a gear mechanism according to another embodiment is characterized in that the motor rotation shaft is fitted into the rotation shaft portion of the outer rotor via a vibration interference material.
Furthermore, the electric motor with a gear mechanism according to another embodiment is characterized in that the gear shaft is rotatably supported by a pair of front and rear bearings having one end fixed to the inner peripheral surface of the motor frame.

Furthermore, an electric motor with a gear mechanism according to another embodiment is characterized in that the motor frame is fixed to a gear housing that houses the gear mechanism so that the position in the axial direction can be adjusted.
Still further, an electric motor with a gear mechanism according to another embodiment is characterized in that a phase detection mechanism for detecting the phase of the outer rotor is disposed on the gear housing side of the outer rotor.

Moreover, the electric motor with a gear mechanism according to another embodiment is characterized in that a reaction force relieving portion for relieving an axial reaction force of the gear shaft is formed at an axial end portion of the pair of bearings.
Furthermore, an electric motor with a gear mechanism according to another embodiment is characterized in that a gear formed on the gear shaft is constituted by a worm that meshes with a worm wheel.
Furthermore, in the electric power steering device according to one embodiment, the electric motor with a gear mechanism according to any one of the above-described embodiments is applied to a steering assist mechanism that transmits a steering assist force to the steering system. It is characterized by.

  According to the present invention, the rotating shaft portion of the outer rotor is supported on the one end side of the gear shaft, one end side of which is supported by a pair of front and rear bearings on the motor frame and the other end side is formed with the gear, and the outer outer frame is supported on the motor frame. A stator is placed opposite the rotor, and a vibration damping member is placed between the motor rotating shaft and the rotating shaft of the outer rotor, so that torque ripples and electromagnetic vibrations generated by the motor due to vibration interference material are transmitted to the gear shaft. The transmission of these vibrations and electromagnetic vibrations to the gear shaft can be suppressed, the operating noise can be reduced, and the connecting portion between the motor rotation shaft and the gear shaft can be reduced. There is no need to provide a separate vibration isolation mechanism, and the length of the integral gear shaft in the axial direction can be shortened accordingly.

In addition, since the vibration buffer member is interposed between one end of the gear shaft and the rotating shaft portion of the outer rotor, the vibration buffer member can be used to damp the resonance peak at the resonance frequency due to the inertia of the outer rotor and the spring. It is possible to reduce the operating noise of the electric motor.
Further, since both the gear shaft and the motor can be supported on the motor frame, and there is no need to provide a bearing holding portion on the gear side of the gear shaft, an effect that the motor configuration can be simplified and reduced in size can be obtained.

Furthermore, since the electric motor is of the outer rotor type, the reduction rate of the axial length of the gear housing can be improved.
Furthermore, by attaching the motor frame to the gear housing so that the position of the gear frame can be adjusted in the axial direction, the meshing state when the gear is composed of a worm and a worm wheel can be optimized, and the gear meshing state is optimized. Therefore, it is not necessary to separately provide a pressing mechanism member for the operation, and the operation noise can be reduced.

Furthermore, by providing a reaction force mitigating mechanism for mitigating the axial reaction force on the bearing that supports the gear shaft, the gear shaft can be supported by a floating structure, and this floating structure can also exhibit a vibration damping effect. it can.
Furthermore, by applying the gear mechanism-equipped electric motor having the above-described effect to the steering assist mechanism of the power steering apparatus, it is possible to provide an electric power steering apparatus that has a low operating noise and can be miniaturized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram showing an embodiment of the present invention. In the figure, reference numeral 1 denotes an electric power steering apparatus. The electric power steering apparatus 1 includes a steering mechanism 2 that is steered by a driver. Yes.
The steering mechanism 2 includes a steering shaft 4 having an input shaft 4a and an output shaft 4b through which a steering force applied from a driver is transmitted to the steering wheel 3, and the steering shaft 4 is one end of the input shaft 4a. Is connected to the steering wheel 3, and the other end is connected to one end of the output shaft 4b via a steering torque sensor 5 as steering torque detecting means.

The steering force transmitted to the output shaft 4 b is transmitted to the lower shaft 7 via the universal joint 6 and further transmitted to the pinion shaft 9 via the universal joint 8. The steering force transmitted to the pinion shaft 9 is transmitted to the tie rod 11 via the steering gear mechanism 10 to steer a steered wheel (not shown).
Here, the steering gear mechanism 10 is configured in a rack-and-pinion type having a pinion 10a connected to the pinion shaft 9 and a rack 10b meshing with the pinion 10a, and the rack 10b transmits the rotational motion transmitted to the pinion 10a. It has been converted to straight movement.

