JPH09131033A - Plane facing type brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plane facing type brushless motor, which can make the length of a driving coil long without increasing the maximum outer diameter of the driving coil and can thereby make the torque of the motor larger. SOLUTION: This motor is constituted of a rotor having a rotary shaft 3, which is rotatably supported with a bearing 6 held on a base member 7, a rotor yoke 2 attached to the rotary shaft 3 and an annular magnet 1 fixed to the rotor yoke 2, and a stator comprising a driving coil group 4, which is arranged so as to face the annular magnet 1, and a stator substrate 5 supporting the driving coil group 4. At this time, the angle formed by both coil sides of a driving coil 4a is made substantially equal to the opening angle of the maximum exclusive region assigned for one driving coil 4a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a face-to-face brushless motor, and more particularly to a brushless motor suitable for an optical scanner used in a laser printer, a digital copying machine or the like.

[0002]

2. Description of the Related Art Conventionally, regarding the shape of a drive coil of a brushless motor, "control motor technology utilization manual"
On page 176 of "Sogaku Denshi Shuppansha" (published in February 1987), "The coil pitch is matched with the pole pitch of the field magnet.", And the opening angle of the drive coil is the opening angle of the magnetic pole of the annular magnet. Equalization is disclosed. That is, when the number of magnetic poles of the annular magnet is 8,
The drive coil has an opening angle of 360 ° / 8 poles = 45 °.

When designing a face-to-face type brushless motor, if the layout is designed in consideration of miniaturization,
As shown in FIG. 7, the maximum outer diameter Dmax of the drive coil 40a
Is limited. At this time, the length of the drive coil 40a effective for the torque of the motor is the coil effective length Ly between the coil center outer diameter Dg and the coil center inner diameter Dn.

Further, in Japanese Unexamined Patent Publication No. 62-281748, as shown in FIG. 8, the drive coil 140 is more than the opening angle θc of the maximum occupation area allocated to the drive coil 140a.
It is disclosed that the outside opening angle θo of a is small.

[0005]

However, in the first prior art described above, the maximum opening angle of the drive coil 40a is set to 45 degrees and the outer opening angle θo is set to 45 when the number of magnetic poles of the annular magnet is eight. It was smaller than the degree. Also in the second conventional technique, the outer opening angle θo is smaller than the maximum opening angle θc.

Therefore, even if there is a structural allowance in the coil inner diameter direction Dn, the adjacent drive coils 40a (140)
There is a problem that the length Ly of the drive coil 40a (140a) cannot be lengthened in the center direction because the contact a) occurs. Therefore, the drive coil 40a (140a) does not need to have a large outer diameter to obtain a large torque.
There was a problem that the length could not be increased.

Therefore, in order to obtain a large torque, for example, if the volume of the annular magnet is increased, downsizing becomes difficult, the cost also increases, the moment of inertia of the rotating body increases, and the startup of the motor slows down. I have a problem.

As another method of obtaining a large torque, if a material of the annular magnet having a large maximum energy product (for example, a rare earth cobalt magnet) is used, not only the cost is increased but also the magnetization distribution is steep, resulting in uneven torque. However, there is a problem that it is necessary to take measures against torque unevenness.

Therefore, an object of the present invention is to increase the length of the drive coil and increase the coil width without increasing the maximum outer diameter of the drive coil, thereby increasing the torque of the motor. An object of the present invention is to provide a face-to-face brushless motor capable of increasing the size.

[0010]

In order to achieve the above object, the present invention employs the following means. That is,
2. A surface-opposed brushless motor according to claim 1, wherein the rotor includes a rotating shaft rotatably supported by a bearing held by a base member, a rotor yoke attached to the rotating shaft, and an annular magnet fixed to the rotor yoke. A surface-opposed DC brushless motor including a drive coil group arranged to face the annular magnet and a stator including a stator substrate holding the drive coil group, wherein both sides of the drive coil are formed. It is characterized in that the angle is substantially the same as the opening angle of the maximum occupied area allocated for one drive coil. In this way, since the opening angle of the maximum occupied area allocated for the drive coil and the angle formed by both coil sides of the drive coil are substantially the same, even if both sides of the drive coil are extended in the center direction. There is no contact.

A surface-opposed brushless motor according to a second aspect of the present invention is the surface-opposed brushless motor according to the first aspect, wherein the annular magnets have the same opening angle of the magnetic poles and the number of magnetic poles is 2P (P is an even number of 4 or more). It is characterized by consisting of the field.

