JPS6230628B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus having two document placement surfaces.

JP-A-49-91453 and JP-A-50-106641 are conventional devices that have two document placement surfaces, but they simply divide the document placement surface into two and make separate copies, and the dividing position is determined by the document placement surface. It is in the center of the mounting surface. Therefore, when opening a book manuscript whose size is smaller than the mounting table and copying one page or the left and right pages separately, it is difficult to find a mounting position. Further, when copying the left and right pages of the same original onto one sheet, it is necessary to transfer the original to one side, which is time-consuming and requires a large mounting surface.

The present invention aims to eliminate the above-mentioned drawbacks, and provides an image forming apparatus having an original mounting surface having two original mounting surfaces, and a scanning means for exposing and scanning the above-mentioned mounting surface. Means for changing the two-division position of the first and second surfaces according to the desired size to perform exposure scanning while distinguishing between the first and second surfaces, the scanning start position is constant regardless of the size and the desired size is achieved. a first mode (AB) in which image formation by exposure scanning on the first surface whose dividing position has been changed and image formation through exposure scanning on the second surface are successively completed; A second mode (A, B, or H) in which an image is formed by exposing and scanning only one of the first and second surfaces, and a second mode (A, B, or H) in which the first and second surfaces whose division positions have been changed are treated as one surface. a selection means 37 for selecting one of the third modes (F) in which one image formation is performed by exposure scanning from a scanning start position; This image forming apparatus has means (FIGS. 12, 13, and 14) for controlling exposure scanning by the scanning means.

As a result, even if the original size changes, various types of image formation can be easily performed without having to find a place to place the original or moving the original.

That is, a first storage section 16 that can store a plurality of sheets;
A second storage section 30 that can store the sheet after the image formation on the first surface is completed in a preparation position, and the second storage section 30 that can store the sheet after the image formation on the first surface is completed without ejecting the sheet to form the image on the second surface. a first control means (FIG. 16) for storing sheets in the second storage section; a sheet detection means (generates a signal PDPC) in the second storage section; and when the detection means detects a sheet, the sheet is fed from the second storage section. The image forming apparatus has a second control means (FIG. 15) for controlling the image forming apparatus.

The operation of the copying machine will be explained with reference to FIG. The original 3 is placed on the transparent plate 2 of the original table, and the optical system is composed of movable reflection mirrors 4, 5, a lens 7, and fixed reflection mirrors 8, 9. That is, the optical path length of the original 3 is kept equal by the movable reflective mirror 4 that moves together with the illumination lamp 6 and the movable reflective mirror 5 that moves in the same direction at half the moving speed of the movable reflective mirror 4. While hanging down, it is further exposed to a slit through a lens 7 and fixed reflection mirrors 8 and 9.
The image is formed onto the drum 1.

The surface of the drum 1 consists of a photoreceptor whose photoreceptor layer is covered with a transparent insulating layer.
It is positively charged by the positive charger 11 which is supplied with a positive high-voltage current. Next, exposure section 1
2, the document 3 on the transparent plate 2 of the document table is illuminated by the illumination lamp 6, and an image is formed on the drum 1 by the movable reflection mirrors 4, 5, the lens 7, and the fixed reflection mirrors 8, 9. At the same time as exposing the original image, the photoreceptor is subjected to alternating current neutralization by an alternating current discharger 13 to which an alternating current high voltage current is supplied from a high voltage power supply 10.

Next, the entire surface is exposed by the entire surface exposure lamp 14, and an electrostatic latent image is formed on the surface of the photoreceptor drum, which enters the developing device 15.

Development is performed by powder development using a magnetic sleeve method, and the electrostatic latent image is visualized.

Next, copy machine 1 was sent from cassette 16.
7 is brought into close contact with the drum 1. The transfer charger 18 positively charges the copy paper using the high voltage power supply 10 and transfers the image on the drum 1 onto the copy paper.

The copy paper after the transfer is separated from the drum 1 by a separating section 19 and guided to a fixing section 20. On the other hand, the remaining toner on the drum surface (photoreceptor) is cleaned by the plate 21 pressed against it, and the next cycle can be repeated again.

Based on the above configuration, it will be explained how to easily copy on both the front and back sides of copy paper. First, regarding the paper conveyance system, the copy paper 17 whose front surface has been copied is discharged to the second paper feeding means 50 by the discharge roller 22. Then, after a predetermined number of front side copies have been completed, they are stacked on the second sheet feeding means 50, and after they are aligned by an alignment means, which will be described later, a back side copying process begins. Copy paper 1 loaded on second paper feeding means 50
7' is held with its tip A abutting against the stopper plate 70, but the stopper plate 70 is released by the operation of the solenoid 71.
The copy paper 17' slides up to the feed roller sections 73 and 74, and then, by the rotation of the feed roller 73, the copy paper is fed one by one into the guide plates 75 and 76, passes through the conveyance roller 28, and returns to the registration roller 29.
The paper is sent to the transfer device by a feed signal under the control of
The paper is then discharged onto the tray 51 by the paper discharge rollers 22. Here, the element shown at 24 is a jam detection element that detects whether or not the copy paper conveyed from the first or second paper feeding means is ejected by the ejection roller 22 without jamming. Furthermore, the feeding roller portions 73 and 74 are not in contact with each other and have a slight gap. Therefore, when the copy paper is fed into the feeding roller section in the surface copying process, by rotating the roller 74 in the direction of the arrow shown in FIG.
If the roller 74 is about to be pinched, the roller 74 moves back to a point beyond the reach of the roller 74, and is subjected to the alignment action. In this way, the copy paper is fully prepared before entering the reverse copying process.

Next, the paper ejection tray 51 will be explained in detail. In the surface copying process, as shown in FIG. 1, the swinging member 52, which forms part of the paper ejection tray 51 that can swing around the rotating shaft of the ejection roller 22, is activated by a solenoid or the like (not shown). It has been pushed up to the position shown by the two-dot chain line. Therefore, the copy paper that has passed through the fixing section 20 and is discharged by the discharge roller 22 is stacked on the second paper feeding means 50.

On the other hand, in the backside copying process, the swinging member 52
returns to the position indicated by the solid line, and therefore the discharge roller 2
2, the copy paper 17' is ejected from the ejection tray 51.
will be loaded on.

Next, the operation of the optical system during double-sided copying will be explained with reference to FIGS. 2 and 3.

