JPH0743977A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] Adverse effects such as adhesion of the fixing oil to the photosensitive drum that occurs during double-sided copying without reducing the amount of the fixing oil applied to the fixing roller and avoiding the adhesion of the fixing oil to the recording material. To prevent the occurrence of. [Structure] Normal copy mode S1 and double-sided copy mode S
2 is set, and when copying the second side, the recording material is separated during dummy rotation of the transfer drum, and the fixing oil is removed from the transfer sheet after the transfer step of the recording material carried on the transfer sheet 5f is completed. , Operate the oil removal roller. This prevents the fixing oil from adhering to the photosensitive drum during double-sided copying.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a laser beam printer.

[0002]

2. Description of the Related Art In recent years, color copiers have been remarkably popularized and developed, and products employing an ink jet system, a thermal transfer system, a silver salt photographic system, an electrophotographic system, etc. are becoming popular. Among them, the color copying apparatus to which the electrophotographic method is applied is remarkable in widespread use because it has advantages of high speed and high image quality.

As one of the electrophotographic methods,
A latent image is formed on the photosensitive drum according to the color separation signal of the original image, and development and visualization is performed with colored toner, and transferred to the transfer drum at each development to form a multicolor toner image on the transfer drum. There is a system in which a color image is obtained by transferring the toner image onto a sheet and then fixing the toner image with a fixing device.

In such an electrophotographic image forming apparatus, a heat roller system is widely used as a fixing device for fixing a toner image formed on a recording material. The rollers used in the heat roller type fixing device are formed by coating the roller body with a material that has good mold release properties such as fluorine resin or silicone rubber and that has excellent heat resistance and wear resistance, and forms the outer layer. is doing.

When the image quality is emphasized, as in the case of an electrophotographic color copying machine, silicone rubber is often used as the outer layer of the roller. This silicone rubber is slightly inferior to the fluororesin in releasability, but the releasability can be improved as compared with the fluororesin by applying silicone oil as a release agent on the surface thereof.

[0006]

However, in the image forming apparatus using the above-mentioned conventional fixing device, an image is formed on both sides of the recording material, that is, when a so-called double-sided copy image is formed, a fixing process for the first side is performed. Since the recording material undergoes the toner image transfer process on the photosensitive drum with the silicone oil (hereinafter referred to as fixing oil) attached, the fixing oil on the recording material adheres to the photosensitive drum, resulting in an image defect. This image defect is transferred to the surface of the transfer drum by the transfer process of the second surface because the fixing oil adhered to the toner image surface of the first surface is not fixed on the recording material, and the transfer sheet and the photosensitive drum are in direct contact with each other. By doing so, it has been confirmed that the toner adheres to the surface of the photosensitive drum and causes image unevenness due to non-uniformity of latent image potential, fogging due to toner adhesion to oil at the time of development, and defective cleaning, resulting in image defects. .

By the way, there is a relationship as shown in the graph of FIG. 15 between the offset amount of the fixing roller and the application amount of the fixing oil. In the figure, the horizontal axis shows the amount of oil applied,
The offset amount is taken on the vertical axis, and the oil application amount is measured by measuring the oil application amount per A4 1 sheet, and the offset amount is obtained by fixing a fixed number of recording materials onto which a fixed amount of toner has been transferred and fixing the offset toner to the web. It was collected and collected and the reflection density was measured. As is clear from the graph of FIG. 15, the offset property is almost proportional to the oil application amount at first, that is, the offset property improves as the oil application amount increases, but when the fixing oil application amount exceeds a certain amount. The improvement in the offset property of the fixing roller is saturated.

Although it is possible to reduce the degree of image defects by reducing the amount of fixing oil applied, if the amount of fixing oil applied to the fixing roller is reduced until there is no image defect as described above. It is known that the offset property is not improved and the offset occurs after a short period of use.

On the other hand, in the fixing process of the image forming apparatus using the electrophotographic system, that is, in the process of mixing and developing the four color toners, when the images are fixed on various recording materials under the same fixing condition, Since the heat capacity differs depending on the type, a large difference occurs in fixing property, color development and glossiness, and pictorial reproducibility cannot be guaranteed. For example, 80g / m, 156g / m, and OHP
The optimum fixing conditions differ greatly for each type of paper.

