JP2000038146A - Motor assisted power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor-assisted power steering device capable of preventing backlash, wear, etc., in a tilt-pivot part of a reduction gearbox. SOLUTION: A lower bracket 9 is shaped into a roughly U-shape the lower part of which is open to hold a tilt-pivot part 31 of a reduction gear over, and is turnably connected to the reduction gear cover by a flange bolt 33, namely a shaft member, and a flange nut 37. Cylindrical bushes 47 made of a steel pipe are respectively forced into left and right bush-holding holes 43, 45 of the tilt-pivot part 31, and a shank 35 of the flange bolt 33 is slidably in contact with the inner peripheral surface of a shaft hole 49 formed on the axis of the bushes 47. Further, the outer end of the both the bushes are projected a specified amount from the tilt-pivot part 31, and are slidably brought into contact with the inside surfaces of the lower bracket 9. The inside diameter of the shaft hole 49 is set so that there is almost no clearance between the shank 35 of the flange bolt 33 and it.

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, and more particularly, to a technique for preventing rattling and abrasion at a tilt pivot portion of a reduction gear cover.

[0002]

2. Description of the Related Art In recent years, as a power steering apparatus for an automobile, an electric power steering apparatus using an electric motor as a power source has been proposed in order to suppress the driving loss of an engine and to be applicable to a light vehicle having a small displacement. (Hereinafter E
PS: Electric Power Steerin
g system) is being developed.
The EPS is classified into a column assist type, a pinion assist type, and the like according to a mounting portion of the electric motor, and assist is provided to a steering shaft, a steering gear pinion, and the like according to the type. Column assist type E
In the PS, a part of the steering column is formed by a reduction gear box section including a reduction gear box made of an aluminum alloy casting and a reduction gear cover, and an electric motor is attached to the reduction gear box. The rotation of the electric motor is transmitted to an output shaft forming a part of the steering shaft after being reduced by a worm reduction mechanism housed in a reduction gear box.

[0003] On the other hand, since a steering device of an automobile is used (steered) by an unspecified number of drivers, it is desirable that the position of the steering wheel can be adjusted according to the physique and driving posture of the individual. In order to respond to such a demand, not only passenger cars but also freight cars and the like often employ a tilt mechanism. The tilt mechanism is a mechanism for adjusting the position of the steering wheel in a vertical direction, and includes a tilt pivot for swingably supporting the steering column and a tilt lever unit for fixing the steering column at a desired position (swing angle). And so on. In addition, as a tilt mechanism, a hip swing tilt system in which a tilt pivot is arranged near a connecting portion between a steering column and an intermediate joint (intermediate joint),
Although a tilting tilt system disposed between a steering wheel and a steering column is known, the latter method is generally adopted because the tilt of the steering wheel greatly changes during position adjustment.

[0004]

SUMMARY OF THE INVENTION Column assist type EP
When the hip swing mechanism is adopted for S, a tilt pivot is often provided on the reduction gear cover, but this causes a problem that rattling at the tilt pivot and wear on the reduction gear cover occur. Normally, in the above-described configuration, as shown in FIG. 11, a reduction gear cover is sandwiched between U-shaped brackets fixed to the vehicle body side, and then the reduction gear cover and the bracket are connected to a shaft member (bolt or bolt) serving as a tilt pivot. (Pin etc.). Normally, the gap between the shaft member and the through hole needs to be as small as possible to eliminate backlash. However, when the thickness of the tilt pivot portion in the reduction gear cover is large, the axial length of the through hole inserted through the shaft member is reduced. Therefore, it is difficult to increase the processing accuracy, and it is inevitable that a relatively large play is generated between the through hole and the shaft member. In the conventional hydraulic power steering, the force for applying rotation to the tire is obtained from the rack and pinion, so that it is not necessary to apply a larger torque than the column side. On the other hand, in the EPS, a force for giving rotation to the tire is generated by a column. The reaction force of the generated force is received by the bracket on the vehicle body side from the reduction gear cover via a shaft member (bolt, pin, or the like) serving as a tilt pivot. More specifically, the generated reaction force is transmitted from the reduction gear cover to the shaft member serving as the tilt pivot, but the force is not received by the entire shaft member, but is mainly received at both ends of the shaft member. In other words, a force is applied to both ends (71 in FIG. 11) of the through hole through which the shaft member is inserted, and the force is continuously applied to this portion, and the wear proceeds. Normally, the shaft member is made of iron, and the reduction gear cover forming the through-hole is a relatively soft aluminum alloy casting. Therefore, a portion of the through-hole provided in the reduction gear cover that comes into contact with both ends of the shaft member receiving the reaction force. Will wear selectively. Further, the inner peripheral surface of the through-hole is worn by sliding contact with the shaft member during the tilt operation, and the above-described operation may be further increased after long-term use.

