JPS6310831B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing temperature control device in a copying machine.

Conventionally, the fixing temperature control device has (1) two heating elements and an exposure lamp in the heat fixing device connected to the same power source, and during copying, current is constantly passed to one heating element and the exposure lamp is connected to the other heating element. A device that allows current to flow only when the light is turned off is known from Utility Model Application Publication No. 47-25040. (2) In the heat fixing device, the temperature of the heater whose temperature changes faster among the two heaters is detected and both heaters are controlled, and when the exposure lamp is turned on, the heater whose temperature changes faster is turned off and the exposure lamp is turned off. Utility Model Publication No. 51-18774 proposes a system that turns on the heater whose temperature changes faster when the lights are turned off. However, in the former case (1), since current is constantly passed through one heating element, the temperature of the roller cannot be controlled, and in order to balance the temperature, the electric power is limited and the electric power cannot be used effectively. Therefore, there is a drawback that the rise time is slow. The latter (2) also does not use electricity advantageously. In other words, when combining exposure lamp on/off with heater on/off, it is better to use the heater with faster temperature change than to combine exposure lamp on/off with exposure lamp on/off. It is more efficient to use electric power if the temperature of the heater is detected and controlled as the main heating element, and the heater whose temperature changes slowly is turned on and off as the auxiliary heating element in accordance with the exposure lamp.

The present invention combines the heat source control timing of the heat fixing device and the exposure lamp timing to efficiently supply heat to the fixing unit, thereby effectively utilizing electric power and realizing power saving of the copying machine. The purpose is to provide a temperature control device.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a heat fixing device in a copying machine to which the present invention is applied. The fixing roller 1 and the pressure roller 2 are pressed against each other and heat is supplied by internal heaters 3 and 4, and they rotate in opposite directions to heat the toner 6 and fix it when the transfer paper 5 passes between them. let The heaters 3 and 4 are controlled by a fixing temperature control device, and the surface temperature of the fixing roller 1 is detected by a temperature control element, such as a thermistor 7.
Both heaters 3 and 4 are turned on during startup, and when the fixing roller 1 reaches a certain temperature, both heaters 3 and 4 are turned off by a detection signal from the thermistor 7. Thereafter, both heaters 3 and 4 are turned on and off repeatedly in order to keep the fixing roller 1 and pressure roller 2 at a constant temperature. During the copy cycle, heater 3 on the thermistor side
is repeatedly turned on and off by the detection signal from the thermistor 7, while the other heater 4
In order to replenish the heat absorbed by the copy paper 5, the pressure roller 2 turns on the exposure lamp at a different timing, regardless of the detection signal from the thermistor 7, thereby maximizing power supply. . That is, the heater 4 is turned off when the exposure lamp is turned on and turned on when the exposure lamp is turned off. For example, in a copying machine where the exposure lamp performs scanning, if the exposure lamp is turned on when the exposure lamp goes forward and turned off when it goes back, the heater 4 can be turned off when the exposure lamp goes forward, and turned on when the exposure lamp goes back, and the effect can be achieved within a certain limited amount of power. Heat can be supplied to the fixing section in a consistent manner, and good fixing can be performed with relatively low power.

FIG. 2 shows an embodiment of the present invention, which is a fixing temperature control device in the heat fixing device.

