JPS6371871A - Toner density controller for copying machine - Google Patents

Abstract

PURPOSE:To execute toner density control with high precision and to always maintain stable and appropriate picture density by variably controlling the oscillation frequency of a reference oscillator in accordance with a temperature and a humidity detected by means of a temperature detector and a humidity detector under operation. CONSTITUTION:In a micro computer system, programs for executing various kinds of processings are stored in a ROM8, and the addresses are designated by a program counter 14. An instruction read from the ROM8 is set in an instruction register 16, and a decoding control part 17 decodes an instruction code. With an accummulator 12 as one operand, all operations are executed. Namely, if an operation instruction is set in the register 16, the address part of the instruction reads the operand from a RAM 9, and the operation of the operand and the contents of the accummulator 12 is executed in an operation part 11, and the result is stored in the accumulator 12. If an input/output instruction is set, an outside device is selected through an interface 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Section IIF This invention relates to a toner concentration control device for a developer consisting of a magnetic carrier and a resin toner in a dry plain paper copying machine.

As shown in the block diagram of FIG. 1, a conventional toner density control device for such a dry two-component developer uses a detection coil 1, which is an air-core solenoid coil, to flow the developer through it. The oscillation frequency fi of the oscillator 2 is determined by using the fact that the reactance changes depending on the mixture ratio of the carrier (iron powder) and toner (styrene resin: insulating) in the developer, and the resonance frequency changes. The toner concentration is detected and converted to j! by the comparator 3. Compare the base frequency f2 from the quasi-oscillator 4, and calculate the change Δf (Δf=f
, -f) is certain, 7! When the standard is exceeded, amplifier 5
Some devices replenish toner by driving a relay or the like on the toner replenishing device i2 via a toner replenishing device.

In this device, if the reference frequency f2 is set to be equal to the oscillation frequency f of the oscillator 2 at one time of proper toner, the toner concentration will always be controlled to be proper.

However, as a result of various experiments, it has become clear that the above-mentioned oscillation frequency f varies depending on the temperature and humidity even when the toner concentration is the same.

Therefore, the conventional toner concentration control device as shown in FIG. 1 cannot always accurately detect toner concentration, so there is a problem in that highly accurate toner concentration control cannot be performed.

OBJECTS It is an object of the present invention to solve the above-mentioned problems, to enable highly accurate toner density control, and to always maintain a stable and appropriate image density.

(2) In order to achieve the above-mentioned objects, the present invention includes: an oscillator that outputs a signal with an oscillation frequency that corresponds to the toner concentration of a developer made of a magnetic carrier and a resin toner based on the resonance frequency of a detection coil; and 1. an oscillation frequency variable means. a reference oscillator that outputs a signal at a reference frequency, a comparator that compares the output signal of the advance oscillator and outputs a signal according to the frequency difference, and replenishes toner using the output signal of the comparator. a toner replenishing device that detects the temperature and humidity inside the copying machine; a temperature detection device and a humidity detection device that detect the temperature and humidity inside the copying machine; The present invention provides a toner concentration control device for a copying machine characterized by comprising means for controlling an oscillation frequency variable means of an oscillator and correcting the oscillation frequency.

Hereinafter, a detailed explanation will be given based on one embodiment of the present invention.

FIG. 2 is a diagram showing the architecture of a microcomputer system used in a copying machine to which the present invention is applied.

In the figure, 7 is a central processing unit (hereinafter abbreviated as "r'cpU"), and arithmetic units 11. Accumulator 12
and index register 13. Program counter 1
4. It also includes a counter stack 15, an instruction register 16, a decoding control section 17, and the like.

8 is a fixed storage device for program storage (hereinafter referred to as FROMJ).
9 is a constant speed access memory device (hereinafter abbreviated as rRAMJ) for storing data, and 10 is an input/output interface.

In such a microcomputer system,
Programs for performing various processes are stored in the ROM 8, and their addresses are designated by the program counter 14. The instruction read from the ROM 8 is set in the instruction register 16, and the decoding control unit 17
The instruction code is decoded by

All operations are performed with accumulator 12 as one operand. That is, when an arithmetic instruction is placed in the instruction register 16, an operand is read from the RAM 9 by the address field of the instruction, and an operation between this and the contents of the accumulator 12 is executed in the arithmetic unit 11.
The result is stored in the accumulator 12. Also,
In the case of an input/output command, an external device is selected through the input/output interface 10, and the contents of the accumulator 12 are transferred to the external device, or data and flags are transferred from the external device to the accumulator 42.

