JP2021162777A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can accurately detect the amount of wear of an OCL layer of an image carrier (photoreceptor).SOLUTION: An image forming apparatus 300 comprises: an electrifier 4 that electrifies the surface of a photoreceptor 3 through corona discharge; a current monitor circuit 64 that detects a photoreceptor influx current Ipc to the photoreceptor 3; and a CPU 70 that, after the electrifier 4 electrifies the surface of the photoreceptor 3 to have a predetermined potential and the current monitor circuit 64 detects the photoreceptor influx current Ipc flowing into the photoreceptor 3, calculates the film thickness d of the photoreceptor 3 from the photoreceptor influx current Ipc.SELECTED DRAWING: Figure 4

Description

The present invention relates to an image forming apparatus.

In recent image forming apparatus, a corona-charged scorotron method is adopted as a charging method. This image forming apparatus is composed of a wire electrode, a stabilizer, a grid, and an insulating resin block at the end. By applying a DC voltage of several kV to the wire electrode, a corona discharge is caused to control the grid applied voltage. The surface of the image carrier (photoreceptor) is uniformly charged.

Further, in a transfer-type image forming apparatus that repeatedly uses an image carrier (electrophotographic photosensitive member, electrostatic recording dielectric, etc.) as a charged body, the surface of the image carrier is gradually surfaced by charging treatment and durable paper transfer. As it is scraped off, the thickness (thickness) of the surface of the image carrier gradually decreases.

In response to such a change in film thickness, the image forming apparatus needs to measure, for example, the surface potential of the image carrier with a surface potential measuring sensor to control the potential. In this case, if the surface potential sensor is used, the initial cost of the device increases accordingly. Further, in cartridge type copiers and printers, since there is no area for mounting the surface potential sensor in the apparatus, there is no method for dealing with fluctuations in the film thickness of the image carrier in relatively inexpensive multifunction devices and printers.

Therefore, with respect to such fluctuations in the film thickness of the image carrier, the film thickness of the image carrier is adjusted for the purpose of maintaining a constant charge stability without having a surface potential measurement sensor of the image carrier. Means for detection are being studied.

However, in an electrophotographic photosensitive member provided with a corona charger as a charging means for an image carrier without a surface potential measurement sensor, wire current flows not only to the image carrier but also to the shield and grid, so that the image carrier The capacitance cannot be derived, and the film thickness of the image carrier cannot be calculated.

Therefore, in the image forming apparatus using the non-contact type charging means, the current value flowing from the non-contact type charging means to the image carrier and the voltage value applied to the charging means from the power source are detected, and the detected current. An image forming apparatus has been proposed that accurately and stably detects the thickness of an image carrier based on a value and a voltage value (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2000-89624

In recent years, with the aim of increasing the durability of the image carrier surface (photoreceptor surface) for a long period of time against such changes in the film thickness of the image carrier surface (photoreceptor surface), the image carrier surface (photoreceptor surface) An image carrier (photoreceptor) having a surface protective layer (OCL: OverCoating Layer) on the surface of the photoconductor is used. Here, one of the characteristics required for the OCL layer is that it has little influence on the original electrostatic characteristics of the image carrier (photoreceptor), and the dielectric constant is low so that the electrical characteristics are stable. It is composed of an insulating composition. For example, the OCL layer is composed of a mixture of urethane and silicon.

In the case of a highly durable image carrier (photoreceptor), the image carrier (photoreceptor) wears from the OCL layer on the outside. However, since the ratio of the capacitance component of the OCL layer to the capacitance component formed by all the layers of the image carrier (photoreceptor) is low, the amount of change in the photoconductor inflow current is small with respect to the amount of wear of the OCL layer. Moreover, since there is no sensitivity, it is difficult to accurately detect the film thickness of the image carrier (photoreceptor).

Therefore, an object of the present invention is to provide an image forming apparatus capable of accurately detecting the amount of wear of the OCL layer of an image carrier (photoreceptor).

That is, the above problem of the present invention is solved by the following configuration.

(1) A charged portion that charges the surface of the photoconductor by corona discharge,
A current monitor circuit that detects the current flowing into the photoconductor and
After the charging unit charges the surface potential of the photoconductor to a predetermined potential, the current monitor circuit detects the photoconductor inflow current flowing into the photoconductor, and the film of the photoconductor is detected from the photoconductor inflow current. A control unit that calculates the thickness and
An image forming apparatus comprising.

(2) Provided with a static eliminator for statically eliminating the surface potential of the photoconductor.
The control unit
With the static eliminator turned off, the charging portion charges the surface of the photoconductor, charges the surface potential of the photoconductor to a predetermined potential, and then the second and subsequent laps in which the photoconductor rotates on a drum. The photoconductor inflow current is detected, and the film thickness of the photoconductor is calculated from the photoconductor inflow current.
The image forming apparatus according to (1).

(3) The control unit
In the first lap and the second and subsequent laps in which the photoconductor rotates the drum, the control value at which the charged portion charges the surface of the photoconductor is set to the same value.
The image forming apparatus according to (1) or (2).

(4) The charged portion includes a discharge wire and a shield grid for performing corona discharge.
The control unit
The difference between the wire current flowing through the discharge wire and the grid current flowing through the shield grid is obtained, and the difference is calculated as the photoconductor inflow current.
The image forming apparatus according to any one of (1) to (3).

(5) A surface potential sensor for detecting the surface potential of the photoconductor is provided.
The control unit
The film thickness of the photoconductor is calculated based on the surface potential detected by the surface potential sensor and the photoconductor inflow current detected by the current monitor circuit.
(The image forming apparatus according to any one of 1 to (4).

(6) Equipped with a temperature sensor that detects the environmental temperature
The control unit
The resistance component constituting the surface potential is corrected according to the environmental temperature detected by the temperature sensor.
The image forming apparatus according to any one of (1) to (5).

(7) The control unit
From the transition of the film thickness of the photoconductor, the life period of the photoconductor is predicted.
The image forming apparatus according to any one of (1) to (6).

