JP2007216917A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device, which has a small resistance generated in an inner side and reduces rattling sound. <P>SOLUTION: The steering device is equipped with: a worm gear mechanism 11 including a worm shaft 14 driven by an electric motor, and a worm wheel 15 meshing with the worm shaft 14; a housing for storing the worm gear mechanism 11; a lubricant G stored in the housing; an intermediate member 49 which is interposed between one side surface 18 of the worm wheel 15 and the lower end surface 48 of a sensor housing 8, and is integrally rotated with the worm wheel 15; and an electromagnet 50 for adjusting the clearance C between the lower end surface 48 and the intermediate member 49. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus.

  Some vehicles, such as automobiles, include an electric power steering device that assists steering by applying the power of an electric motor to a steering mechanism (see Patent Documents 1 and 2). The output of the electric motor is given to the steering shaft via, for example, a drive gear connected to the output shaft of the electric motor and a driven gear meshing with the drive gear, and is transmitted from the steering shaft to the steering mechanism. The meshing region between the driving gear and the driven gear is filled with grease so that the meshing of both is smooth.

In Patent Document 1, a grease reservoir is provided in the vicinity of the meshing region between the drive gear and the driven gear. In Patent Document 2, a guide member is provided for guiding the grease pushed out from the meshing region between the drive gear and the driven gear to the driven gear.
Japanese Patent Laid-Open No. 2001-301631 Japanese Patent Laid-Open No. 11-29057

  In general, meshing between the drive gear and the driven gear requires an appropriate backlash to reduce frictional resistance. However, for example, when driving on a rough road and receiving a reaction force (reverse input) from the tire, a rattling sound (rattle sound) may be generated due to the backlash. In the configurations of Patent Documents 1 and 2, grease is filled in the meshing region between the drive gear and the driven gear, and rattle noise can be reduced.

However, at low temperatures where the viscosity of the grease is relatively high, the viscosity resistance of the grease at the meshing portion between the drive gear and the driven gear increases, resulting in a high drive loss and a decrease in steering feeling. I will.
The present invention has been made under such a background, and an object of the present invention is to provide an electric power steering device that can reduce rattle noise and can prevent generation of unnecessary resistance.

  In order to achieve the above object, the present invention provides a transmission mechanism (11) including a drive gear (14) driven by an electric motor (12) for assisting steering and a driven gear (15) meshing with the drive gear (14). 11) housing (7), lubricant (G) accommodated in the housing (7), side surface (18) of the driven gear (15) and the opposing surface of the housing (7) facing this ( 48), an intermediate member (49; 49A), one of the side surface (18) of the driven gear (15) and the opposed surface (48) of the housing (7), and the intermediate member (49; 49A). And an interval adjusting member (50) that adjusts the interval (C; CA) between the motor and the electric power steering device (claim 1).

In addition, the alphanumeric characters in parentheses represent corresponding components in the embodiments described later. The same applies hereinafter.
According to the present invention, the distance between the intermediate member and the side surface of the driven gear or the facing surface of the housing facing the driven gear can be adjusted by the distance adjusting member. Thereby, said space | interval in which a lubricant exists can be adjusted, and the influence of the viscosity of the lubricant with respect to a driven gear can be adjusted.

In other words, when the interval in which the lubricant is present is relatively narrow, the viscous resistance of the lubricant can be reliably imparted to the driven gear. Thereby, it is possible to reduce the impact when the driven gear comes into contact with the drive gear due to reverse input from the tire or the like when traveling on a rough road or the like, and to reduce rattle noise.
On the other hand, by making the interval where the lubricant is present relatively wide, it is possible to reduce the viscous resistance due to the lubricant with respect to the driven gear. As a result, it is possible to prevent unnecessary resistance from acting on the driven gear, and the driven gear can be smoothly rotated when the viscosity of the lubricant is high or when driving on a flat road. And the deterioration of steering feeling can be prevented.

  In the present invention, the intermediate member (49) may be capable of rotating in conjunction with the driven gear (15) (claim 2). In this case, by relatively narrowing the interval between the intermediate member and the housing, the viscous resistance of the lubricant between the intermediate member and the housing is reliably applied to the driven gear via the intermediate member. be able to. Further, by making the interval between the intermediate member and the housing relatively wide, the viscous resistance imparted to the intermediate member by the lubricant between the intermediate member and the housing can be reduced. Thereby, it is possible to prevent unnecessary resistance from acting on the driven gear that rotates in conjunction with the intermediate member.

