JP2003280483A - Image forming apparatus and copying machine using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To drastically reduce toner consumption which is cause by toner sticking in a black band at the time of the start of the machine and at the time of the stop of the machine or to restrict sticking of carrier to a photoreceptor. <P>SOLUTION: In the copying machine, a photoreceptor 1 and a developing roll 3 are constituted so as to be drivable independently of each other. When the machine is started, rotation of the developing roll 3 is stopped during the passage of the leading end of an electrified part of the surface of the photoreceptor 1 through a nip area d-e, and the rotation of the developing roll 3 is started before the leading end of an image formation allowable area reaches the nip area d-e. Conversely when the machine is stopped, control is exerted so that the rotation of the developing roll 3 is stopped before the back end of the electrified part reaches the nip area d-e after the passage of the back end of the image formation allowable area of the surface of the photoreceptor 1 through the nip area d-e. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic recording system and a copying machine using the same.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus of this type and a copying machine using the same have been as follows.

That is, in the developing process employing the electrophotographic recording system, the charger is arranged to face the photoconductor, and the surface of the photoconductor is charged to a negative potential by applying a negative voltage from the charger ( For example, the surface potential Va = −75
0 [V]). Furthermore, the surface of the photoconductor charged to a negative potential is
An electrostatic latent image is formed by exposure. The latent image forming portion has a higher potential than the non-latent image portion (for example, the potential VL of the latent image forming portion = -100 [V]).

A developing device is provided downstream of the charging device in the rotational direction of the photosensitive member. When a bias voltage is applied to the magnet roller of the developing device and the surface of the photoconductor on which the electrostatic latent image is formed passes near the magnet roller, toner adheres from the magnet roller to the latent image forming portion.

Further, a transfer device is arranged further downstream than the magnet roller. By applying a positive charge from the opposite side of the recording surface of the recording paper, the toner in the latent image forming portion is transferred to the recording paper. In this way, the toner adheres to the recording paper to form an image.

By the way, in the developing process, the toner attached to the surface of the magnet roller is negatively charged, and is uniformly attached to the surface of the magnet roller while being carried by the carrier which is positively charged. In order to cause the toner to jump to the latent image forming portion on the surface of the photoconductor, a bias voltage having a lower potential than the latent image forming portion but higher than the non-latent image area is applied to the magnet roller. Particularly, recently, in order to improve the developing ability, a DC component (for example, -550 [V]) is used as the bias voltage of the magnet roller.
A (DC + AC) bias method in which an AC component (for example, 1.5 k [V]) is superimposed on the DC voltage has been adopted.

On the other hand, if the carrier of the magnet roller jumps to the photosensitive member, the carrier damages the surface of the photosensitive member and the life of the photosensitive member is shortened, which is not preferable. Therefore, the present inventors have developed a technique for preventing carrier adhesion to the photoconductor by controlling the bias voltage application start timing and application stop timing when the machine is started and stopped. The carrier adhesion prevention measures developed by the present inventors will be specifically described below.

When the machine is started up, the charger is driven when the photosensitive member comes to a stable rotation. However, a nip region between the charged photosensitive member surface and the magnet roller (the photosensitive member surface and the development held on the magnet roller). The surface of the photoconductor in the vicinity of the magnet roller is 0 [V] until the area in contact with the agent reaches the nip area. Therefore, if the bias voltage of the magnet roller is turned on at the same time when the charging device is turned on, the entire surface of the photoconductor passing through the nip region becomes a high potential (relatively higher by 550 [V]) and before the start of exposure. Toner adheres to the non-image forming area, and a black area is recorded before the image forming area. On the other hand, in order to prevent the toner from adhering to the non-image forming area, the bias voltage of the magnet roller is applied after the surface of the photoconductor charged to the negative potential Va completely passes through the nip area between the magnet roller and the non-image forming area. It should be turned on, but with this, a part of the surface of the photoconductor charged to Va (= -750 [V]) before turning on the bias voltage (when the developing roll side is 0 [V]) passes through the nip area. Because
At this time, there arises a problem that the carrier adheres to the photoconductor.

Therefore, conventionally, the bias voltage of the magnet roller is turned on immediately before the tip of the charging portion charged to the negative potential Va by the charger reaches the nip area with the magnet roller, thereby preventing carrier adhesion and producing black. The area was prevented from expanding.

Even when the machine is stopped, the same problem as when the machine is started occurs. Therefore, the bias voltage of the magnet roller is turned off immediately after the trailing end of the charging portion charged to Va by the charger passes through the nip area with the developing roller. Was.

[0011]

However, the conventional technique has the following problems. That is, if a phenomenon that toner adheres in a black band occurs each time the machine is started and stopped, useless toner that is not directly related to image recording is consumed, so that the toner consumption amount increases. There was a problem.

[0012] Therefore, the present invention has been made in view of the above problems, and therefore, the toner consumption due to the black belt-shaped toner adhering at the time of machine start-up and machine stop can be significantly reduced, or An object of the present invention is to provide an image forming apparatus and a copying machine capable of extending the life of the photoconductor by suppressing the carrier from adhering to the photoconductor.

[0013]

According to the present invention, when the machine starts, the rotational driving of the developing means is stopped when the tip of the charging portion on the surface of the photoconductor passes through the nip area, and the tip of the image forming area is at the nip area. When the machine is stopped, the rear end of the charging unit is in the nip region after the rear end of the image forming area on the surface of the photoconductor has passed the nip region. It is controlled so that the rotational drive of the developing means is stopped before the arrival.

As a result, the rotation of the developing means is stopped when the black band is generated when the machine is started and stopped, so that it is possible to suppress the toner consumption due to the generation of the black band.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In a first aspect of the present invention, a photosensitive member, a charging unit for charging the surface of the photosensitive member, an exposing unit for exposing an imageable area of the charged surface of the photosensitive member, and exposing Developing means for adhering toner to the exposed portion, driving means for driving the developing means separately from the photosensitive member, charging by the charging means is started at the start of the recording operation, and the charging portion causes the photosensitive member and the developing portion to develop. And a control unit for applying a bias voltage in a state where the driving of the developing unit is stopped before entering the nip region with the unit.

According to the present invention having such a configuration, the photoconductor and the developing means are driven separately and independently, and the developing is performed before the charging portion enters the nip region between the photoconductor and the developing means. By applying a bias voltage to the developing unit while stopping the driving of the unit, the surface of the photoconductor is not covered until the charging unit reaches the nip region after the bias voltage is applied to the developing unit. Although the toner adheres in a black band shape, since the surface of the developing means facing the photoconductor is the same surface, after the toner jumps from the same surface to the photoconductor, the toner moves from the same surface to the photoconductor. Even if the toner runs out and the photoconductor rotates, the phenomenon in which toner newly flies is suppressed. As a result, even if the surface of the photoconductor passing through the nip region has a high potential with respect to the developing unit, the amount of toner attached to the photoconductor decreases as the rotation of the photoconductor progresses, and the toner is wasted. The amount can be reduced.

