JP4036359B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus, and more particularly, to a structure for preventing a shift in meshing position and rattling between meshing tooth surfaces in a gear transmission mechanism that transmits an auxiliary steering force from an electric motor to an output shaft of a steering mechanism. In the gear transmission mechanism, the distance between the shafts of the meshing gear at the time of power transmission is kept constant to prevent displacement of the meshing position and rattling between the meshing tooth surfaces. The present invention relates to an electric power steering device that achieves smooth transmission.
[0002]
[Prior art and problems to be solved]
As an electric power steering device for a vehicle, the auxiliary steering force from the electric motor is decelerated by a gear transmission mechanism such as a worm gear mechanism and transmitted to the output shaft of the steering mechanism, and the auxiliary steering force is applied to the steering force applied to the steering wheel. In the related art, the wheel is steered with a light torque.
[0003]
By the way, the gear transmission mechanism has a problem that the gear swings due to the fluctuation of the transmission torque during the gear meshing operation at the time of power transmission. When the swing is larger than a predetermined amount, the meshing position shifts in the gear meshing or abnormal rattling occurs between the meshing tooth surfaces, and the teeth collide with each other. A phenomenon of generating a sound occurs, resulting in premature wear of the meshing tooth surface of the gear, and depending on the degree of the swing, a serious meshing trouble may be caused.
[0004]
The occurrence of the phenomenon due to the gear swing as described above may hinder the smooth transmission of the auxiliary steering force in the electric power steering apparatus, and may cause a deterioration in the comfortable steering feeling of the vehicle. Absent.
[0005]
Therefore, in the electric power steering device, the gear swing during the gear meshing operation of the gear transmission mechanism must be suppressed as much as possible. There is a problem that it is necessary to reliably prevent the occurrence of a large swing exceeding a predetermined amount, which is a cause of abnormal rattling between tooth surfaces.
[0006]
Therefore, from the above viewpoint, specific examples of the structural problems of the conventional electric power steering apparatus (see, for example, JP-A-10-138936, JP-A-10-297505, JP-A-2001-171531, etc.) ) To explore based on.
[0007]
In the electric power steering apparatus 01 disclosed in Japanese Patent Laid-Open No. 2001-171513 shown in FIGS. 2 and 3, as shown in FIG. 2, the output shaft 03 has steering applied to a steering wheel (not shown). A force is transmitted, and an auxiliary steering force from an electric motor (not shown) is transmitted via the worm gear mechanism 04.
[0008]
The output shaft 03 is supported by the housing 0Hb supported by the first and second bearings 03a and 03b which are the one side bearing and the other side bearing, and the support structure is substantially the same as that of the worm gear mechanism 04. The mounting position is biased toward one side (the right side in FIG. 2), and the support intervals of the bearings 03a and 03b are relatively narrow, and the output shaft 03 is in a so-called cantilevered state. .
[0009]
Further, since the worm wheel 04b of the worm gear mechanism 04 is attached to the shaft portion 03e extending from the bearing support portion of the first bearing 03a of the output shaft 03, the action by the meshing torque at the time of transmitting the auxiliary steering force is achieved. Since the force acts on the output shaft 03 as a displacement force (unbalanced load), the output shaft 03 has a structure that easily swings.
[0010]
The shaft portion 03e extended from the output shaft 03 is affected by the acting force due to the change in the meshing torque during the transmission of the auxiliary steering force and the torque change from the input shaft based on the steering operation. It will swing as shown.
[0011]
The swinging movement of the shaft portion 03e extended from the output shaft 03 changes the distance between the attachment shafts of the gears of the worm 04a and the worm wheel 04b, and the worm wheel 04b attached to the shaft portion 03e. Swaying of the two gears, resulting in a shift in the meshing position of both gears and a change in the gap between the tooth surfaces, and abnormal rattling between the meshing tooth surfaces and the contact between the tooth surfaces of the teeth. It will cause the generation of sound.
As a result, the tooth surfaces of the two gears are prematurely worn, and the normal meshing state of the gears is lost, and the smooth torque transmission in the transmission of the auxiliary steering force is hindered. .
[0012]
Further, as described above, since the mating tooth surfaces of the worm 04a and the worm wheel 04b are prematurely worn, measures for maintaining an appropriate backlash amount between the tooth surfaces are indispensable. , B are used for adjustment, and there is a problem that the adjustment must be made as necessary.
[0013]
[Means for Solving the Problems and Effects of the Invention]
The present invention has a problem based on the structural factor in the conventional electric power steering device, that is, the meshing position shift and the tooth surface at the time of transmitting the auxiliary steering force in the conventional electric power steering device. The invention according to claim 1 is an improvement of the device for solving the problem of occurrence of abnormal rattling, and the invention according to claim 1 receives the main steering force and the auxiliary steering force from the electric motor, and is rotatably supported in the housing. And an output for steering from the output shaft to a rack shaft via a pinion gear, and the input of the auxiliary steering force to the output shaft is the output the electric power steering apparatus to be made through the engagement of the one of the gears mounted on the shaft the electric motor other gear connected to a rotation shaft of the housing Both said housing with a coupling means while being divided into an input side housing and the output-side housing is detachably coupled, one of gears other gear meshes of the auxiliary steering force, via the cup-shaped body portion A first bearing that is integrally fixed to the steering mechanism output shaft and pivotally supports one side portion of the steering mechanism output shaft on an annular shaft mounting flange portion adjacent to the input side housing of the output side housing. And a second bearing that rotatably supports the other side portion of the steering mechanism output shaft adjacent to the pinion gear at the end of the output side housing, the steering mechanism output shaft rotates to the output side housing. is rotatably supported, said inner ring of the first bearing is fitted to the steering mechanism output shaft, radially outward of the first bearing and the other of the one gear and the auxiliary steering force In a state where the vehicle is disposed, the outer peripheral portion of the cup-shaped main body portion is integrally fixed to the one gear, and the inner peripheral mounting flange of the cup-shaped main body portion is away from the first bearing. Thus, it is bent in the axial direction and integrally fitted and fixed to the steering mechanism output shaft.
[0014]
In the first aspect of the present invention, the input of the auxiliary steering force to the output shaft is made through the meshing of one gear attached to the output shaft and the other gear connected to the rotating shaft of the electric motor. In the electric power steering apparatus to be made, the support of the output shaft that is freely rotatable in the housing is located at one side position in the vicinity of the auxiliary steering force input position of the output shaft and in the vicinity of the output position for steering of the output shaft. The bearing support portion is provided at the other side position, and the support by the bearing support portion at the one side position of the output shaft is such that the meshing center of the one gear and the other gear is on a radial extension line passing through the support center. The position of the torque fluctuation is applied to the extension line when the auxiliary gear is engaged with the other gear because the auxiliary steering force is transmitted. The action point coincides with the support center of the one bearing support, the swinging motion of the output shaft is almost completely suppressed, and the distance between the shafts of the two gears is kept constant, and the one gear is maintained. Therefore, the shift of the meshing position and the occurrence of abnormal rattling are almost completely prevented. As a result, an appropriate backlash amount is maintained and smooth auxiliary steering force can be transmitted, and wear of the meshing tooth surface can be greatly reduced. It is not necessary to adjust the amount.
[0015]
In the invention described in claim 2, since the one gear is a worm wheel and the other gear is a worm, particularly in the meshing of a staggered gear that is likely to cause a shift in the meshing position or rattling. For the reasons described in 1 above, the shift of the meshing position and the occurrence of abnormal rattling are almost completely prevented, and the auxiliary steering force is transmitted smoothly.
[0016]
According to a third aspect of the present invention, the one gear has a cup-shaped recess structure in its main body, and a bearing support portion at one position of the output shaft is accommodated in the cup-shaped recess structure. Thus, the support by the bearing support portion at the one side position is such that the meshing center of the one gear and the other gear is positioned or substantially positioned on the radial extension line passing through the support center. Therefore, in addition to the effect described in claim 1, since the bearing support portion on one side of the output shaft is located in the cup-shaped recess structure of the one gear body portion, the gear and the bearing Since the support portions are arranged so as to overlap each other in the axial direction of the output shaft, the electric power steering device can be miniaturized.
[0047]
[Brief description of the drawings]
FIG. 1 is a diagram showing an electric power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a conventional electric power steering apparatus.
FIG. 3 is an explanatory diagram showing the occurrence of rattling of a gear meshing portion in an auxiliary steering force transmission mechanism of a conventional electric power steering device.
[0048]
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Input shaft, 2a ... Bearing, 2b ... Torsion bar, 3 ... Output shaft, 3a ... 1st bearing, 3b ... 1st 2 bearings, 3c ... bearing support center, 3d ... pinion gear, 3e ... extended shaft, 4 ... worm gear mechanism, 4a ... worm, 4b ... worm wheel, 4c・ ・ ・ Gear meshing center 4d ・ ・ ・ Worm wheel main body 4e ・ ・ ・ Cup-shaped recess structure 4f ・ ・ ・ Mounting flange 4g ・ ・ ・ Ring part 5 ・ ・ ・ Rack shaft 5a ... rack teeth, 6 ... rack support, 6a ... pressing means, 7 ... torque sensor, 8 ... detection coil, 9 ... bolt, Ha ... input side housing, Hb ... Output housing, Hb1 ... Ring bearing mounting flange, Hb2 ... Bearing Only part

