JP2013050546A - Developing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine a state of developer stored in a developing unit by means of rotation of developing means.SOLUTION: A rotary developing part 21 includes developing units 210Y, 210M, 210C, 210K equipped with sensors 121Y, 121M, 121C, 121K, respectively, for measuring toner density. An image forming device with the rotary developing part 21 measures toner density for a certain developing unit, in a state (0°) where the developing unit faces a photoreceptor drum 111 and other states (90°, 180°, 270°), to determine the state of the developer on the basis of the difference between the measured toner densities. For example, the image forming device determines that the developer is solidified in the developing unit when the difference between the toner densities measured in four states is less than a predetermined threshold (or there is little difference).

Description

  The present invention relates to a developing device and an image forming apparatus.

  For a two-component developer containing toner and carrier, there are an optical method and a magnetic method as a method for measuring the toner density, which is the mixing ratio of toner and carrier. For example, the optical method measures the toner density using the difference between the toner color and the carrier color, and the magnetic method measures the toner permeability by measuring the magnetic permeability of the carrier that is a magnetic material. The concentration is measured. That is, the magnetic permeability is an alternative measurement of toner concentration here.

  When measuring the toner density magnetically, there is a measurement error caused by the bulk of the developer as a known problem (see, for example, Patent Documents 1 and 2). Although the measurement error here is the same as the toner concentration, the total amount of developer in the developing device is different, so that the measured toner concentration (ie magnetic permeability) is also different as a result. It is due. Further, since the developer is powder, it exists in a state containing air, and the difference in density (that is, the ratio containing air) can also contribute to measurement errors.

  Further, Patent Document 3 describes the problem that the agglomerated toner adheres to the detection surface of the toner density sensor in addition to the problem of the bulk density of the developer. In order to solve this problem, the invention described in Patent Document 3 controls the opening of the detection surface so that the detection surface is exposed only when necessary.

JP 2001-356484 A (paragraph 0004 etc.) JP 2002-148927 (paragraph 0004 etc.) JP 2005-266058 A (paragraph 0008 etc.)

  An object of the present invention is to determine the state of the developer contained in the developing device by utilizing the rotation of the developing means.

  According to a first aspect of the present invention, there is provided a developing device having a support member that supports a plurality of developing units that store a developer including toner and a carrier, and the plurality of developing units are alternately opposed to the photosensitive member. A developing unit that applies toner to the photoconductor; and the developing unit that rotates the support and causes the developing unit to face the photoconductor when any of the plurality of developing units applies toner. A driving means for driving; a measuring means for measuring a toner density in the developing device using a sensor provided in at least one of the plurality of developing devices; and the developing device having the measuring means is connected to the photoreceptor. It is determined whether or not there is an abnormality in the developer state in the developing device based on the difference in the plurality of toner densities respectively measured by the measuring unit when the positional relationship is at a plurality of positions. It has a configuration and a determination unit.

The developing device according to a second aspect of the present invention is the developing device according to the first aspect, wherein the developing means is provided in a transport path in which the developer of the developing device moves, and the development in the transport path is performed. An auger that conveys the agent while stirring, and the determination means is measured by the measurement means when the auger stops operating and the positional relationship of the auger with respect to the sensor satisfies a predetermined condition. It further has a configuration for performing determination using toner density.
According to a third aspect of the present invention, there is provided the developing device according to the second aspect, further comprising a control unit that controls the operation of the auger so that the auger stops at a position that satisfies the condition.
According to a fourth aspect of the present invention, there is provided the developing device according to any one of the first to third aspects, wherein the determination unit is configured to perform the development when the difference between the plurality of toner densities is less than a first threshold value. The apparatus further includes a configuration for determining that the developer is stuck.
A developing device according to a fifth aspect of the present invention is the developing device according to any one of the first to fourth aspects, wherein the determination unit is configured such that the difference between the plurality of positions is expressed by a predetermined rotation angle. When the difference between the plurality of toner concentrations is less than a second threshold value, the developer amount is further determined to be excessive.
A developing device according to a sixth aspect of the present invention is the developing device according to any one of the first to fifth aspects, wherein the determination unit is configured such that the difference between the plurality of positions is expressed by a predetermined rotation angle. When the difference between the plurality of toner densities exceeds a third threshold value, the apparatus further determines that the developer amount in the developing device is insufficient.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive member; and the developing device according to any one of the first to sixth aspects that applies toner to the photosensitive member. An image forming unit to be formed; and a process execution unit that executes a process according to a measurement result by the measurement unit and a determination result by the determination unit.

