JPH0756583B2 - Heat fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention [Field of Industrial Application] The present invention relates to a heat fixing device, and more particularly, to a transfer material having an unfixed toner image passing between a pressure roller and a heating roller. 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. 1 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 a transfer material. An oil coating mechanism for preventing offset, 7 is a thermistor as a temperature detector, and 8 and 8 are 800 W heaters provided in the upper and lower pressure rollers 1 and 3.

The vertical pressure rollers 1 and 3 are, for example, metal pipes 1a and 3a.
The surface of is coated with Teflon (trade name) 1b, 3b to 25 μm,
The fixing roller 2 has, for example, a structure in which the surface of a metal pipe 2a is covered with RTV silicone rubber 2b in a thickness of 5 mm. Each of these rollers 1 to 3 is rotatably supported by an apparatus main body (not shown) so as to be rotatable in an arrow direction, and the offset preventing oil O applied to the surface of the upper pressure roller 1 by the oil applying mechanism 6 is applied to each of the above rollers. It is applied to the surfaces of 1-3 by the rotation of each roller.

When the image recording apparatus to which the above heat fixing device is applied is operated, the rotation of the rollers 1 to 3 and the energization of the heaters 8 and 8 are started in conjunction with this operation, and the temperature of the upper pressure roller 1 is detected. The detection signal of the thermistor 7 is used to control the energization amount of the heaters 8 and 8 to keep the rollers 1 to 3 at a predetermined heating temperature.

In this state, when the transfer material 5 passing through the transport path 4 passes between the fixing roller 2 and the lower pressure roller 3, the transfer material 5
Is heated from both front and back sides by both rollers 2 and 3, and the unfixed toner T carried on the surface is melted and fixed. During this fixing, the temperature of both rollers 2, 3 can be heated and melted according to the characteristics of the toner T, for example, the temperature of the fixing roller 2 is 145 ° C.,
The energization amount of the heaters 8 is controlled by the detection signal of the thermistor 7 so that the temperature of the upper pressure roller 1 becomes 153 ° C. and the temperature of the lower pressure roller 3 becomes 153 ° C.

[Problems to be solved by the invention]

However, in the above temperature control, the transfer material 5 is continuously supplied.
When the paper passes between the rollers 1 and 2, the difference in heat capacity between the rollers 2 and 3, that is, the heat capacity of the roller 2 is larger than that of the roller 3, so that the temperature of the roller 3 drops.

FIG. 7 is a diagram showing temperature changes of the rollers 1 to 3 when fixing a full-color copy and a mono-color copy of an electrophotographic color copying apparatus using the above heat fixing apparatus.
The figure (a) shows the case of full color copy, and the figure (b) shows the case of mono color copy. In FIGS. 10A and 10B, A is a temperature change graph of the upper pressure roller 1, B is a temperature change graph of the fixing roller 2, and C is a temperature change graph of the lower pressure roller 3, which are based on continuous fixing. The temperature drop of the lower pressure roller 3 is obvious. In this case, the copying speed of the full-color copy is 5 sheets / minute for the A4 size transfer material, and the copying speed of the mono-color copy is 15 sheets / minute for the A4 size transfer material.

On the other hand, in full-color copying, since the toner amounts are large in three or four colors, the upper portion of the toner is in contact with the fixing roller 2 having a high heating temperature and is well melted, but is in contact with the lower portion, that is, the surface of the transfer material 5. The toner in the vicinity is less likely to melt, and the adhesive force of the toner to the transfer material is reduced as compared with a monocolor copy using one color toner. In other words, the toner image before fixing is yellow from the upper layer of the full-color copy,
In the case of three layers of magenta and cyan, it is necessary to set the fixing roller to a high temperature in order to surely melt the lowest cyan layer. However, when the temperature of the fixing roller 2 is too high, the toner on the surface of the fixing roller 2 is offset.

Therefore, in order to enhance the fixing power for such a transfer material and prevent the offset, it is necessary to perform the back surface heating at a stable temperature from the back surface of the transfer material and to lower the fixing roller temperature to some extent to perform the fixing. . As a result, heat is evenly supplied to the multi-layered toner layer as a whole, and effective heat fusion fixing can be performed.

However, such backside heating is not particularly required during monocolor copying. Therefore, in order to save the power of the heat fixing device, it is preferable to turn off the heater 8 in the lower pressure roller 3 or lower the heating temperature during the monocolor copying.

The present invention solves the conflicting problems described above.

