JP3849751B2 - 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 an electric power steering apparatus that can effectively prevent foreign substances from entering.
[0002]
[Prior art]
As an electric power steering device for a vehicle, the rotational output of an electric motor serving as an auxiliary steering torque is decelerated by a gear device and transmitted to the output shaft of a steering mechanism, assisting the steering force applied to the steering wheel, Those configured to perform steering are known. In such an electric power steering device, the worm gear mechanism provided in the housing is used to transmit power to the output shaft while reducing the rotation of the electric motor, and the rack shaft meshed with this is either axially Has been moved to.
[0003]
[Problems to be solved by the invention]
By the way, in the steering mechanism, a dustproof boot is usually provided so that foreign matter does not enter between the rack housing and a tie rod connected to the rack shaft and moving in the axial direction to steer the wheel. However, since the dustproof boot is exposed below the vehicle body, it may be damaged by a stepping stone or the like. In such a case, muddy water or the like may enter the rack housing from between the tie rod and the rack housing, and may enter the worm gear chamber from around the output shaft. In order to reduce noise, the worm wheel of the worm gear mechanism is often formed with resin teeth, and since the resin part absorbs and swells due to the invading muddy water, the operation of the reduction mechanism part may not be performed smoothly. Furthermore, there is a possibility of causing early wear of the tooth surface.
[0004]
On the other hand, in the electric power steering apparatus disclosed in Japanese Patent Application Laid-Open No. 10-258749, an oil seal is provided in front of the worm gear chamber so that the muddy water and the like do not enter the worm gear chamber. However, in such a conventional technique, there is a problem that the apparatus configuration becomes long in the axial direction in order to provide the oil seal. In addition, since the oil seal is incorporated, there is a problem that the assembling work takes time.
[0005]
In view of the above problems, an object of the present invention is to provide an electric power steering device that can effectively prevent foreign substances from entering without causing an increase in size.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an electric power steering apparatus according to a first aspect of the present invention includes a housing, a motor attached to the housing and generating an auxiliary steering force on a rotating shaft, and a steering force for steering a wheel. An output shaft that outputs, a bearing with a seal that rotatably supports the output shaft with respect to the housing, a rotation shaft of the motor, and a power transmission mechanism that couples the output shaft so that power can be transmitted, An inner ring of the bearing is press-fitted into the output shaft, and a seal member is disposed between the housing and the outer ring of the bearing .
Furthermore, an electric power steering apparatus according to a second aspect of the present invention includes a housing, a motor that is attached to the housing and generates an auxiliary steering force on a rotating shaft, and an output shaft that outputs the steering force to steer the wheels. A bearing with a seal that rotatably supports the output shaft with respect to the housing, a rotation shaft of the motor, and a power transmission mechanism that connects the output shaft so that power can be transmitted. A seal member is press-fitted into the housing and disposed between the inner ring of the bearing and the output shaft.
[0007]
[Action]
According to the electric power steering apparatus of the present invention, a housing, a motor attached to the housing and generating an auxiliary steering force on a rotating shaft, an output shaft for outputting a steering force to steer a wheel, and the housing A bearing that rotatably supports the output shaft, a rotating shaft of the motor, and a power transmission mechanism that connects the output shaft so as to be able to transmit power, between the housing and the outer ring of the bearing. Alternatively, since a seal member is disposed between the inner ring of the bearing and the output shaft, the worm gear chamber passes through the outer peripheral side or the inner peripheral side of the bearing without changing the axial length of the apparatus. Can be effectively prevented.
[0008]
The seal member is, for example, an O-ring disposed on the inner peripheral surface of the housing facing the outer ring of the bearing or in a peripheral groove formed on the outer peripheral surface of the output shaft facing the inner ring of the bearing. However, it is not limited to this.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing the electric power steering apparatus according to the first embodiment of the present invention cut along the axis of the input shaft.
[0010]
In FIG. 1, an input shaft 2 and an output shaft 3 extend within a housing 1 composed of a main body 1a and a lid member 1b. The hollow input shaft 2 has an upper end connected to a steering shaft (not shown), and the steering shaft is connected to a steering wheel (not shown). The input shaft 2 is rotatably supported with respect to the housing 1 by a bearing 4. A torsion bar 5 having an upper end pin-coupled to the input shaft 2 and a lower end connected to the output shaft 3 by press-fitting extends in the input shaft 2. The input shaft 2 and the lid member 1 b of the housing 1 are sealed with a seal 7 above the bearing 4.
