JPH06258906A - Controller for curl correction device of image forming device - Google Patents

Abstract

PURPOSE:To actuate a curl correction device at an early stage by calculating the actuation information thereof not by using the information of the last color toner image but by using an estimated value when it is arranged in a full-color electrophotographic copying machine. CONSTITUTION:In the full-color electrophotographic copying machine 1, photosensitive drums 7-7c forming four different color toner images are arranged. Then, the color toner images are superposed and transferred on a paper supported by a transfer belt device 6. The density of the color toner images formed on the drums 7-7c is calculated and control information is outputted to the curl correction device provided in a curl correction unit 30. However, the density of the image formed on the last drum 7c is estimated and the information of the image density of the paper is outputted at an early stage. Then, the curl correction device is made to stand by in an actuating state. Besides, the correcting direction and the correcting amount of a curl can be set making correspond to difference between the image density of both sides as for both-side copying.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for correcting a curl generated on a recording paper by connecting a curl correction device to a recording paper discharge part, and more particularly to a color electrophotographic copying machine for making a color copy. Control of the curl correction device of the image forming apparatus, which makes it possible to estimate the image density information of the color to be transferred last based on the information of the density of the color to be formed first, and to perform the curl correction action. Regarding the device.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine or a printer, a toner image forming means using an electrophotographic system is arranged on a photosensitive drum provided as an image bearing member, The toner image formed on the drum is transferred onto a sheet and fixed by a fixing device to form a recording sheet. In the image forming apparatus, one photoconductor drum is used in a monochromatic copying machine or the like that uses only black toner. In the color electrophotographic copying machine, for example, Japanese Patent Laid-Open No. 1-107280 discloses. As shown, four photoconductor drums are arranged along the paper path. Then, means for forming toner images of different colors are arranged on the respective photosensitive drums, a color toner image is formed according to the information obtained by scanning the document, and the color toner image is superposed on the paper. The toner of all colors is melted through a fixing device to make a color copy.

In the image forming apparatus as described above,
Since the four colors of toner are transferred to the paper fixed through the fixing device in an overlapping manner, the density of the image becomes very large, and the paper is curled when it is ejected. The problem of being easy to do arises. If the paper curls, the edges of the paper may curl up when storing it in the sorter tray.
Problems such as the following sheets not being stored properly occur. Further, the unevenness of the paper may reduce the number of papers that can be accommodated in the tray, which may hinder the post-processing work of the recording paper. Therefore, in order to correct the curl generated on the paper so that the post-processing work of the paper can be easily performed, a curl correction device is provided after the fixing device to correct the curl generated on the paper. hand,
It is performed so that the work of accommodating the tray can be performed normally.

As the curl correction device, for example, a device disclosed in Japanese Patent Laid-Open No. 60-31464 is used. In the above-mentioned conventional curl correcting device, the pressing roll is pressed against the belt member, and the paper passing between both members is acted so as to be rapidly curved toward the side opposite to the curl generation direction. In this way, the curl generated on the paper is corrected. Further, in the above-mentioned device, by adjusting the force for pressing the pressing roll according to the information on the thickness of the paper so that the curl correction action according to the thickness of the paper can be performed, the excess It is made so as not to give a proper bending action. Further, by using the above-described curl correction device, even when the paper is curled, the work of storing it in the sorter can be performed in a good state, and the post-processing work of copying can be easily performed. It is possible to

[0005]

However, when the above-described curl correction device is used, the degree of curl generated on the paper is different between copying using only black toner and making a full-color copy. There is a big difference. In other words, in the case of full color copy, in addition to black toner,
Three color toners of cyan, magenta, and yellow are transferred onto the paper, and the amount of the four color toners used is extremely dark compared to a monochrome copy using only black toner. This is because the image density of is a very large value. Therefore, when the curl correction performance is set only based on the information on the thickness of the paper, there is a problem that the curl correction operation is not properly performed for the full-color copy. Further, in a full-color copy in which images are formed on both sides of a sheet, if the densities of the images formed on the front and back sides of the sheet are different, the direction of curl generated on the sheet and the size of the curl are different. When the curl correction device is provided as a means for correcting curl in one direction, there is also a problem that the curl correction effect cannot be exhibited in a good state.

