JP2011209490A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that includes a charging roller for charging an image carrier in contact with the image carrier, and prevents image flow by cleaning the image carrier while preventing toner from being wasted during cleaning.SOLUTION: Before cleaning (S10), a current to be obtained when a preset measurement voltage is applied to a charging roller from a charging device, is measured (S4). Based on the measured current value, an amount of toner to be supplied for cleaning (S10) is set (S5 to S9). Specifically, the amount of toner to be supplied is set larger as the measured current value is higher, and vice versa.

Description

  The present invention relates to an electrophotographic image forming apparatus adopting a contact charging method in which a charging roller is brought into contact with an image carrier to charge the image carrier, and in particular, a discharge product on the surface of the image carrier. The present invention relates to a technique for preventing image flow caused by adhesion.

In general, when an amorphous silicon photosensitive drum or the like is used as an image carrier in an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine, discharge products such as NOx and SOx are generated by charging and discharging. . In a high humidity environment, the discharge product absorbs moisture and adheres to the surface of the amorphous silicon photosensitive drum. As a result, the electrical resistance of the surface of the amorphous silicon photoconductor drum is lowered and the electrostatic latent image cannot be held, so-called image flow occurs, resulting in an image defect. In addition, even when paper dust generated from the paper on which image formation is performed adheres to the image carrier, the surface resistance of the image carrier decreases due to moisture absorption of the paper dust, and image flow occurs.
Here, as a technique for preventing such an image flow caused by moisture adhering to the image carrier, it is known that the image carrier is heated by a heater to release the moisture. However, with this method, the power consumption by the heater hinders the power saving of the image forming apparatus, so that it is difficult to meet the recent demand for energy saving. Further, in order to perform heating with the heater, a certain amount of preparation time is required from the start of operation. For this reason, for example, when heating by the heater is performed when the image forming apparatus is turned on, there is a problem that the waiting time from when the power is turned on until the first image forming process is executed becomes longer.

In contrast, for example, in Patent Document 1, in an image forming apparatus using an amorphous silicon photosensitive drum, a toner containing an abrasive is supplied to the amorphous silicon photosensitive drum, and a cleaning roller is brought into contact with the amorphous silicon photosensitive drum. It has been proposed to remove discharge products and the like by rotating them in a state and rubbing the surface of the amorphous silicon photosensitive drum. In this case, since it is not necessary to use a heater, the power consumption can be reduced, and the demand for energy saving can be met.
By the way, the amount of discharge products adhering to the surface of the amorphous silicon photosensitive drum increases due to aging of the amorphous silicon photosensitive drum. Further, the discharge product generated by charging the amorphous silicon photosensitive drum also adheres to the surface of the charging roller that contacts the amorphous silicon photosensitive drum. Then, the discharge product adhering to the surface of the charging roller may move from the charging roller to the surface of the amorphous silicon photosensitive drum.
Therefore, even after the deterioration of the amorphous silicon photoconductor drum or when the discharge product is transferred from the charging roller to the amorphous silicon photoconductor drum, in order to sufficiently remove the discharge product, the toner supply amount at the time of cleaning is previously set. It is conceivable to set a large number.

JP 2004-126296 A

However, if the toner supply amount is always set to a large amount, wasteful toner consumption will occur due to cleaning of the photosensitive drum before the deterioration of the amorphous silicon photosensitive drum or when the amount of discharge product adhering to the charging roller is small. Is a problem.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is an image forming apparatus including a charging roller that contacts an image carrier and charges the image carrier. An object of the present invention is to provide an image forming apparatus capable of preventing an image flow by cleaning a carrier and preventing waste of toner consumption during the cleaning.

In order to achieve the above object, the present invention provides a charging device for charging the image carrier by rotating the charging roller while applying a voltage to a charging roller in contact with the image carrier, and the charging device charged by the charging device. An exposure device for forming an electrostatic latent image on the image carrier, a developing roller for developing the electrostatic latent image on the image carrier by supplying toner to the image carrier, and the developing roller A predetermined amount of toner is supplied to the image carrier, and at least the image carrier is rotated while a predetermined cleaning member is in contact with the surface of the image carrier. Applied to an image forming apparatus comprising a cleaning control means for cleaning a surface, before the start of the cleaning by the cleaning control means, Current measuring means for measuring a current when a preset measurement voltage is applied from the charging device to the charging roller; and the cleaning control means based on the current value measured by the current measuring means in the cleaning. The image forming apparatus includes a toner supply amount setting unit that sets the toner supply amount. Here, the image carrier is, for example, an amorphous silicon photosensitive drum.
In general, in the image forming apparatus, as the number of discharge products adhering to the charging roller increases, the current leaking to the image carrier increases when a charging bias is applied to the charging roller. Therefore, if the current when the measurement voltage is applied to the charging roller is measured as in the present invention, the water content of the discharge product adhering to the image carrier and the charging roller is estimated from the current value. be able to.
Therefore, according to the present invention, the correspondence relationship between the current value measured by the current measuring unit and the toner supply amount at the time of cleaning by the cleaning unit can be prevented so that image flow on the image carrier can be prevented. By setting in advance, it is possible to prevent waste of toner consumption when cleaning the image carrier.
Specifically, the toner supply amount setting means increases the toner supply amount as the current value measured by the current measurement means increases, and decreases the toner supply amount as the current value measured by the current measurement means decreases. It is conceivable that the setting is small.

