JP3449118B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to a copier, a facsimile
For image forming devices such as millimeters and printers,
The surface of the uniformly charged image carrier is attenuated by image exposure.
To form an electrostatic latent image, which is charged to the same polarity as the charging polarity.
Toner and carrier charged to the opposite polarity to the charged polarity
Reversal of developing the electrostatic latent image using a two-component developer containing
Power supply for charging in an image forming apparatus using a developing method;
This is related to ON / OFF control of the power supply for developing bias.
is there. [0002] 2. Description of the Related Art In an image forming apparatus of this kind, an image forming apparatus is used.
At the start of image formation, charging means is almost simultaneously with the start of driving of the image carrier.
When the surface of the image carrier starts to be charged by
From where it was facing the charging means when stopped
Image up to where it was facing the developer carrier of the developing device
The surface of the carrier bears developer without being charged by the charging means.
It will face the holding body. At the end of image formation,
Almost at the same time as the end of driving of the image carrier, image carrying by the charging means
When the charging of the body surface is terminated, the charging of the surface of the image carrier is stopped.
Although the uncoated surface does not face the developer carrier,
The charged part of the image carrier surface faces the developer carrier
there's a possibility that. [0003] By the way, image formation using the reversal development system
Uncharged, uncharged surface of the image carrier in the device
When the region faces the developer carrier, the image carrier surface
The same magnitude as the voltage applied when facing the charged area of the surface
When a developing bias voltage of
Is the toner between the carrier and the developer carrier
Thus, an electric field is formed in a direction to transfer the image to the surface of the image carrier.
Due to this electric field, toner is deposited on the uncharged area on the surface of the image carrier.
Because it adheres, the toner is wasted wastefully,
The toner consumption of the entire apparatus increases. Further, the non-charged area on the surface of the image carrier is
For developing bias when it reaches the developing position facing the carrier
When the power is turned off, the image carrier and the developer carrier
During the period, the toner is transferred from the developer carrier to the surface of the image carrier.
The electric field in the direction opposite to the direction of the transfer,
Image carrier from the developer carrier
An electric field is formed on the surface of the carrier to transfer the image.
Carriers adhere to uncharged areas on the body surface. this
The electric field in the opposite direction applies the developing bias voltage even during image formation.
Between the applied developer carrier and the non-image area on the surface of the image carrier.
Is formed, but the electric field strength is higher than the electric field during image formation.
Carrier is transferred to the image carrier
It is easy to adhere. Thus, in the opposite direction
Carrier adhesion due to the electric field is caused by the above toner and high
When a two-component developer containing a resistance carrier is used, toner
And the carrier are mixed and agitated so that the toner has the specified polarity.
When the carrier is charged by friction, the carrier has a polarity opposite to that of the toner.
Because it will charge you. Conventionally, wasteful consumption of the toner is prevented.
For this purpose, a developing bias voltage is applied to the developer
The charging start time of the image carrier is determined by the development start time when the image starts.
Electrophotographic device that delays until image position is reached (image formation
(Japanese Patent Application Laid-Open No. 54-12843)
reference). [0006] However, the actual image
The forming apparatus is disclosed in JP-A-54-12843.
Even if the control as shown in the
If the ON / OFF timing of the power supply for
Completely prevents both carrier and toner waste
There was a case that could not be prevented. For example, for an image forming apparatus
ON timing of power supply for developing bias at the start of image formation
Is earlier than the predetermined timing, the toner
Unnecessary adhesion occurs and the power supply for developing bias is turned on
If the scanning is slow, carrier adhesion to the image carrier will occur.
May be. Also, for example, the end of image formation of the image forming apparatus
Power supply for development bias is turned off at the time of
If the timing is earlier than the predetermined timing, the image carrier
Carrier adhesion occurs and the power supply for developing bias is turned on.
If the imaging is slow, wasteful adhesion of toner to the image carrier may occur.
May be born. In addition, the above-mentioned carrier adhesion and toner absence
The reason why both of the useless attachments cannot be completely prevented is that the image
A potential change occurs at the boundary between the charged and uncharged areas on the carrier surface.
