JP2665237B2 - Color recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a color recording apparatus such as a color printer, a color facsimile, and a color copying machine, and more particularly, to a transfer position of a transfer paper by a reciprocally movable transfer paper transport body. The present invention relates to a color recording apparatus that forms a color image on transfer paper by a superimposition transfer method in which images are reciprocated with respect to each other to superimpose images for each color separation.

(Prior Art) A photoreceptor is subjected to image exposure for each color separation of a document image to form an electrostatic latent image corresponding to each color, and then to a photoconductor for each color separation using a developer corresponding to each color. The latent image formed thereon is visualized, and the visualized image obtained for each color separation is transferred to a predetermined transfer position by a transfer paper transport belt capable of reciprocating and stopping operations. The transfer paper is transferred to the transfer section when the transfer paper transport belt moves forward (forward rotation), and the transfer is performed. When the transfer paper transport belt moves backward (reverse rotation), the transfer paper is transferred. The operation of returning to the previous position and stopping / waiting is sequentially repeated for each color transfer, and after the final color transfer is completed, the transfer paper is conveyed to a fixing device, and the image transferred to the transfer paper is fixed to correspond to the original image. 2. Description of the Related Art A superposition type color recording apparatus for obtaining a color image is known (for example, See, for example, JP-A-62-186282).

Here, the color recording apparatus described in the above publication is provided with a transfer paper separating static eliminator (13) for separating the transfer paper of the final color transfer paper from the transfer paper transport belt,
The transfer paper separating static eliminator (13) is arranged near a driving roller (2) for driving the transfer paper transport belt that supports the most downstream end side of the transfer paper transport belt (1). The static elimination was performed so as to separate from the transfer paper transport belt.

(Problems to be Solved by the Invention) By the way, as in the color recording apparatus described in the above publication,
Simply arranging the transfer paper separating static eliminator (13) in the vicinity of the drive roller (2) for driving the transfer paper transport belt causes the following problems.

When the transfer paper size is large, the transfer paper transport belt (1)
During forward movement, the leading edge of the transfer paper is separated from the transfer paper transport belt (1) at a portion corresponding to the drive roller (2), and at the time of backward movement, the rear end of the transfer paper is transferred at a portion corresponding to the driven roller (3). The transfer paper transport belt (1) is reciprocated so as to separate from the transport belt (1). In such a case, the corona application by the transfer charger (12) is performed twice or three times according to the number of transfers. If the electrostatic attraction between the transfer paper and the transport belt becomes very strong as the repetition is repeated, the leading and trailing ends of the transfer paper cannot be separated from the transfer paper transport belt (1) and are caught in the paper, resulting in transport failure. May be. Therefore, in order to prevent this, it is easy to separate the transfer paper by operating the transfer separation static eliminator (13) not only when the transfer paper is separated and discharged at the end of the final color transfer process but also during the reciprocation of other transfer processes. However, in the arrangement position of the transfer separation static eliminator (13) such as the color recording apparatus described in the above publication,
Since the transfer paper is discharged only from the leading edge to the position of the separation static eliminator (13), the transfer paper and the transfer paper transport belt are charged between the charge elimination area and the area where the charge is not removed to the rear end of the paper. Since the potentials are different, the transfer efficiency in the next transfer process differs between the charge removal region and the subsequent region up to the trailing edge of the paper, resulting in a problem that transfer image unevenness occurs.

Further, in the above method, since the trailing end side of the paper is not neutralized, there remains a problem that the transport failure at the time of the backward movement is not solved at all.

The present invention has been made in view of the above circumstances, and even when a color image is obtained by superimposing color-separated images by repeating a plurality of transfer steps, a uniform transfer image over the front surface of the transfer paper is obtained. It is an object of the present invention to provide a color recording apparatus which can be obtained and prevent transfer paper conveyance failure in a transfer paper conveyance section.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, an electrostatic latent image forming apparatus for forming an electrostatic latent image corresponding to each color for each color separation on a photosensitive member rotated at a constant speed. A developing process of developing a latent image formed on the photoconductor at each color separation using a developer corresponding to each color, and a reciprocating operation of an image visualized at each color separation. The transfer process of transferring to a transfer sheet conveyed to a predetermined transfer section by a transfer sheet conveyer capable of multi-stop operation is sequentially repeated, and the transfer sheet conveyer reciprocates one transfer sheet a plurality of times. In the color recording apparatus for superimposing and transferring the image for each color separation on the photoreceptor and after the final color transfer, transferring the transfer paper to a fixing device and fixing the image transferred to the transfer paper to obtain a color image, A charger is installed on the upstream side of the transfer unit, and the charger is used for transferring during forward movement. When the transfer paper is fed to the paper transporting body, it operates as a paper attraction means, and functions as a paper attraction and static elimination charger which operates as a paper neutralization means at the time of resumption after image transfer.

