JP2010072553A - Image forming device and method of measuring film thickness - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device which can measure the film thickness of the surface of a developer retainer by comparing the measurement of the film thickness of the developer retainer using a second amount of accumulated charges calculated without passing the second initialization process, and to provide the method of measuring film thickness. <P>SOLUTION: A control section 40 executes: a first operation for removal of electricity by applying a direct current voltage to a charger 13 at a direct current electric source 12 and remove electricity by a neutralizing lamp 18 to initialize a photoreceptor roll 11; a first thickness detection operation calculating the amount of the first accumulated charge of the photoreceptor roll 11 at a calculation unit 30 of charge amount by charging the photoreceptor roll 11 with a first direct current voltage V1; a second operation for removal of electricity which is the same as that of the first operation for removal of electricity; and a second thickness detection operation by charging the photoreceptor roll 11 with a second direct current voltage V2 above the first direct current voltage V1 to calculate the second amount of accumulated charges of the photoreceptor roll 11 at the calculation section 30 of the amount of charges. Subsequently, a calculation section 50 for film thickness calculates the film thickness of the surface of the photoreceptor roll 11 based on the first and second amounts of accumulated charges and the first and second direct current voltages V1 and V2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a film thickness measuring method.

  A toner that has a film on its surface and includes a photoreceptor that is an example of a developer holding body that is charged, forms an electrostatic latent image, and develops the electrostatic latent image with toner, and is formed on the photoreceptor In an image forming apparatus that fixes an image on a recording medium, a technique for measuring the film thickness of the surface of the photoreceptor is known.

  For example, in Patent Document 1, the film thickness on the surface of the photoconductor is used based on the slope of the line of the VI characteristic determined by the voltage V applied to the charging roll for charging the photoconductor and the charging current I flowing at that time. Techniques have been proposed to detect when the limit has been reached and to encourage replacement.

  Patent Document 2 proposes a technique for calculating the film thickness of the surface of the photoconductor from the amount of charge obtained by integrating the direct current flowing from the charging roll, the developing roll, and the transfer roll to the photoconductor.

Further, Patent Document 3 discloses that the amount of charge obtained based on an excess of measurement current generated when a direct current component current is supplied to a photoreceptor through a charging roll is used to remove the surface of the photoreceptor. There has been proposed a technique for preventing the photoconductor from being erroneously determined as the replacement time even though the film thickness has not reached the use limit.
JP-A-5-223513 JP 2007-187930 A JP 2007-327992 A

  The present invention accurately measures the film thickness of the surface of the developer holder, compared to the measurement of the film thickness of the developer holder using the second accumulated charge amount calculated without going through the second initialization process. An object of the present invention is to provide an image forming apparatus and a film thickness measuring method that can be used.

The image forming apparatus according to claim 1 comprises:
A developer holding body having a film on the surface and receiving charging, formation of an electrostatic latent image, and development of the electrostatic latent image with toner is recorded, and a toner image formed on the developer holding body is recorded. An image forming apparatus for measuring a film thickness of the surface of the developer holder in an image forming apparatus fixed on a medium,
A first initialization process for initializing the potential of the developer holder;
First charge accumulation for charging the developer holding body initialized in the first initialization process with a first DC voltage and calculating a first accumulated charge amount of the developer holding body due to the charging. process,
A second initialization process for initializing the potential of the developer holder, and a second direct current different from the first direct current voltage in the developer holder initialized in the second initialization process. Control means for performing a film thickness measurement sequence comprising a second charge accumulation process for charging with a voltage and calculating a second accumulated charge amount of the developer holding member due to the charge;
The first accumulated charge amount and the second accumulated charge amount calculated by the execution of the film thickness measurement sequence by the control means, the first DC voltage and the first accumulated charge amount employed in the film thickness measurement sequence. And a film thickness calculating means for calculating the film thickness of the surface of the developer holder based on the DC voltage of 2.

  The image forming apparatus according to claim 2, wherein in the first initialization process and the second initialization process, the developer holding body is set to be higher than any of the first DC voltage and the second DC voltage. It is a process in which the developer holding member is discharged by charging with a high initialization DC voltage.

  The image forming apparatus according to claim 3, wherein the film thickness calculation unit includes a differential voltage between the first DC voltage and the second DC voltage, the first accumulated charge amount, and the second accumulated charge amount. And calculating the film thickness of the surface of the developer holder based on the difference voltage and the difference charge amount.

