JP4863059B2 - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric drive type power steering device which is improved in assembling workability and can be miniaturized. <P>SOLUTION: The electric drive type power steering device 1 has an electric motor 18 comprising a brushless motor for an assistant of steering disposed coaxially with a steering shaft 4. A first connection substrate 29 for connecting coils 37, 38, 39 in each phase of the brushless motor and electric power supply lines 40, 41, 42, and a second connection substrate 30 for a neutral point connection of the brushless motor are disposed in both sides sandwiching the brushless motor in the axial direction S of the steering shaft 4. The electric wire density can be relaxed. The assembling workability can be improved. The first and second connection substrates 29, 30 can be miniaturized, and the structure also can be simplified. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an electric power steering apparatus.

The electric power steering apparatus has an electric motor for obtaining a steering assist force. This electric motor is a brushless motor, and is coaxially disposed on the steering shaft (see, for example, Patent Document 1).
A brushless motor typically has a plurality of coils and a single connection substrate for connecting the plurality of coils. This connection board is disposed at any end in the axial direction of the electric motor.
JP 2005-145436 A

By the way, in a brushless motor for assisting steering, since the number of coils tends to increase, electric wires are densely packed around the connection board, and assembly workability is lowered. Further, when the number of coils increases, the connection substrate increases, and as a result, the electric motor tends to increase in size.
Further, in Patent Document 1, since it is necessary to secure a space for the electric motor in the axial direction of the steering shaft, the steering shaft tends to be long in the axial direction. On the other hand, the space for accommodating the steering shaft in the vehicle is restricted. Accordingly, there is a demand for suppressing the increase in size of the electric motor and thus the electric power steering device.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electric power steering device that has good assembly workability and can be miniaturized.

An electric power steering apparatus according to the present invention includes a brushless motor for assisting steering arranged coaxially with a steering shaft, a connection board for connecting each phase of the brushless motor to a power supply line, and a neutral point connection for the brushless motor. The substrate is disposed on both sides of the brushless motor sandwiched in the axial direction of the steering shaft , the neutral point connection substrate has a single-layer structure, and the neutral point connection substrate is entirely formed of the brushless motor. It arrange | positions at the radial inside of a stator, It is characterized by the above-mentioned. According to the present invention, it is possible to reduce the degree of density of electric wires between each phase of the corresponding brushless motor and the power supply line around each substrate, and to improve the assembly workability. Since fewer wires are connected to each substrate, the structure of the substrate can be simplified and the size can be reduced. Therefore, it is possible to reduce the size of the electric motor, and hence the electric power steering device.

In the present invention, the whole of the neutral point connection for the substrate, than are disposed radially inward of the brushless motor stator, adjacent to the rotor for axially there radially inward of the stator It is possible to reduce the size of the electric motor and thus the electric power steering device in the axial direction by effectively utilizing the space that has been vacant conventionally.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus according to an embodiment of the present invention. Please refer to FIG.
The electric power steering apparatus 1 steers the steered wheel 2 by a steering shaft 4 that transmits a steering torque applied to a steering wheel 3 as a steering member in order to steer the steered wheel 2, and the steering torque from the steering shaft 4. For example, a steering mechanism 5 comprising a rack and pinion mechanism, and an intermediate shaft 6 provided between the steering shaft 4 and the steering mechanism 5 as a shaft coupling for transmitting rotation therebetween.

  The steering shaft 4 is inserted into the steering column 7 and is rotatably supported by the steering column 7. The steering column 7 is supported on the vehicle body 9 via a bracket 8. A steering wheel 3 is connected to one end 4a of the steering shaft 4 and is rotatably supported. An intermediate shaft 6 is connected to the other end 4 b of the steering shaft 4.

The intermediate shaft 6 includes a power transmission shaft 10, a universal joint 11 provided at one end of the intermediate shaft 6, and a universal joint 12 provided at the other end of the intermediate shaft 6.
The steering mechanism 5 supports a pinion shaft 13 as an input shaft, a rack bar 14 as a steered shaft extending in a lateral direction of the automobile (a direction orthogonal to the straight traveling direction), the pinion shaft 13 and the rack bar 14. And a rack housing 15. The pinion teeth 13a of the pinion shaft 13 and the rack teeth 14a of the rack bar 14 mesh with each other.