A second aspect of the present invention is a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an image forming area on the charged surface of the photoconductor, and a toner for the exposed portion. And a driving means for driving the developing means separately from the photoconductor, and at the start of the recording operation, charging by the charging means is started, and the charging part causes the nip between the photoconductor and the developing means. An image forming apparatus including a control unit that applies a bias voltage with the driving of the developing unit stopped before entering the area and drives the developing unit before the exposing unit exposes the image forming area. It is a device.

According to the present invention having such a configuration, the photoconductor and the developing means are driven separately and independently, and the developing unit is operated before the charging portion enters the nip region between the photoconductor and the developing means. By applying a bias voltage to the developing unit while stopping the driving of the unit, the surface of the photoconductor is not covered until the charging unit reaches the nip region after the bias voltage is applied to the developing unit. Although the toner adheres in a black band shape, since the surface of the developing means facing the photoconductor is the same surface, after the toner jumps from the same surface to the photoconductor, the toner moves from the same surface to the photoconductor. Even if the toner runs out and the photoconductor rotates, the phenomenon in which toner newly flies is suppressed. As a result, even if the surface of the photoconductor passing through the nip region has a high potential with respect to the developing unit, the amount of toner attached to the photoconductor decreases as the rotation of the photoconductor progresses, and the toner is wasted. The amount can be reduced. Further, since the developing means is driven before the exposing means exposes the image forming area, the developing means having the toner uniformly attached to the surface thereof faces the photoconductor before the exposing area reaches the nip area. And is well developed.

A third aspect of the present invention is a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an imageable area on the charged surface of the photoconductor, and a toner for the exposed portion. And a driving means for driving the developing means separately from the photoconductor, and at the end of the recording operation, after the trailing edge of the image forming area in the image forming area passes through the nip area, the developing operation is performed. And a control unit that stops the driving of the developing unit with a bias voltage applied to the unit.

According to the present invention having such a configuration, the photosensitive member and the developing means are independently driven, and the rear end of the image forming area in the charged image forming area is the photosensitive member. After passing through the nip region with the developing unit, by stopping the driving of the developing unit in a state where a bias voltage is applied to the developing unit, after the rear end of the imageable region passes through the nip region, Toner adheres to the surface of the photoconductor in the form of a black band, but since the surface of the developing unit facing the photoconductor is on the same surface, the amount of toner on the same surface decreases due to the adhesion of the toner to the photoconductor. To do. As a result, even if the surface of the photoconductor passing through the nip region has a high potential with respect to the developing unit, the amount of toner attached to the photoconductor decreases as the rotation of the photoconductor progresses, and the toner is wasted. The amount can be reduced.

A fourth aspect of the present invention is a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an imageable area of the charged surface of the photoconductor, and a toner for the exposed portion. And a driving means for driving the developing means separately from the photoconductor, and at the end of the recording operation, after the trailing edge of the image forming area in the image forming area passes through the nip area, the developing operation is performed. And a control means for stopping the driving of the developing means in a state in which the bias voltage is applied to the developing means, and turning off the bias voltage of the developing means after the trailing end of the charging unit passes through the nip region. Is.

According to the present invention having such a configuration, the photosensitive member and the developing means are independently driven, and the rear end of the image forming area in the charged image forming area is the photosensitive member. After passing through the nip region with the developing unit, by stopping the driving of the developing unit in a state where a bias voltage is applied to the developing unit, after the rear end of the imageable region passes through the nip region, Toner adheres to the surface of the photoconductor in the form of a black band, but since the surface of the developing unit facing the photoconductor is on the same surface, the amount of toner on the same surface decreases due to the adhesion of the toner to the photoconductor. To do. As a result, even if the surface of the photoconductor passing through the nip region has a high potential with respect to the developing unit, the amount of toner attached to the photoconductor decreases as the rotation of the photoconductor progresses, and the toner is wasted. The amount can be reduced. Further, since the bias voltage of the developing means is turned off after the rear end of the charging section passes through the nip area, carrier jump can be prevented from occurring and the photoreceptor can be prevented from being damaged.

A fifth aspect of the present invention is a photoconductor, a charging unit for charging the surface of the photoconductor, an exposing unit for exposing an image forming area on the charged surface of the photoconductor, and a toner for the exposed portion. And a driving means for driving the developing means separately from the photoconductor, and at the start of the recording operation, charging by the charging means is started, and the charging part causes the nip between the photoconductor and the developing means. An image forming apparatus including: a control unit that applies a bias voltage of a DC component while the driving of the developing unit is stopped before entering the area.

According to the present invention having such a configuration, the photoconductor and the developing means are driven separately and independently, and the development is performed before the charging portion enters the nip region between the photoconductor and the developing means. By applying a bias voltage of a DC component to the developing means while the driving of the means is stopped, the photosensitive member of the photoconductor can be operated from the time when the bias voltage is applied to the developing means until the charging unit reaches the nip region. Toner adheres to the surface in the form of a black band, but since the surface of the developing unit facing the photoconductor is on the same surface, the amount of toner on the same surface decreases due to the adhesion of the toner to the photoconductor. As a result, even if the surface of the photoconductor passing through the nip region has a high potential with respect to the developing unit, the amount of toner attached to the photoconductor decreases as the rotation of the photoconductor progresses, and the toner is wasted. The amount can be reduced.

Further, since the bias voltage applied to the developing means before the charging portion enters the nip region between the photoconductor and the developing means is only the DC component, only the DC component is applied, and the black band-like shape is generated at the start of the recording operation. It is possible to reduce the amount of useless toner that adheres to the carrier and prevent carrier adhesion.

A sixth aspect of the present invention is a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an imageable area on the charged surface of the photoconductor, and a toner for the exposed portion. And a driving means for driving the developing means separately from the photoconductor, and at the start of the recording operation, charging by the charging means is started, and the charging part causes the nip between the photoconductor and the developing means. A bias voltage of DC component is applied in a state where the driving of the developing unit is stopped before entering the area, and the developing unit is driven before the exposing unit exposes the image forming area, and AC is applied to the DC component. An image forming apparatus comprising: a control unit that applies a bias voltage in which components are superimposed to the developing unit.

According to the present invention having such a configuration, the photoconductor and the developing means are driven separately and independently, and the development is performed before the charging portion enters the nip region between the photoconductor and the developing means. By applying a bias voltage of a DC component to the developing means while the driving of the means is stopped, the photosensitive member of the photoconductor can be operated from the time when the bias voltage is applied to the developing means until the charging unit reaches the nip region. Toner adheres to the surface in the form of a black band, but since the surface of the developing unit facing the photoconductor is on the same surface, the amount of toner on the same surface decreases due to the adhesion of the toner to the photoconductor. As a result, even if the surface of the photoconductor passing through the nip region has a high potential with respect to the developing unit, the amount of toner attached to the photoconductor decreases as the rotation of the photoconductor progresses, and the toner is wasted. The amount can be reduced.

