JP7176350B2 - Image forming apparatus, image forming method, and program - Google Patents

Description

The present invention relates to an image forming apparatus, an image forming method, and a program.

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, there is a process of uniformly charging the surface potential of a photoreceptor. In this process, a contact DC charging method is adopted in which a DC voltage is applied to the charging roller, and the charging roller is brought into contact with the surface of the photoreceptor to discharge to the surface of the photoreceptor, thereby charging the photoreceptor.
In this contact DC charging method, the surface potential of the photoreceptor is charged to a target potential by generating discharge between the charging roller and the surface of the photoreceptor.
In the contact DC charging method, since the charging roller is in contact with the surface of the photoreceptor, the photoreceptor film on the surface is scraped off as the photoreceptor rotates.
As the film thickness becomes thinner, the relationship between the voltage applied to the charging roller and the voltage charged on the surface of the photoreceptor changes, making it impossible to maintain the surface potential of the photoreceptor necessary for image formation. As a result, defects occur in the printed image, necessitating replacement of the photoreceptor.
Further, when the photoreceptor film is completely scraped off, the surface of the photoreceptor cannot hold electric charge, and the charging performance is remarkably deteriorated. Therefore, the photoreceptor needs to be replaced.
In order to solve these problems, conventionally, the number of rotations of the photoreceptor is used to calculate the thickness of the photoreceptor, thereby controlling the voltage applied to the charging roller and judging the life of the photoreceptor. ing.
When the number of rotations of the photoreceptor during charging is used to predict the actual amount of photoreceptor film thickness scraping,
(1) Usage environment of the user (2) Pressure in the photoreceptor unit when the blade comes into contact with the photoreceptor (3) The nip pressure in the developing section greatly varies depending on the pressure. .

As a solution to this problem, Japanese Patent Application Laid-Open No. 2002-100000 discloses a charging bias-type detector for the purpose of accurately detecting the amount of scraping of the film thickness of the photoreceptor rather than calculating the amount of scraping of the film thickness of the photoreceptor from the number of rotations of the photoreceptor. A technique has been disclosed in which the film thickness of the photoreceptor is obtained from the slope of the charging DC current characteristic.
In Patent Document 2, for the purpose of improving the accuracy of the film thickness estimation result of the photoreceptor, based on the operation information, from the estimation arithmetic expression of the film thickness of the photoreceptor that is derived and stored for each model and operation period A technique of estimating and calculating the wear amount (thickness reduction amount) of the photoreceptor is disclosed.
Japanese Patent Laid-Open No. 2002-200000 discloses that the absolute value of the voltage applied to the charging member is increased during film thickness determination rather than during image formation for the purpose of improving the accuracy of the film thickness detection result of the photoreceptor. A technique of varying the applied voltage is disclosed.

However, the conventional method has a problem that the film thickness is erroneously predicted when abnormal results are obtained due to factors such as noise.
Although Patent Literatures 1 to 3 aim to improve the accuracy of film thickness estimation results, the technical content relates to improving calculation accuracy in control for indirectly estimating film thickness.
However, Patent Documents 1 to 3 cannot solve the problem that the film thickness is erroneously predicted when an abnormal result is obtained due to noise or the like.
One embodiment of the present invention has been made in view of the above, and an object thereof is to accurately calculate a predicted film thickness range corresponding to the current running distance with respect to the calculated estimated film thickness. be.

In order to solve the above-mentioned problems, the invention according to claim 1 provides a voltage applying section that applies a charging bias to a charging member that charges the circumferential surface of a rotating photoreceptor, and an output that flows from the charging member to the photoreceptor. and a current detector that generates a feedback signal representing current, wherein the voltage value related to the charging bias applied to the charging member and the current value related to the output current flowing through the photoreceptor are detected. Based on the film thickness calculation means for calculating the film thickness of the photoreceptor, the travel distance calculation means for calculating the travel distance of the photoreceptor during charging, and the calculated film thickness calculated by the film thickness calculation means. Calculated film thickness storage means for storing travel distances in association with each other, and film thickness estimation for calculating estimated film thicknesses at present based on calculated film thicknesses and travel distances at a plurality of times obtained from the calculated film thickness storage means. and a film thickness range predicting means for calculating a predicted film thickness range corresponding to the current running distance based on the estimated film thickness calculated by the film thickness estimating means, wherein the film thickness range predicting means , the smaller the value of the previous estimated film thickness, the narrower the estimated film thickness range .

According to the present invention, the predicted film thickness range corresponding to the current running distance can be calculated with high accuracy for the estimated film thickness.

1 is a sectional view showing a schematic mechanical configuration of an image forming apparatus to which the invention is applied; FIG. 1 is a diagram showing the overall configuration of an electrophotographic process employed in the image forming apparatus 1 according to the first embodiment of the invention; FIG. 1 is a functional block diagram showing the configuration of main parts of an image forming apparatus according to a first embodiment of the present invention; FIG. 4 is a graph showing IV characteristics; FIG. FIG. 4 is a graph including IV characteristics when noise occurs; FIG. 2 is a graph showing the relationship between the slope of the IV characteristic of a photoreceptor and the film thickness in a temperature/humidity environment; 4 is a diagram showing an overview of film thickness estimation processing by a film thickness estimation unit of the image forming apparatus 1 according to the first embodiment of the present invention; FIG. FIG. 10 is a diagram showing an overview of the influence of variations in the calculated film thickness of the photoreceptor calculated by the film thickness calculator; FIG. 4 is a diagram showing an outline of a predicted film thickness range when estimating a photoreceptor film thickness; 4 is a flowchart showing main processing of the image forming apparatus according to the first embodiment of the present invention; 4 is a flowchart of a subroutine showing abnormality determination processing by an abnormality determination unit of the image forming apparatus according to the first embodiment of the present invention; FIG. 10 is a diagram showing an overview of usage rate calculation processing employed in the image forming apparatus according to the second embodiment of the present invention; 9 is a flowchart showing usage rate calculation processing by the image forming apparatus according to the second embodiment of the present invention; FIG. 11 is a functional block diagram showing the configuration of main parts of an image forming apparatus according to a third embodiment of the present invention; FIG. 4 is a graph showing the relationship between the running distance of the photoreceptor and the film thickness;

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail with reference to embodiments shown in the drawings.
The present invention has the following configuration in order to accurately calculate a predicted film thickness range corresponding to the current running distance with respect to the estimated film thickness.
That is, the image forming apparatus of the present invention includes a voltage applying section that applies a charging bias to a charging member that charges the peripheral surface of a rotating photoreceptor, and a current that generates a feedback signal representing the output current flowing from the charging member to the photoreceptor. and a detection unit, wherein the film thickness of the photoreceptor is calculated based on the voltage value related to the charging bias applied to the charging member and the current value related to the output current flowing through the photoreceptor. a film thickness calculation means, a travel distance calculation means for calculating a travel distance of the photosensitive member during charging, a calculated film thickness storage means for storing the calculated film thickness calculated by the film thickness calculation means in association with the travel distance, Film thickness estimating means for calculating an estimated film thickness at the present time based on the calculated film thickness and travel distance obtained from the calculated film thickness storage means, and based on the estimated film thickness calculated by the film thickness estimating means and a film thickness range prediction means for calculating a predicted film thickness range corresponding to the current running distance.
With the above configuration, it is possible to accurately calculate a predicted film thickness range corresponding to the current running distance for the estimated film thickness.
The features of the invention described above will be explained in detail with reference to the following drawings. However, unless there is a specific description, the constituent elements, types, combinations, shapes, relative arrangements, etc. described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention. .
The features of the present invention described above will be described in detail below with reference to the drawings.

<First Embodiment>
FIG. 1 is a cross-sectional view showing a schematic mechanical configuration of an image forming apparatus to which the present invention is applied.
Referring to FIG. 1, the flow of image formation in image forming apparatus 1 will be briefly described by taking a copy mode as an example.
In the image forming apparatus 1, in a copy mode, an automatic document feeder (ADF) 2 sequentially feeds a bundle of documents to an image reading device 3, and the image reading device 3 reads image information. The read image information is converted into optical information by a writing unit 4 as writing means via image processing means. It is later exposed by light information from the writing unit 4 to form an electrostatic latent image.
The electrostatic latent image on the photoreceptor 6 is developed by the developing section 7 into a toner image. This toner image is transferred to the transfer paper by the transport belt 8 . The toner image is fixed on the transfer paper by the fixing unit 9, and the transfer paper is discharged.

<Electrophotographic Process Adopted for Image Forming Apparatus According to First Embodiment>
FIG. 2 is a diagram showing the overall configuration of an electrophotographic process employed in the image forming apparatus 1 according to the first embodiment of the invention.
FIG. 2 shows the configuration of a typical direct DC charging type electrophotographic process, including a photosensitive member 6, a charging roller (charging member) 12, an exposure unit 13, a developing unit 7, a display panel 14, a transfer roller 15, and a blade. 16, a static eliminator 17, a high-voltage power source (charging) 18, a current/voltage detector 19, and a control unit 10.
A photoreceptor 16 is circulated, and a DC high voltage generated by a high voltage power supply 18 is applied to a charging roller (charging member) 12 to uniformly charge the surface of the photoreceptor 6 . After that, the exposure unit 13 emits image light corresponding to the image signal, and the surface of the photoreceptor 6 is exposed to the image light, forming an electrostatic latent image on the surface of the photoreceptor 6 .

The developing unit 7 develops the electrostatic latent image on the surface of the photoreceptor 6 into a toner image, and the toner image on the photoreceptor 6 is transferred to a recording medium by the transfer roller 15 . After that, the image is formed on the recording medium by being fixed by the fixing means.
Further, after the electric charge on the surface of the photoreceptor 6 is removed by the LED light emitted by the static eliminator 17, the charging process is performed.
The control unit 10 includes an A/D converter (ADC) 10a, a CPU (central processing unit) 10b, a ROM (read only memory) 10c, and a RAM (random access memory) 10d.
The display panel 14 displays the usage rate of the photoreceptor 6 as a value between 0% and 100%.

<Control section>
FIG. 3 is a functional block diagram showing the configuration of main parts of the image forming apparatus according to the first embodiment of the invention.
Control unit 10 shown in FIG.
The motor drive unit 21 drives the motor according to the drive instruction from the control unit 30, and rotates the photoreceptor 6 according to the rotation of the motor.
The temperature/humidity detection unit 11 detects the ambient temperature/humidity around the photoreceptor 6 .
When the voltage application unit 24 acquires a voltage command value indicating the voltage value to be applied to the photoreceptor 6 from the control unit 30 , the voltage application unit 24 adjusts the applied voltage so as to correspond to the voltage command value. A voltage is applied to the photoreceptor 6 .
The current/voltage detector 19 generates a feedback signal representing the output current/voltage flowing from the charging roller 12 to the photoreceptor 6, and outputs the feedback signal to the A/D converter 10a.