When the steering wheel 3 is steered, the steering torque is transmitted to the steering mechanism 5 via the steering shaft 4 and the like. Thereby, the steering wheel 2 can be steered.
The electric power steering apparatus 1 can obtain a steering assist force according to the steering torque. That is, the steering device 1 includes an electric motor 18 (hereinafter referred to as a brushless motor) including a torque sensor 16 that detects steering torque, an ECU (Electronic Control Unit) 17 as a control unit, and a brushless motor for steering assistance. It is also called).

In the present embodiment, the electric motor 18 is provided in association with the steering column 7 and is disposed coaxially with the steering shaft 4. The electric motor 18 and a part of the steering column 7 constitute a part of the motor unit 19 as will be described later.
The steering column 7 has a column tube 20 and a housing 21. A housing 21 accommodates and supports the torque sensor 16 and the electric motor 18.

  The steering shaft 4 has an input shaft 22, an output shaft 23, and a torsion bar 24. A lower portion of the steering shaft 4 in the axial direction is divided into an input shaft 22 and an output shaft 23. The input shaft 22 and the output shaft 23 are connected to each other on the same axis via a torsion bar 24. The input shaft 22 is connected to the steering wheel 3 via a connecting shaft 25 as an axial upper portion of the steering shaft 4. The output shaft 23 is connected to the pinion shaft 13 through the intermediate shaft 6 and the like. When steering torque is input to the input shaft 22, the torsion bar 24 is elastically torsionally deformed, whereby the input shaft 22 and the output shaft 23 are relatively rotated.

The torque sensor 16 is provided in association with the torsion bar 24 of the steering shaft 4 and detects torque based on the amount of relative rotational displacement between the input shaft 22 and the output shaft 23 via the torsion bar 24. The torque detection result is given to the ECU 17.
The ECU 17 controls the electric motor 18 based on the above torque detection result, a vehicle speed detection result given from a vehicle speed sensor (not shown), and the like.

  When the steering wheel 3 is operated, the steering torque is detected by the torque sensor 16, and the electric motor 18 generates a steering assist force according to the torque detection result and the vehicle speed detection result. The steering assist force is transmitted from the output shaft 23 to the pinion shaft 13, and is transmitted to the steering mechanism 5 along with the movement of the steering wheel 3, whereby the steering wheel 2 is steered and the steering is assisted.

FIG. 2 is a partial cross-sectional view of a main part of the electric power steering apparatus 1 of FIG. Please refer to FIG. 1 and FIG.
The electric motor 18 is accommodated in the housing 21. The electric motor 18 includes a cylindrical rotor 26 and a cylindrical stator 27. The stator 27 is fixed to the housing 21 and surrounds the rotor 26. The rotor 26 is fixed so as to rotate integrally with the output shaft 23 of the steering shaft 4. The output shaft 23 is rotatably supported by the housing 21 via a bearing 28.

The electric power steering apparatus 1 includes a position detection sensor (not shown) for detecting the rotation angle of the rotor 26 and first and second connection boards called bus bars for electrical connection inside the brushless motor. 29,30.
The motor unit 19 includes the above-described parts, that is, the housing 21, the output shaft 23, the rotor 26, the stator 27, the bearing 28, the position detection sensor, the first connection board 29, and the second connection. And a working substrate 30.

The housing 21 includes a cylindrical portion 31 whose both ends are open, a first end wall 32 fixed to one end portion of the cylindrical portion 31, and a second end portion fixed to the other end portion of the cylindrical portion 31. And an end wall 33.
The outer periphery of the stator 27 is fixed to the inner periphery of the cylindrical portion 31. In the axial direction S of the output shaft 23, first and second end walls 32 and 33 are disposed on both sides of the stator 27. The first and second end walls 32 and 33 have an annular shape, and are fixed to corresponding ends of the cylindrical portion 31 at the outer peripheral edge. The interior surrounded by the cylindrical portion 31 and the first and second end walls 32 and 33 is sealed, and the rotor 26 and the stator 27 are accommodated in the interior. Further, the inner circumferences of the first and second end walls 32 and 33 each have a holding portion for holding the bearing 28.

