JPH052328A - Simultaneous developing and cleaning type image forming device - Google Patents

Abstract

PURPOSE:To drastically shorten a preparatory rotation time and to perfectly remove residual toner by cleaning. CONSTITUTION:The image forming device of a simultaneous developing and cleaning system is provided with a surface potential detecting means 30 for detecting the surface potential Vdet of a photosensitive drum 1 and a preparatory rotation continuing control means 40. A high-quality image formation enabling state is automatically detected based on the detected surface potential Vdet of the photosensitive drum 1 and previously set reference surface potential Vset, and the preparatory rotation is continued until the enabling state is attained. Then, a resistance value detecting means 35 is provided in place of the detecting means 30.

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 of a cleaning simultaneous developing system.

[0002]

2. Description of the Related Art A developing device and a waste toner collecting device including a scraping blade are arranged on both sides of a photosensitive drum with a transfer device interposed therebetween, and development and cleaning of residual toner on the photosensitive drum are performed independently. In contrast to the well-known image forming apparatus, the present applicant has previously proposed an image forming apparatus shown in FIG. 5 which is a so-called simultaneous developing cleaning system in which development and cleaning are performed at the same time (for example, JP-A-3-7972). According to this simultaneous development cleaning method, epoch-making effects such as reduction of running cost due to reduction of toner consumption, downsizing of the apparatus, and cleaning without damaging the photosensitive drum can be obtained.

In FIG. 5, 1 is a photosensitive drum as a latent image carrier, 2 is a charger, 3 is a developing device, and 7 is a transfer device. Further, the developing device 3 is of a contact type one-component non-magnetic developing system using an elastic conductive roller (developing roller) 6 as a developer (toner) carrier, and the one-component toner T0 housed in the box 4 is Charging brush 5 made of silicone rubber, etc.
The charged toner T1 is supplied to the photosensitive drum 1 for development.

Reference numeral 20 is a control device, which is the main motor 1
1, the laser emission source 12, the developing bias power source (-Vb) switch 14, the charger power source (-Vo) switch 13 and the like are driven and controlled at the timing shown in FIG. The opening / closing device 15 of the transfer device 7 and the like are also drive-controlled. Further, the photosensitive drum 1 is rotated at a constant speed by a driver (not shown) serving as a rotation driving unit and a main motor 11.

In the image forming apparatus having such a structure, when the controller 20 starts the rotational driving of the main motor 11 at time t1 in FIG. 6, the photosensitive drum 1 and the developing roller 6 are synchronously rotated at a constant speed. Further, the peripheral surface of the photosensitive drum 1 is charged to the charging potential −Vo during image formation by the charger 2, and the exposed portion irradiated with the laser scanning beam B after time t2 has the potential −Vr. The unexposed area has a charging potential of −V.
It remains o. On the other hand, the developing roller 6 is also charged to the developing bias potential −Vb.

As shown in FIG. 7C, the charging potential -Vr of the exposed portion has the same polarity as the developing bias potential -Vb to the developing roller 6, but its absolute value is low (| Vr | <| Vb |).
Therefore, the charged toner T1 on the developing roller 6 is attracted to the exposed portion as the developing toner T3 by the action of the electric field, as shown in FIGS. That is, it is developed [FIG. 7 (C)]. The toner T remaining on the developing roller 6
4 is collected in the developing device 3 and reused.

The developing toner T3 is then transferred to the opposite surface (front surface) of the paper P by the transfer device 7 of FIG. 5 (which is turned on at time t2 of FIG. 6), and as shown in FIGS. As shown, it is transferred as image toner T5.

On the other hand, the toner (T6) may remain on the photosensitive drum 1 even after the transfer. This residual toner T6
Is charged to the above potential -Vo in the charger 2 as shown in FIG. However, as shown in FIG. 7B, the residual toner T6 that has adhered to the exposed portion after that is charged to a potential -Vr whose absolute value is lower than the developing bias potential -Vb during exposure as shown in FIG. Absent. Rather,
This is advantageous because it can be effectively used for the development shown in FIG.

