JPH0410069B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a double-sided copying machine capable of forming copied images on both sides of copy paper. BACKGROUND ART Conventionally, in order to reduce the volume of copies, many double-sided copying machines have been proposed that are capable of forming copied images on both sides of copy paper. This double-sided copying machine forms a copy image of a first original on the front side of copy paper, and forms a copy image of a second original on the back side of the copy paper. However, in general, the first original size and the second original size are not necessarily the same, and if the back side copy is made at the same copying magnification as the front side copy of the first original, the second original size will be larger than the first original original size. If it is large,
The copied image of the second document cannot fit on the back side of the copy paper, and the image is cut off. In order to prevent such copying errors from occurring, the operator must change the copying magnification when copying the back side, but this often results in copying errors. Purpose The present invention has been made in view of the above points, and its purpose is to prevent a copying error from occurring when copying the back side of a first original and a second original, even if the sizes of the first original and the second original are different. Provides a double-sided copy machine. Summary In order to achieve the above object, a double-sided copying machine according to the present invention includes a means for detecting the size of a document, a means for feeding copy paper of a plurality of sizes, a means for setting a predetermined copying magnification, The above prescribed copy magnification and the first
means for calculating an optimum copy paper size of the copy paper from the size of the second original, and means for calculating an optimum copy magnification from the size of the copy paper and the size of the second original;
Copy control means for feeding copy paper corresponding to the optimum copy paper size and executing the copying operation at the predetermined copying magnification during front-side copying, and for executing the copying operation at the optimum copying magnification during back-side copying. The gist is that. Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 schematically shows an embodiment of a copying machine equipped with a copying machine main body and a document feeder (hereinafter referred to as DF). The machine is equipped with a three-stage paper feed section that can each load different types of copy paper. A photoreceptor drum 30 is located at the center of the image forming means as shown by arrow a.
A charging charger 31, a developing device 32, a transfer charger 33, a copy paper separation charger 34, a cleaning device 35, and an eraser lamp 36 are arranged around the charger. The image forming optical system 40 is installed below the document table glass 39 so that the document image can be scanned.
The illumination light 1 is reflected by the original on the glass 39,
First mirror 42, second mirror 43, third mirror 4
4. The photosensitive drum 30 is exposed in a slit shape through the projection lens 45 and the fourth mirror 46. In this case, the light source 41 and the first mirror 42 are connected to the photosensitive drum 3.
For a circumferential speed V of 0 [V/m; m is the copying magnification]
The second mirror 43 and the third mirror 44 move in the direction of arrow b at a speed of (V/2m). On the other hand, the paper feeding section is composed of an upper paper feeding section 1, a middle paper feeding section 2, and a lower paper feeding section 3, and the upper paper feeding section 1 and the middle paper feeding section 2 are provided with removable paper feeding cassettes 4 and 5. An automatic paper feeding system is adopted, and the lower paper feeding section 3 adopts an elevator automatic paper feeding system in which the copy paper loading table 6 is pushed up in sequence, and the top layer is picked up by paper feeding rollers 7, 8, and 9, respectively. is being fed. In addition, a feeding section is formed from each paper feeding section 1, 2, 3 to a transfer section by various guide rollers, guide plates, etc., and a timing roller pair 10 provided just before the transfer section is used for each paper feeding section. The leading edges of the copy sheets selectively fed from sheets 1, 2, and 3 and the image forming section on the photosensitive drum 30 are synchronized. The conveyor belt 47 that conveys the copy paper after transfer is
The fixing device 48 is equipped with a suction means (not shown) inside the fixing device 48 with the copy paper adsorbed on the belt surface.
Transport to. A switching means 60 is provided downstream of the fixing device 48 for selectively guiding the fixed copy paper to a tray 49 or a paper refeeding mechanism to be described later. The paper refeeding mechanism includes a reversing path 61 provided vertically below the switching means 60, and a forward/reverse roller 6.
