JP2899016B2 - Multiple transfer device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiple transfer apparatus using a transfer material holder in a color copying apparatus or the like.

[Conventional technology]

FIG. 16 is a cross-sectional view for explaining a developing and transferring mechanism in a conventional color copying apparatus, and shows, for example, a case of a rotary type developing device.

In this figure, reference numeral 61 denotes a paper feed roller for feeding the transfer paper 63. Reference numeral 62 denotes a registration roller, which is wound around by a suction means 75 which is a part of the transfer drum 64 at a certain timing. Reference numeral 74 denotes a rotary movable developing device which is disposed around the photosensitive drum 72, and sequentially develops by each color developing device (magenta 68, cyan 67, yellow 66, black 65). A charger 69 charges the photosensitive drum 72 uniformly.

A transfer charger 70 transfers the toner image developed on the photosensitive drum 72 to the transfer paper 63. Reference numeral 71 denotes a cleaner unit that collects toner remaining on the photosensitive drum 72. A fixing roller 73 fixes the toner transferred to the transfer paper 63 by heat and pressure.

As described above, the conventional color copying apparatus includes a transfer drum 64 in which a high-resistance film (transfer sheet) is wound around a drum frame, a photosensitive drum 72, and an abutting and releasing freely arranged around the photosensitive drum 72. The transfer paper 63 composed of developing devices 65 to 68 for a plurality of colors and fed from the paper feed mechanism
Is wound around the transfer drum 64 by suction means (not shown) provided at a part of the photosensitive drum 72, an image is exposed on the photosensitive drum, and one of a plurality of developing devices is brought into contact with the photosensitive drum 72 to perform development. Transfer is performed on transfer paper. By repeating this operation a plurality of times, different color toners are transferred to the transfer paper 63, separated from the transfer drum 64 by the separating means, and further fixed by the fixing roller 3, thereby obtaining a color image output.

[Problems to be solved by the invention]

Usually, in order to increase the throughput, a color copying sequence is executed using a minimum necessary developing color.

In the case of a movable developing device, a long moving time may be required depending on the position (arrangement) of the developing device to be used. In the relationship between this long moving time and the interval (paper interval) between the transfer paper adsorbed on the transfer drum 64 and the time required for the transfer drum to move (hereinafter, referred to as the time required for paper-making or the time between papers), When the developing unit cannot be moved between the transfer units, the transfer unit with the transferred toner is passed through the transfer position without performing the transfer operation and idling, thereby securing the moving time of the developing unit.

However, when performing this idle rotation, in order to prevent retransfer development in which the toner transferred to the transfer paper returns to the photosensitive drum again, in a state where the transfer drum 64 and the photosensitive drum 72 are separated by the releasing means. Release means for performing idle rotation and making contact when performing the transfer operation is required. However, there was a disadvantage that cost up and control became complicated.

[Means for solving the problem]

In order to solve the above-described problems, the present invention provides a movable developing device that can be brought into contact with and released from a photosensitive drum and has a plurality of developing devices, and a transfer drum that can wind a plurality of transfer papers. In a multi-transfer apparatus for forming a color image by superimposing and transferring a developer of a different color onto the transfer paper wound around the transfer drum, the exchange time of each developing device used for a color image to be formed is reduced. Adjusting means for adjusting the timing of feeding the transfer paper to the transfer drum according to the size of the transfer paper to be used, and the distance between the transfer papers when a plurality of transfer papers are wound around the transfer drum When using a plurality of developing devices such that the exchange cannot be completed within the time required for the transfer drum to move, control means for reducing the number of transfer paper wound around the transfer drum, Those having.

[Action]

According to the present invention, it is possible to prevent the toner held on the transfer material from being retransferred to the photosensitive drum and obtain good throughput without complicating the configuration and control of the apparatus. .

〔Example〕

FIG. 1 is a cross-sectional view for explaining the structure of a color copying apparatus showing one embodiment of the present invention. Reference numeral 1 denotes a reader unit, a document table (platen glass) 11, a document irradiation lamp 12, an image forming lens.
13, an image pickup device (for example, a charge-coupled device such as a CCD) 14, an optical motor 15, and the like, and a document irradiation lamp
An original scanning unit that scans and moves together with the unit 12 is read at a constant speed determined according to a preset magnification or the like. An operation unit described later is provided around the document table (platen glass) 11, and a switch for setting various modes related to a copy sequence, a display for display, and a display are provided.

