JPH08275418A - Five-phase brushless motor - Google Patents

Abstract

PURPOSE: To reduce the difference between the maximum and minimum values of torque generated at a brushless motor. CONSTITUTION: A recessed groove 5a which is long in axial direction and has a circular section is formed at either position with an electrical angle of 36, 72, 108, or 144 degrees, for example at a position which is shifted by 72 degrees clockwise, in peripheral direction from the boundary between N and S poles of each magnetic pole of a permanent magnet 5 for constituting a rotor, thus making a position which is shifted by an electrical angle of 72 degrees in peripheral direction from the boundary between the N and S poles to be a low magnetic flux density region. Namely, the magnetic flux density at a position which is shifted in peripheral direction by an electrical angle of 72 degrees clockwise from a point a11 which is the boundary of S and N poles is made lower than that of a normal permanent magnet where no recessed groove 5a is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a brushless motor, and more particularly, it is intended to minimize fluctuations in output torque with respect to rotational position.

[0002]

2. Description of the Related Art Conventionally, for example, a brushless motor in which an outer circumference is surrounded by a plurality of exciting coils, such as three phases, around a rotor magnetized in the circumferential direction alternately and at equal intervals. Then, the magnetic flux density distribution of the permanent magnets constituting the rotor was sinusoidal as shown in FIG.

[0003]

Here, for example, in a conventional three-phase brushless motor, three-phase exciting coils a,
b and c are star-connected in a Y shape, and each excitation coil a to c
When an exciting current as shown in FIG. 14 is supplied, that is, when driven by a two-phase excitation method that switches the energization state every 60 degrees in electrical angle, the torque generated in each exciting coil is the magnetic flux density distribution of the permanent magnet of the rotor. 13 is a sine wave in FIG. 13, a mountain-shaped waveform that changes depending on the rotational position of the rotor is drawn as shown in the lower part of FIG. Then, since the sum of the torques generated in the coils becomes the torque generated in the motor, the torque of the motor changes depending on the rotational position of the rotor as shown in the upper part of FIG. In this case, the torque ripple (the maximum value T fluctuation difference between the _max and the minimum value _{T min ΔT = T ma x -T} min of torque), about relative average torque _{(= (T max + T min} ) / 2) 15 It will be about%.

It can be said that such a torque ripple is smaller than that of other types of brushless motors. However, considering that the torque ripple is used as a drive source of a power steering device of an automobile, for example, torque fluctuations in the steering system are caused by the driver. It is preferable to be as small as possible in order to make the steering feel uncomfortable.
A torque ripple of about 5% is too uncomfortable, and even in the case of a 5-phase brushless motor, the torque ripple is at most about 8%, and further reduction of the torque ripple has been desired.

Therefore, the present invention has been made in view of the unsolved problems of the prior art, and an object thereof is to provide a brushless motor capable of minimizing torque ripple. There is.

[0006]

In order to achieve the above object, in a five-phase brushless motor according to a first aspect of the present invention, an S-pole and an N-pole are alternately magnetized on the outer peripheral surface in the circumferential direction at equal intervals. 5 comprising a rotatable rotor, a 5-phase exciting coil arranged in a star connection so as to surround the outer peripheral surface of the rotor, and a drive circuit for supplying an exciting current to the 5-phase exciting coil In the phase brushless motor, the drive circuit is a four-phase excitation drive circuit that sequentially switches the excitation coils that supply the excitation current one by one and supplies the excitation currents to the four-phase excitation coils simultaneously. It is characterized in that the low magnetic flux density region is formed at a position deviated from the boundary of the magnetic poles in the circumferential direction by any one electrical angle of 36 degrees, 72 degrees, 108 degrees and 144 degrees.

