JPH10171325A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device in which time required for electrification is short and which hardly causes fogging. SOLUTION: As for this image forming device 2; in an electrification stage for applying specified surface electric potential to a photoreceptor drum 10 which has nearly its term of service life, a peeling voltage from a peeling charger 16b and AC voltage from a precleaning charge eliminating device are impressed on the drum 10 simultaneously with the electrification of surface electric potential by an electrifying device, 12, so that the time taken until the surface electric potential of the drum 10 attains saturation surface potential is reduced. Thus, the image having no fogging is provided. Then, the time required to finish printing is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus for forming an image by using an electrophotographic process and a control method of the image forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic process, a photoconductor having photoconductivity is charged to a predetermined potential and then irradiated with light corresponding to an image to selectively control the potential of the photoconductor. The latent image is attenuated to form a latent image, and a toner image obtained by developing with a toner as a developer is transferred to a transfer-receiving material, thereby forming a copy image of an object to be copied or an image to be printed.

Around the photoreceptor, a charging device for applying a predetermined surface potential to the photoreceptor, a developing device for developing a latent image on the photoreceptor surface with toner to form a toner image, and a toner image on the photoreceptor are recorded. A transfer device for transferring to the material and a cleaning device for removing the transfer residual toner remaining on the surface of the photoconductor and erasing the charge distribution on the surface of the photoconductor are arranged in order along the direction in which the photoconductor is rotated. I have.

[0004]

In general, in the above-described image forming apparatus, if the amount of electric charge held by the photoreceptor, that is, the surface potential is not stable, the image obtained when the toner image obtained by development is transferred to paper Since the density fluctuates greatly, exposure by the exposure device, that is, image formation is stopped until the surface potential of the photoconductor charged by the charging device reaches the saturated surface potential.

It is known that, when image formation is repeated and the charging ability of the photosensitive member is reduced, the time from the start of charging by the charging device to the time when the surface potential reaches the saturated surface potential is increased. Thus, if the number of times image formation is repeated approaches the number of times that repetitive image formation is possible, which is set according to the type and characteristics of the photoconductor, that is, the end of life, the surface of the photoconductor is charged at the initial charging time. Since the potential does not reach the saturation potential, particularly in a printer device using the reversal developing method, undesired toner adheres to the non-exposed portion in a region where the surface potential does not reach the saturation potential, and fog occurs There's a problem.

For this reason, a method has been proposed in which the surface potential is reliably set to a saturated surface potential by extending the charging time based on the result of measuring the surface potential of the photoreceptor or in accordance with the number of image formations. .

However, in the method of increasing the charging time, the time from when the image formation is instructed to when the sheet on which the image is formed is output, that is, the first copy increases. In this case, if non-continuous copy or printouts are repeated one by one, the time required until all image formation is completed is greatly increased as compared with the case where the same document is continuously copied. Problem. SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus in which the time required for charging is short and fogging does not easily occur.

[0008]

SUMMARY OF THE INVENTION The present invention has been made based on the above-mentioned problems, and includes a charging means for charging an image carrier to a predetermined surface potential, and a charging means for charging the image carrier to a predetermined surface potential. Exposure means for exposing the image carrier to form an electrostatic image, and developing means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image, Transfer means for transferring the developer image formed on the image carrier by the developing means to a transfer material; and transferring the developer image onto the transfer material by the transfer means. Charge erasing means for erasing the charge retained by the residual developer remaining on the surface; and peeling for releasing the transfer-receiving material on which the developer image has been transferred by the transfer means from the electrostatic attraction with the image carrier. Means and the image carrier by the charging means Charge starting time, there is provided an image forming apparatus characterized by and a control means for actuating at least one of the release means and the charge erasing means.

Further, the present invention provides a charging device for charging an image carrier to a predetermined surface potential, and an exposure device for exposing the image carrier charged to a predetermined surface potential by the charging device to form an electrostatic image. Means, developing means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image, and the developer formed on the image carrier by the developing means Transfer means for transferring an image to a transfer material, and charge for erasing the charge retained by the residual developer remaining on the image carrier after the developer image is transferred to the transfer material by the transfer means. Erasing means, peeling means for releasing the transfer material on which the developer image has been transferred by the transfer means from electrostatic attraction with the image carrier, and starting charging of the image carrier by the charging means. The peeling means and the charge erasing means There is provided an image forming apparatus characterized by and a control means for operating each. Further, the present invention provides a charging unit for charging the image carrier to a predetermined surface potential, an exposure unit for exposing the image carrier charged to a predetermined surface potential by the charging unit to form an electrostatic image, Developing means for supplying a developer to the electrostatic image formed on the image carrier by the exposing means to form a developer image; and covering the developer image formed on the image carrier by the developing means. Transfer means for transferring to a transfer material,
After the developer image is transferred to the transfer material by the transfer unit, a charge erasing unit that erases a charge held by the remaining developer remaining on the image carrier, and the image carrier by the charging unit And control means for activating the charge erasing means at the same time as the start of charging of the image forming apparatus.

Still further, according to the present invention, a charging means for charging an image carrier to a predetermined surface potential, and an image is formed by exposing the image carrier charged to a predetermined surface potential by the charging means. Exposure means, development means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image, and the development formed on the image carrier by the development means Transfer means for transferring the developer image onto the transfer material, peeling means for releasing the transfer material onto which the developer image has been transferred by the transfer means from electrostatic attraction with the image carrier, and charging means And a control means for operating the peeling means at the same time as the start of charging of the image carrier by the image forming apparatus.

