JPH0934302A - Picture forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a picture forming device holding a good fixation performance and reducing curl quantity by maintaining a temperature difference between a heating roller and a pressing roller in the prescribed range. SOLUTION: A fixation section 13 has a heating roller 14 and a pressing roller 15, and they are provide with heat sources 16, 17 inside respectively. Each heat source 16, 17 is connected to a temperature control section 18, and controls surface temperature automatically. The temperature control section 18 turns on or turns off the heat source 16 of the heating roller 14 at the time of rotation of the heating roller 14, the heat source 17 of the pressing roller 15 at the time of turning off, by a heat source switching means 24 in a main body control section 14, and attains temperature control of the pressing roller 15 during copying. A fixation characteristic is improved and curl quantity is reduced by utilizing usable electric power utmost and reducing temperature difference between the heating roller and the pressing roller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus provided with a heat source and a surface temperature detecting means for both a heating roller and a pressure roller.

[0002]

2. Description of the Related Art A so-called heat roller system is often used for a fixing portion of an image forming apparatus such as an electronic copying machine. This is one in which a heater as a heating source is built into one roller called a heating roller, and a transfer paper on which an image has been transferred is passed between the heater and a pressure roller which is in pressure contact with the roller to heat-fix the toner image. is there. Since there is an optimum temperature for thermal fixing of the toner image, turning on / off of the heater is automatically controlled so as to maintain a predetermined temperature range including the optimum temperature. In the automatic control, a thermistor as a temperature sensitive element is brought into sliding contact with a heating roller, and the output of this thermistor is sent to a temperature control unit to automatically adjust the power supply to the heater.

However, even if the temperature of the heating roller is controlled within a predetermined range in this way, the fixing performance depends on the conditions of the outside air temperature and the outside air humidity. That is, when the outside air temperature is low, the temperature of the transfer paper is low, and when the outside air humidity is high, the transfer paper absorbs moisture to increase the water content and the fixing performance tends to be deteriorated. This is because the temperature rise of the paper at the heating roller nip is different even if the temperature of the heating roller is the same.

In order to prevent such deterioration of the fixing performance, in the conventional image forming apparatus, for example, the actual development number 55-12.
No. 22, a copying machine for controlling the electric power supplied to the heater of the fixing device according to the output of the detector for detecting the humidity, and the outside air temperature and the outside air as described in JP-A-4-42186. Various proposals have been made for a means for detecting humidity and a fixing device for controlling the temperature of the heating roller according to the output thereof, or an image forming apparatus for detecting the water content of paper to control the temperature of the heating roller.

Although these methods are effective means for improving the fixing property, it is generally known that when the water content of the paper increases, the paper curls toward the pressure roller having a low temperature. This tendency becomes more remarkable as the temperature difference between the heating roller and the pressure roller increases. Such an increase in the amount of curl lowers the paper passing performance and causes a jam.

On the other hand, as a means for reducing the curl after fixing when the water content of paper is high, for example, Japanese Patent Laid-Open No. 1-10
As described in Japanese Patent No. 9387, both the heating roller and the pressure roller are provided with a heat source, and when the humidity of the paper is above a certain value detected before fixing, the heat source in the pressure roller is energized to supply the heat to the pressure roller. An image forming apparatus has been proposed in which the temperature is kept above a certain value. This is also effective as a means for reducing the heat transferred from the heating roller to the pressure roller and preventing the temperature of the heating roller from decreasing.

By the way, since the electric power that can be used during the operation of the image forming apparatus is limited, when both the heating roller and the pressure roller are equipped with heaters, the heating roller is usually rotated when the heating roller rotates. Only the heater on the side is energized. That is, when the image forming apparatus is powered on and is in a ready state, the humidity detecting means detects the humidity of the transfer sheet and sends a signal to the control section. Power supply to the heat source of the pressure roller starts, but the heat source on the heating roller side is turned on during copying when the heating roller rotates.
ON / OFF control while the pressure roller heat source is OF
It was F.

