JPH11146618A - Dc brush-less motor and rotor therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotor for a DC brushless motor and a DC brushless motor which can attain high torque without generating a dead position. SOLUTION: The rotor 2 for a DC brushless motor is provided with a cylindrical magnet 11 and a rotating shaft 14 which passes and is fixed to the hollow part of the cylindrical magnet 11, whereas the cylindrical magnet 11 involves a magnetic pole detection area 12 which has rectangular wave flux distribution characteristics for the machine angle of the motor and is formed on one end side in the axial direction of the rotating shaft 14, and a torque generating area 13 formed on the other end side in the axial direction of the rotating shaft 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor for a DC brushless motor having a rotary shaft penetrated and fixed to a cylindrical magnet, and a DC brushless motor having the rotor.

[0002]

2. Description of the Related Art As a rotor for a DC brushless motor of this type, for example, a rotor 71 shown in FIG. 9 is conventionally known. The rotor 71 has a configuration in which a rotating shaft 14 is fixedly penetrated through a hollow portion of a cylindrical magnet 72. The rotating shaft 14 is formed by fixing a rotor core 16 to a motor shaft 15. Rotor core 16 is generally formed by laminating silicon steel plates, which are magnetic materials.

[0003] The cylindrical magnet 72 is generally formed of a so-called isotropic magnet or a so-called radial anisotropic magnet. Here, the isotropic magnet refers to a magnet manufactured by press-molding magnetic fine powder without performing an orientation treatment in a magnetic field, and the radial anisotropic magnet refers to a magnetic fine powder in a magnetic field shown in FIG. Means a magnet produced by press molding after orientation treatment in the direction shown in FIG.
In this case, regardless of the type of magnet, the magnetic poles N and S are alternately magnetized in the outer circumferential direction of the cylindrical magnet 72 as shown in FIG. 8, and as shown in FIG. In addition, a magnetic flux distribution characteristic of the magnetic pole with respect to the mechanical angle of the motor is formed in a rectangular wave shape. FIG. 8 shows a state when the magnet is magnetized to eight poles.

On the other hand, DC brushless motors using this rotor 71 are generally opposed to the rotor 71 with a phase difference of 120 degrees in mechanical angle, as shown in FIG. Three Hall ICs
33a, 33b, 33c and three stator coils (not shown) are provided on the stator side.

In such a DC brushless motor, the Hall ICs 33a, 33b,
3c detects the rotation angle of the rotor 71 by detecting the magnetic pole of the opposed cylindrical magnet 72. Next, based on the detected rotation angle of the rotor 71, the rotation of the rotor 71 is controlled by energizing one of the three stator coils. By repeating these, the DC brushless motor generates a predetermined torque and maintains the rotation of the rotor 71.

[0006]

However, such a DC brushless motor has a problem that it is difficult to meet a demand for a higher torque. That is, the torque of the DC brushless motor is generated by an electromagnetic interaction between the current flowing through the stator coil and the magnetic flux of the cylindrical magnet 72. Therefore, in order to increase the torque,
What is necessary is just to increase the electric current passed through the stator coil or to increase the magnetic flux. However, if a large current flows through the stator coil, the diameter of the winding must be increased,
This leads to an increase in the size of the motor. On the other hand, the magnetic flux is distributed in a rectangular wave shape in the conventional cylindrical magnet 72 as described above, and therefore, a region near the polarity where the magnetic flux changes (hereinafter, this region is also referred to as a “magnetic flux polarity change region”) Although the magnetic flux of ()) is relatively large, generally, the magnetic flux at the central portion of the magnetic pole is slightly small. In this case, the central portion of the magnetic pole contributes most to the generation of torque, but it is difficult to increase the magnetic flux at the central portion of the magnetic pole in an isotropic magnet or the like with the current technology.