Still further, according to the present invention, a charging means for charging an image carrier to a predetermined surface potential, and an image is formed by exposing the image carrier charged to a predetermined surface potential by the charging means. Exposure means, development means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image, and the development formed on the image carrier by the development means Transfer means for transferring the developer image onto the transfer material, and erasing the charge retained by the residual developer remaining on the image carrier after the developer image is transferred onto the transfer material by the transfer means. A charge erasing unit, a peeling unit that releases the transfer-receiving material on which the developer image has been transferred by the transfer unit from electrostatic attraction with the image carrier, the peeling unit and the charge erasing unit, Band of the image carrier by charging means Control means for operating at a predetermined timing so as to shorten the time required for the surface potential held by the image carrier to reach the saturated surface potential at the start of the image forming apparatus. It is.

Still further, according to the present invention, a charging means for charging an image carrier to a predetermined surface potential, and an image is formed by exposing the image carrier charged to a predetermined surface potential by the charging means. Exposure means, development means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image, and the development formed on the image carrier by the development means Transfer means for transferring the developer image onto the transfer material, and erasing the charge retained by the residual developer remaining on the image carrier after the developer image is transferred onto the transfer material by the transfer means. Charge erasing means, peeling means for releasing the transfer material on which the developer image has been transferred by the transfer means from electrostatic attraction with the image carrier, and at least one of the peeling means and the charge erasing means By the above charging means Control means for operating at a predetermined timing so as to shorten the time required for the surface potential held by the image carrier to reach the saturated surface potential in accordance with the start of charging of the image carrier. A forming apparatus is provided.

Still further, according to the present invention, a charging means for charging an image carrier to a predetermined surface potential, and an image is formed by exposing the image carrier charged to a predetermined surface potential by the charging means. Exposure means, development means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image, and the development formed on the image carrier by the development means Transfer means for transferring the developer image onto the transfer material, and erasing the charge retained by the residual developer remaining on the image carrier after the developer image is transferred onto the transfer material by the transfer means. The charge erasing means and the charge erasing means are provided with a predetermined timing so as to shorten the time required for the surface potential held by the image carrier to reach the saturated surface potential in accordance with the start of charging of the image carrier by the charging means. Control to operate with There is provided an image forming apparatus comprising: the stage, a.

Still further, according to the present invention, a charging means for charging an image carrier to a predetermined surface potential, and an image is formed by exposing the image carrier charged to a predetermined surface potential by the charging means. Exposure means, development means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image, and the development formed on the image carrier by the development means Transfer means for transferring the developer image onto the transfer material, peeling means for releasing the transfer material on which the developer image has been transferred by the transfer means from electrostatic attraction with the image carrier, and peeling means Control means for operating at a predetermined timing so as to shorten the time required for the surface potential held by the image carrier to reach the saturated surface potential in accordance with the start of charging of the image carrier by the charging means. Characterized by There is provided an image forming apparatus.

Still further, according to the present invention, a charging means for charging an image carrier to a predetermined surface potential, and an image is formed by exposing the image carrier charged to a predetermined surface potential by the charging means. Exposure means and a development means for supplying a developer charged to the same polarity as the electrostatic image to the electrostatic image formed on the image carrier by the exposure means to form a developer image by reversal development, Transfer means for transferring the developer image formed on the image carrier by the developing means to a transfer material; and transferring the developer image onto the transfer material by the transfer means. Charge erasing means for erasing the charge retained by the remaining developer remaining on the above, the charge erasing means,
In accordance with the start of charging the image carrier by the charging means,
The present invention provides an image forming apparatus comprising: a control unit that operates at a predetermined timing so as to shorten a time required for the surface potential held by the image carrier to reach a saturated surface potential.

Still further, according to the present invention, a charging means for charging an image carrier to a predetermined surface potential, and an image is formed by exposing the image carrier charged to a predetermined surface potential by the charging means. Exposure means and a development means for supplying a developer charged to the same polarity as the electrostatic image to the electrostatic image formed on the image carrier by the exposure means to form a developer image by reversal development, Transfer means for transferring the developer image formed on the image carrier by the developing means to a transfer material; and transferring the developer material on which the developer image has been transferred by the transfer means to the image carrier. The peeling means for releasing from electrostatic attraction and the peeling means are adapted to start charging of the image carrier by the charging means, and shorten the time until the surface potential held by the image carrier reaches the saturated surface potential. Operate at predetermined timing There is provided an image forming apparatus, characterized in that it comprises a control unit, the to.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, an image forming apparatus, for example, a laser exposure type copying apparatus 2 has a cylindrical shape rotatably formed and is to be recorded by a laser beam supplied from a laser exposure apparatus described later. The photosensitive drum 10 on which an electrostatic latent image corresponding to an image is formed,
Have.

Around the photosensitive drum 10, a charging device 12 for charging the surface of the photosensitive drum 10 to a predetermined potential along the rotation direction of the photosensitive drum 10 indicated by an arrow a.
A developing device 14 for inverting and developing the electrostatic latent image by supplying a toner having the same polarity as the charged polarity of the photosensitive drum 10 as a developer to the latent image formed on the photosensitive drum 10 by a laser exposure device described later; A transfer device 16 for transferring the toner image on the photosensitive drum 10 developed by the device 14 onto a sheet as a recording medium, and erasing the transfer residual toner that has not been transferred to the sheet by the transfer by the transfer device 16, that is, the charge of the residual toner Pre-cleaning charge erasing device 1
7. A cleaning device 18 that scrapes and collects residual toner on the photosensitive drum 10 and a static eliminator 20 that removes residual charge on the surface of the photosensitive drum 10 are arranged in this order.

