JP2003140516A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device equipped with a preliminary static eliminator whose deterioration in lapse of time is suppressed to the minimum, and for obtaining a normal image even in the case the preliminary static eliminator is deteriorated. SOLUTION: The image forming device is provided with a photoreceptor, an initial electrifying part for electrifying the surface of the photoreceptor, a latent image forming part for exposing the photoreceptor and forming the latent image, a developing part for electrostatiaclly sticking toner on the latent image and forming a toner image, a transfer part for electrostatically transferring the toner image to a transfer material, a preliminary static eliminating part for applying a charge having a polarity opposite to that of the charge applied by the transfer part and preliminarily static eliminating the photoreceptor, a static eliminating part for static eliminating the photoreceptor electrified by the preliminary static eliminating part, a charge generation measuring part for measuring the charge generation in the preliminary static eliminating part, and a preliminary static elimination control part for controlling the charge generation in the preliminary static eliminating part so that the surface potential of the photoreceptor can be within a prescribed extent based on the measurement result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus capable of forming a normal image for a long period of time without showing a reverse polarity history.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine and a printer to which electrophotography is applied, a latent image is formed by exposing a photoconductor which is initially charged to charge a surface to a predetermined potential. An image is formed on the transfer material by applying toner to the toner to form a toner image and transferring the obtained toner image to a transfer material, for example, copy paper to fix the toner image.

In the image forming apparatus, at the time of the exposure, a portion of the surface of the photosensitive member which is exposed to light becomes conductive and the surface potential is attenuated, and a portion which is not exposed to the light is charged. The surface potential is retained. Therefore, at the time of forming a toner image, a toner having a polarity opposite to the surface potential at the time of charging the photoconductor is used, and the toner is attached to a portion on the surface of the photoconductor which is not exposed to light, thereby forming a positive image. Can be formed. On the contrary, it is possible to form a negative image by using a toner having the same polarity as the surface potential and adhering the toner to a light-exposed portion on the surface of the photoconductor.

In the image forming apparatus, not only a positive exposure / development method of forming a positive image by using a toner having a polarity opposite to the surface potential but a negative image by using a toner having the same polarity as the surface potential are used. A negative exposure / development method for forming a film is also widely used.

[0005]

However, in the negative exposure / development method, a voltage having a polarity opposite to the initial charging potential, which is the surface potential of the photoconductor at the time of initial charging, is applied by a charging means such as a corotron. The toner image on the surface of the photoconductor is transferred by applying it to copy paper.

Therefore, at the time of transferring the toner image, charges having a polarity opposite to the initial charging potential are applied to the surface of the photoconductor, so that the charge is removed after the toner image is transferred and before the photoconductor is recharged. However, it has been difficult to completely remove the reverse polarity history resulting from the application of the opposite polarity charges to the photoconductor from the surface of the photoconductor.

If the history of reverse polarity remains on the surface of the photoconductor, the initial charging potential may be reduced, and as a result, image defects such as fog on the white background of the image and uneven image density may occur.

In the photoconductor, a non-sheet passing portion which is a portion not covered by the copy paper at the time of transferring the toner image, specifically, between one copy paper and the next copy paper on the surface of the photoconductor. Since the surface of the photoconductor is exposed in the gap and the portion outside the transfer material, charges of opposite polarity are likely to be applied during transfer of the toner image. Therefore, the reverse polarity history appears particularly prominently in the portion of the photoconductor.

As a method of avoiding the reverse polarity history,
A method is conceivable in which the applied voltage of the transfer device is reduced so that the reverse polarity history does not remain even in the non-sheet passing portion.

However, when the above method is adopted, the transfer function for transferring the toner image onto the copy sheet in the image forming apparatus is deteriorated, and an image having a sufficient density cannot be formed on the copy sheet. .

When a corotron utilizing positive corona discharge is used for the initial charging, a grid plate is added to the corotron to correct the discharge unevenness at the time of negative charging, so that the initial charging potential becomes predetermined. It is also known to increase the output of the corotron wire until the output reaches a value to cancel the reverse polarity history.

However, even by the above method,
The reverse polarity history could not be removed.

Therefore, a preliminary static eliminator such as a corotron is provided between the transfer device for transferring the toner image in the image forming apparatus and the static eliminator for neutralizing the photoconductor after the toner image transfer. A method of removing the reverse polarity history by changing the surface potential of the photoconductor from negative to positive by applying a positive charge and then removing the charge was examined.

According to the above method, normal charging without reverse polarity history is possible in the next initial charging.

However, when the amount of positive charges generated in the preliminary charge eliminator is reduced due to deterioration of the preliminary charge eliminator over time, sufficient reverse polarity history removal performance may not be obtained. For example, when a corotron is used as a preliminary static eliminator, when the charge generation amount is set to be small in the initial state, the reverse polarity history removal performance is likely to be insufficient, but the voltage applied to the corotron wire must be increased in advance. When the positive charge generation amount is set to be large, the higher the applied voltage is, the more the adhesion of the discharge product to the wire is promoted, so that the deterioration of the preliminary charge removal component value with time is often accelerated.