According to the first and seventh aspects, the state of the developer stored in the developing device can be determined using the rotation of the developing means.
According to the configuration of the second aspect, it is possible to reduce the influence of the deviation of the measurement result due to the difference in the positional relationship of the auger as compared with the case where the measurement is performed without setting the reference.
According to the configuration of the third aspect, it is possible to prevent the positional relationship of the auger with respect to the photosensitive member from being changed at that time.
According to the configuration of claim 4, it is possible to determine that the state where the developer is stuck is abnormal.
According to the fifth aspect of the present invention, it is possible to determine that an excessive amount of developer is abnormal.
According to the configuration of the sixth aspect, it is possible to determine that the developer amount is insufficient as an abnormality.

Block diagram showing configuration of image forming apparatus Diagram showing the configuration of the image forming unit Diagram showing the configuration of the rotary development unit Diagram showing the internal configuration of the developer unit Diagram showing the internal configuration of the developer unit The figure which shows the output value of the sensor at the time of rotation of a 1st auger The figure which illustrates schematic structure of the developing device at the time of using a slip ring Block diagram showing the functional configuration of the control unit The figure which shows the relationship between a developer amount (g) and the output value (V) of a sensor when the toner density is maintained to be the same. Flow chart showing operation of image forming apparatus The figure which shows the image development apparatus which has a developing device of 6 colors.

[Summary of the Invention]
According to the present invention, in a developing device and an image forming apparatus having a so-called rotary type developing unit, the state of the developer in the developing device is measured, and whether or not the state of the developer is abnormal based on the measurement result is determined. The main feature is to determine the above. The present invention utilizes the rotation of the rotary type developing means, and based on the difference between the measurement results when the developing means is in a plurality of postures (that is, in the rotated state) It is judged whether it is in such a state. Here, the state of the developer means the amount of developer in the developing device (hereinafter referred to as “developer amount”) in addition to the state where the developer aggregates and adheres to a specific location. Is included.

[Embodiment]
FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 includes an image forming unit 110, a sensor unit 120, an acquisition unit 130, a UI (User Interface) unit 140, and a control unit 150.

  The image forming unit 110 is a unit that forms an image on a recording medium with a developer, and corresponds to an example of the image forming unit of the present invention. That is, the image forming unit 110 is a unit that forms an image by an electrophotographic method. In this embodiment, the developer is a two-component developer containing toner and carrier. The recording medium is a medium for recording an image, and is, for example, a paper, but the material and size thereof are not limited to a specific one.

  The image forming unit 110 includes the developing device 20. The developing device 20 is a so-called rotary developing device, and includes a rotary developing unit 21 and a driving unit 22. The rotary developing unit 21 is a unit that applies toner to the photosensitive drum 111 described later, and corresponds to an example of the developing unit of the present invention. The drive unit 22 is a unit that drives the rotary developing unit 21 so as to rotate, and corresponds to an example of the drive unit of the present invention. The drive unit 22 is configured by a motor or a gear.

  The sensor unit 120 constitutes a part of the measurement unit of the present invention and is a unit for measuring the toner density. Here, the toner concentration refers to a mixing ratio of toner and carrier in the developer. In the present embodiment, the sensor unit 120 measures the magnetic permeability of the carrier instead of the toner concentration itself. Here, the state where the toner concentration is high indicates a state where the toner is more than the carrier. In the present embodiment, the sensor unit 120 employs a configuration that measures the magnetic permeability of a carrier that is a magnetic material. The sensor unit 120 supplies a signal representing the magnetic permeability to the control unit 150.

  The acquisition unit 130 is means for acquiring image data. The acquisition unit 130 acquires image data from an external device such as a personal computer. Alternatively, the acquisition unit 130 may acquire image data via a reading unit that optically reads a document or a communication unit that transmits and receives image data. The acquisition unit 130 acquires image data using a communication interface corresponding to the external device or means of the counterpart.

  The UI unit 140 is a means for exchanging information with the user. The UI unit 140 includes a display unit such as a liquid crystal display, a sound emitting unit (buzzer, speaker, etc.) for reproducing sound such as a warning sound, and a button for receiving a user operation. The UI unit 140 may be a display unit having a touch screen, that is, a unit that displays an image and receives a user operation. Note that the notification of information to the user may be performed by only one of the display unit and the sound emitting unit.

