JPH1115238A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a recorded image with desired density regardless of the unstable electrified state of a photoreceptor at the beginning of the starting time of an image forming action and to prevent a ghost image caused by the unstable electrified state from being formed in the recorded image. SOLUTION: This image forming device is provided with the turning photoreceptor drum 1, a main electrifier 2 initially electrifying the drum 1, an ROS 3 exposing the drum 1 electrified by the electrifier 2 according to image information, a developing unit 4 forming a toner image by developing an electrostatic latent image formed on the drum 1 and a second electrifier 5 or 7 disposed on a more downstream side than the unit 4 and on a more upstream side than the electrifier 2 in the rotating direction of the drum 1 and set for electrifying or discharging the drum 1 Besides, it is provided with a preliminary electrification control means preliminarily electrifying the drum 1 by the electrifier 5 or 7 in a fixed time immediately after the drum 1 is started to be rotated before it is initially electrified by the electrifier 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a laser printer.
The present invention relates to an improvement for shortening the time from the start of an image forming operation to the discharge of a first recording sheet on which a recording image is formed as much as possible.

[0002]

2. Description of the Related Art In an electrophotographic copying machine or a laser printer, a rotating photosensitive member is initially charged to a predetermined surface potential, and then the photosensitive member is exposed in accordance with image information to form an electrostatic latent image. Then, after developing the electrostatic latent image with toner to make it a visible image, the toner image is transferred to a recording sheet to form a recording image corresponding to the image information on the recording sheet. In addition, in this type of image forming apparatus, in addition to a charger for initially charging a photoconductor, a transfer charger for electrostatically transferring a toner image from a photoconductor to a recording sheet, and a recording sheet on which the toner image has been transferred is peeled from the photoconductor. A charging device for removing the toner image before being transferred onto the recording sheet, a pre-transfer charging device for removing the toner image before being transferred to the recording sheet, and the like are arranged around the photoreceptor.

In the process of forming such a recorded image, in a developing step of visualizing the electrostatic latent image, in order to prevent a so-called fogging phenomenon in which toner adheres to a background portion of the electrostatic latent image, A predetermined developing bias voltage is applied between the photosensitive drum and the developing device, and the toner adheres to the photosensitive drum according to the potential difference between the image portion of the electrostatic latent image formed by exposure and the developing bias potential. I do. Therefore, the amount of toner adhered to the photoconductor, that is, the density of the recorded image is greatly affected by the relative potential difference between the image portion potential of the electrostatic latent image and the developing bias potential, and the surface of the photoconductor during the initial charging is The density of the recorded image fluctuates due to fluctuations in the potential, the exposure intensity when forming an electrostatic latent image, or the development bias potential.

If the developing bias potential is constant, the image density is determined by the image portion potential of the electrostatic latent image, but the electrostatic latent image itself is initially charged to a predetermined surface potential. Because it is formed by exposing the exposed photoconductor,
To form a high-quality recorded image without density unevenness,
In such initial charging, it is important that the photoconductor is charged to a uniform surface potential.

[0005]

However, when the photoreceptor whose surface potential has been reduced due to dark decay is charged together with the resumption of the image forming operation, the charge applied to the photoreceptor is trapped in the photosensitive layer. The surface potential of the photoreceptor does not rise sufficiently until a sufficient charge is applied and the trap is saturated, as shown in FIG.
At the beginning of the initial charging, there has been a phenomenon that the surface potential of the photoconductor drops without reaching the expected surface potential.

For this reason, if the photosensitive member is exposed immediately after the start of rotation of the photosensitive member to form an electrostatic latent image, an area on the photosensitive member whose surface potential does not reach a predetermined value (hereinafter, this area is referred to as an area). An electrostatic latent image is formed on the “low-charge area”, so that not only a recorded image of a desired density cannot be formed, but also a recorded image formed on a recording sheet corresponds to the low-charge area. There has been a problem that a ghost image becomes apparent.

On the other hand, in order to solve such a problem, Japanese Patent Publication No. 57-68853 discloses a warm-up cycle in which the first several rotations of the photoreceptor after the copy start button is pressed. Further, there is disclosed an image forming apparatus which saturates traps in a photosensitive layer with electric charges to stabilize the surface potential of a photoreceptor and performs an image forming operation following the warm-up cycle.