Therefore, as described above, it has been considered to set the strength of curl correction in the curl correction device in accordance with the state of curl generated on the paper. For that purpose, for example, by using the density information of the toner image transferred on the paper, the size of the curl generated on the paper is estimated, and the curl correction performance is set according to the estimated curl value. You can also However, in a full-color electrophotographic copying machine, since the curl correction device is often arranged in a position close to the fixing device, the pressure roll of the curl correction device is moved by using the density information of the toner image to correct the curl correction device. There is a problem that the moving speed of the paper is high with respect to the time required for changing the performance. In order to solve such a problem, it is possible to easily solve the problem by setting a sufficient distance between the fixing device and the curl correction device, but the device becomes extra large. The problem occurs and it is not practical.

Further, in the color electrophotographic copying machine as described above, for the paper on which the image is formed on the first side,
The image on the second side may be transferred to the back side to make a double-sided copy. As described above, the paper on which the image has already been formed on the first side is generally fed from the manual feed tray in many cases. However, when the number of sheets is large, single-sided copy paper is placed in the paper feed tray. It is stored and fed in the normal copy mode. However, when the toner image on the second side is transferred to the single-sided copy sheet to make a double-sided copy, the density of the image formed on the first side and
If there is a difference in the image density between the image density transferred to the first surface and the image density, there is a problem in that the paper curls and the curl sizes are different. However, the problem of curling when an image is formed on the second side of a single-sided copy sheet as described above is not considered in a conventional electrophotographic copying machine or the like, and an apparatus that takes such measures is not available. The current situation is that there are none.

[0008]

SUMMARY OF THE INVENTION As described above, the present invention solves the problem in the case where a curl correction device is connected to an electrophotographic copying machine. When the image is transferred, the image density information of the last one color of the toner images of a plurality of colors to be transferred is calculated using the average value of the image density information of the previous multiple colors, and the estimated value is calculated. Provided is a controller for a curl correction device of an image forming apparatus, which can set a pressing force on a sheet by the curl correction device, and can correct curls in different directions based on information on the density difference of the first surface. The purpose is to provide such a device.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a plurality of image carriers are arranged, and a mechanism for forming toner images of different colors is arranged on each image carrier, and the image carrier is formed on the image carrier. An image forming apparatus that superimposes the transferred toner image on a sheet and fixes it through a fixing device to form a recording sheet, and a curl correction device for the recording sheet discharge section of the image forming apparatus Further, the present invention relates to an apparatus provided with a mechanism for sending the curl to a post-processing unit in a state of correcting the curl. In the present invention, with respect to the image bearing member,
Each measuring means for measuring the toner consumption of each color is provided, and among the information of the toner consumption of each color, the average value of the information excluding the information of the color to be transferred last is estimated as the information of the final color, A unit for outputting information on the curl correction strength to the curl correction device according to the density of the color toner image is provided, and a mechanism for controlling the curl correction device is configured. Further, in the present invention, the curl correction device connected to the image forming apparatus constitutes a unit by combining two devices having different curl correction directions, and information on the difference in the density of the color toner images formed on the front and back sides of the paper. Based on this, a mechanism for estimating the curl direction of the paper, selecting a curl correction device corresponding to the curl direction of the paper, and correcting the curl corresponding to the density of the color toner image can be configured. it can.

Further, in the present invention, a manual feed tray is arranged as a paper feed means of the image forming apparatus, and the image density of the first side of the single-sided copy paper is detected in the paper feed path for feeding paper from the manual feed tray. Means can also be provided. In addition to the above configuration, in the present invention, a unit for detecting the image density of the first side of the single-sided copy sheet is provided in the single-sided copy sheet conveying path of the image forming apparatus, and the image density of the document corresponding to the second side is provided. Information and the image density information of the first surface are input to the control means, and based on the information of the density difference of the color toner images formed on the front and back sides of the paper, the direction of the curl generated on the paper is determined. The control means is provided with a means for estimating the size of the curl, and the curl correction device is arranged in the discharge section of the image forming apparatus by combining two devices having different curl correction directions, and the curl correction is performed in the direction in which the curl of the paper occurs. It is possible to configure a mechanism that selects a curl correction device correspondingly and performs a curl correction operation corresponding to a difference in density of color toner images.

