JP2008309921A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can obtain a toner image of high image quality free from void by controlling a pure water contact angle that affects adhesion between toner and an image carrier, and can stabilize and extend its service life by suppressing the wear of a cleaning blade for cleaning the residual toner on the image carrier. <P>SOLUTION: The electrophotographic image forming apparatus includes: a JOB pure water contact angle acquiring data table by which the pure water contact angle of the face of the image carrier is acquired from an average print rate and transfer current value used in image formation in a JOB; a target pure water contact angle determination data table by which at least one combinations of the width of a toner band and transfer current value is obtained based on the acquired pure water contact angle in order to obtain a target pure water contact angle; and a control means. Through the JOB pure water contact angle acquiring data table and the target pure water contact angle determination data table, the control means determines the width of the toner band and the transfer current value, which correspond to the target pure water contact angle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic method, and more particularly, to prevention of text image blanking during image formation and deterioration of a cleaning blade for cleaning an image carrier.

  In the image forming apparatus disclosed in Patent Document 1, a printing area calculated by the printing area counting unit is set in advance while suppressing a reduction in copy productivity and toner consumption in order to prevent frictional damage of the cleaning blade. If it is less than the value, a toner band is created to improve the lubricity of the blade and avoid damage to the blade.

  Further, in the image forming apparatus shown in Patent Document 2, when a toner band is formed on an image carrier and lubricated, an image having a larger average particle diameter than that of a normal toner is used by changing a developing bias waveform. I am doing so. This prevents the cleaning blade from being damaged by wear.

However, Patent Document 1 and Patent Document 2 do not touch on the elimination of the appearance of a missing character as an image defect when the average printing rate decreases.
JP 2005-43333 A JP 2006-138925 A

  The present invention controls the pure water contact angle that affects the situation of the adhesion force between the toner and the image carrier to obtain a high-quality toner image that does not cause voids and to clean the residual toner on the image carrier. An object of the present invention is to provide an image forming apparatus that suppresses the wear of the cleaning blade and achieves a stable and long life.

This object is achieved by any one of the following technical means 1 to 3.
1. Developing means for creating a toner image on the image carrier using toner having a lubricant in the external additive;
Transfer means for transferring the toner image of the image carrier to a transfer member;
A transfer current detecting means for detecting a transfer current value of the transfer means;
Blade type cleaning means for removing transfer residual toner of the image carrier;
A toner band creating means for creating a toner band in a non-image area between images;
Detection means for detecting the average printing rate;
A pure water contact angle grasping data table for determining the pure water contact angle of the surface of the image carrier from the average printing rate and transfer current value during image formation in JOB;
A target pure water contact angle determination data table for determining at least one of a combination of a width of a toner band and a transfer current value for obtaining a target pure water contact angle based on the obtained pure water contact angle in the JOB. And control means,
The control means determines a toner band width and a transfer current value corresponding to a target pure water contact angle via the JOB medium pure water contact angle grasping data table and the target pure water contact angle determination data table. An image forming apparatus.
2. 2. The image forming apparatus according to claim 1, wherein the JOB medium pure water contact angle grasping data table and the target pure water contact angle determining data table are stored in a memory in the image forming apparatus.
3. The transfer current value, average printing rate, toner band width and pure water contact angle in the JOB pure water contact angle grasping data table and the target pure water contact angle determination data table are divided into a plurality of the image carrier in the axial direction. 3. The image forming apparatus according to item 1 or 2, wherein the image forming apparatus is determined for each area.

  By the image forming apparatus of the present invention, the pure water contact angle on the image carrier is ascertained from the average printing rate and the transfer current value, and there is no hollowing out corresponding to the pure water contact angle. Abrasion was suppressed, and the target pure water contact angle was obtained. Based on this, the width of the toner and the transfer current value created between the images were determined, and prevention of voids and suppression of wear of the cleaning blade were achieved.

  An example of an embodiment according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional configuration diagram showing an embodiment of an image forming apparatus of the present invention.

  This color image forming apparatus is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an endless belt-shaped intermediate transfer body unit 7, and a paper feeding / conveying means (reference numeral None) and a fixing device as the fixing means 24. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  An image forming unit 10Y that forms a yellow image includes a photosensitive drum 1Y as a first image carrier, a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, and a primary unit arranged around the photosensitive drum 1Y. A primary transfer roller 5Y as a transfer unit and a cleaning unit 6Y are provided.

  The image forming unit 10M that forms a magenta image includes a photosensitive drum 1M as a first image carrier, a charging unit 2M disposed around the photosensitive drum 1M, an exposing unit 3M, a developing unit 4M, a primary unit A primary transfer roller 5M as a transfer unit and a cleaning unit 6M are provided.

