JP2005250192A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To bring an image forming apparatus into a specific color printable condition in a short period of time, the image forming apparatus having a development unit to which a plurality of cartridges having toner of specific color can be attached. <P>SOLUTION: Among the plurality of development cartridges attached to the development unit prior to a printing operation, a printing preparing operation is performed only for the development cartridge 4Ka, thereby bringing the apparatus into a printable condition. Therefore, when the printing preparing operation finishes for the one (priority cartridge) of the development cartridges attached to the development unit, the printing preparing operation is completed. Accordingly, since the apparatus is brought into the printable condition in a short period of time, a user does not need to wait for the printing preparing operation for a time longer than necessary. This shortens the time needed for the user to wait. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus and an image forming method in which one of cartridges mounted in a developing unit is positioned at a developing position and a printing operation of a specific color is performed using toner in the cartridge. Is.

  Conventionally, an image forming apparatus that forms an image using a plurality of developing cartridges is widely known. For example, Patent Document 1 describes a color image forming apparatus including a rotary developing unit in which four developing cartridges are arranged radially around a rotation axis. In this apparatus, one of the four developing cartridges is selectively positioned to face a latent image carrier such as a photosensitive member by rotationally driving the rotating shaft thereof, thereby latent images on the latent image carrier. Is developed and transferred onto an intermediate transfer medium. Then, while switching the developing cartridge, the development and transfer processes are repeated in the same manner as described above, thereby superimposing a plurality of color toner images to form a color image.

  In the color image forming apparatus described above, toners of different colors (yellow, cyan, magenta, and black) are accommodated in the four developing cartridges in order to execute a color image printing operation. For this reason, when a monochrome image is printed using the image forming apparatus, there is a problem that the timing of shortage of black toner is earlier than when a monochrome image is printed by a monochrome-only image forming apparatus. Therefore, in order to solve such a problem, the black developing cartridge is mounted at the position where the developing cartridge for yellow, cyan and / or magenta is installed, and the black toner in the one black developing cartridge is removed. An apparatus that switches to another black developing cartridge when it runs out and executes a monochrome printing operation has been proposed (see, for example, Patent Document 2).

Japanese Patent Laying-Open No. 2003-215862 (5th page, FIG. 1) JP 2002-351190 A (5th and 6th pages, FIG. 4)

  By the way, in order to print an image satisfactorily using the toner in the developing cartridge, it is necessary to perform a print preparation operation on the cartridge in advance. Optimization processing (patch processing) is executed as a typical print preparation operation. For example, in the apparatus described in Patent Document 1, optimization (patch) processing (patch condition of the present invention) is performed at an appropriate timing before the printing operation, for example, immediately after the apparatus is turned on, or after the apparatus is warmed up. Equivalent to “control process”). In this optimization processing, the optimum values of the development bias and exposure power as density control factors that affect the image quality are calculated based on the density detection result of the solid image or halftone image formed as a patch image. Then, when executing the printing operation, the developing bias and the exposure power are set to the optimum values thus obtained. As a result, optimum printing operation conditions can be obtained. Then, by executing the printing operation under the printing operation conditions optimized in this way, an image can be formed with good and stable image quality. Thus, in view of the importance of the print preparation operation, various proposals have been made for the print preparation operation in the color image forming apparatus.

  On the other hand, in the apparatus described in Patent Document 2, that is, an apparatus in which a plurality of developing cartridges that contain black toner are mounted, a printing preparation operation that is important for executing a good printing operation is not sufficiently considered. For example, as an optimization process for a cartridge mounted on the developing unit, it is conceivable to apply the optimization process described in Patent Document 1 as it is. In other words, the optimization process is performed on the cartridge positioned at the developing position while sequentially switching the cartridge mounted on the developing unit to the developing position. For this reason, for example, when all black developing cartridges are installed instead of yellow, cyan, and magenta developing cartridges, the optimization process is repeated four times before the printing operation. In other words, the printing operation can be executed if the printing preparation operation is completed for one of the developing cartridges installed in the developing unit, but the optimization processing for all the developing cartridges must be completed. In this case, the printing operation cannot be executed. As a result, there is a problem that the user has to wait for a long time until the apparatus is ready for printing.

  The present invention has been made in view of the above problems, and an image forming apparatus having a developing unit in which a plurality of cartridges having toner of a specific color can be mounted enables the specific color to be printed in a short time. Objective.

