JP2018189762A - Image formation apparatus, program and abnormality detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus, program and abnormality detection method which can more correctly detect abnormality.SOLUTION: An image formation apparatus includes: an image carrier; an electrification member which is brought into contact with the surface of the image carrier and rotates around a prescribed rotational shaft following rotation of the image carrier; an electrification drive unit which electrifies the surface of the image carrier by applying voltage to the electrification member rotating following rotation of the image carrier; an acquisition unit which acquires the electric characteristic value of the electrification member corresponding to the current amount flowing in the electrification member; acquisition control means which causes the acquisition unit to perform the characteristic value acquisition operation of acquiring the electric characteristic value of the electrification member over the rotation cycle of the electrification member while applying the prescribed inspection voltage to the electrification member by the electrification drive unit; and detection means which detects abnormality of the electrification member on the basis of the fluctuation range of the electric characteristic value acquired by the characteristic value acquisition operation and the length of the fluctuation period in which the electric characteristic value continuously becomes the value outside the prescribed reference range.SELECTED DRAWING: Figure 4

Description

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

  2. Description of the Related Art Conventionally, there is an image forming apparatus that forms an electrostatic latent image by exposing the surface of a charged image carrier and transferring a toner image obtained by developing the electrostatic latent image onto a recording medium to form an image. is there. As a method for charging the surface of an image carrier in an image forming apparatus, a contact charging method in which a voltage is applied to a charging roller (charging member) that rotates in contact with the image carrier is widely used.

  In such a contact charging method, the amount of charge on the surface of the image carrier is an amount corresponding to the amount of current flowing through the charging member when a voltage is applied to the charging member, so that there is an abnormality in the surface state and resistance value of the charging member. If the amount of current is changed, the amount of charge on the surface of the image carrier becomes insufficient or excessive. If the charge amount is excessive or insufficient, a toner image with an appropriate density is not formed, leading to a poor image quality of the recorded image.

  On the other hand, by measuring the amount of current flowing to each position on the surface of the charging member and detecting whether the charging member is abnormal based on whether the measured current amount is within an appropriate range, There is a technique for suppressing the occurrence of image quality defects in a recorded image (for example, Patent Document 1).

Japanese Patent Laid-Open No. 9-179385

  However, the ease of visual recognition of image quality defects caused by charging member abnormalities is not limited to the fluctuation range of the current amount flowing through the charging member, but also to the width of the abnormal region where the current amount is abnormal. The larger the abnormal area is, the more defective the image quality that can be visually recognized due to a smaller current amount abnormality. For this reason, the uniform abnormality detection method based only on the current amount as in the conventional technique has a problem in that it is not possible to accurately detect abnormality of the charging member that causes image quality defects that can be visually recognized.

  An object of the present invention is to provide an image forming apparatus, a program, and an abnormality detection method capable of detecting an abnormality of a charging member more accurately.

In order to achieve the above object, the invention of the image forming apparatus according to claim 1 comprises:
An image forming apparatus for transferring a toner image obtained by developing an electrostatic latent image on the surface of an image carrier to a recording medium to form an image on the recording medium,
The image carrier rotating about a predetermined rotation axis;
A charging member that contacts the surface of the image carrier and rotates around a predetermined rotation axis as the image carrier rotates;
A charging drive unit that charges the surface of the image carrier by applying a voltage to the charging member that rotates as the image carrier rotates;
An acquisition unit for acquiring an electrical characteristic value of the charging member corresponding to an amount of current flowing through the charging member;
The acquisition unit performs a characteristic value acquisition operation for acquiring an electrical characteristic value of the charging member over the rotation period of the charging member while applying a predetermined inspection voltage to the charging member by the charging driving unit. Acquisition control means
Based on the fluctuation range of the electrical characteristic value acquired by the characteristic value acquisition operation and the length of the fluctuation period in which the electrical characteristic value is continuously outside the predetermined reference range, the charging member Detecting means for detecting an abnormality;
It is characterized by having.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect,
The acquisition control unit applies the inspection voltage having a magnitude that generates a discharge between the surface of the image carrier and the surface of the charging member to the charging member by the charging driving unit. Yes.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect,
The fluctuation range is a difference from a predetermined reference value.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect,
The detection means detects an abnormality of the charging member based on the length of the fluctuation period acquired for each of a plurality of different reference ranges.
Each of the plurality of reference ranges is a range in which any one of an upper limit value and a lower limit value is defined.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect,
The plurality of reference ranges are
A first reference range in which the upper limit value is greater than the reference value;
A second reference range in which the lower limit value is smaller than the reference value;
It is characterized by including.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects,
The detection means calculates an abnormality level related to the degree of abnormality of the charging member based on a combination of the fluctuation range and the length of the fluctuation period,
The image forming apparatus includes a coping unit that performs a predetermined coping operation related to coping with the abnormality of the charging member according to the abnormality level calculated by the detection unit.

According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect,
The coping means includes a history relating to at least one of the abnormal level, a cumulative rotation speed of the charging member, a cumulative rotation time, a cumulative movement distance of the surface, and a cumulative number of image formations performed using the charging member. The countermeasure action is performed based on the information.

The invention according to claim 8 is the image forming apparatus according to claim 6,
The detection means calculates a first abnormality level based on the electrical characteristic value acquired by the first characteristic value acquisition operation by the acquisition unit, and is performed after the first characteristic value acquisition operation. 2nd abnormality level is calculated based on the electrical characteristic value acquired by the characteristic value acquisition operation of 2,
The coping means includes the first abnormal level, the second abnormal level, and the charging member in a period from the end of the first characteristic value acquisition operation to the start of the second characteristic value acquisition operation. And the history information relating to at least one of the number of times of image formation performed using the charging member, and the coping operation is performed. .

The invention according to claim 9 is the image forming apparatus according to any one of claims 6 to 8,
The coping operation includes an operation of acquiring a usable period of a predetermined replacement target unit including the charging member based on the abnormality level.

According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the sixth to ninth aspects,
The coping operation includes an operation of changing a setting relating to a magnitude of a voltage applied to the charging member in order to charge the surface of the image carrier in accordance with the abnormal level.

According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the sixth to tenth aspects,
The detection means calculates the abnormality level based on a combination of the fluctuation range in the fluctuation period and the length of the fluctuation period for each of the plurality of fluctuation periods,
The coping means performs the coping operation based on a plurality of abnormal levels corresponding to the plurality of fluctuation periods.

The invention according to claim 12 is the image forming apparatus according to any one of claims 1 to 11,
The acquisition control unit causes the acquisition unit to perform the characteristic value acquisition operation for detection of abnormality by the detection unit and the characteristic value acquisition operation performed for a predetermined purpose other than detection of the abnormality,
The number of acquisitions of the electrical characteristic value in the rotation period in the characteristic value acquisition operation for detecting the abnormality is the electrical characteristic in the rotation period in the characteristic value acquisition operation performed for the predetermined purpose. It is characterized by being more than the number of acquisitions of values.

According to a thirteenth aspect of the present invention, in the image forming apparatus of the twelfth aspect,
An image carrier driving unit that rotationally drives the image carrier;
The acquisition control means is configured such that the moving speed of the surface of the image carrier in the characteristic value acquisition operation for detecting the abnormality is the speed of the image carrier in the characteristic value acquisition operation performed for the predetermined purpose. The operation of the image carrier driving unit is controlled so as to be smaller than the moving speed of the surface.

The invention according to claim 14 is the image forming apparatus according to any one of claims 1 to 13,
The acquisition control unit causes the acquisition unit to perform the characteristic value acquisition operation for detection of abnormality by the detection unit and the characteristic value acquisition operation performed for a predetermined purpose other than detection of the abnormality,
The detection means is characterized in that the abnormality is detected when a distribution of the electrical characteristic values acquired by the characteristic value acquisition operation performed for the predetermined purpose satisfies a predetermined distribution condition.

According to a fifteenth aspect of the present invention, in the image forming apparatus of the fourteenth aspect,
The detection means is characterized in that, when the abnormality is detected, the distribution condition is changed so that the distribution condition is relaxed.

