JPS62141998A - Driving method of brushless motor - Google Patents

Abstract

PURPOSE:To reduce the torque pulsation in the current pattern of the stator winding by using the induction voltage waveform of winding for detection and by flowing the analogous current to this induction voltage. CONSTITUTION:On the stator side, windings for detection 3A-3C are wound in addition to the stator windings 1A-1C. These windings for detection 3A-3C are arranged so that the induction voltages E fA-E fC induced thereby may be in the same phase as in the induction voltages EA-EC related to the phase induction voltages of the stator windings 1A-1C. A speed control output signal 16, the PLL output signal of a PLL circuit 9, and the induction voltages E fA-E fC related to the signals of windings for detection 3A-3C are multiplied by the multipliers 7A-7C. Thus the waveform of the stator winding current and that of the induction voltage of the winding for detection are controlled so as to be analogous.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for driving a brushless motor.

In particular, the present invention relates to a brushless motor Z drive method suitable for controlling the motor current according to a pattern.

[Conventional technology]

There are roughly two types of driving methods for brushless motors that have a magnetic field.

One of them is as shown in Fig. 6, which is an explanatory diagram of the motor's induced voltage, fJi flow, by adjusting the stator winding current to match the phase of the induced voltage E^~Ec of the motor's stator winding. 1^〜I
This is a method of flowing C over the entire cycle.

In the case of this first method, if the waveform of the induced voltage E^~Ec is a sine wave, it is best to make the winding current Δ~Ic of the motor's stator a sine wave because the output torque of the motor is the largest, and , the pulsation of the output torque is also small ν90.And when performing control to keep the speed of the motor constant, the waveform of the motor stator winding current can be left as is, and the overall Control is performed to change the size.

Therefore, the pattern of the motor stator winding current is
It needs to be done somehow.

The second method is to flow current only when the induced voltage in the stator winding of the motor is large, as shown in FIG. 7, which is an explanatory diagram of the induced voltage and current of the motor. FIG. 7 is an example of a three-phase motor, and only one phase of the winding current of the motor's stator is shown. This method is also called a 120 degree energization method in the case of a three-phase motor.

This second method is described in Japanese Utility Model Application No. 50-68218.

As described in Japanese Patent Application Laid-Open No. 50-116911, it was wound around the stator of the motor as an on/off signal for the drive element of the brushless motor. It is known to utilize the induced voltage of a separate winding for detection.

However, this second method has the disadvantage that torque pulsations occur, as shown in FIG. 7, even if the winding current of the motor stator is constant.

On the other hand, as mentioned above, the first method produces less torque pulsation, but conventionally, as described in JP-A-55-5010, it is used to create a pattern of the winding current of the motor's stator. , digital integrator.

1) A /A converter is required, which has the disadvantage of being expensive.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional technology, even if the torque pulsation is small, a digital integrator, a D/A converter, etc. are required to create the pattern of the winding current of the stator of the motor. It had the disadvantage of being expensive.

The aim of the invention is to eliminate the drawbacks of the prior art mentioned above.

That is, the object of the present invention is to provide a method for driving a brushless motor that has a simple structure and that drives a stator by creating a stator winding current pattern that reduces torque pulsations in the brushless motor.

[Means for solving problems]

When a detection winding is wound around the stator separately from the stator winding, an induced voltage is also generated in the detection winding.

In the present invention, by using the induced voltage of the detection winding itself as a pattern of the stator winding current, a simple method for driving a brushless motor with small torque pulsation is obtained.

[Effect]

By using the induced voltage waveform of the detection winding as a pattern of winding current in the stator of a brushless motor and making it similar to this induced voltage, it is possible to obtain small torque pulsations. be.

〔Example〕

Examples of the present invention will be described with reference to each episode.

FIG. 1 is a block diagram of a brushless motor used for carrying out an embodiment of the present invention, FIG. 2 is a schematic sectional view of the motor body, and FIG. 3 is an induced voltage thereof.