By the way, the current flowing from the charging roller to the image carrier changes not only by the electrical resistance of the surface of the image carrier and the charging roller but also by the linear velocity of the image carrier during the cleaning. Therefore, it is desirable that the toner supply amount setting means sets the toner supply amount according to the ratio between the current value measured by the current measuring means and the linear velocity of the image carrier at the time of the measurement.
More specifically, Idc / v, which is the ratio between the current value Idc [μA] measured by the current measuring means and the linear velocity v [mm / s] of the image carrier, is x, and the toner supply amount is When y [mg] is set, it is conceivable that the toner supply amount setting means sets the toner supply amount so as to satisfy y ≧ 400x−200. This conditional expression y ≧ 400x−200 can prevent the image flow by sufficiently removing the discharge products adhering to the surface of the image carrier based on the results of previous experiments as will be described later. Is predetermined.
Further, it is desirable that the toner supply amount setting means sets the toner supply amount so as to satisfy y ≧ 400x−200 within a range equal to or less than a preset upper limit amount. Thereby, it is possible to prevent the total amount y of the toner supply amount from being set abnormally large due to some abnormality.
Here, the toner supply amount setting means may be, for example, any one of a time for applying a developing bias to the developing roller, a potential difference between the developing roller and the image carrier, and the number of times of performing the cleaning operation in one cleaning. It is conceivable that the toner supply amount is set by setting a plurality. Of course, these are merely examples, and the setting content is not limited to these parameters as long as the toner supply amount can be changed.
By the way, a temperature / humidity detecting means for detecting the temperature and humidity of the image forming apparatus is further provided, and the toner supply amount setting means has a predetermined condition in which the temperature and humidity detected by the temperature / humidity detecting means are preset. If the cleaning is performed on the condition that the above is satisfied, the necessity of the cleaning can be appropriately judged and the cleaning can be performed only when necessary, and wasteful toner consumption can be prevented. Can do.

  According to the present invention, a correspondence relationship between the current value measured by the current measuring unit and the toner supply amount at the time of cleaning by the cleaning unit is set in advance so as to prevent image flow on the image carrier. By doing so, it is possible to prevent waste of toner consumption during the cleaning of the image carrier.

1 is a block diagram showing a schematic configuration of a multifunction machine X according to an embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a schematic configuration of an image forming unit 5 of the multifunction machine X according to the embodiment of the present invention. 6 is a flowchart for explaining an example of a procedure of cleaning control processing executed by the multifunction machine X according to the embodiment of the present invention. The table | surface which shows the experimental result for defining the cleaning conditions which concern on embodiment of this invention. The table | surface which shows the experimental result for defining the cleaning conditions based on Example 1 of this invention. The graph which shows the experimental result for defining the cleaning conditions based on Example 1 of this invention. 9 is a flowchart for explaining another example of the procedure of the cleaning control process. The table | surface which shows the experimental result for defining the cleaning conditions based on Example 2 of this invention. The graph which shows the experimental result for defining the cleaning conditions which concern on Example 2 of this invention. 9 is a flowchart for explaining another example of the procedure of the cleaning control process.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
First, a schematic configuration of the multifunction machine X according to the embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, a multifunction machine X according to an embodiment of the present invention includes a control unit 1, an operation display unit 2, an image reading unit 3, an image processing unit 4, an image forming unit 5, a fixing device 6, a temperature and humidity. The image forming apparatus is schematically configured to include a detection unit 7 and the like. The present invention can also be applied to, for example, an electrophotographic copying machine, a facsimile machine, a printer apparatus, and the like.
The control unit 1 has peripheral devices such as a CPU and ROM, RAM, etc., and the CPU controls the MFP X by executing processing according to a predetermined control program stored in the ROM. Control. For example, the control unit 1 executes a cleaning control process (see the flowchart of FIG. 3) described later. The control unit 1 may be configured by an electronic circuit such as an integrated circuit (ASIC).

The operation display unit 2 has a liquid crystal display, a touch panel, various operation keys, and the like for displaying various types of information on the multifunction machine X and performing input operations by the user.
The temperature / humidity detection unit 7 (corresponding to temperature / humidity detection means) has a thermometer and a hygrometer for measuring the temperature and humidity outside the multi-function device X, and the temperature / humidity detection unit 7 measured the temperature and humidity. The temperature and humidity are input to the control unit 1. The temperature / humidity detection unit 7 may be provided inside the image forming unit 5 to detect the temperature and humidity in the image forming unit 5. The temperature and humidity detected by the temperature / humidity detection unit 7 are used as indicators for determining whether or not to execute a cleaning control process described later.

The image reading unit 3 has a CCD or the like for reading an image of a document placed on a document table (not shown) or a document conveyed by an automatic document feeder (ADF, not shown).
The image processing unit 4 performs various types of image processing on the image data read by the image reading unit 3 or image data input from the outside.
The image forming unit 5 forms a toner image on a sheet supplied from a paper supply cassette (not shown) based on the image data input from the image processing unit 4. The fixing device 6 melts and fixes the toner image formed on the sheet by the image forming unit 5 on the sheet.

