JPS6120970A - Heat fixing device - Google Patents

Abstract

PURPOSE:To reduce the electric power consumption and to attain stable back heating by controlling the temperature of a fixing roll in case of monocolor copy and controlling the temperature of a pressuring roll in case of full color copy. CONSTITUTION:Since the quantity of toner is large in case of full color copy, a heater 8 is controlled by the thermistor 9 of a pressuring roll 3 to heat the roll stably from the rear face of a transfer material, and the multilayered toner is fused sufficiently. Since the quantity of toner is small in case of monocolor copy, the temperature of a fixing roll 2 is controlled by a thermistor 7 to reduce the heating temperature of a heat roll 1 brought into contact with the rear face of the transfer material, and the power consumption is reduced. Thus, the power consumption is reduced in case of monocolor copy, and back heating at a stable temperature from the rear face of the transfer material is performed in case of full color copy.

Description

Detailed Description of the Invention A. Object of the Invention [Industrial Field of Application] The present invention relates to a heat fixing device, in particular, a heat fixing device that allows a transfer material having an unfixed toner image to pass between a fixing roller and a heating roller that are in pressure contact with each other. The present invention relates to a heat fixing device that fixes an unfixed toner image.

[Conventional technology]

FIG. 6 shows an outline of a conventional heat fixing device of this type, where l is an upper pressure roller, 2 is a fixing roller, 3 is a lower pressure roller, 4 is a conveying path, 5 is a transfer material, and 6 is an offset. A prevention oil application mechanism, 7 a thermistor as a temperature detector, and 8.8 a 800W heating heater provided in the upper and lower pressure rollers 1.3.

The above-mentioned upper and lower pressure rollers 1.3 are, for example, metal pipes 1a,
25gm of Teflon (trade name) 1b, 3b on the surface of 3a
The fixing roller 2 is made of, for example, gold Jj4 vibrator 2a.
The surface is coated with RTV silicone rubber 2b to a thickness of 5 m. These rollers l to 3 are each rotatably supported by an apparatus body (not shown) in the direction of the arrow, and offset prevention oil O applied to the surface of the maxillary pressure roller l by an oil application mechanism 6 is applied to each of the rollers l. -3 surfaces by rotation of the respective rollers.

When the image recording apparatus to which the heat fixing device described in I- is applied is operated, rotation of rollers 1 to 3 and energization of heater 8.8 are started in conjunction with this operation, and 1-pressure roller l
The amount of current supplied to the heater 8.8 is controlled by the detection signal from the thermistor 7 which detects the temperature of the rollers 1 to 3, thereby maintaining each roller 1 to 3 at a predetermined heating temperature.

In this state 181, when the transfer material 5 that has passed through the conveyance path 4 passes between the contact roller 2 and the lower processing roller 3, the transfer material 5 is heated from both the front and back sides by both rollers 2.3, and is carried on the surface. The unfixed toner T is melted and fixed. During this fixing, the temperature of both rollers 2.3 is set to a temperature at which the toner T can be heated and melted, for example, the temperature of the fixing roller 2, depending on the characteristics of the toner T.
Set the thermistor 7 so that the temperature of the upper pressure roller 1 becomes 153°C and the temperature of the lower working roller 3 becomes 153°C.
The amount of electricity supplied to the heater 8.8 is controlled by the detection signal.

[Problem that the invention seeks to solve]

However, in the temperature control described above, the transfer material 5 is continuously heated.
When the roller passes between the rollers 2.3, the temperature of the roller 3 decreases due to the difference in heat capacity between the rollers 2.3, that is, the heat capacity of the roller 2 is larger than that of the roller 3.

FIG. 7 is a diagram showing the temperature changes of each roller 1 to 3 when the above heat fixing device is used to fix a full color copy and a monochrome copy of an electrophotographic color copying device.
FIG. 5(a) shows the case when full-color copying is performed, and FIG. 2(b) shows the case when monochrome copying is performed. Same figure (a), (b)
, A is a temperature change graph of the upper pressure roller l, B is a temperature change graph of the fixing roller 2, and C is a temperature change graph of the lower processing roller 3.
The temperature drop is obvious. In this case, the copying speed for full-color copying is 5 sheets/minute on A4 size transfer material, and the blind copying speed for monochrome copying is 15 sheets/minute on A4 size transfer material.