The control unit 10 shown in FIG. 2 is composed of a microcomputer having, for example, a CPU 10b, a ROM 10c, and a RAM 10d, as described above.
The CPU 10b reads the operating system OS from the ROM 10c, expands it on the RAM 10d, starts the OS, reads application software programs (processing modules) from the ROM 10c, and executes various processes under the control of the OS. 2 is realized.

The control unit 30 includes a film thickness calculation unit 30a, a calculated film thickness storage unit 30b, a film thickness estimation unit 30c, an abnormality determination unit 30c1, a film thickness range prediction unit 30d, an out-of-range number counting unit 30d1, and a film thickness estimation information storage unit 30e. , an estimated film thickness error calculation unit 30f, a usage rate calculation unit 30g, a comparison unit 30k, a travel distance calculation unit 30h, an estimated film thickness storage unit 30i, and a film thickness determination calculation unit 30j.
The film thickness calculator 30a calculates the slope of the IV characteristic of the photoreceptor based on the current value related to the output current flowing through the photoreceptor 6 and the voltage value related to the charging bias applied to the charging member. , the film thickness is calculated based on the slope of the IV characteristic.

The calculated film thickness storage unit 30b associates the calculated film thickness calculated by the film thickness calculation unit 30a with the travel distance calculated by the travel distance calculation unit 30h, and stores them in the RAM 10d.
The film thickness estimator 30c calculates the current estimated film thickness based on the calculated film thicknesses and traveled distances obtained at a plurality of times from the calculated film thickness storage unit 30b. The film thickness estimator 30c calculates the estimated film thickness corresponding to the current traveled distance according to the least squares method, based on the calculated film thicknesses and the traveled distances obtained from the calculated film thickness storage 30b.
The film thickness estimator 30c calculates the estimated film thickness error ΔDe based on the temperature/humidity information detected by the temperature/humidity detector 11 .

Based on the estimated film thickness estimated by the film thickness estimating unit 30c, the film thickness range predicting unit 30d calculates a possible estimated film thickness range Dmin to Dmax of the current film thickness.
A film thickness range prediction unit 30d calculates a predicted film thickness range Dmin to Dmax based on the estimated film thickness and the estimated film thickness error ΔDe.
The film thickness range prediction unit 30d calculates the predicted film thickness range Dmin to Dmax so that the smaller the value of the previous estimated film thickness, the narrower the predicted film thickness range Dmin to Dmax.
The film thickness range prediction unit 30d calculates a predicted film thickness range Dmin to Dmax corresponding to the current running distance using the estimated film thickness error ΔDe based on the previous estimated film thickness.

When estimating the next estimated film thickness, the abnormality determination unit 30c1 determines whether or not the estimated film thickness falls within the predicted film thickness range Dmin to Dmax predicted by the film thickness range prediction unit 30d. Determines whether the film thickness is valid or invalid.
The abnormality determination unit 30c1 invalidates the estimated film thickness when the estimated film thickness is outside the range on the thick film side of the predicted film thickness range Dmin to Dmax predicted by the film thickness range prediction unit 30d. .
The abnormality determination unit 30c1 validates the estimated film thickness that is out of range on the thin film side when the number of out-of-range counts counted by the out-of-range counting unit 30d1 is continuously counted for a predetermined number of times or more.
When the estimated film thickness becomes valid, the abnormality determination unit 30c1 discards the most recent estimated film thickness that is stored in the estimated film thickness storage unit 30i.
When the out-of-range number of times counted by the out-of-range number-of-range counting section 30d1 is continuously counted less than a certain number of times, the abnormality determination section 30c1 causes the thickness estimating section 30c to execute the thickness estimation process again. .

The out-of-range count unit 30d1 determines that the estimated film thickness estimated by the film thickness estimation unit 30c is on the thick film side with respect to the estimated film thickness range Dmin to Dmax predicted by the film thickness range prediction unit 30d. Number of out-of-range cases when the predicted film thickness range Dmin to Dmax is outside, or when the estimated film thickness estimated by the film thickness estimation unit 30c is on the thin side and is outside the predicted film thickness range Dmin to Dmax. to count.
The out-of-range count unit 30d1 is provided in the film thickness range prediction unit 30d, and calculates the estimated film thickness range Dmin to Dmax predicted by the film thickness range prediction unit 30d by the film thickness estimation unit 30c. Count the number of times the film thickness is out of range on the thin film side.
The film thickness estimation information holding unit 30e stores film thickness estimation information (FIG. 6 ).
The estimated film thickness error calculation unit 30f calculates an estimated film thickness error ΔDe between the film thickness estimation information and the estimated film thickness based on the film thickness estimation information and the estimated film thickness.

The comparison unit 30k calculates the maximum wear film when the film of the photoreceptor is scraped to the maximum, which can be calculated based on the predicted film thickness range lower limit value Dmin predicted by the film thickness range prediction unit 30d and the traveling distance of the photoreceptor 6. Compare with thickness value.
The usage rate calculator 30g calculates the usage rate of the photoreceptor 6 based on the lower limit value of the predicted film thickness range or the maximum shaved film thickness value, whichever is larger, as the comparison result of the comparator 30k.
The usage rate calculator 30g calculates the usage rate of the photoreceptor 6 based on the lower limit value of the predicted film thickness range predicted by the film thickness range prediction section 30d.
The traveling distance calculation unit 30h measures the time during which the motor for rotating the photoreceptor 6 is rotating and the voltage application unit 24 is applying voltage to the photoreceptor 6 via the charging roller 12, using the timer 10e. By multiplying the application time by the unit number of rotations per second, the running distance of the photosensitive member 6 during charging is calculated.

The usage rate display control section 30m converts the usage rate of the photoreceptor 6 calculated by the usage rate calculation section 30g into a value between 0% and 100%, and displays it on the display panel .
The estimated film thickness storage unit 30i stores the estimated film thickness estimated by the film thickness estimation unit 30c by adding valid/invalid information related to the estimated film thickness determined by the abnormality determination unit 30c1.
The film thickness determination calculation unit 30j determines and outputs an effective one of the estimated film thicknesses stored in the estimated film thickness storage unit 30i as the film thickness.
The control unit 30 calculates the voltage value to be applied to the photoreceptor 6 based on the feedback signal generated by the current/voltage detection unit 19 via the A/D conversion unit 10a, and uses this voltage value as the voltage command value. It is controlled to adjust the applied voltage by applying it to the voltage application unit 24 .

<IV characteristic detection>
Under the control of the control unit 30, a plurality of different voltages are applied to the photosensitive member to charge it, the current at the time of application is detected, the IV characteristic is calculated, and the film thickness is detected from the slope of the characteristic (Patent Reference 1).
In order to derive IV characteristics during charging, the control unit 10 applies a plurality of different voltages and detects the charging current at that time via the A/D converter 10a.

It is assumed that voltages are applied at four points in a plurality of control steps as a plurality of different voltages. At this time, the control steps are the following [S1] to [S5].
[S1] A charging voltage of voltage V1 is applied, and the current I1 at that time is detected.
[S2] A charging voltage of voltage V2 is applied, and the current I2 at that time is detected.
[S3] A charging voltage of voltage V3 is applied, and the current I3 at that time is detected.
[S4] A charging voltage of voltage V4 is applied, and the current I4 at that time is detected.
[S5] When performing [S1] to [S4], the film thickness calculator 30a derives the slope m of the IV characteristic from the applied voltage and the detected current (see FIG. 4), and calculates the slope of the IV characteristic. A film thickness D (see FIG. 6) of the photosensitive member 6 corresponding to m is calculated.
The calculated film thickness storage unit 30b associates the current travel distance L calculated by the travel distance calculation unit 30h with the calculated film thickness D calculated by the film thickness calculation unit 30a, and stores them in the RAM 10d.
Note that the voltages V1 to V4 are assumed to have different voltage values. At least two or more different current-voltage pairs (I1, V1) to (I4, V4) may be stored in the calculated film thickness storage unit 30b.

<IV characteristic graph>
FIG. 4 is a graph showing IV characteristics.
The film thickness calculator 30a obtains the film thickness of the photosensitive member based on the slope m of the IV characteristic graph shown in FIG. 4 (see Patent Document 2).
Specifically, when the photoreceptor 6 is charged via the charging roller (charging member) 2, the current Idc flowing between the charging roller 2 and the photoreceptor 6 and the thickness D of the photosensitive layer of the photoreceptor 6 Between them, Idc=k/D (K is a constant) holds.
As described above, the film thickness calculator 30a calculates the slope of the IV characteristic of the photoreceptor based on the current value related to the output current flowing through the photoreceptor 6 and the voltage value related to the charging bias applied to the charging member. is calculated, and the film thickness is calculated based on the slope of the IV characteristic.

<IV characteristics when noise occurs>
FIG. 5 is a graph including IV characteristics when noise occurs.
The ○ mark shown in FIG. 5 is the IV characteristic when there is no noise, and the Δ mark is the IV characteristic when there is noise.
In the control steps [S1] to [S5] described above, by calculating the slope m of the IV characteristic, the film thickness D can be calculated from the slope m.
However, as shown in FIG. 5, there is a problem that an erroneous film thickness De is calculated from an _erroneous slope me when an abnormal IV characteristic occurs due to noise or the like.

<Relationship between slope and film thickness under temperature and humidity environment>
FIG. 6 is a graph showing the relationship between the slope of the IV characteristic of the photoreceptor and the film thickness under the temperature and humidity environment.
Ideally, the relationship between the slope of the IV characteristic and the film thickness should be constant. However, as shown in FIG. 6, in the low temperature and low humidity LL environment (eg, 10° C., 15%), the normal temperature and normal humidity MM environment (eg, 23° C., 50%), the high temperature and high humidity HH environment (eg, 27° C., 80%).
The film thickness of the photoreceptor is about 34 μm when it is new, and the film thickness at which replacement is judged to be necessary is, for example, 13 μm.
In the film thickness detection control, the film thickness is obtained from the slope of the IV characteristic when the charging bias is changed at several points (see Patent Document 2).
As shown in FIG. 6, the relationship between the slope m of the IV characteristic and the film thickness changes remarkably as the film thickness decreases. As shown in FIG. 5, when a large inclination is detected due to variations, the calculated film thickness of the photoreceptor is smaller than the actual film thickness.
When the film thickness falls below the minimum film thickness threshold value Dref for reliably charging the surface of the photoreceptor, for example, in an image forming apparatus that uses the result of film thickness detection to determine the life span, the film thickness is affected by temperature, humidity, and noise. Due to the abnormal IV characteristic calculated in 1, the end of life is unexpected.

