JP2012123276A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that solves a problem in which: when a cartridge, which is required to be subjected to toner stirring sequence in initial preparation operations, is not used in printing operation, starting printing operation after the completion of the toner stirring sequence resulted in a decrease in productivity.SOLUTION: When printing operation is designated during toner stirring sequence in initial preparation operations, an image forming apparatus interrupts the toner stirring sequence to suppress a decrease in productivity, which occurs due to the stirring of toner.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, and a facsimile.

  2. Description of the Related Art Conventionally, an image forming apparatus employs a method in which a developing unit that accommodates toner is formed as an integral cartridge, and the cartridge can be attached to and detached from the image forming apparatus main body. According to this method, the user can perform maintenance of the image forming apparatus without depending on the service person, so that convenience can be improved. However, in this method, if a cartridge is not used for a long period of time and kept in a certain posture, a toner called a tapping phenomenon occurs in which the toner stored in the storage unit is biased toward one side and is solidified. There is a possibility.

  In order to eliminate such a tapping state, Patent Document 1 discloses a method of rotating the rotary holding the cartridge and stirring the toner.

JP-A-11-184200

  However, in the method as disclosed in Patent Document 1, when toner agitation is required, image formation is started after the agitation of the toner is completed, so that the time required for the agitation of the toner is downtime and productivity may be reduced. There was sex.

  The invention according to the present application has been made in view of the situation as described above, and an object thereof is to suppress a decrease in productivity caused by stirring the toner.

  To achieve the above object, one image carrier, a plurality of developers for forming an image on the image carrier, and an image for forming each of the plurality of developers on the image carrier. An image forming operation for forming an image on the image carrier by the developing device by moving the developing device to the image forming position by the developing rotary. An agitation operation of agitating the developer contained in the developer by moving or stopping the development rotary without forming an image on the image carrier by the developer. The image forming apparatus includes a control unit that interrupts the stirring operation and performs the image forming operation when an instruction for the image forming operation is received during the stirring operation.

  According to the configuration of the present invention, it is possible to suppress a decrease in productivity that occurs when the toner is agitated.

Schematic configuration diagram of an image forming apparatus Block diagram for explaining an example of a system configuration of an image forming apparatus A flowchart showing a toner agitation sequence when the developing rotary 23 is driven to rotate once. A flowchart showing a toner agitation sequence when the development rotary 23 is rotationally driven to the black development contact position. The figure showing the state of the development rotary 23 when moved to the home position, yellow development contact position, magenta development contact position, cyan development contact position, and black development contact position Flow chart for explaining the operation of the toner stirring sequence performed in the initial preparation operation Flowchart for explaining the operation of the toner agitation sequence performed in the printing operation A graph showing the relationship between the number of times that the toner stirring sequence has been performed and the number of times that the remaining toner stirring sequence has been performed Flowchart of delaying the start of the next image formation and performing the toner agitation sequence when the period until the next image formation is started is shorter than the minimum time required for the toner agitation sequence

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are not necessarily essential to the solution means of the invention.

(First embodiment)
FIG. 1 is a schematic configuration diagram of an image forming apparatus. First, the detailed configuration of each part will be described according to the operation.

(Charging part)
The drum unit 13 is configured integrally with a photosensitive drum 15 that is a drum-shaped image carrier and a cleaning container 14 of a cleaning device that also serves as a holder for the photosensitive drum 15. The drum unit 13 is detachable from the main body of the image forming apparatus, and is configured such that the unit can be replaced according to the lifetime. A cleaner blade 16 and a charging roller 17 serving as a primary charging unit are disposed on the periphery of the photosensitive drum 15. The photosensitive drum 15 is rotated in the direction of the arrow according to the image forming operation by a driving force of a driving roller (not shown). The surface of the photosensitive drum 15 is uniformly charged by bringing the charging roller 17 into contact with the photosensitive drum 15 and applying a voltage to the charging roller 17.

