JPS58194076A - Temperature controller for copying machine - Google Patents

Abstract

PURPOSE:To prevent the safety of the temperature sensor of a heat fixing device from degrading during a breakdown by stopping copying operation after discharging copying forms remaining in a passage when it is judged that the breaking of wire occurs to a fixing device temperature detection part. CONSTITUTION:If the breaking of the sensor 1 or sensor lead wire occurs during the operation of the copying machine, a microcomputer 20 outputs a control signal to a driving group 40 to inhibit forms from being fed from a form dish and if there is a form in the passage near the fixing device, the form is discharged by carrying on the copying operation and then the machine stops. When there is no form in the passage, the machine stops operating immediately. For this purpose, a heater 33 is turned on the off under control based upon the output of an AND circuit 4, but microcomputer control may be employed. The heater 33 is provided in a heat roller 31 contacting the presser roller 32 of a fixing part E. The sensor 1 uses a thermistor, etc., which decreases in resistance value according to a temperature rise.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device for a copying machine, and more particularly to a temperature control device for a copying machine that does not reduce safety in the event of failure of a temperature sensor of a heat fixing device.

If a thermistor with a negative temperature coefficient of resistance (resistance value decreases as the temperature rises) is used as a temperature sensor in the heat fuser of a copying machine, if the wire connecting the thermistor and the control circuit breaks. , the controller may determine that the thermistor has a large resistance value, and therefore the temperature of the thermal fixing device is low, and may continue to supply power to the fixing device. As a countermeasure, determine in advance the maximum resistance value of the thermistor within the operating temperature of the thermal fuser, compare this value with the resistance value of the thermistor, and if the resistance value of the thermistor is large, the thermal fuser A temperature control device for a copying machine has been proposed which immediately stops the operation of the copying machine when an abnormality occurs.

However, according to this temperature control device for copying machines, if the operation of the copying machine is immediately stopped when the abnormal resistance value phenomenon occurs, flammable copy paper will remain in the heating and fixing section. However, when the broken lead wire is restored, the sum of the reduced resistance value due to the temperature rise of the thermistor and the resistance value of the broken part may maintain a resistance value smaller than the maximum set resistance value mentioned above. This may cause the temperature to rise close to the flammable temperature of copy paper.

The present invention has been made in view of the above, and in order to prevent safety from decreasing even if there is a temperature rise when a temperature sensor for a thermal fuser having a negative temperature coefficient of resistance fails, a failure detection signal of the temperature sensor is provided. To provide a temperature control device for a copying machine, which stops copying operation after discharging copy paper remaining in a copy paper path to the outside of the copying machine in response to the copy paper path.

The temperature control device for a copying machine according to the present invention will be explained in detail below.

FIG. 1 shows an embodiment of the present invention, which includes a band section A around the periphery.
A photosensitive drum 30 on which an exposure section B, a development section C1, a transfer section D, a fixing section E1 and a cleaning section F are arranged, and a heater 33 built into a heating roller 31 arranged in contact with a pressure roller 32 of the fixing section E. , a sensor l such as a thermistor whose resistance value decreases in response to a rise in the temperature of the heater 33, and a sensor l.
including resistors R1, Rz, R3, R4, T? , 5, has an operational amplifier 2.3 and an AND circuit 4, and when the surface temperature of the heating roller 31 is below a predetermined temperature, the heater 33 of the heating roller 32 is energized to reach the predetermined temperature. Thermal fuser temperature control circuit 10 outputs a disconnection signal when the sensor L and the sensor lead wire are disconnected, and the heater 33 is connected to the heater 33 in response to the signal output from the thermal fuser temperature control circuit. It has a control relay circuit 6 that turns on and off the AC power source 5, an input interface, ROM, RAM, OPU, output interface, etc., and inputs, processes, and copies the disconnection signal output from the thermal fixing device temperature control circuit IO. A microcomputer 20 that outputs a control signal to operate a drive group 40 that controls machine operation;
A console display section 50 that displays a predetermined display based on the control of
, a console command section 60 for inputting various operation commands, a clock and reset circuit 70, and a group of various sensors 80.

In the above configuration, the operation will be described with reference to FIG. 2. The output signals VO1 and Voz of the operational amplifiers 2 and 3 in the thermal fixing device temperature control circuit 101c are expressed by the following equations (1) and (2), respectively. It will be done.

(2) Here, E is the voltage AI of Vcc, the amplification rate A2 of the operational amplifier 2 is the amplification rate Vot of the operational amplifier 3, Vot=1, and the power is supplied to the heater 33 when Vo is 2-1, which will be described later. (control relay circuit 6 is on).

Vol=o, and the voltage to the heater 33 is reduced. Stop power supply (control relay circuit road 6 is off).

From equation (2), if sensor 1 is operating normally and the resistance value Rt responds within a predetermined range, then VO2=
1, but if there is a disconnection, Rt→ω and Voz=o
As a result, a disconnection signal is generated.

When the disconnection signal (VO2=l+) of the thermistor 1 is activated, the output signal "1" and "f)" from the AND circuit 4 turns the AC power on and off via the control relay 6, and the heating roll 3117)i The temperature is maintained within the predetermined temperature range and operation of the copier continues.

If the sensor l and the sensor lead wire are disconnected for some reason during operation of the copying machine (if the Vol-○ signal is output), the microcomputer 20 outputs a control signal to the drive group 40. If there is copy paper in the passage near the heat fuser, the copying operation is continued and the paper is ejected from the copying machine.

After that, the copying operation is stopped. When copy paper is licked in the path near the heat fixing device, the copying operation is stopped immediately.

In the above embodiment, the output of the AND circuit 4 is used to control the heater 3.
The on/off of 3 is controlled by the microcontroller 20.
It may be controlled by

As explained above, according to the temperature control device for a copying machine according to the present invention, when it is determined that a disconnection has occurred in the fuser temperature detection section, the copy paper remaining in the copy paper path is ejected, and then the copying operation is performed. Since the temperature detection section is stopped, even if a wire breakage occurs in the temperature detection section, safety will not be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a safety device for a copying machine according to the present invention. FIG. 2 is a flow chart showing one embodiment of the present invention. Explanation of symbols l... Temperature sensor 2, 3... Operational amplifier 4...
・AND circuit 6... Control relay circuit 10... Heat fixing device temperature control circuit 20... Microcomputer 30... Photosensitive drum 31.
... Heating roller 33 ... Heater 7 = 40 ... Drive group 50 ... Console display section 60
... Console instruction section 7t1 ... Clock and reset circuit 80 ... Sensor group patent applicant Fuji Xerox Co., Ltd. agent Agent Nobuyuki Matsuhara Patent attorney Nobuyuki Mura
Seiji, Patent Attorney, Taira 1) Tadao, Patent Attorney, Atsushi Ueshima -8-

Claims (1)

[Scope of Claims] A temperature detection unit that detects the temperature of the heating roll of the fixing unit, a disconnection detection unit that detects a disconnection of the temperature detection unit, and a power supply to the heater for the heating roll according to the temperature of the heating roll. In a copying machine, the copying machine includes a control section that controls the copying operation when the wire breakage is detected, and stops the copying operation when the wire breakage is detected. A temperature control device for a copying machine, characterized in that a copying operation is stopped after discharging the temperature outside the copying machine.