JPH0733242Y2 - Transfer device of color image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a transfer device of a color image forming apparatus such as a color copying machine.

(Prior Art) Transfer paper in which an image for each color formed on an image bearing member such as a photoconductor is transferred to the dielectric belt for each color, and is closely adhered to the transfer paper transporting dielectric belt. There is already known a color image forming apparatus in which a color image is transferred by bringing it into contact with the image. Then, the transfer paper supported by the dielectric belt is reciprocally moved in the transfer section a number of times corresponding to the number of colors. In this case, the transfer paper is supported by the dielectric belt, but if the relative position with respect to the belt shifts during movement, the color shift of the multicolor image formed on this will occur, and the image quality will be significantly reduced. It will be damaged. For this reason, there is provided a means for performing a corona discharge for contacting the transfer paper with respect to the dielectric belt before the transfer of the image of the first color to bring the transfer paper into contact with the belt.

On the other hand, the transfer paper closely supported by the dielectric belt is brought into contact with the photoconductor when the image is transferred, but when the dielectric belt is reversely run to transfer the image of the next color, Is separated from the surface of the photoconductor in order to prevent the disturbance. Such operation is
This is performed by selectively moving a belt contact / separation switching roller installed in the inner space of the dielectric belt in a direction in which the dielectric belt and the photoconductor are brought into contact with or separated from each other.

(Problems to be Solved by the Invention) When applying corona charging by a corona charger for adsorbing transfer paper to a dielectric belt, it is necessary to dispose a counter electrode corresponding to the corona charger on the back side of the belt. As this counter electrode, it may be possible to use a roller as a counter electrode of a static eliminator that removes static electricity from the dielectric belt.However, the adsorption corona charging position and the static elimination corona charging position on the dielectric belt depend on the belt length. Since it is necessary to select the optimum position, there is a problem in that the counter electrode for static elimination cannot be used also as the counter electrode for adhesion. Further, the adsorption corona charging must be performed on the dielectric belt whose traveling path is changed by the belt contact / separation switching roller described above. There is a problem that can not be combined with.

(Means for Solving the Problem) The present invention focuses on the existence of a belt contact / separation switching roller whose relative position with respect to the dielectric belt is constant, and the roller is formed of a conductive material, and the roller is attracted to a transfer paper. It is also characterized in that it is also used as the counter electrode of the corona charger.

(Operation) When the transfer paper is brought into close contact, the dielectric belt is moved by the belt contact / separation switching roller in the direction of coming into contact with the image carrier, and the distance from the corona charger for adsorbing the transfer paper is set to a predetermined value. Is kept at. In this state, when the transfer paper is supplied, the corona charger starts its operation, and when the rear end of the transfer paper passes through the charger, the operation is stopped. When the transfer of the image of one color is completed, the dielectric belt runs in reverse and moves the transfer paper to the standby position. At this time, the belt contact / separation switching roller moves the belt in a direction in which the belt is separated from the image carrier, and avoids contact between the moving image of the transfer sheet and the image carrier.

(Embodiment) Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings.

FIG. 1 shows a schematic structure of an example of a color copying machine equipped with the transfer device of the present invention, FIG. 2 shows a timing chart of the basic operation of this copying machine, and FIG. 3 shows the same drive control system. There is. In these figures, a print switch start signal (see FIG. 2 (a)) is output by the print switch.
Is issued, the ON signal of the PC drive motor is output, and the photoconductor belt 1 (hereinafter referred to as "PC belt") is rotated in the clockwise direction by the PC drive roller 2 which is driven by the PC drive motor 36. It can be rotated with. The PC belt 1 is stretched around a PC driving roller 2 and a driven roller 3. At the same time, the transfer paper transport belt 17 composed of a dielectric belt stretched around the drive roller 18 and the driven roller 19 is also transferred to the transfer drive motor 39.
First starts normal rotation (see FIGS. 2 (g), (h), and (j)), and rotates in the forward direction at the linear velocity VF. The traveling speeds of the PC belt 1 and the transfer paper transport belt 17 are controlled so as to rotate under the condition of VP = VF.

