JP6265112B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus capable of switching an operation mode.

  Patent Document 1 describes a phenomenon that may occur when the process speed of the image forming apparatus is switched from the full speed mode to the deceleration mode. In other words, when the process speed is switched to the deceleration mode, the developer transport speed in the developing device may rapidly decrease, and the developer may be biased in the developing device. As a result, the toner density in the developing device varies. If an image is output in a state where the toner density varies, density unevenness may occur in the output image.

  Therefore, in the image forming apparatus described in Patent Document 1, if the deceleration mode (1/2 speed of the full speed mode) is set during printing in the full speed mode, the process speed is set to 3/4 speed of the full speed mode. Decelerate and drive at 3/4 speed for a predetermined time. Then, after a predetermined time has elapsed, the process speed is reduced to 1/2 speed of the full speed mode, and image output is executed.

  In this image forming apparatus, when the process speed is switched from the full speed mode to the deceleration mode, the developer transport speed in the developer container gradually decreases, so that the bias of the developer can be suppressed. As a result, it is possible to suppress uneven density in the output image immediately after switching from the full speed mode to the deceleration mode.

JP 2011-128514 A

  However, since the image forming apparatus described in Patent Document 1 is driven at a 3/4 speed for a predetermined time, an image cannot be formed on the sheet during the predetermined time. As a result, when the process speed is switched to the deceleration mode, the number of sheets on which an image can be formed per certain time is reduced.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image that can suppress the influence of a change in the behavior of the developer while suppressing a decrease in the number of sheets on which an image can be formed per fixed time. It is to provide a forming apparatus.

  According to one aspect of the present invention, the image forming apparatus can switch the operation mode. The image forming apparatus includes a transport unit, an image forming unit, a drive source, a replenishing unit, and a control unit. The conveyance unit conveys the sheet. The image forming unit includes a developing unit that develops with a developer, and forms an image on the sheet using the developer. The drive source drives the transport unit and the image forming unit. The replenishing unit replenishes the developing unit with the developer. The control unit controls the drive source to change the sheet conveyance speed, and switches the operation mode when the developer replenishment start condition is satisfied after the change in the sheet conveyance speed. The replenishing unit is controlled to replenish the developer after switching the operation mode.

  According to the present invention, it is possible to suppress the influence of a change in the behavior of the developer while suppressing a decrease in the number of sheets on which an image can be formed per fixed time.

1 is a cross-sectional view illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a diagram illustrating an internal structure of a developing device of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 10 is a diagram illustrating a change in developer behavior caused by a reduction in sheet conveyance speed of the image forming apparatus according to the second exemplary embodiment of the present invention. FIG. 10 is a diagram illustrating a change in behavior of a developer sensor due to a reduction in sheet conveyance speed of an image forming apparatus according to a second exemplary embodiment of the present invention. It is a figure which shows the replenishment threshold value which the image forming apparatus which concerns on Embodiment 2 of this invention uses. 6 is a flowchart illustrating a first stage of operation of the image forming apparatus according to the second exemplary embodiment of the present invention. 10 is a flowchart illustrating a subsequent stage of the operation of the image forming apparatus according to the second exemplary embodiment of the present invention. 10 is a flowchart illustrating a first stage of operation of the image forming apparatus according to the third exemplary embodiment of the present invention. 14 is a flowchart illustrating a subsequent stage of the operation of the image forming apparatus according to the third exemplary embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof is not repeated. In the embodiment, the X axis, the Y axis, and the Z axis are orthogonal to each other, the X axis and the Y axis are parallel to the horizontal plane, and the Z axis is parallel to the vertical line.

(Embodiment 1)
With reference to FIG. 1, an image forming apparatus 1 according to Embodiment 1 of the present invention will be described. In the first embodiment, the image forming apparatus 1 is a color printer. The image forming apparatus 1 includes a feeding unit 10, a transport unit 20, an image forming unit 30, a developer supply unit 80, a discharge unit 90, a drive source 95, and a control unit 100.

  The control unit 100 controls each element of the image forming apparatus 1 such as the feeding unit 10, the conveyance unit 20, the image forming unit 30, the developer supply unit 80, the discharge unit 90, and the drive source 95. For example, the control unit 100 includes a processor such as a central processing unit (CPU) and / or an application specific integrated circuit (ASIC), and a storage unit. The storage unit includes a main storage device such as a semiconductor memory, and an auxiliary storage device such as a semiconductor memory and / or a hard disk drive.

  The feeding unit 10 includes a cassette 11 that stores a plurality of sheets P. The sheet P is, for example, a sheet made of paper or a synthetic resin. The feeding unit 10 feeds the sheet P from the cassette 11 to the conveyance unit 20. The conveyance unit 20 includes a plurality of conveyance rollers, and conveys the sheet P to the image forming unit 30. The image forming unit 30 forms an image (color image or monochrome image) on the sheet P using a developer. The conveyance unit 20 conveys the sheet P on which an image is formed to the discharge unit 90. The discharge unit 90 discharges the sheet P to the outside of the image forming apparatus 1.

  The image forming unit 30 includes an exposure unit 31, an M unit 32M, a C unit 32C, a Y unit 32Y, a BK unit 32BK, an intermediate transfer belt 33, a secondary transfer roller 34, and a fixing unit 35.

  The exposure unit 31 irradiates each of the M units 32M to BK units 32BK with light based on the image data, and forms an electrostatic latent image on each of the M units 32M to BK units 32BK. The M unit 32M forms a magenta developer image based on the electrostatic latent image, the C unit 32C forms a cyan developer image based on the electrostatic latent image, and the Y unit 32Y generates an electrostatic latent image. A yellow developer image is formed based on the image, and the BK unit 32BK forms a black developer image based on the electrostatic latent image.

  Four color developer images are superimposed and transferred onto the outer surface of the intermediate transfer belt 33 to form a color developer image, that is, a color image. The secondary transfer roller 34 transfers the color image formed on the outer surface of the intermediate transfer belt 33 to the sheet P. The fixing unit 35 heats and pressurizes the sheet P to fix the color image on the sheet P.

  Each of the M unit 32M to the BK unit 32BK includes a photosensitive drum 50, a charger 51, a developing device 52 (developing unit), a primary transfer roller 53, and a cleaner 54.

  The photosensitive drum 50 rotates around the rotation axis. The charger 51 charges the peripheral surface of the photosensitive drum 50. Light is irradiated on the peripheral surface of the photosensitive drum 50 by the exposure unit 31 to form an electrostatic latent image. The developing device 52 attaches a developer to the electrostatic latent image, develops the electrostatic latent image, and forms a developer image on the peripheral surface of the photosensitive drum 50. That is, the developing device 52 develops the electrostatic latent image with the developer. The primary transfer roller 53 transfers the developer image formed on the peripheral surface of the photosensitive drum 50 to the outer surface of the intermediate transfer belt 33. The cleaner 54 removes the developer remaining on the peripheral surface of the photosensitive drum 50.

  The plurality of developing devices 52 develop the electrostatic latent image with developers of different colors. In other words, the developing devices 52 of the M units 32M to BK units 32BK are formed on the peripheral surfaces of the photosensitive drums 50 of the M units 32M to BK units 32BK by magenta, cyan, yellow, and black developers, respectively. The formed electrostatic latent image is developed. As a result, four color developer images are formed.

  The image forming unit 30 uses the BK unit 32BK when forming a monochrome image on the sheet P. The operation of the BK unit 32BK is the same as that in the case of forming a color image.

  The developer supply unit 80 includes a developer container 80M that stores a magenta developer to be supplied to the developer 52 of the M unit 32M, and a developer that stores a cyan developer to be supplied to the developer 52 of the C unit 32C. A container 80C, a developer container 80Y containing a yellow developer to be supplied to the developing device 52 of the Y unit 32Y, and a developer container 80BK containing a black developer to be supplied to the developing device 52 of the BK unit 32BK. Including.

