JPS63191177A - Control system for fixing heater - Google Patents

Abstract

PURPOSE:To prevent a fixing from the deterioration in fixing performance and the increase of power consumption due to a peripheral temperature and the delay of heat transmission from the fixing heater by forming plural comparators for comparing the output of a temperature measuring device with a reference value, selecting the outputs of the comparators and controlling the heating power of the fixing heater. CONSTITUTION:When power is supplied to the fixing device, the surface temperature of a roller 2-1 is raised as shown by a solid line and the temperature of a thermister is raised with a slight delay as shown by a dotted line. When the temperature of the thermister corresponds to a reference voltage E1, a current supply time is set to t1, and in case of a reference voltage E2, set to t2, and the current supply time values t1, t2 are stored in a ROM 8-4 or a RAM 8-5 so as to correspond to the reference voltages E1, E2. A microprocessor 8-1 searches the contents of the ROM 8-4 or the RAM 8-5 successively from an output N1 based on the input outputs N1-Nn of A/D converters, selects the current supply time corresponding to logic '1' at first and emits a light emitting diode 6 during the current supply time. Consequently, the heating of a lamp 4 is controlled by the current supply time and the surface temperature of the roller can be kept at a fixed value.

Description

[Detailed Description of the Invention] [Summary] This invention solves the problem of reducing fixing performance and increasing power consumption due to ambient temperature and delay in heat conduction from a fixing heater when fixing a toner image onto recording paper in an image recording device. In order to prevent this, a plurality of comparison circuits are provided to compare the output of the temperature measuring device with a reference value, and the output of the comparison circuit is selected to control the heating power of the fixing heater.

[Industrial application field]

The present invention relates to a fixing device for an image recording apparatus, and more particularly to a fixing heater control method for controlling the temperature of the fixing device.

Image recording devices are widely used in facsimile machines, printers, and the like. This image recording apparatus forms a latent image based on information on an insulating recording medium using a developing device, and attaches magnetic toner to this latent image to form a toner image. This toner image is copied onto recording paper, and the toner image is heated by a fixing device and fixed to the recording paper.

The above-mentioned fixing device is required to maintain a constant fixing temperature and consume less power in order to improve print quality.

[Conventional technology]

The fixing device is constructed as shown in FIG.

That is, the recording paper 1 on which the toner image has been formed is sent between members for thermal fixation, that is, rotating rollers 2-1 and 2-2. One roller 2-2 presses the recording paper 1 against the roller 2-1. A fixing heater, that is, a lamp 4 for heating the roller 2-1 is provided inside the roller 2-1.
A thermistor 3 for measuring the surface temperature of the roller 2-1 is provided close to the roller 2-1.

In order to control the roller temperature of the above-mentioned fixing device, conventional
This is done using the control circuit shown in the figure.

That is, the thermistor 3 is supplied with voltage 1 via the resistor R1. One end A of the thermistor 3 is connected to the comparison circuit 5, and the other end B is grounded. A reference voltage E indicating that the roller has reached the fixing temperature is input to the input terminal of the comparator circuit 5.

The output of the comparator circuit 5 is connected to the midpoint between the resistor R2 and the light emitting diode 6 via a gate circuit (not shown). A voltage 2 is supplied to the resistor R2. A trier diode 7 is provided to receive the light from the light emitting diode 6, and the diode 7 is connected to an AC power source A via a lamp 4.
This is the structure in which C is supplied.

Now, in order to bring the roller 2-1 to a temperature T1 suitable for fixing, the reference voltage E is set as follows.

E is determined so that the resistance R1/(R+ + Rτ) of the v, x thermistor is equal to E. The resistance Rt of the thermistor 3 tends to decrease as the temperature increases. Therefore, when power is turned on to the fuser, since the temperature of the fuser is low, the resistance R of the thermistor at that time is greater than the resistance at a temperature T suitable for fusing, and the light emitting diode 6
emits light and the tri-arc diode 7 becomes conductive.

Therefore, an AC voltage is supplied to the lamp 4, and the lamp 4 generates heat, raising the temperature of the roller 2-1.