Therefore, the type of recording material is automatically determined, or the user of the apparatus specifies the type of recording material.
The fixing conditions are being changed. As the fixing conditions to be changed, a set temperature, a fixing nip, a pressing force, etc. may be considered, but it is necessary to change the fixing speed so that a fixing time suitable for each recording material can be obtained. It is excellent in cost and general.

FIG. 17 is a graph showing the relationship between the fixing speed depending on the type of recording material and the glossiness which is an index of the fixing property.
According to this graph, it can be seen that a certain glossiness can be ensured by compensating for the difference in heat capacity due to the type of recording material with the fixing speed.

On the other hand, it is desirable that the image forming speed on the recording material is a constant speed in order to optimize image quality, transfer efficiency and copy speed.

A problem when the fixing speed is changed according to the recording material is that when the toner image is transferred to the recording material and then the toner image is fixed in the fixing step, a difference in the conveying speed of the recording material occurs. When the image is generated, the slackened image of the recording material is disturbed.

In order to solve this problem, a sufficient distance is provided between the transfer process (recording material separating portion) and the fixing process, that is, a distance corresponding to the maximum length of the recording material that can be passed. Will be required.

However, if the distance from the transfer process to the fixing process is increased, the transport path to the paper discharge becomes longer, so that the time until the first copy (FCOT) becomes longer and the size of the apparatus becomes larger. there were.

FIG. 17 shows a sequence of a transfer process, a separation process and a fixing process in a conventional image forming apparatus.

As shown in part A of FIG. 17, since the distance L from the separating portion to the fixing device is longer than the maximum length of the recording material, the recording material is not subjected to the separating operation and the fixing operation at the same time. In such an apparatus configuration, the fixing speed v _p
Even if the printing speed was delayed, there was no problem by making the time interval (paper interval) until the next fixing sufficiently long.

However, as shown in part B of FIG. 17, when the distance L from the separating portion to the fixing device is short and the length of the recording material is longer than the separation fixing distance, the separating operation and the fixing operation are simultaneously performed. become. In such a device configuration, when the fixing speed v _p is slowed, the recording material sags, and image disturbance such as image rubbing occurs.

Therefore, an object of the present invention is to provide an image forming apparatus which does not reduce the amount of the fixing oil applied to the fixing roller, avoids the fixing oil from adhering to the recording material, and does not cause any adverse effect during double-sided copying. That is.

A further object of the present invention is to provide an image forming apparatus which does not cause image distortion due to a change in fixing speed even if the distance between the transfer step and the fixing step is not longer than the length of the recording material.

[0021]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention is
The electrostatic latent image formed on the image carrier by exposure is developed with a plurality of color developing agents to form a visible image, and the visible image is transferred to the recording material carried on the recording material carrier in a multiple transfer manner to form a color image. In the image forming apparatus in which the recording material is separated from the recording material carrier after the formation of the image and fixed by the fixing unit, the visible image is formed on the image carrier by the colored developer a plurality of times, and A first image forming mode in which electrostatic transfer is repeated on a recording material carried on a recording material carrier, the recording material is separated from the recording material carrier, and the toner image on the recording material is fixed by the fixing means. And a visible image is formed on the image carrier by a colored developer a plurality of times, and electrostatic transfer is repeatedly performed on the recording material carried on the recording material carrier, and the recording material after the electrostatic transfer is completed. Is passed through the transfer area at least once and separated from the recording material carrier. An image forming apparatus characterized by a second image forming mode for fixing the toner image on the recording material.

Preferably, the fixing means is a fixing device for fixing a recording material carrying an unfixed toner image on the recording material by sandwiching the recording material with a pair of elastic bodies and heating and pressing the toner image. An oil removing member for removing the fixing oil on the recording material carrier, and means for indicating that the image formation on the recording material is the second surface of both sides, and the second means is instructed by the means. The image forming mode 2 is executed, and after the transfer of the toner image to the recording material is completed, the oil removing member is operated with respect to the recording material carrier after the recording material is separated.

Preferably, the recording material carrying speed of the recording material carrier and the fixing means is both variable, and the recording material carrying speed of the fixing means is different from the image forming step speed according to the information about the recording material. In selecting the speed, the second
At the same time that image forming mode 2 is executed, after the transfer of the toner image to the recording material is completed, the recording material carrying speed of the recording material carrying member and the recording material carrying speed of the fixing means are set to substantially the same speed.

