JPH0370459A - Flat brushless motor - Google Patents

Abstract

PURPOSE:To manufacture a thin and high output motor with low cogging product at low cost by putting the salient pole parts of the stator core of a case rotating flat brushless motor in nine pieces, and forming six pieces of rotor magnets out of rubber magnets. CONSTITUTION:A stator core 4, which has nine pieces of salient poles 5 radially, is mounted on the housing 1 of a bearing 2, which supports a spindle 3 freely in rotation. A coil 9 is wound around the salient pole 5. The ratio of the area of the top enlarged part 8 of the salient pole 5 to the sectional area of the winding part 7 is set to 2-4. Six pieces of rotor magnets 11 consisting of rubber magnets, wherein the polarities are inverted alternately, are attached to the inner periphery of the circumference of a cup-shaped rotor yoke 10. The outside diameter D of the stator core 4 is set to 40-80mm, and the thickness T is set to 4-8mm. Hereby, a thin and high output motor can be manufactured at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a circumferentially opposed flat brushless morph in which the outer circumferential surface of a stator core and the inner circumferential surface of a rotor magnet are opposed to each other via an air gap.

[Conventional technology]

As a flat brushless morph such as a spindle motor, a shaft (spindle) is rotatably supported in a housing, a radial stator core is fixed to the housing, and a coil is wound around each salient pole of the stator core. For example, Japanese Patent Laid-Open No. 19949-1989 discloses a circumferentially opposed flat brushless morph having a structure in which an externally rotating rotor is fixed from a rotor yoke and a rotor magnet.

This type of motor is suitable for pivotally supporting and rotating a laser disk scanner or the like with high precision.

[Technical problem to be solved by the invention] Flat brushless motors are required to be thinner and have higher torque in response to the miniaturization and lighter weight of precision equipment in which they are used, and at the same time, it is necessary to maintain high torque. At the same time, there is also a need to reduce cogging and reduce costs.

However, in conventional structures, maintaining a thin structure and high output and reducing costs are completely contradictory, and it has been extremely difficult to achieve both.

The present invention was made in view of such technical problems, and an object of the present invention is to provide a spindle motor type flat brushless motor that is thin and maintains high torque while achieving low cogging and cost reduction. shall be.

[Means for solving problems]

In the present invention, a shaft is rotatably supported in a housing, a radial stator core is fixed to the housing, a coil is wound around each salient pole of the stator core, and an outer body consisting of a rotor yoke and a rotor magnet is attached to the shaft. In flat brushless motors with a fixed rotating rotor,
With a configuration in which the magnet is formed of a rubber magnet, the number of the salient pole portions of the stator core is set to 9, and the number of magnetic poles in the circumferential direction of the magnet is set to 6, respectively,
The present invention provides a flat brushless motor that is thin and maintains high output while reducing costs.

〔Example〕 The present invention will be specifically described below with reference to the drawings.

FIG. 1 is a central vertical cross-sectional view of a flat brushless motor according to the present invention, and FIG. 2 is a cross-sectional view taken along line n-' in FIG.

1 and 2, a shaft (spindle) 3 is rotatably supported in the center of a housing (bearing housing) 1 via a bearing 2.2.

A radial stator core 4 is fixed to the outer periphery of the housing 1, and a predetermined number of coils 9 are attached to the stator core 4.
is wrapped.

FIG. 3 is a partial perspective view of the stator core 4 and coil 9.

This stator core 4 is constructed by laminating punched steel plates,
A plurality of salient pole portions 5 are formed at equally spaced positions in the circumferential direction. A slot (groove) 6 is formed between each salient pole portion 5 .

Each salient pole portion 5 has a winding portion 7 and an enlarged tip portion 8.
The coil 9 is wound around the coil 9.

On the other hand, a cup-shaped rotor yoke 10 is fixed to one end of the shaft 3, and an annular rotor magnet 11 is fixed to the inner surface around the rotor yoke 10. The rotor of the formula is constructed.

FIG. 4 is a perspective view of the rotor.

The rotor magnet 11 is made of a permanent magnet, and has a plurality of magnetic poles (N pole, S pole) formed in the circumferential direction.

A front portion 112 is fixed to the housing l in parallel with the stator yoke 4.

before this! A circuit board 13 is bonded to the inner surface of the rotor magnet 12 (the surface of the rotor magnet 11 examples).

Figure 5 is before the above! 12 is a perspective view of the inner surface side of FIG.

The circuit board 13 is provided with a Hall element 14 for detecting the magnetic pole of the rotor magnet 11, and a drive circuit that sequentially supplies current to each coil 9 in accordance with the output signal of the Hall element 14. There is.