<Overview of film thickness estimation processing>
FIG. 7 is a diagram showing an overview of film thickness estimation processing by the film thickness estimation unit 30c of the image forming apparatus 1 according to the first embodiment of the present invention.
FIG. 7 shows an outline of the abnormality determination process performed on the estimated film thickness of the photoreceptor 6. The vertical axis represents the calculated film thickness Dc of the photoreceptor 6, and the horizontal axis represents the running distance L of the photoreceptor 6. there is
In order to determine whether the calculated film thickness is normal or abnormal, the calculated film thickness value Dc calculated by the film thickness calculation unit 30a in the past is associated with the photoreceptor travel distance L calculated by the travel distance calculation unit 30h. It is stored in the storage unit 30b, and the film thickness estimating unit 30c calculates the slope m and the intercept of the calculated film thickness Dc value with respect to the photosensitive member running distance L (line 41 in FIG. 7).
Based on these calculation results, an estimated film thickness De estimated from the photoreceptor running distance L can be obtained.
Based on the calculated film thickness Dc value acquired from the calculated film thickness storage unit 30b, the film thickness estimating unit 30c calculates the transition of the calculated film thickness Dc with respect to the photoreceptor running distance L by, for example, the least squares method. An estimated film thickness De located on a line segment 41 indicated by 7 is obtained.
The film thickness estimator 30c calculates the estimated film thickness De corresponding to the current running distance L according to the least squares method based on the calculated film thickness Dc and the running distance L at a plurality of points in time. can improve the estimation accuracy of

<Influence of Variation on Calculated Film Thickness of Photoreceptor>
FIG. 8 is a diagram showing an overview of the influence of variations in the calculated film thickness Dc of the photosensitive member calculated by the film thickness calculator 30a.
As shown in FIG. 8, it is necessary to consider variations in the slope m of the IV characteristic obtained from the calculated film thickness Dc.
Factors that cause the slope m to vary include the following.
(1) Variation in charging bias output voltage V (2) Variation in detected value I of charging current (3) Variation in resistance between photoreceptor 6 and charging roller 12 Since it is determined by the configuration of hardware such as the circuit board for outputting the charging bias and the photosensitive member 6 , it is uniquely determined depending on the model of the image forming apparatus 1 . The variation upper and lower limits of the slope m hardly depends on the calculated slope m, and there is no problem even if it is regarded as a constant value. Variations in the calculated film thickness Dc can be calculated from the upper and lower limits (see FIG. 8).

Here, when the calculated value m of the slope is large=the calculated film thickness Dc is small, the variation in the calculated film thickness Dc due to the variation in slope becomes small, as indicated by the line 45 in FIG.
Conversely, when the calculated value of the slope is small=the calculated film thickness is large, the variation in the calculated film thickness Dc due to the variation in the slope increases as indicated by the line 47 in FIG.
Thus, the width of the calculated film thickness Dc variation varies depending on the result of the calculated film thickness Dc, and the width of the calculated film thickness Dc variation can be determined based on the value of the calculated film thickness Dc.

Since the correlation between the slope m and the calculated film thickness Dc fluctuates depending on the temperature and humidity environment, the width of the variation is determined in consideration of the environmental influence in FIG. Therefore, by detecting the current temperature/humidity using the temperature/humidity detection unit 11 and correcting the correlation equation of the slope m-calculated film thickness Dc, the range of variation can be suppressed.
Based on the same theory as the variation in the calculated film thickness Dc, the estimated film thickness error calculator 30f calculates the estimated film thickness De (see FIG. 7) obtained by the film thickness estimator 30c based on the estimated film thickness De. An estimated film thickness error ΔDe is calculated. For example, when defined by the following linear function, the coefficient α and the intercept β can be determined based on actual measurement data unique to the model of the image forming apparatus 1 .
ΔDe=α×De+β Formula (1)

The film thickness estimator 30c corrects the estimated film thickness De based on the temperature/humidity information detected by the temperature/humidity detector 11, which has the advantage of increasing the prediction accuracy of the estimated film thickness De.
Further, the film thickness estimation unit 30c corrects the estimated film thickness error ΔDe based on the temperature and humidity information detected by the temperature/humidity detection unit 11, thereby increasing the prediction accuracy of the estimated film thickness error ΔDe. be.

The film thickness range prediction unit 30d calculates a film thickness range upper limit value Dmax and a film thickness range lower limit value Dmin as the range that the film thickness can take at the present point in time using the following equations (2) and (3).
The film thickness range prediction unit 30d subtracts the value obtained by multiplying the minimum wear rate Vsmin by the running distance (Ln-Le) from the previous film thickness estimation from the value obtained by adding the estimated film thickness error ΔDe to the estimated film thickness De. Then, the film thickness range upper limit value Dmax is calculated.
Dmax=De+ΔDe−Vsmin×(Ln−Le) Equation (2)
On the other hand, the film thickness range prediction unit 30d obtains a value obtained by subtracting the estimated film thickness error ΔDe from the estimated film thickness De by multiplying the maximum wear rate Vsmax by the running distance (Ln−Le) from the previous film thickness estimation. is subtracted to calculate the film thickness range lower limit value Dmin.
Dmin=De−ΔDe−Vsmax×(Ln−Le) Equation (3)
The traveled distance (Ln−Le) from the previous film thickness estimation is a value obtained by subtracting the previous traveled distance Le from the current traveled distance Ln.

The film thickness range prediction unit 30d calculates a predicted film thickness range Dmin to Dmax corresponding to the current running distance L based on the estimated film thickness De calculated by the film thickness estimation unit 30c. can be calculated with high accuracy.
The film thickness range prediction unit 30d calculates the predicted film thickness range Dmin to Dmax based on the estimated film thickness De and the estimated film thickness error ΔDe. There is an advantage that the thickness error ΔDe is reduced and the prediction accuracy of the predicted film thickness range Dmin to Dmax is increased.

Note that the minimum wear rate Vsmin and the maximum wear rate Vsmax described above indicate the minimum and maximum rates at which the film thickness of the photoreceptor can be worn, respectively. Both the minimum wear speed Vsmin and the maximum wear speed Vsmax are determined as values specific to the model of the image forming apparatus 1, and the following are the main influencing factors.
(1) Pressure of the cleaning blade (2) Pressure of the developing nip (developing roller and photoreceptor) (3) Environment (in a low temperature environment, the cleaning blade becomes hard and easily worn)

<Predicted film thickness range>
FIG. 9 is a diagram showing an outline of the predicted film thickness range Dmin to Dmax when estimating the photoreceptor film thickness.
In general, the film thickness of the photoreceptor 6 is given an allowable range of ±10% in the initial state. The thickness Dsmin is a possible initial value of the calculated film thickness Dc of the photoreceptor on the vertical axis. Furthermore, below the vertical axis, there is a minimum film thickness threshold value Dref representing the limit value of the film thickness at which an abnormality occurs.
Reference numeral 48 is a line segment representing the transition when the film thickness is the thickest. That is, it is a line segment representing the transition when the photoreceptor 6 is scraped from the initial maximum film thickness Dsmax at the minimum wear rate Vsmin.
On the other hand, reference numeral 49 is a line segment representing the transition when the film thickness is the thinnest. That is, it is a line segment representing the transition when the photoreceptor 6 is scraped from the initial minimum film thickness Dsmin to the maximum wear rate Vsmax.
A predicted film thickness range 51 shown in FIG. 9 can be predicted as a range from the film thickness range upper limit value Dmax to the film thickness range lower limit value Dmin. This predicted film thickness range 51 varies depending on the estimated film thickness De.
In the present embodiment, if there are calculated film thicknesses Dcu1 to Dcu4 as shown in FIG. 9 as an example of the calculated film thickness Dc exceeding the film thickness range upper limit value Dmax of the predicted film thickness range 51, they are all ignored. .
On the other hand, as an example of the calculated film thickness Dc below the film thickness range lower limit value Dmin of the predicted film thickness range 51, when the calculated film thicknesses Dcd1 to Dcd3 continue three times as shown in FIG. The calculated film thickness Dcd3 is made valid.
From the above-described calculation formulas (2) and (3), due to the theory shown in FIG. Become.
Therefore, as shown in FIG. 9, the film thickness of the photoreceptor 6 is worn away and the estimated film thickness De becomes thinner (the photoreceptor running distance L is longer), the more accurately the film thickness can be estimated. it becomes possible to

FIG. 9 shows an outline of the abnormality determination process performed on the estimated film thickness De of the photoreceptor 6, where the vertical axis represents the calculated film thickness Dc of the photoreceptor 6 and the horizontal axis represents the running distance L of the photoreceptor 6. ing.
As shown in FIG. 9, the predicted film thickness range 51 obtained from the result of the estimated film thickness De is such that as the photoreceptor travel distance L increases and the estimated film thickness De decreases, the predicted film thickness at that photoreceptor travel distance L increases. The range Dmin to Dmax is narrowed. That is, the first range indicated by reference numeral 51 shifts to the second range 52, and the predicted film thickness range Dmin to Dmax narrows. As a result, the estimated film thickness range Dmin to Dmax at the current running distance can be calculated with high accuracy.
The film thickness range prediction unit 30d performs calculation so that the predicted film thickness range Dmin to Dmax becomes narrower as the value of the previous estimated film thickness De is smaller. There is an advantage that the film thickness error ΔDe is reduced and the prediction accuracy of the predicted film thickness range Dmin to Dmax is increased.

<Abnormality determination processing>
Next, referring to FIG. 9, the abnormality determination process when the calculated film thickness Dc outside the estimated film thickness range 51 is calculated will be described.
If the calculated film thickness Dc exceeds the film thickness range upper limit value Dmax, the calculated film thickness Dc is invalidated. In this case, since the film thickness is thicker than expected, it is determined that the film thickness is more advantageous (not shaved) than the actual film thickness.
When judging the life of the photoreceptor 6 based on the calculated film thickness Dc, the calculated film thickness Dc is treated as invalid to avoid the risk of making an advantageous decision.

Conversely, when the calculated film thickness Dc falls below the film thickness range lower limit value Dmin, the calculated film thickness Dc is treated as invalid at first.
However, if it is true that the lower limit of the film thickness range lower limit value Dmin is broken, there is a problem that an abnormal image is generated unless it is determined early and fed back to the control process.
Therefore, when a result outside the range is obtained, the film thickness detection is performed again at an early stage, and the truth of the calculated film thickness outside the range is quickly judged.
The out-of-range number counting unit 30d counts the out-of-range number of times, and when the calculated film thickness Dc becomes the lower limit crack state continuously for a certain number of times (for example, three times), the film thickness is actually thin. Therefore, the calculated film thickness Dc for the lower limit crack is validated.

