JPH01221767A - Image forming device - Google Patents

Abstract

PURPOSE:To realize the miniaturization of the device by enabling the use of a small diameter image carrier by controlling the electrostatic charge potential of the image carrier at the time of scanning each original based on the electrostatic charge starting reference responding to each original. CONSTITUTION:A primary electrifying device 10, which evenly charges electrostatically the surface of a photosensitive drum surface, a grid 10a, which can adjust the electrostatic charge voltage, a developing unit 11, which visualizes the latent image formed on the drum 9 with developers such as toner, a transfer electrifying device 12, which transfers the toner image onto a transfer paper S, a transferring material, a cleaning unit 13, which eliminates the toner remaining on the surface of the drum 9, and a front exposure lamp 14, which destaticizes the residual potential from the surface of the drum 9, are provided around the photosensitive drum 9. Then the charge potential of the photosensitive drum 9 at the time of scanning of each original based on the charge start responding to each original is controlled. Therefore, the positions of charge means and the detecting means for the charge reference are not limited, unlike the case when the charge starting reference is uniform. Thus, a photosensitive body of a small diameter can be used, realizing a miniaturization of the device.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus such as a copying machine, and particularly to an image forming apparatus having a quick copy function.

(Prior art) Conventionally, in this type of device, a leading edge margin is formed on the transfer paper by changing the potential of a charger for charging the photosensitive drum, and by omitting a lamp for forming the leading edge margin, the area around the photosensitive drum is changed. There are known methods that simplify the process. In such an apparatus, the leading edge margin is formed as shown in FIG. 5, for example. That is, the photosensitive drum 100
A charger 101 is disposed at a distance C from the exposure position R, while a document scanning position detection sensor 102 is disposed at that interval from the image tip position of the document, and the scanning optical system passes through the sensor 102. It is assumed that the predetermined scanning speed has already been reached.
moving the scanning optical system for a predetermined time or distance according to the copying magnification as a reference without discharging the charger 101;
When the scanning optical system reaches the image tip, the charger 101 is discharged to form a tip margin of about 2 mm.

In this case, in an apparatus that performs quick copying of a document, when forming the leading edge margin of the second side, the signal obtained by the sensor 102 is used as a reference, and the setting conditions of a common adjustment means such as a timer are adjusted. By performing the same scanning and discharge as on the first surface, an appropriate margin is formed at the tip of the second surface.

(Problem to be Solved by the Invention) Incidentally, in recent years, small-diameter photosensitive drums are often used in order to downsize devices. The means for this must be arranged closely around the drum.

However, in such a conventional example, since the leading edge margin formation during quick shooting is performed based on the signal obtained by the same detection sensor 102, the distance between the charger 101 and the exposure position 8 and the distance between the detection sensor 102 and The distance between the image tip positions 2 has a certain relationship (°C: β×100), and as a result, the band minimum copying magnification (%) cannot be brought sufficiently close to the exposure position.
It is not possible to use a small-diameter photosensitive drum in which each means is crowded. Furthermore, since the detection sensor 102 is disposed at a position where the moving speed of the scanning optical system should be constant, the distance from when the scanning optical system starts moving until it reaches the image tip is long, and the driving time is There was a problem in that the image formation speed was not increased due to the length of the image forming process.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is to miniaturize the device by using a small-diameter photoreceptor, and to rapidly form continuous images. An object of the present invention is to provide an image forming apparatus that can perform the following steps.

(Means for Solving the Problems) In order to achieve the above object, the present invention continuously scans a plurality of originals and exposes an image carrier to form an image corresponding to each original. In an image forming apparatus having a function of forming a non-image area in each of the images by controlling the charging potential of the image carrier during document scanning, each It is characterized in that the charging potential of the image carrier is controlled during scanning of the original.

(Function) In the present invention having the above configuration, the charging potential of the image carrier during scanning of each original is controlled based on charging start criteria corresponding to each original, and a non-image area is formed in each image. do. Therefore, the position of the charging means and the position of the means for detecting the charging standard are not limited as would be the case when the charging start standard is the same.

(Example) The present invention will be explained below based on the drawings.

