JP2000175418A - Brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To centrally wind an armature coil with one phase at a time for each tooth of a stator in a sensorless system. SOLUTION: Armature coils U21-W21 are centrally wound by one phase at a time for each tooth 20 of a stator 19. By forming a permanent magnet 26 for field, so that a magnetization surface facing an armature coil 21 is in a circular recessed surface shape, a magnetic flux distribution for the armature coil of each permanent magnet 25 changes in a rotary direction. As a result, even if only one permanent magnet 26 faces a non-energized phase coil, a magnetic flux that is interlinked with a non-energized phase coil changes due to the rotation of a magnet rotor 23, and an induction voltage is generated in the non-energized phase coil. By detecting the induction voltage, the rotary position of the magnet rotor 23 can be detected, thus driving a brushless motor 14 in a sensorless system, regardless of the central winding system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensorless brushless motor which does not require a position detecting element such as a Hall element for detecting a rotational position of a magnet rotor.

[0002]

2. Description of the Related Art In general, a brushless motor is designed to detect the rotational position of a magnet rotor by a position detecting element such as a Hall element, and to sequentially switch an energizing phase based on the detection signal, thereby driving the magnet rotor to rotate. ing. 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. A brushless motor is needed.

In a conventional sensorless brushless motor, for example, a three-phase armature coil is Y-connected, and an induced voltage generated in a non-energized phase coil during rotation of the motor is detected at a neutral point of the Y-connection. The rotational position of the magnet rotor is detected based on the voltage signal, and the energized phases are sequentially switched.

[0004]

By the way, there are so-called "distributed winding" and "concentrated winding" in the method of winding the armature coil. In the distributed winding, since the armature coil is wound over a plurality of teeth of the stator, a plurality of permanent magnets arranged on the outer periphery of the magnet rotor face the non-energized phase coil. For this reason, with the rotation of the magnet rotor, the magnetic flux linked to the non-energized phase coil changes, and an induced voltage is generated in the non-energized phase coil.

However, in the distributed winding, since the armature coil is wound over a plurality of teeth, it is difficult to wind the armature coil, the assemblability is deteriorated, and the coil ends of the plural phases are overlapped. There is a disadvantage that the end becomes large and the motor becomes large and the motor efficiency is lowered.

On the other hand, in the concentrated winding, as shown in FIG. 5, the armature coils U3, V3, W3
Are wound one by one, so that the armature coils U3, V3,
The winding of W3 is easy and the assembling property is good. Moreover, since the coil end is smaller than that of the distributed winding, the motor can be downsized,
It can satisfy the demand for motor efficiency improvement.

However, in the concentrated winding, only one permanent magnet 2 faces the non-energized phase coil.
Is magnetized radially anisotropic, and the magnetic flux distribution on the magnetized surface is constant in the rotation direction, so that even when the magnet rotor 4 rotates, there is no change in the magnetic flux linked to the non-energized phase coil. No induced voltage is generated in the non-energized phase coil. For this reason, in the concentrated winding, the rotation position of the magnet rotor 4 cannot be detected based on the induced voltage of the non-energized phase coil, and a position detection element is required. Therefore, in the conventional sensorless type brushless motor, the distributed winding must be adopted, and there are disadvantages peculiar to the distributed winding, such as a reduction in assemblability, an increase in the size of the motor, and a reduction in motor efficiency.

The present invention has been made in view of such circumstances, and accordingly, it is an object of the present invention to rotate a magnet rotor in a sensorless manner while concentratedly winding armature coils of each phase. An object of the present invention is to provide a brushless motor capable of realizing improved assemblability, downsizing of a motor, and improvement of motor efficiency.

[0009]

In order to achieve the above object, the brushless motor according to the first aspect of the present invention is a sensorless type brushless motor. Each permanent magnet is formed such that the magnetic flux distribution with respect to the armature coil changes in the rotation direction. As a result, even when only one permanent magnet faces the coil of the non-energized phase, the magnetic flux linked to the coil of the non-energized phase changes with the rotation of the magnet rotor. An induced voltage is generated in the coil. For this reason, it is possible to detect the rotational position of the magnet rotor based on the induced voltage of the non-energized phase coil, which is impossible with the conventional concentrated winding, even though the concentrated winding is performed, and the magnet rotor is rotationally driven in a sensorless manner. Can be. In addition, by adopting the concentrated winding, the assemblability can be improved, and the demand for downsizing the motor and improving the motor efficiency can be satisfied.

In this case, it is preferable that at least the central portion of the magnetized surface of the permanent magnet facing the armature coil is formed in a concave shape. If you do this,
Even if the concave magnetized surface of each permanent magnet is magnetized to radial anisotropy, which is relatively easy to magnetize, the magnetic flux density for the armature coil is large at the center of the permanent magnet and small at the periphery. The magnetic flux distribution for the armature coil changes in the rotation direction.

In the brushless motor of the present invention described above, the rotational position of the magnet rotor can be detected by the induced voltage generated in the non-energized phase coil without using the position detecting element. It can be used as a drive motor for a fuel pump of a vehicle. In this way, it is possible to obtain the effects of improving the assemblability, miniaturizing the motor, and improving the motor efficiency as compared with a conventional fuel pump using a distributed winding type brushless motor.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment in which the present invention is applied to a fuel pump of a vehicle will be described below with reference to FIGS. As shown in FIG. 2, the fuel pump 11 is configured by incorporating a pump unit 13 and a brushless motor 14 in a cylindrical housing 12. Explaining the configuration of the pump section 13, a pump chamber is composed of a pump casing 15 and a pump cover 16 fixed to one end of the cylindrical housing 12 by press fitting, caulking, or the like, and an impeller 17 is housed in the pump chamber. . The impeller 17 is fitted on a rotating shaft 24 of the brushless motor 14.

On the other hand, the brushless motor 14
This is a brushless motor of a phase full-wave drive system, and is configured as follows. A cylindrical stator 19 is fitted and fixed in the cylindrical housing 12. As shown in FIG. 1, for example, 12 teeth 20 are formed on this stator 19 at equal pitches. The three-phase armature coils U21, V21, and W21 of the three-phase and the W-phase are concentratedly wound one by one.

On the inner peripheral side of the stator 19, a magnet rotor 23 is arranged. The magnet rotor 23 includes a rotor core 25 fitted on a rotating shaft 24,
The rotor core 25 includes, for example, eight field permanent magnets 26 fixed to the outer periphery of the rotor core 25 by bonding or the like. As shown in FIG. 1, at least the central portion of the magnetized surface of each permanent magnet 26 facing the armature coil 21 is formed in an arcuate concave shape, and the N pole and the S pole are arranged alternately. . In this way, if the magnetized surface of each permanent magnet 26 is formed in an arcuate concave shape, the armature coil 21 of each permanent magnet 26 is formed.
Is large at the center of the permanent magnet 26,
It becomes smaller in the peripheral portion, and the magnetic flux distribution to the armature coil 21 changes in the rotation direction.

[0015] As shown in FIG.
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 drive control circuit 31 of a three-phase full-wave drive system is assembled to the bearing holder 30, and the energized phases are sequentially switched by the drive control circuit 31 when the motor is driven.
A housing cover 33 having a discharge port 32 is fitted into an opening of the cylindrical housing 12 on the drive control circuit 31 side.

The pump unit 1 is driven by a brushless motor 14.
When the impeller 17 is driven to rotate, 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 a discharge port (not shown) of the pump casing 15. ) Is discharged into the cylindrical housing 12. The fuel flows through a gap between the stator 19 and the magnet rotor 23, is discharged from a discharge port 32 of the housing cover 33 into a fuel pipe (not shown), and is sent to a fuel injection valve (not shown).

As shown in FIG. 3, a three-phase armature coil U
21 to W21 are Y-connected. The drive control circuit 31 has a control unit 34 to which a control signal is input from an engine control circuit (not shown), and energizes the armature coils U21 to W21 of each phase based on the output of the control unit 34. Transistors Tr1 to Tr for switching the
6 are provided. These six Tr1 to Tr6 are:
The armature coil U of each phase is connected in a bridge between the battery voltage (+ B) side and the ground side in pairs, and the intermediate connection point of the two transistors of each pair is Y-connected.
It is connected to one end of 21 to W21. Flywheel diodes D1 to D6 are connected in parallel between the emitters and collectors of the transistors Tr1 to Tr6.

Further, the armature coils U21 to U21 of each phase
Are input to the + input terminal of the amplifier 35 via the resistors R1, R2, and R3, respectively. The neutral points of the Y-connected armature coils U21 to W21 are connected to the-input terminal of the I have. As a result, the amplifier 35 detects the voltage between both input terminals, that is, the neutral point voltage Vs, and
As shown in (1), the neutral point voltage Vs is differentiated and converted into a switching signal Ps, and the switching signal Ps is output to the control unit 34.

The drive control circuit 31 drives the brushless motor 14 by energizing the two-phase armature coils among the three phases. At this time, the drive control circuit 31 detects the induced voltage generated in the coil of the non-energized phase by the neutral point voltage Vs, and based on the switching signal Ps that changes according to the neutral point voltage Vs, the drive control circuit 31 While detecting the rotational position, the transistors Tr1 to Tr6 are sequentially switched to sequentially switch the energized phases.

For example, when the U-phase coil U21 is in the non-energized phase, the U-phase coil U21
However, as described above, each permanent magnet 26
Is formed in an arcuate concave shape, and the magnetic flux distribution with respect to the armature coil 21 changes in the rotation direction. As the magnet rotor 23 rotates, the magnetic flux linked to the U-phase coil U21 changes. An induced voltage is generated in the U-phase coil U21. Thereby, as shown in FIG. 4, the U-phase coil U2
1 is in the non-energized phase, the voltage E across the U-phase coil U21 is increased with the rotation of the magnet rotor 23.
u changes. Similarly, even during the period when the V-phase coil V21 is in the non-energized phase, the voltage Ev across the V-phase coil V21 changes with the rotation of the magnet rotor 23, and the W-phase coil W21 is in the non-energized phase. During the period, the W-phase coil W
The voltage Ew across the terminal 21 changes. As a result, in the entire rotation region, the neutral point voltage Vs changes according to the rotation position of the magnet rotor 23, and the switching signal Ps changes accordingly. Accordingly, the drive control circuit 31 sequentially switches the energized phases according to the rotational position of the magnet rotor 23 by sequentially switching the transistors Tr1 to Tr6 based on the switching signal Ps.

As described above, in the brushless motor 14 of the concentrated winding type, only one permanent magnet 26 is opposed to the coil of the non-energized phase, but in the present embodiment, the magnetized surface of each permanent magnet 26 is circular. Since the magnetic flux distribution is changed in the rotation direction by being formed in a concave shape, the magnetic flux linked to the non-energized phase coil changes with the rotation of the magnet rotor 23, and the magnetic flux distribution is changed to the non-energized phase coil. An induced voltage is generated.
For this reason, the switching signal Ps corresponding to the rotational position of the magnet rotor 23 can be obtained from the induced voltage of the coil in the non-energized phase, and the magnet rotor 23 can be driven to rotate in a sensorless manner, even in the concentrated winding method. . In addition, by adopting the concentrated winding method, the assemblability is improved, and the demands for downsizing the motor and improving the motor efficiency can be satisfied.

In the present embodiment, only the central portion of the magnetized surface of the permanent magnet 26 is formed in an arcuate concave shape, but the entire magnetized surface may be formed in an arcuate concave shape. The surface may be formed with irregularities other than the arcuate concave surface, or the magnetization strength of the magnetized surface may be changed in the rotation direction. In short, the magnetic flux distribution to the armature coil changes in the rotation direction. The shape or the magnetization pattern may be adopted.

In addition, the present invention is not limited to a three-phase brushless motor, and may be applied to a two-phase or four-phase brushless motor. The driving method may be used. Further, the application range of the present invention is not limited to the drive motor of the fuel pump 11, but can be used as a drive motor of various devices.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a motor part of a fuel pump showing one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a fuel pump.

FIG. 3 is a circuit diagram showing an electrical configuration of the brushless motor.

FIG. 4 shows the electrical angle and the voltage E across the armature coil of each phase.
Waveform diagram showing a relationship among u, Ev, Ew, neutral point voltage Vs, and switching signal Ps.

FIG. 5 is a cross-sectional view of a conventional concentrated winding type brushless motor.

[Explanation of symbols]

11: fuel pump, 13: pump section, 14: brushless motor, 19: stator, 20: teeth, 23: magnet rotor, 26: permanent magnet, 31: drive control circuit,
34: control unit, 35: amplifier, Tr1 to Tr6: transistor, U21, V21, W21: armature coil.

Continued on front page F term (reference)

Claims (3)

[Claims] 1. A stator having an armature coil of each phase and a magnet rotor having a field constituted by a plurality of permanent magnets are opposed to each other, and an energized phase is determined based on an induced voltage generated in a non-energized phase coil. In the brushless motor that rotationally drives the magnet rotor by sequentially switching, the armature coil is concentratedly wound one phase at a time for each tooth formed on the stator, and each of the permanent magnets has a magnetic flux with respect to the armature coil. A brushless motor, wherein the distribution is formed so as to change in the rotation direction. 2. The brushless motor according to claim 1, wherein each of the permanent magnets has at least a central portion of a magnetized surface facing the armature coil formed in a concave shape. 3. The brushless motor according to claim 1, wherein the brushless motor is used as a drive motor for a fuel pump of a vehicle.