JP2002357953A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-quality image forming device capable of preventing a back surface staining phenomenon occurring on a sheet by preventing the fogging of toner caused in an area not electrified yet on an image carrier. SOLUTION: A power source 11 for generating developing bias and a power source 12 for generating blade bias generate electric field going toward a developing roller 10 from a developing blade 13 when the polarity of the toner is negative, and generate electric field going toward the blade 13 from the roller 10 when the polarity of the toner is positive, and the area of the roller 10 regulated by the blade 13 in a state where the electric field is generated is positioned in a developing area when a non-electrified area on a photoreceptor drum 1 is positioned in the developing area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine having a function of forming an image on a recording medium such as a sheet.
The present invention relates to an image forming apparatus such as a printer or a facsimile machine.

[0002]

2. Description of the Related Art Conventionally, as this type of image forming apparatus,
Those using electrophotography are widely used. In general, in an electrophotographic process, charging, exposure, and development are sequentially performed on a photoreceptor, an image visualized by toner is transferred onto a recording medium such as a sheet, and the unfixed toner image is fixed by final fixing. This is to obtain an output image.

[0003] Here, as a developing method, a developing roller is used to perform development by contacting with a photoreceptor (hereinafter referred to as a contact developing method), and a developing method is performed in a state where the developing roller is not in contact with the photoreceptor. The following two methods are known to be performed (hereinafter, referred to as a non-contact developing method).
JP-A-62-237771 and JP-A-1-23956.
As disclosed in Japanese Patent Application Laid-Open No. HEI 6-204, a developing roller is elastically brought into contact with the surface of a photoreceptor.
As disclosed in Japanese Patent No. 247478, there is a developing roller in which a resin thin plate sleeve is provided on the surface of a roller made of an elastic material.

FIG. 6 is a diagram showing an example of a known image forming apparatus using a contact developing method as a developing method (hereinafter, this is referred to as a conventional example).

Reference numeral 101 denotes a photosensitive drum that rotates in the direction of arrow A. The photosensitive drum 101 rotates in the direction of arrow B to which a charging bias is applied by a power supply device (not shown) for charging the surface of the photosensitive drum 101 around the photosensitive drum 101. Charging roller 1
02, a developing bias was applied by an exposure device 103 for forming an electrostatic latent image on the surface of the photosensitive drum 101 and a power supply device (not shown) for forming a toner image on the electrostatic latent image on the surface of the photosensitive drum 101 The developing roller 110 rotating in the direction of arrow D, the developing blade 111, the developing device 104 including the toner supply roller 112, and the transfer rotating in the direction of arrow C for transferring the toner image on the surface of the photosensitive drum 101 to the recording paper P There is a cleaning device 106 for collecting the toner remaining on the surface of the photosensitive drum 101 without being transferred to the roller 105 and the recording paper P and cleaning the surface of the photosensitive drum 101. Then, there is a fixing device 107 for fixing the recording paper P on which the transfer of the toner image has been completed.

Next, the operation of the image forming apparatus at the start of image formation will be described.

First, rotation of the photosensitive drum 101 is started by a driving device (not shown), and at the same time, the charging roller 102 is driven by rotation of the photosensitive drum 101, and rotation of the developing roller 110 is started by a driving device (not shown).

Next, a charging bias is applied to the charging roller from a power supply device (not shown) to apply a potential to the surface of the photosensitive drum 101.
An electrostatic latent image is formed on one surface, and then a developing bias is applied to the developing roller 110 from a power supply device (not shown) to start developing the toner on the photosensitive drum 101.

[0009]

However, in the case of the above-described prior art, the following problems have occurred.

Before the formation of the electrostatic latent image, the photosensitive drum 101
The potential of the surface of the photosensitive drum 101 in a section from the position where the charging roller 102 is in contact with the position where the developing roller 110 of the developing device 104 is in contact with the photosensitive drum 101 becomes almost 0 V as a result of dark attenuation. I have.

For this reason, this 0V section is defined by the developing roller 11
0, the toner charged strongly negatively becomes zero.
It adheres to the photosensitive drum 101 in the V section and causes fog.

