JPH08227232A - Color image forming device - Google Patents

Abstract

PURPOSE: To ensure the attraction of paper to a paper holding member and the transfer of a toner image to the attracted paper by means of a single electrifier without causing a jam. CONSTITUTION: The color image forming device is equipped with the transfer electrifier 17 which is arranged inside the paper holding member 12 and opposite a transfer position Q, attracts the paper P, supplied to the transfer position Q, toward the paper holding member 12, and also transfers the toner image on the surface of an image carrier 9 to the attracted paper P. It is further equipped with a transfer-electrifier-actuation controller which, when the paper P is supplied to the transfer position Q, actuates the transfer electrifier 17 before the front end of the paper P reaches the transfer position Q and, when the front end of the paper P attracted to the paper holding member 12 reaches the transfer position Q after two or more rotations are made, actuates the transfer electrifier 17 after the passage of the front end of the paper P through the transfer position Q.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image recording apparatus such as a color electrophotographic copying machine or a color printer, and in particular, toner images of different colors are formed on a surface of an endless image carrier and toner images of respective colors are formed. The present invention relates to an apparatus for forming a color image on a sheet by sequentially transferring the sheets onto the sheet attracted to an endless sheet attracting surface of a sheet carrying member.

[0002]

2. Description of the Related Art Most of conventional color image forming apparatuses of this type have an endless sheet suction surface (that is,
(Transfer drum surface or endless paper carrying belt surface, etc.)
An electrostatic charger for adsorbing the sheet and a transfer charger for transferring the toner image on the surface of the image carrier to the adsorbed sheet are separately provided. As described above, providing the charging and transfer chargers separately requires a large number of parts and increases costs.

The following technique (J01) is known as a conventional technique for reducing the number of parts. (J01) Japanese Unexamined Patent Publication No. 5-27606 In order to reduce the number of chargers arranged near the paper carrying member, a charger for adsorbing the paper on the paper carrying member and a charge removal of the paper after the toner image transfer A technology in which the same charger is used to perform the charging, and the polarity of the charger is changed according to the required function.

(Problem of (J01)) The above (J01) describes the technical idea that the charging and discharging chargers are constituted by a single charging device. The technical idea of configuring the charger by one charger is not disclosed. The reason for this is considered to be based on the following ideas (a) and (b). That is, (a) Ordinarily, it is considered difficult to reliably and satisfactorily transfer the toner image of the first color at the same time when the sheet is adsorbed by the single charger arranged at the transfer position. (B) Therefore, when the sheet is attracted to the sheet carrying member and the toner image is transferred to the attracted sheet by the single charger arranged at the transfer position, only the sheet is attracted when the sheet is attracted. It is necessary to rotate the sheet carrying member once and transfer the toner image to the attracted sheet from when the sheet carrying member enters the second rotation. With such a method, the number of rotations of the paper carrying member required to form an image of, for example, four colors (Y, M, C, K) on the paper is (the number of times the toner image of four colors is transferred + the paper 1 rotation for adsorption) = (4
+1) = 5, so it has to rotate 5 times. That is, compared to the conventional method in which a transfer charger is provided on the downstream side of the adsorption charger and the toner image is transferred to the sheet attracted on the upstream side on the downstream side, the number of rotations of the sheet carrying member is increased, Image formation time becomes long. Based on the above-mentioned ideas (a) and (b), it is considered that (J01) does not disclose the technical idea in which the attraction and transfer chargers are constituted by one charger.

[0005]

The following techniques (J02) and (J03) are known as conventional techniques for realizing the functions of the attraction and transfer chargers by a single charger. (J02) Japanese Unexamined Patent Publication No. 63-43177, the following description is given on page 3, upper column, right column, line 6 to lower column, left column, line 2 of this publication. "The transfer paper that has entered this contact portion is electrostatically attracted to the Mylar film on the peripheral surface of the transfer drum by the output of the transfer charger and is wound around the transfer drum .... The transfer drum is a photosensitive belt. The image is written from the scanner 8 by the output signal from the sensor at the moment when the transfer sheet passes through the transfer sheet leading edge detection sensor 113 at the moment when the transfer sheet rotates at the peripheral speed equal to 4. "See from this description and FIG. , (J02), the sheet is adsorbed and the toner image is transferred by one charger arranged at the transfer position. However,
The toner image is not transferred when the paper is adsorbed when the paper is supplied to the transfer position. In other words, during the one rotation of the transfer drum (sheet carrying member) after the leading edge of the sheet is attracted, only the sheet is attracted and the toner image is not transferred. When the suction of the paper onto the transfer drum (paper carrying member) is completed and the sucked paper tip moves to the transfer position and enters the second rotation, the transfer of the first color is performed.