  In the present invention, the intermediate member (49A) may include a held portion (51A) held by the housing (7) (Claim 3). In this case, by making the distance between the intermediate member and the driven gear relatively narrow, the viscous resistance of the lubricant between the intermediate member and the driven gear can be reliably imparted to the driven gear. . Further, by making the interval between the intermediate member and the driven gear relatively wide, the viscous resistance imparted to the driven gear by the lubricant between the intermediate member and the driven gear can be reduced. Thereby, it is possible to prevent unnecessary resistance force from acting on the driven gear.

In the present invention, the intermediate member (49; 49A) may include a leaf spring (claim 4). In this case, the intermediate member can be realized with a simple configuration using a leaf spring.
In the present invention, the intermediate member (49; 49A) may include a magnetic body, and the interval adjusting member (50) may include an electromagnet (50) capable of magnetically attracting the intermediate member (49; 49A). (Claim 5). In this case, the interval can be easily adjusted with a simple configuration in which the intermediate member is magnetically attracted by the electromagnet.

In the present invention, the intermediate member (49; 49A) may face at least the side surface (18a) of the tooth portion (17) of the driven gear (15) (Claim 6). In this case, the intermediate member can guide the lubricant to the meshing region of the drive gear and the driven gear, and the meshing region can be more reliably lubricated.
In the present invention, the intermediate member (49; 49A) may face at least a region in the lower side of the side surface (18) of the driven gear (15) in the vertical direction (V) (Claim 7). In this case, the lubricant drooped by gravity can be guided to the intermediate member.

  In the present invention, the drive gear (14) may include a worm shaft (14), and the driven gear (15) may include a worm wheel (15). In this case, the reduction ratio of the transmission mechanism can be increased, and sufficient steering assistance can be performed even with a relatively small electric motor.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing a schematic configuration of an electric power steering apparatus according to an embodiment of the present invention. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is an enlarged view of a main part of FIG.
Referring to FIG. 1, in the electric power steering apparatus (hereinafter simply referred to as a steering apparatus), a first steering shaft 2 as an input shaft connected to a steering member 1 such as a steering wheel, a rack and pinion mechanism, and the like. A second steering shaft 3 as an output shaft connected to a steering mechanism 100 (not shown) is connected via a torsion bar 4 so as to be relatively rotatable. The first and second steering shafts 2 and 3 are arranged to be inclined with respect to the vertical direction V, and are directed to the lower side of the vertical direction V toward the front side of the vehicle. In the following, the axial direction of the first and second steering shafts 2 and 3 is simply referred to as the axial direction S.

  The torsion bar 4 passes through the first and second steering shafts 2 and 3. An upper end 4a of the torsion bar 4 is connected to the first steering shaft 2 by a connecting pin 5 so as to be integrally rotatable, and a lower end 4b of the torsion bar 4 is connected to the second steering shaft 3 by a connecting pin 6 so as to be integrally rotatable. Has been. The lower end of the second steering shaft 3 is connected to the steering mechanism 100 via an intermediate shaft (not shown).

The first and second steering shafts 2 and 3 are supported by the housing 7. The housing 7 is made of, for example, an aluminum alloy and is attached to a vehicle body (not shown). The housing 7 includes a sensor housing 8 and a gear housing 9 that are fitted together.
The sensor housing 8 has a cylindrical shape and houses the torque sensor 10 and the first steering shaft 2. The gear housing 9 has a cylindrical shape, and an annular edge portion 9 a at the upper end thereof is fitted into an annular step portion 8 a at the outer periphery of the lower end of the sensor housing 8. The gear housing 9 houses a worm gear mechanism 11 as a transmission mechanism and the second steering shaft 3.

  Referring to FIGS. 1 and 2, worm gear mechanism 11 is for transmitting the power (steering assisting force) of steering assisting electric motor 12 to steering mechanism 100. The worm gear mechanism 11 meshes with the worm shaft 14 as a drive gear connected to the output shaft 12a of the electric motor 12 via a joint 13 such as a spline joint so as to transmit power, and is engaged with the second worm shaft 14. A worm wheel 15 is provided as a driven gear that can rotate integrally with the intermediate portion of the steering shaft 3 and is restricted from moving in the axial direction. The housing 12b of the electric motor 12 is fixed to the flange 9b of the gear housing 9 using bolts (not shown).

