JPH0888731A - Image forming device - Google Patents

Abstract

PURPOSE: To obtain an image forming device in which an original is preliminarily scanned without causing reduction in an image forming speed. CONSTITUTION: The device is provided with an original feeder 80 feeding an original from one end of an original platen 12 to a prescribed position on an original placing section, a light source 14 provided movably along the original platen 12 and an image read section 4 reading the image of an original placed onto the original platen 12. The image read section 4 applies preliminary scanning to the original with a light emitted from the light source 14 arranged to one end of the original platen 12 while the original feeder 80 feeds the original from one end of the original platen 12 to a prescribed position and moves the light source 14 along the original to apply main scanning to the original after the original is fed to a prescribed position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to
The present invention relates to an image forming apparatus equipped with an automatic document feeder.

[0002]

2. Description of the Related Art As an image forming apparatus, for example, a digital copying machine, a document placed on a document placing table of a copying machine body is
It is known to have a function of scanning (pre-scanning) with a scanner in advance to read specific image information from a document, and then again scanning the document with a scanner (main scanning) to read document information for image formation. . For example, after the image information relating to the image density of the document is read by the prescan, the document information for image formation is read from the document by the main scan, and the document for image formation is read according to the specific image density information obtained by the prescan. By processing the information, it is possible to make a copy with the optimum print density according to the original image.

Generally, a scanner is provided with a light source that irradiates a document through a document table and a mirror that deflects light reflected from the document in a predetermined direction. These light sources and mirrors are mounted on the document table. It is mounted on a carriage that can move along. Then, the main scan of the original is performed by moving the carriage along the original while illuminating the original with a light source. The pre-scan is also performed in the same manner as the main scan.

On the other hand, as this type of digital copying machine, an automatic document feeder (hereinafter referred to as ADF) for automatically feeding a document on a document table is provided, and a plurality of documents supplied from the ADF are sequentially copied onto copy sheets. What to copy is known. A plurality of documents set on the ADF are
The sheets are automatically fed one by one onto the document table of the copying machine body by a conveyor belt or the like.

When the above-described prescan and main scan are performed while the document is automatically fed using the ADF, these prescan and main scan are performed by the same operation as described above.

[0006]

However, in the above-mentioned digital copying machine, when the prescan is performed before the main scan, it is necessary to scan the document twice, and accordingly, the carriage of the scanner is also scanned twice. It is necessary to repeat the same movement operation. Therefore, in this case, the reading speed of the original document is reduced to about 1/2, and the image forming speed originally possessed by the copying machine is reduced as compared with the case where the copying is executed without performing the prescan.

Although it is possible to increase the moving speed of the carriage during prescan in order to increase the image reading speed, in this case, it becomes difficult to control each component and noise accompanying the movement of the carriage also increases.

Further, the wind blows on the light source such as the fluorescent lamp according to the movement of the carriage. However, if the moving speed of the carriage is increased, the amount of wind hitting the fluorescent lamp increases, and as a result, the fluorescent lamp is It will be cooled and the life of the fluorescent lamp will be shortened.

For the above reasons, the speedup of prescan is limited and it is difficult to improve the image forming speed. The present invention has been made in view of the above points, and its purpose is to:
An object of the present invention is to provide an image forming apparatus capable of prescanning a document without causing a decrease in image forming speed.

[0010]

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention is a document for sending a document from one end side of the document placing section to a predetermined position on the document placing section. An image reading unit for reading an image of an original document placed on the original document placing unit, which has a light source movably provided along the original document placing unit and emits light through the original document placing unit. And are equipped with. The image reading means arranges the light source at the one end of the document placing section while the document is fed from the one end side of the document placing section to the predetermined position by the document feeding device, and the document is irradiated by the light emitted from the light source. Is pre-scanned, and after the document is sent to the predetermined position, the light source is moved along the document to perform main scanning of the document by irradiation light from the light source.

An image forming apparatus according to a second aspect of the present invention is a document feeding device that feeds a document from one end side of the document placing portion to a predetermined position on the document placing portion, and a standby state that is separated from the document placing portion. Between the position and the reading start position facing the one end of the document placing section, and along the document placing section, the light source is provided so as to be movable and emits light through the document placing section. An image reading unit that reads an image of a document placed on the document placing section is provided. Then, the image reading means arranges the light source at the reading start position while the original is fed from the one end side of the original placing portion to the predetermined position by the original feeding device and pre-reads the original by irradiation light from the light source. After scanning, the document is sent to the predetermined position, the light source is moved along the document from the standby position through the reading start position, and a driving unit for performing a main scan of the document by irradiation light from the light source is provided. I have it.

