JP2001296705A - Image forming device and exposure potential control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device and an exposure potential control method for avoiding an aging exposure causing the increase of start-up time, for example, after resetting when the device is started up and further having a restraining effect not only to the lowering phenomenon of VL by exposure memory but also to density fluctuation caused by the increase of the VL by the exposure memory. SOLUTION: In a pre-electrification section, the surface potential of photoreceptor drums 1Y to 1K in the pre-electrification section is made higher than the surface potential of the image forming areas of the drums 1Y to 1K in the case of forming a latent image by electrifiers 2Y to 2K, and also the drums 1Y to 1K are pre-exposed by exposure devices 3Y to 3K.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc., which preferably forms an image by an electrophotographic method, and an exposure potential control method applied to such an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus using electrophotography, an image carrier that holds toner on an electrostatic latent image generally includes:
It is composed of a metal drum or a metal belt having a photosensitive layer composed of a charge generation layer and a charge transport layer.

The image carrier is driven in a fixed direction by a print start signal.

A bias is applied to the image carrier by a charging device (corona charger, charging roller, image carrier carrying magnetic particles, etc.) to charge or charge the surface of the image carrier to a certain potential. Perform injection.

The surface potential at this time is called a VD potential. Further, based on a signal from the controller, the surface of the image carrier is irradiated with on / off controlled laser light or LED light (exposure). At the light irradiation position, an electrostatic latent image is formed on the surface of the image carrier because the potential decreases. The potential of the exposed portion is referred to as VL or VL potential (hereinafter, also simply referred to as VL or VL potential).

[0006] A constant bias (development bias) is applied to the developing device filled with the toner arranged opposite to the image carrier.
To transfer the toner, to which a predetermined charge has been applied, to an electrostatic latent image on an image carrier such as a photosensitive drum, thereby visualizing the electrostatic latent image (development).

The amount of toner on the image carrier during development is determined by the relationship between the exposure potential VL, which is the potential when the image carrier is exposed, and the developing bias.

A bias having a polarity opposite to that of the toner on the image carrier is provided on a transfer member such as a transfer roller or a transfer belt which is disposed adjacent to the image carrier and moves in the forward direction at substantially the same speed as the image carrier. Is applied, and in this state, the toner carried on the image carrier is moved onto the transfer material by passing the transfer material between the transfer material and the transfer material.

Incidentally, during the above-described image forming operation, the photosensitive layer of the image carrier is affected by the exposure memory due to the laser beam. That is, the VL potential after laser exposure changes depending on the state of use of the image carrier. This leads to a change in the amount of toner on the image carrier, and the print image density cannot be determined.

Therefore, conventionally, a pre-exposure light source as an appropriate light source has been installed in the apparatus to suppress the exposure memory, and the exposure light source irradiates light to the surface of the image carrier before the charging operation of the image carrier. So-called pre-exposure.

However, in recent years, with the miniaturization of the apparatus, there is a case where a light source (pre-exposure light source) cannot be installed in the apparatus.

[0012] The exposure memory is particularly susceptible to use after a long period of non-use of the apparatus. For this reason, recently, in an image forming apparatus which is miniaturized and does not have a pre-exposure device, a method of suppressing fluctuation of the VL potential due to the exposure memory is disclosed in Japanese Patent Application Laid-Open No. 11-2027.
Proposals such as the technique disclosed in Japanese Patent Publication No. 05-2005 have been made.

In the method proposed in the above, during the initial check for starting the apparatus, the image carrier is rotated while being driven.
At least the entire image forming area in the longitudinal direction on the surface of the image carrier is irradiated with laser for a certain period of time so that the photosensitive layer in the image forming area is uniformly affected by the exposure memory, and VL
Aging exposure that stabilizes the potential is introduced.

