JPH10201200A - Brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single-phase brushless motor which is highly efficient and can be driven in optional direction by solving the theme that it can not start by itself, in the start property of a single-phase brushless motor. SOLUTION: This is one comprising a stator 12 where a single-phase coil is wound, and a rotor 13 which has at least two permanent magnets 14 and pole pieces 15 consisting of material higher in permeability than these permanent magnets 14 and in which the pole pieces 15 are arranged outside the permanent magnets 14, and this is a single phase system of brushless motor where the rotor 13 is surrounded by the stator 12, and the thicknesses of the pole pieces 15 are made asymmetry about the center between the two permanent magnets 14 so that the air gap between the rotor 13 and the stator 12 may be equal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-phase brushless motor that can be used for a fan motor or the like in the industrial or consumer fields.

[0002]

2. Description of the Related Art As shown in FIG. 10, a conventional inner rotor type brushless motor has a stator 32 wound with a stator coil 31, a stator 32 and a predetermined air gap 39.
And a rotor 34 that is rotatably disposed in a state in which A ring-shaped permanent magnet 34 having magnetic poles having different polarities alternately formed at a predetermined angle on the outer peripheral surface of the rotor 33.
Is arranged. In the configuration as described above, the excitation current in the positive direction and the negative direction is alternately applied to the stator coil 31 to generate torque and drive to rotate.

[0003]

However, in the above-described conventional configuration, the torque characteristic with respect to the position (rotation angle θ) of the rotor 33 is as shown in FIG. There is a point. This dead point is always present in the single-phase brushless motor of this configuration regardless of the magnetized shape and the drive waveform shape of the permanent magnet 34, and if the rotor stops at this dead point, the motor is turned off. No matter how much power is supplied, there is a fundamental problem that torque cannot be obtained and self-start operation cannot be performed.

To solve this fundamental problem of the single-phase brushless motor, as shown in FIG.
2 is made non-uniform, and when the stator coil 41 is not energized, the rotor 43 is shifted from the dead center.
A method of coping with the start by stopping the operation is known in the related art.

However, this method has a problem that, since the air gap 49 is made non-uniform, the air gap 49 becomes large, the effective magnetic flux density is reduced, and the efficiency is reduced.

[0006] These conventional techniques also have the following problems. FIG. 13A shows a voltage waveform induced in the stator coil 31 or 41.
When a voltage is externally applied to the stator coil 31 or 41 that generates such an induced voltage waveform as shown in FIG. 3B, the exciting current of the stator coil 31 or 41 becomes as shown in FIG. The rear portion of the current waveform has a raised shape.

The exciting current waveform has such a shape because the induced voltage generated in the stator coil 31 or 41 at the rear portion of the waveform is reduced, so that the potential difference from the externally applied voltage increases. This is because the voltage applied to the internal impedance of the stator coil 31 or 41 increases.

Thus, the stator coil 31 or 41
When the exciting current waveform rises and the value becomes excessive,
The copper loss determined by the product of the resistance component of the stator coil 31 or 41 and the square of the exciting current increases, and the efficiency of the motor decreases.

In addition, a power element having a large power capacity capable of withstanding the excessive exciting current is required to drive the motor, so that the driving circuit becomes large and the cost increases.

Further, when the exciting current becomes excessive, FIG.
As shown in (c), the change of the exciting current at the time of commutation also becomes large, which causes electric noise and noise / vibration.

As described above, there are many problems caused by the fact that the rear portion of the exciting current rises and the value thereof becomes excessively large.
Alternatively, it is possible to control the voltage applied to 41 so that the rear portion of the exciting current does not rise, but this requires a complicated control circuit for controlling the applied voltage to stator coil 31 or 41. Therefore, it cannot be a sufficient measure in terms of size and cost.

The present invention solves such a conventional problem, and enables self-starting operation without a decrease in efficiency due to a decrease in effective magnetic flux density, and furthermore, a loss due to copper loss and noise and vibration during commutation. It aims to provide a small single-phase brushless motor.