Reference numeral 2 denotes a transfer paper feeder, which includes paper feed rollers 30 and 31, pick-up rollers 32 and 33, and feeds transfer paper 63 and the like in accordance with a drive command from the controller 16.

Reference numeral 3 denotes an image forming unit which includes a scanner motor 17, a polygon mirror 18, a photosensitive drum 19, and a cleaner unit 20, and a controller unit 16 processes an output of the image sensor 14 and outputs a signal from a laser light source based on an image signal. The laser beam forms an image on the photosensitive drum 19 to form an electrostatic latent image.

Reference numeral 4 denotes an image transfer unit, which includes an adsorption charger 21, a transfer charger 22, a separation charger 23, a voltage unit 24, a separation pressing roller 25, and a separation claw 2.
6, a transfer drum 63, a suction roller 28, a registration roller 29, and the like. The transfer paper 63 fed by forming a certain amount of loop at the position of the registration roller 29 by the paper feeding roller 30 or the paper feeding roller 31 is formed. The transfer paper 63 is fed again at the timing when the registration roller 29 synchronizes the image head position with the photosensitive drum 19. Then, the transfer paper 63 fed by the driving of the registration roller 29 is electrostatically attracted to the transfer drum 27 by the attraction roller 28 and the attraction charger 21 serving as counter electrodes. The transfer charger 22 transfers each color developer developed on the photosensitive drum 19 to a transfer paper.
Transfer to 63. The separation charger 23 serving as a charge removing charger removes the charge of the transfer paper 63 and weakens the attraction force with the transfer drum 27. At this time, a high voltage is applied to the transfer paper 63 by the high voltage unit 24 in order to prevent the fine movement of the developer due to the peeling discharge.

Reference numeral 5 denotes a developing unit, which includes developing units 5a to 5d, and is reciprocated in a direction indicated by an arrow by a motor described later.
In addition, the developing sleeve is configured to be able to approach / retreat to a predetermined position of the photosensitive drum 19 by a lifter mechanism (lift-up mechanism) (not shown) so that the developing sleeve can contact the photosensitive drum 19. The developing devices 5a to 5d store, for example, black, yellow, cyan, and magenta developing materials in this order.

A fixing unit 6 fixes the toner on the transfer paper 63 by the fixing roller 6a and the processing roller, and discharges the toner to the discharge tray 6b.

The controller 61 also serves as an adjusting means, and a driving means for reciprocating the developing devices 5a to 5d sequentially moves the selected developing devices 5a to 5d to approach / retreat to a predetermined position of the photosensitive drum 19. Then, the electrostatic latent image formed on the photosensitive drum 19 is visualized in each color. Then, the image developed on the photosensitive drum 19 is transferred onto the transfer paper 63 attracted to the transfer drum 27 by winding means (consisting of the attracting and fixing device 21 and the attracting roller 28). At this time, the controller unit 16
The paper feed timing of the transfer paper 63 to be sequentially attracted to 27 is selected as the transfer paper size and the photosensitive drum 19 of each of the developing devices 5a to 5d.
Is adjusted based on the arrangement state with respect to the transfer drum 63, the plurality of transfer papers 63 are attracted to the transfer drum 27 at predetermined intervals, and the timing for feeding the subsequent transfer paper 63 to the transfer drum 27 is determined.

Here, the process of adsorbing the transfer paper 63 to the transfer drum 27 and separating the transfer paper 63 will be described.

Since the attraction charger 21 is a corona charger having a characteristic opposite to that of the toner, and the attraction roller 28 is a conductive roller, the attraction roller 28 is grounded and serves as a counter electrode of the attraction charger 21, and the transfer paper 63 is charged. To make the transfer sheet 63 stick to the transfer sheet.

