JPH0545978A - Image forming apparatus and document scanning apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] When an original having a short length in the conveying direction is step-fed by an automatic document feeder, the image of the original that has already been formed and remains on the original table is transferred to the image carrier. To provide an image forming apparatus capable of surely forming an image only on a document at a predetermined position without appearing above. A means for exposing and scanning a document placed on a document table, and an exposure scanning means for exposing and scanning a first document placed at a first position on the document table, and then performing a first scan Second document provided in the document transport direction with respect to the first position on the document table.
On the image carrier, and a transporting unit that transports the second document to the first position on the document table, an image forming unit that forms an image of the document that has been exposed and scanned on the image carrier, and When the means for erasing the formed image and the exposure scanning means perform exposure scanning over the second position of the document table, the exposure scanning means moves to the second position of the document table formed on the image carrier. And a control means for controlling the erasing means so as to erase the image of the placed document.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document scanning device having an automatic document feeding device, and an image forming apparatus such as an electronic copying machine having the document scanning device.

[0002]

2. Description of the Related Art Generally, in an electronic copying machine having an automatic document feeder, the automatic document feeder conveys a document set on a document stacking section to a predetermined position on a document table. Then, when the document is set at a predetermined position on the document table, the exposure scanning device provided below the document table is driven to expose and scan the image of the document. The image of the original document scanned by exposure forms an electrostatic latent image on the photoconductor, and the developer toner is supplied to the electrostatic latent image from the developing device to make the image of the document visible on the photoconductor. To be done. The visible image of the original is transferred onto a sheet by a transfer device and then fixed on the sheet by a fixing device. On the other hand, in the automatic document feeder, at the same time when the exposure scanning by the exposure scanning device is completed, this document is further conveyed and discharged from the document table.
At the same time, the next original is conveyed from the original stacking section to a predetermined position on the original table. In this way, in the conventional electronic copying machine having the automatic document feeder, the documents are successively conveyed from the document stacking section, the documents are exchanged, and the documents are copied.

In the electronic copying machine having the conventional automatic document feeder as described above, regardless of the size of the document, the documents are conveyed one by one to a predetermined position on the document table, and the exposure scanning of the document is completed. Then, the process of discharging the exposed and scanned original document from the original plate and at the same time transporting the next original document to a predetermined position on the original plate is repeated. However, according to this method, even when an A4 size document having a short length in the conveyance direction is to be replaced, the same time is required to replace the maximum size (A3 size) document. There was a problem.

In order to solve the above-mentioned problems, in recent years, when an original having a short length in the original conveying direction is replaced, the exposed and scanned original is completely discharged before the next original is conveyed. Instead, an electronic copying machine having an automatic document feeder that can carry out so-called step conveyance, in which the next original is conveyed when the exposed and scanned original is conveyed to a predetermined position on the original table, is conceivable. ing.

By the way, when an electronic copying machine having such an automatic document feeder is used to copy a document having a short length in the document conveying direction by step conveyance, for example, a paper having a size larger than the size of the document is used. There is a case where is selected and copying is performed at the same size. At this time, the exposure scanning device performs exposure scanning according to the size of the selected sheet.
Here, when a document having a short length in the document transport direction is step-transported by the automatic document feeder, the previous document remains on the document table as described above. Therefore, in such a case, when the image forming operation for forming the image of the original on the paper is performed, the previous original (the original that has already been copied)
There is a problem that the image of is formed on the paper.

[0006]

As described above, in the image forming apparatus having the conventional automatic document feeder, the next original is conveyed when the exposed and scanned original is conveyed to a predetermined position on the original table. When performing the so-called step conveyance, when the exposure range by the exposure scanning device is longer than the length of the original in the conveying direction, an unnecessary image of the copied original is formed on the image carrier. There was a problem.

Therefore, in order to solve the above-mentioned problems, the present invention has already completed the image formation remaining on the document table when the document having a short length in the transport direction is step-transported by the automatic document feeder. An object of the present invention is to provide an image forming apparatus capable of surely forming an image only on an original document at a predetermined position without the image of the original document appearing on the image carrier.

[0008]

In order to achieve the above object, an image forming apparatus of the present invention comprises a document table on which a document is placed,
Exposure scanning means for exposing and scanning the original placed on the original table, and exposure scanning means for exposing and scanning the first original placed at the first position on the original table. Conveying means for conveying one original to a second position provided in the original conveying direction with respect to the first position on the original table and for conveying a second original to the first position on the original table, An image forming unit that forms an image of an original document that is exposed and scanned by the exposure scanning unit on an image carrier, a unit that erases the image formed on the image carrier by the image forming unit, and the exposure scanning unit. When exposure scanning is performed beyond the second position of the document table, the image of the document placed on the image carrier at the second position of the document table is erased by the image forming unit. And a control means for controlling the erasing means. The features.

Further, the document scanning apparatus of the present invention comprises a document table on which a document is placed, an exposure scanning means for scanning the document placed on the document table while exposing the document, and the exposure scanning means on the document table. After performing exposure scanning of the first document placed at the first position of the first document, the first document is moved to the second position provided in the document transport direction with respect to the first position of the document table. When the conveying means conveys the second original to the first position of the original table and the exposure scanning means scans beyond the second position of the original table, the exposure is not performed. And a control means for controlling.