(Exposure part)
Exposure is performed by the scanner unit 30 in order to form a latent image on the photosensitive drum 15 that is uniformly charged by the charging unit. When the image information developed from the controller (not shown) is received, the laser (not shown) of the scanner unit 30 irradiates the mirror 31 with laser light corresponding to the image information. The mirror 31 is rotated at a high speed by a scanner motor 31a, and the laser beam reflected by the mirror 31 is selectively exposed to the surface of the photosensitive drum 15 rotating at a constant speed via the imaging lens 32 and the reflecting mirror 33. Is done.

(Development part)
The developing unit that forms a toner image on the photosensitive drum 15 develops the latent image formed on the photosensitive drum 15 by the exposure unit with toner. The developing unit contains toner as developer of each color of yellow, magenta, cyan, and black, and includes a detachable yellow developing device 20Y, a magenta developing device 20M, a cyan developing device 20C, and a black developing device 20Bk. . Each of these developing devices is detachably held on a developing rotary 23 as a developing device moving means. When a toner image is formed, each developing device is rotated about an axis 22 while being held on the developing rotary 23. Moving.

  Then, after the developing roller of the developing device of the color to be developed stops at the developing contact position that is an image forming position for forming the toner image on the photosensitive drum 15, the toner image is formed on the photosensitive drum 15. At the time of color image formation, the development rotary 23 rotates every rotation of the intermediate transfer member 9, and the developer moves to the image forming position in the order of the yellow developer 20Y, the magenta developer 20M, the cyan developer 20C, and the black developer 20Bk. The toner image can be formed. The intermediate transfer member 9 rotates four times, and each of the yellow, magenta, cyan, and black toner images is multiplex-transferred. As a result, a color image is formed on the intermediate transfer member 9. Here, the developing rotary 23 has been described as the developing device moving means, but is not limited thereto. For example, a holder that slides the developing device to the left and right and moves it to the image forming position can be used as the developing device moving means.

  FIG. 1 shows a state in which the yellow developing device 20Y is stopped at the development contact position corresponding to the drum unit 13. The yellow developing device 20Y sends the toner to the application roller 20YR by a mechanism for sending the toner in the container. Then, a thin layer of toner is applied to the outer periphery of the developing roller 20YS and a charge is applied to the toner (friction charging) by the blade 20YB pressed against the outer periphery of the applying roller 20YR and the developing roller 20YS. In this state, a latent image formed on the photosensitive drum 15 is developed with toner by applying a developing bias to the developing roller 20YS facing the photosensitive drum 15 on which the latent image is formed. The magenta developing device 20M, the cyan developing device 20C, and the black developing device 20Bk are also developed with toner by the same mechanism. Each developing roller of each color developing device is connected to a developing high-voltage power source or driving source provided for each color provided in the image forming apparatus when the developing device for each color is moved to the development contact position. Then, a voltage is selectively applied sequentially and driven for each color development.

(Primary transfer part)
The toner image formed on the photosensitive drum 15 at the developing unit is multiplex-transferred onto the intermediate transfer member 9. The intermediate transfer member 9 rotates in the direction of the arrow shown in the figure. In the drawing, the configuration when the intermediate transfer member 9 is a belt is shown, but the configuration is not limited to a belt, and for example, an intermediate transfer drum or a transfer material carrier may be used. By rotating the intermediate transfer member 9 four times, the toner images of the respective colors are transferred in the order of yellow, magenta, cyan, and black, and a color image is formed on the intermediate transfer member 9. In the non-image area on the outer periphery of the intermediate transfer member 9, a home position mark (hereinafter referred to as an HP mark) 9b and a HP mark 9b, which are reference points for use as a reference for the timing of starting image formation for each color, are detected. An optical sensor 9a is provided.