[0008]

However, when a large number of transfer sheets are continuously passed, the heat of the pressure roller is taken by the transfer sheet being copied when the heat source of the pressure roller is cut off. As the temperature decreased, the temperature difference between the two fixing rollers increased, and it was difficult to maintain good fixing performance, and the curl reduction effect tended to weaken.

Further, in the two-step control system in which the heat source of the pressure roller is energized when the outside air humidity is a certain value or more like the conventional image forming apparatus, the fixing performance cannot be sufficiently improved depending on the environmental conditions. It was also difficult to secure a curl amount below a certain value.

The present invention solves the above-mentioned drawbacks of the conventional image forming apparatus and maintains the temperature difference between the heating roller and the pressure roller within a predetermined range to maintain good fixing performance and curl amount. An object of the present invention is to provide an image forming apparatus that can reduce the number of images. Also, to provide an image forming apparatus capable of achieving optimum fixing temperature combination of a heating roller and a pressure roller by finely adapting to environmental conditions such as outside air temperature and outside air humidity, maintaining good fixing performance and reducing curl amount. It is an object.

[0011]

In order to solve the above-mentioned problems, the invention according to claim 1 has a heating roller which has a heat source inside and is provided with a surface temperature detecting means, and a heating roller which rotates in pressure contact with the heating roller. A pressure roller having a heat source inside and provided with a surface temperature detecting means, a temperature control section for controlling the power supply to each heat source by inputting signals output from these both surface temperature detecting means, and this temperature control section In an image forming apparatus having a main body control unit that is connected to turn on or off the heat source of the heating roller when rotating the heating roller and controls not to turn on both heat sources at the same time, the main body control unit is configured to rotate the roller. Sometimes, it is characterized by comprising heat source switching means for turning on or off the heat source of the pressure roller when the heat source of the heating roller is turned off.

As described above, when the heating roller is rotating, the heat source of the heating roller is turned on or off by automatic control to maintain the surface temperature suitable for fixing, but since the amount of power used is limited, both heat sources of the heating roller and the pressure roller are used. The main body control unit controls the temperature control unit so that the lights do not light at the same time. When the surface temperature of the heating roller exceeds a predetermined temperature, the surface temperature detecting means outputs a signal to the temperature control unit to cut off the power supply to the heat source of the heating roller. At this time, in the main body control section, the heat source switching means sends a signal to the temperature control section to start supplying power to the heat source of the pressure roller. While the heat source of the heating roller is off, the temperature controller automatically controls the heat source of the pressure roller so that the surface temperature of the pressure roller reaches a predetermined temperature. When the surface temperature of the heating roller drops, power supply to the heat source of the heating roller is restarted, and at the same time, the heat source of the pressure roller is turned off.

An image forming apparatus according to a second aspect of the present invention includes a heating roller having a heat source inside and a surface temperature detecting means.
A pressure roller that rotates in pressure contact with this heating roller and has a heat source inside and is provided with surface temperature detecting means, and a temperature that controls the power supply to each heat source by inputting the signals output from both surface temperature detecting means. A controller, temperature and humidity detecting means for detecting temperature and humidity of the transfer paper conveyed between the heating roller and the pressure roller, temperature and humidity inside the apparatus or temperature and humidity of the environment where the transfer paper is installed, and the temperature control An image forming apparatus having a main body control unit connected to a unit for controlling energization of both heat sources by a signal from a temperature / humidity detection unit, the main body control unit is configured to at least combine the surface control temperatures of the heating roller and the pressure roller. Two or more types are set, and optimal temperature selection means for outputting the combination of the surface control temperatures of one to the temperature control section based on the output signal of the temperature / humidity detection means is provided.

As described above, at least two or more combinations of surface control temperatures of the heating roller and the pressure roller are set in the main body control section. The optimum temperature selection unit in the main body control unit that receives the output signal of the temperature / humidity detection unit has good fixability at the temperature / humidity of the transfer paper, the temperature / humidity of the device or the temperature / humidity of the environment where the transfer paper is installed. A combination of surface control temperatures of the heating roller and the pressure roller, which are less likely to curl, is selected, and the respective control temperatures are output to the temperature control unit.