According to a second aspect of the present invention, there is provided a five-phase brushless motor having a rotatable rotor in which an S pole and an N pole are alternately magnetized in the circumferential direction in the circumferential direction at equal intervals, and the rotor is star-connected to the rotor. In a five-phase brushless motor including a five-phase exciting coil arranged so as to surround the outer peripheral surface of the motor and a drive circuit for supplying an exciting current to these five-phase exciting coils, Is a two-phase excitation drive circuit that sequentially switches the excitation coils for supplying the excitation current to the two-phase excitation coils at the same time, and the electrical angle is 72 degrees or 108 from the boundary of the magnetic poles of the rotor.
It is characterized in that a low magnetic flux density region is formed at a position displaced in the circumferential direction by an electrical angle of degrees.

[0008]

The five-phase brushless motor according to the first aspect is excited at the time when the output torque of the motor, which is the sum of the torques generated in the coils when the five-phase brushless motor is driven by the four-phase excitation drive circuit, becomes maximum. In order to reduce the torque generated in one of the inner coils, an electrical angle of 36 in the circumferential direction from the boundary between the S pole and the N pole of the magnetic pole of the rotor.
Since the low magnetic flux density region is formed at a position deviated by any one of electrical degrees of 72 degrees, 72 degrees, 108 degrees and 144 degrees, the maximum value of the output torque of the motor is reduced by that amount, and the torque ripple is reduced. It

Further, in the five-phase brushless motor according to the second aspect, when the output torque of the motor, which is the sum of the torques generated in the coils when the five-phase brushless motor is driven by the two-phase excitation drive circuit, becomes maximum. In order to reduce the torque generated in one of the excited coils, the electrical angle is shifted by 72 or 108 electrical degrees in the circumferential direction from the boundary between the S and N poles of the rotor magnetic poles. Since the low magnetic flux density region is formed at the position, the maximum value of the output torque of the motor is correspondingly reduced, and the torque ripple is reduced.

The method of forming the low magnetic flux density region of the five-phase brushless motor according to the first and second aspects is not particularly limited, and it is possible to devise, for example, magnetizing, or a permanent magnet. It is also possible to form a concave portion, a void or the like at the center position in the circumferential direction as appropriate.

[0011]

EXAMPLES Examples of the present invention will be described below. FIG.
FIG. 3 is a front sectional view showing the structure of a 5-phase brushless motor according to the first embodiment of the present invention. This 5-phase brushless motor 1 includes a cylindrical housing 2, a rotary shaft 4 which is arranged along the axis of the housing 2 and is rotatable by bearings 3a and 3b, and a motor drive which is fixed to the rotary shaft 4. Permanent magnet 5 and a five-phase exciting coil 6a fixed to the inner peripheral surface of the housing 2 so as to surround the permanent magnet 5.
6b, 6c, 6d and 6e wound stator 6
The rotary shaft 4 and the permanent magnet 5 form a rotatable rotor 7.

A ring-shaped permanent magnet 8 for phase detection is fixed to the rotor 7 in proximity to one end of the rotary shaft 4, and the permanent magnet 8 has an S pole and an N pole. The poles are magnetized alternately in the circumferential direction at equal intervals. On the other hand, on the inner end surface of the housing 2 on the side where the bearing 3b is disposed, a support substrate 10 made of a ring-shaped thin plate is provided via a stay 9 so that the insulating portion on the inside faces the permanent magnet 8. On the surface of the support substrate 10 facing the permanent magnet 8 side, the phase detection element 11 made of, for example, a Hall element is fixed so as to face the permanent magnet 8. In addition, the phase detection element 11 is actually the excitation coils 6a to 6e.
5 are provided at appropriate intervals in the circumferential direction in accordance with the driving timing, but FIG. 1 is a sectional view, and only one of them is shown.