FIG. 1 shows an embodiment of an image forming apparatus according to the present invention. In the figure, reference numeral 1 denotes a document placing glass on which a document is placed, and is provided at the upper part of the main body of the apparatus. Reference numeral L denotes an original illumination lamp for scanning an original, which is integrated into a unit together with a reflecting mirror 2 that reflects original image light. Reflection mirrors 3 and 4 guide the image light reflected by the reflection mirror 2 to the imaging lens 5, and are incorporated into the mirror unit at an angle of 90@ to each other. The imaging lens 5 is a zoom lens, which is driven by a pulse motor M that drives the optical system, and is adapted to perform variable-magnification copying of an original image. Furthermore, 6,7
and 8 are reflecting mirrors that guide the image light formed by the imaging lens 5 to a photosensitive drum 9 as an image carrier. Further, S is a sensor for detecting the home position of the optical system.

Around the photosensitive drum 9, means for forming an image by a known electrophotographic method are provided at predetermined positions. That is, 1O is a primary charger that uniformly charges the surface of the photosensitive drum, and has a grid 10a whose charging voltage can be adjusted. 12 is a transfer charger that transfers this toner image onto transfer paper S as a transfer material; 13 is a drum 9;
A cleaning unit 14 for removing toner remaining on the surface of the drum 9 is a pre-exposure lamp for eliminating residual potential on the surface of the drum 9.

A cassette 15 containing transfer paper of a predetermined size can be inserted below the photosensitive drum 9. A switch 16 for detecting the presence or absence of transfer paper in the cassette 15 when the cassette is inserted, and a switch group 17 serving as detection means for detecting the size of the cassette 15, that is, the size of the transfer paper, are provided in the vicinity thereof. be. Further, 18 is a pickup roller that sends out the transfer paper, 19 and 20 are paper feed rollers that convey the transfer paper via the conveyance guide 21, and 22 are registration rollers that feed the transfer paper to the transfer section at a predetermined timing. In addition, in this embodiment, a manual feed guide 2 is provided near the registration roller 22 so that the transfer paper can also be fed manually.
3 is provided.

26 is a conveyance unit that conveys the transfer paper from the transfer section to the fixing unit 27. The fixing unit 27 has a fixing section including a heat roller and a pressure roller, and further includes a paper discharge roller that discharges the transfer paper from the fixing section onto a paper discharge tray 31 .

In the above configuration, when forming an image, the document illumination lamp L first stops at a position detected by the home position sensor S, or more specifically, at a position that is a predetermined distance backward from the position where the home position sensor S is detected. ing. Then, with the start of document scanning, the pulse motor M, which is the drive source of the optical system, is activated in the direction in which the optical system moves forward (
So-called slow-up control is performed in which the pulse rate is gradually increased until it reaches the drive pulse rate corresponding to the selected magnification value (rightward in the figure). That is,
The moving speed of the document illumination lamp L is gradually accelerated until it reaches the target position. Thereafter, the optical system scans at a predetermined speed, and the optical image of the original is guided to the photosensitive drum 9 via the mirrors 2, 3, 4, the imaging lens 5, and the mirror 6.7.

On the other hand, since the surface of the photosensitive drum 9 is uniformly charged by the primary charger 10 and rotates in the direction of the arrow, a latent image corresponding to the original image is sequentially formed on the surface of the drum 9, and this latent image is developed. The toner image is developed by the unit 11 as a toner image. Then, this toner image is transferred onto the transfer paper by the action of the transfer charger 12. In this case, cassette 1
The transfer sheets stacked in the transfer sheet 5 are taken out one by one from the top by a pick-up roller 18, and are moved along a transfer sheet guide 21 to a transfer position by sheet feeding rollers 19, 20 and registration rollers 22. Further, the transfer paper, on which the toner image has been transferred by the transfer charger 12, is transported by a transport unit to a fixing unit 27, where the image is fixed. Thereafter, the transfer paper that has been fixed is discharged by a paper discharge roller 30 and placed on a paper discharge tray 31.

