JP4192555B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image forming technique such as a printer, a copying machine, and a facsimile machine, and more particularly to an image forming technique that employs wet development as a developing method.
[0002]
[Prior art]
Conventionally, a charged photosensitive member is exposed by an exposure unit to form an electrostatic latent image on the photosensitive member, and toner is attached to the photosensitive member by a developing unit to visualize the electrostatic latent image to form a toner image. An electrophotographic image forming apparatus which has been formed and transferred to a transfer medium to obtain a predetermined image has been put into practical use. Here, as a developing method of the developing means, a wet developing method using a developer in which toner is dispersed in a liquid carrier is known. This wet development system has the advantages that the average particle diameter of the toner is as small as 0.1 to 2 μm, so that a high-resolution image can be obtained, and a uniform image can be obtained because of the high fluidity of the liquid. Therefore, various devices have been proposed (see, for example, Patent Document 1). In this apparatus, a high-viscosity and high-concentration developer is applied onto a developing roller, and the developer is supplied to the latent image surface of the photosensitive member by bringing the developer into contact with the photosensitive member.
[0003]
[Patent Document 1]
Japanese Unexamined Patent Publication No. 7-209922 (paragraph [0038], FIG. 1)
[0004]
[Problems to be solved by the invention]
By the way, when the developer on the developing roller is in contact with the photosensitive member, for example, if a bias is applied so that the charged toner moves toward the developing roller, the charged toner is prevented from moving to the photosensitive member. Can do. However, in the case of a liquid carrier, it is inevitable that the liquid carrier adheres to the photosensitive member, and therefore, the movement of the liquid carrier to the photosensitive member cannot be prevented. Even in the conventional apparatus described in Patent Document 1, since the developer on the developing roller is always in contact with the photosensitive member, the liquid carrier always moves from the developing roller to the photosensitive member. As a result, the liquid carrier is wasted when the developer is not needed depending on the toner image formation mode.
[0005]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a method thereof that can prevent the liquid carrier from being consumed in vain.
[0006]
[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 that moves in a moving direction while carrying an electrostatic latent image on the surface thereof. Exposure means for forming the electrostatic latent image on the latent image carrier, and the latent image carrier Against Place Developer in which toner is dispersed in a liquid carrier by positioning at a fixed developable position Before A toner image is formed by supplying the latent image to a latent image carrier to visualize the electrostatic latent image. And a developing means that is movable between the developable position and a separated position that is separated from the latent image carrier and is not in contact with the developer, and rotates at a predetermined peripheral speed. And A4 size or smaller Corresponding to the moving direction of the toner image rotation direction Round In 2 It becomes possible to carry Intermediate transfer belt with protrusions at predetermined positions And a toner image formed on the latent image carrier. Intermediate transfer belt Transfer means to transfer to And a vertical synchronization sensor that outputs a detection signal when it detects the passage of the protrusion every round of the intermediate transfer belt, and the detection when two toner images of the predetermined size are carried on the round of the intermediate transfer belt. Control means for outputting image request signals after a predetermined time T1, T2 (T2> T1) from the signal output time point, and controlling the formation of the electrostatic latent image and the toner image based on each image request signal; Comprising the control means, Above One round of the intermediate transfer belt In The predetermined size Toner image 1 When carrying it, An image request signal is output after a predetermined time T1 from the output time of the detection signal, and the formation of the electrostatic latent image and the toner image are controlled based on the image request signal, and a predetermined time from the output time of the detection signal. After T2, without outputting the image request signal, The developing means The Positioned at the spaced position Do It is characterized by that.
[0008]
this According to the configuration, the developing solution in which the developing means is positioned at a predetermined developable position with respect to the latent image carrier that moves in the moving direction while carrying the electrostatic latent image on the surface, and the toner is dispersed in the liquid carrier. Is supplied from the developing means to the latent image carrier, and the electrostatic latent image is visualized to form a toner image. Intermediate transfer belt Transcribed above. here, Intermediate transfer belt Above, Predetermined size below A4 size Corresponding to the moving direction of the toner image rotation direction Round In 2 It is possible to carry it, and One round of the intermediate transfer belt In 1 When the toner image is carried, the developer is not brought into contact with the latent image carrier by separating the developing means from the latent image carrier corresponding to the non-carrying area where the toner image is not carried. Thereby, it is possible to prevent the liquid carrier from being wasted. Since no toner is required in the non-carrying area, the developer does not come into contact with the latent image carrier corresponding to the non-carrying area, and there is a problem even if the developer is not supplied to the latent image carrier. Never do.
