JP2013167874A - Wet type image forming apparatus, method for adjusting image forming condition, and method for determining image noise - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wet type image forming apparatus capable of appropriately determining whether or not a decrease in image density of a toner image is caused by an occurrence of image noise.SOLUTION: A wet type image forming apparatus 100 includes: a first density detection sensor 41 for detecting image density of a patch image on a photoreceptor 21 before transfer; a second density detection sensor 42 for detecting the image density of the patch image as residuals on the photoreceptor 21 after the transfer; and a third density detection sensor 43 for detecting the image density of the patch image on an intermediate transfer roller 31 after the transfer. The image density of the patch image transferred onto the intermediate transfer roller 31 is calculated as a calculation value, from a difference between a detection result of the first density detection sensor 41 and the detection result of the second density detection sensor 42. Whether or not a difference between the calculation value and the detection result of the third density detection sensor 43 is a predetermined value or less is determined.

Description

  The present invention relates to a wet image forming apparatus that forms an image using a developer, an image forming condition adjusting method thereof, and an image noise that determines whether image noise is generated in an image formed by a wet electrophotographic method. It relates to the determination method.

  In an image forming apparatus employing an electrophotographic system, the surface of a photoreceptor is charged and the surface is exposed by an exposure unit. An electrostatic latent image is formed on the photoreceptor. Toner is supplied from the developing means to the electrostatic latent image. The toner adheres to the electrostatic latent image to form a toner image on the photoreceptor. The toner image is transferred from the photoreceptor to the recording medium. The toner image on the recording medium is fixed by fixing means. Through the above image forming process, an image is formed on the recording medium.

  As disclosed in Japanese Patent Application Laid-Open No. 11-184255 (Patent Document 1) and Japanese Patent Application Laid-Open No. 11-184256 (Patent Document 2), a wet image forming apparatus using a developer is known in recent years. The particle size of toner particles used in the wet image forming apparatus is smaller than the particle size of toner particles used in the dry image forming apparatus. With toner particles having a smaller particle size (for example, the average particle size is 0.1 μm to 2 μm), a high-resolution image expressed to a fine portion of the image is formed on the recording medium.

  In a wet image forming apparatus, an electrostatic latent image formed on a photoreceptor is visualized as a toner image by a developer. After the toner image is formed, the transfer of the toner image to the transfer member (recording medium or intermediate transfer roller) is performed by the action of a transfer electric field with a carrier liquid interposed in the transfer portion. When various image forming conditions such as toner charge amount, carrier liquid amount, and transfer electric field strength are not properly adjusted during the transfer, a high-quality image is formed on the recording medium. I can't.

  Japanese Patent Application Laid-Open No. 11-160926 (Patent Document 3) discloses a first density detecting means for detecting an upstream image density on an intermediate transfer roller before image transfer, and a downstream image after image transfer on the intermediate transfer roller. An image forming apparatus including a second density detecting unit that detects density is disclosed. This publication describes image forming conditions (γ characteristics) corresponding to changes in transfer efficiency or environmental changes due to image density based on the difference between upstream image density before image transfer and downstream image density after image transfer. It is stated that a high-quality image can be formed on a recording medium by adjusting.

Japanese Patent Laid-Open No. 11-184255 JP-A-11-184256 JP-A-11-160926

  If the image forming conditions are not properly adjusted, the amount of toner moving from the image carrier to the transfer member when transferring the toner image is insufficient (in other words, the transfer efficiency is low), Image noise such as image flow or granular unevenness may occur in the toner image after transfer. Whether the toner movement amount is insufficient or image noise is generated, the image density of the toner image transferred to the transfer member is lower than when the toner image does not occur.

  Image flow, which is one of the image noises, means that the image density of the toner image transferred to the transfer member is low as a result of the toner and carrier liquid contained in the toner image before transfer being squeezed at the entrance of the transfer nip. It is a phenomenon. When the image flow occurs, for example, the upstream portion in the toner image becomes dark and the downstream portion in the toner image becomes light. Image flow occurs when the pressure at the transfer nip is stronger than necessary, when the carrier liquid contained in the toner image before transfer is more than necessary, and when the electrostatic force acts on the toner contained in the toner image before transfer. This is likely to occur when the moving force is weak (when the toner charge amount is insufficient or the transfer bias is insufficient).

  Granular unevenness, which is one of image noises, is a phenomenon in which toner particles contained in a toner image transferred to a transfer member are present in a granular form (granular form). The granular unevenness is likely to occur when the amount of toner image to be transferred is small and the toner image (toner and carrier liquid) before transfer is not squeezed at the entrance of the transfer nip portion. The case where the amount of toner image is small includes a case where both the amount of toner and the amount of carrier liquid are small, a case where only the amount of toner is small, and a case where only the amount of carrier liquid is small.

  Image noise such as image flow or granular unevenness occurs both when the toner movement amount is insufficient and when the toner movement amount is not insufficient. That is, image noise such as image flow or granular unevenness is caused when the amount of toner that moves from the image carrier to the transfer member when transferring the toner image is insufficient (in other words, appropriate transfer efficiency is obtained). Even when the toner image is transferred, the amount of toner that moves from the image carrier onto the transfer member is not insufficient (in other words, appropriate transfer efficiency is obtained). Even if).

  In the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 11-160926 (Patent Document 3), the toner density transferred to the member to be transferred has a low image density. It is impossible to distinguish whether it is caused by the occurrence of image noise or image noise. In the image forming apparatus disclosed in the publication, even when the image density of the toner image transferred onto the member to be transferred is lowered, it is not possible to take measures corresponding to the cause of the reduction. It is difficult to form a quality image on a recording medium.

  The present invention relates to an image noise determination method capable of appropriately determining whether or not the cause of a decrease in the image density of a toner image transferred onto a member to be transferred is due to generation of image noise. An object of the present invention is to provide a wet image forming apparatus and an image forming condition adjusting method thereof.

  A wet image forming apparatus according to the present invention includes an image carrier that carries a toner image formed by developing with a developer containing a carrier liquid and toner, and a developer carrier that carries the developer. Image forming means for forming the toner image on the image carrier, a transfer member to which the toner image on the image carrier is transferred, and a transfer bias between the image carrier and the transfer member. A first density detecting means for detecting an image density of the toner image as a patch image on the image carrier before being transferred to the member to be transferred, and the patch image being transferred to the transferred member. Second density detecting means for detecting an image density of the patch image as a residue on the image carrier after being transferred onto the member; and the patch on the transfer member transferred from the image carrier. Detect image density A third density detecting unit; and a determination unit to which detection results of the first, second, and third density detecting units are input. The image forming unit is configured to apply the patch image on the image carrier. And the determining means determines the difference between the image density of the patch image detected by the first density detecting means and the image density of the patch image detected by the second density detecting means on the member to be transferred. The image density of the patch image transferred to the image is calculated as a calculated value, and the determining means determines whether the difference between the calculated value and the image density of the patch image detected by the third density detecting means is less than a predetermined value. Determine whether or not.

  Preferably, the determination unit is arranged on the image carrier based on a difference between an image density of the patch image detected by the first density detection unit and an image density of the patch image detected by the second density detection unit. Then, the movement amount of the toner moved onto the transfer member is calculated, and the determination unit determines whether or not the movement amount of the toner is equal to or larger than a predetermined movement amount.

  Preferably, adjustment means for adjusting image forming conditions is further provided, and image noise is generated when the difference between the calculated value and the image density of the patch image detected by the third density detection means is not less than the predetermined value. The image forming condition is adjusted by the adjusting unit so that the difference between the calculated value and the image density of the patch image detected by the third density detecting unit is equal to or less than the predetermined value. Is done.

  Preferably, the adjusting unit is configured to transfer the transferred member of the image carrier so that a difference between the calculated value and the image density of the patch image detected by the third density detecting unit is equal to or less than the predetermined value. At least one of adjusting the pressure contact force to the image and adjusting the amount of the carrier liquid contained in the patch image on the image carrier.

  Preferably, the adjustment unit adjusts the bias value of the transfer bias so that a difference between the calculated value and the image density of the patch image detected by the third density detection unit is equal to or less than the predetermined value. And / or adjusting the charge amount of the toner contained in the patch image on the image carrier.

  Preferably, the image forming apparatus further includes an adjusting unit that adjusts an image forming condition. If the toner moving amount is not equal to or greater than the predetermined moving amount, it is determined that the toner moving amount is insufficient. Adjusting the bias value of the transfer bias and adjusting the charge amount of the toner contained in the patch image on the image carrier so that the toner movement amount is equal to or greater than the predetermined movement amount. Do at least one of the following:

  An image noise determination method according to the present invention is an image noise determination method for determining whether image noise is generated in an image formed using a wet image forming apparatus, wherein the wet image forming apparatus includes: An image carrier that carries a toner image that has been visualized by a developer containing a carrier liquid and a toner, and a developer carrier that carries the developer, and the toner image is placed on the image carrier. An image forming unit formed on the image carrier, a transfer member to which the toner image on the image carrier is transferred, a transfer unit for applying a transfer bias between the image carrier and the transfer member, and the target A first density detector for detecting an image density of the toner image as a patch image on the image carrier before being transferred to the transfer member; and the patch image after the patch image is transferred onto the transfer member. Residue on image carrier Second density detecting means for detecting the image density of the patch image, third density detecting means for detecting the image density of the patch image on the transfer member transferred from the image carrier, and Determination means to which detection results of the first, second and third density detection means are input, and the image noise determination method is such that the image forming means places the patch image on the image carrier. The transfer member is determined based on the difference between the image density of the patch image detected by the first density detector and the image density of the patch image detected by the second density detector. The step of calculating the image density of the patch image transferred above as a calculated value, and the determining means determines that a difference between the calculated value and the image density of the patch image detected by the third density detecting means is a predetermined value. Whether or not A determination step, and determining that image noise has occurred when the difference between the calculated value and the image density of the patch image detected by the third density detection means is not less than or equal to the predetermined value. The

  Preferably, the determination unit is arranged on the image carrier based on a difference between an image density of the patch image detected by the first density detection unit and an image density of the patch image detected by the second density detection unit. A step of calculating the amount of movement of the toner moved onto the member to be transferred, and a step of determining whether the amount of movement of the toner is equal to or greater than a predetermined amount of movement, If the toner movement amount is not equal to or greater than the predetermined movement amount, it is determined that the toner movement amount is insufficient.