On the other hand, the residual toner T6 adhering to the unexposed portion shown in FIG. 7B remains at the charging potential -Vo having the same polarity as the developing bias potential -Vb of the developing roller 6 and a high absolute value. Therefore, as shown in FIG. 7C, the residual toner T6 is attracted to the developing roller 6 side by the electric field action. That is, the residual toner T6 attached to the unexposed portion
Are removed from the photosensitive drum 1, and it is understood that cleaning is performed here. Further, the removed residual toner T6 can be reused as the supplied toner T1 in FIGS. 5 and 7C.

Thus, the cleaning is performed at the upstream position where the photosensitive drum 1 and the developing roller 6 come into contact with each other, and subsequently, the development is simultaneously performed at the downstream side.

[0011]

By the way, in order to form an image with such an apparatus, preparatory work such as preparatory rotation for raising the photosensitive drum 1 to a prescribed number of revolutions and stabilization of each potential is required. For this reason, the control device 20 drives and controls each unit at the timing shown in FIG.

Here, P2- of the photosensitive drum 1 shown in FIG.
The peripheral surface portion between P1 contacts the developing roller 6 without passing through the charger 2 at the start of the preparatory rotation. Therefore, as a matter of course, the peripheral surface portion between P2 and P1 is not charged to the charging potential −Vo during image formation, and depending on the length of the stop time, as shown in FIG. The value may be a low residual potential −Vs.

Then, development (| Vb |) shown in FIG.
-| Vr |) electric field effect (| Vb |-| Vs |)
Will occur. That is, the supplied toner T1 carried on the developing roller 6 to which the developing bias potential −Vb is applied is
P2-P1 of the photosensitive drum 1 having the residual potential -Vs
A large amount adheres to the peripheral surface area. Originally, the opposite phenomenon to cleaning occurs. If left unattended, not only will it scatter after passing through the developing roller 6 to contaminate the inside of the apparatus, but also the image quality will deteriorate.

Therefore, in order to eliminate this inconvenience,
The peripheral surface portion between P2 and P1 must be passed through the charger 2 to be charged to the charging potential -Vo during image formation, and the essential cleaning must be performed. However, if the amount of the residual toner attached to the relevant portion is large, the residual toner may not be charged to a predetermined value (-Vo) even if it passes through the charger 2 several times during the preparatory rotation, and sufficient cleaning can be performed. Absent. Thus, the preparation rotation time of the photosensitive drum 1 must be considerably lengthened, which hinders rapid image formation.

Moreover, whether or not the entire peripheral surface of the photosensitive drum 1 has been completely cleaned is determined by whether or not the image on the paper P after transfer is of high quality. For this reason, when it is actually determined that the cleaning is incomplete, the result is that the paper P is wasted, power consumption, and the image forming operation are delayed. In order to eliminate such concerns, the actual preparation rotation time is likely to be longer than necessary.

On the other hand, a large amount of residual toner T6 adheres to the peripheral surface portion between P2 and P1 and has a predetermined value (-V).
It is not always the case that o) is difficult to be charged. In other words, even if there is a case where it is sufficient to pass the part through the charger 2 only once, for example, the lengthy preparatory rotation time set from the viewpoint of eliminating the above-mentioned concern is spent, which is completely wasted.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus of the simultaneous developing cleaning system capable of performing a complete cleaning and rapidly forming a high-quality image while significantly shortening the preparation rotation time.

[0018]

According to the present invention, the potential difference between the photosensitive drum side and the developing roller side during the preparatory rotation prevents the reverse cleaning phenomenon and enables regular cleaning.
And it automatically detects whether high-quality image formation is possible,
When it is determined that a high-quality image can be formed, the preparatory rotation is ended. In other words, the preparatory rotation is continued until high-quality image formation is possible, and the preparatory rotation time can be set to a necessary minimum time. The above-mentioned objects are achieved.

