JP4418045B2 - Electric motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric motor and a yoke body used therefor, and more particularly to detection of a rotor position of a brushless DC motor.
[0002]
[Prior art]
A brushless DC motor, which is a kind of electric motor, does not have mechanical contact portions such as a brush and a commutator as compared with a brushed DC motor. For this reason, there is an advantage that there is no inconvenience that sparks are generated due to wear between the brush and the commutator, and noise accompanying the generation of the sparks adversely affects the surrounding electronic circuit.
[0003]
The configuration of this brushless DC motor will be described with reference to FIG.
[0004]
The brushless DC motor 1 has a casing 2. A bearing 3 is attached to the bottom of the casing 2, and a rotary shaft 4 is rotatably attached via the bearing 3.
[0005]
A rotor 5 is attached to the rotating shaft 4. The rotor 5 is composed of a rotor yoke 6 and, for example, four magnets 7 arranged on the outer peripheral side of the rotor yoke 6 at predetermined intervals, or by insertion of a cylindrical magnet. .
[0006]
A stator 8 is provided on the inner periphery of the casing 2. The stator 8 includes a stator core 9 attached to the inner wall surface of the casing 2, a magnetic pole 10 projecting radially inward from the stator core 9, and a coil 11 wound around a standing portion of the magnetic pole 10. ing.
[0007]
Here, a detecting magnet 12 and a hall sensor 13 are provided in order to detect the rotational position of the rotor 5 by rotational driving and to conduct a current in a direction corresponding to the change of the magnetic flux to the coil 11. The detection magnet 12 and the hall sensor 13 are provided so as to face each other close to each other.
[0008]
The Hall sensor 13 is attached to a support substrate 14 that supports the Hall sensor 13 so as to face each other in this manner. The support substrate 14 is attached and fixed to the casing 2 in order to fix the relative position to the rotating shaft 4. Has been.
[0009]
The detection magnet 12 provided to face the Hall sensor 13 is attached to the rotating shaft 4 by a yoke 15. As shown in FIG. 7, the yoke 15 has an insertion hole 16 for inserting the rotating shaft 4. A flange portion 17 is formed around the insertion hole 16, and the yoke 15 is attached and fixed to the rotary shaft 4 at this portion.
[0010]
An outer peripheral wall 18 is formed at the outer peripheral side end of the yoke. The detection magnet 12 is inscribed in the outer peripheral wall 18, thereby attaching and fixing the detection magnet 12, and preventing the detection magnet 12 from splashing outward during rotation driving.
[0011]
[Problems to be solved by the invention]
By the way, the yoke 15 is made of a magnetic material such as a steel plate and causes magnetic flux to pass therethrough. As described above, since the magnetic body exists on the outer peripheral side of the detection magnet 12, the magnetic flux leaks inside the magnetic body, and the amount of the magnetic flux directed to the Hall sensor 13 is reduced.
[0012]
For this reason, the accuracy of the output waveform generated from the hall sensor 13 is lowered, and therefore, when the signal of the hall sensor 13 is used for the motor rotation logic, it is easily affected by torque ripple, vibration, noise and efficiency. It has become.
[0013]
The present invention has been made based on the above circumstances, and an object of the present invention is to provide an electric motor and a yoke body used for the same that prevent a decrease in magnetic flux density toward the Hall sensor.
[0014]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, an invention according to claim 1 is an electric motor comprising a stator attached to a casing, a rotor coaxially attached to the stator, and a rotating shaft to which the rotor is attached. And are formed so as to be integrally driven with the rotating shaft, and are formed so that the polarities are alternately different along the circumferential direction of the rotating shaft, and at a predetermined distance in the axial direction of the rotating shaft with respect to the rotor and the stator. A detection magnet provided at a distance, a support member provided at a predetermined distance in the axial direction of the rotating shaft with respect to the rotor and the stator, and a radial outer periphery while being fixed to the rotating shaft. At the end are claw portions that contact and fix the outer periphery of the detection magnet at a predetermined pitch along the circumferential direction, and a proximity to the detection magnet. Mounted on said support member so as to face, an electric motor, characterized by comprising a magnetic sensing means for detecting a magnetic change of the detecting magnet.
[0015]
According to a second aspect of the present invention, in the electric motor according to the first aspect, the claw portion contacts and fixes the detection magnet at the circumferential center of each polarity.