[0011]
Around the lower end of the input shaft 2, a detection device that detects a steering torque, that is, a torque sensor 6 is provided based on the torsion bar 5 that is an elastically deformable member being twisted in proportion to the received torque. The torque sensor 6 is a rotary non-contact torque sensor, and detects relative angular displacement between the input shaft 2 and the output shaft 3 based on torsion of the torsion bar 5 as a change in impedance in a predetermined magnetic circuit. The signal is output as an electric signal to a control circuit (not shown).
[0012]
A pinion gear 3a is formed at the center of the output shaft 3 and meshes with the rack teeth 11a of the rack shaft 11 extending in the direction perpendicular to the paper surface. The rack shaft 11 is supported from the back by a known rack support device 12 including a rack guide 12a, a spring 12b, and a lock member 12c, and is pressed toward the pinion gear 3a.
[0013]
A worm wheel 13 is fixedly attached to the outer periphery of the upper end of the output shaft 3 by press fitting or the like. A worm wheel 13 having resin teeth meshes with a worm 30a connected to a rotating shaft 30 of an electric motor (not shown). The electric motor is connected to a control circuit (not shown). The control circuit inputs information such as the output of the torque sensor 6 and the vehicle speed, and supplies predetermined electric power to the electric motor to obtain an appropriate auxiliary torque. Is generated. The worm wheel 13 and the worm 30a constitute a power transmission mechanism.
[0014]
The output shaft 3 is rotatably supported by bearings 14 and 15. More specifically, the upper bearing 14 is fitted in the vicinity of the worm wheel 13 at the upper end of the output shaft 3. Further, a lower bearing 15 is fitted to the lower end of the output shaft 3. The outer ring of the lower bearing 15 is fixed to the step portion 1 e of the housing 1 by screwing the screw cover 9 into the housing 1. On the other hand, the inner ring of the lower bearing 15 is attached to the output shaft 3 by screwing a nut 17 into the output shaft 3. In addition, since the bearing 15 is an angular contact type with little axial backlash, the output shaft 3 can be positioned in the axial direction by using the bearing 15.
[0015]
FIG. 2 is an enlarged view showing a portion II of the configuration of FIG. As shown in FIG. 1, an outer ring 14 a of an upper bearing 14 that is a bearing with a seal is attached to a step portion 1 c formed on a main body 1 a of the housing 1 by press-fitting. On the other hand, the inner ring 14b of the upper bearing 14 has a loose-fit relationship with the outer peripheral surface of the output shaft 3, but as shown in FIG. 2, the outer peripheral surface of the output shaft 3 facing the inner ring 14b has A circumferential groove 3b is formed, and an O-ring 18 is disposed in the circumferential groove 3b. The O-ring 18 that functions as a seal member seals between the inner ring 14 b of the upper bearing 14 and the output shaft 3. The upper side of the upper bearing 14 is a worm gear chamber A (see FIG. 1).
[0016]
Next, the operation of the embodiment according to the present invention will be described below.
If the vehicle is in a straight traveling state and no steering force is input to the input shaft 2 via a steering wheel and a steering shaft (not shown), the torque sensor 6 does not generate an output signal. Does not occur.
[0017]
When the driver steers a steering wheel (not shown) when the vehicle is about to turn a curve, the torsion bar 5 is twisted according to the steering force, and a relative rotation occurs between the input shaft 2 and the output shaft 3. . The torque sensor 6 outputs a signal according to the direction and amount of the relative rotation. Based on this signal, the electric motor rotates to generate an auxiliary steering force. The rotation of the electric motor is decelerated by the worm gear mechanism (13, 30a) and transmitted to the output shaft 3, thereby supporting the movement of the rack shaft 11.
[0018]
According to the present embodiment, since the O-ring 18 is arranged between the inner ring 14b of the upper bearing 14 and the output shaft 3, the dustproof boot (not shown) is damaged and the rack shaft 11 side is damaged. Even when foreign matter such as muddy water enters, it can be effectively prevented from passing through the inner peripheral side of the upper bearing 14 and reaching the worm gear chamber A. Since the upper bearing 14 is a bearing with a seal that prevents the lubricating oil from leaking from the inside, the passage of foreign matter through the upper bearing 14 is also prevented. Furthermore, since the outer ring 14a of the upper bearing 14 and the stepped portion 1c are in a close relationship by press-fitting, it is possible to prevent foreign matter from passing between them. Accordingly, entry of foreign matter from the output shaft 3 side into the worm gear chamber A is prevented. In addition, even when the O-ring 18 is provided, the axial length of the apparatus and the dimensions around the bearing are not enlarged, and a compact configuration can be maintained. Further, the O-ring 18 has a function of suppressing the vibration even when vibration occurs between the upper bearing 14 and the output shaft 3.