(Intermediate transfer member cleaning means)
The rotary image forming apparatus includes an ICL roller 39 as a cleaning unit for removing the toner image on the intermediate transfer member 9, and cleans the intermediate transfer member 9. The ICL roller 39 can be brought into contact with or separated from the intermediate transfer member 9, and the intermediate transfer member 9 is cleaned by the contact with the ICL roller 39.

  Next, a series of operations for primary transfer of four colors of yellow, magenta, cyan, and black onto the intermediate transfer body 9 by the image forming apparatus will be described. In order to form an image, the surface of the photosensitive drum 15 is uniformly charged by the charging roller 17. The charged photosensitive drum 15 is exposed by the scanner unit 30 to first form a yellow image latent image. Simultaneously with the formation of the latent image, the yellow developing device 20Y is driven, and development is performed by applying a voltage having the same polarity as the charging of the photosensitive drum 15 so that the yellow toner adheres to the latent image on the photosensitive drum 15. In order to primarily transfer the toner image formed on the photosensitive drum 15 to the intermediate transfer member 9, a voltage having a polarity different from that of the toner image formed on the photosensitive drum 15 is applied to the primary transfer roller 40. The toner image is primarily transferred onto the intermediate transfer member 9.

  When the yellow toner image is primarily transferred to the intermediate transfer member 9, the development rotary 23 rotates, and the magenta developing device 20 </ b> M that performs image formation next rotates and moves to the photosensitive drum 15 for development contact position. To stop. A magenta toner image is formed on the latent image formed by charging and exposing the photosensitive drum 15 in the same manner as yellow. The toner image formed on the photosensitive drum 15 is primarily transferred to the intermediate transfer member 9 in the same manner as yellow. Subsequently, cyan and black latent images are formed and developed, and primary transfer to the intermediate transfer member 9 is performed, and a color image is formed on the surface of the intermediate transfer member 9 by multiple transfer of toners of four colors of yellow, magenta, cyan, and black. .

  FIG. 2 is a block diagram for explaining an example of the system configuration of the image forming apparatus. First, the video controller 202 will be described. A CPU 204 controls the entire video controller. A nonvolatile storage unit 205 stores various control codes executed by the CPU 204, and corresponds to a ROM, an EEPROM, a hard disk, or the like. A temporary storage RAM 206 functions as a main memory, work area, and the like for the CPU 204. A host I / F unit 207 is an input / output unit for printing data and control data with the external device 201 such as a host computer. The print data received by the host I / F unit 207 is stored in the RAM 206 as compressed data.

  A data decompression unit 208 decompresses the compressed data. Arbitrary compressed data stored in the RAM 206 is expanded into image data in line units. The decompressed image data is stored in the RAM 206. A DMA control unit 209 transfers image data in the RAM 206 to the engine I / F unit 211 according to an instruction from the CPU 204. Alternatively, arbitrary compressed data in the RAM 206 is transferred to the data decompression unit 208. Alternatively, the image data output from the data decompression unit 208 is transferred to the RAM 206. A panel I / F unit 210 receives various settings and instructions from the user from a panel unit provided in the printer main body. Reference numeral 211 denotes an engine I / F unit which is a signal input / output unit for the printer engine 203, which transmits a data signal from an output buffer register (not shown) and controls communication with the printer engine. A system bus 212 has an address bus and a data bus. Each of the above-described components is connected to the system bus 212 and can access each other.

