JP2002278306A - Wet image forming device - Google Patents

Abstract

(57) Abstract: Provided is a wet image forming apparatus that can determine erroneous detection of a liquid developer concentration with a simple configuration. SOLUTION: A liquid collecting means for collecting and reusing an undeveloped liquid developer which has not been developed on the photosensitive drum 11 and an untransferred liquid developer which has not been transferred onto the transfer paper 16 into a liquid developer accommodating section 18, and a liquid. In a printer having a liquid concentration detection unit 32 for detecting the concentration of the developer 1, a storage unit for storing an image area ratio of an image formed for each transfer sheet 16, and a numerical value of the image area ratio stored in the storage unit A processing unit for predicting the liquid concentration of the liquid developer accommodating unit 18 after the collected and reused liquid developer is injected, and a liquid concentration predicted by the processing unit and a liquid concentration detecting unit 32. And a judging means for judging that the liquid concentration detecting means 32 has erroneously detected when the difference between the liquid concentrations compared by the comparing means is equal to or larger than a predetermined numerical value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet image forming apparatus such as a copying machine, a facsimile, and a printer, and more particularly, to a developer carrier using an image carrier and a liquid developer in a liquid developer container. Developing means for forming a liquid developer thin layer on the image carrier, developing the latent image on the image carrier with the liquid developer thin layer, and transferring the visualized image to a recording medium. Means for recovering an undeveloped liquid developer that has not been developed on the image carrier and an untransferred liquid developer that has not been transferred to the recording medium in the liquid developer container and reusing the liquid developer The present invention relates to a wet image forming apparatus having a liquid developer concentration detecting unit for detecting the concentration of the liquid developer in the liquid developer storage section.

[0002]

2. Description of the Related Art Conventionally, as a developing device of this type of wet image forming apparatus, Japanese Patent Application Laid-Open No. Hei 7-244433 discloses a developing device in which a developing roller and a liquid supply means for the developing roller are provided in a liquid storage means. A device in which a roller, a liquid supply unit, and a liquid storage unit are integrated is disclosed.

FIG. 8 shows one embodiment of the developing device.
As shown in FIG. 1, a tank 2 serving as a storage means for storing the liquid developer 1, a supply means 3 disposed soaked in the liquid developer 1 stored in the tank 2, a developing roller 4, a regulating blade 5 and a wiping blade 6.

The supply means 3 includes a pair of gear-shaped rolls 8 and 9 having substantially the same length as the developing roller 4 and a pair of gear-shaped rolls 8 and 9.
And a case 10 that covers the liquid developer 1 stored in the tank 2 by rotating the gear-shaped roll pairs 8 and 9 in opposite directions.
To supply. Liquid developer 1 supplied to developing roller 4
After the thickness of the electrostatic latent image forming drum 7 is adjusted by the regulating blade 5,
The above electrostatic latent image is visualized. The liquid developer 1 on the developing roller 4 not used for the development is wiped off by the wiping blade 6. Incidentally, the tank 2, the supply means 3, the developing roller 4, the regulating blade 5, the wiping blade 6
Are provided in one cartridge and can be replaced at a time. Further, the developing roller 4 and the electrostatic latent image forming drum 7 are respectively driven to rotate by driving devices (not shown).

In the developing device disclosed in Japanese Patent Application Laid-Open No. Hei 7-244433, a visible image on the electrostatic latent image forming drum 7 is transferred to a transfer material directly or after being once transferred to an intermediate transfer member. . The untransferred liquid developer not transferred to the transfer material is cleaned by a cleaning device (not shown) and discarded. As described above, the untransferred liquid developer is discarded, which causes a rise in running cost. Further, in the above-described developing device, it is difficult to stably maintain the concentration of the liquid developer because the concentration of the liquid developer in the developing device is not detected or adjusted.

Therefore, the present applicant has filed Japanese Patent Application No. 11-3038.
No. 90 proposes a wet image forming apparatus that collects the untransferred liquid developer that has adhered to the latent image carrier and the intermediate transfer body during image formation but has not been finally transferred to the transfer material and reuses it for development. are doing. Since the toner and the carrier liquid are consumed in the developing step and the transferring step, the liquid concentration of the untransferred liquid developer changes. Therefore, if the untransferred liquid developer is reused for development, the concentration of the liquid developer in the developing device changes, and a desired image density may not be obtained. Therefore, in the wet image forming apparatus proposed in Japanese Patent Application No. 11-303890, a liquid concentration detecting means using an optical sensor is provided to detect the concentration of the liquid developer in the developing device. The liquid developer or the carrier liquid is supplied to control the concentration of the liquid developer to a predetermined value.

[0007]

However, if mixed paper dust, dust, or coarse particles of toner are present in the liquid developer, the optical sensor erroneously detects the liquid developer, and the liquid concentration detecting means can accurately detect the dust. In some cases, the concentration of the liquid developer could not be detected. Since the concentration is adjusted based on the detection result of the liquid concentration detecting means, if the liquid concentration detecting means makes an erroneous detection, the concentration of the liquid developer in the developing device is not maintained at a predetermined concentration, and the density of the formed image is reduced. High quality images cannot be obtained because they are too light or too dark. It is conceivable to prevent the erroneous detection by providing a plurality of liquid concentration detecting means and comparing the detected values with each other, but this increases the cost and size of the developing device.

The present invention has been made in view of the above background, and an object of the present invention is to provide a wet image forming apparatus capable of judging erroneous detection of a liquid developer concentration with a simple configuration. is there.

