JP2006301264A - Image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and a process cartridge aiming at the improvement of accuracy in successively detecting the residual amount of developer. <P>SOLUTION: In the image forming apparatus capable of detecting the residual amount of developer according to the change of capacitance, a value B showing a capacitance value near which a void image is formed is calculated from a value A showing that the detected capacitance is maximum. The residual amount is successively detected from the ratio Z=(V-A)/(B-A) of a difference (B-A) between them to a difference (V-A) between the detected value V of the capacitance value at such a time and the value A showing that the capacitance is maximum. A plurality of calculation expressions to calculate the value B showing the capacitance value near which the void image is formed are prepared, and the residual amount is successively detected by selecting the proper calculation expression in accordance with the average printing rate of the output image. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an image forming apparatus and a process cartridge using an electrophotographic method, and in particular, a process cartridge, a developing device formed into a cartridge, and the like using a storage unit mounted in the main body of the image forming apparatus. The present invention relates to an image forming apparatus, a cartridge, and an image forming system that can detect and notify the amount of developer in a cartridge that can be attached to the apparatus main body.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus such as an electrophotographic copying machine or a laser beam printer forms a latent image by irradiating an electrophotographic photosensitive member with light corresponding to image information, and a developing unit is used for the latent image. Then, a developer is supplied to make a visible image, and an image is formed on the recording medium by transferring the image from the photosensitive member to the recording medium. A developer container is connected to the developing means, and the developer is consumed by forming an image.

  In such an image forming apparatus, the electrophotographic photosensitive member and developing means as process means acting on the electrophotographic photosensitive member for the purpose of exchanging consumables such as the electrophotographic photosensitive member and developer and simplifying maintenance. In addition, there is a process cartridge system in which a charging unit, a cleaning unit, a developer container and a waste developer container are integrated as a process cartridge as shown in FIG. According to this process cartridge system, the maintenance of the apparatus can be performed by the user himself / herself without depending on the service person, so that the operability can be remarkably improved. Therefore, this process cartridge system is widely used in electrophotographic image forming apparatuses.

  In this cartridge type image forming apparatus, the user can form an image again by replacing the cartridge when, for example, the developer runs out. Therefore, such an image forming apparatus may be provided with a means for detecting when the developer is consumed and notifying the user, that is, a developer amount detecting device.

  The developer amount detecting device includes a developer remaining amount detecting means capable of detecting a developer remaining amount level in order to know at any time how much developer remaining in the cartridge can be used for image formation. It is provided in the cartridge or the image forming apparatus main body. In particular, it is possible not only to notify the user that the developer has been exhausted but also to further improve the convenience for the user if the amount of developer can be detected and notified in sequence.

  As this developer remaining amount detecting means, there is a capacitance measuring system that includes at least a pair of input side and output side electrodes and detects the developer amount by measuring the capacitance between both electrodes. As one of the methods, a plate antenna method is known. In the plate antenna method, for example, in the case of adopting a developing method in which an AC bias is applied to a developer carrier provided in the developing means, a sheet metal serving as an electrode is provided at a location facing the developer carrier, This utilizes the fact that the capacitance between the developer carrier and between the sheet metal and the sheet metal changes according to the amount of developer such as insulating toner.

  That is, if the space between the sheet metal and the developer carrier or between the sheet metal and the sheet metal is filled with the developer, the electrostatic capacity between them increases, and the space between the two increases as the developer decreases. The ratio of air to air increases and the capacitance decreases. Therefore, if the capacitance between the sheet metal and the developer carrier or the relationship between the capacitance between the sheet metal and the developer amount is obtained in advance, the developer amount level can be determined by measuring the capacitance. Can be detected.

  The output value of the remaining amount detection is output by comparing the measured value of the capacitance between the two or more plate antennas arranged in the developer container with the capacitance value of the reference capacitor, and converting it to a voltage value. Things are generally known. The transition of the output value of the remaining amount detection varies depending on the detection circuit configuration, and the output voltage decreases as the capacitance value between the plate antennas decreases, and the output voltage value increases as the capacitance value decreases. It is.

  In the case of the developer remaining amount detection means using the plate antenna method described above, the electrostatic capacity between the developer carrying member and the sheet metal as an electrode, or the electrostatic capacity between the sheet metal as an electrode depends on the positional relationship. Even if there is no developer between them, the absolute value of the capacitance increases if the distance between them is close, and decreases if the distance between them is far.

