JPS631598Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brushless motor suitable for use as a motor for players, tape recorders, etc.

BACKGROUND ART Brushless motors have been known in which the excitation coils of each phase are energized in both directions in order to improve the utilization rate of the excitation coils. FIG. 1 is a drive circuit diagram of such a three-phase bidirectional energizing brushless motor, and FIG. 2 is a graph for explaining its operation.

The motor shown in Fig. 1 is equipped with a two-pole field magnet 1 on the rotor side, and three-phase coils 2a, 2b, 2c star-connected at 120° intervals on the stator side, and 3-phase coils 2a, 2b, 2c with a 30° delay between these coils. It includes phase difference position detection elements 3a, 3b, and 3c. Since the field magnet 1 is magnetized in a trapezoidal waveform, magnetic fluxes indicated by φa, φb, and φc in FIG. 2a act on each of the coils 2a to 2c. Each detection element 3a, 3b,
3c, a detection signal having a pulse width of 180° is obtained with a phase delay of 120° in electrical angle as shown in A, B, and C of FIG. 2b. These detection signals are transformed in the logic circuit 4 into drive signals with a pulse width of 120° as shown in A1, A2...C1, C2 in FIG. Transistor TA1 with push-pull connection connected,
Supplied to TA2, TB1, TB2, TC1, and TC2. Therefore, drive currents corresponding to these drive signals flow through the coils 2a to 2c, and the motor is driven to rotate.

The drive signal is formed based on a logical formula written corresponding to each waveform in FIG. 2c, so that any two coils are always energized. for example,
In the range of 30° to 90°, the drive signals A1 and B2 are at a high level, so the transistors TA1 and TB2 are turned on, and as shown by the dashed line in FIG. A current flows through the ground line, causing the rotor 1 to rotate counterclockwise. Similarly, at other rotation angles, any two coils are selectively energized and the rotational torque shown in FIG. 2d is generated.

In the motor shown in Figure 1, the field magnet 1 is magnetized in a trapezoidal waveform, but the flat part is
It is technically difficult to maintain a constant angle over 120°. Therefore, as shown in Figure 2d, 30°,
Torque partially decreases at 90°, 150°... position,
Torque ripple occurs.

The present invention provides a motor with reduced torque ripple.

The brushless motor of the present invention includes a rotor (field magnet 1) magnetized in a trapezoidal waveform as shown in FIG.
a, 3b, 3c), the first switch element and the second
(n+1) pairs of switch means (transistors TA1, TA2 to
TD1, TD2), and n coils 2a, 2b, in which one end of each coil is commonly connected, and the common connection point and the other end of each coil are connected to the series connection point of each of the switching means. 2c.

Based on the output signal of the rotor position detection means, the respective switch elements (transistors TD1 and TD2) of the switch means connected to the common connection point are turned on and off alternately at an electrical angle of 360°/2n. on the other hand,
In response to the on operation of the first switch element (transistor TD1) constituting this switch means, the second switch elements (transistors TA2, TB2, TC2) of the other switch means are turned on in sequence, and this switch means is also turned on. By sequentially turning on the first switch elements (transistors TA1, TB1, TC1) of the other switch means in response to the on operation of the second switch element (transistor TD2), the trapezoidal magnetization waveform is The structure is such that each coil is sequentially energized within the center area of the bottom.

This configuration eliminates the drop in torque at a specific rotation angle.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a drive circuit diagram of a three-phase bidirectional current-carrying brushless motor to which the present invention is applied, and FIG. 4 is a graph for explaining its operation. The basic configuration of this brushless motor is almost the same as that shown in FIG. 1, and includes a two-pole field magnet and star-connected three-phase coils 2a, 2b, and 2c. Each position detection element 3a, 3b, 3c is arranged with a phase lag of 60 degrees with respect to each coil 2a, 2b, 2c. The field magnet 1 is magnetized in a trapezoidal waveform, and a flat trapezoidal waveform magnetic flux acts in an angular range of approximately 120° as shown by φa, φb, and φc in FIG. 4a. The current supply terminals of each of the coils 2a to 2c are connected to a pair of push-pull connection transistors TA1-TA2, TB1-TB2, respectively, as in FIG.
TC1 and TC2 are connected, and the common connection point of each coil is connected to a pair of push-pull connected transistors TD1 and TD2.