  In order to achieve the above object, an image forming apparatus according to the present invention has a latent image carrier capable of carrying an electrostatic latent image, a developing unit detachably provided with a plurality of cartridges having toner of a specific color, Control means for selectively positioning a cartridge mounted on the developing unit at a developing position and executing a printing operation for developing an electrostatic latent image on the latent image carrier using toner in the cartridge; And the control means sets one of the cartridges mounted on the developing unit as a priority cartridge, and performs the printing on the cartridge before executing the printing operation in order to enable the printing operation by the cartridge. The print preparation operation is performed only for the priority cartridge.

  The image forming method according to the present invention includes: a latent image carrier capable of carrying an electrostatic latent image; and a developing unit in which a plurality of cartridges having a specific color toner are detachably provided. In the image forming method for selectively performing positioning of the cartridge mounted on the cartridge at a developing position and developing the electrostatic latent image on the latent image carrier using the toner in the cartridge, the printing Prior to execution of the operation, one of the cartridges mounted on the developing unit is set as a priority cartridge, and a print preparation operation performed on the cartridge in order to enable printing operation by the cartridge is performed. It is characterized only by

  In order to develop an electrostatic latent image using toner stored in a cartridge, that is, to execute a printing operation, it is necessary to execute a printing preparation operation on the cartridge prior to the printing operation. Therefore, in the present invention, one of the cartridges mounted on the developing unit prior to execution of the printing operation is set as the priority cartridge, and the print preparation operation is performed only for the priority cartridge. In the invention configured as described above, the print preparation is completed when the print preparation operation of one of the cartridges attached to the developing unit is completed. Therefore, since the specific color can be printed in a short time, the waiting time of the user can be shortened.

Here, the “print preparation operation” includes all operations that need to be performed on the cartridge prior to the printing operation in order to enable the printing operation by the cartridge. Specifically, the following operations and processes are included:
(1) Installation confirmation operation for confirming cartridge installation in the development unit;
(2) Conformity confirmation operation for confirming that the cartridge mounted on the developing unit is a cartridge having toner of a specific color;
(3) Life confirmation operation for confirming that the amount of toner necessary for executing the printing operation remains in the cartridge mounted on the developing unit;
(4) Stirring treatment for rotating the toner carrier at least one turn;
(5) Condition control processing for adjusting the printing operation condition when executing the printing operation by the cartridge to a predetermined optimum condition;
Each of these operations and processes, or a combination thereof, is a “print preparation operation”, but the content itself can be appropriate depending on the configuration of the apparatus and the operation status.

  Further, it is desirable that M (M ≧ 2) cartridges are mounted on the developing unit. In the invention configured as described above, even if the remaining amount of toner in one cartridge decreases and the printing operation cannot be performed, the printing operation can be continued by switching to the next cartridge.

  Here, an embodiment in which the present invention is embodied in an image forming apparatus (color printer) described in Patent Document 1 will be described with reference to the drawings. In other words, in this embodiment, a description will be given by specifically embodying printing with monochrome toner using black toner accommodated in four developing cartridges, that is, monochrome printing.

  FIG. 1 is a view showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. The apparatus 1 is an image forming apparatus that forms a monochrome image using only black (K) toner. In the image forming apparatus 1, when an image signal is given to the main controller 11 from an external device such as a host computer, the engine controller 10 controls each part of the engine unit EG in accordance with a command from the main controller 11 to obtain a predetermined image. A forming operation is executed, and a monochrome image corresponding to the image signal is formed on the sheet S.

  In the engine unit EG, the photosensitive member 22 is provided to be rotatable in the arrow direction D1 in FIG. A charging unit 23, a rotary developing unit 4 and a cleaning unit 25 are arranged around the photosensitive member 22 along the rotation direction D1. The charging unit 23 is applied with a predetermined charging bias, and uniformly charges the outer peripheral surface of the photoconductor 22 to a predetermined surface potential. The cleaning unit 25 removes toner remaining on the surface of the photoconductor 22 after primary transfer, which will be described later, and collects it in a waste toner tank provided inside. The photosensitive member 22, the charging unit 23, and the cleaning unit 25 integrally constitute the photosensitive member cartridge 2, and this photosensitive member cartridge 2 is detachably attached to the main body of the apparatus 1 as a whole.