B. Structure of the Invention [Means for Solving the Problems] The present invention for solving the above-described problems is to provide a pair of rotating bodies for fixing the unfixed toner image by sandwiching and conveying a recording material carrying the unfixed toner image. , A first heater that heats the first rotating body that is in contact with the unfixed toner image, a second heater that heats the second rotating body that is not in contact with the unfixed toner image, and a surface temperature of the first rotating body A heat fixing device having a first detecting means for detecting the temperature, a second detecting means for detecting the surface temperature of the second rotating body, and a control means for controlling the surface temperature of the rotating body based on a detection signal of the detecting means. In the above, the control means turns off the power supply to the second heater when fixing a single color unfixed toner image, and controls the power supply to the first heater based on the detection signal of the first detection means, thereby controlling a plurality of colors. When fixing the unfixed toner image of And controlling both the power supply to the means for sensing current and the second heater signal to the first heater based on.

〔Example〕

FIG. 1 is a schematic view showing an embodiment of the present invention, and
The same parts as those in the figure are designated by the same reference numerals and the description thereof will be omitted. In FIG. 1, 9 is a thermistor as a temperature detecting member for detecting the temperature of the lower pressure roller 3.

FIG. 2 shows an operation panel 10 of an image recording apparatus (not shown) to which the heat fixing device of the present invention is applied. The switch 11 is operated when full color copying is performed, and the switch 12 is operated when mono color copying is performed. Manipulate. When the switch 11 is pressed, the fixing temperature is controlled by the detection signal of the thermistor 9 which detects the temperature of the lower pressure roller 3 by the control means shown in the block diagram, so that the temperature of the fixing roller 2 is maintained at 140 degrees. The temperature control is performed by turning on and off the power supply path (block diagram) for the 8 and 8. When the switch 12 is pressed, the fixing temperature is the thermistor 7 which detects the temperature of the upper pressure roller 1.
Of the fixing roller 2 is controlled by turning off the power feeding path of the heater 8 in the lower pressure roller 3 and turning on and off only the power feeding path of the heater 8 in the upper pressure roller. Keep the temperature at 135 degrees.

Here, the fixing temperature in full color is higher than the fixing temperature in mono color, because the toner layer is thick as described above, so it is necessary to heat it sufficiently. That is, it is necessary to sufficiently melt the toner layers of three colors or four colors to mix the colors.

By selecting the full-color copy mode or the mono-color copy mode with the switch as described above, by controlling the heating temperature of the fixing roller and the pressure roller according to the state of the unfixed toner in the selected mode,
The toner image can be stably and reliably fixed on the transfer material.

FIG. 3 shows the temperature change with respect to the number of copies of each heating roller of the fixing device configuration shown in FIG. 1, where FIG. 3 (a) is for full-color copying and FIG. 3 (b) is for mono-color copying. Is. 1A and 1B, A is a temperature change graph of the upper pressure roller 1, B is a temperature change graph of the fixing roller 2, and C is a temperature change graph of the lower pressure roller 3.

As is clear from FIG. 3A, the transfer material 5 can be stably heated from the back surface thereof at all times during full-color copying, so that the multilayer unfixed toner layers can be well melt-mixed and fixed. Further, as is clear from FIG. 3B, the temperature C of the lower pressure roller 3 is the lowest at the time of monocolor copying, which means that the lower pressure roller 3 consumes less power and saves power. Has been achieved. In this case, the temperature of the lower pressure roller 3 finally drops by 5 ° C. due to the temperature drop of the lower pressure roller 3, but this temperature drop of the fix roller is small in the toner amount in the fixing of the monocolor copy. Toner near the boundary with the transfer material is difficult to melt, and no offset occurs,
Further, since the color mixing property is not required, there is no problem in the fixing property.

FIG. 4 shows a fixing device having a two-roller structure in another embodiment. The fixing roller 13 and the pressure roller 13 ′ are metal pipes 13
This is a structure in which the HTV silicone rubber layer 13b is coated on a. For full-color copying, the pressure roller on the non-toner side
By the detection signal of the thermistor 9 which detects the temperature of 13 ',
A control means (not shown) controls the temperature of the fixing roller 13 so that the temperature of the fixing roller 13 is kept at 140 degrees by turning on / off the power supply path to the heater 8.8 of 800 W (the pressure roller 13 'is made higher than the fixing roller 13). I do. When performing mono-color copying, the power supply path of the heater 8 in the pressure roller 13 'is turned off by the detection signal of the thermistor 7 which detects the temperature of the fixing roller on the toner side, and the power of the heater 8 in the fixing roller 13 is supplied. Only the path is turned on / off to perform temperature control so that the temperature of the fixing roller 13 is maintained at 135 ° C. (the pressure roller 13 'is higher than the fixing roller).