After that, the fogging toner is transferred to and adheres to the transfer roller 105 of the transfer unit when it comes into contact with the transfer unit. Then, the toner adhered to the transfer roller 105 removes the first recording paper P Is transferred to the back side of the first recording sheet P when passing through the transfer means, and there is a problem that the first recording sheet P is stained on the back side.

Further, depending on the degree of dirt on the transfer roller 105 or the like, the back dirt on the recording paper does not disappear only on the first sheet, but it is equivalent to the dirt attached to the uncharged area on the photosensitive drum 101 every time an image is formed. When the amount of toner is repeatedly transferred to the transfer roller 105 or the like, the stain on the transfer roller 105 also progresses, and the back stain cannot be removed only on the first recording sheet P but spreads over a plurality of recording sheets P. Will occur.

In particular, in the case of the contact developing system, since the photosensitive drum 101 and the developing roller 110 are in contact with each other, even when the potential difference between the photosensitive drum 101 and the developing roller 110 is smaller than in the case of the non-contact developing system, Photosensitive drum 101
More toner adheres on top.

Further, the fogging is a cause of waste of toner, which leads to an increase in toner consumption.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to prevent fogging of toner from occurring in an uncharged area on an image carrier, and to generate toner on a sheet. An object of the present invention is to provide a high-quality image forming apparatus capable of preventing a back stain phenomenon.

[0017]

According to the present invention, there is provided an image bearing member on which an electrostatic latent image is formed, charging means for charging the image bearing member, and a developer. A developer carrying member for carrying, and a developer regulating member that abuts on a surface of the developer carrying member to regulate an amount of the developer on the developer carrying member; Developing means for developing the electrostatic latent image formed thereon with the developer in a developing area, wherein the image forming apparatus transfers the developed image developed by the developing means to a transfer material to form an image. When the polarity of the developer is negative, an electric field is generated from the developer regulating member toward the developer carrier, and when the polarity of the developer is positive, the developer is separated from the developer carrier. An electric field generating means for generating an electric field directed to the regulating member, When an uncharged area on the image carrier that is not charged by the charging unit is located in the developing area, the developing area includes the developer regulating member in a state where the electric field is generated by the electric field generating unit. It is also preferable that the region of the developer carrying member regulated by the above is located.

The electric field generating means includes a developing bias power supply for applying a developing bias to the developing means, and a developing bias power supply which is larger than the developing bias power applied by the developing bias power supply when the polarity of the developer is negative. When the polarity is positive, the electric field is generated by voltage applying means for applying a voltage smaller than the developing bias to the developer regulating member, and the non-charged area on the image carrier is When located in the developing region, it is also preferable that the developing region includes a region of the developer carrier that is regulated by the developer regulating member to which the voltage is applied by the voltage applying unit. It is.

After the developing operation by the developing means is completed, the voltage is applied to the developer regulating member by the voltage applying means for a predetermined time to generate the electric field. It is also preferable to stop the driving operation of the image carrier substantially simultaneously.

After the driving operation of the developer carrier and the driving operation of the image carrier are stopped almost simultaneously by applying the voltage to the developer regulating member for a predetermined time by the voltage applying means, When the developing operation by the developing unit is started again, it is preferable that the start of the driving operation of the image carrier and the start of the charging operation by the charging unit are performed substantially simultaneously.

The image carrier and the developer carrier are rotating bodies having a substantially circular cross section. The diameters of the image carrier and the developer carrier are R and r, respectively. An angle in a rotation direction of the image carrier with respect to a line connecting a rotation center and a position on the image carrier charged by the charging unit, wherein the rotation center of the image carrier and the developer Let θ be the angle to the line connecting the rotation center of the carrier,
An angle in a rotation direction of the developer carrier with respect to a line connecting a rotation center of the developer carrier and a position where the developer regulating member abuts on the developer carrier; If the angle between the rotation center of the image carrier and the rotation center of the image carrier is ψ, and the moving speeds of the surfaces of the image carrier and the developer carrier are V1 and V2, respectively, R × θ / V1) <(r × ψ / V2)

The predetermined time is defined as the position at the angle か ら from a line connecting the rotation center of the developer carrier and the rotation center of the image carrier, and a voltage is applied by the voltage applying means. It is also preferable that the region of the developer carrier regulated by the developer regulating member is at least a time required to reach the developing region.

