JPS5854884A - DC motor control method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for improving the efficiency of relatively high-output DC brushless motors used in room air conditioners, washing machines, and the like.

For example, the rotor is a flat ring-shaped permanent magnet that is magnetized in the thickness direction and its magnetic poles are divided into multiple parts in the circumferential direction, and the position at which the magnetic field direction switches as it rotates is detected. The so-called direct current brushless motor, which generates torque by switching the current flowing through the armature coil, is attracting attention for its easy speed control and long life, and is relatively popular in conventional audio equipment. In addition to low-output devices, in recent years they have also come to be used in devices that require relatively high output, such as room air conditioners and washing machines.

FIG. 1 shows an outline of such a countercurrent brushless motor.

In the figure, 1 is a magnet rotor, 2 is an armature coil, 3 is a changeover switch circuit, 4 is a changeover control circuit, and 5 is a DC power supply.

As shown in FIG. 2(a), the magnet rotor 1 is, for example, a flat ring-shaped magnet 1-1. ! :, Yoke 1-2 made of a disk-shaped vulcanizable material. And shaft 1
-3, and the Madai-t1-1 is magnetized in the thickness direction, and the magnetized state is alternately polarized at equal intervals along the circumferential direction of the ring. It is magnetized into multiple divisions 7 so that

The armature coil 2 is wound in multiple phases, such as three phases, and current from a power source 5 is sequentially and alternately supplied depending on the rotational position of the rotor 1 to generate torque in the rotor 1.

The switching control circuit 4 functions to supply a control signal to the changeover switch circuit 3 according to the rotational position of the rotor 1, and is therefore provided with a rotor rotational position detection device (not shown).

Note that a Hall element is normally used as this rotor rotational position detection device, and the rotational position is detected by reversing the direction of the field magnetic field by the rotor 1.

Therefore, this type of motor has a relatively long life as mentioned above because there are no worn parts such as brushes and commutators, and the speed can be easily controlled by simply changing the armature voltage. It is possible to obtain a motor that combines the features of a DC motor.

Figure @3 is a characteristic diagram showing the relationship between the source voltage and rotation speed in a general DC motor, where I is the characteristic at a load torque T, and a9 is the characteristic at a larger load torque Tt (i.e., TI<12), and it is assumed that by changing the power supply voltage V (which can be thought of as the same as the armature voltage), the torque can be kept constant and controlled to any rotational speed N. I understand.

By the way, in recent years, resource saving and
Energy conservation has become a hot topic, and as a result, careful consideration has been required to improve the efficiency of motors.

However, from this point of view, the conventional DC brushless motor described above has the drawback that sufficient efficiency has not yet been achieved.

In other words, in the above-mentioned I current brushless motor, the power supply voltage of the TIf armature coil 2 is determined regardless of the field magnetic field distribution by the rotor 1, so the electric motor does not contribute to the generation of torque. Since there are many child current components, it is difficult to obtain sufficient optical efficiency.This will be explained with reference to FIG.

In FIG. 4, (a) is the magnet 1-1 of the rotor 1.
(b) shows the distribution state of the magnetic field due to this, and the magnetic field at the part where the magnetic field changes from the N pole to the S pole or from the S pole to the N pole of magnet 1-1. The change does not occur in a step-like manner, but instead becomes a gentle, almost linear change state as shown by the arrows in FIG. 4(b).

On the other hand, since the current flowing through some parts of the electric machine coil 2 in this part is only switched by the changeover switch circuit 3, there are almost no steps in the part where the magnetic poles of the magnet 1-1 are switched, as shown in FIG. 4(C). It is changing like this.

Since the magnitude of torque in such a motor is proportional to the product of the strength of the field magnetic field by the magnet 1-1 and the current of the electrode coil 2, Even though the same electrode coil current is flowing in these parts as in other parts, the amount of torque generated is smaller than in other parts.

On the other hand, the loss remains almost constant if the current flowing through the armature coil 2 is the same, so in the end, the field due to the magnet 1-1! Since the ratio of loss to torque generated in each part where the A magnetic field is reversed is large, sufficient efficiency cannot be obtained.

An object of the present invention is to provide a countercurrent bushingless motor that can sufficiently improve efficiency and meet energy savings, while eliminating the drawbacks of the prior art described above.