  In addition, due to manufacturing process cartridges, it is inevitable that individual differences such as those having a wide space between sheet metals and narrow ones occur.

For this reason, as in Patent Document 1, the output value when the developer remaining amount detecting means detects the maximum amount of developer, that is, the maximum capacitance is stored in the storage device, and the developer remaining amount is stored using that value. It has been proposed to detect the amount of developer accurately in accordance with each cartridge by detecting the level of the amount.
JP 2002-99185 A

  The output value of the remaining amount detection was output by comparing the measured value of the capacitance between the plate antennas arranged in the developer container with the capacitance value of the reference capacitor and converting it to a voltage value. Is. The transition of the output value of the remaining amount detection can be such that the output voltage decreases as the capacitance value between the plate antennas decreases, or the output voltage value increases as the capacitance value decreases, depending on the detection circuit configuration.

  FIG. 2A shows the result of measuring the remaining amount of developer and the transition of the output voltage using a circuit in which the output voltage increases as the capacitance decreases.

  The output voltage value when the electrostatic capacity changes (the state in which the developer has decreased) is maintained by holding the output voltage value in which the electrostatic capacity is maximum (the state where the developer remains sufficiently) in the storage means. ) And the amount of change in the output value from the value when the held capacitance is maximum, the remaining amount is detected sequentially.

  In the sequential remaining amount detection, first, an output voltage value indicating a predetermined capacitance value in the vicinity where a blank image is generated is calculated from the output voltage value when the capacitance is maximum. Generally, the electrostatic capacity value at which the amount of developer becomes small and printing becomes impossible, or the electrostatic capacity value at the time when the remaining amount of developer immediately before white spots is small (hereinafter referred to as “PAE (plate antenna antenna Calculated as “Empty)”.

  Here, PAE will be described.

  FIG. 2B shows the relationship between PAE and the voltage value at which the accumulated electrostatic capacity is maximized by performing an experiment using a plurality of process cartridges having the same configuration.

  The developer filling amount during the experiment is 350 g, and the output voltage value when the electrostatic capacity is maximum when the paper is continuously passed with a fixed printing pattern and the output voltage when the remaining amount in the developer container is 35 g as PAE. The value is plotted. As shown in FIG. 2B, the voltage value at which the electrostatic capacitance is maximum has individual differences among the individual cartridges, but the relationship with the PAE can be expressed by a linear function as shown in Equation [1].

PAE = a × (Voltage value indicating maximum capacitance) + b (1)
(A and b are constants and are obtained based on accumulation of experimental data)

  Therefore, an output voltage value indicating a predetermined developer remaining amount can be obtained from a voltage value indicating the maximum electrostatic capacity by a calculation formula regardless of individual differences among cartridges.

  Further, as shown in FIG. 2A, the difference ΔV between the PAE and the output voltage value when the electrostatic capacitance is maximum, the remaining amount detection output voltage value V and the output voltage value when the electrostatic capacitance is maximum, The change ratio Z is derived from the difference ΔV ′ as shown in the following equation [2].

  The change ratio Z obtained by the equation [2] is compared with a correlation table (hereinafter simply referred to as “correlation table”) indicating the relationship between the change ratio Z as shown in Table 1 and the remaining amount to be displayed. The remaining amount is displayed appropriately. Table 1 shows an example of a correlation table when PAE = the remaining amount detection output value when the display remaining amount is 2%.

  Then, when the change ratio Z reaches a predetermined value, the user is notified that the remaining amount of the developer is small (this notification is hereinafter referred to as “toner OUT display”).

  By such a method, it is possible to detect the remaining developer level without eliminating individual cartridge differences.

  However, as described in Patent Document 1 above, the output value when the maximum electrostatic capacity is detected is stored in the storage device, and the level of the developer remaining amount is detected using the value to eliminate individual cartridge differences. The developer remaining amount detected by the developer remaining amount detecting means may not match the developer amount actually remaining in the developing device.

  That is when an image with a very high printing rate continues to be output or when an image with a very low printing rate continues to be output.

  Details will be described.

  FIG. 3 shows the relationship between the remaining amount of developer and the remaining amount detection output voltage value.

  The image forming apparatus used here uses a type of circuit in which the output voltage increases as the capacitance value decreases. The output of the image was performed by continuous printing and continued until the amount of the developer became small and a defective image was generated (hereinafter, this defective image is referred to as “white spot”).