[0010]

The first document is transported to the first position on the document table by the transporting means. And in this first position, the first
The original document is exposed and scanned by the exposure scanning means. The image of the first original document scanned by exposure is formed on the image carrier by the image forming means. When the exposure scanning is completed, the first document is carried to the second position on the document table by the carrying means. At the same time, the second document is carried to the first position on the document table by the carrying means. In this way, documents are exchanged one after another. Here, when the original document at the first position on the original table is exposed and scanned, when the exposure scanning unit also performs the exposure scanning to the original document at the second position on the original table due to the image forming magnification, etc. The image of the original document at the second position is formed on the image carrier. At this time, when the erasing unit erases the image of the document at the second position to form an image of the document at the first position of the document table, an unnecessary image (that is, the second image of the document table is deleted). The image of the original at the position) is not formed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the image forming apparatus of the present invention is applied to an electronic copying machine will be described in detail below with reference to the drawings.

FIG. 1 is a schematic explanatory view of the electronic copying machine 1.
Around the photosensitive drum 11 in the center of the main body 2, a charging device 12, an LED erasing array 13, an exposure position 14a by an exposure system 14, a developing device 15, and a transfer peeling charger 1.
6, a cleaning device 17, and a discharge lamp 18 are provided. Here, the exposure system 14 refers to a portion surrounded by a broken line in FIG. Further, on the right side of the main body 2, cassettes 19a and 19b for accommodating the paper P and a manual paper feed tray 19c are provided.
Is provided. And in the main body 2, a cassette 19
a, 19b and pickup rollers 20a, 20b and 20c for taking out the paper P from the manual paper feed table 19c, and the paper P taken out and fed by the pickup rollers 20a, 20b, 20c through the photoconductor drum 11 and the main body 2 Paper transport path 22 leading to the left paper ejection tray 21
Are formed. Here, this paper transport path 22 is shown in FIG.
This paper transport path 2 indicated by the alternate long and short dash line in FIG.
The first and second separation rollers 23a and 23b registration roller pair 24 are provided on the upstream side of the second photosensitive drum 11, and the conveyance belt 25 and the fixing roller pair 26 are provided on the downstream side.
A paper discharge roller pair 27 is provided. Here, the configuration of the exposure system 14 shown by the broken line in FIG. 1 will be described.
The exposure system 14 includes an exposure lamp 37 and a first reflection mirror 31.
, A second carriage 38 provided with a second reflection mirror 32 and a third reflection mirror 33, a lens 39, and fourth to sixth reflection mirrors 34, 35. , 36. The first carriage 30 is adapted to reciprocate along a document table 40 provided on the upper surface of the main body 2. Then, in order to keep the optical path length constant, the second carriage 38 reciprocates at a speed half that of the first carriage 30.

A document table 40 on which the document D is placed is provided on the upper surface of the main body 2. An original feeding device 50 is provided which is openable and closable with respect to the original table 40, holds the original D so as to be in close contact with the original table 40, and conveys the original D. Further, the document table 40
A document stopper 42 for aligning a document to be placed is provided in the vicinity of. Next, the document feeding device 50 will be described with reference to FIG. This document feeder 50
Includes a supply unit 51, a transport unit 61, and a reversal discharge unit 71.

The supply unit 51 sequentially separates the set originals D one by one and supplies them to the conveying unit 61, and a supply tray 52 for setting a plurality of originals D in a stacked state,
A pickup roller 53 for taking out the documents D set on the supply tray 52 one by one, and a delivery roller 5 for delivering the documents D taken out by the pickup roller 53.
4 and an aligning roller pair 55 that conveys the document D delivered by the delivery roller 54 while aligning it. An empty sensor 5 for detecting the presence / absence of the document D is provided on the delivery roller 54 side of the supply tray 52.
6 is provided. Also, the aligning roller pair 55
A registration sensor 57 is provided in front of. Further, behind the aligning roller pair 55, a size sensor 58 for detecting the document D size is provided.

The conveying section 61 conveys the original D supplied from the above-mentioned supplying section to the original table 40 of the main body 2 and also conveys the original D from the original table 40 to the reversal discharging section 71 after the exposure of the original D is completed. To do. The transport unit 61 is wrapped around belt rollers 62 and 63, and an endless transport belt 64 that transports the document D supplied from the supply unit 51 along the document table 40, and the transport belt 64 on the document table 40. It is composed of a plurality of belt pressing rollers 65 that press against each other.

The reversing and discharging section 71 is for reversing or discharging the document D conveyed from the conveying section 61 as required. The reversal discharge unit 71 includes a reversal roller group 72 that reverses the document D conveyed from the conveyance unit 61 to the front and back and guides the document D to the conveyance unit 61 again, and a discharge roller 73 that guides the document D to a discharge tray 76. It consists of A discharge sensor 74 is provided in the middle of the reversing roller group 72. Further, a flapper 7 for changing the conveyance direction of the document D is provided between the reversing roller group 72 and the discharge roller 73.
5 is rotatably provided. In the normal case, the flapper 75 is set so as to guide the document D conveyed from the conveying section 61 to the sheet discharge tray 76 via the sheet discharge rollers 73.

Next, FIG. 3 shows an external view of the operation panel 41 provided on the surface of the main body 2 of the electronic copying machine 1. On the operation panel 41, a ten key 41a for inputting numerical values such as a copy magnification and the number of copies, a copy key 41b for instructing the start of copying, and an LED display section 41c for displaying information from a CPU described later. Etc. are provided. Further, on the operation panel 41, a step feed mode selection key 41d for selectively setting whether or not the automatic document feeder 50 is in a step feed mode in which a step feed operation described later is performed, and a size of a sheet used for copying. A paper size selection key group 41e for selecting is provided.

