JP2003048551A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To coaxially connect a rotation shaft of an electric motor to an assist shaft. SOLUTION: In this electric power steering device 10, a motor case 31 of the electric motor 30 and a housing 11B are fixed to each other in a positioned state by a positioning pin 100.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electric power steering system.

[0002]

2. Description of the Related Art An electric power steering system is disclosed in
As described in JP-A-9-84300, a motor case of an electric motor is fixed to a housing, an assist shaft of a steering device is supported by the housing, and an assist shaft is connected to a rotating shaft of the electric motor.

[0003]

In the electric power steering apparatus, unless the rotating shaft of the electric motor and the assist shaft are coaxially connected, the rotating shaft and the assist shaft are twisted and rotated, resulting in friction loss. Is large and the rotation performance deteriorates.

In order to reduce the number of bearings used for the rotating shaft of the electric motor and the bearing supporting member, only one end of the rotating shaft is supported by the bearing, and the other end is connected to the assist shaft through a connecting body. The twisting of the rotary shaft and the assist shaft becomes remarkable because the rotary shaft and the assist shaft are not coaxially connected to each other.

An object of the present invention is to make it possible to coaxially connect a rotary shaft of an electric motor and an assist shaft in an electric power steering system.

[0006]

According to a first aspect of the present invention, a motor case of an electric motor is fixed to a housing, an assist shaft of a steering device is supported by the housing, and an assist shaft is connected to a rotating shaft of the electric motor. In the electric power steering device as described above, the motor case and the housing of the electric motor are fixed while being positioned by the positioning pins.

According to a second aspect of the present invention, in addition to the first aspect, the positioning pin is a hollow dowel pin, and a bolt is inserted into the hollow portion of the dowel pin.

According to a third aspect of the present invention, in addition to the first or second aspect of the invention, the motor case of the electric motor is a yoke.

According to a fourth aspect of the present invention, in addition to any one of the first to third aspects, only one end portion of the rotating shaft of the electric motor is supported by the motor case via a bearing, and the other end portion is a connecting body. It is configured to be concentrically coupled to the assist shaft via.

[0010]

According to the invention of claim 1, the following effects are obtained. By fixing the motor case and housing of the electric motor in a state where they are positioned by the positioning pins, the rotation shaft of the electric motor and the assist shaft supported by the housing can be connected coaxially, and twisting of the rotation shaft and the assist shaft occurs. Can be avoided, friction loss can be reduced, and rotation performance can be improved.

Even when the electric motor is disassembled from the housing and then reassembled, the reproducibility of the coaxial connection between the rotary shaft and the assist shaft can be ensured, and the maintainability can be improved.

According to the invention of claim 2, there is the following effect. By using the positioning pin as a hollow dowel pin and inserting the fixing bolt of the motor case into the hollow part of the positioning pin, the outer diameter of the mounting portion of the motor case and the housing can be made as small as possible, and the size can be reduced. .

According to the invention of claim 3, there is the following action. By configuring the motor case of the electric motor with the yoke itself, the accuracy of assembly of the rotary shaft to the motor case can be improved, and the accuracy of coaxial connection between the rotary shaft and the assist shaft can be improved.

According to the invention of claim 4, there is the following action. In order to reduce the number of bearings used for the rotating shaft of the electric motor and the bearing support member, only one end of the rotating shaft is supported by the bearing, and the other end is connected to the assist shaft through the connecting body. By connecting the rotary shaft and the assist shaft coaxially, it is possible to avoid twisting of the rotary shaft and the assist shaft.

[0015]

1 is a partially cutaway front view of an electric power steering apparatus, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is taken along line III-III of FIG. 4 is a sectional view taken along line IV-IV in FIG. 3, FIG. 5 shows a magnet holder, (A) is a side view, (B) is a front view, and (C) is a sectional view.
6 is a cross-sectional view taken along the line C-C, FIG. 6 is a cross-sectional view showing the connecting portion between the rotating shaft and the assist shaft of FIG. 3, and FIG. 7 is VII of FIG.
FIG. 8 is a main-portion cross-sectional view showing a modified example of attachment of the motor case, taken along the line -VII.

