JP2002365858A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which prevents the occurrence of streaks on an image caused by the fusion of a developer regulating member, does not give rise to unevenness on the image and does not contaminate the rear surface of a recording material by preventing surface fogging of an image carrying member. SOLUTION: This image forming device has developing means for developing an electrostatic latent image in a contact segment between the developer carrying member and an image carrying member, developing bias impressing means for impressing a developing bias to the developer carrying means and blade bias impressing means for impressing a blade bias to the developer regulating means. The blade bias is impressed to the developer regulating means in the state that the absolute value of the difference between surface dark part potential of the image carrying member electrostatically charged by electrostatic charging means and the developing bias voltage impressed to the developer carrying member by the developing bias impressing means is maintained greater than that in the image forming or further the device has contact and separation means which is capable freely bringing into contact and separating the image carrying member with and from the developer carrying member and the blade bias is impressed to the developer regulating means by separating the image carrying member and the developer carrying member by the contact and separation means in non-image forming.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, and an image forming apparatus such as an electrostatic recording apparatus.

[0002]

2. Description of the Related Art As a conventional image forming apparatus, for example, there is an image forming apparatus using a non-magnetic one-component contact developing means as a developing means.

FIG. 1 schematically shows a sectional view of a main part of the image forming apparatus. The image forming apparatus includes a photosensitive drum 10 as an image carrier. Then, a predetermined charging bias is applied to a charging roller 11 which is a charging unit which rotates following the photosensitive drum 10 by a charging bias power supply device 24 which is a charging bias applying unit, and the surface of the photosensitive drum 10 is uniformly charged. You.

[0004] Next, an electrostatic latent image is formed on the surface of the photosensitive drum 10 by an exposure device 12 as exposure means. Then, the electrostatic latent image formed on the photosensitive drum 10 is developed by a developing device 13 as a developing unit, and is visualized as a developer image (toner image).

Here, the developing device 13 will be described.
In the developing device 13, a developer (toner) 21 is filled in the toner container 20. When the toner supply roller 18 and the developing roller 16 as a developer carrier come into contact with each other, the toner 21 is supplied onto the developing roller 16, and the toner 21 is optimally layered by the developing blade 17 as a developer regulating member. Is regulated and charged. Then, a developing bias is applied to the developing roller 16 by the developing bias power supply device 23 of the developing bias applying unit, and a developer image, that is, a toner image is formed on the photosensitive drum 10 at a contact portion between the developing roller 16 and the photosensitive drum 10. Done.

Then, a predetermined transfer bias is applied to the transfer roller 26 by a transfer bias power supply device (not shown), and the toner image formed on the photosensitive drum 10 is transferred onto a recording material P as a transfer material. , An unfixed image is formed. Then, the recording material P is conveyed to the fixing device 30 to fix the unfixed image on the recording material P, and is conveyed to the paper discharge tray 35, thereby completing the image formation.

Further, the photosensitive drum 10 is not transferred at the time of transfer.
The transfer residual toner remaining on the cleaning blade 14
Is collected in the waste toner container 15 and the photosensitive drum 10
The top is cleaned.

As described above, when an image is continuously output using the image forming apparatus, a streak is generated on the image, and the streak sometimes makes it difficult to view a halftone image.

When the cause of the occurrence of the streak is examined, an adhering substance is present on the developing blade 17 at a nip portion where the developing roller 16 and the developing blade 17 are in contact with each other. It was found that when the output was continued, the deposits were fused non-uniformly on the developing blade 17.

Investigation of the fused material on the developing blade 17 reveals that the external additive of the toner, such as silica, is mainly formed as a fused material.
This silica is negatively charged with respect to the toner matrix, the developing roller 16 and the developing blade 17, and during the image formation, the toner is negatively charged by the frictional charging of the developing roller 16 and the developing blade 17 with the toner. As a result, the developing blade 17 is positively charged. In particular, the developing blade 17
Is a metal or conductive material, the developing blade 1
Current flows from 7 to the developing roller 16. At that time, the negatively charged silica contained in the external additive of the toner is released from the toner, and the positive developing blade 17 is removed.
Then, it was found that the toner first moved to the side and adhered to the developing blade 17 at first, and eventually became a fusion of the developing blade and appeared as streaks on the image.

