JP2963780B2 - Cleanerless image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleanerless image forming apparatus having no residual toner cleaning device.

[0002]

2. Description of the Related Art In an image forming apparatus, for example, a laser printer, a charging unit charges a photoconductor of a photoconductor drum, and forms an electrostatic latent image by exposing and recording information on the charged photoconductor with a laser beam. A toner is attached to the electrostatic latent image in a developing unit, and the toner image is transferred to a sheet in a transfer unit. Then, the sheet on which the toner image has been transferred is heat-fixed by a fixing unit, and printing is completed. Further, the toner remaining on the photosensitive drum after the transfer is removed by a cleaning device, and the photosensitive member is neutralized to prepare for the next charging.

Recently, a cleaning device for removing toner remaining on a photoreceptor after transfer has been abolished in order to reduce the size and cost of a laser printer.
So-called cleaner-less laser printers are becoming widespread. This cleanerless type is disclosed in Japanese Patent Application Laid-Open No. 59-13 / 1984.
The residual toner is collected in the developing section as disclosed in Japanese Patent Application Laid-Open No. 3573/1991, or is disturbed by a toner uniforming device as disclosed in Japanese Patent Application Laid-Open No. 62-203182, so that the deterioration in image quality is not noticeable in practical use. .

[0004]

However, the method of recovering the residual toner in the developing section or the method of disturbing the toner in the toner uniforming device is not always enough to treat the residual toner. In other words, in the method in which the residual toner is collected in the developing unit, even if the rubber hardness of the developing roller used in the developing unit and the pressing force to the photosensitive drum are initially set to the optimal conditions, the number of printed sheets may increase due to aging. As a result, the residual toner increases as the number of printed sheets increases with the passage of time even if the elasticity of the toner uniforming brush is initially set to the optimal condition in the method of disturbing the toner with a toner uniforming device. As a result, there is a problem that image quality is reduced.
In addition, when a toner uniform brush is used, if a pattern with many black backgrounds continues, there is a problem that the residual toner held by the brush saturates and exceeds a permissible limit, releasing toner and deteriorating image quality. Further, in the case of a toner which is difficult to transfer due to a variation in particle diameter and characteristics, there is a problem that a large amount of residual toner remains and image quality deteriorates. Therefore, an object of the present invention is to provide a cleaner-less image forming apparatus capable of preventing a deterioration in image quality due to residual toner.

[0005]

The invention corresponding to claim 1 is:
A cleanerless image forming apparatus that forms an electrostatic latent image by exposing a charged photoconductor to form an electrostatic latent image, attaches toner to the electrostatic latent image, and then transfers the image to paper to form an image. Means, an exposure means for exposing a blank sheet pattern or a pattern close to a blank sheet to the photoreceptor every time the counting means counts a predetermined number of sheets, and a blank sheet pattern or a pattern close to a blank sheet exposed by the exposure means Is provided on the sheet.

According to a second aspect of the present invention, there is provided an exposure means for exposing a blank paper pattern or a pattern close to a blank paper to a photoreceptor under a set condition after the counting means has counted a predetermined number of sheets. is there.

[0007]

In the present invention having such a configuration, when the counting means counts a predetermined number of sheets, the photosensitive member is exposed to a blank sheet pattern or a pattern close to a blank sheet, and the exposed blank sheet pattern or a pattern close to the blank sheet is printed on a sheet. Transcribe. As a result, the residual toner moves from the photoconductor to the paper.

After the counting means has counted the predetermined number of sheets, a blank sheet pattern or a pattern close to a blank sheet is set on the photosensitive member at a set condition, for example, at the time when a printing operation is started, or when continuous printing is completed. Is exposed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a photosensitive drum whose surface is covered with a photosensitive member. The photosensitive drum 1 is driven to rotate clockwise as indicated by an arrow in the figure. Around the photosensitive drum 1, a charging charger 2, an exposing unit 3, a developing unit 4, a transfer charger 5, a residual toner uniforming member 6, and a discharging lamp 7 are arranged according to an electrophotographic process. The charging charger 2 charges the photoconductor of the photoconductor drum 1 uniformly.

The exposing unit 3 irradiates a laser beam 3a from a laser scanner unit (not shown) to the photoreceptor of the photoreceptor drum 1 based on the recorded information to form an electrostatic latent image of the information by exposure. Has become.

The developing section 4 is provided with a developing roller 8 in contact with the surface of the photosensitive drum 1. The developing roller 8 is rotated in the direction of the arrow in FIG. The toner contained in the storage container 9 is adhered to the exposure unit while collecting the toner, and a toner image is formed.