The index register 13 is used for address modification, and the counter stack 15 is used as nesting of subroutines.

FIG. 3 shows an embodiment in which the present invention is applied to a copying machine controlled by a microcomputer as described above.
FIG. 2 is a block diagram showing the relationship between a microcomputer, a temperature sensing device, and a humidity sensing device.

In the figure, 11 is a microcomputer with ROM8
The program includes a program for the copying process, a program for checking abnormalities and safety, a program for correcting the reference frequency according to temperature and humidity (described later), and the elapsed time after the copying machine stops operating (hereinafter simply referred to as "stop time"). A program for correcting the base frequency at the initial stage of operation is stored.

The RAM 9 stores various input data and stop time data during the copying operation. The microcomputer 11 is backed up by a battery or the like so that it continues to operate even when the copying machine is turned off.

Various signals are exchanged with the copying machine through the input/output interface 10 of the microcomputer 11, and sequence control of the copying process, monitoring of ambient conditions, abnormality and safety checks, and display are performed. , illustration of parts not directly related to this invention is omitted.

The temperature inside the copying machine is detected as a voltage signal by a temperature detection device using a temperature sensor 20 such as a thermistor or thermocouple, which is amplified by an amplifier 21 and then sent to an A-D converter 2.
2 is converted into a digital number 43 and input to the input/output interface 10 of the microcomputer 11.

Similarly, the humidity inside the copying machine is detected as a voltage equal sign by a humidity detection device using a humidity sensor 23 such as a crystal sensor, and is sent to the input/output interface 10 as a digital signal via an amplifier 24 and an A-D converter 25. is input.

INT is an interrupt signal generated when the power of the copying machine is turned off, that is, when the operation is stopped and the developer is no longer stirred and flowed.

FIGS. 4 and 5 are diagrams showing different examples of means for generating this interrupt signal and measuring the stop time.

In either case, the microcomputer 11 is backed up by a battery E so that only the microcomputer 11 can operate even if the power is turned off.

And fl! When the if switch is on, AC?
? ! The microcomputer 11 is powered by a DC power source obtained by rectifying and smoothing the power supply, and a capacitor C is charged to the DC power supply voltage via a resistor R.

Therefore, when the power switch is turned off, the power plug is pulled out, or the power is turned off due to a power outage, etc., the electric charge stored in the capacitor C starts discharging via the resistor R and the power supply circuit, and the electric charge at point a The potential of D CM11 decreases, and D CM11
The position detection sensor detects this, inverts its output, and issues an interrupt signal to the microcomputer 11, "Dl."

D2 is a diode for preventing backflow.

In the case of FIG. 4, upon input of the interrupt signal, the clock pulses are counted using the clock oscillator built in the microcomputer 11 and stored in the RAM 9 of FIG.

The example in FIG. 5 can be applied when the ACm source is supplied even when the power switch is off. l! The source input is half-wave rectified by diode D3, and Schmitt buffer 27
The waveform is shaped into a square wave pulse by
The data is inputted to the microcomputer 11 via the input/output interface 10 shown in the figure to be counted.

The stop time 31 determined by counting these pulses is:
It is executed after entering the interrupt processing routine after an interrupt occurs.

OUT, ~OUT in FIG. 3 indicates that CPtJ7 is in RO according to temperature and humidity data and stop time data.
As a result of calculation 2 determination based on the correction program written in M8, the signal is outputted through the input/output interface 10, and the reference frequency, that is, the oscillation frequency of the reference oscillator is controlled by this signal.

The basic configuration of the toner concentration control device of this embodiment is the same as that shown in FIG. By controlling this, the reference frequency f2 is corrected.

As the reference oscillator, an LC circuit, a PLL (phased locked loop), an IC oscillator, etc. can be used. In that case, it is easy and cost-effective to digitally select the values necessary for correction. It can be done cheaply.

FIG. 6 is a circuit diagram of an embodiment in which SigneTex's timer IC (NE/5E555) is used as the reference oscillator. In this case, the oscillation frequency f, / is the resistance R
It is determined by the value of A s RB and the capacitor Cx (the combined capacitance of the connected capacitors among c1 to C), and is expressed as follows. S and ~S are analog switches, and the output signal OUT of the microcomputer 11 shown in Fig. 3 is connected to each control terminal.
, ~0UT4 are applied, and when 1° is applied to the control terminal, the analog switch is turned on, and the capacitor connected in series with it is connected to the oscillation circuit.

Therefore, all outputs of the microcomputer 11 are 0.
°, when all analog switches Si to Ss are off, only capacitor Cs is connected, and the oscillation frequency f,
I is f z '” 1-46 / (RA + 2 RB
) Cs, and if this is the reference frequency without correction, when one or more of OUT, ~OUT, reaches 1°, the analog switch controlled by it turns on, and the correction capacitor Any one or more of C8 to C9 is inserted in parallel to capacitor C6, and the oscillation frequency f2'' is lowered to correct the reference frequency.

FIG. 7 shows an embodiment in which an oscillator using an LC circuit is used as the reference oscillator.The reference oscillator 4' has an oscillation coil L, and the iron core 31 is connected to the coil L to drive a pulse motor 32 or the like. The reactance of the coil L is changed by changing the reactance of the coil L, thereby changing its oscillation frequency.

In this case, the oscillation frequency f21 becomes f2' 1/2xfr, and the correction frequency Δf becomes Δf1/2πf, where ΔL is the reactance change of the coil L.

In this case as well, the position of the iron core 31 may be controlled by sending rotation pulses from the pulse motor 32 using the output OUT of the microcomputer 11 shown in FIG. A linear motor may be used instead of a pulse motor.

Next, in these embodiments, a specific example of correction of the reference frequency f2 with respect to a change in the oscillation frequency f of the oscillator 2 corresponding to the resonant frequency of the detection coil 1 shown in FIG. 1 due to temperature and humidity will be described.

FIG. 8 is a characteristic curve showing the change in the oscillation frequency f in a developing agent with an appropriate toner concentration depending on the temperature and humidity obtained by repeating various experiments, and the reference frequency f2 is corrected accordingly. There is a need.

To give a concrete numerical example of the frequency curve F~F, F:
580KHz F, : 578KHz F, : 576
KHzF: 574KHzF, 8572KHz
F: 570KHz. However, this value varies depending on various conditions and is determined experimentally.

In Figure 8, the X-axis shows temperature (°C) and the Y-axis shows humidity (%).1For example, if we break down the x and y factors into 8 bit patterns and redraw Figure 8, we get Figure 9. This results in 64 combinations.

Temperature is decomposed into 8 bits between 0 and 50℃, and humidity is between 0 and 50℃.
90% of the data is broken down into 8 bits.

The larger the number of decomposition bits, the more accurate control can be expected, but when using a microcomputer, about 8 bits is appropriate.

When the X-axis is assigned to the A register in the CPU 7 of the microcomputer 11 and the Y-axis is assigned to the B register, the results are as shown in FIGS. 10(A) and 10(B).

Correction data corresponding to the characteristic curve of FIG. 9 is isometrically stored in the ROM 8 of FIG.

The CPU 7 collates the A1 register and the B register according to an arithmetic instruction, determines where the bit is set among bits D0 to D7, and selects data corresponding to the set bit 1- from the ROM 9.

For example, when the total temperature is 35°C and the humidity is 60%, the A register will contain the information shown in Figure 10 (c).

Assume that the B register has a value of 1° as shown in FIG.

The CPU 7 determines that these are A register (040), B register (010), and when they are ORed, A+B has a bit pattern as shown in Figure 10 (e), so (0
50), and the corresponding frequency curve F2
pick out.

Then, output the output that should set the reference frequency to F2 through the input/output interface 10, and turn on any of the analog switches 81 to S in the reference oscillator in FIG. 6, for example, so that the oscillation frequency becomes F2. Make it.

