JPS6157963A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To suppress unnecessary toner consumption and to stabilize development by providing a means which starts driving a developing machine a time, which is required for movement of a photosensitive body from an electrifying means to a developing means, behind the operation start time of the electrifying means when the operation of a copying machine is started. CONSTITUTION:The application of a high voltage to an electrifier 2 is started simultaneously with the start of driving of a photosensitive drum 1, and driving of the developing machine is started when a development driving start slit 8 passes the position of a photo sensor 10. The output of the photosensor is turned on because the photo sensor 10 detects a reference position slit 9 at the operation stop time of an electrophotographic device, and this output is turned off a little after the driving start because the photo sensor is shielded by a disc 7. When the photo sensor detects the development driving start slit 8, the output of the photosensor is turned on, and driving of the developing machine which is stopped till now is started simultaneously. When the photo sensor 10 detects the reference position slit 9, driving of the developing machine is stopped simultaneously with the stop of driving of the photosensitive drum, and the applied voltage to the electrifier is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic apparatus, and more particularly to an electrophotographic apparatus capable of obtaining reversal developed images.

Conventional technology ili? In the case of a development method in which toner charged to the opposite polarity to the I-electrode potential is attached to unexposed areas (dark areas) under a low development bias to obtain uneven development, the charging means is started to operate almost at the same time as the copying operation starts. , and it is common to start driving the developing machine at the same time. Negative (reversal) in which a developing bias voltage of the same level as the potential of the non-exposed area is applied, and toner charged to the same polarity as the band of the photoconductor is attached to the photoconductor part corresponding to the exposed area (bright area). Various electrophotographic apparatuses equipped with a developing device have been proposed, but in these electrophotographic apparatuses as well, the negative developing apparatus starts operating almost simultaneously with the start of operation of the copying machine.

Problems to be Solved by the Invention However, in the case of reversal development, the charging means is turned on almost simultaneously with the start of operation of the copying machine, that is, at the same time as the start of operation of the copying machine.
If the developing machine is driven almost at the same time as the charging means starts operating, the uncharged photoreceptor portion C will pass through the developing machine 6, as shown in Figure aS7 (A). At that time, that area is reversely developed and a large amount of toner is deposited on the photoreceptor. This toner may be removed from the photoreceptor by the transfer means, causing toner stains inside the copying machine.
Poor cleaning may occur, and in some cases, toner may reach the exposure means of the next cycle, resulting in black bands on the image. At the same time, as shown in FIG. 7(B), an unnecessary large amount of toner is consumed and a large amount of toner rushes into the cleaner, resulting in toner spillage.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electrophotographic apparatus suitable for reversal development that solves the above-mentioned problems of reversal development.

Means for Solving the Problems and Operation In order to solve the problems of the prior art described above, the present invention provides, at the start of operation of the copying machine, from the start of operation of the charging means.
The present invention is characterized in that means is provided for starting the driving of the developing machine with a delay corresponding to the travel time of the photoreceptor from the charging means to the developing means. In other words, according to the present invention, if J: as shown in FIG. Toner 5 never arrives at C.

In the above explanation with reference to FIGS. 1 and 7, the case where the photoconductor is uniformly positively charged and reverse development is performed with positive polarity toner is described, but the present invention is not limited to this, and the photoconductor is charged negatively. It goes without saying that the present invention can be similarly applied to the case where reversal development is performed using negative polarity toner.

FIG. 2 is a diagram showing an example of a means for detecting the timing to start driving the developing machine, in which a rotation angle detecting disc 7 fixed integrally with the photosensitive drum 1 and a reference position slit are used. A method is shown in which separate drive start slits 8 are provided and passage through these slits is detected by a photosensor 10. That is, the application of high voltage to the charger 2 is started at the same time as driving of the photosensitive drum 1 is started, and the development is started so that the driving of the developing device is started when the slit 8 passes the position of the photosensor 10. It is composed. When stopping the operation, the driving of the photosensitive drum 1 is stopped when the reference position slit 9 is detected by the photosensor 10. Due to the inertia of the photoconductor drum and photoconductor drum drive system, if the rotation angle from when the drive stop position is detected until it actually comes to rest cannot be ignored, the deflection angle between slits 8 and 9 can be calculated as the charger position. The deviation angle θ between the development position and the development position is corrected using known means such as a method of widening the deviation angle θ.

FIG. 3 is a timing chart diagram that does not show the operation of the detection means of FIG. 2, in which a voltage is applied to the charger at the same time as the photosensitive drum is driven. When the electrophotographic apparatus stops operating, the photo sensor 10 detects the reference position slit 9, so the photo sensor output is ON''C, and the photo sensor output is activated for a while from the beginning, and the photo sensor is activated by the disk 7. Riz0
It becomes OFF because it is distorted. Furthermore, when the photosensor detects the developing device drive start slit 8, the photosensor output is turned on, and at the same time, the driving for each developing device, which has been stopped until now, is started. Next, when the photosensor 10 detects the reference position slit 9, the driving of the photosensitive drum and the developing machine are stopped simultaneously, and the voltage applied to the charger is also turned off.
becomes.

Next, referring to FIG. 4, this figure shows another method for detecting the time to start driving the developing machine. A potential sensor 21 is provided, and the timing to start driving the developing machine is detected by detecting the potential of the photoreceptor immediately before entering the current a8N. That is, at the same time as starting the driving of the photosensitive drum 1, application of 8 voltages to the charger 2 is started,
When the potential sensor 21 detects a high potential, driving of the current aFA is started at the same time or after a certain period of time. In the figure, the potential pincer 21 is fixed to the outer wall of the developer holder, but it can be installed anywhere as long as it is near the developer. Furthermore, it is not limited to the upstream side of the developing roll, but the normal side (the permanent part appears after a certain delay from the charging start position of the photoreceptor, so
The potential hinge 21 may be provided downstream of the developing roll.