2, a receiving roller 63, an intermediate tray 64, and a paper refeeding roller 65 are provided, and the copy paper after single-sided copying is transferred to the reversing path 6 by the normal rotation of the forward/reverse roller 62.
When the trailing edge of the copy sheet reaches the lower part of the branching part 61a, the forward rotation is stopped and the reverse rotation is started.
The paper is stored in the paper feed path, and is sent to the paper feed path again by a paper refeed roller 65 driven by a paper refeed signal. The copying machine 50 having the above configuration is capable of normal copying in which a copied image is formed on one side of a copy sheet, and double-sided copying in which a copied image is formed on both sides of the copy paper.Switching is performed by operating the mode switching key (SW17). In addition, each copy operation is performed using the print key.
The process is started by turning on SW16 or by setting a document by DF100, which will be described later. During normal copying, the photosensitive drum 30 is charged, image exposed, and developed based on the rotation in the direction of the arrow a, and the toner image is selectively fed from each paper feed section 1, 2, and 3. The toner is transferred onto copy paper, and the copy paper is conveyed from a conveyor belt 47 to a fixing device 48, where the toner is heated and fixed, and then discharged onto a tray 49. The photosensitive drum 30 continues to rotate even after the transfer, and residual toner and residual charge are removed to prepare for the next copying. On the other hand, during double-sided copying, the toner image formed on the photoreceptor drum 30 is first transferred onto copy paper selectively fed from each copying section 1, 2, and 3, as in normal copying. After being heated and fixed by the fixing device 48, the copy paper after fixing is led to a reversing path 61 by a switching means 60, and is stored in an intermediate tray 64 via a forward/reverse roller 62 and a storage roller 63 to complete the surface copying. do. Next, the back side original is set and back side copying is started. That is, paper refeed clutch CL4
is turned on to drive the paper re-feeding roller 65 to re-feed the copy paper stored in the intermediate tray 64, transfer the toner image to the back side thereof, and heat and fix it in the fixing device 48, after which the switching means Tray 4 through 60
Discharge at 9. As described above, the copying operation of the copying machine 50 has three modes: normal copy mode, front copy mode (double-sided copy mode), and back copy mode (double-sided copy mode). Furthermore, as will be described later, the copying machine 50 has an automatic magnification setting function (hereinafter referred to as AMS) that automatically calculates and sets the optimum copy magnification at that time when the original size and copy paper size are specified in cooperation with the DF 100. It is equipped with an automatic paper selection function (hereinafter referred to as APS) that calculates the optimal size at that time and automatically selects the paper source containing the copy paper by specifying the document size and copy magnification. Therefore, AMS mode and APS mode copying can be performed for each of the above three copy modes. On the other hand, switches SW ₁ to SW ₄ , SW ₆ to _{SW 9} , SW ₁₁
~SW ₁₄ is a micro switch installed in parallel to each paper feed section 1, 2, 3, and is used to control the size of the copy paper in the cassettes 4, 5 and on the loading table 6, and whether it is vertical or horizontal with respect to the paper feeding direction. Detect whether it is installed in the The sizes that can be copied, that is, the copy paper sizes that can be set in each paper feed section 1, 2, and 3, are, for example, "A3" and "A4".
"A5", "A6", "B4", "B5", "B6", and "A4"
For "A5" and "B5", vertical and horizontal orientation can be selected. In addition, the switches SW ₁ to _{SW 4} and SW ₆ to _{SW 9} also detect the attachment and detachment of the cassettes 4 and 5, which indirectly detects the presence or absence of copy paper in the paper feed sections 1 and 2. means. The size and loading direction of the copy paper in each paper feed section 1, 2, and 3 can be set using a switch.
ON/OFF of SW ₁ to _{SW 4} , SW ₆ to _{SW 9} , SW ₁₁ to SW ₁₄
It is detected using a 4-bit code corresponding to the off combination, and is stored in the RAM of the first CPU 301, which will be described later.
