JP4201181B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus provided with a heat source and a surface temperature detecting means in both a heating roller and a pressure roller.
[0002]
[Prior art]
A so-called heat roller system is frequently used for a fixing portion of an image forming apparatus such as an electronic copying machine. This is because a heater as a heating source is built in a single roller called a heating roller, and a toner image is heat-fixed by passing a transfer sheet on which an image has been transferred between the pressure roller and the pressure roller. is there. Since there is an optimum temperature for thermal fixing of the toner image, the heater is turned on / off automatically so as to maintain a predetermined temperature range including the optimum temperature. In the automatic control, a thermistor as a temperature sensitive element is slidably contacted with the heating roller, and the output of the thermistor is sent to the temperature control unit to automatically adjust the power supply to the heater.
[0003]
However, even if the temperature of the heating roller is controlled within a predetermined range as described above, the fixing performance depends on the state 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 and the moisture content increases, so that the fixing performance tends to deteriorate. This is because even if the temperature of the heating roller is the same, the temperature rise of the paper at the heating roller nip differs.
[0004]
In order to prevent such deterioration of the fixing performance, in the conventional image forming apparatus, for example, the power supplied to the heater of the fixing device is controlled according to the output of the detector that detects humidity as described in Patent Document 1. A copying apparatus, a fixing device that controls the temperature of the heating roller according to the output and means for detecting the outside air temperature and outside air humidity described in Patent Document 2, or the moisture content of the heating roller by detecting the moisture content of the paper Various image forming apparatuses that control the temperature have been proposed.
[0005]
These methods are effective means for improving the fixing property, but it is generally known that when the moisture content of the paper is high, the paper curls on the pressure roller side having a low temperature. Becomes more prominent when the temperature difference between the heating roller and the pressure roller increases. Such an increase in the curl amount deteriorates the paper passing performance and causes a jam.
[0006]
On the other hand, as a means for reducing curling after fixing when the moisture content of the paper is high, for example, as described in Patent Document 3, both the heating roller and the pressure roller are provided with heat sources, and the humidity of the paper is adjusted before fixing. There has been proposed an image forming apparatus in which a heat source in a pressure roller is energized to make the pressure roller temperature equal to or higher than a certain value when the detected value is equal to or higher than a predetermined value. This is also effective as means for reducing the heat transferred from the heating roller to the pressure roller and preventing the temperature of the heating roller from decreasing.
[0007]
By the way, since there is a limit to the power that can be used during operation of the image forming apparatus, when both the heating roller and the pressure roller are equipped with heaters, the heater on the heating roller side is usually used when the heating roller rotates. Only energized. In other words, when the image forming apparatus is turned on and is in a ready state, the humidity detecting means detects the humidity of the transfer paper and sends a signal to the control unit. The energization of the heat source of the pressure roller is started. During the copying operation in which the heating roller rotates, the heat source on the heating roller side is turned on / off while the heat source of the pressure roller is turned off.
[0008]
[Patent Document 1]
Japanese Utility Model Publication No. 55-1222 [0009]
[Patent Document 2]
Japanese Patent Laid-Open No. 4-42186
[Patent Document 3]
Japanese Patent Laid-Open No. 1-109387
[Problems to be solved by the invention]
However, when a large number of transfer papers are continuously passed, the heat of the pressure roller is taken away by the transfer paper being copied in a state where the heat source of the pressure roller is cut off, so that the temperature decreases and the two fixing rollers The temperature difference between the two increases, it is difficult to maintain good fixing performance, and the curl reduction effect tends to fade.
[0012]
Also, in the two-step control method in which the heat source of the pressure roller is energized when the outside air humidity is a certain value or more as in the conventional image forming apparatus, the fixing performance cannot be sufficiently improved depending on the environmental conditions, and the constant performance is constant. It was also difficult to secure a curl amount below the value.
[0013]
The present invention eliminates 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, thereby maintaining good fixing performance and reducing the curl amount. An object of the present invention is to provide an image forming apparatus. Further, it is possible to provide an image forming apparatus capable of realizing a combination of an optimum temperature of a heating roller and a pressure roller by finely adapting to an environmental condition such as an outside air temperature and an outside air humidity, and maintaining good fixing performance and reducing a curl amount. It is an object.
[0014]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a heating roller having a heat source therein and provided with a surface temperature detecting means, and a heating roller provided in contact with the heating roller and rotated to rotate and provided with a heat source therein and provided with a surface temperature detecting means. pressure roller and the temperature of both the surface temperature detecting means to input signals to output a temperature control unit for controlling power supply to each heat source, instrumentation置内temperature and humidity or transfer paper installed in that environment And a temperature / humidity detecting means for detecting the humidity, and a main body control section for controlling the energization of both heat sources by a signal from the temperature / humidity detecting means connected to the temperature control section,
The main body control unit sets two or more combinations of surface control temperatures of the heating roller and the pressure roller, and outputs one surface control temperature to the temperature control unit based on an output signal of the temperature / humidity detection means. Equipped with an optimum temperature selection means,
The optimum temperature selection means is configured so that as the humidity detected by the temperature / humidity detection means increases, the sum of the surface control temperatures increases and the difference in the surface control temperatures decreases. The image forming apparatus is characterized in that a combination of surface control temperatures is set so as to lower the surface control temperature and increase the surface control temperature of the pressure roller.