The document table of this embodiment has a size that covers A3 size, and a case where a double-sided copy of an A4 size book is to be made on A4 size copy paper is taken as an example.

The document placement surface is in the center, A side and B side (each A4
Two A4-sized pages can be placed on the document table at the same time. That is, in this case, the center can be said to be the dividing position that divides the A side and the B side into two. First, the case of A-side copying will be explained with reference to FIG. 2. Like a normal copying machine, the illumination section of the optical system and mirrors 6 and 7 have their starting positions immediately in front of the A-side document table, and are controlled by the photosensitive drum. When the exposure process for side A starts and the exposure is completed, the optical system mirror and illumination unit 4,
6 stops at positions 4a and 6a.

At this time, the movable reflection mirror 5 also moves to the position 5a.

Next, the case of side B copying will be explained with reference to FIG. After the surface exposure process is completed, the optical system
Stop at positions 4c, 5c, and 6c.

The length of the exposure stroke for side A (same for side B) is the length l of side A plus the slit width and allowance for starting and stopping the movement. Therefore, the optical system is the second
When copying side A is completed and moving on to copying side B as shown in the diagram, it is necessary to move back optical systems 4, 5, and 6 to align them with the optical system start positions (4b, 5b, 6b) for copying side B. There is.

Similarly, when moving to A-side copying after completion of B-side copying, the optical system must be aligned with the optical system start position (4, 5, 6) shown in FIG.

The feature of this embodiment is that it is possible to copy two sides of a document without replacing each time, but it is also easy to copy both the front and back sides of each copy sheet, and to copy the front side and then the back side. A device that automatically performs this can be easily realized.

Next, the following convenient features can be added by determining these sides A and B to be the original platen mounting surface for front-side copying, and the B-side to be the original platen mounting surface for back-side copying.

By utilizing the fact that the optical system start positions for A-side copying and B-side copying are different, etc., a signal is issued to distinguish between the two processes, and the following can be carried out.

When copying side A First, it is displayed that it is a front copy.

Further, after the copying is completed, an instruction or warning means is provided so that the copy paper is set in a paper feeding state for front side copying.

Alternatively, the system may be further automated to feed the paper for back side copying after copying is completed. That is, the copy paper that has been copied is discharged from the discharge roller to the second paper feeding means 50, and is arranged by the alignment means to be in the back side copy paper feeding state.

Also, when copying side B, First, it is displayed that it is a reverse side copy.

Furthermore, after copying is completed, an instruction or warning is issued to discharge the copy paper onto the tray, or the copy paper is actively automated and discharged onto the tray.

In this way, it is possible to improve operability by changing the display and operation of the copying machine for A-side copying and B-side copying.

Generally, books are bound on the right side, as shown in Figure 8.
There are two types of left binding, but in both cases, the front side of each sheet of paper is usually an odd numbered page, and the back side is an even numbered page. Therefore, if odd-numbered pages are placed on side A and even-numbered pages are placed on side B, there is no distinction between right binding and left binding, and in either case, error-free double-sided copying becomes possible. In this case, the book is as shown in Figure 8.
By binding on the left (a, b) and binding on the right (c, d), the book will be placed upside down. This is also one of the advantages that by determining sides A and B to be front copy and back copy, respectively, convenient instructions can be given for operation.

In addition, if the copying is performed in the order of A-side copying, B-side copying, that is, front-side copying, then back-side copying, in this embodiment, the copied paper is stacked on the tray with the back side facing up, so the pages are They are arranged in order and are extremely convenient.

Although the present invention has been described above using a copying machine with a stationary document table as an embodiment, the present invention is not limited thereto; in the case of a copying machine with a reciprocating document table, the document table can be moved relative to both sides A and B. Moreover, it can be applied not only to copying machines of the transfer type but also to other types of copying machines having a document table, for example, all types of copying machines such as the electrofax type.

Next, copying operations when using this copying machine will be explained in detail with reference to FIGS. 4 and 5.
40 is a main switch that turns on and off the power to the copying machine.

Reference numeral 31 is a copy number setting dial which allows setting of 1 to 99 copies by aligning the scale of the dial with the index, and 32 is a copy number display tube that indicates the number of copies that have been made. Reference numeral 34 is a copy start button for copying multiple copies, and if you wish to copy only one copy, press another copy start button 35 to copy only one copy regardless of the instruction on the number of copies set dial 31. . Reference numeral 36 is a shading selection dial that determines the darkness or lightness of the image, and 37 is a selection dial for copy types such as A-side, B-side, single-sided, and double-sided (AB). Here, "for side A" means that when this dial 37 is set to A, indicator lamp A lights up and only side A of the document table is copied. Furthermore, after copying a predetermined number of sheets, the paper feed plate 30
The copy sheets stacked on the paper are aligned by the swinging arm 77 and the correction plate 78, and are prepared for copying on the B side.

Next, when the dial 37 is set to B, the indicator lamp B lights up and only the B side on the document table is copied, and the A side copy is completed on the paper feed plate 30 regardless of whether multiple copies or one copy are made. While the copied paper is present, the copy paper is supplied from there, and when there is no copy paper, the copy paper is supplied from the cassette 16, but after copying is completed, the copy paper is fed to the paper ejection tray 5.
1 is discharged. When the single-sided dial 37 is set, neither indicator lamps A nor B will light up. As with conventional copying machines, copies up to A3 size can be made on one side of the copy paper, and the copy paper that has been copied on one side is ejected to the paper ejection tray 51 as is.

Next, set the dial 37 for AB and set the number of copies dial to a predetermined number of copies, and the A-side copying process will be repeated for the predetermined number of copies. When the copying process for the A-side predetermined number of copies is completed, the B-side will be automatically copied. The copying process begins, a predetermined number of copies are made on the B side, and the copy sheets that have been copied on the B side are discharged to a paper discharge tray.

This operating method provides various conveniences regarding double-sided copying. For example, when copying both the front and back sides of a document, such as the pages of a general book, there are cases where the front and back sides cannot be placed on their respective document placement surfaces at the same time.

Even in this case, when copying several consecutive pages of a book, open the book, place it on the document stand, place each opened page on its own document placement surface, and first set the selection dial 37 for side B, and select the first page. The original on side B is copied onto the back side of the second sheet of copy paper and then ejected, and then the selection dial 37 is set for side A, and the original on side A is copied onto the front side of the second sheet of copy paper.