On the other hand, a so-called polar anisotropic magnet has been conventionally known as a magnet having a high magnetic flux at the center of the magnetic pole.
In this case, the polar anisotropic magnet is used to move the magnetic fine powder in a magnetic field as shown in FIG.
It is manufactured by press forming in a state where it is oriented in the direction shown in (b). The magnetization of the magnetic pole is the same as that of an isotropic magnet or the like, but the magnetic flux distribution characteristics of the magnetic pole with respect to the mechanical angle are isotropic. Unlike a sex magnet or the like, as shown in FIG. 7B, it is formed in a sine wave shape. Therefore, at the magnetic pole center portion, the rotor formed of the polar anisotropic magnet has a higher magnetic flux than the rotor formed of the isotropic magnet or the radial anisotropic magnet. Therefore, it is conceivable to use this polar anisotropic magnet as a material for the rotor.

However, a DC brushless motor using a rotor formed of a polar anisotropic magnet has a problem that a so-called dead point occurs. That is, in order to reliably control the rotation of the rotor, the magnetic pole N and the magnetic pole S of the cylindrical magnet 72 are alternately and continuously provided by the Hall ICs 33a to 33c at every 45 degrees in mechanical angle without phase shift. Need to be detected. On the other hand, in the cylindrical magnet 72 formed of a polar anisotropic magnet, the magnetic flux is small and the magnetic flux changes slowly in the magnetic flux polarity change region. In a brushless motor, Hall ICs 33a to 33c for detecting magnetic poles are used.
However, as a result of the inability to accurately detect the position where the polarity of the magnetic pole is switched, there is another problem that it is difficult to perform appropriate energization control of the stator coil.

The present invention has been made in view of the above problems, and provides a rotor for a DC brushless motor and a DC brushless motor capable of achieving high torque without generating a dead center. Aim to be.

[0010]

According to a first aspect of the present invention, there is provided a DC brushless motor rotor comprising a cylindrical magnet, and a rotating shaft fixedly inserted through a hollow portion of the cylindrical magnet. In rotors for DC brushless motors,
The cylindrical magnet has a magnetic flux distribution characteristic of a rectangular wave with respect to the mechanical angle of the motor, a magnetic pole detection region formed at one end in the axial direction of the rotating shaft, and a sinusoidal magnetic flux with respect to the mechanical angle of the motor. And a torque generating region formed on the other end of the rotating shaft in the axial direction.

In this DC brushless motor rotor,
In the magnetic pole detection area, since the magnetic flux distribution characteristics of the magnetic pole are rectangular waves, the magnetic pole center does not have a large magnetic flux density, but in the magnetic flux polarity change area, the magnetic flux sharply changes relative to the mechanical angle. Changes. In this case, in the magnetic flux polarity change region, it is possible to have a magnetic flux density sufficiently exceeding the detection threshold value of the Hall IC as the magnetic pole detection means. Therefore, the Hall IC can reliably detect the magnetic pole, and the energization of the stator coil can be accurately controlled. As a result, no dead center is generated. On the other hand, in the torque generation area, the magnetic flux distribution characteristics of the magnetic poles are sinusoidal, so in the magnetic flux polarity change area, the magnetic flux density changes gently with respect to the mechanical angle, but the magnetic pole center has high magnetic flux in the center. It becomes possible. For this reason, in the center of the magnetic pole, the motor using this rotor can generate a high torque due to the electromagnetic interaction between the current flowing through the energized stator coil and the magnetic flux having a large value.

A DC brushless motor rotor according to a second aspect of the present invention is the DC brushless motor rotor according to the first aspect, wherein the magnetic flux distribution in the magnetic pole detection area and the magnetic flux distribution in the torque generation area are relative to the mechanical angle of the motor. And are formed in the same phase.

In this DC brushless motor rotor,
Since the magnetic flux distribution in the torque generation region and the magnetic flux distribution in the magnetic pole detection region are formed in the same phase with respect to the mechanical angle of the motor, the Hall IC as the magnetic pole detection means is located on the radial side of the rotating shaft. Irrespective of the position on the axial side, the magnetic flux in the magnetic pole detection region can be accurately detected without being affected by the magnetic poles in the torque generation region.

According to a third aspect of the present invention, in the rotor for a DC brushless motor according to the first or second aspect, the magnetic pole detection region is formed so that its magnetic pole can be detected from the axial side of the rotating shaft. It is characterized by having.

