JPH07271116A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the contamination of a transfer roller from occurring and to obtain a stable high-quality image over a long term by controlling developing bias in accordance with a toner amount adhering to a non-image part area on an image carrier after development and making the toner amount adhering to the non-image part area equal to or under a specified amount. CONSTITUTION:The density of the non-image part area on the surface of a photoreceptor 1 is detected by a reflection type density sensor 20, and a detection signal voltage (Vsg) is obtained. Then, whether or not the Vsg is a proper value is judged. The toner adhering amount causing a failure when the toner adhering to the non-image part area on the surface of the photoreceptor 1 adheres to the transfer roller 8 is >=0.012mg/cm<2>, and the Vsg in such a case is smaller than 3.5V. Therefore, in the case of the Vsg is <=3.5V, the toner amount adhering to the non-image part area is equal to or above the specified amount, so that the absolute value of the developing bias is increased to a negative side by a specified value in order to decrease the toner adhering amount to the area.

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 such as an optical printer such as a laser printer using an electrophotographic process, a copying machine, and a facsimile machine.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a laser printer, the surface of a drum-shaped or belt-shaped image bearing member is charged by a charger and then exposed by an exposure device to form an electrostatic latent image. Is formed, and the latent image is visualized by the developer from the developing device, then transferred onto the transfer material from the paper feeding device using the transfer device, and fixed by the fixing device.

In recent years, in such an image forming apparatus, a transfer device employing a transfer roller has been used for the purpose of ozoneless. In a transfer device employing a transfer roller, a transfer material is conveyed between an image carrier carrying a developed image and a transfer roller pressed against the image carrier.
At this time, a voltage having a polarity opposite to the polarity of the developer on the image carrier is applied to the transfer roller, so that the transfer material receives the developed image from the image carrier. Therefore, the charge is applied to the transfer material in a state where the transfer roller is in contact with the transfer material, and the amount of ozone generated is much smaller than that in the transfer apparatus employing the conventional corona discharge device.

In the conventional transfer device using the transfer roller as described above, the transfer roller is always in contact with the surface of the image carrier at a predetermined pressure.

[0005]

However, such a transfer roller has a transfer roller at the start and end of image formation, and also during non-transfer such as between transfer materials during continuous image formation. Since the toner is in direct contact with the image carrier, the toner adhering to the non-image area, which is an area other than the latent image forming area on the surface of the photoconductor, is transferred to the transfer roller. Needless to say, such toner adhering to the transfer roller is very small, but over time it becomes non-negligible contamination, and the toner adhering to the transfer roller stains the back side of the transfer material, or the transfer roller becomes dirty. It may change the transfer characteristics between the laser and the photoconductor. Therefore, a good transferred image cannot be obtained.

In order to prevent the developer in the non-image area on the image carrier from adhering to the transfer roller at times other than the above-mentioned transfer, the transfer roller has conventionally carried the image carrier only during transfer. Although it is configured to press against the body, a dedicated contacting / separating mechanism therefor is required, which is not preferable in terms of cost and space.

The present invention has been made in view of the above points, and prevents toner stains on the non-image area on the image carrier during development, thereby preventing contamination of the transfer roller. Therefore, an object of the present invention is to provide an image forming apparatus capable of obtaining a stable high-quality image for a long period of time.

[0008]

In order to achieve the above object, the present invention has an image carrier, a latent image forming means for forming a latent image on the image carrier, and a latent image formed on the image carrier. An image forming apparatus comprising: a developing unit that develops an image; and a transfer roller that presses the image carrier and electrostatically transfers the developed image formed on the image carrier to a transfer material. An image forming apparatus having density detecting means for detecting the density of the surface of the carrier and developing bias control means for controlling the developing bias in accordance with the density of the non-image area of the surface of the image carrier detected by the density detecting means. provide.

To achieve the above object, the present invention develops an image carrier, a latent image forming means for forming a latent image on the image carrier, and a latent image formed on the image carrier. An image forming apparatus comprising: a developing unit; and a transfer roller that presses the image carrier and electrostatically transfers a developed image formed on the image carrier to a transfer material. Lubricant applying means for applying a lubricant, density detecting means for detecting the density of the surface of the image carrier, and the lubricant according to the density of the non-image area on the surface of the image carrier detected by the density detecting means. An image forming apparatus having a lubricant application control means for controlling the operation of the application means.