At this time, if the calculated film thickness Dc before it is determined to be below the lower limit remains, there is a problem that the gradient m for estimating the estimated film thickness De becomes gentle and the determination is made on the advantageous side. Calculation film thicknesses Dc calculated in the past should be discarded, except for the calculation film thickness Dc that is below the lower limit.
In addition, regardless of whether the upper limit is exceeded or the lower limit is broken, if the out-of-range number counting unit 30d1 continues to determine that it is out of range for a specified number of times or more, the reliability of the film thickness estimation process itself is suspected. , the above-described problem can be avoided by not reflecting the subsequent results of the estimated film thickness De in the control.

<Main processing>
FIG. 10 is a flow chart showing main processing of the image forming apparatus 1 according to the first embodiment of the present invention.
At step S5, the controller 30 is in a standby state.
In step S10, the control unit 30 starts the film thickness calculation execution determination.
In step S15, the control unit 30 determines whether or not the film thickness calculation execution condition is satisfied. Here, if the film thickness calculation execution condition is satisfied (S15, Yes), the process proceeds to step S20. On the other hand, if the film thickness calculation execution condition is not satisfied (S15, NO), the process returns to step S5.
In step S20, the controller 30 executes a film thickness calculation operation. That is, the control section 30 outputs a voltage command value indicating the voltage value to be applied to the photoreceptor 6 to the voltage application section 24 . The voltage application unit 24 adjusts the applied voltage so as to correspond to the voltage command value, and applies the voltage to the photoreceptor 6 via the charging roller 12 .
In step S25, the film thickness calculator 30a calculates the photosensitive member film thickness Dc from the relationship between the charging bias and the charging current.
In step S30, the calculated film thickness storage unit 30b stores the calculated film thickness Dc and the travel distance information L calculated as described above.
In step S35, the control unit 30 calls a subroutine (FIG. 11) for abnormality determination processing.

<Abnormality determination processing>
FIG. 11 is a flowchart of a subroutine showing abnormality determination processing by the abnormality determination unit 30c1 of the image forming apparatus 1 according to the first embodiment of the present invention.
As described above, the abnormality determination unit 30c1 determines whether or not the calculated film thickness Dc is within the predicted film thickness range Dmin to Dmax based on the result of the previous estimated film thickness De. The thickness Dc determines whether it is valid or invalid.
In step S110, the film thickness estimator 30c estimates the current estimated film thickness De based on the calculated film thickness Dc acquired from the calculated film thickness storage unit 30b. At this time, the film thickness estimator 30c estimates the current estimated film thickness De according to the method of least squares based on the calculated film thicknesses Dc obtained at a plurality of times from the calculated film thickness storage unit 30b.
In step S115, the film thickness range prediction unit 30d calculates the film thickness range upper limit value Dmax based on the equation (2), and calculates the film thickness range lower limit value Dmin based on the equation (3).

In step S120, the abnormality determination section 30c1 determines whether or not the latest calculated film thickness Dc is within the following range (Dmin to Dmax).
Dmin≤(latest Dc)≤Dmax Equation (4)
When estimating the next film thickness, the abnormality determination unit 30c1 determines whether the estimated film thickness De is valid or invalid by determining whether or not the estimated film thickness De falls within the predicted film thickness range Dmin to Dmax. By determining whether the estimated film thickness De is valid or invalid, the accuracy of the estimated film thickness De is improved, and the accuracy of the next film thickness estimation can be further improved.

When the latest calculated film thickness Dc is within the range of the above formula (4), the process proceeds to step S123, and as initialization processing, the value of the out-of-range consecutive number counter K is set to 0 (K=0 ).
Next, in step S125, it is determined that the latest calculated film thickness Dc is valid, and the process returns to the main routine.
When the latest calculated film thickness Dc is not within the range of the above formula (4), the process advances to step S128, and the out-of-range number counter 30d1 increments the out-of-range number counter K (K=K+1). do.
Next, the process proceeds to step S130, and when the out-of-range counter K is equal to or greater than a predetermined number of times, the calculated film thickness Dc is continuously
Dmin>(latest Dc) Equation (5)
It is determined whether or not

When the latest calculated film thickness Dc satisfies the condition of the above formula (5), the process proceeds to step S135, the abnormality determination section 30c1 determines that the latest calculated film thickness Dc is valid, and returns to the main routine.
When the estimated film thickness De estimated by the film thickness estimating unit 30c is out of range on the thin film side with respect to the estimated film thickness range Dmin to Dmax predicted by the film thickness range predicting unit 30d, the abnormality determination unit 30c1 The abnormality determination unit 30c1 is provided with an out-of-range number counter 30d1 that counts the number of out-of-range times, and the abnormality determination unit 30c1 determines that the number of out-of-range counters K counted by the out-of-range number-of-range counting unit 30d1 has been counted continuously for a predetermined number of times or more. In this case, the estimated film thickness De that is out of range on the thin film side is determined to be valid.

The abnormality determination unit 30c1 validates the estimated film thickness De that is out of range on the thin film side when the number of out-of-range counts counted by the out-of-range count unit 30d1 is continuously counted for a predetermined number of times or more. Thus, when the estimated film thickness D on the thin film side continues, it is determined that there is a tendency that the film thickness of the photoreceptor 6 is shaved, and by validating it, control on the safe side can be performed. .
When the estimated film thickness De becomes valid, the abnormality determination unit 30c1 discards the estimated film thickness De that is stored in the estimated film thickness storage unit 30i one or more times before the most recent estimated film thickness De. It is possible to prevent the estimated film thickness calculated under the influence of the thickness De from being recognized on the thick side.
The abnormality determination unit 30c1 applies the estimated film thickness estimated by the film thickness estimation unit 30c to image formation when the out-of-range number of times counted by the out-of-range number counting unit 30d1 is continuously counted for a predetermined number of times or more. By not using it for such control, it is possible to avoid the problem that an abnormal state occurs due to the use of an invalid estimated film thickness.

When the latest calculated film thickness Dc does not satisfy the condition of the above formula (5), the process proceeds to step S140, the abnormality determination section 30c1 determines that the calculated film thickness Dc is invalid, and returns to the main routine.
The abnormality determining unit 30c1 invalidates the estimated film thickness De when the estimated film thickness De is out of the range on the thick film side of the predicted film thickness range Dmin to Dmax predicted by the film thickness range prediction unit 30d. Judge as.
The abnormality determining unit 30c1 invalidates the estimated film thickness De when the estimated film thickness De is out of the range on the thick film side of the predicted film thickness range Dmin to Dmax predicted by the film thickness range prediction unit 30d. By doing so, it is possible to prevent the problem of generating an abnormal image by judging that the life has not yet been reached even though the life has actually been reached.
The abnormality determination unit 30c1 continuously counts the out-of-range number counted by the out-of-range counting unit 30d1 for the predicted film thickness range Dmin to Dmax predicted by the film thickness range prediction unit 30d when the out-of-range number is less than a predetermined number. If the estimated film thickness De is abnormal, the film thickness estimating section 30c is caused to execute the film thickness estimating process again.

<Effect of the first embodiment>
Unlike the prior art, in order to determine whether the calculated film thickness Dc is normal or abnormal, the estimated film thickness De and the photoreceptor running distance L at the time of past film thickness estimation are stored, and the estimated film thickness With respect to the value of De, considering the upper and lower limits of the estimated film thickness error ΔDe, which can be defined by the function of the estimated film thickness De, and the upper and lower limits of the film thickness wear rate, can be calculated.
This predicted film thickness range Dmin to Dmax fluctuates depending on the previous estimated film thickness De. It is possible to determine the presence or absence of an abnormality and calculate the estimated film thickness De with high accuracy.

<Second embodiment>
In the first embodiment, the correlation between the slope of the IV characteristic and the calculated film thickness Dc changes depending on the noise environment and the humidity and temperature environment. determines the width.
In contrast, in the second embodiment, the current atmospheric temperature and humidity are detected by the temperature/humidity detection unit 11, and the correlation between the slope m and the calculated film thickness Dc is corrected, thereby suppressing the width of the variation. It is characterized by
Based on the same theory as the variation in the calculated film thickness Dc, the estimated film thickness error calculator 30f calculates the estimated film thickness error ΔDe based on the estimated film thickness De obtained with reference to FIG. can be stipulated.
For example, when defined by a linear function such as Equation (11), the estimated film thickness error ΔDe, the coefficient α, the estimated film thickness De, and the intercept β can be determined based on model-specific actual measurement data.
ΔDe=α×De+β Formula (11)

When calculating the usage rate of the photoreceptor, the lower limit of the possible range of film thickness (lower limit of film thickness range Dmin) can be calculated by the following equation (12).
The film thickness range prediction unit 30d subtracts the value obtained by multiplying the maximum wear rate Vsmax by the running distance (Ln−Le) from the previous film thickness estimation from the value obtained by subtracting the estimated film thickness error ΔDe from the estimated film thickness De. Then, the film thickness range lower limit value Dmin is calculated.
Dmin=De−ΔDe−Vsmax×(Ln−Le) Equation (12)
The maximum wear speed Vsmax indicates the maximum speed at which the film thickness of the photoreceptor can be worn. The maximum wear rate Vsmax is determined as a value specific to the model, and the following are the main influencing factors.
(1) Pressure of the cleaning blade (2) Pressure of the developing nip (developing roller and photoreceptor) (3) Environment (in a low temperature environment, the cleaning blade becomes hard and wears easily)

<Overview of usage rate calculation processing>
FIG. 12 is a diagram showing an overview of usage rate calculation processing employed in the image forming apparatus 1 according to the second embodiment of the present invention.
In the second embodiment, in order to avoid prematurely determining that the life of the photoreceptor has ended using abnormal data when calculating the usage rate Ur of the photoreceptor, as shown in FIG. Then, the usage rate calculation process is performed using the film thickness range lower limit value Dmin.
In FIG. 12, the horizontal axis indicates the running distance L of the photoreceptor when calculating the usage rate Ur when judging the life of the photoreceptor, and the vertical axis indicates the estimated film thickness De of the photoreceptor.
By the way, conventionally, the usage rate Ur (%) is calculated based on the estimated minimum film thickness Dmin_cal (reference numeral 49) when the photoreceptor 6 is scraped at the maximum wear rate Vsmax assumed from the initial film thickness of the photoreceptor. was
Here, the estimated minimum film thickness Dmin_cal is calculated by subtracting a value obtained by multiplying the maximum wear rate Vsmax by the running distance L of the photosensitive member from the initial film thickness Ds, as shown in Equation (13).
Dmin_cal=Ds−Vsmax×L Formula (13)

In the second embodiment, the film thickness range lower limit value Dmin is calculated based on the estimated film thickness De at the time of the previous film thickness estimation, and the usage rate Ur is calculated based on this film thickness range lower limit value Dmin. , the usage rate Ur is calculated with higher accuracy depending on the degree of film thickness estimation.
The film thickness range lower limit value Dmin is indicated by reference numeral 62 in FIG.
This maximum wear film thickness Dsmax is compared with the film thickness range lower limit value Dmin, and in the range 64 where Dmin<Dmin_cal, the usage rate Ur is calculated based on the estimated minimum film thickness Dmin_cal.
On the other hand, in the range 65 where Dmin>Dmin_cal, the usage rate Ur is calculated based on the film thickness range lower limit value Dmin.
In this way, by using the larger one of the estimated minimum film thickness Dmin_cal and the film thickness range lower limit value Dmin to calculate the usage rate Ur, it is possible to further improve the accuracy of determining the usage rate Ur and the life of the photoreceptor. can. The reason for this is that the actual film thickness of the photoreceptor 6 is smaller than the maximum abrasion film thickness.
It is conceivable that the film thickness range lower limit value Dmin (reference numeral 62) has become an abnormal value due to the influence of noise.
Further, the accuracy of the estimated film thickness error ΔDe can be improved as the photoreceptor 6 wears according to Equation (12) described above.
Reference numeral 63 shown in FIG. 12 denotes a film thickness value used for calculating the usage rate Ur.
Accompanying this, the accuracy of film thickness estimation can be improved when the traveling distance L of the photosensitive member 6 is long and the film thickness is thin. Therefore, in the second embodiment, the accuracy can be further improved by estimating the thickness of the photosensitive member and calculating the usage rate Ur after the running distance L of the photosensitive member exceeds a certain threshold value.