  The worm wheel 15 includes an annular metal core 16 coupled to the second steering shaft 3 and a tooth forming portion that surrounds the metal core 16 and is held by the metal core 16 and has a plurality of teeth formed on the outer periphery. 17. The metal core 16 is a metal member, and the tooth forming portion 17 is a synthetic resin member. The cored bar 16 is inserted into the mold when the resin for forming the tooth forming part 17 is formed, for example, and the cored bar 16 and the tooth forming part 17 are integrally formed.

The cored bar 16 is formed in an annular shape and is thinner than the tooth forming part 17 in the axial direction S. The inner peripheral surface of the core metal 16 is press-fitted and fixed to the outer peripheral surface of the second steering shaft 3. A gap A between the outer periphery of the tooth forming portion 17 and the annular portion 9c of the gear housing 9 facing the tooth forming portion 17 is made as narrow as possible so that the amount of the lubricant G filled can be reduced. Has been.
The meshing region B of the worm shaft 14 and the worm wheel 15 is disposed in the lower part of the worm wheel 15 in the vertical direction V. Appropriate backlash is provided for the meshing between the worm shaft 14 and the worm wheel 15, and the meshing of both is smooth.

In the gear housing 9, the meshing region B is filled with a lubricant G. In the present embodiment, in addition to the meshing region B, the lubricant G is filled in substantially the entire circumference of the portion 18 a in the tooth forming portion 17 of the one side surface 18 of the worm wheel 15. The lubricant G may be filled in the entire gear housing 9.
Examples of the lubricant G include grease or lubricating oil containing buffer fine particles. The buffer material fine particles are made of rubber or resin, and the average particle diameter is 50 μm to 300 μm. The consistency of the grease with the buffer material fine particles added is, for example, NLGI No. 2-No. 000. The viscosity of the lubricating oil with the buffer material fine particles added is 5 to 200 mm ² / s (40 ° C.).

Referring to FIG. 1, the second steering shaft 3 is rotatably supported by first and second bearings 19 and 20 that are disposed with the worm wheel 15 sandwiched in the axial direction S. The first and second bearings 19 and 20 are, for example, rolling bearings.
The outer ring 19 a of the first bearing 19 is fitted and held in a bearing holding hole 21 provided in the cylindrical protrusion 8 b at the lower end of the sensor housing 8. The upper end surface of the outer ring 19 a of the first bearing 19 is in contact with the annular step portion 22, and movement in the axial direction relative to the sensor housing 8 is restricted. On the other hand, the inner ring 19b of the first bearing 19 is press-fitted and fixed to the second steering shaft 3 by an interference fit. The lower end surface of the inner ring 19 b faces the upper end surface of the core 16 of the worm wheel 15.

  The outer ring 20 a of the second bearing 20 is fitted and held in the bearing holding hole 23 at the lower end of the gear housing 9. The lower end surface of the outer ring 20 a of the second bearing 20 is in contact with the annular step portion 24, and movement in the axially downward direction with respect to the gear housing 9 is restricted. The inner ring 20b of the second bearing 20 is attached to the second steering shaft 3 such that the inner ring 20b can rotate integrally and the relative movement in the axial direction is restricted. The inner ring 20 b is sandwiched between a step portion 25 of the second steering shaft 3 and a nut 26 that is fastened to a screw portion of the second steering shaft 3.

The aforementioned connecting pin 5 connects the third steering shaft 27 disposed coaxially with the first steering shaft 2 so as to be integrally rotatable with the first steering shaft 2. The third steering shaft 27 passes through a tube 28 as a steering column fitted to the sensor housing 8.
The upper portion of the first steering shaft 2 is rotatably supported by the sensor housing 8 via a third bearing 29 made of, for example, a needle roller bearing. The reduced diameter portion 30 at the lower part of the first steering shaft 2 and the hole 31 at the upper part of the second steering shaft 3 restrict the relative rotation of the first and second steering shafts 2 and 3 within a predetermined range. And a predetermined play in the rotational direction.