Further, according to a third aspect of the present invention, in the image forming apparatus, a document feeding device for feeding a document from one end side of the document placing section to a predetermined position on the document placing section and along the document placing section are provided. An image reading unit that is movably provided, has a light source that emits light through the document placing unit, and reads an image of the document placed on the document placing unit is provided. The image reading means arranges the light source at the one end of the document placing portion and irradiates the light from the light source while the document is fed from the one end side of the document placing portion to the predetermined position by the document feeding device. The document is pre-scanned by light, and after the document has been sent to the predetermined position, the light source is moved along the document to drive the document by the irradiation light from the light source. A drive unit capable of switching the document feed speed between a first speed and a second speed higher than the first speed; and a document feed speed of the drive unit during the prescan, the second speed And a switching means for switching to.

[0013]

According to the image forming apparatus of the first aspect of the present invention configured as described above, when the document is pre-scanned, the light source of the image reading means faces the one end of the document placing portion in advance by the driving means. The original is irradiated with light to scan the original while being moved to the position and fed by the original feeding device from one end of the image placing section to a predetermined position on the original placing section. As a result, desired image information is read from the document. Then, after the original reaches the predetermined position,
The drive unit moves the light source along the document, and the main scan of the document is performed by the light from the light source. Thereby, the image information used for image formation is read from the document.

Therefore, according to the above-mentioned image forming apparatus, the document can be pre-scanned without moving the light source of the image reading means along the document on the document placing portion. It is possible to significantly reduce the formation time.

Further, according to the image forming apparatus of the second aspect of the present invention configured as described above, when the document is prescanned, the light source is moved to the reading start position in advance by the driving means, and the document is fed. Thus, the original is irradiated with light to be scanned until the original is fed from one end of the image placing section to a predetermined position on the original placing section. When the main scan is subsequently performed, the light source is moved to the standby position separated from the document placing section, and then moved along the document on the document placing section via the reading start position.

Therefore, according to the image forming apparatus having the above-described structure, the document can be pre-scanned without a decrease in the image forming speed, as in the image forming apparatus according to the first aspect. Further, by moving the light source from the standby position during the main scan, it is possible to accelerate the moving speed of the light source to a desired moving speed before reaching the reading start position, and as a result, obtain stable image information. It becomes possible.

Further, according to the image forming apparatus of the third aspect of the present invention, when the document is prescanned, the document feeding speed of the document feeding device is switched to the second speed which is higher than the normal feeding speed. . Therefore, the document reading speed at the time of prescan is increased, and the image can be formed at a speed almost equal to that of the normal image formation without prescan.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic digital copying machine will be described in detail below with reference to the drawings. As shown in FIG. 1, the digital copying machine includes an apparatus main body 10, and in the apparatus main body 10, an image reading unit (scanner) 4 that functions as a reading unit, an image forming unit 6 that functions as an image forming unit, Is provided.

The image reading section 4 is disposed on the upper surface of the apparatus main body 10, and is an original placing table 12 made of transparent glass on which an object to be read, that is, an original D is placed, and the original placing table 12
A size plate 12a that is disposed at one end of the sheet and indicates the position where the document D should be placed.

On the upper surface of the apparatus main body 10, a document placing table 12 is provided.
Automatic document feeder 80 (hereinafter,
ADF). This ADF80
Is arranged so as to be openable and closable with respect to the document mounting table 12, and also functions as a document retainer that brings the document D mounted on the document mounting table 12 into close contact with the document mounting table 12.

As shown in FIGS. 1 and 2, the ADF 80
Is a document tray 82 on which the document D is placed, an empty sensor 81 for detecting the presence or absence of the document, a pickup roller 83 for taking out the document from the document tray 82 one by one, a paper feed roller 84 for conveying the taken out document, and a document. Is provided with an aligning roller pair 85 for aligning the leading end of the document, an aligning sensor 86 provided upstream of the aligning roller pair for detecting arrival of a document, and a size sensor 87 for detecting the size of the document D.