The image forming apparatus according to claim 4 further includes a film thickness storage unit that stores an initial film thickness of the surface of the developer holder.
The film thickness calculation means calculates the current film thickness of the developer holder surface based on the initial film thickness stored in the film thickness storage means or a film thickness calculated in the past based on the initial film thickness. It is calculated.

The image forming apparatus according to claim 5
A developer holding body having a film on the surface and receiving charging, formation of an electrostatic latent image, and development of the electrostatic latent image with toner is recorded, and a toner image formed on the developer holding body is recorded. An image forming apparatus fixed on a medium,
A first initialization process for initializing the potential of the developer holder;
First charge accumulation for charging the developer holding body initialized in the first initialization process with a first DC voltage and calculating a first accumulated charge amount of the developer holding body due to the charging. process,
A second initialization process for initializing the potential of the developer holder, and a second direct current different from the first direct current voltage in the developer holder initialized in the second initialization process. Control means for performing a film thickness measurement sequence comprising a second accumulated charge process for charging with a voltage and calculating a second accumulated charge of the developer holding member due to the charging;
The first accumulated charge amount and the second accumulated charge amount calculated by the execution of the film thickness measurement sequence by the control means, the first DC voltage and the first accumulated charge amount employed in the film thickness measurement sequence. And a film thickness calculating means for calculating the film thickness of the surface of the developer holder based on the DC voltage of 2.

An image forming apparatus according to claim 6 is provided.
A developer holder having a film on the surface and rotating during operation;
Charging means for charging the developer holding member with at least DC charging among DC charging for charging with a DC voltage and AC charging for charging with an AC voltage superimposed on the DC voltage;
A latent image forming unit that forms an electrostatic latent image on the developer holding member by irradiating the developer holding member charged by the charging unit with light having a pattern corresponding to an image signal;
Developing means for developing the electrostatic latent image formed on the developer holder by the latent image forming means with toner and forming a toner image on the developer holder;
Transfer means for transferring a toner image formed on the developer holder by the developing means onto a recording medium;
A charge eliminating unit disposed on the downstream side in the rotation direction of the developer holding body with respect to the transfer unit and discharging the developer holding body;
Fixing means for fixing the toner image transferred onto the recording medium by the transfer means onto the recording medium;
While the charging means charges the developer holder by direct current charging, the current flowing between the charging means and the developer holder is measured, and the accumulated charge of the developer holder based on the current is measured. Charge amount calculating means for calculating the amount;
A first initialization process in which the charging means is charged with an initializing DC voltage for initializing the developer holding body to charge the developer holding body, and the charge removing means discharges the developer holding body;
The charging means is charged with the developer holding body initialized in the first initialization process with a first DC voltage for charge accumulation, and the charge amount calculating means is charged with the development during the charging. A first accumulated charge process for calculating a first accumulated charge amount of the agent holder,
The developer holding body is charged with the same initializing DC voltage as the initializing DC voltage for initializing the developer holding body to the charging means, and the developer holding body is placed on the charge eliminating means. A second initializing process for neutralizing the charge, and the developer holding body initialized in the second initializing process is connected to the charging means by a second different from the first DC voltage for charge accumulation. Control means for charging with a DC voltage and causing the charge amount calculation means to execute a film thickness measurement sequence comprising a second accumulated charge process for calculating a second accumulated charge amount of the developer holding body during the charging. When,
The first accumulated charge amount and the second accumulated charge amount calculated by the execution of the film thickness measurement sequence by the control means, the first DC voltage and the first accumulated charge amount employed in the film thickness measurement sequence. And a film thickness calculating means for calculating the film thickness of the surface of the developer holder based on the DC voltage of 2.

The film thickness measuring method according to claim 7 is provided with a developer holder having a film on the surface and receiving charging, formation of an electrostatic latent image, and development of the electrostatic latent image with toner, and the developer holder. A film thickness measuring method for measuring the film thickness of the surface of the developer holder in an image forming apparatus for fixing a toner image formed thereon onto a recording medium,
A first initialization process for initializing the potential of the developer holder;
First charge accumulation for charging the developer holding body initialized in the first initialization process with a first DC voltage and calculating a first accumulated charge amount of the developer holding body due to the charging. process,
A second initialization process for initializing the potential of the developer holder;
The developer holding body initialized in the second initialization process is charged with a second DC voltage different from the first DC voltage, and the second accumulated charge of the developer holding body due to the charging is charged. Based on the second charge accumulation process for calculating the amount, the first accumulated charge amount and the second accumulated charge amount, and the first DC voltage and the second DC voltage. It has the film thickness calculation process which calculates the film thickness of a holding body surface.