However, when such a warm-up cycle is provided, an electrostatic latent image cannot be formed on the photoreceptor during the warm-up cycle. There is a problem that it takes a long time to discharge from the wastewater and production efficiency has to be reduced. In addition, there is also a problem that the photoconductor is excessively charged by the amount corresponding to the warm-up cycle, so that the photoconductor is deteriorated earlier by that amount.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object of the present invention is to provide a photoconductor having a desired density regardless of an unstable charging state at the beginning of an image forming operation. It is an object of the present invention to provide an image forming apparatus capable of forming a recorded image and preventing a ghost image due to the unstable charging state of the photoconductor from being generated in the recorded image.

[0010]

In order to achieve the above object, the present inventors propose the following four inventions. That is, the first invention comprises a rotating photoconductor, a first charging unit for initially charging the photoconductor, and an exposing unit for exposing the photoconductor charged by the first charging unit in accordance with image information. Developing means for developing the electrostatic latent image formed on the photoreceptor by the exposure to form a toner image; and a downstream side of the developing device and an upstream side of the first charging means with respect to the rotation direction of the photoreceptor. And an image forming apparatus provided with a second charging means for charging or discharging the photosensitive member, the second charging means being driven within a fixed time immediately after the rotation of the photosensitive member is started, and the drive output thereof being And a pre-charging control means for pre-charging the photoreceptor prior to the initial charging by the first charging means is provided.

According to the above technical means, the preliminary charging control means serves as a second charging means as a transfer charger, a peeling charger or a pre-transfer charger before the initial charging of the photosensitive member by the first charging means. Pre-charge the photoreceptor using
Since the trap inside the photosensitive layer is saturated with the electric charge before the initial charging is performed, a low charging area is not formed at the time of the initial charging, and the surface potential of the photoconductor is stabilized without performing a warm-up cycle. Can be achieved.

A second invention provides a rotating photosensitive member,
A charging unit for initially charging the photoconductor, an exposure unit for exposing the photoconductor charged by the charging unit in accordance with image information, and developing the electrostatic latent image formed on the photoconductor by the exposure. In an image forming apparatus provided with a developing unit for forming a toner image, after the rotation of the photoconductor starts, the charging unit drives the charging unit by initial charging in the first cycle and initial charging in the second cycle and thereafter. An initial charging control means for changing the output is provided.

According to such a technical means, the initial charging control means controls the driving output of the charging means by the initial charging corresponding to the first rotation of the photosensitive member and the initial charging after the second rotation. Since the voltage applied to the charging means or the value of the current to be applied to the charging means is changed, the initial charge in the first rotation saturates the trap inside the photosensitive layer and gives the photoconductor a surplus amount of electric charge. By applying the minimum amount of charge necessary for obtaining a desired surface potential to the photoconductor in the initial charging after the eye, a stable surface potential can be applied to the photoconductor from the beginning of the toner image formation.

On the other hand, a third aspect of the present invention relates to a photoreceptor that has been subjected to the initial charging only once by the charging unit after the rotation of the photoreceptor starts, and a photoreceptor that has received the initial charging two or more times. An exposure intensity control means for changing the exposure intensity of the exposure means between the surface area and the surface area is provided.

According to the third aspect, the exposure intensity to the surface area of the photoreceptor, that is, the lowly charged area, which has been subjected to the initial charging by the charging means only once by the exposure intensity control means, The exposure intensity for the surface area of the photoreceptor that has been subjected to two or more exposures has been changed. By adjusting the image part potential of the electrostatic latent image, the image part potential and the developing bias can be adjusted even for the low charge area. The potential difference between the potentials can be set to a value corresponding to a desired image density, and a recorded image can be formed even when the surface potential of the photoconductor is not stabilized.

According to a fourth aspect of the present invention, the surface area of the photoreceptor which has been subjected to the initial charging by the charging means only once after the start of the photoreceptor, and the surface area of the photoreceptor which has received the initial charging twice or more. And a bias control means for changing the intensity of a developing bias voltage applied between the developing means and the photosensitive member in the region.