Further, the ADF 80 is provided with a conveyor belt 88 arranged so as to cover almost the entire document placing table 12.
The document D fed from the one end side of the document placing twelfth side, that is, the size plate 12a side to the document placing table 12 by the sheet feeding roller 84 and the aligning roller pair 85 is conveyed by the conveying belt 8
The sheet 8 is sent to a predetermined position on the document placing table and positioned there.

In the ADF 80, a reversing roller 90, a non-reversing sensor 93, a flapper 91, and a discharge roller 92 are arranged at the end opposite to the aligning roller pair 85 with the conveyor belt 88 interposed therebetween. After the image information of the document D is read by the document reading unit 4 of the apparatus main body 10, the document D is sent out from the document placing table 12 by the conveyor belt 88, and passes through the reversing roller 90, the flapper 91, and the discharge roller 92. And is discharged onto the document discharge section 94 on the upper surface of the ADF 80.

When reading the back side of the document D, the flapper 9
The original D conveyed by the conveyor belt 88 by switching 1 is reversed by the reversing roller 90, and then conveyed again to a predetermined position on the original placing table 12 by the conveyor belt 88.

As will be described later, the ADF 80 includes a paper feed motor 95 for driving the pickup roller 83, the paper feed roller 84, and the aligning roller pair 85, a conveyor belt 88, a reversing roller 90, and a paper discharge roller 92. And a conveyance motor 96 for driving the. The drive speeds of the paper feed motor 95 and the transport motor 96 can be switched between a first speed for feeding the original at a normal feeding speed and a second speed for feeding the original at a speed higher than the normal speed.

The image reading unit 4 provided in the apparatus main body 10 directs light reflected from the light source 14 such as a fluorescent lamp for illuminating the document D placed on the document table 12 and the document D in a predetermined direction. It has a first mirror 15 for deflecting, and these light source and first mirror are attached to a first carriage 16 arranged below the document table 12 in the apparatus main body 10.

The first carriage 16 is the original table 12
And a standby position A in which the light source 14 is located away from the document placing table 12 by a drive motor 13 which will be described later via a toothed belt or the like (not shown), and the light source is at one end of the document placing table. It is reciprocally moved between a reading start position B located opposite to and a terminal position C located opposite to the other end of the document placing table.

A second carriage 18 that is movable in parallel with the document placing table is disposed below the document placing table 12. On the second carriage 18, the first mirror 1
Second and third mirrors 20 and 21 for sequentially deflecting the reflected light from the document D deflected by 5 are attached at right angles to each other. The second carriage 18 is driven by the first carriage 16 by a toothed belt or the like that drives the first carriage 16, and at the same time, the original is placed at a speed half that of the first carriage. It is moved in parallel along the table 12.

Below the document table 12, an imaging lens 22 for focusing the reflected light from the third mirror 21 on the second carriage 18 and a reflected light focused by the imaging lens are received. And a CCD sensor 24 for photoelectric conversion. The imaging lens 22 is movably arranged in a plane including the optical axis of the light deflected by the third mirror 21 via a drive mechanism, and by moving itself, the reflected light is reflected at a desired magnification. Form an image. Then, the CCD sensor 24
The incident reflected light is photoelectrically converted, and an output signal as an electric signal corresponding to the read document D is converted into a signal conversion unit 14 which will be described later.
Output to 3.

As shown in FIG. 1, the image forming section 6 is provided with a laser exposure device 26 which functions as an exposure means.
The laser exposure device 26 includes a semiconductor laser 27 as a light source.
And an optical device 28. The optical device 28 changes the intensity of the laser light emitted from the laser 27 in accordance with the image information of the document D read by the image reading unit 4, and an image carrier described later. To the photoconductor drum as.

The optical device 28 imparts a focusing property to the laser light from the laser 27 and converts it into a laser light having a substantially circular cross-sectional shape, and a laser light that has passed through the first lens. An optical deflecting device 30 for deflecting along the axial direction of the photoconductor drum, and a photoconductor according to the deflection angle of the laser beam in order to sequentially image the deflected laser light on a desired position on the photoconductor drum. Second and third lenses 31, 32 that adjust the distance from the optical axis on the drum to the position where the laser light is to be imaged, and the first and second lenses that turn the laser light back toward the photosensitive drum. Mirror 33,
34, and.