  In the image forming apparatus according to claim 1, the film thickness of the surface of the developer holder is compared with the measurement of the film thickness of the developer holder using the second accumulated charge amount calculated without going through the second initialization process. Can be measured with high accuracy.

  In the image forming apparatus of the second aspect, the charging potential of the developer holding member can be stabilized.

  In the image forming apparatus according to the third aspect, the film thickness on the surface of the developer holding member can be measured with higher accuracy than in the case where the configuration according to the third aspect is not provided.

  In the image forming apparatus of the fourth aspect, the current film thickness on the surface of the developer holding member can be measured with higher accuracy than in the case where the configuration of the fourth aspect is not provided.

  In the image forming apparatus according to claim 5, the film thickness of the surface of the developer holding member can be increased only by direct current charging as compared with the case where the first and second initialization processes for initializing the potential of the developer holding member are not provided. It can be calculated with high accuracy.

  In the image forming apparatus according to claim 6, the film thickness of the surface of the developer holder can be increased only by direct current charging as compared with the case where the first and second initialization processes for initializing the potential of the developer holder are not provided. It can be calculated with high accuracy.

  In the film thickness measuring method according to claim 7, the film thickness of the surface of the developer holder can be obtained only by direct current charging as compared with the case where the first and second initialization processes for initializing the potential of the developer holder are not provided. Can be measured with high accuracy.

  Embodiments of the present invention will be described below.

  FIG. 1 is a schematic configuration diagram of a printer which is an embodiment of an image forming apparatus.

  The printer 10 shown in FIG. 1 includes a photoreceptor roll 11 that is an example of a developer holding body that has a film on its surface and rotates in the direction of arrow A during operation.

  Further, the printer 10 includes a DC power supply unit 12 that supplies a DC voltage, and a charger 13 that is an example of a charging unit that DC-charges the photosensitive roll 11 with a DC voltage supplied from the DC power supply unit 12. Is provided.

  The printer 10 further includes a latent image forming unit that forms an electrostatic latent image on the photosensitive roll 11 by irradiating the photosensitive roll 11 charged by the charger 13 with light having a pattern corresponding to the image signal. An exposure unit 14 is provided as an example.

  Further, the printer 10 is a developing unit that develops an electrostatic latent image formed on the photoreceptor roll 11 by the exposure device 14 with toner to form a toner image on the photoreceptor roll 11. A vessel 15 is provided. The developing device 15 has a developer container 15_1 containing a two-component developer containing toner and a magnetic carrier, and holds the developer in the developer container 15_1 so as to face the surface of the photoreceptor roll 11. The developing roll 15_2 is rotated.

  Further, the printer 10 includes a transfer roll 16 that is an example of a transfer unit that transfers a toner image formed on the photoreceptor roll 11 by the developing unit 15 onto a recording sheet that is an example of a recording medium. It has been.

  The printer 10 includes a cleaning member 17. The cleaning member 17 is disposed on the surface of the photoreceptor roll 11 that has passed through the transfer area, such as toner, paper powder, or discharge products generated during charging that could not be transferred to the recording paper in the transfer area. It is a member that scrapes off.

  Further, the printer 10 is provided with a static elimination lamp 18 that is disposed on the downstream side of the transfer roll 16 and the cleaning member 17 in the rotation direction of the photosensitive roll 11 and neutralizes the photosensitive roll 11 as an example of a static elimination means. ing.

  Further, the printer 10 is provided with a fixing device 19 which is an example of a fixing unit that heats and pressurizes the toner image transferred onto the recording paper by the transfer roll 16 and fixes the toner image on the recording paper. The fixing device 19 includes a fixing roll 19_1 having a heating mechanism and a pressure roll 19_2 provided so as to face the fixing roll 19_1.