According to such a technical means, the bias control means receives a developing bias potential with respect to the surface region of the photosensitive member which has been subjected to the initial charging by the charging means only once and the initial charging at least twice. Since the developing bias potential with respect to the surface area of the photoconductor is changed, the potential difference between the image area potential and the developing bias potential is desired even in the low charging area of the photoconductor by adjusting the developing bias potential. The image density can be set to a value corresponding to the image density, and a recorded image can be formed even when the surface potential of the photoconductor is not stabilized.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings. First Embodiment FIG. 1 shows a schematic configuration of a laser printer to which the present invention is applied. In the figure, reference numeral 1 denotes a photosensitive drum having a photosensitive layer on the surface, reference numeral 2 denotes a main charger for initially charging the photosensitive drum 1 to a predetermined background portion potential, and reference numeral 3 denotes modulation based on image information. The photosensitive drum 1 with a light beam
Raster scanning device (ROS) for writing an electrostatic latent image on the photosensitive drum 1, a developing device 4 for developing the electrostatic latent image formed on the photosensitive drum 1 with toner, and a reference numeral 5 for a toner image on a recording sheet A pre-transfer charger for neutralizing the surface of the photosensitive drum 1 in preparation for transfer of the photosensitive drum 1;
A transfer charger for electrostatically transferring the toner image developed on the recording sheet conveyed along the broken line in the drawing. 8 is a cleaner for removing residual toner and paper dust from the surface of the photosensitive drum 1 after the transfer of the toner image, and 9 is a potential history remaining on the surface of the photosensitive drum 11. Reference numeral 10 denotes a fixing unit that heats and fixes an unfixed toner image transferred on a recording sheet to the recording sheet.

In the laser printer according to the present embodiment having the above-described configuration, the charging process by the main charger 2, the exposure process by the ROS 3, and the development by the developing device 4 are performed with the rotation of the photosensitive drum 1 in the process direction. Through the steps, a toner image corresponding to the image information is formed on the photosensitive drum 1,
Such a toner image is transferred to a recording sheet in a transfer area where the photosensitive drum 1 and the transfer charger 6 face each other. The recording sheet onto which the toner image has been transferred is discharged to a sheet discharge tray (not shown) via a fixing device 10, and the cleaner 8 removes residual toner and paper dust from the surface of the photosensitive drum 1 after the transfer process. And the like are removed. And
After the residual potential on the surface of the photosensitive drum 1 is removed by exposure to the charge removing lamp 9, the photosensitive drum 1 is again subjected to the charging process by the main charger 2 and is used for forming the next toner image.

The photosensitive drum 1 has a surface provided with an insulating property by forming a photosensitive layer on a peripheral surface of a conductive substrate.
Is left behind, its surface potential decreases with time due to dark decay, and the charges trapped in the traps inside the photosensitive layer are also lost. Therefore, even when the photosensitive drum 1 is initially charged by the main charger 1 when the image forming operation is restarted, the surface potential of the photosensitive drum 1 is sufficiently increased until the trap inside the photosensitive layer is saturated by the charge. Instead, a low-charge area as shown in FIG. 8 is generated.

For this reason, in the present embodiment, the photosensitive drum 1 is mounted on the photosensitive drum 1 rather than the main charger 2 so that the image forming operation can be started from the beginning of the rotation of the photosensitive drum 1 by preventing the occurrence of the low charging area. The pre-transfer charger 5 and the peel-off charger 7 provided on the upstream side in the rotation direction are used to preliminarily charge the photosensitive drum 1, and after this pre-charging, the main charger 2 performs initial charging. doing.

More specifically, as shown in the timing chart of FIG.
Immediately after the drum motor for controlling the rotation of the photosensitive drum 1 starts rotating, the pre-transfer charger 5 and the peeling charger 7 are driven.
Precharging is started, and the surface area of the photosensitive drum 1 that has been precharged by the chargers 5 and 7 is the main charger 2
The main charger 2 is driven at a timing when the photosensitive drum 1 reaches the opposing position, and the photosensitive drum 1 already charged
The electric charge is applied to the surface region of the substrate.

