JP2015191191A - image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to control a failure of a toner conveyance section and toner conveyance, without arranging a sensor for toner conveyance means.SOLUTION: An image forming apparatus supplies toner corresponding to the amount consumed by developing means, via toner conveyance means 247, from a toner container 120 to the developing means, determines whether the toner container is empty or not, according to toner concentration detected by toner concentration detection means, calculates the number of trial toner supply operations when empty is determined, supplies toner of the amount defined in advance via the toner conveyance means, up to the calculated number of trials, when attachment/detachment of the toner container is detected by toner container detection means after empty is determined, and determines that the toner conveyance means fails when concentration detected by the toner concentration detection means does not exceed a reference value after supplying toner by the calculated number of trials.

Description

  The present invention relates to an image forming apparatus.

  In an electrophotographic image forming apparatus, toner in the developing unit is consumed every time an image is formed. In order to compensate for this consumption, a configuration is known in which toner is temporarily supplied from a storage container containing toner to the buffer unit, and toner in the buffer unit is supplied to the developing device. This image forming apparatus is provided with detection means for detecting the ratio of toner to the developer contained in the developing device (hereinafter referred to as toner density). The amount of toner replenished from the buffer unit to the developing device is controlled so that the toner density detected by the detection means becomes a predetermined value.

  When the conveying member provided in the buffer unit fails, the developing device is not replenished with toner. As a result, there is a possibility that an image defect or the like due to toner shortage in the developing device may occur, or toner clogging may occur in the buffer unit. When toner clogging occurs in the buffer unit, the toner concentration in the developing device does not increase, and the toner replenishment operation is continued from the storage container in an attempt to increase the toner concentration. As a result, the amount of toner that can be tolerated in the buffer unit is exceeded and the toner is replenished from the storage container to the buffer unit.

  For example, Patent Document 1 describes an image forming apparatus that includes a unit that detects the amount of toner in the toner transport unit and predicts the toner amount in the toner transport unit using the toner amount in the toner transport unit and the toner density in the developing device. Has been.

JP-A-7-209981

  However, in such an image forming apparatus, it is necessary to newly provide a means for detecting the toner amount in the buffer unit in addition to the means for detecting the toner density in the developing device. An object of the present invention is to provide an image forming apparatus capable of suppressing toner overflow from a buffer unit without providing a new sensor.

  In order to solve the above problems, the present invention has the following configuration. That is, a developing unit that performs development using toner, a toner container that stores toner and is detachable from the image forming apparatus, and a toner transport that transports toner from the mounted toner container to the developing unit Forming means, toner density detecting means for detecting the density of toner held by the developing means, and toner container detecting means for detecting whether or not the toner container is mounted on the image forming apparatus. A first control unit configured to execute a replenishment operation from the toner container to the developing unit for the amount of toner consumed by the developing unit via the toner conveying unit; and the first control unit. First determining means for determining whether or not the toner container is empty according to the toner concentration detected by the toner concentration detecting means after the toner replenishment operation is controlled by When it is determined that the toner container is empty, a calculation unit that calculates the number of trials of toner replenishment operation based on the amount of toner conveyed by the toner conveying unit, and the toner container is empty. If the toner container detecting means detects that the toner container has been detached after it is determined that there is a predetermined amount of toner through the toner conveying means, with the calculated number of trials as the upper limit. As a result of executing the toner replenishing operation from the toner container to the developing means, the density detected by the toner density detecting means exceeds a reference value. If not, a second determining unit that determines that the toner conveying unit is out of order.

  According to the present invention, it is possible to suppress toner overflow from the buffer unit without providing a new sensor.

2 is an explanatory diagram of a configuration of an image forming apparatus. FIG. The block diagram of the replenishment structure which concerns on this embodiment. FIG. 3 is a perspective view of a toner supply path of a developing device from a toner bottle according to the present embodiment. 6 is a flowchart of a printing operation according to the present embodiment. 6 is a flowchart of toner supply according to the embodiment. 6 is a flowchart of toner replenishment after the determination of the absence of toner according to the present embodiment. Explanatory drawing at the time of the toner absence determination which concerns on this embodiment. FIG. 6 is a diagram illustrating a relationship between a free capacity of a toner conveyance unit and a threshold value N according to the present embodiment. The figure which shows the example of a display of UI screen which concerns on this embodiment. Explanatory drawing of the toner bottle insertion / extraction detection which concerns on this embodiment.