[0010]

According to the present invention, the developing bias is controlled according to the toner amount adhered to the non-image area on the image carrier after development, and the toner amount adhered to the non-image area is always regulated. Since the amount is less than or equal to the amount, contamination of the transfer roller is prevented in advance.

Further, according to the present invention, the amount of lubricant applied to the surface of the image carrier is controlled according to the amount of toner adhering to the non-image area on the image carrier after development, and the non-image described above is controlled. Since the amount of toner attached to the partial area is always less than the specified amount, contamination of the transfer roller is prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is a block diagram of the essential parts showing a first embodiment of the image forming apparatus of the present invention.

In FIG. 1, at the time of image formation, the photosensitive member 1, which is an image carrier, rotates in the direction of the arrow in the figure, and the surface of the photosensitive member 1 is
First, it is charged to a potential of about -800 V by the action of the charging roller 2 which is in pressure contact with the surface of the charging device. next,
The surface of the photoconductor 1 is irradiated with light corresponding to an image by exposure light 3 from an exposure device (not shown), and the surface thereof has an image portion potential Vd of about −800 V and a background portion potential Vl of about −100.
An electrostatic latent image of V is formed. Further, the non-image area, which is an area other than the latent image forming area on the surface of the photoconductor 1, is set to about −100V as in the background area.

Then, the photosensitive member 1 further rotates, and the electrostatic latent image has a developing bias Vb of about -300 in the developing sleeve.
Under the action of the developing device 4 to which V is applied, it is developed with a positively charged developer. That is, the positively charged developer is attracted by the potential difference of Vb-Vd in the image portion, and receives the repulsive force due to the potential difference of Vb-Vl in the background portion and the non-image portion area. Next, the surface of the photoconductor 1 is irradiated with the entire surface of the developed image formed thereon by the pre-transfer charge eliminating lamp 5 to reduce the latent image potential of the image portion.

In this way, the developed image subjected to the action of the pre-transfer charge eliminating lamp 5 reaches the pressure contact portion between the transfer roller 8 composed of an elastic body and the photosensitive body 1 by further rotation of the photosensitive body 1. At this time, the transfer paper 7, which is a transfer material, is conveyed by the registration roller 6 between the photoconductor 1 and the transfer roller 8 at the same timing as the developed image on the photoconductor 1, and the transfer roller 8 is transferred.
The transfer paper 7 receives the transfer of the developed image from the photosensitive member 1 by the voltage having the polarity opposite to the polarity of the developer on the photosensitive member 1 applied to the transfer paper 7. The transfer paper 7 which has received the action of the transfer roller 2 is brought into close contact with the photoconductor 1 by an electrostatic force, so that the charge removing needle 9 as a charge removing means removes the charges on the transfer paper 7.

The transfer paper 7 from which the charge has been removed is separated from the photoconductor 1, guided by the carrying guide 10 and carried to the fixing device 11, and the transferred image on the transfer material 7 is fixed to the fixing device 11.
The fixed image is formed by the action of. On the other hand, although there is an untransferred toner that has not been transferred on the surface of the photoconductor 1 that has been acted by the transfer roller 8, the photoconductor 1 is further rotated to clear.
This untransferred toner is affected by the operation of the steering device 12.
Are removed.

In this embodiment, an organic photoconductor is used as the photoconductor 1. Further, the developing device 4 is a two-component magnetic brush developing device which holds a two-component developer consisting of a positively charged toner and a carrier in a brush shape on the developing sleeve by a magnetic force and performs the development. The development system shall be used.

In this embodiment, the density of the non-image area on the surface of the photoconductor 1 which has been developed is measured by the reflection type density sensor 2.
Optically detected by 0. This reflection type density sensor 20
Is a pattern which is conventionally provided for the purpose of controlling the toner density of a two-component developing device and is formed on the photoconductor under a certain condition.
Similar to the one that detects the density of the image, the light is emitted from the light emitting element toward the surface of the photoconductor, and the reflected light is received by the light receiving element. Is measured. The output of the reflection type density sensor 20 in this embodiment is 4V when there is no toner on the surface of the photosensitive member and the amount of reflected light from the surface of the photosensitive member is large, and when the amount of reflected light is large on the surface of the photosensitive member and the amount of reflected light is small. Is set to 0V. Further, as the reflection type density sensor 20 in this embodiment, the reflection type density sensor 20 provided for the purpose of controlling the toner density of the two-component developing device as described above may be commonly used.