[0009]
In order to achieve the above object, an image forming apparatus according to the present invention includes a latent image carrier configured to carry an electrostatic latent image on a surface thereof, and Exposure means for forming the electrostatic latent image on the latent image carrier; The developer in which the toner is dispersed in the liquid carrier 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 development position, thereby the latent image carrier. To supply A developer carrying member, a developable position where the developer on the developer carrier is brought into contact with the latent image carrier at the development position, and the developer on the developer carrier is the latent image carrier. It is configured to be movable between separated positions that do not touch A developer carrier and a toner in a developer supplied from the developer carrier to the latent image carrier are attached to the latent image carrier, and the electrostatic latent image is visualized to form a toner image. Image forming means, and a toner image formed on the latent image carrier can be carried on the surface thereof. The endless belt whose surface passes through a predetermined transfer position by rotating, and is configured to be able to carry two toner images of a predetermined size of A4 size or less side by side in the rotation direction. Department was provided An image carrier and a toner image formed on the latent image carrier Above Transfer means for transferring to the surface of the image carrier at a transfer position And a vertical synchronization sensor that outputs a detection signal when the passage of the protrusion is detected every round of the image carrier, and when the two toner images of the predetermined size are carried on the image carrier. Control means for outputting an image request signal after a predetermined time T1, T2 (T2> T1) from the output time point, and controlling the formation of the electrostatic latent image and the toner image based on each image request signal, The control means includes Around the image carrier by the transfer means The predetermined size Toner image 1 Transcribed Set When An image request signal is output after a predetermined time T1 from the output time of the detection signal, and the formation of the electrostatic latent image and the toner image are controlled based on the image request signal, and a predetermined time from the output time of the detection signal. After T2, without outputting the image request signal, The developer carrying member is retracted from the developable position to the separated position.
[0010]
According to this configuration, the developer carrying member is configured to be movable between the developable position and the separation position, and the developer carrying the toner dispersed in the liquid carrier is carried on the surface of the developer carrier and the latent image carrier. The toner is conveyed to an opposite development position, and is supplied to the latent image carrier by contacting the latent image carrier at the development position. The toner in the developer supplied from the developer carrier to the latent image carrier adheres to the latent image carrier, and the electrostatic latent image on the latent image carrier is visualized to form a toner image. The formed toner image is transferred to the surface of the image carrier at a predetermined transfer position. Here, the surface of the image carrier passes through the transfer position by rotating. Endless belt And around that Predetermined size below A4 size Side by side in the rotation direction 2 It is configured to be able to be carried, and it is placed around the image carrier by the transfer means. 1 When the toner image is transferred, the developer carrier is retracted from the developable position to the separated position while corresponding to the non-transfer area on the image carrier. This prevents the developer on the developer carrier from coming into contact with the latent image carrier, thereby preventing the liquid carrier from being wasted. Since no toner is required in the non-transfer area where the toner image is not transferred, the developer is supplied to the latent image carrier when the developer does not contact the latent image carrier during the non-transfer area. Even without it, it will not cause any trouble.
[0011]
Further, when a plurality of developing solutions containing different colors of toner are supplied to the latent image carrier as the developing solution to form a color toner image, the liquid carriers contained in the developing solutions are respectively It is possible to prevent wasteful consumption.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 is a diagram showing an internal configuration of a printer which is a first embodiment of an image forming apparatus according to the present invention, FIG. 2 is a block diagram showing an electrical configuration of the printer, and FIG. 3 is a development view of an intermediate transfer belt. . This printer is a wet development type image forming apparatus that forms a single color image using a developer containing black (K) toner, and a print command signal including an image signal is sent from an external device such as a host computer to the 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 it from the paper feed cassette 3 disposed in the lower part 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 “transfer paper”) 4.
[0013]
The engine unit 1 includes a photoreceptor unit 10, an exposure unit 20, a development unit 30, a transfer unit 40, and the like. Among these units, the photoreceptor unit 10 includes a photoreceptor 11, a charging unit 12, a charge removal 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 belt 41 and the like.
[0014]
In the photoconductor unit 10, the photoconductor 11 is provided so as to be rotatable in an arrow direction 15 in FIG. 1 (clockwise direction in the drawing). A charging unit 12, a developing roller 31, an intermediate transfer belt 41, a charge eliminating unit 13, and a cleaning unit 14 are disposed around the photoconductor 11 along the rotation direction 15. Further, 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 this 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). It has a function as a charging means.
[0015]
A light beam 21 formed by, for example, a laser is irradiated 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 photosensitive member 11 with a light beam 21 in accordance with a control command given from the exposure control unit 112, and forms an electrostatic latent image corresponding to an image signal on the photosensitive member 11. It has a function as an exposure means. For example, when a print command signal including an image signal is given 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 controls the exposure control unit in response to a command from the CPU 101 of the main control unit 100. A control signal corresponding to the image signal is output to 112 at a predetermined timing. Then, in response to a control command from the exposure control unit 112, the light beam 21 is irradiated from the exposure unit 20 to the photoconductor 11, and an electrostatic latent image corresponding to the image signal is formed on the photoconductor 11. Thus, in this embodiment, the photoconductor 11 corresponds to the “latent image carrier” of the present invention.
