JP3674206B2 - Brushless motor - Google Patents

Description

[0001]
BACKGROUND 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 an industrial field or a consumer field.
[0002]
[Prior art]
As shown in FIG. 10, a conventional inner rotor type brushless motor has a stator 32 around which a stator coil 31 is wound, and a rotation rotatably disposed in a state where the stator 32 and a predetermined air gap 39 exist. And a child 34. On the outer peripheral surface of the rotor 33, ring-shaped permanent magnets 34 in which magnetic poles having different polarities are alternately formed at a predetermined angle are arranged. In the configuration as described above, the excitation current in the positive direction and the negative direction is alternately passed through the stator coil 31 to generate torque and drive the rotation.
[0003]
[Problems to be solved by the invention]
However, in the above-described conventional configuration, the torque characteristics with respect to the position of the rotor 33 (rotation angle θ) are as shown in FIG. 11, and there are positions at which the torque periodically becomes zero, so-called dead points. This
The dead center of the permanent magnet 34 is always present in the single-phase brushless motor of this configuration regardless of the magnetized shape and drive waveform shape of the permanent magnet 34. When the rotor stops at the position of this dead point, the motor is turned off. No matter how energized, there is a fundamental problem that torque cannot be obtained and self-starting operation cannot be performed.
[0004]
In response to this fundamental problem of the single-phase brushless motor, as shown in FIG. 12, the air gap 49 between the rotor 43 and the stator 42 is made non-uniform so that when the stator coil 41 is not energized, death occurs. A method of dealing with the start-up by stopping the rotor 43 at a position deviated from the point is known as the prior art.
[0005]
However, this method has a problem that since the air gap 49 is not uniform, the air gap 49 becomes large, the effective magnetic flux density is reduced, and the efficiency is lowered.
[0006]
Further, these conventional techniques have the following problems.
FIG. 13A shows a voltage waveform induced in the stator coil 31 or 41. The stator coil 31 or 41 that generates such an induced voltage waveform is externally shown in FIG. When the voltage is applied in this way, the excitation current of the stator coil 31 or 41 becomes a shape in which the rear part of the current waveform is raised as shown in FIG.
[0007]
The excitation current waveform has such a shape because the induced voltage generated in the stator coil 31 or 41 at the rear of the waveform decreases, and the potential difference from the voltage applied from the outside increases, and the stator coil This is because the voltage applied to the internal impedance of 31 or 41 increases.
[0008]
Thus, when the excitation current waveform of the stator coil 31 or 41 rises and its 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 excitation current increases. As a result, the efficiency of the motor is reduced.
[0009]
In addition, a power element having a large power capacity that can withstand this excessive excitation current is required to drive the motor, and the drive circuit portion becomes large and the cost increases.
[0010]
If the excitation current is excessive, as shown in FIG. 13C, the change in the excitation current at the time of commutation becomes large, which causes electric noise, noise, and vibration.
[0011]
As described above, there are many problems caused because the rear part of the exciting current rises and its value becomes excessive. For example, the voltage applied to the stator coil 31 or 41 is controlled to control the exciting current. Although it is possible to prevent the rear part from rising, this requires a complicated control circuit for controlling the voltage applied to the stator coil 31 or 41, and sufficient measures are taken in terms of size and cost. Cannot be.
[0012]
The present invention solves such a conventional problem, and is capable of self-starting operation without a reduction in efficiency due to a decrease in effective magnetic flux density, and also has low loss due to copper loss, noise and vibration during commutation, and the like. The object is to provide a single-phase brushless motor.
[0013]
[Means for Solving the Problems]
In order to solve this problem, the single-phase brushless motor of the present invention is The pole piece has a stator around which a coil is wound, at least two permanent magnets and a pole piece made of a material having a higher magnetic permeability than the permanent magnet, and the air gap between the stator and the stator is uniform. A rotor having an asymmetric thickness with respect to the center of the permanent magnet, and excitation means connected to the stator coil, wherein the excitation means generates an excitation current of the stator coil as a first value. Or the second value or the third value, wherein the first value and the second value have opposite signs, and the excitation current of these values is switched alternately to switch the rotor. Driven in a desired direction, wherein the third value is a value having the same sign as the first value or the second value but having a different size, and the rotor is near the dead center And the first value or the If it cannot be activated by the value of 2, the exciting current of the stator coil is set as the third value to avoid dead center, and then the exciting current of the stator coil is set as the first value or the second value as desired. Generate starting torque in the driving direction and start the rotor It is a thing.