  In Embodiment 1, the developer is a two-component developer. That is, the developer includes toner and a carrier (for example, a magnetic carrier). The developer container 80M to the developer container 80BK accommodate toner in the developer.

  The drive source 95 is, for example, a motor, and a plurality of driven parts (for example, the photosensitive drum 50, the developing device 52, the primary transfer roller 53, the intermediate transfer belt 33, the image forming part 30) via a gear train. The secondary transfer roller 34, the fixing unit 35, the feeding unit 10, the conveying unit 20, and the discharging unit 90) are connected. Then, the drive source 95 drives a plurality of driven parts based on a control signal output from the control part 100. Specifically, each driven part is a rotating body or includes a rotating body, and each rotating body rotates via a gear train by rotating the rotating shaft of the drive source 95. The conveying speed of the sheet P (hereinafter referred to as “sheet conveying speed”) is determined by the peripheral speed of each rotating body. The peripheral speed is the speed at the maximum radius position of the rotating body that is rotating.

  The controller 100 changes the sheet conveyance speed by changing the peripheral speed of each driven part by changing the rotational speed of the rotary shaft of the drive source 95 (that is, the rotational speed of the rotary shaft per unit time). To do. That is, the image forming apparatus 1 can change the sheet conveyance speed.

  Next, an operation mode of the image forming apparatus 1 will be described with reference to FIG. The image forming apparatus 1 can switch the operation mode by the control unit 100.

  The image forming apparatus 1 has, as operation modes, a standard speed mode (first speed mode) in which the sheet conveyance speed is the first speed value, and a deceleration mode (second speed value in which the sheet conveyance speed is smaller than the first speed value). Second speed mode). For example, the second speed value is ½ of the first speed value.

  Hereinafter, switching between the standard speed mode and the deceleration mode will be described. The control unit 100 controls the drive source 95 so as to change the rotation speed of the rotation shaft of the drive source 95 to change the sheet conveyance speed. As a result, the operation mode is switched from the standard speed mode to the deceleration mode, or is switched from the deceleration mode to the standard speed mode. When the operation mode is switched from the standard speed mode to the deceleration mode, the sheet conveyance speed is reduced. When the operation mode is switched from the deceleration mode to the standard speed mode, the sheet conveyance speed is accelerated.

  The control unit 100 switches the operation mode according to, for example, the type of the sheet P, the density of the image formed on the sheet P, or the operation mode of the image forming apparatus 1. For example, the control unit 100 reduces the sheet conveyance speed when the sheet P is thick paper, when it is requested to form a high-density image, or when the operation mode of the image forming apparatus 1 is the silent mode. Thus, the drive source 95 is controlled to switch the operation mode from the standard speed mode to the deceleration mode.

  In addition, the image forming apparatus 1 has a single color mode in which the image forming unit 30 forms a monochrome image (that is, a single color image) on the sheet P as an operation mode, and a color image (that is, multiple images) on the sheet P. Color image).

  Hereinafter, switching between the single color mode and the multicolor mode will be described. The control unit 100 controls the image forming unit 30 to drive the BK unit 32BK and stop the M unit 32M to the Y unit 32Y, and switches the operation mode from the multicolor mode to the single color mode. On the other hand, the control unit 100 controls the image forming unit 30 to drive the M unit 32M to the BK unit 32BK, and switches the operation mode from the single color mode to the multicolor mode.

  Next, the developing device 52 will be described with reference to FIGS. FIG. 2 is a view showing the internal structure of the developing device 52. In FIG. 2, the developing unit 52 of the M unit 32M is shown. The structure of the developing unit 52 of the C unit 32C to the BK unit 32BK is the same as the structure of the developing unit 52 of the M unit 32M, and the description thereof is omitted.

  As shown in FIG. 1, the developing device 52 includes a first stirring member 60, a second stirring member 61, a magnetic roller 62, and a developing roller 63. As shown in FIG. 2, the developing device 52 further includes a developer sensor 64 and a housing 65. In FIG. 2, the magnetic roller 62 and the developing roller 63 are omitted for simplification of the drawing.

  The housing 65 accommodates the first stirring member 60, the second stirring member 61, the magnetic roller 62, the developing roller 63, and the developer sensor 64. The housing 65 also functions as a container for storing the developer. The housing 65 has a partition wall 66. The inside of the housing 65 is partitioned by a partition wall 66 into a first stirring chamber 65a and a second stirring chamber 65b. Inside the housing 65, a passage 65 c and a passage 65 d are formed at both ends of the partition wall 66. In the casing 65, a developer circulation path 75 is formed by the first stirring chamber 65a, the passage path 65c, the second stirring chamber 65b, and the passage path 65d.

  The first stirring member 60 is disposed in the first stirring chamber 65a, and the second stirring member 61 is disposed in the second stirring chamber 65b. In the first embodiment, each of the first stirring member 60 and the second stirring member 61 is a screw. Each of the first stirring member 60 and the second stirring member 61 is driven by a drive source 95 to rotate. In the first embodiment, the time for the first stirring member 60 to make one rotation (that is, the rotation period of the first stirring member 60) and the time for the second stirring member 61 to make one rotation (that is, the rotation period of the second stirring member 61). Is the same.

  The developer is conveyed while being stirred in the circulation path 75 by the first stirring member 60 and the second stirring member 61, and circulates in the circulation path 75 in the circulation direction D1 to the circulation direction D4. As a result, the toner in the developer is charged. The developer is conveyed to the magnetic roller 62 by the second stirring member 61, and further adhered to the peripheral surface of the photosensitive drum 50 via the developing roller 63. As a result, the electrostatic latent image formed on the peripheral surface of the photosensitive drum 50 is developed, and a developer image is formed.

  The developer sensor 64 detects the amount of developer stored in the developing device 52, specifically, the amount of developer in the circulation path 75. In the first embodiment, the developer sensor 64 is a light transmission type sensor, and includes a light emitting unit 64a and a light receiving unit 64b facing each other. The light emitting part 64a and the light receiving part 64b are respectively disposed on one and the other of the two wall parts forming the first stirring chamber 65a. The two wall portions face each other and intersect the axis of the first stirring member 60. Each of the light emitting part 64a and the light receiving part 64b is disposed in the vicinity of the intersection of the axis of the first stirring member 60 and the wall part.

  The output signal of the light receiving unit 64b is processed as follows. That is, the rotation cycle of the first stirring member 60 is divided into a plurality of fixed periods, and the output signal of the light receiving unit 64b is sampled every fixed period. Then, an average value of a plurality of output signals sampled in one rotation cycle (that is, a specified period) of the first stirring member 60 is calculated. The control unit 100 processes the average value as a sensor value from the developer sensor 64.

  Since the developer sensor 64 is a light transmission type sensor, the higher the sensor value level, the smaller the amount of developer in the circulation path 75 of the developing device 52, and the lower the sensor value level, the more the developing device. This indicates that the amount of developer in the circulation path 75 of 52 is large.

  Next, replenishment of developer to the developing device 52 will be described with reference to FIG. The developing device 52 has a developer supply port 67. The supply port 67 is formed in the housing 65 of the developing device 52. The replenishing port 67 is disposed above the first stirring chamber 65a upstream of the center in the longitudinal direction of the first stirring chamber 65a in the circulation direction D1 of the first stirring chamber 65a.

  The image forming apparatus 1 (FIG. 1) further includes four developer supply sections 69 (supply sections) corresponding to the developing devices 52 of the M unit 32M to the BK unit 32BK (FIG. 1). In FIG. 2, a developer supply unit 69 corresponding to the M unit 32M is shown. Each of the four developer replenishing units 69 replenishes the corresponding developing device 52 with the developer. The configuration of the developer replenishment unit 69 corresponding to each of the C unit 32C to the BK unit 32BK is the same as the configuration of the developer replenishment unit 69 corresponding to the M unit 32M, and a description thereof will be omitted.

