JP2000181274A - Thermal fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To straighten the curl of a sheet to which fixing processing has been performed and to accelerate the drop of a fixing temperature by one means by making the fixing temperature drop to a target temperature in a short time and improving the efficiency of an image forming device further. SOLUTION: An air spraying means 118 spraying air (outside air) is installed under a path between a pair of fixing rollers 114a and 114b of a fixing device 114 and a pair of internal paper ejecting rollers 115. In the case of using a sheet other than an OHP sheet such as plain paper, the means 118 takes vertical posture X1 so as to straighten the curl by spraying the air to the sheet to which the fixing processing has been performed, In the case of using the OHP sheet, the means 118 takes inclined posture X2 so as to make the fixing temperature drop to the target temperature by spraying the air to the roller 114a being a fixing heat source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device (heat fixing type fixing device) provided in an electrophotographic image forming apparatus (copier, printer, facsimile, etc.).

[0002]

2. Description of the Related Art FIG. 3 shows the overall structure of a conventional electrophotographic image forming apparatus.

Here, the configuration of the main part will be described along the flow of a sheet (transfer material).

The image forming apparatus includes two cassette sheet feeding units 100A and 100B and one manual sheet feeding unit 100C.
Is provided, and a selected one of these paper feeding units is provided.
The sheet is fed from one end. The standard sheet S1 that is frequently used is fed from the cassette sheet feeding units 100A and 100B, and the non-standard type sheet S2 that is not frequently used is fed from the manual sheet feeding unit 100C.

The sheets S1 stacked on the cassette sheet feeding units 100A and 100B are fed out by the feeding roller 101 in order from the top sheet, and the separation roller pair 1
02 are separated one by one and the conveying roller pair 103
And reaches the registration roller pair 110 in the rotation stopped state.

The sheet S2 stacked on the manual sheet feeding section 100C is sequentially fed out from the uppermost sheet by a feeding roller 107, separated one by one by a separation roller pair 108, and conveyed by a conveyance roller pair 109. The rotation reaches the registration roller pair 110 in the rotation stopped state.

The sheets S 1 and S 2 arriving at the registration roller pair 110 are moved between the photosensitive drum 111 rotating clockwise and the transfer charger 112 by the registration roller pair 110 which starts rotating at a predetermined timing. It is sent to the transfer unit. Then, the toner image on the photosensitive drum 111 is transferred to the sheets S1 and S2 passing through the transfer unit by the transfer charger 112.

The sheets S1 and S2, to which the toner images have been transferred, have passed through the transfer section, and are conveyed to a heat fixing device 114 by a conveying belt 113. Then, the heat fixing device 11
By applying heat and pressure while passing through the fixing nip between the fixing roller (with a built-in heater) 114a and the pressure roller 114b in 4, the toner image in the unfixed state is fixed on the sheet surface.

The sheets S1 and S2 which have passed through the fixing nip of the heat fixing device 114 and have been subjected to fixing processing are
The paper is discharged onto a paper discharge tray (not shown) outside the apparatus by the pair of paper discharge rollers 15 and a pair of paper discharge rollers 116.

In this image forming apparatus, double-sided image formation in which images are formed on both sides of a sheet and multiplex image formation in which images are formed on the same side of a sheet can be performed. A detailed description of is omitted. After the sheets in the duplex image forming mode and the multiple image forming mode have passed through the heat fixing device 114,
7 again reaches the registration roller pair 110.

In the case of the present image forming apparatus, the manual paper feeder 10
Sheets of various materials are fed from 0C, and some of them are easily deformed by heat. Therefore, the fixing temperature of the heat fixing device 114 is set according to the material of the sheet to be used.

When the fixing temperature of the heat fixing device 114 is set to a constant temperature in accordance with plain paper, for example, the heat-sensitive OHP sheet S1 is thermally deformed and wraps around the fixing roller 114a as shown in FIG. Situation occurs. For this reason, when the OHP sheet S1 is used, the fixing temperature of the thermal fixing device 114 is set to a temperature lower by 10 ° C. to 20 ° C. than the temperature when plain paper is used.

In the conventional heat fixing device 114, the fixing temperature is lowered to the target temperature by natural fall.

[0014]

However, such a method has a problem that it takes time until the fixing temperature reaches a target temperature.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in view of the above circumstances. A heat fixing apparatus capable of lowering a fixing temperature to a target temperature in a short time and further improving the efficiency of an image forming apparatus. The purpose is to provide. It is another object of the present invention to provide a heat fixing device that can perform curl correction of a sheet after a fixing process and promotion of a decrease in a fixing temperature by one unit.