  An image forming condition adjustment method for a wet image forming apparatus according to an aspect of the present invention includes the image noise determination method according to the present invention, and the wet image forming apparatus further includes an adjusting unit for adjusting the image forming condition. And when the difference between the calculated value and the image density of the patch image detected by the third density detector is not less than or equal to the predetermined value, the image forming condition is that the calculated value and the third density detector are The adjustment unit adjusts the difference between the detected image density of the patch image and the predetermined value or less.

  Preferably, the adjusting unit is configured to transfer the transferred member of the image carrier so that a difference between the calculated value and the image density of the patch image detected by the third density detecting unit is equal to or less than the predetermined value. At least one of adjusting the pressure contact force to the image and adjusting the amount of the carrier liquid contained in the patch image on the image carrier.

  Preferably, the adjustment unit adjusts the bias value of the transfer bias so that a difference between the calculated value and the image density of the patch image detected by the third density detection unit is equal to or less than the predetermined value. And / or adjusting the charge amount of the toner contained in the patch image on the image carrier.

  An image forming condition adjustment method for a wet image forming apparatus according to another aspect of the present invention includes the image noise determination method according to the present invention, and the wet image forming apparatus includes an adjusting unit for adjusting the image forming condition. In addition, when the toner movement amount is not equal to or greater than the predetermined movement amount, the adjustment means adjusts the bias value of the transfer bias so that the toner movement amount is equal to or greater than the predetermined movement amount. And / or adjusting the charge amount of the toner contained in the patch image on the image carrier.

  According to the present invention, it is possible to appropriately determine whether or not the cause of the decrease in the image density of the toner image transferred onto the transfer member is due to the occurrence of image noise. A determination method, a wet image forming apparatus, and an image forming condition adjusting method thereof can be obtained.

1 is a diagram schematically showing an overall configuration of a wet image forming apparatus in Embodiment 1. FIG. 1 is a block diagram showing an electrical configuration of a wet image forming apparatus in Embodiment 1. FIG. FIG. 6 is a diagram illustrating a relationship between an image density (vertical axis) of a toner image and a toner adhesion amount (horizontal axis) in the toner image. FIG. 4 is a diagram for explaining the relationship between the amount of carrier liquid contained in a toner image on an image carrier (photosensitive member) and aggregation of toner particles (the amount of carrier liquid contained in a toner image is a predetermined value or more). If any). FIG. 5 is a diagram for explaining the relationship between the amount of carrier liquid contained in a toner image on an image carrier (photosensitive member) and aggregation of toner particles (the amount of carrier liquid contained in a toner image is larger than a predetermined value); If less). FIG. 3 is a diagram illustrating the contents of an image forming condition adjustment method executed by the wet image forming apparatus in the first embodiment. 3 is a diagram illustrating an image forming condition adjustment method (image noise determination method) executed by the wet image forming apparatus in Embodiment 1. FIG. FIG. 10 is a diagram illustrating an image forming condition adjustment method (image noise determination method) executed by a wet image forming apparatus according to a modification of the first embodiment. FIG. 4 is a diagram schematically showing an overall configuration of a wet image forming apparatus in a second embodiment. 6 is a diagram schematically showing an overall configuration of a wet-type image forming apparatus in Embodiment 3. FIG.

  Embodiments based on the present invention will be described below with reference to the drawings. In the description of each embodiment, when referring to the number, amount, or the like, the scope of the present invention is not necessarily limited to the number, amount, or the like unless otherwise specified. In the description of each embodiment, the same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.

[Embodiment 1]
A wet image forming apparatus 100 according to the present embodiment will be described with reference to FIGS. FIG. 1 is a diagram schematically illustrating the overall configuration of the wet image forming apparatus 100. FIG. 2 is a block diagram illustrating an electrical configuration of the wet image forming apparatus 100.

  As shown in FIG. 1, the wet image forming apparatus 100 forms an image on a recording paper 55 (recording medium). Although details will be described later, the recording paper 55 is transported between the intermediate transfer roller 31 and the transfer roller 37 along a predetermined transport direction AR55. The wet image forming apparatus 100 is based on a print command signal from a user or the like in a state where predetermined image forming conditions are set by executing each step of an image forming condition adjusting method ST100 (see FIG. 6) described later. Normal image formation is performed on the recording paper 55.

  As shown in FIG. 2, the wet image forming apparatus 100 includes a main control unit 60, an engine unit 70, and an engine control unit 80. A print command signal including an image signal is given to the main controller 60 from an external device (not shown) such as a host computer. The main control unit 60 includes an interface 62, a CPU 64 (Central Processing Unit), and an image memory 66. An image signal given from an external device through the interface 62 is stored in the image memory 66.

  The CPU 64 receives a print command signal including an image signal through the interface 62. The CPU 64 converts the received print command signal into job data in a format suitable for the operation instruction of the engine unit 70, and sends the job data to the engine control unit 80 (CPU 84). The memory 82 in the engine control unit 80 includes a ROM (Read Only Memory) and a RAM (Random Access Memory).

  The CPU 84 stores data relating to the image signal sent from the external device through the CPU 64 in the memory 82. The ROM of the memory 82 stores a control program for the CPU 84 (control means). The control program also includes preset fixed data (predetermined image forming conditions). The RAM of the memory 82 temporarily stores control data of the engine unit 70 and a calculation result by the CPU 84.

  The engine control unit 80 controls each unit of the engine unit 70 in accordance with job data (control signal) received from the main control unit 60. With this control, the wet image forming apparatus 100 can form an image corresponding to the above-described image signal on the recording paper 55 (see FIG. 1) in a state where predetermined image forming conditions are set.

  Referring to FIGS. 1 and 2, the engine unit 70 (see FIG. 2) includes a developing unit 10, a photoreceptor unit 20, an intermediate transfer unit 30, a first density detection sensor 41 (first density detection means), and a second. A density detection sensor 42 (second density detection means), a third density detection sensor 43 (third density detection means), and a fixing unit 50 are provided.

(Developing unit 10)
As shown in FIG. 1, the developing unit 10 includes a developing tank 11, a developer 12, a supply roller 13, a delivery roller 14, a developing roller 15 (developer carrying member), a charger 16, a static eliminator 17, and a developing bias. A generator 18 is included.

  The developer 12 is stored in the developer tank 11. The developer 12 includes an insulating liquid that is a carrier liquid, a toner that develops an electrostatic latent image, and a dispersant that disperses the toner in the carrier liquid. The developer 12 is produced, for example, as follows. First, 100 parts of a polyester resin and 15 parts of copper phthalocyanine are sufficiently mixed using a Henschel mixer (registered trademark). The obtained mixture is melted and kneaded using a co-rotating twin-screw extruder in which the heating temperature of the roll is set to 100 ° C.

  The melted and kneaded mixture is cooled and pulverized to obtain a pulverized toner. Thereafter, 75 parts of IP2028 (manufactured by Idemitsu Kosan Co., Ltd.), 25 parts of pulverized toner, and 0.8 part of V216 (manufactured by ISP) as a dispersant are mixed. The developer 12 is obtained by mixing these for 1 hour using a sand mill. In this case, the particle size of the toner particles contained in the developer 12 is 2.0 μm. The value of the particle size is a value measured by a laser diffraction particle size distribution analyzer SALD-2200 (manufactured by Shimadzu Corporation).

  The memory 10M (see FIG. 2) of the developing unit 10 includes a manufacturing lot, a use history, a built-in toner characteristic, a remaining amount of the developing solution 12, or a toner concentration (TC: Toner concentration) (carrier in the developing solution). Various data relating to the ratio of the toner particle amount to the liquid amount) are stored. The memory 10M manages various kinds of information such as consumables management related to the developing unit 10.

  A toner supply pump 11T and a carrier liquid supply pump 11C are connected to the developing tank 11, respectively. The toner replenishment pump 11T is driven by a pump driving unit 91T (see FIG. 2), and supplies a high-concentration developer into the developing tank 11. The carrier liquid supply pump 11 </ b> C is driven by a pump drive unit 91 </ b> C (see FIG. 2) and supplies carrier liquid into the developing tank 11.

  For example, when the CPU 84 controls the pump drive unit 91T and the toner supply pump 11T is driven, a high-concentration developer is supplied into the developing tank 11 and the toner concentration of the developer 12 increases. On the other hand, when the pump drive unit 91C is controlled by the CPU 84 and the carrier liquid supply pump 11C is driven, the carrier liquid is supplied into the developing tank 11 and the toner concentration of the developing liquid 12 is lowered. As described above, the toner concentration of the developer 12 in the developing tank 11 can be appropriately adjusted by controlling the operations of the pump driving units 91T and 91C.

  Therefore, the toner replenishment pump 11T, the pump drive unit 91T, the carrier liquid supply pump 11C, and the pump drive unit 91C are adjusting means (toner for adjusting the image forming conditions (toner concentration in the developer 12) of the wet image forming apparatus 100. Density adjustment means). The toner density adjusting means may be provided as necessary.