An explanatory diagram of the current, FIG. 4 is a time chart diagram of the starting circuit, and FIG. 5 is an output diagram of the PLL circuit.

According to this embodiment, the motor is a three-phase brushless motor, and the rotor 2 uses a permanent magnet.

First, in Fig. 1, the stator windings 1^ to 1c include the rotor 2.
When the motor rotates, a sinusoidal voltage is induced as shown in the induced voltages E^ to EC in FIG.

Furthermore, detection windings 3A to 3c are wound on the stator side, separately from the stator windings 1Δ to 1c. The detection windings 3^ to 3c have an induced voltage E1 induced therein.
^~Ezc is arranged so as to be in the same phase as the induced voltage E^~Ec related to the phase induced voltage of the stator windings 1^~1c.

In other words, as shown in Fig. 3, the induced voltage E^ in the stator winding 1^ and the induced voltage E^ in the detection winding 3^! ^ is an in-phase signal.

Components other than the stator and nine rotors described above constitute the control circuit.

Therefore, in the configuration shown in FIG. 1, the PLL (Phase Locked Loop) related to the speed control circuit
The circuit 9 and the starting circuit 10 command the magnitude of the motor stator winding current 1^~IC.

That is, the starting circuit 10 operates to perform synchronous starting by sequentially passing starting signals 15^ to 1.5c related to current/current when starting the motor. At the time of synchronous starting, a signal for stopping the operation of the PLL circuit 9 is input from the starting circuit 1o as an inhibition signal 12 to the inhibition signal input terminal INH of the PLL circuit 9,
When starting is completed, the inhibition signal 12 from the starting circuit 10 stops being output.

One of the induced voltages Ex^-Eic related to the signals of the detection windings 3^-3C is input to the PLL circuit 9 as a feedback frequency signal 14 through a signal line. and,
The PLL circuit 9 outputs a signal corresponding to the phase difference between the frequency fo of the reference frequency signal 11 and the frequency J of the feedback frequency signal 14.

The speed control output signal 16, which is the PLL output signal of the PLL circuit 9, and the induced voltage E related to the signals of the detection windings 3^ to 3C
xΔ~Etc is output as a value multiplied by 1 multipliers 7^~7C.

Each of the multiplier output signals 17 of the multipliers 7^ to 7C and the starting signals 15^ to 1 related to the output signal of the starting circuit 10
5c is added by adder circuits 8^ to 8C.

After the starting circuit 10 stops, the output signal of the starting circuit 10 becomes O, so that only the speed control output signal 16 of the PLL circuit 9 is sent to the adders 6^ to 6c.

The signal is transmitted as a servo amplifier input signal 18 to a servo amplifier comprised of amplifiers 5^-5c and current detectors 4^-4c.

The servo amplifier described above has a current detector 4 for each phase.
Control is performed so that the difference between the output of 4c and the servo amplifier input signal 18 becomes O.

That is, the stator winding currents ^-Ic, which correspond to the multiplier output signals 17 of the multipliers 7^-7c, flow to the stator windings 1^-1c of the motor.

As described above, the present invention is characterized in that the waveform of the winding current in the stator of the motor and the waveform of the induced voltage in the detection winding are controlled to be similar.

As shown in FIG. 3, focusing on the A phase, the induced voltage E^ in the stator winding of the motor and the induced voltage Ei^ in the detection winding are made to be in phase. And of the detection winding.

A stator winding current I^ similar to the induced voltage Ez^ is flowing.

Motor speed control involves changing the amplitude of the stator winding current without changing its waveform pattern.

The advantage of this configuration is that the current waveform pattern can be created with a simple configuration.

Moreover, compared to the conventional 120-degree energizing type, there is an advantage that torque pulsation is much smaller.

FIG. 2 shows the structure of the motor main body described above, and shows a longitudinal section of the motor main body using magnets as a field.

The stator wire windings 1^-lc and the detection windings 3^-3c are collectively referred to as stator winding 1 and detection winding 3.