As described above, when the transfer paper 63 adsorbed on the transfer sheet is transferred between the positions where the transfer chargers 22 are provided, a charge having a polarity opposite to that of the toner is applied to the rear surface of the transfer sheet to transfer the first color, and the developing device Move sequentially from 5a to 5d. When the four-color development / transfer process is completed, the suction force of the transfer paper 63 on the transfer sheet is weakened, and an AC corona discharge is applied from a pair of separation chargers 23 opposed to each other across the transfer sheet to remove the charge. . Then, the roller 25 is pressed against the transfer sheet by partially pressing the inside of the transfer sheet to separate from the transfer sheet,
The outer separation pressing roller 41 shown in FIG. 2 is pressed against the transfer sheet.

As a result, the curvature of the transfer sheet locally changes, and the separation claw 26 intervenes between the transfer sheet and the transfer sheet 63 to facilitate the separation of the transfer sheet 63 from the transfer sheet. At this time, an AC corona discharge is applied from the high voltage unit 24 in order to prevent image disturbance due to peeling discharge.

FIG. 2 is a sectional view of an essential part for explaining the peeling process of the transfer paper 63 by the separation claw 26 shown in FIG. 1, and the same components as those in FIG. 1 are denoted by the same reference numerals.

Reference numeral 41 denotes an outer separation pressing roller, which interlocks with the separation pressing roller 25 to change the curvature of the transfer sheet and separate the transfer paper 63 from the transfer sheet.

FIG. 3 is a block diagram for explaining the configuration of the controller section 16 shown in FIG. 1. A CPU 42 controls the copy sequence according to a control program stored in a ROM 43. A RAM 44 functions as a work memory for the CPU 42 and stores various types of flag information input from the operation unit 51. An I / O port 45 receives the image data output from the image sensor 14 shown in FIG. 1 and outputs a synchronization control signal required for image reading.

46 is a position sensor (ITOP sensor), which is a transfer drum
27, and outputs an image leading end signal ITOP to the CPU 42 for determining the transfer timing.

Reference numeral 47 denotes a developing device motor controller which drives a motor 48 to position and move a developing device table (not shown) on which the developing devices 5a to 5d shown in FIG. For example, in a case where image formation of four colors is performed and transfer paper is used.
When a plurality of sheets (up to two sheets in this embodiment) are attracted to the transfer drum 27, the feed timing of the next transfer sheet 63 is delayed by a half rotation of the transfer drum 27 as described later. The CPU 42 determines the sheet feeding and suction timing to perform the processing. An image processing circuit 49 performs various color separation image processing on the read image data input through the I / O port 45,
Generate a video signal that modulates the laser light source. An optical motor controller 50 controls the driving of the optical motor 15 for reciprocating the original scanning unit. 51 is an operation unit.

Next, an image processing operation in the copying apparatus shown in FIG. 1 will be described.

The transfer paper 63 fed by the pick-up roller 32 or the pick-up roller 33 is conveyed to the registration roller 29 by the feed roller 30 or the feed roller 31 to remove the skew and form a fixed amount of loop to form the transfer drum 37. Wait until it is time to wind around. Next, the registration roller 29 rotates, and the transfer paper 63 is suctioned to the transfer drum 27 by the suction charging device 21 and the suction roller 28 also serving as a counter electrode thereof. At about the same time, the optical system (original operation unit) starts scanning, and the image read by the image element 14 is taken into the image processing circuit 49 via the I / O port 45 shown in FIG. .

Then, in the image processing circuit 49, color separation is performed, various color correction processes (for example, known gamma correction processes and the like) are performed, the laser beam is converted to laser light, and the laser beam is deflected and scanned by the polygon mirror 18, and is uniformly charged by the charger. The exposed photosensitive drum 19 is exposed to form a latent image.

The developing unit on which the developing unit 5d for magenta toner, the developing unit 5c for cyan toner, the developing unit 5b for yellow toner, and the developing unit 5a for black toner are placed horizontally moves the latent image at a predetermined timing. And a developing process is performed.

The toner image formed on the photosensitive drum 19 is transferred to a transfer charger.
It is transferred to the transfer paper 63 and the like which is attracted by 22. After repeating this series of operations several times for the required developing colors, the separating charger 23 weakens the attraction force and separates and pushes the rollers together while applying a high pressure by the high voltage unit 24 that prevents image disturbance due to peeling discharge due to separation. 25 and outer separating press and roll 41
The sheet is separated by the separation claw 26 at the place where the curvature is separated by (see FIG. 2), fixed by the fixing roller 6a, and then discharged to the discharge tray 6b.