[0016]
The electrostatic latent image formed in this way 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, a coating roller 34 that pumps the developing solution 32 stored in the tank 33 and applies it to the developing roller 31, and the developing solution on the coating roller 34. A regulation blade 35 that uniformly regulates the thickness of the layer, a cleaning blade 36 that removes the developer remaining on the developing roller 31 after supplying the toner to the photosensitive member 11, and a memory 37 (FIG. 2) described later are provided.
[0017]
The developing roller 31 rotates at a circumferential speed substantially equal to that of the photoconductor 11 in the direction of following the photoconductor 11 (counterclockwise in FIG. 1). The application roller 34 rotates in the same direction as the developing roller 31 (counterclockwise in the figure) at a peripheral speed of about twice. The developing roller 31 is supported so as to be movable toward and away from the photoreceptor 11. That is, for example, when the actuator 39 (FIG. 2) composed of a solenoid or a motor is driven by the contact / separation drive unit 118 (FIG. 2), the contact position (solid line in FIG. 1) and the separation position (broken line in FIG. 1). Reciprocate between. The contact position is a developable position where the developer carried on the developing roller 31 can contact the photoconductor 11 and the toner can be supplied to the photoconductor 11, and the separation position is the developer where the developer is the photoconductor 11. It is the position which does not touch. The position control of the developing roller 31 will be described later.
[0018]
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, a dispersant that uniformly disperses the color pigment, and the like. Is dispersed in a liquid carrier. In this embodiment, for example, silicone oil such as polydimethylsiloxane oil is used as the liquid carrier, the toner concentration is 5 to 40% by weight, and the low-concentration developer (toner concentration is 1 to 2) often used in the wet development system. The concentration is higher than (% by weight). The type of the liquid carrier is not limited to silicone oil, and the viscosity of the developer 32 is determined by the liquid carrier to be used, each material constituting the toner, the toner concentration, etc. In this embodiment, For example, the viscosity is 50 to 6000 mPa · s.
[0019]
In this embodiment, the interval between the photosensitive member 11 and the developing roller 31 (developing gap = thickness of the developing solution layer) is set to 5 to 40 μm, for example, and the developing nip distance (the developing solution layer is the photosensitive member 11 and the developing roller 31). In this embodiment, the distance in the circumferential direction in contact with both is set to 5 mm, for example. 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, and in this embodiment using a high-concentration developer, the development gap can be shortened. Accordingly, the moving distance of the toner moving in the developer by electrophoresis 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 can be performed at a high speed. It will be possible.
[0020]
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 regulation 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 photosensitive member 11 as the developing roller 31 rotates. For example, the toner in the developer is positively charged by the action of a charge control agent or the like.
[0021]
Then, a developing solution carried on the developing roller 31 at the developing position 16 is supplied from the developing roller 31 and adheres to the photosensitive member 11, and a developing bias Vb (for example, Vb) applied to the developing roller 31 from the developing bias generator 114. = DC + 400V), the toner moves in the developing solution from the developing roller 31 to the photoconductor 11, and the electrostatic latent image is visualized. Further, the developer remaining on the developing roller 31 without adhering to the photoconductor 11 is scraped off by the cleaning blade 36 and returns to the tank 33 by its own weight. Thus, in this embodiment, the developing roller 31 corresponds to the “developer carrier” of the present invention, and the developing bias generator 114 corresponds to the “image forming unit” of the present invention.
[0022]
The toner image formed on the photoconductor 11 as described above is conveyed to a primary transfer position 44 facing the intermediate transfer belt 41 as the photoconductor 11 rotates. The intermediate transfer belt 41 is stretched around tension rollers 41A and 41B, a driving roller 41C, and a driven roller 41D. The drive roller 41C is rotationally driven together with the photoconductor 11 by a photoconductor drive motor (not shown). The intermediate transfer belt 41 rotates at a circumferential speed substantially equal to that of the photoconductor 11 in the direction of following the photoconductor 11 (arrow 52 in FIG. 1), and the primary transfer bias (for example, DC-400V) from the transfer bias generator 115. Is applied, the toner image on the photoreceptor 11 is primarily transferred to the intermediate transfer belt 41. Residual charges on the photoconductor 11 after the primary transfer are removed by a charge removal unit 13 made of an LED or the like, and a residual developer is removed by a cleaning unit 14.
[0023]
As shown in FIG. 3, the intermediate transfer belt 41 is an endless belt formed by joining substantially rectangular sheet bodies at a seam 51. In FIG. 3, an arrow 52 indicates the rotational drive direction, and an arrow 53 indicates the rotational axis direction. The intermediate transfer belt 41 has a protrusion 54 provided on one end side (the upper side in FIG. 3) in the rotation axis direction 53, and also includes a transfer prohibition area 55 and a transfer permission area 56. The transfer prohibition area 55 is set from one end to the other end in the rotation axis direction 53 within a predetermined size range on both sides of the joint 51. The transfer permission area 56 is an area other than the transfer prohibition area 55, and is set to a rectangular area excluding one end and the other end in the rotation axis direction 53, and the toner image is primary in the transfer permission area 56. Transcribed.