Japanese Patent Application Laid-Open No. 11-202705 mainly proposes an aging exposure in the apparatus which is performed after the apparatus is reset, such as when the apparatus is turned on, after a jam is cleared, or when various consumables of the apparatus are replaced. It has information and changes the aging time as needed.

It has also been proposed to change the aging exposure time in a timely manner in accordance with the use condition of the photosensitive drum, or to perform the aging exposure immediately before executing the density correction control by the density detection means of the toner image formed on the image carrier. Have been.

[0016]

However, in the case of the above-described prior art, the following problems have occurred. The aging exposure during the initial check at the time of starting the apparatus described above leads to an increase in the starting time,
It causes the user's usability to deteriorate.

Excessive laser irradiation due to aging exposure on the photosensitive layer of an image carrier such as a photosensitive drum may cause damage to the photosensitive layer and accelerate deterioration of the photosensitive layer.

Further, with only the aging exposure, the effect of the aging exposure at the time of starting up the apparatus is weakened at the time of image formation output after the apparatus has been left for a long time in the power-on state. I have not done it.

Regarding this point, Japanese Patent Application Laid-Open No. 11-2027
The technique disclosed in Japanese Patent Publication No. 05-2005 proposes that exposure memory can be suppressed by performing aging exposure immediately before first printing.

However, the exposure to the photosensitive drum surface potential lower than the charged potential of the photosensitive drum at the time of image formation in this proposal has an insufficient effect on suppressing the exposure memory.

This is because, as described in paragraphs 14 and 16 of the “Problem to be Solved by the Invention” in the above proposal, “the effect of the exposure memory is a decrease in VL and an increase in image density” This is because the VL potential fluctuation due to the influence of the exposure memory is assumed to be in a narrow range in which the VL potential decreases.

The fluctuation of the VL potential due to the exposure memory, which is a problem in the present invention, may not only decrease the absolute value of VL but also increase the absolute value of VL.

In such a case, an increase in VL causes a change in image density. Further, during continuous printing, a decrease in image density also occurs with an increase in the number of output sheets.

The present invention has been made in view of the above circumstances,
For example, the aging exposure that leads to an increase in the start-up time, such as after a reset at the start-up of the device, as proposed in Japanese Patent Application Laid-Open No. 11-202705, is abolished. In addition, an object of the present invention is to provide an image forming apparatus and an exposure potential control method which have an effect of suppressing density fluctuation due to an increase in VL due to an exposure memory.

[0025]

In order to achieve the above object, an image forming apparatus according to the present invention comprises: a photosensitive member for carrying an electrostatic latent image; a charging means for charging the surface of the photosensitive member; And an exposing unit for exposing the surface of the photoreceptor charged by the unit to form an electrostatic latent image, wherein the image forming apparatus is charged by the charging unit after an image output command is issued. In a pre-charging section until an electrostatic latent image is formed on the body by the exposure unit, the surface potential of the photoconductor in the pre-charging section is changed to the image formation of the photoconductor when the latent image is formed. The surface potential of the region is made higher by the charging unit, and the photoconductor is pre-exposed by the exposure unit in the pre-charging section.

Further, the entirety of the image forming area in the longitudinal direction of the photoreceptor surface in the pre-charging section is pre-exposed by the exposing means.

The apparatus further comprises an atmosphere detecting means for detecting a temperature and a humidity of the apparatus main body, and in a pre-charging section in which a surface potential higher than a surface potential of a region where a latent image is formed on the photosensitive member is set. The pre-exposure performed by the exposure unit is performed based on detection information of the atmosphere detection unit.

Further, the pre-exposure time of the region where the latent image is formed on the photoconductor in the pre-charging section is an integral multiple of the rotation period of the photoconductor. And

In a pre-charging section, when the pre-exposure is performed while the apparatus main body is left for a predetermined time in a region where a latent image is formed on the photoconductor, a charging start position on the photoconductor is determined. A further feature is that the pre-exposure is not performed on one rotation portion of the photoconductor drive, and the pre-exposure is performed on the area after the second rotation.