Here, a schematic configuration of the image forming unit 5 will be described with reference to FIG.
The image forming unit 5 is provided corresponding to each color of black (Bk), yellow (Y), cyan (C), and magenta (M). In the multi-function machine X, the toner images of the respective colors formed by the plurality of image forming units 5 are sequentially superimposed and transferred onto the intermediate transfer belt 60, and the color image formed on the intermediate transfer belt 60 is transferred to the sheet. Is transcribed. Since the image forming unit 5 has the same configuration, only one of them will be described here. Of course, the present invention can also be applied to a monochrome-compatible image forming apparatus having one image forming unit 5.
As shown in FIG. 2, the image forming unit 5 includes a photosensitive drum 50, a charging device 51, an exposure device 52, a developing roller 53, a transfer roller 54, a cleaning device 55, a charge eliminating device 56, and the like.
The photoconductor drum 50 is an amorphous silicon photoconductor whose surface is made of conductive amorphous silicon and carries an electrostatic latent image and a toner image.
The charging device 51 includes a charging roller 511 disposed in contact with the surface of the photosensitive drum 50, and a charging bias including a preset AC component Vpp and DC component Vdc is applied to the charging roller 511. This is a contact charging type charging device that charges the surface of the photosensitive drum 50 to a predetermined potential by rotating the charging roller 511 while applying the voltage.
The exposure device 52 exposes the surface of the photosensitive drum 50 charged by the charging device 51 to form an electrostatic latent image based on image data. The neutralization device 56 neutralizes (resets) the charged potential of the photosensitive drum 50 after image formation.

The developing roller 53 develops the electrostatic latent image formed on the surface of the photosensitive drum 50 by supplying toner stored in a toner storage unit (not shown) to the photosensitive drum 50. The toner supplied from the developing roller 53 to the photosensitive drum 50 is, for example, 2 parts by weight of titanium oxide (particle diameter 0.1 μm, resistance 1 × 10 7 Ωcm) and 0.5 weight with respect to 100 parts by weight of toner particles. In this toner, part of the hydrophobic silica is externally added as an abrasive.
Here, toner particles can be prepared by dispersing a colorant of each color in a binder resin together with a positive charge control agent, a release agent such as wax, and other compounding agents. It exists in the range of about 5-10 micrometers. Of course, the toner particles can be used alone as a developer by blending a magnetic agent such as magnetite, but can also be used as a two-component developer in combination with a magnetic carrier such as ferrite.
On the other hand, as the abrasive contained in the toner, for example, alumina, silicon carbide, magnetite, tin oxide, strontium titanate, inorganic powder subjected to surface conductive treatment, and the like are suitable. The abrasive is preferably externally added to the toner particles as a fine powder having a particle size of 0.1 to 3.0 μm. Further, in order not to deteriorate the charging characteristics of the toner, the volume solid resistance value is in the range of 1 × 10 2 to 1 × 10 10 Ωcm, and the addition amount is in the range of 0.3 to 5 parts by weight per 100 parts by weight of the toner particles. It is desirable to be in
Incidentally, the toner supply amount from the developing roller 53 to the photosensitive drum 50 is the potential difference between the developing roller 53 and the photosensitive drum 50 (hereinafter referred to as “developing bias”) or the developing bias to the developing roller 53. Varies depending on the time of applying (bias application time). Specifically, the toner supply amount increases as the developing bias increases, and increases as the bias application time increases.
The transfer roller 54 transfers the toner image developed on the photosensitive drum 50 to the intermediate transfer belt 60.

The cleaning device 55 includes a polyurethane polyurethane cleaning roller 551 disposed in contact with the photosensitive drum 50, a cleaning blade 552 disposed in contact with the photosensitive drum 50, the cleaning roller 551, and the cleaning roller 551. A toner collecting unit 553 for collecting toner removed from the photosensitive drum 50 by the cleaning blade 552; The cleaning roller 551 rotates in a state where the toner containing the abrasive is interposed in a contact portion with the photosensitive drum 50, and slidably rubs against the photosensitive drum 50 to thereby surface the surface of the photosensitive drum 50. To clean.
The cleaning roller 551 has a diameter of 14 mm, a surface hardness of 30 degrees, a contact pressure with the photosensitive drum 50 of 60 g / cm, and is rotated at a peripheral speed of 162 m / min. At this time, the rotation direction of the cleaning roller 551 is the forward direction (same direction) as that of the photosensitive drum 50 at the contact portion with the photosensitive drum 50, and the rotational speed of the cleaning roller 551 is the rotation speed of the photosensitive drum. The speed is 1.2 times the peripheral speed of the photosensitive drum 50 so as to slide on the drum 50. The rotation direction of the cleaning roller 551 may be opposite to the surface of the photosensitive drum 50.

In the multifunction machine X, a discharge product is generated by charging / discharging of the photosensitive drum 50, and the discharge product absorbs moisture and adheres to the surface of the photosensitive drum 50 and the charging roller 511. If moisture adheres to the surface of the photosensitive drum 50, the electrical resistance of the portion may be reduced, and so-called image flow may occur.
Therefore, in the multifunction machine X, the cleaning unit 55 executes cleaning control processing (see the flowchart in FIG. 3) described later by the control unit 1, thereby cleaning the surface of the photosensitive drum 50 by the cleaning device 55. . Here, the control unit 1 when executing the cleaning control process corresponds to a cleaning control means.
Specifically, the control unit 1 supplies a predetermined amount of toner to the photosensitive drum 50 from the developing roller 53 when the cleaning device 55 cleans the photosensitive drum 50, and The surface of the photosensitive drum 50 is cleaned by rotating the photosensitive drum 50 and the cleaning roller 551 while the cleaning roller 551 and the cleaning blade 552 are in contact with the surface of the photosensitive drum 50.
At this time, toner is supplied from the developing roller 53 to the photosensitive drum 50 by applying a predetermined developing bias to the developing roller 53. The toner supply amount varies depending on, for example, the application time of the predetermined developing bias.

