JPH0430184A - Multiple pastel color printer - Google Patents

Abstract

PURPOSE:To shorten a loss time and to prevent a developing liquid and a recording sheet from being uselessly consumed by providing a roller rotation control means sucking/removing the developing liquid and a sucking means at every roller type developing heads. CONSTITUTION:When developing is carried out, only the developing roller of one selected developing head unit 27a is rotated to feed the developing liquid to a developing action part. Simultaneously, the sucking pump 30 of the selected unit 27a is operated to suck and remove the developing liquid stuck to the surface of the recording sheet. Therefore, even if the recording sheet comes in contact with the following developing head, it is not feared that a printed image is disturbed. When the developing is finished, the rotation of the developing roller 28 is controlled and the recording sheet 22 is continuously fed while the pump 30 is operated. The sheet 22 is pressed to a carrying roller 34 by a pinch roller 35, and tentatively taken up on a taking up roller 37. A sensor 24 detects the travelling position of the sheet 22 and controls a writing position by a recording head 25, so as to prevent positional deviation of respective color images. Thus, the loss of the developing liquid, the recording sheet, a printing time, etc., can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is a method for forming images of different colors on the same surface of a recording sheet that is transported back and forth using an electrostatic recording head and a plurality of wet color developing heads. This invention relates to a multi-pass color printer that sequentially overlaps each other.

[Prior Art] A multi-pass color printer that sequentially forms images of different colors on the same side of a recording sheet is
USP 4500045, JP 59-105660, JP 59-143844, JP 62-
It is publicly known in Japanese Patent No. 59983 and the like.

The above-mentioned apparatus generally includes a recording head for forming an electrostatic latent image on a recording sheet, a plurality of wet developing heads each applying a developer of a different color for developing the electrostatic latent image, and a recording head for forming an electrostatic latent image on a recording sheet. The apparatus further includes a recording sheet conveying means for reciprocating the sheet between the recording head and the developing head and then passing the sheet through the recording head and the developing head.

Figure 10 and Figure 1 are from the above-mentioned Japanese Patent Application Laid-Open No. 62-599.
The figures are taken from Publication No. 83, [Figure 10 is an explanatory diagram of a developing device, and Figure 11 shows an example of the configuration of a multi-pass color printer. In FIG. 10, 1 is the pulled-out recording sheet, 2 is a suction groove type developing head, 3 is the recording sheet 1 of the above-mentioned developing head, the developing side is a developer, a liquid container, 5 is a suction pump, and 6 is piping. .

In this device, when the suction pump 5 is operated while the surface of the developing groove 3 is covered with the recording sheet 1, negative pressure is created in the developing groove 3, and the developer in the container 4 is sucked up to the developing groove 3. Too much flow inside. Development is thus performed. Since negative pressure is applied to the developing groove 3, it acts to remove excess developer attached to the surface of the recording sheet 1. A dedicated suction drying groove 7 is provided in order to more reliably perform the suction removal action of the excess developer.

In the configuration example of the multi-pass color printer shown in FIG. 11, an electrostatic latent image is formed on the recording sheet 1 fed out from the recording sheet roll IR by the action of a recording head 8 such as a multi-stylus electrostatic recording head. be done. Developing head 28
A selected one 2a of the development heads 28-2d is in a raised operating position, and the other development heads 28-2d are in a lowered retracted position.

9 is a dedicated suction drying head, 10 is its suction pump, 1
1 is a drainage container, 12 is a recording sheet feeding port, and 13 is a take-up roller.

When printing the first color, recording sheet 1 is
In the figure, the sheet is conveyed toward the skin, and a latent image is formed and developed. During development, since the development heads 2a to 2d themselves have a suction and removal action of the developer by negative pressure suction force, there is no need to operate the pump 10 of the suction drying head 9.

When the development is completed and the suction pump 5 of the development head 2 is stopped, the suction drying action by the development head 2 is no longer performed. Therefore, the surface of the recording sheet remains wet with the developer. In order to eliminate this problem, in this device, the developing head 2a that has completed development is lowered, and the pump 10 is lowered.
While operating the recording sheet 1, the wet portion of the recording sheet 1 is passed through the position where the suction drying head 9 is disposed. By doing this, the developer is removed by suction.