[Image forming apparatus]
An image forming apparatus according to the present invention and a control configuration thereof will be described with reference to FIGS. FIG. 1 is a cross-sectional view for explaining the outline of the configuration of the image forming apparatus 10. In FIG. 1, photoconductors 11a to 11d are photoconductors corresponding to four colors of yellow, magenta, cyan, and black, respectively. Around the photoconductor 11a, a charging device 12a, an exposure device 13, a developing device 14a, and a photoconductor cleaning device 15a are arranged. The charging device 12a uniformly charges the surface of the photoreceptor 11a. The exposure device 13 projects a laser beam modulated based on image information to be recorded on the charged surface of the photoreceptor 11a. The developing device 14a develops the image latent image (electrostatic latent image) formed on the surface of the photoconductor 11a by the laser light projected from the exposure device 13. The photoreceptor cleaning device 15a cleans and collects toner remaining after the toner image on the surface of the photoreceptor 11a is transferred to the intermediate transfer belt 16. The developing device 14a is supplied with toner from a toner bottle 120a which is a toner container. The periphery of the photoconductors 11b to 11d has the same configuration as that of the photoconductor 11a except that the color of toner used and the irradiation position of the exposure device 13 are different. The photoconductor 11, the charging device 12, the developing device 14, and the photoconductor cleaning device 15 are integrated for each color and are called a process unit.

  Further, an intermediate transfer belt 16 to which a toner image on each photoconductor is transferred is disposed, and primary transfer rollers 17a to 17d are disposed at positions facing the respective photoconductors with the intermediate transfer belt 16 interposed therebetween. The toner image on the photosensitive member is transferred to the intermediate transfer belt 16 by the behavior of the primary transfer roller 17. An intermediate transfer belt cleaning device 18 is disposed around the intermediate transfer belt 16 to collect toner remaining after the toner image on the surface of the intermediate transfer belt 16 is transferred to a recording medium.

  A secondary transfer roller 19 is disposed at a position where the toner on the intermediate transfer belt 16 is transferred to the recording medium. Due to the behavior of the secondary transfer roller 19, the toner image on the intermediate transfer belt 16 is transferred to the recording medium. The recording medium P fed from the paper feeding device 20 is conveyed so as to pass the transfer position between the intermediate transfer belt 16 and the secondary transfer roller 19. A fixing device 21 that fixes the toner image transferred to the recording medium P and a paper discharge tray 22 that abolishes the recording medium P after printing are arranged on the downstream side in the transport direction of the recording medium P that has passed the transfer position. Yes. The toner recovered by the photoconductor cleaning device 15 and the intermediate transfer belt cleaning device 18 is discharged to a recovery toner box 30 disposed in the image forming apparatus 10.

[Operation outline]
Next, an outline of the operation of the image forming apparatus 10 will be described. The photoreceptor 11 is rotated at a constant speed in the direction of arrow A by a driving device (not shown). A laser beam modulated based on image information to be recorded from the exposure device 13 is projected onto the surface of the photoconductor 11 uniformly charged by the charging device 12 to form an image latent image. The image latent image on the photoconductor 11 is developed with toner loaded in the developing device 14 to form a toner image.

  When the toner image on the photoconductor 11 comes to the primary transfer position to the intermediate transfer belt 16 by the rotation of the photoconductor 11 in the direction of arrow A, the toner image is transferred to the intermediate transfer belt 16 by the action of the primary transfer roller 17. . Residual toner on the photoconductor 11 that has not been transferred at the primary transfer position is collected by the photoconductor cleaning device 15, and the surface of the photoconductor 11 is cleaned to prepare for the next image formation. The collected toner is discharged to the collected toner box 30.

