JP2000060070A - Brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recognize the position of a rotor at first startup and to start the rotor without using a Hall element or the like for detecting the position of the rotor of a brushless motor. SOLUTION: This brushless motor 14 is formed so that one or more permanent magnets 34a for regulating stopping position is fixed to a bearing holder 30 and the respective permanent magnets 34a face the end surface of a magnet 26 of a magnet rotor 23. The magnet rotor 23 is stopped at a specific stopping position by magnetic force of the permanent magnets 34a for regulating the stopping position at stopping of a motor, and energization is started from a specific phase armature coil 21 corresponding to the specific stopping position at starting up of the motor. It is thus possible to start up in substantially the same condition as in the case, where the position of the magnet rotor 23 is detected at the first startup without the use of a Hall element or the like for detecting the position of the magnet rotor 23 and conduct operation in a position detecting operation mode from the first startup.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor which does not require a means for detecting the position of a magnet rotor at the time of starting.

[0002]

2. Description of the Related Art In general, a brushless motor detects the position of a magnet rotor by a position detecting element such as a Hall element and sequentially switches energization to armature coils of each phase based on the detection signal. Is driven to rotate. However, when a brushless motor is used as a drive motor for an electric fuel pump of an automobile, for example, the brushless motor is immersed in fuel, and the reliability of the position detection element cannot be guaranteed in the fuel. It becomes necessary.

In recent years, voltage signals induced in armature coils of each phase during rotation of a brushless motor have been detected,
There is known a driving method in which the position of the magnet rotor is determined based on the voltage signal and the energization to the armature coils of each phase is switched. However, a voltage signal is induced in the armature coil only while the magnet rotor is rotating, and no voltage signal is induced while the magnet rotor is stopped. Therefore, in this driving method, the position of the magnet rotor cannot be detected when the motor is started.

To solve this problem, Japanese Patent Laid-Open No.
As described in Japanese Patent Application Laid-Open No. 0895, when the motor is started, a special signal for generating a rotating magnetic field is given to the armature coil of each phase regardless of the position of the magnet rotor, and the synchronous operation for rotatingly driving the magnet rotor is performed. Start in mode,
Thereafter, when the rotation speed becomes equal to or more than a predetermined value, the operation mode is switched from the synchronous operation mode to the position detection operation mode, and the energization to each phase armature coil is switched based on a voltage signal induced in the armature coil of each phase. It has been proposed.

[0005]

However, as in the above-mentioned known example, in the starting method in which the motor is started in the synchronous operation mode, the motor must be started at a relatively low speed in order to avoid step-out, and it takes time to start. Would. Moreover, when switching from the synchronous operation mode to the position detection operation mode, it is difficult to shift to the position detection operation mode while maintaining a stable operation state, and mechanical vibration is generated or the drive current is instantaneously changed. There is a possibility that an excessive load is applied to the semiconductor switching element due to an increase.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and accordingly, it is an object of the present invention to provide a brushless motor that starts without detecting the position of a magnet rotor at the time of starting the motor. An object of the present invention is to provide a brushless motor that can solve the problems of mechanical vibration and drive current increase accompanying switching of operation modes, and can improve both startability, quietness, and operation stability.

[0007]

To achieve the above object, a brushless motor according to a first aspect of the present invention stops a magnet rotor at a specific stop position by a magnetic force of a permanent magnet for restricting a stop position when the motor stops. Then, when the motor is started, energization is started from the armature coil of the specific phase corresponding to the specific stop position. That is, the magnet rotor can always be stopped at the specific stop position by the magnetic force of the stop position regulating permanent magnet when the motor stops, so that the motor can always be started from the specific stop position. Therefore, even if there is no Hall element or the like for detecting the position of the magnet rotor, the magnet rotor can be started in a state in which the position of the magnet rotor is accurately recognized at the start of the operation, and the operation can be performed in the position detection operation mode from the start of the start. . As a result, the starting performance can be improved, the starting time can be shortened, and mechanical vibration and driving current increase due to the switching of the operation mode as in the prior art can be improved as compared with the conventional driving method that starts in the synchronous operation mode. Problems can be solved and quietness and operation stability can be improved.

In the case where a plurality of permanent magnets for regulating the stop position are used, the permanent magnets are arranged so as to generate a magnetic attraction force with each magnetic pole of the magnet rotor. good. With this configuration, even if the magnetic force per permanent magnet is small, the magnetic force of the plurality of permanent magnets can reliably stop the magnet rotor at a specific stop position. The size can be reduced.

