JP2009092708A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of securing the uniformity in an adhering quantity of lubricant applied to the surface of an image bearer regardless of presence/absence of toner forced consumption and quantity of toner by a simple and low-cost method. <P>SOLUTION: This image forming apparatus includes: a developing means 7 for developing an electrostatic latent image formed on the image bearer 1 with input image data by laser exposure with toner beared on a developing roller; rotatable raised bristles 18e which are arranged in contact with the image bearer 1 for applying the lubricant 18c to the image bearer 1; and a lubricant coating means 18b whose raised bristles 18e always come into contact with the lubricant 18c, wherein the lubricant coating means 18b is installed in an image bearer cleaning unit 18 for cleaning the image bearer, the developing means 7 forcedly consumes a computed forced toner consumption quantity, and the lubricant coating means 18b performs a lubricant coating mode after the operation end of toner forced consumption. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a PPC, a laser printer, a facsimile machine, and a multifunction machine including these, which includes a lubricant application mechanism.

2. Description of the Related Art Conventionally, in an image forming apparatus configured as a copying machine, a composite machine thereof, or the like, it is known that a lubricant is applied to the surface of an image carrier on which a toner image is formed while being driven to rotate ( For example, see Patent Documents 1 to 5).
Patent Document 1 discloses an image carrier that forms a toner image on a surface while being rotated, a transfer device that transfers the toner image to a transfer material, and a transfer residue that adheres to the surface of the image carrier after the toner image is transferred. A cleaning member that removes the toner and cleans the surface of the image carrier, and a lubricant application member that has a brush that contacts the surface of the image carrier and applies a lubricant to the surface of the image carrier while being driven to rotate. A configuration is disclosed.
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 a lubricant is applied 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 non-uniform, unevenness in the amount of adhesion causes image A toner image formed on the body surface may have a non-uniform toner adhesion amount, resulting in uneven density in the toner image, and the formed image quality may deteriorate.
In other words, the amount of toner adhering to the surface of the image carrier with a large amount of lubricant adhering decreases, and conversely, a large amount of toner adheres to the portion with a small amount of adhering lubricant, resulting in uneven density in the toner image. To do. In particular, density unevenness is likely to occur in a low density toner image.
Furthermore, in the case of one-component contact development, if the static friction coefficient of the image carrier becomes 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 adhesion 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 for controlling such insufficient or excessive application of lubricant during a normal job, Patent Document 2 discloses an image forming apparatus that applies a lubricant while bringing a brush of a lubricant application member into contact with the surface of a photoreceptor. In addition, there is disclosed a technique that eliminates uneven application of lubricant with a simple configuration and prevents the occurrence of uneven image density. Patent Document 3 discloses a technique for preventing filming and always supplying a stable lubricant, but it is not sufficient for solving the above-mentioned conventional problems.
In recent years, as shown in Patent Documents 4 and 5, a mode for forcibly consuming toner has been studied as a countermeasure against toner deterioration with time (such as a fogging image countermeasure) due to output of a low image area.
If the image area of the document is smaller than the specified value (minimum image area for maintaining a good quality image), for example, if the specified value is 5%, 0.5% document will force 4.5% of toner. Will consume.
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 a large image area such as a solid image or a 50% image is obtained. Toner is consumed.
JP-A-56-154778 Japanese Patent Laid-Open No. 10-260614 Japanese Patent Laid-Open No. 7-334058 JP-A-2005-92156 Japanese Patent No. 3029648

However, the lubricant applied on the photoreceptor is peeled off mainly by the toner that comes into contact with it, and is transferred or cleaned together with the toner. Therefore, the amount of lubricant attached on the photoconductor is different after the output image, the white solid part (blank paper part) and the black solid part (toner adhesion part).
When the toner is forcibly consumed, all of the developed toner is collected for cleaning, so that a large amount of toner is present in the cleaning unit for a while, and more lubricant is peeled off from the photoreceptor than when the paper is passed.
Further, when there is a lubricant application brush in the cleaning unit, a large amount of toner is input to the brush during the forced toner consumption, so that the lubricant application capability temporarily decreases. Therefore, when the toner is forcibly consumed, there is a problem that the amount of the lubricant applied to the photoreceptor is extremely reduced or the amount of adhesion is uneven.
In view of the above, the object of the present invention is to reduce the amount of lubricant applied to the surface of the image carrier by a simple and low-cost method regardless of whether toner is forcibly consumed or the amount of toner. An object of the present invention is to provide an image forming apparatus capable of ensuring uniformity.

