JP2009015230A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus capable of obtaining a good image by ensuring uniformity of the amount of lubricant applied to the surface of an image carrier irrespective of the amount of toner consumed by the forced toner consumption operation.
Development means for developing an electrostatic latent image formed on the surface of an image carrier with toner, and lubrication for supplying lubricant to the surface of the image carrier by rotating in contact with the surface of the image carrier In the image forming apparatus having the lubricant supply means 15 for performing the agent application operation, the print pixel count means 41 that counts the number of print pixels that are the pixels to which the toner should be attached from the input image data, and the print pixel count means The difference between the pixel count number obtained by the above and the predetermined pixel number is obtained, and if the value is small, the forced toner consumption is calculated according to the difference, and the toner that forcibly consumes the toner by operating the developing means 30 When the forced consumption operation is performed, the control unit 24 operates the lubricant supply unit 15 to perform the lubricant application operation.
[Selection] Figure 1

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, a copying machine having a lubricant supply means, and a multifunction machine in which these are integrated.

  2. Description of the Related Art Conventionally, an image forming apparatus configured as a copying machine or a combination machine thereof includes an image carrier on which a toner image is formed on a surface while being rotated, and a transfer device that transfers the toner image to a transfer material. The image bearing member has a cleaning member that removes residual toner adhering to the surface of the image carrier after the toner image is transferred and cleans the surface of the image carrier, and a brush that is in contact with the surface of the image carrier, and is rotated while being driven. A configuration including a lubricant application member that supplies a lubricant to the body surface is known as a patent document.

  In this type of image forming apparatus, since the lubricant is applied to the surface of the image carrier, the coefficient of friction with respect to the toner on the surface of the image carrier can be reduced, whereby the toner image formed on the surface of the image carrier can be reduced. Occurrence of transfer failure when transferring to a transfer material can be suppressed, and the image quality of the transferred toner image can be improved. In particular, it is possible to suppress the occurrence of a character part dropout phenomenon in which a part of a character image is lacking in a worm-eaten shape and to improve the image quality. Further, it has the effect of preventing toner filming on the surface of the image carrier and suppressing the abrasion of the surface layer, and contributes to extending the life of the image carrier.

  However, if the lubricant is supplied to the surface of the image carrier, the coefficient of friction with respect to the toner on the surface decreases, so if the amount of lubricant adhering to the surface of the image carrier becomes uneven, the unevenness of the amount of adhesion causes the image carrier. In some cases, the toner image formed on the body surface has a non-uniform toner adhesion amount, resulting in uneven density in the toner image, and the formed image quality may deteriorate. That is, the toner adhesion amount decreases on the surface portion of the image carrier where the lubricant adhesion amount is large, and conversely, a large amount of toner adheres to the portion where the lubricant adhesion amount is small, thereby causing uneven density in the toner image. Will occur. In particular, uneven density tends to occur in a low-density toner image.

  Further, in the case of one-component contact development, if the static friction coefficient of the image carrier is too low, image omission (a part of dots, characters, lines, etc. will be lost) in the image formed on the image carrier. . In the one-component contact development, a thin toner layer is formed on the developing roller, brought into contact with the image carrier, and the toner on the developing roller is moved to the surface of the image carrier by an electric field or an adhesion force to the surface of the image carrier. In the case of contact development, since the developing roller is brought into direct contact with the image carrier, if the coefficient of static friction on the surface of the image carrier is made too low, the toner image formed on the image carrier is easily scraped off by the developing roller. turn into.

  As a method of controlling such a lack of lubricant application or excessive application during a normal job, Patent Document 2 discloses an image forming apparatus that supplies a lubricant while bringing the brush of the lubricant application member into contact with the surface of the photoreceptor. Discloses a technique that eliminates uneven application of lubricant by a simple configuration and prevents the occurrence of uneven image density. Patent Document 3 prevents filming and always supplies a stable lubricant. Although a technique is disclosed, it is not sufficient for solving the conventional problems. In recent years, Patent Documents 4 and 5 disclose modes in which an operation for forcibly consuming toner is taken as a countermeasure against toner deterioration with time (such as a fogging image countermeasure) due to a low image area output.