In the phase detecting elements 11a to 11e, when the magnetic pole of the permanent magnet 8 facing the phase detecting elements 11a to 11e is the N pole, a sensor signal as a position detecting signal of "H", and when the S pole is "L", the sensor signal is "L". Output the sensor signal of ", and each phase detection element 1
The rotational position of the rotor 7 is recognized by utilizing the fact that the outputs of 1a to 11e are changed by the magnetic poles of the permanent magnet 8 facing it, and the drive circuit 64, which will be described later, correspondingly recognizes the rotational position of the rotor 7 in five phases. The exciting coils 6a to 6e are energized by a four-phase exciting method in which four phases are simultaneously energized to energize the exciting coils one by one, and the rotor 7 is appropriately rotated.

On the other hand, the permanent magnet 5 constituting the rotor 7 is
As shown in FIG. 2, which is a plan view showing the magnetized state,
Three south poles and three north poles are magnetized alternately at equal intervals in the circumferential direction. Here, in this case, the S pole and the N pole are 3
A total of 6 poles are applied to each pole, but if the S poles and N poles are magnetized alternately in the circumferential direction and at equal intervals, the S poles and N poles are Two poles are all right,
Other multiple poles may be used.

As shown in FIG. 2, each magnetic pole of the permanent magnet 5 has a groove 5 having a semicircular cross section which is long in the axial direction.
a is formed, and this position is a low magnetic flux density region. That is, the magnetic flux densities at positions 72 degrees clockwise in the circumferential direction from the point a ₁₁ which is the boundary between the S pole and the N pole are lower than those of a normal permanent magnet in which the concave groove 5a is not formed. The electrical angle is 0 to 360.
As shown by the solid line in FIG. 3, the magnetic flux density distribution in the range of degrees is dented at positions of 72 degrees and 252 degrees in electrical angle as compared with the normal magnetic flux density distribution shown by the broken line that changes sinusoidally. Distribution.

On the other hand, the coil circuit 35 is formed of five-phase exciting coils 6a to 6e, and is star-connected in a Y shape as shown in FIG. 4, and the outer peripheral surface of the rotor 7 is separated by an electrical angle of 72 degrees. It is arranged so as to surround it. Here, in the four-phase excitation method, the motor current flows in four phases, but the current is inversely proportional to the coil resistance. Therefore, in order to flow the current in a well-balanced manner in each phase, the coil resistance of each excitation coil 6a to 6e Are all formed to be equal.

Further, in the stator 6, for example, 30 slots are formed on an inner peripheral surface of a stator core (not shown) at equal intervals, and the same number of convex portions are formed between the slots. Of these, 10 convex portions are formed. Each of these exciting coils 6 as a set
A to 6e are wound around. Therefore, the development view of the winding of one set of the above-mentioned convex portions is as shown in FIG. 5, and it is formed so that the electrical angle between the convex portions 41 to 50 is 360 degrees.

The exciting coil 6a has convex portions 41 and 4
5 is wound around the convex portions 42 to 44, the exciting coil 6b is wound around the convex portions 43 and 47 around the convex portions 44 to 46, and the exciting coil 6c is similarly wound around the convex portions 45 and 4.
As shown in FIG. 9, each of the five convex portions is surrounded and wound, one end of which is collectively connected and the other end is connected to the drive circuit 64.

The drive circuit 64 is, as shown in FIG.
Individual transistors (field effect transistors) Ta1, T
b1, Tc1, Td1, Te1, Ta2, Tb2, Tc
2, Td2, Te2. In particular,
Series-related transistors Ta1-Ta2, transistors Tb1-Tb2, transistors Tc1-Tc2, transistors Td1-Td2, transistors Te1-Te
2 are arranged in parallel between both terminals of the power source, and each transistor Ta1-Ta2 and transistor Tb
1-Tb2, transistors Tc1-Tc2, transistors Td1-Td2, and transistors Te1-Te2 are connected to the outer ends of the exciting coils 6a to 6e (on the side opposite to the center side of the star connection).

