JP2002079951A - Electrically-operated power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically-operated power steering device capable of securing a large speed reducing ratio by a worm shaft and a worm wheel, and reducing a cost and compacting the device by cutting the number of parts. SOLUTION: This electrically-operated power steering device is equipped with a direct-current electric motor M for generating an auxiliary torque corresponding to a steering torque, the worm shaft 10 installed on an output axis 5 of the direct-current electric motor M, and the worm wheel 12 for transmitting the auxiliary torque generated by the direct-current electric motor M to a steering system by being interlocked with the worm shaft 10. In the device, the worm shaft 10 is formed integrally with the output axis 5 of the direct- current electric motor M, and the opposite side of the worm shaft 10 to the output shaft 5 is formed as an open end without support by a bearing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus that generates an auxiliary torque according to a steering torque by an electric motor.

[0002]

2. Description of the Related Art As a conventional electric power steering apparatus, for example, an electric power steering apparatus disclosed in Japanese Patent Application Laid-Open No. H8-207795 is disclosed. That is, in this conventional electric power steering apparatus, as shown in FIG. 4, an electric motor 101 for generating an auxiliary torque corresponding to a steering torque and one end of a motor shaft (output shaft) 102 of the electric motor 101 are connected. A worm shaft 103 meshes with the worm shaft 103 to provide a steering system with the electric motor 101.
Worm wheel 10 that transmits the auxiliary torque generated by the worm
And a connecting part 1 for connecting the motor shaft 102 and the worm shaft 103 to respective open ends of the motor shaft 102 and the worm shaft 103.
05, bearings 106, 107,
8 to be rotatably supported.

[0003]

However, in the conventional electric power steering apparatus, as described above, the motor shaft 102 and the worm shaft 10
3 is rotated at three points.
The increase in the axial length of 02 is contrary to the compactness of the apparatus, and the number of parts of the bearings 106, 107, 108 increases, which is disadvantageous in terms of cost. Further, since the worm shaft 103 and the worm wheel 104 generally require a high meshing property, when the worm wheel 104 is displaced in the radial direction by a radial input from the steering system, the worm Both ends of the shaft 103 are bearings 10
7, 108, the worm shaft 10
Since there is no radial escape on the 3 side, the worm shaft 1
There is a possibility that a meshing portion between the worm wheel 03 and the worm wheel 104 may be damaged.

As a solution to the above problem, for example, it is conceivable to omit the bearing 108 at the end of the worm shaft 103, but the bearing 107 is connected to the connecting portion 105 between the motor shaft 102 and the worm shaft 103. In the provided structure, it is impossible to omit the bearing 108 on the end portion side of the worm shaft 103 to make the cantilever state due to the strength of the connecting portion 105.

Further, as shown in FIG. 1 of JP-A-11-29058, an apparatus using a hypoid pinion and a hypoid gear instead of the worm shaft and the worm wheel is disclosed. In this apparatus, the hypoid pinion is cantilevered. Although it is in a state, there is a problem that the speed reduction ratio is insufficient in the speed reduction structure using the hypoid pinion and the hypoid gear.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has a large reduction ratio by a worm shaft and a worm wheel, while reducing costs and reducing the size of the apparatus by reducing the number of parts. It is an object of the present invention to provide an electric power steering device capable of performing the following.

[0007]

In order to achieve the above object, an electric power steering apparatus according to claim 1 of the present invention includes an electric motor that generates an auxiliary torque corresponding to a steering torque, and an output shaft of the electric motor. An electric power steering device comprising: a worm shaft provided; and a worm wheel that meshes with the worm shaft and transmits an auxiliary torque generated by the electric motor to a steering system, wherein the worm shaft is formed integrally with an output shaft of the electric motor. At the same time, the opposite side of the worm shaft from the output shaft is an open end without support by a bearing.

According to a second aspect of the present invention, in the electric power steering apparatus according to the first aspect, the output shaft and the worm shaft of the electric motor are rotatably supported by bearings provided at both ends of the output shaft. That means.

According to a third aspect of the present invention, there is provided the electric power steering apparatus according to the second aspect, wherein the output shaft has a locking large diameter larger than a diameter of an output shaft of a portion supported by the bearing. A diameter portion is formed, and the axial end face of the large diameter portion for locking is arranged so as to abut on one axial end face of at least one bearing.