Further, in the above-mentioned color recording apparatus, when necessary in a transfer process before the final color transfer process, the leading end of the transfer paper is discharged by a paper separation static eliminator installed downstream of the transfer unit when the transfer paper moves forward, and image transfer is performed. At the time of a later return movement, the trailing end of the paper is neutralized by a paper suction / static neutralization charging unit installed upstream of the transfer unit.

Further, in the above-described color recording apparatus, in the transfer process before the final color transfer process, the charge elimination area by the paper separation and charge eliminator and the paper adsorbing / discharging / charging device is set at the paper leading end and the paper trailing end outside the image transfer area of the transfer paper. It is characterized as an area.

(Operation) In the color recording apparatus having the above-described configuration, the paper adsorbing / discharging / charging device installed on the upstream side of the transfer unit serves as a paper adsorbing unit when the transfer paper is fed to the transfer paper transporting body in the forward movement. It operates as a paper discharging means when returning after image transfer, and when necessary in a transfer process before the final color transfer process, a paper separating and discharging device installed downstream of the transfer unit is used to transfer the paper. When the paper is moved, the leading end of the transfer paper is neutralized, and when the paper is moved back after the image is transferred, the trailing end of the paper is neutralized by the paper adsorbing and neutralizing charger installed upstream of the transfer unit. The paper leading edge and the paper trailing edge region outside the image transfer area of the transfer paper ensure that the leading edge of the paper is neutralized during the backward movement, and that the trailing edge of the paper is reliably eliminated during the forward movement. Sometimes the leading or trailing edge of the transfer paper gets caught Is prevented, and a conveyance failure is prevented.

In addition, since the above-described static elimination for preventing the conveyance failure is performed only on the paper front end and the paper rear end outside the image transfer area of the transfer paper,
Without causing uneven charging in the image transfer area of the transfer paper,
The occurrence of transfer image unevenness is prevented.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an example of a color recording apparatus suitable for carrying out the present invention, FIG. 2 is a timing chart showing basic operations of the color recording apparatus, and FIG. The control systems are shown in FIG.
In FIG. 3, reference numeral 1 denotes a photoreceptor belt (hereinafter referred to as "PC belt"), reference numeral 2 denotes a PC drive roller for supporting and rotating one end of the PC belt 1, and reference numeral 3 denotes a PC belt. PC driven roller for rotatably supporting the other end side.
Charger for charging the belt 1;
An optical writing unit for forming an electrostatic latent image corresponding to each color, reference numerals 7, 9, 11, and 13 denote developing units for developing latent images corresponding to each color, and reference numerals 6, 8, 10, and 12 denote the above. Developing rollers mounted on each of the developing units 7, 9, 11, and 13, reference numerals 14, 13, and 34 denote transfer paper, and reference numeral 15
Is a paper feed roller for feeding the transfer paper 14 into the recording apparatus, reference numeral 16 is a registration roller, and reference numeral 17 is a transfer unit serving as a transport unit for transporting the fed transfer paper 14 to a transfer unit and a fixing unit. A paper transport belt, reference numeral 18 is a drive roller for supporting and rotating one end side of the transfer paper transfer belt 17, a reference numeral 19 is a driven roller for rotatably supporting the other end side of the transfer paper transport belt 17, Reference numeral 20 denotes a belt contact / separation switching roller for moving the transfer paper transport belt 17 toward and away from the PC belt 1, reference numeral 21 denotes a transfer corona for transferring a developed image on the PC belt 1 to the transfer paper 14, and reference numeral 22. Reference numeral 23 denotes a charge removing corona for removing charge from the transfer paper transport belt 17, and reference numeral 23 denotes a transfer paper suction charger for electrostatically attracting the transfer paper 14 to the transfer paper transport belt 17. Functions as a paper adsorber / static charger that removes electricity. Further, reference numeral 24 denotes a transfer paper separating static eliminator for separating the transfer paper electrostatically attracted to the transfer paper transport belt 17, and reference numeral 25 removes paper dust, developer, etc. attached to the transfer paper transport belt 17. Reference numeral 26 denotes a paper path switching member for switching the transfer direction of the transfer paper after transfer, reference numeral 27 denotes a paper leading end guide plate, reference numeral 28 denotes a paper trailing end guide plate, and reference numeral 29 denotes a transfer end after transfer. PC belt cleaner for removing residual toner on the PC belt 1, reference numeral 30 denotes a static eliminator for removing static electricity from the PC belt 1, reference numeral 31 denotes a fixing unit for fixing an image transferred to transfer paper, reference numeral 31a. Is a fixing roller pair of the fixing unit 31, reference numeral 32 is a discharge tray for discharging transfer paper after image fixing, reference numeral 35 is a color image reading device for reading a color image of a document, reference numeral 36 is a PC drive roller. PC drive motor for rotating drive 2
Reference numeral 36 denotes an encoder, reference numeral 38 denotes a rotation detection sensor attached to the shaft of the PC drive roller 2, reference numeral 39 denotes a transfer drive motor for driving the transfer paper transport belt 17 drive roller 18, and reference numeral 40 detects rotation of the transfer drive motor 39. The encoder 41 is a servo control drive circuit 42 for the PC drive motor 36 and a transfer drive motor.
A main control circuit for controlling the servo control drive circuit 43 for 39 is shown.