[0016]
A third aspect of the present invention is the electric motor according to the first or second aspect, wherein the detection magnet is provided on a radially outer peripheral side of the yoke.
[0017]
The invention according to claim 4 is characterized in that the magnetic detection means is attached so as to face the radially outer peripheral side of the detection magnet. It is an electric motor.
[0018]
According to a fifth aspect of the present invention, the magnetic detection means is provided with control means for controlling the timing of energizing the stator coil and controlling the number of rotations corresponding to the rotational position of the rotor after detecting the rotational position of the rotor. The electric motor according to claim 1, wherein the electric motor is provided.
[00 19 ]
As a result of taking the above-mentioned means, the following operation occurs. According to the first aspect of the present invention, since the claw portions that contact and fix the outer periphery of the detection magnet are formed at a predetermined pitch along the circumferential direction of the yoke body at the radially outer circumferential end portion of the yoke body, the rotation When the shaft is driven to rotate, it has a function to prevent the detection magnet from scattering outward, and a conventional outer peripheral wall is formed, and the detection magnet is scattered outward by this outer peripheral wall. Compared with a configuration that prevents the magnetic field from being reduced, it is possible to prevent a reduction in magnetic force from the detection magnet toward the magnetic detection means. Further, it is possible to mechanically position the magnet and the yoke.
[002 0 ]
For this reason, the accuracy of the output waveform generated from the magnetic detection means is not lowered, and therefore, even if the signal generated from the magnetic detection means is used for the motor rotation logic, the influence of torque ripple, vibration, noise and efficiency is not achieved. It is difficult to receive.
[002 1 ]
According to the second aspect of the present invention, since the claw portion contacts and fixes the detection magnet at the circumferential center of each polarity, at the switching portion of the magnetization waveform pole detected by the magnetic detection means, the yoke Is similar to the configuration not provided on the outer periphery of the detection magnet.
[002 2 ]
For this reason, it becomes possible to prevent the ON / OFF duty ratio from changing and the accuracy of rotor position detection from deteriorating.
[002 3 ]
According to the invention of claim 3, since the detection magnet is provided on the radially outer side of the yoke, the magnetic force generated from the detection magnet is also generated from a position corresponding to the radially outer side of the yoke. Therefore, if the magnetic force is detected at this position, accurate detection can be performed.
[002 4 ]
According to the invention of claim 4, since the magnetic detection means is attached so as to face the radially outer peripheral side of the detection magnet, it is possible to improve the detection accuracy of the magnetic force.
[002 5 ]
According to the invention of claim 5, the magnetic detection means is provided with a control means for controlling the timing (rotation logic) and the number of rotations of energizing the stator coil corresponding to the rotational position of the rotor after detecting the rotational position of the rotor. Therefore, it is possible to flow current at an appropriate timing with respect to the brushless DC motor, and it is possible to improve motor efficiency.
[002 6 ]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[002 7 ]
FIG. 1 is a side sectional view showing a configuration of a brushless DC motor 20 which is a kind of the electric motor of the present invention. The brushless DC motor 20 has a frame 21. The frame 21 is formed of a thermosetting resin so that its external appearance becomes a cylindrical shape.
[002 8 ]
For example, a bearing 22 such as a bearing is located on the cylindrical bottom side of the frame 21 (on the end side along the axis of the central axis of the cylindrical shape). For this reason, a recess 23 for attaching the bearing 22 is formed on one end side along the central axis of the frame 21, and the frame 21 for locking the bearing 22 is formed on the other end side along the central axis. A locking portion 24 formed in a concave shape when viewed from the inside is formed.
[00 29 ]
In the present embodiment, a ring-shaped concave portion 25 is formed on the outer diameter side of the locking portion as viewed from the outside of the frame 21.
[003 0 ]
Such a bearing 22 is attached, and the rotary shaft 26 is rotatably supported by the bearing 22 so that the rotational drive of the brushless DC motor 20 can be well guided.
