JP2015106110A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to properly detect the amount of toner remaining in a developer container, independent of any influence of changes in dielectric constant due to moisture absorption of the toner.SOLUTION: A control processing section 91 detects the amount of toner remaining in a developer container 4b, on the basis of an integrated value x of image information signals used in image formation, in a predetermined period, and an amount of change Δy in induction voltage Vi to be obtained by capacitance change between an electrode member 4h and a developing roller 4a in a measurement period of the integrated value x.

Description

  The present invention relates to an image forming apparatus using an electrophotographic system.

  Examples of the image forming apparatus using the electrophotographic method include an electrophotographic copying machine, an electrophotographic printer such as an LED (Light Emitting Diode) printer, and a laser beam printer. Furthermore, an electrophotographic facsimile apparatus, an electrophotographic word processor, and the like are included.

  The cartridge that can be attached to and detached from the image forming apparatus main body includes an electrophotographic photosensitive member as an image bearing member, a charging unit that charges the electrophotographic photosensitive member, a developing unit that supplies a developer to the electrophotographic photosensitive member, and a cleaning unit for the electrophotographic photosensitive member. At least one of the cleaning means.

  In the process cartridge, at least one of a charging unit, a developing unit, and a cleaning unit and an electrophotographic photosensitive member are integrally formed into a cartridge, and the cartridge can be attached to and detached from the image forming apparatus main body. Alternatively, at least the developing means and the electrophotographic photosensitive member are integrally formed into a cartridge, and the cartridge can be attached to and detached from the image forming apparatus main body.

  An electrophotographic image forming apparatus such as a copying machine or a laser beam printer forms an electrostatic latent image by irradiating an electrophotographic photosensitive member (hereinafter referred to as a “photosensitive member”) corresponding to image information with light corresponding to image information. To do. Then, a developer is supplied to the electrostatic latent image by developing means to visualize it as a toner image, and further, the toner image is transferred from the photosensitive member to the recording material to form a toner image on the recording material. .

  The developing device is provided with a developer container containing toner as a developer, and the toner is consumed by forming a toner image. Each of the developing device, the photosensitive member, the charging unit, and the like is configured to be detachable from the image forming apparatus as a cartridge. Alternatively, the photosensitive member is integrally formed with other components to form a process cartridge.

  When the toner runs out, the user can form a toner image on the recording material again by replacing the developing device (developing cartridge) in a cartridge or the process cartridge provided with the developing device.

  Toner stored in a developer container of a process cartridge or a developing cartridge (hereinafter simply referred to as “cartridge”) is consumed by forming an image. A toner remaining amount detecting device is provided that detects that the remaining amount of toner stored in the developer container is too low when it is determined that the threshold value is below a preset threshold. When it is detected by the toner remaining amount detection device that the remaining amount of toner is too low, a message to that effect is displayed on the display unit provided on the operation panel.

  As a toner remaining amount detecting device, for example, as described in Patent Documents 1 and 2, an electrode member is arranged in a developer container to detect the remaining amount of toner from the remaining toner capacitance. . In such a toner remaining amount detecting device, for example, as shown in FIG. 3, a developing roller 4 a in the developer container 4 b of the developing device 4 is disposed in the vicinity of the photosensitive drum 1. Opposite to the developing roller 4a, a conductive rod-shaped electrode member 4h having an outer diameter of about 1 mm is disposed so as to be buried in the toner t accommodated in the developer container 4b. A toner remaining amount detecting device 53 is connected to the electrode member 4h.

  Here, the principle of detecting the remaining amount of toner t in the developer container 4b by the electrode member 4h will be described. For example, the capacitance between the developing roller 4a and the electrode member 4h, which changes depending on the amount of toner t accommodated in the developer container 4b of the developing device 4, can be represented by an equivalent capacitor 57 shown in FIG.

  3 and 4, an AC bias power source 41 and a DC bias power source 42 are connected in series as the developing bias power source 7 to the developing roller 4a. As shown in FIG. 4, the AC bias power supply 41 is connected to an equivalent capacitor 57 composed of the developing roller 4a shown in FIG. 3 and an electrode member 4h. The AC bias power supply 41 generates, for example, a rectangular wave having a frequency of 2400 Hz and a peak-to-peak voltage Vpp of 1600V.

  In the circuits shown in FIGS. 3 and 4, an induced voltage Vi is induced in the electrode member 4h by an electrostatic induction from an alternating voltage applied from the alternating current bias power source 41 to the developing roller 4a. The current flowing through the electrode member 4h is detected by the toner remaining amount detecting device 53 connected to the electrode member 4h. The induced voltage Vi induced in the electrode member 4 h detected by the remaining toner amount detecting device 53 varies depending on the capacitance of the equivalent capacitor 57.

  In other words, it varies with the dielectric constant between the developing roller 4a and the electrode member 4h, which varies depending on the amount of toner t interposed between the developing roller 4a and the electrode member 4h. Generally, the relative dielectric constant of toner t is about 3, and the relative dielectric constant of air is about 1. For this reason, if the amount of toner t interposed between the developing roller 4a and the electrode member 4h is large, the induced voltage Vi induced in the electrode member 4h increases.

  A toner remaining amount detection signal obtained by the toner remaining amount detecting device 53 is received by a CPU (Central Processing Unit) 54 provided in a print recording engine unit (not shown). The CPU 54 controls permission and prohibition of the image forming process. In other words, when it is determined that the remaining amount of toner detected by the remaining toner amount detecting device 53 is less than a preset threshold value in order to prevent image blanking due to a decrease in toner t, the remaining amount of toner t. Is displayed on an operation display unit (not shown).

  FIG. 5 shows the relationship between the remaining amount of toner in the developer container 4b and the induced voltage Vi induced in the electrode member 4h. When the toner t in the developer container 4b is full, the remaining amount of toner in the developer container 4b is, for example, 400 g, and the induced voltage Vi at this time is 1.80V. When the remaining amount of toner decreases due to consumption of toner t due to image formation, the induced voltage Vi induced in the electrode member 4h decreases. The remaining amount of toner that causes white spots in the image is 75 g, and the induced voltage Vi at that time is 1.45V.

  For this reason, the remaining amount of toner having a latitude (latitude; an area where the image can be satisfied. An allowable range) is 110 g with respect to white spots in the image. When the induced voltage Vi induced in the electrode member 4h at this time becomes 1.60 V as a threshold for the lower limit of the toner amount, the image formation prohibition notification is performed.