  The developer supply unit 69 supplies developer to the developing device 52 through the supply port 67. Specifically, the developer supply unit 69 includes a supply motor 70 and a conveyance member 71. The replenishment motor 70 rotates the transport member 71 based on a control signal output from the control unit 100. For example, the conveying member 71 is a screw. The developer accommodated in the developer container 80 </ b> M is transported toward the supply port 67 by the rotation of the transport member 71, falls from the supply port 67, and is supplied to the circulation path 75. In the first embodiment, since the toner of the developer is stored in the developer container 80M, the toner of the developer is supplied to the circulation path 75.

  During a period in which the developer is supplied to the developing device 52, the M unit 32M to the BK unit 32BK (FIG. 1) are stopped, and the job for forming an image on the sheet P is interrupted. The M unit 32M to the BK unit 32BK are driven after the developer replenishment is completed, and the job for forming an image on the sheet P is resumed. However, when the operation mode is the single color mode, the BK unit 32BK is driven without being stopped even during a period in which the developer is supplied to the developing device 52 of the M unit 32M to the Y unit 32Y. May be continued.

  Next, the developer replenishment control according to the change (deceleration or acceleration) of the sheet conveyance speed will be described with reference to FIG. The control unit 100 controls the drive source 95 (FIG. 1) so as to change the sheet conveyance speed. Then, the control unit 100 switches the operation mode when the developer replenishment start condition is satisfied after the change in the sheet conveyance speed, and sets the developer replenishment unit 69 so that the developer is replenished after the operation mode is switched. Control.

  According to the first exemplary embodiment, the image forming apparatus 1 can shorten the developer replenishment time and suppress the influence of the change in developer behavior when the developer replenishment start condition is satisfied after the sheet conveyance speed is changed. The operation mode is switched to a mode that can be performed, and then the developer can be replenished. Alternatively, the image forming apparatus 1 switches the operation mode to a mode in which only the developing device 52 that stores the developer that does not satisfy the replenishment start condition is used, so that the developer that stores the developer that satisfies the replenishment start condition. 52 can be replenished with developer. As a result of these controls, the effect of changes in developer behavior due to changes in the sheet conveyance speed (for example, good for the sheet P is suppressed) while suppressing the decrease in the number of sheets P on which images can be formed per fixed time. An image defect (that is, density unevenness) that a clear image is not formed can be suppressed.

  Here, the change in the behavior of the developer is larger when the sheet conveyance speed is decelerated than when the sheet conveyance speed is accelerated. Therefore, hereinafter, in the first embodiment, the control unit 100 switches the operation mode when the developer replenishment start condition is satisfied after the sheet conveyance speed is reduced, and replenishes the developer after the operation mode is switched. The developer replenishing unit 69 is controlled.

  Specifically, the control unit 100 controls the drive source 95 (FIG. 1) so as to reduce the sheet conveyance speed. Then, the control unit 100 switches the operation mode and replenishes the developer after switching the operation mode when the replenishment start condition is satisfied within a predetermined period immediately after the sheet conveyance speed is decelerated. The replenishing unit 69 is controlled. Therefore, the influence of the change in the behavior of the developer can be effectively suppressed. This is because the behavior of the developer is particularly unstable in the period immediately after the sheet conveyance speed is decelerated.

  Further, the controller 100 replenishes the developer without switching the operation mode when the replenishment start condition is satisfied in a period after the elapse of a predetermined period immediately after the sheet conveyance speed is decelerated. The replenishing unit 69 is controlled. This is because when the sheet conveyance speed is reduced and the time elapses, the behavior of the developer becomes stable.

  Further, when the replenishment start condition is satisfied during execution of a job for forming an image on the sheet P within a predetermined period immediately after the sheet conveyance speed is decelerated, the control unit 100 interrupts the job and supplies the developer. In parallel, the image forming unit 30 is controlled to execute a standby job in the operation mode after switching. As a result, it is possible to further suppress the decrease in the number of sheets P on which an image can be formed per certain time. Then, the control unit 100 controls the image forming unit 30 so that the operation mode is restored after completion of the replenishment of the developer after the operation mode is switched, and the interrupted job is resumed. As a result, the interrupted job can be completed.

  Hereinafter, the predetermined period immediately after the sheet conveyance speed is decelerated may be referred to as “anomalous control period”, and the period after the elapse of the predetermined period may be referred to as “general control period”. Further, controlling the developer replenishing unit 69 so as to replenish the developer without switching the operation mode may be referred to as “general rule control”. In the first embodiment, switching the operation mode and controlling the developer supply unit 69 to supply the developer after switching the operation mode may be referred to as “anomalous control”. By executing irregular control of developer replenishment only during the irregular control period of the irregular control period and the general control period, the developer replenishment control can be optimized.

(Embodiment 2)
With reference to FIGS. 1 and 2, an image forming apparatus 1 according to a second embodiment of the present invention will be described. The configuration of the image forming apparatus 1 according to the second embodiment is the same as the configuration of the image forming apparatus 1 according to the first embodiment shown in FIGS. Embodiment 2 shows a specific example of developer replenishment according to Embodiment 1, and development is performed after the operation mode is switched from the deceleration mode to the standard speed mode when the developer replenishment start condition is satisfied in the irregular control period. Replenish the agent. Hereinafter, the replenishment of developer in the second embodiment will be described in detail.

  As shown in FIGS. 1 and 2, the control unit 100 controls the drive source 95 so that the operation mode is switched from the deceleration mode to the standard speed mode when the developer replenishment start condition is satisfied within the irregular control period. . Then, the control unit 100 controls the developer replenishing unit 69 so that the developer is replenished after the operation mode is switched from the deceleration mode to the standard speed mode. In the second embodiment, the control unit 100 determines that the developer replenishment start condition is satisfied when the amount of developer detected by the developer sensor 64 is equal to or less than the replenishment threshold.

  According to the second embodiment, the control unit 100 switches the operation mode to the standard speed mode and replenishes the developer in the standard speed mode when the developer replenishment start condition is satisfied within the irregular control period. Accordingly, the developer replenishment time can be shortened, and the time during which the M units 32M to BK units 32BK of the image forming unit 30 are stopped can be shortened. As a result, it is possible to suppress a decrease in the number of sheets P on which an image can be formed per certain time.

  As described in the first exemplary embodiment, during the period when the developer is supplied to the developing device 52, the M unit 32M to the BK unit 32BK are stopped, and the job for forming an image on the sheet P is interrupted. Accordingly, when the developer replenishment time is increased, the number of sheets P on which an image can be formed per certain time decreases. Therefore, in Embodiment 2, the operation mode is switched to the standard speed mode to shorten the developer replenishment time.

  Further, in the second embodiment, when the developer replenishment start condition is satisfied within the irregular control period, the influence of the change in the behavior of the developer can be suppressed by switching the operation mode to the standard speed mode. For example, an image defect (that is, density unevenness) in which a good image is not formed on the sheet P can be suppressed.

  Next, with reference to FIG. 2 and FIG. 3, the change in the behavior of the developer due to the reduction in the sheet conveying speed, the reason why the developer replenishment time can be shortened, and the reason why the image defect can be suppressed will be described. . FIG. 3 is a diagram showing a change in the behavior of the developer, and shows the developer T in the first stirring chamber 65a immediately after the sheet conveyance speed is reduced. In FIG. 3, the first stirring member 60 is omitted for simplification of the drawing, but the first stirring member 60 rotates in the rotation direction R.

  Ideally, the developer T is preferably stirred so that the locus of the developer T draws a circle C. However, when the sheet conveyance speed is reduced, that is, when the rotation speed of the rotation shaft of the drive source 95 is reduced, the rotation speed of the first agitating member 60 driven by the drive source 95 (that is, the first agitation). The number of rotations of the member 60 per unit time) and the rotation speed of the second stirring member 61 (that is, the number of rotations of the second stirring member 61 per unit time) are also reduced. Therefore, immediately after the sheet conveyance speed is reduced, the behavior of the developer T may be temporarily unstable.