[0014]
By the above means, the position of the rotor can be avoided from the dead center while keeping the air gap uniform, so that the self-starting operation can be performed without reducing the efficiency due to the decrease of the effective magnetic flux density. In addition, since the excitation current does not become excessive, a single-phase brushless motor with small copper loss and low electrical 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 includes a stator around which a single-phase coil is wound, at least two permanent magnets, and a pole piece made of a material having a higher magnetic permeability than the permanent magnets. The pole piece is arranged so that the rotor is surrounded by the stator, and the thickness of the pole piece is uniform so that the air gap between the rotor and the stator is uniform. Is a single-phase brushless motor that is asymmetric with respect to the center of the permanent magnet, and the rotor position can be avoided from the dead center while keeping the air gap uniform, so there is no reduction in efficiency due to a decrease in effective magnetic flux density. The self-starting operation becomes possible.
[0016]
The present invention also includes a stator around which a coil is wound, a rotor having at least two permanent magnets and a pole pin made of a material having a higher magnetic permeability than the permanent magnet, and the pole pin is disposed inside the permanent magnet. The stator is surrounded by the rotor, and the pole piece has a thickness with respect to the center of the permanent magnet so that an air gap between the rotor and the stator is uniform. This is an asymmetric brushless motor, and can suppress the rise of current due to the backlash of the induced voltage switching.
[0017]
In addition, the present invention is a brushless motor in which the shape of the permanent magnet is an arc, and the magnetic flux of the permanent magnet can be made uniform and easy to process.
[0018]
Further, the present invention has a stator around which a coil is wound, at least two permanent magnets, and a pole piece made of a material having a higher magnetic permeability than the permanent magnet, and an air gap between the stator and the stator becomes uniform. As described above, the pole piece has a thickness asymmetric with respect to the center of the permanent magnet, and excitation means connected to the stator coil, and the excitation means excites the stator coil. The current is the first value, the second value, or the third value, and the first value and the second value have opposite signs, and the excitation currents of these values are switched alternately. The rotor is driven in a desired direction, and the third value has the same sign as the first value or the second value, and has a different magnitude. If the child is near dead center and said first If it cannot be started by the value or the second value, the exciting current of the stator coil is set to the third value to avoid dead center, and then the exciting current of the stator coil is set to the first value or the second value. This is a brushless motor that generates a starting torque in a desired driving direction as a value and starts the rotor, and can suppress the rise of current due to the backlash of induced voltage switching.
[0019]
Further, the present invention has a stator around which a coil is wound, at least two permanent magnets, and a pole piece made of a material having a higher magnetic permeability than the permanent magnet, and an air gap between the stator and the stator becomes uniform. The pole piece thickness is asymmetric with respect to the permanent magnet center
A rotor and excitation means connected to the stator coil, wherein the excitation means sets the excitation current of the stator coil to a first value or a second value; When the first value and the second value are opposite to each other, and the rotor is in the vicinity of the dead point and the rotor cannot be started by the first value, the excitation current of the stator coil is If the dead point is avoided as the second value, or if the rotor is in the vicinity of the dead point and the rotor cannot be activated by the second value, the exciting current of the stator coil is set as the first value. A brushless motor that avoids the dead point and then switches the exciting current between the first value and the second value so that the rotor starts and continues to drive in a desired direction. Efficient current rise due to switching splash It is possible to suppress clause.
[0020]
Further, the present invention provides a brushless motor having a stator around which a single-phase coil is wound, and is provided with an excitation means, so that the position of the rotor can be avoided from the dead center while keeping the air gap uniform. The self-starting operation can be performed without reducing the efficiency due to the decrease of.