JP 2001-228697 A JP 2004-086176 A

  As shown in FIGS. 3 and 4, in the toner remaining amount detecting device 53, the induced voltage Vi induced in the electrode member 4h is determined by the capacitance between the developing roller 4a and the electrode member 4h. That is, it depends on the dielectric constant that varies depending on the amount of toner between the developing roller 4a and the electrode member 4h.

  When the humidity environment in which the developing device 4 is installed changes, the induced voltage Vi varies even with the same amount of toner t. When a fine powder such as toner t is used, moisture is contained between the powders, and the capacitance of toner t is greatly changed.

  For example, in the case of the absorbed toner t, the dielectric constant of the toner t in the proper environment (temperature 23 ° C., humidity 50%) increases, and in the case of the dry toner t, the dielectric constant of the toner t in the appropriate environment decreases. End up. This change in capacitance due to moisture absorption and drying is detected as a change in toner amount. As a result, there may be a case where an image defect or incorrect information is presented to the user. In a high-temperature and high-humidity environment, the amount of toner remaining in the developer container 4b is reduced, and white spots of the image may occur. On the other hand, in a low temperature and low humidity environment, the remaining amount of toner in the developer container 4b increases, and the running cost increases.

  FIG. 6 shows the remaining amount of toner in the developer container 4b in the high temperature and high humidity environment (temperature 30 ° C., humidity 80%) and the low temperature and low humidity environment (temperature 15 ° C., humidity 10%), and induction induced by the electrode member 4h. The relationship with the voltage Vi is shown. As shown in FIG. 6, the remaining amount of toner in the developer container 4b is 80 g when the induced voltage Vih in the high-temperature and high-humidity environment reaches 1.60 V, which is the threshold for the lower limit of the toner amount. On the other hand, the remaining amount of toner in the developer container 4b is 140 g when the induced voltage Vil in the low temperature and low humidity environment reaches 1.60 V which is the threshold for the lower limit of the toner amount. As described above, the relationship between the remaining amount of toner in the developer container 4b and the induced voltage Vi is greatly different from the change in the dielectric constant of the toner t due to the temperature and humidity environment difference.

  SUMMARY OF THE INVENTION The present invention solves the above-described problems, and an object of the present invention is to accurately detect the remaining amount of toner in a developer container without being influenced by the influence of change in dielectric constant due to moisture absorption of toner. An image forming apparatus is provided.

  In order to achieve the above object, a typical configuration of an image forming apparatus according to the present invention includes an image carrier on which an electrostatic latent image is formed, and developing means for supplying toner to the image carrier. The developing means includes a developer container that contains toner, a developer carrier that carries and transports the toner in the developer container and supplies the toner to the electrostatic latent image of the image carrier, and the developer carrier. An AC voltage is applied to the developer carrier by the developer bias power source, an electrode member spaced apart from the developer carrier within the developer container, and the developer bias power source. A toner remaining amount detecting means for detecting the remaining amount of toner in the developer container based on an induced voltage induced in the electrode member in accordance with a capacitance between the developer carrying member and the electrode member And the toner remaining amount detecting means has a predetermined period. In, and detecting the integrated value x of the image information signals to be used for image formation, the toner remaining amount of the developer container from the variation Δy of the induced voltage.

  According to the above configuration, the integrated value of the image information signal used for image formation is calculated in a predetermined period by the video count method of counting and integrating the number of development dots of the entire image. In this predetermined period, an induced voltage obtained by a change in capacitance between the developer carrier and the electrode member during the measurement period of the integrated value of the image information signal used for image formation is detected.

  When the amount of change in the induced voltage is equal to or less than a predetermined value, it is detected that the toner in the developer container has decreased. That is, when there is almost no change in the induced voltage with respect to the toner consumption, it is detected that the amount of toner in the developer container has decreased, so that errors due to changes in the temperature and humidity environment can be prevented. As a result, the remaining amount of toner can be accurately detected without being influenced by the change in the dielectric constant due to the moisture absorption of the toner.

1 is an explanatory cross-sectional view illustrating a configuration of an image forming apparatus according to the present invention and a block diagram of a control system. It is a cross-sectional explanatory view showing the configuration of the developing means. FIG. 2 is a cross-sectional explanatory view and a control system block diagram showing a configuration of a toner remaining amount detecting means provided between a developer carrying member and an electrode member. FIG. 3 is a block diagram showing a circuit configuration in which an electrostatic capacity between a developer carrier and an electrode member is regarded as an equivalent capacitor. FIG. 5 is a diagram illustrating a relationship between toner weight in a developer container and induced voltage induced in an electrode member. It is a figure which shows the relationship between the toner weight in a developer container accompanying an environmental change, and the induced voltage induced by an electrode member. FIG. 5 is a diagram illustrating a relationship between toner weight in a developer container and induced voltage induced in an electrode member. It is a figure explaining the method to count the image density information of an image information signal. It is a figure which shows the relationship between the number of dots in the predetermined area | region in the video count detection, and the toner consumption per dot. FIG. 6 is a diagram illustrating a relationship between a toner weight in a developer container accompanying an environmental change and an induced voltage induced in an electrode member in the embodiment. (A)-(c) is sectional explanatory drawing which shows the quantity and surface state of the toner in a developer container. FIG. 6 is a schematic diagram for explaining electrical resistance when current is supplied to toner. 6 is a flowchart for explaining a toner amount lower limit detection operation in the present embodiment. 12 is a flowchart for explaining a toner amount lower limit detection operation in another embodiment.

<Image forming apparatus>
An embodiment of the image forming apparatus 8 according to the present invention will be specifically described with reference to the drawings. An image forming apparatus 8 shown in FIG. 1 is a copying machine. As shown in FIG. 1, the image forming apparatus 8 includes a print recording engine unit 10 that executes an image forming operation, and a controller unit 9 that serves as a control unit that controls various operations in the print recording engine unit 10. It is configured. Various control signals from a control processing unit 91 provided in the controller unit 9 are sent to the print recording engine unit 10.

  First, the print recording engine unit 10 of the image forming apparatus 8 is configured, for example, as a process cartridge 11 that is detachable from the main body of the image forming apparatus 8 as shown in FIG. The print recording engine unit 10 as the process cartridge 11 includes a photosensitive drum 1 serving as an image carrier on which an electrostatic latent image is formed. Further, a developing device 4 is provided as developing means for supplying the toner t to the photosensitive drum 1. Furthermore, it has the cleaning apparatus 6 which has the cleaning blade 6a used as a cleaning means. Furthermore, it has a charging roller 2 as charging means for charging the surface of the photosensitive drum 1.

  The photosensitive drum 1 is a rotating drum type electrophotographic photosensitive member. In the photosensitive drum 1 of this embodiment, an organic photoconductor (OPC) layer is formed as a photosensitive layer 1a on the outer peripheral surface of an aluminum drum base 1b. The photosensitive drum 1 has an outer diameter of about 30 mm. The photosensitive drum 1 is rotationally driven at a predetermined process speed (94.5 mm / second in this embodiment) in the direction of arrow A in FIG.

  A charging bias voltage is applied by the charging roller 2 to the photosensitive drum 1 rotating in the direction of arrow A in FIG. As a result, the surface of the photosensitive drum 1 is charged to a predetermined potential. The surface of the charged photosensitive drum 1 is irradiated with laser light 3a corresponding to image information emitted from a laser scanner 3 serving as exposure means.

  Laser light 3a emitted from the laser scanner 3 is swept by a rotating polygon mirror 3b, and is spot-imaged on the surface of the photosensitive drum 1 by a lens 3c such as an fθ lens and a mirror 3d that directs the laser light 3a in the direction of the photosensitive drum 1. Is done. The fθ lens has a lens characteristic (fθ characteristic) that forms an image having a size (f × θ) obtained by multiplying the focal length f of the fθ lens when the laser beam 3a enters at an angle θ. In this way, the laser beam 3a scans the surface of the photosensitive drum 1 in a direction (main scanning direction) substantially parallel to the rotation axis of the photosensitive drum 1, thereby forming an electrostatic latent image.

  The electrostatic latent image formed on the surface of the photosensitive drum 1 is developed with the toner t supplied from the developing device 4. A recording material P is conveyed from a recording material feeding unit (not shown) to a transfer unit between the photosensitive drum 1 and a transfer roller 5 serving as a transfer unit in contact with the photosensitive drum 1 at an appropriate timing. The toner image formed by development on the surface of the photosensitive drum 1 is transferred to the recording material P by applying a transfer bias voltage at the transfer portion.

  The recording material P onto which the toner image has been transferred through the transfer section is separated from the surface of the photosensitive drum 1 and conveyed to a fixing section (not shown) provided outside the process cartridge 11 to fix the toner image onto the recording material P. Is done. Further, the toner t remaining on the surface of the photosensitive drum 1 after the transfer is separated by being scraped off by the sliding contact force of the cleaning blade 6 a disposed so as to be in pressure contact with the surface of the photosensitive drum 1. The toner t scraped off by the cleaning blade 6a is stored in a collected toner storage portion 6b provided in the cleaning device 6 holding the cleaning blade 6a.

<Developing device>
Next, the configuration of the developing device 4 that visualizes the electrostatic latent image formed on the surface of the photosensitive drum 1 with the toner t as a developer will be described with reference to FIG. As shown in FIG. 2, the developing device 4 as a developing unit includes a developer container 4b that stores toner t. Further, a developing roller 4a serving as a developer carrying member for carrying and transporting the toner t in the developer container 4b (in the developer container) and supplying the toner t to the electrostatic latent image formed on the surface of the photosensitive drum 1 is provided. Yes. Further, as shown in FIG. 4, a developing bias power source 7 for applying a developing bias voltage including an AC voltage to the developing roller 4a is provided. A developing bias voltage is applied from the developing bias power source 7 to the developing roller 4 a to supply the toner t to the surface of the photosensitive drum 1.

  As shown in FIG. 2, the developer container 4b serving as a developer container of the developing device 4 includes a developing chamber 4c and a toner chamber 4d. The developing chamber 4c is provided with a stirring member 4e that uniformly stirs the toner t in the developing chamber 4c. The toner chamber 4d is provided with a stirring member 4f for uniformly stirring the toner t in the toner chamber 4d and transporting the toner t to the developing chamber 4c.

  The developing roller 4a of this embodiment is a developer carrying member in which a rotatable sleeve is disposed on the outer periphery of a plurality of fixed magnetic poles. The toner t carried on the surface of the developing roller 4a is uniformly regulated by a developing blade 4g serving as a toner layer thickness regulating means, and then conveyed to a developing area facing the photosensitive drum 1. Then, the electrostatic latent image formed on the surface of the photosensitive drum 1 is developed with or without contact with the photosensitive drum 1 by a developing bias voltage applied to the developing roller 4a. The developing device 4 is driven in conjunction with the developing roller 4a and the stirring members 4e and 4f.

  The developing bias voltage applied to the developing roller 4 a from the developing bias power source 7 is composed of an AC voltage output from the AC bias power source 41 and a DC voltage output from the DC bias power source 42. Due to the potential difference between the electrostatic latent image portion on the surface of the photosensitive drum 1 and the developing bias voltage applied to the developing roller 4 a by the developing bias power source 7, the toner t on the surface of the developing roller 4 a is electrostatically charged on the surface of the photosensitive drum 1. Supply to the latent image and develop. The AC bias power supply 41 generates a rectangular wave having a frequency of 2400 Hz and a peak-to-peak voltage Vpp of 1600 V, for example, and the DC bias power supply 42 generates a DC voltage of −440 V, for example.

  In addition, a rod-shaped electrode member 4h is provided in the developing chamber 4c (in the developer container) so as to face and separate in parallel in the vicinity of the developing roller 4a. The electrode member 4h is disposed so as not to be positioned on the rotation locus of the stirring member 4e in the developing chamber 4c. Further, as shown in FIG. 11B, the outer diameter upper vertex 4h1 of the electrode member 4h is disposed below the horizontal plane h including the outer diameter upper vertex 4a1 of the developing roller 4a.

  The electrode member 4h of the present embodiment is formed of a conductive metal rod having a diameter of 4 mm. For example, in this embodiment, stainless steel (SUS) is used to prevent rust of the electrode member 4h. As shown in FIG. 1, an induced voltage detector 91d is connected to the electrode member 4h. The electrode member 4h is disposed so as to be buried in the toner t when the toner t is sufficiently contained in the developer container 4b.

<Toner remaining amount detecting means>
The toner remaining amount detection using the electrode member 4h in the present embodiment will be described. In this embodiment, the developing roller 4a and the electrode member 4h are regarded as equivalent capacitors 57 each having an electrode, and the capacitance that varies according to the amount of toner interposed between the developing roller 4a and the electrode member 4h is detected. . An AC voltage is applied from the AC bias power supply 41 to the developing roller 4a.

  Then, an induced voltage Vi composed of an alternating voltage is induced by the electrode member 4h disposed in the vicinity of the developing roller 4a by electrostatic induction. The current flowing through the electrode member 4h is detected as an induced voltage Vi by the induced voltage detector 91d connected to the electrode member 4h. An induced voltage Vi is converted into a signal and calculated by a CPU (Central Processing Unit) 91a serving as a control means.

  The induced voltage Vi changes as the capacitance of the equivalent capacitor 57 changes. That is, it changes with the dielectric constant between the electrodes, which changes depending on the amount of toner t interposed between the developing roller 4a and the electrode member 4h. Generally, the relative dielectric constant of toner t is about 3, and the relative dielectric constant of air is about 1. For this reason, if the amount of toner t interposed between the developing roller 4a and the electrode member 4h is large, the induced voltage Vi induced in the electrode member 4h increases.

  The principle of toner remaining amount detection in this embodiment will be described. A control processing unit 91 serving as toner remaining amount detecting means performs the following control. When an AC voltage is applied to the developing roller 4a by the AC bias power source 41 of the developing bias power source 7, an induced voltage Vi induced in the electrode member 4h according to the electrostatic capacity between the developing roller 4a and the electrode member 4h is set. Detected by the induced voltage detector 91d. Then, the remaining amount of toner in the developer container 4b is detected based on the induced voltage Vi detected by the induced voltage detector 91d.

  In the present embodiment, as shown in FIG. 4, an equivalent capacitor 57 is assumed by regarding the developing roller 4a and the electrode member 4h as electrodes. An induced voltage Vi is induced in the electrode member 4h corresponding to the electrostatic capacity between the developing roller 4a and the electrode member 4h by the developing bias voltage applied to the developing roller 4a. This induced voltage Vi is detected by the induced voltage detector 91d. That is, the induced voltage Vi induced in the electrode member 4h is detected from the amount of toner t interposed between the developing roller 4a and the electrode member 4h in the developer container 4b.

  The electrostatic capacity between the developing roller 4a and the electrode member 4h decreases due to consumption of the toner t. For this reason, the induced voltage Vi induced in the electrode member 4h decreases. However, as shown in FIG. 7, there is a region b in which the induced voltage Vi does not decrease with the consumption of the toner t. This is when the boundary surface t1 between the toner layer and the air layer in the developer container 4b is in contact with the electrode member 4h, as shown in FIG. 11B.

  The toner t is a dielectric like air. The relative dielectric constant of the toner t is about 3, and the relative dielectric constant of air is about 1. The component of toner t contains a slight amount of a conductive material, and a very small amount of current flows. In particular, as shown in FIG. 12, the surface resistances Rc of the toners ta and tb are lower than the internal resistances Ra and Rb of the toners ta and tb.

  Therefore, when the boundary surface t1 between the toner layer and the air layer in the developer container 4b is in contact with the electrode member 4h, the behavior as the equivalent capacitor 57 is not exhibited. The developing bias voltage applied to the developing roller 4a causes a current to flow through the electrode member 4h via the boundary surface t1 between the toner layer and the air layer in the developer container 4b. As a result, the equivalent capacitor 57 in which the developing roller 4a and the electrode member 4h are regarded as electrodes does not change in electrostatic capacity, and is induced in the electrode member 4h with respect to the change in the weight of the toner t in the developer container 4b. The induced voltage Vi does not change.

  In the present embodiment, such a principle is applied to detect that the amount of toner in the developer container 4b has decreased. The electrode member 4h is disposed in the vicinity of the developing roller 4a. For this reason, as shown in FIG. 11B, the electrode member 4h buried in the toner layer when the remaining amount of toner in the developer container 4b decreases is the boundary surface t1 between the toner layer and the air layer. Exposed from.

  As a result, as shown in FIG. 7, a region b where the change in the induced voltage Vi induced in the electrode member 4h with respect to the consumption of the toner t in the developer container 4b is almost eliminated is reached. At that time, as shown in FIG. 11B, the toner t in the developer container 4b decreases, and the boundary surface t1 between the toner layer and the air layer is in contact with the electrode member 4h.

  A control processing unit 91 serving as a toner residual detection unit performs the following control. An induced voltage Vi induced in the electrode member 4h obtained by a change in electrostatic capacitance between the electrode member 4h and the developing roller 4a during the measurement period of the integrated value x of the image information signal used for image formation in a predetermined period. Detected by the induced voltage detector 91d. When the amount of change in the induced voltage Vi (the amount of change in the induced voltage) is Δy and the constant is z, when the following equation 1 is obtained, the remaining amount of toner in the developer container 4b is the lower limit of the predetermined amount. Detect that the value has fallen below.

[Equation 1]
Δy / x ≦ z

  Then, control is performed at the following timing by a control processing unit 91 serving as a toner residual detecting unit. That is, the timing for detecting the remaining amount of toner in the developer container 4b from the integrated value x of the image information signal used for image formation and the amount of change Δy of the induced voltage in the predetermined period shown in Equation 1 is as follows. It is as follows. That is, it is performed when the induced voltage Vi induced in the electrode member 4h becomes a predetermined value or less.

  The consumption amount of the toner t can be calculated from the video count count value by using a video count method in which the number of image information amounts of the entire image of the image information signal in a predetermined period is counted and integrated.

  The toner remaining amount detection control in the developer container 4b using the induced voltage Vi induced in the electrode member 4h is always performed during the image forming operation (printing operation). That is, in FIG. 1, the analog detection signal output from the electrode member 4h to the induced voltage detection unit 91d by the toner remaining amount detection control operation during the image forming operation is always sampled at a minute interval of, for example, about 4 msec by the CPU 91a as the control means. Is done. Then, 100 sampling signal values, that is, 0.4 sec are treated as one block section. Then, an average value k of the sampling signal in the one block section is calculated.

  An average induced voltage signal as an average toner remaining amount value based on an electrostatic capacity corresponding to the remaining amount of toner in the developer container 4b will be viewed roughly in relation to the remaining amount of toner in the developer container 4b. Then, for example, it is represented by a curve of the induced voltage Vi shown in FIG. In FIG. 7, the horizontal axis represents the toner weight as the remaining amount of toner in the developer container 4b, and the vertical axis represents the induced voltage Vi induced in the electrode member 4h. As shown in FIG. 7, when the toner t in the developer container 4b is full, the remaining amount of toner in the developer container 4b is 400 g. As the toner t is consumed, the induced voltage Vi that becomes an average remaining toner value based on the electrostatic capacity of the remaining amount of toner also starts to decrease.

<Controller section>
Next, the configuration of the controller unit 9 will be described with reference to FIG. As shown in FIG. 1, an induced voltage detection unit 91d and a video counter detection unit 91i are connected to a CPU 91a of a control processing unit 91 which is a toner remaining amount detection unit provided in the controller unit 9. Further, a ROM (Read Only Memory) 91b in which various other control programs are stored is connected. Further, RAM (Randam Access Memory) 91c for temporarily storing various data during execution of the control program is connected.

  The control processing unit 91 is connected to a document reading device 92 serving as a scanner unit used for a copy (copying) function and a printer interface 93 for receiving image data to be printed out from an external device. Further, a modem 94 such as a facsimile machine that receives image data from the telephone network is connected. A plurality of types of image data are captured by the image signal processing unit 91e in the control processing unit 91 through each of the document reading device 92, the printer interface 93, and the modem 94 as these three types of image data capturing units.

  Next, control operations from image signal processing to exposure by the laser scanner 3 will be described. Data to be printed out is sent to the image signal processing unit 91e as an electrical signal from the document reading device 92 serving as a scanner unit used in the copy function shown in FIG. 1 and the printer interface 93 that receives image data to be printed out from an external device. . Further, data to be printed out from a modem 94 such as a facsimile machine that receives image data from the telephone network is sent as an electric signal to the image signal processing unit 91e.

  The image signal processing unit 91e converts these data into video signals for each scanning line, and the pulse width modulation unit 91f generates laser drive pulses E, I, and W having a width (time length) corresponding to the level. Form and output. That is, as shown in FIG. 8A, a wider laser driving pulse W is formed for a high-density pixel image signal. Further, a narrower laser driving pulse E is formed for a low density video signal. Then, an intermediate-width laser drive pulse I is formed for each medium-density video signal.

  In FIG. 1, laser drive pulses E, I, and W output from a pulse width modulation unit 91f are supplied to a laser scanner 3, and the laser scanner 3 emits laser light 3a for a time corresponding to the pulse width. Therefore, the laser scanner 3 is driven for a longer time with respect to the high density pixel and is driven with a shorter time for the low density pixel. Therefore, the photosensitive drum 1 is exposed to a longer range in the main scanning direction for high density pixels by an optical system including the laser scanner 3, the rotary polygon mirror 3b, the lens 3c, the mirror 3d, and the like, and for the low density pixels. A shorter range is exposed in the main scanning direction.

  That is, the size (area) of the electrostatic latent image varies depending on the pixel density. Therefore, the toner consumption amount for the high density pixel is larger than the toner consumption amount for the low density pixel. FIG. 8D shows an electrostatic latent image L of low density pixels, an electrostatic latent image M of medium density pixels, and an electrostatic latent image H of high density pixels from the left.

  The control processing unit 91 is connected to a display unit 96 that displays the operation state of the image forming apparatus 8 and operation messages. Further, a key input unit 97 for outputting an operation command signal is connected. Then, the image data appropriately output based on the operation command and the received content is sent to the print recording engine unit 10 shown in the upper part of FIG. 1 together with video signals based on the image data together with various control signals. Thereby, an appropriate image forming operation (printing operation) is executed. During the image forming operation (printing operation), the remaining toner amount detecting operation is executed by the control processing unit 91 serving as a remaining toner amount detecting unit.

  In the present embodiment, a document reading device 92, a printer interface 93, and a modem 94, which are three types of image data capturing units, are provided. A video signal obtained from the image data captured via these is counted for each pixel by an image signal processing unit 91e serving as a video counter detection unit. Thus, the toner consumption is counted. Then, the CPU 91a calculates the remaining amount of toner based on the toner consumption count result and the toner remaining amount detection result.

  First, a video count counting method by the video counter detection unit 91i serving as a toner consumption amount detection unit will be described. In the video count counting method, the toner consumption amount of the developing device 4 is predicted from the exposure amount (time) in the exposure of the photosensitive drum 1 for forming an electrostatic latent image.

  The output signal converted by the pulse width modulator 91f is supplied to one input terminal of the AND gate 91h, and the other input terminal of the AND gate 91h is output from the clock pulse oscillator 91g in FIG. 8B. The clock pulses shown are supplied. As a result, as shown in FIG. 8 (c), the number of clock pulses corresponding to the pulse width of each of the laser drive pulses E, I, and W shown in FIG. The number of clock pulses corresponding to is output.

  The number of clock pulses shown in FIG. 8C is integrated by the video counter detector 91i. The accumulated clock pulse number that becomes the pulse accumulated signal accumulated by the video counter detection unit 91i is the amount of toner consumed from the developer container 4b to form one pixel (one dot) of the toner image. Mostly supported.

  The toner remaining amount detection using the electrode member 4h and the toner consumption amount detection by the video count method will be described. The video counter detection unit 91i serving as the toner consumption amount detection unit divides one page of the recording material P into a plurality of regions, and distinguishes whether the image in each region is a solid image or a line image depending on the number of dots in each region. . Then, the toner consumption per dot is determined according to the image type of each area. Multiply it by the number of dots to find the amount of toner consumed in each area. Then, the toner consumption amount is obtained by adding the toner consumption amounts of the respective regions.

  The image forming apparatus 8 of the present embodiment is a 600 dpi (dot / inch) copying machine. For example, the image formable area of the recording material P of letter size (216 mm × 279 mm) is 204 mm × 269 mm. When this is converted into dots, it is 4819 dots × 6354 dots. Therefore, in this embodiment, one page is divided into 40 × 60 = 2400 areas. One area has a size of approximately 4.7 mm × 4.2 mm (120 dots × 106 dots).

  When a video signal is sent from the pulse width modulation unit 91f to the laser scanner 3 as a signal for emitting the laser beam 3a, a horizontal synchronizing signal (BD signal) comes to the head of the scanning line. Then, a video signal comes after a certain time from the horizontal synchronizing signal (BD signal). For this reason, the start position of the video signal can be found by detecting the horizontal synchronizing signal (BD signal). The dot count in each region starts counting from zero again at regular intervals. The counting result is sent to the memory and stored for each counted area. In this way, the number of pixel dots in the scanning direction of the laser beam 3a in each region can be counted. Further, the number of scanning lines can be determined by counting the horizontal synchronizing signal (BD signal).

  In the present embodiment, the count result at the same position as the counted area of the previous scanning line is added to the previous counted result as the same area up to 106 times of the horizontal synchronization signal (BD signal). The count result in the scanning direction at the same position is stored in a new area every 106 times of the horizontal synchronizing signal (BD signal). Thus, a number from 0 to 12720 (120 dots × 106 times) is stored as the number of pixels for each area.

  At this time, in particular, in counting in the scanning line direction, a slight error may occur even if it is performed every predetermined time. Each region does not always have a scanning direction of 120 dots, and there is some increase or decrease. However, in this embodiment, the toner consumption per dot is determined for every 3000 dots. This has no significant effect on the division error in the scanning direction. In this way, the number of dots for each region is counted and stored in the RAM 91c serving as storage means.

  Next, the number of dots in each region is converted into a toner consumption amount by multiplying the value of the toner consumption conversion table shown in FIG. 9 by the CPU 91a serving as a multiplying means, and the RAM 91c stores the toner consumption amount for each region. Remembered.

  If the number of dots is small in each area, it is regarded as a line image. If there are a large number of dots in each area, it is regarded as a solid image. The number of pixel dots in the previously obtained area is multiplied by the value in the toner consumption conversion table shown in FIG. 9 to calculate the toner consumption for each area. The values in the toner consumption conversion table shown in FIG. 9 are values unique to the image forming apparatus 8. It is necessary to perform a test in advance with the image forming apparatus 8 to determine the numerical value of the toner consumption conversion table shown in FIG. In this embodiment, the sections D1 to D4 of the toner consumption conversion table shown in FIG. 9 are divided into four types of toner consumption according to the number of dots in the area. The section D of the toner consumption conversion table shown in FIG. 9 may be any section as long as it is two or more sections, and can be set as appropriate according to the memory capacity, calculation speed capability, and the like.

For example, when the toner consumption amount in the image forming operation of the letter-size recording material P is obtained using the toner consumption amount conversion table shown in FIG. 9, the number of areas per page is 2,400. Assume that the video count count result is 600 areas where the number of dots is 0, and 1000 areas (section D1) where the number of dots is 2000. Further, it is assumed that the region with 5000 dots (section D2) is 500, the region with 8000 dots (section D3) is 200, and the region with 10,000 dots (section D4) is 100. Then, using each numerical value of toner consumption per dot (× 10 ⁻⁹ g) for each section D1 to D4 of the toner consumption conversion table shown in FIG. It can be obtained by an expression.

[Equation 2]
{0 × 600} + {2000 × 43 × 10 ⁻⁹ × 1000} + {5000 × 36 × 10 ⁻⁹ × 500} + {8000 × 31 × 10 ⁻⁹ × 200} + {10000 × 26 × 10 ⁻⁹ × 100} = 0.2516 (g)

  When the CPU 91a serving as an adding means adds all the toner consumption amounts calculated for each area calculated by the equation (2), the toner consumption amount for one page of the recording material P is obtained. The result is stored in the RAM 91c.

  In the conventional toner remaining amount detection, the user is notified that the remaining amount of toner has reached the lower limit value when the induced voltage Vi becomes a certain threshold value or less. However, as shown in FIG. 10, when the temperature and humidity environment in which the developing device 4 is installed changes, the amount of toner in the developer container 4b is the same due to the effect of the change in the dielectric constant due to moisture absorption and drying of the toner t. However, the induced voltage Vi induced in the electrode member 4h varies.

  As a result, the remaining amount of toner in the developer container 4b varies when notifying the user that the toner amount has reached the lower limit value. FIG. 10 shows the inside of the developer container 4b in a high temperature and high humidity environment (temperature 30 ° C./humidity 80%), a low temperature and low humidity environment (temperature 15 ° C./humidity 10%), and an appropriate environment (temperature 23 ° C./humidity 50%). The relationship between the toner remaining amount and the induced voltage Vi is shown.

  For example, in the conventional toner remaining amount detection, the case where the induced voltage Vi reaches 1.60 V may be set as the lower limit value of the remaining amount of toner. In this case, the remaining amount of toner in the developer container 4b is 110 g when the induced voltage Vir reaches 1.60 V from the curve of the induced voltage Vir in the appropriate environment (temperature 23 ° C./humidity 50%) in FIG. .

  On the other hand, when the induced voltage Vih reaches 1.60 V from the curve of the induced voltage Vih in the high temperature and high humidity environment (temperature 30 ° C./humidity 80%) in FIG. 10, the remaining amount of toner in the developer container 4b is 75 g. . Further, from the curve of the induced voltage Vil in the low temperature and low humidity environment (temperature 15 ° C./humidity 10%) in FIG. 10, the remaining amount of toner in the developer container 4b when the induced voltage Vil reaches 1.60 V is 145 g. As described above, even if the induced voltage Vi induced in the electrode member 4h is detected to detect the remaining amount of toner in the developer container 4b, the actual remaining amount of toner varies depending on the temperature and humidity environment.

  In the present embodiment, the toner remaining amount detection method in which the induced voltage Vi induced in the electrode member 4h is detected by the induced voltage detection unit 91d, and the total number of development dots of the entire image is counted by the video counter detection unit 91i. The toner consumption detection method is used. As a result, it is suitably detected that the toner t in the developer container 4b has decreased, without being affected by fluctuations in the temperature and humidity environment.

  FIGS. 11A to 11C show the state of the remaining amount of toner in the developer container 4b in each of the areas a to c on the curve of the induced voltage Vi shown in FIG. As shown in FIG. 7, the curve of the induced voltage Vi shows that there is almost no fluctuation of the induced voltage Vi in the region b. In this region b, the change in the weight of the toner t in the developer container 4b cannot be detected by the induced voltage Vi. That is, in the region b, the induced voltage Vi hardly varies with the consumption of the toner t.

  Further, the curve of the induced voltage Vi shown in FIG. 7 is compared with the state of the toner t in the developer container 4b shown in FIGS. Then, a region b where the induced voltage Vi does not decrease with respect to the consumption of the toner t is a boundary surface t1 between the surface of the toner layer and the air layer in the developer container 4b, as shown in FIG. Is in contact with the electrode member 4h.