When only one permanent magnet is used for regulating the stop position, the width of the permanent magnet is set to be substantially equal to the width of one magnetic pole of the magnet rotor. It is good to form it. By doing so, 1
Even a single permanent magnet can generate a relatively large magnetic force, and the magnet rotor can be reliably stopped at a specific stop position.

Further, noting that the magnetizing direction of the magnet rotor is oriented in the radial direction, a permanent magnet for regulating the stop position is provided on the inner or outer circumferential surface of the magnet rotor. It is good to provide in the position which opposes. With this configuration, the orientation of magnetization of the magnet rotor can be made to coincide with the orientation of magnetization of the permanent magnet for stopping position regulation. The permanent magnet for stopping position regulation can be reduced in size.

By the way, as the magnetic force of the stop position regulating permanent magnet is increased, the performance of stopping the magnet rotor at a specific stop position is enhanced. On the other hand, the magnetic force of the stop position regulating permanent magnet during motor driving is increased. Has a greater effect on the rotation of the magnet rotor, and torque ripple (uneven rotation) is more likely to occur.

In consideration of such circumstances, a degaussing coil is wound around the permanent magnet for stopping position regulation, and the direction of the magnetic field of the permanent magnet is applied to the degaussing coil during motor driving. Current to generate a magnetic field in the opposite direction to cancel the magnetic field of the permanent magnet, to turn off the current to the degaussing coil when the motor is stopped, or to temporarily turn off the current after turning on in the opposite direction. You may do it.

According to this configuration, the magnetic field of the permanent magnet for stopping position is canceled by the magnetic field of the degaussing coil during driving of the motor. Therefore, a permanent magnet having a strong magnetic field is used as the permanent magnet for stopping position control. However, the magnet rotor can be smoothly rotated without being affected by the magnetic field of the permanent magnet, and torque ripple (rotational unevenness) can be reduced.

On the other hand, when the motor is stopped, the energization of the degaussing coil is turned off, so that the magnetic force of the permanent magnet for stopping position control is effectively applied, and the magnet rotor is reliably stopped at a specific stopping position. it can. In this case, since a permanent magnet having a strong magnetic field can be used as the permanent magnet for regulating the stop position, extremely high stopping performance can be obtained. Furthermore, if the degaussing coil is temporarily energized in the reverse direction when the motor is stopped, the magnetic force of the degaussing coil is used for regulating the stop position of the magnet rotor in addition to the magnetic force of the permanent magnet for stopping position regulation. And the stopping performance can be further improved.

The present invention described above is applicable regardless of the number of poles of the magnet rotor and the number of poles (number of slots) of the stator. In general, in a brushless motor, as the least common multiple of the number of poles of the magnet rotor and the number of poles of the stator increases, the cogging torque of the magnet rotor tends to decrease. Even if the magnetic force of the permanent magnet is small, the magnet rotor can be rotated to a specific stop position against the cogging torque by the magnetic repulsion / magnetic attraction between the permanent magnet and the magnet rotor. However, if the number of poles of the magnet rotor and the number of poles of the stator are excessively increased to increase the least common multiple (reduce the cogging torque), the structure becomes complicated and the cost increases.

In consideration of this point, when the number of poles of the magnet rotor is set to 8 and the number of poles (the number of slots) of the stator is set to 9, the least common multiple is 8 × 9 = 7.
2, and the cogging torque can be sufficiently reduced with a relatively small number of poles. If the cogging torque is small, it is possible to use a permanent magnet having a small magnetic force as the permanent magnet for stopping position regulation, thereby reducing torque ripple (rotational unevenness) caused by the magnetic force of the permanent magnet for stopping position regulation. it can.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment (1)] An embodiment (1) in which the present invention is applied to an electric fuel pump of an automobile will be described below with reference to FIGS. Electric fuel pump 11
Is constructed by incorporating a pump unit 13 and a brushless motor 14 in a cylindrical housing 12. Pump part 1
Reference numeral 3 denotes a pump casing 15 fixed to one end of the cylindrical housing 12 by press fitting, caulking or the like, and a pump cover 1.
6 form a pump chamber, in which an impeller 17 is housed. The impeller 17 is fitted on a rotating shaft 24 of the brushless motor 14.

On the other hand, the brushless motor 14 is a three-phase brushless motor, and has the following configuration. A cylindrical stator core 19 is fitted and fixed in the cylindrical housing 12. As shown in FIG. 2, for example, nine slots 20 (nine magnetic poles) are formed in the stator core 19, and each slot 20 has , A three-phase armature coil 21 is mounted. The arrangement of the armature coils 21 of each phase is U-phase (U1, U2, U3), V-phase (V1, V2, V3), W
The order of the phases (W1, W2, W3). As a result, 9
A pole stator 22 is configured.

On the inner peripheral side of the stator core 19, a magnet rotor 23 is arranged. The magnet rotor 23 includes a rotor core 25 fitted on a rotating shaft 24.
And eight field magnets 26 fixed to the outer periphery of the rotor core 25 by bonding or the like. The eight magnets 26 have N poles and S poles alternately as shown in FIG. Are arranged in a row. Thus, an eight-pole magnet rotor 23 is configured.

As shown in FIG. 1, the magnet rotor 23
One end of the rotating shaft 24 is rotatably supported by a bearing cylinder 28 at the center of the pump casing 15 via a bearing 27, and a bearing 29 supporting the other end of the rotating shaft 24 is fixed in the cylindrical housing 12. The bearing holder 30 is assembled. A motor drive circuit 31 is mounted on the bearing holder 30. When the motor is driven, the motor drive circuit 31
Accordingly, the energization to the armature coils 21 of each phase is sequentially switched. A housing cover 3 having a discharge port 32 is provided in an opening of the cylindrical housing 12 on the side of the motor drive circuit 31.
3 is fitted.

The pump unit 13 is driven by a brushless motor 14.
When the impeller 17 is rotated, fuel in a fuel tank (not shown) is sucked into a pump chamber from a suction port (not shown) of the pump cover 16 and the pump casing 1
5 is discharged into the cylindrical housing 12 from a discharge port (not shown). This fuel flows through the gap between the stator core 19 and the magnet rotor 23 and flows through the housing cover 33.
Is discharged from a discharge port 32 into a fuel pipe (not shown),
It is sent to a fuel injection valve (not shown).

In this embodiment (1), in order to stop the magnet rotor 23 at a specific stop position when the motor stops, for example, two permanent magnets 34a, 3 for regulating the stop position are provided.
4b is fixed to the bearing holder 30, and each permanent magnet 34a,
34b is arranged so as to face the end surfaces of two magnets 26 adjacent to the magnet rotor 23. As shown in FIG. 2, each of the permanent magnets 34a and 34b is formed to have a width (pitch angle) of about 1/2 of the magnet 26 or a width slightly smaller than the width thereof. At positions almost corresponding to the magnetic poles (U1, U3) at both ends of
Also, at a specific stop position, the two permanent magnets 34a, 34
b is a position where the opposite end surfaces of the two magnets 26 coincide with the opposite end surfaces of the two magnets 26, and the radial position is that the inner peripheral surfaces of the permanent magnets 34a and 34b
This is the position that coincides with the inner peripheral surface of.

Each of the permanent magnets 34a and 34b has a magnetizing direction oriented in a radial direction. One of the permanent magnets 34a has an S pole on the outer peripheral side, an N pole on the inner peripheral side, and the other permanent magnet 34b.
Is an N pole on the outer circumference side and an S pole on the inner circumference side. This allows
When the motor stops, a magnetic attractive force acts between the two permanent magnets 34a, 34b and the two magnets 26, 26 of the magnet rotor 23 at a specific stop position, and the magnetic attractive force causes the magnet rotor 23 to be specified. At the stop position.

After the brushless motor 14 is turned off, the permanent magnets 34a and 34b and the magnet rotor 23 are turned off.
Forcibly rotate the magnet rotor 23 to a specific stop position due to the magnetic repulsion between the permanent magnets 34a and 34b.
The torque due to the magnetic repulsion between the magnet rotor 23 and the permanent magnets 34a and 34b is set to be larger than the cogging torque of the magnet rotor 23 and smaller than the torque ripple during rated motor rotation.

The brushless motor 1 configured as described above
4 will be described. During driving of the motor, a current is sequentially passed from the motor drive circuit 31 to the armature coils 21 of each phase, and the magnet rotor 23 is driven to rotate. At this time, the motor drive circuit 31 detects a voltage signal induced in the armature coil 21 of each phase, determines the rotational position of the magnet rotor 23 based on the voltage signal, and Is switched (that is, operation is performed in the position detection operation mode).

When the power of the brushless motor 14 is turned off, the rotation speed of the magnet rotor 23 is gradually reduced, and the magnet rotor 23 is about to stop. At this time, since the torque due to the magnetic repulsion between the magnet rotor 23 and the permanent magnets 34a and 34b is larger than the cogging torque of the magnet rotor 23, if the magnet rotor 23 does not reach a specific stop position, two Permanent magnet 34
The magnet rotor 23 is forcibly rotated to a specific stop position against the cogging torque by a magnetic repulsive force between the magnet rotor 23a and the magnet rotor 23. This allows
When the magnet rotor 23 reaches a specific stop position,
Two permanent magnets 34a and 34b and the magnet rotor 23
A magnetic attraction force acts between the magnet rotor 23 and the magnetic attraction force, and the magnet rotor 23 is stopped and held at a specific stop position.

As a result, since the motor can always be started from a specific stop position when the motor is started, it is always possible to start the brushless motor 14 by energizing the armature coil 21 of a specific phase corresponding to the specific stop position. it can.

In this case, the magnet rotor 23 can always be started from a specific stop position.
Can be started in substantially the same state as when detecting the position of
It is possible to operate in the position detection operation mode from the beginning of startup. As a result, the start-up performance can be improved and the start-up time can be shortened, as compared with the conventional drive system that starts in the synchronous operation mode. Moreover, since there is no need to switch from the synchronous operation mode to the position detection operation mode after the motor is started, it is possible to eliminate the problems of mechanical vibration and drive current increase associated with the conventional operation mode switching, resulting in quietness and operation stability. Can be improved.

Generally, in the brushless motor 14, the cogging torque of the magnet rotor 23 tends to decrease as the least common multiple of the number of poles of the magnet rotor 23 and the number of poles of the stator 22 increases. Even when the permanent magnets 34a and 34b for stopping position regulation have a small magnetic force at the time of stopping,
The magnet rotor 23 can be rotated to a specific stop position by the magnetic repulsive force / magnetic attraction force between the magnet rotor 23a and the magnet rotor 23. However, if the number of poles of the magnet rotor 23 and the number of poles of the stator 22 are excessively increased in an attempt to increase the least common multiple (reduce the cogging torque), the structure becomes complicated and the cost increases.

In consideration of this point, in this embodiment (1), the number of poles of the magnet rotor
Since the number of poles (the number of slots) is set to 9 poles, its least common multiple becomes as large as 8 × 9 = 72, and the cogging torque can be sufficiently reduced with a relatively small number of poles. If the cogging torque is small, the magnet rotor 23 can be forcibly rotated to a specific stop position against the cogging torque even if permanent magnets having a small magnetic force are used as the stop position regulating permanent magnets 34a and 34b. It becomes possible. Moreover, by using the permanent magnets 34a and 34b having a small magnetic force, torque ripple (rotational unevenness) caused by the magnetic force of the permanent magnets 34a and 34b can be reduced.

[Embodiment (2)] Next, an embodiment (2) of the present invention will be described with reference to FIGS. The difference from the first embodiment is that two permanent magnets 35a and 35b for regulating the stop position are fixed to the end face of the stator core 19, and the permanent magnets 35a and 35b are connected to the magnet rotor 23.
The other configuration is the same as that of the embodiment (1).

In this case, each of the permanent magnets 35a, 35b
As shown in FIG. 4, the magnet 26 is formed to have a width (pitch angle) of about 1/2 of the magnet 26 or a slightly smaller width, and the circumferential position is determined by the magnetic poles (U1, U1) at both ends of the U-phase magnetic pole.
3) At a position almost corresponding to, and at a specific stop position,
The end faces of the two permanent magnets 35a and 35b on the opposite sides coincide with the end faces of the two magnets 26 on the opposite sides, and the positions in the radial direction are the permanent magnets 35a and 35b.
Is a position where the inner peripheral surface of the stator core 19 coincides with the inner peripheral surface of the stator core 19.

Each of the permanent magnets 35a and 35b has a magnetizing direction oriented in a radial direction. One of the permanent magnets 35a has an N-pole on the outer peripheral side and an S-pole on the inner peripheral side, and the other permanent magnet 35b
Is an S pole on the outer circumference side and an N pole on the inner circumference side. This allows
When the motor stops, a magnetic attractive force acts between the two permanent magnets 35a and 35b and the two magnets 26 and 26 of the magnet rotor 23 at a specific stop position, and the magnetic attractive force causes the magnet rotor 23 to be specified. At the stop position.

In this embodiment (2), the permanent magnets 35a and 35b for regulating the stop position are opposed to the outer peripheral surface of the magnet rotor 23, so that the magnetizing orientation of the permanent magnets 35a and 35b is changed. Magnet 26
Can be made to coincide with the magnetization orientation direction. Therefore, a large magnetic force can be generated between the small permanent magnets 35a and 35b and the magnet rotor 23, and the size of the permanent magnets 35a and 35b can be reduced.

[Embodiment (3)] The embodiment (3) of the present invention shown in FIGS. 5 and 6 is different from the embodiment (1) in that one stop position regulating permanent magnet 36 is provided. That is, the permanent magnet 36 is fixed to the bearing holder 30 so as to face the end face of the magnet 26 of the magnet rotor 23, and the other configuration is the same as that of the first embodiment.

In this case, as shown in FIG. 6, the permanent magnet 36 is formed to have a width (pitch angle) of about one magnet 26, and the circumferential position is the center magnetic pole (U2) of the U-phase magnetic pole. ), And the radial position is a position where the inner peripheral surface of the permanent magnet 36 coincides with the inner peripheral surface of the magnet 26.

Although the permanent magnet 36 is magnetized in the radial direction, the magnetization directions of the left half and the right half are opposite to each other. N
The outer half of the right half is the N pole, and the inner half is the S pole. Thus, when the motor is stopped, the magnetic poles on both sides of the permanent magnet 36 and the magnet rotor 2 are stopped at a specific stop position.
A magnetic attraction force acts between the two magnets 26, 26, and the magnet rotor 23 is held at a specific stop position by the magnetic attraction force. Instead of the permanent magnet 36, a permanent magnet corresponding to the left half and a permanent magnet corresponding to the right half may be combined.

[Embodiment (4)] Next, an embodiment (4) of the present invention will be described with reference to FIGS. In the embodiment (4), the magnet 37 of the magnet rotor 23 is used.
Are projected from the end face of the rotor core 25 toward the bearing holder 30, and two permanent magnets 38a,
38b is fixed to the bearing holder 30, and each permanent magnet 38
a and 38b are opposed to the inner peripheral surfaces of two magnets 37 protruding from the rotor core 25. Magnet 37
Are formed so that the inner peripheral surface is convex and the central part of the outer peripheral surface is concave in order to improve the orientation of the magnetic flux.

In this case, each of the permanent magnets 38a, 38b
As shown in FIG. 8, the magnet 37 is formed to have a width (pitch angle) of about 1/2 of the magnet 37 or a width slightly larger than it, and the circumferential position is determined by the magnetic poles (U1, U1) at both ends of the U-phase magnetic pole.
3) At a position almost corresponding to, and at a specific stop position,
Opposite end surfaces of the two permanent magnets 38a and 38b are located at positions corresponding to the opposite end surfaces of the two magnets 37.

Each of the permanent magnets 38a and 38b has a magnetizing direction oriented in a radial direction, and one of the permanent magnets 38a has an S pole on the outer peripheral side, an N pole on the inner peripheral side, and the other permanent magnet 38b.
Is an N pole on the outer circumference side and an S pole on the inner circumference side. This allows
When the motor stops, a magnetic attractive force acts between the two permanent magnets 38a and 38b and the two magnets 37 and 37 of the magnet rotor 23 at a specific stop position, and the magnetic attractive force causes the magnet rotor 23 to be specified. At the stop position.

[Embodiment (5)] The embodiment (5) of the present invention shown in FIG.
A permanent magnet 38c for regulating the stop position of the pawl is added. The added permanent magnet 38c is the other permanent magnet 38.
a, 38b, and the magnetization direction is the same as that of the first permanent magnet 38a. The circumferential position of the added permanent magnet 38c is determined by the first magnetic pole (V
This is a position substantially corresponding to 1), and is a position where the end face of the permanent magnet 38c coincides with the end face of the magnet 37 at a specific stop position.

As described above, even if three or more permanent magnets for regulating the stop position are provided or the sizes of the respective permanent magnets are made different, the magnet rotor 23 is used by the magnetic force of the respective permanent magnets when the motor is stopped. Can be stopped at a specific stop position.

[Embodiment (6)] The embodiment (6) of the present invention shown in FIG. 10 is different from the embodiment (4) in that only one permanent magnet 39 for regulating the stop position is provided. The permanent magnet 39 is magnetized in the radial direction, and has an S pole (or N pole) on the outer circumference side and an N pole (or S pole) on the inner circumference side.
The permanent magnet 39 is formed to have a width (pitch angle) of about one magnet 26. Other configurations are
This is the same as the embodiment (4).

[Embodiment (7)] In an embodiment (7) of the present invention shown in FIGS. 11 and 12, two permanent magnets 40a and 40b for regulating a stop position are arranged on the opposite side by 180 °. Each permanent magnet 40a, 40b is opposed to the inner peripheral surface of two magnets 37 protruding from the rotor core 25. The inner peripheral side of the protruding portion of each magnet 37 is formed in a concave shape so as to make the gap between the outer peripheral surface of each of the permanent magnets 40a and 40b uniform. Each permanent magnet 40a,
The width of 40b is formed to be substantially the same pitch angle as the width of almost one magnet 26. Other configurations are the same as those in the embodiment (6).

In this embodiment (7), each permanent magnet 4
0a, 40b are curved in an arc shape to make each permanent magnet 40a,
The gap between the outer peripheral surface of the magnet 40b and the inner peripheral surface of the magnet 37 is made uniform, but as shown in FIG.
The flat permanent magnets 41a and 41b may be used.

[Embodiment (8)] In the embodiment (8) of the present invention shown in FIGS. 14 and 15, for example, two permanent magnets 44a and 44b for regulating the stop position are provided at the axial center of the stator core 25. The permanent magnets 44a and 44b are arranged at the center part on the inner peripheral side of the stator core 25 by being fitted and fixed in two slot openings. Other configurations are
This is the same as the embodiment (1).

In this structure, no axial force acts between the permanent magnets 44a, 44b and the magnet rotor 23, and axial vibration during rotation of the magnet rotor 23 can be prevented.

[Embodiment (9)] In the embodiment (9) of the present invention shown in FIGS. 16 and 17, two permanent magnets 42a and 42b for regulating the stop position are provided with degaussing coils 43a and 43b.
b is wound. Each of the permanent magnets 42a and 42b is disposed at a position corresponding to the magnetic poles (U1 and U3) at both ends of the U-phase magnetic pole. One of the permanent magnets 42a has an S pole on the outer periphery, an N pole on the inner periphery, and the other. The outer peripheral side of the permanent magnet 42b is N
The pole and the inner circumference are S poles.

While the motor is being driven, each of the degaussing coils 43a,
43b to generate a magnetic field in a direction opposite to the direction of the magnetic field of each of the permanent magnets 42a and 42b.
The magnetic fields of 2a and 42b are canceled. Therefore, even if the permanent magnets 42a and 42b having a strong magnetic field are used,
a, 42b without being affected by the magnetic field.
3 can be rotated smoothly, and torque ripple (rotational unevenness) can be reduced.

On the other hand, when the motor is stopped, the degaussing coil 4
The power supply to 3a and 43b is turned off. Thus, when the motor stops, the permanent magnets 42a and 42b for regulating the stop position are provided.
By effectively operating the magnetic force, the magnet rotor 23 can be reliably stopped at a specific stop position. In this case, as the permanent magnets 42a and 42b for regulating the stop position,
Since a permanent magnet having a strong magnetic field can be used, extremely high stopping performance can be obtained.

When the motor stops, each degaussing coil 4
The power may be temporarily turned off in the opposite direction to 3a and 43b and then turned off. By doing so, each permanent magnet 42
a, 42b, and each degaussing coil 43a, 4b.
The magnetic force 3b can also be used for regulating the stop position of the magnet rotor, and the stop performance can be further improved.

[Other Embodiments] In each of the embodiments (1) to (8), similarly to the embodiment (9), a demagnetizing coil may be wound around each permanent magnet.

In the embodiment (1) and the like, a plurality of permanent magnets for regulating the stop position are arranged only on one side of the magnet rotor 23 in the axial direction. It may be arranged separately on both sides in the direction. In this manner, the axial force acting on the magnet rotor 23 from the stop position regulating permanent magnet can be canceled, and the magnet rotor 23
Axial vibration at the time of rotation can be prevented.

In each of the above embodiments, the number of poles of the magnet rotor 23 is eight and the number of poles (the number of slots) of the stator 22 is nine, but any other number of poles may be used. Needless to say, it's good.

In addition, the present invention is not limited to a three-phase brushless motor, but may be applied to a two-phase or four-phase or more brushless motor. The present invention can be applied to the brushless motor described above.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an electric fuel pump showing an embodiment (1) of the present invention.

FIG. 2 is a cross-sectional view taken along line AA of FIG.

FIG. 3 is a longitudinal sectional view of an electric fuel pump showing an embodiment (2) of the present invention.

FIG. 4 is a cross-sectional view taken along the line BB of FIG. 3;

FIG. 5 is a longitudinal sectional view of an electric fuel pump showing an embodiment (3) of the present invention.

FIG. 6 is a cross-sectional view taken along line CC of FIG. 5;

FIG. 7 is a longitudinal sectional view of an electric fuel pump showing an embodiment (4) of the present invention.

FIG. 8 is a cross-sectional view taken along line DD of FIG. 7;

FIG. 9 is a cross-sectional view of an electric fuel pump showing an embodiment (5) of the present invention.

FIG. 10 is a cross-sectional view of an electric fuel pump showing an embodiment (6) of the present invention.

FIG. 11 is a longitudinal sectional view of an electric fuel pump showing an embodiment (7) of the present invention.

FIG. 12 is a cross-sectional view taken along line EE in FIG. 11;

FIG. 13 is a cross-sectional view of an electric fuel pump showing a configuration example in a case where a flat permanent magnet is used as a stop position regulating permanent magnet in the embodiment (7).

FIG. 14 is a longitudinal sectional view of an electric fuel pump showing an embodiment (8) of the present invention.

FIG. 15 is a cross-sectional view taken along line FF of FIG. 14;

FIG. 16 is a longitudinal sectional view of an electric fuel pump showing an embodiment (9) of the present invention.

FIG. 17 is a transverse sectional view taken along the line GG of FIG. 16;

[Explanation of symbols]

11: Electric fuel pump, 13: Pump section, 14: Brushless motor, 19: Stator core, 20: Slot, 2
DESCRIPTION OF SYMBOLS 1 ... Armature coil, 22 ... Stator, 23 ... Magnet rotor, 24 ... Rotating shaft, 25 ... Rotor core, 26 ... Magnet, 30 ... Bearing holder, 31 ... Motor drive circuit, 3
2 ... Discharge ports, 34a, 34b, 35a, 35b, 36 ...
Permanent magnet for stopping position regulation, 37 ... magnet, 38
a, 38b, 38c, 39, 40a, 40b, 41a,
41b, 42a, 42b ... permanent magnets for regulating the stop position,
43a, 43b: degaussing coils, 44a, 44b: permanent magnets for regulating the stop position.

Claims (6)

[Claims] 1. A brushless motor that rotates a magnet rotor by causing a stator having armature coils of each phase to face a magnet rotor and sequentially switching energization to the armature coils of the phases. Providing a stop position regulating permanent magnet for stopping the magnet rotor at a specific stop position by magnetic force when stopping, and starting energization from an armature coil of a specific phase corresponding to the specific stop position when starting the motor. A brushless motor. 2. A permanent magnet for stopping position regulation, wherein a plurality of permanent magnets are provided, and at the specific stopping position, each permanent magnet is arranged so as to generate a magnetic attractive force with each magnetic pole of the magnet rotor. The brushless motor according to claim 1, wherein the brushless motor is provided. 3. The permanent magnet for stopping position regulation is provided only one, and the width of the permanent magnet is formed to be substantially the same pitch angle as the width of one magnetic pole of the magnet rotor. The brushless motor according to claim 1, wherein: 4. The permanent magnet for stopping position regulation according to claim 1, wherein the permanent magnet is arranged at a position facing an inner peripheral surface or an outer peripheral surface of the magnet rotor. Brushless motor. 5. A demagnetizing coil is wound around the stop position regulating permanent magnet, and a magnetic field in a direction opposite to the direction of the magnetic field of the permanent magnet is generated in the demagnetizing coil during driving of the motor. So as to cancel the magnetic field of the permanent magnet,
The brushless motor according to any one of claims 1 to 4, wherein the current to the degaussing coil is turned off when the motor stops, or the current is temporarily turned off in the opposite direction and then turned off. 6. The magnet rotor having eight poles,
The brushless motor according to any one of claims 1 to 5, wherein the number of poles of the stator is nine.