JPH0412381A - Liquid developing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[0001]

[Industrial application field]

The present invention relates to a liquid developing device employed in image forming apparatuses such as electrophotographic or electrostatic recording type copying machines, facsimile machines, printers, etc., and more specifically, the present invention relates to a liquid developing device used in image forming apparatuses such as electrophotographic or electrostatic recording type copying machines, facsimile machines, printers, etc. The present invention relates to a liquid developing device that performs development using a developing head disposed facing a conveyance path. [0002]

[Conventional technology]

A liquid developing device that develops an image to be developed on a recording medium by filling a developer supply groove extending in the width direction of the recording medium provided on the developing head surface facing the recording medium transport path with a developer is disclosed in, for example, Japanese Patent Laid-Open No. Publication No. 179477/1983, Japanese Patent Application Publication No. 1-185
It is known from Publication No. 569 and the like. In this type of liquid developing device, with the developer supply groove blocked by a recording medium such as electrostatic recording paper, a negative pressure generating means such as a pump motor is driven to develop the recording medium onto the image head surface. At the same time, an image to be developed, such as an electrostatic latent image, is developed with the developer supplied to the developer supply groove, and after development is completed, the developer in the developer supply groove is collected into a developer tank. [0003]

[Problem to be solved by the invention]

However, according to the above configuration, even if the supply of the developer to the developer supply groove is simply stopped and the developer in the developer supply groove is collected into the developer tank by the weight of the developer, the problem will not be solved as shown in FIG. In addition, the meniscus developer remains at the corner formed by the upper inner surface of the developer supply groove and the recording medium, so if the recording medium is transported in this state, the remaining developer will adhere to the recording medium and stain it. However, if the recording medium is electrostatic recording paper (portion A in Figure 7), there is a problem that this dirty area cannot be used for image formation and is wasted. Ta. Further, a plurality of developing heads to which developer solutions of each color are supplied are selectively brought to a developing position facing the recording medium conveyance path, and the recording medium is conveyed back and forth across the developing position to perform color development. When the developing head is retracted to the standby position with the developer remaining in the corner, the remaining liquid attached to the upper part of the inner surface of the developer supply groove will be removed here. There is a risk of staining the recording medium when it dries and hardens and is moved to the development position for reuse for development. There was a problem that there was a risk of contamination. In order to prevent this, before retracting to the standby position, the recording medium is conveyed with the developing head left in the developing position after development is completed, so that the residual developer adheres to the recording medium. Not only is the above-mentioned recording medium wasted, but the reciprocating width of the recording medium is increased by the amount of transport required, resulting in a problem that the color development time becomes longer. [0004] In addition, when a paper jam occurs in the electrostatic recording paper while the electrostatic latent image formed on the electrostatic recording paper is being developed by the developing head, and conveyance of the electrostatic recording paper is stopped, negative pressure is applied. Even if the generating means is immediately turned off, developer remains in the developing head. There is a problem in that a large amount of this developer may adhere to the electrostatic recording paper, staining the conveying means for the electrostatic recording paper and the operator's hands and clothes. [0005] The present invention has been made in view of the problems of the prior art, and its first purpose is to drain the developer in the developer supply groove into the developer tank after development is completed. It is an object of the present invention to provide a liquid developing device capable of efficiently removing developer remaining at a corner formed by the upper inner surface of a developer supply groove and a recording medium when recovering the liquid. The purpose is to provide a liquid developing device that does not leave any developer in the developing head even if the electrostatic recording paper becomes jammed while the electrostatic latent image formed on the electrostatic recording paper is being developed by the developing head. . [0006]

[Means to solve the problem]

In order to achieve the above first object, the invention according to claim 1 supplies a developer to a developer supply groove extending in the width direction of the recording medium provided on the development head surface facing the recording medium transport path. In a liquid developing device that develops an image to be developed on a recording medium by filling the liquid, the amount of air flowing into the developer supply groove from the gap between the head surface and the recording medium after the completion of development is determined by the amount of air flowing in during development. It is also characterized by increasing the size. [0007] Further, in order to achieve the above second object, the invention according to claim 3 includes a developer supply groove extending in the width direction of the recording medium on the developing head surface facing the recording medium transport path. a developer tank containing a developer, a developer supply path forming means from the developer tank to the developer supply groove, and a developer recovery path forming means from the developer supply groove to the developer tank. , a negative pressure generating means provided in the developer recovery path and generating negative pressure in the developer supply groove, a valve that switches the developer supply path between a communication state and a cutoff state, and a valve that controls switching of the valve. A control means and a negative pressure control means for controlling the drive of the negative pressure generating means are provided, and after the completion of development, the valve control means switches the valve to cut off the developer supply path, and then the above-mentioned In a liquid developing device in which the negative pressure control means continues to drive the negative pressure generation means, when a state occurs in which conveyance of the recording medium is stopped during development, the valve control means cuts off the developer supply path. The negative pressure control means continues to drive the negative pressure generation means for a certain period of time after switching the valve to achieve the desired result. [0008]