Hereinafter, an example of the procedure of the cleaning control process executed by the control unit 1 will be described with reference to the flowchart of FIG. In the figure, S1, S2,... Represent processing procedure (step) numbers.
The cleaning control process is executed by the control unit 1 on condition that the multifunction machine X is turned on or returned from the power saving mode. Further, it may be executed in response to an operation input to the operation display unit 2. Of course, it is executed every time the image forming process (printing process) in the multi-function device X is completed, every time a preset predetermined time elapses, or every time a predetermined number of image forming processes are executed. It is also conceivable.

(Steps S1, S2)
First, in step S <b> 1, the control unit 1 detects the temperature and humidity outside the multifunction device X by the temperature / humidity detection unit 7.
Next, the control unit 1 determines whether the temperature and humidity detected in step S1 satisfy preset environmental conditions (S2). The environmental conditions are set in advance as high-humidity conditions in which discharge products generated in the image forming unit 5 absorb moisture and adhere to the photosensitive drum 50 and the charging roller 511, and image flow is likely to occur. Is. For example, the environmental condition corresponds to any of the following (1) to (4) when the temperature is T (° C.) and the humidity is H (%).
(1) 10 ≦ T <22,75 ≦ H
(2) 22 ≦ T <24, 70 ≦ H
(3) 24 ≦ T <30, 65 ≦ H
(4) 30 ≦ T, 50 ≦ H
Here, when the environmental conditions are satisfied (Yes in S2), such as when the temperature T is 25 ° C. and the humidity H is 67% (corresponding to the above (3)), the processing is performed on that condition. The process proceeds to step S3, and the cleaning of the photosensitive drum 50 by the cleaning device 55 is executed in step S10 described later. On the other hand, when the environmental conditions are not satisfied, such as when the temperature T is 25 ° C. and the humidity H is 62% (when none of the above (1) to (4) is satisfied) (No side of S3) Since the possibility of image flow is low, the process proceeds to step S11 to be described later without cleaning the photosensitive drum 50.

(Steps S3 and S4)
In step S3, the control unit 1 drives the photosensitive drum 50, the intermediate transfer belt 60, the transfer roller 54, and the like. Hereinafter, the linear velocity of the photosensitive drum 50 at this time is defined as a linear velocity v. The linear velocity v of the photosensitive drum 50 is equivalent to that used as a reference linear velocity in the copying machine X, for example. At this time, a reverse bias is applied to the transfer roller 54, and transfer from the photosensitive drum 50 to the intermediate transfer belt 60 is prevented. At this time, no charging bias is applied to the charging roller 511 of the charging device 50.
Subsequently, the control unit 1 controls the charging device 50 to apply a preset measurement bias to the charging roller 511 of the charging device 50 and measure the current value at that time (S4). Hereinafter, the measured current value is referred to as a measured current Idc. Here, the control unit 1 and the charging device 50 when performing such measurement processing correspond to current measuring means.
At this time, the measurement bias is a charging bias in which an AC component Vpp500V and a DC component Vdc500V are superimposed. As described above, the Vpp of the measurement bias is set lower than the charging bias during the normal image forming process so that the photosensitive drum 50 is not destroyed even if a leak occurs. Further, the higher the value of the AC component Vpp is, the more discharge products are generated on the photosensitive drum 50. On the other hand, the removal of moisture absorbed in the charging roller 511 is accelerated. Therefore, it is desirable that the value of the AC component Vpp is set to about 500 V, for example, so that the amount of discharge products generated in consideration of these does not exceed the rate of moisture removal.

  In the subsequent steps S5 to S9, the control unit 1 determines the amount of toner supplied from the developing roller 53 to the photosensitive drum 50 when the cleaning device 55 cleans the photosensitive drum 50. Set based on Idc. Here, the control unit 1 when executing the setting process corresponds to a toner supply amount setting unit. Of course, in addition to the control unit 1, when the cleaning device 55 is provided with an integrated circuit such as an ASIC or a control device such as an MPU for controlling the operation of the cleaning device 55, the control device A cleaning control process may be executed. In this case, the control device corresponds to a cleaning control unit and a toner supply amount setting unit.

ここに，前記クリーニング条件設定情報Ｔ１は，前記制御部１のＲＯＭに予め記憶されたものであって，前記測定電流Ｉｄｃとクリーニング条件Ａ１〜Ａ３との対応関係を定めたものである。前記クリーニング条件Ａ１〜Ａ３各々では，前記クリーニング時における現像バイアスの印加時間，即ち前記クリーニング時におけるトナー供給量が異なる。具体的に，前記測定電流値Ｉｄｃが高いほど前記トナー供給量が多く，前記測定電流値Ｉｄｃが低いほど前記トナー供給量が少なくなるように前記現像バイアスの印加時間が設定されている。
前記測定電流Ｉｄｃは，前記感光体ドラム５０及び前記帯電ローラ５１１の表面の電気抵抗によって変動し，その表面の電気抵抗は，該感光体ドラム５０及び帯電ローラ５１１の表面に付着した放電生成物の水分によって変動する。従って，前記測定電流Ｉｄｃを測定することで，前記感光体ドラム５０及び前記帯電ローラ５１１の表面の電気抵抗，即ち放電生成物の付着量を推定することができる。そして，上記表１は，前記測定電流Ｉｄｃから推定される放電生成物の付着がある場合に，前記クリーニング装置５５による前記感光体ドラム５０のクリーニングによって，該感光体ドラム５０における像流れを問題がない程度まで改善することができるトナー供給量を，現像バイアスの印加時間［ｍｓ］によって設定したものである。なお，前記トナー供給量は，現像バイアスの印加時間に限らず，例えば前記感光体ドラム５０と前記現像ローラ５３との電位差（現像バイアス）や，一度のクリーニング（Ｓ１０）におけるクリーニング動作の実行回数（クリーニング時間）によっても変動するため，これらの一つ又は複数を設定することにより，前記トナー供給量を設定するものであってもよい。例えば，一度のクリーニングにおけるクリーニング動作の実行回数が２回であれば，その都度トナー供給が行われるため，トナー供給量が２倍になる。 Specifically, the control unit 1 sets the toner supply amount at the time of cleaning based on the measured current Idc and the cleaning condition setting information T1 shown in Table 1 below.

