JPS62157079A - Method of controlling fixing power in color copying machine - Google Patents

Abstract

PURPOSE:To efficiently use the calorific value of a heat source by setting the calorific value of a heating means of a fixing roll larger than that of a pressure roll and reducing the fed power of the heating means of the fixing roll to feed heating means of the fixing roll and the pressure roll in case of color copying and feeding only the heating means of the fixing roll in case of monochromatic copying. CONSTITUTION:A fixing device 4 is provided with a fixing roll 5 and a pressure roll 6 pressed to the fixing roll 5 and heating means constituted as heaters 7 and 8 are incorporated in these rolls. In case of color copying, the power to the heater 7 is reduced to an about half of the full wave power but the power to the heater 8 is fed as it is. A half wave component of the supply power is fed to the heater 7. In case of monochromatic copying, all of the power to be supplied to heaters 7 and 8, namely, the full wave power is fed to the heater 7 of the fixing roll 5 but power supply to the heater 8 of the pressure roll 5 is stopped. Thus, even the lowest toner layer is fixed surely because heaters 7 and 8 of the fixing roll 5 and the pressure roll 6 are heated together in case of color copying.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a fixing power control method for controlling power supplied to a fixing device in a color copying machine.

Conventional technology Conventionally, a heat roller fixing device used in copying machines, etc. has a built-in heater only in the fixing roller that contacts the surface of the copy paper carrying the unfixed toner image, and the pressure roller has a fta heating means. Generally, it is not provided.

However, the toner image transferred to the copy paper is 6 colors or 4 colors.
In the case of full color, in which the toner is layered, the thickness of each toner layer is about 4 to 5 times that of a single color, and 30 to 40 μm is deposited. For this reason, heating from the fixing roller alone does not melt the toner near the copy paper, that is, the lowest layer of toner, resulting in defective fixing. In order to prevent this fixing failure, it is conceivable to increase the amount of heat from the fixing roller, but in this case, the amount of heat is excessive and hot offset occurs. Therefore,
In color copying machines, a fixing roller and a pressure roller are provided with heaters.

Also, even though it is a color copying machine, it is a matter of course that the copying speed can be changed between full color and monochrome.For example, when full color is used, it copies 5 sheets per minute, and when it is monochrome, it copies 5 sheets per minute. It is configured to hold 20 sheets.

However, in order to guarantee the fixing performance of 20 sheets per minute during monochrome copying, it becomes necessary to significantly increase the amount of heat generated by the heater on the fixing roller side, which contributes to the fixing, compared to full color copying. That is, in an apparatus in which a fixing roller and a pressure roller are provided with heaters as shown in the graph of FIG. 7, when monochrome copies are made continuously, the temperature of the rollers decreases. Therefore, it becomes necessary to increase the heat generating layer of the heater of the fixing roller to the extent that this decrease is compensated for.

Thus, when designing a color copying machine, the general power supply
0VI SA will have insufficient capacity, for example 100V20
There was a problem that A and 200v systems had to be used.

In order to solve this problem, when the exposure lamp is on, the power of the fixing heater is halved, and in the case of upper and lower heaters, the pressure roller heater is not turned on when the exposure lamp is on, but it is turned on when the exposure lamp goes out. There is also a method to do this, but in the above proposal, the temperature of the fixing/pressure roller could not be maintained, resulting in defective fixing.

Purpose The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a fixing control method that efficiently uses the amount of heat of a heating source.

Structure To achieve this objective, the present invention sets the heat generation layer of the heating means of the fixing roller to be larger than the amount of heat generated by the heating means of the pressure roller. The present invention has been achieved by reducing the amount of power supplied to the heating means of the fixing roller and the pressure roller, and during monochrome copying, supplying power to the heating means of the fixing roller and stopping the supply of power to the heating means of the pressure roller.

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

FIG. 1 is a diagram schematically showing a color copying machine to which the present invention is applied, in which reference numeral 1 denotes a photosensitive drum, 2 a transfer drum, and 3 a paper feeding device.

In this color copying machine, when color copying, in which images of multiple colors are copied onto copy paper, is selected, the copy paper fed from the paper feeder 6 is clamped to a transfer drum, and the photosensitive drum is attached to the copy paper. For example, magenta, cyan, yellow, black, etc. formed on the photosensitive drum 1 are transferred for each color. Thereafter, the copy paper is removed from the transfer drum and sent to the fixing device 4. Furthermore, if monochrome copying in which a single color image is copied onto copy paper is selected, the image is sent to the fixing device 4 immediately after the transfer. Therefore, the copying speed is different between color copying and monochrome copying, and in this example, it is assumed that 5 sheets can be copied per minute during color copying and 20 sheets per minute can be copied during monochrome copying.

Although a brief explanation of the color copying machine has been given above, a more detailed explanation will be omitted since it is not the gist of the present invention.

As shown in FIG. 2, the fixing device 4 has a fixing roller 5 and a pressure roller 6 that comes into pressure contact with the fixing roller 5, and each roller has a built-in heating means configured as a heater 7.8. has been done. In this case, the heater 7 of the fixing roller 5 is set to so and ow, and the heater 8 of the pressure roller is set to 400W.