[0013]

SUMMARY OF THE INVENTION In order to solve this problem, a single-phase brushless motor according to the present invention comprises a stator having a single-phase coil wound thereon, at least two permanent magnets, and a magnetic permeability higher than that of the permanent magnets. A rotor having a pole piece made of a high material and having the pole pin disposed outside the permanent magnet, wherein the rotor is surrounded by the stator, and the rotor and the stator are The thickness of the pole piece is made asymmetrical with respect to the center of the permanent magnet so that the air gap between them becomes uniform.

By the above means, the position of the rotor can be avoided from the dead center while keeping the air gap uniform.
Self-starting operation becomes possible without a decrease in efficiency due to a decrease in effective magnetic flux density. Moreover, since the exciting current does not become excessive, a single-phase brushless motor having small copper loss and small electric noise, noise and vibration during commutation can be realized.

[0015]

DETAILED DESCRIPTION OF THE INVENTION In order to solve the above problems, the present invention comprises a stator having a single-phase coil wound thereon, at least two permanent magnets, and a pole piece made of a material having a higher magnetic permeability than the permanent magnets. A rotor in which the pole pins are arranged outside the permanent magnet, wherein the rotor is surrounded by the stator, and an air gap between the rotor and the stator becomes uniform. A single-phase brushless motor in which the thickness of the pole piece is asymmetric with respect to the center of the permanent magnet as described above, and the position of the rotor can be avoided from the dead center while keeping the air gap uniform,
Self-starting operation becomes possible without a decrease in efficiency due to a decrease in effective magnetic flux density.

Further, the present invention has a stator having a coil wound thereon, at least two permanent magnets, and a pole pin made of a material having a higher magnetic permeability than the permanent magnet, wherein the pole pin is disposed inside the permanent magnet. The stator is surrounded by the rotor, and the thickness of the pole piece is adjusted to the center of the permanent magnet so that the air gap between the rotor and the stator becomes uniform. The motor is an asymmetric brushless motor, and it is possible to suppress the rise of current due to the switching of the induced voltage.

Further, the present invention is a brushless motor in which the shape of the permanent magnet is made into an arc shape, the magnetic flux of the permanent magnet can be made uniform, and processing is easy.

Further, the present invention has a stator having a coil wound thereon, at least two permanent magnets, and a pole piece made of a material having a higher magnetic permeability than the permanent magnets. A rotor having an asymmetric thickness with respect to the center of the permanent magnet so that the pole piece has a uniform thickness; and exciting means connected to a coil of the stator, wherein the exciting means comprises a stator. The exciting current of the coil is set to a first value, a second value, or a third value, wherein the first value and the second value have opposite signs, and the exciting current of these values is Alternately driving the rotor in a desired direction, wherein the third value has the same sign as that of the first value or the second value and has a different size. When the rotor is near the dead center, , Said first value or said second
In the case where the motor cannot be started due to the above value, the excitation current of the stator coil is set to the third value to avoid the dead center. This is a brushless motor in which a starting torque is generated in a direction to start a rotor, and it is possible to suppress a rise in current due to a jump of switching of an induced voltage.

Further, the present invention has a stator having a coil wound thereon, at least two permanent magnets, and a pole piece made of a material having a higher magnetic permeability than the permanent magnets. A rotor having an asymmetric thickness with respect to the center of the permanent magnet so that the pole piece has a uniform thickness; and exciting means connected to a coil of the stator, wherein the exciting means comprises a stator. The exciting current of the coil is set to a first value or a second value, wherein the first value and the second value have opposite signs, and the rotor is near a dead center, When the rotor cannot be started by the first value, the excitation current of the stator coil is set to a second value to avoid a dead point, or when the rotor is near the dead point and the second value If the rotor cannot be started due to A dead point is avoided by setting the exciting current of the stator coil to a first value, and thereafter, the exciting current of the first value and the exciting value of the second value are set so that the rotor starts and continues to be driven in a desired direction. This is a brushless motor that is switched, and can efficiently suppress the rise of current due to the surge of switching of the induced voltage.