JP 56-154778 A Japanese Patent Laid-Open No. 10-260614 Japanese Patent Laid-Open No. 7-334058 JP 2005-92156 A Japanese Patent No. 3029648

  When the toner as described in Patent Documents 4 and 5 is forcibly consumed, if the image area of the document is smaller than a specified value (minimum image area for maintaining a good image), for example, the specified value is 5%. Then, in the case of a 0.5% original, 4.5% of toner is forcibly consumed. In addition, if forced consumption is performed for each print, the print speed is reduced (productivity is reduced). Generally, several sheets are collected at the end of the job, and the toner has a large image area such as a solid image or a 50% image. It is consumed.

  The lubricant applied on the image carrier is peeled off mainly by the toner that comes into contact therewith, and is transferred or cleaned together with the toner. Accordingly, the amount of lubricant adhering on the image carrier is different after the output image, the white solid portion (blank portion) and the black solid portion (toner adhering portion).

  In the case of forced toner consumption, since all the developed toner is collected for cleaning, a large amount of toner is present in the cleaning portion for a while, and more lubricant is peeled off from the photoreceptor than when the paper is passed (cleaning). If there is a brush, the toner is present in the nip for a while and the lubricant is stripped off). For this reason, when the toner is forcibly consumed, there is a problem in that the amount of lubricant applied to the image carrier is extremely reduced and the amount of adhesion is uneven.

  Therefore, in the present invention, a uniform image of the lubricant applied to the surface of the image carrier is ensured by a simple and low-cost method, regardless of the amount of toner consumed by the forced toner consumption operation, and a good image is obtained. An object of the present invention is to provide an image forming apparatus capable of obtaining the above.

  In order to achieve the above object, in the image forming apparatus according to the first aspect, when the forced toner consumption operation is performed, the lubricant application operation for applying the lubricant to the surface of the image carrier is also performed.

  That is, developing means for developing the electrostatic latent image formed on the image carrier surface with toner, and lubricant application for applying a lubricant to the image carrier surface by rotating in contact with the image carrier surface In an image forming apparatus having a lubricant supply means for performing an operation, a print pixel count means for counting the number of print pixels, which are pixels to which toner is attached, from the input image data, and a pixel count number by the print pixel count means On the other hand, the difference is obtained in comparison with a predetermined number of pixels, and if the value is small, the forced toner consumption is calculated according to the difference, and the forced toner consumption operation for operating the developing unit to forcibly consume the toner is performed. In this case, the apparatus has a control means for operating the lubricant supply means to perform the lubricant application operation.

  3. The image forming apparatus according to claim 2, further comprising a cleaning member that removes residual toner on the image carrier, and the control unit operates the lubricant supply unit after the forced toner consumption operation is completed to It is characterized in that a coating operation is executed.

  The image forming apparatus according to claim 3 is characterized in that the lubricant application amount by the lubricant application operation is changed in accordance with the forced consumption amount of toner by the developing means.

  The image forming apparatus according to claim 4 is characterized in that the lubricant application amount is changed by changing the operating time of the lubricant supply means.

The image forming apparatus according to claim 5 is characterized in that at least the image carrier is rotated at least once during the lubricant application operation. The uniformity of lubricant adhesion amount on the surface of the image carrier is improved. The image forming apparatus according to claim 6, wherein the lubricant is made of a metal stearate.

  According to the present invention, it is possible to reduce the amount of lubricant adhering to the image carrier and uneven coating due to the difference in the amount of toner supplied to the image carrier due to forced toner consumption. Therefore, it is possible to provide an image forming apparatus which can be controlled to have a good image without abnormal images such as density unevenness and transfer failure.

  In particular, when the forced toner consumption operation is performed, the lubricant application operation for applying the lubricant to the surface of the image carrier is also performed, so that the lubricant taken away from the photoreceptor by the forced consumption toner can be replenished. It is possible to prevent unevenness of the lubricant adhesion amount.