  A supply roller 13 is provided so as to come into contact with the developer 12 in the developing tank 11. As the supply roller 13 rotates, the developer 12 is pumped up on the surface of the supply roller 13. The developer 12 is carried on the surface of the supply roller 13. The developer 12 carried on the supply roller 13 is conveyed toward a portion where the supply roller 13 and the delivery roller 14 are opposed to each other by the rotation of the supply roller 13.

  The developer 12 on the supply roller 13 is transferred from the supply roller 13 to the transfer roller 14 in a state where an excessive amount is scraped off by the doctor blade 13T. The developer 12 is carried on the surface of the delivery roller 14. The developer 12 carried on the delivery roller 14 is conveyed toward a portion where the delivery roller 14 and the development roller 15 face each other by the rotation of the delivery roller 14.

  The developer 12 on the delivery roller 14 is delivered from the delivery roller 14 to the development roller 15. The developer 12 is carried on the surface of the developing roller 15. By supplying the developing solution 12 in the developing tank 11 to the developing roller 15 through the supply roller 13 and the delivery roller 14, the film thickness becomes uniform on the surface of the developing roller 15 in the longitudinal direction of the developing roller 15. A thin layer of the developer 12 adjusted as described above is formed.

  A peripheral speed control unit 94 (see FIG. 2) is connected to the delivery roller 14 in the present embodiment. The peripheral speed control unit 94 is controlled by the CPU 84 to change the relative speed (speed ratio) of the transfer roller 14 to the developing roller 15. In accordance with the change in the speed ratio, the amount of the developer 12 transported from the delivery roller 14 onto the developing roller 15 (the amount of the developer 12 carried on the developing roller 15) can be adjusted appropriately. .

  Therefore, the delivery roller 14 and the peripheral speed control unit 94 serve as an adjusting unit (developing solution amount adjusting unit) that adjusts the image forming conditions (the amount of the developing solution 12 carried on the developing roller 15) of the wet image forming apparatus 100. Can function. The developer amount adjusting means may be provided as necessary.

  The developer 12 on the developing roller 15 is conveyed toward the developing position 24 by the rotation of the developing roller 15. The development position 24 is a portion where the development roller 15 and a photoreceptor 21 described later are in contact with each other. When the developer 12 is transported toward the developing position 24, the toner particles in the developer 12 having a thin layer formed thereon can be charged to an appropriate charge amount by the charger 16. The voltage applied to the charger 16 is, for example, +3 kV to +5 kV.

  The charger 16 can function as an adjustment unit (toner charge amount adjustment unit) that adjusts the charge amount of toner contained in a toner image (and a patch image) formed on the photoreceptor 21 after development. The toner charge amount adjusting means may be provided as necessary. The developer 12 containing charged toner particles is further conveyed toward the developing position 24 by the rotation of the developing roller 15.

  The developing roller 15 is disposed with a certain amount of pressing with respect to the photoreceptor 21 of the photoreceptor unit 20 described below. A predetermined developing bias (for example, −450 V) is applied to the developing roller 15 by the developing bias generator 18. By applying the developing bias, the developer 12 of the developing roller 15 visualizes (visualizes) the electrostatic latent image formed on the photoreceptor 21.

(Photoreceptor unit 20)
The photoconductor unit 20 includes a photoconductor 21, a charger 22, an exposure device 23, a pre-transfer charger 25, a carrier liquid amount adjusting unit 34, a static eliminator 27, and a cleaning blade 28. As described above, the drum-shaped photoconductor 21 is provided so as to be in contact with the developing roller 15. As the photoconductor 21, for example, a photoconductor made of amorphous silicon is used. The photoconductor 21 rotates in the direction of the arrow AR21. The rotational speed of the photoconductor 21 is, for example, 400 mm / s.

  Around the photoconductor 21, along the rotation direction of the photoconductor 21 (arrow AR21 direction), the charger 22, the exposure device 23, the developing roller 15 (development position 24), the pre-transfer charger 25, and the carrier liquid amount adjusting means. 34, a first density detection sensor 41 (to be described later), an intermediate transfer roller 31 (transfer unit 26), a second density detection sensor 42 (to be described later), a static eliminator 27, and a cleaning blade 28 are arranged in this order.

  The charger 22 is connected to a charging bias generator 95 (see FIG. 2). The surface of the photoreceptor 21 is uniformly charged to a predetermined surface potential (for example, −700 V) by the charger 22. The exposure device 23 is connected to an exposure control unit 93 (see FIG. 2). The surface of the photoreceptor 21 is exposed based on predetermined image information by the exposure device 23.

  Specifically, a print command signal including an image signal is given from an external device such as a host computer to the CPU 64 of the main control unit 60 through the interface 62. In response to a command from the CPU 64, the CPU 84 outputs a control signal corresponding to the image signal to the exposure control unit 93 at a predetermined timing. In response to a control command from the exposure controller 93, a light beam is emitted from the exposure device 23 onto the surface of the photoconductor 21. An electrostatic latent image corresponding to the image signal is formed on the surface of the photoreceptor 21.

  Although details will be described later, the exposure apparatus 23 in the present embodiment controls the exposure amount, exposure range, and exposure timing based on normal image information, and forms a patch image. It is also controlled by each value of necessary exposure amount, exposure range, and exposure timing. By controlling the exposure device 23 in this way, an electrostatic latent image corresponding to a patch image (details will be described later) is formed on the surface of the photoreceptor 21.

  As described above, a predetermined developing bias is applied to the developing roller 15 (developing position 24) by the developing bias generator 18. An electric field is formed between the developing roller 15 and the photoconductor 21 due to the development potential difference formed between the developing roller 15 and the photoconductor 21.

  When the electrostatic latent image is transported to the developing position 24 on the photoconductor 21, the toner particles in the developer 12 carried on the developing roller 15 are caused by the action of the electric field formed by the developing bias generator 18. Electrostatically moves from the surface of the developing roller 15 to the surface of the photoreceptor 21. At this time, not only the toner particles but also the carrier liquid adheres to the surface of the photoreceptor 21.

  The electrostatic latent image formed on the surface of the photoreceptor 21 is visualized (visualized) as a toner image (or a patch image described later). The image forming means in the present embodiment forms a toner image (and a patch image) on the photosensitive member 21 (image carrier), and assumes that the developing unit 10 (developing roller 15), the exposure device 23, and the exposure control unit 93. Is included.

  The developer 12 remaining on the developing roller 15 without moving from the developing roller 15 to the photosensitive member 21 is neutralized by the static eliminator 17. The charge removal amount of the developer 12 by the charge eliminator 17 is, for example, −3 kV to −5 kV. The discharged developer 12 is scraped off from the surface of the developing roller 15 by the cleaning blade 15T and then collected. The collected developer 12 is transported to the toner concentration adjusting means and then transported again into the developing tank 11 with the toner concentration adjusted appropriately.

  The photoreceptor 21 moves the toner image toward the transfer unit 26 (primary transfer unit) while carrying a toner image (or a patch image described later) formed on the surface. The transfer portion 26 is a portion where the photosensitive member 21 and an intermediate transfer roller 31 described below are in contact with each other. A toner image (or a patch image, which will be described later) on the photosensitive member 21 conveyed toward the transfer unit 26 is appropriately adjusted to a predetermined charge amount by the pre-transfer charger 25 before transfer to the intermediate transfer roller 31. Can.

  The voltage applied to the toner image (and patch image) by the pre-transfer charger 25 is, for example, +3 kV to +5 kV. Similar to the charger 16, the pre-transfer charger 25 can function as an adjustment unit (toner charge amount adjustment unit) that adjusts the charge amount of toner contained in the toner image (and patch image) on the photoreceptor 21. . The toner charge amount adjusting means may be provided as necessary. The toner image on the photoconductor 21 is transported toward the transfer unit 26 by the rotation of the photoconductor 21 after the surface potential is adjusted.

  The carrier liquid amount adjusting means 34 is disposed so as to face the toner image (and patch image) formed on the photoreceptor 21. The carrier liquid amount adjusting means 34 is located downstream of the development position 24 and upstream of the first concentration detection sensor 41 in the rotation direction of the photoconductor 21 (the direction of the arrow AR21).

  After the toner image is formed on the surface of the photoconductor 21 at the development position 24, the photoconductor 21 holds the toner image formed on the surface and puts the toner image at a position facing the carrier liquid amount adjusting unit 34. Move towards. The carrier liquid amount adjusting means 34 in the present embodiment includes a prewetting device 32 and a squeeze device 33.

  The pre-wet device 32 has a roller 32 </ b> R disposed to face the photoconductor 21. The pre-wet device 32 supplies the carrier liquid 32P (pre-wet liquid) to the toner image (or patch image) on the photoconductor 21 by being controlled by the pre-wet control unit 97 (see FIG. 2).

  By supplying the carrier liquid 32P to the toner image (or patch image) on the photoconductor 21 through the roller 32R, the amount of the carrier liquid contained in the toner image on the photoconductor 21 can be increased. By increasing the rotation speed of the roller 32R, the amount of the carrier liquid 32P supplied to the toner image on the photoreceptor 21 can be increased. By reducing the rotational speed of the roller 32R, the amount of the carrier liquid 32P supplied to the toner image on the photoconductor 21 can be reduced.

  The squeeze device 33 has a roller 33 </ b> R disposed to face the photoconductor 21. The squeeze device 33 is controlled by the squeeze control unit 98 (see FIG. 2), and collects the carrier liquid absorbed from the toner image (or patch image) on the photoreceptor 21 by the blade 33Q.

  By recovering the carrier liquid from the toner image (or patch image) on the photoconductor 21 through the roller 33R, the amount of the carrier liquid contained in the toner image on the photoconductor 21 can be reduced. By increasing the rotation speed of the roller 33R, the amount of carrier liquid recovered from the toner image on the photoconductor 21 can be increased. By reducing the number of rotations of the roller 33R, the amount of carrier liquid recovered from the toner image on the photoreceptor 21 can be reduced.