  For example, immediately after the sheet conveyance speed is reduced and the rotation speeds of the first stirring member 60 and the second stirring member 61 are reduced, the developer T is temporarily smoothly circulated in the circulation direction D1 to the circulation direction D4. Or the locus of the developer T may temporarily have a shape in which a part of the circle C is cut out relatively large (that is, a relatively large gap G is temporarily formed). . Further, the developer conveyance speed is also reduced.

  In general, when the developer T is supplied to the first stirring chamber 65a through the supply port 67 during a period in which the relatively large gap G is formed, the following phenomenon may occur. . That is, of the replenished developer T, the amount of the developer T entering the gap G is larger than the amount of the developer T conveyed in the circulation direction D1. In addition, the developer T that has entered the gap G stays and accumulates below the replenishing port 67, and the phenomenon that the developer T flows in the reverse direction of the circulation direction D1, that is, the reverse flow phenomenon of the developer T occurs. In particular, since the developer transport speed is low, the developer T is likely to stay and accumulate, and the reverse flow phenomenon of the developer T is likely to occur. Accordingly, the replenishment of the developer T immediately after the sheet conveyance speed is decelerated further hinders the smooth circulation of the developer T in the circulation direction D1. As a result, the toner in the developer T is not sufficiently charged, and an image defect in which a good image cannot be formed on the sheet P may occur.

  On the other hand, when the sheet conveyance speed is accelerated, the behavior of the developer is more stable than when the sheet conveyance speed is decelerated. That is, the developer is smoothly circulated in the circulation direction D1 to the circulation direction D4, and the gap G is small. Therefore, even immediately after the sheet conveyance speed is accelerated, the behavior of the developer is relatively stable. For the same reason, it is unlikely that the smooth recirculation of the developer T in the circulation direction D1 is hindered by the replenishment of the developer T immediately after the sheet conveyance speed is accelerated. Therefore, even if the developer replenishment amount is increased immediately after the sheet conveyance speed is accelerated, the behavior of the developer is unlikely to become unstable, and the possibility of image defects is low.

  Therefore, in the second embodiment, when the developer replenishment start condition is satisfied within the irregular control period, the sheet conveyance speed is accelerated and the operation mode is switched to the standard speed mode. Then, the developer is replenished in the standard speed mode. When the developer is replenished, the developer replenishment time is shortened by increasing the developer replenishment amount. Further, even after switching to the standard speed mode, the behavior of the developer is relatively stable, so that the possibility of image failure is low.

  Specifically, the developer replenishment time is shortened as follows. That is, the control unit 100 determines the amount of developer replenished per unit time to be replenished in the standard speed mode when the developer replenishment start condition is satisfied within the irregular control period, and the developer replenishment start within the general control period. When the condition is satisfied, the developer replenishing unit 69 is controlled so as to increase the amount of developer replenished per unit time to be replenished in the deceleration mode. As a result, the developer replenishment time can be shortened. For example, the control unit 100 increases the rotation speed of the rotation shaft of the replenishment motor 70 (that is, the rotation speed of the rotation shaft per unit time) or shortens the cycle when the replenishment motor 70 is intermittently driven. By doing this, the developer replenishment amount per unit time is increased, and the developer replenishment time is shortened.

  Next, execution of a job for forming an image on the sheet P will be described with reference to FIG. The control unit 100 controls the image forming unit 30 to interrupt the job in the deceleration mode when the replenishment start condition is satisfied during execution of the job in the deceleration mode (second job) within the irregular control period. Then, the control unit 100 controls the drive source 95 so that the operation mode is switched from the deceleration mode to the standard speed mode, and performs a standby job (first job) in the standard speed mode in parallel with the replenishment of the developer. The image forming unit 30 is controlled to execute. The job in the deceleration mode is a job for forming an image on the sheet P in the deceleration mode, and the job in the standard speed mode is a job for forming an image on the sheet P in the standard speed mode.

  According to the second embodiment, when the developer replenishment start condition is satisfied within the irregular control period and the operation mode is switched to the standard speed mode, the standby in the standard speed mode is in parallel with the developer replenishment. Run the job. As a result, it is possible to further suppress the decrease in the number of sheets P on which an image can be formed per certain time. Then, the control unit 100 controls the image forming unit 30 to return the operation mode to the deceleration mode after completion of the developer replenishment and to resume the interrupted job in the deceleration mode. As a result, the interrupted job can be completed.

  Next, with reference to FIG. 2 and FIG. 4, a change in the behavior of the developer sensor 64 due to the reduction in the sheet conveyance speed will be described. FIG. 4 is a diagram illustrating a change in behavior of the developer sensor 64. The vertical axis represents the sheet conveyance speed or the amount of developer detected by the developer sensor 64 (hereinafter referred to as “developer detection amount”), and the horizontal axis represents time. In the second embodiment, the detected amount of developer is a value obtained by converting the sensor value of the developer sensor 64 into the amount of developer in the circulation path 75 of the developing device 52. The solid line indicates the sheet conveyance speed, and the broken line indicates the detected amount of developer.

  The period α is a period when the operation mode is the standard speed mode. The unstable behavior period β1 of the developer is a period immediately after the operation mode is switched from the standard speed mode to the deceleration mode, that is, a period immediately after the sheet conveyance speed is decelerated. In the unstable period β1, the behavior of the developer in the circulation path 75 is not constant. Therefore, during the unstable period β1, the developer sensor 64 detects a certain amount of developer in the developing device 52 (specifically, the circulation path 75), and the developer in the stable period γ1 of the developer behavior. The detected amount is smaller than the detected amount. The stable period γ1 of the developer behavior is a period following the unstable period β1 when the operation mode is the same as the mode in the unstable period β1. In the stable period γ1, the behavior of the developer in the circulation path 75 is constant. The period δ is a period after the operation mode is switched from the deceleration mode to the standard speed mode.

  In the period α, the unstable period β1, the stable period γ1, and the period δ, the actual amount of developer in the circulation path 75 is constant.

  However, when the sheet conveyance speed is reduced from v0 to v1, the detected amount of developer decreases from d3 to d1 in the unstable period β1. This is because the unstable period β1 is a period immediately after the sheet conveying speed is decelerated, and as described with reference to FIG. 3, the behavior of the developer is unstable. That is, in the unstable period β1, the developer is not smoothly circulated in the circulation direction D1 to the circulation direction D4, and a relatively large gap G is formed. Since the developer sensor 64 is a light transmission type sensor, if the gap G is large, the sensor value increases and the detected amount of developer decreases.

  In the stable period γ1, the detected amount of the developer increases from d1 to d2, and the sensor value and the detected amount by the developer sensor 64 are stable. This is because the behavior of the developer is stabilized in the stable period γ1. That is, the developer is smoothly circulated in the circulation direction D1 to the circulation direction D4, and the gap G is reduced. Since the developer sensor 64 is a light transmission type sensor, when the gap G becomes small, the sensor value becomes small and the detected amount of developer increases.

  When the sheet conveyance speed is accelerated from v1 to v0, the detected amount of developer increases from d2 to d3 in the period δ. When the sheet conveying speed is accelerated, the behavior of the developer is more stable than when the sheet conveying speed is decelerated. That is, the developer is smoothly circulated in the circulation direction D1 to the circulation direction D4, and the gap G is small. Therefore, even immediately after the sheet conveyance speed is accelerated, in the period δ, the sensor value and detection amount by the developer sensor 64 are stable, and the toner is appropriately charged, so that a good image is formed on the sheet P. The

  Next, with reference to FIG. 2 and FIG. 5, a replenishment threshold for determining whether or not developer replenishment is necessary will be described. FIG. 5 is a diagram illustrating a supply threshold value. The vertical axis indicates the sheet conveyance speed, the replenishment threshold, or the detected amount of developer, and the horizontal axis indicates time. The solid line indicates the sheet conveyance speed, the alternate long and short dash line indicates the replenishment threshold, and the broken line indicates the developer detection amount.

