JPH03296082A - Roller type developing device - Google Patents

Abstract

PURPOSE:To simplify constitution and to produce a small-sized device by setting a gap between the protruding outer periphery on the developing liquid surface of a developing roller and the inner surface of an airtight case body, so that the width of the gap of the downstream side is narrower than that of the upstream side, while viewing the gap in the rotational direction of the developing roller to make a slit- shaped opening part as a base point. CONSTITUTION:The gap between the protruding outer periphery on the developing liquid surface of the developing roller 30 and the inner surface of the airtight case body 25 is set so that the gap width (t) of the downstream side is narrower than the gap width T of the upstream side, as the slit-shaped opening part 29 is taken as the base point and the gap is viewed in the rotational direction of the developing roller 30. Therefore, air current taken in from the slit shaped opening part 29 as leakage air flows in the part (t) at high speed, and this high speed air current acts as an air doctor blade removing the developing liquid of the surface of the developer roller 30. On the other hand, the wide gap T is present on the upstream side of the slit-shaped opening part 29, so that the speed of the leakage air flowing therein is slow, and the developing liquid layer of the outer periphery of the developing roller 30 is carried without acting on a development acting part. Thus, the constitution is simplified and the small-sized device can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a developing device applied to an electrostatic recording device, and particularly to a developing device that circulates a developing solution through a developing head using negative pressure suction means, and The present invention relates to a roller type developing device that develops an electrostatic latent image on a recording medium by rotating a developing roller that is provided on its outer peripheral surface so as to be able to carry a developer.

[Prior Art] A rotatably supported developing roller is arranged opposite to a recording medium on which an electrostatic latent image is formed, with a small gap therebetween.
A developing device configured such that by rotating the developing roller with at least a portion of the developing roller immersed in a developer, a developer layer supported on the surface of the developing roller acts on the electrostatic latent image to perform development. The equipment. For example, JP-A-60-28
No. 678 (USP No. 445833) and the like.

Figure 6 is a diagram quoted from the same publication. In the same figure,
1 is a tray, 2 is a developing roller, 3 is a doctor blade,
4 is a backup roller, 5 is a recording medium such as recording paper, 8
9 is a developer supply port, 9 is a developer discharge port, 10 is a wiper roller, and G is a gap in the developing action area.

A gap G between the developing roller 2 and the recording medium 5 is set by a backup roller 4 to 0.1 to 0.5 mm. The developing roller 2 rotates in the direction of the arrow at a high speed of several hundred to several thousand revolutions per minute.

The developer poured from the developer supply port 8 is placed above the doctor blade 3, and due to its viscosity, the developer roller 2
The material is bound and supported on the surface of the material. The developing solution layer supported on the surface of the developing roller forms a reservoir in the developing area and acts on the electrostatic latent image on the recording medium 5. Development is thus performed. The recording medium 5 is conveyed to the right in the figure. Excess developer adhering to the surface of the recording medium 5 that has passed the position of the developing roller 2 is wiped off by the wiper roller 10. After the development is completed, the backup roller 4 is pulled up and raised by the plunger 6. Therefore, the recording medium 5 is separated from the developing roller 2. At this time, the excess developer remaining on the recording surface is released onto the recording medium. It is spread thinly.The recording surface of the recording medium 5 is thus dried, and a series of developing operations is completed.

The roller type developing device having the above structure has the advantage of not only being able to create a strong potential gradient necessary for toner electrophoresis, but also being able to efficiently send the developer to the developing area. However, a liquid layer with uneven density is formed on the surface of the developing roller, depending on the state of the electrostatic latent image and corresponding to the amount of toner consumed. For this reason, the liquid layer is scraped off with a doctor blade 3 to constantly renew the liquid layer on the surface of the developing roller.

Further, in the conventional apparatus having the above configuration, a large amount of surplus developer adheres to the recording surface of the recording medium 5 that has passed through the developing section including the developing roller 2. A wiper roller 10 is provided to remove this excess developer.

For this reason, the device shown in FIG. 6 has the disadvantage that the overall configuration is complicated and large. The contact type blade increases the rotational load on the developing roller 2, and also has the problem of abrasion and deterioration. Furthermore, after the development is completed, the developer remaining on the surface of the recording medium is spread on the recording medium with the wiper roller IO and dried, so the portion of the recording medium where the developer is spread is applied. And the developer is wasted. Moreover, since the developer solvent evaporates into the air, there are problems such as environmental pollution.

In order to solve the above-mentioned latter problem, the present inventor proposed the following in Japanese Patent Application No. 01-284248, which is the applicant's earlier application.
We proposed a roller-type developing device that uses a negative pressure suction type developer circulation system.

Figures 7 and 8 are figures quoted from the above application;
FIG. 7 is a diagram showing a combination of a longitudinal sectional front view of the developing head cut along the longitudinal direction and a diagram of the piping connections of a developer reservoir and a suction pump connected to the developing head. FIG. 8 is a longitudinal side view of the developing head taken along a direction perpendicular to the longitudinal direction.

In FIGS. 7 and 8, P is a recording medium such as recording paper, 11 is an airtight box, 12 is a developing roller, 12a,
12b is a roller shaft, 12c is a roller drive shaft, 13 is a slit-shaped opening formed on the top surface of the box, 14 is a hollow part of the box, 15 is a developer supply port, 16 is a developer discharge port, 17
18 is a developer storage, 18 is a suction pump, 19a to 19c are piping tubes, 20 is a slit-like suction drying groove, 21 is a separation groove, and 22 is a communication hole. Note that the slit-shaped opening 1
The length of the recording medium P is set to be slightly shorter than the width of the recording medium P.

Now, the recording medium P on which the electrostatic latent image has been formed is placed on the slit-shaped opening 13 with the recording surface facing downward, and the slit-shaped opening 18 is covered with the recording medium P. Suppose you run . Then, the recording medium P seals the slit-shaped opening 13 due to the negative pressure effect. As a result, the negative pressure within the hollow portion 14 of the airtight box body 11 increases, and the developer is sucked up from the developer reservoir 17 by the suction force of the negative pressure. This sucked up developer is transferred to piping tube 1
9a, supply port 15. flows into the hollow part 14 through
The whole or lower part of the hollow part 14 is immersed. After that, the developer outlet 16. Piping tube 19b, suction pump 18. The liquid is returned to the developer reservoir 17 through the piping tube 19c.

When the developing roller 12 is rotated while the recording medium P is being conveyed, the developing solution adheres to the surface of the developing roller 12 with viscosity and reaches a developing action area formed at the center of the slit-shaped opening 13 . The electrostatic latent image is thus developed. Note that since negative pressure is always acting on the slit-shaped opening 13, excess developer is removed by suction from the surface of the recording medium P passing over the slit-shaped opening 13. Therefore, the surface of the recording medium P that has passed over the slit-shaped opening 13 is normally in a dry state. However, if the suction effect at the slit-shaped opening 13 weakens, the above-mentioned drying effect will decrease. Therefore, to compensate for this, dedicated slit-shaped suction drying grooves 20 and separation grooves 21 are provided.

The slit-shaped suction drying groove 20 communicates with the negative pressure section via a small diameter communication hole 22. Therefore, even if surplus developer remains on the recording surface of the recording medium P, this surplus developer is suctioned and removed by the slit-shaped suction drying groove 20, so that the recording medium P becomes almost completely dry. .

In an apparatus having such a configuration, the excess developer is recovered, so that the wiper roller 1O as shown in FIG. 6 is not required. Moreover, there is no problem of the developer solvent being vaporized and dissipated into the air. Therefore, there is an advantage that a compact and highly convenient developing head can be realized.

However, in the apparatus shown in FIGS. 7 and 8, since the slit-shaped opening 13 is under negative pressure, the recording medium P is sucked and deflected, causing a gap between the developing roller 12 and the recording medium P. The problem was that it was difficult to maintain the gap.

[Problems to be Solved by the Invention] As described above, the device shown in FIG. 6 has the drawback that the overall configuration is complicated and large. Moreover, there is a problem that the contact type blade increases the rotational load on the developing roller 2 and also deteriorates due to wear. Furthermore, after the development is completed, the developer remaining on the surface of the recording medium is spread on the recording medium with the wiper roller 10 and dried, so the portion of the recording medium where the developer is spread and Developing solution is wasted. Moreover, since the developer solvent evaporates into the air, there are problems such as environmental pollution.

Furthermore, in the devices shown in FIGS. 7 and 8, the wiper roller 10 shown in FIG. 6 is not needed because surplus developer is recovered. Moreover, there is no problem of the developer solvent being vaporized and dissipated into the air. Therefore, there is an advantage that a compact and highly convenient developing head can be realized. However, since the slit-shaped opening is under negative pressure, the recording medium is sucked and deflected, making it difficult to maintain the gap between the developing roller and the recording medium. In order to improve this point, it is convenient to form an uneven portion on the surface of the developing roller to maintain the developing gap. However, if such measures are taken, there is a problem that it becomes difficult to apply the doctor blade 3 as shown in FIG.

Note that the doctor blade 3 shown in FIG.
By installing the present invention in the apparatus shown in the figure, it is possible to realize an apparatus that has the advantages of both apparatuses, especially an apparatus that has advantages in uniform development, speeding up, and prevention of fogging in non-image areas. However, a problem arises in that the structure inside the small and simplified airtight box 11 becomes complicated and large. In addition, when the developing head constructed as described above is to be realized as a developing head having a long developing width such as a color electrostatic plotter, special measures are required to uniformly support the blade.

Another problem is that if the blade housed in the airtight box 11 is damaged, it is extremely difficult to replace it.

SUMMARY OF THE INVENTION An object of the present invention is to provide a device that does not require a contact type doctor blade or wiper roller, has a simple structure, can be manufactured in a small size, and can remove the uneven liquid phase on the surface of the developing roller, thereby achieving good development. As well as being able to
It is an object of the present invention to provide a roller type developing device which has advantages such as being able to recover excess developer and having no problem of the developer solvent being vaporized and dissipated into the air.

[Means for Solving the Problems] In order to solve the above problems and achieve the objectives, the present invention takes the following measures as basic means.

That is, as a developing head, a slit-shaped opening is provided on the top surface that serves as the recording medium transport surface, and a developer supply port and a developer discharge port are provided at the bottom.
An airtight box whose other parts have an airtight structure, and an outer circumferential surface that is capable of supporting a developer so as to face the recording medium with a small gap through a slit-like opening of the airtight box. The developing roller is arranged facing the slit-shaped opening and is rotatably driven by a drive source, the outer circumferential surface of the developing roller protruding above the developer surface and the inner surface of the airtight box. When viewed from the slit-shaped opening in the direction of rotation of the developing roller, the gap width T on the downstream side is set to be narrower than the gap width T on the upstream side. .

[Effects] As a result of taking the above measures, the following effects occur. On the downstream side of the slit-shaped opening, a narrow gap exists between the outer peripheral surface of the developing roller protruding above the liquid surface and the inner surface of the airtight box.

Therefore, the airflow that is taken in as a fair through the slit-like opening flows through this portion at high speed.

This high-speed airflow acts as an air doctor blade that removes the developer from the surface of the developing roller. on the other hand,
On the upstream side of the slit-shaped opening, a wide gap exists between the outer peripheral surface of the developing roller protruding above the liquid level and the inner surface of the airtight box. Therefore, the flow rate of leak air flowing here is slow. Therefore, the developer layer on the outer circumferential surface of the developing roller is transported to the developing section without any hindrance.

[Embodiment] Fig. 1 is a diagram showing a first embodiment of the present invention, showing the head structure by cutting the developing head along the longitudinal direction, and the piping connection state of related members connected to the developing head. FIG. FIG. 2 is a cross-sectional view showing the central portion of the developing head in the same embodiment taken along a direction perpendicular to the longitudinal direction.

In FIGS. 1 and 2, 25 is an airtight box body, 25a
is a central member, 25b and 25c are end sealing members, 26 is a developer supply port, 27 is a developer discharge port, 28 is a liquid level regulation end,
29 is a slit-shaped opening, 30 is a developing roller, 31 is a roller drive shaft, 32 is a roller support shaft, 33 is a bearing bush, 34 is a sill ring, 35 is a bearing, 36 is a bearing stop, 37a, 37b are side seals, 38 is a developer storage, 39 is a suction pump, 40a, 40b.

40c is a piping tube.

The airtight box body 25 has bottomed cylindrical end sealing members 25b and 25C integrally joined to both ends of a gutter-like central member 25a having a slit-like opening 29 on the upper end surface. . The developing roller 30 is rotatably housed in the airtight box 25.

That is, the roller support shaft 32 of the developing roller 25 is rotatably supported by a bushing 33, and the roller drive shaft 31 is rotatably supported by a bearing 35.

End sealing member 2 enclosing the developing roller shaft 31, 32
There is a relatively large space inside 5b and 25c. Therefore, a developer supply port 26 is attached to the lower part of the end sealing member 25b. Further, a developer discharge port 27 is attached to the lower part of the end sealing member 25c. The upper end portion of the developer discharge port 27 is extended to a slightly higher position, and the upper end surface thereof serves as a liquid level regulating end 28.

The seal ring 34 is used to prevent liquid leakage through the gap between the outer peripheral surface of the roller drive shaft 31 and the inner peripheral surface of the bearing 35, and to maintain airtightness. Side seal 37
a and 37b are provided to prevent the air taken in from the slit opening 29 from flowing through these portions, but if this gap is narrow, they may not be provided.

As shown in FIG. 2, an inner surface of the airtight box central member 25a on the downstream side when viewed from the rotational direction Q of the developing roller 30;
There is a gap 1t-0 between the outer peripheral surface of the developing roller 30 and the outer peripheral surface of the developing roller 30.
, a minute gap of about 1 to 0.5 mm is formed. This minute gap is for forming a high-velocity airflow in this part. On the other hand, there is a gap width T - 1.0 mm or more between the inner surface of the airtight box central member 25H on the upstream side as seen in the rotation direction Q of the developing roller 30 and the outer peripheral surface of the developing roller 30. A relatively large gap has formed. This gap is
The purpose is to form an air current with a relatively slow flow rate in this portion so that the developer carried on the surface of the developing roller is not removed by the air current flowing here.

If the gap between the roller end and the airtight box body at both ends of the developing roller 30 is wide, a large amount of leak air flow path is formed in this part, and the air flow passing through the gear knob t is reduced, which reduces the effect of the present invention. To avoid this, either set the end gap narrower or close the side seals 37a, 37
b.

From the developer storage 38 to the developer supply port 26, from the discharge port 27 to the suction pump 39, and from the suction pump 39 to the developer storage 3
The piping tube 4 is connected so as to form a developer circulation path leading to the
0a, 40b, and 40c are arranged. The length of the slit-like opening 29 is slightly shorter than the width of the recorded P. When the suction pump is operated with the recording paper P covering the slit-shaped opening, the recording paper P is attracted onto the slit-shaped opening 29 and the opening 29 is sealed due to the negative pressure action of the suction pump. Stop. However, the slit-shaped opening 2
Since the upper surface of the airtight box existing around 9 has some unevenness, near leakage occurs due to the unevenness.

The leaked air is taken into the airtight box body 25 through the slit-shaped opening 29.

When the slit opening 29 is sealed, the inside of the airtight box becomes negative pressure. Due to the action of this negative pressure, the developer reservoir 38
The developer inside is sucked up and flows into the airtight box body 25. When the developer level inside the airtight box body 25 rises and exceeds the liquid level regulation end 28 for a while, the developer flows out from the discharge port 27, and the leak air that flows in through the slit-shaped opening 29 flows out, and the inflow leak air and the discharge are discharged. At the liquid level position where the amount of leaked air becomes equal, the liquid level stops rising and a steady state is reached. In a steady state, the gap t is set so that it is on or in contact with the liquid surface.

When the developing roller is rotated in the direction of arrow Q, the developing solution is adhered to and carried on the surface of the developing roller 30 due to its viscosity, and is carried to the slit-shaped opening 29 . Then, a developer pool is formed at the position where the recording paper P is closest to the developing roller 30 due to its surface tension. The charged toner particles are electrophoresed based on a strong potential gradient created by electrostatic charges on the surface of the recording paper between the developing roller 30 and the recording paper P, thereby performing development.

The liquid layer on the surface of the developing roller 30 that has passed through the developing area includes areas where the toner concentration has decreased, areas where the toner concentration has not changed, and areas where the toner concentration has increased. The area where the toner density has decreased corresponds to the electrostatic latent image, and occurs when most of the toner is consumed. A region where the toner density does not change is a region that does not correspond to an electrostatic latent image, and occurs when toner is not consumed at all. The area where the toner concentration has rather increased is
This occurs when a portion does not correspond to an electrostatic latent image, has not consumed any toner, and, for example, there is a large solid image area nearby. In other words, the charges in the conductive layer of the recording paper released during development change the potential of the conductive layer, thereby concentrating the toner and causing it to bunch up.

When these liquid layers pass through a minute gap of t formed between the developing roller 30 on the surface of the developing solution and the inner wall of the airtight box body 25, the leak air flow with a high flow rate flows therethrough. scraped off by. The scraped liquid layer then flows into the developer and diffuses. Further, the developer on the surface of the developing roller 30 is replaced by the diffusion effect of the air flow generated near the liquid surface.

Therefore, it is preferable that the position of the minute gap having a width of t be somewhat close to the liquid surface rather than a position that is too far above the liquid surface.

Even if a part of a small gap with a width of t is below the liquid level, if the end of the developing roller 30 is sealed, the development will be carried out in the gap area due to the action of a strong leak air flow. There is no problem because the action of removing the liquid occurs.

As will be described later, if the small gap is used only for the purpose of removing the developer from the surface of the developing roller 30 after development is completed, the purpose can be achieved even if the gap is located sufficiently far above the liquid level. .

The leak air flow taken in from the slit opening 29 also passes through a path upstream of the slit opening 29 . However, since the gap of width T provided on this side is relatively large, the flow velocity is not very high. Therefore, no acting force is generated to the extent that the developer is scraped off from the developing roller 30.

The amount of leaked air and the height of the developer solution level can be controlled by using a suction pump with a constant displacement capacity, such as a vane pump. That is, if the diameter of the developer supply port 26 is made smaller, the amount of developer supplied decreases, and the amount of near leak increases accordingly, so that the level of the developer decreases somewhat.

In this way, the amount of leak air necessary to remove the developer from the surface of the developing roller can be secured.

As mentioned in the explanation of the above-mentioned Japanese Patent Application No. 01-2B424B, or as shown in FIGS. 1 and 2, in a suction circulation type roller type developing device, the recording paper is Since the developing roller is deflected by suction, it is quite difficult to stably maintain a small gap between the developing roller and the recording paper P. In order to solve this problem, it is convenient to provide minute irregularities on the surface of the developing roller, hold the developer in the recesses, and bring the recording paper into contact with the surface of the roller, that is, on the above-mentioned projections. . However, in a developing roller provided with such an uneven portion, a doctor blade as shown in FIG. 6 is extremely inappropriate because it does not act on the recessed portion.

The present invention can effectively operate even on a developing roller having such uneven portions as described below, and achieve the object.

FIGS. 3 and 4 show a second example in which the present invention is applied to a roller type developing device equipped with a developing roller having an uneven surface.
It is a figure showing an example. Note that this embodiment is an embodiment in which improvements have also been made to the gap forming portion and the slit-like opening.

FIG. 3 is a sectional view taken in a direction perpendicular to the axial direction of the roller of the developing head. Reference numeral 25a indicates an airtight box body, 41 indicates an uneven developing roller, 42 indicates a gap forming member, 43 indicates a slit-shaped opening member, and 29 indicates a slit-shaped opening.

The developing roller 41 shall have a shallow unevenness of about 0.1 to 1 mm, more preferably about 0.3 to 0.5 mm, on its surface, and if it is made by groove processing, the groove width of about 1 mm is knurled, It is processed into a shape such as a spiral or a groove parallel to the roller axis. Such processing can be easily carried out by cutting, extrusion using a die, or cutting.

The gap forming member 42 is manufactured separately from the airtight box 25 and supported by the box. In the case of the uneven roller 41, the gap forming member 42 can be pressed against the surface of the developing roller, and if it is made of a compressed elastic material such as rubber or foamed elastomer, the developing roller 41 and the gap forming member 42 can come into contact with each other. There is no risk of damage to both, even if
It's convenient.

Further, in the illustrated example, the slit-shaped opening 29 is formed by adhering a member 43 made of a material that is hard and difficult to deform, such as a stainless steel thin plate, to the upper surface of the window of the airtight box body 25. According to this configuration, since the thickness of the plate forming the slit-shaped opening 29 can be reduced, the developing roller 41
By keeping the diameter constant, it is possible to narrow the width of the slit-like opening 29, and it is possible to prevent the recording medium from falling heavily onto the surface of the developing roller. Further, the upper surface of the developing head slides with the recording medium in contact with it due to negative pressure, which acts to wear out the head surface, but this wear can be reduced.

Furthermore, if the surface of the developing head is rough during the process in which the surface of the recording medium slides on the upper surface of the developing head, streaks may be formed on the surface of the recording paper that is strongly rubbed. Therefore, it is necessary to process the surface to a mirror finish, but in the case of a thin plate like No. 43, it is convenient because the material is supplied with a mirror finish. The slit-like opening 29 can be easily formed by punching or laser processing.

When the developing roller 41 is rotated in the direction of the arrow during development, the increased developer is mainly supported within the grooves of the developing roller 41 and reaches the developing action area. In the developing area, the recording medium is drawn inside the slit-shaped opening 29 by negative pressure and passes through a position supported by the developing roller 41 at the 5th minute. The toner in the developer filling the recesses makes a large contribution to the progress of development. Therefore, the developing gap is determined by the depth of the groove of the developing roller 41, and an extremely stable state can be maintained. When the roller surface that has passed through the developing area reaches the position of the gap forming member 42, the developer is sucked out from inside the groove by the action of high-speed airflow, or is stirred by the high-speed airflow generated near the developer surface. The action replaces the developer in the groove.

By the way, in order to remove the developing solution from the roller surface by the action of the air current as described above, it is more suitable to have the cross section of the groove in a shape without edges on the bottom surface, as shown in FIG.

As explained in the first and second embodiments above, this apparatus has a low load, a high developing ability, and the recording paper portion that passes through the developing section is dry, resulting in less developer consumption. It has advantages. However, there is a problem in that the developer remains attached to the portion of the recording paper that is in contact with the developing head after the development is completed. By removing this, the separate developer removing means described above can be made unnecessary.

FIG. 5 is a time chart diagram illustrating an embodiment that takes the above points into consideration. In the figure, the horizontal axis shows the passage of time; ing.

In the developing step X, the suction pump is operated differentially, and the developing roller rotates in a direction in which its surface escapes from the liquid level, passes through the developing action area, passes through a narrow gap area, and returns to below the liquid level. Further, the recording medium is transported such that the surface on which the electrostatic latent image is formed passes through a developing portion one after another.

When the development process X is completed, the process moves to a liquid pool removal process Y. The suction pump continues to rotate, and the direction of rotation of the developer roller is switched to the opposite direction. When the developer roller leaves the liquid surface, it first passes through a narrow gap to remove the developer from its surface.

After that, it reaches the developing area, and the developer in the pool formed at the closest position between the developing roller and the recording medium is attached to its surface and carried away. If the recording medium is moved during this time, the recording medium will also have the effect of removing the developer in the puddle, so the puddle will disappear more quickly, but the recording medium will be wasted accordingly. Therefore, the recording medium may be stopped.

Even if the liquid pool disappears, the recording medium remains wet, so the suction pump continues to operate to dry it, and the recording medium is moved to allow the wet surface to escape from the slit opening. During this time, since no developer is attached to the surface of the developing roller, the developing roller may be rotated or may be stopped. When the wetting of the recording medium is removed by the negative pressure suction action of the slit-shaped opening, all development-related steps are completed. In devices such as multi-pass color electrostatic plotters that move the recording medium back and forth to form overlapping images of different colors, the direction of movement of the recording medium after development is the same as that during development, as shown by the chain line. It is advantageous to reverse the direction to reduce wasted portions of the recording medium and time for rewinding the recording medium.

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 the Invention] As explained above, according to the present invention, there is no contact type doctor blade or wiper roller, the structure is simple and can be manufactured in a small size, and the uneven concentration liquid phase on the surface of the developing roller can be removed. It is possible to provide a roller type developing device which has advantages such as being able to perform good development, recovering excess developer, and eliminating the problem of the developer solvent being vaporized and dissipated into the air.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing a first embodiment of the present invention.
The figure is a diagram showing the head structure cut along the longitudinal direction of the developing head and the state of piping connections of related members connected to the developing head. FIG. 3 is a cross-sectional view taken along a direction perpendicular to the direction of the drawing. 3 and 4 are diagrams showing a second embodiment of the present invention,
FIG. 3 is a cross-sectional view of a developing head equipped with a developing roller having an uneven surface formed thereon, and FIG. S is a cross-sectional view showing a modified example of the developing roller. FIG. 5 is a time chart diagram for explaining a third embodiment of the present invention. FIGS. 6 to 8 are diagrams for explaining the prior art. 25... Airtight box body, 25a... Central member, 25b. 25c... End sealing member, 26... Developer supply port,
27...Drain port, 28...Liquid level regulation end, 29...
Slit-shaped opening, 30...Developing roller, 31...
Roller drive shaft, 32... Roller support shaft, 33... Bearing is a bush, 34 is a seal ring, 35... Bearing, 36... Bearing stop, 37a, 37b...
・Side seal, 38-9. Developing solution reservoir, 39... Suction pump, 40a40b, 40c... Piping tube. Figure 1

Claims (3)

[Claims] (1) A developer reservoir that stores a developer in which toner particles are dispersed, and a developer that acts on the electrostatic latent image formed on the recording surface of the recording medium by using the developer stored in the developer reservoir. In order to visualize images, a developing head has a slit-shaped opening on the top surface, and by operating with the slit-shaped opening of this developing head covered with a recording medium, a negative pressure suction effect is generated, and this negative pressure suction a suction pump that operates to suck up a developer from the developer reservoir and flow it through the developer head, and then circulate the developer back to the developer reservoir, the developer head A slit-shaped opening is provided on the top surface, which is the recording medium transport surface, and a developer supply port and a developer discharge port are provided at the bottom.
An airtight box whose other parts have an airtight structure, and an outer circumferential surface that is capable of supporting a developer so as to face the recording medium with a small gap through a slit-like opening of the airtight box. The developing roller is arranged facing the slit-shaped opening and is rotatably driven by a drive source, the outer circumferential surface of the developing roller protruding above the developer surface and the inner surface of the airtight box. A roller characterized in that the gap between the two rollers is set such that the gap width T on the downstream side is narrower than the gap width T on the upstream side when viewed in the rotation direction of the developing roller from the slit-shaped opening as a base point. type developing device. (2) In the roller type developing device according to claim 1, the surface of the developing roller is processed with an uneven portion, and the recording medium is conveyed in contact with the upper surface of the convex portion of the uneven portion. A roller type developing device characterized in that it is provided as follows. (3) In the roller type developing device according to claim 1, after the development is completed, the development roller is rotated in the opposite direction to that during development with the suction pump kept operating, and then the recording medium is conveyed. The roller type developing device is characterized in that the suction pump is driven and controlled so as to stop the operation of the suction pump.