In this DC brushless motor rotor,
When used in a DC brushless motor, a Hall IC for detecting a magnetic pole is arranged on the axial side of the rotating shaft. Therefore, even when the magnetic poles of both regions are not formed in the same phase, the Hall IC can accurately detect the magnetic poles of the magnetic pole detection region without being affected by the magnetic poles of the torque generation region. It becomes possible.

A DC brushless motor rotor according to a fourth aspect of the present invention is the DC brushless motor rotor according to the second aspect, wherein the magnetic pole detection region is formed so that its magnetic pole can be detected from the radial direction side of the rotating shaft. It is characterized by the following.

In this DC brushless motor rotor,
The magnetic poles of both regions are directed toward the radial direction of the rotating shaft.
Therefore, when this rotor is used in a DC brushless motor, the magnetic flux in the magnetic pole detection region contributes to the generation of torque. For this reason, it is possible to effectively use the magnetic flux in the magnetic pole detection area.

A DC brushless motor according to claim 5 is
A DC brushless motor rotor according to any one of claims 1 to 4 is provided.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, an embodiment in which a DC brushless motor rotor and a DC brushless motor according to the present invention are applied to a three-phase DC brushless motor will be described below. The conventional rotor 71
The same reference numerals are used for the same components as described above, and the detailed description thereof is omitted.

FIG. 2 is a sectional view of a DC brushless motor 1 (hereinafter, also simply referred to as "motor") according to the present invention. As shown in the figure, a motor 1 has a rotor 2 corresponding to a rotor for a DC brushless motor in the present invention.
And a stator 3.

As shown in FIGS. 1 and 2, the rotor 2 has a rotating shaft 1 formed by fixing a rotor core 16 to a motor shaft 15.
4 is penetrated and fixed to the hollow portion of the cylindrical magnet 11.

Here, the cylindrical magnet 11 is made of a magnetic pole detection region 12 formed at one end of the motor shaft 15 using an isotropic or radially anisotropic magnet as a material. And a torque generating region 13 formed on the other end side of the motor shaft 15. Magnetic pole detection area 12
Is, for example, as shown in FIG.
Similarly, magnetic poles N and S are alternately and octagonally magnetized in the outer circumferential direction of the cylindrical magnet 11, and the magnetic flux distribution of the magnetic poles with respect to the mechanical angle of the motor as shown in FIG. The characteristic is formed in a rectangular wave shape. As shown in FIG. 8, for example, the torque generating region 13 is configured such that the magnetic poles N and the magnetic poles S are alternately arranged in the outer circumferential direction of the cylindrical magnet 11 and magnetized to eight poles, similarly to the magnetic pole detection region 12. I have. Further, as shown in FIG. 7B, the torque generation region 13 has a magnetic flux distribution characteristic of the magnetic pole with respect to the mechanical angle of the motor which is sinusoidal and has the same phase as the magnetic flux distribution characteristic of the magnetic pole detection region 12. It is magnetized.

As shown in FIG. 2, the stator 3 includes a motor frame 31, three stator coils 32U, 32V,
It comprises a stator coil 32 composed of 32W and Hall ICs 33a to 33c for detecting magnetic poles (in FIG. 1, Hall ICs 33a and 33b are shown). In this case, the stator coils 32U, 32V, 32
W is disposed on the inner wall side of the motor frame 31 so as to face the torque generating region 13 and the Hall ICs 33a, 3
The reference numerals 3b and 33c are spaced apart from the cylindrical magnet 11 in the axial direction of the motor shaft 15 so as to face the magnetic pole detection region 12.

Next, the control device 4 for driving the motor 1 will be described with reference to FIG.

As shown in the figure, the control device 4 comprises a logic unit 5 to which the above-mentioned three Hall ICs 33a, 33b, 33c are connected, and the above-mentioned stator coils 32U, 32C.
V, 32W.

The logic unit 5 includes inverters 51a to 51c,
52a-52c and AND gates 53a-53c, 54
a to 54c and a pulse oscillation circuit 55 for controlling the rotation speed of the motor 1.

The logic unit 5 controls the rotation direction of the motor 1 based on the magnetic pole detection signals Sa to Sc detected by the Hall ICs 33a to 33c, respectively, among the three stator coils 32U, 32V, and 32W. Drive signals S1a to S1c and drive signals S2a to S2c of high level signals (hereinafter, referred to as “H signal”) are output to the drive unit 6 so that any two are energized simultaneously. At this time, the pulse oscillating circuit 55 outputs a pulse signal having a duty ratio of 0 to 100% to the AND gates 54a to 54a.
54c to control the rotation speed of the motor 1 by substantially changing the pulse width of the drive signals S2a to S2c.

The drive section 6 includes six drive circuits 61a to 61a.
61f and three transistor circuits 62a, 62b, 6
2c (hereinafter referred to as “transistor circuit 6
2 "). Hereinafter, each component will be described. Each transistor circuit 62
Are configured identically, the transistor circuit 62
Only a will be described, and the components of each transistor circuit 62 will be distinguished by adding a to c to the reference numerals.

Each of the drive circuits 61a to 61f receives the drive signals S1a to S1c and S2a to S2c, and receives the FETs 63a to 63c and the FET 64a in the transistor circuit 62.
Drive signals for driving the gates of .about.64c are generated and output. On the other hand, the transistor circuit 6
Reference numeral 2 includes a p-channel FET 63 for supplying a current to the stator coil 32 and an n-channel FET 64 for flowing a current to the ground via the stator coil 32. The FET 63 has a drain connected to the DC power supply line 68 and a source connected to the FET
64 is connected to the drain. The source of the FET 64 is connected to the ground. In addition, both FETs
Protection diodes 65 and 66 for absorbing a back electromotive force are connected in series between the drains and sources of the transistors 63 and 64, and a stator coil 32 is connected to a connection point 67 between the source of the FET 63 and the drain of the FET 64. Are connected at one end.

Next, drive control of the motor 1 by the control device 4 will be described with reference to FIGS.

First, an outline of the operation of the control device 4 will be described. The Hall ICs 33a to 33c detect the magnetic poles formed in the opposing magnetic pole detection area 12, and then
As shown in FIG.
, And outputs the magnetic pole detection signals Sa to Sc. In this case, the L signal and the H signal indicate a magnetic pole detection signal at a low level and a magnetic pole detection signal at a high level, respectively. Modes 1 to 6 are shown in FIG.
Corresponds to each period divided every 15 ° between the mechanical angles 0 ° to 90 °. In this case, the magnetic pole detection area 12
Are formed in a rectangular wave shape as shown in FIG. 7A, so that the Hall ICs 33a to 33c can accurately detect the magnetic pole. For this reason, the control device 4 can accurately perform the energization control shown in FIG. 5 according to the mechanical angle.

More specifically, in the control device 4, for example, during the mode 1, the Hall IC 33a outputs the magnetic pole detection signal Sa of the L signal, and the Hall ICs 33b and 33c output the magnetic pole detection signals Sb and Sc of the H signal. When output, the logic unit 5 outputs the drive signal S1a and the drive signal S2c generated by the logical operation to the drive unit 6. Thereby, the FE of the transistor circuit 62a is
T63a and FET 64c of the transistor circuit 62c
Operate, current is supplied to the stator coil 32U and the stator coil 32W connected in series. Therefore, stator coils 32U and 3U
Positive and negative currents flow through 2W, respectively, and a positive torque is generated in rotor 2. As a result, motor 1 rotates in a predetermined direction. Hereinafter, such an operation is referred to as mode 1
The driving unit 6 outputs drive signals S1a to S1c and 2a to 2c based on the magnetic pole detection signals Sa to Sc output in each mode, so that the motor 1 The motor continuously rotates in a predetermined direction and generates a predetermined torque.

