JPS6027275B2 - DC motor speed control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that controls the constant speed and speed of a DC motor by detecting the position of a rotor made of permanent magnets using a Hall element and switching the drive current flowing through a field coil. .

A Hall element is arranged around the stator in a relationship that detects magnetic flux with respect to the magnetic poles of the rotor, and the Hall voltage induced in this element is used to sequentially change the drive current flowing through the field coil. It generates torque, and this torque rotates the rotor of the motor.

As a speed control device that controls the speed of a brushless DC motor using such a Hall element to a constant value, conventionally known methods and devices include, for example, an output from a tachogenerator that rotates in synchronization with a rotor. Compare the signal with a reference signal corresponding to a preset reference rotation speed,
A method and a speed control device have been used to control the direct current flowing to the Hall element based on the differential output. Alternatively, without using the above-mentioned tachogenerator, use the generated voltage generated in the field coil and use it as a signal corresponding to the speed of the motor, and compare this signal with a reference signal corresponding to the reference rotation speed. However, a method and apparatus for controlling the speed of a DC motor by controlling the amount of current flowing through the field coil based on the differential output are also known, for example, from US Pat. No. 3,517,28.

An object of the present invention is to detect a rotational position of a rotor having a permanent magnet using a Hall element, and to control the drive current flowing through a field coil by switching the DC motor. A speed regulating means is used to convert the signal into a DC signal having a level corresponding to the frequency. using a comparison means to obtain a difference signal by comparing the signals with the
By controlling the gain of an amplifier that amplifies the output of the Hall element according to the level of the difference signal,
An object of the present invention is to provide a constant speed control device for a motor that maintains the rotational speed of a rotor at a constant level by controlling the amount of current that sequentially flows through the field coils of the motor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a speed control device for a DC motor according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a system diagram showing the configuration of a speed control device according to the present invention. In the figure, a Hall element 1 that generates a Hall voltage is in a fixed relationship with the stator of the motor, and at least one pair of elements are arranged at a predetermined angle apart to detect the rotational position of the rotor. By doing so, changes in the magnetic flux during rotation of the rotor containing permanent magnets can be detected as a function of the rotation angle. A control circuit 2 that controls the current supplied to the field coil is connected to the output side of the Hall element 1.

The amplification and drive circuit 3 is connected to the control circuit 2. The field coils of the brushless DC motor 4 are connected to the amplification and drive circuit 3, respectively. This DC motor 4 is
It consists of a rotor having magnetic poles of opposite polarity and a stator having at least one pair of field coils disposed in torque generating relationship about the rotor. A conversion circuit 5 that converts the Hall voltage into a DC signal is connected to the output side of the Hall element 1. A comparison circuit 6 is connected to an external reference signal generation circuit 7 for rotating the rotor at a constant speed and the conversion circuit 5, compares the signals from both circuits, and sends an output signal of the difference to the control circuit 2. connected to communicate. The function of the constant speed control mechanism of such a brushless DC motor will be described.

The output signal of the Hall element 1 becomes an alternating current voltage with a frequency corresponding to the speed of the motor. This voltage is input to the control circuit 2, and the same signal is input to the signal conversion circuit 5. This conversion circuit 5 converts the above-mentioned AC voltage into a DC signal with a level corresponding to its frequency. Therefore, the DC signal is a signal whose level changes over time in response to the rotational speed of the rotor. This signal is applied to one input terminal of the comparison circuit 6. On the other hand, a DC voltage at a constant level corresponding to a predetermined speed of the motor is applied from a separately provided reference signal generation circuit 7 to the other input terminal of the comparison circuit 6, and the two DC voltages are compared. Therefore, as the output of the comparator circuit, an output signal (voltage) representing the difference between the signal corresponding to the speed of the motor and the reference signal is obtained. This world power signal is input to the control circuit 2 described above. In this control circuit, the output signal from the comparator circuit 6 is selectively supplied to the amplification and drive circuit according to the output voltage from the Hall element 1, and the mode of current supply to the field coils is controlled so that each coil is connected to the rotor magnetic pole. Switch sequentially to generate the maximum torque based on the relationship.
The output signal of the control circuit 2 is amplified by the amplification and drive circuit 3 and then supplied to each field coil of the motor. FIG. 2 is a circuit connection diagram showing one embodiment of the speed control device according to the present invention.

