JP2011069899A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device which adopts a system in which excess developer is discharged from a discharge port while the developer is supplied thereto, and develops an electrostatic latent image formed on a surface of a photoreceptor while a plurality of developing units integrally move and rotate, and for which such support that color material is not supplied excessively to the developing device without using a means for detecting concentration of the color material in the developer. <P>SOLUTION: When determining that a density difference of a patch image is equal to or above a replenishment decision threshold, a controller 11 specifies a cause that the density difference of the patch image does not become under the replenishment decision threshold even when processing for supplying toner is repeated on the basis of the cumulative rotational frequency of a replenishment screw D5 and the cumulative rotational frequency of a conveying tool C2. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus.

  In a developing device using a two-component developer having a toner as a color material and a carrier as a magnetic powder, the developer is prevented in order to prevent the developer from being stirred and deteriorated over a long period in the developing device. In some cases, an excessive developer is discharged from the discharge port (hereinafter referred to as trickle method) while being supplied. For example, Patent Document 1 discloses a technique for controlling the replenishment and discharge of a developer with high accuracy in a developing device that uses a two-component developer employing a trickle system. Further, in a developing device (hereinafter referred to as a rotary developing device) that develops an electrostatic latent image formed on the surface of a photoconductor while a plurality of developing devices rotate and move integrally, the developer is conveyed while being stirred. The toner concentration in the agitating and conveying space is measured by a sensor, and the toner supply amount is changed based on the result. For example, Patent Document 2 discloses a technique in which a sensor disposed in the vicinity of a stirring and conveying space detects toner concentration based on magnetic permeability.

JP-A-10-090991 JP-A-01-253769

  The present invention employs a system in which excess developer is discharged from a discharge port while being supplied with a developer, and an electrostatic latent image formed on the surface of a photoconductor while a plurality of developing devices rotate and move integrally. An object of the present invention is to provide a developing apparatus that develops the toner without providing a means for detecting the density of the color material in the developer so that the color material is not excessively supplied to the development apparatus.

  According to the first aspect of the present invention, there is provided a container having a first conveying means for accommodating a color material and conveying the color material, and a color material supplied from the container by the rotation of the first conveying means. An adjustment chamber having a second transfer means for transferring, and a magnetic material added to the color material supplied from the adjustment chamber by the rotation of the second transfer means to be charged while stirring and transferring; A plurality of developing units each having a developing chamber having a discharge port for discharging a magnetic body, each of which accommodates a latent image formed on the image holding body while rotating integrally. Developing means for developing with a color material and forming an image on the image carrier, transfer means for transferring the image formed on the image carrier to a transfer body, and detecting the density of the image transferred by the transfer means Detecting means for detecting and an image formed by the developing means are predetermined. When the difference between the density and the density of the image detected by the detection unit is equal to or greater than the threshold value, the difference between the predetermined density of the image formed by the developing unit and the density of the image detected by the detection unit is the threshold value. An image forming apparatus comprising: a specifying unit that identifies the cause of the above based on the number of rotations of the second conveying unit and the number of rotations of the first conveying unit.

  According to a second aspect of the present invention, in the configuration according to the first aspect, the specifying unit is configured to determine a transfer capability of the first transfer unit and a capacity of the container with respect to a rotation speed of the second transfer unit. A storage means for storing a first threshold value determined in accordance with the second threshold value determined in accordance with a transfer capability of the second transfer unit and a capacity of the developing device; If the number of rotations of the means is equal to or greater than the second threshold value, and the number of rotations of the first transport means is less than the first threshold value in the previous period, a failure has occurred in the own apparatus as the cause. An image forming apparatus that identifies the presence of the image forming apparatus.

  According to a third aspect of the present invention, in the configuration according to the second aspect, when it is specified by the specifying means that a failure has occurred, a process of reducing the amount of the color material in the developing chamber is performed. An image forming apparatus characterized by comprising means.

  According to a fourth aspect of the present invention, in the configuration according to the first aspect, the specifying unit is configured to determine a transfer capacity of the first transfer unit and a capacity of the container with respect to a rotation speed of the second transfer unit. Storage means for storing a first threshold value determined in accordance with the second threshold value determined in accordance with a transfer capability of the second transfer unit and a capacity of the developing device, and the second transfer unit. If the number of rotations of the means is equal to or higher than the second threshold and the number of rotations of the first conveying means is equal to or higher than the first threshold in the previous period, the cause is the color stored in the container. An image forming apparatus is characterized in that a material shortage is specified.

  According to a fifth aspect of the present invention, in the configuration of the first to fourth aspects, the image forming apparatus according to any one of the first to fourth aspects further includes a notifying unit that notifies the cause specified by the specifying unit. It is.