A steering assist mechanism 12 that transmits a steering assist force to the output shaft 4b is connected to the output shaft 4b of the steering shaft 4. The steering assist mechanism 12 includes a worm speed reducer 13 connected to the output shaft 4 b and a brushless motor 14 as an electric motor that generates a steering assist force connected to the worm speed reducer 13.
The brushless motor 14 receives the steering torque applied to the steering wheel 3 detected by the steering torque sensor 5 and transmitted to the input shaft 4a, and the vehicle speed output from the vehicle speed sensor 15 that detects the vehicle speed. Drive control is performed by the control device 16 to which the detection value is inputted.

  The control device 16 refers to a control map that stores the relationship between the steering torque and the steering assist command value using the vehicle speed detection value as a parameter, calculates a steering assist command value, and calculates the calculated steering assist command value and the brushless motor. Based on the flowing motor current, feedback control is performed to calculate a motor current command value, and the calculated motor current command value is supplied to a motor drive circuit 17 constituted by an inverter circuit. A three-phase motor drive current is generated based on a command value and an angle detection signal from a rotor position sensor 18 that detects a rotor rotation angle of the brushless motor 14 described later, and this three-phase motor drive current is supplied to the brushless motor 14. As a result, the brushless motor 14 generates a steering assist force according to the steering assist command value.

  As shown in FIG. 2, the worm reducer 13 is a gear shaft in which a worm wheel 13b connected to the output shaft 4b and a worm 13c meshing with the worm wheel 13b are integrally formed in a gear housing 13a. And a worm shaft 13d. Here, one end of the worm shaft 13d on the brushless motor 14 side is rotatably supported by a cylindrical motor frame 21 attached to the gear housing 13a.

That is, the motor frame 21 includes a cylindrical portion 21a, a flange portion 21b formed on the end surface of the cylindrical portion 21a on the gear housing 13a side, and a cylindrical bearing housing portion that protrudes from the flange portion 21b to the gear housing 13a side. 21c.
Also, a large-diameter motor frame mounting recess 13f is formed on the right end surface of the worm shaft storage portion 13e for storing the worm shaft 13d of the gear housing 13a. A small-diameter recess 13g is formed on the inner peripheral side of the motor frame mounting recess 13f, and a case mounting surface 13h for mounting the motor case is formed on the outer peripheral side of the motor frame mounting recess 13f. Has been.

The motor frame 21 is fixed to the gear housing 13a by bolts 24 in a state where the flange portion 21b is in-slot coupled into the motor frame mounting recess 13f of the gear housing 13a.
Further, the rolling bearing 22 is housed and fixed in the bearing housing portion 21c of the motor frame 21, and the rolling bearing 23 is housed and fixed on the inner peripheral surface on the right end surface side of the cylindrical portion 21a. One end side of the shaft 13d on the brushless motor 14 side is rotatably supported.

A central opening 13j extending from the right end surface side to the vicinity of the rolling bearing 22 is bored at one end side rotatably supported by the rolling bearings 22 and 23 of the worm shaft 13d, and a cylindrical shape is formed in the central opening 13j. A rotation shaft portion 31 a of the outer rotor 31 constituting the brushless motor 14 is fixed via the vibration buffer member 25.
The outer rotor 31 includes a disc-shaped end plate portion 31b formed at the right end of the rotating shaft portion 31a, a cylindrical portion 31c that faces the gear housing 13a on the outer peripheral surface of the end plate portion 31b, and the cylindrical portion 31c. The permanent magnet 31d is formed on the inner peripheral surface.

A stator core 32 is fixed to the outer peripheral surface of the motor frame 21 facing the permanent magnet 31d. A rotor position sensor 18 using a magnetic detection element such as a Hall element is disposed so as to be close to and opposed to the open end surface side of the cylindrical portion 31c of the outer rotor 31.
Furthermore, a step formed on the motor frame 21 between the inner ring gear side of the rolling bearing 22 fixed to the motor frame 21 and the flange portion 13i of the worm shaft 13d and the outer ring rolling bearing 22 side of the rolling bearing 23. Worm reaction force mitigating members 26 and 27 serving as dampers for mitigating the reaction force in the axial direction of the worm shaft 13d are respectively disposed between the worm shaft 13d and 21d.