Area may occur, or the power supply for developing bias may be turned ON / OFF.
Transient change in development bias voltage when OFF
Can also be mentioned. The potential change on such an image carrier
If there is a transient change in the developing region or the developing bias voltage,
Control as disclosed in Japanese Unexamined Patent Publication No. 54-12843.
Is performed, the ON / OFF of the developing bias power supply
The developing bias voltage and the surface of the image carrier
Depending on the magnitude relationship between the potential of
Generates an electric field that transfers to the image carrier, such as a carrier
The carrier and waste toner.
There is a possibility that both of the wearing cannot be completely prevented. [0008] Here, the carrier is mainly formed by electrostatic attraction.
Adheres to the surface of the image carrier, but the carrier is
Centrifugation due to gravity or rotation of the developer carrier
The force works strongly, and this gravity or centrifugal force is larger than the electrostatic attraction.
If it does, it will fall from the surface of the image carrier. Also the statue
Even if the number of carriers attached to the carrier surface is small,
Dropping from the surface of the image carrier while using the forming device for a long time
Transfer carrier below the image carrier in the device
There is a possibility that the transfer roller and the transfer path of the transfer material may be contaminated. On the other hand, the toner adhered to the surface of the image carrier
Is sufficiently charged to a predetermined polarity,
The force of adhering to the image carrier is stronger than that of the carrier. Change
In addition, the toner is lighter than gravity by the action of gravity or centrifugal force.
The electrostatic attraction is smaller than gravity or centrifugal force.
Overwhelmingly strong, separated from the image carrier surface by gravity or centrifugal force
Absent. Fall from the image carrier in the actual image forming apparatus
Most of the toner separates the transfer material from the image carrier.
The separation claw that separates the leading end of the transfer material
Image the toner image at the top of the image area in a short time when rubbing the surface
It was peeled off from the surface of the carrier. From the viewpoint of contamination inside the apparatus,
Rear adhesion is not desirable, but the toner adhesion
There is no obstacle. Adhesion of toner and carrier to image carrier
It's difficult to balance them so they don't happen together
If the priority is to prevent wasteful toner consumption,
Priority on preventing equipment contamination
Will be the choice. Here, the inside of the device is contaminated by the carrier.
The life of contaminated parts and units
Or cause a failure. On the other hand,
Although the cost is not desirable, the toner consumed by the image forming apparatus
If included, the overall toner cost will be slightly higher
Only to shorten the life of the unit or cause a failure.
It will not be. The present invention has been made under the above background.
The purpose is to start image formation and end image formation.
When the power supply for developing bias is turned on / off during operation
To the image carrier when switching the developing bias voltage
To prevent the carrier from adhering to the image carrier.
Minimize waste toner consumption by minimizing toner adhesion
It is an object of the present invention to provide an image forming apparatus capable of performing the above. [0012] [MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
ToThe invention of claim 1 isCharges the surface of the image carrier uniformly
Member for charging and applying voltage to the charging member
Charging means having a power supply for use, and an image charged by the charging means
The potential of the surface of the carrier is attenuated by image exposure, and the image carrier is
Exposure means for forming an electrostatic latent image thereon, and charging of the charging means
Toner charged to the same polarity as polarity and polarity opposite to the charged polarity
Supports two-component developer containing neutrally charged carrier
The developer carrier and the same polarity as the charged polarity on the developer carrier.
Power supply for developing bias to apply
Developing means havingImage forming apparatus,image
When the charging start end of the carrier surface faces the developer carrier
Starts applying the developing bias voltage to the developer carrier
The end of charging on the surface of the image carrier is opposite to the developer carrier.
So that the application of the developing bias voltage is stopped when
Then, the charging power supply and the developing bias power supply are turned ON / O.
A control means for performing FF control is provided, and a power supply for the developing bias is provided.
By ON / OFFThe developing bias voltage changes transiently.
The charging start end or the charging end of the surface of the image carrier.
At the end, the absolute value of the potential of the surface of the image carrier changes.