That is, the invention of claim 1 forms an exposed portion and an unexposed portion irradiated with a laser scanning beam on the peripheral surface of the photosensitive drum that has passed through the charger, and develops the photosensitive drum side and a developing bias applied. Using the potential difference from the roller side, the residual toner adhering to the unexposed area is adsorbed to the developing roller side to clean the unexposed area and at the same time toner is supplied from the developing roller side to the exposed area for development. In an image forming apparatus of the cleaning simultaneous development type, the surface potential detecting means for detecting the surface potential of the photosensitive drum and the photosensitive drum until the surface potential detected by the photosensitive drum surface potential detecting means reaches a preset reference surface potential. A preliminary rotation continuation control means for continuing the preliminary rotation operation of the drum is provided.

According to a second aspect of the present invention, the peripheral portion of the photosensitive drum that has passed through the charger is provided with an exposed portion and an unexposed portion irradiated with a laser scanning beam, and the photosensitive drum side and the developing bias are applied. Using the potential difference from the roller side, the residual toner adhering to the unexposed area is adsorbed to the developing roller side to clean the unexposed area and at the same time toner is supplied from the developing roller side to the exposed area for development. In an image forming apparatus of the simultaneous developing and cleaning type, until the resistance value detecting means for detecting the resistance value between the photosensitive drum and the developing roller and the resistance value detected by the resistance value detecting means become a preset reference resistance value. A preparatory rotation continuation control means for continuing the preparatory rotation operation of the photosensitive drum is provided.

[0021]

According to the first aspect of the invention, when the photosensitive drum is preliminarily rotated, the surface potential detecting means automatically detects the surface potential of the photosensitive drum. Then, the preparatory rotation continuation control means continues the preparatory rotation operation until the preset reference surface potential becomes equal to the detected surface potential, that is, until high-quality image formation becomes possible. Therefore, if the reference surface potential is set in advance to a value at which the reverse cleaning phenomenon cannot occur, a high-quality image can be quickly formed with the minimum preparation rotation time.

Further, in the invention of claim 2, when the photosensitive drum is preliminarily rotated, the resistance value detecting means automatically detects the resistance value between the photosensitive drum and the developing roller. Then, the preparatory rotation continuation control means continues the preparatory rotation operation until the preset reference resistance value becomes equal to the detected resistance value, that is, until high-quality image formation is possible. Therefore,
If the reference resistance value is set in advance to a value at which the reverse cleaning phenomenon does not occur, a high-quality image can be quickly formed with the minimum preparation rotation time.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) As shown in FIG. 1, an image forming apparatus of the main development simultaneous cleaning system is basically the same as the conventional structure shown in FIG. Continuation control means 40 is provided, and the preparatory rotation is continued until the surface potential (Vdet) of the photosensitive drum 1 prevents a reverse cleaning phenomenon and normal cleaning can be performed, that is, high-quality image formation becomes possible. .

First, as shown in FIG. 1, the surface potential detecting means 30 is composed of a detection roller 31 which can be contacted with and removed from the peripheral surface of the photosensitive drum 1 and can be rotated, and the detection roller 31 and the ground G. And a potential detector 32 connected between them. The detection roller 31 has a certain length in the width direction of the photosensitive drum 1 (the direction perpendicular to the paper surface of FIG. 1), and is basically formed so as to make line contact with the peripheral surface of the photosensitive drum to detect the average value. ing. On the other hand, the potential detector 32 outputs the detected surface potential equivalent signal Vdet.

The detection roller 31 includes a CPU, RO
The control device 20 including M, RAM and the like contacts the peripheral surface of the photosensitive drum 1 at the start of the preparatory rotation (time t1) in FIG. 2 and disengages when the determination signal JUD described later is output.