  When a cleaning member that removes residual toner on the image carrier is provided, a large amount of toner is supplied to the cleaning member during forced toner consumption, so that the efficiency of lubricant application decreases. By performing the operation, it is possible to efficiently apply the lubricant, and thus it is possible to prevent unevenness in the amount of lubricant attached.

  By changing the amount of lubricant applied according to the amount of forced toner consumption, when the amount of forced consumption is large, the lubricant application unevenness can be prevented by increasing the time for applying the lubricant, and excessive application of the lubricant. Can be prevented. Further, when the forced toner consumption is small, the application time can be shortened and the adjustment time can be shortened.

  By rotating the image carrier at least once or more during the lubricant application operation, the uniformity of the amount of lubricant attached to the surface of the image carrier is improved. Therefore, the amount of lubricant attached should always be controlled to an optimum and stable state. Therefore, it is possible to provide an image forming apparatus that can obtain a good image without abnormal images such as density unevenness and transfer failure.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of a color image forming apparatus according to an embodiment of the present invention. In FIG. 1, a photosensitive member that carries an electrostatic latent image formed by laser writing and a developed toner image is a photosensitive belt 1 as a flexible belt-like image carrier in this apparatus. . The photosensitive belt 1 is installed between the rotation rollers 2, 31 and 32, and is rotated (sub-scanned) in the direction of arrow A (clockwise) in the drawing by the rotation drive of the rotation roller 2, and the belt surface is It is configured to be an image forming surface.

  As means for forming an electrostatic latent image and a toner image on the photosensitive belt 1, a charging charger 4 for uniformly charging the surface of the photosensitive belt 1, a laser writing unit 5, color developing devices 6a, 6b, 6c, 6d. The color developing devices 6a, 6b, 6c, and 6d are composed of developing units for magenta, cyan, yellow, and black, which are color constituent colors. The developing unit used here includes means for developing with a one-component developer (toner).

  The image forming apparatus according to this embodiment includes the intermediate transfer belt 10 because the image on the photosensitive belt 1 is formed on the transfer paper 17a via the intermediate transfer member. The intermediate transfer belt 10 is installed between the rotation rollers 11 and 12, and is rotated in the arrow B direction (counterclockwise direction) in the drawing by the rotation driving of the rotation roller 11. The photosensitive belt 1 and the intermediate transfer belt 10 are in contact with each other at a portion where the rotation roller 32 of the photosensitive belt 1 is provided. On the intermediate transfer belt 10 side of the contact portion, a conductive bias roller 13 is in contact with the back surface of the intermediate transfer belt 10 under predetermined conditions. Constituent elements related to transfer paper processing include a paper feed unit (paper feed cassette) 17, a paper feed roller 18, transport roller pairs 19 a and 19 b, registration roller pairs 20 a and 20 b, and an intermediate transfer belt 10. A transfer roller 14 for transferring the image, a fixing device 80, a pair of paper discharge rollers 81a and 81b, and a paper discharge stack portion 82.

  Here, an image forming operation of the color image forming apparatus will be described. In FIG. 1, a photosensitive belt 1 as a flexible belt-shaped image carrier is uniformly charged by a charging charger 4, and then light emission is controlled by a laser writing unit 5 based on image information. Upon receiving the scanning exposure of the laser, an electrostatic latent image is formed on the surface. Image information used in one step of scanning exposure while rotating the photosensitive belt 1 to form an electrostatic latent image is monochromatic image information obtained by separating a desired full-color image into magenta, cyan, yellow, and black color information. Based on this information, the emission of the semiconductor laser is controlled. The generated laser beam is scanned and optical path adjusted by the laser writing unit 5 and output as writing beam light L. The electrostatic latent image formed based on the single color image information is converted into magenta (M), cyan (C), yellow (Y), and black (Bk) toners by the color developing devices 6a, 6b, 6c, and 6d. Each color image is developed, and each color image is sequentially formed on the photosensitive belt 1. Each single color image of M, C, Y, Bk formed on the photosensitive belt 1 rotating in the direction of arrow A in FIG. 1 is rotated in the direction of arrow B in FIG. 1 in synchronization with the photosensitive belt 1. The intermediate transfer belt 10 is sequentially overlaid and transferred by the action of a predetermined transfer bias applied to the bias roller 13. The images of M, C, Y, and Bk superimposed on the intermediate transfer belt 10 pass from a paper feed table (paper feed cassette) 17 through a paper feed roller 18, transport roller pairs 19a and 19b, and resist roller pairs 20a and 20b. The transfer roller 14 collectively transfers the transfer paper 17a conveyed to the transfer unit. After the transfer is completed, the transfer paper 17a is fixed by the fixing device 80 to complete a full-color image, and the print image is discharged to the paper discharge stack section 82 through the paper discharge roller pair 81a and 81b.

