JP2004157181A - Image forming apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To steadily form a toner image of satisfactory image quality in an image forming apparatus and an image forming method of transferring toner image to a transfer medium. <P>SOLUTION: A CPU 113 executes a control program stored in a memory 116, thereby, a patch image is formed on an intermediate transfer roller of a transfer unit 40, the patch image is irradiated with light from a light emitter 461, a light receiver 462 receives light from the patch image, whether or not a received-light signal from the light receiver 462 is within a tolerable range is determined, and the image forming condition is controlled and stored in the memory 116 when the received-light signal is outside the tolerable range. Upon entry of a print instruction signal from an external apparatus via a main controller 100, a printing operation is performed under the image forming condition stored in the memory 116. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophotographic image forming technique for a printer, a copying machine, a facsimile machine, and the like, and more particularly to an electrophotographic image forming technique using wet development as a developing method.
[0002]
[Prior art]
Conventionally, a charged photoconductor is exposed by an exposure unit to form an electrostatic latent image on the photoconductor, and toner is adhered to the photoconductor by a development unit to visualize the electrostatic latent image to form a toner image. An electrophotographic image forming apparatus that forms a toner image and transfers the toner image to a transfer medium has been put to practical use. Here, as a developing method of the developing means, a wet developing method using a developing solution in which toner is dispersed in a liquid carrier is known. This wet development method has the advantages that a high-resolution image can be obtained because the average particle diameter of the toner is as small as 0.1 to 2 μm, and a uniform image can be obtained because of high fluidity due to liquid. ing.
[0003]
In this image forming apparatus, it is conventionally known that image quality such as image density can be controlled by changing image forming conditions including various elements such as a bias potential applied to each section of the apparatus. Further, the image density of the toner image may be different due to individual differences of the apparatuses, aging, and changes in the surrounding environment such as temperature and humidity. Therefore, a density control technique for controlling the image density by adjusting the image forming conditions that affect the image density among the above elements has been conventionally proposed (see Patent Document 1). In the apparatus described in Patent Document 1, a test patch image is formed, light is irradiated toward the patch image, light from the patch image is received, and the image density of the patch image is detected. Image forming conditions such as the surface potential of the photoconductor and the toner concentration of the developing solution are controlled based on the detection result.
[0004]
[Patent Document 1]
JP-A-8-292622 (paragraph [0016], FIG. 2)
[0005]
[Problems to be solved by the invention]
By the way, in the conventional image forming apparatus, a developer having a relatively low toner concentration has been used. In recent years, however, a developer having a relatively high toner concentration has been used for the following reasons. . That is, at a low toner concentration, a large amount of developing solution is required to secure a sufficient amount of toner, so that it is difficult to reduce the size of the device, and furthermore, the volatile solvent, which is often used as a liquid carrier, needs to be removed from the device. This is because the configuration of the apparatus becomes complicated in order to prevent the leakage of data. Further, when the concentration of the developer is increased, the viscosity becomes higher. For this reason, the density control technology described in Patent Document 1, which is based on the premise that a developer having a relatively low toner concentration is used, is directly applied to an image forming apparatus using a developer having a relatively high toner concentration and a high viscosity. It is difficult to do.
[0006]
The present invention has been made in view of the above problems, and develops a latent image on a latent image carrier using a high-density, high-viscosity developer to form a toner image, and then transfers the toner image to a transfer medium. It is an object of the present invention to stably form a toner image having good image quality in an image forming apparatus and an image forming method for transferring.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to the present invention includes a latent image carrier configured to be able to carry a latent image on a surface thereof, a toner dispersed in a liquid carrier, and a toner concentration of about 5 to 40. The developing solution, which is in a weight percentage, is conveyed to a developing position facing the latent image carrier while being carried on the surface thereof, and is brought into contact with the latent image carrier at the developing position, whereby the latent image carrier is transferred to the latent image carrier. A developer carrier to be supplied, and a toner in a developer supplied from the developer carrier to the latent image carrier is adhered to the latent image carrier, and the latent image is visualized to form a toner image. Image forming means, a transfer means for transferring the toner image on the latent image carrier to a transfer medium at a predetermined transfer position, and irradiating light toward the toner image as a patch image transferred to the transfer medium. Light-emitting unit and receives light from the patch image That is an optical sensor having a light receiving portion, characterized in that a control means for controlling the image forming conditions that affect the density of the toner image based on a photodetection signal from the photodetection unit.