  The used process cartridge is as shown in FIG. 4, and includes a developer container, a sheet-like stirring member, a developing roller, and a developing blade. As shown in FIG. 5, plate antennas 31 and 32 are provided in the vicinity of the developing roller so as to be longitudinally uniform.

  Transition A in FIG. 3 is a transition when an image with a printing rate of 50% is continuously output, Transition B is a transition when an image with a printing rate of 5% is continuously output, and Transition C is a transition with a printing rate of 1.5%. This is the transition when the image continues to be output.

  In the case of Transition A in which an image with a printing rate of 50% is continuously output, the minimum value of the output voltage is larger than that with a printing rate of 5%, and the remaining amount of developer when a blank image is generated. It is increasing. This is because when the printing rate is 50% compared to the printing rate of 5%, the developer is consumed more than the developer is pushed between the plate antennas by the rotation of the stirring member, and the capacitance value does not increase. is there. In addition, the remaining amount of developer when a blank image is generated is larger than when the printing rate is 5%. When the printing rate is 5%, an image with a high printing rate is output with high quality. This is because a sufficient amount of developer is required.

  Next, the transition C in which an image with a printing rate of 1.5% is continuously output will be described.

  The minimum value of the output voltage is small as compared with the printing rate of 5%, and the remaining amount of developer is large when a white spot image is generated.

  This is because the developer consumption is small compared with the printing rate of 5%, and the developer is pushed in between the plate antennas one after another by the rotation of the stirring member, and the density of the developer increases, resulting in an increase in the capacitance value. Because. Further, a part of the pushed-in developer is pressed and adhered to the plate antenna. For this reason, even when a white-out image is generated, the remaining amount of the developer is large and the capacitance is increased. Therefore, in the case of the example shown here, the output voltage value at the time of occurrence of the blank image is smaller than the output value at the printing rate of 5%.

  As described above, the output voltage value of the remaining amount detection varies depending on the printing rate to be printed.

  As described above, even when the remaining amount can be detected successively by calculating the PAE and eliminating individual differences between the cartridges as in the conventional configuration, it is not possible to cope with the change in the output value according to the printing rate. For this reason, depending on the printing rate of the output image, the accuracy of the remaining amount detection deteriorates and the following problems may occur.

  1) When the output of the high printing rate image continues, a blank image is generated before the toner OUT display is performed.

  2) When the output of the low printing rate image continues, the period from the toner OUT display to the occurrence of the white spot image is long.

  Therefore, further improvement is desired from the aspect of usability to notify the user of accurate information.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and a process cartridge that solve the above-mentioned problems and perform with high precision regardless of the use state of the process cartridge.

In order to achieve the above object, the first invention related to the present application is:
A developer accommodating portion for accommodating the developer; a developer remaining amount detecting means provided in the developer container for measuring a capacitance according to the remaining amount of the developer; and a value indicating the maximum value of the capacitance. In an image forming apparatus in which a process cartridge having a non-volatile storage means to be held is detachable, and the remaining amount of developer is sequentially detected by the amount of change in capacitance.
The storage means stores a value indicating the maximum capacitance value, calculates a value indicating a capacitance value in the vicinity where the white spot image is generated from the value indicating the maximum capacitance value,
When the remaining amount is detected sequentially during the period when the capacitance decreases, the difference between the value indicating the maximum capacitance and the value obtained by the selected calculation formula, the value indicating the maximum capacitance, and at that time The remaining amount of the developer is sequentially detected based on the ratio to the difference between the detected capacitance values.
The image forming apparatus is characterized in that a plurality of calculation formulas for calculating a value indicating a capacitance value in the vicinity of a white spot are stored, and the calculation formula is selected according to an average print rate of an output image.

  With the above configuration, the remaining amount can be detected sequentially and stably regardless of the usage state of the developer.

The second invention is
The value indicating the capacitance value near the white spot is
(Value indicating the capacitance value near white spots) = a × (value indicating the maximum capacitance value) + b
(A and b are constants)
Is calculated by
The image forming apparatus according to the first invention is characterized in that a plurality of calculation formulas having different values of the constant b are held.

  With the above configuration, the remaining amount can be detected sequentially and stably regardless of the usage state of the developer.