Further, the photoreceptor is characterized in that a charge injection layer is provided on a surface layer.

[0031] The present invention is characterized in that charge injection is performed on the charge injection layer using magnetic particles.

Further, according to the present invention, there is provided an exposure potential control method, comprising: a photosensitive member for carrying an electrostatic latent image; charging means for charging the surface of the photosensitive member; An exposure means for controlling an exposure potential of an image forming apparatus having at least an exposure means for forming an electrostatic latent image by charging the photosensitive member by the charging means after an image output command is issued. In the pre-charging section until the formation of the electrostatic latent image on the photoconductor by the exposure unit, the surface potential of the photoconductor in the pre-charging section is set to the time when the latent image is formed by the charging unit. And a step of pre-exposing the photoconductor charged by the charging unit in the pre-charging section by the exposing unit. And wherein the Rukoto.

Therefore, according to the configuration of the present invention, it is possible to suppress a change in image density due to a change in VL as an exposure potential on the electrophotographic photosensitive drum due to exposure according to the use environment of the image forming apparatus.

[0034]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The materials, shapes, relative arrangements, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

In the following drawings, the same members as those described in the above-mentioned drawings are denoted by the same reference numerals.

(First Embodiment) A first embodiment of an image forming apparatus according to the present invention will be described with reference to FIGS. However, the description of the first, second, and third embodiments of the image forming apparatus according to the present invention described below is based on the first, second, and third embodiments of the exposure potential control method according to the present invention. It also serves as an explanation.

The image forming apparatus shown in FIG. 1 is a color image forming apparatus which is a color electrophotographic copying machine of the present embodiment using an LED exposing device. FIG. 1 shows an overall structural diagram of a first embodiment of an image forming apparatus according to the present invention. However, this exposure device uses a laser beam and may be a single-color copier in practicing the present invention.

The following description is made with reference to the image forming apparatus shown in FIG. 1 for convenience. This color image forming apparatus has a digital image reader section at the top and a digital color image printer section at the bottom.

In the reader section, a document 9 is placed on a document table glass 10 and a color separation image signal from the document 9 obtained by exposing and scanning an exposure CCD reading sensor 11 is obtained.

The color separation signal is processed by a video processing unit (not shown) via a circuit (not shown) and sent to a printer unit.

In the printer section, photosensitive drums 1Y, 1M, 1C and 1K (hereinafter abbreviated as photosensitive drums 1) as photosensitive members of the present invention, which are image carriers rotating in the direction of the arrow shown in the figure, are rotatably supported. Around the photosensitive drum 1, chargers 2Y, 2M, 2 as charging means of the present invention are provided.
C, 2K (hereinafter abbreviated as charging device 2), developing devices 4Y, 4
Image forming units such as M, 4C, and 4K (hereinafter abbreviated as developing device 4) and a transfer belt 5 are arranged.

The photosensitive drum 1 is uniformly charged by the charger 2 and is exposed on the photosensitive drum 1 as exposure means 3Y, 3M, 3 as exposure means of the present invention, which comprises, for example, an LED exposure device.
A light image is irradiated by C and 3K, and a latent image is formed on the outer surface. Next, the electrostatic latent image on the photosensitive drum 1 is developed by the developing device 4 and is visualized as a toner image.

F1, F2, and F3 are fans for circulating and exhausting air in the apparatus, and SW2 is a switch for turning on and off temperature control in the apparatus.

When a reading command for the original 9 (usually in a state where the copy key is pressed) or the image forming apparatus operates as a printer, for example, when a print JOB command is transmitted from a PC, the image forming apparatus is stored in the image forming apparatus. The temperature / humidity information of the environment sensor CS1 as the atmosphere detecting means of the present invention is read in accordance with an instruction of the installed internal CPU (not shown).
The absolute water content at this time is calculated.

