JPH04253072A - Wet type image forming device - Google Patents

Abstract

PURPOSE:To always maintain an excellent recorded image regardless of the difference of material quality caused by the type of a recording sheet by detecting scattered light to decide the recording sheet and controlling the image forming conditions of a device according to the decided output. CONSTITUTION:Two kinds of developer liquids, for instance, the developer liquid of the toner concentration of 60g/l is housed in a tank 15, and the developer liquid of the toner concentration of 120g/l is housed in a tank 17. When a recording sheet P is fed from a cassette 30 accompanying with a copying action, first, the surface state of the recording sheet P is detected at the positions of a pair of rollers 34 by a recording sheet detecting sensor 20. At this time, when the detection of a plane sheet is obtained, the developing liquid K1 housed in the tank 15 is supplied to a developing part, and when the detection of the recording sheet P having a rough surface compared with the plane sheet, the developing liquid K2 having a high toner concentration is supplied from the tank 17.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus that forms images by a wet electrophotographic process. [0002] In image forming apparatuses that apply wet electrophotography, such as plain paper copiers (PPCs), laser printers, and plain paper facsimile machines, in order to obtain good images on all types of recording paper, In the past, efforts have been made to optimize various conditions such as development, transfer, and fixing. However, in general, the material and surface condition differ depending on the type of recording paper, such as PPC paper, art paper, OHP sheet, second original paper, and recycled paper, which has recently been attracting attention, and the fixability of toners changes. Therefore, the optimal conditions for obtaining the best image are different for each type of recording paper, and in order to always obtain a good image, it is necessary to perform control to set the optimal conditions for image formation for each recording paper. There is. For example, with the increase in the amount of high-quality paper used for PPC, in order to obtain good images, the air knife squeeze method, corona squeeze method, reverse squeeze roller method, etc. are used to remove excess developer on the surface of the photoreceptor before transfer. was carried out,
Image quality is improved by reducing the amount of remaining developer. [0003] However, as a result of removing the developer in these conventional techniques, when recording paper with poor smoothness is fed, toner electrophoresis occurs in the developer during transfer. There has been a problem in that the developer layer required for this cannot be uniformly formed between the photoreceptor and the recording paper. The present invention was made based on this background, and it detects differences in the types of recording paper, especially the surface roughness, and
It is an object of the present invention to provide an image forming apparatus that can always obtain good image quality by performing electrophotographic process control suitable for each recording paper. [0004] The above object includes an exposure device, a photoreceptor carrying an electrostatic latent image formed by exposure of the exposure device, and a developer containing toner to develop the latent image. Wet type, comprising: a developing device that develops a toner image; a transfer device that transfers the toner image onto a recording sheet; and a paper feeding device that conveys and supplies the recording sheet to a position facing the photoreceptor that faces the transfer device. The image forming apparatus includes a recording sheet determining means for irradiating the recording sheet with light and detecting at least the scattered light to determine the recording sheet, and an image forming condition of the image forming apparatus according to the determination output of the recording sheet determining means. and a control means for controlling, and the developing device has at least two developing tanks, the developing tanks store developing solutions having different toner concentrations, and the controlling means controls the developer to be supplied from the developing tank according to the determination output. This is achieved by the first means for controlling the selection of a developing solution and performing a developing operation. The above object also includes an exposure device, a photoconductor that carries an electrostatic latent image formed by exposure of the exposure device, and a developer that develops the latent image into a toner image using a developer containing toner.
In a wet image forming apparatus equipped with a transfer device that transfers the toner image onto a recording sheet, and a paper feed device that conveys and supplies the recording sheet to a position facing the photoreceptor facing the transfer device, the recording sheet is irradiated with light. , comprising a recording sheet determining means for determining the recording sheet by detecting at least the scattered light, and a control means for controlling image forming conditions of the image forming apparatus according to a determination output of the recording sheet determining means, the control means is achieved by a second means for controlling the charging potential of the photoreceptor in accordance with the determination output. The above object further includes an exposure device, a photoreceptor that carries an electrostatic latent image formed by exposure of the exposure device, and a developer that develops the latent image into a toner image using a developer containing toner. In a wet image forming apparatus equipped with a transfer device that transfers the toner image onto a recording sheet, and a paper feed device that conveys and supplies the recording sheet to a position facing the photoreceptor facing the transfer device, the recording sheet is irradiated with light. , comprising a recording sheet determining means for determining the recording sheet by detecting at least the scattered light, and a control means for controlling image forming conditions of the image forming apparatus according to a determination output of the recording sheet determining means, the control means is achieved by a third means for controlling the surface movement speed of the photoreceptor in accordance with the determination output. [0005] The recording sheet determining means detects at least the scattered light scattered from the irradiated recording sheet to determine