WO2023148997A1

WO2023148997A1 - Electric power steering device

Info

Publication number: WO2023148997A1
Application number: PCT/JP2022/027247
Authority: WO
Inventors: 祥史黒川
Original assignee: 日本精工株式会社
Priority date: 2022-02-02
Filing date: 2022-07-11
Publication date: 2023-08-10

Abstract

[Problem] To achieve a structure of an electric power steering device with which a size reduction can be attained for a housing in an assist mechanism and an increase mountability to a vehicle can be attained. [Solution] A housing 7 has a pinion accommodation section 16 that accommodates at least a tip half 73 of a pinion shaft 13 and a gear housing section 17 that accommodates each of a worm wheel 50 and a worm shaft 51, the gear housing section 17 is formed separately from the pinion accommodation section 16 and is secured to the pinion accommodation section 16, the pinion shaft 13 is supported by bearings 21, 22 so as to be free to rotate relative to the pinion accommodation section 16 without being supported so as to be free to rotate relative to the gear housing section 17, and the worm shaft 51 is supported so as to be free to rotate relative to the gear housing section 17.

Description

electric power steering device

The present disclosure relates to an electric power steering device.

2. Description of the Related Art Generally, a steering device for an automobile transmits the rotation of a steering wheel rotated by a driver to a pinion shaft on the steering side of a steering gear unit via a steering shaft, an intermediate shaft, etc., and rotates the pinion shaft on the steering side. A rudder angle is imparted to the steered wheels based on conversion into linear motion of the rack shaft of the steering gear unit, which meshes with the steering-side pinion shaft.

In the field of such steering devices, in order to reduce the force required to rotate the steering wheel, electric power steering devices are widely used that are configured to apply an assist driving force to the steering force transmission path. There are various types of electric power steering devices that differ in the position at which the assist driving force is applied.

For example, in JP-A-2016-179760, an assist driving force is applied to a rack shaft by an assist-side pinion shaft that is rotationally driven by an electric motor, which is separate from the steering-side pinion shaft that is rotationally driven by the steering wheel. , describes a dual-pinion electric power steering device.

A conventionally known dual-pinion electric power steering device includes a rack shaft and a steering-side pinion shaft that constitute a steering mechanism, an assist-side pinion shaft that constitutes an assist mechanism, a worm reduction gear, and an electric motor. It has

The rack shaft has steering-side rack teeth on the outer peripheral surface of the one-side portion in the axial direction, and assist-side rack teeth on the outer peripheral surface of the other-side portion in the axial direction. The steering-side pinion shaft has steering-side pinion teeth that mesh with the steering-side rack teeth on its outer peripheral surface, and is driven to rotate by rotating the steering wheel. The assist-side pinion shaft has, on its outer peripheral surface, assist-side pinion teeth that mesh with the assist-side rack teeth, and is rotationally driven by an electric motor. The electric motor has a motor output shaft and rotationally drives the assist-side pinion shaft via a worm speed reducer. The worm speed reducer has a worm wheel fixed to the assist-side pinion shaft so as not to rotate relative to it, and a worm shaft connected to the motor output shaft and meshing with the worm wheel. During driving of the automobile, an assist driving force is applied to the rack shaft from the electric motor via the worm speed reducer and the assist-side pinion shaft. This reduces the force required to rotate the steering wheel.

FIG. 6 shows a specific structure of an assist mechanism of a dual-pinion electric power steering device described in Japanese Patent Application Laid-Open No. 2017-214048.

The assist mechanism portion 101 of the electric power steering apparatus 100 having a conventional structure includes an assist-side pinion shaft 103 meshing with the rack shaft 102, and a worm reduction gear 104 that transmits rotation of an electric motor (not shown) to the assist-side pinion shaft 103. Prepare. The worm speed reducer 104 is connected to a worm wheel 105 externally fitted and fixed to the base end of the assist-side pinion shaft 103 so as not to rotate relatively, and is connected to the motor output shaft of the electric motor and meshed with the worm wheel 105. not with a worm shaft.

The assist-side pinion shaft 103 and the worm reduction gear 104 are housed in a housing 106 fixed to the vehicle body. The assist-side pinion shaft 103 is rotatably supported by a pair of

rolling bearings

107 and 108 with respect to the housing 106 .

The housing 106 has a pinion accommodating portion 109 having a cylindrical shape with a bottom, and a gear housing portion 110 which is configured separately from the pinion accommodating portion 109 and fixed to the open end of the pinion accommodating portion 109 . . Further, the gear housing portion 110 has a housing portion main body 111 and a cover 113 that covers the opening portion 112 of the housing portion main body 111 . A front half portion of the assist-side pinion shaft 103 is accommodated in the pinion accommodating portion 109 . On the other hand, the gear housing portion 110 accommodates the worm wheel 105 and the worm shaft that constitute the worm speed reducer 104 .

The tip of the assist-side pinion shaft 103 is rotatably supported with respect to the pinion accommodating portion 109 by a rolling bearing 107 . The rolling bearing 107 is externally fitted on the tip of the assist-side pinion shaft 103 and internally fitted on the inner peripheral surface of the pinion accommodating portion 109 . Further, an intermediate portion of the assist-side pinion shaft 103 is rotatably supported by a rolling bearing 108 with respect to a housing portion main body 111 of the gear housing portion 110 . The rolling bearing 108 is externally fitted to the intermediate portion of the assist-side pinion shaft 103 and internally fitted to a cylindrical bearing support portion 115 provided in the central portion of the bottom plate portion 114 of the accommodation portion main body 111 .

The outer ring that constitutes the rolling bearing 108 includes a side surface of an inward flange portion 116 provided on the inner peripheral surface of the bearing support portion 115 and an annular retaining member (screw ) 117 in the axial direction. In addition, the inner ring that constitutes rolling bearing 108 extends axially between stepped surface 118 provided on the outer peripheral surface of assist-side pinion shaft 103 and retaining ring 119 that is engaged with the outer peripheral surface of assist-side pinion shaft 103 . is sandwiched. For this reason, the assist-side pinion shaft 103 is fixed to the accommodating portion main body 111 by using the rolling bearing 108 so as not to be displaced relative to the housing portion main body 111 in the axial direction.

As described above, the intermediate portion of the assist-side pinion shaft 103 is rotatably supported by the rolling bearing 108 with respect to the gear housing portion 110 . Therefore, the worm wheel 105 fixed to the assist-side pinion shaft 103 is rotatably supported with respect to the gear housing portion 110 . Furthermore, the worm shaft is also rotatably supported with respect to the gear housing portion 110 by a plurality of bearings (not shown).

Therefore, in the assist mechanism portion 101 of the electric power steering apparatus 100 having the conventional structure, the worm wheel 105 and the worm shaft constituting the worm reduction gear 104 are each rotatably supported with respect to the gear housing portion 110. .

JP 2016-179760 A JP 2017-214048 A

In the assist mechanism portion 101 of the electric power steering device 100 having a conventional structure, the worm wheel 105 is inserted and arranged inside the gear housing portion 110, so that the housing portion main body 111 is provided with the assist-side pinion shaft 103 on the base end side in the axial direction ( 6) is provided. Also, in order to prevent foreign matter such as moisture and dust from entering the housing portion main body 111 through the opening 112 , the opening 112 is closed with a cover 113 .