The image forming section 6 also has a rotatable photosensitive drum 36 as an image carrier disposed substantially at the center of the apparatus main body 10, and the surface of the photosensitive drum 36 from the laser exposure device 26. The desired electrostatic latent image is formed by exposure with laser light.

Around the photosensitive drum 36, a charger 37 for charging the surface of the photosensitive drum to a predetermined electric charge, and a toner as a developer are supplied to the electrostatic latent image formed on the surface of the photosensitive drum to obtain a desired toner. Developing device 38 for developing with image density,
A transfer material fed from a paper cassette described later, that is, a peeling charger 39 for separating the copy paper P from the photoconductor drum is integrally provided, and the toner image formed on the photoconductor drum is transferred to the paper P. Transcription charger 4
0, a peeling claw 42 for peeling a copy sheet from the surface of the photoconductor drum, a cleaning device 44 for cleaning the toner remaining on the surface of the photoconductor drum, and a static eliminator 45 for discharging the surface of the photoconductor drum.

On the right side of the image reading unit 4 in the apparatus main body 10, there are a toner hopper 71 containing toner as a developer and a toner conveying auger unit 72 for supplying toner from the toner hopper to the developing device 38. It is provided.

An upper cassette 48, a middle cassette 49, and a lower cassette 50, which can be pulled out from the apparatus body, are arranged in a laminated state in the lower part of the apparatus body 10. The upper cassette 48, the middle cassette 49, and the lower cassette 50 each have an A4 size (A4-size) placed horizontally.
R) copy paper, B4 size copy paper and A3
About 500 copy sheets of each size are stored.

A large-capacity feeder 51 is provided on the side of these cassettes, and this large-capacity feeder accommodates about 3000 sheets of copy paper of a frequently used size, for example, A4 size copy paper. .

In the apparatus main body 10, a conveying path 5 extending from each cassette and the large-capacity feeder 51 through a transfer portion located between the photosensitive drum 36 and the transfer charger 40.
2 is formed, and the fixing device 53 is provided at the end of the conveying path. A discharge port 54 is formed on the side wall of the apparatus main body 10 facing the fixing device 53, and a discharge tray 55 is formed at the discharge port.
Is installed.

Pickup rollers 56 are provided near the upper cassette 48, the middle cassette 49, the lower cassette 50, and near the large-capacity feeder 51 to take out the sheets one by one from the cassette or the large-capacity feeder. The transport path 52 is provided with a large number of paper feed roller pairs 57 that transport the copy paper P taken out by the pickup roller 56 through the transport path 52.

A registration roller pair 58 is provided upstream of the photosensitive drum 36 in the transport path 52. The registration roller pair 58 corrects the inclination of the taken-out copy paper P, aligns the leading edge of the toner image on the photoconductor drum 36 with the leading edge of the copy paper P, and is the same as the moving speed of the outer peripheral surface of the photoconductor drum. The copy paper P is fed to the transfer unit at a speed. A pre-aligning sensor 59 for detecting the arrival of the copy paper P is provided in front of the registration roller pair 58, that is, on the paper feed roller 57 side.

The copy sheets P taken out one by one from each cassette or the large-capacity feeder 51 by the pickup roller 56 are sent to the registration roller pair 58 by the paper feed roller pair 57. Then, the copy paper P is sent to the transfer unit after the front end of the copy paper P is aligned by the pair of registration rollers 58. At the transfer portion, the developer image formed on the photosensitive drum 36, that is, the toner image is transferred to the transfer charger 4
0 is transferred onto the paper P.

The copy paper P on which the toner image has been transferred is subjected to AC corona discharge from the peeling charger 39 and the peeling claw 4.
It is separated from the surface of the photoconductor drum 36 by the action of 2 and is conveyed to the fixing device 53 via the conveyor belt 60 which constitutes a part of the conveyance path 52. Then, after the developer image is melted and fixed on the copy paper P by the fixing device 53, the copy paper P is discharged onto the paper discharge tray 55 through the discharge port 54 by the paper feed roller pair 61 and the paper discharge roller pair 62. .

On the large-capacity feeder 51, a manual feed port 73 is formed on the side wall of the apparatus main body 10, and the manual feed guide 7 is directed from the manual feed port toward the registration roller pair 58.
4 is extended. In the vicinity of the manual feed guide 74, a manual feed pickup roller 75 that conveys the copy paper inserted from the manual feed port 73 to a predetermined position, and a pair of paper feed rollers 76 that conveys the copy paper to the registration roller pair 58.
Is provided.

