JP2006280088A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brushless motor that can easily detect a zero-cross point precisely and thereby can perform a high-precision drive control even at low speed. <P>SOLUTION: In the brushless motor 1 provided with a motor body 2 comprising a stator 7 including stator winding 7b and a rotor 6 including a rotor core 6a and rotor magnets 6c provided at the outside circumference of the rotor core 6a, predetermined air gaps (magnetic flux medium portions) 6e that has permeability smaller than that of the rotor cores 6a are formed between the rotor core 6a and boundary portions between the N pole and S pole of the rotor magnets 6c, by providing recessed portions 6d formed by cutting out the outside circumferential portions of the rotor cores 6a that face the boundary portions between the N pole and S pole of the rotor magnets 6c. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a brushless motor, and more particularly to a brushless motor suitable for a pump mounted on a vehicle such as an automobile.

In recent years, for example, in an automobile, it is considered that an electric pump constituting a hydraulic power source is mounted and energy is saved by appropriately operating the pump. Further, by using an electric pump, even when the engine is stopped due to idle stop or the like, it is possible to supply hydraulic pressure to a drive system such as a transmission to support the operation of the drive system.
The pump motor as described above generally uses a three-phase DC brushless motor that does not require a mechanical rectifying mechanism such as a commutator or a brush. Further, the motor is in a high temperature environment. Since it is disposed in the engine compartment, a sensorless type that does not require a sensor for detecting the rotor rotational position is used.
As a conventional brushless motor, for example, as described in Patent Document 1 below, a motor that uses a ring magnet that is easier to assemble and has fewer parts as a rotor magnet than a conventional segment magnet is proposed. ing.

JP 2004-242424 A

By the way, in a sensorless type brushless motor, normally, a counter electromotive force (induced voltage) generated in each of the three-phase stator windings during rotation of the motor is detected, and the detected induced voltage passes through a zero potential (zero crossing). By detecting the point), the rotational position of the rotor is grasped, and drive control of the motor is performed.
However, in the conventional brushless motor as described above, the amount of change in the induced voltage in the vicinity of the zero cross point is small, and particularly when used at a low rotational speed as in the case of the pump motor for vehicle use, There is a problem that it is difficult to detect the zero cross point accurately and easily. As a result, it has been difficult to perform motor drive control with high accuracy.

  In view of the conventional problems as described above, the present invention provides a brushless motor that can easily detect the zero-cross point easily even when the rotational speed is low, and thus enables highly accurate drive control. For the purpose.

The present invention is a brushless motor including a motor body having a stator including a stator winding, and a rotor core and a rotor including a rotor magnet provided on the outer peripheral side of the rotor core,
A magnetic flux medium portion having a permeability smaller than the permeability of the rotor core is provided on the outer peripheral portion of the rotor core facing the boundary portion between the N pole and the S pole of the rotor magnet.

  In the brushless motor configured as described above, in the rotor core, a magnetic flux medium having a magnetic permeability smaller than the magnetic permeability of the rotor core at the outer peripheral portion facing the boundary between the N pole and S pole of the rotor magnet on the outer peripheral side. By providing the portion, the inventors of the present invention have found that even when the motor is rotating at a low rotational speed, the waveform of the induced voltage generated in the stator winding in the vicinity of the zero cross point can be made steep. That is, when the magnetic flux medium part is provided, compared with the case where the magnetic flux medium part is not formed, a part of the circumferential magnetic flux density generated on the surface of the rotor magnet is weakened, and the waveform is shaped. The change of the induced voltage in the stator winding near the zero cross point could be increased. In addition, the waveform of the induced voltage in the vicinity of the zero cross point could be changed abruptly by changing the size of the magnetic flux medium portion or the like according to the motor speed. The present invention has been completed based on the above-described knowledge, and by providing a magnetic flux medium portion having a permeability smaller than the permeability of the rotor core between the rotor core and the boundary portion between the N and S poles, Even when the motor is rotating at a low rotational speed, it is possible to easily detect the zero-cross point easily.

Further, in the brushless motor, the magnetic flux medium portion is formed by cutting out an outer peripheral portion of the rotor core that faces a boundary portion between the N pole and the S pole of the rotor magnet, and thereby the rotor core and the N pole of the rotor magnet. It is preferable that the air gap is formed by a predetermined air gap formed between the boundary with the S pole.
In this case, the magnetic flux medium part is provided in the rotor core only by forming a predetermined air gap by cutting out the outer peripheral part of the rotor core facing the boundary part, and a motor that can easily detect the zero cross point easily. Easy to configure.