The CPU controls the exposure amount of the exposure device 3 based on the detection result of the environment sensor CS1. That is, the CPU calculates the required development Vcont potential in this environment from the recording device based on the value of the water content calculated based on the detection information detected by the environment sensor CS1. The value of the development Vcont changes depending on the environment because the physical properties of the toner used in the developing device, for example, the charging performance changes depending on the ambient moisture content.

In calculating the development Vcont, the relationship between the water content and the required development Vcont potential as shown in FIG. 2 is stored in a table, for example, as shown in Table 1 of FIG. , Calculated by linear interpolation according to the result of the water content. FIG. 2 shows the image forming apparatus according to the first embodiment of the present invention,
FIG. 8 is a graph showing the environmental fluctuation of the development contrast potential for obtaining the proper density. FIG. 8 shows the environmental fluctuation of the development contrast potential for obtaining the proper density used in the first embodiment of the image forming apparatus according to the present invention. 2 shows a table (Table 1).

Next, a method of calculating the latent image potential and the developing sleep potential of the developing device will be described with reference to FIG. FIG.
FIG. 5 shows a graph of environmental fluctuation of the charged potential of the photosensitive drum and the potential of the exposure unit used in the first embodiment of the image forming apparatus according to the present invention. However, in FIG. 3, the exposure potential VL is shown as an exposure portion potential Vl for convenience.

For example, when the temperature is read as 23 ° C./5% by the environment sensor CS1 in FIG.
[G / kg].

At this time, according to Table 1 in FIG.
As the cont potential, development Vcont = 280 V is selected. When the Vback potential, which is a background fog prevention potential, is added to the required development Vcont, a required latent image Vcont potential formed on the surface layer of the photosensitive drum 1 is obtained.
The expression is as follows.

Necessary latent image Vcont = necessary development Vcont + Vback = 280 V + 200 V = 480 V (1)

Next, a procedure for setting the charging potential and the exposure potential of the photosensitive drum 1 will be described. Just as the required development Vcont changes according to the state of the surrounding environment, the exposure portion potential of the photosensitive drum 1 is also suitable for the environment because the exposure sensitivity of the photosensitive drum 1 changes according to the relative humidity and the amount of moisture in the surrounding environment. You need to find the value.

Further, the graph shown in FIG. 3 is a result obtained by experimentally determining a change in the potential of the exposed portion due to the amount of moisture in the surrounding environment with respect to the charged potential in the photosensitive drum of the present embodiment.

The result of FIG. 3 is stored as table data in the image forming apparatus. According to the reading value of the environment sensor CS1, in order to obtain the calculated latent image Vcont = 480V at the water content of 1.0 [g / kg], if the charging potential: Vd = 700V is selected from the result of FIG. Exposure portion potential Vl = 220 V is obtained, and required latent image Vco
nt = 480 V can be satisfied.

As a result, the developing potential is changed to the charging potential Vd = 7.
By setting 500 V by subtracting the non-image portion potential Vback = 200 V from 00 V, the calculated required development Vcont = 280 V can be accurately obtained. Developing bias potential V = charging potential Vd−Vback (2)

Here, the charging method in this embodiment is as follows.
Pulverized magnetic carrier (resistance value 10 ⁴ to 10 ⁷ Ω) formed by pulverization on magnetized mag roller sleeve or polymerization method
cm) is carried on a mag roller and fixed at a fixed distance from the surface of the photosensitive drum 1, for example, a distance of about 500 to 600 μm. An injection method in which a bias in which an AC component is superimposed is applied to the bias is employed.

When the injection method in this embodiment is used, the value of the charging potential Vd of the photosensitive drum and the value of D
Since the C component bias becomes almost equal, it is possible to obtain Vdc = Vd.

Further, the photosensitive drums 1Y to 1K used in the present embodiment are, as shown in FIG.
a, a photosensitive layer (a charge generation layer 1b, a charge transport layer 1c, and a charge injection layer 1d) is applied thereon. FIG. 4 is a sectional view of an electrophotographic photosensitive member applied to the image forming apparatus shown in FIG.