  Then, the light beam L is irradiated from the exposure unit 6 toward the outer peripheral surface of the photosensitive member 22 charged by the charging unit 23. The exposure unit 6 exposes the light beam L onto the photosensitive member 22 in accordance with an image signal given from an external device, and forms an electrostatic latent image corresponding to the image signal. Thus, in this embodiment, the photoconductor 22 corresponds to the “latent image carrier” of the present invention.

  The electrostatic latent image thus formed is developed with toner by the developing unit 4. The developing unit 4 is configured as a support frame 40 that is rotatably provided around a rotation axis that is orthogonal to the paper surface of FIG. 1, and is configured as a cartridge that is detachable with respect to the support frame 40, and includes four developing cartridges 4Ka that contain black toner. To 4 kd, and a rotary drive (not shown) for rotating them integrally. The developing unit 4 is controlled by the engine controller 10. Based on a control command from the engine controller 10, the developing unit 4 is driven to rotate, and the developing cartridges 4Ka to 4Kd selectively abut against the photosensitive member 22 or face each other with a predetermined gap therebetween. When positioned at a predetermined developing position, toner is applied to the surface of the photosensitive member 22 from the developing roller 44 provided in the developing cartridge. As a result, the electrostatic latent image on the photosensitive member 22 is developed with the toner in the selected developing cartridge (printing operation). The visualization of the electrostatic latent image by the developing cartridge positioned at the developing position in this way corresponds to the “printing operation by the cartridge” of the present invention.

  The toner image developed by the developing unit 4 as described above is primarily transferred onto the intermediate transfer belt 71 of the transfer unit 7 in the primary transfer region TR1. The transfer unit 7 includes an intermediate transfer belt 71 that is stretched over a plurality of rollers 72 to 75, and a drive unit that rotates the roller 73 to rotate the intermediate transfer belt 71 in a predetermined rotation direction D2. Yes. The transfer unit 7 transfers the black toner image formed on the photosensitive member 22 onto the intermediate transfer belt 71 to form a monochrome image, and is taken out from the cassette 8 one by one along the conveyance path F. The monochrome image is secondarily transferred onto the sheet S conveyed to the secondary transfer region TR2.

  At this time, in order to correctly transfer the image on the intermediate transfer belt 71 to a predetermined position on the sheet S, the timing of feeding the sheet S to the secondary transfer region TR2 is managed. Specifically, a gate roller 81 is provided on the transport path F on the front side of the secondary transfer region TR2, and the gate roller 81 rotates in accordance with the timing of the circumferential movement of the intermediate transfer belt 71. S is sent to the secondary transfer region TR2 at a predetermined timing.

  Further, the sheet S on which the monochrome image is thus formed is conveyed to the discharge tray portion 89 provided on the upper surface portion of the apparatus main body via the fixing unit 9, the pre-discharge roller 82 and the discharge roller 83. Further, when images are formed on both sides of the sheet S, when the rear end portion of the sheet S on which the image is formed on one side as described above is conveyed to the reversal position PR behind the pre-discharge roller 82. The rotation direction of the discharge roller 83 is reversed, whereby the sheet S is conveyed in the direction of the arrow D3 along the reverse conveyance path FR. Then, the sheet is again placed on the transport path F before the gate roller 81. At this time, the surface of the sheet S to which the image is transferred by contacting the intermediate transfer belt 71 in the secondary transfer region TR2 is first transferred. It is the opposite surface. In this way, images can be formed on both sides of the sheet S.

  A density sensor 60 is disposed in the vicinity of the roller 75. The density sensor 60 is provided to face the surface of the intermediate transfer belt 71 and measures the image density of the toner image formed on the outer peripheral surface of the intermediate transfer belt 71 as necessary. Based on the measurement result, this apparatus adjusts the operating conditions of each part of the apparatus that affects the image quality, for example, the developing bias applied to each developing cartridge, the intensity of the light beam L, and the like.

  The density sensor 60 is configured to output a signal corresponding to the image density of a region of a predetermined area on the intermediate transfer belt 71 using, for example, a reflection type photosensor. The CPU 101 can detect the image density of each part of the toner image on the intermediate transfer belt 71 by periodically sampling the output signal from the density sensor 60 while rotating the intermediate transfer belt 71.