As described above, when the cover 113 closes the opening 112 provided in the housing portion main body 111, the axial direction of the assist-side pinion shaft 103 (vertical direction in FIG. direction), the height dimension of the housing 106 in the assist mechanism portion 101 increases. Specifically, the height dimension H _X (see FIG. 6) from the meshing portion E between the rack shaft 102 and the assist-side pinion shaft 103 to the upper end portion of the housing 106 increases. Therefore, the vehicle mountability of the electric power steering apparatus 100 is likely to deteriorate.

Further, it is conceivable to interpose a sealing member in the fitting portion 120 in order to ensure the sealing performance of the fitting portion 120 between the housing portion main body 111 and the cover 113. As the total length of the fitting portion 120 is increased, the height dimension and the radial dimension of the housing 106 in the assist mechanism portion 101 are likely to be further increased.

The present disclosure has been made to solve the above problems, and an object of the present disclosure is to provide an electric power steering device that can improve mountability on a vehicle by downsizing the housing of the assist mechanism. .

An electric power steering device according to one aspect of the present disclosure includes a housing, a pinion shaft, a bearing, a worm wheel, and a worm shaft.

The pinion shaft has pinion teeth on its outer peripheral surface.

The bearing rotatably supports the pinion shaft with respect to the housing.

The worm wheel is fixed to the pinion shaft such that it cannot rotate relative to the pinion shaft or can rotate slightly relative to the pinion shaft.

The worm shaft meshes with the worm wheel.

The housing has a pinion accommodating portion that accommodates at least the front half of the pinion shaft, and a gear housing portion that accommodates the worm wheel and the worm shaft.

The gear housing portion is configured separately from the pinion housing portion, and is fixed to the pinion housing portion.

The pinion shaft is not rotatably supported by the gear housing, but is rotatably supported by the pinion accommodating portion by means of the bearing.

The worm shaft is rotatably supported by the gear housing portion.

In the electric power steering device according to one aspect of the present disclosure, the pinion shaft can be fixed to the pinion accommodating portion using the bearing so as to prevent relative displacement in the axial direction.

In the electric power steering device according to one aspect of the present disclosure, the worm wheel is fixed to the base end of the pinion shaft, and the pinion shaft uses the bearing arranged around the tip of the pinion shaft. As a result, it is possible to fix the pinion accommodating portion so that it cannot be displaced relative to the pinion accommodating portion in the axial direction. That is, the bearing for fixing the pinion shaft to the pinion accommodating portion so as to prevent relative displacement in the axial direction can be arranged around the tip portion of the pinion shaft. In this case, another bearing for supporting the pinion shaft with respect to the pinion housing can be arranged around the intermediate portion of the pinion shaft.

In the electric power steering device according to one aspect of the present disclosure, the pinion housing portion can be composed of a plurality of pinion housing portion constituent bodies combined in the axial direction of the pinion shaft.

In the electric power steering apparatus according to one aspect of the present disclosure, the plurality of pinion housing portion structures are composed of a first pinion housing portion structure that houses the front half portion of the pinion shaft and an intermediate portion that houses the pinion shaft. The pinion shaft is axially aligned with respect to the second pinion housing structure by using the bearing arranged around the intermediate portion of the pinion shaft. relative displacement can be fixed. That is, the bearing for fixing the pinion shaft to the pinion accommodating portion so as to prevent relative displacement in the axial direction can be arranged around the intermediate portion of the pinion shaft. In this case, another bearing for supporting the pinion shaft with respect to the pinion accommodating portion can be arranged around the tip portion of the pinion shaft.

In the electric power steering device according to one aspect of the present disclosure, the gear housing portion may include a wheel accommodation portion that accommodates the worm wheel and a worm accommodation portion that accommodates the worm shaft.

Further, the wheel housing portion may have a substantially cylindrical shape with a bottom, and may have an opening portion which is open on the tip end side of the pinion shaft in the axial direction and has an inner diameter larger than the outer diameter of the worm wheel. .

In this case, the wheel accommodating portion is arranged from the wheel tube portion arranged around the worm wheel and the end portion of the wheel tube portion located on the axial direction base end side of the pinion shaft. , and a closing plate portion extending radially inward.

An electric power steering device according to one aspect of the present disclosure can include a rack shaft and a steering-side pinion shaft.

The rack shaft has steering-side rack teeth on a portion of the outer peripheral surface of the one axial side portion in the circumferential direction, and has the pinion teeth on a portion of the outer peripheral surface of the other axial side portion in the circumferential direction. It has meshing assist side rack teeth.

The steering-side pinion shaft has steering-side pinion teeth on its outer peripheral surface that mesh with the steering-side rack teeth, and is rotationally driven by the operation of the steering wheel.

Thus, when the rack shaft having the steering-side rack teeth and the assist-side rack teeth, and the steering-side pinion shaft are further provided, the pinion shaft functions as the assist-side pinion shaft. Thus, the electric power steering device according to one aspect of the present disclosure is a dual-pinion electric power steering device.

On the other hand, when a rack shaft having only rack teeth meshing with the pinion teeth is used, and a configuration in which a steering shaft is connected to the pinion shaft is adopted, the electric power steering according to one aspect of the present disclosure The device is a pinion assist type (single pinion type) electric power steering device.

According to the electric power steering device according to one aspect of the present disclosure, it is possible to reduce the size of the housing in the assist mechanism section and improve mountability on the vehicle.

FIG. 1 is a schematic diagram of an electric power steering device of a first example of an embodiment of the present disclosure. FIG. 2 is a perspective view of the electric power steering apparatus of the first example, with some members omitted. FIG. 3 is a cross-sectional view corresponding to the AA line cross section of FIG. FIG. 4 is a schematic cross-sectional view corresponding to the BB line cross section of FIG. FIG. 5 is a diagram corresponding to FIG. 4 regarding the electric power steering device of the second example of the embodiment of the present disclosure. FIG. 6 is a cross-sectional view of an assist mechanism portion of an electric power steering device having a conventional structure.

[First example]
A first example of an embodiment of the present disclosure will be described with reference to FIGS. 1 to 4. FIG. In the following description, the front-rear direction means the front-rear direction of the vehicle, the up-down direction means the up-down direction of the vehicle, and the left-right direction means the width direction of the vehicle. The left-right direction coincides with the axial directions of the rack shaft 11 and the rack accommodating portion 14 . 1 and 2, and the other axial side of the rack shaft 11 and the rack accommodating portion 14 refers to the left side of the rack shaft 11 and the rack accommodating portion 14 in FIGS. pointing to the right.

[Overall Configuration of Electric Power Steering Device]
The electric power steering device 1 of this example is of a dual pinion type. That is, the electric power steering device 1 includes a rack shaft 11 and two pinion shafts, namely, a steering-side pinion shaft 10 and an assist-side pinion shaft 13 . , and an assist driving force is input to the rack shaft 11 from the pinion shaft 13 on the assist side. In this example, the assist-side pinion shaft 13 corresponds to a pinion shaft to which the electric power steering device according to one aspect of the present disclosure is applied.