After the toner on the surface of the PC belt 1 is removed by the cleaning device 29, the charge is neutralized by the static eliminator 30 so that the surface potential of the PC belt 1 becomes approximately OV. After that, the PC belt 1 is uniformly charged on the entire surface by the charger 4. A slight amount of ozone is generated by the corona discharge of the charger 4. This ozone decomposes in a short time when the discharge is stopped, but in consideration of the adverse effect on the surface of the PC belt, air is sent from the rear of the charger or air is taken in by a fan or the like.

A rotation detection sensor 38 is provided on the shaft of the PC drive roller 2, and a detection pulse is generated for each rotation of the roller, as shown in FIG. 2 (d). In the case of the example shown in FIG. 2, the semiconductor laser (hereinafter referred to as “LD”) of the optical writing unit 5 is started to be controlled and driven at the timing of the third pulse of the rotation detection sensor, and the Y image of the yellow image is first begun. Optical writing based on the image data is started, and an electrostatic latent image is formed on the PC belt 1 at point E. As an optical writing unit, other types of laser, L
Other types of optical writing units such as ED arrays, LCD arrays may be used. The image data to be written is read by the color image reading unit 35 into, for example, three color separation lights of blue, green and red, and a known image calculation process is performed on the basis of the intensity level of each color light to obtain yellow ( Y), magenta (M), cyan (C), and black (Bk). In addition to the color image reading unit 35, writing may be performed based on image data output from another color image processing system (for example, color facsimile, word processor, personal computer, etc.). Yellow (Y) to visualize electrostatic latent image
Developing device 7, magenta (M) developing device 9, cyan (C) developing device 1
The 1, black (Bk) developing device 13 is normally placed at a position where the developing rollers 6, 8, 10, 12 are not brought into contact with the surface of the PC belt 1. Then, only before the latent image surface of the corresponding color reaches the developing roller position of each color until immediately after passing, the developing device of the corresponding color is pressed and moved to bring the developing roller into contact with the photosensitive surface by a predetermined amount. Face each other so as to be in a state. Further, as shown in FIGS. 2 (n) to 2 (p), only the developing device opposed to the photosensitive surface starts driving in order to have a developing function.

First, since the latent image of the Y image is formed, the Y developing device 7 is driven in contact with the surface of the photoconductor at a timing relative to the surface (see FIG. 2 (m)), and this is visualized. Image.

After this, the PC belt 1 proceeds to the transfer process,
At this time, the transfer paper conveyance belt 17 switches the vertical position of the belt contact / separation switching roller 20 so that the transfer portion of the PC belt 1 wound around the PC driving roller 2 comes into contact with and separates from the belt surface. . When the printing operation starts, the transfer paper transport belt 17 is driven at the speed VF, and then the belt contact / separation switching roller 20 is moved to the upper position as shown by the solid line in FIG. The belt 1 is brought into contact (see FIG. 2 (t)).

Here, the belt contact / separation switching roller 20 will be described with reference to FIG. The corona charger 23 that performs a corona discharge for adsorption to bring the transfer paper 14 fed by the paper feed roller 15 of the paper feed unit into close contact with the transfer paper transport belt 17 made of a dielectric material is used for the belt surface at the solid line position. Are fixedly arranged at a predetermined distance. Belt facing the charger 23
A belt contact / separation switching roller 20 is disposed in contact with the back surface of the roller 17. At least the surface of the roller 20 is formed of a conductive material, and is rotatably supported by a shaft 48a of a support arm 48 which is swingable about a pivot 49. A part of the support arm faces a sensor 45 that detects contact / separation of the rollers. One end of the lever 46 faces the shaft 48a from below so that it can be engaged. Lever 46
It is swingably provided about a shaft 47, and the other end is connected to a movable portion of a solenoid 44. solenoid
The switch 44 is turned on prior to the start of the transfer process, which will be described later, and swings the lever 46 to move the belt contact / separation switching roller 20 to the upper position shown by the solid line. When the roller 20 moves to the upper position, the transfer paper transport belt 17 that is in contact with the roller 20 is moved to the solid line position so that the surface of the transfer paper transport belt 17 contacts the PC belt 1.
The timing of contact and separation of the transfer paper transport belt 17 with respect to the PC belt 1 is shown in FIG. When the roller 20 is moved and the transfer paper transport belt 17 comes into contact with the PC belt 1, the transfer paper transport belt 17 and the suction corona charger 23 are opposed to each other at a predetermined interval. At this time, the relative position between the roller 20 as the counter electrode and the charger is also predetermined. When the predetermined transfer operation is completed and the belt 17 reversely travels, the solenoid 44 is turned off.
20 is lowered to move the belt 17 to the separated position shown by the alternate long and short dash line to separate the belt from the PC belt 1.