  Note that the toner on the photosensitive belt 1 is cleaned as the final step of image formation on the photosensitive belt 1 in FIG. For this purpose, a cleaning brush 15 a is provided as a cleaning member of the cleaning unit 15 that is always in contact with the photosensitive belt 1. Similarly, the intermediate transfer belt 10 is also provided with a cleaning device 16. The cleaning brush 16a serving as a cleaning member of the cleaning device 16 is held at a position separated from the surface of the intermediate transfer belt 10 during the image forming operation, and after the formed image is transferred onto the transfer paper 17a, the surface of the intermediate transfer belt 10 is transferred. Abut. Further, the photosensitive belt 1, the charging charger 4, the intermediate transfer belt 10, the cleaning unit 15, and the cleaning device 16 can be integrated so as to be detachable from the main body as a process cartridge.

  Next, the control system of the color image forming apparatus shown in FIG. 1 will be described. FIG. 2 is a schematic block diagram showing an example of a control system of the color image forming apparatus shown in FIG. As shown in the figure, in addition to the functions described so far, an operation display unit 21, a main operation unit 22, an image memory unit 23, and the like are provided. The operation display unit 21 includes a touch panel or the like fixed to a housing of a machine body (not shown), and includes a display unit that displays an image for the user and an operation unit that receives a key input from the user. Then, an image is displayed based on a control signal from the main control unit 24 serving as the control means of the present invention, and input information received by the operation unit is output to the main control unit 24. The main control unit 24 is composed of a well-known computer including a ROM, RAM, CPU, and the like (not shown), and controls the entire machine. The intermediate transfer unit 25, the secondary transfer roller 26, the fixing unit 27, the paper feeding unit 28, and the operation display unit 21 are electrically connected. Further, the image memory unit 23, the laser writing unit 5, the photosensitive unit 29, the developing unit 30, and the like are also electrically connected.

  The developing unit 30 includes a developing bias power supply circuit 31, K, C, M, and Y developing rollers 32 to 35 serving as developing members, and K, C, and Y that disconnect driving force to the developing rollers 32 to 35. A developing motor drive circuit 40 for driving the M and Y electromagnetic clutches 36 to 39 and the developing motor 30A is provided.

  Color image information sent from a personal computer or a scanner (not shown) is temporarily stored in the image memory unit 23 via the main control unit 24, and then written in the optical writing unit 5 as color separation image data for each color. It is sent to the control circuit 41. The write control circuit 41 drives the semiconductor laser 44 while rotating the polygon mirror 43 by driving the polygon motor 42 as a drive source based on the color separation image data sent. The laser beam LD emitted from the semiconductor laser 44 by this driving is reflected by the regular hexahedron polygon mirror 43 and is changed in the main scanning direction, and the photoreceptor belt of the photoreceptor unit 29 is passed through a reflection mirror (not shown). 1 is optically scanned. The photosensitive unit 29 includes various driving units 45 and a charge power supply circuit 46.

  The write control circuit 41 calculates the number of write pixels based on the color separation image data of each color and transmits the result to the main control unit 24. The main control unit 24 performs predetermined control on each color developing device based on the calculated value of the number of write pixels sent from the write control circuit. That is, the writing control circuit 41 constitutes a printing pixel counting means that counts the number of printing pixels that are pixels to which toner is attached from the input image data.