Further, since the bias voltage applied to the developing means before the charging portion enters the nip region between the photoconductor and the developing means is only the DC component, only the DC component is applied, and the black band-like shape is generated at the start of the recording operation. It is possible to reduce the amount of useless toner that adheres to the carrier and prevent carrier adhesion. Further, before the exposing means exposes the image forming area, the developing means is driven and a bias voltage in which the AC component is superimposed on the DC component is applied to the developing means.
When the imageable area reaches the nip area (DC + A
C) Since it has a bias voltage, high developing ability can be exhibited.

A seventh aspect of the present invention is a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an imageable area on the charged surface of the photoconductor, and a toner for the exposed portion. To the developing means, a driving means for driving the developing means separately from the photoconductor, and a DC voltage to the developing means while the image forming area passes through the nip area between the photoconductor and the developing means. A bias voltage in which an AC component is superimposed on the component is applied, and at the end of the recording operation, after the trailing edge of the image forming area in the image forming area passes through the nip area, the bias voltage of the AC component to the developing unit. Is turned off to stop the driving of the developing means, and the image forming apparatus.

According to the present invention having such a configuration, the photosensitive member and the developing means are driven separately and independently, and the rear end of the image forming area in the charged image forming area is the photosensitive member. AC to the developing means after passing through the nip area with the developing means
By turning off the bias voltage of the component and stopping the driving of the developing unit, after the rear end of the image forming area passes through the nip area, the toner adheres to the surface of the photoconductor in a black band shape. Since the surface of the developing unit facing the photoconductor is on the same surface, the amount of toner on the same surface is reduced by the adhesion of toner to the photoconductor. As a result, even if the surface of the photoconductor passing through the nip region has a high potential with respect to the developing unit, the amount of toner attached to the photoconductor decreases as the rotation of the photoconductor progresses, and the toner is wasted. The amount can be reduced.

Further, when the machine is stopped, the bias voltage of the AC component to the developing means is turned off after the trailing edge of the image forming area passes through the nip area, so that only the DC component is applied and a black band is formed at the end of the recording operation. It is possible to reduce the amount of useless toner that adheres and prevent carrier adhesion.

An eighth aspect of the present invention is directed to a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an image forming area on the charged surface of the photoconductor, and a toner for the exposed portion. To the developing means, a driving means for driving the developing means separately from the photoconductor, and a DC voltage to the developing means while the image forming area passes through the nip area between the photoconductor and the developing means. A bias voltage in which an AC component is superimposed on the component is applied, and at the end of the recording operation, after the trailing edge of the image forming area in the image forming area passes through the nip area, the bias voltage of the AC component to the developing unit. Is turned off to stop the driving of the developing means, and to turn off the bias voltage of the DC component to the developing means after the trailing end of the charging section has passed through the nip region. is there.

According to the present invention having such a configuration, the photosensitive member and the developing means are driven separately and independently, and the trailing end of the image forming area in the charged image forming area is the photosensitive member. AC to the developing means after passing through the nip area with the developing means
By turning off the bias voltage of the component and stopping the driving of the developing unit, the toner adheres to the surface of the photoconductor in the form of a black band after the rear end of the image forming area passes through the nip area. Since the surface of the developing unit facing the photoconductor is on the same surface, the amount of toner on the same surface is reduced by the adhesion of toner to the photoconductor. As a result, even if the surface of the photoconductor passing through the nip region has a high potential with respect to the developing unit, the amount of toner attached to the photoconductor decreases as the rotation of the photoconductor progresses, and the toner is wasted. The amount can be reduced.

Further, since the bias voltage of the AC component to the developing means is turned off after the trailing edge of the image forming area passes through the nip area when the machine is stopped, only the DC component is applied, and a black band is formed at the end of the recording operation. It is possible to reduce the amount of useless toner that adheres and prevent carrier adhesion. Further, since the bias voltage of the DC component to the developing means is turned off after the rear end of the charging section passes through the nip area, carrier jump can be prevented and the photoreceptor can be prevented from being damaged.

A ninth aspect of the present invention is a photosensitive member, a charging unit for charging the surface of the photosensitive member, an exposing unit for exposing an image forming area on the charged surface of the photosensitive member, and a toner for the exposed portion. And a driving means for driving the developing means separately from the photoconductor, and at the start of the recording operation, charging by the charging means is started, and the charging part causes the nip between the photoconductor and the developing means. And a control means for applying a bias voltage while the driving of the developing means is stopped before entering the area.

According to the present invention having such a configuration, the same operation and effect as those of the image forming apparatus of the first aspect can be obtained.

A tenth aspect of the present invention is to provide a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an image forming area on the charged surface of the photoconductor, and a toner for the exposed portion. And a driving means for driving the developing means separately from the photoconductor, and at the start of the recording operation, charging by the charging means is started, and the charging part causes the nip between the photoconductor and the developing means. And a control means for applying a bias voltage with the driving of the developing means stopped before entering the area and driving the developing means before the exposing means exposes the imageable area. Is.

According to the present invention having such a configuration, the same operational effect as that of the image forming apparatus of the second aspect can be obtained.

An eleventh aspect of the present invention is a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an imageable area on the charged surface of the photoconductor, and a toner for the exposed portion. And a driving means for driving the developing means separately from the photoconductor, and at the end of the recording operation, after the trailing edge of the image forming area in the image forming area passes through the nip area, the developing operation is performed. And a control means for stopping the driving of the developing means in the state where a bias voltage is applied to the means.

According to the present invention having such a configuration, the same operational effects as those of the image forming apparatus of the third aspect are exhibited.

A twelfth aspect of the present invention is directed to a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an image forming area on the charged surface of the photoconductor, and a toner for the exposed portion. And a driving means for driving the developing means separately from the photoconductor, and at the end of the recording operation, after the trailing edge of the image forming area in the image forming area passes through the nip area, the developing operation is performed. And a control means for stopping the driving of the developing means in a state in which a bias voltage is applied to the means and for turning off the bias voltage of the developing means after the trailing end of the charging unit has passed through the nip region. is there.

According to the invention configured as described above, the fourth
The same operational effects as those of the image forming apparatus of this aspect are exhibited.

A thirteenth aspect of the present invention is to provide a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an image forming area of the charged surface of the photoconductor, and a toner for the exposed portion. And a driving means for driving the developing means separately from the photoconductor, and at the start of the recording operation, charging by the charging means is started, and the charging part causes the nip between the photoconductor and the developing means. And a control means for applying a bias voltage of a DC component while the driving of the developing means is stopped before entering the area.

According to the present invention having such a configuration, the same operational effects as those of the image forming apparatus of the fifth aspect are exhibited.

A fourteenth aspect of the present invention is to provide a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an imageable area on the charged surface of the photoconductor, and a toner for the exposed portion. And a driving means for driving the developing means separately from the photoconductor, and at the start of the recording operation, charging by the charging means is started, and the charging part causes the nip between the photoconductor and the developing means. A bias voltage of DC component is applied in a state where the driving of the developing unit is stopped before entering the area, and the developing unit is driven before the exposing unit exposes the image forming area, and AC is applied to the DC component. And a control means for applying a bias voltage having components superposed thereon to the developing means.