In addition, since the exciting means is provided in the brushless motor having the stator of the present invention in which the single-phase coil is wound, the position of the rotor can be avoided from the dead center while keeping the air gap uniform. Self-starting operation becomes possible without a decrease in efficiency due to a decrease in effective magnetic flux density.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a single-phase brushless motor according to a first embodiment of the present invention. In FIG. 1, reference numeral 12 denotes a stator, on which a stator coil 11 is wound. Reference numeral 13 denotes a rotor, which is constructed by inserting two permanent magnets 14 having an arc-shaped cross section from the axial direction into a position radially inward from the outer peripheral surface of the rotor 13. The pole piece 1 is located between the permanent magnet 14 and the air gap 19.
5 is disposed, and the pole piece 15 is
4 is made of a material having a higher magnetic permeability than, for example, an electromagnetic steel sheet or pure iron. Further, the thickness of the pole piece 15 is asymmetric with respect to the center 14 a of the permanent magnet 14. In other words, the thickness of the pole piece 15 (the distance between the magnet 14 and the air gap) is not all the same.
The rotor 13 having the above-described configuration is disposed inside the stator 12 so as to be rotatable in a state where the stator 12 and the predetermined air gap 19 are uniformly present.

The operation of the single-phase brushless motor according to the present embodiment configured as described above will be described.

FIG. 2 shows the generated torque with respect to the position of the rotor (rotation angle θ). According to FIG. 2, it can be seen that the torque with respect to the position of the rotor 13 changes depending on the magnitude and direction of the exciting current of the stator coil 12, and in particular, the dead center position where the torque becomes zero moves. This is because the thickness of the pole piece 15 is made asymmetric with respect to the center of the permanent magnet 14.

In the conventional single-phase brushless motor shown in FIG. 10, the position of the dead center does not move due to the exciting current of the stator coil 31 as shown in FIG.

In the present invention, the position of the dead center can be moved by the exciting current of the stator coil 11 as described above.

By taking advantage of this fact, the self-starting operation of the single-phase brushless motor becomes possible. That is, for example, at the time of startup, an exciting current different from that during normal operation is applied to the stator coil 11.
The rotor 1 from the dead center position during normal operation.
3 can be avoided, thereby enabling self-activation.

As shown in FIG. 1, since the air gap 19 between the rotor 13 and the stator 12 is uniform, the motor can be driven with high efficiency without reducing the effective magnetic flux density.

On the other hand, in the present invention, an induced voltage is induced in the stator coil 11 as shown in FIG.

The reason why the induced voltage has a waveform shape as shown in FIG. 3A is that the pole pieces 15 are arranged so as to be asymmetric with respect to the center of the permanent magnet 14.

When a voltage shown in FIG. 3B is externally applied to the stator coil 11 that generates such an induced voltage,
The excitation current waveform is as shown in FIG.
The swelling at the rear part of the waveform as shown in FIG.

Therefore, the exciting current of the stator coil 11 does not become excessively large, and the copper loss proportional to the square of the exciting current can be kept small.

Further, since the exciting current is small, a power element having a small power capacity can be used for driving the motor, so that the drive circuit can be reduced in size and cost.

Further, as shown in FIG. 3C, the change of the exciting current at the time of commutation becomes gentle, and electric noise, vibration and noise can be suppressed.

It should be noted that it is not necessary to control the voltage applied to the stator coil 11 in order to realize these effects.
For example, it is only necessary to apply a simple rectangular wave voltage to the stator coil 11. Therefore, no complicated control circuit is required.

As described above, according to the present embodiment, the position of the dead center of the rotor 13 can be moved by the exciting current of the stator coil 11, so that the rotor 13 can be started by itself.

Further, since the air gap 19 has a uniform structure, the motor can be driven with high efficiency without reducing the effective magnetic flux density.

Further, since the induced voltage waveform has a waveform shape as shown in FIG. 3 (a), the exciting current does not become excessive, copper loss can be suppressed, and electric noise, vibration and noise during commutation are also reduced. You can do it.

