JPH0359677B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching governor device for a DC motor, and its purpose is to provide an extremely efficient switching governor device based on a conventionally known bridge detection type electronic governor circuit, and to be highly resistant to environmental changes. The objective is to realize a device with good rotational speed stability.

A bridge detection type electronic governor device, as shown in FIG. 1, is well known as a device for controlling the rotational speed of a DC motor at a constant speed with an extremely simple configuration without requiring a special speed generator.

In Figure 1, the low resistance side of the bridge circuit is configured by DC motor 1 and resistor 2, and resistor 3
and resistor 4 constitute the high resistance side of the bridge circuit. When the equilibrium condition of the bridge circuit is satisfied, a speed voltage dependent on the rotational speed of the DC motor 1 appears between the detection terminals a and b.

This speed voltage is determined by a reference voltage source 6 by a comparator 5.
If the speed voltage is smaller than the reference voltage, the base current of the power supply control transistor 7 increases and the power supply current to the DC motor 1 is increased; For example, the base current of the power supply control transistor 7 decreases, thereby reducing the power supply current to the DC motor 1. As a result, the DC motor 1 can maintain its rotational speed constant even when the load fluctuates.

In Fig. 1, the capacitor 8 is inserted for the purpose of absorbing the spark noise generated between the brush and commutator of the DC motor 1, and the capacitor 9 is inserted to absorb the spark noise generated between the brushes and the commutator of the DC motor 1. It was inserted to prevent imbalance and high frequency oscillation.

Furthermore, since the armature winding of the DC motor 1 is made of copper wire, a resistor 2 is used to maintain the balance of the bridge circuit even when the ambient temperature changes.
are often made of copper wire (Japanese Patent Publication No. 18018/1973 or Publication of Utility Model Publication No. 8646/1983).

By the way, in the electronic governor device shown in FIG. 1, the power supply control transistor 7 is in an active state in the normal state, and a voltage equal to the output voltage of the battery 30 minus the voltage between the power supply terminals c and d of the bridge circuit is always applied. Therefore, there is a problem of extremely poor power efficiency. This is not limited to bridge detection type electronic governor devices, but also applies to governor devices using a speed generator.

As a method for solving this problem, a pulse drive system for a DC motor as shown in US Pat. No. 3,624,474, for example, can be considered. However, passing a pulse current through a DC motor has the drawback that interference radio waves are generated from the motor windings, and because the Q of the motor windings cannot be increased too much, desirable results cannot be obtained.

On the other hand, for example, in Japanese Patent Application Laid-Open No. 53-47911, a pulse current is supplied to a chiyoke coil connected in series to a DC motor with a capacitor connected to both ends, and the DC motor is continuously supplied with a pulse current. A method for passing current through is shown. According to this method, no interference radio waves are generated from the windings of the DC motor, and the Q of the choke coil itself can be increased, so that the characteristics can be considerably improved.

The present invention was made based on the fact that the chiyoke coil is made of the same material (copper silver) as the motor windings and has an appropriate internal resistance. The low-resistance side of the bridge circuit is configured by a DC motor, and a pulse current generated by self-excited oscillation is supplied between the power supply terminals of the bridge circuit, and the detection terminal on the low-resistance side of the bridge circuit is connected to the low-resistance side of the bridge circuit. and a first one for reducing AC impedance and smoothing the pulse current at the detection terminal on the high resistance side, respectively.
This is because the second capacitor is connected.

FIG. 2 is a circuit diagram of the switching governor device in the process of achieving the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals. In FIG. 2, a chiyoke coil 10 and a DC motor 1 are connected in series to form the low resistance side of the bridge circuit, and the output of a comparator 5 for error detection is connected to the inverting input terminal of a comparator 11 for pulse width modulation. (-), and the output of a sawtooth wave generator 12 as a high frequency switching carrier generator is applied to the non-inverting input terminal (+) of the comparator 11.
The output of is applied to the base of a switching transistor 7' for power supply control.