According to the present invention, deterioration of the preliminary static eliminator over time is minimized, and even if the value of the preliminary static eliminator is deteriorated,
An object of the present invention is to provide an image forming apparatus capable of stably obtaining a normal image without reverse polarity history for a long period of time.

[0017]

According to a first aspect of the present invention, there is provided a photosensitive member, an initial charging unit that charges the surface of the photosensitive member to a predetermined voltage, and a photosensitive member whose surface is charged by the initial charging unit. An exposure unit that exposes a body to form a latent image on the surface of the photoreceptor, and a toner image is formed by electrostatically attaching toner to the surface of the photoreceptor on which the latent image is formed. A developing unit, a transfer unit that electrostatically transfers the toner image formed in the developing unit onto a transfer material, and a charge having a polarity opposite to that of the charge applied by the transfer unit are applied to pre-electrify the photoreceptor. An image forming apparatus, comprising: a preliminary charge removing section, and a charge removing section that removes charge from a photoconductor that has been subjected to preliminary charge removal in the preliminary charge removing section. And the measurement in the charge generation amount measurement unit Based on results, the charge-generating amount of the photosensitive member to an image forming apparatus characterized by comprising a preliminary neutralization controller for controlling the pre-charge eliminating unit to be held in a predetermined range.

In the image forming apparatus, as described above, the charge generation amount is maintained within a predetermined range based on the measurement result of the charge generation amount in the preliminary charge removal unit in the charge generation amount measurement unit. Since the preliminary static eliminator is controlled, even when the preliminary static eliminator is deteriorated, the electric charges applied to the transfer material in the transfer unit may remain and the surface potential of the photoconductor may decrease or rise. To be prevented. Therefore, in the image forming apparatus, a normal image having no reverse polarity history can be stably obtained for a long period of time.

Examples of the image forming apparatus include an image forming apparatus using an electrophotographic technique such as an electrophotographic copying machine and a laser printer. The image forming apparatus may form a monochrome image or a color image.

In the charge generation amount measuring unit, the surface potential of the photosensitive member or the current flowing into the photosensitive member when the charge is applied in the preliminary charge removing unit is measured,
Based on the obtained measured value, the charge generation amount in the preliminary charge eliminating portion can be obtained. Further, when using a corona charger to be described later as the pre-electrification unit, the corona charger is usually controlled by a constant voltage, and the amount of charge generated per unit time is proportional to the current flowing through the corona charger,
The charge generation amount may be obtained by measuring the current.

When the preliminary static eliminator deteriorates, the amount of charges generated in the preliminary static eliminator generally decreases. The decrease in the amount of generated electric charges can be understood as a decrease in the surface potential of the photoconductor and a decrease in current flowing into the photoconductor. Further, when a corona charger is used as the preliminary static eliminator, it can be regarded as a decrease in the current flowing through the corona charger. Therefore, the charge generation amount measurement unit,
Deterioration of the preliminary charge eliminator can be detected from changes in the surface potential of the photoconductor, a decrease in current flowing into the photoconductor, a decrease in current flowing into the corona charger, and the like.

When the charge generation amount measurement unit detects the deterioration of the preliminary charge removal unit, the preliminary charge control unit increases the amount of charge generation, for example, by increasing the voltage applied to the preliminary charge removal unit based on the detection result. Control to let. Thereby, the surface potential of the photoconductor can be maintained within a predetermined range.

Examples of the charge generation amount measuring unit include a surface potential sensor and an inflow current measuring device described later.

The other components of the image forming apparatus will be described below.

On the surface of the photoreceptor, charging in the initial charging section, formation of a latent image in the exposing section, formation of a toner image in the developing section, transfer of a toner image in the transferring section, and in the preliminary charge removing section. The charge application and the charge removal in the charge removal unit are repeatedly performed in this order.

Therefore, as the photoconductor, a photoconductor on the surface of which is formed a photosensitive layer that circulates through the initial charging section, the exposing section, the developing section, the transfer section, the preliminary charge removing section, and the charge removing section. Is used.

As the photosensitive member, specifically, a photosensitive drum which is a drum having a photosensitive layer made of selenium, a selenium alloy, an organic photosensitive member, or the like on its surface and rotating in a fixed direction around an axis, Examples thereof include a photosensitive belt having the above-mentioned various photosensitive layers formed on the surface of the belt, and a photosensitive drum is generally used.