Period at least partially overlaps, and the two periods
In the overlapping portion, the absolute value of the potential of the surface of the image carrier is
In order to be less than the absolute value of the developing bias voltage,For charging
ON / OFF timing of power supply and power supply for the developing bias
Is set. In the first aspect of the present invention, the control means charges the battery.
ON / OFF control of power supply for developing and power supply for developing bias,
In the image forming start operation of the apparatus, charging of the surface of the image carrier is opened.
When the starting end faces the developer carrier, the developer carrier
When the application of the developing bias voltage of
The charging start end of the carrier reaches the position facing the developer carrier
In the meantime, the uncharged area on the image carrier
Do not face the developer carrier to which the bias voltage is applied.
And the toner of the same polarity as the developing bias voltage is applied to the surface of the image carrier.
The electric field in the direction in which the image carrier and the developer carrier
Avoid formation between them. Further, in the image forming end operation of the apparatus, an image is formed.
When the charging end of the surface of the carrier faces the developer carrier
The application of the developing bias voltage to the developer carrier is stopped
As a result, the charging end of the image carrier is brought into contact with the developer carrier.
After passing through the opposite position, the uncharged area of the image carrier
Does not face the developer carrier to which the image bias voltage is applied
So that toner having the same polarity as the developing bias voltage
The electric field in the direction of transferring to the body surface is applied to the image carrier and developer
Avoid being formed between the body. Then, ON / OF of the developing bias power supply
The developing bias voltage is transiently changed by Fperiod
At the charging start end or charging end end of the image carrier surface
The period during which the absolute value of the potential on the body surface is
At least partly overlaps, and the two periods overlap
And the absolute value of the potential on the surface of the image carrier isDevelopment bias voltage
Power supply and developing via so that the absolute value of
By setting the ON / OFF timing of the power supply for
During the transient change of the developing bias voltage
Carrier charged to the opposite polarity to the charged potential on the body
Transfer from the image carrier to the surface of the image carrierRudenThe world carries the image
So that it is not formed between the developer and the developer carrier. Further, the developing bias voltage changes transiently.
ingPeriod, charge start end or charge end of image carrier surface
Period during which the absolute value of the potential of the surface of the image carrier changes at the end
And at least partly overlap each other,
Compared to the case of not overlappingTable of the image carrier
Between the surface potential value and the developing bias voltage valueApproaching,developing
The toner of the same polarity as the bias voltage is transferred to the surface of the image carrier.
Electric field is formed between the image carrier and the developer carrier.
Shorten the time taken. [0017] [0018] [0019] [0020] [0021] DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an electrophotographic image forming apparatus.
An embodiment applied to an image forming apparatus will be described. Ma
First, referring to FIG. 1, an outline of an image forming apparatus according to the present embodiment will be described.
The schematic configuration will be described. This image forming apparatus is
As an image carrier that is rotated at a predetermined linear speed
And a photoconductor 1 around the photoconductor 1.
1 as a charging means for uniformly charging to a predetermined potential of negative polarity
The charging device 2 forms an image on the uniformly charged surface of the photoreceptor 1
Image exposure device 3 for image exposure by irradiating corresponding light, negative polarity
Contains positively charged toner and positively charged carrier
A developing sleeve as a developer carrier for carrying a two-component developer
Developing device 5 as a developing means having photoreceptor 4, photosensitive member 1
Transfer the upper toner image to a transfer paper (not shown) as a transfer material
The transfer device 6 performs the transfer of the toner remaining on the photoconductor 1 after the transfer.
Cleaning device 7 for removing toner, residue on photoconductor 1
A static eliminator 8 for removing charges is provided. The charging device 2 faces the surface of the photoreceptor 1.
And a charging member (not shown).
A predetermined voltage is applied from a high-voltage power supply 9 as a power supply for
You. Further, the developing sleeve 4 of the developing device 5
The same as the charging voltage from the high-voltage power supply 10 as the bias power supply
A polarity developing bias voltage is applied. These two high
Voltage power supplies 9 and 10 are CPU, RAM, ROM, I / O
Control device 1 as control means including an interface and the like
1 controls ON / OFF. A normal image in the image forming apparatus having the above configuration
During image formation, the photoconductor 1 is driven to rotate in the direction of the arrow,
For example, when the electric device 2 is uniformly charged to a predetermined potential of negative polarity.
