JPS5828834B2 - Motor Denryu Souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor such as a DC brushless motor in which the current flowing through the main winding that generates rotational torque is sequentially switched in accordance with a position signal indicating the rotational position of the rotor. This provides a novel configuration that limits the motor current at startup or when rotation is restricted.

Generally, excessive current flows through a DC motor when it is started or stopped, and a power supply device that supplies current to the motor must be able to withstand these currents.

Further, when the motor rotation is restricted or overloaded, the main winding of the motor generates heat, resulting in inconvenience such as burnout of the motor.

Conventional countermeasures to this problem include inserting a resistor between the power supply and the motor when starting the motor, lowering the voltage of the power supply, and other methods to protect the motor and power supply from overcurrent. A time lag fuse was used on the input side.

To do this, it is necessary to use a switch to switch between the start-up and steady-state states of the motor, and the time lag fuse has the disadvantage that once it is activated, it cannot be used again.

Furthermore, in consumer equipment that uses small motors (e.g. tape recorders, video tape recorders, record players, etc.), it is difficult to use the method described above when there is a risk that the motor may become constrained, so the load exceeds a certain value. The motor escapes from restraint by slipping in the parts that transmit the motor's power (for example, the belt, idler, etc.) when

Therefore, there is a problem that the slip of the power transmission section differs between when the load is light and when the load is heavy.

The present invention provides a method for limiting motor current that eliminates the above-mentioned drawbacks, and is particularly applicable to brushless motors to fully exhibit its effects.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic structural diagram of a brushless motor, and FIG. 2 is a partial plan view of FIG. 1.

In these figures, a motor housing 1 includes a stator core 2 and a stator core 2 that constitute a brushless motor.
A main winding 3 is wound around a stator core in a three-phase configuration, and a rotary shaft 4 is provided with an annular magnet 5 magnetized to have multiple magnetic poles, with its inner magnetic pole surface facing the stator core 2. A holding rotor 6 is provided, and constitutes a stator section and a rotor section of the brushless morph.

The rotor wheel is attached to the boss 7, and is rotatably attached to the housing 1 together with the rotary shaft 4 via bearings 8a and Bb at both ends of the boss 7.

On the other hand, as shown in a partial view in FIG. 2, a position detection stake 9 having three pairs of protrusions is provided inside the stator 2, and a position detection rotor 10, which indicates the rotational position of the potter's wheel, is mounted on the boss 7. installed.

The position detection stator 9 includes primary coils 11a, 1
1b, 11c, and secondary coils 12a, 12b, 12
c is provided, and on the other hand, the outer periphery of the position detection rotor 10 is provided with a pair of primary coil and secondary coil 11a, respectively.
In order to change the electromagnetic coupling between 2a, 11b and 12b, and 11c and 12C, it has protrusions made of silicon steel plate, soft iron, or the like.

The operation of the motor section configured in this manner will be explained using the motor drive circuit shown in FIG. 3.

An AC signal is supplied from the oscillation circuit 13 having an oscillation frequency of several 101 fG (z) to the primary coils 11a, 11b, 11c, and the secondary coils 12a,
12b or 12c.

Therefore, the secondary coils 12a, 12b. A predetermined AC signal is induced in each of 12C.

In the state shown in FIG. 2, since the protrusion of the position detection rotor 10 is close to the primary coil 11a and the secondary coil 12a,
The electromagnetic coupling between the primary coil 11a and the secondary coil 12a is the same as that of the other primary coils 11b, 11c and secondary coils 12b, 12C.
It will be denser compared to.

Therefore, the largest AC signal is transmitted to the secondary coil 12a.

The AC signal transmitted in this way is passed through rectifier circuits 14a, 14b, 14c consisting of diodes, resistors, and capacitors.
The output is applied to the current switching transistor 15a, 1 for switching the motor current flowing to the main winding 3.
sb, connected to the base of 15c.

And current switching transistors 15a, 15b15C
constitute a three-differential circuit, so their emitters are tied together and connected to the collector of a control transistor 17 via a resistor 16.

Now, when a predetermined DC voltage is applied to the power supply terminal 1B and the control input terminal 19, the secondary coils 12a and 12b.

The AC signal transmitted to 12c is rectified by a rectifier circuit 14a.

14b and 14c.

And here it is rectified and smoothed, bias resistance 20.21
Current switching transistor 1 to which a bias voltage is applied
5a.

It is applied to the bases of 15b and 15c.