[0008]
In order to achieve the above object, an image forming method according to the present invention provides a method of dispersing a toner in a liquid carrier and applying a developer having a toner concentration of about 5 to 40% by weight to the surface of the developer carrier. A developing solution supply step of supplying the developing solution to the latent image carrier by carrying the developer to a developing position opposed to the latent image carrier while contacting the latent image carrier at the developing position; A toner in a developing solution supplied from the liquid carrier to the latent image carrier is attached to the latent image carrier, and a latent image formed on the latent image carrier is visualized to form a toner image. An image forming step, a step of transferring the toner image on the latent image carrier to a transfer medium at a predetermined transfer position, and a step of irradiating light toward the toner image as a patch image transferred to the transfer medium. Receiving light from the patch image It is characterized by comprising the step of controlling the image forming conditions that affect the density of the toner image based on the received light signal.
[0009]
According to these configurations, light is radiated toward a toner image as a patch image on a transfer medium, light from the patch image is received, and image formation that affects the density of the toner image is performed based on the received light signal. Conditions are controlled.
[0010]
By the way, of the developer in which the toner is dispersed in the liquid carrier, on the latent image carrier, the toner is attracted to the surface of the latent image carrier by a latent image potential (contrast potential) to form a lower layer, and the lower layer is formed on the surface layer. A layer of a liquid carrier is formed. Similarly, on the transfer medium, the toner is attracted to the surface of the transfer medium by the transfer bias to form a lower layer, and a liquid carrier layer is formed on the lower layer. As a result, almost all of the toner particles are transferred to the transfer medium, but part of the liquid carrier remains on the latent image carrier, and the rest is transferred to the transfer medium. Therefore, when the toner image is transferred from the latent image carrier to the transfer medium, the amount of the liquid carrier contained in the developer decreases before and after the transfer.
[0011]
The supply of the developer from the developer carrier to the latent image carrier is performed by bringing the developer carried on the developer carrier into contact with the latent image carrier at the developing position. Then, the toner is attracted to the surface of the latent image carrier by the latent image potential applied during this contact, and the toner image is formed (developed). Thereafter, the developer that has been in contact with both the developer carrier and the latent image carrier is separated into a developer that remains remaining attached to the developer carrier and a developer that moves to the latent image carrier.
[0012]
Further, in transferring the toner image from the latent image carrier to the transfer medium, the developer on the latent image carrier is brought into contact with the transfer medium at the transfer position, and the toner is transferred to the transfer medium by a transfer bias applied during this contact. This is done by being attracted to the surface. Thereafter, the developer that has been in contact with both the latent image carrier and the transfer medium is separated into a developer that remains while being attached to the latent image carrier and a developer that moves to the transfer medium.
[0013]
In these cases, when the developer has a high viscosity, such as a developer having a toner concentration of about 5 to 40% by weight, for example, as shown in FIG. At the time of separating from the state in which both the latent image carrier 202 and the latent image carrier 202 are in contact with each other, a thread pulling phenomenon occurs in which the thread is not easily separated, but is once pulled and then separated. When such a stringing phenomenon occurs, for example, as shown in FIG. 9, the developer 200 has a high viscosity and thus does not return to a smooth shape. It will be formed on the surface. When irregularities are formed on the surface of the developing solution for forming the patch image, for example, as shown in FIG. 10, when the patch image is irradiated with light (arrows in the figure), the developing solution depends on the irregularities. The direction of refraction of light (broken line in the figure) on the surface of the device varies. If the direction of refraction of the light varies, a stable light receiving signal cannot be obtained by the light receiving unit.
[0014]
Such a stringing phenomenon is likely to occur when the amount of the liquid carrier is large, and the size of the protrusion when it occurs is large. That is, when the developing solution is separated into the developing solution carrier and the latent image carrier at the developing position, the amount of the liquid carrier is large, so that the stringing phenomenon easily occurs. For this reason, irregularities are likely to be formed on the surface of the developer for forming a patch image on the latent image carrier.
[0015]
On the other hand, when the developer is separated into the latent image carrier and the transfer medium at the transfer position, the amount of the liquid carrier is smaller than that at the development position, so that the stringing phenomenon hardly occurs. Therefore, the surface of the developer for forming the patch image on the transfer medium has almost no irregularities and is almost smooth as compared with the patch image on the latent image carrier. As a result, when the patch image on the transfer medium is irradiated with light, the refraction direction of the light on the surface of the developing solution is almost constant, and the refraction direction is hardly varied as compared with the patch image on the latent image carrier. Absent.
[0016]
Therefore, according to the above-described configuration in which the patch image on the transfer medium is irradiated with light, a light receiving signal can be obtained stably, so that image forming conditions can be suitably controlled. This makes it possible to stably form a toner image with good image quality.
[0017]
Further, when the light receiving section adopts a configuration in which light irradiated by the light emitting section receives specularly reflected light that is specularly reflected in the patch image, the received light amount of the specularly reflected light is equal to a developer surface for forming the patch image. Fluctuates greatly due to variations in the refraction direction at However, as described above, the surface of the developer that forms the patch image on the transfer medium has almost no irregularities compared to the patch image on the latent image carrier, and is almost smooth. Is almost constant. Therefore, a light receiving signal at the light receiving section can be obtained stably.
[0018]
Preferably, the liquid carrier has a viscosity of about 5 to 3000 mPa · s. That is, when the viscosity is about 3000 mPa · s or more, the viscosity is too high, and the stringing phenomenon easily occurs.On the other hand, when the viscosity is about 5 mPa · s or less, the volatility of the liquid carrier increases. This is because a configuration for preventing the liquid carrier from leaking out of the device is required, and the device configuration is complicated. Here, the viscosity of the liquid carrier is about 5 to 3000 mPa · s, but the viscosity of the developer including the toner may be about 50 to 6000 mPa · s.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a diagram showing an internal configuration of a printer which is an embodiment of an image forming apparatus according to the present invention, FIG. 2 is a diagram showing a patch sensor arranged to face an intermediate transfer roller, and FIG. 3 is an electrical configuration of the printer FIG. This printer is a wet development type image forming apparatus that forms a monochromatic image using a developing solution containing black (K) toner. A print command signal including an image signal from an external device such as a host computer is transmitted to a main control unit. 100, the engine control unit 110 controls each part of the engine unit 1 in accordance with a control signal from the main control unit 100, and conveys the sheet from the sheet cassette 3 disposed at the lower portion of the apparatus main body 2. An image corresponding to the image signal is printed out on transfer paper, copy paper, and paper (hereinafter referred to as “recording medium”) 4.
[0020]
The engine unit 1 includes a photoreceptor unit 10, an exposure unit 20, a developing unit 30, a transfer unit 40, and the like. Among these units, the photoconductor unit 10 includes a photoconductor 11, a charging unit 12, a charge removing unit 13, and a cleaning unit 14. The developing unit 30 includes a developing roller 31 and the like. Further, the transfer unit 40 includes an intermediate transfer roller 41 and the like.
[0021]
In the photoreceptor unit 10, the photoreceptor 11 is provided rotatably in an arrow direction 15 (clockwise direction in the figure) of FIG. Around the photoreceptor 11, a charging unit 12, a developing roller 31, an intermediate transfer roller 41, a charge removing unit 13, and a cleaning unit 14 are arranged along a rotation direction 15 thereof. A surface area between the charging unit 12 and the developing roller 31 is an irradiation area of the light beam 21 from the exposure unit 20. In the present embodiment, the charging unit 12 includes a charging roller, and a charging bias is applied from the charging bias generation unit 111 to uniformly charge the outer peripheral surface of the photoconductor 11 to a predetermined surface potential Vd (for example, Vd = DC + 600 V). And has a function as a charging unit.
[0022]
A light beam 21 formed by, for example, a laser is emitted from the exposure unit 20 toward the outer peripheral surface of the photoconductor 11 uniformly charged by the charging unit 12. The exposure unit 20 exposes the photoconductor 11 with the light beam 21 in accordance with a control command given from the exposure control unit 112, and forms an electrostatic latent image on the photoconductor 11 corresponding to an image signal. It has a function as an exposure unit. For example, when a print command signal including an image signal is provided from an external device such as a host computer to the CPU 101 of the main control unit 100 via the interface 102, the CPU 113 responds to a command from the CPU 101 of the main control unit 100 to cause the exposure control unit to execute. A control signal corresponding to the image signal is output to the device 112 at a predetermined timing. Then, a light beam 21 is emitted from the exposure unit 20 to the photoconductor 11 in response to a control command from the exposure control unit 112, and an electrostatic latent image corresponding to an image signal is formed on the photoconductor 11. When forming a patch image as needed, a control signal corresponding to a patch image signal of a predetermined pattern (for example, a solid image) set in advance is provided from the CPU 113 to the exposure control unit 112, and A corresponding electrostatic latent image is formed on the photoconductor 11. As described above, in this embodiment, the photoconductor 11 corresponds to the “latent image carrier” of the present invention.
[0023]
The electrostatic latent image thus formed is visualized by toner supplied from the developing roller 31 of the developing unit 30. The developing unit 30 includes, in addition to the developing roller 31, a tank 33 that stores the developing solution 32, an application roller 34 that draws up the developing solution 32 stored in the tank 33 and applies the developing solution 32 to the developing roller 31, A regulating blade 35 for uniformly regulating the thickness of the layer, a cleaning blade 36 for removing the developing solution remaining on the developing roller 31 after supplying the toner to the photoreceptor 11, a toner concentration adjusting unit 37, and a memory 38 described later (FIG. 3) ). The developing roller 31 rotates at a peripheral speed equal to that of the photoconductor 11 in a direction (counterclockwise in FIG. 1) that follows the photoconductor 11. The application roller 34 rotates in the same direction as the developing roller 31 (counterclockwise in the figure) at a peripheral speed that is about twice as high.
[0024]
In the present embodiment, the developer 32 is a toner composed of a color pigment, an adhesive such as an epoxy resin that adheres the color pigment, a charge control agent that gives a predetermined charge to the toner, and a dispersant that uniformly disperses the color pigment. Are dispersed in a liquid carrier. In the present embodiment, for example, a silicone oil such as polydimethylsiloxane oil is used as a liquid carrier, and the toner concentration is 5 to 40% by weight, and a low-concentration developer (toner concentration of 1 to 2) often used in a wet development method is used. (% By weight) and the viscosity of the liquid carrier is 5 to 3000 mPa · s. Note that the type of the liquid carrier is not limited to silicone oil, and the viscosity of the developer 32 is determined by the materials used for the liquid carrier and the toner used, the toner concentration, and the like. For example, the viscosity is set to 50 to 6000 mPa · s, which is higher than that of a low concentration developer.
[0025]
In the present embodiment, the distance between the photoconductor 11 and the developing roller 31 (development gap = thickness of the developer layer) is set to, for example, 5 to 40 μm, and the developing nip width (the developing solution layer is Is set to, for example, 5 mm in the present embodiment. In the case of the low-concentration developer described above, a development gap of 100 to 200 μm is required to increase the amount of toner, whereas in the present embodiment using a high-concentration developer, the development gap can be reduced. Therefore, the moving distance of the toner that moves by electrophoresis in the developing solution is shortened, and a higher electric field is generated even when the same developing bias is applied, so that the developing efficiency can be improved and the developing speed can be increased. You can do it.
[0026]
The toner concentration adjusting section 37 includes a supply tank 371 in which a developer having a higher toner concentration than the developer 32 stored in the tank 33 is stored and a supply tank 372 in which the liquid carrier is stored. When the toner supply pump 373 operates, the high-concentration developer is supplied from the supply tank 371 to the tank 33 to increase the toner concentration of the developer 32. On the other hand, when the carrier supply pump 374 operates, the liquid carrier is removed from the supply tank 372. 33, the toner concentration of the developer 32 decreases. The pumps 373 and 374 are driven by pump driving units 118 and 119. As described above, by controlling the operation of the pumps 373 and 374, the toner concentration of the developer 32 in the tank 33 is adjusted.
[0027]
In the developing unit 30 having such a configuration, the developer 32 stored in the tank 33 is pumped up by the application roller 34, and the thickness of the developer layer on the application roller 34 is uniformly regulated by the regulating blade 35. The developing solution 32 adheres to the surface of the developing roller 31 and is conveyed to the developing position 16 facing the photoconductor 11 as the developing roller 31 rotates. The toner is positively charged, for example, by the action of a charge control agent or the like. At the developing position 16, the toner is transferred from the developing roller 31 by a developing bias Vb (for example, Vb = DC + 400 V) applied from the developing bias generator 114 to the developing roller 31. Moving to the photoconductor 11, the electrostatic latent image is visualized. Thus, in this embodiment, the developing roller 31 corresponds to the “developer liquid carrier” of the present invention, and the developing bias generator 114 corresponds to the “image forming unit” of the present invention.
[0028]
The toner image formed on the photoconductor 11 as described above is conveyed to a primary transfer position 44 facing the intermediate transfer roller 41 as the photoconductor 11 rotates. The intermediate transfer roller 41 rotates at a peripheral speed substantially equal to that of the photoconductor 11 in a direction (counterclockwise in FIG. 1) that follows the photoconductor 11, and a primary transfer bias (for example, DC- When 400 V is applied, the toner image on the photoconductor 11 is primarily transferred to the intermediate transfer roller 41. Residual charges on the photoreceptor 11 after the primary transfer are removed by a charge removing unit 13 composed of an LED or the like, and a residual developing solution is removed by a cleaning unit 14. Thus, in this embodiment, the intermediate transfer roller 41 corresponds to the “transfer medium” of the present invention, and the transfer bias generator 115 corresponds to the “transfer unit” of the present invention.
[0029]
A secondary transfer roller 42 is disposed at an appropriate position of the intermediate transfer roller 41 (in FIG. 1, vertically below the intermediate transfer roller 41), and a primary transfer toner image primary-transferred to the intermediate transfer roller 41 is transferred to the intermediate transfer roller 41. With the rotation of 41, the sheet is conveyed to a secondary transfer position 45 facing the secondary transfer roller 42. On the other hand, the recording medium 4 accommodated in the paper feed cassette 3 is transported to a secondary transfer position 45 by a transport drive unit (not shown) in synchronization with the transport of the primary transfer toner image. The secondary transfer roller 42 rotates at a peripheral speed equal to that of the intermediate transfer roller 41 in a direction (clockwise in FIG. 1) that follows the intermediate transfer roller 41. For example, when -100 μA is applied by constant current control, the toner image on the intermediate transfer roller 41 is secondarily transferred to the recording medium 4. The residual developing solution on the intermediate transfer roller 41 after the secondary transfer is removed by the cleaning unit 43. The recording medium 4 onto which the toner image has been secondarily transferred is conveyed along a predetermined transfer paper conveyance path 5 (indicated by a dashed line in FIG. 1), and the toner image is fixed by the fixing unit 6. Is discharged to a discharge tray provided in the printer. An operation display panel 7 composed of, for example, a liquid crystal display and a touch panel is provided on the upper surface of the apparatus main body 2 to receive an operation instruction from a user and display predetermined information to notify the user.
[0030]
A patch sensor 46 is arranged between the photoconductor 11 around the intermediate transfer roller 41 and the secondary transfer roller 42 so as to face the intermediate transfer roller 41. As shown in FIGS. 2 and 3, the patch sensor 46 is a reflection-type optical sensor having a light-emitting unit 461 made of, for example, an LED, and a light-receiving unit 462 made of, for example, a photodiode. As shown in FIG. 2, the inclination angle between the optical axis of the light emitting unit 461 and the normal line of the surface of the intermediate transfer roller 41 is θ1, and the inclination angle between the optical axis of the light receiving unit 462 and the normal line of the surface of the intermediate transfer roller 41 is formed. The inclination angles are made equal at θ1, and both the light emitting unit 461 and the light receiving unit 462 are disposed at the bottom of a thin hole formed along the optical axis. With this configuration, the regular light reflected from the light emitted from the light emitting unit 461 in the patch image on the intermediate transfer roller 41 is received by the light receiving unit 462. As shown in FIG. 3, the light emitting unit 461 operates based on a control signal from the CPU 113 to irradiate light toward the patch image 47 (FIG. 5) transferred onto the intermediate transfer roller 41, and specularly reflects the light. The light receiving section 462 receives the light and sends a light receiving signal corresponding to the image density to the CPU 113. As described above, in this embodiment, the patch sensor 46 corresponds to the “optical sensor” of the present invention.
[0031]
3, the main control unit 100 includes an image memory 103 for storing an image signal provided from an external device via an interface 102. The CPU 101 transmits a print command signal including the image signal from the external device. When received through the interface 102, the job data is converted into job data in a format suitable for the operation instruction of the engine unit 1, and is sent to the engine control unit 110. The memory 116 of the engine control unit 110 includes a ROM that stores a control program of the CPU 113 including preset fixed data, and a RAM that temporarily stores control data of the engine unit 1 and calculation results by the CPU 113. The CPU 113 stores in the memory 116 data relating to the image signal transmitted from the external device via the CPU 101.
[0032]
The memory 38 of the developing unit 30 stores data on the manufacturing lot of the developing unit 30, the use history, the characteristics of the built-in toner, the remaining amount of the developer 32, the toner concentration, and the like. The memory 38 is electrically connected to a communication unit 39, and the communication unit 39 is attached to, for example, the tank 33. When the developing unit 30 is mounted on the apparatus main body 2, the communication unit 39 is configured to be opposed to the communication unit 117 of the engine control unit 110 within a predetermined distance, for example, within 10 mm. Data can be transmitted and received in a non-contact state by wireless communication. As a result, the CPU 113 manages various kinds of information such as the management of consumables related to the developing unit 30. In this embodiment, data transmission / reception is performed in a non-contact manner using electromagnetic means such as wireless communication. However, for example, connectors are provided in the apparatus main body 2 and the developing unit 30, respectively. When the developing unit 30 is mounted, data transmission and reception may be performed mutually by mechanically fitting the two connectors. The memory 38 is preferably a non-volatile memory capable of storing data even when the power is off or the developing unit 30 is detached from the apparatus main body 2. Such a non-volatile memory is, for example, a flash memory or the like. An EEPROM, a ferroelectric memory, or the like can be used.
[0033]
FIG. 4 is a diagram illustrating a transfer state of a patch image from a photoconductor to an intermediate transfer roller, and FIG. 5 is a diagram illustrating a developer layer that forms a patch image on the intermediate transfer roller. The patch image is formed on the photoconductor 11 in the same manner as a normal toner image, and is transferred to the intermediate transfer roller 41, except that the patch pattern is not based on a print command signal from an external device but an image pattern is set in advance. That is, as shown in FIG. 4, the toner 322 is attracted to the surface of the photoconductor 11, and is conveyed to the primary transfer position 44 in a state where the liquid carrier 321 is laminated on the surface layer. Then, the toner 322 moves from the photoconductor 11 and is attracted to the surface of the intermediate transfer roller 41 by the primary transfer bias applied from the transfer bias generator 115. Thereafter, the liquid carrier 321 separates with the rotation of the photoconductor 11 and the intermediate transfer roller 41. However, since the liquid carrier amount is smaller at the primary transfer position 44 than at the developing position 16, as shown in FIG. No stringing phenomenon occurs during separation. As a result, as shown in FIG. 5, the surface of the developer 32 that forms the patch image 47 on the intermediate transfer roller 41 is substantially smooth. In the present embodiment, since the patch image 47 is a solid image, the toner 322 is densely arranged on the intermediate transfer roller 41 to form a solid image as shown in FIG.
[0034]
FIG. 6 is a flowchart showing a patch processing routine. A control program for patch processing is stored in the memory 116 of the engine control unit 110. Then, the following patch processing is executed by the CPU 113 controlling each unit of the apparatus according to the control program. First, a patch image 47 is formed on the photoconductor 11 (# 10), and the patch image 47 is transferred from the photoconductor 11 to the intermediate transfer roller 41 (# 12). Then, light is emitted from the light emitting section 461 toward the patch image 47 on the intermediate transfer roller 41 (# 14), and a light receiving signal from the light receiving section 462 that has received the reflected light from the patch image 47 is taken into the CPU 113. (# 16). Then, it is determined whether or not the received light receiving signal is within a preset allowable range (# 18). If it is within the allowable range (YES at # 18), this routine is terminated and If not (NO in # 18), the image forming conditions are controlled, and the controlled image forming conditions are written in the memory 116 to update the image forming conditions stored in the memory 116 (# 20).
[0035]
An example of control of image forming conditions will be described. If the light receiving signal of the light receiving unit 462 exceeds the allowable range in step # 18, the patch image 47 has insufficient density. For example, the surface potential Vd is reduced and the exposure energy is reduced. , The developing bias Vb is increased, and the toner density in the tank 33 is increased. On the other hand, if the light receiving signal of the light receiving unit 462 is less than the allowable range, the density of the patch image 47 is excessive, and thus the respective values are changed in reverse.
[0036]
The image forming conditions thus controlled may be written in the memory 38 of the developing unit 30. Then, the image forming conditions in the memory 38 may be written into the memory 116 at an appropriate timing, for example, at the reception timing of the print command signal. As described above, in this embodiment, the CPU 113 corresponds to the “control unit” of the present invention.
[0037]
FIG. 7 is a flowchart showing a print processing routine. When a print command signal is input from an external device via the main control unit 100, first, image forming conditions such as the charging bias Vd, exposure energy, and developing bias Vb stored in the memory 116 are set (# 30). ). Then, a printing operation is performed under the set image forming conditions (# 32). As described above, since the printing operation is performed under the image forming conditions controlled by the patch processing, high-quality image formation can be performed.
[0038]
As described above, according to the present embodiment, since the light is emitted from the light emitting unit 461 toward the patch image 47 on the intermediate transfer roller 41, the surface of the developer 32 forming the patch image 47 is substantially Can be smoothed. As a result, the direction of refraction of light on the surface of the developer 32 becomes almost constant without variation, so that the regular reflection light from the patch image 47 irradiated by the light emitting unit 461 is reliably received by the light receiving unit 462. Accordingly, a stable light receiving signal can be obtained by the light receiving unit 462. Therefore, by controlling the image forming conditions based on the light receiving signal from the light receiving unit 462, it is possible to set the optimum image forming conditions, thereby always responding to a change in the state of the apparatus due to aging and the like. Images can be formed with high quality.
[0039]
Note that the present invention is not limited to the above embodiment, and various changes can be made to the above described one without departing from the gist thereof. For example, in the above embodiment, the intermediate transfer roller is used. 41, the primary transfer of the toner image on the photoconductor 11 to the intermediate transfer roller 41 at the primary transfer position 44, and then the secondary transfer to the recording medium 4 by the secondary transfer roller 42 at the secondary transfer position 45. However, the present invention is not limited to this. For example, the intermediate transfer roller 41 may be omitted, the secondary transfer roller 42 may be disposed at the primary transfer position 44, and the toner image on the photoconductor 11 may be directly transferred to the recording medium 4. In this case, the patch sensor 46 may be arranged at a position facing the recording medium 4 after the transfer. In this embodiment, the recording medium 4 corresponds to the “transfer medium” of the present invention.
[0040]
Further, in the above-described embodiment, the printer which prints an image given from an external device such as a host computer on transfer paper is described. However, the present invention is not limited to this, and includes a copying machine, a facsimile machine, and the like. The present invention can be applied to a general electrophotographic image forming apparatus. In the above-described embodiment, the present invention is applied to a monochrome image forming apparatus. However, the present invention is not limited to this, and the present invention can be applied to a color image forming apparatus. .
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an internal configuration of a printer according to an embodiment of the invention.
FIG. 2 is a diagram showing a patch sensor arranged to face a photoconductor.
FIG. 3 is a block diagram showing an electrical configuration of the printer.
FIG. 4 is a diagram illustrating a transfer state of a patch image from a photoconductor to an intermediate transfer roller.
FIG. 5 is a view showing a developer layer for forming a patch image on an intermediate transfer roller.
FIG. 6 is a flowchart illustrating a patch processing routine.
FIG. 7 is a flowchart illustrating a print processing routine.
FIG. 8 is a diagram illustrating a stringing phenomenon.
FIG. 9 is a diagram showing irregularities formed on the surface of a developer.
FIG. 10 is a view for explaining variation in the direction of refraction of light on the surface of a developer.
DESCRIPTION OF REFERENCE NUMERALS 11 photoconductor (latent image carrier), 31 developing roller (developer carrier), 32 developer, 41 intermediate transfer roller (transfer medium), 46 patch sensor (optical sensor) 47, patch image, 113, CPU (control means), 114, developing bias generating section (image forming means), 115, transfer bias generating section (transfer means), 321, liquid carrier, 322, toner, 461, light emitting section , 462... Light receiving section

Claims (4)

A latent image carrier configured to carry a latent image on its surface,
A developer in which a toner is dispersed in a liquid carrier and has a toner concentration of about 5 to 40% by weight is conveyed to a developing position facing the latent image carrier while being carried on the surface thereof. A developer carrier to be supplied to the latent image carrier by contacting the latent image carrier,
Image forming means for attaching a toner in a developer supplied to the latent image carrier from the developer carrier to the latent image carrier, and visualizing the latent image to form a toner image;
Transfer means for transferring the toner image on the latent image carrier to a transfer medium at a predetermined transfer position,
A light emitting unit that irradiates light toward a toner image as a patch image transferred to the transfer medium, and a light sensor having a light receiving unit that receives light from the patch image,
An image forming apparatus comprising: a control unit that controls image forming conditions that affect the density of the toner image based on a light receiving signal from the light receiving unit. The image forming apparatus according to claim 1, wherein the light receiving unit receives specularly reflected light obtained by regularly reflecting light emitted by the light emitting unit in the patch image. The image forming apparatus according to claim 1, wherein the viscosity of the liquid carrier is about 5 to 3000 mPa · s. The developer is dispersed in a liquid carrier and the developer having a toner concentration of about 5 to 40% by weight is carried on the surface of the developer carrier while being conveyed to a developing position facing the latent image carrier. A developer supply step of supplying the developer to the latent image carrier by contacting the latent image carrier in
The toner in the developer supplied to the latent image carrier from the developer carrier is attached to the latent image carrier, and the latent image formed on the latent image carrier is visualized to form a toner image. Forming an image forming step;
Transferring the toner image on the latent image carrier to a transfer medium at a predetermined transfer position,
Irradiating light onto a toner image as a patch image transferred to the transfer medium,
Receiving light from the patch image;
Controlling an image forming condition affecting the density of the toner image based on the light receiving signal.

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