Therefore, in order to prevent the developing blade from fusing, the blade bias power supply device 22 of the blade bias applying means is set closer to the developing blade 17 than the developing bias applied to the developing roller 16 during image formation. There is a method of applying a bias (blade bias) having a high potential (absolute value) in the polarity direction.

[0012]

However, when a blade bias is applied during image formation, the charging of the toner between the developing roller 16 and the developing blade 17 becomes non-uniform, causing unevenness on the image. There was something.

If the blade bias is reduced in order to avoid unevenness on the image, the effect of the blade bias is weakened. As a result, fusion of the developing blade occurs or the blade bias is applied for a long time. As a result, fusion may occur on the developing roller 16 side.

Therefore, by applying a blade bias to the developing blade 17 at the timing between the sheets before the start of the image formation, after the end of the image formation, and after the end of the predetermined number of image formation, the fusion of the developing blade is prevented. However, in this case, while the blade bias is applied, the surface potential of the developing roller 16 momentarily becomes higher than usual due to the blade bias, and the photosensitive drum 10
Because the potential difference between the toner and the charged surface of the photosensitive drum 10 becomes small, the ground fogging phenomenon occurs, and the toner may be transferred onto the photosensitive drum 10 in some cases. Therefore, before the start of image formation, after the end of image formation, or between sheets, the toner is transferred onto the photosensitive drum 10, and the toner contaminates the transfer roller 26. The back surface of P was sometimes stained.

Accordingly, an object of the present invention is to prevent the occurrence of streaks on an image due to fusion of a developer regulating member,
An object of the present invention is to provide an image forming apparatus which does not cause unevenness on an image and prevents the background fogging phenomenon of the image bearing member and does not stain the back surface of the recording material.

[0016]

The above object is achieved by an image forming apparatus according to the present invention. In summary, a first aspect of the present invention provides an image carrier, a charging unit for charging a surface of the image carrier, a charging bias applying unit for applying a charging bias to the charging unit, and the charged image carrier. Exposure means for forming an electrostatic latent image corresponding to image data on the surface, a developer carrier for carrying the developer, and a developer regulating member for regulating the layer thickness of the developer on the developer carrier are included. Developing means for developing the electrostatic latent image at a contact portion between the developer carrier and the image carrier to form a developer image on the image carrier; and a developing bias applied to the developer carrier. And a blade bias applying unit for applying a blade bias to the developer regulating member, wherein the image carrier charged by the charging unit during non-image formation Surface dark area The blade bias is applied to the developer regulating member in a state where the absolute value of the difference between the developing bias voltage and the developing bias voltage applied to the developer carrier by the developing bias applying unit is larger than that during image formation. An image forming apparatus is provided.

According to a second aspect of the present invention, there is provided an image carrier, charging means for charging the surface of the image carrier, and exposure means for forming an electrostatic latent image corresponding to image data on the charged surface of the image carrier. And a developer carrying member that carries the developer and a developer regulating member that regulates the layer thickness of the developer on the developer carrying member are included, and a contact portion between the developer carrying member and the image carrying member is included. Developing means for developing the electrostatic latent image to form a developer image on the image carrier, developing bias applying means for applying a developing bias to the developer carrier, and a blade for the developer regulating member. And a blade bias applying unit for applying a bias. The image forming apparatus further includes a contact / separating unit configured to allow the image carrier and the developer carrier to be separated from and separated from each other, and the contact / separating unit during non-image formation. The image carrier and the developing By separating the carrier, to provide an image forming apparatus and applying the blade bias to the developer regulating member.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 An embodiment of the present invention will be described below with reference to FIG.

The overall configuration of the image forming apparatus of this embodiment is as described above. Next, each member of the image forming apparatus and further, a characteristic portion of the present invention will be described in detail.

In this embodiment, the photosensitive drum 10 as an image carrier has an organic photosensitive member (OPC) coated on the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm. CdS, Se or the like may be applied.
The photosensitive drum 10 rotating in the direction of arrow A by a driving unit (not shown) at a process speed of 100 mm / sec is driven by the charging roller 11 which is driven by the photosensitive drum 10 and rotates in the direction of arrow B. It is uniformly charged.