Claims (3)

The output shaft of the steering mechanism to which the main steering force and the auxiliary steering force from the electric motor are input and which is rotatably supported in the housing, and the output for steering from the output shaft via the pinion gear are rack shafts The auxiliary steering force is input to the output shaft through the meshing of one gear attached to the output shaft and the other gear connected to the rotating shaft of the electric motor. In the electric power steering device made,
The housing is divided into an input-side housing and an output-side housing, and the two housings are detachably coupled with coupling means,
One gear meshing with the other gear of the auxiliary steering force is integrally fixed to the steering mechanism output shaft through a cup-shaped main body,
A first bearing that pivotally supports one side portion of the steering mechanism output shaft on an annular shaft mounting flange portion adjacent to the input side housing of the output side housing, and adjacent to a pinion gear of the steering mechanism output shaft The steering mechanism output shaft is rotatably supported by the output side housing with a second bearing that rotatably supports the other side portion at the output side housing end,
An inner ring of the first bearing is fitted to the steering mechanism output shaft;
In a state where the one gear and the other gear of the auxiliary steering force are arranged radially outward of the first bearing,
The outer peripheral portion of the cup-shaped main body is integrally fixed to the one gear, and the inner peripheral mounting flange of the cup-shaped main body is bent in the axial direction in a direction away from the first bearing. An electric power steering device characterized by being integrally fitted and fixed to an output shaft of a steering mechanism.   The electric power steering apparatus according to claim 1, wherein the one gear is a worm wheel, and the other gear is a worm.   The one gear is attached to the output shaft at a shaft portion extending from the bearing support portion at the one side position of the output shaft toward the one end portion, and the one gear is a main body thereof. The cup-shaped recess structure is provided in the part, and the bearing support portion at one side position of the output shaft is accommodated in the cup-shaped recess structure, whereby the support by the bearing support portion at the one side position is 2. The electric power steering apparatus according to claim 1, wherein the meshing center of the one gear and the other gear is positioned or substantially positioned on a radially extending line passing through the support center.

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