In the figure, Hall elements 1, 2 are arranged so as to be able to detect magnetic flux with respect to the magnetic pole. Resistors R, , R2 are input current limiting resistors for the Hall element, and R3 and R4 are bias setting resistors for the amplifier connected to the Hall element. The emitter of the power amplification transistor Tr is the resistor R, .
R2, the collector is connected to the positive terminal of power supply B via the main switch SW, and the lead wire is connected to the lead wire SO, and the base is connected to the lead wire SO, via the resistor 5. has been done. This resistor 5 is a current setting resistor for operating the Zener diode, ZD, in the Zener region, and the base of the transistor Tr is connected in series with this resistor.
The emitter voltage compensation diode D and the emitter diode ZD are connected, and these are connected to the negative terminal of the power source via a lead wire e2. These elements Tr, , R5, D, , ZD form a voltage stabilizing circuit. Output terminals a, b, c, of Hall elements 1, 2,
DC amplifiers A, , A3, and A4 are connected to d.

The mixing circuit 8 is for mixing the outputs of the Hall elements, and the bases of the coupling transistors Trg to Tr, 2 are connected to the output terminals a to d. Resistance R, 6~R
, 9 are emitter follower resistors of the transistors Tr9 to Tr,2, and are for making the inputs of the transistors high impedance. coupling capacitor C
, ~C4, the emitter of the transistor is connected to the amplifier A
5. Comparator 6 is an amplification transistor T
r7 and Tr8, load resistors R9 to R,o, and balance adjustment resistors R, . , an emitter resistor R,2.

One input terminal g of this comparator is connected to the aforementioned amplifier via a digital-to-analog converter 5. The other input terminal h is connected to a reference signal generator 7, and the latter has a current setting resistor R,3 for operating the Zener diode in the Zener region, and a Zener diode ZD. , and a balancing resistor R,4. The output terminal of the comparator 6 is connected to the coupling amplifier 6' by a coupling resistor R.
The amplifier 6' is formed from a transistor Tr6 and a load resistance term 7. The output terminal of this amplifier is the same as that of the amplifiers A, , A2, A3, A
It is connected to the other input terminal of 4. transistor T
r2 to Tr5 form a motor drive circuit,
Its input terminals are connected to amplifiers A, .about., and its output terminals are connected to field coils L, .about.L4 of the motor, respectively.

The transistors Tr2 to Tr2 are connected to the lead wire Soe2 via an emitter resistor R6. Next, the operation of the apparatus shown in FIG. 2 will be explained. When the power switch SW is closed, a constant current flows to the Hall elements 1, 2 through the transistor Tr of the constant voltage circuit. Hall element day, day 2
Due to changes in the magnetic field caused by the magnetic poles of the rotor that are in contact with this (in the case of two poles), the output terminals a, b, c, and d have the phases shown in Fig. 3 A, B, C, and D, respectively. Hall voltage is generated. The waveform of this output signal is a voltage waveform similar to a sine waveform, and is connected to the circuits of amplifiers A, .
It is further branched and sent to a mixing circuit. In this circuit, signals for each phase from the Hall elements are combined, and a combined waveform as shown in FIG. 3E is obtained at the output terminal e of the circuit. This composite signal is amplified by amplifier A3, producing at its output terminal f a signal waveform having a frequency as shown in FIG. 3F. Since the frequency of this signal gives information corresponding to the rotational speed of the rotor, a digital-to-analog converter converts the signal corresponding to the frequency of this synthesized Hall voltage into the signal shown in Fig. 3G whose level is proportional to the frequency. It is converted into a DC signal as shown. After that, this analog signal is sent to 1 of comparator 6.
is applied to the other input terminal g. The other input terminal h has
A DC signal as shown in FIG. 3 H' is applied from a reference signal generator 7 at a constant level corresponding to the set speed of the motor. These two DC signals are compared by a comparator 6.