In order to achieve this objective, the present invention detects the field magnetic field distribution and changes the magnitude of the current flowing through the armature coil according to the distribution state, so that the ratio of torque and loss is kept almost constant. It is characterized by a unique point.

Embodiments of the current motor control system according to the present invention will be explained below with reference to the drawings.

FIG. 5 shows an embodiment of the present invention, including a magnet rotor 1, an armature coil 2, a changeover switch circuit 3, and a sub-side changeover circuit 4.
, the blood flow power source 5 is the same as the conventional example shown in Fig. 1, and 3-i is a swinging transistor, 3-2 is a diode for retention, 6 is a Hall element for magnetic field detection, and 7 is a pulse width modulation circuit. , 8 is a switch circuit.

The switching control circuit 4 is basically the same as the circuit in the conventional example shown in FIG. The difference is that the control signal is in the form of a pulse. Therefore, in this embodiment, the current flowing through the armature coil 2 is a pulse current 1p as shown in FIG. It is a coil current. Therefore, by changing the pulse width of this pulse current IP, that is, by changing its duty ratio, the current i of the armature coil 2 can be arbitrarily controlled.

Transistor U-1 is turned on and off by control signals from switching control circuits E and 4, and controls the on-off and direction of the current flowing through the armature coil 2.

The diode 3-2 functions to insulate the transistor 3-1 from surges generated by turning the transistor 3-1 on and off.

The Hall probe 6 is placed in the magnetic field 4'fl produced by the rotor 1, and generates a signal representing the strength and direction of the magnetic field as the rotor 1 rotates.

The pulse width modulation circuit 7 is operated by the detection signal from the Hall cable 6, and generates a pulse signal P of a constant frequency whose pulse width changes according to the strength of the magnetic field generated by the rotor 1. When the rate of change in direction of the signal from the Hall cable 6 decreases, that is, when the rotational speed of the rotor 1 decreases from a predetermined value, a signal S is generated to switch the switch circuit 8 to a position opposite to that shown in FIG. .

However, the frequency of the pulse signal P at this time is sufficiently higher than the rate of change in direction of the detection signal obtained from the Hall cable 6, that is, the frequency at the maximum rotational speed of the rotor 1 in normal use. For example, a frequency of several kHz to several tens of kHz is selected.

The switch circuit 8 is normally switched to the position shown in the figure.
The output voltage distribution of the power supply 5 is switched to (1), but when the signal S is supplied, it is switched to the opposite position as shown, and the power supply voltage is switched to (2). The relationship of V r < V 2 is maintained between these voltages (2) and (2).

FIG. 7 shows an embodiment showing a specific example of the pulse width modulation circuit 7, in which 7-1 is an amplifier, 7-2 is a monostable multivibrator (OMV), 7-3 is a clock generator, and 7-4 is an amplifier. 7-5 is a waveform shaping circuit, and 7-5 is a curse number-voltage conversion circuit (F/V
), 7-6 is a comparator, 7-7 is a reference voltage source, and 7-8 is an amplifier.

OM V' 7-2 is the number K from the lock generator 7-3
It is triggered by a clock pulse with a frequency of Hz to several tens of KHz, and the width of the output pulse changes depending on the level of the signal supplied from the Hall element 6 via the amplifier 7-1, and the field magnetic field distribution due to the rotor 1 changes. A pulse signal P whose pulse width is modulated is generated accordingly.

Further, the output of the amplifier 7-1 is transmitted from the waveform shaping circuit 7-4 to the F
/v7-5 and represents the rotational speed of rotor 1'
The voltage becomes 1 voltage and is supplied to one input of the comparator 7-6.

Since the reference blood pressure is supplied to the other input of the J:lZ comparator 7-6, a signal is output to the output of the comparator 7-6 only when the rotational speed of the rotor 1 exceeds a predetermined value. will appear. Therefore, if the output of the comparator 7-6 is inverted and amplified by the amplifier 7-8, a signal S can be obtained.

Next, the operation of the embodiment shown in FIG. 5 will be explained.

As explained in the conventional example shown in FIG. - Controls the off and direction to generate torque in the magnet rotor 1, thereby rotating the rotor 1.