Referring to FIG. 2, worm shaft 14 is rotatably supported by fourth and fifth bearings 34 and 35 held by gear housing 9. The fourth and fifth bearings 34 and 35 are, for example, rolling bearings.
Inner rings 34 b and 35 b of the fourth and fifth bearings 34 and 35 are fitted in corresponding constricted portions of the worm shaft 14. Further, the outer rings 34 a and 35 a of the fourth and fifth bearings 34 and 35 are held in corresponding bearing holding holes 40 and 41 of the gear housing 9, respectively.

Further, the outer ring 34 a of the fourth bearing 34 that supports the one end portion 14 a of the worm shaft 14 is positioned in contact with the step portion 42 of the gear housing 9. On the other hand, the inner ring 34b of the fourth bearing 34 abuts on the positioning step 43 of the one end portion 14a of the worm shaft 14, thereby restricting the movement of the worm shaft 14 toward the other end portion 14b (joint side end portion). Has been.
The inner ring 35b of the fifth bearing 35 that supports the vicinity of the other end portion 14b of the worm shaft 14 abuts on the positioning step portion 44 of the worm shaft 14 toward the one end portion 14a side of the worm shaft 14. Movement is regulated.

  Further, the outer ring 35a of the fifth bearing 35 is urged toward the fourth bearing 34 by a preload adjusting screw member 45. The screw member 45 is screwed into a screw hole 46 formed in the gear housing 9 to apply a preload to the fourth and fifth bearings 34 and 35 and to position the worm shaft 14 in the axial direction. A lock nut 47 is engaged with the screw member 45 to fix the screw member 45 after the preload adjustment.

Referring to FIG. 1, a lower end surface 48 as an opposing surface of the sensor housing 8 is formed on an annular flat surface orthogonal to the axial direction S and surrounds the first bearing 19. The side surface 18 is opposed to the substantially entire surface of the portion 18 a in the tooth forming portion 17 in the axial direction S.
A feature of the present embodiment is that an intermediate member 49 is provided between one side surface 18 of the worm wheel 15 and the lower end surface 48 of the sensor housing 8, and the intermediate member 49 serves as an electromagnet as a distance adjusting member. This is in that it can be driven by 50.

Referring to FIG. 3, intermediate member 49 is interposed between one side surface 18 of worm wheel 15 and lower end surface 48 of sensor housing 8, and can rotate integrally with worm wheel 15 (interlocking rotation is possible). ing. That is, the intermediate member 49 rotates relative to both the sensor housing 8 and the gear housing 9.
The intermediate member 49 is configured by an annular leaf spring and has elasticity. Examples of the material of the intermediate member 49 include magnetic materials such as metals. The thickness of the intermediate member 49 is, for example, as thin as less than 1 mm. The cross-sectional shape of the intermediate member 49 is formed in a shape that follows the cross-sectional shape of the one side surface 18 of the worm wheel 15.

The intermediate member 49 includes an inner diameter part 51, an outer diameter part 52, and an intermediate part 53 positioned between the inner diameter part 51 and the outer diameter part 52.
The inner diameter portion 51 is sandwiched between a portion 18 b of the one side 18 of the worm wheel 15 on the core metal 16 and a lower end surface 54 of the inner ring 19 b of the first bearing 19, so that the inner diameter portion 51 can rotate integrally with the worm wheel 15. And positioned in the axial direction S. That is, the inner diameter portion 51 is fixed to the worm wheel 15.

The intermediate portion 53 is disposed in a gap between the one side surface 18 of the worm wheel 15 and the first bearing 19. The intermediate portion 53 is configured not to contact both the worm wheel 15 and the first bearing 19.
The outer diameter portion 52 is disposed radially outward with respect to the first bearing 19, and a portion 18 a in the tooth forming portion 17 of one side surface 18 of the worm wheel 15 and a lower end surface 48 of the sensor housing 8. Is intervening between. The outer diameter portion 52 extends outward in the radial direction so as not to contact the worm shaft 14. A lubricant G is interposed between the outer diameter portion 52 and the lower end surface 48 of the sensor housing 8.