If there is a difference between the two signal levels, an output signal corresponding to the difference is input to the transistor Tr6 via the resistor R8.
For example, when the rotational speed of the motor is lower than the reference speed, the voltage at point h is higher than the voltage at point g among both input terminals of the comparator, so the collector potential of transistor Tr6 is higher than that of transistor Tr7. becomes low, and therefore the base potential of transistor Tr6 also rises to a considerable extent,
The conductivity of the transistor T[6 is reduced, providing relatively less power to the amplifier A, ~. This amplifier has a logic function as shown in the figure, and produces an output only when the output signal from the Hall element and the output signal from the transistor Tr6 are input simultaneously, and the level of the output signal is equal to the level of the signal from the Hall element. It is proportional and amplified. The operation of this amplifier will be explained in detail.

For example, while the output signal from the output terminal d of the Hall element applied to one input terminal of the amplifier A is lower than the signal level at the other input terminal of the amplifier A, that is, the output signal level of the transistor Tr6, The output of amplifier A remains zero. On the other hand, when the output signal from the output terminal d of the Hall element ratio exceeds the output signal level of the transistor Tr6, the output terminal of the amplifier A receives a signal proportional to the output signal level from the output terminal d of the Hall element 2, and An output with an amplified level is generated. And this state is the output terminal d of Hall element 2
This continues as long as the output signal level from the transistor Tr6 exceeds the output signal level from the transistor Tr6.

Thereafter, when the output signal level from the output terminal d of the Hall element 2 becomes lower than the output signal level of the transistor Tr6, the output of the amplifier A becomes zero again as in the above case.

It goes without saying that the other amplifiers A2 to A4 operate in the same manner as the amplifier A. Currents supplied to the driving transistors T to Tr5 are controlled by the output signals of the amplifiers A and A4. That is, the transistor Tr2 has the voltage shown in FIG. 3D.
The power supplied to Tr3 as shown in FIG. 3 L proportional to the Hall voltage shown in FIG. 3 is supplied to Tr3, the power shown in FIG. A power as shown in FIG. 3J proportional to the Hall voltage shown in B,
Further, as shown in FIG. 3 1, which is proportional to the Hall voltage shown in FIG. 3A, the V supply power shown in FIG. Current is supplied to the coils in a predetermined order. Since the time or amount of current flowing through this coil is controlled by a control signal corresponding to the output signal of the comparator 6, as a result, the speed of the motor increases, and after a predetermined time, the speed is constant at a speed that matches the reference signal. It will be driven. Note that the dotted lines in FIG. 3 1 to L' indicate the Hall voltages input to each amplifier A, to A4. In the above example, four coils arranged at 900 rotation angles were used as field coils, but in Fig. 4, the number of coils used was limited to two. An example of the case is shown below.

If the four terminals J', K', 1', and m' in FIG. 4 are connected to the terminals i, k, 1, and m in FIG. 2, the same circuit as in FIG. 2 can be used for the other circuits. In the figure, resistors R2o, R2
, , R22, and R23 are transistors Tr, 3, Tr
,5, Tr,7 and Tr,9.

Diodes D3, D4, D5 and D6 direct the current. Transistor Tr, 3, Tr, 4, T
r, 5, Tr, 6: Tr, 7, T, 8; Tr, 9 and T
So 2. and form a combimentary amplification circuit. The field coils connect the common emitter terminals of transistors Tr,3 and Tr,4, and the common emitter terminals of transistors Tr,5 and Tr. 6
The field coil is connected to a common emitter terminal of transistors Tr, 7, Tr, 8 and a common emitter terminal of transistors Tr, 9, Tr2o. The above two field coils L and L6, the motor rotor R (the illustration shows an example of two-pole mounting), and the Hall elements 1, . The arrangement positional relationship with Day 2 is shown in FIG.

Note that the Hall element may be provided at a position facing the end surface of the rotor. Next, the operation of the embodiment shown in FIGS. 4 and 5 will be explained.