[0024]
As shown in FIG. 3A, an A3 size toner image 57 having a long side direction in the rotational drive direction 52 can be transferred to the transfer permission area 56. Further, as shown in FIG. 3B, the transfer permission area 56 is divided into two sub areas 56A and 56B, and is equal to or smaller than A4 size, which is a short side direction in the rotation driving direction 52 around the intermediate transfer belt 41. Two toner images (for example, A4 and B5 sizes) can be primarily transferred. In the following, image formation control in which two toner images are primarily transferred around the intermediate transfer belt 41 is referred to as “two-sheet pickup control”. FIG. 3B shows an A4 size toner image 58.
[0025]
The vertical synchronization sensor 46 is composed of, for example, a photo interrupter having a light emitting unit (for example, LED) and a light receiving unit (for example, a photodiode) disposed to face each other, and is disposed on one end side in the rotation axis direction 53 of the rotating intermediate transfer belt 41. The detection signal is output by detecting the passage of the protrusion 54. The detection signal output from the vertical synchronization sensor 46 is used as a vertical synchronization signal Vsync that serves as a reference for image formation control by the engine control unit 110.
[0026]
A secondary transfer roller 42 is disposed opposite to an appropriate position of the intermediate transfer belt 41 (vertically below the driven roller 41C in FIG. 1), and the primary transfer toner image primarily transferred to the intermediate transfer belt 41 is the intermediate transfer belt 41. Is conveyed to a secondary transfer position 45 that faces the secondary transfer roller 42 as the rotation of. On the other hand, the transfer paper 4 accommodated in the paper feed cassette 3 is conveyed to the secondary transfer position 45 by a conveyance drive unit (not shown) in synchronization with the conveyance of the primary transfer toner image. The secondary transfer roller 42 rotates at a peripheral speed equal to that of the intermediate transfer belt 41 in the direction of following the intermediate transfer belt 41 (clockwise in FIG. 1), and the secondary transfer bias ( For example, when −100 μA) is applied under constant current control, the toner image on the intermediate transfer belt 41 is secondarily transferred to the transfer paper 4. The residual developer on the intermediate transfer belt 41 after the secondary transfer is removed by the cleaning unit 43.
[0027]
The transfer paper 4 onto which the toner image has been secondarily transferred in this manner is conveyed along a predetermined transfer paper conveyance path 5 (indicated by the one-dot chain line in FIG. 1), and the toner image is fixed by the fixing unit 6. It is discharged to the discharge tray provided in the. Further, an operation display panel 7 including a liquid crystal display and a touch panel, for example, is disposed on the upper surface of the apparatus main body 2, and accepts operation instructions from the user and displays predetermined information to notify the user. Thus, in this embodiment, the intermediate transfer belt 41 corresponds to the “image carrier” of the present invention, and the transfer bias generator 115 corresponds to the “transfer means” of the present invention.
[0028]
In FIG. 2, the main control unit 100 includes an image memory 103 for storing an image signal given from an external device via an interface 102, and the CPU 101 receives a print command signal including the image signal from the external device. When it is received via the interface 102, it is converted into job data in a format suitable for the operation instruction of the engine unit 1 and sent to the engine control unit 110.
[0029]
The memory 116 of the engine control unit 110 includes a ROM that stores a control program for the CPU 113 including preset fixed data, a RAM that temporarily stores control data for the engine unit 1, calculation results by the CPU 113, and the like. The CPU 113 stores data relating to the image signal sent from the external device via the CPU 101 in the memory 116.
[0030]
The memory 37 of the developing unit 30 stores data relating to the manufacturing lot, usage history, built-in toner characteristics, remaining amount of the developer 32, toner density, and the like. The memory 37 is electrically connected to the communication unit 38, and the communication unit 38 is attached to the tank 33, for example. When the developing unit 30 is attached to the apparatus main body 2, the communication unit 38 is arranged to face 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 information such as consumables management related to the developing unit 30.
[0031]
In this embodiment, data transmission / reception is performed in a non-contact manner using electromagnetic means such as wireless communication. For example, a connector is provided in each of the apparatus main body 2 and the developing unit 30, and the apparatus main body 2 is provided with a connector. When the developing unit 30 is mounted, data transmission and reception may be performed by mechanically fitting both connectors. The memory 37 is preferably a non-volatile memory that can store the data even when the power is off or the developing unit 30 is detached from the apparatus main body 2. Examples of the non-volatile memory include a flash memory. EEPROM, ferroelectric memory, or the like can be used.
[0032]
FIG. 4 is a diagram for explaining the movement of the liquid carrier between two rollers (here, the photosensitive member 11 and the developing roller 31). The developer layer in the region A remains in a state where the developer 32 is applied to the developer roller 31 by the application roller 34. That is, the developer 32 in the region A is in a state where the toner 322 is dispersed in the liquid carrier 321. The developer layer in the region B is in a state where the developer 32 on the developing roller 31 is in contact with the photoconductor 11 and is nipped between the rollers 31. Then, the developer layer nipped between the rollers 31 and 11 in the region B is separated as the rollers 31 and 11 rotate, and the developer layer in the region C on the photoconductor 11 side and the developer roller 31 side are separated. The developer layer in region D is formed.