In order to solve the above-mentioned problems, the invention described in claim 1 is a development that develops an electrostatic latent image formed by input image data by laser exposure on an image carrier with toner carried on a developing roller. Means and a lubricant application means which is arranged in contact with the image carrier and in which a rotatable raising brush for applying a lubricant to the image carrier is always in contact with the lubricant. The means is installed in an image carrier cleaning unit for cleaning the image carrier, the developing means forcibly consumes the calculated forced toner consumption, and the lubricant application means performs the operation of forced toner consumption. An image forming apparatus that performs a lubricant application mode after completion is characterized.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the lubricant application unit changes a lubricant application amount in the lubricant application mode in accordance with a forced consumption amount of the toner. It is characterized by.

According to a third aspect of the present invention, the image processing apparatus includes a print pixel count unit that counts the number of print pixels that are pixels to which toner is to be attached from the input image data. The difference is obtained by comparing the number of pixels, and when the difference is small, the forced toner consumption is calculated according to the difference, the toner is forcibly consumed by the developing means, and the counted pixels are formed during normal image formation. 2. The image forming apparatus according to claim 1, wherein control is performed to change the amount of lubricant applied according to the number, and after the forced consumption of toner, the ratio of the amount of lubricant applied to the number of pixels, which is the amount of toner consumed, is increased. And
According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the second or third aspect, wherein the control of the lubricant application amount depends on a change in a rotation time of the lubricant application means.
The invention according to claim 5 is the image forming apparatus according to any one of claims 1 to 4, wherein the lubricant application mode is conditional on rotation of the image carrier at least one rotation or more. And
According to a sixth aspect of the invention, there is provided the image forming apparatus according to any one of the first to fifth aspects, wherein the lubricant comprises a metal stearate.

  According to the present invention, it is possible to reduce the amount of lubricant adhering to the image carrier and uneven application due to the difference in the amount of toner input to the image carrier due to forced toner consumption. Therefore, it is possible to provide an image forming apparatus free from abnormal images such as density unevenness and transfer failure.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The apparatus of the embodiment described below is applied to a color image forming apparatus used as a color copying machine, but can be similarly applied to a monochrome image forming apparatus.
FIG. 1 is a schematic diagram showing the overall configuration of an embodiment of a color image forming apparatus according to the present invention. In the color image forming apparatus 10 of FIG. 1, the photosensitive member that carries the electrostatic latent image formed by laser writing and the developed toner image is the photosensitive belt 1 as a flexible belt-like image carrier. .
The photosensitive belt 1 is installed between the rotation rollers 2, 3, and 4, and is rotated (sub-scanned) in the direction of arrow A (clockwise) in the figure by the rotational drive of the rotation roller 2, and the belt surface is The image forming surface is configured.
As means for forming an electrostatic latent image and a toner image on the photosensitive belt 1, a charging charger 5 for uniformly charging the surface of the photosensitive belt 1, a laser writing unit 6, color developing devices 7a and 7b, 7c and 7d (indicated by reference numeral 7 when no color is specified).

The color developing devices 7a, 7b, 7c, and 7d are composed of developing units of magenta, cyan, yellow, and black, which are color constituent colors. The developing unit used here has a configuration in which development is performed with a one-component developer (toner).
Further, the color image forming apparatus of the present embodiment has an intermediate transfer belt 8 because the image of the photosensitive belt 1 is formed on a transfer sheet via an intermediate transfer member. The intermediate transfer belt 8 is installed between the rotation rollers 9 and 11, and is rotated in the arrow B direction (counterclockwise direction) in the drawing by the rotation driving of the rotation roller 9.
The photosensitive belt 1 and the intermediate transfer belt 8 are in contact with each other at a portion where the rotating roller 4 of the photosensitive belt 1 is provided. On the intermediate transfer belt 8 side of the contact portion, a conductive bias roller 12 is in contact with the back surface of the intermediate transfer belt 8 under predetermined conditions.
Constituent elements relating to transfer paper processing include a paper feed table (paper feed cassette) 13, a paper feed roller 14, conveyance roller pairs 15 a and 15 b, registration roller pairs 16 a and 16 b, and an intermediate transfer belt 8. A secondary transfer roller 17 for transferring the image, a fixing device 20, a pair of paper discharge rollers 21 a and 21 b, and a paper discharge stack unit 22.