Light corresponding to an image is illuminated on the surface of the light body 1 by the image exposure device 3.
And the potential of the portion corresponding to the image is attenuated.
As a result, an electrostatic latent image is formed on the photoconductor 1. This photoconductor
1 is a negative electrode supplied from the developing sleeve 4.
The toner image is developed by the toner having the characteristic property and becomes a toner image. Exposure
The toner image on the body 1 is transferred onto transfer paper (not shown) by the transfer device 6.
Transcribed. Toner remaining on photoconductor 1 after transfer
Is removed by the cleaning device 7 and the residual
After the load is removed, it is ready for the next image formation. Next, referring to the time chart of FIG.
At the start of image formation and at the end of image formation of the image forming apparatus having the above configuration.
The control at the time of completion will be described. This image forming apparatus
At the start of image formation, press the start button to
After starting the rotation drive of No. 1, the high voltage power supply 9 for charging is turned on.
Then, uniform charging of the surface of the photoconductor 1 is started. And this
Start of charging on the surface of the photoreceptor
(The tip in the direction) faces the developing sleeve 4
The application of the developing bias voltage to the developing sleeve 4 is started.
As described above, the high-voltage power supply 10 for developing bias is turned on. At the end of image formation, a high voltage for charging
After the power supply 9 is turned off and uniform charging of the photoconductor 1 is completed,
End of charging of photoconductor surface
(The rear end in the direction) faces the developing sleeve 4.
Develop bias to stop application of image bias voltage
Of the high voltage power supply 10 is turned off. Then, the entire surface of the photoconductor 1
When the charge is removed, the rotation drive of the photoconductor 1 is turned off.
To. As shown in FIG. 2, charging and developing bias
ON / OFF control of the high voltage power supply for
A photosensitive is applied to the developing sleeve 4 to which the bias voltage is applied.
Since the non-charged areas on the body surface hardly face each other,
The toner on the image sleeve 4 is transferred to an uncharged area on the surface of the photoconductor.
Reduce wasteful toner consumption due to transfer and adhesion
Can be. Next, the high-voltage power supply 10 for developing bias
Change of developing bias voltage when turning ON / OFF
And photoreceptor 1 by turning on / off high-voltage power supply 9 for charging
The potential gradient at the charge start end and the charge end end
ON / OF of two high-voltage power supplies 9, 10 set in consideration
The F timing will be described. Turning on the high voltage power supply 10 for the developing bias
Apply to developing sleeve 4 during transient response due to / OFF
While the developing bias voltage is changing, the developing sleeve 4
Is generally several mm to 20 mm
mm. Here, the line of the photoconductor 1 of the image forming apparatus
The speed is 10mm / sec for slow ones and fast for
It is 500 mm / sec. Also, a high
Output voltage (ON / OFF of the voltage supply 10)
The transient response time of the output voltage
It takes 10 to change from 10% to 90% of the ias voltage.
It is about msec to 100 msec. Photoconductor 1
Is applied to the developing sleeve 4 as the linear velocity is higher.
During the transition of the developing bias voltage, the developing three
So that the distance on the photoconductor 1 opposite to the
To shorten the transient response time of the output voltage of the high-voltage power supply 10.
Is designed so that even if the linear speed of the photoconductor is
The separation is within 20 mm. On the other hand, the photosensitive member 1 is charged uniformly.
Between a charged area and a non-uniformly charged area
The width where the potential of the transition is inclined is the high voltage power supply for charging.
9 Transient response time of output signal by ON / OFF
And the charge distribution on the photoreceptor 1 by the electric device 2.
You. Output signal is transient by ON / OFF of high voltage power supply 9
The distance that the photoreceptor surface moves while changing
As in the case of the image bias, generally about several mm to 20 mm
Degrees. On the other hand, the charge amount on the photoconductor 1 by the charging device 2
The cloth is a contact type using a charging roller etc. as a charging member.