According to the first aspect of the present invention, when the rotary developing device adopting the trickle method performs density adjustment, the difference between the density of the image to be formed by the developing device and the density of the image measured by the image density sensor is The cause which became more than a threshold value can be specified from the rotation speed of the replenishment screw D5 and the rotation speed of the conveyance tool C2.
According to the second aspect of the present invention, the cause of the difference between the density of the image to be formed by the developing unit and the density of the image measured by the image density sensor being equal to or greater than the threshold is determined based on the rotational speed of the replenishing screw D5 and the conveying tool. It can be identified as a failure from the rotational speed of C2.
According to the third aspect of the present invention, when it is determined that a failure has occurred, a process for reducing the amount of the color material in the developing chamber can be attempted.
According to the fourth aspect of the present invention, the cause of the difference between the density of the image to be formed by the developing unit and the density of the image measured by the image density sensor being equal to or greater than the threshold is determined based on the rotation speed of the replenishing screw D5 and the conveying tool. It can be specified that the color material is insufficient from the rotational speed of C2.
According to the fifth aspect of the present invention, the cause of the difference between the density of the image to be formed by the developing unit and the density of the image measured by the image density sensor being equal to or greater than the threshold value is determined based on the rotational speed of the supply screw D5 and the conveying tool. When specified from the rotation speed of C2, it can be notified.

1 is a block diagram illustrating a configuration of an image forming apparatus 1 according to an embodiment of the present invention. 2 is a diagram illustrating a structure of an image forming unit 16 according to the same embodiment. FIG. It is a figure which shows the structure of the image development part 164 which concerns on the embodiment. It is a figure which shows the structure of the container C and the developing device D which concern on the embodiment. 5 is a flowchart for explaining the operation of the image forming apparatus 1 instructed to print according to the embodiment. 4 is a flowchart for explaining the operation of the image forming apparatus 1 during density correction according to the embodiment. 10 is a flowchart for explaining the operation of the image forming apparatus 1 when specifying a fault location according to a modification of the embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

(1) Configuration FIG. 1 is a block diagram illustrating a configuration of the image forming apparatus 1.
The image forming apparatus 1 uses, for example, printing or scanning to form an image on a recording sheet that is an example of a recording medium using toner that is an example of a color material, or to read an image formed on the recording sheet. It is a device that integrates functions such as copying. The image forming apparatus 1 includes a control unit 11, a storage unit 12, an operation unit 13, a display unit 14, an image reading unit 15, and an image forming unit 16.

  The control unit 11 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and the CPU executes a program stored in the ROM or the storage unit 12. Thus, each part of the image forming apparatus 1 is controlled. The storage unit 12 is a nonvolatile auxiliary storage device such as an HD (Hard Disk) and functions as an example of a storage unit that stores various programs and data. The operation unit 13 includes a power switch and a plurality of keys. The operation unit 13 receives a user operation and supplies a signal corresponding to the operation to the control unit 11. The display unit 14 includes a VRAM (Video RAM), a liquid crystal display, and a liquid crystal drive circuit. Based on information supplied from the control unit 11, the display unit 14 displays the progress of processing, information for guiding operations to the user, and the like. It functions as an example of the notification means. The image reading unit 15 includes an optical system member constituted by a CCD (Charge Coupled Device), reads an image formed on a recording sheet by the optical system member, and generates image data representing the read image. The image forming unit 16 includes a photosensitive drum 161, a charging unit 162, an exposure unit 163, a developing unit 164, a transfer unit 165, a fixing unit 166, a paper supply unit 167, and an image density sensor 168. An image based on image data generated by the image reading unit 15 or image data received from the outside by a communication unit (not shown) such as a host device is formed on a recording sheet.

FIG. 2 is a diagram illustrating the structure of the image forming apparatus 1.
The paper supply unit 167 includes a paper supply source 167a and a conveyance unit for conveying the recording paper from the paper supply source 167a via a conveyance path S indicated by a dotted line in the drawing. The paper supply source 167a includes a means for storing recording paper. The transport means includes a transport roll and a resist roll for transporting the recording paper. The photosensitive drum 161 is a cylindrical member including a conductive drum base and a photoconductive film in which an OPC (Organic Photo Conductor) is formed on the surface of the drum base. The photosensitive drum 161 functions as an example of an image holding member that rotates at a predetermined peripheral speed in the direction of arrow a in the drawing with the center of the drum base as a rotation axis while maintaining a state in contact with the intermediate transfer belt. To do. The charging unit 162 is a charging member whose surface is in contact with the surface of the photosensitive drum 161, and charges the surface of the photosensitive drum 161 to a predetermined polarity and potential while rotating according to the rotation of the photosensitive drum 161. . The exposure unit 163 includes a laser emission source, a polygon mirror, and the like, and forms an electrostatic latent image by irradiating image-modulated laser light toward the peripheral surface of the photosensitive drum 161. An electrostatic latent image is a latent image formed by the difference between the potential of an exposed area and the potential of an unexposed area.

