JPH0731435B2 - Fixing device for color recording device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat roller fixing device for a color recording apparatus.

Conventional technology In the full-color copying machine of the color separation image superposition transfer system,
The toner images of three colors of yellow, magenta, and cyan, or four colors of which black is added to these, which are sequentially formed on the photoconductor, are transferred by superimposing them on the same transfer paper. It becomes thicker than that of single-color copying, and when fixing with a heating roller type fixing device, the transfer paper is pinched and fixed because the lowermost toner layer to the uppermost toner layer are heated to an appropriate temperature. A fixing device is known in which heaters are provided on both the roller and the pressure roller, and the transfer paper is heated from both sides to sufficiently melt the toner layers of three or four colors.

FIG. 1 is a diagram showing a schematic configuration of a heating roller fixing device of this type. This fixing device has a fixing roller 1 and a pressure roller 2 which are in pressure contact with each other and rotate in the directions shown by the arrows in the drawing, and heaters 3a and 3b are provided in the respective rollers, and the circumference of each roller is set. A thermistor 4 as a temperature detector is provided in contact with the surface. The fixing roller 1 is provided with a releasable oil coating member 5 for preventing offset.

An example of a conventional fixing device will be described. In the fixing roller 1 described above, for example, a surface of a metal pipe having a diameter of 40 mm is coated with polytetrafluoroethylene resin of 30 μm, and a pressure roller 2 is used.
For example, the surface of a metal pipe having a diameter of 34 mm is coated with RTV silicone rubber to a thickness of 3 mm. The heaters 3a and 3b respectively provided in both rollers are set to 400 W, and each is made to blink by the thermistor 4 to independently control the temperature of the fixing and pressure rollers. In this state, the transfer material 6 passes between the rollers 1 and 2 and is heated, and the unfixed toner image 7 is fixed.

Now, changing the process speed between the full-color copy mode and the single-color copy mode is not performed by a normal transfer machine, and therefore, for example, yellow, magenta, cyan,
Copies per unit time in the case of full-color copy mode and transferring superposed four color black, is _^1/4 when the single-color copy mode, for example, 5 sheets / min in A4 size in full color copy mode, In single color copy mode, A4 size is 20 sheets / minute. Even if the process speed is changed, the copying speed does not become the same in the full color copy mode and the single color copy mode.

For example, set the control temperatures of the fixing roller and the pressure roller to 180
When the heaters 3a and 3b are controlled by the thermistor 4 by setting the temperature to 160 ° C. and 160 ° C., the heat of the roller is absorbed by the transfer material 6 and the toner 7 during continuous copying, and the heater is continuously turned on. Also, the temperature of the roller decreases and becomes saturated at a certain temperature. FIGS. 2 (a) and 2 (b) are curves showing temperature changes with time of the fixing roller and the pressure roller in the full color mode and the single color mode, respectively, when continuous copying is performed at the above copying speed. is there. In the figure, the curve shows the temperature of the fixing roller and the curve shows the temperature of the pressure roller. In the single-color copy mode, the copying speed is higher than that in the full-color copy mode, so that the temperature of the roller falls sharply and the saturation temperature becomes low.

Further, FIGS. 3A and 3B are graphs showing fixing, pressure roller temperature and fixing area in the full color mode and the single color copy mode, respectively. A region between the two curves is a region where good fixing is possible, hot offset occurs in a region above the curve indicating the upper limit, and fixing is not performed in a region below the curve indicating the lower limit. The fixing area is wider in the single color copy mode than in the full color copy mode. In these figures, the copy start 1 indicated by is obtained from FIGS. 2 (a) and 2 (b).
The first sheet and the points indicating the temperatures of both rollers after 1 minute, 2 minutes, ... As shown in FIG. 3 (a),
In the full-color mode, not only at the start but also 1
It can be seen that the temperatures of both rollers are still in the fixing area after 2 minutes, but in the single-color copy mode, the temperature is in the unfixed area after 2 minutes of continuous copying and the fixing failure occurs.

When fixing in a single-color copy mode with a fixing device having a heater for the fixing roller and the pressure roller, the heating of the pressure roller is turned off for power saving because the monochrome toner layer is thin and back heating is not required. For example, JP-A-61-209
No. 70 publication. As a result, the power consumption can be reduced, but the problem of defective fixing during continuous copying in the monochromatic copy mode cannot be solved. To ensure good fixing, it is sufficient to set the capacity of the heater in the fixing roller to, for example, 700 W. However, if this is done, the heater in the fixing device alone can be combined with 1400 W in combination with 400 W in the pressure roller. (11A) will be consumed. Since the current capacity of outlets in general offices is almost 100V15A, if 11A is used for the heater of the fixing device, only 4A will remain, and a color recording device will not work. Generally, copying speed is 20 sheets /
In the case of a minute class analog color copier, the power distribution is
It is usually 400 W for the optical system, 200 W for the drive charging system, 100 W for other systems, and 700-800 W for the fixing system. With a digital color recording device, the optical system can be 100 to 200 W, but in any case, it is necessary to reduce the power distribution to the fixing device as much as possible.