As shown in FIGS. 1 and 2, the electric power steering apparatus 10 includes an aluminum alloy gear housing 1 fixed to a vehicle body frame or the like by a bracket (not shown).
1 (first to third gear housings 11A to 11C). Then, a pinion shaft 14 is connected to a steering shaft 12 to which a steering wheel is coupled via a torsion bar 13, a pinion 15 is provided on the pinion shaft 14, and a rack shaft 16 provided with a rack 16A meshing with the pinion 15 is provided. It is supported on the first gear housing 11A so as to be movable left and right. Steering shaft 12 and pinion shaft 14
A steering torque detection device 17 is provided between them. still,
The steering shaft 12 and the pinion shaft 14 are bearings 12A, 1
It is supported by the gear housing 11 via 4A and 14B.

As shown in FIG. 2, the steering torque detecting device 17 includes two detecting coils 17A surrounding a cylindrical core 17C engaged with the steering shaft 12 and the pinion shaft 14,
17B is provided in the third gear housing 11C. The core 17C includes a vertical groove 17E that engages with the guide pin 17D of the pinion shaft 14 and is movable only in the axial direction, and also includes a spiral groove 17G that engages with the slider pin 17F of the steering shaft 12. As a result, the steering torque applied to the steering wheel is applied to the steering shaft 12, and when the torsion bar 13 elastically deforms, a relative displacement in the rotational direction occurs between the steering shaft 12 and the pinion shaft 14. The rotation direction displacement of the pinion shaft 14 causes the core 17C to be displaced in the axial direction, and the inductance of the detection coils 17A and 17B changes due to the magnetic change around the detection coils 17A and 17B due to the displacement of the core 17C. . That is, when the core 17C moves to the steering shaft 12 side, the inductance of the detection coil 17A closer to the core 17C increases, and the inductance of the detection coil 17B closer to the core 17C decreases. Can be detected.

The rack shaft 1 in the first gear housing 11A
As shown in FIG. 2, a rack guide 19 is built in a cylinder portion 18 provided in a portion facing the pinion 15 with one end of the rack 6 interposed therebetween.
9A) is elastically urged toward the rack shaft 16 by a spring 21 back-supported by a cap 20 attached to the cylinder portion 18, presses the rack 16A of the rack shaft 16 against the pinion 15, and one end of the rack shaft 16 is pushed. Support slidably. The other end of the rack shaft 16 is supported by the bearing 22. In addition, the tie rods 23A, 23 on the left and right are connected to the middle portion of the rack shaft 16 by connecting bolts 22A, 22B.
B is connected.

As shown in FIG. 3, a motor case 31 of the electric motor 30 is fixed to the second gear housing 11B, and an assist shaft 33 is connected to a rotary shaft 32 of the electric motor 30 via a connecting body 80. Both ends of the assist shaft 33 are supported by the second gear housing 11B by bearings 91 and 92 such as ball bearings. And the assist shaft 3
A worm gear 37 is integrally provided at an intermediate portion of the No. 3, and a worm wheel 38 meshing with the worm gear 37 is fixed to an intermediate portion of the pinion shaft 14. The torque generated by the electric motor 30 is applied as a steering assist force to the rack shaft 16 through the meshing of the worm gear 37 and the worm wheel 38 and the meshing of the pinion 15 and the rack 16A, and is supplied to the steering shaft 12 by the driver. To assist the steering force.

Here, the electric motor 30 is constructed as follows. That is, the electric motor 30 is, as shown in FIG.
A cylindrical yoke 52 made of a magnetic material such as iron,
A magnet holder 53 made of a cylindrical body 53A formed of an insulating resin material that forms magnet housing compartments 53B at a plurality of positions in the inner circumference of the yoke 52 in the circumferential direction, and the magnet holder 53 is housed and positioned in the magnet housing compartment 53B. The stator 51 includes a magnet 54 to be held, and a magnet cover 55 (not shown) formed of an ultrathin plate of a non-magnetic material that is press-fitted inside the magnet 54 that is positioned and held by the magnet holder 53.