  An image forming unit 10C that forms a cyan image includes a photosensitive drum 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a primary unit arranged around the photosensitive drum 1C. A primary transfer roller 5C as a transfer unit and a cleaning unit 6C are provided.

  The image forming unit 10K that forms a black image includes a photosensitive drum 1K as a first image carrier, a charging unit 2K, an exposing unit 3K, a developing unit 4K, and a primary transfer unit arranged around the photosensitive drum 1K. Primary transfer roller 5K and cleaning means 6K.

  Developing units 4Y, 4M, 4C, and 4K, which are developing means, are yellow (Y), magenta (M), cyan (C) or charged with the same polarity as the charging polarity of the photosensitive drums 1Y, 1M, 1C, and 1K. A two-component developer (which may be a one-component developer) made of toner of each color of black (K) is accommodated. Each developing device includes, for example, developing rollers 4Y1, 4M1, 4C1, and 4K1, which are developer carriers formed of a cylindrical nonmagnetic stainless steel or aluminum material having a thickness of 0.5 to 1 mm and an outer diameter of 15 to 25 mm. Is provided.

  The developing rollers 4Y1, 4M1, 4C1, and 4K1 are kept in contact with the photosensitive drums 1Y, 1M, 1C, and 1K with a predetermined gap, for example, 100 to 1000 μm by abutting rollers (not shown). The rotation direction is 1Y, 1M, 1C, 1K and the forward or reverse direction.

  At the time of development, a photoconductive drum 1Y, 1M, 1C, 1K is applied to the developing rollers 4Y1, 4M1, 4C1, 4K1 by applying a developing bias voltage that superimposes an AC voltage on the DC voltage or DC voltage of the same polarity as the toner. Non-contact reversal development is performed on the upper exposure units 3Y, 3M, 3C, and 3K.

  Generally, so-called external additives are added to toners for the purpose of improving fluidity and cleaning properties. Among these, as a lubricant related to the present invention, for example, zinc stearate is used. Salt of aluminum, copper, magnesium, calcium, zinc oleate, salt of manganese, iron, copper, magnesium, etc., zinc of palmitic acid, salt of copper, magnesium, calcium, etc., zinc of linoleic acid, calcium, etc. And salts of higher fatty acids such as salts, zinc of ricinoleic acid, salts of calcium, and the like. In addition, a lubricant is mixed with the external additive.

  The amount of these external additives added is about 0.01 to 10% by mass with respect to the toner.

  As shown in FIG. 2, the intermediate transfer body unit 7 is wound around a plurality of rollers 71, 72, 73, 74, and is supported by a semiconductive endless belt-like endless belt-like intermediate transfer body 70 ( Hereinafter, it is referred to as an intermediate transfer belt.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred onto the intermediate transfer belt 70 rotated by the primary transfer rollers 5Y, 5M, 5C, and 5K, and the combined color image. Is formed.

  The transfer material P as a recording medium housed in the paper feed cassette 20 is fed by a paper feed means 21 and passes through a plurality of intermediate rollers 22A, 22B, 22C, 22D and a registration roller 23, and then a secondary transfer roller 5A. The color images are transferred onto the transfer material P at once.

  The transfer material P onto which the color image has been transferred is fixed by the fixing device 24, sandwiched between the paper discharge rollers 25, and placed on the paper discharge tray 26.

  The above describes the state in which the image is formed on one side of the transfer material P. However, in the case of double-sided copying, the paper discharge switching member 27 is switched, the paper guide portion 28 is opened, and the transfer material P is indicated by an arrow. It is conveyed in the direction a.

  Further, the transfer material P is transported downward by the transport mechanism 29, switched back by the paper reversing unit 30, and transported into the duplex copying paper supply unit 31 with the rear end portion of the transfer material P serving as the leading end portion. .

  The transfer material P moves the conveyance guide 32 provided in the double-sided copy paper supply unit 31 in the paper supply direction, and re-feeds the transfer material P with the paper supply rollers 33A, 33B, 33C, 33D. To the conveyance path R.

  In this manner, as described above, the transfer material P is again conveyed to the secondary transfer position, the toner image is transferred to the back surface of the transfer material P, fixed by the fixing device 24, and then discharged to the discharge tray 26. To do.

  Further, after the color image is transferred to the transfer material P by the secondary transfer roller 5A, the residual toner is removed by the cleaning unit 6A from the intermediate transfer belt 70 from which the transfer material P is separated by curvature.