(8) Further provided with an encoder for detecting the rotational position of the photoconductor in the circumferential direction.
The control unit
When the difference in film thickness of the photoconductor is equal to or greater than a predetermined threshold value due to the film thickness distribution in the circumferential direction of the photoconductor according to the rotational position of the photoconductor detected by the encoder, the photoconductor Judge that it has reached the end of its life,
The image forming apparatus according to any one of (1) to (7).

(9) The control unit is
Notifying the operation panel of the predicted life time of the photoconductor or the photoconductor determined to have reached the end of its life.
The image forming apparatus according to (7) or (8).

According to the present invention, the image forming apparatus can accurately detect the amount of wear of the OCL layer of the image carrier (photoreceptor).

It is a figure explaining the structural example of the image forming apparatus which concerns on 1st Embodiment. It is a figure for demonstrating the structure around the intermediate transfer belt more concretely. It is a figure for demonstrating various devices connected to a CPU. It is explanatory drawing which showed the structure of the main part of the image forming apparatus of 1st Embodiment. FIG. 5 is an explanatory diagram showing a concept in which a charger charges the surface of a photoconductor in a state where the CPU turns off the static elimination unit in the image forming apparatus of the first embodiment. It is explanatory drawing which showed the equivalent circuit of the photoconductor in the image forming apparatus of 1st Embodiment. FIG. 5 is a flowchart showing a process in which the CPU of the image forming apparatus of the first embodiment calculates the film thickness of the photoconductor. It is a flowchart which showed the process which the CPU of the image forming apparatus of 1st Embodiment predicts the life time of a photoconductor. It is explanatory drawing which showed the relationship between the film thickness of a photoconductor and the life of a photoconductor by a CPU. It is explanatory drawing which showed the notification of the life time of a photoconductor on the operation panel of an image forming apparatus. It is explanatory drawing which showed the structural example of the image forming apparatus of 5th Embodiment. FIG. 5 is a flowchart showing a process in which the CPU of the image forming apparatus of the fifth embodiment measures the film thickness of the photoconductor at each position in the circumferential direction of the photoconductor. It is explanatory drawing which showed the cross section of the internal structure of the photoconductor of the present image forming apparatus. It is explanatory drawing which showed the structure of the impedance component in a photoconductor. It is explanatory drawing which showed the photoconductor inflow current generated in the photoconductor in the conventional image forming apparatus. It is explanatory drawing which showed the equivalent circuit of the photoconductor.

Hereinafter, embodiments for carrying out the present invention will be described in detail. The embodiments described below are examples for realizing the present invention, and should be appropriately modified or changed depending on the configuration of the apparatus to which the present invention is applied and various conditions. It is not limited to the embodiment of. In addition, a part of each embodiment described later may be appropriately combined and configured. The same members are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

<Outline of this technology>
FIG. 13 is an explanatory view showing a cross section of the internal structure of the photoconductor 3 of the current image forming apparatus. The photoconductor 3 has a substantially cylindrical shape, and has an undercoat layer UCL (UnderCoating Layer), a charge generation layer CGL (Charge Generation Layer), and a charge transport layer CTL on a cylinder of an aluminum substrate ALN (ALumiNium). (Charge Transport Layer) and an overcoat layer OCL (OverCoating Layer) are laminated.

The aluminum substrate ALN is formed of an aluminum-based drum shape. In the photoconductor 3, positive (+) and negative (−) charges are generated in the portion of the charge generation layer CGL that is exposed to light. The negative (−) charge is transferred from the undercoat layer UCL to the aluminum substrate ALN. The positive (+) charge is transported to the surface of the photoconductor 3 through the charge transport layer CTL.

The overcoat layer OCL is provided on the surface of the photoconductor 3 in order to prevent the photoconductor 3 from being worn. The positive (+) charges transported through the charge transport layer CTL are formed to cancel the negative (−) charges already charged on the surface of the overcoat layer OCL.

As a result, the overcoat layer OCL, which is the surface of the photoconductor 3, has a negative (-) charge and a non-negative (-) charge, and an electrostatic image called an electrostatic latent image is formed. Will be done.

Here, the characteristics required for the overcoat layer OCL are that it mechanically protects the lower layer, prevents toner, paper dust, etc. from adhering to the surface of the photoconductor 3 during the electrophotographic process, and is the original property of the photoconductor 3. It has little effect on the electrostatic characteristics of. In particular, in order to reduce the influence on the electrostatic characteristics, the overcoat layer OCL is often composed of an insulating composition having stable electrical characteristics.

The impedance component of the photoconductor 3 is shown in FIG. FIG. 14 is an explanatory diagram showing the configuration of the impedance component in the photoconductor 3.

As shown in FIG. 14, the impedance component is composed of the resistance component and the capacitance component of the undercoat layer UCL, the charge generation layer CGL, the charge transport layer CTL, and the overcoat layer OCL, respectively. Here, the thickness of the overcoat layer OCL is about 1.0 [μm] to several [μm], while the thickness of the charge transport layer CTL is 20 [μm] to 30 [μm]. The thickness of the charge generation layer CGL is 0.2 [μm] to 1.0 [μm], and the thickness of the undercoat layer UCL is 0.1 [μm] to 1.0 [μm]. The thickness of the charge transport layer CTL is dominant.

Further, the impedance component of the overcoat layer OCL is composed of a resistor Rocl which is a resistance component of the overcoat layer OCL and a capacitance Cocl which is a capacitance component, and the capacitance Cocl has a value smaller than the resistance Rocl (Rocl). >> Cocl). Further, the capacity Cocl, which is a capacity component of the overcoat layer OCL, is a capacity value of another capacity component Cother (capacity component Cctl of the charge transport layer CTL, capacity component Ccgl of the charge generation layer CGL, and capacity component of the undercoat layer UCL. Compared to Cucl), the value is considerably smaller (Cother >>> Cocl).

FIG. 15 is an explanatory diagram showing the photoconductor inflow current Ipc generated in the photoconductor 3 in the conventional image forming apparatus. As shown in FIG. 15, a conventional image forming apparatus includes a photoconductor 3, a charger 4, and a static elimination unit (static elimination device) 9.