As shown in FIG. 1, the electric power steering apparatus 1 includes a steering wheel 2, a steering shaft 3, a steering column 4, a pair of

universal joints

5a and 5b, an intermediate shaft 6, and a housing 7. , a steering mechanism unit 8 and an assist mechanism unit 9 .

The steering shaft 3 is rotatably supported inside a steering column 4 supported by the vehicle body. A steering wheel 2 that is steered by the driver is attached to the rear end of the steering shaft 3 . A front end of the steering shaft 3 is connected to a steering-side pinion shaft 10 forming a steering mechanism 8 via a universal joint 5a, an intermediate shaft 6 and another universal joint 5b. Therefore, the rotational motion of the steering wheel 2 is transmitted to the steering-side pinion shaft 10 . The rotational motion of the steering-side pinion shaft 10 is converted into axial linear motion of the rack shaft 11 that constitutes the steering mechanism portion 8 . Thereby, a steering angle is given to the left and right steered wheels 12 . Further, the electric power steering apparatus 1 applies the assist driving force of the electric motor 47 constituting the assist mechanism 9 to the rack shaft 11 via the assist-side pinion shaft 13, and the driver rotates the steering wheel 2. reduce the steering force required to

<housing>
The housing 7 is a casting made by die-casting a light alloy such as an aluminum-based alloy, and is fixed to the vehicle body.

The housing 7 includes a rack accommodating portion 14, a steering-side pinion accommodating portion 15, an assist-side pinion accommodating portion 16, a gear housing portion 17, a steering-side guide accommodating portion 18, an assist-side guide accommodating portion 19, and a plurality of Mounting

portions

20a and 20b are provided. In this example, the assist-side pinion housing portion 16 corresponds to the pinion housing portion to which the electric power steering device according to one aspect of the present disclosure is applied.

Except for the gear housing portion 17, the housing 7 of this example includes a rack accommodating portion 14, a steering-side pinion accommodating portion 15, an assist-side pinion accommodating portion 16, a steering-side guide accommodating portion 18, an assist-side guide accommodating portion 19, and a mounting part. The

parts

20a and 20b are constructed integrally. The gear housing portion 17 is fixed to the assist-side pinion housing portion 16 .

In this example, the structures of the assist-side pinion accommodating portion 16 and the gear housing portion 17 are devised in order to reduce the size of the housing 7 in the assist mechanism portion 9 . Specifically, the gear housing portion 17 does not have the function of rotatably supporting the assist-side pinion shaft 13, and only the assist-side pinion accommodating portion 16 has the function. As a result, the cover is omitted from the gear housing portion 17, and the size of the housing 7 in the assist mechanism portion 9 is reduced.

Specifically, in this example, the housing 7 includes an assist-side pinion accommodating portion 16 that accommodates at least the front half portion 73 of the assist-side pinion shaft 13, and a gear housing portion that accommodates the worm wheel 50 and the worm shaft 51, respectively. 17, the gear housing portion 17 is configured separately from the assist-side pinion housing portion 16 and fixed to the assist-side pinion housing portion 16, and the assist-side pinion shaft 13 is connected to the gear housing The worm shaft 51 is rotatably supported with respect to the gear housing portion 17 without being rotatably supported with respect to the portion 17, but is rotatably supported with respect to the assist side pinion accommodating portion 16 by rolling

bearings

21 and 22. Supported.

The structure of each part constituting the housing 7 will be described below.

《Rack storage part》
The rack accommodating portion 14 is a cylindrical member extending in the left-right direction. The rack accommodating portion 14 is open at both ends in the axial direction. An axial intermediate portion of the rack shaft 11 is accommodated inside the rack accommodating portion 14 . The rack accommodating portion 14 is arranged substantially horizontally.

《Steering-side pinion housing》
The steering-side pinion accommodating portion 15 is a portion that accommodates the front half portion of the steering-side pinion shaft 10 , and is arranged at a portion of the rack accommodating portion 14 on one axial side in the circumferential direction. Specifically, the steering-side pinion housing portion 15 is disposed on the front side portion (the front side portion in FIG. 2) of the rack housing portion 14 on one side in the axial direction. The steering-side pinion housing portion 15 is arranged with its central axis directed in the vertical direction, and has a bottomed cylindrical shape with only an upper end portion being open. The steering-side pinion housing portion 15 is arranged in a twisted positional relationship with respect to the rack housing portion 14 . In other words, the central axis of the steering-side pinion accommodating portion 15 and the central axis of the rack accommodating portion 14 are in a twisted positional relationship. In this example, the central axis of the steering-side pinion housing portion 15 is the center axis of the rack housing portion 14 when viewed from the front-rear direction, which is the direction orthogonal to the central axis of the steering-side pinion housing portion 15 and the central axis of the rack housing portion 14 . It is not arranged in a direction orthogonal to the central axis, but is inclined with respect to the orthogonal direction. The internal space of the steering-side pinion housing portion 15 communicates with the internal space of the rack housing portion 14 .

《Assist side pinion housing》
The assist-side pinion accommodating portion 16 is a portion that accommodates the front half portion 73 of the assist-side pinion shaft 13 , and is arranged in a portion of the rack accommodating portion 14 on the other side in the axial direction in the circumferential direction. Specifically, the assist-side pinion housing portion 16 is arranged on the front side portion (the front side portion in FIG. 2) of the rack housing portion 14 on the other side in the axial direction. The assist-side pinion accommodating portion 16 is arranged with its central axis directed in the vertical direction. Note that the central axis of the assist-side pinion accommodating portion 16 and the central axis of the assist-side pinion shaft 13 match. Therefore, the axial direction of the assist-side pinion accommodating portion 16 and the axial direction of the assist-side pinion shaft 13 are vertical directions, respectively. In this example, the axial base end side of the assist-side pinion shaft 13 corresponds to the upper side, and the axial leading end side of the assist-side pinion shaft 13 corresponds to the lower side.

Inside the assist-side pinion accommodating portion 16, the assist-side pinion shaft 13 is rotatably supported by a plurality of (two in the illustrated example) rolling

bearings

21 and 22.

The assist-side pinion accommodating portion 16 includes a tubular portion main body 23 having a stepped cylindrical shape with open ends on both sides in the vertical direction, and an outward flange projecting radially outward from the upper end portion of the tubular portion main body 23 . and a first fixed flange 24 having a shape. The tubular body 23 and the first fixed flange 24 are integrally formed.

The cylindrical portion main body 23 includes a small-diameter cylindrical portion 25 that constitutes the upper portion of the cylindrical portion main body 23 , a large-diameter cylindrical portion 26 that constitutes the lower portion of the cylindrical portion main body 23 , and a lower end portion of the small-diameter cylindrical portion 25 . and a connecting portion 27 that connects the upper end portion of the large-diameter cylindrical portion 26 . An intermediate portion of the assist-side pinion shaft 13 is accommodated inside the small-diameter tubular portion 25 , and a tip portion of the assist-side pinion shaft 13 is accommodated inside the large-diameter tubular portion 26 . A rolling bearing 21 for rotatably supporting the tip of the assist-side pinion shaft 13 is fitted in the large-diameter cylindrical portion 26 . A female screw portion is provided on the inner peripheral surface of the opening side portion of the large-diameter cylindrical portion 26 .

