JPH0998557A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress increase of coil inductance loss in high speed rotation by decreasing the number of times for switching conduction of coil. SOLUTION: The motor comprises a fixed armature 22 where a coil is wound around a plurality of salient poles, and an annular rotary magnet 26 disposed oppositely to the fixed armature 22 wherein the working r.p.m. of motor is 8000 r.p.m. or above and the rotary magnet 26 has less than eight poles. When the coil comprises a three-phase coil, the number of poles of rotary magnet 26 and the number of salient poles 22a of fixed armature 22 may have following combinations, two poles and three salient poles, four poles and three salient poles, four poles and six salient poles, six poles and nine salient poles, eight poles and six salient poles, eight poles and nine salient poles, and eight poles and twelve salient poles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor applicable to, for example, a drum of a digital video tape recorder or an 8 mm video tape recorder.

[0002]

2. Description of the Related Art A motor shown in FIG. 5 is known as a motor applied to a drum of a video tape recorder or the like. In FIG. 5, a cylindrical fixing member 28 is screwed to the lower end surface side of the substrate 24. Holes 24 in the substrate 24
a is formed. The diameter of the hole 24a is the same as the diameter of the central hole of the fixing member 28.
And the hole of the fixing member 28 communicate with each other. The core holder 2 is provided on the lower end surface side of the substrate 24 and on the outer peripheral side of the fixing member 28.
3 is attached. The fixed armature 22 is attached to the lower end surface of the core holder 23. Fixed armature 2
2 is constituted by laminating a plurality of core plates, has a plurality of salient poles 22a on the outer periphery, and each salient pole 22a
A coil 21 is wound around. Core holder 23,
The fixed armature 22 is fixed to the substrate 24 with screws 32. The tip of the fixed shaft 27 is press-fitted and fixed in the hole 24 a of the substrate 24 and the hole of the fixing member 28 communicating with the hole 24 a.

An inner ring of a ball bearing 29 is fitted and fixed to the outer peripheral surface of the fixed shaft 27 below the fixing member 28. Further, the outer ring of the ball bearing 29 has the frame 3
0 is attached. Frame 30 has a peripheral wall 3 in the center
0c, and the outer peripheral surface of the ball bearing 30 is attached to the inner peripheral surface of the peripheral wall 30c. further,
A rotor case 25 is attached to the frame 30. The rotor case 25 has a hole in the center, the hole is fitted to the peripheral wall 30c, and the lower end surface of the rotor case 25 is placed on and fixed to the upper end surface of the frame 30. The rotor case 25 has a cup-like shape and covers the fixed armature 22 and the fixed member 23 formed on the lower end surface side of the substrate 24 from below.
A rotating magnet 26 is attached to the inner surface of the peripheral wall of the rotor case 25. The inner peripheral surface of the rotary magnet 26 faces the salient poles 22a of the fixed armature 22 with a constant gap. Therefore, by controlling the energization of the coil 21 wound around the salient pole 22a of the fixed armature 22, the rotary magnet 26 is biased and the rotor case 25 is rotationally driven. Along with this, the frame 30 is also driven to rotate.

[0004]

In a normal video tape recorder or the like, the number of magnetic poles formed on the inner peripheral surface of the rotary magnet 26 is 12, and the number of salient poles 22a (number of slots) of the fixed armature 22 is 9. It was configured to get high speed rotation. The rotation speed of the drum motor is usually about 1800 rpm, but in a digital video tape recorder or the like, the recording speed of the tape is increased, so that the rotation speed is 8000 r.
It is necessary to rotate at high speed with pm to 10,000 rpm. The drum motor used in such a digital video tape recorder or the like having a large rotational speed is composed of the rotary magnet 2
The number of magnetic poles formed on the inner peripheral surface of 6 and the number of salient poles 22a of the fixed armature 22 are increased so that the number of magnetic poles is 12 and the number of salient poles 22a is 9.

When the number of magnetic poles of the rotary magnet 26 is increased, cogging at the time of rotation is reduced and the motor characteristic is improved, but the salient pole 22a of the fixed armature 22 is improved.
Therefore, the number of energization switching to the coil 21 (switching number) increases, and the coil inductance loss increases in proportion to this.

The present invention has been made in order to solve the problems of the prior art as described above, and reduces the number of energization switching to the coil to suppress an increase in coil inductance loss during high speed rotation. The purpose is to provide.

[0007]

According to the first aspect of the present invention,
A motor provided with a fixed armature in which coils are wound around a plurality of salient poles, and an annular rotary magnet that is arranged so as to face the fixed armature, wherein the rotation speed of the motor is 8000 rpm or more, and The number of magnetic poles of the rotating magnet is eight or less.

According to a second aspect of the present invention, when the coil is a three-phase coil, the number of magnetic poles of the rotating magnet and the number of salient poles of the fixed armature are two, three, four, and three. 4 poles and 6 poles, 6 poles and 9 poles, 8 poles and 6 poles, 8 poles and 9 poles, 8 poles and 1 pole
It is characterized in that it is two.