  During the image forming process, the primary transfer roller 5K is always in pressure contact with the photosensitive drum 1K, and the other primary transfer rollers 5Y, 5M, and 5C correspond to the photosensitive drums 1Y, 1M, and 1C, respectively, only during color image formation. Pressure contact.

  The image forming units 10Y, 10M, 10C, and 10K are arranged in tandem in the vertical direction, and an endless belt-shaped intermediate transfer body unit 7 is arranged on the left side of the photosensitive drums 1Y, 1M, 1C, and 1K in the drawing.

  The intermediate transfer body unit 7 includes an intermediate transfer belt 70 formed of a semiconductive endless belt constituting an intermediate transfer body as a second image carrier that is wound around a plurality of rollers and is rotatably supported. Have.

  The intermediate transfer belt 70 is stretched so as to circumscribe the drive roller 73, the support rollers 71 and 72, and the secondary transfer backup roller 74, and is provided so that the rotation direction of the intermediate transfer belt 70 is clockwise.

  Further, a secondary transfer roller 5A is provided through the intermediate transfer belt 70 so as to face the secondary transfer backup roller 74, and a cleaning unit 6A for the intermediate transfer belt 70 is provided.

  Similarly, primary transfer rollers 5Y, 5M, 5C, and 5K for each color are provided to face the photoreceptors 1Y, 1M, 1C, and 1K with the intermediate transfer belt 70 interposed therebetween.

The intermediate transfer belt 70 as an intermediate transfer member is an endless belt having a volume resistance of 10 ⁶ to 10 ¹² Ω · cm. For example, polycarbonate (PC), polyimide (PI), polyamide imide (PAI), polyvinylidene fluoride (PVDF), etrafluoroethylene-ethylene copolymer (ETFE) and other resin materials, EPDM, NBR, CR, polyurethane and other rubber materials are dispersed with conductive fillers such as carbon, or ionic conductive materials. It is preferable to set the thickness to about 50 to 200 μm in the case of a resin material and about 300 to 700 μm in the case of a rubber material.

  The intermediate transfer belt 70 is driven by rotation of a driving roller 73 by a driving motor (not shown).

  The primary transfer rollers 5Y, 5M, 5C, and 5K are provided to face the photosensitive drums 1Y, 1M, 1C, and 1K with the intermediate transfer belt 70 interposed therebetween, and the intermediate transfer belt 70 and the photosensitive members 1Y, 1M, 1C, and A transfer zone is formed between 1K and 1K. Each color formed on the photosensitive drums 1Y, 1M, 1C, and 1K by applying a DC voltage having a polarity opposite to that of the toner to the primary transfer rollers 5Y, 5M, 5C, and 5K to form a transfer electric field in the transfer area. The toner image is transferred onto the intermediate transfer belt 70.

The primary transfer rollers 5Y, 5M, 5C, and 5K, which are the first transfer means for each color, are made of polyurethane, EPDM, silicone on the peripheral surface of a conductive metal core (not shown) such as stainless steel having an outer diameter of 8 mm, for example. In a solid state or foamed sponge state in which the volume resistance is about 10 ⁵ to 10 ⁹ Ω · cm, by dispersing a conductive filler such as carbon or containing an ionic conductive material in a rubber material such as It is formed by covering a semiconductive elastic rubber (not shown) having a thickness of 5 mm and a rubber hardness of about 20 to 70 ° (Asker-C).

  The secondary transfer roller 5A for transferring to the surface of the transfer material P is provided to face the secondary transfer backup roller 74 that is grounded with the intermediate transfer belt 70 interposed therebetween, and a DC voltage having a polarity opposite to that of the toner is supplied from a DC power source (FIG. The superimposed toner image carried on the intermediate transfer belt 70 is transferred onto the surface of the transfer material P via the secondary transfer roller 5A.

The secondary transfer roller 5A, which is a second transfer means for retransferring the color toner image on the intermediate transfer belt 70 onto the transfer material, has a circumference of a conductive core bar (not shown) such as stainless steel having an outer diameter of 8 mm. On the surface, a conductive filler such as carbon is dispersed in a rubber material such as polyurethane, EPDM, or silicone, or an ionic conductive material is contained, so that the volume resistance is about 10 ⁵ to 10 ⁹ Ω · cm. In a solid state or a foamed sponge state, it is formed by coating a semiconductive elastic rubber (not shown) having a thickness of 5 mm and a rubber hardness of about 20 to 70 ° (Asker-C).