The charging roller 11 has a diameter of 12 mm, and has a multilayer structure in which a stainless steel cylindrical body as a metal core is provided with urethane rubber as a base layer and an elastic layer made of a fluororesin as a surface layer. Here, a metal such as aluminum or an aluminum alloy may be used as a material of the metal core, and NBR, EPD may be used as a base layer of the elastic layer.
A rubber material such as M or silicone rubber may be used, and ether urethane or nylon may be used as a surface layer of the elastic layer. The charging roller 11 is connected to a charging bias power supply 24 serving as a charging bias applying unit, so that a predetermined charging bias is applied.

Next, an electrostatic latent image is formed on the surface of the photosensitive drum 10 by an exposure device 12 as exposure means. According to the image signal color-separated into each color corresponding to the input signal,
A semiconductor laser (not shown) emits light, and the laser light is reflected by a polygon mirror (not shown) rotating at a high speed, and irradiates the photosensitive drum 10 through an imaging lens (not shown). The electrostatic latent image formed on the photosensitive drum 10 by the laser beam irradiation is developed by a developing device 13 as a developing unit, and is visualized as a developer image (toner image).

Here, the developing device 13 will be described.
In this embodiment, a non-magnetic one-component contact developing method is used as a developing method. In the toner container 20 of the developing device 13, a developer (toner) 21 which is a non-magnetic one-component toner is provided.
Is filled with 200 g. The developing device 13 is a contact-type developing device. When the toner supply roller 18 comes into contact with the developing roller 16 serving as a developer carrier, and toner adheres to the developing roller 16 from the toner supply roller 18, the developing roller 16 Top is supplied with toner. The toner supply roller 18 that rotates in the direction of arrow E (the direction in which the contact portion with the developing roller 16 moves in the opposite direction to the developing roller 16)
Has a diameter of 1 in which urethane foam is provided around a cylindrical body of a metal such as aluminum, an aluminum alloy, and stainless steel.
This is a 4 mm sponge roller.

The developing roller 16 is driven in a direction indicated by an arrow D (a rotation direction opposite to the rotation direction arrow A) by driving means (not shown).
The developing roller 16 was rotated at a surface speed of 70 mm / sec. The developing roller 16 had a diameter of 14 mm. A urethane rubber was provided as a base layer around a stainless steel cylinder, and a urethane rubber mixed with carbon was provided thereon as a surface layer. It was a multilayer structure, but not limited to this, aluminum, aluminum,
Using a metal cylinder such as aluminum alloy or stainless steel, the base layer of the elastic layer is made of rubber material such as NBR, EPDM, silicone rubber or urethane rubber, and the surface layer is made of ether urethane or nylon What was done can be used.

The toner on the developing roller 16 is regulated and charged to an optimum layer thickness by a developing blade 17 which is a developer regulating member. Developing blade 17 of this embodiment
Is a straight-shaped phosphor bronze plate having spring elasticity, but is not limited thereto. A stainless steel plate may be used as a material, and the shape may be an L-shape. Further, a predetermined blade bias is applied to the developing blade 17 at a predetermined timing by a blade bias power supply device 22 which is a blade bias applying unit.

When an image is formed, a developing bias of -400 V is applied to the developing roller 16 by a developing bias power supply device 23 which is a developing bias applying means. A toner image is formed on the drum 10.

The recording material P, which is a transfer material, is fed from the recording material cassette 40 in synchronization with the formation of the toner image on the photosensitive drum 10. A transfer roller 26 that rotates in the direction of arrow C (in the direction opposite to the rotation direction arrow A) facing the photosensitive drum 10 is installed, and a predetermined transfer bias is applied by a transfer bias power supply device (not shown). Then, the toner image is transferred from the photosensitive drum 10 to the recording material P, and an unfixed image is formed. Then, the recording material P is conveyed to the fixing device 30, where the unfixed image is fixed on the recording material P, and is conveyed to the paper discharge tray 35, thereby completing the image formation.

The untransferred toner remaining on the photosensitive drum 10 without being transferred during the transfer step is collected by a cleaning blade 14 into a waste toner container 15, the surface of the photosensitive drum 10 is cleaned, and the above-described image formation is repeated again. .

The operation of the image forming apparatus of this embodiment before the start of image formation, after the end of image formation, and between sheets will be described in detail with reference to FIG.