Next, the preparatory rotation continuation control means 40 operates as shown in FIG.
, The reference value setter 25 for setting the reference surface potential (Vset) is compared with the reference surface potential (Vset) and the detected surface potential (Vdet), and | Vdet | ≧ | Vs
In the case of et |, it is composed of a comparison means 26 that outputs a determination signal JUD that considers that high-quality image formation is possible, and a control means (20).

In the case of this embodiment, this control means is the above-mentioned control device 20 for controlling the drive of the entire device.
(The constituent elements such as CPU and ROM and their functions) are used to rotate the main motor 11 as the rotation driving means of the photosensitive drum 1 until the determination signal JUD is continuously input for the set time Ts. It is formed to continue and output a signal to the control device 20 to permit scanning by the laser scanning beam B after the signal JUD is input.

In the case of this embodiment, the control means (20) determines that the judgment signal JUD is reached after a certain time (for example, the time during which the surface portion P1 shown in FIG. 1 can pass through the charger 2 at least once). It is formed to judge the continuity of. Therefore, the set time Ts can be a short time required for the photosensitive drum 1 to rotate, for example, 1/4.

However, the longer the set time Ts, the more
Since the reverse cleaning phenomenon can be completely prevented and regular cleaning can be performed more reliably, the time setting device 21 is provided in this embodiment so that it can be variably set.

The controller 20 and the preparatory rotation continuation control means (20) are designed to start and stop each means at the timing shown in FIG.

Next, the operation will be described. First, the reference surface potential (Vset) and the set time Ts selected from various conditions are set in the reference value setter 25 and the time setter 21. In this embodiment, the set time Ts is set to the photosensitive drum 1
Is set as the time for only 1/2 rotation from the state shown in FIG. The reference surface potential Vset will be described later.

Now, at the time t1 in FIG. 2, the controller 20 causes the main motor 11, the laser emission source 12, the switch 13 of the power source (-Vo) for the charger, the developing bias power source (-).
When the switch 14 etc. of Vb) is driven to start the preparatory rotation,
The photosensitive drum 1 starts rotating clockwise in FIG.

Then, the preparatory rotation continuation control means 40 (2
5, 26, 20) continues the preparatory rotation of the photosensitive drum 1 until the high quality image can be formed.

That is, the detection roller 31 is brought into contact with the peripheral surface of the photosensitive drum 1 based on a signal from the control device 20 at time t1. Then, the surface potential equivalent signal Vdet of the relevant portion is input from the potential detector 32. here,
The comparing means 26 compares the detected surface potential (Vdet) with a preset reference surface potential (Vset), and
When Vdet | ≧ | Vset |
Output D.

Then, when the judgment signal JUD is continuously input for the set time Ts as shown in FIG. 2, the control means (20) outputs a signal to the control device 20 to the effect that a high quality image can be formed. . That is, until then, the controller 20 is caused to continue the rotation of the main motor 11 and the scanning of the laser scanning beam B is not permitted. That is, the preparatory rotation is continued until time t3 in FIG.

More specifically, as shown in FIG. 3, P2-P1 of the photosensitive drum 1 at the start of preparatory rotation (t1).
The residual potential at the peripheral surface portion (see FIG. 1) is -Vs (for example,-
50 V), the charging potential by the charger 2 is −Vo (for example, −500 V), and the developing bias potential to the developing roller 6 is −Vo.
When Vb (for example, −200 V) is set, the peripheral surface portion between P2 and P1 (specifically, the residual toner T attached to the peripheral portion).
6) comes into contact with the developing roller 6 with the polarity being lower than the developing bias potential (−Vb) and the absolute value being low (−Vs + α) even though the toner has passed through the charger 2 once, as shown in FIG.
The reverse cleaning phenomenon occurs as in the conventional example described in the above.