Next, with reference to FIGS. 4 to 8, a description will be given of the movement operation of the developing devices 5a to 5d shown in FIG.

FIG. 4 is a state transition diagram illustrating the movement transition of the developing devices 5a to 5d shown in FIG.

As can be seen from this figure, when the developing process is performed from the first color to the fourth color with respect to the rotation axis of the photosensitive drum 19 (indicated by a dotted line in the figure), the developing sleeves of the developing devices 5a to 5d are used. The developing sleeve moves at a high speed to a position where the axis coincides, and the developing sleeve contacts the photosensitive drum 19 as shown in FIG. 1 by a lift mechanism (not shown).

The sleeve interval of each of the developing devices 5a to 5d is ld.

FIG. 12 shows the time required for replacing each developing device. In FIG. 12, DVHP indicates the home position of the developing unit moving table.The position is detected by a sensor (not shown) at power-on, at the start of copying, and at the end of copying. Is controlled by the developing device motor controller 47 based on the relative positional relationship between the developing positions. In this embodiment, the DVHP (developing device home position) is M (magenta) developing 5d and C (cyan).
Since the center of the developing device 5c and the rotation axis of the photosensitive drum 19 are overlapped with each other, in FIG. 12, T _MH = T _HM = T _CH = T _HC.
Becomes Further a _{T MC = T CM = T MY} = T YM = T MK = T KM for sleeve spacing the developing units are equal ld respectively. Likewise
T _MY = T _YM = T _CK = T _KC .

In addition, the magnitude relations are T _HM <T _MC <T _MY <T _MK as is apparent from the moving distance.

5 and 6 are cross-sectional views showing a state in which the transfer paper is attracted to the transfer drum 27 shown in FIG. FIG. 5 shows a state in which only one transfer sheet is attracted to the transfer drum 27,
FIG. 6 shows a state in which two transfer sheets are attracted to the transfer drum 27.

In FIGS. 5 and 6, lt ₁ and lt ₂ indicate the sheet-to-sheet distances,
Assuming that the rotation speed Vt of the transfer drum 27 is Tt ₁ = lt ₁ / Vt> T _MC ,
The diameter of the transfer drum 27 is determined so that Tt ₂ = lt ₂ / Vt> _TMC . Since the movement time for moving to the adjacent developing position, such as the movement from the magenta developing device to the cyan developing device, is shorter than the time required between the transfer sheets adsorbed on the transfer drum 27, even if the idle rotation is not performed. The developing device can be moved within the time required between sheets.

This suppresses retransfer to the photosensitive drum due to idle rotation.

FIG. 7 is a sectional view for explaining the output timing of the image leading edge signal ITOP.

As can be seen from this figure, the image tip signal ITOP is transferred to the transfer position.
It is generated when the position Pn is at a distance li (distance from the laser writing position Pl to the transfer position Pm) from Pm, and is attracted to the transfer drum 27 so that the top of the transfer paper 63 overlaps the position Pn. The image developed by the abutted developing sleeve is transferred to a predetermined position of the transfer paper 63 attracted to the transfer drum 27.

As described above, when the latent image is generated on the photosensitive drum 19 when the transfer timing signal ITOP is generated, control is performed so that the developed toner image is finally transferred to the transfer paper 63 attracted from the position Pn.

Similarly to the developing unit movement control, the original scanning unit shown in FIG. ₁ is controlled so that back scanning can be performed in a time shorter than the times Tt ₁ and Tt ₂ .

8, 9, 10, and 11 are timing charts for explaining the sheet developing operation according to the present invention, and FIGS. 8 (a), 9 (a), 10, and 10. FIG. 11 (a) shows a one-sheet loading mode in which one sheet of transfer paper is attracted to the transfer drum and operated. FIGS. 8 (b), 9 (b) and 11 (b) show the transfer drum 27. Indicates a two-sheet loading mode in which two sheets of transfer are adsorbed and operated.

In these figures, the PF is a paper feed signal and rises after a lapse of a predetermined time from the transmission of both image leading edge signals ITOP, and falls after the transfer paper 63 is completely fed.