Next, FIG. 4 shows the overall control system of the electronic copying machine 1 of this embodiment. C that controls the entire electronic copying machine 1
CPU that controls the PU 80 and the automatic document feeder 50
Reference numeral 100 is connected to each other, and they exchange various interface signals described later with each other.

On the input side of the CPU 80 which controls the main body 2, various input switches on the operation panel 41 and various switches necessary for other control of the copying machine 1 through an input interface 81 such as a data selector. A detector 82 such as a sensor is connected. On the output side of the CPU 80, a display driver 84 that drives various display units 83 such as the LED display unit 41c on the operation panel 41, a lamp control unit 85 that controls the exposure lamp 37 of the exposure system 14, a motor, a solenoid, and the like. Drive driver 8 for driving various drive systems 86
7, a charging device 12, a high-voltage power supply 90 for driving a charging device 89 such as the transfer peeling charger 16, and the like are connected. Further, the LED erasing array 13 is connected to the output side of the CPU 80 via the LED erasing array controller 91,
Lighting of the LEDs that form the LED erasing array 13 is controlled by the CPU 80. Further, the CPU 80 has a memory group 9 including a ROM 93 in which a control program and the like are stored and a RAM 94 in which various data required for control are stored.
2 is connected so that input / output is possible. Further, the CPU 80 has a timer 95 for measuring time, and controls the entire electronic copying machine 1 by operating each of the above elements at a predetermined timing according to the output from the timer 95. ..

Next, the control system of the automatic document feeder 50 will be described. CPU 10 for controlling the automatic document feeder
On the output side of 0, the paper feed motor 101 for driving the pickup roller 53 and the delivery roller 54, the aligning roller 55, the conveyor belt 64, the reversing roller group 7
2. Transport motor 10 for driving the paper discharge roller 73 and the like
2. The flapper solenoid 103 for driving the flapper 75 has drivers 104, 105, 10 respectively.
It is connected via 6. The input side of the CPU 100 has an input interface 10 such as a data selector.
Various sensors such as the empty sensor 56, the registration sensor 57, the size sensor 58, and the discharge sensor 74 are connected to each other through 7. Further, on the input side of the CPU 100, a first pulse generator 108 for generating a clock pulse by a rotary encoder (not shown) attached to the paper feed motor 101 and a clock pulse by a rotary encoder (not shown) attached to the carry motor 102. The second pulse generator 109 for generating is connected.

The interface signals exchanged between the CPU 80 of the main body 2 and the CPU 100 of the automatic document feeder 50 will be described. CPU80 of main body 2
The interface signal exchanged between the CPU 100 of the automatic document feeder 50 and the automatic document feeder 50 is performed by an asynchronous serial communication system.

There are seven types of interface signals from the CPU 80 of the main body 2 to the CPU 100 of the automatic document feeder 50, for example, as described below. In order to set the double-sided document transport mode or the single-sided document transport mode, a double / single-sided selection signal (hereinafter referred to as ORG-BOTH) is output. To start the document replacement operation, a document feed signal (hereinafter referred to as ORG-IN) is output. To eject the document, a document ejection signal (hereinafter referred to as ORG-OUT) is output. To inform whether the automatic document feeder 50 is in the normal document transport mode or the test mode, a mode signal (hereinafter referred to as MO
(Called DE) is output. When the automatic document feeder 50 is in the test mode, a test code signal (hereinafter referred to as TEST) is output, and various test operations are performed by transmitting the coded signal.
An adjustment code signal (hereinafter referred to as ADJUST) is output in order to adjust the transport amount of the document transported when the automatic document feeder 50 is in the normal document transport mode. In order for the automatic document feeder 50 to perform an operation at the same timing as when a document is conveyed, assuming that a document is pseudo when there is no document, the aging signal (hereinafter referred to as AGIN
(Referred to as G) is output.

Further, the CPU 10 of the automatic document feeder 50
There are ten types of interface signals (signals indicated by the automatic document feeder) from 0 to the CPU 80 of the main body 2 as shown below. An original set signal (hereinafter referred to as ORG-RDY) is output to indicate whether or not the original D is set on the paper feed tray 2. When the automatic document feeder 50 is in the jam state, a jam signal (hereinafter referred to as DF-JAM) is output. Paper feed motor 101 or transport motor 1 of the automatic document feeder 50
When the operation abnormality occurs in 02, an error signal (hereinafter referred to as DF-ERR) is output. When the error signal (DF-ERR) or jam signal (DF-JAM) is output, the content of the error or jam is coded, and an error code signal (hereinafter referred to as ERR-COD) is sent to the copying machine main body 2. Is output as. While the automatic document feeder 50 is operating from the start of the document replacement operation to the end of the document size detection, an in-operation signal (hereinafter referred to as DF-ACT) is output. Platen 4
A position where the document stopper 42 on 0 and one side of the document D are completely in contact with each other (hereinafter, this position is referred to as an exposure position)
When the document D is set at, a document stop signal (hereinafter referred to as ORG-STP) is output. The open / closed state of the transport unit 51 of the automatic document feeder 50 or the open / close cover of the paper feed unit 61 is output as an open signal (hereinafter referred to as DF-OPN). Further, the detected document size is a document size signal (hereinafter referred to as SIZE0, SIZE1, SIZE2, SIZE, respectively) consisting of a 4-bit code.
3)). In the two-sided document conveying operation, whether the first side of the document is set to the exposure position downward or the second side of the document is set downward is output as a document front / back signal (hereinafter referred to as ORG-FACE). In order to indicate whether or not the document D is in the first-out position, a first-out signal (hereinafter referred to as PRE-FED) is output.