[0015]
In this way, at least two types of combinations of surface control temperatures of the heating roller and the pressure roller are set in the main body control unit. The optimum temperature selection means in the main body control unit that receives the output signal of the temperature / humidity detection means has good fixability at the temperature / humidity of the transfer paper, the temperature / humidity of the device or the environment where the transfer paper is installed. A combination of the surface control temperatures of the heating roller and the pressure roller that hardly cause curling is selected, and each control temperature is output to the temperature control unit.
[0016]
The combination of the surface control temperatures of the heating roller and pressure roller is set as follows. That is, when the moisture content of the transfer paper becomes large, or when the humidity in the apparatus becomes large, or when the humidity in the environment where the apparatus is installed is large, the surface control temperature of the heating roller and the pressure roller. 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. Conversely, when the moisture content of the transfer paper is small, the combination is such that the sum of the surface control temperatures is small and the difference is large. That is, when the moisture content of the transfer paper is high, the total heat supplied from the heat sources of both the heating roller and the pressure roller is increased to prevent deterioration of the fixing performance, and at the same time the temperature on the pressure roller side is increased. The curl amount of the transfer paper is reduced by reducing the temperature difference between the two.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the image forming apparatus according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus. In this image forming apparatus 1, the transfer paper 3 stored in the paper feed cassette 2 is sent out one by one by the paper feed roller 4 and the heavy running prevention means 5, guided by a guide plate (not shown), and inserted into the transport roller 6. The transfer paper 3 sent out from the conveying roller 6 is inserted into the registration roller 7 and sent out to the transfer area of the transfer processing section. Thereafter, the transfer paper 3 passes through the photosensitive drum 8, the transfer charger 9, and the release charger 10 to carry a toner image, is mounted on the transport belt 12 through 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).
[0018]
The fixing unit 13 includes a heating roller 14 covered with a non-adhesive material to which toner does not adhere to the surface, and a pressure roller 15 that is pressed against the heating roller 14 by a biasing member such as a tension coil spring (not shown). Heat sources 16 and 17 are provided inside the roller. The fixing unit 13 causes the transfer paper 3 on which the toner image is formed to pass between the heating roller 14 and the pressure roller 15, and heat-fixes the toner image therebetween. The heat sources 16 and 17 are connected to a temperature control unit 18 and automatically control the surface temperature of each roller based on the control of the main body control unit 19.
[0019]
Details of the fixing unit 13 will be described with reference to FIG. Around the heating roller 14, a roller wrap preventing claw 20 and a cleaning web 21 are disposed, and a temperature sensor 22 supported by an appropriate bracket (not shown) is disposed in contact with or close to the roller surface. Similarly, a temperature sensor 23 is attached to the pressure roller 15. These temperature sensors 22 and 23 use small thermistors or thermocouples, and their outputs are sent to the temperature control unit 18 to perform ON-OFF switching so as to realize a predetermined temperature range.
[0020]
The temperature control unit 18 selectively controls the heat sources 16 and 17 under the control of the main body control unit 19 provided in the image forming apparatus 1. That is, when the heating roller 14 is rotated and copying is performed, the heat source 16 of the heating roller 14 is turned on or off to adjust the surface temperature. When the heat source 16 is energized, the heat source 17 on the pressure roller 15 side is adjusted. Is controlled to turn off. This is because there is a limit to the power that can be used while the image forming apparatus 1 is in operation. If the power used for the heat source 16 of the heating roller 14 is W1, and the 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). The main body control unit 19 that selectively controls the heat sources 16 and 17 is provided with a heat source switching unit 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. For this reason, the temperature of the pressure roller 15 can be adjusted even during copying.
[0021]
The state of the heat source switching will be described with reference to FIG. FIG. 3 is a graph showing the relationship between the power consumption of the heating roller and pressure roller during copying and the elapsed time. When the surface temperature of the heating roller 14 exceeds a predetermined temperature range during copying, the temperature sensor 22 outputs a 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 means 24 of the main body control unit 19 to control the temperature control unit 18 to start supplying power to the heat source 17 of the pressure roller 15. As shown in FIGS. 3A and 3B, while the heat source 16 of the heating roller 14 is turned 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 decreases, the power supply to the heat source 16 is resumed and the heat source 17 of the pressure roller 15 is turned off.
[0022]
In this way, the surface temperature of the pressure roller 15 is kept high by making maximum use of the power that can be used even during copying, and the temperature difference between the heating and pressure rollers is reduced, thereby improving the fixability and Reduce curl.