For example, a code table for switches SW ₁ to _{SW 4} is shown in Table 1. In this table, "0" indicates the switch is on, and "1" indicates the switch is off. If all the switches are off, it means that the cassette 5 is not installed in the paper feed section 1, that is, there is no copy paper. will be detected.

[Table] In addition, the micro switches installed in paper feed sections 1 and 2
SW ₅ and SW ₁₀ directly detect the presence or absence of copy paper in the cassettes 4 and 5, respectively. The photoelectric switch SW ₁₅ provided on the loading table 6 of the paper feed section 3 also connects to the loading table 6.
The presence or absence of copy paper on the top is directly detected. It should be noted that another micro switch SW ₂₄ provided in the paper feed section 3 is used to detect the top layer of copy paper in order to control the degree of rise of the mounting table 6. On the other hand, the DF 100 is removably installed on the upper surface of the main body of the copying machine 50. As explained below, DF
When it is detected that the printer 100 is electrically connected to the main body of the copying machine 50 and installed at a predetermined position,
The controls of the DF 100 and the copying machine 50 are related to each other, and when a document is inserted into the DF 100, the copy start mode of the copying machine 50 is set to the print key.
From the manual start mode in which the copying operation is started by turning on SW ₁₆ , the copying operation is started by the start signal sent from the DF100.
Switched to DF start mode. DF start mode means that when a document is inserted into the DF 100, the DF 100 starts operating while the copying machine 50 remains in a standby state, and feeds the inserted document along the top surface of the document placement glass of the copying machine 50. The DF 100 is stopped at a predetermined position and a start signal is issued to the copying machine 50 to start the above-described copying operation. When the final scanning movement for the original is completed, the copying machine 50 issues an original discharge signal to the DF 100. Then, the DF100 transfers the original to the output tray 109.
Paper is ejected upward. To explain in detail the operation of the above DF,
In the DF 100, when the first sensor SEN1 detects a document inserted between the pair of pinch rollers 106 and 111, the pair of pinch rollers 106 and 111 are pressed against each other and the belt 107 is driven. Thereafter, the pinch roller pair 106, 111 is driven with a slight delay, and the gate stopper 11 is driven.
2 opens and the original is sent out. The sent out document is conveyed by the belt 107 over the top surface of the document placement glass 16, and is stopped after a certain period of time (timer) after the trailing edge passes the fourth sensor SEN4.
Next, the belt 107 is driven in the reverse direction to bring the trailing edge of the document into contact with the stopper 113 (see FIG. 1) and stops, thereby completing the document feeding operation. When the original is stopped on the original placing glass 16,
A signal is sent from the DF 100 to the copying machine 50, and a copying operation is started. Scanning optical system 1 associated with copying operation
When the scanning movement of 0 is completed, the DF is removed from the copying machine 50.
100, the belt 107 is driven again to transport the original on the original placing glass 16 in the ejection direction. Note that, if the copying machine 50 is in the multi-copy mode, the document ejecting operation does not start until the scanning movement related to the final copy is completed. FIG. 2 shows an embodiment for detecting the document size. The inserted document is fed onto the platen 39 by the pair of pinch rollers 106 and 111, and the length of the document at this time is determined by the pulse signal generated by the pulse disk 114 and sensor SEN3. is input to the second CPU 302 and measured. That is, as shown in FIG. 3, which will be described later, the output of the sensor SEN3 is logically summed with the sensor SEN1 that detects the passing document and the pinch roller drive output, and is input to the second CPU 302, so that the document passes through the sensor SEN1. The document length signal is obtained by counting the number of pulses during the scanning. In addition, sensor SEN4 is used to classify the length of the document in the width direction.For example, in the case of an A4 or B5 size document, it is placed in a position such that SEN4 is ON if it is placed horizontally, and SEN4 is OFF if it is placed vertically. , this makes it impossible to judge using the length signal alone.