  The transfer unit 165 is an example of a transfer unit, and includes an intermediate transfer belt 165a, a support roll 165b, a primary transfer roll 165c, a secondary transfer roll 165d, and a counter roll 165e. The intermediate transfer belt 165a is an endless belt member. The intermediate transfer belt 165a is rotated in the direction of arrow c in a state where the inner peripheral surface thereof is stretched by a plurality of support rolls 165b, a primary transfer roll 165c, and a secondary transfer roll 165d. It is done. The primary transfer roll 165c is provided at a position facing the photosensitive drum 161 with the intermediate transfer belt 165a interposed therebetween, and a toner image formed on the surface of the photosensitive drum 161 is an outer peripheral surface of the intermediate transfer belt 165a which is an example of a transfer member. Primary transfer. The secondary transfer roll 165d secondarily transfers the toner image transferred to the outer peripheral surface of the intermediate transfer belt 165a onto the recording sheet in a region where the intermediate transfer belt is sandwiched between the secondary transfer roll 165e. The fixing unit 166 includes a heating roll 166a and a pressure roll 166b that are opposed to each other with the conveyance path S interposed therebetween. The fixing unit 166 fixes the toner image on the recording paper by applying pressure and heat to the recording paper on which the toner image is secondarily transferred by the heating roll 166a and the pressure roll 166b. The image density sensor 168 is a sensor that measures the density of the toner image transferred to the intermediate transfer belt 165a, and is provided at a position facing the peripheral surface of the intermediate transfer belt 165a. The image density sensor 168 functions as an example of a detection unit. The control unit 11 controls a developing unit 164 described later based on the image density measured by the image density sensor 168.

FIG. 3 is a diagram illustrating the structure of the developing unit 164.
The developing unit 164 is an example of a developing unit, and is a developing device that develops an electrostatic latent image formed on the surface of the photoconductor while a plurality of developing devices are integrally rotated, that is, a rotary type developing device. . Around the rotation axis D14, each container C that stores toner of each color of yellow (Y), magenta (M), cyan (C), and black (K) is spaced at intervals of 90 degrees of the central angle. Developing devices Dy, Dm, Dc, and Dk are provided. The developing devices Dy, Dm, Dc, and Dk are sequentially moved to a predetermined developing position P facing the photosensitive drum 161 by rotating in the direction of the arrow b in the figure about the rotation axis D14. The electrostatic latent image formed on the photosensitive drum 161 is developed by approaching the photosensitive drum 161. Since the developing units Dy, Dm, Dc, and Dk have almost the same configuration, they are referred to as a developing unit D when there is no need to distinguish them. In the developing device D, a two-component developer having a toner containing a dye or a pigment based on a polyester resin and a carrier that is a magnetic powder is used.

FIG. 4 is a view showing the structure of the container C and the developing device D.
The container C is a member that can be attached to and detached from the developing unit 164, and includes a cylindrical casing C1 that stores a predetermined amount of toner of each color, and a conveyance tool C2 that is stored in the casing C1. I have. The transport tool C2 is, for example, a wire wound spirally in accordance with the inner diameter of the housing C1. The transport tool C2 is rotated in the direction of the arrow i in the figure, whereby the toner contained in the housing C1 is discharged to the discharge port C3 which is an opening provided at the end of the housing C1. It functions as an example of a first transport unit that transports while stirring. The toner discharged from the discharge port C3 of the container C is supplied to the adjustment chamber D1 of the developing device D. The control unit 11 causes the storage unit 12 to store the cumulative number of rotations of the transport tool C2 counted from 0 each time the container C is replaced. It means that the larger the cumulative number of revolutions, the smaller the amount of toner in the container C. The cumulative number of rotations of the transport tool C2 may be calculated using the period during which the control unit 11 rotates the transport tool C2, or a count mechanism for counting the number of rotations is provided in the transport tool C2. The control unit 11 may calculate using the counter mechanism.