Turn over one page of the book, set the dial 37 for side B, copy it to the back of the second copy paper, then set the dial 37 for side A, copy it to the front of the third copy paper, and turn the book again. Turn over the sheets, use dial 37 for side B, copy on the back of the third sheet of copy paper, then set dial 37 for side A, copy on the front of the fourth sheet of copy paper, and so on. Two-sided originals placed on the loading surface are not copied onto both sides of the same copy paper, but are copied onto one side of the first copy paper and the other side of the second copy paper. . However, even in this case, the two sides to be copied are placed on the document table at the same time. Of course, when making multiple copies, it is sufficient to turn the number set dial to a predetermined number of copies and copy sides A and B alternately in the same way.

In addition, as mentioned above, it is necessary to set the manuscript surface so that the odd numbered pages of the book are on side A and the even numbered pages of the book are on side B to save operational effort. It is.

Also, to determine which page of the book on the manuscript table is being copied, the indicator lamps for side A and side B will indicate which page is being copied.
They can be easily distinguished because they are lit near the sides as 39 for side A and 38 for side B, respectively.

Next, if the two sides of the original can be separated and placed on sides A and B on the document table at the same time, and you want to copy them onto both sides of a single sheet of copy paper, you can perform double-sided copying as follows. .

First, set the number of copies you need using the number set dial 3.
1, then turn the selection dial 37 to AB.
When the user presses the copy start button 34 for convenience, the required number of double-sided copies can be automatically made. At this time, since both indicator lamps 39 and 38 of both A and B are lit, it can be confirmed that double-sided copying is being performed automatically.

In the above description of this embodiment, the case where the document table has a size that covers A3 size and copies an A4 size book or the like onto A4 size copy paper is taken as an example. The purpose of the present invention is to further improve the above functions and to
Side copy, B side copy (for example, B5 size book)
(Copy side A and side B on B5 size copy paper)
The object of the present invention is to provide a device that can be easily operated.

Therefore, as mentioned above, this embodiment has a manuscript table large enough to cover A3 size, and can copy an A4 size book onto A4 size copy paper on side A and side B. , it is possible to copy A-side and B-side of a B5-sized book onto B5-sized copy paper in the same way. This point will be explained with reference to FIGS. 5, 6, and 7.

FIG. 5 shows that the operation panel of the copying apparatus according to the present invention can be moved in the direction of the arrow according to the size of the original to be copied on the A side or the B side. A setting member 91 is added to specify the position at which the surface and the B surface are divided.

For example, when copying the A-side and B-side of an A4-sized book as a manuscript, according to the present invention, the book is placed with both sides open on the area surrounded by the dotted line on the manuscript table in Fig. 5. , A4 with uneven book edges
If you want to copy side A and side B of a B5 size book as a manuscript, place the book on the double-opened area surrounded by the two-dot chain line. Place the book so that the edge of the book is aligned with the two-dot chain line of the index B5. So, for example, if you want to copy side A and side B of a B5 size book, place the B5 size book with both sides open on the document table as described above, and place the setting member 91 at the B5 size index. If you slide it up to this point, you can copy A-side and B-side of B5 size in the same way as A-side and B-side copy of A4 size as described above.

Therefore, the internal mechanism interlocked with the setting member 91 will be explained with reference to FIGS. 6 and 7, and the reason thereof will be explained.

136, 137, 138, 1 shown in Figures 6 and 7
39 is the same microswitch as shown in FIG. 10a.

Here, the mechanism interlocked with the setting member 91 will be explained. The setting member 91 is fixed to a setting member mounting plate 93, and micro switches 136, 137, and 138 are fixed to the setting member mounting plate 93. Further, the setting member mounting plate 39 is slidable with its elongated hole being guided by a slide guide pin 94 attached to a plate 90 fixed to the main body. The plate 90 is also toothed and meshes with a gear 97 rotatably attached to a pin 96 attached to a setting member mounting plate 93.

Moreover, the micro switch 13 is mounted on the mounting plate 99.
9 is fixed, and the elongated hole portion of this mounting plate 99 can be slid freely by a pin 98 fixed to a plate 95 fixed to the main body side, and this mounting plate is also cut with gears. It meshes with 97.

Therefore, if the setting member 91 is slid by a length a in FIG. 7, the mounting plate 99 will be slid by a length 2a in the same direction, and the micro switch 139 will also be slid by a length 2a.

By doing this, in Figure 10a, the length of l ₁ = l ₂ = A4 size width becomes, for example, l ₁ - a = l ₁ ′ (l ₁ ′ = B5 size width length), and l ₂ ′ = l ₂ −a, then l ₁ ′=
l ₂ '=length equal to the width of B5 size, which can be achieved by using the mechanism shown in FIG. 7.

According to this, not only is it possible to make A-side and B-side copies of a desired size (A4 size or less in the example), but the moving distance of the optical system is also shortened for small sizes, and the period of the copying cycle is shortened. ) The number of copies per unit time can be increased.

To further explain the operation, move the setting member 91 from the document size index A4 to B5 as shown in FIG. do it.

As explained above, it is an object of the present invention to make A-side and B-side copies of various different sizes possible with simple operations.

Further, in this embodiment, the micro switches 136, 13
Setting member mounting plate 93 to which 7,138 is fixed
If it moves by a, the mounting plate 99 to which the micro switch 139 is attached will automatically move by 2a in the same direction, but in this case, only the setting member mounting plate 93 will move and the micro switch 139 will be fixed. Even if there is a B-side copy, the exposure process for copying on the B side becomes a little longer, but it is still convenient when making copies of various different sizes.

As described above, one of the features of this copying apparatus is that it can perform double-sided copying without any operational complexity in any double-sided copying case that may occur.

The present invention provides first and second paper feeding devices and a document platen A.
Although the explanation has been made in relation to side and B side, in a copying machine that does not have a double-sided copying function, the document loading side can be differentiated into side A and side B, and two pages of original can be placed at the same time. You can also do that.

In this case, for example, both pages of a double-page book are automatically and continuously copied onto one side of two sheets of copy paper. Further, as for copy paper, there is no problem with sheet-like materials such as transparent paper and offset master paper.