The gate voltage of each of the transistors Ta1 to Te2 is controlled on the basis of the outputs of the phase detecting elements 11a to 11e described above. Specifically, the directions and magnitudes of the exciting currents to the exciting coils 6a to 6e are as shown in FIG.
The timing of ON / OFF of Te2 to Te2 is as shown by the gate signals (upper row) and (lower row) in Table 1 below. Here, in FIG. 6, the a phase corresponds to the exciting coil 6a, the b phase corresponds to the exciting coil 6b, each phase corresponds to each exciting coil, and the e phase corresponds to the exciting coil 6e. . In addition, in Table 1, "1" represents ON and "0" represents OFF.

[0021]

[Table 1]

In FIG. 6, assuming that it is in the state of d1, for example, this corresponds to the section K1 of Table 1, so that the upper side transistors Ta1 and Tb1 and the lower side transistors Tc2 and Td2 are turned on. Since the transistors other than are turned off, the exciting coils 6a and 6b
To the exciting coil 6c and 6d, a current flows from the outer end side to the exciting coil 6c and 6d from the wire connection side. At this time, since the coil resistances of the exciting coils are all equal, the current flowing in each exciting coil is I The current flowing through the 5-phase brushless motor 1 is I, when the speed is / 2. As a result, in the winding development view of FIG. 5, a current flowing upward in FIG. 5 flows on both sides of the convex portions 41, 42, 50, and a current flowing downward in FIG. 5 flows on both sides of the convex portions 45 to 47. Therefore, the N pole is generated in the convex portions 43 and 44, and the S pole is formed in the convex portions 48 and 49.
A pole occurs. Therefore, the rotor 7 rotates due to the magnetic attraction force and the repulsive force between the S pole or N pole of the rotor 7 and the S pole or N pole generated in the convex portion.

When the rotor 7 rotates and shifts to the state of d2 in FIG. 6, this corresponds to the section K2 of Table 1, so that the upper side transistors Ta1 and Tb1 and the lower side transistors Td2 and Te2 are turned on. , The other transistors are turned off, so the exciting coil 6
Current flows from the outer end side to a and 6b, and the exciting coil 6d
An electric current flows from the connection side to 6 and 6e. by this,
In the winding development view of FIG. 5, a current flowing upward in FIG. 5 flows on both sides of the convex portions 41 to 43, and a current flowing downward in FIG. 5 flows on both sides of the convex portions 46 to 48. And 45 generate N poles, and the convex portions 49 and 5
An S pole is generated at 0. Then, similarly to the above, the rotor 7
The rotor 7 further rotates due to the magnetic attraction force and the repulsive force between the S pole or N pole and the S pole or N pole generated in the convex portion. By repeating this operation, each transistor is activated at the timing shown in Table 1, and as shown in FIG. 6, the exciting coil that sequentially excites one phase at an electrical angle of 36 degrees is switched, and one phase is switched at an electrical angle. By exciting for 144 degrees, the S pole or the N pole generated in each convex portion of the stator 6 is sequentially moved, whereby the rotor 7 is continuously rotated.

The magnetic flux density distribution of the permanent magnet 5 is shown in FIG.
If the current flowing in the exciting coils 6a to 6e is as shown in FIG. 6, the exciting coils 6a to 6e
Since the torque generated in 6e is proportional to the product of the amount of magnetic flux orthogonal to each exciting coil 6a to 6e and the exciting current flowing in each exciting coil 6a to 6e, as shown by the solid line in the lower part of FIG. Become.

For example, in terms of the exciting coil 6b, since the exciting current is not supplied during the electrical angle from 0 degree to 18 degrees, the exciting coil 6b does not generate torque (in FIG. 7,
This is indicated by a broken line. ). Then, the generated torque gradually increases from the electrical angle of 18 degrees to 54 degrees, but since the magnetic flux density distribution around it is concave around 72 degrees, as shown in FIG. The torque generated in the exciting coil 6b becomes small once after passing the angle of 54 degrees, gradually rises after reaching 72 degrees, reaches the maximum at 90 degrees, and reaches the maximum of 162 degrees after passing 90 degrees. The generated torque gradually decreases, and since the exciting current is not supplied from 162 degrees to 180 degrees, no torque is generated. When the electrical angle exceeds 198 degrees, the exciting coil 6
Reverse current is supplied to b.