According to a fourth aspect of the present invention, in the electric power steering apparatus according to any one of the first to third aspects, a housing accommodating the worm shaft and the worm wheel and a casing of the electric motor are separate members. Wherein the casing of the electric motor is a means which is fitted to a housing for accommodating the worm shaft and the worm wheel.

[0011]

In the electric power steering apparatus according to the first aspect of the present invention, as described above, by forming the worm shaft integrally with the output shaft of the electric motor, the supporting strength of the worm shaft is increased, while the output of the worm shaft is increased. The side opposite to the shaft is an open end without support by a bearing, thereby reducing costs by reducing the number of parts and making the apparatus compact.

In the electric power steering apparatus according to the second aspect, as described above, both ends of the output shaft are rotatably supported by the bearings, so that the output shaft of the motor is inclined inside the casing of the motor and makes internal contact. Can be reliably prevented, and even if the worm wheel is displaced in the radial direction, breakage of the meshing portion between the two can be prevented by the relief action due to the bending of the worm shaft.

According to the third aspect of the present invention, as described above, the output shaft is positioned in the axial direction by the locking large-diameter portion formed on the output shaft.
Thereby, the meshing accuracy between the worm shaft and the worm wheel can be maintained.

According to a fourth aspect of the present invention, as described above, the casing of the electric motor formed of separate members and the housing for accommodating the worm shaft and the worm wheel are connected to each other by a stake-fitting. The deflection of the motor casing with respect to the housing is reduced, thereby reducing the displacement of the worm shaft formed integrally with the output shaft of the motor,
The engagement accuracy between the worm shaft and the worm wheel can be kept high.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. First, a configuration of an embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is an overall schematic view showing an electric power steering apparatus according to an embodiment of the present invention. As shown in FIG. 1, when a steering wheel SW is manually rotated, the rotation is performed by a rack L & pinion P. This is converted into a linear motion of the rack L, whereby the left and right front wheels TL, T
The direction of R can be changed (steered). The pinion P is reduced by a DC electric motor (electric motor) M by a reduction gear (worm shaft 10 and worm wheel 12).
By being configured to be rotatable via the G, the manual steering force is assisted.

The drive of the DC electric motor M is controlled by a microcomputer incorporated in a vehicle-mounted control unit ECU based on a signal from a torque sensor TS for detecting a manual steering force.
Auxiliary control of the steering force is performed manually. In the figure, R is a fail-safe relay, and B is a vehicle-mounted battery.

Next, FIG. 2 is a cross-sectional view showing a DC electric motor M and a reduction gear G in the electric power steering apparatus according to the embodiment of the invention, and FIG. 3 is a half view showing an output shaft 5 of the DC electric motor M. It is sectional drawing, As shown in these figures, the DC electric motor M is comprised by the bottomed cylindrical main-body part 21 with the motor casing 2 and the side wall member 22 with which the inlay was fitted inside the opening part. Have been.

A mounting flange 21a protrudes from the outer circumference of the open end of the bottomed cylindrical main body 21, and a mounting flange 22a facing the mounting flange 21a protrudes from the outer circumference of the side wall member 22. Is formed. On the outer side of the side wall member 22 in the axial direction, two large and small intaglio fitting portions 22b and 22c are formed, and an insertion hole 22d is formed in the axis of the side wall member 22.

The motor casing 2 includes a stator 3 provided on the inner periphery of a bottomed cylindrical main body 21 and an armature 4 rotatably provided in the motor casing 2.
, A commutator 6 provided on the output shaft 5 side, and an armature 4 provided on the side wall member 22 side and rotatably contacting the commutator 6 to supply a DC current supplied from a power source. And a brush 7 for switching the direction of the supply current in accordance with the rotation of the armature 4.

One end of the output shaft 5 with the armature 4 interposed therebetween is formed with a concave portion 21c formed so as to protrude outward at the center of the bottom portion 21b of the bottomed cylindrical main body 21.
Is rotatably supported via a rear bearing 8, and the other end is rotatably supported via a front bearing 9 in an intaglio fitting portion 22 c of the side wall member 22.

