JPS6227038Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a control device for reducing torque pulsation in a self-limiting synchronous motor such as a transistor motor. In a permanent magnet rotating field type audio motor, etc., when torque ripple occurs and speed fluctuations occur, the sound quality deteriorates, so it is necessary to take measures to reduce the ripple. Motor torque is defined as being proportional to the product of current and magnetic flux density, but even if the motor current can be controlled constant, the field magnetic flux often varies sinusoidally depending on the rotor position. It cannot be fixed. Therefore, in order to reduce the torque ripple, for example, we detect the back electromotive force induced in the armature winding, and then generate a waveform that is inversely proportional to the alternating current, which flows to the armature winding. A method of reducing torque pulsation by correcting and controlling the current value has been considered. However, in this case, because an induced electromotive force proportional to the rotor rotational speed is used, it may be difficult to obtain a sufficiently large electromotive force value when the rotor rotational speed is low, or due to changes in the rotor rotational speed. When the electromotive force value fluctuates, there is a drawback that it is difficult to obtain a desired current command for reducing torque pulsation. Further, as a means for detecting back electromotive force, it is often necessary to provide a separate winding in addition to the armature winding, which has the disadvantage of complicating the configuration.

This invention was made to compensate for the above-mentioned unsatisfactory points.Since the magnetic flux density interlinking with the armature winding is determined by the rotor position, the speed control pulse is read as the rotor position detection pulse. It is an object of the present invention to provide a control device that reduces torque pulsation by controlling the current in an armature winding by increasing or decreasing the current value in accordance with the current value.

Figure 1a shows an example of the motor control circuit according to the present invention, Figure 1b shows the relationship between the rotor and stator, which are the main components of the motor, viewed from above, and Figure 1c shows the A-A It shows a cross section.

In Figure 1, Vd is a DC power supply, T1 to T6
are transistors, and the stator coils of the motor, that is, the armature windings MU to MW, are connected in a three-phase star shape between the contacts u to w of these upper and lower transistors. Also, TR is a current control transistor, and RO is a resistor. 110 is a distributor, and 120 is a ripple compensation circuit. 141 is buffer amplifier, 15
1 is a one shot circuit, 161 is a smoothing circuit, 17
1, 172, and 173 are amplifiers, respectively.

In Figure 1b, 1 is a disk fixed to the rotating shaft,
A rotor field magnet 2 is integrally coupled to its lower part.
It is assumed that the magnet 2 has a toroidal shape, its center substantially coincides with the center of the rotating shaft, and it is magnetized into four poles substantially equally at every 90 degrees of mechanical angle. Further, the outer periphery of the soft magnetic disk 1 is evenly provided with concavities and convexities as shown in the figure. Reference numeral 3 denotes a stator magnetic path material made of a soft magnetic material, on which a total of three stator coils MU to MW arranged at 120° pitch are fixed flatly. Reference numerals 101 to 103 denote Hall elements as means for detecting the position of the rotor, and three Hall elements are arranged at every 120 degrees in mechanical angle and attached to the stator magnetic path material 3. 130 is a pulse generator, 131 is a light emitting element, and 132 is a light receiving element, which are also attached to the stator magnetic path material 3 via a fixed frame 133.

Now, the operation of this embodiment shown in FIG.
This will be explained with reference to FIGS.

The rotor field magnet 2 is magnetized with four poles at every mechanical angle of 90 degrees, and FIG. 3a shows the magnetized state. Here, the positive side is the N pole and the negative side is the S pole, and the magnetic flux density directly below is shown in mechanical angle.
90° is 180° in terms of electrical angle, and the part in parentheses in figure a indicates the electrical angle. At mechanical angle
Hall elements 101 to 103 serving as rotor position detection means provided every 120 degrees detect the polarity of the magnetic flux of the rotor magnet. If the rotor position is detected by determining the polarity of the Hall electromotive force which is the output of these elements using the comparators 201 to 203 shown in FIG. 2, position signals such as those shown in FIG. 3 b to d can be obtained. It will be done. The distributor 110 periodically fires any two of the transistors T1 to T6 in response to the position signal so that they are always energized, but since this operation is generally known for transistor motors, the explanation will be omitted. . At the same time, the comparator 201
~203 are respectively differentiated by differentiating circuits 211~2.
13, add those three outputs,
Further, positive side and negative side one shot circuits 221, 2 activated by a rising input signal and a falling input signal
As a result of inputting the signal to the post-OR circuit 230 via the signal 22, the output signal S1 shown in FIG. 3e is obtained.