The photosensitive layer is usually an insulator, and has a characteristic that it becomes conductive when irradiated with light having a specific wavelength. This is because a hole-electron pair is generated in the charge generation layer 1b by light irradiation, and these serve as carriers of the charge flow.

The developing device 4 includes four developing units 4Y to 4K for separately storing four color developers of a yellow developer, a magenta developer, a cyan developer, and a black developer.
A fixed distance at a position facing the outer peripheral surface of, for example, 300
Development of latent image development is performed using a two-component developer fixed at ~ 600 µm. Here, in implementing the present invention, 2
Instead of a developing device using a component developer, a developing method such as a magnetic-component developing method or a contact-component developing method may be used.

On the other hand, the transfer material P accommodated in the paper feed cassette 13A (13B) is fed by the registration roller 14 at an appropriate timing, carried on the transfer belt 5, and conveyed in the direction of the arrow shown in the figure. Transfer applying members 6Y, 6M, 6C, 6K disposed above transfer belt 5
A transfer voltage is applied by a transfer application member (hereinafter, abbreviated as a transfer application member), and the toner image on the photosensitive drum 1 is transferred.

The transfer belt 5 is formed by stretching a dielectric sheet or the like, and the transfer material P is adsorbed on the transfer belt 5 by a semiconductor charging roller 15 for adsorption and a conductor roller.

The toner image is sequentially transferred from yellow on the photosensitive drum 1Y to black on the photosensitive drum 1K. The toner image transferred onto the transfer material P is carried on a transfer belt 5 and is conveyed to a fixing device 7 where a predetermined amount of heat and pressure are applied to fix the toner image.

Next, using the above-described image forming apparatus,
The object of the present invention and a more detailed description of the solution will be described.

In the above-described image forming apparatus, by exposing the photosensitive drums 1Y to 1K from the exposure devices 3Y to 3K, hole / electron pairs are generated in the charge generation layer. The holes move through the charge generation layer to the charge injection layer and recombine with the negative charges. As a result, the amount of negative charges on the surface layer (charge injection layer) of the photosensitive drum decreases, and the absolute value of the surface potential decreases. The surface potential on the photosensitive drum in this state is substantially equal to the VL potential.

However, the VL potential on the photosensitive drum attenuated by exposure changes depending on the exposure amount and also changes depending on the magnitude of the surface potential. Here, FIG. 5 shows a relationship between the exposure amount E (μW / dot) of the photosensitive drum A and the potential (V) on the photosensitive drum. FIG. 5 is a graph showing the relationship between the exposure amount of the photosensitive drum (drum A) and the potential used in the first embodiment of the image forming apparatus according to the present invention.
As shown in FIG. 5, it can be seen that as the exposure amount increases, the potential on the drum attenuates nonlinearly.

FIG. 6 shows the result of the measurement of the EV characteristic when the exposure for two rotations of the drum was given. FIG. 6 is a graph showing the relationship between the exposure amount and the potential of the photosensitive drum (drums A and B) used in the first embodiment of the image forming apparatus according to the present invention. From this figure, as the amount of exposure given to the surface layer of the photosensitive drum is increased, if the value of the amount of exposure is small, the VL potential of the portion that has been exposed once (the VL potential of the second rotation of the drum) is increased in the first rotation. Larger than
It can be seen that when a certain exposure amount is given, the potential of the second rotation of the drum is higher than that of the first rotation. When such a change in the VL potential occurs, an image defect such as a decrease in density occurs.

Although the photosensitive drum has the same basic characteristics as the above-described photosensitive drum, the amount of (hole-electron pairs) generated in the charge generation layer with respect to the amount of exposure and the charge transfer speed differ in the charge transport layer. FIG. 6 shows an EV characteristic when exposure for two rotations of the drum B is continuously given. As shown in FIG. 6, the potential on the drum with respect to the exposure amount is different, but it can be seen that the tendency is the same as that of the photosensitive drum A.