Here, an image forming operation of the color image forming apparatus shown in FIG. 1 will be described. In FIG. 1, a photosensitive belt 1 as a flexible belt-like image carrier is uniformly charged by a charging charger 5 and then emitted by a laser writing unit 6 based on image information. As a result of the scanning exposure, 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 an optical device 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 7a, 7b, 7c, and 7d. Each color image is developed, and each color image is sequentially formed on the photosensitive belt 1.
Each monochrome image of M, C, Y, and 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. On the intermediate transfer belt 8, the images are sequentially superimposed and transferred by the action of a predetermined transfer bias applied to the bias roller 12.

The images of M, C, Y, and Bk superimposed on the intermediate transfer belt 8 are passed from a paper feed table (paper feed cassette) 13 through a paper feed roller 14, transport roller pairs 15a and 15b, and registration roller pairs 16a and 16b. Then, the image is transferred all at once by the secondary transfer roller 17 onto the transfer paper P conveyed to the transfer section.
After the transfer is completed, the transfer paper P is fixed by the fixing device 20 to complete a full-color image, and the print image is discharged to the paper discharge stack unit 22 through the paper discharge roller pair 21a and 21b.
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 blade 18a that is always in contact with the photosensitive belt 1 is provided.
Similarly, the intermediate transfer belt 8 is also provided with a cleaning device 19. The cleaning brush 19a of the cleaning device 19 is held at a position separated from the surface of the intermediate transfer belt 8 during the image forming operation. After the formed image is transferred onto the transfer paper P, it is brought into contact with the surface of the intermediate transfer belt 8. The
Further, the photosensitive belt 1, the charger 5, the intermediate transfer belt 8, the cleaning blade 18a, and the cleaning device 19 can be integrated so as to be detachable from the main body as a process cartridge.

FIG. 2 is a schematic block diagram showing an example of a control system of the color image forming apparatus. Next, the control system of the color image forming apparatus shown in FIG. 1 will be described. As shown in FIG. 2, in addition to the functions described so far, that is, the intermediate transfer unit 23, the secondary transfer roller 17, the fixing unit 24, and the paper feeding unit 25, the operation display unit 30, the main control unit 31, and the image A memory unit 32 and the like are provided.
The operation display unit 30 includes a touch panel fixed to a housing of a machine main 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.
An image is displayed based on a control signal from the main control unit 31, and input information received by the operation unit is output to the main control unit 31. The main control unit 31 includes a ROM, a RAM, a CPU (not shown), etc., and controls the entire machine.
The intermediate transfer unit 23, the secondary transfer roller 17, the fixing unit 24, the paper feeding unit 25, and the operation display unit 30 are electrically connected. Further, the image memory unit 32, the optical unit 33, the photosensitive unit 34, the developing unit 35, and the like are also electrically connected.

Color image information sent from a personal computer or scanner (not shown) is temporarily stored in the image memory unit 32 via the main control unit 31, and then the optical writing unit 33 as color separation image data for each color. Is sent to the write control circuit 33a. The writing control circuit 33a drives the semiconductor laser while driving the polygon motor 33b based on the transmitted color separation image data to rotate the polygon mirror.
The laser beam LD emitted from the semiconductor laser by this driving is reflected by a regular hexahedron polygon mirror and is changed in the main scanning direction, while passing through a reflection mirror (not shown), the photosensitive belt of the photosensitive unit 34. 1 is optically scanned.
The write control circuit 33 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 31. The main control unit 31 performs predetermined control for each color developing device based on the calculated value of the number of write pixels sent from the write control circuit 33.
In FIG. 2, the photosensitive unit 34 further includes various driving systems 34a, a charge power supply circuit 34b, the developing unit 35, the electromagnetic clutch 35a for each color, the developing motor driving circuit 35b, the developing bias power supply circuit 35c, and the developing roller for each color. 35d is shown.