When the developing operation is performed continuously, it is preferable that the electric field generating means does not operate and the electric field is not generated.

It is also preferable that the developer is a non-magnetic one-component developer.

[0025]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The material, shape, and their relative arrangement should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, and are not intended to limit the scope of the invention to the following embodiments.

(Embodiment 1) Referring to FIGS.
An image forming apparatus according to the first embodiment will be described. FIG. 1 is a schematic sectional view of the image forming apparatus according to Embodiment 1 of the present invention.

Reference numeral 1 denotes a photosensitive drum as an image carrier,
It rotates in the direction of arrow A at a peripheral speed of 120 mm / sec with a diameter of 30 mm. The charging roller 2 serving as a charging unit for charging the surface of the photosensitive drum 1 is
, And driven by the charging bias generating power supply 3 at a frequency of 1200 Hz and a voltage of 2000 Vp.
A charging bias in which an AC voltage of p and a DC voltage of −600 V are superimposed is applied, and the surface of the photosensitive drum 1
It is uniformly charged at a dark section potential of 600V.

Next, according to the image data input to the image forming apparatus, scanning is performed by the exposure means 4 which is ON / OFF controlled, and a light potential of about -150 is applied to the surface of the photosensitive drum 1.
An electrostatic latent image which is V is formed.

This electrostatic latent image is converted as a non-magnetic one-component developer carried on a developing roller 10 serving as a developer carrying member which is in contact with the surface of a photosensitive drum 1 in a developing device 5 as a developing means in a developing area. The toner is visualized to form a toner image.

At this time, a developing bias of a DC voltage of -350 V is applied to the developing roller 10 from a developing bias generating power supply 11 as a developing bias power supply, and the negatively charged toner is formed on the photosensitive drum 1 by an electrostatic force. Transferred to latent image.

The toner image on the surface of the photosensitive drum 1 is transferred to a transfer material (recording paper P as a recording medium such as a sheet or an intermediate transfer member) by a transfer roller 6 as a transfer means, and fixed to the recording paper P by a fixing means 8. It is fixed to obtain a permanent image.

Then, the toner remaining on the surface of the photosensitive drum 1 without being transferred to the recording paper P is collected by the cleaning device 7, and the surface of the photosensitive drum 1 is cleaned.

Next, the developing device 5 will be described with reference to FIG. In this embodiment, a non-magnetic one-component contact developing method is used as a developing method.

A developing roller 10 serving as a developer carrier rotates in the direction of arrow D at a peripheral speed of 160 mm / sec at a diameter of 16 mm and is in contact with the photosensitive drum 1. A DC voltage of −350 V is applied by the power supply 11. The developing roller 10 of the present embodiment is an elastic rubber roller composed of urethane rubber for the base layer and urethane rubber containing silicon particles for the surface layer.

The developing blade 13 as a developer regulating member regulates and charges the toner layer on the developing roller 10 to an optimum layer thickness, and further supplies the developing blade 13 with a blade bias generating power supply as a voltage applying means. The configuration 12 allows a DC blade bias to be applied. The developing blade 13 of the present embodiment is a SUS straight blade. Here, the electric field generating means is:
Power supply 11 for developing bias as a developing bias power supply
An electric field is generated by the power supply 12 for generating a blade bias as a voltage applying means.

The toner supply roller 14 supplies toner onto the developing roller 10 and rotates in the direction of arrow E.
Further, the toner container 15 stores toner and supplies the toner to the toner supply roller 14.

Next, the operation of the image forming apparatus of this embodiment after the completion of image formation will be described.

When the next image data is continuously input to the image forming apparatus after the image formation, the rotation of the photosensitive drum 1 and the developing roller 10 is not stopped, and the blade bias is applied to the developing blade 13. Without this, the next image forming operation is repeated.