The change in the torque of the exciting coil 6b between 180 and 360 degrees is the same as the change in the torque between 0 and 180 degrees, and the change in the exciting coil 6e is the change in the torque of the exciting coil 6b. Is exactly the same except that it is delayed by 36 degrees. Similarly, the torque change of the exciting coil 6c is 72 degrees with the torque change of the exciting coil 6b, and the torque change of the exciting coil 6a is 10 degrees with the torque change of the exciting coil 6b.
The torque change of the exciting coil 6d is 8 degrees and the torque change of the exciting coil 6b are exactly the same, except that they are delayed by 144 degrees, respectively.

Since the torque generated in the five-phase brushless motor 1 is the sum of the torques generated in the four excited excitation coils, it has a waveform as shown by the solid line in the upper part of FIG. Here, originally, the waveform of the torque of the five-phase brushless motor 1 is the sum of the torques of the four exciting coils as shown by the solid line in the lower part of FIG. 36 degrees, 72 degrees, 108
The maximum should be at the positions of degrees, 144 degrees, 180 degrees, ..., 334 degrees, and 360 degrees, but in the first embodiment,
Since the groove 5a is formed at the position where the maximum torque is generated, the maximum value T _max of the motor torque becomes small.

As described above, according to the configuration of this embodiment, the maximum value T _max of the motor torque can be reduced without decreasing the minimum value T _min of the motor torque.
The torque ripple determined by the difference between them can be suppressed. By the way, the present inventors have found that the electric angle of the permanent magnet 5 is 7
The magnetic flux density around 2 degrees was reduced by about 20% 5
When actually measuring the torque of the phase brushless motor 1,
The torque ripple is about 3%. Therefore, the torque ripple of the conventional three-phase brushless motor is about 15%, and when actually measuring the torque of the five-phase brushless motor when the low magnetic flux density region is not formed in the permanent magnet 5, the torque ripple is about 8%. It was confirmed that the torque ripple of the motor torque can be dramatically reduced because it is about the same.

Therefore, the five-phase brushless motor according to the present embodiment has a small fluctuation in output torque and a smooth phase switching, and thus is applied as a drive source of an electric power steering apparatus for an automobile, for example. In this case, it is preferable that the driver does not feel a sense of discomfort due to output torque fluctuations via the steering wheel.

Further, in the five-phase brushless motor of this embodiment, the concave groove 5 is formed only at one place of each magnetic pole forming the permanent magnet 5.
Since the low magnetic flux density region is formed by providing a, it is easy to form and the amount of processing for forming one concave groove 5a can be small. Therefore, the low magnetic flux density region can be formed with high accuracy. Therefore, stable torque can be obtained. Further, since the processing is easy and the processing amount is small, it can be realized at a low cost.

Further, since a large effect can be obtained in a small low magnetic flux density region in the five-phase brushless motor, for example, even in a three-phase brushless motor, it is possible to reduce the torque change by forming the groove to form the low magnetic flux density region. It is possible, but it is necessary to make the concave groove large, and sufficient effect cannot be obtained in the low magnetic flux density region obtained by devising the magnetization, but in the case of a 5-phase brushless motor, it is stable only by devising the magnetization. The obtained torque can be easily obtained.

Further, this five-phase brushless motor has a low probability of causing a motor abnormality due to brush abrasion or the like like a brush motor, and the five-phase brushless motor is a three-phase brushless motor even when an abnormality occurs. Since the abnormality can be detected more reliably as compared with, the loss of energy due to the brush can be avoided because there is no brush. Therefore, for example, if applied as a drive source of an electric power steering device,
Since it is not necessary to provide an electromagnetic clutch device that transmits and cuts off the assist force unlike the conventional electric power steering device, it is possible to avoid problems such as the influence of the electromagnetic clutch device on inertia and the weight. Further effects can be obtained.