FIG. 3 is an enlarged configuration diagram showing the photosensitive member cleaning unit together with its peripheral configuration. In FIG. 3, the photoconductor cleaning unit 18 contacts the photoconductor belt 1 and scrapes off transfer residual toner from the surface thereof, a solid lubricant 18 c, and scrapes off the lubricant from this to the photoconductor belt 1. An application brush 18b to be applied and an urging means (not shown) for urging the solid lubricant 18c toward the application brush 18b are configured.
The photosensitive member cleaning unit 18 has a function as a cleaning device for cleaning the transfer residual toner on the photosensitive belt 1 and a function as a lubricant supplying device for supplying a lubricant to the surface of the photosensitive belt 1. .

FIG. 4 is a schematic view showing the configuration of the application brush. 3 and 4, the application brush 18b is erected on a shaft member 18d extending in the width direction (depth direction in the drawing) of the photosensitive belt 1 in FIG. 3 and an outer peripheral surface thereof. For example, the base fabric 18f in which the plurality of raised brushes are implanted is wound around and fixed to the shaft member 18d.
The length of the base fabric 18f is adjusted so that the raised hair 18e can be brought into contact with at least the entire width direction of the photosensitive belt 1. The shaft member 18d is rotatably supported by two bearings (not shown) provided on both side walls of the unit case.
A rotation driving force from a developing motor (not shown) is transmitted to the shaft member 18d by a developing motor driving circuit 35b (FIG. 2) via a brush clutch (not shown).
When the brush clutch is turned on, the shaft member 18d rotates in the direction of the arrow (clockwise) in the figure by transmitting the rotational driving force. By this rotation, the solid lubricant 18c is scraped off and adhered to the raised portions 18e of the application brush 18b, and then applied to the surface of the photoreceptor belt 1. Therefore, when the application brush 18b is driven to rotate, the photosensitive member cleaning unit 18 is driven as a lubricant supply device.
In the illustrated example, since the application brush 18b rotates at the contact portion with the photosensitive belt 1 in a direction in which the surface of the application brush 18b moves in the direction opposite to the belt moving direction, the solid lubricant 18c attached to the raised hair 18e is efficiently used. It is applied to the belt surface.

In addition, the example in which the lubricant is supplied to the photosensitive belt 1 by the coating method as the photosensitive member cleaning unit 18 that is a lubricant supply device has been described. You may make it supply by a system. In the present embodiment, zinc stearate is used as a solid lubricant for optimization.
Another solid lubricant is, for example, a dry solid hydrophobic lubricant. 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 and the like. Can be mentioned.
As representative examples, zinc oleate, manganese oleate, iron oleate, cobalt oleate, lead oleate, magnesium oleate, copper oleate, palmitic acid, cobalt cobalt palmitate, copper palmitate, magnesium palmitate, Examples thereof include aluminum palmitate and calcium palmitate.
Representative examples also include 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.
As described above, the above-described various materials can be used as the solid lubricant 18c. At present, a metal stearate salt can be expected to be most effective as such a solid lubricant.