In an image forming apparatus using a photosensitive drum as a photosensitive member, an initial charging section, an exposing section, a developing section, a fixing section, a preliminary charge removing section are provided around the photosensitive drum along the rotation direction of the photosensitive drum. Further, since the static elimination units can be arranged in this order, the image forming apparatus can be formed compactly.

The initial charging section has a function of charging the surface of the photosensitive member, which has been discharged by the discharging section, to a predetermined voltage.

In the initial charging section, the surface of the photoconductor may be positively charged or negatively charged. However, since a more stable positive corona discharge can be used, It is common to charge the surface positively. To charge the surface of the photoconductor,
Corona charger that charges the surface of the photoconductor using corona discharge, corona charger such as scorotron, and charging that charges the surface of the photoconductor with a charging member such as a conductive brush or conductive roller to which a voltage is applied. Although a contact charger such as a roller or a charging brush can be used, the corona charging can be applied in a non-contact manner and the amount of charge applied to the surface of the photoconductor can be controlled by increasing or decreasing the applied voltage. Vessels are preferred.

In the developing section, a toner image is obtained by using either a positive polarity toner charged to the same polarity as the initial charging potential or a reverse polarity toner charged to the opposite polarity to the initial charging potential. However, a positive polarity toner is generally used. When the photoconductor is positively charged in the initial charging unit, positively charged toner charged to a positive potential is used as the positive polarity toner.

When development is carried out using the positive polarity toner in the developing section, the light-exposed portion of the surface of the photoreceptor loses the electric charge, and the non-exposed portion of the surface remains the electric charge. Therefore, when the positive polarity toner is attached to the surface of the photoconductor after exposure, the positive polarity toner is attached to the light-exposed portion of the surface of the photoconductor, so that a negative image is obtained.

In the transfer section, the toner image obtained in the developing section is transferred to the transfer material by charging the transfer material to a polarity opposite to the charge of the toner used in the developing section. it can. Therefore, when developing using the positively charged toner in the developing section, it is general that the transfer material is negatively charged in the transfer section.

Examples of the transfer material include copy papers that are commonly used in electrophotographic copying machines and laser printers, as well as OHP films.

The preliminary charge erasing section has a function of neutralizing the electric charges applied to the photoconductor by the fixing section so that the surface of the photoconductor can be effectively neutralized by the charge erasing section.

In the preliminary charge removing section, the corona charger and the contact charger described in the initial charging section can be used, but the corona charger is preferable.

Examples of the static elimination section include those used in known electrophotographic copying machines and laser printers, and specifically, static elimination lamps and static elimination corotrons can be used.

According to a second aspect of the present invention, the developing section comprises:
The present invention relates to an image forming apparatus that forms a toner image by adhering a toner having a charge of the same polarity as an initial charging potential, which is the surface potential of the photosensitive member in the initial charging unit, to the surface of the photosensitive member.

In the image forming apparatus, a toner image is formed by irradiating the surface of the photoconductor charged by the initial charging unit with laser light and adhering the positive toner to the portion irradiated with the laser light. Can be formed. Therefore, the image forming apparatus is suitable as a laser printer.

According to a third aspect of the invention, the transfer portion is
The present invention relates to an image forming apparatus that transfers the transfer material by applying a charge having a polarity opposite to an initial charging potential at the time of the initial charging.

The transfer section in the image forming apparatus can be preferably used for transferring the toner image formed by the positive polarity toner onto the transfer material.

According to a fourth aspect of the present invention, the initial charging section and the preliminary charge removing section positively charge the surface of the photoconductor, and the transfer section negatively charges the transfer material to form a toner image. The present invention relates to an image forming apparatus that transfers an image onto the transfer material.

In the image forming apparatus, a corotron or the like which uses a highly stable positive corona discharge can be used in the initial charging section and the preliminary charge removing section.

In the transfer section, a negative charge is applied to the photoconductor by negatively charging the transfer material, but the surface of the photoconductor is positively charged in the preliminary charge removal section. By doing so, the negative charges applied in the transfer section are neutralized. Therefore, the charge removal of the photoconductor is smoothly performed in the charge removal unit. Therefore, a particularly stable initial charge potential is obtained in the initial charge unit, so that the quality of the obtained image is particularly stable.

According to a fifth aspect of the present invention, the charge generation amount measuring section includes a surface potential sensor for measuring the surface potential of the photoconductor when the charge is applied in the preliminary charge removing section. Based on the surface potential measured by the sensor,
The present invention relates to an image forming apparatus for obtaining a charge generation amount in the preliminary charge removal section.

Further, the surface potential of the photoconductor rises when a positive charge is applied in the preliminary charge eliminating portion. And
The greater the amount of the positive charges applied, the greater the degree of increase in potential. Therefore, by measuring the surface potential of the photoconductor, it is possible to know the amount of charges generated in the preliminary charge eliminating portion.

In the image forming apparatus, since the surface potential sensor is used to measure the surface potential of the photoconductor, the surface potential can be easily measured without contact.

