JPH0340392B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device for a heating roller fixing device of a copying machine.

A heating roller fixing device is provided with a fixing roller and a pressure roller as a pair of rollers, between which transfer paper with the image side facing the fixing roller is sandwiched and conveyed, and both rollers usually have a heater inside. It's summery.

This is intended to shorten the warm-up time by providing a heater on the pressure roller and transmitting this heat to the fixing roller. Since both rollers are rotating during warm-up, heat is transferred efficiently and evenly.

The heating roller fixing device is configured in this way, but when the exposure lamp installed inside the copying machine lights up, power is applied to both the heater on the fixing roller side and the heater on the pressure roller side. The rated wattage may be exceeded, and even if it is not, the power consumption will increase.
Conventionally, in such cases, heater energization control has been performed.

In this case, the energization control is performed when the exposure lamp is turned on.
The heater on the fixing roller side and the heater on the pressure roller side were alternately energized.

Before explaining the energization timing chart of this conventional example, the structures of the fixing roller and the pressure roller will be explained based on FIGS. 1a and 1b.

FIGS. 1a and 1b are sectional views of the fixing roller and the pressure roller, respectively.

First, the fixing roller shown in FIG. 1A will be described. The fixing roller 1 is provided with a heater penetrating inside a cylindrical core member 2, and further provided with a silicone rubber layer 4 on its surface. Both ends of this core metal member 2 have a small diameter, and are supported by a fixed front plate 5 and a fixed rear plate 6, respectively. Further, a driving gear 7 is provided on the outside of the rear side plate 6 and fixed to one end of the core metal member 2. The silicone rubber layer 4 is not provided over the entire large diameter portion of the core member 2, but is sufficient if it is wide enough to contact the entire width of the transfer paper, and the exposed portion of the core member 2 is A temperature sensor 8 consisting of a thermistor is provided in contact with.

Figure b shows the pressure roller 9, and a heater 10 is provided inside. Further, the surface of this pressure roller 9 is coated with a synthetic resin coating. Similarly to the fixing roller 1, a drive gear 11 and a temperature sensor 12 are provided.

The drive gear 11 meshes with the rollers, and the rollers rotate while being in contact with each other. Reference numeral 13 denotes a pressure lever for pressing the pressure roller 9 in the direction of the fixing roller 1.

FIG. 2 shows the energization waveform of the conventional example described above.

In the figure, 1 shows an exposure lamp ON signal, 2 shows an energization waveform of the heater 3 on the fixing roller 1 side, and 3 shows an energization waveform of the heater 10 on the pressure roller 9 side.

The energization waveforms shown in 2 and 3 are for the fixing roller 1 and the fixing roller 1, respectively.
This is based on the on/off control signal for the set temperature of the pressure roller 3. That is, until the exposure lamp ON signal 1 rises, the energization waveforms 2 and 3 are independently controlled on and off for each set temperature. However, once the exposure lamp ON signal 1 is output, the energization to the heater 3 on the fixing roller 1 side is turned on and off at regular intervals in 2, regardless of the energization request for the heater 10 on the pressure roller 9 side. It starts (oscillates). At this time, if the heater 10 is also requested to be energized in synchronization with the energization request for the heater 3, an on output is output at 3 at the off timing at 2, as shown in the figure. That is, the heater 3 and the heater 10 are alternately energized. However, when oscillating at 2, heater 1
If there is no request for energization to 0, no output waveform will be generated at 3, and in that case, only the energization to heater 3 will be turned on and off. In this case, for example, even if there is a request for energization as shown by the broken line in 2, the energization will not be carried out as requested, and the temperature of the fixing roller 1 will drop, resulting in defective fixing. A situation arose.

Furthermore, even if the heater 10 is requested to be energized in synchronization with the heater 3 as described above, the energization of the heater 10 on the pressure roller 9 side will account for only a portion of the total energization of the heater 3 on the fixing roller 1 side. The deficiency could not be compensated for, and the fixing efficiency was still lowered.

The present invention has been made in view of such conventional examples, and its purpose is to reduce the power consumption of the entire copying machine by controlling the power supply to the heating roller fixing device when the exposure lamp is turned on. It is an object of the present invention to provide a temperature control device that does not reduce fixing efficiency while controlling the temperature.

To this end, the control device is configured to give priority to the energization of the heater on the fixing roller side over the energization of the heater on the pressure roller side.

The present invention will be explained below based on the illustrated embodiments.

FIG. 3 is a block diagram of a temperature control device according to an embodiment of the present invention.