In the present invention, the reference surface potential (-Vset) set in the reference value setting unit 25 has the same polarity as the developing bias potential (-Vb) shown in FIG.
If you select the value shown by the dotted line (eg -250V),
Like the detected surface potential (-Vdet) indicated by the dotted line, the preparatory rotation continues until the absolute value becomes higher with the same polarity than that value (-Vset = -250V) (scanning by the laser scanning beam B is denied. )it can.

That is, the detected surface potential (-Vdet) is
If it is impossible to cause the reverse cleaning phenomenon in relation to the developing bias potential (-Vb), the preparatory rotation can be ended regardless of the length of time. According to the implementation results, the preparation rotation time (t1-t of the conventional example shown in FIG.
2), the preparation rotation time (t1-t) shown in FIG.
It was confirmed that in 3), the time required was almost half or less.

At the time of image formation after the time t3 in FIG. 2, the potential of the unexposed portion not irradiated with the laser scanning beam B is approximately the same as the charging potential -Vo, for example, -500V.
Similarly, the residual toner T6 attached to the unexposed portion is -50.
It is 0V. Thus, a large potential difference (| Vo |-| Vb |) as shown in FIG. 7C is generated between the residual toner T6 (-Vo) and the developing roller 6 (-Vb).
Due to this electric field action, the residual toner T6 is attracted to the developing roller side. That is, the unexposed portion on the photosensitive drum 1 is cleaned.

On the other hand, the exposure section (-Vr) and the developing roller 6
A potential difference (| Vb |-| Vr |) is generated between (-Vb) and the developing roller 6 side having the same polarity and a high absolute value. Therefore, the supplied toner T1 is attracted to the exposed portion having a low absolute value. To be done. That is, development is performed. The potential −Vr is −50V, for example.

According to this embodiment, however, the surface potential detecting means 30 and the preparatory rotation continuation controlling means 40 are provided, and the surface potential (-Vdet) of the photosensitive drum 1 is set to the reference surface potential (-Vset). ), The preparatory rotation can be completed at the time when a high-quality image can be formed.Therefore, the reverse cleaning phenomenon can be completely prevented and the high-quality image formation can be performed while promoting the regular cleaning phenomenon. Can be done quickly.

The surface potential detecting means 30 comprises a detection roller 31 and a potential detector 32, and the control device 20 allows the detection roller 31 to come into contact with and separate from the photosensitive drum 1. Sometimes the surface potential can be reliably detected during preparatory rotation without disturbing.

Further, the preparatory rotation continuation control means 40 is formed of the reference value setting device 25, the comparison device 26 and the control means (20), and the reference surface potential (-Vset) can be arbitrarily selected and set. 2 has a wide applicability and can be operated in response to the charging potential (-Vo), the developing bias potential (-Vb), etc.

Further, the control means (20) sets the set time T
With the judgment signal JUD being continuously input for s,
Since it is formed so as to determine whether or not high-quality image formation is possible, the peripheral surface potential of the photosensitive drum 1 can be checked in a stable manner overall, and a partial reverse cleaning phenomenon can be eliminated.

Furthermore, the control means (20) does not judge whether or not high quality image formation is possible until the peripheral surface portion between P2 and P1 shown in FIG. 1 passes through the charger 2 once. With this configuration, the residual toner T6 attached to the relevant portion can be reliably cleaned.

(Second Embodiment) In the second embodiment, it is determined whether or not the first embodiment can prevent a reverse cleaning phenomenon from the surface potential (-Vdet) of the photosensitive drum 1 and form a high quality image. Although the judgment is made, the judgment is made by the resistance value between the photosensitive drum 1 and the developing roller 6.

That is, in the configuration of the second embodiment, the resistance value detecting means 35 shown in FIG. 4 is provided instead of the surface potential detecting means 30 (31, 32) in the first embodiment, except that the configuration shown in FIG. The configuration is the same as that of the first embodiment. However, the reference resistance value with respect to the detected resistance value is set in the reference value setting device 25 which constitutes the preparatory rotation continuation control means 40.

