JP2010089631A - Electric motor with gear mechanism and electric power steering device using electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor with a gear mechanism capable of suppressing transmission of vibration and electromagnetic vibration by torque ripple generated in the electric motor to a gear shaft when the gear shaft and a rotary shaft of the electric motor are integrally constituted; and an electric power steering device using the electric motor. <P>SOLUTION: In this electric motor, a free end of the gear shaft 13d which is supported on a gear housing 13a by a pair of front and rear rolling bearings and integrally forms a gear is made as a motor rotary shaft 30, a rotor 31 is arranged in the motor rotary shaft 30, a stator 32 is arranged in a fixed part opposed to an outer peripheral surface of the rotor 31, and a vibration cushioning material 58 is arranged between the motor rotary shaft 30 and the rotor 31. <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.

  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 It is an object of the present invention to provide an electric motor with a gear mechanism capable of suppressing transmission of electromagnetic vibration to a gear shaft, and an electric power steering device using the same.

  In order to achieve the above object, an electric motor with a gear mechanism according to a first aspect of the present invention uses a free end of a gear shaft that is supported by a gear housing with a pair of front and rear rolling bearings to form a gear as a motor rotation shaft, and the motor rotation shaft. The rotor is disposed on the stator, the stator is disposed on the fixed portion facing the outer peripheral surface of the rotor, and the vibration damping material is disposed between the motor rotation shaft and the rotor.

The electric motor with gear mechanism according to claim 2 is characterized in that, in the invention according to claim 1, one end of a stator core constituting the stator is in-row coupled to the gear housing.
Furthermore, the electric motor with a gear mechanism according to a third aspect is the rotation according to the first or second aspect, wherein the rotation angle of the rotor is detected between the rolling bearing on the rotor side of the gear housing and the rotor. It is characterized in that a detector accommodating portion for accommodating the angle detector is provided.

Furthermore, an electric motor with a gear mechanism according to a fourth aspect is the invention according to any one of the first to third aspects, wherein the gear formed on the gear shaft is constituted by a worm that meshes with a worm wheel. It is characterized by.
Still further, an electric motor with a gear mechanism according to a fifth aspect is the preload mechanism according to the fourth aspect, wherein the worm of the gear shaft is preloaded on the worm wheel side at one rolling bearing position supporting the gear shaft. And a reaction force relaxation mechanism for relaxing the axial reaction force at the other rolling bearing position.

  According to a sixth aspect of the present invention, in the electric power steering apparatus according to the sixth aspect, the electric motor with a gear mechanism according to any one of the first to fifth aspects is applied to a steering assist mechanism that transmits a steering assist force to a steering system. It is characterized by that.

  According to the present invention, a free end of a gear shaft that is supported by a pair of front and rear rolling bearings on a gear housing and integrally formed with a gear is used as a motor rotation shaft, a rotor is arranged on the motor rotation shaft, and the outer peripheral surface of the rotor Since the stator is arranged in the fixed portions facing each other and the vibration damping material is arranged between the motor rotation shaft and the rotor, the gear shaft can be supported in a cantilever state on the gear housing, and the rolling bearing is provided on the rotor and stator side. Since it is not necessary to provide a holding part, the effect that a motor structure can be reduced in size simply is acquired.

  In addition, vibration due to torque ripple generated by the electric motor and electromagnetic vibration can be absorbed by the vibration buffering material, and transmission of these vibration and electromagnetic vibration to the gear shaft can be suppressed, thereby reducing operating noise. Therefore, there is no need to provide a separate vibration isolation mechanism at the connecting portion between the motor rotation shaft and the gear shaft, and the axial length of the integral gear shaft can be shortened accordingly. .

In addition, since the vibration damping material is interposed between the motor rotation shaft and the rotor yoke, the resonance peak at the resonance frequency due to the inertia of the rotor and the spring can be damped by the vibration damping material, and the operating noise of the electric motor can be reduced. Can be reduced.
Furthermore, by connecting the one end of the stator core constituting the stator to the gear housing in-situ, there is no need to provide a flange for fixing the electric motor to the gear housing, and the entire configuration can be simplified and miniaturized.