Note that the sawtooth wave generator 12 is also shown in the aforementioned US Pat. No. 3,624,474 and is generally well known, so a detailed explanation of its configuration will be omitted.

Further, capacitors 8' and 9' for smoothing the pulse current are connected to both ends of the DC motor 1 and to both ends of the resistor 4 constituting the high resistance side of the bridge circuit, respectively, to supply power to the bridge circuit. An idling diode 13 is connected between terminals c and d.

Now, in the circuit shown in Fig. 2, if the rotational speed of the DC motor increases due to changes in the load, the output level of the comparator 5 decreases, and as a result,
The slice level of the sawtooth wave by the comparator 11 decreases, and the period during which the comparator 11 draws in the base current of the switching transistor 7' becomes shorter, and the average current of the current pulses output from the collector of the transistor 7', that is, DC. The average current supplied to the motor 1 decreases, causing the rotational speed of the DC motor 1 to decrease. When the rotational speed of the DC motor 1 falls below the specified value, the average current supplied to the DC motor 1 increases through a completely opposite process.

The advantages of the circuit shown in FIG.
The series loss due to the internal resistance does not increase compared to the original bridge detection type electronic governor circuit, and furthermore, the temperature change in the internal resistance of the choke coil 10 and the temperature change in the resistance value of the armature winding of the DC motor 1 are the same. Another point is that because they are similar, the bridge circuit can maintain balance even with changes in ambient temperature.

On the other hand, the disadvantage of the circuit shown in FIG. 2 is that it requires an extra comparator 11 and sawtooth wave generator 12 compared to the circuit shown in FIG. 1, making the configuration more complicated.

SUMMARY OF THE INVENTION In view of the above drawbacks, the switching governor device of the present invention provides a device that does not require an extra comparator or sawtooth wave generator.

FIG. 3 shows a circuit diagram in one embodiment of the present invention. To explain the operation of the device shown in Fig. 3, first, when the rotation of the DC motor 1 is stopped, the potential of the non-inverting input terminal (+) of the comparator 5 is higher than that of the inverting input terminal (-). As a result, the comparator 5 supplies sufficient base current to the switching transistor 7' so that the switching transistor 7' is turned on.
As a result, a voltage approximately equal to the power supply voltage is supplied between the power supply terminals of the bridge circuit, and the DC motor 1
starts. When the rotation speed of the DC motor 1 increases to a value set by the reference voltage source 6 and further exceeds this value, the comparator 5 stops supplying the base current to the switching transistor 7'.
Switching transistor 7' is turned off.
As a result, the rotational speed of the DC motor 1 decreases, and as a result, the comparator 5 again supplies the base current to the switching transistor 7', and the switching transistor 7' is turned on. As a result, in the device shown in FIG. 3, the switching transistor 7' is repeatedly turned on and off so that the rotational speed of the DC motor 1 reaches a preset value. Despite having a similar configuration, the device shown in FIG. 1 does not perform a switching operation, whereas the device shown in FIG. While the alternating current balance of the circuit is stabilized, the device shown in FIG. This is due to the fact that a larger phase delay is generated in the path leading to this, and the alternating current balance of the bridge circuit is also intentionally disrupted.

To explain in more detail, first, in the circuit shown in Fig. 1, if the resistance value of resistor 2 is increased and the balance of the bridge circuit is intentionally disturbed, only the generated voltage component of DC motor 1 will be present between points a and b. Instead, a supply voltage component from the collector side of the transistor 7 is also included, and this component acts to apply positive feedback to the negative feedback loop for rotational speed control. This has been well known as a hunting phenomenon that occurs when the resistance value of the resistor 2 is increased. In the circuit of FIG. 3, the impedance of the chiyoke coil 10 acts in the same way as increasing the resistance value of the resistor 2 in the circuit of FIG. An AC feedback loop for generating a high-frequency switching carrier is formed, which includes a parallel circuit of the resistor 15, the comparator 5, and the switching transistor 7'. capacitor 1
In the parallel circuit of 4 and resistor 15, capacitor 14
is one element for forming an AC feedback loop, and the resistor 15 is one element for forming a feedback loop for speed control. According to experiments, in the circuit shown in Fig. 3, the capacitances of capacitors 8, 9, and 14 were set to 47μF, respectively.
It has been confirmed that when 0.47 μF and 100 pF are selected, the frequency of the switching carrier is approximately 30 KHz when the inductance of the chiyoke coil 10 is 127 μH, and approximately 70 KHz when the inductance is 47 μH.