<Usage rate calculation processing>
FIG. 13 is a flowchart showing usage rate calculation processing by the image forming apparatus 1 according to the second embodiment of the present invention.
In step S210, the comparison unit 30k determines whether or not the traveling distance L of the photoreceptor 6 is greater than the threshold value Lref.
When the traveling distance L of the photoreceptor 6 is greater than the threshold Lref, the process proceeds to step S215, and the film thickness range prediction unit 30d calculates the film thickness range lower limit value Dmin based on the previous estimated film thickness De.
That is, the film thickness range prediction unit 30d obtains a value obtained by subtracting the estimated film thickness error ΔDe from the estimated film thickness De and multiplying the maximum wear rate Vsmax by the running distance (Ln−Le) from the previous film thickness estimation. is subtracted to calculate the film thickness range lower limit value Dmin.
Dmin=De−ΔDe−Vsmax×(Ln−Le) Equation (14)

The estimated film thickness error ΔDe is calculated by subtracting the current estimated film thickness De from the previous estimated film thickness De.
The film thickness range prediction unit 30d calculates the predicted film thickness range Dmin to Dmax corresponding to the current running distance L using the estimated film thickness error ΔDe based on the previous estimated film thickness De. Since the estimated film thickness error ΔDe decreases as the film thickness decreases, the accuracy of prediction of the predicted film thickness range Dmin to Dmax can be improved.

In step S220, the comparison unit 30k determines whether or not the film thickness range lower limit value Dmin is greater than the maximum wear film thickness.
If the film thickness range lower limit value Dmin is larger than the estimated minimum film thickness Dmin_cal (range 64), the process proceeds to step S225, and the usage rate calculation unit 30g uses the film thickness range lower limit value Dmin to calculate the usage rate Ur. .
That is, the usage rate calculator 30g calculates the usage rate Ur of the photoreceptor 6 based on the film thickness range lower limit value Dmin (equation (14)) predicted by the film thickness range prediction section 30d. Using the initial film thickness Ds and the film thickness Dref required to prevent an abnormal image from appearing, the usage rate Ur can be calculated from the ratio between the scraping amount Ds−Dmin from the initial film thickness and the scraping allowable amount Ds−Dref.
Ur = (Ds-Dmin)/(Ds-Dref) x 100 Formula (15)
The usage rate calculation unit 30g can improve the accuracy of the usage rate calculation by calculating the usage rate of the photoreceptor 6 based on the predicted film thickness range lower limit value Dmin.
After the travel distance L of the photoreceptor 6 calculated by the travel distance calculation unit 30h exceeds a certain threshold value, the usage rate calculation unit 30g calculates the usage rate of the photoreceptor 6 based on the predicted film thickness range lower limit value Dmin. By calculating, the accuracy of prediction of the usage rate of the photoreceptor 6 can be improved.

On the other hand, if the running distance L of the photosensitive member 6 is not greater than the threshold value Lref (S210, No), or if the film thickness range lower limit value Dmin is not greater than the estimated minimum film thickness Dmin_cal (range 65), step S230 , the usage rate calculator 30g calculates the usage rate Ur of the photoreceptor 6 using the estimated minimum film thickness Dmin_cal (equation (13)).
Ur=(Ds−Dmin_cal)÷(Ds−Dref)×100 Equation (16)
The usage rate calculator 30g calculates the usage rate of the photoreceptor 6 based on the larger value of the predicted film thickness range lower limit value Dmin or the estimated minimum film thickness Dmin_cal, which is already recorded in the ID information of the process cartridge. When the calculated usage rate Ur is lower than the usage rate information already recorded, the usage rate information already recorded in the ID information, etc., should not be updated so that the usage rate decreases and the user is not confused. do.

<Effects of Second Embodiment>
Unlike the prior art, in order to determine whether the calculated film thickness Dc is normal or abnormal, the estimated film thickness De and the photoreceptor running distance L at the time of past film thickness estimation are stored, and the photoreceptor running distance is stored. The slope α and the intercept β of the film thickness value with respect to L are calculated. Based on these calculation results, an estimated film thickness De can be estimated from the travel distance L of the photosensitive member.
A film thickness range lower limit value Dmin, which is the lower limit value of the possible range of film thicknesses when judging the life of the photosensitive member 6, based on the most recent estimated film thickness De and an estimated film thickness error ΔDe based on the estimated film thickness De. Calculate
Using this lower limit value, the usage rate Ur is calculated to judge the service life. This film thickness range lower limit value Dmin is based on the previous estimated film thickness De. By considering the possible range of the film thickness based on De, the usage rate Ur of the photosensitive member can be calculated with high accuracy.

<Third Embodiment>
<Control unit>
FIG. 14 is a functional block diagram showing the configuration of main parts of an image forming apparatus according to the third embodiment of the invention. 14 that are the same as those shown in FIG. 3 have the same configuration, and description thereof will be omitted.
The third embodiment is characterized by including a usable remaining days calculation unit 30p, an estimated film thickness/date/time information storage unit 30p1, a difference value determination unit 30p2, and an elapsed days determination unit 30p3.

The remaining usable days calculation unit 30p calculates the remaining usable days of the photosensitive member 6 and the developing unit 7 based on the lower limit value of the film thickness range.
The remaining usable days calculation unit 30p calculates the current estimated film thickness calculated by the film thickness estimation unit 30c, the date and time information, and the travel distance of the photoreceptor obtained from the estimated film thickness/date and time information storage unit 30p1. is calculated based on the estimated film thickness at the time of exceeding , and the date and time information.
The remaining usable days calculation unit 30p calculates the current estimated film thickness and date/time information calculated by the film thickness estimation unit 30c, and the estimated film thickness acquired from the estimated film thickness/date/time information storage unit 30p1. Based on the estimated film thickness and the date and time information, the remaining usable days of the photoreceptor 6 and the developing section 7 are calculated.
When the difference value determination unit 30p2 determines that the difference value of the estimated film thickness from a certain time to the current time is equal to or greater than a certain threshold value, the remaining usable days calculation unit 30p determines that the photoreceptor 6 and the development unit 7 Calculate the number of remaining usable days.
The remaining usable days calculation unit 30p calculates the remaining usable days of the photoreceptor and the developing unit when the elapsed days determination unit 30p3 determines that the number of days elapsed from a certain point to the present time is equal to or greater than a certain threshold. calculate.

The estimated film thickness/date and time information storage unit 30p1 stores the estimated film thickness and date and time information at the time when the running distance of the photosensitive member calculated by the running distance calculation unit 30h exceeds a certain threshold.
The difference value determination unit 30p2 determines whether or not the difference value of the estimated film thickness from a certain time to the current time is equal to or greater than a certain threshold.
The elapsed days determination unit 30p3 determines whether or not the number of elapsed days from a certain time point to the present time is equal to or greater than a certain threshold.

<Summary of Remaining Available Days Calculation Process>
The remaining usable days calculation unit 30p calculates the remaining usable days of the developing unit 7 based on the estimated film thickness De and the usage rate Ur described above. By calculating the remaining usable days by the remaining usable days calculating section 30p, it becomes easier for the user or the service person to grasp the approximate period until the new developing section 7 is prepared.
Based on the formula (17), the remaining usable days calculation unit 30p divides the value obtained by subtracting the usage rate Ur [%] from 100 [%] by the usage rate Ur [%], and calculates the replacement date The number of remaining days of use Dl is calculated by dividing the number of days of use Du from the day.
Dl = (100-Ur [%]) ÷ (Ur [%] ÷ Du) Equation (17)

Here, the remaining usable days calculation unit 30p divides the value obtained by subtracting the current estimated film thickness De from the initial film thickness Ds by the value obtained by subtracting the threshold value Dref from the initial film thickness Ds based on the equation (18). Then, the value is multiplied by 100 to calculate the usage rate Ur [%].
Ur [%] = (Ds-De)/(Ds-Dref) x 100 Equation (18)

Further, the remaining usable days calculation unit 30p calculates the value obtained by subtracting the threshold value Deref from the current estimated film thickness De based on the equation (19) as the value obtained by subtracting the current estimated film thickness De from the initial film thickness Ds. Further, the value is divided by the number of days Du of use from the replacement date of the photoreceptor 6 to calculate the remaining number of usable days.
Dl = (De-Deref)/((Ds-De)/Du) Equation (19)
becomes.
Generally, the remaining usable days Dl are calculated based on the traveling distance L of the photoreceptor 6 and the number of printed sheets Np as follows.

The remaining usable days calculation unit 30p calculates a value obtained by subtracting the current travel distance L of the photoreceptor from the specified life travel distance Ld based on the formula (20). The remaining number of usable days Dl is calculated by dividing the travel distance L by the number of days Du from the date of replacement.
Dl = (Ld-L)/(L/Du) Equation (20)

Alternatively, the remaining usable days calculation unit 30p calculates a value obtained by subtracting the current number of printed sheets Np from the number of sheets of life Nl based on the expression (21), and calculates the calculated value by subtracting the current number of printed sheets Np from the replacement date. The number of remaining usable days Dl is calculated by dividing by the value obtained by dividing by the number of days of use Du.
Dl = (Nl - Np) ÷ (Np ÷ Du) Equation (21)
Since the running distance Ld and the number of sheets N, which are defined by the life, are set to values with a margin for the photoreceptor film thickness D, the photoreceptor 6 (developing section 7) can actually be used for a longer time. .
By calculating the usage rate Ur based on the estimated film thickness De described above and calculating the remaining usable days Dl based on the usage rate Ur, the remaining usable days Dl can be associated with the film thickness. This makes it possible to improve the accuracy of the remaining usable days Dl.