The charger 4 applies a potential V0 to the surface of the photoconductor 3, and the photoconductor 3 rotates in the rotation direction RD. The static elimination unit 9 is usually provided upstream of the charger 4 in order to uniformly charge the surface of the photoconductor 3, and statically eliminates the surface of the photoconductor 3 each time the photoconductor 3 rotates once.

Next, the photoconductor inflow current Ipc flowing through the photoconductor 3 will be described. FIG. 16 is an explanatory diagram showing an equivalent circuit of the photoconductor 3.

As shown in FIG. 16, the photoconductor 3 of the conventional image forming apparatus shown in FIG. 15 can be represented by an equivalent circuit of a resistor R which is a resistance component and a capacitance C which is a capacitance component. In this case, as shown in FIG. 15, since the static elimination unit 9 eliminates the potential V0 charged on the photosensitive member 3 each time the photosensitive member 3 rotates once, the photoconductor inflow current Ipc is a capacitive component. It flows into the capacity C as a charging current.

Here, a method of calculating the film thickness d of the photoconductor 3 will be described. First, when the surface potential of the photoconductor 3 is V0, the amount of electric charge stored in the capacitance C is represented by the equation (1).

Further, the charged charge amount Q of the photoconductor 3 is calculated by integrating the photoconductor inflow current Ipc of the photoconductor 3 with time.

The capacitance C of the photoconductor is represented by the formula (3).

Therefore, the film thickness d of the photoconductor 3 can be calculated by the equation (4).

In this way, the photoconductor inflow current Ipc can be calculated from the equivalent circuit of FIG. However, as shown in FIG. 14, when the photoconductor 3 is a highly durable product having the overcoat layer OCL, the surface of the photoconductor 3 is worn away from the overcoat layer OCL. In this case, since the ratio of the capacitance component of the overcoat layer OCL to the capacitance component composed of all the layers of the photoconductor 3 is low in the overcoat layer OCL, the photoconductor is relative to the amount of wear of the overcoat layer OCL. Since the amount of change in the inflow current Ipc is small and the overcoat layer OCL is insensitive, it is difficult to accurately calculate the film thickness d of the photoconductor 3.

Therefore, the image forming apparatus of the present invention aims to accurately detect the amount of wear of the overcoat layer OCL layer of the photoconductor 3.

<First Embodiment>
[Overall schematic configuration of the image forming apparatus]
FIG. 1 is a diagram illustrating a configuration example of the image forming apparatus 300 according to the first embodiment. In the first embodiment, the image forming apparatus 300 is an electrophotographic image forming apparatus such as a laser printer or an LED (Light Emitting Diode) printer.

As shown in FIG. 1, the image forming apparatus 300 includes an intermediate transfer belt 1 as a belt member in a substantially central portion inside. Below the lower horizontal portion of the intermediate transfer belt 1, four image-forming units 2Y, 2M, 2C, and 2K corresponding to each color of yellow, magenta, cyan, and black, respectively. Are arranged side by side along the intermediate transfer belt 1. These image forming units 2Y, 2M, 2C, 2K include photoconductors 3Y, 3M, 3C, 3K configured to be able to support a toner image, chargers 4Y, 4M, 4C, 4K, and exposure devices 5Y, 5M. , 5C, 5K, developing rollers 6Y, 6M, 6C, 6K, and cleaning blades 8Y, 8M, 8C, 8K, respectively.

When it is not necessary to specify any of the photoconductors 3Y, 3M, 3C, and 3K, it is simply indicated as the photoconductor 3. When it is not necessary to specify any of the chargers 4Y, 4M, 4C, and 4K, it is simply displayed as the charger 4.

Around each of the photoconductors 3Y, 3M, 3C, and 3K, which are image carriers, there are chargers 4Y, 4M, 4C, and 4K for charging the corresponding photoconductors in order along the rotation direction, and an exposure apparatus. 5Y, 5M, 5C, 5K, developing rollers 6Y, 6M, 6C, 6K, and primary transfer rollers 7Y, 7M, 7C, facing each photoconductor 3Y, 3M, 3C, 3K with the intermediate transfer belt 1 in between. 7K and cleaning blades 8Y, 8M, 8C, 8K are arranged respectively.

The secondary transfer roller 11 is pressure-welded to the portion of the intermediate transfer belt 1 supported by the intermediate transfer belt drive roller 10, and the secondary transfer to the paper P is performed in this region. A fixing heating unit 20 including a fixing roller 21 and a pressure roller 22 is arranged at a position downstream of the transport path W behind the secondary transfer region.

A paper cassette 30 is detachably arranged at the bottom of the image forming apparatus 300. The paper P loaded and stored in the paper feed cassette 30 is sent out one by one from the uppermost paper to the transport path W by the rotation of the paper feed roller 31.

Further, an operation panel 80 is arranged on the upper part of the image forming apparatus 300. As an example, the operation panel 80 is composed of a screen in which a touch panel and a display are superposed on each other, and physical buttons.

Further, the image forming apparatus 300 includes a paper ejection roller 50, a paper ejection tray 55, and a CPU (Central Processing Unit) 70. The CPU 70 is designed to perform overall control of the image forming apparatus 300.

In the above example, the image forming apparatus 300 employs a tandem type intermediate transfer method, but the present invention is not limited to this. Specifically, it may be an image forming apparatus adopting a cycle method, or an image forming apparatus adopting a direct transfer method of directly transferring toner from a developing device to a printing medium.

[Approximate operation of image forming apparatus]
Next, the schematic operation of the image forming apparatus 300 having the above configuration will be described. When an image signal is input from an external device (for example, a personal computer) to the CPU 70 that functions as a control device for the image forming apparatus 300, the CPU 70 converts the image signal into yellow, cyan, magenta, and black to convert the digital image signal into yellow, cyan, magenta, and black. Based on the created and input digital signal, each exposure device 5Y, 5M, 5C, 5K of each image forming unit 2Y, 2M, 2C, 2K is made to emit light to perform exposure.