The third invention is
The average print rate of the output image is
In the first or second invention, the determination is made based on the number of prints when the amount of the developer in the cleaning container in which the developer that has not been transferred from the image carrier to the recording paper in the transfer step reaches a predetermined amount. It is an image forming measure.

  With the above configuration, the remaining amount can be detected sequentially and stably regardless of the usage state of the developer.

The fourth invention is:
A developer accommodating portion for accommodating the developer; a developer remaining amount detecting means provided in the developer container for measuring a capacitance according to the remaining amount of the developer; and a value indicating the maximum value of the capacitance. Non-volatile storage means for holding,
A process cartridge that is detachable from the image forming apparatus according to any one of the first to third aspects.

  With the above configuration, the remaining amount can be detected sequentially and stably regardless of the usage state of the developer.

According to the first invention of the present invention,
A developer accommodating portion for accommodating the developer; a developer remaining amount detecting means provided in the developer container for measuring a capacitance according to the remaining amount of the developer; and a value indicating the maximum value of the capacitance. In an image forming apparatus in which a process cartridge having a non-volatile storage means to be held is detachable, and the remaining amount of developer is sequentially detected by the amount of change in capacitance.
The storage means stores a value indicating the maximum capacitance value, calculates a value indicating a capacitance value in the vicinity where the white spot image is generated from the value indicating the maximum capacitance value,
When the remaining amount is detected sequentially during the period when the capacitance decreases, the difference between the value indicating the maximum capacitance and the value obtained by the selected calculation formula, the value indicating the maximum capacitance, and at that time The remaining amount of the developer is sequentially detected based on the ratio to the difference between the detected capacitance values.
By an image forming apparatus, wherein a plurality of calculation formulas for calculating a value indicating a capacitance value near a white spot are held, and the calculation formula is selected according to an average print rate of an output image.
Stable developer sequential detection can be performed regardless of the usage status of the developer.

According to the second invention,
The value indicating the capacitance value near the white spot is
(Value indicating the capacitance value near white spots) = a × (value indicating the maximum capacitance value) + b
(A and b are constants)
Is calculated by
The image forming apparatus according to the first invention, wherein a plurality of calculation formulas having different values of the constant b are held.
Stable developer sequential detection can be performed regardless of the usage status of the developer.

According to the third invention,
The average print rate of the output image is
The first or the second determination is based on the number of printed sheets when the amount of the developer in the cleaning container in which the developer that has not been transferred from the image carrier to the recording paper in the transfer step reaches a predetermined amount. According to the image forming apparatus described in the invention of 2,
Stable developer sequential detection can be performed regardless of the usage status of the developer.

According to the fourth invention,
A developer accommodating portion for accommodating the developer; a developer remaining amount detecting means provided in the developer container for measuring a capacitance according to the remaining amount of the developer; and a value indicating the maximum value of the capacitance. Non-volatile storage means for holding,
A process cartridge that is detachable from the image forming apparatus according to any one of the first to third inventions,
Stable developer sequential detection can be performed regardless of the usage status of the developer.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

(First embodiment)
An embodiment of an electrophotographic image forming apparatus to which a process cartridge constructed according to the present invention can be mounted will be described with reference to the drawings.

  As shown in FIG. 4, the process cartridge B welds a developer frame 11 having a developer storage container 4 for storing a developer, and a developing frame 12 for holding a developing roller 5a, a developing blade 5c, and the like. A developing unit (developing device) C is integrally formed, and further, a cleaning frame 13 in which a cleaning unit such as the photosensitive drum 1, the cleaning blade 7a and the waste developer container 7b and the charging roller 2 are attached to the developing unit C. Are integrally formed into a cartridge.

  The process cartridge B is detachably mounted on the image forming apparatus main body by the user as shown in FIG.

  The image forming apparatus A sequentially detects the remaining amount according to the consumption of the developer T in the developing device C.

  Here, the developer remaining amount detecting means of the present embodiment will be described in detail.

  In this embodiment, the developer remaining amount detecting means 30 has a plate antenna.

  As shown in FIG. 5, in this embodiment, the plate antenna has an output sheet metal 32 provided over the entire longitudinal direction at a position facing the developing roller 5a, and a longitudinal length substantially equal to the output sheet metal 32, An input sheet metal 31 is provided so as to face the output sheet metal 32.