FIG. 4 shows a more specific version of the circuit shown in FIG. 3, and the same parts as in FIG. 3 are given the same reference numerals. In FIG. 4, a well-known bandcap constant voltage circuit 16 is used to generate a reference voltage across a resistor 18 built into the comparator 5 through a constant current circuit 17. Note that a resistor 19 and a variable resistor 20 connected between detection terminals a and b of the bridge circuit are elements for changing the rotational speed of the DC motor 1.

The embodiments of the present invention are not limited to the above embodiments, and various modifications are possible.

For example, as shown in FIG. 5, a resistance element 21 can be inserted between the chiyoke coil 10 and the DC motor 1 to adjust the DC balance of the bridge circuit, or the resistance element 21 can be used to detect the high resistance side of the bridge circuit. Instead of the capacitor 9' connected to the terminal, a smoothing circuit consisting of a resistor 22 and a capacitor 23 can be connected as equivalent to the capacitor 9'. Furthermore, a Zener diode 24 can also be used as the idling diode.

As described above, in the DC motor switching governor device of the present invention, the series circuit of the DC motor 1 and the chain coil 10 constitutes the low resistance side, and the series circuit of the first resistance element 3 and the second resistance element 4 constitutes the low resistance side. a bridge circuit forming a high resistance side; a first capacitor 8' connected to both ends of the DC motor;
a second capacitor 9' connected to the detection terminal on the high resistance side of the bridge circuit; and an idling diode 1 connected in parallel to the bridge circuit.
3 or 24 and a comparator 5 that detects the potential difference between the detection terminal of the bridge circuit and compares it with a reference voltage.
and a switching transistor 7' that is driven by the comparison output signal of the comparator and supplies power to the bridge circuit, and an oscillation device that generates a high-frequency switching carrier in the choke coil, the comparator, and the switching transistor. The circuit is characterized in that it is configured to form a loop and supply a pulse current whose average value changes depending on the potential difference between the power supply terminals of the bridge circuit.It has an extremely simple circuit configuration and has high temperature stability. A device with good power efficiency and good power efficiency can be obtained, and a great effect can be obtained.

[Brief explanation of drawings]

1 and 2 are circuit connection diagrams of a device according to the prior art, and FIGS. 3, 4, and 5 are circuit connection diagrams of a switching governor device for a DC motor according to the present invention. 1...DC motor, 3...Resistance, 4...Resistance,
5... Comparator, 7'... Switching transistor, 8'... Capacitor, 9'... Capacitor, 1
0...Chiyoke coil, 13...Idling diode, 14...Capacitor, 15...Resistor.

Claims (1)

[Claims] 1 A bridge circuit in which a series circuit of a DC motor and a chiyoke coil constitutes a low resistance side, and a series circuit of a first resistance element and a second resistance element constitutes a high resistance side, is connected to both ends of the DC motor. The first
, a second capacitor connected to a detection terminal on the high resistance side of the bridge circuit, an idling diode connected in parallel to the bridge circuit, and a detection terminal of the bridge circuit. a comparator for comparing the voltage with a reference voltage;
a parallel circuit of a third resistance element and a third capacitor connected between a connection point between the DC motor and the chiyoke coil and a detection side input terminal of the comparator;
A switching transistor is driven by a comparison output signal of the comparator and supplies power to the bridge circuit, and forms an oscillation loop that generates a high-frequency switching carrier between the choke coil, the comparator, and the switching transistor. A switching governor device for a DC motor, characterized in that the switching governor device is configured to supply a pulse current whose average value changes depending on the potential difference between the power supply terminals of the bridge circuit.