In addition, when copying by manual feeding, the manual feeding tray 23
When you place the transfer paper on top and insert it up to the paper feed sensor 25,
After the transfer paper is fed into the transfer section by the conveyance roller 20, the original image is copied through the process described above.

Next, a method of forming a margin at the leading edge of the image and a method of aligning the leading edge with the transfer paper will be explained based on FIG. 2.

As a means to prevent toner adhesion in non-image areas,
Generally, static eliminating means using a light source such as an LED lamp or a fuse lamp is used, but in this embodiment, static electricity is removed from the photosensitive drum 9 by controlling the voltage value of the grid 10a provided in the wide charger 10. It is said that This is to reduce the number of members around the photosensitive drum 9 and to enable the use of a photosensitive drum with a smaller diameter. however,
In this case, the distance A between the exposure point R of the photosensitive drum 9 and the grid 10a of the charger 10 should be set to be sufficiently shorter than the distance B between the home position sensor S and the original contact position, that is, the image tip. Therefore, in this embodiment, the voltage of the grid 10a is switched from a low level to a predetermined voltage after a predetermined time according to the magnification selection value from the time when the document illumination lamp L starts moving, so that the leading edge of the document is A margin of 2 mm is to be provided between.

On the other hand, when aligning the leading edge margin formed on the photosensitive drum 9 in this way with the transfer paper, the distance C between the exposure point R and the transfer section Q is smaller than the distance between the registration roller 22 and the transfer section. Because of the short length, before the image at the leading edge of the document is actually exposed on the photosensitive drum 9, it is necessary to re-feed the transfer material waiting at the position of the registration roller 22 and send it toward the transfer section.

Therefore, in this embodiment, the leading edge of the image is aligned with the transfer paper as follows. First, the original illumination lamp L starts moving, moves by a distance E, and when the target speed is reached, the home position sensor Detected by S. The value obtained by dividing the value of distance B + 2 mm from the timing of passing this home position sensor S by the speed according to the selected magnification is the value that the document illumination lamp L reaches the white board end F after passing the home position sensor S. Let this time be X. In addition, the value obtained by subtracting the time required for the image at the exposure point R of the photosensitive drum 9 to reach the transfer section from the time from when the registration roller 22 starts refeeding the paper until the transfer paper reaches the transfer section is y. Then, the time required to feed the transfer paper 2 mm to this y (2 mm ÷ 10
0 mm/s = 0.02 sec, but conveyance speed = 100 mm/s) (Equation (1)).

(% formula %) In other words, the registration roller 22
By activating and refeeding paper, it is possible to obtain a transfer paper image with a margin of 2 mm according to the selected magnification.

The scanning distance of the optical system including the lamp L etc. is set to a predetermined distance according to the cassette size data, magnification data, etc. When the target position is reached, slowdown control is performed and the optical system stops, and then the home position sensor S is scanned again. Perform slow-up control and constant speed control in the direction to move backward. Then, when the home position sensor S is detected, slowdown control is performed to stop the vehicle at a predetermined position regardless of the selected magnification.

Next, the leading edge margin control during page continuous shooting will be explained in detail using the block diagram of FIG. 3 and the flowchart of FIG. 4.

First, in steps 81 to S3 (the number of steps, the same applies hereinafter), when the power is turned on to the apparatus, it enters a standby state in which image formation is possible if there are no copy prohibition conditions, and a copy start signal to perform quick copying is manually input. The page speed copying process is started. In this case, the number of copies set is “n”
In this case, make n copies of the first side, then make n copies of the second side.

Next, at 84 to Sll, when the document scanning system drive timing is reached, the microcomputer MC outputs an excitation pattern to the pulse motor drive circuit 40, rotates the pulse motor M, and moves the optical system. At this timing, the charging ON timer data shown in Table 4 and 1
A timer T1 for operating the primary charger 10 is started based on the data of the face edge margin adjustment volume.

This charging ON timer data is stored as data in the ROM of the microcomputer MC in advance according to the logic shown below. And pulse motor M
is driven under slow-up control by the microcomputer MC, and when this control is completed, it outputs an excitation pattern of a constant frequency corresponding to the copying magnification, causing the optical system to scan at a constant speed.