[0024]

Embodiments of the image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Embodiment 1 FIG. 1 is an overall configuration diagram showing a first embodiment of an image forming apparatus according to the present invention. In this embodiment, the color image forming apparatus has a digital color image reader section on the upper part and a digital color image printer section on the lower part.

In the image reader section, the original 30 is placed on the original table glass 31 and exposed and scanned by the exposure lamp 32, whereby the reflected light image from the original 30 is transferred to the lens 33.
The light is focused on the full-color sensor 34 to obtain a color separation image signal. The color-separated image signal is processed by a video processing unit (not shown) via an amplifier circuit (not shown) and sent to a digital color image printer section.

In the digital color image printer section,
The photosensitive drum 1, which is an image bearing member, is a photosensitive member made of an organic photoconductor, which will be described later, and is rotatably supported in the direction of the arrow. Around the photosensitive drum 1, a pre-exposure lamp 11, a corona charger 2, Laser exposure optical system 3, potential sensor 12, four developing devices 4y, 4c, 4m, 4Bk having different colors, on-drum light amount detecting means 13, transfer device 5, cleaning device 6
Are placed.

In the laser exposure optical system 3, the image signal from the reader section is converted into an optical signal for image scan exposure by a laser output section (not shown), and the converted laser light is reflected by the polygon mirror 3a. , Is projected onto the surface of the photosensitive drum 1 via the lens 3b and the mirror 3c.

Photosensitive drum 1 at the time of image formation at the print section
Is rotated in the direction of the arrow, and the photosensitive drum 1 after the charge is removed by the pre-exposure lamp 11 is uniformly negatively charged by the charger 2, and the light image E is emitted for each separated color to form a latent image. .

Next, a predetermined developing device is operated to reverse-develop the latent image on the photosensitive drum 1 to form a toner image on the photosensitive drum 1 with a negative toner having a resin base. The developing device selectively approaches the photosensitive drum 1 in accordance with each separated color by the operation of the eccentric cams 24y, 24c, 24m, and 24Bk to perform development.

Further, the toner image on the photosensitive drum 1 is transferred from the recording material cassettes 7a, 7b, 7c to the recording material supplied to the transfer position facing the photosensitive drum 1 via the transport system and the transfer device 5. The transfer device 5 includes a transfer drum 5a,
It has a transfer charger 5b, an attraction charger 5c for electrostatically attracting the recording material, an attraction roller 5g facing the attraction charger 5c, an inner charger 5d, and an outer charger 5e. The transfer drum 5a, which is rotatably driven, has a transfer sheet 5f, which is a recording material carrier for supporting a recording material, stretched integrally on a cylinder in an opening area of its peripheral surface. A polycarbonate film or the like is used for the transfer sheet 5f.

On the other hand, the recording material is transferred from the cassette 7 to the transfer device 5
Is fed to the suction charger 5c and the suction roller 5 facing the suction charger 5c.
The toner image is electrostatically attracted onto the transfer sheet 5f by g, and the toner images are transferred to the recording material one by one in synchronization with the color separation toner image described above by the transfer charger 5b.

As shown in FIG. 1, since only one color image is formed in one image forming step, the document color separation step is performed by the number of toner colors, that is, yellow (Y) and magenta. (M), cyan (C), and black (B) are repeated four times, and similarly, in synchronization with each color separation, latent image formation, development, and transfer according to each color component are repeated to form a full-color image. To be done.

In the case of forming a full-color image, when the transfer of the four color toner images is completed in this way, the recording material is separated from the transfer drum 5a by the action of the separating claw 8a, the separating push-up roller 8b and the separating charger 5h, The toner image on the recording material is guided to the fixing device 9, and the toner image on the recording material undergoes mixed color development in the fixing step and is discharged to the tray 10 to complete one color copy.

On the other hand, the post-transfer photosensitive drum 1 is subjected to the side image forming step after the residual toner on the surface is cleaned by the cleaning device 6.

When images are formed on both sides of the recording material,
Immediately after the recording material is discharged from the fixing device 9, the conveyance path switching guide 19 is driven, the conveyance vertical path 20 is passed, and then the reversing path 21a.
Then, the reversing roller 21b is reversely rotated, and the trailing end of the recording material when fed to the reversing path 21a is made to be the leading end and is retracted in the direction opposite to the feeding direction, and is temporarily stored in the intermediate tray 22. Next, an image is formed again on the other surface of the recording material by the above-mentioned image forming step.