Identify sizes such as A4, A5, B5, B6, etc. With the above configuration, the size of the original is determined and the second
The CPU 302 encodes it and sends it to the first CPU 301. 1st CPU 30 that receives the above document size code
1 is a function AMS that uses the copy paper size code stored in the RAM and the original size code to automatically set the optimum copy magnification when the copy paper size and original size are specified, and the original size and copy function. APS function that automatically selects the paper source loaded with copy paper of the optimum size when the magnification is specified.
have. The AMS mode is set by operating the AMS mode key SW18. In this mode DF
When a document is inserted into the 100, the second CPU 302 determines the size of the document, codes it, and sends it to the first CPU.
301. The first CPU 301 is DF10
The optimum copying magnification is calculated from the original size signal sent from 0 and the copy paper size code set in the paper feed section selected by the operator, and if the copying magnification is within the specifications of the copying machine 50. While setting the magnification, if it is outside the specifications, the operator is informed by appropriate means that there is no optimum copying magnification and is prompted to manually set the copying magnification.
Table 2 shows the relationship between the original size, the copy paper size, and the copy magnification calculated and set based on them in this AMS mode. For example, the copy paper size is "A5 landscape" and the original size is "A4 landscape".
If so, the optimum copying magnification is calculated as "0.707x" and this magnification is set. Furthermore, if the copy paper size is "B6" and the original size is "A3 portrait", there is no optimal magnification, so the operator is prompted to manually set the copy magnification.

【table】

[Table] On the other hand, the APS mode is set by operating the DPS mode key SW ₁₉ . In this mode
When a document is inserted into DF100, the second CPU302
determines the document size and encodes it.
Send to 1CPU. The first CPU 301 calculates the optimal copy paper size from the original size signal sent from the DF 100 and the copy magnification signal input by the operator, and selects the paper feed section in which copy paper of that size is set. If the size of copy paper is not set, or if the size is outside the specifications of the copying machine 50, the operator is notified by appropriate means that there is no copy paper of the optimum size, and a cassette of the optimum size is set. , or prompts manual selection of paper feed section or manual setting of copy magnification. Table 3 shows the relationship between the document size, copy magnification, and copy paper size calculated and selected based on them in this APS mode. For example, if the original size is "B5 horizontal",
If the copy magnification is "0.789x", the optimum copy paper size is calculated as "A5", and the paper feed section in which "A5" size copy paper is set is selected. Also,
Original size is "A3 vertical", copy magnification is "1.420x"
If so, there is no optimal copy size, so the operator is prompted to manually select the paper feed section.

[Table] Copying machine 50 and DF1 having the above configuration
00, as shown in FIG. 3, the first CPU 301 and the second CPU 302 respectively operate in relation to each other.
The operation is controlled by. The first CPU 301 operates on a numeric keypad 303, a print key SW ₁₆ , a mode switching key SW ₁₇ , an AMS mode key SW ₁₈ , an APS mode key SW ₁₉ , and the other keys disposed on an operation panel (not shown) of the copying machine 50.
It is connected via a decoder 306 to a key matrix 300 including SW ₁ to _{SW 15} and the like, a display device 304 that displays the number of copies according to the operation of the numeric keypad 303, a light emitting diode 305 for various displays, and the like. In addition, in order to control the operation of the copying machine, the first CPU 301 outputs a main motor, a developing motor, a clutch lens moving motor,
It is connected to a drive circuit (not shown) such as an optical system drive motor and a charger, as well as a cassette empty display E1 during automatic paper selection and an optimum magnification no display E2 during automatic magnification selection, and further,
A first CPU 301 that controls the operation of the DF 100 and transmits signals related to the operation via the interrupt signal output PCO, the data input terminals Sin and Sout, and the data sample and output clock SCK.
2CPU 302 is connected. The second CPU 302 has a DF10 at its input port.