VIDEO is an image signal composed of a magenta image signal VIDEO M, a cyan image signal VIDEO C, a yellow image signal VIDEO Y, and a black image signal VIDEO K, and is output for a time corresponding to the transfer paper size from the rise of each signal ITOP signal. DV is a signal indicating that development is in progress, and is composed of magenta, cyan, yellow, and black development signals, like the image signal VIDEO.
The development signal VD is a signal that is turned on while the image signal VIDEO is developing a latent image formed by exposing the uniformly charged photosensitive drum 19 by modulating a laser beam. DR
Is a developing device drive signal, in which one transfer sheet 63 is attracted to the transfer drum 27 (one sheet mode), and in a four-color mode using four developing devices (FIG. 8A), the developing device movement distance because there is but travel time t _3d = T _KM from largest fourth color developing device (wander) 5a to the first color developing device (magenta) 5d smaller than sheet time Tt _1, the developing unit movement time when all (T _MC , T _CY , T
_YK, T _KM) is smaller than Tt _1, can continue executing a color copying sequence of the next transfer sheet 63 without idling.
FIG. 8B shows the timing in a four-color mode in which two transfer papers 63 are attracted to the transfer drum 27 (two-sheet setting mode) and four developing units of magenta, cyan, yellow, and black are used. It is a chart.

In this case, the moving time td when moving to the adjacent developing unit
= T _MC = T _CY = T _YK is shorter than the paper interval time Tt ₂ so that the sequence can be executed without any problem. However, since the maximum developing device movement time t _3d = T _KM in the 4-color mode is longer than the paper interval time Tt ₂ The next paper feed is delayed by one ITOP (half rotation of the transfer drum), and the time for this half rotation of the transfer drum is used to move from the black developing device to the magenta developing device. Is executed.

FIGS. 13 (a) to 13 (d) are state transition diagrams for explaining sheet feed timings in the four-color / two-sheet loading mode according to the present invention, and the same components as those in FIG. 1 are denoted by the same reference numerals. .

FIG. 13 (a) shows a state where the toner image of the final color (black) is being transferred on the second transfer material 63b on which two sheets are placed. No.
FIG. 13B shows a state immediately after the lift state of the black developing device 5a is released after the final color development of the second transfer material 63b on which two sheets are placed. FIG. 13 (c) shows the next two sheets 1
The state in which the transfer material 63c is fed is shown. At this time the first
The developer base is moved so that the color (magenta) can be developed. FIG. 13D shows the first transfer material 63 to be placed on the next two sheets.
This shows a state in which c is sucked and the second transfer material 63d is being fed.

Next, a four-color copying sequence in the two-sheet printing mode will be described with reference to FIG.

As shown in FIG. 13 (a), the transfer papers 63a and 63b are attracted to the image leading edge position A and the image leading edge position B which are the reference of the transfer drum 27. Developing device 5 that is the final color developing device for transfer paper 63b
When the developed toner image is transferred to the photosensitive drum 19 by a, the transfer paper 63a is separated from the transfer drum 27 first. Thereafter, when the developing operation on the transfer paper 63b is completed, the lift-up mechanism of the developing device 5a is released, and the developing device 5a becomes movable (13 (b)).

Then, the developing device table on which the developing devices 5a to 5d are mounted is transferred to a predetermined position. To move the developing device 5d, which is the next developing color, to the axial center position of the photosensitive drum 19, the time t _3d = T _KM is required as described above, but the time for the interval between two transfer papers 63 is required. since larger than tt _2, even for the developing operation for that paper feed and transfer sheet even if the sheet feeding operation is too late, to adsorb the next transfer sheet 63c to the transfer position a of the transfer drum 27 Fig. 8 (b)
(See the paper feed signal PF indicated by the dotted line.) Therefore, the next transfer paper 63c is replaced with the second transfer paper 63b during the previous image sequence.
In FIG. 13 (c), the sheet is fed with the feed timing delayed by a half rotation of the transfer drum 27 so that the transfer position B of the next transfer sheet becomes the leading transfer position of the next transfer sheet.
The suction roller 28 is brought into contact with the transfer drum 27 so as to suck the ink, and is prepared.