The charging device 12 includes a corona wire 12a and a grid electrode 12b. The charging device 12 is connected to a charging voltage generation circuit 102 and a grid bias voltage generation circuit 104, which will be described later with reference to FIG.
0 is charged to a predetermined potential.

The developing device 14 holds a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed at a predetermined ratio on the outer periphery, and will be described later with reference to FIG. The toner negatively charged by the developing bias voltage from the developing bias
And a developing roller 14a that adheres to the electrostatic latent image formed in the image forming apparatus. The two-component developer and the developing roller 14
a is housed in the housing 14b. Developing device 1
Reference numeral 4 denotes an arrangement in which the outer peripheral surface of the photoconductor drum 10 and the surface of the developing roller 14a are substantially parallel to each other, and is formed on the sleeve along the magnetic force lines generated from the main magnetic pole of the magnet medium of the developing roller 14a. Carrier ears
The toner adhering to the (spike) by the mirror image force is formed by the potential of the electrostatic latent image on the photosensitive drum 10 and the developing bias voltage in a developing region where the photosensitive drum 10 and the developing roller 14a face each other. Using the electric field, the photosensitive drum 1
The electrostatic latent image is developed by moving toward the latent image on the zero.

The transfer device 16 has a corona discharge type transfer charger 16a similar to the charging device 12 and a similar corona discharge type peeling charger 16b, and a transfer bias voltage generating circuit 107 which will be described later with reference to FIG.
a, connected to the stripping voltage generation circuit 107b,
4, the toner image formed on the surface of the photosensitive drum 10 by supplying the toner is electrostatically attracted to a sheet and transferred.
Further, the toner image electrostatically attached to the sheet is peeled off from the photosensitive drum 10 together with the sheet.

The pre-cleaning charge erasing device 17 is a corona discharge device similar to the charging device 12, and is connected to a pre-cleaning AC voltage generating circuit 108 described later with reference to FIG. By providing a voltage to the photosensitive drum 10, the transfer of the toner image and the separation of the sheet by the transfer device 16
The charge of the residual toner remaining on the surface of No. 0 is erased.

The cleaning device 18 includes the photosensitive drum 1
The surface of the photosensitive drum 10 has a blade 18a which is pressed against the surface of the photosensitive drum 10 to scrape off the transfer toner on the surface of the photosensitive drum 10. The remaining toner on the surface of the photosensitive drum 10 is scraped off and collected in a predetermined area.

The static eliminator 20 is a lamp that provides a predetermined amount of static elimination light, and erases the residual potential remaining on the surface of the photosensitive drum 10. Above the photosensitive drum 10, that is, above the apparatus main body, an image reading unit 30 that reads an image of a document D to be copied as light brightness information is arranged.

The image reading section 30 includes a document table 31 for holding the document D, an illumination lamp 32 for illuminating the document D placed on the document table 31, and an illumination light emitted from the illumination lamp 32 condensed on the document D. The first reflector 33 guides the reflected light from the document D in a direction parallel to the document table.
The light reflected by the first mirror 34
° Bending second mirror 35 and second mirror 35
And a third mirror 36 for bending the light bent by 90 ° and guiding the light again in a direction parallel to the original table. The illumination lamp 32 and the first to third mirrors 34 are provided by using a scanning motor (not shown). , 35 and 36 are moved along the original table 31 to transmit the image of the original D placed on the original table 31 to the subsequent CCD sensor 38 as light brightness information. As is well known, the second mirror 35 and the third mirror 36 are driven by the first mirror 34 by a driving mechanism (not shown) at half the speed at which the first mirror 34 is moved.

In a plane including the optical axis of the light turned back by the third mirror 36, an imaging lens 37 for giving a converging property to the reflected light from the document D and the reflected light focused by the imaging lens 37 are photoelectrically applied. A CCD sensor 38 for conversion is provided.

In the vicinity of the photosensitive drum 10 and at a position where the surface of the photosensitive drum 10 can be irradiated with light corresponding to the original image, the photosensitive drum 10 given a predetermined surface potential by the charging device 12 Laser exposure device 4 for irradiating the surface of the laser beam with a laser beam whose light intensity has been changed based on an image
0 is arranged.

A predetermined size is set at a position corresponding to the direction in which the photosensitive drum 10 is rotated and which corresponds to the upstream side in the direction in which the toner image developed by the developing device 14 is conveyed by the rotation of the photosensitive drum 10. The first and second paper cassettes 52 # having a size display mechanism (not shown) for displaying the size of the recording paper contained therein, which are formed so as to be capable of accommodating the recording paper (transfer material). Two slots 50a and 50b are formed. 1st, 2nd
In the slots 50a and 50b, the size of the recording paper accommodated in the cassette 52 # is set based on a size display (not shown) set corresponding to the size of the paper accommodated in the cassette 52 #. Size detection sensors 51a and 51b for notifying the CPU 102 of the size are provided.

Further, above the first slot 50a,
By-pass passage 53 that enables the feeding of recording materials other than the standard type
It is formed integrally with the first slot 50a. In the manual passage 53, a paper guide 53a for preventing the paper guided in the passage from being inclined with respect to the direction in which the paper is transported is arranged. The paper guide 53a is the size of the paper.
(Width), and a paper sensor 53b that detects the size (width) of the paper inserted into the manual passage 53 by detecting the position of the paper guide 53a. Are formed so that they can be input.