Next, a disk 1 made of a soft magnetic material that is integrally connected to the rotor field magnet 2 is evenly provided with unevenness as shown in FIG. A light emitting element 131 and a light receiving element 132
A pulse generator 130 consisting of stator magnetic path material 3
It is attached to via a fixed frame 133. Therefore, for example, when the concave part of the disc 1 exists between 131 and 132, the light from 131 can be received by the 132, and conversely, when the convex part of the disc 1 exists, the light from 131 can be received. The light beam 132 is in a state where it cannot receive light because it is blocked by the convex portion. By amplifying the output from the light-receiving element 132 in a buffer amplifier 141 and passing it through a one-shot circuit 151, for example, an output pulse S2 shown in FIG. 3F can be obtained. Here, Figure 3 f
In this case, 12 recesses are provided in the disc 1 integrally connected to the rotor field magnet 2 at a mechanical angle of 90 degrees, and 48 pulses are generated for one rotation of the rotor (360 degrees in mechanical angle). Since the frequency of this pulse is proportional to the rotational speed, f in the figure can also be said to be the rotational speed detection pulse of the rotor.

Now, the MU, MV, and MW phase currents that flow according to the position signals shown in Figure 3 b to d are as shown in Figure 3 g, h, and j when energizing at 120°, and these phase currents are as shown in Figure 3 g, h, and j. The magnitude corresponds to the DC input current i _t of the inverter composed of transistors T1 to T6. On the other hand, if the magnetized state of the rotor field magnet 2 is sinusoidal as shown in Figure 3a, the magnetic flux density of the gap that contributes to motor drive between the rotor and stator will increase or decrease as shown in Figure 3k. The distribution is as follows. Therefore, when the inverter current i _t is constant, the generated torque shows a torque waveform including pulsations that is approximately proportional to the distribution of magnetic flux density shown in Fig. 3k in order to show a torque value proportional to the magnetic flux density. That will happen.

However, instead of keeping the inverter current, that is, the motor armature winding current i _t, at a constant value, it is controlled so that _it increases when the magnetic flux density k in the figure decreases, as shown in Figure 3n. If control is performed so that i _t decreases when the magnetic flux density increases, the increase or decrease in the magnetic flux density and the increase or decrease in the inverter current will cancel each other out, making it possible to significantly reduce motor drive torque pulsations. Incidentally, if the rotor magnet magnetic flux is not a sine wave as shown in FIG. 3a but a square wave, the torque pulsation will be extremely small, but square wave magnetization cannot actually be performed in the method of magnetizing the magnet. Even if the state is close to that at the time of magnetization, if the rotor magnet is installed in the motor at a position facing the stator with an air goat, the interaction between adjacent magnetic poles of different polarities causes the joint between the different polarities to The closer the magnets are to each other, the more the magnetic flux that creates a closed loop only between the magnets increases, and the effective magnetic flux required to generate the driving torque of the motor decreases. Therefore, in an actual motor of this type, the magnetic flux distribution is as shown in Figure 3a.
It becomes something like this.

In carrying out the current control as shown in FIG. 3n, the present invention is executed as follows.

The output v _f obtained by smoothing the signal S2 shown in FIG. 3 f by the smoothing circuit 161 in FIG. 1 a is:
It is added to the set speed signal _vs , and the deviation thereof is amplified by the amplifier 171. This _output is acts as a current command signal, the main circuit output current is detected by the resistor RO, and is added to the signal if fed back via the amplifier ₁₇₂ with a different sign. This deviation is amplifier 1
As a result of the amplification in step 73, the output Is is obtained.

