JPH0119145B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to rotation control of a heat roll in an electrophotographic printing apparatus when loading paper into the printing apparatus.

FIG. 1 is an example of a diagram showing the principle of an electrophotographic printing apparatus. An outline of the principle will be explained below.

Laser light emitted from a laser oscillator 1 enters an optical modulator 2. Dot data in which the character image has been decomposed is sent to the optical modulator drive circuit 3 that drives the optical modulator 2, so the laser light that enters the optical modulator 2 is modulated according to the dot data. . The modulated laser beam passes through a reflecting mirror 4 and reaches a rotating polygon mirror 5. The laser beam is transmitted by a rotating polygon mirror 5.
The surface of the photosensitive drum 6 is scanned by.
Since the surface of the photosensitive drum 6 is uniformly charged in advance by the charger 7, an electrostatic latent image is formed on the surface of the photosensitive drum 6 each time the laser beam scans. The photosensitive drum 6 rotates at a constant circumferential speed, and the electrostatic latent image is carried onto the developing device 8 and developed by sucking the toner inside the developing device. The developed surface of the photosensitive drum is conveyed to a transfer device 9. Paper 16 is transported by paper feed tractor 10;
It runs in front of the transfer device 9 at a constant speed, and is pressed against the surface of the photosensitive drum 6 by a paper pushing mechanism 11.

The toner image on the surface of the photosensitive drum carried before the transfer device 9 is transferred onto the paper 16 by the transfer device 9. The transferred toner image on the paper is heated through a preheating plate 12, and then transferred to a heat roll 13 heated to a high temperature and a back-up roll 14.
The film is bonded to the paper through heat and pressure and fixed.

The principle of the electrophotographic printing apparatus has been outlined above with reference to FIG.

The temperature of the heat roll 13 is one of the important factors that influences fixing performance. heat roll 13
If the temperature is too low, the fixation will be incomplete and the character image on the paper will peel off. On the other hand, if it is too high, the character image of the toner on the paper is
3, and the attached image may be printed on another part of the paper or the paper may become yellowed. Therefore, the temperature of the heat roll 13 is controlled to be kept substantially constant. Further, in order to be able to start printing and fixing at any time, the temperature of the heat roll 13 is controlled to be kept constant even in the non-printing state.

Temperature control of the heat roll is generally performed using a non-contact type temperature sensor. FIG. 2 is a diagram showing an example of the principle. In the figure, 17 is a temperature measuring element, 18 is a sensor head for sensing the signal from the temperature measuring element, 19 is an amplifier for amplifying the signal from the sensor head, 20 is a counter,
21 is a flip-flop, 23 is an electronic switch drive circuit, 22 is an electronic switch, and 24 is a heat roll drive motor. The temperature of the heat roll is controlled by this method by placing the temperature measuring element 17 attached to the surface of the heat roll facing the sensor head 18. Furthermore, the heat roll is continuously rotated in order to keep the surface temperature of the heat roll as uniform as possible.
That is, the temperature of the heat roll 13 is measured by the temperature measuring element 1.
7, and when the temperature measuring element faces the sensor head 18, it is determined based on the signal from the sensor head whether or not to energize a heater for heating the heat roll (not shown). If the temperature of the temperature sensing element 17 is higher than the detection temperature unique to that temperature sensing element, even if the temperature sensing element 17 faces the sensor head 18, the signal from the sensor head 18 passes through the amplifier 19 and becomes a signal for setting the flip-flop 21. It won't happen. Since flip-flop 21 is not set, electronic switch drive circuit 23 is not energized. Therefore, since the electronic switch 22 is not driven, the heater for heating the heat roll (not shown) is also not energized.

When the temperature of the temperature sensing element 17 is lower than the detection temperature unique to that temperature sensing element, when the temperature sensing element 17 faces the sensor head 18, the signal from the sensor head passes through the amplifier 19 to the flip-flop 21.
It becomes a signal to set the flipflop 21
The signal that sets the counter 20 also has the function of resetting the counter 20. When the flip-flop 21 is set, the electric switch driving circuit 23 is energized, so that the electronic switch 22 is driven to energize a heater (not shown) for heating the heat roll. On the other hand, the counter 20 reset by the signal that sets the flip-flop 21 is
It is counted up by the clock signal CLK1. When the counter 20 counts up to a predetermined value, the signal from the counter 20 resets the flip-flop 21. When flip-flop 21 is reset, electronic switch drive circuit 23 is de-energized. Therefore, the electronic switch 22 is no longer driven;
Electricity is no longer supplied to the heater for heating the heat roll (not shown). However, when the temperature sensing element 17 and the sensor head 18 face each other next, if the temperature of the temperature sensing element is lower than the detection temperature unique to that temperature sensing element, the signal from the sensor head 18 is transmitted to the amplifier 1.
9, set the flip-flop 21,
Since this becomes a signal to reset the counter 20, the above operation is performed again.