[003 1 ]
The outer periphery and side part of the stator 30 are covered with resin. The stator 30 is attached to the inner wall surface of the frame 21. The stator 30 is made of a metal stator core 31 laminated in an annular shape, a plurality of magnetic poles 32 provided at a predetermined interval in the circumferential direction from the stator core 31, and projecting radially inward, and the magnetic poles A coil 33 having three phases of a U phase, a V phase, and a W phase wound around 32 is provided. The magnetic pole 32 protrudes toward both sides in the circumferential direction at the protrusion 32a shown in FIG. 2 and the tip of the protrusion 32a, and is disposed on the axial center side of the stator core 31 so as to face the rotor 34. And the opposite portion 32b.
[003 2 ]
The rotor 34 includes a rotor yoke 35 made of, for example, mild steel and a magnet 36 disposed on the outer periphery of the rotor yoke 35, and the rotor 34 is attached to the outer periphery of the rotating shaft 26. The magnet 36 has a configuration in which, for example, two N poles and two S poles are alternately closely attached along the outer periphery of the rotor yoke 35. Or the structure which attached the cylindrical magnet may be sufficient.
[003 3 ]
The rotary shaft 26 has a tip projecting from the brushless DC motor 20 and can be connected to other members.
[003 4 ]
A detection magnet 37 is attached to the rotating shaft 26 existing between the rotor 34 and the bearing 22. The detection magnet 37 is fixed to the rotary shaft 26. In order to fix the magnet 37 to the rotary shaft 26, a yoke 38 as a metal yoke body is provided.
[003 5 ]
The yoke 38 is provided such that a flange portion 39 for contacting the rotary shaft 26 with a predetermined area is in contact with the rotary shaft 26, and the flange portion 39 is radially outward from the rotary shaft 26. It becomes the disk shape part 40 so that it may face. A detecting magnet 37 is provided on the disk-shaped portion 40. The detection magnet 37 is formed in a donut shape having an insertion hole 41 through which the rotary shaft 26 can be inserted. The insertion hole 41 is formed to have a larger hole diameter than the outer diameter of the rotating shaft 26. Accordingly, the rotation shaft 26 can be inserted satisfactorily, and the detection magnet 37 is configured to be positioned on the outer peripheral side of the yoke 38.
[003 6 ]
Here, in order to prevent the detection magnet 37 from splashing outward due to the centrifugal force generated in the detection magnet 37 when the rotary shaft 26 is driven to rotate, the radial projection end of the yoke 38 is applied to the rotary shaft 26. A claw portion 42 that is bent in a parallel direction is formed on the yoke 38. The claw portion 42 is formed so as to protrude by a predetermined length in a direction parallel to the rotation shaft 26, and is formed so as to grasp the detection magnet 37 on the inner diameter side. A plurality of (two or more) claw portions 42 are formed at a predetermined pitch along the circumferential direction of the yoke 38.
[003 7 ]
The claw portion 42 is formed so that the width thereof is not so wide in consideration of the effect of this on the magnetic flux. That is, the claw portion 42 is formed to have a width that does not impair the function of preventing the detection magnet 37 from scattering.
[003 8 ]
The claw portion 42 is provided so as to be positioned at the center of the outer periphery of each of the N-pole and S-pole detection magnets 37.
[00 39 ]
A Hall sensor 43 (Hall IC) is provided as a magnetic detection means so as to be close to and opposed to the detection magnet 37. The hall sensor 43 is attached to a support plate 44 as a support member attached and fixed to a predetermined position of the frame 21. The support plate 44 is configured to have a cutout portion in which a portion corresponding to the rotation shaft 26 is cut out so as not to prevent the rotation drive of the rotation shaft 26.
[004 0 ]
The mounting position of the hall sensor 43 with respect to the support plate 44 is attached to a portion facing the outer peripheral side of the detection magnet 37.
004 1 ]
The hall sensor 43 is connected to a control means (not shown). This control means controls the brushless DC motor 20 to conduct an appropriate amount of current based on the detection result of the rotational position of the rotor 34 detected by the hall sensor 43.
[004 2 ]
The operation of the brushless DC motor 20 having the above configuration will be described below.
[004 3 ]
When the brushless DC motor 20 is operated by conducting a predetermined current, the magnet 37 for detection is also rotationally driven along with the rotational driving of the rotating shaft 26. In this detection magnet 37, N poles and S poles are alternately arranged along the circumferential direction of the yoke 38. Therefore, the Hall sensor 43 arranged to face the detection magnet 37 detects a change in magnetic flux as the detection magnet 37 is rotationally driven.