  Further, the printer 10 includes a recording paper storage unit 20 that stores recording paper, and a paper transport unit 21 that pulls out the recording paper from the recording paper storage unit 20 and transports the recording paper to a predetermined transport path. Yes.

  Further, the printer 10 includes a charge amount calculation unit 30 which is an example of a charge amount calculation unit. The charge amount calculation unit 30 measures the current flowing between the charger 13 and the photoreceptor roll 11 while the charger 13 charges the photoreceptor roll 11 by DC charging, and based on this current, The accumulated charge amount of the body roll 11 is calculated.

  The printer 10 further includes a control unit 40 that is an example of a control unit and a film thickness calculation unit 50 that is an example of a film thickness calculation unit. In addition, the printer 10 includes a film thickness storage unit 60 that stores the film thickness C0 of the surface of the photoreceptor roll 11 in the initial state and the capacitance C0 measured at this time. In addition, an embodiment of a film thickness measuring method is applied to the image forming apparatus of this embodiment.

  Here, a process cartridge 100 is constituted by the film thickness storage unit 60, the photoconductor roll 11 and the developing unit 15, and the process cartridge 100 is loaded so that it can be pulled out from the inside of the printer 10. Yes.

  First, the general operation of the printer 10 will be described.

  In the printer 10, charges are applied by the charger 13 to the surface of the photoreceptor roll 11 that has been neutralized by the neutralizing lamp 18. Further, the surface of the photoreceptor roll 11 to which the electric charge is applied is irradiated with light having a pattern corresponding to the image signal by the exposure device 14, and an electrostatic latent image is formed on the photoreceptor roll 11. Next, the electrostatic latent image is developed by causing the developer accommodated in the developer accommodating body 15_1 constituting the developing device 15 to be held on the rotating developing roll 15_2 and transported to the developing position. This developed image is transferred by the transfer roll 16 onto the recording paper that has been drawn from the recording paper storage portion 18 by the paper transport portion 19 and transported in the direction of arrow B in the transfer area determined by the photoreceptor roll 11 and the transfer roll 16. The Thereafter, the image is fixed by being heated and pressurized by the fixing device 19, and an image is formed on the recording paper.

  In addition, the unnecessary material adhering to the surface of the photoreceptor roll 11 that has passed through the transfer region is scraped off by the cleaning member 17 to prepare for the next image forming cycle.

  Next, the control part 40 and the film thickness calculation part 50 are demonstrated with reference to FIG. 1 and FIG.

  FIG. 2 is a diagram illustrating a flow of operations in the control unit and the film thickness calculation unit.

  In the control unit 40, first, a first static elimination operation (P1) (an example of a first initialization process) shown in FIG. 2 is performed. In the first static elimination operation (P1), the initialization DC voltage Vr sufficient for discharging is applied from the DC power supply unit 12 to the charger 13. As a result, the surface potential of the photoreceptor roll 11 becomes constant. Here, when a DC voltage Vr (for example, 1300 V) for obtaining a DC voltage VH (for example, 600 V) in a normal image forming process is applied, for example, after the emergency stop due to a paper jam or the like, Residual potential may remain. In the direct current charging, the direct current voltage VH can be controlled to increase, but it is difficult to decrease the direct current voltage VH. For this reason, a DC voltage Vr (for example, 1500 V) for charging at a potential higher than the expected residual potential is applied. By doing so, the DC voltage VHr of 700 V, for example, is fixed regardless of the presence or absence of the residual potential. Thereafter, the DC voltage is turned off, and the static elimination lamp 18 is turned on with a light amount necessary for static elimination. Here, while the photoconductor roll 11 is rotated by two to three turns, the static elimination lamp 18 is turned on and static elimination is performed. As a result, the potential decreases to Rp (for example, 50 V). The residual charge at this time is defined as Qrp1.