[0023]
Next, another embodiment in which the main body control unit is provided with the optimum temperature selection 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, since the configuration of the fixing unit is the same as that shown in FIG. 2, the same reference numerals are given and detailed description thereof is omitted. In this embodiment, a temperature detection unit 25 and a humidity detection unit 26 for detecting the temperature and humidity of the transfer paper 3 are provided, and the detected values are output to the optimum temperature selection unit 27 in the main body control unit 119.
[0024]
The main body control unit 119 is connected to the temperature control unit 18 and performs ON / OFF control of the heat sources 16 and 17. In the optimum temperature selection means 27, at least two kinds of combinations of surface control temperatures of the heating roller 14 and the pressure roller 15 are set.
[0025]
The optimum temperature selection means 27 that has received the output signals of the temperature detection means 25 and the humidity detection means 26 controls the surface of the heating roller 14 and the pressure roller 15 that have good fixability and less curl at the temperature and humidity of the transfer paper 3. A combination of 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 can be considered.
(1) 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 moisture content.
(Example) When the water content of the paper is less than 5%; the heating roller set temperature TH = 200 ° C. and the pressure roller temperature TP = 100 ° C. At this time, TH + TP = 300 ° C. and TH−TP = 100 ° C. When the water content of the paper is 5 to 8%; TH = 190 ° C., TP = 130 ° C. At this time, TH + TP = 320 ° C. and TH−TP = 60 ° C. When the moisture content of the paper increases to 8% or more; TH = 180 ° C., TP = 160 ° C. At this time, TH + TP = 340 ° C. and TH−TP = 20 ° C.
[0026]
By setting TH and TP in this manner, when the moisture 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, so By increasing the temperature to maintain good fixing performance and increasing the temperature on the pressure roller 15 side, the temperature difference between the two is reduced and the transfer paper is prevented from curling on the pressure roller 15 side.
[0027]
Note that the combination of TH and TP depending on the environmental conditions is not limited to those described above, and any combination is possible as long as it is a combination of surface control temperatures that have good fixability and are less likely to curl at the temperature and humidity of the transfer paper. Is possible. For example, (2) when the temperature of the transfer paper is low, only the surface control temperature (TP) of the pressure roller is raised, the sum of the surface control temperatures (TH + TP) becomes large, and the difference in surface control temperatures (TH-TP) ) Is small, or (3) when the moisture content of the transfer paper is large 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 set a combination that increases the temperature (TP), increases TH + TP, and decreases TH-TP.
[0028]
【The invention's effect】
The image forming apparatus according to the present invention includes an optimum temperature selection unit that sets at least two kinds of combinations of surface control temperatures of the heating roller and the pressure roller in the main body control unit, and thus depends on the environmental conditions of the outside temperature and the outside humidity. A combination of the optimum temperature of the heat roller and pressure roller that are finely matched can be realized.
[0029]
In addition, the optimum temperature selection means of the main body control unit controls the surface control temperature when the moisture content of the transfer paper is large, the humidity in the device is large, or the humidity in the environment where the device is installed is large. Since the combination of surface control temperatures is set so that the sum of these becomes large and the difference between them becomes small, the total amount of heat supplied from the heat sources of both the heating roller and pressure roller when the moisture content of the transfer paper is high Is increased to prevent deterioration of the fixing performance, and at the same time, the temperature on the pressure roller side is increased and the temperature difference between the two is reduced to reduce the curl amount of the transfer paper.
[Brief description of the 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 showing power consumption and elapsed time of a heating roller / pressure roller.
FIG. 4 is a schematic configuration diagram of a fixing unit according to another embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Transfer paper 13 Fixing part 14 Heating roller 15 Pressure roller 16 Heat source 17 Heat source 18 Temperature control part 19 Main body control part 22 Temperature sensor 23 Temperature sensor 24 Heat source switching means 25 Temperature detection means 26 Humidity detection means 27 Optimal temperature Selection means

Claims (1)

A heating roller having a heat source therein and provided with a surface temperature detection means;
A pressure roller rotating in pressure contact with the heating roller and provided with a heat source inside and provided with a surface temperature detection means;
A temperature control unit that controls the power supply to each heat source by inputting the signals output by both surface temperature detection means ,
A temperature and humidity detecting means for detecting the temperature and humidity of the environment in which it is installed in a temperature and humidity or transfer paper instrumentation置内,
A main body control unit connected to the temperature control unit to control energization of both heat sources by a signal from the temperature and humidity detection means;
The main body control unit sets two or more combinations of surface control temperatures of the heating roller and the pressure roller, and outputs one surface control temperature to the temperature control unit based on an output signal of the temperature / humidity detection means. Equipped with an optimum temperature selection means,
The optimum temperature selection means is configured so that as the humidity detected by the temperature / humidity detection means increases, the sum of the surface control temperatures increases and the difference in the surface control temperatures decreases. An image forming apparatus, wherein a combination of surface control temperatures is set so as to lower the surface control temperature and increase the surface control temperature of the pressure roller.

Images