The rotor 2 of the motor is supported by bearings 21 and 22, and the rotor 2 is equipped with permanent magnets 2.
0. The shaft 19 rotates together. On the stator side of the stator, a stator iron plate 23 is arranged with a slight distance from the permanent magnet 20, and a fixed pre-wound ml is wound around the stator iron plate 23.

Then, a detection winding iron plate 24 having the same shape as the stator iron plate 23 is placed, and the detection winding 3 is wound around the detection winding iron plate 24. Since the detection winding 3 does not require current to flow therethrough, it may be a thinner wire than the stator winding 1, and the number of windings may be smaller.

Further, since the stator iron plate 23 and the detection winding iron plate 24 can have the same specifications, there is an advantage that no phase shift occurs between the induced voltages between the stator winding 1 and the detection winding 3.

Furthermore, if the stator windings are distributed windings, the induced voltages in both windings can be sinusoidal.

As described above, the advantage of making the waveform of the induced voltage of the motor a sine wave is that torque pulsation can be further reduced.

That is, if we consider a three-phase motor, the torque T is expressed by the following equation (1).

TcwI8・EA+ IB-EB+IC-Ec= I
mEojsin2(ωt)+5in2(ωt+12
0) +5in2(ωt +240)) = I, EO
,X 2.5
---(1) As shown in equation (1), T is a constant value and no torque pulsation occurs.

Here, (1) in equation (1) is the peak value of the stator winding current, Eom is the peak value of the induced voltage, and ωt is the electrical angle of the motor.

Similarly, torque pulsations do not occur in a two-phase motor.

In the device according to the present invention, since induced voltage is utilized, a starting circuit is required.

That is, the signal of the detection winding does not appear unless the motor rotates. Therefore, it is necessary to rotate the motor in some way.

FIG. 4 shows the starting circuit 10 used in FIG.
This shows a time chart of the signals.

When a start signal related to the start/stop signal 13 is input to the starting circuit 10 (changes from O to 1), it outputs square wave starting signals 15^ to 15c. Each starting signal, which is a square wave output signal, has three signals 120 degrees out of phase.
Although phase signals are output, FIG. 4 shows the starting signal 158 which is only the A phase signal.

It outputs the inhibition signal 12 to the PLL circuit 9 at the same time as outputting the square wave starting signal 15^.

Then, increase the frequency of the square wave starting signal,
After raising the frequency to the operating frequency of the PLL circuit, the output is stopped. In this way, the output signal
The motor starts.

If the waveform of the induced voltage is used as the pattern of the motor stator winding current, the induced voltage Et in the detection winding will be proportional to the rotational speed, so as the motor speed increases, the current command will change. The magnitude increases and a gap occurs where the motor speed increases more and more.

For this reason, in the embodiment of FIG. 1, the output signal of the PLL circuit as shown in FIG. 5 is provided.

FIG. 5 shows the magnitude of the signal with respect to one rotational speed.

changes from the value to a negative value. Therefore, PLL circuit 9
The multiplication result of the speed control output signal of and the output signal of the detection winding, that is, the multiplier output signal 17 of the multipliers 7^ to 7c.
increases linearly up to the illustrated PLL range (1), and becomes a negative value beyond the same range VQ. A negative value here means that the phase is reversed.

In this embodiment, the PL and L circuits are used for the speed control circuit that is the speed control section, but the multiplication result of the detection winding signal and the speed control output signal of the speed control section is If it has a characteristic that decreases with time, it can be implemented without any problem even if it is not a PLL circuit.

The present invention can be a particularly effective means for multipolar motors.

The reason for this is that the current pattern depends on the sensing winding.

Since the detection winding can use the entire circumference of the stator of the motor, it is possible to obtain a highly accurate signal with respect to the rotation angle of the motor. For example, even if the number of poles of the motor is 15,014, sufficient accuracy can be expected.

In order to create a conventional current pattern corresponding to detailed positions in a multi-pole brushless motor as described above, a very large number of encoder output pulses would be required.