Next, a first film thickness detection operation (M1) (an example of a first accumulated charge process in the present invention) is performed. In the first film thickness detection operation (M1), a constant first DC voltage V1 (for example, 1000 V) that exceeds the discharge start voltage is applied to the charger 13 in a state in which the static elimination lamp 18 is turned off, and the photoconductor. The roll 11 is charged. The first DC voltage V1 is a DC voltage that satisfies V1 <Vr. The direct current Idc at this time is monitored by the charge amount calculation unit 30 and integrated. Here, the charge on the first round of the photoreceptor roll 11 is q1, and the second and third rounds are q2 and q3, respectively. Since the charge is saturated when the photosensitive roll 11 is charged for the period up to the third turn, q3≈0. However, when there is a leak or leakage current of the photoreceptor roll 11, it does not become zero. At this time, the charge q4 in the fourth round is regarded as the leakage charge amount Q leak,
Qm1 = (q1 + q2 + q3) −3 × Q leak; Q leak = q4... (1)
Thus, the first accumulated charge amount Qm1 accumulated in the photosensitive roll 11 during this measurement period can be accurately obtained. Note that the total charge amount Q1 accumulated in the photoreceptor roll 11 at this time is:
Q1 = Qrp1 + Qm1 (2)
It is.

  Further, a second static elimination operation (P2) (an example of a second initialization process) is performed. In the second static elimination operation (P2), charging is performed with the same DC voltage Vr as the DC voltage Vr applied in the first static elimination operation (P1), and a constant DC voltage VHr is obtained. If V1 <Vr is not secured, the same DC voltage VHr is not obtained in the second static elimination operation (P2). In general, DC charging varies depending on the film thickness, environment, and the like of the photoconductor roll 11, but during a series of sequences (the first charge removal operation (P1) and the second charge removal operation (P2)). (Between) and the DC voltage VHr at this time is constant. Thereafter, as in the first static elimination operation (P1), the photosensitive roll 11 is rotated by the same number of times with the same light amount, and static elimination is performed. As a result, the potential of the photoreceptor roll 11 is lowered to Rp. The residual charge at this time is defined as Qrp2. The sensitivity characteristic of the photoconductor roll 11 also varies depending on the film thickness and environment of the photoconductor roll 11 and is generally not constant. However, it may be considered that it does not vary greatly between a series of sequences. can get. Therefore, the residual charges are also equal.

Qrp2 = Qrp1 (3)
Next, a second film thickness detection operation (M2) (an example of a second accumulated charge process according to the present invention) is performed. The second film thickness detection operation (M2) is the same measurement sequence as the first film thickness detection operation (M1). However, the second DC voltage V2 (for example, 1200 V) different from the first DC voltage V1 in the first film thickness detection operation (M1) is applied. The second DC voltage V2 exceeds the discharge start voltage. In addition, if it differs from the 1st DC voltage V1, there will be no restriction | limiting in particular in a DC voltage, but if it is close to the 1st DC voltage V1, an error will become large. Similar to the equation (1), the charge amount calculation unit 30 calculates the second accumulated charge amount Qm2 accumulated in the photoreceptor roll 11 during this measurement period. At this time, the total amount of charge accumulated on the photoconductor roll 11 is similar to the equation (2),
Q2 = Qrp2 + Qm2 (2-1)
It becomes.

  Further, in the film thickness calculation unit 50, based on the first accumulated charge amount Qm1 and the second accumulated charge amount Qm2, the first DC voltage V1 and the second DC voltage V2, as follows, The film thickness of the surface of the photoreceptor roll 11 is calculated.

The electrostatic capacity C of the photoreceptor roll 11 is given by the relationship Q = CV.
Q1 = CV1, Q2 = CV2 (4)
It becomes. Here, taking the difference,
C (V2-V1) = Q2-Q1 (4-1)
It becomes. Substituting the formulas (2) and (2-1), the charge at the time of Rp is canceled by the formula (3),
C (V2-V1) = (Qrp2 + Qm2)-(Qrp1 + Qm1) = Qm2-Qm1 (5)
It becomes. Since V1 (= 1000V) and V2 (= 1200V) are given and Qm1 and Qm2 are also measured quantities, the capacitance C can be obtained from the equation (5).

  Here, the film thickness D of the photoreceptor roll 11 is easily obtained because it is inversely proportional to the capacitance as follows.

D × C = ε × L × 2πr = constant (where ε is the dielectric constant, L is the length of the charging roll, and r is the radius of the photoreceptor roll 11) (6)
Further, the film thickness calculation unit 50 reads the initial film thickness D0 stored in the film thickness storage unit 60 and the capacitance C0 measured at this time. Here, for example, when the capacitance at the N-th measurement is Cn, the film thickness Dn of the photoreceptor roll 11 can be obtained without knowing a detailed value such as a dielectric constant. That is,
Dn × Cn = D0 × C0 (7)
Therefore, from this equation (7), the film thickness Dn of the photoreceptor roll 11 is
Dn = D0 (C0 / Cn) (7-1)
It becomes.