A worm shaft 10 is integrally formed at the end of the output shaft 5 rotatably supported by the front bearing 9 (see FIG. 3).
Is exposed to the outside of the side wall member 22 through the insertion hole 22d.

As shown in FIG. 3, the output shaft 5 has a locking portion whose armature 4 side has a diameter larger than the diameter of the output shaft 5 at a portion supported by the rear bearing 8 and the front bearing 9. Large diameter portions 5a and 5b are formed, and the axial end surfaces of the locking large diameter portions 5a and 5b are arranged so as to contact the axial end surfaces of the rear bearing 8 and the front bearing 9 on the armature 4 side, respectively. Thus, the output shaft 5 and the worm shaft 10 are axially positioned with respect to the motor casing 2.

Returning to FIG. 2, the reduction gear G is composed of a worm wheel 12 provided on the column shaft 1 side housed in a housing 11 and the worm shaft 10 formed integrally with the output shaft 5. ing.

Then, the worm shaft 10 integrally formed with the output shaft 5 is inserted into the housing 11 from the opening 11a formed on the side surface of the housing 11, and both of the side wall members 22 of the motor casing 2 are fitted to both the seals. The mating portions 22b and 22c are fitted in two large and small mounting holes 11b and 11c formed on the side surface of the housing 11, and the mounting flange 21a and the mounting flange 22a are fixed to the housing 11 with the bolts 13. 1 is assembled with the DC electric motor M.

That is, the output shaft 5 and the worm shaft 10 are rotatably supported by rear bearings 8 and front bearings 9 provided at both ends of the output shaft 5, respectively. The side opposite to the output shaft 5 is in an open end state without being supported by a bearing.

According to the embodiment of the present invention, the configuration and operation described above provide the following functions and effects. That is, by forming the worm shaft 10 integrally with the output shaft 5 of the DC electric motor M, the supporting strength of the worm shaft 10 is increased while the worm shaft 1 is formed.
By setting the side opposite to the output shaft 5 at 0 as an open end without support by a bearing, the bearing portion on the housing 11 side is omitted, so that the cost can be reduced by reducing the number of parts such as bearings. With housing 1
Since a portion for accommodating a bearing member such as a bearing need not be formed on one side, the device can be made compact.

Further, since both ends of the output shaft 5 are rotatably supported by a rear bearing 8 and a front bearing 9, the output shaft 5 of the DC electric motor M is inclined inside the motor casing 2 of the DC electric motor M to make internal contact. Can be reliably prevented, and even if the worm wheel 10 is displaced in the radial direction, the worm shaft 10 has an open end without support by a bearing on the side opposite to the output shaft 5, so that the worm wheel 10 can be released by the bending action. Thus, it is possible to prevent the engagement portion between the two from being damaged.

Further, the output shaft 5 is positioned in the axial direction by the large diameter portions 5a and 5b for locking formed on the output shaft 5, whereby the worm shaft 10 and the worm wheel 12 mesh with each other. Accuracy can be maintained.

Further, the motor casing 2 of the DC electric motor M, which is composed of separate members, and the housing 11 accommodating the worm shaft 10 and the worm wheel 12 are connected to each other by two-stage large and small stake-fittings. Of the worm shaft 10 integrally formed on the output shaft 5 of the DC electric motor M, and therefore the engagement accuracy between the worm shaft 10 and the worm wheel 12 can be reduced. Can be maintained at a high state.

Although the embodiments of the present invention have been described with reference to the drawings, the specific configuration is not limited to those embodiments of the present invention, and there are design changes and the like without departing from the gist of the present invention. Are also included in the present invention.

For example, in the embodiment of the present invention, the seal fitting portion between the motor casing 2 of the DC electric motor M and the housing 11 is formed in two stages, but may be formed in only one stage. Further, in the embodiment of the invention, the large diameter portions 5a and 5b for locking are formed at two places of the output shaft 5, but only one of them may be provided.

[0033]

As described above, in the electric power steering apparatus according to the first aspect of the present invention, as described above, the worm shaft provided on the output shaft of the electric motor is formed integrally with the output shaft of the electric motor. At the same time, the worm shaft has a means opposite to the output shaft as an open end without support by a bearing, thereby securing a large reduction ratio by the worm shaft and the worm wheel,
The effect is obtained that the cost can be reduced and the device can be made compact by reducing the number of parts.