  Next, the printer engine 203 will be described. The printer engine 203 is roughly composed of an engine control unit 220 and an engine mechanism unit 230. The engine mechanism unit 230 is a part that operates according to various instructions from the engine control unit 220. Details of the engine mechanism unit 230 will be described first, and then details of the engine control unit 220 will be described. The laser / scanner system 231 includes a laser light emitting element, a laser driver circuit, a scanner motor, a rotary polygon mirror, a scanner driver, and the like. This is a portion where a latent image is formed on the photosensitive drum by exposing and scanning the photosensitive drum with laser light in accordance with image data sent from the video controller 202. The image forming system 232 is a part that forms a toner image based on the latent image formed on the photosensitive drum on the recording material. It is composed of process elements such as a cartridge, an intermediate transfer belt, and a fixing device, and a high-voltage power supply circuit that generates various biases (high voltage) for image formation. The cartridge includes a developing roller and a developing device. Further, the cartridge is provided with a non-volatile memory tag, and the CPU 221 or the ASIC 222 reads / writes various information to / from the memory tag. The paper feed / conveyance system 233 is a part that controls the feeding and conveyance of the recording material, and includes various conveyance system motors, a paper supply / discharge tray, various conveyance rollers, and the like. Although a cartridge having a developing roller and a developing device has been described as an example here, for example, a process cartridge having a charging roller, a photosensitive drum, and the like can also be used.

  The sensor system 234 is a sensor group for collecting necessary information when the CPU 221 and the ASIC 222 described later control the laser / scanner system, the image forming system, and the paper feed / conveyance system. This sensor group includes at least a variety of well-known sensors, such as a fixing device temperature sensor, a toner remaining amount detection sensor, a density sensor for detecting image density, a paper size sensor, a paper leading edge detection sensor, and a paper conveyance detection sensor. It is. Information detected by these various sensors is acquired by the CPU 221 and reflected in the print sequence control. The sensor system in the figure is described separately as a laser / scanner system 231, an image forming system 232, and a paper feed / conveyance system 233, but may be considered to be included in any of the mechanisms.

  Next, the engine control unit 220 will be described. A CPU 221 uses the RAM 223 as a main memory and work area, and controls the engine mechanism unit 230 described above according to various control programs stored in the nonvolatile storage unit 224. More specifically, the CPU 221 drives the laser / scanner system 231 based on a print control command and image data input from the video controller 202 via the engine interface 211 and the controller interface 225. The CPU 221 controls various print sequences by controlling the image forming system 232 and the paper feed / conveyance system 233. Further, the CPU 221 drives the sensor system 234 to obtain information necessary for controlling the image forming system 232 and the paper feed / conveyance system 233. On the other hand, under the instruction of the CPU 221, the ASIC 222 performs control of each motor and the high voltage power source control such as the developing bias in executing the above-described various print sequences. Note that some or all of the functions of the CPU 221 may be performed by the ASIC 222, and conversely, some or all of the functions of the ASIC 222 may be performed by the CPU 221 instead. Further, a part of the functions of the CPU 221 and the ASIC 222 may be provided with separate dedicated hardware so that the dedicated hardware can perform the function.

  A series of agitating operations (hereinafter referred to as a toner agitation sequence) for agitating the toner as the developer contained in the developing unit by the image forming apparatus will be described with reference to FIGS. 3 to 5. FIG. 3 is a flowchart showing a toner stirring sequence when the developing rotary 23 is driven to rotate once. FIG. 4 is a flowchart showing a toner agitation sequence when the developing rotary 23 is rotationally driven to the black developing contact position. 5 shows a home position (FIG. 5A), a black development contact position (FIG. 5B), a yellow development contact position (FIG. 5C), and a magenta development contact position (FIG. 5D). )), And a state of the development rotary 23 when sequentially moved to the cyan development contact position (FIG. 5E).