  By performing the static elimination operation and the film thickness detection operation as described above a plurality of times, the film thickness can be obtained accurately even if an AC power source using an AC transformer is not provided. When the AC voltage supplied from the AC power source is applied to the photoconductor roll 11, the deterioration of the photoconductor roll 11 is accelerated. Therefore, in the printer 10 having only the DC power source according to this embodiment, the photoconductor roll 11 is used. To prolong life.

  In the present embodiment, an example of the charger 13 that DC charges the photoreceptor roll 11 with a DC voltage is shown, but the charging means is not limited to this, and a contact type using a brush or the like instead of the roll. Charging means, and non-contact charging means using a corotron charger, a scorotron charger, etc., and the developer holder is charged with a direct current charged with a direct current voltage and a voltage obtained by superimposing the alternating current voltage on the direct current voltage. Any charging means may be used as long as it is charged with at least direct current charging.

  In the present embodiment, the film thickness calculation unit 50 calculates the current film thickness on the surface of the photoreceptor roll 11 based on the initial film thickness D0 stored in the film thickness storage unit 60. The thickness calculation means is not limited to this, and the current film thickness of the developer holder surface is calculated based on the film thickness calculated in the past based on the initial film thickness stored in the film thickness storage means. May be. In this case, the film thickness of the surface of the developer holding body can be obtained more accurately than in the case where the film thickness of the surface of the developer holding body is calculated based only on the initial film thickness.

  Further, in the present embodiment, a printer has been described as an example of the image forming apparatus according to the present invention. However, any image forming apparatus may be used as long as it is used not only for a copying machine but also for an electrophotographic apparatus.

1 is a schematic configuration diagram of a printer that is an embodiment of an image forming apparatus. It is a figure which shows the flow of operation | movement in a control part and a film thickness calculation part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printer 11 Photoconductor roll 12 DC power supply unit 13 Charger 14 Exposure unit 15 Developer 15_1 Developer developer 15_2 Developer roll 16 Transfer roll 17 Cleaning member 18 Static elimination lamp 19 Fixing device 19_1 Fixing roll 19_2 Pressure roll 20 Recording paper storage unit DESCRIPTION OF SYMBOLS 21 Paper conveyance part 30 Charge amount calculation part 40 Control part 50 Film thickness calculation part 60 Film thickness memory | storage part 100 Process cartridge

Claims (7)