Next, the electrical control method according to the present invention will be explained using the above embodiments. FIG. 9 is a block diagram in which devices related to control are divided by function. First, 1
01 is the power input section, door switch, safety devices such as shut-off in case of jam, drum home position set when turning on the power,
It also includes various reset devices such as those for resetting the control circuit, which will be described later, and a warm-up setting device if necessary. Next, numeral 103 is a device for checking the presence or absence of a cassette in the first paper feeding device, copy paper, and replenishment of developer and other consumables, similar to the conventional device. 105 is a copy selection dial;
Includes copy number setting dial, copy start, and copy stop buttons. The signals from these three parts are input to the central control unit (hereinafter referred to as CPU) of 107, which generates operation command signals to various operation parts for copying. It can be roughly divided into parts. First, 1
09 is a part for selectively instructing various copying operations set by 105 including a drum copy rotation command.

Further, reference numeral 111 is a part that generates a transport rotation command signal which is further required after the development and transfer process of copying.

Next, 113 is a part that generates commands to move the optical system, that is, forward, backward, and stop, 115 is a part that generates a command signal to set the copy in the second paper feeding device for back side copying, and 117 is a part that generates a command signal to set the copy in the second paper feeding device for backside copying. This is a second paper feeding device or, in normal times, a device that feeds copy paper from a cassette to a transfer position. As above
The CPU 107 issues operation command signals to each operation execution section. 121 is in the action execution section
Components that do not require feedback to the CPU 107, such as a lamp for irradiating a document, a high-voltage power supply operation section, etc., are included as in a conventional copying machine. Also 12
3 is a drum rotation operation unit, which includes a drum rotation position detection device at a necessary position, and its signal is sent to the CPU 107.
Feedback will be provided to Furthermore, 125 is also an optical system movement unit, which also includes a position detection device and a CPU
107. Also, 127 is
A copy paper detection device is installed at a necessary location in the copy paper path and generates a paper detection signal, which is input to 107.

Next, 131 is a jam detection device, which is used to confirm the normal conveyance of copy paper, and is no different from that in conventional devices. Reference numeral 129 denotes various display devices, which are parts that control necessary display on the panel surface.

Although the configuration has been briefly explained above, parts related to the present invention will be explained in more detail below with reference to the drawings.

First, in Figure 10a, 135, 136, 13
Reference numerals 7, 138, and 139 indicate position detection devices for the optical system 4, which are composed of microswitches, but other object detection devices such as photodetectors may be used in addition to this example. Here, 135 also means the home position (start position) for one-sided copying or A-side copying, and 136 also means the start position for B-side copying.

Next, 138 also means the back position during single-sided half-size copying and A-side copying, and 138
9 also means the back position during single-sided full-size copying and B-side copying. Therefore, in the case of a single-sided half-size copy, the optical system 4 moves forward from the position of the position detector 135 to the position 138, and in the case of a single-sided full-size copy, it advances from 135 to 139. Also, in the case of A-side copying, it is exactly the same as single-sided half-size copying, and in the case of B-side copying, 1
Move forward from position 36 to position 139. Here, assuming that this embodiment is a half-size A4 version and a full-size A3 version, the positional relationship of each position detection device may be as follows in order to effectively implement the present invention.
That is, the part corresponding to l ₁ in Figure 10a and
l The part corresponding to ₂ should match the vertical width of the A4 size paper in the direction of travel. Therefore l ₃ which is the sum of l ₁ and l ₂
corresponds to the vertical width of the A3 version in the direction of travel. Assuming that the original is placed at the position of the length shown in each of these, the movement range of the optical system that irradiates it and derives the optical image signal reflected on the original image is from l ₁ , l ₂ , and l ₃ in each case. It is best to move with some extra length. That is, starting position 13
5 or 136 have a distance margin of α ₁ and α ₃ from the left end of l ₁ (or l ₃ ) and l ₂ , respectively,
Further, it is preferable that the back position 138 or 139 be provided with a distance of α ₂ or α ₄ from the right end of l ₁ or l ₂ (or l ₃ ), respectively. Therefore, in this case, the start position 136 and the back position 138 are located apart from the center position 140 by α ₃ and α ₂ in the left and right directions, respectively.

Next, a signal generating device for counting the number of copies may be provided as an optical system position detecting device at the position shown at 137 in FIG. 10a. Conventionally, this type of signal has been generated using a paper feed command signal (described later), a paper detection signal in a copy paper path, or a signal from another optical system position detection means or a drum rotation position detection device. or In this embodiment, an optical system position detecting means located between 136 and 138 is provided to detect this signal, and the signal from there is used as a copy count signal to explain the subsequent operation. By combining this signal and the optical system advance execution signal, both signals are generated at the same time when copying one-sided half-size, one-sided full-size, side A, and side B. This is only done once during the process, and is very convenient for subsequent operations.

In FIG. 1, reference numerals 24, 133, and 134 denote paper detection means, and paper detection means for detecting the presence of copy paper in a second paper feeding device (not shown) is a lamp-photosensitive element pair or an ultrasonic transmitter/receiver pair. ,
It can be configured with a micro switch, etc.
In this embodiment, in order to avoid complication of explanation, the following explanation will be made by simply assuming that the signal from this detection section is at a high level when paper is being detected, and at a low level when paper is not being detected. Furthermore, the positions of these paper detection units and the role of signals from them in the copying process will be explained when explaining the paper feeding operation and the operation of setting copy paper into the second paper feeding device.

Next, this circuit is a control circuit constructed mainly using digital binary logic circuits. First, in order to simplify the following explanation, the digital logic symbols and some circuit units used in this circuit example will be explained in advance. First, Figure 11-a 5
10 is a positive AND gate, input terminal 51
1,512 has two terminals, or 3 or more terminals after 513, and those with two input terminals, or those with three or more input terminals, have all terminals at high level, that is, logic 1 (hereinafter simply referred to as 1). When the output terminal 514 becomes 1, the output terminal 514 becomes 0, and if there is even one low level, that is, a logic 0 (hereinafter simply written as 0), the output terminal 514 becomes 0. Next, the 11th-
Fig. 516 shows an inverter; if the input terminal 517 is 1, the output terminal 518 is 0; if 517 is 0, the output terminal 518 is 1. Also, No. 11-c
FIG. 520 shows a positive OR gate, which has two input terminals 521 and 522, or three or more input terminals after 523, and if at least one of these input terminals is 1, the output terminal 524 is 1.
becomes.