Next, the operation in such a configuration will be described. First, turn on the power switch (not shown),
After a lapse of a predetermined time, the copying machine main body 2 becomes ready (copyable). At this time, the CPU 80 enters a state in which the copy key 41b provided on the operation panel 41 can be received, and an interface signal between the CPU 80 and the CPU 100 can be transmitted and received.

In this state, first, the operation during single-sided document conveyance will be described. When the documents D ... Are set on the paper feed tray 52, the empty sensor 56 is turned on,
Detects the presence of a document. Then, the CPU 100 causes the ORG-
The RDY signal is output to the CPU 80.

Here, the operator operates the operation panel 41.
When the upper copy key 41b is turned on, the CPU 80
Output the RG-IN signal. CPU100 is this ORG
When the -IN signal is received, the DF-ACT signal is turned on and the ORG-STP signal is turned off, and the document feeding operation of the automatic document feeder 50 is started. That is, CPU1
00, the paper feed motor 101 is turned on, which drives the pickup roller 53 and the delivery roller 54, and the document D set on the paper feed tray 52.
Are taken out one by one from below and are conveyed to the aligning roller 55. The CPU 100 uses the paper feed tray 52.
The document feeding motor 101 is stopped a certain time after the leading edge of the first document D1 conveyed from the ON position turns on the registration sensor 57, and the document D1 is aligned with the aligning roller 55.
Is struck by. Next, the CPU 100 rotates the transport motor 102 in the forward direction to rotate the transport belt 64, the reversing roller group 72, and the discharge roller 73 in the discharge direction to perform the document discharge operation. The case where the residual document D0 exists is considered. Remaining original D
When the discharge operation of 0 is completed, that is, when it is detected that the rear end of the remaining document D0 reaches the discharge sensor 71, the document D1 conveyed to the aligning roller 55 is fed to the conveyance belt 64. The document D1 passes through a size sensor 58 for detecting the width in the direction perpendicular to the document transport direction,
When the trailing edge of the document D1 passes the registration sensor 57, the SIZE0 to 3 signals are set based on the detection result of the size sensor 58, and the DF-ATC signal is turned off. Further, the transport amount of the document D1 is counted by counting the number of pulses from the first pulse generator 108 from the time when the DF-ACT signal is turned off. When counting the amount of the rear end of the document D1 that exceeds the left end of the document stopper 42 by a certain amount (for example, 5 mm), the transport motor 102 is stopped and then the transport motor 102 is rotated in the reverse direction, so that the document D1 is returned. Is punched against the left end of the document stopper 42, and the transport operation of the first document D1 is completed. The automatic document feeder 50 is set a certain time before the conveyance operation of the first document D1 is completed.
The ORG-STP signal is output from the CPU 100 to the CPU 80 of the main body 2. CPU of this body 2
Upon receiving the ORG-STP signal, the 80 turns on the exposure lamp 37 and starts the activation of the first carriage 30. Here, the fixed time period corresponds to the time period required for the first carriage 30 to reach the exposure scanning start point 59 from the start point. Here, the exposure scanning start point 59 is the boundary line between the document stopper 42 and the document table 41 described above. As a result, the exposure scanning of the document D1 can be started at the same time when the conveying operation of the document D1 is completed.

When the conveyance of the first document D1 is completed, the first carriage 30 scans and the document D1 is exposed and scanned by the control of the CPU 80 on the main body 2 side as described above.
The exposure range (that is,
The range in which the first carriage 30 performs the exposure scanning is determined from the size of the paper P selected by the paper size selection key group 41e on the operation panel 41 and the copy magnification.
Here, the length L1 of the side parallel to the conveyance direction of the selected paper P is X mm, and the set copy magnification is Y%.
And At this time, the first carriage 30 performs exposure scanning from the exposure scanning start point 59 to a point separated by X × 100 / Y mm. For example, assume that the copy magnification is 75%, the size of the selected paper P is A4, and the paper P is accommodated in the direction in which the short side is parallel to the transport direction. At this time, the length of the short side of A4 size is 21
Since it is 0 mm, the first carriage 30 performs exposure scanning from the exposure scanning start point 59 to a point 280 mm (210 × 100/75). As another example, the copy magnification is 1
The size of the paper P selected at 00% is A3,
It is assumed that the paper P is stored with its long side parallel to the transport direction. At this time, since the long side of the A3 size is 420 mm, the first carriage 30 is 420 mm (420 × 100/420 mm) from the exposure scanning start point 59.
Exposure scanning is performed up to point 100). The above-described determination of the exposure range and the movement control of the first carriage 30 are performed by the C of the main body 2.
It is performed by the PU 80.

Now, as described above, the first original D1 is printed.
Automatic document feeder 50 while the exposure scanning of
The CPU 100 carries the second document D2 to the position of the aligning roller 55 by the same control as the above-described carrying operation of the first document D1. (The position of the aligning roller 55 is hereinafter referred to as a first-out position).
The second document D1 is on standby at this first-out position.

When the exposure scanning of the first original D1 is completed, the CPU 80 on the main body side sends the CP on the automatic original feeder side.
The ORG-IN signal is output to U100. When the CPU 100 receives the ORG-IN signal, 2
The conveyance operation of the first document D2 from the first-out position is started.