An object of the present invention is to solve the above-mentioned problems of the heat roller fixing device of the conventional color recording apparatus, to reduce the power distribution to the heaters provided in each roller of the fixing device, and to ensure good fixing. It is an object of the present invention to provide a fixing device that is used.

To achieve the above object, the present invention enables the fixing device having the above structure to turn on the heaters in both the fixing and pressing rollers during multicolor recording, and to turn on only the heater inside the fixing roller during single color recording. The output of the heater in the fixing roller during single-color recording is made larger than the output of the heater in the fixing roller during multi-color recording, and the amount of current distributed to the heater of the fixing device during multi-color recording and single-color recording is It is characterized in that a control means for controlling so as to be approximately equal is provided.

An embodiment in which the present invention is applied to a fixing device of a full-color copying machine will be described in detail below with reference to the drawings. The mechanical structure of the fixing device is the same as that shown in FIG. 1, but the heater 3a in the fixing roller 1 is 800 W, the heater in the pressure roller 2 is
800W is put into 3b, and the upper and lower heaters 3a and 3b
Lights up alternately (for example, every 1 second) as shown in FIG.
Each roller has a set temperature (for example, the fixing roller has 180
Repeat blinking until the temperature reaches ℃ and the pressure roller reaches 160 ℃. After each roller reaches the set temperature, each heater is time-divided so that the possible lighting times do not overlap, as shown in FIG. 4, and the heater is turned on by the thermistor 4 provided for each roller to maintain the set temperature. It is controlled so that it flashes within a possible time and does not light during the time when it cannot light, regardless of the signal from the thermistor 4.

Next, by selecting a full color copy mode or a single color copy mode by a switch (not shown), the control circuit as shown in FIG. 5 (a) causes the upper and lower heaters 3a, 3a, and 3d in the full color mode as shown in FIG. The lighting possible times of 3b are time-divided so that they do not overlap with each other, and the thermistors provided on the respective rollers are controlled so as to blink during the lighting possible time and not light during the lighting impossible time. It is not always necessary that the two heaters have the same turn-on time each time. For example, the heater 3a on the fixing roller side can be used.
The heater 3b on the pressure roller side may be turned on alternately for 2 seconds and for 1 second. By controlling in this way, in the full color mode, the fixing roller 1 and the pressure roller 2 are both 800 W heaters 3a, 3b provided inside each.
The heating is controlled by blinking by the thermistor 4, but since the times that can be turned on are time-divided so that they do not overlap each other, both heaters do not turn on at the same time, and the entire heater of the fixing device does not turn on. Only 8A current flows through.

Next, in the case of the monochrome copy mode, as shown in FIG.
The heater 3a in the fixing roller 1 is always in a lightable state,
Flashes under the control of the thermistor that contacts the fixing roller. On the other hand, the heater 3b in the pressure roller 2 is always placed in a non-lightable state. As a result, the temperature of the heater of the fixing roller 1 can be controlled with an output of substantially 800 W, so that the temperature of the fixing roller does not drop to the unfixed area in FIG. It is possible to continuously obtain the copies fixed on. FIG. 7 shows changes in the temperatures of the fixing roller and the pressure roller in this case.

In FIGS. 7 and 2A, during continuous copying, the temperature of the fixing roller, which has dropped once, rises again after about 1 minute and returns to the set temperature because the temperature of the atmosphere inside the fixing device is high. This is because

Next, the operation of the control circuit shown in FIG. 5 (a) will be described together with the timing chart shown in FIG. 5 (b).

In FIG. 5 (a), when the temperature of the thermistors TH ₁ and TH ₂ is lower than the set temperature, the outputs of the voltage comparators CMP1 and CMP2 become “H”, and when the temperature is higher than the set temperature, the voltage comparator CMP.
The output of 1 and CMP2 becomes "L". TM1 is a timer that repeatedly outputs an on / off signal at a predetermined frequency and duty ratio. In the full-color mode, the monochromatic signal from the control unit is "L", so the output of OR gate OR1 is the inverted output of timer TM1 and this is connected to one input of AND gate AND1. For,
The upper heater H1 is a timer while the output of the voltage comparator CMP1 is "H".
Turns on and off in synchronization with the inverted signal of TM1.

On the other hand, for the lower heater H2, the output of the AND gate AND3 becomes the same as the output of the timer TM1 when the monochromatic signal is “L”, and since this is connected to one input of the AND gate AND2, the lower heater H2 is While the output of voltage comparator CMP2 is "H", it turns on / off in synchronization with the output signal of timer TM1.

That is, in the full color mode, the upper heater H1 and the lower heater H2 are alternately turned on according to the output of the timer TM1.

In the monochromatic mode, the monochromatic signal is "H", so the output of the OR gate OR1 is always "H" regardless of the output of the timer TM1. Therefore, the upper heater H1 is turned on in synchronization with the output of the voltage comparator CMP1.・ Turn off.