  A toner agitation sequence when the developing rotary 23 is driven to rotate one round will be described with reference to the flowchart of FIG. 3 and a diagram illustrating the state of the developing rotary 23 of FIG. FIG. 5A shows the position of the development rotary 23 when the printing operation is not performed (hereinafter referred to as the home position). The cyan developing device is located upstream of the developing rotary 23 in the rotation direction and the black developing device is located downstream, and the developing roller and the photosensitive drum 15 are not in contact with each other. When the developing rotary 23 is located at the home position, the user can access the black cartridge by opening the door for accessing the cartridge. In S101, the CPU 221 starts to move the development rotary 23 from the home position to the black development contact position. In S102, the CPU 221 checks whether or not the development rotary 23 has been moved to the black development contact position. In S103, the CPU 221 stops the developing rotary 23 at the black developing contact position for a predetermined time. The state of the developing rotary 23 at this time is as shown in FIG. Each developing unit stores toner, and each has a space inside. As the developing rotary 23 rotates, the posture of each developing device also changes, and the toner flows inside. When the predetermined time has elapsed, in S104, the CPU 221 starts to move the development rotary 23 to the yellow development contact position. In S105, the CPU 221 checks whether or not the development rotary 23 has been moved to the yellow development contact position. In S106, the CPU 221 stops the developing rotary 23 at the yellow developing contact position for a predetermined time. The state of the developing rotary 23 at this time is as shown in FIG. When the predetermined time has elapsed, in S107, the CPU 221 starts to move the development rotary 23 to the development contact position of magenta. In S108, the CPU 221 checks whether the development rotary 23 has been moved to the magenta development contact position. In S109, the CPU 221 stops the developing rotary 23 at the developing contact position of magenta for a predetermined time. The state of the developing rotary 23 at this time is as shown in FIG. When the predetermined time has elapsed, in S110, the CPU 221 starts moving the development rotary 23 to the cyan development contact position. In S111, the CPU 221 checks whether or not the development rotary 23 has been moved to the cyan development contact position. In S112, the CPU 221 stops the developing rotary 23 at the cyan developing contact position for a predetermined time. The state of the development rotary 23 at this time is as shown in FIG. After stopping for a predetermined time at the cyan development contact position, in S113, the CPU 221 starts to move the development rotary 23 to the home position. In S <b> 114, when the developing rotary 23 moves to the home position, the CPU 221 ends the toner stirring sequence.

  Next, a toner agitation sequence when the development rotary 23 is rotationally driven to the black development contact position will be described with reference to the flowchart of FIG. 4 and the drawing showing the state of the development rotary 23 of FIG. In step S201, the CPU 221 starts to move the development rotary 23 from the home position to the black development contact position. In S202, the CPU 221 checks whether or not the development rotary 23 has been moved to the black development contact position. In S203, the CPU 221 stops the developing rotary 23 at the black developing contact position for a predetermined time. When the predetermined time has elapsed, in S204, the CPU 221 starts moving the developing rotary 23 to the home position. In S205, the CPU 221 ends the toner agitation sequence when the development rotary 23 moves to the home position.

  In this way, by repeatedly rotating and stopping the developing rotary 23, the toner of each developing device flows and the toner can be agitated. When the development rotary 23 described with reference to FIG. 3 is driven to rotate once, it is rotated to the development contact position for black as described with reference to FIG. In this case, it has moved only to the black development contact position. As a result, when the development rotary 23 is driven to rotate once, when the toner is rotated to the black development contact position, the execution time of the toner agitation sequence is shortened. However, when the development rotary 23 is driven to rotate only one turn, when the development rotary 23 is driven to the black development contact position, the time for which the development rotary 23 is rotationally driven is approximately ¼. The effect is also about 1/4. As an example, the toner agitation sequence when the development rotary 23 is driven to rotate once and the toner agitation sequence when the development rotary 23 is moved to the black development contact position have been described. However, the number of rotations of the development rotary 23 is not limited to one round, and the multiple-rotation development rotary 23 may be rotated until the toner can be sufficiently stirred. Here, the toner stirring sequence by rotating the developing rotary 23 has been described, but the toner stirring sequence is not limited to this. For example, the toner may be stirred by rotating a stirring rod or the like inside the developing device. In such a case, it is possible to control the state until the toner is sufficiently stirred by counting the stirring time instead of the rotational speed of the rotary.