As a result, the electrostatic latent image formed on each of the photoconductors 3Y, 3M, 3C, and 3K is developed by each developing roller 6Y, 6M, 6C, and 6K to obtain a toner image of each color. The toner images of each color are sequentially superposed on the intermediate transfer belt 1 moving in the direction of arrow A in FIG. 1 by the action of the primary transfer rollers 7Y, 7M, 7C, and 7K, and are first transferred.

The toner image thus formed on the intermediate transfer belt 1 is collectively secondarily transferred to the paper P by the action of the secondary transfer roller 11.

The paper P on which the toner image is secondarily transferred reaches the fixing heating unit 20. The toner image is fixed on the paper P by the action of the heated fixing roller 21 and the pressure roller 22. The paper P on which the toner image is fixed is discharged to the paper ejection tray 55 via the paper ejection roller 50.

[Electrical configuration]
Next, the electrical configuration connected to the CPU 70 will be described with reference to FIGS. 2 and 3. FIG. 2 is a diagram for more specifically explaining the configuration around the intermediate transfer belt 1. FIG. 3 is a diagram for explaining various devices connected to the CPU 70.

As shown in FIGS. 2 and 3, corresponding charging power supplies 63Y, 63M, 63C, 63K are connected to the chargers 4Y, 4M, 4C, 4K, respectively. Each of the charging power supplies 63Y, 63M, 63C, 63K applies a predetermined negative voltage to the corresponding charging devices 4Y, 4M, 4C, 4K. In parallel with these, the corresponding constant current sources 65Y, 65M, 65C, and 65K are connected, respectively. Further, between the charging power supplies 63Y, 63M, 63C, 63K, the connection nodes of the constant current sources 65Y, 65M, 65C, 65K, and the ground, there is a current monitor circuit 64Y, 64M, 64C, 64K. Each is connected. Each of the current monitor circuits 64Y, 64M, 64C, and 64K includes a current sensor.

The corresponding developing power supplies 60Y, 60M, 60C, 60K are connected to each of the developing rollers 6Y, 6M, 6C, and 6K. Each of the developing power supplies 60Y, 60M, 60C, 60K is configured to include corresponding DC power supplies 61Y, 61M, 61C, 61K and corresponding AC power supplies 62Y, 62M, 62C, 62K. As a result, a voltage obtained by superimposing a DC voltage and an AC voltage is applied to each of the developing rollers 6Y, 6M, 6C, and 6K.

A common primary transfer power source 68 is connected to the primary transfer rollers 7Y, 7M, 7C, and 7K. That is, a common transfer bias Vt is applied to the primary transfer rollers 7Y, 7M, 7C, and 7K. A voltage sensor 66 is arranged between the primary transfer power source 68 and the ground potential. In another aspect, the image forming apparatus 300 may have an independent primary transfer power source for each of the primary transfer rollers 7Y, 7M, 7C, and 7K.

A secondary transfer power source 67 is connected to the secondary transfer roller 11. The CPU 70 includes various power supplies (charged power supplies 63Y, 63M, 63C, 63K, developing power supplies 60Y, 60M, 60C, 60K, primary transfer power supply 68, secondary transfer power supply 67) and various sensors (current monitor circuits 64Y, 64M, It is connected to 64C, 64K, and voltage sensor 66), respectively. The CPU 70 transmits control signals to various power supplies and controls the outputs of the various power supplies. Further, the various sensors are configured to transmit the measurement result to the CPU 70.

In addition to the above-mentioned devices, the CPU 70 includes a RAM (Random Access Memory) 510, a ROM (Read Only Memory) 520, a storage device 530, an operation panel 80, a static elimination unit 9, a surface potential sensor 91, and a temperature sensor 92. It is electrically connected to each of them.

The ROM 520 stores the control program 522. The RAM 510 is realized by, for example, a DRAM (Dynamic Random Access Memory). The RAM 510 can function as a working memory that temporarily stores data and image data necessary for the CPU 70 to execute the control program 522.

The storage device 530 is realized by, for example, a hard disk drive.

The operation panel 80 outputs information (for example, touched coordinates on the touch panel) representing the operation content of the user to the CPU 70.

The static elimination unit (static eliminator) 9 eliminates the surface potential charged on the surface of the photoconductor 3. The static elimination unit 540 is usually provided upstream of the charger 4 in order to uniformly charge the surface of the photoconductor 3.

The surface potential sensor 91 is a sensor that measures the potential on the surface of the photoconductor 3, and outputs the measurement result to the CPU 70. The surface potential sensor 91 is an arbitrary component.

The temperature sensor 92 is a sensor that measures the temperature inside the photoconductor 3, and outputs the measurement result to the CPU 70. The temperature sensor 92 is an arbitrary component.

[Structure of an image forming apparatus according to the present invention]
The image forming apparatus 300 according to the first embodiment includes a charger 4 that charges the surface of the photoconductor by corona discharge, a current monitor circuit 64 that detects the current Ipc that flows into the photoconductor 3, and the charger 4. Charges the surface potential of the photoconductor 3 to a predetermined potential, and then the current monitor circuit 64 detects the photoconductor inflow current Ipc flowing into the photoconductor 3, and the film thickness of the photoconductor 3 is derived from the photoconductor inflow current Ipc. It is configured to include a CPU 70 for calculating the above. Further, the charger 4 includes a discharge wire 41 and a shield grid 42.

According to the first embodiment, the CPU 70 detects the photoconductor inflow current Ipc flowing into the photoconductor 3 by the current monitor circuit 64, and calculates the film thickness of the photoconductor 3 from the photoconductor inflow current Ipc.

As a result, the image forming apparatus 300 of the first embodiment can accurately detect the amount of wear of the OCL layer of the photoconductor 3.

FIG. 4 is an explanatory diagram showing a configuration of a main portion of the image forming apparatus 300 of the first embodiment. The same configurations as those of the conventional image forming apparatus shown in FIG. 15 are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

As shown in FIG. 4, a charger 4, a static elimination unit 9, a surface potential sensor 91, and a temperature sensor 92 are arranged around the photoconductor 3 of the image forming apparatus 300. The charger 4 is configured by connecting a constant current source 65Y, a charging power supply 63Y, and a current monitor circuit 64Y.

