JPH1120723A - Work gear structure in electrical power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate regulation of a backlash in a worm gear and correction of a defect in the mounting position of the worm so as to accomplish absorption of irregularity of gear parts, reduction of hitting noise and vibration, and improvement of steering responsiveness and steering feeling in a worm gear structure for an electric power steering device. SOLUTION: In a worm gear structure in which a worm 12 driven by means of steering assisting motor 16 is engaged with a worm wheel 11 installed to a steering column 8 interlockingly connected to a steering wheel, a means supporting the worm shaft 13 slidably in the axial direction is constructed of bearings 14, 15, which support both end parts of the worm shaft 13 individually, and means (an adjusting nut 18, a cap 20) which can regulate the axis directional position of the worm shaft 13 via either/both of the bearings 14, 15. Tooth thickness of the worm 12 is continuously varied along the gear trace.

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 in which a worm driven by a steering assist electric motor is meshed with a worm wheel mounted on a steering shaft interlocked with a steering wheel. More specifically, the present invention relates to a worm gear structure in an electric power steering device that facilitates adjustment of backlash of the worm gear.

[0002]

2. Description of the Related Art In an electric power steering apparatus, when a speed reducer of the worm gear type as shown in FIGS. 6 and 7 is used, the backlash amount t of the worm gear is reduced due to variations in individual parts. indeterminate but, as shown in Figure 8, when t is at the optimum value greater than t _0, or occurs slapping sound and vibrations, lowered the responsiveness of the steering, not comfortable steering feeling can be obtained Such a problem occurred. On the other hand, if t is smaller than the optimum value, smooth engagement between the worm 012 and the worm wheel 011 cannot be obtained.

Further, in the above-mentioned conventional motor, the shaft 013 of the worm 012 is unilaterally inserted through a bearing 014 by screwing a lock nut 018 into a screw hole 017 formed in the steering gear box 02. Since the positioning is performed in such a direction, it is difficult to adjust the position in the axial direction from side to side.

For this reason, the backlash can be adjusted by adjusting the axial position of the worm shaft 013, the local wear of the worm teeth can be compensated, and the worm mounting position (the worm mounting position) can be adjusted. It is also difficult to correct the problem of the position of the gear wheel meshing with the worm wheel). 08 is an output shaft (pinion shaft), and 016 is a motor for assisting steering.

An attempt to solve such a problem is disclosed in Japanese Patent Application Laid-Open No. Hei 2-74467. In this device, one of a worm wheel and a worm constituting a worm gear is divided into two in the axial direction, and the two divided worm wheels or worms are coaxially connected to each other by imparting restorability against twisting. The worm wheel or worm connected by the connecting means is meshed with the worm or worm wheel in a state where they are coaxially twisted.

In the above-mentioned publication, since the worm wheel or the worm is configured as described above, an opposing circumferential rotating force is applied to the worm wheel or the worm in opposition to torsion. In the direction in which each tooth acts in the direction of rotation of the worm or worm wheel,
Closely meshed with the worm or worm wheel teeth. As a result, there is no backlash and the teeth of the worm and the teeth of the worm wheel are always meshed,
When the steering assist force is transmitted from the electric motor to the steering shaft,
The occurrence of striking sounds and vibrations is reduced, steering responsiveness is improved, and a relatively comfortable steering feeling is obtained.

However, in the above-mentioned publication, since the worm wheel or the worm is divided into two parts, the structural strength is inevitably reduced. Further, a separate connecting means is required and the structure becomes complicated. Was.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a worm gear structure in an electric power steering apparatus which overcomes the above-mentioned drawbacks, and the invention described in claim 1 is linked to a steering wheel. To the worm wheel attached to the connected steering shaft,
In a worm gear structure in an electric power steering apparatus in which a worm driven by a steering assist electric motor is meshed, means for supporting the worm shaft slidably in the axial direction supports both ends of the worm shaft, respectively. A worm gear structure in an electric power steering device, comprising: a bearing that performs the control of the axial position of the worm shaft via one or both of the two bearings.

According to the first aspect of the present invention, as described above, when the tooth thickness of the worm is continuously changed along the tooth trace, the optimum adjustment of the backlash of the worm gear and the worm The compensation of the local wear of the teeth, the correction of the worm mounting position, and the like can be easily performed by sliding the worm shaft in the axial direction.

Further, the invention described in claim 2 is:
In a worm gear structure in an electric power steering device in which a worm driven by an electric motor for steering assistance is meshed with a worm wheel mounted on a steering shaft interlocked with a steering wheel, the tooth thickness of the worm may be The means for supporting the worm shaft slidably in the axial direction is a bearing that supports both ends of the worm shaft, and one of the two bearings. A worm gear structure in the electric power steering device, characterized by comprising means for regulating the axial position of the worm shaft via one or both.