  The input sheet metal 31 and the output sheet metal 32 constituting the electrode pair as the plate antenna can be used without any particular limitation as long as they are basically materials through which current can flow. In the present embodiment, SUS is used as the material for the sheet metals 31 and 32.

  In this embodiment, the developing roller 5a and the input sheet metal 31 are a developing bias applying unit (a voltage applying unit provided in the image forming apparatus main body A in a state where the process cartridge B is mounted in the image forming apparatus main body A). (Not shown).

  When a developing bias of 1700 Vpp, a 2600 Hz AC bias and a -450 V DC bias is applied to the developing roller 5a and the input sheet metal 31, the developing roller 5a and the output sheet metal 32 facing the developing roller 5a are applied. An alternating current flows between the input sheet metal 31 and the output sheet metal 32, and the combined current value of both is measured by the current measuring device 33.

  In this way, the combined capacitance based on the capacitance between the developing roller 5a and the output sheet metal 32 and between the input sheet metal 31 and the output sheet metal 32 is measured from the current value measured by the current measuring device 33. The

  In this way, the input sheet metal 31 and the output sheet metal 32 that are plate antennas are arranged in the developing device C, and as the developer T in the developing device C decreases, the space between the input sheet metal 31 and the output sheet metal 32 is increased. By observing the electrostatic capacity between the developing roller 5a and the output sheet metal 32, the amount of developer in the developer container 4 can be known at any time.

  FIG. 7 shows a circuit configuration for detecting the developer amount in the process cartridge.

  As for the developer amount, when a predetermined AC bias is output from a developing bias circuit as a developing bias applying means, the applied bias is applied to the reference capacitor C1, the developing roller 5a, and the input sheet metal 32, respectively. As a result, a voltage V1 is generated at both ends of the reference capacitor C1, and a current corresponding to the capacitance (C2 + C3) is generated on the output sheet metal 31 side. This current is converted into a voltage V2.

  The detection circuit of the current measuring device generates a voltage V3 from the voltage difference between the voltage V1 generated across the input reference capacitor C1 and the voltage V2 between the electrode pairs, and outputs the voltage V3 to the AD converter. The AD converter outputs the result of digital conversion of the analog voltage V3 to the controller 23. The control unit 23 obtains the developer amount in the process cartridge from the voltage value V converted into the digital value.

  Next, the storage means of this embodiment will be described.

  The storage means used in this embodiment is provided on the waste developer container side of the process cartridge B as shown in FIG. 4, and when inserted into the image forming apparatus as shown in FIG. Communicates with the control unit. In this embodiment, a contact-type readable / writable memory is used as the storage means 20.

  As the storage means 20 to be used, an electronic memory using a normal semiconductor such as a nonvolatile memory, a combination of a volatile memory and a backup battery can be used without particular limitation.

  Next, the control configuration of the storage means (hereinafter also referred to as a memory) 20 in the present embodiment will be described.

  As shown in FIG. 4, a memory 20 is arranged on the process cartridge B side, and a control unit provided in the image forming apparatus main body A includes a developer remaining amount detection unit, a developer remaining amount, and a display remaining amount. It has a quantity correlation table.

  The minimum value of the detected voltage value (hereinafter referred to as “PAF (plate antenna full)) in a state where the developer is sufficiently filled in the developer storage container 4 of the process cartridge in the memory 20 is referred to as PAF. ) Information, developer remaining amount Y% value information, and the like are stored.

  The value of the PAF is updated as needed when the detected voltage value V indicates the minimum (the capacitance is the maximum value) while the image forming apparatus is operating.

  Next, detection of the remaining amount of developer will be described.

  The calculation of the developer remaining amount is performed by a correlation table indicating the relationship between the change ratio Z held in advance in the control unit 23 and the display remaining amount. The change rate Z is calculated from the residual amount detection output voltage value V obtained from the developer amount detection means, the PAF value stored in the memory, and the PAE value calculated from the PAF value, and the value is calculated from the correlation table. The corresponding remaining amount is displayed by comparison.

  Next, features of the present invention will be described.

  The feature of the present invention is that the control unit 23 holds in advance three types of PAE calculation formulas corresponding to the printing rate, and selects the PAE calculation formula according to the average printing rate of the output image.

  In this embodiment, the PAE calculation formula is selected based on the average printing rate M at the number of printed sheets S, and the average printing rate M is obtained from the number of print pixels N by the following formula.