After printing the first color, roll recording sheet 1
After winding it back to R, the recording sheet 1 is conveyed again and prints of the next color are made.

FIG. 12 is a diagram showing another type of wet developing head.

The figure is published in Japanese Patent Application Laid-Open No. 60-28678 (USP 4454).
833). In the figure, 14 is a developer tray, 15 is a developing roller, 16 is a doctor blade, 1
4a is a developer supply port, 14b is a drain port, 17a is a plunge +-17b is a backup roller, 18 is a wiper roller, 19 is a cleaning blade, and 20m and 20b are water-filled recording sheet feeding rollers. The recording sheet 1 is positioned with its back side supported by a backup roller 17b. Note that the same roller 17b and the developing roller 15
and are facing each other through a minute gap of 0.1 to 0.5 mm.

When the developing roller 15 rotates in the direction of the arrow, the developing solution adhering to the roller surface is applied to the recording sheet 1 to perform development. The developer that is carried onto the surface of the recording sheet is removed by a wiper roller 18. When the development is completed, the plunger 17a pulls up the backup roller 17b to separate the recording sheet 1 from the developing roller 15.

Multi-pass color printers employing such a roller developing head are known in Japanese Patent Application Laid-open No. 59-105660, Japanese Patent Application Laid-open No. 59-143844, No. υ5P4500045, and the like. In either printer, only the backup roller of one selected developing head is lowered to set the recording sheet 1 at the developing position.

[Problems to be Solved by the Invention] In this way, in a multi-pass color printer that uses a conventional wet type development head, only one selected development head operates, and the other development heads process the recording sheet with developer. A mechanism is required to control the position of the developing head or the recording sheet conveyance path so that it is in a retracted position to prevent contamination.

The reason why such a configuration is necessary is that the developing head itself
This is because the recording sheet was not equipped with a function to remove the developer applied to the recording sheet after development and a function to prevent new developer from being applied.

As a result, the configuration of parts of the printer related to development has become complicated and large. Further, the loss of developer, recording, sheet, and time consumed in the developer removal process after completion of development was too large to be ignored.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to have a developing section structure that is small and simple, and that has less waste in the step of removing the developer from the recording sheet after development, that is, less loss of developer, recording sheet, process time, etc. An object of the present invention is to provide a multi-pass color printer having the following functions.

[Means for Solving the Problems] In order to solve the above-mentioned problem am and achieve the objectives, the present invention has taken the following measures as basic means.

Multiple wet-type development heads are used as roller-type development heads,
For each developing head, after the completion of development, Ii! A roller rotation control means and a suction means are added which act to suction and remove the developer from the image acting section and the recording sheet surface, and a plurality of developing heads are fixedly arranged at a developing acting position facing the recording sheet running surface,
During the forward movement of the recording sheet, one selected developing head is put into operation, and after the development is completed, the same developing head is operated in a mode that removes the developer from the developing area and the recording sheet, and the other developing heads are In the backward movement process of the head and the recording sheet, the developing head is brought into an inoperative state without separating the developing head and the recording sheet.

[Effect]

As a result of taking the above measures, the following effects occur.

That is, since there is no mechanism for moving the developing head up and down or for changing the path of the recording sheet, the developing section can be made smaller and simpler. Furthermore, since there is no need to move the developing head or change the conveyance path of the recording sheet, the processing time after development is completed is shortened.

Further, by the action of the roller rotation control means and the suction means for each developing head, the process after the completion of development is quickly completed, so that loss time can be shortened and wasteful consumption of developer and recording sheets can be prevented.

[Embodiment] FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention. In the figure, 21 is a recording paper roll, 22 is a pulled-out recording paper sheet, 23 is a guide roller, 24 is a sensor, 25 is a recording head, 26 is a pressure roller, 27 is a developing section, and 27a
-27d are each developing head unit, 28 is a developing roller,
29 is a rotation control means, 30 is a suction pump, 31 is a developer container, 32 is piping, 33 is a guide plate, 34 is a conveyance roller, 35 is a pinch roller, 36 is a guide brake),
37, the winding roller is wetted with water.