[0021]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0022]
(Example 1)
FIG. 1 shows a single-phase brushless motor in a first embodiment of the present invention. In FIG. 1, reference numeral 12 denotes a stator, and a stator coil 11 is wound around the stator 12. Reference numeral 13 denotes a rotor, which is constructed by inserting and incorporating two permanent magnets 14 having a circular arc cross section at a position radially inward from the outer peripheral surface of the rotor 13. A pole piece 15 is disposed between the permanent magnet 14 and the air gap 19, and the pole piece 15 is made of a material having a higher magnetic permeability than the permanent magnet 14, such as an electromagnetic steel plate 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 so as to be rotatable inside the stator 12 with the stator 12 and a predetermined air gap 19 uniformly present.
[0023]
The operation of the single-phase brushless motor according to this embodiment configured as described above will be described.
[0024]
FIG. 2 shows the generated torque with respect to the rotor position (rotation angle θ).
As can be seen from FIG. 2, the torque with respect to the position of the rotor 13 varies depending on the magnitude and direction of the excitation current of the stator coil 12, and the dead center position where the torque becomes zero moves in particular. This is because the thickness of the pole piece 15 is asymmetric with respect to the center of the permanent magnet 14.
[0025]
In the conventional single-phase brushless motor shown in FIG. 10, the dead center position is not moved by the excitation current of the stator coil 31 as shown in FIG.
[0026]
In the present invention, the dead center position can be moved by the exciting current of the stator coil 11 as described above.
[0027]
By utilizing this in reverse, the self-starting operation of the single-phase brushless motor becomes possible. That is, for example, by passing an exciting current different from that during normal operation to the stator coil 11 at the time of startup, the rotor 13 can be avoided from the dead center position during normal operation, thereby enabling self-starting.
[0028]
Further, as shown in FIG. 1, since the air gap 19 between the rotor 13 and the stator 12 is made uniform, the effective magnetic flux density is not reduced and the motor can be driven with high efficiency.
[0029]
On the other hand, in the present invention, an induced voltage as shown in FIG. 3A is induced in the stator coil 11.
[0030]
The reason why the induced voltage has a waveform as shown in FIG. 3A is that the thickness of the pole piece 15 is asymmetric with respect to the center of the permanent magnet 14.
[0031]
When the voltage shown in FIG. 4B is applied from the outside to the stator coil 11 that generates such an induced voltage, the excitation current waveform becomes as shown in FIG. The bulge at the rear of the waveform as shown is eliminated.
[0032]
Therefore, the exciting current of the stator coil 11 does not become excessive, and the copper loss proportional to the square of the exciting current can be kept small.
[0033]
Since the exciting current is small, a power element with a small power capacity can be used to drive the motor, and the drive circuit portion can be reduced in size and cost.
[0034]
Further, as shown in FIG. 3C, the change in the excitation current during commutation becomes gentle, and electrical noise, vibration and noise can be suppressed.
[0035]
In order to realize these effects, it is not necessary to specifically control the voltage applied to the stator coil 11. For example, a simple rectangular wave voltage need only be applied to the stator coil 11. Therefore, a complicated control circuit is not necessary.
[0036]
As described above, according to the present embodiment, since the dead center position of the rotor 13 can be moved by the excitation current of the stator coil 11, it can be self-actuated using this.
[0037]
Further, since the air gap 19 has a uniform structure, the effective magnetic flux density does not decrease and the motor can be driven with high efficiency.
[0038]
Furthermore, since the induced voltage waveform has a waveform shape as shown in FIG. 3A, the excitation current is not excessive, copper loss can be suppressed, and electrical noise, vibration and noise during commutation can be reduced. is there.
[0039]
These effects can be realized by a simple drive circuit.
In the present embodiment, the shape of the permanent magnet 14 is an arc shape that can be processed relatively easily and the dimensional accuracy can be easily secured. However, the permanent magnet 14 is not necessarily an arc shape.