  Unlike the primary transfer rollers 5Y, 5M, 5C, and 5K, the secondary transfer roller 5A comes into contact with toner, and therefore, the surface may be coated with a material having good releasability such as a semiconductive fluororesin or urethane resin. The secondary transfer backup roller 74 is formed by dispersing a conductive filler such as carbon in a rubber or resin material such as polyurethane, EPDM, or silicone on the peripheral surface of a conductive core bar (not shown) such as stainless steel, It is formed by coating a semiconductive material containing a conductive material with a thickness of about 0.05 to 0.5 mm.

  The cleaning unit 6A of the intermediate transfer belt 70, which is an intermediate transfer body cleaning unit, is provided opposite to the driven roller 6A2 with the intermediate transfer belt 70 interposed therebetween in FIG. 2, and a cleaning blade 6A1 for cleaning the intermediate transfer belt 70, A blade holder 6A3 for holding the cleaning blade 6A1 and a pressing spring 6A4 for pressing the blade holder 6A3 and pressing the cleaning blade 6A1 against the intermediate transfer belt 70 are configured.

  With the rear end portion (root portion) held by the blade holder 6A3 by the pressing of the pressing spring 6A4, the load is applied with the front end portion of the cleaning blade 6A1 directed in the direction opposite to the rotation direction of the intermediate transfer belt 70 (counter direction). The intermediate transfer belt 70 is brought into contact with the belt.

  Further, as shown in FIG. 3, the cleaning units 6Y, 6M, 6C, and 6K of the image forming units 10Y, 10M, 10C, and 10K are provided to face the photosensitive drums 1Y, 1M, 1C, and 1K. Then, cleaning blades 6Y1, 6M1, 6C1, 6K1 for cleaning the respective photosensitive drums, blade holders 6Y3, 6M3, 6C3, 6K3 for holding the cleaning blades 6Y1, 6M1, 6C1, 6K1, and the blade holders 6Y3, 6M3, 6K3, It comprises springs 6Y4, 6M4, 6C4, and 6K4 that urge the 6C3 and 6K3 against the photosensitive drums.

  The leading ends of the cleaning blades 6Y1, 6M1, 6C1, and 6K1 with the rear ends (base portions) held by the blade holders 6Y3, 6M3, 6C3, and 6K3 by the biasing springs 6Y4, 6M4, 6C4, and 6K4 Is brought into contact with the photosensitive drums 1Y, 1M, 1C, and 1K in a state where a load is applied in the direction opposite to the rotation direction of the photosensitive drums 1Y, 1M, 1C, and 1K (counter direction).

  The cleaning blades 6A1, 6Y1, 6M1, 6C1, and 6K1 are made of rubber elastic material, and urethane rubber, silicon rubber, fluorine rubber, chloropyrene rubber, butadiene rubber, and the like are known as the material. Of these, urethane rubber is particularly preferred because of its excellent wear characteristics compared to other rubbers.

  The photosensitive drums 1Y, 1M, 1C, 1K and the intermediate transfer belt 70 are left on the peripheral surface of the intermediate transfer belt 70 by cleaning blades 6Y1, 6M1, 6C1, 6K1, and 6A1 that can come into contact with and release from the intermediate transfer belt 70. The transferred toner is cleaned.

  This cleaning blade is obtained by adhering a plate-like urethane rubber having a thickness of 1 to 3 mm and a JIS-A hardness of 60 to 80 ° on a sheet metal holder so that the free length becomes about 5 to 12 mm. It is in contact with the photosensitive drums 1Y, 1M, 1C, and 1K and the intermediate transfer belt 70 at about ˜490 mN.

  The blade tip may be coated with fluorine to prevent the cleaning blades 6Y1, 6M1, 6C1, 6K1, and 6A1 from rolling up, or conductive urethane rubber may be used so that the other side is not charged.

  Next, the image forming process will be described with reference to FIG.

  As the image recording is started, the photosensitive drum 1Y of the yellow (Y) image forming unit 10Y is rotated counterclockwise as indicated by the arrow in FIG. 1 by starting a driving motor (not shown) of the photosensitive drum 1Y. At the same time, application of a potential to the Y photosensitive drum 1Y is started by the charging action of the Y charging portion 2Y.

  After the Y photosensitive drum 1Y is applied with an electric potential, the Y exposure means 3Y starts to write an image using an electric signal corresponding to the first color signal, that is, the Y image data, and the surface of the Y photosensitive drum 1Y. An electrostatic latent image corresponding to the Y image of the original image is formed.

  The latent image is reversely developed in a contact or non-contact state by the developing roller 4Y1 of the Y developing means 4Y, and yellow (Y) toner is formed on the photosensitive drum 1Y according to the rotation of the Y photosensitive drum 1Y. An image is formed.

  By counting this electrical signal, the printing area for the Y image is detected and the average printing rate is calculated.

