JPS5847840Y2 - Brushless DC motor - Google Patents

Description

[Detailed description of the invention] The present invention relates to a brushless DC motor, and in particular improves efficiency by preventing the currents sequentially flowing through the stator coils from overlapping each other with other phases, and for this purpose, it does not use logic circuits etc. In this case, an inexpensive and simple means such as a resistor or a diode is used.

In a brushless DC motor, for example, 3
Φ8. Φ6. Φ.

As shown in , the magnetic flux due to the rotor is interlinked, and the electrical angle is 18
Torque is generated by energizing each coil over a range of 0°.

In principle, the coil should be energized within a range of 120°, but in reality, it is necessary to energize the coil within a range of 180° to avoid blanking.
is energized within the range of

In this case, as shown by the shaded area regarding Φ8 in Fig. 1, in the range where Φ8 is small (30° range before and after), the generated torque is small because the torque is proportional to the magnetic flux. By not allowing current to flow through the coil, efficiency can be improved by, for example, 15%.

The present invention has been devised based on these points, and it is an object of the present invention to provide a brushless DC motor that is simple in construction and extremely practical.

Hereinafter, one embodiment of the present invention will be described. In FIG. 2, 1a, 1b, and IC each indicate a detection element that detects the position of a rotor made of a permanent magnet.

As the detection element, a magnetically sensitive element (Hall element, saturable inductor), a photosensitive element (phototransistor), etc. can be used, and as an example, a magnetoresistive element may be used.

When a magnetoresistive element is placed in a magnetic field with a drive current applied from a power supply terminal through a resistor, its resistance changes, and its output terminal produces a voltage that changes depending on the magnitude and direction of the magnetic field acting on it. appears, and output voltages of opposite phases are generated at the two output terminals.

The outputs Sa and S8 of the detection element 1a are used as two inputs of an amplifier, for example, a differential amplifier 2a, and similarly the outputs Sa and S8 of the detection element 1a
The outputs S and S of b are input to the differential amplifier 2b,
The outputs Sc and Sc of the detection element 1C are input to the differential amplifier 2C.

These differential amplifiers 2a, 2b, 2C have one input Sa,
When Sb, So is smaller than the other human power Sa, Sb, So, the output P8. P,, PC becomes a positive voltage (high level), and in the opposite relationship, the output P8. Pb, Pc are O
v (low level).

These outputs P, Pb, and PC are supplied to the bases of switching transistors 3 a , 3 b , and 3 C forming the drive circuit.

The emitters of transistors 3a, 3b, and 3C are grounded,
Coils 4a, 4b, between the respective collectors and the power supply terminals.
4C is inserted.

The coils 4 a , 4 b , and 4 C are wound around a core (not shown) and constitute a stator.

When the rotor rotates with the above configuration, the differential amplifiers 2a, 2
b, from 2C (P, →Pb-+Po-+P8 →Pb...
A high level output appears in the order of 4a→4b→4C→4a.

In this example, the output of the - differential amplifier is fed back to the input side of the previous differential amplifier according to the energization order via a resistor, so that the currents flowing sequentially through the coils 4a, 4b, and 4C overlap each other and the other phases. I tried not to do that.

That is, the output PC of the differential amplifier 2C is fed back via the resistor 5b to one input terminal of the differential amplifier 2b to which the output Sb of the detection element 1b is supplied, and the output Pb of the differential amplifier 2b is fed back to the resistor 5a. The output P8 of the differential amplifier 2a is fed back to one input terminal of the differential amplifier 2a to which the output S8 of the detection element 1a is supplied via the resistor 5C, and the output Sc of the detection element 1C is supplied via the resistor 5C. It is fed back to one input terminal of the differential amplifier 2C.

In one embodiment of the present invention described above, the detection elements 1a, 1b, and the IC
When the flux linkage caused by the rotor changes as shown in FIG. 3A, the output of the detection element 1alb and IC becomes as shown in FIG. 3BCD.

