JP2003271029A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which prevents image defects caused by sticking of carrier, even in the case that a switch is turned off because a door is opened or closed in the course of image formation. <P>SOLUTION: The image forming apparatus has: an image carrier, an electrifying means, an exposure means, a developing means disposed downstream from an electrifying means of an image forming process and used for developing a latent image with developer held on a developer carrier, a transfer means used for transferring a toner image developed with the developer onto transfer paper, a fixing means for fixing the transferred toner under heat, and a control means. In the image forming apparatus, a destaticizing means which destaticizes a surface potential applied to the image carrier is disposed around the image carrier and between the electrifying means and the developing means, and a control means operates the destaticizing means based upon an information about a drop in the input voltage of a power source for driving a high voltage substrate, which is supplied to at least the electrifying means and the developing means. <P>COPYRIGHT: (C)2003,JPO

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 a carrier for an image carrier, which occurs when a door opening / closing switch or a main switch is turned off during image formation, or is turned on immediately after being turned off. The present invention relates to an image forming apparatus that prevents image defects caused by adhesion.

[0002]

2. Description of the Related Art An example of a conventional image forming apparatus will be described. After negatively charging an image carrier (also referred to as a photosensitive drum), a latent image near zero potential is formed by laser light,
After that, the latent image on the image carrier is developed by a developer carrier to which a negative developing bias voltage having the same polarity as that of the image carrier is applied, then transferred by a transfer unit, separated by a separating unit, and then a fixing unit. It is designed to be fixed and image-formed.

In such an image forming apparatus, when an abnormal operation such as opening an opening / closing door is performed during a normal image forming sequence, the developing bias voltage output and the charging voltage output are turned off by turning off the door opening / closing switch. . But,
Since the photoconductor drum continues to rotate due to inertia, the charged region of the photoconductor drum passes through the developing region, and the carrier adheres to the photoconductor drum from the zero V developer carrier to which the developing bias voltage is not applied. There was a problem that the phenomenon occurred. Adhesion of the carrier may damage the surface of the photosensitive drum, the fixing roller, or the like, which causes image loss due to the damage. Therefore, as an improvement, a technique is disclosed in which the developing bias voltage is temporarily held when the above-described abnormal operation is performed.

An example of the image forming apparatus will be described with reference to the drawings. FIG. 5 is a diagram showing a part of the configuration of a conventional image forming apparatus, and FIG. 6 is a diagram showing a time chart of essential parts of FIG. More specifically, FIG. 6A is a time chart of the door opening / closing switch, FIG. 6B is a time chart of the charging output signal, FIG. 6C is a time chart of the rotation of the photosensitive drum, and FIG. FIG. 6E is a time chart of the developing bias output signal, and FIG. 6E is a time chart of charging the photosensitive drum at the developing unit position. The left side of the drawing shows a case where the door opening / closing switch is turned off and the right side of the drawing shows a case where the door opening / closing switch is turned on immediately after turning off.

As shown in FIGS. 5 and 6, 201 is a main switch, 202 is a DC power source, 203 is a door opening / closing switch,
205 is a voltage drop detection circuit, 300 is control means, 204
Is a high-voltage power supply that supplies the charging means 103 and the developing means 104, and M is a motor that drives the photosensitive drum.

After the photosensitive drum 102 is negatively charged by the charging means 103, a latent image close to zero potential is formed by a laser beam (not shown), and then the photosensitive drum 102.
Of the developer carrying member 104a to which a negative developing bias voltage of the developing means 104 having the same polarity as the above is applied.
After developing the latent image on 02, it is transferred by the transfer means 105,
After separating by the separating unit 106, the image is fixed and fixed by the fixing unit 180.

In this image forming apparatus, a magnetic brush developing system developing means 104 using a two-component developer is used.
The developing means 104 has a cylindrical developer carrier 104a rotatably supported by a magnet roll formed of a magnet body having a plurality of magnetic poles therein.
The magnetic carrier having the toner particles adhered to the surface thereof is held and conveyed to the developing area for development.