According to another aspect of the image forming apparatus of the present invention, the optimum temperature selecting means has a high water content of the transfer paper, or has a high humidity in the apparatus, or has a humidity of an environment in which the apparatus is installed. Is set, the combination of the surface control temperatures is set such that the sum of the surface control temperatures becomes large and the difference in the surface control temperatures becomes small.

As described above, the combination of the surface control temperatures of the heating roller and the pressure roller is set as follows. That is, when the water content of the transfer paper is high, the humidity inside the apparatus is high, or the humidity of the environment in which the apparatus is installed is high, the surface control temperature of the heating roller and the pressure roller is high. The combination is set so that the sum of the two becomes large and at the same time the difference between the two surface control temperatures becomes small. On the contrary, when the water content of the transfer paper is small, the combination of the surface control temperatures is set to be small and the difference is large. That is, when the water content of the transfer paper is high, the total amount of heat supplied from the heat sources of both the heating roller and the pressure roller is increased to prevent the fixing performance from deteriorating, and at the same time the temperature of the pressure roller side is increased. By reducing the temperature difference between the two, the curl amount of the transfer paper is reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image forming apparatus of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus. The image forming apparatus 1 feeds the transfer papers 3 stored in the paper feed cassette 2 one by one by the paper feed roller 4 and the overrun preventing means 5, guides them to a guide plate (not shown), and inserts them into the conveyance roller 6. The transfer paper 3 delivered from the transport roller 6 is inserted into the registration roller 7 and delivered to the transfer area of the transfer processing section. After that, the transfer paper 3 passes through the photoconductor drum 8, the transfer charger 9, and the peeling charger 10 to carry a toner image, is placed on the conveyor belt 12 via the separation claw 11, and is sent to the fixing unit 13. The transfer paper 3 heated and pressurized in the fixing unit 13 fixes the toner image and is sent to a paper discharge tray (not shown).

The fixing portion 13 has a heating roller 14 whose surface is coated with a non-adhesive material that does not adhere to toner, and a pressure roller 15 which is pressed against the heating roller 14 by a biasing member such as a tension coil spring (not shown). The heat sources 16 and 17 are provided inside each roller. The fixing unit 13 applies the transfer paper 3 on which the toner image is formed to the heating roller 14 and the pressure roller 1.
The toner image is bitten and passed between the five, and the toner image is thermally fixed in the meantime. The heat sources 16 and 17 are connected to a temperature control unit 18, and the surface temperature of each roller is automatically controlled under the control of the main body control unit 19.

Details of the fixing unit 13 will be described with reference to FIG. Around the heating roller 14, a roller winding preventing claw 20 and a cleaning web 21 are arranged, and a temperature sensor 22 supported by an appropriate bracket (not shown) is arranged in contact with or close to the roller surface. Similarly, the pressure roller 15 is also provided with a temperature sensor 23. These temperature sensors 22 and 23 use small thermistors or thermocouples, and their outputs are respectively sent to the temperature control unit 18 to perform ON-OFF switching so as to realize a predetermined temperature range.

Further, the temperature controller 18 is controlled by the main body controller 19 provided in the image forming apparatus 1 to selectively control the heat sources 16 and 17. That is, when the heating roller 14 is rotating to perform copying, the heat source 16 of the heating roller 14 is turned on or off to adjust the surface temperature thereof, but when the heat source 16 is energized, the heat source 17 on the pressure roller 15 side is turned on. Is controlled to turn off. This is because the electric power that can be used while the image forming apparatus 1 is operating is limited,
When the electric power used for the heat source 16 of the heating roller 14 is W1 and the electric power used for the heat source 17 of the pressure roller 15 is W2,
The maximum value of the total power that can be used by these heat sources 16 and 17 during copying is W1 (W1> W2). In this way, the main body control unit 19 that selectively controls the heat sources 16 and 17 is provided with the heat source switching means 24 for turning on or off the heat source 17 of the pressure roller 15 when the heat source 16 of the heating roller 14 is turned off. Therefore, the temperature of the pressure roller 15 can be adjusted even during copying.