Now, the transfer paper 14 is fed by the feed roller 15 at a timing according to the number of pulses of the encoder 37 of the PC drive motor 36 (see FIG. 2 (q)). The progress of the transfer sheet is temporarily stopped by the registration roller 16 and conveyed toward the surface of the transfer sheet conveying belt 17 at a timing so as to coincide with the image position formed on the PC belt 1 (see FIG. 2 ( r)). The transferred transfer paper is subjected to corona charging with a predetermined polarity by the transfer paper suction corona charger 23 (see FIG. 2 (x)) to be in close contact with the transfer paper transfer belt, and during transfer or during transfer of the transfer paper. There is no misalignment with the belt.
At this time, the belt contact / separation switching roller 20 functions as a counter electrode for corona discharge of the transfer paper adsorption charger 23. The transfer paper transport belt 17 is neutralized by the entire surface corona discharge by the static eliminator 22 prior to the transfer process of the first color (see FIG. 2 (w)). Further, at this time, the transfer paper transport belt 17 is
A cleaning process is performed by the belt cleaner 25.

Now, when the front end of the visualized Y image on the PC belt reaches the TS point which is a predetermined distance from the transfer position T point, the main drive circuit 41 sends the transfer drive motor forward rotation start signal S ₁ to the transfer drive motor. It is input to the control drive circuit 43 of 39 (see FIG. 2 (h)). However, at the time of start S _1, it is already in forward rotation (see FIG. 2 (j)), and the forward rotation operation is continued. The output timing of the transfer drive motor forward rotation start signal S ₁ is substantially the distance l ₁ from the transfer position T to the front end of the transfer paper.
This is the time when the RT point, which is the front position of, is reached. At this time, the front end of the Y image on the PC belt 1 is at a distance l ₁ from the transfer position T.
In the control example shown in FIG. 2, the Y image data writing start timing (E
From the point), the PC drive roller 2 is rotated by four rotations and further rotated by the number of pulses P ₀ of the encoder 37 of the PC drive motor 36 (FIG. 2, (d), (e), (f), (See (h)). When the time t ₁ has elapsed from the start signal S ₁ , the leading edge of the Y image and the leading edge of the transfer paper both move the distance l ₁ and move to the transfer position T 1.
Then, the Y image transfer is started by receiving the corona discharge by the transfer corona charger 21 (see FIG. 2 (s)).
Encoder PC drive motor 36 at time t ₁ at this time (P
The pulse number of C) 37 is P ₁ , and the pulse number of the encoder (T) 40 of the transfer drive motor 39 is PT ₁ (FIG. 2 (e),
(See (k)). As the resolution of both encoders, if the belt movement length per pulse is the same, then P ₁ = PT ₁ , and if the ratio of both is α, then P ₁ = PT _1.
1 and PT ₁ are values corresponding to the coefficient α. Hereinafter, description will be made on the assumption that the condition of P ₁ = PT ₁ is satisfied. The number of pulses of the encoder (PC) 37 is input to the control circuit 42.