[0005] As described above, if there is play between the through hole and the shaft member, it causes micro-vibration in the bracket during running of the vehicle. In addition, in the EPS, since the torsional torque acts on the reduction gear box when the electric motor is started, generation of abnormal noise or the like due to this is inevitable. On the other hand, in the conventional device, since the reduction gear cover and the bracket are in contact with a relatively large contact surface, there is a problem that the frictional resistance at the time of the relative rotation increases and the tilt operability decreases. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric power steering device that prevents rattling, wear, and the like in a tilt pivot portion of a reduction gear cover.

[0006]

In order to solve the above problems, according to the present invention, a reduction gear box and a reduction gear cover which constitute a part of a steering column and are used for holding a reduction gear mechanism and an electric motor are provided. To connect the reduction gear cover to the vehicle body, a vehicle body side bracket for sandwiching the reduction gear cover, and a shaft member that penetrates the reduction gear cover and the vehicle body side bracket and becomes a fulcrum when the steering column is tilted. The present invention proposes an electric power steering device having a cylindrical bush internally fitted into a penetrating portion of the shaft member in the reduction gear cover. According to the present invention, for example, by fitting a bush made of a steel pipe, a metal shell, or the like as a material into both ends of the through portion of the reduction gear cover, the fitting accuracy between the through hole and the shaft member can be relatively easily increased. Abrasion of the through-hole (bush) due to sliding with the shaft member can be minimized.

According to a second aspect of the present invention, in the electric power steering apparatus according to the first aspect, the bush comprises:
We propose an inner cylinder made of an elastic material fixed to the inner peripheral surface of an outer cylinder made of a metal material. According to the present invention, by using a synthetic resin, a synthetic rubber, or the like for the inner cylinder, a tapping sound due to a play with the shaft member is hardly generated.

According to a third aspect of the present invention, in the electric power steering apparatus according to the first or second aspect, the bush has an outer end protruding from the reduction gear cover. According to the present invention, since the inner surface of the bracket and the end surface of the bush come into contact with each other, frictional resistance is reduced and tilt operability is improved.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing a vehicle cabin side portion of an EPS according to the present invention, and reference numeral 1 in the figure denotes a steering column which is arranged in an inclined manner. The steering column 1 is fixed to a vehicle body side member 5 via a lower bracket 9 and a steel pipe upper steering column (hereinafter abbreviated as an upper column) 7 fixed to the vehicle body side member 5 via an upper bracket 3. And a reduction gear cover 12 and a reduction gear box 11 made of cast aluminum alloy. Reduction gear box 11 and reduction gear cover 12
Are fastened by bolts. An upper steering shaft 15 is rotatably supported by the upper column 7, and an output shaft 17 is rotatably supported by the reduction gear cover 12.

A steering wheel 19 is mounted on the rear end of the upper steering shaft 15, and a lower steering shaft 23 is connected to a front end of the output shaft 17 via a universal joint 21. The electric motor 2 is provided on the side of the reduction gear box 11.
The rotation force is transmitted to the output shaft 17 via a worm reduction mechanism (not shown). In the drawing, a member indicated by reference numeral 27 is a tilt lever, and when operated by a driver, the upper column 7 is released from a tilt adjustment mechanism (not shown), and the steering column 1 swings up and down around a tilt pivot TP. I do.