Further, in order to remove the adhered powder on the transfer sheet 5f of the transfer drum 5a and the adhered oil on the recording material, the fur brush 15, the oil removing roller 16, and the oil removing roller 16 via the transfer sheet 5f. The backup brushes 17 facing each other are used for cleaning. Such cleaning is performed before or after image formation, and at any time when a jam, that is, a paper jam occurs.

Further, by operating the eccentric cam 25 at a desired timing and operating the cam follower 5i integrated with the transfer drum 5a, the gap between the transfer sheet 5f and the photosensitive drum 1 can be arbitrarily set. There is. For example, the distance between the transfer drum and the photosensitive drum can be increased during standby or when the power is off.

FIG. 2 is a block diagram showing the fixing device 9 in detail.

In the figure, the fixing device 9 is a fixing roller 9.
01 and a pressure roller 902 facing this. The fixing roller 901 is composed of an aluminum core 905 and an outer layer 906 coated on the core 905. As the material of the outer layer, for example, an addition type silicone rubber composed of linear polydimethylsiloxane having a molecular weight of 20,000 to 200,000 and having a terminal vinyl group blocked as described in JP-A-61-144675 is used. It is disclosed to exhibit releasability. Recently, it is composed of a linear polydimethylsiloxane having a terminal vinyl group blocked with a viscosity of 80,000 poise or more, and a structural unit containing at least one of a tetrafunctional group and a trifunctional group and having two or more vinyl groups. It has been proposed to use an addition-type silicone rubber obtained by curing a polysiloxane mixture containing at least a resinous organosiloxane.

The pressure roller 902 is formed by forming an outer layer 908 on an aluminum core 907 with HTV silicone rubber to a predetermined thickness and further forming a resin film 909 on the surface thereof.

Further, the fixing roller 901 and the pressure roller 9
A halogen heater 910, 924 serving as a heating source
Are provided respectively, and the thermistor 916 controls the on / off of the current to the halogen heaters 910 and 924. As a result, the fixing roller 901 and the pressure roller 90
The temperature of 2 is a temperature suitable for fixing the unfixed toner image 913 on the recording material 914 on the recording material 914, for example, 17
Maintained at 0 ° C. Fixing roller 901 and pressure roller 9
Reference numeral 02 designates arrows b1 and b
It is rotated in two directions.

Further, adjacent to the fixing roller 901, a releasing agent applying device 903 for improving the releasing property of the toner from the fixing roller 901 is provided. The release agent applying device 903 includes an oil tank 925 containing the fixing oil 912, a first scooping roller 922 dipped in the fixing oil 912, a second scooping roller 921 and a second scooping roller 921 contacting the first scooping roller 922. The application roller 911 is provided for applying the fixing oil supplied to the fixing roller 901 to the fixing roller 901. In addition, the application roller 911
A blade 920 for controlling the application amount of the fixing oil applied to the fixing roller 901 is disposed so as to abut.

The release agent coating device 90 having the above-mentioned configuration
3, the fixing oil 912 in the oil tank 925
Is applied to the application roller 911 via the first and second scooping rollers 922 and 921, the application amount is adjusted by the blade 920, and then applied to the fixing roller 901. The amount of oil applied is 0.1 g per A4 sheet.
It is a degree.

Further, a cleaning device 904 for cleaning the toner offset on the surface of the fixing roller 901 is provided on the opposite side of the release agent applying device 903 with the fixing roller 901 interposed therebetween. The cleaning device 904 includes a non-woven fabric 919 that cleans the surface of the fixing roller and a pressing roller 918 that brings this into contact with the surface of the fixing roller 901.

Further, the pressure roller 902 is also arranged so that a cleaner 923 for cleaning the toner offset on the surface thereof comes into contact with the pressure roller 902.

In the fixing device 9 having the above-mentioned general structure, the recording material 91 carrying the unfixed toner image 913.
4 is conveyed by a conveying device (not shown) in the direction of arrow a, guided by an entrance guide 915, and a toner image 913 is fixed between the fixing roller 901 and the pressure roller 902 which rotate in the directions of arrows b1 and b2. Pass through as if touching. Then, while passing therethrough, the pressure applied by the fixing roller 901 and the pressure roller 902 and the heat controlled by the halogen heater 910 at a predetermined temperature via the fixing roller 901 causes the recording material 914 to move. The unfixed toner image 913 is fixed on the recording material 914.
The recording material 914 which has been fixed is discharged to the outside of the image forming apparatus through the exit guide 917.