[004 4 ]
Here, in the configuration in which the outer peripheral wall is formed at the radially projecting end of the yoke 38, as compared with the B line in the configuration in which no outer peripheral wall is provided as shown by the C line in FIG. A decrease in magnetic flux intensity was observed.
[004 5 ]
However, in the present invention, instead of the above-described outer peripheral wall, a claw portion 42 is formed to prevent scattering of the detection magnet 37, and the area of the claw portion 42 is formed in a small area. Therefore, the ratio of the claw portion 42 to the outer peripheral surface of the detection magnet 37 is greatly reduced as compared with the outer peripheral wall described above.
[004 6 ]
That is, in the configuration of the present invention, as shown by line A in FIG. 5A, a decrease in magnetic flux is observed only in the portion corresponding to the claw portion 42, and the outer peripheral wall 18 is not provided in the other portion. It is similar to the resulting waveform.
[004 7 ]
As a result, the flow (magnetic force) of the magnetic flux toward the Hall sensor 43, which is caused by the magnetic flux passing through the outer peripheral wall, is not reduced, and the detectability of the magnetic flux change by the Hall sensor 43 is deteriorated. It becomes possible to prevent. That is, in the present invention, it can be said that waveform changes are minimized.
[004 8 ]
Further, since the above-described distortion of the magnetized waveform does not occur, it is difficult to be influenced by the hysteresis width of the Hall sensor 43. That is, in the conventional configuration, the magnetic flux passes through the outer peripheral wall 18 of the yoke, whereby the magnetic flux density toward the Hall sensor 43 changes, the waveform becomes smaller, and the influence of the hysteresis width becomes relatively larger. That is, as shown in the D line (in the case of the present invention) and the E line (in the conventional case) in FIG. 5B, the outer periphery of the waveform switching portion from the N pole to the S pole due to the change in the magnetization waveform. As compared with the configuration without the wall 18, the ON / OFF duty ratio waveform is shifted.
[00 49 ]
However, according to the present invention, the configuration in which the yoke 38 is not provided and the switching portion of the magnetized waveform from the N pole to the S pole hardly change. For this reason, there is no fear that the ON / OFF duty ratio is shifted due to the influence of the hysteresis width, and the reliability is improved.
[005 0 ]
As a result, even if a signal emitted from the hall sensor 43 toward the control means (not shown) is used for controlling the current conduction amount for rotating the motor, this signal has no influence on torque ripple, vibration, noise, etc. Since it is difficult to receive, the rotational drive of the brushless DC motor 20 can be performed satisfactorily.
005 1 ]
That is, according to the present invention, the efficiency of the brushless DC motor 20 can be improved.
005 2 ]
In addition, since the hall sensor 43 is disposed so as to face the outer peripheral side of the detection magnet 37, it is compared with the case where the hall sensor 43 is disposed so as to face the inner peripheral side of the detection magnet 37. Therefore, it is difficult to be affected by mechanical accuracy. That is, it is possible to detect the magnetic flux more favorably on the outer peripheral side than on the inner peripheral side.
005 3 ]
Although one embodiment of the present invention has been described above, the present invention can be variously modified in addition to this. This is described below.
[005 4 ]
In the above-described embodiment, the configuration in which, for example, two N poles and S poles of the detection magnet 37 are alternately mounted has been described. However, the present embodiment is not limited to this, and three of the detection magnets 37 are alternately mounted. A configuration may be used, or a configuration in which four sheets are alternately mounted may be employed.
[005 5 ]
Moreover, although the case where this invention was applied to the brushless DC motor 20 was described in the said embodiment, this invention is not restricted to the case where it applies to the brushless DC motor 20, You may apply to another motor. Absent.
[005 6 ]
In addition, various modifications can be made without departing from the scope of the present invention.
[005 7 ]
【The invention's effect】
As described above, according to the first and sixth aspects of the present invention, the claw portion that contacts and fixes the outer periphery of the detection magnet is provided along the circumferential direction of the yoke body at the radially outer peripheral end portion of the yoke body. Since it is formed with a predetermined pitch, the detection magnet moves from the detection magnet to the magnetic detection means as compared with a configuration in which a conventional outer peripheral wall is formed and the outer peripheral wall prevents the detection magnet from splashing outward. Reduction of magnetic force can be prevented.