  The adjusting chamber D1 of the developing device D is formed in a cylindrical shape having the main scanning direction as a longitudinal direction. In the adjustment chamber D1, an adjustment chamber inlet D3 communicating with the discharge port C3 of the container C and an adjustment chamber outlet D4 communicating with the developing chamber D2 are formed at both ends in the longitudinal direction. The adjusting chamber D1 is provided with a replenishing screw D5 that is a conveying member. When the replenishing screw D5 is rotated in the direction of the arrow e in the figure, it functions as an example of a second conveying means for conveying the toner in the adjusting chamber D1 from the adjusting chamber inlet D3 toward the adjusting chamber outlet D4. The size and shape of the replenishing screw D5 and the number of revolutions per unit time are such that the adjusting chamber is rotated once when the replenishing screw D5 is rotated in the adjusting chamber D1 when a sufficient amount of toner exceeds a predetermined amount. It is designed such that a predetermined amount (hereinafter referred to as a unit supply amount) of toner is supplied from D1 to the developing chamber D2. The control unit 11 adjusts the amount of toner replenished from the adjustment chamber D1 to the developing chamber D2 by controlling the number of rotations per unit time of the replenishment screw D5. However, a predetermined amount of toner as described above is not always supplied from the adjustment chamber D1 to the development chamber D2. This is because, in the case of the developing unit 164 using the rotary method, the force applied to the toner when the developing device D is rotated about the rotation axis D14, or the toner applied when the replenishing screw D5 rotates. This is because the density of the toner in the adjustment chamber D1 is likely to occur due to the applied force.

  To the developing chamber D2 of the developing device D, toner is supplied from the adjusting chamber D1, and a carrier is supplied from a supply source (not shown). A partition D11 extending in the main scanning direction is provided in the developing chamber D2, and the developing chamber D2 is divided into a first developing chamber D9 and a second developing chamber D10 by the partition. In this partition wall, holes are provided in one end and the other end in the longitudinal direction, and the first developing chamber D9 and the second developing chamber D10 communicate with each other through the holes. The first developing chamber D9 is provided with a first stirring screw D6 having a longitudinal direction in the main scanning direction. The first agitating screw D6 rotates in the direction of the arrow f in the drawing, so that the toner and carrier (hereinafter collectively referred to as a developer) in the first developing chamber D9 are transferred to the first developing chamber D9. It is a conveyance member conveyed in the direction which goes to the other edge part from one edge part of the longitudinal direction. The second developing chamber D10 is provided with a second stirring screw D7 and a developing roll D8 having a longitudinal direction in the main scanning direction. The second agitating screw D7 rotates in the direction of the arrow g in the drawing, so that the developer in the second developing chamber D10 is transferred from the other end in the longitudinal direction of the second developing chamber D9 to one end. It is a conveyance member conveyed in the direction which goes to. That is, the first stirring screw D6 and the second stirring screw D7 respectively convey the developer in the developing chamber D2 by conveying the developer in opposite directions. The first stirring screw D6 and the second stirring screw D7 charge the developer by stirring while conveying the developer. The developing roll D8 is composed of a magnet roll arranged in a fixed state inside and a developing sleeve provided rotatably on the outer periphery of the magnet roll. Further, the developing roll D8 attracts the developer to the surface by the magnetic attraction force of the magnet roll, and develops the toner by attaching the toner to an area corresponding to the electrostatic latent image formed on the surface of the photosensitive drum 161. Do. Further, on the side surface of the first developing chamber D9, the developing in the adjusting chamber D1 which has become excessive due to the carrier whose surface is deteriorated due to continuous stirring with the toner and the charging performance is deteriorated or the toner supplied from the container C is excessive. For the purpose of discharging the agent, a discharge port D12 which is an opening is provided. When the developer is discharged from the discharge port D12 of the developing device D, the developer is stored in a collection container D13 that is a detachable member. However, when the toner exceeding the capacity of the collection container D13 is supplied from the container C to the development unit D as a surplus, the developer that cannot be discharged into the collection container D13 fills the development unit D. The developer overflowing from the developing device D stains the inside of the image forming apparatus 1.

  Such a situation where the developer overflows from the developing device D may occur even if a sensor for measuring the toner density (hereinafter referred to as a toner density sensor) is provided in the developing chamber D2. More specifically, the developing device D provided in the rotary type developing unit 164 is rotated around the rotation axis D14, and the density applied to the developer is easily generated by the force applied to the developer during the rotation. Become. That is, the toner density sensor measures the toner density of the developer having a density that is large regardless of where the toner density sensor is provided in the developing chamber D2, and therefore the toner density varies depending on the measurement location. It will be. For example, it is assumed that the toner density sensor measures that the density of the developer at the location where the toner density is measured is rough and the toner density is low. Also in this case, since the control unit 11 determines that toner needs to be supplied from the container C to the developing device D, toner that does not need to be supplied is supplied from the container C to the developing device D. It will end up.