The electromagnet 50 is for adjusting the distance C between the intermediate member 49 and the lower end surface 48 of the sensor housing 8, and can attract the intermediate member 49 magnetically. The electromagnet 50 is embedded in the lower end portion 8 d of the sensor housing 8 and is opposed to the outer diameter portion 52 of the intermediate member 49 in the axial direction S.
The electromagnet 50 is disposed at least in the lower end portion of the gear housing 9 in the vertical direction V, and faces the region of the outer diameter portion 52 in the vertical direction V. In the present embodiment, a plurality of electromagnets 50 are provided at intervals in the circumferential direction of the intermediate member 49 so that the magnetic force of the electromagnet 50 is applied over the entire circumferential direction of the outer diameter portion 52 of the intermediate member 49. It has become. Only one electromagnet 50 may be provided at the lower end in the vertical direction V.

  With reference to FIG. 1, the torque sensor 10 also functions as a traveling state detection means for detecting the traveling state of the vehicle. Specifically, a reverse input enters the second steering shaft 3 from a steered wheel (not shown) via the steering mechanism 100, and the second steering shaft 3 is reciprocated minutely due to backlash of the worm gear mechanism 11. When a motion (meshing vibration) is generated, this reciprocating motion is detected by the torque sensor 10. The output signal of the torque sensor 10 is given to the control unit 55.

Further, the steering device is provided with a temperature sensor 56, and an output signal of the temperature sensor 56 is given to the control unit 55. The control unit 55 includes a CPU, a RAM, and a ROM, and controls on / off of the electromagnet 50 based on the output signal of the torque sensor 10 and the output signal of the temperature sensor 56.
In the steering apparatus having the above schematic configuration, for example, the temperature is low and the temperature detected by the temperature sensor 56 is equal to or lower than a predetermined temperature, or the vehicle is traveling on a flat road and is detected by the torque sensor 10. When the frequency of the second steering shaft 3 is equal to or lower than a predetermined value (for example, about 20 Hz), the electromagnet 50 is not turned on. As a result, as shown in FIG. 3, the distance C between the lower end surface 48 of the sensor housing 8 and the outer diameter portion 52 of the intermediate member 49 is maintained relatively wide. Since the gap C is wide, the viscous resistance applied to the worm wheel 15 from the lubricant G between the lower end surface 48 and the outer diameter portion 52 of the intermediate member 49 via the intermediate member 49 is relatively small.

  On the other hand, referring to FIG. 1, for example, when traveling on a rough road and the frequency of the second steering shaft 3 detected by the torque sensor 10 is greater than a predetermined value, the electromagnet 50 is turned on. The Thereby, as shown in FIG. 4, the entire circumference of the outer diameter portion 52 of the intermediate member 49 is magnetically attracted by the electromagnet 50, and between the lower end surface 48 of the sensor housing 8 and the outer diameter portion 52 of the intermediate member 49. The interval C is in a relatively narrow state. Since the interval C is narrow, the viscous resistance applied to the worm wheel 15 from the lubricant G between the lower end surface 48 and the outer diameter portion 52 of the intermediate member 49 via the intermediate member 49 is relatively large.

As described above, according to the present embodiment, the following operational effects can be achieved. That is, the distance C between the intermediate member 49 and the lower end surface 48 of the sensor housing 8 can be adjusted by the electromagnet 50. Thereby, the above-mentioned interval C where the lubricant G exists can be adjusted, and the influence of the viscosity of the lubricant G on the worm wheel 15 can be adjusted.
That is, when the distance C is relatively narrow, the viscous resistance due to the shearing of the lubricant G between the intermediate member 49 and the lower end surface 48 of the sensor housing 8 is reliably transmitted to the worm wheel 15 via the intermediate member 49. Can be granted. Thereby, the impact when the worm wheel 15 contacts the worm shaft 14 due to the reverse input from the steered wheel or the like when traveling on a rough road can be reduced, and the rattle noise can be reduced.

  Further, by making the interval C relatively wide, the viscous resistance that the lubricant G between the intermediate member 49 and the lower end surface 48 of the sensor housing 8 gives to the intermediate member 49 (worm wheel 15) is reduced. can do. Thereby, it is possible to prevent unnecessary resistance from acting on the worm wheel 15 that rotates integrally with the intermediate member 49. As a result, the worm wheel 15 can be smoothly rotated at low temperatures when the viscosity of the lubricant G is high, or when traveling on a flat road, thereby preventing an increase in driving loss and preventing deterioration in steering feeling.