Next, correction for the transient stirring characteristics at the initial stage of operation will be explained. It has been experimentally confirmed that the bulk density of the developer changes depending on the stop time, and that the oscillation frequency f at the beginning of the start of operation changes depending on the stop time, as shown in FIG. 11, for example.

However, the temperature and humidity shall be kept constant.

Therefore, the relationship between this stop time and frequency is stored in ROM9.
According to the count data that is the measured value of the stop time mentioned above, the CPU 7 selects the frequency to be corrected at the beginning of operation, controls the reference oscillator mentioned above, and controls the reference frequency f2 for a certain period of time. Correction can be made.

Figure 12 shows the microcomputer 1 in Figure 3 in that case.
1 is a general flow diagram of toner density control processing according to No. 1, in which stop time data after start (start of operation of the copying machine) is sensed, and the reference frequency is corrected accordingly. After a certain period of time has elapsed, the correction is stopped and returned to the normal value, the temperature and humidity data are sensed, and the reference frequency is corrected accordingly.

These detection and control routines may be stored in subroutines of a computer sequence and called and checked at appropriate times.

In this way, the reference frequency is corrected according to the change in bulk density due to the elapsed time after the copier stops operating, as well as the ambient conditions such as temperature and humidity, so it is possible to always perform highly accurate toner concentration control. , so copies with proper uniform image density are always obtained.

However, as can be seen from Fig. 11, if the copying machine stops operating for a relatively short time, the shift in the oscillation frequency at the start of operation is extremely small, and under normal usage conditions it will last for a long time (for example, 100 hours). Since the copying machine is never left unused during the above period, there is no problem even if the correction of the reference frequency according to the stop time is omitted.

Effects According to the present invention, highly accurate toner density control can be performed at all times, thereby making it possible to always obtain copies with stable and appropriate image density.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional toner density control device to which the present invention is applied, FIG. 2 is a block diagram showing the architecture of a microcomputer system used in a copying machine to which the present invention is applied, and FIG. A block diagram showing the relationship between a microcomputer, a temperature detection device, and the temperature detection device in an embodiment of the present invention; FIGS. 4 and 5 are diagrams showing different examples of stop time measuring means, respectively; FIGS. 6 and 7 The figures are circuit diagrams showing different examples of the reference oscillator in the embodiments of the present invention, Figure 8 is a characteristic curve diagram showing changes in oscillation frequency due to temperature and humidity, and Figure 9 is the X-axis and Y-axis of Figure 8. Figures 10 (a) to (a) are frequency curve diagrams showing each bit pattern broken down into eight bit patterns.
e) is a diagram showing the assignment of the A register and B register in the CPU and an example of the bit pattern during operation; FIG. 11 is a curve diagram showing the relationship between the operation stop time and the oscillation frequency at the initial stage of operation; FIG. 12 This figure is a general flow diagram of toner density control processing by the microcomputer 11 of FIG. 3. 1... Detection coil 2... Oscillator 3... Comparator 4, 4'... Reference oscillator 6... Toner supply device 7... Central processing unit (CPU) 8...
Fixed memory bag rirl (ROM) 9... Constant velocity call ratio storage device (RAM) 10... Input/output interface 11... Microcomputer 20... Temperature a sensor 23... Humidity sensor 26.
...DC? 1st place detection buffer 27...Schmitt buffer 30...Timer ICZr1...Iron core 32...Pulse motor E...Backup batteries 81-S5...Analog switch Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 I □Temperature - snout temperature fiMc) Figure 10 A
register date jisda
1, 1. 10o1000
Q-1+)

Claims (1)

[Claims] 1. An oscillator that outputs a signal with an oscillation frequency according to the toner concentration of a developer made of magnetic carrier and resin toner based on the resonance frequency of the detection coil, and a reference oscillator that has an oscillation frequency variable means and outputs a signal with a reference frequency. a comparator that compares the output signals of the two oscillators and outputs a signal according to the frequency difference; a toner replenishing device that replenishes toner according to the output signal of the comparator; and a temperature and humidity inside the copying machine. a temperature detection device and a humidity detection device for detecting the oscillation frequency of the reference oscillator according to the temperature and humidity detected by the temperature detection device and the humidity detection device during operation of the copying machine; 1. A toner concentration control device for a copying machine, comprising: means for correcting the oscillation frequency.