Stabilization and equalization of the coating amount of the solid lubricant 18c applied to the photoreceptor belt 1 has been studied for some time, and uniform coating is possible. The problem to be solved by the present invention is an insufficient amount of lubricant adhering to the photoreceptor belt 1 due to forced toner consumption, and unevenness associated therewith, which is performed as a countermeasure against toner deterioration and the like.
The solid lubricant 18c applied on the photoreceptor belt 1 adheres to the toner that is mainly consumed and decreases. Of course, since the solid lubricant 18c is always applied, the output does not cause unevenness in the output of characters or lines normally used.
However, if the collected toner is forcibly attached to the photosensitive belt 1 as in the case of forced toner consumption, and the toner is collected by the cleaning unit 18 without being transferred, the toner is naturally attached on the photosensitive belt 1. The solid lubricant 18c is peeled off by the applied toner, but since a large amount of toner is also input to the application brush 18b in contact with the photosensitive belt 1, the solid lubricant 18c attached to the application brush 18b is also removed. It will be.
At this time, if the application brush 18b is rotated, a large amount of toner that is forcibly consumed adheres to the entire interior of the application brush 18b, and after the toner is forcibly consumed, the lubricant on the photosensitive belt 1 is used. The amount of adhesion and the amount of lubricant in the application brush 18b are rapidly reduced.
In this case, due to a decrease in the amount of lubricant of the application brush 18b, the lubricant application capacity temporarily decreases in the subsequent application of the lubricant, and the amount of lubricant adhering on the photoreceptor belt 1 increases very soon after forced consumption. do not do. Therefore, it takes a long time to apply the lubricant (time in the application mode) until stabilization.
In the present invention, during the forced consumption, the application brush 18b for applying the solid lubricant 18c is stopped, whereby the forcibly consumed toner can be minimized from adhering to the application brush 18b, and is not rotated. The solid lubricant 18c is not scraped off except for the contact portion with the photoreceptor belt 1. Therefore, the application time (the time of the application mode) until the lubricant adhesion amount on the photosensitive belt 1 is stabilized can be shortened.

FIG. 5 is a conceptual diagram illustrating the relationship between the amount of lubricant adhering to the photoreceptor belt and the change due to forced toner consumption. FIG. 6 is a conceptual diagram that graphically shows the relationship between the amount of lubricant adhering to the photoreceptor belt and the change in rotation time due to forced toner consumption when the application brush is rotated and stopped.
Referring to FIGS. 3 to 6, according to FIG. 5, when the toner forced consumption amount increases, the lubricant adhesion amount on the photosensitive belt 1 becomes lower than the lower limit of the optimum range. In FIG. 6 showing the difference in the coating ability between when the application brush 18b is rotated and when it is stopped during forced toner consumption, the application brush so that the amount of lubricant adhering on the photoreceptor belt 1 falls within the optimum range. It is necessary to control the rotation time of 18b. However, it can be seen from FIG. 6 that if the application brush 18b is stopped, the rotation time (application mode time) of the application brush 18b is shorter.

The toner forced consumption operation 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 predetermined 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.
During a series of print jobs, the lubricant application brush clutch is basically turned on. At the end of the job, the clutch is turned off, the application brush 18b is stopped, and then forced toner consumption is performed.
If the cumulative pixel count 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 sheet, 3568167 × 3% = 1037045 pixels, and if counter 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.

FIG. 7 is a flowchart showing a flow of forced toner consumption + lubricant application mode. In FIG. 7, after the print command is started, the application brush clutch is turned on (S1). Y = Y + X (S2), and Y is the A4 horizontal (LEF: Long Edge Feed) conversion sheet passing number. X is a value for setting A4 width 210 mm as a unit length, and varies depending on the transfer paper length L.
If the length of the transferred transfer paper (image length) 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).
The number of pixels A is accumulated for each sheet passing (B = B + A) (S3). Next, it is determined whether or not the job is finished (S4). If finished, the application brush clutch is turned off (S5). 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 the viewpoint of productivity.
In the embodiment, it is determined whether or not the cumulative number is 10 or more (Y ≧) (S6). If the cumulative number is 10 or more, the toner is forcibly consumed at the end of the job after the sheet is passed. If the cumulative number is not 10 or more, the flow is terminated, and Y and B pixels are held (S7).

Next, the toner forced consumption amount C is calculated (S8). The toner forcible consumption C can be calculated by C = 3568167 × Y (sheets) × Z (%) − B. It is determined whether or not C> 0 (S9). If C> 0, a forced consumption pattern (Y = 0, B = 0) is created (S10), the lubricant application mode is performed (S12), and the process ends. (S13). If C> 0, the process ends (Y = 0, B = 0). When C <0, the forced consumption is 0 and is not implemented.
As the forced consumption pixel 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 that pass through one job increases. Therefore, considering the adjustment time, a pattern with a high image area is desirable. In this embodiment, a solid image having an area ratio of 100% is used.
As described above, after the forced toner consumption, the lubricant application mode is performed to apply the lubricant to the photosensitive belt 1 (FIG. 3). The lubricant application mode is an operation of rotating the photosensitive belt 1 and the lubricant application brush 18b for a predetermined time.