  The intermediate transfer belt 16 is rotated at a constant speed in the direction of arrow B by a driving device (not shown). By this rotation, the recording medium P is fed from the paper feeding device 20 in accordance with the timing at which the toner image on the intermediate transfer belt 16 comes to the secondary transfer position. At the secondary transfer position, the toner image is transferred to the recording medium by the action of the secondary transfer roller 19. Residual toner on the intermediate transfer belt 16 that has not been transferred at the secondary transfer position is collected by the intermediate transfer belt cleaning device 18, and the surface of the intermediate transfer belt 16 is cleaned to prepare for the next image formation. The collected toner is discharged to the collected toner box 30. The recording medium P to which the toner has been transferred is subjected to fixing processing by the fixing device 21 and is discharged to the paper discharge tray 22.

[System configuration]
The overall system block diagram will be described with reference to FIG. The control unit 300 performs system control of the image forming apparatus 10 in FIG. The control unit 300 includes a CPU 301, a ROM 302, and a RAM 303. The CPU 301 performs system control of the image forming apparatus 10 by executing a control program, and a ROM 302 in which the control program is written and a RAM 303 that temporarily stores variables used for control are connected by an address bus and a data bus. .

  The UI 330 performs a status display of the image forming apparatus 10 such as selection of an image forming mode / finishing mode of a recording material, a toner bottle no-toner display described later, and a toner transport unit failure display. The mode setting information selected here is stored in the RAM 303. Upon receiving an operation instruction from the UI 330, the CPU 301 operates the bottle motor 121, the development motor 126, and the like based on input signals of various sensors such as the density sensor 124 and the toner bottle detection sensor 125 connected to the CPU 301, thereby forming an image. Perform the action.

  The bottle motor 121 is a driving source for driving the toner bottle 120 to replenish toner. By rotating and driving the toner bottle 120, the toner is conveyed to the toner conveying unit 246. A specific toner replenishing method will be described later with reference to FIG.

  The density sensor 124 is a sensor as toner density detection means for detecting the toner density inside the developing device 14. The density sensor 124 detects the magnetic permeability of the developer by using the inductance of the coil. If the magnetic permeability is higher than the reference value, the density sensor 124 determines that the toner in the developing device 14 is in a low state. If the magnetic susceptibility is lower than the reference value, it is determined that the amount of toner in the developing device 14 is large. Here, the reference value is defined and held in advance. The output signal of the density sensor 124 is input to the CPU 301, and the CPU 301 determines the toner density in the developing device 14 by performing AD conversion on the input signal. The developing motor 126 is a driving source for driving the charging device 12 and the conveying screw 240 attached to the developing device 14.

  The toner bottle detection sensor 125 is a sensor as a toner container detection unit that detects whether a toner bottle is attached to the image forming apparatus 10. With reference to FIG. 10, a method for determining the insertion / extraction of the toner bottle will be described. 10A to 10C are toner supply paths. When the value of the toner bottle detection sensor 125 changes from “Yes” as shown in FIG. 10A to “No” as shown in FIG. 10B, the toner bottle is removed from the image forming apparatus 10. judge. On the other hand, when the value of the toner bottle detection sensor 125 changes from “none” as shown in FIG. 10B to “present” as shown in FIG. It is determined that it is attached to. The CPU 301 detects the presence / absence and insertion / extraction of a toner bottle based on a signal from the toner bottle detection sensor 125.

[About toner supply]
The toner supply of the image forming apparatus according to the present invention will be described with reference to FIG. FIG. 3 is a perspective view schematically showing a system in which toner is supplied to the developing device 14. The toner supply configuration is provided for each of yellow, magenta, cyan, and black, and the same configuration is used for all colors.

  The toner is stored in a removable toner bottle 120, and the toner bottle 120 is rotated by the bottle motor 121, whereby the toner is conveyed from the toner delivery port 245 to the toner conveyance unit 246. The toner transported to the toner transport section 246 is transported in the toner transport section 246 in the longitudinal direction by the buffer screw 247 and transported into the developing device 14 from the replenishing port 248. The toner conveyed into the developing device 14 is consumed by being conveyed by a conveying screw 240 and forming an image by developing means (not shown). On the wall surface of the developing device 14, a density sensor 124 for detecting the toner density in the developing device is installed facing the conveying screw 240.