[0011]

As described above, in the full-color electrophotographic copying machine, when the color toner images of a plurality of colors are transferred onto the paper, the color toner which is transferred before the transfer without using the image density information of the final toner image. By using the average value of the image densities of the images, it is possible to make the curl correction device stand by at the operating position before the paper enters the curl correction device. Even when the apparatus is configured in a state where the fixing device and the curl correction device are very close to each other, the curl correction device can accurately perform the sheet processing operation. Further, when two curl correction devices having different curl correction directions are combined to form a curl correction unit, when a full-color copy is formed on both sides of the paper, the curl direction corresponding to the curl occurs on the paper,
A device that performs the curl correction function can be configured.

Further, in the present invention, the means for detecting the image density of the first side when recording the image of the second side on single-sided copy paper to make a double-sided copy corresponds to the manual feed tray. It can be arranged at a predetermined position on the paper transport path or the transport path for single-sided copy paper. And
Image density information obtained by the image reading device;
It is possible to compare the image density information of the surface with the direction and size of the curl, and perform the curl correction operation of an appropriate value. Two curl corrections arranged downstream of the fixing device can be performed. The device can be used to perform curl correction.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A controller for a curl correction device of an image forming apparatus according to the present invention will be described with reference to the illustrated example. In the example shown in FIG. 1, a curl correction device is arranged for a full-color electrophotographic copying machine 1, and a sheet created as a full-color copy is corrected for curl through the curl correction device.
The case where the sorter 38 is stored in the tray is shown. The full-color electrophotographic copying machine 1 shown in FIG. 1 has a paper feeding tray 2 at the paper feeding portion, as in the case of a general electrophotographic copying machine.
A plurality of paper feeding means, which are a combination of the paper feeding device 3 and the paper feeding device 3, are arranged, and an intermediate tray 4 for accommodating a sheet prepared as a single-sided copy sheet and sending it out for copying on the back side is arranged for automatic double-sided copying. Configured as a machine. In the automatic double-sided copying machine, the paper sent from the paper feed tray or the intermediate tray is sent toward the image transfer section through the paper transport path 5, and the reverse tray is used to store the single-sided copy paper in the intermediate tray. 9 is provided.

Further, in the full-color electrophotographic copying machine 1, the paper is conveyed to the conveyor belt device 6 in a state where the paper is electrostatically adsorbed or when the leading end of the paper is locked by using a clip means. Is provided to transfer the color toner image from the photosensitive drum along the paper conveyance path by the conveyance belt device. The full-color electrophotographic copying machine of the present invention is provided with four photosensitive drums 7 to 7c corresponding to the above-described sheet conveying device, and although not shown in the drawing corresponding to these photosensitive drums. As in the case of a general color electrophotographic copying machine, a mechanism for developing color toner images of black, yellow, magenta, and cyan colors and a mechanism for writing image information on the photosensitive drums are arranged. To do. Then, a color toner image is formed on the photosensitive drum based on the information of the image obtained by scanning the document set on the image reading device, and the color toner image is transferred onto the paper in a superimposed manner and fixed by the fixing device 8. A color copy sheet is sent toward the sorter 38.

A curl correction unit 30 is arranged between the full-color electrophotographic copying machine 1 and the sorter 38. The curl correction unit 30 corrects the curl generated on the paper and stores it in the sorter. When performing other post-processing operations, no problems occur. In the curl correction device, the curl of the paper is abruptly curved in the opposite direction to correct the curl, and a jam occurs when the curl of the paper passes through the discharge path and the return path. To be able to prevent The curl correction device provided in the curl correction unit is shown in FIG.
The curl correction device 10 used in the device of the present invention is configured as shown in FIG. 2 and presses the pressing roll 15 against the belt 11 to rapidly bend the belt 11 and A means for allowing the paper to pass through is used. The belt 11 is supported by rolls 12 and 13 arranged at a narrow interval, and the pressing roll 15 presses the intermediate portion of the belt 11. A cam driven member 17 is provided at an end of a link member 16 that supports the pressing roll 15, and a pressing mechanism by a cam member 20 is provided for the cam driven member 17.

Then, the pressing roll 15 and the belt 11
The sheet conveyed in the direction of the arrow X is guided to the nip portion of the curl correcting device 10 through the gap between and, and the curl removing action is performed by the action of sharply curving the sheet. In the curl correction device of the present invention configured as described above, the cam 21 is rotated by driving the shaft 21, and the amount of protrusion of the pressing roll 15 toward the belt 11 is adjusted by the cam member. By doing so, the degree of curvature of the belt can be set.