The main control circuit 41 includes a well-known CPU, RAM and ROM.
, An I / O port, an input / output interface, a counter circuit, etc., and a control program and control data according to various copying processes are stored in advance in the ROM of the storage device. Have been.

Here, first, the transfer operation of the color recording apparatus having the basic configuration shown in FIGS. 1 and 3 will be described.

In FIGS. 1 to 3, a print switch is used to start a print operation (see FIG. 2 (a)).
Is issued, control by the main control circuit 41 is started, an ON signal of the PC drive motor is output, and the PC belt 1
It is rotated clockwise at a linear velocity VP by the PC drive roller 2 which is rotated by the PC drive motor 36. In addition, PC belt 1
Is wound around the PC drive roller 2 and the PC driven roller 3. At the same time as the rotation of the PC belt 1, the transfer driving motor 39 also rotates forward (see FIG. 2 (g)) of the transfer paper transport belt 17, which is a dielectric belt stretched over the drive roller 18 and the conventional roller 19. ), (H), and (j)), and is rotated at a linear velocity VF in the forward movement direction. The traveling speed of the PC belt 1 and the transfer paper transport belt 17 is 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 removed by the charge remover 30 to make the surface potential approximately 0 V. After that, the PC belt 1 is uniformly charged on the front surface by the charger 4. Is done.

As the static eliminator 30, a light irradiating type or a type that applies a static elimination corona, or a combination thereof is used. In the case of a well-known negative-positive process, the toner is a PC belt. Since the toner is adhered to an uncharged portion on the surface, the charging by the charger 4 must uniformly charge the entire surface of the PC belt 1. Further, the charging by the charger 4 is performed uniformly by corona discharge, and at the time of this discharge, a small amount of ozone is generated. This ozone is decomposed in a short time when the discharge is prevented, but may have an adverse effect on the surface of the PC belt 1 and impair the sharpness of the image. Therefore,
A fan or the like is attached to send electricity from the back of the charger, or ozone is removed by suction to prevent the influence of ozone.

By the way, the axis of the PC drive roller 2 has a rotation detection sensor
As shown in FIG. 2 (d), a detection pulse is generated for each rotation of the roller. In the case of the example shown in FIG. 2, the control of the semiconductor laser (hereinafter, referred to as LD) of the optical writing unit 5 is started at the timing of the third pulse of the rotation detection sensor, and first, based on the Y image data of the yellow image. Then, an optical latent image is formed on the PC belt 1 at a point E in the drawing. still,
Optical writing units include other types of lasers, LEDs
Other types of optical writing units, such as arrays, LCD arrays, etc., may be used. The image data to be written is read by, for example, three color separation lights of blue, green, and red, respectively, by the color image reading unit 35, and performs a known image calculation process based on the intensity level of each color light.
The image data is written image data of each color of yellow (Y), magenta (M), cyan (C), and black (Bk). Note that, 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, a color facsimile, a word processor, a personal computer, or the like).

A yellow (Y) developing device 7, a magenta (M) developing device 9, a cyan (C) developing device 11, and a black (B
k) Developing device 13 usually includes developing rollers 6, 8, 10, and 12 on a PC.
It is placed in a position where it does not contact the surface of the belt 1. Then, only during the period from immediately before the latent image surface of the corresponding color reaches the developing roller position of each color to 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. It faces so that it may be in a state. In addition, 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.

As described above, first, since a latent image of the Y image is formed on the photosensitive surface, the Y developing device 7 is brought into contact with the photosensitive surface at a timing with respect to the surface and driven (FIG. 2 ( m)) to visualize this.