The output S, (indicated by a solid line) of the detection element 1a and S, (indicated by a thin line) are in opposite phases to each other, and the output P8 of the differential amplifier 2a is in a range of 120° such that (S, < S,) in FIG. As shown in E, the level becomes high, which turns on the transistor 3a and causes current to flow through the coil 4a.

Moreover, the outputs Sb and S of the detection element 1b are (sb<sb)
In the range of 120°, the output Pb of the differential amplifier 2b becomes high level as shown in FIG. 3F, which turns on the transistor 3b and causes a current to flow through the coil 4b.

Furthermore, the outputs Sc and Sc of the detection element 1C are (S, <Sc
), the output PC of the differential amplifier is the third
As shown in Figure G, the level becomes high, which turns on the transistor 3C and causes current to flow through the coil 4C.

Therefore, the currents that sequentially flow through the coils 4 a , 4 b , and 4 C do not overlap with each other in other phases.

As an example, to explain in detail the operation of the outputs S, , S, of the detection element 1a and the output Pb of the differential amplifier 2b, first, S8 becomes larger than S8 due to the linkage magnetic flux Φ8, as shown in FIG. 3B. , the output P8 of the differential amplifier 2a becomes high level as shown in FIG. 3E.

If the output P is not fed back, Sa and P8 will change as shown by the broken lines in FIG. The output Sa of 1a increases, and (sa>
sa), the output Pa becomes a low level, and the transistor 3a is thereby turned off.

In this case, the amount of feedback of the output Pb of the differential amplifier 2b is determined by the ratio of the internal resistance of the resistor 5a and the detection element 1a,
This resistor 5a is larger than the internal resistance.

Therefore, if the output Pb becomes a low level, the detection element 1a will be activated again.
The output Sa becomes the original value, and at this point (S8>S
Because of the relationship a), the output P8 remains at a low level.

Output Sb of other detection element 1b and output P of differential amplifier 2C
C and the output S of the detection element 1C.

The relationship between P8 and the output P8 of the differential amplifier 28 is also the same as described above.

According to the above-mentioned operation, in addition to the magnetic flux linkage Φ8 shown in FIG. The target mounting positions are adjusted so that a deviation of 30 degrees occurs, and torque can be generated in a range where the interlinkage magnetic flux Φ8 with respect to the coil 4a is large.

The same applies to other phases.

As is clear from the above description, according to the present invention, it is possible to prevent the currents flowing sequentially through the coils 4a, 4b, and 4C from overlapping each other with other phases, and to prevent the currents from overlapping each other with other phases, and to maintain a range in which the magnetic flux linkage to the coils is large. Since torque is generated in the engine, efficiency can be improved.

Furthermore, according to the present invention, the resistor 5 is
It is only necessary to add a, 5b, and 5c, and the configuration is simpler than when using a logic circuit including a switching transistor, which has great practical advantages.

Diodes may be used instead of the resistors 5a, 5b, and 5C.

Note that if the rotation direction of the rotor is opposite to the above explanation, the energization order will naturally be reversed, and in this case, the output of the - amplifier will be fed back to the input side of the amplifier of the phase after the energization order. Become.

Further, it goes without saying that the number of poles and the number of phases are not limited to two poles and three phases as in the above embodiment.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram used to explain the present invention, FIG. 2 is a connection diagram of an embodiment of the present invention, and FIG. 3 is a waveform diagram of each part used to explain its operation. 1 a, 1 b, I C are detection elements, 2 a, 2 b, 2 C
are differential amplifiers, 4a and 4b. 4C is a coil.

Claims (1)

[Scope of utility model registration request] A rotor made of permanent magnets, multiple detection elements that detect the position of this rotor, multiple differential amplifiers that amplify this detection output, and the output of this differential amplifier is supplied to flow current to each of multiple coils. a plurality of drive circuits, the output of the differential amplifier - is fed back via a resistor or diode to the inverting input side of the other differential amplifier of the previous or subsequent phase according to the order of energization; A brushless DC motor in which the currents that sequentially flow through the plurality of coils do not overlap with other phases.