Next, as shown in FIG. 13 (d), the transfer paper 63c is attracted to the image leading end position B. At the start of the transfer paper 63c suction process, the developing device 5d completes moving to the axial center position of the photosensitive drum 19, and the developing sleeve is in contact with the photosensitive drum 19 by the lift-up mechanism. All development and transfer operations can be performed.

As described above, the subsequent transfer sheet 63c is not fed again to the transfer position A where the first transfer sheet 63a is sucked, but the idle rotation of the above-described half rotation is performed. Is used to move the developing units 5A to 5d, and the second transfer paper 63c is placed next to the image leading edge position B where the second transfer paper 63b was adsorbed in the previous color copying sequence. The sheet feeding operation is controlled so as to be able to absorb the toner, and the next copy sequence is restarted with a minimum waiting time, thereby preventing a decrease in throughput.

Next, a three-color mode in which a color copying sequence is performed using three developing units of magenta 5d, cyan 5c, and yellow 5b will be described with reference to FIGS. 9 (a) and 9 (b).

FIG. 9A is a timing chart in the single-sheet mode in the three-color mode. Maximum developing unit movement time t _3d = T _KM maximum developing unit movement time in 3-color mode than t _2d = T _YM small for all one placed between the minimum paper mode time Tt ₁ within at is in this case 4-color mode Can be moved.
A color copying sequence can be executed without an idle rotation sequence.

FIG. 9B is a timing chart in a two-sheet setting mode in which two sheets are attracted to a transfer sheet in a three-color mode.

In the present embodiment, the maximum developing unit movement time t _2d = T _YM in the three-color mode is longer than the inter-sheet time Tt ₂ of two sheets, and thus, as in the four-color mode, a half rotation of the transfer drum 27, Next 2
Delay the timing of feeding the first transfer paper to be stacked,
Using this time, the developing device is moved from yellow to magenta.

FIG. 10 (a) shows two developing units, magenta 5d and yellow 5b.
4 is a timing chart of a two-color mode for outputting a red color using a color. In this case, the time T _MY required to move the developing device for yellow development after the completion of magenta development becomes longer than the sheet interval when two sheets are placed, and therefore, in the two-color mode using magenta and yellow, The color transfer sequence is executed in the one-sheet setting mode in which one transfer sheet is attracted to the transfer drum 27 without performing the sheet setting. On the other hand, in the case of a size capable of stacking two sheets in the two-color mode using magenta and yellow, two sheets are stacked and a half-turn empty space is obtained in order to obtain the moving time for the moving time of the developing device from magenta to yellow. A method of performing rotation is also conceivable. However, in this case, since the transfer from the final color to the first color is not performed, the transfer paper on which the two sheets are placed is not separated, and the transfer drum is half-rotated idly while the magenta toner is transferred while being suctioned. Becomes Then, the first transfer sheet adsorbed passes through the transfer position by performing a process for preventing re-transfer without transferring anything while transferring the magenta toner, and the second transfer sheet is rotated by half an idle rotation. Therefore, the toner is separated by performing a yellow developing / transferring operation. Then, the developing / transferring operation of yellow of the transfer sheet adsorbed on the first sheet is performed.

In order to prevent retransfer, for example, a method of performing processing by changing the control of the transfer high voltage between the first and second sheets and a releasing means for idling the photosensitive drum 19 and the transfer drum 27 are necessary. Problems arise in terms of complexity and cost.

For this reason, when the developing unit replacement time other than the movement of the developing unit from the final developing color to the first developing color becomes longer than the inter-sheet time as in the present invention, even if two sheets of transfer paper can be adsorbed, 2 The above-mentioned problem can be solved by controlling not to put the sheets.

FIG. 11 (a) is a timing chart of a single-sheet loading mode in a two-color mode using a magenta developing device and a cyan developing device. FIG. 11 (b) is a timing chart of a two-sheet printing mode using the same color. In this case, since the developing device to be used is in contact with the developing device, the developing device movement _TMC is smaller than the paper interval time Tt ₂ when the two sheets are placed, so that the two sheets can be placed. Also able to perform final color developing unit (cyan) a first color developing device from 5c color copying sequence without idling of the half-turn to become smaller than the movement time T _CM paper between time Tt ₂ to (magenta) 5d.

Next, the paper feed developing operation according to the present invention will be described with reference to FIGS. 14 (a) to (d).

FIGS. 14 (a) to 14 (d) are flow charts for explaining an example of a paper feed developing procedure according to the present invention. In addition,
(1) to (23) show each step.

First, the color mode, the number of copies, the paper size, and the like are determined by an operation unit (not shown). When the copy start key in the operation unit is pressed (1), the CPU 42 determines the paper size information from the paper supply unit 2. (2) Then, a developing device to be used next is determined (3).

Then, it is determined whether or not the determined paper size and whether two transfer papers 63 are placed on the transfer drum 27 from the developing device to be used, that is, whether or not the transfer paper 63 can be attracted to the transfer drum 27 by two sheets (4). If the size is such that two sheets cannot be picked up, the process proceeds to step (19) and thereafter, the color copying sequence is executed by picking up one sheet. Conversely, if the size is such that two sheets can be adsorbed, the time required for movement from the developing device used is obtained from FIG. 12, and it is determined whether the time between moving the developing device is less than the time required between sheets when two sheets are placed. (5). For example, in the above-described monochromatic color mode of blue, magenta and cyan developing units are used, but since all the movement times are shorter than the inter-paper time, the process proceeds to step (13) and thereafter. In the case of the single color mode of magenta, cyan, yellow, and black, only one developing device is used. Therefore, the developing device moving time is considered to be "0" and the process proceeds to step (13) and thereafter.

If there is greater than the sheet interval time Tt ₂ when placed two even one of the time required for the developing unit movement to be performed in the color copying sequence proceeds to step (6), then the larger ones final It is checked whether it is only the time required to move from the color developing device to the developing device for the first color (6). In this embodiment, the developing operation is performed in the order of magenta, cyan, yellow, and black in any color mode. Therefore, in the case of the four-color mode, the final color developer is black 5a, the first color developer is magenta 5d, and so on. In the red single color mode, the final color developing device is yellow 5b and the first color developing device is magenta 5d.

In the judgment of step (6), the first color developing device
If only the movement time of the color developing device is longer than the inter-sheet time, the next paper feeding operation is delayed by half a rotation of the transfer drum. In this case, even if the developing unit is moved, the two transfer papers are separated at the separation position because the final development color is being transferred, and pass through the transfer position again with the toner image placed on the transfer paper. There is no. For this reason, the transfer condition becomes constant, and the color copy sequence can be executed only by the half rotation of the idle rotation.
There is a feature that the throughput is not reduced.

The color mode in which such processing is performed is a three-color mode or a four-color mode, and the developing operation for continuously applying two transfer papers with the selected developing device is performed (7), (8).

Then, the used developing device is a developing device of the final color, for example, 4
In the color mode, it is determined whether or not the black developing unit 5a is used (9). If NO, the developing unit motor controller 47 is instructed to move the next developing unit to the axial position of the photosensitive drum 19 (12). Returning to step (7), the process proceeds to the next development processing.

On the other hand, in the determination of step (9), if YES, it is determined whether or not copying of the designated number has been completed (10). If YES, the process is terminated. Thus, the developing device motor controller 47 is instructed to move to the developing device of the first color using this time (11).

On the other hand, if the result of step (6) is NO,
When two sheets 63 can be attracted to the transfer drum 27 and the maximum movement time of the developing device in the color mode is smaller than the time Tt ₂ required between sheets as in the blue monochromatic mode described above, , The developing operation is performed twice consecutively (13), (1
Four).

Next, it is determined whether or not the last color developing unit is the developing unit 5d (15). If NO, proceed to step (16) and move to the next developing unit and return to step (13). It is determined whether the process is completed (16). If YES, the process is terminated. If NO, the developing unit 5a for the first color is moved to the axial center position of the photosensitive drum 19 (17), and the process returns to step (13). Repeat until done.

On the other hand, in the judgment of step (6), the first color developing device
If the moving time of the developing unit becomes longer than the time when the color developing unit is moved, the transfer paper may or may not pass through the transfer position with the toner image on even if two sheets are placed. In addition, the transfer conditions are different between the first and second sheets, and the control becomes complicated. Therefore, in this case, jumping to step (19) is performed in order to execute the sequence on one sheet as in the red single color mode described above, without performing the two sheets.