A developer holder for holding the developer;
A first initialization process for initializing the potential of the developer holder;
A first charge accumulation for charging the developer holding body initialized in the first initialization process with a first DC voltage and calculating a first accumulated charge amount of the developer holding body due to the charging. process,
A second initialization process for initializing the potential of the developer holder, and a second direct current different from the first direct current voltage in the developer holder initialized in the second initialization process. Control means for performing a film thickness measurement sequence comprising a second charge accumulation process for charging with a voltage and calculating a second accumulated charge amount of the developer holder due to the charging;
The first accumulated charge amount and the second accumulated charge amount calculated by execution of the film thickness measurement sequence by the control means, the first DC voltage and the first accumulated charge amount employed in the film thickness measurement sequence. An image forming apparatus, comprising: a film thickness calculating unit that calculates a film thickness of the surface of the developer holding body based on a DC voltage of 2.   In the first initialization process and the second initialization process, the developer holding member is charged with an initialization DC voltage that is higher than both the first DC voltage and the second DC voltage. The image forming apparatus according to claim 1, wherein the developer holding member is a process of discharging.   The film thickness calculating means calculates a differential voltage between the first DC voltage and the second DC voltage, and a differential charge amount between the first accumulated charge amount and the second accumulated charge amount. 2. The image forming apparatus according to claim 1, wherein a film thickness of the surface of the developer holding member is calculated based on the differential voltage and the differential charge amount. A film thickness storage means for storing an initial film thickness of the developer holder surface;
The film thickness calculation means calculates the current film thickness of the developer holder surface based on the initial film thickness stored in the film thickness storage means or a film thickness calculated in the past based on the initial film thickness. The image forming apparatus according to claim 1, wherein the image forming apparatus calculates the image forming apparatus. A developer holding body having a film on the surface and receiving charging, formation of an electrostatic latent image, and development of the electrostatic latent image with toner is recorded, and a toner image formed on the developer holding body is recorded An image forming apparatus fixed on a medium,
A first initialization process for initializing the potential of the developer holder;
A first charge accumulation for charging the developer holding body initialized in the first initialization process with a first DC voltage and calculating a first accumulated charge amount of the developer holding body due to the charging. process,
A second initialization process for initializing the potential of the developer holder, and a second direct current different from the first direct current voltage in the developer holder initialized in the second initialization process. Control means for performing a film thickness measurement sequence comprising a second accumulated charge process for calculating a second accumulated charge of the developer holding member due to the charging by charging with a voltage;
The first accumulated charge amount and the second accumulated charge amount calculated by execution of the film thickness measurement sequence by the control means, the first DC voltage and the first accumulated charge amount employed in the film thickness measurement sequence. An image forming apparatus, comprising: a film thickness calculating unit that calculates a film thickness of the surface of the developer holding body based on a DC voltage of 2. A developer holder having a film on the surface and rotating during operation;
Charging means for charging the developer holding body with at least DC charging among DC charging for charging with a DC voltage and AC charging for charging with a voltage obtained by superimposing an AC voltage on the DC voltage;
A latent image forming means for forming an electrostatic latent image on the developer holding body by irradiating the developer holding body charged by the charging means with light of a pattern according to an image signal;
Developing means for developing the electrostatic latent image formed on the developer holder by the latent image forming means with toner to form a toner image on the developer holder;
Transfer means for transferring a toner image formed on the developer holder by the developing means onto a recording medium;
A charge eliminating unit disposed on the downstream side in the rotation direction of the developer holding body with respect to the transfer unit and discharging the developer holding body;
Fixing means for fixing the toner image transferred onto the recording medium by the transfer means onto the recording medium;
While the charging unit charges the developer holding member by DC charging, a current flowing between the charging unit and the developer holding member is measured, and an accumulated charge of the developer holding member is measured based on the current. Charge amount calculating means for calculating the amount;
A first initialization process in which the charging means is charged with an initializing DC voltage for initializing the developer holding body, and the developer holding body is discharged with the charge removing means;
The developer holding member initialized in the first initialization process is charged by the charging unit with a first DC voltage for charge accumulation, and the development during the charging is performed by the charge amount calculating unit. A first accumulated charge process for calculating a first accumulated charge amount of the agent holder,
The charging means is charged with the same initializing DC voltage as the initializing DC voltage for initializing the developer holding body, and the developer holding body is charged to the neutralizing means. A second initialization process for neutralizing the charge, and the developer holding body initialized in the second initialization process is connected to the charging means in a second different from the first DC voltage for charge accumulation. Control means for charging with a DC voltage and causing the charge amount calculating means to execute a film thickness measurement sequence comprising a second accumulated charge process for calculating a second accumulated charge amount of the developer holding body during the charging. When,
The first accumulated charge amount and the second accumulated charge amount calculated by execution of the film thickness measurement sequence by the control means, the first DC voltage and the first accumulated charge amount employed in the film thickness measurement sequence. An image forming apparatus, comprising: a film thickness calculating unit that calculates a film thickness of the surface of the developer holding body based on a DC voltage of 2. A developer holding body having a film on the surface and receiving charging, formation of an electrostatic latent image, and development of the electrostatic latent image with toner is recorded, and a toner image formed on the developer holding body is recorded A film thickness measuring method for measuring a film thickness of the surface of the developer holder in an image forming apparatus fixed on a medium,
A first initialization process for initializing the potential of the developer holder;
A first charge accumulation for charging the developer holding body initialized in the first initialization process with a first DC voltage and calculating a first accumulated charge amount of the developer holding body due to the charging. process,
A second initialization process for initializing the potential of the developer holder;
The developer holding body initialized in the second initialization process is charged with a second DC voltage different from the first DC voltage, and the second accumulated charge of the developer holding body due to the charging is charged. Based on the second charge accumulation process for calculating the amount, the first accumulated charge amount and the second accumulated charge amount, and the first DC voltage and the second DC voltage. A film thickness measuring method comprising a film thickness calculating process for calculating a film thickness on the surface of the holder.

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