According to the present invention having such a configuration, the same operational effects as those of the image forming apparatus of the sixth aspect are exhibited.

A fifteenth aspect of the present invention is a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an imageable area on the charged surface of the photoconductor, and a toner for the exposed portion. To the developing means, a driving means for driving the developing means separately from the photoconductor, and a DC voltage to the developing means while the image forming area passes through the nip area between the photoconductor and the developing means. A bias voltage in which an AC component is superimposed on the component is applied, and at the end of the recording operation, after the trailing edge of the image forming area in the image forming area passes through the nip area, the bias voltage of the AC component to the developing unit. Is turned off to stop the driving of the developing means, and the copying machine.

According to the present invention having such a configuration, the same operation and effect as those of the image forming apparatus of the seventh aspect are exhibited.

A sixteenth aspect of the present invention is a photoconductor, a charging means for charging the surface of the photoconductor, an exposing means for exposing an imageable area on the charged surface of the photoconductor, and a toner for the exposed portion. To the developing means, a driving means for driving the developing means separately from the photoconductor, and a DC voltage to the developing means while the image forming area passes through the nip area between the photoconductor and the developing means. A bias voltage in which an AC component is superimposed on the component is applied, and at the end of the recording operation, after the trailing edge of the image forming area in the image forming area passes through the nip area, the bias voltage of the AC component to the developing unit. Is turned off to stop the driving of the developing means, and after the trailing end of the charging section has passed through the nip region, the control means for turning off the bias voltage of the DC component to the developing means is provided. .

According to the present invention having such a configuration, the same operational effects as those of the image forming apparatus of the eighth aspect are exhibited.

An embodiment of an image forming apparatus and a copying machine according to the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a configuration diagram of a portion related to an electrophotographic process in an image forming unit provided in the copying machine according to the present embodiment. The copying machine shown in FIG. 1 includes a photoconductor 1 exposed by an exposure device (not shown), a charger 2 for charging the surface of the photoconductor 1, a developing roll 3 rotatably held by a developing unit, A transfer device 4 for transferring the toner image adhering to the surface of the photoconductor to the recording paper, and a charge eliminating unit 5 for eliminating the charge on the surface of the photoconductor are provided. In the present embodiment, the photoconductor 1 and the developing roll 3 can be independently and rotationally driven by the configuration described later. These electrophotographic process components are controlled by the electrophotographic process control block 10.

The electrophotographic process control block 10 includes a charging voltage controller 11 for controlling ON / OFF of the charging voltage of the charger 2, a bias voltage controller 12 for controlling the bias voltage of the developing roll 3, and a transfer of the transfer device 4. ON / OF of voltage
A transfer voltage control unit 13 for controlling F, a photoconductor drive control unit 14 for controlling rotary drive of the photoconductor 1, and a developing roll drive control unit 15 for controlling rotary drive of the developing roll 3 are provided.

In particular, a motor M1 is provided as a drive source for rotationally driving the photoconductor 1, and a motor M2 is provided as a drive source for rotationally driving the developing roll 3. And the motor M1
Is controlled by the photoconductor drive control unit 14, and the motor M2 is controlled by the developing roll drive control unit 15 independently of the rotational drive of the photoconductor 1.

The number of driving sources for rotating the photoconductor 1 and the developing roll 3 may be one, but a means for enabling the photoconductor 1 and the developing roll 3 to be driven and controlled independently of each other is a transmission mechanism. Need to be installed in the middle of.

In the copying machine, in addition to the electrophotographic process control block 10, a fixing temperature control unit for controlling the fixing unit, an exposure device for exposing a latent image on the photoconductor, and a conveyance drive control block for controlling the conveyance of recording paper. Etc., and the whole is controlled by the controller 17.

Next, the electrophotographic process control block 10
Bias voltage control unit 12 and photoconductor drive control unit 14
Details of control performed by the developing roll drive control unit 15 will be described.

FIG. 2 is a timing chart of the bias voltage, the charging voltage and the like from the time the machine is started to the time it is stopped in the case of one copy. At time t0, a start key (not shown) on the operation panel is pressed, and then at time t1, the photoconductor drive control unit 14 starts driving the motor M1.

At time t2 when the photosensitive member 1 to which the rotational driving force of the motor M1 is transmitted becomes stable, the charging voltage control unit 11 controls the charging device 2 to cause the photosensitive member 1 to face the a-b portion. Then, the application of the charging voltage (Va = −750 [V]) is started. As a result, the facing portion a− between the charger 2 and the photoreceptor 1
The surface of the photoconductor passing through b is charged to -750 [V].
This charging portion enters between d and e which is a nip region between the photoconductor 1 and the developing roll 3 by the rotation of the photoconductor 1.

In this embodiment, as shown in FIG. 3, at the time t3 immediately before the tip of the charging unit in the photosensitive member rotation direction reaches the nip region d-e, the bias voltage control unit 1 is operated.
2 causes the developing roll 3 to have a DC component (Vb
= -550 [V]) is applied.

At time t3, the potential of the surface of the photosensitive member in the nip area de is 0 [V] because it is the surface of the photosensitive member immediately before the charging portion charged to −750 [V], and thus the developing roll 3 The toner that has adhered to the surface of and is charged at −550 [V] will adhere to the surface of the photoconductor in the nip area de. Immediately after that, the charged portion of −750 [V] enters the nip area d−e, so that the developing potential in the nip area de is −550 [V] (Va = 0 [V]) to +20.
It rises to 0V (= -550-(-750)). Therefore, after that, the adhesion of the toner to the surface of the photoconductor stops.
As a result, the toner adheres to the surface of the photoconductor in the nip area d-e in a black band shape.

At this time, the amount of toner adhered to the surface of the photoconductor is
It depends on the relative potential between the surface of the photoconductor and the surface of the developing roll in the nip regions d-e. In this embodiment,
By making the bias voltage of the developing roll 3 only the DC component, the AC component was superimposed on the DC component, which has a significantly higher developing ability than when only the DC component is applied (DC + AC).
As compared with the case where the bias voltage is applied, the toner adhesion amount can be significantly reduced.

Further, in the present embodiment, as shown in FIG. 2, when the rotational driving of the photoconductor 1 is started at time t1, the developing roll 3 is rotationally driven by a drive system different from the photoconductor 1.
Has not been driven to rotate. The developing roll 3 is rotationally driven at time t4 after the leading end of the charging unit has passed through the nip region d-e and before the leading end of the image forming region reaches the nip region d-e. To control.

FIG. 4 is a diagram showing the relationship between the image of the amount of toner developed on the surface of the photoconductor 1 at the time of startup, the bias voltage of the developing roll 3, and the rotational driving timing of the photoconductor 1 and the developing roll 3. A region R1 shown in the figure is an uncharged portion immediately before the DC component of the bias voltage is applied, and a region R2 is the tip of the charging portion at the point e of the nip region d-e after the DC component of the bias voltage is applied. The region R3 is a region corresponding to the period until reaching, and the region R3 is a region from the tip of the charging unit to the image forming region. As shown in the figure, the rotation of the developing roller 3 is stopped until the area R2 where the black band at the tip of the charging portion is generated completely passes through the nip area d-e. Then, at time t4 when the area R3 immediately before the image forming area is reached, the rotational driving of the developing roller 3 is started.