When the next image data is not input to the image forming apparatus, the conventional image forming apparatus rotates the developing roller 10 and the photosensitive drum 1 and applies the charging voltage immediately after the completion of image formation. Has been completed, so that an amount of toner necessary for normal image formation is carried on the developing roller 10, and when the next image formation is performed, the contact position between the photosensitive drum 1 and the charging roller 2 is changed. Therefore, the amount of toner adhering to the uncharged area up to the contact position of the photosensitive drum 1 with the developing roller 10 has increased.

On the other hand, in this embodiment, the uncharged area (uncharged area) of the photosensitive drum 1 is
0, the blade bias generating power supply 1 is located in the developing region and the vicinity thereof.
Developing blade 1 to which blade bias is applied by
3 is located in the area of the developing roller 10 regulated.

That is, in the present embodiment, in the ending operation after the end of image formation, a blade bias of -300 V DC is applied to the developing blade 13 from the blade bias generating power supply 12 for 0.5 second.
And the rotation of the photosensitive drum 1 are stopped at the same time, and the charging bias generating power supply 3 terminates the application of the charging bias at the same time as the rotation of the photosensitive drum 1 is stopped, and then terminates the application of the blade bias. Developing roller 10
Can be temporarily reduced.

FIG. 2 shows the relationship between the applied voltage of the developing blade 13 to the developing roller 10 when a blade bias is applied to the developing blade 13 and the amount of toner coating on the developing roller 10. As shown in the figure, a developing bias is applied to the developing roller 10 by applying a plate bias having a polarity opposite to the polarity of the charge of the toner.
The upper toner amount decreases.

With this configuration, the amount of toner carried on the developing roller 10 when a blade bias of -300 V DC is applied to the developing plate 13 is reduced to the amount of toner necessary for normal image formation. from .5mg / cm ^2, temporarily it can be reduced to 0.2 mg / cm ^2.

That is, power supply 1 for generating blade bias
According to 2, the blade bias is set so that the voltage becomes larger than the developing bias applied from the developing bias generating power supply 11 when the toner polarity is negative, and becomes smaller than the developing bias when the toner polarity is positive. Is applied to the developing blade 13 to generate an electric field for causing the toner to flow from the developing roller 10 to the developing blade 13, so that the amount of toner on the developing roller 10 can be reduced.

Next, a start operation when the next image data is input to the image forming apparatus while the image forming apparatus is stopped will be described with reference to FIG.

In the starting operation, even if the charging step of the charging roller 2 is started simultaneously with the start of the driving of the photosensitive drum 1, even if the charging roller 2 on the outer periphery of the photosensitive drum 1 comes into contact with the developing roller 10 (position A). An uncharged area up to the contact position (position B, development area) is formed.

In the present embodiment, the outer peripheral length of the photosensitive drum 1 from the position A to the position B is 20 mm.

Accordingly, when the driving of the developing roller 10 is started at the same time as the driving of the photosensitive drum 1, the peripheral speed of the developing roller 10 is about 1.3 times faster than the peripheral speed of the photosensitive drum 1. Developing roller 1 in contact with charged area
The outer peripheral length of 0 corresponds to 26 mm.

Therefore, it is necessary to reduce the amount of toner carried on the developing roller 10 from the contact position (position B) of the outer peripheral surface of the developing roller 10 by at least 26 mm to the upstream position. Therefore, the outer peripheral length of the developing roller 10 from the developing blade contact position (position C) of the developing roller 10 to the photosensitive drum contact position (position B) of the present embodiment is 28 mm.
Is determined so that the toner carrying amount on the developing roller 10 is 0.2 mg / c.
The area of m ² was wider than the area corresponding to the uncharged area.

As a result, the amount of toner adhering to the uncharged area in the start operation is 0.2 mg / c of the amount of toner adhering when the amount of toner carried on the developing roller 10 is not reduced in advance.
As compared with m ² , the adhesion amount was very small, about 0.07 mg / cm ² .

In the start operation, since the developing bias is not applied to the developing roller 10 and the potential is grounded, the developing roller 10 has an amount smaller than the amount of toner adhering to the light portion potential in the developing process. I have. Incidentally, the amount of the toner which is transferred to the light portion potential in the developing step is about 0.7 mg / cm ² .