  The control unit 150 is a unit that controls the operation of the image forming apparatus 10 and corresponds to an example of a control unit of the present invention. The control unit 150 supplies image data to the image forming unit 110 and gives necessary instructions to the image forming unit 110. The control unit 150 is realized by a computer having a CPU (Central Processing Unit) and a memory, a dedicated integrated circuit such as an ASIC (Application Specific Integrated Circuit) and an FPGA (Field-Programmable Gate Array), or their cooperation. The

  FIG. 2 is a diagram illustrating a configuration of the image forming unit 110. In addition to the developing device 20 described above, the image forming unit 110 includes a photosensitive drum 111, a charging roll 112, an exposure device 113, an intermediate transfer belt 114, a primary transfer roll 115, a plurality of support rolls 116, A next transfer roll 117, a fixing device 118, and a cleaning blade 119 are included.

  The photosensitive drum 111 is a member that holds an electrostatic latent image and a toner image and rotates in a direction indicated by an arrow A1 in the drawing, and corresponds to an example of the photosensitive member of the present invention. The photoconductive drum 111 has a photoconductive layer that changes its surface potential when irradiated with light. The charging roll 112 is a member that contacts the photosensitive drum 111 and charges it. The means for charging the photosensitive drum 111 is not limited to a roll shape but may be a brush shape, or may be a type that does not contact the photosensitive drum 111 such as a corotron or a scorotron. The exposure device 113 is a unit that irradiates the charged photosensitive drum 111 with light and partially generates a potential difference to form an electrostatic latent image.

  The intermediate transfer belt 114 is an endless belt-like member that moves the toner image. The intermediate transfer belt 114 is supported by a plurality of support rolls 116, and changes its position by being rotated in a direction indicated by an arrow A2 in the drawing. At least one of the support rolls 116 is driven by a driving unit such as a motor to rotate the intermediate transfer belt 114.

  The primary transfer roll 115 is a member that transfers the toner image formed on the photosensitive drum 111 to the intermediate transfer belt 114. The primary transfer roll 115 generates a potential difference with the photosensitive drum 111, and transfers the toner image from the photosensitive drum 111 to the intermediate transfer belt 114. The secondary transfer roll 117 is a means for transferring the toner image transferred to the intermediate transfer belt 114 to a recording medium conveyed along the broken arrow A3 in the drawing. The fixing device 118 is means for applying heat and pressure to the recording medium onto which the toner image has been transferred to fix the toner on the recording medium.

  The cleaning blade 119 is a means for removing toner that has not been transferred by the secondary transfer roll 117. The toner removed by the cleaning blade 119 includes toner remaining on the intermediate transfer belt 114 without being sufficiently transferred to the recording medium by the secondary transfer roll 117 and toner that does not need to be transferred to the recording medium. The toner that does not need to be transferred to the recording medium is, for example, toner that is forcibly discharged from the rotary developing unit 21 in order to adjust the toner density. The means for removing the toner is not limited to the blade shape but may be a brush shape.

  FIG. 3 is a diagram illustrating a configuration of the rotary developing unit 21. The rotary developing unit 21 shown in FIG. 1 accommodates toners of four colors, yellow (Y), magenta (M), cyan (C), and black (K), and is provided so as to face the photosensitive drum 111. A rotary developing device. However, the toner stored in the rotary developing unit 21 is not necessarily limited to these colors.

  The rotary developing unit 21 includes developing devices 210Y, 210M, 210C, and 210K, and a support 215. The developing devices 210Y, 210M, 210C, and 210K are provided with sensors 121Y, 121M, 121C, and 121K, respectively. The sensors 121Y, 121M, 121C, and 121K are constituent elements of the sensor unit 120, and are means for measuring the magnetic permeability in this embodiment.

  The developing units 210Y, 210M, 210C, and 210K are units that respectively store a developer of a color corresponding to a code and apply the developer to the photosensitive drum 111 as necessary. For example, the developing device 210Y contains yellow toner, and the developing device 210M contains magenta toner. The support 215 is a columnar member that supports the developing devices 210Y, 210M, 210C, and 210K. The support 215 has a shaft portion 216 and is configured to rotate around the shaft portion 216. In the present embodiment, the support body 215 supports the developing devices 210Y, 210M, 210C, and 210K so that each of the developing devices 210Y, 210M, 210C, and 210K is disposed at an angle of 90 ° with the shaft portion 216 as the center.