Power is supplied to the fixing device 4 configured as described above as follows.

First, during color copying, the power supplied to the heater 7 is reduced to about half of the full-wave power, and the power is supplied to the heater 8 as is. In this case, the heater 7 is supplied with a half-wave of the supplied power as indicated by the 'Nj section in FIG. Next, Toniro 1
When taking one photo, the heater 7.8 is supplied with [l (total power to be supplied,
That is, full-wave power is supplied to the heater 7 of the fixing roller 5, and power supply to the heater 8 of the pressure roller 5 is stopped.

By controlling in this way, during color copying, the heaters 7.8 of the fixing roller 5 and the pressure roller 6 do not generate heat, and the bottom toner layer is also reliably fixed.

In addition, when copying a single color, a fixing roller 5 that contributes to fixing the copy is provided.
By increasing the amount of heat generated by the heater 7, the desired temperature can be maintained even during continuous copying.

Based on the fixing force control method of the present invention, experiments were conducted to determine how the roller temperature during color copying and monochrome copying was changed depending on the copying time. The results are shown in the graph of FIG. As is clear from this graph, even if monochrome copying is performed continuously, the roller temperature does not drop, and the source disappears during call offset and the like.

FIG. 5 shows another embodiment of the present invention, showing a method of reducing the power supply to the heater 7 to half the full-wave power during color copying. Turn off. That is, power is supplied to the heater 7 for one cycle indicated by diagonal lines in FIG. In this case as well, the same effects as in the above practical example can be obtained.

FIG. 6 shows yet another embodiment of the present invention. In this embodiment, two heaters 7.7a are built into the fixing roller 5, and a heater 8 is built into the pressure roller 6.
．． 7a and 8 use heaters with approximately the same calorific value, for example, 400W.

During color copying, only the heater 7 of the fixing roller 5 and the heater 8 of the pressure roller 6 are supplied with power and turned on, and the heater 7a is not supplied with power. Also, during monochrome copying, the heater 7
．． 7a, and the power supply to the heater 8 is stopped.

By controlling in this manner, not only the same effects as in the above embodiment can be obtained, but also the control itself becomes simple.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be modified in various ways. For example, it is most advantageous for the heating means to consist of a heater built into the fixing roller and the pressure roller, but it may also be a heating means that heats each roller from the outside.

It should be noted that the present invention is not limited to the color copying machine having only one photosensitive drum as shown in FIG. 1, but can of course be applied to a color copying machine that uses a side-by-side method such as a three-drum type color copying machine.

Effects The present invention is configured as described above, and even when the power supplied to the fixing section is constant, the amount of heat to the heating means can be used efficiently, and even when making color copies or monochrome copies, the amount of heat can be efficiently used. Fixation was obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a color copying machine to which the present invention is applied;
Fig. 2 is an enlarged view of the fixing main part in Fig. 1, Fig. 3 is an explanatory diagram showing the method of supplying power to the heating means of the fixing roller, and Fig. 4 is a copy during color copying and monochrome copying according to the present invention. A graph showing changes in roller temperature with respect to time, FIG. 5 is an explanatory diagram showing another method of supplying power to the heating means of the fixing roller, FIG. 6 is an explanatory diagram showing another embodiment of the present invention, and FIG. 4 is a graph showing changes in roller temperature with respect to copying time during color copying and monochrome copying using a conventional fixing device. 5... Fixing roller 6... Pressure roller 7, 7a
, 8...Heater Koko'-H legs (minutes)

Claims (6)

[Claims] (1) The copying speed differs between color copying, in which images of multiple colors are copied onto copy paper, and monochrome copying, in which one color image is copied onto copy paper, and heating means are provided for each of the fixing roller and pressure roller. In the fixing power control method for a color copying machine, the amount of heat generated by the heating means for the fixing roller is larger than the amount of heat generated by the heating means for the pressure roller. During color copying, power is supplied to the heating means for the fixing roller and pressure roller by reducing the power supply to the heating means for the fixing roller, and during monochrome copying, power is supplied to the heating means for the fixing roller and pressure is applied. The control method described above, characterized in that power supply to the roller heating means is stopped. (2) The control method according to claim 1, wherein the amount of heat generated by the heating means for the fixing roller is set to be approximately twice as large as the amount of heat generated by the heating means for the pressure roller. . (3) The control method according to claim 1 or 2, characterized in that during the color copying, the power supply force of the heating means for the fixing roller is reduced by approximately half. (4) According to any one of claims 1 to 3, the electric power supplied to the heating means of the fixing roller during color copying is a half-wave of the electric power. control method. (5) According to any one of claims 1 to 3, the electric power supplied to the heating means of the fixing roller during color copying is turned on and off every cycle of the electric power. Control method described. (6) Any one of claims 1 to 3, wherein the heating means for the fixing roller includes two heaters, and power is supplied to only one heater during the color copying. Control method described in .