The invention according to claim 6 relates to the image forming apparatus, wherein the surface potential sensor also has a function of measuring an initial charging potential in the initial charging section.

In the image forming apparatus, an initial charging potential sensor for measuring the initial charging potential is provided on the downstream side of the initial charging section, and based on the measurement result of the initial charging potential sensor,
It is common practice to control the initial charging section so that the photoconductor is charged to a predetermined initial charging potential. Moreover, as the initial charging potential sensor, it is general to use a normal surface potential sensor.

Therefore, the surface potential sensor for measuring the surface potential of the photoconductor can also be used as the initial charging potential sensor.

In the image forming apparatus, since the surface potential sensor for measuring the surface potential of the photoconductor is also used as the initial charging potential sensor, the structure can be simplified.

According to a seventh aspect of the present invention, the charge generation amount measuring section includes an inflow current measuring device for measuring an inflow current into the photoconductor when the charge is applied by the preliminary charge removing section. The image forming apparatus obtains the amount of electric charge generated in the preliminary charge eliminating unit based on the measurement result of the inflow current in the inflow current measuring apparatus.

When electric charges are applied to the photoconductor in the preliminary charge removal section, a current corresponding to the amount of charge generated in the charge removal section per unit time flows into the photoconductor. This current is the inflow current. Therefore, if the inflow current is measured, the amount of charge generated in the static elimination unit per unit time can be known.

Here, when the charge generation amount per unit time in the preliminary charge removal unit decreases, the inflow current also decreases, and when the charge generation amount per unit time in the preliminary charge removal unit increases, the inflow current also increases. To increase.

Therefore, by continuously measuring the inflow current and controlling the preliminary charge removal section so that the inflow current maintains a predetermined value, the amount of charge generated in the preliminary charge removal section can be kept constant. Therefore, the surface potential of the photoconductor can be kept constant.

Since the inflow current can be easily measured, the amount of electric charge generated in the preliminary charge eliminating portion can be easily obtained in the image forming apparatus.

According to an eighth aspect of the present invention, the charge generation amount measuring unit is based on the charge generation amount in the preliminary charge eliminating unit,
When the charge generation amount measuring unit determines that the preliminary charge removal unit has deteriorated and the degree of deterioration, and the charge generation amount measurement unit determines that the preliminary charge removal unit has deteriorated, the preliminary charge removal control unit increases the charge generation amount in the preliminary charge removal unit. The present invention relates to an image forming apparatus that controls the preliminary static eliminator to perform the above.

As described above, when the preliminary charge erasing unit deteriorates, the amount of charge generated generally decreases even if a voltage of the same strength is applied, and the charge imparted to the photoconductor in the transfer unit is sufficiently reduced. It becomes impossible to neutralize.

Therefore, when the charge generation amount measuring unit detects the deterioration of the preliminary charge eliminating unit, the preliminary charge eliminating control unit performs the preliminary charge eliminating so that the charge imparted to the photoconductor in the transfer unit can be sufficiently neutralized. Increase the amount of electric charge generated in the part.

In the charge generation amount measuring section, the deterioration of the preliminary charge eliminating section can be understood as a decrease in the surface potential of the photosensitive member or a decrease in the inflow current when the charge is applied in the preliminary charge eliminating section.

The invention according to claim 9 relates to an image forming apparatus, wherein the preliminary charge elimination control section controls the amount of charges generated in the preliminary charge elimination section by increasing or decreasing the voltage applied to the preliminary charge elimination section.

In the image forming apparatus having the corona charger as the preliminary charge eliminating section, the amount of charge generated in the preliminary charge eliminating section can be increased by increasing the voltage applied to the corona charger. By decreasing the voltage, it is possible to reduce the amount of charges generated in the preliminary charge eliminating portion.

The invention is particularly suitable for the image forming apparatus.

The invention described in claim 10 relates to an image forming apparatus, wherein the photosensitive member is a photosensitive drum formed in a drum shape.

As described above, in the image forming apparatus, the initial charging section, the exposing section, the developing section, the fixing section, the preliminary charge removing section, and the charge removing section can be arranged around the photosensitive drum. It can be made compact.

[0066]

BEST MODE FOR CARRYING OUT THE INVENTION 1. Embodiment 1 FIG. 1 shows a schematic configuration of an example of an image forming apparatus according to the present invention.