  The developing devices 210Y, 210M, 210C, and 210K have the same function, although the developers to be stored are different. The sensors 121Y, 121M, 121C, and 121K also have the same function of measuring magnetic permeability, although the measurement target developers are different. Therefore, in the following, when there is no need to distinguish between them, these will be collectively referred to as “developer 210” and “sensor 121”.

  In the following, the attitude of the developing device 210 is expressed as follows. That is, the state in which the developing device 210 faces the photosensitive drum 111 is referred to as “the developing device is in the developing position”. The development position is a position of the developing device 210 when the developing device 210 performs development. Further, the other posture of the developing device 210 is expressed by a rotation angle based on the developing position. That is, when the developing device 210 is at the developing position (the state of the developing device 210Y in FIG. 3), the rotation angle is set to “0 °”, and when the developing device 210 is rotated clockwise by 1/4 (from the developing device 210M in FIG. 3). When the rotation angle is 90 °, and when the rotation angle is further rotated 1/4 (the state of the developing device 210C in FIG. 3), the rotation angle is 180 ° and when the rotation angle is further rotated 1/4. The rotation angle of (the state of the developing device 210K in FIG. 3) is “270 °”.

  FIG. 4 is a diagram illustrating an internal configuration of the developing device 210. The developing device 210 includes a first auger 211, a second auger 212, a mag roll 213, and a regulating member 214. Further, a first transport path 210a and a second transport path 210b, which are spaces for transporting the developer, are formed inside the developing device 210. The developing device 210 supplies toner and a carrier to the first transport path 210 a and moves them to the second transport path 210 b while stirring and transporting them with the first auger 211, and then to the mag roll 213 via the second auger 212. And supply toner. The first transport path 210a and the second transport path 210b are partitioned by an inner wall, and the inner wall is provided with a notch for the toner to circulate.

  The first auger 211 and the second auger 212 are members that convey toner while stirring. The first auger 211 is provided inside the first conveyance path 210a, and the second auger 212 is provided inside the second conveyance path 210b. The mag roll 213 faces and contacts the photosensitive drum 111 and applies toner to the photosensitive drum 111. The regulating member 214 is a member for limiting the amount of toner (layer thickness) that adheres to the mag roll 213.

  FIG. 5 is a diagram showing the internal configuration of the developing device 210 from a direction different from that in FIG. As shown in the figure, the first auger 211 has a shaft 211a, a spiral 211b, and a paddle 211c, and is configured to rotate around the shaft 211a. The developer in the first transport path 210a is stirred and transported by the spiral 211b as the shaft 211a rotates. The sensor 121 has a detection surface 121a provided so as to be in contact with the developer in the first transport path 210a. The paddle 211c is provided at a position facing the detection surface 121a and rotates together with the shaft 211a. The paddle 211c has a flat plate shape and has a function of attracting the developer to the detection surface 121a.

  The detection surface 121a is provided at a position where the surface is covered with the developer when the developer 210 is in the development position and the amount of the developer is desired. More specifically, such a position is below the shaft 211a when the developing device 210 is in the developing position. This is because the developer accumulates below the first conveyance path 210a due to its own weight. However, it is better to avoid the position of the detection surface 121a directly below the shaft 211a. This is because at this position, the developer is actually scarce and the developer is measured even in a state where stirring and transport are not possible.

  FIG. 6 is a diagram illustrating the output value of the sensor 121 when the first auger 211 is rotated, and the output value when the developing device 210 is in the developing position. The output value of the sensor 121 indicates the magnitude of the magnetic permeability, and is represented here by the voltage (V). As shown in the figure, the output value of the sensor 121 shows the first peak value when the spiral 211b passes in front of the detection surface 121a, and the second output value when the paddle 211c passes in front of the detection surface 121a. And the paddle 211c drops rapidly after passing in front of the detection surface 121a. The second peak value depends on the shape and size of the paddle 211c, but here is larger than the first peak value.

  The developing device 210 is configured such that the output value of the sensor 121 is supplied to the control unit 150 at a plurality of rotation angles. The developing device 210 of the present embodiment is configured to maintain electrical connection by a known slip ring. However, the configuration for realizing electrical connection during rotation is not limited to this, and for example, the sensor 121 may be configured to transmit an output value by a wireless signal.

  FIG. 7 is a diagram illustrating a schematic configuration when a slip ring is used. The developing device 210 has electrodes 123Y, 123M, 123C, and 123K on the surface of the shaft portion 216, and has lead wires 122Y, 122M, 122C, and 122K inside the shaft portion 216. The inside of the shaft portion 216 is hollow. The lead wires 122Y, 122M, 122C, and 122K electrically connect any of the sensors 121Y, 121M, 121C, and 121K to the corresponding electrodes 123Y, 123M, 123C, and 123K, respectively. All of these rotate as the support 215 rotates. On the other hand, the wire brushes 124Y, 124M, 124C, and 124K and the lead wires 125Y, 125M, 125C, and 125K are provided so as not to move by the rotation of the support 215, and are electrically connected to the electrodes 123Y, 123M, 123C, and 123K. maintain. The lead wires 125Y, 125M, 125C, and 125K supply the output values of the sensors 121Y, 121M, 121C, and 121K to the control unit 150.

  FIG. 8 is a block diagram illustrating a functional configuration of the control unit 150. The control unit 150 implements a toner density calculation unit 151, a determination unit 152, and a process execution unit 153. The toner concentration calculation unit 151 realizes a function corresponding to the measurement unit of the present invention in cooperation with the sensor unit 120. The toner concentration calculation unit 151 calculates the toner concentration in each color developing device 210 based on the magnetic permeability measured by the sensor 121. The toner density has a regular correlation with the magnetic permeability measured by the sensor 121 when the developer amount is in a desired state.

  FIG. 9 is a diagram showing the relationship between the developer amount (g) and the output value (V) of the sensor 121 when the toner density is kept the same. As shown in the figure, the output value of the sensor 121 changes in correlation with the toner density except when the developer amount is excessive or insufficient. Therefore, the developer amount range in which the output value of the sensor 121 accurately reflects the developer amount (a range indicated by a broken line in the drawing) may be a desirable state. In the present embodiment, a state where the developer amount is outside such a range is regarded as an abnormal state of the developer. This state is a state in which the regularity regarding the increase in the developer amount and the increase in the magnetic permeability is lost. In other words, it cannot be guaranteed that the actual toner density is accurately measured from the output value of the sensor 121. State.

  The determination unit 152 is a unit that determines whether there is an abnormality in the state of the developer based on the measurement result by the sensor unit 120, and corresponds to an example of the determination unit of the present invention. The determination unit 152 includes a storage unit 154 and a comparison unit 155 in more detail. The storage unit 154 stores a target value of toner density. The comparison unit 155 reads the target value stored in the storage unit 154 and compares it with the toner concentration calculated by the toner concentration calculation unit 151. Further, the comparison unit 155 executes a process of comparing toner densities measured in different postures, in addition to a process of comparing the toner density and the target value.

  Note that the target value of the toner density may be stored outside the control unit 150, such as a storage device provided separately in the image forming apparatus 10. In this case, it is sufficient for the control unit 150 to have a configuration for reading the target value from the external storage device.

  The process execution unit 153 is a unit that executes a process according to the measurement result by the sensor unit 120 or the determination result by the determination unit 152, and corresponds to an example of the process execution unit of the present invention. The process executed by the process execution unit 153 is, for example, a process for controlling the operation of each color developing device 210 or a process for notifying the user that there is an abnormality in the developer state. Further, the processing executed by the processing execution unit 153 includes processing for adjusting the amount of toner or carrier.

  The configuration of the image forming apparatus 10 is as described above. Under this configuration, the image forming apparatus 10 executes a process for forming an image according to the image data. Since the image forming apparatus 10 includes the rotary type developing device 20, when forming a color image of two or more colors, the support 215 is rotated and the necessary developing device 210 is alternately opposed to the photosensitive drum 111. Form an image. When forming an image, the image forming apparatus 10 controls the posture of the support 215 so that any of the developing devices 210Y, 210M, 210C, and 210K faces the photosensitive drum 111.

  Further, the image forming apparatus 10 measures the toner density inside the developing device 210 at an appropriate timing while forming an image in this way, and supplies or forcibly discharges the toner or carrier as necessary. The toner density is controlled to maintain a desired state. What is used for this control is the toner density measured with the developing device 210 in the developing position.

  In addition, the image forming apparatus 10 measures the toner density even when the developing device 210 is at a position other than the development position in order to determine the validity of the measured toner density itself. That is, the image forming apparatus 10 measures the toner density inside the developing device 210 at a plurality of positions (that is, postures) having different positional relationships with respect to the photosensitive drum 111. The operation of the image forming apparatus 10 using the measurement result of the sensor 121 is specifically as follows.

  FIG. 10 is a flowchart showing the operation of the image forming apparatus 10 for determining the state of the developer. The process described in this flowchart is only a process for a specific color. However, in the image forming apparatus 10, such a process is actually executed in parallel for four colors.

  The control unit 150 of the image forming apparatus 10 first determines whether or not the developing device 210 of a specific color is driven at the developing position (step S1), and waits for processing until driving is started. If the developing device 210 is being driven at the developing position, the control unit 150 measures the toner density (step S2). At this time, the control unit 150 acquires an output value as shown in FIG. The control unit 150 extracts a component (for example, a second peak value) that has a particularly high correlation with the toner concentration from the output value that changes in this way, and calculates the toner concentration using this component.

The controller 150 repeatedly calculates the toner density while the developing device 210 is being driven and the first auger 211 and the second auger 212 are rotating. That is, the control unit 150 determines whether or not the developing device 210 is being driven (step S3), and if it is being driven, executes the process of step S2 again.
On the other hand, when the driving of the developing device 210 is stopped, the control unit 150 calculates the toner density when the first auger 211 is stopped, and stores this (step S4). The controller 150 stores the toner density calculated at this time as the toner density at the developing position (that is, the toner density when the rotation angle is 0 °). That is, the control unit 150 performs a determination described later on the basis of the toner density when the first auger 211 is stopped.

  The output value of the sensor 121 varies depending on the positional relationship with the first auger 211 as shown in FIG. Therefore, the control unit 150 does not use the toner density measured when the first auger 211 is naturally stopped as a reference, but the positional relationship between the sensor 121 and the first auger 211 satisfies a predetermined condition. At this point, the driving of the developing device 210 may be controlled to stop, and the toner density measured at this time may be used as a reference. Here, the predetermined condition is, for example, that the toner density shows the second peak value. That is, the control unit 150 stops driving the developing device 210 when the spiral 211b or the paddle 211c is at a specific position (more specifically, a position where an error from the specific position is within a predetermined range). To control the drive. In this way, the positional relationship between the sensor 121 and the first auger 211 does not change from time to time.

  In the developing device 20, when the development of one color is completed, the development of another color is started. That is, at this time, the control unit 150 rotates the support 215 so that the developing device 210 of another color faces the photosensitive drum 111. Further, the control unit 150 measures and stores the toner density of the developing device 210 when the rotation angle is 90 °, 180 °, and 270 ° in accordance with the rotation of the support 215 (steps S5, S6, and S7). ). These measurements are preferably performed during a period in which another developing device 210 (the developing device 210 at the developing position at that time) is being driven. In these cases, the driving of the developing device 210 is assumed to be stopped (still stopped) after being stopped when the rotation angle is 0 °. Then, the positional relationship between the sensor 121 and the first auger 211 is maintained in a state in which the toner density at the development position is stored without performing special control in each posture. As a configuration for realizing this, for example, a configuration in which the driving force is transmitted only to the developing device 210 at the developing position and not transmitted at other positions can be mentioned.

  When the control unit 150 stores the toner density at each of the four types of positions (rotation angles of 0 °, 90 °, 180 °, and 270 °), the difference between these toner concentrations is less than the first threshold (Th1). Whether or not (step S8). Specifically, the control unit 150 specifies the maximum value and the minimum value from the four toner densities, and determines whether or not the difference between the maximum value and the minimum value is less than the first threshold value.

  When the toner density difference is less than the first threshold, the controller 150 determines the magnetic permeability of the developer fixed on the detection surface 121a by the sensor 121 (not the magnetic permeability of the entire developer inside the developing device 210). Judge that it is measuring. This is because there is almost no difference in toner density at each rotation angle because it cannot occur in a state where the developer amount is desirable. In a state in which the developer amount is desirable, for example, when the rotation angle is 0 °, the detection surface 121a is covered with the developer, whereas when the rotation angle is 180 ° (or 270 °), the detection surface. The air in the developing device 210 is interposed between 121a and the developer. Therefore, in these two cases, there should be a significant difference in the measured toner density.

  When it is determined that the developer is stuck on the developing device 210 (more specifically, the detection surface 121a), the control unit 150 performs a sticking process (step S9). The process at the time of fixing is, for example, a process for notifying the user that the developer is fixed by voice or an image. Alternatively, as the fixing process, the control unit 150 may rotate the first auger 211 or rotate the support 215 so as to promote the peeling off of the fixed developer, or the sensor 121. It is also possible to stop using this measurement result and replenish toner and carrier to the developing device 210 without depending on the measurement result of the sensor 121. Note that if a means (piezoelectric element or the like) that applies vibration to the developing device 210 or the detection surface 121a is provided, the control unit 150 may execute a process of applying vibration by the means as a process at the time of fixing.