The output shaft 23 is held by the bearing 28 and passes through the first and second end walls 32 and 33. The output shaft 23 is arranged concentrically on the inner periphery of the cylindrical portion 31 and the stator 27.
The rotor 26 has a cylindrical shape and has an outer periphery and an inner periphery. The rotor 26 includes a rotor body 26a and a rotor magnet 26b attached to the outer periphery of the rotor body 26a so as to be integrally rotatable. The rotor magnet 26b is made of a permanent magnet, and is formed in an annular shape. On the outer periphery of the rotor magnet 26b, magnetic poles of N and S poles are alternately formed in a plurality of locations in the circumferential direction. The rotor body 26 a is formed separately from the output shaft 23 of the steering shaft 4. The inner periphery of the rotor body 26 a is fitted and fixed to the outer periphery of the output shaft 23.

The inner circumference of the stator 27 is arranged close to the outer circumference of the rotor 26 so as to face the radial direction R through a gap in the radial direction R.
The stator 27 includes an annular yoke 34, a plurality of stator cores 35 that are connected to the inner periphery of the yoke 34 and arranged to face the rotor 26, a plurality of insulators 36 assembled to the stator cores 35, and And a plurality of coils 37, 38, 39 wound around the insulator 36 (see FIG. 3 for the coils 38, 39).

The stator core 35 extends inward in the radial direction R from the inner periphery of the yoke 34 along the radial direction R of the yoke 34 (corresponding to the radial direction R of the stator 27). The base end of the stator core 35 is fixed to the inner periphery of the yoke 34. The plurality of stator cores 35 are evenly arranged in the circumferential direction.
Each of the coils 37, 38, 39 has an electric wire coated with insulation. Each electric wire is wound around the insulator 36, and is wound around the stator core 35 via the insulator 36. One end of the electric wire of each coil 37, 38, 39 is connected to the first connection substrate 29. The other ends of the wires of the coils 37, 38, 39 are connected to the second connection substrate 30.

  The first connection substrate 29 and the second connection substrate 30 are arranged on both sides of the brushless motor sandwiched in the axial direction S of the steering shaft 4. Inside the housing 21, two annular spaces 21a surrounding the output shaft 23 are defined on both sides in the axial direction of the brushless motor. One annular space 21 a is partitioned between the rotor 26 and the stator 27 and the end wall 32 in the axial direction S. The other annular space 21 a is partitioned between the rotor 26 and the stator 27 and the end wall 33 in the axial direction S. A second connection substrate 30 is disposed in one annular space 21a near the steering wheel 3. A first connection substrate 29 is arranged in the other annular space 21a.

The first wiring board 29 is disposed adjacent to the rotor 26 and the stator 27 of the brushless motor in the axial direction S, and is supported by the cylindrical portion 31 of the housing 21 via a bracket (not shown). .
The second wiring board 30 is disposed adjacent to the brushless motor rotor 26 in the axial direction S, and is supported by the cylindrical portion 31 of the housing 21 via a bracket 49. A part 30a of the second wiring board 30 is disposed inward in the radial direction R of the predetermined portion 27a of the stator 27 of the brushless motor.

  Specifically, the part 30 a of the second connection substrate 30 is an end portion of the second connection substrate 30 near the rotor 26 in the axial direction S. The predetermined portion 27 a of the stator 27 is a portion protruding from the end portion of the rotor 26 in the axial direction S and formed by the coils 37, 38, 39. Further, the annular space 21 a described above has regions 21 b that are adjacent to both ends of the rotor 26 in the axial direction S and are inward in the radial direction R of the predetermined portion 27 a of the stator 27. Conventionally, this area 21b is an empty space, but in this embodiment, a part 30a of the second wiring board 30 is accommodated.

  FIG. 3 is a wiring diagram of the coils 37, 38, 39 of FIG. 2 and 3, the plurality of coils 37, 38, 39 include three-phase coils 37, 38, 39 to which three-phase AC phases are applied, that is, a U-phase coil 37, and V It has a phase coil 38 and a W phase coil 39. The plurality of coils 37, 38, and 39 are arranged in the circumferential direction in the order of the U phase, the V phase, and the W phase. The coils 37, 38, and 39 each having one U phase, one V phase, and one W phase adjacent in the circumferential direction form a set. The stator 27 has a plurality of sets, specifically, four sets of the above-described three-phase coils 37, 38, and 39 as a whole. FIG. 3 shows one set.

In each set, one end of the electric wire as a terminal of one end of each coil 37, 38, 39 is connected to the first connection substrate 29. Three power supply lines 40, 41, and 42 corresponding to the above-described three phases are connected to the first wiring board 29. Each power supply line 40, 41, 42 includes a covered electric wire.
Further, the other end of the electric wire as the terminal of the other end of each coil 37, 38, 39 is connected to the second connection substrate 30. The three-phase coils 37, 38, 39 of each group are Y-connected (star-connected) to each other, and a neutral point N is formed at the connection portion.

The brushless motor may have at least one set of three-phase coils 37, 38, and 39. In the present embodiment, a description will be given in accordance with a case where four sets of three-phase coils 37, 38, and 39 are provided.
FIG. 4 is a partial cross-sectional view of the first connection substrate 29 when viewed from the direction A of FIG. Referring to FIGS. 3 and 4, the first connection substrate 29 has an annular shape. The first wiring board 29 has first, second and third conductors 43, 44, 45 and an insulator 46. The insulator 46 insulates the conductors 43, 44, 45 from each other and insulates a part of each conductor 43, 44, 45 from the outside. First, second, and third conductors 43, 44, 45 are alternately stacked in three layers along the radial direction R via insulators 46.

  Each conductor 43, 44, 45 has an arc-shaped portion and a plurality of, for example, four extending portions extending outward in the radial direction R from the arc-shaped portion. The arc-shaped portion has a long band shape in the circumferential direction, and when viewed from the axial direction S, the band extends in a curved shape. The arc-shaped portions of the conductors 43, 44, and 45 are formed with different diameters, and are concentrically spaced apart from each other in the radial direction R. The extending portion is provided in the number of the above-described sets. A terminal is disposed at the extended end of the extended portion. In FIG. 4, only the insulator 46 has a cross section. In addition, the extending portion of the conductor 44 is illustrated as overlapping the arc-shaped portions of the conductors 43 and 45, but is insulated from each other. Similarly, the extending portions of the conductor 43 are illustrated as overlapping the arc-shaped portion of the conductor 45, but are insulated from each other.

  One end of each set of U-phase coils 37 is connected to the first conductor 43, and a corresponding power supply line 40 is connected to the first conductor 43. Similarly, one end of each pair of V-phase coils 38 is connected to the second conductor 44, and a corresponding power supply line 41 is connected thereto. One end of each set of W-phase coils 39 is connected to the third conductor 45, and a corresponding power supply line 42 is connected thereto.

FIG. 5 is a partial cross-sectional view of the second connection substrate 30 when viewed from the direction A in FIG. 2. Referring to FIGS. 3 and 5, the second connection substrate 30 has an annular shape. The second wiring board 30 has a plurality of, for example, four conductors 47 and an insulator 48. The insulator 48 insulates the four conductors 47 from each other and insulates a part of each conductor 47 from the outside.
Each conductor 47 has an arc-shaped portion and a plurality of, for example, three extending portions extending outward in the radial direction R from the arc-shaped portion. The arc-shaped portion has a long band shape in the circumferential direction, and when viewed from the axial direction S, the band extends in a curved shape. The diameters of the arc-shaped portions of the conductors 47 are equal to each other. The four conductors 47 are arranged side by side in the circumferential direction and separated from each other. A terminal is disposed at the extended end of the extended portion. The other end of a set of three-phase coils 37, 38, 39 corresponding to a predetermined pair is connected to the terminal of each conductor 47.

  As described above, the electric power steering apparatus 1 of the present embodiment includes the electric motor 18 as a brushless motor for assisting steering disposed coaxially with the steering shaft 4. A first connection substrate 29 for the coils 37, 38, 39 of each phase of the brushless motor and the power supply lines 40, 41, 42, and a second connection substrate 30 as a neutral point connection substrate for the brushless motor. Are arranged on both sides of the brushless motor sandwiched in the axial direction S of the steering shaft 4.

According to the present embodiment, the density of electric wires between the coils 37, 38, 39 of each phase of the corresponding brushless motor and the power supply lines 40, 41, 42 is reduced around the connection boards 29, 30. As a result, the assembly workability can be improved with respect to the connection work between the connection boards 29 and 30 and the electric wires.
Further, since the number of wires to be connected to each connection board 29, 30 is small, the structure of each connection board 29, 30 can be simplified and the size can be reduced. For example, a single conventional wiring board requires a four-layer structure. On the other hand, the first connection board 29 which is a bus bar of the power line in the present embodiment has a three-layer structure, and the second connection board 30 which is a neutral point bus bar is a single layer. Layer structure.

  Accordingly, the layout flexibility of each of the connection substrates 29 and 30 increases as the connection substrates 29 and 30 become smaller. For example, at least one of the connection substrates 29 and 30 (in the present embodiment, the second connection substrate 29, 30). It is also possible to arrange at least a part of the connection board 30) in a narrow space. Therefore, it is possible to reduce the size of the electric motor 18 and thus the electric power steering apparatus 1.

Further, a part 30a of the second wiring board 30 is arranged inward in the radial direction R of the stator 27 of the brushless motor. In this case, the space that was previously vacant in the radial direction R of the stator 27 and adjacent to the rotor 26 in the axial direction S is effectively used, and the electric motor 18 and thus the electric power steering device 1 are moved in the axial direction S. It can be downsized.
In order to obtain this effect, it is more preferable that the entire second connection substrate 30 is disposed inward in the radial direction R of the stator 27 of the brushless motor. In short, it is only necessary that at least a part of the second wiring board 30 is disposed inside the radial direction R of the stator 27 of the brushless motor.

  Further, since the electric motor 18 is disposed coaxially with the steering shaft 4, the outer diameter of the rotor 26 tends to increase. Therefore, a space for arranging the connection boards 29 and 30 adjacent to the rotor 26 in the axial direction S and between the outer periphery of the steering shaft 4 and the inner periphery of the predetermined portion 27a of the stator 27 in the radial direction R. The area 21b of the annular space 21a can be ensured large and easily.

Moreover, the following modifications can be considered about this embodiment. In the following description, differences from the above-described embodiment will be mainly described, and the same components are denoted by the same reference numerals and description thereof is omitted.
FIG. 6 is a partial cross-sectional view of a main part of the electric power steering apparatus 1 according to the second embodiment of the present invention. In this embodiment, a second connection substrate 30 as a neutral point connection substrate is disposed adjacent to the stator 27 of the brushless motor in the axial direction S.

Further, any one of the first and second connection substrates 29 and 30 may be disposed closer to the steering wheel 3.
In the first connection substrate 29 of each of the above-described embodiments, the stacking direction of the plurality of conductors 43, 44, 45 is the radial direction R, but may be another direction, for example, the axial direction S. In addition, various design changes can be made within the scope of matters described in the claims.

It is a mimetic diagram of a schematic structure of an electric power steering device of a 1st embodiment of the present invention. It is sectional drawing of the principal part of FIG. 1, and mainly shows a motor unit. It is a wiring diagram of the coil of FIG. It is a fragmentary sectional view of the 1st board | substrate for a connection of FIG. It is a fragmentary sectional view of the 2nd board | substrate for a connection of FIG. It is sectional drawing of the principal part of the electric power steering apparatus of the 2nd Embodiment of this invention, and mainly shows a motor unit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 4 ... Steering shaft, 18 ... Electric motor (brushless motor), 27 ... Stator, 29 ... First connection board (connection board with electric power supply line), 30 ... Second connection Substrate (neutral point connection substrate), 30a ... a part of neutral point connection substrate, 37, 38, 39 ... coil (each phase of brushless motor), 40, 41, 42 ... power supply line, S ... Axial direction, R ... radial direction

Claims (1)

It has a brushless motor for steering assistance arranged coaxially with the steering shaft,
The connection board for each phase of the brushless motor and the power supply line and the neutral connection board for the brushless motor are arranged on both sides of the brushless motor in the axial direction of the steering shaft .
2. The electric power steering apparatus according to claim 1, wherein the neutral point connection board has a single-layer structure, and the neutral point connection board is disposed radially inward of the stator of the brushless motor .

Images