Here, a case where the door opening / closing switch 203 of the opening / closing door is turned off during image formation will be described. In addition,
The same applies to the main switch 201 of the apparatus body. First, the door open / close switch 203 is turned off during image formation.
When F is reached, the high voltage power output of the charging means 103 is turned off, but the high voltage power output of the developing means 104 is temporarily turned on.
To maintain. Further, although the power supplied to the photoconductor drum 102 is turned off, the photoconductor drum 102 continues to rotate due to inertia.

[0009]

However, as a problem of the prior art, when the door opening / closing switch 203 is turned from ON to OFF during image formation, the time charts on the left side of FIGS. 6D and 6E are shown. Door open / close switch 20
In the prior art, the high-voltage output of the developing means is temporarily turned on by turning off 3 in the conventional technique. However, if the time during which the high-voltage output is on is short, when the photosensitive drum 102 rotates by inertia, There is a problem that image defects due to the carrier adhesion to the photoconductor drum 102 are likely to occur. Even if the door open / close switch 203 is turned off, the developing bias is still on, and if the developing bias output continues to be on in an uncharged area on the surface of the photosensitive drum 102, the surface of the photosensitive drum 102 is charged. There is also a problem that a non-covered area occurs, and the toner adheres to the photosensitive drum due to a potential difference, causing toner fogging, and deterioration of a quality image is likely to occur.

Next, the door opening / closing switch 203 during image formation.
When the door opening / closing switch 203 is turned off and then turned on immediately, the developing bias output of the developing means 104 remains ON, but the charging means 103 is turned on. The high-voltage power supply output of is kept off until the recovery operation mode which is the rotation operation mode is completed. In this state, the photosensitive drum 102 starts rotating as a recovery operation.

However, during the image formation, the door opening / closing switch 20
If 3 turns off and then turns on within a short time,
As shown in the time charts on the right side of (d) and (e), when the developing bias remains OFF and the charging potential on the surface of the photosensitive drum 102 is not fully attenuated and remains, the carrier adheres to the photosensitive drum 102. Then, there is a problem that image defects are likely to occur.

The present invention has been made in view of the above problems, and an object of the first invention is to prevent damage caused by adhesion of a carrier to a photosensitive drum even when a door opening / closing switch or a main switch is turned off during image formation. An object of the present invention is to provide an image forming apparatus that is free from image loss and the like.

An object of the second invention is to provide an image forming apparatus which is free from image loss due to damage caused by carrier adhesion to the photosensitive drum even when the door opening / closing switch and the main switch are turned on immediately after they are turned off. To provide.

[0014]

The above-mentioned object of the first invention can be achieved by the following means.

(1) Image carrier, charging means for applying a surface potential to the image carrier, exposing means for exposing the charged surface of the image carrier to form a latent image, and an image forming process. Developing means for developing the latent image with the developer carried on the developer carrying member and downstream of the charging means, transfer means for transferring the toner image developed with the developer onto transfer paper, and the transferred toner image In an image forming apparatus having a fixing unit for heating and fixing the image carrier, and a control unit, a discharging unit for discharging the surface potential of the image carrier to which a surface potential is applied is provided with the charging unit position and the developing unit around the image carrier. The image is characterized in that it is arranged between the means positions, and the control means operates the static elimination means based on at least the input voltage drop information of the power source driving the high voltage substrate supplied to the charging means and the developing means. Forming equipment .

The above object of the second invention can be achieved by the following means. (2) Image carrier, charging means for applying a surface potential to the image carrier, exposing means for exposing the charged surface of the image carrier to form a latent image, and the charging in the image forming process. Developing means for developing the latent image with the developer carried on the developer carrying member, the transfer means for transferring the toner image developed with the developer onto the transfer paper, and the heat-fixing of the transferred toner image. In the image forming apparatus having the fixing unit and the control unit, a discharging unit for discharging the surface potential of the image carrier to which a surface potential is applied is provided at the charging unit position and the developing unit position around the image carrier. The control means is provided between the charging means and the developing means, and based on the input voltage rise information of the power source for driving the high-voltage substrate, the static elimination is performed at the same time as or before the operation of the image carrier. Start operation of means Controlled so as to, after that, the image forming apparatus and controls to stop the operation of the high voltage power supply output ON simultaneously or said discharging means before ON of the charging means and the developing means in the recovery operation mode.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A schematic structure of an image forming apparatus of an embodiment including the first invention and the second invention will be described. Figure 1
FIG. 1 is a sectional view showing a schematic configuration of an image forming apparatus of an embodiment.

