JPH02246758A - Manufacture of brushless motor - Google Patents

Abstract

PURPOSE:To achieve stabilized rotation by setting the fixing position of a magnetism detecting element such that radial magnetic force distribution of a magnet cancels out sensitivity error of the magnetism detecting element. CONSTITUTION:Magnitude of sensitivity error of a magnetism detecting element 9a is measured before the magnetism detecting element 9a is fixed, then a position having such strength of field as cancelling the sensitivity error of the magnetism detecting element 9a is determined based on the magnitude of sensitivity error and radial magnetic force distribution of a magnet 7 thereafter the magnetism detecting element is secured to that position. Since radial magnetic force distribution of the magnet 7 cancels out the sensitivity error of the magnetism detecting element 9a, fluctuation of driving torque due to sensitivity error of the magnetism detecting element 9a can be prevented.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a thin brushless motor that is installed in the drive unit of a compact disc player, etc., and in particular, a method for manufacturing a thin brushless motor that eliminates variations in rotational torque and enables stable operation. The present invention relates to a method of manufacturing a brushless motor. [Prior Art] FIG. 5 is a cross-sectional view of a brushless motor, FIG. 6 is a plan view of a fixed portion thereof, and FIG. 7 is a plan view of a rotor. This brushless motor has multiple coils 2 on the base l.
is installed. At the center of this coil 2 is a bearing 3.
is permanently installed. The lower end of the shaft 5 is supported by the bearing 3, and the shaft 5 is supported approximately at the center by the bearing 4. A rotor 6 is fixed to this shaft 5. This rotor 6 consists of a ring-shaped magnet 7 and a yoke 8 that holds the ring-shaped magnet 7. In the coil 2, this magnet 7 is opposed to the driving part 2a extending in the radial direction with a predetermined interval therebetween. In this brushless motor, the magnet 7 has N poles and S poles arranged alternately in the circumferential direction, and these magnetic poles and
A rotational force is applied to the rotor 6 by the current flowing in the radial direction in the drive portion 2a of the coil 2. In addition, in this brushless motor, for example, in order to rotate the rotor 6 clockwise in FIG. A current is passed in the direction away from the axis 5, and when the south pole is on top, a current in the opposite direction must be passed.In order to control such current, a magnetic sensing sensor is installed on the same plane as the coil 2. Hall elements 9a and 9b as elements
is permanently installed. The Hall elements 9a and 9b detect the magnetic poles of the magnet 7 located above them, and the current flowing through the coil 2 is controlled based on this detection signal. [Problem to be Solved by the Invention I] The Hall elements 9a and 9b are designed to output a voltage depending on the direction and strength of the magnetic field that crosses them. However, in general, the sensitivity of the Hall element has a large variation, with an error as large as ±40 to 50%. Conventionally, this Hall element 9a. 9b was attached by predetermining a fixing part at a constant distance from the center of the shaft 5, and uniformly gluing the fixing part to this fixing part. Therefore, if there is a sensitivity error in the Hall element, an erroneous signal will be output according to this sensitivity error, and a corresponding error will occur in the amplitude of the current flowing through the coil 2. Become. When this happens, as shown in the diagram in Figure 8 (the horizontal axis shows the rotation angle of the rotor and the vertical axis shows the drive torque), there will be a large fluctuation in the drive torque, which will cause a large fluctuation in the drive torque when driving a compact disc, etc. In such a case, the reproduction accuracy will be adversely affected and power consumption will be wasted. The present invention has been made by focusing on the above-mentioned conventional problems, and by appropriately setting the fixing position of the magnetic sensing element, current can be passed through the coil at an accurate cycle, and the driving torque can be stabilized. It is an object of the present invention to provide a brushless motor that has improved performance and reduced power consumption.

[Means to solve the problem]

A method of manufacturing a brushless motor according to the present invention is as follows. A rotor is constituted by a ring-shaped magnet in which magnetic poles are arranged alternately in the circumferential direction and a yoke that supports the magnet, and a yoke is wound around the fixed part along the surface of the magnet. A method for manufacturing a brushless motor, in which a plurality of coils and a magnetic sensing element for detecting the magnetic poles of a magnet are fixedly installed opposite to the magnet, the method comprising: measuring an error in sensitivity of the magnetic sensing element; (b) Of the fixed part to which a magnetic field of varying strength is applied along the radial direction by the magnet, so that the error in the sensitivity of the magnetic sensing element measured in the step (a) is canceled out. and (C) fixing the magnetic sensing element at the position determined in step (b) above. .

[Effect]

According to the above means, the magnetic sensing element is attached to the fixed part by measuring the magnitude of the sensitivity error of the magnetic sensing element before work, and based on the magnitude of the sensitivity error and the magnetic force distribution in the radial direction of the magnet. The position where the strength of the magnetic field that cancels out the sensitivity error of the magnetic sensing element is determined, and the magnetic sensing element is fixed at that position. Therefore, the sensitivity error of the magnetic sensing element can be canceled out by the magnetic force distribution in the radial direction of the magnet. Therefore, it is possible to prevent fluctuations in the drive torque from occurring due to sensitivity errors in the magnetic sensing element, as in the prior art. [Example] Hereinafter, an example of the present invention will be described with reference to the drawings. First, we will explain the structure and principle of a brushless motor in Figures 5 to 7.
This will be explained in detail using figures. The structure of the brushless motor is the same as that described in the related art, and a coil 2 and Hall elements 9a and 9b, which are magnetic sensing elements, are fixedly installed on a base l. Further, a rotor 6 is fixed to a shaft 5 which is rotatably supported by bearings 3 and 4. This rotor 6
consists of a ring-shaped magnet 7 and a yoke 8 supporting the ring-shaped magnet 7. This brushless motor is of a two-phase drive type. 7th
As shown in the figure, the magnet 7 is divided into eight equal parts in the circumferential direction, and each part is alternately N pole. They are arranged in order of south pole. That is, the N and S poles are
They are distributed at an angle of 45 degrees with respect to the center of the rotor 6. On the other hand, each coil 2 is wound in a triangular shape in a direction along the surface of the magnet 7, and a driving portion 2 extending in the radial direction
a is wound around the support portion of the shaft 5 so that the opening angle θ is 45 degrees. There are four coils 2,
Two opposing coils are connected to each other by windings 2b and 20, and two sets are connected in series. Two of the connected coils 2 are group A, and the other two coils 2 are group B. In addition, the adjacent drive parts 2 of the coils 2 of the adjacent groups A and B
The opening angle α between a and 2a from the center of rotation is 22.5
It is arranged so that the In addition, the Hall elements 9a and 9b are connected to the coils 2 of group A on the left and right.
and coil 2 of group B.
In addition, the two Hall elements 9a and 9b are arranged at an opening angle of a (22.5 degrees) with respect to the center of rotation6.
The Hall element 9a on one side controls the current flowing through the two coils 2 of group A, and the Hall element 9b controls the current flowing through the two coils 2 of group A.
This is for controlling the current flowing through the two coils 2 of the set. The operation of this brushless motor will be explained. The magnetic poles arranged alternately in the magnet 7 are detected by Hall elements 9a and 9b. One Hall element 9
Starting from the polarity of the magnet 7 detected by a, a trigonometric waveform current is passed through the coils 2 of group A. Further, a current having a trigonometric function waveform is caused to flow through the coils 2 of group B starting from the polarity of the magnet 7 detected by the other Hall element 9b. The arrangement angle of the magnetic poles of magnet 7 is 9
0 degrees, and the arrangement angle of the two Hall elements 9a and 9b is 22.5 degrees (l of the arrangement angle of the magnetic poles in the magnet 7).
/4) Therefore, the coil 2 of the 5A group and the coil 2 of the B group have waveform currents whose wavelength periods are shifted by l/4, for example, one group has a sine wave and the other group has a cosine wave. As a result, the rotor is always driven in one direction with a constant torque. Next, a method of position adjustment and fixing of the Hall element to the fixing part (base l), which is a feature of the present invention, will be explained. Before incorporating the Hall element 9a or 9b into a brushless motor, its sensitivity characteristics are measured. This measurement is performed by placing the Hall element to be used in a standardized magnetic field of a constant strength, and This is done by measuring the output voltage from the FIG. 4 is a diagram in which the horizontal axis represents the strength of the magnetic field and the vertical axis represents the output voltage of the Hall element. The output voltage of a standard Hall element with no sensitivity error is a straight line shown by a dotted line in the diagram of FIG. However. If there is a sensitivity error in the Hall element, an output voltage as shown by the solid line in the diagram of FIG. 4 is generated. Therefore, if a Hall element is placed within the standardized magnetic field H mentioned above, the difference between the detected output voltage of the Hall element used and the output voltage of a standard Hall element can be measured, and the degree of sensitivity error of the Hall element can be determined. Understand immediately. Therefore, depending on the sensitivity error, the installation distance of the Hall elements 9a or 9b from the center of the shaft 5 is changed (see FIG. 1), and the Hall elements 9a, 9b are fixed at appropriate positions. That is, magnet,
The strength of the magnetic field due to the door varies in the radial direction of the magnet 7 as shown in the diagram of FIG. Therefore, a position with a magnetic field strength that cancels out the sensitivity error of the Hall elements 9a and 9b is selected, and the position is numerically determined as a dimension from the center of the shaft 5, and then the position is determined before installation. The installation position of the Hall element is determined numerically according to the sensitivity error of the measured Hall element, and the Hall element is fixed.1 For example, as shown in Figure 4, if the sensitivity of the Hall element to be used is more sensitive than the standard one, In this case, the Hall elements 9a and 9b may be installed at a position close to the edge of the magnet 7, that is, at a position where the magnetic field is weak. In this way, if the fixed position of the Hall element is determined by canceling the sensitivity error of the Hall element by the magnetic field generated by the magnet, the driving torque of the rotor 6 will always be constant, as shown in FIG. 9. The diagram in FIG. 9 shows the rotation angle of the rotor on the horizontal axis and the magnitude of the driving torque on the vertical axis. Note that one of the two Hall elements 9a and 9b may be fixed at the same position at all times, and only one fixed position may be selected based on the above conditions. Further, as shown in FIG. 3, a guide groove 1a extending in the radial direction about the shaft 5 is formed on the pace 1, and a Hall element 9a or 9b is inserted therein. An appropriate fixing position may be selected by moving the Hall element along the guide groove 1a. In this way, the arrangement angle of the Hall element will always be accurate. Note that it is possible to use a guide mechanism other than the guide groove 1a. [Effects of the Invention] As described above, according to the present invention, the fixed position of the magnetic sensing element is set at such a position that the error in the sensitivity of the magnetic sensing element is canceled out by the magnetic force distribution in the radial direction of the magnet. Therefore, fluctuations in the driving torque due to sensitivity errors of the magnetic sensing element do not occur, and stable rotation can be obtained. Additionally, unnecessary power consumption is eliminated, leading to power savings.

[Brief explanation of drawings]

Fig. 1 is a side cross-sectional view showing the fixed part of the magnetic sensing element of the brushless morph according to the present invention, Fig. 2 is a diagram showing the strength of the magnetic field due to magnetlide, and Fig. 3 is a plan view showing the guide mechanism of the magnetic sensing element. Figure 4 is a diagram showing the sensitivity of the magnetic sensing element, Figure 5 is a sectional view showing the entire brushless morph, Figure 6 is a plan view showing its fixed part, and Figure 7 is a plane view showing the magnet. 8 is a diagram showing the driving torque of the motor showing the problems of the conventional method, and FIG. 9 is a diagram showing the driving torque of the motor showing the effects of the present invention. l...Base, 2...Coil%6...Rotor, 7
...Magnet, 8...Yoke, 9a, 9b...
Magnetic sensing element.

Claims (1)

[Claims] 1. A rotor is constituted by a ring-shaped magnet in which magnetic poles are arranged alternately in the circumferential direction and a yoke that supports the magnet, and a yoke is wound around the fixed part along the surface of the magnet. A method for manufacturing a brushless motor in which a plurality of coils and a magnetic sensing element for detecting magnetic poles of a magnet are fixedly installed opposite to the magnet, the method comprising: (a) measuring an error in sensitivity of the magnetic sensing element; (b) The error in the sensitivity of the magnetic sensing element measured in the step (a) of the fixed part to which a magnetic field of varying strength is applied along the radial direction by the magnet is canceled out. and (c) fixing a magnetic sensing element at the position determined in step (b). manufacturing method