A pair of transistors TA1-TA2, TB1
-TB2, TC1-TC2, TD1-TD2 each constitute a switch means, and TA1, TB1, TC
1, TD1 are the first switch elements, and TA
2, TB2, TC2 and TD2 constitute second switch elements.

From each detection element 3a, 3b, 3c, as shown in FIG.
As shown in A, B, and C, the phase is 60° behind the interlinkage magnetic fluxes φa, φb, and φc of each coil, and the pulse width is
A detection signal of 180° can be obtained. These detection signals are supplied to the logic circuit 4 and transformed into drive signals such as A1, A2...D1, D2 according to the logic formula shown in FIG. , TA2...TD1 and TD2 are turned on and the motor is driven to rotate.

Each drive signal is a trapezoidal wave coil linkage magnetic flux φa, φb,
It becomes high level in the 60° section approximately in the center of φc, and any one of the coils 2a to 2c is energized every 60° by the transistors TA1, TA2, . . . TC1, TC2. Transistor TD1, TD2
are turned on alternately by 60 degrees to allow the energized coils to flow the supply current from the power source 5 and the return current to the ground line, respectively, through the common connection point of the coils. For example, in the range of 60° to 120° as shown in Figure 4c, the drive signal A1 is at a low level and D2 is at a high level, so transistors TA1 and TD2 are turned on, as shown by the dashed line in Figure 3. , a current flows from the power supply 5 to the ground line via TA1 → coil 2a → TD2. Assuming that the current in coil 2a is in the positive direction, the current in coil 2c is
A current is passed in the reverse direction through the coil 2b, in the reverse direction through the coil 2a, in the forward direction through the coil 2c, and so on.

As a result, a substantially constant resultant torque is obtained over the entire rotation angle as shown in FIG. 4d. That is,
Since the coils of each phase are energized only within a 60° range from the center of the upper base (120°) of the trapezoidal wave where the flux linkage is approximately constant, torque ripples as shown in Fig. 2(d) do not occur. However, compared to the motor shown in FIG. 1, since only one coil is energized at all times, the generated torque is reduced.

Note that the present invention can be applied to a two-phase or three-phase or more phase brushless motor.

As described above, the present invention performs conduction control of each switch means based on the output signal of the rotor position detection means, thereby controlling the connection between the common connection point of n coils connected in a star connection and the other end of each coil. energizes in both directions sequentially, and the energization period is
By setting the angle to 360°/2n, torque can be obtained from the uniformly magnetized portion of the field magnet. This makes it possible to reduce torque ripple.

[Brief explanation of the drawing]

Fig. 1 is a drive circuit diagram of a conventionally known three-phase bidirectional current-carrying brushless motor, Fig. 2 is a graph for explaining the operation of the motor shown in Fig. 1, and Fig. 3 is a three-phase bidirectional current-carrying method according to the present invention. FIG. 4 is a graph for explaining the operation of the motor shown in FIG. 3, which is a motor drive circuit diagram when the method is applied to a brushless motor. In addition, in the symbols used in the drawings, 2
a, 2b, 2c...coil, 4...logic circuit,
TA1 to TD2...transistors.

Claims (1)

[Claims for Utility Model Registration] A rotor magnetized in a trapezoidal waveform, a rotor position detection means, and (n+1) pairs of switch means in which a first switch element and a second switch element are connected in series; The rotor position detecting means comprises n coils having one end of each coil connected in common, and the common connection point and the other end of each coil connected to a series connection point of each of the switching means, Based on the output signal, the respective switch elements of the switch means connected to the common connection point are turned on and off alternately at an electrical angle of 360°/2n, and the first switch element constituting the switch means is turned on. The second switch elements of the other switch means are sequentially turned on in response to the on operation of the second switch elements constituting the switch means, and the first switch elements of the other switch means are sequentially turned on in response to the on operation of the second switch elements constituting this switch means. 1. A brushless motor characterized in that, when turned on, each coil is sequentially energized within the center range of the upper base of a trapezoidal magnetized waveform.