(Problem of (J02)) In the technique of (J02), when the paper is adsorbed, the transfer drum (paper carrying member) is rotated once only to adsorb the paper, and the toner on the adsorbed paper is absorbed. Since the transfer of the image is performed from the time when the transfer drum (paper carrying member) enters the second rotation, as described in (b) above, the transfer of the toner image to the paper adsorbed on the upstream side on the downstream side is performed. Compared with the conventional method, the number of rotations of the transfer drum (paper carrying member) increases, and the image forming time becomes longer.

(J03) Technology disclosed in Japanese Patent Laid-Open No. 5-72915 In this publication, a transfer sheet is attracted to a dielectric sheet (transfer sheet carrier) by a single charger, and a first color is applied to the transfer sheet. A technique for simultaneously transferring toner images is described. When the adsorption of the paper and the transfer of the toner image of the first color are performed at the same time, the power supply capacity is not increased in order to prevent a shortage of the adsorption current and the transfer current.
A method of changing the volume resistivity of the first color toner is adopted.

(Problem of (J03)) The technique of (J03) has a problem that a special toner must be prepared as the toner for forming the toner image of the first color.

In view of the above circumstances, the present invention provides the following (O0
The content of 1) is the subject. (O01) To ensure that a sheet is attracted to a sheet carrying member and a toner image is transferred to the attracted sheet by using one charger without causing a jam. (O02) To ensure that the toner image of the first color can be transferred at the same time as the suction of the paper without using a special toner.

Conventionally, the paper adsorption has been performed by a DC positive component output charger. Since the charger of the positive component output of the same polarity is used in the subsequent image transfer, if the discharge is made from the leading edge of the paper during image transfer, that force will outweigh the attraction of the leading edge of the paper to the transfer film, and the leading edge of the paper will Peel off the transfer film and wrap it around the photosensitive drum jam (PO
Pjam) may occur. Therefore, the POP
In order to avoid the occurrence of jam, the discharge start timing of the conventional transfer charger is set at a position 3 mm from the front end of the paper.

The present inventor has found that the above-mentioned problems (O01), (O0
In order to solve 2), a test device that directly feeds the paper to the transfer position was manufactured, and the change in the paper suction state and the influence on the image transfer were investigated. Then, the discharge start timing of the test device is set to a position 3 mm from the front end of the paper, similarly to the discharge start timing of the conventional transfer charger.
Evaluation of the sheet suction state of the test device is performed by (1) registration variation, (2) color shift, (3) sheet suction force,
(4) jam around the image carrier (photosensitive drum) jam (P
OPjam). As a result, (1) registration variation is within ± 1.6 mm, (2) color misregistration is ± 30 μm, and (3) paper suction force is 20 gf / square cm.
As described above, it has the same performance as the conventional configuration.
However, (4) POP jam frequently occurred on high-humidity paper.

As a result of experiments and consideration for solving this problem, it was found that the problem can be solved by adjusting the discharge timing of the charger. That is, when the first color is transferred at the same time as the sheet is adsorbed, the charger is activated before the leading edge of the sheet reaches the transfer position, and when the second and subsequent colors are transferred, the leading edge of the sheet passes the transfer position. By operating the charger from the POPja
It was possible to reduce m. This is because when performing paper suction and toner image transfer at the same time when the paper is fed to the transfer position,
As in the conventional case, when the discharge is started from the position 3 mm from the front end of the paper, naturally the front end of the paper is not adsorbed to the transfer film (paper carrying member). For this reason,
It is considered that POP jam frequently occurred on the high-humidity paper. The present invention has been completed through the processes such as the experiments and consideration described above.

[0013]

The present invention devised to solve the above problems will now be described. The elements of the present invention are to facilitate correspondence with the elements of the embodiments described later. Note that the reference numerals of the elements of the embodiments are enclosed in parentheses. The reason why the present invention is described in association with the reference numerals of the embodiments described later is to facilitate the understanding of the present invention and not to limit the scope of the present invention to the embodiments.