The first fixed flange 24 is for fixing the gear housing portion 17 to the assist-side pinion accommodating portion 16, and has through holes 28 at a plurality of places in the circumferential direction of the radially outer portion.

The first fixed flange 24 has a bearing support portion 29 having a substantially cylindrical shape in the radial middle portion of the upper surface. The bearing support portion 29 is a portion that internally fits and supports a rolling bearing 22 for rotatably supporting the intermediate portion of the assist-side pinion shaft 13 , and is arranged coaxially with the tubular portion main body 23 .

In this example, the bearing support portion provided in the gear housing portion in the conventionally structured electric power steering device is provided in the assist-side pinion housing portion 16 . Therefore, the assist-side pinion accommodating portion 16 of the present example rotatably supports the tip portion and the intermediate portion of the assist-side pinion shaft 13 .

The lower opening of the assist-side pinion accommodating portion 16 is closed by a bottomed cylindrical cap 30 screwed onto the inner peripheral surface of the large-diameter cylindrical portion 26 . On the other hand, the upper opening of the assist-side pinion accommodating portion 16 opens into the internal space of the gear housing portion 17 . The internal space of the assist-side pinion housing portion 16 communicates with the internal spaces of the rack housing portion 14 and the gear housing portion 17 .

The assist-side pinion accommodating portion 16 is arranged in a torsional positional relationship with respect to the rack accommodating portion 14 . In this example, the central axis of the assist-side pinion accommodating portion 16 is the center axis of the rack accommodating portion 14 when viewed from the front-rear direction, which is the direction orthogonal to the central axis of the assist-side pinion accommodating portion 16 and the central axis of the rack accommodating portion 14 . It is not arranged in a direction orthogonal to the central axis, but is inclined with respect to the orthogonal direction. Note that when implementing the electric power steering device according to one aspect of the present disclosure, the center of the assist-side pinion accommodating portion when viewed from a direction orthogonal to the central axis of the assist-side pinion accommodating portion and the central axis of the rack accommodating portion The axis can also be arranged in a direction perpendicular to the central axis of the rack housing.

《Gear housing》
The gear housing portion 17 is a portion that accommodates the worm speed reducer 46 that constitutes the assist mechanism portion 9 , is configured separately from the assist-side pinion accommodating portion 16 , and is fixed above the assist-side pinion accommodating portion 16 . .

The gear housing portion 17 of this example does not have the function of rotatably supporting the assist-side pinion shaft 13 . In other words, unlike the conventional structure shown in FIG. 6, the gear housing portion 17 does not have a bearing support portion for fixing the rolling bearing 22 that rotatably supports the intermediate portion of the assist-side pinion shaft 13 . Instead, the gear housing portion 17 has an opening 31 at its lower end through which the worm wheel 50 constituting the worm speed reducer 46 can be inserted.

The gear housing portion 17 includes a wheel accommodation portion 32 and a worm accommodation portion 33 .

(Wheel storage part)
The wheel accommodation portion 32 is a portion that accommodates the worm wheel 50 that constitutes the worm speed reducer 46, and has a substantially bottomed cylindrical shape. In this example, the base end portion of the assist-side pinion shaft 13 to which the worm wheel 50 is fitted and fixed, and the bearing support portion 29 are also accommodated in the wheel accommodation portion 32 .

The wheel housing portion 32 has an opening 31 that opens downward. The opening 31 has a circular shape and an inner diameter larger than the outer diameter of the worm wheel 50 . Therefore, in this example, the worm wheel 50 can be inserted through the opening 31 into the wheel accommodating portion 32 .

The wheel housing portion 32 integrally includes a wheel tubular portion 34 arranged around the worm wheel 50 and a closing plate portion 35 extending radially inward from the upper end portion of the wheel tubular portion 34. . The closing plate portion 35 has a disk shape and closes the upper end opening of the wheel cylinder portion 34 . The opening 31 is configured by a lower end opening of the wheel tube portion 34 . In the illustrated example, the inner diameter of the wheel tube portion 34 is the same as the inner diameter of the opening 31 over the entire length in the axial direction. Further, the axial dimension (vertical dimension) of the wheel tubular portion 34 is slightly larger than the sum of the thickness dimension of the worm wheel 50 and the axial dimension of the rolling bearing 22 .

The wheel housing portion 32 has a second fixed flange 36 protruding radially outward from the outer peripheral surface of the wheel tubular portion 34 . A female screw hole 37 is provided in the second fixed flange 36 .

The gear housing portion 17 is fixed to the upper side of the assist-side pinion housing portion 16 using the second fixing flange 36 provided in the wheel housing portion 32 . Specifically, in a state in which the second fixed flange 36 provided in the gear housing portion 17 is superimposed on the first fixed flange 24 provided in the assist-side pinion accommodating portion 16, the through hole of the first fixed flange 24 is The bolt 71 through which the second fixing flange 36 is inserted is screwed into the female screw hole 37 of the second fixing flange 36 . Thereby, the gear housing portion 17 is fixed to the upper side of the assist-side pinion accommodating portion 16 . With the gear housing portion 17 fixed to the assist-side pinion housing portion 16 in this manner, the opening 31 of the gear housing portion 17 is closed by the assist-side pinion housing portion 16 . Further, the bearing support portion 29 of the assist-side pinion housing portion 16 is housed in the wheel housing portion 32 , and the wheel housing portion 32 is arranged coaxially with the assist-side pinion housing portion 16 .

The wheel accommodating portion 32 of this example has an opening 31 through which the worm wheel 50 can be inserted, in a state in which the gear housing portion 17 is fixed to the assist-side pinion accommodating portion 16, rather than the upper end portion exposed to the outside. It is provided at the lower end that is closed by the side pinion accommodating portion 16 . Therefore, in this example, it is possible to omit the cover from the closing plate portion 35 of the wheel housing portion 32 that constitutes the gear housing portion 17 . In other words, there is no need to separately form the wheel tube portion 34 and the closing plate portion 35 that closes the upper end opening of the wheel tube portion 34 .

(Worm storage part)
The worm housing portion 33 is a portion that houses the worm shaft 51 that constitutes the worm speed reducer 46 , and is arranged in a portion of the wheel housing portion 32 in the circumferential direction. Specifically, the worm housing portion 33 is arranged on the front side portion of the wheel housing portion 32 . Further, the worm housing portion 33 is configured integrally with the wheel housing portion 32 . The central axis of the worm housing portion 33 is arranged at a twisted position relative to the central axis of the wheel housing portion 32 and substantially parallel to the central axis of the rack housing portion 14 .

A worm shaft 51 is rotatably supported inside the worm housing portion 33 by a plurality of (two in the illustrated example) rolling

bearings

38 and 39 .

The worm housing portion 33 has a cylindrical shape with a bottom, and has an opening that opens to one side in the axial direction of the rack housing portion 14 . Further, the worm housing portion 33 has an outward flange-shaped mounting flange portion 40 on the outer peripheral surface of the end on the opening side. The internal space of the worm housing portion 33 and the internal space of the wheel housing portion 32 communicate with each other. It should be noted that when implementing the electric power steering apparatus according to one aspect of the present disclosure, the opening of the worm housing portion and the mounting collar portion can also be provided on the other side of the rack housing portion in the axial direction.