  The period α is a period when the operation mode is the standard speed mode, similarly to the period α in FIG. The irregular control period β2 (predetermined period) is a period immediately after the operation mode is switched from the standard speed mode to the deceleration mode, that is, a period immediately after the sheet conveyance speed is decelerated. In the second embodiment, the irregular control period β2 is constant. The general control period γ2 (period after the elapse of a predetermined period) is a period that follows the irregular control period β2 when the operation mode is the same as the mode in the irregular control period β2. The period δ is a period after the operation mode is switched from the deceleration mode to the standard speed mode, similarly to the period δ of FIG.

  The control unit 100 has a first supply threshold TH1, a second supply threshold TH2, and a third supply threshold TH3 as supply thresholds. The first supply threshold TH1 is set to a value that is smaller than the second supply threshold TH2 and is less likely to be supplied with developer than the second supply threshold TH2. The second supply threshold TH2 is set to a value that is smaller than the third supply threshold TH3 and is less likely to be supplied with developer than the third supply threshold TH3.

  The control unit 100 uses the third supply threshold value TH3 in the standard speed mode. Therefore, in the period α and the period δ, the control unit 100 determines that the replenishment start condition is satisfied when the detected amount of the developer is equal to or less than the third replenishment threshold TH3, and supplies the developer to the developer replenishment unit 69. Replenish. Specifically, in the period α and the period δ, the control unit 100 drives the replenishment motor 70 when the detected amount of developer becomes equal to or less than the third replenishment threshold value TH3, and causes the developer to be supplied to the developing device 52. Replenish.

  The control unit 100 uses the first supply threshold TH1 in the irregular control period β2. Therefore, in the irregular control period β2, the control unit 100 determines that the replenishment start condition is satisfied when the detected amount of developer becomes equal to or less than the first replenishment threshold TH1. Then, the control unit 100 replenishes the developer by switching the operation mode to the standard speed mode.

  In the second embodiment, the irregular control period β2 coincides with the unstable period β1 (FIG. 4). The unstable period β1 can be specified by simulation or data measurement, for example. Therefore, the irregular control period β2 is set so that the irregular control period β2 coincides with the unstable period β1. Therefore, in the irregular control period β2, the developer sensor 64 detects a certain amount of developer in the developing device 52 (specifically, the circulation path 75), which is larger than the detected amount of developer in the general control period γ2. Indicates a small detection amount. The irregular control period β2 may be set to be shorter than the unstable period β1, or may be set to be longer than the unstable period β1.

  The control unit 100 uses the second supply threshold TH2 in the general control period γ2. Therefore, in the general rule control period γ2, the control unit 100 determines that the replenishment start condition is satisfied when the detected amount of the developer is equal to or less than the second replenishment threshold TH2, and replenishes the developer replenishment unit 69 with the developer. Let Specifically, in the general rule control period γ2, the control unit 100 drives the supply motor 70 to supply the developer to the developing device 52 when the detected amount of the developer becomes equal to or less than the second supply threshold TH2. To do. In the second embodiment, the general control period γ2 coincides with the stable period γ1 (FIG. 4). Note that the control unit 100 can also accelerate the sheet conveyance speed and change the operation mode from the deceleration mode to the standard speed mode within the irregular control period β2. In this case, the period δ is started without passing through the general control period γ2.

  In the irregular control period β2 and the general control period γ2, since the detected amount of developer is smaller than in the period α and the period δ, each of the first supply threshold TH1 and the second supply threshold TH2 is set to be smaller than the third supply threshold TH3. It is small. Accordingly, it is possible to appropriately determine whether or not developer replenishment is necessary in the irregular control period β2 and the general control period γ2.

  In the irregular control period β2 corresponding to the unstable period β1, the detected amount of developer is smaller than in the general control period γ2 corresponding to the stable period γ1, so the first supply threshold TH1 is made smaller than the second supply threshold TH2. ing. Therefore, it is possible to more appropriately determine whether or not developer replenishment is necessary in the irregular control period β2.

  Hereinafter, in the second embodiment, the drive source 95 is controlled so that the operation mode is switched from the deceleration mode to the standard speed mode, and the developer is replenished after the operation mode is switched from the deceleration mode to the standard speed mode. Control of the replenishing unit 69 may be referred to as “anomalous control”.

  Next, the operation of the image forming apparatus 1 will be described with reference to FIGS. 1, 2, and 5 to 7. 6 and 7 are flowcharts showing the operation of the image forming apparatus 1.

As shown in FIG. 6, in step S1, the control unit 100 controls the drive source 95 so that the operation mode is switched from the standard speed mode to the deceleration mode.
In step S3, it is determined whether or not the period is the irregular control period β2.

If it is determined that the period is the irregular control period β2 (Yes in step S3), the process proceeds from step S3 to step S5.
In step S5, the control unit 100 sets the supply threshold value to the first supply threshold value TH1. Then, the process proceeds from step S5 to step S9.

On the other hand, when it is determined that the period is not the irregular control period β2 (No in step S3), that is, when it is determined that the period is the general control period γ2, the process proceeds from step S3 to step S7.
In step S7, the control unit 100 sets the supply threshold value to the second supply threshold value TH2. Then, the process proceeds from step S7 to step S9.

In step S9, the control unit 100 controls the image forming unit 30 to execute the job in the deceleration mode.
In step S11, the control unit 100 determines whether or not the job in the deceleration mode has been completed.

If it is determined that the job is completed (Yes in step S11), the process ends.
On the other hand, if it is determined that the job has not been completed (No in step S11), the process proceeds from step S11 to step S13.

  In step S13, the control unit 100 determines whether or not the detected amount of developer in the developing device 52 of at least one of the M units 32M to BK units 32BK is equal to or less than the currently set replenishment threshold. judge. The currently set supply threshold is one of the first supply threshold TH1 set in step S5 and the second supply threshold TH2 set in step S7.

  If it is determined that the detected amount of developer is not less than or equal to the supply threshold (No in step S13), that is, if it is determined that the supply start condition is not satisfied, the process proceeds from step S13 to step S3. Then, the process proceeds from step S3 to step S9 via step S5 or step S7, and the job in the deceleration mode is continuously executed.

On the other hand, if it is determined that the detected amount of developer is not more than the replenishment threshold (Yes in step S13), that is, if it is determined that the replenishment start condition is satisfied, the process proceeds from step S13 to step S15.
In step S15, the control unit 100 controls the image forming unit 30 so as to interrupt the job in the deceleration mode.
In step S17, the control unit 100 determines whether or not the period is the irregular control period β2.

If it is determined that the period is the irregular control period β2 (Yes in step S17), the process proceeds from step S17 to step S22 in FIG.
On the other hand, when it is determined that the period is not the irregular control period β2 (No in step S17), the process proceeds from step S17 to step S18.

In step S <b> 18, the control unit 100 executes general developer replenishment control. Step S18 includes step 19 and step S21.
In step S19, the control unit 100 controls the developer supply unit 69 so as to supply the developer to the developing device 52 that stores the developer for which the supply start condition is satisfied. Note that the control unit 100 controls the developer replenishment unit 69 so as not to replenish the developer with respect to the developing device 52 that stores the developer that does not satisfy the replenishment start condition.
In step S <b> 21, the control unit 100 determines whether or not the developer supply has been completed.

  If it is determined that developer replenishment has not been completed (No in step S21), the process proceeds from step S21 to step S19. Steps S19 and S21 are executed until the developer replenishment is completed.

  On the other hand, when it is determined that the supply of developer has been completed (Yes in step S21), the process proceeds from step S21 to step S3. Then, the process proceeds from step S3 to step S9 via step S5 or step S7, and the job in the deceleration mode is resumed.