Below the conveying path 52, the copy sheet P which has passed through the fixing device 53 is turned over and the registration roller pair 5 is turned on again.
A reversing mechanism 64 for sending to 8 is provided. Reversing mechanism 64
Is a temporary stacking unit 65 for temporarily stacking copy sheets P.
Then, the reversing path 66 branched from the conveying path 52 and reversing the copy sheet P passing through the fixing device 53 and guiding it to the temporary stacking section 65.
And a pickup roller 67 for picking up the copy papers P stacked in the temporary stacking unit one by one, and a paper feed roller 69 for feeding the taken-out papers to the registration roller pair 58 through the transport path 68. A distribution gate 70 that selectively distributes the copy paper P to the discharge port 54 or the reversal path 66 is provided at a branch portion between the transport path 52 and the reversal path 66.

When performing double-sided copying, the copy paper P that has passed through the fixing device 53 is guided to the reversing path 66 by the sorting gate 70, temporarily accumulated in the inverted state in the temporary accumulating portion 65, and then picked up. It is sent to the registration roller pair 58 through the transport path 68 by the roller 67 and the paper feed roller pair 69. Then, the copy paper P is aligned by the registration roller pair 58, and then sent to the transfer portion again, and the toner image is transferred to the back surface of the copy paper P. After that, the copy paper P is discharged onto the paper discharge tray 55 via the conveyance path 52, the fixing device 53, and the paper discharge roller 62.

The above-mentioned transport path 52, pickup roller 56, paper feed roller pair 57, aligning roller pair 58,
The conveyor belt 60, the reversing mechanism 64, etc. constitute the paper feeding mechanism 148 in the present invention.

An operation panel 78 shown in FIG. 3 is provided on the front portion of the upper surface of the apparatus body 10. The operation panel 78 includes a display unit 100, a numeric keypad 102, various mode setting keys 104 for setting various operation modes, a document size key 106 for setting a document size, a paper size key 108 for selecting a paper size, and an ADF 80. Speed switching key 107 for switching the document feeding speed according to, a cassette selection key 110 for selecting a paper feed cassette, an automatic paper selection key 112 for automatically selecting a paper size according to the detected document size, a document size and a paper An automatic magnification selection key 114 for automatically selecting a copy magnification according to the size, a copy start key 116, and many other keys are provided.

The display section 100 displays a first display section 118 for displaying various messages indicating the operating procedure of the copying machine, a magnification, a set number of sheets, etc., and an operating state of the copying machine and a selected paper feed cassette. The second display section 120 is provided.

The mode setting key 104 is a double-sided copy key 1 for selecting and setting various double-sided copy modes.
21, an image density correction mode key 122 for correcting the print image density to an optimum value according to the image density of the original, and an inclination for correcting the image in the normal orientation when the original is set on the original placing table with inclination. A correction key 124, an edit key 126 for selecting and setting an edit mode for trimming and masking, a sheet insert mode for inserting a blank sheet on an arbitrary page, and a sheet copy mode for copying and inserting a sheet on an arbitrary page and An insertion mode key 128 to be set and various other mode setting keys are included.

When, for example, the image density correction mode, the tilt correction mode, the edit mode, etc. are selected from the various copy modes described above, the image reading unit 4 temporarily outputs specific image information from the document, as will be described later. After reading
That is, after the prescan is performed, the image reading unit 4 again reads the image of the document (main scan), and the image is formed according to the image information read by the main scan.

FIG. 4 schematically shows the configuration of the control system and drive system of the copying machine configured as described above.
As can be seen from this figure, the control system includes a main control unit 130 that controls the operation of the entire copying machine. The main control unit includes an image forming unit 6 including a drive motor, a high-voltage transformer, and a paper feed mechanism 148. And the operation panel 78 are connected. Further, the main control unit 130 stores a ROM 132 in which a control program is stored, and a RAM 134 which stores numerical data such as the number of copies and a copy magnification input from the operation panel 78, and performs enlargement / reduction processing of image data and the like. An image memory 152 for temporarily storing the image data sent from the image reading unit 4 or the image data input from an external device (not shown) is connected.