(2) Operation FIG. 5 is a flowchart for explaining the operation of the image forming apparatus 1 instructed to print.
The control unit 11 of the image forming apparatus 1 determines whether or not it has been instructed to perform a process of forming an image based on image data received from the outside on a recording sheet (hereinafter, this process is referred to as printing) ( Step S51), the process of step S51 is repeated until a print instruction is given (step S51; NO). Here, the user operates the operation unit 13 to instruct printing. When the control unit 11 detects that a print instruction has been issued (step S51; YES), the amount of toner used to form an image corresponding to the image data on the recording paper (hereinafter referred to as toner consumption amount). calculate. This toner consumption amount is calculated based on the ratio (hereinafter referred to as image density) of the pixel group constituting the image formed on the recording paper in the area where the image can be formed on each recording paper. . For example, when the image density is 15%, the control unit 11 sets the amount of toner that can cover 15% of the area where the image can be formed on the recording paper as the toner consumption amount. The amount of toner stored in the developing device D (for example, the developing chamber D2) is decreased by an amount corresponding to the toner consumption calculated as described above. When the amount of toner stored in the developing chamber D2 is insufficient, there arises a problem that the print quality is deteriorated, such as unevenness in the density of the image formed on the recording paper. Therefore, the control unit 11 specifies the amount of toner corresponding to the toner consumption amount as the amount of toner (toner supply amount) to be supplied from the container C to the developing chamber D2 (step S52).

  Next, the control unit 11 controls the image forming unit 16 to form an image corresponding to the image data on the recording paper (step S53). Immediately after the start of image formation, the control unit 11 controls the rotation of the replenishing screw D5 provided in the adjustment chamber D1 of the developing unit 164, and an amount of toner corresponding to the toner consumption specified in step S52. Is supplied from the adjusting chamber D1 to the developing chamber D2 (step S54). More specifically, the control unit 11 rotates the supply screw D5 by a value obtained by dividing the toner supply amount by the unit supply amount described above. With the above processing, the toner density inside the adjustment chamber D1 is increased by the amount of toner replenished by performing the processing in step S53.

  However, the amount of toner replenished when the replenishing screw D5 rotates depends on the toner density distribution in the adjustment chamber D1. Therefore, the control unit 11 causes the image density sensor 168 to detect the density of the patch image formed on the intermediate transfer belt 165a, thereby confirming whether or not the toner density in the developing chamber D2 has a predetermined value. To do. Hereinafter, the process of correcting the toner density in the developing chamber D2 to a predetermined value is referred to as density correction.

FIG. 6 is a flowchart for explaining the operation of the image forming apparatus 1 during density correction.
The control unit 11 functioning as an example of the specifying unit determines whether or not it is time to execute density correction (step S61), and repeats the process of step S61 until it is time to execute density correction (step S61; NO). The control unit 11 determines that it is time to perform density correction, for example, between processing of forming an image or after forming a predetermined number of images (step S61; YES). In this case, the control unit 11 first controls the exposure unit 163 and the development unit 164 of the image forming unit 16 to form a patch image on the intermediate transfer belt 165a (step S62). The patch image is formed on the basis of a predetermined density by toner of each color of yellow (Y), magenta (M), cyan (C), and black (K). This predetermined density is stored in the storage unit 12 as image data of a patch image. The patch image formed on the intermediate transfer belt 165a moves to the measurement area of the image density sensor 168 as the intermediate transfer belt 165a rotates. The control unit 11 controls the image density sensor 168 to measure the density of the patch image located in the measurement area (step S63). Here, the storage unit 12 is based on the difference between the density determined in advance as the image data of the patch image and the actually measured density of the patch image (hereinafter referred to as the density difference of the patch image). It is assumed that a reference value (hereinafter referred to as a replenishment determination threshold value) for determining whether or not toner replenishment is necessary is stored in the developing chamber D2. Then, the control unit 11 calculates the density difference of the patch image from the difference between the density predetermined as the image data of the patch image formed in step S62 and the density of the patch image measured in step S63. Further, the control unit 11 determines whether or not the calculated patch image density difference is less than the replenishment determination threshold value stored in the storage unit 12 (step S64). This supply determination threshold value functions as an example of a threshold value.

  When the control unit 11 determines that the density difference between the patch images is equal to or greater than the replenishment determination threshold value (step S64; NO), the cumulative number of rotations of the replenishment screw D5 in the density correction process and the replenishment screw D5 in the density correction process. It is determined whether the number is less than the number that can be rotated (hereinafter referred to as an abnormality determination threshold) (step S66). That is, the abnormality determination threshold is an example of a second threshold. Here, the cumulative rotation speed of the supply screw D5 is the number of rotations of the supply screw D5 in the density correction process, and is stored in the storage unit 12. In addition, it is assumed that an abnormality determination threshold is stored in the storage unit 12 as a threshold of the number that the supply screw D5 can rotate in the density correction process. More specifically, the abnormality determination threshold is a value for regulating the amount of toner that can be replenished to the developing chamber D2 in one density correction process, and the conveyance capability of the replenishing screw D5 and the capacity of the developing chamber D2. And calculated from When the replenishing screw D5 rotates more than the abnormality determination threshold, excessive toner is supplied to the developing chamber D2, and the inside of the image forming apparatus 1 may be contaminated with the developer overflowing from the developing chamber D2. is there.