Using a charging device and a corona wire as a charging member
There is a difference with the charging device. In the case of a contact-type charging device,
Corona discharge occurs in a narrow area near the contact point with the optical body 1
Therefore, the width of the charge distribution on the surface of the photoreceptor 1 is narrow, about several mm.
Degrees. Also, transfer multiple corona wires to the photoconductor surface.
In the case of charging devices arranged in the direction of movement, the charging
The width of the distribution is wider than the distance between the corona wires at both ends.
It is easy to think that one corona wire
Charge to the potential,
Rona wire is for improving the uniformity of the potential
Then, the distribution of charge by the first corona wire is supported.
It becomes arrangement. Therefore, the width at which the charging potential is inclined is
Most of the charging device with one corona wire
There are many things that do not change, about 10 mm or less
You. Therefore, the change between the charged area and the non-charged area on the surface of the photoconductor is changed.
The width at which the charging potential of the junction is inclined is several mm to 30 m.
m. The output voltages of the high-voltage power supplies 9 and 10 are
The transient response varies between devices. For example, a development
Transient response due to ON / OFF of high voltage power supply 10 for EAS
Of developing bias voltage applied to developing sleeve 4
The speed depends on the individual variation of the high-voltage power supply 10 used for the device,
Fluctuates due to changes in the operating environment and temperature changes due to self-heating of the power supply.
You. The charged area on the surface of the photoreceptor and the non-charged area
The slope of the charging potential at the transition between the
Similar to the case of the bias voltage,
In addition, individual variations in charging devices, environmental fluctuations, and deterioration over time
It fluctuates. In addition, the layout position and the parallelism
Photoreceptor caused by mechanical fluctuation factors such as fluctuation
Of the relative positions of the charging device 2 and the developing device 5 with respect to
The pitch is about 1 mm in the circumferential distance on the photoconductor 1.
Control variation by the CPU of the control device 11 is 1 mm
There is a degree. Such variation and feeling of inclination of the charging potential
The variation in the inclination of the amount of the developing toner on the optical body 1, the charging device
Of the relative positions of the developing device 2 and the developing device 5,
There is variation, and furthermore, this variation is caused by environmental fluctuation and aging.
Because of the fluctuation, the ON / OFF timer of the charging high voltage power supply 9
ON / O of high voltage power supply 10 for imaging and developing bias
By adjusting the FF timing, the toner
-Eliminate both adhesion (development) and carrier adhesion at the same time
Is almost impossible. Therefore, in the image forming apparatus of this embodiment,
These variations take into account fluctuations, and
-The photoconductor 1 and the developing sleeve 4
Direction in which carriers do not transfer and adhere to photoconductor 1 during
A certain margin so that the electric field of
ON / OFF timing of high voltage power supply 9, 10
are doing. Here, take margin too much and ON / OFF
When the timing is set, the toner is developed on the photoconductor 1.
And the width of the black belt becomes wider, resulting in more wasteful toner consumption.
On the contrary, the above margin is calculated too small and ON / OFF
When the timing is set, carrier adhesion on photoreceptor 1
Will occur. Therefore, the above variation and fluctuation are evaluated.
And take an appropriate margin according to the evaluation result.
Set ON / OFF timing of high voltage power supplies 9 and 10
It is desirable. FIG. 3A and FIG.
Variations such as transient response of image bias voltage and inclination of charging potential
Evaluate the key and fluctuation and turn on the high voltage power supplies 9 and 10
FIG. 7 is an explanatory diagram showing a setting example in which the setting is set. Horizontal in the figure
The axis is the coordinate of the surface moving direction on the photoconductor 1, and the vertical axis is
(Charging potential and developing bias voltage). Fruit in the figure
Line A is the charged potential on the photoconductor 1, and broken line B is
Bias voltage when facing the photoreceptor surface
Pressure. Also, t1 and t2 on the horizontal axis are respectively charged.
O of the high voltage power supply 9 for developing and the high voltage power supply 10 for developing bias
N operation is supported. FIG. 3A shows the transient response of the developing bias voltage.