Further, the main control unit 130 includes a sub control unit 138 for controlling the operations of the ADF 80 and the image reading unit 4.
Are connected via the interface 136.
The sub control unit 138 includes a drive circuit 140 for driving the paper feed motor 95 and the carry motor 96 of the ADF 80 at a first feed speed or a second feed speed higher than this, a dimension sensor 87, an aligning sensor 86, and a reversing unit. Sensor 93,
And the empty sensor 81 is connected. The paper feed motor 96, the transport motor 96, and the drive circuit 140 are
The multiple control unit 138, the main control unit 130, and the operation panel 78, which constitute the drive unit in the present invention, constitute the speed switching means in the present invention.

Further, the sub control unit 138 includes a drive circuit 142, CC for driving the drive motor 13 of the image reading unit 4.
A signal conversion unit 143 that converts the output signal from the D sensor 24 into a binary signal, and a light source drive circuit 15 that drives the light source 14.
0, ROM 144 in which a control program is stored, and RA for storing various data and performing arithmetic processing
M146 is connected.

The drive motor 13, the drive circuit 142, the light source drive circuit 150, the sub-control unit 138 and the main control unit 130 constitute the drive means in the present invention. The signal conversion circuit 143 is an A / D conversion circuit 1 that converts an analog image signal output from the CCD sensor 24 into a digital signal.
54, a signal converted into a digital signal through a resolution conversion circuit 155 and an A / D conversion circuit 154 for matching the image data output from the CCD sensor 24 with a specific resolution to the resolution in the image forming unit 6 to the CCD. CC due to individual error of the sensor 24 and ambient temperature change
Shading correction circuit 1 for correcting fluctuations in threshold level with respect to an output signal from the D sensor 24
56, an image quality improving circuit 157 that separates the image data that has passed through the shading correction circuit 156 into, for example, a luminance signal and a color difference signal, and then performs filtering, trimming, masking, edge enhancement, character specification, etc. An image of the read original is provided with a binarization circuit 158 that binarizes the image data in order to change the intensity of the laser light emitted from the semiconductor laser 27 of the laser exposure device 30 based on the output image data. Is converted into a binary print signal.

Next, the operation of copying an original by the digital copying machine configured as described above will be described with reference to the flowchart shown in FIG. 5 and the timing chart shown in FIG.

First, when the power source of the digital copying machine is turned on, various initial operations such as heating operation of the heating roller of the fixing device 53 and jam paper detection operation are performed. After the power is turned on, when there is a key input such as magnification change, density setting, cassette selection, etc. through the operation panel 78, the main control unit 130
Executes a predetermined key input process according to the key input.
Here, when the copy mode that requires prescanning of the original, for example, the image density correction mode is selected, the main control unit 130 instructs the sub control unit 138 to perform prescanning.

Subsequently, when the copy start key 116 on the operation panel 78 is pressed, the sub control unit 138 causes the ADF 80
Based on the signal from the empty sensor 81, it is determined whether or not a document is set on the document tray 82.

When the document is set in the ADF 80, the drive motor 13 is driven via the drive circuit 142 under the control of the sub control unit 138, and the first image reading unit 4 is driven.
The carriage 16 is moved to the standby position A. continue,
After the light source 14 is turned on, the first carriage 16 is moved to the reading start position B, and black and white shading correction is performed by the shading correction circuit 156 during the movement.

When the movement of the first carriage 16 is completed, the sheet feeding motor 95 and the conveying motor 96 of the ADF 80.
Is driven to start feeding the document D. Then, after the original D is aligned by the aligning roller 16,
The document D is fed from one end side of the document table 12 toward a predetermined position on the document table, and the document D is pre-scanned during this time.

That is, since the first carriage 16 of the image reading section 4 is arranged at the reading start position B, the document D is irradiated with light emitted from the light source 14 while being fed from one end of the document placing table 12 to a predetermined position. Received, and as a result, prescan is performed. In addition, the aligning sensor 8 of the ADF80
6 from the detection of the leading edge of the document to the lapse of a predetermined time from the detection of the trailing edge of the document D by the aligning sensor, that is, after the document reaches one end of the document table 12. An image valid signal is output from the sub control unit to the image reading unit 4 until the predetermined position is reached.
Then, while the image valid signal is being output, the reflected light from the document D due to the prescan is photoelectrically converted by the CCD sensor 24, and then converted into desired image data by the signal conversion unit 143, and the image forming unit 6 is formed. Is sent to the image processing circuit. The image processing circuit reads, from the input image information, specific image information necessary for the selected copy mode, for example, information regarding image density, and stores the obtained information in the image memory 152.

