JPH04289759A - brushless motor - Google Patents

Abstract

PURPOSE:To provide a brushless motor having reduced dimensions in which fluctuation of characteristics is suppressed by improving accuracy in the fixing position of a pole sensor. CONSTITUTION:In case of a three-phase brushless motor as shown on the drawing, first, second and third phase coils are wound, respectively, around a plurality of adjacent stator teeth 21, 22, 23 (stator tooth group), stator teeth 24, 25, 26 and stator teeth 27, 28, 29. Since the number of rotor pole is higher by one or two than the number of stator teeth although the stator tooth pitch Ps is approximately same as the rotor pole pitch Pp, slot opening between the stator tooth groups is widened and pole sensors 9u, 9v, 9w can be installed. Since the pole sensors 9u-9w are installed with reference to a stator core 1, they are installed with high accuracy and fluctuation of motor characteristics is suppressed. Furthermore, rotor magnet 4a is shortened in axial length and thereby motor dimensions are decreased.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor used for drive control of office automation equipment and the like.

0002

[Prior Art] In recent years, with the cost reduction of drive circuits for servo motors used for drive control of OA equipment, etc., brushless motors, which are maintenance-free, long-life, low-noise, etc., are being replaced by brushed DC motors. has been rapidly replaced by

FIG. 5 shows an example of a conventional brushless motor with an inner rotor type 3-phase 8-pole 12-slot motor.
Shown below. The stator is composed of a stator core 1 in which 12 stator teeth are arranged at an even pitch Ps, a slot insulator 2 made of molded resin, etc., and a stator coil 3.The rotor has a main magnetic pole part as a magnetic pole. It is composed of an integral ring-shaped rotor magnet 4a (main magnetic pole) magnetized in the radial direction at a pitch Pp, a rotor yoke 5, and a shaft 6. 12 is frame, 9u, 9v, 9
w is a position where a pole sensor, which will be described next, is placed.

FIG. 6 is a cross-sectional view of the brushless motor shown in FIG. 5. Hall ICs 9u, 9v, and 9w are pole sensors, which are connected and fixed to the board 10 and sense the magnetic field of the rotor magnet 4a, which is the main magnetic pole. The position of the rotor is detected. 4b is a magnetized FG for FG (frequency generator)
The FG magnet 4b is magnetized with multiple poles in the axial direction, and an FG pattern (not shown) for detecting the magnetic flux of the FG magnet 4b is arranged on the opposing substrate 10. A substrate 10 is fixed to the stator core 1 via a spacer 11.

Since a three-phase DC brushless motor generally conducts current through 120°, the induced voltage and the output timing of the pole sensor are generally set as shown in FIG. Therefore, the positional relationship between the stator core, each phase stator coil, and the pole sensor is as shown in FIG. 8 when the stator is viewed from inside. At this time, each pole sensor may be arranged independently at a position shifted by an integral multiple of 360 degrees in electrical angle, or may be shifted by 180 degrees to invert the output.

[0006]

[Problems to be Solved by the Invention] However, in such a conventional configuration, the positioning accuracy of the pole sensor depends on the accuracy of the board and other intervening parts, as well as the overall assembly accuracy. There was a problem with the accuracy of the sensor output timing, which manifested itself in variations in motor characteristics and differences in characteristics between forward and reverse rotations, which was an obstacle to improving quality and productivity.

In addition, in order to obtain a sufficient sensor output, it is necessary to place the pole sensor close to and facing the magnetic pole of the magnet 4a, but in order to do so, the magnet 4a is made longer than the stator core as shown in FIG. It is necessary to protrude toward the sensor side, which hinders miniaturization and cost reduction of the motor.

Furthermore, when skewing the magnetization of the magnet 4a in order to improve the cogging torque and the induced voltage waveform, the axial positioning also becomes a factor in accuracy.
The problem is that the sensor timing becomes even worse.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a brushless motor with good positional accuracy of a pole sensor.

0010

[Means for Solving the Problems] In order to achieve the above object, the brushless motor of the present invention makes the slot pitch Ps and the magnetic pole pitch Pp approximately equal, and one phase is continuously formed by c adjacent stator teeth. The pole sensors are arranged in m wide slot openings obtained by setting the number p of rotor magnetic poles to the number given by the relational expression described later.

[0011]

[Operation] By arranging the pole sensor in the slot opening as in the above means, the stator core itself is used as a positioning member for the pole sensor, so the positioning of the pole sensor becomes highly accurate. Even when skewing the magnet, it is easy to maintain high positioning accuracy by arranging the pole sensor in the axial center of the stator core.

0012

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that components that are the same as or equivalent to those explained in FIGS. 5 to 8 of the conventional example are given the same reference numerals, and detailed explanations are omitted.