From the above results, it can be seen that when a charged photosensitive drum is exposed to light to form a latent image, the fluctuation of the VL potential caused by the influence of the exposure memory depends on the absolute value of VL depending on the amount of exposure given to the photosensitive layer. It can be seen that there is a phenomenon in which increases, decreases, or fluctuates.

The use of the region where the VL is increased by the exposure memory to secure a larger latent image contrast potential is considerably advantageous in that the usable range of the image forming conditions (developing contrast potential) of the image forming apparatus is widened. There is.

In the area where the VL potential of the electrostatic latent image formed on the photosensitive drum by the exposure memory is increased, the electrostatic latent image formation after the image forming instruction proposed in the above-mentioned Japanese Patent Application Laid-Open No. 11-202705 is described. The confirmation was made by pre-exposure control such that the front surface of the photosensitive drum was exposed before.

However, as a result, there was no effect of reducing the VL potential fluctuation, and a problem that the image density was lowered occurred. For this reason, in the present embodiment, in order to reduce the increase in the VL potential due to the above-mentioned exposure memory, the charging device is charged on the surface of the photosensitive drum after the image output command, and the latent image is formed by irradiation with the exposure device. In the pre-charging section until the charging is performed, the surface of the photosensitive drum is charged so as to have a surface potential higher than the surface potential on the photosensitive drum set to form a predetermined image density. Pre-exposure control is performed by irradiating with an exposure device.

Here, the pre-charging section is a time interval from the image output command to the charging on the surface of the photosensitive drum by the charging device and the irradiation from the exposure device to form the latent image as described above. However, since the photosensitive drum is rotating at a predetermined speed, this charging section can be regarded as a predetermined area on the photosensitive drum.

Thus, the amount of increase in VL by the exposure memory is increased and the VL is increased to a region where there is no VL increase phenomenon, as compared with the case where the pre-exposure is performed at the surface potential equal to or lower than the surface potential during image formation. Became possible. In this state, the latent image is formed by lowering to a surface potential at which a desired image density can be obtained.

For this reason, in the related art, as shown in the graph of the conventional example in FIG. 7A, the VL potential fluctuates due to the exposure memory. As shown in the graph of (1), a uniform VL potential can be obtained in the electrostatic latent image forming area, and image formation can be stabilized. Here, FIG. 7 shows a transition graph of the potential on the drum according to the first embodiment of the image forming apparatus according to the present invention, as compared with a conventional example.

Further, since the above-mentioned pre-exposure is performed in the pre-charging section, it is possible to prevent the start-up time from increasing as in the prior art, thereby improving the convenience for the user.

Note that the surface potential at which a desired image density is obtained is different from the VL potential when exposure is performed by the exposure means with respect to the surface potential used in ordinary latent image formation.
The increase in VL is experimentally obtained in advance experimentally, and stored in a storage device (not shown) or the like in the apparatus.
It is desirable to set the surface potential so as to obtain a predetermined image density.

As a method for this, in the present embodiment, the amount of fluctuation in the case of performing “Vd-UP and pre-exposure at the time of pre-rotation” on the relation table of Vd-VL with respect to the atmosphere information (absolute water content) is calculated. Store table data and Vd-V
A method of correcting the relationship of L is performed.

(Second Embodiment) Next, an image forming apparatus according to a second embodiment of the present invention will be described. However, the structure of the image forming apparatus of the present embodiment is the same as the structure of the above-described first embodiment, and a description thereof will be omitted.

As described above, in the first embodiment, during the pre-charging section before the latent image is formed, the surface potential is set to be larger than that at the time of forming the latent image, and the pre-exposure is performed by irradiating with the exposure device. , VL potential was stabilized.