According to the second aspect of the present invention, as described above, the worm tooth thickness is continuously changed along the tooth streaks, and the worm shaft is slidably supported. The backlash of the worm gear can be easily adjusted to an optimal amount.

Thus, when the steering assist force is transmitted from the electric motor to the steering shaft, the occurrence of tapping sound and vibration is reduced, steering responsiveness is improved, and a comfortable steering feeling can be obtained. In addition, the precision of the parts, such as the pitch between the axes of the worm and the worm wheel, is reduced, and the manufacture of the parts is facilitated.

In addition, since the axial position of the worm shaft can be regulated via one or both of the right and left bearings, the worm shaft can be slid in the axial direction while keeping the combination of the bearing and the worm shaft. The structure of the means for supporting the worm shaft so as to be slidable in the axial direction becomes easy.

According to the third aspect of the present invention, the means for regulating the axial position of the worm shaft via the two bearings has substantially the same structure on the left and right. The structure is simplified, and the number of parts is reduced, so that its manufacture is facilitated. In addition, since the axial positions of the two bearings are also regulated, play in mounting the two bearings to the worm shaft can be absorbed.

Further, by configuring the invention according to claim 1 or 2 as described in claim 4, it is easy to adjust the screwing position of the cap for regulating the axial position of one of the bearings. Thus, the position of the worm shaft in the axial direction can be regulated, and the operation of the means for regulating the axial position of the worm shaft via the bearing is facilitated.

According to the fifth aspect of the present invention, by simply screwing the bolt, one end of the worm shaft is rotatably and axially moved to the one bearing. The fixing means can be fixed so that the fixing means can be easily configured.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment (Embodiment 1) of the invention described in claims 1 to 3 of the present application shown in FIGS. 1 to 4 will be described below. In FIG. 1, an electric power steering device 1 includes a steering wheel (not shown) connected to an input shaft 3 in a steering gear box 2, and a rack 5 in a gear housing integrated with the steering gear box 2 and oriented in the vehicle width direction. Is connected to the front wheel via a tie rod (not shown). When the input shaft 3 is rotated left and right by operating the steering wheel, the rack 5 in the gear housing moves left and right, and the front wheel is moved right and left. Is to be turned.

In the steering gear box 2, an output shaft 8 located on the same axis as the input shaft 3 is connected to a ball bearing 6.
The input shaft 3 and the output shaft 8 are rotatably supported via two bearings, a needle bearing 7 and a torsion bar 9.
Are connected so as to be relatively twistable.

A pinion 10 is formed on the output shaft 8, and the rack 5 is loosely fitted in the gear housing so as to be movable left and right.
Are engaged with the pinion 10, and when the output shaft 8 is rotated left and right, the rack 5 moves left and right.

A worm wheel 11 is integrally fitted on the upper portion of the output shaft 8 and is directed in a direction perpendicular to the output shaft 8 so that the worm wheel 11 as shown in FIG.
A shaft (worm shaft) 13 of a worm 12 meshing with 11 is rotatable in the steering gear box 2 via ball bearings 14 and 15 fitted to both ends thereof, and slides in the axial direction as described later. Possible, supported.

The end of the worm shaft 13 on the bearing 14 side is
The output shaft 8 is connected to the rotating shaft of the electric motor 16 via a serration connecting portion 22 and a clutch (not shown), and when the clutch is set to the connected state and the electric motor 16 rotates.
Is decelerated and driven to rotate.

Here, the tooth thickness s on the pitch line of the worm 12
From the small tooth thickness s ₁ to a large tooth thickness s ₂ of the other end of the one end,
It is created to increase continuously along the tooth ridge (see FIGS. 2 and 3).

The bearing 15 fitted to one end of the worm shaft 13 is screwed into one of the screw holes 19 formed in the steering gear box 2 to close the screw hole 19 on the inner periphery of the cap 20. The bearing 14 fitted to the right end by contacting the stepped portion 20a and the adjustment nut 18 screwed into the other screw hole 17 formed in the steering gear box 2 is fitted to the other end. The worm 12 is positioned in the left direction in contact with the tip of the worm wheel 11, and in this manner, when the worm 12 meshes with the worm wheel 11, an optimal normal-direction backlash t _opt (see FIG. 4) is formed, and It is rotatably supported in the gear box 2.

The lock nuts 21 and 29 are further tightened between the steering gear box 2 and the cap 20 and the adjustment nut 18 in order to fix the screwing positions into the screw holes 19 and 17. . If backlash adjustment of the worm gear is necessary, loosen the lock nuts 21 and 29 and adjust the screw amounts of the cap 20 and the adjustment nut 18 into the screw holes 19 and 17 respectively to adjust the optimal normal direction (or Circumferential direction)
A backlash t _opt is obtained.