These effects can be realized by a simple driving circuit. In the present embodiment, the shape of the permanent magnet 14 is formed into an arc shape that can be processed relatively easily and the dimensional accuracy is easily ensured, but it is not always necessary that the shape be an arc shape.

For example, a non-arc-shaped permanent magnet is used, and the thickness of a pole piece disposed between the non-arc-shaped permanent magnet and the air gap is adjusted so that the air gap is uniform. May be asymmetrical with respect to the center of

Further, since the pole piece 15 is disposed between the permanent magnet 14 and the air gap 19, there is no fear that the permanent magnet 14 is scattered by centrifugal force during high-speed rotation, which is more suitable for high-speed rotation. Motor can also be realized.

In this embodiment, the inner rotor type single-phase brushless motor has been described. However, it is needless to say that the present invention can be applied to an outer rotor type single-phase brushless motor.

(Embodiment 2) FIG. 4 shows a single-phase brushless motor according to a second embodiment of the present invention. In FIG. 4, except that the exciting means 16 configured to set the exciting current of the stator coil 11 to the first value, the second value, or the third value is connected to the stator coil 11. Is similar to the first embodiment in FIG.
Portions having the same function are denoted by the same reference numerals, and detailed description thereof will be omitted.

The operation of the single-phase brushless motor according to the second embodiment configured as described above will be described.

FIGS. 5 and 6 show the rotor 13 similar to FIG.
(Rotation angle .theta.). In particular, when the exciting current to the stator coil 11 by the exciting means 16 is set to the first value, it is indicated by a sign opposite to the first value. A case where the second value has substantially the same size and a case where the third value has the same sign as the first value and has a larger size are shown.

First, consider the case where the rotor is stopped at the point M0 in FIG. In this case, the excitation torque of the stator coil 11 is set as the first value and the starting torque T1
And the rotor 13 can be driven in the forward direction from the point M1.

Conversely, a starting torque T2 is generated using the exciting current of the stator coil 11 as a second value,
Can be driven in the reverse direction from the point M2.

As described above, when the rotor 13 is stopped at a position where the starting torque can be generated by any one of the first value and the second value, the desired direction can be obtained without any problem. The rotor 13 can be started.

However, when the rotor 13 stops at the point A0 in FIG. 5 or the point B0 in FIG. 6, that is, when the rotor 13 stops at the dead center, the exciting current is changed to the first value or the second value. However, the generated torque is zero, and the rotor 13 cannot be started.

The operation when the rotor 13 is stopped at the dead center will be described below. First, FIG.
, The case where the rotor 13 is stopped at the point A0 will be described.

In this case, even if an exciting current of the first value is applied to the stator coil 11, the generated torque is zero and the rotor 13
Can not start. That is, the point A0 is a dead point when the exciting current is set to the first value.

Therefore, the third exciting current is supplied to the stator coil 11
So that it flows. Then, the negative torque shown at the operating point C1 acts on the rotor 13 and starts moving toward the operating point C0. Eventually, the rotor 13 reaches the point C0 and stably stops, but at this time, the rotor 13 is at a position shifted from the dead point A0.

Therefore, by setting the exciting current to the first value when the point C0 is reached, the starting torque TA1 is generated as shown in FIG. 5A, and the rotor 13 is moved in the forward direction from the point A1. Can be started.

Conversely, when reaching the point C0, the exciting current is set to the second value to generate the starting torque TB1 as shown in FIG. 5B, and the rotor 13 is rotated in the reverse direction from the point B1. Can also be launched.

As described above, when starting cannot be performed even when the exciting current is set to the first value, the dead point A0 is set to the exciting current as the third value.
In this case, the rotor 13 can be started in a desired direction by the excitation current having the first value or the second value.

The dead point A0 is set as the third value of the exciting current.
When avoiding the point, the rotor 13 is stably stopped at the point C0, but it is not always necessary to stop the rotor 13 at the point C0.

For example, as shown in FIG. 5C, after the exciting current is set to the third value, the rotor 13 is set to the first value at the point C2 on the way from the operating point C1 to the point C0. Then, the starting torque TA2 is generated, and the rotor 13 can be started in the normal rotation direction from the point A2.