As shown in FIG. 2 (enlarged sectional view taken along the line AA in FIG. 1) and FIG. 3 (enlarged view in section B in FIG. 2), the lower bracket 9 is attached to the tilt pivot portion 3 of the reduction gear cover 12.
1 has a substantially U-shape with an open lower portion to hold the flange bolt 33 and the flange nut 33 serving as a shaft member.
7 and rotatably connected to the reduction gear cover 12. Further, a through hole 41 into which the flange bolt 33 is loosely fitted is formed in the tilt pivot portion 31 of the reduction gear cover 12, and bush holding holes 43 and 45 having relatively large diameters are formed at the left and right ends of the through hole 41. Is formed. In the case of this embodiment, cylindrical bush 47 made of steel pipe whose perspective is shown in FIG.
Are press-fitted, and the shank 35 of the flange bolt 33 is in sliding contact with the inner peripheral surface of a shaft hole 49 formed in the shaft center of the bush 47. The outer ends of both bushes are separated from the tilt pivot 31 by a predetermined amount a (0.1 to 1 m).
m) projecting and slidingly contacting the inner surface of the lower bracket 9. The inner diameter of the shaft hole 49 is set so that there is almost no clearance with the shank 35 of the flange bolt 33.

Hereinafter, the operation of the present embodiment will be described. When the vehicle is running or when the electric motor 25 is started, various vibrations are generated on the steering column 1 including the reduction gear cover 12 due to vehicle body vibration, torsion torque, and the like. However, in the present embodiment, since the shaft hole 49 between the flange bolt 33 and the bush 47 is set so as to have almost no clearance, there is almost no play between the two. Therefore, even if these vibrating forces are present, the reduction gear box portion 10 does not vibrate, and no abnormal noise or slight vibration of the steering wheel due to the collision between the reduction gear cover 12 and the flange bolt 33 is generated. Also, the reduction gear cover 12
Is in contact with the flange bolt 33 via a relatively hard bush 47 pressed into the bush holding holes 43 and 45. The reaction force from the reduction gear cover 12 is transmitted to the bush 47, but since the bush has a relatively large outer diameter, the surface pressure generated in the bush holding holes 43 and 45 is smaller than that without the bush. The reaction force is transmitted to the flange bolt 33 via the bush 47. As described above, the bush is made of a relatively hard material so that the flange bolt 3
Wear due to sliding contact with No. 3 hardly occurs. By receiving the reaction force at both ends of the through hole 41 of the tilt pivot portion 31, the processing accuracy only at the outer diameter press-fitting portion of the bush 47 can be improved. It is not necessary to increase the dimensional accuracy of the through holes 41 except for the bush holding holes 43 and 45.
Since the bush holding holes 43 and 45 have a relatively short length in the axial direction, they can be easily processed by a drill or the like, and at the same time, it is easy to secure the accuracy of the diameter.

Next, a modification of the shape and structure of the bush 47 will be described with reference to the drawings. FIG. 5 (perspective view), FIG. 6
A bush 47 shown in (longitudinal sectional view) is a first modified example, and a flange 51 is formed at one end of the bush 47 used in the above-described embodiment. According to this modification, the protrusion a of the bush 47 becomes uniform because the flange 51 abuts on the end face of the tilt pivot portion 31, and the accuracy of the axial dimension must be increased when the bush holding holes 43 and 45 are processed. Disappears.

A bush 47 shown in FIGS. 7 (perspective view) and FIG. 8 (longitudinal sectional view) is a second modified example, in which a synthetic resin, synthetic rubber, etc. It has a double structure in which an inner cylinder 55 made of an elastic material is fixed. According to this modification, the reduction gear cover 12 is attached to the lower bracket 9.
However, even when the inner cylinder 55 is slightly moved, the inner cylinder 55 is elastically deformed, so that the noise caused by the contact between the metals is completely suppressed.

