JP2007182176A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent increase of friction and fluctuation of torque. <P>SOLUTION: A pair of bearings 15, 16 is interposed at front and rear sides in a vehicle direction of a worm wheel 12 and the bearing on the vehicle front side is fixed to an output shaft 5 by a stop ring 17. The bearing 15 of four-point contact on the vehicle front side is fixed to the output shaft 5 and in the bearing 16 on the vehicle rear side, a clearance with the output shaft 5 is set to a loose fit. A ring-like elastic body 18 is interposed between the bearing 16 on the loose fit side and the output shaft 5. Accordingly, even when the clearance between the output shaft 5 and the bearing on the loose fit side is made large, since a play is narrowed by the elastic body 18, hitting sound by contact can be prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention detects a steering torque applied to an input shaft by a torque sensor, generates an auxiliary steering torque from an electric motor corresponding to the detected steering torque, decelerates it by a gear reduction mechanism, and transmits it to an output shaft. The present invention relates to an electric power steering apparatus.

  In a steering system of an automobile, a so-called power steering device that performs steering assist using an external power source is widely adopted. Conventionally, vane type hydraulic pumps have been used as power sources for power steering devices, and many of these hydraulic pumps are driven by an engine. However, this type of power steering device has a large engine drive loss due to the constant drive of the hydraulic pump (several horsepower to about 10 horsepower at the maximum load), so it can be used in light vehicles with small displacement. It was difficult, and it was unavoidable that the fuel consumption of a car with a relatively large displacement was reduced to a level that could not be ignored.

  In order to solve these problems, an electric power steering device (Electric Power Steering, hereinafter referred to as EPS) using an electric motor as a power source has attracted attention in recent years. The EPS uses an in-vehicle battery as a power source for the electric motor, so there is no direct engine drive loss, and since the electric motor is started only at the steering assist time, a decrease in driving fuel consumption is suppressed, and electronic control is performed. It has the feature that it can be done very easily.

  In EPS, an auxiliary steering torque is generated from an electric motor in response to a steering torque applied to a steering wheel, and is decelerated by a power transmission mechanism (reduction gear) and transmitted to an output shaft of the steering mechanism. Yes.

  In EPS using a worm gear mechanism as the power transmission mechanism (reduction gear), a worm wheel meshes with a worm on the drive shaft side of the electric motor, and this worm wheel is connected to an output shaft (for example, a pinion) of a steering mechanism. Shaft, column shaft).

  By the way, in Patent Document 1, the worm wheel is formed by fixing a synthetic resin gear ring to the outer periphery of a metal wheel, and is a cold forging molded product, which is a cylindrical shape that is externally fitted and press-fitted to an output shaft. It has a boss part. The output shaft is supported by the hermetic rolling bearing immediately after the worm wheel, and is supported by the sealed rolling bearing via the boss portion of the worm wheel. The roller bearing with seal is held on the cover and the output shaft via a taper snap ring. In the fitting portion of the rolling bearing with seal, an annular reduced diameter portion (escape groove) as an escape portion is formed on the outer peripheral surface of the output shaft, and thereby an annular gap is defined between the boss portion and the boss portion. . Further, a pair of fitting and press-fitting surfaces are formed on the outer peripheral surface of the output shaft on the left and right sides of the annular reduced diameter portion. Due to the presence of the gap, even if the boss portion is press-fitted into the output shaft, the diameter of the boss portion does not increase at the fitting portion of the roller bearing with seal. Further, since the output shaft and the boss part are fitted and press-fitted by a pair of fitting and press-fitting surfaces that are separated from each other, the fixing strength between the two is increased. As a result, the distance between the rolling bearing and the rolling bearing with seal is shortened, and the gear housing is shortened, and the worm wheel and the rolling bearing with seal are securely fixed.

In Patent Document 2, since an O-ring is arranged between the housing and the outer ring of the upper bearing or between the upper bearing and the output shaft, the upper bearing is not changed without changing the axial length of the apparatus. It is possible to effectively prevent foreign matter that reaches the worm gear chamber through the outer peripheral side or the inner peripheral side.
Japanese Patent Laid-Open No. 2004-203212 JP 2001-315650 A

  However, when the output shaft is fixed to a bearing (contacted at 4 points) with a retaining ring or nut, the shaft and the bearing that should be a clearance fit between the shaft due to misalignment and runout of the cover, gear housing, shaft, etc. Interference may occur.

