JPS62147945A - Brushless motor - Google Patents

Abstract

PURPOSE:To change starting characteristics without altering the number of revolution by mutually displacing the central position of the magnetization of a section oppositely faced to a Hall element for a rotor pole and the central position of the magnetization of a section oppositely faced to a stator pole in the direction of rotation. CONSTITUTION:The central position of apparent magnetization (the position of a broken line) working to a stator is displaced to a rotation side from the central position of magnetization (the position of a chain line) in pole width detected by a Hall element 6. N and S shown in broken lines represent the apparent centers of a rotor pole in the interaction of a permanent magnet rotor 1 under non-excitation and stator poles 3a, 3b, and N and S are displaced to the rotation side from magnetomotive force by exciting currents and interaction (N and S shown in solid lines) with a permanent magnet, thus displaying the same effect as the displacement angle of the magnetic pole 3b in narrow width is increased. On the other hand, the changeover timing of coil currents is made the same as conventional devices, and the number of revolutions is not changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to a two-phase brass DC motor using a Hall element for detecting the position of a rotor.

1 Backlift Technology 1 As shown in the fISi diagram, this type of motor is designed by alternately providing wide magnetic poles 3a and narrow magnetic poles 3b as stator magnetic poles, and by deviating the narrow magnetic poles 3 in the direction of rotation. Obtains startup characteristics. In a motor with this type of structure, if you want to arbitrarily change the rotation speed or starting characteristics, changing the shape of the stator or the position of the Hall element will increase the cost, so conventionally it was necessary to adjust the magnetic force of the permanent magnet rotor. and adjusting the magnetomotive force of the coil. However, this conventional method has the following problems.

For example, if the magnetomotive force of the coil is reduced in order to lower the rotational speed of a motor configured as described above, the torque generated by the current will decrease and starting performance will deteriorate. When the magnetic force of the motor is reduced, the current increases and the rotational speed increases. In a motor in which the shape of the stator and the position of the Hall element are determined in this way, it is extremely difficult and time-consuming to adjust the rotation speed and starting characteristics. Figures 3 (α) and (b) show the relationship between the magnetomotive force of the coil and the magnetic force of the permanent magnet, respectively, and in the figure, N is the rotation speed, ■ is the coil current, and Vs is the fill voltage. It is.

[Objective of the Invention 1 The present invention has been made in view of the above problems, and its purpose is to easily change the rotation speed and starting characteristics without changing the stator shape or the Hall element position. To provide a brushless motor structure that can

[Disclosure 1 of the Invention] The brushless motor according to the present invention includes a permanent magnet rotor that is alternately magnetized at regular intervals, and one of the adjacent magnetic poles is displaced from the equally spaced position toward the rotation direction side. Equipped with a salient pole type stator whose magnetic pole width is narrower than the other magnetic pole, and a Hall element that is fixed to the stator side and detects the polarity of the rotor magnetic pole passing through.The Hall element switches the current in the stator coil. In a brushless motor, the position of the rotor magnetic pole facing the Hall element and the position facing the stator magnetic pole are shifted in the axial direction from each other, and the magnetization center position of the part of the rotor magnetic pole facing the Hall element and the stator magnetic pole are shifted from each other in the axial direction. The magnetization center position of the opposing part is shifted from each other in the rotational direction, and the width can be substantially changed by changing the magnetization distribution without changing the stator or rotor molding die. The feature is that the same effect as changing the deflection angle of the narrow magnetic pole or the mounting position of the Hall element can be obtained.

FIG. 1 shows an embodiment of the motor of the present invention, in which a permanent magnet rotor 1 is fixed to a cup-shaped yoke 2, and a stator has a wide magnetic pole [i 3 rs and a narrow magnetic pole 3b]. The narrow magnetic poles 3b are arranged alternately and are offset in the rotational direction by 20 to 40 degrees in electrical angle. 4 is each stator magnetic pole 3a,
A coil 3b is wound around the rotor shaft, and 5 is a rotor shaft fixed to the cup-shaped yoke 2, which is rotatably supported by a frame (not shown). 6 is a Hall element, stator magnetic pole 3a
Figure 2 shows the magnetization distribution of each magnetic pole of the permanent magnet rotor 1, and h is the rotation angle. The axial width of the child magnetic pole, h2, indicates the axial width and position of the stator magnetic pole, and h indicates the position of the Hall element. The dogleg-shaped solid line in the center shows the center of magnetization in the method of the present invention, that is, the peak position of the strength of magnetic force, and the chain line shows the center of the rotor magnetic poles, that is, the position of the conventional magnetization center. According to this magnetization method, it is possible to shift the upper center position (dotted line position) of the apparent force acting on the stator in the direction of rotation than the center position of the magnetic pole width detected by the Hall element (dash line position). . The broken line N in Figure 1,
S is the apparent center of the rotor magnetic pole in the interaction between the permanent magnet and the stator magnetic pole when not energized, and this is the center of the interaction between the magnetomotive force due to the excitation current and the permanent magnet (solid line N, Since it is shifted in the rotational direction from S), the same effect as that of increasing the deflection angle of the narrow magnetic pole 3b is achieved. On the other hand, since the magnetic poles detected by the Hall element and their timing are the same as before, the switching timing of the coil current is almost the same as before, and the rotation speed does not change.

In this way, the starting characteristics can be changed without changing the rotational speed, and conversely, the rotational speed can be changed without impairing the starting characteristics.

[Effect 1 of the Invention As described above, according to the present invention, in a brushless motor in which one of the adjacent stator magnetic poles is shifted in the rotational direction from an equidistant position and the width of the magnetic pole is narrower than that of the other magnetic pole, the rotating While shifting the position of the child magnetic pole facing the Hall element and the position facing the stator magnetic pole from each other in the axial direction,
Since the magnetization center position of the part of the rotor magnetic pole facing the Hall element and the magnetization center position of the part facing the stator magnetic pole are shifted from each other in the rotation direction, it is possible to effectively The same effect as changing the deflection angle of the upper narrow magnetic pole or the mounting position of the Hall element can be obtained, and the rotation speed can be increased very easily and inexpensively without changing the stator or rotor molding die. This has the advantage that it is possible to adjust the start-up vfff.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the brushless motor of the present invention, FIG. 2 is a schematic front view showing the magnetized state of the rotor of the same as above,
ft53 (a) and (b) are characteristic diagrams of plasticine smoke of the same type as the present invention. 1 is a permanent magnet rotor, 2 is a cup-shaped yoke, 3 is a salient pole type stator, 3a is a wide magnetic pole, 3b is a narrow magnetic pole, 4 is a coil, 5 is a thin rotor, and 6 is a Hall element.

Claims (1)

[Claims] (1) NS Permanent magnet rotor that is alternately magnetized at equal intervals, and a salient pole type in which one of the adjacent magnetic poles is offset in the rotational direction from the equally spaced position, and the width of that magnetic pole is narrower than the other magnetic pole. In a brushless motor that is equipped with a stator and a Hall element that is fixed to the stator side and detects the polarity of the rotor magnetic pole passing through, the Hall element switches the current of the stator coil. and the position facing the stator magnetic poles are shifted from each other in the axial direction, and the magnetization center position of the portion of the rotor magnetic pole facing the Hall element and the magnetization center position of the portion facing the stator magnetic pole are shifted from each other. A brushless motor is characterized by being shifted in the direction of rotation.