JPS5852668A - Heat fixing roller - Google Patents

Abstract

PURPOSE:To obtain a device which holds set temperature, specially, fixing ready temperature sufficiently even on inferior conditions while suppressing the rotation of rollers as much as possible. CONSTITUTION:In a timer 20, the time (t) when the temperature of a heat roller 1 attains to set temperature T1 on limit conditions of a power voltage and ambient temperature where a failure in fixing does not occur due to heat transfer from the heat roller 1 to a press-contacting roller 3 is set. When the time when the surface temperature of the heat roller 1 rises up to the set temperature T1 is shorter than the time (t) of the timer 20, the output of a comparator 7 is inverted from ''H'' to ''L'' before an AND gate 18 is opened, setting a flip-flop 8. Consequently, one input to the AND gate 18 goes down to ''L'' and the AND gate 18 is never opened even if the timer 20 generates an output. Therefore, a transistor 10 is still turned off and neither the heat roller 1 nor the press-contacting roller 3 rotates.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing section of an electrophotographic copying machine, and more particularly to a heat fixing roller that includes rollers that are pressed against each other and that is provided with a heat source on the roller that comes into contact with a cri toner image on a copy sheet without being fixed. .

Generally, a heat fixing roller is composed of two rollers, an upper and a lower roller, and the ten rollers that mainly come into contact with the toner image transferred onto the copy paper are heat rollers that have a heater inside.
The lower roller is a pressure roller that is pressed against the second heat roller. Normally, after the power is turned on for these two rollers, when the temperature at the temperature detection position of the upper roller reaches a predetermined temperature, the ready lamp will light to indicate that copying is possible, and printing will begin in this state. When the button is pressed, the drive motor rotates for the first time and is energized. The reason why the rotation of the drive motor is started as late as possible is to avoid operating the device as much as possible when unnecessary.

Here, the heat fixing roller is provided with a temperature detection means, and after a predetermined temperature is detected by the detection means, the temperature control circuit maintains the predetermined temperature. be controlled in order to Normally, the above rollers are controlled to a set temperature, but if the power supply voltage is lower than a predetermined voltage, or if the ambient temperature is lower than the normal temperature, it will be difficult to control the temperature to a predetermined temperature for the following reasons. .

As mentioned above, the heat fixing roller has a built-in heater only in the lower roller of the upper and lower rollers, and at this time, heat is transferred from the heater to the roller 1 and then mainly to the upper roller. It is transmitted to the lower roller from the contact portion between the roller and the lower roller. However, since neither roller rotates until the ready lamp is turned on, the above-mentioned contact area () is always the same part. The temperature of the parts of the roller other than the contact area is close to the ambient temperature.

In this state, when you press the print button and start the copying process, the heat recording and fixing roller rotates as the aforementioned drive motor rotates, but at this time, the temperature has risen to a predetermined temperature and Since the roller is in contact with the lower roller, which is at approximately the ambient temperature, the upper roller will lose the heat of the human face. Even so, under normal conditions and conditions, the temperature control circuit for the heat fixing roller increases the input to the heater in the roller to maintain the temperature of the second roller at a predetermined temperature. is possible.

However, if the ambient temperature is low or the power supply voltage is lower than the specified voltage, it is not possible to supply the same amount of heat as the heat taken away even if the input to the heater is increased as much as possible. First, the temperature of the upper roller inevitably falls not only below a predetermined temperature but also below the lower limit temperature for fixing. Therefore, even if the copy paper holding the transferred toner image on its surface passes through this thermal fixing roller, the fixing of the toner image is incomplete.

Therefore, the present applicant proposed Japanese Patent Application No. 56-102686B "Thermal Fixing Roller". This is done by rotating the pressure roller, which is the lower roller, until, for example, the heat roller reaches a set temperature.This preheats the pressure roller and minimizes the heat transferred to the pressure roller during copying. This is to maintain the surface temperature of the heat roller at a fixing temperature even under conditions where the fixation is not possible.