《Steering side guide housing》
The steering-side guide accommodating portion 18 is a portion that accommodates a steering-side rack guide (not shown), and is arranged in a portion of the rack accommodating portion 14 that is diametrically opposite to the steering-side pinion accommodating portion 15 . . That is, the steering-side guide housing portion 18 is arranged in the rear portion of the rack housing portion 14 at the same axial position as the steering-side pinion housing portion 15 . The steering-side guide housing portion 18 has a cylindrical shape and extends radially about the central axis of the rack housing portion 14 . The steering-side guide accommodating portion 18 of this example extends in the front-rear direction. A rear end opening of the steering-side guide accommodating portion 18 is closed with a cap (not shown). The internal space of the steering-side guide housing portion 18 also communicates with the internal space of the rack housing portion 14 .

《Assist side guide storage part》
The assist-side guide accommodating portion 19 is a portion that accommodates an assist-side rack guide (not shown), and is arranged in a portion of the rack accommodating portion 14 that is diametrically opposite to the assist-side pinion accommodating portion 16 . . That is, the assist-side guide accommodating portion 19 is arranged in the rear portion of the rack accommodating portion 14 at the same axial position as the assist-side pinion accommodating portion 16 . The assist-side guide housing portion 19 has a cylindrical shape and extends radially about the central axis of the rack housing portion 14 . The assist-side guide accommodating portion 19 of this example extends in the front-rear direction. A rear end opening of the assist-side guide accommodating portion 19 is closed with a cap (not shown). The internal space of the assist-side guide housing portion 19 also communicates with the internal space of the rack housing portion 14 .

《Mounting part》
A plurality of mounting

portions

20a, 20b are used to fix the housing 7 to the vehicle body. The housing 7 is fixed to the vehicle body using fixing members such as bolts and studs inserted through the mounting

portions

20a and 20b.

<Steering mechanism>
The steering mechanism section 8 has a steering-side pinion shaft 10, a rack shaft 11, and a steering-side rack guide (not shown), and converts rotational motion of the steering wheel 2 into linear motion of the rack shaft 11 in the axial direction.

《Steering side pinion shaft》
The steering-side pinion shaft 10 has steering-side pinion teeth 41 on the outer peripheral surface of the front half. The steering-side pinion shaft 10 is rotatably supported inside the steering-side pinion housing portion 15 using a plurality of bearings (not shown). The steering-side pinion shaft 10 is arranged coaxially with the steering-side pinion housing portion 15 . The steering-side pinion shaft 10 is connected to the steering wheel 2 via

universal joints

5a and 5b and an intermediate shaft 6, and rotates as the steering wheel 2 is steered. The rotation of the steering-side pinion shaft 10 is converted into linear motion of the rack shaft 11 and pushes and pulls the tie rods 42 connected to both ends of the rack shaft 11 in the axial direction. As a result, steering angles are imparted to the left and right steered wheels 12 .

《Rack Axis》
The rack shaft 11 is a rod-shaped member made of metal such as carbon steel. The rack shaft 11 is arranged with its axial direction (longitudinal direction) oriented in the left-right direction. The rack shaft 11 has steering-side rack teeth 43 that mesh with the steering-side pinion teeth 41 provided on the outer peripheral surface of the steering-side pinion shaft 10 on a part of the outer peripheral surface of the rack shaft 11 in the axial direction. Assist-side rack teeth 44 meshing with assist-side pinion teeth 49 provided on the outer peripheral surface of the assist-side pinion shaft 13 are provided on a part of the outer peripheral surface of the other axial side portion in the circumferential direction. In this example, the rack shaft 11 has steering-side rack teeth 43 on the front side surface of one axial side portion, and has assist-side rack teeth 44 on the front side surface of the other axial side portion. That is, in this example, the phases of the steering-side rack teeth 43 and the assist-side rack teeth 44 in the circumferential direction are matched. However, when implementing the electric power steering apparatus according to one aspect of the present disclosure, the phases of the steering-side rack teeth and the assist-side rack teeth in the circumferential direction can be made different.

The rack shaft 11 extends axially inside the rack accommodating portion 14 in a state in which its axial direction is oriented in the left-right direction and both ends in the axial direction protrude from openings on both sides in the left-right direction of the rack accommodating portion 14 . It is supported so that it can move back and forth. Both ends of the rack shaft 11 in the axial direction are connected to tie rods 42 via spherical joints 45 .

《Steering side rack guide》
The steering-side rack guide presses the rack shaft 11 toward the steering-side pinion shaft 10 and is arranged inside the steering-side guide accommodating portion 18 . Thus, the steering-side rack guide is arranged so as to sandwich the rack shaft 11 with the steering-side pinion shaft 10 . As the steering-side rack guide, for example, a sliding rack guide including pads and elastic members can be used. The steering-side rack guide presses the rack shaft 11 toward the steering-side pinion shaft 10 to reduce backlash at the meshing portion between the steering-side pinion teeth 41 and the steering-side rack teeth 43 . This prevents the generation of abnormal noise at the meshing portion between the steering-side pinion teeth 41 and the steering-side rack teeth 43 .

<Assist Mechanism>
The assist mechanism 9 applies an assist driving force to the rack shaft 11 to reduce the steering force required for the driver to operate the steering wheel 2 . The assist mechanism portion 9 includes an assist-side pinion shaft 13 , a worm speed reducer 46 , an electric motor 47 , an assist-side rack guide (not shown), and a torque sensor 48 .

《Assist side pinion shaft》
The assist-side pinion shaft 13 has assist-side pinion teeth 49 meshing with the assist-side rack teeth 44 of the rack shaft 11 on the outer peripheral surface of the front half portion 73 .

The assist-side pinion shaft 13 is not rotatably supported by the gear housing portion 17, but is rotated with respect to the assist-side pinion accommodating portion 16 using a plurality of (two in the illustrated example) rolling

bearings

21 and 22. freely supported.

Specifically, the tip of the assist-side pinion shaft 13 is rotatably supported with respect to the assist-side pinion accommodating portion 16 by a rolling bearing 21 . The rolling bearing 21 is externally fitted to the tip of the assist-side pinion shaft 13 and internally fitted to the large-diameter tubular portion 26 forming the tubular portion main body 23 of the assist-side pinion accommodating portion 16 . An intermediate portion of the assist-side pinion shaft 13 is rotatably supported with respect to the assist-side pinion accommodating portion 16 by a rolling bearing 22 . The rolling bearing 22 is externally fitted to the intermediate portion of the assist-side pinion shaft 13 and internally fitted to a bearing support portion 29 provided on the first fixed flange 24 of the assist-side pinion accommodating portion 16 .