As a result, the developing roll 3 is stopped rotating while the surface of the photosensitive member, which is 0 [V] immediately before the charging portion, passes through the nip area d-e. Will continue to face the surface of the photoconductor. Here, most of the toner that jumps from the developing roll 3 to the side of the photoconductor 1 is the toner attached to the position facing the photoconductor 1. Therefore, immediately after the bias voltage of the DC component is applied to the developing roll 3, the toner adhering to the position facing the photoconductor 1 jumps to the photoconductor 1 side. Since the toner runs out, the amount of toner that jumps from the developing roll 3 to the photoconductor 1 is extremely reduced.

FIGS. 5A and 5B show comparative examples of toner consumption in the black band portion. FIG. 5A shows the toner consumption amount according to the present embodiment, and FIG. 5B shows the toner consumption amount when the developing roll is rotated as in the conventional case. Note that it is difficult to actually compare the toner consumption amounts, so the comparison is made as the image density when the toner attached to the photoconductor 1 is recorded on the recording paper. As shown in FIG. 7A, when the developing roll 3 is stopped as in the present embodiment, the toner consumption is almost completely lost in the latter half of the black band, but shown in FIG. As described above, when the developing roll 3 is rotated, the toner consumption amount is not reduced. This is because when the developing roll 3 is rotated, even if the toner on the facing surface facing the photoconductor 1 when the bias voltage is applied runs out, another toner adheres as the developing roll 3 rotates. It is considered that the roll surface becomes a new facing surface and the toner is continuously supplied.

In this way, the photoconductor 1 and the developing roll 3 are independently driven, and the developing roll is moved before the charging portion enters the nip region d-e between the photoconductor 1 and the developing roll 3. By applying a bias voltage to the developing roll 3 while the driving of the developing roller 3 is stopped, the photosensitive member is exposed from the application of the bias voltage to the developing roll 3 until the charging unit reaches the nip region de. Toner adheres to the surface of the body 1 in a black band, but since the surface of the developing roll 3 facing the photoconductor 1 is the same surface, after the toner jumps from the same surface to the photoconductor 1, The toner that moves from the same surface to the photoconductor 1 disappears, and even if the photoconductor 1 rotates, a phenomenon in which toner newly jumps is suppressed. as a result,
The surface of the photoconductor passing through the nip area de is the developing roll 3
On the other hand, even if the potential is high, the amount of toner adhering to the photoconductor 1 decreases as the rotation of the photoconductor 1 progresses, and the amount of wasteful toner consumption can be reduced.

Further, as shown in FIG. 2, when a predetermined time elapses after the DC component of the bias voltage is applied to the developing roll 3, the rotation of the photoconductor 1 corresponds to the leading end position of the paper size on the photoconductor surface. Part reaches the exposure position,
When a predetermined time corresponding to the image start position elapses from the leading edge of the sheet and time t5 is reached, the portion corresponding to the leading position of the image size reaches the exposure position.

The exposure apparatus completes preparation for electrostatic latent image formation by exposure by time t5, and starts electrostatic latent image formation from the leading edge of the image size in which the image appears. The exposed portion of the surface of the photosensitive member is charged to a potential such that toner adheres but carrier does not adhere.

On the other hand, the time t when the portion corresponding to the leading edge of the image size on the surface of the photoconductor reaches the nip area de.
At 6, when the bias voltage controller 12 determines the bias voltage of the developing roller 3 from the DC component up to that point,
The control for superimposing the C component is started. That is, before the latent image starting point on the surface of the photoconductor reaches the nip area de by the rotation of the photoconductor 1, the AC component of the bias voltage is changed to D
Superimpose it on the C component.

As a result, when the latent image start point in the image forming area corresponding to the image size passes through the nip area d-e, the DC component has a developing ability higher than the DC component of the bias voltage. Development is performed by the bias voltage on which the AC component is superimposed.

In the above description, the AC component is superimposed on the bias voltage for the developing roll 3 when the head of the image forming area corresponding to the image size reaches the point d of the nip area d-e. When the latent image is not formed from the head of the image forming area, the AC component may be superimposed on the bias voltage after waiting until just before the latent image start point.
Thereby, unnecessary adhesion of toner and carrier can be further reduced.

When the head of the image forming area (or the latent image starting point) reaches the point d of the nip area d-e due to the rotation of the photosensitive member 1, the AC component is superimposed on the DC component of the bias voltage. However, it is necessary to apply the AC component of the bias voltage earlier in consideration of the rise time. Therefore, at time t3 and time t6, the bias voltage AC
If the rising time of the component is slower than the rotation speed of the photoconductor 1, it may be reversed.

FIG. 6 shows a potential change on the surface of the photoconductor at the time of starting the machine. R1, R2 and R3 shown in FIG.
Corresponds to R1, R2 and R3 shown in FIG. In the region R2, black belt-shaped toner adhesion occurs due to the DC component of the bias voltage. The section of the region R2 is the nip region d.
Since the relative potential between the surface of the photoreceptor and the developing roller 3 at −e is 550 [V] (the surface of the photoreceptor is on the high potential side), the toner is attached. Further, in the area R3 corresponding to the charging portion, the relative potential between the surface of the photoconductor and the developing roll 3 in the nip area de falls to 200 [V] (the surface of the photoconductor is at the high potential side), and toner is attached. Is gone. Then, in the image forming area, a bias voltage in which an AC component is superimposed on a DC component of the bias voltage (DC + AC) is applied.

As described above, since the developing device 3 drives the developing roll 3 before exposing the image forming area, the toner uniformly adheres to the surface before the exposing area reaches the nip area d-e. The developing roll 3 faces the photoconductor 1 and is well developed.

Next, the bias voltage control when the machine is stopped will be described. Time t in the timing chart shown in FIG.
At 7, the latent image formation by the exposure of one page on the photoconductor 1 is completed.

After the latent image formation is completed, the rear end of the image forming area passes the point e of the nip area d-e due to the rotation of the photosensitive member 1, but in the present embodiment, the rear end of the image forming area is formed. At time t8 after the point e has passed, the bias voltage control unit 12 performs voltage control so that only the AC component of the bias voltage is turned off in advance.

Further, the rear end of the charging portion is the nip area d-e.
The developing roll drive controller 15 controls to stop the rotational driving of the developing roll 3 at time t9 before reaching point d. At this time, the photoconductor 1 keeps rotating.

After that, at time t10, the charging voltage controller 11 turns off the charging voltage of the charger 2. After the charging voltage is turned off, the charging potential V0 of the surface of the photoconductor passing through the facing portions ab of the charger 2 becomes 0 [V]. This 0
The DC component of the bias voltage is turned off at time t11 immediately after the boundary between the charging portion of [V] and the charging portion of −750 [V] has passed the point e of the nip area d-e due to the rotation of the photoconductor 1. In addition, the bias voltage controller 12 performs voltage control.
Further, the rotation drive of the photoconductor 1 is stopped at time t12 when the charging unit of 0 [V] passes the point i which is the facing portion of the charge removal unit 5 due to the rotation of the photoconductor 1.