When the Y-image transfer process proceeds, the leading edge of the transfer sheet is separated from the transfer sheet transport belt 17, and is guided by the sheet path switching member 26 placed in the solid line position to advance onto the sheet leading edge guide plate 27. Then, when the Y image transfer process further progresses and the rear end of the transfer paper passes the transfer position T by the length l ₂ , that is,
From the start S ₁ time, the transfer paper is
when the user moves the t ₁ + t ₂ has passed the length l ₁ + l _p (transfer sheet size) + distance l _2, the transfer drive motor reverse rotation signal (Fig. 2 (i), (j) see) is emitted is Reverse the motor. Simultaneously with or prior to this reverse rotation signal, the belt contact / separation switching roller 20 is lowered to the position indicated by the broken line in FIG. 4 to move the transfer paper transport belt 17 in a direction to separate it from the PC belt 1 (the first). (See FIG. 2 (t)).

By the reverse rotation of the transfer drive motor, the transfer paper conveying belt 17 and the transfer paper supported by the transfer belt 17 are reversely moved at the speed VR (> VF) in the direction of the right arrow in FIG. At this time, the belt
The 17 can make a quick return at time t ₃ of the distance traveled at time t ₁ + t ₂ . At the time of this return, the rear end of the transfer paper is separated from the transfer paper transport belt 17 and advances to the upper surface of the paper rear end guide plate 28, and the transfer paper is accurately moved by a predetermined distance indicated by reference numeral 33 (the front end of the paper). Is at the position of the RT point.), And then waits for time t ₄ (see FIG. 2 (j)) in preparation for the next M image transfer.

On the other hand, in the case of the PC belt 1, the formation process of the second color M image has already been executed during the transfer of the first color Y image.
That is, the writing unit 5 based on the M image data
The electrostatic latent image formation of the optical writing by the control and driving of is started at the time when the PC driving roller 2 rotates an integral number of times from the start of writing the Y image, that is, at the time when the PC driving roller 2 rotates four times in the example shown in FIG. ), (G)). Also, the developing device is Y
The Y developing device was contacted and driven only in the image area, but before the second color M image area arrived, the Y developing device 7 was separated from the surface of the PC belt 1 and stopped (Fig. 2 (m)). reference)
However, instead of this, the M developing device 8 contacts the surface of the PC belt.
It is driven (see FIG. 2 (n)) to prepare for visualization of the M image.

When the leading edge of the M image reaches the TS point, four rotations of the PC drive roller 2 and the PC start from the M image data writing start timing.
The transfer drive motor forward rotation start signal S ₂ (see FIG. 2 (h)) is input to the control drive circuit 43 at the time when the drive motor encoder 37 rotates and moves corresponding to the number of pulses P ₀ . Simultaneously with or slightly after this, the belt contact / separation switching roller 20 is raised to the position indicated by the solid line in FIG. 4, and the belt 17 is brought into contact with the PC belt 1 before the leading edge of the transfer paper reaches at least point T. Now, at the time t ₁ from the timing of the forward rotation start signal S ₂ , the PC belt 1
As in the case of the Y image, the number of pulses of the PC drive motor encoder (PC) is P ₁ , and the movement distance of the PC belt 1 is l ₁ . Therefore, the transfer paper also, during this time t ₁ ,
To be the same PT ₁ as the number of pulses in the first color timing S ₁ from the time t ₁ during which together with launch from the state of zero velocity to VF (= VR), in this case both also with P ₁ = PT ₁ is Position control is performed so that they match. As a result, the leading edge of the transfer paper is moved by the distance l ₁ again at time t ₁ , and the Y image of the first color and the M image of the second color are aligned on the transfer paper.

After that, the same process as the above-described process is repeated for each color, and finally the process proceeds to the process following the writing of the Bk image data.

When the Bk image transfer process is started, the paper path switching guide plate 26 is moved to the position indicated by the chain line in FIG. 1, and the transfer paper during the transfer process is separated from the belt from its leading end while being neutralized by the paper separation charger 24. Then, it is conveyed toward the fixing device 31. When the transfer of the Bk image, which is the final step, is completed, the transfer drive motor 39 continues to rotate in the normal direction to convey the transfer paper (see FIGS. 2 (j), (u), (v), and (y)). . Fuser 31
The transfer paper having the toner image fixed thereon is discharged onto the paper discharge tray 32 as a color print. Then, when the final copy is discharged, each motor, the fixing device, and the paper feeding system are stopped. From the timing when the trailing edge of the image area of the first copy passes through the static eliminator 22, the static electricity is applied to the transfer paper transport belt 17 by the static elimination corona.