Next, the control procedure of this embodiment will be described with reference to FIG. First, the density of the non-image area on the surface of the photoconductor 1 is detected by the reflective density sensor 20 to detect the detection signal voltage Vsg.
To get Next, it is determined whether Vsg is an appropriate value. That is, since the detection target is the non-image area and only a very small amount of toner is present in the area, Vsg is usually 2.5.
It does not fall below V. Therefore, when Vsg is 2.5 V or less, it is considered that there is some abnormality and this is displayed, and the operation of the image forming apparatus is stopped.

Next, when Vsg is larger than 2.5 V, Vsg is compared with a preset comparison signal voltage Vr. Here, FIG. 3 shows the relationship between the toner adhesion amount on the surface of the photoconductor 1 and the detection signal voltage when the density of the non-image area of the photoconductor 1 is detected. In the image forming apparatus of this embodiment, the toner adhering to the non-image area of the surface of the photoconductor 1 adheres to the transfer roller 8 to cause a trouble. The toner adhering amount is 0.012 mg / cm. ² or more, and the detection signal voltage in this case is smaller than 3.5V. Therefore, in this embodiment, Vr = 3.5 is set, and when Vsg is larger than this, the toner adhering to the non-image area is below the specified amount, and the control ends. On the other hand, Vsg is 3.5
If it is V or less, the toner amount adhering to the non-image area is equal to or larger than the specified amount, so that the developing bias Vb is set to the negative side in order to reduce the toner adhering amount to the area. Is increased by a predetermined value.

That is, as described above, in the non-image area, the toner receives a repulsive force due to the potential difference of Vb-Vl. Therefore, the repulsive force is increased by increasing Vb to the minus side, and thereby the repulsive force is increased. The amount of toner attached to the non-image area on the surface of the photoconductor 1 is reduced. In this way, such control is repeated, and the control ends when the detection signal voltage Vsg becomes equal to or lower than the comparison signal voltage Vr.

Here, since the toner adhesion amount to the non-image area on the surface of the photosensitive member 1 gradually changes depending on the use environment and the use condition, it is not necessary to perform the above control for each image formation. The control may be performed when the power is turned on or every predetermined number of sheets. Further, since the above-mentioned control is performed between transfer materials for image formation, problems such as a decrease in image forming speed do not occur.

Next, a second embodiment of the present invention will be described with reference to FIG. In the figure, the components denoted by the same reference numerals are the same as those in FIG.

In the second embodiment, as shown in FIG. 4, a solidified zinc stearate 13 is provided inside the cleaning device 12. And the application brush 1
4 is arranged to rub the zinc stearate 13 and the photoconductor 1 as well. Therefore, the application brush 1
When 4 rotates in the direction of the arrow in the figure, the untransferred toner on the photoconductor 1 is removed, and zinc stearate 13 is rubbed and polished and supplied to the surface of the photoconductor 1 little by little. The rotation direction of the coating brush 14 may be opposite to the arrow direction in the figure.

Then, the fine powder of zinc stearate 13 supplied onto the photoconductor 1 spreads thinly on the surface of the photoconductor 1 by being rubbed with the cleaning blade 15 to reduce the surface energy. When the surface energy-reduced portion reaches the developing portion where the developing device 4 acts, the toner is easily separated from the photoconductor 1, so that the non-image portion area is formed at the same time when the image portion is developed. The attached unnecessary toner is scraped off by being rubbed by the magnetic brush of the developing device 4. Therefore, unnecessary toner adhering to the non-image area of the photoconductor 1 is reduced, and the transfer roller 8
The pollution of can be prevented.

However, since the fine powder of zinc stearate 13 supplied onto the photosensitive member 1 has the above-mentioned effect, the developing efficiency is lowered when it is supplied in excess. Therefore, in this embodiment, the coating brush 14 is operated for a predetermined time only when the amount of toner attached to the non-image area of the photoconductor 1 becomes equal to or more than the specified amount.