The photosensitive drum 10 and each of the slots 50a, 50
0b, the cassettes 52 # are arranged corresponding to the respective slots 50a, 50b and inserted into the slots.
Paper feed roller 5 that pulls out one sheet of paper from each of ‥‥
4a, 54b, transport rollers 56a, 56b for sending out the paper drawn by the paper feed rollers 54a, 54b toward the photosensitive drum 10, and temporarily transfer the paper directed to the photosensitive drum 10 by the transport rollers 56a, 56b. To correct the inclination of the sheet with respect to the direction in which the sheet is conveyed, and align the leading end of the toner image on the photosensitive drum 10 with the leading end of the sheet to move the surface of the photosensitive drum 10. An aligning roller 58 that feeds a sheet at a speed equal to the above is disposed. The sheet supplied from the manual passage 53 is guided toward the transport roller 56a.

In the vicinity of the aligning roller 58, in order to stop the sheet via the aligning roller 58,
An aligning switch 58a for detecting the leading edge of the sheet being conveyed is provided.

The toner image formed on the photosensitive drum 10 is transferred to a position corresponding to the downstream of the photosensitive drum 10 in the rotation direction, and the sheet is transported to transport the sheet on which the toner is electrostatically attached. A belt 60, a fixing device 62 for heating the toner transferred to the paper and pressing the toner on the paper to fix the toner on the paper, and a paper discharge roller for discharging the paper on which the toner image is fixed to a paper output tray outside the copying machine 2 64
Is arranged.

FIG. 2 is a block diagram showing a control block mainly showing an image forming section of the laser exposure type copying apparatus shown in FIG. As shown in FIG. 2, each mechanism of the laser exposure type copying apparatus 2 includes a CPU 1 serving as a main controller.
00. The CPU 100 has a ROM section for storing an initial program for operating the apparatus 2 or unique data, for example, a RAM section for storing variable data such as the number of copies and paper size inputted from an operation panel (not shown), And the photosensitive drum 1
A non-volatile memory (NVM) that stores data held for a certain period, such as a sensitivity of 0 (charge elimination speed) and a reference output level of a toner density sensor (not shown) corresponding to the characteristics of the developer supplied to the developing device 14. Are connected.

The corona wire 12a of the charging device 12 generates a corona discharge output of a predetermined polarity when a charging voltage is applied from the charging voltage generating circuit 102, and the photosensitive drum 10
A predetermined charge is applied to the surface. The charging voltage is determined by the CPU
It is output in response to a charging voltage control signal input from 100 to the charging voltage generation circuit 102. The grid electrode 12b of the charging device is connected to the grid bias voltage generation circuit 1
Based on a predetermined magnitude of the grid bias voltage Vg provided by the power supply circuit 04, the amount of electric charge provided from the corona wire 12a to the surface of the photosensitive drum 10, that is, the surface potential of the photosensitive drum 10 is stabilized. The grid bias voltage Vg is output in response to a grid bias voltage signal instructed from the CPU 100 to the grid bias voltage generation circuit 104. Note that the grid bias voltage V
g is set to, for example, -580V. Accordingly, the initial value of the surface potential Vo of the photosensitive drum 10 is approximately -58
It becomes 0V.

The developing roller 14a of the developing device 14 has C
The developing bias voltage Vd generated by the developing bias voltage generating circuit 106 is applied in response to the developing bias voltage control signal from the PU 100. This developing bias voltage Vd
Is to prevent the toner from adhering to the image portion on the surface of the photoreceptor drum 10 and the toner from adhering to the non-image portion, that is, the region where the image information is not exposed from the exposure device 40, thereby causing white fog on the paper The optimum magnitude is set according to the magnitude of the potential of the image area and the magnitude of the charging potential changed by the exposure and the polarity of the charging of the toner. The developing bias voltage Vd is set to, for example, -400V.

Here, the contrast potential Vc capable of providing a predetermined contrast with respect to the developing bias voltage Vd without fogging in the non-image portion is | V
and set to, for example, 130 V, the lower limit of the surface potential Vo of the photosensitive drum 10 required in a normal image forming process is -530 V.

The transfer device 16 includes a transfer bias generation circuit 1
07a, a predetermined transfer bias voltage is applied to transfer the toner image formed on the photoreceptor drum 10 to the sheet, and the toner image is electrostatically attached to the sheet by the peeling voltage from the peeling voltage generating circuit 107b. The existing toner image is peeled off from the photosensitive drum 10 together with the paper.

The pre-cleaning charge erasing device 17 is supplied with the AC toner neutralization voltage from the pre-cleaning AC voltage generating circuit 108, so that the transfer device 16 transfers the toner image and peels off the paper, and thereafter, the pre-cleaning charge eraser 17 The charge of the remaining residual toner is erased to suppress the abrasion of the surface of the photosensitive drum 10 due to the separation and collection of the residual toner by the blade 18a of the cleaning device 18 and to reduce the occurrence of cleaning failure.

The cleaning device 18 is constituted by a blade press-contact mechanism capable of linear movement connected to a mechanism component drive circuit (not shown), for example, a solenoid or the like.
By pressing the blade 18a against the outer peripheral surface of the photosensitive drum 10, residual toner on the surface of the photosensitive drum 10 is removed.
Scrape off the surface. The blade 18a maintains the elasticity and prevents the image forming operation from being fixed to the surface of the photosensitive drum 10 when the image forming operation is interrupted for a long time, that is, prevents the photosensitive layer 10 from being adversely affected when the power is not supplied. For the purpose of non-image formation, the contact with the surface of the photosensitive drum 10 (pressure contact with the surface of the photosensitive drum 10) is released during non-image formation.

The static eliminator 20 is a lamp that provides a predetermined amount of static elimination light, and erases the residual potential remaining on the surface of the photosensitive drum 10. Next, the printing operation of the laser exposure type copying apparatus shown in FIGS. 1 and 2 will be described in detail.