(1) First, before the start of image formation, a charging bias of -1200 V is applied by the charging bias power supply 24 simultaneously with the rotation of the photosensitive drum 10.
At the same time, the developing roller 16 is rotated, and at the same time, in order to prevent ground fogging occurring at the start of rotation of the photosensitive drum 10, the developing bias power supply device 23
A reverse bias of V is applied.

(2) Then, the developing bias of -300 V is applied to the developing roller 16 at the same time when the charged portion on the photosensitive drum 10 reaches the nip portion of the developing roller 16.

(3) Then, the blade bias power supply 22
As a result, a blade bias of -800 V is applied to the developing blade 17.

(4) After 3 seconds, the blade bias is set to -400 V, and at the same time, the developing bias is set to -40.
After the voltage is set to 0 V, image formation is started, and exposure is started by the exposure device 12.

(5) The latent image formation by exposure, toner image formation by development, paper feed, transfer, fixing, and paper discharge described above with reference to FIG. 1 are repeated to form a predetermined number of transfer materials. Do it for

(6) In this embodiment, a blade bias is applied every 30 sheets between sheets during continuous printing.
When continuously printing 30 or more transfer materials, the exposure device 12 is set to $ FF at the end of image formation on the 30th sheet, and after image formation, the developing bias is changed from -400 V to -300 V, and the blade bias is changed from -400 V to -400 V. Set to 800V.

(7) After 3 seconds, the developing bias is
The blade bias is returned from −800 V to −400 V at the same time as the return from 300 V to −400 V, and then the image forming of the 31st sheet is started, and the exposure device 12 is set to ΔN.

(8) After the completion of image formation, first, the exposure of the exposure device 12 is set to $ FF, and the blade bias is set to -40.
At the same time as changing from 0V to -800V, the developing bias is changed from -400V to -300V.

(9) After 3 seconds, the rotation of the photosensitive drum 10 is stopped, and at the same time, the rotation of the developing roller 16 is stopped. At the same time, the application of the charging bias, the developing bias, and the blade bias is stopped.

Using the image forming apparatus shown in FIG. 1, a sample image with an image ratio of 5% is used and the above (1) to (9)
When the durability test was carried out by the operation of the above, the durability test was performed until the toner disappeared without any streak on the image on the transfer material, the back surface of the transfer material was not stained. .

As described above, by applying a blade bias to the developing blade before the start of image formation, after the end of image formation, and between sheets, generation of streaks on the image due to fusion of the developing blade is caused. Could be prevented.

Further, since no blade bias was applied during the exposure of the photosensitive drum, there was no unevenness on the image.

Further, simultaneously with the application of the blade bias,
By changing the developing bias so that the difference between the dark portion potential on the photosensitive drum and the developing bias becomes larger, the fog generated when the blade bias is applied does not cause ground fog on the photosensitive drum, so that the transfer roller is not stained. The back surface of the transfer material was not stained.

It is needless to say that the magnitude of various biases in the image forming step is not limited to this.

Embodiment 2 This embodiment is characterized in that the charging bias is changed simultaneously when the blade bias is applied. The configuration of the image forming apparatus according to the present embodiment is the same as that of the image forming apparatus according to the first embodiment described with reference to FIG. The operation between the back and the sheet interval will be described in detail with reference to FIG.

(1) First, before the start of image formation, a charging bias of -1300 V is applied by the charging bias power supply 24 at the same time as the rotation of the photosensitive drum 10 to set the surface potential on the photosensitive drum 10 to -800 V. Further, simultaneously with the rotation of the developing roller 16, the developing bias power supply 23
A reverse bias of +600 V is applied to prevent ground fogging that occurs at the start of rotation of the photosensitive drum 10.

(2) When the surface potential on the photosensitive drum 10 becomes -800 V reaches the nip where the photosensitive drum 10 and the developing roller 16 come into contact with each other, the developing roller 23 16 to -40
A developing bias of 0 V is applied, and at the same time, a blade bias of −800 V is applied to the developing blade 17 by the blade bias power supply 22.

(3) After 3 seconds, the charging bias is
The surface potential on the photosensitive drum 10 is lowered to -700 V from 1300 V to -1200 V.

(4) The portion where the surface potential on the photosensitive drum 10 is -700 V is the photosensitive drum 10 and the developing roller 1
At the same time as the contact nip portion with No. 6 is reached, the blade bias is changed from -800 V to -400 V, and then exposure of the exposure device 12 is started to start image formation.