As shown in FIG. 5D, when the exciting current is set to the second value at the point C3 on the way from the point C1 to the point C0, the starting torque TB2 is generated, and the rotor 13 is moved to the point B2.
Can be activated in the reverse direction from a point.

Next, a case where the rotor 13 is stopped at the point B0 will be described with reference to FIG. In this case, even if an exciting current of the second value is supplied to the stator coil 11, the generated torque is zero and the rotor 13 cannot be started.
That is, the point B0 is a dead point when the exciting current is set to the second value.

Therefore, the third exciting current is supplied to the stator coil 11
So that it flows. Then, the negative torque shown at the operating point C4 acts on the rotor 13 and starts moving toward the operating point C0. Eventually, the rotor 13 reaches the point C0 and stops stably, but at this time, the rotor 13 is at a position shifted from the dead point B0.

Therefore, by setting the exciting current to the first value when the point C0 is reached, the starting torque TA1 is generated as shown in FIG. 6A, and the rotor 13 is moved in the normal rotation direction by A1.
Can start from a point.

Conversely, when the point C0 is reached, the starting current TB1 is generated as shown in FIG. 6B by setting the exciting current to the second value, and the rotor 13 is rotated in the reverse direction by B1.
You can also start from a point.

As described above, when starting cannot be performed even when the exciting current is set to the second value, the exciting current is set to the third value and the dead center B0
In this case, the rotor 13 can be started in a desired direction by the excitation current having the first value or the second value.

The dead point B0 is set as the third value of the exciting current.
When avoiding the point, the rotor 13 is stably stopped at the point C0, but it is not always necessary to stop the rotor 13 at the point C0.

For example, as shown in FIG. 6C, after the exciting current is set to the third value, the rotor 13 is set to the first value at the point C5 on the way from the operating point C4 to the point C0. , A starting torque TA3 is generated, and the rotor 13 can be started in the normal rotation direction.

As shown in FIG. 6D, when the exciting current is set to the second value at the point C6 on the way from the point C4 to the point C0, the starting torque TB3 is generated, and the rotor 13 is moved to the point B3.
Can be activated in the reverse direction from a point.

As described above, according to the present embodiment, when the excitation current cannot be started even when the excitation current is set to the first value or the second value, the excitation current is set to the third value which is larger than these values. It avoids the point position and allows self-starting.

In this embodiment, the case where the magnitude of the excitation current having the third value is larger than the magnitude of the excitation current having the first value or the second value has been described. Need not be large. For example, even if the third value is smaller than the first value or the second value, the dead center position can be avoided in the same manner.

In this embodiment, the exciting current is set to the third
After avoiding the dead center position as the value of, the exciting current is switched to the first value or the second value at each operating point shown in FIG. 5 or FIG. 6 to generate the starting torque. The timing for switching to the first value or the second value is as follows:
A predetermined value may be elapsed after the excitation current of the third value starts flowing through the stator coil 11, or the position of the rotor 13 may be detected by a Hall element or the like and switched based on the position detection signal. It may be.

It is needless to say that, in addition to the effects described above, this embodiment also has all the effects shown in the first embodiment.

(Embodiment 3) FIG. 7 shows a single-phase brushless motor according to a third embodiment of the present invention. In FIG. 7, the exciting means 17 configured to set the exciting current of the stator coil 11 to the first value or the second value is
Except for the configuration connected to the stator coil 11, the configuration is the same as that of the first embodiment in FIG. 1, and the portions having the same functions are denoted by the same reference numerals and detailed description thereof will be omitted.

The operation of the single-phase brushless motor according to the third embodiment configured as described above will be described.

FIGS. 8 and 9 show the rotor 11 similar to FIG.
(Rotation angle .theta.). In particular, when the exciting current to the stator coil 11 by the exciting means 17 is set to a first value, the torque is opposite to the first value. The case where the second value is substantially the same is shown.

First, consider the case where the rotor is stopped at the point M0 in FIG. In this case, the excitation torque of the stator coil 11 is set as the first value and the starting torque T1
And the rotor 13 can be driven in the forward direction from the point M1.