The photosensitive drum 10 is controlled by a motor control circuit 11 in response to a motor drive signal output from the CPU 100.
For example, the rotation speed of the main motor driven by a motor driving pulse input to the main motor (not shown) from 0 to the main motor (not shown) causes the moving speed of the outer peripheral surface to be 127 mm / sec (hereinafter, mm).
/ S). At the same time, supply of electric charge by the corona charging member 12a of the charging device 12 and grid 12b
The surface of the photosensitive drum 10 is uniformly brought to a predetermined surface potential by the grid bias voltage applied to
Charged (-580 V in this embodiment)
.

Subsequently, image data to be copied or printed, that is, image information corresponding to an image of a document, or image signals supplied from a host device (not shown) is printed on the surface of the photosensitive drum 10 by the laser exposure device 40. A laser beam whose intensity has been modulated in accordance with the printed signal is emitted.

By the irradiation of the laser beam by the laser exposure device 40, an electrostatic latent image corresponding to the print signal (image data) is formed on the surface (outer peripheral surface) of the photosensitive drum 10.
The electrostatic latent image thus formed is developed by the toner held by the developing roller 14a of the developing device 14 and is converted into a toner image. In this developing step, the chain-shaped carrier ears formed on the outer peripheral surface of the developing roller 14a along the lines of magnetic force generated from the main magnetic pole of a magnet (not shown) fixed inside the developing roller 14a. In the developing area where the photoconductor drum 10 and the developing roller 14a face each other, the toner adhered by the mirror image force is applied to the toner by the electric field formed by the potential of the electrostatic latent image on the photoconductor drum 10 and the developing bias voltage. Is moved, a toner image is formed on the surface of the photosensitive drum 10.

The toner image formed on the photosensitive drum 10 is transferred by the aligning roller 58 at a transfer position where the photosensitive drum 10 and the transfer device 16 are opposed to each other. (Or the leading edge of the original including the toner image) and the leading edge of the sheet, the transfer device 16
While being sequentially transferred from the photosensitive drum 10 together with the paper.

The toner image transferred to the sheet is conveyed to the fixing device 62 together with the sheet by the conveyor belt 60,
The sheet is fixed on the sheet by the fixing device 62. The sheet on which the toner image has been fixed is discharged to a discharge tray 6 via a discharge roller 64.
6 and sequentially stacked.

The photosensitive drum 10 on which the toner image has been transferred onto the paper is continuously rotated by rotation of a main motor (not shown). As a result, the remaining toner is moved toward the pre-cleaning charge erasing device 17, and after the remaining charge is erased by the pre-cleaning charge erasing device 17,
The photosensitive drum 10 is removed by the cleaning device 18.

The photoreceptor drum 10 is further rotated, whereby the charge is removed at a charge removing position facing the charge removing device 20 and is subsequently used for the next image formation. In this way, a series of image formation is repeated.

As described above, when the number of times image formation is repeated approaches the number of repetitive image formations set in accordance with the type and characteristics of the photosensitive drum 10, that is, the end of life, It is known that the surface potential Vo of the photosensitive drum 10 does not reach the saturation potential during the charging time of. That is, in a laser exposure type printer using the reversal developing method, undesired toner adheres to the non-exposed portion in the area on the photosensitive drum 10 where the surface potential Vo has not reached the saturation potential, and Occurs.

FIG. 3 shows the developing device 14, the transfer device 16, the pre-cleaning charge erasing device 17 and the photosensitive drum 10
FIG. 2 is a schematic diagram of an image forming unit mainly showing a photosensitive drum 10 for explaining a positional relationship of FIG.

FIG. 4 shows the image forming section shown in FIG.
Change in surface potential charged on the photosensitive drum 10 (attenuation)
6 is a graph showing the state of FIG. As shown in FIG. 3, an angle θ1 formed by a charging center to which a surface potential is given by the charging device 12 and a line connecting the developing roller 14a of the developing device 14 and the center of the photosensitive drum 10 is 81.4 °. Therefore, the time during which the surface potential of the photoconductor drum 10 attenuates due to dark decay between the charging by the charging device 12 and the development by the developing device 14 is 0.335 seconds.

Here, the developing roller 14a of the developing device 14
The surface potential meter is set at the position (2), and the photosensitive drum 10 '(10' for identification) on which image formation has been repeated until the end of the life is charged to -580 V to reduce the surface potential Vl at the developing position. The measured value was -500V. This indicates that a loss of 80 V has occurred due to deterioration of the charging ability of the photosensitive layer of the photosensitive drum 10 '.

In this case, since the surface potential has not reached the saturated surface potential, the contrast potential Vc becomes 100
V. Therefore, the photosensitive drum 10 'immediately after the start of charging
When the image data is exposed by the laser exposure device 40, as described above, an undesired fog occurs in the toner image formed by the development.

By the way, as shown in FIG. 4, when the photosensitive drum 10 'is continuously rotated to the second rotation,
The surface potential Vl rises to -580V. As described above, when the photosensitive drum 10 ′ has rotated at least one rotation or more, that is, when the charging by the charging device 12 is continued twice or more, the surface potential of the photosensitive drum 10 ′ may reach the saturated surface potential. Is recognized. However, as already described in the section of the prior art, the image forming process is suppressed until the surface potential of the photosensitive drum 10 'reaches the saturated surface potential. Time will be increased.

Next, a method for reducing the time required for the surface potential of the photosensitive drum to reach the saturated surface potential will be described based on the results shown in FIG. FIG. 5 shows the saturation surface potential of the photosensitive drum 10 in the image forming section shown in FIG. 3, the peeling voltage provided to the photosensitive drum 10 from the transfer device 16 (particularly the peeling charger 16b) and the pre-cleaning charge erasing device 17, and 9 is a graph showing a relationship with an AC toner static elimination voltage.