On the other hand, since the output of the AND gate AND3 is always "L" regardless of the output of the timer TM1, the output of the AND gate AND2 is always "L", and the lower heater H2 is not turned on.

That is, in the single color mode, the lower heater H2 is always off, and only the upper heater H1 is turned on / off according to the output of the voltage comparator CMP1.

Next, another embodiment shown in FIG. 8 will be described. In this embodiment, two heaters of 400 W are provided inside the fixing roller 1.
The pressure roller 2 is provided with one heater 3b of 400 W. The heaters 3a and 3b are always in the thermistor 4 at the time of start-up, standby and full-color mode, respectively.
The two heaters 3a and 3c in the fixing roller 1 are controlled to blink by the thermistor in the monochrome mode.
The heater 3b in the pressure roller 2 is always turned off. Even with this method, sufficient fixability was obtained in both the full-color mode and the single-color mode.

An example of the control circuit in this case is shown in FIG.

In the figure, the operation of the voltage comparators CMP1 and CMP2 is similar to that of the control circuit shown in FIG. In full color mode,
Since the monochromatic signal is "L", the output of the AND gate AND4 is always "L", and the upper heater 3c (H3) is always off. The upper heater 3a (H1) and the lower heater 3b (H2) are turned on / off according to the outputs of the voltage comparators CMP1 and CMP2.

In the single color mode, the single color signal is "H", so the output of the AND gate AND5 is always "L" and the lower heater 3b (H
2) is always off, and the upper heaters 3a (H1) and 3c (H3) are turned on and off according to the output of the voltage comparator CMP1.

Further, as another embodiment, as in the first embodiment, each of the fixing roller and the pressure roller is provided with a heater of 800 W, and in the full color copy mode, both are half-wave controlled and used as 400 W respectively, and in the single color mode. Only the heater in the fixing roller is full-wave controlled and used as 800 W, the heater in the pressure roller is turned off, and the heaters used are controlled to blink by the thermistor. I was able to achieve it.

Effects As described above, according to the present invention, sufficient fixability can be obtained in both the full-color copy mode and the single-color copy mode without increasing the power distribution to the heater of the fixing device.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of the constitution of a fixing device to which the present invention is applied, and FIG. 2 is a graph showing changes in temperature of a fixing roller and a pressure roller by a conventional control method of the device (a). Is in the full-color mode, (b) is in the single-color mode, and FIG. 3 is a graph showing the relationship between the temperature of the fixing roller and the pressure roller and the fixing area in the conventional apparatus, and (a) is in the full-color mode. (B) is for the single color mode, and FIG. 4 is a timing diagram of heater turn-on timing at the time of start-up, standby and full-color mode of the above apparatus, FIG.
FIG. 5 (a) is a circuit diagram showing an example of the control circuit, FIG. 5 (b) is its timing diagram, FIG. 6 is a heater lighting possible timing diagram in the monochrome mode of the apparatus, and FIG. FIG. 8 is a graph showing a temperature change of the fixing roller and the pressure roller in the monochromatic copy mode of the apparatus, FIG. 8 is a sectional view showing another embodiment of the present invention, and FIG. 9 is a circuit diagram showing an example of its control circuit. is there. 1 ... Fixing roller, 2 ... Pressure roller, 3a, 3b, 3c ... Heater, 4 ... Thermistor (roller temperature detecting means), 6 ...
… Transfer material, 7… Toner image

Claims (4)

[Claims] 1. A heating roller fixing device of a color recording device in which the number of recordings per unit time is different between single-color recording and multi-color recording, the fixing roller and the pressure roller being in pressure contact with each other, and the inside of each of them. And a heater that is flickered by the detection signal of the temperature detecting means of each roller, and passes the transfer material carrying the unfixed toner image between the pair of rollers so that the toner image side contacts the fixing roller. In this case, the heaters in both the fixing and pressure rollers can be turned on during multicolor recording, and only the heater in the fixing roller can be turned on during single color recording. Output of the heater inside the fixing roller during single color recording Is greater than the output of the heater in the fixing roller during multi-color recording, and the current distribution to the heater of the fixing device is controlled to be substantially equal during multi-color recording and single-color recording. A fixing device, characterized in that provided. 2. The above control means sets the lighting time of the heaters in both the fixing and pressing rollers in a time-divided manner so as not to overlap each other during the multi-color recording, and only the heater in the fixing roller during the single-color recording. The fixing device according to claim 1, wherein switching control is performed such that the fixing device can be always turned on. 3. The fixing roller is provided with two heaters, one of which has a capacity substantially equal to that of the pressure roller, and the control means fixes at the time of multi-color recording. Another one heater in the roller and a heater in the pressure roller can be turned on, and switching control is performed so that only two heaters in the fixing roller can be turned on during single-color recording. Claim 1 to
The fixing device according to the item. 4. The capacities of the heaters in the fixing roller and the pressure roller are substantially equal to each other, and the control means controls the heaters in both rollers by half-wave during the multi-color recording, and in the fixing roller during the single-color recording. The fixing device according to claim 1, wherein only the heater is full-wave controlled.