The image forming apparatus 100 according to the first embodiment is
With respect to the initial charging corotron 4, the photosensitive drum 2 having a photosensitive layer on its surface and rotating in the counterclockwise direction as indicated by an arrow a in FIG. LED exposure that is provided on the downstream side (hereinafter, simply referred to as “downstream side”) along the rotation direction a of the photosensitive drum 2 and exposes the surface of the photosensitive body 2 charged by the initial charging corotron 4 to form a latent image. Device 6 and LED
A surface potential sensor 8 located downstream of the exposure device 6 for measuring the surface potential of the photoconductor 2 exposed in the LED exposure device 6, and a positively charged toner located downstream of the surface potential sensor 8 and positively charged. And a developing device 10 for forming a toner image on the surface of the photosensitive drum 2 by adhering the latent image formed on the LED exposure device 6 to the latent image and developing the latent image.
0, which is a sheet feeding device 1 including a series of rollers for feeding a copy sheet P, which is an example of the transfer material of the present invention, from the copy sheet cassette 26 to the surface of the photosensitive drum 2.
2 and a transfer corotron 14 which is adjacent to the downstream side of the sheet feeding device 12 and generates a negative charge to transfer the toner image formed on the surface of the photosensitive drum 2 to the copy sheet P supplied from the sheet feeding device 12. And a peeling corotron 16 located downstream of the transfer corotron 14 for peeling the copy paper P on which the toner image has been transferred from the surface of the photosensitive drum 2 by applying an alternating voltage and a positive bias voltage in a superimposed manner. A cleaning device 18 located downstream of the peeling corotron 16 for removing the toner remaining on the surface of the photosensitive drum 2 after the transfer of the toner image; and a cleaning device 18 provided downstream of the cleaning device 18 for generating a positive charge. A preliminary charge-eliminating corotron 20 for removing the negative charging history imparted by the transfer corotron 14 from the surface of the photosensitive drum 2, It located downstream of the neutralizing corotron 20, and to remove the surface potential of the photosensitive drum 2, and a charge removing lamp 22 for resetting to zero volts near a front of the surface potential of charged in the initial charging corotron 4.

The image forming apparatus 100 is further based on the surface potential of the photoconductor 2 measured by the surface potential sensor 8,
A preliminary static elimination corotron control circuit 24 for controlling the voltage applied to the preliminary static elimination corotron 20 is provided.

Photoreceptor 2, initial charging corotron 4, LED
The exposure device 6, the developing device 10, the transfer corotron 14, the pre-electrification corotron 20, the anti-electrification lamp 22, the surface potential sensor 8, and the pre-electrification corotron control circuit 24 are respectively a photoreceptor, an initial charging unit, and an initial charging unit in the image forming apparatus of the present invention.
It corresponds to the exposure section, the developing section, the transfer section, the preliminary charge removal section, the charge removal section, the charge generation amount measurement section, and the preliminary charge removal control section. The surface potential sensor 8 particularly corresponds to the surface potential sensor in the charge generation amount measurement unit.

The operation of the image forming apparatus 100 will be described below.

In the initial charging corotron 4, the surface of the photosensitive drum 2 is charged to a predetermined potential, for example + 500V.

When the initial charging corotron 4 is not controlled at all, the charging potential of the photosensitive drum 2 in the initial charging corotron 4, that is, the initial surface potential, is determined by the image forming apparatus 10.
The surface potential sensor 8 changes before the toner image is formed or during the transfer of the toner image.
The surface potential of the photosensitive drum 2 is measured by the feedback control of the voltage applied to the initial charging corotron 4 based on the surface potential data so that the initial charging potential is always + 500V.

+ 500V at initial charging corotron 4
The photosensitive drum 2 that has been charged to 1 is exposed by the LED exposure device 6. The surface potential of the surface of the photosensitive drum 2 exposed to the light from the LED exposure device 6 decreases to +50 V, while the area not exposed to the light is held at +500 which is the initial charging potential. As a result, a latent image corresponding to the image to be formed is formed.

The developing device 10 attaches positively charged toner to the latent image formed on the surface of the photosensitive drum 2 in the LED exposure device 6 to form a toner image.

When the toner image is formed in the developing device 10, the copy paper P is supplied to the surface of the photosensitive drum 2 by the paper feeding device 12. Since the copy paper P is negatively charged by the transfer corotron 14, the positively charged toner forming the toner image is electrostatically adsorbed on the copy paper P. As a result, the toner image is transferred to the copy paper P.

Copy paper P on which the toner image is transferred
Is peeled from the surface of the photosensitive drum 2 by superimposing and applying an AC voltage and a positive bias voltage in the peeling corotron 16.

Here, since the transfer corotron 14 applies a negative charge to the non-sheet passing portion of the surface of the photosensitive drum 2 which is not covered with the copy paper P, the surface of the photosensitive drum is negative. Electric potential, for example −
It is charged to 300V. However, when the AC voltage and the positive bias voltage are applied to the peeling corotron 16, the surface potential of the photosensitive drum 2 rises to −150V.

Since about 20% of the positively charged toner remains on the surface of the photosensitive drum 2 after the transfer of the toner image, the surface is cleaned by the cleaning device 18 to remove the positively charged toner.