The recording material on which the toner is fixed by the fixing device in this manner holds the fixing oil used for improving the releasability on the surface thereof, and in particular, the image surface on which the toner adheres. In the above, the fixing oil remains without being adsorbed on the recording material.

By the way, the fixing oil remaining without being adsorbed on the recording material is transferred to the surface of the transfer sheet 5f of the transfer drum 5a during double-sided copying. For this reason, the transfer device 5 is provided with an oil removing roller 16 for removing the transferred fixing oil. As a result, the fixing oil attached to the transfer sheet 5f is scraped off and absorbed. As the oil removing roller 16, there has been proposed a roller-like material or a web-like material that is suitable for scraping and absorbing the fixing oil. The present invention is not limited to the structure of this oil removing roller.

Next, the operation of the image forming apparatus having the above-described structure for double-sided copying of a color image will be described. In particular, the timing for removing the fixing oil on the recording material will be described.

The basic idea of the image forming sequence is as follows. 1. In order to prevent the fixing oil from adhering to the photosensitive drum, the oil removing roller is operated before the transfer sheet surface having the first fixing oil adheres to the photosensitive drum directly; Set the oil removal roller at a time other than the time when the photosensitive drum is exposed and the time when the toner is transferred from the photosensitive drum to the recording material so that vibrations during operation do not affect the image. It is to make it work.

Therefore, it is necessary to operate the oil removing roller when the final copy is completed, and also to operate so that the transferred image is not disturbed by the operation of the oil removing roller so as not to overlap with the transfer process in time. .

FIG. 3 shows a flowchart for selecting the image forming sequence control. First, depending on whether the copy to the recording material is the second side copy, the normal copy mode S0
Alternatively, the double-sided copy mode S1 is executed.

The normal copy mode S0 is executed based on the image forming sequence shown in FIG. The double-sided copy mode S1 is executed based on the image forming sequence shown in FIG. 5 so as to satisfy the above basic idea.

In the sequence of FIGS. 4 and 5, the timing of the transfer step, the separation step, and the oil removal step, which are the process configurations of the transfer drum, will be focused and described.

In the sequence of the normal copy mode S0,
As shown in FIG. 5, the transfer step of transferring the toner image of the final color on the photosensitive drum onto the recording material carried on the transfer sheet and the separating step of separating the recording material from the transfer sheet are executed in parallel. . In this case, the oil removing roller does not operate.

On the other hand, in the second side copy sequence in the double-sided copy mode S1 shown in FIG. 5, the transfer drum is further rotated without performing the step of separating the recording material from the transfer sheet until the transfer of the final color is completed. When, that is,
The recording material separation process is executed when the transfer drum is rotated dummy. Then, after the transfer process for the recording material carried on the transfer sheet is completed, the oil removing roller is operated to remove the fixing oil from the transfer sheet.

At this time, a cleaning member such as a fur brush for removing toner from the transfer sheet is also operated. The cleaning member is preferably arranged upstream of the oil removing member with respect to the rotation of the transfer drum in order to prevent the oil removing member from becoming dirty.

Second Embodiment Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to FIGS. 6 and 7.

In this embodiment, the image forming apparatus has means for detecting the type and length of the recording material, and the image forming sequence is controlled according to the detection result and the distance L from the transfer section to the oil removing roller. Is characterized by. For example, when the length of the recording material is short and the transfer process and the separation process do not overlap in time, the dummy rotation can be omitted.

In the flowchart for selecting the sequence control shown in FIG. 6, first, it is judged whether or not the copy to the recording material is the second side copy.

When it is determined that the copy is for the second side, the size L _P of the recording material in the feeding direction is compared with the distance L from the transfer position to the oil removing roller. When the paper size L _P is larger than the distance L from the transfer unit to the oil removing unit, the double-sided copy mode S1 is executed. On the other hand, when the paper size L _P is shorter than the distance L from the transfer unit to the oil removing unit, the second double-sided copy mode S2 is executed.