The opening/closing detection switch SPW of No. 0 and the first to fourth document sensors SEN1 to SEN4 are connected, and the output port is connected to a drive circuit (not shown) for a motor that drives pinch rollers 106, 111, etc., and a pair of pinch rollers 106, 111, etc. 111 is connected to a drive circuit (not shown) for a solenoid to be crimped. Note that terminals B1 and B2 in the figure are connected to the main motor (not shown) of the copying machine 50 and the DF100, respectively.
A motor (not shown) that drives the belt 107 inside
A motor pulse signal is generated in synchronization with the rotation of the motor, and this synchronizes the mechanical drive with the control by the CPU. As described above, the first and second CPUs 301 and 302 associated with the copying machine 50 and the DF 100 execute the processes shown in the flowcharts of FIGS. 4, 5, 6, and 7 while exchanging signals with each other. FIG. 4 is a flowchart that generally shows the processing executed by the first CPU 301, and the steps are a double-sided flag F ₀ indicating that the copying machine 50 is in the double-sided copy mode, and a double-sided copy mode in the double-sided copy mode. Initialization is performed such as resetting the surface flag F ₁ indicating the start of the copying operation and the copying start flag F ₂ indicating the start of the copying operation. In this step, a timer (main timer) for defining the length of one routine is set. This timer may be an internal timer of the first CPU 301 or an external timer. This step processes input signals from the numeric keypad and external switches, outputs them to the motor and solenoid display, and stores the copy paper size set in each paper feed section 1, 2, and 3 in the internal RAM. conduct. The step is a process for switching the mode of the copying machine 50 to double-sided copying mode or normal copying mode, and when the mode switching key SW ₁₇ is operated, the state of the copying machine 50 is determined, If it is a copy mode, it is switched to a normal copy mode, and if it is a normal copy mode, it is switched to a double-sided copy mode. Note that during the copying operation, operation of the mode switching key SW ₁₇ is not accepted. The details of this step will be explained later using FIG. 5. The step is to set a copy start flag to "1" to start the copying machine operation according to each copy mode. In AMS mode, calculate and set the optimum copy magnification, APS
In the mode, calculation and setting of the optimum copy paper size is also executed in this step. In the step, the copy start flag _F2 is judged, and if it is "1", the process advances to the step, and if it is "0".
If so, proceed to step. In the step, copy processing is executed according to each copy mode. In this step, data is transmitted to and received from the DF 100. The transmission and reception processing of the DF 100 is processed by an interrupt from the first CPU 301. In the step, it is determined whether the timer time set in the step has expired or not, and if it has, the process returns to the step, and if it has not finished, the step is looped and the length of one routine is adjusted. Next, the mode switching subroutine of the step will be explained with reference to FIG. Step 401
Then, it is determined whether the copying machine 50 or DF 100 is in operation, and if it is in operation, the process returns without performing the following processing, and if it is not in operation, it proceeds to step. That is, if the copying operation is in progress, the operation of the mode switching key SW17 is not accepted. Steps 402 to 405 are the process of switching from normal copy mode to duplex copy mode.
At step 402, it is determined that the mode switching key SW17 has been operated, and at step 403, the double-sided copy flag _F0
is determined to be “0”, step 404
In step 405, the flag F ₀ indicating the double-sided copy mode is set to "1", and in step 405, the flag F ₁ indicating the front copy mode in the double-sided copy mode is set.
Set to “1”. That is, when the operation of the mode switching key SW17 is detected in the normal copy mode, the process is switched to the double-sided copy mode. On the other hand, steps 401 to 407 are processes for switching from double-sided copy mode to normal copy mode, and in step 402 it is determined that the mode switch key SW17 has been operated, and in step 403, the double-sided flag F ₀ is set.
is “1”, and the surface flag F ₁ is “1” at step 406.