As already described with reference to FIG. 4, the surface potential of the photosensitive drum 10 reaches the saturated surface potential after the second charging by the charging device. This means that one of the characteristics of the charging ability of the photosensitive drum 10 is that the time until all charges held by the photosensitive layer disappears when an electric field is applied to the photosensitive layer is changed. Suggestive.

Hereinafter, as shown in FIG. 5, before the charging of the surface potential on the photosensitive drum 10 by the charging device 12,
By providing an AC output of a predetermined magnitude from each of the peeling charger 16b of the transfer device 16 and the pre-cleaning charge erasing device 17, the time until the surface potential of the photosensitive drum 10 reaches the saturated surface potential can be reduced. . FIG. 6 shows an example of the control.

As is clear from FIG. 5, at least when the AC output is provided by the peeling charger 16b of the transfer device 16, the contrast potential Vc is set to 130V or more when the developing bias voltage is -400V. Is obtained. That is, by outputting the AC peeling voltage also from the peeling charger 16b of the transfer device 16 in synchronization with the start of charging by the charging device 12, the same effect as if the position of the second rotation of the photosensitive drum 10 has been obtained is obtained. Can be

The same effect can be obtained by the AC toner discharging voltage by the charge erasing device 17 before cleaning. In this case, as shown in FIG.
The angle between b and the charging device 12 is the angle θ2 between the charging device 12 and the pre-cleaning charge erasing device 17 = 104.6.
The sum of the angle θ3 and the angle θ3 = 62.1 ° formed between the pre-cleaning charge erasing device 17 and the peeling charger 16b of the transfer device 16, that is, 166.7 °, while θ2 = 10
Since it is only 4.6 °, conventionally, the time until the second rotation reaches, that is, the time until the surface potential of the photosensitive drum 10 reaches the saturation surface potential can be reduced by 70% or more. As shown in FIG. 5, when the AC output of either the peeling charger 16b or the pre-cleaning charge erasing device 17 exceeds a certain level, the toner image may not be transferred or the residual toner may be left at the leading end during the transfer of the toner image. When the toner is scraped off from the photosensitive drum 10, a secondary action such as deterioration of the cleaning property indicating the degree of ease of scraping occurs. Therefore, the outputs of the peeling charger 16b and the pre-cleaning charge erasing device 17 are used for image formation. It must be set optimally for the process.

FIG. 6 shows an example of control for outputting a predetermined magnitude of AC output from each of the peeling charger 16b and the pre-cleaning charge erasing device 17 simultaneously with the start of charging by the charging device 12 shown in FIG. It is a timing chart.

As shown in FIG. 6, as compared with the conventional control shown by the dotted line, as shown by the solid line,
It can be seen that the timing at which the peel-off voltage generation circuit 107b and the pre-cleaning AC voltage generation circuit 108 that output a predetermined AC output to the b.

FIG. 7 is a timing chart shown in FIG. 6, in which charging by the charging device 12 is started and AC before cleaning by the charge erasing device 17 before cleaning is performed.
6 is a graph showing a state in which the surface potential of the photosensitive drum 10 changes by applying a voltage and applying a peeling voltage by the peeling charger 16b.

As is apparent from FIG. 7, the photosensitive drum 1
The surface potential Vl of 0 is set such that the contrast potential Vc becomes 130 V after 0.765 seconds from the rotation of the photosensitive drum 10.
Reaches the potential A which can be set as above, and further 0.25
After 5 seconds, for size B where the effect on image density is negligible. In this example, the saturation surface potential is -580 V, the potential A reaches -540 V, and the potential B reaches -565 V, and the contrast potential Vc can be secured. As is clear from the above description, the pre-charging may be performed by operating at least one of the peeling charger 16b and the pre-cleaning charge erasing device 17.
It goes without saying that both operations may be performed.

[0063]

As described above, according to the image forming apparatus of the present invention, in the charging step of applying a predetermined surface potential to the photosensitive drum approaching the end of its life, the peeling voltage (AC) from the peeling charger and the cleaning By applying the AC voltage from the pre-charge erasing device to the photosensitive drum at the same time as the charging by the charging device, the time required for the surface potential of the photosensitive drum to reach the saturated surface potential can be reduced. Thereby, an image without fogging can be provided. Further, the time required until the end of printing is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an image forming apparatus to which a transfer device control method according to an embodiment of the present invention is applied;

FIG. 2 is a block diagram mainly showing an image forming unit of the image forming apparatus shown in FIG. 1;

FIG. 3 is a schematic diagram showing a positional relationship of elements forming an image forming unit of the image forming apparatus shown in FIG.

FIG. 4 is a graph showing a change in surface potential of a photosensitive drum of the image forming section shown in FIG. 3;

FIG. 5 is a diagram showing the relationship between the saturation surface potential of the photosensitive drum, the peeling voltage supplied from the transfer device and the pre-cleaning charge erasing device to the photosensitive drum in the image forming section shown in FIG.
5 is a graph showing a relationship with a toner static elimination voltage.