(5) By repeating the image forming operations of forming a latent image by exposure, forming a toner image by development, feeding, transferring, fixing, and discharging as described above with reference to FIG. Do for

(6) In the present embodiment, a blade bias is applied every 30 sheets between sheets during continuous printing.
When 30 or more transfer materials are continuously printed, the exposure device 12 is set to $ FF at the end of image formation on the 30th sheet, the charging bias is changed from -1200 V to -1300 V after image formation, and the surface potential of the photosensitive drum 10 is changed. -800V.

(7) The portion where the surface potential on the photosensitive drum 10 is -800 V is the photosensitive drum 10 and the developing roller 1
The blade bias is increased from -400 V to -800 V at the same time as the contact nip portion of No. 6 is reached.

(8) After 3 seconds, the charging bias is
The surface potential on the photosensitive drum 10 is lowered to -700 V from 1300 V to -1200 V.

(9) The portion where the surface potential on the photosensitive drum 10 is -700 V is the photosensitive drum 10 and the developing roller 1
6 and at the same time when the blade bias is changed from -800 V to -400 V, the exposure apparatus 1
The image forming of the 31st sheet is started after the exposure of No. 2 is started.

(10) After the exposure of the exposure device 12 is completed,
After the image formation is completed, the charging bias is set to -1200V.
, And the surface potential of the photosensitive drum 10 is set to -800V.

(11) The blade bias is raised from -400V to -800V at the same time when the portion of the photosensitive drum 10 having a surface potential of -800V reaches the contact nip between the photosensitive drum 10 and the developing roller 16. .

(12) After three seconds, the photosensitive drum 10
At the same time, the rotation of the developing roller 16 is also stopped, and the application of the charging bias, the developing bias, and the blade bias is stopped.

Using the image forming apparatus shown in FIG. 1 and a sample image with an image ratio of 5%,
When the durability test was performed in the operation of (9), the durability test was performed until no streaks on the image were seen on the transfer material, the back surface of the transfer material was not stained, and the toner was exhausted. Was completed.

As described above, by applying a blade bias to the developing blade before the start of image formation, after the end of image formation, and between sheets, generation of streaks on an image due to fusion of the developing blade is caused. Could be prevented.

Further, since no blade bias was applied during image formation, there was no unevenness on the image.

In this embodiment, when the blade bias is applied, the charging bias is changed so that the difference between the dark portion potential on the photosensitive drum and the developing bias is increased at the same time. No fogging phenomenon occurs on the photosensitive drum, so that the transfer roller was not stained and the back surface of the transfer material was not stained.

As described above, in order to avoid the background fogging phenomenon of the photosensitive drum, there is a method of changing the charging bias as in the present embodiment other than the method of changing the developing bias as in the first embodiment.

It is needless to say that the magnitude of various biases in the image forming step is not limited to this.

Embodiment 3 This embodiment is characterized in that the photosensitive drum and the developing roller are separated from each other when the blade bias is applied.

The configuration of the image forming apparatus of the present embodiment is almost the same as that of the image forming apparatus of the first embodiment. Therefore, the description of the same configuration as that of the first embodiment will be omitted, and the configuration specific to the present embodiment will be omitted. explain.

FIG. 4 is a sectional view of the image forming apparatus according to the present embodiment. In this embodiment, the photosensitive drum 10 and the image forming apparatus shown in FIG. A contact separation unit (contact separation unit) 19 for separating the developing roller 16 is provided. In the present embodiment, the contact and separation device 19 is provided near the outside of the developing device 13,
For example, by moving the developing device 13 left and right in the direction of the arrow G which is a horizontal direction in FIG. 4, the photosensitive drum 10 and the developing roller 16 come into contact with or separate from each other.

The operation of the image forming apparatus of the present embodiment before the start of image formation, after the end of image formation, and between sheets will be described.
This will be described in detail with reference to FIG.

(1) First, before the start of image formation, the photosensitive drum 10 and the developing roller 16 are separated from the beginning. First, the developing roller 16 is rotated. Then, a blade bias of −400 V is applied to the developing blade 17 by the blade bias power supply 22.

(2) Then, after 3 seconds, a developing bias of -400 V is applied to the developing roller 16 by the developing bias power supply 23.