If the step feed mode selection key 41d on the operation panel 41 is pressed, the CPU 100 of the automatic document feeder 50 controls the automatic document feeder 50 in the "step feed mode". When the step feed mode is selected, the CPU 100 refers to the result of detection by the size sensor 58 of the length of the first document D1 in the transport direction. When the length of the first document D1 in the transport direction is shorter than a predetermined length (for example, the length of the short side of A4 size), the step transport operation described in detail below is performed. To do.

The step conveying operation means that when the original D1 being conveyed to the exposure position on the original table 40 is replaced with the next original D2, the original D1 at the exposure position is discharged to the discharge tray 76. This is an operation in which the front end of the document D1 is conveyed to the position of the discharge sensor 74 provided in the reversal discharge unit 71 of the automatic document feeder 50 without waiting for the paper, and is made to stand by. The standby position of the document D1 at this time is called a step position. By performing this step conveyance operation, before the first document D1 currently at the exposure position is conveyed to the discharge tray 76 to a position where it can be ejected, the second document to be conveyed next to the exposure position. The transport of the original document D2 can be started. Therefore, it is possible to reduce the time required for document replacement. In this step conveyance operation, when the third original D3 is conveyed from the first-out position to the exposure position, the second original D2 at the exposure position is present.
Is conveyed to the step position, and the first document D1 at the step position is discharged onto the paper discharge tray 76. At this time, the CPU 100 refers to the size of the document D at the step position and the distance from the step position to the discharge roller 73, and the leading end of the discharged document D is discharged onto the discharge tray 76 by a certain distance. When the predetermined distance is reached, the rotation plate of the conveyance motor 102 is lowered to reduce the conveyance speed of the discharged document D so that the document D is discharged while being aligned.

On the other hand, the CPU 100 uses the size sensor 5
As a result of referring to the detection result of the length of the first original document D1 in the conveyance direction by 8, the length of the first original document D1 fed from the paper feed tray 52 at the exposure position in the conveyance direction is previously determined. Specified length (eg length of short side of A4 size)
When the size is longer, the CPU 100 controls the automatic document feeder 50 so as not to perform the step conveyance operation. Here, the above-described step conveyance operation can be performed only on the document D whose length in the conveyance direction is equal to or smaller than a predetermined value. The length equal to or smaller than the predetermined value means a length equal to or smaller than half the length d1 of the document table 40 in the exposure scanning direction. This is because the length of the document D in the transport direction is d.
This is because when the length is 1/2 or more, the originals overlap each other on the original table 40. This will be described later in detail with reference to FIG. That is, the CPU 100 of the automatic document feeder 50 refers to the detection result of the length of the document D in the transport direction by the size sensor 58 even when the step feed mode selection key 41d on the operation panel 41 is pressed. If the length of the document D is not less than the predetermined length (d1 / 2), the step conveyance operation is controlled not to be performed. CP at this time
U100 waits at the first-out position by driving the aligning roller 55 when the first document D1 at the exposure position has reached the position where it can be discharged to the discharge tray 76. The second document D2 is conveyed to the exposure position. That is, when the step transport operation is not performed, the operation of transporting the second document D2 to the exposure position and the operation of discharging the first document D1 to the paper discharge tray 76 are simultaneously performed. At this time, the CPU
Reference numeral 100 refers to the size of the document D at the exposure position and the distance from the exposure position to the paper discharge roller 73, and the front end of the discharged document D is discharged onto the paper discharge tray 76 by a predetermined distance. When the predetermined distance is reached, the rotating plate of the transport roller 102 is lowered to reduce the transport speed of the discharged document D, so that the document D is controlled to be discharged while being aligned.

This document exchange operation is a series of document D ...
When the originals D ... Are no longer present on the paper feed tray 52, the empty sensor 56 is turned off, and the CPU 100 of the automatic document feeder turns off the ORG-RDY signal.
When the CPU 80 of the main body receives the OFF of the ORG-RDY signal, it outputs the ORG-OUT signal and discharges the document D which is being conveyed onto the paper discharge tray 76. When the CPU 100 of the automatic document feeder receives the ORG-OUT signal,
When the document is exchanged in the step transport operation, the document Dn at the step position and the document D (n + 1) at the exposure position
Perform the discharging operation. The control of this paper discharge operation is performed as follows. First, the document D (n + 1) at the exposure position, the size of the document Dn at the step position, and the distance determined from the step position to the paper discharge roller 73 (the leading end of the document Dn at the step position is a constant distance). , Discharge roller 73
When the paper is conveyed up to the distance
Reference numeral 100 lowers the number of rotations of the carry motor 102 and starts decelerating the document carrying speed. The original D (n + 1) at the step position and the original Dn at the exposure position are ejected to the paper ejection tray 76 so as to be aligned at the reduced conveyance speed. And C
In the PU 100, after a certain time has passed after the trailing edge of the document D (n + 1) at the exposure position has passed the ejection sensor 74, the conveyance motor 10
Stop 2.

Next, the document discharge operation by the ORG-OUT signal when the document is not exchanged in the step conveying operation will be described. The document discharge operation in this case is an operation of transporting the document D (n + 1) at the exposure position to the discharge tray 76, and is performed under the same control as the document discharge operation at the time of document exchange when it is not the step transport operation. .. The document discharging operation at the time of document replacement in the case of non-step conveyance has already been described, and therefore description thereof will be omitted here. This completes the operation for single-sided document transportation.