When the prescan of the original document D is completed and the original document is placed at a predetermined position on the original document table 12, the main scan of the original document is started, so that the first carriage 16 once sets the reading start position B. From the standby position A,
From the standby position to the reading start position, the document table 12
Is moved in parallel below. In this way, by starting the movement of the first carriage 16 at the standby position A, the acceleration period of the first carriage can be provided between the standby position and the reading start position. As a result, the first carriage 16 reaches a predetermined moving speed when it reaches the reading start position, and thereafter can move along the document D at a stable speed.

While the first carriage 16 moves along the document D, the light from the light source 14 is applied to the document D through the document table 12 to perform the main scan of the document. Then, the reflected light from the document D is photoelectrically converted by the CCD sensor 24, converted into image data by the signal conversion unit 143, and then sent to the image processing circuit of the image forming unit 6.
The image data is subjected to desired processing by the image processing circuit based on the image information obtained by the prescan, and then sent to the laser exposure device 26 of the image forming unit 6.

On the other hand, in the image forming section 6, when the image forming operation is started, the photosensitive drum 36 is rotated at a desired speed, and at the same time, the surface of the photosensitive drum 36 is charged with a desired charge by the charging charger 37. Are uniformly charged by.

Then, the semiconductor laser 27 of the laser exposure device 26 emits intensity-modulated laser light in accordance with the supplied image data, and the optical device 28 irradiates the surface of the photosensitive drum 36. Thereby, the photosensitive drum 3
An electrostatic latent image corresponding to the image data is formed on the 6th surface. This electrostatic latent image is developed by the toner supplied from the developing device 38, and transferred as a toner image on the copy paper P by the transfer charger 40.

The copy paper P on which the toner image is transferred is peeled from the photosensitive drum 36 by the peeling charger 39 and the peeling claw 42, and then conveyed to the fixing device 53, where the toner image is fused and fixed on the paper P. To be done. Then, the paper P to which the toner image is fixed is discharged to the discharge tray 55. The above-described prescan, main scan, and image forming operation are performed on the document D placed on the document tray 82 of the ADF 80.
The process is repeated until all of the originals are exhausted, and the copy of the original is completed.

In the copy mode described above, in order to increase the document reading speed during prescan, AD
The document feeding speed of F80 may be switched. That is, when the speed switching key 107 provided on the operation panel 78 is pressed in advance, the sub-control unit 138 outputs a speed switching signal to the drive circuit 140 when starting document feeding by the ADF 80.
In response to this, the drive circuit 140 controls the currents supplied to the paper feed motor 95 and the carry motor 96, and switches the drive speeds of these motors from the first speed to the second speed.
Therefore, the document is sent to the document table 2 at a feeding speed higher than the normal speed, and the time of prescan performed during this time is shortened.

On the other hand, when the copy start key is pressed in the state where the copy mode requiring the prescan is set and the document is not set in the ADF 80,
That is, when the document is manually set at a predetermined position on the document table 12, the document prescan is performed in the same process as the conventional process.

That is, after the light source 14 is turned on, the first carriage 16 moves from the standby position A to the reading start position B.
It is moved along the document on the document table via the. As a result, the document is pre-scanned by the irradiation light from the light source 14, and the image information necessary for the selected copy mode is read.

Subsequently, the first carriage 16 is returned to the standby position A, and again passes through the reading start position B and is moved along the original on the original table. As a result, the main scan of the document is performed, and the image information for image formation is read. After that, image formation is performed by the same operation as described above.

When the copy mode requiring the pre-scan is not set, the document is set to the predetermined position on the document placing 12th by the ADF 80 or manually, and only the main scan of the document is performed. . Then, based on the image information read by the main scan, image formation is executed by the same operation as described above.

According to the digital copying machine configured as described above, when the original is automatically fed by the ADF 80 and the copy mode requiring the prescan is executed, the original is placed from one end side of the original placing table. The first carriage 16 on which the light source 14 is mounted while being sent to a predetermined position above
Is placed at the reading start position, the document moves on the fixed light source, and as a result, the document is pre-scanned. Then, after the document reaches the specified position,
The main scan is immediately performed by moving the first carriage along the document.