  The operation of performing the toner agitation sequence in the period from the formation of the first image to the start of the formation of the second image will be described with reference to FIGS. FIG. 6 is a flowchart for explaining the operation of the toner agitation sequence performed in the initial preparation operation. FIG. 7 is a flowchart for explaining the operation of the toner agitation sequence performed in the printing operation. The initial preparation operation referred to here is a sequence for performing a plurality of preparation operations such as reading of a memory tag of a cartridge and a toner agitation sequence necessary for the printer engine 203 to perform a printing operation. FIG. 8 is a graph showing the relationship between the number of times that the toner stirring sequence has been performed and the number of times that the remaining toner stirring sequence has been performed.

  First, the operation for interrupting the toner agitation sequence performed in the initial preparation operation after cartridge replacement will be described with reference to the flowchart of FIG. In S301, the CPU 221 determines whether it is necessary to perform the toner agitation sequence. Examples of conditions that require the toner leveling sequence include the case where the cartridge is replaced or the printer engine 203 is stopped for a long time. There are cases where it was. The CPU 221 reads the memory tag of the cartridge. Before determining whether or not it is necessary to perform the toner agitation sequence, the memory tag is read, and the read memory tag information and the memory tag information held in the nonvolatile storage unit 224 are obtained. If they are different, it is determined that the cartridge has been replaced. When it is not necessary to perform the toner stirring sequence, the process proceeds to the next operation to be performed in the initial preparation operation.

  In S302, the CPU 221 starts the toner stirring sequence when it is necessary to execute the toner stirring sequence. In step S303, the CPU 221 checks whether a print command is received from the video controller 202 during the toner agitation sequence. In S303, if a print command has not been received, in S304, the CPU 221 checks whether the toner agitation sequence is completed. When the toner stirring sequence is completed, the process proceeds to the next operation to be performed in the initial preparation operation.

  When a print command is received from the video controller 202 in S303, the CPU 221 checks in S305 whether or not to interrupt the toner agitation sequence. The condition for interrupting the toner agitation sequence is, for example, a case where a cartridge that requires the toner agitation sequence is not used in the printing operation instructed from the video controller 202. If the condition for interrupting the toner stirring sequence is not satisfied in S305, the process proceeds to S304. If the condition for interrupting the toner agitation sequence is satisfied in S305, the CPU 221 interrupts the toner agitation sequence in S306. In step S <b> 307, the CPU 221 stores the number of rotations in which the toner agitation sequence is performed in the RAM 223 or the nonvolatile storage unit 224, and proceeds to the next operation to be performed in the initial preparation operation. The position of the development rotary 23 when starting the toner agitation sequence performed in the initial preparation operation is the home position, and the position when ending or interrupting is also the home position. Therefore, when the toner agitation sequence is interrupted, the number of laps in which the toner agitation sequence stored in the RAM 223 or the non-volatile storage unit 224 is performed is in units of one lap.

  Thus, even when the toner agitation sequence is being performed in the initial preparation operation, that is, when the printing operation is instructed during the agitation operation, the productivity generated by the agitation of the toner by interrupting the toner agitation sequence. Can be suppressed. However, if the toner stirring sequence in the initial preparation operation is interrupted, a cartridge with insufficient toner stirring remains. FIG. 6 is a diagram showing the relationship between the number of laps performed before the interruption and the number of laps necessary to be performed after the interruption (hereinafter referred to as the remaining number of laps) when the toner stirring sequence is interrupted. As shown in FIG. 6, when the toner stirring sequence in the initial preparation operation is interrupted, it is necessary to perform the toner stirring sequence after the printing operation for the remaining number of rotations according to the number of rotations performed before the interruption. . If the number of laps that must be performed in the toner stirring sequence is X, the number of laps performed before interruption in the initial preparation operation is Y, and the remaining number of laps is Z, Z = XY.