On the other hand, during full-color copying, the amount of toner is large with three or four colors overlapping, so even if the upper part of the toner contacts the fixing roller 2 with high heating temperature and is well melted, it contacts the lower part, that is, the surface of the transfer material 5. Toner in the vicinity is difficult to melt, and the adhesion of the toner to the transfer material is reduced compared to monochrome copying using one color toner. In other words, the toner images before fixing are sequentially yellow and yellow starting from the top layer of the full-color copy.
If there are three layers, magenta and cyan, it is necessary to set the fixing roller at a high temperature in order to reliably melt down to the lowest cyan layer. However, if the temperature of the fixing roller 2 is made too high, a phenomenon occurs in which the toner on the surface of the fixing roller 2 is offset.

Therefore, in order to increase the fixing power for such transfer materials and to prevent offset, it is necessary to heat the back side of the transfer material at a more stable temperature than the back side of the transfer material and lower the fusing temperature to some extent. There is. As a result, heat is uniformly supplied to each layer of the multi-layered toner, and effective heating, fusing and fixing can be performed.

However, during monochrome copying, such backside heating is not particularly required. Therefore, in order to save power in the heating and fixing device, the heating heater 8 in the substructure roller 3 is turned off or turned off during monochrome copying. It is preferable to lower the heating temperature.

The present invention solves the above contradictory problems.

Summary: Structure of the Invention [Means for Solving the Problems] A temperature detection member is provided on each of a pair of heating rollers, and the temperature detection member is used depending on the toner state, for example, a signal for switching between monochrome and full color, so that it can be used to switch between monochrome and full color. When there is little toner, a temperature sensing member is used to control the temperature of the fixing roller to lower the heating temperature of the heating roller that contacts the back of the transfer material to save power, and when there is a lot of toner such as full color temporary This heat fixing device uses a temperature detection member that controls the temperature of the pressure roller to heat the back surface of the transfer material at a stable temperature to fix the material.

〔Example〕

FIG. 1 is a schematic diagram showing one embodiment of the present invention.
Components that are the same as those in the drawings are given the same reference numerals and their explanations will be omitted. In FIG. 1, reference numeral 9 denotes a thermistor as a temperature detection member for detecting the temperature of the lower front pressure roller 3.

Figure 2 shows an image recording apparatus (
(not shown), in which a switch 11 is operated to perform a full color copy, and a switch 12 is operated to perform a monochrome copy. switch t
When i is pressed, the fixing temperature is controlled by the detection section t'f of the thermistor 9 that detects the temperature of the lower front pressure roller 3 by the control means shown in the block diagram, and the temperature of the fixing roller 2 is increased to 1.
Temperature control is performed by turning on and off the power supply path (block diagram) to heater 8.8 so as to maintain the temperature at 40 degrees. When the switch 12 is pressed, the fixing temperature is controlled by the detection signal of the thermistor 7 that detects the temperature of the pressure roller l, the power supply path of the heater 8 in the lower front pressure roller 3 is turned off, and the upper jaw pressure roller The temperature of the fixing roller 2 is maintained at 135 degrees by controlling only the power supply path of the heater 8 inside the fixing roller on and off.

Here, the reason why the full color temporary fixing temperature is higher than the monochrome temporary fixing temperature is because, as described above, the toner layer is thicker, so it is necessary to heat it sufficiently. In other words, it is necessary to sufficiently melt one layer of three or four color toners to mix the colors.

As described above, by selecting full color copy mode or monochrome copy mode with the switch, the heating temperature of the fixing roller and pressure roller is controlled according to the state of unfixed toner in the selected mode, and transfer is performed. A toner image can be stably and reliably fixed on the material.

Figure 3 shows the temperature change of each heating roller of the fuser configuration shown in Figure 1 with respect to the number of copies, with (a) showing the case during full-color copying, and (b) showing the case during mono-color copying. It is. In FIGS. 3A and 3B, A is a temperature change graph of the upper jaw pressure roller 1, B is a temperature change graph of the fixing roller 2, and C is a temperature change graph of the lower front pressure roller 3.

As is clear from FIG. 3(a), during full-color copying, the transfer material 5 can always be stably heated from the back side thereof, so that one layer of unfixed toner can be well melted and mixed to be fixed. Furthermore, as is clear from FIG. 3(b), the temperature C of the lower front pressure roller 3 is the lowest during monochrome copying, which means that the lower front pressure roller 3 consumes less power and saves power. indicates that this has been achieved. In this case, the temperature of the fixing roller 2 will eventually drop by 5°C due to the temperature drop of the lower front pressure roller 3, but this temperature drop of the fixing roller is due to the small amount of toner when fixing a monochrome copy. The toner near the interface with the transfer material is difficult to melt, no offset occurs, and color mixing properties are not required, so there is no problem with its fixability.