Therefore, unlike the conventional case, it is not necessary to move the light source along the original in order to perform the prescan of the original, and the original is required in a time substantially equivalent to that in the normal copy mode in which the prescan is not performed. Image information can be read. As a result, it is possible to form an image at the image forming speed of the copying machine.

The image reading speed during prescan depends on the document feeding speed by the ADF 80.
The drive circuit 140 of the ADF 80 increases the feed speeds of the paper feed motor 95 and the carry motor 96, so that the document reading time of prescan can be easily shortened. As a result, it is possible to further improve the decrease in the image forming speed due to the prescan. Further, such an increase in the document feeding speed can be easily performed as compared with the case where the moving speed of the carriage of the image reading unit is increased.

[0073]

As described above in detail, according to the image forming apparatus of the present invention, when the document is pre-scanned, the light source of the image reading means faces the one end portion of the document placing portion in advance by the driving means. It is possible to scan the original by irradiating the original with light until the original is moved to the position where the original is fed from the one end side of the image placing section to a predetermined position on the original placing section by the original feeding device. it can. Therefore, the document can be pre-scanned without moving the light source of the image reading unit along the document on the document placing section, and the image reading time can be shortened. As a result, it is possible to provide an image forming apparatus that does not cause a reduction in image forming speed even when performing prescan.

[Brief description of drawings]

FIG. 1 is a sectional view showing the entire digital copying machine according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing an automatic document feeder and an image reading unit of the digital copying machine.

FIG. 3 is a plan view showing an operation panel of the digital copying machine.

FIG. 4 is a block diagram schematically showing a configuration of a control system and a drive system of the digital copying machine.

FIG. 5 is a flowchart showing a copying operation of the digital copying machine.

FIG. 6 is a timing chart showing the operation of the digital copying machine during prescan.

[Explanation of symbols]

4 ... Image reading unit, 6 ... Image forming unit, 12 ... Document placing table, 14 ... Light source, 16 ... First carriage, 78 ... Operation panel, 80 ... Automatic document feeder, 106 ... Document size key, 130 ... Main Control unit, 138 ... Sub control unit, 140 ...
Drive circuit.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location G06F 15/64 325 E

Claims (3)

[Claims] 1. A document feeding device that feeds a document from one end side of the document placing part to a predetermined position on the document placing part, and a document feeding device that is movably provided along the document placing part and passes through the document placing part. An image reading unit that has a light source that emits light and that reads an image of a document placed on the document placing unit, wherein the image reading unit is provided from the one end side of the document placing unit by the document feeding device. While the document is being sent to the above specified position,
The light source is arranged at the one end of the document placing section to pre-scan the document by irradiation light from the light source, and after the document is sent to the predetermined position, the light source is moved along the document to move from the light source. An image forming apparatus, comprising: a driving unit that performs a main scan of an original with irradiation light. 2. A document feeding device for feeding a document from one end side of the document placing section to a predetermined position on the document placing section, a standby position separated from the document placing section, and the one end of the document placing section. An image of an original document placed on the original document placement unit, which is movably provided between the reading start position and the original document placement unit and has a light source for irradiating light through the original document placement unit. And an image reading unit for reading the document, wherein the image reading unit is configured to feed the document to the predetermined position from one end side of the document placing unit by the document feeding device,
The light source is arranged at the reading start position to prescan the original document by irradiation light from the light source, and after the original document is sent to the predetermined position, the light source is moved from the standby position to the original document through the reading start position. An image forming apparatus comprising: a driving unit that is moved along a line to perform a main scan of a document by irradiation light from a light source. 3. A document feeding device for feeding a document from one end side of the document placing portion to a predetermined position on the document placing portion, and a document feeding device provided so as to be movable along the document placing portion and passing through the document placing portion. An image reading unit that has a light source that emits light and that reads an image of a document placed on the document placing unit, wherein the image reading unit is provided from the one end side of the document placing unit by the document feeding device. While the document is being sent to the above specified position,
The light source is arranged at the one end of the document placing section to pre-scan the document by irradiation light from the light source, and after the document is sent to the predetermined position, the light source is moved along the document to move from the light source. The document feeding device is provided with a driving unit for performing a main scan of the document by irradiation light, and the document feeding device is capable of switching the document feeding speed between a first speed and a second speed higher than the first speed. An image forming apparatus comprising: a switching unit that switches the document feeding speed of the driving unit to the second speed during prescanning.