[0009]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: an image carrier; and a liquid developer thin film formed on the developer carrier by using a liquid developer in a liquid developer accommodating portion. Developing means for forming a layer, developing the latent image on the image carrier with the thin liquid developer layer to visualize the image, transferring means for transferring the visualized image to a recording medium, and A liquid collecting unit that collects and reuses the undeveloped liquid developer that has not been developed on the carrier and the untransferred liquid developer that has not been transferred to the recording medium into the liquid developer storage unit; In a wet image forming apparatus having liquid concentration detecting means for detecting the concentration of a liquid developer in a developer container, a storage means for storing an image area ratio of an image formed for each recording medium, and a storage means for storing the image area ratio Based on the numerical value of the image area ratio obtained, A processing unit for predicting the liquid concentration of the liquid developer storage unit after the liquid developer has been injected, a liquid concentration predicted by the processing unit, and a liquid concentration detected by the liquid concentration detection unit. And a judging means for judging that the liquid concentration detecting means has erroneously detected when the difference between the liquid concentrations compared by the comparing means is a predetermined value or more. Things.

In this wet image forming apparatus, the liquid concentration predicted by the arithmetic processing unit based on the image area ratio stored in the storage means is compared with the liquid concentration detected by the liquid concentration detection means. When the difference between the compared liquid concentrations is equal to or greater than a predetermined value, it is determined that the liquid concentration detecting means has erroneously detected. Here, the image area ratio can be easily obtained from the image data. Further, the storage unit, the arithmetic processing unit, the comparison unit, and the determination unit use, for example, a programmable controller already provided in the wet image forming apparatus, and execute the sequence on the programmable controller to detect the liquid concentration. A special device for judging erroneous detection of the means may not be separately provided. Therefore, for example, compared to a case where two liquid concentration detecting means are provided and the detection values are compared with each other to determine erroneous detection, cost reduction and space saving can be achieved. Can be determined.

According to a second aspect of the present invention, in the wet image forming apparatus of the first aspect, a reference density of a liquid developer used in the developing means is set in advance, and an image of an image formed on the recording medium is set. The smaller of the difference between the maximum value of the liquid developer concentration that does not affect the density and the reference density or the difference between the minimum value of the liquid developer concentration that does not affect the image density and the reference density To a number less than or equal to the value of
The size of the predetermined numerical value is set.

Normally, if the concentration of the liquid developer used in the developing means is within a range of several percent with respect to the reference density, the density of the formed image is not largely affected and the liquid developer can be used sufficiently. In this wet image forming apparatus, the difference between the maximum value of the liquid developer concentration that does not affect the image density of the image formed on the recording medium and the reference density, or the liquid developer concentration that does not affect the image density The magnitude of the predetermined numerical value is set to a numerical value equal to or smaller than the smaller one of the differences between the minimum value of the above and the reference density. Therefore, when the liquid developer in the liquid developer storage unit has a concentration close to the reference concentration, a predetermined numerical value which is a difference between the liquid concentration predicted by the arithmetic processing unit and the liquid concentration detected by the liquid concentration detecting unit. Is the difference between the maximum value of the liquid developer concentration that does not affect the image density of the image formed on the recording medium and the reference density, or the minimum value of the liquid developer concentration that does not affect the image density and the reference value. If the difference from the density is a numerical value equal to or smaller than the smaller value, erroneous detection is not determined, and the image density of the formed image is maintained.

According to a third aspect of the present invention, in the wet image forming apparatus according to the first or second aspect, the liquid concentration predicted by the arithmetic processing unit and the liquid concentration detected by the liquid concentration detecting means are:
When the relationship of predicted liquid concentration-detected liquid concentration <0 is satisfied, the determining means determines that the liquid concentration detecting means has erroneously detected.

Depending on the image area ratio, there is an image area ratio at which the liquid developer concentration in the liquid developer storage section increases or an image area ratio at which the liquid developer concentration decreases. When the liquid developer concentration decreases, the replenishing liquid developer needs to have a higher concentration in order to restore the reference concentration. However, in managing the replenishment amount and the liquid developer concentration of the liquid developer, it is easier to dilute the thickened developer. Therefore, it is desirable to avoid such control that the liquid developer concentration decreases.
In this wet image forming apparatus, when the relationship of predicted liquid concentration-detected liquid concentration <0 is satisfied, the liquid developer concentration decreases by determining that the liquid concentration detecting unit has erroneously detected. Can be prevented.

According to a fourth aspect of the present invention, in the wet image forming apparatus of the first, second or third aspect, the numerical value of the image area ratio used in the arithmetic processing section is stored in the storage means as 20 or more. Is characterized by using the average value of the image area ratios.

The number of images having an image area ratio for which an average value is obtained is 2
If the value is smaller than 0, the displacement is easily affected by the large image area ratio, and the liquid concentration predicted by the arithmetic processing unit may be predicted to be far apart from the actual liquid concentration of the liquid developer storage unit. However, the reliability of the liquid concentration predicted by the arithmetic processing unit cannot be ensured. In this wet image forming apparatus, the numerical value of the image area ratio used for the calculation in the calculation processing unit is:
Since the average value of the image area ratios of 20 or more stored in the storage unit is used, the reliability of the liquid concentration predicted by the arithmetic processing unit can be secured.

According to a fifth aspect of the present invention, in the wet image forming apparatus of the first, second, third or fourth aspect, the liquid concentration detecting means separates the optical sensor and the liquid to be subjected to the concentration detection into a plurality of different thicknesses. A liquid carrying member formed and carried so as to have, as data for liquid concentration detection, using an integrated value of output data of the optical sensor for the plurality of thicknesses carried on the liquid carrying member. It is a feature.