<Travel distance and film thickness of photoreceptor>
FIG. 15 is a graph showing the relationship between the traveling distance L of the photosensitive member and the film thickness D. As shown in FIG.
As shown in FIGS. 8 and 15, in the initial state where the film thickness D of the photoreceptor is large, that is, when the travel distance of the photoreceptor is short, the range of the estimated film thickness De is widened as shown in FIG. , and the accuracy of the estimated film thickness De is degraded.
Therefore, by calculating the remaining usable days Dl from a state in which the film has been shaved to some extent and the film thickness D has become thin, the calculation accuracy of the remaining usable days Dl can be further improved.
Based on the equation (22), the remaining usable days calculation unit 30p calculates a value obtained by subtracting the threshold value Dref from the estimated film thickness De at the present time as the estimated film thickness De ( P3) in FIG. 15 is divided by the value obtained by subtracting the estimated film thickness De at the present time, and this value is further divided by the elapsed days Dp from a certain point in time when the traveling distance L of the photoreceptor has progressed. Calculate Dl.
Dl = (De-Dref)/((De-De)/Dp) Equation (22)
The remaining usable days calculation unit 30p obtains the remaining usable days Dl according to the formula (22), so that it is possible to predict the remaining usable days Dl based only on the data in which the estimated film thickness De is highly accurate. becomes.

In addition, due to the result of determination of the estimated film thickness difference value ΔDe by the difference value determination unit 30p2, which will be described later, the remaining usable days calculation unit 30p calculates the current estimated film thickness De from the current estimated film thickness De based on the equation (23). The value obtained by subtracting the threshold value Dref is divided by the value obtained by subtracting the current estimated film thickness De from the value De1 (P4 in FIG. 15) at the time when the estimated film thickness De becomes equal to or less than a predetermined value. is divided by the number of days Dp that has passed since the estimated film thickness De became the predetermined film thickness D, to calculate the remaining usable days Dl.
Dl = (De-Dref)/((De1-De)/Dp) Equation (23)
The remaining usable days calculation unit 30p obtains the remaining usable days Dl according to the formula (23), so that it is possible to predict the remaining usable days Dl based only on the data in which the estimated film thickness De is highly accurate. becomes.

<Estimated film thickness difference value>
Here, the difference value determination unit 30p2 subtracts the current estimated film thickness Detn from the estimated film thickness Det1 at a certain point in time when the photoreceptor travel distance L has progressed, based on the equation (24). It is calculated as the value ΔDe.
ΔDe = (Det1-Detn) Equation (24)
Then, the difference value determination unit 30p2 determines whether or not the estimated film thickness difference value ΔDe from a certain time point to the current time point is equal to or greater than a certain threshold.

Alternatively, the difference value determination unit 30p2 calculates a value obtained by subtracting the current estimated film thickness De from the predetermined film thickness D as the estimated film thickness difference value ΔDe based on Equation (25).
ΔDe = (D-De) Equation (25)
Then, the difference value determination unit 30p2 determines whether or not the estimated film thickness difference value ΔDe from a certain time point to the current time point is equal to or greater than a certain threshold.
If the estimated film thickness difference value ΔDe calculated by the equation (24) or (25) is a large value to some extent, an error is likely to occur in estimating the film abrasion rate (amount of film abrasion per day). It is desirable to start calculating the remaining usable days Dl based on the thickness De when the estimated film thickness De becomes smaller than a certain threshold value Deref.

For the same reason, the elapsed days determining unit 30p3 determines whether or not the number of elapsed days from a certain time to the current time is equal to or greater than a certain threshold.
Elapsed days Dp from a certain point in time when the photoreceptor running distance L has progressed, or the elapsed days Dp from the point in time when the estimated film thickness De reaches a predetermined film thickness, and the remaining usable days Dl from the point in time when a certain threshold value Dpref is exceeded. It is desirable to calculate

<Effect of the third embodiment>
Unlike the conventional technology, the remaining usable days calculation unit 30p calculates the remaining usable days Dl of the photoreceptor 6 and the developing unit 7 based on the lower limit of the estimated film thickness range. It is possible to improve the prediction accuracy of the remaining usable days Dl rather than calculating from information.
Current estimated film thickness calculated by the film thickness estimating unit 30c, date and time information, and estimated film thickness at the time when the traveling distance of the photosensitive member obtained from the estimated film thickness/date and time information storage unit 30p1 exceeds a certain threshold , and the date and time information, the remaining days Dl of usage of the photoreceptor 6 and the developing unit 7 are calculated, thereby improving the prediction accuracy of the film scraping rate and the prediction accuracy of the remaining days Dl of usage. be able to.
The current estimated film thickness calculated by the film thickness estimating unit 30c and date and time information, the estimated film thickness when the estimated film thickness obtained from the estimated film thickness/date and time information storage unit 30p1 is equal to or less than a certain threshold, and By calculating the remaining usable days Dl of the photoreceptor 6 and the developing unit 7 based on the date and time information, it is possible to improve the prediction accuracy of the film scraping rate and improve the calculation accuracy of the remaining usable days Dl. can.
When it is determined that the estimated film thickness difference value ΔDe from a certain point to the present time is equal to or greater than a certain threshold, the remaining usable days Dl of the photoreceptor 6 and the developing unit 7 are calculated to reduce the effect of the measurement error. It is possible to improve the calculation accuracy of the remaining usable days Dl.
When it is determined that the number of days elapsed from a certain point in time to the present time is equal to or greater than a certain threshold value, the remaining usable days Dl of the photoreceptor 6 and the developing unit 7 are calculated, thereby preventing the effects of measurement errors. , the calculation accuracy of the remaining usable days Dl can be improved.

<Summary of Actions and Effects of Mode Examples of the Present Embodiment>
<First aspect>
The image forming apparatus 1 of this embodiment includes a voltage applying section 24 that applies a charging bias to the charging roller 12 that charges the circumferential surface of the rotating photoreceptor 6, and a feedback signal representing the output current flowing from the charging roller 12 to the photoreceptor 6. based on the voltage V associated with the charging bias applied to the charging roller 12 and the current I associated with the output current flowing through the photoreceptor 6, A film thickness calculation unit 30a for calculating the film thickness of the photoreceptor 6, a travel distance calculation unit 30h for calculating the travel distance L of the photoreceptor 6 during charging, and a calculated film thickness Dc calculated by the film thickness calculation unit 30a. Based on the calculated film thickness storage unit 30i that stores the travel distance L in association with the calculated film thickness Dc at a plurality of times and the travel distance L acquired from the calculated film thickness storage unit 30i, the current estimated film thickness De is calculated. A film thickness range prediction unit 30d for calculating a predicted film thickness range Dmin to Dmax corresponding to the current running distance L based on the film thickness estimating unit 30c and the estimated film thickness De calculated by the film thickness estimating unit 30c. and.
According to this aspect, by calculating the predicted film thickness range Dmin to Dmax corresponding to the current running distance L based on the estimated film thickness De, the predicted film thickness range can be calculated with high accuracy.

<Second aspect>
Based on the calculated film thickness Dc and the traveled distance L obtained at a plurality of times from the calculated film thickness storage unit 30i, the film thickness estimator 30c of this aspect calculates the estimated film thickness corresponding to the current traveled distance L according to the least-squares method. It is characterized by calculating the thickness.
According to this aspect, based on the calculated film thickness Dc and the traveled distance L at a plurality of times, the estimated film thickness De corresponding to the current traveled distance L is calculated according to the method of least squares. Estimation accuracy can be improved.

<Third aspect>
When estimating the next film thickness, the film thickness estimation unit 30c of this embodiment determines whether or not the estimated film thickness De falls within the predicted film thickness range Dmin to Dmax predicted by the film thickness range prediction unit 30d. It is characterized by having an abnormality determination section 30c1 that determines whether the estimated film thickness De is valid or invalid by doing so.
According to this aspect, when estimating the next film thickness, it is determined whether the estimated film thickness De is valid or invalid by determining whether or not the estimated film thickness De falls within the predicted film thickness range Dmin to Dmax. By determining whether the estimated film thickness De is valid or invalid, the accuracy of the estimated film thickness De is improved, and the accuracy of the next film thickness estimation can be further improved.

<Fourth Aspect>
The image forming apparatus of this aspect includes a film thickness estimation information holding unit 30e that holds film thickness estimation information representing the relationship between the charging bias-charging current gradient used in the film thickness estimation unit 30c and the film thickness of the photoreceptor 6; an estimated film thickness error calculating means for calculating an estimated film thickness error ΔDe between the estimated film thickness information and the estimated film thickness De based on the estimated film thickness information and the estimated film thickness De; The section 30d is characterized by calculating a predicted film thickness range Dmin to Dmax based on the estimated film thickness De and the estimated film thickness error ΔDe.
According to this aspect, the estimated film thickness range Dmin to Dmax is calculated based on the estimated film thickness De and the estimated film thickness error ΔDe. There is an advantage that ΔDe is reduced and the prediction accuracy of the predicted film thickness range Dmin to Dmax is increased.

<Fifth aspect>
The film thickness range prediction unit 30d of this aspect is characterized in that calculation is performed such that the smaller the value of the previous estimated film thickness De, the narrower the predicted film thickness range Dmin to Dmax.
According to this aspect, the smaller the value of the previous estimated film thickness De, the narrower the estimated film thickness range Dmin to Dmax. There is an advantage that the error ΔDe is reduced and the prediction accuracy of the predicted film thickness range Dmin to Dmax is increased.

<Sixth Aspect>
In the image forming apparatus of this aspect, the temperature/humidity detection unit 11 that detects the current temperature/humidity and the film thickness estimation unit 30c calculate the estimated film thickness De based on the temperature/humidity information detected by the temperature/humidity detection unit 11. It is characterized by correcting.
According to this aspect, there is an advantage that the prediction accuracy of the estimated film thickness De is improved by correcting the estimated film thickness De based on the temperature/humidity information.

<Seventh Aspect>
The image forming apparatus of this aspect includes a temperature/humidity detection unit 11 that detects the current temperature/humidity, and a film thickness estimation unit 30c based on the temperature/humidity information detected by the temperature/humidity detection unit 11, an estimated film thickness error ΔDe is corrected.
According to this aspect, there is an advantage that the prediction accuracy of the estimated film thickness error ΔDe is improved by correcting the estimated film thickness error ΔDe based on the temperature/humidity information.

<Eighth aspect>
The abnormality determining unit 30c1 of this aspect determines the estimated film thickness when the estimated film thickness De is out of the range of the estimated film thickness Dmin to Dmax predicted by the film thickness range predicting unit 30d on the thick film side. It is characterized by invalidating De.
According to this aspect, when the estimated film thickness De is out of range on the thick film side, the estimated film thickness De is invalidated. It is possible to prevent the problem of generating an abnormal image by determining that the image is not correct.