The photosensitive drum 2 whose surface has been cleaned by the cleaning device 18 is given a positive charge by the preliminary charge eliminating corotron 20. As a result, the surface potential of the non-sheet passing portion on the surface of the photosensitive drum 2 rises to a positive potential, for example + 100V.

The surface of the photosensitive drum 2 to which a positive charge has been applied by the pre-electrification corotron 20 is a static elimination lamp 2.
By 2, the charge is removed until the surface potential becomes +50 V or less, for example.

However, when the pre-electrification corotron 20 deteriorates and cannot sufficiently give positive charges to the surface of the photosensitive drum 2, the surface potential of the non-sheet passing portion may not rise to the positive potential.

Therefore, the preliminary static elimination corotron control circuit 24
In the above, the presence or absence of deterioration of the pre-electrification corotron 20 is determined, and when the pre-electrification corotron 20 is deteriorated, the voltage applied to the pre-electrification corotron 20 is increased to make the surface potential of the non-sheet passing portion positive. Try to be.

FIG. 2 shows the flow of the first procedure for determining the deterioration of the preliminary static charge corotron 20 in the preliminary static charge corotron control circuit 24.

As shown in FIG. 2, the pre-electrification corotron control circuit 24 turns off the initial charging corotron 4, the LED exposure device 6, and the developing device 10 before the image formation, and the surface potential sensor 8 and the transfer corotron 14 are turned off. Peeling corotron 1
6 and pre-electrification static electricity corotron 20 and static electricity elimination lamp 22 are turned on
To Then, the surface potential sensor 8 measures the surface potential of the photosensitive drum 2.

At this time, if the preliminary charge-eliminating corotron 20 is not deteriorated, the surface potential of the photosensitive drum 2 is positive, but if the preliminary charge-eliminating corotron 20 is deteriorated, the surface potential of the photosensitive drum 2 is negative. .

Therefore, when the surface potential sensor 8 detects a positive surface potential, it is judged that the preliminary static elimination corotron is not deteriorated, and the applied voltage of the preliminary static elimination corotron is set to the potential when the preliminary corotron 20 is new. For example, +4.
Leave at 8 kV. On the other hand, when the surface potential sensor 8 detects a negative surface potential, the preliminary static elimination corotron 2
It is judged that 0 has deteriorated and the applied voltage of the preliminary static elimination corotron is increased from +4.8 kV, for example, by +100 V until the surface potential sensor 8 detects a positive potential, thereby increasing the charge generation amount in the preliminary static elimination corotron 20. Let

FIG. 3 shows a second procedure for determining the deterioration of the preliminary charge-eliminating corotron 14 in the preliminary charge-eliminating corotron control circuit 24.

In the image forming apparatus shown in FIG. 1, for example, the voltage applied to the transfer corotron 14 is -5 kV, and the surface potential of the photosensitive drum 2 is after the toner image is transferred to the copy sheet P by the transfer corotron 14. It is assumed that the voltage is 300V and the voltage is −150V after the copy paper P is peeled by the peeling corotron 16.

At this time, when the voltage applied to the transfer corotron 14 is lowered to -6 kV, the surface potential of the photosensitive drum 2 becomes, for example,-after the transfer of the toner image.
After dropping to 350V and peeling the copy paper P, -2
Since the voltage drops to 00V, the surface potential of the photosensitive drum 2 after passing through the pre-electrification corotron 14 decreases, and may become negative in some cases.

Therefore, in the second procedure, as shown in FIG.
As shown in FIG.
Is turned on, the applied voltage of the transfer corotron 14 is lowered from, for example, −5 kV to −6 kV, and the surface potential of the photosensitive drum 2 at this time is measured by the surface potential sensor 8.

If the initial charging potential measured by the surface potential sensor 8 is + 500V, the preliminary static elimination corotron 2
It is determined that 0 is not deteriorated, and the applied voltage of the preliminary static elimination corotron is maintained at +4.8 kV. On the other hand, when the initial charge potential is lower than + 500V, it is determined that the preliminary charge-eliminating corotron 20 has deteriorated, and the applied voltage of the preliminary charge-eliminating corotron 20 is increased by 100V, for example, until the initial charge potential becomes 500V.

In the image forming apparatus 100, the preliminary static elimination corotron control circuit 24 determines whether the preliminary static elimination corotron 20 is deteriorated or not according to one of the above two procedures, and based on the result, the preliminary static elimination corotron 20 is determined. Since the applied voltage is gradually increased, the minimum voltage that does not cause image deterioration due to the reverse polarity history is applied to the preliminary static elimination corotron 20 even if the preliminary static elimination corotron 20 deteriorates, and is unnecessary. No high voltage is applied to the

Therefore, the deterioration of the preliminary charge-eliminating corotron 20 can be suppressed, and even when the preliminary charge-eliminating corotron 20 has deteriorated, the progress of the deterioration can be suppressed. Further, even if the preliminary charge-removing corotron 20 deteriorates due to long-term use, image deterioration due to reverse polarity history can be effectively prevented.