FIG. 5 is a timing chart for the operation of the detection means shown in FIG. 4, and the potential sensor output is OFF even after the photoreceptor drum starts driving until it detects a charged portion of the photoreceptor. At the same time, it turns ON. Potential sensor output is ON
After a short poem period has passed, the development drive starts.

However, this drive for each development may be started at the same time as the potential sensor output is turned on, as described above. This fruit Jim
(In the case of Mr. m, there is no need to detect the reference position, so
Driving of the photosensitive drum can be stopped at any position. Simultaneously with the stopping of the photosensitive drum, the developing machine is also stopped, and the voltage applied to the charger is also turned off.

Embodiment Next, the present invention will be explained in detail with reference to the embodiment shown in FIG.

FIG. 6 is one embodiment of the present invention, showing a copier printer using a liquid crystal light valve.

A rotation angle detection disc 7 is attached to the photosensitive drum 1, and a photosensor 10 and a slit detection circuit 15 detect the passage of the rotation angle detection disc 7 through a reference position slit 9 and a developing drive start slit 8. To detect. The photosensitive drum 1 is rotated by a drum driving device (not shown), and when the striking machine is stopped, the rotation of the drum is stopped by (-1) at the same time as the reference position n slit 9 is detected. body drum 1
The rotation angle detection disc 7 is stopped at the position shown in FIG.

Around the photoreceptor drum 1, there is a charger 2, an original image exposure device consisting of an original platen 11 made of a transparent member, a lens 12, and an original illumination system 13, and a liquid crystal light valve that scans and exposes the photoreceptor according to an image signal. A unit 14 and a developing device 6 are provided. When used as a separate copy, exposure is performed by an exposure device 11, 12 and 13 for document a, and when used as a printer, exposure is performed by a liquid crystal light valve unit 14. The liquid crystal light valve unit 14 includes a fluorescent lamp, a condensing lens, a transmissive liquid crystal panel, a liquid crystal panel drive circuit, and a converging optical fiber lens, and changes the transmittance of the transmissive liquid crystal panel according to the image signal. Then, exposure corresponding to the image is performed on the photoreceptor drum.

Exposure by the document a exposure device is normal image exposure, but in the case of exposure by the liquid crystal light valve unit 14, reverse exposure is recommended because normal image exposure may cause stains in the background of the image due to uneven light irradiation. is common, and this embodiment also performs reverse exposure.

When used as a printer, application of eight voltages to the charger 2 is started simultaneously with the start of rotation of the photoreceptor drum. Each θ2 between the reference position slit of the rotation angle detection disc 7 and the developing device drive start slit 8 is set equal to the angle θ1 between the charger 2 and the developing roll 3, and the passage through the drive start slit 8 for each development is detected by a photo sensor. 1Q and from the time when the slit detection circuit 15 detects the development, the drive control circuit 16 is activated to start supplying the dowel to the photosensitive drum.

When using as a copying machine, use LCD light valve unit 1
No. 4 is used, a document image exposure device consisting of No. 11, No. 12 and No. 13 is used, a low voltage is used for the developing bias, and the driving of the developing machine is started at the same time as the copying operation starts.

Effects of the Invention Since the present invention is configured to delay the start of driving of the developing machine during reversal development, the following effects can be achieved. (1) Wasteful consumption of 1 to 3 can be suppressed. (2) There is no burden on the cleaning device (1F), which causes poor cleaning. (3) There is no toner spilling from the cleaning device, so there is less dirt from toner inside the device. (
4) Development can be stabilized by suppressing rapid consumption of toner in the development chamber and by suppressing wasteful consumption of toner charged homogeneously with the latent image.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the copying machine according to the present invention after the start of operation, where A shows the state immediately after the start of operation, B shows the state after a certain period of time has elapsed, and FIG. 2 shows when the developing machine starts to be driven. Fig. 3 is a diagram showing an example of a means for detecting timing, A is a right side view, and Fig. 3 is a timing chart diagram showing the operation of the detecting means in Fig. 2. , FIG. 4 is a schematic diagram showing another method for detecting the timing to start driving the developing machine, and FIG. 5 is a timing diagram showing the operation of the detection means in FIG. 4.
Figure 7 shows one embodiment of the present invention, and is a schematic configuration diagram of a printer device using a liquid crystal light valve unit. FIG. S7 is an explanatory diagram illustrating the wasteful consumption of toner caused by starting the drive for development at the same time as the operation of the conventional copying stone starts. 1: Photoconductor drum 2: Charger 3: Developing roll 4: Developing machine driving means 5: Toner 6: Developing machine 7: Rotation angle detection disc 8 Developing hoe drive start slit 9: Reference position slit 1Q: Photo Sensor 12: Lens 13: Original & Angle between slit

Claims (1)

[Claims] A charging device that uniformly charges the surface of the photoreceptor, an exposure device that exposes the pre-charged photoreceptor to a light image, and a developing bias that is equal to the surface potential of the photoreceptor in the dark area where the light image is not exposed. In an electrophotographic apparatus, the electrophotographic apparatus has a developing bias applying means for applying a developing bias, and a developing means for rotating a cylindrical developing roll by a driving means to adhere toner to a bright area of a photoconductor where an optical image has been exposed to obtain a reverse developed image. , an electronic device characterized in that, at the start of the operation of reversal development, the start of the operation of the charging means is delayed by the time required for the photoreceptor to move the distance from the charging means to the developing means, and then the driving of the developing means is started. Photographic equipment.