  Further, as shown in FIG. 2, each of the developing cartridges 4Ka to 4Kd is provided with memories 91 to 94 for storing data relating to the manufacturing lot and usage history of the developing cartridge, the remaining amount of the built-in toner, and the like. Further, each of the developing cartridges 4Ka to 4Kd is provided with wireless communication devices 49Ka, 49Kb, 49Kc, and 49Kd. Then, if necessary, these selectively communicate with the wireless communication device 109 provided on the main body side in a non-contact manner, and data is transmitted between the CPU 101 and each of the memories 91 to 94 via the interface 105. Various information such as consumable management for the developing cartridge is managed by sending and receiving. In this embodiment, non-contact data transmission / reception is performed using electromagnetic means such as wireless communication. However, a connector is provided on the main body side and each developing cartridge side, and the connector is mechanically fitted. By doing so, you may make it mutually transmit / receive data.

  In FIG. 2, reference numeral 113 denotes an image memory provided in the main controller 11 for storing an image given from an external device such as a host computer via the interface 112, and reference numeral 117 denotes a calculation result in the CPU 111 and other information. It is a RAM that temporarily stores data. Reference numeral 106 is a ROM for storing a calculation program executed by the CPU 101, control data for controlling the engine unit EG, and the like. Reference numeral 107 is a RAM for temporarily storing calculation results in the CPU 101 and other data. is there.

  By the way, in the apparatus configured as described above, it is necessary to execute the print preparation operation in advance before executing the printing operation by each of the developing cartridges 4Ka to 4Kd. The “print preparation operation” means an operation or a process performed on the developing cartridges 4Ka to 4Kd prior to the printing operation in order to enable the printing operation by the developing cartridges 4Ka to 4Kd. In this embodiment, the following operations and processes are performed as “print preparation operations”.

(1) Checking operation:
This attachment confirmation operation is an operation for confirming that the developing cartridge is securely attached to the support frame 40 of the developing unit 4. Specifically, the data is transmitted and received between the CPU 101 and each of the memories 91 to 94 by wireless communication performed between the main body side and each developing cartridge side. In this regard, the same applies to the (2) conformity confirmation operation described below. Of course, in addition to the non-contact method such as wireless communication, the attachment confirmation may be performed by a contact method using a limit switch or the like.

(2) Conformity check operation:
This conformity confirmation operation is an operation for confirming that the developing cartridge mounted on the support frame 40 of the developing unit 4 is a developing cartridge that contains black toner. In particular, in this embodiment, a monochrome image forming apparatus is configured by mounting a developing cartridge for black at a position where a developing cartridge for yellow, cyan, and / or magenta used as a color image forming apparatus is installed. Therefore, there is a possibility that a user, an operator, or the like erroneously attaches the developing cartridge. Therefore, the conformity confirmation operation is executed to prevent the development cartridge for yellow, cyan or magenta from being used accidentally.

(3) Life check operation:
This life confirmation operation is an operation for confirming that the toner amount necessary for executing the printing operation remains sufficiently in the developing cartridge mounted on the support frame 40 of the developing unit 4. By executing this life checking operation, problems such as density unevenness and fading of an image formed by the printing operation are prevented in advance.

(4) Stir processing:
This stirring process is a process of rotating the developing roller 44 corresponding to the “toner carrier” of the present invention at least once. The reason for executing this stirring process is as follows. In this type of image forming apparatus, if the printing operation is performed for a long time after the power is off or the operation is stopped without performing the printing operation (image forming operation) even when the power is on, It has been conventionally known that periodic density unevenness may appear. In the present specification, this phenomenon is referred to as “abandoned banding phenomenon”.

  This neglected banding phenomenon is difficult because the toner is left on the developing roller 44 of each developing cartridge for a long time and is not easily separated from the developing roller 44, and the degree thereof is not uniform on the surface of the developing roller 44. It is considered that the toner layer on the developing roller 44 is gradually non-uniform. Therefore, in the image forming apparatus according to this embodiment, when the neglected banding generation requirement such that the period in which the operation is stopped exceeds a predetermined period is satisfied, a signal “stirring is required” is generated to empty the developing roller 44. It is turning. That is, the developing roller 44 is rotated at least once by a rotation drive unit (not shown) on the main body side. As a result, the toner layer on the surface of the developing roller 44 is refreshed and the toner layer in a more uniform state is used for the development process, and therefore, density unevenness due to the neglected banding phenomenon is less likely to occur.