As shown in FIG. 1, the image forming apparatus 100.
Is a photoconductor drum (also referred to as an image carrier) 102, a charging unit 103 that applies a surface potential to the photoconductor drum, and an exposure unit 109 that exposes the charged surface of the photoconductor drum to form a latent image. A discharging unit 108A for discharging the surface potential of the photosensitive drum 102, a developing unit 104 for developing a latent image formed downstream of the charging unit 103 in the image forming process with a developer carried on a developer carrier, and a developer. The transfer means 105 transfers the toner image developed in 1. onto the transfer paper P, the fixing means 180 heat-fixes the transferred toner image, and the control means 200.

On the upper part of the image forming apparatus 100, a document placing plate 101 on which a document G is placed is provided. The original G is a mirror 11 that moves integrally with the exposure lamp 110.
1 and V that moves half the movement distance of this mirror 111
Mirrors 112 and 113 formed in a mold, and an imaging lens 1
14 and CCD 115.

A charging means 103, a discharging means 108A, a developing means 104, a transferring means 105, a separating means 106, a cleaning device 107 and the like are arranged in the order of operation on the outer periphery of the photosensitive drum 102.

Digital image data read by the CCD 115 is superimposed on laser light emitted from a laser (not shown) and scanned by the polygon mirror 116. The scanned laser light is reflected by the mirrors 117 and 118, and the fθ lens 119 and the cylindrical lens 12 are reflected.
0, the charging means 103 on the photosensitive layer surface via the mirror 121.
The photosensitive drum 102 to which the electric charge has been applied is exposed to form an electrostatic latent image.

In the charge eliminating means 108A, the photosensitive drum 102 is
The surface potential of is removed. The developing unit 104 develops the electrostatic latent image to form a visible image as a toner image on the photosensitive layer surface of the photosensitive drum 102. Further, the control means 200 controls the static elimination means and the like, which will be described in detail later.

A paper feed unit 130 for double-sided copying and paper feed units 140, 150 and 160 are arranged vertically below the image forming apparatus 100, and the paper feed units 140, 150 and 160 are arranged in the paper feed units 140, 150 and 160. Usually, transfer sheets P as recording media of different sizes are stored. For example, when the transfer paper P stored in the paper feed unit 140 is selected, only one transfer paper P is fed by the paper feed roller 141, and this transfer paper P is transported by the transport roller 142.

Similarly, the paper feeding unit 150 or 16
When the transfer paper P stored in 0 is selected, only one transfer paper P is fed by the paper feed rollers 151 or 161, and the transfer paper P is transported by the transport rollers 152 or 162.

Then, the transfer paper P is conveyed along the conveying path 170 toward the photosensitive drum 102 on which the toner image is formed. Then, the transfer sheet P is temporarily stopped by the pair of registration rollers 172, and the transfer sheet P is fed so that the toner image formed on the photosensitive drum 102 and the transfer sheet P coincide with each other.

Next, the toner image on the photosensitive drum 102 is transferred onto the transfer paper P by the transfer means 105, and the transfer paper P is separated from the surface of the photosensitive drum 102 by the separating means 106. Then, the transfer paper P is transported by the transport device 173 to the fixing device 180 which is a fixing unit.

The fixing device 180 includes a heating roller 181 and a pressure roller 182, and the toner image on the transfer sheet P is stably fixed on the transfer sheet P by the heating roller 181 and the pressure roller 182. . Transfer paper P that has been fixed
Is discharged by the paper discharge guide roller 174. In the case of single-sided copying, the paper discharge switching member 175 moves down and the transfer paper P is discharged to the paper discharge tray 176 as it is.

In the case of double-sided copying, the sheet discharge switching member 175 is raised, the transfer sheet guide portion 177 is opened, and the transfer sheet P is conveyed downward. Furthermore, the transfer paper P
Is conveyed downward and switched back by the transfer paper reversing unit 179, and the rear end of the transfer paper P becomes the front end and is conveyed into the double-sided copying paper feeding unit 130.