  The toner supply is controlled according to the value output from the density sensor 124. That is, the CPU 301 drives the bottle motor 121 according to the value of the density sensor 124. When the value of the density sensor 124 is lower than the reference value, a necessary toner supply amount is calculated. Then, the CPU 301 replenishes the toner amount calculated by driving the bottle motor 121 based on the calculated toner replenishment amount. Note that the value of the density sensor 124 varies depending on the toner density in the developing device 14. That is, the value of the density sensor 124 changes depending on the density of the image being printed. The toner bottle 120 is in the “no toner” state if the density in the developing device 14 does not return to the reference value within a predetermined time even though the bottle motor 121 is driven to replenish toner. It is determined.

[Printing operation]
FIG. 4 is a flowchart of the printing operation of this embodiment, and the printing operation of this apparatus will be described using this flowchart. This flowchart is realized by the CPU 301 reading and executing a program stored in the ROM 302 or the like in parallel with a toner replenishment operation described later with reference to FIG.

  After the power is turned on, the image forming apparatus 10 enters a print standby state, and the CPU 301 determines whether or not “no toner” (S401). The determination method of “no toner” will be described later with reference to FIG.

  If it is not “no toner” (NO in S401), the CPU 301 determines that the printing is possible and proceeds to S402. If there is a print instruction in a printable state (YES in S402), CPU 301 forms an image in accordance with the print instruction (S403). Thereafter, the CPU 301 determines whether or not “no toner” in a process to be described later with reference to FIG. 5 (S403). If it is determined that there is no toner (YES in S404), image formation is interrupted and the process returns to the print standby state (S401). If not “no toner” (NO in S404), the CPU 301 determines whether or not all pages to be printed have been completed based on the print instruction (S405). When printing of all pages to be printed is completed (YES in S405), CPU 301 ends the printing operation and returns to the print standby state (S401). If there is an unprinted page (NO in S405), the process returns to S403, and the CPU 301 prints the next page.

[Toner supply operation]
FIG. 5 is a flowchart of toner supply according to the present embodiment. The toner replenishment of the image forming apparatus 10 will be described using the flowchart of FIG. This flowchart is realized by the CPU 301 reading and executing a program stored in the ROM 302 or the like in parallel with the printing operation described above.

  The CPU 301 compares the value of the density sensor 124 with a reference value and determines whether or not toner replenishment is necessary (S501). The reference value for determining whether or not replenishment is necessary is such that even if an image having a high density value in image formation is printed on the next page, the image formation is not affected by a density defect due to lack of toner. A value is used. When the value of density sensor 124 is lower than the reference value (NO in S501), CPU 301 calculates the amount of toner necessary for replenishment based on the value of density sensor 124 (S502). The CPU 301 starts a replenishment operation of the calculated amount of toner (S503). Thereafter, the CPU 301 starts a timer (not shown) that measures the time since toner replenishment (S504).

  If the value of the density sensor 124 is equal to or higher than the reference value after controlling the toner replenishment operation (YES in S505), the CPU 301 determines that the toner density has been recovered and ends the timer (S508). Then, the process returns to S501. When the value of density sensor 124 is lower than the reference value (NO in S505), CPU 301 determines whether or not a certain time has elapsed since the start of measurement (S506). Here, the predetermined time is defined and held in advance. If the elapsed time is less than the predetermined time (NO in S506), the process returns to S505, and CPU 301 compares density sensor 124 with a reference value. If the predetermined time or more has elapsed (YES in S506), CPU 301 determines “no toner” and ends the timer (S507). The first determination means is realized by the processing so far. Then, the process proceeds to S601 illustrated in FIG. The toner replenishment after the transition to S601 is the toner replenishment after the determination of the absence of toner. Details of toner replenishment after the determination of the absence of toner will be described later with reference to FIG. In this specification, the toner supply control in FIG. 5 is referred to as the toner supply control in FIG. The toner supply control in FIG. 6 is also referred to as a second control.