Here, the cleaning condition setting information T1 is stored in advance in the ROM of the control unit 1, and defines the correspondence between the measured current Idc and the cleaning conditions A1 to A3. In each of the cleaning conditions A1 to A3, the developing bias application time during the cleaning, that is, the toner supply amount during the cleaning is different. Specifically, the developing bias application time is set such that the higher the measured current value Idc, the larger the toner supply amount, and the lower the measured current value Idc, the smaller the toner supply amount.
The measurement current Idc varies depending on the electric resistance of the surfaces of the photosensitive drum 50 and the charging roller 511, and the electric resistance of the surface of the discharge product adhered to the surfaces of the photosensitive drum 50 and the charging roller 511. Varies with moisture. Therefore, by measuring the measurement current Idc, it is possible to estimate the electrical resistances of the surfaces of the photosensitive drum 50 and the charging roller 511, that is, the amount of discharge product attached. Table 1 shows that there is a problem in image flow on the photosensitive drum 50 due to cleaning of the photosensitive drum 50 by the cleaning device 55 when there is a discharge product estimated from the measured current Idc. The toner supply amount that can be improved to a certain extent is set by the development bias application time [ms]. The toner supply amount is not limited to the application time of the development bias. For example, the potential difference (development bias) between the photosensitive drum 50 and the development roller 53, or the number of times the cleaning operation is performed in one cleaning (S10) ( The toner supply amount may be set by setting one or more of them. For example, if the number of executions of the cleaning operation in one cleaning is two, toner supply is performed each time, so the toner supply amount is doubled.

Here, a method for setting the cleaning condition setting information T1 in Table 1 will be described. FIG. 4 shows a result of an experiment performed in advance in the multifunction machine X.
Specifically, experimental results 1 to 12 shown in FIG. 4 show that when the measured value of the measured current Idc is each value, the cleaning device 55 performs cleaning for 90 seconds while changing the developing bias application time. Thereafter, the charging potential of the surface of the photosensitive drum 50 is 280 V, the DC component Vdc of the developing bias is 160 [V], the AC component Vpp is 1.3 [kV], and the frequency is 3 [kHz], and the printing rate is 25% ( The measurement result of the degree of image flow that occurred when test printing of 600 dpi, 1 × 1 dot) is shown.
The image flow “◯” in FIG. 4 indicates that the image flow has been sufficiently improved to a predetermined standard or higher, and that the image flow “×” is improved to the predetermined standard. Indicates no. The predetermined standard may be appropriately changed according to the image quality required in the multifunction machine X.

The cleaning condition setting information T1 in Table 1 is measured based on the experimental results 1 to 12 shown in FIG. 4 so that the image flow is improved by cleaning the photosensitive drum 50 by the cleaning device 55. The correspondence relationship between the current Idc and the cleaning conditions A1 to A3 is set in advance.
Specifically, in the cleaning condition setting information T1 in Table 1, when the measured current Idc is not less than 50 [μA] and not more than 150 [μA], the cleaning condition is that the developing bias application time is 500 [ms]. A1 is associated. Similarly, when the measurement current Idc is larger than 150 [μA], the cleaning condition A2 in which the developing bias application time is 1000 [ms] is associated.
Here, when the charging bias is applied and a leak occurs and the measurement current Idc exceeds 500 [μA], a high voltage detection circuit (not shown) is activated and the output of the high voltage is forcibly stopped. The measurement current Idc is extremely lowered to a value lower than 50 [μA]. Therefore, when the measurement current Idc is less than 50 [μA], the cleaning condition A3 corresponding to the developing bias application time of 3000 [ms] with the largest toner supply amount is associated. Of course, in the image forming apparatus in which the forced stop by the high voltage detection circuit is not performed, the cleaning condition A3 may be associated when the measurement current Idc exceeds 500 [μA].
Accordingly, if cleaning is performed by selecting any of the cleaning conditions A1 to A3 according to the cleaning condition setting information T1 in Table 1, the toner supply amount increases as the measured current Idc increases. It is possible to prevent the image flow from occurring on the drum 50.

(Steps S5 to S9)
Specifically, in step S5, the control unit 1 determines whether or not the measured current Idc measured in step S4 is 50 [μA] or more and 150 [μA] or less.
Here, when the measurement current Idc is 50 [μA] or more and 150 [μA] or less (Yes side of S5), the control unit 1 sets the cleaning condition A1 that is set in advance as the cleaning condition in the cleaning. (S7). On the other hand, if the measurement current Idc is not 50 [μA] or more and 150 [μA] or less (No in S5), the process proceeds to step S6.
In step S6, the control unit 1 determines whether or not the measurement current Idc is less than 50 [μA].
If the measured current Idc is not less than 50 [μA] (No in S6), the control unit 1 sets the cleaning condition for the cleaning to the preset cleaning condition A2 (S8). . On the other hand, when the measured current Idc is less than 50 [μA] (Yes in S6), the control unit 1 sets the cleaning condition for the cleaning to the preset cleaning condition A3 (S9).

