JP2012220625A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sequentially and highly accurately detect a residual amount of a toner despite the amount of toner by a simple configuration.SOLUTION: The image forming apparatus includes: an attachable/detachable developing unit for storing developer; a detection mylar 351 having a detecting object electrode 361 and being rotatable about a rotary shaft inside the developing unit; a stirring mylar 34 circulatingly operating about the rotary shaft inside the developing unit; a capacitive sensor electrode 321 disposed on an exterior package of the developing unit; a capacitive sensor 33 detecting an electrostatic capacitance between the detecting object electrode 361 and the capacitive sensor electrode 321 and outputting data on the detected electrostatic capacitance; and a CPU 40 for determining the amount of the developer in the developing unit based on the data output from the capacitive sensor 33.

Description

  The present invention relates to detection of a remaining amount of toner that is a developer in an electrophotographic image forming apparatus such as a laser printer, a copying machine, or a facsimile.

  In the conventional image forming apparatus, there is an example in which the remaining amount of toner in the toner container is detected by a capacitance detection device. For example, in the toner remaining amount detection device described in Patent Document 1, a flexible member is connected and fixed to one end of a stirring member that stirs the toner in the toner container, and a detection target is attached to the tip of the flexible member. The electrostatic capacity detection device is disposed below the toner container. As the agitating member rotates, the flexible member connected to the agitating member also rotates following and rotates into the toner. When the surface of the toner in the toner container is higher than the connection position between the flexible member and the stirring member, the flexible member enters the toner at the connection position with the stirring member, and the entire flexible member becomes soft. While being deformed, the toner rotates and moves in the same orbit (trajectory) as the connecting portion. Therefore, the detection target at the tip of the flexible member also rotates and moves along the same track as the flexible member. However, when the amount of toner decreases, the surface of the toner becomes lower than the connection position between the flexible member and the stirring member, and the connection portion of the stirring member does not enter the toner, the vicinity of the tip of the flexible member becomes The object to be detected slides on the toner surface, and the detected object also slides on the toner surface. As the remaining amount of toner gradually decreases, the height of the toner surface in the toner container gradually decreases, and the position of the detection object that slides and moves on the toner surface gradually decreases. That is, when the amount of toner decreases below a certain amount, the position of the detection object that moves on the surface of the toner also decreases according to the remaining amount of toner, and approaches the bottom surface of the toner container.

  On the other hand, the electrostatic capacitance detection device can detect the electrostatic capacitance between the electrostatic capacitance detection device and the detection object moving on the toner surface. And the electrostatic capacitance between an electrostatic capacitance detection apparatus and a to-be-detected body changes according to the distance between both. Since the electrostatic capacity detection device is disposed at the lower part of the toner container, when the toner amount decreases and the height of the toner surface gradually decreases, the position of the detection object on the toner surface also decreases. The distance between the capacitance detection device and the detected object is reduced, and the capacitance between them is reduced. That is, the electrostatic capacitance between the electrostatic capacitance detection device and the detection object changes according to the remaining amount of toner.

Japanese Patent No. 4137703

  However, the configuration of the conventional toner remaining amount detecting device includes the following problems. As described in Patent Document 1, when the toner is in a certain amount or more, the connecting portion between the flexible member and the agitating member enters the toner, so that the trajectory drawn by the flexible member and the detection target ( The trajectory is almost the same. As a result, when the amount of toner exceeds a certain amount, the distance between the electrostatic capacitance detection device and the detection target hardly changes, so that the detected electrostatic capacitance hardly changes, and the remaining amount of toner is successively and accurately determined. It cannot be detected.

  The present invention has been made in such a situation, and an object of the present invention is to accurately detect the remaining amount with a simple configuration regardless of the amount of toner.

  In order to solve the above-described problems, the present invention has the following configuration.

  (1) A detachable developing unit that stores developer, a first electrode, a first member that is rotatable around a rotation axis in the developing unit, and a rotation axis in the developing unit. A second member that rotates, a second electrode disposed on an exterior of the developing unit, a capacitance between the first electrode and the second electrode, and the detected capacitance; An image forming apparatus comprising: an output unit that outputs data; and a determination unit that determines an amount of developer in the developing unit based on the data output from the output unit.

  According to the present invention, the remaining amount can be detected with high accuracy with a simple configuration regardless of the amount of toner.

Sectional drawing which shows the whole structure of the image forming apparatus of Examples 1-3. Sectional drawing of the developing unit and electrostatic capacitance sensor of Examples 1-3 The perspective view of the developing unit of Examples 1-3, and the figure which shows the circuit structure around an electrostatic capacitance sensor The figure which shows the operation | movement of the stirring mylar of the developing unit of Examples 1-3, and a detection mylar The figure which shows operation | movement of the detection mylar when there is much toner of Examples 1-3, and when there are few The figure which shows the characteristic graph and table T1 of Example 1. FIG. 10 is a flowchart illustrating a processing sequence of toner remaining amount detection according to the first exemplary embodiment. The graph which shows a mode that the detection level of an electrostatic capacitance sensor changes by the free fall of the detection mylar of Example 1. The characteristic graph according to the sensor sensitivity of Example 2, and the characteristic graph which changed the sensor sensitivity according to the toner remaining amount The figure which shows the characteristic table according to the sensor sensitivity of Example 2. 7 is a flowchart illustrating a processing sequence for toner remaining amount detection according to the second embodiment. The figure which shows the characteristic graph and table T4 of Example 3. 10 is a flowchart illustrating a processing sequence of toner remaining amount detection according to the third exemplary embodiment.