Further, in the five-phase brushless motor as in this embodiment, the rotor can be made thinner as compared with the brushed motor that has been conventionally applied as a drive source for an electric power steering apparatus, so that the inertia acting on the rotor can be further improved. It is also suitable as a drive source for an electric power steering device because it can be made small. Next, a second embodiment of the present invention will be described.

FIG. 9 is a plan view of the permanent magnet 5 similarly to FIG. 2 of the first embodiment, and since the other construction is the same as that of the first embodiment, its illustration and description will be omitted. In the second embodiment, as in the first embodiment, the six permanent magnets 5A to 5F having the same fan-shaped cross section, in which the S poles and the N poles are lined up in the circumferential direction, are attached to the rotary shaft 4 (see FIG. 1). The permanent magnets 5 are arranged so as to surround the same and constitute the permanent magnet 5 equivalent to that of the first embodiment. Then, the permanent magnet 5A is rotated counterclockwise in the circumferential direction from the point a ₁₂ which is the boundary between the permanent magnets 5A and 5B by an electrical angle of 7 degrees.
The N pole is magnetized up to the point a ₁₃ position, which is offset by 2 degrees, and
_The S pole is magnetized from ₁₃ to a point a ₁₄ which is a boundary between the permanent magnets 5A and 5F. Also, permanent magnets 5C and 5
E is also magnetized similarly to the permanent magnet 5A.

On the other hand, the permanent magnet 5B is magnetized to the N pole between the boundary point a ₁₂ and a point a ₁₅ which is deviated by an electrical angle of 108 degrees in the clockwise direction in the circumferential direction, and the permanent magnets 5B and 5C from the point a ₁₅ are magnetized. The S pole is magnetized up to the point a ₁₆ which is the boundary between and. And, like the permanent magnet 5B, the permanent magnets 5D and 5
E is magnetized. And these permanent magnets 5A-5
E is arranged such that magnets having different magnetized states are adjacent to each other and the same poles are in contact with each other. For example, the N pole of one permanent magnet and the N pole of the other permanent magnet which are adjacent to each other have an electrical angle of 180 °. It has become a degree.

Then, chamfers 5b are formed on the outer peripheral surface side end portions of the permanent magnets 5A to 5F. Therefore, when the permanent magnets 5A to 5F are combined as shown in FIG. 9, the chamfers 5b of the adjacent permanent magnets 5A to 5F are located at an electrical angle of 72 degrees clockwise from the boundary between the S pole and the N pole. A low magnetic flux density area is formed. Therefore, even with the configuration of this embodiment, it is possible to obtain the same operational effect as that of the first embodiment, and, like the first embodiment, the corner portions of the permanent magnets 5A to 5F. Since the low magnetic flux density region can be formed by shaving the flat surface, there is an advantage that the manufacturing cost can be reduced as compared with the configuration of the first embodiment which requires groove processing. Further, in this low magnetic flux density region, a desired shape may be formed by molding from the beginning, instead of cutting the corner portions of the permanent magnets 5A to 5F.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 10 is a plan view of the permanent magnet 5 similarly to FIG. 2 of the first embodiment, and since other configurations are similar to those of the first embodiment, the illustration and description thereof will be omitted. In the third embodiment, as in the second embodiment, S in the circumferential direction is applied.
Six permanent magnets 5A to 5F having the same fan-shaped cross section in which the poles and the N poles are lined up are arranged so as to be surrounded by the rotating shaft 4 (see FIG. 1) to form the permanent magnet 5 equivalent to the first embodiment. There is. The permanent magnets 5A to 5F have an electrical angle of 7 in the circumferential direction from the boundary between the S pole and the N pole, as in the second embodiment.
The permanent magnets 5A to 5F are magnetized so that the positions displaced by 2 degrees or 108 degrees become the connection points with the adjacent permanent magnets.
Permanent magnet 5A so that a slight gap 5c is formed between
The circumferential dimension of 5F is slightly smaller than 1/6 of the circumferential dimension of the permanent magnet 5 in the first embodiment.