Furthermore, in this example, the outer ring that forms the rolling bearing 21 that supports the tip of the assist-side pinion shaft 13 is fitted in the large-diameter tubular portion 26 with a clearance fit, and the connecting portion that forms the tubular portion main body 23. 27 and a bottomed cylindrical cap (screw) 30 screwed onto the inner peripheral surface of the large-diameter cylindrical portion 26 in the axial direction. An inner ring forming the rolling bearing 21 is externally fitted to the tip of the assist-side pinion shaft 13 by an interference fit. For this reason, the assist-side pinion shaft 13 is fixed to the assist-side pinion accommodating portion 16 using the rolling bearing 21 so as not to be displaced relative to the assist-side pinion accommodating portion 16 in the axial direction (vertical direction). Appropriate preload is applied to the rolling bearing 21 by tightening with the cap 30 . Instead of the cap, a retaining ring engaged with the inner peripheral surface of the large-diameter cylindrical portion 26 may be used to prevent axial movement of the assist-side pinion shaft. As the rolling bearing 21, for example, a ball bearing capable of supporting radial load and thrust load can be used.

On the other hand, with respect to the rolling bearing 22 that supports the intermediate portion of the assist-side pinion shaft 13, the outer ring is internally fitted in the bearing support portion 29 with a clearance fit, and the inner ring is fitted in the intermediate portion of the assist-side pinion shaft 13. It is fitted on the outside with an interference fit. For this reason, the assist-side pinion shaft 13 is not fixed to the assist-side pinion accommodating portion 16 using the rolling bearing 22 so as not to be displaced relative to the assist-side pinion accommodating portion 16 in the axial direction. A radial ball bearing, for example, can be used as the rolling bearing 22 .

The assist-side pinion shaft 13 is rotatably supported by a plurality of rolling

bearings

21 and 22 and is arranged coaxially with the cylindrical portion main body 23 that constitutes the assist-side pinion accommodating portion 16 . The assist-side pinion shaft 13 is rotationally driven by an electric motor 47 via a worm reduction gear 46 .

《Worm reducer》
The worm speed reducer 46 includes a worm wheel 50 and a worm shaft 51 , reduces the rotation of the electric motor 47 , that is, increases the drive torque of the electric motor 47 and transmits it to the assist side pinion shaft 13 .

(worm wheel)
The worm wheel 50 has wheel teeth 52 on its outer peripheral surface and is housed in the wheel housing portion 32 that constitutes the gear housing portion 17 . The worm wheel 50 is externally fitted and fixed to the base end portion (upper end portion) of the assist side pinion shaft 13 so as to be relatively unrotatable. For this reason, the worm wheel 50 of this example is not rotatably supported by the gear housing portion 17 , and is attached to the assist-side pinion accommodating portion 16 via the assist-side pinion shaft 13 by the plurality of rolling

bearings

21 and 22 . are more rotatably supported. Note that when implementing the electric power steering device according to one aspect of the present disclosure, the worm wheel can also be externally fitted and fixed so as to allow slight relative rotation with respect to the assist-side pinion shaft.

(worm shaft)
The worm shaft 51 has worm teeth 53 meshing with the wheel teeth 52 at the intermediate portion of the outer peripheral surface. It is rotatably supported using

bearings

38 and 39 . Specifically, the distal end of the worm shaft 51 is rotatably supported by a rolling bearing 38 , and the proximal end of the worm shaft 51 is rotatably supported by a rolling bearing 39 . In this example, the worm shaft 51 is arranged on the front side of the worm wheel 50 . Also, the central axis of the worm shaft 51 is arranged substantially parallel to the central axis of the rack shaft 11 .

《Electric motor》
The electric motor 47 applies an assist driving force to the rack shaft 11 via the worm speed reducer 46 and the assist-side pinion shaft 13 , and has a motor body 54 and a motor output shaft 55 .

The motor main body 54 is configured by accommodating coils, cores, etc. (not shown) inside a motor housing 56 having a substantially cylindrical shape. The motor output shaft 55 is rotatably supported inside the motor housing 56 using a plurality of bearings (not shown). A distal end portion of the motor output shaft 55 axially protrudes from the motor housing 56 and is connected to a proximal end portion of the worm shaft 51 so as to transmit torque.

The electric motor 47 is fixed to the gear housing portion 17 by screwing a bolt 58 inserted through a motor-side flange 57 provided on the motor housing 56 into the mounting flange portion 40 of the worm housing portion 33 .

《Assist side rack guide》
The assist-side rack guide presses the rack shaft 11 toward the assist-side pinion shaft 13 and is arranged inside the assist-side guide accommodating portion 19 . Thus, the assist-side rack guide is arranged so as to sandwich the rack shaft 11 with the assist-side pinion shaft 13 . As the assist-side rack guide, for example, a roller-type rack guide including rollers, holders, and elastic members can be used. The assist-side rack guide presses the rack shaft 11 toward the assist-side pinion shaft 13 to reduce backlash at the meshing portion between the assist-side pinion teeth 49 and the assist-side rack teeth 44 . This prevents the generation of abnormal noise at the meshing portion between the assist-side pinion teeth 49 and the assist-side rack teeth 44 .

《Torque sensor》
The torque sensor 48 is arranged around the base end of the steering-side pinion shaft 10 and detects the magnitude and direction of torque input to the steering-side pinion shaft 10 . As a result, the torque sensor 48 outputs a signal corresponding to the torque input to the steering-side pinion shaft 10 to the electronic control unit of the electric motor 47 . As the torque sensor 48, for example, various torque sensors such as a non-contact torque sensor using the magnetostrictive effect can be used.

The assist mechanism section 9 drives and controls the electric motor 47 based on the output signal of the torque sensor 48 . As a result, the driving torque generated by the electric motor 47 is transmitted to the rack shaft 11 via the worm speed reducer 46 and the assist-side pinion shaft 13 as assist driving force. As a result, the steering force required for the driver to operate the steering wheel 2 is reduced.

According to the electric power steering device 1 of this example, the size of the housing 7 in the assist mechanism section 9 can be reduced, and the mountability on the vehicle can be improved.

That is, in this example, the assist-side pinion shaft 13 is not rotatably supported by the gear housing portion 17, but is rotatably supported by the assist-side pinion accommodating portion 16 using the plurality of rolling

bearings

21 and 22. are doing. As a result, the gear housing portion 17 does not need to be provided with a bearing support portion for supporting the rolling bearing. be able to. Therefore, the opening 112 and the cover 113 (see FIG. 6) provided in the conventional structure can be omitted from the upper end (covering plate portion 35) of the gear housing portion 17. FIG. As a result, the vertical height dimension of the housing 7 in the assist mechanism portion 9 can be shortened, and the size of the housing 7 in the assist mechanism portion 9 can be reduced.

Specifically, the height dimension H (see FIG. 4) from the meshing portion E between the assist-side rack teeth 44 and the assist-side pinion teeth 49 to the upper end of the housing 7 can be shortened. Therefore, it is possible to improve the vehicle mountability of the electric power steering apparatus 1 . In other words, when the electric power steering device 1 is arranged in the engine room, the gear housing portion 17 can be arranged so as to avoid interference with peripheral members. Mountability can be improved.

Since there is no need to provide a cover on the gear housing portion 17, there is no need to provide a sealing member for ensuring sealing of the fitting portion between the gear housing portion 17 and the cover. Therefore, the cost can be reduced, and the height dimension H and the radial dimension of the housing 7 in the assist mechanism portion 9 can be reduced. Also, the sealing performance of the gear housing portion 17 can be improved.