In the curl correction device 10, in order to change the rotation angle of the cam member 20 and adjust the curl correction action on the paper, a cam member rotation angle adjusting means can be used. In the means for controlling the pressing force of the pressing roll, the cam member 2 is attached to the shaft 21.
A plurality of claw members 24, 24a and 24b are provided around the indexing disc 23 provided together with the indexing disc 23, and an engaging claw 26 operated by a solenoid 25 is provided to the indexing disc 23. The provided locking means is arranged. Further, the claw member provided on the indexing disc 23 is set according to the distance that the pressing roll 15 presses against the belt, and the claw member provided on the indexing disc 23 is set by the engaging claw 26. The amount of pressing can be set arbitrarily at the locked position. Then, in the curl correction device 10, the cam shaft 21 is driven by the motor 22 to stop the cam member 20 at a position where the specified pressing amount is obtained, and the pressing amount of the pressing roll 15 with respect to the belt is regulated. You can

In the image forming apparatus equipped with the curl correction device 10, in addition to the information on the paper quality of the paper stored in the paper feed tray or the like, the information on the toner consumption read value for forming the color toner image, and the like. It is possible to cause the curl correction action in the curl correction device to be performed by using the information of 1. The curl correction device as described above is provided with control means as shown in the block diagram of FIG. 3 in order to control the pressing force of the pressing roll 15 against the belt 11. In the block diagram of FIG. 3, the control device 40
The memory means 42 and 43 are arranged for the CPU 41, and the curl correction direction information 51 and the curl correction amount information 52 are output from the output section 50 based on the information input through the input section 44. The output is performed, and the switching of the guide mechanism for the sheet and the control of the motor 22 that drives the pressing roll are performed.

Information input to the control device via the input section 44 includes image density detection section 45 provided in the main body of the color electrophotographic copying machine, image density of the first surface 46, and image of the second surface. Density 47 information and paper quality information 48,
The information 49 of temperature and humidity is used. The information of the image density of the first surface or the image density of the second surface, which is input to the control device, uses the information of the toner consumption read value when the color toner image is formed on the photosensitive drum. In a full-color electrophotographic copying machine using a photoconductor drum, the toner image formed on each photoconductor drum is input with the calculated value of the toner consumption read value as information of the image density detection unit. When the copy is one-sided, only the information of the image density 46 of the first side is used as the information of the image density detecting unit, and the information of the image quality of the first side and the information of the paper quality and the temperature and humidity are The information is used by the control device to set the curl correction direction and the correction amount.

In order to output control information for driving the pressure roll of the curl correction device in the control device 40 shown in FIG. 3, in the present invention, the toner consumption amount in the color toner image to be finally transferred is set. There is provided a mechanism for outputting information for driving the motor of the curl correction device by using information of the previous color toner image without using information of the read value. In the full-color electrophotographic copying machine shown in FIG. 1, the four photosensitive drums 7 to 7c are
When forming color toner images of different colors,
The following formula is used to calculate the toner consumption amount read value of the color toner image to be finally transferred. First, the toner consumption reading value is calculated for the first color black toner, and the value is set as K. If the read value of toner consumption of yellow for the second color is Y, and the read value of toner consumption of magenta for the third color is M, the last 4
The toner consumption reading C for cyan of the color is (K + Y +
M) / 3 = C can be calculated, and the image density of the color copy using the four color toners can be estimated.

In the copy made by transferring the four color toner images as described above, the image density is calculated as follows, and the pressing roll is directed to the belt according to the calculated value. It is possible to perform a curl correction action by pressing with a button. First, when forming a toner image with one color of toner for the paper size used,
Assuming that the maximum amount of toner that can be used is R, the image density D of the four color toners is D = 100 × (K + Y +
It can be determined by the formula of (M + C) / (R × 4) (%). Therefore, in the control device of the present invention, when the color toner images of four colors are transferred to make a full-color copy, the toner consumption amount read value of the fourth color is read from the information of the toner consumption amount of the first three colors. Is calculated, the image density to be formed on the paper is calculated, and the curl correction performance in the curl correction device can be set according to the information of the image density.