In order to solve the above-mentioned problems, the transfer device of the color image forming apparatus (U) of the present invention has the following requirements (Y01) a moving endless image carrier ( 9) Toner image forming devices (1 to 8 + 10 to 16) for sequentially forming toner images of a plurality of colors on the surface, (Y02) The image carrier (9) at a transfer position (Q) in contact with the surface of the image carrier (9). ) A paper carrying member (12) having an endless paper attracting surface that moves in the same direction as the surface, (Y03) The first color toner image formed on the surface of the image carrier (9) is transferred to the transfer position (Q ), Paper feed devices (18 to 20) for feeding the paper (P) at the same timing, (Y04)
The sheet (P) is disposed inside the sheet carrying member (12) so as to face the transfer position (Q), and the sheet (P) supplied to the transfer position (Q) is sucked onto the sheet suction surface and is sucked ( Transfer charger (17) for transferring the toner image on the surface of the image carrier (9) to (P), (Y05) when the paper (P) is supplied to the transfer position (Q), the paper (P) The transfer charger operation control device (S1 + M + 32) for operating the transfer charger (17) before the leading edge reaches the transfer position (Q), (Y06) the leading edge of the paper (P) attracted to the sheet carrying member (12) The toner image forming device (1 to 8 + 10 to 16) that forms toner images of the second and subsequent colors on the surface of the image carrier (9) at the same timing when the transfer position (Q) is reached after the second rotation. , (Y07)
When the front end of the paper (P) attracted to the paper carrying member (12) reaches the transfer position (Q) after the second rotation, the front end of the paper (P) passes through the transfer position (Q). To the transfer charger operation control device (S1 + M + 32) for operating the transfer charger (17).

[0015]

Next, the operation of the present invention having the above features will be described. In the transfer device of the color image forming apparatus (U) of the present invention having the above-mentioned characteristics, the toner image forming apparatus (1 to 8 + 1) is used.
0 to 16) sequentially form toner images of a plurality of colors on the moving surface of the endless image carrier (9). The endless sheet suction surface of the sheet carrying member (12) moves in the same direction as the surface of the image carrier (9) at the transfer position (Q) in contact with the surface of the image carrier (9). Paper feeder (18-2
0) supplies the paper (P) at the same timing when the first color toner image formed on the surface of the image carrier (9) reaches the transfer position (Q). The transfer charger (17) disposed inside the paper carrying member (12) so as to face the transfer position (Q) has the transfer position (Q).
The sheet (P) supplied to the sheet is sucked onto the sheet suction surface, and the toner image on the surface of the image carrier (9) is transferred onto the sheet sucked (P). The transfer charger operation control device (S1 + M + 32), when the sheet (P) is supplied to the transfer position (Q), before the leading edge of the sheet (P) reaches the transfer position (Q), 17) is activated. Therefore, the paper sheet (P) fed to the transfer position (Q) is surely fed from the leading edge of the paper sheet carrying member (1).
It is adsorbed on the paper adsorption surface of 2).

The toner image forming device (1-8 + 10-1)
6) is for carrying the image at the same timing when the front end of the paper (P) adsorbed on the endless paper adsorbing surface of the paper carrying member (12) reaches the transfer position (Q) after the second rotation. The transfer charger operation control device (S1 + M + 32) for forming the toner images of the second and subsequent colors on the surface of the body (9)
Is the paper (P) attracted to the paper carrying member (12).
When the front end reaches the transfer position (Q) after the second rotation, the transfer charger (17) is operated after the front end of the sheet (P) passes the transfer position (Q). In this way, at the time of image transfer after the second rotation, when the transfer charger (17) is operated after the front end of the paper (P) has passed the transfer position (Q), the paper suction of the front end of the paper (P) is performed. The front end of the sheet (P) is peeled off from the sheet adsorbing surface of the sheet supporting member (12) or is wound around the image carrier (9) (photosensitive drum) jam (POPja) without weakening the adsorption force to the surface.
It is possible to prevent the occurrence of m).

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments.

(Embodiment) FIG. 1 is an overall explanatory view of a color image forming apparatus (digital color copying machine) according to an embodiment of the present invention. FIG. 2 is an enlarged view of a main part of FIG. FIG. 3 is an explanatory diagram of a control circuit portion of the embodiment. FIG. 4 is a flow chart showing the operation of the transfer charger of the embodiment.

In FIG. 1, light emitted from a lamp 2 for illuminating an original that moves along the lower surface of an original (not shown) placed on a platen 1 and reflected by the original is reflected by a moving mirror unit 3 and a lens. 4, it is converged on the image reading unit 6 via the fixed mirror 5. An exposure system (2-5) is constructed from the elements indicated by the reference numerals 2-5. The image reading unit 6
Is composed of a color CCD sensor having a large number of photoelectric conversion elements and filters of three colors of R, G, and B.
The image reading unit 6 converts the original image into an electric signal for each color, and the electric signal is input to the optical writing signal output device 7.