Originally, the pre-transfer charger 5 functions to remove the surface potential of the photosensitive drum 1, while the peeling charger 7 performs the function to remove the charge from the recording sheet. An AC voltage is applied to the peeling charger 7, but in such preliminary charging, it is necessary to apply a charge of the same polarity as that of the main charger 2 to the photosensitive drum 1. In this preliminary charging, the same charge as that of the main charger 2 is applied. Polar DC voltage is applied to the pre-transfer charger 5 and the peeling charger 7. Therefore,
The high voltage power supply 12 to which the pre-transfer charger 5 and the peeling charger 7 are connected is configured so that it can be used by switching between AC voltage and DC voltage, and the output voltage is controlled by the power supply controller 13 connected to the high voltage power supply 12. And the application timing is controlled. The precharging is performed during one rotation of the photoconductor drum 1. When the precharging is started and the first round of the photoconductor drum 1 is completed, the outputs of the pre-transfer charger 5 and the peeling charger 7 are output. Is returned to the original output for discharging the photosensitive drum 1 or the recording sheet.

When the photosensitive drum 1 is precharged by the pre-transfer charger 5 and the peeling charger 7 in this manner, traps inside the photosensitive layer are trapped by the charges given to the photosensitive drum 1 by the precharge. Since the main charging device 2 overlaps the surface area of the photoreceptor drum 1 which has already been pre-charged and performs initial charging since the surface area is saturated, a low-charge area is not generated, as shown by a broken line in FIG. The photosensitive drum 1 can be uniformly charged to a predetermined surface potential from the beginning. Therefore, in this example, the writing of the electrostatic latent image can be started when the surface area of the photoconductor drum 1 started from the position facing the pre-transfer charger 5 reaches the exposure position by the ROS 3, and as a result, It is possible to start a substantial image forming operation from a stage before the rotation of the photoconductor drum 1 to shorten the time from the start of the rotation of the photoconductor drum 1 to the transfer of the toner image to the first recording sheet. You can do it.

In the example shown in FIG. 2, precharging is performed using both the pre-transfer charger 5 and the peeling charger 7, but the trap in the photosensitive layer is sufficiently saturated by precharging only one of them. If possible, precharging may be performed by only one of the pre-transfer charger 5 or the peeling charger 7. In this case, considering the rotation direction of the photosensitive drum 1, the position of the peeling charger 7 is closer to the exposure position than the position of the pre-transfer charger 5.
Preliminary charging using the peeling charger 7 can shorten the time from the start of rotation of the photosensitive drum 1 to the start of exposure.

On the other hand, the output of the charger required to charge the photosensitive drum 1 to a predetermined surface potential varies depending on the degree of fatigue of the photosensitive layer and the humidity of the surrounding atmosphere, and as shown in FIG. As the cumulative number of rotations increases, the photosensitive drum 1 becomes more difficult to be charged, and as shown in FIG. 4, becomes harder to charge even when the humidity increases. Therefore, the photosensitive drum 1
As the cumulative rotation speed of
The trap inside the photosensitive layer is unlikely to be saturated even by the pre-charging, and there is a concern that a low-charging area is generated even after the pre-charging.

Therefore, in this embodiment, a cycle counter (not shown) for counting the number of prints on the recording sheet.
The output of the pre-transfer charger 5 and / or the peeling charger 7 at the time of preliminary charging is changed based on the output signal of
The output at the time of preliminary charging is increased as the cumulative number of rotations increases. Further, a thermo-hygrometer 11 is provided around the photoconductor drum 1, and the pre-transfer charger 5 at the time of pre-charging also according to the humidity of the atmosphere around the photoconductor drum 1.
And / or the output of the peeling charger 7 is controlled to completely prevent the occurrence of the low charging area.

Further, the photosensitive drum 1 can be pre-charged by using the transfer charger 6 without using the pre-transfer charger 5 and the peeling charger 7. When a toner image is formed by a negative development method using a toner charged to a negative polarity, the initial charging polarity of the photosensitive drum 1 is negative, and the transfer voltage applied to the transfer charger 6 is the charging polarity of the toner. When the transfer charger 6 is used for preliminary charging, a DC voltage having a negative polarity is applied for a time corresponding to one rotation of the photosensitive drum 1, and thereafter, the recording sheet is Before being transferred to the transfer position, it is necessary to apply a normal positive polarity DC voltage to the transfer charger 6.