Next, the operation when the two-sided document is conveyed will be described. Even when the two-sided document is transported, the operation until the first document D1 is transported to the aligning roller 55 is the same as the one-sided document transportation described above. That is, the CPU 100 stops the leading edge of the document D1 at the position of the aligning roller 55 and then rotates the transport motor 102 in the forward direction to rotate the transport belt 74, the reversing roller group 72, and the discharge roller 73 in the discharge direction. Perform the document ejection operation. This takes into consideration the case where the residual original D0 exists on the original glass 1.

When the discharging operation of the remaining original D0 is completed, the original D1 conveyed to the aligning roller 55 is sent to the conveying belt 74. The CPU 100 uses the document D1
Passes through the size sensor 58 for detecting the width in the direction perpendicular to the document conveying direction, and when the rear end of the document D1 passes through the registration sensor 57, the SIZE0 to 3 signals are set. Then, after a lapse of a fixed time after the trailing edge of the document D1 passes through the registration sensor 57, the flapper solenoid 103 is turned on to set the flapper 75 in the direction in which the document D1 is inverted. The document D1 is transported on the document table 40 by the transport belt 74, and a predetermined time has passed after the leading edge of the document D1 passed the ejection sensor 74 (at this time, the document D1
The front end of 1 is the reversing discharge portion 71 and the belt roller 63 on the discharge side.
CPU 100 has a conveyance motor 102.
After stopping, the rotation direction of the conveyance motor 102 is reversed to convey the document D1 toward the document stopper 42. The CPU 100 of the automatic document feeder turns off the DF-ACT signal a certain time before the leading edge of the document D1 reaches the document stopper 42, and sets the ORG-STP signal when the leading edge of the document D1 reaches the document stopper 42. At the same time, the carry motor 102 is stopped. The transport amount of the document D1 at this time is determined by counting the pulses output from the first pulse generator 108 after the leading edge of the document D1 has passed the ejection sensor 74.

When the ORG-STP signal is output from the CPU 100, the main body side CPU 80 turns on the exposure lamp of the exposure system 14, and then starts scanning the first carriage 30. This starts the exposure scanning of the document. When the exposure scanning of the document is completed, the CPU 80 on the main body side outputs the ORG-IN signal in order to reverse the document D1.
When the CPU 100 of the automatic document feeder receives the ORG-IN signal, the transport motor 102 is rotated in the forward direction to transport the document D1 at the exposure position toward the reverse discharge unit 71, and the reverse discharge unit 71 transports the document D1. Then, the inverted document D1 is conveyed to the exposure position. While the exposure scanning of the inverted document D is being performed, the CPU
By the control of 100, the first-out feeding operation of the second document D2 is performed, and the next ORG-IN signal is sent to the CPU 80
When the document is output from the document feeder, the document feeder performs the document replacement operation. The document exchange operation is the same as that in the case of single-sided document conveyance described above, and therefore the description thereof is omitted here.

Next, the operation of forming an image of the original D, which has been conveyed and exposed and scanned as described above, on the paper P will be described. The image of the original document that has been exposed and scanned by the exposure system 14 is irradiated onto the exposure position 14a on the photosensitive drum 11. The surface of the photoconductor drum 11 is uniformly charged in advance by the charging device 12, and the charge on the surface of the photoconductor drum 11 disappears by being exposed, so that the image of the original document remains on the photoconductor drum 11. It is formed as a latent image. The photoconductor drum 11 is rotated in the clockwise direction at a predetermined peripheral speed, and the electrostatic latent image of the document D is developed by the developing device 15.
When the position is reached, a developer such as toner is supplied from the developing device 15 to the electrostatic latent image on the photoconductor drum 11. As a result, a toner image of the document D is formed on the photosensitive drum 11. When the photosensitive drum 11 is further rotated and the toner image reaches the position of the transfer separation charger 16, the toner image is transferred onto the sheet P by the action of the transfer charger.

On the other hand, in synchronization with the input of the copy key 41b on the operation panel 41, the paper size selection key group 41e on the operation panel 41 is selected from the paper feed cassettes 19a and 19b. The paper P is taken out from the paper feed cassette that accommodates the size of paper. The paper P is taken out from the paper feed cassette 19a or 19b by the pickup roller 20a or 20b. If the number of sheets P taken out by the pickup roller 20a or 20b is two or more, the sheet feeding / separating roller 23a or 23 is used.
By rotating b in the opposite direction, the excess paper P is pulled back to the paper feed cassette 19a or 19b. Paper feed
The paper P fed by the separation roller 23 a or 23 b is conveyed to the registration roller pair 24. And
The sheet P is conveyed to the position of the transfer peeling charger 16 described above while being synchronized with the rotation of the photosensitive drum 11 by the action of the registration roller pair 24.

The sheet P on which the image of the document D is formed by the transfer process is separated from the photosensitive drum 11 by the action of the peeling charger of the transfer peeling charger 16, and is conveyed to the fixing roller pair 26 via the conveying belt 25. It Then, the image of the document D is fixed on the paper P by the action of the heat roller forming the fixing roller pair 26. After this,
The paper P is discharged onto the paper discharge tray 21 by the paper discharge roller pair 27.