According to the present invention, the image forming apparatus 10 includes a developing device 6 that develops an electrostatic latent image formed by laser exposure on the photosensitive belt 1 with toner carried on a developing roller, and the photosensitive belt 1. A rotatable brushed brush 18e that is disposed in contact with the photosensitive belt 1 and applies a solid lubricant to the photosensitive belt 1 has an application brush 18b that is always in contact with the solid lubricant 18c.
The image forming apparatus 10 also counts the number of print pixels, which are pixels to which toner is attached, from the input image data by the main control unit 31 (print pixel counting means). The difference is obtained in comparison with a predetermined number of pixels, and when the difference is small, the forced toner consumption is calculated according to the difference and the toner is forcibly consumed from the developing device 6.
In this case, the application brush 18b as the lubricant application means is installed in the photosensitive belt cleaning unit. During the toner forced consumption operation, the rotation of the application brush 18b is stopped, and after the forced consumption operation is completed, the application brush 18b is rotated to execute the lubricant application mode.
In this way, by stopping the rotation of the application brush 18b during the forced toner consumption, it is possible to minimize the peeling of the lubricant from the lubricant application brush 18b by the toner, and the lubricant application ability of the brush is reduced. It is suppressed and unevenness in the amount of lubricant attached can be prevented.
Also, the lubricant application amount is changed according to the forced toner consumption amount, and when the toner forced consumption amount is large, the lubricant application unevenness can be prevented by increasing the lubricant application amount and the lubricant application. Excessiveness can be prevented. Further, when the forced consumption is small, the application time can be reduced and the adjustment time can be shortened.

FIG. 8 is a flowchart showing the flow of the lubricant application mode. In FIG. 8, in the lubricant application mode, the lubricant application time is calculated (S20), the application brush clutch is turned on (S21), and it is determined whether the lubricant application time is 2 × m> P (S22).
If 2 × m> P, the lubricant is applied for 2 × m> Vp seconds (S23), the application brush clutch is turned off (S25), and the process ends (S26). If 2 × m> P is not satisfied in step (S22), a P / Vp second lubricant is applied (S24).
The lubricant application time is increased in proportion to the forced toner consumption. In the image forming apparatus of the present embodiment, the amount of lubricant adhering to the photoreceptor belt 1 is applied by applying the lubricant to the toner forced consumption portion imaged on the photoreceptor belt 1 (FIG. 3) about twice. Can be returned to the state before forced consumption. However, when the amount of forced consumption is small, the amount of toner input to the application brush is also small, so that one lubricant application is possible.

The forced length of toner is assumed to be 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) for forced toner consumption can be expressed as m = C / 6969/600 × 25.4 = C / 166422. Thus, the lubricant application time can be expressed as 2 × m / Vp. Here, Vp is the photosensitive member linear velocity (mm / second). The reason for doubling is to apply twice.
Also, assuming that the circumference of the photosensitive belt 1 is P (mm), the execution time of the lubricant application mode is 2 × m> P, 2 × m / Vp seconds, 2 × m ≦ P, P / Vp seconds.
When the length of the forced toner consumption operation is short, the time for which the lubricant application mode is performed may be shorter than the circumference of the photoreceptor belt. In this case, a place where no toner is applied may occur, resulting in uneven lubricant application. There is. For this reason, at least one rotation of the photoreceptor belt 1 can be applied with the lubricant. In this way, by applying the lubricant to the photoreceptor belt 1 for one rotation or more, the uniformity of the lubricant adhesion amount on the photoreceptor belt 1 is improved.
For example, when the circumference of the photoreceptor belt 1 is φ40 = 15.6 mm and the linear velocity of the photoreceptor belt 1 is 150 mm / second, when m = 62.8 mm or more, 2 × m / Vp second lubricant application mode When m = 62.8 mm or less, 125.6 / 150 = 0.837 seconds, the lubricant application mode is executed.

