JPH10178768A - Fan motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fan motor of simple structure that enables to stabilize the bias of a drive circuit and the reduce the cost for electronic components applicable to the drive circuit by reducing vibration, when the polarity is switched during operation, and thereby reducing noise during operation and noise produced due to vibration, when the motor is installed in a machine and the quantity of power generated is coils during rotation. SOLUTION: A triangular coil 7 is formed by bifilar winding using a first coil 5 and a second coil 6 and is disposed, so that the center of the coil 7 coincides with the rotational axis of a rotor. The first coil 5 and the second coil 6 are connected with a drive circuit that switches polarity, and the currents passed through the coils are reversed when the polarity is switched. Therefore, the magnetic fields produced in the coil are canceled out, and the attractive force and the repulsive force produced in magnets and the coil are reduced. Thus vibration in the axial direction during motor running can be reduced. Further, the quantity of power generated in the coil can be minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan motor in which a magnet attached to a rotor and a coil attached to a stator face each other so as to be parallel to a rotation axis of the rotor.

[0002]

2. Description of the Related Art In recent years, the performance of personal computers has rapidly improved,
Accordingly, heat generated from each electronic component such as a CPU increases, and a cooling fan motor is indispensable. Not only in the case of a personal computer but also in an electronic system device, when a cooling fan motor is mounted, quietness is required.

[0003]

By the way, in a fan motor of a type in which a facing direction of a magnet attached to a rotor and a coil attached to a stator is arranged so as to be parallel to a rotation axis of the rotor. The arrangement in which a large number of coils are arranged on the stator has a drawback in that the rotor is attracted and repulsed when the polarity is switched during operation, causing vibration. Also, since an induced electromotive force is generated in the coil, the differential amplifier circuit, which is the drive circuit,
During start-up and operation, the coil current changes greatly, making it impossible to stabilize the bias voltage. In addition, due to power generation noise, electronic components used in the circuit must have high withstand voltage.

[0004] It is an object of the present invention to reduce the noise at the time of operation and the noise at the time of mounting the device by reducing the vibration at the time of polarity switching during operation, and to reduce the power generation of the rotating coil. It is an object of the present invention to provide a fan motor with a simple structure, which can stabilize the bias of a drive circuit and reduce the cost of electronic components that can be used in the drive circuit by suppressing the size of the fan motor.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a fan motor according to the present invention is arranged so that a facing direction of a magnet attached to a rotor and a coil attached to a stator are parallel to a rotation axis of the rotor. In the fan motor of the type arranged in such a manner, the triangular coil is arranged facing the center of the rotor so that the center thereof coincides with the rotation axis, and the triangular coil is wound twice. A drive circuit for switching the polarity is connected to the two-turn coil to reduce the amount of power generated in the coil and to form a triangular shape with the magnet generated in the direction parallel to the rotation axis when the polarity is switched. It is configured to reduce the attraction and repulsion of the coil. Further, the polarity switching in the present invention,
This is performed by detecting the direction of the magnetic field with a magnetic sensor.

[0006]

According to the above construction, the vibration of the fan motor at the time of polarity switching can be reduced with a simple structure. In addition, since the amount of power generated by the rotating coil can be suppressed, the bias of the drive circuit can be stabilized. Further, it is possible to use an electronic component having a low withstand voltage, thereby reducing the cost.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram for explaining a positional relationship between a magnet of a fan motor and a triangular coil according to the present invention. FIG. 1 shows a triangular coil attached to a stator with a magnet attached to a rotor on the upper side. FIG. 4 shows a plan view in which a coil is arranged on a lower side. The triangular coil 7 which was formed by winding bundled with the first coil (L ₁₎ 5 the second coil (L ₂₎ 6, the first coil (L ₁₎ 5 and the second
A drive current is passed through each of the coils (L ₂ ) 6.

The triangular coil 7 is arranged at a position where the center of the coil 7 coincides with the center of the rotor. The Hall element 3 is installed at a position 30 degrees away from the vertex of the triangular coil 7. The magnet 1 is configured by alternately arranging S poles 1a and N poles 1b on a rotor.
S pole 1a from the position of Hall element 3 by coking torque
And stop at a position advanced 15 degrees from the boundary between the N pole 1b.

FIG. 2 is a plan view and a side view showing a positional relationship between a magnet and a triangular coil of the fan motor according to the present invention. Fig. 2 shows the position of the magnet 1 of the rotor.
When in the positional relationship shown in (a), the rotational torque is zero.
At this time, the area of the magnet 1 applied to the triangular coil 7 is about 50% larger in the N pole 1b than in the S pole 1a in FIG. As a result, the rotor receives suction or repulsion torque. In the example of FIG. 2A, the rotor receives a suction force. That is, as shown in the model diagram of FIG.
The magnetic field generated in the coil generates an S pole on the side facing the N pole of the magnet, so that the magnet is attracted. The suction position is near the apex of the triangle of the coil 7, which causes vibration during the operation of the fan motor. Next, when the current direction is switched in FIG. 2, a repulsive force is generated.