Further, the image forming apparatus 100 has a feature that it can be constructed only by adding the preliminary static elimination corotron control circuit 24 to the conventional image forming apparatus, and it is not necessary to provide a new sensor or the like.

In the image forming apparatus 100, in the case of controlling the voltage applied to the preliminary charge-eliminating corotron 20 according to the second procedure, in addition to the above-mentioned features, the surface potential sensor 8
Since the voltage applied to the pre-electrification corotron 20 can be controlled even if a positive voltage can be detected, an advantage that an inexpensive product can be used as the surface potential sensor 8 can be obtained.

2. Embodiment 2 FIG. 4 shows the outline of the configuration of another example of the image forming apparatus according to the present invention. 4, the same reference numerals as those in FIG. 1 denote the same constituent elements as those shown in FIG. 1 unless otherwise specified.

In the image forming apparatus 102 according to the second embodiment, the surface potential of the photosensitive drum 2 immediately after the positive charge is applied in the preliminary charge-eliminating corotron 20 between the preliminary charge-eliminating corotron 20 and the charge-eliminating lamp 22. A surface potential sensor 28 is provided. Then, the preliminary static elimination corotron control circuit 24 controls the preliminary static elimination corotron 20 based on the measurement result of the surface potential sensor 28.

Except for the above points, the image forming apparatus 102
Has the same configuration as the image forming apparatus according to the first embodiment.

The operation of the image forming apparatus 102 will be described below.

The image forming apparatus 102 is the same as the image forming apparatus of the first embodiment in the steps from the charging of the photosensitive drum 2 by the initial charging corotron 4 to the discharging by the discharging lamp 22.

However, unlike the image forming apparatus according to the first embodiment, the surface potential sensor 28 measures the surface potential of the photosensitive drum 2 immediately after the positive charge is applied by the preliminary charge-eliminating corotron 20. If the surface potential measured by the surface potential sensor 28 is positive, the preliminary static elimination corotron control circuit 24 determines that the preliminary static elimination corotron 20 is not deteriorated or the deterioration is not progressing, and the preliminary static elimination is performed. The voltage applied to the corotron 20 is maintained as it is. On the other hand, if the surface potential is 0 or negative, the preliminary static elimination corotron control circuit 24 determines that the deterioration of the preliminary static elimination corotron 20 has progressed, and reserves until the surface potential measured by the surface potential sensor 28 becomes positive. The voltage applied to the static elimination corotron 20 is increased.

Also in the image forming apparatus of the second embodiment, since the minimum voltage that does not cause image deterioration due to reverse polarity history is applied to the pre-charging corotron 20, deterioration of the pre-charging corotron 20 is suppressed, and Even when the preliminary static elimination corotron 20 deteriorates, the progress of the deterioration can be suppressed. Furthermore, even if the preliminary charge-removing corotron 20 deteriorates due to long-term use, image deterioration due to reverse polarity history can be effectively prevented.

Further, the voltage applied to the pre-electrification corotron 20 in real time without turning off the initial charging corotron 4, the LED exposure device 6, the developing device 10, the transfer corotron 14, the paper feeding device 12, and the peeling corotron 16. Since the control can be performed, the deterioration of the preliminary charge removal corotron 20 and the image deterioration due to the reverse polarity history can be prevented more effectively than the image forming apparatus according to the first embodiment.

3. Embodiment 3 FIG. 5 shows a schematic configuration of still another example of the image forming apparatus according to the present invention. 5, the same reference numerals as those in FIG. 1 denote the same constituent elements as those shown in FIG. 1 unless otherwise specified.

As shown in FIG. 5, in the image forming apparatus 104 according to the third embodiment, the inflow current curve for measuring the amount of the inflow current to the photosensitive drum 2 when the charge is applied by the preliminary charge removal corotron 20. Equipped with 30. Inflow ammeter 30
Is located between the preliminary static elimination corotron 20 and the static elimination lamp 22, and corresponds to the inflow current measuring device in the image forming apparatus of the present invention.

When the inflow current to the photosensitive drum 2 measured by the inflow ammeter 30 becomes smaller than a certain value, the preliminary charge removal corotron control circuit 24 determines that the preliminary charge removal corotron 20 has deteriorated, and the inflow current is determined. The voltage applied to the pre-electrification corotron 20 is increased until the pre-electrification corotron 20 returns to a value before deterioration.

The image forming apparatus 104 according to the third embodiment is
Except for the above points, the image forming apparatus according to the second embodiment has the same configuration.