However, the amount of adhered toner of 0.2 mg / cm ² in the conventional configuration is an amount sufficient to contaminate the transfer means with toner. In this embodiment, it is 0.07 mg
/ Cm ^{2, which is} a very small amount.

Then, the attached toner is applied to the developing roller 10.
Since the toner is in a state of being left as it is carried on the toner, the amount of charge of the toner is also reduced, so that even if the toner adheres slightly on the photosensitive drum 1, it is electrostatically transferred. Since the amount of toner transferred to the means is further reduced, as a result, generation of back stain on the recording paper immediately after the start of image formation was not observed.

Next, using the image forming apparatus of the present embodiment and the conventional image forming apparatus, a temperature of 25 ° C. and a humidity of 50% were used.
In the intermittent mode, the operation of stopping the operation of the image forming apparatus for 20 seconds after the completion of printing one sheet using a pattern with a printing ratio of 5% on A4 size paper and then restarting the image formation is repeated. When a printing durability test of 3,000 sheets was performed, the toner consumption was about 83 g when the conventional image forming apparatus was used, whereas the toner consumption was about 83 g when the image forming apparatus of the present embodiment was used. Reduced the toner consumption to about 75 g.

As described above, after the image formation, the developing bias is applied to the developing blade 13 provided for regulating the toner on the developing roller 10 to an optimum layer thickness when the polarity of the toner is negative. When the toner bias is higher than the developing bias applied from the developing power supply 11 and the polarity of the toner is positive, the blade bias is applied by the blade bias generating power supply 12 so as to have a voltage lower than the developing bias. After the thickness of the upper toner layer is reduced, the driving of the photosensitive drum 1, the driving of the developing roller 10, the charging bias, and the blade bias are stopped.

As a result, it is possible to prevent the fogging of the toner in the uncharged area on the photosensitive drum 1 which occurs at the start of the next image formation, and to prevent the back stain phenomenon which occurs on the recording paper P. Can be suppressed.

(Embodiment 2) FIGS. 4 and 5 show Embodiment 2 of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The present embodiment derives a relational expression relating to the diameter and the moving speed of the surface of the photosensitive drum and the developing roller, and the positional relationship between the charging roller, the photosensitive drum, the developing roller and the developing blade. A design and production of an image forming apparatus capable of preventing fogging on the photosensitive drum, preventing a back stain on recording paper, and suppressing an increase in toner consumption. It is.

FIG. 4 is a schematic sectional view of a main part of an image forming apparatus according to Embodiment 2 of the present invention.

R is the diameter of the photosensitive drum 1 and θ is the rotation direction of the photosensitive drum 1 from the straight line connecting the contact position (position A) of the charging roller 2 on the outer periphery of the photosensitive drum 1 and the rotation center of the photosensitive drum 1. An angle r to a straight line connecting the contact position (position B) between the photosensitive drum 1 and the developing roller 10 is represented by r.
A diameter of 0, ψ is a contact position (position C) between the developing roller 10 and the developing blade 13 with respect to the rotation direction of the developing roller 10.
From the straight line connecting the photosensitive drum 1 to the developing roller 10 (position B).

The other components in this embodiment, the reference numerals in the drawing, and the operation of the image forming apparatus are the same as those in the first embodiment. After the image formation is completed, the next image data is input to the image forming apparatus. In this case, without stopping the rotation of the photosensitive drum 1 and the developing roller 10,
Further, the next image forming operation is repeated without applying a blade bias to the developing blade 13.

When the next image data is not input to the image forming apparatus after the image formation is completed, the blade bias of -300 V DC is applied to the developing blade 13 from the power supply 12 for generating blade bias to 0. 5
After that, the rotation of the developing roller 10 and the rotation of the photosensitive drum 1 are simultaneously stopped, and the power supply 3 for charging bias generation terminates the application of the charging bias at the same time as the rotation of the photosensitive drum 1 is stopped. By ending the application, the amount of toner carried on the developing roller 10 can be temporarily reduced.

In this embodiment, from the position at which the photosensitive drum 1 contacts the charging roller 2 on the outer periphery of the photosensitive drum 1 (position A) to the position at which the photosensitive drum 1 contacts the developing roller 10 (position B). The moving time is R × θ / 180 / V1, where the moving speed of the surface of the photosensitive drum 1 is V1.