[0040]
For example, a non-arc-shaped permanent magnet is used, and the thickness of the pole piece arranged between the non-arc-shaped permanent magnet and the air gap is set at the center of the non-arc-shaped permanent magnet so that the air gap is uniform. Alternatively, it may be asymmetric.
[0041]
Further, since the pole piece 15 is arranged 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, and a motor suitable for higher-speed rotation is provided. It can also be realized.
[0042]
In the present embodiment, the inner rotor type single-phase brushless motor is shown, but it goes without saying that it can be applied to an outer rotor type single-phase brushless motor.
[0043]
(Example 2)
FIG. 4 shows a single-phase brushless motor in the second embodiment of the present invention. In FIG. 4, except that the excitation means 16 configured to set the excitation 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 the same as that of the first embodiment shown in FIG.
[0044]
The operation of the single-phase brushless motor in the second embodiment configured as described above will be described.
[0045]
5 and 6 show the generated torque with respect to the position of the rotor 13 (rotation angle θ), as in FIG. 2. In particular, the exciting current to the stator coil 11 by the exciting means 16 is expressed as a first value. And a second value whose magnitude is almost the same as that of the first value, and a third value whose magnitude is the same as that of the first value. Shows about the case.
[0046]
First, consider the case where the rotor is stopped at point M0 in FIG. In this case, the starting torque T1 can be generated with the exciting current of the stator coil 11 as the first value, and the rotor 13 can be driven in the forward direction from the point M1.
[0047]
Conversely, the starting torque T2 can be generated with the exciting current of the stator coil 11 as the second value, and the rotor 13 can be driven in the reverse direction from the point M2.
[0048]
As described above, when the rotor 13 is stopped at a position where the starting torque can be generated by either the first value or the second value, the rotor is moved in a desired direction without any problem. 13 can be activated.
[0049]
However, if the rotor 13 stops at the point A0 in FIG. 5 or the point B0 in FIG. 6, that is, stops at the dead point, the exciting current is generated as the first value or the second value. The torque is zero and the rotor 13 cannot be started.
[0050]
Thus, the operation | movement in case the rotor 13 has stopped at the dead center is demonstrated below. First, the case where the rotor 13 is stopped at the point A0 will be described with reference to FIG.
[0051]
In this case, even if an excitation current having the first value is passed through the stator coil 11, the generated torque is zero and the rotor 13 cannot be started. That is, the A0 point is a dead point when the exciting current is the first value.
[0052]
Therefore, a third exciting current is passed through the stator coil 11. 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 stops stably. At this time, the rotor 13 is shifted from the dead point A0.
[0053]
Accordingly, 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 started in the forward direction from the point A1. Can do.
[0054]
Conversely, when the point C0 is reached, the excitation current is set to the second value to generate the starting torque TB1 as shown in FIG. 5B, and the rotor 13 is started in the reverse direction from the point B1. You can also.
[0055]
As described above, when the excitation current cannot be started even with the first value, the excitation current is set to the third value to avoid the dead point A0, and the excitation current having the first value or the second value is used in a desired direction. The rotor 13 can be activated.
[0056]
Although the rotor 13 is stably stopped at the point C0 when the exciting current is the third value and the dead point A0 is avoided, it is not always necessary to stop at the point C0.
[0057]
For example, as shown in FIG. 5C, when the excitation current is set to the third value and 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, the starting torque is set. TA2 is generated and the rotor 13 can be started in the forward direction from the point A2.
[0058]
Further, as shown in FIG. 5D, when the excitation 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 rotated in the reverse direction from the point B2. Can be started.
[0059]
Next, the case where the rotor 13 is stopped at the point B0 will be described with reference to FIG. In this case, even if an excitation current having a second value is passed through 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 the second value.
[0060]
Therefore, a third exciting current is passed through the stator coil 11. 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. At this time, the rotor 13 is shifted from the dead point B0.
[0061]
Accordingly, 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 started from the point A1 in the forward rotation direction. Can do.
[0062]
Conversely, when the point C0 is reached, the excitation current is set to the second value to generate the starting torque TB1 as shown in FIG. 6B, and the rotor 13 is started from the point B1 in the reverse direction. You can also.