Conversely, the starting current T2 is generated by using the exciting current of the stator coil 11 as the second value, and the
Can be driven in the reverse direction from the point M2.

As described above, when the rotor 13 is stopped at a position where the starting torque can be generated by any one of the first value and the second value, the desired direction can be obtained without any problem. The rotor 13 can be started.

However, when the rotor 13 is stopped at the point A0 in FIG. 8, the generated torque is zero even if the exciting current is set to the first value, and the rotor 13 cannot be started.

Similarly, when the rotor 13 is stopped at the point B0 in FIG. 9, the generated torque is zero even if the exciting current is set to the second value, and the rotor 13 cannot be started.

As described above, the rotor 13 is connected to the A in FIG.
The operation in the case of stopping at the point 0 or the point B0 in FIG. 9, that is, at the dead center will be described below.

First, a case where the rotor 13 is stopped at the point A0 will be described with reference to FIG. In this case, even if an exciting current of the first value is supplied to the stator coil, the generated torque is zero and the rotor 13 cannot be started. That is, the point A0 is a dead point when the exciting current is set to the first value.

Therefore, the second exciting current is supplied to the stator coil 11
So that it flows. Then, the negative torque shown at the operating point B4 acts on the rotor 13 and starts moving toward the operating point B5, and the rotor 13 is shifted from the dead point A0.

Therefore, by setting the exciting current to the first value when the point B5 is reached, the starting torque TA4 is generated as shown in FIG.
Can start from a point.

Further, with the exciting current kept at the second value,
As shown in FIG. 8B, the rotor can be started in the reverse direction from the point B4 by the starting torque TB4.

As described above, when the excitation current cannot be started even when the excitation current is set to the first value, the excitation current is set to the second value and the dead center A0 is set.
In this case, the rotor 13 can be started in a desired direction by the excitation current having the first value or the second value.

Next, a case where the rotor 13 is stopped at the point B0 will be described with reference to FIG.

In this case, even if an exciting current of the second value is applied to the stator coil 11, the generated torque is zero and the rotor 13
Can not start. That is, the point B0 is a dead point when the exciting current is set to the second value.

Therefore, the first exciting current is supplied to the stator coil 11
So that it flows. Then, the negative torque shown at the operating point A5 acts on the rotor, and the rotor 11 starts moving so as to avoid the dead point B0.

In order to start the rotor 13 in the normal rotation direction after avoiding the dead point B0, as shown in FIG. 9 (a), when the operating point A0 is reached, the exciting current is reduced to a second value. The rotor 13 is driven by the negative torque shown in the operating point B4.
Is further moved to the operating point B6, and when reaching the point B6, the exciting current is moved to the operating point A6 as the first value to generate the starting torque TA6.

Alternatively, when the operating point reaches the operating point A0, the rotor 1 is moved to the operating point A7 using the inertia of the rotor 11.
3 can be moved to generate the starting torque TA7 indicated by the operating point A7, and the rotor 13 can be started in the normal rotation direction.

Here, while the rotor 13 is moved to the operating point A7 by using inertia, the amount of movement can be increased by setting the exciting current to zero, and the starting torque TA7 is set to a larger value to increase the positive value. Starting in the turning direction can be further ensured.

After avoiding the dead point B0, the rotor 13
Can be started in the reverse rotation direction, as shown in FIG. 9 (b), when the operating point A0 is reached, the starting current TB4 may be generated with the exciting current as the second value.

As described above, when starting cannot be performed even when the exciting current is set to the second value, the exciting current is set to the first value and the dead center B0
In this case, the rotor 13 can be started in a desired direction by the excitation current having the first value or the second value.

The dead point B0 is set as the exciting current as the first value.
After avoiding the point, it has been described that the exciting current is set to the second value when the rotor 13 reaches the point A0, but this is not necessarily the case.

