JPS6188755A - Three phase brushless motor - Google Patents

Abstract

PURPOSE:To reduce the torque ripple of a brushless motor, by providing auxiliary poles changing the magnetized wave of a rotor magnet partly. CONSTITUTION:So far as a three phase brushless motor is concerned, three phase coils are arranged at an interval of an electrical angle 120 deg. multiplied by an integral number, and a rotor magnet M is magnetized in eight poles for example, and main poles 1S, 1N are organized so that they may alternately confront the torque action side in the radial direction of each coil. The respective coils are electrically conducted by switch elements every 120 deg. or every 180 deg. in succession. Then, on the center of the flux width in the rotary direction of the main poles 1S, 1N of the rotor magnet M (at any position of 30 deg., 90 deg., or 150 deg. off the range of the main poles), auxiliary poles 3N, 3S for reducing the effective flux of the main poles 1S, 1N partly are provided. Then, the peak position (90 deg. and 270 deg.) for flux distribution of sine wave form is greatly concaved, and the synthesized torque ripple can be greatly reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a three-phase brushless smoke designed to reduce torque ripple.

Conventional techniques As the energization method for a two-phase brushless morph, three-phase 120° energization in a negative phase direction, a three-phase unidirectional 180° energization, and a three-phase 180° bidirectional energization method are known.

In either case, the three-phase coils are arranged at intervals that are an integral multiple of 120 degrees in electrical angle, and the rotational position of the rotor magnet is detected by a ball element (orientation element) to determine the interlinkage magnetic flux of each coil. The three-phase coil is switched and energized according to the polarity.

Therefore, since the torques of each phase are basically synthesized at intervals of 120 degrees in electrical angle, torque ripples occur in principle.

If this motor is used in the tape running system of a tape recorder or VTR, or the phono motor of a player, it will cause deterioration in playback quality such as wow and flags in playback audio and jitter in video.

Problems to be Solved by the Invention Therefore, in the past, the magnetization of the rotor magnet was made into a trapezoidal waveform to reduce the difference between peak and dip of the resultant torque, or alternatively, the magnetization was made into a triangular waveform so that the resultant torque was kept at a constant value. Measures were taken to prevent this.

However, in the case of trapezoidal wave-like magnetization, the amount of effective magnetic flux that contributes to torque generation is reduced, and the efficiency of the motor may be significantly reduced. In addition, it is very difficult to correctly perform triangular wave magnetization, and the reality is that it has not been possible to obtain an ideal constant torque. The present invention has been made in view of this problem, and it is an object of the present invention to reduce torque ripple by simple means without reducing output torque.

Summary of the Invention The three-phase brushless smoke according to the present invention has a main pole at at least one location approximately 30°, 90°, and 150° in electrical angle from the boundary of the main poles (Is, IN) formed on the rotor magnet (M). Compensating poles (3N, 3S) to partially reduce magnetic flux
) is provided.

In a working three-phase brushless motor, the torques of each phase that live with a phase difference of 120 degrees in electrical angle are combined, so the phase difference is 30 degrees in each electrical angle.
, 90”, 150°, 210°, 270° and 330°
Torque ripple peaks are likely to occur at these locations. Therefore, by providing a commutative electrode corresponding to the peak, the peak is recessed and torque ripple is reduced.

Embodiment FIG. 1 is a route diagram showing the basic configuration of a three-phase brushless smoke to which the present invention is applied, and includes a three-phase coil LA.

LB and LC are arranged at intervals of an integral multiple of 120" in electrical angle, and the coils LA' and LB' are arranged symmetrically with these coils.
, LC' are coupled in series with LA, LB, and LC, respectively. The rotor magnet M is magnetized to have, for example, eight poles, and the main poles IS and IN alternately face the torque acting sides of the respective coils in the radial direction.

FIG. 2 is a diagram of a bidirectional current-carrying type drive circuit, in which each coil LA is connected to an output stage DA-DC of a 5EPP configuration.

LB and LC are driven by switching. Switching is performed every 60 degrees in electrical angle, for example, first the current in coil LA is divided into coils LB and LC, and then at the next timing, the current in LC is reversed and sent to LA.

LC current flows to LB, and at the next timing, LA
Six types of energization modes are performed cyclically, such as reversing the current and branching it from LC to LA and LB. The rotational position of the rotor magnet M is detected by Hall elements HA, HB, and HC, and based on the detection output, a switching signal for driving each element of the output stages DA-DC is logically formed in the switching circuit 2.

Figure 3 is a drive circuit diagram of a unidirectional current type (120° or 180°), where each coil LA-LC is connected to a switch element TA-T.
The current is applied sequentially every 120° or every 180° at C.

The switching signal is sent to the Hall element HA- as in FIG.
It is formed by the switching circuit 2 based on the output of the HC.

Next, Fig. 4 is a magnetization pattern diagram of the rotor magnet M when the present invention is applied to a three-phase bidirectional 180' current-carrying type brushless smoke, and Fig. 5 is an operating waveform diagram (current, magnetic flux, torque). . The current flowing through each phase coil LA-LC is as shown in Figure 5 a"-c, a current of magnitude l flows through one coil every 60 degrees, and the above-mentioned current flows through the other two coils. 1/2 current in the opposite direction is passed.As shown in Fig. 5e, the torque becomes 1 in the central 60° section of the sinusoidal interlinkage flux shown by the dotted line in Fig. The size becomes 1/2 in the 60° section.