The first embodiment is configured as described above. Therefore, when the tooth thickness s of the worm 12 is continuously changed along the tooth trace, optimal adjustment of the backlash t of the worm gear, The compensation of the local wear of the teeth of the worm 12 and the correction of the problem of the mounting position of the worm 12 (the meshing position between the worm 12 and the worm wheel 13), etc.
It can be easily done by sliding 13 in the axial direction.

If the teeth of the worm 12 are locally worn, the worm shaft 13 is slid in the axial direction as described above, so that one of the left and right portions is newly added to the worm wheel 11.
The wear can be easily compensated for by using the gears for engagement.

The backlash t of the worm gear is
The motor is optimally adjusted as described above.
When the steering assist force is transmitted from the steering shaft 16 to the steering shaft (output shaft) 8, the generation of tapping sound and vibration is reduced, steering responsiveness is improved, and a comfortable steering feeling can be obtained. Also, the pitch l between the axes of the worm 12 and the worm wheel 11
(Refer to FIG. 3) The accuracy of the parts is eased, and their manufacture becomes easy.

Further, the worm shaft 13 is provided via bearings 14 and 15.
The axial position of the worm shaft 13 can be regulated, so that the combination of the bearings 14 and 15 and the worm shaft 13 can be left as they are, and the worm shaft 13 can be slid in the axial direction by integrating these components. The structure of the supporting means is made easier.

The means for slidably supporting the worm shaft 13 includes two bearings 14 and 15 and an adjusting nut 1 for regulating the axial position of the worm shaft 13 via the two bearings 14 and 15.
8. Since the means is constituted by the cap 20, the means have substantially the same structure on the left and right, the structure is simplified, the number of parts is reduced, and the manufacture thereof is facilitated.

In particular, if the diameters of the screw hole 17 and the screw hole 19 are the same, the adjustment nut 18 and the cap 20 can have substantially the same structure except for the presence or absence of the top plate. Are also substantially the same, so that the structure of the means is further simplified and its manufacture is further facilitated.

In addition, double bearings 14, 15 comprising ball bearings
The outer ring is provided with an adjusting nut 18 and a cap 20 that regulate the axial position of the worm shaft 13 via these bearings 14 and 15,
Since the bearings 14 and 15 are pushed in the directions of each other, play in mounting the bearings 14 and 15 to the worm shaft 13 can be absorbed.

Next, an embodiment (Embodiment 2) of the invention described in claims 4 and 5 of the present application shown in FIG. 5 will be described. The second embodiment differs from the first embodiment in the configuration of the means for supporting the worm shaft 13 so as to be slidable in the axial direction.

The means for regulating the axial position of the worm shaft 13 via one of the bearings 14, 15 for supporting both ends of the worm shaft 13 is constituted as follows. . A cap 20 is screwed into a screw hole 19 formed in the gear box 2, and the cap 20 closes the screw hole 19 and holds the bearing 15 in an inner peripheral step portion 20 a. It acts to regulate the axial position of the bearing 15. The screwing position of the cap 20 into the screw hole 19 is fixed by the lock nut 21.

One of the worm shafts 13 (right side in FIG. 5)
A flange 23 is formed on the outer periphery of the distal end of the bearing, and the flange 23 can be engaged with the outer surface of the inner ring of the bearing 15 composed of a ball bearing. In addition, a concave portion 24 is provided on the end face of the end portion.
Is formed, and a ball (steel ball) 25 is fitted into the concave portion 24,
A bolt 26 is screwed into a screw hole in the top plate of the cap 20 so that the tip of the cap 25 contacts the ball 25.
The screw-in position 20 can be fixed by a lock nut 27.

As a result, the bolt 26 presses the end face of one end of the worm shaft 13 in the axial direction via the ball 25 to bring the flange 23 into contact with the outer face of the inner ring of the ball bearing 15. One end of the worm shaft 13 is fixed to the bearing 15 so as to be rotatable and immovable in the axial direction.

The other one of the two bearings 14, 15
Is fixed in a bearing insertion hole 28 formed in the gear box 2 so as to support the other end of the worm shaft 13 movably in the axial direction.

In the second embodiment, the worm shaft 13 can be easily adjusted only by adjusting the screwing position of the cap 20 for restricting the axial position of the one bearing 15 because of the above-described configuration.
Of the worm shaft 13 via the bearings 14 and 15 can be easily operated.