  The Y toner image formed on the Y photosensitive drum 1Y by the above image forming process is intermediated by the Y primary transfer roller 5Y serving as the first transfer means in the Y transfer area (not indicated). The image is transferred onto the transfer belt 70.

  Next, the image is synchronized with the Y toner image on the intermediate transfer belt 70, and a potential is applied by the charging action of the M charging means 2M by the magenta (M) image forming unit 10M. The image is written by the electrical signal corresponding to the color signal of M, that is, the M image data.

  By counting this electric signal, the printing area for the M image is detected and the average printing rate is calculated.

  Subsequently, the M toner image formed on the M photosensitive drum 1M by the contact or non-contact reversal development of the M developing means 4M by the developing roller 4M1 is transferred to the primary transfer of M in the M transfer area (not indicated). An M toner image is superimposed on the Y toner image by the roller 5M.

  By a similar process, the Y and M superimposed toner images are synchronized, and the C image by the third color signal formed on the C photosensitive drum 1C by the cyan (C) image forming unit 10C. A C toner image corresponding to the data is formed. The toner image is formed so as to be superimposed on the Y and M toner images by the C primary transfer roller 5C in the C transfer region (not indicated).

  By counting the electrical signal which is the third color signal, the print area for the C image is detected and the average print rate is calculated.

  Further, K image data based on the fourth color signal, which is synchronized with the superimposed toner images of Y, M, and C and is formed on the K photosensitive drum 1K by the black (K) image forming unit 10K. A K toner image corresponding to is formed. Then, the toner image is formed on the intermediate transfer belt 70 on the intermediate transfer belt 70 by being superposed on the Y, M, and C toner images by the K primary transfer roller 5K in the K transfer region (no sign). A superimposed color toner image of M, C, and K is formed.

  By counting the electric signal which is the fourth color signal, the printing area for the K image is detected and the average printing rate is calculated.

  Further, the high voltage applied to each primary transfer roller 5Y, 5M, 5C, and 5K as the transfer means is controlled at a constant current, and the transfer current value is shown in FIG. 3 as the transfer current detection means 5Y1, 5M1, 5C1, 5K1. Detected by.

  The transfer residual toner remaining on the peripheral surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K for each color after transfer is the photosensitive drums 1Y, 1M, and 1C of the cleaning units 6Y, 6M, 6C, and 6K for the respective colors. The cleaning blade (see FIG. 2) 6Y1, 6M1, 6C1, and 6K1 constituting the cleaning member in contact with 1K is rubbed and cleaned.

  In synchronization with the formation of the superimposed color toner image on the intermediate transfer belt 70, the transfer material P separated and conveyed one by one from the paper feed cassette 20 as transfer material storage means is a timing roller 23 as transfer material feeding means. The intermediate transfer belt 70 is transferred onto the intermediate transfer belt 70 by the secondary transfer roller 5A, which is conveyed to the transfer area (no sign) of the secondary transfer roller 5A, which is the second transfer means, and to which a DC voltage having the opposite polarity to the toner is applied. The superimposed color toner images are collectively retransferred onto the transfer material P.

  When a toner band image to be described later is formed, the toner band image is transferred to the secondary transfer roller 5A, but is removed by the cleaning means 5B provided on the secondary transfer roller 5A.

  The transfer material P onto which the color toner image has been transferred is neutralized by a neutralization electrode (not shown) that is a separation means, and is conveyed to the fixing device 24. The transfer material P is applied with heat and pressure between the fixing roller 24A and the pressure roller 24B so that the toner image on the transfer material P is fixed, and then is discharged to the discharge tray 26 by the discharge roller 25. Discharged.

  The transfer residual toner remaining on the peripheral surface of the intermediate transfer belt 70 after the transfer is cleaned by the cleaning unit 6A. That is, the intermediate transfer belt 70 is rubbed by the cleaning blade 6A1, which is a cleaning member provided opposite to the cleaning counter roller 6A2 with the intermediate transfer belt 70 therebetween, and the residual toner is removed and cleaned.

  In the image forming apparatus, when the image formation is repeated and the transfer rate is lowered, an image defect called hollowing out occurs, and conversely, when the transfer rate is raised, the cleaning blade is sometimes worn excessively, and the image is lost. There has been a problem that the cleaning performance of the photosensitive member surface as a carrier is lowered.

  In order to solve such a problem in the present invention, it is created between data obtained by measuring the contact angle of pure water on the surface of a photoreceptor as an image carrier, a transfer current value at that time, an average printing rate, and further between images. The relationship between the width of the toner band and the pure water contact angle obtained by the combination was examined. Thus, a data table was obtained by experimentally examining data corresponding to a range in which character omission does not occur and in which no cleaning blade stagnation or wear occurs.