Further, 502 in FIG. 11-d is a preset counter, and the overall function of this circuit is that the data signal from the preset dial for the number of copies is input to the PD input terminal 5.
26, the data digit is set in the internal counter by adding the preset command signal as 1 from the PRS input terminal 528. Also
CP terminal 527 is a clock input terminal, and when a pulse is applied from this terminal, the output of the internal counter is the set data from terminal 526 minus the number of pulses. Q terminal 531 is
This is a terminal that outputs 0 when the output of the internal counter becomes 0, and the R terminal 529 is a reset input terminal, and when 1 is added from this terminal, both the set input and Q output of the internal counter are reset to 0. Further, the DIS terminal 530 is an output terminal for displaying the counter output. This preset counter 502
The overall functionality of is used in the circuit of the present invention as described above. In order to satisfy this overall function, in addition to the above-mentioned counter circuit, a 0 detection circuit and an encoder for converting a decimal signal into a binary signal are included internally, but these are directly related to the present invention. Since there is no such thing, detailed explanation will be omitted. Next, 11-e
The flip-flop circuit 533 shown in the figure is a D-type edge trigger and flip-flop used in the embodiment of the present invention, but is not limited thereto. The functions of this D-type edge trigger and flip-flop (hereinafter simply referred to as FF) are:
When a change from 0 to 1 is applied to the CP terminal 536, the data of 1 or 0 of the D input terminal 535 at that time is output from the Q output terminal 538 and held. In addition, the R input terminal 534 is a reset input terminal and is output to the output terminal 538 regardless of the D and CP input terminals.
Set the output to 0. Similarly, the S input terminal 537 makes the output terminal 538 1. here,
In general, many of the R and S input terminals exhibit their functions when they are set to 0, but for the sake of simplicity, the following description will be made assuming that they function when they are set to 1. Further, the Q terminal 539 outputs a level opposite to that of the output terminal 538.

Each circuit using each of the above logic elements will be described in detail.

First, the control circuit corresponding to the copy selection section is
Shown in Figure 2. In Fig. 12, first, the copy selection signals from the operation panel are: single-sided copy (hereinafter referred to as S copy), A-side duplicate copy (hereinafter referred to as A-copy), B-side copy (hereinafter referred to as B-copy), and double-sided automatic copy. (hereinafter referred to as AB copy), the terminals 149, 151, 153, 155
is input as 1 from

In addition, if a half-size cassette signal (hereinafter referred to as HSCP) and a full-size cassette signal (hereinafter referred to as FSCP) are used as signals for the copy paper cassette in the first paper feeder installed, terminals 145 and 147 is entered as . Furthermore, a signal when the copy button is pressed (hereinafter referred to as CCP), a signal when the copy stop button is pressed (hereinafter referred to as CSP), and a copy number data signal set by the multi-copy dial (hereinafter referred to as MCD)
) are terminals 159, 157, and 161, respectively.
, except for MCD, which is input as 1, and MCD is input as a predetermined input group. Further, signals (hereinafter referred to as PDPE and PDPC, respectively) that become 1 when there is paper in the cassette and in the second paper feeder are input from terminals 150 and 148, respectively.

Furthermore, a copy count clock pulse signal (hereinafter referred to as CCCP) which generates 1 when the optical system passes the position of the position detection device 137 in FIG. System forward signal (hereinafter written as OFL)
is input as 1 while the optical system is moving forward. Further, from the terminal 166, an A copy execution signal (hereinafter referred to as ACPL), which will also be described later, is inputted as 1 during execution of the A copy. First, when CCP is applied as 1 from the normal terminal 159 to the PRS terminal of the preset counter (hereinafter referred to as PSCNT) 202 via the two-input OR gate 191, the CCP from the terminal 161 is applied as 1.
The MCP data added to the PD terminal of PSCNT is
It is stored inside the PSCNT circuit 202, and the Q output terminal becomes 1 at this time, and this signal is used for B copy, A copy, full size S (single-sided) copy (hereinafter referred to as F copy), and half size S copy ( This is the first condition for generating each command signal (hereinafter referred to as H copy). The second condition is that the copy paper or cassette loading signal is output to the gates 196 and 19.
7, 198, and 199, but first the output is a half-size copy command signal (hereinafter referred to as
A PDPE signal and an HSCP signal are applied to the input terminal of a gate 199 (written as HCCP). Next, the PDPE signal and the FSCP signal are applied to the input terminal of a gate 198 whose output is a full-size copy command signal (hereinafter referred to as FCCP), and the gate whose output is a double-sided A copy command signal (hereinafter referred to as ACCP). A PDPE signal and an HSCP signal are applied to the input terminal of 197. Furthermore, the second condition for the output of the gate 196, which outputs a double-sided B copy command signal (hereinafter referred to as BCCP), is that copy paper exists in the half-size cassette or exists in the second paper feeder. In order to meet this condition, first the PDPE signal and HSCP signal are input as two inputs.
Applied to each input terminal of AND gate 200, the output of gate 200 and the PDPC signal can be applied to gate 196 via a two-input OR gate 195.