A means for fixing one end of the worm shaft 13 to one bearing 15 so as to be rotatable and immovable in the axial direction is provided by a flange 23 formed on the outer periphery of the distal end of the one end of the worm shaft 13. , The ball 25, the bolt 26, and the lock nut 27, so that the bolt 26 is screwed in, and only a pressing force is applied in the axial direction to the end surface of one end of the worm shaft 13 through the ball 25. In addition, one end of the worm shaft 13 can be fixed to one bearing 15 so as to be rotatable and immovable in the axial direction, and the configuration of the fixing means is simplified.

In addition, the same effects as those of the first embodiment can be obtained. As compared with the first embodiment, the means capable of regulating the axial position of the worm shaft 13 via the left and right bearings 14 and 15 cannot be configured to have substantially the same configuration on the left and right. Can be omitted.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view of an electric power steering apparatus according to an embodiment (Embodiment 1) of the invention described in claims 1 to 3 of the present application.

FIG. 2 is a partial cross-sectional view taken along line II-II of FIG. 1, showing a worm gear structure.

FIG. 3 is a partially enlarged view of FIG. 2;

FIG. 4 is an enlarged view of a meshing portion of the teeth of FIG. 3;

FIG. 5 is a partial cross-sectional view of a worm gear structure of an electric power steering apparatus according to an embodiment (Embodiment 2) of the invention described in claims 4 and 5 of the present application, which is similar to FIG. 2; FIG.

FIG. 6 is a diagram showing a conventional example.

FIG. 7 is a partially enlarged view of FIG. 6;

FIG. 8 is an enlarged view of a meshing portion of the teeth of FIG. 7;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering gear box, 3 ... Input shaft, 5 ... Rack, 6 ... Bearing, 7
... (needle) bearing, 8 ... output shaft, 9 ... torsion bar, 10 ... pinion, 11 ... worm wheel, 12 ... worm, 13 ... worm shaft, 14, 15 ... bearing, 16 ... electric motor, 17 ...
Screw hole, 18 ... Adjustment nut, 19 ... Screw hole, 20 ... Cap,
21 ... lock nut, 22 ... serration connection part, 23 ... tsuba,
24 ... recess, 25 ... ball (steel ball), 26 ... bolt, 27 ... lock nut, 28 ... bearing insertion hole, 29 ... lock nut.

Claims (5)

[Claims] 1. A worm gear structure in an electric power steering apparatus in which a worm driven by an electric motor for steering assistance is meshed with a worm wheel attached to a steering shaft interlocked to a steering wheel. The means for slidably supporting in the axial direction can regulate the axial position of the worm shaft via a bearing for supporting both ends of the worm shaft, and either or both of the bearings. And a worm gear structure in the electric power steering apparatus. 2. A worm gear structure in an electric power steering apparatus in which a worm driven by an electric motor for steering assistance is meshed with a worm wheel mounted on a steering shaft interlocked with a steering wheel. A means for supporting the worm shaft slidably in the axial direction, the bearing supporting both ends of the worm shaft, and a bearing for supporting both ends of the worm shaft. Means for controlling the axial position of the worm shaft via one or both of the above. 3. A means capable of regulating the axial position of the worm shaft via both of the bearings is screwed into one of the screw holes formed in the gear box to close the screw hole and provide one of the screw holes. A cap for regulating the axial position of the bearing,
A lock nut for fixing the screwing position of the cap, an adjusting nut screwed into the other screw hole formed in the gear box to regulate the axial position of the other bearing, and a screwing position of the adjusting nut. 3. The worm gear structure in the electric power steering apparatus according to claim 1, wherein the worm gear comprises a lock nut to be fixed. 4. A means capable of regulating the axial position of the worm shaft via one of the two bearings is screwed into a screw hole formed in the gear box to close the screw hole, A cap for regulating the axial position of the bearing,
A lock nut for fixing a screw-in position of the cap, and means for fixing one end of the worm shaft to the one bearing so as to be rotatable and immovable in the axial direction, and the other of the two bearings 3. The electric motor according to claim 1, wherein the first worm shaft is fixed to a bearing insertion hole formed in the gear box, and supports the other end of the worm shaft so as to be movable in the axial direction. 4. Worm gear structure in a power steering device. 5. A means for fixing one end of said worm shaft to said one bearing so as to be rotatable and immovable in the axial direction, said one bearing comprising a ball bearing, and one end of said worm shaft. And a ball fitted in a recess formed in the end face of the end part, and screwed into a screw hole of the top plate of the cap, and pressing the end face in the axial direction through the ball. The bolt according to claim 4, wherein the flange is configured to contact the outer surface of the inner ring of the ball bearing with a lock nut for fixing a position of the bolt to be screwed into the screw hole. Worm gear structure in an electric power steering device.