Further, from the position where the developing roller 10 comes into contact with the developing blade 13 on the outer periphery of the developing roller 10 (position C),
Contact position between photosensitive drum 1 and developing roller 10 (position B)
The time required to move the developing roller 10 is V2
Then, it becomes r × ψ / 180 / V2.

Then, the photosensitive drum 1 is
Since it is sufficient to move in a shorter time than 0, R × θ / 180
/ V1 <r × ψ / 180 / V2, and R × θ / V1
<R × ψ / V2 (Formula 1) To prevent fogging on the photosensitive drum 1 that occurs at the start of image formation and to prevent a back stain phenomenon that occurs on the recording paper P when satisfying the relationship represented by (Equation 1). And an image forming apparatus capable of suppressing an increase in toner consumption can be designed.

In the present embodiment, R = 30 mm, r = 16 mm, θ = 60 °, ψ = 17, which satisfy Expression 1.
When an image was output by performing the same operation as in the first embodiment with a configuration of 5 °, V1 = 120 mm / s, and V2 = 170 mm / s, fog on the photosensitive drum 1 generated at the start of image formation was also reduced. In addition, it was possible to form an image satisfactorily without generating back stains on the recording paper P.

The predetermined time during which the blade bias is applied to the developing blade 13 by the power supply 12 for generating blade bias is such that the area of the developing roller 10 regulated by the developing blade 13 to which the blade bias has been applied is the developing roller 10. From the contact position (position C) between the photosensitive drum 1 and the developing blade 13
The time may be any time required to reach the contact position (position B) between the developing roller 10 and the developing roller 10. Then, in the start operation, if the charging step of the charging roller 2 is started at the same time when the driving of the photosensitive drum 1 is started, it is possible to prevent the toner from fogging in the uncharged area.

As in the case of the first embodiment, an image forming apparatus is used for 20 seconds after printing one sheet on a sheet of A4 size in an environment of a temperature of 25 ° C. and a humidity of 50% using a pattern with a printing rate of 5%. In the intermittent mode of stopping the operation of
When a printing durability test was performed on 0 sheets, the toner consumption was reduced to about 75 g even when the image forming apparatus of the present embodiment was used.

As described above, the image forming apparatus is designed by using the relational expression relating to the diameter and the moving speed of the surface of the photosensitive drum and the developing roller and the positional relation between the charging roller, the photosensitive drum, the developing roller and the developing blade. And
Further, after the image formation is completed, a developing blade 13 provided to regulate the toner on the developing roller 10 to an optimum layer thickness is provided.
In addition, when the polarity of the toner is negative, the blade bias is set to be larger than the developing bias applied from the power source 11 for developing bias, and when the polarity of the toner is positive, the blade bias is set to a voltage smaller than the developing bias. By applying the power from the blade bias generation power supply 12, the toner layer thickness on the developing roller 10 is reduced, and then the driving of the photosensitive drum 1, the driving of the developing roller 10, the charging bias, and the blade bias are stopped.

As a result, it is possible to prevent the fogging of the toner in the uncharged area on the photosensitive drum 1 which occurs at the start of the next image formation, and to prevent the back-stain phenomenon which occurs on the recording paper P. It is possible to easily design and manufacture an image forming apparatus capable of suppressing an increase in the number of images.

[0071]

As described above, according to the present invention,
When the developer carrier is located in the non-charged area on the image carrier, the amount of the developer carried on the developer carrier can be reduced. Fog can be prevented, and a back stain phenomenon that occurs in a conventional recording medium can be prevented, and further, an increase in developer consumption can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing a relationship between an applied voltage of a developing blade to a developing roller according to the first embodiment and a toner coating amount on the developing roller.

FIG. 3 is a schematic sectional view showing a main part of the image forming apparatus according to the first embodiment;

FIG. 4 is a schematic sectional view showing a main part of an image forming apparatus according to a second embodiment.

FIG. 5 is a schematic sectional view showing a main part of an image forming apparatus according to a second embodiment.