FIG. 4 shows a fixing device having a two-roller configuration in another embodiment. The fixing roller 13 and the pressure roller 13 are metal pipes 13. This is a structure in which an HTV silicone rubber layer 13b is coated on top of a. When performing full color copying, the power supply path to the 800W heaters 8 is turned on and off by a control means (not shown) based on a detection signal from the thermistor 9 that detects the temperature of the pressure roller l3' on the non-toner side. Keep the temperature of the fixing roller 13 at 140 degrees (fixing roller 13
The pressure roller 13 is heated to a higher temperature). When performing monochrome copying, the power supply path of the heater 8 in the pressure roller l3' is turned off by the detection part-J of the thermistor 7 that detects the temperature of the fixing roller on the toner side, and the heater in the fixing roller 13 is switched off. Temperature control is performed so that only the power supply path No. 8 is turned on and off to maintain the temperature of the fixing roller 13 at 135° C. (the pressure roller 13 is kept at a higher temperature than the fixing roller).

FIG. 5 shows a fixing device having a two-roller configuration shown in FIG. 4, which reduces the temperature change of each heating roller with respect to the number of copies.
FIG. 4(a) shows the case when full-color copying is performed, and FIG. 12(b) shows the case when monochrome copying is performed. In the same figures (a) and (b), A is a temperature change graph of pressure roller l3', B
is a temperature change graph of the fixing roller 13. From this graph, it is clear that the present invention has the effect of reducing power consumption during monochrome copying and heating the backside of the transfer material at a temperature more stable than the backside of the transfer material during full-color copying, even in a fuser with a two-wood roller configuration. .

C. More than the effects of the invention, δAs mentioned above, according to the present invention, when the amount of toner is large as in full-color copying, the temperature detection of the thermistor that detects the heating temperature of the lower roller that comes into contact with the back surface of the transfer material The temperature is controlled by a signal, and when the amount of toner is small, such as in monochrome copying, the temperature is controlled by a thermistor that controls the temperature of the fixing roller that comes into contact with the surface of the transfer material, resulting in stable backside heating during full-color copying. is obtained, one layer of unfixed toner in a multilayer can be well melted and mixed, and during monochrome copying, the heating temperature at which the transfer material comes into contact with the back side can be lowered, thereby achieving the effect of saving power.

In the explanation of this example, the copying speed for full color copying is 5 sheets/minute for A4 size, and for monochrome copying at A4 size.
Although the description has been given using a copying speed of 15 sheets/minute, the effects of the present invention are not limited to this copying speed; for example,
If the copying speed for full-color copying and the copying speed for monochrome copying are the same, for example, even if the copying speed is 5 pages per minute, by implementing the present invention, power consumption will be saved during monochrome copying,
During full-color copying, backside heating with a more stable temperature can be obtained from the backside of the transfer material.

As a result of implementing the present invention, when copying in monochrome.

Compared to the conventional case where both heaters housed in a pair of rollers were turned on to perform heating, the heater in the roller on the side that contacts the back of the transfer material is turned off and only the heater in the other roller is turned on. By turning it off and controlling the temperature, the power consumption that used to be 5 Kw/hour per 1000 monochrome A4 copies was reduced to 3.5 Kw/hour, resulting in a 30% power saving.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of the heat fixing device of the present invention;
FIG. 2 is a diagram of an operation panel of an image forming apparatus to which the heat fixing device of the present invention is applied, FIG. 3 is a diagram of temperature changes of each heating roller in FIG. 1, FIG. 4 is a schematic diagram of another embodiment, and FIG. 6 is a schematic diagram of a conventional heat fixing device, and FIG. 7 is a diagram of temperature changes of each heating roller in the device. 1 is the main pressure roller, 2 is the fixing roller, 3 is the lower pressure roller, 7.9 is the thermistor, and 8.8 is the heater. Patent applicant Canon Co., Ltd. 1 Agent Fuku 1)
1-1) Low or m- 0 crush! ,lk￥

Claims (1)

[Claims] (1) In a heat fixing device in a color recording device, at least the fixing roller on the unfixed image side and the pressure roller are heated and brought into contact with each other, and the recording material having the unfixed image is passed between both rollers, and the unfixed image is In a heat fixing device that fixes
A temperature detection member that controls the temperature of the fixing roller, a temperature detection member that controls the temperature of the pressure roller, and a temperature detection member that controls the temperature of the fixing roller when fixing a monochromatic developed image are used. A temperature sensing member is used to control the temperature on the pressure roller side when copying a multi-color developed image, and means is provided for switching and controlling fixing conditions according to the state of the image on the recording material. Heat fixing device.