For example, when transferring color toner images of three colors to make a color copy, for the toner consumption readings Y and M of the color toner images of the first and second colors, the cyan of the third color is read. The toner consumption reading C is C =
The estimated value is calculated using the formula of (Y + M) / 2.
Then, the image density D of the entire color image transferred to the paper is D = 100 × (Y + M + C) / (4 × R) (%)
Calculate by the formula. Therefore, the control device provided in the full-color electrophotographic copying machine of the present invention does not directly read the toner consumption amount read value and directly inputs the information of the color toner image to be transferred last time, but the toner consumption of the plurality of color toners is increased. By calculating as an estimated value based on the detected value of the amount reading value, the control information of the curl correction device output from the control device is output at an early stage and before the leading edge of the paper enters the curl correction device, A state in which curl correction can be performed can be set.

It is not possible to set the curl correction performance of the curl correction device by calculating the density of the image formed on the paper in accordance with the above-described image density calculation formula, estimating the state of the curl that occurs on the paper. Also in the case of double-sided copying, the first side and the second side are respectively performed. Then, the image density information on both sides is compared, and the curl correction amount based on the direction in which the curl correction is performed on the paper and the difference between the image density on the first side and the image density on the second side based on such information. And. Therefore, in the curl correction unit 30 shown in FIG. 1, two curl correction devices having different curl correction directions are arranged to correspond to the curl correction direction information output from the control device, and one curl correction device You can set the mode to use.

In the curl correction unit, as shown in FIG.
Alternatively, as shown in FIG. 5, two curl correction devices having different curl correction directions can be used in combination. In the curl correction unit 30 shown in FIG. 4,
Two curl correction devices 31, 3 via the branch gate 33
2 are arranged in parallel, the upper curl correction device 31 corrects an upward curl, and the lower curl correction device 32 is arranged as a device that corrects a downward curl. Then, based on the information of the curl correction surface based on the difference in image density between the first surface and the second surface output from the control device, the curl correction device to be operated is selected, and the selected curl correction device is selected. The force for pressing the pressing roll is set so that the curl correction action is performed on the paper.

In the example shown in FIG. 5, two curl correction devices 36 and 37 having different curl correction directions are arranged in series to form a curl correction unit 35. In the curl correction unit 35, one curl correction device is operated in accordance with the curl direction, and the other curl correction device constitutes a mechanism that does not apply a pressing action to the paper. Then, according to the curl direction of the double-sided copy, the pressure roll of one curl correction device is pressed toward the belt according to the information output from the control device, and the curl correction operation is performed according to the difference in the image density of both sides. Can be done. Therefore, in the curl correction unit shown in FIG. 1, the curl of the paper can be corrected by providing the curl correction unit as shown in FIG. 4 or FIG. It is possible to exert a correction action according to.

In the apparatus of the present invention configured as described above, when a plurality of copies are made based on one original, the curl correction value initially read and set is used in the curl correction apparatus. It is possible to configure the control means for performing the curl correction action. For example, when performing the curl correction action, storing the respective toner consumption amount read values causes a problem that the amount of information to be stored becomes large, but only the curl correction values are stored. Storing a memory does not impose a large burden on the memory because the memory capacity is relatively small. Therefore, the control device of the present invention can easily perform the curl correction operation even when a plurality of color copies are made from one type of original.

Then, using the control method as described above,
By using a curl correction unit capable of exerting a curl correction action on an arbitrary surface of the paper, it becomes possible to appropriately correct the curl generated on the paper. Further, the curl correcting apparatus of the present invention can be applied to any color printer in addition to being applied to a color electrophotographic copying machine, and can be used for post-processing work such as storing paper in a paper output tray of a sorter. When performing, the post-processing operation of the paper can be easily performed. Further, as the curl correction device, in addition to using a mechanism for setting the pressing force of the pressing roll in a plurality of steps, it is also possible to use a mechanism capable of setting the pressing force in a stepless manner. The mechanism of is not limited to the illustrated mechanism, and any mechanism can be used.