[Effect]

The invention according to claim 1 provides a developing head provided on the surface of the developing head facing the recording medium conveyance path when a recording medium on which an image to be developed such as an electrostatic latent image is formed is conveyed by an electrostatic recording head or the like. A developer supply groove extending in the width direction of the recording medium is filled with a developer to develop the image to be developed on the recording medium, and when the end of the image to be developed passes through the developer supply groove and development is completed, the head By making the amount of air flowing into the developer supply groove from the gap between the surface and the recording medium larger than the amount of air flowing in during development, the corner formed by the upper part of the inner surface of the developer supply groove and the recording medium can be It acts to remove the remaining developer by suction. [0009] Further, the invention according to claim 3 is characterized in that, when a situation occurs during development in which conveyance of the recording medium is stopped, the valve control means operates the valve to shut off the developer supply path. For a certain period of time after switching, the negative pressure control means continues to drive the negative pressure generating means, thereby removing the developer remaining at the corner formed by the upper part of the inner surface of the developer supply groove and the recording medium. It acts to remove by suction. [00101

[Example] An example in which a liquid developing device according to the present invention is applied to a developing device of an electrostatic recording type image forming apparatus will be described. FIG. 1 is a schematic diagram of an electrostatic recording type image forming apparatus employing a liquid developing device according to a first embodiment of the present invention. First, to explain the outline of the operation of this image forming apparatus, in FIG. The leading end passes over the electrostatic recording head 2 and developing head 3 which are inactive, and is held between a drive roller 4 and a pinch roller 5. In this state, an image forming operation standby state is established. When the image forming operation starts, the drive roller 4 starts rotating, an electrostatic latent image is recorded on the recording paper by the electrostatic recording head 2, and this electrostatic latent image is developed on the developing head 3. Continuing to convey the recording paper, just before the leading edge of the developed image passes the cutter 6, the cutter 6 is driven to cut off the remaining part of the leading edge of the recording paper, and then immediately after the trailing edge of the developed image passes the cutter 6, the drive roller 4 is stopped, the cutter 6 is driven to cut the recording paper, and while only the paper ejection roller pair 7 is rotated, the sheet-shaped recording paper is ejected onto a paper ejection tray (not shown). [0011] Next, the liquid developing device of this embodiment will be described in detail. As shown in the perspective view of FIG. 2(a), this liquid developing device extends in the width direction of the recording paper on the developing head surface facing the recording paper conveyance path of a box-shaped developing head 3 that is elongated in the width direction of the recording paper. Two developer supply grooves 8.9 are provided, and the ends of the two developer supply grooves 8.9 on the upper front side in the drawing are as shown in FIG.
(a) The developer is supplied from the developer tank 10 containing the developer to the developer supply groove 8.9 through a hole penetrating the back side of the developing head surface as shown by the broken line in the central cross section seen from the earthy side. It is connected to a supply pipe 11 which is a supply path forming means, and the other end is connected to a developer recovery path from a developer supply groove 8.9 to a developer tank 10 through a hole penetrating the back side of a similar developing head surface. It is connected to a recovery pipe 12 which is a forming means. This supply pipe 11 is provided with an electromagnetic valve 13 that switches the supply pipe 11 between a communication state and a cutoff state, and a recovery pipe 12 is provided with a solenoid valve 13 that switches the supply pipe 11 between a communication state and a cutoff state. A pump motor 14 is provided as a negative pressure generating means. Switching of the electromagnetic valve 13 and driving of the pump motor 14 are controlled by electromagnetic valve control means and negative pressure control means provided in a control section 15 that controls the operation of the entire apparatus. [0012] In the above configuration, when the image forming operation is started after the standby state, the pump motor 14 starts to be driven while leaving the electromagnetic valve 13 that communicates the supply pipe 11 from the standby state as it is. By this, the developer supply groove 8.9
A developer tank 10 is placed in the developer supply groove 8.9 which is closed with recording paper and is in a so-called sealed state with negative pressure inside.
The developer is supplied from the supply pipe 11 to fill the developer, while the developer supply groove 8 is filled with the developer by the recovery pipe 12.