Further, the intermediate member 49 can be realized with a simple configuration using a leaf spring.
Further, the intermediate member 49 is made of a magnetic material, and the outer diameter portion 52 of the intermediate member 49 is attracted by the magnetic attractive force of the electromagnet 50. As described above, the distance C between the intermediate member 49 and the lower end surface 48 of the sensor housing 8 can be easily adjusted with a simple configuration in which the outer diameter portion 52 of the intermediate member 49 is magnetically attracted by the electromagnet 50. .

Further, by causing the outer diameter portion 52 of the intermediate member 49 to face the one side surface 18a of the tooth forming portion 17 of the worm wheel 15, the lubricant G is guided to the tooth forming portion 17 and further to the meshing region B. Can do. As a result, the meshing region B can be more reliably lubricated.
Further, the intermediate member 49 is opposed to a lower region in the vertical direction V of the one side surface 18 a of the tooth forming portion 17 of the worm wheel 15. As a result, the lubricant G hanging down due to gravity can be guided to the intermediate member 49.

Further, by using the worm gear mechanism 11, the reduction ratio can be increased, and sufficient steering assistance can be performed even with a relatively small electric motor 12.
In the present embodiment, an electric motor or the like may be used as the interval adjusting member, and the interval C may be adjusted by moving the outer diameter portion 52 of the intermediate member 49 in the axial direction S by the driving force of the electric motor. Further, as the running state detecting means, an imaging means such as a CCD camera may be used to detect the running state based on the obtained image.

  Further, the entire intermediate member 49 may be movable in the axial direction S with respect to the housing 7. Further, a transmission mechanism other than the worm gear mechanism 11 may be used. A parallel shaft gear mechanism can be exemplified as such a transmission mechanism. The parallel shaft gear mechanism may be configured using a spur gear, or may be formed using a helical gear. Moreover, you may form a transmission mechanism using a hypoid gear. Further, a cross shaft gear mechanism including a bevel gear may be used.

FIG. 5 is a sectional view showing a schematic configuration of a main part of another embodiment of the present invention. In the following, points different from the embodiment shown in FIG. 1 will be mainly described, and the same components are denoted by the same reference numerals and description thereof will be omitted.
Referring to FIG. 5, the present embodiment is characterized in that intermediate member 49 </ b> A is rotatable relative to worm wheel 15.

The intermediate member 49A includes a cylindrical inner diameter portion 51A as a held portion and an annular outer diameter portion 52A extending radially outward from the lower end of the inner diameter portion 51A. The inner diameter portion 51 </ b> A is fixed to the outer peripheral surface of the outer ring 19 a of the first bearing 19 by, for example, press fitting. That is, the inner diameter portion 51 </ b> A is held by the sensor housing 8 via the first bearing 19.
The outer diameter portion 52 </ b> A is disposed between the one side surface 18 a of the tooth forming portion 17 and the lower end surface 48 of the sensor housing 8. The intermediate member 49 </ b> A faces at least a lower part (all in the present embodiment) region in the vertical direction V of one side surface 18 a of the tooth forming portion 17 of the worm wheel 15. The electromagnet 50 adjusts the distance CA between the one side surface 18a of the tooth forming portion 17 of the worm wheel 15 and the outer diameter portion 52A of the intermediate member 49A.

  With the above schematic configuration, for example, when traveling on a rough road and the frequency of the second steering shaft 3 detected by the torque sensor 10 is greater than a predetermined value, the electromagnet 50 is not turned on. Thereby, the space | interval CA between 52 A of outer diameter parts of 49 A of intermediate members, and the tooth | gear formation part 17 of the worm wheel 15 maintains a relatively narrow state. Due to the narrow interval CA, the viscous resistance applied to the worm wheel 15 from the lubricant G between the outer diameter portion 52A and the tooth forming portion 17 is relatively large.

  On the other hand, the temperature of the second steering shaft 3 detected by the torque sensor 10 is low and the temperature detected by the temperature sensor 56 is equal to or lower than a predetermined temperature or is traveling on a flat road. Is less than or equal to a predetermined value, the electromagnet 50 is turned on. Thereby, as shown in FIG. 6, the entire circumference of the outer diameter portion 52A of the intermediate member 49A is magnetically attracted by the electromagnet 50, and between the outer diameter portion 52A of the intermediate member 49A and the tooth forming portion 17 of the worm wheel 15. The interval CA (the maximum value thereof) is made relatively wide. Since the gap CA is wide, the viscous resistance applied to the worm wheel 15 from the lubricant G between the outer diameter portion 52A and the tooth forming portion 17 is relatively small.