  If the controller 11 determines in step S66 that the cumulative rotation speed of the replenishing screw D5 is less than the abnormality determination threshold value (step S66; YES), it is assumed that sufficient toner has not been replenished in the developing chamber D2. The replenishing screw D5 is controlled to replenish a predetermined amount of toner to the developing chamber D2 (step S67). Further, the control unit 11 stores in the storage unit 12 a value obtained by adding the number of rotations of the replenishment screw D5 to the cumulative rotation number of the replenishment screw D5 in the process of step S67 (step S68), and performs the processes after step S62. Perform again.

  On the other hand, if the control unit 11 determines in step S66 that the cumulative rotation number of the replenishing screw D5 is equal to or greater than the abnormality determination threshold value (step S66; NO), the patch may be repeated even if the toner replenishing process in step S67 is repeated. Investigate why the difference in image density does not fall below the supply determination threshold. First, the control unit 11 determines whether or not the cumulative number of rotations of the transport tool C2 stored in the storage unit 12 is less than a threshold value indicating a decrease in the remaining amount (step S69). This value is stored in the storage unit 12 and is a value for determining that the remaining amount of toner stored in the container C is significantly reduced when the transport tool C2 rotates beyond the threshold value. That is, the threshold value indicating the remaining amount decrease is an example of a first threshold value. When the control unit 11 determines that the accumulated rotational speed is equal to or greater than the threshold value indicating a decrease in the remaining amount (step S69; NO), as the cause, sufficient toner is contained in the container C and the adjustment chamber D1 that are toner supply sources. Therefore, it is determined that sufficient toner is not supplied to the developing chamber D2. Then, the control unit 11 displays on the display unit 14 that the remaining amount of toner in the container C has decreased and that it is time to replace the container C (step S70). Further, when the control unit 11 determines that the accumulated rotational speed is less than the threshold value indicating a decrease in the remaining amount (step S69; YES), the controller 11 specifies that the developing device D or the image density sensor 168 has failed as the cause. . This is because the density of the patch image detected by the image density sensor 168 is less than the replenishment determination threshold value even though sufficient toner is accommodated in the container C of the developing device D and sufficient replenishment is performed. By not becoming. Then, the control unit 11 displays on the display unit 14 that a failure has occurred in the image forming unit 16, and stops the function of the image forming unit 16 (step S71).

  Note that when the control unit 11 determines that the patch image density difference in step S64 is less than the replenishment determination threshold (step S64; YES), it displays that the remaining amount of toner in the container in step S70 has decreased. When the processing to complete or the processing to display that a failure has occurred in step S71 is completed, the accumulated rotational speed of the supply screw D5, which is a variable stored in the storage unit 12, is described as 0 and the concentration The correction process is terminated (step S65).

  According to the above embodiment, when the control unit 11 determines that the density difference between the patch images is equal to or greater than the replenishment determination threshold value, the control unit 11 determines that the cumulative rotation number of the replenishment screw D5 and the cumulative rotation number of the transport tool C2 are the same. Based on this, the reason why the density difference of the patch image does not become less than the replenishment determination threshold value even if the process of replenishing toner is repeated is specified and notified. The user performs necessary work according to this notification. Therefore, the situation where the toner is excessively supplied to the developing device is suppressed without using the toner concentration sensor.