The developer from 9 is collected into a developer tank 10 to circulate the developer. At this point, the drive roller 4 starts rotating and the recording head starts recording an electrostatic latent image on the recording paper, and the electrostatic latent image on the recording paper conveyed onto the developing head 3 is developed. At this time, the developer supply groove 9 on the downstream side in the recording paper transport direction not only performs a developing function, but also serves as a barrier between the developing head surface and the recording paper surface (developing head surface side) due to minute irregularities on the recording paper surface. The air flowing into the developer supply groove 9 from the gap also performs the function of removing excess developer that has adhered to the recording paper. [0013] When the rear end of the electrostatic latent image on the recording paper passes the developing head surface and the development is completed, the solenoid valve 13 is switched while the pump motor 14 is driven, and the supply pipe 11 is shut off. By doing this, most of the developer in the developer supply groove 8.9 etc. is quickly collected into the developer tank 10, and after that, all the negative pressure generated by the pump motor 14 is recorded as being in front of the developer head. The developer supply groove 8.9 is designed to suck air from the gap between the paper surface and the developer supply groove 8.9 into the developer supply groove 8.9.
and sucks up the developer remaining on the recording paper. Such residual developer is sucked for a set time, and when the trailing edge of the developed image passes the cutter 6, the cutter 6 is driven to cut the recording paper, and at the same time, the rotation of the drive roller 4 is stopped and the The drive of the pump motor 14 is stopped, and the solenoid valve 13 is switched to bring the supply pipe 11 into communication. FIG. 3 is a flowchart of the above operation with a sign spread of 4 1181 (8,), and FIG. 5 is a timing chart thereof. Here, regarding the solenoid valve 13, the switching to shut off the supply pipe 11 is indicated as "electromagnetic valve ON", and the reverse switching is indicated as "electromagnetic valve 0FFJ". By setting the conveyance speed to 16 mm/sec and conveying the recording paper even after development is completed, the developer remaining at the corner formed by the upper inner surface of the developer supply groove 8.9 and the recording paper adheres to the recording paper. Length in the recording paper transport direction of dirt caused by dirt (length on the recording paper from the position where the developing head 3 is facing when the solenoid valve 13 is switched to shut off the supply pipe 12 to the position where there is no dirt) When the length of the solenoid valve 1 was measured, it was 30 to 70 mm (portion B in Figure 6).
3, the same measurement was carried out with the supply pipe 11 kept in communication and the drive of the pump motor 14 stopped.
The length of the dirty recording paper in the direction of conveyance is 300 to 400 mm (
6), and it was confirmed that the length of the stain on the recording paper in the conveyance direction could be reduced by 270 to 330 mm. Note that this reduction in stain length is equivalent to a recording paper transport time of 16.85 seconds (270/16) to 20.6 seconds (
330/16), and when color development is performed by transporting the recording paper back and forth across the developing head 3, there is no need to ensure an extra reciprocating transport width, and the color development time can be shortened. [0015] Next, based on FIG.
An example will be explained. The difference between this embodiment and the first embodiment is that in the first embodiment, the pump motor 14
The driving state of the pump motor 14 is the same during development and during the subsequent suction period of the developer remaining in the developer supply groove 8.9 and the recording paper. A frequency converter 16 (
(The part surrounded by the broken line in Figure 1) is provided, and by supplying a higher frequency alternating current during the suction period than during development, the pump function is improved during the suction period compared to during development. This is the point of changing the driving state. FIG. 4 shows a flowchart of the control, in which the solenoid valve 13 is switched to start the above-mentioned suction, and the pump motor 1 is switched to the wave number H, and the rotation of the pump motor 14 is increased.
8. Powerful developer supply groove with improved pump function.
9 and the developer remaining on the recording paper is sucked, and then the drive of the pump motor 14 is stopped to end the residual developer suction period and the frequency setting value is returned to the frequency during development. [0016] In each of the above embodiments, the end time of the suction period for the residual developer after the end of development coincides with the end time of conveyance of the recording paper, but the present invention is not limited to this. .9 and from the viewpoint of preventing staining of the recording paper due to suction of developer remaining on the recording paper, etc., it is possible to set it independently of the end time of conveyance of the recording paper. Further, in order to better remove the excess developer on the recording paper, a separate head dedicated to sucking the excess developer may be provided downstream of the developing head 3 in the recording paper transport direction. Further, the number of developer supply grooves on the development head surface is not limited to two, but may be - or three or more. Furthermore, in each of the above embodiments, the developer is supplied to the developing head 3 from one developer tank 10, but the developer of different colors can be supplied to the developing head 3 through an appropriate liquid path switching means such as a valve. A developing device for color development can be created by selectively connecting any one of the plurality of developer tanks accommodated therein and the tank containing cleaning solution for cleaning developer supply