JPH0119585B2 - - 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. The dot data obtained by decomposing the character image 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.
The paper 16 is fed by a paper feed tractor 10 and runs at a constant speed in front of the transfer device 9, 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 1.
4, and is thermocompression bonded to the paper 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. Moreover, 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, a signal from the sensor head is used to determine 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 does not pass through the amplifier 19 and become a signal for setting the flip-flop 21. . 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 not energized either.

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 is passed 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 electronic switch drive circuit 23 is energized, so the electronic switch 22 is driven to energize a heater for heating the heat roll (not shown). 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 transferred to the amplifier 19.
Since the signal is used to set the flip-flop 21 and 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 leading edge of the paper must be passed between the heat roll 13 and the back-up roll 14, which are continuously rotating. At this time, the 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., and it is difficult to remove the rolled up paper, which is extremely inconvenient.

An object of the present invention is to control the temperature of the heat roll to keep it approximately 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 and alternately clockwise and counterclockwise only during 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. Less 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.

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. That is, 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 a high level, rotation of the heat roll is prohibited.)
The oscillation time of one shot is 1 heat roll.
It is assumed that the time required for the round is set.

35 is a triggerable flip-flop. The output of this triggerable flip-flop is sent to the heat roll control circuit 26 to determine the direction of rotation of the heat roll drive motor. For convenience of explanation, it is assumed that when the output of the triggerable flip-flop 35 is at a high level, the heat roll drive motor rotates clockwise, and when the output of the triggerable flip-flop 35 is at a low level, the heat roll drive motor rotates counterclockwise. .

[2] Explanation of signal names TRAC PAPER SET-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 Figure 1, when loading paper,
The paper is set on the paper feed tractor 10, and then passed between the preheating plate 12, the heat roll 13, and the back-up roll 14, and is conveyed to the paper folding device 15.

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,
The TRAC PAPER SET-P signal becomes High level. Next, before passing the paper between the preheating plate 12, heat roll 13, and back-up roll 14, when a lever provided to make it easier to pass the paper through is operated, the A SIG-P signal is activated.
Becomes High level. At this time, Nand Gate 2
Flip-flop 29 is set by the output of 8. When the flip-flop 29 is set, its 0 side output goes low, and the output of the OR gate 31 no longer resets the counter 32. From this point on, the counter 32 receives the clock signal.
It is counted up by CLK2. When counter 32 counts up to a predetermined number, its output triggers one shot 33. Therefore, the one shot 33 oscillates. When the one shot 33 oscillates, its first side output triggers the triggerable flip-flop 35, so the triggerable flip-flop 35, which has been in the set state, is reset and its first side output becomes Low level. That is, the heat roll drive motor 2
An instruction is given to rotate 4 to the left. Also, when the one shot 33 oscillates, its 0 side output is
Since it becomes a low level, the output of the AND gate 30 becomes a low level. and gate 30
Since the low level output is sent to the motor drive circuit 27, the rotation inhibition state of the heat roll drive motor 24 is released, and the heat roll rotates. Since the heat roll control circuit 26 is instructed to rotate the heat roll drive motor 24 to the left, the heat roll drive motor 24 rotates to the left. The rotation continues only while the output of the AND gate 30 is at a low level, that is, while the one shot 33 is oscillating. In this example, the oscillation time of the one shot 3 is set to correspond to one revolution of the heat roll, so the heat roll makes one revolution and then stops. Further, when the one shot 33 oscillates, its first side output triggers the one shot 34, so the one shot 34 oscillates. The 1 side output of the one shot 34 resets the counter 32 via the OR gate 31.

From the point in time when the counter 32 is reset, the counter 32 is counted up again by the clock signal CLK2. When the counter 32 counts up to a predetermined number, its output triggers the one shot 33. Therefore, the one shot 33 oscillates. One shot 33
When oscillates, its first side output triggers the triggerable flip-flop 35, so the triggerable flip-flop 35 is set this time, and its first side output becomes High level. That is, an instruction is given to the heat roll control circuit 26 to rotate the heat roll drive motor 24 to the left.
Also, when the one shot 33 oscillates, its 0 side output goes to low level, so the AND gate 3
The output of 0 becomes Low level. and gate 3
Since the low level output of 0 is sent by the motor drive circuit 27, the rotation inhibition state of the heat roll drive motor 24 is released, and the heat roll rotates.
Since the heat roll control circuit 26 is instructed to rotate the heat roll drive motor 24 clockwise, the heat roll drive motor 24 rotates clockwise. The rotation continues only while the output of the AND gate 30 is at a low level, that is, while the one shot 33 is oscillating. In this example, as described above, the oscillation time of the one shot 33 is set to correspond to one revolution of the heat roll, so the heat roll makes one revolution and then stops. Also,
When the one shot 33 oscillates, its first side output triggers the one shot 34, so the one shot 34 oscillates. The 1 side output of the one shot 34 resets the counter 32 via the OR gate 31.

Since flip-flop 29 remains set, counter 32 again receives clock signal CLK.
The count is increased by 2. Thereafter, the above-described operations are repeated. That is, while the flip-flop 29 is set, the heat roll drive motor 24 rotates intermittently, and rotates clockwise and counterclockwise alternately.

After the paper has been conveyed to the paper folding device 15, when the various levers are locked in order to finally set the paper, the B SIG-N signal goes low and the flip-flop 29
is reset. When flip-flop 29 is reset, its first output goes to low level, so the output of AND gate 30 also goes to low level. Therefore, no rotation prohibition signal is sent to the motor drive circuit 27. That is, when the flip-flop 29 is reset, the heat roll drive motor 24 rotates continuously. Furthermore, since the flip-flop 35 is set by the 1st output of the flip-flop 29, the 1st output of the flip-flop 35 becomes High level, so the heat roll drive motor 24 always rotates clockwise. This rotation direction is the same as the rotation direction before the heat roll performs the intermittent rotation operation.

Even if the heat roll drive motor 24, ie, the heat roll 13, is rotated as described above, the temperature measuring element 17 and the sensor head 18 can face each other, as can be seen from FIG. 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 reset counter 20 is set in advance by the clock signal CLK1. Power is supplied only until the count is counted up to the specified value.

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

As explained above, the present invention attempts to rotate the heat roll intermittently and alternately to the right and to the left when loading paper into a printing device, and to rotate it continuously after paper loading is complete. It is something. Moreover, this can be done without lowering the temperature of the heat roll.

According to the present invention, when the paper loading operation is performed, the heat roll is rotated intermittently and alternately between left rotation and right rotation.
Static electricity is less likely to be generated on the heat roll and the paper, and the paper is less likely to stick to the heat roll. Also, even if the paper occasionally sticks to the heat roll, it will not wrap around in one direction. This effect can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of an electrophotographic printing apparatus. 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 developer, and 9 is a transfer 10 is a paper feeding tractor, 11 is a paper pushing mechanism, 12 is a preheating plate, 13 is a heat roll, 14 is a back-up roll, 15 is a paper folding device, and 16 is paper. FIG. 2 is a diagram showing the principle of temperature control of the heat roll. In the figure, 17 is a temperature measuring element, 18 is a sensor head, 19 is an amplifier, 20 is a counter, 2
1 is a flip-flop, 22 is an electronic switch, 2
3 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, 33 and 34 are one-shots, and 35 is a triggerable flip-flop. It is.

Claims (1)

[Claims] 1 Heat roll, heat roll drive motor, drive circuit for driving the heat roll drive motor, control circuit for controlling the rotation of the heat roll, and from the start of paper loading until the completion of paper loading means for generating a signal indicating a period of time, means for sending a rotation prohibition signal of the heat roll drive motor to the drive circuit or control circuit during the period, means for counting the duration of the rotation prohibition signal, and the counting means. means for canceling the rotation prohibition signal for a specified time when the rotation prohibition signal reaches a predetermined number;
and a means for reversing the heat roll of an electrophotographic printing device.