JP4090404B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus provided with a charge eliminating means on the surface of a photoreceptor.

In an electrophotographic image forming apparatus, the surface of a photoconductor moves as the drum-shaped photoconductor rotates, and the surface of the photoconductor is charged by a charging unit, and the charged photoconductor surface is exposed by an exposure unit. Forming an electrostatic latent image corresponding to the image to be processed, developing the electrostatic latent image as a toner image by the developing means, and transferring the toner image from the surface of the photosensitive member to a transfer material such as recording paper by the transferring means. An image is formed by passing through the step of causing the image to be formed.
Here, as in the case of continuous printing of a plurality of images, when image formation is performed by charging the surface of the photoconductor again within a short time after image formation is completed, the latent image memory on the surface of the photoconductor is used for later processing. There may be a so-called ghost in which the previously processed image is reflected in the processed image.
In order to prevent the occurrence of a latent image memory that causes such a ghost, it is common to neutralize the surface of the photosensitive member by a neutralizing means as a pre-charging process.
On the other hand, Patent Document 1 discloses an image forming apparatus that does not perform static elimination when forming an image on the first side of a photoreceptor, and eliminates static electricity on the second and subsequent sides.
JP 2003-76076 A

By the way, in recent electrophotographic image forming apparatuses, the number of times of image forming processing per hour (the number of times the photosensitive member is used per hour) is increasing due to the increase in processing speed. Life expectancy is an important requirement.
However, static elimination causes photoconductor fatigue, and ozone exposure occurs due to recharging from an uncharged state after static elimination, which promotes photoconductor wear (thin film loss). In this case, there is a problem that the life of the photoreceptor is deteriorated.
Further, as disclosed in Patent Document 1, the effect of extending the life of the photosensitive member (deterioration preventing effect) is small simply by eliminating the charge removal on the first side.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus capable of extending the life of a photosensitive member by suppressing the frequency of static elimination while preventing the occurrence of ghosts. It is in.

To achieve the above object, the present invention comprises a charging means for charging the surface of a photoreceptor, an exposure means for exposing the charged photoreceptor surface to form an electrostatic latent image corresponding to a processing target image, An image forming apparatus comprising: a developing unit that develops an electrostatic latent image as a toner image; and a transfer unit that transfers the toner image onto a transfer material from the surface of the photosensitive member. been made to control and charge removing means for neutralizing the body surface before charging by said charging means, whether to perform charge elimination by the charge eliminating means, pre Symbol processing target image is a text image or solid image binary In this case, when the image to be processed is formed as a binary solid image, or the image formation of one image to be processed in which the circumferential length of the photosensitive member is shorter than the circumferential length of the photosensitive member. Body surface If applicable to at least any one of a case where a plurality of times continuously processed using the same region, and characterized by being provided with a neutralization control means for controlling not to perform the neutralization by the discharger The image forming apparatus is configured.
As a result, it is possible to control so as not to perform static elimination when the image content or image processing content is less likely to cause a ghost, so that it is possible to prevent occurrence of a ghost and always perform normal (maximum width) static elimination. However, it is possible to extend the life of the photoreceptor by reducing the frequency of static elimination.
For example, ghosting is noticeable in halftone images (images with halftone dots and fine lines), but ghosting is not noticeable in binary text images and solid images, and so neutralization is performed only for halftone images. It is conceivable to do so.
In addition, when a high-quality mode in which a ghost is likely to appear is selected and input by the user, static elimination is performed, and a low-quality mode in which the ghost is not conspicuous (a mode for forming a processing target image as a binary image) is selected and input. In such a case, it is conceivable to perform control so as not to perform static elimination.

Also, electrodeposition in the image forming apparatus of the child photographic method, when the length in the circumferential direction of the photosensitive body is circumference plurality consecutively processes the short processing target image than the photoreceptor (multiple copies successively image formation), In some cases, a latent image is formed on the surface of the photosensitive member at a timing synchronized with the circumference of the circumferential surface of the photosensitive member by detecting a timing mark provided on the photosensitive member. In such an image forming apparatus, one processing target image is processed a plurality of times using the same area on the surface of the photoreceptor, and no ghost is generated even if static elimination is not performed. Thereby, the frequency of static elimination can be suppressed while preventing the occurrence of ghost.
In the image forming apparatus as described above, the surface potential of the photosensitive member after being charged a plurality of times by the charging unit without performing the neutralization by the neutralizing unit in a state where the transfer by the transfer unit is not performed. The present invention is preferably applied when the difference between the surface potential of the photoconductor and the surface potential of the photoconductor after charging by the charging unit once after the neutralization by the neutralizing unit is 30 V or more.
When the difference between the surface potentials is small (less than 30 V), a ghost of a level that can be visually recognized does not usually occur, so that the necessity for static elimination is low. On the other hand, when the difference in surface potential is large (30 V or more), it is necessary to eliminate static electricity depending on the type of processing target image, processing content, and the like. This will contribute to the extension of the lifespan.