In the second double-sided copy mode S2, the image forming sequence as shown in FIG. 7 is executed. In this case, since the transfer process and the operation of the oil removing roller do not overlap with each other in time, the dummy rotation of the transfer drum can be omitted.

Third Embodiment Next, a third embodiment of the image forming apparatus according to the present invention will be described with reference to the flowchart of FIG.

When the recording material is held on the transfer sheet of the transfer drum by electrostatic attraction, if the circumference of the transfer drum is more than twice the length of the recording material to be attracted, two or more recording materials are transferred. It is carried out by holding the same at the same time. With such a configuration, it is possible to increase throughput during continuous copying.

In this embodiment, the case where an image is formed in a system capable of adsorbing two recording materials on a transfer sheet is shown.
In such a system, when copying an even number of sheets, the fixing oil that has adhered to the transfer sheet does not adhere to the photosensitive drum because the recording material is present in the transfer section.
However, when making an odd number of copies, since only one recording material is adsorbed on the transfer sheet at the time of the final copy, the transfer sheet with the fixing oil directly contacts the photosensitive drum at the transfer section, and Fixing oil adheres to the drum.

In order to prevent such fixing oil from adhering to the photosensitive drum, sequence control is executed according to the flow chart shown in FIG.

First, depending on whether the copy to the recording material is the second side copy, it is determined whether the normal copy S0 or the second side copy mode.

Next, when it is determined that the mode is the second side copy mode, it is determined whether or not two sheets are attracted to the transfer drum. A copy of a recording material that cannot adsorb two sheets or a single copy of a small size is copied in the normal copy sequence S0. When the two-sheet suction mode is executed for copying a plurality of small-sized sheets, the third copy mode S3 is executed if the number of copies is an even number, and the fourth copy mode S4 is executed if the number of copies is an odd number. Different formation sequences.

In the case of the sequence of the third copy mode S3, suction and transfer of two sheets each are repeated, and in the final two-copy sequence, the dummy rotation of the transfer drum is performed to separate the recording material and the oil from the transfer sheet. The removal sequence is executed and the process ends.

On the other hand, in the case of the sequence of the fourth copy mode S4, first one copy is executed and the remaining copies are set to an even number, and then the suction transfer is repeated in the two-sheet suction mode. By adsorbing one of the first copies, it is possible to prevent the transfer sheet having the fixing oil attached thereto from directly contacting the photosensitive drum in the subsequent copies.

Fourth Embodiment Next, a fourth embodiment of the image forming apparatus according to the present invention will be described with reference to the flowchart of the image forming sequence shown in FIG.

In the present embodiment, in the second-side copy mode of the image forming apparatus having the two-sheet attraction mode by electrostatic attraction, first, the sequence for double-sided printing is selected according to the paper size L _P , and the separating means is selected. When the paper size L _P is smaller than the distance L to the fixing unit, the second side copy sequence is further selected depending on whether or not a plurality of recording materials are held by the recording material support member by electrostatic attraction. .

First, it is judged whether or not it is the second side copy. If it is not the second side copy, the normal copy mode S0 is executed.

Next, for the second side copy, the paper size L _P
Is larger than the distance L from the transfer position to the oil removing roller, the double-sided copy mode S1 is executed.

Further, it is the second side copy and the paper size L _P
Is shorter than the distance L from the transfer position to the oil removing roller, and if one copy is made, double-sided second-side copy mode S2
Is executed.

Further, it is the second side copy and the paper size L _P
Is shorter than the distance L from the transfer position to the oil removing roller and is an even number of continuous copies, the third copy mode S
3 is executed.

Further, it is the second side copy and the paper size L _P
Is shorter than the distance L from the transfer position to the oil removing roller and is an odd number of continuous copies, the fourth copy mode S
4 is executed.

Fifth Embodiment Next, a fifth embodiment of the image forming apparatus according to the present invention will be described with reference to the flow chart of the image forming sequence shown in FIG.

This embodiment is applied when the recording material type information specifies a recording material such as thick paper or OHP and it is determined that the fixing speed needs to be changed. This is called a cardboard mode for convenience.

In this embodiment, in the thick paper mode, after the transfer of the final color to the recording material is completed, the dummy rotation of the transfer drum is performed,
The transfer drum speed and the fixing roller speed are selected according to the information of the recording material, and the recording material is separated from the transfer drum and then fixed.