Now suppose that the Hall element 2 faces the north pole of the rotor, and a Hall voltage is generated at the output terminals c and d of the Hall element, with the voltage at c being higher than the voltage at d. This voltage causes the transistors Tr, 3, Tr, 6 of the transistor drive circuit to become conductive, while the other transistors remain non-conductive. Therefore, at this time, the current flows from the positive terminal of power supply E to the lead wire e,
1 transistor Tr, 3-coil L5-transistor T
r, 6-Lead wire so e2 flows to the negative terminal of source E. As a result, torque for rotating the rotor R is generated in the G2 portion of the coils (see FIG. 5). As the rotor rotates, the Hall element changes its rotational position. The current is detected by G.G. and the current is sequentially supplied to the coils, and as shown in FIG. 4, the supply direction of G.G. , G2 can be rotated by generating rotational torque. 6th
The figure shows a second embodiment of the present invention, in which the mixing circuit 8 in the first embodiment shown in the second figure is composed of coupling capacitors C5 to C8 and uses two power supplies.

Elements having the same functions as those in FIG. 2 are given the same reference numerals and their explanations will be omitted. As described above, in the speed control device of the present invention, by utilizing the fact that the frequency of the rotor position detection signal by the Hall element corresponds to the motor speed, this is converted into an analog quantity, and a signal corresponding to the reference speed is generated. Therefore, the speed control performance is much improved compared to the conventional method and device that detects the generated voltage generated in the field coil and uses it as a rotor position detection signal. In addition, conventional speed control circuits are affected by temperature because they use semiconductor elements such as diodes and transistors, but in the present invention, the peak can be controlled independently of the waveform of the output voltage of the Hall element. Since the method of determining the speed of the motor by detecting only the high frequency that is counted digitally is adopted, the temperature dependence in the analog speed detection method as described above can be eliminated. Furthermore, although Hall elements are used in pairs, the influence of variations in the performance of each Hall element is also affected by the present invention, which detects only the frequency of the output signal waveform of these elements.
There is no bad result, and therefore, it is possible to provide an inexpensive speed control device in which the Hall element can be easily selected and incorporated into the motor.

Furthermore, since the input current of the Hall element is held constant and the output current of the Hall element is controlled by the output signal from the comparison means, the speed of the DC motor is controlled, so that the temperature of the Hall element is Since the temperature is almost constant, there is an advantage that the speed of the motor does not fluctuate due to changes in the temperature characteristics of the Hall element.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a speed control device according to the present invention, FIG. 2 is an electric circuit connection diagram showing an embodiment of the speed control device according to the present invention, and FIGS. 3 A to L is the second
Signal waveform diagrams at each part of the circuit connection diagram shown in the figure,
Figure 4 is a circuit connection diagram of a modified part of the circuit connection diagram shown in Figure 2 so that two coils are used as Kaiji coils, and Figure 5 is a circuit connection diagram of the part of the circuit connection diagram shown in Figure 2 that has been modified to use two coils as Kaiji coils. FIG. 6, a perspective view showing the arrangement around the rotor, is an electric circuit connection diagram showing another embodiment of the speed control device according to the present invention. R...rotor, L~-...field coil, day, ~day2...
Detecting means, 5... Means for converting into an analog signal, 7.
...Reference signal generation means, 6. Comparison means, 2. Controlling means, 3. Driving means. Figure 1 Figure 4 Figure N Ship Figure 3 Figure 5 Figure 6

Claims (1)

[Claims] 1. A DC motor that detects the rotational position of a rotor with permanent magnets using a Hall element supplied with a constant control current, and controls the motor speed by switching the drive current flowing through each field coil based on the detection output. In the speed control device, a conversion means converts a signal with a frequency corresponding to the speed induced in the Hall element into a DC signal having a level corresponding to the frequency, and a standard that generates a reference voltage corresponding to a preset reference speed. a speed signal generating means, a comparing means for comparing a reference signal from the generating means and a DC signal from the converting means to obtain signals of both signals, and an output signal from the Hall element and a difference signal of the comparing means. and an amplifier whose output is controlled according to the difference signal in order to vary the speed of the motor is provided, and the amplifier controls the amount of current sequentially flowing through the field coil. DC motor speed control device.