Then, as shown in FIG. 10, when the permanent magnets 5A to 5F are combined so that the same poles face each other,
A gap 5 is formed at a position offset by 72 electrical degrees in the clockwise direction from the boundary point a ₁₇ of the S pole and the N pole of the permanent magnet 5A, which is the N pole formed by the adjacent permanent magnets, for example, the permanent magnets 5A and 5B.
A low magnetic flux density region is formed by c. Then, the low magnetic flux density region is formed by the gap 5c at the position of the S pole formed by the permanent magnets 5A and 5F, which is deviated from the boundary point a ₁₇ counterclockwise by an electrical angle of 108 degrees. Similarly, a low magnetic flux density region is formed in each magnetic pole.
Therefore, even with the configuration of this embodiment, it is possible to obtain the same effects as the first embodiment. Further, since it is not necessary to chamfer the permanent magnets 5A to 5F, there is an advantage that the manufacturing cost can be further reduced as compared with the second embodiment.

In addition to the permanent magnet 5 in which the low magnetic flux density region is formed as shown in the above-mentioned first to third embodiments, for example, clockwise from the boundary between the S pole and the N pole of the permanent magnet 5. It is also possible to apply the permanent magnet 5 in which a low magnetic flux density region is formed by forming a long circular hole in the axial direction in a portion close to the outer peripheral surface at a position displaced by 72 degrees in electrical angle. However, it is possible to obtain the same effect as that of the first embodiment.

In the first to third embodiments described above, the low magnetic flux density region is formed at the position shifted by 72 electrical degrees in the clockwise direction in the circumferential direction from the boundary between the S pole and the N pole.
For example, in the clockwise direction in the circumferential direction, an electrical angle of 36 degrees, or 10
Even when the low magnetic flux density region is formed at a position shifted by 8 degrees or 144 degrees by devising the magnetization, it is possible to obtain the same effect as that of the first to third embodiments.

In each of the above-described embodiments, the shape of the permanent magnet 5 is appropriately devised so that the low magnetic flux density region is formed at a position deviated by a predetermined electrical angle from the boundary between the S pole and the N pole. However, for example, the low magnetic flux density region may be formed by devising the magnetization, for example, without processing the permanent magnet. In addition, in the configuration of each of the above embodiments, in order to maintain the impact resistance of the processed permanent magnet, the periphery of the permanent magnet may be covered with a cylindrical cover.

Further, in each of the above-mentioned embodiments, the case where the 5-phase brushless motor is driven by the 4-phase excitation drive system has been described, but the same operational effect can be obtained even when the 5-phase brushless motor is driven by the 2-phase excitation drive system. Obtainable. In this case, the position where the low magnetic flux density region is formed is a position displaced from the boundary of each magnetic pole in the circumferential direction by an electrical angle of 72 degrees or 108 degrees. The directions and magnitudes of the exciting currents to the exciting coils 6a to 6e are specifically as shown in FIG. Then, when the five-phase brushless motor is driven at the timing shown in FIG.
The torque generated in 6e is shown by the solid line in the lower part of FIG. 12, and the torque generated in the 5-phase brushless motor is
Since it is the sum of the torques generated in the two excited excitation coils, the waveform is as shown by the solid line in the upper part of FIG.