The rectifier switching transistors 15a, 15b, and 15c constitute a three-differential circuit as described above, and the rectifier circuit 1
Among 4a, 14b, and 14c, only the current switching transistor connected to the rectifier circuit from which the largest signal is extracted is turned on.

The emitter current flowing through the current switching transistor in the on state is determined by the level shift resistor 22 connected to the emitter of the control transistor 17, the feedback resistor 23, the detection resistor 24, and the DC voltage applied to the control input terminal 19. be done.

In the case of FIG. 2, as mentioned above, the AC signal of the secondary coil 12a is the largest, so only the current switching transistor 15a is turned on, and its collector current is amplified by the amplification transistor 25a, and the main winding A current flows through 3a.

Further, when the current switching transistors 15b and 15c are in the on state, the current switching transistors 15b and 15c are respectively in the on state.
Amplification transistors 25b corresponding to 15C,
25c and the individual main windings 3b.

A current flows through 3c.

In addition, in FIG. 1, the above-mentioned main windings 3a and 3b.

3c are collectively indicated as the main winding 3.

As described above, when a current flows through the main winding 3a, attraction and repulsion forces act between the magnet 5 and the magnetic field generated by the current, and the rotor 6 moves in the direction shown by the arrow 26 in FIG. And the position detection rotor 10 rotates.

Therefore, the protrusion of the position detection rotor 10 is connected to the primary coil 1.
1b, close to the secondary coil 12b, and this time, the main winding 3b
Current begins to flow.

Therefore, attractive and repulsive forces come to act between the magnetic field caused by this current and the magnetic field caused by the magnet 5, and the rotor 6 further rotates in the direction of the arrow 26.

In this way, as the rotor 6 rotates, the main windings 3a, 3b, and 3b through which current flows are sequentially switched, and the rotor 6 continues to rotate.

In the brushless motor configured in this way and its drive circuit, the main windings 3a, 3b.

As a method for limiting the motor current flowing through 3c to a constant value, (2) detect the motor current using the voltage of the detection resistor 24 and change the voltage applied to the power supply terminal 18;

Detect the motor current and control input terminal 19 in the same way as ■ and ■.
change the control voltage applied to the

Methods such as the following are possible, but in the method (2), a large motor current flows through the power terminal 18, so the elements (for example, transistors, cyrisks, etc.) that control the voltage of the power terminal 18 require large electric power. Furthermore, in method (2), if the output impedance of the preceding stage circuit coupled to the control input terminal 19 is low, it is difficult to control the voltage at the control input terminal 19.

Therefore, there are drawbacks such as restrictions on the pre-stage circuit coupled to the control input terminal 19, and the universality of the motor drive circuit shown in FIG. 3 is lost.

Therefore, in this embodiment, the current is distributed to the main windings 3a, 3b, and 3c in order to have the universality of the motor drive circuit and to ensure that the current limiting element operates with low power. Switching transistor 15a.

A configuration is used in which the DC bias of 15b and 15c is changed.

Returning to FIG. 3 again, in this motor drive circuit, in order to compensate for variations in the current amplification factors of the current switching transistors 15a, 15b, 15C1 and the amplifying transistors 25a, 25b, 25c, each of the main windings 3a, 3b, 3c
A detection resistor 24 commonly connected to each main winding 3a, 3
The currents flowing through the transistors b and 3c are detected, and a feedback resistor 23 applies negative feedback to the emitter of the control transistor 17.

Here, the level shift resistor 22 connected between the power supply terminal 18 and the emitter of the control transistor 17 levels-shifts the emitter potential of the control transistor 17, that is, the control input potential of the control input terminal 19.
To increase the rate of change in the current flowing through the main windings 3a, 3b, 3c with respect to the change in the transfer conductance of the motor drive circuit, that is, the control input voltage at the control input terminal 19, by changing the amount of negative feedback of the feedback resistor 23. It also compensates for the decrease in transfer conductance of the motor drive circuit that occurs when the current limit value of the current limit circuit described later is set to a wide range and at the same time the current limit value is set to a particularly small value. be.

On the other hand, a filter 27 composed of a resistor and a capacitor is connected to the detection resistor 24, and one end of its output is connected to a voltage dividing resistor 28 between ground for determining the power supply limit value. The other end is connected to the pace of current limiting transistor 29.

The collector of the current limiting transistor 29 is connected to the connection point between the bias resistors 20 and 21 to form a current limiting circuit.

In addition, a bypass capacitor 3 is connected in parallel with the bias resistor 21.
0 is set.