The optical writing signal output device 7 converts the document image reading signals input for each color of R, G, B into digital signals of four colors of Y, M, C, K and stores them, and stores them in a predetermined manner. Is read out at the timing of, and output to the light beam writing device 8 as a means for writing an electrostatic latent image. The light beam writing device 8 writes an electrostatic latent image corresponding to each color on the image carrier 9. Around the image carrier 9, a charging charger 10 for uniformly charging the surface of the image carrier 9, and a developing device for developing the electrostatic latent image written on the image carrier 9 into toner images of respective colors. 11, a paper carrying member 12 composed of a transfer drum, a charge eliminating corotron 14, and a cleaner unit 15 are arranged. The developing device 11 includes Y (yellow), M (magenta), and C
The developing device for each color of (cyan) and K (black) is provided, and the electrostatic latent image is developed with the toner of each color. The cleaner unit 15 supports a cleaning device 15a, the charging charger 10 and a static eliminator 16 including a red LED. The symbols 1 to 8 and 10
A toner image forming device (1 to 8 + 10 to 16) for forming a toner image on the surface of the image carrier 9 is constituted by the elements indicated by 16.

The cylindrical (that is, endless or endless) paper attracting surface of the paper carrying member 12 is rotationally moved, and a transfer corotron 17 for attracting paper and transferring a toner image is fixed inside the paper carrying member 12. It is arranged in a state. The transfer corotron 17 is arranged at a transfer position Q where the surface of the sheet carrying member 12 and the surface of the image carrier 9 come into contact with each other. The paper P stored in the paper feed tray 18 is taken out by the paper take-out roll 19 and conveyed, and temporarily stopped by the registration roll 20. The temporarily stopped sheet P is ejected from the registration roll 20 at the same timing as the toner image on the surface of the image carrier 12 moves to the transfer position Q.
It is supplied to the transfer position Q. A sheet feeding device (18 to 20) is constituted by the elements indicated by the reference numerals 18 to 20 and the like. The leading edge of the paper P supplied to the transfer position Q by the paper feeding device (18 to 20) is adsorbed on the paper adsorbing surface on the surface of the paper carrying member 12. Simultaneously with the suction of the sheet, the toner image of the first color is transferred from the surface of the image carrier 9 to the sheet P.

The sheet carrying member 12 makes four revolutions with the sheet P adsorbed. The Y (yellow), M (magenta), C (cyan), and K at the transfer position Q where the transfer corotron 17 is arranged every one rotation.
The toner images of respective colors (black) are sequentially transferred onto the paper P. A paper sensor S1 is provided which is close to the surface of the paper carrying member 12 and detects the position of the leading edge of the paper P adsorbed to the endless (cylindrical) paper adsorbing surface. When the second and subsequent color toner images are formed on the surface of the image carrier 9, when the leading edge position of the paper P attracted to the paper attraction surface of the paper bearing member 12 is detected by the paper sensor S1, The light beam writing device 8 is configured to write an electrostatic latent image corresponding to the toner image on the surface of the image carrier 9.

In FIG. 1, the paper P on the paper carrying member 12 has the respective colors (Y, M, C, K) on the image carrier 9 at the transfer position Q while the paper carrying member 12 rotates four times.
After the toner image is transferred, the toner image is peeled off by the peeling claw 21, passes through the fixing unit 22, and is discharged to the paper discharge tray 23. A post-transfer jam sensor 26, a charge eliminating corotron 27, and a cleaner 28 are arranged around the sheet carrying member 12. The post-transfer jam sensor 26 is arranged on the downstream side of the transfer position Q and detects the presence / absence of the paper P based on the amount of light reflected from the surface of the paper carrying member 12. If there is no sheet P after the transfer onto the sheet P, a jam signal is output.