In this wet image forming apparatus, the integrated value of the output of the optical sensor for the plurality of thicknesses is used as liquid concentration detection data. The integrated value of the output of the optical sensor, that is, the area of the output signal (output waveform) of the optical sensor changes according to the amount of reflected light or transmitted light as the optical characteristic of the concentration detection target liquid. If the integrated value is used as liquid concentration detection data, the liquid concentration can be detected. Further, the noise level of the output signal of the optical sensor is suppressed by integration.

According to a sixth aspect of the present invention, in the wet-type image forming apparatus of the fifth aspect, the liquid holding member is sandwiched between one disk portion having a diameter gradually changing, and the disk portion is sandwiched from both sides.
A configuration in which a roller-shaped member integrally formed with two disk portions of the same diameter having a diameter larger than the maximum diameter of the disk portion is used, and rotation driving means for rotating the roller-shaped member is provided. It is a feature.

In this wet image forming apparatus, as the liquid carrying member, one disk portion whose diameter changes stepwise, and the disk portion is sandwiched from both sides and has a diameter larger than the maximum diameter of the disk portion. A roller-shaped member integrally formed with two disks having the same diameter is used. Thereby, the liquid to be subjected to the concentration detection can be formed in a plurality of thicknesses corresponding to the steps formed between the one disk part and the two disk parts. Further, by continuously rotating the roller-shaped member, a plurality of film thicknesses can be formed continuously, so that the liquid concentration can be detected continuously.

According to a seventh aspect of the present invention, in the wet image forming apparatus of the sixth aspect, a film thickness regulating member for regulating a film thickness of the liquid carried on the roller member, and a cleaning for cleaning the liquid after detecting the concentration of the liquid. And a liquid transport path for collecting and transporting the liquid cleaned by the cleaning member, and all of them are integrally formed.

In this wet image forming apparatus, a regulating member for regulating the film thickness of the liquid carried on the roller member, a cleaning member for cleaning after detecting the concentration of the liquid, and a liquid for cleaning the liquid cleaned by the cleaning member are collected. And a liquid transport path for transporting the components, and these components are all configured as a single unit, so that the number of components can be reduced.

According to an eighth aspect of the present invention, in the wet image forming apparatus according to the sixth or seventh aspect, when the determining means determines that the liquid concentration detecting means has erroneously detected, the roller-shaped member is moved to the liquid state. It is characterized by having control means for controlling so as to rotate by a predetermined angle in the direction opposite to the rotation direction at the time of density detection.

When foreign matter such as paper powder is mixed in the liquid developer, the foreign matter is caught between the roller-shaped member and the film thickness regulating member, so that a uniform film thickness cannot be formed. Then, the accurate liquid concentration is not detected by the liquid concentration detection means, and the determination means determines that the detection is erroneous. Therefore, in this wet image forming apparatus, when the determining means determines that the liquid concentration detecting means has erroneously detected, the roller-shaped member is rotated by a predetermined angle in a direction opposite to the rotation direction at the time of detecting the liquid concentration. As a result, foreign matter caught between the roller-like member and the film thickness regulating member is removed. As a result, a liquid developer layer having a uniform thickness is formed again on the roller-shaped member, and the liquid concentration can be accurately detected by the liquid concentration detecting means.

The ninth aspect of the present invention is the first aspect of the present invention.
In the wet image forming apparatus of 4, 5, 6, 7 or 8, the liquid developer has a solid content concentration of 5% or more and 40% or more.
[%] Or less, and a liquid developer having a viscosity of 100 [mPas] to 10,000 [mPas] is used.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic printer (hereinafter simply referred to as a "printer") which is a liquid developing type image forming apparatus will be described below. First, an outline of the printer according to the present embodiment will be described. FIG. 1 is a main schematic configuration diagram of the printer according to the present embodiment.

A charging unit 12, a developing unit 13, an intermediate transfer body 14, a photosensitive drum cleaning unit 15, and the like are arranged around a photosensitive drum 11 as a latent image carrier. Further, an image formed on the intermediate transfer body 14 is transferred to a transfer paper 16 by a transfer roller 17 provided opposite to the intermediate transfer body 14.

In the above configuration, the photosensitive drum 11 is driven to rotate at a constant speed in the direction of the arrow at the time of printing by a driving means such as a motor (not shown). Then, after being uniformly charged by the charging unit 12, the writing light LB is irradiated and imaged based on the image information by an optical writing unit (not shown) to form an electrostatic latent image on the photosensitive drum 11. Then, the electrostatic latent image is developed by the developing unit 13, and an image is formed on the photosensitive drum 11. The image formed on the photoconductor drum 11 is transferred onto an intermediate transfer body 14 that is driven at the same speed as the photoconductor drum 11. The image on the intermediate transfer body 14 is transferred to a transfer paper 16 conveyed from a paper feed cassette (not shown) to a transfer section.
Is transferred by the transfer roller 17. After the transfer is completed, the transfer paper 16 is fixed by a fixing unit (not shown) and is discharged. The liquid developer 1 on the photoconductor drum 11 that has not been transferred onto the intermediate transfer body 14 is removed from the photoconductor drum 11 by the photoconductor drum cleaning unit 15. The photosensitive drum cleaning unit 11 was provided with a screw for transporting the removed developer (hereinafter, referred to as “untransferred developer”), and a flow path capable of returning to the developing device was provided. Further, a control valve is provided in the passage of the photosensitive drum cleaning unit. Further, the control valve is configured to open and close the flow path by the solenoid. The untransferred developer on the intermediate transfer member 14 is removed by an intermediate transfer member cleaning unit (not shown).
After that, the residual potential of the surface of the photosensitive drum 11 is removed by a not-shown discharge lamp to prepare for the next print.