(3) At the same time, the photosensitive drum 10 is rotated, and a charging bias of -1200 V is applied by the charging bias power supply 24 to bring the surface potential on the photosensitive drum 10 to -700 V.

(4) Next, after the portion on the photosensitive drum 10 where the surface potential has become -700 V reaches the portion where the nip between the photosensitive drum 10 and the developing roller 16 is reached, the contact / separation device 19 exposes the photosensitive drum. The image forming is started by bringing the drum 10 into contact with the developing roller 16, and exposure is started by the exposure device 12.

(5) By repeating the image forming operations of forming a latent image by exposure, forming a toner image by development, feeding, transferring, fixing, and discharging as described above with reference to FIG. Do for

(6) In the present embodiment, a blade bias is applied every 30 sheets between sheets during continuous printing.
When continuously printing 30 or more transfer materials, the exposure device 12 is set to $ FF at the end of image formation on the 30th sheet, and after image formation, the photosensitive drum 10 and the developing roller 16 are separated by the contact separation device 19, Blade bias -4
Change from 00V to -800V.

(7) Three seconds after (6), the blade bias is returned from -800 V to -400 V, and then the photosensitive drum 10 and the developing roller 16 are brought into contact by the contact / separation device 19. While the photosensitive drum 10 and the developing roller 16 are separated from each other, the photosensitive drum 10 and the developing roller 16 are kept rotating, and the charging bias is kept at -1200 V. Then, after the photosensitive drum 10 and the developing roller 16 come into contact with each other, the exposure device 12 is set to ΔN to start the image formation of the 31st sheet.

(8) After the completion of image formation, first, the exposure of the exposure device 12 is stopped, and the photosensitive drum 10 and the developing roller 16 are separated by the contact separating device 19.

(9) The developing bias is changed from -400V to 0V.
Then, the developing roller 16 is rotated for 3 seconds while the blade bias is kept at -400V.

(10) After 3 seconds, the blade bias is changed from -400 V to 0 V, and the rotation of the developing roller 16 is stopped.

(11) Regarding the application of the charging bias and the rotation of the photosensitive drum 10, after the photosensitive drum 10 and the developing roller 16 are separated by the contact separating device 19, the charging bias is changed from -1200V to 0V.

(12) After the separation, the photosensitive drum 10
After the rotation, the rotation of the photosensitive drum 10 is stopped.

Using the above image forming apparatus, a durability test was performed using a sample image having an image ratio of 5%. As a result, no streaks were observed on the image on the transfer material. No back surface was stained, and a durability test could be performed until the toner was exhausted.

As described above, by applying a blade bias to the developing blade before the start of image formation, after the end of image formation, and between sheets, generation of streaks on the image due to fusion of the developing blade is caused. Could be prevented.

Further, since no blade bias was applied during the exposure of the photosensitive drum, no unevenness occurred on the image.

Further, when the blade bias is applied, the photosensitive drum and the developing roller are separated from each other, and then the blade bias is applied. When image formation is to be performed subsequently, the photosensitive drum and the developing roller are stopped after the blade bias application is completed. Contact, and then perform the next image formation, which occurs at the time of blade bias application,
Since the phenomenon of fogging on the photosensitive drum does not occur,
The transfer roller was not stained, and the back surface of the transfer material was not stained.

It is needless to say that the magnitude of various biases in the image forming step is not limited to this.

Further, in Examples 1, 2, and 3, a non-magnetic one-component developer was used. However, the present invention can be applied to an image forming apparatus using a magnetic one-component developer and a two-component developer. The configuration of the image forming apparatus is not limited to those shown in FIGS.

[0086]

As described above, the image forming apparatus according to the first aspect of the present invention develops an electrostatic latent image at a contact portion between a developer carrier and an image carrier and develops the electrostatic latent image on the image carrier. A non-image forming apparatus including a developing unit for forming a developer image, a developing bias applying unit for applying a developing bias to a developer carrier, and a blade bias applying unit for applying a blade bias to a developer regulating member; At the time of formation, the absolute value of the difference between the surface dark area potential of the image carrier charged by the charging unit and the developing bias voltage applied to the developer carrier by the developing bias applying unit is larger than that during image formation. Then, a blade bias is applied to the developer regulating member, and the image forming apparatus according to the second aspect of the present invention further includes a contact separation unit capable of separating the image carrier and the developer carrier from each other. Sometimes contact By the intermediary means, the image carrier and the developer carrier are separated from each other, and a blade bias is applied to the developer regulating member, thereby preventing the occurrence of streaks on the image due to the fusion of the developer regulating member, There is an effect that unevenness on an image does not occur, and furthermore, a phenomenon that ground fogging does not occur on the image carrier does not occur, and contamination of the transfer unit and the recording material can be avoided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention.