A cap 30 for fixing the assist-side pinion shaft 13 to the assist-side pinion accommodating portion 16 so as to prevent relative displacement in the axial direction can be arranged inside the large-diameter cylindrical portion 26 . That is, in this example, the cap 30 can be arranged below the meshing portion E between the assist-side rack teeth 44 and the assist-side pinion teeth 49 . For this reason, as in the conventional structure shown in FIG. The height dimension H from the meshing portion E to the upper end portion of the housing 7 can be shortened compared to the case where it is provided above the meshing portion with 103 .

In this example, unlike the conventional structure shown in FIG. 6, there is no need to provide the inward flange portion 116 between the worm wheel 50 and the rolling bearing 22 that rotatably supports the intermediate portion of the assist-side pinion shaft 13. . Therefore, also from this aspect, the height dimension H from the meshing portion E to the upper end portion of the housing 7 can be shortened.

[Second example]
A second example of the embodiment of the present disclosure will be described with reference to FIG.

In this example, a plurality of assist-side pinion accommodating portions 16a for rotatably supporting the assist-side pinion shaft 13 are combined in the vertical direction matching the axial direction of the assist-side pinion shaft 13 (two in the illustrated example). ) are composed of the pinion accommodating

portion constituents

59 and 60 of FIG. The structure of the gear housing portion 17 is the same as that of the gear housing portion 17 of the first example.

The assist-side pinion housing portion 16 a includes a first pinion housing portion forming body 59 housing the front half portion 73 of the assist-side pinion shaft 13 and a second pinion housing portion forming body 60 housing an intermediate portion of the assist-side pinion shaft 13 . and

The first pinion housing portion forming body 59 includes a cylindrical body 61 having a bottomed cylindrical shape and a first fixing member having an annular shape projecting radially outward from an upper end portion of the outer peripheral surface of the cylindrical body 61 . and a plate portion 62 .

A rolling bearing 21 a is fitted inside the inner peripheral surface of the cylindrical body 61 at the end (lower side).

The first fixing plate portion 62 has a stepped cross-sectional shape in which the vertical position changes stepwise upward as it goes radially outward. The first fixed plate portion 62 includes an inner diameter side plate portion 63 arranged at the radially inner end portion, an intermediate plate portion 64 arranged at the radially intermediate portion, and an outer diameter side plate portion 65 arranged at the radially outer side. a small-diameter connecting cylinder portion 66 that connects the radially outer end portion of the inner diameter side plate portion 63 and the radially inner end portion of the intermediate plate portion 64; the radially outer end portion of the intermediate plate portion 64 and the outer diameter side plate; It has a large-diameter connecting cylinder portion 67 that connects with the radially inner end portion of the portion 65 .

The second pinion housing portion structure 60 includes a bearing support portion 29a having a cylindrical shape, a second fixed plate portion 68 having an annular shape projecting radially outward from the outer peripheral surface of the bearing support portion 29a, and an annular support plate portion 69 projecting radially inward from the upper end portion of the inner peripheral surface of the bearing support portion 29a.

The bearing support portion 29a is a portion that internally fits and supports a rolling bearing 22a for rotatably supporting the intermediate portion of the assist-side pinion shaft 13, and has a female screw portion on the inner peripheral surface of the lower end portion. The second fixing plate portion 68 has substantially the same outer diameter as the first fixing plate portion 62 . The support plate portion 69 has an inner diameter through which the base end portion of the assist-side pinion shaft 13 can be inserted.

The assist-side pinion housing portion 16 a of this example is configured by connecting the first pinion housing portion forming body 59 and the second pinion housing portion forming body 60 with bolts 72 . Specifically, the lower end portion of the bearing support portion 29a forming the second pinion housing portion forming body 60 is connected to the small diameter connecting cylindrical portion of the first fixed plate portion 62 forming the first pinion housing portion forming body 59. 66 , and the radially outer portion of the second fixed plate portion 68 forming the second pinion housing portion forming body 60 is connected to the first fixing plate portion 62 forming the first pinion housing portion forming body 59 . The radially outer portion of the second fixing plate portion 68 and the outer diameter side plate portion 65 of the first fixing plate portion 62 are connected by bolts 72 while being superimposed on the outer diameter side plate portion 65 . In the illustrated example, the gear housing portion 17 is mounted above the assist-side pinion housing portion 16a using a bolt 72 for connecting the first pinion housing portion structure 59 and the second pinion housing portion structure 60. Fixed.

In the case of this example as well, the assist-side pinion shaft 13 is not rotatably supported by the gear housing portion 17, but is supported by a plurality of (two in the illustrated example) rolling bearings with respect to the assist-side pinion accommodating portion 16a. It is rotatably supported using 21a and 22a.

Specifically, the tip of the assist-side pinion shaft 13 is rotatably supported with respect to the first pinion housing portion structure 59 by a rolling bearing 21a. The rolling bearing 21 a is externally fitted on the tip of the assist-side pinion shaft 13 and internally fitted on the inner peripheral surface of the tubular body 61 at the far end thereof. Further, an intermediate portion of the assist-side pinion shaft 13 is rotatably supported with respect to the second pinion housing portion forming body 60 by a rolling bearing 22a. The rolling bearing 22 a is externally fitted to the intermediate portion of the assist-side pinion shaft 13 and internally fitted to the bearing support portion 29 a provided in the second pinion accommodating portion structure 60 .

In this example, the outer ring that forms the rolling bearing 22a that supports the intermediate portion of the assist-side pinion shaft 13 is internally fitted in the bearing support portion 29a with a clearance fit, and the support that forms the second pinion housing portion forming body 60. It is axially sandwiched between a side surface of the plate portion 69 and an annular retaining member (screw) 70 screwed onto the inner peripheral surface of the bearing support portion 29a. An inner ring forming the rolling bearing 22a is externally fitted to the middle end portion of the assist-side pinion shaft 13 by an interference fit. For this reason, the assist-side pinion shaft 13 is fixed to the second pinion housing portion forming body 60 by using the rolling bearing 22a so as not to be displaced relative to each other in the axial direction. Further, the rolling bearing 22a is applied with an appropriate preload by being tightened by the retaining member 70. As shown in FIG. As the rolling bearing 22a, for example, a ball bearing capable of supporting radial load and thrust load can be used.

On the other hand, the assist-side pinion shaft 13 is not fixed to the first pinion housing portion forming body 59 by the rolling bearing 21a so that relative displacement in the axial direction is impossible. A radial needle bearing, for example, can be used as the rolling bearing 21a.

In the case of this example as well, the assist-side pinion shaft 13 is not rotatably supported with respect to the gear housing portion 17, but is rotatably supported with respect to the assist-side pinion accommodating portion 16a by using a plurality of rolling

bearings

21a and 22a. Since it is supported, the size of the housing 7 in the assist mechanism portion 9 can be reduced, and the mountability to the vehicle can be improved.

It should be noted that the assembly method (assembly procedure) for the structure of this example is not particularly limited. For example, the gear housing portion 17, the first pinion housing portion forming body 59, and the second pinion housing portion forming body 60 can be assembled at the same time, or the first pinion housing portion forming body 59 and the second pinion housing portion forming body can be assembled together. The gear housing portion 17 may be fixed to the assist-side pinion accommodating portion 16a after forming the assist-side pinion accommodating portion 16a by connecting the component 60 first. Alternatively, the gear housing portion 17 and the first pinion housing portion forming body 59 may be connected first, and then the second pinion housing portion forming body 60 may be fixed.