  Furthermore, by providing a preload mechanism for preloading the worm toward the worm wheel on one of the rolling bearings supporting the gear shaft, and providing a reaction force relaxation mechanism for reducing the axial reaction force on the other rolling bearing, the gear shaft Can be supported by a floating structure, and even this floating structure can exhibit a vibration damping effect.

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 formed based on a command value and an angle detection signal from a resolver 36 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. The brushless motor 14 generates a steering assist force corresponding to the steering assist command value.

  As shown in FIG. 2, the worm speed reducer 13 is a worm shaft 13d that is integrally formed with a worm wheel 13b that is connected to the output shaft 4b and that is engaged with the worm wheel 13b. It is configured. Here, the end of the worm shaft 13d opposite to the brushless motor 14 is rotatably supported by a rolling bearing 13e fixed to the gear housing 13a, and the substantially central portion in the axial direction of the worm shaft 13d is supported by the gear housing 13a. It is rotatably supported by a fixed rolling bearing 13f.

Further, a preload mechanism 21 that presses the worm 13c toward the worm wheel 13b with a constant pressure is provided outside the rolling bearing 13e in the axial direction.
Further, worm reaction force mitigating mechanisms 24 serving as dampers for mitigating the reaction force in the axial direction of the worm shaft 13d are disposed on the left and right sides of the rolling bearing 13f of the gear housing 13a.
On the other hand, as shown in FIG. 2, the brushless motor 14 has a worm shaft 13 d with its free end protruding rightward from the gear housing 13 a so that a motor rotation shaft 30 is integrally formed. A rotor 31 is attached to the motor rotation shaft 30. It is fixed. For this reason, the rotor 31 is held in a cantilever state by the worm shaft 13d.

  A stator 32 is disposed at a position facing the outer peripheral surface of the rotor 31. In the stator 32, the outer peripheral surface on the left end side of the stator core 34 around which the coil 33 is wound is in-row coupled to the spigot hole portion 13 i formed in the motor mounting surface 13 h of the gear housing 13 a, and the outer peripheral surface and the right end surface of the stator 32 are connected. Is covered with a bottomed cylindrical case 35 fixed to the gear housing 13a.

A resolver stator 37 constituting a resolver 36 as a rotation angle detector for detecting the rotation angle of the rotor 31 is fixed between the rolling bearing 13f of the gear housing 13a and the stator 32, and a motor rotating shaft facing the resolver stator 37 is fixed. A resolver rotor 38 is disposed at 30.
A rotor position detection signal line (not shown) led out from the bus bar 41 and resolver stator 37 connected to the coil end portion of the coil 33 of the stator 32 is led out from a lead-out hole 13j formed in the gear housing 13a. Has been.

Further, as shown in FIGS. 3A and 3B, the rotor 31 is bonded to a cylindrical rotor yoke 51 through which the motor rotating shaft 30 is inserted, and an outer peripheral surface of the rotor yoke 51 at equal intervals in the circumferential direction. For example, the permanent magnet 52 includes eight permanent magnets 52 and a synthetic resin cap 53 that covers the outer peripheral surfaces of the permanent magnets 52.
The rotor yoke 51 is provided with end plates 54 and 55 at both ends in the axial direction, respectively. The end plates 54 and 55 and the rotor yoke 51 are fixed by, for example, four fastening shafts 56 penetrating them. The rotor yoke 51 is formed with a cross-shaped separation groove 57 that radially separates the motor rotating shaft 30 side and the permanent magnet 52 side, and the vibration damping material 58 is filled in the separation groove 57. ing. Here, the separation groove 57 includes four reverse U-shaped portions 57a formed between the adjacent tightening shafts 56, and an arc portion 57b that connects the reverse U-shaped portions 57a to the motor rotating shaft 30 side. Are connected and formed into an annular shape.

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 13e and 13f disposed in the gear housing 13a, and the free end of the worm shaft 13d is used as the motor rotation shaft 30. Since the rotor 31 is integrally formed, it is not necessary to provide a rolling bearing on the brushless motor 14 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 of 14 can be shortened to reduce the size, and the number of parts can be reduced to reduce the assembly man-hours.