An electrostatic latent image is formed on the recording sheet 22 pulled out from the roller 21 by the recording head 25 .

The recording head 25 is a multi-stylus electrostatic recording head,
An ion flow control type recording head or the like is applied.

The recording sheet 22 conveyed in the right-hand direction reaches the developing section 27 . The developing section 27 is composed of a plurality of roller developing type developing head units 27a to 27d. A suction pump 30 and a rotation control means 29 for controlling the rotation of the developing roller 28 are connected to each unit so as to operate independently.

Although the detailed structure of the embodiment will be explained separately, the suction pump 30 is operated to generate a suction action on each of the developing head units 27a to 27d to suction and remove the adhering developer from the surface of the recording sheet.

After the development is completed, the developing roller rotation control means 29 controls the rotation of the developing roller 28 to cut off the supply of the developer to the developing section of each head, and also acts to remove the developer from the developing section. .

During development, the recording sheet 22 is conveyed toward the right.

Further, only the developing roller of the selected one developing head unit 27a rotates to send the developer to the developing section. At the same time, the suction pump 30 of the selected developing head unit 27g is operated to suction and remove the developer attached to the surface of the recording paper. Therefore, the surface of the recording sheet 22 that has passed through the developing head unit becomes dry. Therefore, even if the recording sheet comes into contact with a subsequent developing head, there is no risk of disturbing the printed image. Therefore, there is no need to lower and retract the other developing head units.

When the development of a predetermined area is completed, the rotation of the developing roller 28 is controlled while the suction pump 30 is kept operating, and the recording sheet 22 is continued to be fed. For example, when the rotation of the developing roller 28 is stopped, the supply of the developing solution is cut off, and the developing solution that was in the developing area is carried away by the recording sheet 22. The developer on the recording sheet 22 is then removed by the action of the suction pump. Thus, the developing head units 27a to 27
After the portion in contact with the recording sheet 22 in d becomes dry, the operation of the suction pump 30 is stopped and the recording sheet 22 is removed.
Wind it back to the starting position and move on to the printing process for the next color.

The recording sheet 22 is moved between the pinch roller 3 and the transport roller 34.
5. The fed recording sheet 22 is then temporarily wound up by a winding roller 37. Of course, if the length of the sheet 22 is short, the take-up roller 37 can be omitted.

The sensor 24 detects the running position of the recording sheet 22 and controls the writing position by the recording head 25. In this way, the images of each color are prevented from shifting in position.

FIGS. 2 to 4 are diagrams showing an example of the structure of a wet roller developing head unit suitable for application to the apparatus of the present invention. Figure IJ2 is a diagram showing the cross-sectional structure of the developing head along the roller axis and the connection state of related units, Figure 3 is a cross-sectional view of the developing head in a direction perpendicular to the above-mentioned cross section, and Figure 4 shows a preferred configuration example of the developing roller. FIG.

In FIGS. 2 to 4, 40 is a hollow base, 4°a is a central member, 40b and 40C are end sealing members, 41 is a developer supply port, 42 is a drain port, 43 is a liquid level regulating end, 44 is a hollow part, 45 is a slot/slot window, 46 is a roller drive shaft, 47 is a support shaft, 48 is a bearing bush, 49 is a sealing, 5o
51 is a bearing, 51 is a bearing stop, 52 is a roller drive motor, 53 is a recording sheet conveyance motor, 54 is a controller, 32a, 32b, 32c are piping tubes, 55
The spiral groove on the circumferential surface of the developing roller is filled with water.

The hollow base body 40 has a cross-sectional shape as shown in FIG. That is, with respect to the central member 40a, the end sealing member 40
When b and 40c are joined and the roller 28 is assembled, the portion excluding the developer supply port 41, liquid drain port 42, and slit window 45 becomes an airtight hollow box. The roller 28 is supported at one end by a bushing 48 and by a bearing 50 at the other end. The shaft on the bearing side is kept airtight by a sealing 49. Drive shaft 46 is also coupled to motor 52 . The developing roller 28 is located at the slit window 45.
are arranged so that their upper circumferential surfaces are approximately at the same height. The length of the slit window 45 is set to be slightly shorter than the width of the recording sheet to be developed.