(Step S10)
In step S10, the control unit 1 executes the cleaning according to any of the cleaning conditions A1 to A3 set in advance in steps S5 to S9.
For example, when the measured current Idc is 20 [μA] (Yes side in S6), the cleaning condition A3 is set based on the cleaning condition setting information T1 in Table 1, that is, the developing bias application time. Is set to 3000 [ms], and cleaning by the cleaning device 55 is executed. Therefore, the discharge product adhering to the surface of the photosensitive drum 50 can be sufficiently removed, and the image flow on the photosensitive drum 50 can be prevented.

(Step S11)
Thereafter, the control unit 1 executes a calibration process such as general density correction, and shifts the multifunction machine X to a standby state in which an image forming process or the like can be performed. For example, the operation display unit 1 displays a Ready display. And so on.
At this time, the time until the multifunction device X enters the standby state varies depending on the length of the cleaning execution time in step S10. In the multifunction device X, the time depends on the actual state of the image forming unit 5. Since the toner supply amount is set appropriately and cleaning is performed, the cleaning does not take more time than necessary, so the waiting time until the standby state is not increased.

As described above, in the multifunction device X, the cleaning control process is executed, so that the toner supply amount at the time of cleaning the photosensitive drum 50 by the cleaning device 55 is based on the measured current Idc. The higher the measured current value Idc, the larger the toner supply amount, and the lower the measured current value Idc, the smaller the toner supply amount, and the degree of cleaning of the photosensitive drum 50 is changed.
Therefore, the cleaning conditions can be set within a range that is recognized as necessary depending on the state of adhesion of the discharge products to the photosensitive drum 50 and the charging roller 511 and the moisture absorption state, and waste of toner supply amount and cleaning time can be set. Can be prevented.
In the configuration having a plurality of image forming units 5 corresponding to a plurality of colors as in the multifunction machine X, the control unit 1 may perform the cleaning control process for each of the image forming units 5. For example, it is conceivable to set a cleaning condition for cleaning each of the image forming units 5 according to the total value of the measurement currents Idc in each of the image forming units 5.

In the embodiment, the case where the cleaning condition is set based on the measurement current Idc has been described as an example.
On the other hand, the measurement current Idc measured in the step S4 varies according to the linear velocity v of the photosensitive drum 50 at the time of the measurement. Specifically, when the same amount of discharge product is adhered on the surface of the photosensitive drum 50, the measurement current Idc is measured under two measurement conditions with different linear speeds v of the photosensitive drum 50. The measured current Idc measured when the linear velocity v is fast is larger than the measured current Idc measured when the linear velocity v is slow. In other words, even if the measurement current Idc measured under the two measurement conditions is the same, if the linear velocity v when the measurement current Idc is measured is different, the surface of the photosensitive drum 50 is actually formed. The amount of attached discharge product is different. For this reason, the amount of discharge product deposited on the surface of the photosensitive drum 50 cannot be accurately estimated only by the measurement current Idc.
Therefore, it is conceivable to set the cleaning condition in accordance with not only the measurement current Idc but also the ratio between the measurement current Idc and the linear velocity of the photosensitive drum 50 when the measurement current Idc is measured in step S4. It is done. Hereinafter, Idc / v that is a ratio of the measurement current Idc and the linear velocity v of the photosensitive drum 50 is referred to as a current linear velocity ratio Idc / v.

ここに，前記クリーニング条件設定情報Ｔ２は，前記制御部１のＲＯＭに予め記憶されたものであって，前記電流線速比Ｉｄｃ／ｖとクリーニング条件Ａ１１〜Ａ１４との対応関係を定めたものである。前記クリーニング条件Ａ１１〜Ａ１４各々では，現像バイアスの印加時間及びクリーニング動作回数が異なり，即ちトナー供給量が異なる。なお，前述したように，前記クリーニング条件Ａ１１〜Ａ１４各々に対応するトナー供給量は，現像バイアスの印加時間及びクリーニング動作回数（クリーニング時間）の他，現像バイアスなどによっても変動するため，これらの一つ又は複数を定めたものであってもよい。 In this case, the control unit 1 sets the toner supply amount at the time of cleaning based on the current linear velocity ratio Idc / v and the cleaning condition setting information T2 shown in Table 2 below.

Here, the cleaning condition setting information T2 is stored in advance in the ROM of the control unit 1, and defines the correspondence between the current linear velocity ratio Idc / v and the cleaning conditions A11 to A14. is there. In each of the cleaning conditions A11 to A14, the developing bias application time and the number of cleaning operations are different, that is, the toner supply amount is different. As described above, the toner supply amount corresponding to each of the cleaning conditions A11 to A14 varies depending on the developing bias as well as the developing bias application time and the number of cleaning operations (cleaning time). One or more may be defined.