Also, if the lubricant application amount is adjusted in proportion to the number of pixels per page during normal printing (the on-time of the brush clutch is changed in proportion to the number of pixels), this proportionality factor is increased. Thus, the application time can also be determined. For example, when the P / Vp second clutch is normally turned on for 864,442 pixels, it is set to 2 P / Vp seconds in the lubricant application mode after forced toner consumption.
In addition, when control is performed to change the lubricant application amount according to the counted number of pixels during normal image formation, the ratio of the lubricant application amount to the number of pixels (toner consumption amount) Increase after forced consumption.
As a result, the lubricant application amount for a certain number of pixels (toner consumption amount) is increased after the forced consumption of the toner to cope with an increase in untransferred toner. The lubricant taken off from the photoreceptor belt 1 by the forcibly consumed toner can be replenished, and unevenness in the amount of adhered lubricant can be prevented.
As described above, the image forming apparatus according to the present invention can reduce the amount of lubricant adhering to the photoreceptor belt and uneven coating due to the difference in the amount of toner input to the image carrier due to forced toner consumption. Therefore, it is possible to always control the lubricant adhesion amount to an optimum and stable state, and to provide an image forming apparatus free from abnormal images such as density unevenness and transfer failure.

1 is a schematic diagram showing an overall configuration of an embodiment of a color image forming apparatus according to the present invention. It is a schematic block diagram which shows an example of the control system of a color image forming apparatus. FIG. 3 is an enlarged configuration diagram showing a photosensitive member cleaning unit together with its peripheral configuration. It is the schematic which shows the structure of an application brush. FIG. 3 is a conceptual diagram illustrating a relationship between a lubricant adhesion amount on a photoreceptor and a change due to forced toner consumption in a graph. FIG. 5 is a conceptual diagram illustrating a graph of a relationship between a lubricant adhesion amount on a photoconductor and a change due to rotation time due to forced toner consumption when an application brush is rotated and stopped. It is a flowchart which shows the flow of toner forced consumption + lubricant application mode. It is a flowchart which shows the flow of lubricant application mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive belt), 6 Developing means (developing apparatus), 10 Image forming apparatus (color image forming apparatus), 13 Paper feed unit, 18 Image carrier cleaning unit, 18b Lubricant applying means (application brush) 18c Lubricant, 18e Brushed, 30 Operation display section, 31 Main control section (print pixel counting means, forced toner consumption calculation section), 32 Image memory section, 33 Optical writing unit, 34 Photosensitive unit, 35 Developing means ( Development unit), 35d development roller

Claims (6)

  A developing unit that develops an electrostatic latent image formed by input image data by laser exposure on the image carrier with toner carried on a developing roller, and the image carrier is disposed in contact with the image carrier. A rotatable brushing for applying a lubricant to the lubricant, and a lubricant application means that is always in contact with the lubricant. The lubricant application means is installed in an image carrier cleaning unit for cleaning the image carrier. And the developing means forcibly consumes the calculated forced toner consumption, and the lubricant application means implements a lubricant application mode after the operation of forced toner consumption is completed. .   The image forming apparatus according to claim 1, wherein the lubricant application unit changes a lubricant application amount in the lubricant application mode according to a forced consumption amount of the toner.   Print pixel count means for counting the number of print pixels that are pixels to which toner is to be attached from the input image data, and comparing the counted pixel count number with a predetermined pixel number to obtain a difference, When the difference is small, the forced toner consumption is calculated according to the difference, the toner is forcibly consumed by the developing unit, and the lubricant application amount is changed according to the counted number of pixels during normal image formation. 2. The image forming apparatus according to claim 1, wherein after control is performed and the toner is forcibly consumed, the ratio of the lubricant application amount to the number of pixels as the toner consumption amount is increased.   4. The image forming apparatus according to claim 2, wherein the control of the lubricant application amount depends on a change in a rotation time of the lubricant application means.   5. The image forming apparatus according to claim 1, wherein the lubricant application mode is based on a condition that the image carrier is rotated at least one rotation or more.   The image forming apparatus according to claim 1, wherein the lubricant is made of a metal stearate.

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