If it is determined that this is the case, the double-sided flag F ₀ is set to "0" in step 407. That is, when an operation of the mode switching key SW17 is detected in the double-sided copy mode and not in the back-side copy mode, the process switches to the normal copy mode. Therefore, when the double-sided copy mode is in the back-side copy mode, that is, when the copy paper on which the front side has been copied is stored in the re-feed tray 64, the mode is not switched, and the copy paper is not placed in the intermediate tray 64. Prevent it from being left unattended. FIG. 6 is a flowchart showing details of the step copy start subroutine. step
At step 501, it is determined whether or not the mode is DF start mode in which an original is inserted into the DF 100. If it is the DF start mode, the process proceeds to step 502, where the double-sided flag _F0 is determined, and it is set to "1", that is, whether it is double-sided copy mode or not. If this is the case, proceed to step 503 and determine the front surface flag _F1 .
Proceed to 504 to determine whether it is in AMS mode,
If it is the AMS mode, the process proceeds to step 505, where the optimum copy magnification is calculated from the size of the copy paper and the original size signal sent from the second CPU 302 of the DF 100. If NO in step 502, that is, normal copy mode is determined, proceed directly to step 504.
Proceed to. In addition, if it is determined NO in step 503, that is, the reverse side copy mode is selected, the step is directly executed.
Proceed to 505. Therefore, in the back copy mode of the double-sided copy mode, AMS mode processing is automatically executed. In step 506, it is determined whether the optimum copy magnification calculated in step 505 is within the specifications of the copying machine 50. If it is within the specifications, the optimum copy magnification is set in step 507, and if it is outside the specifications, the step
Proceeding to step 510, the operator is informed by appropriate display means _F2 that there is no optimum copying magnification. In step 508, the copy start signal sent from the DF100 is judged, and if it is "1", the step is started.
Proceeding to step 509, the copy start flag _F2 is set to "1" and the process returns. If NO in step 504, the process proceeds to step 511 to determine whether or not the mode is APS mode. If the mode is APS mode, the process proceeds to step 512 where the copy magnification set by the spelator and the second CPU of DF100 are determined.
The optimal copy paper size is calculated from the original size signal transmitted from step 302, and the process proceeds to step 513. In step 513, it is determined whether or not the calculated optimum copy paper size is stored in the RAM. If it is, the process proceeds to step 514 and selects the paper source in which copy paper of that size is set. Proceed to step 508. Also, step 513
If it is determined that the optimum copy paper size is not stored in the RAM, the process proceeds to step 515 and the appropriate display means _E1 notifies the operator that copy paper of the optimum copy paper size has not been set. On the other hand, if it is determined in step 501 that the mode is not DF start mode, that is, manual start mode, the process proceeds to step 516 to determine whether the print key SW16 has been operated, and if there is an operation, the process proceeds to step 517 to set the copy start flag F. ₂ to “1”
and return. FIG. 7 is a flowchart showing details of the step copy processing subroutine. Step 701
Then, the double-sided flag F ₀ is determined, and if it is "1", the process proceeds to step 702 and the front surface flag F ₁ is determined, and if it is "1", the process proceeds to step 703 to execute the front side copying process. If the front side flag _F1 is "0" in step 702, the process advances to step 704, where the back side copying process is executed. Furthermore, the steps
If double-sided flag F ₀ is “0” in 701, step
The process advances to step 705 and normal copy processing is executed. In step 706, it is determined whether the copying process executed in steps 703 to 705 is the final copy. If not, the process returns to step 701 to repeat the copying operation, and if it is the final copy, the process proceeds to step 707. Determine whether or not the mode is the DF start mode. If the mode is the DF start mode, set the document discharge signal to "1" in step 708.