[0033]
In region B, if a bias voltage is applied so that the positively charged toner moves from the photoconductor 11 toward the developing roller 31, the toner density at the portion in contact with the developing roller 31 is the highest, and as the distance from the developing roller 31 increases. The toner density gradually decreases, and a layer of the liquid carrier 321 that does not contain toner can be formed in the portion in contact with the photoreceptor 11. Since the layer of the liquid carrier 321 not containing toner has the lowest viscosity, the developer 32 is considered to be separated by the layer of the liquid carrier 321. Therefore, the liquid carrier 321 moves to the photoconductor 11 to form a region C including only the liquid carrier 321, while a region D in which the developer 32 including the toner 322 is carried on the developing roller 31 is formed.
[0034]
As described above, when the developing roller 31 is disposed at the contact position, although the movement of the toner 322 to the photosensitive member 11 can be prevented by application of a bias voltage, the developing solution 32 carried on the developing roller 31. The liquid carrier 321 on the surface layer is inevitably moved to the photoconductor 11, and the liquid carrier 321 is consumed. Therefore, in this embodiment, the developing roller 31 is retracted to the separation position at a timing when the developing solution 32 is unnecessary, thereby preventing the liquid carrier 321 from being wasted.
[0035]
FIG. 5 is a timing chart showing an example of an operation sequence of each part of the engine unit 1. Here, it is assumed that a print command signal for forming three images by the two-sheet taking control is given. When a print command signal including an image signal is given to the main control unit 100 from an external device such as a host computer, the engine control unit 110 starts operation of each unit of the engine unit 1 in response to the control signal from the main control unit 100. To do.
[0036]
That is, the intermediate transfer belt 41 rotates at a predetermined peripheral speed, and the vertical synchronization signal Vsync is periodically output. The first image request signal Vreq is output after a predetermined time T1 from the falling time t1 of the vertical synchronization signal Vsync, and the first image signal VK1 is output in synchronization with the falling of the image request signal Vreq. The formation of the electrostatic latent image is started, and the second image request signal Vreq is output after a predetermined time T2 (> T1) from the falling time t1 of the vertical synchronization signal Vsync, and is synchronized with the falling of the image request signal Vreq. Then, the second image signal VK2 is output and the formation of the electrostatic latent image is started.
[0037]
The developing bias is turned on after a predetermined time T3 and T4 from time t1, and further turned off after a predetermined time determined in advance by the transfer paper size. As a result, the toner image TK1 is primarily transferred to the sub area 56A downstream of the rotation driving direction 52 in the transfer permission area 56 of the intermediate transfer belt 41, and the toner image TK2 is transferred to the transfer permission area of the intermediate transfer belt 41. 56, primary transfer is performed on the sub-region 56B on the upstream side in the rotational drive direction 52.
[0038]
On the other hand, the transfer paper 4 is fed from the paper feed cassette 3 toward the secondary transfer position 45 in synchronism with the primary transfer, and the secondary transfer roller after a predetermined time from the falling point t1 of the vertical synchronization signal Vsync. Application of the secondary transfer bias to 42 is turned on. As a result, the toner image TK1 that is primarily transferred to the sub-area 56A that is downstream of the rotation driving direction 52 in the transfer permission area 56 of the intermediate transfer belt 41 is secondarily transferred to the first transfer paper 4. . Further, the next transfer paper 4 is conveyed from the paper feed cassette 3 in time with the next toner image TK2, and the application of the secondary transfer bias is turned on after a predetermined time from the time t1. As a result, the toner image TK <b> 2 that is primarily transferred to the sub area 56 </ b> B upstream of the rotation drive direction 52 in the transfer permission area 56 of the intermediate transfer belt 41 is transferred to the second transfer paper 4. Thus, the two image formations are completed.
[0039]
Then, in synchronism with the falling time t2 of the next vertical synchronizing signal Vsync, the first (third in total) image formation is performed in the same manner as described above. That is, the image request signal Vreq is output after a predetermined time T1 from the time t2, and the image signal VK3 is output in synchronization with the fall of the image request signal Vreq. Further, from time t2, the developing bias is turned on after a predetermined time T3, and is kept on for a time determined by the transfer paper size to form the first toner image TK3. Thereafter, the developing bias is turned off. Is done.
[0040]
Since the formation of the three images by the print command signal is completed, the image request signal Vreq for the second sheet is not output after the predetermined time T2 from the falling time t2 of the vertical synchronization signal Vsync. Therefore, the actuator 39 is driven at time t3 after the developing bias for forming the toner image TK3 is turned off (for example, after a predetermined time T2 from the falling time t2 of the vertical synchronization signal Vsync), and the developing roller 31 is moved. Retreat from the contact position to the separated position.