  As shown in FIG. 7, in step S <b> 22, the control unit 100 executes irregular control for developer replenishment. Step S22 includes step S23, step S25, and step S27. In step S23, the control unit 100 controls the drive source 95 so that the operation mode is switched from the deceleration mode to the standard speed mode. And the control part 100 performs the process of step S25 and step S27, and the process of step S29-step S33 in parallel.

In step S25 after step S23, the control unit 100 controls the developer replenishing unit 69 so that the developer is replenished to the developing device 52 that contains the developer that satisfies the replenishment start condition. In this case, the control unit 100 controls the developer replenishing unit 69 so that the developer replenishment amount becomes larger than the developer replenishment amount in the general rule control (step S18), thereby shortening the developer replenishment time. . Note that the control unit 100 controls the developer replenishment unit 69 so as not to replenish the developer with respect to the developing device 52 that stores the developer that does not satisfy the replenishment start condition.
In step S27, the control unit 100 determines whether or not the developer replenishment has been completed.

If it is determined that developer replenishment has not been completed (No in step S27), the process proceeds from step S27 to step S25. Steps S25 and S27 are repeated until the developer replenishment is completed.
On the other hand, when it is determined that the developer replenishment is completed (Yes in step S27), the process proceeds from step S27 to step S1 in FIG. Even when it is determined that the developer replenishment is completed, the control unit 100 may advance the process to step S1 after the job is completed when the job is not completed (No in step S33).
As shown in FIG. 7, in step S29 after step S23, the control unit 100 determines whether there is a waiting job in the standard speed mode.

  If it is determined that there is no job waiting in the standard speed mode (No in step S29), the process proceeds from step S29 to step S1 in FIG. However, even when it is determined that there is no job, if the replenishment of the developer is not completed (No in step S27), the control unit 100 advances the process to step S1 after the replenishment of the developer is completed.

On the other hand, as shown in FIG. 7, when it is determined that there is a job waiting in the standard speed mode (Yes in step S29), the process proceeds from step S29 to step S31.
In step S31, the control unit 100 controls the image forming unit 30 to execute a standby job in the standard speed mode.
In step S33, the control unit 100 determines whether or not the job in the standard speed mode has been completed.

If it is determined that the job has not been completed (No in step S33), the process proceeds from step S33 to step S31. Until the job is completed, the processes of step S31 and step S33 are repeated.
On the other hand, if it is determined that the job is completed (Yes in step S33), the process proceeds from step S33 to step S1 in FIG. However, even when it is determined that the job is completed, the control unit 100 proceeds to step S1 after the developer supply is completed if the developer supply is not completed (No in step S27).

  After the positive determination (Yes) in step S27, after the negative determination (No) in step S29, or after the positive determination (Yes) in step S33, the operation mode is changed in step S1, as shown in FIG. The standard speed mode is switched to the deceleration mode, and the job in the deceleration mode is resumed in step S9.

  As described above with reference to FIGS. 1, 2, 6, and 7, according to the second embodiment, the number of sheets P on which an image can be formed per certain time is reduced. , The influence of changes in the behavior of the developer can be suppressed. In addition, the second embodiment has the same effects as the first embodiment.

(Embodiment 3)
With reference to FIGS. 1 and 2, an image forming apparatus 1 according to a third embodiment of the present invention will be described. The configuration of the image forming apparatus 1 according to the third embodiment is the same as the configuration of the image forming apparatus 1 according to the first embodiment shown in FIGS. The third embodiment shows a specific example of developer replenishment according to the first embodiment. When the developer replenishment start condition is satisfied in the irregular control period, the development is performed after the operation mode is switched from the multicolor mode to the single color mode. Replenish the agent. Hereinafter, the replenishment of developer in the third embodiment will be described in detail.

  As shown in FIGS. 1 and 2, the control unit 100 excludes the developing device 52 (the developing device 52 of the BK unit 32BK) used in the single color mode among the four developing devices 52 in the multicolor mode within the irregular control period. When the condition for starting the supply of developer stored in at least one developing device 52 (at least one of the developing devices 52 of the M unit 32M to Y unit 32Y) is satisfied, the operation mode is changed from the multicolor mode to the single color mode. The image forming unit 30 is controlled to switch to the mode. Then, the control unit 100 controls the developer supply unit 69 so that the developer is supplied to the developing device 52 after the operation mode is switched from the multicolor mode to the single color mode. In this case, the developing device 52 to which the developer is replenished is a developing device 52 that stores the developer that satisfies the replenishment start condition.

  According to the third embodiment, the controller 100 starts the replenishment start condition for the developer stored in at least one of the developing devices 52 of the M units 32M to 32B in the multicolor mode within the irregular control period. When is established, the operation mode is switched to the monochrome mode. In the single color mode, the developing unit 52 of the M unit 32M to the Y unit 32Y is not used. Therefore, in the monochromatic mode, the developer is supplied to the developing device 52 that stores the developer that satisfies the supply start condition among the developing devices 52 of the unused M units 32M to Y unit 32Y.

  On the other hand, using the BK unit 32BK in parallel with the developer replenishment to the developer 52 containing the developer satisfying the replenishment start condition among the developing units 52 of the M units 32M to 32Y, the sheet P A job for forming a monochrome image can be executed. Since the job is executed even while the developer is being replenished, it is possible to suppress a reduction in the number of sheets P on which an image can be formed per certain time. Further, since the developer is not replenished to the developing device 52 of the BK unit 32BK, it is possible to suppress the influence of the change in the behavior of the developer due to the reduction in the sheet conveyance speed. For example, an image defect (that is, density unevenness) in which a good monochrome image is not formed on the sheet P can be suppressed.

  In addition, in the multicolor mode within the irregular control period, the control unit 100 includes a developer 52 that contains a developer that does not satisfy the replenishment start condition among the developers 52 except for the developer 52 used in the single color mode. On the other hand, the developer supply unit 69 is controlled so as not to supply the developer. Accordingly, excessive supply of the developer is prevented, and the developer can be supplied efficiently.

  Next, execution of a job for forming an image on the sheet P will be described with reference to FIG. When the developer replenishment start condition is satisfied during execution of a job in the multicolor mode within the irregular control period, the control unit 100 interrupts the job in the multicolor mode and switches the operation mode from the multicolor mode to the single color mode. Thus, the image forming unit 30 is controlled. Then, the control unit 100 controls the image forming unit 30 so as to execute a standby job in the monochrome mode in parallel with the supply of the developer. The job in the multicolor mode is a job for forming a multicolor image on the sheet P, and the job in the single color mode is a job for forming a single color image on the sheet P.

  According to the third embodiment, a job in the single color mode is executed in parallel with the replenishment of the developer to the developing unit 52 that stores the developer that satisfies the replenishment start condition among the developing units 52 of the M units 32M to 32Y. Can be executed. As described above, when the developer is replenished, both the job in the multi-color mode and the job in the single-color mode are not interrupted at the same time, so that the number of sheets P that can form an image per certain time is further suppressed. it can. Then, the control unit 100 controls the image forming unit 30 so that the operation mode is returned to the multicolor mode after the developer replenishment is completed, and the interrupted job in the multicolor mode is resumed. As a result, the interrupted job in the multicolor mode can be completed.

  Hereinafter, in the third exemplary embodiment, the image forming unit 30 is controlled so that the operation mode is switched from the multicolor mode to the single color mode, and after the operation mode is switched from the multicolor mode to the single color mode, the single color among the developing devices 52 is selected. Control of the developer supply unit 69 so as to supply the developer to the developing devices 52 other than the developing device 52 used in the mode may be referred to as “anomalous control”.

  Next, the operation of the image forming apparatus 1 will be described with reference to FIGS. 1, 2, 5, 8, and 9. 8 and 9 are flowcharts showing the operation of the image forming apparatus 1.