For example, in order to start in the normal rotation direction, as shown in FIG.
As shown in (c), after the excitation current is set to the first value, the rotor 13 moves from the operating point A5 to the point A0 in the middle of the operating point A5.
After the rotor 13 is further moved to the operating point B8 by the reverse torque indicated by the operating point B7, the exciting current is moved to the operating point A9 as the first value, and the motor is started. The torque TA9 may be generated.

In order to start the motor in the reverse rotation direction, it is necessary to use FIG.
As shown in (d), at point A10 on the way from point A5 to point A0, the exciting current is set to the second value and the starting torque TB9
May be generated.

As described above, according to this embodiment, if the excitation current cannot be started even when the excitation current is set to the first value, the excitation current is set to the second value.
To avoid the dead center position when the exciting current is set to the first value so that the self-starting is possible. When the excitation current cannot be started even when the excitation current is set to the second value, the excitation current is set to the first value, and the self-start can be performed by avoiding the dead center position when the excitation current is set to the second value.

As described above, in this embodiment, the motor is self-started by two values of the exciting current, so that the configuration of the exciting means 17 can be further simplified.

In this embodiment, the exciting current is set to the first
After avoiding the dead center position as the value of
Alternatively, the excitation current is switched at each operating point shown in FIG. 9 to generate the starting torque, but the timing of switching the excitation current is determined by switching the excitation current of the first value or the second value to avoid dead center. A predetermined time may have elapsed since the start of flowing through the stator coil 11, or the position of the rotor 13 may be detected by a Hall element or the like, and switching may be performed based on the position detection signal.

It goes without saying that, in addition to the effects described above, this embodiment also has all the effects shown in the first embodiment. In the present invention, it goes without saying that the present invention can be applied not only to the inner rotor type single-phase brushless motor but also to the outer rotor type single-phase brushless motor.

[0100]

As is clear from the description of the above embodiment,
According to the first and third aspects of the present invention, the position of the dead center of the rotor can be moved by the exciting current of the stator coil. Further, since the air gap has a uniform structure, the motor can be driven with high efficiency without reducing the effective magnetic flux density. In addition, the exciting current does not become excessive, copper loss can be suppressed, and electric noise, vibration and noise during commutation can be reduced. These effects can be realized by a simple driving circuit. In addition, since the pole piece is arranged between the permanent magnet and the air gap, there is no fear of the permanent magnet being scattered by the centrifugal force during high-speed rotation, and a motor suitable for higher-speed rotation can be realized. it can. Further, since the starting torque for starting uses the driving torque of the motor, the starting torque can be easily increased.

Further, according to the second aspect of the present invention, it is possible to suppress the surge of the current due to the jump of the induced voltage at the time of switching, and it is possible to drive the motor efficiently.

According to the fourth aspect of the present invention, a permanent magnet having a stable magnetic flux can be used for the rotor as a whole, so that a brushless motor with no unevenness and high performance can be provided.

According to the fifth aspect of the present invention, when the exciting current cannot be started even when the exciting current is set to the first value or the second value, the rise of the current due to the jump of the induced voltage at the time of switching can be suppressed and the efficiency can be improved The motor can be driven.

According to the sixth aspect of the present invention, since the motor is self-started by two values of the exciting current, the structure of the exciting means is further simplified, and the induced voltage jumps during switching. As a result, the rise of current can be suppressed, and the motor can be efficiently driven.

Further, when the invention according to claim 7 is used for a single-phase motor, the position of the dead center of the rotor can be moved by the exciting current of the stator coil. It becomes possible. Further, since the air gap has a uniform structure, the motor can be driven with high efficiency without reducing the effective magnetic flux density. In addition, the exciting current does not become excessive, copper loss can be suppressed, and electric noise, vibration and noise during commutation can be reduced. These effects can be realized by a simple driving circuit. In addition, since the pole piece is arranged between the permanent magnet and the air gap, there is no fear of the permanent magnet being scattered by the centrifugal force during high-speed rotation, and a motor suitable for higher-speed rotation can be realized. it can. Further, since the starting torque for starting uses the driving torque of the motor, the starting torque can be easily increased.