Since the number of magnetic poles and the number of salient poles are not large, the number of energization switchings to the coil, the number of switchings, and the generation of coil inductance loss are suppressed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a motor according to the present invention will be described below with reference to the drawings. In addition,
Since the basic structure of the motor is the same as that of the conventional technique shown in FIG. 5, the description thereof will be omitted and the rotating magnet 26, the fixed armature 22 and the like will be mainly described.

First, as shown in FIG. 1, the relationship between the number of magnetic poles of the rotary magnet 26 and the motor characteristics and loss (coil inductance loss) was examined. The rotation speed of the motor in this case is fixed at 9000 rpm. Motor characteristics (efficiency) when the number of magnetic poles of the rotating magnet 26 is two
Is more than Ross. Although the efficiency and the loss both increase as the number of magnetic poles increases, the increase in the efficiency becomes slower particularly when the number of magnetic poles exceeds 6. When the number of magnetic poles is 8, the loss and the efficiency substantially match, and when the number of magnetic poles is more than 8, the loss exceeds the efficiency. Therefore, it can be understood that in order to form a motor with reduced loss, it is sufficient to set the loss within a range in which the efficiency is higher, that is, the number of magnetic poles is 2 or more and 8 or less.

In a motor having eight or less magnetic poles, the combination of the number of magnetic poles of the rotary magnet 26 and the number of salient poles 22a of the fixed armature 22 is two or three as shown in FIG. Figure 2
4 poles and 3 poles as shown in FIG. 2B, 4 poles and 6 poles as shown in FIG. 2C, 8 poles and 6 poles as shown in FIG. 2D, and FIG. 2E. There are a total of 7 sets of 6 poles and 9 poles, 8 poles and 9 poles, and 8 poles and 12 poles (not shown). By using one of these 7 combinations, 8
The desired characteristics can be obtained even at a high speed of 000 rpm or more, and moreover, the number of times of switching can be reduced and the coil inductance loss can be reduced.

The rotating magnet 26 has eight magnetic poles and the fixed armature 22 has six salient poles 22a.
The NT characteristics were examined with a motor having six magnetic poles of 12 and a fixed armature 22 having nine salient poles 22a. This result
This is shown in FIGS. In the motor shown in FIG. 3 in which the number of magnetic poles of the rotating magnet 26 is 8 and the number of salient poles 22a of the fixed armature 22 is 6, the torque is approximately 0.5 mNm, 100 at 9000 rpm.
The torque is about 0.4 mNm at 00 rpm, which satisfies the required characteristics. On the other hand, in the motor shown in FIG. 4 in which the rotating magnet 26 has 12 magnetic poles and the fixed armature 22 has 9 salient poles 22a, the torque is 0.5 at 9000 rpm.
The torque does not reach 0.4 mNm at mrpm and 10,000 rpm, and the required characteristics cannot be satisfied. This is because the current flowing through the coil 21 increases as the load applied to the motor increases, but since the number of magnetic poles of the rotating magnet 26 is 12 and the number of salient poles 22a is 9, the coil 21 through which large current flows The number of energization switching of the coil is significantly increased from that shown in FIG.
This is because the inductance loss will increase. From the graphs of FIGS. 3 and 4 as described above, when the rotation speed of the motor is 8000 rpm or more, it is possible to obtain desired motor characteristics by setting the number of magnetic poles of the rotating magnet to 8 poles or less, Moreover, it can be understood that the number of switching the energization of the coil 21 can be reduced to reduce the coil inductance loss.

[0014]

According to the present invention, when the number of revolutions of the motor used is 8000 rpm or more, the number of magnetic poles of the rotary magnet is set to 8 or less, so that desired motor characteristics can be obtained and the number of energization switching to the coil can be reduced. Coil inductance due to decrease
Loss can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the number of magnetic poles of a magnet, the characteristics of a motor, and loss.

FIG. 2 is an enlarged plan view of an essential part showing an embodiment of a motor according to the present invention.

FIG. 3 is a diagram showing an NT characteristic of a motor when the number of magnetic poles of a rotating magnet is 8 and the number of salient poles of a fixed armature is 6.

FIG. 4 is a diagram showing an NT characteristic of a motor when the number of magnetic poles of a rotating magnet is 12 and the number of salient poles of a fixed armature is 9.

FIG. 5 is a sectional view showing an example of a conventional motor.

[Explanation of symbols]

 21 coil 22 fixed armature 22a salient pole 26 rotating magnet

Claims (2)

[Claims] 1. A motor provided with a fixed armature in which a plurality of salient poles are wound with a coil, and an annular rotary magnet arranged to face the fixed armature, wherein the motor has a rotational speed of 8000 rpm. The motor described above is characterized in that the number of magnetic poles of the rotating magnet is eight or less. 2. When the coil is a three-phase coil, the combination of the number of magnetic poles of the rotating magnet and the number of salient poles of the fixed armature is two poles and three poles, four poles and three poles, four poles and six poles. , 6 poles and 9
2. The motor according to claim 1, wherein the motor has 8 poles and 6 poles, 8 poles and 9 poles, 8 poles and 12 poles.