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention. In the figure, 1 is a stator core, which in this embodiment has 3 phases and 9 slots. A stator coil 3 is wound on the slot insulator 2. Stator coil 3 is shown in Figure 3.
The wire connection is as shown in FIG. 1, in which the U-phase coil is wound around adjacent stator teeth 21-23, the V-phase coil is wound around stator teeth 24-26, and the W-phase coil is wound around stator teeth 27-29. The first feature of the brushless motor according to the present invention lies in the stator teeth and stator coil. That is, there are m-phase stator coils 3, and the stator coils of each phase are wound around c consecutive stator teeth alternately in the forward and reverse directions, forming one group for each phase. Therefore, there are mc stator teeth in total. On the other hand, the number of rotor poles P is 1 or 2 more than the number of stator teeth. This relationship is shown in the formula below.

When cm is an odd number p=cm+1 When cm is an even number p=cm+2 m: Number of phases c: Number of stator teeth in 1 group p: Number of rotor poles The number of rotor poles is larger than the number of stator teeth, and the stator tooth pitch Ps is Since it is almost equal to the rotor pole pitch Pp, the stator tooth groups of each phase (for example, stator teeth 21, 22, 2
3) and the next phase stator teeth group (24, 25, 26) are wider than the other slot openings. For example, the slot opening between stator teeth 23 and 24 in FIG. 1 is wider than the slot opening between stator teeth 22 and 23.

The second feature of the present invention is that the wide slot openings are utilized to arrange pole sensors there (9u, 9v, 9w in FIG. 1). FIG. 2 is a sectional view of the motor of FIG. 1. The difference from the conventional example shown in FIG. 6 is that since the pole sensors 9u, 9v, and 9w are arranged in the slot openings, the magnet 4a can be shortened, and the overall length of the motor is therefore shortened. As shown in FIG. 1, the pole sensor is housed in a recess provided in the slot insulator 2 to ensure an accurate mounting position.

When the rotor poles are formed with straight magnetization, the axial position of the pole sensor is the same as the magnet 4a.
Anywhere is fine as long as it is facing the However, when skew magnetization is used to improve cogging torque and induced voltage waveforms, the axial position of the pole sensor must be accurate. In some cases, a measure may be provided.

(Embodiment 2) FIG. 4 shows a second embodiment of the present invention. The stator core is divided into three units 1a, 1b, and 1c, which are wound, and then joined together with caulking 13 to streamline the winding work. Other joining methods include screwing, adhesion, resin molding, etc., and it is only necessary to select a method that is compatible with manufacturing capacity.

[0018]

As is clear from the above description, according to the present invention, pole sensors can be ideally arranged using a simple method, so that a brushless motor with stable characteristics and good productivity can be obtained. Further, the size of the pole sensor does not affect the axial size of the motor, and the length of the magnet can be kept to the minimum necessary, so it is possible to provide a small and low-cost brushless motor.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a stator and rotor in a first embodiment of a brushless motor according to the present invention.

[Figure 2] Cross-sectional view of the same brushless motor

[Figure 3] Layout diagram of the windings and pole sensor of the same brushless motor

FIG. 4 is a configuration diagram of a stator and a rotor in a second embodiment of the brushless motor according to the present invention.

[Figure 5] Configuration diagram of the stator and rotor of a conventional brushless motor

[Figure 6] Cross-sectional view of the same brushless motor

[Figure 7] Diagram showing stator induced voltage and pole sensor output timing

[Figure 8] Layout diagram of windings and pole sensor of conventional brushless motor

[Explanation of symbols]

1 Stator core 1a Unit (stator tooth group unit) 1b
Same as above 1c Same as above 2 Slot insulator 3 Stator coil 4a Rotor magnet (magnet rotor) 9u
pole sensor 9v pole sensor 9w pole sensor

Claims (4)

[Claims] Claim 1: A magnet rotor having magnetic poles with equal pitches, the number of which is 1 or 2 larger than the number of stator teeth, and m groups of stator teeth each consisting of c consecutively adjacent stator teeth. , a stator core in which the pitch of the c stator teeth in the first group is equal to the rotor magnetic pole pitch, and the stator tooth pitch forming the boundary between the stator tooth groups is larger than the rotor magnetic pole pitch, and a one-phase stator coil. is arranged in an m-phase stator coil formed by connecting coils wound around each of the c stator teeth in the first group, and a slot opening at the boundary between the stator tooth groups. A brushless motor equipped with m pole sensors. 2. The brushless motor according to claim 1, wherein the pole sensor is located approximately at the center of the stacked thickness of the stator core, and the magnet rotor has skewed magnetic poles. 3. The brushless motor according to claim 1, wherein the slot insulator of the stator is provided with a guide or a stopper for housing the pole sensor. 4. The brushless motor according to claim 1, wherein the stator core is constructed by combining m separate units of stator tooth groups.