At the same time, the level of the signal from the Hall element 6 changes to the fourth level.
It changes in accordance with the change in the magnetic field generated by the rotor 1 shown in FIG. 1 (1). Therefore, the pulse width of the pulse signal P generated from the pulse IIQ[M circuit 7 also changes according to the strength of the field magnetic field, and this is supplied to the switching control circuit 4, so that
The waveform of the ML flow applied to the armature coil 2 is shown in Figure 8 (
a) It becomes a pulse as shown in (Ll), and the pulse width changes according to the field magnetic field distribution of the rotor 1.

As a result, the current i flowing through the coil 2 is
It is similar to the strength of the field magnetic field due to υ, and the armature coil 2 is
Since the current consumption is also reduced and the ratio between torque and loss is prevented from increasing, efficiency can be greatly improved.

Although not shown in detail in FIG. 5, the pulse width modulation circuit 7 is also used to control the rotational speed of the motor, and the pulse width modulation circuit 7 changes the pulse signal P in proportion to the frequency of the signal from the Hall element 6.
This makes the pulse width narrower. Therefore, when the rotational speed of the rotor 1 increases, the waveform of the current flowing through the armature coil 2 becomes as shown in FIG. 8(a), and the average current t decreases. ), and the average current i increases, so the rotation speed can be controlled to be approximately constant. Therefore, the voltages V+ and V2 (V, <V2) of one and two magnitudes are taken out from the power supply 5, and these are switched by the switch circuit 8. In the following cases, if the stain source voltage is switched to (2) by the signal S, the rise of the rotational speed can be improved.

In addition, from the standpoint of switching loss of the transistor 3-1, the waveform shown in (bi in Fig. 8) is most efficient, so when the rated load condition is applied, the waveform shown in Fig. 8 (bi) is most efficient.
It is desirable to set the power supply voltage (2) and the duty ratio of the pulse signal P so that the W current shown in b) flows through the Vt armature coil.

By the way, in the above embodiment, the field magnetic field distribution due to the rotor 1 is detected by the Hall element 6.

However, since the main function of the Hall element used in such current brushless motors is to detect the reversal position of magnetic field polarity, it is not suitable for detecting the strength of the magnetic field. For this purpose, it is necessary to prepare a special Hall element, which tends to increase costs.

Furthermore, due to structural limitations of the motor, it may be impossible to provide a magnetic field sensor at a position where accurate magnetic field distribution can be detected, and in such cases, the above-described embodiments cannot be applied.

FIG. 9 shows an embodiment of the present invention that can be applied to such a case. This embodiment mainly shows only the parts corresponding to the Hall element 6 and pulse width modulation circuit 7 in the embodiment of FIG. 5, and the other parts are the same as the embodiment of FIG.

In FIG. 9, 10 is a waveform shaping circuit, 11°, 15 is a counter, 12 is a clock pulse generator, 13.16 is a memory controller, 14.17 is a memory, and 18 is a digital-to-analog converter (A-A). be. The switching control circuit 4 is the same as the embodiment shown in FIG.
is for detecting the magnetic field polarity reversal position in a normal DC brushless morph.

Next, the operation of this embodiment will be explained.

The pulse output from the Hall element 6 every time the magnetic polarity is reversed is input to the counter 11 via the waveform shaping circuit 10.
The interval is converted into a count number N of clock pulses from the clock pulse generator 12. Therefore, this count number N changes depending on the rotational speed of the rotor 1.

On the other hand, the memory 17 stores sampling values Hs of the field magnetic field distribution (1) by the rotor 1 as shown in FIG.

Therefore, if this sampling value Hs is read out from the memory 17 in the 11th order with the field i polarity reversal period, the air shift/child coil current l can be controlled in accordance with the if ff distribution.

Now, this magnetic field polarity reversal period has a count number N. Therefore, during this count number N, the memory 17 must be accessed every n cycles shown in FIG. 10. 75: Oh, the value n/N at this time is memory 17
It is predetermined corresponding to the number of samplings stored in .

Now, since the count number NFi changes depending on the rotational speed of the rotor 1, the period n must be obtained from this changing count number N. Therefore, a memory 14 is provided and controlled by a memory controller 13.

In this way, n is obtained from N, and this is input to the counter 15, and clock pulses are counted in period n, and a signal is generated at the output every period n.