The charger 4 includes a discharge wire 41 and a shield grid 42. The CPU 70 obtains a difference between the wire current Ic flowing through the discharge wire 41 and the grid current Ig flowing through the shield grid 42, and calculates the difference as the photoconductor inflow current Ipc.

As shown in FIG. 2, chargers 4Y, 4M, 4C, and 4K are arranged around each of the photoconductors 3Y, 3M, 3C, and 3K, and all have the same configuration.

The charging power supply 63 is connected to the shield grid 42 of the charging device 4 and applies a predetermined negative voltage to the charging device 4. A constant current source 65 is connected to the charger 4 in parallel with the charging power supply 63. The constant current source 65 causes a constant current to flow from the discharge wire 41 of the charger 4 toward itself. Further, a current monitor circuit 64 is connected between the connection node of the charging power supply 63 and the constant current source 65 and the ground.

The grid current Ig is a current component that returns from the charging power supply 63 to the charging power supply 63 again via the constant current source 65 and the charger 4. The wire current Ic is a current component that flows from the charger 4 into the photoconductor 3Y, flows through the ground to the current monitor circuit 64Y, and flows in the current monitor circuit 64Y in the opposite direction.

The current monitor circuit 64 detects the current Ipc of the photoconductor flowing into the photoconductor 3. The CPU 70 obtains a difference between the wire current Ic flowing through the discharge wire 41 and the grid current Ig flowing through the shield grid 42, and calculates the difference as the photoconductor inflow current Ipc. That is, the CPU 70 measures the current value obtained by subtracting the grid current Ig from the wire current Ic as the photoconductor inflow current Ipc into the photoconductor 3 by the current monitor circuit 64.

Further, the image forming apparatus 300 includes a static elimination unit 9, a surface potential sensor 91, and a temperature sensor 92. In the CPU 70, with the static elimination unit 9 turned off, the charger 4 charges the surface of the photoconductor 3, charges the surface potential of the photoconductor 3 to a predetermined potential, and then the photoconductor rotates in a drum. After the second lap, the photoconductor inflow current Ipc is detected, and the film thickness of the photoconductor 3 is calculated from the photoconductor inflow current Ipc.

That is, in the CPU 70, for example, during non-printing such as in the calibration mode, the current monitor circuit 64 flows into the photoconductor 3 after the charger 4 charges the surface potential of the photoconductor 3 to a predetermined potential. Ipc is detected, and the film thickness of the photoconductor 3 is calculated from the photoconductor inflow current Ipc.

The surface potential sensor 91 will be described in the second embodiment, and the temperature sensor 92 will be described in the third embodiment.

FIG. 5 is an explanatory diagram showing a concept in which the charger 4 charges the surface of the photoconductor 3 in the image forming apparatus 300 of the first embodiment in a state where the CPU 70 turns off the static elimination unit 9.

As shown in FIG. 5, in the image forming apparatus 300 of the first embodiment, after the surface potential of the photoconductor 3 is charged to a predetermined potential V0, the film thickness of the photoconductor 3 is based on the photoconductor inflow current Ipc. Calculate the thickness d. In the CPU 70 of the first embodiment, with the static elimination unit 9 turned off, the charger 4 charges the surface of the photoconductor 3, and the surface potential of the photoconductor 3 is charged to a predetermined potential V0. The photoconductor inflow current Ipc is detected after the second lap in which the photoconductor 3 rotates on the drum (rotation direction RD), and the film thickness of the photoconductor 3 is calculated from the photoconductor inflow current Ipc.

In this case, since the surface potential of the photoconductor 3 is adjusted to a desired potential V0 after two rotations of the drum, the current consumption by the resistance component of the photoconductor 3 flows. The photoconductor inflow current Ipc is also referred to as a dark current, and in the present embodiment, the current consumed by the resistance component of the photoconductor 3 corresponds to the photoconductor inflow current Ipc.

FIG. 6 is an explanatory diagram showing an equivalent circuit of the photoconductor 3 in the image forming apparatus 300 of the first embodiment.

As shown in FIG. 6, in the image forming apparatus 300 of the first embodiment, electric charges are accumulated in the capacitance C by turning off the static elimination by the static elimination unit 9. Therefore, the photoconductor inflow current Ipc flowing through the photoconductor 3 becomes a current flowing through the resistor R, which is a resistance component.

Here, when the surface potential of the photoconductor 3 is the desired potential V0, the relationship with the photoconductor inflow current Ipc flowing through the resistor R is represented by the equation (5).

The resistance value of the resistor R is represented by the equation (6).

Therefore, the film thickness d of the photoconductor 3 can be calculated by the formula (7).

As a result, the image forming apparatus 300 of the first embodiment can accurately calculate the film thickness d of the photoconductor 3. In this case, the CPU 70 can accurately detect the amount of wear of the OCL layer of the photoconductor 3 even if the photoconductor 3 is provided with the OCL layer.

Next, a process in which the CPU 70 of the image forming apparatus 300 of the first embodiment calculates the film thickness d of the photoconductor 3 will be described with reference to a flowchart.

FIG. 7 is a flowchart showing a process in which the CPU 70 of the image forming apparatus 300 of the first embodiment calculates the film thickness d of the photoconductor 3.

First, the CPU 70 of the image forming apparatus 300 accepts the setting of the charging control parameter of the charging device 4 (step S001). The value of the charge control parameter of the charger 4 is a fixed value. Then, in the CPU 70, the charger 4 charges the surface of the photoconductor 3 with the static elimination unit 9 turned off (step S003).

The CPU 70 determines whether or not the surface potential of the photoconductor 3 has reached the desired potential V0 (step S005), and when the surface potential of the photoconductor 3 reaches the desired potential V0 (Yes in step S005), the current From the current value measured by the monitor circuit 64, the photoconductor inflow current Ipc is measured (step S007).