The bush 47 shown in FIGS. 9 (perspective view) and FIG. 10 (longitudinal sectional view) is a third modified example, and has features of the first modified example and the second modified example. Things. That is, the inner cylinder 55 made of an elastic material such as synthetic resin or synthetic rubber is fixed to the inner peripheral surface of the outer cylinder 53 made of steel pipe,
A flange 51 is formed at one end of the outer cylinder. According to this modification, the protrusion amount a of the bush 47 becomes uniform, and it is not necessary to increase the accuracy of the axial dimension in processing the bush holding holes 43 and 45. In addition, abnormal noise due to contact between metals is completely suppressed. Can be

The description of the specific embodiment has been completed.
The aspects of the present invention are not limited to the above embodiment.
For example, in each of the above embodiments, the present invention is applied to an EPS in which a reduction gear box portion is disposed at a lower end of a steering column, but is applied to an EPS in which a reduction gear box portion is disposed in an intermediate portion of a steering column. May be.
In the present embodiment, an example in which the cylindrical bush is fitted inside the reduction gear cover has been described. However, it is also possible to fit the cylindrical bush inside the reduction gear box. Further, in the above embodiment, the steel pipe is used as the material of the bush. However, a gunmetal, an oil-impregnated sintered alloy or the like may be used. May be used. Further, in the above embodiment, a flange bolt is used as a shaft member and the flange bolt is fastened with a flange nut. However, a pin made of a steel rod or a steel pipe is used, and this is fixed by a C-type retaining ring or the like. You may. Furthermore, specific configurations of the electric assist mechanism and the tilt mechanism, and specific shapes of the steering shaft, the steering column, and the like can be appropriately changed without departing from the gist of the present invention.

[0017]

As described above, according to the electric power steering apparatus of the present invention, a reduction gear cover which forms a part of the steering column and is used for holding the reduction gear mechanism and the electric motor, and the reduction gear An electric power having a vehicle body side bracket for holding the reduction gear box and a shaft member passing through the reduction gear cover and the vehicle body side bracket and serving as a fulcrum at the time of tilting of the steering column in order to connect the gear cover to the vehicle body. In the steering device, since a cylindrical bush is fitted into a through portion of the shaft member in the reduction gear cover, for example, a bush made of a steel pipe, a metal shell, or the like is pressed into both ends of the through portion of the reduction gear cover. The fitting accuracy between the through hole and the shaft member can be relatively easily increased, and the bushing due to sliding with the shaft member can be improved. Wear it is possible to suppress very little of.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the structure of a steering device according to the present invention on the passenger compartment side.

FIG. 2 is an enlarged sectional view taken along line AA in FIG.

FIG. 3 is an enlarged view of a portion B in FIG. 2;

FIG. 4 is a perspective view of a bush.

FIG. 5 is a perspective view showing a bush according to a first modification.

FIG. 6 is a longitudinal sectional view showing a bush according to a first modification.

FIG. 7 is a perspective view showing a bush according to a second modification.

FIG. 8 is a longitudinal sectional view showing a bush according to a second modification.

FIG. 9 is a perspective view showing a bush according to a third modification.

FIG. 10 is a longitudinal sectional view showing a bush according to a third modification.

FIG. 11 is a view similar to FIG. 2 showing a lower bracket of a conventional steering device as a cross section.

[Explanation of symbols]

 1 Steering column 9 Lower bracket 11 Reduction gear box 25 Electric motor 31 Tilt pivot 33 Flange bolt 41 Through hole 43, 45 Bush holding hole 47 Bush 49 ‥‥ Shaft hole 51 ‥‥ Flange 53 ‥‥ Outer cylinder 55 ‥‥ Inner cylinder TP ‥‥ Tilt pivot

Claims (3)

[Claims] 1. A reduction gear box and a reduction gear cover which constitute a part of a steering column and are used for holding a reduction gear mechanism and an electric motor, and hold the reduction gear cover so as to connect the reduction gear cover to a vehicle body. An electric power steering apparatus comprising: a vehicle body side bracket; and a shaft member that penetrates through the reduction gear cover and the vehicle body side bracket and serves as a fulcrum when the steering column is tilted, wherein the shaft member penetrates through the reduction gear cover. An electric power steering device characterized in that a cylindrical bush is fitted inside the portion. 2. The electric power steering apparatus according to claim 1, wherein the bush is formed by fixing an inner cylinder made of an elastic material to an inner peripheral surface of an outer cylinder made of a metal material. 3. The bush according to claim 1, wherein an outer end of the bush protrudes from the reduction gear cover.
Or the electric power steering device according to 2.