grooves and the like when changing colors into one. can. Further, a set of the developing head 3 and developer tank 10 as in each of the above embodiments is provided for each color, and any one of the developing heads 3 is selectively moved to the recording paper conveyance path by an appropriate developing head 3 elevating means. By arranging it to the side, it can also be used as a developing device for color development. Further, in the above embodiment, a liquid developing device employed in an electrostatic recording type image forming apparatus is described, but it can also be adopted in an electrophotographic type image forming apparatus. This has the advantage of being able to omit the surplus developer removing device that was provided separately from the device, and reducing the burden on the cleaning device for the surface of the photoreceptor. [0017] Next, an embodiment in which the liquid developing device according to the present invention is applied to an electrostatic recording color image forming apparatus that forms color images will be described with reference to FIGS. 8 to 12. FIG. 8 is a schematic configuration diagram of this color image forming apparatus. The image form sign square root 4 1? shown in FIG. 1 above? , 361 (IU) The same reference numerals are used for the components corresponding to the IU-forming devices. In the color image forming apparatus of this example, a pair of transport rollers 40 is provided in a recording paper transport path between the recording head 2 and a feed-out shaft on which a recording paper (not shown) is wound into a roll. A cyan developing head 3C, a magenta developing head 3M, and a yellow developing head 3Y, which supply a cyan developer, a magenta developer, and a yellow developer to the recording paper, are supported by lifting means (not shown) below the recording paper conveyance path. It is arranged as follows. Of these developing heads, this elevating means selectively positions the developing head used for development at an operating position where it contacts the recording paper, and positions the developing head not used for development at a standby position where it is retracted downward. be. These developing heads have the same structure, and the developer supply means from the developer tank and the on-site solution recovery means to the on-site tank also have the same structure. Hereinafter, these structures related to the cyan developing head 3C will be explained. As shown in FIGS. 9 and 10, the developing head surface of the developing head 3c has three developer supply grooves 8, 50.9 extending in the width direction of the recording paper, and a similar pattern between adjacent developer supply grooves. Atmospheric grooves 51 and 52 are provided extending in the width direction of the recording paper. These developer supply grooves 8, 50.9 have one end connected to the supply pipe 11 provided with the electromagnetic valve 13 through a hole penetrating the back side of the development head surface, similar to the example shown in FIG. A recovery pipe 12 is connected to the other end and has a pump motor 14 provided through a through hole on the back side of a similar developing head.
It is connected to the. The atmospheric grooves 51 and 52 communicate with the atmosphere through a hole 53 penetrating through the back side of the developing head surface at the end on the side where the collection pipe 12 is connected in the width direction of the recording paper. These atmospheric grooves 51 and 52 extend from the gap between the developing head surface portion upstream in the recording paper transport direction and the recording paper surface (development head surface side) with respect to the developer supply groove 8 on the most upstream side in the recording medium transport direction. air from the gap between the developing head surface portion downstream in the recording paper transport direction and the recording paper surface (developing head surface side) to the developer supply groove 9 on the most downstream side in the recording paper transport direction. In addition to the inflow of air, the atmospheric groove 51
．． Developer supply grooves 8 and 50 are provided adjacent to each other.
．． 9, air flows in from the gap between the developing head surface portion on the side where the atmospheric grooves 51 and 52 are formed and the recording paper surface (developing head surface side), thereby causing air to flow into the corner portions etc. This strengthens the ability to remove residual developer. The recovery pipe 12 is connected to the atmosphere through a branch pipe 41 provided with a pressure gauge 45, a solenoid valve 43, and a negative pressure regulating valve 44 between the developing head 3C and the pump motor 14. An open branch pipe 42 is formed. This negative pressure adjustment valve 44 is configured so that when the negative pressure in the developer supply grooves 8 and 50.9 is too large, air sucked into the developer supply groove 850.9 is incorporated into the developer in the form of bubbles. If the negative pressure in the developer supply grooves 8, 50.9 is too small, the developer supply grooves 8, 50.9 may
Insufficient flow of the developer in the developer may cause uneven image density, and the negative pressure in the developer supply grooves 8 and 50.9 depends on the planar smoothness of the recording paper used. This is for adjusting the negative pressure within the grooves 8, 50.9 to an optimum level. The solenoid valve 43 communicates the negative pressure adjustment valve 44 with the collection pipe 12 when it is in the OFF state, and blocks the negative pressure adjustment valve 44 from the collection pipe 12 when it is in the ON state. This is to turn it on when recovering the developer, thereby preventing air from being introduced from the branch pipe 44 and increasing the developer recovery power. [0018] In the above configuration, the portion of the recording paper (hereinafter referred to as recording paper) that has already been fed out is connected to the electrostatic recording heads 2 and 3.
