JPH0389291A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent higher potential from being generated on the surface of a photosensitive body than necessary by changing a current impressed on a corona discharger for electrostatic charging at a prefatigue stage according to the change of the surface circumferential speed of the photosensitive body. CONSTITUTION:A memory 9 in which measured time (ti) by a timer 3 and the value of the voltage Vi of an electrostatic charger outputted corresponding to the time (ti) are stored in a pair is connected to a microcomputer 1. When a copying button is depressed in a state where an image processing action is not executed, the driving of a main motor 7 is started and the rotation of the photosensitive drum rises. At this time, the photosensitive drum rises with time lag, for example, about 0.1-0.2 seconds. At the same time, the microcomputer 1 resets the timer 3. When detected time (t) by the timer 3 becomes t1, the voltage value V1 corresponding to the time t1 is retrieved from the memory 9 and impressed on an electrostatic charger 5. Then, the voltage Vi is impressed at the time (ti).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic M image forming apparatus, such as a copying machine, which includes a pre-fatigue step.

[Prior art]

Conventionally, among photoreceptors used in image forming devices such as copying machines and laser beam printers, organic photoreceptors and arsenic-based
In the case of selenium photoconductors, it takes some time to eliminate the cards inside the photoconductor and stabilize the photoconductor during the charging process, so even if you try to optimize the conditions of each process,
Note that it may not be possible to remove changes in copy density from the first to several copies at the start of image processing. For this reason, when the switch to start image processing is turned on, the charging and discharging processes are repeated for about 1 to 5 cycles before the actual image forming process is started, and then the true image processing operation is started.
For example, an image forming apparatus disclosed in Japanese Unexamined Patent Publication No. 60-241080 discloses such a technique, in which an attempt has been made to avoid the above-mentioned initial density change.

[Problem to be solved by the invention]

The process of repeating the charging and discharging process prior to the actual image processing process as described above is called the pre-copying process or the pre-fatigue process, and is used to stabilize the charging performance at the time the actual image processing begins. It is an excellent technology in that it can be done. Since the pre-fatigue process described above is performed before the start of the image processing operation, in order to shorten the first copy time,
Boat fishing is carried out when the main motor that drives the drum etc. is started.

However, when the main motor starts to drive, there is always a time lag until the rotating body reaches a constant rotational speed. Therefore, during the above time lag, the surface speed of the photoreceptor is slower than during normal image processing, so the charging efficiency (corona discharge efficiency) by the charger increases, and until the above time lag passes, the surface speed of the photoreceptor becomes slower than during normal image processing. A charge with a higher potential than the charging potential of is formed.

If an abnormally high potential area is formed on the surface of the photoreceptor as described above, even if the next exposure process is performed, the potential of the high potential area cannot be lowered sufficiently to a level where it will not be developed, and the developing area When passing through the toner, a band of toner adheres to the toner.

Since such a toner image has a so-called solid black state and has a large amount of toner attached to it, when it passes through a cleaning device, it damages the cleaning blade and causes cleaning failure. This is because the solid black toner image as described above exceeds the permissible ability to be scraped off by the cleaning blade.

Furthermore, as described above, a large amount of toner is discharged from the developing section, so there is a problem that the amount of toner consumed is large.

Furthermore, in the pre-fatigue step, a series of image processing processes are performed without transporting the transfer paper, so there is a problem that toner directly adheres to the transfer charger, making the transfer charger extremely dirty.

Furthermore, as described above, a high potential far exceeding the appropriate voltage is formed on the surface of the photoreceptor, causing dielectric breakdown of the photoreceptor, leading to image defects and even pinholes.

Therefore, it is an object of the present invention to prevent an unnecessarily high potential from being formed on the surface of a photoreceptor in the pre-fatigue process, thereby solving the various problems described above when introducing the pre-fatigue process.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an image forming apparatus that performs a pre-fatigue process including charging and neutralizing a photoreceptor prior to an image forming operation, and provides a corona discharge for charging during the pre-fatigue process. This image forming apparatus is characterized in that the current applied to the electric appliance is changed in accordance with the change in the surface circumferential speed of the photoreceptor.

Among the above configuration requirements, various methods can be considered as means for changing the applied current according to changes in the circumferential speed of the photoreceptor. There may be a method in which the corona current is changed by a predetermined degree within a certain range, or a method in which the speed of the photoreceptor or the motor that drives it is detected and a corona current is applied according to each speed.

[Effect]

In the present invention, as described above, the corona current is changed according to the circumferential speed of the photoreceptor, so the potential applied to the photoreceptor surface is about the same as that during normal copying processing, and the potential applied to the photoreceptor surface is approximately the same as that during normal copying processing. The potential is such that it can be sufficiently removed in the electricity removal step provided with the normal amount of light. Therefore, toner is not consumed more than necessary, cleaning failures or cleaning blades are not damaged, and the transfer charger is also prevented from becoming dirty. Further, since only a voltage within the allowable limit for the photoreceptor is applied, problems such as dielectric breakdown do not occur.

〔Example〕

Next, embodiments embodying the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.

Here, FIG. 1 is a block diagram for explaining the control contents of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a flowchart showing the procedure of the same control contents, and FIG. 3 is an example of memory contents. This is a graph showing.

It should be noted that the following examples are merely examples embodying the present invention, and are not intended to limit the technical scope of the present invention.

