JPS6139881A - Speed controller of copying machine - Google Patents

Abstract

PURPOSE:To control the speed of a DC motor constantly even if the load of the motor is varied by supplying an output full-wave rectified from an AC through chopping means and a smoothing circuit to the motor. CONSTITUTION:An AC power output from an AC power source 1 is full-wave rectified by a full-wave rectifier 2, and then applied to a chopper 3. The chopper 3 is pulse-width controlled in response to a signal (a) of a frequency in response to the rotating speed of a motor from a motor position detector 6, a phase reference signal REF, a rotating speed signal C of a DC motor from an F/F converter 8, and a triangular wave (e) from a reference triangular wave generator 10. The output of the chopper 3 is smoothed by a smoothing circuit made of a choke coil 13 and a capacitor 14, and applied to a DC motor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a speed control device for a copying machine,
In particular, the present invention relates to a speed control device for a copying machine that does not require changing the power supply even if the load on the motor increases.

(Prior Art) In a copying machine, a motor for driving an optical device,
Motors used to drive photosensitive drums, motors to drive developing devices, motors to transport copy paper, etc.
There is a method of controlling these motors using a DC motor control method.

In the DC motor control system of this fifth copying machine, a completely smoothed DC power source is used as its power source.

(Problems to be Solved by the Invention) The above-described conventional techniques had the following problems.

As described above, since a completely smoothed DC power source is used as a power source for the DC motor control system, there is a problem in that as the motor load increases, it is necessary to change to a power source with a larger capacity. Moreover, this has caused a problem in that the cost for the power supply increases.

The present invention has been made to solve the above-mentioned problems.

(Means and effects for solving the problems) In order to solve the above problems, the present invention provides a drive motor that includes:
A speed control device for a copying machine using a DC motor includes means for full-wave rectifying alternating current obtained from an AC power source, means for chopping the full-wave rectified output, and smoothing the output of the chopping means to control the output of the DC motor. a phase comparison means for comparing the phase of the rotational position of the DC motor with the phase of the reference speed signal; and a mixing amplification means for mixing and amplifying the output of the phase comparison means and the rotational speed signal of the motor. and pulse width modulation means for converting the output of the mixing amplification means into pulse width information, and the chopping means is controlled by the output of the pulse width modulation means, even if the load of the DC motor fluctuates. The feature is that the speed of the motor is controlled to be constant.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

Further, FIG. 2 shows a time chart of the main signals of FIG. 1. Note that the symbols in FIG. 2 correspond to the symbols in FIG. 1.

An AC voltage output from an AC power source 1 such as a commercial power source is full-wave rectified by a full-wave rectifier circuit 2 .

The full-wave rectified voltage is applied to the chopper 3.

Incidentally, a load 5 such as a photosensitive drum is connected to the DC motor 4 of the copying machine, and the load 5 receives driving force from the DC motor 4 and is driven. Further, a motor position detector 6 such as a tachometer is connected to the DC motor 4, and a signal a having a frequency corresponding to the rotational speed of the motor is output from the motor position detector 6.

Now, if the reference signal REF input to the phase comparator 7 has a waveform as shown in FIG. 2, and the signal a has the waveform shown in FIG. A high level signal is output only during the phase lag period as shown in FIG. 3(C). Note that the waveform in Figure 2a is
This shows that the load 5 connected to the DC motor 4 increases between pulse a1 and pulse a2, and the phase of signal a changes.

The F/V (frequency/voltage) converter 8 is a circuit that converts the frequency of the signal a into a DC voltage. For this reason, F/
The V (frequency/voltage) converter 8 outputs a signal C which is a DC voltage corresponding to the rotational speed of the DC motor 4.

The signal C is a mixed amplifier (M
ixingAmp) 9. As a result, the output signal C of the phase comparator 7 is compared with the output signal C of the F/V (frequency/voltage) converter 8, and an output corresponding to the difference is smoothed and output. Output signal d of the mixing amplifier 9
The waveform of is approximately as shown in FIG. 2(d). 10 is a reference triangular wave generation circuit, which outputs a signal having a waveform as shown in FIG. 2(e).

The output signal d of the mixing amplifier 9 and the triangular wave e outputted from the reference triangular wave generating circuit 10 are input to a comparator 11,
Their sizes are compared. The comparator 11 determines that the signal e is d
Outputs a high level signal when the value is greater than 1. Therefore, the output signal of the comparator 11 has a PWM (pulse width modulation) waveform as shown in FIG.
The pulse width of pulse f1 in Figure (f) is thicker than the pulse width of pulse f2.

The output signal f of the comparator 11 is transmitted to the pulse transformer 12
is applied to the chopper 3 via.

The chopper 3 can be constructed of, for example, a PNP transistor, and since the signal is applied to its base, the chopper 3 is conductive only when the signal f is at a low level, and becomes non-conductive when the signal f is at a high level. .

Therefore, when the rotation speed of the DC motor 4 becomes slower, the conduction period of the chopper 3 becomes longer, and conversely, when the rotation speed of the DC motor 4 becomes faster, the conduction period becomes shorter. Figure 2 (0)
The shaded area indicates the waveform of the output signal of the chopper 3.

The output signal g of the chopper 3 is smoothed by a smoothing circuit made up of the choke coil 13 and the capacitor 14, and converted into a direct current. This DC voltage is applied to the DC motor 4 to operate it.

In this embodiment, when the load 5 increases and the rotational speed of the DC motor 4 slows down, the conduction period of the chopper 3 becomes longer and the voltage applied to the DC motor 4 becomes larger.

Therefore, the rotational speed of the DC motor 4 is increased until the output signal a of the motor position detector 6 matches the frequency of the reference signal REF. Conversely, when the load 5 decreases and the rotation speed of the DC motor 4 increases, the conduction period of the chopper 3 becomes shorter and the voltage applied to the DC motor 4 becomes smaller. Therefore, the rotational speed of the DC motor 4 is delayed until the output signal a of the motor position detector 6 matches the frequency of the reference signal REF.

Furthermore, according to the present embodiment, even if the load 5 becomes larger or smaller, there is no need to change the capacity of the AC power supply 1, making handling convenient and reducing costs.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved.

In a DC motor control system for a copying machine, there is no need to change the AC power supply even if the motor load increases, making handling convenient and reducing costs.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a time chart of the main signals of FIG. 1.

Claims (1)

[Claims] (1) In a speed control device for a copying machine using a DC motor as a drive motor, there is provided a means for full-wave rectifying alternating current obtained from an alternating current power source, a means for chopping the full-wave rectified output, and a means for chopping the full-wave rectified output. means for smoothing the output and applying it to the DC motor; phase comparison means for comparing the phase of the rotational position of the DC motor with the phase of the reference speed signal;
A mixing amplification means for mixing and amplifying the output of the phase comparison means and the rotational speed signal of the motor, and a pulse width modulation means for converting the output of the mixing amplification means into pulse width information,
A speed control device for a copying machine, characterized in that the chopping means is controlled by the output of the pulse width modulation means so that the speed of the DC motor is controlled to be constant even if the load on the DC motor fluctuates.