(5) Patch processing (condition control processing):
This patch process is an optimization process for adjusting the printing operation condition when executing the printing operation by the developing cartridge to a predetermined optimum condition. This is a process similar to that conventionally used for stabilizing image quality. In this embodiment, a “patch control required” signal is generated at an appropriate timing immediately after the apparatus is turned on, and patch processing is executed in parallel with warming up of the apparatus. Patch processing is also generated when a “patch control required” signal is generated at the timing when the sleep mode is released, when the device cover that was in the open state is closed, or when the replacement of the developing cartridge is completed. Execution request occurs.

  Next, a print preparation process executed prior to the print process in the apparatus shown in FIG. 1 will be described with reference to FIGS. In order to help the understanding of the contents of the invention, a case where four developing cartridges 4Ka to 4Kd are mounted on the developing unit 4 as shown in FIG.

  FIG. 3 is a flowchart showing print preparation processing executed by the image forming apparatus shown in FIG. FIG. 4 is a schematic diagram showing the print preparation operation. In this apparatus, the CPU 101 controls each part of the apparatus according to a program stored in the ROM 106 at an appropriate timing before executing a printing operation, for example, a timing immediately after turning on the power, and the print preparation process shown in FIG. 3 is executed. The That is, in this embodiment, the CPU 101 functions as the “control unit” of the present invention.

  First, data is transmitted and received between the CPU 101 and each of the memories 91 to 94 by wireless communication, and various types of information such as consumables management for the developing cartridges 4Ka to 4Kd are temporarily stored in the RAM 107. Based on the information stored in the memory 107, the developing cartridge 4Ka closest to the developing position among the mounted cartridges 4Ka to 4Kd is set as the “priority cartridge” of the present invention, and the mounting cartridge 4Ka is checked for mounting (steps). S1), a conformity confirmation operation (step S2) and a life confirmation operation (step S3) are executed (FIG. 4A).

  In step S4, it is determined whether or not a “stirring required” signal is generated. This is a process for preventing the neglected banding phenomenon. Therefore, if the “stirring required” signal is not generated, the process proceeds to step S6 as it is. If the signal is generated, the stirring process (step S5) shown in FIG. 5 is performed for the developing cartridge 4Ka. Executed.

  FIG. 5 is a flowchart showing the stirring process in the apparatus of FIG. In this stirring process, as shown in FIG. 4B, among the four developing cartridges, the cartridge 4Ka is moved to the developing position (step S51). As a result, the developing roller 44 (DR in FIG. 4B) of the developing cartridge 4Ka is mechanically connected to the rotation drive unit on the main body side. Then, the developing roller 44 is rotated at least once by the rotation driving unit to refresh the toner layer on the surface of the developing roller 44, and the developing cartridge 4Ka is agitated (step S52).

  When the agitation process (step S5) is completed in this way, the process proceeds to step S6, where it is determined whether or not a “patch control required” signal is generated. This is a process for adjusting the printing operation condition to a predetermined optimum condition. Therefore, if the “patch control required” signal is not generated, the development unit 4 is moved to the HP (step S8), and then the print preparation process is terminated, while the signal is generated. If so, the patch processing (step S7) shown in FIG. 6 is executed for the developing cartridge 4Ka.

  FIG. 6 is a flowchart showing patch processing in the apparatus of FIG. In this patch processing, in order to maintain an image formed by executing a printing operation with a constant image quality, a patch image is formed while variously changing and setting the printing operation conditions, and the image density is detected. Is a process of adjusting the printing operation condition based on the above. In this patch processing, the development bias and exposure power are adjusted as control factors that affect the image quality among the operation parameters that determine the operation conditions of each part of the apparatus. Various other operating parameters that function as control factors are known, and there are many well-known techniques regarding the principle and control method of image quality control using these parameters. Briefly described.

  First, for the developing cartridge 4Ka, the optimum developing bias, that is, the optimum value of the developing bias applied to the developing roller 44 during the printing operation is calculated. Specifically, as shown in FIG. 4B, the developing cartridge 4Ka is selectively moved to the developing position (step S70), and each bias value is set while changing the developing bias in multiple stages for the developing cartridge 4Ka. Then, a patch image having a predetermined pattern is formed (step S71). Then, the image density of each patch image is detected by the density sensor 60 (step S72).