In order to achieve the above object, the program invention according to claim 16 provides:
An image carrier that rotates about a predetermined rotation axis, a charging member that contacts the surface of the image carrier and rotates about the predetermined rotation axis as the image carrier rotates, and the image carrier A charging drive unit that charges the surface of the image carrier by applying a voltage to the charging member that is rotating along with the rotation of the charging member, and an electric charge of the charging member that corresponds to the amount of current flowing through the charging member. An image forming unit configured to transfer a toner image obtained by developing an electrostatic latent image on the surface of the image carrier to a recording medium and forming an image on the recording medium. The computer installed in the forming device
The acquisition unit performs a characteristic value acquisition operation for acquiring an electrical characteristic value of the charging member over the rotation period of the charging member while applying a predetermined inspection voltage to the charging member by the charging driving unit. Acquisition control means,
Based on the fluctuation range of the electrical characteristic value acquired by the characteristic value acquisition operation and the length of the fluctuation period in which the electrical characteristic value is continuously outside the predetermined reference range, the charging member Detection means for detecting an abnormality,
It is characterized by making it function as.

In order to achieve the above object, the invention of the abnormality detection method according to claim 17 comprises:
An image carrier that rotates about a predetermined rotation axis, a charging member that contacts the surface of the image carrier and rotates about the predetermined rotation axis as the image carrier rotates, and the image carrier A charging drive unit that charges the surface of the image carrier by applying a voltage to the charging member that is rotating along with the rotation of the charging member, and an electric charge of the charging member that corresponds to the amount of current flowing through the charging member. An image forming unit configured to transfer a toner image obtained by developing an electrostatic latent image on the surface of the image carrier to a recording medium and forming an image on the recording medium. An abnormality detection method for the charging member in a forming apparatus,
The acquisition unit performs a characteristic value acquisition operation for acquiring an electrical characteristic value of the charging member over the rotation period of the charging member while applying a predetermined inspection voltage to the charging member by the charging driving unit. Get step,
Based on the fluctuation range of the electrical characteristic value acquired by the characteristic value acquisition operation and the length of the fluctuation period in which the electrical characteristic value is continuously outside the predetermined reference range, the charging member A detection step for detecting an anomaly;
It is characterized by including.

  According to the present invention, there is an effect that the abnormality of the charging member can be detected more accurately.

1 is a diagram illustrating a schematic configuration of an image forming apparatus. 2 is a block diagram illustrating a main functional configuration of the image forming apparatus. FIG. It is a figure explaining the structure and operation | movement of a charging roller and a power supply part. It is a schematic diagram which shows the example of the measurement result of the electric current value in a charging roller. It is a figure which shows the table data used for calculation of an abnormal level. It is a flowchart which shows the control procedure of the abnormality detection process of a charging roller. It is a figure which shows the example of the voltage used for adjustment operation of the voltage between peaks. It is a figure which shows the example of the measurement result of the electric current value corresponding to the voltage between several peaks. It is a figure which shows the relationship between the voltage between peaks, and the average value of an electric current value. It is a figure which shows the table data used for calculation of an abnormal level in a modification.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of an image forming apparatus, a program, and an abnormality detection method of the invention will be described with reference to the drawings.

<Configuration of image forming apparatus>
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 1 according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a main functional configuration of the image forming apparatus 1.
The image forming apparatus 1 includes a paper supply unit 2, a paper discharge unit 3, a control unit 10 (acquisition control unit, detection unit, coping unit, computer), an image forming unit 20, a storage unit 30, and an operation unit 40. A display unit 50, a scanner 60, a transport unit 70, a communication unit 80, a bus 90, and the like. These units are connected via a bus 90.
In the image forming apparatus 1, a sheet (recording medium) stored in the sheet supply unit 2 is conveyed by a conveyance roller 71 of a conveyance unit 70, and an image is formed on the conveyed sheet by an image forming unit 20 in an electrophotographic manner. It is formed and discharged to the paper discharge unit 3.

  The control unit 10 includes a CPU 11 (Central Processing Unit), a RAM 12 (Random Access Memory), and a ROM 13 (Read Only Memory).

  The CPU 11 reads and executes the control program 131 stored in the ROM 13 and performs various arithmetic processes.

  The RAM 12 provides a working memory space to the CPU 11 and stores temporary data.

  The ROM 13 stores various control programs 131 executed by the CPU 11, setting data, and the like. Instead of the ROM 13, a rewritable nonvolatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

  The control unit 10 including the CPU 11, the RAM 12, and the ROM 13 performs overall control of each unit of the image forming apparatus 1 in accordance with the control program 131. For example, the control unit 10 causes the conveyance unit 70 to convey the sheet, and causes the image forming unit 20 to form an image on the sheet based on the image data stored in the storage unit 30.

  The storage unit 30 is configured by a DRAM (Dynamic Random Access Memory) or the like, and stores image data acquired by the scanner 60, image data input from the outside via the communication unit 80, history information to be described later, and the like. . These data and information may be stored in the RAM 12.

  The image forming unit 20 forms an image on a sheet based on the image data stored in the storage unit 30. The image forming unit 20 includes an image carrier 21 that is a drum-shaped photoconductor that carries an electrostatic latent image on the surface, an image carrier drive unit 211 (FIG. 2) that rotates the image carrier 21, and an image carrier. A cleaning unit 22 that removes residual toner on the surface of the body 21, a charging roller 23 (charging member) that uniformly charges the surface of the image carrier 21, and a power source unit 234 that applies voltage to the charging roller 23 (charging drive). Development unit) (FIG. 2), an exposure unit 24 that exposes the surface of the charged image carrier 21 to form an electrostatic latent image, and develops the electrostatic latent image using a developer containing toner. Then, the developing unit 25 that forms a toner image on the surface of the image carrier 21 and the formed toner image are primarily transferred to the intermediate transfer belt 261 in the transfer region, and then secondarily transferred from the intermediate transfer belt 261 to the sheet. Transfer unit 26 and toner image on paper Comprising a fixing portion 27 for fixing. Among the above, the image carrier 21, the cleaning unit 22, the charging roller 23, the exposure unit 24, and the developing unit 25 constitute an image forming unit.

  Four image forming units are provided corresponding to each color of Y (yellow), M (magenta), C (cyan), and K (black), and Y, M, C along the lower horizontal surface of the intermediate transfer belt 261 are provided. , K in order. In each image forming unit, along the outer peripheral surface of the image carrier 21, a cleaning unit 22, a charging roller 23, an exposure unit 24, and a developing unit 25 are arranged in this order. Among the image forming units, the image carrier 21, the cleaning unit 22, and the charging roller 23 constitute a replacement target unit U. This replacement target unit U can be replaced when the usable period has elapsed.

The image carrier 21 is driven by an image carrier drive unit 211 to rotate around a predetermined rotation axis. A photosensitive layer made of a resin containing an organic photoconductor is formed on the outer peripheral surface of the image carrier 21.
The image carrier driving unit 211 rotationally drives the image carrier 21 at a rotation speed specified by a control signal from the control unit 10.

  The cleaning unit 22 has a flat plate-like cleaning blade made of an elastic body, and is brought into contact with the surface of the image carrier 21 so that the cleaning blade adheres to the surface of the image carrier 21 and is transferred to the intermediate transfer belt 261. Foreign matter such as toner remaining without being removed is removed.

The charging roller 23 is a cylindrical member that abuts on the surface of the image carrier 21 and rotates following a predetermined rotation axis as the image carrier 21 rotates.
The power supply unit 234 uniformly charges the surface of the image carrier 21 by applying an AC bias voltage, in which an AC voltage is superimposed on a DC voltage, as the charging drive voltage to the driven rotating charging roller 23. Let
Detailed configurations and operations of the charging roller 23 and the power supply unit 234 will be described later.

  The exposure unit 24 includes an LD (Laser Diode) as a light emitting element. The exposure unit 24 exposes the surface of the image carrier 21 charged by the charging roller 23 by irradiating a laser beam, thereby exposing the electrostatic latent image on the image carrier 21. Form an image. In FIG. 1, four exposure units 24 corresponding to the four image forming units are provided. Instead, the laser light from the single exposure unit 24 is separated by an anti-transmission mirror or the like. In other words, it may be configured to be guided to the image carrier 21 of each imaging unit.

  The developing unit 25 includes a developing sleeve (developing roller) disposed so as to face the surface of the image carrier 21. The developing unit 25 supplies the developer containing the toner supplied from a toner bottle (not shown) to the surface of the developing sleeve having a predetermined developing bias potential, so that the toner in the developer is image-bearing from the developing sleeve surface. A toner image is formed on the surface of the image carrier 21 by being attached to the electrostatic latent image on the surface of the body 21.

The transfer unit 26 is stretched around the two belt conveyance rollers 262, the four primary transfer rollers 263 arranged to face each image carrier 21, and the belt conveyance rollers 262 and the primary transfer roller 263. The intermediate transfer belt 261, the belt cleaning unit 264 that removes toner remaining on the intermediate transfer belt 261, and the belt conveyance roller 262 being driven by the rotation of the belt conveyance roller 262 while being urged against the belt conveyance roller 262. A secondary transfer roller 265 that rotates.
In the transfer unit 26, the intermediate transfer belt 261 rotates while the bias voltage having a polarity opposite to that of the toner is applied to the primary transfer roller 263, so that the toner is transferred from the surface of the rotating image carrier 21 to the intermediate transfer belt 261. Transcribed. Further, after the toner of each color of Y, M, C, and K is superimposed and transferred, the sheet passes between the secondary transfer roller 265 to which a predetermined bias voltage is applied and the intermediate transfer belt 261, so that the intermediate The color toner image is transferred from the transfer belt 261 to the paper. The toner remaining on the intermediate transfer belt 261 without being transferred to the paper is removed by the cleaning blade of the belt cleaning unit 264.

  The fixing unit 27 heats and pressurizes the sheet on which the toner image is transferred to fix the toner image on the sheet. The fixing unit 27 includes a pair of rollers including a heating roller and a pressure roller that sandwich the sheet. The heating roller is heated to a predetermined target temperature (for example, a temperature within a range of 180 ° C. or higher and 200 ° C. or lower) by a heater as a heating source. The pressure roller is urged toward the heating roller by an elastic member (not shown). The sheet on which the toner image has been transferred passes through the nip portion between the heating roller and the pressure roller, whereby the toner image is fixed on the sheet. The sheet on which the toner image is fixed is transported by the transport roller 71 of the transport unit 70 and sent to the paper discharge unit 3.

  The operation unit 40 includes input devices such as operation keys and a touch panel arranged on the screen of the display unit 50, converts an input operation on these input devices into an operation signal, and outputs the operation signal to the control unit 10.

  The display unit 50 includes a display device such as an LCD (Liquid crystal display). Under the control of the control unit 10, the state of the image forming apparatus 1, an operation screen including operation buttons to be input to the touch panel, and the like Is displayed.

  The scanner 60 reads an image formed on a sheet under the control of the control unit 10 to generate image data, and causes the storage unit 30 to store the generated image data.

  The transport unit 70 includes a plurality of transport rollers 71 that move the paper by rotating in a state where the paper is sandwiched, and the transport roller 71 is rotationally driven under the control of the control unit 10 so that the paper is moved along a predetermined transport path. Transport. The transport unit 70 may include a reversing mechanism (not shown) that reverses the front and back of the paper on which the fixing process has been performed by the fixing unit 27 and transports the paper to the secondary transfer roller 265.

  Under the control of the control unit 10, the communication unit 80 communicates with a computer or other image forming apparatus on the network to transmit / receive image data, print job data, and the like.

<Configuration and operation of charging roller and power supply unit>
Next, the configuration and operation of the charging roller 23 and the power supply unit 234 will be described.
FIG. 3 is a diagram illustrating the configuration and operation of the charging roller 23 and the power supply unit 234.
The charging roller 23 is a cylindrical member having a diameter of about 12 [mm] provided to be rotatable about a rotation axis (coaxial with the rotation axis of the image carrier 21) extending in a direction perpendicular to the drawing in FIG. The charging roller 23 includes a cylindrical cored bar 231 extending along the rotation axis, a conductive elastic layer 232 formed around the cored bar 231, and a surface layer of the charging roller 23 provided around the elastic layer 232. And a surface layer 233 to be formed.

The cored bar 231 is made of a conductive member such as a metal.
The elastic layer 232 is made of an elastic material such as epichlorohydrin rubber, nitrile rubber, ethylene-propylene-diene rubber, silicone rubber, urethane rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber, natural rubber, ketjen black or acetylene black. It can be constituted by a mixture of a conductive agent such as carbon black, graphite, metal powder, conductive metal oxide, ionic conductive agent or the like.
The surface layer 233 is a resin layer containing organic fine particles or inorganic fine particles having an average particle diameter of several μm to several tens μm, and protects the surface of the charging roller 23 and imparts a predetermined surface roughness to the surface. Provided for.
The charging roller 23 is urged toward the surface of the image carrier 21 by a spring member (not shown). As a result, the charging roller 23 rotates following the rotation of the image carrier 21. In the present embodiment, the rotational speeds of the image carrier 21 and the charging roller 23 in the normal image recording operation are adjusted so that the moving speed of the surface is about 145 [mm / sec]. The rotation period of the charging roller 23 at this time is about 0.26 [seconds].

The core bar 231 of the charging roller 23 is electrically connected to the power supply unit 234.
The power supply unit 234 includes an AC power supply unit 234a that generates an AC voltage having a peak-to-peak voltage Vpp specified by the control unit 10, and a DC power supply unit 234b that generates a DC voltage having a magnitude specified by the control unit 10. I have. The power supply unit 234 supplies a charging drive voltage obtained by superimposing the AC voltage generated by the AC power supply unit 234a on the DC voltage generated by the DC power supply unit 234b to the metal core 231 of the charging roller 23. These AC power supply unit 234a and DC power supply unit 234b constitute a charging drive unit.
In addition, the power supply unit 234 includes a current measurement unit 234c (acquisition unit) that measures the amount of current (current value, electrical characteristic value) flowing through the charging roller 23. The current measurement unit 234c outputs information related to the measured current amount to the control unit 10.

  The power supply unit 234 applies a charging drive voltage to the charging roller 23 that rotates following the rotation of the image carrier 21, so that an image in the vicinity of both sides of the contact portion between the image carrier 21 and the charging roller 23 is applied. A discharge is generated in the gap between the surface of the carrier 21 and the surface of the charging roller 23, thereby applying a charge to the surface of the image carrier 21 to uniformly charge the surface. In the present embodiment, the DC voltage by the DC power supply unit 234b is −600 [V], the peak-to-peak voltage Vpp of the AC voltage superimposed by the AC power supply unit 234a is 1800 [V], and −600 ± (1800/2). A voltage that oscillates between [V] is applied to the charging roller 23. If the peak-to-peak voltage Vpp is too large, ions generated by the discharge increase and adhere to the charging roller 23, leading to characteristic deterioration. Therefore, the peak-to-peak voltage Vpp is possible within a range where an appropriate amount of discharge occurs. It is desirable to adjust to as small a value as possible. A method for adjusting the peak-to-peak voltage Vpp will be described later.

<Charging roller abnormality detection method>
Next, a method for detecting an abnormality in the charging roller 23 will be described.
The amount of charge on the surface of the image carrier 21 is an amount corresponding to the amount of current flowing through the charging roller 23 when a charging driving voltage is applied to the charging roller 23. In the charging roller 23, if the surface state of the surface layer 233 or a change in resistance value (abnormality of the charging roller 23) occurs due to contamination or deterioration, the amount of current fluctuates, and the charge amount on the surface of the image carrier 21 is appropriate. The excess and deficiency from. In an area where the charge amount is excessive or insufficient, a toner image having an appropriate density is not formed by the developing unit 25, leading to poor image quality of the recorded image.