A motor case 35 covers the outer rotor 31 from the outside, and is fixed to the case mounting surface 13h of the gear housing 13a.
Next, the operation of the above embodiment will be described.
When the steering wheel 3 is steered, the steering assist command value is calculated by the control device 16 based on the steering torque detected by the steering torque sensor 5 and the vehicle speed detected by the vehicle speed sensor 15. The steering assist command value is supplied to the motor drive circuit 17, and the brushless motor 14 is rotationally driven by the motor drive circuit 17 to generate a steering assist torque. The generated steering assist torque is transmitted to the steering shaft 4 via the worm speed reducer 13.

  At this time, the worm shaft 13d of the worm speed reducer 13 is rotatably supported by rolling bearings 22 and 23 disposed on the motor frame 21, and the brushless end is supported by the rolling bearings 22 and 23 of the worm shaft 13d. Since the rotating shaft portion 31a of the outer rotor 31 of the motor 14 is supported via the vibration damping member 25, the rolling bearings 22 and 23 connect the rotating shaft portion 31a of the outer rotor 31 of the brushless motor 14 and the worm shaft 13d. Both can be supported at the same time, and it is not necessary to provide a separate bearing on the outer rotor 31 side, the overall length of the worm shaft 13d can be shortened, and the axial length of the brushless motor 14 can be shortened. The projecting length can be shortened to reduce the size, and the number of parts can be reduced to reduce the assembly man-hours. Rukoto can.

Further, since the rotation shaft portion 31a of the outer rotor 31 of the brushless motor 14 is inserted into the central opening 13j formed on one end side of the worm shaft 13d and is fixedly supported via the vibration buffer member 25, the worm shaft 13d. The overall length can be greatly shortened.
In addition, since the stator core 32 is fixed to the outer peripheral surface of the motor frame 21 that rotatably supports the worm shaft 13d, the machined portion is small, and the inner peripheral surface and the outer peripheral surface can be accurately processed. The gap accuracy between the outer rotor 31 and the permanent magnet 31d of the outer rotor 31 can be ensured, and the imbalance between the cogging torque and the radial attractive force can be reduced.

And since the brushless motor 14 is comprised by the outer rotor type | mold, the shortening rate of an axial direction length can be improved and the whole axial length can be shortened more. For this reason, the reduction of the axial resonance frequency is slight, and the influence on vibration and noise can be reduced.
Further, since the vibration buffer member 25 is interposed between the worm shaft 13d and the rotating shaft portion 31a of the outer rotor 31, vibration or electromagnetic vibration caused by torque ripple generated in the outer rotor 31 is caused by the vibration buffer member 25. Can be prevented from transmitting vibrations due to torque ripple and electromagnetic vibrations to the worm shaft 13d, and damping of the resonance peak at the resonance frequency due to the inertia of the rotor and the spring by the vibration damping member. It is possible to reduce the operating noise of the electric motor.

  Furthermore, since the worm shaft 13d and the rotating shaft portion 31a of the outer rotor 31 are integrated, the resonance frequency in the axial direction of the worm shaft 13d is lowered, and there is a concern about vibration and noise problems. Since the worm reaction force relaxation members 26 and 27 are provided on the worm shaft 13d, the worm reaction force relaxation members 26 and 27 serve as a floating mechanism and can exhibit a vibration buffering effect.

  Further, the motor frame 21 that supports the outer rotor 31 and the stator core 32 is in-row coupled from the axial direction of the worm shaft 13d to the motor frame mounting recess 13f of the gear housing 13a and fixed by bolts 24. Since the shaft 13d is rotatably supported, the worm 13c and the worm wheel 13b are meshed by adjusting the axial position with a washer, a slip sheet, or the like when the motor frame 21 is mounted on the motor frame mounting recess 13f. The state can be optimized, and this can also prevent the generation of abnormal noise due to the engagement between the worm 13c and the worm wheel 13b.

Furthermore, the rotor position sensor 18 can be arranged on the gear housing 13a side, and the lead wire of the brushless motor 14 and the harness of the position detection signal line of the rotor position sensor 18 can be pulled out from the same position.
By configuring the brushless motor 14 with a geared electric motor in this way, the configuration of the electric power steering device 1 can be reduced in size, and the buffer against other components when the electric power steering device 1 is mounted on a vehicle can be reduced. Restrictions can be relaxed and mounting properties can be improved, and standardization can be facilitated. Further, the overall number of parts of the electric power steering apparatus 1 can be reduced and the size thereof can be reduced, so that the quality, the reliability, and the cost can be reduced.