  That is, the pure water contact angle grasping data table for JOB obtained by experimentally collecting the pure water contact angle in JOB from the average printing rate and transfer current value during image creation in JOB, and the pure water contact angle in JOB obtained from the table. Corresponding target pure water contact angle determination data tables were prepared so as to obtain target pure water contact angles in which hollow holes and wear of the cleaning blade were suppressed. A necessary toner band width and transfer current value can be obtained from the target pure water contact angle determination data table.

  Here, the surface of the photosensitive drum is in a state where a lubricant mixed with the additive in the toner is attached. As shown in the schematic diagrams of FIGS. 4A and 4B, the pure water contact angle is determined when a drop of pure water is dropped on a contact surface (here, a photosensitive drum surface as an image carrier) to be measured. The tangent drawn to the water droplet from the intersection of the contact surface and the water droplet surface refers to an angle Θ at which the water droplet is stretched with respect to the contact surface. When this angle Θ is large as shown in 4 (b), the wettability is poor, and when it is small as shown in 4 (a), the wettability is improved. That is, the quality of toner carrying is determined.

  The transfer current value is a value when constant current control is performed to obtain a high voltage transfer voltage of 0.2 to 8.0 kV.

  Now, when the toner band image is formed on the photosensitive drum with the additive containing the lubricant applied around the toner particles, the toner band image is transferred to the intermediate transfer member by the transfer means. Is left and adhered on the photosensitive drum as the transfer current value changes. As the adhesion amount increases, the pure water contact angle on the surface of the photosensitive drum changes so as to increase transfer. However, when it becomes too large, the wear of the cleaning blade increases.

  That is, when the pure water contact angle is small and the adhesiveness is high, the transferability is deteriorated, and the toner image undergoing image formation is referred to as being void and no image is formed. Then, as shown in the graph of FIG. 5 (a), when the pure water contact angle is increased to reach the best state with no voids, the state is maintained even if the pure water contact angle is increased further. I understood. Conversely, when printing 50,000 sheets of A4 size, for example, with a pure water contact angle that is too higher than the target pure water contact angle, as shown in the graph of FIG. It was found that even if the thickness is good, the wear of the cleaning blade increases, and the cleaning performance of the photosensitive member surface as the image carrier is lowered.

  In other words, printing at the target pure water contact angle indicates that image formation can be stably maintained in a state where there is no void and the cleaning blade has low wear and high cleaning performance.

  In the graph of FIG. 5A, the evaluation of the sensitivity of the blank rank is as follows: ◎: A4 size paper with no blank at all; Is a state where one of the hollows is small but can be easily recognized, and x is a state where there are many hollows and is not practical. As a guideline for the evaluation of the cleaning blade, the cleaning performance is good if the wear is 12 μm or less, and if it exceeds about 25 μm, the cleaning performance deteriorates.

  In the image forming apparatus, for example, it is understood that the pure water contact angle of the surface of the photoreceptor as the image carrier at that time is determined by the average printing rate and transfer current value during image creation. The average printing rate and transfer current value are determined by measuring each area divided in the rotation axis direction of the photosensitive drum.

  A table 1 shown in FIG. 6 is a pure water contact angle grasping data table in JOB that summarizes the results in the job (current state) in a table format.

  In this way, even in a region where the pure water contact angle in the JOB is low, the transfer current value and the width of the toner band created between images are determined, and accordingly the pure water contact angle is corrected to be high, thereby forming an image. It has been found that there is no occurrence of the above-described defect in the toner image inside, and the pure water contact angle at point G shown in FIGS. 5A and 5B, which is a region where wear of the cleaning blade is suppressed, can be achieved. . It can be said that the pure water contact angle at the point G is the lowest pure water contact angle among the pure water contact angles having the best hollow-out rank.

  In order to obtain the corrected pure water contact angle of the target region, which is the so-called pure water contact angle at point G, the target pure water contact angles obtained in Table 1 are summarized as shown in FIG. It is a table group of Table 2 as a water contact angle determination data table. The pure water contact angle in the JOB obtained from the table 1 of FIG. 6 is selected from the table group of the table 2 shown in FIG. Thus, for example, the selected table 2 (A) shown in FIG. 8 is selected from the plurality of target pure water contact angle data table groups, and the target pure water contact angle and the corresponding toner band width are selected. The transfer current value can be selected.