  The number S of prints is not particularly limited as long as the capacitance value measured by the remaining amount detecting means is not reduced, and a desired number of prints can be set according to the developer filling amount of the process cartridge to be used.

  The following three types of PAE calculation formulas were prepared in the control unit of the image forming apparatus according to the average printing rate M. In this embodiment, when the point at which the whiteout image occurs is 0% of the remaining amount of toner, the output voltage value when the remaining amount of toner is 2% is set as the PAE value, and experimental data as shown in FIG. 3 is accumulated. The following [1] to [3] obtained in the above were prepared.

[1] When M ≧ 30; PAE = 0.88 × PAF + 0.75
[2] When 2 ≦ M <30; PAE = 0.88 × PAF + 1.05
[3] When M <2; PAE = 0.88 × PAF + 1.15

  A calculation formula for obtaining the change ratio Z from the remaining amount detection output value V is as follows.

    Rate of change Z = (residual amount detection output value V-PAF) / (PAE-PAF)

  The correlation table showing the relationship between the change rate Z and the remaining display amount was the one shown in Table 2 obtained by accumulating experimental data.

  The remaining amount detection is performed in units of 2% when the remaining amount is 20% or less, and when the remaining amount of toner is detected, “toner OUT display” is performed to notify the user that the remaining amount of toner is small.

  As the correlation table, one type of correlation table can be used regardless of the printing rate.

  As can be seen from the output transition when the printing rate is different in FIG. 3, the areas of the remaining amount of the developer in which the output voltage changes are the same even when the printing rate is different, and the occurrence of white spots is greatly different depending on the printing rate. The output difference between the output voltage value at the time and the output voltage value when the developer remains sufficiently. In other words, the correlation table in Table 2 shows the ratio of the remaining amount detection output value, so by obtaining an appropriate PAE value, the same correlation table is used to sequentially detect the remaining amount with high accuracy regardless of the printing rate. It becomes possible.

  Here, the flow of control will be described using the flowchart of FIG.

  It is determined whether the number of prints exceeds a predetermined value (step 1).

  If it exceeds the predetermined value, the average printing rate is calculated (step 2).

  A PAE calculation formula corresponding to the average printing rate is selected (step 3).

  The output value V of the remaining amount detecting means, the selected PAE calculation formula, the change rate Z obtained from the PAF value, and the correlation table are compared to determine the remaining amount to be displayed (step 4).

  Next, a print test was performed using the image forming apparatus having the configuration of this embodiment.

conditions:
・ Cartridge used: 350 g developer filling (nominally printable 6000 sheets at 4% printing rate)

・ Printing conditions: continuous printing,
Evaluation [1]: Passing an image sample with a printing rate of 40% until a blank image is generated Evaluation [2]: Passing an image sample with a printing rate of 2% until a blank image is generated

  The desired number of printed sheets S was S = 4000.

  For comparison, a similar printing test was performed with an image forming apparatus having a conventional configuration that does not employ the present invention. The PAE calculation formula [2] is used as the PAE calculation formula of the conventional configuration.

  The evaluation results are as shown in FIG.

  In the conventional configuration, there is a deviation between the actual remaining amount and the remaining display amount. In evaluation [1], a white-out image is generated when the remaining display amount is 6%. In evaluation [2], there was a deviation from the actual remaining amount.

  On the other hand, in the configuration of the present embodiment, the deviation from the actual remaining amount in both the evaluation [1] and the evaluation [2] is about 0 to 2%, and the remaining amount can be detected accurately until a blank image is generated.

  As shown in FIG. 9A, the transition of the output value differs between when the image sample with a printing rate of 40% is continuously output and when the image sample with a printing rate of 2% is continuously output. This is because the image forming apparatus having the configuration no longer corresponds to the transition of the remaining amount detection output voltage.

  On the other hand, in the configuration of this embodiment, since an appropriate PAE calculation formula is selected according to the printing rate, the remaining amount can be detected with high accuracy regardless of the printing rate.

  For the sake of specific explanation, FIG. 9B and the transition of the output voltage of the remaining amount detection shown in FIG. 10 in which the area A in FIG. 9B is enlarged will be described. On the horizontal axis, the actual remaining developer amount and the point at which a white-out image occurs is defined as 0% remaining amount.