FIG. 3 is an explanatory diagram of a control portion of an embodiment of the color image forming apparatus (digital color copying machine) U of the present invention. The control unit of this embodiment shown in FIG. 3 uses a microcomputer M. The microcomputer M stores an I / O (input / output interface) that adjusts the level of an input / output signal for a connected device and a ROM that stores a control program of the image forming apparatus.
(Read-only memory), CPU (central processing unit) that executes processing in accordance with the program stored in the ROM, RAM (random access memory) used to temporarily store data when the processing is executed ),
In addition, it is composed of a clock oscillator and the like. In addition to the sheet sensor S1, the microcomputer M is connected to a temperature sensor (not shown) of the fixing unit 22 and other signal output elements. Further, the microcomputer M includes an exposure system drive device 31, a transfer charger drive circuit 32, an image carrier rotation drive device 33, a registration roll drive device (a solenoid for turning on / off transmission of rotational power to the registration roll 20) 34, and other control elements. It is connected to the. The microcomputer M processes the input signals from the signal output elements such as the paper sensor S1 according to the program stored in the ROM, and outputs the output signals according to the processing result to the control elements. Has been done. A transfer charger operation control device (S1 + M + 32) is constituted by the paper sensor S1, the microcomputer M, the transfer charger drive circuit 32 and the like.

(Operation of Embodiment) Next, the operation of the color image forming apparatus U of the embodiment 1 having the above-mentioned structure will be described. When a color original is placed on the platen 1 and a copy switch (not shown) is input, the exposure system driving device 31 (see FIG. 3).
This drives the exposure system (2-5) shown in FIG.
The exposure system (2-5) forms an image of the reflected light from the color original document on the original document reading unit 6 which is composed of a color CCD sensor. The document reading unit 6 separates the amount of incident reflected light of the color document into three colors, RGB, and reads them, and outputs them to the optical writing signal output device 7. The optical writing signal output device 7 outputs the document image reading signals input for each color of R, G, B to Y, M, C, K.
The four-color digital signals are converted and stored, and the Y digital signal is first read at a predetermined timing and output to the light beam writing device 8 as a unit for writing the electrostatic latent image. The light beam writing device 8 writes an electrostatic latent image corresponding to the Y color on the surface of the image carrier 9 uniformly charged by the charging charger 10.

The electrostatic latent image corresponding to the Y color is the developing device 1.
1 develops a Y toner image and moves it to the transfer device Q. The paper P is supplied to the transfer position Q from the paper feeding device (18 to 20) at the same timing as the movement of the Y toner image to the transfer position Q. A transfer charger 17 disposed inside the paper carrying member 12 so as to face the transfer position Q.
Is for adsorbing the paper P supplied to the transfer position Q to the endless paper adsorbing surface (that is, the surface of the cylindrical paper carrying member 12) and adsorbing the paper P on the surface Y of the image carrier 9. The toner image (first color toner image) is transferred. By the time the leading edge of the paper P on which the Y toner image of the first color is transferred reaches the position of the paper sensor S1, the exposure system (2
The writing of the Y electrostatic latent image by (5) is completed. When the leading edge of the sheet P is detected by the sheet sensor S1, the writing of the electrostatic latent image of M of the second color by the exposure system (2-5) is started.

When the front end of the paper P on which the Y toner image has been transferred reaches the transfer position Q, the transfer charger 17 transfers the M toner image of the second color. Then, the subsequent transfer of the C toner image and the K toner image is performed by the M
It is performed in the same manner as the transfer of the toner image. As mentioned above,
The paper P on which the toner images of Y, M, C and K are sequentially transferred is
It is peeled off by the peeling claw 21 and passes through the fixing unit 22. At this time, the toner image of each color on the paper P is fixed. The paper P on which the toner image is fixed is discharged onto the paper discharge tray 2
It is discharged to 3.

The transfer charger 17 holds the paper P when the paper P is supplied to the transfer position Q.
Adhesion to the surface (endless paper suction surface) and first to paper P
The operation start timing is different between the case of transferring the toner images of the colors and the case of transferring the toner images of the second and subsequent colors. Therefore, the operation of the transfer charger 17 of the above-described embodiment having the above-described configuration will be described next with reference to the flowchart showing the operation of the transfer charger 17 shown in FIG. The processing of each step of the flowchart of FIG.
This is performed according to the program stored in the ROM of (computer C). In step ST1 of FIG. 4, it is determined whether or not the image forming step currently being performed is the first color step (Y toner image forming step). If yes (Y), the process proceeds to step ST2, and if no (N), step ST3
Move on to.

In step ST2, the paper feeding device (18
It is determined whether the leading edge of the paper P fed from the registration roll 20 of (1) to (20) has reached the transfer position Q. This judgment is made based on whether or not a predetermined time (time until the leading edge of the paper P reaches the transfer position Q) has elapsed since the transfer of the paper P by the registration roll 20 was started. If no (N), step ST2 is repeated, and if yes (Y), the process proceeds to step ST4. In step ST4, the transfer charger 17 starts to discharge. That is, the fed paper P
Reaches the transfer position Q and discharge is started at the same time. The discharge can be started at an appropriate time before the paper P reaches the transfer position Q.