Next, as a third condition, the signal from the copy selection dial (FIG. 5, 37) is
It is added to 97, 198, 199,
First, the S copy signal is applied to gates 199 and 198. Further, the A copy signal is applied to the input terminal of the gate 197 via the two-input OR gate 182, and the B copy signal is applied to the input terminal of the gate 196 via the two-input OR gate 185. In the case of copying, the third condition is that the AB copy selection signal that must be made when copying A and B is also output from the OR gate 18 as the output of the two-input AND gates 181 and 184, respectively.
2,185 other input terminals to the gate 19
7,196, in the copying process, when the copy button is pressed during AB copying, first copy A is performed for the set number of copies, then copy B is performed again for the set number of copies, and the process ends. In order to achieve this control, first, inverter 1 of BCCP is connected to each input terminal of two-input AND gate 193.
By adding the inverted signal via 92 and the CCP signal, the output of gate 193 becomes 1 when there is no B copy command (0) and the copy button is pressed.
is added to the terminal of FF203, and at this time FF2
The Q terminal of 03 becomes 1. Since this Q output signal is applied as 1 to gate 181 and the AB copy signal is applied to the other input terminal of gate 181, the output of gate 181 becomes 1 and satisfies the third condition for A copy. In addition, in the case of the last A copy, even if the Q output terminal of PSCNT becomes 0 and ACCP becomes 0, the ACPL signal (A copy execution signal) does not become 0 yet, as described later, and at this time, the 3 inputs
By applying the AB copy signal, the ACPL signal, and the inverted signal from the ACCP inverter 137 to each input terminal of the AND gate 186, the output becomes 1, which is applied to one input terminal of the two-input AND gate 190. The other input terminal indicates that it is moving forward, i.e.
When OFL is 1, CCCP is added as 1 via a two-input AND gate 194. This gate 19
The output of 4 is connected to the two-input AND gate 188 via the inverter 189 while the output of the gate 186 is still 0.
is applied as 1 to one input terminal of PSCNT through the other input terminal of gate 188.
is applied to the CP pin as a clock pulse. Therefore, in the case of copies other than AB copy, the output of gate 188 is directly counted by PSCNT 202, but in AB copy, the output of gate 194 becomes 1 during the execution of the last A copy, and the output is counted through gate 188. When ACCP is applied to the CP terminal of the PSCNT 202 and the Q output becomes 0, the output of the gate 197 becomes 0 as described above, and when ACCP becomes 0, the output of the gate 186 becomes 1 and the output of the gate 188, that is, the CP terminal of the PSCNT becomes 0. The applied signal is 0
Then, the output of gate 190 becomes 1.
It is added as 1 to the PRS terminal of PSCNT 202 via OR gate 191, and PSCNT 202 is set again and the Q output terminal becomes 1. At this time, the output of the gate 190 is further applied to the R terminal of the FF 203, and the Q output becomes 0, so the Q of this FF 203 is
The output is inverted to 1 via the inverter 183 and applied to one input terminal of the gate 184,
The output of the gate 184 becomes 1, and conversely the output of the gate 181 becomes 1.
Since the output of becomes 0, the third condition in gate 196 is satisfied and BCCP becomes 1.
ACCP will not be 1 this time. Therefore, the B copy is further performed for the set number of copies, and the AB copy ends. In addition, in the PSCNT202, the set number of sheets data is given by the NCD signal input from the terminal 161, and the data output from the DIS terminal is
After the PSCNT 202 is set by the signal applied to the PRS terminal, the number of clock pulses applied from the CP terminal, ie, the signal DISP indicating the number of copies to be executed, is outputted to a display section (not described in detail) at the terminal 175.

With the above process, terminals 173, 163, 17
B copy command signal from 1,169 respectively
BCCP, A copy command signal ACCP, single-sided full-size copy command signal FCCP, and single-sided half-size copy command signal HCCP are output. Next, Figure 10b
13, the generation process of each copy execution signal and transport rotation signal will be explained. First, Figure 10b
, 402 is a photosensitive drum, 401 is a micro switch for detecting the rotational position of the drum, and 403 is a photosensitive drum.
cams a, 403b, 404a, and 404b that drive the microswitch 401 are shown around the drum 402 for convenience, and an arrow 405 indicates the rotation direction. Here each cam is micro switch 4
When the signal reaches the actuator section 01 and drives the microswitch, a signal 1 is generated by a pulse generating circuit (not shown) and applied to the control circuit. In this embodiment, the signal 1 generated by the cam 403a is the normal stop position of the photosensitive drum. This signal will be written as DHPA below. Additionally, 403b and 403b are used to detect the rotational position of the photosensitive drum.
04a and 404b are provided, and the cam 403b is located at a position rotated 180 degrees from the cam 403a, and is provided to improve the time efficiency of half-size copying, the details of which will be described later. The signal of 1 generated by the cam 403b is hereinafter written as DHPB. Furthermore, the cams 404a and 404b serve as timing pulses for the generation of each copy execution signal, as described later by DHPA and DHDB, and generate a timing signal for starting the forward movement of the optical system after a certain period of time delay from the generation of the copy execution signal. , respectively below.
Write OSPA, OSPB, and micro switch 4
02 may be a plurality of units corresponding to each cam in order to separate each signal, and in the following explanation, the DHPA, DHPB, OSPA,
OSPB is performed assuming that the signal lines have already been separated. In FIG. 13, first, terminals 169, 17
HCCP from 1,167,173 respectively,
ECCP, ACCP, BCCP signals are input, and FF
It is added to each D terminal of 228, 224, 225, and 226.

Each copy command signal further includes HCCP, ACCD,
BCCP is applied to each input terminal of the three-input OR gate 219, and the output of the gate 219 and FCCP are further applied to each input terminal of the two-input OR gate 220.The output of the gate 220 is first directly connected to one of the two-input AND gates 217. The signal is applied to the input terminal, is inverted and delayed via inverters 214, 215, and 216, and is also applied to the other input terminal of gate 217. Therefore, when any copy command signal is generated and the output of gate 220 becomes 1, the output of gate 217 is output to inverters 214, 215, 2.
It becomes 1 for the signal delay time caused by 16 and passes through the inverter 218 to the two-input AND gate 223.
is applied to one input terminal of the gate 238, and the output of the two-input OR gate 238 is applied to the other input terminal of the gate 238.
DHPB input from terminal 237 is input to the input terminal of
The output of the gate 219 is passed through a two-input AND gate 239, and the DHPA input from the terminal 210 is added. Furthermore, the output of the gate 223 is connected to each of the FFs 228, 224, 225, 226.
Added to CP terminal. Therefore, the four flip-flops are clocked by DHPA when each copy command signal is already 1, or by DHPB when copying other than full size, that is, when the output of gate 219 is 1; Also
When DHPA or DHPB becomes 1 and the drum is in a stopped state, the delay time due to the inverters 214, 215, 216, the gate 217, and the inverter 21 from the rise of any copy command signal.
8. Each signal is delayed by the delay time due to gate 223.
A clock pulse for FF is generated and the Q output terminal becomes 1. At this time, HCCP, FCCP,
In response to the generation of ACCP and BCCP copy command signals, FF228, 224, 22 in each case
The Q outputs of 5 and 226 become 1 and each terminal 23
6, 231, 116, and 234 are output as single-sided half-size, single-sided full-size, A, and B copy execution signals (hereinafter referred to as HCPL, FCPL, ACPL, and BCPL, respectively). These copy signals occur after the corresponding copy command signal becomes 0.
Set to 0 by DHPA or DHPB. Also
HCPL, FCPL, ACPL, BCPL are further 4 input OR
When applied to each input terminal of gate 230, the output is a signal indicating the presence of any copy execution signal (hereinafter referred to as
(written as CPL) and is output from the terminal 232 to the subsequent circuit. In addition, the output of the inverter 214 and the output of the two-input OR gate 222 are applied to each input terminal of the two-input AND gate 221, and the output is applied to the FF2.
The DHPA signal is applied to the D terminal of FF227, and the DHPA signal is applied to the CP terminal of FF227.
Each input terminal of 2 is connected to a paper detecting device 2 located at the copy paper ejection roller (22 in FIG. 1) from the terminal 213.
By adding the detection signal A (PDPA) from 4 and the output signal of FF227, when DHPA becomes 1, the Q output of FF227 becomes 0 without any copy command signal, that is,
When the output is 1 or when the copy paper is still being ejected, the Q output of the FF 227 becomes 1, and when the drum rotates once and DHPA occurs again, it returns to 0 if the copy paper has been ejected. The Q output of this FF227 is sent to the terminal 23 as a transport rotation signal (hereinafter referred to as FIL).
Output from 5. Also, two-input OR gate 229
The CPL and FIL signals are applied to each input terminal of the drum, and the output can be outputted from the terminal 233 as a drum rotation signal, but a circuit (not shown) prevents the drum from stopping at any position other than the position where DHPA is generated. are doing. Next, Figure 10a and 1
4, the process of generating an optical system forward signal (hereinafter referred to as OFL) and a backward signal (hereinafter referred to as OBL) will be explained. First, in Figure 10a, position 135
A signal that generates 1 at optical system home position A (hereinafter referred to as OHPA) and a signal that generates 1 at position 136, that is, optical system home position B (hereinafter referred to as OHPB) and positions 138, 1.
Signals that generate 1 at 39, that is, optical system home positions A and B (hereinafter referred to as OBPA and OBPB, respectively)
) are terminals 211 and 21 in Figure 14, respectively.
Input from 2,267,268. Here, first, the Q output of FF281 is output from the terminal 165 as OFL, and the output is also output from the two-input AND gate 2.
In other words, it is output as OBL from the terminal 290 through the two-input AND gate 285, which satisfies another condition.
OHPB and BCCP are applied to each input terminal of gate 285, and OHPA is applied to each input terminal of a two-input OR gate 282.
The output of 82 is sent to gate 2 via inverter 283.
84 in addition to the other input terminal. accordingly
When the output of FF281 is 1, that is, when the optical system is not moving forward, the optical system is at home position A, or in the case of double-sided B copying, the optical system is at home position B. Otherwise, the output of the gate 284 becomes 1 and the optical system retreats.