The transfer paper P is a double-sided copy paper feeding unit 130.
The transfer belt 131 provided in the above position moves in the paper feed direction, the paper feed roller 132 re-feeds the transfer paper P, and the transfer paper P is guided to the transport path 170. Again, as described above, the transfer paper P is conveyed in the direction of the photosensitive drum 102, the toner image is transferred to the back surface of the transfer paper P, the fixing device 180 fixes the toner image, and the paper is discharged to the paper discharge tray 176.

Next, the structure of the essential parts of the present invention will be described. FIG. 2 is a diagram showing a configuration of a main part of FIG. As shown in FIG. 2, the charge removing unit 108A is an LED light emitting element, and removes charge from the charged photosensitive drum 102. The charge removing unit 108A is the charging unit 10 around the photosensitive drum 102.
It is arranged between the position 3 and the position of the developing means 104. In this embodiment, an example in which it is arranged near the developing means 104 is shown.

The main switch 201 is a switch provided upstream of the DC power source 202 of the image forming apparatus, the DC power source 202 is a power source for supplying power to the high voltage power source 204, and 203 is a door opening / closing switch. Reference numeral 205 denotes a voltage drop detection circuit that detects a voltage drop when the door opening / closing switch is turned off. The high voltage power source 204 is the developing means 10.
4, charging means 103, transfer means 105 and separation means 1
It is a power supply that supplies high voltage to 06. Further, M is a motor for driving the photosensitive drum 102.

The control means 200 controls the charge removing means 108A to operate based on the input voltage drop information of the power source of the high voltage substrate supplied to the charging means 103 and the developing means 104.

Further, the control means 200 controls the surface potential of the photosensitive drum 102 at the developing means position G (FIG. 2) after the developing bias is turned off so that the surface of the photosensitive drum 102 is eliminated by the electricity removing means 108A.

Next, FIG. 3 is a diagram showing a time chart of the main part of FIG. 3A is a time chart of the door opening / closing switch, FIG. 3B is a time chart of the charging output signal, FIG. 3C is a time chart of the static elimination output signal, and FIG.
(D) is a time chart of rotation of the photosensitive drum, FIG.
3E is a time chart of charging the photosensitive drum at the developing unit position G, and FIG. 3F is a time chart of the developing bias output signal. The left side of the figure is the door open / close switch O
The case of turning off from N is shown, and the right side of the figure shows the case of turning on immediately after the door opening / closing switch is turned off.

Now, the charge eliminating means for eliminating the charge on the photosensitive drum will be described. FIG. 4 is a sectional view showing the structure of the charge eliminating means.

The static eliminating means 108A shown in FIG.
The charge is removed by the light emitted from the ED light emitting element.
The static eliminator 108B shown in (b) is static eliminator by a static eliminator brush which can be pressure-bonded and released by an example of mechanical grounding.
Further, the charge eliminating means 108C shown in FIG. 4C uses irradiation of a semiconductor laser. The surface potential of the photosensitive drum may be removed by irradiation with the exposure laser used in the exposure unit.

Here, the prevention of carrier adhesion to the photosensitive drum when the door opening / closing switch 203 is turned off during image formation of the image forming apparatus will be described.

During the image formation, the door opening / closing switch 203 is turned off.
When the power is turned off, the power-down detection circuit 205 detects the off state and sends it to the control means 200. Here, under the control of the control unit 200, the outputs of the high voltage power source 204 of the charging unit 103 and the developing unit 104 are turned off. At the same time, the power of the motor M supplying the photosensitive drum 102 is also turned off,
Although the driving of the motor M is stopped, the photosensitive drum 102 continues to rotate for a while due to inertia.

After the output of the developing bias in the developing means 104 is turned off, the surface potential of the photosensitive drum 102 at the developing means position G is removed by the operation of the removing means 108A, and the developing means 104 is also operated by the high voltage power source. Since it is off, carrier adhesion to the photosensitive drum 102 is prevented.