According to the present invention, it is possible Iyo controlled so that perform neutralization if Gore paste is difficult image content and image processing contents generation, while preventing the occurrence of the ghost, neutralization frequently than always performing neutralization It is possible to extend the life of the photoreceptor by suppressing the degree .

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a flowchart showing the procedure of charge removal control in the image forming apparatus X according to the embodiment of the present invention, FIG. 2 is a side sectional view showing the entire configuration of the image forming apparatus X, and FIG. It is a block diagram showing the schematic structure of the principal part.

First, the configuration of the image forming apparatus X according to the embodiment of the present invention will be described with reference to the side sectional view of FIG. 2 and the block diagram of FIG.
The image forming apparatus X has a copier mode (copy mode), a printer mode, and a FAX mode as print modes. Operation input from an operation unit (not shown) and print job from an external host device such as a personal computer are performed. Is selected by the control unit (to be described later).
As shown in FIG. 2, the image forming apparatus X is roughly divided into a document reading unit 10, a paper feeding unit 20, a printing unit 30, and a paper discharge unit 40, and the document reading unit 10 is arranged above the paper feeding unit 20. A paper discharge unit 40 is provided at an intermediate position between the document reading unit 10 and the paper supply unit 20.
Hereinafter, the copier mode will be described from the above processing modes.
After the user places a document on the platen glass 11 of the document reading unit 10 (scanner unit), the sheet (recording paper) is placed on the sheet feeding cassette 21 of the sheet feeding unit 20 or the manual feed tray 23 provided on the side of the apparatus. After inputting the condition input key (number of printed sheets / printing magnification, etc.) on an operation panel (not shown) disposed on the front surface of the apparatus and operating the start key on the operation panel (an example of an image formation request) ) To start the copy operation.
When the start key is operated, a main drive motor (not shown) starts and each drive gear rotates. Thereafter, the paper feed roller 22 or 22a rotates to feed (feed) the paper into the apparatus, and the fed paper reaches the registration roller 31 (roller pair) and is captured. The registration roller 31 temporarily stops the paper so as to synchronize with the leading edge (image formation start portion) of the image formed on the photosensitive drum 32, and the leading edge of the paper is uniformly pressed against the registration roller 31. Thus, the leading edge position of the paper is corrected.

On the other hand, in the document reading unit 10, the copy lamp 12a (light source) is turned on, and the exposure starts when the copy lamp unit 12 moves in the direction of the arrow. Irradiation light applied to the document by the copy lamp 12a becomes reflected light (reflected light from the document) including image information of the document, and the reflected light is transmitted from the first mirror 12b provided in the copy lamp unit 12 to the second light. Reading is performed by inputting to the CCD 16 from the mirror 13, the third mirror 14, and the optical lens 15.
The image information read in this way is converted into an electrical signal by a CCD circuit (not shown), and the image information signal is subjected to image processing under a set condition, and the laser scanner unit. 33 as print data.

On the other hand, a part of the circumferential surface of the photosensitive drum 32 is charged to a predetermined charging potential in the entire axial direction by the charging unit 34 (an example of a charging unit), and the entire circumferential surface is rotated by rotating the photosensitive drum 32. Is charged to a predetermined charging potential. The surface of the charged photoconductor 32 moves to the next process by the rotation of the photoconductor drum 32.
Next, in the laser scanner unit 33 (an example of an exposure unit), a laser beam emitted from the semiconductor laser is deflected by a polygon mirror (rotating polygonal mirror) having a plurality of reflecting surfaces in the rotation direction and various optical systems. Irradiated to the photosensitive drum 32. As a result, the laser beam is scanned on the photosensitive drum 32 charged by the charging unit 34, and an electrostatic latent image is formed on the photosensitive drum 32. Thereafter, the toner on the MG roller 35a (an example of the developing unit) in the developing tank 35 is attracted to the surface of the photosensitive drum 32, and the electrostatic latent image is developed according to the potential gap on the photosensitive drum 32 by the toner. Imaged.
Further, a sheet (recording sheet) to be imaged is conveyed in the direction of the photosensitive drum 32 by the registration roller 31 at the same timing, and is transferred onto the photosensitive drum 32 by a transfer unit 36 (corona charger, an example of transfer means). Toner is transferred to the paper. The toner remaining on the photosensitive drum 32 is scraped off by the cleaning blade 37 a of the drum unit and collected by the cleaner unit 37.
The surface of the photosensitive drum 32 from which the toner has been removed by the cleaning blade 37a is neutralized as necessary by the neutralizing device 39 (an example of a neutralizing unit) while moving to the charging unit 34 (that is, the transfer unit). After the transfer by the unit 36, the charge is removed before charging by the charging unit 34).