The controller 54 controls ON-OFF of the suction pump 30, rotation speed, direction, ON, -0 of the roller drive motor 52.
It has functions that can independently control FF control, the rotational direction and speed of the recording seed feed motor 53, ON-OFF control, etc.

When the recording sheet on which the electrostatic latent image is formed is placed above the slit window 45 and the suction pump 30 is started while being conveyed across the slit window 45, a negative pressure is created inside the airtight box. This negative pressure causes the recording sheet to be attracted to the slit window 45, thereby sealing the window 45. When the negative pressure increases further, the developer is sucked up from the developer container 31 by the negative pressure and flows into the hollow portion 44 of the developing head from the developer supply port 42 .

When the liquid level rises and exceeds the liquid level regulation end 43, the liquid drain port 42
A mixture of developer and air flows out.

When the amount of air that is removed becomes the same as the amount of air that leaks from the minute gap between the recording sheet and the peripheral surface of the slit window 45, the liquid level stops rising and becomes stable.

In this state, the lower part of the roller 28 is in the developer solution.

When the developing roller 28 is rotated at a speed of several hundred revolutions per minute or more, the developing solution viscously adheres to the roller surface and is carried upward. The developer adheres to the recording sheet at the position where it is closest to the recording sheet, and a band-shaped liquid pool is formed.

The developing roller 28 and the recording sheet 2 act as developing electrodes.
Due to the high potential gradient formed between the two latent images, the toner in the developer is electrophoresed, and development progresses efficiently. The developer that has consumed the toner is carried away by the developing roller 28 and diffused into the developer below the surface of the developer.

Since negative pressure is always acting on the slit window 45, there is an air flow that leaks through the minute gap between the peripheral surface of the slit window 45 and the recording sheet 22. The developer applied to the surface of the recording sheet 22 passing above the slit window 45 is always collected into the hollow section 44 inside the slit window 45 together with the above-mentioned air flow. (This acts to dry the surface of the recording sheet 22.

When the predetermined area of the recording sheet on which the electrostatic latent image has been formed passes over the slit window 45, the rotation of the developing roller 28 is switched to low-speed rotation in the reverse direction while feeding the recording sheet 22 with the suction pump 30 operating.

When the rotation speed of the developing roller 28 becomes low, the amount of the developing solution adhering to the roller surface decreases, and the supply of the developing solution to the developing section is cut off. Further, the developer in the puddle formed in the developing area is subjected to the action of gravity, adheres to the surface of the recording sheet, and is carried away.

When the liquid pool is removed, the developing roller 28 becomes dry. Therefore, the rotation of the roller 28 is stopped. Further, the developer applied to the surface of the recording sheet 22 is supplied to the suction pump 3.
It is removed by suction with a negative pressure of 0. (Then, all parts that come into contact with the recording paper become dry. Then, the suction pump 30
Stop the operation and rewind the recording sheet to the starting position.

By repeating such operations while sequentially selecting the developing head units 27a to 27d,
The color print is completed.

FIG. 4 is a diagram showing a preferred example of the configuration of the developing roller. In the roller developing device, the gap between the developing roller 28 and the recording sheet greatly influences the developing performance. Generally 0.
It is said that it is preferable to stably maintain a gap of about 1 to 0.3 mm. In the suction roller developing head explained in FIGS. 2 and 3, the slit window 4
Since negative pressure is applied to the recording sheet 5, the recording sheet 22 is pulled toward the rollers, making the traveling position unstable. Therefore, by forming grooves 55 on the surface of the roller as shown in FIG. 4, the recording sheet 22 is supported in contact with the tops of the grooves, and the developer is retained and acted upon in the valleys of the grooves 55. The top and valley portions that are in contact with the sheet 22 have different effects, resulting in uneven development. Therefore, the groove 55 is formed in a spiral shape so that the supporting position of the recording sheet 22 can be moved. The greater the inclination angle of the grooves 55, the greater the unevenness prevention effect. Therefore, it is more preferable to perform groove processing in the form of a multi-thread thread.