[0028]

Second Embodiment The present invention can also be applied to an apparatus for making a double-sided copy by transferring a toner image on the back side of a single-sided copy sheet. In the apparatus shown in FIG. 6, a paper feed system from the manual feed tray is arranged with respect to the main body of the copying machine, single-sided copy sheets are stored in the manual feed tray, and a means for making a double-sided copy can be configured. The image forming apparatus 1A shown in FIG. 6 has the image reading device 50 for scanning the image of the document D arranged on the upper portion of the main body of the device, similarly to a general color electrophotographic copying machine, and scans the image of the document D. It constitutes means for outputting information to the image writing device 55. In the image reading device 50,
The digital reading means is configured to irradiate a document with light output from the light emitting member 51, reflect the reflected light through a plurality of mirrors 52 and 52a, and use a lens 53 to CCD. An image is formed on the photoelectric conversion means such as. Then, the light received by the CCD is output as an electric signal, and the light signal of the color image is detected by being divided for each color.
Writing is performed via an image writing device to each of a plurality of photosensitive drums arranged along the paper transport path.

Incidentally, in the color electrophotographic copying machine, as shown in FIG. 1, a plurality of photosensitive drums are arranged to constitute a mechanism for sequentially superposing and transferring color toner images on a sheet. Then, the photosensitive drum 7 is arranged for one transfer drum 70. Then, a mechanism for transferring the toner image formed on the photoconductor drum to the sheet through the transfer drum is configured. Further, in the color electrophotographic copying machine 1A, a curl correction unit 30 that is a combination of two curl correction devices as shown in FIG. A mechanism that can perform the curl correction operation is configured. Then, for the curl correction unit, information from the image density detecting device 60 of the second surface provided in the image reading device 50 and the image density detecting means of the first surface arranged in the paper transport path described later is used. Thus, the paper is distributed to the two curl correction devices and the curl correction operation is performed by the designated curl correction device.

In the color electrophotographic copying machine 1A, in addition to the paper feeding means from the paper feeding tray, the paper feeding means from the manual feeding tray 65 is provided so that the paper already prepared as a single-sided copy is fed from the manual feeding tray 65. You can make paper and make double-sided copies. A sheet feeding device 66 is arranged on the manual feed tray 65 to feed the single-sided copy sheets one by one, and the single-sided copy sheet is conveyed in the image transfer section by using the conveyance belt device 6 in the sheet conveyance path. I do. The single-sided copy sheet P fed from the manual feed tray 65 has the image P1 already formed on the first side, and the image corresponding to the second side P2 is newly written, but the sheet P is not printed. The curl occurs depending on the difference between the density of the image already described on the first surface and the density of the image newly written on the second surface.

Therefore, in the present invention, the detecting means 56 for detecting the image density of the first side of the sheet is arranged in the sheet conveying path from the manual feed tray 65. The image density detecting means 56 is composed of a light emitting means by a lamp 57, a lens 58 and a light receiving means 59, and detects the image density using the information of the light reflected on the first side of the single-sided copy sheet. Further, the detection means can be arranged in correspondence with the paper transport path from the paper feed tray.
A detection unit is arranged at the confluence of the paper feed path from the manual feed tray and the paper feed tray so that the image density of the first side of the single-sided copy sheet can be detected. As described above, the information from the image density detecting means 56 of the first surface arranged on the sheet conveying path and the information from the image density detecting means 60 of the second surface provided in the image reading apparatus are controlled by the control shown in FIG. With the device
The operation of outputting the curl direction and the curl correction amount information to the curl correction unit, and distributing the two-sided copy discharged from the fixing device to the two curl correction devices,
The curl correction strength can be controlled for the designated curl correction device.

When a large amount of single-sided copy sheets are accommodated in the paper feed tray and double-sided copies are continuously made,
For both modes when making a double-sided copy by inserting a small number of single-sided copy sheets from the bypass tray,
The curl correction is performed based on the information on the density difference between the images on the first and second surfaces. Further, in the curl correction unit 30 provided in the color electrophotographic copying machine, as shown in FIG.
As shown in FIG. 3, two curl correction devices having different curl correction directions may be arranged in series. Therefore, as described above, even when a double-sided copy is created using a single-sided copy sheet on which an image has already been formed on the first side, it is possible to perform a double-sided copy by combining the means for detecting the image density of the first side. The curl that occurs can be estimated and the curl correction operation can be performed. In double-sided copying that is ejected toward the ejection tray or the like, the curl can be stored without curling, and post-processing of the copy can be easily performed. Means can be configured.