  FIG. 7 is an explanatory diagram showing the state of toner from the toner bottle 120 to the toner transport unit 246 when it is determined that there is no toner. If a toner replenishment operation is performed when a failure has occurred in the toner transport unit 246, the toner transport unit 246 cannot transport the toner to the supply port 248 and cannot discharge the toner into the developing device. On the other hand, since toner is supplied from the toner bottle 120 to the toner transport unit 246, the toner is accumulated in the toner transport unit 246. If such a state continues, the supplied toner exceeds the amount of toner that can be accommodated in the toner transport unit 246, and the toner overflows from the toner bottle 120 and the toner delivery port 245 of the toner transport unit 246. Note that the toner supply after the determination of the absence of toner is larger than the toner supply performed in parallel with the printing operation. Details of toner replenishment after the determination of the absence of toner will be described later.

  In the present embodiment, the number of attempts to supply toner after determining the absence of toner is held as the number of supply attempts. The upper limit value of the number of supply trials is set as a threshold value N. By comparing the number of replenishment attempts and the threshold value N, control is performed so that the toner does not overflow from the toner bottle 120 and the toner delivery port 245 of the toner transport unit 246. Hereinafter, a calculation method and a comparison method of the threshold value N will be described.

[Calculation of the number of trials to determine that the toner transport unit is out of order]
If the toner bottle 120 becomes empty during the printing operation and it is determined that there is no toner in S506 of FIG. 5, no toner is accumulated in the toner transport unit 246 as shown in FIG. This is because the toner transport unit 246 is configured to transport the toner from the supply port 248 to the developing device 14 as soon as the toner is replenished from the toner bottle 120, and the toner transport unit 246 is always empty. It is in a close state. Further, as described above, the developer 14 is not empty at the time when it is determined as “no toner” so as not to affect image formation due to insufficient density due to toner shortage, etc., and some toner remains. It is in the state.

  However, if an abnormality occurs such that the buffer screw 247 is unable to convey the toner, and the toner cannot be conveyed to the developing device 14 and it is determined that there is no toner, the toner is transferred from the toner bottle 120 to the toner conveying unit 246. Will continue to be replenished. If the toner is excessively replenished, the amount of toner that can be stored in the toner transport unit 246 will be exceeded, and the toner will overflow from the toner bottle 120 and the toner delivery port 245 of the toner transport unit 246. Therefore, it is necessary to determine a threshold value for determining that there is a failure in the toner transport unit 246 so that the toner does not overflow between the toner bottle 120 and the toner delivery port 245 of the toner transport unit 246. For this purpose, it is necessary to determine a threshold value for determining that the toner transport unit 246 is out of order in consideration of the free capacity of the toner transport unit 246.

  Normally, the free capacity in the toner transport unit 246 is always near empty. However, when it is assumed that the toner transport unit 246 is out of order, the free space in the toner transport unit 246 at the timing when it is determined that there is no toner varies depending on the density of the printed image. . For example, when an image having a high density value is printed, more toner is replenished. In such a state, when it is determined that “no toner”, it is assumed that the toner is already stored in the toner transport unit 246 (FIG. 7B). Conversely, when an image with a low density value is printed, a small amount of toner is replenished. Therefore, in this state, when it is determined that “no toner”, the amount of toner accumulated in the toner transport unit 246 is assumed to be smaller than that in the case of printing a dark image (FIG. 7 ( c)).

The free capacity of the toner transport unit 246 (that is, the amount until the supplied toner overflows) is the amount of toner replenished from the toner bottle 120 and the toner capacity that can be stored in the toner transport unit 246 (can be stored in the toner transport unit). Quantity). For example, it is calculated by the following formula (1).
Free capacity = capacity of toner transport section−replenishment toner amount (1)

The threshold value N for determining that the toner transport unit 246 is out of order is determined based on the free capacity of the toner transport unit 246 obtained by the above equation (1). The capacity of the toner transport unit 246 is fixed, and in this embodiment, it is 24 cm ³ . As described above, the toner replenishment amount is determined by the toner consumption amount. That is, it can be obtained from the density of the image being printed.

The toner replenishment after the determination of the absence of toner is a toner replenishment operation for returning to a state in which an image can be formed when the toner bottle 120 is not empty. For this reason, in the replenishment amount calculation process (S502) before determining that there is no toner, the amount of toner to be replenished is controlled according to the value of the density sensor 124. On the other hand, the replenishment amount in the toner replenishment after the determination of the absence of toner is a constant replenishment amount per trial, and is 4 cm ^{3 in} this embodiment. The toner replenishment after the determination of the absence of toner is a toner replenishment performed after it is determined that there is no toner, and therefore a larger amount of toner is replenished than the toner replenishment during the printing operation.