On the other hand, the sheet on which the toner has been transferred passes between the heating roller 38a and the pressure roller 38b of the fixing device 38 (fixing step), and heat and pressure are applied, so that the unfixed toner on the sheet is transferred to the sheet. Then, the sheet is melted and fixed to the sheet discharge tray 42 by the sheet discharge roller 41. The heating roller 38a is heated by a heater 38c provided therein.
In addition, when it is detected by a predetermined sensor that a document is placed on the document tray 19 included in the document reading unit 10, the paper feed roller 51 rotates when a predetermined start key operation is performed. Then, the document placed on the document tray 19 is sent into the document reading unit 10 and is transported through a predetermined transport path Rt1. A registration roller 53 is provided on the conveyance path Rt1, and the original is captured by the registration roller 53 and positioned at the leading end of the original, and then conveyed to the original reading position at a predetermined timing.
On the other hand, the document being conveyed is exposed while the copy lamp unit 12 is stopped at a predetermined stop position (document reading position). The process of reading the document image by the reflected light from the document obtained by this exposure is as described above.
The document whose image has been read in this way is discharged to the document discharge unit 18.

  Further, as shown in FIG. 3, the image forming apparatus X includes a communication unit 61 that performs communication control with a predetermined host device via a communication line, and an operation / display that is an input / output unit including a liquid crystal touch panel and the like. , An image memory 63 that is a storage means for print data received from the host device and image data read from a document, a setting memory 64 that is a storage means for various setting information, a CPU and its peripheral devices (ROM) A control unit 65 that controls the entire image forming apparatus X by executing processing according to a predetermined program stored in the ROM, and shading correction and data format (data type) of the image data ) Conversion, print data (image data) received by the communication unit 61, and image data read by the image reading unit 10 How the are provided with an image processing unit 66 for performing various image processing discriminate whether such a type of image data. The control unit 65 controls the image processing unit 66, the image reading unit 10, the printing unit 30, the paper feeding unit 20, and the like, and performs the control of the printing unit 30. Controls whether or not to perform static elimination.

Next, the procedure of control processing of the static eliminator 39 by the control unit 65 will be described using the flowchart of FIG. In the following, S1, S2,... Represent processing procedure (step) numbers.
The following processing is executed by the control unit 65 every time an image forming job (such as a print job from the host device or a document image copy job) occurs. Alternatively, it may be performed each time image formation for one page (one sheet) of recording paper is performed.
First, when an image forming job is generated, the control unit 65 is set to process the processing target image in either the “high image quality mode” or the “saving mode (low image quality mode)”. Is checked (S1, S2).
In the case of a print job received from the host device, the processing mode is set in the print job (set by the user on the host device side). In the case of a job for copying a document image, the operation / display mode is set. Set by the user from section 62.
Here, the “high quality mode” is a process for forming a halftone image by forming halftone dots and fine lines, and the “saving mode” is a process for forming a binary solid image.
If it is determined in S1 that the “high quality mode” is set, the static eliminator 39 is turned “ON” (actuated) to perform static elimination (S7), and in S2, the “saving mode” is set. If it is determined that the static electricity is removed, the static eliminator 39 is set to “OFF” (stopped) so as not to perform static elimination (S6).