[Brief description of the drawings]

FIG. 1 is a sectional view of a single-phase brushless motor according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing torque characteristics with respect to the position of a rotor of the single-phase brushless motor in FIG. 1;

FIG. 3 is an explanatory diagram showing an induced voltage waveform and an exciting current waveform of the single-phase brushless motor in FIG. 1;

FIG. 4 is a sectional view of a single-phase brushless motor according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating the operation of the single-phase brushless motor in FIG. 4;

FIG. 6 is a diagram illustrating the operation of the single-phase brushless motor in FIG.

FIG. 7 is a sectional view of a single-phase brushless motor according to a third embodiment of the present invention.

FIG. 8 is a diagram illustrating the operation of the single-phase brushless motor in FIG. 7;

FIG. 9 is a diagram illustrating the operation of the single-phase brushless motor in FIG. 7;

FIG. 10 is a longitudinal sectional view of a conventional single-phase brushless motor.

11 is an explanatory diagram showing a torque characteristic with respect to a position of a rotor of the single-phase brushless motor in FIG. 10;

FIG. 12 is a sectional view of a single-phase brushless motor according to another conventional example.

FIG. 13 is an explanatory diagram showing an induced voltage waveform and an exciting current waveform of the single-phase brushless motor in FIGS. 10 and 12;

[Explanation of symbols]

 11, 31, 41 Stator coil 12, 32, 42 Stator 13, 33, 43 Rotor 14, 34 Permanent magnet 45 Pole piece 16, 17 Exciting means 19, 39, 49 Air gap

Claims (7)

[Claims] A stator having a single-phase coil wound thereon, at least two permanent magnets, and a pole piece made of a material having a higher magnetic permeability than the permanent magnets, wherein the pole pieces are provided outside the permanent magnets. And a rotor arranged around the rotor, wherein the rotor is surrounded by the stator, and the thickness of the pole piece is adjusted so that an air gap between the rotor and the stator becomes uniform. Single-phase brushless motor asymmetric with respect to the center. 2. A stator having a coil wound thereon and at least two stators.
A rotor having two permanent magnets and a pole piece made of a material having a higher magnetic permeability than the permanent magnets, and a rotor having the pole pieces disposed inside the permanent magnets. A brushless motor surrounded by a rotor and having a thickness of the pole piece asymmetrical with respect to the center of the permanent magnet so that an air gap between the rotor and the stator is uniform. 3. The brushless motor according to claim 2, further comprising a stator wound with a single-phase coil. 4. The brushless motor according to claim 1, wherein the shape of the permanent magnet is an arc. 5. A stator having a coil wound thereon and at least two stators.
One permanent magnet and a pole piece made of a material having a higher magnetic permeability than the permanent magnet. , And exciting means connected to the stator coil, wherein the exciting means sets the exciting current of the stator coil to a first value, a second value, or a third value. Wherein the first value and the second value have opposite signs, and drive the rotor in a desired direction by alternately switching the exciting currents of these values, The third value is a value having the same sign as that of any one of the first value and the second value and different in magnitude, and the rotor is near a dead center, and the first value or the If it cannot be started by the second value, Avoiding dead center by setting the exciting current of the stator coil to the third value, and then generating the starting torque in a desired driving direction by setting the exciting current of the stator coil to the first value or the second value; A brushless motor that starts the rotor. 6. A stator having a coil wound thereon and at least two stators.
One permanent magnet and a pole piece made of a material having a higher magnetic permeability than the permanent magnet. And an exciting means connected to the stator coil, wherein the exciting means sets the exciting current of the stator coil to a first value or a second value. The first value and the second value have opposite signs to each other, and when the rotor is near the dead center and the rotor cannot be started by the first value, the excitation of the stator coil is performed. Avoiding dead center with current as the second value, or when the rotor is near dead center and cannot be started by the second value,
A dead point is avoided by setting the exciting current of the stator coil to a first value, and then the exciting current of the first value and the second value is set so that the rotor starts and continues to be driven in a desired direction. Brushless motor to switch between. 7. The brushless motor according to claim 5, further comprising a stator wound with a single-phase coil.