  Such abnormalities in the charging roller 23 include changes in the cross-linked state of the surface layer 233 of the charging roller 23, thinning of the surface layer 233 due to contact with the image carrier 21, generation of cracks in the surface layer 233, and toner and its This may be caused by adhesion of foreign matters such as external additives. For example, when a crack occurs in the surface layer 233, a current flows in the crack portion and an abnormal discharge occurs, resulting in a difference in charge amount from the surroundings, leading to uneven color in the recorded image. Moreover, if the cracks are connected in a range having a certain spread, the amount of current increases in a wide range, leading to color unevenness in a wider range. In addition, even when the resistance value of the charging roller 23 locally fluctuates due to adhesion of foreign matter, the current amount is similarly different from the surroundings, resulting in poor image quality such as color unevenness in the recorded image.

  Here, the degree of image quality failure in the recorded image due to the abnormality of the charging roller 23, that is, the ease of visual recognition, is not only the fluctuation range of the amount of current flowing through the charging roller 23 but also the abnormality in which the amount of current is abnormal. It is also influenced by the width of the area, and the larger the abnormal area, the lower the image quality that can be visually recognized due to an abnormality of a smaller current amount. Therefore, even if the fluctuation range from the appropriate value (predetermined reference value) of the current amount in the abnormal region is the same, if the shape of the abnormal region is a line shape, no visible image quality defect occurs, and the abnormal region When the shape of the region is a planar shape, an event that a visually inferior image quality defect occurs may occur.

Therefore, in the present embodiment, abnormality detection of the charging roller 23 is performed in consideration of the size of the abnormal region in the charging roller 23.
When detecting an abnormality of the charging roller 23 in the image forming apparatus 1, the charging roller 23 is applied over at least the rotation period of the charging roller 23 while applying a predetermined inspection voltage to the charging roller 23 from the power supply unit 234. Is obtained by the current measuring unit 234c. Hereinafter, an operation of measuring a current value as an electrical characteristic value in the abnormality detection operation of the charging roller 23 is referred to as a characteristic value acquisition operation. Here, the peak-to-peak voltage Vpp in the inspection voltage is set to a magnitude that causes discharge between the surface of the image carrier 21 and the surface of the charging roller 23.

FIG. 4 is a schematic diagram illustrating an example of a measurement result of a current value in the charging roller 23.
In FIG. 4, the time change of the electric current value measured in the rotation period of the charging roller 23 by the characteristic value acquisition operation is schematically shown. This current value may be a measurement value in a single rotation cycle, or may be an average value of measurement values in a plurality of rotation cycles. In the present embodiment, the moving speeds of the surfaces of the image carrier 21 and the charging roller 23 in the characteristic value acquisition operation are about 72 [mm / second], which is ½ that of normal image recording. The rotation period of the roller 23 is about 0.52 [seconds]. Then, by measuring the current value at the maximum detection frequency by the current measuring unit 234c, 90 times of current value measurement is performed per rotation period.

  In the example of FIG. 4, current peaks P1, P2, and P4 whose current values fluctuate in the positive direction from the reference value I0 are formed, and current peaks P3 that fluctuate in the negative direction from the reference value I0 are formed. Each of these current peaks P <b> 1 to P <b> 4 (hereinafter also simply referred to as current peak P) corresponds to an abnormal region of the charging roller 23. Here, the reference value I0 can be calculated from the current value data over the rotation period. The calculation method of the reference value I0 is not particularly limited, but is a method of using a representative value (average value or median value) of current values over the rotation period, and a method of using approximate values of current values at the bottom of each peak. Etc.

  When the current value in FIG. 4 is measured, the fluctuation width D and the fluctuation period length W (fluctuation time) of each current peak P are calculated. Here, the fluctuation range D is a deviation width from the reference value I0. In addition, the fluctuation period is a period in which the current value is continuously outside the predetermined reference range. The reference range includes a range defined by an upper limit value larger than the reference value I0 (first reference range) and a range defined by a lower limit value smaller than the reference value I0 (second reference range). In addition, the first reference range includes a plurality of reference ranges having different upper limit values (in this embodiment, + I1, + I2,...), And the second reference range has different lower limit values (this embodiment). In the form, -I1, -I2, ...) there are a plurality of reference ranges. The length W of the fluctuation period of the current peak P is a period in which the current value is outside the range of the reference range having the largest absolute value of the upper limit value or the lower limit value among the plurality of reference ranges. For example, for the current peak P1, since the current value is outside the range of the two reference ranges having + I1 and + I2 as upper limit values, the length of the period during which the absolute value exceeds the maximum upper limit value + I2 W1 is calculated as the length W of the fluctuation period of the current peak P1. Similarly, the length W2 of the fluctuation period of the current peak P2 is the length of the period exceeding the upper limit value + I1, and the length W3 of the fluctuation period of the current peak P3 is less than the lower limit value −I1. The length W4 of the fluctuation period of the current peak P4 is the length of the period exceeding the upper limit value + I1.

  When the variation width D and the variation period length W are calculated for each current peak P, the degree of abnormality in the abnormal region corresponding to the current peak P based on the combination of the variation width D and the variation period length W. An abnormal level related to is acquired. Then, a predetermined coping operation related to coping with the abnormality of the charging roller 23 is executed according to the acquired abnormality level. When at least some of the abnormal levels for the plurality of current peaks P are different from each other, a coping operation corresponding to the highest abnormal level among the acquired abnormal levels is executed.

FIG. 5 is a diagram showing table data used for calculation of an abnormal level.
The table data in FIG. 5 is data stored in the ROM 13 (or the storage unit 30), and is a combination of the fluctuation range D (7 levels) of the current value at the current peak P and the length W (7 levels) of the fluctuation period. Is stored in association with the abnormal level. Specifically, when the fluctuation width D (absolute value) is I6 or more and the fluctuation period length W is T1 or more, and when the fluctuation width D is I4 or more and the fluctuation period length W is T4 or more. And when the fluctuation range D is less than I2, the fluctuation range D is less than I4, and the length W of the fluctuation period is not less than T1 and less than T4, and The abnormal level 3 is assigned to the case where the fluctuation range D is less than I5 and the length W of the fluctuation period is less than T1, and the abnormal level 2 is assigned to cases other than these cases.

  Here, the abnormality level indicates a larger abnormality as the value is smaller. Specifically, the abnormal level 1 is an abnormal level that requires immediate replacement of the replacement target unit U including the charging roller 23, and the abnormal level 2 is that the charging roller 23 can be used continuously, but the replacement time is short. The abnormal level 3 is an abnormal level when the charging roller 23 has no abnormality or the abnormality is negligible. Further, the boundary value of each level of the fluctuation range D and the boundary value of each level of the length W of the fluctuation period are set based on the fluctuation width and the fluctuation period value of the charging roller 23 in which an abnormality has actually occurred. . In FIG. 5, the abnormality level is set in three stages, but the abnormality level may be set more finely. Further, the number of levels of the fluctuation width D and the fluctuation period length W is not limited to seven.

In the present embodiment, when the largest abnormal level among the abnormal levels corresponding to the plurality of current peaks P in the rotation period of the charging roller 23 is the abnormal level 1, prompt replacement of the replacement target unit U is promoted. A warning is displayed on the display unit 50.
In addition, when the largest abnormality level is abnormality level 2, a warning display indicating that the replacement time of the replacement target unit U is near is displayed on the display unit 50.
Further, when the largest abnormality level is the abnormality level 3, the display relating to the replacement of the replacement target unit U is not performed.