The heat source switching situation will be described with reference to FIG. FIG. 3 is a graph showing the relationship between the power used by the heating roller and the pressure roller during copying and the elapsed time. If the surface temperature of the heating roller 14 exceeds a predetermined temperature range during copying, the temperature sensor 22 outputs the signal to the temperature control unit 18 to cut off the power supply to the heat source 16. At the same time, a signal is sent to the heat source switching unit 24 of the main body control unit 19 to control the temperature control unit 18 so as to start the power supply to the heat source 17 of the pressure roller 15. As shown in FIGS. 3A and 3B, the heating roller 1
While the heat source 16 of No. 4 is off, the heat source 17 is ON-OFF controlled so that the surface temperature of the pressure roller 15 reaches a predetermined temperature. When the surface temperature of the heating roller 14 drops, the power supply to the heat source 16 is restarted and the heat source 17 of the pressure roller 15 is turned off.

As described above, the surface temperature of the pressure roller 15 is kept high by maximally utilizing the available electric power even during copying, and the temperature difference between the heating and pressure rollers is reduced, so that the fixing property is improved. And improve curl.

Next, another embodiment in which the main body control section is provided with the optimum temperature selecting means will be described with reference to FIG. FIG. 4 is a schematic configuration diagram of a fixing unit according to another embodiment. Also in this embodiment, the fixing unit has the same structure and operation as those shown in FIG. 2, and therefore, the same reference numerals are given and detailed description thereof is omitted. In this embodiment, a temperature detecting means 25 for detecting the temperature and humidity of the transfer paper 3 and a humidity detecting means 26 are provided, and the detected values are output to the optimum temperature selecting means 27 in the main body control section 119.

The main body control unit 119 is connected to the temperature control unit 18 to control ON / OFF of the heat sources 16 and 17. At least two types of combinations of the surface control temperatures of the heating roller 14 and the pressure roller 15 are set in the optimum temperature selection means 27.

The optimum temperature selecting means 27, which receives the output signals of the temperature detecting means 25 and the humidity detecting means 26, has a good fixing property at the temperature and humidity of the transfer paper 3 and is resistant to curling, and the heating roller 14 and the pressure roller 15. A combination of the surface control temperatures is selected, and each control temperature is output to the temperature control unit 18. For example, assuming that the set temperature of the heating roller is TH and the set temperature of the pressure roller is TP, the following setting examples are possible. A plurality of optimum temperature combinations are set such that the value of TH + TP is large and the value of TH-TP is small under the condition of higher paper water content. (Example) When the water content of the paper is less than 5%; heating roller set temperature T
H = 200 ° C., pressure roller temperature TP = 100 ° C.
At this time, TH + TP = 300 ° C, TH-TP = 100 ° C
It is. When the water content of the paper is 5 to 8%; TH = 190 ° C.,
TP = 130 ° C. TH + TP = 320 at this time
C, TH-TP = 60C. Also, when the water content of the paper increases to 8% or more; TH = 180 ° C., TP = 16
Set to 0 ° C. At this time, TH + TP = 340 ° C, TH-T
P = 20 ° C.

By setting TH and TP in this way,
When the water content of the transfer paper 3 is high, the total amount of heat supplied from the heat sources 16 and 17 of both the heating roller 14 and the pressure roller 15 is increased to increase the temperature at the nip and maintain good fixing performance. By increasing the temperature of the pressure roller 15 side, the temperature difference between the two is reduced, and the transfer paper is pressed by the pressure roller 1.
Do not curl to the 5 side.

The combination of TH and TP depending on the environmental conditions is not limited to the above-mentioned one, and may be any combination of surface control temperatures which have good fixing property and hardly curl at the temperature and humidity of the transfer paper. Can be combined. For example, when the temperature of the transfer paper is low, only the surface control temperature (TP) of the pressure roller is increased, the sum of the surface control temperatures (TH + TP) becomes large, and the difference of the surface control temperature (T
(H-TP) is small, or when the water content of the transfer paper is high and the temperature of the transfer paper is low, the surface control temperature (TH) of the heating roller is lowered and the surface control of the pressure roller is controlled. It is also possible to increase the temperature (TP) and set a combination such that TH + TP becomes large and TH-TP becomes small.