Thereafter, the PC belt 1 proceeds to the transfer process.
At this time, the vertical position of the belt contact / separation switching roller 20 is switched so that the transfer paper transporting bell 17 comes into contact with or separates from the belt surface at the transfer portion of the PC belt 1 wound around the PC drive roller 2. Next, 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, and presses the transfer paper transport belt 17 to contact the PC belt 1. (See FIG. 2 (t)).

Then, 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 paper is temporarily stopped by the registration roller 16, and the transfer paper is conveyed toward the surface of the transfer paper conveyance belt 17 at a timing so as to match the image position formed on the PC belt 1 (see FIG. 2 ( r)). The transferred transfer paper is subjected to corona charging of a predetermined polarity by a transfer paper suction corona charger 23 (see FIG. 2 (x)) and brought into close contact with the transfer paper transfer belt 17, and during transfer and transfer thereof. So that 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 suction charger 23. The transfer paper transport belt 17 is used to remove the static electricity before the first color transfer process.
The charge is eliminated by the front corona discharge at 22 (see FIG. 2 (w)). At this time, the transfer paper transport belt 17
Is subjected to a cleaning process by the belt cleaner 25.

By the way, the tip of the visualized Y image on the PC belt 1 is
Upon reaching the TS point a predetermined distance from the transfer position T point, the transfer drive motor forward rotation start signal S ₁ is input to the drive control circuit 43 of the transfer drive motor 39 from the main control circuit 41 (second
FIG. (H)). However, the start S ₁ point is already forward rotation in (see FIG. 2 (j)), and continues the forward operation as it is. The output timing of the transfer driving motor forward rotation start signals S ₁ is substantially the distance from the leading edge of the transfer sheet is a transfer position T is
l This is the point in time when the robot arrives at the RT point, which is the position before ₁ . At this time, the tip of the Y image of the PC belt 1 is 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
(Point), it is a time point when the rotation of the PC drive roller 2 has been performed by 4 rotations and further by the pulse number P ₀ of the encoder 37 of the PC drive motor 36 (FIGS. 2 (d), (e), (f), (H)).

When the time t ₁ has elapsed from the start signal S ₁ , the leading end of the Y image and the leading end of the transfer paper have both reached the transfer position T by moving a distance l _1, and have been subjected to corona discharge by the transfer corona charger 21 to receive the Y image. Transfer is started (see FIG. 2 (s)). At this time, the encoder (PC) 37 of the PC drive motor 36 at the time t ₁
The number of pulses is P ₁ , the encoder (T) 4 of the transfer drive motor 39
0 number of pulses is PT ₁ (FIG. 2 (e), see (k)). Here, as the resolution of both encoders, if the belt movement length per pulse is the same for each, P ₁ = PT
_1, also, if the ratio therebetween is alpha, P ₁ and PT ₁ becomes a value corresponding to the coefficient alpha.

The following description is based on the premise that the condition of P ₁ = PT ₁ is satisfied. The pulse number of the encoder (PC) 37 is P ₁
Are input to the control circuits 41 and 42.

By the way, when the Y image transfer process proceeds, the leading end of the transfer paper is separated from the transfer paper transport belt 17 and guided by the paper path switching member 26 placed at the solid line position, and advances on the paper leading end guide plate 27. I do. Then, the process proceeds more Y image transfer process, when the transfer sheet trailing edge has passed the transfer position T by a length l _2, that is, the transfer sheet from the start S ₁ point as indicated by reference numeral 34,
After the lapse of time t ₁ + t ₂ length l ₁ + lp (transfer sheet size) + l ₂
Transfer distance, the transfer drive motor reverse rotation signal (second
(See FIGS. (I) and (j)) to rotate the motor in reverse. Simultaneously with or before this reverse rotation signal, the belt contact / separation switching roller 20 is moved to a lower position to move the transfer paper transport belt 17 in a direction to separate it from the PC belt 1.