  FIG. 3 is an enlarged configuration diagram showing the photoconductor cleaning unit 15 together with its peripheral configuration. The cleaning unit 15 shown in FIG. 3 (a) is a photosensitive member that contacts the photosensitive belt 1 as a cleaning member that scrapes off transfer residual toner from the surface of the belt 15a, a solid lubricant 15c, and a lubricant from the cleaning brush 15a. An application brush 15b serving as an application member applied to the body belt 1 and an urging means (not shown) that urges the solid lubricant 15c toward the application brush 15b are configured.

  The cleaning unit 15 shown in FIG. 3 (b) is a photosensitive member that contacts the photoreceptor belt 1 as a cleaning member that scrapes residual toner from its surface and scrapes the lubricant from the cleaning blade 15d and solid lubricant 15c. An application brush 15b serving as an application member applied to the body belt 1 and an urging means (not shown) that urges the solid lubricant 15c toward the application brush 15b are configured.

  That is, in this embodiment, the cleaning unit 15 has a function as a cleaning unit that cleans the transfer residual toner on the photosensitive belt 1 and a function as a lubricant supply unit that supplies a lubricant to the surface of the photosensitive belt 1. That is why.

  In FIG. 3, the application brush 15b has a shaft member extending in the width direction (depth direction in the drawing) of the photosensitive belt 1, and a plurality of raised hairs erected on the outer peripheral surface thereof. For example, it is formed by winding and fixing a base fabric (not shown) in which a plurality of raised brushes are implanted around a shaft member. The length of the photosensitive belt 1 is adjusted so that the raised portions can be brought into contact with at least the entire width direction of the photosensitive belt 1. The shaft member is rotatably supported by two bearings (not shown) provided on both side walls of the unit case. A rotation driving force of the developing motor is transmitted to the application brush 15b via a brush clutch 50 constituted by an electromagnetic clutch. The brush clutch 50 is connected to the main control unit 24 via a signal line, and is configured to be turned on / off based on a control signal from the main control unit 24. Then, the rotational driving force is transmitted to the application brush 15b to rotate the application brush 15b in the direction of the arrow (clockwise) in the figure. By this rotation, the solid lubricant 15c is scraped off and attached to the raised brush of the application brush 15b, and then applied to the surface of the photoreceptor belt 1 by being supplied. Therefore, when the application brush 15b is rotationally driven, the cleaning unit 15 operates as a lubricant supply means, and the lubricant application operation is executed.

  In the illustrated example, the coating brush 15b rotates at the contact portion with the photosensitive belt 1 in a direction in which the surface of the coating brush 15b moves in the direction opposite to the belt moving direction, so that the lubricant 15c adhering to the raised hair is efficiently transferred to the belt surface. Can be applied. Further, in the present embodiment, an example in which the lubricant is supplied to the photosensitive belt 1 by the coating method as the photosensitive member cleaning unit 15 as the lubricant supply means has been shown, but a liquid lubricant is supplied by the infiltration method, etc. You may make it supply by another system.

  In this embodiment, the use of zinc stearate as the solid lubricant is most effective and can be optimized. As the lubricant, metal stearate is used, and as another solid lubricant, for example, a dry solid hydrophobic lubricant is used. Typical examples include zinc stearate, barium stearate, lead stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, cadmium stearate, magnesium stearate, olein Zinc acid, Manganese oleate, Iron oleate, Cobalt oleate, Lead oleate, Magnesium oleate, Copper oleate, Palmitic acid, Cobalt zinc palmitate, Copper palmitate, Magnesium palmitate, Aluminum palmitate, Calcium palmitate Relatively higher fatty acids such as lead caprylate, lead caproate, zinc linolenate, cobalt linolenate, calcium linolenate, and cadmium ricolinolenate. Natural wax such as carnauba wax may also be used.

  Stabilization and uniformization of the amount of lubricant applied to the photoreceptor belt 1 has been studied for some time, and uniform application is possible. The problem this time is insufficient amount of lubricant adhering to the photoreceptor belt 1 due to forced toner consumption and unevenness caused by the forced toner consumption. The lubricant applied on the photosensitive belt 1 adheres to the consumed toner and decreases. Of course, since the lubricant application is always performed, the unevenness of the application does not occur at the output of characters and lines normally used.