A three-phase winding system (U, ■, W) is adopted for excitation of the coil 9.

FIG. 6 is a diagram showing the connection state of each coil 9.

Therefore, according to the present invention, a shaft 3 is rotatably supported in a housing l, a radial stator core 4 is fixed to the housing l, and each salient pole portion 5 of the stator core 4 is fixed to the housing l.
In a flat brushless morph in which a coil 9 is wound around the shaft 3 and an external rotor consisting of a rotor yoke 10 and a rotor magnet 11 is fixed to the shaft 3, the magnet is formed of a rubber magnet, and the protrusion of the stator core is fixed to the shaft 3. A configuration is adopted in which the number of pole parts is set to nine, and the number of magnetic poles in the circumferential direction of the magnet is set to six.

The rubber magnet forming the rotor magnet 11 is made by mixing and dispersing magnetic powder such as ferrite powder into rubber, vulcanizing the rubber to form an annular magnetic rubber member, and then inserting it into a predetermined magnetic pole. It is made into a permanent magnet by magnetizing it in an array.

According to the flat brushless morph having the above configuration, first, since the rotor magnet 11 is formed of the rubber magnet, it can be manufactured at a lower cost in terms of processing equipment, processing steps, and material costs compared to conventional ferrite or plastic magnets. Therefore, it was possible to significantly reduce the cost of the magnet 11.

Furthermore, by using the rubber magnet 11, the disadvantages of plastic magnets can be overcome, and the following advantages can be obtained.

In other words, in plastic magnets, when plastic mixed with magnetic powder is injection molded in a mold, the magnetization distribution is disturbed at the weld line between the gates (the place where the flowing tip of the molten plastic meets in the mold). In addition, during molding, especially when applying an anisotropic magnetic field in the radial direction, uneven orientation of anisotropy tends to occur depending on the flow of the plastic. There was a drawback that variations were likely to occur and the cogging torque (i) and its variation were large.

In addition, in the case of sintered ferrite magnets, the annular ones are pressed and molded, so when an anisotropic magnetic field is applied in the radial direction, some degree of uneven magnetization occurs, which is not the case with plastic magnets. , the value of cogging torque and its dispersion were not small.

On the other hand, rubber magnets are manufactured by applying a uniform magnetic field in the thickness direction to a large sheet, cutting it into strips, curving it into an annular shape, and joining both ends. , the anisotropic orientation unevenness is extremely small, and as a result, the multipolar form of magnetization and the peak of the magnetic flux density are uniform, and the cogging torque value and its dispersion are also small.

Fig. 8 is a graph showing the magnet surface magnetic flux density distribution in the circumferential direction of the plastic magnet (A) and the rubber magnet (B), and Fig. 9 is a graph showing the rotor rotation of the plastic magnet (A) and the rubber magnet (B). It is a graph which shows the fluctuation state of the cogging torque with respect to an angle.

In FIG. 8(A), α indicates the degree of unevenness in the peak value of the magnetic flux density in the case of the above-mentioned plastic magnet, and β indicates the state of disturbance in the magnetic flux distribution due to the above-mentioned weld line.

FIG. 8(B) shows the case of a rubber magnet, and it can be seen that the multipole magnetization shapes and magnetic flux density peak values are uniform.

In FIG. 9 (A), in the case of a plastic magnet, the cogging torque value itself is large due to the magnetic flux distribution as shown in FIG. x and y are larger.

On the other hand, in the case of a rubber magnet, (B
), because of the magnetic flux distribution as shown in FIG. 8(B), the cogging torque value is small and its variation is small.

In addition, the number of salient pole parts 5 of the stator core 4 is set to 9, and the number of magnetic poles of the rotor magnet 11 is set to 6, so that the number of slots (same as the number of salient pole parts 5) in the conventional motor of this type is 6.
And since the number of magnetic flux has been increased compared to the 4iff pole structure,
If other conditions are the same, the output torque can be improved by increasing the magnetic flux energy.

Generally, in order to increase the starting torque, it is necessary to increase the number of magnetic poles, and in order to improve the linearity of torque characteristics (for high speeds), it is necessary to decrease the number of magnetic poles.

FIG. 7 is a graph showing the magnitude of the starting torque and the quality of linearity with respect to the number of slots and the number of magnetic poles.

In general, coil inductance delays the rise of current at the start of commutation, so in multi-polar motors, the linearity of torque characteristics tends to decrease in a high rotation range.

For this reason, it is not a good idea to increase the number of slots and the number of magnetic poles too much in a high-speed motor, and there is a limit to the number of slots and magnetic poles.