In this way, the CPU 70 measures the photoconductor inflow current Ipc with the current monitor circuit 64 in a state where the surface potential of the photoconductor 3 is fixed at a desired potential V0, and the Ic flowing through the discharge wire 41 and the shield grid 42. The difference from the Ig flowing in the photoconductor is obtained, and the difference is calculated as the photoconductor inflow current Ipc.

Further, the CPU 70 sets the control value at which the charger 4 charges the surface of the photoconductor 3 to a desired potential V0 in the first and second laps after the drum rotation of the photoconductor 3.

That is, in this case, the CPU 70 of the first embodiment applies a photoconductor inflow current Ipc, which flows into the photoconductor 3 after the second lap of drum rotation after the surface potential of the photoconductor 3 is charged to a desired potential V0. Since it is detected, the film thickness d of the photoconductor 3 can be calculated from the photoconductor inflow current Ipc flowing through the resistor R, which is the resistance component of the photoconductor 3 shown in FIG.

As a result, the CPU 70 can calculate the film thickness d of the photoconductor 3 by the above-mentioned formula (7) (step S009).

As described above, the image forming apparatus 300 of the first embodiment includes a charger 4, a current monitor circuit 64, and a CPU 70. As a result, the CPU 70 detects the photoconductor inflow current Ipc flowing into the photoconductor 3 after the charger 4 charges the surface potential of the photoconductor 3 to a predetermined potential V0, and the photoconductor 4 receives the photoconductor inflow current Ipc. The film thickness d of the photoconductor 3 is calculated from the inflow current Ipc.

According to the image forming apparatus 300 of the first embodiment, the CPU 70 can accurately calculate the film thickness d of the photoconductor 3, so that the amount of wear of the OCL layer of the photoconductor 3 can be detected accurately. can.

In the image forming apparatus 300 of the first embodiment, with the static elimination unit 9 turned off, the surface potential of the photoconductor 3 is charged to a predetermined potential V0, and then the photoconductor 3 drum-rotates 2 The photoconductor inflow current Ipc is detected after the first lap, and the film thickness of the photoconductor 3 is calculated from the photoconductor inflow current Ipc.

As a result, the CPU 70 can measure the photoconductor inflow current Ipc from the resistance component of the resistor R without being affected by the capacitance component of the photoconductor 3 and without the photoconductor inflow current Ipc flowing in the capacitance C. Therefore, the film thickness d of the photoconductor 3 can be calculated with high accuracy.

Further, since the CPU 70 sets the control value for charging the surface of the photoconductor 3 to be the same in the first lap and the second and subsequent laps in which the photoconductor 3 rotates the drum, the electric charge charged on the photoconductor 3 is set. With the quantity Q fixed, the detection of only the photoconductor inflow current Ipc can be made highly accurate.

<Second embodiment>
The image forming apparatus of the second embodiment is configured to include the surface potential sensor 91 having the configuration of the image forming apparatus 300 of the first embodiment. Therefore, the CPU 70 calculates the film thickness d of the photoconductor 3 based on the surface potential detected by the surface potential sensor 91 and the photoconductor inflow current Ipc detected by the current monitor circuit 64.

In this case, the CPU 70 uses the above equation (7) to determine the film of the photoconductor 3 based on the surface potential detected by the surface potential sensor 91 and the photoconductor inflow current Ipc detected by the current monitor circuit 64. The thickness d can be calculated.

As described above, the CPU 70 of the image forming apparatus of the second embodiment is based on the surface potential detected by the surface potential sensor 91 and the photoconductor inflow current Ipc detected by the current monitor circuit 64, and the photoconductor 3 Since the film thickness of the photoconductor 3 can be calculated, the film thickness d of the photoconductor 3 can be calculated with higher accuracy.

<Third embodiment>
The image forming apparatus of the third embodiment is configured to include the temperature sensor 92 of the configuration of the image forming apparatus 300 of the first embodiment. Therefore, the CPU 70 can correct the resistance component constituting the surface potential according to the environmental temperature detected by the temperature sensor 92.

In this case, as an example, the CPU 70 calculates the corrected resistivity corrected according to the environmental temperature detected by the temperature sensor 92. The corrected resistivity ρ1 is represented by, for example, the equation (8).

By substituting ρ1 represented by the formula (8) into ρ of the formula (7), the CPU 70 can reflect the resistivity according to the temperature of the photoconductor 3.

As described above, the CPU 70 of the image forming apparatus of the third embodiment can correct the resistance component constituting the surface potential according to the environmental temperature detected by the temperature sensor 92. The film thickness d can be calculated with high accuracy.

<Fourth Embodiment>
The CPU 70 of the image forming apparatus of the fourth embodiment predicts the life period of the photoconductor 3 from the transition of the film thickness d of the photoconductor 3 in addition to the configuration of the first embodiment.

The process of predicting the life time of the photoconductor 3 by the CPU 70 of the image forming apparatus of the fourth embodiment will be described with reference to a flowchart.

FIG. 8 is a flowchart showing a process in which the CPU 70 of the image forming apparatus of the first embodiment predicts the life time of the photoconductor 3.

First, the CPU 70 of the image forming apparatus 300 determines whether or not it is the detection timing of the film thickness d of the photoconductor 3 (step S101), and in the case of the detection timing of the film thickness d of the photoconductor 3 (Yes in step S101). ), The film thickness d of the photoconductor 3 is calculated (step S103).

Here, whether or not the timing of detecting the film thickness d of the photoconductor 3 is determined is determined by the drum rotation speed of the photoconductor 3 and the mileage of the photoconductor 3. Further, the drum rotation speed of the photoconductor 3 and the mileage of the photoconductor 3 are determined in advance by a predetermined threshold value.

The CPU 70 records the calculated film thickness d of the photoconductor 3 in the storage device 530 (step S105). The CPU 70 determines whether or not the film thickness d of the current photoconductor 3 has a margin with respect to the specified life value (step S107), and if there is a margin with respect to the specified life value (Yes in step S107). ), Return to step S101, and continue the printing process and the like.

On the other hand, when the current film thickness d does not have a margin with respect to the specified life value (No in step S107), the CPU 70 predicts the life time of the photoconductor 3 from the history / transition of the film thickness d of the photoconductor 3. (Step S109).

FIG. 9 is an explanatory diagram showing the relationship between the film thickness d of the photoconductor 3 and the life of the photoconductor 3 by the CPU 70. In the image forming apparatus 300, as the cumulative number of prints increases, the film thickness d becomes thinner due to the consumption of the photoconductor 3. Therefore, regarding the life of the photoconductor 3, for example, when the film thickness d of the life of the photoconductor 3 is set to 30 [μm], the CPU 70 determines the film thickness of the photoconductor 3 as the number of prints of the image forming apparatus 300 elapses. The cumulative number of prints when d reaches 30 [μm] is calculated, and the life period of the photoconductor 3 is predicted.

Returning to FIG. 8, the CPU 70 notifies the operation panel 80 of the predicted life time of the photoconductor 3 (step S111), and ends the process of predicting the life time of the photoconductor 3.

FIG. 10 is an explanatory diagram showing notification of the life period of the photoconductor 3 by the CPU 70 on the operation panel 80 of the image forming apparatus.

As shown in FIG. 10, the CPU 70 informs the user, for example, that "the time to replace the photoconductor is approaching" and "prediction of replacement: XX month x day" to the operation panel 80 of the image forming apparatus. Notify. Note that FIG. 10 shows an example in which the CPU 70 notifies the operation panel 80 of the image forming apparatus, and the present invention is not limited to this.

For example, the CPU 70 can display "the remaining 3000 sheets can be printed" or "the remaining film thickness of the photoconductor is XX mm" on the operation panel 80 of the image forming apparatus. , Also, a warning sound may be output.

As described above, the CPU 70 of the image forming apparatus of the fourth embodiment can predict the life time of the photoconductor 3 with high accuracy from the transition of the film thickness d of the photoconductor 3. As a result, the user can replace the photoconductor 3 in advance before the end of the life of the photoconductor 3.

<Fifth Embodiment>
The image forming apparatus of the fifth embodiment further includes an encoder that detects the rotational position of the photoconductor 3 in the circumferential direction, and the CPU 70 determines the photoconductor 3 according to the rotational position of the photoconductor 3 detected by the encoder. Based on the film thickness distribution in the circumferential direction of 3, when the difference in the film thickness d of the photoconductor 3 is equal to or greater than a predetermined threshold value, it is determined that the photoconductor 3 has a lifetime.

FIG. 11 is an explanatory diagram showing a configuration example of the image forming apparatus 300a of the fifth embodiment. As shown in FIG. 11, the image forming apparatus 300a of the fifth embodiment is configured to further include an encoder EN in the photoconductor 3. In this case, the CPU 70 calculates the film thickness distribution of the photoconductor 3 in the circumferential direction according to the rotational position of the photoconductor 3 detected by the encoder EN. Then, the CPU 70 determines that the photoconductor 3 has reached the end of its life when the difference in the film thickness d of the photoconductor 3 is equal to or greater than a predetermined threshold value based on the film thickness distribution of the photoconductor 3.

In FIG. 11, the photoconductor 3 is assumed to rotate in the rotation direction RD as an example. The CPU 70 calculates the film thickness d of the photoconductor 3 when the position PS0 of the photoconductor 3 is located in the vicinity of the charger 4. Similarly, the CPU 70 calculates the film thickness d of the photoconductor 3 when the positions PS1 to PS7 of the photoconductor 3 are located in the vicinity of the charger 4, and the film thickness d in the circumferential direction of the photoconductor 3 is calculated. Calculate the distribution.

In this case, the CPU 70 of the image forming apparatus 300a of the fifth embodiment determines that the photoconductor has reached the end of its life when the difference in the film thickness d of the photoconductor 3 in the circumferential direction of the photoconductor 3 is equal to or greater than a predetermined threshold value. can do.

Next, the life prediction process of the photoconductor executed by the CPU 70 of the image forming apparatus 300a of the fifth embodiment will be described with reference to a flowchart. As an example, the initial value of the film thickness d of the photoconductor 3 is 50 [μm].

FIG. 12 is a flowchart showing a process in which the CPU 70 of the image forming apparatus 300a of the fifth embodiment measures the film thickness d of the photoconductor 3 at each position in the circumferential direction of the photoconductor 3.

First, the CPU 70 of the image forming apparatus 300a determines whether or not it is the detection timing of the film thickness d of the photoconductor 3 (step S201), and in the case of the detection timing of the film thickness d of the photoconductor 3 (Yes in step S201). ), The reference alignment of the photoconductor 3 is executed (step S203).

Whether or not the timing of detecting the film thickness d of the photoconductor 3 is determined is determined by the drum rotation speed of the photoconductor 3 and the mileage of the photoconductor 3. Further, the drum rotation speed of the photoconductor 3 and the mileage of the photoconductor 3 are determined in advance by a predetermined threshold value.

The execution of the reference alignment of the photoconductor 3 (step S203) can be performed by the CPU 70 based on, for example, when the position PS0 of the photoconductor 3 is located in the vicinity of the charger 4. At position PS0, the film thickness distribution for one circumference of the photoconductor 3 in the circumferential direction of the photoconductor 3 is calculated (step S205).

When the CPU 70 calculates the film thickness distribution for one circumference of the photoconductor 3 in the circumferential direction of the photoconductor 3, the CPU 70 determines whether or not the difference between the "upper limit-lower limit of the film thickness in the circumferential direction of the photoconductor 3" is within the specified range. (Step S207), and if the difference between "upper limit-lower limit of film thickness in the circumferential direction of the photoconductor 3" is within the specified range, the process returns to step S201.

In this case, the specified range is set to, for example, 10 [μm], and the CPU 70 determines whether or not the difference between the "upper limit-lower limit of the film thickness in the circumferential direction of the photoconductor 3" is within 10 [μm].

Next, the CPU 70 determines whether or not it is the detection timing of the film thickness d of the photoconductor 3 (step S201), and then executes the reference alignment of the photoconductor 3 (step S203), for example, the position of the photoconductor 3. The reference is when the PS1 is located in the vicinity of the charger 4. Then, the CPU 70 calculates the film thickness distribution for one circumference of the photoconductor 3 in the circumferential direction of the photoconductor 3 at the position PS1 of the photoconductor 3 (step S205).