  As a result, the bearing that fixes the output shaft is distorted, causing an increase in friction and torque fluctuation, which is not preferable for the EPS function.

  For example, if the clearance between the bearing and the output shaft is increased, the output shaft is prevented from being twisted, but contact-specific hitting noise is likely to occur.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an electric power steering apparatus that can prevent an increase in friction and torque fluctuation.

In order to achieve the above object, an electric power steering apparatus according to the present invention detects a steering torque applied to an input shaft by a torque sensor, and generates an auxiliary steering torque from an electric motor in response to the detected steering torque. In the electric power steering device that is decelerated by the gear reduction mechanism and is transmitted to the output shaft,
The output shaft is rotatably supported through two bearings,
One bearing is fixed to the output shaft,
The other bearing is set to a clearance gap between the output shaft,
An elastic body is interposed between the bearing on the clearance gap side and the output shaft.

The electric power steering apparatus according to the present invention detects the steering torque applied to the input shaft by a torque sensor, generates auxiliary steering torque from the electric motor in response to the detected steering torque, and decelerates by the gear reduction mechanism. In the electric power steering device that transmits to the output shaft,
The output shaft is rotatably supported through two bearings,
One bearing is fixed to the output shaft,
The other bearing is set to a clearance gap between the output shaft,
The fixing member for fixing the one bearing to the output shaft is provided with an elastic body and a stopper portion.

  Preferably, the one bearing fixed to the output shaft is a four-point contact bearing.

  Preferably, the fixing member is a retaining ring.

  According to the present invention, even when the clearance between the output shaft and the bearing on the clearance gap side is large, the play due to the contact can be prevented because the elastic body is loose.

  Further, even when the elastic body provided on the retaining ring is twisted together with the output shaft, since the twist is not transmitted to the four-point contact bearing, an increase in friction can be prevented. When a large axial force is generated by the meshing of the gear, the stopper portion receives a load, so there is no concern about durability.

  Hereinafter, an electric power steering apparatus according to an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a longitudinal sectional view of an electric power steering apparatus according to a first embodiment of the present invention.

  In the column assist type electric power steering apparatus, an upper column (not shown) is slidably fitted to the lower column 2 of the steering column. A hollow upper shaft (not shown) and a solid lower shaft 4 (input shaft) that are spline-fitted in a telescopic slidable manner and a solid lower shaft 4 (input shaft) are rotatably supported in these columns.

  An output shaft 5 is connected to the vehicle front side of the lower shaft 4 (input shaft). An intermediate shaft (not shown) is connected to the front side of the output shaft 5 via a universal joint UJ.

  A base end of a torsion bar 6 is press-fitted and fixed on the vehicle front side of the lower shaft 4 (input shaft). The torsion bar 6 extends inside a hollow output shaft 5 and has a distal end. Is fixed to the end of the output shaft 5.

  A torque sensor part TS is provided on the vehicle rear side of the output shaft 5. That is, a detection groove 7 of the torque sensor unit TS is formed on the vehicle rear side of the output shaft 5, and a sleeve 8 of the torque sensor unit TS is disposed outside the groove 7 in the radial direction. is there. The sleeve 8 has a vehicle rear side end fixed to a vehicle front side end of the lower shaft 4 (input shaft) by caulking or the like. A coil 9 and a substrate are provided outside the sleeve 8 in the radial direction.

  A worm wheel 12 meshed with a worm (not shown) connected to a drive shaft of an electric motor (not shown) is attached to the output shaft 5.

  The worm (not shown) and the worm wheel 12 are housed in a rear housing 13 (gear housing) and a front housing 14 (cover).

  A pair of bearings 15 and 16 are interposed in the front and rear of the worm wheel 12 in the vehicle direction, and the bearing 15 on the vehicle front side is fixed to the output shaft 5 by a retaining ring 17. The retaining ring 17 may be a nut.

  Therefore, the steering force generated when the driver steers the steering wheel (not shown) is applied to the steered wheels (not shown) via the input shaft 4, the torsion bar 6, the output shaft 5, and the rack and pinion type steering device. Communicated. Further, the rotational force of the electric motor (not shown) is transmitted to the output shaft 5 via the worm (not shown) and the worm wheel 12, and the rotational force and the rotation of the electric motor (not shown). By appropriately controlling the direction, an appropriate steering assist torque can be applied to the output shaft 5.