[0010] The motor of this type uses the suction,
As is clear from the repulsion torque characteristic, the repulsion torque is generated in the axial direction with the polarity switching position being the maximum. In the case of the bipolar drive, a rectangular wave as shown in FIG. 3C is obtained, and a large suction repulsion torque is generated. If the current waveform at the time of polarity switching is made gentle, the suction repulsion will be reduced to some extent, but there will be a problem in circuit stability and the like. Therefore, in the present invention, as described above, the triangular coil 7 is formed by two windings in order to further reduce the torque in the axial direction including before and after the polarity switching.

FIG. 4 is a circuit diagram showing an embodiment of a drive circuit for a fan motor according to the present invention. The first coil (L
₁ ) One end of 5 and the second coil (L ₂ ) 6 is connected to the power supply side, and the other end is connected to the collectors of the transistor (Tr ₁ ) 10 and the transistor (Tr ₂ ) 11, respectively. The bases of the transistor (Tr ₁ ) 10 and the transistor (Tr ₂ ) 11 are connected to the output terminals a and b of the Hall element 3, respectively. Protective resistors (R ₁ ) and (R ₂ ) are connected to the power terminal and the ground terminal of the Hall element 3, respectively. Transistor (Tr ₁ ) 10 and transistor (T
A bias resistor (R) 14 is connected to the emitter of r ₂ ) 11.

This circuit is a differential amplifying circuit, and the first coil (L ₁ ) 5 depends on the magnitude of the output signal of the Hall element 3.
And the second coil (L ₂ ) 6 is saturated. The surface magnetic field of the magnet is as shown in FIG. 5A, and the Hall element 3 amplifies this and outputs it to the terminals a and b as a Hall output voltage. In this circuit, current flows through both the first coil (L ₁ ) 5 and the second coil (L ₂ ) 6 for differential amplification before and after the polarity switching. Since the direction of this current is opposite for both coils as shown in FIG. 6, the magnetic field generated in each coil is negated. Therefore, the attraction and repulsion generated between the magnet and the coil in the axial direction is reduced, and the vibration in the axial direction during rotation of the motor can be reduced. FIG. 5C shows a waveform of a current flowing through both coils due to the above operation. At the time of current switching, the waveform has a rising and falling slope compared to FIG.

FIG. 7 is a diagram for explaining a position where the amount of power generation of the coil is minimized. When the motor torque is maximum, the neutral point of the magnet NS is rotated to the vertex position of the triangular coil as shown in FIG.
By arranging the two-turn coil at the center of rotation of the magnet, power generation to the coil is minimized. As shown in FIG. 7 (b), the generated electromotive force generated in the coil during rotation is such that the direction of movement of the coil is not perpendicular to the magnet magnetic flux, so that the power generation in the coil has a small value according to Fleming's right-hand rule. . By winding two triangular coils in this way and arranging them in the center with respect to the rotor, the counter electromotive force generated in the two coils is canceled, thereby minimizing the amount of power generation and driving at the time of current switching. The gradient at the time of current reversal can be made gentle.

[0014]

As described above, according to the present invention, since two triangular coil windings are wound at the same time, only one coil is required, and vibration during motor fan operation can be reduced with a relatively simple structure. Can be smaller. In addition, since the generation of the back electromotive force during rotation can be suppressed by mutually canceling out by the two coils, the bias of the drive circuit is stabilized, and a low withstand voltage electronic component can be used. This has the effect of lowering the unit price and improving reliability.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a stop positional relationship between a magnet of a fan motor and a triangular coil according to the present invention.

FIG. 2 is a plan view and a side view showing a positional relationship between a magnet and a triangular coil of the fan motor according to the present invention.

FIG. 3 is a diagram for explaining a mechanism that generates a suction force and a repulsion force.

FIG. 4 is a circuit diagram showing an embodiment of a fan motor drive circuit according to the present invention.

5A is a waveform diagram illustrating a surface magnetic field of a magnet, FIG. 5B is a waveform diagram illustrating voltages at points a and b in FIG. 5, and FIG. 5C is a waveform diagram illustrating coil current characteristics.

FIG. 6 is a diagram showing directions of generating magnetic fields of two coils.

FIG. 7 is a diagram for explaining a position where the amount of power generation of a coil is minimized.

[Explanation of symbols]

 1a ... S pole of magnet 1b ... N pole of magnet 1 ... Magnet 3 ... Hall element (magnetic sensor) 4 ... Coking angle (15 degrees) 5 ... First coil 6 ... Second coil 7 ... Triangular coil 8,9 ... Yoke 10,11 ... Transistor 12,13,14 ... Resistance 15 ... Current direction

Claims (2)

[Claims] 1. A fan motor of a type in which a facing direction of a magnet attached to a rotor and a coil attached to a stator is arranged so as to be parallel to a rotation axis of the rotor. The triangular coil is wound two times while being arranged facing the center of the rotor so that the center thereof coincides with the rotation axis, and a drive circuit for switching polarity is connected to the two-turned coil. The power generation amount generated in the coil is reduced, and the attraction and repulsion between the magnet and the triangular coil generated in the direction parallel to the rotation axis when switching the polarity is reduced. Fan motor. 2. The fan motor according to claim 1, wherein the polarity switching is performed by detecting a magnetic field direction by a magnetic sensor.