The temperature detection circuit 8 includes a thermistor 7 and resistors 9 and 1.
Bridge circuit consisting of 0,22 and voltage comparator 11
When the surface temperature of the fixing roller 1 exceeds a certain temperature, the output A becomes "0". When the output A of the temperature detection circuit 8 is "1", the driver 12 turns off the main heater switch 13 to supply AC power to the main heater 3 from the power supply 14, but when the output A becomes "0", the main heater switch 13 is turned off. The switch 13 is turned off to turn off the main heater 3. As the main heater switch 13 and the subheater switch 15, a thyristor, a triax, a solid state relay, or a normal relay is used. The copy sequence control circuit 16 controls each part of the copying machine, including the exposure lamp and scanner, in sequence to perform a copying operation.
It outputs control signals such as a scanner return signal B and an exposure lamp lighting signal C. The scanner return signal B is output when the scanner consisting of an exposure lamp and a movable optical system is returned to the home position at the end of scanning, and the exposure lamp lighting signal C is output at the time of scanning when the exposure lamp is turned on. The sub-heater control circuit 17 controls the sub-heater 4 according to each step of the copy operation.
Inverter 18, OR circuit 19 and AND circuit 2
Consists of 0. The inverter 18 inverts the exposure lamp lighting signal C and applies it to the AND circuit 20, and the OR circuit 19 ORs the output A of the temperature detection circuit 8 and the scanner return signal B (A+B) and applies it to the AND circuit 20. The circuit 20 takes the AND (A+B) of these input signals C and A+B. When the copying machine is on standby (not copying), the scanner return signal B and the exposure lamp lighting signal C are "0".
Since the output of the inverter 18 is "1", the output A of the temperature detection circuit 8 is applied to the driver 21 via the OR circuit 19 and the AND circuit 20. Then, if the output A is "1", the driver 21 turns on the sub-heater switch 15 to supply AC power to the sub-heater 4 from the power supply 14, and if the output A becomes "0", the driver 21 turns on the sub-heater switch 15.
is turned off to turn off the sub-heater 4. When the copying operation is started and the exposure lamp is lit, the exposure lamp lighting signal C is "1" and the output C of the inverter 18 is "0", so the sub-heater 4 is not lit. When the exposure is completed and the exposure lamp is turned off and the scanner moves to the return operation, the exposure lamp lighting signal C becomes "0", the output C of the inverter 18 becomes "1", and the scanner return signal B becomes "1". Output of the AND circuit 20 (A+B)
Since C becomes "1", the sub-heater 4 lights up.

In the above embodiment, the surface temperature of the fixing roller 1 is detected by the thermistor 7, but the thermistor 7 detects the surface temperature of the roller whose temperature changes faster among the fixing roller and the pressure roller 2, and the temperature inside this roller is detected by the thermistor 7. Switch 1 using the heater as the main heater
3 may be turned on and off, and the heater in the roller whose temperature changes slower may be used as a sub-heater, and the switch 15 may be used to turn on and off the heater.

As described above, according to the present invention, the temperature of either the fixing roller or the pressure roller is detected and both heat sources are controlled simultaneously during standby, and during the copy cycle, the heat source of the roller whose temperature is being detected is used. During the copy cycle, the other heat source is turned off when the exposure lamp is turned on and turned on when the exposure lamp is turned off in order to replenish the heat taken by the fixing roller and pressure roller by the material to be fixed. Since heat is supplied to the maximum extent possible, heat can be efficiently supplied to the fixing section and power saving of the copying machine can be realized. Moreover, by using the above-mentioned control to supply power to the exposure lamp and the heat source of the fixing section at predetermined timings within the limited power provided by the copying machine's power supply, the limited power can be fully utilized. The function of the heat source of the fixing section can be fully utilized, the rise time of the fixing section can be shortened, and the fixing temperature can be easily controlled using one temperature sensing element. Furthermore, when the exposure lamp is turned on, the electric power supplied to one heat source is sent to the exposure lamp to make effective use of the electric power, and when the exposure lamp is turned on, the other heat source is controlled according to the detection signal of the temperature detection element. It is possible to maintain the roller at an appropriate temperature.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an example of a heat fixing device, and FIG. 2 is a block diagram showing an embodiment of the present invention. 1... Fixing roller, 2... Pressure roller, 3, 4
... Heater, 7 ... Thermistor, 8 ... Temperature detection circuit, 12, 21 ... Driver, 13, 15 ...
...Switch, 14...Power source, 16...Copy sequence control circuit, 17...Sub-heater control circuit.

Claims (1)

[Claims] 1. In a heat fixing device that includes a fixing roller and a pressure roller that are pressed against each other, and each of the fixing roller and the pressure roller has a heat source, the temperature of either the fixing roller or the pressure roller is detected by a temperature detection element. During standby, both heat sources are controlled simultaneously, and during the copy cycle, only the heat source of the roller whose temperature is detected among the fixing roller and pressure roller is controlled, and the exposure lamp of the other heat source is lit during the copy cycle. A fixing temperature control device characterized in that it is turned off at times and turned on when an exposure lamp is turned off.