Now, the output signal S1 from the OR circuit 230 shown in FIG. 3e and the pulse signal S2 shown in FIG. 3f are sent to the shift register 240 in FIG.
give it as input. As shown in Figure 3e and f,
The signal S1 exists between every predetermined number of pulses in the pulse train of the signal S2, and now the S1 signal presets the shift register 241 to the state shown in FIG. Assume that 1 bit is shifted by 1 bit for each pulse.
Now, if S1 is given as a preset input to 241 at time _t0 , the _b0 bit is set to "1", and the base current is given to transistor Q1 via resistor R11 at its output, causing Q1
turns on. Amplifier 251 with a sufficiently high gain acts as a positive phase amplifier, and its gain is determined by resistor R17 and transistor Q in parallel with resistor R16.
The other input Is to 251, which is determined by the resistor R14 connected by the ON state of G1, is amplified by its gain _g1 to obtain a value _I1 . This value is held until just before time t ₁ , but when signal S2 is applied to shift register 241 at time t ₁ , Q1 is turned off and transistor Q2 is turned on via resistor R12, causing the amplification. In the circuit 251, R15 is connected to a resistor R16 in place of the resistor R14, and the Is input is amplified with a gain _g2 different from that described above to obtain the value _I2 . This value is held until just before time t ₂ , and when the next pulse of signal S2 is applied to 241 at time t ₂ , Q2 is turned off, and the positive-sequence amplifier consisting only of resistors R16 and R17 is turned off. The comparison amplifier 251 has a gain g ₃ ,
As a result of positive phase amplification of Is, a value of I ₃ is obtained. This value is held until just before time t3, and when the pulse of signal S2 is applied to 241 at time t3, transistor Q2 is turned on again and I ₂ is obtained by gain g ₂ as in the case of time t1. It will be done. This value is held until just before time t4, at which time Q2 turns off and transistor Q1 turns on again, and the output of amplifier 251 becomes I ₁ as before.
obtain the value. This value is held until just before time t5, but at time t5, the output of the amplifier 251 remains at the value of I ₁ in accordance with the operation at time t ₀ . The subsequent operation is a repetition of the above-mentioned operation, and the situation is illustrated in FIG. 3m. Here, the aforementioned gain relationship is g ₁ >g ₂ >g ₃ . Therefore, needless to say, the relationship I ₁ > I ₂ > I ₃ holds true for the outputs I ₁ , I ₂ , and I ₃ of the amplifier 251. That is, when resistor R17 is constant, R15>R14. The step-like change shown in Fig. 3 m is caused by resistor R1.
Any changes can be made by adjusting the values of 7 to R14. In reality, the current waveform can be approximately approximated to the one shown in FIG. 3n, including the influence of the time constant due to the inductance of the motor, and the current it flowing through the transistor _TR can be controlled using this waveform. Needless to say, the current i _t flowing through the transistor TR is, in other words, the inverter current composed of the transistors T1 to T6, that is, the armature winding MU of the motor.
Since this is a current flowing through the MW, if _the current i _t is as shown in FIG. As a result, torque pulsation generated by the motor can be almost eliminated. The current shown in figure m flows through the armature and contributes to the reduction of torque ripple, which is the purpose of this invention. However, if the following current is delayed due to the armature time constant etc., the current as shown in figure n appears. Therefore, in practice, a waveform like n contributes more to ripple reduction.

According to the configurations shown in Figures 1 and 2, the current flowing through the armature winding is adjusted to a desired value by linking the output pulse of the pulse generator used for motor speed control to the rotor position detection pulse. Since the torque pulsation can be reduced by controlling the torque pulsation, there is no need to separately provide a torque pulsation reduction means, and the motor configuration becomes simple. In addition, since the output pulse of the pulse generator and the rotor position detection pulse can be obtained regardless of the magnitude of the rotor rotation speed, the armature winding current can be controlled at all times without being restricted by the rotor rotation speed. It is possible to quickly reduce pulsation.

FIG. 4 is a diagram illustrating the control circuit and its operation in another embodiment of the present invention. There are 9 pulses for every mechanical angle of 90°, so that 9 pulses are obtained for every 90° mechanical angle. FIG. 4a shows a counter circuit that should replace the shift register 241 in FIG. 2, and it receives the S1 signal shown in FIG. 4b and the S2 signal shown in FIG. A logic circuit provided to generate an I _r signal. The pulse period of the signal S1 in Figure b is 60 degrees in electrical angle. Three pulses of the signal S2 in c in the figure appear within an electrical angle of 60°, and S1, S2
Assume that the current command value Iout is obtained as shown in the figure d using the output _b0 of the logic circuit which inputs . The armature current of the motor actually has a waveform like the one shown in the figure e due to the influence of the time constants of each element of the motor, and as in the previous example, the non-uniform distribution of magnetic flux density is a factor that causes torque pulsation. This will have a counteracting effect.