Table-1 Table-2 Table-3 Table-4 Tables-1 to 3 are data tables built into the ROM of the microcomputer. First, Table-1 is a table of excitation pattern output frequencies during slow-up; N
Slow-up is performed from IIL1 to the table position specified by the copy magnification. Table 2 shows document scanning speed data, and predetermined data is selected according to the copying magnification. Table -
3 is a slow-up end table function according to the copy magnification.

For example, if the distance from the drive start position of the exposure unit to the image tip is 24 mm, the pulse motor M is
When the exposure unit is configured to move by 0.12 [mm] when rotated by p, at the document scanning system drive timing, according to Table 3, the slow-up end table is as follows:
When the copy magnification is 100%, a value of "15" is obtained. In other words, the movement distance of the exposure unit during slow-up is:
15 (step)X O, 12 (mm) = 1.8
(mm), and the time required during that time is shown in Table 1! The value obtained by adding lhl to 15 is 28.5 (mS). After the slow-up is completed, an excitation pattern is output based on the frequencies shown in Table 2. For example, when the copy magnification is 100%, excitation patterns are sequentially output every 1.2 [mS]. Therefore, the time from the end of slow-up to reaching the tip of the image is ((24-1,8)
70.12)X 1.2 [mS] = 222
[mS] As a result, when the copying magnification is 100%, the time from driving the pulse motor M until the exposure unit reaches the image tip is (28,5+222)
=250.5 [mS]. Further, as described above, if the time required for the charging position of the photosensitive drum to be charged by the primary charger 10 shown in FIG. 2 to reach the exposure point R due to rotation of the photosensitive drum 9 as X, then Time after subtracting this X (28,5+222) -x
[mS] (Table 4) By operating the charger 10 via the high voltage unit 41, an appropriate leading edge margin can be obtained when copying the first side. This time X is 1
It can be arbitrarily set using data for adjusting the edge margin of the face. In addition, tables obtained in the same manner for other copying magnifications -
Timer T1.4 is activated by the data of T1. The charger 10 is operated to form the leading edge margin of the first side.

Next, S6. S12. According to the procedure shown in S13, after the first side has been copied, the second side is copied. In this case, when the original scanning system drive timing is reached, the exposure unit is moved in the same way as when copying the first side. Immediately after the exposure unit passes the home position sensor S, the timer T2 is activated. This timer T2 operates the charger 10 after a predetermined time based on the data of the second side leading edge margin adjustment signal consisting of the cassette size, copy magnification, and volume. It is assumed that the exposure unit finishes slowing up and is moving at a constant speed before reaching the home position sensor.

After that, the copying process is performed, and when the copying of the second side is completed, 32
It returns to standby mode.

(Effects of the Invention) In the present invention having the above-described configuration and operation, the image carrier is The position of the charging means can be arbitrarily selected,
Since an image carrier with a small diameter can be used, the apparatus can be downsized.

In addition, since non-image areas can be formed separately depending on the document, if one of the non-image areas is started at the same time as the document is scanned, the document scanning distance can be shortened and the image forming time can be shortened. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of an embodiment of an image forming apparatus according to the present invention, FIG. 3
The figure is a block diagram showing a control system for forming a leading edge margin in the same embodiment, FIG. 4 is a flowchart showing the procedure for forming a leading edge margin in the same embodiment, and FIG. 5 is an explanatory diagram showing a conventional leading edge margin forming method. be. Explanation of symbols 1...Original table 9...Photosensitive drum (image carrier) 10...-Blower electric device 10a...Grid L.
・・Document illumination lamp M・・・Pulse motor MC・・
・Microcomputer S... Home position sensor TI, T2... Timer Figure 3 Figure 4

Claims (1)

[Claims] A function to form an image corresponding to each document by continuously scanning a plurality of documents and exposing an image carrier to light, and by controlling the charging potential of the image carrier during document scanning. In the image forming apparatus having a function of forming a non-image area in each image, the charging potential of the image carrier is controlled at the time of scanning each document based on charging start criteria corresponding to each document. Features of the image forming device.