In the present invention, the number of salient pole portions 5 (same as the number of slots 6) is nine, and the number of the rotor magnets 11 is set to nine, taking into consideration the balance between securing the starting torque and linearity of torque characteristics as described above. The number of magnetic poles was selected to be six.

Incidentally, the rubber magnet 11 generally has a lower magnetic flux density than conventional permanent magnets such as ferrite, and if left as is, the output torque will be lower than that of the conventional structure.

However, in the configuration of the present invention, the number of salient pole portions 5 and the number of magnetic poles of the rotor magnet 11 are increased to 9 and 6 to increase the number of magnetic fluxes.
Even if 1 is used, the overall effective magnetic flux number can be maintained at the same level or higher.

Therefore, according to the configuration of the present invention, by using a rubber magnet as the rotor magnet 11 while ensuring sufficient output torque, it was possible to achieve low cogging and significant cost savings.

Furthermore, by utilizing the increase in output torque due to the increase in the number of magnetic fluxes, it is possible to make the motor thinner while ensuring sufficient torque. At this time, the thickness T of the stator core 4 could be reduced to a range of 4s to 8 plates, and the thickness could be reduced by about 20% to 30% compared to the conventional structure.

In addition, regarding the shape and dimensions of the salient pole portion 5 of the stator core 4, the ratio of the outer circumferential area of the enlarged tip portion 8 to the cross-sectional area of the winding portion 7 is set to be smaller than that of the conventional structure, and is selected from 2 to 4. It is preferable.

The reason for this is, as mentioned above, because the number of magnetic flux paths has been increased, the leakage magnetic flux of the winding section 7 tends to increase and losses tend to occur. This is because if the cross-sectional area is made relatively large, energy efficiency can be improved by eliminating or reducing leakage magnetic flux.

That is, the outer diameter is 40m+a ~ 80mm and the thickness T
In a flat and thin stator core with a length of about 4 m to 8 m, if the coil volume is increased and the winding part 7 is made thinner to ensure torque, the cross-sectional area ratio of the enlarged tip part 8 to the winding part 7 will increase, and the torque will increase. Magnetic saturation of the core occurs in the region where is large.

As a result, non-linearity of torque characteristics appears in this large torque region, resulting in a decrease in torque.

From these facts, the cross-sectional area ratio of the enlarged tip portion 8 to the winding portion 7 is 21 to 4:l in order to prevent torque reduction.
The range of is optimal.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a shaft is rotatably supported in a housing, a radial stator core is fixed to the housing, and a coil is wound around each salient pole of the stator core, In a flat brushless motor comprising an externally rotating rotor fixed to the shaft by a rotor yoke and a rotor magnet, the magnet is formed of a rubber magnet, the number of the salient poles of the stator core is nine, and the magnet is formed of a rubber magnet. Since the number of magnetic poles in the circumferential direction is set to six, it is possible to obtain a flat brushless morph that is thin and maintains high output while achieving low cogging and cost reduction.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an embodiment of a flat brushless motor according to the present invention, FIG. 2 is a cross-sectional view taken along line -H in FIG. 2, and FIG. 3 is a stator core and a FIG. 4 is a perspective view of the shaft and rotor in FIG. 1, FIG. 5 is a perspective view of the inside of the front cover in FIG. 1, and FIG. 6 is a partial perspective view of each coil in FIG. 2. Wiring diagram showing the connection state, Figure 7 is a graph showing the magnitude of starting torque and linearity of torque characteristics with respect to the number of poles, Figures 8 and 9 are magnetic flux density distribution and cogging torque of plastic magnet and rubber magnet, respectively. This is a graph showing. l...- Housing, 3...- Axis (spindle), 4...- Stator core, 5...- Salient pole portion, 9-- Coil, 10... ...--Rotor yoke, 11--Rotor magnet, D--...
−・−Outer diameter of stator core, T・−・Thickness of stator core. Figure 1 Figure Figure Figure ■ Figure Figure Figure Entrance, To Chichi (3) (6) (9) (12) C18)

Claims (1)

[Claims] (1) A shaft is rotatably supported in a housing, a radial stator core is fixed to the housing, and a coil is wound around each salient pole of the stator core, and an outer shaft consisting of a rotor yoke and a rotor magnet is mounted on the shaft. In the flat brushless motor having a fixed rotor, the magnet is formed of a rubber magnet, and the number of the salient pole portions of the stator core is set to 9, and the number of magnetic poles in the circumferential direction of the magnet is set to 6. A flat brushless motor characterized by: