JPS619152A - Dc brushless motor - Google Patents

Abstract

PURPOSE:To obtain an inexpensive 2-phase DC brushless motor which can be reduced in thickness by providing a current flow controller for switching currents to coils when the output of a magnet detector is inverted to set the current flow- ing periods of the respective phases to half period. CONSTITUTION:Phase coils 7-1-7-4 are annularly disposed on a printed board 5, and magnetic detectors 10-1, 10-2 are respectively mounted at the positions displaced at 45 deg. of an electric angle in the opposite rotation direction from the center line of the coils in the bores of the coils 7-1, 7-2. Further, the currents flowed to the coils 7-1-7-4 are switched when the outputs of the detectors 10-1, 10-2 are inverted, and a logic circuit for setting the current flowing periods of the respective phases to half period is provided. Thus, since the permanent magnet is not necessarily magnetized in a sinusoidal wave, the entire motor can be reduced in thickness.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a direct current brushless electric motor, and in particular, it can be used as a driving electric motor for a floppy disk drive device, and has a simple structure, can be manufactured at low cost, and can be made thin. The present invention relates to a two-phase DC brushless motor.

[Background of the invention]

Conventionally, in a two-phase DC brushless motor in which the energization period of each phase is a half cycle, the permanent magnet of the rotor is generally magnetized in a sine wave to make the output of a magnetic detector into a sine wave. A method was adopted in which the current flowing through each phase was controlled using the signal obtained by comparing the outputs of the devices. The reason for this is that when a permanent magnet is magnetized with a square wave, the output of the magnetic detector also becomes a square wave, and the potential difference between the outputs of the magnetic detector compared before and after the optimal phase for switching the current flowing to each phase becomes small, causing noise. This is because the operation becomes unstable due to the influence of factors such as. However, compared to permanent magnets magnetized by square waves, permanent magnets magnetized by sine waves have lower magnetic flux density and less effective magnetic flux when they are made of the same material and shape, and it is difficult to obtain the desired induced voltage constant. In order to increase the permeance coefficient, permanent magnets require a large thickness or a coil with a large number of turns, and in order to suppress variations in characteristics between products, precision is required for sine wave magnetization. The drawback was that it was expensive.

[Purpose of the invention]

An object of the present invention is to provide a two-phase DC brushless motor that can be made thinner and cheaper.

[Summary of the invention]

The feature of the present invention is that from the position of the magnetic detector of a conventional two-phase DC brushless motor, the electrical angle is 45 in the counter-rotation direction of the rotor.
The point is that a logic circuit is provided to generate a command signal for energizing each coil from the shifted position of the magnetic detector and the output of the magnetic detector. Depending on the position of the magnetic detector and the logic circuit, it is possible to configure a two-phase direct current brushless motor using square-wave magnetized permanent magnets in which the energization period of each phase is half a cycle. Therefore, since the magnetic flux density can be high, it is possible to make the permanent magnet thinner and the electric motor thinner.

[Embodiments of the invention]

A conventional example of a two-phase DC motor will be explained with reference to FIGS. 1 and 2. FIG. 1(a) is a sectional view showing the configuration of main parts.

In Fig. 1, 1 is the rotor shaft, 2 is the rotor yoke, and 3 is the rotor shaft.
are permanent magnets, and these r, 2.3 constitute the rotor of the electric motor. 4 is a stator yoke, 5 is a printed circuit board,
6 is a bearing section. FIG. 1(b) shows coils 7-1.7-2.7-3.7-4. and a layout diagram of magnetic detectors 8-1 and 8-2. These 7-1
．． 7-3 constitutes the first phase of the motor, and 7-2 and 7-4 constitute the second phase of the motor. FIG. 1(c) shows the magnetization section of the permanent magnet 3, and FIG. 1(d) shows the magnetization section of the permanent magnet 3.
The waveform (1) in FIG. 1(d) shows that magnetization is performed in a sinusoidal manner with a period of 120 degrees in mechanical angle.

Figure 2 shows the output of the magnetic detector and the first phase obtained from it.

This shows the energization section to the second phase. (1) in Figure 2
, is the output waveform of the magnetic detector 8-1, (2) 9, □ in Fig. 2
Yuffi! 188-2 (7) 8 points, □2°. (1)
``f is the waveform obtained by inverting the waveform in (1), and (2)' in Figure 2 is the waveform obtained by inverting the waveform in (2).Phase A is the waveform obtained by inverting the waveform in (1). Phase B is the phase where the potential of waveform (2)' is higher than the potential of waveform (2)'.
), Phase C is the phase where the potential of waveform (1)' is higher than the potential of waveform (2), and phase C is the phase where the potential of waveform (2)' is higher than the potential of waveform (1)'. Phase E, which is a phase in which the potential of waveform (1) becomes higher than that of waveform (2)', is equivalent to phase A. The energizing section A-B is the section between phase A and phase B, the energizing section B-C is the section between phase B and phase C, the energizing section C-'D is the section between phase C and phase C, and the energizing section D- E is the interval between the phase difference and the phase E. The energized section of the second phase is the energized section A-B and the energized section C-D, and the energized section of the first phase is the energized section B-C and the energized section DE, and the current flows in the energized sections A-B and C-. By setting the currents in opposite directions and setting the currents flowing in the current-carrying sections B-C and CD in the opposite directions, it is possible to drive a two-phase brushless motor. However, in this method, the switching of energization between the first phase and the second phase is carried out in phases A, B, C, and D.
, E waveforms (1), (2), (1)', (2)
' This is done using the phase obtained from '. Phase A, B, C, D,
In order to make the phase of E accurate, Fig. 1(c) and (d)
It is necessary to perform sinusoidal magnetization with high accuracy, and therefore the permanent magnet 3 is more expensive than a permanent magnet magnetized in a square wave. Also, compared to permanent magnets magnetized in a square wave pattern, if the shape and material are the same, the effective magnetic flux will be lower, so in order to obtain the desired induced voltage constant, it is necessary to increase the number of turns of the coil. If the same coil were used, the drawback was that a thicker permanent magnet would have to be used in order to obtain an effective magnetic flux.

In order to eliminate the above-mentioned disadvantages, we devised a two-phase DC brushless motor having the structure shown in FIG.

FIG. 3(a) is a sectional view showing the main structure. Figure 3 (
b) Coil 7-1.7-2.7-3 on the printed circuit board
．． 7-4 and magnetic detection elements 10-1 and 10-2. Similarly to FIG. 1(b), coils 7-1 and 7-
3 constitutes a first phase, and coils 7-2 and 7-4 constitute a second phase. The magnetic detectors 10-1 and 10-2 in FIG. 3(b) are electrically connected in the counter-rotational direction of the permanent magnet compared to the positions of the magnetic detectors 8-1 and 8-2 in FIG. 1(b). It is characterized by a 45° deviation at the corners. FIG. 3(e) shows the magnetization sections of the permanent magnet 9, and FIG. 3(d) shows the magnetization specifications of the permanent magnet 9.

In FIG. 3(d), waveform (1) shows that the permanent magnet 9 is magnetized in a square waveform with a phase of 120 degrees in mechanical angle.

Figure 4 shows the first phase from the output waveform of the magnetic detector.

A circuit configuration for generating a signal that determines the second-phase energization section is shown. 10-1.10-2 is a magnetic detector, 11-1
．． 11-2 is a comparator, 12-1゜12-2 is an inverter, 13-1, 13-2゜13-3, 13-4 is a 2-man power 1
It is an AND circuit of output, input negative logic, and output positive logic. F
, G is the output of the comparator 11-1.11-2, H and I are the outputs of the inverter 12-1.12-2, J, and L9M are,
AND circuit 13-1.13-2, 1.3
-3.1.3-4 output. Figure 5 shows F in Figure 4,
G.H.

(2) In "J," the waveforms of L and M are shown.

Due to the relationship between the energizing sections shown in Fig. 5, the first phase is energized by M
, and J to energize the second phase.

If the L signal is used, a two-direction brushless motor can be driven.

Here, if we apply the circuit in Figure 4 while keeping the position of the magnetic detector 8-1 and 8-2 in Figure 1(b), the phase relationship between the energized section and the induced voltage in the first and second phases will be Figure 6(a)
become that way. Particularly, as shown in Fig. 6(b), a portion of the coil is extracted, and when the coil is energized with such a phase relationship, the current is larger and the torque is smaller than when energized with the phase relationship shown in Fig. 6(c). Does not occur effectively. In order to obtain the phase relationship as shown in Figure 6(c), the energized section must be 4 electrical degrees.
It is enough to advance by 5 degrees. For that purpose, magnetic detector 8-1.8
-2' position is shifted by 45 degrees in electrical angle in the counter-rotational direction of the rotor. Since the number of poles of the permanent magnetic flux is six as shown in FIG. 3(c), in this embodiment, the phase relationship shown in FIG. 6(c) can be obtained by shifting by 15'' in mechanical angle.
Pusher 8□□1. .

oh. 17.1□. , ear, 4,2 pu, but it can also be configured with 4 as shown in FIG. Coil 1.4-1.14-3. IL-5, 14-7 constitutes the first phase, 1472.14-jin 14-6.14
-8 constitutes the second phase.

The magnetic detector 15-1 is located at a position offset from the center line of the coil 14-1 by 45 inches in electrical angle in the counter-rotational direction of the rotor, and the magnetic detector 15-2 is located at a position offset by an electrical angle of 45 inches from the center line of the coil 14-2. It is located at a position offset in the counter-rotation direction of the 45" rotor. 7th
Figure (b) shows the permanent magnet 16 when the configuration of (a) is used, and shows magnetization sections 4. FIG. 7(c) shows the permanent magnet 16
The waveform (1) in FIG. 7(C) shows that the magnet is magnetized in a rectangular waveform with a mechanical angle period of 60°.

As can be seen from FIG. 7(b), since the number of poles of the permanent magnet is 12, the electrical angle 456 is 7.5 degrees in mechanical angle.

Also, as shown in Fig. 8, the first phase is connected to the coil 14-1゜14-
3.14-5, 2nd phase coil 14-2゜14-4.1
4.6, it is also possible to use three coils, each having one equivalent. In this case as well, the permanent magnet 16 shown in FIG. 7(b) is used.

〔Effect of the invention〕

As detailed above, the two-phase DC brushless motor with this structure switches the energization of the first and second phases by reversing the output waveform of the magnetic detector, thereby energizing each phase for half a cycle. Since the period can be given, it is no longer necessary to magnetize the permanent magnet in a sinusoidal waveform, and it is possible to use a permanent magnet magnetized in a square waveform, so that the electric motor can be made thinner.

[Brief explanation of the drawing]

Sections 1 (a) to (d) and FIG. 2 show conventional examples,
Figure 1 (a) is a sectional view showing the main part configuration, (b) is a layout diagram of the coil and magnetic detector, (c) is a diagram of the magnetization division of the permanent magnet, and (d) is the magnetization specification of the permanent magnet. 2 is a phase relationship diagram of the output waveform of the magnetic detector and the energized section to the coil, and FIGS. 3(a) to 8(d) to 8 show embodiments of the present invention. Figure (a) is a sectional view showing the main part configuration, (b) is a layout diagram of the coil and magnetic detector, (c) is a diagram of the magnetization division of the permanent magnet, (d) is a magnetization specification diagram of the permanent magnet, Figure 4 is a circuit diagram for creating a energization command signal to the coil from the output of the magnetic detector, Figure 5 is the circuit time chart of Figure 4, and Figure 6 (a
) is a time chart of the energization period and induced voltage when the magnetic detector is in the position of Fig. 1(b) and the circuit of Fig. 4 is applied, and Fig. 6(b) is a time chart of the induced voltage in Fig. 6(a). FIG. 6(e) is a diagram showing the phase relationship between the energized section and the induced voltage in this embodiment, and FIG. 7(a), (b), and (c) are diagrams showing a part of the A coil is used, (a) is a layout diagram of the coil and magnetic detector, (b) is a diagram of the magnetization division of the permanent magnet, (c
) Figure 8 is a diagram showing the magnetization specifications of a permanent magnet, and an arrangement diagram of the coils and magnetic detector when three coils are used in one phase. DESCRIPTION OF SYMBOLS 1... Rotor shaft, 2... Rotor yoke, 3... Permanent magnet, 4... Stator yoke, 5... Printed circuit board, 6... Bearing part, 7-. 1.7-2.7-3.7-4
...Coil, 8-1.8-2...Magnetic detector, 9.
...Permanent magnet, 10-1.10-2...Magnetic detector,
11-1゜11-2... Comparator, 12-1.12-2
...Inverter, 13-1.13-2.13-3.1
3-4 shoes...AND circuit, 14-1
．． 14-2.14-3゜14-4.14-5.14. −
6.14-7.14-8...Coil, 15-1.15
-2...Magnetic detector.

Claims (1)

[Claims] 1. A rotor formed of a permanent magnet made in the shape of a hollow disk, with half the circumference remaining as the N pole and half the circumference magnetized as the S pole, and a rotating hub that rotatably supports this permanent magnet. , a plate-shaped stator yoke, a printed circuit board placed on this stator yoke, a plurality of coils placed on this printed circuit board, and a permanent magnet placed on this printed circuit board that detects the rotational position. It includes a plurality of magnetic detectors, a bearing section attached to a stator yoke, and an energization control circuit that receives the output of the magnetic detector and controls the current flowing through each coil to drive and control the rotor in a fixed direction. A direct current brushless motor, characterized in that it is equipped with an energization control circuit that switches the current flowing through each coil when the output of a magnetic detector is reversed, and makes the energization period of each phase half a cycle.