As shown in FIG. 8, in step S51, the control unit 100 controls the drive source 95 so that the operation mode is switched from the standard speed mode to the deceleration mode.
The processing from step S53 to step S57 is the same as the processing from step S3 to step S7 in FIG.

In step S59, the control unit 100 controls the image forming unit 30 to execute the job in the multicolor mode.
In step S61, the control unit 100 determines whether or not the job in the multicolor mode is completed.

If it is determined that the job is completed (Yes in step S61), the process ends.
On the other hand, if it is determined that the job is not completed (No in step S61), the process proceeds from step S61 to step S63.

  In step S63, the control unit 100 determines whether or not the detected amount of developer in the developing device 52 of at least one of the M units 32M to Y units 32Y is equal to or less than the currently set replenishment threshold. judge. The currently set supply threshold is either the first supply threshold TH1 set in step S55 or the second supply threshold TH2 set in step S57.

  If it is determined that the detected amount of developer is not less than or equal to the supply threshold (No in step S63), that is, if it is determined that the supply start condition is not satisfied, the process proceeds from step S63 to step S53. Then, the process proceeds from step S53 to step S59 via step S55 or step S57, and the job in the multicolor mode is continuously executed.

On the other hand, if it is determined that the detected amount of developer is equal to or less than the replenishment threshold (Yes in step S63), that is, if it is determined that the replenishment start condition is satisfied, the process proceeds from step S63 to step S65.
In step S65, the control unit 100 controls the image forming unit 30 so as to interrupt the job in the multicolor mode.
In step S67, the control unit 100 determines whether or not the period is the irregular control period β2.

If it is determined that the period is the irregular control period β2 (Yes in step S67), the process proceeds from step S67 to step S73 in FIG.
On the other hand, when it is determined that the period is not the irregular control period β2 (No in step S67), the process proceeds from step S67 to step S68.

  In step S <b> 68, the control unit 100 executes general developer replenishment control. The general rule control in step S68 is the same as the general rule control in step S18 in FIG. 6, and includes the same processing as in steps S19 and S21. After step S68, the process proceeds from step S53 via step S55 or step S57 to step S59, and the job in the multicolor mode is resumed.

  As shown in FIG. 9, in step S <b> 73, the control unit 100 determines whether there is a waiting job in the single color mode.

If it is determined that there is no waiting job in the monochrome mode (No in step S73), the process proceeds from step S73 to step S74.
In step S <b> 74, the control unit 100 executes general developer replenishment control. The general rule control in step S74 is the same as the general rule control in step S18 in FIG. 6, and includes the same processing as in steps S19 and S21. After step S74, the process proceeds from step S53 to step S59 via step S55 or step S57, and the job in the multicolor mode is resumed.

On the other hand, if it is determined that there is a waiting job in the monochrome mode (Yes in step S73), the process proceeds from step S73 to step S78.
In step S <b> 78, the control unit 100 executes irregular control for developer replenishment. Step S78 includes step S79, step S81, and step S83.

  In step S79, the control unit 100 controls the image forming unit 30 to switch the operation mode from the multicolor mode to the single color mode. And the control part 100 performs the process of step S81 and step S83, and the process of step S85 and step S87 in parallel.

In step S81 after step S79, the control unit 100 replenishes the developer to the developing device 52 that stores the developer that satisfies the replenishment start condition among the developing devices 52 of the M units 32M to Y units 32Y. The developer supply unit 69 is controlled. In this case, the control unit 100 controls the developer replenishment unit 69 so that the developer replenishment amount becomes larger than the developer replenishment amount in the general rule control (step S68, step S74), and the developer replenishment time. To shorten. Note that the control unit 100 does not replenish the developer with respect to the developer 52 that stores the developer that does not satisfy the replenishment start condition among the developers 52 of the M units 32M to 32Y. The replenishing unit 69 is controlled.
In step S83, the control unit 100 determines whether or not the developer replenishment has been completed.

If it is determined that developer replenishment has not been completed (No in step S83), the process proceeds from step S83 to step S81. Steps S81 and S83 are repeated until the developer supply is completed.
On the other hand, if it is determined that the replenishment of developer has been completed (Yes in step S83), the process proceeds from step S83 to step S89. Even when it is determined that the developer replenishment is completed, the control unit 100 may advance the process to step S89 after the job is completed when the job is not completed (No in step S87).

In step S88 after step S79, the control unit 100 controls the image forming unit 30 to execute the job in the single color mode.
In step S87, the control unit 100 determines whether the job is completed.

If it is determined that the job is not completed (No in step S87), the process proceeds from step S87 to step S85. Steps S85 and S87 are repeated until the job is completed.
On the other hand, when it is determined that the job is completed (Yes in step S87), the process proceeds from step S87 to step S89. However, even when it is determined that the job is completed, if the replenishment of the developer is not completed (No in step S83), the control unit 100 advances the process to step S89 after the replenishment of the developer is completed.

  In step S89, the control unit 100 controls the image forming unit 30 to switch the operation mode from the single color mode to the multicolor mode. Then, the process proceeds from step S89 to step S53 in FIG. Then, the process proceeds from step S53 to step S59 via step S55 or step S57, and the job in the multicolor mode is resumed.

  As described above with reference to FIGS. 1, 2, 5, 8, and 9, according to the third embodiment, the number of sheets P on which an image can be formed per certain time is reduced. While suppressing, the influence of the change in the behavior of the developer can be suppressed. In addition, the third embodiment has the same effects as the first embodiment.

  The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof (for example, (1) to (9) shown below). In order to facilitate understanding, the drawings schematically show each component as a main component, and the thickness, length, number, and the like of each component shown in the drawings are different from the actual for convenience of drawing. In some cases. Moreover, the shape, dimension, etc. of each component shown by said embodiment are an example, Comprising: It does not specifically limit, A various change is possible in the range which does not deviate substantially from the effect of this invention.

  (1) The control unit 100 may change the irregular control period based on the size before the change of the sheet conveyance speed and the size after the change of the sheet conveyance speed. Specifically, the control unit 100 may change the length of the irregular control period according to the difference between the size before the change of the sheet conveyance speed and the size after the change of the sheet conveyance speed. In this case, the length of the irregular control period can be optimized. For example, as the difference between the sheet conveyance speed before deceleration and the sheet conveyance speed after deceleration (hereinafter referred to as “speed difference”) is larger, the control unit 100 lengthens the irregular control period and the speed difference is smaller. The shorter the irregular control period. This is because the larger the speed difference, the longer the unstable period of the developer behavior, and the smaller the speed difference, the shorter the unstable period of the developer behavior.

  (2) The output signal or sensor value of the developer sensor 64 may be compared with a supply threshold (first supply threshold, second supply threshold, and third supply threshold). The process of comparing the output signal or sensor value of the developer sensor 64 with the supply threshold value is substantially the same as the process of comparing the detected amount of developer by the developer sensor 64 with the supply threshold value.

  (3) The developer sensor 64 is not limited to a light transmission type sensor. For example, the developer sensor 64 is a magnetic permeability sensor. The magnetic permeability sensor detects the magnetic permeability of the developer in the developing device 52. Based on the magnetic permeability, the mixing ratio (that is, toner concentration) of the developer toner and magnetic carrier contained in the developing device 52 is obtained. The higher the toner concentration, the larger the amount of developer in the developing device 52, and the lower the toner concentration, the smaller the amount of developer in the developing device 52.

  (4) The toner containers and the carrier may be stored in the developer containers 80M to 80BK, and the toner and the carrier may be supplied to the developing device 52 from the developer containers 80M to 80BK. Further, the developer is not limited to a two-component developer. For example, the developer stored in the developer containers 80M to 80BK is a one-component developer made of toner. Further, although the magnetic roller 62 and the developing roller 63 are provided, instead of these, a single roller for attaching the developer to the photosensitive drum 50 may be provided.