In the brushless motor, the rotor is provided with a shaft extending in the axial direction of the motor main body, and the rotor portion of the pump is connected to the shaft on one end side in the axial direction of the motor main body. It is preferable that they are assembled together.
In this case, a compact and inexpensive pump unit in which the motor body and the pump are integrated can be easily configured. In addition, since the motor main body that can easily detect an accurate zero cross point is integrated in the pump, the motor main body and the rotor of the pump driven by the motor main body can be rotationally driven with high accuracy. A pump unit having excellent performance can be easily configured.

In the brushless motor, a controller for controlling the driving of the motor body may be integrally assembled on the other end side in the axial direction of the motor body.
In this case, a brushless motor with a controller that can easily detect the zero-cross point and can perform high-precision drive control can be configured compactly and at low cost. In addition, when the rotor part of the pump is integrally assembled on the one end side in the axial direction of the motor body, the pump, the motor body, and the controller are compact, cost-effective and high performance arranged in series. A simple pump unit can be configured.

  According to the present invention, the waveform of the induced voltage generated in the stator winding near the zero cross point can be made steep even when rotating at a low rotational speed. It is possible to provide a brushless motor that can easily detect points accurately and perform high-precision drive control.

Hereinafter, preferred embodiments of the brushless motor of the present invention will be described with reference to the drawings. In the following description, a case where the present invention is applied to an on-vehicle pump motor mounted on a vehicle such as an automobile will be described as an example.
FIG. 1 is a cross-sectional view of a brushless motor according to an embodiment of the present invention. In the figure, a pump motor 1 according to the present embodiment includes a motor body 2 composed of a three-phase star-connected DC brushless motor, and one end side and the other end of the motor body 2 in the axial direction. On the side, the pump 3 and the controller 4 are respectively assembled. Further, the motor 1 is a sensorless type that does not require a sensor such as a hall element used for driving control of the motor main body 2, and the sensor according to the high temperature environment is provided even when the motor 1 is disposed in the engine compartment of the vehicle. Thus, the motor 1 does not cause the abnormalities and the operational abnormalities caused by the abnormalities. That is, the motor 1 has a large operation guaranteed range of the motor 1 and the pump 3 and is not provided with a mechanical rectifying mechanism, so that the commutator and the brush in this mechanism do not generate wear or noise. A compact and low-noise motor with excellent durability and few parts.

  The motor body 2 is of an inner rotor type with reference to FIG. 2, and has a rotor 6 in a motor case 5 and a stator 7 provided on the outer periphery of the rotor 6. The motor case 5 is formed in a rectangular tube shape so that an insulator 16 (described later) having a substantially rectangular outer shape can be accommodated. The motor case 5 includes a first cylindrical portion 5a that constitutes a motor chamber that accommodates the motor body 2, a second cylindrical portion 5b that constitutes a controller chamber that accommodates the controller 4, and first and second A partition portion 5c is provided between the second cylindrical portions 5a and 5b inside the case and partitions the motor chamber and the controller chamber.

  The rotor 6 includes a rotor core 6a, a shaft 6b extending from the rotor core 6a in the axial direction of the motor body 2, and a rotor magnet 6c made of a permanent magnet that is externally fitted and fixed to the core 6a. Further, the rotor magnet 6c uses a radial anisotropic ring magnet, and constitutes the motor 1 with a simple assembly operation and a small number of parts. That is, in this rotor 6, after the ring-shaped magnetic member is fitted and fixed to the outer periphery of the rotor core 6a, a plurality of, for example, two N poles and two S poles are provided on the motor body 2 as illustrated in FIG. The magnetic member is magnetized so as to be provided in parallel with the axial direction of the magnetic member, so that the magnetic member is configured as a rotor magnet 6c. For example, the four N · S poles are formed of separate fan-shaped magnetic members. Compared to the case where the rotor magnet 6c is configured by the segment magnets, the number of parts of the rotor 6 and the motor 1 is reduced, and the rotor 6 and the motor 1 that are easy to assemble are configured.