  Hereinafter, the form for implementing this invention is demonstrated in detail by an Example.

[Outline of image forming apparatus]
FIG. 1 is a cross-sectional view showing the overall configuration of a color laser printer that is an example of the image forming apparatus of the present embodiment. The configuration and basic operation of the color laser printer will be described with reference to FIG. A color laser printer (hereinafter referred to as a main body) shown in FIG. 1 includes process cartridges 5Y, 5M, 5C, and 5K that are detachable from the main body 101. These four process cartridges 5Y, 5M, 5C, and 5K have the same structure, but toners (developers) of different colors, that is, yellow (Y), magenta (M), cyan (C), and black (K). ) In that an image is formed. Hereinafter, Y, M, C, and K may be omitted. The process cartridge 5 is composed of three units: a developing unit, an image forming unit, and a waste toner unit. The developing unit includes a developing roller 3, a toner supply roller 12, a toner container 23, and a stirring mylar 34. Further, the image forming unit includes a photosensitive drum 1 and a charging roller 2 which are image carriers. The waste toner unit has a cleaning blade 4 and a waste toner container 24.

  A laser unit 7 is disposed below the process cartridge 5, and the laser unit 7 performs exposure based on an image signal to the photosensitive drum 1. The photosensitive drum 1 is charged to a predetermined negative potential by the charging roller 2, and then an electrostatic latent image is formed by the laser unit 7. The electrostatic latent image is reversely developed by the developing roller 3 and negative toner is adhered, and Y, M, C, and K toner images are formed on the respective photosensitive drums 1. The intermediate transfer belt unit includes an intermediate transfer belt 8, a driving roller 9, and a secondary transfer counter roller 10. Further, a primary transfer roller 6 is disposed inside the intermediate transfer belt 8 so as to face each photosensitive drum 1, and a transfer bias is applied to the primary transfer roller 6 by a bias applying unit (not shown). .

  The toner image formed on the photosensitive drum 1 rotates in the arrow direction of the photosensitive drum 1, and the intermediate transfer belt 8 rotates in the arrow A direction. Further, a positive bias is applied to the primary transfer roller 6 by a bias applying means (not shown), whereby the toner image on the photosensitive drum 1 is placed on the intermediate transfer belt 8 in the order of Y, M, C, K. Primary transfer is performed, and the four color toner images are conveyed to the secondary transfer roller 11 in a state where they overlap. The feeding / conveying device includes a paper feed roller 14 that feeds the transfer material P from the paper feed cassette 13 that houses the transfer material P, and a transport roller pair 15 that transports the fed transfer material P. Then, the transfer material P conveyed by the feeding / conveying device is conveyed to the secondary transfer roller 11 by the registration roller pair 16.

  The toner image is transferred from the intermediate transfer belt 8 to the transfer material P by applying a positive bias to the secondary transfer roller 11 so that the toner image on the intermediate transfer belt 8 is transferred to the transfer material P conveyed. Transcribed. The transfer material P onto which the toner image has been transferred is conveyed to the fixing device 17 and heated and pressed by the fixing film 18 and the pressure roller 19 to fix the toner image on the surface of the transfer material P, and the paper discharge roller. Ejected by pair 20. The toner remaining on the surface of the photosensitive drum 1 after being transferred to the intermediate transfer belt 8 is removed by the cleaning blade 4, and the removed toner is collected in a waste toner container 24. Further, after the secondary transfer to the transfer material P, the toner remaining on the intermediate transfer belt 8 is removed by the transfer belt cleaning blade 21, and the removed toner is collected in the waste toner container 22.

  The control board 80 is also equipped with a one-chip microcomputer (hereinafter referred to as CPU) 40 for controlling the main body, and a storage unit such as a RAM and a ROM for storing table data and the like. The CPU 40 collectively controls the operation of the main body, such as control of a drive source (not shown) related to conveyance of the transfer material P, a drive source (not shown) of the process cartridge 5, control related to image formation, control related to failure detection, and the like. To do. Further, the CPU 40 includes a timer therein. The ROM of the storage unit stores a program for controlling the image forming operation of the image forming apparatus and various data. The RAM of the storage unit is used for calculation of data necessary for controlling the image forming operation of the image forming apparatus, temporary storage, and the like. The timer is used for time measurement and the like. The video controller 42 controls light emission of the laser in the laser unit based on the image data. The video controller 42 also interfaces with the user via a control panel (not shown), and the remaining amount of toner of each color is displayed in a bar graph form on the control panel.

[Configuration of development unit and capacitance sensor]
FIG. 2 is a cross-sectional view of the developing unit constituting the process cartridge 5 and the electrostatic capacity sensor installed on the bottom surface of the developing unit. In the developing unit of the process cartridge 5 shown in FIG. 2, there are a developing roller 3 and a toner replenishing roller 12. Further, in the toner container 23, there are a toner 28 corresponding to each color and a stirring mylar 34 for stirring the toner 28. is there. The agitating mylar 34 (second member) is provided on a rotating shaft 29 in the toner container 23 and performs a revolving operation around the rotating shaft 29 that is rotated by a motor (not shown). The rotation shaft 29 is also provided with a flexible detection mylar 351 (first member) for detecting the remaining amount of the toner 28, and the detection mylar 351 is rotatable with respect to the rotation shaft 29. is there. Further, the detection mylar 351 includes a conductive detection electrode 361 (first electrode) in the vicinity of the tip in the circumferential direction.

  A capacitance sensor substrate 331 installed near the bottom surface of the process cartridge 5 shown in FIG. 2 is provided in the main body 101. The capacitance sensor substrate 331 includes the capacitance sensor 33 and the capacitance. Peripheral circuit components (not shown) of the sensor 33 are mounted. The capacitance sensor 33 detects a change in capacitance by the capacitance sensor electrode 321 using a difference between the capacitance by the capacitance sensor electrode 321 and the capacitance by the reference electrode 320. The capacitance sensor substrate 331 is provided with a capacitance sensor electrode 321 and a reference electrode 320 in a copper foil pattern. The bottom surface of the exterior of the developing unit is close to the capacitance sensor electrode 321 (second electrode) when the process cartridge 5 is mounted on the main body 101. In this state, the capacitance sensor 33 detects the capacitance generated when the detected electrode 361 disposed in the detection mylar 351 comes close to the capacitance sensor electrode 321.

  FIG. 3A shows a perspective view of the process cartridge 5. The detection mylar 351 is rotatable with respect to the rotation shaft 29. Therefore, when the stirring mylar 34 rotates in the direction opposite to the gravity (in the rising direction), the detection mylar 351 rotates along with the toner 28 while being lifted up by the stirring mylar 34. On the contrary, when the stirring mylar 34 rotates in the direction of gravity (downward direction), the detection mylar 351 freely falls in the direction of gravity before the stirring mylar 34 due to its own weight after the toner 28 has dropped. The configuration of the detection mylar 351 may be any configuration as long as the toner 28 stirred by the stirring mylar 34 falls and then drops onto the toner 28, and is limited to the configuration of FIG. is not.

  Further, the capacitance sensor 33 and the peripheral circuit only need to be capable of detecting capacitance, and an analog integrated circuit can be substituted. In this embodiment, the capacitance sensor electrode 321 is formed on the capacitance sensor substrate 331 provided in the main body 101. However, the capacitance sensor electrode 321 may be installed near the bottom surface of the developing unit. The capacitance sensor electrode 321 may be formed directly. In that case, when the process cartridge 5 is mounted on the main body 101 by providing an electrical contact between the capacitance sensor substrate 331 and the capacitance sensor electrode 321, the capacitance sensor substrate 331 and the capacitance sensor electrode. 321 may be connected.

[Circuit configuration of capacitance sensor]
FIG. 3B is a diagram illustrating a connection relationship among the capacitance sensor 33, the CPU 40, the reference electrode 320, and the capacitance sensor electrode 321 in the present embodiment. In FIG. 3B, AVDD of the capacitance sensor 33 is an analog power supply terminal, DVDD is a digital power supply terminal, and bypass capacitors 46 and 47 are provided to remove noise at the respective power supply terminals. A reference electrode 320 is connected to the SREF terminal, and a capacitance sensor electrode 321 is connected to the SIN terminal. In addition, data transmission / reception is performed between the CPU 40 and the capacitance sensor 33 by serial communication. From the CPU 40, a clock signal for communication synchronization is supplied to the CL terminal of the capacitance sensor 33, and the 8-bit corresponding to the detected capacitance value is received from the capacitance sensor 33 via the SD terminal. Detection data is output to the CPU 40. Conversely, setting data for controlling the capacitance sensor 33 is input from the CPU 40 to the capacitance sensor 33 via the SD terminal.

  As described above, the capacitance sensor 33 detects the difference between the capacitance between the detected electrode 361 and the capacitance sensor electrode 321 and the capacitance between the reference electrode 320 and thereby detects the capacitance sensor electrode. A change in capacitance of 321 is detected. The capacitance sensor 33 includes an amplification circuit that amplifies the difference between the detected capacitances. The sensitivity of the capacitance sensor 33 indicating the amplification factor of the amplifier circuit can be set from the CPU 40 to the capacitance sensor by serial communication, and can be set in 92 steps from 1 to 92. When the sensitivity of the capacitance sensor 33 is set as high as 92, since a smaller change in capacitance can be captured, even if the detected electrode 361 is far away from the capacitance sensor electrode 321, Capacitance can be detected. On the other hand, when the sensitivity of the capacitance sensor 33 is set to 1 low, if the change in the capacitance is small, the change in the capacitance cannot be detected, so that the detected electrode 361 is the capacitance sensor electrode 321. If it is far away, the change in capacitance cannot be detected. The capacitance sensor 33 of this embodiment is equipped with a circuit for adjusting sensitivity. The capacitance sensor only needs to have a configuration capable of changing the sensitivity when detecting the capacitance between the capacitance sensor electrode 321 and the detected electrode 361, and the capacitance used in this embodiment. It is not limited to sensors.

[Operation of stirring mylar and detection mylar]
FIG. 4 is a diagram illustrating the operations of the stirring mylar 34 and the detection mylar 351 that detect the remaining amount of the toner 28 in the toner container 23. FIG. 4A shows an initial state of the rotation operation, and the stirring mylar 34 is in a state where the tip portion is located at the highest point, and the detection mylar 351 is rotatable with respect to the rotation shaft 29. Therefore, a state in which the vehicle falls freely by its own weight and is stationary on the toner 28 is shown. FIG. 4 (b) is a diagram showing a state where the stirring mylar 34 is rotating together with the detection mylar 351. The rotating shaft 29 rotates from the state of FIG. 4A, and accordingly, the stirring mylar 34 rotates and contacts the detection mylar 351 stationary on the toner 28. The agitating mylar 34 rotates upward along with the detection mylar 351, and the toner 28 is also pushed upward by the detection mylar. Since the toner 28 has fluidity, before the stirring mylar 34 reaches the highest point, the toner 28 starts to spill from the stirring mylar 34 to the bottom surface of the toner container 23 and accumulates on the bottom surface of the toner container 23. FIG. 4C is a diagram showing a state when the stirring mylar 34 reaches the highest point. When the stirring mylar 34 reaches the highest point together with the detection mylar 351, and the rotation shaft 29 further rotates, the detection mylar 351 is rotatable with respect to the rotation shaft 29. The descent (free fall) of the accumulated toner 28 starts. On the other hand, since the stirring mylar 34 is connected to the rotating shaft 29, the stirring mylar 34 gradually follows the detection mylar 351 and follows the rotation operation of the rotating shaft 29.

  Next, FIG. 5 is a diagram illustrating the state of the detection mylar 351 when the remaining amount of the toner 28 is large and small. FIGS. 5A and 5B are diagrams showing the operation state of the detection mylar 351 when the remaining amount of the toner 28 is relatively large, and FIG. 5A is the state of FIG. 5 (b) corresponds to the state of FIG. 4 (a). In the state of FIG. 5A, the stirring mylar 34 pushes the toner 28 upward while contacting the detection mylar 351 in accordance with the rotation of the rotating shaft 29. Since the toner 28 has fluidity, as shown in FIG. 5A, before the stirring mylar 34 reaches the highest point, the toner 28 starts to spill from its own weight onto the bottom surface of the toner container 23, and the toner container It accumulates on the bottom surface of 23. Thereafter, when the rotating shaft 29 rotates and the stirring mylar 34 reaches the highest point, the detection mylar 351 is rotatable with respect to the rotating shaft 29 and thus starts to descend by its own weight. Then, the detection mylar 351 falls after the toner 28 is accumulated on the bottom surface of the toner container 23, and stops on the surface of the toner 28. FIG. 5B shows the state of the detection mylar 351 at that time. When the remaining amount of the toner 28 is large, the height from the bottom surface of the toner container 23 to the surface of the toner 28 is increased. The stop position of the mylar 351 is the position of the height 901.

  Next, FIGS. 5C and 5D are diagrams showing the operation state of the detection mylar 351 when the remaining amount of the toner 28 is relatively small, and FIG. This corresponds to the state of b), and FIG. 5D corresponds to the state of FIG. In the state of FIG. 5C, as described above, the stirring mylar 34 pushes the toner 28 upward while contacting the detection mylar 351 in accordance with the rotation of the rotating shaft 29. When the remaining amount of the toner 28 is small, the toner moves from the stirring mylar 34 to the bottom surface of the toner container 23 at a later timing, that is, at a position where the tip of the stirring mylar 34 is higher than when the remaining amount of toner is large. It starts to spill and accumulates on the bottom surface of the toner container 23. Thereafter, when the rotating shaft 29 rotates and the stirring mylar 34 reaches the highest point, the detection mylar 351 is rotatable with respect to the rotating shaft 29 and thus starts to descend by its own weight. Then, the detection mylar 351 falls after the toner 28 is accumulated on the bottom surface of the toner container 23, and stops on the surface of the toner 28. FIG. 5D shows the state of the detection mylar 351 at that time. When the remaining amount of the toner 28 is small, the height from the bottom surface of the toner container 23 to the surface of the toner 28 becomes low. The stop position of the mylar 351 is at a height 902.

  The height of the surface of the toner 28 accumulated on the bottom surface of the toner container 23 changes according to the remaining amount of the toner 28 in the toner container 23, so that the height of the position where the detection mylar 351 has fallen due to its own weight and stopped. There will be a difference. Thereby, a difference also arises in the capacitance between the detected electrode 361 and the capacitance sensor electrode 321 provided in the detection mylar 351. Then, the capacitance sensor 33 detects the difference in capacitance, and the CPU 40 can detect the distance between the detection mylar 351 and the capacitance sensor electrode 321 based on the detection level from the capacitance sensor 33, and as a result, The remaining amount of toner 28 can be calculated.

[Detection characteristics of remaining toner detection]
Next, the toner remaining amount detection characteristics in this embodiment will be described with reference to FIG. In this embodiment, the detection level of the capacitance sensor 33 is output to the CPU 40 as 8-bit data. In the following description, the detection level is expressed by a decimal number.

  FIG. 6A is a characteristic graph showing the relationship between the remaining amount of the toner 28 in the toner container 23 and the detection level of the capacitance sensor 33. The vertical axis indicates the detection level, and the horizontal axis indicates the remaining toner amount (%). ). The sensitivity of the capacitance sensor 33 in FIG. 6A is set to 69 from the CPU 40 using serial communication. As shown in the characteristic graph of FIG. 6A, in this embodiment, when the remaining amount of the toner 28 in the toner container 23 is 100%, the detection level of the capacitance sensor 33 is 135. On the other hand, when the remaining amount of the toner 28 is 0%, the detection level of the capacitance sensor 33 is 253.

  FIG. 6B is a table T1 in which the correspondence relationship between the detection level of the capacitance sensor 33 and the remaining amount of toner (%) is tabulated from the characteristic graph of FIG. The remaining amount of toner 28 corresponding to the detection level not explicitly shown in the table T1 can be obtained by linear interpolation of the known remaining amount of toner 28 described in the table T1. Here, since the measured detection level is a value in the present embodiment, the measured detection level changes as the measurement conditions change. The same applies to the numerical values in the table T1 for determining the remaining amount of toner 28. Information in the table T1 is written in a factory in a ROM of a storage unit or a ROM provided in the process cartridge 5 in advance. The information in the table T1 written in the ROM provided in the process cartridge 5 is read by the CPU 40 when the process cartridge 5 is mounted on the main body 101, and stored in the RAM of the storage unit of the control board 80. . Also in Examples 2 and 3 to be described later, the table information is recorded in the ROM and RAM of the recording unit by these methods. Note that the above-described method of recording the table information at the time of shipment is an example, and the present invention is not limited to this.

[Toner remaining amount detection processing sequence]
Next, the processing sequence for detecting the remaining amount of toner in this embodiment will be described with reference to the flowchart of FIG. The processing shown in FIG. 7 is executed by the CPU 40 based on a control program stored in the ROM of the storage unit, and the processing of the flowcharts in the following embodiments is also executed by the CPU 40. The CPU 40 does not perform all the processing shown in the flowchart. For example, when an integrated circuit (ASIC) for characteristic use is mounted on the image forming apparatus, a function for executing any processing in the flowchart. May be provided to the ASIC.

  In step 101 (hereinafter referred to as S101), the CPU 40 rotates the stirring mylar 34. In this embodiment, the time required for one rotation of the stirring mylar 34 is about 1 second. In S102, the CPU 40 performs serial communication with the capacitance sensor 33 and sets the sensitivity of the capacitance sensor to 69. Then, the CPU 40 resets and starts the timer and starts reading the detection level by the capacitance sensor 33.

  In S103, the CPU 40 receives the read data of the detection level from the capacitance sensor 33 by serial communication. In S <b> 104, the CPU 40 determines whether or not the detection mylar 351 has started free fall under its own weight based on the detection level corresponding to the capacitance between the detected electrode 361 and the capacitance sensor electrode 321 provided in the detection mylar 351. To do. Here, the manner in which the detection level of the capacitance sensor 33 changes due to free fall due to the weight of the detection mylar 351 will be described with reference to FIG. FIG. 8 is a graph showing how the detection level of the capacitance sensor 33 changes over time due to the free fall of the detection mylar 351. The vertical axis shows the detection level of the capacitance sensor, and the horizontal axis shows Indicates time (seconds). In FIG. 8, t1 indicates the timing when the stirring mylar 34 is rotated and the detection operation by the capacitance sensor 33 is started, and t2 indicates that the detection mylar 351 lifted up to the highest point by the stirring mylar 34 is free-falling due to its own weight. Indicates the start timing. Until t2, the detection electrode 361 provided in the detection mylar 351 is separated from the capacitance sensor electrode 321. Therefore, the detection level output from the capacitance sensor 33 to the CPU 40 is a low level (10 or less). ing. However, when the detection mylar 351 starts to fall freely, the distance between the detected electrode 361 and the capacitance sensor electrode 321 is rapidly reduced, and accordingly, the detection level output from the capacitance sensor 33 to the CPU 40 also increases. To do. When the detection mylar 351 falls on the toner 28 and stops, the distance between the detected electrode 361 and the capacitance sensor electrode 321 becomes constant, so that the detection level of the capacitance sensor 33 is also stabilized at a constant value. . In this embodiment, as shown at t3 in FIG. 8, the CPU 40 sets the rising threshold of the detection level indicating that the detection mylar 351 has started free fall to 50. The CPU 40 detects that the detection mylar 351 has started free fall due to its own weight by detecting the timing (t3) when the rising threshold is exceeded from the low level (10 or less).

  In S104, if the CPU 40 determines that the capacitance between the detected electrode 361 and the capacitance sensor electrode 321 does not exceed a certain value and does not detect the rising of the detection level, the CPU 40 proceeds to S108. If the CPU 40 determines in S104 that the rising of the detection level has been detected, the process proceeds to S105. In S <b> 105, the CPU 40 determines whether or not the detection mylar 351 that has started free fall has dropped on the toner 28 and has stopped on the toner surface. In this embodiment, the CPU 40 determines that the detection mylar 351 has stopped on the toner surface when the change in the detection level output from the capacitance sensor 33 is 2 or less for 0.05 seconds (50 milliseconds) or more. To do. Note that the detection level fluctuation range and time setting for detecting the timing at which the detection mylar 351 stops on the toner surface vary depending on the development unit configuration, the capacitance sensor, and the peripheral circuit. Therefore, it is not limited to this. In S105, when the state where the fluctuation range of the detection level output from the capacitance sensor 33 to the CPU 40 is 2 or less continues for 0.05 seconds or more, the CPU 40 proceeds to S106, and if not, The process proceeds to S108.

  In S108, the CPU 40 reads the timer value from the timer, determines whether or not 2 seconds or more have elapsed since the detection of the detection level by the capacitance sensor 33, and returns to S103 if it is less than 2 seconds. When two seconds or more have elapsed, the CPU 40 proceeds to S109. In S109, the detection level of the capacitance sensor 33 does not exceed the rising threshold value for two seconds or more. Determine and notify the video controller 42.

  In S106, the CPU 40 compares the detection level output from the capacitance sensor 33 in S103 with the detection level of the table T1 stored in the ROM of the storage unit, and calculates the remaining amount of the corresponding toner 28. In S107, the CPU 40 notifies the video controller 42 of the remaining amount of toner 28 calculated in S106.

  As described above, according to the present exemplary embodiment, the remaining amount can be detected with high accuracy regardless of the amount of toner with a simple configuration. In this embodiment, the remaining amount of toner corresponding to the capacitance is calculated by detecting the capacitance between the detection electrode of the detection mylar and the capacitance sensor electrode installed on the bottom surface of the developing unit. As a result, the remaining amount can be sequentially detected until the toner is full from the full state.

  In Example 1, with the sensitivity of the electrostatic capacity sensor being constant, the magnitude of the electrostatic capacity between the detected electrode of the detection mylar and the electrostatic capacity sensor electrode on the bottom surface of the developing unit is detected, and the remaining toner is detected. The amount was calculated. On the other hand, in this embodiment, an example in which the sensitivity of the remaining amount of toner is further improved as compared with the first embodiment by changing the sensitivity of the capacitance sensor in accordance with the remaining amount of toner will be described. . The configurations of FIGS. 1, 2, and 3 described in the first embodiment and the detection operations of FIGS. 4 and 5 are also applied to this embodiment. Further, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is given in the first embodiment, so that the description in this embodiment is omitted.

[Detection characteristics of remaining toner detection]
FIG. 9A is a characteristic graph of the remaining amount of toner 28 and the detection level of the capacitance sensor for each sensitivity set in the capacitance sensor 33. The vertical axis represents the detection level, and the horizontal axis represents the remaining amount of toner. (%). In FIG. 9A, the remaining amount of toner 28 and the electrostatic capacity at a sensitivity of 46 are plotted with a solid line, a sensitivity of 69 is plotted with a dashed-two dotted line, and a sensitivity of 92 is plotted with a broken line. 3 is a graph showing characteristics of a detection level of a sensor 33. Referring to the characteristic graph in the case of sensitivity 69 in FIG. 9A, the detection level of the capacitance sensor 33 with respect to the change in the remaining amount of toner in the region where the remaining amount of toner 28 is 25% or less and the region where 60% or more is present. It can be seen that the rate of change of the toner becomes small and it is difficult to determine the remaining amount of toner with high accuracy.

  Looking at the characteristic graph in the case of sensitivity 92, the change in the remaining amount of toner in the region 903 where the remaining amount of toner 28 is large (the remaining amount of toner 28 is 60% to 100%) compared to the characteristic graph of sensitivity 69. The rate of change in the detection level of the capacitance sensor 33 with respect to is large. In addition, the characteristic graph in the case of sensitivity 46 shows that the remaining amount of toner in the region 904 where the remaining amount of toner 28 is smaller than the characteristic graph of sensitivity 69 (the remaining amount of toner is 0% to 25%). The rate of change in the detection level of the capacitance sensor 33 with respect to the change is large. Therefore, if a larger sensitivity is set in the capacitance sensor 33 in the region 903 of FIG. 9A and a smaller sensitivity is set in the capacitance sensor 33 in the region 904, the capacitance is detected. Compared to the case of Example 1, the detection accuracy of the remaining amount of toner 28 can be improved.

  FIG. 9B is a diagram in which the region is divided by the sensitivity set in the capacitance detection of the characteristic graph of FIG. In this embodiment, the sensitivity set in the capacitance sensor 33 is sensitivity 46 in a region 905 where the remaining amount of toner is less than 25%, and sensitivity 69 in a region 906 where the remaining amount of toner is 25% or more and less than 60%. The sensitivity 92 is set in the region 907 where the remaining amount of toner is 60% or more. Note that the sensitivity set according to the remaining amount of toner varies depending on the development unit configuration, the capacitance sensor 33 and the peripheral circuit, and is not limited to the values set in this embodiment.

  Tables T1 to T3 in FIG. 10 are tables in which the correspondence relationship between the detection level of the capacitance sensor 33 and the remaining amount of toner (%) is tabulated from the characteristic graph of FIG. 9A. The table T1 in FIG. 10A is a sensitivity 69, the table T2 in FIG. 10B is a sensitivity 46, and the table T3 in FIG. The remaining amount of toner 28 corresponding to the detection level not explicitly shown in each table can be obtained by linear interpolation of the remaining amount of known toner 28 described in the table. Here, since the measured detection level is a value in the present embodiment, the measured detection level changes as the measurement conditions change. The same applies to the numerical values in each table for determining the remaining amount of toner 28.

[Toner remaining amount detection processing sequence]
Next, a processing sequence for detecting the remaining amount of toner in this embodiment will be described with reference to the flowchart of FIG. The processing of S201 to S205, S212, and S213 in FIG. 11 is the same as S101 to S105, S108, and S109 in the flowchart of FIG.

  In S206, as described above, in order to set the sensitivity of the capacitance sensor 33 in accordance with the remaining amount of the toner 28, the CPU 40 sets the toner at the sensitivity 69 from the detection level output from the capacitance sensor 33 in S203. Judge the remaining amount. If it is determined that the detection level is greater than 225 and the remaining amount of toner 28 at sensitivity 69 is less than 25%, the CPU 40 proceeds to S207. In S207, the sensitivity of the capacitance sensor 33 is switched to 46, and the process proceeds to S210. If it is determined in S206 that the detection level is 225 or less, the CPU 40 proceeds to S208, and in S208, it is determined whether or not the detection level is greater than 155. If the detection level is greater than 155, the remaining amount of toner 28 is 25% or more and less than 60%, so the CPU 40 keeps the sensitivity of the capacitance sensor 33 at 69 and does not perform the switching operation, and proceeds to S210. move on. When the detection level is 155 or less, it is determined that the remaining amount of the toner 28 is 60% or more, and the CPU 40 proceeds to S209. In S209, the sensitivity of the capacitance sensor 33 is switched to 92, and the process proceeds to S210.