In the figure, I ₁ and I ₂ are inverters, A ₁ and A ₂ are AND circuits, and OR is an OR circuit _.
is the inverted output of the fixing roller side temperature comparison circuit 14,
The output of the pressure roller side temperature comparison circuit 15 and the output of the exposure lamp ON signal 16 are input. Further, the fixing roller heater control circuit 17 receives a signal from the fixing roller side temperature comparison circuit 14 and controls the heater 3 on the fixing roller 1 side.
The pressure roller heater control circuit 18 receives the output of the OR circuit OR and controls the heater 10 on the pressure roller 9 side. AND circuit A ₂ is the output of the pressure roller side temperature comparison circuit 15 and the exposure lamp on signal 1
The inverted output of the AND circuit _A1 and _A2 is input to the OR circuit OR.

Next, the control operation in this block diagram will be explained. First, the heater 3 on the fixing roller 1 side, the pressure roller side temperature comparison circuit 15, the exposure lamp on signal 1
The fixing roller heater control circuit 17 performs on/off control at a set temperature without being influenced by the fixing roller heater 6.

On the other hand, regarding the heater 10 on the pressure roller 9 side, first of all, when the exposure lamp ON signal 16 is output, the presence of the inverter I ₁ and the status of the input terminal of the AND circuit A ₁ and the input terminal of the OR circuit OR As is clear from the above, the pressure roller heater control circuit 18 turns on and off under the condition that the fixing roller side temperature comparison circuit 14 outputs no output.

Next, if the exposure lamp ON signal 16 is not output, it is inverted by the inverter _I2 , and the AND circuit
Since a high level input is made to one input terminal of _A2 , in this case, the fixing roller side temperature comparison circuit 1
Regardless of the presence or absence of the output No. 4, if there is an output from the pressure roller side temperature comparison circuit 15, the heater 10 will be energized as is.

In this block diagram, a fixing roller side temperature comparison circuit 14 and a pressure roller side temperature comparison circuit 15 are shown.
Both are output when the temperatures detected by the temperature sensors 8 and 12 of the fixing roller 1 and the pressure roller 9 become lower than their respective set temperatures.

As is clear from this block diagram, the fixing roller 1
The heater 3 on the side is controlled to be turned on and off at the set temperature without being influenced by anything else, but the heater 10 on the pressure roller 9 side is controlled to turn on and off to the fixing roller 1 when the exposure lamp on signal 16 is output. It is possible to energize only under the condition that the heater 3 on the side is not energized. This state is shown in FIG. 4. If the heater 3 is energized when the exposure lamp ON signal 16 is output, the heater 10 will be energized even if a energization request is made at the same timing as shown by the broken line in 3. This means that it will not be done. In the figure, 1, 2, and 3 are the same as in FIG. 2.

FIG. 5 is a characteristic diagram showing the fixable area with the fixing roller temperature T ₁ on the vertical axis and the pressure roller temperature T ₂ on the horizontal axis, and the hatched portion is the fixable area.

That is, the fixable temperature is determined by the correlation between the fixing roller temperature T ₁ and the pressure roller temperature T ₂ as shown in this characteristic diagram.

As explained above, the present invention separately controls the energization of the heaters of the fixing roller and pressure roller when the exposure lamp off signal is output, and applies the electricity only when the heater on the fixing roller side is not energized when the exposure lamp on signal is output. Since the energization of the heater on the pressure roller side is controlled by the temperature detection output of the temperature sensor, it is possible to achieve more effective fusing conditions for the fusing heating device without increasing the power consumption of the copying machine. Control is performed in which the energization of the heater on the roller side is given priority over the energization of the heater on the pressure roller side, and it is possible to prevent fixing failure from occurring when the exposure lamp on signal is output.

[Brief explanation of drawings]

FIG. 1a is a longitudinal sectional view of the fixing roller, FIG. 1b is a longitudinal sectional view of the pressure roller, FIG. 2 is a timing chart of energization in a conventional example, and FIG. 4 is a timing chart of energization according to the present invention, and FIG. 5 is a characteristic diagram showing a temperature range in which fixing can be performed by the fixing roller and the pressure roller. 1... Fixing roller, 3, 10... Heater, 9... Pressure roller, 16... Exposure lamp on signal.

Claims (1)

[Claims] 1. A heating roller fixing device consisting of a fixing roller and a pressure roller each having a heater inside, and configured to sandwich and convey a transfer sheet with the image side facing the fixing roller between these rollers, In a temperature control device for a heating roller fixing device, which has a control circuit in which each roller is provided with a temperature detection means and controls energization of the heater of each roller based on the output of each temperature detection means, when an exposure lamp off signal is output, each of the above-mentioned The control circuit separately controls the output from each temperature detection means, and when the exposure lamp ON signal is output,
When the fixing roller heater is energized, the pressure roller heater is not forcibly energized, and when the fixing roller heater is not energized, the pressure roller heater is controlled by the pressure roller temperature detection means. 1. A temperature control device for a heating roller fixing device, comprising a control means for controlling energization according to output.