[0016]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a heat fixing device for fixing an unfixed toner image on a sheet surface by heating a sheet on which a toner image has been transferred.

Further, in order to achieve the above object, the present invention is characterized in that the image forming apparatus further comprises a temperature lowering promoting unit for promoting the fixing temperature to fall to a target temperature.

Further, in order to achieve the above-mentioned object, the present invention provides a first posture when blowing air to a fixing-processed sheet to correct the curl of the sheet, and a fixing temperature by blowing air to a fixing heat source. It is characterized by having air blowing means capable of changing the attitude to the second attitude when urging the user to descend.

[0019]

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

FIG. 1 shows the overall configuration of an image forming apparatus provided with the heat fixing device of the present invention.

The basic structure of the present image forming apparatus is not different from that of the conventional image forming apparatus (FIG. 3). Therefore, here, only the characteristic points (part of the invention) of the image forming apparatus will be described.

The fixing roller pair 114 of the heat fixing device 114
Air blowing means 118 for blowing air (outside air) is provided below the path between the inner paper discharge rollers 115a and 114b. The air blowing unit 118 includes a curl correcting unit that corrects a curl on a sheet that has passed through the nip between the pair of fixing rollers 114a and 114b, and a temperature lowering unit that promotes a reduction in the fixing temperature of the thermal fixing device 114 to a target temperature. Used as a means.

When used as the curl correcting means, the air blowing means 118 is in a vertical position (first position) indicated by reference numeral X1, and blows air toward the sheet passing through the nip between the pair of fixing rollers 114a and 114b. .

When the air blowing means 118 is used as the temperature lowering promoting means, the attitude of the air blowing means 118 is inclined (second attitude) indicated by the reference symbol X2.
And blows air toward the fixing roller 114a.

In the case of this image forming apparatus, OHP such as plain paper is used.
When a sheet other than the sheet is used, the heat fixing device 11 is used.
The fixing temperature of No. 4 is set to the normal temperature N1 ° C. And
At this time, the air blowing means 118 performs sheet curl correction in the X1 posture. When an OHP sheet is used, the fixing temperature of the thermal fixing device 114 is set to an OHP-compatible temperature N2 ° C. which is lower by 10 ° C. to 20 ° C. than the normal temperature N1 ° C. Then, at this time, the air blowing means 118 is set in the X2 posture to urge the fixing temperature to drop.

The air blowing means 118 is normally in the position X1, but changes the position from the position X1 to the position X2 when the OHP sheet feeding is selected. Further, the air blowing means 118 in the posture of X2 makes the fixing temperature equal to the target temperature N.
When the temperature drops to 2 ° C., the posture is changed from the posture of X2 to the posture of X1.

FIG. 2 shows the detailed structure of the air blowing means 118.

The air blowing means 118 is provided for the suction duct 1
18-1, the spray duct 118-2, and both ducts 11
8-1 and fan motor 118- interposed between 118-2
3 The inlet of the suction duct 118-1 is connected to a louver 119-1 formed in the front door 119 of the image forming apparatus main body. The blowing duct 118-2 is provided with a plurality of outlets 118-4 arranged in the width direction of the path. When the fan motor 118-3 is driven, the outside air a enters the suction duct 118-1 via the louver 119-1, passes through the fan motor 118-3, and blows the air to the blowing duct 1.
Air is blown out from each air outlet 118-4 of 18-2.

The air blowing means 118 is installed so as to be rotatable in the sheet conveying direction around a cylindrical suction duct 118-1. The suction duct 118-1 is rotatably supported by bearings (pillow blocks) 118-5 and 118-6 fixed to the main body of the image forming apparatus.
7 is driven to rotate. Motor 1
The drive of 18-7 is transmitted to the suction duct 118-1 via gears 118-8 and 118-9.

The driving of the motor 118-7 is controlled by a CPU (posture changing means) 118-10. CPU11
Reference numeral 8-10 denotes a motor 118-7 based on sheet type information input from the operation unit 118-11 of the image forming apparatus main body and temperature information from the temperature sensor 118-12 that measures the temperature state of the heat fixing device 114. Control.

The CPU 118-10 is an OHP for plain paper or the like.
When a sheet other than the sheet is selected, the air blowing means 118 is set to the position of X1. In this position, the air blowing unit 118 blows air on the sheet on which the fixing process has been performed to correct the curl.