[0063]
In this way, when the excitation current cannot be started even with the second value, the excitation current is set to the third value to avoid the dead point B0, and the first value or the second value of the excitation current causes the desired direction. The rotor 13 can be activated.
[0064]
Although the rotor 13 is stably stopped at the point C0 when the exciting current is the third value and the dead point B0 is avoided, it is not always necessary to stop at the point C0.
[0065]
For example, as shown in FIG. 6C, when the excitation current is set to the third value and 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, the starting torque TA3 is generated, and the rotor 13 can be activated in the forward rotation direction.
[0066]
Further, as shown in FIG. 6 (d), when the exciting current is set to the second value at the point C6 in the middle from the point C4 to the point C0, the starting torque TB3 is generated, and the rotor 13 is rotated in the reverse direction from the point B3. Can be started.
[0067]
As described above, according to the present embodiment, the excitation current can be started even when the first value or the second value is set.
If not, the exciting current is set to a third value larger than these values so as to avoid the dead center position and enable self-starting.
[0068]
In the present embodiment, the case where the magnitude of the third value of the excitation current is larger than the magnitude of the first value or the second value of the excitation current has been described, but the third value is particularly large. There is no need. 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.
[0069]
In this embodiment, the excitation current is set to the third value and the dead point position is avoided, and then the excitation current is switched to the first value or the second value at each operating point shown in FIG. The starting torque is generated, but the timing for switching the excitation current to the first value or the second value may be after a predetermined time has elapsed since the third value of excitation current started to flow through the stator coil 11. Alternatively, the position of the rotor 13 may be detected by a Hall element or the like and switched based on this position detection signal.
[0070]
In addition to the effects described above, it goes without saying that this embodiment also has all the effects shown in the first embodiment.
[0071]
(Example 3)
FIG. 7 shows a single-phase brushless motor according to a third embodiment of the present invention. 7 except that the exciting means 17 configured to set the exciting current of the stator coil 11 to the first value or the second value is connected to the stator coil 11 in FIG. The parts having the same function are the same as those in the first embodiment, and the same reference numerals are given and the detailed description thereof is omitted.
[0072]
The operation of the single-phase brushless motor in the third embodiment configured as described above will be described.
[0073]
8 and 9 show the torque generated with respect to the position of the rotor 11 (rotation angle θ), as in FIG. 2. In particular, the excitation current to the stator coil 11 by the excitation means 17 is expressed as a first value. And the case where the second value is the same as the first value but has the same sign as the first value.
[0074]
First, consider the case where the rotor is stopped at point M0 in FIG. In this case, the starting torque T1 can be generated with the exciting current of the stator coil 11 as the first value, and the rotor 13 can be driven in the forward direction from the point M1.
[0075]
Conversely, the starting torque T2 can be generated with the exciting current of the stator coil 11 as the second value, and the rotor 13 can be driven in the reverse direction from the point M2.
[0076]
As described above, when the rotor 13 is stopped at a position where the starting torque can be generated by either the first value or the second value, the rotor is moved in a desired direction without any problem. 13 can be activated.
[0077]
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.
[0078]
Similarly, when the rotor 13 is stopped at the point B0 in FIG. 9, the generated torque is zero even if the excitation current is set to the second value, and the rotor 13 cannot be started.
[0079]
The operation when the rotor 13 is stopped at the point A0 in FIG. 8 or the point B0 in FIG. 9, that is, the dead point will be described below.
[0080]
First, the case where the rotor 13 is stopped at the point A0 will be described with reference to FIG. In this case, even if the first value of exciting current is passed through the stator coil, the generated torque is zero and the rotor 13 cannot be started. That is, the A0 point is a dead point when the exciting current is the first value.
[0081]
Therefore, the second exciting current is caused to flow through the stator coil 11. Then, the negative torque shown at the operating point B4 acts on the rotor 13, starts moving toward the operating point B5, and the rotor 13 is shifted from the dead point A0.