In this embodiment, the discharging means 108A is arranged in the vicinity of the developing means 104 and substantially at the same position as the developing means 104, so that the output of the high voltage power source 204 is OF.
The static eliminator 108A is operated at the same timing as F.

Incidentally, the discharging means 108A is the developing means 104.
If it is not near, the destaticizing unit 108A is operated before the output of the high-voltage power source 204 is turned off, and the developing unit 10A is activated.
After the output of the developing bias in No. 4 is turned off, the surface potential of the photosensitive drum 102 at the developing unit position G is eliminated.

Next, the door opening / closing switch 20 of the image forming apparatus
The prevention of carrier adhesion and the like when 3 is turned off and then immediately turned on will be described.

The door opening / closing switch 203 is turned off during image formation.
When F is turned on and immediately turned on, the photoconductor drum 102 enters the recovery operation mode, and the photoconductor drum 102 starts rotating immediately after inertial rotation. However, the charging means and the developing means do not work until the rotation of the photosensitive drum 102 is stabilized. The charge removing unit 108A is the photosensitive drum 102.
At the same time as or before the operation of, the operation of the charge eliminating unit 108A is started, and the surface potential remaining on the surface of the photoconductor drum 102 that has not completely disappeared is eliminated on the surface of the photoconductor drum 102 at the developing unit position G. Therefore, the carrier is prevented from adhering to the photosensitive drum 102.

After that, the operation of the discharging means 108A is stopped at the same time as or before the high voltage power output of the charging means 103 and the developing means 104 is turned on in the recovery operation mode.

Although the decharging means has been described as being arranged near the developing means position around the photosensitive drum, it can be arranged between the charging means position and the developing means position around the photosensitive drum.

In the embodiment, the door opening / closing switch 203 interlocking with the opening / closing door formed in the image forming apparatus is used as the input voltage drop or rise information of the power source for driving the high voltage substrate supplied to the charging means 103 and the developing means 104. Although described, the same is true even if the main switch 201 of the apparatus main body or the power supply / external power supplied from the outside to the image forming apparatus is detected.

As described above, even if the door opening / closing switch, the main switch, etc. are turned off, or even if the door opening / closing switch, the main switch, etc. are turned on immediately after turning off during image formation, the photosensitive drum is not turned on. Image defects due to carrier adhesion are eliminated.

In the embodiment, the example of the image bearing member is the photoconductor drum 102, but the same applies to the photoconductor belt.

In the above embodiment, the image forming apparatus of the embodiment including the first invention and the second invention has been described, but the image forming apparatus of only the portion related to the first invention, and
It goes without saying that the image forming apparatus may be only the portion related to the second invention.

[0050]

The above-mentioned structure has the following effects.

According to the first aspect of the present invention, the discharging means for discharging the surface potential of the photosensitive drum to which the surface potential is applied is disposed between the charging means position and the developing means position around the photosensitive drum. Since the control unit operates the charge eliminating unit based on at least the input voltage drop information of the power source of the high voltage substrate supplied to the charging unit and the developing unit, even if the door opening / closing switch or the main switch is turned off during image formation, Image defects due to carrier attachment to the body drum are eliminated. It should be noted that toner is prevented from adhering to the photosensitive drum, and a high-quality image without toner fogging can be obtained.

According to the fourth aspect of the invention, the discharging means for discharging the surface potential of the photosensitive drum to which the surface potential is applied is disposed between the charging means position and the developing means position around the photosensitive drum. The control means controls to start the operation of the static eliminator before or at the same time as the operation of the photosensitive drum based on at least the input voltage increase information of the power source of the high voltage substrate supplied to the charging means and the developing means, and then the recovery operation. Before the high voltage power output of the charging means and the developing means in the recovery operation is turned on, or at the same time, the operation of the charge removing means is controlled to be stopped. Therefore, it is turned on immediately after the door opening / closing switch and the main switch are turned off during image formation. Even in this case, the image defect caused by the carrier adhesion to the photosensitive drum is eliminated. It should be noted that toner is prevented from adhering to the photosensitive drum, and a high-quality image without toner fogging can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to an embodiment.

FIG. 2 is a cross-sectional view showing a main configuration of FIG.