Here, the OHPA signal is applied to the D terminal of FF281 via the two-input OR gate 278, and
The OHPB and BCPL signals are applied to the respective input terminals of the two-input AND gate 274, and the output of the gate 274 and the output of the FF281 are connected to the two-input AND gate 2.
75 to each input terminal of gate 27
The output of FF 281 is also applied to the D terminal of FF 281 via the other input terminal of gate 278. That is,
OHPB if OHPA is 1 or B copy
Even if is 1 and is not moving forward (OFL is 0), 1 is added to the D terminal.

At this time, if CPL is 1, this is the second input
Since it is applied to one input terminal of the AND gate 280, the three-input OR gate 27 of the OSPA
9 and is further applied to the CP terminal of the FF 281 via the other input terminal of the gate 280.
The output becomes 1 and the optical system moves forward. In addition, when half-size copying and A and B copying are performed continuously, in order to increase time efficiency, forward movement is started and the copying is performed by OSPB, which occurs when the drum rotates 180 degrees from the occurrence of OSPA. Able to execute the process. This is HCPL,
ACPL and BCPL signals are three input OR gate 276
in addition to one input terminal of the two-input AND gate 277 via
OSPB is connected to FF281 via the other input terminal of gate 277 and further via gates 279 and 280.
It is added to the CP terminal and the optical system can move forward again. In the case of B copy, after the optical system starts moving forward from home position A, it reaches optical system home position B, OHPB becomes 1, the output of gate 274 becomes 1, and gates 279, 28
When it is applied to the CP terminal of FF281 through 0, the output terminal is 0, so the output of gate 275 is 0, and therefore 0 is added to the D terminal of FF281. The Q output becomes 0 and forward movement stops, and at the same time the output of the gate 275 becomes 1 again and 1 is added to the D terminal via the gate 278, causing the next OSPA or
The optical system starts moving forward again due to OSPB.

That is, the optical system advancement timing can be synchronized with the rotational position of the photosensitive drum. Next, the optical system is reversed (starting to retreat) as follows. first,
HCPL and ACPL are applied to each input terminal of the two-input OR gate 271, and the output of the gate 271 and
Since OBPA is applied to each input terminal of the two-input AND gate 272, half-size copy and A
In the case of copying, when OBPA occurs, gate 27
The output of 2 becomes 1 and is applied to the R terminal of FF 281 via the 2-input OR gate 273, the Q output becomes 0, and the output becomes 1, stopping forward movement and at the same time starting backward movement. Further, in the case of full-size copying and double-sided B copying, when OBPB becomes 1, 1 is applied to the R terminal of FF 281 via gate 273, and the optical system is reversed.

Next, FIG. 15 shows a copy paper feed control circuit.

As mentioned above, in this embodiment, the timing of paper feeding is synchronized with the start of movement of the optical system, that is, when the optical system advances a certain distance from the home position. The signal from the position detection device that is currently located a certain distance away from the optical system home position A is defined as paper feed start pulse A (hereinafter referred to as PFSA), and similarly, the signal from the position detection device that is located a certain distance away from the optical system home position B is Until now, the signal from the position detecting device existing at the position is called paper feed start pulse B (hereinafter referred to as PFSB), and the position detecting device generates a signal of 1 only while the optical system passes that position. This is the same as the explanation. Furthermore, as mentioned above, in the case of B copying, the copy paper must be fed from the second paper feeding device shown in FIG. It is determined whether or not paper can be fed based on the signal from the cassette (hereinafter referred to as PDPC). Even if this PDPC is 0, if a half-size cassette is installed and there is copy paper in it, it will be fed from the cassette. It is made to look like paper. In Figure 15, PFSA and OFL and
Since the inverted signal via the BCPL inverter 307 is applied to each input terminal of the three-input AND gate 305, if PFSA becomes 1 while the optical system is moving forward during a copy other than B copy, the output of the gate 305 becomes 1.
terminal 31 via the two-input OR gate 311
2 is output as a signal (PFCC) instructing paper feeding from the cassette.