The combined torque of each phase is as shown in FIG. 5d, and includes many torque ripples. In principle, a ripple of .

Therefore, as shown in the magnetization pattern diagram in Fig. 4, commutating poles 3N and 3S are provided approximately in the center of the magnetic flux in the rotational direction of the main poles IS and IN of the rotor magnet M to locally reduce the effective magnetic flux of the main pole. There is. These complementary poles 3N, 3S are the main poles IS, IN
The polarity may be opposite to that of the main pole, or it may be an unsaturated weak bond (H portion or non-magnetized portion) having the same polarity as the main pole.These supplements i3N.

Due to 3S, the peak positions (90° and 270°) of the sinusoidal magnetic flux distribution are greatly depressed, as shown by the solid line in FIG. 5f. For this reason, the peaks of the torque waveforms of each phase are depressed as shown in Figure 5, and the ripple of the combined torque is greatly reduced as shown in Figure 5g. Actual measurement shows that the torque ripple is approximately 4.4%.
Met.

Next, FIG. 6 is a diagram of the magnetization pattern of the rotor magneto (M) when the present invention is applied to a three-phase, one-way, 120' current-carrying type brushless smoke, and FIG. 7 is an operating waveform diagram. Figure 7a
As shown in FIG. 7-c, the current flowing through the coils LA-LC of each phase is switched by 120 degrees in electrical angle, and a torque including ripples as shown in FIG. 7d is generated. In principle, a ripple of 1 +0.5 is included.

Therefore, in order to reduce the ripple, as shown in the magnetization pattern diagram of FIG. 6, commutating poles 3N and 3sa'x of opposite polarity are provided at the center of each main pole Is and IN in the rotational direction. This interpolation is the main pole IS as in Fig. 4.

The positions are 90° and 270° from the boundary of IN, and as a result, the effective magnetic flux of the main pole Is, IN is locally reduced at its peak position, so the peak of the torque ripple collapses as shown in Figure 7e. As a result, a fairly flat torque can be obtained. Actual measurements showed that the torque ripple decreased to 14.3%.

Next, FIG. 8 is a magnetization pattern diagram of the rotor magnet M when the present invention is applied to a three-phase single-direction 180° current-carrying type brushless smoke, and FIG. 9 is an operating waveform diagram. Figure 9a
As shown in Fig. 9-c, the current flowing through the coils LA-LC of each phase is sequentially applied at 180° electrical angle, and a torque including ripples as shown in Fig. 9d is generated.In principle, the ripple of is included.

Therefore, in order to reduce the ripple, as shown in the magnetization pattern diagram in Fig. 8, the main poles Is and IN are rotated at 30°, 90°, 150°, 210°, 270° and 330° along the rotational direction. Compensating poles 3S and 3N having opposite polarity to the main pole are provided at positions , in order to locally reduce the effective magnetic flux of the main pole. These complementary poles 3S.

3N corresponds to each peak position of the torque ripple in Figure 9d, and since the magnetic flux involved in torque generation decreases at these positions, the peaks of the torque ripple collapse and become almost flat as shown in Figure 9e. Torque can be obtained. According to actual measurements, the ripple decreased to about 3.5%.

In addition, in the embodiment shown in FIG. 8 described above, even if the commutating poles 3S and 3N are provided only at the positions of 90° and 270°, the effect of reducing torque ripple can be obtained to the extent that it can be achieved.
Even if the commutating poles are provided only at the 0° and 330° positions, the effect can be obtained. Further, it may be provided only at one of 30° and 150° (210° and 330°).

Effects of the Invention According to the present invention, torque ripple can be significantly reduced by a simple means of partially changing the magnetization waveform of the rotor magnet, and an inexpensive and high-performance brushless morph can be obtained.

[Brief explanation of drawings]

Figure 2 is a route diagram showing the basic configuration of a three-phase brushless smoke to which the present invention can be applied, Figure 2 is a drive circuit diagram of a bidirectional energization type that drives the motor in Figure 1, and Figure 3 is a unidirectional drive circuit diagram. The current-carrying type drive circuit diagram, Figure 4, shows the present invention as a three-phase bidirectional drive circuit.
A diagram of the magnetization pattern when applied to an 80° current-carrying type brushless smoke, Fig. 5 is a diagram of operating waveforms of current, magnetic flux, and torque in the case of Fig. 4, and Fig. 6 is a diagram of the magnetization pattern when applied to a three-phase unidirectional 120° current-carrying type. When applied to brushless smoke, the pattern diagram is shown, and Figure 7 is an operation waveform diagram similar to Figure 5 in the case of Figure 6.
FIG. 8 shows the three-phase one-way 18o of the present invention. FIG. 9, a magnetization pattern diagram when applied to an energized brushless morph, is an operation waveform diagram similar to FIG. 5 in the case of FIG. 8. In addition, in the symbols used in the drawings, IS, IN-・
---Main pole 3S, 3 N-----One counter pole LA LB LC ------------------- Coil M----
・－－－－－－－－－・－Rotor magnet HA
HB HC ・-・-・-・・・・・-# −) Lt element.

Claims (1)

[Claims] A commutating pole for partially reducing the main pole magnetic flux is provided at at least one location approximately 30°, 90°, or 150° electrically from the boundary of the main pole formed on the rotor magnet. Three-phase brushless motor.