(3) Modification (3-1) Modification 1
In the above embodiment, the control unit 11 displays on the display unit 14 that a failure has occurred and that the remaining amount of toner in the container C has decreased. However, the control unit 11 is not limited to this, and outputs a signal indicating that an abnormality has occurred in an external device such as a host device from a communication unit (not shown) to the display unit or the like of the external device. An abnormality may be displayed. In other words, the method for notifying the image forming apparatus 1 of the abnormality may be any method that allows a person who uses the image forming apparatus 1 to know that an abnormality has occurred in the image forming apparatus 1.
Further, after displaying that a failure has occurred in the process of step S71 of FIG. 6, the control unit 11 may further perform a process of specifying a location where the failure has occurred.
FIG. 7 is a flowchart for explaining the operation of the image forming apparatus 1 when a failure location is specified.
Here, as a premise, the control unit 11 executes the processing of the flowchart of FIG. 6 to perform, for example, density correction processing for the developing device Dy, and a failure has occurred in either the developing device Dy or the image density sensor 168. Is detected. In response to this detection, the control unit 11 rotates the developing unit 164 about the rotation axis D14 in the direction of the arrow b in FIG. 3, thereby developing different from the developing device Dy that may be malfunctioning. The developing device, for example, the developing device Dm is moved to the developing position P facing the photosensitive drum 161 (step S711). Then, the control unit 11 controls the exposure unit 163, the developing device Dy, and the like to form a patch image on the intermediate transfer belt 165a (step S712). This patch image is formed based on a predetermined density stored in the storage unit 12. The patch image formed on the intermediate transfer belt 165a moves to the measurement area of the image density sensor 168 as the intermediate transfer belt 165a rotates. The control unit 11 controls the image density sensor 168 to measure the density of the patch image located in the measurement region (step S713). Then, the control unit 11 calculates the density difference of the patch image from the difference between the density predetermined as the image data of the patch image formed in step S712 and the density of the patch image measured in step S713. Then, the control unit 11 determines whether the calculated patch image density difference is less than a replenishment determination threshold value that is a reference value for determining whether or not the developing chamber D2 stored in the storage unit 12 needs to be replenished with toner. It is determined whether or not (step S714). Here, it is assumed that the control unit 11 determines that the density difference between the patch images is less than the replenishment determination threshold value stored in the storage unit 12 (step S714; YES). In this case, since the measurement result of the image density sensor 168 is different between step S63 in FIG. 6 and step S713 in FIG. 7, the control unit 11 determines that the image density sensor 168 is functioning normally. . Then, the control unit 11 detects that a failure has occurred in the developing device Dy because the image density sensor 168 is functioning normally among the developing device Dy and the image density sensor 168 identified as the failure location in the processing of FIG. (Step S715). Then, the control unit 11 displays on the display unit 14 that a failure has occurred in the developing device Dy of the image forming unit 16 and stops the function of the image forming unit 16 (step S716).
On the other hand, it is assumed that the control unit 11 determines that the density difference of the patch image is greater than or equal to the replenishment determination threshold value stored in the storage unit 12 (step S714; NO). In this case, since the measurement results of the image density sensor 168 are the same in step S63 in FIG. 6 and step S713 in FIG. 7, the control unit 11 replenishes toner in the same manner as the processing in FIG. Also, it is determined that there is a possibility that the density difference between the patch images does not become less than the supply determination threshold. Then, the controller 11 specifies that the cause of the density difference of the patch images not being less than the replenishment determination threshold without performing the toner replenishment is the failure of the image density sensor 168 (step S717). Then, the control unit 11 displays on the display unit 14 that a failure has occurred in the image density sensor 168, and stops the function of the image forming unit 16 (step S718). By adopting this configuration, the control unit 11 specifies not only the fault location in the image forming unit 16 but also the image density sensor 168 or the developing unit 164 constituting the image forming unit 16.
(3-2) Modification 2
In the above-described embodiment, the control unit 11 develops the amount of toner (toner consumption) consumed when forming an image instructed to be printed on a recording sheet from the adjustment chamber D1 during the print processing corresponding to the instruction. Control was made to replenish chamber D2. However, the control method in which the control unit 11 replenishes toner for the toner consumption amount from the adjustment chamber D1 to the development chamber D2 is not limited to this. For example, it is assumed that the image forming apparatus 1 receives a plurality of print instructions successively. In this case, the control unit 11 collects the toner consumption amount according to the subsequent print instruction and the toner consumption amount according to the preceding print instruction, from the adjustment chamber D1 during the print processing according to the preceding print instruction. It may be controlled to replenish the developing chamber D2. That is, the control unit 11 may perform control so that the toner consumption corresponding to the print instruction is supplied from the adjustment chamber D1 to the development chamber D2 at any timing.

(3-3) Modification 3
In the above embodiment, as a member for transporting the developer, the transport tool C2, the replenishing screw D5, the stirring screw D6, and the stirring screw D7 are used. However, the member for transporting the developer is not particularly limited as long as the member can transport the developer in response to the control from the control unit 11.

(3-4) Modification 4
By providing a sensor for detecting the amount of developer inside the collection container D13, the control unit 11 detects in advance that the amount of developer inside the collection container D13 exceeds the volume of the collection container D13. It may be configured. Furthermore, the control unit 11 controls the display unit 14 or a communication unit (not shown) to notify an external device such as a host device of an abnormality using a detection signal of a sensor provided in the collection container D13 as a trigger. Also good.