  (5) The image forming apparatus 1 is not limited to the standard speed mode and the deceleration mode, and may have three or more modes that set three or more different sheet conveyance speeds as operation modes.

  (6) The image forming apparatus 1 may be a color printer that uses a developer of a plurality of colors other than four colors. In the first or second embodiment, the image forming apparatus 1 may be a printer that uses only a single color developer. Further, the image forming apparatus 1 is not limited to a printer, and is, for example, a copying machine, a facsimile machine, or a multifunction machine.

  (7) In the second and third embodiments, the developer replenishment amount by the irregular control is made larger than the developer replenishment amount by the general rule control. However, the developer replenishment amount by the irregular control may be the same as or less than the developer replenishment amount by the general control. Further, the replenishment threshold value during the irregular control period and the replenishment threshold value during the general control period may be set to the same value. In this case, the supply threshold value in the irregular control period and the supply threshold value in the general control period may be set to the first supply threshold value TH1 or the second supply threshold value TH2.

  (8) In FIG. 7, step S29 to step S33 may be executed after the positive determination (Yes) in step S27. In FIG. 9, step S85 and step S87 may be executed after the positive determination (Yes) in step S83.

  (9) The image forming apparatus 1 according to the modification of the present invention has a first supply mode and a second supply mode as operation modes. The developer replenishment amount per unit time replenished in the second replenishment mode is smaller than the developer replenishment amount per unit time replenished in the first replenishment mode. For example, the developer supply amount per unit time supplied in the second supply mode is set so as not to affect the image quality of the image formed on the sheet P.

  When the developer replenishment start condition is satisfied during execution of a job for forming an image on the sheet P within the irregular control period, the control unit 100 determines whether the job can be completed by the developer in the developing device 52. To do. When determining that the job can be completed, the control unit 100 sets the operation mode to the second supply mode, controls the developer supply unit 69 to supply the developer, and continues the job. The image forming unit 30 is controlled. On the other hand, when determining that the job cannot be completed, the control unit 100 sets the operation mode to the first supply mode, controls the developer supply unit 69 to supply the developer, and interrupts the job. The image forming unit 30 is controlled.

  According to this modification, even when the developer replenishment start condition is satisfied, if the job can be completed by the developer in the developing device 52, the job is continued. Accordingly, it is possible to suppress a decrease in the number of sheets P on which an image can be formed per fixed time. In addition, since the amount of developer replenished per unit time to be replenished in the second replenishment mode is small, it is possible to suppress the influence of the change in developer behavior caused by the change in the sheet conveyance speed.

  The present invention can be used in the field of image forming apparatuses that form images on sheets.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 20 Conveying part 30 Image forming part 52 Developing device (developing part)
69 Developer Supply Section (Supply Section)
95 Drive source 100 Control unit P sheet

Claims (11)

An image forming apparatus capable of switching an operation mode,
A transport unit for transporting the sheet;
An image forming unit that includes a developing unit that develops with a developer, and forms an image on the sheet using the developer;
A drive source for driving the transport unit and the image forming unit;
A replenishing unit for replenishing the developer to the developing unit;
A control unit that controls the drive source so as to change the conveyance speed of the sheet,
The operation mode includes a first speed mode in which the sheet conveyance speed is a first speed value, and a second speed mode in which the sheet conveyance speed is a second speed value smaller than the first speed value. ,
When the replenishment start condition is satisfied within a predetermined period immediately after the sheet conveyance speed is decelerated from the first speed value to the second speed value, the control unit changes the operation mode from the second speed mode. The drive source is controlled to be switched to the first speed mode, and the replenishing unit is controlled to replenish the developer after the operation mode is switched from the second speed mode to the first speed mode. , Image forming apparatus. The controller is
Determine whether the period is the predetermined period,
The replenishment is performed so that the developer is replenished without switching the operation mode from the second speed mode to the first speed mode when the replenishment start condition is satisfied in a period after the lapse of the predetermined period. The image forming apparatus according to claim 1 , wherein the image forming apparatus controls the unit. The image forming unit executes a first job for forming an image on the sheet in the first speed mode, and executes a second job for forming an image on the sheet in the second speed mode;
The control unit controls the image forming unit to interrupt the second job when the replenishment start condition is satisfied during execution of the second job within the predetermined period, and the operation mode is set to the first mode. Controlling the drive source to switch from the two-speed mode to the first speed mode, and controlling the image forming unit to execute the first job on standby in parallel with the replenishment of the developer; the image forming apparatus according to claim 1 or claim 2.   If the developer replenishment is not completed after the first job is completed, the control unit may change the operation mode from the first speed mode to the second speed mode after the developer replenishment is completed. The image forming apparatus according to claim 3, wherein the driving source is controlled so as to be switched to and the suspended second job is resumed.   When the first job is not completed after the developer replenishment is completed, the control unit changes the operation mode from the first speed mode to the second speed mode after the first job is completed. The image forming apparatus according to claim 3, wherein the driving source is controlled so as to be switched, and the interrupted second job is resumed. An image forming apparatus capable of switching an operation mode,
A transport unit for transporting the sheet;
An image forming unit that includes a developing unit that develops with a developer, and forms an image on the sheet using the developer;
A drive source for driving the transport unit and the image forming unit;
A replenishing unit for replenishing the developer to the developing unit;
A control unit that controls the drive source so as to change the conveyance speed of the sheet;
With
As the operation mode, the image forming unit has a single color mode for forming a single color image on the sheet, and the image forming unit has a multicolor mode for forming a multicolor image on the sheet,
A plurality of the developing units are provided,
The plurality of developing sections are developed with different color developers ,
Before Symbol supply unit, a plurality are provided corresponding to the plurality of developing units,
Each of the plurality of replenishing units replenishes the corresponding developing unit with the developer,
The control unit includes the developing unit among the plurality of developing units in the multicolor mode within a predetermined period immediately after the sheet conveyance speed is decelerated from a first speed value to a second speed value smaller than the first speed value. When the developer replenishment start condition stored in at least one developing unit other than the developing unit used in the single color mode is satisfied, the image forming unit is switched so that the operation mode is switched from the multicolor mode to the single color mode. controls, the controls the supply portion so as to replenish the developer to the at least one developing unit after the operation mode is switched from the multicolor mode to the monochrome mode, images forming device. In the multicolor mode within the predetermined period, the control unit includes a developing unit that stores the developer that does not satisfy the replenishment start condition among the developing units other than the developing unit used in the single color mode. The image forming apparatus according to claim 6 , wherein the replenishing unit is controlled not to replenish the developer.   The controller is
  Determine whether the period is the predetermined period,
  When the replenishment start condition is satisfied in a period after the predetermined period has elapsed, the replenishment unit is controlled to replenish the developer without switching the operation mode from the multicolor mode to the single color mode. The image forming apparatus according to claim 6 or 7. When the replenishment start condition is satisfied during execution of a job for forming the multicolor image on the sheet within the predetermined period, the control unit interrupts the job and the operation mode is changed from the multicolor mode. The image forming unit is controlled to switch to the single color mode, and the image forming unit is controlled to execute a standby job for forming the single color image on the sheet in parallel with the replenishment of the developer. The image forming apparatus according to any one of claims 6 to 8 .   When the developer replenishment is not completed after the job for forming the single color image is completed, the control unit may change the operation mode from the single color mode to the multicolor after the developer replenishment is completed. The image forming apparatus according to claim 7, wherein the image forming unit is controlled to switch to a mode, and the job for forming the interrupted multicolor image is resumed.   If the job for forming the monochrome image is not completed after the developer replenishment is completed, the control unit may change the operation mode from the monochrome mode after the job for forming the monochrome image is completed. The image forming apparatus according to claim 7 or 8, wherein the image forming unit is controlled to switch to the multicolor mode, and the job for forming the interrupted multicolor image is resumed.

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