  In this embodiment, this phenomenon is applied to detect that the toner t in the developer container 4b has decreased. Consumption of the toner t in the developer container 4b reduces the electrostatic capacity between the electrode member 4h and the developing roller 4a. As a result, the induced voltage Vi induced in the electrode member 4h decreases as shown in FIG. However, in the region b on the induced voltage Vi curve shown in FIG. 7, the induced voltage Vi does not decrease with respect to the consumption of the toner t.

  This is when the boundary surface t1 between the surface of the toner layer and the air layer in the developer container 4b is in contact with the electrode member 4h, as shown in FIG. 11 (b). The toner t is a dielectric like air. The relative dielectric constant of the toner t is about 3, and the relative dielectric constant of air is about 1. The component of toner t contains a slight amount of a conductive material, and a very small amount of current flows.

  FIG. 12 is a schematic diagram for explaining electrical conduction between two toner particles. In FIG. 12, it is assumed that the electrical resistance (internal resistance) when a current flows through the toner ta is Ra, and the electrical resistance (internal resistance) when a current flows through the toner tb is Rb. Furthermore, when the electric resistance (surface resistance) when current is passed through the surfaces of the toners ta and tb is Rc, the relationship expressed by the following formula 3 is established.

[Equation 3]
Ra + Rb ≧ Rc

  Considering the relationship of the above equation 3 with the toner t in the developer container 4b shown in FIG. 11, the electric resistance of the boundary surface t1 between the surface of the toner layer and the air layer in the developer container 4b is Lower than electrical resistance. Therefore, as shown in FIG. 11B, there is a state where the boundary surface t1 between the surface of the toner layer and the air layer in the developer container 4b is in contact with the electrode member 4h. In this state, the developing roller 4a and the electrode member 4h are short-circuited via the boundary surface t1 of the toner t that behaves as a conductor, and the behavior as the equivalent capacitor 57 is not exhibited.

  Therefore, a current flows through the electrode member 4h via the boundary surface t1 of the toner t due to the developing bias voltage applied from the developing bias power source 7 to the developing roller 4a. Therefore, as shown in FIG. 11B, in the region b on the curve of the induced voltage Vi shown in FIG. 7 where the boundary surface t1 of the toner t in the developer container 4b is in contact with the electrode member 4h, the developing roller 4a. Of the electrostatic capacity between the electrode member 4h and the electrode member 4h is not seen. As a result, there is no change in the induced voltage Vi induced in the electrode member 4h with respect to the change in the weight of the toner t.

  As shown in FIG. 11, the electrode member 4h is disposed in the vicinity of the developing roller 4a. Therefore, when the remaining amount of toner in the developer container 4b decreases, the electrode member 4h embedded in the toner t is exposed from the boundary surface t1 between the surface of the toner layer and the air layer. As a result, when the change in the induced voltage Vi almost disappears with respect to the consumption of the toner t as shown by the region b on the curve of the induced voltage Vi shown in FIG. 7, the toner t in the developer container 4b decreases. Can be set as

  In this embodiment, the video count count value detected by the video counter detection unit 91i indicating the consumption amount of the toner t is detected. Furthermore, the induced voltage Vi induced in the electrode member 4h detected by the induced voltage detector 91d is detected. By combining these, it is detected that the toner t in the developer container 4b has decreased when the fluctuation value of the induced voltage Vi is small with respect to the toner consumption.

  FIG. 13 is a flowchart for performing toner remaining amount detection control according to this embodiment. In step S1 in FIG. 13, the video counter detection unit 91i calculates an integrated value x of image information signals used for image formation in a predetermined period corresponding to toner consumption. Next, in step S2, the amount of change Δy in the induced voltage Vi is detected by the induced voltage detector 91d during the measurement period.

  Then, in step S3, the integrated value x of the image information signal used for image formation in a predetermined period as the toner consumption amount, and the toner consumption amount using the changes Δy, z of the induced voltage Vi during the measurement period as constants. At this time, it is determined whether or not the relationship expressed by the following equation 4 holds.

[Equation 4]
Δy / x ≦ z

  In step S3, if the relationship expressed by the equation 4 holds, the process proceeds to step S4 to notify the user that the toner amount has reached the lower limit value. In step S3, if the relationship expressed by the equation (4) does not hold, the process proceeds to step S5 where it is determined that the toner amount has not yet reached the lower limit value and there is no abnormality, and the image forming operation is continued. .

  In the present embodiment, the integrated value x (value converted to toner consumption) of the image information signal used for image formation in a predetermined period corresponding to the toner consumption by the video counter detection unit 91i may be 20 g. At that time, it is determined whether or not the toner amount has reached the lower limit value based on the change amount Δy of the induced voltage Vi detected by the induced voltage detection unit 91d. Further, the change amount Δy of the induced voltage Vi is set to 0.03 V as a constant (threshold value) z when determining whether or not the toner amount has reached the lower limit value.

  At this time, the integrated value x of the image information signal used for image formation and the change amount Δy of the induced voltage Vi detected by the induced voltage detecting unit 91d in the predetermined period corresponding to the toner consumption amount by the video counter detecting unit 91i are stored in the RAM 91c. Stored from time to time. As for the induced voltage Vi, only the induced voltage Vi in the range retroactive to the past by the amount of toner consumption by 20 g from the latest induced voltage Vi at the present time is stored in the RAM 91c. The latest induced voltage Vi is stored, and at the same time, the induced voltage Vi that is traced back by 20 g in toner consumption from the latest state is deleted.

  When the induced voltage Vi per 20 g of toner consumption is detected based on the curve of the induced voltage Vi shown in FIG. 7 by the control shown in FIG. 13, the toner amount in the developer container 4b becomes about 100 g. It can be detected at b that the toner amount has reached the lower limit. Further, even if the influence of the fluctuation of the induced voltage Vi accompanying the fluctuation of the temperature and humidity environment shown in FIG. 10 is considered, the amount of toner in the developer container 4b is about 100 g in the curve of the induced voltage Vir in the appropriate environment. It can be detected that the toner amount has reached the lower limit in the region b.

  Further, in the curve of the induced voltage Vih in a high temperature and high humidity environment, it can be detected that the toner amount has reached the lower limit in the region b where the toner amount in the developer container 4b is about 95 g. Further, from the curve of the induced voltage Vil in a low temperature and low humidity environment, it can be detected that the toner amount has reached the lower limit in the region b where the toner amount in the developer container 4b is about 105 g. Accordingly, it is possible to detect whether or not the toner amount has reached the lower limit with a very small error compared to the conventional toner remaining amount detecting method that detects only the induced voltage Vi and detects the remaining amount of toner. .