[0043]

As described above, according to claim 1,
According to the phase brushless motor, when driven by the four-phase excitation drive circuit, any one of 36 degrees, 72 degrees, 108 degrees and 144 degrees in electrical angle in the circumferential direction from the boundary between the S pole and the N pole of the rotor is used. Since the low magnetic flux density region is formed at the position shifted by the electrical angle, the maximum value of the output torque can be reduced, so that the torque ripple can be suppressed.

According to the five-phase brushless motor of the second aspect, when driven by the two-phase excitation drive circuit, the electrical angle is 72 degrees or 108 degrees in the circumferential direction from the boundary between the S pole and the N pole of the rotor. Since the low magnetic flux density region is formed at the position deviated by the electrical angle of, the maximum value of the output torque can be reduced, and the torque ripple can be suppressed.

[Brief description of drawings]

FIG. 1 is a front sectional view of a 5-phase brushless motor of the present invention.

FIG. 2 is a plan view of the permanent magnet of the first embodiment.

FIG. 3 is a distribution diagram of magnetic flux density according to the first embodiment.

FIG. 4 is a circuit diagram showing a connection state of an exciting coil and a drive circuit.

FIG. 5 is a development view of windings of a stator 6.

FIG. 6 is a waveform diagram of an excitation current in a four-phase excitation drive system.

FIG. 7 is a waveform diagram of torque generated in each exciting coil and the motor in the four-phase excitation driving method.

FIG. 8 is a waveform diagram of torque generated in each exciting coil and the motor when the low magnetic flux density region is not formed.

FIG. 9 is a plan view of a permanent magnet of a second embodiment.

FIG. 10 is a plan view of a permanent magnet of a third embodiment.

FIG. 11 is a waveform diagram of an excitation current in a two-phase excitation drive method.

FIG. 12 is a waveform diagram of torque generated in each excitation coil and the motor in the two-phase excitation drive system.

FIG. 13 is a distribution diagram of magnetic flux density of a conventional three-phase brushless motor.

FIG. 14 is a waveform diagram of an exciting current of a conventional three-phase brushless motor.

FIG. 15 is a waveform diagram of torque generated in each exciting coil and the motor of the conventional three-phase brushless motor.

[Explanation of symbols]

 1 5 Phase Brushless Motor 4 Rotation Shaft 5 Permanent Magnet 5A to 5F Permanent Magnet 5a Recessed Groove 5b Chamfer 5c Gap 6a to 6c Excitation Coil 7 Rotor 64 Drive Circuit

Claims (2)

[Claims] 1. A rotatable rotor in which S poles and N poles are magnetized alternately and equidistantly in the circumferential direction on the outer peripheral surface, and the rotor is arranged in star connection so as to surround the outer peripheral surface of the rotor. In a 5-phase brushless motor including a 5-phase exciting coil and a drive circuit for supplying an exciting current to these 5-phase exciting coils, the drive circuit sequentially switches the exciting coils for supplying the exciting current one by one. Is a four-phase excitation drive circuit for simultaneously supplying an excitation current to the four-phase excitation coil, and the electrical angle is 36 degrees from the boundary of each magnetic pole of the rotor,
A five-phase brushless motor characterized in that a low magnetic flux density region is formed at a position displaced in the circumferential direction by any one electrical angle of 72 degrees, 108 degrees, and 144 degrees. 2. A rotatable rotor in which S-poles and N-poles are magnetized alternately and equidistantly in the circumferential direction on the outer peripheral surface, and star-connected and arranged so as to surround the outer peripheral surface of the rotor. In a 5-phase brushless motor including a 5-phase exciting coil and a drive circuit for supplying an exciting current to these 5-phase exciting coils, the drive circuit sequentially switches the exciting coils for supplying the exciting current one by one. Is a two-phase excitation drive circuit that simultaneously supplies an excitation current to the two-phase excitation coil, and is displaced in the circumferential direction by an electrical angle of 72 degrees or 108 degrees from the boundary between the magnetic poles of the magnetic poles of the rotor. A five-phase brushless motor having a low magnetic flux density region formed at a position.