By the reverse rotation of the transfer drive motor 39, the transfer paper transport belt
The transfer paper 17 and the transfer paper supported thereon are reversed and run at a speed VR (> VF) in the direction of the right arrow in FIG. At this time, the distance traveled by the belt 17 at time t ₁ + t ₂ can be quickly returned at time t ₃ . At the time of this return, the transfer paper trailing end is separated from the transfer paper transport belt 17 and advances to the upper surface of the paper trailing end guide plate 28, and this transfer paper moves accurately by a predetermined distance indicated by reference numeral 33 (paper leading end). Is at the position of the RT point)
And stops, and 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 M image of the second color has already been performed even during the transfer of the Y image of the first color.
That is, the writing unit 5 based on the M image data
The formation of the electrostatic latent image of the optical writing by the control / drive is started when the PC drive roller 2 has rotated an integer number of times from the start of the Y image writing, in the example shown in FIG. ), (G)). The developing device is Y
The Y developing device 7 was in contact with 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 PC belt 1 and stopped (FIG. 2 ( m)), instead of this, the developing roller 8 of the M developing device 9 is brought into contact with and driven by the surface of the PC belt 1 (see FIG. 2 (n)) to prepare for visualization of the M image.

Then, when the leading end of the M image reaches the TS point, the PC drive roller 2 starts moving from the M image data writing start timing.
Motor transfer driving at the time that the number of pulses P ₀ corresponded rotational movement of the rotary component and PC drive motor encoder 37 forward start signal S
₂ (see FIG. 2 (h)) is input to the control drive circuit 43. Simultaneously or slightly later, the belt contact / separation switching roller 20 is moved to the upper position and presses the transfer paper transport belt 17, and the transfer paper transport belt is moved before the leading end of the transfer paper reaches at least the point T.
17 is brought into contact with the PC belt 1.

Well, the time from the timing of the forward start signal S ₂ signal
PC belt 1 at t _1, as in the case of the previous Y image, P ₁ is the number of pulses of the PC drive motor encoder (PC) 37, PC belt 1
The moving distance of has become a l _1. Therefore, during even the time t ₁ towards the transfer paper, VF from the state of the speed 0 (= VR) so that the timing S ₁ of the first color in the same PT ₁ as the number of pulses at the time t ₁ both during this rises to And again in this case P
₁ = PT ₁ and both control the position to match. Accordingly, the leading end of the transfer paper has moved by the distance l ₁ 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.

Thereafter, the same process as described above is repeated for each color,
Finally, the process proceeds to the process following the writing of the Bk image data.

In the Bk image transfer process, the paper path switching guide plate 26 is moved to the dashed line position in FIG. 1, and the transfer paper during the transfer process is transferred from the leading end thereof by the transfer paper separating and discharging unit 24 while the transfer paper is discharged. It is separated from the transport belt 17 and transported toward the fixing device 31. Then, when the transfer of the Bk image, which is the last step, is completed, the transfer drive motor 39 continues the forward rotation and conveys the transfer paper (FIGS. 2 (j), (u),
(V), (y)). The transfer paper on which the toner image has been fixed by the fixing roller pair 31a of the fixing device 31 is discharged onto a discharge tray 32 as a color print. At this time, the transfer paper transport belt 17 is applied with a charge removing corona from the timing when the rear end of the image area of the first copy has passed the charge remover 22, and is uniformly discharged, and when the final copy is discharged, Each motor, fixing device, and paper feeding system are stopped.

Here, as shown in FIG. 2, when the repeat operation is performed, after writing the first Bk image data, the process proceeds to the Y image data writing process of the second sheet, and the operation control of the transfer paper transport belt 17 is performed. Also, the same operation as the first one is repeated. After the transfer, the residual toner is removed from the PC belt 1 by the cleaner 29, the residual charge is removed by the charge remover 30, and the PC belt 1 travels to the charger 4. Finally, the last color print is discharged to the paper output tray 32 and the PC belt 1
Then, the operation is stopped after the transfer paper transport belt 17 is cleaned and neutralized, and returns to the initial state.

In the above description, the order of image formation is changed from Y image ⇒ M image ⇒ C
Image ⇒ Bk image, and the arrangement of developing units is Y,
Although M, C, and Bk are used, the present invention is not limited to this.

Also, a method of optically writing an electrostatic latent image of each color with an LD or the like using digital image-processed image data of each color has been described. However, an analog optical image of a normal electronic copying machine is exposed at a predetermined timing at an exposure position E. Irradiation and image formation may be performed to perform color recording.

Further, the above description is about full-color printing by superimposing four colors. However, when two or three of these colors are superimposed, image formation and transfer of necessary colors are performed twice or three times.
After the rotation is continued, the recording operation may be terminated, and the operation control is performed in such a manner.