FIG. 3 is a diagram showing a time chart of the main part of FIG.

FIG. 4 is a cross-sectional view showing a configuration of a charge eliminating unit.

FIG. 5 is a diagram showing a part of a configuration of a conventional image forming apparatus.

6 is a diagram showing a main part time chart of FIG. 5;

[Explanation of symbols]

102 image carrier (photosensitive drum) 103 charging means 104 developing means 108A, 108B, 108C static eliminator 200 control means 201 Main switch 203 Door open / close switch P transfer paper G Developing position

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tokio Shiroichi             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company (72) Inventor Nori Sasamoto             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company (72) Inventor Yoshiteru Katayama             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             In the company F term (reference) 2H027 DA03 DA26 DE07 ED09 ED26                       EE06                 2H035 AA09 AA14 AB06 AC03 AZ01

Claims (8)

[Claims] 1. An image carrier, a charging unit for applying a surface potential to the image carrier, an exposing unit for exposing the surface of the image carrier after being charged to form a latent image, and an image forming process. A developing unit that is formed downstream of the charging unit and develops the latent image with a developer carried on a developer carrier, a transfer unit that transfers the toner image developed with the developer onto a transfer paper, and a transferred toner image. In an image forming apparatus having a fixing unit for heating and fixing and a control unit, a discharging unit for discharging the surface potential of the image carrier to which a surface potential is applied is provided with the charging unit position around the image carrier and the developing unit. The image forming device is arranged between the positions, and the control unit operates the charge eliminating unit based on at least input voltage drop information of a power source that drives a high-voltage substrate supplied to the charging unit and the developing unit. apparatus. 2. The image according to claim 1, wherein after the development bias output is turned off in the developing means, the surface potential of the image carrier at the developing means position is eliminated by the operation of the electricity eliminating means. Forming equipment. 3. The charge eliminating means is based on at least input voltage rise information of a power source for driving a high voltage substrate supplied to the charging means and the developing means, at the same time as or before the operation of the image carrier. To start the operation of the charging means and the developing means in the recovery operation mode at the same time as or at the time of turning on the high voltage power output of the developing means.
The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled so as to stop the operation of the charge removing unit. 4. An image carrier, a charging means for applying a surface potential to the image carrier, an exposing means for exposing the surface of the image carrier after being charged to form a latent image, and an image forming process. A developing unit that is formed downstream of the charging unit and develops the latent image with a developer carried on a developer carrier, a transfer unit that transfers the toner image developed with the developer onto a transfer paper, and a transferred toner image. In an image forming apparatus having a fixing unit for heating and fixing and a control unit, a discharging unit for discharging the surface potential of the image carrier to which a surface potential is applied is provided with the charging unit position around the image carrier and the developing unit. The control means is disposed between the positions, and at least simultaneously with or before the operation of the image carrier, based on the input voltage rise information of the power source for driving the high voltage substrate supplied to the charging means and the developing means. Operation of the static elimination means Image formation, characterized in that it is controlled so as to start, and thereafter, the operation of the static elimination means is stopped at the same time as or before the high voltage power output of the charging means and the developing means is turned on in the recovery operation mode. apparatus. 5. The image forming apparatus according to claim 1, wherein the charge removing unit is arranged in the vicinity of the developing unit position around the image carrier. 6. A door opening / closing switch which is interlocked with an opening / closing door formed in the image forming apparatus is turned on / off, at least when the input voltage drop or rise information of a power source for driving a high voltage substrate supplied to the charging means and the developing means is used. It is detected by ON / OFF of a main switch of the apparatus main body, a drop signal of a voltage drop detection circuit of a power supply line, or a power failure / energization of electric power externally supplied to the image forming apparatus. Item 6. The image forming apparatus according to any one of items 1 to 5. 7. The static elimination means irradiates a semiconductor laser, and an irradiation laser used as an exposure means in combination,
7. The image forming apparatus according to claim 1, wherein the surface potential of the image carrier is removed by light emission of an LED light emitting element or mechanical grounding. 8. The image forming apparatus according to claim 1, wherein the image carrier is a photoconductor drum or a photoconductor belt.