FIG. 7 shows the relationship between the change timing of the bias voltage condition when the machine is stopped and the toner development amount on the surface of the photoconductor. A region R4 shown in the figure is a region from the rear end of the image forming region to the rear end of the charging portion, and a region R5 is a boundary portion between the rear end of the charging portion and the non-charging portion (0 [V] region). Yes, the region R6 is a non-charged portion.

As shown in the figure, after the rear end of the image forming area has passed the point e of the nip area d-e, the bias voltage A
Only the DC component is turned off until the rear end of the charging portion of −750 [V] charged by the charger 2 in the succeeding area of the image forming area is passed through the point e of the nip area d-e. The application of the bias voltage is continued. And -750
The bias voltage is turned off after the rear end of the charging portion of [V] has passed the point e of the nip area d-e. At this time, since the charging portion reaching the nip area de is 0 [V],
Even if the bias voltage is turned off, toner and carrier do not adhere to the photoconductor side. The region R5 in FIG.
DC of the bias voltage when the tip of the charging unit of 0 [V] following the charging unit of 50 [V] passes through the nip region d-e.
This is the portion where toner adheres due to the components. When the bias voltage applied to the developing roll 3 is completely turned off, the toner is no longer attached.

By performing the bias voltage control according to the present embodiment, the toner adhesion amount can be greatly reduced as compared with the case where the bias voltage of (DC + AC) is applied from the beginning.

Moreover, in this embodiment, the developing roll 3 is rotated after the trailing edge of the image forming area has passed through the nip area de and before the non-charged portion reaches the nip area de. It has been stopped.

As a result, since the developing roller 3 is not rotating during the period from the rear end of the charging portion to the surface of the photosensitive member of 0 [V] immediately after the charging portion passing through the nip area d-e, the toner is attached. The same surface of the developing roll 3 continues to face the surface of the photoconductor. Here, most of the toner that jumps from the developing roll 3 to the side of the photoconductor 1 is the toner attached to the position facing the photoconductor 1. Therefore, 0
Immediately after the surface of the photoconductor of [V] enters the nip area d-e, the toner adhering to the position facing the photoconductor 1 flies to the photoconductor 1 side. Since the toner does not exist on the same surface, the toner that jumps from the developing roll 3 to the photoconductor 1 is extremely reduced.

As described above, when the machine is stopped, the DC component of the bias voltage is applied even after the trailing edge of the image forming area has passed the point e of the nip area d-e, so that carrier adhesion can be prevented. The rear end of the image forming area is the nip area d.
After passing the point e of −e, the AC component of the bias voltage is changed to O
The bias voltage of only the DC component is applied until the trailing end of the −750 [V] charging portion, which is the area subsequent to the image forming area and is charged by the charger 2, passes the point e of the nip area d-e. Therefore, the bias voltage of the developing roll 3 becomes only the DC component in the region R5 in which the charging portion of 0 [V] enters the nip region d-e, and D
DC, which has significantly higher developing ability than applying only C component
Compared to the case of applying a bias voltage of (DC + AC) in which the AC component is superimposed on the component, the toner adhesion amount can be significantly reduced. In addition, the charging unit of 0 [V] has a nip area d-
Since the developing roll 3 is stopped in the area R5 that comes into the area e, the toner reduction effect can be further improved.

In the above-described embodiment, when the machine is started, the DC component is first applied, and then the (AC + DC) bias voltage is generated (applied) in the image forming area.
When the machine is stopped, the AC component is turned off first, and the DC component is turned off after the trailing end of the charging section passes through the nip region. However, by performing the rotation control of the developing roll 3 as described above, the toner consumed due to the generation of the black band is limited to a partial area of the surface of the developing roll 3, so that the bias control may not be performed. Toner consumption can be suppressed.

In FIG. 8, the photosensitive member 1 and the developing roll 3 are separately driven, and a bias voltage D to the developing roll 3 is applied.
It is the figure which showed the example which turns ON and OFF the C component and the AC component simultaneously. As shown in the figure, the bias voltage of the developing roller 3 is applied as (AC component + DC component) before the tip of the charging portion reaches the point d of the nip region d-e in the region R2.

FIG. 9 is a time chart when the bias voltage is controlled as shown in FIG. At time t0, a start key (not shown) on the operation panel is pressed,
After that, at time t1, the photoconductor drive control unit 14 starts driving the motor M1.

At time t2 when the photosensitive member 1 to which the rotational driving force of the motor M1 is transmitted becomes stable, the charging voltage control unit 11 controls the charging device 2 to move the photosensitive member 1 to the facing portion ab of the photosensitive member 1. Then, the application of the charging voltage is started. As a result, the surface of the photoconductor passing through the facing portion ab between the charger 2 and the photoconductor 1 is charged to −750 [V]. Time t3 immediately before the tip of the charging unit in the rotation direction of the photoconductor reaches the nip region de.
At the developing roll 3 by the bias voltage control unit 12.
The control is performed so that the DC component (Vb = -550 [V]) and the AC component of the bias voltage are applied to.

Further, as shown in FIG. 9, when the rotational drive of the photoconductor 1 is started at time t1, the developing roll 3 which is rotationally driven by a drive system different from the photoconductor 1 is not yet rotationally driven. In the developing roll 3, the tip of the charging portion has a nip area d.
The control is performed such that the rotation driving is started at time t4 that belongs to the period after the front end of the image forming area reaches the nip area d-e after passing -e.

As a result, the developing roll 3 (AC component +
Immediately after the bias voltage (DC component) is applied, the toner adhering to the position facing the photoconductor 1 jumps to the photoconductor 1 side, but after that, the toner disappears on the same surface of the developing roll 3. The amount of toner that jumps from the developing roll 3 to the photoconductor 1 is extremely reduced.

FIGS. 10A and 10B show a comparative example of the toner amount in the black band portion. 10A shows the toner amount according to this example, and FIG. 10B shows the toner amount when the developing roll is rotated as in the conventional case.
It should be noted that the image density when the toner attached to the photoconductor 1 is recorded on the recording paper is compared. As shown in FIG. 7A, when the developing roll 3 is stopped as in this example, the toner consumption is almost completely lost in the latter half of the black band, but as shown in FIG. When the developing roll 3 is rotated, the toner consumption amount is not reduced.

As described above, the photoconductor 1 and the developing roll 3 are separately driven independently of each other, and the developing roll is moved before the charging portion enters the nip region d-e between the photoconductor 1 and the developing roll 3. By applying a bias voltage to the developing roll 3 while the driving of the developing roller 3 is stopped, the photosensitive member is exposed from the application of the bias voltage to the developing roll 3 until the charging unit reaches the nip region de. Toner adheres to the surface of the body 1 in a black band, but since the surface of the developing roll 3 facing the photoconductor 1 is the same surface, after the toner jumps from the same surface to the photoconductor 1, The toner that moves from the same surface to the photoconductor 1 disappears, and even if the photoconductor 1 rotates, a phenomenon in which toner newly jumps is suppressed. as a result,
The surface of the photoconductor passing through the nip area de is the developing roll 3
On the other hand, even if the potential is high, the amount of toner adhering to the photoconductor 1 decreases as the rotation of the photoconductor 1 progresses, and the amount of wasteful toner consumption can be reduced.