According to the second embodiment, as shown in FIG. 4, the actual resistance value between the photosensitive drum 1 and the developing roller 6, that is, the developing bias potential (-Vb) shown in FIG. 3 and the surface of the photosensitive drum 1. Since it is possible to indirectly detect the potential difference from the potential (corresponding to -Vdet or -Vo), that is, the electric field strength and its directionality, it is possible to determine the prevention of the reverse cleaning and the like. Therefore, the same operation as that of the first embodiment is performed. Produce an effect. Furthermore, the resistance value detecting means 35 need not be in contact with the surface of the photosensitive drum 1 as shown in FIG. 4, so that the structure is simple.

[0049]

As described above, according to the invention of claim 1,
Since the surface potential detection means and the preparatory rotation continuation control means are provided and the preparatory rotation can be ended when high-quality images can be formed, the waste of the conventional example in which the time is set uniformly The cleaning time can be swept away, the preparation rotation time can be significantly shortened, and a high-quality image can be formed quickly while ensuring complete cleaning.

According to the second aspect of the invention, the resistance value detecting means for detecting the resistance value between the photosensitive drum and the developing roller and the preparatory rotation continuation controlling means are provided.
In addition to the same effect as in the case of the invention of claim 1, the structure can be further simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention.

FIG. 2 is also a timing chart for explaining the operation.

FIG. 3 is likewise a diagram for explaining a reference surface potential.

FIG. 4 is a diagram for explaining a resistance value detecting means of a second embodiment of the present invention.

FIG. 5 is an overall configuration diagram of a conventional example.

FIG. 6 is a timing chart for explaining the operation of the conventional example.

FIG. 7: Conventional charging-exposure-cleaning simultaneous development-
FIG. 6 is a diagram for explaining a transfer operation.

FIG. 8 is a diagram for explaining the problems of the conventional example.

[Explanation of symbols]

1 photosensitive drum 2 charger 3 developer 6 developing roller 7 Transfer device 11 Main Motor 12 Laser emission source 20 Control device (control means) 25 Reference value setting device 26 Comparison means 30 Surface potential detection means 31 Detection roller 32 potential detector 35 Resistance value detecting means 40 Preparation rotation continuation control means T1 supply toner T6 residual toner Vdet detection surface potential Vset reference surface potential JUD judgment signal Ts set time

Claims (2)

[Claims] 1. An exposed portion and an unexposed portion formed by irradiating a laser scanning beam on a peripheral surface of a photosensitive drum which has passed through a charger,
Utilizing the potential difference between the photosensitive drum side and the developing roller side to which the developing bias is applied, the residual toner adhering to the unexposed area is adsorbed to the developing roller side to clean the unexposed area and at the same time to the exposed area. In an image forming apparatus of a simultaneous cleaning type in which toner is supplied from the developing roller side for development, the surface potential detecting means for detecting the surface potential of the photosensitive drum and the surface potential detected by the photosensitive drum surface potential detecting means are set in advance. An image forming apparatus of simultaneous cleaning type, which is provided with a preparatory rotation continuation control means for continuing the preparatory rotation operation of the photosensitive drum until the reference surface potential is set. 2. An exposed portion and an unexposed portion irradiated with a laser scanning beam are formed on the peripheral surface of the photosensitive drum which has passed through the charger,
Utilizing the potential difference between the photosensitive drum side and the developing roller side to which the developing bias is applied, the residual toner adhering to the unexposed area is adsorbed to the developing roller side to clean the unexposed area and at the same time to the exposed area. In an image forming apparatus of the simultaneous development type which supplies toner from the developing roller side to develop, a resistance value detecting means for detecting a resistance value between the photosensitive drum and the developing roller, and a resistance value detected by the resistance value detecting means. An image forming apparatus of simultaneous developing cleaning system, characterized by further comprising: preparatory rotation continuation control means for continuing the preparatory rotation operation of the photosensitive drum until becomes a preset reference resistance value.