Here, a method for setting the cleaning condition setting information T2 in Table 2 will be described. 5 and 6 show the results of experiments performed in advance on the multifunction machine X. FIG.
Specifically, the experimental results 1 to 45 shown in FIGS. 5 and 6 indicate that when the current linear velocity ratio Idc / v is each value, the developing bias application time and the number of cleaning operations (for example, 90 seconds per time) Then, the cleaning device 55 performs cleaning, and thereafter, the charging potential of the surface of the photosensitive drum 50 is 280 V, the DC component Vdc of the developing bias is 160 [V], and the AC component Vpp is 1.3 [kV]. , The measurement result of the degree of image flow that occurs when test printing is performed with a frequency of 3 [kHz] and a printing rate of 25% (600 dpi, 1 × 1 dot).
5 and 6 indicates that the image flow degree “◯” has been sufficiently improved to a predetermined standard or more that there is no problem with the image flow. An image stream “x” indicates that the image quality has not been improved to the predetermined standard. The predetermined standard may be appropriately changed according to the image quality required in the multifunction machine X.
The cleaning condition setting information T2 in Table 2 is such that the image flow is improved by cleaning the photosensitive drum 50 by the cleaning device 55 based on the experimental results 1 to 45 shown in FIGS. , The correspondence relationship between the current linear velocity ratio Idc / v and the cleaning conditions A11 to A14 is set in advance.
Specifically, in the cleaning condition setting information T2 in Table 2, when the current linear velocity ratio Idc / v is not less than 0.22 and less than 0.65, the developing bias application time is 500 [ms], and the cleaning is performed. The cleaning condition A11 whose operation count is “1” is associated. Similarly, when the current linear velocity ratio Idc / v is 0.65 or more and less than 1.0, the cleaning condition A12 in which the developing bias application time is 1000 [ms] and the number of cleaning operations is “1” is supported. If the current linear velocity ratio Idc / v is 1.0 or more, the developing bias application time is 3000 [ms] and the cleaning operation number of times “1” is associated with the cleaning condition A13. It has been. Further, when the current linear velocity ratio Idc / v is less than 0.22, a cleaning condition A14 in which the developing bias application time is 5000 [ms] and the number of cleaning operations is “2” is associated. .
Accordingly, if any one of the cleaning conditions A11 to A14 is selected according to the cleaning condition setting information T2 shown in Table 2 and cleaning is performed, it is possible to prevent the image flow from occurring on the photosensitive drum 50.

Therefore, as shown in FIG. 7, the control unit 1 executes steps S21 to S28 instead of the steps S5 to S9 (see FIG. 3) of the cleaning control process. Note that the same processing procedure number as the processing procedure described in the above embodiment is given the same processing procedure number, and the description thereof is omitted.
First, in step S21, the control unit 1 calculates a current linear velocity ratio Idc / v that is a ratio of the measured current Idc [μA] and the linear velocity v [mm / s] of the photosensitive drum 50.
Subsequently, in steps S22 to S28, the controller 1 determines the amount of toner supplied from the developing roller 53 to the photosensitive drum 50 during cleaning by the cleaning device 55 as the current linear velocity ratio Idc / v. It is set based on the cleaning condition setting information T2. Here, the control unit 1 when executing the setting process corresponds to a toner supply amount setting unit.

Specifically, first, in step S22, the control unit 1 determines whether or not the current linear velocity ratio Idc / v calculated in step S21 is not less than 0.22 and less than 0.65.
Here, when the current linear velocity ratio Idc / v is not less than 0.22 and less than 0.65 (Yes in S22), the control unit 1 sets the cleaning condition for the cleaning in advance. The condition A11 is set (S25). On the other hand, when the current linear velocity ratio Idc / v is not 0.22 or more and less than 0.65 (No side of S22), the process proceeds to step S23.

  In step S23, the controller 1 determines whether or not the current linear velocity ratio Idc / v is 0.65 or more and less than 1.0. Here, when the current linear velocity ratio Idc / v is 0.65 or more and less than 1.0 (Yes in S23), the control unit 1 sets the cleaning condition for the cleaning in advance. The condition A12 is set (S26). On the other hand, when the current linear velocity ratio Idc / v is not 0.65 or more and less than 1.0 (No side of S23), the process proceeds to step S24.

  Further, in step S24, the control unit 1 determines whether or not the current linear velocity ratio Idc / v is 1.0 or more. Here, when the current linear velocity ratio Idc / v is 1.0 or more (Yes in S24), the control unit 1 sets the cleaning condition in the cleaning to the preset cleaning condition A13. (S27). On the other hand, when the current linear velocity ratio Idc / v is not 1.0 or more (No in S24), the control unit 1 sets the cleaning condition for the cleaning to the preset cleaning condition A14 ( S28).

Thereafter, the control unit 1 performs the cleaning according to any one of the cleaning conditions A11 to A14 set in advance in steps S21 to S28.
For example, when the current linear velocity ratio Idc / v is 1.3 (Yes in S24), the developing bias application time is 3000 [ms] based on the cleaning condition setting information T2 in Table 2 above. The cleaning condition A13 where the number of cleaning operations is “1” is set, and cleaning by the cleaning device 55 is executed.
Therefore, the discharge product adhering to the surface of the photosensitive drum 50 can be sufficiently removed, and the image flow on the photosensitive drum 50 can be prevented.