Next, the control procedure of this embodiment will be described with reference to FIG. First, the density of the non-image area on the surface of the photoconductor 1 is detected by the reflective density sensor 20 to detect the detection signal voltage Vsg.
To get Next, it is determined whether Vsg is an appropriate value. Similar to the first embodiment, when Vsg is 2.5 V or less, it is considered that there is some abnormality and this is displayed, and the operation of the image forming apparatus is stopped.

Next, when Vsg is larger than 2.5 V, Vsg is compared with a preset comparison signal voltage Vr. Also in this embodiment, Vr = 3.5 is set, and when Vsg is larger than this, the toner adhering to the non-image area is below the specified amount, and the control is ended. on the other hand,
When Vsg is 3.5 V or less, the amount of toner adhering to the non-image area is equal to or more than the specified amount, so the application brush 14 is operated for a predetermined time. Thus, this control is repeated, and the detection signal voltage Vsg becomes equal to the comparison signal voltage Vr.
The control ends when the following occurs.

In this embodiment, zinc stearate was used as the lubricant to be applied to the photoconductor 1, but in addition, barium stearate, lead stearate, iron stearate, nickel stearate, cobalt stearate, Copper stearate, strontium stearate, calcium stearate, cadmium stearate, magnesium stearate, zinc oleate, manganese oleate, iron oleate, cobalt oleate, lead oleate, magnesium oleate, copper oleate, zinc oleate , Cobalt palmitate, copper palmitate, magnesium palmitate, aluminum palmitate, calcium palmitate, lead caprylate, lead caproate,
Metal salts of fatty acids such as zinc linolenate, cobalt linolenate, calcium linolenate, zinc ricolinolenate and cadmium licolinolenate, relatively higher fatty acids such as stearic acid and palmitic acid, commercially available from Kapot Corporation. Colloidal high-salt silica powder such as existing Cab-O-Sil powder can be used as a lubricant.

[0030]

As described above, according to the present invention, the developing bias is controlled in accordance with the toner amount adhered to the non-image area on the image bearing member after development, so that the non-image area is controlled. Since the amount of toner that adheres is always below the specified amount,
It is possible to prevent contamination of the transfer roller. Therefore, it is possible to prevent back stains on the transfer material and fluctuations in transfer characteristics.
A stable high-quality image can be obtained for a long period of time.

According to the present invention, the amount of lubricant applied to the surface of the image bearing member is controlled according to the amount of toner attached to the non-image area on the image bearing member after development, and the above-mentioned non-image Since the toner amount adhering to the partial area is always less than the specified amount, it is possible to prevent the transfer roller from being contaminated.
Therefore, it is possible to prevent back stains on the transfer material and fluctuations in the transfer characteristics, and to obtain stable high-quality images for a long period of time.

[0032]

[Brief description of drawings]

FIG. 1 is a main part configuration diagram showing an embodiment of the present invention.

FIG. 2 is a main part configuration diagram showing an embodiment of the present invention.

FIG. 3 is a main part configuration diagram showing an embodiment of the present invention.

FIG. 4 is a main part configuration diagram showing an embodiment of the present invention.

FIG. 5 is a main part configuration diagram showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 3 Exposure light 4 Developing device 7 Transfer paper 8 Transfer roller 12 Cleaning device 13 Zinc stearate 14 Coating brush 15 Cleaning blade 20 Reflective density sensor

Claims (2)

[Claims] 1. An image carrier, a latent image forming means for forming a latent image on the image carrier, a developing means for developing the latent image formed on the image carrier, and a pressure contact with the image carrier. An image forming apparatus having a transfer roller for electrostatically transferring a developed image formed on the image carrier to a transfer material, a density detecting unit for detecting the density of the surface of the image carrier, An image forming apparatus comprising: a developing bias control unit that controls a developing bias in accordance with the density of a non-image area on the surface of an image carrier detected by the density detecting unit. 2. An image carrier, latent image forming means for forming a latent image on the image carrier, developing means for developing the latent image formed on the image carrier, and pressure contact with the image carrier. And a transfer roller for electrostatically transferring the developed image formed on the image carrier to a transfer material, in an image forming apparatus, a lubricant applying unit for applying a lubricant on the image carrier. A density detecting means for detecting the density of the surface of the image carrier, and a lubricant application for controlling the operation of the lubricant applying means according to the density of the non-image area of the surface of the image carrier detected by the density detecting means. An image forming apparatus having a control unit.