The image forming apparatus according to this embodiment, as shown in FIG.
In terms of hardware, there is no particular difference from the conventional general copying machine described in, for example, Japanese Unexamined Patent Publication No. 60-241080, except that it is equipped with a blank lamp.

That is, as shown in FIG. 1, a copy button 2 is connected to an input section of a microcomputer 1 that controls the entire copying machine, along with many switches provided on an operation section. Reference numeral 3 denotes a timer operated by a clock 7 which determines the control cycle of the microcomputer 1, and is clocked or reset by a command from the microcomputer 1.

A driver circuit 4 is installed on the output side of the microcomputer 1.
A charger 5, blank lamp 6, and main motor 7 are connected via m+ 4h and 4c, respectively. The main motor 7 has a pulse plate and a microcomputer 1 which converts the amount of rotation of the pulse plate into an electrical pulse signal.
A pulse generator 8 is connected which includes an optical sensor for transmitting signals to the pulse generator. Such a pulse generator 8 may be of any type as long as it can rotate in synchronization with the main motor 7. For example, it may be a pulse generator 8 that is directly connected to the main motor 7, or a pulse plate and a light source that are provided in the drive system from the main motor to the photoreceptor. A sensor or the like may be used, or a rotary encoder or the like may be used.

In addition, the micro combinator 1 has the time 1L measured by the timer 3 and the charger voltage v output corresponding to this.
A memory 9 in which values of L are stored in pairs is connected.

The storage contents of the memory 9 are set for each model. FIG. 3 shows an example of the stored contents of such memory 9.

In this embodiment, it is assumed that the photosensitive drum almost completely stands up t0 seconds after the start of rotation of the photosensitive drum.

Next, the processing procedure of this image forming apparatus will be explained with reference to the flowchart shown in FIG.

In addition, in the following explanation, S1. S2... is a processing element) [(step) number 0 When the copy button is pressed in a state where no image processing operation is being performed (Sl), the main motor 7 starts to be driven, and the photoreceptor drum is rotated. The rotation starts (32), and at this time the photoreceptor drum has a rotation speed of, for example, 0.1
It gradually starts up with a time lag of about 0.2 seconds to 0.2 seconds. At the same time, the microcomputer 1 resets the timer 3 (S3).

In S4, the detection time t by the timer 3 first reaches 1. When the detection time t reaches tl, the voltage value V corresponding to t shown in FIG. 3 is retrieved from the memory 9 and applied to the charger 5.

When the application to the charger 5 ends, the detection time t continues to be 1.
(Start-up time of main motor 7) is determined (35) L. If not, the process returns to S4, and S4
．． The routine of S5 is repeated, and a voltage of V is applied at LL seconds.

When the detection time t reaches to, the pre-fatigue process original zero standard voltage v0 is applied to the charger 5 (S6), and the pre-fatigue process is maintained until the required time 1e of the pre-fatigue process is reached (s7), V
o is the charger voltage used during normal copying operation or a voltage slightly lower than that, and a voltage is selected that does not cause development by subsequent irradiation with the blank lamp 6.

Further, when the pre-fatigue process is completed, the routine moves to a normal copying operation (S8). Thereafter, the well-known copying operation is performed for the set number of copies, and the process ends.

In the pre-processing step in the above embodiment, the main charger 5 was used for charging and the blank lamp 6 was used to erase the charge, but a halogen lamp for image formation could be used instead of the blank lamp 6. You can also do it. In this case, the surface of the photosensitive drum is irradiated with light from a halogen lamp reflected on a white sheet pasted on the back of the document table.

Further, a transfer device is used for charging, and a discharge lamp is used to erase the charge, but a blank lamp 6 can also be used.

In addition, in the above embodiment, the stored content of the memory 9 is "a pair of the detection time and the corresponding applied voltage", but it is also "the pair j of the rotational speed of the main motor or photosensitive drum and the corresponding applied voltage". In this case, the rotational speed of the main motor or photosensitive drum is detected based on the pulse signal from the pulse generator 8, and the corresponding applied voltage is retrieved from the memo I79.

[Effect of Crab Sun Moon]

As described above, the present invention performs a pre-fatigue process including charging and neutralizing the photoreceptor prior to the image forming operation!
i-Image forming apparatus, characterized in that the current applied to the charging corona discharger during the pre-fatigue step is changed in accordance with changes in the surface circumferential speed of the photoreceptor. Since it is a forming device, an appropriate voltage that is not too high is applied to the surface of the photoreceptor, so there is no problem of forming a high potential that would cause dielectric breakdown of the photoreceptor. Since static electricity can be removed sufficiently, there is no problem such as toner adhering to the area.
Therefore, toner consumption does not increase, and problems such as poor cleaning, damage to the cleaning blade, and dirt on the transfer charger are solved.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining the control content of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a flowchart showing the procedure of the control content, and FIG. 3 is a graph showing an example of memory content. It is. [Explanation of symbols] 1... Microcomputer 3... Timer 5... Charger 6... Static elimination lamp 7... Main motor 8... Pulse generator 9... Memory

Claims (1)

[Claims] (1) In an image forming apparatus that performs a pre-fatigue process including charging and neutralizing the photoreceptor prior to image forming operation, the current applied to the corona discharger for charging during the pre-fatigue process is applied to the photoreceptor. An image forming apparatus characterized in that the image forming apparatus changes according to a change in the surface circumferential speed of the image forming apparatus.