  Further, the rotor core 6a is formed with a recess 6d by cutting out the outer peripheral portion thereof into a semicircular cross section along the axial direction of the motor body 2. Further, as shown in FIG. 2, the recess 6 d is formed so as to face the boundary portion between the adjacent north and south poles of the rotor magnet 6 c, and is formed at intervals of 90 ° around the axis of the rotor 6. There are places. In this way, by forming the recess 6d in the facing portion facing the boundary portion between the N pole and the S pole on the outer peripheral side of the rotor core 6a, the magnetic permeability is smaller than that of the rotor core 6a made of, for example, a silicon steel plate or a carbon steel plate. A predetermined air gap 6e as a magnetic flux medium portion is provided between the rotor core 6a and the rotor magnet 6c, and the controller 4 can accurately and easily set a zero cross point of an induced voltage generated in a stator winding 7b described later. (The details will be described later).

The stator 7 is provided with a stator core 7a and the stator winding 7b wound around the core 7a. Specifically, as illustrated in FIG. 2, the stator core 7 a includes a plurality of, for example, six teeth disposed at equal intervals around the axis of the motor body 2, and each of the teeth includes an insulator 15. 16 bobbin portions 15a, 16a (FIG. 1) are interposed, and stator windings 7b of any of U, V, and W phases are wound. That is, the motor main body 2 is a three-phase six-slot motor having two teeth for each of the U, V, and W phases, and the two slots of each phase are point-symmetric with respect to the axis of the motor main body 2. In the position.
The insulators 15 and 16 are made by molding with a synthetic resin having electrical insulating properties (for example, polyphenylene sulfide (PPS) or 66 nylon), and the bobbin portion on the different axial direction side of the motor body 2. 15a and 16a are formed. In FIG. 2, the bobbin portions 15a and 16a are not shown for simplification of the drawing.
More specifically, in the insulator 15, the bobbin portion 15 a extends from the ring-shaped base to the other end side in the axial direction of the motor body 2, and the bobbin portion 15 a is one end in the axial direction of the motor body 2. The stator core 7a is covered from the part side.

  On the other hand, the insulator 16 has a bobbin portion 16 a that extends from a frame-shaped (frame-shaped) base portion having a substantially rectangular outer shape toward one end portion in the axial direction of the motor body 2. The bobbin portion 16a is placed on the stator core 7a from the other end side in the axial direction of the motor body 2 through a through hole (not shown) formed in the partition portion 5c of the motor case 5. The ends of the portions 15a and 16a are inserted into each other at the axial central portion of the stator core 7a, thereby constituting a winding frame of the stator winding 7b for each tooth. In addition, since the bobbin portions 15a and 16a form the winding frame as described above, the dielectric strength between the stator core 7a and the stator winding 7b is increased, and the stator configured by the heat-resistant insulation-coated conductive wire. The coating of the winding 7b can be reliably prevented from being damaged by the stator core 7a.

  In addition, the above-mentioned inlator 16 is formed with attachment portions for attaching the printed circuit board 18 of the controller 4 with bolts 21 at the four corners of the base, and among the attachment portions at the four corners, Three conductive members that respectively constitute power supply lines from the controller 4 to the U-phase, V-phase, and W-phase stator windings 7b are integrally provided (not shown). And in this insulator 16, when the attachment part and the printed circuit board 18 are connected with the volt | bolt 21, the wiring part 18a of the said circuit board 18 and the stator winding 7b of each phase pass through a corresponding conductive member. The motor body 2 and the controller 4 can be electrically connected without increasing the radial dimension of the motor body 2. As a result, a compact, low-cost and high-performance pump unit in which the pump 3, the motor body 2, and the controller 4 are arranged in series in this order can be configured.

The pump 3 is a trochoid pump which is a kind of internal gear pump, and includes a rotor portion 8 integrally assembled on one end side of the shaft 6b, a pump case 9 housing the rotor portion 8, and the pump And a pump plate 10 attached to the shaft end surface of the case 9.
The rotor portion 8 is provided with an inner gear 8a having teeth on the outer periphery and an outer gear 8b having teeth on the inner periphery that mesh with the teeth of the inner gear 8a. The inner gear 8a is attached to the shaft 6b so as to be integrally rotatable. On the other hand, the outer gear 8b is rotatably provided in the pump case 9, and when the inner gear 8a rotates according to the rotation of the shaft 6b, a pump action is generated between the inner gear 8a and the outer gear 8b. . Due to this pumping action, oil introduced between the gears 8a and 8b from the suction port (not shown) formed in the pump plate 10 passes through the discharge port (not shown) provided in the plate 10 and Supplied to each part of the vehicle. Thus, the motor main body 2 and the pump 3 are integrated by sharing the shaft 6b, thereby achieving compactness and a reduction in the number of members.

  The pump case 9 is attached to the motor case 5 by being press-fitted into the first cylindrical portion 5 a of the motor case 5. Further, a seal member 11 is installed between the pump case 9 and the pump plate 10 to prevent oil in the pump 3 from leaking outside. Further, a seal member 12 is provided between the pump case 9 and the shaft 6b to prevent oil in the pump 3 from leaking to the motor body 2 side. The pump case 9 is provided with a ball bearing 13 that supports one end of the shaft 6b. The ball bearing 14 is installed in the partition portion 5c of the motor case 5 and supports the other end of the shaft 6b. At the same time, the ball bearing 13 rotatably supports the shaft 6b.

The controller 4 controls the drive of the motor body 2 and is attached to the second cylindrical portion 5b and the partition portion 5c of the motor case 5 and the opening end of the second cylindrical portion 5b. A printed circuit board 18 is provided inside the controller chamber surrounded by a lid member 17 that covers the side. In the controller 4, the printed circuit board 18 is connected to the connector pin 23 inside the connector shell 22 attached to the side surface of the motor case 5, and the controller 4 is connected to a harness (not shown) connected to the connector pin 23. Thus, it can be connected to an electric device (not shown) on the vehicle side such as an ECU or a battery.
On the printed circuit board 18, as illustrated in FIG. 1, a motor control unit 19 that is configured by an IC, a microcomputer, and the like and inputs a speed command (rotational speed command) from the vehicle ECU. And a motor driver (motor drive unit) 20 including a bridge circuit using a power switching element such as a MOSFET is mounted.

  Specifically, referring also to FIG. 3, the motor control unit 19 is provided with an induced voltage detection circuit 19 a and a rotor rotation position detection circuit 19 b, and the induced voltage detection circuit 19 a is connected to the motor body 2. , An induced voltage (back electromotive force) generated in each of the U-phase, V-phase, and W-phase stator windings 7b is detected. Further, the rotor rotational position detection circuit 19b detects a zero cross point where the induced voltage detection value from the induced voltage detection circuit 19a becomes the reference voltage value (zero potential), and the magnetic pole of the rotor 6 (motor body 2) at the present time. Detect position. The motor control unit 19 generates a control signal for each power switching element of the motor drive unit 20 from the detected rotor (magnetic pole) position, and outputs the control signal to the motor drive unit 20. In the motor driving unit 20, the switching element is turned on / off by the control signal, and the driving unit 20 applies the U-phase, V-phase, and W-phase stator windings 7b of the motor body 2 to each other. A voltage from a battery (not shown) is applied. As a result, in the motor body 2, a current flows through each stator winding 7 b, and the motor body 2 rotationally drives the pump 3.

  As described above, in the present embodiment, a predetermined air gap (magnetic flux medium portion) 6e is provided by providing the recess 6d in the outer peripheral portion of the rotor core 6a facing the boundary portion between the N pole and the S pole of the rotor magnet 6c. Is formed between the rotor core 6a and the boundary between the N pole and the S pole. Thereby, even when the motor 1 is rotating at a low rotational speed, a change in the magnetic field (magnetic flux density) of the rotor magnet 6c passing through the stator winding 7b in the vicinity of the zero-cross point compared to the case where no air gap is formed. Can be increased. More specifically, by providing the air gap 6e, the magnetic flux of the magnetic field of the rotor magnet 6c applied from the N pole to the stator winding 7b through the rotor core 6a and the S pole has a higher permeability than the air gap 6e. That is, it passes through the inner side of the rotor core 6a that is easy to flow. For this reason, a part of the circumferential magnetic flux density waveform generated on the surface of the rotor magnet is weakened, and the change in the magnetic flux density of the rotor magnet in the vicinity of the zero cross point accompanying the rotation of the rotor 6 can be increased. As a result, it is possible to increase the change in the induced voltage in the stator winding 7b near the zero cross point and make the waveform of the induced voltage steep, so that the motor control unit 19 of the controller 4 has an accurate zero cross point. Can be easily detected. Therefore, the controller 4 can drive and control the motor body 2 with high accuracy even when the motor body 2 is rotated at a low rotational speed.