Due to this temperature rise, the resistance Rj of the thermistor 3 decreases to E, and the voltage supplied to the lamp 4 is cut off. Therefore, the roller temperature of the fixing device is maintained at a temperature TI suitable for fixing.

[Problem that the invention seeks to solve]

The conventional fixing heater control method described above requires a temperature change on the roller surface due to the time delay in heat conduction from the lamp to the roller surface, especially due to changes in the time delay due to ambient temperature, and to cut off the entire voltage supplied to the lamp. There were problems in that it was difficult to maintain the temperature at a temperature of

In view of the above-mentioned conventional situation, it is an object of the present invention to provide a fixing heater control method that can save labor and stably obtain a required fixing temperature.

[Means for solving problems]

In the present invention, the fixing device is provided with a plurality of comparison circuits, each comparison circuit has a different reference value, and a selection circuit is provided for selecting the comparison circuit.

[Effect]

A selection circuit selects a comparison circuit, and the output of this comparison circuit controls the energization time of the fixing heater, thereby enabling fine temperature control.

〔Example〕

FIG. 1 is a block diagram of an embodiment showing a fixing heater control system according to the present invention. The same parts as in FIG.

The part surrounded by the dashed line shown in part C of FIG.
It is 0. This A-D converter 5-0 compares the voltage output from the thermistor 3 with reference voltages E1 to E in respective comparison circuits 5-1 to 5-n. If the voltage is lower than the reference voltage, the corresponding comparator circuit outputs a logic value "1".

The selection circuit 8 surrounded by a dashed line in the first diagram includes a microprocessor 8-1, an input/output board 8-2, 8-3, a ROM 8-4, and a RAM 8-5.

In this ROM 8-4 or RAM 8-5, energization times t1 to t for energizing the lamps corresponding to the reference voltages E and -E, respectively, are registered. This energizing time is
This was determined experimentally.

For example, when power is applied to the fixing device, the surface temperature of the roller 2-1 rises as shown by the solid line in FIG. 2, while the temperature of the thermistor rises a little later as shown by the dotted line. When the thermistor temperature corresponds to the reference voltage E1, the energization time is t! In the case of reference voltage E2, energization time t2
The ROM 8-
4 or RAM 8-5.

The microprocessor 8-1 sequentially stores data in the ROM 8-1 from N1 according to the outputs N1 to N-yb of the input A-D converter.
4 or RAM 8-5 and first logic ``1''
Select the energization time corresponding to , and cause the developed photodiode 6 for this energization time to emit light. Therefore, the heating of the lamp 4 is controlled by the energization time.

As described above, by finely controlling the energization time, temperature overshoot due to delay in heat conduction of the fixing device can be prevented, and the roller surface temperature can be kept constant.

〔Effect of the invention〕

As is clear from the above description, the present invention is extremely effective in improving the temperature quality of the fixing device, finely controlling the lamp, and saving labor.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment showing the fixing heater control method according to the present invention, FIG. 2 is a schematic diagram for explaining the energization time of the present invention, and FIG. 3 is a perspective view of main parts showing the mechanical part of the fixing device. 4 are circuit diagrams showing a control circuit of a conventional fixing device. In the figure, 1 is a recording paper, 3 is a thermistor, 4 is a lamp, 5-1 to 5-n are comparison circuits, and 8 is a selection circuit. September 1 from Futo] Camellia visit 2 47 Daika Tomoe dakabu ℃
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Claims (1)

[Scope of Claims] A member (2) that contacts the recording paper (1) and heat-fixes the toner image on the recording paper, and a temperature measuring device (3) that measures the surface temperature of the member.
) and a fixing heater (4) that heats the member (2), a comparison circuit (5-1 to 5-n) for comparing the output of the temperature measuring device (3) with a reference value is provided. The fixing heater (4) is provided with a plurality of reference values selected by a selection circuit (8) that sequentially makes the reference values different and selects the output of the comparison circuit.
) A fixing heater control method characterized by controlling the energization time.