  In S <b> 210, the CPU 40 reads the detection level from the capacitance sensor 33 again using the sensitivity according to the remaining amount of the toner 28 determined in the processes from S <b> 206 to S <b> 209. Then, the CPU 40 compares the read detection level with the detection level of the table corresponding to the corresponding sensitivity stored in the ROM of the storage unit, and calculates the remaining amount of the toner 28. In S211, the CPU 40 notifies the video controller 42 of the remaining amount of toner 28 calculated in S210.

  As described above, according to the present exemplary embodiment, the remaining amount can be detected with high accuracy regardless of the amount of toner with a simple configuration. That is, the sensitivity of the electrostatic capacity sensor is switched according to the remaining amount of toner, and the remaining amount of toner is calculated based on a table corresponding to the sensitivity and the detection level from the electrostatic capacity sensor. In this case, it is possible to further improve the detection accuracy of the remaining amount of toner.

  In Example 1, with the sensitivity of the electrostatic capacity sensor being constant, the magnitude of the electrostatic capacity between the detected electrode of the detection mylar and the electrostatic capacity sensor electrode on the bottom surface of the developing unit is detected, and the remaining toner is detected. The amount was calculated. Further, in the second embodiment, the detection accuracy of the remaining amount of toner is improved as compared with the first embodiment by changing the sensitivity of the capacitance sensor in accordance with the remaining amount of toner. In this embodiment, with the detection mylar stopped on the toner surface, the sensitivity of the capacitance sensor is swept, and the remaining amount of toner is calculated from the sensitivity value when the target value of the detection level matches the measured value. An example in which the calculation accuracy of the remaining amount of toner is further improved by calculation will be described. In Examples 1 and 2, the remaining amount of toner was sequentially detected while the stirring mylar was rotating. However, in this embodiment, since it takes time to sweep the sensitivity of the capacitance sensor, the rotating operation of the stirring mylar is stopped and the remaining amount is detected while the detection mylar is stopped on the toner surface. And

  The configurations of FIGS. 1, 2, and 3 described in the first embodiment and the detection operations of FIGS. 4 and 5 are also applied to this embodiment. Further, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is given in the first embodiment, so that the description in this embodiment is omitted.

[Detection characteristics of remaining toner detection]
FIG. 12A is a characteristic graph showing the relationship between the remaining amount of toner 28 whose measured value matches the target value of the detection level of the capacitance sensor 33 and the sensitivity of the capacitance sensor when the sensitivity is swept. Yes, the vertical axis indicates the sensitivity, and the horizontal axis indicates the remaining amount of toner (%). In this embodiment, the target value of the detection level of the capacitance sensor 33 is set to 150. For example, a point 908 in FIG. 12A sweeps the sensitivity of the capacitance sensor 33 when the remaining amount of the toner 28 is 66%, and the static level when the detection level of the capacitance sensor reaches the target value 150. It shows that the sensitivity of the capacitance sensor is 69. The same applies to points 909 and 910. The point 909 indicates that the sensitivity of the capacitance sensor 33 is 46 when the remaining amount of toner 28 is 35%, and the point 910 indicates that the remaining amount of toner 28 is 100%. It shows that the sensitivity of the capacitance sensor 33 is 92, respectively. As a result, when the relationship between the remaining amount of toner and the sensitivity of the capacitance sensor when the detection level of the capacitance sensor 33 reaches 150 is plotted according to the remaining amount of each toner 28, FIG. It becomes the characteristic graph of (a). In this characteristic graph, since the relationship between the remaining amount of toner 28 and the sensitivity of the detected capacitance sensor 33 is linear, Example 1 and Example 2 are used until the toner is fully loaded until it becomes empty. The remaining amount of toner can be sequentially detected with higher accuracy. The target value of the detection level of the capacitance sensor 33 used here and the relationship between the remaining amount of toner and the sensitivity vary depending on the development unit configuration, the capacitance sensor, and the peripheral circuit. It is not limited to graphs.

  FIG. 12B is a table T4 that tabulates the correspondence between the sensitivity of the capacitance sensor 33 and the remaining amount of toner (%) from the characteristic graph of FIG. The remaining amount of toner 28 corresponding to the sensitivity not explicitly shown in the table T4 can be obtained by linear interpolation of the remaining amount of the known toner 28 described in the table T4. Here, since the measured sensitivity of the capacitance sensor 33 is the value in this embodiment, the sensitivity of the measured capacitance sensor also changes if conditions such as the capacitance sensor and the peripheral circuit change. The same applies to the numerical values in the table T4 for determining the remaining amount of toner 28.

[Toner remaining amount detection processing sequence]
Next, the processing sequence for detecting the remaining amount of toner in this embodiment will be described with reference to the flowchart of FIG. The processes of S301 to S304, S314, and S316 in FIG. 13 are the same as S101 to S104, S108, and S109 in the flowchart of FIG.