When the photosensitive drum 1 is pre-charged by using the pre-transfer charger 5 and the like, the surface area of the pre-charged photosensitive drum 1 passes through the position facing the static elimination lamp 9. It is desirable that the static elimination lamp 9 be turned off without being turned on until the operation is completed. Even if the static elimination lamp 9 is kept on, the charge trapped in the trap inside the photosensitive layer is not lost by the preliminary charging, and the photosensitive drum 1 is charged to a predetermined surface potential by the initial charging by the main charger 2. However, since the charge at the time of preliminary charging remains on the surface of the photosensitive drum 1 when the light is turned off, the surface potential of the photosensitive drum 1 can be more easily improved by the initial charging, and the low charging can be achieved. The generation of regions can be more effectively prevented.

Second Embodiment In the first embodiment described above, the photosensitive drum 1 is pre-charged by using the pre-transfer charger 5 and the like, thereby preventing the occurrence of a low-charge area at the beginning of the rotation of the photosensitive drum 1. However, in this embodiment, the main charger 2 is driven with an output larger than the normal output after the rotation of the photosensitive drum 1 is started, thereby preventing the occurrence of the uncharged area on the photosensitive drum 1. Is what you do.

More specifically, as shown in FIG. 5, immediately after the image forming operation is started and the drum motor for controlling the rotation of the photosensitive drum 1 starts to rotate, the main charger 2 is driven to drive the photosensitive drum. Although the initial charging of 1 is started, after the driving of the main charger 2 is started and until the photosensitive drum 1 makes one rotation, the output of the main charger 2 is set to an enhanced high output at normal time,
When the photosensitive drum 1 makes one rotation while the output is high, the main charger 2 is driven at a normal output. As shown in FIG. 1, the high voltage power supply 14 to which the main charger 2 is connected is a variable power supply capable of arbitrarily changing the voltage applied to the charger, and the applied voltage is controlled by a power supply controller 15 connected to the high voltage power supply 14. The value and the application timing are controlled.

When the output of the main charger 2 is set to a high output at the beginning of the driving, the photosensitive drum 1 is charged while the trap inside the photosensitive layer is saturated with the charge only by the initial charging of the main charger 2. Can be increased to a predetermined value, and the photosensitive drum 1 can be uniformly charged to the predetermined surface potential from the beginning as shown by the broken line in FIG. Therefore, in this example, the writing of the electrostatic latent image can be started from the time when the surface area of the photosensitive drum 1 started from the position facing the main charger 2 reaches the exposure position by the ROS 3, and the photosensitive drum 1 can be started. The time from the start of rotation to the transfer of the toner image to the first recording sheet can be shortened compared to the first embodiment.

In this embodiment, the output value of the main charger 2 at the time of high output is controlled to an optimum value by using a cycle counter for counting the number of accumulated prints or an output signal of the thermo-hygrometer 11. preferable.

Third Embodiment In the above-described first and second embodiments, the occurrence of a low-charge area due to the initial charging of the photosensitive drum 1 itself is prevented.
Photosensitive drum 1 when writing an electrostatic latent image by
In the third embodiment, while the low charging area is generated by the initial charging, the exposure intensity of the photoconductor drum 1 by the ROS 3 is controlled, thereby obtaining the static potential. The potential difference between the image portion potential of the electro-latent image and the developing bias potential is maintained at a predetermined value, so that a toner image of a predetermined density can be obtained.

More specifically, as shown in FIG. 6, after the image forming operation is started and the drum motor for controlling the rotation of the photosensitive drum 1 starts rotating, the main charger 2 is driven to drive the photosensitive drum. The initial charging of the photosensitive drum 1 is started, and the exposure of the photosensitive drum by the ROS 3 is started in the same manner as in the normal toner image forming process to form an electrostatic latent image. However, during the period from the start of driving of the main charger 2 to the rotation of the photosensitive drum 1 by one rotation, it is expected that the low charging area shown in FIG. For this reason, in the surface area of the photosensitive drum 1 which has been subjected to the initial charging by the main charger 2 only once, the exposure intensity is set to be lower than usual to write the electrostatic latent image, while the main charging is performed. An electrostatic latent image is written at a normal exposure intensity on the surface area of the photosensitive drum 1 which has been subjected to the initial charging by the unit 2 twice or more. As shown in FIG. 1, the ROS 3 has an exposure controller 1 for controlling a drive current of a semiconductor laser which is a source of laser light.
The exposure controller 16 controls the light amount of the laser beam.
The exposure intensity may be controlled by controlling the drive current of the semiconductor laser to control the light intensity of the laser beam itself, or by controlling the spot diameter of the laser beam on the surface of the photosensitive drum 1.