As shown in FIG. 1, the developing unit 13 in the printer according to the present embodiment includes a developing section 21, a developing roller 22, a developer collecting section 23, and a developer accommodating section (hereinafter, referred to as a developer accommodating section).
This is referred to as a “developer adjustment section”. ) 18 and toner bottle 19
And a carrier bottle 20. The liquid developer 1 used in the present embodiment has a viscosity of 1
Within the range of 00 to 10000 mPas, the toner concentration is 5 to 5.
Use the one in the range of 40%. More specifically, for example, one having a viscosity of 300 mPas and a toner concentration of 15% is used.

The developing section 21 has a storage tank 24 in which the liquid developer 1 is stored, an application roller 25 for applying the liquid developer 1 to the developing roller 22, and a pair of liquid rollers 1 for supplying the liquid developer 1 to the application roller. Screws 26 a and 26 b and a regulating blade 27 for regulating the amount of the liquid developer 1 on the surface of the application roller 25 are provided. Storage tank 24 is 100 ~
150 cc of the liquid developer 1 can be stored. The liquid developer 1 is transported from the developer adjusting section 18 into the storage tank 24 by the transport pump 34. When the pair of screws 26a and 26b are driven, the liquid surface of the liquid developer 1 in the storage tank 24 rises, and the rising portion contacts the application roller 25, so that the liquid developer 1
5 is supplied. The amount of the liquid developer 1 supplied to the application roller 25 is regulated by the regulating blade 27, and about 30 cc of the liquid developer is applied to the development roller 22 per minute. Note that the storage tank 2 is controlled by the transport pump 34.
When the liquid developer 1 is excessively supplied to the developing roller 4, the developer collecting section 18 collects the undeveloped toner on the developing roller 22.
And is collected by the developer adjusting section 18.

The developer collecting section 23 mainly includes a wiping roller 28 and a cleaning blade 29, and cleans the liquid developer 1 (hereinafter, referred to as “undeveloped developer”) remaining on the surface of the developing roller 22. The cleaned undeveloped developer is transported to the developer adjusting unit 18 by the transport screw. Then, in order to reuse the undeveloped developer and the untransferred developer in the developer adjusting unit 18, the developer concentration adjustment and the toner particle dispersion processing are performed.

In the developing unit 13 of the printer according to the present embodiment, of the components of the developing unit 13, the developing unit 21, the developing roller 22, and the developer collecting unit 2
Numeral 3 is provided in one cartridge (a portion surrounded by a dashed line in the drawing), and this cartridge can be removed from the printer main body when maintenance or replacement is performed.

Next, the developer adjusting section 18 will be described.
FIG. 2 is a top view as seen from the direction of arrow A in FIG. 1, with the lid 35 removed. FIG. 3 is an exploded perspective view of the developer adjusting section 18. The developer adjusting section 18 is configured as shown in FIG.
As shown in FIG. 5, an adjustment tank 30 as storage means for storing the liquid developer 1, a concentration detecting means 32 for detecting the concentration of the liquid developer 1 stored in the adjustment tank 30, and a liquid for the liquid developer 1. A liquid amount detecting means 31 for detecting the amount, a stirring means 33 for stirring the liquid developer 1, a transport pump 34 for transporting the liquid developer 1 (see FIG. 1) which can be rotated forward and backward, and an upper part of the adjusting tank 30. And a lid 35 detachably attached to the cover.

First, the liquid amount detecting means 31 of the liquid developer 1 in the adjusting tank 30 will be described. Developer adjusting section 18
Adjustment tank 30 is formed of a cylindrical opaque resin container, and a pair of transparent glass blocks 3
8a and 8b are provided. One glass block 38
A light emitting element 39 (see FIG. 2) is provided in a, and a light receiving unit 40 is provided in the other glass block 38b at a position facing the light emitting unit 39. The light emitting element 39 and the light receiving element 40 are located at positions corresponding to the lower limit (level A), the standard amount (level B), and the upper limit (level C) of the liquid developer 1 stored in the container, respectively. 39a,
b, c and the light receiving sections 40a, b, c are arranged to face each other. Then, the emitted light emitted from the light emitting section 39 reaches the inside of the adjustment tank 30 through one glass block 38a, and is received by the light receiving section 40 through the other glass block 38b.

As the liquid amount detecting means 31, for example, a light transmission type photoelectric switch can be used. The photoelectric switch includes a light emitting unit 39 including a light emitting element such as an LED,
The light receiving unit 40 includes a light receiving element such as a photodiode, and outputs a signal that is ON when light is blocked. When the liquid developer 1 does not exist on the optical path, the detection signal is not output because the amount of light transmitted from the light emitting unit 39 to the light receiving unit 40 is large. On the other hand, when the liquid developer 1 exists on the optical path, the light emitted from the light emitting unit 39 is blocked by the liquid developer 1 and the amount of transmitted light reaching the light receiving unit 40 decreases. That is, when the transmitted light amount reaching the light receiving unit 40 is small, it is determined that the liquid developer 1 is present, and the light receiving unit 40 outputs a detection signal.

As described above, the light emitting section 39 and the light receiving section 40
Is disposed at three positions corresponding to the liquid amount. That is, the lower limit (level A) includes the light emitting unit 39a and the light receiving unit 4
The light emitting unit 39b and the light receiving unit 40b are arranged at 0a, the standard amount (level B), and the light emitting unit 39c and the light receiving unit 40c are arranged at the upper limit amount (level C). This makes it possible to detect the level of the liquid amount of the liquid developer 1. This detection signal is input to a main controller (not shown).