[0041]
FIG. 6 is a flowchart showing an example of the position control routine of the developing roller. A developing roller position control program is stored in the memory 116 of the engine control unit 110 in advance. The CPU 113 controls each part of the apparatus according to the program, whereby the following position control is executed.
[0042]
First, it is determined whether or not the print command signal received from the external device via the main control unit 100 (CPU 101) is the two-shot control (# 10), and if the two-shot control is used (YES in # 10). ), It is determined whether the number is an odd number (# 12). If the two-sheet pickup control is not performed (NO in # 10) or if it is not an odd number (NO in # 12), this routine is terminated. On the other hand, if it is an odd number (YES in # 12), the process waits until the first sheet on the final circumference of the intermediate transfer belt 41 is completed (NO in # 14), and the development of the first sheet on the final circumference is completed ( (Yes in # 14), the actuator 39 is driven to move the developing roller 31 and retract to the separated position (# 16), and this routine is finished.
[0043]
By executing the position control routine shown in FIG. 6, the sequence of the movement operation of the developing roller 31 shown in FIG. 5 is realized. Note that after the developing roller 31 is arranged at the separated position, the developing roller 31 may be kept waiting at the separated position until the next print command signal is input.
[0044]
As described above, according to the first embodiment, the developing roller 31 is configured to be movable between the contact position and the separation position, and the position control of the developing roller 31 is controlled according to the form of the toner image to be formed. Like to do. That is, as a form of the toner image to be formed, when the second sheet is not formed in the two-sheet taking control, the developing roller 31 is separated while corresponding to the second sheet (non-transfer area where the toner image is not transferred). Evacuated to position. As a result, it is possible to prevent the liquid carrier 321 from being wasted.
[0045]
(Second Embodiment)
FIG. 7 is a diagram showing an internal configuration of a printer which is the second embodiment of the image forming apparatus according to the present invention. The second embodiment differs greatly from the first embodiment in that there is a developing unit for each color of black (K), cyan (C), magenta (M), and yellow (Y) in order to form a color image. The other configurations are basically the same as those of the first embodiment. Accordingly, the same components are denoted by the same reference numerals and description thereof is omitted here.
[0046]
In the second embodiment, developing units 30K, 30C, 30M, and 30Y are provided corresponding to the respective toner colors. These developing units 30K, 30C, 30M, and 30Y are configured to be independently movable between a contact position and a separated position by an actuator 39 (FIG. 2). Here, the contact position is a developable position where the developer on the developing rollers 31K, 31C, 31M, and 31Y of the developing units 30K, 30C, 30M, and 30Y contacts the photoconductor 11, and the separated position is the developer. Is a position that does not come into contact with the photoreceptor 11.
[0047]
For the yellow color, for example, an electrostatic latent image corresponding to the yellow color is formed on the photoconductor 11 based on the job data from the main control unit 100, and the developing unit 30Y is selectively arranged at the contact position to be photosensitive. After the developer is supplied to the body 11 to develop the electrostatic latent image to form a toner image, the toner image is primarily transferred to the surface of the intermediate transfer belt 41 at the primary transfer position 44 to be the primary transfer toner. Get a statue. The same applies to other toner colors.
[0048]
In the printer configured as described above, a toner image is formed for each color of black (K), cyan (C), magenta (M), and yellow (Y), and the toner image is transferred to the surface of the intermediate transfer belt 41. A full-color primary transfer toner image is formed by superimposing the above. Then, when the four color toner images are superimposed, the secondary transfer roller 42 moves from the separation position (broken line in FIG. 7) to the transferable position (solid line in FIG. 7). The primary transfer toner image is conveyed to the secondary transfer position 45, while the transfer paper 4 in the paper feed cassette 3 is conveyed to the secondary transfer position 45 in synchronization with the running operation of the intermediate transfer belt 41. As in the first embodiment, the primary transfer toner image is secondarily transferred to the transfer paper 4. As described above, in the second embodiment, the developing units 30K, 30C, 30M, and 30Y correspond to “developing means” of the present invention, and the developing rollers 31K, 31C, 31M, and 31Y respectively correspond to “ It corresponds to a “developer carrier”.
[0049]
FIG. 8 is a timing chart showing the operation sequence of the second embodiment. Also here, as in the first embodiment, it is assumed that a print command signal for forming three images by two-sheet taking control is given. The operation of each unit of the engine unit 1 has already started by time t1 in FIG. 8, and yellow (Y), magenta (M), cyan (C) corresponding to the first image on the intermediate transfer belt 41. The first toner image is superimposed, and the second toner image of yellow (Y), magenta (M), and cyan (C) corresponding to the second image is superimposed.