  If the CPU 40 determines in S304 that the detection level rise has been detected, the process proceeds to S305. In S <b> 305, the CPU 40 stops the rotation of the stirring mylar 34 before the stirring mylar 34 rotates and contacts the detection mylar 351. The rotation of the stirring mylar 34 is stopped when the detection mylar 351 is stopped on the toner surface of the toner container 23 and the CPU 40 sweeps the sensitivity of the capacitance sensor 33 from 1 to 92 to This is because it takes time to read the detection level of the capacitance sensor. When the time required for the CPU 40 to sweep the sensitivity of the capacitance sensor 33 and read the detection level is shorter than the time during which the detection mylar 351 is stopped on the toner surface, the stirring mylar 34 is rotated. The remaining amount of toner 28 may be detected.

  In S <b> 306, the CPU 40 determines whether the detection mylar 351 that has started free-falling has fallen onto the toner 28 and stopped on the toner surface. Also in the present embodiment, as in the first and second embodiments, the CPU 40 detects the detection mylar 351 when the variation of the detection level output from the capacitance sensor 33 is 2 or less for 0.05 seconds (50 milliseconds) or more. Is determined to have stopped on the toner surface. Note that the detection level fluctuation range and time setting for detecting the timing at which the detection mylar 351 stops on the toner surface vary depending on the development unit configuration, the capacitance sensor, and the peripheral circuit. Therefore, it is not limited to this. If the state in which the fluctuation range of the detection level output from the capacitance sensor 33 to the CPU 40 is 2 or less continues for 0.05 seconds or more, the CPU 40 proceeds to S307, and if not, proceeds to S315. . In S315, the CPU 40 reads the timer value from the timer, determines whether or not 2 seconds or more have elapsed from the start of reading the detection level by the capacitance sensor 33, and returns to S306 if it is less than 2 seconds. When two seconds or more have elapsed, the CPU 40 proceeds to S316, and since the detection level of the capacitance sensor 33 has not exceeded the rising threshold for two seconds or more in S316, Determine and notify the video controller 42.

  In S307, in order to sweep the sensitivity of the capacitance sensor 33 and continuously read the detection level of the capacitance sensor, the CPU 40 performs serial communication with the capacitance sensor 33 to increase the sensitivity of the capacitance sensor. Set to the initial value of 1.

  In S308, the CPU 40 determines whether or not the sensitivity set in the capacitance sensor 33 by serial communication is 92 or less. If the sensitivity of the set capacitance sensor 33 is greater than 92, the process proceeds to S316. In S316, the capacitance is determined. The abnormality of the sensor 33 is notified to the video controller 42. If the sensitivity is 92 or less, the process proceeds to S309. In S309, the CPU 40 reads the detection level from the capacitance sensor 33 again, and in S310, compares the detection level with the target value 150. If the measured value of the detection level of the capacitance sensor 33 matches the target value, the CPU 40 proceeds to S312. If the measured value of the detection level does not match the target value in S310, the CPU 40 proceeds to S311 to perform serial communication with the capacitance sensor 33, increases the sensitivity of the capacitance sensor 33 by 1, and returns to S308. .

  In S312, the CPU 40 compares the sensitivity value of the capacitance sensor 33 set at that time with the sensitivity of the table T4 stored in the ROM of the storage unit, and calculates the remaining amount of the corresponding toner 28. To do. In S313, the CPU 40 notifies the video controller 42 of the remaining amount of toner calculated in S312.

  As described above, according to the present exemplary embodiment, the remaining amount can be detected with high accuracy regardless of the amount of toner with a simple configuration. In other words, with the detection mylar stopped on the toner surface, the sensitivity of the capacitance sensor is swept, and the remaining amount of toner is calculated from the sensitivity when the target value of the detection level matches the measured value. The detection accuracy of the remaining amount of toner can be improved as compared with Example 1 and Example 2.

  In the first to third embodiments, for the sake of easy understanding, the description has been given of collating the detection level of the capacitance sensor obtained by one detection with the table. However, if the data is averaged a plurality of times and then controlled so as to collate with each table, it can be expected that the detection accuracy is further improved. In the first to third embodiments, an example in which the developing unit is integrated is given. However, a replenishing toner container in which the developing roller and the toner container are separated is also detected inside the toner container. The present invention can be applied by providing an electrode and a detection mylar.

321 Capacitance sensor electrode 33 Capacitance sensor 34 Stirring mylar 351 Detection mylar 361 Detected electrode 40 1-chip microcomputer (CPU)

Claims (7)

A detachable developing unit for storing the developer;
A first member that includes a first electrode and is rotatable about a rotation axis in the developing unit;
A second member that circulates around a rotation shaft in the developing unit;
A second electrode disposed on the exterior of the developing unit;
Output means for detecting a capacitance between the first electrode and the second electrode and outputting data relating to the detected capacitance;
An image forming apparatus comprising: determination means for determining the amount of developer in the developing unit based on the data output from the output means.   2. The image forming apparatus according to claim 1, wherein the first member follows a rotating operation of the second member until the first member freely falls by its own weight.   The image forming apparatus according to claim 1, wherein the second member has a function of stirring the developer in the developing unit.   4. The image forming apparatus according to claim 1, wherein the first electrode is provided near a tip in a circumferential direction of the first member. 5.   The output means includes setting means for setting an amplification factor of the data, and amplification means for amplifying the data in accordance with the amplification factor set by the setting means. 5. The image forming apparatus according to any one of 4 above.   The image forming apparatus according to claim 5, wherein the output unit changes an amplification factor of the data according to a remaining amount of the developer.   The image forming apparatus according to claim 5, wherein the output unit changes the amplification factor of the data in a state where the rotation of the first member is stopped.

Images