Next, the means 32 for detecting the concentration of the liquid developer 1 in the adjusting tank 30 will be described. Concentration detecting means 32
As shown in FIG. 3, a liquid carrying roller 42 rotatably held by a support plate 41 provided on the lower surface of the lid 35, an optical sensor 43 provided on the upper surface of the lid 35, And the main motor 44. Liquid carrying roller 4
2 has a configuration in which an eccentric disk portion 42b and two disk portions 42a of the same diameter sandwiching the eccentric disk portion 42b from both sides and having a diameter larger than the diameter of the eccentric disk portion 42b are integrally formed. I have. The liquid carrying roller 42 is partially immersed in the liquid developer 1 and rotated, and a developer regulating blade is provided in a concave portion on a circumferential surface formed at a step between the eccentric disk portion 42b and the two disk portions 42a. Then, the liquid developer 1 to be subjected to the concentration detection is filled, and the liquid developer 1 is formed in a plurality of different film thicknesses corresponding to the concave portions. The light emitted from the light emitting portion of the optical sensor 43 passes through the detection hole 35e of the lid 35,
The developer liquid film formed in the concave portion is irradiated. The light applied to the developer liquid film passes through the developer liquid film and passes through the eccentric disk portion 4.
The light is reflected by the cylindrical surface 2b. Optical sensor 4
The light receiving unit 3 receives the light and outputs an analog value corresponding to the intensity of the reflected light. While rotating the liquid carrying roller 42, the analog value of the optical sensor 43 that is continuously output for the developer film of the plurality of thicknesses is integrated and compared with a value obtained in advance to obtain the liquid developer. Detect concentration. Then, after detecting the developer concentration, the concave portion which is the developer concentration detecting surface is cleaned by a cleaning blade (not shown) which comes into contact with the concave portion.

In the density detecting means 32 having the above structure, an example has been described in which the liquid developer density is detected using the output detected by the reflection type optical sensor 43. Alternatively, a transmission type optical sensor may be used. In this case, the liquid carrying roller 42 composed of the two disk portions 42a and the eccentric disk portion 42b is formed of a transparent member such as glass or resin, and a light source is installed therein as a light emitting portion of the optical sensor. A light receiving portion of an optical sensor that receives the transmitted light intensity from the light source is provided outside the roller. Thereby, the concentration of the liquid developer can be detected using the output detected by the transmission type optical sensor.

Next, the stirring means 33 for the liquid developer 1 in the adjusting tank 30 will be described. Inside the adjustment tank 30, a pair of stirring blades 33a,
b is provided. These stirring blades 33a and 33b are mounted on a drive shaft (not shown), and are rotated by a drive unit (not shown) to stir the liquid developer 1 in the adjustment tank 30. Note that a cylindrical container is used as the adjustment tank 30, and a pair of stirring blades 33a,
Since the distance between the tip of b and the inner peripheral surface of the container can be kept as small as possible, no liquid pool occurs. Thus, the liquid developer 1 can be uniformly agitated at a lower rotation speed as compared with a square or elliptical tank in which a liquid pool easily occurs.

The lid 35 has a hole 35 for toner supply.
a, carrier liquid supply hole 35b, photosensitive drum cleaning liquid recovery hole 35c, developing roller recovery hole 35d
Are provided, and toner and the like are supplied to the adjustment tank 30 through the respective holes.

In the printer having the above-described configuration, the replenishment control of the liquid developer when the liquid developer 1 of the developer adjusting section 18 is consumed by the printing of the image and becomes smaller than a predetermined liquid amount will be described. . The liquid developer supply program starts when a print start signal is input from a personal computer or the like or when the printer is idling. The liquid amount is detected by the liquid amount detecting means 31 at a predetermined cycle, and when it is detected that the liquid amount of the liquid developer 1 is equal to or less than the specified amount, the toner bottle 19 or the carrier The supply of at least one of the developer and the carrier liquid from the bottle 20 is started. Note that, in addition to the replenishment program, the liquid concentration detection program starts when a print start signal is input from a personal computer or the like or when the printer is idling. Then, the concentration of the liquid developer in the adjusting tank 30 of the developer adjusting section 18 is detected by the concentration detecting means 32 at a predetermined cycle, and the detection result is stored in a storage medium such as a memory of the main controller. . The replenishment program and the liquid concentration detection program are respectively executed,
The replenishment program uses the data stored in the storage medium by the liquid concentration detection program to replenish the developer and carrier,
Further, it is configured to determine the collection of the untransferred developer to the developer adjustment unit 18.

FIG. 4 shows the liquid developer 1 in the adjustment tank 30.
9 is a flowchart showing a control for replenishment of a developer and the like when the liquid amount becomes equal to or less than a predetermined liquid amount. First, the adjustment tank 30
When the liquid amount of the liquid developer 1 in the inside becomes equal to or less than a predetermined liquid amount, the latest liquid developer concentration data stored in the storage medium is acquired by executing the liquid concentration detection program (Step 1). This density data is compared with the carrier supply start developer density (step 2). Then, when the newest liquid developer concentration data is less than the carrier supply developer concentration, the developer is supplied from the toner bottle 19 (step 3).

On the other hand, in the above step 2, when the newest liquid developer concentration data is equal to or higher than the carrier supply developer concentration, the supply of the carrier from the carrier bottle 20 is performed (step 4). When the carrier liquid is replenished,
Thereafter, replenishment of the untransferred developer and the undeveloped developer is performed (step 5). Then, it is determined whether or not the system is terminated. If the system is terminated, the supply control is terminated. If the system is not terminated, the system enters a standby state until the liquid amount of the liquid developer 1 in the adjustment tank 30 becomes equal to or less than a predetermined liquid amount. (Step 6). After the developer has been replenished in step 3, the liquid concentration in the adjustment tank 30 after the developer replenishment is measured by the concentration detecting means 32.
If the detected density is lower than the reference developer density, the untransferred developer and the undeveloped developer are supplied in step 5. On the other hand, if the detected density is equal to or higher than the reference developer density, it is determined whether or not the system is terminated in step 6.