[0019]
FIG. 3 is a cross-sectional view similar to FIG. 1 showing an electric power steering apparatus according to the second embodiment. The second embodiment is different from the first embodiment only in the configuration around the upper bearing 14, and the description of the other configurations is omitted.
[0020]
The inner ring 14 b of the upper bearing 14 that is a bearing with a seal is attached to the outer peripheral surface of the output shaft 3 by press fitting. On the other hand, the outer ring 14a of the upper bearing 14 has a loose-fitting relationship with the inner peripheral surface of the step portion 1c formed on the main body 1a of the housing 1, but as shown in FIG. A circumferential groove 1d is formed on the inner circumferential surface, and an O-ring 18 'is disposed in the circumferential groove 1d. The O-ring 18 ′ functioning as a seal member seals between the outer ring 14a of the upper bearing 14 and the main body 1a. The upper side of the upper bearing 14 is a worm gear chamber A.
[0021]
According to the present embodiment, since the O-ring 18 ′ as a seal member is disposed between the outer ring 14a of the upper bearing 14 and the main body 1a, the dustproof boot (not shown) is damaged and the rack is Even when foreign matter such as muddy water enters from the shaft 11 side, it can be effectively prevented from passing through the outer peripheral side of the upper bearing 14 and reaching the worm gear chamber A. Since the upper bearing 14 is a bearing with a seal that prevents the lubricating oil from leaking from the inside, the passage of foreign matter through the upper bearing 14 is also prevented. Furthermore, since the inner ring 14b of the upper bearing 14 and the output shaft 3 are in a close relationship by press-fitting, it is possible to prevent foreign matter from passing between them. Accordingly, entry of foreign matter from the output shaft 3 side into the worm gear chamber A is prevented. In addition, even when the O-ring 18 'is provided, the axial length of the apparatus and the dimensions around the bearing are not enlarged, and a compact configuration can be maintained. Further, the O-ring 18 ′ also has a function of suppressing this even when vibration occurs between the upper bearing 14 and the main body 1a.
[0022]
As described above, the present invention has been described in detail with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be appropriately changed and improved without departing from the spirit thereof. Of course there is. For example, the sealing member may be formed by filling not only the O-ring but also, for example, a liquid packing that exhibits hermeticity when solidified into the circumferential groove.
[0023]
【The invention's effect】
As described above, according to the electric power steering apparatus of the present invention, the housing, the motor attached to the housing and generating the auxiliary steering force on the rotating shaft, and the steering force for steering the wheel are output. An output shaft; a bearing that rotatably supports the output shaft with respect to the housing; a rotation shaft of the motor; and a power transmission mechanism that connects the output shaft so as to be capable of transmitting power. Since a seal member is disposed between the outer ring of the bearing or between the inner ring of the bearing and the output shaft, the outer circumferential side or inner circumference of the bearing can be changed without changing the axial length of the apparatus. Foreign matter that reaches the worm gear chamber through the side can be effectively prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an electric power steering apparatus according to a first embodiment, cut in an axial direction of an input shaft.
FIG. 2 is an enlarged view showing a II part in the power steering apparatus of FIG. 1;
FIG. 3 is a cross-sectional view similar to FIG. 1, showing an electric power steering apparatus according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Housing 2 Input shaft 2b Convex part 3 Output shaft 5 Torsion bar 5e Lower circumference groove 6 Torque sensor 18, 18 'O-ring

Claims (2)

A housing;
A motor attached to the housing and generating an auxiliary steering force on a rotating shaft;
An output shaft that outputs steering force to steer the wheels;
A bearing with a seal that rotatably supports the output shaft with respect to the housing;
It consists of a power transmission mechanism that connects the rotation shaft of the motor and the output shaft so that power transmission is possible
An electric power steering apparatus in which an inner ring of the bearing is press-fitted into the output shaft, and a seal member is disposed between the housing and an outer ring of the bearing .   A housing;
  A motor attached to the housing and generating an auxiliary steering force on a rotating shaft;
  An output shaft that outputs steering force to steer the wheels;
  A bearing with a seal that rotatably supports the output shaft with respect to the housing;
  It consists of a power transmission mechanism that connects the rotation shaft of the motor and the output shaft so that power transmission is possible
  An electric power steering apparatus in which an outer ring of the bearing is press-fitted into the housing, and a seal member is disposed between the inner ring of the bearing and the output shaft.

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