  For example, in Table 2, an image area area with an average printing ratio of 5% and a non-image area area with an average printing ratio of 0% are selected, and the transfer current value is -40 μA. 103 ° is selected in the area area and 87 ° is selected in the non-image area area. Then, the above-described toner band width and transfer current value in the image area can be selected using the table of (103 °) shown in Table 2 (A) of FIG.

  Similarly, the above-described toner band width and transfer current value in the non-image area can be selected using the (87 °) table shown in Table 2 (B) of FIG.

  In the selection, when the priority is given to the stabilization patch image, the toner band width is fixed with a priority, for example, 2 mm, and when the toner consumption is prioritized, the toner band width is maximized or minimized. Thus, the transfer current value is made to follow these toner band widths.

  The control process is shown by a flow in FIG.

  Star is input at St1, JOB is input at St2, JOB is formed by the average average printing rate and transfer current value at St3, and is divided into area 1 of the image area and area 2 of the non-image area at St4. Then, the current average printing rate and transfer current value are detected, and the current pure water contact angles are calculated on a plurality of areas divided in the axial direction in St5 by comparing them with a table 1 that is built in and stored. The target contact angle determination data table is selected by selecting the courses (A) and (B) in each area depending on whether the input is performed so that the toner consumption is prioritized in St6 or the stabilization of the patch image is prioritized. The target pure water contact angle, transfer current value, and toner band width are determined by 2 (A) and 2 (B), respectively, a predetermined number of images are formed and printed at St7, and a series of processes is repeated.

  This flow is controlled as shown in the following control block diagram of FIG.

  An image signal that the image exposure unit exposes to the surface of the photoreceptor as an image carrier is measured, and an average printing rate is obtained. The transfer current value is obtained by the primary transfer means. In addition, the toner band width is fixed to a predetermined value and is input through the operation unit depending on whether the input is performed so as to prioritize the toner consumption amount or the patch image stabilization is prioritized.

  On the other hand, Table 1 and Table 2 are stored in the image forming apparatus as a pure water contact angle gripping data table and a target pure water contact angle determination data table in JOB, respectively.

The measurement data and input data are collated with the tables 1 and 2, and controlled by the control means 101 so as to form a target image with no voids. Wear is also suppressed.
Example 1
This is a case where toner consumption is controlled with priority.

An average printing rate of 5%, a transfer current value of −40 μA, A4 size, 500 sheets were printed.
The current pure water contact angle from the average printing rate and the detected transfer current value is 103 ° from Table 1.

  The pure water contact angle 103 ° obtained from Table 1 is applied to Table 2 (A) corresponding to the table of 103 ° in Table 2, and the toner band width and transfer current corresponding to the target pure water contact angle 105 ° are applied. Determine the value. At this time, since priority is given to the consumption of the toner, a toner band width of 8 mm is input and collated with Table 2 (A), and −50 μA is selected and determined.

  Under these conditions, a toner band was prepared every 10 sheets, and 50,000 sheets of A4 size were printed at an average printing rate of 5% and a transfer current value of −40 μA.

As a result, the abrasion amount of the cleaning blade was 10 μm, and no defective cleaning occurred, and there was no occurrence of missing 6 pt characters.
Example 2
This is a case where the stabilization batch is controlled with priority.

An average printing rate of 5%, a transfer current value of −40 μA, A4 size, 500 sheets were printed.
The current pure water contact angle from the average printing rate and the detected transfer current value is 103 ° from Table 1.

  The pure water contact angle 103 ° obtained from Table 1 is applied to Table 2 (A) corresponding to the table of 103 ° in Table 2, and the toner band width and transfer current corresponding to the target pure water contact angle 105 ° are applied. Determine the value. At this time, since the stabilization batch is prioritized, it is determined by giving priority to the toner band width of 2 mm, and the transfer current value of −60 μA−65 μA is determined correspondingly.

  Under these conditions, a toner band was prepared every 10 sheets, and 50,000 sheets of A4 size were printed at an average printing rate of 5% and a transfer current value of −40 μA.

As a result, the abrasion amount of the cleaning blade was 10 μm, and no defective cleaning occurred, and there was no occurrence of missing 6 pt characters.
Example 3
An average printing rate of 5%, a transfer current value of −40 μA, A4S size (vertically long), and 500 sheets were printed. Since the A4 size is sent vertically, it is divided into two areas of an image area and a non-image area in the axial direction of the photosensitive drum.

  In the image area, the current pure water contact angle from the average printing rate of 5% and the detected transfer current value of −40 μA is 103 ° from Table 1.

  In the non-image area, the current pure water contact angle from the average printing rate of 0% and the detected transfer current value of −40 μA is 87 ° from Table 1.