  The amount of carrier liquid contained in the toner image on the photoreceptor 21 can be adjusted appropriately by the carrier liquid amount adjusting means 34. Therefore, the pre-wet device 32, the pre-wet control unit 97, the squeeze device 33, and the squeeze control unit 98 are used for image forming conditions of the wet image forming device 100 (amount of carrier liquid contained in the toner image on the photoconductor 21). It can function as an adjusting means (carrier liquid amount adjusting means) that adjusts. The carrier liquid amount adjusting means 34 may be provided as necessary.

  The toner image on the photoconductor 21 reaches the detection target range of the first density detection sensor 41 by the rotation of the photoconductor 21 after passing through the portion where the photoconductor 21 and the carrier liquid amount adjusting unit 34 face each other. .

(First concentration detection sensor 41)
The first density detection sensor 41 is downstream of a portion where the photoconductor 21 and the carrier liquid amount adjusting unit 34 face each other in the rotation direction of the photoconductor 21 (in the direction of the arrow AR21) and upstream of the transfer unit 26. And located so as to face the surface of the photoreceptor 21. The first density detection sensor 41 is used in an image forming condition adjustment method ST100 described later, and the image density of a toner image as a patch image carried on the surface of the photoreceptor 21 before being transferred to the intermediate transfer roller 31. Is detected.

  The first concentration detection sensor 41 in the present embodiment includes a light emitting unit 44 and a light receiving unit 45. Predetermined detection light is emitted from the light emitting unit 44 toward the toner image as a patch image positioned between the developing position 24 (carrier liquid amount adjusting unit 34) and the transfer unit 26 on the surface of the photoreceptor 21. . The reflected light of the detection light reflected on the toner image as the patch image is received by the light receiving unit 45.

  Depending on the intensity of the reflected light received by the light receiving unit 45, the first density detection sensor 41 is a toner image as a patch image carried on the surface of the photoreceptor 21 before being transferred to the intermediate transfer roller 31. And the detection result (image density C1 in FIG. 6) is sent to the CPU 84 (see FIG. 2).

  The toner image (patch image) on the photosensitive member 21 passes through a portion where the photosensitive member 21 and the first density detection sensor 41 face each other, and is further conveyed toward the transfer unit 26 by the rotation of the photosensitive member 21. The

(Intermediate transfer unit 30)
The intermediate transfer unit 30 includes an intermediate transfer roller 31, a transfer bias generator 35 (primary transfer bias generator), a transfer roller 37, a transfer bias generator 38 (secondary transfer bias generator), and a cleaning blade 39. .

  As described above, the intermediate transfer roller 31 is disposed so as to contact the photoreceptor 21. Intermediate transfer roller 31 rotates in the direction of arrow AR31. Around the intermediate transfer roller 31, along the rotation direction of the intermediate transfer roller 31 (in the direction of the arrow AR 31), the photoconductor 21, a third density detection sensor 43 described later, a transfer roller 37 (transfer unit 36), and a cleaning blade 39 are arranged in order.

  A transfer portion 26 (primary transfer portion) is formed between the photoconductor 21 and the intermediate transfer roller 31. A predetermined transfer bias (for example, +600 V) is applied to the intermediate transfer roller 31 by the transfer bias generator 35 (transfer means). An electric field is formed between the photoconductor 21 and the intermediate transfer roller 31 due to a potential difference formed between the photoconductor 21 and the intermediate transfer roller 31.

  The toner image conveyed to the transfer unit 26 by the rotation of the photoconductor 21 is transferred from the surface of the photoconductor 21 to the surface of the intermediate transfer roller 31 (transfer target member) by the action of the electric field formed by the transfer bias generating unit 35. Next is transferred. The toner image remaining on the surface of the photoconductor 21 without being primarily transferred is neutralized by the static eliminator 27 and then scraped off from the surface of the photoconductor 21 along with dirt on the surface of the photoconductor 21 by the cleaning blade 28. And collected.

  Although details will be described later, the patch image formed on the photosensitive member 21 is also applied to the intermediate transfer roller from the surface of the photosensitive member 21 by the action of the electric field formed by the transfer bias generating unit 35 as in the case of a normal toner image. It is transferred to the surface of 31. A patch image is formed on the surface of the intermediate transfer roller 31 by the transfer. The patch image as a residual portion remaining on the surface of the photoconductor 21 without being primarily transferred is detected by the second density detection sensor 42 (details will be described later), and after being neutralized by the static eliminator 27. Then, the cleaning blade 28 scrapes off the surface of the photoconductor 21 along with dirt on the surface of the photoconductor 21 and collects it.

  Here, the transfer bias generator 35 used in the primary transfer may be configured to be able to adjust the bias value of the transfer bias. In this case, the transfer bias generator 35 changes the bias value of the transfer bias applied to the intermediate transfer roller 31 by being controlled by the CPU 84 (see FIG. 2). Even when the amount of carrier liquid in the toner image before the primary transfer is constant, the toner that moves from the photosensitive member 21 to the intermediate transfer roller 31 when the toner image is transferred by adjusting the transfer bias. Insufficient amount of toner can be suppressed (in other words, transfer efficiency can be increased), and image noise such as image flow or granular unevenness can be suppressed in the toner image after transfer. .

  Accordingly, the transfer bias generating unit 35 in this case can function as an adjusting unit configured to be able to adjust the image forming conditions (the bias value of the transfer bias) of the wet image forming apparatus 100. The configuration in which the transfer bias generator 35 can adjust the bias value of the transfer bias may be adopted as necessary.

  The intermediate transfer unit 30 of the present embodiment further includes a pressure contact force adjusting unit 30M (see FIG. 2). The pressing force adjusting unit 30 </ b> M changes the inter-axis distance between the rotating shaft of the photoconductor 21 and the rotating shaft of the intermediate transfer roller 31. By changing the inter-axis distance by the press contact force adjusting unit 30M, it is possible to adjust the press contact force in the transfer unit 26 between the photoconductor 21 and the intermediate transfer roller 31.

  As the distance between the shafts becomes longer, the pressure contact force decreases and the amount of toner image reduction also decreases. When the distance between the shafts is shortened, the pressure contact force is increased, and the amount of aperture of the toner image is increased. By adjusting the distance between the axes, it is possible to suppress a shortage of the amount of toner moving from the photosensitive member 21 to the intermediate transfer roller 31 when transferring the toner image, or to transfer the image to the toner image after transfer. It is possible to suppress the occurrence of image noise such as granular unevenness.

  Accordingly, the pressure contact force adjusting unit 30M in this case can function as a pressure contact force adjusting unit configured to be able to adjust the image forming conditions of the wet image forming apparatus 100 (pressure contact force of the photosensitive member 21 to the intermediate transfer roller 31). it can. The pressing force adjusting means may be provided as necessary.

  The pressing force adjusting unit 30M can be configured as follows, for example. The photoconductor 21 and the intermediate transfer roller 31 are respectively supported by a rotation shaft (not shown), and the intermediate transfer roller 31 (for example, a cylindrical roller having a rigid body on the center side and an elastic layer on the surface). A pair of rotating rollers are attached to the rotating shaft so as to be positioned on both outer sides in the axial direction of the intermediate transfer roller 31. The rotation shaft of the intermediate transfer roller 31 is supported by a slide mechanism that can increase or decrease the distance between the rotation shaft of the photosensitive member 21 (for example, a cylindrical roller made of a rigid material) and the rotation shaft of the intermediate transfer roller 31. The slide mechanism is fixed to a side wall in the wet image forming apparatus 100.

  A cam shaft (not shown) is provided so as to extend along a direction parallel to the rotation axis of the photoconductor 21, and this cam shaft is connected to a motor. A pair of eccentric cams is attached to the camshaft so as to contact each of the pair of rotating rollers. When the motor rotates the cam shaft, the rotational position (phase) of the eccentric cam is changed. By controlling the rotational position of the eccentric cam, the inter-axis distance between the rotational shaft of the photoconductor 21 and the rotational shaft of the intermediate transfer roller 31 is adjusted. By adjusting the distance between the axes, it is possible to increase or decrease the pressure contact force of the photoconductor 21 to the intermediate transfer roller 31.

(Second concentration detection sensor 42)
The second density detection sensor 42 is located downstream of the transfer unit 26 and upstream of the static eliminator 27 in the rotation direction of the photoconductor 21 (in the direction of the arrow AR21), and is disposed to face the surface of the photoconductor 21. Is done. The second density detection sensor 42 is used in an image forming condition adjustment method ST100 described later, and after the patch image is transferred to the intermediate transfer roller 31, a toner image (residual image) remaining on the surface of the photoreceptor 21 is left. Min) image density.

  The second concentration detection sensor 42 in the present embodiment includes a light emitting unit 46 and a light receiving unit 47. Predetermined detection light is emitted from the light emitting unit 46 toward the toner image (residual part) as a patch image positioned between the transfer unit 26 and the charge eliminator 27 on the surface of the photoreceptor 21. The reflected light of the detection light reflected on the patch image is received by the light receiving unit 47.

  In accordance with the intensity of the reflected light received by the light receiving unit 47, the second density detection sensor 42 has an image of the patch image as a residual part on the photoconductor 21 after the patch image is transferred onto the intermediate transfer roller 31. The density is detected, and the detection result (image density C2 in FIG. 6) is sent to the CPU 84 (see FIG. 2).

  As will be described in detail later, the CPU 84 (see FIG. 2) as a determination unit detects the image density (C1) of the patch image detected by the first density detection sensor 41 and the image of the patch image detected by the second density detection sensor 42. Based on the difference from the density (C2), the moving amount of the toner moved from the photosensitive member 21 to the intermediate transfer roller 31 is calculated, and it is determined whether or not the moving amount of the toner is equal to or larger than a predetermined moving amount.