Therefore, the memory controller 16 is operated for a period n after the pulse for each reversal of magnetic field polarity is inputted from the waveform shaping circuit 10.
Each time, the memory 17 is accessed and the sampling values Hs shown in FIG. 10 are sequentially read out.

The thus read sampling value Hs is converted into an analog value by the D-A18, and is supplied as a pulse signal P representing the strength of the magnetic field to the switching control circuit 4, which controls the armature coil current according to the magnetic field distribution.

Therefore, according to this embodiment, if the standard field magnetic field distribution by the rotor 1 is measured in advance and stored in the memory 17, there is no need to detect the field magnetic field distribution by the Hall element 6. It is possible to obtain a highly versatile control system that can change the current in the armature coil 2 in accordance with the field magnetic field distribution and can sufficiently improve the expensive control system that can detect the strength of the magnetic field.

By the way, in the above embodiment, in order to change the current flowing through the armature coil 2 in accordance with the field magnetic field distribution of the rotor 1, the current in the armature coil is made into a pulse, and the pulse width is changed. Although a so-called chopper control method is adopted in which the current value is controlled gradually, the embodiments of the present invention are not limited to this, and the current may be controlled continuously.

Furthermore, as is clear from the waveform diagram in FIG. 4(b), the field magnetic field distribution due to the magnet rotor 1 is particularly significant only in the portion where the polarity of the magnetic field is reversed. Therefore, the current flows to the armature coil 2 in accordance with the field magnetic field distribution.
When controlling the magnitude of the current, almost the same effect can be expected by controlling only the portion where the magnetic field polarity is reversed, rather than over the entire region of the field magnetic field.

In the embodiments of the present invention, each requires a fairly complicated circuit configuration, but if configured using an LSI, the cost can be sufficiently reduced, and there is almost no possibility that the versatility of the present invention will be impaired.

As explained above, according to the present invention, it is possible to reduce the component of the military first coil current that does not significantly contribute to torque generation in a DC brushless motor, thereby eliminating the drawbacks of the conventional technology and improving the efficiency of the DC brushless motor. It is possible to provide a DC motor control method that can be sufficiently improved to save energy.

[Brief explanation of drawings]

Figure 1 is a block diagram showing an example of a DC brushless motor, Figures 2 (a) and (b) are a front view and top view of the magnetic rotor, and Figure 3 is a characteristic diagram showing the rotation speed characteristics of the DC motor. , FIGS. 4(a) to (C) are explanatory diagrams showing the relationship between the nm distribution due to the magnet rotor and the 11L Isogo coil current, and FIG. 5 shows an embodiment of the trickling flow mork control method according to the present invention. Block diagram, Figure 6 is a waveform diagram of armature coil current by chopper control method, Figure 7 is a block diagram showing one embodiment of a pulse width modulation circuit, Figure 8 (a), (
bl is a waveform diagram showing the armature coil current, FIG. 9 is a block diagram showing another embodiment of the pulse width modulation circuit, and FIG. 10 is an explanatory diagram showing the contents stored in the memory. 1... Macnet rotor, 2... W, state coil,
3... Changeover switch circuit, 4... Changeover control circuit, 5
...DC power supply, 6. Hall element, 7. Pulse width modulation circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 6

Claims (1)

[Claims] (1) In a DC brushless motor that switches the armature coil current by detecting the polarity reversal position of the field magnetic field,
A DC motor control system characterized by being configured to improve efficiency by controlling the current value of each armature coil according to the magnetic field distribution of the field. (2) Permissible DC motor control according to claim 1, characterized in that the control operation of the current value of the armature coil is performed only in a region near the polarity reversal position of the field magnetic field. method. (3) Range of % permissible time requirement In paragraph 1 or 2, the above! A switching means for turning on and off the current of the 8-element coil at high speed is provided, and the above-mentioned 'iIt child coil value is controlled by changing the on/off duty ratio by the switching means. Characteristic DC motor control method. (41%) In any one of claims 1 to 3, the detection of the field distribution by the field is configured to be performed by means for detecting the position of polarity reversal of the field magnetic field. (5) In any one of claims 1 to 3, a memory means for storing a magnetic field distribution due to the field detected in advance is provided, and the memory means A direct current motor control method, characterized in that the current value of the armature coil is controlled according to data read from the armature coil.