The transfer charger 5 transfers a toner image from the photosensitive drum 1 to the paper 11 by applying a desired voltage to the paper 11 conveyed in the direction of the arrow in FIG. The sheet on which the toner image has been transferred is then heat-fixed, for example, by a fixing device (not shown). The residual toner equalizing member 6 is configured to even out the residual toner remaining on the photosensitive drum 1 after transfer by using a brush. The discharging lamp 7 discharges the photosensitive drum 1 after the transfer to prepare for the next charging.

FIG. 2 is a block diagram showing a main circuit configuration.
21 is a CPU (central processing unit) constituting the control unit main body,
Reference numeral 22 denotes a program ROM (read only memory) in which program data for the CPU 21 to control each section is stored. Reference numeral 23 denotes a work area for data processing and information for printing, which are image-developed and stored. A RAM (random access memory) in which areas are formed, a specific pattern print data ROM 24 storing print data of a blank paper pattern or a pattern close to a blank paper, 2
Reference numeral 5 denotes a specific pattern printing start counter for counting the number of sheets to be printed; 26, an interface for exchanging information with a host computer and receiving print information from the host computer; 27, an operation panel provided with various keys and lamps; And 28, a mechanism control circuit for driving and controlling the photosensitive drum 1, the charging charger 2, the laser scanner unit, the developing roller 8, the transfer charger 5, the charge removing lamp 7, and the like in accordance with an electrophotographic process. An interface and a one-line buffer memory for performing control for outputting print data line by line, taking in key signals from the operation panel 27, and outputting display signals.

The CPU 21 performs the control shown in FIG. 3 in addition to the normal print control. That is, when a printing start operation is performed, first, the printing start counter 25
Is the predetermined number of sheets N that is set in advance.
i (note that i = 1,2,3,…)
If it has not reached, the number of prints N counted by the counter 25 after printing one page is incremented by +1. Then, it is checked whether the next print data exists.

If there is the next print data, it is checked whether or not the number of prints N counted by the print start counter 25 has reached a predetermined number of prints Ni. If there is no next print data, the process is terminated. .

When N = Ni in the check as to whether or not the number of prints N has reached the predetermined number of prints Ni, a blank or near blank pattern is called from the specific pattern print data ROM 24 and blank printing is performed. At this time, the specific pattern print data is set so as to perform, for example, halftone printing of "Now cleaning printing" at the beginning of printing. Ni is, for example, i × N1 (where i = 1, 2, 2, 3)
…).

In the embodiment having such a configuration, when a print operation is started and print information is received by the interface 26 from the host computer, the CPU 21 develops the print information in the RAM 23 in an image pattern,
The data is output to the mechanism control circuit 28 via the interface and the one-line buffer memory 29.

As a result, the photoreceptor drum 1 rotates, and the photoreceptor is uniformly charged by the charger 2. After that, an electrostatic latent image is formed on the photoreceptor by a laser beam based on an image pattern. The toner is adhered to the electrostatic latent image by the rotation of the developing roller 8 to form a toner image, and the toner image is transferred to the sheet 11 conveyed and supplied by the operation of the transfer charger 5. Then, the transferred paper is thermally fixed by the fixing device, and printing of one page is completed. Further, the residual toner remaining on the photoreceptor surface after the transfer is averaged over the entire surface by the residual toner equalizing member 6, further discharged by the discharge lamp 7 and prepared for the next charging. Therefore, when printing is performed over a plurality of pages, the above operation is repeated.

Each time one page is printed, a counter 25 is printed.
Counts the number of prints N. Then, the printing operation is repeated several times, and when the number of prints N counted by the counter 25 reaches the predetermined number N1, the blank sheet printing is started immediately at that time. The blank toner printing removes the residual toner on the photoconductor. Further, at this time, the character printing of "Now cleaning printing" is performed in halftone, so that the operator can confirm that blank printing has been performed.

When blank printing is completed, the predetermined number Ni becomes N2, that is, 2N1. Therefore, when the counter 25 again counts the same number of prints N after the blank page printing, the next blank page printing is performed. However, the counter 25
Is 2N. Thus counter 2
Every time 5 counts the number N of printed sheets, blank printing is performed, and residual toner is removed from the photoconductor.

Therefore, even if the residual toner increases as the number of prints increases due to the aging of the developing roller 8 and the residual toner equalizing member 6, if the blank paper is printed before the image quality is reduced, the residual toner is reduced. As a result, the image quality can be prevented from lowering.

FIG. 4 shows styrene acrylic magnetic toner A, styrene acrylic nonmagnetic toner B,
C is a graph showing the relationship between the number of printed sheets and the background smear (%) due to residual toner when using a nonmagnetic D of polyester type. It can be seen that the percentage of background dirt suddenly increases when more sheets are used. If the background dirt is 1% or less, the image quality is practically not reduced, but if it exceeds 1%, the image quality is reduced. The background stain is (unused paper reflectance)-(white reflectance after printing).

