JPS5836184A - Speed adjusting circuit for dc brushless motor - Google Patents

Abstract

PURPOSE:To maintain the rotating speed of a motor constant irrespective of a load variation by employing a voltage control amplifier which receives a sinusoidal voltage from a position detecting Hall element and a deviation signal between a DC voltage proportional to the rotating speed and a reference voltage. CONSTITUTION:The output signal frequencies of Hall elements 2, 3 are decreased due to the reduction in the rotating speed of a motor at the time of increasing the load, amd the output of an AC/DC converter 9 is decreased. As a result, the output voltage of a differential amplifier 11 is increased, and the gains of voltage control amplifiers 6, 7 are increased. Accordingly, the inputs of power amplifiers 12, 13 are increased, and the supplying currents to stator coils 14, 15 are increased. Thus, the motor is returned to the rotating speed set by a reference voltage 16. Since the output frequency of the Hall elements 2, 3 are, on the contrary, raised due to the increase in the rotating speed at the time of reducing the load, the output voltage of the amplifier 11 is decreased, the supplying current to the stator coils 14, 15 are reduced, and the motor is returned to the set speed.

Description

[Detailed Description of the Invention] The inventive feature is the speed vI41B for keeping the oral transmission speed of the in-brushless motor constant against load fluctuations! This circuit is a speed-reliable DC brushless motor equipped with a first trochanter made of a permanent magnet, a stator tF wire provided close to the outer circumference of the rotor, and a magnetically sensitive element for detecting the rotor position. As for circuits, both the ones proposed and the ones that have been proposed have complicated configurations, which have the drawback of requiring a lot of effort and being expensive. For example, JP-A-55-1030
No. 91 is the speed rIi1 of the DC brushless motor! I(
(b) Although a specific example of the method is disclosed, the present vI4 circuit has an extremely complicated configuration that requires a multiplier, a pulse generator, and an F-V converter as its constituent elements. In particular, the use of a multiplier and an F-■ converter not only increases the production cost of the device, but also requires a lot of work to increase the offset voltage of the multiplier, and has the drawback of easily causing deterioration of motor characteristics. was.

The invention is a speed adjustment circuit for an i[R brushless motor that eliminates the above-mentioned drawbacks and has constant speed characteristics over a wide range of rotational speeds even when subjected to large load fluctuations. . A practical example of the present invention will be explained below in the first example. 1 is a cylindrical rotor made of a permanent magnetic material, which generates a sinusoidal voltage in the Hall element 2.3 as it rotates. It is magnetized like this. The T shown in Fig. 1 indicates a two-phase case, and since the Hall elements 2.3 are arranged at right angles, a sinusoidal waveform voltage of constant amplitude with a phase difference of 90° is generated as the cylindrical rotor rotates 10 times. occurs. The sinusoidal signal from the Hall element 2.3 is supplied as an input to a voltage control amplifier 6, I via a voltage amplifier 4.5, and a DC voltage proportional to the rotational speed is supplied to a differentiating circuit 8 and a DC converter 9. and is applied to the input of a differential amplifier 110 that performs spring calibration with a reference voltage. The output voltage of the differential amplifier 11, that is, the deviation signal, acts as a control voltage for the voltage control amplifier 6.70.

Since the voltage control amplifier 6.7 has a characteristic that the gain increases in proportion to its control voltage, the input voltages maintain a phase difference of 90° and have a magnitude corresponding to the control voltage from the differential amplifier 11. Amplified, V-power conversion type power amplifier 12
．． 13 &: More power amplified and fixed advance winding! 114.1
5 as a two-phase sinusoidal current. As described above, a two-phase sinusoidal current that completely corresponds to the rotation of the cylindrical rotor 1 is applied to the fixed prewinding 14 and 15, resulting in a constant torque regardless of the rotor angle. sustained.

Next, the differential circuit 8, which is a component of the uninvented speed adjustment circuit.
and AC-D (one rotation speed of three converters 9: voltage conversion operation will be explained).

The sine wave signal from the voltage amplifier 4 in FIG. 1 is expressed by the following equation.

e=sinωt −・−−・(1) In the above equation, ω represents the angular velocity of the rotor. To differentiate the equation (1), 7 dθ e = −ωco sωt −−−・−(2) t, and A(3-DC converter 9 is the absolute value average (b)
If n is composed of
The operation of a DC brushless motor having a speed adjustment circuit configured as above, which can obtain a current voltage proportional to the rotation speed, will be explained with reference to Fig. 1. First, when the load on the motor increases, the rotation speed of the rotor 10 increases. Down, Hall element 2
．． The frequency of the sine wave Oi generated at 3 becomes lower, and the output voltage of the 50-DC converter 9 decreases T. the result,
Since the output voltage of the differential amplifier 11 increases and the gain of the voltage control amplifier 6.1 increases, the power amplifier 12.13
As the input voltage increases, the current supplied to the stator windings 14 and 15 increases, and the generated torque increases (as a result, the rotation speed of the rotor 10 increases and returns to the rotation speed set by the reference voltage 16). Ru.

Conversely, when the load on the motor decreases, the rotational speed of the rotor 10 increases, so the frequency of the sine wave signal generated in the Hall element 2.3 increases, and the output voltage of the MU0-DO converter 9 increases. As a result, the output voltage of the differential amplifier 11 becomes smaller, and the gain of the voltage control amplifier 6, T, decreases.
The input voltage of the power amplifier 12.13 decreases, the current supplied to the stator winding 14.15 decreases, and the generated torque decreases, so the rotation speed of the rotor 1 decreases and the rotation is set by the reference voltage 16. Return to speed.

FIG. 2 shows an example of actually measured speed/torque characteristics of a DC brushless motor equipped with an inventive speed adjustment circuit.

As described above, the present invention makes it possible to maintain the rotational speed of the motor at a constant value by a simple means, compared to the conventional speed adjustment circuit of the 1jLfIL brushless motor, despite large load fluctuations.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, and FIG. 2 is a graph showing speed:torque characteristics according to the embodiment of the present invention. 1...Cylindrical rotor 2.3...Hall element 6.1...-Voltage control amplifier 9...ACj-DC converter 11...・
・Differential amplifier 14.15... Stator winding 16... Base ** pressure Figure 1

Claims (1)

[Claims] It consists of a cylindrical rotor made of a permanent magnetic material, a stator winding provided close to the outer periphery of the rotor, and a Hall element as a means for detecting the position of the cylindrical rotor. , the cylindrical rotor is magnetized to generate a sinusoidal voltage in the Hall element in synchronization with the rotational speed,
The above sinusoidal voltage is amplified and input to a voltage control amplifier, and is differentiated into a DC voltage proportional to the rotational speed via a M C-DC converter, and this M current voltage is combined with a reference voltage that can be changed by any means. It has a voltage control amplifier that is controlled by this deviation signal and amplifies the output of this voltage control amplifier and supplies it to the stator winding to compensate for load fluctuations. A speed adjustment circuit for a DC brushless motor, characterized in that the rotational speed of the motor is maintained at a constant value regardless of the rotation speed.