  When the image density of each patch image is obtained, the relationship between the development bias and the image density can be determined from these values. Based on this relationship, the value of the development bias that matches the predetermined target density based on the relationship. Is calculated. Thereby, the optimum developing bias is obtained (step S73). However, if the optimum value is not within the development bias variable range of the apparatus, the value closest to the optimum value calculated in the variable range is set as the optimum development bias.

  When the optimum developing bias is obtained for the developing cartridge 4Ka in this way, the optimum exposure power for the developing cartridge 4Ka, that is, the intensity of the light beam L when forming an electrostatic latent image corresponding to the cartridge on the photosensitive member 22 is subsequently obtained. Is calculated (steps S74 to S76). The processing here is the same as the above-described optimum development bias calculation processing (steps S70 to S73) except that the control factor is exposure power instead of the development bias, but a patch image to be formed as necessary. These image patterns may be different. In this case, it is preferable to use the optimum value obtained previously as the setting value of the developing bias. In this way, the optimum developing bias and optimum exposure power are respectively obtained for the developing cartridge 4Ka, and the patch processing is ended.

  By performing such a print preparation operation (mounting confirmation operation, conformity confirmation operation, life confirmation operation, stirring process, patch process), as shown in FIG. 4C, the developing cartridge 4Ka improves the printing operation. The printer is ready for printing. Returning to FIG. 3, the developing unit 4 is moved to the home position (HP) and waits (step S8). The execution of the image forming operation by the engine unit EG is permitted, and the subsequent printing operation is executed under this optimum condition, so that it is possible to form an image with a desired image quality and stably. .

  As described above, according to this embodiment, prior to the execution of the printing operation, the printing preparation operation is executed only for the developing cartridge 4Ka among the developing cartridges attached to the developing unit 4 so as to be in a printable state. Guided. Therefore, when the print preparation operation for one of the developing cartridges mounted in the developing unit 4 (corresponding to the “priority cartridge” of the present invention) is completed, the print preparation operation is completed. Therefore, since the printing can be performed in a short time, it is possible to prevent the user from waiting more than necessary for the print preparation operation, and to reduce the waiting time of the user.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, a maximum of four developing cartridges can be mounted on the support frame 40 of the developing unit 4, and the developing cartridges 4Ka to 4Kd are mounted at all mounting positions. The present invention can be applied to an apparatus in which a developing cartridge is mounted only at a position. That is, even in an apparatus in which the number M of developing cartridges (M ≧ 2) smaller than the number of mountable developing cartridges is mounted on the developing unit 4, one of these M developing cartridges is set as a priority cartridge. By performing the print preparation operation only for the cartridge, it is possible to make it possible to print with a specific color in a short time. In the above embodiment, the number that can be mounted is four, but this number is arbitrary, and the number M is arbitrary as long as it is 2 or more and not more than the number that can be mounted. Therefore, for example, the developing unit 4 is configured so that the number of support frames 40 that can be mounted is 5 or more, and the yellow, cyan, and magenta developing cartridges are mounted at the three mounting positions, respectively, and the remaining The present invention can also be applied to an image forming apparatus in which a black developing cartridge is mounted at the mounting position.

  In the above embodiment, the developing cartridge 4Ka closest to the developing position is set as the priority cartridge, and the print preparation operation is performed on the cartridge. However, the print preparation operation may be performed on other developing cartridges. . For example, as described above, various kinds of information such as consumable management related to the developing cartridge are temporarily stored in the RAM 107 before the print preparation process is executed. Therefore, the print preparation process is performed based on a part of the information. A developing cartridge to be performed, that is, a priority cartridge may be determined.

  In the above embodiment, the present invention is applied to the image forming apparatus in which the specific color is black, but the specific color is not limited to this.

  In the above-described embodiment, a rotary developing method in which a plurality of developing cartridges are mounted on the developing unit 4 is employed. Therefore, the toner stored in each developing cartridge as the developing unit 4 rotates is stirred in the cartridge. Thus, the toner can be made uniform. Therefore, the toner agitation may be executed by the rotation operation of the developing unit 4 as the print preparation operation. Further, conventionally, there is a case where a member such as an agitator or an auger bar is arranged in the developing cartridge to stir the toner in the developing cartridge or actively supply the toner to the developing roller side. Therefore, in an apparatus equipped with a member such as an agitator or an auger bar, operations such as toner agitation and toner supply by the member may be executed as a print preparation operation.