In the case of single-color image recording, the developing unit for that color is brought into contact with and driven by the PC belt 1 until the predetermined number of sheets is completed, and the transfer paper transport belt 17 is kept in contact with the PC belt. In this case, the paper path switching guide plate 26 is held at the dashed line position in FIG. 1 and guides the transfer paper toward the fixing device 31.
Therefore, in the repeat recording, the print creation speed is 4/3 times higher in the case of three colors, twice as high in the case of two colors, and four times in the case of single color as compared with the case of recording four colors.
Further, the color of the developer is not limited to the four colors described above, and it is also possible to use blue, green, red and other desired colors in combination as needed.

The basic configuration and the copying operation of the color recording apparatus have been described above with reference to FIGS. 1 to 3.
In the configuration shown in FIG. 1, the transfer paper separating static eliminator 24 for separating the transfer paper after the final color transfer from the transfer paper transport belt 17 is used.
Is disposed at the position of the drive roller 18 for driving the transfer paper transport belt that supports the most downstream end side of the transfer paper transport belt 17.

However, when the transfer paper separating static eliminator 24 is simply arranged near the drive roller 18 for driving the transfer paper transport belt 17, the same problem as in the case of the recording apparatus shown in the related art occurs.

That is, when the transfer paper size is large, the forward end of the transfer paper separates from the transfer paper transport belt 17 at a portion corresponding to the drive roller 18 during the forward movement of the transfer paper transport belt 17, and the rear end of the transfer paper at the time of the backward movement. The transfer paper transport belt 17 is reciprocated so as to be separated from the transfer paper transport belt 17 at a portion corresponding to the driven roller 19, and in such a case, the corona application by the transfer corona charger 21 is performed twice in accordance with the number of transfers, If the electrostatic attraction force between the transfer paper and the transport belt 17 becomes very strong as the transfer is repeated three times, the leading and trailing ends of the transfer paper cannot be separated from the transfer paper transport belt 17 and are caught in the transfer paper, resulting in poor transport. May occur. Therefore, in order to prevent this, not only at the time of transfer paper separation and discharge at the end of the final color transfer process, but also at the time of reciprocation of other transfer processes, the transfer / separation static eliminator 24 is operated to facilitate separation of the transfer paper. Although a method is conceivable, at the disposition position of the transfer / separation neutralizer 24 as shown in FIG. 1, if the static electricity is simply removed, the transfer paper is only discharged from the leading end to the position of the separation neutralizer 24. The charge potential of the transfer paper and the transfer paper transport belt 17 is different between the charge removal region and the region up to the trailing edge of the paper thereafter,
A problem arises in that the transfer efficiency during the next transfer process differs between the above-described charge removal region and the region up to the trailing edge of the paper thereafter, causing unevenness in the transferred image.

Further, in the above method, since the trailing edge of the paper is not eliminated at all, there remains a problem that there is no effect on the conveyance failure at the time of returning.

Therefore, in the present invention, in the color recording apparatus having the configuration shown in FIG. 1, the transfer paper suction charger 23 installed on the upstream side of the transfer unit is used when the transfer paper 14 is fed.
As described above, the transfer paper and the transfer paper transport belt 17 are operated as a static electricity eliminator for discharging the transfer paper and the transfer paper transport belt 17 at the time of the return movement after the completion of the transfer for each color during the transfer process for each color separation, as described above. . In other words, according to the present invention, the transfer paper suction charger 23 is provided with the transfer paper suction charger 23 as necessary.
Functions as a paper adsorber / discharger that performs static elimination for separation, and ensures that the trailing edge of the transfer paper is neutralized and separated when the transfer paper is moved back, preventing transport failure when the transfer paper is moved back. That is.

In addition to the above-described configuration, in the present invention, even in a transfer process other than the final color transfer process, if necessary, the leading end side of the transfer paper is discharged by the paper separating and discharging device 24 when the transfer paper moves forward. With this configuration, at the time of forward movement during each transfer process, the leading end of the transfer paper is neutralized by the paper separating / static eliminator 24, and at the time of backward movement, the rear end of the transfer paper is subjected to the above-described paper suction / static elimination. Charger for paper adsorption 23 that functions as dual-purpose charger
The end of the transfer paper is reliably separated from the transfer paper transport belt 17 in both forward and backward movements,
Entanglement of the transfer paper conveyance belt 17 is prevented, and conveyance failure is almost completely prevented.

Next, a specific configuration example of the paper suction charger 23 that functions as the paper feeding / discharging charger will be described with reference to FIG.

In FIG. 4, a paper suction charger 23 has a high voltage supply constituted by an alternating current (AC) high voltage output circuit (including a trigger circuit) and a direct current (DC) high voltage output circuit (including a trigger circuit). It is connected to a power supply 44 and is provided so as to be able to apply an AC voltage for static elimination and a DC voltage for charging.