When the largest abnormality level is the abnormality level 2 or the abnormality level 3 that does not require immediate replacement, the usable period (life) of the replacement target unit U is calculated and displayed on the display unit 50. The usable period can be calculated by the following method, for example. That is, first, an abnormality level (first abnormality level) in the characteristic value acquisition operation (first characteristic value acquisition operation) performed in the past and an abnormality in the current characteristic value acquisition operation (second characteristic value acquisition operation). Level (second abnormal level) is acquired, and after these first abnormal level and the second abnormal level are executed, the first characteristic value acquisition operation is executed and before the second characteristic value acquisition operation is executed. Based on history information relating to at least one of the number of rotations of the charging roller 23, the rotation time, the surface moving distance, and the number of times of image formation using the charging roller 23 (the number of sheets). Calculate the possible period. Specifically, the usable period becomes shorter as the difference between the first abnormality level and the second abnormality level becomes larger, and the rotation number, rotation time, and surface movement distance of the charging roller 23 in the history information. Alternatively, the calculation is performed so that the smaller the number of image formations, the shorter.
Note that the usable period may be calculated in advance in association with each abnormal level, and the usable period corresponding to the acquired abnormal level may be used. In addition, instead of the above, an abnormal level is calculated based on the most recent characteristic value acquisition operation, and the abnormal level, the accumulated rotation speed from the start of use of the transport roller 23, the accumulated rotation time, and the accumulated surface The usable period may be calculated based on the movement distance and the history information relating to at least one of the cumulative number of image formations.

  Each of the warning display, the caution display, the display of the usable period, and the calculation of the usable period in the display unit 50 described above corresponds to a coping operation, and the control unit 10 and the display unit 50 perform these coping operations. The coping means is configured.

<Charge roller abnormality detection start control (1)>
Next, control for starting the abnormality detection operation of the charging roller 23 will be described.
In the image forming apparatus 1 of the present embodiment, in the normal image forming operation, the current value is measured over the rotation period of the charging roller 23 by the current measuring unit 234c at a predetermined timing, and the current value distribution in the rotation period is obtained. Such a value (here, standard deviation) is detected (hereinafter, this detection is referred to as preliminary detection). The preliminary detection is an operation that does not involve the detection of the length of the fluctuation period of the current peak, and is a detection operation that does not aim at detecting the abnormality of the charging roller 23 described above. Therefore, the characteristic value acquisition operation for the preliminary detection corresponds to the characteristic value acquisition operation performed for the purpose other than the abnormality detection of the charging roller 23.
The predetermined timing includes the end of the image forming operation related to the print job, the power-on of the image forming apparatus 1, the continuous image formation on a predetermined number of sheets, and the inside of the image forming apparatus 1. The case where the temperature or humidity fluctuates more than a predetermined value.

In this preliminary detection, since the rotation speed of the charging roller 23 is set at the time of normal image formation, it is twice the speed in the above-described abnormality detection operation of the charging roller 23, and the number of current value measurements per rotation cycle. Is 1/2 (45 times) of the abnormality detection operation. Therefore, each operation is set such that the number of current value acquisitions in the characteristic value detection operation in the abnormality detection operation is greater than the number of current value acquisitions in the preliminary detection.
In the preliminary detection, the standard deviation of the current value is calculated. When the standard deviation of the current value is out of the predetermined standard deviation reference range (when the current value distribution satisfies the predetermined distribution condition), the rotational speeds of the image carrier 21 and the charging roller 23 are 1. The abnormality detection operation including the characteristic value acquisition operation described above is started.

  When the abnormality detection operation is started according to the result of preliminary detection, the standard deviation reference range is expanded so that the standard deviation calculated in the preliminary detection is within the standard deviation reference range. The standard deviation reference range setting is changed. That is, the distribution condition is changed so that the distribution condition is relaxed.

  Below, the control procedure by the control part 10 of the abnormality detection process of the charging roller 23 performed by the image forming apparatus 1 will be described. Here, an example in which preliminary detection is performed at the end of the image forming operation relating to the print job will be described.

FIG. 6 is a flowchart showing the control procedure of the abnormality detection process of the charging roller 23.
When a print job is input from the outside via the communication unit 80, the control unit 10 starts a normal image recording operation related to the print job (step S101). Here, the control unit 10 outputs a control signal to the image carrier driving unit 211 so that the moving speed of the surfaces of the image carrier 21 and the charging roller 23 is about 145 [mm / sec]. 21 is rotated.

  The control unit 10 determines whether or not the recording of all the images related to the print job has been completed (step S102). When it is determined that the recording of any image is not completed (“NO” in step S102), the control unit 10 executes the process of step S102 again. If it is determined that all the images have been recorded (“YES” in step S102), the control unit 10 causes the power supply unit 234 to perform the above-described preliminary detection operation (step S103).

  The control unit 10 determines whether or not the standard deviation of the measured current value is outside the standard deviation reference range (step S104). When it is determined that the standard deviation is within the standard deviation reference range (“NO” in step S104), the control unit 10 ends the abnormality detection process.

  When it is determined that the standard deviation is out of the standard deviation reference range (“YES” in step S104), the control unit 10 changes the standard deviation reference range as described above (step S105). A control signal is output to the carrier driving unit 211 to reduce the rotational speeds of the image carrier 21 and the charging roller 23 by half (step S106), and the power supply unit 234 acquires characteristic values related to the abnormality detection operation. An operation is performed (step S107: acquisition step).

The control unit 10 calculates the fluctuation range D and the fluctuation period length W of each current peak P based on the acquired current value data (step S108), calculates the abnormal level by the method described above, and calculates The various coping operations according to the abnormal level are executed (step S109). The process of step S108 and step S109 corresponds to a detection step.
When the process of step S109 ends, the control unit 10 ends the abnormality detection process.

<Charge roller abnormality detection start control (2)>
Next, another example of the control for starting the abnormality detection operation of the charging roller 23 will be described.
As described above, in the image forming apparatus 1 of the present embodiment, the peak-to-peak voltage Vpp of the AC voltage generated by the AC power supply unit 234a of the power supply unit 234 is as small as possible within a range in which an appropriate amount of discharge occurs. It is desirable that Further, since the discharge amount with respect to the peak-to-peak voltage Vpp depends on the environmental conditions (temperature and humidity), the consumption state of the charging roller 23, and the like, the operation for adjusting the peak-to-peak voltage Vpp is performed at a predetermined timing. As will be described below, this adjustment operation includes an operation of measuring a current value in the charging roller 23 with a plurality of different charging driving voltages. The operation for detecting the standard deviation of the current value measured at this time can be the above-described preliminary detection. Even in this case, in the preliminary detection, when the standard deviation of the current value falls outside the standard deviation reference range, the abnormality detection operation is started.

Hereinafter, the adjustment operation of the peak-to-peak voltage Vpp will be described.
The adjustment operation of the peak-to-peak voltage Vpp is performed at the end of the image forming operation related to the print job, when the image forming apparatus 1 is turned on, when image formation is continuously performed on a predetermined number of sheets, and the image forming apparatus 1. This is performed when the temperature or humidity of the inside fluctuates by a predetermined value or more.

In the adjustment operation of the peak-to-peak voltage Vpp, first, a plurality of charging drive voltages having different peak-to-peak voltages Vpp are applied to the charging roller 23 and current values are measured.
FIG. 7 is a diagram illustrating an example of voltages used for the adjustment operation of the peak-to-peak voltage Vpp. As shown in FIG. 7, the plurality of peak-to-peak voltages Vpp used for the adjustment operation are, for example, four peak-to-peak voltages Vpp1 to Vpp4 selected in a range less than the discharge start voltage and a range greater than or equal to the discharge start voltage. There can be a total of eight of the four selected peak-to-peak voltages Vpp5 to Vpp8. For example, the peak-to-peak voltages Vpp1 to Vpp4 can be 1300 [V], 1400 [V], 1500 [V], and 1600 [V], respectively, and the peak-to-peak voltages Vpp5 to Vpp8 are 1900 [V], respectively. 2000 [V], 2100 [V], 2200 [V]

  A combination of these eight peak-to-peak voltages Vpp1 to Vpp8 is obtained by referring to table data stored in advance in the ROM 13 (or the storage unit 30). The table data may be stored with an optimum combination of peak-to-peak voltages Vpp1 to Vpp8 for each environmental condition (temperature and humidity). In this case, the image forming apparatus 1 is provided with a temperature detection unit and a humidity detection unit (not shown), and by referring to the table data based on the temperature and humidity detection results, the peak-to-peak voltages Vpp1 to Vpp1 suitable for the current environment are obtained. A combination of Vpp8 is acquired.