According to a second aspect of the present invention, in the electric power steering apparatus according to the first aspect, the output shaft and the worm shaft of the electric motor are rotatably supported by bearings provided at both ends of the output shaft. With this configuration, it is possible to reliably prevent the output shaft of the motor from tilting and making internal contact inside the casing of the motor, and even when the worm wheel is radially displaced, By the relief action, it is possible to prevent breakage of the meshing portion between the two.

According to a third aspect of the present invention, there is provided the electric power steering apparatus according to the second aspect, wherein the output shaft has a locking large diameter larger than a diameter of an output shaft of a portion supported by the bearing. A diameter part is formed, and the axial end face of the large diameter part for locking is arranged so as to abut on one axial end face of at least one bearing, so that the output shaft is positioned in the axial direction. As a result, the engagement accuracy between the worm shaft and the worm wheel can be maintained.

According to a fourth aspect of the present invention, in the electric power steering apparatus according to any one of the first to third aspects, a housing accommodating the worm shaft and the worm wheel and a casing of the electric motor are separate members. The casing of the electric motor is a means that is fitted to the housing that houses the worm shaft and the worm wheel, so that the bending of the electric motor casing with respect to the housing is reduced. Therefore, the displacement of the worm shaft integrally formed with the worm shaft is also reduced, so that the engagement accuracy between the worm shaft and the worm wheel can be kept high.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram showing an electric power steering device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a DC electric motor and a reduction gear portion in the electric power steering device according to the embodiment of the present invention.

FIG. 3 is a half sectional view showing an output shaft of a DC electric motor in the electric power steering device according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a DC electric motor and a reduction gear portion in a conventional electric power steering apparatus.

[Explanation of symbols]

 B Battery ECU Control Unit G Reduction Gear L Rack M DC Electric Motor (Electric Motor) P Pinion R Failsafe Relay SW Steering Wheel TL Left Front Wheel TR Right Front Wheel TS Torque Sensor 1 Column Shaft 2 Motor Casing 3 Stator 4 Armature 5 Output Shaft 5a Large-diameter portion for locking 5b Large-diameter portion for locking 6 commutator 7 brush 8 rear bearing 9 front bearing 10 worm shaft 11 housing 11a opening 11b mounting hole 11c mounting hole 12 worm wheel 13 bolt 21 bottomed cylindrical main body 21a Mounting flange 21b Bottom 21c Concave portion 22 Side wall member 22a Mounting flange 22b Inlay fitting part 22c Inlay fitting part 22d Insertion hole

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigetoshi Kumazaki 1370 Onna, Atsugi-shi, Kanagawa F-term in Unisia Gex Co., Ltd. (reference) 3D033 CA03 CA04 CA16 3J009 DA17 DA18 EA06 EA19 EA32 EB01 EB23 EB24 EC02 FA08 5H607 AA11 AA12 BB01 BB14 BB27 CC03 CC05 DD07 DD08 DD17 EE32 EE36 FF24 GG07 GG08

Claims (4)

[Claims] 1. An electric motor for generating an auxiliary torque according to a steering torque, a worm shaft provided on an output shaft of the electric motor, and meshing with the worm shaft to transmit an auxiliary torque generated by the electric motor to a steering system. An electric power steering device comprising a worm wheel and the worm shaft, wherein the worm shaft is formed integrally with an output shaft of the electric motor, and the opposite side of the worm shaft from the output shaft is an open end without support by a bearing. Characteristic electric power steering device. 2. The electric power steering apparatus according to claim 1, wherein an output shaft and a worm shaft of the electric motor are rotatably supported by bearings provided at both ends of the output shaft. 3. The output shaft has a locking large-diameter portion having a diameter larger than the diameter of the output shaft at a portion supported by the bearing, and the locking large-diameter portion has at least one axial end face. The electric power steering device according to claim 2, wherein the electric power steering device is arranged so as to abut on one axial end surface of the bearing. 4. A housing accommodating the worm shaft and the worm wheel and a casing of the electric motor are formed as separate members, and the casing of the electric motor is fitted with a housing to accommodate the worm shaft and the worm wheel. The electric power steering device according to any one of claims 1 to 3, wherein: