JP2004304945A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the size of a motor by reducing the length of a motor shaft. <P>SOLUTION: In the brushless motor 1, a sensor signal line 27 is wired utilizing a space 29 formed at the outside-diameter side of a Hall element 8 in a bracket 14 that has been a dead space. A sensor magnet 20 and the Hall element 8 are disposed in parallel with the radial direction, to reduce the size of the motor by making the axial length of the motor short. The sensor magnet 20 is installed at the end of a magnet holder 19 and fixed to a rotor 7 by a magnet cover 21 together with a rotor magnet 17. A coupler for the sensor signal line 27 and a coupler for a power line 31 may be integrally formed at the bracket 14. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an inner rotor type brushless DC motor, and more particularly to a brushless motor used as a drive source of an electric power steering device.
[0002]
[Prior art]
In general, a brushless motor detects a change in the magnetic pole of a magnet provided on a rotor side with a magnetic detection element such as a Hall element to detect a rotor rotation position, and based on that, appropriately switches an excitation coil on a stator side and drives the rotor to rotate. I have. FIG. 5 is a cross-sectional view showing a configuration of a conventional brushless motor. As shown in FIG. 5, the brushless motor 51 includes a motor unit 52 provided with a rotor and a sensor unit 53 provided with a magnetic detection element. These motor unit 52 and sensor unit 53 are generally arranged in series along the axial direction.
[0003]
The motor section 52 includes a rotor 54 and a stator 55. The rotor 54 includes a rotor core 57 fixed to a rotor shaft 56 and a magnet holder 58 attached to the outer periphery of the rotor core 57. A rotor magnet 59 is attached to the magnet holder 58, and the rotor magnet 59 is adhered and fixed to the outer periphery of the rotor core 57. The rotor shaft 56 is rotatably supported by bearings 61a and 61b. The stator 55 includes a stator core 63 around which the drive coil 62 is wound, and a metal yoke 64 that houses the stator core 63. The yoke 64 has a bottomed cylindrical shape, and a bracket 65 of the sensor unit 53 is fixed to an open end thereof.
[0004]
The sensor section 53 is provided with a ring-shaped sensor magnet 66 bonded and fixed to the rotor shaft 56 and a Hall element 67 arranged to face the sensor magnet 66. The magnetic poles of the sensor magnet 66 are magnetized in the same number of poles corresponding to the rotor magnet 59. The Hall element 67 sends out a signal in accordance with the change in the magnetic pole of the sensor magnet 66, and thereby the rotational position of the rotor 54 is detected.
[0005]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-354755 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-156696
[Problems to be solved by the invention]
However, in the brushless motor 51 as shown in FIG. 5, the motor unit 52 and the sensor unit 53 are arranged in series along the axial direction, and both are mounted so as to be stacked in the axial direction. For this reason, there has been a problem that the axial length of the motor becomes longer and the motor becomes larger.
[0007]
On the other hand, since the rotor magnet 59 and the sensor magnet 66 are adhered and fixed to the rotor core 57 and the rotor shaft 56, a step of adhering them is required, and there is a problem that the number of steps is increased accordingly. In addition, in order to ensure reliability, in addition to bonding, it is necessary to provide an engagement projection 68 on the rotor shaft 56 as a means for preventing the rotation of the rotor shaft, resulting in an increase in manufacturing cost.
[0008]
An object of the present invention is to reduce the motor shaft length to reduce the size of the motor. Another object of the present invention is to eliminate the adhesion of the rotor magnet and the sensor magnet and to reduce the product cost.
[0009]
[Means for Solving the Problems]
A brushless motor according to the present invention includes a stator having a stator core around which a drive coil is wound, a yoke accommodating the stator core, a rotor to which a rotor magnet is attached, and which is rotatably disposed inside the stator. A driven member that rotates with the rotor, a rotation detection member that is provided adjacent to the driven member and outputs a rotation detection signal with the rotation of the rotor, is coupled to the yoke, and the rotation detection member is housed therein. It has a bracket and a signal line connected to the rotation detecting member and wired in a space formed on the outer diameter side of the rotation detecting member in the bracket.
[0010]
In the present invention, the signal line is wired using the outer diameter side space of the rotation detecting member in the bracket which was dead space in the conventional brushless motor, so that the axial length is longer than that of the conventional motor. And the size of the motor can be reduced.
[0011]
Further, another brushless motor of the present invention includes a stator on which a drive coil is wound, and a rotor magnet rotatably provided inside the stator and having a plurality of magnetic poles formed along a circumferential direction. It has a rotor, a driven member that rotates with the rotor, and a rotation detection member that is arranged radially side by side with the driven member and that outputs a rotation detection signal as the rotor rotates.
[0012]
In the present invention, the driven member and the rotation detecting member are arranged side by side in the radial direction, so that the axial length of the motor is smaller than that of the conventional brushless motor in which they are arranged in series in the axial direction. Therefore, the size of the motor can be reduced.
[0013]
In the brushless motor, the rotor is a rotating shaft, a rotor core fixed to the rotating shaft, and the rotor magnet is attached to an outer peripheral portion thereof, and the rotor magnet is fixed to the rotating shaft adjacent to the rotor core. It has a magnet holder in which an arm portion that accommodates and regulates its circumferential movement extends along the axial direction, and a magnet cover that is mounted outside the rotor magnet and regulates the radial movement of the rotor magnet. It is good also as composition. In this case, the driven member may be attached to the magnet holder, and the driven member may be covered with the magnet cover.
[0014]
Thus, the rotor magnet accommodated in the magnet holder is fixed to the outer periphery of the rotor core by the binding force of the magnet cover without using an adhesive. Therefore, the rotor magnet can be made to have an adhesive-less structure, so that an adhesive application operation and an adhesive curing time during the manufacturing process are not required, so that the number of steps is reduced and the manufacturing cost is reduced. Further, unlike the conventional brushless motor, a projection for preventing rotation of the magnet is not required on the rotating shaft, and the cost of parts can be reduced. Also, the driven member can be fixed to the magnet holder by the binding force of the magnet cover, and the driven member can also have an adhesive-less structure.
[0015]
Further, in the brushless motor, a signal line coupler having the signal line terminal on the bracket, and a power line coupler formed separately from the signal line coupler and having a power line terminal for supplying power to the drive coil And may be integrally molded. As a result, the dead space can be reduced as compared with the conventional brushless motor, and the size of the motor can be reduced. In addition, the assemblability of the signal lines and the power supply lines is improved, the number of assembling steps is reduced, and the cost is reduced. Further, since the signal line coupler and the power supply line coupler are separated, the influence of noise emitted from the power supply line on the signal in the signal line can be reduced.
[0016]
On the other hand, another brushless motor of the present invention includes a motor unit including a stator on which a drive coil is wound, a rotor to which a rotor magnet is attached, and which is rotatably disposed inside the stator. A driven member that is disposed adjacent to the rotor in the axial direction and rotates together with the rotor, and a rotation detection member that is provided close to the driven member and outputs a rotation detection signal in accordance with the rotation of the rotor. And a overlapping portion provided at a joint between the motor unit and the sensor unit, and a part of the motor unit and a part of the sensor unit are arranged in a radial direction. .
[0017]
In the present invention, since the motor section and a part of the sensor section are arranged side by side in the radial direction to form the overlapping section, they are compared with a conventional brushless motor in which they are arranged in series in the axial direction to face each other. As a result, the dead space can be kept small, the axial length of the motor can be reduced, and the size of the motor can be reduced.
[0018]
In addition, in the brushless motor, a ring-shaped sensor magnet magnetized with the same number of poles as the rotor magnet is used as the driven member, and the rotation detection member captures a change in magnetic pole caused by rotation of the sensor magnet. A magnetic detection element that outputs a rotation detection signal may be used.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing a configuration of a brushless motor according to a first embodiment of the present invention, and FIG. 2 is an exploded perspective view of the brushless motor of FIG. The brushless motor 1 (hereinafter abbreviated as motor 1) in FIGS. 1 and 2 is used as a drive source of an electric power steering device, and when a driver operates a steering wheel, a steering assist force according to a steering angle, a vehicle traveling speed, and the like. Supply. A rotor shaft (rotating shaft) 2 of the motor 1 is connected to an input shaft of a gear box (not shown) via a joint 3. After the rotation of the motor 1 is appropriately reduced in the gear box, the rotation is transmitted to the steering column, and the steering force is assisted by the rotation force of the motor 1.
[0020]
The motor 1 also includes a motor unit 4 and a sensor unit 5, similarly to the motor 51 of FIG. The motor unit 4 includes a stator 6 and a rotor 7, and a Hall element (magnetic detection element; rotation detection member) 8 is disposed in the sensor unit 5. The rotor 7 is rotatably arranged inside the stator 6, and the motor 1 is a so-called inner rotor type brushless motor.
[0021]
The stator 6 includes a stator core 12 around which a drive coil 11 is wound, and a metal yoke 13 that houses the stator core 12. The stator core 12 is formed by laminating metal plates made of a magnetic material, and the driving coil 11 is wound around salient poles projecting from the inner peripheral side to form windings. The yoke 13 is formed in a cylindrical shape with a bottom by a magnetic material, and a bracket 14 made of aluminum die-cast (or made of synthetic resin) is attached to the open end side.
[0022]
The rotor 7 is provided with a rotor shaft 2. The rotor shaft 2 is rotatably supported by bearings 15a and 15b attached to the yoke 13 and the bracket 14, respectively. A rotor core 16 formed by laminating metal plates made of a magnetic material is fixed to the rotor shaft 2. Six segment-shaped rotor magnets 17 are attached to the outer periphery of the rotor core 16. A side plate 18 is attached to an axial end of the rotor core 16.
[0023]
Further, a magnet holder 19 made of synthetic resin is fixed to the rotor shaft 2. The magnet holder 19 is provided with a shaft mounting portion 19a fixed to the rotor shaft 2, and an arm portion 19b formed to project in the axial direction from the shaft mounting portion 19a. At the end of the shaft mounting portion 19a, a sensor magnet mounting portion 19c to which a sensor magnet (driven member) 20 is mounted is cut out. The segment-shaped rotor magnet 17 is housed between the arm portions 19b of the magnet holder 19, and the ring-shaped sensor magnet 20 is externally mounted on the sensor magnet mounting portion 19c.
[0024]
An aluminum magnet cover 21 is provided outside the rotor magnet 17. The rotor magnet 17 is covered with the magnet cover 21 in a state where the movement in the circumferential direction is restricted by the magnet holder 19, and the movement in the radial direction is restricted. The rotor magnet 17 is fixed to the outer periphery of the rotor core 16 without using an adhesive by the binding force between the magnet cover 21 and the magnet holder 19. The sensor magnet 20 attached to the magnet holder 19 is also provided with the magnet cover 21 and fixed to the magnet holder 19 by the binding force.
[0025]
Thus, the motor 1 has a structure in which the rotor magnet 17 and the sensor magnet 20 are not bonded. Therefore, an adhesive application operation and an adhesive curing time during the manufacturing process are not required, so that the number of steps is reduced and the manufacturing cost is reduced. Further, unlike the motor 51 shown in FIG. 5, a protrusion for preventing rotation of the magnet is not required on the rotor shaft 2, and the cost of parts can be reduced.
[0026]
On the sensor unit 5 side, a Hall element 8 is arranged radially outside the sensor magnet 20. The Hall element 8 is provided with a total of three U, V, and W components, one for each phase, and faces the sensor magnet 20 with a predetermined gap. The magnetic poles of the sensor magnet 20 are magnetized in the same number of poles corresponding to the rotor magnet 17. In the motor 1, the rotor magnet 17 has a six-pole configuration, and the sensor magnet 20 is also magnetized to six poles in the circumferential direction. Then, the Hall element 8 sends out a signal in accordance with a change in the magnetic pole of the sensor magnet 20, whereby the rotational position of the rotor 7 is detected.
[0027]
The Hall elements 8 are arranged at the tip of the sensor holder 22 attached to the bracket 14 in a circumferential direction. The sensor holder 22 is formed of a synthetic resin and is mounted in a sensor mounting hole 23 provided at the center of the bracket 14. A printed board 24 is mounted outside the sensor holder 22, and the sensor holder 22 and the printed board 24 are fixed to the bracket 14 by screws 25. An end cap 26 is attached to the outer end of the bracket 14 to cover components housed in the bracket 14 such as the printed circuit board 24 from the outside.
[0028]
A sensor signal line 27 for sending a detection signal output from the Hall element 8 to a control device (not shown) is connected to the printed circuit board 24. As shown in FIG. 1, the sensor signal line 27 extends from the printed circuit board 24 to the inside of the motor, and is drawn out of the motor from the side of the bracket 14 via the rubber grommet 28. At this time, the sensor signal line 27 is wired through a space 29 formed radially outside the Hall element 8 and reaches the inner wall 14 a of the bracket 14.
[0029]
A power supply line 31 for supplying power to the drive coil 11 is connected to a diagonal position that is separated from the sensor signal line 27 by about 120 degrees in the circumferential direction. As described above, in the motor 1, the power supply line 31 and the sensor signal line 27 are not provided side by side, and are arranged so that they do not approach more than necessary. Thereby, the distance between the power supply line 31 through which a relatively large current flows and the sensor signal line 27 is maintained, and the effect of noise emitted from the power supply line 31 on the signal in the sensor signal line 27 can be reduced. it can. Therefore, the rotor position detection error due to the influence of noise is suppressed, the motor 1 can be efficiently rotated, and the torque ripple can be reduced. In particular, in the case of a motor for an electric power steering device, the torque ripple affects the steering feeling.
[0030]
The power supply line 31 is drawn out of the motor via a rubber grommet 32 attached to the side of the bracket 14. An opening 33 is formed in the bracket 14 at a position where the power line 31 is attached, and a rubber grommet 32 is attached to the opening 33. A terminal holder unit 34 is mounted inside the opening 33 using the space 29. The power supply line 31 is fixed to the terminal 35 of the terminal holder unit 34. Since the bracket 14 is provided with the large opening 33, the workability in connecting (welding) the power supply line 31 and the terminal 35 is good, and the number of steps can be reduced accordingly.
[0031]
Here, in the conventional brushless motor, as shown in FIG. 5, there is an unused space on the outer peripheral side of the sensor magnet 66 in the sensor section 53, and the existence of this dead space increases the axial length of the motor. Had contributed. On the other hand, in the motor 1, in the space 29 corresponding to the dead space, the sensor magnet 20 and the Hall element 8 are arranged on the inner diameter side, and the sensor signal line 27 and the terminal holder unit 34 are arranged on the outer diameter side. Have been. Further, unlike the case of FIG. 5, the sensor magnet 20 and the Hall element 8 are arranged side by side in the radial direction. That is, in the motor 1, the motor unit 4 and the sensor unit 5 are not simply stacked in series, but a part of them is arranged in parallel to form the overlapping unit 36.
[0032]
As described above, in the motor 1, the space 29 is not a mere dead space, and the components of the sensor unit 5 are efficiently stored therein. For this reason, the dead space problem in the conventional motor is solved, and, as schematically shown in FIG. 3, the axial length of the motor 1 is reduced by S in the figure as compared with the motor 51 of FIG. . Therefore, the size of the motor can be further reduced, and the weight of the product can be reduced and the cost can be reduced.
[0033]
(Embodiment 2)
Next, a brushless motor according to a second embodiment of the present invention will be described. FIG. 4 is a sectional view showing the configuration. Note that the same reference numerals are used for the same parts and members as in the first embodiment, and description thereof will be omitted.
[0034]
The brushless motor 41 (hereinafter abbreviated as “motor 41”) in FIG. 4 has a structure in which the bracket 14 is formed of a synthetic resin, and the connection between the sensor signal line 27 and the power supply line 31 is a direct coupler. On the bracket 14, a signal line coupler 42 and a power line coupler 43 are formed integrally with the bracket body 14b. A signal terminal 44 is accommodated in the signal line coupler 42. The signal terminal 44 is connected to the printed board 24 via a terminal plate 45 insert-molded in the bracket 14. On the other hand, a power supply terminal 46 is accommodated in the power supply line coupler 43. The power terminal 46 is connected to the terminal holder unit 34 via a terminal plate 47 insert-molded in the bracket 14.
[0035]
As described above, the motor 41 has a structure in which the signal terminal 44 and the power supply terminal 46 are separately formed as direct couplers, and are integrated with the bracket 14. Terminal plates 45 and 47 for connecting the terminals 44 and 45 to the printed circuit board 24 and the terminal holder unit 34 are also integrally formed in the bracket 14 by insert molding. For this reason, the dead space can be reduced as compared with the conventional brushless motor, and the size of the motor can be reduced. In addition, the assemblability of the signal lines and the power supply lines is improved, the number of assembling steps is reduced, and the cost is reduced. Further, since welding between the lead wire and the terminal plate is unnecessary, electrical connection between the power supply wire 31 and the drive coil 11 is also facilitated. In addition, since the electrical connection function is integrated into both couplers 42 and 43, the management of product quality is also facilitated. Further, since the signal line coupler 42 and the power supply line coupler 43 are separated, the influence of noise emitted from the power supply line 31 on the signal in the sensor signal line 27 can be reduced.
[0036]
The present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made without departing from the scope of the invention.
For example, in the above-described embodiment, an example has been described in which the detection of the rotational position of the rotor is performed by a Hall element. However, the present invention can also be applied to a method in which the detection is performed by a resolver. In that case, a resolver rotor is used instead of the sensor magnet 20, and a resolver stator is provided at that position instead of the Hall element 8.
[0037]
In the above-described embodiment, an example is shown in which the present invention is applied to a column assist type electric power steering device. However, the present invention can also be applied to other types of electric power steering devices such as a rack assist type. In addition, the brushless motor of the present invention is applicable to uses other than the electric power steering device, for example, industrial machines such as robots and IT devices such as personal computers.
[0038]
【The invention's effect】
According to the brushless motor of the present invention, the signal line is wired using the outer diameter side space of the rotation detecting member in the bracket, which has been a dead space in the conventional brushless motor, so that compared to the conventional brushless motor. The axial length can be shortened, and the size of the motor can be reduced.
[0039]
According to another brushless motor of the present invention, since the driven member and the rotation detecting member are arranged side by side in the radial direction, compared to a conventional brushless motor in which they are arranged in series in the axial direction and opposed to each other, The axial length of the motor can be reduced, and the size of the motor can be reduced.
[0040]
Furthermore, by fixing the rotor magnet accommodated in the magnet holder to the outer periphery of the rotor core by the binding force of the magnet cover, the rotor magnet can be attached to the rotor core without using an adhesive. Therefore, an adhesive application operation and an adhesive curing time during the manufacturing process are not required, so that the number of steps is reduced and the manufacturing cost is reduced. Further, unlike the conventional brushless motor, a projection for preventing rotation of the magnet is not required on the rotating shaft, and the cost of parts can be reduced.
[0041]
In addition, by integrally molding the signal line coupler and the power supply line coupler on the bracket, the dead space can be reduced as compared with the conventional brushless motor, and the motor can be reduced in size. In addition, the assemblability of the signal lines and the power supply lines is improved, the number of assembling steps is reduced, and the cost is reduced. Further, since the signal line coupler and the power line coupler are separated, the influence of noise emitted from the power line on the signal in the signal line can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration of a brushless motor according to a first embodiment of the present invention.
FIG. 2 is an exploded perspective view of the brushless motor of FIG.
FIG. 3 is an explanatory diagram schematically showing a difference in axial length between the brushless motor of FIG. 1 and a conventional brushless motor.
FIG. 4 is a cross-sectional view illustrating a configuration of a brushless motor according to a second embodiment of the present invention.
FIG. 5 is a cross-sectional view illustrating a configuration of a conventional brushless motor.
[Explanation of symbols]
1 brushless motor 2 rotor shaft (rotary axis)
3 Joint 4 Motor unit 5 Sensor unit 6 Stator 7 Rotor 8 Hall element (magnetic detection element; rotation detection member)
Reference Signs List 11 Drive coil 12 Stator core 13 Yoke 14 Bracket 14a Inner wall 14b Bracket body 15a, 15b Bearing 16 Rotor core 17 Rotor magnet 18 Side plate 19 Magnet holder 19a Shaft mounting portion 19b Arm portion 19c Sensor magnet mounting portion 20 Sensor magnet (driven member)
21 Magnet cover 22 Sensor holder 23 Sensor mounting hole 24 Printed circuit board 25 Screw 26 End cap 27 Sensor signal line 28 Rubber grommet 29 Space 31 Power supply line 32 Rubber grommet 33 Opening 34 Terminal holder unit 35 Terminal 36 Overlapping section 41 Brushless motor 42 Signal line coupler 43 power line coupler 44 signal terminal 45 terminal plate 46 power terminal 47 terminal plate 51 brushless motor 52 motor section 53 sensor section 54 rotor 55 stator 56 rotor shaft 57 rotor core 58 magnet holder 59 rotor magnets 61a, 61b bearing 62 drive coil 63 stator core 64 Yoke 65 Bracket 66 Sensor magnet 67 Hall element 68 Engagement projection

Claims (7)

A stator including a stator core around which a drive coil is wound, and a yoke for housing the stator core;
A rotor to which a rotor magnet is attached, and which is rotatably disposed inside the stator;
A driven member that rotates with the rotor,
A rotation detection member that is provided in proximity to the driven member and that outputs a rotation detection signal in accordance with the rotation of the rotor, is coupled to the yoke, and a bracket that houses the rotation detection member;
A signal line connected to the rotation detection member and wired in a space formed on the outer diameter side of the rotation detection member in the bracket. A stator around which a drive coil is wound;
A rotor provided rotatably inside the stator and having a rotor magnet attached with a plurality of magnetic poles formed along a circumferential direction;
A driven member that rotates with the rotor,
A brushless motor, comprising: a rotation detection member that is arranged radially side by side with the driven member and that outputs a rotation detection signal as the rotor rotates. 3. The brushless motor according to claim 1, wherein the rotor is fixed to the rotating shaft, the rotor core having the outer periphery fixed with the rotor magnet, and fixed to the rotating shaft adjacent to the rotor core. 4. An arm portion for accommodating the rotor magnet and restricting the circumferential movement thereof; a magnet holder extending along the axial direction; and a magnet holder mounted outside the rotor magnet for restricting the radial movement of the rotor magnet. A brushless motor, comprising: 4. The brushless motor according to claim 3, wherein the driven member is attached to the magnet holder, and the magnet cover covers the driven member. 2. The brushless motor according to claim 1, wherein the bracket has a signal line coupler having a terminal of the signal line, and a power supply having a terminal of a power supply line formed separately from the signal line coupler and supplying power to the drive coil. A brushless motor characterized by being integrally molded with a wire coupler. A motor unit including a stator on which a driving coil is wound, a rotor magnet attached, and a rotor rotatably disposed inside the stator;
A driven member that is disposed adjacent to the motor portion in the axial direction and rotates together with the rotor, and a rotation detection member that is provided close to the driven member and outputs a rotation detection signal in accordance with the rotation of the rotor. A sensor unit provided;
A brushless motor provided at a joint between the motor unit and the sensor unit, and having a superimposed portion in which a part of the motor unit and a part of the sensor unit are arranged in a radial direction. . 7. The brushless motor according to claim 1, wherein the driven member is a ring-shaped sensor magnet magnetized to have the same number of poles as the rotor magnet, and the rotation detection member is a sensor magnet of the sensor magnet. 8. A brushless motor, which is a magnetic detection element that outputs a rotation detection signal by detecting a change in magnetic pole due to rotation.

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