  On the other hand, as shown on the left side of the curve a of the induced voltage Vi shown in FIG. 7, the toner consumption is increased even when the amount of toner in the developer container 4b is large, that is, even when the toner weight in FIG. There is no fluctuation of the induced voltage Vi with respect to the above. In order to prevent erroneous detection in this case, toner remaining amount detection control is performed when the induced voltage Vi is equal to or lower than the threshold voltage Va in the region a of the curve of the induced voltage Vi shown in FIG.

  FIG. 14 is a flowchart for performing the remaining toner amount detection control shown in FIG. 13 and includes steps for performing the remaining toner amount detection control when the induced voltage Vi is equal to or lower than the threshold voltage Va in the region a of the induced voltage Vi curve shown in FIG. It is the added flowchart. As shown in FIG. 7, when the amount of toner in the developer container 4b is large, the induced voltage Vi also increases. For this reason, when the induced voltage Vi is high, it is not detected whether the toner amount based on the amount of change Δy of the induced voltage Vi accompanying toner consumption has reached the lower limit.

  Steps S1 to S3 shown in FIG. 14 are the same as steps S1 to S3 shown in FIG. In step S3 of FIG. 14, when the relationship expressed by the above equation 4 is established, the process proceeds to step S6, and the induced voltage Vi is compared with the threshold voltage Va. In this embodiment, the threshold voltage Va is set to 1.70V. In step S6, if the induced voltage Vi is 1.70 V (threshold voltage Va) or more, the process proceeds to step S5, and whether or not the toner amount due to the change amount Δy of the induced voltage Vi accompanying toner consumption has reached the lower limit value. Detection is not performed and it is determined that there is no abnormality, and the image forming operation is continued.

  If the induced voltage Vi is smaller than 1.70 V (threshold voltage Va) in step S6, the process proceeds to step S4 to notify the user that the toner amount has reached the lower limit value. In step S3, if the relationship expressed by equation (4) does not hold, the process proceeds to step S5, where the toner amount has not yet reached the lower limit value and it is determined that there is no abnormality, and the image forming operation is continued. To do. This can prevent erroneous detection that the toner amount has reached the lower limit when the amount of toner in the developer container 4b is large.

  As shown in FIG. 11 (b), the outer diameter upper vertex 4h1 of the electrode member 4h is preferably disposed below the horizontal plane h including the outer diameter upper vertex 4a1 of the developing roller 4a. If the electrode member 4h is located above the developing roller 4a, the toner member replenishment in the developer container 4b may not cause the electrode member 4h to be buried in the toner t. May not be done properly.

  According to the above configuration, the toner t in the developer container 4b decreases due to the relationship between the consumption amount of the toner t detected by the video counter detection unit 91i and the change amount Δy of the induced voltage Vi induced in the electrode member 4h. Is detected. The control is performed when the induced voltage Vi is equal to or lower than a predetermined value. Thus, the remaining toner amount detection control is performed when the remaining toner amount in the developer container 4b is within a predetermined amount. As a result, it is possible to prevent erroneous detection in a region where the induced voltage Vi hardly changes with respect to toner consumption when a large amount of toner t is contained in the developer container 4b.

  In addition, the electrode member 4h is sufficiently placed in the toner t in the developer container 4b by disposing the outer diameter upper vertex 4h1 of the electrode member 4h below the horizontal plane h including the outer diameter upper vertex 4a1 of the developing roller 4a. It is possible to detect that the toner t is reduced with an appropriate weight.

  In the present embodiment, the toner t in the developer container 4b is simply generated when the induced voltage Vi induced in the electrode member 4h corresponding to the electrostatic capacity between the developing roller 4a and the electrode member 4h becomes equal to or lower than the threshold value. It does not detect that there are fewer. The integrated value x of the image information signal used for image formation is detected in a predetermined period by a video count method in which the video counter detection unit 91i counts and integrates the number of development dots of the entire image.

  Then, an induced voltage Vi obtained by a change in capacitance between the developing roller 4a and the electrode member 4h during the measurement period of the integrated value x of the image information signal used for image formation in this predetermined period is detected. When the change amount Δy of the induced voltage Vi is equal to or less than a predetermined value, it is detected that the toner t in the developer container 4b has decreased.

  That is, it is detected that the toner t in the developer container 4b has decreased when there is almost no change Δy in the induced voltage Vi with respect to the consumption amount of the toner t. For this reason, it is possible to prevent errors due to changes in the temperature and humidity environment. As a result, the remaining amount of toner can be accurately detected without being affected by the change in the dielectric constant due to moisture absorption of the toner t.

Vi: induced voltage x: integrated value (integrated value of image information signal used for image formation in a predetermined period)
Δy ... change amount z of induced voltage Vi ... constant 1 ... photosensitive drum (image carrier)
4a: Developing roller (developer carrier)
4b: Developer container 4h: Electrode member
91 ... Control processing unit (toner remaining amount detecting means)

Claims (3)

An image carrier on which an electrostatic latent image is formed;
Developing means for supplying toner to the image carrier;
Have
The developing means includes
A developer container for containing toner;
A developer carrier for carrying and transporting toner in the developer container and supplying the electrostatic latent image on the image carrier;
A developing bias power source for applying an alternating voltage to the developer carrier;
An electrode member provided apart from the developer carrier in the developer container;
Based on an induced voltage induced in the electrode member in accordance with a capacitance between the developer carrier and the electrode member when an AC voltage is applied to the developer carrier from the development bias power source. Toner remaining amount detecting means for detecting the remaining amount of toner in the developer container;
Have
The toner remaining amount detecting means detects the toner remaining amount in the developer container from an integrated value x of image information signals used for image formation and a change amount Δy of the induced voltage during a predetermined period. An image forming apparatus.   The timing at which the remaining amount of toner in the developer container is detected from the integrated value x and the amount of change Δy in the induced voltage by the toner remaining amount detecting means is determined by the induced voltage induced in the electrode member being a predetermined value. The image forming apparatus according to claim 1, wherein the image forming apparatus is implemented when:   3. The image forming apparatus according to claim 1, wherein an outer diameter upper apex of the electrode member is disposed below a horizontal plane including an outer diameter upper apex of the developer carrying member. .

Images