However, according to the above invention, both rollers are always rotated regardless of the ambient temperature or power supply voltage, and the idea of avoiding rotation of the rollers as much as possible is not satisfactory. Therefore, if the rollers were to be constantly rotated, there would be problems with noise or durability.

The present invention provides an apparatus capable of suppressing the rotation of the roller as much as possible and sufficiently maintaining the set temperature, especially the fixing temperature, even under adverse conditions.

That is, the present invention stops the roller without rotating it under normal conditions, and rotates the roller only under non-normal conditions. Therefore, in order to determine whether the conditions are normal or not, the present invention makes the determination based on the time it takes for the heat roller to reach the set temperature. The time required for the hot roller to rise is always constant under certain conditions, and this time can be easily determined through experiments and the like. Therefore, it is also possible to determine the rise time under the limit conditions of the power supply voltage and ambient temperature in which fixing failure does not occur due to heat being taken away from the heat roller by the pressure roller. In other words, if the heat roller reaches the set temperature within the rising time under the limit conditions, the fixing temperature can be maintained even if copying is performed thereafter, and fixing failure will not occur.

According to the present invention, the following time period is set, and when the time required for the heating roller to rise to the set temperature exceeds this time period, both rollers are rotated to preheat the pressure roller, thereby preventing fixing failure.

Hereinafter, the heat fixing roller of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a side sectional view showing a heat fixing roller according to the present invention. In the figure, an upper roller 1 is a heat roller equipped with a heater 2 inside, a lower roller 3 is a pressure roller that is pressed against a heat roller 1 with an appropriate pressure, and these rollers 1,
3 constitutes a heat fixing roller. By rotating the rollers 1 and 3 in the direction of the arrow, the fed copy paper 4 is sandwiched between the rollers 1 and 3, and the toner image 5 formed on the upper surface is fixed by the heat of the heat roller 1. The rollers 1 and 3 are driven by rotation of a main motor (not shown).

FIG. 2 is a circuit diagram for driving the heater 2 of the heat roller 1, which controls the drive of the rollers 1 and 3 of the present invention with respect to the set temperature T1 of the surface of the heat roller 1. Reference numeral 6 in the figure represents a temperature detection element that is attached to the surface of the heat roller 1 shown in FIG. 1 and detects the surface temperature of the heat roller I. For example, as the temperature increases, the resistance value decreases →
→ No. 6 (resistance R4Lf)
is connected in series with resistor R3, and the voltage between it and the ground is V)
is supplied. Resistors R1 and R2 are connected in parallel to this series connection circuit of thermistor 6 and resistor R3.

Further, reference numeral 7 is a comparator for maintaining the heat roller 1 at a set temperature, and the negative terminal is divided by resistors R1 and R2, which is the reference value of the set temperature (180°C), and the voltage is applied to the + side of 7. Attach a →no-miscro resistor R4 to the terminal and a resistor of 180℃ or higher (
(or equal), the output of the comparator 7 is inverted to ■, ``''. In other words, if the temperature is below the set temperature T1, the output of the comparator 7 is 'I(').

The output of this comparator 7 is supplied to the set input terminal - of the flip-flop 8.
is set when the output power of the comparator 7 is "L"'. The reset input terminal of the flip-flop 8 is supplied with an initial reset signal IR output when the copying machine is powered on.

The reset output Q of this flip-flop 8 is supplied to one input terminal of an AND gate 18. The output of this AND gate 18 is supplied to the base of a transistor 10 via an OR gate 9. transistor 10
is a switching element for supplying the voltage "-■" to the main motor relay 11 for rotating the main motor M. That is, the base of the transistor 10 is "IT"
Then, the transistor 10 becomes conductive, the relay 11 is energized, and its contacts are turned on, causing the main motor M to rotate.

The set output Q of the flip-flop 8 is supplied to the base of a transistor 12 via an AND gate 19, and by switching the transistor 12, the ready lamp 13 is driven to blink.

Further, the output of the comparator 7 is supplied to the base of the transistor 14 and drives the heater control circuit 15.

If the output of the comparator 7 is lower than "IT'", that is, the set temperature (180° C.), the voltage +V is supplied to the heater control circuit 15, and the heater 2 of the heat roller 1 is controlled to be supplied with power. As a result, the temperature of the heat roller 1 is increased, and when the set temperature is reached, power supply to the heater 2 is stopped.

Historically, control signals from the copying process control circuit 16 are supplied to other input terminals of the OR gate 9. The copying process control circuit 16 performs well-known copying control according to the human power of operating the print switch 17. When driving the main motor M, the copying process control circuit 16 sends a drive signal ('T('') to the OR gate 9. This copying process control circuit 1 outputs
6 executes copying control in response to the operation of the print switch 17, but if the copying is possible (ready) state, that is, the heat roller 1 has not reached the set temperature, a control signal is output without executing copying control. There's nothing to do.

A signal from the copying process control circuit 16 is supplied to the other input terminal of the AND gate 19.

The confidence from the control circuit 16 is "■,"' when the copying machine is in operation, and "'" when the copying machine is stopped.
H"'. In other words, if the print switch 17 is operated when copying is possible, AND gate 1 is activated.
One input terminal of 9 becomes ■7", and the AND gate 19
The output becomes It L"'. Therefore, the ready lamp 13 goes out.

Further, the other input terminal of the AND gate 18 is supplied with a signal from a timer 20 which is a time setting means. As explained above, this timer 20 operates under the conditions of the power supply voltage and ambient temperature limits that will not cause fixing failure due to heat being taken away from the heat roller 1 by the pressure roller 3.
A time t for the heat roller 1 to reach the set temperature TI is set.

This time [is set with some safety factor in mind. The timer 20 counts the time from when the power is turned on, and the time E
This is a time circuit that outputs "II"' after the elapse of time and is cleared when the power is turned off.

-1- In the circuit configuration described above, the operation thereof will be explained according to the time charts shown in FIGS. 3 and 4.

First, explanation will be given according to the time chart i in FIG.

When the main power source of the copying machine is turned on, an initial reset signal QIR ('II') is output, and the flip-flop 8 is reset. The timer 20 also starts counting time. By resetting the flip-flop 8, its reset output Q becomes ant game 1.18.
is input to one side.

On the other hand, the surface temperature of the heat roller 1 does not reach the set temperature T+ (180°C) at the same time as the power is turned on, and → the voltage divided by the no-mister 6 is higher than the voltage divided by the resistors RI and R2. High, the 114 force of comparator 7 is “II” old,
The heater control circuit 15 is driven. That is, power is supplied to the heater 2 of the heat roller 1 to heat the heat roller 1.

Then, the temperature of the heat roller 1 gradually increases.

” - If the surface temperature of the heat recording roller l reaches the set temperature 'r1, the comparator 7 will open before the AND gate 18 opens.
is inverted from It H++ to "(-++", and the flip-flop 8 is set. Therefore, one side of the AND gate 18 becomes "°L', and the AND gate 18 sets the timer 2
It will not open even if a zero output occurs.

Therefore, the transistor 10 is ON, and the heat roller 1 and pressure roller 3 are turned on [r! There will be no rollover. At this time,
The AND gate 19 outputs the set output Q of the flip-flop 8 and the copying process control circuit 17 because the copying operation is not in progress.
It opens when a higher “H” belief is input, and transistor 1
2 is turned ON. As a result, the ready lamp 13 lights up to indicate the copy ready state.

The above operation is under normal conditions and timer 2
Before time 0 has elapsed, the heat roller 1 reaches the set temperature TI, and the main motor M is no longer rotated as shown in the time chart of FIG. Even if the print switch 17 is operated in this state and copying is performed, the heat absorbed by the pressure roller is small, and the surface temperature of the heat roller 1 is set to the fixing temperature.
Alternatively, the set temperature TI can be maintained and no fixing failure occurs.

Next, the operation will be explained according to the time chart shown in FIG. When the power supply voltage is lowered for some reason or under conditions where the ambient temperature is low, the time it takes for the heat roller 1 to rise to the set temperature T1 after the power is turned on becomes longer. That is, before the output of the comparator 7 is inverted from ``■1'' to ``■,'', the timer 20 outputs the time [II after elapsed time] signal as shown in FIG. Therefore, Antogame-1
・18 opens, or game] ・Is that belief through 9?
added to the base of transistor 10, transistor 1o
turns on. As a result, the main motor relay 11 is energized, and as the main motor M rotates, the heat roller 1 and the pressure roller 3 are rotated.

As a result of this rotation, the heat of the heat roller 1 is transferred to the pressure roller 3, and its surface temperature gradually rises. Further, the heat roller 1 also continues to be supplied with electric power and gradually rises. If the surface temperature of the heat roller 1 does not reach the set temperature TI after the time set by the timer 20 has elapsed, the output of the comparator 7 will be "'H".
'' to 11 L 11, flip-flop 8
is set. By setting the flip-flop 8, the AND gate 19 is opened, and the signal is supplied to the transistor 12, which lights up the ready lamp 13 to indicate the copy ready state. At this time, the output Q is “
By inverting from “H” to “Ll’, the AND gate 18
is closed, the transistor 10 becomes non-conductive, the rotation of the main motor M is stopped, and the rotation of the heat roller 1 and the pressure roller 3 is stopped. Also, the output of comparator 7 is L.
++, the heater control circuit 15 stops driving the heater 2. In other words, the heat roller 1 is set at a temperature T
Control is executed to maintain the value at 1.

If the print switch 17 is operated in the above-mentioned state, the copying process control circuit 16 executes copying control since the signal indicating the copyable state is input.

Then, by outputting the drive signal of the main motor M,
Transistor 1° is made conductive via OR gate 19, and main motor M is driven. As a result, the heat roller 1 and the pressure roller 3 are rotated, and the toner image on the copy paper 4'' is fixed. In this case, the pressure roller 3 ('') and the heat roller 1 have been rotated in advance until they reach the set temperature 'F1, and are not heated only partially, but are fully preheated as a whole.

3) The heat of the heat roller 1 is not taken away by the pressure roller 3 even if it is rotated in accordance with the double control. Therefore, there is no sudden temperature change of the heat roller 1, and the heater control circuit 15 can maintain the set temperature T+ (or (fixing temperature) even under adverse conditions.

As explained above, according to the heat fixing roller of the present invention,
The roller is driven to rotate based on the time it takes for the heat roller to reach the set temperature TI, and the pressure roller side is preheated before copying is possible only under adverse conditions such as low ambient temperature.
Under soil and mud condition 1, it is possible to minimize the heat absorbed by the pressure roller during copying, and the set temperature of the heat fixing roller is
The temperature of r1 can be easily controlled. Further, rotation of the roller can be suppressed as much as possible.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing a heat fixing roller according to the present invention;
FIG. 2 is a circuit configuration diagram showing a specific example for implementing the present invention, and FIGS. 3 and 4 are time charts for explaining the operation of the present invention. 1: Heat roller, 2: Heater, 3: Pressure roller, 4:
Copy paper, 5: toner image, 6: → no-mister, 7: comparator for detecting set temperature T1, 11: main motor relay, 13 day lamp, 15: heater control circuit,
16: copying process control circuit, 20: timer. Agent Patent Attorney Aihiko Fukushi

Claims (1)

[Claims] 1. In a heat fixing roller consisting of a heat roller equipped with an internal heat source and a pressure roller that is pressed against the heat roller, the time required for the heat roller to reach a set temperature under limit conditions that do not cause fixing defects is determined. , Is it long or short for the surface temperature of the heat roller to reach the set temperature with respect to the time [?
(1) A heat fixing roller comprising roller rotation control means for rotating a heat recording roller and a pressure roller.