By controlling the exposure intensity corresponding to the low-charge area on the photosensitive drum 1 in this manner, the potential of the image portion of the electrostatic latent image formed in the low-charge area and the static potential formed in the other areas are controlled. Since the balance with the image portion potential of the electrostatic latent image can be maintained, the potential difference between the developing bias potential and the image portion potential of the electrostatic latent image can be uniformly maintained in the low charging area and the other areas. It is possible to prevent the occurrence of a density step corresponding to the low charging area on the toner image developed from the electrostatic latent image. Therefore, also in this example, the surface area of the photosensitive drum 1 started from the position facing the main charger 2 is the ROS 3
The writing of the electrostatic latent image can be started from the point in time when the exposure position is reached, and the writing of the electrostatic latent image is performed after stabilizing the surface potential of the photosensitive drum 1 by performing a dummy cycle. In comparison, the time from the start of rotation of the photosensitive drum 1 to the transfer of the toner image to the first recording sheet can be significantly reduced.

In this embodiment, it is preferable that the exposure intensity by the ROS 3 is controlled to an optimum value by using a cycle counter for counting the number of accumulated prints or an output signal of the thermo-hygrometer 11.

Fourth Embodiment In the third embodiment described above, by controlling the exposure intensity of the photosensitive drum 1 by the ROS 3, the potential difference between the image portion potential of the electrostatic latent image and the developing bias potential is maintained at a predetermined value. In the fourth embodiment, the developing bias potential is changed between the low charging area on the photosensitive drum 1 and the other areas, so that the potential of the image portion of the electrostatic latent image, the developing bias potential, and the like are also changed. Is maintained at a predetermined value so that a toner image having a predetermined density can be obtained.

More specifically, as shown in FIG. 7, after the image forming operation is started and the drum motor for controlling the rotation of the photosensitive drum 1 starts to rotate, the main charger 2 is driven to drive the photosensitive drum. 1 starts the exposure of the photosensitive drum by the ROS 3 in the same manner as in the normal toner image forming process to form an electrostatic latent image. To form a toner image. However, during the period from the start of driving of the main charger 2 to the rotation of the photosensitive drum 1 by one rotation, it is expected that the low charging area shown in FIG. Therefore, when developing the electrostatic latent image, the developing bias potential is set lower than usual for the surface area of the photosensitive drum 1 which has been subjected to the initial charging by the main charger 2 only once, and the developing is performed. On the other hand, the surface area of the photosensitive drum 1 that has been subjected to the initial charging by the main charger 2 twice or more is developed with a normal developing bias potential. As shown in FIG. 1, a bias power source 1 for applying a developing bias voltage is applied to a developing roller 41 of a developing device 4.
7 is connected, and a bias controller 18 connected to the bias power supply 17 controls the application intensity and application timing of the developing bias voltage.

When an electrostatic latent image is formed by exposing a low-charged area at a normal exposure intensity, the potential of the image portion of the electrostatic latent image is lower than the potential of the image portion of the electrostatic latent image formed in other areas. Although it is expected that the developing bias potential is low, the developing bias potential is controlled in accordance with the low charging area on the photosensitive drum 1 as described above.
The potential difference between the developing bias potential and the image portion potential of the electrostatic latent image can be kept uniform between the low charging area and the other areas,
It is possible to prevent the occurrence of a density step corresponding to the low charging area on the toner image developed from the electrostatic latent image.
Therefore, similarly to the third embodiment, in this embodiment, the writing of the electrostatic latent image is started from the time when the surface area of the photosensitive drum 1 started from the position facing the main charger 2 reaches the exposure position by the ROS 3. In comparison with the case where a dummy cycle is performed to stabilize the surface potential of the photosensitive drum 1 and then the electrostatic latent image is written, the first sheet from the start of rotation of the photosensitive drum 1 The time required until the toner image is transferred to the recording sheet can be remarkably reduced.