[0082]
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. 8A, and the rotor 13 is started from the point A4 in the forward rotation direction. Can do.
[0083]
Further, with the exciting current kept at the second value, the rotor can be started from the point B4 in the reverse direction by the starting torque TB4 as shown in FIG. 8B.
[0084]
In this way, when the excitation current cannot be started even with the first value, the excitation current is set to the second value to avoid the dead point A0, and then the desired direction is determined by the first value or the second value of the excitation current. The rotor 13 can be activated.
[0085]
Next, the case where the rotor 13 is stopped at the B0 point will be described with reference to FIG.
[0086]
In this case, even if an excitation current having a second value is passed through 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 the second value.
[0087]
Therefore, the first exciting current is caused to flow through the stator coil 11. Then, the negative torque shown at the operating point A5 acts on the rotor, and the rotor 11 starts to move so as to avoid the B0 point which is a dead point.
[0088]
In order to start the rotor 13 in the forward rotation direction after avoiding the dead point B0, as shown in FIG. 9A, the excitation current is set to the second value when the operating point A0 is reached, The rotor 13 is further moved to the operating point B6 by the negative torque shown at the operating point B4, and when reaching the B6 point, the exciting current is moved to the operating point A6 as the first value, and the starting torque TA6 is set. It only has to be generated.
[0089]
Alternatively, when the operating point A0 is reached, the rotor 13 is moved to the operating point A7 using the inertia of the rotor 11 and the starting torque TA7 indicated by the operating point A7 is generated. The child 13 can be activated in the forward direction.
[0090]
Here, while moving the rotor 13 to the operating point A7 using inertia, if the exciting current is made zero, the moving amount can be increased, and the starting torque TA7 is set to a larger value in the forward rotation direction. Can be further ensured.
[0091]
In order to start the rotor 13 in the reverse direction after avoiding the dead point B0, as shown in FIG. 9B, the excitation current is started as the second value when the operating point A0 is reached. The torque TB4 may be generated.
[0092]
In this way, when the excitation current cannot be started even with the second value, the excitation current is set to the first value to avoid the dead point B0, and then the desired direction is determined by the first value or the second value of the excitation current. The rotor 13 can be activated.
[0093]
It has been described that the excitation current is set to the first value and the excitation current is set to the second value when the rotor 13 reaches the point A0 after avoiding the dead point B0. However, the present invention is not limited to this. .
[0094]
For example, to start in the forward rotation direction, as shown in FIG. 9C, after the exciting current is set to the first value, the rotor 13 is at the point A8 on the way from the operating point A5 to the point A0. After the rotor 13 is further moved to the operating point B8 by the reverse torque indicated by the operating point B7 as the second value, the excitation current is moved to the operating point A9 as the first value, and the starting torque TA9. May be generated.
[0095]
In order to start in the reverse direction, as shown in FIG. 9D, the starting torque TB9 may be generated with the exciting current as the second value at the point A10 in the middle from the point A5 to the point A0.
[0096]
As described above, according to this embodiment, when the excitation current cannot be started even with the first value, the excitation current is set to the second value, and the dead center position when the excitation current is set to the first value is avoided. Can be started automatically. If the excitation current cannot be started even with the second value, the excitation current is set to the first value, and the dead point position when the excitation current is set to the second value is avoided so that the self-start can be performed.
[0097]
As described above, in this embodiment, the motor is self-started by two values of excitation current, so that the configuration of the excitation means 17 can be further simplified.
[0098]
In this embodiment, the excitation current is set to the first value or the second value to avoid the dead center position, and then the excitation current is switched at each operating point shown in FIG. 8 or FIG. 9 to generate the starting torque. However, the timing for switching the excitation current may be after a predetermined time has elapsed since the excitation current of the first value or the second value has started to flow through the stator coil 11 to avoid dead center, or The position of the rotor 13 may be detected by a Hall element or the like and switched based on this position detection signal.
[0099]
In addition to the effects described above, it goes without saying that this embodiment also has all the effects shown in the first embodiment. Needless to say, the present invention is applicable not only to an inner rotor type single-phase brushless motor but also to an outer rotor type single-phase brushless motor.