On the other hand, when a predetermined time elapses after the bias voltage of (AC component + DC component) is applied to the developing roll 3, the rotation of the photoconductor 1 exposes the portion corresponding to the leading end position of the paper size on the photoconductor surface. At time t5, when a predetermined time corresponding to the image start position has passed from the leading edge of the sheet and time t5 has arrived, the portion corresponding to the leading position of the image size reaches the exposure position.

The exposure apparatus completes preparation for electrostatic latent image formation by exposure by time t5, and starts electrostatic latent image formation from the leading edge of the image size where the image appears. The exposed portion of the surface of the photosensitive member is charged to a potential such that toner adheres but carrier does not adhere.

On the other hand, at time t6, latent image formation by exposing one page of the photosensitive member 1 is completed. After the latent image formation is completed, the rear end of the image forming area passes through the point e of the nip area d-e by the rotation of the photoconductor 1. Further, at time t before the rear end of the charging unit reaches the point d of the nip area de.
7, the developing roll drive control unit 15 controls so that the rotational drive of the developing roll 3 is stopped. At this time, the photoconductor 1 keeps rotating.

After that, at time t8, the charging potential controller 11 turns off the charging voltage of the charger 2. Charge voltage is O
After the FF, the charging potential V0 of the surface of the photoconductor passing through the facing portions ab of the charger 2 becomes 0 [V]. This 0 [V]
The bias voltage control unit turns off the (DC component + AC component) of the bias voltage at time t9 immediately after the boundary between the voltage and −750 [V] has passed the point e of the nip region de by the rotation of the photoconductor 1. 12 performs voltage control. Furthermore, 0
The rotation drive of the photoconductor 1 is stopped at time t10 when the charging unit of [V] passes through the facing portion of the static eliminator 5 due to the rotation of the photoconductor 1.

As a result, since the developing roller 3 is not rotating during the period in which the surface of the photosensitive member, which is 0 [V] immediately after the charging portion, passes through the nip area d-e from the rear end of the charging portion, toner adheres. The same surface of the developing roll 3 continues to face the surface of the photoconductor. Therefore, immediately after the surface of the photosensitive member of 0 [V] enters the nip area d-e, the toner attached to the position facing the photosensitive member 1 jumps to the photosensitive member 1 side, but after that, the development is performed. Since the toner is not present on the same surface of the roll 3, the toner flying from the developing roll 3 to the photosensitive member 1 is extremely reduced.

[0099]

As described above in detail, according to the present invention, it is possible to significantly reduce the toner consumption amount due to the adhesion of toner in a black belt shape when the machine is started or stopped, or the photoconductor It is possible to provide an image forming apparatus and a copying machine capable of extending the life of the photoconductor by suppressing the carrier from adhering to the image forming apparatus.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a copying machine according to an embodiment of the present invention.

FIG. 2 is a timing chart of the copying machine according to the embodiment.

FIG. 3 is a diagram showing an ON timing of a bias voltage of a DC component in the copying machine according to the embodiment.

FIG. 4 is a diagram showing a drive timing of a photoconductor and a developing roll and a bias voltage application timing at the time of starting the machine in the embodiment.

5A is a diagram showing an image density when a black band generated by the above-described embodiment is transferred onto a paper; FIG. 5B is an image density when a black band generated by a conventional method is transferred onto a paper; Figure

6 is a diagram showing a relationship between each region shown in FIG. 4 and a charging potential.

FIG. 7 is a diagram showing a drive timing and a bias voltage timing of a photoconductor and a developing roll when the machine is stopped in the embodiment.

FIG. 8 is a diagram showing a drive timing of a photoconductor and a developing roll and a bias voltage application timing at machine startup in a modified example in which a bias voltage control method is changed.

FIG. 9 is a timing chart in the above modification.

FIG. 10A is a diagram showing an image density when a black band generated by the above modification is transferred onto a paper; FIG. 10B is a diagram showing an image density when a black band generated by a conventional method is transferred onto a paper;

[Explanation of symbols]

1 photoconductor 2 charger 3 developing roll 4 Transfer device 5 Static elimination unit 10 Electrophotographic process control block 11 Charging voltage controller 12 Bias voltage controller 13 Transfer voltage controller 14 Photoconductor drive controller 15 Development roll drive controller 17 Controller

Continued front page    (72) Inventor Yoshihiro Komatsu             2-3-8 Shimo-Meguro, Meguro-ku, Tokyo Matsushita             Dentsu System Co., Ltd. (72) Inventor Takanori Horiuchi             2-3-8 Shimo-Meguro, Meguro-ku, Tokyo Matsushita             Dentsu System Co., Ltd. F-term (reference) 2H027 EC12 ED02 ED03 ED06 ED08                       ED09 EE02 EE04 EE05 EF06                       EF13 FA33                 2H073 AA02 BA04 BA09 BA13 BA41                       CA03                 2H077 AD06 AD36 DB08 DB12 DB13                       DB14 DB22

Claims (16)