However, in this embodiment, when the exposure history is given on the photosensitive drum as the photosensitive member of the present invention by pre-exposure to stabilize the VL potential, the exposure time is synchronized with the drum rotation cycle.

As a result, in this embodiment, the same effect as that of the first embodiment of the image forming apparatus according to the present invention can be obtained, and the accumulated amount of history on the surface of the photosensitive drum becomes uniform. , A more uniform VL potential can be obtained.

(Third Embodiment) Next, a third embodiment of the image forming apparatus according to the present invention will be described. However, the structure of the image forming apparatus of the present embodiment is the same as the structure of the above-described first embodiment, and a description thereof will be omitted.

In the first embodiment, the pre-exposure is performed in the pre-charging section with the surface potential higher than that during the formation of the latent image. In the second embodiment, the pre-exposure time is adjusted to the drum rotation period. VL stabilization of the setting was performed.

However, it was not assumed that the image forming apparatus was left for a long time.

When the surface of the photosensitive drum is charged by the charging means on the photosensitive drum as the photosensitive member of the present invention after being left for a long time, the surface potential may not be stable for one rotation of the drum from the charging opening position. . This unstable state is because there are cases where the surface potential is lower than the set surface potential and does not sufficiently reach the set target value.

As described above, in a region where the surface potential is not sufficiently stabilized when the photosensitive drum is left for a long time (standby state),
When the pre-exposure was performed, a difference occurred before and after the VL potential was stabilized after the exposure was performed, and the influence of the history was large. Therefore, the VL value was disturbed, and the electrostatic latent image was formed. In this case, the VL potential is affected.

For this reason, in this embodiment, in the case where the photosensitive drum is left undisturbed for a long period of time, the area of the surface potential in the first cycle from the start of charging when the charge is not stable on the photosensitive drum is avoided, and the pre-exposure is performed after two rounds of the drum. Was carried out.

As described above, in this embodiment, the same effect as that of the first embodiment of the image forming apparatus according to the present invention can be obtained, and a more stable VL potential can be obtained. .

In order to determine whether the apparatus has been left for a long period of time, a time measuring device is provided in the image forming apparatus (not shown). The control is performed so that the pre-exposure is not performed for the circumference. Of course, the above time
It is not limited to 30 minutes, for example, 20 minutes, 40 minutes
Minutes, one hour, one hour or more can be set.

[0090]

As described above, according to the present invention,
The surface potential of the photoconductor in the pre-charging section is set to be higher than the surface potential of the image forming area of the photoconductor when the latent image is formed by the charging unit. By performing the pre-exposure, it is possible to prevent the image density fluctuation due to the VL fluctuation due to the exposure memory of the photoconductor, and to obtain a good image.

[Brief description of the drawings]

FIG. 1 is an overall structural diagram of a first embodiment of an image forming apparatus according to the present invention.

FIG. 2 is an environment variation graph of a development contrast potential for obtaining an appropriate density, which is used in the first embodiment of the image forming apparatus according to the present invention.

FIG. 3 is a graph showing environmental fluctuations of a charged potential of a photosensitive drum and a potential of an exposed portion used in the first embodiment of the image forming apparatus according to the present invention.

FIG. 4 is a sectional view of an electrophotographic photosensitive member applied to the image forming apparatus shown in FIG.

FIG. 5 is a graph showing a relationship between an exposure amount and a potential of a photosensitive drum (drum A) used in the first embodiment of the image forming apparatus according to the present invention.

FIG. 6 is a graph showing a relationship between an exposure amount and a potential of a photosensitive drum (drums A and B) used in the first embodiment of the image forming apparatus according to the present invention.

FIG. 7 is a transition graph of a potential on a drum according to the first embodiment of the image forming apparatus according to the present invention, as compared with a conventional example.

FIG. 8 is an environment fluctuation table (Table 1) of a development contrast potential for obtaining an appropriate density, which is used in the first embodiment of the image forming apparatus according to the present invention.