Here, the AC component output trigger input of x ₂ shown in FIG. 4, the control circuit (not shown) both the DC bias component for triggering input x ₁ (e.g., a main control circuit and the like shown in FIG. 3) Then, a voltage in which an AC component and a DC component are superimposed as shown by a broken line in FIG. 5, for example, is applied to the paper suction charger 23. In this case, the paper suction charger 23
Functions to operate as a charger for adsorbing paper.

Next, the OFF a DC bias component for triggering inputs x _1, when giving only the AC component output trigger input of x _2, as shown in solid line in FIG. 5, the AC component to the center value and zero potential A voltage is applied to the paper suction charger 23. In this case, the paper suction charger 23 is operated as a static eliminator for removing the transfer paper.

Note that the above-mentioned paper adsorbing charger 23 is replaced with a paper separating static eliminator.
When necessary, an AC component voltage as shown by the solid line in FIG. 5 is applied to 24 so that only the static elimination operation is performed.

Next, the operation of the color printing apparatus according to the present invention will be described with reference to the timing chart shown in FIG.

In Figure 1 and Figure 3 to Figure 6, as shown in the timing chart of FIG. 6, in the present invention, when the transfer paper sheet feeding, as described above, AC components of x ₂ shown in FIG. 4 and output trigger input, both a DC bias component for trigger input of x ₁ is operated by applying to the paper attraction charger 23 (FIG. 6 (x _1), (x ₂₎ see) the transfer paper 14 The transfer paper is conveyed to the transfer belt 17. Then, in the transfer process, the image is transferred to the transfer paper, and the leading end of the transfer paper is
The paper separation static eliminator 24
(See FIG. 6 (y)) to facilitate separation of the paper at the leading end of the transfer paper at the drive roller 28.

Next, after the first transfer operation, the transfer paper transport belt 17
When backward to the position before transfer of the transfer sheet by reversing, AC component of the paper attraction charger 23 timed only before and after the transfer sheet trailing end reaches the paper attraction charger 23 x ₂ It is operated only by the output trigger input (see FIG. 6 (x ₂ )), the transfer paper and the transfer paper transport belt 17 are neutralized, and the paper is separated by the driven roller 19 at the rear end of the transfer paper at the time of return. make it easier.

Here, the area where the charge is removed at the front and rear ends of the transfer sheet at a time is about 5 mm from the front and rear ends of the transfer sheet, respectively, and only outside the substantial color image transfer area. To eliminate static electricity. If the static elimination area is set in this way, the image area is not affected by static elimination,
The charging potential in the image area of the transfer paper and the transfer paper transport belt is kept uniform, the transfer efficiency in the next transfer process becomes uniform, and the entire image in the image area is uniformly and uniformly transferred to the transfer paper. An image without transfer unevenness is obtained.

Regarding the paper separation, if the leading edge and the trailing edge of the transfer paper are separated from each other, the subsequent area is separated and transported as it is, so that no transport failure occurs.

Also, in order to prevent the static elimination areas at the leading and trailing ends of the transfer paper from being eroded into the image area, a paper separating static eliminator 24,
It works effectively if the opening of the paper suction charger 23 is narrowed.

Next, in the second and subsequent transfer steps, the same repetitive operation as in the first transfer step is performed.
In response to the repetition of the reciprocating movement of 17, the paper separation static eliminator 24 and the paper adsorption charger 23 as the static eliminator are operated, and during the final color transfer / discharge process, the paper separation static eliminator 24 is moved from the leading end of the transfer paper. The operation is performed so that the entire region up to the rear end is uniformly discharged (see FIG. 6 (y)).

In the above description, the voltage applied to the charger 23 for both paper adsorption and static elimination is “AC component + DC bias component” during transfer paper adsorption, and only “AC component” is applied during static elimination. The present invention is not limited to this, and it suffices to apply appropriate voltages that are effective for paper adsorption and static elimination, respectively.

Although the application of the voltage to the paper separation static eliminator 24 has been described as the AC component, the application is not limited to the AC component, and an appropriate neutralization voltage effective for paper separation may be applied. .

In the timing chart shown in FIG. 6, the charge is removed from the leading and trailing ends of the transfer paper during the reciprocation in all the transfer steps. It is sufficient to perform the necessary number of charge removals, and it is not necessary to perform the charge removal in all the transfer steps. For example, the application of the transfer corona at the time of transfer may be repeated, and the static elimination operation may be performed during the second and subsequent transfer strokes, where it is considered that electrostatic attraction between the transfer paper and the transfer paper transport belt becomes particularly strong. is there.