That is, the sequence is controlled according to the detection result of the paper thickness, OHP, etc. or the detection result of the designating means.

In the flow chart for selecting the sequence control shown in FIG. 10, first, it is determined whether the normal copy mode S1 or the thick paper copy mode S5 is required according to the necessity of changing the fixing condition.

The sequence of the thick paper copy mode S5 will be described with reference to the timing chart shown in FIG. In the figure, the drive speed switching timing of the transfer drum, the transfer timing of the toner image from the photosensitive drum to the recording material attached on the transfer drum, the separation operation timing, and the fixing operation timing are shown.

As shown in the figure, after the transfer was completed, the rotational speed of the transfer drum was changed in accordance with the fixing speed, and then the toner image transferred multiple times to the recording material was passed through the transfer area again while holding it. After that, that is, when the transfer drum idles, the recording material is separated from the recording material holding member and fixed.

In the idle rotation operation of the transfer drum, the setting of the photosensitive drum potential and the transfer condition are set to be substantially the same as the setting for normal copying.

Sixth Embodiment Next, a sixth embodiment of the image forming apparatus according to the present invention will be described with reference to the flowchart of the image forming sequence shown in FIG.

This embodiment comprises means for selecting the type and length of the recording material, a plurality of fixing speed selecting means, and transfer drum speed selecting means corresponding thereto, and after the transfer of the final color onto the recording material is completed. The transfer drum speed and the fixing roller speed are selected according to the information of the recording material, and the recording material is separated from the transfer drum and then fixed.

That is, it is characterized in that a paper thickness detection or designation means and a paper size detection means are provided, and the sequence is controlled according to the detection results.

In the flowchart for selecting the sequence control shown in FIG. 12, first, the normal copy mode S1 and the thick paper copy mode are determined according to the necessity of changing the fixing conditions.

[0091] In the case of thick paper copy mode, the distance L from the separation means to the fixing means, sheet size L _P are compared,
If the paper size L _P is large, the fifth copy mode S5 is executed.

From the distance L from the separating means to the fixing means,
When the paper size L _P is small, it is further determined whether or not a plurality of recording materials are held on the transfer sheet by electrostatic attraction.

When it is judged that the copy is one copy,
The sixth copy mode S6 is executed. When holding a plurality of recording materials, the seventh copy mode S7 is executed.

Next, the sequence of the above fifth, sixth and seventh copy modes S5, S6 and S7 will be described using a timing chart. The following sequence diagram shows the drive speed switching timing of the transfer drum, the transfer timing of the toner image from the photosensitive drum to the recording material stuck on the transfer drum, the separation operation timing, and the fixing operation timing.

In the sequence of the fifth copy mode S5,
As shown in the timing chart of FIG. 11 described above, after the transfer is completed, the rotation speed of the transfer drum is changed in accordance with the fixing speed, and then the transfer area is changed while holding the toner images multi-transferred onto the recording material. After passing again, that is, when the transfer drum is idle, the recording material is separated from the recording material holding member and fixed.

In the sequence of the sixth copy mode S6 in which only one sheet is copied, as shown in FIG. 13, after the transfer is completed, the recording material is separated from the transfer sheet and fixed.

When a plurality of recording materials are held, that is, in the sequence of the seventh copy mode, as shown in FIG. 14, after the transfer is completed, the recording material holding only one toner image is separated and fixed. To do. For other recording materials,
The recording material is separated from the transfer sheet and fixed after passing through the transfer area again while holding the toner images sequentially and sequentially transferred, that is, when the transfer drum is idle. At this time,
The transfer drum is idled a plurality of times so that the separated recording material does not overlap the fixing of the first recording material.

The photosensitive drum potential and the transfer condition setting in the idle rotation of the transfer drum are almost the same as those in the normal copying.

[0099]

As is apparent from the above description, in the image forming apparatus according to the present invention, the visible image is formed on the image carrier by the colored developer a plurality of times, and the recording carried on the recording material carrier is carried out. A first image forming mode in which the recording material is separated from the recording material carrier by repeating electrostatic transfer onto the material, and the toner image on the recording material is fixed by the fixing means, and a color developer is applied to the image carrier. Visualization is performed a plurality of times, electrostatic transfer is repeatedly performed on the recording material supported by the recording material carrier, and the recording material after the electrostatic transfer is passed through the transfer area at least once, and the recording material is transferred. A second image forming mode in which the toner image on the recording material is separated from the carrier is fixed, so that the amount of the fixing oil applied to the fixing means is not reduced and the fixing oil is fixed on the recording material. Image bearing during double-sided copying, avoiding adhesion of The occurrence of adverse effects associated with the fixing oil adhering to it can be prevented.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an image forming apparatus embodying the present invention.