Other configurations and effects of the second example are the same as those of the first example.

Although each example of the embodiment of the present disclosure has been described above, the electric power steering device according to one aspect of the present disclosure is not limited to this, and can be modified as appropriate without departing from the technical idea of the invention. . Also, the structures of the respective examples of the embodiments of the present disclosure can be appropriately combined and implemented as long as there is no contradiction.

When implementing the electric power steering device according to one aspect of the present disclosure, the structures of the pinion accommodating portion and the gear housing portion are not limited to the structures shown in the respective examples of the embodiments of the present disclosure, and may be changed as appropriate. can be done. Moreover, the bearing that rotatably supports the pinion shaft with respect to the pinion accommodating portion is not limited to a rolling bearing, and a sliding bearing can also be used. Further, the number of bearings that rotatably support the pinion shaft with respect to the pinion accommodating portion is not limited to two, and may be three or more. Furthermore, the directions of the central axes (axial directions) of the pinion shaft and the pinion accommodating portion are not limited to the structures shown in each example of the embodiments of the present disclosure, and can be changed as appropriate. Further, when implementing the electric power steering device according to one aspect of the present disclosure, the formation positions (phases) of the steering-side rack teeth and the assist-side rack teeth provided on the rack shaft are set according to the embodiments of the present disclosure. The positions are not limited to those shown in the examples, and can be changed as appropriate.

Furthermore, the electric power steering device according to one aspect of the present disclosure is not limited to the dual pinion type electric power steering device as described in each example of the embodiments of the present disclosure, and the pinion shaft connected to the steering shaft It can be applied to a pinion assist type electric power steering device configured to apply an assist driving force directly to the

REFERENCE SIGNS LIST 1 electric power steering device 2 steering wheel 3 steering shaft 4 steering column 5a, 5b universal joint 6 intermediate shaft 7 housing 8 steering mechanism portion 9 assist mechanism portion 10 steering side pinion shaft 11 rack shaft 12 steering wheel 13 assist side pinion shaft 14 rack Accommodating portion 15 Steering-side pinion accommodating portion 16, 16a Assist-side pinion accommodating portion 17 Gear housing portion 18 Steering-side guide accommodating portion 19 Assist-side guide accommodating portion 20a, 20b Mounting portion 21a Rolling bearing 22a Rolling bearing 23 Tubular portion main body 24 First Fixed flange 25 small-diameter tubular portion 26 large-diameter tubular portion 27 connecting portion 28 through hole 29, 29a bearing support portion 30 cap 31 opening portion 32 wheel housing portion 33 worm housing portion 34 wheel tubular portion 35 closing plate portion 36 second fixed flange 37 Female screw hole 38 Rolling bearing 39 Rolling bearing 40 Mounting flange 41 Steering-side pinion teeth 42 Tie rod 43 Steering-side rack teeth 44 Assist-side rack teeth 45 Spherical joint 46 Worm reduction gear 47 Electric motor 48 Torque sensor 49 Assist-side pinion teeth 50 Worm Wheel 51 Worm shaft 52 Wheel tooth 53 Worm tooth 54 Motor main body 55 Motor output shaft 56 Motor housing 57 Motor-side flange 58 Bolt 59 First pinion housing structure 60 Second pinion housing structure 61 Cylindrical body 62 First fixed plate Part 63 Inner diameter side plate portion 64 Intermediate plate portion 65 Outer diameter side plate portion 66 Small diameter connecting cylinder portion 67 Large diameter connecting cylinder portion 68 Second fixed plate portion 69 Support plate portion 70 Retaining member 71 Bolt 72 Bolt 73 Front half portion 100 Electric power Steering device 101 assist mechanism 102 rack shaft 103 assist-side pinion shaft 104 worm reduction gear 105 worm wheel 106 housing 107 rolling bearing 108 rolling bearing 109 pinion housing 110 gear housing 111 housing main body 112 opening 113 cover 114 bottom plate 115 Bearing support portion 116 Inward flange portion 117 Retaining member 118 Step surface 119 Retaining ring 120 Fitting portion

Claims

a housing;
a pinion shaft having pinion teeth on its outer peripheral surface;
a bearing that rotatably supports the pinion shaft with respect to the housing;
a worm wheel fixed to the pinion shaft;
a worm shaft meshed with the worm wheel;
with
The housing has a pinion accommodating portion that accommodates at least the front half of the pinion shaft, and a gear housing portion that accommodates the worm wheel and the worm shaft,
The gear housing portion is configured separately from the pinion housing portion and fixed to the pinion housing portion,
The pinion shaft is not rotatably supported by the gear housing but is rotatably supported by the pinion housing by the bearing,
The worm shaft is rotatably supported with respect to the gear housing,
Electric power steering device.
The electric power steering apparatus according to claim 1, wherein the pinion shaft is fixed to the pinion accommodating portion by using the bearing so as to prevent axial relative displacement.
The worm wheel is fixed to the base end of the pinion shaft,
The pinion shaft is fixed to the pinion accommodating portion using the bearing arranged around the tip portion of the pinion shaft so as to be unable to move relative to each other in the axial direction.
An electric power steering apparatus according to claim 2.
The electric power steering apparatus according to any one of claims 1 to 3, wherein the pinion housing portion is composed of a plurality of pinion housing portion constituent bodies combined in the axial direction of the pinion shaft.
The plurality of pinion housing portion constituents have a first pinion housing portion constituent that accommodates the front half portion of the pinion shaft and a second pinion housing portion constituent that accommodates an intermediate portion of the pinion shaft,
The pinion shaft is fixed to the second pinion housing structure by utilizing the bearing arranged around the intermediate portion of the pinion shaft so as to be unable to move relative to each other in the axial direction.
An electric power steering system according to claim 4 depending on claim 2.
The gear housing portion has a wheel accommodating portion that accommodates the worm wheel and a worm accommodating portion that accommodates the worm shaft,
The wheel housing portion has a substantially bottomed cylindrical shape, and has an opening opening on the tip end side in the axial direction of the pinion shaft and having an inner diameter larger than the outer diameter of the worm wheel.
An electric power steering apparatus according to any one of claims 1 to 5.
The wheel housing portion extends radially inward from a wheel tube portion disposed around the worm wheel and an end portion of the wheel tube portion located on the base end side in the axial direction of the pinion shaft. 7. The electric power steering apparatus according to claim 6, which integrally has a covering plate portion extending toward the upper portion.
An assist-side rack that has steering-side rack teeth on a circumferential part of the outer peripheral surface of the one-side portion in the axial direction and meshes with the pinion teeth on a part of the outer peripheral surface of the other-side portion in the axial direction in the circumferential direction. a rack shaft having teeth;
a steering-side pinion shaft having steering-side pinion teeth meshing with the steering-side rack teeth on an outer peripheral surface thereof, the steering-side pinion shaft being rotationally driven by the operation of the steering wheel;
comprising
An electric power steering apparatus according to any one of claims 1 to 7.