[0100]
【The invention's effect】
As is apparent from the description of the above embodiment, according to the first and third aspects of the invention, the dead center position of the rotor can be moved by the exciting current of the stator coil, and this is used for self-starting. Is possible. Furthermore, since the air gap has a uniform structure, the effective magnetic flux density does not decrease and the motor can be driven with high efficiency. Further, the excitation current is not excessive, copper loss can be suppressed, and electrical noise, vibration and noise during commutation can be reduced. These effects can be realized by a simple drive 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 scattering due to centrifugal force during high-speed rotation, and a motor suitable for higher-speed rotation can be realized. it can. Moreover, since the starting torque for starting uses the driving torque of the motor, the starting torque can be easily increased.
[0101]
Further, the invention according to claim 2 can suppress the rise of current due to the jump of the induced voltage at the time of switching, and can drive the motor efficiently.
[0102]
Further, according to the invention described in claim 4, since a permanent magnet having a stable magnetic flux as a whole can be used for the rotor, it is possible to provide a brushless motor with good performance without unevenness.
[0103]
According to the fifth aspect of the present invention, when the exciting current cannot be started as the first value or the second value, it is possible to suppress the rise of current due to the jump of the induced voltage at the time of switching, and drive the motor efficiently. can do.
[0104]
According to the sixth aspect of the invention, since the motor is self-started by two values of excitation current, the configuration of the excitation means is further simplified, and the current caused by the jump of the induced voltage at the time of switching. Can be suppressed, and the motor can be driven efficiently.
[0105]
Moreover, since the dead center position of the rotor can be moved by the exciting current of the stator coil by using the invention of the seventh aspect for the single-phase motor, it can be self-started using this. . Furthermore, since the air gap has a uniform structure, the effective magnetic flux density does not decrease and the motor can be driven with high efficiency. Further, the excitation current is not excessive, copper loss can be suppressed, and electrical noise, vibration and noise during commutation can be reduced. These effects can be realized by a simple drive 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 scattering due to 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 rotor position of the single-phase brushless motor in FIG.
FIG. 3 is an explanatory diagram showing an induced voltage waveform and an exciting current waveform of the single-phase brushless motor in FIG.
FIG. 4 is a sectional view of a single-phase brushless motor according to a second embodiment of the present invention.
FIG. 5 is an operation explanatory diagram of the single-phase brushless motor in FIG.
6 is an operation explanatory diagram 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.
8 is an operation explanatory diagram of the single-phase brushless motor in FIG.
9 is an operation explanatory diagram of the single-phase brushless motor in FIG. 7. FIG.
FIG. 10 is a longitudinal sectional view of a conventional single-phase brushless motor.
FIG. 11 is an explanatory diagram showing torque characteristics with respect to the rotor position of the single-phase brushless motor in FIG.
FIG. 12 is a cross-sectional view of a single-phase brushless motor in another conventional example
13 is an explanatory diagram showing an induced voltage waveform and an excitation current waveform of the single-phase brushless motor in FIGS. 10 and 12. FIG.
[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 Excitation means
19, 39, 49 Air gap

Claims (1)

A stator around which a coil is wound, at least two permanent magnets, and a pole piece made of a material having a higher magnetic permeability than the permanent magnet, and the pole piece so that an air gap between the stator and the stator is uniform. A rotor having an asymmetric thickness with respect to the center of the permanent magnet, and excitation means connected to the stator coil, wherein the excitation means generates an excitation current of the stator coil as a first value. Or the second value or the third value, and the first value and the second value have opposite signs, and the excitation current of these values is switched alternately to switch the rotor. Driven in a desired direction, wherein the third value is a value having the same sign as the first value or the second value but having a different magnitude, and the rotor is near the dead center And the first value or the If the actuator cannot be activated with a value of 2, the dead current is avoided by setting the exciting current of the stator coil as the third value, and then the exciting current of the stator coil is set as the first value or the second value as desired. A brushless motor that generates a starting torque in the driving direction and starts the rotor.

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