The answer is relatively gentle, and the photoconductor 1
The width of the inclined portion of the upper charging potential is wide, and
It is a setting example when the fluctuation is small. FIG. 3 (b)
Is different from the case of FIG.
Transient response is relatively steep, and photosensitivity accompanying turning on of high voltage power supply 9
The width of the slope of the charged potential on the body 1 is relatively narrow, and
This is a setting example in the case of large variations and fluctuations. These two
In the setting example of the two figures, the above variation and fluctuation are taken into account.
Then, the development is performed by turning on the high voltage power supply 10 for the development bias.
When the bias voltage is transiently changed, the developing sleeve 4
Of the charged potential of the photoconductor 1 passing through the position facing
Under the condition that the value is equal to or less than the absolute value of the developing bias voltage,
So that the value of the charging potential approaches the value of the developing bias voltage.
The ON timing of the high voltage power supplies 9 and 10 is set. As described above, according to the present embodiment, the developing
Variations and variations such as transient response of
Of the high voltage power supply 9 and 10
The image at the start of image formation.
During the transition of the bias voltage, the positive polarity carry
Is transferred from the developing sleeve 4 to the surface of the photoreceptor 1.
An electric field is not formed between the photoconductor 1 and the developing sleeve 4.
Carrier on the developing sleeve 4 adheres to the photoreceptor 1
And prevent carrier contamination in the equipment.
You. Also, as shown in the above example, the high voltage power supplies 9 and 10 are turned on.
By setting the timing, the negative polarity toner
An electric field that transfers from the image sleeve 4 to the surface of the photoconductor 1
It is difficult to form between the photoconductor 1 and the developing sleeve 4
Therefore, toner adhesion to the photoconductor 1 is minimized to
-Prevent consumption. Actually, the negative polarity on the development soove 4
Black image formed by developing the toner on the photoreceptor 1
The width was measured to be several mm to 20 mm.
Was. FIGS. 3A and 3B show image formation.
An example of setting the ON timing of the high voltage power supplies 9 and 10 at the start
As shown in FIG.
When performing FF, the same as the ON timing,
Variations and variations such as transient response of
Of the high-voltage power supplies 9 and 10
Setting. More specifically, high pressure for developing bias
Transient change of developing bias voltage by turning off power supply 10
While passing through the position facing the developing sleeve 4
The absolute value of the charged potential of the photoconductor 1 is determined by the developing bias voltage.
High-voltage power supplies 9 and 10 so as to be smaller than the absolute value of the pressure.
OFF timing is set. This allows high-voltage power
When turning off 9 and 10, the cap on the developing sleeve 4
The rear does not adhere to the photoreceptor 1 and the carrier device
Inside can be prevented. In the image forming apparatus of the above embodiment,
When the high-voltage power supply 10 for developing bias is turned off,
0 V when the developing sleeve 4 is at the ground potential
Or photoreceptor that has a slight potential due to residual charge
A small amount of toner may be developed on the surface of No. 1. This
In order to prevent the development of the toner of
When the area is opposed to the developing sleeve 4,
The potential difference between the surface potential and the potential of the developing sleeve 4 is determined by the photosensitive member.
1 when the charged region faces the developing sleeve 4
Polarity opposite to the charged potential so that the properties and size are the same
May be applied to the developing sleeve 4. FIG. 4 shows that the uncharged area of the photosensitive member 1 is
Voltage opposite to the charging polarity when facing
Of image formation control in image forming apparatus
FIG. At the start of image formation of this image forming apparatus
Press the start button to open the rotation drive of the photoconductor 1.
And at the same time, turn on the high voltage power supply 10 for developing bias
And a first developing bias voltage V1 having a polarity opposite to the charging potential.
Starts to be applied to the developing sleeve 4. After that, charge high
To turn on the voltage source 9 to start uniform charging of the surface of the photoreceptor 1
You. The charging start end of the photoreceptor surface is
Voltage applied to the developing sleeve 4 when facing the developing sleeve 4
The normal second current from the first developing bias voltage V1
Switch to image bias voltage V2. Also, the image formation ends
At times, the charging high-voltage power supply 9 is turned off and the photosensitive
After the charging is completed, the end of charging on the photoreceptor surface is
The electric charge applied to the developing sleeve 4 when facing the sleeve 4
From the second developing bias voltage V2 to the first developing bias.