When the CPU 70 calculates the film thickness distribution for one circumference of the photoconductor 3 in the circumferential direction of the photoconductor 3, the CPU 70 determines whether or not the difference between the "upper limit-lower limit of the film thickness in the circumferential direction of the photoconductor 3" is within the specified range. (Step S207).

Here, since the distribution of the film thickness d of the photoconductor 3 is basically evenly thinned, the difference between the "upper limit-lower limit of the film thickness in the circumferential direction of the photoconductor 3" is ideally 0. The value is close to [μm].

However, for example, when a large amount of printing is performed and the photoconductor 3 of the image forming apparatus 300a is overused, or when the image forming apparatus 300a is not used for a long time and the photoconductor 3 is loaded, " There may be a difference in the "upper limit-lower limit" of the film thickness of the photoconductor 3 in the circumferential direction.

Therefore, the CPU 70 predicts the life when the difference between the "upper limit-lower limit of the film thickness of the photoconductor 3 in the circumferential direction" exceeds the specified range (predetermined threshold value: for example, 10 [μm]) (No in step S207). The result is notified to the operation panel 80 (step S209), and the life prediction process of the photoconductor 3 is completed.

In this case, the CPU 70 of the image forming apparatus 300a can notify the life time of the photoconductor 3 as in FIG. 10, indicating that the operation panel 80 of the image forming apparatus is approaching the replacement time of the photoconductor 3. Is notified.

As described above, the CPU 70 of the image forming apparatus of the fifth embodiment is subject to the photosensitivity according to the film thickness distribution of the photoconductor 3 in the circumferential direction according to the rotational position of the photoconductor 3 detected by the encoder. When the difference in the film thickness d of the body 3 is equal to or greater than a predetermined threshold value, it is determined that the photoconductor 3 has reached the end of its life. As a result, the user can replace the photoconductor 3 in advance before it is time to replace the photoconductor 3.

300 Image forming apparatus 1 Intermediate transfer belt 2Y, 2M, 2C, 2K Image drawing unit 3Y, 3M, 3C, 3K Photoreceptor 4Y, 4M, 4C, 4K Charger (charged part)
5Y, 5M, 5C, 5K Exposure device 6Y, 6M, 6C, 6K Development roller 7Y, 7M, 7C, 7K Primary transfer roller 8Y, 8M, 8C, 8K Cleaning blade 9 Static elimination unit (static eliminator)
10 Intermediate transfer belt drive roller 11 Secondary transfer roller W Transport path 21 Fixing roller 22 Pressurizing roller 20 Fixing heating unit 30 Paper cassette P Paper 31 Paper paper roller 80 Operation panel 70 CPU
50 Paper ejection roller 55 Paper ejection tray 60Y, 60M, 60C, 60K Development power supply 61Y, 61M, 61C, 61K DC power supply 62Y, 62M, 62C, 62K AC power supply 63Y, 63M, 63C, 63K Charged power supply 64Y, 64M, 64C, 64K current monitor circuit (current sensor)
642Y, 643Y Current monitor circuit 65M, 65C, 65K Constant current source VSY, VSM, VSC, VSK Voltage sensor 66 Voltage sensor 67 Secondary transfer power supply 68 Primary transfer power supply 510 RAM
520 ROM
530 Storage device 522 Control program

Claims (9)

A charged part that charges the surface of the photoconductor by corona discharge,
A current monitor circuit that detects the current flowing into the photoconductor and
After the charging unit charges the surface potential of the photoconductor to a predetermined potential, the current monitor circuit detects the photoconductor inflow current flowing into the photoconductor, and the film of the photoconductor is detected from the photoconductor inflow current. A control unit that calculates the thickness and
An image forming apparatus comprising. A static eliminator for removing the surface potential of the photoconductor is provided.
The control unit
With the static eliminator turned off, the charging portion charges the surface of the photoconductor, charges the surface potential of the photoconductor to a predetermined potential, and then the second and subsequent laps in which the photoconductor rotates on a drum. The photoconductor inflow current is detected, and the film thickness of the photoconductor is calculated from the photoconductor inflow current.
The image forming apparatus according to claim 1. The control unit
In the first lap and the second and subsequent laps in which the photoconductor rotates the drum, the control value at which the charged portion charges the surface of the photoconductor is set to the same value.
The image forming apparatus according to claim 1 or 2. The charged portion includes a discharge wire and a shield grid that perform corona discharge.
The control unit
The difference between the wire current flowing through the discharge wire and the grid current flowing through the shield grid is obtained, and the difference is calculated as the photoconductor inflow current.
The image forming apparatus according to any one of claims 1 to 3. A surface potential sensor for detecting the surface potential of the photoconductor is provided.
The control unit
The film thickness of the photoconductor is calculated based on the surface potential detected by the surface potential sensor and the photoconductor inflow current detected by the current monitor circuit.
The image forming apparatus according to any one of claims 1 to 4. Equipped with a temperature sensor that detects the environmental temperature
The control unit
The resistance component constituting the surface potential is corrected according to the environmental temperature detected by the temperature sensor.
The image forming apparatus according to any one of claims 1 to 5. The control unit
From the transition of the film thickness of the photoconductor, the life period of the photoconductor is predicted.
The image forming apparatus according to any one of claims 1 to 6. An encoder for detecting the rotational position of the photoconductor in the circumferential direction is further provided.
The control unit
When the difference in film thickness of the photoconductor is equal to or greater than a predetermined threshold value due to the film thickness distribution in the circumferential direction of the photoconductor according to the rotational position of the photoconductor detected by the encoder, the photoconductor Judge that it has reached the end of its life,
The image forming apparatus according to any one of claims 1 to 7. The control unit
Notifying the operation panel of the predicted life time of the photoconductor or the photoconductor determined to have reached the end of its life.
The image forming apparatus according to claim 7 or 8.

Images