  If it is determined that the toner movement amount is equal to or greater than the predetermined movement amount, it is determined that the transfer efficiency is appropriate and the toner movement amount is sufficient. On the other hand, when it is determined that the toner movement amount is not equal to or greater than the predetermined movement amount, it is determined that the transfer efficiency is not appropriate and the toner movement amount is insufficient. The predetermined movement amount as the determination threshold is appropriately set by multiplying the value of the image density (C1) of the patch image detected by the first density detection sensor 41 by a predetermined coefficient (for example, transfer efficiency 90%). You may make it do.

  The patch image as the remaining portion on the photoconductor 21 is neutralized by the static eliminator 27 after passing through the portion where the photoconductor 21 and the second density detection sensor 42 face each other. Thereafter, the patch image is scraped from the surface of the photoconductor 21 by the cleaning blade 28 together with dirt on the surface of the photoconductor 21 and collected.

(Third concentration detection sensor 43)
The third density detection sensor 43 is located downstream of the transfer unit 26 and upstream of the transfer unit 36 in the rotation direction of the intermediate transfer roller 31 (in the direction of the arrow AR31), and faces the surface of the intermediate transfer roller 31. Placed in. The third density detection sensor 43 is used in an image forming condition adjustment method ST100 described later, and detects the image density of a toner image as a patch image on the intermediate transfer roller 31 transferred from the photoreceptor 21.

  The third concentration detection sensor 43 in the present embodiment includes a light emitting unit 48 and a light receiving unit 49. Predetermined detection light is emitted from the light emitting unit 48 toward a toner image as a patch image located between the transfer unit 26 and the transfer unit 36 on the surface of the intermediate transfer roller 31. The reflected light of the detection light reflected on the patch image is received by the light receiving unit 49.

  In accordance with the intensity of the reflected light received by the light receiving unit 49, the third density detection sensor 43 detects the image density of the toner image as the patch image on the intermediate transfer roller 31 transferred from the photoconductor 21, and The detection result (image density C3 in FIG. 6) is sent to the CPU 84 (see FIG. 2).

  As will be described in detail later, the CPU 84 (see FIG. 2) as a determination unit detects the image density (C1) of the patch image detected by the first density detection sensor 41 and the image of the patch image detected by the second density detection sensor 42. From the difference from the density (C2), the image density of the patch image transferred onto the intermediate transfer roller 31 is calculated as a calculated value (reference value). Further, the CPU 84 calculates a difference between the calculated value (C1-C2) and the image density (C3) of the patch image detected by the third density detection sensor 43, and determines whether or not the difference is equal to or less than a predetermined value. judge. If the difference ((C1-C2) -C3) is less than or equal to a predetermined value, it is determined that no image noise has occurred. If the difference is not less than or equal to a predetermined value, image noise has occurred. It is determined that

  Referring to FIG. 3, when obtaining the above image densities C1, C2, and C3, the image density (vertical axis) of the toner image and the toner adhesion amount (horizontal axis) as shown in FIG. ) May be used. These relationships are stored in a memory 82 (see FIG. 2), for example, as a reference table that can be called in advance. In this case, the image density of the patch image detected by each of the density detection sensors 41 to 43 is converted into the adhesion amount (content) of toner in the patch image by the reference table. The calculated values (C1-C2) and ((C1-C2) -C3) can also be calculated based on the difference between the adhesion amounts.

  Referring to FIGS. 1 and 2 again, the patch image transferred from the photosensitive member 21 onto the intermediate transfer roller 31 is processed by the CPU 84 using the above adjustment means (toner density adjustment means, developer amount adjustment means, carrier liquid amount adjustment). Intermediate transfer roller while adjusting the image forming conditions to be appropriate by controlling at least one of a toner, a toner charge amount adjusting means, a transfer means capable of adjusting a bias value, and a pressing force adjusting means) The image is transferred onto the image 31 (details will be described later).

  The CPU 84 determines that the image formation condition when the amount of movement of the toner obtained from (C1-C2) is equal to or greater than the predetermined amount of movement, and the value of ((C1-C2) -C3) is a predetermined value. Image forming conditions at the following times are acquired as calculation results and stored in the memory 82 in the engine control unit 80. When the wet image forming apparatus 100 performs normal image formation, the image forming conditions are adjusted according to the calculation result obtained by the CPU 84, and primary transfer is performed under the optimum image forming conditions.

  As described above, the transfer portion 36 (secondary transfer portion) is formed between the intermediate transfer roller 31 and the transfer roller 37. The transfer unit 36 is a part where the intermediate transfer roller 31 and the transfer roller 37 are in contact with each other. The intermediate transfer roller 31 moves the toner image toward the transfer unit 36 while carrying the toner image.

  The recording paper 55 onto which the toner image is transferred from the intermediate transfer roller 31 passes through the transfer unit 36 along the transport direction AR55 by the intermediate transfer roller 31 that rotates in the direction of the arrow AR31 and the transfer roller 37 that rotates in the direction of the arrow AR37. . A predetermined transfer bias (for example, +1200 V) is applied to the transfer roller 37 by the transfer bias generator 38. Due to the potential difference formed between the intermediate transfer roller 31 and the transfer roller 37, an electric field is formed between the intermediate transfer roller 31 and the recording paper 55.

  The toner image conveyed to the transfer unit 36 by the rotation of the intermediate transfer roller 31 is secondarily transferred from the surface of the intermediate transfer roller 31 to the surface of the recording paper 55 by the action of the electric field formed by the transfer bias generating unit 38. . By the transfer, an image corresponding to the toner image is formed on the surface of the recording paper 55. The toner remaining on the surface of the intermediate transfer roller 31 without being subjected to the secondary transfer is scraped off and collected together with dirt on the surface of the intermediate transfer roller 31 by the cleaning blade 39. The recording paper 55 on which the toner image is secondarily transferred is conveyed toward the fixing unit 50.

(Fixing unit 50)
The fixing unit 50 includes fixing rollers 51 and 52. The toner particles in the toner image transferred to the recording paper 55 are heated and pressed by the fixing rollers 51 and 52. The toner image transferred to the recording paper 55 is fixed on the surface of the recording paper 55 by these heating and pressurization. Thereafter, the recording paper 55 is discharged to the outside through a paper discharge device (not shown).

  As described above, the image forming process in the wet image forming apparatus 100 is completed. Regarding the above configuration, the developing roller 15 and the intermediate transfer roller 31 are configured in a roller shape in the present embodiment, but may be configured in a belt shape. When the intermediate transfer roller 31 has a belt-like configuration, it is easy to adjust the pressure contact force between the intermediate transfer roller 31 and the photosensitive member 21 using the pressure contact force adjusting unit 30M. It becomes possible.

(Granular unevenness)
4 and 5, the amount of carrier liquid 11CA contained in the toner image on the photoreceptor 21 and the aggregation (granularity) of the toner particles 11TA with respect to the granular unevenness that may occur when the primary transfer is performed. This will be described based on the relationship with (unevenness). 4 shows that the carrier liquid 11CA shown in FIG. 4 is collected in the upstream portion of the transfer unit 26. Depending on the amount of the carrier liquid 11CA contained in the toner image on the photoconductor 21, granular unevenness is likely to occur or granular unevenness is less likely to occur.

  When the above-described granular unevenness occurs, toner particles on the intermediate transfer roller 31 as a member to be transferred even if the amount of toner transferred to the intermediate transfer roller 31 is constant without changing the transfer efficiency. Since the distribution (arrangement position) of 11TA changes, the image density (the amount of reflected light) of the toner image after transfer is optically reduced. The cause of the decrease in the image density of the toner image is not limited to the granular unevenness, and the image density of the toner image also decreases when the transfer efficiency decreases and the toner adhesion amount itself on the intermediate transfer roller 31 decreases. .

  As shown in FIG. 4, the toner image on the photoconductor 21 is conveyed to the transfer unit 26 (transfer nip unit) by the rotation of the photoconductor 21. When the amount of the carrier liquid 11CA included in the toner image is equal to or greater than a predetermined value, a good liquid bridge 11E is formed between the photoconductor 21 and the intermediate transfer roller 31 on the upstream side of the transfer nip portion by the carrier liquid 11CA. Is formed.

  The toner particles 11TA included in the toner image on the photosensitive member 21 start moving toward the intermediate transfer roller 31 after a good liquid bridge 11E is formed by the carrier liquid 11CA in the toner image. In other words, after the liquid bridge 11E is formed at the position P1 in FIG. 4, the toner particles 11TA start electrostatic movement by the action of the electric field at the position P2 in FIG. Therefore, when the amount of the carrier liquid 11CA included in the toner image is equal to or larger than a predetermined value, the toner particles are not aggregated in a part of the region, and the granular unevenness hardly occurs.

  Referring to FIG. 5, on the other hand, when the amount of carrier liquid 11CA included in the toner image is smaller than a predetermined value, sufficient liquid bridge 11E is not formed. The toner particles 11TA included in the toner image on the photoreceptor 21 start electrostatic movement toward the intermediate transfer roller 31 before the appropriate liquid bridge 11E is formed by the carrier liquid 11CA in the toner image.

  Specifically, before the liquid bridge 11E is formed at the position P3 in FIG. 5, the toner particles 11TA start to move by the action of the electric field at the position P2 in FIG. Therefore, when the amount of the carrier liquid 11CA included in the toner image is smaller than a predetermined value, the toner particles are aggregated in a part of the region, and granular unevenness occurs. When granular unevenness occurs, for example, the uniformity of the solid portion in the image formed on the intermediate transfer roller 31 is impaired, and it becomes difficult to form a high-quality image.

  As described at the beginning, the granular unevenness is likely to occur when the toner image (toner and carrier liquid) before transfer is not squeezed at the entrance of the transfer nip portion. Therefore, as a measure for suppressing the occurrence of granular unevenness, for example, the amount of carrier liquid conveyed to the transfer unit 26 can be increased by using carrier liquid amount adjusting means.

  Referring to FIG. 6, as a measure for suppressing the occurrence of granular unevenness, it is also effective to lower the transfer bias in the transfer unit 26 using a transfer unit capable of adjusting the bias value. It is also effective to increase the pressure contact force between the rollers in the transfer nip portion using the pressure contact force adjusting means. Although not shown in FIG. 6, it is also effective to increase the amount of carrier liquid contained in the toner image before transfer using a developer amount adjusting means. It is also effective to increase the amount of carrier liquid before transfer using the carrier liquid amount adjusting means.

  On the other hand, the image flow is a phenomenon in which the image density of the toner image transferred to the transfer member decreases as a result of the toner and carrier liquid contained in the toner image before transfer being squeezed at the entrance of the transfer nip. is there. In the case of image flow, since the carrier liquid and the toner are squeezed and stayed temporarily at the entrance of the transfer nip, the toner flows downstream from the area where the patch image is formed. For this reason, the second density detection sensor Even though the toner amount C2 (or image density) of the patch image detected at 42 does not increase, the toner amount C3 of the patch image detected by the third density detection sensor 43 decreases.

  Here, as a countermeasure for suppressing the occurrence of image flow, the transfer bias in the transfer unit 26 is increased using a transfer unit capable of adjusting a bias value, or the toner image before transfer is transferred using a toner charge amount adjusting unit. The amount of toner contained in the toner is increased, the pressure contact force between the rollers in the transfer nip portion is reduced using the pressure contact force adjusting means, or the amount of the carrier liquid conveyed to the transfer portion 26 using the carrier liquid amount adjusting means. It is effective to reduce this. Although not shown in FIG. 6, it is also effective to reduce the amount of carrier liquid contained in the toner image before transfer using a developer amount adjusting means. It is also effective to reduce the amount of toner and / or the amount of carrier liquid contained in the toner image before transfer using the toner density adjusting means.

(Image forming condition adjusting method ST100)
With reference to FIGS. 1, 2, and 7, in wet image forming apparatus 100 according to the present embodiment, when a normal image is formed on recording paper 55, the density of the image decreases. In order to suppress this, an image forming condition adjustment method ST100 (see FIG. 7) is executed. Although details will be described later, the image forming condition adjustment method ST100 includes an image noise determination method. According to this determination method, intermediate transfer is performed based on the value of (C1-C2) -C3 obtained from the patch image. When the image density of the image transferred to the roller 31 is lowered, it can be distinguished with high accuracy that it is caused by the occurrence of image noise.

  At least one of the adjustment means (toner density adjustment means, developer amount adjustment means, carrier liquid amount adjustment means, toner charge amount adjustment means, transfer means capable of adjusting the bias value, and pressure contact force adjustment means. In the image forming condition adjusting method ST100, the density of the image formed on the recording paper 55 during normal image formation is set to a desired value or more.

  The image forming condition adjusting method ST100 is, for example, immediately after the wet image forming apparatus 100 is turned on, after a predetermined number of images are formed by the wet image forming apparatus 100, and / or by the wet image forming apparatus 100. This is carried out after a predetermined time has elapsed since the formation of. The timing at which the image forming condition adjusting method ST100 is executed is stored in, for example, the memory 82 of the engine control unit 80 in the wet image forming apparatus 100. The memory 82 also stores a control program for executing the image forming condition adjustment method ST100.

  When the CPU 84 determines that the predetermined condition is satisfied, the main control unit 60 and the engine control unit 80 execute the image forming condition adjustment method ST100 for each device constituting the wet image forming apparatus 100 according to the control program. Send a signal to implement. When the image forming condition adjustment method ST100 is executed, the CPU 84 changes various image forming conditions and writes the changed image forming conditions in the memory 82, whereby the image forming conditions stored in the memory 82 are updated. Is done.

  Hereinafter, the image forming condition adjusting method ST100 in the present embodiment will be described more specifically. When the image forming condition adjustment method ST100 is executed, first, the CPU 84 obtains information on the exposure amount, the exposure range, and the exposure timing necessary for the exposure device 23 to form a patch image on the photosensitive member 21. Read from the memory 82. The CPU 84 controls the exposure device 23 through the exposure control unit 93. The exposure device 23 forms an electrostatic latent image corresponding to the patch image on the photoconductor 21.

  The electrostatic latent image is conveyed to the developing position 24. The electrostatic latent image is visualized at the developing position 24 by the action of the electric field formed by the developing bias generator 18. A patch image is formed on the surface of the photoreceptor 21 at a portion downstream of the development position 24 and upstream of the transfer portion 26 (primary transfer portion) (sequence ST1). The patch image formed on the photoconductor 21 moves toward the transfer unit 26 by the rotation of the photoconductor 21.

  When the patch image on the photoconductor 21 reaches the detection range of the first density detection sensor 41, the first density detection sensor 41 detects the toner amount C1 of the patch image on the photoconductor 21 before the primary transfer ( Sequence ST2). The first density detection sensor 41 may detect the toner amount C1 as the image density. The patch image on the photoreceptor 21 in which the toner amount C1 is detected is transferred onto the intermediate transfer roller 31 by the action of the electric field formed by the transfer bias generator 35 (sequence ST3).

  Prior to the primary transfer, the primary transfer bias value (initial value) is set in advance based on predetermined conditions (such as the usage environment of the wet image forming apparatus or the usage state of the wet image forming apparatus). Yes. The patch image transferred onto the intermediate transfer roller 31 is conveyed toward the transfer unit 36 (secondary transfer unit) by the rotation of the intermediate transfer roller 31.

  When the patch image as the residue on the photoreceptor 21 after the primary transfer reaches the detection range of the second density detection sensor 42, the second density detection sensor 42 determines the toner amount C2 (or image density) of the patch image. ) Is detected (sequence ST4).

  The CPU 84 serving as a determination unit performs photosensitivity based on the difference between the toner amount (C1) of the patch image detected by the first density detection sensor 41 and the toner amount (C2) of the patch image detected by the second density detection sensor 42. The movement amount of the toner moved from the body 21 onto the intermediate transfer roller 31 is calculated, and it is determined whether or not the movement amount of the toner is equal to or larger than a predetermined movement amount (sequence ST5).

  When it is determined that the toner movement amount is not equal to or greater than the predetermined movement amount, the transfer efficiency is not appropriate (for example, the transfer efficiency is less than 90% at this time), and it is determined that the toner movement amount is insufficient. (NO in sequence ST5). In this embodiment, in order to increase the transfer efficiency, the transfer bias Vb in the transfer unit 26 is increased (adjusted) using a transfer unit capable of adjusting the bias value, and toner charging is performed as adjustment of the image forming conditions. At least one of increasing (adjusting) the charge amount CHG of the toner contained in the toner image before transfer is performed using the amount adjusting means (sequence ST6).

  The sequences ST1 to ST6 are repeated until it is determined in the sequence ST5 that the toner movement amount is equal to or greater than the predetermined movement amount. When changing the image forming conditions, after the first patch image of the plurality is primarily transferred, each adjusting unit sequentially changes the image forming conditions for the patch image to be primarily transferred thereafter. As described above, various image forming conditions may be adjusted continuously or discretely.

  Assume that it is determined in sequence ST5 that the amount of toner movement is greater than or equal to a predetermined amount of movement (YES in sequence ST5). In this case, it is determined that the transfer efficiency is appropriate (at this time, for example, the transfer efficiency is 90% or more). When the patch image transferred onto the intermediate transfer roller 31 by the primary transfer reaches the detection range of the third density detection sensor 43, the third density detection sensor 43 uses the toner amount C3 (or image density) of the patch image. Is detected (sequence ST7).

  The CPU 84 as a determination unit determines whether or not the value of (C1-C2) -C3 obtained from the patch image is a predetermined value (for example, 0.2) or less (sequence ST8). Here, whether or not the value of (C1-C2) -C3 is within a certain allowable range obtained under the set values of the transfer bias Vb and the toner charge amount CHG that are currently set. Determined.

  In other words, here, the image density of the patch image transferred to the intermediate transfer roller 31 is the maximum density (or its maximum density) that can be obtained under the currently set transfer bias Vb and toner charge amount CHG. It is determined whether or not the vicinity has been reached. When the value of (C1-C2) -C3 is not less than or equal to a predetermined value (outside the allowable range), it is determined that image noise has occurred (NO in sequence ST8).

  In this embodiment, in order to suppress image noise, as the adjustment of the image forming conditions, the transfer bias Vb in the transfer unit 26 is adjusted using a transfer unit capable of adjusting the bias value, and the toner charge amount adjusting unit Is used to adjust the charge amount CHG of the toner contained in the toner image before transfer (sequence ST9). Here, the adjustment of the transfer bias Vb and / or the toner charge amount CHG within the range in which the transfer efficiency is determined to be appropriate in the sequence ST5 (within a range in which the predetermined transfer efficiency (90% or more) can be maintained). Is done.

  Sequences ST7 to ST9 are repeated until it is determined in sequence ST8 that the value of (C1-C2) -C3 is equal to or less than a predetermined value. Although not shown in FIG. 7, a new patch image is formed under the image forming conditions adjusted through sequence ST9, the toner amount C3 of the patch image is detected, and the determination process of sequence ST8 is performed. And so on.

  In sequence ST8, it is determined that the value of (C1-C2) -C3 is equal to or less than a predetermined value obtained under the set values of the transfer bias Vb and the toner charge amount CHG that are currently set ( YES in sequence ST8). In this case, it is determined that the density of the toner image obtained under the set values of the transfer bias Vb and the toner charge amount CHG set at the present time has reached the maximum density (or the vicinity thereof). It is determined that the set transfer bias Vb and the toner charge amount CHG are appropriate.

  CPU 84 determines whether or not the value of (C1-C2) -C3 obtained from the patch image is equal to or smaller than a predetermined value (sequence ST10). Here, it is determined whether or not the value of (C1-C2) -C3 is included in a certain allowable range required during normal image formation. The predetermined value in sequence ST8 and the predetermined value in sequence ST10 may be the same value or different from each other. When the value of (C1-C2) -C3 is within the allowable range (YES in sequence ST10), image forming condition adjustment method ST100 ends (sequence ST11).

  On the other hand, when the value of (C1-C2) -C3 is outside the allowable range (NO in sequence ST10), in order to suppress image noise, in this embodiment, the pressure contact force adjusting means is used as the adjustment of the image forming conditions. At least one of adjusting the pressure contact force between the rollers in the transfer nip portion and adjusting the amount of the carrier liquid conveyed to the transfer portion 26 using the carrier liquid amount adjusting means. (Sequence ST12).

  A new patch image is formed under the image forming conditions adjusted through the sequence ST12, the toner amount C3 of the patch image is detected (sequence ST13), and the determination process of the sequence ST10 is performed again. Sequences ST10 to ST13 are repeated until it is determined in sequence ST10 that the value of (C1-C2) -C3 is equal to or less than a predetermined value. As described above, the image forming conditions to be used during normal image formation are set.

  As described with reference to FIG. 6, adjusting the transfer bias Vb, the toner charge amount CHG, the transfer nip pressure, the carrier liquid amount, and the like depends on whether these values are increased or decreased. It becomes a measure against unevenness and a measure against image flow. For example, it is assumed that the granular unevenness of the image noise is first generated (see FIG. 6). If the toner amount (image density) of the patch image transferred onto the intermediate transfer roller 31 has increased (if it tends to increase) after adjustment of the image forming conditions, the decrease in the image density is granular unevenness, The adjustment of the image forming conditions is repeated until the toner amount of the patch image falls within the allowable range.

  On the other hand, if the toner amount (image density) of the patch image transferred onto the intermediate transfer roller 31 has decreased (if it tends to decrease) after the adjustment of the image forming conditions, the decrease in the image density indicates the image flow. However, the image forming condition is adjusted so as to be in the opposite direction to that described above (see FIG. 6). Such measures are similarly applied to the transfer bias, the toner charge amount, the pressure contact force at the transfer nip, and the carrier liquid amount at the time of transfer, thereby suppressing the occurrence of image noise. . This is common in the sequences ST9 and ST12.

As an actual control flow, it is assumed that, for example, granular unevenness of image noise is initially generated, the toner amount is 1.0 g / m ² , the primary transfer bias Vb is 600 V, and the transfer efficiency is 90% or more. After that, the transfer bias Vb is lowered to 400V, for example. The transfer bias Vb of 400 V corresponds to a lower limit value that can ensure transfer efficiency of 90% or more. After adjusting the image forming conditions, the value of (C1-C2) -C3 is, for example, 0.3. This value is not more than the predetermined value (0.2) in the sequence ST10 although it is not more than the predetermined value in the sequence ST8 (allowable range by adjusting the transfer bias Vb and the toner charge amount CHG).

As a sequence ST12, the amount of the carrier liquid conveyed to the transfer unit 26 using the carrier liquid amount adjusting means is increased by, for example, 0.5 g / m ² while maintaining the primary transfer bias Vb at 400V. Let After adjusting the image forming conditions, the value of (C1-C2) -C3 is, for example, 0.15. This value is equal to or less than a predetermined value (0.2) in sequence ST10. As described above, the optimum image forming conditions to be used during normal image formation are set.

On the other hand, as the sequence ST12, the amount of carrier liquid transported to the transfer unit 26 using the carrier liquid amount adjusting means is set to 0.5 g / m ^2, for example, with the primary transfer bias Vb maintained at 400V. In some cases, the value of (C1-C2) -C3 becomes 0.45, for example. This indicates that the cause of the decrease in image density is due to the image flow of the image noise. This value is not less than or equal to the predetermined value (0.2) in sequence ST10.

In this case, when the primary transfer bias Vb is maintained at 400 V, the amount of carrier liquid conveyed to the transfer unit 26 using the carrier liquid amount adjusting means is usually 0.5 g / m ^2, for example. Less than. After adjusting the image forming conditions, the value of (C1-C2) -C3 is, for example, 0.15. This value is equal to or less than a predetermined value (0.2) in sequence ST10. As described above, the optimum image forming conditions to be used during normal image formation are set.

(Action / Effect)
In wet image forming apparatus 100 in the present embodiment, CPU 84 adjusts (optimizes) the image forming conditions by executing image forming condition adjusting method ST100. Under the image forming conditions set to be used at the time of normal image formation, it is possible to obtain an appropriate transfer efficiency and to suppress the occurrence of image noise.

  As described above, in the wet image forming apparatus, the toner image is transferred in a state where the carrier liquid is interposed in the transfer portion. When image noise occurs in the image after transfer, the image density decreases. By directly measuring the image density of the image transferred onto the transfer target member (intermediate transfer roller 31), the level of decrease in image density can be estimated.

  However, even when the transfer efficiency is lowered, the density of the image transferred onto the transfer member is lowered. For this reason, if the density of the image transferred onto the transfer member decreases only from the measurement result of the density of the image transferred onto the transfer member, is it due to the occurrence of image noise? Therefore, it cannot be clearly distinguished whether it is caused by a decrease in transfer efficiency or the like.

  On the other hand, in the wet image forming apparatus 100, the image density (C1) of the patch image on the photoconductor 21 before the transfer detected by the first density detection sensor 41 and the transfer detected by the second density detection sensor 42. The image density of the patch image transferred onto the intermediate transfer roller 31 is calculated as a calculated value (reference value) based on the difference from the image density (C2) of the patch image as the remaining portion on the subsequent photoconductor 21. Is done. Furthermore, the difference between the calculated value (C1−C2) and the image density (C3) of the patch image on the intermediate transfer roller 31 detected by the third density detection sensor 43 is calculated.

  The wet image forming apparatus 100 acquires, as a calculation result, an image forming condition when this value is equal to or less than a predetermined value based on the value of (C1-C2) -C3 obtained from the patch image. According to the value of (C1-C2) -C3 obtained from the patch image, it is caused by the occurrence of image noise when the image density of the image transferred to the intermediate transfer roller 31 is lowered. Can be distinguished with high accuracy.

  That is, the detected value (C3) of the toner image on the intermediate transfer roller 31 actually detected is lower than the estimated value of the image density of the toner image on the intermediate transfer roller 31 estimated from (C1-C2). In this case, it can be determined that image noise has occurred. When the detected value (C3) of the toner image on the intermediate transfer roller 31 actually detected is higher than the estimated value of the image density of the toner image on the intermediate transfer roller 31 estimated from (C1-C2). It can be determined that no image noise has occurred.

  According to the wet image forming apparatus 100, it is possible to appropriately detect that the change in the image density of the toner image generated during the image forming process is caused by the image noise, and to adjust the image forming conditions more appropriately. Therefore, a high-quality image can be formed on the recording paper 55 based on the appropriate image forming conditions.

  In the present embodiment, it is determined whether or not the transfer efficiency is appropriate in sequence ST5, but sequence ST5 may be performed as necessary. Even when the sequence ST5 is not performed, according to the value of (C1-C2) -C3 obtained from the patch image, when the image density of the image transferred to the intermediate transfer roller 31 is lowered. Therefore, it can be distinguished with high accuracy that it is caused by the occurrence of image noise.

  In the present embodiment, a plurality of patch images are formed on the intermediate transfer roller 31 by the image forming unit. On the other hand, as the patch image formed by the image forming unit, one continuous patch image may be formed. Even when the patch image is formed as a series of long images, the image forming condition adjustment method ST100 is performed in the same manner as described above for each partial portion (for each region) in the longitudinal direction, and thus occurred during the image forming process. It is possible to appropriately detect that the change in the image density of the toner image has occurred due to the occurrence of image noise and adjust the image forming conditions more appropriately, and based on the appropriate image forming conditions A high-quality image can be formed on the recording paper 55.

[Modification]
FIG. 8 is a diagram illustrating an image forming condition adjustment method ST200 (image noise determination method) executed by the wet image forming apparatus according to the modification of the first embodiment. In the image forming condition adjusting method ST200, after the sequences ST9 and ST12 are executed, it is determined again in the sequence ST5 whether or not the transfer efficiency is appropriate.

  Even in this configuration, as in the first embodiment, according to the value of (C1-C2) -C3 obtained from the patch image, when the image density of the image transferred to the recording paper 55 is reduced. It is possible to detect with high accuracy that it is caused by the occurrence of image noise and adjust the image forming conditions more appropriately, and to record high-quality images based on the appropriate image forming conditions 55 can be formed.

[Embodiment 2]
In the first embodiment described above, the image forming condition setting method and the image noise determination method are performed based on the image densities (C1 to C3) of the patch images before and after the primary transfer. As in the wet image forming apparatus 200 shown in FIG. 9, the image forming condition setting method and the image noise determination method may be performed based on the image density of the patch image before and after the secondary transfer.

  The image forming means in the present embodiment forms a toner image (and a patch image) on the intermediate transfer roller 31 (image carrier), and includes the developing unit 10, the photosensitive unit 20, and the transfer bias generator 35. Contains.

  In the wet image forming apparatus 200, the first density detection sensor 41 is disposed so as to face a portion upstream of the transfer portion 36 on the surface of the intermediate transfer roller 31 (image carrier). The carrier liquid amount adjusting means 34 is provided on the upstream side of the first concentration detection sensor 41.

  The second density detection sensor 42 is disposed so as to face a portion of the surface of the intermediate transfer roller 31 that is downstream of the transfer unit 36. The third density detection sensor 43 is disposed so as to face a portion downstream of the transfer unit 36 and upstream of the fixing unit 50 on the surface of the recording paper 55 (transfer target member).

  Even in this configuration, as in the first embodiment, according to the value of (C1-C2) -C3 obtained from the patch image, when the image density of the image transferred to the recording paper 55 is reduced. It is possible to detect with high accuracy that it is caused by the occurrence of image noise and adjust the image forming conditions more appropriately, and to record high-quality images based on the appropriate image forming conditions 55 can be formed.

[Embodiment 3]
In the first and second embodiments, the intermediate transfer roller 31 is used. As in the wet image forming apparatus 300 shown in FIG. 10, the intermediate transfer roller may not be used. In this case, the photosensitive member 21 corresponds to an image carrier, and the recording paper 55 corresponds to a recording medium. The image forming means in the present embodiment forms a toner image (and a patch image) on the photosensitive member 21 (image carrier), and assumes that the developing unit 10 (developing roller 15), the exposure device 23, and the exposure control unit 93. Is included.

  Even in this configuration, as in the first and second embodiments, the image density of the image transferred to the recording paper 55 is reduced according to the value of (C1-C2) -C3 obtained from the patch image. In this case, it is possible to detect with high accuracy that the image noise is caused and to adjust the image forming conditions more appropriately, and to produce a high-quality image based on the appropriate image forming conditions. It can be formed on the recording paper 55.

  As mentioned above, although each embodiment based on this invention was described, each embodiment disclosed this time is an illustration and restrictive at no points. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  10 developing unit, 10M, 82 memory, 11 developing tank, 11C carrier liquid supply pump, 11CA, 32P carrier liquid, 11E liquid bridge, 11T toner supply pump, 11TA toner particles, 12 developer, 13 supply roller, 13T doctor blade, 14 Transfer roller, 15 Development roller, 15T, 28, 39 Cleaning blade, 16, 22 Charger, 17, 27 Charger, 18 Development bias generator, 20 Photoreceptor unit, 21 Photoreceptor, 23 Exposure device, 24 Development position , 25 Pre-transfer charger, 26, 36 Transfer unit, 30 Transfer unit, 30M Pressure contact force adjustment unit, 31 Intermediate transfer roller, 32 Pre-wet device, 32R, 33R roller, 33 Squeeze device, 33Q blade, 34 Carrier liquid level adjustment Means, 35, 38 Transfer bias generating unit, 37 Transfer roller, 41 First density detection sensor, 42 Second density detection sensor, 43 Third density detection sensor, 44, 46, 48 Light emitting part, 45, 47, 49 Light receiving part , 50 fixing unit, 51, 52 fixing roller, 55 recording paper, 60 main control unit, 62 interface, 64, 84 CPU, 66 image memory, 70 engine unit, 80 engine control unit, 91C, 91T pump drive unit, 93 exposure Control unit, 94 peripheral speed control unit, 95 charging bias generation unit, 97 pre-wet control unit, 98 squeeze control unit, 100, 200, 300 wet image forming apparatus, AR55 transport direction, C1, C2, C3 toner amount (image density) ), ST100, ST200 Image forming condition adjusting method.

Claims (12)

An image carrier for carrying a toner image formed by developing with a developer containing a carrier liquid and toner;
An image forming means for forming the toner image on the image carrier including a developer carrier for carrying the developer;
A member to which the toner image on the image carrier is transferred;
Transfer means for applying a transfer bias between the image carrier and the transfer member;
First density detection means for detecting an image density of the toner image as a patch image on the image carrier before being transferred to the transfer member;
Second density detecting means for detecting an image density of the patch image as a residue on the image carrier after the patch image is transferred onto the transfer member;
Third density detection means for detecting an image density of the patch image on the transfer member transferred from the image carrier;
Determination means to which detection results of the first, second and third concentration detection means are input,
The image forming means forms the patch image on the image carrier,
The determination means is transferred onto the transfer member from the difference between the image density of the patch image detected by the first density detection means and the image density of the patch image detected by the second density detection means. Calculating the image density of the patch image as a calculated value;
The determination unit determines whether or not a difference between the calculated value and the image density of the patch image detected by the third density detection unit is a predetermined value or less;
Wet image forming apparatus. The determination unit is configured to detect the density of the patch image detected by the first density detection unit and the image density of the patch image detected by the second density detection unit from above the image carrier. Calculating the amount of movement of the toner moved onto the transfer member;
The determination unit determines whether the movement amount of the toner is equal to or greater than a predetermined movement amount;
The wet image forming apparatus according to claim 1. An adjustment unit for adjusting image forming conditions;
If the difference between the calculated value and the image density of the patch image detected by the third density detecting unit is not less than or equal to the predetermined value, it is determined that image noise has occurred, and the image forming condition is determined by the calculation The adjustment means adjusts the difference between the value and the image density of the patch image detected by the third density detection means to be equal to or less than the predetermined value;
The wet image forming apparatus according to claim 1. The adjusting means presses the image carrier against the member to be transferred so that a difference between the calculated value and the image density of the patch image detected by the third density detecting means is equal to or less than the predetermined value. And adjusting at least one of adjusting the amount of the carrier liquid contained in the patch image on the image carrier,
The wet image forming apparatus according to claim 3. The adjusting unit adjusts the bias value of the transfer bias so that a difference between the calculated value and the image density of the patch image detected by the third density detecting unit is equal to or less than the predetermined value; Performing at least one of adjusting a charge amount of the toner included in the patch image on the image carrier,
The wet image forming apparatus according to claim 3 or 4. An adjustment unit for adjusting image forming conditions;
When the movement amount of the toner is not equal to or greater than the predetermined movement amount, it is determined that the movement amount of the toner is insufficient, and the adjustment unit causes the movement amount of the toner to be equal to or greater than the predetermined movement amount. Adjusting at least one of adjusting a bias value of the transfer bias and adjusting a charge amount of the toner included in the patch image on the image carrier.
The wet image forming apparatus according to claim 2. An image noise determination method for determining whether image noise has occurred in an image formed using a wet image forming apparatus,
The wet image forming apparatus includes:
An image carrier for carrying a toner image formed by developing with a developer containing a carrier liquid and toner;
An image forming means for forming the toner image on the image carrier including a developer carrier for carrying the developer;
A member to which the toner image on the image carrier is transferred;
Transfer means for applying a transfer bias between the image carrier and the transfer member;
First density detection means for detecting an image density of the toner image as a patch image on the image carrier before being transferred to the transfer member;
Second density detecting means for detecting an image density of the patch image as a residue on the image carrier after the patch image is transferred onto the transfer member;
Third density detection means for detecting an image density of the patch image on the transfer member transferred from the image carrier;
Determination means to which detection results of the first, second and third concentration detection means are input,
The image noise determination method is as follows:
The image forming means forming the patch image on the image carrier;
The determination means is transferred onto the transfer member from the difference between the image density of the patch image detected by the first density detection means and the image density of the patch image detected by the second density detection means. Calculating the image density of the patch image as a calculated value;
The determination unit includes a determination step of determining whether a difference between the calculated value and the image density of the patch image detected by the third density detection unit is equal to or less than a predetermined value;
If the difference between the calculated value and the image density of the patch image detected by the third density detection means is not less than or equal to the predetermined value, it is determined that image noise has occurred,
Image noise determination method. The determination unit is configured to detect the density of the patch image detected by the first density detection unit and the image density of the patch image detected by the second density detection unit from the image carrier. Calculating the amount of movement of the toner moved onto the transfer member;
The determination means further comprises a step of determining whether or not the movement amount of the toner is equal to or greater than a predetermined movement amount;
If the toner movement amount is not equal to or greater than the predetermined movement amount, it is determined that the toner movement amount is insufficient.
The image noise determination method according to claim 7. The image noise determination method according to claim 7 or 8, comprising:
The wet image forming apparatus further includes an adjusting unit for adjusting image forming conditions,
When the difference between the calculated value and the image density of the patch image detected by the third density detecting unit is not less than or equal to the predetermined value, the image forming condition is detected by the calculated value and the third density detecting unit. Adjusted by the adjusting means so that a difference from the image density of the patch image is equal to or less than the predetermined value;
An image forming condition adjusting method for a wet image forming apparatus. The adjusting means presses the image carrier against the member to be transferred so that a difference between the calculated value and the image density of the patch image detected by the third density detecting means is equal to or less than the predetermined value. And adjusting at least one of adjusting the amount of the carrier liquid contained in the patch image on the image carrier,
An image forming condition adjusting method for a wet image forming apparatus according to claim 9. The adjusting unit adjusts the bias value of the transfer bias so that a difference between the calculated value and the image density of the patch image detected by the third density detecting unit is equal to or less than the predetermined value; Performing at least one of adjusting a charge amount of the toner included in the patch image on the image carrier,
The method for adjusting image forming conditions of the wet image forming apparatus according to claim 9. The image noise determination method according to claim 8,
The wet image forming apparatus further includes an adjusting unit for adjusting image forming conditions,
If the toner movement amount is not equal to or greater than the predetermined movement amount, the adjustment means adjusts the bias value of the transfer bias so that the toner movement amount is equal to or greater than the predetermined movement amount; and At least one of adjusting the charge amount of the toner contained in the patch image on the image carrier,
An image forming condition adjusting method for a wet image forming apparatus.

Images