JPH04299093A - Controller for brushless motor - Google Patents

Abstract

PURPOSE:To realize smooth operation of motor at all times regardless of error in the fixing position of a Hall element for detecting the rotor position. CONSTITUTION:Resistance elements 23A, 23B, 23C are connected in parallel with three-phase stator coils 12A, 12B, 12C and a peak detection signal 25a, corresponding to the peak of differential voltage at the neutral point of the stator coil and the resistance element, is fed to CL terminal of a flip-flop 26. Selection logic signals 22a-22f generated based on the output signals from Hall elements 13A-13C are fed to D terminal of the flip-flop and then held at Q terminal of the flip-flop to produce a driving signal 26a. The driving signal is fed to switching transistors 21A-21F. Error of fixing position of the Hall element causes error in the output timing of the selection logic signal but since the peak detection signal is obtained with accurate timing at all times, output timing of driving signal is regulated optimally resulting in smooth operation of motor.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a control device for a brushless motor, and in particular can always achieve good motor operation even if there are fluctuations in ambient temperature or assembly errors in the rotor position detection sensor. Regarding a control device.

0002

2. Description of the Related Art An example of a brushless motor and a control device is shown in FIG. In the figure, a brushless motor 1 has a rotor 1
1, different magnetic poles are alternately formed on the outer periphery of the rotor 11, and three-phase star-connected stator coils 12A, 12B, 12C surround the rotor 11. It is provided. Inside the motor 1, three Hall elements 13A, 13B, and 13C are provided as position sensors close to the outer periphery of the rotor 11 at predetermined intervals. The rotational position of the rotor is detected and identified.

The output signals 13a, 13b, 13c of each of the Hall elements 13A to 13C are input to a logic signal generation circuit 22 of the control device 2, and based on this, a selection logic signal 22a is generated.
, 22b, . . . , 22f are generated and output. The control device 2 is provided with six switching transistors 21A to 21F, which are connected in series in pairs, and each pair is connected in parallel to the battery 3. The feeding ends of the stator coils 12A-12C are connected to the connection points of the paired transistors 21A-21F, and the selection logic signals 22a, 22b, . . . , 22f are applied to the gates of each transistor 21A-21F. I am typing.

[0004] Switching transistors 21A to 21F
are selectively brought into conduction as appropriate by the selection logic signals 22a, 22b, . . . , 22f, and the stator coils 12A-
12C is energized to form a rotating magnetic field and drive the rotor 11 to rotate.

[0005]

[Problem to be solved by the invention] By the way, smooth motor
In order to realize the motor operation, selection logic signals 22a, 22b are required.
, ..., Hall element 1 that determines the timing of 22f generation
Although the output signals 13a to 13c of 3A to 13C need to be accurate, errors may occur in the mounting angle position of the Hall element.On the other hand, there may be cases where a photocoupler or encoder is used in place of the Hall element. The timing of the output signal may deviate by several percent due to instrumental differences, temperature drift, etc. Therefore,
In order to solve this problem, it has conventionally taken a great deal of effort to adjust the mounting position and output of the sensors, and the selection and use of sensors with uniform characteristics has led to an increase in costs.

[0006] The present invention has been made to solve this problem, and an object of the present invention is to provide a brushless motor control device that can always realize smooth motor operation without incurring the trouble of adjusting the position sensor or increasing costs. shall be.

[0007]

[Means for Solving the Problems] To explain the structure of the present invention, a rotor 11 has magnetic poles of different polarities alternately formed on the outer periphery;
Three-phase star-connected stator coils 12A, 12B, 1 are provided around the rotor 11 and form a rotating magnetic field.
A control device 2 for a brushless motor 1 comprising a plurality of switching elements 21A, 21B, 21C that respectively energize the stator coils 12A to 12C.
,, 21D, 21E, 21F, and position sensors 13A, 13B, 13C for detecting the rotational position of the rotor 11,
A logic signal generation circuit 22 receives the output signals of the position sensors 13A to 13C and generates and outputs selection logic signals 22a, 22b, . . . , 22f for selectively operating the switching elements 21A to 21C; - Resistance elements 23A, 23B, 23C connected in parallel to the stator coils 12A to 12C, and provided between the logic signal generation circuit 22 and each switching element 21A to 21C, The above stator coils 12A to 12
The voltage difference between the neutral point of C and the neutral points of the resistance elements 23A to 23C is detected, and the selection logic signal 22a, 22b..., 22f is applied to each switching element 21A at the timing when the voltage difference reaches its peak. 21F.