(Effects of the Invention) As described above, in the color recording apparatus according to the present invention, the charger for both paper adsorption and static elimination installed upstream of the transfer unit transfers the paper to the transfer paper transport body during forward movement. It operates as a paper suction unit when feeding paper, operates as a paper discharging unit when the image transfer paper moves backward, and is installed downstream of the transfer unit when necessary in a transfer process before the final color transfer process. When the transfer paper goes forward, the leading end of the transfer paper is discharged by the paper separating / discharger, and at the time of return after the image transfer, the rear end of the paper is moved by the above-mentioned paper adsorber / discharger, which is installed upstream of the transfer unit. By configuring to eliminate electricity,
At the time of forward movement, the leading edge of the paper is reliably neutralized.At the time of backward movement, the trailing edge of the paper is reliably neutralized.At the time of reciprocating movement, the leading and trailing edges of the transfer paper are prevented from being caught, thereby preventing poor conveyance. You.

In addition, since the above-described static elimination for preventing the conveyance failure is performed only on the paper front end and the paper rear end outside the image transfer area of the transfer paper,
Non-uniform charging does not occur in the image transfer area of the transfer paper, and the occurrence of non-uniform transfer images is prevented.

Therefore, according to the present invention, in a color recording apparatus that obtains a color image by repeating a plurality of transfers, a transfer failure of the transfer paper during reciprocation of the transfer paper can be prevented beforehand and the transport performance can be stabilized. Moreover, a uniform and uniform transfer image can be obtained over the entire surface of the transfer paper.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a color recording apparatus suitable for carrying out the present invention, FIG. 2 is a timing chart showing basic operations of the color recording apparatus, and FIG. FIG. 4 is a perspective view including a block diagram showing a control system, FIG. 4 is a schematic configuration diagram of a charger for both paper adsorption and static elimination according to the present invention, and FIG. 5 is a voltage waveform applied to the charger having the configuration shown in FIG. FIG. 6 is a timing chart showing an operation example when the present invention is applied to the color printing apparatus shown in FIG. 1 photoreceptor 2 photoreceptor drive roller 5 optical writing unit 7,9,11,13 developing units for each color 14,3
3,34 transfer paper, 17 transfer paper transport belt, 18 transfer paper transport belt drive roller, 23 charger for both paper adsorption and static elimination, 24 paper separation and static eliminator, 31 fixing 35, color image reading device, 36, photoconductor drive motor, 37, 40
... Encoder, 39 ... Transfer drive motor for transfer paper transfer belt drive, 41 ... Main control circuit, 42 ... Servo control drive circuit for photoconductor drive motor, 43 ... Servo control drive circuit for transfer drive motor, 44 …… High-voltage power supply for the paper adsorber / discharger.

Claims (3)

(57) [Claims] An electrostatic latent image forming step of forming an electrostatic latent image corresponding to each color on a photosensitive member rotated at a constant speed for each color separation; and forming the electrostatic latent image using a developer corresponding to each color. A developing step of visualizing a latent image formed on the photoreceptor for each decomposition,
The transfer process of transferring the visualized image for each color separation onto transfer paper conveyed to a predetermined transfer unit by a transfer paper conveyer capable of reciprocating operation and stop operation is sequentially repeated, and the transfer paper conveyer The transfer paper is reciprocated a plurality of times to transfer the image for each color separation on the photoreceptor in an overlapping manner, and after the final color transfer is completed, the transfer paper is conveyed to a fixing device, and the image transferred to the transfer paper is transferred. In a color recording apparatus that obtains a color image by fixing the paper, a charging device is installed upstream of the transfer unit, and the charging device operates as a paper suction unit when feeding the transfer paper to the transfer paper transporting body during forward movement. A color recording apparatus which functions as a paper adsorbing / discharging charger which operates as a paper discharging means at the time of return after image transfer. 2. A color printing apparatus according to claim 1, wherein
When necessary in the transfer process before the final color transfer process, the leading edge of the transfer paper is discharged by the paper separation static eliminator installed downstream of the transfer unit when the transfer paper moves forward, and the trailing edge of the paper is returned when the image is transferred back. A color recording apparatus characterized in that a portion of the image forming unit is neutralized by a charger for both paper adsorption and static elimination installed upstream of the transfer unit. 3. A color printing apparatus according to claim 2, wherein
In the transfer process before the final color transfer process, the charge removal area by the paper separation charge eliminator and the paper suction / discharge combined use charger is a paper leading end and a paper trailing end outside the image transfer area of the transfer paper. Color recording device.