  As described above, according to the present embodiment, the following operational effects can be achieved. That is, the interval CA can be adjusted by the electromagnet 50. Thereby, the interval CA where the lubricant G is present can be adjusted, and the viscosity of the lubricant G with respect to the worm wheel 15 can be adjusted. That is, by making the interval CA relatively narrow, the viscous resistance of the lubricant G between the outer diameter portion 52A of the intermediate member 49A and the worm wheel 15 can be reliably applied to the worm wheel 15. . Thereby, the impact when the worm wheel 15 contacts the worm shaft 14 due to the reverse input from the steered wheels or the like when traveling on a rough road can be reduced, and the rattle noise can be reduced.

  Further, by relatively widening the gap CA between the outer diameter portion 52A of the intermediate member 49A and the worm wheel 15, the lubricant G between the outer diameter portion 52A of the intermediate member 49A and the worm wheel 15 is provided. Can reduce the viscous resistance applied to the worm wheel 15. Thereby, it is possible to prevent unnecessary resistance force from acting on the worm wheel 15. As a result, the worm wheel 15 can be smoothly rotated when the viscosity of the lubricant G is high, such as when the vehicle is running on a flat road, and an increase in driving loss can be prevented and the steering feeling can be prevented from deteriorating.

In the present embodiment, the intermediate member 49 </ b> A may be provided only for a half circumference in the circumferential direction of the worm wheel 15. In this case, the intermediate member 49 </ b> A is provided in the lower half of the vertical direction V in the worm wheel 15. The intermediate member 49 </ b> A is opposed to a lower region in the vertical direction V on one side surface 18 a of the tooth forming portion 17 of the worm wheel 15.
The present invention is not limited to the contents of the above-described embodiments, and various modifications can be made within the scope of the claims.

It is sectional drawing which shows schematic structure of the electric power steering apparatus of one embodiment of this invention. It is sectional drawing which follows the II-II line | wire of FIG. It is an enlarged view of the principal part of FIG. It is sectional drawing for demonstrating a motion of an intermediate member. It is sectional drawing which shows schematic structure of the principal part of another embodiment of this invention. It is sectional drawing for demonstrating a motion of an intermediate member.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 7 ... Housing, 11 ... Worm gear mechanism (transmission mechanism), 12 ... Electric motor, 14 ... Worm shaft (drive gear), 15 ... Worm wheel (driven gear), 18 ... One side of worm wheel (side of driven gear) ), 18a... Part of one side of the worm wheel in the tooth forming portion (side surface of the tooth portion of the driven gear), 48... (The sensor housing) lower end surface (opposite surface of the housing), 49, 49A. 50: Electromagnet (interval adjusting member), 51A: Inner diameter (intermediate member) inner diameter portion (held portion), C, CA: Space, G: Lubricant, V: Vertical direction.

Claims (8)

A transmission mechanism including a drive gear driven by an electric motor for assisting steering and a driven gear meshing with the drive gear;
A housing that houses the transmission mechanism;
A lubricant contained in the housing;
An intermediate member interposed between the side surface of the driven gear and the opposing surface of the housing facing the side surface;
An electric power steering apparatus comprising: an interval adjusting member that adjusts an interval between any one of a side surface of the driven gear and the opposed surface of the housing and the intermediate member.   2. The electric power steering apparatus according to claim 1, wherein the intermediate member is capable of rotating in conjunction with a driven gear.   The electric power steering apparatus according to claim 1, wherein the intermediate member includes a held portion held by a housing.   4. The electric power steering apparatus according to claim 2, wherein the intermediate member includes a leaf spring.   5. The electric power steering apparatus according to claim 1, wherein the intermediate member includes a magnetic body, and the interval adjusting member includes an electromagnet capable of magnetically attracting the intermediate member.   6. The electric power steering apparatus according to claim 1, wherein the intermediate member is opposed to at least a side surface of the tooth portion of the driven gear.   7. The electric power steering apparatus according to claim 6, wherein the intermediate member opposes at least a region in the lower side in the vertical direction on the side surface of the driven gear.   7. The electric power steering apparatus according to claim 1, wherein the drive gear includes a worm shaft, and the driven gear includes a worm wheel.

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