[Claims] 1. A photoconductor, a charging unit for charging the surface of the photoconductor, an exposing unit for exposing an image forming area of the charged surface of the photoconductor, and a developing unit for attaching toner to the exposed portion. A driving unit that drives the developing unit separately from the photoconductor, and when the recording operation starts, the charging unit starts charging, and the developing unit is operated before the charging unit enters the nip region between the photoconductor and the developing unit. An image forming apparatus comprising: a control unit that applies a bias voltage while the driving of the unit is stopped. 2. A photoconductor, a charging unit for charging the surface of the photoconductor, an exposing unit for exposing an image forming area of the charged surface of the photoconductor, and a developing unit for attaching toner to the exposed portion. A driving unit that drives the developing unit separately from the photoconductor, and when the recording operation starts, the charging unit starts charging, and the developing unit is operated before the charging unit enters the nip region between the photoconductor and the developing unit. Control means for applying a bias voltage with the driving of the means stopped and driving the developing means before the exposing means exposes the imageable area;
An image forming apparatus equipped with. 3. A photoconductor, a charging unit for charging the surface of the photoconductor, an exposing unit for exposing an image forming area on the charged surface of the photoconductor, and a developing unit for attaching toner to the exposed portion. Driving means for driving the developing means separately from the photosensitive member, and a bias voltage is applied to the developing means after the trailing edge of the image forming area in the image forming area passes through the nip area at the end of the recording operation. An image forming apparatus comprising: a control unit that stops the driving of the developing unit in this state. 4. A photosensitive member, a charging unit for charging the surface of the photosensitive member, an exposing unit for exposing an image forming area on the charged surface of the photosensitive member, and a developing unit for attaching toner to the exposed portion. Driving means for driving the developing means separately from the photosensitive member, and a bias voltage is applied to the developing means after the trailing edge of the image forming area in the image forming area passes through the nip area at the end of the recording operation. In this state, the driving of the developing unit is stopped, and the control unit turns off the bias voltage of the developing unit after the trailing end of the charging unit has passed through the nip region. 5. A photoconductor, a charging unit for charging the surface of the photoconductor, an exposing unit for exposing an image forming area on the charged surface of the photoconductor, and a developing unit for attaching toner to the exposed portion. A driving unit that drives the developing unit separately from the photoconductor, and when the recording operation starts, the charging unit starts charging, and the developing unit is operated before the charging unit enters the nip region between the photoconductor and the developing unit. An image forming apparatus comprising: a control unit that applies a bias voltage of a DC component while the driving of the unit is stopped. 6. A photosensitive member, a charging unit for charging the surface of the photosensitive member, an exposing unit for exposing an image forming area on the charged surface of the photosensitive member, and a developing unit for attaching toner to the exposed portion. A driving unit that drives the developing unit separately from the photoconductor, and when the recording operation starts, the charging unit starts charging, and the developing unit is operated before the charging unit enters the nip region between the photoconductor and the developing unit. A bias voltage of a DC component is applied with the driving of the means stopped, the developing means is driven before the exposing means exposes the imageable area, and a bias voltage in which an AC component is superimposed on the DC component is applied. An image forming apparatus, comprising: a control unit that applies a voltage to the developing unit. 7. A photosensitive member, a charging unit for charging the surface of the photosensitive member, an exposing unit for exposing an image forming area on the charged surface of the photosensitive member, and a developing unit for attaching toner to the exposed portion. A driving unit that drives the developing unit separately from the photoconductor, and an AC component on the DC component are superimposed on the developing unit while the image forming area passes through the nip region between the photoconductor and the developing unit. When the recording operation is completed, the bias voltage of the AC component to the developing means is turned off after the trailing edge of the image forming area in the image forming area passes through the nip area, and the developing means is turned off. An image forming apparatus comprising: a control unit that stops driving of the image forming apparatus. 8. A photosensitive member, a charging unit for charging the surface of the photosensitive member, an exposing unit for exposing an image forming area on the charged surface of the photosensitive member, and a developing unit for attaching toner to the exposed portion. A driving unit that drives the developing unit separately from the photoconductor, and an AC component on the DC component are superimposed on the developing unit while the image forming area passes through the nip region between the photoconductor and the developing unit. Bias voltage is applied, and at the end of the recording operation, after the trailing edge of the image forming area in the image forming area passes through the nip area, the bias voltage of the AC component to the developing means is turned off to turn off the developing means. And a control unit for turning off the bias voltage of the DC component to the developing unit after the trailing end of the charging unit has passed through the nip region. 9. A photoreceptor, a charging means for charging the surface of the photoreceptor, an exposing means for exposing an image forming area on the charged surface of the photoreceptor, and a developing means for attaching toner to the exposed portion. A driving unit that drives the developing unit separately from the photoconductor, and when the recording operation starts, the charging unit starts charging, and the developing unit is operated before the charging unit enters the nip region between the photoconductor and the developing unit. And a control means for applying a bias voltage while the driving of the means is stopped. 10. A photoconductor, a charging unit for charging the surface of the photoconductor, an exposing unit for exposing an image forming area of the charged surface of the photoconductor, and a developing unit for attaching toner to the exposed portion. A driving unit that drives the developing unit separately from the photoconductor, and when the recording operation starts, the charging unit starts charging, and the developing unit is operated before the charging unit enters the nip region between the photoconductor and the developing unit. A control unit for applying a bias voltage with the driving of the means stopped and for driving the developing means before the exposing means exposes the image forming area. 11. A photoconductor, a charging unit for charging the surface of the photoconductor, an exposing unit for exposing an image forming area on the charged surface of the photoconductor, and a developing unit for attaching toner to the exposed portion. Driving means for driving the developing means separately from the photosensitive member, and a bias voltage is applied to the developing means after the trailing edge of the image forming area in the image forming area passes through the nip area at the end of the recording operation. A control means for stopping the driving of the developing means in this state. 12. A photoconductor, a charging unit for charging the surface of the photoconductor, an exposing unit for exposing an image forming area on the charged surface of the photoconductor, and a developing unit for adhering toner to the exposed portion. Driving means for driving the developing means separately from the photosensitive member, and a bias voltage is applied to the developing means after the trailing edge of the image forming area in the image forming area passes through the nip area at the end of the recording operation. Control means for stopping the driving of the developing means in this state, and turning off the bias voltage of the developing means after the trailing end of the charging section has passed through the nip region. 13. A photoreceptor, a charging means for charging the surface of the photoreceptor, an exposing means for exposing an image forming area on the charged surface of the photoreceptor, and a developing means for attaching toner to the exposed portion. A driving unit that drives the developing unit separately from the photoconductor, and when the recording operation starts, the charging unit starts charging, and the developing unit is operated before the charging unit enters the nip region between the photoconductor and the developing unit. And a control means for applying a bias voltage of a DC component while the driving of the means is stopped. 14. A photoconductor, a charging unit for charging the surface of the photoconductor, an exposing unit for exposing an image forming area on the charged surface of the photoconductor, and a developing unit for attaching toner to the exposed portion. A driving unit that drives the developing unit separately from the photoconductor, and when the recording operation starts, the charging unit starts charging, and the developing unit is operated before the charging unit enters the nip region between the photoconductor and the developing unit. A bias voltage of a DC component is applied with the driving of the means stopped, the developing means is driven before the exposing means exposes the imageable area, and a bias voltage in which an AC component is superimposed on the DC component is applied. And a control means for applying the above to the developing means. 15. A photoconductor, a charging unit that charges the surface of the photoconductor, an exposure unit that exposes an imageable region of the surface of the charged photoconductor, and a developing unit that attaches toner to the exposed portion. A driving unit that drives the developing unit separately from the photoconductor, and an AC component on the DC component are superimposed on the developing unit while the image forming area passes through the nip region between the photoconductor and the developing unit. When the recording operation is completed, the bias voltage of the AC component to the developing means is turned off after the trailing edge of the image forming area in the image forming area passes through the nip area, and the developing means is turned off. And a control means for stopping the driving of the copying machine. 16. A photoconductor, a charging unit for charging the surface of the photoconductor, an exposing unit for exposing an image forming area on the charged surface of the photoconductor, and a developing unit for attaching toner to the exposed part. A driving unit that drives the developing unit separately from the photoconductor, and an AC component on the DC component are superimposed on the developing unit while the image forming area passes through the nip region between the photoconductor and the developing unit. Bias voltage is applied, and at the end of the recording operation, after the trailing edge of the image forming area in the image forming area passes through the nip area, the bias voltage of the AC component to the developing means is turned off to turn off the developing means. And a control means for turning off the bias voltage of the DC component to the developing means after the trailing end of the charging portion has passed through the nip region.