The carrier replenishment start developer concentration in the above step 2 is determined by the relationship of upper limit developer concentration ≧ carrier replenishment start developer concentration> reference toner concentration> lower limit developer concentration. The replenishment of the untransferred developer and the replenishment of the undeveloped developer in step 5 are performed by the developer adjusting unit 1 by the transport screw based on the developer reuse control program.
8 and is reused. The undeveloped developer has a higher developer concentration than the reference developer concentration, while the untransferred developer concentration has a lower developer concentration than the reference developer concentration.

In this embodiment, the undeveloped developer recovered from the developing roller 22 or the scraping roller 28 and the untransferred developer recovered from the photoconductor cleaning unit 15 are developed by a transporting means such as a transport screw. The developer is conveyed to the developer adjusting section 18, where the detection of the developer concentration, the detection of the amount of the developer, and the re-dispersion of the developer are performed. Approximately 200 cc of developer is always stored in the developer adjusting unit 18, and the required amount of developer is supplied to the developing unit by a conveying means such as a gear pump. Accordingly, although the undeveloped developer and the untransferred developer are mixed in the developer adjusting unit 18, the liquid developer concentration does not fluctuate so rapidly because the liquid developer 1 always stored is present.

Next, the determination of erroneous detection by the density detecting device 32 will be described. As described above, the density detector 32 measures the optical reflection density of the liquid developer layer on the liquid carrying roller 42. This liquid carrying roller 4
The analog output value of the reflection type optical sensor 43 is integrated over one round of the two to convert it into a liquid developer concentration. That is, the liquid developer concentration is stored in the storage medium.

Then, the image area ratio is calculated for each print job by the image area ratio storage and accumulation program, and is stored in a storage medium corresponding to the print job. Therefore, a table for calculating the predicted liquid developer concentration value is prepared in the storage medium, and the predicted developer concentration of the liquid developer concentration in the developer adjusting unit 18 is calculated.

FIG. 5 is an example of the table, and is a graph showing the relationship between the image area ratio and the collected and reused undeveloped developer and untransferred developer (hereinafter referred to as "collected developer"). is there. As for the collected developer that is collected and reused by the developer adjusting unit 18, the concentration of the collected developer with respect to the image area ratio is predicted as shown in the graph of FIG. The collected developer is subjected to developer concentration adjustment and redispersion by the developer adjusting unit 18, and is mixed with the liquid developer 1 held in the developer adjusting unit 18 in advance. In the present embodiment, the description is made using the developer adjustment unit 18. However, when the developer adjustment unit 18 is not provided, the liquid developer concentration may be predicted based on the graph of FIG. Further, the estimation of the concentration of the collected developer performed in the present embodiment is an example, and the actual image area changes depending on the paper interval, the setting of the developable area, and the like, and is not limited thereto.

The recovered developer is mixed with the liquid developer 1 previously held in the developer adjusting section 18 and has a developer concentration as shown in FIG. Here, the liquid developer concentration of the developer adjusting unit 18 is greatly affected by the liquid amount of the liquid developer 1 held in the developer adjusting unit 18. In the present embodiment, as shown in the graph of FIG. 6, the liquid amount of the liquid developer 1 in the developer adjusting section 18 is set to 50 cc, 100 cc, and 200 cc, and the same image area ratio is repeated for 100 prints. The prediction value is calculated in a state where the calculation is not performed. Therefore, the average value of the image area ratio for 100 sheets stored in the storage medium is called, and the average value can be used to predict the liquid developer concentration of the developer adjusting unit 18 based on the graph of FIG. In this embodiment, the capacity of the developer adjusting section 18 is set to 20.
The test was performed at 0 cc.

Here, if error processing such as allowing the liquid developer 1 to be retracted from the developing unit 21 to the developer adjusting unit 18 during maintenance is considered, the smaller the capacity of the developer adjusting unit 18 is, the better. good. However, if it is too small, the fluctuation of the liquid developer concentration is too large, and it becomes difficult to control the liquid developer concentration. For example, if the capacity of the developer adjusting section 18 is 5
When 0 cc is set, the average value of the image area ratio data stored in the storage medium is 1
It is necessary to average not with the number of prints but with a small number of prints. The estimation of the liquid developer concentration of the developer adjustment unit 18 performed in the present embodiment is an example, and the actual image area changes depending on the paper interval, the setting of the developable area, and the like.
It is not limited to this.

FIG. 7 is a graph showing the relationship between the image area ratio and the developer concentration in the developer adjusting section in 20 prints. As shown in FIG. 7, by reducing the number of prints to be averaged from 100 prints to 20 prints, the reduction range is also reduced. Therefore, when the amount of the liquid developer in the developer adjusting section 18 is small, it is necessary to reduce the number of prints for averaging the image area.

It should be noted that there is a slight time lag until the collected developer is transported and collected by the developer adjusting section 18. That is, the collected developer in which the print information of a plurality of sheets is averaged is collected. Therefore, an image area ratio for 20 prints on the print job storage medium may be averaged, and the predicted density value may be calculated based on the average image area ratio for the 20 prints. In the present embodiment, the image area ratio of 20 prints is used as an average value, but the present invention is not limited to this, and it is sufficient if the print area is 20 prints or more.

As described above, it was possible to predict the developer concentration of the recovered developer based on the image area ratio, or the developer concentration of the developer adjusting section.