[0008]

[Operation] In the device having the above structure, if there is a mounting error or a fluctuation in the ambient temperature, the signal output timing of the position sensor changes, and an error also occurs in the timing of the selection logic signal generated and output based on this. By the way, since the peak of the voltage difference between the neutral points always appears at a predetermined rotational position of the rotor, the selection logic signal should be output to the switching element at the timing when the voltage difference peaks. For example, the switching element is always operated at a desired timing, and smooth operation of the motor is realized.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below with reference to FIG. 2, focusing on the differences from the conventional one. In the figure, stator coil 12A,
12B and 12C are star-connected resistance elements 23A,
23B and 23C are connected in parallel, and the neutral point voltages of these stator coils 12A to 12C and resistance elements 23A to 23C are respectively input to a differential amplifier circuit 24 constituting a timing adjustment circuit. The differential amplified signal 24a is input to the peak detection circuit 25, and the peak detection signal 25a is input to the CL terminal of the D-flip-flop 26. This flip-flop 26 receives selection logic signals 22a, 22b, . . . output from the logic signal generation circuit 22. 22f are provided (only one of them is shown in the figure), and each selection logic signal 22a, 22b, . 22f is input to the D terminal of each flip-flop 26.

The Q terminal of each flip-flop 26 is connected to C
The input to the D terminal is output and held at the timing of the peak detection signal 25a input to the L terminal, and the drive signal 26a is output.
becomes. Each Q terminal output is input to the NO contact of each switching relay 27, while the selection logic signal 22a is directly input to the NC contact of the switching relay 27. Switching relay 2
The C contact of NO. 7 is connected to the base of each transistor 21A, and each switching relay 27 is activated after a certain period of time when the power is turned on by the output of the timer circuit 28, and the C contact and NO.
The contacts are switched into conduction.

By the way, in the case of the 4-pole 12-slot motor shown in FIG. 2, the hall elements 13A, 13B, 13C are originally installed in X, Y, It should be set accurately at each position of Z, but
In this example, smooth motor operation is guaranteed if the motor is installed within the range of 0° to 15° (0° to 30° in electrical angle) in the opposite direction to the motor rotation direction (arrow in the figure). Ru. This will be explained with reference to FIG.

Output signal 13 of Hall elements 13A to 13C
As shown in the figure, a to 13c are shifted before timings X, Y, and Z (to the left in the figure). Therefore, the selection logic signals 22a, 22 generated based on such output signals
b, . . . , 22f are also shifted earlier than the appropriate timing. On the other hand, since the differential amplified signal 24a which amplifies the voltage difference between the neutral points is a triangular wave having a peak at every 60° electrical angle more accurately than 0°, the peak detection signal 25a has a peak at 60°. This becomes a short pulse every time, and this is the C of the flip-flop 26.
Input to L terminal.

Thus, the selection logic signals 22a, 22b, . . . , 22f input to the D terminal of each flip-flop 26
is sampled at the timing of the peak detection signal 25a, outputted to the Q terminal, and held, thereby obtaining drive signals 26a to 26f that do not rise or fall at accurate timing.

Since the voltage difference between the neutral points can only be obtained after the rotor 11 starts rotating, the voltage difference between the neutral points can be obtained only after the rotor 11 starts rotating.
s, the relay contacts C and NC are conductive, and the selection logic signals 22a, 22b, ..., 22f are directly applied to each transistor 21.
After the rotor starts rotating, conduction occurs between C and NO, and driving signals 26a to 26f are output to the transistors 21A to 21F, realizing smooth motor operation. Note that the selection logic signals 22a, 22b,..., 22
Since f is output for a very short time when the rotor is started, it does not adversely affect motor operation.

According to this embodiment, the circuit can be realized at low cost by simply adding several ICs to the conventional circuit.

Note that instead of operating the switching relay using a timer, the switching relay may be operated when the motor rotational speed exceeds a predetermined value. Further, other magnetoelectric conversion elements, optical elements, etc. can be used in place of the Hall element.

[0017]

As described above, according to the control device of the present invention, even if an error occurs in the output of the rotor position detection element, it is possible to always achieve good motor operation, and it is possible to reduce the time and effort required for adjustment. Since this is not necessary, significant cost reductions are possible.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a control device.

FIG. 2 is a schematic cross-sectional view of the motor.

FIG. 3 is a signal time chart.

FIG. 4 is a circuit diagram of a conventional device.

[Explanation of symbols]

1 Brushless motor 11 Rotor 12A, 12B, 12C Stator coil 2 Control device 21A, 21B, 21C, 21D, 21E, 21F
Switching transistor (switching element) 22
Logic signal generation circuit 23A, 23B, 23C Resistance element

Claims (1)

[Claims] 1. A brushless motor comprising a rotor in which magnetic poles of different polarity are formed alternately, and a stator coil connected in a three-phase star connection and provided around the rotor to form a rotating magnetic field. A control device for a rotor, comprising a plurality of switching elements that respectively energize the stator coils, a position sensor that detects the rotational position of the rotor, and an output signal of the position sensor that is input to the switching element. a logic signal generation circuit that generates and outputs a selection logic signal for selectively operating the circuit, a resistance element connected in parallel to the stator coil in a three-phase star connection, and a circuit between the logic signal generation circuit and each switching element. is provided at A control device for a brushless motor comprising a timing adjustment circuit for outputting to each switching element.