FIG. 5 shows the temperature change with respect to the number of copies of each heating roller of the fixing device having the two-roller structure shown in FIG.
The figure (a) shows the case of full color copy, and the figure (b) shows the case of mono color copy. In FIGS. 7A and 7B, A is a temperature change graph of the pressure roller 13 ′ and B is a temperature change graph of the fixing roller 13. From this graph, it is clear that even in the fixing device having the two-roller structure, there is the effect of the present invention that the power consumption during monocolor copying and the backside heating at a stable temperature from the backside of the transfer material can be obtained during fullcolor copying. .

C. Effect of the Invention As described above in detail, according to the present invention, the temperature detection signal of the thermistor that detects the heating temperature of the lower roller that contacts the back surface of the transfer material when the amount of toner is large such as in full-color copying. The temperature is controlled by a thermistor that controls the temperature of the fixing roller that contacts the surface of the transfer material when the amount of toner is small, such as in monocolor copying, so stable backside heating is achieved during full-color copying. Obtained,
You can fuse and mix the multi-layered unfixed toner layer well,
At the time of mono-color copying, the effect of lowering the heating temperature that contacts the back surface of the transfer material and achieving power saving can be obtained.

In the description of this embodiment, the copying speed of full-color copying is 5 sheets / minute for A4 size and 15 sheets / minute for A4 size for mono-color copying, but the effect of the present invention is limited to this copying speed. However, for example, when the copying speed of the full-color copy and the copying speed of the mono-color copy are the same, for example, even if it is 5 sheets / minute, according to the embodiment of the present invention, power saving is achieved during the mono-color copy, and the full-color copy is performed. During copying, the back surface of the transfer material can be heated from the back surface at a stable temperature.

As a result of carrying out the present invention, in the case of a mono-color copy, as compared with the conventional case in which both heaters housed in a pair of rollers are turned on to perform heating, the heater in the roller on the side contacting the back surface of the transfer material By turning off the switch and turning on and off only the heater in the other roller to control the temperature, the power consumed at 5 Kw / hour per 1000 mono color A4 copies is reduced to 3.
It was 5Kw / hour and we were able to save 30% of electricity.

[Brief description of drawings]

FIG. 1 is a schematic view showing one embodiment of the heat fixing device of the present invention,
FIG. 2 is an operation panel diagram of an image forming apparatus to which the heat fixing device of the present invention is applied, FIG. 3 is a temperature change diagram of each heating roller in FIG. 1, FIG. 4 is a schematic diagram of another embodiment, and FIG. FIG. 6 is a temperature change diagram of each heating roller, FIG. 6 is a schematic diagram of a conventional heat fixing device, and FIG. 7 is a temperature change diagram of each heating roller in the device. 1 is an upper pressure roller, 2 is a fixing roller, 3 is a lower pressure roller, 7 and 9 are thermistors, and 8 and 8 are heaters.

Continuation of the front page (56) Reference JP-A-57-89785 (JP, A) JP-A-55-53379 (JP, A) JP-A-58-87575 (JP, A) JP-A-53-55036 (JP , A) JP 53-129656 (JP, A) JP 54-33040 (JP, A) JP 60-211483 (JP, A) JP 60-252380 (JP, A) JP 60-263173 (JP, A) JP-A-60-86574 (JP, A) JP-A-60-143370 (JP, A) JP-A-60-169875 (JP, A) JP-B-5-60106 (JP, A) B2)

Claims (1)

[Claims] 1. A first heater for heating a pair of rotors for fixing an unfixed toner image by sandwiching and transporting a recording material carrying an unfixed toner image and a first rotor for contacting the unfixed toner image. A second heater for heating the second rotating body on the side not contacting the unfixed toner image; a first detecting means for detecting the surface temperature of the first rotating body; and a first detecting means for detecting the surface temperature of the second rotating body. 2. A heating and fixing device having two detection means and a control means for controlling the surface temperature of the rotating body based on the detection signal of the detection means, wherein the control means is the second fixing means when fixing a single color unfixed toner image. When the energization of the heater is turned off and the energization of the first heater is controlled based on the detection signal of the first detection means, and when fixing the unfixed toner images of a plurality of colors, the above-mentioned detection signal of the second detection means is used. Energize the first heater and to the second heater A heating and fixing device characterized in that it controls both the energization of the heat fixing device.