[005 8 ]
For this reason, the accuracy of the output waveform generated from the magnetic detection means is not lowered, and therefore, even if the signal generated from the magnetic detection means is used for the motor rotation logic, the influence of torque ripple, vibration, noise and efficiency is not achieved. It is difficult to receive.
[00 59 ]
According to the invention described in claim 2, since the claw portion fixes the detection magnet at the center in the circumferential direction of each polarity, in the switching portion of the magnetization waveform pole detected by the magnetic detection means, This is the same as the configuration in which the yoke is not provided on the outer periphery of the detection magnet.
[006 0 ]
For this reason, it becomes possible to prevent the ON / OFF duty ratio from changing and the accuracy of rotor position detection from deteriorating.
006 1 ]
According to the third aspect of the present invention, since the detection magnet is provided on the outer peripheral side in the radial direction of the yoke, the magnetic force generated from the detection magnet is also generated from a position corresponding to the outer peripheral side in the radial direction of the yoke. Therefore, if the magnetic force is detected at this position, accurate detection can be performed.
[006 2 ]
According to the fourth aspect of the invention, since the magnetic detection means is attached so as to face the radially outer peripheral side of the detection magnet, it is possible to improve the detection accuracy of the magnetic force.
[006 3 ]
According to the fifth aspect of the present invention, the magnetic detection means is provided with a control means for controlling the timing (rotation logic) and rotation speed of energizing the stator coil corresponding to the rotational position of the rotor after detecting the rotational position of the rotor. Therefore, it is possible to flow a current at an appropriate timing with respect to the brushless DC motor, and it is possible to improve the motor efficiency.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing a shape of a brushless DC motor according to an embodiment of the present invention.
FIG. 2 is a front sectional view showing the shape of the brushless DC motor according to the embodiment.
3A and 3B are diagrams showing the shape of a yoke according to the embodiment, where FIG. 3A is a side sectional view, and FIG. 3B is a front view.
4A and 4B are diagrams showing the shape of a detection magnet according to the embodiment, where FIG. 4A is a side sectional view, and FIG. 4B is a front view.
5A and 5B are diagrams showing a relationship between magnetic flux intensity and rotor rotational position according to the embodiment, wherein FIG. 5A is a diagram showing a relationship between magnetic flux intensity and rotor rotational position, and FIG. 5B is a hysteresis width and ON / OFF. The figure which shows the relationship of a duty ratio.
FIG. 6 is a diagram showing a configuration of a conventional brushless DC motor.
FIG. 7 is a view showing the shape of a conventional yoke.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 20 ... Brushless DC motor 21 ... Casing 26 ... Rotating shaft 30 ... Stator 34 ... Rotor 37 ... Detection magnet 38 ... Yoke 42 ... Claw part 43 ... Hall sensor 44 ... Support plate

Claims (5)

In an electric motor comprising a stator attached to a casing, a rotor coaxially attached to the stator, and a rotating shaft to which the rotor is attached,
It is provided so as to be integrally driven with the rotating shaft, is formed so that the polarities are alternately different along the circumferential direction of the rotating shaft, and is separated from the rotor and stator by a predetermined distance in the axial direction of the rotating shaft. A magnet for detection provided
A support member provided at a predetermined distance from the rotor and the stator in the axial direction of the rotating shaft;
A yoke body that is fixedly attached to the rotating shaft, and a claw portion that contacts and fixes the outer periphery of the detection magnet is formed at a predetermined pitch along the circumferential direction at the radially outer end portion;
A magnetic detection means attached to the support member so as to be in close proximity to the detection magnet and detecting a magnetic change of the detection magnet;
An electric motor comprising:   2. The electric motor according to claim 1, wherein the claw portion is configured to contact and fix the detection magnet at the circumferential center of each polarity.   The electric motor according to claim 1, wherein the detection magnet is provided on a radially outer peripheral side of the yoke.   The electric motor according to any one of claims 1 to 3, wherein the magnetic detection means is attached so as to face a radially outer peripheral side of the detection magnet.   The magnetic detection means is provided with control means for controlling the timing of energizing the stator coil and controlling the number of rotations corresponding to the rotational position of the rotor after the rotational position of the rotor is detected. The electric motor according to any one of claims 1 to 4.

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