In this embodiment, the developing bias potential applied between the developing device 4 and the photosensitive drum 1 is a cycle counter for counting the number of accumulated prints, a thermo-hygrometer 1
It is preferable to control to an optimum value using the output signal of 1.

[0042]

As described above in detail, according to the image forming apparatus of the present invention, a recorded image having a desired density can be obtained regardless of the unstable charging state of the photosensitive member at the beginning of the image forming operation. Can be formed, and the occurrence of a ghost image in a recorded image due to the unstable charging state of the photoconductor can be prevented.

Further, since the above effect can be obtained without stabilizing the charged state of the photosensitive member by providing a dummy cycle or the like, a recorded image can be formed on a recording sheet immediately after the rotation of the photosensitive member is started. Therefore, the time until the first recording sheet is discharged from the apparatus can be significantly reduced, and the productivity can be dramatically improved.

[Brief description of the drawings]

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

FIG. 2 is a timing chart showing control of output timing of each charger and output value of a pre-transfer charger in the first embodiment.

FIG. 3 is a graph showing a relationship between a charger output required for charging a photoconductor to a predetermined potential and a cumulative number of rotations of a photoconductor drum.

FIG. 4 is a graph showing a relationship between a charger output required to charge a photoconductor to a predetermined potential and humidity.

FIG. 5 is a timing chart showing output timing of a main charger and control of the output value in a second embodiment.

FIG. 6 is a timing chart showing a relationship among an output timing of a main charger, an exposure start timing, and an exposure intensity in a third embodiment.

FIG. 7 is a timing chart showing the output timing of the main charger, the application timing of the developing bias voltage, and the control of the output value of the developing bias voltage in the fourth embodiment.

FIG. 8 is a graph showing the fluctuation of the surface potential of the photoconductor at the beginning of the image forming operation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... Main charger, 3 ... Raster scanning device (exposure means), 4 ... Developer (developing means), 5 ... Pre-transfer charger, 6 ... Transfer charger, 7 ... Peeling charger, 9 ... static elimination lamp

Claims (4)

[Claims] 1. A rotating photoconductor, a first charging unit for initially charging the photoconductor, an exposure unit for exposing the photoconductor charged by the first charging unit in accordance with image information, Developing means for developing the electrostatic latent image formed on the photoreceptor to form a toner image, and a developing means arranged downstream of the developing device and upstream of the first charging means in the rotation direction of the photoreceptor. An image forming apparatus provided with a second charging means for charging or discharging the photoconductor, wherein the second charging means is driven and the driving output thereof is controlled within a certain time immediately after the rotation of the photoconductor is started. , The first
An image forming apparatus comprising: a pre-charging control unit for pre-charging a photoconductor before initial charging by a charging unit. 2. A rotating photoconductor, a charging unit for initially charging the photoconductor, an exposure unit for exposing the photoconductor charged by the charging unit in accordance with image information, and a photoconductor on the photoconductor by the exposure. An image forming apparatus comprising: a developing unit that develops an electrostatic latent image formed on a photosensitive drum to form a toner image; An image forming apparatus, comprising: an initial charging control unit that changes a driving output of the charging unit during the subsequent initial charging. 3. A rotating photoreceptor, a charging unit for initially charging the photoreceptor, an exposing unit for exposing the photoreceptor charged by the charging unit in accordance with image information, and And a developing means for developing the electrostatic latent image formed on the photosensitive member to form a toner image, wherein the photosensitive member has been subjected to initial charging by the charging means only once after the rotation of the photosensitive member has started. And an exposure intensity control means for changing the exposure intensity of the exposure means between the surface area of the photosensitive member and the surface area of the photoreceptor which has been subjected to the initial charging twice or more. 4. A rotating photoreceptor, a charging unit for initially charging the photoreceptor, an exposing unit for exposing the photoreceptor charged by the charging unit in accordance with image information, and And a developing means for developing the electrostatic latent image formed on the photosensitive member to form a toner image.
Surface area of the photoreceptor that has only been
An image forming apparatus, comprising: a bias control unit that changes the intensity of a developing bias voltage applied between the developing unit and the photoconductor in a surface region of the photoconductor that has been received more than once.