If no mode is set, the processing target is a job for multiple printing of the same image (multiple copies), and the length of the image (the circumferential length on the photosensitive drum 32). ) Is shorter than the circumference of the photosensitive drum 32 (S3, S4). If the condition is satisfied, the static eliminator 39 is set to “OFF” to eliminate static charges. Is not performed (S6).
In the image forming apparatus X, a timing mark and a timing mark detecting means for detecting passage of the timing mark are provided on the rotating shaft of the photosensitive drum 32 or a flange provided on the rotating shaft. Then, when the length of the processing target image in the circumferential direction of the photosensitive drum 32 is shorter than the peripheral length of the photosensitive drum 32, a single processing target image is processed in succession (a plurality of copies of the continuous image). In the case of (formation), the controller 65 controls the recording of the latent image by the laser scanner unit 33 to start in synchronization with the detection timing of the timing mark. As a result, each time the circumferential surface of the photosensitive drum 32 goes around, one processing target image is continuously processed a plurality of times using the same area on the surface of the photosensitive drum 32. In this case, since no ghost is generated even if static elimination is not performed, control is performed so that static elimination is not performed.

On the other hand, if the condition is not satisfied, it is further determined whether or not the processing target image is a halftone image (S5). If it is determined that the image is a halftone image, the static eliminator 39 is turned on. The neutralization is performed (S7), and if the image is not a halftone image (binary text image or solid image), the neutralization device 39 is set to “OFF” so that the neutralization is not performed (S6).
Here, whether or not the image is a halftone image is determined by the image processing unit 66 by using a known halftone dot detection method or fine line detection method. When a halftone dot or fine line is detected, it is determined that the image is a halftone image.
For example, an edge of an image is detected, and black and white binarization is performed for the edge. Then, the number of times of black and white inversion is counted, and when the number of times exceeds a predetermined threshold, it is determined as a halftone dot.
After controlling the static elimination ON / OFF as described above, it is checked whether or not the job processing is completed (printing is completed) (whether there is an image forming process for the next page) (S8). If not completed, the process returns to S1 for the next page and the above-described processing is repeated. If the processing is completed, the control processing ends.
As described above, when it is difficult for ghosts to occur (when “saving mode (low image quality mode)” is set, when the image is not a halftone image, or when one image to be processed is used using the same area on the surface of the photosensitive drum 32. (When processing multiple times in succession), control is performed so that static elimination is not performed. Therefore, the frequency of static elimination is always suppressed compared to the case where normal (maximum width) static elimination is performed while preventing ghosting. Can extend the service life.
Although the above embodiment controls ON / OFF of static elimination, it is controlled so as to reduce the degree of static elimination instead of turning off static elimination by adjusting the static elimination potential of the static elimination device 39. Even if it does, the degree of ozone exposure is weakened and the life of the photoreceptor can be extended.

  The present invention is applicable to an electrophotographic image forming apparatus.

5 is a flowchart showing a procedure of charge removal control in the image forming apparatus X according to the embodiment of the present invention. FIG. 3 is a side sectional view showing the overall configuration of the image forming apparatus X. 2 is a block diagram illustrating a schematic configuration of a main part of the image forming apparatus X. FIG.

Explanation of symbols

X ... image forming apparatus 10 ... image reading unit 18 ... document discharge unit 20 ... paper feeding unit 30 ... printing unit 31, 53 ... registration roller 32 ... photoconductor drum 33 ... laser scanning unit 34 ... charging unit (charging means)
35 ... developing tank 35a ... MG roller (developing means)
36. Transfer unit (transfer means)
38... Fixing device 39... Static elimination device (static elimination means)
40 ... paper discharge unit 61 ... communication unit 62 ... operation / display unit 63 ... image memory 64 ... setting memory 65 ... control unit (static elimination control means)
66 Image processing units S1, S2,... Processing procedure (step)

Claims (1)

A charging unit for charging the surface of the photoconductor; an exposure unit for exposing the charged surface of the photoconductor to form an electrostatic latent image corresponding to an image to be processed; and developing for developing the electrostatic latent image as a toner image An image forming apparatus comprising: means; and transfer means for transferring the toner image onto the transfer material from the surface of the photoconductor.
Neutralizing means for neutralizing the surface of the photoreceptor after being transferred by the transferring means before charging by the charging means;
Be one that controls whether to perform charge elimination by the charge eliminating means, pre Symbol processed image be a text image or solid image binary images forming the target image with a solid image of binary If, or the one in the case where the length in the circumferential direction of the photosensitive body is continuously processed multiple times by using the same region of the photosensitive member of one shorter than the circumferential length said processing an image formation of the target image the photoreceptor surface A static elimination control means for controlling so as not to perform static elimination by the static elimination means when at least one of
An image forming apparatus comprising:

Images