  When the peak-to-peak voltages Vpp1 to Vpp8 used for the adjusting operation are acquired, as shown in FIG. 7, the power supply unit 234 determines the peak-to-peak voltage of the AC voltage generated by the AC power supply unit 234a from Vpp1 to Vpp8. The DC voltage generated by the DC power supply unit 234b is superimposed on the AC voltage and applied to the charging roller 23. The switching interval of the peak-to-peak voltage Vpp is set to be longer than the rotation period of the charging roller 23. In addition, with the application of the charging drive voltage, the current value is measured by the current measuring unit 234c over the rotation period of the charging roller 23 in each supply period of the peak-to-peak voltages Vpp1 to Vpp8.

  FIG. 8 is a diagram illustrating an example of measurement results of current values corresponding to a plurality of peak-to-peak voltages Vpp1 to Vpp8. A time c in FIG. 8 is a rotation cycle of the charging roller 23. Thus, the current value increases as the peak-to-peak voltage increases from Vpp1 to Vpp8.

When the current values are measured, average values Iac1 to Iac8 of the current values corresponding to each of peak-to-peak voltages Vpp1 to Vpp8 are calculated.
FIG. 9 is a diagram showing the relationship between the peak-to-peak voltages Vpp1 to Vpp8 and the average values Iac1 to Iac8 of the current values.
As shown in FIG. 9, the average value of the current value is plotted against the magnitude of the peak-to-peak voltage, and among these, the peak-to-peak voltages Vpp1 to Vpp4 below the discharge start voltage based on the average values Iac1 to Iac4 of the current values A straight line L1 representing the relationship with the current value is obtained using the least square method. Further, based on the average values Iac5 to Iac8 of the current values, a straight line L2 representing the relationship between the peak-to-peak voltages Vpp5 to Vpp8 that are equal to or higher than the discharge start voltage and the current value is obtained using the least square method. And the intersection of the straight line L1 and the straight line L2 is acquired as the discharge start voltage Vth in the environmental condition of the said adjustment operation. A predetermined value is added to the discharge start voltage Vth to set a peak-to-peak voltage Vpp in image formation.

  In such an adjustment operation of the peak-to-peak voltage Vpp, a standard deviation is calculated for the measured current value of FIG. 8, and the standard deviation of the current value according to any of the peak-to-peak voltages Vpp1 to Vpp8, or each peak-to-peak voltage Vpp1. When the average value of the standard deviations related to ˜Vpp8 is outside the standard deviation reference range, the abnormality detection operation of the charging roller 23 is started after the adjustment operation of the peak-to-peak voltage Vpp is completed.

(Modification)
Then, the modification of the said embodiment is demonstrated. The present embodiment is different from the above-described embodiment in that the abnormal level calculation standard and coping action are set separately for the current peak P having a current value larger than the reference value I0 and the current peak P smaller than the reference value I0. And different. Hereinafter, differences from the above embodiment will be described.

FIG. 10 is a diagram showing table data used for calculating an abnormal level in the present modification.
FIG. 10A shows table data when the fluctuation range D at the current peak P is larger than the reference value I0 (when it is on the + side with respect to the reference value I0). In this table data, any one of the abnormal levels 1 to 4 is assigned to the combination of the absolute value of the fluctuation range D and the length W of the fluctuation period. Further, each of the abnormal levels 1 to 4 is associated with coping actions 1 to 4.
On the other hand, FIG. 10B shows table data when the fluctuation range D at the current peak P is smaller than the reference value I0 (when it is on the negative side with respect to the reference value I0). In this table data, any one of the abnormal levels 1, 5 to 7 is assigned to the combination of the absolute value of the fluctuation range D and the length W of the fluctuation period. Also, each of the abnormal levels 1, 5-7 is associated with coping actions 1, 5-7.

In this way, by setting the abnormality level and the coping operation separately for the + side and the − side, it is possible to take a more flexible and appropriate countermeasure against the abnormality of the charging roller 23. For example, as the coping operation 6 corresponding to the abnormal level 6 in FIG. 10B, the setting is changed so that the magnitude of the charging drive voltage supplied to the image carrier 21 is increased. Can compensate for the lack of value.
10A and 10B, the number of abnormal level stages, the boundary value of each level of the fluctuation range D, the boundary value of each level of the length W of the fluctuation period, and The number of levels of the fluctuation range D and the fluctuation period length W may be different from each other.

As described above, the image forming apparatus 1 according to the present embodiment transfers the toner image obtained by developing the electrostatic latent image on the surface of the image carrier 21 to a sheet and forms an image on the sheet. In the image forming apparatus 1, the image carrier 21 rotates around a predetermined rotation axis, and abuts on the surface of the image carrier 21, and rotates around the predetermined rotation axis as the image carrier 21 rotates. To the charging roller 23, the power supply unit 234 that charges the surface of the image carrier 21 by applying a voltage to the charging roller 23 that rotates as the image carrier 21 rotates, and the charging roller 23. The control unit 10 includes a current measurement unit 234c that acquires a current value as an electrical characteristic value of the charging roller 23 corresponding to the amount of current, and the control unit 10. The control unit 10 controls the charging roller 23 with a predetermined value by the power supply unit 234. Do not apply inspection voltage The characteristic value acquisition operation for acquiring the current value of the charging roller 23 over the rotation period of the charging roller 23 is performed by the current measurement unit 234c (acquisition control unit), and the current value acquired by the characteristic value acquisition operation is obtained. An abnormality of the charging roller 23 is detected based on the fluctuation width D and the length W of the fluctuation period in which the current value is continuously outside the predetermined reference range (detecting means).
The length W of the current value fluctuation period represents the length of the charging roller 23 in the rotating direction of the abnormal region where the surface state or resistance value is abnormal in the charging roller 23. Therefore, according to the above-described configuration in which the abnormality is detected based on the fluctuation range D of the current value and the length W of the fluctuation period, the charging roller 23 is more accurately considered in consideration of the size of the abnormal region in the rotating direction of the charging roller 23. Abnormalities can be detected. For example, even when the fluctuation range D is small and no abnormality is detected depending on the fluctuation range D, if the length W of the fluctuation period is long, the charging roller 23 can be accurately detected based on the current peak P related to the fluctuation period. Abnormalities can be detected.

  In addition, the control unit 10 causes the power supply unit 234 to apply an inspection voltage having a magnitude that generates a discharge between the surface of the image carrier 21 and the surface of the charging roller 23 (acquisition control unit). . Since the absolute value of the fluctuation range D of the current peak P can be increased by measuring the current using the inspection voltage having such a magnitude, the abnormality of the charging roller 23 can be detected more accurately. .

  Further, by setting the fluctuation range D as a difference from the predetermined reference value I0, it is possible to detect the abnormality by specifying the degree of abnormality at each position in the circulation direction on the same basis.

  Further, the control unit 10 detects an abnormality of the charging roller 23 based on the length W of the variation period acquired for each of a plurality of different reference ranges (detection means), and the reference range includes an upper limit value and a lower limit value. Either one of the values is a defined range. Thereby, when there are a plurality of abnormal areas whose current values are outside the reference range, the magnitude of the abnormality in each abnormal area can be appropriately specified to accurately detect the abnormality.

  The plurality of reference ranges include a first reference range whose upper limit value is larger than the reference value and a second reference range whose lower limit value is smaller than the reference value. Thereby, it is possible to appropriately detect an abnormality in which the current value increases and an abnormality in which the current value decreases. For example, the problem that the current value increases due to the occurrence of a crack in the surface layer 233 and the problem that the current value decreases due to the increase in the resistance value of the surface layer 233 can be separately and accurately specified. .

  Further, the control unit 10 calculates an abnormal level related to the degree of abnormality of the charging roller 23 based on the combination of the fluctuation range D and the length W of the fluctuation period (detection means), and the image forming apparatus 1 is calculated. A control unit 10 and a display unit 50 are provided as coping means for performing a predetermined coping operation related to coping with the abnormality of the charging roller 23 according to the abnormality level. As a result, it is possible to perform appropriate countermeasures according to the degree of abnormality with easy processing.