Developing processing is performed in the normal single-sheet loading mode (19), and it is determined whether or not the last developing device 5a is present (20). If NO, the next developing device is moved to the axial center position of the photosensitive drum 19 ( 23) Return to step (19).

On the other hand, if the determination in step (20) is YES, it is determined whether or not the designated number of copies has been completed (21). If YES, the process is terminated. If NO, the developing device 5d for the first color is set to the photosensitive drum.
Move to the axis of 19 (22) and return to step (19).

In the above-described embodiment, the description has been made on the assumption that the transfer drum 27 and the photosensitive drum 19 are rotating at a constant speed.
The transfer drum 27 and the photosensitive drum 19 may be driven by, for example, a stepping motor so that the speed can be reduced or stopped at an arbitrary position, and the developing device may be moved in a time required between sheets on the transfer drum. In this case, the maximum throughput can be obtained by controlling the time required between sheets by a motor corresponding to the moving time of the developing device.

Although not included in the color mode shown in FIG. 15 in the above-described embodiment, even when the copying operation is performed using the cyan developing device 5c and the black developing device 5a, the two sheets are not placed, and The same effect can be obtained by stacking the sheets.

〔effect〕

As described above, according to the present invention, the transfer timing of the transfer material is controlled based on the used developing device, the replacement time of the next used developing device from the used developing device, and the size of the transfer material. In this case, it is possible to prevent the toner on the transfer material wound around the transfer drum from being retransferred to the photosensitive drum without complicating the configuration and control of the apparatus, and to obtain a good throughput.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a color copying apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a main part illustrating a separation process of transfer paper by a separation claw illustrated in FIG. FIG. 3 is a block diagram for explaining the configuration of the controller unit shown in FIG. 1, FIG. 4 is a state transition diagram for explaining the movement transition of the developing unit shown in FIG. 1, and FIGS. FIG. 4 is a cross-sectional view illustrating a state in which the transfer paper is attracted to the transfer drum shown in FIG.
FIG. 7 is a cross-sectional view for explaining the output timing of the transfer timing signal, FIGS. 8, 9, 10, and 11 are timing charts for explaining the sheet feeding and developing processing operation according to the present invention, and FIG. FIGS. 13 (a) to 13 (d) are diagrams showing movement times between the respective developing units, and FIGS. 13 (a) to 13 (d) are state transition diagrams for explaining sheet feeding timing based on transfer of a plurality of sheets according to the present invention. FIGS. 14 (a) to 14 (d). ) Is a flowchart for explaining an example of a paper feed development processing procedure according to the present invention. FIG. 15 is a diagram showing correspondence between color modes and use of a developing device. FIG. 16 is a development transfer configuration in a conventional color copying apparatus. FIG. In the figure, 1 is a leader unit, 2 is a transfer paper feeding unit, 3 is an image forming unit, 4 is an image transferring unit, 5 is a developing unit, 5a to 5d are developing units, 16
Is a controller unit, 19 is a photosensitive drum, 27 is a transfer drum,
28 is a suction roller.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 13/01 G03G 15/01-15/01 117 G03G 15/00 303 G03G 21/00 370-502 G03G 21/02- 21/04 G03G 21/14

Claims (2)

(57) [Claims] The transfer drum includes a movable developing device that can be brought into contact with and released from the photosensitive drum and has a plurality of color developing devices, and a transfer drum that can wind a plurality of transfer papers. In a multi-transfer device that forms a color image by superimposing and transferring a developer of a different color onto the transfer paper wound around the paper, the replacement time of each developing device used for the color image to be formed and the transfer paper used Adjusting means for adjusting the timing of feeding the transfer paper to the transfer drum according to the size; and the transfer drum moving the distance between the transfer papers when a plurality of transfer papers are wound around the transfer drum. Control means for reducing the number of sheets of transfer paper wound around the transfer drum when using a plurality of developing devices such that the replacement cannot be completed within the time required for the transfer. Multiple transfer device that. 2. If the replacement of the developing unit is not completed within the above-mentioned time, and if only the developing unit of the last color of the movable developing unit is the developing unit of the first color, the control means sets the number of windings. 2. The multi-transfer device according to claim 1, wherein the value is not reduced.