Now, assuming an overload condition when starting the motor, in such a condition the motor rotation speed is low (or stopped), a high voltage is applied to the control input terminal 19, and the control transistor 17 is A large collector current flows.

Therefore, current switching transistors 15a, 15b,
15c, and in turn, the amplification transistors 25a and 25b
, 25c, a large motor current flows through the main windings 3a, 3b, and 3c.

Therefore, the voltage across the detection resistor 24 commonly connected to these main windings 3a, 3b, and 3c becomes high.

The voltage of the detection resistor 24 is passed through the filter 27 to the main winding 3a.
, 3b, and 3c are removed, the voltage is divided by the voltage dividing resistor 28 and the output resistor of the filter 27, and added to the current limiting transistor 29.

When the divided voltage exceeds the forward pace and emitter potential of the current limiting transistor 29, the current limiting transistor 29 starts to conduct, and the collector current flows through the current limiting transistor 29 and the current switching transistor 1.
The pace bias voltages of 5a, 15b, and 15c become lower.

Therefore, current switching transistors 15a, 15b, 1
5c collector current and hence the main windings 3a, 3b
, 3c is prevented from increasing, and the motor current is limited to a constant value.

In the case of this embodiment, the value of the motor current to be current limited is such that the potential across the detection resistor 24 (the product of the motor current and the detection resistor 24) is greater than or equal to the forward pace-to-emitter potential of the current limiting transistor 29. Certain things are a condition.

Therefore, if it is desired to set the motor current value to be limited to a small value, the value of the detection resistor 24 must be set to a large value.

In this way, when the value of the detection resistor 24 is increased, the amount of negative feedback to the control transistor 17 increases, resulting in a decrease in the transfer conductance of the motor drive circuit described above.

However, this drawback is solved by reducing the amount of negative feedback to the control transistor 17 by decreasing the value of the level shift resistor 22 or increasing the value of the feedback resistor 23, resulting in the problem that the above-mentioned transfer conductance decreases. can be easily solved.

Further, in the above embodiments of the present invention, the rotational position detection section of the motor section includes a position detection rotor, a position detection stator,
Although we have described the case of using the primary coil and secondary coil installed in it, the position detection method uses a light source such as a lamp or a light emitting diode, and a photodetector element (for example, a photodiode, etc.) that detects the light from the light source. A method using a phototransistor, CDS, etc.), a method in which a shutter provided between the light source and the photodetector element is rotated together with the rotor of the motor section, or a method using the rotor's magnetic flux itself, or a part that rotates integrally with the rotor. The same effects as those shown in the embodiments of the present invention can also be obtained by a method in which a magnet is provided and a Hall element, a reed switch, or the like is used to detect the magnetic flux.

As described above in detail, according to the present invention, the motor current can be limited without affecting the control circuit connected to the motor drive circuit.

Further, even if the limit value of the motor current is set over a wide range, the gain of the motor drive circuit can be prevented from changing, which has an extremely large effect.

[Brief explanation of drawings]

FIG. 1 is a schematic structural diagram of one embodiment of the present invention, and FIG.
FIG. 3 is a plan view of the main part in the figure, and FIG. 3 is a motor drive circuit diagram in an embodiment of the present invention. 3... Main winding, 5... Magnet, 6
...Rotor, 10...Position detection rotor,
11a, 11b. 11c...Quadratic coil, 12a, 12b
, 12C... Secondary coil, 14a, 14b,
14c... Rectifier circuit, 15a, 15b, 15c
...Current switching transistor, 18...
Power supply terminal, 19... Control input terminal, 22...
... Level shift resistor, 23 ... Feedback resistor, 2
4...Detection resistor, 27...Filter,
29...Current limiting transistor.

Claims (1)

[Claims] 1 The current flowing through the main winding indicates the rotational position of the rotor.
It has a current detection resistor that is switched by the position detection signal of the AC signal transmitted to the next coil and detects the current flowing through the main winding as a voltage change, and one end of the current detection resistor is connected to a current limiting transistor via a smoothing filter. The collector-emitter path of the current limiting transistor is connected in parallel with the bias resistor of each of the secondary coils, and one end of the current detecting resistor is connected to the emitter of the control transistor via a feedback resistor. , a motor characterized in that the limit value of the current flowing through the main winding and the transfer gain of the control transistor can be set arbitrarily by connecting the emitter to a power supply terminal via a level shift resistor. Current limiting device.