  The coping means includes history information relating to at least one of an abnormal level, a cumulative rotation number of the charging roller 23, a cumulative rotation time, a cumulative movement distance of the surface, and a cumulative number of times of image formation performed using the charging roller. Then, a coping operation is performed on the basis of (coping means). Thereby, it is possible to perform an appropriate coping operation in consideration of the time change rate of abnormality occurring in the charging roller 23.

  In addition, the control unit 10 calculates the first abnormality level based on the current value acquired by the first characteristic value acquisition operation by the current measurement unit 234c, and the first abnormality level is performed after the first characteristic value acquisition operation. The second abnormality level is calculated based on the current value acquired by the second characteristic value acquisition operation, and the coping means finishes the first abnormality level and the second abnormality level and the first characteristic value acquisition operation. At least one of the number of rotations of the charging roller 23, the rotation time, the moving distance of the surface, and the number of times of image formation performed using the charging roller 23 in a period after the start of the second characteristic value acquisition operation. And taking action based on the history information. Thereby, it is possible to perform an appropriate coping operation in consideration of the time change rate of abnormality occurring in the charging roller 23.

  The coping operation includes an operation of acquiring a usable period of a predetermined replacement target unit U including the charging roller 23 based on the abnormal level. Accordingly, it is possible to accurately calculate the usable period of the charging roller 23, that is, the lifetime, and to display and operate the user to prompt the user to replace the replacement target unit.

  The coping operation includes an operation of changing a setting related to the magnitude of the voltage applied to the charging roller 23 in order to charge the surface of the image carrier 21 in accordance with the abnormal level. Thereby, the current value in the charging roller 23 can be adjusted to an appropriate range, and the charging roller 23 can be continuously used after the abnormality of the detected charging roller 23 is suppressed.

  Further, the control unit 10 calculates an abnormal level for each of a plurality of fluctuation periods based on a combination of the fluctuation width D in the fluctuation period and the length W of the fluctuation period (detection means), and a plurality of coping means are provided. The coping operation is performed based on a plurality of abnormal levels corresponding to the fluctuation period. As a result, the abnormality of the charging roller 23 can be detected by accurately specifying the magnitude of the abnormality in the abnormal region for each abnormal region corresponding to the current value fluctuation period.

  In addition, the control unit 10 causes the current measurement unit 234c to perform a characteristic value acquisition operation for detecting an abnormality of the charging roller 23 and a characteristic value acquisition operation performed for a predetermined purpose other than the detection of the abnormality ( Acquisition control means), the number of acquisitions of the current value in the rotation period in the characteristic value acquisition operation for detecting the abnormality is greater than the number of acquisitions of the current value in the rotation period in the characteristic value acquisition operation performed for the predetermined purpose. There are also many. As a result, the abnormal region can be detected with high resolution in the circulation direction in the abnormality detection operation. Therefore, it is possible to accurately detect the length of the abnormal region in the circulation direction, and it is possible to appropriately detect the abnormal region having a slight length in the rotation direction.

  Further, the image forming apparatus 1 includes an image carrier driving unit 211 that rotationally drives the image carrier 21, and the control unit 10 controls the surface of the image carrier 21 in the characteristic value acquisition operation for detecting the abnormality. The operation of the image carrier driving unit 211 is controlled so that the movement speed is smaller than the movement speed of the surface of the image carrier 21 in the characteristic value acquisition operation performed for a predetermined purpose (acquisition control means). Thereby, the frequency | count of acquisition of the electric current value in abnormality detection operation can be increased easily.

  In addition, the control unit 10 causes the current measurement unit 234c to perform a characteristic value acquisition operation for detecting an abnormality of the charging roller 23 and a characteristic value acquisition operation performed for a predetermined purpose other than the detection of the abnormality ( (Acquisition control means), and anomaly detection is performed when the distribution of current values acquired by the characteristic value acquisition operation performed for the predetermined purpose satisfies a predetermined distribution condition (detection means). Thereby, abnormality detection can be performed only when there is a high possibility that abnormality has occurred in the charging roller 23. As a result, the execution frequency of the abnormality detection operation can be suppressed and the formation efficiency of the normal image can be improved.

  In addition, when the abnormality is detected, the control unit 10 changes the distribution condition so that the distribution condition is relaxed (detection unit). Thereby, it is possible to suppress the occurrence of a problem that the abnormality detection operation is repeatedly executed with high frequency for the charging roller 23 in which the same abnormality occurs.

  In addition, the control program of the present embodiment causes the control unit 10 (computer) provided in the image forming apparatus 1 to rotate the charging roller 23 while applying a predetermined inspection voltage to the charging roller 23 by the power supply unit 234. The acquisition control means for causing the current measurement unit 234c to perform the characteristic value acquisition operation for acquiring the current value of the charging roller 23 over the period, the fluctuation range D of the current value acquired by the characteristic value acquisition operation, and the current value are continuous. Then, based on the length W of the fluctuation period that is a value outside the predetermined reference range, it is made to function as a detection unit that detects an abnormality of the charging roller 23. According to such a program, the abnormality of the charging roller 23 can be detected more accurately in consideration of the size of the abnormal region in the rotating direction of the charging roller 23.

  Further, the abnormality detection method for the charging roller 23 according to the present embodiment is such that the power supply unit 234 applies a predetermined inspection voltage to the charging roller 23 while the charging roller 23 is rotated over the rotation period of the charging roller 23. Acquisition step for causing the current measurement unit 234c to perform the characteristic value acquisition operation for acquiring the current value, the fluctuation range D of the current value acquired by the characteristic value acquisition operation, and the fluctuation in which the current value continuously falls outside the predetermined reference range. A detection step of detecting an abnormality of the charging roller 23 based on the length W of the period. According to such a method, the abnormality of the charging roller 23 can be detected more accurately in consideration of the size of the abnormal region in the rotating direction of the charging roller 23.

The present invention is not limited to the above-described embodiments and modifications, and various modifications can be made.
For example, in the above-described embodiment and the modification, the replacement target unit U has been described as an example of replacement. However, the present invention is not limited to this. For example, only the charging roller 23 may be replaceable.

  In the embodiment and the modification, the abnormality detection is performed based on the fluctuation range D of the current value in the charging roller 23 and the length W of the fluctuation period. Anomaly detection may be performed based on a characteristic characteristic value, for example, a fluctuation range related to a resistance value or a length of a fluctuation period.

  In the embodiment and the modification described above, the rotational speeds of the image carrier 21 and the charging roller 23 are made different between the preliminary detection and the abnormality detection, so that the number of times of measurement of the current value per rotation cycle in the abnormality detection operation is relative. However, the present invention is not limited to this. For example, the rotation speeds of the image carrier 21 and the charging roller 23 may be the same in the preliminary detection and the abnormality detection, and the current value detection frequency in the abnormality detection operation may be made larger than the current value detection frequency in the preliminary detection.

  Further, in the above embodiment and the modification, when the abnormality detection operation is started based on the measurement result of the current value in the preliminary detection, the standard deviation of the current value is the standard as the distribution condition for the current value distribution in the preliminary detection. Although the description has been made using the example in which the deviation is outside the reference range, the distribution condition is not limited to this. For example, the fact that the fluctuation range of the current peak in the preliminary detection is outside a predetermined range may be a distribution condition for starting the abnormality detection operation.

  In the embodiment and the modification, the fluctuation level D and the fluctuation period length W are calculated for each current peak P to calculate an abnormal level, and an abnormality among a plurality of abnormal levels related to the plurality of current peaks P is detected. Although the description has been given using the example in which the coping action is selected based on the largest abnormality level, the present invention is not limited to this. For example, the fluctuation range of the current value in the entire rotation cycle (Dmax-min in FIG. 4) and the maximum value of the length of the fluctuation period with respect to a specific reference range (for example, the reference range corresponding to + I1 and −I1 in FIG. 4). The abnormal level and the coping action may be determined based on the maximum value of the period outside the range.