It is also conceivable that the control unit 1 sets the toner supply amount at the time of cleaning based on a preset conditional expression in the cleaning control process.
Here, FIGS. 8 and 9 show the results of experiments performed in advance in the multifunction machine X. FIG.
Specifically, experimental results 1 to 42 shown in FIGS. 8 and 9 indicate that when the current linear velocity ratio Idc / v is each value, the developing bias application time, the toner supply amount per cleaning operation, and the cleaning Cleaning is performed by the cleaning device 55 by changing the number of operations. Thereafter, the charging potential of the surface of the photosensitive drum 50 is 280 [V], the DC component Vdc of the developing bias is 160 [V], and the AC component Vpp is 1 3 shows a measurement result of the degree of image flow that occurred when test printing was performed with a printing rate of 25% (600 dpi, 1 × 1 dot) at a frequency of 3 [kV] and a frequency of 3 [kHz]. In FIGS. 8 and 9, the image flow degree “◯” indicates that the image flow is sufficiently improved up to a predetermined standard that is not problematic, and the image flow degree “Δ” is at least that level. An image stream “x” indicates that the image quality has not been improved to the predetermined standard. The predetermined standard may be appropriately changed according to the image quality required in the multifunction machine X.
Then, as shown in FIG. 9, from the distribution of the case where the degree of improvement in image flow after cleaning obtained as the experimental results 1 to 42 is “◯” or “Δ” and “×”. If the total toner supply amount is y [mg] and the current linear velocity ratio Idc [μA] / V [mm / s] is x, the image flow is generated if at least the conditional expression y ≧ 400x−200 is satisfied. It can be seen that prevention is possible.
Accordingly, if the cleaning condition is set so as to satisfy the conditional expression (y ≧ 400x−200) and the cleaning is performed, it is possible to prevent the occurrence of image flow on the photosensitive drum 50.

Therefore, as shown in FIG. 10, the control unit 1 executes steps S31 to S32 in place of the steps S5 to S9 (see FIG. 3) of the cleaning control process. Note that the same processing procedure number as the processing procedure described in the above embodiment is given the same processing procedure number, and the description thereof is omitted.
First, in step S31, the control unit 1 calculates a current linear velocity ratio Idc / v that is a ratio of the measured current Idc [μA] and the linear velocity v [mm / s] of the photosensitive drum 50.
Subsequently, in step S32, the control unit 1 sets the cleaning condition so as to satisfy y ≧ 400x−200. Specifically, as shown in FIG. 8, the total amount y of the toner supply amount may be adjusted by changing the developing bias application time, the toner supply amount for one cleaning operation, and the number of cleaning operations. . Of course, it is also possible to change the developing bias.

At this time, if the total amount y of the toner supply amount is set to the smallest value within the range satisfying the conditional expression y ≧ 400x−200, that is, y = 400x−200, the toner supply during the cleaning is performed. The discharge product can be sufficiently removed from the surface of the photosensitive drum 50 while the amount is reduced most, and the occurrence of image blur can be prevented. Of course, a certain margin may be given to the value.
If an upper limit is not set for the toner supply amount at the time of cleaning, there is a possibility that the total amount y of toner supply amount may be set abnormally large due to some abnormality. Therefore, it is desirable to set the total amount y of the toner supply amount so as to satisfy y ≧ 400x−200 in a range of, for example, 1000 [mg] or less set in advance (that is, 1000 ≧ y ≧ 400x−200). Thus, by setting the upper limit of the toner supply amount at the time of cleaning, it is possible to prevent the toner from being consumed significantly during the cleaning.

1: control unit 2: operation display unit 3: image reading unit 4: image processing unit 5: image forming unit 6: fixing device 7: temperature / humidity detection unit 50: photosensitive drum 51: charging device 511: charging roller 52: exposure Device 53: Development roller 54: Transfer roller 55: Cleaning device 551: Cleaning roller 552: Cleaning blade 553: Toner recovery unit 56: Static elimination device

Claims (8)

A charging device for charging the image carrier by rotating the charging roller while applying a voltage to a charging roller in contact with the image carrier, and an electrostatic latent image on the image carrier charged by the charging device An exposure device to be formed; a developing roller for developing an electrostatic latent image on the image carrier by supplying toner to the image carrier; and a toner supply amount preset from the developing roller to the image carrier And a cleaning control means for cleaning the surface of the image carrier by rotating at least the image carrier in a state where a predetermined cleaning member is in contact with the surface of the image carrier. An image forming apparatus comprising:
Current measuring means for measuring a current when a preset measurement voltage is applied from the charging device to the charging roller before the cleaning by the cleaning control means;
Toner supply amount setting means for setting the toner supply amount in the cleaning by the cleaning control means based on the current value measured by the current measuring means;
An image forming apparatus comprising:   The toner supply amount setting means sets the toner supply amount larger as the current value measured by the current measurement means is higher, and sets the toner supply amount smaller as the current value measured by the current measurement means is lower. The image forming apparatus according to claim 1, wherein   2. The toner supply amount setting means sets the toner supply amount in accordance with a ratio between a current value measured by the current measurement means and a linear velocity of the image carrier at the time of the measurement. The image forming apparatus according to any one of 2. Idc / v, which is the ratio between the current value Idc [μA] measured by the current measuring means and the linear velocity v [mm / s] of the image carrier, is x, and the toner supply amount is y [mg]. When,
The image forming apparatus according to claim 3, wherein the toner supply amount setting unit sets the toner supply amount so as to satisfy y ≧ 400x−200.   The image forming apparatus according to claim 4, wherein the toner supply amount setting unit sets the toner supply amount so as to satisfy y ≧ 400x−200 within a range equal to or less than a preset upper limit amount.   The toner supply amount setting means sets one or more of a developing bias application time to the developing roller, a potential difference between the developing roller and the image carrier, and the number of times of performing the cleaning operation in one cleaning. The image forming apparatus according to claim 1, wherein the toner supply amount is set. A temperature / humidity detecting means for detecting the temperature and humidity of the image forming apparatus;
7. The cleaning device according to claim 1, wherein the toner supply amount setting unit executes the cleaning on condition that the temperature and humidity detected by the temperature / humidity detection unit satisfy predetermined conditions set in advance. The image forming apparatus described in 1.   The image forming apparatus according to claim 1, wherein the image carrier is an amorphous silicon photosensitive drum.

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