Since toner supply after the determination of no toner is constant, the supply amount per trial is constant, and the threshold value N for determining that the toner transport unit 246 is out of order is determined by the free capacity of the toner transport unit 246. In this embodiment, it is determined according to the correspondence between the free capacity of the toner conveying unit 246 and the threshold value N shown in FIG. In other words, the larger the available capacity, the greater the number of toner supply trials. In the present embodiment, the threshold N is 2 or more because the free capacity of the toner transport unit 246 never falls below 8 cm ³ when it is determined that “no toner”.

When the free capacity is obtained by the equation (1), as shown in FIG. 8, the threshold value of the number of trials for determining that the toner transport unit 246 is out of order is uniquely determined. For example, in the case of FIG. 7B, the free capacity of the toner transport unit 246 is calculated as 10 cm ^{3 according} to the equation (1), that is, the free capacity is 8 cm ³ or more and less than 12 cm ³ . The threshold value N for determining that is malfunctioning is 2. On the other hand, in the case of FIG. 7C, the free capacity of the toner transport unit 246 is calculated as 18 cm ³ by the equation (1), that is, the free capacity is 16 cm ³ or more and less than 20 cm ³ . The threshold value N for determining that is malfunctioning is found to be 4.

  In this way, the threshold value N for the number of toner replenishment trials for determining that the toner transport unit 246 is out of order is obtained. With this threshold value N, the replenishment can be stopped without overflowing the replenished toner from between the toner bottle 120 and the toner delivery port 245 of the toner transport unit 246. A method of using the calculated threshold value N will be described later with reference to FIG.

[Toner replenishment operation after toner out determination]
With reference to the flowchart of FIG. 6, toner replenishment after toner absence determination according to the present embodiment will be described. This flowchart is a continuation of S506 of the flowchart of FIG. In addition, FIG. 9 shows a display example of a UI screen based on the determination result of each step of FIG.

  The CPU 301 displays a screen (FIG. 9A) on the UI 330 for notifying the user that the toner is out and prompting the user to replace the toner bottle (S601). Thereafter, the CPU 301 calculates a threshold value N for determining the abnormality of the toner transport unit 246 by the above-described calculation method (S602). Next, the CPU 301 initializes a variable for the number of supply attempts to 0 (S603).

The CPU 301 determines whether or not the number of replenishment attempts is equal to or greater than the threshold value N−1 (S604). When the number of replenishment trials is less than N−1 (NO in S604), CPU 301 waits until toner bottle detection sensor 125 detects the insertion / extraction of toner bottle 120, as described above with reference to FIG. 10 (S605). ). When insertion / extraction of toner bottle 120 is detected (YES in S605), CPU 301 executes toner replenishment after determining the absence of toner (S606). As described above, in the present embodiment, a toner amount of 4 cm ³ is supplied to the toner transport unit 246. Then, the CPU 301 increments the number of replenishment trials by 1 (S607).

  Thereafter, the CPU 301 determines whether or not the value of the density sensor 124 is higher than the reference value (S608). If the value of density sensor 124 is equal to or greater than the reference value (YES in S608), CPU 301 cancels the “no toner” screen displayed in S601 (S609). Then, the process proceeds to S501 in FIG. When the value of the density sensor 124 is lower than the reference value (NO in S608), the CPU 301 displays a screen (FIG. 9B) for requesting the user to check whether the toner bottle 120 is not empty (FIG. 9B). S610). Then, the process returns to S604. The screen shown in FIG. 9B is displayed so as to replace the toner bottle 120 that is not empty, so that the number of replenishment attempts is counted up by inserting and removing the empty toner bottle 120 many times. It plays a role in preventing this.