Since the image forming apparatus 104 according to the third embodiment can also control the voltage applied to the preliminary charge-eliminating corotron 20 in real time, the deterioration of the preliminary charge-eliminating corotron 20 and the image deterioration due to the reverse polarity history are applied to the first embodiment. It can be prevented more effectively than the image forming apparatus.

[0109]

As described above, according to the present invention,
Provided is an image forming apparatus which can suppress deterioration of the preliminary charge eliminating portion with time to a minimum and can stably obtain a normal image without reverse polarity history for a long period of time even if the preliminary charge eliminating portion deteriorates.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is a flow chart showing an example of a procedure for controlling the voltage applied to the pre-electrification corotron based on the surface potential of the photosensitive drum measured by the surface potential sensor in the image forming apparatus shown in FIG. .

FIG. 3 is a flow chart showing another example of a procedure for controlling the voltage applied to the preliminary static elimination corotron based on the surface potential of the photosensitive drum measured by the surface potential sensor in the image forming apparatus shown in FIG. is there.

FIG. 4 is a schematic diagram illustrating a configuration of an image forming apparatus according to a second exemplary embodiment.

FIG. 5 is a schematic diagram illustrating a configuration of an image forming apparatus according to a third exemplary embodiment.

[Explanation of symbols]

2 photosensitive drum 4 Initial charging corotron 6 LED exposure device 8 Surface potential sensor 10 Development device 14 Transfer Corotron 16 peeling corotron 20 Preliminary static elimination corotron 22 Static elimination lamp 24 Preliminary static elimination corotron control circuit 28 Surface potential sensor 30 Inflow ammeter

Claims (10)

[Claims] 1. A photoconductor, an initial charging unit that charges the surface of the photoconductor to a predetermined voltage, and a latent image on the surface of the photoconductor by exposing the photoconductor whose surface is charged by the initial charging unit. An exposure unit that forms a toner image, a developing unit that electrostatically attaches toner to the surface of the photoconductor on which a latent image is formed in the exposure unit to form a toner image, and a toner image formed in the developing unit. To the transfer material electrostatically, a preliminary charge eliminator for preliminarily neutralizing the photoconductor by applying a charge having a polarity opposite to that of the charge imparted by the transfer portion, and a preliminary charge eliminator in the preliminary static eliminator. An image forming apparatus comprising a charge eliminating unit for eliminating charge of the photoconductor, wherein a charge generation amount measuring unit for measuring a charge generation amount in the preliminary charge eliminating unit, and a charge generation amount measuring unit based on a measurement result. , Charge generation amount of the photoconductor An image forming apparatus characterized in that it comprises a preliminary neutralization controller for controlling the pre-charge eliminating unit to be held in a predetermined range. 2. The developing unit is provided on the surface of the photoconductor,
The image forming apparatus according to claim 1, wherein a toner image is formed by adhering a toner having a charge of the same polarity as an initial charging potential which is a surface potential of the photoconductor in the initial charging unit. 3. The image forming apparatus according to claim 2, wherein the transfer section transfers the transfer material by applying a charge having a polarity opposite to an initial charging potential at the initial charging to the transfer material. 4. The initial charging section and the preliminary charge removing section positively charge the surface of the photoconductor, and the transfer section transfers the toner image to the transfer material by negatively charging the transfer material. The image forming apparatus according to claim 3. 5. The charge generation amount measuring unit comprises a surface potential sensor for measuring the surface potential of the photoconductor when the charge is applied in the preliminary charge eliminating unit, and the surface potential measured by the surface potential sensor is measured. The image forming apparatus according to any one of claims 1 to 4, wherein the charge generation amount in the preliminary charge eliminating portion is calculated based on the basis. 6. The image forming apparatus according to claim 5, wherein the surface potential sensor also has a function of measuring an initial charging potential in the initial charging unit. 7. The charge generation amount measuring unit is provided with an inflow current measuring device for measuring an inflow current into the photoconductor when electric charges are applied in the preliminary charge eliminating unit, and the inflow current measuring device includes: The image forming apparatus according to any one of claims 1 to 4, wherein the charge generation amount in the preliminary charge eliminating portion is obtained based on a measurement result of an inflow current. 8. The charge generation amount measurement unit determines the presence or absence and the degree of deterioration of the preliminary charge removal unit based on the charge generation amount in the preliminary charge removal unit, and the charge generation amount measurement unit determines the preliminary charge removal unit. When it is determined that the preliminary static elimination unit has deteriorated, the preliminary static elimination control unit controls the preliminary static elimination unit so as to increase the amount of charges generated in the preliminary static elimination unit.
The image forming apparatus according to claim 1. 9. The preliminary charge-elimination control unit controls the amount of charges generated in the preliminary charge-elimination unit by increasing or decreasing a voltage applied to the preliminary charge-elimination unit. Image forming apparatus. 10. The image forming apparatus according to claim 1, wherein the photosensitive member is a photosensitive drum formed in a drum shape.