  If it is not determined in step S8 that the developer is stuck, the control unit 150 determines the difference in toner density when the rotation angle is 0 ° and 180 °, and when the rotation angle is 0 °. A difference in toner density in the case of 270 ° is calculated, and it is determined whether both of them are less than the second threshold (Th2) (step S10). Note that the control unit 150 may calculate only one of these differences and compare it with the second threshold value, or may set different threshold values for comparison with these differences. Further, the difference in toner density is expressed here as an absolute value.

  When the controller 150 determines that the difference calculated in step S10 is less than the second threshold, the controller 150 determines that the developer amount in the developing device 210 is excessive. This is because when the rotation angle is 180 ° or 270 °, the detection surface 121a is positioned above the shaft 211a, so that if the developer amount is appropriate, the toner density is higher than when the rotation angle is 0 °. This is because it should be measured smaller. Therefore, when the developer amount is appropriate (especially at the upper limit), the second threshold is expected to be measured when the rotation angle is 0 ° and the toner concentration and rotation angle are 180 ° or 270. It may be determined based on the toner density expected to be measured at the time of °.

  When it is determined that the developer amount is excessive, the control unit 150 performs excessive processing (step S11). The excess processing is, for example, processing for forcibly discharging the developer from the developing device 210 or notifying the user that the developer amount is excessive by voice or image. Alternatively, the excess processing may stop the use of the measurement result of the sensor 121 and replenish the developing device 210 with toner or carrier without using the measurement result of the sensor 121.

  If it is not determined in step S10 that the difference in toner density is less than the second threshold, the control unit 150 calculates the difference in toner density when the rotation angle is 0 ° and 90 °, which is the third difference. It is determined whether or not the threshold value (Th3) is exceeded (step S12). When the controller 150 determines that this difference exceeds the third threshold, the controller 150 determines that the amount of developer in the developing device 210 is insufficient. In both cases where the rotation angle is 0 ° and 90 °, the detection surface 121a is positioned below the shaft 211a, so that if the developer amount is appropriate, there should be no significant difference in toner density. is there. The third threshold is measured when the developer amount is appropriate (especially at the lower limit thereof) and the toner concentration and rotation angle expected to be measured when the rotation angle is 0 ° are 90 °. It may be determined based on the toner density expected to be generated.

  When it is determined that the developing material is insufficient, the control unit 150 executes a shortage process (step S13). The shortage process is, for example, a process of supplying the developer into the developing device 210 or notifying the user that the amount of the developer is insufficient by voice or an image. Alternatively, the shortage process may be such that the use of the measurement result of the sensor 121 is stopped and the developing device 210 is replenished with toner or carrier without depending on the measurement result of the sensor 121. In addition, the control unit 150 may execute other processing for stabilizing the developer.

  When any one of the fixing process, the excess process, and the shortage process is finished, the control unit 150 determines whether or not the image formation is continued (step S14). If the image formation is continuing, the control unit 150 executes the processing from step S1 again. On the other hand, if the image formation is not performed, the control unit 150 ends the processing related to the determination of the developer state.

  As described above, the image forming apparatus 10 not only measures the toner density at the development position, but also measures the toner density at a plurality of positions having different positional relationships with the photosensitive drum 111 other than the development position. To determine the state of the developer that cannot be obtained simply by measuring the toner density at the development position (the state where the developer is fixed, the state where the developer amount is excessive, or the amount of the developer is insufficient) Is realized.

[Modification]
Embodiments of the present invention are not limited to the above-described embodiments, and may be, for example, the following forms. Moreover, these forms may be combined with each other by using them together or by replacing a part thereof as necessary.

(1) The developing device of the present invention may be a so-called rotary developing device, and is not particularly limited as long as the number of colors is two or more. Further, the developing devices of the respective colors are not necessarily the same size, and the developing device of the specific color may be configured larger than the other. In this case, the arrangements of the developing devices do not need to be equally spaced by 90 ° about the rotation axis.

  FIG. 11 is a diagram showing a developing device 20a having six color developing devices. The developing device 20a includes developing devices 2101, 1022, 2103, 2104, 2105, and 2106, a support 215a, and sensors 1211, 1212, 1213, 1214, 1215, and 1216. The image forming apparatus 10 may include a developing device 20a instead of the developing device 20.