  If the number of supply trials is equal to or greater than the threshold value N−1 (YES in S604), the CPU 301 displays a screen (FIG. 9C) indicating that a failure determination will be made at the next toner bottle insertion / removal (S611). As a result, when the toner supply after the next toner absence determination is attempted, if the toner density in the developing device 14 does not increase, it is determined that a failure has occurred. Thereafter, the CPU 301 waits until the insertion / extraction of the toner bottle 120 is detected (S612). When insertion / extraction of toner bottle 120 is detected (YES in S612), CPU 301 executes toner replenishment after determining the absence of toner (S613). Thereafter, the CPU 301 determines whether or not the value of the concentration sensor 124 is higher than the reference value after stirring the buffer screw 247 and the conveying screw 240 for a sufficient time (S614). If the value of the density sensor 124 is equal to or greater than the reference value as a result of executing the toner replenishment operation after the determination of the absence of toner (YES in S614), the process proceeds to S609. On the other hand, if the value of density sensor 124 is lower than the reference value (NO in S614), there is a possibility that toner will overflow if more toner is supplied, so CPU 301 is in a state where toner supply is prohibited. (S615). Then, the CPU 301 displays a failure screen (FIG. 9D) on the UI 330 (S616). This prohibition operation with respect to toner replenishment is provided to prevent overflow of toner, and the status of prohibiting replenishment is stored even when the power is turned OFF / ON. The supply prohibition state can be canceled through a predetermined screen or command by, for example, a service person.

  When the number of replenishment trials exceeds the threshold value N in S615, it is possible to prevent the toner from overflowing by controlling so as not to start the toner replenishment operation.

  As described above, according to this embodiment, it is possible to determine the state where the toner bottle is empty and the state where there is a possibility that the toner transport unit is out of order even in the configuration without the means for detecting the toner amount in the toner transport unit 246. The user can be prompted to perform a correct operation according to the situation. Further, since it is not necessary to provide a means for detecting the amount of toner in the toner conveying unit 246, the apparatus can be inexpensive and have a small configuration.

121 bottle motor, 124 density sensor, 125 toner bottle detection sensor, 126 developing motor, 300 control unit, 301 CPU, 302 ROM, 303 RAM, 330 UI

Claims (6)

Developing means for developing using toner;
A toner container that contains toner and is detachable from the image forming apparatus;
Toner conveying means for conveying toner from the mounted toner container to the developing means;
Toner density detecting means for detecting the density of toner held by the developing means;
An image forming apparatus having toner container detecting means for detecting whether or not the toner container is attached to the image forming apparatus;
First control means for performing a replenishment operation from the toner container to the developing means for the amount of toner consumed by the developing means via the toner conveying means;
First determination means for determining whether or not the toner container is empty according to the toner concentration detected by the toner concentration detection means after control of the toner replenishment operation by the first control means;
Calculating means for calculating the number of trials of toner replenishment operation based on the amount of toner being conveyed by the toner conveying means when it is determined that the toner container is empty;
If it is determined that the toner container is detached after the toner container is determined to be empty, the toner container is detected in advance via the toner conveying means with the calculated number of trials as an upper limit. Second control means for executing a toner replenishing operation from the toner container to the developing means with a defined amount of toner;
Second determination means for determining that the toner conveying means is faulty when the density detected by the toner density detection means does not exceed a reference value as a result of executing the toner supply operation for the calculated number of trials; An image forming apparatus comprising:   If the density detected by the toner density detection means does not exceed the reference value as a result of executing the toner replenishment operation less than the calculated number of trials, the second determination means further includes the toner container. The image forming apparatus according to claim 1, wherein it is determined that there is a possibility that an empty toner container is attached in the removal / removal of the toner container detected by the detection unit. The calculating means includes
From the amount of toner replenished by the first control means and the amount of toner that can be stored in the toner transport means, the free capacity of the toner transport means is calculated,
3. The image forming apparatus according to claim 1, wherein the number of trials of toner replenishment is calculated according to a free capacity of the toner conveying unit.   4. The image forming apparatus according to claim 1, wherein the second determination unit prohibits a toner replenishing operation when it is determined that the toner conveying unit is out of order. 5. .   5. The image forming apparatus according to claim 4, further comprising means for receiving an instruction to cancel the state in which toner replenishment is prohibited.   6. The image forming apparatus according to claim 1, further comprising a display unit that displays a determination result by the first or second determination unit.

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