  As shown in FIG. 9B, the change amount of the output value from the PAF value to the remaining amount 2% is Δ0.98V when the printing rate is 40%, and is different from Δ0.61V when the printing rate is 2%. Yes. However, as shown in FIG. 10, in the conventional image forming apparatus, when the printing rate is 2%, PAE = 0.88 × 1.40 + 1.05 = 2.28V and Δ (PAE−PAF) = 0.88V. The actual Δ change amount is smaller than 0.98V. For this reason, the display remaining amount is displayed smaller than the actual remaining amount, and the toner remaining amount when the toner OUT is displayed is increased.

  When the printing rate is 40%, PAE = 0.88 × 1.78 + 1.05 = 2.62V and Δ (PAE−PAF) = 0.84V, which is larger than the actual Δ variation. For this reason, the remaining amount of display is displayed more than the actual remaining amount, and a phenomenon that a blank image occurs before the toner OUT display has occurred. As described above, since the conventional image forming apparatus cannot cope with the change Δ in the remaining amount detection output voltage depending on the printing rate, the developer remaining amount detection accuracy is shifted.

  On the other hand, in the configuration of this embodiment, by selecting a PAE calculation formula according to the printing rate, when the printing rate is 2% as shown in FIG. 10, PAE = 0.88 × 1.40 + 1.15 = 2.38V, Δ When (PAE−PAF) = 0.98V and the printing rate is 40%, PAE = 0.88 × 1.78 + 0.80 = 2.37V, Δ (PAE−PAF) = 0.58V, and the actual change amount Δ Get closer to. Accordingly, it is possible to sufficiently cope with the fact that the change amount Δ of the actual remaining amount detection output voltage value varies depending on the printing rate, and it is possible to accurately detect the remaining amount.

  As described above, the remaining amount can be detected stably and accurately by selecting an appropriate PAE calculation formula in accordance with the printing rate.

(Second embodiment)
The feature of this embodiment is that the remaining amount of waste toner in the waste toner container is detected, the average print rate of the output image is judged based on the number of prints when the predetermined amount of waste toner is reached, and an appropriate PAE calculation formula is selected. Thus, the remaining amount of the developer is sequentially detected.

  The process cartridge, waste toner amount detection means, and image forming apparatus used in this embodiment will be described.

  As in the first embodiment, the process cartridge of this embodiment uses a process cartridge in which a photosensitive drum, a cleaning device, and a developing device are integrated as shown in FIG. The cleaning device has a cleaning blade and a waste toner collection container for collecting waste toner.

  In addition, it has a non-volatile storage means, and holds values of the number of prints, the remaining amount of developer Y%, and PAF.

  Next, the waste toner amount detection means used in this embodiment will be described. As shown in FIG. 11A, the waste toner container used in this embodiment is provided with a conducting member 40 and a conducting member 41 having a support portion 42 as shown in FIG. The conducting member 40 is a swingable sheet-like member supported at one end by the receiving container, and the conducting member 41 is a conducting member provided on the lower surface of the containing container. When the waste toner is not stored, the conducting members 40 and 41 are in contact with each other, and there is conduction between the conducting members 41 arranged in the container. When the waste toner is stored in the storage container and the amount of waste toner increases, the conductive member 40 is pushed by the waste toner to be in a non-contact state with the conductive member 41, and the conductive toner is cut off, so that the amount of waste toner reaches a predetermined amount. Is detected.

  The developing device is provided with a plate antenna in the same manner as in the above-described embodiment, and detects the remaining amount in the developing container by a change in capacitance.

  In the image forming apparatus, three types of PAE calculation formulas are prepared. When the amount of waste toner is detected to reach a predetermined value, the number of prints is read from the storage means, and the PAE calculation formula is selected according to the number of prints. Performs developer remaining amount detection.

  Here, using the configuration of the present embodiment, a print test using an actual machine was performed in the same manner as in the first embodiment.

  The following evaluations [1] and [2] were performed until a blank image was generated.

Evaluation [1] Continuous printing of 40% printing image until white-out images are generated Evaluation [2] Continuous printing of 1.5% printing rate until white-out images are generated

  In the test, a process cartridge having a developer filling amount of 350 g was used in the same manner as in Example 1. About 6000 sheets can be printed in a continuous test with a 4% coverage image.

  In this embodiment, the conductive members 40 and 41 are arranged so that it can be detected that the amount of waste toner has reached 10 g. A waste toner amount of 10 g is equivalent to printing 3000 sheets with a 4% printing rate image.