FIG. 2 is a schematic configuration diagram of the fixing device in FIG.

FIG. 3 is a flowchart showing an image forming sequence for explaining the first embodiment of the image forming apparatus according to the present invention.

FIG. 4 is a copy sequence diagram showing a normal copy mode.

FIG. 5 is a copy sequence showing a double-sided copy mode in the first embodiment.

FIG. 6 is a flowchart showing an image forming sequence for explaining a second embodiment of the image forming apparatus according to the present invention.

FIG. 7 is a copy sequence showing a double-sided copy mode in the second embodiment.

FIG. 8 is a flowchart showing an image forming sequence for explaining a third embodiment of the image forming apparatus according to the present invention.

FIG. 9 is a flowchart showing an image forming sequence for explaining a fourth embodiment of the image forming apparatus according to the present invention.

FIG. 10 is a flowchart showing an image forming sequence for explaining a fifth embodiment of the image forming apparatus according to the present invention.

FIG. 11 is a copy sequence showing a double-sided copy mode in the fifth embodiment.

FIG. 12 is a flowchart showing an image forming sequence for explaining a sixth embodiment of the image forming apparatus according to the present invention.

FIG. 13 is a copy sequence showing a copy mode (S6) in the sixth embodiment.

FIG. 14 shows another copy mode (S in the sixth embodiment).
7 is a copy sequence showing 7).

FIG. 15 is a graph showing a relationship between an oil application amount and an offset amount.

FIG. 16 is a graph showing the relationship between fixing speed and image glossiness.

FIG. 17 is a copy sequence of a conventional image forming apparatus.

[Explanation of symbols]

 1 Photosensitive Drum (Image Carrier) 5f Transfer Sheet (Recording Material Carrier) 9 Fixing Device (Fixing Means) 901 Fixing Roller (Elastic Body) 902 Pressure Roller (Elastic Body)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location G03G 15/20 104 107 (72) Inventor Takashi Hasegawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Kiya Non non corporation

Claims (3)

[Claims] 1. An electrostatic latent image formed by exposure on an image carrier is developed with a plurality of color developing agents to form a visible image, and the visible image is multiplexed on the recording material carried on the recording material carrier. In an image forming apparatus in which a recording material is transferred to form a color image, and then the recording material is separated from the recording material carrier and fixed by a fixing unit, a plurality of visible images are formed on the image carrier by a colored developer. When the recording material carried on the recording material carrier is repeatedly electrostatically transferred, the recording material is separated from the recording material carrier, and the toner image on the recording material is fixed by the fixing means. The image forming mode of No. 1 and a visible image on the image carrier by the colored developer are performed a plurality of times, and electrostatic transfer is repeated on the recording material carried on the recording material carrier to perform the electrostatic transfer. The recording material after completion is passed through the transfer area at least once to transfer the recording material. Separated from the body, the image forming apparatus characterized by a second image forming mode for fixing the toner image on the recording material. 2. A fixing device for fixing the toner image on the recording material by sandwiching a recording material carrying an unfixed toner image between a pair of elastic bodies to heat and pressurize the toner image. An oil removing member for removing the fixing oil on the recording material carrier, and means for indicating that the image formation on the recording material is the second surface of both sides, and the second means is instructed by the means. 2. The image forming mode 2 is executed, and after the transfer of the toner image onto the recording material is completed, the oil removing member is operated with respect to the recording material carrier after the recording material is separated. Image forming apparatus. 3. The recording material conveying speed of the fixing means, wherein the recording material conveying speed of the recording material carrying member and the fixing means are both variable, and different from the image forming process speed according to the information about the recording material. When the second image forming mode 2 is executed, the recording material conveying speed of the recording material carrier and the recording material conveying speed of the fixing unit are set at the same time when the transfer of the toner image onto the recording material is completed. The image forming apparatus according to claim 1, wherein the speeds are substantially the same.