  Further, in the above-described embodiment, the configuration in which the toner stored in the developing cartridge is used up is adopted. However, in an apparatus employing a replenishing type developing cartridge that replenishes toner as necessary, a toner replenishing operation is performed as a print preparation operation. May be further executed.

  In the above embodiment, the four developing cartridges 4Ka to 4Kd having the same shape are used. However, developing cartridges having different shapes may be used. In the above embodiment, the present invention is applied to a so-called rotary type image forming apparatus in which the rotary developing unit 4 is arranged for one photoconductor 22. The present invention can also be applied to an elevator type image forming apparatus in which a developing cartridge moves up and down and develops with each developing cartridge, or a so-called tandem type image forming apparatus.

  Further, the present invention is not limited to the configuration of the above-described embodiment. For example, an apparatus for forming an image of a specific color by installing a development unit equipped with a plurality of development cartridges having toner of a specific color, or a transfer other than an intermediate transfer belt The present invention can be applied to an apparatus including a medium (transfer drum, transfer sheet, etc.), and also to other image forming apparatuses such as a copying machine and a facsimile apparatus.

1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus in FIG. 1. 3 is a flowchart showing print preparation processing executed by the image forming apparatus in FIG. 1. FIG. 2 is a schematic diagram illustrating a print preparation operation executed by the image forming apparatus in FIG. 1. The flowchart which shows the stirring process in the apparatus of FIG. The flowchart which shows the patch process in the apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 4 ... Developing unit, 4Ka-4Kd ... Developing cartridge, 10 ... Engine controller (control means), 22 ... Photoconductor (latent image carrier), 40 ... Support frame, 44 ... Developing roller (toner carrier), 101 ... CPU (Control means)

Claims (8)

A latent image carrier capable of carrying an electrostatic latent image;
A developing unit in which a plurality of cartridges having toner of a specific color are detachably provided, and a cartridge mounted on the developing unit is selectively positioned at a developing position, and the latent image is formed using toner in the cartridge. Control means for executing a printing operation for developing the electrostatic latent image on the carrier,
The control means sets one of the cartridges mounted on the developing unit as a priority cartridge, and prepares printing to be performed on the cartridge before the printing operation is performed in order to enable the printing operation by the cartridge. An image forming apparatus, wherein the operation is performed only for the priority cartridge.   The image forming apparatus according to claim 1, wherein the control unit executes an attachment confirmation operation for confirming attachment of a cartridge to the developing unit as the print preparation operation.   3. The image forming apparatus according to claim 1, wherein the control unit performs a conformity confirmation operation for confirming that a cartridge mounted on the developing unit is a cartridge having the specific color toner as the print preparation operation. .   The control means executes a life confirmation operation for confirming that a toner amount necessary for executing the printing operation remains in a cartridge mounted on the developing unit as the printing preparation operation. 4. The image forming apparatus according to any one of items 3 to 3. Each of the plurality of cartridges includes a toner carrier that conveys the toner to a position facing the latent image carrier by rotating in a predetermined direction while carrying the toner on the surface thereof.
The image forming apparatus according to claim 1, wherein the control unit executes a stirring process of rotating the toner carrier at least one round as the print preparation operation.   6. The control unit according to claim 1, wherein the control unit executes, as the print preparation operation, a condition control process for adjusting a printing operation condition when executing a printing operation using a cartridge mounted on the developing unit to a predetermined optimum condition. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 1, wherein M (M ≧ 2) cartridges are mounted on the developing unit. A latent image carrier capable of carrying an electrostatic latent image, and a developing unit in which a plurality of cartridges having toner of a specific color are detachably provided,
In an image forming method of performing a printing operation of selectively positioning a cartridge mounted on the developing unit at a developing position and developing an electrostatic latent image on the latent image carrier using toner in the cartridge. ,
Prior to the execution of the printing operation, one of the cartridges mounted on the developing unit is set as a priority cartridge, and a print preparation operation performed on the cartridge to enable the printing operation by the cartridge is performed. An image forming method, which is performed only for a priority cartridge.

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