FIG. 2 is a timing chart illustrating an operation of the image forming apparatus according to the first exemplary embodiment.

FIG. 3 is a timing chart illustrating an operation of the image forming apparatus according to the second exemplary embodiment.

FIG. 4 is a schematic configuration diagram illustrating another example of the image forming apparatus of the present invention.

FIG. 5 is a timing chart illustrating an operation of the image forming apparatus according to the third exemplary embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Photosensitive drum (image carrier) 11 Charging roller (charging means) 12 Exposure device (exposure means) 13 Developing device (developing means) 16 Developing roller (developer carrier) 19 Contact separation device (contact separation device) 17 Developing blade (Developer regulating member) 22 Blade bias power supply (blade bias applying means) 23 Development bias power supply (developing bias applying means) 24 Charging bias power supply (charging bias applying means)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/08 506 G03G 15/08 506A 21/14 21/00 372 F term (Reference) 2H027 EA01 EA05 EB01 EC18 ED03 ED08 ED09 EE01 EF07 EF09 EF11 EF12 2H073 AA03 BA02 BA12 BA13 BA21 CA02 2H077 AA11 AC04 AD02 AD06 AD13 AD23 AD35 AE03 BA07 DB08 DB12 DB14 DB25 EA14 EA15 FA13 FA16 FA23 FA27 GA03 GA12 GA16 GA22 GB HA29 HB12 HB43 HB45 HB48 JA02 MA03 MA20 NA02 PA02 PA10 PA22

Claims (4)

[Claims] 1. An image carrier, a charging unit for charging the surface of the image carrier, a charging bias application unit for applying a charging bias to the charging unit, and a charged image carrier surface corresponding to image data. Exposing means for forming a formed electrostatic latent image, a developer carrying member for carrying a developer, and a developer regulating member for regulating a layer thickness of the developer on the developer carrying member; Developing means for developing the electrostatic latent image at a contact portion with the image carrier to form a developer image on the image carrier, and applying a developing bias to apply a developing bias to the developer carrier. Means, a blade bias applying means for applying a blade bias to the developer regulating member, in the image forming apparatus, during non-image formation, the surface dark portion potential of the image carrier charged by the charging means, The current Applying the blade bias to the developer regulating member in a state where the absolute value of the difference from the developing bias voltage applied to the developer carrier by a bias applying unit is larger than that during image formation. Image forming apparatus. 2. The method according to claim 1, wherein the magnitude of the developing bias is changed before and after the image is formed, so that a non-image is formed.
2. The image according to claim 1, wherein an absolute value of a difference between a charged surface dark portion potential of the image carrier and the developing bias voltage applied to the developer carrier is larger than that during image formation. Forming equipment. 3. The method according to claim 1, wherein the magnitude of the charging bias is changed before and after the image is formed, so that a non-image is formed.
2. The image according to claim 1, wherein an absolute value of a difference between a charged surface dark portion potential of the image carrier and the developing bias voltage applied to the developer carrier is larger than that during image formation. Forming equipment. 4. An image carrier, a charging unit for charging the surface of the image carrier, an exposure unit for forming an electrostatic latent image corresponding to image data on the charged surface of the image carrier, and a developer. A developer carrying member to be carried and a developer regulating member for regulating a layer thickness of the developer on the developer carrying member are included, and the electrostatic latent is formed at a contact portion between the developer carrying member and the image carrying member. Developing means for developing an image to form a developer image on the image carrier, developing bias applying means for applying a developing bias to the developer carrier, and a blade for applying a blade bias to the developer regulating member And a bias applying unit. The image forming apparatus further includes: a contact separating unit configured to allow the image carrier and the developer carrier to be separated from and separated from each other. And the developer carrier. Is allowed, the image forming apparatus and applying the blade bias to the developer regulating member.