[Explanation of symbols]

 1a Aluminum cylinder 1b Charge generation layer 1c Charge transport layer 1d Charge injection layer 1Y, 1M, 1C, 1K Photosensitive drum 2Y, 2M, 2C, 2K Charger 3Y, 3M, 3C, 3K Exposure device 4Y, 4M, 4C, 4K Development Device 5 Transfer belt 6Y, 6M, 6C, 6K Transfer applying member 7 Fixing device 8 Convey tray 9 Document 10 Document platen glass 11 CCD reading sensor 13A, 13B Paper cassette 14 Registration roller 15 Semiconductor charging roller CS1 Environmental sensor F1, F2 F3 fan P transfer material SW2 switch

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 21/14 F term (Reference) 2H003 BB11 DD03 EE11 2H027 DA11 DA14 DA38 DE07 EA01 EA02 EA05 ED03 ED26 EE06 EF02 2H035 AA11 AA24 AB04 AC02 AC06 2H076 AB05 AB42 CA09 CA16 CA18 9A001 BB06 HH34 JJ35 JJ48 KK42

Claims (8)

[Claims] 1. A photoreceptor carrying an electrostatic latent image, a charging unit for charging the surface of the photoreceptor, and an exposure for exposing the surface of the photoreceptor charged by the charging unit to form an electrostatic latent image And an image forming apparatus, at least in a pre-charging section from when an image output command is issued to when an electrostatic latent image is formed on the photoconductor by the exposure means after the image output command is issued. The surface potential of the photoconductor in the pre-charging section is made larger by the charging unit than the surface potential of the image forming area of the photoconductor when a latent image is formed, and in the pre-charging section, An image forming apparatus, wherein the photoconductor is pre-exposed by the exposure unit. 2. The image forming apparatus according to claim 1, wherein the entirety of the image forming area in the longitudinal direction of the photoconductor in the pre-charging section is pre-exposed by the exposing unit. 3. An apparatus for detecting the temperature and humidity of the apparatus main body, comprising: an atmosphere detection unit for detecting a temperature and a humidity of the apparatus main body; The image forming apparatus according to claim 1, wherein the pre-exposure performed by the exposure unit is performed based on detection information of the atmosphere detection unit. 4. A region where a latent image is formed on the photoreceptor,
4. The image forming apparatus according to claim 1, wherein a time of the pre-exposure by the exposure unit in a pre-charging section is a time that is an integral multiple of a rotation cycle of the photoconductor. 5. . 5. An area where a latent image is formed on the photoconductor,
In the pre-charging section, when the pre-exposure is performed in a state where the apparatus main body is left for a predetermined time, the pre-exposure is not performed for one rotation of the driving of the photoconductor from the charging start position on the photoconductor, and The image forming apparatus according to claim 1, wherein pre-exposure is performed on a region after the rotation. 6. The image forming apparatus according to claim 1, wherein the photosensitive member is provided with a charge injection layer on a surface layer. 7. The image forming apparatus according to claim 6, wherein charge injection is performed on the charge injection layer using magnetic particles. 8. A photoconductor carrying an electrostatic latent image, charging means for charging the surface of the photoconductor, and exposure for forming an electrostatic latent image by exposing the surface of the photoconductor charged by the charging means. Means for controlling an exposure potential of an image forming apparatus including at least an image output command, wherein after the image output command is issued, the photoconductor is charged by the charging unit and the photoconductor is charged on the photoconductor by the exposure unit. In a pre-charging section until an electrostatic latent image is formed, the surface potential of the photoconductor in the pre-charging section is set to the surface of the image forming area of the photoconductor when the latent image is formed by the charging unit. An exposure potential control method, comprising: a step of making the potential higher than a potential; and a step of pre-exposing the photoconductor charged by the charging unit by the exposure unit in the pre-charging section.