With reference to the flowchart of FIG. 7, an operation performed between the image formation and the image formation in the printing operation will be described with respect to the toner agitation sequence that needs to be performed the remaining number of times after the interruption. The period between image formation is a period from the end of the development of the previous image to the start of the development of the next image. Here, the execution time of the toner stirring sequence and T (msec), the shortest execution time _T 1, 2 th short implementation time _T 2, i-th short implementation time and _{T i.} Further, the execution amount of the toner stirring sequence is V (circumference), the smallest execution amount is V ₁ , the second smallest execution amount is V ₂ , and the i-th smallest execution amount is V _i . The execution time of the execution amount V _i is T _i .

  In step S401, the CPU 221 performs preprocessing for image formation (hereinafter referred to as a pre-rotation sequence). In S402, the CPU 221 forms an image for one sheet. In step S403, the CPU 221 checks whether there is a next print instruction. If there is no next print instruction, in S406, the CPU 221 checks whether or not it is necessary to execute the toner agitation sequence. Examples of conditions that require the toner agitation sequence include a case where the toner agitation sequence is interrupted in the initial preparation operation and a case where the printer engine 203 has been stopped for a long time. If it is determined in S406 that it is not necessary to execute the toner agitation sequence, the CPU 221 performs post-processing of the image forming operation (hereinafter referred to as a post-rotation sequence) in S408. If it is determined in S406 that the toner agitation sequence needs to be performed, in S407, the CPU 221 performs the toner agitation sequence for the remaining number of rotations, and then performs the post-rotation sequence in S408.

  If there is a next print instruction in S403, the CPU 221 checks in S404 whether or not it is necessary to perform a toner agitation sequence. If it is determined that it is not necessary to execute the toner stirring sequence, the CPU 221 forms an image for the next sheet in S415. If it is determined that the toner agitation sequence needs to be executed, in step S405, the CPU 221 executes the toner agitation sequence to determine whether the toner agitation sequence can be executed between image formation. It is checked whether the necessary cartridge is used for the next image formation. For example, if the cartridge that needs to perform the toner agitation sequence is a yellow cartridge and the next image formation is monochrome printing, the yellow cartridge is not used for monochrome printing, so the toner agitation sequence between image formations To implement.

If the cartridge is necessary to carry out the toner stirring sequence is not used for the next image formation, in S409, CPU 221 is set to i = 1, in S410, the period until the start of the formation of the execution time T ₁ and the next image Compare Execution time T ₁ is the case longer than the period until the start of the formation of the next image, in S415, CPU 221 forms a next image for one sheet. Comparative case execution time _{T 1} is shorter than the period until the start of the formation of the next image, in S411, CPU 221 is set to i = i + 1, at S412, the period until the start of the formation of the execution time _{T 2} and the next image To do. Of it is shorter than the period until the start of the formation of the next image execution time T _2, or the same, in S412, CPU 221 compares the implementation amount V ₂ and the remaining number of turns corresponding to the execution time T _2. If the implementation amount V ₂ less than the remaining number of laps performs similar processing in execution time T _3.

If execution time _{T i} is longer than the period until the start of the formation of the next image, in S416, CPU 221 has performed the toner stirring sequence of exemplary amount _{V i-1} and the corresponding implementation time _{T i-1,} in S415 Next, an image for one sheet is formed. In S413, if the execution amount V _i is greater than or equal to the remaining number of rotations, the CPU 221 executes the toner agitation sequence of the execution amount V _i corresponding to the execution time T _{i in} S414, and the next one sheet. Form an image. Thereafter, the same flow is repeated until there is no more print operation instruction.

  Assuming that the remaining number of rotations is A (circumference) and the number of rotations of the toner agitation sequence performed in the period until the start of the next image formation is B (circumference), if A ≦ B, the next image is formed. There is no need to perform a toner agitation sequence after completion. If A> B, after the formation of the next image is completed, it is necessary to perform a toner agitation sequence between the subsequent and subsequent image formations. If the number of times of performing the toner stirring sequence for the number of rotations B (circumference) is C (times), it is necessary to perform the toner stirring sequence between image formation until A ≦ B × C.