Switch to the bias voltage V1. Then, the entire surface of the photoconductor 1
Turns off the rotation drive of the photoreceptor 1 when is removed
At the same time, the high-voltage power supply 10 for developing bias is turned off.
You. As described above, the development applied to the development sleeve 4
When switching the bias voltage,
When the development bias voltage is
The potential of the photoconductor surface passing through the position facing the
Under the condition that the pair value is equal to or less than the absolute value of the developing bias voltage,
So that the value of the charging potential approaches the value of the developing bias voltage.
Set ON / OFF timing of high voltage power supply 9, 10
You. As a result, when the voltage is switched, the key to the photoconductor 1 is changed.
Carrier can be reliably prevented, and
Minimize toner adhesion and prevent wasteful toner consumption
You. In the above embodiment, the photosensitive member 1 and the
Adopted a reversal development method in which the charging potential of the toner is negative.
Although the image forming apparatus has been described, the present invention
It can be applied without being limited to the charging polarity. For example, feeling
A reversal developing method in which the charging potential of the photoconductor 1 and the toner is positive.
The same effect can be obtained when the formula is adopted.
Things. [0043] Claims of the InventionOneAccording to the invention, image formation is started
Power supply for developing bias in operation and image formation end operation
ON / OFFKiniThe developing bias voltage changes transiently.
During charging, charge to the opposite polarity to the charge potential on the image carrier
Carrier is transferred from the developer carrier to the image carrier surface.
MoveRudenA field is formed between the image carrier and the developer carrier.
The carrier on the developer carrier is attached to the image carrier.
And prevent contamination of the equipment by the carrier.
There is an effect that. Further, an image forming start operation and an image forming end
When the power supply for developing bias is turned on / off during operation
Kini, Toner of the same polarity as the developing bias voltage
The time for forming an electric field that transfers to the surface is shortened.
As a result, toner adhesion to the image carrier is minimized and wasteful toner
There is an effect that the consumption of the corner can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. FIG. 2 is a time chart of control of the image forming apparatus. FIGS. 3A and 3B are explanatory diagrams showing a relationship between a change in a charged potential of a photoconductor and a change in a developing bias voltage of the image forming apparatus. FIG. 4 is a time chart of control of an image forming apparatus according to a modification. [Description of Signs] 1 Photoconductor 2 Charging device 4 Developing sleeve 5 Developing device 9 High voltage power supply 10 for charging High voltage power supply 11 for developing bias 11 Control device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/06-13/095 G03G 15/06-15/095

Claims (1)

(57) Claims 1. A charging member having a charging member for uniformly charging the surface of an image carrier, a charging power supply for applying a voltage to the charging member, and Exposure means for attenuating the potential of the charged image carrier by image exposure to form an electrostatic latent image on the image carrier, a toner charged to the same polarity as the charging polarity of the charging means, and the charging means Developing means having a developer carrier for carrying a two-component developer containing a carrier charged to a polarity opposite to the polarity, and a developing bias power supply for applying a developing bias voltage having the same polarity as the charged polarity to the developer carrier. Wherein the application of a developing bias voltage to the developer carrier starts when the charging start end of the image carrier surface faces the developer carrier, and the surface of the image carrier is End of the charging roller faces the developer carrying member. Developing as application of the bias voltage is stopped, ON the power and power for developing bias the charging when
/ Control means for OFF control is provided, the developing Ba by ON / OFF of the developing bias power supply
The period during which the bias voltage is transiently changed, and the surface of the image carrier
Of the surface of the image carrier at the charging start end or the charging end end of
The period during which the absolute value of
And where the two periods overlap, the image carrier
The absolute value of the surface potential is equal to or less than the absolute value of the developing bias voltage.
An ON / OFF timing of the charging power supply and the developing bias power supply so as to be as follows.