When the original D is step-fed to perform copying using the electronic copying machine having the above-described structure, two originals (that is, presently located at the present exposure position) within the exposure range of one exposure scan. There are cases where the document D2 and the document D1) that has been exposed and is currently at the step position exist. In this case, the CPU 80 of the main body 2 of the electronic copying machine 1 of the present embodiment controls so that the image of the document at the step position is not formed on the paper P. That is, in the case where the document is stepwise fed, when the first carriage 30 performs the exposure scanning beyond the exposure restriction point 60 which is a predetermined distance from the exposure scanning start position 59, the first carriage 30 causes the exposure restriction to occur. The control is performed so as not to form an image of a document or the like in a portion which is exposed and scanned beyond the point 60. Here, the exposure scanning position 59 and the exposure limiting position 60 when performing step conveyance
The relationship between the document position and the document position will be described with reference to FIG. As described above, for example, when the length parallel to the exposure scanning direction of the document table 40 is d1 and the distance from the end of the document table 40 to the discharge sensor 74 of the discharge reversal unit 71 is d2,
The exposure limit point 60 is, for example, d1 from the position (exposure scanning start position 59) at the boundary between the document stopper 42 and the document table 40.
Between a point separated by 1/2 and a point separated by (d1 / 2 + d2) (for example, (d1 + d2) / 2 from the exposure scanning start position)
It is a separated point). This is because, as described above, the length of the maximum size document D with which the document transport device 50 of the electronic copying machine 1 of the present embodiment can perform the step transport operation is d1 / 2, and this size is Manuscript D
Is at the step position (the position at the time when the leading edge of the document reaches the position of the discharge sensor 74 of the discharge reversing unit 71), the end portion of the document D on the sheet feeding unit 51 side is at the exposure scanning start position This is because it is located at a position apart from 59 by (d1 / 2 + d2).

The CPU 80 on the main body 2 side is provided inside the CPU 80 when the first carriage 30 performs exposure scanning from the exposure scanning start point 59 over the exposure restriction point 60 in the step feed mode. Timer 95
Referring to the output from the LED erasing array 13 at a predetermined timing when the image of the portion which is exposed and scanned beyond the exposure limiting point 59 is formed on the photosensitive drum 11.
Light all. As a result, the charge on the photoconductor drum 11 is removed, and control is performed so that an electrostatic latent image of an unnecessary image is not formed on the photoconductor drum 11. Here, a method of calculating the timing for fully lighting the LED erasing array 13 will be described. The time required for the first carriage 30 whose exposure lamp 37 is lit to start scanning is T1, the time it takes for the first carriage 30 that has started scanning to reach the exposure scanning start point 59 is T2, and the first carriage 30 performs exposure scanning. The time from the start point 59 to the exposure limit point 60 is T3, and the time required for the photosensitive drum 11 to rotate the distance between the LED erasing array 13 and the exposure position 14a is T4.
Then, the timing T5 when all the LED erasing array 13 is turned on is

[0043]

## EQU1 ## T5 = T1 + T2 + T3-T4. Note that these timings are based on the timing T0 of turning on the exposure lamp 37. Here, in the above calculation formula, (T1 + T2 + T3) to T4
Explaining the meaning of subtracting
This is because the electric charge on the photoconductor drum 11 must already be removed when the exposure position 14a reaches the exposure position 14a. This T4 is a value obtained by dividing the distance d3 between the LED erasing array 13 and the exposure position 14a shown in FIG. 6 by the peripheral speed Vd of the photosensitive drum 11 when the peripheral speed of the photosensitive drum 11 is Vd ( d3 / Vd). The data T5 of the timing at which all the LED erasing arrays 13 are turned on is
It is calculated when the copy key 41b on the operation panel 41 is turned on and is stored in the RAM 94 of the memory group 92.

Here, for example, in the electronic copying machine 1 of the present embodiment, the document D having a size of L1 (L1 <d1 / 2) in the transport direction is step-transported, and the image of this document D is copied at the copy magnification Y. The control of exposure scanning in the case of forming on a sheet P having a size of L2 with respect to the transport direction in% will be described with reference to FIG. First, the CPU 80 on the main body side
The exposure range R is calculated with reference to the copy magnification set on the operation panel 41 and the length of the paper size selected by the paper size selection key group 41e in the carrying direction.
It is stored in the RAM 74 (step 1). Here, the exposure range R is a range on the document table 40 in which the first carriage 30 turns on the exposure lamp 37 and scans.
Subsequently, the CPU 80 turns on the exposure lamp 37 (step 2) and starts scanning the first carriage 30 (step 3). Thereafter, the CPU 80 calculates the value of the exposure range R calculated in step 1 and stored in the RAM 74, and the previously set and stored value of the exposure limit point 60 ((d
1 + d2) / 2) are compared (step 4). When the exposure range R is larger than (d1 + d2) / 2, after a predetermined time (T5 described above) has elapsed from the start of scanning (step 5), all the LED erasing arrays 13 are turned on (step 6), and the photosensitive drum Remove the charge on 11. When the first carriage 30 finishes the exposure scanning in the exposure range R stored in the RAM 74 (step 7), LE
The D erasing array 13 is turned off (step 8), and the exposure scanning control is ended. In step 4, if the exposure range R is smaller than (d1 + d2) / 2, the LED
The first carriage 3 without turning on the erase array 13
0 is scanned (step 9), and the exposure scanning control ends.