  In this way, even when the toner agitation sequence is interrupted in the initial preparation operation, the decrease in productivity caused by the agitation of toner is suppressed by performing the toner agitation sequence between image formations. It becomes possible to do.

  Using the flowchart of FIG. 9, when the period until the next image formation is started is shorter than the minimum necessary time for performing the toner stirring sequence, the start of the next image formation is delayed. A method for performing the toner stirring sequence will be described. In addition, the same code | symbol is attached | subjected about the operation | movement similar to what was demonstrated with the flowchart of previous FIG. 7, and description here is abbreviate | omitted.

In S410, CPU 221 compares the time to start the formation of the execution time _{T 1} and the next image. If better time to formation of the next image is started is shorter than the execution time T _1, at S501, CPU 221 than the implementation time T ₁ towards the period until formation of the next image is started Also, the start of the next image is delayed so that it becomes longer or the same. Assuming that the period until the start of the next image formation is L (msec) and the time for delaying the start of the next image formation is M (msec), the next image formation is performed until L + M ≧ T ₁ . Delay start. When the start of the next image formation is delayed, the toner stirring sequence of the execution amount V ₁ corresponding to the execution time T ₁ is executed, and the next one image is formed.

Toner agitation sequence executed in the period until the start of the next image formation, the period until the start of the next image formation is L (msec), the time for delaying the start of the next image formation is M (msec) The number of rotations of the toner is B (laps), and the number of times the toner agitation sequence of the loops B (laps) is performed is C (times). Then, the total execution time of the toner stirring sequence is (L + M) × C (msec). This time corresponds to the execution time T _Z of the toner stirring sequences remaining laps Z (peripheral). The total execution time of the toner stirring sequence is (L + M) × C (msec), but the total time for delaying the start of image formation is M × C (msec). Thus, the toner agitation sequence of the remaining number of rotations Z (periphery) (execution time T _Z = (L + M) × C) can be performed while suppressing the delay in starting image formation to M × C (msec). .

  Thus, even when the period until the start of the next image formation is shorter than the minimum time necessary for performing the toner stirring sequence, the start of the next image formation is delayed, A toner stirring sequence is performed during image formation. As a result, it is possible to suppress a decrease in productivity that occurs when the toner is agitated.

20Y Yellow developing unit 20M Magenta developing unit 20C Cyan developing unit 20B Black developing unit 23 Development rotary 202 Video controller 220 Engine control unit 221 CPU

Claims (5)

One image carrier;
A plurality of developing units for forming an image on the image carrier;
Developing device moving means that can move each of the plurality of developing devices to an image forming position for forming an image on the image carrier,
An image forming operation in which the developing device is moved to the image forming position by the developing device moving means and an image is formed on the image carrier by the developing device, and an image is formed on the image carrier by the developing device. And an agitation operation for agitating the developer contained in the developing device,
When the image forming operation command is received during the stirring operation, the developing device before stirring is completed by the stirring operation is continued if necessary for image formation, and before stirring is completed by the stirring operation. An image forming apparatus comprising control means for interrupting the stirring operation to form an image if the developing unit is not necessary for the image forming operation.   The developing device moving means is a developing rotary, and the control means agitates the developer stored in the developing device by repeatedly moving and stopping the developing rotary as the stirring operation. The image forming apparatus according to claim 1.   The said control means moves the said developing device to an image formation position by the said development rotary as said stirring operation, and stops the said development rotary for a predetermined time, without performing image formation. Image forming apparatus.   4. The control unit according to claim 1, wherein after the stirring operation is interrupted and the image forming operation is performed, the stirring operation is performed again before starting the next image forming operation. 2. The image forming apparatus according to item 1.   When the control means interrupts the stirring operation and performs the image forming operation and does not have time to perform the stirring operation again before starting the next image forming operation, at least the stirring operation is performed. The image forming apparatus according to claim 4, wherein the timing for starting the next image forming operation is delayed by a time that can be performed.

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