FIG. 5 is a diagram showing an improved embodiment in which the rotation of the developing roller 28 is controlled to efficiently cut off the supply of developer. In FIG. 5, 60 is a hollow base, 56 is an upper cap, 57 is a magnetic blade, 58 is a developing roller, and 59
indicates each stopper.

The magnetic blade 57 is a blade made of a flexible magnet such as a rubber magnet, and can slide by being magnetically attracted to the surface of the developing roller 58 made of a magnetic material. A gap is created between the stopper 59 and the developing roller 58, through which the magnetic blade 57 cannot pass. Further, a gap 56 between the developing roller 58 and the upper inner wall of the hollow substrate 60 allows the developer attached to the surface of the developing roller to pass through, but prevents the magnetic blade 57 from passing through.

During development, the developing roller 58 rotates in the direction of the arrow, and the magnetic blade 57 is positioned against the stopper 59 and slides on the roller surface. Therefore, the developer that has consumed the toner adhering to the roller surface is forcibly removed by the peeling action caused by the sliding of the blade. Then, new developer is replenished onto the roller surface and acts to increase the developing ability.

When the developing roller 58 is rotated in the opposite direction after the development is completed, the magnetic blade 57 is positioned in front of the gap 56. Note that this position is set so that it is above the developer surface. The developer adhering to the developing roller 58 due to the above-mentioned reverse rotation is forcibly removed by the magnetic blade 57.
The supply of developer to the developing section is cut off. In this case, the rotational speed of the developing roller 58 does not need to be particularly low.

Therefore, the liquid pool in the developing area can be efficiently removed by the developing roller 58.

By the way, the rotation control of the developing roller 58 and the feeding control of the recording sheet 22 in the suction drying process after the completion of development can be changed in many ways other than those described above.

FIG. 6 is a timing diagram for explaining the change. In the figure, X in the horizontal axis direction represents a developing process, Y represents a liquid pool removal process, and 2 represents a suction drying process.

In the liquid pool removal step Y, the rotation of the developing row 558 is stopped to cut off the supply of the developer, and the liquid pool can be attached to the recording sheet and removed.

Further, when rotating at a low speed, it may be in the same direction as during development. When the roller 58 is rotated, since the roller has the effect of removing the developer, the feeding of the recording sheet 22 can be stopped and wasteful consumption of the sheet can be suppressed.

In the suction drying step 2, the rotation of the developing roller 58 may be stopped. Further, the recording sheet 2.2 can be conveyed in the unwinding direction to save unnecessary consumption of the recording sheet 22 and time required for unwinding the recording sheet 22.

Above, in FIGS. 2 to 4 and 85, examples of developing head units applied to a suction roller developing device have been illustrated, but a developing head with a different configuration equipped with a developing roller and a suction drying element may also be used. It may be a unit.

FIG. 7 is a diagram showing an embodiment of another developing head unit that can be well applied to the present invention, and is based on the structure of claim 3.

In the figure, 70 is a tray with an open top surface, 71 is a developing roller, 72 is a stopper, 73 is a suction slit, 74 is an upper gap, 75 is a delay port, 76 is a piping joint, 7
7 indicates a magnetic blade, and 78 indicates a throttle valve.

A developing roller 71 is housed in a tray 70 with its upper surface open, and a suction slit 73 is provided on the downstream side of the developing roller at approximately the same height as the upper surface of the developing roller when viewed in the recording sheet conveyance direction during development. 4. The suction slit 73 reaches a piping joint 76 via the communication lower 5 and is connected to the suction pump 30. A pipe is connected from the developer container 31 to the suction side of the suction pump 30 via a throttle valve 78, and the discharge side of the suction pump 30 is connected to the tray 70.
is connected to. Further, piping for returning the developer from the tray 70 to the developer container 31 is provided.

The suction slit portion is covered with a recording sheet slightly wider than the length of the suction slit 73, and the recording sheet 22 is moved in the direction of the arrow across the developing head.