A surface-opposed brushless motor according to a third aspect of the present invention is the surface-opposed brushless motor according to the second aspect, wherein the drive coil group is composed of three or six drive coils so that they do not overlap each other. It is characterized by being arranged.

A surface-opposing brushless motor according to a fourth aspect is the surface-opposing DC brushless motor according to any one of the first to third aspects, wherein the base member is made of a non-magnetic material, and a magnetic path of a magnetic flux emitted from the annular magnet. Is formed in an open magnetic circuit.

A surface-opposed brushless motor according to a fifth aspect is the surface-opposed brushless motor according to any of the first to third aspects, wherein the base member is made of a magnetic material and a magnetic path of a magnetic flux emitted from the annular magnet is formed as a closed magnetic path. It is characterized by having done.

A surface-opposed brushless motor according to a sixth aspect of the present invention is the surface-opposed brushless motor according to any one of the first to fifth aspects, characterized in that a stator yoke is arranged above the base member.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional view of a rotary polygon mirror scanning device equipped with a face-to-face brushless DC motor according to an embodiment of the present invention.

As shown in the figure, the rotor portion of the face-to-face brushless DC motor has a rotating shaft 3 rotatably supported by a base member 7 via a bearing 6 and a rotating shaft 3 via a flange 9. An annular magnet 1 fixed to the upper part of the rotor, an annular rotor yoke 2 fixed to the upper surface of the annular magnet 1, and a spring 11 as an elastic member on the flange 9.
The rotary polygon mirror 10 fixed via the.

The flange 9 is made of a material such as aluminum, brass or plastic, and the rotor yoke 2 is made of a material such as iron. The annular magnet 1 has the same opening angle (45
The N poles and the S poles are alternately magnetized in 8 degrees. The number of poles for this magnetization may be an even number of 8 or more.

The stator of the face-to-face brushless DC motor is fixed to the base member 7 made of aluminum, plastic or the like for supporting the bearing 6 and the base member 7 with screws 12 or the like, and has a slight gap in the annular magnet 1. And
The stator substrate 5 facing in parallel, the drive coil group 4 fixed to the stator substrate 5 on the side opposite to the annular magnet 1, and the upper part of the base member 7 facing the drive coil group 4 with a slight gap therebetween. An annular stator yoke 8 made of iron, silicon, or a steel plate is fixed to the. In the drive coil group 4, six drive coils 4a are fixed at an equal angle of 60 degrees. The number of drive coils 4a may be three.

By arranging the stator yoke 8 above the base member 7 as described above, the magnetic path of the magnetic flux emitted from the annular magnet 1 is formed in a closed magnetic path, so that the leakage magnetic flux is reduced and the magnetic flux flows to the drive coil group 4. The effective flux linkage of
High torque can be obtained. Further, by disposing the stator yoke 8, the base member 7 can be arbitrarily selected regardless of whether it is a magnetic material or a non-magnetic material.

By forming the base member 7 from a non-conductive material or a non-conductive material and a non-magnetic material, the magnetic path of the magnetic flux emitted from the annular magnet 1 is formed as an open magnetic path.
Since the hysteresis loss and the eddy current loss do not occur by forming the open magnetic circuit in this manner, the efficiency can be improved in the high-speed rotation region where the loss due to the hysteresis loss and the loss due to the eddy current are larger than the loss due to the leakage magnetic flux. Further, since the stator yoke is removed, the cost can be reduced and the motor can be made thinner.

By forming the base member 7 from a magnetic material, the magnetic path of the magnetic flux emitted from the annular magnet 1 is formed into a closed magnetic path. By forming the closed magnetic path in this way, the magnetic path of the magnetic flux emitted from the annular magnet 1 is formed in the closed magnetic path, so that the leakage magnetic flux is reduced and the drive coil group 4 is formed.
Since the effective interlinkage magnetic flux increases, a high torque is obtained, and the stator yoke 8 is removed, the cost can be reduced and the motor can be made thinner.

FIG. 2 is a diagram showing a drive coil according to the present invention. In the drive coil 4a, the inside opening angle is set to 54 degrees with the dimensions shown in FIG. Further, the angle formed by both coil sides 4b of the drive coil 4a is substantially the same as the opening angle of the maximum occupied area allocated for one drive coil 4a. That is, when there are six drive coils as in this example, as shown in FIGS.
The angle formed by the outer portions of both coil sides 4b of a was set to 60 degrees. Here, “substantially the same” includes an angle range that produces the same effect.