Proceed to step 709, and if you are in manual start mode, proceed directly to step 709. Note that the document discharge signal is a signal sent to the second CPU 302 of the DF 100, and upon receiving this signal, the DF 100 discharges the document onto the discharge tray 109. Steps 709 to 713 are flag processing after the copying process. In step 709, the double-sided flag F ₀ is determined. If it is "1", the process proceeds to step 710 and the front flag F ₁ is determined; step 711
to set the surface flag F ₁ to “0”, and also set the surface flag F ₁ to “0”.
is “0”, step 712 sets the surface flag F ₁
Set it to “1” and proceed to step 713. step
If the double-sided flag F ₀ is "0" in step 709, the process directly advances to step 713. At step 713, the copy start flag _F2 is set to "0" and the process returns. As a result of the above-described processing, in back side copying in double-sided copying, the original size detected by the DF 100 to be back side copied fits perfectly on the copy paper on which front side copying has been performed. The optimum copying magnification is automatically selected and the copying operation is performed. In the above example, the original size is DF
100 has been shown as an example in which the document size is determined while the document is being conveyed, it can be easily modified to provide a reflective sensor on the copying machine side and perform the same size determination as described above, and other document size determination means may also be used. Many proposals have been made, and any of them may be adopted as appropriate. Also,
The copying machine 50 is only one example having a configuration capable of double-sided copying, and if it is a double-sided copying mechanism that performs front-side copying of a first original and then back-side copying of a second original, it can perform front-side copying. Perform a certain number of sheets in a row,
A type that performs continuous copying on the back side,
Moreover, regardless of the type of copying of the front side and the back side of each sheet, they can be employed. moreover,
In the above embodiment, the copy magnification is automatically set according to the size of the second document, but when the size of the second document is different from the size of the first document, the copy magnification is automatically set according to the size of the second document. It may also prompt the user to change the copy magnification. Effects As is clear from the above description, the double-sided copying machine according to the present invention forms a front side copy image of the first original on the front side of copy paper, and a back side copy image of the second original on the back side. In a double-sided copying machine that forms
means for detecting the size of the original; means for feeding copy paper of a plurality of sizes; means for setting a predetermined copy magnification; and means for determining the optimum copy paper from the predetermined copy magnification and the size of the first original. means for calculating the copy paper size; means for calculating the optimum copy magnification from the copy paper size and the size of the second document; Since the double-sided copying machine is characterized in that it is equipped with a copying control means that executes a copying operation at a predetermined copying magnification, and executes a copying operation at the above-mentioned optimum copying magnification when copying the back side, the first original; Even if the size of the second original is different, the optimal copy paper size is automatically set when copying the front side, and the copy magnification is automatically set to the optimal copy magnification when copying the back side, so that mistakes can be made when copying. It never happens.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration of a copying machine main body and a document transport device DF of a double-sided copying machine according to the present invention;
Fig. 2 is a diagram showing the document size detection means provided in the DF, Fig. 3 is a circuit diagram showing the microcomputer that controls the copying machine and the DF, and its input/output relationship;
Fig. 4 is a flowchart that generally shows the control executed by the microcomputer for controlling the copying machine, Fig. 5 is a flowchart showing details of the mode switching subroutine, and Fig. 6 is a flowchart showing details of the copying start subroutine. FIG. 7 is a flowchart showing details of the copy processing subroutine. 1... Upper paper feed section, 2... Middle paper feed section, 3... Lower paper feed section,
30... Photosensitive drum, 50... Copying machine main body, 61...
Reversing path, 64...Intermediate tray, 65...Refeeding roller, 100...Document transport device, 114...Pulse disk, SEN1-SEN4...Document sensor, SW1-SW
4, SW6 to SW9, SW11 to SW14...Switches for copy paper size detection.

Claims (1)

[Claims] 1. In a double-sided copying machine that forms a front side copy image of a first original on the front side of copy paper and forms a back side copy image of a second original on the back side, the size of the original is detected. means for feeding copy paper of a plurality of sizes; means for setting a predetermined copy magnification; and calculating an optimal copy paper size of the copy paper from the predetermined copy magnification and the size of the first original. means for calculating an optimum copying magnification from the size of the copying paper and the size of the second document; and means for calculating an optimum copying magnification from the size of the copying paper and the size of the second document; A double-sided copying machine characterized by comprising a copying control means for executing a copying operation and for executing the copying operation at the above-mentioned optimum copying magnification when copying the back side.