The recording sheet 22 is attracted to the suction slit 73 by the negative pressure action of the suction pump 30 . and suction pump 30
The path to the inlet becomes negative pressure.

By creating a negative pressure in the path from the developer container 31 to the suction port, the developer is sucked out from the container 31 and sent into the tray 70 via the pump 30. When the developer level rises to a position where the lower part of the developing roller 71 is immersed, the developer returns to the developer container 31 via an overflow opening (not shown). The throttle 78 is used to optimize the amount of circulating fluid and the negative pressure of the pump, but is not essential. When the developing roller 71 rotates, development is performed at the position where the developing roller 71 and the recording sheet 22 are closest to each other. The developer adhering to the recording sheet 23 is collected through the suction slit 73, and the suction-dried recording sheet 22 passes through the developing head section.

After the development of a predetermined area is completed, the rotation of the developing roller 71 is controlled in the same manner as explained in FIGS. 2 to 4. By doing so, the supply of the developer to the developing section is cut off and the developer is operated to be removed from the developing section. During this time, the suction pump 30 continues to operate. In this way, the developer is removed from the development action section, and the developer is suctioned away from the recording sheet 22. Afterwards, the suction pump is stopped. The recording sheet is also rewound.

The functions and effects of the stopper 72, magnetic blade 77, and upper gap 74 are the same as those explained in FIG. 5. Note that instead of the magnetic blade 77 shown in FIGS. 5 and 7, a blade made of an elastic member that is pressed against the roller surface' by elastic force may be used. Further, it is possible to configure the developing head without a blade, as in FIGS. 2 to 4.

By the way, the above-mentioned developing head unit itself has a compact structure, and the developing heads can be fixedly arranged, so it is possible to drive and control multiple developing heads using a single motor and clutch. Become.

FIGS. 8 and 9 are diagrams showing an embodiment constructed based on claim 4, in which the drive system of the developing head roller is simplified and costs are reduced.

FIG. 8 is a top view of the developing section, and FIG. 9 is a side view illustrating the roller drive system of the developing section. In FIGS. 8 and 9, 27a to 27d are developing heads corresponding to each color, 28 is a developing roller, 45 is a slit window, 46 is a roller drive shaft, and 8
0a to 80d are electromagnetic clutches, 81a to 81d are belt pulleys, 90 is a motor and electromagnetic clutch controller, 91 is a motor, 92 is a motor boot, and 93 to 96 are belts.

Electromagnetic clutches 80a to 80a are mounted on the drive shaft 46 of the developing roller 28.
80d are attached to each. That is, one disk of the clutch 80 is fixed to the shaft, and the other disk is free with respect to the shaft.

Pulleys 81a to 81d are fixed to this other disk.

The pulleys 81a to 81d each have two stages, and belts 94, 95, and 96 are passed between adjacent pulleys. In this way, when one pulley rotates, all pulleys rotate at the same time. Pulleys 81a to 81d
A belt 93 is passed between one of the pulleys 81d and a pulley 92 of a motor 91, and when the motor 91 rotates, all the pulleys can be rotated.

The controller 90 controls the rotational speed of the motor 91 in nine rotational directions;
In addition to controlling 0N-OFF etc., the club from ~8
One of 0d is selectively ON-OFF controlled.

For example, when the developing head 2731 is selected, the operation is as follows. First, the motor 91 is rotated at a speed of one rotation in the rotational direction that meets the requirements during development, and the clutch 80 is turned on. By doing this, development is performed. When the development is completed, the rotation of the motor is reduced, rotated in the opposite direction, or even stopped. Then, the developer is removed from the reservoir in the developing area. After such processing is completed, the clutch 80a is turned off.

After the recording sheet 22 is rewound, another developing head is selected and similar control is performed. In this way, the creation of color prints can proceed.

Note that the present invention is not limited to the embodiments described above, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[Effects of invention According to the present invention, the following effects can be expected.

(1) It has a small, simple and simple configuration, including developer, recording sheet,
A multi-pass printer with less loss in printing time etc. can be realized.

(2) More specifically, a mechanism for changing the developing head position and recording sheet path can be omitted, and a small and simple multi-pass printer can be realized.

(3) Furthermore, the time required to change the developing head or recording sheet path can be reduced, and a multi-pass printer can be realized in which the time required for printing is shortened.

(4) Also, unnecessary consumption of recording sheets can be reduced, and an economical multi-pass printer can be realized.

(5) Furthermore, it is possible to realize a multi-pass printer in which the developer carried out by the recording paper can be efficiently recovered and used again.

(6) Also, the motor that drives the developing roller has been standardized.
A small, low-cost multi-pass printer can be realized.

[Brief explanation of the drawing]

1 to 4 are diagrams showing a first embodiment of the present invention.
The figure shows the configuration of the printer, and FIGS. 2 to 4 are diagrams showing the configuration of the roller development unit of the printer. FIG. 5 is a sectional view showing the configuration of the main parts of a second embodiment of the present invention. FIG. 6 is a timing chart showing an example of controlling the developing roller and recording sheet in each of the embodiments. FIG. 7 is a diagram showing the configuration of a third embodiment of the present invention. FIGS. 8 and 9 are a top view and a side view showing the configuration of a fourth embodiment of the present invention. FIGS. 10 to 12 are explanatory diagrams of the prior art. 21... Recording paper roll, 22... Pulled out recording paper sheet, 23... Guide roller, 24... Sensor,
25... Recording head, 26... Pressure roller, 27
... Developing section, 278-27d... Each developing head unit, 28... Developing roller, 29... Rotation control means, 30... Suction pump, 31... Developer container, 32
... Piping, 33 ... Guide plate, 34 ... Conveyance roller, 35 ... Pinch roller, 36 ... Guide plate, 37 ... Winding roller. Applicant's agent Patent attorney Atsushi Tsuboi 8111 wll Figure

Claims (4)

[Claims] (1) A recording head for forming an electrostatic latent image on a recording sheet, and a plurality of wet developing systems using different color developers for developing the electrostatic latent image formed by this recording head. and a recording sheet conveying means that reciprocates the recording sheet between the recording head and the developing head and then passes the recording sheet, and sequentially superimposes images of different colors on the same surface of the recording sheet. In a multi-pass color printer, the plurality of wet development heads are roller-type development heads, and each development head sucks developer from the development action section and the recording sheet surface after development is completed. A roller rotation control means and a suction means are added to act to remove the recording sheet, and a plurality of developing heads are fixedly arranged at a developing operation position facing the recording sheet running surface,
During the forward movement of the recording sheet, one selected developing head is put into operation, and after the development is completed, the same developing head is operated in a mode that removes the developer from the developing area and the recording sheet, and the other developing heads are A multi-pass color printer characterized in that during the backward movement process of the head and the recording sheet, the developing head is brought into an inoperative state without separating the developing head and the recording sheet. (2) In the multi-pass color printer according to claim 1, the wet roller developing head is a suction roller developing head in which the developing roller is housed in an airtight box body having a slit window in the portion facing the recording sheet. , comprising a suction pump connected to the roller developing head, a roller rotation means, and a rotation control means, the suction pump and the rotation control means can be independently controlled, and the suction pump is activated after the development is completed. A multi-pass color printer characterized in that the recording sheet is conveyed while the developing roller is controlled to a rotational state different from that during development. (3) In the multi-pass color printer according to claim 1, the wet roller developing head is a developing head having a suction slit at a position adjacent to the developing roller on the downstream side when the recording sheet moves forward; comprising a suction pump connected to the suction slit, a roller rotation means, and a rotation control means, the suction pump and the rotation control means being able to be independently controlled;
A multi-pass color printer characterized in that after the completion of development, the recording sheet is conveyed while the suction pump is kept in operation and the development roller is controlled to a rotational state different from that during development. (4) The multi-pass color printer according to claim 1, further comprising means for transmitting rotation of a single motor to a plurality of developing roller shaft positions, and a rotational force transmitted by this means to each roller shaft. 1. A multi-color printer characterized in that a clutch is provided which selectively engages, and the rotation of a roller of a selected developing head is controlled in conjunction with the reciprocating movement of a recording sheet.