Moreover, since the outer peripheral surface of the stator core 34 of the stator 32 constituting the brushless motor 14 on the side of the gear housing 13a is in-row coupled to the in-hole portion 13i formed in the gear housing 13a, the brushless motor 14 is fixed to the gear housing 13a. Therefore, the entire configuration can be simplified and miniaturized.
In addition, a separation groove 57 that separates the permanent magnet 52 side and the motor rotating shaft 30 side is formed in the rotor yoke 51 of the rotor 31, and the vibration damping material 58 is filled in the separation groove 57. The material 58 can insulate the vibration caused by the torque ripple and electromagnetic vibration generated in the rotor 31 to suppress the vibration caused by the torque ripple and the electromagnetic vibration from being transmitted to the worm shaft 13d, and the inertia and spring of the rotor. The resonance peak at the resonance frequency can be damped by the vibration buffer material, and the operation sound of the electric motor can be reduced.

  Further, since the worm shaft 13d and the motor rotating shaft 30 are integrated, the resonance frequency in the axial direction of the worm shaft 13d is lowered, so there is a concern about vibration and noise problems. Since the preload mechanism 21 and the worm reaction force mitigating mechanism 24 are provided, the preload mechanism 21 and the worm reaction force mitigating mechanism 24 become a floating mechanism and can exhibit a vibration buffering effect.

  By configuring the brushless motor 14 in this way, the configuration of the electric power steering device 1 can be reduced in size, and the restriction on the buffering with other components when the electric power steering device 1 is mounted on a vehicle is relaxed and attached. 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 the resolver 36 is applied as a rotation angle detector for detecting the rotation angle of the rotor has been described. However, the present invention is not limited to this, and a magnetic detection element such as a Hall element or a rotary encoder Any rotation angle detector such as 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.

Further, in the above-described embodiment, the preload mechanism 21 that presses the worm 13c toward the worm wheel 13b is not limited to the above-described configuration, and any preload can be used as long as the worm 13c can be preloaded to the worm wheel 13b. Mechanisms can be applied.
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 brush motor can be applied. In this case, the resolver 36 is omitted. can do.

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. It is a figure which shows a rotor, Comprising: (a) is sectional drawing, (b) is the sectional view on the AA line of (a).

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, 13f ... Rolling bearing, 14 ... Brushless motor, 16 ... Control device, 17 ... Motor drive circuit, 21 ... Preload mechanism, 22 ... Worm anti-warm Force relaxation mechanism, 30 ... motor rotation shaft, 31 ... rotor, 32 ... stator, 35 ... case, 36 ... resolver, 51 ... rotor yoke, 52 ... permanent magnet, 53 ... cap, 57 ... separation groove, 58 ... vibration buffer

Claims (6)

  The free end of the gear shaft that is supported by a pair of front and rear rolling bearings on the gear housing and forms a gear is used as the motor rotation shaft, the rotor is disposed on the motor rotation shaft, and the stator is disposed on the fixed portion facing the outer peripheral surface of the rotor An electric motor with a gear mechanism, wherein a vibration damping material is disposed between the motor rotation shaft and the rotor.   2. The electric motor with a gear mechanism according to claim 1, wherein one end of a stator core constituting the stator is in-row coupled to the gear housing.   The detector accommodating part which accommodates the rotation angle detector which detects the rotation angle of the said rotor between the rolling bearing by the side of the said rotor of the said gear housing, and the said rotor is arrange | positioned. The electric motor with a gear mechanism described in 1.   The electric motor with a gear mechanism according to any one of claims 1 to 3, wherein the gear formed on the gear shaft is configured by a worm that meshes with a worm wheel.   A preload mechanism that preloads the worm of the gear shaft toward the worm wheel is disposed at one rolling bearing position that supports the gear shaft, and a reaction force relaxation mechanism that relieves axial reaction force at the other rolling bearing position. The electric motor with a gear mechanism according to claim 4, wherein the electric motor is provided.   6. An electric power steering apparatus, wherein the electric motor with a gear mechanism according to claim 1 is applied to a steering assist mechanism that transmits a steering assist force to a steering system.

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