Since the temperature of the heat roll is controlled based on the principle as explained above, the heat roll is continuously rotated even in a non-printing state.

In an electrophotographic printing apparatus as shown in FIG. 1, sheets are loaded in advance up to the sheet folding device 15 before printing is started. When loading paper to the paper folding device 15, the starting edge of the paper must be passed between the continuously rotating heat roll 13 and the back-up roll. At this time, the starting edge of the paper sometimes got caught up in the continuously rotating heat roll 13. The heat roll 13 is generally at a high temperature of over 100°C,
It is not easy to remove the paper that has been tangled up.
It was extremely inconvenient.

An object of the present invention is to control the temperature of the heat roll to be kept almost constant in order to eliminate the above-mentioned drawbacks of the prior art and to enable printing and fixing to be started at any time.

The present invention focuses on the following points and attempts to control the heat roll so that it rotates intermittently only during the paper loading operation.

If the temperature sensing element is opposed to the sensor head, the temperature of the heat roll can be detected.

When the temperature measuring element faces the sensor head, if the temperature of the temperature measuring element is lower than the detection temperature unique to the temperature measuring element, the heater for heating the heat roll is energized for a specified period of time.

Since the heat roll has a large heat capacity, its temperature will not drop suddenly.

It takes time for the printed surface to reach the heat roll, and the heat roll reaches a predetermined temperature within that time. (When the paper loading operation is finished, the heat roll is rotated continuously.) Since the heat roll is not continuously rotated, there is less static electricity generated on the heat roll and the paper, and the paper is heated. No more sticking to the roll.

FIG. 3 is a diagram showing an embodiment of the present invention.

[1] Configuration 24 is a heat roll drive motor for driving the heat roll.

27 is a motor drive circuit for supplying current to the heat roll drive motor 24.

26 is a heat roll control circuit for controlling the rotation of the heat roll during non-printing and during printing, respectively.

32 is a counter for setting the period of intermittent rotation of the heat roll.

33 is a one shot for canceling the rotation prohibition instruction to the motor drive circuit 27. In other words, only while this one shot is oscillating,
The rotation prohibition signal (output signal of the AND gate 30) to the motor drive circuit 27 becomes "absent".

(When the output signal of the AND gate 30 is at High level, rotation of the heat roll is prohibited.) [2] Explanation of signal name TRAC PAPER SHT-P: When paper is set on the paper feed tractor 10,
This is a signal that becomes high level.

A SIG-P: This is a high level signal that is generated when starting the operation of setting paper in the printing device.

B SIG-N: This is a low level signal that is generated when the operation of setting paper in the printing device is completed.

[3] Operation Description First, the method of loading paper into the printing device will be explained using FIG. 1. In FIG. 1, when loading paper, the paper is transferred to the paper feed tractor 10.
The paper is further conveyed to a paper folding device 15 through a preheating plate 12, a heat roll 13, and a back-up roll 14.

Although not described in this specification, a function for operating only the paper feed tractor 10 is generally provided. Therefore, even after the paper is set on the paper feed tractor 10, the paper can be sent out by the paper feed tractor 10. The sent paper is carried to the paper folding device 15 as described above. Before passing the paper between the preheating plate 12, the heat roll 13, and the back-up roll 14, various levers, etc., which are not shown in FIG. 1, are provided to make it easier to pass the paper through. do. (Release the various levers, etc.) After the paper has been conveyed to the paper folding device 15, the various levers mentioned above are locked in order to finally set the paper. This completes loading paper into the printing device.

How the heat roll 13 operates in the present invention when the sheet is loaded into the printing apparatus as described above will be described with reference to FIG. When paper is set on the paper feed tractor 10,
TRAC PAPER SET-P signal becomes High level. Next, before passing the paper between the preheating plate 12, the heat roll 13, and the back-up roll 14, when a heat roll opening/closing lever (not shown) provided to make it easier to pass the paper through is operated, the heat roll A paper loading signal generating means consisting of a roll opening/closing lever and a switch linked thereto generates the A SIG-P signal, which becomes High level. At this time, the flip-flop 29 is set by the output of the NAND gate 28. When flip-flop 29 is set, its 0 side output is
The output of the OR gate 31 becomes low level, and the output of the OR gate 31 no longer resets the counter 32. From this point on, the counter 32 is counted up by the clock signal CLK2. When counter 32 counts up to a predetermined number, its output triggers one shot 333. Therefore, the one shot 33 oscillates. The output of the AND gate 30 is at a low level during the period when the one shot 33 is oscillating, and since there is no rotation inhibition signal, the motor drive circuit 27 rotates the heat roll drive motor 24.

When the oscillation of the one shot 33 stops, the output of the AND gate 30 goes high again, a rotation prohibition signal is sent to the motor drive circuit 27, and the rotation of the heat roll drive motor 24 is stopped.

On the other hand, when the one shot 33 oscillates, the one shot 34 oscillates due to its first side output, and the first side output of the one shot 34 resets the counter 32 through the OR gate 31. Since the flip-flop 29 remains set, the counter 32 is counted up again by the clock signal CLK2. The above-mentioned operations are then repeated. That is, while the flip-flop 29 is set, the heat roll drive motor 24 rotates intermittently.

After the paper has been conveyed to the paper folding device 15, when the heat roll opening/closing lever is locked in order to finally set the paper, the B SIG-N signal becomes Low level and the flip-flop 29 is reset. be done. The paper loading signal corresponding to the state from the start to completion of paper loading is the set state from when the A SIG-P signal goes high until the B SIG-N signal goes low. Generated as a flip-flop output signal. flipflop 29
When is reset, its 1st output becomes low level, so the output of AND gate 30 also becomes low level.
become the level. Therefore, the motor drive circuit 27
The rotation prohibition signal disappears. That is, since the flip-flop 29 has been reset,
The heat roll drive motor 24 does not rotate intermittently, but is continuously rotated by the heat roll control circuit 26.

As can be seen from FIG. 2, even if the heat roll drive motor 24 rotates intermittently, the temperature detection element 17
and the sensor head 18 may be opposed to each other. The operation when facing each other is as already described above. That is, although it is not shown in FIG. 2 for one facing, if the heater for heating the heat roll is energized, the counter 20 that has been reset is set to a predetermined value by the clock signal CLK1. Power is supplied only until the value is counted up.

Further, since heat rolls generally have a large heat capacity, the temperature does not drop suddenly.

As explained above, the present invention rotates the heat roll intermittently when loading paper into a printing device,
After paper loading is completed, it is intended to rotate continuously. Moreover, this can be done without lowering the temperature of the heat roll.

According to the present invention, since the rotation of the heat roll is intermittently during the paper loading operation,
It is possible to obtain the effect that static electricity is less generated on the heat roll and the paper, and the paper is no longer wrapped around the heat roll.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of an electrophotographic printing device.
In the figure, 1 is a laser oscillator, 2 is an optical modulator,
3 is an optical modulator drive circuit, 4 is a reflecting mirror, 5 is a rotating polygon mirror, 6 is a photosensitive drum, 7 is a charger, 8 is a developing device, 9 is a transfer device, 10 is a paper feeding tractor,
11 is a paper extrusion mechanism, 12 is a preheating plate, 1
3 is heat roll, 14 is back up roll,
15 is a paper folding device, and 16 is paper. FIG. 2 is a block diagram showing the principle of temperature control of the heat roll. In the figure, 17 is a thermometer element;
18 is a sensor head, 19 is an amplifier, 20 is a counter, 21 is a flip-flop, 22 is an electronic switch, 23 is an electronic switch drive circuit, 24 is a heat roll drive motor, and 25 is a power source. FIG. 3 is a block diagram showing one embodiment of the present invention. In the figure, 26 is a heat roll control circuit, 27 is a motor drive circuit, 28 is a NAND gate, 29 is a flip-flop, 30 is an AND gate, 31 is an OR gate, 32 is a counter, and 33 and 34 are one shots.

Claims (1)

[Claims] 1. A heat roll, a heat roll drive motor, a drive circuit that drives the heat roll drive motor, a control circuit that controls the drive circuit to continuously drive the heat roll to rotate when the printing device is operated, and a printing device. a paper loading signal generation means for generating a signal indicating a paper loading period from the start of paper loading to the completion of paper loading in the paper running system of the paper loading system; A means for intermittent rotation of the heat roll, comprising means for transmitting the rotation prohibition signal for a period of time, means for counting the duration of the rotation prohibition signal, and means for canceling the prohibition signal for a specified time when the count of the counting means reaches a predetermined number. A heat roll control method for an electrophotographic printing device, characterized in that the heat roll is driven to rotate intermittently when paper is loaded.