6 is a timing chart showing an example of control for outputting a peeling output and an AC output before cleaning simultaneously with the start of charging by the charging device shown in FIG. 5;

FIG. 7 is a graph showing a change in surface potential due to the application of an AC voltage before cleaning and the application of a peeling voltage together with the start of charging by the charging device according to the timing chart shown in FIG. 6;

[Explanation of symbols]

 2 ... Laser exposure type copying machine (image forming apparatus), 10 ... Photoconductor drum (image carrier), 12 ... Charging device, 14 ... Developing device, 16 ... Transfer device, 16a ... Transfer charger, 16b ... Separation charger, 17 ... Charge erasing device before cleaning, 18 ... Cleaning device, 20 ... Static elimination device, 31 ... Document table, 32 ... Illumination lamp, 33 ... Reflector, 37 ... Imaging lens, 38 ... CCD sensor, 40 ... Laser exposure device, 52 ... Cassette 58 58 Aligning roller 60 Conveyor belt 62 Fixing device 100 CPU 100a Memory 102 Charging voltage generating circuit 104 Grid bias voltage generating circuit 106 Development bias voltage generating circuit 107a ... Transfer bias voltage generation circuit 107b ... Peel voltage generation circuit 10 ... pre-cleaning AC voltage generation circuit.

[Procedure amendment]

[Submission date] February 13, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above-mentioned problems, and includes a charging means for charging a rotating image carrier to a predetermined surface potential, and a charging means for charging the rotating image carrier to a predetermined surface potential. Exposure means for exposing the charged image carrier to form an electrostatic image, and charging the electrostatic image formed on the image carrier by the exposure means with the exposure means
Developing means for supplying a developer charged to the same polarity as the charge polarity of the image carrier to form a developer image; and applying the developer image formed on the image carrier by the developing means to a transfer-receiving material.
Transfer means for electrostatically transferring, and a rotation direction of the image carrier
Along the line downstream of the transfer unit and upstream of the charging unit.
And the developer image is transferred by the transfer unit.
The transfer material is released from electrostatic attraction with the image carrier.
Separating means, and between the separating means and the transferring means.
And an electric field is formed between the carrier and the image carrier.
Ri, the developer images on the transfer material by said transfer means
After the transfer, the residual developer remaining on the image carrier is
Charge erasing means for erasing the retained charge, and control means for activating at least one of the peeling means and the charge erasing means in accordance with the start of charging of the image carrier by the charging means. To provide an image forming apparatus.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

Further, the present invention provides a charging means for charging a rotating image carrier to a predetermined surface potential, and forming an electrostatic image by exposing the image carrier charged to a predetermined surface potential by the charging means. Exposing means, and an electrostatic image formed on the image carrier by the exposing means is charged by the charging means.
Developing means for supplying a developer charged to the same polarity as the charge polarity of the image carrier to be formed to form a developer image; and electrostatically transferring the developer image formed on the image carrier by the developing means. <br/> A transfer means for transferring to a transfer material, and a rotation method of the image carrier
Downstream of the transfer means along the direction, and of the charging means.
The transfer- receiving material provided upstream and to which the developer image has been transferred by the transfer means is electrostatically attracted to the image carrier.
Releasing means for releasing the image bearing member from the predetermined position in accordance with the start of charging of the image carrier by the charging means.
And an image forming apparatus comprising: a control unit that operates the image forming apparatus.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

Further, the present invention provides a charging means for charging a rotating image carrier to a predetermined surface potential, and forming an electrostatic image by exposing the image carrier charged to a predetermined surface potential by the charging means. an exposure means for, in the electrostatic image formed on the image carrier by the exposure means, strip by said charging means
Electrostatic developing means, the developer image formed on the image carrier by the developing means a developer charged to the same polarity as the charging polarity of the image bearing member which is conductive and supplies to form a developer image
A transfer means for electrically transferring the image to the transfer material,
Downstream of the transfer means along the rotational direction, the charging means
Disposed in the upstream, the after the developer image has been transferred to the transfer material by the transfer means, a charge erasing means for erasing the charge remaining developer remaining on said image bearing member is held, the charge It is an object of the present invention to provide an image forming apparatus comprising: a control unit that operates an erasing unit at a predetermined timing in accordance with the start of charging of the image carrier by the charging unit.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Deleted

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Deleted

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Deleted

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Deleted

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Deleted

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Deleted

[Procedure amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0062

[Correction method] Change

[Correction contents]

As is apparent from FIG. 7, the photosensitive drum 1
The surface potential Vl of 0 is set such that the contrast potential Vc becomes 130 V after 0.765 seconds from the rotation of the photosensitive drum 10.
Reaches the potential A which can be set as above, and further 0.25
After 5 seconds, for size B where the effect on image density is negligible. In this example, the saturation surface potential is -580 V, the potential A reaches -540 V, and the potential B reaches -565 V, and the contrast potential Vc can be secured. As is clear from the above description, the pre-charging may be performed by operating at least one of the peeling charger 16b and the pre-cleaning charge erasing device 17.
It goes without saying that may be caused to both operate.

Claims (10)