(3-5) Modification 5
When the control unit 11 identifies the cause as a failure of any member of the image forming unit 16 (step S69; YES), the control unit 11 controls the image forming unit 16 to develop the developing chamber D2 of the developing unit 164. Control for reducing the amount of the developer may be performed. For example, the control unit 11 exposes the photosensitive drum 161 to the exposure unit 163 and further develops the developing unit 164, whereby the developer in the developing chamber D2 is supplied to the surface of the photosensitive drum 161. Further, since the developer supplied to the surface of the photosensitive drum 161 is collected by a cleaning member (not shown) that scrapes off the developer and the like attached to the surface of the photosensitive drum 161, the inside of the image forming apparatus 1 is soiled. There is nothing. That is, the control unit 11 and the image forming unit 16 function as an example of a processing unit.

(3-6) Modification 6
In the embodiment described above, the control unit 11 determines whether or not a failure has occurred based on the rotation speeds of the supply screw D5 and the transport tool C2. However, the determination of whether or not a failure has occurred is not limited to the rotation speed of the supply screw D5 and the conveying tool C2. For example, the control unit 11 may determine whether or not a failure has occurred based on the time when the control unit 11 controls the replenishment screw D5 and the conveyance tool C2, and the amount of toner conveyed by the replenishment screw D5 and the conveyance tool C2. good.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 11 ... Control part, 12 ... Memory | storage part, 13 ... Operation part, 14 ... Display part, 15 ... Image reading part, 16 ... Image forming part, 161 ... Photosensitive drum, 162 ... Charging part, 163 DESCRIPTION OF SYMBOLS Exposure unit, 164: Development unit, C: Container, C1: Housing, C2: Transport tool, C3: Discharge port, D: Development unit, D1: Adjustment chamber, D2: Development chamber, D3: Adjustment chamber inlet, D4 ... adjusting chamber outlet, D5 ... replenishing screw, D6 ... first stirring screw, D7 ... second stirring screw, D8 ... developing roll, D9 ... first developing chamber, D10 ... second developing chamber, D11 ... Partition, D12 ... discharge port, D13 ... collection container, D14 ... rotating shaft, 165 ... transfer section, 165b ... support roll, 165e ... opposing roll, 165c ... primary transfer roll, 165a ... intermediate transfer belt, 165d ... primary transfer roll, 166... Fixing unit, 1 6b ... pressure roll, 166a ... heating roller, 167 ... sheet supplying unit, 167a ... paper source, S ... conveyance path, 168 ... image density sensor.

Claims (5)

A container having a first conveying means for accommodating the color material and conveying the color material; and a second conveying means for conveying the color material supplied from the container by the rotation of the first conveying means. An adjustment chamber provided, and a magnetic material added to the color material supplied from the adjustment chamber by the rotation of the second conveying means to be charged while stirring and conveying, and a discharge port for discharging the color material and the magnetic material A plurality of developing units each having a developing chamber provided therein, while developing and moving the latent image formed on the image holding body with the color material accommodated in each of the containers while integrally rotating. Developing means for forming an image on a holding member;
Transfer means for transferring the image formed on the image carrier to a transfer body;
Detection means for detecting the density of the image transferred by the transfer means;
When the difference between the predetermined density of the image formed by the developing unit and the density of the image detected by the detecting unit is equal to or greater than a threshold value, the predetermined density of the image formed by the developing unit and the detection A specifying means for specifying the cause of the difference between the image density detected by the means being equal to or greater than a threshold value based on the rotational speed of the second transport means and the rotational speed of the first transport means;
An image forming apparatus comprising: The specifying means is:
For the rotation speed of the second transport means, a first threshold value determined according to the transport capacity of the first transport means and the capacity of the container, the transport capacity of the second transport means, and the A storage means for storing a second threshold value determined according to the capacity of the developing device;
If the rotation speed of the second transport means is equal to or higher than the second threshold value, and the rotation speed of the first transport means is less than the first threshold value, the cause is The image forming apparatus according to claim 1, wherein a failure has been identified. The image forming apparatus according to claim 2, further comprising a processing unit configured to perform a process of reducing the amount of the color material in the developing chamber when the specifying unit determines that a failure has occurred. The specifying means is:
Regarding the rotation speed of the second transport means, a first threshold value determined according to the transport capacity of the first transport means and the capacity of the container, the transport capacity of the second transport means, and the A storage means for storing a second threshold value determined according to the capacity of the developing device;
When the rotation speed of the second transfer means is equal to or higher than the second threshold value, and further, when the rotation speed of the first transfer means is equal to or higher than the first threshold value, the cause is the container. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus identifies that the color material accommodated in the container is insufficient. The image forming apparatus according to claim 1, further comprising a notifying unit that notifies the cause specified by the specifying unit.

Images