  However, in the case where a certain amount of toner is forcibly adhered onto the photoreceptor belt 1 as in the case of forced toner consumption, and the toner is not transferred but completely collected by the cleaning unit 15, it naturally adheres to the photoreceptor belt 1. Although the lubricant is peeled off by the toner, since a large amount of toner is input to the cleaning brush 15a and the blade 15d that are in contact with the photosensitive belt 1, the lubricant is further peeled off from the surface of the photosensitive belt 1 at the nip portion. It will be. Accordingly, after the forced toner consumption, the amount of lubricant adhering on the photoreceptor belt 1 is drastically reduced.

  In particular, as shown in FIG. 3A, when the lubricant application brush 15b and the cleaning brush 15a are used in combination, a large amount of toner is input to each brush during forced toner consumption. Decreases. Therefore, it is better to perform the lubricant application operation (mode) after the forced consumption ends. In the case of a configuration such as the lubricant application brush 15b and the cleaning blade 15d as shown in FIG. 3B in which the lubricant application brush 15b and the photoconductor cleaning brush 15a are not used together, the lubricant is used in parallel with the forced toner consumption. Even if the application is performed, there is no problem, and the adjustment time is shortened, which is desirable.

  Next, the concept of change due to toner forced consumption of the amount of lubricant adhering on the photoreceptor belt 1 and the concept of change due to the rotation time of the application brush 15b will be described with reference to FIGS. In FIG. 6, the vertical axis represents the amount of lubricant adhering to the photoreceptor belt, and the horizontal axis represents the toner forced consumption amount. In FIG. 7, the vertical axis represents the amount of lubricant adhering to the photoreceptor belt, and the horizontal axis represents the rotation time of the application brush. As shown in FIG. 6, the relationship between the lubricant adhesion amount on the photosensitive belt and the forced toner consumption amount falls outside the optimum range because the lubricant adhesion amount decreases as the consumption amount increases. Further, as shown in FIG. 7, the relationship between the lubricant adhesion amount on the photoreceptor belt 1 and the application brush rotation time is such that the lubricant adhesion amount increases as the application brush rotation time increases. For this reason, it is preferable to control the application brush rotation time so that the lubricant adhesion amount on the photosensitive belt 1 falls within the optimum range.

  Here, the forced toner consumption operation (mode) will be described.

  When the number of pixels of the print data is A and the number of pixels is equal to or less than the specified number of pixels, the number of pixels corresponding to the difference is accumulated, and the photoconductor is formed in the non-image area after the series of print jobs. The belt 1 is exposed and developed, and the toner is forcibly consumed.

  If the cumulative pixel count by the write control circuit 41 is B, it can be expressed as B = B + A.

  For example, when the resolution is 600 dpi and one sheet of A4 paper is passed, the effective image area is 295 × 210 = 61950 mm 2, and the number of pixels is 61950 / 25.42 × 6002 = 34568167 pixels.

  If the specified value of forced toner consumption is Z (%), the toner belt 1 is forced to consume (exposure) the difference from B. For example, when Z = 3%, if A4 is 1 horizontal, 3568167 × 3% = 1037045 pixels, and if the count number B is 1037045 pixels or less, forced toner consumption is performed on the photosensitive belt 1. The toner forced consumption amount is 1037045-B pixels.

  In other words, in this embodiment, the main control unit 24 operates the electromagnetic clutches 36 to 39 of the developing unit 30 and the developing motor drive circuit 40 to execute a forced toner consumption operation for forcibly consuming the toner on the photosensitive belt 1. And a function of operating the lubricant supply means (cleaning unit) 15 to perform the lubricant application operation.

  Next, the forced toner consumption operation (mode) + lubricant application operation (mode) controlled by the main control unit 24 will be described with reference to FIGS.

  The process of forced toner consumption operation (mode) shown in FIG. 4 is started by starting a print command. Then, it is assumed that the A4 landscape (LEF) converted sheet passing sheet number after the start is Y. X is a value for setting A4 width 210 mm as a unit length, and differs depending on the paper length L. If the paper length (image length) passed is L, it can be expressed as X = L / 210. Therefore, X = 1 in the A4 side, and X = 2 in the A3 length (SEF: short edge feed). In step S1, Y is calculated by such an expression.