<Ninth Aspect>
The abnormality determining unit 30c1 of this aspect determines that the estimated film thickness De estimated by the film thickness estimating unit 30c is out of range on the thin film side with respect to the estimated film thickness range Dmin to Dmax predicted by the film thickness range predicting unit 30d. The abnormality determination unit 30c1 is provided with an out-of-range number counting unit 30d1 that counts the number of out-of-range times when the out-of-range number of times is counted. In this case, the estimated film thickness De, which is out of range on the thin film side, is validated.
According to this aspect, when the number of out-of-range times is continuously counted for a certain number of times or more, the estimated film thickness De that is out of range on the thin film side is validated, so that the estimated film thickness D on the thin film side If this continues, it is determined that there is a tendency that the film thickness of the photoreceptor 6 is shaved, and by validating it, control on the safe side can be performed.

<Tenth Aspect>
The abnormality determination unit 30c1 of this aspect is characterized in that, when the estimated film thickness De becomes valid, the estimated film thickness De that is stored in the estimated film thickness storage unit 30i one or more times before is discarded. do.
According to this aspect, when the estimated film thickness De becomes effective, the past estimated film thickness De is discarded and the estimated film thickness De stored in the estimated film thickness storage unit 30i is discarded. It is possible to prevent the estimated film thickness calculated under the influence of the thickness De from being recognized on the thick side.

<Eleventh Aspect>
The abnormality determining unit 30c1 of this aspect determines that the estimated film thickness De estimated by the film thickness estimating unit 30c is on the thick film side with respect to the estimated film thickness range Dmin to Dmax predicted by the film thickness range predicting unit 30d. When the estimated film thickness De estimated by the film thickness estimating unit 30c is outside the predicted film thickness range Dmin to Dmax, or when the estimated film thickness De estimated by the film thickness estimation unit 30c is on the thin side and is outside the predicted film thickness range Dmin to Dmax Equipped with an out-of-range number counting unit 30d1 that counts the number of out-of-range times, the abnormality determination unit 30c1, when the out-of-range number of times counted by the out-of-range number counting unit 30d1 is continuously counted less than a certain number of times, The film thickness estimating section 30c is caused to execute the film thickness estimating process again.
According to this aspect, when the out-of-range number of times counted by the out-of-range number counting unit 30d1 is continuously counted less than a certain number of times, the thickness estimating unit 30c is caused to perform the film thickness estimation process again. Thus, it is possible to quickly determine whether the estimated film thickness De is abnormal.

<Twelfth Aspect>
The abnormality determining unit 30c1 of this aspect determines the number of times the estimated film thickness De estimated by the film thickness estimating unit 30c is outside the range of the estimated film thickness Dmin to Dmax predicted by the film thickness range predicting unit 30d. The abnormality determination unit 30c1 is provided with a film thickness estimation unit It is characterized in that the estimated film thickness estimated by 30c is not used for control related to image formation.
According to this aspect, when the counted out-of-range number of times is continuously counted for a predetermined number of times or more, the estimated film thickness estimated by the film thickness estimation unit 30c is not used for the control related to image formation. , it is possible to avoid the problem of generating an abnormal condition using an invalid estimated film thickness.

<Thirteenth Aspect>
The image forming apparatus 1 of this aspect is characterized by comprising a usage rate calculation section 30g that calculates the usage rate of the photoreceptor 6 based on the predicted film thickness range lower limit value Dmin predicted by the film thickness range prediction section 30d. do.
According to this aspect, by calculating the usage rate of the photoreceptor 6 based on the predicted film thickness range lower limit value Dmin, the accuracy of the usage rate calculation can be improved.

<14th Aspect>
The image forming apparatus 1 of this aspect includes a travel distance calculation unit 30h that calculates the travel distance L of the photoreceptor 6,
The predicted film thickness range lower limit value Dmin predicted by the film thickness range prediction unit 30d, and the maximum wear film thickness value when the film of the photoreceptor 6 wears to the maximum, which can be calculated based on the running distance L of the photoreceptor 6; and a usage rate calculation section 30g calculates the usage rate of the photoreceptor 6 based on the larger value of the predicted film thickness range lower limit value Dmin or the maximum wear film thickness value It is characterized by
According to this aspect, by calculating the usage rate of the photoreceptor 6 based on the larger value of the predicted film thickness range lower limit value Dmin or the maximum wear film thickness value, it is already recorded in the process cartridge ID information or the like. If the calculated usage rate is lower than the usage rate information already recorded, the usage rate information already recorded in the ID information, etc. shall not be updated so that the usage rate will decrease and the user will not be confused. do.

<Fifteenth Aspect>
The film thickness range prediction unit 30d of this aspect is characterized by calculating the predicted film thickness range lower limit value Dmin corresponding to the current running distance L using the estimated film thickness error ΔDe based on the previous estimated film thickness De. do.
According to this aspect, the estimated film thickness range lower limit value Dmin corresponding to the current running distance L is calculated using the estimated film thickness error ΔDe based on the previous estimated film thickness De. Since the estimated film thickness error ΔDe decreases as D decreases, the accuracy of prediction of the predicted film thickness range lower limit value Dmin can be improved.

<16th Aspect>
The usage rate calculation unit 30g of this aspect calculates the lower limit of the predicted film thickness range predicted by the film thickness range prediction unit 30d after the travel distance L of the photoreceptor 6 calculated by the travel distance calculation unit 30h exceeds a certain threshold value. The usage rate of the photosensitive member 6 is calculated based on the value Dmin.
According to this aspect, after the travel distance L of the photoreceptor 6 calculated by the travel distance calculation unit 30h exceeds a certain threshold, the usage rate of the photoreceptor 6 is calculated based on the predicted film thickness range lower limit value Dmin. By doing so, the accuracy of prediction of the usage rate of the photoreceptor 6 can be improved.

<17th Aspect>
The image forming apparatus 1 of this aspect is characterized by comprising a remaining usable days calculation unit 30p that calculates the remaining usable days Dl of the photoreceptor and the developing unit based on the lower limit value of the predicted film thickness range. .
According to this aspect, by calculating the remaining usable days Dl of the photoreceptor 6 and the developing unit 7 based on the lower limit value of the predicted film thickness range, it is possible to use more than calculating from the number of sheets and travel distance information. It is possible to improve the prediction accuracy of the number of remaining days Dl.

<18th Aspect>
The image forming apparatus 1 of this aspect includes an estimated film thickness and date/time information storage unit that stores the estimated film thickness and date/time information at the time when the travel distance of the photosensitive member calculated by the travel distance calculation unit 30h exceeds a certain threshold. 30p1, the remaining usable days calculation unit 30p stores the current estimated film thickness calculated by the film thickness estimation unit 30c, date and time information, and the estimated film thickness/date and time information storage unit 30p1. Based on the estimated film thickness at the time when the distance exceeds a certain threshold and the date and time information, the remaining usable days Dl of the photoreceptor 6 and the developing unit 7 are calculated.
According to this aspect, the current estimated film thickness calculated by the film thickness estimating unit 30c and the date and time information and the traveling distance of the photosensitive member obtained from the estimated film thickness/date and time information storage unit 30p1 exceed a certain threshold. By calculating the remaining usable days Dl of the photoreceptor 6 and the developing unit 7 based on the estimated film thickness at the time and the date and time information, the prediction accuracy of the film scraping rate is improved, and the remaining usable days Dl are improved. can improve the prediction accuracy of

<19th Aspect>
The image forming apparatus 1 of this aspect includes an estimated film thickness/date and time information storage unit 30p1 that stores date and time information and an estimated film thickness when the estimated film thickness is equal to or less than a certain threshold, and the remaining usable days calculation unit 30p. is the current estimated film thickness calculated by the film thickness estimating unit 30c, the date and time information, and the estimated film thickness obtained from the estimated film thickness/date and time information storage unit 30p1, when the estimated film thickness is equal to or less than a certain threshold. , and the date and time information, the remaining usable days Dl of the photoreceptor 6 and the developing unit 7 are calculated.
According to this aspect, when the current estimated film thickness calculated by the film thickness estimating unit 30c and the date and time information and the estimated film thickness acquired from the estimated film thickness/date and time information storage unit 30p1 become equal to or less than a certain threshold By calculating the remaining usable days Dl of the photoreceptor 6 and the developing unit 7 based on the estimated film thickness and the date and time information, the prediction accuracy of the film scraping rate is improved, and the remaining usable days Dl are calculated. Accuracy can be improved.

<Twentieth aspect>
The image forming apparatus 1 of this aspect includes a difference value determination unit 30p2 that determines whether or not the estimated film thickness difference value ΔDe from a certain time point to the current time point is equal to or greater than a certain threshold value, and the remaining usable days calculation unit 30p , when the difference value determination unit 30p2 determines that the estimated film thickness difference value ΔDe from a certain time point to the current time point is equal to or greater than a certain threshold value, the remaining usable days Dl of the photoreceptor 6 and the developing unit 7 are calculated. It is characterized by
According to this aspect, when it is determined that the estimated film thickness difference value ΔDe from a certain point to the present time is equal to or greater than a certain threshold, the remaining usable days Dl of the photoreceptor 6 and the developing unit 7 are calculated. , the calculation accuracy of the remaining usable days Dl can be improved without being affected by measurement errors.

<21st Aspect>
The image forming apparatus 1 of this aspect includes an elapsed days determination unit 30p3 that determines whether or not the number of days elapsed from a certain time point to the present time is equal to or greater than a certain threshold value. When the unit 30p3 determines that the number of days elapsed from a certain time point to the present time is equal to or greater than a certain threshold value, it calculates the remaining usable days Dl of the photoreceptor 6 and the developing unit 7. FIG.
According to this aspect, when it is determined that the number of days elapsed from a certain time point to the present time is equal to or greater than a certain threshold value, the remaining usable days Dl of the photoreceptor 6 and the developing unit 7 are calculated. It is possible to improve the calculation accuracy of the remaining usable days Dl without being affected by the

<22nd Aspect>
In the image forming method of this embodiment, a voltage applying section 24 that applies a charging bias to the charging roller 12 that charges the circumferential surface of the rotating photoreceptor 6 and a feedback signal representing the output current flowing from the charging roller 12 to the photoreceptor 6 are used. and a current detection unit that generates a , a film thickness calculation step for calculating the film thickness of the photoreceptor 6, a travel distance calculation step for calculating the travel distance L of the photoreceptor 6 during charging, and a travel distance to the calculated film thickness Dc calculated by the film thickness calculation step. A film thickness for calculating an estimated film thickness De at the present time based on a calculated film thickness saving step that associates and saves L, and the calculated film thickness Dc at a plurality of points in time and the travel distance L obtained from the calculated film thickness saving step. and a film thickness range prediction step of calculating a predicted film thickness range Dmin to Dmax corresponding to the current running distance L based on the estimated film thickness De calculated by the film thickness estimation step. Characterized by
Since the operation and effects of the twenty-second mode are the same as those of the first mode, the description thereof will be omitted.