FIG. 6 is a schematic sectional view of a conventional image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 charging roller 3 power supply for generating charging bias 4 exposing means 5 developing device 6 transfer roller 7 cleaning device 8 fixing means 10 developing roller 11 power supply for generating developing bias 12 power supply for generating blade bias 13 developing blade

Continued on the front page F term (reference) 2H027 DA16 DA17 DA21 DA22 DA38 DD05 EA05 ED09 EE02 EF06 EF13 2H073 AA03 BA02 BA09 BA12 BA13 BA23 BA25 2H077 AC04 AD06 AD13 AD16 AD35 DA01 DB08 EA15 GA17

Claims (8)

[Claims] An image carrier on which an electrostatic latent image is formed; charging means for charging the image carrier; a developer carrier for carrying a developer; and a contacting surface of the developer carrier. A developer regulating member for regulating the amount of the developer on the developer carrier, and developing the electrostatic latent image formed on the image carrier by the exposure means in the development area with the developer. An image forming apparatus that transfers a developed image developed by the developing unit to a transfer material to form an image, wherein when the polarity of the developer is minus, the developer regulating member is An electric field generating means for generating an electric field toward the developer carrier, and when the polarity of the developer is positive, generating an electric field from the developer carrier toward the developer regulating member; Non-band not charged by the above charging means When the region is located in the developing region, the region of the developer carrier that is regulated by the developer regulating member in a state where the electric field is generated by the electric field generating unit is located in the developing region. An image forming apparatus comprising: 2. The electric field generating means includes: a developing bias power supply for applying a developing bias to the developing means; and a developing bias power applied by the developing bias power supply when a developer has a negative polarity. A voltage application unit for applying a voltage smaller than the developing bias to the developer regulating member when the polarity of the developer is positive; and generating the electric field by: When the region is located in the developing region, the region of the developer carrier that is regulated by the developer regulating member to which the voltage is applied by the voltage applying unit is located in the developing region. The image forming apparatus according to claim 1, wherein: 3. After the developing operation by the developing means is completed, the voltage applying means applies the voltage to the developer regulating member for a predetermined time to generate the electric field, and then drives the developer carrier. The image forming apparatus according to claim 2, wherein the operation and the driving operation of the image carrier are stopped substantially simultaneously. 4. A driving operation of the developer carrier and a driving operation of the image carrier are substantially simultaneously stopped by applying the voltage to the developer regulating member for a predetermined time by the voltage applying means. 4. The method according to claim 3, wherein when the developing operation by the developing unit is started again after the start, the start of the driving operation of the image carrier and the start of the charging operation by the charging unit are performed substantially simultaneously. The image forming apparatus as described in the above. 5. The image bearing member and the developer bearing member are rotators having a substantially circular cross section, and the image bearing member and the developer bearing member each have a diameter of:
R and r are angles in the rotation direction of the image carrier with respect to a line connecting a rotation center of the image carrier and a position on the image carrier charged by the charging unit. The angle between the rotation center of the carrier and the line connecting the rotation center of the developer carrier is defined as θ, and the rotation center of the developer carrier and the developer regulating member contact the developer carrier. An angle in a rotational direction of the developer carrier with respect to a line connecting the contacting position, and an angle between a line connecting the rotation center of the developer carrier and the rotation center of the image carrier with ψ, 4. The image forming apparatus according to claim 1, wherein, when the moving speeds of the surfaces of the image carrier and the developer carrier are V1 and V2, respectively, the following inequality is satisfied: (R × θ / V1) <(r × ψ / V2). Any one of 1 to 5
Item 10. The image forming apparatus according to item 1. 6. The predetermined time means that the voltage is applied by the voltage applying means at a position located at the angle か ら from a line connecting the rotation center of the developer carrier and the rotation center of the image carrier. 6. The image forming apparatus according to claim 5, wherein a region of the developer carrier regulated by the developer regulating member is at least a time until the region reaches the developing region. 7. The method according to claim 1, wherein when the developing operation is performed continuously, the electric field generating means does not operate and does not generate the electric field. Image forming device. 8. An image forming apparatus according to claim 1, wherein said developer is a non-magnetic one-component developer.