  -The PAE calculation formula prepared the following three types of calculation formulas obtained by accumulation of experimental data similarly to Example 1. In this embodiment, a PAE calculation formula is selected as follows according to the number of prints M when 10 g of waste toner is detected.

[1] When M <1000; PAE = 0.88 × PAF + 0.80
[2] When 1000 ≦ M <5000; PAE = 0.88 × PAF + 1.05
[3] When M ≧ 5000; PAE = 0.88 × PAF + 1.15

  The correlation table used was the same as that shown in Example 1.

  The operation of this embodiment will be described with reference to the flowchart of FIG.

  It is confirmed whether the amount of waste toner has reached a predetermined amount (step 1).

  If the amount of waste toner has reached a predetermined amount, the number of printed sheets M held at that time is read (step 2).

  One of PAE calculation formulas [1] to [3] is selected according to the number of prints M (step 3).

  The display remaining amount is determined using the selected PAE calculation formula, the output value V of the remaining amount detecting means, and the correlation table (step 4).

  By performing the processing as described above, the remaining amount of developer can be detected with high accuracy regardless of the print rate of the output image in the configuration of the present embodiment, as in the first embodiment.

  By selecting an appropriate PAE calculation formula in accordance with the printing status as described above, the remaining amount can be detected stably and accurately.

The flowchart of Example 1 which shows this invention (A) is a figure which shows transition of remaining amount detection output value, (b) is a figure which shows the relationship between an output voltage when a electrostatic capacitance is the maximum, and a PAE output voltage. Diagram showing change in remaining amount detection output value (printing rate difference) Diagram showing process cartridge Perspective view showing developer remaining amount detecting means Diagram showing image forming apparatus The figure which shows the circuit structure for detecting a developing agent residual amount. The figure which shows the evaluation result (remaining amount detection result) of Example 1. Figure showing output transition by printing rate Figure showing transition of output voltage of remaining amount detection The figure which shows a difference waste toner amount detection means The flowchart which shows Example 2. A diagram showing a conventional image forming apparatus

Explanation of symbols

A image forming apparatus B process cartridge C developing device T developer 1 photosensitive drum 2 charging roller 4 developer container 5a developing roller 5c developing blade 7a cleaning blade 7b cleaning container 11 developer frame 12 developing frame 13 cleaning frame 20 Storage means 23 Control section 30 Developer remaining amount detection means 31 Output sheet metal 32 Input sheet metal 33 Current measuring devices 40, 41 Conducting section 42 Support section

Claims (4)

A developer accommodating portion for accommodating the developer; a developer remaining amount detecting means provided in the developer container for measuring a capacitance according to the remaining amount of the developer; and a value indicating the maximum value of the capacitance. In an image forming apparatus in which a process cartridge having a non-volatile storage means to be held is detachable, and the remaining amount of developer is sequentially detected by the amount of change in capacitance.
The storage means stores a value indicating the maximum capacitance value, calculates a value indicating a capacitance value in the vicinity where the white spot image is generated from the value indicating the maximum capacitance value,
When the remaining amount is detected sequentially during the period when the capacitance decreases, the difference between the value indicating the maximum capacitance and the value obtained by the selected calculation formula, the value indicating the maximum capacitance, and at that time The remaining amount of the developer is sequentially detected based on the ratio to the difference between the detected capacitance values.
An image forming apparatus, comprising: a plurality of calculation formulas for calculating a value indicating a capacitance value near a white spot, and selecting the calculation formula according to an average print rate of an output image. The value indicating the capacitance value near the white spot is
(Value indicating the capacitance value near white spots) = a × (value indicating the maximum capacitance value) + b
(A and b are constants)
Is calculated by
The image forming apparatus according to claim 1, wherein a plurality of calculation formulas having different values of the constant b are held. The average print rate of the output image is
2. The method according to claim 1, wherein the determination is made based on the number of printed sheets when the amount of the developer in the cleaning container in which the developer that has not been transferred from the image carrier to the recording paper in the transfer step reaches a predetermined amount. The image forming apparatus according to 2. A developer accommodating portion for accommodating the developer; a developer remaining amount detecting means provided in the developer container for measuring a capacitance according to the remaining amount of the developer; and a value indicating the maximum value of the capacitance. Non-volatile storage means for holding,
4. A process cartridge that is detachable from the image forming apparatus according to claim 1.