  The pure water contact angle 103 ° obtained from Table 1 is applied to Table 2 (A) corresponding to the table of 103 ° in Table 2, and the toner band width and transfer current corresponding to the target pure water contact angle 105 ° are applied. Determine the value. In this case, if the transfer current value is given priority and input, the transfer current value of −65 μA is determined, and correspondingly, the toner band width is 2 mm in the image area 1 and 12 mm in the non-image area 2. decide.

  Under these conditions, a toner band was prepared for every 10 sheets, and 50,000 sheets of A4S size (vertically long) were printed at an average printing rate of 5% and a transfer current value of −40 μA.

As a result, the amount of wear of the cleaning blade was 10 μm, no cleaning failure occurred, and there was no occurrence of missing 6 pt characters.
Comparative Example 1
Without creating a toner band, a target pure water contact angle of 105 ° was obtained with a pure water contact angle of 103 ° in JOB at an average printing rate of 5% and a transfer current value of −40 μA. In this state, a transfer current value of −50 μA and a pure water contact angle of 103 ° (that is, lower than the target contact angle of 105 °) were printed on 50,000 sheets of A4 size. As a result, many missing 6pt characters occurred.
Comparative Example 2
With an average printing rate of 5% and a transfer current value of −40 μA, a pure water contact angle in JOB of 103 ° was obtained. On the other hand, a target pure water contact angle determination data table of 103 ° had a band width of 10 mm, a transfer current value of −50 μA, A pure water contact angle of 105 ° was not selected, and a band width of 10 mm, a transfer current value of −55 μA, and a pure water contact angle of 106 ° were selected, and A4 size 50,000 sheets were printed.

  As a result, no void occurred, but the amount of wear of the cleaning blade was about 25 μm, and a cleaning failure occurred.

1 is a cross-sectional configuration diagram illustrating an embodiment of an image forming apparatus. FIG. 2 is a schematic configuration diagram illustrating an intermediate transfer body unit. FIG. 3 is a partially enlarged configuration diagram around a photosensitive drum. It is a schematic diagram which shows a pure water contact angle. (A) is a graph which shows the sensitivity evaluation of a hollow rank with respect to a pure water contact angle, (b) is a graph which shows the relationship of the abrasion of a cleaning blade with respect to a pure water contact angle. It is Table 1 which shows an example of the pure water contact angle grasping | ascertainment data table in JOB used for this invention. It is Table 2 which shows the table group of the target pure water contact angle determination data table used for this invention. It is a figure of Table 2 (A) shown as an example obtained from Table 2 which is a table group of the target pure water contact angle determination data table used for this invention. It is a figure of Table 2 (B) shown as an example obtained from Table 2 which is a table group of the target pure water contact angle determination data table used for this invention. It is a flowchart which shows the process of control of this invention. 3 is a control block diagram of the image forming apparatus of the present invention. FIG.

Explanation of symbols

1Y, 1M, 1C, 1K Photosensitive drums 3Y, 3M, 3C, 3K Image exposing means 4Y, 4M, 4C, 4K Developing means 5Y, 5M, 5C, 5K Transfer means 6Y, 6M, 6C, 6K Cleaning means 6Y1, 6M1 , 6C1, 6K1 Cleaning blade 7 Intermediate transfer member unit 7
70 Intermediate transfer belt 101 Control means 105 Operation unit

Claims (3)

Developing means for creating a toner image on the image carrier using toner having a lubricant in the external additive;
Transfer means for transferring the toner image of the image carrier to a transfer member;
A transfer current detecting means for detecting a transfer current value of the transfer means;
Blade type cleaning means for removing transfer residual toner of the image carrier;
A toner band creating means for creating a toner band in a non-image area between images;
Detection means for detecting the average printing rate;
A pure water contact angle grasping data table for determining the pure water contact angle of the surface of the image carrier from the average printing rate and transfer current value during image formation in JOB;
A target pure water contact angle determination data table for determining at least one of a combination of a width of a toner band and a transfer current value for obtaining a target pure water contact angle based on the obtained pure water contact angle in the JOB. And control means,
The control means determines a toner band width and a transfer current value corresponding to a target pure water contact angle through the JOB pure water contact angle grasping data table and the target pure water contact angle determination data table. An image forming apparatus. The image forming apparatus according to claim 1, wherein the JOB medium pure water contact angle grasping data table and the target pure water contact angle determining data table are stored in a memory in the image forming apparatus. The transfer current value, average printing rate, toner band width and pure water contact angle in the JOB pure water contact angle grasp data table and target pure water contact angle determination data table are divided into a plurality of the image carrier in the axial direction. The image forming apparatus according to claim 1, wherein the image forming apparatus is determined for each area.

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