The electric motor 30 also has a rotor 56 that is inserted inside the stator 51 and fixed to the rotary shaft 32. The rotor 56 includes an armature core 57 and a commutator 58 provided on the outer circumference of the rotary shaft 32.

As shown in FIG. 4, the electric motor 30 is made of an insulating resin material that forms a brush 61 that is brought into contact with the commutator 58 of the rotor 56 and a brush holding portion 62B that holds the brush 61 in position. The brush holder 62 is composed of a short cylindrical body 62A. In addition, the electric motor 30 connects the brush 61, which is positioned and held by the brush holder 62, to the connection terminal 63 via the pigtail.
It has a power supply connector 63 that is connected to A and is integrally formed with the brush holder 62 by an insulating resin material that incorporates the connection terminal 63A.

In the electric motor 30, when electric power is supplied to the amateur core 57 from the brush 61 through the commutator 58 of the rotor 56, the magnetic force lines of the amateur core 57 cause the stator 51 to move.
By turning off the magnetic field generated by the magnet 54, the rotor 56 rotates.

However, the electric motor 30 has the following characteristic structure. (1) In the electric motor 30, the yoke 52 is a cylindrical body with one end open and the other end closed, and the yoke 52 is the motor case 31. The yoke 52 has a flange portion 52A at one end fixed to the housing 11B and a closing portion 52B at the other end.

(2) As shown in FIG. 5, the magnet holder 53 has a cylindrical body 53A having a magnet accommodating compartment 53B.
And the outer periphery of the cylindrical body 53A is spigot-joined to the yoke 52, and the concave engagement portion 62C of the brush holder 62 is formed.
The convex engaging portion 53C that engages with the cylindrical body 53A is continuously formed on the outer periphery of the cylindrical body 53A to form a convex shape at a specific position in the circumferential direction. .

(3) As shown in FIG. 4, the brush holder 62 is an injection-molded body made of an insulating resin material, and forms a short cylindrical body 62A having a brush holding portion 62B.
Brush holding portions 62B are formed at a plurality of positions in the circumferential direction of the end plate on the side opposite to the rotor along the inner circumference of A.
The spring 64 and the brush 61 are housed in and the brush 61 is pressed against the commutator 58 of the rotor 56 by the spring force of the spring 64. In the brush holder 62, one end of the outer periphery of the short cylinder 62A is spigot-coupled to the yoke 52 that constitutes the motor case 31, and the other end of the outer periphery of the short cylinder 62A is spigot-joint to the housing 11B.

(4) The brush holder 62 has a grommet 66
Is attached and assembled. The grommet 66 is a connecting portion between the housing 11B and the motor case 31 (yoke 52), and is a connector seal portion 6 that is loaded into a connector insertion portion 68 that is cut out in the flange portion 67 of the housing 11B.
6A and an O-ring 66B loaded in a ring groove portion 69 formed in the flange portion 67 of the housing 11B are integrally provided. In the brush holder 62, the connector seal portion 66A of the grommet 66 is attached to the power supply connector 63, and the O-ring 6 of the grommet 66 is attached to the short cylindrical body 62A of the brush holder 62.
6B is attached to the housing 11B and the motor case 3
1 (yoke 52) is liquid-tightly assembled to the connection portion.

(5) According to the above (2) to (4), the electric motor 30
Is fixed to the housing 11B as follows.

A grommet 66 is attached to the brush holder 62. The tubular body 53A of the magnet holder 53 is attached to the motor case 31 (yoke 52) of the electric motor 30 by the spigot joint. Then, one end side of the short cylindrical body 62A of the brush holder 62 is spigot-joined to the motor case 31 (yoke 52). At this time, the concave engaging portion 62C of the brush holder 62 is engaged with the convex engaging portion 53C of the magnet holder 53.