  The developing devices 2101, 1022, 2103, 2104, 2105, and 2106 are arranged at intervals of 60 ° when viewed from the shaft portion 216a. The support body 215a rotates around the shaft portion 216a. The color of toner used in the developing device 20a is, for example, orange or green in addition to four colors of cyan, magenta, yellow, and black. Further, the toner color may include so-called special colors (fluorescent color, metallic color, etc.).

  In the developing device 20a, for example, the toner density is measured at positions where the rotation angles with respect to the developing position are 0 °, 60 °, 120 °, 180 °, 240 °, and 300 °. The comparison with the second threshold value is performed using, for example, the difference between the toner concentration measured at the development position (that is, 0 °) and the toner concentration when the rotation angle is 180 ° or 240 °. The comparison with the third threshold value is performed using, for example, the difference between the toner concentration measured at the development position (that is, 0 °) and the toner concentration when the rotation angle is 60 ° or 120 °. The processing related to the determination of the developer state is common to the processing in the above-described embodiment (see FIG. 10) except that the position where the toner density is measured and the number of stored toner densities are different.

(2) The position for measuring the toner density is not necessarily the development position. The position for measuring the toner density may be a plurality of positions having different positional relationships with respect to the photoconductor, and the specific positions are not limited. However, when the position where the toner density is measured corresponds to the developing position of the developing device or another developing device, it is not necessary to stop at any other position (for purposes other than development).

(3) The sensor of the present invention is not limited to a magnetic sensor that measures magnetic permeability, and may be an optical sensor. This is because even an optical sensor may cause a measurement error problem due to fixing of the developer. Here, the optical sensor measures the toner density by utilizing the difference between the toner color and the carrier color.

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 110 ... Image forming part 120 ... Sensor part 130 ... Acquisition part 140 ... UI part 150 ... Control part 151 ... Toner density calculation part 152 ... Determination part 153 ... Process execution part, 154: Storage unit, 155: Comparison unit, 20, 20a ... Developing device, 21 ... Rotary developing unit, 210, 210Y, 210M, 210C, 210K, 2101, 1022, 2103, 2104, 2105, 2106 ... Developer, 215 ... Support body, 22 ... drive unit

Claims (7)

A developing unit having a support for supporting a plurality of developing units containing a developer containing toner and a carrier, and applying the toner to the photosensitive member by alternately facing the developing units to the photosensitive member;
A driving unit that rotates the support and drives the developing unit so that the developing unit faces the photoconductor when any of the plurality of developing units applies toner;
Measuring means for measuring toner density in the developing device using a sensor provided in at least one of the plurality of developing devices;
Based on the difference in the plurality of toner densities respectively measured by the measuring unit when the developing unit having the measuring unit is at a plurality of positions having different positional relationships with respect to the photoconductor, the development in the developing unit is performed. A developing device comprising: determination means for determining whether or not the state of the agent is abnormal. The developing means includes
Provided in a transport path in which the developer of the developer moves, and has an auger that transports the developer in the transport path while stirring;
The driving means includes
Stop the operation of the auger until the developing unit moves from a position facing the photoconductor to another position,
The determination means includes
The developing device according to claim 1, wherein the determination is performed based on the toner density measured by the measuring unit when the auger stops operation. Control means for controlling the drive means so that the auger stops when the positional relationship of the auger with respect to the sensor satisfies a predetermined condition;
The determination means includes
The developing device according to claim 2, wherein the determination is performed based on a toner density measured by the measurement unit when a positional relationship of the auger with respect to the sensor satisfies the condition. The determination means includes
4. The developer according to claim 1, wherein when the difference between the plurality of toner densities is less than a first threshold, it is determined that the developer is stuck in the developing device. 5. Development device. The determination means includes
In the case where the difference between the plurality of positions is represented by a predetermined rotation angle, when the difference between the plurality of toner densities is less than a second threshold, it is determined that the developer amount in the developing device is excessive. The developing device according to claim 1, wherein The determination means includes
When the difference between the plurality of positions is represented by a predetermined rotation angle, when the difference between the plurality of toner densities exceeds a third threshold value, it is determined that the developer amount in the developing device is insufficient. The developing device according to claim 1, wherein An image forming means for forming an image on a recording medium with toner, comprising: a photosensitive member; and a developing device according to claim 1 for applying toner to the photosensitive member;
An image forming apparatus comprising: a process execution unit that executes a process according to a measurement result by the measurement unit and a determination result by the determination unit.

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