When the OHP sheet is selected, the CPU 118-10 controls the motor 118-7 so that the air blowing means 118 assumes the X2 position. In this position, the air blowing means 118 blows air to the fixing heat source to lower the temperature of the heat fixing device 114 to the OHP sheet corresponding temperature N2 ° C.

The CPU 118-10 controls the motor 118-7 so that when the fixing temperature drops to the target temperature N2 ° C. due to the air blowing action, the air blowing means 118 assumes the X1 position for correcting the curl. I do.

In the present image forming apparatus, when the fixing temperature is lowered to the target temperature (N2 ° C.), the outside air is directly blown onto the fixing roller 114a having a built-in heater as a heat source, so that the temperature can be reduced in a short time. As a result, the efficiency of the image forming apparatus is improved.

Some electrophotographic image forming apparatuses include a curl correcting means for correcting the curl of a sheet by blowing air onto the sheet passing through the heat fixing device. Since the attaching means 118 also serves as the curl correcting means and the temperature lowering promoting means, the cost is not increased and the image forming apparatus is large in size as compared with a configuration in which the curl correcting means and the temperature lowering promoting means are separately installed. There is an advantage that does not become.

In the present embodiment, the air blowing means 118 serves as both the curl correcting means and the temperature lowering promoting means, but may be used exclusively as the temperature lowering means.

In this embodiment, when the OHP sheet is used, the fixing temperature is lowered to the target temperature by using the air blowing means 118. However, not only when the OHP sheet is used, but also when the OHP sheet is used. The air blowing means 118 can be widely used as an accelerating means.

The air blowing means 11 according to the present embodiment
In the case of 8, the entire air blowing means is configured to rotate, but at least the blowing duct 118-2 including the blow-out port 118-4 may be configured to be rotatable between the postures X1 and X2. I just need.

[0039]

As described above, according to the present invention,
Since the fixing temperature is lowered to the target temperature by using the temperature lowering promoting unit, the target temperature can be reached in a short time, and the efficiency of the image forming apparatus is further improved.

Further, according to the present invention, the correction of the curl on the sheet subjected to the fixing process and the promotion of the temperature decrease of the fixing temperature are performed by one air blowing means.
The cost and the size of the image forming apparatus are not increased as compared with the configuration in which the air blowing means for curl correction and the air blowing means for accelerating the temperature lowering of the fixing temperature are separately provided.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing an overall configuration of an image forming apparatus provided with a heat fixing device of the present invention.

FIG. 2 is a vertical sectional front view showing a configuration of an air blowing means which is a characteristic part of the present invention.

FIG. 3 is a vertical sectional side view showing the overall configuration of a conventional image forming apparatus.

FIG. 4 is a longitudinal sectional side view for explaining a problem in a conventional image forming apparatus.

[Explanation of symbols]

 114 Thermal fixing device 114a Fixing roller (fixing heat source) 118 Air blowing means (temperature lowering promoting means) 118-10 CPU (posture changing means) a Air S1, S2 sheet X1 Vertical posture (first posture) X2 Slant posture (Second posture)

Claims (7)

[Claims] 1. A thermal fixing device for fixing a toner image in an unfixed state on a sheet surface by heating a sheet on which a toner image has been transferred. A heat fixing device comprising: 2. The heat fixing device according to claim 1, wherein the temperature lowering promoting unit is an air blowing unit that blows air. 3. A thermal fixing device for fixing an unfixed toner image on a sheet surface by heating a sheet on which a toner image has been transferred, wherein air is blown onto the fixed sheet to perform curl correction of the sheet. And a second position when air is blown to the fixing heat source to promote a decrease in the fixing temperature. 4. The heat fixing device according to claim 3, further comprising a posture changing unit for changing a posture of the air blowing unit. 5. The apparatus according to claim 1, wherein the attitude changing means shifts the air blowing means from the first attitude to the second attitude when using an OHP sheet.
The heat fixing device according to claim 4, wherein the posture is changed to the posture of (1). 6. The heat fixing device according to claim 2, wherein the air blowing unit takes in and blows low-temperature air outside the main body of the image forming apparatus. 7. An image forming apparatus for transferring a toner image to a fed sheet, and then heating the sheet to which the toner image has been transferred to fix the unfixed toner image on the sheet surface. 7. An image forming apparatus comprising: the heat fixing device according to claim 1 as a fixing unit for fixing the toner image to a sheet surface.