Here, the effect of the air gap 6e by the recess 6d will be described in detail with reference to FIG. In this simulation, when the motor body 2 having the rotor 6 and the stator 7 having the number of poles shown in FIG. 2 is rotated at a rotational speed of 2400 rpm, for example, the induced voltage generated in the U-phase stator winding 7b The voltage value was obtained by a predetermined calculation, and the waveform of the induced voltage was obtained. Further, the total size (area) of the air gap 6e by the four recesses 6d shown in FIG. 2 is set to about 85% of the size of the rotor core 6a when these air gaps are not formed.
As shown by the solid line 50 in FIG. 4, in the present embodiment, the voltage value of the induced voltage is greatly increased in the vicinity of the zero cross point 50a, and the dotted line showing the result of the conventional equivalent product in which no air gap is formed. Compared to 60, it was confirmed that the waveform became sharper in the vicinity of the zero cross point 50a. As a result, it was confirmed that the motor control unit 19 can easily detect an accurate zero cross point as compared with the conventional equivalent. Further, according to another simulation result by the inventor of the present invention, when rotating at a rotation speed lower than the above-mentioned rotation speed, by slightly increasing the size of the recess 6d (air gap 6e), the vicinity of the zero cross point 50a. It has been demonstrated that the waveform of the induced voltage can be changed abruptly.

  In the above description, the case where the pump and the controller are applied to an on-vehicle pump motor integrated with the motor body has been described. However, the present invention relates to a rotor core and a rotor magnet provided on the outer peripheral side of the rotor core. In this case, a magnetic flux medium portion having a magnetic permeability smaller than the magnetic permeability of the rotor core may be provided on the outer peripheral portion of the rotor core facing the boundary portion between the N pole and the S pole of the rotor magnet. The motor types such as the number and their uses are not limited to the above. Specifically, the present invention can be applied to various motors constituting a drive source such as a compressor, a fan, or an electric vehicle.

  In the above description, the air gap as the magnetic flux medium part is formed between the boundary part by providing a notch part (recessed part) in which the outer peripheral part of the rotor core is notched in a semicircular shape in cross section. However, the magnetic flux medium portion of the present invention is not limited to this. For example, the magnetic flux medium portion smaller than the magnetic permeability of the rotor core is filled on the rotor core side by filling the notch with the nonmagnetic material. May be provided. However, the case where the magnetic flux medium part is configured by the air gap as described above is preferable in that the magnetic flux medium part can be easily configured. In addition to the above description, an air gap having a shape other than a semicircular cross section may be used. Further, when the N and S poles of the rotor magnet are magnetized at a predetermined skew angle with the axial direction of the motor body, the recess for forming the air gap is formed with respect to the axial direction of the motor body. For example, it may be inclined at the skew angle. Further, the rotor magnet may be composed of a magnet different from a ring magnet such as a segment magnet. The pump directly connected to the motor shaft is not limited to the trochoid pump. However, when using an internal gear pump such as the above-mentioned trochoid pump, involute, paracoid, hypocycloid, etc., a pump unit with a built-in motor is easier and lower noise than other pump types. It is preferable at the point which can be comprised.

It is sectional drawing of the brushless motor which concerns on one embodiment of this invention. It is sectional drawing which shows the principal part structure of the motor main body shown in FIG. It is a block diagram which shows the principal part structure of the controller shown in FIG. It is a graph which shows the simulation result of the induced voltage which arises in the stator winding | winding shown in FIG. 1 when a motor is rotated.

Explanation of symbols

1 Pump motor (brushless motor)
2 Motor body 3 Pump 4 Controller 6 Rotor 6a Rotor core 6b Shaft 6c Rotor magnet 6d Recess 6e Air gap (magnetic flux medium part)
7 Stator 7b Stator winding 8 (Pump) rotor

Claims (4)

A brushless motor comprising a motor body having a stator including a stator winding, and a rotor core and a rotor including a rotor magnet provided on the outer peripheral side of the rotor core,
A magnetic flux medium portion having a magnetic permeability smaller than the magnetic permeability of the rotor core is provided on the outer peripheral portion of the rotor core facing the boundary portion between the N pole and the S pole of the rotor magnet.
A brushless motor characterized by that.   The magnetic flux medium portion is formed by cutting out an outer peripheral portion of the rotor core that faces a boundary portion between the N pole and the S pole of the rotor magnet, and thereby a boundary portion between the rotor core and the N pole and the S pole of the rotor magnet. The brushless motor according to claim 1, comprising a predetermined air gap formed between the two. The rotor is provided with a shaft extending in the axial direction of the motor main body, and a rotor portion of a pump is integrally assembled with the shaft on one end side in the axial direction of the motor main body. The brushless motor according to 1 or 2.   The brushless motor according to any one of claims 1 to 3, wherein a controller that performs drive control of the motor main body is integrally assembled on the other end side in the axial direction of the motor main body.

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