[Claims] A charging means for charging the image carrier to a predetermined surface potential; an exposure means for exposing the image carrier charged to a predetermined surface potential by the charging means to form an electrostatic image; Developing means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image; and transferring the developer image formed on the image carrier by the developing means Transfer means for transferring to the material, after the developer image is transferred to the material to be transferred by the transfer means, charge erasing means for erasing the charge held by the residual developer remaining on the image carrier, The transfer member on which the developer image has been transferred by the transfer unit, a peeling unit that releases from electrostatic attraction with the image carrier, and the charging unit starts charging the image carrier with the charging unit.
An image forming apparatus comprising: a control unit that operates at least one of the peeling unit and the charge erasing unit. A charging means for charging the image carrier to a predetermined surface potential; an exposure means for exposing the image carrier charged to a predetermined surface potential by the charging means to form an electrostatic image; Developing means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image; and transferring the developer image formed on the image carrier by the developing means Transfer means for transferring to the material, after the developer image is transferred to the material to be transferred by the transfer means, charge erasing means for erasing the charge held by the residual developer remaining on the image carrier, The transfer member on which the developer image has been transferred by the transfer unit, a peeling unit that releases from electrostatic attraction with the image carrier, and the charging unit starts charging the image carrier with the charging unit.
An image forming apparatus comprising: a control unit that operates each of the peeling unit and the charge erasing unit. A charging means for charging the image carrier to a predetermined surface potential; an exposure means for exposing the image carrier charged to a predetermined surface potential by the charging means to form an electrostatic image; Developing means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image; and transferring the developer image formed on the image carrier by the developing means Transfer means for transferring to the material, after the developer image is transferred to the material to be transferred by the transfer means, charge erasing means for erasing the charge held by the residual developer remaining on the image carrier, An image forming apparatus comprising: a control unit that activates the charge erasing unit when the charging unit starts charging the image carrier. A charging means for charging the image carrier to a predetermined surface potential; an exposure means for exposing the image carrier charged to a predetermined surface potential by the charging means to form an electrostatic image; Developing means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image; and transferring the developer image formed on the image carrier by the developing means Transfer means for transferring the material image onto the material, peeling means for releasing the transfer material on which the developer image has been transferred by the transfer means from electrostatic attraction with the image carrier, and the image carrier by the charging means An image forming apparatus, comprising: a control unit that activates the peeling unit at the same time as the start of charging. A charging means for charging the image carrier to a predetermined surface potential; an exposure means for exposing the image carrier charged to a predetermined surface potential by the charging means to form an electrostatic image; Developing means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image; and transferring the developer image formed on the image carrier by the developing means Transfer means for transferring to the material, after the developer image is transferred to the material to be transferred by the transfer means, charge erasing means for erasing the charge held by the residual developer remaining on the image carrier, Peeling means for releasing the transfer material on which the developer image has been transferred by the transfer means from electrostatic attraction with the image carrier; and separating the peeling means and the charge erasing means with the image by the charging means. In accordance with the start of charging of the carrier, Image forming apparatus characterized by and a control means for operating at a predetermined timing so that the surface potential carrier held to shorten the time to reach the saturation surface potential. 6. A charging means for charging the image carrier to a predetermined surface potential, an exposure means for exposing the image carrier charged to a predetermined surface potential by the charging means to form an electrostatic image, Developing means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image; and transferring the developer image formed on the image carrier by the developing means Transfer means for transferring to the material, after the developer image is transferred to the material to be transferred by the transfer means, charge erasing means for erasing the charge held by the residual developer remaining on the image carrier, Peeling means for releasing the transfer material on which the developer image has been transferred by the transfer means from electrostatic attraction with the image carrier; and at least one of the peeling means and the charge erasing means, the charging means Charging of the image carrier by To the combined, the image forming apparatus characterized by and a control means for operating at a predetermined timing so as to shorten the time until the surface potential the image carrier is held reaches saturation surface potential. A charging means for charging the image bearing member to a predetermined surface potential; an exposure means for exposing the image bearing member charged to a predetermined surface potential by the charging means to form an electrostatic image; Developing means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image; and transferring the developer image formed on the image carrier by the developing means Transfer means for transferring to the material, after the developer image is transferred to the material to be transferred by the transfer means, charge erasing means for erasing the charge held by the residual developer remaining on the image carrier, Control means for operating the charge erasing means at a predetermined timing so as to shorten the time required for the surface potential held by the image carrier to reach the saturated surface potential in accordance with the start of charging of the image carrier by the charging means; And having An image forming apparatus comprising. A charging means for charging the image carrier to a predetermined surface potential; an exposure means for exposing the image carrier charged to a predetermined surface potential by the charging means to form an electrostatic image; Developing means for supplying a developer to the electrostatic image formed on the image carrier by the exposure means to form a developer image; and transferring the developer image formed on the image carrier by the developing means Transfer means for transferring the material image onto the material, peeling means for releasing the transferred material on which the developer image has been transferred by the transfer means from electrostatic attraction with the image carrier, Control means for operating at a predetermined timing so as to shorten the time required for the surface potential held by the image carrier to reach the saturated surface potential in accordance with the start of charging of the image carrier according to (1). Image forming device. 9. A charging means for charging the image carrier to a predetermined surface potential, an exposure means for exposing the image carrier charged to a predetermined surface potential by the charging means to form an electrostatic image, and Developing means for supplying a developer charged to the same polarity as the electrostatic image to the electrostatic image formed on the image carrier by the exposure means to form a developer image by reversal development; Transfer means for transferring the developer image formed on the image carrier to a transfer material; and a residual portion remaining on the image carrier after the developer image is transferred to the transfer material by the transfer means. Charge erasing means for erasing the charge held by the developer; and adjusting the charge erasing means to start charging of the image carrier by the charging means until the surface potential held by the image carrier reaches a saturated surface potential. Predetermined ties to reduce the time of Image forming apparatus characterized by and a control means for operating in a ring. A charging means for charging the image carrier to a predetermined surface potential; an exposure means for exposing the image carrier charged to a predetermined surface potential by the charging means to form an electrostatic image; Developing means for supplying a developer charged to the same polarity as the electrostatic image to the electrostatic image formed on the image carrier by the exposure means to form a developer image by reversal development; Transfer means for transferring the developer image formed on the image carrier to a transfer material; and transferring the transfer material on which the developer image has been transferred by the transfer means from electrostatic attraction to the image carrier. Releasing means for releasing, and a predetermined timing for reducing the time required for the surface potential held by the image carrier to reach the saturated surface potential in accordance with the start of charging of the image carrier by the charging means. Control means for operating with An image forming apparatus, comprising.