On the other hand, for example, styrene-acrylic magnetic toner A is used as the toner, and when the predetermined number N1 is 1,250, 1,250, 2,500,
As a result of performing blank printing on every 3,750 sheets,..., As shown in FIG. 5, the background stain was always suppressed to 1% or less, and about 0.5%, and deterioration in image quality was prevented.

In this embodiment, since the counter 25 counts the total number of printed sheets, a counter for counting the life of the photosensitive drum 1 by the number of printed sheets without using a dedicated counter is also used. Can also. Next, second and third embodiments of the present invention will be described with reference to the drawings.

FIG. 6 shows a second embodiment. When a printing operation is started, the CPU 21 first sets a flag F to "0". Then, one page printing is performed, and the number of prints N counted by the counter 25 is incremented by +1. Subsequently, it is checked whether the number of prints N has reached the predetermined number N0.

In this manner, one-page printing is repeated as long as there is print data, and the number of prints N counted by the counter 25 is incremented by one every time one page is printed. Then, the printing operation is repeated several times, and when the number of prints N reaches the predetermined number N0, the flag F is set to "1".

When the print data is exhausted, it is determined that the flag F is "1" and blank printing is performed. Then, the number of prints N counted by the counter 25 is reset to “0”.

In this way, even if the number of prints N counted by the counter 25 during the continuous printing of a plurality of sheets reaches the predetermined number N0, blank printing is not performed until a series of printing is completed. In this embodiment, the same effects as in the above embodiment can be obtained.

FIG. 7 shows a third embodiment, in which the CPU 21
When the printing operation is started, first, it is checked whether or not the flag F is "1". If the flag F is not "1", one page is printed, and the number of prints N counted by the counter 25 is incremented by +1. Subsequently, it is checked whether the number of prints N has reached the predetermined number N0.

In this manner, one-page printing is repeated as long as there is print data, and the number of prints N counted by the counter 25 is incremented by one every time one page is printed. Then, the printing operation is repeated several times, and when the number of prints N reaches the predetermined number N0, the flag F is set to "1". If the flag F is "1" at the start of printing, blank printing is performed, the flag F is set to "0", and normal printing is performed.

In this way, the number of prints N counted by the counter 25 during printing is equal to the predetermined number N0.
Is reached, blank printing is not performed until the next printing operation is started. In this embodiment, the same effects as in the above embodiment can be obtained.

[0033]

As described above in detail, according to the present invention, it is possible to provide a cleaner-less type image forming apparatus capable of preventing a deterioration in image quality due to residual toner.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a main circuit configuration of the embodiment.

FIG. 3 is a flowchart showing print control of the main part of the embodiment.

FIG. 4 is a graph showing the relationship between the number of printed sheets and background stain when blank printing is not performed using various toners.

FIG. 5 is a graph showing the relationship between the number of prints and background contamination in the embodiment.

FIG. 6 shows a second embodiment of the present invention, and is a flowchart showing main part print control.

FIG. 7 shows a third embodiment of the present invention, and is a flowchart showing main part print control.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... Charging charger, 3 ... Exposure part,
4 developing unit, 5 transfer charger, 6 residual toner uniforming member, 8 developing roller, 21 CPU, 24 specific pattern print data ROM, 25 specific pattern print start counter.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-174486 (JP, A) JP-A-3-82588 (JP, A) JP-A-2-87253 (JP, U) JP-A-60- 6171 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/22 G03G 15/08 G03G 21/10 G03G 21/14

Claims (2)

(57) [Claims] 1. A cleanerless image forming apparatus for forming an electrostatic latent image by exposing a charged photoreceptor to form an electrostatic latent image, attaching toner to the electrostatic latent image, and transferring the toner to a sheet to form an image. Counting means for counting the number of sheets, exposing means for exposing a blank sheet pattern or a pattern close to a blank sheet to the photoreceptor each time the counting means counts a predetermined number of sheets set in advance, and a blank sheet exposed by the exposing means A cleanerless image forming apparatus, comprising a transfer unit for transferring a pattern or a pattern close to a blank sheet onto a sheet. 2. A cleanerless image forming apparatus for forming an electrostatic latent image by exposing a charged photoreceptor to form an electrostatic latent image, attaching toner to the electrostatic latent image, and then transferring the electrostatic latent image to a sheet to form an image. Counting means for counting the number of sheets, exposing means for exposing a blank paper pattern or a pattern close to blank paper to the photoconductor under a set condition after the counting means has counted a predetermined number of sheets, and the exposing means A cleaner-less type image forming apparatus comprising a transfer unit for transferring an exposed blank paper pattern or a pattern close to a blank paper to a paper.