  In step S2, the number of pixels A is accumulated for each sheet passing (B = B + A). In steps S3 and S4, the timing of forced toner consumption is determined from the end of the print job and the number Y of sheets to be passed. Although the timing of forced toner consumption can be set for each sheet, it is usually performed at a job end or at an optimum interval from productivity. In this embodiment, it is performed at the end of the job after passing a cumulative of 10 or more sheets. If the sheet passing number Y is not greater than or equal to the predetermined value (10) in step S4, the sheet passing number Y and the image B are held in step S9, and this control is finished.

  When the number Y of sheets to be passed becomes equal to or greater than the predetermined value (10), the process proceeds to step S5 to calculate (calculate) a forced toner consumption C. The toner forcible consumption C can be calculated by C = 3568167 × Y (sheets) × Z (%) − B. In step S6, the forced consumption amount C of toner is determined. When C <0, the forced consumption amount is 0. The process proceeds to step S10, where Y = 0 and B = 0, and this control ends.

  In step S6, if C> 0, the process proceeds to step S7 to create a pixel pattern for forced consumption. As this image pattern, dots, lines, and solids are conceivable, but since the number of pixels is accumulated and forced toner consumption is performed at the job end, the amount of forced toner consumption increases as the number of sheets passed in one job increases. Considering the adjustment time, a pattern with a high image area is desirable. In this embodiment, a solid image with an area ratio of 100% is used, and the laser writing unit 5, the photosensitive belt 1 and the developing unit 30 are operated to form a forced consumption pixel pattern, and a forced toner consumption operation is executed. To do. In step S8, after the forced toner consumption is performed, a lubricant application operation (mode) is performed. In the lubricant application operation (mode), the photosensitive belt 1 and the application brush 15b shown in FIG. 3 are rotated for a predetermined time. It is an operation.

  The lubricant application operation (mode) will be described with reference to the flowchart shown in FIG. In step S11 of FIG. 5, the lubricant application time is calculated. In this embodiment, the lubricant application time is increased in proportion to the forced toner consumption. In the image forming apparatus of this embodiment, the lubricant adhesion amount on the photosensitive belt 1 is in a state before forced consumption by applying the lubricant to the toner forced consumption portion formed on the photosensitive belt 1 about twice. It is possible to return to However, when the amount of forced consumption is small, the amount of toner input to the cleaning brush 15a is small, so that it is possible to apply the lubricant once.

  First, in calculating the lubricant application time T, the toner forced consumption is set to a solid image with an area ratio of 100%, and the writing length m is calculated. If the effective writing width in the main scanning direction is 295 mm, the number of pixels is 295 / 25.4 × 600 = 6969 pixels. Therefore, the writing length m (mm) of the forced toner consumption can be expressed by m = C / 6969/600 × 25.4 = C / 164622. That is, the lubricant application time T can be expressed by 2 × m / Vp. Here, Vp is a photosensitive belt linear velocity (mm / second). The reason for doubling is to apply twice.

Also, assuming that the circumferential length of the photosensitive member is P (mm), the execution time of the lubricant application mode is
When 2 × m> P, 2 × m / Vp seconds, and when 2 × m ≦ P, P / Vp seconds.
When the toner forced consumption length is short, the time for performing the lubricant application operation (mode) may be shorter than the entire circumference of the photoreceptor belt. In this case, a place where no lubricant is applied may occur, which may result in uneven lubricant application. Therefore, the main control unit 24 operates each unit so that the lubricant can be applied at least for one rotation of the photosensitive belt.

  For example, the circumferential length of the photoconductor is φ40 = 15.6 mm, the linear velocity of the photoconductor belt is 150 mm / sec, and when m = 62.8 mm or more, 2 × m / Vp sec, the lubricant application mode is performed, and m = 62 When the length is less than or equal to 8 mm, 125.6 / 150 = 0.837 seconds and the lubricant application mode is performed.