Next, in step ST5, it is determined whether or not the transfer is completed. In this judgment, the rear end of the sheet P is the transfer position Q.
Depending on whether or not the vehicle passed. If no (N), step ST5 is repeated. If yes (Y), the process moves to step ST6. In step ST6, the discharge is stopped. Then, the process returns to step ST1.

If it is the image forming process for the second and subsequent colors in step ST1, the determination is no (N), and the process proceeds to step ST3. In step ST3, it is determined whether or not the leading edge of the sheet attracted to the surface of the sheet carrying member 12 (an endless sheet attracting surface) reaches a position 3 mm past the transfer position Q. This judgment is made for a predetermined time (when the transfer position Q is set to 3 when the leading edge of the paper P passes the paper sensor S1).
Judgment is made based on whether or not the time required to reach the position after mm has passed. If no (N), step ST
Repeat 3 and if yes (Y), move to step ST4. The processes after step ST4 are the same as described above.

(Modifications) The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above-mentioned embodiments, and is within the scope of the gist of the present invention described in the claims. Thus, various changes can be made. A modified embodiment of the present invention is illustrated below.

(H01) As the paper carrying member, it is possible to use an endless belt instead of using a cylindrical drum. (H02) When the paper P is fed from the paper feeding device (18 to 20) to the transfer position Q, it is necessary to set the transfer time of the paper P by the registration roll 20 to detect that the front end of the paper P has reached the transfer position Q. Instead of using it, it is possible to use a sensor (not shown) that detects the leading edge position of the paper P provided separately. (H03) The present invention can be applied to a color image forming apparatus such as a color printer other than the color copying machine. (H04) The image carrier may be composed of a photosensitive belt instead of the photosensitive drum.

[0034]

The color image forming apparatus of the present invention described above is
The following effects can be achieved. (E01) By using one charger, it is possible to securely attract the sheet to the sheet carrying member and transfer the toner image to the attracted sheet without causing a jam. (E02) It is possible to surely transfer the toner image of the first color at the same time as adsorbing the paper without using a special toner. (E03) Cost reduction and reliability improvement can be realized by reducing the number of parts. (E04) In the case where the transfer charger configured to attract the paper and transfer the toner image is configured by a corotron, as compared with the case where the adsorption corotron and the transfer corotron are separately provided,
Since the total operating time of the corotron is shortened, ozone O3
It is possible to reduce the occurrence of

[Brief description of drawings]

FIG. 1 is an overall explanatory diagram of a color image forming apparatus (digital color image forming apparatus) according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is an explanatory diagram of a control circuit portion of the same embodiment.

FIG. 4 is a flowchart showing the operation of the transfer charger of the embodiment.

[Explanation of symbols]

P ... Paper, Q ... Transfer position, U ... Color image forming device, 9
... image carrier, 12 ... paper carrier, 17 ... transfer charger,
(1-8 + 10-16) ... Toner image forming device, (18-
20) ... Paper feeding device, (S1 + M + 32) ... Transfer charger operation control device,

Claims (1)

[Claims] 1. A transfer device of a color image forming apparatus having the following requirements, and (Y01) a toner image forming apparatus for sequentially forming toner images of a plurality of colors on a moving endless image carrier surface. , (Y02) a paper carrying member having an endless paper attracting surface that moves in the same direction as the surface of the image carrier at a transfer position in contact with the surface of the image carrier, (Y03) a member formed on the surface of the image carrier. A sheet feeding device that supplies a sheet at the same timing when the toner image of the first color reaches the transfer position, (Y04) is arranged inside the sheet supporting member so as to face the transfer position, and is supplied to the transfer position. A transfer charger for adsorbing the sheet onto the sheet adsorbing surface and transferring the toner image on the surface of the image carrier to the adsorbed sheet, (Y05) When the sheet is supplied to the transfer position, the tip of the sheet is Transfer charger operation controller for actuating the transfer charger before reaching the shooting position. (Y06)
The toner image forming device (Y07) that forms a toner image of a second color or later on the surface of the image carrier at the same timing when the leading edge of the sheet attracted to the sheet carrying member reaches the transfer position after the second rotation. ) The transfer charger operation control for operating the transfer charger after the paper front end passes through the transfer position when the front end of the paper attracted to the paper carrying member reaches the transfer position after the second rotation. apparatus.