In the present embodiment, the bearing 15 on the front side of the vehicle is fixed to the output shaft 5, and the bearing 16 on the rear side of the vehicle is set between the output shaft 5 with a clearance. The bearing 15 on the front side of the vehicle is a four-point contact bearing. A ring-shaped elastic body 18 is interposed between the bearing 16 on the clearance gap side and the output shaft 5. The ring-shaped elastic body 18 is loose.

  Therefore, even when the clearance between the output shaft 5 and the bearing 16 on the gap clearance side is large, the elastic body 18 is rattling, so that it is possible to prevent hitting sound due to contact. Further, an increase in friction and torque fluctuation can be prevented.

(Second Embodiment)
FIG. 2 is a longitudinal sectional view of an electric power steering apparatus according to the second embodiment of the present invention.

  3A is a front view of a retaining ring (fixing member) that fixes a bearing on the front side of the vehicle, FIG. 3B is a side view thereof, and FIG. 3C is a cross-sectional view thereof.

  In the present embodiment, the column assist type electric power steering apparatus has the same basic structure as that of the first embodiment described above, and the description thereof is omitted.

  A pair of bearings 15 and 16 are interposed before and after the worm wheel 12 in the vehicle direction, and the bearing 15 on the vehicle front side is fixed to the output shaft 5 by a retaining ring 17.

In the present embodiment, the bearing 15 on the front side of the vehicle is fixed to the output shaft 5, and the bearing 16 on the rear side of the vehicle is set between the output shaft 5 with a clearance. The bearing 15 on the front side of the vehicle is a four-point contact bearing. A retaining ring 20 (fixing member) that fixes the bearing on the front side of the vehicle is provided with an elastic body 21 and a stopper portion 22. The plurality of elastic bodies 21 and the plurality of stopper portions 22 are provided alternately in the circumferential direction.

  Therefore, even if the elastic body 21 provided on the retaining ring 20 is twisted together with the output shaft 5, no twisting is transmitted to the four-point contact bearing 15 on the front side of the vehicle, so that an increase in friction and torque fluctuation can be prevented. . When a large axial force is generated by the meshing of the gear, the stopper portion 22 receives a load, so there is no concern about durability.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible.

1 is a longitudinal sectional view of an electric power steering device according to a first embodiment of the present invention. It is a longitudinal cross-sectional view of the electric power steering apparatus which concerns on 2nd Embodiment of this invention. (A) is a front view of the retaining ring (fixing member) which fixes the bearing of the vehicle front side, (b) is the side view, (c) is the sectional drawing.

Explanation of symbols

2 Lower column (column tube)
4 Lower shaft (input shaft)
5 Output shaft 6 Torsion bar 7 Detection groove 8 Sleeve 9 Coil TS Torque sensor 12 Worm wheel 13 Rear housing (gear housing)
14 Front housing (cover)
15, 16 Bearing 17 Retaining ring 18 Elastic body 20 Retaining ring (fixing member)
21 Elastic body 22 Stopper part

Claims (4)

An electric power steering device that detects a steering torque applied to the input shaft by a torque sensor, generates an auxiliary steering torque from the electric motor in response to the detected steering torque, decelerates the gear by a gear reduction mechanism, and transmits it to the output shaft In
The output shaft is rotatably supported through two bearings,
One bearing is fixed to the output shaft,
The other bearing is set to a clearance gap between the output shaft,
An electric power steering apparatus, characterized in that an elastic body is interposed between the bearing on the clearance gap side and the output shaft. An electric power steering device that detects a steering torque applied to the input shaft by a torque sensor, generates an auxiliary steering torque from the electric motor in response to the detected steering torque, decelerates the gear by a gear reduction mechanism, and transmits it to the output shaft In
The output shaft is rotatably supported through two bearings,
One bearing is fixed to the output shaft,
The other bearing is set to a clearance gap between the output shaft,
An electric power steering apparatus characterized in that an elastic body and a stopper portion are provided on a fixing member for fixing the one bearing to the output shaft.   The electric power steering apparatus according to claim 1 or 2, wherein the one bearing fixed to the output shaft is a four-point contact bearing.   The electric power steering apparatus according to claim 2, wherein the fixing member is a retaining ring.

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