  In the embodiment and the modification, the control unit 10 of the image forming apparatus 1 performs various processes related to abnormality detection (calculation of the fluctuation range D of the current value and the length W of the fluctuation period, calculation of the abnormal level, and countermeasure operation). However, at least a part of these processes may be executed by an external information processing apparatus.

  Although several embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, and includes the scope of the invention described in the claims and equivalents thereof. .

1 Image forming apparatus 10 Control unit (acquisition control means, detection means, coping means, computer)
131 Control Program 20 Image Forming Unit 21 Image Carrier 211 Image Carrier Driving Unit 22 Cleaning Unit 23 Charging Roller (Charging Member)
234 Power supply unit 234a AC power supply unit (charging drive unit)
234b DC power supply unit (charging drive unit)
234c Current measurement unit (acquisition unit)
24 Exposure unit 25 Development unit 26 Transfer unit 27 Fixing unit D Fluctuation width W Fluctuation period length I0 Reference value U Unit to be replaced

Claims (17)

An image forming apparatus for transferring a toner image obtained by developing an electrostatic latent image on the surface of an image carrier to a recording medium to form an image on the recording medium,
The image carrier rotating about a predetermined rotation axis;
A charging member that contacts the surface of the image carrier and rotates around a predetermined rotation axis as the image carrier rotates;
A charging drive unit that charges the surface of the image carrier by applying a voltage to the charging member that rotates as the image carrier rotates;
An acquisition unit for acquiring an electrical characteristic value of the charging member corresponding to an amount of current flowing through the charging member;
The acquisition unit performs a characteristic value acquisition operation for acquiring an electrical characteristic value of the charging member over the rotation period of the charging member while applying a predetermined inspection voltage to the charging member by the charging driving unit. Acquisition control means
Based on the fluctuation range of the electrical characteristic value acquired by the characteristic value acquisition operation and the length of the fluctuation period in which the electrical characteristic value is continuously outside the predetermined reference range, the charging member Detecting means for detecting an abnormality;
An image forming apparatus comprising:   The acquisition control means applies the inspection voltage having a magnitude that generates a discharge between the surface of the image carrier and the surface of the charging member to the charging member by the charging driving unit. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the fluctuation range is a difference from a predetermined reference value. The detection means detects an abnormality of the charging member based on the length of the fluctuation period acquired for each of a plurality of different reference ranges.
The image forming apparatus according to claim 3, wherein each of the plurality of reference ranges is a range in which one of an upper limit value and a lower limit value is defined. The plurality of reference ranges are
A first reference range in which the upper limit value is greater than the reference value;
A second reference range in which the lower limit value is smaller than the reference value;
The image forming apparatus according to claim 4, further comprising: The detection means calculates an abnormality level related to the degree of abnormality of the charging member based on a combination of the fluctuation range and the length of the fluctuation period,
6. The image forming apparatus according to claim 1, further comprising a coping unit that performs a predetermined coping operation related to coping with the abnormality of the charging member according to the abnormality level calculated by the detection unit. The image forming apparatus according to claim 1.   The coping means includes a history relating to at least one of the abnormal level, a cumulative rotation speed of the charging member, a cumulative rotation time, a cumulative movement distance of the surface, and a cumulative number of image formations performed using the charging member. The image forming apparatus according to claim 6, wherein the coping operation is performed based on information. The detection means calculates a first abnormality level based on the electrical characteristic value acquired by the first characteristic value acquisition operation by the acquisition unit, and is performed after the first characteristic value acquisition operation. 2nd abnormality level is calculated based on the electrical characteristic value acquired by the characteristic value acquisition operation of 2,
The coping means includes the first abnormal level, the second abnormal level, and the charging member in a period from the end of the first characteristic value acquisition operation to the start of the second characteristic value acquisition operation. And the history information relating to at least one of the number of times of image formation performed using the charging member, the coping operation is performed. The image forming apparatus according to claim 6.   The said coping operation | movement contains the operation | movement which acquires the usable period of the predetermined | prescribed replacement | exchange target unit containing the said charging member based on the said abnormality level, The Claim 1 characterized by the above-mentioned. Image forming apparatus.   The coping operation includes an operation of changing a setting relating to a magnitude of a voltage applied to the charging member in order to charge the surface of the image carrier in accordance with the abnormal level. The image forming apparatus according to any one of 6 to 9. The detection means calculates the abnormality level based on a combination of the fluctuation range in the fluctuation period and the length of the fluctuation period for each of the plurality of fluctuation periods,
11. The image forming apparatus according to claim 6, wherein the coping unit performs the coping operation based on a plurality of abnormality levels corresponding to the plurality of fluctuation periods. The acquisition control unit causes the acquisition unit to perform the characteristic value acquisition operation for detection of abnormality by the detection unit and the characteristic value acquisition operation performed for a predetermined purpose other than detection of the abnormality,
The number of acquisitions of the electrical characteristic value in the rotation period in the characteristic value acquisition operation for detecting the abnormality is the electrical characteristic in the rotation period in the characteristic value acquisition operation performed for the predetermined purpose. The image forming apparatus according to any one of claims 1 to 11, wherein the image forming apparatus is larger than a value acquisition count. An image carrier driving unit that rotationally drives the image carrier;
The acquisition control means is configured such that the moving speed of the surface of the image carrier in the characteristic value acquisition operation for detecting the abnormality is the speed of the image carrier in the characteristic value acquisition operation performed for the predetermined purpose. The image forming apparatus according to claim 12, wherein an operation of the image carrier driving unit is controlled to be smaller than a moving speed of the surface. The acquisition control unit causes the acquisition unit to perform the characteristic value acquisition operation for detection of abnormality by the detection unit and the characteristic value acquisition operation performed for a predetermined purpose other than detection of the abnormality,
The detection means detects the abnormality when a distribution of the electrical characteristic values acquired by the characteristic value acquisition operation performed for the predetermined purpose satisfies a predetermined distribution condition. The image forming apparatus according to any one of 1 to 13.   The image forming apparatus according to claim 14, wherein when the abnormality is detected, the detection unit changes the distribution condition so that the distribution condition is relaxed. An image carrier that rotates about a predetermined rotation axis, a charging member that contacts the surface of the image carrier and rotates about the predetermined rotation axis as the image carrier rotates, and the image carrier A charging drive unit that charges the surface of the image carrier by applying a voltage to the charging member that is rotating along with the rotation of the charging member, and an electric charge of the charging member that corresponds to the amount of current flowing through the charging member. An image forming unit configured to transfer a toner image obtained by developing an electrostatic latent image on the surface of the image carrier to a recording medium and forming an image on the recording medium. The computer installed in the forming device
The acquisition unit performs a characteristic value acquisition operation for acquiring an electrical characteristic value of the charging member over the rotation period of the charging member while applying a predetermined inspection voltage to the charging member by the charging driving unit. Acquisition control means,
Based on the fluctuation range of the electrical characteristic value acquired by the characteristic value acquisition operation and the length of the fluctuation period in which the electrical characteristic value is continuously outside the predetermined reference range, the charging member Detection means for detecting an abnormality,
A program characterized by functioning as An image carrier that rotates about a predetermined rotation axis, a charging member that contacts the surface of the image carrier and rotates about the predetermined rotation axis as the image carrier rotates, and the image carrier A charging drive unit that charges the surface of the image carrier by applying a voltage to the charging member that is rotating along with the rotation of the charging member, and an electric charge of the charging member that corresponds to the amount of current flowing through the charging member. An image forming unit configured to transfer a toner image obtained by developing an electrostatic latent image on the surface of the image carrier to a recording medium and forming an image on the recording medium. An abnormality detection method for the charging member in a forming apparatus,
The acquisition unit performs a characteristic value acquisition operation for acquiring an electrical characteristic value of the charging member over the rotation period of the charging member while applying a predetermined inspection voltage to the charging member by the charging driving unit. Get step,
Based on the fluctuation range of the electrical characteristic value acquired by the characteristic value acquisition operation and the length of the fluctuation period in which the electrical characteristic value is continuously outside the predetermined reference range, the charging member A detection step for detecting an anomaly;
An abnormality detection method comprising:

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