The margin of the fluctuation of the liquid developer concentration which can prevent the fluctuation of the image density on the transfer paper 16 due to the fluctuation of the liquid developer concentration has an effect on the image when the liquid developer concentration is 15%. Liquid developer concentration ± 15%
3% developer was used. Therefore, the margin of the developer concentration in this embodiment is ± 3%. However, in the present embodiment, the designated numerical value is set to ± 2%, and a slight margin is provided. That is, when the difference between the liquid developer concentration measured by the concentration detecting means 32 and the predicted developer concentration value predicted from the image area ratio exceeds ± 2%, it is determined that the developer concentration detecting device has erroneously detected. I do.

Further, depending on the image area ratio, there is an image area ratio at which the liquid developer concentration of the developer adjusting section 18 increases or an image area ratio at which the liquid developer concentration decreases. When the concentration of the liquid developer is reduced, the supplied developer needs to have a higher concentration in order to restore the reference developer concentration. However, in managing the supply amount and the liquid developer concentration, it is easier to dilute the thickened developer. Therefore, it is desirable to avoid such control that the liquid developer concentration decreases. Therefore, the difference between the predicted liquid developer concentration and the liquid developer concentration detected by the concentration detecting means is such that the predicted liquid developer concentration−the liquid developer concentration detected by the concentration detecting means <0. At this time, it is possible to prevent the concentration of the liquid developer from decreasing by judging that the detection is erroneous.

In the present embodiment, normally, when erroneous detection is not determined, as described above, the liquid carrying roller 42 is partially immersed in the liquid developer 1 and rotated to rotate the eccentric disk portion 42b and the two disk portions 42a. A developer regulating blade is provided in a concave portion on a circumferential surface formed at a step portion with the liquid developer, and the liquid developer 1 to be subjected to concentration detection is filled, and the liquid developer 1 is supplied to a plurality of different films corresponding to the concave portion. It is formed thick. The optical sensor 43 detects the liquid developer concentration by comparing the integrated value of the reflected light intensity of the developer liquid film formed in the concave portion with a value obtained in advance. However, the liquid developer concentration may be erroneously detected due to some influence. One of the causes is paper dust or dust mixed in the liquid developer,
Coarse particles of toner. When these contaminants are caught between the concave portion and the developer regulating blade, a uniform liquid developer layer cannot be formed, and white stripes are generated. Then, the intensity of the reflected light detected by the optical sensor 43 is strongly detected, and is detected lower than the actual liquid developer concentration. That is, erroneous detection is performed. In order to prevent such a problem, the liquid carrying roller 42 is reversely rotated for a predetermined period to remove the contaminants between the concave portion and the developer regulating blade. Further, since the concave portion which is the developer concentration detecting surface is cleaned by the cleaning blade which comes into contact with the concave portion after detecting the liquid developer concentration, the concave portion surface is cleaned and the developer concentration can be detected satisfactorily.

In the present embodiment, as described above, the liquid developer is dispersed at a solid concentration of 5 to 40% and has a viscosity of 10%.
A liquid developer of 0 to 10,000 mPas was used. In particular, good results were obtained when the solid concentration was 15 to 25%.

[0058]

According to the first to ninth aspects of the present invention, a special controller for judging erroneous detection is executed by, for example, executing a sequence for judging erroneous detection of the liquid concentration detecting means by an already provided programmable controller. It is not necessary to separately provide a simple device, so that cost reduction and space saving can be achieved, and there is an excellent effect that erroneous detection of the liquid concentration detecting means can be determined with a simple configuration.

In particular, according to the second aspect of the present invention, the size of the predetermined numerical value is set to a size that does not affect the image density of the image formed on the recording medium. When the liquid developer in the liquid developer container has a density close to the reference density, there is an excellent effect that erroneous detection is not determined and the image density of the formed image is maintained.

In particular, according to the third aspect of the invention, when the relationship of predicted liquid concentration-detected liquid concentration <0 is satisfied, it is determined that the liquid concentration detecting means has erroneously detected. There is an excellent effect that the concentration of the liquid developer can be prevented from lowering.

In particular, according to the fourth aspect of the present invention, the average value of the image area ratios of 20 or more stored in the storage means is used as the numerical value of the image area ratio used in the calculation by the calculation processing unit. There is an excellent effect that the reliability of the liquid concentration predicted by the arithmetic processing unit can be secured.

In particular, according to the fifth aspect of the present invention, by detecting the liquid concentration based on the integrated value of the output of the optical sensor, the noise level of the signal is suppressed. There is an excellent effect that good detection becomes possible.

In particular, according to the invention of claim 6, the liquid to be subjected to the concentration detection can be formed in a plurality of different film thicknesses corresponding to the steps between one disk and two disks having the same diameter. . Further, since the plurality of film thicknesses can be continuously formed by continuously rotating the roller-shaped member, the liquid concentration can be continuously detected, and the change in the concentration can be detected quickly. There is an excellent effect that you can.

In particular, according to the invention of claim 7, the liquid to be subjected to the concentration detection can be formed in a plurality of film thicknesses according to the distance of the contact portion between the roller member and the film thickness regulating member. Also,
Since the plurality of film thicknesses can be formed continuously by continuously rotating the roller-shaped member, the liquid concentration can be continuously detected, and the change in the concentration can be quickly detected. There is an excellent effect that it can be done.

In particular, according to the invention of claim 8, when foreign matter is caught between the roller-shaped member and the film thickness regulating member, the roller-shaped member is rotated by a predetermined angle in the direction opposite to the rotation direction at the time of detecting the liquid concentration. By rotating, the foreign matter can be removed.
As a result, there is an excellent effect that the liquid developer layer having a uniform thickness is formed again on the roller-like member, and the liquid concentration can be accurately detected by the liquid concentration detecting means.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of a wet image forming apparatus according to an embodiment.

FIG. 2 is a view taken in the direction of the arrow A in FIG. 1, showing a state in which a lid 35 is removed.

FIG. 3 is an exploded perspective view of a developer adjustment unit according to the embodiment.

FIG. 4 is a flowchart of concentration adjustment and liquid amount adjustment according to the embodiment.

FIG. 5 is a graph showing a relationship between an image area ratio and a concentration of a collected liquid developer.

FIG. 6 is a graph showing a relationship between an image area ratio at the time of 100 printing and a liquid developer concentration of a developer adjusting unit.

FIG. 7 is a graph showing a relationship between an image area ratio at the time of 20 printing and a liquid developer concentration of a developer adjusting unit.

FIG. 8 is a schematic configuration diagram of a main part of a developing device of a wet image forming apparatus according to a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 photoconductor drum 13 developing unit 18 developer adjusting unit 19 toner bottle 20 carrier bottle 21 developing unit 22 developing roller 23 developer collecting unit 25 application roller 30 adjustment tank 31 liquid amount detecting means 32 concentration detecting means 33 stirring means 34 transport pump 36 Drain cock 37 Coupling 38a, b Glass block 39 Light emitting unit 40 Light receiving unit

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G03G 15/10 113 (72) Inventor Osamu 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2G059 AA01 BB04 CC20 EE01 JJ14 KK01 MM05 2H074 AA03 BB42 BB54 BB58 CC01 CC03 CC12 CC22 CC62 4F040 AA07 AB20 AC01 BA13 BA14 CB11 CB24 CB40 DA07 DA20 DB22 DB23

Claims (9)

[Claims] A liquid developer thin layer formed on the developer carrier by using an image carrier and a liquid developer in a liquid developer container;
Developing means for developing the latent image on the image carrier with the liquid developer thin layer to visualize the image; transfer means for transferring the visualized image to a recording medium; and developing means for developing the latent image on the image carrier. Liquid collecting means for collecting and reusing the undeveloped liquid developer which has not been transferred and the untransferred liquid developer which has not been transferred to the recording medium into the liquid developer storage, and the liquid in the liquid developer storage In a wet image forming apparatus having a liquid concentration detecting unit for detecting a concentration of a developer, a storage unit for storing an image area ratio of an image formed for each recording medium, and an image area ratio stored in the storage unit An arithmetic processing unit for predicting the liquid concentration of the liquid developer storage unit after the liquid developer collected by the liquid collecting unit is injected, based on the numerical value of And the liquid concentration detected by the above liquid concentration detection means A liquid image forming apparatus, comprising: a comparing unit that determines whether the liquid concentration detecting unit has erroneously detected when the difference between the liquid concentrations compared by the comparing unit is equal to or greater than a predetermined value. apparatus. 2. A wet image forming apparatus according to claim 1, wherein a reference density of a liquid developer used in said developing means is set in advance to influence an image density of an image formed on said recording medium. The difference between the maximum value of the liquid developer density and the reference density, or the difference between the minimum value of the liquid developer density that does not affect the image density and the reference density, whichever is smaller, Wherein the predetermined numerical value is set. 3. The liquid image forming apparatus according to claim 1, wherein the liquid concentration predicted by the arithmetic processing unit and the liquid concentration detected by the liquid concentration detecting means are calculated by the predicted liquid concentration-detection. The liquid image forming apparatus is characterized in that, when the relationship of the liquid concentration <0 is satisfied, the judging means judges that the liquid concentration detecting means has erroneously detected. 4. The wet image forming apparatus according to claim 1, wherein the numerical value of the image area ratio used for the calculation by the arithmetic processing unit is the numerical value of the image area ratio of 20 or more stored in the storage means. A wet type image forming apparatus using an average value. 5. A wet image forming apparatus according to claim 1, wherein said liquid concentration detecting means forms said optical sensor and a liquid to be subjected to concentration detection so as to have a plurality of different thicknesses. A liquid-carrying member for carrying out the liquid-concentration process, wherein an integrated value of output data of the optical sensor for the plurality of thicknesses carried by the liquid-carrying member is used as liquid concentration detection data. Forming equipment. 6. A wet image forming apparatus according to claim 5, wherein said liquid holding member has one disk portion whose diameter changes stepwise, sandwiches said disk portion from both sides, and has a maximum diameter of said disk portion. Wet-type image forming, comprising a roller-shaped member integrally formed with two disks having the same diameter and having a larger diameter, and a rotation driving means for rotating the roller-shaped member is provided. apparatus. 7. A wet image forming apparatus according to claim 6, wherein a film thickness regulating member for regulating the film thickness of the liquid carried on said roller member, a cleaning member for cleaning said liquid after detecting the concentration thereof, and said cleaning member. A liquid transport path for collecting and transporting the liquid cleaned by the member, and all of these are configured as an integral unit. 8. A wet image forming apparatus according to claim 6, wherein said roller-like member is rotated when said liquid density detecting means judges that said liquid density detecting means has erroneously detected said liquid density detecting means. A wet image forming apparatus, comprising: control means for controlling rotation by a predetermined angle in a direction opposite to the direction. 9. The method of claim 1, 2, 3, 4, 5, 6, 7 or 8.
In the wet image forming apparatus, as the liquid developer,
The solid concentration is dispersed in the range of 5% to 40%, and the viscosity is 100 mPas to 10,000 mPa.
s] A wet image forming apparatus using the following liquid developer.