JPS63191175A - Electrophotographic printer - Google Patents

Abstract

PURPOSE:To prevent a fixing device and printing paper from the generation of damage or defective fixing by providing a detecting part for monitoring the ON/OFF time of a heat generating element and detecting abnormality in a temperature detecting element or the temperature detecting element and a temperature detecting circuit. CONSTITUTION:When the temperature detecting circuit 2 or the temperature detecting element 5 generates abnormality, the temperature of a fixing device 3 can not be correctly detected, so that the heat generating element 3 may be always kept at ON or OFF and the temperature of the device 3 can not be controlled. Thereby, the ON or OFF time of the element 4 is monitored by a microprocessor 1a to detect the abnormality in the circuit 2 or the element 4. When the abnormality is detected in the circuit 2 or the element 5, the microprocessor 1a immediately turns off the element 4 to stop printing. Consequently, the fixing device or printing paper can be prevented from damage to be generated at a high temperature or defective fixing at a low temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic printing apparatus, and particularly to an abnormality detection method for a fixing device.

[Conventional technology]

Conventionally, in an electrophotographic printing apparatus, the temperature of the fixing device is detected by a temperature detection element and a temperature detection circuit, and the temperature of the fixing device is controlled by turning on or off a heat generating element in the fixing device.

[Problem that the invention seeks to solve]

In the conventional device described above, the temperature of the fixing device is detected by a temperature detection element and a temperature detection circuit to control the temperature of the fixing device. Therefore, if an abnormality occurs in the temperature detection element or temperature detection circuit, accurate temperature control becomes impossible,
Therefore, problems may arise in which the temperature of the fixing device becomes too low and printing cannot be fixed, or the temperature becomes too high and the fixing device or printing paper burns.

To deal with this problem, the temperature of the fixing device becomes too high, so we installed a temperature fuse or thermostat or other element on the fixing device, and when the temperature of the fixing device becomes abnormally high, the temperature inside the fixing device increases. By cutting off the power to the element, burning of the fixing device and printing paper can be prevented. However, there is no means to prevent the problem that printing cannot be fixed due to low temperature, and there is a drawback that printing continues without fixing.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic printing apparatus that prevents damage to the fixing device and printing paper under high temperatures and defective fixing at low temperatures.

[Means for solving problems]

The present invention detects the temperature of the fixing device using a temperature detection element and a temperature detection circuit, and turns on/off the heating element in the fixing device.
In an electrophotographic printing device that is equipped with a function to control the temperature of the fixing device by This is an electrophotographic printing device characterized by having a section.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention in which a microprocessor is used for temperature control.

In Figure 1, 1a is a microprocessor (detection unit)
, 2 is a temperature detection circuit, 3 is a fixing device, 4 is a heating element, 5
is a temperature detection element. The microprocessor 1a keeps the temperature of the fixing element 3 constant at a target temperature by turning on or off the heating wire 4 according to the temperature detected by the temperature detection circuit 2 based on the output of the temperature detection element 5. Take control. When the temperature detection circuit 2 or the temperature detection element 5 is normal and can correctly detect the temperature of the fixing device 3, the microprocessor 1a repeats 0N10FF of the heating element 4 as shown in FIG. However, if there is an abnormality in the temperature detection circuit 2 or the temperature detection element 5, the temperature of the fixing device 3 cannot be detected correctly, so the heating element 3 is always ON or OFF as shown in FIGS. 3 and 4.
The temperature may become FF, and the temperature of the fixing device 3 may become uncontrollable. Therefore, in the present invention, the heating element 4 is turned ON or OFF by the microprocessor 1a.
It detects an abnormality in the temperature detection circuit 2 or the temperature detection element 5 by monitoring the time that the temperature detection circuit 2 or the temperature detection element 5 is running.If an abnormality in the temperature detection circuit 2 or the temperature detection element 5 is detected, the microprocessor la immediately stops generating heat. element 4 to O
FF L, to stop printing. Therefore, damage to the fixing device or printing paper at high temperatures and poor fixing at low temperatures can be prevented.

(Embodiment 2) FIG. 5 shows a second embodiment of the present invention, in which temperature control is performed by another electronic circuit instead of the microprocessor. That is, in FIG. 5, 1b is a comparator, 2 is a temperature detection circuit, 3 is a fixing device, and 4 is a heating element.

5 is a temperature detection element, 6 is a heating element drive circuit, 7 is a counter circuit, 8 is a counter circuit, and 9 is an OR gate.

In the embodiment, the temperature of the fixing device 3 is detected by the temperature detection element 5, converted into a voltage by the temperature detection circuit 2, and inputted to the input 11 of the comparator 1b. The voltage Vref output by the temperature detection circuit 2 when the temperature of the fixing device 3 reaches the target temperature is input to the input 12 of the comparator 1b.

The output 13 of the comparator 1b becomes H level when input 11 < input 12, and becomes L level when input 11) is input 12. The output 13 of the comparator 1b is the input 61. of the heating element drive circuit 6. It is input to the input cuff 1 of the counter circuit 7 and the input 81 of the counter circuit 8. The output 21 of the temperature detection circuit 2 is output 21 (Vref) when the temperature of the fixing device 3 is lower than the target temperature, and output 21 (Vref when it is higher than the target temperature). When the input 61 is at the L level, the comparator input 11>input 12, that is, it can be determined that the temperature of the fixing device 3 is higher than the target temperature. Lower the temperature. Conversely input 61
is at H level, the heating element 4 is turned on and the fixing device 3 is turned on.
Increase the temperature. Temperature of fixing device 3 and comparator 1b
The relationship between the output 13 of the circuit and the output 62 of the heating element drive circuit 6 is shown in FIG.

The counter circuit 7 counts the time during which the input cuff 1 remains at the H level, and sets the output cuff 1 to the H level when the input cuff 1 remains at the H level for a certain period of time. Output cuff 1 is normally at L level. The counter circuit 8 counts the time during which the input 81 remains at the L level, and sets the output 82 to the H level when the input 81 remains at the L level for a certain period of time. Output 81 is normally at L level. Output cuff of counter circuit 7 and counter circuit 8 2.82
are input to inputs 91 and 92 of OR gate 9, respectively. The output 93 of the OR gate 9 becomes H level when either or both of the inputs 91, 92 are at H level.

An output 93 of the OR gate 9 is connected to an input 63 of the heating element drive circuit 6. The heating element drive circuit 6 is the input 6
3 is at H level, the heating element 4 is turned off. By the way, if an abnormality occurs in the temperature detection element 5, the temperature detection circuit 2, and the comparator 1b, the output 13 of the comparator 1b may continue to be at the H level or L level as shown in FIGS. 7 and 8. The temperature of the fixing device 3 cannot be controlled normally. In the present invention, the comparator 1b
When the output 13 of the OR gate 9 is at the H level or the L level for a certain period of time or more, the output 93 of the OR gate 9 becomes the H level, and the heating element 3 is turned off. Also, by monitoring the output 930 level of the OR gate 9, the temperature detection element 5,
Since an abnormality in the temperature detection circuit 2 and the comparator 1b can be detected, printing is stopped in that case.

〔Effect of the invention〕

As explained above, the present invention enables the heating element to be turned ON or OFF.
By monitoring the time during which the FF is turned on, abnormalities in the temperature detection circuit and temperature detection element are detected, and if an abnormality is detected, the heating element is turned off and printing is stopped. This has the effect of preventing damage or poor fixing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure shows an example of temperature control in the first embodiment, and the figure shows an example of temperature control in the first embodiment.
The figure shows the case where the heating element is always ON in the first embodiment, FIG. 4 shows the case where the heating element is always OFF in the first embodiment, and FIG. 5 shows the case where the heating element is always OFF in the first embodiment. 2
FIG. 6 is a block diagram showing an example of temperature control in the second embodiment. FIG. 7 is a diagram showing a case where the heating element is always ON in the second embodiment. The figure is a diagram showing a case where the heating element is always OFF in the second embodiment. la...Microprocessor 1b...Comparator 2...Temperature detection circuit 3...Fixing device 4...Heating element 5...Temperature detection element 6...Heating element drive circuit 7, 8...・Counter circuit 9...OR gate

Claims (1)

[Claims] (1) In an electrophotographic printing device having a function of detecting the temperature of the fixing device using a temperature detection element and a temperature detection circuit, and controlling the temperature of the fixing device by turning on/off a heating element in the fixing device. 1. An electrophotographic printing apparatus comprising: a detection section that detects an abnormality in a temperature detection element and a temperature detection circuit by monitoring the time during which a heating element is turned on or off.