As shown in FIG. 2, when the repeat operation is performed, after the Bk image data of the first sheet is written, the process of writing the Y image data of the second sheet is continued and the transfer sheet conveyance belt 17
As for the operation control of, the same operation as that from the beginning of the first sheet is repeated. After the transfer, the residual toner is removed from the PC belt 1 by the cleaner 29, and the residual charge is removed by the static eliminator 30 to proceed to the charger 4. Finally, after the last color print is discharged to the paper discharge tray 32 and the PC belt 1 and the transfer paper transport belt 17 are cleaned and discharged, the operation is stopped and the initial state is restored.

In the above description, the order of image formation is Y image → M image → C image → Bk image, and the arrangement of the developing devices is Y, M,
Although C and Bk are used, the present invention is not limited to this.

In addition, the method of optically writing the electrostatic latent image of each color by the LD etc. by the image data of each color subjected to the digital image processing is mentioned. However, at the exposure position E, the analog optical image of the ordinary electrophotographic copying machine is set at a predetermined timing. Alternatively, color recording may be performed by irradiating the image with the image to form an image. Further, the above explanation was for color printing by four-color overlapping. However, when two or three colors among these are to be overlapped, after image formation and transfer of necessary colors are repeated twice or three times. , It suffices to end the recording operation,
Also, the operation control is performed in such a manner. In the case of single-color image recording, the developing device for that color is connected to the PC until the specified number of sheets is finished.
The transfer paper transport belt 17 is contacted and driven by the belt 1 and remains in contact with the PC belt. In this case, the paper path switching guide plate 26 is held at the chain line position in FIG. 1 and guides the transfer paper toward the fixing device 31. Therefore, in repeat recording, the print creation speed is 3 times faster than in 4-color recording.
High-speed processing is performed with 4/3 times for colors, 2 times for 2 colors, and 4 times for single colors. The color of the developer is not limited to the four colors described above, and it is also possible to use a desired color such as blue, green, or red in combination as required.

(Effects of the Invention) As described above, according to the present invention, the belt contact / separation switching roller for contacting / separating the transfer paper conveying belt made of a dielectric material with the image carrier is provided with the corona charger for contacting the transfer paper. Since it has a function as a counter electrode, the device can be simplified. Further, even if there is a belt whose traveling path changes, the relative distance between the charger and the counter electrode does not change when applying the corona discharge for adsorption, so stable corona charging for attracting transfer paper to the dielectric can be performed. .

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a color copying machine equipped with a transfer device according to the present invention, FIG. 2 is a timing chart showing the basic operation of the copying machine, and FIG. 3 is a drive control system of the same. FIG. 4 is a perspective view including a block diagram, and FIG. 4 is a front view showing an essential part of the present invention. 1 ... Image carrier, 14, 33, 34 ... Transfer paper, 17 ... Transfer paper transport belt as dielectric belt, 20 ... Belt contact / separation switching roller, 23 ... Transfer paper suction corona charger.

Claims (1)

[Scope of utility model registration request] 1. An adsorption method in which images of a plurality of colors are transferred to a dielectric belt for each color, and corona charging is performed so that the transfer paper fed from a paper feeding unit is in close contact with the transfer paper conveying dielectric belt. In a color image forming apparatus having a corona charger for use and a belt unit that reversely runs the dielectric belt for each color image transfer, in the image transfer, the dielectric belt is moved in a direction of contacting the image carrier, When the dielectric belt reversely travels after the image transfer, a belt contact / separation switching roller for moving the belt in a direction of separating from the image carrier is formed of a conductive material, and the belt contact / separation switching roller is connected to the dielectric belt. A transfer device of a color image forming apparatus, wherein the transfer device of the color image forming apparatus is arranged so as to be opposed to a corona charger for adsorption and disposed as a counter electrode of the charger.