<23rd Aspect>
A program according to this aspect causes a processor to execute each step in the image forming method according to the twenty-second aspect.
According to this aspect, each step can be executed by a processor.

DESCRIPTION OF SYMBOLS 1... Image forming apparatus 7... Development part 8... Conveyor belt 9... Fixing part 10... Control unit 10a... A/D conversion part 10b... CPU, 10c... ROM, 10d... RAM, 10e... Timer, DESCRIPTION OF SYMBOLS 11... Temperature/humidity detection part 12... Charging roller 13... Exposure part 14... Display panel 15... Transfer roller 16... Blade 16... Photoreceptor 17... Static elimination device 18... High voltage power supply 19... Current voltage Detection unit 21 Motor drive unit 24 Voltage application unit 30 Control unit 30a Film thickness calculation unit 30b Calculated film thickness storage unit 30c Film thickness estimation unit 30c1 Abnormality determination unit 30d Out-of-range number counting unit 30d Film thickness range prediction unit 30d1 Out-of-range number counting unit 30e Film thickness estimation information holding unit 30f Estimated film thickness error calculation unit 30g Use rate calculation unit 30h Running Distance calculation unit 30i Calculated film thickness storage unit 30i Estimated film thickness storage unit 30j Film thickness determination calculation unit 30k Comparison unit 30m Use rate display control unit 30p Remaining usable days calculation unit 30p , 30p1... Estimated film thickness/date and time information storage unit, 30p2... Difference value determination unit, 30p3... Elapsed days determination unit, 51... Predicted film thickness range,

JP-A-5-223513 Japanese Patent Application Laid-Open No. 2009-098279 JP-A-8-334956

Claims (22)

a voltage applying unit that applies a charging bias to a charging member that charges the circumferential surface of the rotating photoreceptor;
an image forming apparatus comprising: a current detection unit that generates a feedback signal representing an output current flowing from the charging member to the photoreceptor,
film thickness calculation means for calculating the film thickness of the photosensitive member based on the voltage value associated with the charging bias applied to the charging member and the current value associated with the output current flowing through the photosensitive member;
travel distance calculation means for calculating the travel distance of the photoreceptor during charging;
a calculated film thickness storage means for storing the calculated film thickness calculated by the film thickness calculation means in association with the running distance;
Film thickness estimating means for calculating an estimated film thickness at a current time based on the calculated film thickness and travel distance at a plurality of times acquired from the calculated film thickness storage means;
a film thickness range prediction means for calculating a predicted film thickness range corresponding to the current running distance based on the estimated film thickness calculated by the film thickness estimation means ;
The image forming apparatus , wherein the film thickness range prediction means performs calculation so that the predicted film thickness range becomes narrower as the value of the previous estimated film thickness is smaller . The film thickness estimating means calculates the estimated film thickness corresponding to the current traveled distance according to the least squares method based on the calculated film thickness and the traveled distance at a plurality of times acquired from the calculated film thickness storage means. 2. The image forming apparatus according to claim 1. The film thickness estimating means determines whether or not the calculated film thickness falls within the predicted film thickness range predicted by the film thickness range predicting means when calculating the next film thickness. 2. The image forming apparatus according to claim 1, further comprising abnormality determination means for determining whether the thickness is valid or invalid. a film thickness estimation information holding means for holding film thickness estimation information representing a relationship between the charging bias-charging current gradient used in the film thickness estimation means and the film thickness of the photoreceptor;
estimated film thickness error calculation means for calculating an estimated film thickness error between the film thickness estimation information and the estimated film thickness based on the film thickness estimation information and the estimated film thickness;
2. The image forming apparatus according to claim 1, wherein said film thickness range prediction means calculates said predicted film thickness range based on said estimated film thickness and said estimated film thickness error. a temperature/humidity detection means for detecting the current temperature/humidity;
2. The image forming apparatus according to claim 1, wherein said film thickness estimating means corrects said estimated film thickness based on temperature and humidity information detected by said temperature and humidity detecting means. a temperature/humidity detection means for detecting the current temperature/humidity;
5. The image forming apparatus according to claim 4 , wherein said film thickness estimating means corrects said estimated film thickness error based on the temperature/humidity information detected by said temperature/humidity detecting means. The abnormality determining means invalidates the calculated film thickness when the calculated film thickness is outside the range on the thick film side with respect to the predicted film thickness range predicted by the film thickness range predicting means. 4. The image forming apparatus according to claim 3. The film thickness range predicting means predicts the film thickness when the calculated film thickness calculated by the film thickness calculating means is out of range on the thin film side with respect to the predicted film thickness range predicted by the film thickness range predicting means. Equipped with an out-of-range number counting means for counting the out-of-range number of times,
When the number of out-of-range counts counted by the out-of-range number-of-range counting means is continuously counted for a predetermined number of times or more, the abnormality determination means validates the calculated film thickness that is out of range on the thin film side. 4. The image forming apparatus according to claim 3, characterized by: 9. When the calculated film thickness becomes valid, the abnormality determination means discards the most recent calculated film thickness that is stored in the calculated film thickness storage means one or more times before. The described image forming apparatus. The film thickness range prediction means determines that the calculated film thickness calculated by the film thickness calculation means is on the thick film side with respect to the predicted film thickness range predicted by the film thickness range prediction means. Out-of-range count for counting the number of out-of-range cases when the thickness is out of the range, or when the calculated film thickness calculated by the film thickness calculation means is on the thin side and is out of the predicted film thickness range. comprising counting means,
When the out-of-range number counted by the out-of-range number counting means is continuously counted less than a predetermined number of times, the abnormality determination means causes the film thickness calculation means to execute the film thickness calculation process again. 4. The image forming apparatus according to claim 3 , wherein: The film thickness range predicting means counts the number of times the calculated film thickness calculated by the film thickness calculating means is out of the predicted film thickness range predicted by the film thickness range predicting means. Equipped with external number counting means,
When the number of out-of-range times counted by the out-of-range number-of-range counting means is continuously counted for a predetermined number of times or more, the abnormality determination means applies the calculated film thickness calculated by the film thickness calculation means to image formation. 4. The image forming apparatus according to claim 3, wherein the image forming apparatus is not used for such control. 2. The image forming apparatus according to claim 1, further comprising usage rate calculation means for calculating a usage rate of said photoreceptor based on a lower limit value of the predicted film thickness range predicted by said film thickness range prediction means. travel distance calculation means for calculating the travel distance of the photoreceptor;
The lower limit value of the predicted film thickness range predicted by the film thickness range predicting means and the maximum wear film thickness value when the film of the photoreceptor wears to the maximum, which can be calculated based on the running distance of the photoreceptor. a comparison means for comparing;
13. The usage rate of the photosensitive member according to claim 12 , wherein the usage rate calculation means calculates the usage rate of the photoreceptor based on a lower limit value of the predicted film thickness range or a maximum abrasion film thickness value, whichever is larger. Image forming device. 2. The image forming apparatus according to claim 1, wherein said film thickness range predicting means calculates a predicted film thickness range corresponding to a current running distance using an estimated film thickness error based on a previous estimated film thickness. . The usage rate calculation means calculates the lower limit value of the predicted film thickness range predicted by the film thickness range prediction means after the travel distance of the photosensitive member calculated by the travel distance calculation means exceeds a certain threshold value. 13. The image forming apparatus according to claim 12 , wherein the usage rate of the photoreceptor is calculated by 5. The apparatus according to any one of claims 1 to 4, further comprising: remaining usable days calculating means for calculating the remaining usable days of the photoreceptor and the developing unit based on the lower limit value of the predicted film thickness range. The described image forming apparatus. Estimated film thickness storage means for storing the estimated film thickness at the time when the traveling distance of the photoconductor calculated by the traveling distance calculating means exceeds a certain threshold and date and time information,
The means for calculating the remaining number of usable days,
The current estimated film thickness calculated by the film thickness estimating means and date and time information, the estimated film thickness at the time when the running distance of the photoreceptor obtained from the estimated film thickness storage means exceeds a certain threshold, and 17. The image forming apparatus according to claim 16 , wherein the number of remaining usable days of the photoreceptor and the developing unit is calculated based on date and time information. Estimated film thickness storage means for storing the estimated film thickness when the estimated film thickness is equal to or less than a certain threshold and date and time information,
The means for calculating the remaining number of usable days,
Current estimated film thickness calculated by the film thickness estimating means and date and time information, and estimated film thickness and date and time information obtained from the estimated film thickness storage means when the estimated film thickness becomes equal to or less than a certain threshold. 17. The image forming apparatus according to claim 16 , wherein the remaining usable days of the photoreceptor and the developing unit are calculated based on . A difference value determination means for determining whether an estimated film thickness difference value from a certain time point to the current time point is equal to or greater than a certain threshold,
The means for calculating the remaining number of usable days,
When the difference value determination means determines that the estimated film thickness difference value from a certain time point to the current time point is equal to or greater than a predetermined threshold value, the remaining number of usable days of the photoreceptor and the developing unit is calculated. The image forming apparatus according to any one of claims 16 to 18 . Elapsed days determination means for determining whether the number of days elapsed from a certain point to the present time is equal to or greater than a certain threshold;
The means for calculating the remaining number of usable days,
3. The number of remaining usable days of the photoreceptor and the developing unit is calculated when the elapsed days determination means determines that the number of days elapsed from a certain time point to the present time is equal to or greater than a predetermined threshold value. 19. The image forming apparatus according to any one of 16 to 18 . a voltage applying unit that applies a charging bias to a charging member that charges the circumferential surface of the rotating photoreceptor;
an image forming method using an image forming apparatus comprising: a current detection unit that generates a feedback signal representing an output current flowing from the charging member to the photoreceptor;
a film thickness calculation step of calculating the film thickness of the photoreceptor based on a voltage value related to the charging bias applied to the charging member and a current value related to the output current flowing through the photoreceptor;
a traveling distance calculating step of calculating a traveling distance of the photoreceptor during charging;
A calculated film thickness saving step for storing the calculated film thickness calculated by the film thickness calculating step in association with the travel distance;
A film thickness estimating step of calculating an estimated film thickness at a current time based on the calculated film thickness and travel distance at a plurality of times obtained from the calculated film thickness storage step;
a film thickness range prediction step of calculating a predicted film thickness range corresponding to the current running distance based on the estimated film thickness calculated by the film thickness estimation step ;
The image forming method , wherein, in the film thickness range prediction step, calculation is performed such that the smaller the value of the previous estimated film thickness, the narrower the predicted film thickness range . 22. A program causing a processor to execute each step of the image forming method according to claim 21 .

Images