FIG. 5 shows another embodiment of the present invention, in which the stator magnetic path material 3 detects the polarity of the N and S poles of the four-pole magnetized rotor field magnet 2 to detect the rotor position. For each of the Hall elements 101 to 103 installed at a pitch of 120 degrees, separate Hall elements 301 to 303 are installed on the stator magnetic path material 3 at a mechanical angle of θ degrees to reduce torque cripple of the motor. A pulse generator 130 is provided. The rotor position detection signals obtained from the Hall electromotive forces of the Hall elements 101 to 103 are shown in FIG. 6a, b, and c, whereas the rotor position detection signals obtained from the Hall elements 301 to 303 are shown in FIG. , f, g, and a, b,
c, e, f, and g each have 2θ in electrical angle.
A phase difference of ° will occur. As a result, a pulse S1 obtained by shaping from a, b, and c shown in the figure d, and a pulse obtained by shaping from e, f, and g shown in the figure h, S2 can be taken out alternately, and the first and second
As in the case of the embodiment shown in FIG. A current command signal Iout is obtained. Same figure j
The armature current that responds to the current command waveform shown in Figure 2 is actually as shown in figure k due to the effect of the motor's time constant, etc., and in relation to the magnetic flux density distribution shown in figure m, when the magnetic flux decreases, the armature current Since the child current increases and the armature current is controlled to decrease when the magnetic flux density increases, the increases and decreases in the magnetic flux density and armature current cancel each other out, making it possible to reduce torque pulsation. . According to the configuration shown in FIG.
By appropriately adjusting the mechanical angle deviation θ° of the setting locations of the means for detecting different positions, the armature winding current can be controlled at will, and the torque can be easily adjusted even for magnetic flux densities that can exhibit various distributions. Needless to say, this embodiment can reduce pulsation and has the same advantages as the first and second embodiments.

Although the above explanation concerns a motor in which a field magnet is arranged in the rotor, the device of the present invention can also be applied to a motor having a winding and a field excited by current through a slip ring. be able to. The same applies to a structure in which the stator has a field and the rotor has an armature winding, and the armature current supplied via the slip ring may be increased or decreased according to the spirit of the present invention. At this time, Figure 1 b, c
It goes without saying that the rotor magnets, Hall elements, etc. shown in 1 are used exclusively as sensors and do not need to provide driving force.

According to the present invention, the armature winding current is controlled by increasing or decreasing the current command value according to the rotor position, so current control is possible regardless of the rotor rotational speed, and torque pulsation can be quickly reduced. It is possible. Further, as a result of making the pulse output used for detecting the speed of the motor correspond to the position of the rotor, torque pulsation can be reduced without providing a separate measure for reducing torque pulsation, which simplifies the motor configuration.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing one embodiment of the present invention, FIG. 3 is a signal waveform diagram for explaining the operation of the circuit shown in FIGS. 1 and 2, and FIGS. FIG. 5 shows another embodiment of the present invention, and FIG. 6 is a signal waveform diagram explaining the operation of FIG. 5. In the figure, 1 is a disk, 2 is a rotor field magnet, 3 is a stator magnetic path material, MU~MW are armature windings, T1~
T6 is the transistor that constitutes the inverter, TR
101 to 103 are current control transistors, and 101 to 103 are current control transistors.
The position detecting means 130 is a second position detecting means. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] An electric motor having a rotor having a field magnetic flux consisting of a plurality of poles and an armature winding consisting of a plurality of phases facing the rotor; a first detection means for detecting the position of the rotor of the electric motor; a plurality of semiconductor switches that switch in accordance with the output of the means and switch and control the current flowing through the armature winding; and a current connected in series with these semiconductor switches to flow the current flowing through the armature winding. a control semiconductor switch; a second detection means for detecting the rotor position at a higher frequency than the rotor position signal detected by the first detection means and providing a signal for speed control; and an output of the first detection means. Based on the output of the second detection means in synchronization with the period of A motor control device comprising: a control element for increasing/decreasing energizing current.