As an example, if 360 degrees of electrical angle is to be divided with an accuracy of 8 pips, an encoder with 150 x 2 δ = 38,400 pulses is required. Decreasing the number of encoder pulses will eventually reduce the accuracy of the current pattern, causing torque pulsations.

Therefore, especially at low speeds, the conventional method has the disadvantage of large torque fluctuations.

In a multi-pole motor, there may be a question as to whether the induced voltage waveform in the windings deviates from a sine wave, but this is due to the structure of the rotor, the shape of the detection iron plate, and even the windings. It is possible to create a sine wave by winding the wire.

Further, in FIG. 2, the stator iron plate 23 and the detection winding iron plate 24 are arranged separately.

However, when the detection winding 3 is wound around the stator iron plate 23,
It is possible to omit the detection winding iron plate 24. At this time, some noise is generated in the detection winding 3 as a reaction to the current in the stator winding 1. In this case, the induced voltage E1 of the detection winding 3 can be removed by passing it through a suitable noise filter.

Therefore, especially when the detection winding is wound around the stator iron plate, there is an effect that the detection section can be constructed at low cost.

As described above, in the above embodiment, the current pattern of the stator winding of the brushless motor is set by using the induced voltage waveform of the detection winding, and a current similar to this induced voltage waveform is caused to flow. Accordingly, the torque pulsation of the brushless motor is small, which has the effect of reducing speed fluctuations.

Furthermore, since the induced voltage of the detection winding is used, the accuracy of the current pattern is improved.

Furthermore, there is no need for a detailed position detection encoder for creating a conventional current pattern, and there is also no need for a memory element, which has the effect of making the brushless motor cheaper.

These effects are particularly effective in multi-polar brushless motors.

〔Effect of the invention〕

In the present invention, the current pattern of the stator winding of the brushless motor is made to flow by using the induced voltage waveform of the detection winding and passing a current similar to this induced voltage.
It is possible to provide a method for driving a brushless motor with small torque pulsation using a brushless motor with a simple configuration.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a brushless motor used in an embodiment of the present invention; Fig. 2 is a schematic sectional view of the motor body; Fig. 3 is an explanatory diagram of the induced voltage and current; Figure 4 is the starting circuit time chart, and Figure 5 is the PL.
The output diagram of the L circuit and FIG. 6.7 are explanatory diagrams of the induced voltage and current, respectively, according to the prior art. 1.1^~1c...Stator winding, 2...Rotor, 3
゜3^~3c...Detection winding, 4^~4c...Current detector, 5^~5c...Amplifier, 6^~6c...Adder, 78~7c...Multiplication device, 8^~8c...addition circuit, 9...speed control circuit, 10...starting circuit, 11
...Reference frequency signal, 12...Prohibition signal, 13...
・Start, stop command, 14...Feedback frequency signal, 15^~15c...Start U'JJ signal, 16
... Speed control output signal, 17 ... Multiplier output signal, 18
...Servo amplifier input signal, 19...Shaft, 2
0...Permanent magnet, 21.22 ・Bearing, 23・
...Stator iron plate. 24...Iron plate for detection winding, E^~Ec...Induced 'r pressure in stator winding, Ez, Ef^~Etc...Induced voltage in detection winding, TA~IC...・Stator winding current,
T...torque. Figure 1 and Figure 2 stamp 7

Claims (1)

[Scope of Claims] 1. A stator having stator windings wound around magnetic poles, a rotor disposed opposite to the stator and having a field, and a winding current of the stator arranged in a fixed pattern. In the brushless motor, the brushless motor has a control circuit that causes the current to flow in a magnitude according to the stator, and a detection winding is provided separately from the stator winding, and the detection winding is wound around the stator.
A method for driving a brushless motor, characterized in that a stator winding current having a pattern similar to the induced voltage in the detection winding is caused to flow. 2. A method for driving a brushless motor according to claim 1, wherein the waveform of the induced voltage in the stator winding and the waveform of the induced voltage in the detection winding are substantially sinusoidal. .