[0050]
Then, the first image request signal Vreq is output after a predetermined time T1 from the falling time t1 of the vertical synchronization signal Vsync, and the black (K) of the first sheet K is synchronized with the falling of the image request signal Vreq. The image signal VK1 is output and the formation of the electrostatic latent image is started. The second black (K) image request signal Vreq is output after a predetermined time T2 (> T1) from the falling point t1 of the vertical synchronization signal Vsync, and in synchronization with the falling of the image request signal Vreq, The second image signal VK2 is output and formation of the electrostatic latent image is started. Further, the developing bias for the first sheet is turned on after a predetermined time T3 from the time t1, and is turned off after a predetermined time determined in advance by the transfer paper size. Further, the developing bias for the second sheet is turned on after a predetermined time T4 from the time t1, and turned off after the predetermined time. Thus, the toner images TK1 and TK2 are further superimposed to form a full-color primary transfer toner image.
[0051]
On the other hand, the transfer paper 4 is transported from the paper feed cassette 3 toward the secondary transfer position 45 in synchronization with the primary transfer of the toner image TK1, and the secondary paper is secondary after a predetermined time from the falling time t1 of the vertical synchronization signal Vsync. Application of the secondary transfer bias to the transfer roller 42 is turned on. As a result, the color toner image that has been primarily transferred to the sub area 56 </ b> A downstream of the rotation driving direction 52 in the transfer permission area 56 of the intermediate transfer belt 41 is secondarily transferred to the first transfer sheet 4. . Further, the next transfer paper 4 is conveyed from the paper feed cassette 3 in time with the next toner image TK2, and the application of the secondary transfer bias is turned on after a predetermined time from the time t1. As a result, the color toner image that has been primarily transferred to the sub area 56 </ b> B that is upstream of the rotation driving direction 52 in the transfer permission area 56 of the intermediate transfer belt 41 is transferred to the second transfer sheet 4.
[0052]
At this time, the developing unit 30K moves from the separated position to the contact position after a predetermined time T5 from the time t1, and retracts to the separated position after the corresponding predetermined time T6 after the application of the developing bias.
[0053]
Then, the first toner image TY3 (corresponding to the third image) is formed in the same manner as described above in synchronization with the falling time t2 of the next vertical synchronization signal Vsync. That is, the image request signal Vreq is output after a predetermined time T1 from the time t2, and the image signal VY3 is output in synchronization with the fall of the image request signal Vreq. Further, from time t2, the developing bias is turned on after a predetermined time T3, and is kept on for a time determined by the transfer paper size to form the first toner image TY3. Thereafter, the developing bias is turned off. Is done. Since the formation of the three images by the print command signal is completed, the image request signal Vreq for the second sheet is not output after the predetermined time T2 from the falling time t2 of the vertical synchronization signal Vsync.
[0054]
At this time, the developing unit 30Y moves from the separation position to the contact position after a predetermined time T5 from time t1 and develops the first sheet and does not develop the second sheet. After a predetermined time T7 (<T6), the evacuation position is retracted.
[0055]
Thereafter, similarly, the first toner images TM3, TC3, and TK3 are formed. That is, the image request signal Vreq is output after a predetermined time T1 from the times t3, t4, t5, and the image signals VM3, VC3, VK3 are output in synchronization with the fall of the image request signal Vreq. Further, from time t3, t4, t5, the developing bias is turned on after a predetermined time T3, and is kept on for a time determined by the transfer paper size, so that the first toner images TM3, TC3, TK3 are formed. Thereafter, the developing bias is turned off.
[0056]
At this time, the developing units 30M, 30C, and 30K move from the separation position to the contact position after a predetermined time T5 from the times t3, t4, and t5, respectively, to perform the first development, and the second development is performed, respectively. Therefore, after the application of the developing bias, the sheet is retracted to the separated position after a predetermined time T7.
[0057]
As described above, according to the second embodiment, the development units 30Y, 30M, 30C, and 30K are configured to be movable between the contact position and the separation position, and development is performed according to the form of the toner image to be formed. Position control of the units 30Y, 30M, 30C, and 30K is performed. That is, when the second image is not formed in the two-sheet taking control as the form of the toner image to be formed, the developing units 30Y, 30M, 30C, and 30K are retracted to the separated positions while corresponding to the second sheet. ing. As a result, as in the first embodiment, it is possible to prevent the liquid carrier 321 from being consumed wastefully.
[0058]
The present invention is not limited to the above embodiment, and various modifications can be made to the above without departing from the spirit thereof. For example, in the above embodiment, the intermediate transfer belt 41 is applicable. Can transfer two images in one round, but is not limited thereto. For example, when n (n is an integer greater than or equal to 3) sheets of the intermediate transfer belt can be made in one rotation, when transferring less than n images in the final rotation, the non-transfer from the end of the transfer to the end of the final rotation It is only necessary to retract the developing roller 31 to the separation position while it corresponds to the image transfer area.
[0059]
In the first embodiment, only the developing roller 31 is configured to be movable. However, the present invention is not limited to this. By configuring the entire developing unit 30 to be movable, the developing roller 31 is separated from the contact position. It may be movable between positions. In this embodiment, the developing unit 30 corresponds to the “developing unit” of the present invention. In the second embodiment, the entire developing units 30Y, 30M, 30C, and 30K are configured to be movable. However, the present invention is not limited to this, and only the developing rollers 31Y, 31M, 31C, and 31K are in contact positions. And may be configured to be movable between the separated positions.
[0060]
Furthermore, in the above-described embodiment, the description has been given using a printer that prints an image provided from an external device such as a host computer on transfer paper. 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.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an internal configuration of a printer according to a first embodiment of the invention.
FIG. 2 is a block diagram showing an electrical configuration of the printer.
FIG. 3 is a development view of an intermediate transfer belt.
FIG. 4 is a diagram illustrating movement of a liquid carrier between two rollers.
FIG. 5 is a timing chart showing an example of an operation sequence.
FIG. 6 is a flowchart showing an example of a position control routine.
FIG. 7 is a diagram illustrating an internal configuration of a printer according to a second embodiment of the invention.
FIG. 8 is a timing chart showing an operation sequence of the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Photosensitive body (latent image carrier), 30, 30Y, 30M, 30C, 30K ... Developing unit (developing means) 31, 31Y, 31M, 31C, 31K ... Developing roller (developer carrier), 41 ... Intermediate Transfer belt (image carrier), 113... CPU, 114... Development bias generator (image forming means), 115 .. transfer bias generator (transfer means)

Claims (3)

A latent image carrier that moves in the moving direction while carrying an electrostatic latent image on its surface ;
Exposure means for forming the electrostatic latent image on the latent image carrier;
By positioning the developable position Jo Tokoro with respect to the latent image bearing member, a developing solution obtained by dispersing toner in a liquid carrier is supplied before Kisenzo carrier and visualizes the electrostatic latent image Developing means that forms a toner image and is movable between the developable position and a separated position that is separated from the latent image carrier and is not in contact with the developer.
Predetermined rotated at a peripheral speed, has a two supportable toner images of a predetermined size or less A4 size around the rotational direction corresponding to the direction of movement, the intermediate transfer belt protruding part is disposed in a predetermined position When,
Transfer means for transferring the toner image formed on the latent image carrier to the intermediate transfer belt ;
A vertical synchronization sensor that outputs a detection signal when the passage of the protrusion is detected every round of the intermediate transfer belt;
When two toner images of the predetermined size are carried around the intermediate transfer belt, the image request signals are output after a predetermined time T1, T2 (T2> T1) from the time when the detection signal is output. Control means for controlling the formation of the electrostatic latent image and the toner image based on
The control means, the toner image of the to one round of the intermediate transfer belt prescribed size when to one carrier, the output image request signal from the output time point of the detection signal after the predetermined time T1, the basis of this image request signal to control the formation and the formation of the toner image of the electrostatic latent image, wherein after a predetermined time from the output time point of a detected signal T2, without outputting the image request signal, positioning the developing means to the separated position An image forming apparatus. A latent image carrier configured to carry an electrostatic latent image on its surface;
Exposure means for forming the electrostatic latent image on the latent image carrier;
The developer in which the toner is dispersed in the liquid carrier 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 development position, thereby the latent image carrier. A developer carrying member to be supplied to the developer carrying position at which the developer on the developer carrier is brought into contact with the latent image carrier at the development position, and the developer on the developer carrier A developer carrier configured to be movable between a separated position that does not contact the image carrier; and
Image forming means for attaching a toner in a developer supplied from the developer carrier to the latent image carrier to the latent image carrier and developing the electrostatic latent image to form a toner image;
The toner image formed on the latent image carrier is configured to be able to carry on the surface thereof, and is composed of an endless belt whose surface passes a predetermined transfer position by rotating, and has a predetermined size of A4 size or less around its circumference. An image bearing member configured to be able to carry two toner images side by side in the rotation direction and provided with a protrusion at a predetermined position ;
A transfer unit that transfers to the surface of the image bearing member a toner image formed on the latent image bearing member at the transfer position,
A vertical synchronization sensor that outputs a detection signal when the passage of the protrusion is detected every round of the image carrier;
When carrying two toner images of the predetermined size on the image carrier, an image request signal is output after a predetermined time T1, T2 (T2> T1) from the detection signal output time point, and based on each image request signal. Control means for controlling the formation of the electrostatic latent image and the toner image,
It said control means Rutoki the toner image is one transfer of the predetermined size around the image bearing member by said transfer means outputs the image request signal from the output time point of the detection signal after a predetermined time T1, The formation of the electrostatic latent image and the formation of the toner image are controlled based on the image request signal, and after the predetermined time T2 from the output time of the detection signal, the developer carrying is carried out without outputting the image request signal. An image forming apparatus, wherein the body is retracted from the developable position to the separated position.   3. The image forming apparatus according to claim 1, wherein a plurality of developing solutions containing different colors of toner are supplied to the latent image carrier as the developing solution to form a color toner image.

Images