The convex engaging portion 53 of the magnet holder 53
The spigot joint of C to the spigot joint part 65 of the housing 11B. At the same time, the short cylinder 62A of the brush holder 62
The other end side of the spigot joint is joined to the spigot joint portion 65 of the housing 11B.

At the same time as the above, the connector seal portion 66A of the grommet 66 is the flange portion 6 of the housing 11B.
The O-ring 66B of the grommet 66 is sealed to the connector insertion portion 68 which is cut out in the housing 7,
It is loaded in the ring groove portion 69 provided in the flange portion 67 of B and is sealed between the flange portion 67 and the flange portion 52A of the yoke 52.

The motor case 31 (yoke 52) of the electric motor 30 includes the motor case 31 (yoke 52) using the magnet holder 53 and the housing 1.
The spigot connection with 1B and the spigot connection between the motor case 31 (yoke 52) using the brush holder 62 and the housing 11B center the housing 11B.
Furthermore, with the positioning pin 100 positioned in the housing 11B, the motor case 3 is fixed by the bolt 70.
1 (yoke 52) flange portion 52A to the housing 11
It is fastened and fixed to the flange portion 67 of B.

The positioning pin 100 is a knock pin, and as shown in FIG. 7, the motor case 31 (yoke 52).
52A of the flange and 6 of the housing 11B
At two positions sandwiching the diametric center of the flange 7, the flange portion 5
2A and the pin hole 102 provided in the flange portion 67, and the motor case 31 (yoke 5
2) and the housing 11B, the rotary shaft 32 and the assist shaft 33.
Are positioned so that they will be coaxially connected.

The bolt 70 is used for the motor case 31 (yoke 5
It is provided beside the positioning pin 100 at two positions sandwiching the diametric center of the flange portion 52A of 2) and the flange portion 67 of the housing 11B.

In the structure of the present invention in which the motor case 31 of the electric motor 30 and the housing 11B are positioned and fixed by the positioning pins 100, the spigot connection between the motor case 31 and the housing 11B using the magnet holder 53 and the brush holder 62 is employed in the above description. Need not necessarily be accompanied by.

Next, the support structure of the rotary shaft 32 and the assist shaft 33 of the electric motor 30 to the motor case 31 and the housing 11B will be described.

(A) Support structure for assist shaft 33 (FIG. 6) The assist shaft 33 is, as shown in FIG.
On the other hand, it is elastically supported bidirectionally in the axial direction, and it is possible to absorb an excessive thrust acting on the assist shaft 33 when the electric power steering device 10 is driven to reverse, or when a curb of a tire is ridden.

Specifically, as shown in FIG. 6, the assist shaft 33 is supported at both ends on the housing 11B by bearings 91 and 92 mounted on both sides of the worm gear 37. The bearing 91 is composed of an angular ball bearing including an inner ring 91A, an outer ring 91B and a rolling element 91C. The inner ring 91A is fitted in a gap so as to be relatively movable in the axial direction on the assist shaft 33, and the outer ring 91B is fitted to the housing 11B. The stepped portion 93 of
It is sandwiched between the stopper rings 94 attached to the housing 11B and fixed to the housing 11B. The bearing 92 is composed of an angular contact ball bearing including an inner ring 92A, an outer ring 92B, and a rolling element 92C, and the like.
The outer ring 92B is positioned in the stepped portion 95 of the housing 11B and press-fitted to be fixed to the outer ring 92B.

The assist shaft 33 has an elastic deforming member 97 interposed between an inner ring 91A of the bearing 91 and a collar-shaped inner ring engaging portion 96 provided on the side of the worm gear 37 with respect to the bearing 91, and the worm gear 37 with respect to the bearing 92. An elastic deforming member 99 is interposed between a collar-shaped inner ring locking portion 98 provided on the side of the inner ring 92 and an inner ring 92A of the bearing 92. The elastic deforming tool 97 and the elastic deforming tool 99 are elastic bodies 97 made of rubber having an annular cross section.
A, 99A and flat disk washers 97B, 97C, 99B, which are joined to both side surfaces of the elastic bodies 97A, 99A by seizure.
99C, the elastic shafts 97A and 99A are incorporated with a certain amount of pre-compression (constant shock absorbing performance) under the above-mentioned loaded state on the assist shaft 33, and as a result, the assist shaft 33 is rotated. Elastically supported in both directions.