In the above embodiment, the case where a configuration using a magnetic detection element such as a Hall element is applied as the rotor position sensor 18 for detecting the rotor rotational position is described, but the present invention is not limited to this. Arbitrary rotor position sensors such as encoders and resolvers can be applied.
In the above-described embodiment, the case where the worm 13c is integrally formed with the worm shaft 13d has been described. However, the present invention is not limited to this, and the worm 13c is separately provided and fixed to the worm shaft 13d by welding, adhesion, or the like. It may be fixed by means.

  Furthermore, in the said embodiment, although the case where the rotating shaft part 31a of the outer rotor 31 was connected via the vibration buffer member 25 in the center opening 13j of the worm shaft 13d was demonstrated, it is not limited to this, The rotating shaft portion 31a of the outer rotor 31 may be connected to the outer peripheral side of the worm shaft 13d via the vibration damping member 25. In this case, the rotating shaft portion 31a is formed in a cylindrical shape and the outer peripheral surface thereof is formed. Is rotatably supported by rolling bearings 22 and 23.

Furthermore, in the above-described embodiment, the case where the brushless motor is applied as the electric motor has been described. However, the present invention is not limited to this, and a motor with a brush can also be applied. Can be omitted.
In the above embodiment, the case where the gear mechanism-equipped electric motor 14 is applied to the column-type electric power steering apparatus 1 has been described. However, the present invention is not limited to this, and the pinion shaft or rack of the steering gear mechanism 10 is not limited thereto. The present invention can also be applied to a pinion type or rack type electric power steering apparatus that transmits a steering assist force to the shaft.

  Moreover, in the said embodiment, although the case where the electric motor 14 with a gear mechanism of this invention was applied to the electric power steering apparatus was demonstrated, it is not limited to this, An electric brake device, other vehicle equipment, etc. The present invention can be applied as a rotational drive source for an arbitrary device, and further can be applied as a rotational drive source for an arbitrary device other than an in-vehicle device.

It is a schematic structure figure showing one embodiment of the present invention. It is sectional drawing which shows the electric motor with a gear mechanism of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering mechanism, 3 ... Steering wheel, 4 ... Steering shaft, 4a ... Input shaft, 4b ... Output shaft, 10 ... Steering gear, 12 ... Steering assist mechanism, 13 ... Worm speed reducer, 13a ... Gear housing, 13b ... Worm wheel, 13c ... Worm, 13d ... Worm shaft, 13e ... Worm shaft housing, 13f ... Motor frame mounting recess, 13g ... Small diameter recess, 13h ... Case mounting surface, 13j ... Center opening, 14 ... Brushless motor, 16 ... control device, 17 ... motor drive circuit, 21 ... motor frame, 22, 23 ... rolling bearing, 24 ... bolt, 25 ... vibration damping member, 26, 27 ... worm reaction force mitigating member, 31 ... outer rotor , 31a ... rotating shaft part, 31b ... end plate part, 31c ... cylindrical part, 31d ... permanent magnet , 32 ... the stator core, 35 ... motor case

Claims (8)

  One end side is rotatably supported by a motor frame attached to the gear housing, and a rotating shaft portion of an outer rotor is supported on the one end side of a gear shaft that forms a gear extending into the gear housing on the other end side, An electric motor with a gear mechanism, wherein a stator is disposed on a motor frame so as to face the outer rotor, and a vibration buffer member is disposed between the motor rotating shaft and the rotating shaft portion of the outer rotor.   2. The electric motor with a gear mechanism according to claim 1, wherein one end of the gear shaft is fitted into a rotation shaft portion of the outer rotor via a vibration interference member.   3. The electric motor with a gear mechanism according to claim 1, wherein the gear shaft is rotatably supported by a pair of front and rear bearings having one end fixed to the inner peripheral surface of the motor frame.   The electric motor with a gear mechanism according to any one of claims 1 to 3, wherein the motor frame is fixed to a gear housing that houses the gear mechanism so that the position of the motor frame can be adjusted in the axial direction.   The electric motor with a gear mechanism according to any one of claims 1 to 4, wherein a phase detection mechanism for detecting a phase of the outer rotor is disposed on the gear housing side of the outer rotor.   The gear mechanism according to any one of claims 1 to 5, wherein a reaction force relaxation portion for relaxing an axial reaction force of the gear shaft is formed at an axial end portion of the pair of bearings. With electric motor.   The electric motor with a gear mechanism according to any one of claims 1 to 6, wherein the gear formed on the gear shaft is configured by a worm that meshes with a worm wheel.   An electric power steering apparatus, wherein the electric motor with a gear mechanism according to any one of claims 1 to 7 is applied to a steering assist mechanism that transmits a steering assist force to a steering system.

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