  According to the image forming apparatus having such a configuration, it is possible to reduce the amount of lubricant adhering to the photosensitive belt 1 due to a difference in the amount of toner supplied to the photosensitive belt 1 due to forced toner consumption and to reduce coating unevenness. It is possible to always control the amount of adhering agent to an optimum and stable state, and to provide an image forming apparatus free from abnormal images such as density unevenness and transfer failure.

  That is, when the forced toner consumption operation is performed, the lubricant application operation is also performed, so that the lubricant taken off from the photoreceptor belt 1 by the forcibly consumed toner can be replenished, and the lubricant adheres. Uneven amount can be prevented.

  In this embodiment, since the lubricant application brush 15b and the cleaning brush 15a are used in combination, a large amount of toner is input to the brush during the forced toner consumption, and the lubricant application efficiency is lowered. Since the coating of the agent is carried out, it is possible to provide an image forming apparatus that can efficiently and stably adhere the lubricant to the photoreceptor belt 1 and that is free from abnormal images such as density unevenness and transfer failure.

  In this embodiment, when the amount of forced toner consumption is large, the amount of lubricant applied is changed according to the amount of forced toner consumption by increasing the lubricant application time. Over application can be prevented. When the forced consumption is small, the application time is shortened, so that the adjustment time can be shortened. Further, since the adjustment of the lubricant application amount is adjusted by changing the rotation time of the existing lubricant application brush 15b, the existing configuration can be used, and there is no abnormal image such as density unevenness or transfer failure. A forming apparatus can be provided.

  In this embodiment, since the lubricant is applied by rotating the photosensitive belt 1 at least once or more, the uniformity of the amount of lubricant adhered on the photosensitive belt 1 can be further improved.

  In this embodiment, a color image forming apparatus such as a color copying machine has been described as an example. However, the image forming apparatus to which the content of the present invention is applied is not limited to the embodiment, and for example, monochrome image formation Needless to say, the present invention can be similarly applied to the entire apparatus, and the same effect as in the present embodiment can be obtained.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus to which the present invention is applied. FIG. 2 is a schematic block diagram illustrating an embodiment of a control system of the color image forming apparatus illustrated in FIG. 1. It is an enlarged view which shows the lubricant supply means applied to FIG. 1, and the surrounding structure. 6 is a flowchart showing the content of a forced toner consumption operation (mode). It is a flowchart which shows the content of lubricant application | coating operation (mode). FIG. 6 is a special drawing showing the relationship between the amount of lubricant adhering to an image carrier and the amount of forced toner consumption. It is a special drawing showing the relationship between the amount of lubricant adhering on the image carrier and the rotation time of the application brush.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier 15 Lubricant supply means 15a, 15d Cleaning member 15c Lubricant 24 Control means 30 Developing means 41 Print pixel count means

Claims (6)

Developing means for developing the electrostatic latent image formed on the surface of the image carrier with toner, and a lubricant coating operation for supplying lubricant to the surface of the image carrier by rotating in contact with the surface of the image carrier. In an image forming apparatus having a lubricant supply means to perform,
Print pixel counting means for counting the number of print pixels, which are pixels to which toner should be attached, from the input image data;
The difference between the number of pixels counted by the print pixel counting means and the predetermined number of pixels is obtained. If the value is small, the forced toner consumption is calculated according to the difference, and the developing means is operated to set the toner count. An image forming apparatus comprising: a control unit that operates the lubricant supply unit to perform the lubricant application operation when performing a toner forced consumption operation that forcibly consumes toner. A cleaning member for removing residual toner on the image carrier;
The image forming apparatus according to claim 1, wherein the control unit operates the lubricant supply unit to execute the lubricant application operation after the forced toner consumption operation is completed.   3. The image forming apparatus according to claim 1, wherein the control unit changes a lubricant application amount by the lubricant application operation in accordance with a forced consumption amount of toner by the developing unit.   4. The image forming apparatus according to claim 3, wherein the control unit changes the lubricant application amount by changing an operation time of the lubricant supply unit.   5. The image forming apparatus according to claim 1, wherein the controller rotates at least one rotation of the image carrier during the lubricant application operation.   The image forming apparatus according to claim 1, wherein the lubricant is made of a metal stearate.

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