JPH04102869A - Safety device for image forming device - Google Patents

Abstract

PURPOSE:To enhance the safety of a device by storing an abnormal signal caused by the occurrence of an abnormal state in a memory, and reading out stored contents when a power supply switch is turned on and stopping energizing the heater of a thermal fixing part. CONSTITUTION:The temperature of the thermal fixing part 1 is detected by a thermistor 6, and when a CPU 7 judges that it is in a normal temperature range, it controls the heater 2 to perform a normal action. And when the abnormal state is detected, the CPU 7 generates the abnormal signal to make a power supply driver 4 stop energizing the heater 2 from the power supply 3. The occurrence of the abnormality is stored in the memory 8 and also the abnormality is displayed. The CPU 7 reads out the stored contents in the memory 8 when the power supply switch is turned on. In the case that the abnormal signal is stored, energizing the heater 2 is stopped, and when the abnormality is recovered, the memory 8 is reset by turning on a setting means 9, and a normal control is returned. Thus, the heating of the thermal fixing part at the time of the occurrence of the temperature abnormality is prevented, so that the safety is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a safety device for an image forming apparatus, and particularly to a temperature control device for a heat fixing section thereof.

(Prior Art) Generally, in an image forming apparatus such as a copying machine or a laser printer, a thermal fixing device for fixing a transferred image to a recording paper has a switching element interposed in a conductive path of a heater and a heated part. A temperature sensor is provided to detect the temperature of the temperature sensor, and the switching element is turned on/off based on the temperature detected by the temperature sensor, and the heater is turned on and off.
The fixing temperature is controlled to be constant. Even if an abnormal state such as heater runaway occurs for some reason, the control element detects the abnormal state based on the temperature detected by the temperature sensor and controls to prohibit conduction to the heater.

(Problems to be Solved by the Invention) In the conventional device described above, for example, when the heater runs out of control due to disconnection of the temperature sensor, the control element cannot detect the abnormal state until a certain period of time has elapsed since the heater was energized.

Therefore, even if a warning message such as a serviceman call message appears on the display of the main unit due to an abnormal condition, if you ignore the message and repeatedly turn the power switch on and off, the heater will not be energized for a certain period of time. As a result, the temperature of the heater will gradually rise, potentially causing a fire or other disaster.

SUMMARY OF THE INVENTION An object of the present invention is to provide a safety device for an image forming apparatus that improves safety when an abnormal temperature occurs in a heat fixing section.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a detection means for detecting the temperature of a heat fixing section, an energization control means for controlling energization to the heat fixing section, and a detection section for detecting the temperature of the heat fixing section. Generates an abnormal signal when an abnormal state of the heat fixing section is detected based on data from the means,
A safety device for an image forming apparatus, comprising: a control means for causing the power supply control means to cut off power supply to the heat fixing section;
A memory is provided for storing data regardless of whether the power is on or off, and the abnormal signal is stored in this memory, and when the power is turned on from off, the control means determines whether or not the abnormal signal is stored in the memory. The apparatus is characterized in that it is configured to detect this and cut off the power supply to the heat fixing section when an abnormal signal is stored, and further includes means for resetting the memory.

(Function) Since the above method is adopted, as long as the abnormal signal generated when a temperature abnormality in the heat fixing unit is detected is stored in the memory, the heat fixing unit will not be affected even if the power is repeatedly turned on and off. Since the current supply is cut off, the heat fixing section is prevented from being inadvertently heated.

Furthermore, when the cause of the temperature abnormality disappears, the memory can be reset, and the safety device will operate in the same way as before the temperature abnormality occurred.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a configuration diagram of an embodiment of the present invention, in which 1 is a heat fixing unit having a heater 2, 3 is a power source for the heater 2, and 4 is a power supply driver which is a power supply control means for controlling power supply to the heater 2. , 5 is a temperature fuse, 6 is a thermistor which is a detection means installed near the heat fixing unit l and detects the temperature, and 7 is a control means which outputs a control signal based on the detection data from the thermistor 6 (CPU). 8 is a non-volatile memory (for example, E"FR
OM: electrically erasable PROM); 9 is a reset means for resetting the memory 8;

In the figure, the temperature of the heat fixing unit 1 is detected by the thermistor 6, and in the normal temperature fluctuation range, the power driver 4 is turned on/off based on the detection data output from the thermistor 6 to the CPU 7, and the power source 3 Heater 2 from
The temperature of the heat fixing section 1 is kept constant by controlling the power supply to the heat fixing section 1.

The operation of the heat fixing section when an abnormality occurs will be explained with reference to the flowchart in FIG. CP by the detection data of thermistor 6
If it is determined in U7 that the temperature state of the heat fixing unit l is within the normal fluctuation range (Sit No), the above-described normal operation control for the heater 2 is performed (Si, -2), and the above-mentioned detection When the CPU 7 detects that the heater 2 of the thermal fixing unit 1 is in an abnormal state based on the data (YES in Sl-), the CPU 7 generates an abnormal signal and causes the power driver 4 to turn off the heater 2 from the power supply 3. 5l-3), and the fact that an abnormal signal has been generated is stored in the memory 8 (Sl-4). Then, a display unit (not shown) provided on the main body of the apparatus displays that the heater is abnormal by displaying a serviceman call message or the like (Sl-5).

FIG. 3 is a flowchart showing the operation when the power switch is turned on. Once the power switch is turned on, the contents of the memory 8 will not be erased regardless of whether the power is turned on or off.
The CPU 7 reads whether or not an abnormal signal is stored in the memory 8. If the abnormal signal is stored in the memory 8 (YES in 32-), the power driver 4 turns on the heater 2 regardless of whether the power switch is on or not. The serviceman call message continues to be displayed (S2-3). If the abnormality signal is not stored in the memory 8 (No in S2-1), the heater 2 is controlled by the normal operation described above (S2-4).

By the above-described operation, even if the power switch is repeatedly turned on and off in an abnormal state of the heater, the power supply to the heater 2 is cut off, so that a fire or the like due to heating of the thermal fixing section 1 can be prevented.

If the heater abnormality is eliminated by repair or replacement, the memory 8 can be reset by turning on the reset means 9 so as to remove the abnormality signal. This results in the same temperature control as before the abnormal signal was generated.

(Effects of the Invention) As described above, according to the present invention, if the heat fixing section is in an abnormal state, by storing the abnormal signal in the memory, the heat fixing section will not be affected even when the power is turned on. Since no electricity is applied, heating of the heat fixing unit can be prevented, and when the abnormal condition is cleared, by resetting the memory, the same control as before the error occurred can be performed, and the temperature of the heat fixing unit can be reduced. It is possible to provide a safety device for an image forming apparatus that increases safety when an abnormality occurs and is moreover practical.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a safety device for an image forming apparatus according to the present invention, and FIGS. 2 and 3 are flowcharts relating to the temperature control operation of this embodiment. DESCRIPTION OF SYMBOLS 1... Heat fixing part, 2... Heater, 3 - Power supply, 4... Current supply control means, 6... Detection means,
7... Control means, 8... Memory, 9... Reset means. Patent applicant Rico Co., Ltd. −

Claims (2)

[Claims] (1) A detection means for detecting the temperature of the heat fixing section, an energization control means for controlling energization to the heat fixing section, and an abnormality signal when an abnormal state of the heat fixing section is detected based on data from the detection means. A safety device for an image forming apparatus is provided with a control means for interrupting the power supply to the heat fixing unit by the power supply control means, the safety device comprising a memory for storing data regardless of whether the power is turned on or off; The abnormal signal is stored in a memory, and when the power is turned on from OFF, the control means detects whether or not the abnormal signal is stored in the memory, and when the abnormal signal is stored, the abnormal signal is transmitted to the heat fixing section. A safety device for an image forming apparatus, characterized in that the device is configured to cut off electricity to the image forming apparatus. (2) The safety device for an image forming apparatus according to claim (1), further comprising means for resetting the memory.