(B) Supporting structure for the rotary shaft 32 (FIGS. 3 and 6) As shown in FIGS. 3 and 6, the rotary shaft 32 of the electric motor 30 has one end on the other end of the motor case 31 (yoke 52). It was supported by a bearing 71 provided at the center of the closed portion 52B, and the other end was made an unsupported structure.

Specifically, one end of the rotary shaft 32 is provided with a bearing 71 constituted by an angular ball bearing including an inner ring 71A, an outer ring 71B and a rolling element 71C.
Supported by 1. Then, the other end of the rotating shaft 32 and one end of the assist shaft 33 are coaxially connected inside the connecting body 80, and the fitting shaft portion (or the fitting hole portion) provided at the other end of the rotating shaft 32. 32A is spigot-joined to a fitting hole portion (or fitting shaft portion) 33A provided at one end of the assist shaft 33.

Further, the fitting shaft portion 32B on the side of the fitting shaft portion 32A of the rotating shaft 32 is inserted into the inside of the connecting body 80, and the large inner diameter portion 80A of the connecting body 80 and the outer periphery of the fitting shaft portion 32B are provided. A torque limiter 81 that slips with a predetermined torque is interposed between the fitting shaft portion 33B on the side of the fitting hole portion 33A of the assist shaft 33 so as to be slidable on the small inner diameter portion 80B of the connection body 80 ( Or serration) bound. The torque limiter 81 includes a large inner diameter portion 80A of the connection body 80 and a fitting shaft portion 32B.
The elastic ring made of spring resin or the like is press-fitted between the outer circumferences of the elastic ring and elastically supported in the radial direction, and the torque normally used in the electric power steering device 10 (torque smaller than the limit torque) is Due to the elastic force, the connecting body 80 and the fitting shaft portion 32B continue to be coupled without slipping, while the tire is riding on a curb during steering and the rack shaft 1
For the impact torque (torque above the limit torque) in which the inertia torque of the electric motor 30 when the stroke of 6 is suddenly stopped exceeds the elastic force of the elastic ring,
The rotating shaft 32 slips with respect to the connection body 80, and functions to prevent the torque of the electric motor 30 from being transmitted to the connection body 80 side.

Therefore, the rotating shaft 32 and the assist shaft 33 of the electric motor 30 are coaxially connected to each other by the spigot connection, and as a result, the end of the rotating shaft 32 on the side connected to the assist shaft 33 is the motor case 31. In contrast, the assist shaft 33 has an unsupported structure in which both ends of the assist shaft 33 are supported at two points on the housing 11B via the bearings 91 and 92 described above, and only one end of the rotary shaft 32 is supported by the bearing 71 described above in the motor case. One point is supported by 31.

In the electric motor 30, the stepped portion 80C at the boundary between the large inner diameter portion 80A and the small inner diameter portion 80B of the connection body 80 is arranged at the stepped portion 32C at the boundary between the fitting shaft portion 32A of the rotating shaft 32 and the fitting shaft portion 32B. An O-ring-shaped (or disc spring-shaped) elastic body 85 is interposed between the end surface of the connecting body 80 and the end surface of the inner ring 91A of the bearing 91 in a state of abutting in the axial direction. Elastic body 85
Can elastically support the rotary shaft 32 toward the anti-assist shaft 33 side in the axial direction, eliminate backlash in the axial direction of the rotary shaft 32, and prevent generation of tapping sound.