the type of recording sheet. The control means selects a developer and performs a developing operation in accordance with the judgment output of the recording sheet judgment means, controls the charging potential of the photoreceptor, or controls the surface movement speed of the photoreceptor. [Embodiments] Hereinafter, embodiments of the present invention will be explained based on the drawings. FIG. 1 is a block diagram of the main parts of a wet-type copying machine. In the figure, reference numeral 1 denotes a photosensitive drum, which is driven to rotate at a constant speed in the direction of arrow a during copying. Then, after being uniformly charged in the dark by the main charger 2, an optical image (irradiation light L) of the document is irradiated and formed by an exposure device (not shown) to carry an electrostatic latent image. Next, the portions of this electrostatic latent image outside the image forming area on both sides in the axial direction of the photoreceptor drum are neutralized and removed by an eraser 4. Furthermore, this electrostatic latent image is visualized while passing through the wet developing device 5 section. on the other hand,
As shown by the broken line arrow from the paper feed section, which will be described later, the conveyance roller 6
A recording paper P is conveyed through the recording paper P, and the visualized toner image is transferred onto this recording paper P under the action of the transfer charger 7. The recording paper P is then transferred to the conveyor belt 8
When the toner image passes through the nip between the heating roller 9 and the pressure roller 10 in the fixing device 11, it receives heat from the heater H of the heating roller 9, and the toner image is fixed. The paper is ejected to the omitted paper ejection tray. On the other hand, residual toner is removed from the photosensitive drum 1 after image transfer while it passes through the cleaning unit 12.
The residual potential is removed by a static eliminator 13 using a static neutralizing charger to prepare for the next copy. In the wet-type developing device 5, a first developing roller 52, a second developing roller 53, and a squeeze roller 54 are arranged in a developing container 51, and the photosensitive drum 51 is
are placed close to each other. That is, the first developing roller 52 and the second developing roller 53 are each held at a very small distance from the surface of the photoreceptor drum 1, for example, 0.1 mm, and the circumferential surface of the photoreceptor drum 1 is spaced as shown by arrows b and c. It rotates in the same direction as the direction of movement, but at a faster speed. Each scraper 55 constituting a cleaning member whose one end is fixed to the developing container 51 comes into contact with each developing roller and constantly cleans the toner on the developing roller. The developer is supplied downward from the developer supply nozzle 14 which is open above the first developing roller 52 . First, this developer is uniformly applied to the photoreceptor drum 1 by the first developing roller 52 and the second developing roller 53.
Used for developing electrostatic latent images. The remaining developer on the photosensitive drum 1 is scraped off by a squeeze roller 54 rotating in the opposite direction to the above roller. The surface of the squeeze roller 54 is also cleaned with a scraper. The surplus developer used for the development is collected from the developer tank 15 or 1 located below the recovery hole 56 provided at the bottom of the developer container 51.
7 will be collected. The developer tank 15 contains a developer K1 used for normal development, and a pump motor M that also serves as agitation is used.
1 through the pipe 16 to the supply nozzle 14. On the other hand, the developing tank 17 contains a developing solution K2 having a higher toner concentration, and is supplied to the developing device 5 via a pipe 18 by a similar pump motor M2. Figure 3
FIG. 2 is a configuration diagram of a paper feeding section. The recording paper P stored in the cassette 30 is called out by a pick-up roller 31, separated one by one by a pair of separation rollers made up of a feed roller 32 and a reverse roller 33, and sent out to a pair of registration rollers 34. Note that 35 is a well-known resist detection sensor, and 20 is a recording paper detection sensor (
recording sheet determination means). Registration detection sensor 35
Almost at the same time as detecting the presence of the recording paper P, the recording paper detection sensor 20 detects scattered light caused by the roughness of the surface of the recording paper P, and determines the type of the recording paper P. FIG. 2 is an explanatory diagram showing how recording paper P is detected. The recording paper detection sensor 20 includes a light emitting section 20a and a light receiving section 20b. Assuming that the surface of the recording paper P is an ideal mirror surface as shown in the figure, the incident light emitted from the light emitting section 20a is reflected on the surface of the recording paper and becomes specularly reflected light RL0, and no scattered light or transmitted light is seen. However, if the surface of the recording paper has irregularities, is transparent, has an uneven composition, or is coated with a substance different from the substrate, the incident light is the component RL0 that is correctly reflected depending on the type of recording paper.
, a transmitted light component PL0, and a generally weak scattered light component. The scattered light is roughly divided into two types: reflected scattered light RL1 and transmitted scattered light PL1. When a conventional reflective optical sensor is used, the light receiving part 20b is placed at a position directly facing the incident light, and the specularly reflected light RL0 is detected, but in this embodiment, the specularly reflected light RL0, which is normally reflected with the maximum intensity, is detected. Not RL0 but reflected scattered light R
It is characterized by detecting L1 or transmitted scattered light PL1. The scattered light detected at a certain position changes depending on the surface condition of the recording paper P and the difference in light transmittance. Table 1 shows the relative values of the measurement examples. As shown in Table 1, since the tendency of scattering differs depending on the recording paper P, it is possible to determine the type of recording paper P based on the relative value of the detected scattered light. [Table 1] Recording paper
Reflected scattered light Transmitted scattered light