It extends above the book developing heads 3C, 3M, and 3Y, and waits for the start of the recording operation with its leading end sandwiched between the drive roller 4 and the pinch roller 5, and assumes a standby state. In this standby state, all the developing heads 3C, 3M, 3
Y is located at a standby position spaced below the recording paper transport path. The recording operation is started after the data processing of recorded information received from an information processing device (not shown) is completed, and the developing head 3C has been moved upwardly to a developing position where the developing head surface is close to the recording paper conveyance path. Developer supply groove 8, 50.9
A developer is supplied from a developer tank 6 containing a cyan developer for the developing head 3C to the developer head 3C, and the recording paper is conveyed by the rotation of the drive roller 4 and the like while the developer is circulated between the two. As a result, an electrostatic latent image is recorded on the recording paper on the electrostatic recording head 2, and the recording paper continues to be conveyed while developing this electrostatic latent image on the developing head 3C. When the development of the electrostatic latent image by the cyan developing head 3C is completed, the cyan developing head 3C is moved to the lower standby position, and the drive roller 4 etc. are rotated in the reverse direction to transfer the image area of the recording paper to the recording head again. 2 Return to top. Next, the formation of electrostatic latent images for magenta and yellow, the vertical movement of the developing head,
Then, the recording paper is conveyed in the same manner as in the case of cyan, and color development is performed. The recording paper, which has completed the final yellow development and has passed through the development head 3Y, continues to move forward, and just before the leading edge of the color developed image passes through the cutter 6, the cutter 6 is rotated and the recording paper is The remaining part of the leading edge is cut off, and immediately after the trailing edge of the color developed image passes through the cutter 6, the cutter 6 is driven to rotate to cut the recording paper, and then the developing head 3Y is retracted to the lower standby position and the process is continued. The recording paper on which the developed image has been formed is ejected from the machine by the rotation of the driving roller. [0019] In the development using 3C, 3M, and 3Y for each development described above, both electromagnetic valves 1342 are turned OFF and the pump motor 14 is turned ON. Thereby, the developer enters the developing head 3 from the developer tank 10 via the supply pipe 11, and is supplied to the developer supply grooves 8, 50, 90 from the liquid inlet hole. The developer flowing through the developer supply grooves 8, 50.9 and used for development enters the recovery pipe 12 from the liquid outlet hole and is returned to the developer tank 10 via the pump motor 14. During this development, the recording paper is attracted to the developer supply grooves 8, 50.90, and negative pressure is generated in the developer supply grooves 8, 50.9. This negative pressure is regulated by adjusting the amount of air taken in by a negative pressure regulating valve so that recording paper conveyance and development can be carried out properly. Each time the development of each color using each development head 3C, 3M, and 3Y is completed (every time the developed image passes the development head in use), both solenoid valves are turned on with the drive roller 4, etc. and the pump motor turned on. is turned off for a certain period of time to increase the negative pressure in the developer supply groove 8. As a result, the developer supply groove 8. ．． 50
．． In addition to collecting the developer present in the corners of 9 and inside them, 1. When finally stopping the supply of developer from the developing head to the transfer paper surface (the state in which the developing head is in the operating position where it contacts the recording paper) to stop the pump motor 14, or
Or, when the developing head is retracted downward while the pump motor 14 remains in the ON state), excessive developer is prevented from remaining on the recording paper. [0020] Next, an explanation will be given of the operation when a recording paper jam occurs during development. If a paper jam occurs during the developing operation, the rotation of the drive roller 4 etc. is stopped and the pump motor 14 is simply turned off.
If only F is used, the above-mentioned operation to prevent developer from remaining on the recording paper after development is not performed, so the developer supply grooves 8 and 5 when the drive roller etc. are stopped are not carried out.
0.9, there is a possibility that a large amount of developer may adhere to the recording paper, staining the conveyance system such as the drive roller 4, or staining the operator's hands and clothes. Especially when retracting the developing head to the standby position below the recording paper,
At the moment when the developing head surface and the recording paper are separated, a large amount of developer adheres to the recording paper. Therefore, in this embodiment, when paper clogging occurs during development, the developer is prevented from remaining on the recording paper to the extent that it contaminates the conveyance system and the like. [0021] Control for this purpose will be specifically explained using FIGS. 11 and 12. First, in a situation where no paper jam has occurred, the first to thirteenth steps are executed to perform the image recording operation described above. Note that the flowchart in FIG. 1 shows the case of monochromatic image recording using one developing head. If the recording paper becomes jammed during development,
The paper jam processing from the 6th step to the 20th step is executed. In this paper jam handling process, first, in the 14th step, the conveyance motor that rotates the drive roller 4, etc. is turned off to stop the conveyance of the recording paper, and in the 15th step, the recording head 2 (write head) is turned off. 0FFL, both electromagnetic valves 13 and 43 are closed in the 16th step (valve-1, valve-2 closed). By closing this electromagnetic valve 13, the supply of developer from the developer tank 10 to the developing head is stopped, and since the electromagnetic valve 43 is also closed, the negative pressure inside the developing head becomes higher than during development. The developer in the developer supply grooves 8 and 509 is collected into the developer tank 10. Also, in the 17th step, the paper jam is displayed on the display on the operation unit. Next, in an 18th step, a predetermined period of time is waited for. This predetermined time t
The time required to collect the developer in the developer supply groove is determined in advance through actual experiments. After this predetermined time t has elapsed, the pump motor 14 is turned off in a 19th step.
FF, and in the 20th step, the developing head is retracted to the lower standby position. [0022] The above embodiment deals with the case where a paper jam occurs during development, but if the outer cover is opened,
It is desirable to perform a similar operation when stopping the conveyance of recording paper in the event of an abnormality in the conveyance drive system or signal system, or in the case of a copy interruption signal generated by an operator's operation. In addition, if there is a copy interruption signal due to a signal system abnormality or an operator's operation, the recording paper part that was being developed is often left in the machine, so the above operation will prevent the paper from being transported to the recording paper. Even if the adhesion of developer to the extent that it stains the system etc. can be removed, the portion of the recording paper with some amount of adhesion of developer remaining must be used for the next image recording when the recording operation is resumed. There is a risk of it being stored away. In order to avoid this, if you stop transporting the recording paper during development due to such reasons, first drive the area where such stains may occur when restarting the recording operation. It is desirable to rotate the rollers 4 and the like to convey the paper, and when it passes the cutter 6, drive the cutter 6 to cut it off, so that it is not used for the next image recording. [0023] As described above, according to the present invention, the amount of air flowing into the developer supply groove after development is made larger than that during development, thereby reducing the amount of air inside the developer supply groove. The developer remaining at the corner formed by the upper side surface and the recording medium can also be quickly removed, so if the recording medium continues to be transported during this period, the developer remaining at the corner etc. will be removed from the recording medium. However, the length of the portion where the stain occurs in the recording medium conveyance direction can be made much smaller than that of the conventional method (for example, the portion A in FIG. 7). (For example, the part B in FIG. 7) has an excellent effect. Further, a plurality of developing heads to which developer solutions of each color are supplied are selectively brought to a developing position facing the recording medium conveyance path, and the recording medium is conveyed back and forth across the developing position to perform color development. Even in this case, since the length of the dirty portion of the recording medium in the recording medium conveyance direction is small, there is no need to secure an extra reciprocating conveyance width, and the color development time can be shortened. Furthermore, regardless of whether the developing device is a monochrome developing device or a color developing device, the developing head is moved between a developing position facing the recording medium transport path and a standby position separated from the developing position.
After the development is completed, the developer remaining at the corner is removed, so there is no risk of staining the recording medium when it is moved to the development position for use again, and there is no need to worry about staining the recording medium. There is no risk of contaminating the [0024] When a situation occurs in which the recording medium is stopped during development, the negative pressure control means is operated for a certain period of time after the valve control means switches the valve to cut off the developer supply path. continues to drive the negative pressure generating means, thereby suctioning and removing the developer remaining at the corner formed by the upper inner surface of the developer supply groove and the recording medium. Even when such a situation occurs, a large amount of developer does not remain attached to the recording medium, and it is possible to prevent staining of the conveyance system and the operator's hands and clothes.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an electrostatic recording type image forming apparatus that employs a liquid developing device according to a first embodiment.

2(a) is a perspective view of the developing head of the liquid developing device of FIG. 1, and FIG. 2(b) is a central sectional view of the developing head of FIG. 2(a) viewed from the earthy side.

FIG. 3 is a flowchart illustrating the operation of the liquid developing device according to the first embodiment.

FIG. 4 is a flowchart illustrating the operation of the liquid developing device according to the second embodiment.

FIG. 5 is a timing chart illustrating the operation of the liquid developing device according to the second embodiment.

[Figure 6] FIG. 2 is a central sectional view of a developing head of a conventional liquid developing device.

[Figure 7] FIG. 3 is a diagram showing the occurrence of stains on electrostatic recording paper.

FIG. 8 is a schematic configuration diagram of an electrostatic recording color image forming apparatus employing a liquid developing device according to a third embodiment.

9 is a schematic configuration diagram of a developing device equipped with the cyan developing head of FIG. 8. FIG.

101 is a sectional view taken along line AA of the cyan developing head in FIG. 9; FIG. 11 is a timing chart illustrating the operation of the color image forming apparatus of FIG. 8. FIG.

12 is a flowchart illustrating the operation of the color image forming apparatus of FIG. 8. FIG.

[Explanation of symbols]

3 Developing head 3C cyan developing head 3M magenta developing head 3Y Yellow developing head 8.9.50 Developer supply groove 10 Developer tank 11 Supply pipe 12 Recovery pipe 13.43 Solenoid valve 14 Pump motor 44 Negative pressure regulating valve 45 Pressure gauge 51.52 Atmospheric groove

[Document base]

drawing

[Figure 1] open half 1″?381 (1/) Sign spread flat 1zJ251 (18)

[Figure 5]

[Figure 6]

[Figure 7] IM Ming Sign spread flat 1Za81 (?U)

[Figure 10]

[Figure 11]

Claims (3)

[Claims] 1. A liquid developing device that develops an image to be developed on a recording medium by filling a developer supply groove extending in the width direction of the recording medium provided on a developing head surface facing a recording medium transport path with a developer. A liquid developing device characterized in that the amount of air that flows into the developer supply groove from the gap between the head surface and the recording medium after the completion of development is made larger than the amount of air that flows during development. 2. A developing head having a developer supply groove extending in the width direction of the recording medium on the developing head surface facing the recording medium transport path, a developer tank containing the developer, and a developer supplying groove from the developer tank. A means for forming a developer supply path to the developer supply groove, a means for forming a developer recovery path from the developer supply groove to the developer tank, and a means provided in the developer recovery path to generate negative pressure in the developer supply groove. a negative pressure generating means, which supplies the developer to the developer supply groove by generating a negative pressure in the developer supply groove when the developer supply groove is blocked by the recording medium; In a liquid developing device that fills a developer supply groove with a developer to develop an image to be developed on a recording medium, a valve that switches a developer supply path between a communicating state and a blocked state, and a valve control that controls switching of the valve. means and a negative pressure control means for controlling the driving of the negative pressure generating means, and after the completion of development, the valve control means switches the valve to cut off the developer supply path, and then the negative pressure is controlled for a certain period of time. A liquid developing device characterized in that the pressure control means continues to drive the negative pressure generation means. 3. When a situation occurs in which conveyance of the recording medium is stopped during development, the valve control means switches the valve to shut off the developer supply path, and then the 3. The liquid developing device according to claim 2, wherein the negative pressure control means continues to drive the negative pressure generating means.