Therefore, according to this embodiment, there are the following effects. Motor case 31 and housing 11 of the electric motor 30
By fixing B in a state of being positioned by the positioning pin 100, the rotating shaft 32 of the electric motor 30 and the assist shaft 33 supported by the housing 11B can be coaxially connected, and the rotating shaft 32 and the assist shaft 33 are twisted together. It is possible to avoid the occurrence, prevent the rotation fluctuation, reduce the friction loss, and improve the rotation performance.

Even when the electric motor 30 is disassembled from the housing 11B and then reassembled, the reproducibility of the coaxial connection between the rotary shaft 32 and the assist shaft 33 can be ensured and the maintainability can be improved.

By constructing the motor case 31 of the electric motor 30 with the yoke 52 itself, the assembling accuracy of the rotary shaft 32 to the motor case 31 can be improved, and the coaxial connection accuracy of the rotary shaft 32 and the assist shaft 33 can be improved. .

In order to reduce the number of bearings used for the rotary shaft 32 of the electric motor 30 and the bearing support member, the rotary shaft 32
Even when only one end of the shaft is supported by the bearing and the other end is coupled to the assist shaft 33 via the connecting body 80, the rotary shaft 32 and the assist shaft 33 are coaxially connected to each other, and the rotary shaft 32 and the assist shaft 33 are connected. It is possible to avoid the twisting of 33.

The modification of FIG. 8 uses a positioning pin 110 made of a hollow dowel pin instead of the positioning pin 100 made of a knock pin. Positioning pin 1
10 is a pin hole 111 provided in the flange portion 52A and a pin hole provided in the flange portion 67 at two positions sandwiching the diametric center of the flange portion 52A of the motor case 31 (yoke 52) and the flange portion 67 of the housing 11B. It is driven into 112. At this time, the bolt 70 is the positioning pin 1
It is inserted into the hollow portion 110A of 10 and is screwed to the flange portion 67 of the housing 11B.

The positioning pin 110 is a hollow dowel pin, and the fixing bolt 70 for the motor case 31 (yoke 52) is used.
By inserting into the hollow portion 110A of the positioning pin 110, the outer diameter of the mounting portion of the motor case 31 (yoke 52) and the housing 11B can be made as small as possible, and the size can be reduced.

Although the embodiment of the present invention has been described above with reference to the drawings, the specific structure of the present invention is not limited to this embodiment, and changes in design within the scope not departing from the gist of the present invention. Even so, it is included in the present invention.

[0052]

As described above, according to the present invention, in the electric power steering device, the rotary shaft of the electric motor and the assist shaft can be connected coaxially.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view of an electric power steering device.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

5A and 5B show a magnet holder, FIG. 5A is a side view, FIG. 5B is a front view, and FIG. 5C is a cross-sectional view taken along line CC.

FIG. 6 is a cross-sectional view showing a connection portion between the rotary shaft and the assist shaft of FIG. 3 taken out and shown.

FIG. 7 is a view taken along the line VII-VII in FIG.

FIG. 8 is a cross-sectional view of essential parts showing a modified example of attachment of a motor case.

[Explanation of symbols]

10 Electric power steering system 11B Gear housing (housing) 30 electric motor 31 motor case 33 Assist axis 52 York 70 volts 80 connection 100,110 Positioning pin 110A hollow part

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Claims (4)

[Claims] 1. An electric power steering device comprising a motor case of an electric motor fixed to a housing, an assist shaft of a steering device supported by the housing, and an assist shaft connected to a rotating shaft of the electric motor. An electric power steering device, characterized in that a motor case and a housing are fixed while being positioned by a positioning pin. 2. The electric power steering device according to claim 1, wherein the positioning pin is a hollow dowel pin, and a bolt is inserted into a hollow portion of the dowel pin. 3. The electric power steering apparatus according to claim 1, wherein the motor case of the electric motor is a yoke. 4. The rotating shaft of the electric motor has only one end supported by the motor case via a bearing and the other end concentrically coupled to the assist shaft via a connector.
The electric power steering device according to any one of 1.