PPC paper medium
small
Coated paper medium
Extremely small
Second original drawing paper
Elementary/middle school

OHP sheet extra small
small
rag paper
large small

Release paper large
Extremely small
Recycled paper medium to large small
Note that the type of recording paper P can be detected more accurately by providing a plurality of light emitting sections 20a and light receiving sections 20b. Table 2 shows a measurement example in which the intensity trends of specularly reflected light RL0 and specularly transmitted light PL0 are added to the measurement results in Table 1. By identifying the recording paper P using such a large amount of information, it becomes possible to make a more detailed distinction than when determining based only on the scattered lights RL1 and PL1. For example, when you want to clearly distinguish between coated paper and PPC paper, the reflected and scattered light RL1 of the two exhibits almost similar values, so detecting the specularly transmitted light PL0 at the same time will cause a difference in the intensity of the transmitted light, resulting in a difference in the transmitted light intensity between the two. Discrimination becomes possible. Therefore, by detecting the specularly transmitted light PL0 at the same time as the scattered light and using that information as a means of discrimination, it becomes possible to distinguish between coated paper and PPC paper. By combining the above methods, many types of paper and sheets can be discriminated. [Table 2]
Reflected scattered light Transmitted scattered light Transmitted light Reflected light



PPC paper medium
Elementary/middle/middle school
coated paper
Medium Very small
very small large
Second original drawing paper small
medium large medium
OHP sheet
Extra Small Small Extra Large Extra Large Rag Paper Large
Small Small Medium
release paper
Large Very small
Very small medium
Recycled paper medium to large
Elementary/middle/middle school
In the present invention, image quality is improved by optimizing various conditions of the electrophotographic process according to the type of recording paper P detected by the recording paper detection sensor 20. Three methods for optimizing electrophotographic process conditions will be described below. The first method is to control the toner concentration of the developer. The degree of development is proportional to the toner particle concentration. Therefore, even if process conditions such as charging potential and exposure amount are kept constant, it is possible to control the amount of toner adhering to the photoreceptor drum 1 by changing the concentration of toner particles in the supplied developer. Therefore, by using the following method, even when recording paper P with a rough surface is fed, standard recording paper P
A transfer image similar to that can be obtained. FIG. 4 is a characteristic diagram showing the relationship between the toner concentration of the supplied developer and the amount of toner adhering to the recording paper. Normal image formation is performed on the premise that a toner image is transferred to plain paper (such as PPC paper), and therefore a developer having a toner concentration of about 50 to 100 (g/l) is used. Therefore, in the wet type developing device 5 shown in FIG.
A developer with a toner concentration of 60 (g/l) is stored in the tank 17, and a developer with a toner concentration of 120 (g/l) is stored in the tank 17, respectively. When recording paper P is fed from the cassette 30 during a copying operation, the surface condition of the recording paper P is first detected by the recording paper detection sensor 20 at the position of the registration roller pair 34. If it is detected that it is plain paper, the developer K1 contained in the tank 15 is supplied to the developing section, and if it is detected that the recording paper P has a larger surface roughness than plain paper,
A developer K2 having a high toner concentration is supplied from a tank 17. 5 to 8 are control flowcharts. In the main control routine shown in FIG.
After turning on the main switch, initialize the device (S1)
, Next, the operator performs various copy mode settings (S2
). Furthermore, the copy conditions are checked (S3), and if the conditions are met, the print key waits (S4). Copy start processing (S5) following print key on
, performs copy operation processing (S6). After the copy is completed (S7), post-copy processing is executed (S8). In the copy operation processing subroutine shown in FIG.
Pulse control processing for operating the copying machine (S10), process condition setting processing (S11), and process control processing (
S12), and the copying operation continues until the preset number of copies is reached (S13). In the subroutine of the process condition setting process shown in FIG.
does not exist (N in S21), process 1, 2, 3, 4
Each flag is turned off (S22). When the registration detection sensor 35 is detecting the recording paper P (Y in S20) and the processing 1 flag to processing 4 flag is not set (S2
3 is N), check the output status and if the output is less than 25%, process 1
flag (S27); if it is 25% or more and less than 50%, a processing 2 flag (S28) is set; if it is 50% or more and less than 75%, a processing 3 flag (S29) is set; if it is 75% or more, a processing 4 flag is set (S30). In the process control process shown in FIG.
If the flag is on (Y in S31), control processing 1 is executed (S32). Similarly, when each process flag of processes 2 to 4 is turned on (Y in S33, S35, S37), each corresponding control process is executed (S34, S36, S38). For example, control process 1 is a process for non-feeding of recording paper P, control process 2 is a process for detecting plain paper, control process 3 is a process for detecting rough paper such as rag paper, recycled paper, etc., and control process 4 is a process for detecting paper P. Take action against paper jams. Specifically, in control process 2, developer K1 is supplied from developer tank 15, and in control process 3, developer K2 is supplied from developer tank 17. The second method is to control the potential contrast during development. Since the degree of development is generally proportional to the potential contrast, it is possible to control the amount of toner adhering to the photoreceptor drum 1 by changing the potential contrast during development, even if process conditions such as exposure amount remain constant. It is possible. Therefore, in the following way,
Even when recording paper P with a rough surface is fed, a transfer image similar to that of standard recording paper P can be obtained. FIG. 9 is a characteristic diagram showing the relationship between the amount of toner attached to the recording paper and the potential contrast during development. Normal image formation is performed by transferring the potential contrast onto plain paper such as PPC paper 125
When set to approximately 0 (V), when feeding recording paper P with poor smoothness such as rag paper, the photoreceptor drum 1
It is difficult to sufficiently reproduce the above toner image on the recording paper P. This is because the toner image and the recording paper P do not come into close contact with each other during transfer due to the unevenness of the surface of the recording paper P. Therefore, in order to obtain a good transferred image, it is necessary to increase the amount of toner adhering to the photoreceptor drum 1 to cover the defective transfer to the recording paper P. Therefore, the potential contrast is changed by about 50 to 150 (V) according to the characteristic diagram of FIG. 9 to control the amount of toner adhesion. Specifically, the above-mentioned Figure 8
In control process 2 in the flowchart, the potential is set to 125
0 (V), and in control process 3, the potential is set to 1350 (V).
). The third method is to control the linear velocity of the photosensitive drum 1 during image formation, that is, the development time. Since the degree of development is generally proportional to the development time, it is possible to control the amount of toner adhering to the photoreceptor drum 1 by changing the development time even if the process conditions such as the exposure amount remain constant. Therefore, by the following method, even when recording paper P with a rough surface is fed, a transferred image similar to that of standard recording paper P can be obtained. FIG. 10 is a graph showing the relationship of toner adhesion amount with respect to different linear speeds of the photosensitive drum 1. When the photoreceptor drum 1 is rotated at 345 mm/sec, which is the speed at which normal image formation is performed by transferring onto standard paper such as PPC paper, when a recording paper P with poor smoothness such as rag paper is fed, the photoreceptor drum 1 It is difficult to sufficiently reproduce the above toner image on the recording paper P. this is,
As mentioned above, during transfer, the toner image and the recording paper P are
This is because they do not adhere tightly due to the unevenness of the surface. Therefore,
In order to obtain a good transferred image, it is necessary to increase the amount of toner adhering to the photoreceptor drum 1 to cover the transfer failure of the recording paper P. Therefore, as shown in Fig. 10, the linear velocity was set to 266
mm/sec to increase the toner adhesion amount. Specifically, in the control process 2 in the flowchart of FIG.
c, and in control process 3, the linear velocity was set to 266 mm/sec.
Set to . Note that switching and setting control of these modes is performed by a CPU (control means) provided in the copying machine. As described above, according to the present invention, there is provided a recording sheet determining means for determining a recording sheet by detecting scattered light, and an image forming apparatus according to the determination output of the recording sheet determining means. According to the invention according to claim 1, the control means controls to select a developer and perform a developing operation according to the determination output. In the invention set forth in claim 2, by controlling the charging potential of the photoreceptor, and in the invention set forth in claim 3, by controlling the surface movement speed of the photoreceptor, the recording sheet Regardless of the differences in the material depending on the type of sheet, for example, the surface roughness of the sheet, the hygroscopicity, etc.
A good recorded image can always be maintained.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of main parts of a wet-type copying machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing how recording paper is detected by a recording paper detection sensor.

FIG. 3 is a configuration diagram of a paper feeding section.

FIG. 4 is a characteristic diagram showing the relationship between developer toner concentration and recording paper toner adhesion amount.

FIG. 5 is a main control flowchart of a copying operation.

FIG. 6 is a flowchart of copy operation processing.

FIG. 7 is a flowchart of process condition setting processing.

FIG. 8 is a flowchart of process control processing.

FIG. 9 is a characteristic diagram showing the relationship between potential contrast and toner adhesion amount on recording paper.

FIG. 10 is a characteristic diagram showing the relationship between the linear velocity of the photoreceptor drum and the amount of toner attached to the recording paper.

[Explanation of symbols]

1 Photoreceptor drum 2 Main charger 5 Developing device 7 Transfer charger 20 Recording paper detection sensor 20a Light emitting part 20b Light receiving part 15, 17 Developing tank

Claims (3)

[Claims] 1. An exposure device, a photoconductor that carries an electrostatic latent image formed by exposure of the exposure device, and a developer that develops the latent image into a toner image using a developer containing toner. In a wet image forming apparatus equipped with a transfer device that transfers the toner image onto a recording sheet, and a paper feed device that conveys and supplies the recording sheet to a position facing the photoreceptor facing the transfer device, the recording sheet is irradiated with light. at least a recording sheet determining means for determining a recording sheet by detecting the scattered light; a control means for controlling image forming conditions of the image forming apparatus according to a determination output of the recording sheet determining means; It has two developing tanks, and the developing tanks store developing solutions with different toner concentrations, and the control means selects the developing solution supplied from the developing tanks according to the determination output and performs a developing operation. A wet image forming apparatus characterized by controlling. 2. An exposure device, a photoreceptor that carries an electrostatic latent image formed by exposure of the exposure device, and a developer that develops the latent image into a toner image using a developer containing toner. In a wet image forming apparatus equipped with a transfer device that transfers the toner image onto a recording sheet, and a paper feed device that conveys and supplies the recording sheet to a position facing the photoreceptor facing the transfer device, the recording sheet is irradiated with light. , comprising a recording sheet determining means for determining the recording sheet by detecting at least the scattered light, and a control means for controlling image forming conditions of the image forming apparatus according to a determination output of the recording sheet determining means, the control means The wet image forming apparatus is characterized in that the charging potential of the photoreceptor is controlled in accordance with the determination output. 3. An exposure device, a photoreceptor that carries an electrostatic latent image formed by exposure of the exposure device, and a developer that develops the latent image into a toner image using a developer containing toner. In a wet image forming apparatus equipped with a transfer device that transfers the toner image onto a recording sheet, and a paper feed device that conveys and supplies the recording sheet to a position facing the photoreceptor facing the transfer device, the recording sheet is irradiated with light. , comprising a recording sheet determining means for determining the recording sheet by detecting at least the scattered light, and a control means for controlling image forming conditions of the image forming apparatus according to a determination output of the recording sheet determining means, the control means The wet image forming apparatus is characterized in that the surface movement speed of the photoreceptor is controlled in accordance with the determination output.