[0033]

Since the apparatus of the present invention is configured as described above, it is possible to transfer color toner images of a plurality of colors onto paper in a full-color electrophotographic copying machine.
By using the average value of the image densities of the color toner images transferred before that without using the image density information of the last toner image, the curl correction device is set to the operating position before the paper enters the curl correction device. Can be put on standby. Even when the apparatus is configured in a state where the fixing device and the curl correction device are very close to each other, the curl correction device can accurately perform the sheet processing operation. Further, when two curl correction devices having different curl correction directions are combined to form a curl correction unit and a full-color copy is formed on both sides of the paper, the curl correction action is performed according to the curl direction generated on the paper. It can be performed. Further, in the present invention, the second side is set for the single-sided copy sheet on which the image is already formed on the first side.
When the image on the surface is transferred, the image density detecting means can be arranged corresponding to each surface of the paper. Further, since it is possible to configure means for performing curl correction corresponding to the curl that occurs in copying, in addition to the case where continuous double-sided copying is continuously performed by an automatic double-sided copying machine, it is already created as single-sided copy paper. The curl correction device can also be applied to the case of making a double-sided copy on a different sheet.

[Brief description of drawings]

FIG. 1 is a side view showing the configuration of a full-color electrophotographic copying machine of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a curl correction device of the present invention.

FIG. 3 is a block diagram showing a configuration of a control device of the present invention.

FIG. 4 is an explanatory diagram of a curl correction unit used in the present invention.

FIG. 5 is an explanatory diagram of a curl correction unit having another configuration used in the present invention.

FIG. 6 is an explanatory diagram of a second embodiment of the present invention.

[Explanation of symbols]

1 full color electrophotographic copying machine, 6 conveyor belt device, 7 to 7c photoconductor drum, 8 fixing device,
10 curl correction device, 11 belt, 15
Pressure roll, 20 cam member, 22 motor,
23 indexing disc, 25 solenoid, 30
・ 35 curl correction unit, 40 control device,
45 image density detection unit, 46 first surface image density information, 47 second surface image density information, 50 image reading device, 56 first surface image density detection device, 60
Image density detector on the second side, 65 manual feed tray.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G03G 21/00 370 8004-2H

Claims (4)

[Claims] 1. A plurality of image carriers are arranged, a mechanism for forming toner images of different colors is arranged on each image carrier, and the toner images formed on the image carriers are transferred onto a sheet of paper. Then, the image forming apparatus for fixing the image through the fixing device to form a recording sheet, and the curl correcting device for the recording sheet discharging section of the image forming apparatus are arranged to correct the curl generated in the sheet, and the post-processing is performed. In a device provided with a mechanism for sending out toward the means, a measuring means for measuring the toner consumption amount of each color is provided for the image carrier, and the transfer amount is finally transferred from the information of the toner consumption amount of each color. Means for outputting the information of the curl correction strength to the curl correction device in accordance with the density of the color toner image by estimating the average value of the information excluding the information of the curl correction. Controller of the curl correction apparatus of the image forming apparatus and performs control for the device. 2. A curl correction device connected to the image forming device is configured by combining two devices having different curl correction directions to form a unit, and uses the information of the difference in the density of the color toner images formed on the front and back sides of the paper. First, the curl direction and the size of the curl that occur on the paper are estimated, and the curl correction device is selected according to the curl direction of the paper to correct the curl corresponding to the density of the color toner image. The controller of the curl correction device for an image forming apparatus according to claim 1. 3. A manual feed tray is arranged as a paper feed means of the image forming apparatus, and a means for detecting the image density of the first side of a single-sided copy sheet is provided in a paper feed path for feeding paper from the manual feed tray. The control device for the curl correction device of the image forming apparatus according to claim 1. 4. A means for detecting an image density of a first side of a single-sided copy sheet is provided in a single-sided copy sheet conveying path of the image forming apparatus, and information of an image density of a document corresponding to a second side and the first side of the image are recorded. 1
Two pieces of image density information of the surface are input to the control means, and the direction of the curl and the size of the curl generated on the paper are estimated based on the information on the difference in the density of the color toner images formed on the front and back sides of the paper. A curl correction device is provided by combining two devices having different curl correction directions in the ejection portion of the image forming apparatus, and the curl correction device is provided in correspondence with the direction in which the paper curls. The control device for the curl correction device of the image forming apparatus according to claim 3, wherein the curl correction operation is performed in accordance with a selected color toner image density difference.