In addition, PFSB, OFL, and BCPL are three input AND
When applied to each input terminal of the gate 306, if PFSB becomes 1 when the optical system moves forward during B copying, the output of the gate 306 becomes 1, but if PDPC is 1 at this time, the output of the gate 306 and the PDPC signal become 1. Since it is applied to each input terminal of the two-input AND gate 310, the output of the gate 310 becomes 1 and is output from the terminal 313 as a paper feed command signal (PFCP) from the second paper feed device. Also, two input AND
Each input terminal of gate 308 is connected to gate 306 and
Since the signal via PDPC inverter 309 is added, when PDPC is 0, gate 3
The output of 08 becomes 1 and becomes a command to feed paper from the cassette via the other input terminal of gate 311.

When this PFCC or PFCP signal is generated (becomes 1), the copy paper is fed from the cassette 16 by the paper feed roller or from the second paper feed means by the feed roller 73 as shown in FIG.
8 to register roller 29 and roller 2
9 rotates again after a certain period of time has elapsed since the generation of the PFCC or PFCP signal, and conveys the copy paper that had arrived up until then in the direction of the transfer position. Although not limited to this paper feeding method, and a specific example of a control circuit is omitted, when paper is fed from the cassette side, the feed rollers 643 and 644 shown in FIG. In the case of paper feeding, the conveyance may be temporarily stopped when the leading edge of the copy paper reaches a predetermined position between the feed rollers 73 and 28, and then the copy paper may be conveyed again in the direction of the transfer position at the appropriate timing.
Further, when the roller 29 is used as a register roller, the copy paper is continuously taken out to the roller 29 at a speed slower than the transfer speed, that is, the copy paper is continuously taken out by the paper feed roller or the feed roller 73 in the cassette 16. Then, when the roller 29 rotates again at a certain timing, the copy paper may be forcibly conveyed by the roller 29 at the normal speed at the time of transfer. In this method, the paper feed roller or the feed roller 73 can be kept rotating continuously for a predetermined period during a plurality of continuous copies, and the control circuit can be simplified.

Here, when PFCP becomes 1 and copy paper is fed from the second paper feeding means, this PFCP signal drives the solenoid 71 shown in FIG. 1 to move the stopper plate 70 and release the role of the stopper.

Next, in the case of A copy, the process control circuit that transports the copy paper after the transfer to the second paper feeding means is connected to the first
This will be explained using FIGS. 16 and 17.

In the A-side copying process, as described above, the copy paper led from the cassette 16 is discharged by the roller 22 after completing the transfer and fixing process.
2 must rise to the top as shown by the two-dot chain line in FIG. This operation can be easily performed using electric means such as a solenoid, but the operation period can be controlled as follows. That is,
After the ACPL reaches 1 and the A-side copying process begins,
Only for a time shorter than the minimum time for the first sheet to be ejected and longer than the maximum time for the last copy sheet to be ejected in the other copying process before the A-side copying process.
The swinging member lift drive command (hereinafter referred to as TUCP) is delayed by TD1.
(written as 1) occurs (makes 1). Furthermore, at this time
It is longer than the time from when the ACPL returns to 0 until the ejection of the last copy of A copy is completed, and shorter than the minimum time from when the next copying process starts and the first copy is ejected. It is sufficient to release TUCP (set it to 0) after a delay of time TD2, and the circuit is shown in FIG. First, the ACPL signal is applied from terminal 166 to delay timer circuit DT327. As shown in the time chart of FIG. 17, this output is delayed from the rising edge of the ACPL signal 166' by the time TD1 mentioned above, and the output 328' of the DT327 rises to 1.
Then, 328' becomes 0 at the falling edge after a delay of the aforementioned TD2 time from the falling edge of 166'. At this time, TD1 and TD2 may be equal. DT327
A specific example of this will be omitted, but it can be easily designed by a person skilled in the art. In Figure 16, DT327
The output is output from the terminal 328 as TUCP.

An example of the electric control circuit according to the embodiment of the present invention has been described above, but details have been omitted from the following to avoid complicating the explanation. First of all, turn on the power
The output of each flip-flop must be reset once when it is turned on, and when the detection signal is generated in each position detection device using a contact-type switching element such as a microswitch, chattering may occur. They also omitted the explanation that all of them used anti-chattering circuits.
Furthermore, various control circuits that are not directly related to the present invention, such as driver circuits and jam detection circuits of each device driven in accordance with each command, are also omitted. Furthermore, the control circuit according to the present invention is by no means limited to the circuit described here.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an apparatus showing an embodiment of the present invention, Figs. 2 and 3 are explanatory diagrams showing the relationship between double-sided copying and the optical system, Fig. 4 is an external view of the apparatus, and Fig. 5 is a top view of the operation panel of the device, Figure 6 is an explanatory diagram of the position of the optical system's micro switch, Figure 7 is a perspective view of the size selection lever, and Figure 8 is a diagram of the case of right-hand binding and left-hand binding of originals such as books. 9 is a block diagram of the electrical control system of this embodiment, FIGS. 10a and 10b are explanatory diagrams of the microswitch position of the optical system and paper feed control,
11 is an example of a digital logic circuit used in this embodiment, FIG. 12 is a copy command signal generation circuit diagram, FIG. 13 is a copy execution signal generation circuit diagram, FIG. 14 is an optical system movement control circuit diagram, and FIG. 15 is a diagram of a copy execution signal generation circuit. The figure shows a sheet feeding command signal generation circuit, and FIGS. 16 and 17 show a stroke control circuit for conveying the A-side copy to the second sheet feeding means after transfer.

Claims (1)

[Scope of Claims] 1. An image forming apparatus having an original document mounting surface having two original mounting surfaces, and a scanning means for exposing and scanning the document mounting surface, comprising: Means for changing the two-divided position of the first and second surfaces according to the desired size to perform exposure scanning while distinguishing between the two surfaces, the scanning start position is constant regardless of the size, and the dividing position is changed according to the desired size. A first mode (AB) in which image formation by exposure scanning of the first surface that has been changed and image formation by exposure scanning of the second surface are successively completed; A second mode (A, B, or H) in which an image is formed by exposure scanning only one side of the surface, and a second mode (A, B, or H) in which an image is formed by scanning only one side of the surface, and a second mode in which the first and second surfaces, whose divided positions have been changed, are treated as one surface and exposed from the above scanning start position. a selection means for selecting any one of a third mode (F) in which one image is formed by scanning; and exposure scanning by the scanning means according to the scanning mode selected by the selection means and the changing means. An image forming apparatus having a means for controlling.