As described above in detail, in the electronic copying machine 1 of the present embodiment, when the original document is replaced by using the automatic document feeder 50, the previous document is discharged and the next document is set at the exposure position. Do not place the previous document on the platen 4
Simultaneously with the operation of transporting to the predetermined position (step position) above 0, the next original is set to the exposure position. for that reason,
The time required for exchanging one original can be shortened and high-speed copying can be performed. When performing this step conveyance, there are cases where two sheets, the original conveyed this time and the exposed original, exist on the original table 40. At this time, depending on the relationship between the paper size and the copy magnification, two originals may fall within the range of one exposure. However, in the electronic copying machine 1 of the present embodiment, by turning on the LED erasing array 13 at a predetermined timing, the image of the document on the photoconductor drum 11 outside the predetermined range of the document table 40 becomes a photoconductor drum. 11 is prevented from being formed as an electrostatic latent image. As a result, the image of the previous document is not formed on the sheet P when the step conveyance is performed. Therefore, only the image of the original document currently at the exposure position can be reliably formed on the sheet.

In the above embodiment, in order to prevent the image of the previous document on the document table 40 from being formed on the sheet, the photoconductor on which the electrostatic latent image of the image of the previous document is to be formed. The electric charge on the drum 11 is previously stored in the LED erasing array 13
However, as another embodiment, a method of adjusting the charge amount of the charging device 12 or a method of adjusting the exposure amount by the exposure lamp 37 can be considered. Regarding the method of adjusting the charge amount, when the position of the photosensitive drum 11 to be exposed reaches the charging device 12, the charging device 12 is turned off to stop the charging of the photosensitive drum 11. This prevents the developer (toner) from adhering to the portion of the photoconductor drum 11 where the image of the previous document is to be exposed, and prevents the image of the previous document from being formed on the paper. Is.
At this time, the charging device 12 is turned off at the first timing.
This is after a predetermined time (T7) has elapsed from the start of the exposure scanning of the carriage. Here, a method of calculating T7 will be described. The first carriage 3 after the exposure lamp 37 is turned on
0 is the time until the scan starts T1, the first scan starts
The time until the carriage 30 reaches the exposure scanning start point 59 is T2, and the first carriage 30 is the exposure scanning start point 5
When the time from reaching 9 to the exposure limit point 60 is T3, and the time required for the photosensitive drum 11 to rotate the distance between the charging device 12 and the exposure position 14a is T6, the charging device 12 is turned off. Timing T7 is

[0047]

## EQU00002 ## T7 = T1 + T2 + T3-T6.

Regarding the method of adjusting the exposure amount,
When the first carriage 30 reaches the exposure limit point 60 of the document table 40 during the exposure scanning, the light amount of the exposure lamp 37 is increased by the control of the lamp control unit 85. As a result, the amount of reflected light from the previous document becomes significantly larger than the amount of reflected light from the document at the present exposure position, and the charge on the photoconductor drum 11 is removed by the reflection from the document. Therefore, the electrostatic latent image of the image of the previous document on the document table 40 is not formed on the photoconductor drum 11, so that it is possible to prevent an unnecessary image from being formed on the sheet.

[0049]

As described above in detail, in the image forming apparatus of the present invention, when a document having a short length with respect to the transport direction is step-transported by the automatic document feeder and the document is exchanged, a predetermined document is placed on the document table. By erasing the image of the document outside the range from the image carrier, it is possible to reliably perform the image forming operation only on the document placed within the predetermined range.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electronic copying machine according to an embodiment.

FIG. 2 is a schematic configuration diagram of an automatic document feeder of the electronic copying machine of this embodiment.

FIG. 3 is an external view of an operation panel of the electronic copying machine of this embodiment.

FIG. 4 is a block configuration diagram of a control system of the electronic copying machine of this embodiment.

FIG. 5 is a diagram for explaining step conveyance of a document.

FIG. 6 is a diagram for explaining a time T4 required for the photosensitive drum to rotate from the position of the LED erasing array to the exposure position.

FIG. 7 is a flow chart for explaining the flow of exposure scanning control when stepwise carrying is performed in the electronic copying machine of this embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electronic copying machine 11 ... Photosensitive drum 13 ... LED erasing array 14 ... Exposure system 14a ... Exposure position 30 ... First carriage 37 ... Exposure lamp 41 ... Operation panel 50 ... Automatic document feeder 59 ... Exposure start point 60 ... Exposure Restriction points 80 ... CPU (main body side) 94 ... RAM 100 ... CPU (automatic document feeder side)

Claims (2)

[Claims] 1. A document table on which a document is placed, exposure scanning means for exposing and scanning the document placed on the document table, and the exposure scanning means is placed at a first position on the document table. After performing the exposure scanning of the first original, the first original is conveyed to a second position provided in the original conveyance direction with respect to the first position of the original table, and the second original is conveyed. Conveying means for conveying the original to the first position on the platen, image forming means for forming an image of the original document scanned by the exposure scanning means on the image carrier, and image forming means for forming the image on the image carrier. And a second plate of the original plate formed on the image carrier by the image forming unit when the exposure scanning unit performs the exposure scanning over the second position of the original plate. To erase the image of the original placed at An image forming apparatus characterized by including a control means for controlling removed by means. 2. A document table on which a document is placed, an exposure scanning means for scanning the document placed on the document table while exposing it, and the exposure scanning means is mounted at a first position on the document table. After performing exposure scanning of the placed first original, the first original is conveyed to a second position provided in the original conveyance direction with respect to the first position of the original table, and the second original is conveyed. And a control means for controlling so as not to perform exposure when the exposure scanning means scans beyond the second position of the document table. A document scanning device characterized by being provided.