[0028]

As described above, in the image forming apparatus according to the first aspect, the heat source switching means for turning on or off the heat source of the pressure roller when the heat source of the heating roller is turned off in the main body control section when the heating roller is rotated. By including the maximum power available even during copying, the surface temperature of the pressure roller is kept high, the temperature difference between the heating and pressure rollers is reduced, and the fixing property is improved. Curling can be reduced.

Further, in the image forming apparatus according to the second aspect of the present invention, the main body control section is provided with the optimum temperature selection means for setting at least two kinds of combinations of the surface control temperatures of the heating roller and the pressure roller, so that the outside air temperature and It is possible to realize a combination of optimum temperatures of the heating roller and the pressure roller, which are finely adapted to the environmental conditions of the outside air humidity.

In the image forming apparatus according to the third aspect of the present invention, the optimum temperature selecting means of the main body control unit is installed when the water content of the transfer paper is high, or when the humidity inside the apparatus is high, or when the apparatus is installed. When the humidity of the transfer paper is high, the combination of surface control temperatures is set so that the sum of the surface control temperatures becomes large and the difference between them becomes small when the humidity of the environment is high. Prevents deterioration of fixing performance by increasing the total amount of heat supplied from both heat sources of the pressure roller,
At the same time, by raising the temperature on the pressure roller side and reducing the temperature difference between the two, it is possible to reduce the curl amount of the transfer paper.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus.

FIG. 2 is a schematic configuration diagram of a fixing unit.

FIG. 3 is a graph of power consumption and elapsed time of a heating roller and a pressure roller.

FIG. 4 is a schematic configuration diagram of a fixing unit according to another embodiment.

[Explanation of symbols]

 1 image forming apparatus 3 transfer paper 13 fixing unit 14 heating roller 15 pressure roller 16 heat source 17 heat source 18 temperature control unit 19 main body control unit 22 temperature sensor 23 temperature sensor 24 heat source switching unit 25 temperature detection unit 26 humidity detection unit 27 optimum temperature Means of selection

Claims (3)

[Claims] 1. A heating roller having a heat source inside and provided with a surface temperature detecting means, a pressure roller rotating in pressure contact with the heating roller and having a heat source inside and provided with a surface temperature detecting means, and both surfaces thereof. A temperature control section for controlling the power supply to each heat source by inputting a signal output by the temperature detection means, and a temperature control section connected to this temperature control section to turn on or off the heat source of the heating roller and both heat sources when the heating roller is rotating. In the image forming apparatus having a main body control unit for controlling not to light at the same time, the main body control unit switches the heat source for turning on or off the heat source of the pressure roller when the heat source of the heating roller is turned off when the roller is rotated. An image forming apparatus comprising means. 2. A heating roller having a heat source inside and provided with a surface temperature detecting means, a pressure roller rotating in pressure contact with the heating roller and having a heat source inside and having a surface temperature detecting means, and both surfaces thereof. A temperature control section for controlling the power supply to each heat source by inputting a signal output by the temperature detection means, and the temperature and humidity of the transfer paper conveyed between the heating roller and the pressure roller,
Temperature / humidity detecting means for detecting the temperature / humidity in the apparatus or the environment in which the transfer paper is installed, and body control for connecting to the temperature control unit and controlling energization of both heat sources by signals of the temperature / humidity detecting means In the image forming apparatus having a unit, the main body control unit sets at least two types of combinations of surface control temperatures of the heating roller and the pressure roller, and the combination of one is set based on the output signal of the temperature / humidity detecting means. An image forming apparatus comprising: an optimum temperature selection unit that outputs a surface control temperature to the temperature control unit. 3. The image forming apparatus according to claim 2, wherein the optimum temperature selecting means is installed when the water content of the transfer paper is high, or when the humidity in the apparatus is high, or the apparatus is installed. An image forming apparatus, wherein a combination of surface control temperatures is set such that a sum of the surface control temperatures becomes large and a difference between the surface control temperatures becomes small when the humidity of the environment becomes high.