The torque generated by the motor 1 is generated by an electromagnetic interaction between a current flowing through each of the stator coils 32U to 32W and a magnetic flux linking the magnetic poles of the torque generating region 13 to each coil. It is obtained from the sum of the component torques of each stator coil. In this case, the component torque for each stator coil is not always generated over the entire mechanical angle section. That is, for example, taking the stator coil 32U as an example, in a section where the mechanical angle corresponding to the magnetic pole center portion is 0 ° to 30 °, a positive component torque is generated due to the electromagnetic interaction between the positive current and the positive magnetic flux. In the sections in which the mechanical angles corresponding to the magnetic flux polarity change area described above are 30 ° to 45 ° and 75 ° to 90 °, no component torque is generated because the energization control is not performed, and the torque corresponds to the center of the magnetic pole. In the section where the mechanical angle is between 45 ° and 75 °, a positive component torque is generated by the electromagnetic interaction between the negative current and the negative magnetic flux. The above torque generation pattern is repeated three times from 90 ° to 360 ° thereafter. Similarly, stator coils 32V, 32V
W also has a different mechanical angle section from the stator coil 32U, but generates a component torque.

In this case, since the magnetic flux distribution in the torque generating area 13 is sinusoidal as shown in FIG. 7B, the magnetic flux is small in the mechanical angle section corresponding to the magnetic flux polarity change area which does not originally contribute to the torque generation. Conversely, the magnetic flux is large in the mechanical angle section corresponding to the magnetic pole center portion that contributes to the torque generation. Therefore, each of the stator coils 33U to 33W
The motor 1 generates a high torque as a whole due to the electromagnetic interaction between the current flowing through the motor and the large magnetic flux at the center of the magnetic pole.

As described above, in the motor 1 according to this embodiment, since the cylindrical magnet 11 is formed by the magnetic pole detection area 12 and the torque generation area 13, a high torque can be obtained without generating a dead point. Can occur.

In this embodiment, the direction of the magnetic flux generated in the magnetic pole detection area 12 is directed to the axial direction of the rotary shaft 14 and the Hall ICs 33a to 33c are disposed on the axial side of the rotary shaft 14. However, the present invention is not limited to this, and the direction of the magnetic flux generated in the magnetic flux detection region is directed to the radial direction of the rotating shaft 14 and the Hall ICs 33a to 33c are You may comprise so that it may be arrange | positioned at the direction side. In this case, since the magnetic flux in the magnetic pole detection area contributes to the generation of torque, the magnetic flux in the magnetic pole detection area can be effectively used.

Also, in the present embodiment, an example has been described in which the phases of the magnetic pole detection region 12 and the torque generation region 13 are in phase. However, the rotor in the present invention is not limited to this. 12 of magnetic flux and torque generating region 1
3 may be different from each other. In this case, it is preferable that the magnetic flux generated by the magnetic pole detection region 12 be directed in the axial direction of the rotating shaft 14. In such a case, the Hall ICs 33a to 33c can accurately detect the magnetic poles of the magnetic pole detection area 12 without being affected by the magnetic poles of the torque generation area 13. Furthermore, the cylindrical magnet in the DC brushless motor rotor according to the present invention,
The magnetic pole detection region and the torque generation region manufactured separately from each other may be bonded to each other, or a cylindrical magnet manufactured in advance may be magnetized to function as the magnetic pole detection region and the torque generation region. May be. Further, the number of magnetic poles in the cylindrical magnet according to the present invention is not limited to the number shown in the embodiment of the present invention. It can be changed as appropriate.

[0038]

As described above, according to the DC brushless motor rotor according to the first aspect, the rotor has a rectangular wave-shaped magnetic flux distribution characteristic with respect to the mechanical angle of the motor and is formed at one end in the axial direction of the rotating shaft. A magnetic pole detection region portion, and a torque generating region portion having a sinusoidal magnetic flux distribution characteristic with respect to the mechanical angle of the motor and formed on the other end side in the axial direction of the rotating shaft to form a cylindrical magnet. Thus, when this rotor is used in a DC brushless motor, the occurrence of a dead center can be prevented, so that the magnetic pole detection means can reliably detect the magnetic pole and generate a high torque. it can.

According to the DC brushless motor rotor of the present invention, the magnetic flux distribution in the magnetic pole detecting area and the magnetic flux distribution in the torque generating area are formed in the same phase with respect to the mechanical angle of the motor. However, when this rotor is used in a DC brushless motor, the magnetic poles in the torque generating region may affect the magnetic pole detection means regardless of whether the magnetic pole detection means is provided on the radial side or the axial side of the rotating shaft. Therefore, the magnetic pole detecting means can accurately detect the magnetic flux in the magnetic pole detection area.

Further, according to the DC brushless motor rotor according to the third aspect, the magnetic pole detection region is formed so that the magnetic pole can be detected from the axial side of the rotating shaft.
When this rotor is used for a DC brushless motor,
Even when the magnetic pole detecting means is not in phase with the magnetic poles of both the magnetic pole detecting area and the torque generating area, the magnetic poles of the torque generating area do not affect the magnetic pole detecting means. The magnetic pole in the magnetic pole detection area can be accurately detected.

According to the DC brushless motor rotor of the fourth aspect, the magnetic pole detection region is formed so that the magnetic pole can be detected from the radial direction of the rotating shaft, so that the magnetic flux of the magnetic pole detection region can be reduced by torque. This can also contribute to the generation, and thus the magnetic flux in the magnetic pole detection region can be effectively used.

According to the DC brushless motor according to the fifth aspect, since the DC brushless motor is provided with the rotor for the DC brushless motor according to any one of the first to fourth aspects, no dead center is generated. High torque can be generated.

[Brief description of the drawings]

FIG. 1 is a perspective view of a rotor in a DC brushless motor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the DC brushless motor according to the embodiment of the present invention.

FIG. 3 is a circuit diagram of a control device that drives the DC brushless motor according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing signal levels output by the Hall IC in each mode in the DC brushless motor according to the embodiment of the present invention.

FIG. 5 is a signal waveform diagram showing a voltage supplied to a stator coil of the DC brushless motor according to the embodiment of the present invention.

6A is a diagram showing a magnetic orientation distribution in a cross section of a cylindrical magnet made of a radial anisotropic magnet, and FIG.
FIG. 3 is a diagram showing a magnetic orientation distribution in a cross section of a cylindrical magnet made of a polar anisotropic magnet.

FIG. 7A is a magnetic flux distribution diagram showing a magnetic flux distribution with respect to a mechanical angle of a cylindrical magnet made of an isotropic magnet and a radial anisotropic magnet, and FIG. FIG. 5 is a magnetic flux distribution diagram showing a magnetic flux distribution with respect to a mechanical angle of a cylindrical magnet.

FIG. 8 shows a Hall I in a conventional DC brushless motor.
It is an arrangement view of C.

FIG. 9 is a perspective view of a rotor in a conventional DC brushless motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC brushless motor 2 Rotor 11 Cylindrical magnet 12 Magnetic pole detection area 13 Torque generation area 14 Rotation axis 15 Motor axis 16 Rotor core

Claims (5)

[Claims] 1. A rotor for a DC brushless motor, comprising: a cylindrical magnet; and a rotating shaft penetrating and fixed to a hollow portion of the cylindrical magnet, wherein the cylindrical magnet has a mechanical angle with respect to a mechanical angle of the motor. A magnetic pole detection region having a rectangular wave-shaped magnetic flux distribution characteristic and formed at one end in the axial direction of the rotating shaft; a sine wave-shaped magnetic flux distribution characteristic with respect to the mechanical angle of the motor; And a torque generating region formed on the other end of the brushless motor. 2. A magnetic flux distribution in a magnetic pole detection area and a magnetic flux distribution in the torque generation area are formed in the same phase with respect to a mechanical angle of the motor.
A rotor for a DC brushless motor as described in the above. 3. The rotor for a DC brushless motor according to claim 1, wherein the magnetic pole detection area is formed so that its magnetic pole can be detected from the axial side of the rotating shaft. 4. The rotor for a DC brushless motor according to claim 2, wherein the magnetic pole detection region is formed so that its magnetic pole can be detected from a radial side of the rotating shaft. 5. A DC brushless motor comprising the DC brushless motor rotor according to claim 1. Description: