JP3192443B2 - Liquid developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developing apparatus used in an image forming apparatus such as a copying machine of an electrophotographic system or an electrostatic recording system, a facsimile, a printer, and the like.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developing apparatus that performs development using a developing head disposed facing a conveyance path of a recording medium on which an electrostatic latent image or the like is formed.

[0002]

2. Description of the Related Art A liquid developing apparatus for developing an image to be developed on a recording medium by filling a developing solution flowing groove extending in a width direction of the recording medium provided on a developing head surface facing a recording medium conveying path with a developing solution. Are known, for example, from Japanese Utility Model Publication No. 52-25155 and Japanese Patent Application Laid-Open No. 61-179476. In a liquid developing device of this type, a negative pressure is generated in the developer circulation groove by driving a negative pressure generating means such as a pump motor while the developer circulation groove is closed by a recording medium such as electrostatic recording paper. The negative pressure causes the recording medium to be sucked into the developing head surface, thereby substantially closing the developing solution circulation groove, and allowing the developing solution in the developing solution tank to pass through a developing solution supply path forming means such as a supply pipe. The developer is supplied to the developer circulation groove, and the developer in the developer circulation groove is collected into the developer tank through a developer collection path forming means such as a collection pipe, and the developer is supplied to the developer tank and the developer circulation groove. By performing the above operation, the developing solution circulation groove is filled with the developing solution to perform a developing operation of an image to be developed such as an electrostatic latent image on the recording medium, and after the developing operation is completed, the driving of the pump motor is continued. The developer in the developer flow channel to the developer tank. Doing drained to. This draining is performed, for example, in a color image recording apparatus that reciprocates a recording medium and repeats electrostatic recording and liquid development for each color.
After completion of recording and developing of one color, in order to speed up the recovery operation of the recording medium, the developed toner image is kept in a non-contact state with the developing head and returned to high speed without disturbing the toner image. If the surplus developer is left on the medium, the recording portion is wetted to prevent a problem in forming a latent image. For example, JP-A-61-17947
Japanese Patent Application Laid-Open No. 6-31664 discloses that at the time of liquid removal, a flow path system is switched so that at least some of a plurality of grooves provided on a developing head surface are connected to the atmosphere. It is described that air is sent into another groove through a gap with a surface, and liquid is drained therefrom. Japanese Patent Application Laid-Open No. 61-179476 discloses that an atmosphere extending longer than the width of a recording medium and communicating with the atmosphere extends in a region of a developing head surface downstream of a developer circulation groove in a recording medium conveying direction. And a suction groove connected to the pump motor. During development, the developing solution flow groove is formed by an air flow or the like flowing into the suction groove over a partition wall between the atmospheric groove and the suction groove. There is disclosed a technique for removing excess developer liquid excessively adhering to the surface of a recording medium. However, this is only for removing the surplus liquid separately from the developer circulation groove.
Providing the air groove and the suction groove is not preferable because the size of the developing head is increased. Therefore, the present applicant previously provided the above-mentioned air groove between the developer circulation grooves, and thereby the excess development was performed by the air flow flowing from the air groove into the downstream developer circulation groove in the recording medium conveyance direction. An invention to remove the liquid was proposed.

[0003]

However, in the above configuration, the developer circulation groove for circulating the developer by using a negative pressure has both the functions of developing and removing the excess developer, while the groove in the atmosphere groove is provided. Is at atmospheric pressure, so during development,
From now on, the amount of air flowing into the developer circulation groove is too large,
There remains a problem that image density unevenness (spotted pattern) tends to occur in a low latent image portion (hereinafter referred to as a highlight portion) having a weak toner adhesion (suction) force. In addition, with the diversification of the market, liquid developing devices that can handle various recording media such as office paper, translucent vision for CAD, glossy paper, matte paper, and OHP transparent film for photographic printing paper have been developed. Is desired. However, development in close contact with the developing head surface, to remove the excess developer, in this type of apparatus, the surface roughness of the recording surface (according as smoothness) and get wet Re characteristics, does not impair the image quality, The conditions for proper removal of the excess developer change. Therefore, it is necessary to adjust the negative pressure when the recording medium is changed. The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to produce a non-uniform image density in a highlight portion and a sufficient surplus developer even during development. Removal (squeeze) is possible, and when the recording medium is separated from the developing head, liquid draining is completed in a short time so that there are no droplets on the medium, and various recording media (different surface roughness / smoothness of recording surface) It is an object of the present invention to provide a liquid developing apparatus having a small developing head having a groove, which can be easily adjusted and coped with.

[0004]

According to a first aspect of the present invention, there is provided a liquid developing apparatus having an opening in a developing head surface facing a recording medium conveyance path, and having an opening in a width direction of the recording medium. A developing head having a plurality of developing solution flow grooves extending therethrough, a developing solution tank for storing the developing solution, a developing solution supply path forming means from the developing solution tank to the developing solution flowing groove; Means for forming a developer recovery path to the liquid tank, and negative pressure generating means for generating a negative pressure in the developer circulation groove when the opening of the developer circulation groove is closed by a recording medium. A negative pressure is generated in the developer circulation groove while the opening of the developer circulation groove is closed with a recording medium, and the recording medium is sucked into the opening of the developer circulation groove and the developer is stored in the developer tank. The electrostatic latent image on the recording medium is developed by circulating That the liquid developing unit, the airflow groove negative pressure state between the plurality of developer circulation groove on the developing head surface provided, and the developer flow channel and the negative pressure generating means
, An air introduction adjusting means communicating with the atmosphere is provided . The invention of claim 2 is
An opening is provided on the developing head surface facing the recording medium transport path.
With a plurality of developer circulation grooves extending in the width direction of the recording medium
A developing head, a developing solution tank for storing the developing solution, and a developing device.
Means for forming a developer supply path from a liquid tank to a developer circulation groove
And a developer recovery path from the developer flow groove to the developer tank
Forming means and the opening of the developer circulation groove is closed by a recording medium.
The negative pressure in the developer flow groove
Pressure generating means, and the opening of the developer flowing groove has a recording medium
A negative pressure is generated in the developer flow groove with the
The recording medium is sucked into the opening of the image liquid circulation groove and the developer is
Is circulated from the developer tank to the developer flow groove.
And a liquid developing device for developing an electrostatic latent image on a recording medium.
Between the plurality of developer flow grooves on the developing head surface.
An air flow groove capable of communicating with air is provided, and the air flow groove is connected to the atmosphere.
Air flow during development and during drainage after development is complete.
Characterized in that a means for converting is provided. Ma
According to a third aspect of the present invention, there is provided the liquid developing apparatus according to the first or second aspect.
In the developing solution flow groove by the negative pressure generating means
The magnitude of the negative pressure generated during
It is characterized by providing a means to change between the time of extraction
It is. Further, the invention of claim 4 is based on claim 1, 2 or
In the liquid developing device of No. 3, the inner surface of the developing solution flow groove
It is characterized by having been subjected to an oil-repellent treatment.

[0005]

According to a first aspect of the present invention, an airflow groove in a negative pressure state is provided between a plurality of developer flow grooves on a developing head surface, and a pressure difference between the negative pressure developer flow groove and the airflow groove is reduced. Is smaller than at atmospheric pressure, thereby reducing the amount of air that flows from the airflow groove into the developer circulation groove through the gap between the developing head surface and the recording medium surface, thereby reducing the amount of airflow when the airflow groove is at atmospheric pressure. To prevent the occurrence of density unevenness in the paper. Further, at the time of draining the liquid, since the airflow groove is not completely sealed, an excess developer removing effect is also generated, and the liquid can be easily drained. Ma
Further, an air introduction adjusting means is provided between the developing solution circulation groove and the negative pressure generating means, so that the negative pressure can be easily adjusted corresponding to recording media having different surface characteristics. The invention according to claim 2 is provided with a means for changing the amount of air flowing between the airflow groove and the atmosphere between during development and at the time of liquid removal after completion of development,
During development, the amount of air flow is adjusted to a relatively low negative pressure in the airflow groove to remove excess developer that does not damage the image. This is to increase the effect of removing the excess developer by setting the inside of the groove to substantially the atmospheric pressure. The invention according to claim 3 is characterized in that the negative pressure
Large negative pressure generated in the developer flow groove by the
Change the size during development and when draining after development is completed
Means for maintaining a relatively low negative pressure in the airflow groove during development.
To remove the excess developer that does not damage the image.
When the liquid is drained after the development, the negative pressure in the developer
Is relatively large to remove excess developer.
To increase.

[0006]

FIG. 1A to FIG. 4 show a first embodiment of the present invention.
It will be described based on. FIG. 2 is a schematic configuration diagram of an electrostatic recording type color image forming apparatus that employs a liquid developing device, which is a developing solution processing device according to the present invention. First, an outline of the operation of the image forming apparatus will be described. In FIG. 2, an electrostatic recording paper (hereinafter, referred to as a recording paper) as a recording medium wound in a roll shape on a pay-out shaft 1 has already been paid out. Are the electrostatic recording head 2 and the four developing heads 3C, 3
It extends above M, 3Y, 3K, and waits for the start of a recording operation in a state where its tip is sandwiched between the driving roller 4 and the pinch roller 5, and then waits. In this standby state, all the developing heads 3C, 3M, 3Y, and 3K are at standby positions separated below the recording paper transport path. When the recording operation is started after the data processing of the recording information received from the information processing apparatus (not shown) is completed, the cyan developing head 3C is moved upward to a developing position where the developing head surface is close to the recording paper transport path. Then, a developer is supplied to a developer circulation groove 31 provided in the development head 3C from a developer tank 6C (see FIG. 1A) disposed below the development head 3C, and the developer is supplied between the two. And the drive roller 4 and the feed shaft 1 start rotating, and an electrostatic latent image is recorded on the recording paper on the electrostatic recording head 2, and the electrostatic latent image is transferred to the developing head 3 C. Continue conveying the recording paper while developing with. 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 feeding shaft 1 and the driving roller 4 are rotated in the reverse direction, so that the image portion of the recording paper is removed. It is returned to the recording head 2 again. Next, the formation of an electrostatic latent image for magenta, yellow , and black, the operation of raising and lowering the developing head, and the operation of transporting the recording paper are performed in the same procedure as in the case of cyan, and color development is performed. However, the final recording sheet passing through the developing head 3 K completed development of the black is a development may leave the forward, rotating the cutter 7 just before the tip of the color developed image passes through a cutter 7 rotary Then, the cutter 7 is rotated to cut the recording paper immediately after the trailing end of the color developed image passes through the cutter 7, and then the rotation of the feeding shaft 1 and the driving roller 4 is started. On the other hand, the developing head 3Y is retracted to the standby position below, and thereafter, the sheet-shaped recording paper is discharged onto a discharge tray (not shown) while rotating only the discharge roller pair 8.

Next, the liquid developing device will be described in detail. The liquid developing devices include three developing heads 3C, 3M, and 3Y using cyan, magenta, and yellow developing solutions, respectively.
A developing head 3K to use black developer for developing the及beauty black image, respectively, each developing head 3C, 3M, 3
A developer tank for storing the developer to be supplied to Y and 3K (only the black developer tank 6K is shown in FIG. 2) and one of these developing heads 3C, 3M, 3Y and 3K is selectively recorded. An elevating means (not shown) driven by a developing head elevating motor is provided to move the paper toward and away from the paper. The developing heads 3C, 3M, 3Y, 3K and the developer circulation system have basically the same structure.

Hereinafter, a description will be given of a cyan developing head 3C as an example with reference to FIGS. 1 (a) and 1 (b) and FIG.
FIG. 1A is a perspective view of a liquid developing device according to an embodiment of the present invention, FIG. 1B is a schematic configuration diagram of the developing device, and FIG.
FIG. 2 is a longitudinal sectional view cut along a plane along the line AA in FIG. The developing head 3C has a rectangular rod shape elongated in the width direction of the recording paper, and has two developing heads formed in the width direction of the recording paper with a length shorter than the width of the recording paper on the developing head surface facing the recording paper conveyance path. Developer circulation grooves 31, 3
2 and an air flow groove 33 formed in the width direction of the recording paper and having a length shorter than the width of the recording paper similarly between the developer circulation grooves 31 and 32. The ends of the two developer flow grooves 31 and 32 on the near side in the drawing are shown in FIG.
As shown in a vertical cross-sectional view taken along a line AA in FIG. 7A and viewed from the direction of the arrow, a developing solution is stored in a developing solution tank 6C through a hole passing through the back side of the developing head surface. It is connected to an electromagnetic three-way valve 10 which is a liquid path switching means provided in a supply pipe 9 which is a developing liquid supply path forming means to the liquid circulation grooves 31 and 32, and a right end thereof has a similar developing head surface. Through a hole penetrating to the back side, it is connected to the first recovery pipe 11 as a developer recovery path forming means from the developer circulation grooves 31 and 32 to the developer tank 6C. The air flow groove 33 is connected to the connection pipe 12 with the atmosphere at a substantially central portion in the longitudinal direction through a hole penetrating the back side of the developing head surface as shown by a broken line in the longitudinal sectional view of FIG. The adjustment valve 40 is connected to 12. The diameter of the communication hole between the airflow groove 33 and the atmosphere, which is determined by the connection pipe 12 and the adjustment valve 40, is such that when the inside of the developer solution flow grooves 31 and 32 is under a negative pressure by driving the pump motor 13, The developer flow grooves 3 are provided between the developer flow grooves 31 and 32 and the air flow grooves 33 through the gap between the developing head surface portion and the recording paper.
It is an important factor in determining the amount of air (see FIG. 3) sucked into the first and the second 32. If the airflow sucked through this gap during the development is too large, the airflow is increased as described above. Part of the toner image on the recording medium, particularly the toner constituting the highlight portion, is scraped off, resulting in uneven density. In order to prevent such unevenness, a weak squeeze is preferable. Therefore, the degree of communication between the air flow groove 33 and the atmosphere is more preferable as the degree of communication between the air flow groove 33 and the air hole 33 through a small hole diameter is improved. In the experiment, the liquid flow groove 3
Assuming that the negative pressure of 1, 32 is P (mmHg), the negative pressure of the airflow groove 33 is 0 when the cross-sectional area of the minimum diameter portion of the communication hole is about 6 mm2, and becomes 0.6 P to P (mmHg) when cut off. For example, the negative pressure P of the liquid flow grooves 31 and 32 is
When the pressure is 0 mmHg, the negative pressure in the airflow groove 33 is 0.6P, and when the negative pressure P in the liquid flow grooves 31 and 32 is smaller than 100 mmHg, the negative pressure in the airflow groove 33 matches this P. When the airflow groove 33 is opened to the atmosphere (a hole of 6 mm2 or more) and the negative pressure is set to 0, the developed image density (ID) becomes extremely thin, and uneven density unevenness occurs in a highlight portion. When observing the image in detail, the ID of the high-density portion also presents an abnormal image in the form of white stripes, and the result of scraping off the toner image developed on the recording surface by the airflow flowing from the airflow groove 33 into the liquid flow grooves 31 and 32 Can be seen. However, if the communication hole is too small and the squeeze is weakened, the recording paper may get wet and dirty,
The liquid draining time when separating the recording paper from the developing head becomes longer. Therefore, it is necessary to maintain at least the negative pressure of the airflow groove 33 at 0.1 (mmHg) or more in consideration of image quality and squeeze. Then, when using various types of recording paper according to the application, depending on the roughness of the recording surface of the recording paper, the recording paper passes between the head surface and the recording paper surface and flows from the airflow groove 33 to the liquid circulation groove 31,
The strength of the airflow flowing into 32 changes. Therefore, by operating the adjustment valve 40, the negative pressure in the airflow groove 33 is adjusted so that an abnormal image due to the airflow does not occur. When various types of recording paper are specified in advance for each application, in order to facilitate the adjustment operation by the user, a usage name is attached to the operation panel, and the adjustment valve 40 is automatically operated by operating the operation panel. May be driven for adjustment. The electromagnetic three-way valve 10 is connected to one end of a second recovery pipe 14 whose other end is connected to the first recovery pipe 11 by a branch pipe. The developer circulation grooves 31, 32 are communicated with the supply pipe 9 and are cut off from the second collection pipe 14, and in the OFF state, the developer circulation grooves 31, 32 are communicated with the second collection pipe 14 and supplied. It blocks off from the pipe 9. First recovery pipe 1
The pump motor 13 is provided on the developer solution tank 6C side from the point where the second recovery pipe 14 is connected. Also, the second recovery pipe 1 of the first recovery pipe 11
An electromagnetic two-way valve 16 to which an air introduction / negative pressure adjusting valve 15 is connected,
Are connected by a branch pipe, and a pressure sensor 17 is connected to the developing head 3C side. This air introduction / negative pressure adjusting valve 15 is used as follows. In addition to the negative pressure of the airflow groove 12, the liquid density grooves 31 and 32
The lower the negative pressure, the better the image quality.
When the negative pressure at 32 is extremely low, the circulating flow rate of the liquid is small, and the density unevenness of the stripe pattern occurs in the shadow portion due to insufficient development. After the development is completed, the liquid is drained before separation by continuously operating the pump 13 with the liquid flow path between the tank 6c and the head 3c shut off by the solenoid valve 10. Cutting is preferred. In order to satisfy such a contradictory requirement of the negative pressure, the air introduction / adjustment valve 15 and the solenoid valve 1
6 is connected as shown in the figure, the negative pressure of the liquid flow grooves 31 and 32 is set to a relatively low level by the adjusting valve 15 during the development, and the adjusting valve 15 is shut off by the electromagnetic valve 16 when the liquid is drained after the development is completed. The negative pressure is increased to effectively exert a function of removing excess liquid that does not impair the image quality during development and a function of rapidly draining liquid after completion of development. In addition, when the recording paper is selected and recorded as described above, when the adjustment valve 40 and the adjustment valve 15 are combined and adjusted, the margin of adjustment can be further increased to increase the margin. When the electromagnetic two-way valve 16 is ON, the air introduction / negative pressure adjusting valve 15 is connected to the first recovery pipe 1.
1 and shuts off the air introduction / negative pressure adjusting valve 15 from the first recovery pipe 11 in the OFF state.

[0009] In the above configuration, in the standby state, the pump motor 13 is stopped, the electromagnetic three-way valve 1 0 and electromagnetic 2-way valve 16 is OFF, the developing head 3C is spaced apart standby position from the recording paper downward positioned. After this waiting state,
When the recording operation is started, the developing head 3C is moved up by the elevating means to a developing position in which the openings of the developing solution flow grooves 31 and 32 on the developing head surface are closed by the recording paper. 0 is turned on to supply the developing head 3C with the supply pipe 9
And drive of the pump motor 13 is started. The openings of the developing solution flow grooves 31 and 32 on the developing head surface are closed by the recording paper. However, a minute gap is formed between the developing head surface and the recording paper surface due to minute irregularities on the recording paper surface. Exists, and the developer flow grooves 31,
Numeral 32 communicates with the atmosphere, and an air flow groove 33 also communicates with the atmosphere via the adjustment valve 40 and the atmosphere connection pipe 12. Also, since the electromagnetic two-way valve 16 keeps the air introduction / negative pressure adjusting valve 15 shut off from the first recovery pipe 11 while being in the OFF state, most of the suction action of the pump motor 13 is caused by the development head surface. Air is drawn from the openings of the developer circulation grooves 31 and 32 through the gap between the sheet and the recording paper surface. As a result, the recording paper is reliably sucked into the opening, closely adhered to the surface of the developing head, and the opening is substantially sealed, and the negative pressure in the developer circulation grooves 31 and 32 rapidly increases. When the negative pressure in the developer circulation grooves 31 and 32 becomes large enough to pump the developer in the developer tank 6C into the developer circulation grooves 31 and 32, the developer in the developer tank 6C becomes A state in which the developing solution flow grooves 31 and 32 are pumped up through the supply pipe 9 and are filled with the developing solution flow grooves 31 and 32 so as to be in contact with the recording paper that closes the openings in the developing solution flow grooves 31 and 32. And is returned into the developer tank 6C via the first recovery pipe 11, so that the developer circulation groove 3
Circulation is provided between the developer tanks 1 and 32 and the developer tank 6C.

When the circulation of the developing solution starts, the electromagnetic two-way valve 16 is turned on to connect the air introduction / negative pressure adjusting valve 15 to the first recovery pipe 11. At the time when the predetermined developer circulation stabilizes, the rotation of the feeding shaft 1 and the driving roller 4 is started, and the recording of the electrostatic latent image by the recording head 2 is started. The electrostatic latent image recorded on the paper is conveyed onto the developing head 3C, and the developing solution is supplied from the openings of the developing solution circulation grooves 31 and 32 to be developed. At this time, the developing solution flow groove 32 not only fulfills the developing function, but also fulfills the surplus developing solution removing function of removing the surplus developing solution attached to the recording paper. This is due to minute irregularities on the recording paper surface during development,
Air flows into the developing solution flow groove 32 from the gap between the developing head surface and the recording paper surface downstream of the developing solution flow groove 32 in the recording paper conveyance direction, and the air flows into the developing paper flow groove 32 due to the air flow. It is considered that excess developer was blown off. The developing head surface between the developing solution flow groove 32 and the air flow groove 33, the developing head surface between the developing solution flow groove 31 and the air flow groove 33, and the development upstream of the developing solution flow groove 31 in the recording paper transport direction. Air also flows into the developer circulation grooves 32 and 31 from the gap between the head surface and the recording paper surface (see FIG. 3).

When the rear end of the electrostatic latent image on the recording paper has passed the developing head surface and development has been completed, the electromagnetic three-way valve 10 is turned off while the pump motor 13 is driven. Electromagnetic 3
By turning off the flow valve 10, the developing head 3C is cut off from the supply pipe 9 and the pumping of the developing solution from the developing solution tank 6C is interrupted. On the contrary, the developing head 3C communicates with the second recovery pipe 14. The developer flow groove 3
The developer in the first and second collection pipes 11 and 32 is collected in the developer tank not only through the first collection pipe 11 but also through the second collection pipe 14.
2 not only can recover the developer in
The developer remaining in the pipe connecting the two-way valve and the developer flow grooves 31 and 32 can also be reliably collected. or,
Immediately after the electromagnetic three-way valve 10 is turned off, the electromagnetic two-way valve 16 is turned off to shut off the air introduction / negative pressure adjusting valve 15 from the first recovery pipe 11, whereby the developer circulation grooves 31,
The negative pressure in 32 is maximized. After collecting this developer,
All of the suction action of the pump motor 13 is
It is directed to the suction of air from the openings 1, 32. As a result, the developer and the like adhering to the inner side surfaces and the like of the developer flowing grooves 31 and 32 can also be collected by suction.

[0012] During the above-mentioned liquid drainage,
By continuing the conveyance of the recording paper, the developer remaining on the developing head surface is thinly applied to the surface of the recording paper to remove the developing solution on the developing head surface. At the time when the developer does not adhere to the recording paper, the driving of the pump motor 13 is stopped, whereby the suction operation of the recording paper to the developing head surface is stopped, and the recording paper is removed from the developing head surface. to isolated et al minute. After a fixed time t has elapsed from the stop of the driving of the pump motor 13, the developing head 3C is moved to the standby position by the elevating means. The predetermined time t is equal to the length of the developer flow groove 31,
Due to a change in the pressure in the developer flowing grooves 31 and 32 at the moment when the negative pressure in the developing head 3C starts moving to the standby position, the developer scatters from the openings of the developer flowing grooves 31 and 32. This is a time required to decrease to such an extent that it does not occur, which is obtained in advance by an experiment, starts counting when the driving of the pump motor 13 is stopped, and uses a timer that generates an output after the elapse of the predetermined time t. , The movement of the lifting / lowering means to the standby position is started. As described above, instead of determining the movement start timing of the developing head 3C to the standby position based on the elapse of the set time after the stop of the pump motor 13, the developer at the moment when the development head 3C starts to move to the standby position is determined. Negative pressures in the developer flow grooves 31 and 32 are determined in advance by experiments so that the developer does not scatter from the openings of the developer flow grooves 31 and 32 due to pressure changes in the flow grooves 31 and 32. Alternatively, when the detected pressure of the pressure sensor 17 provided in the first recovery pipe 11 detects such a negative pressure, the movement of the developing head 3C to the standby position may be started. FIG. 4 is a timing chart of the operation from the time immediately before the end of the development to the time when the liquid is drained and the developing head 3C is moved to the standby position.

Next, a second embodiment of the liquid developing apparatus in which the developer circulation system is modified will be described with reference to FIG. The difference between this embodiment and the first embodiment is that the developer supply pipe 9 and the developer circulation grooves 31 and 32 are switched between a communicating state and a blocking state instead of the electromagnetic three-way valve 10 in the first embodiment. Using the electromagnetic two-way valve 18 and the electromagnetic three-way valve 1 in the first embodiment.
Second recovery pipe 1 connecting 0 and first recovery pipe 11
4 is omitted. In this embodiment, the recovery of the developer from the inside of the developer circulation grooves 31 and 32 after the development is completed is performed only through the first recovery pipe 11, so that the time for draining the liquid is shorter than in the first embodiment. However, there is an advantage that the piping of the pipe is simplified.

As described above, according to each embodiment, the connection pipe 12 and the adjusting valve 40 adjust the diameter of the communication hole between the air flow groove 33 and the atmosphere so that the inside of the air flow groove 33 has a predetermined negative pressure. The reproducibility of the highlight portion and the like and the removal of the excess liquid on the recording paper can be favorably performed. Also, the air flow groove 3 during development
3 and air introduction / negative pressure adjusting means 40 and 15 for adjusting the negative pressure in the developer flow grooves 31 and 32, and the negative pressure in the air flow groove 33 and the developer flow grooves 31 and 32 Regardless of the degree of smoothness (determined by the type of recording paper used)
Since the negative pressure is adjusted so that the optimum development can be performed, various types and types of recording paper can be used.

Next, the amount of air sucked into the developing solution flow grooves 31 and 32 from the air flow groove 33 through the gap between the developing head surface and the recording paper is determined during the development and during the liquid removal after the development is completed. A description will be given of an embodiment in which the squeezing force at the time of draining the liquid is increased. FIG. 6A is a perspective view of the liquid developing device according to the present embodiment, and FIG. 6B is a schematic configuration diagram of the developing device. The developing device is the same as that shown in FIG.
The difference from the developing device shown in FIGS. 7A and 7B is that in the above-described developing device, the flow to the airflow groove 33 determined by the adjustment valve 40 and the connection pipe 12 during the development and when the liquid is drained after the development is completed. While the diameters of the communicating holes are the same, in the developing device of the present embodiment, an electromagnetic three-way valve 41 is provided between the adjustment valve 40 and the connection pipe 12, and the three-way valve is operated during development. The point is that the airflow groove 33 is connected to the adjustment valve 40 side, and is connected to the side of a hole having a relatively large hole diameter (for example, 6 mm ² or more) and communicating with the atmosphere when the liquid is drained after the development is completed. This electromagnetic three-way valve 41
For example, in the ON state, the airflow groove 33 is communicated with the atmosphere by the minute hole on the adjustment valve 40 side, and in the OFF state, the airflow groove 3 has a large hole diameter.
In the case where 3 is communicated with the atmosphere, its ON / OFF control
O at the same timing as the solenoid three-way valve 10 shown in FIG.
N, it may be turned off. According to this example, during development, the airflow groove 33 is set at a relatively low negative pressure to remove excess liquid without damaging the image, and when the liquid is drained after the development is completed, the airflow groove is brought to almost atmospheric pressure. As a result, the squeeze effect is increased, and the liquid can be drained in a short time.
In this example, the liquid circulation system can be simplified as shown in FIG.

In each of the above-described embodiments, the performance of the pump 13 is naturally selected to be high negative pressure and high capacity in order to carry out both the developing and draining processes. The above-mentioned prior art JP-A-61-179476 also discloses that two pump motors are connected in parallel to enhance the drainage effect. However, since the negative pressure is maintained during the development, There is a disadvantage that the image density in the highlight portion is impaired by the function of removing the excess developer. In this regard, in each of the above-described embodiments, the negative pressure is reduced by the electromagnetic valve 16 during the development to reduce the excess developer removing function and maintain high image quality. Further, the developer flow grooves 31, 3
The developing head is raised and lowered to switch between the state where the opening 2 is closed with the recording paper and the state where the developing head is separated from the recording paper. Alternatively, the recording paper transporting means may be raised and lowered.
Further, although adapted to supply the developer from one of the developer tank to the respective developing head, through a suitable liquid path switching means of the valve, such as the one developing head, accommodating the respective colors different developer A plurality of developer tanks and one of tanks containing cleaning liquid for cleaning, such as the developer circulation grooves 31 and 32 at the time of color switching, can be selectively connected to any one of the tanks;
The developing head may be shared by a plurality of developing solution tanks. Further, the above embodiment is a developing device for color development having a plurality of developing heads, but the present invention is also applicable to a monochromatic developing device using one developing head.

Next, another embodiment of the present invention will be described. FIG. 7 is a schematic configuration diagram of an image forming apparatus of an ion flow electrostatic latent image recording / groove type developing system to which the liquid developing apparatus according to the present embodiment can be applied. The outline of this image forming apparatus will be described. A recording material 101 wound in a roll is set, and the leading end of the recording material 101 is placed on an inactive electrostatic recording head (ion flow electrostatic recording head) 102 and a developing head 103. And is sandwiched between the driving roller 4 and the pinch roller 5. When the image forming operation is started in this state, the driving roller 4 starts rotating, an electrostatic latent image is recorded on the recording material by the electrostatic recording head 102, and the electrostatic latent image is recorded on the developing head 103. Recording material 101 while developing
, The cutter 106 is driven just before the leading end of the developed image passes through the cutter 106 to cut off the remaining portion of the leading end of the recording material, and the drive roller 104 is driven immediately after the trailing end of the developed image passes through the cutter 106. Stop rotation and cutter 10
6 is driven to cut the recording material 101, and the discharge roller pair 1
The sheet-shaped recording material 101 is discharged onto a discharge tray (not shown) while rotating only 07.

Next, an example of a liquid developing apparatus applied to the above apparatus will be described with reference to FIGS. 8 and 9. FIG. FIG. 8 is a schematic structural view of the liquid developing device, and FIG. 9 is a sectional view of the developing head. In the liquid developing apparatus according to the present embodiment, the developing solution flow groove 111 (see FIG. 9) is closed by the recording material 101 such as electrostatic recording paper, and the negative pressure generating means such as a pump motor 110 is driven to perform development. A negative pressure is generated in the liquid circulation groove 111, and the recording medium 101 is suctioned to the developing head surface by the negative pressure, whereby the developer circulation groove 111 is sealed,
The developing solution in the developing solution tank 113 is supplied to the developing solution flow groove 111 through a developing solution supply path forming means such as a supply pipe 114, and the developing solution in the developing solution flowing groove 111 is collected by the collecting pipe 11.
5 and the like, and the developer tank 11
While it collected into 3, by circulating the developer in the developer tank 113 and developer circulation groove 111, the developing liquid flow
The passage groove 111 is filled with the developing solution to perform a developing operation of an image to be developed such as an electrostatic latent image on the recording material 101. After the developing operation is completed, the driving of the pump motor 110 is continued to perform the developing operation.
The drainage for collecting the developer in the circulation groove 111 to the developer tank 113 is performed. The two-way valve 116 for the developer provided in the developer supply pipe 114 is released during the development to allow the developer in the developer tank 113 to flow through the developer circulation groove 11.
1 and can be shut off during draining to
Although the inside of the flow groove 111 is in a negative pressure state, the developing solution is not supplied. The air flow groove 112 (see FIG. 9) provided in parallel with the developer flow groove 111 is connected to the atmosphere and becomes the atmospheric pressure at least at the time of draining, and the air flow groove 112 and the developer flow groove 1
11 causes a pressure difference between the airflow grooves 1 on the developing head surface.
Atmospheric flow is generated from 12 toward the developing solution flow groove 111. Squeezing is performed by scraping excess liquid on the recording material 101 by this air flow. air flow
If the groove 112 is connected to the atmosphere during the development, it is excessively squeezed and the developed toner image may be scraped off on the recording material. 120 switches the flow of the atmosphere. Negative pressure adjusting means such as a negative pressure adjusting valve 117 provided in the developing solution collecting pipe 115 is connected to the atmosphere at least at the time of development, and sends an appropriate amount of air to the developing solution collecting pipe 115 so that the developing solution flowing groove 111 is formed. Is controlling the negative pressure. In general, as the negative pressure is higher (the absolute value of the negative pressure is larger), the squeeze effect is improved. Therefore, at the time of draining the liquid, the developer recovery pipe 115 and the atmosphere are shut off by a valve 118 so as to increase the negative pressure.

By the way, the conventional developing head 103 can maintain the developing solution even after the draining is completed as shown in FIG.
And adhering the side walls of the flow channel 111 (square of the side wall) and the bottom wall, and the like developing solution circulation groove 111 adhesion of the recording material 101 and the developing head 103 side when the negative pressure condition worsens, There is a possibility that the air blows in and the developer adhering to the side wall or the bottom wall jumps up and wets the recording material 101.

Therefore, in the developing head 103 of this embodiment, as shown in FIG. 9, an oil-repellent thin film 150 is provided on the side wall and the bottom wall of the developing solution flow groove 111. As a result, when the development is completed and the two-way valve for developer is shut off, the developer in the developer circulation groove 111 does not adhere to the side wall and the bottom wall of the developer circulation groove 111, and the developer flows from the surface of the development head 103. It is sucked and collected by the pump motor 110 together with the introduced atmosphere. Therefore, after the recovery of the developing solution, no liquid remains in the developing solution flow groove 111, and no liquid splash occurs even if the air is blown, so that a problem of wetting the recording material 101 does not occur. Examples of agents having oil repellency include acrylic acid fluoroalkyl ester polymers, poly-IH, IH-pentadecalfluorooctyl methacrylate, fluorinated hydroxy unsaturated esters, perfluoroalkyl ester polymers,
Methyl hydrogen polysiloxane can be used.

[0021]

According to the first to fourth aspects of the present invention, since the air flow grooves in the negative pressure state are provided between the plurality of developer flow grooves on the developing head surface, the negative pressure developer flow grooves and The pressure difference between the air flow groove and the air flow groove is smaller than that when the air flow groove is at atmospheric pressure, and the density unevenness does not occur in the highlight portion. In addition, when the liquid is drained, the air flow groove is not completely sealed, so that a squeeze effect is generated and the liquid can be easily drained. Therefore, high image quality and short time liquid removal can be achieved only by a simple structure in which a hole having an appropriate diameter is provided in the airflow groove. And especially the invention of claim 1
According to the method, since the air introduction adjusting means is provided between the developing solution flow groove and the pump, the negative pressure can be easily adjusted corresponding to recording media having different surface characteristics, thereby achieving high image quality and shortening of liquid drainage. strikes, spread the adjustment range for adaptation to the medium, the greater the margin (many types of media Introduction used, exits in width to set point). Further, according to the invention of claim 2, the air flow rate of the gas Nagaremizo and the atmosphere, means for changing between the developing and when drained after completion of the development is provided, the air flow amount in the developer Excessive developer which does not damage the image is removed by setting a relatively low negative pressure in the airflow groove, and at the time of drainage after the development is completed, the air flow amount is adjusted to be substantially atmospheric pressure in the airflow groove. To increase the effect of removing excess developer, thereby
The liquid can be drained in a shorter time. Also, billing
According to the third aspect of the present invention, the negative pressure generating means causes the development
The magnitude of the negative pressure generated in the liquid flow groove is determined during development and during development.
A means is provided to change between the time when the liquid is drained after the
Is used to obtain a relatively low negative pressure in the
Remove excess developer that does not impair, and drain after development is complete.
The negative pressure in the developer circulation groove becomes relatively large
In this way, the excess developer removing effect is increased,
The liquid can be drained in a shorter time. Also,
According to the fourth aspect of the present invention, the plurality of developing solution flow grooves on the developing head surface are subjected to the oil repellent treatment, so that the developing solution is prevented from adhering to the side walls and the bottom wall of the developing solution flow groove, and the liquid splash Can prevent the recording medium from wetting.

[Brief description of the drawings]

FIG. 1A is a perspective view of a liquid developing device according to an embodiment,
(B) is a schematic configuration diagram of the developing device.

FIG. 2 is a schematic configuration diagram of an electrostatic recording type color image forming apparatus employing a liquid developing device.

FIG. 3 is a longitudinal sectional view cut along a plane along the line AA in FIG.

FIG. 4 is a timing chart illustrating an operation of the liquid developing device.

FIG. 5 is a schematic configuration diagram showing a modification of the liquid circulation path.

FIG. 6A is a perspective view of a liquid developing device according to another embodiment, and FIG. 6B is a schematic configuration diagram of the developing device.

FIG. 7 is a schematic configuration diagram of a main part of an image forming apparatus employing a liquid developing device according to another embodiment.

FIG. 8 is a schematic configuration diagram of the liquid developing device.

FIG. 9 is a sectional view of a developing head of the liquid developing device.

FIG. 10 is an explanatory diagram for explaining a problem of a conventional developing head.

[Explanation of symbols]

3C, 3M, 3Y, 3K ... developing heads 31, 32 ...
Developer supply grooves 6C, 6K ... Developer tank 9 ... Supply pipe 11 ... Recovery pipe 10, 41 ...
Electromagnetic three-way valve 13 ... Pump motor 15 ... Air introduction / negative pressure adjustment valve 18 ... Electromagnetic two-way valve 40 ... Adjustment valve 101 ... Recording medium 102 ... Electrostatic recording head 103 ... Development head 110 ... Pump motor 111 ... Development liquid supply Groove 112 ... Atmosphere groove 113 ... Developer tank 114 ... Supply pipe 115 ... Recovery pipe 116 ... Developer two-way valve 117 ... Negative pressure adjusting valve 118 ... Negative pressure adjusting means opening / closing two-way valve 119 ... Developer tank exhaust pipe 120 … Atmospheric groove open / close two-way valve 150… Oil-repellent thin film

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyoshi Oshima 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Kazuaki Iizuka 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Kenichi Shimizu 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. (72) Inventor Tadahiro Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. (56) References JP-A-61-179476 (JP, A) JP-A-61-179477 (JP, A) JP-A-63-200851 (JP, U) (58) Fields investigated (Int) .Cl. ⁷ , DB name) G03G 15/10 G03G 15/01

Claims (4)

(57) [Claims] A developing head having an opening in a developing head surface facing a recording medium conveyance path and having a plurality of developer flowing grooves extending in a width direction of the recording medium; and a developing solution containing the developing solution. A tank, a means for forming a developing solution supply path from the developing solution tank to the developing solution circulation groove, a means for forming a developing solution collecting path from the developing solution flowing groove to the developing solution tank, and an opening of the developing solution flowing groove formed of a recording medium. When in the closed state, it has a negative pressure generating means for generating a negative pressure in the developing solution flow groove, and has an opening in the developing solution flowing groove closed in the developing solution flowing groove with the recording medium. A liquid for developing an electrostatic latent image on a recording medium by generating a negative pressure and sucking the recording medium into the opening of the developer circulation groove and circulating the developer from the developer tank to the developer circulation groove. In the developing device, a negative pressure is applied between a plurality of developer flowing grooves on the developing head surface. Air flow grooves , and between the developer flow grooves and the negative pressure generating means,
A liquid developing device, comprising: a communicating atmosphere introduction adjusting means . 2. A developing head surface facing a recording medium conveying path.
A plurality of developers having an opening and extending in the width direction of the recording medium
A developing head having a flow groove and a developing solution containing the developing solution
Tank and developer supply from the developer tank to the developer circulation groove.
The supply path forming means and the current flowing from the developer circulation groove to the developer tank;
The image liquid recovery path forming means and the opening of the developer flow groove are
When the body is closed, create a negative pressure in the developer flow groove.
Negative pressure generating means for generating, and an opening of the developing solution flow groove
Negative pressure is generated in the developer flow channel with the
And suck the recording medium into the opening of the developer circulation groove.
At the same time, the developer is circulated from the developer tank to the developer flow groove.
To develop the electrostatic latent image on the recording medium
In the developing device, air is communicated between a plurality of developer flowing grooves on the developing head surface.
Providing an airflow groove through which air can flow, and air between the airflow groove and the atmosphere
Change the flow rate between during development and when draining after the end of development.
A liquid developing device comprising: 3. The developing solution flow groove by the negative pressure generating means.
The magnitude of the negative pressure generated during
Characterized in that a means for changing between the time of draining and the liquid is provided
The liquid developing device according to claim 1. 4. The liquid developing device according to claim 1, wherein an oil-repellent treatment is applied to an inner surface of the developing solution flow groove.