FIG. 3 is a view showing a drive coil according to the present invention and a conventional drive coil in a comparative example in an overlapping manner. In the figure, the drive coil group 4 according to the present invention is shown by a solid line, and the drive coil group of the comparative example is shown. 4'is indicated by a dotted line. As the drive coil 4'of the comparative example shown by the dotted line in FIG. 3, a drive coil having an inner open angle of 45 degrees and an outer open angle of sufficiently smaller than 60 degrees was used. As shown in FIG. 3, in the surface-opposed brushless motor of the present invention, the coil portion Ly effective for generating torque can be designed to be long in the center direction without the adjacent drive coils 4a coming into contact with each other.

In the drive system of the face-to-face brushless motor of the present invention, the drive coil 4 is of the bipolar system connected as shown in FIG. Since the biboler method is adopted in this manner, the utilization factor of the windings is high and the efficiency is high, and thus it is characteristically superior to other methods.

FIG. 5 shows the measurement result of the voltage induced between the U phase and the V phase. In the case of the drive coil group 4 according to the present invention,
The power generation was 5.38V, and the drive coil group 4'of the comparative example generated 4.46V. That is, the drive coil group 4 according to the present invention increased the torque by about 20% as compared with the drive coil group 4'of the comparative example.

FIG. 6 shows an example of a face-to-face type DC brushless motor.
The result of having measured the U-phase applied voltage when rotating at 2000 rpm is shown. The drive coil group 4 of the present invention has less voltage distortion. As a result, noise was reduced and the capacity of the regenerative capacitor was reduced.

From the above specific example, the torque could be increased by 20% without changing the material and size of the driving magnet. In addition, the torque can be increased to 2 without changing the size of the motor.
I was able to increase by 0%. Furthermore, since the shape of the drive coil is only changed, the torque can be increased to 2 without increasing the cost.
I was able to increase by 0%. Moreover, the distortion of the drive voltage is reduced,
The smaller capacity of the regenerative capacitor led to lower costs and reduced noise. In addition, it was possible to wind more windings having a thicker wire diameter, and it was possible to improve motor characteristics.

[0029]

As described above, according to the surface-opposed brushless motor of the present invention, the length of the drive coil can be increased in the central axis direction, so that the maximum outer diameter of the drive coil is not increased. The effective length of the drive coil can be increased, the coil width can be increased, and the torque of the motor can be increased.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view of a rotary polygon mirror scanning device equipped with a face-to-face brushless DC motor according to the present invention.

FIG. 2 is a diagram showing a drive coil according to the present invention.

FIG. 3 is a diagram showing a drive coil according to the present invention and a drive coil of a comparative example in an overlapping manner.

FIG. 4 is a diagram showing a connection state of drive coils.

FIG. 5 is a diagram showing an induced voltage between a U phase and a V phase of a drive coil.

FIG. 6 is a diagram showing a drive voltage in a U phase of a drive coil.

FIG. 7 is a diagram showing a drive coil of a conventional brushless motor.

FIG. 8 is a diagram showing a drive coil of another conventional brushless motor.

[Explanation of symbols]

 1 Annular Magnet 2 Rotor Yoke 2 3 Rotating Shaft 4 Drive Coil Group 4a Drive Coil 4b Coil Side 5 Stator Substrate 6 Bearing 7 Base Member θ Opening Angle

Claims (6)

[Claims] 1. A rotor including a rotary shaft rotatably supported by a bearing held by a base member, a rotor yoke attached to the rotary shaft, and an annular magnet fixed to the rotor yoke, and a rotor facing the annular magnet. In a face-to-face brushless DC brushless motor composed of a drive coil group arranged in such a manner and a stator composed of a stator substrate holding the drive coil group, an angle formed by both coil sides of the drive coil is defined as one drive coil. A face-to-face brushless motor characterized in that the opening angle of the maximum occupied area allocated for is substantially the same. 2. The surface-opposed brushless motor according to claim 1, wherein the annular magnet is composed of 2P (P is an even number of 4 or more) magnetic poles having the same opening angle of magnetic poles. 3. The surface-opposed brushless motor according to claim 2, wherein the drive coil group is composed of three or six drive coils and arranged so as not to overlap each other. 4. The face-to-face brushless DC brushless motor according to claim 1, wherein the base member is made of a non-magnetic material, and the magnetic path of the magnetic flux emitted from the annular magnet is formed as an open magnetic path. . 5. The surface-opposed brushless motor according to claim 1, wherein the base member is made of a magnetic material, and a magnetic path of a magnetic flux emitted from the annular magnet is formed in a closed magnetic path. 6. The surface-opposed brushless motor according to claim 1, wherein a stator yoke is arranged above the base member.