JPS6073641A - Image forming device - Google Patents

Abstract

PURPOSE:To shorten an image formation time and to reduce an image forming device in size on the whole by detecting a form and controlling the image formation time of the next form on the basis of the detection output. CONSTITUTION:The form P conveyed by an aligning roller 11 is sent to an image transfer part 12. The fed form P is charged electrostatically by a charger 13 and a toner image on a photosensitive drum 2 is transferred. A switch 22 for detecting the paper feed state is provided near the aligning roller 11, and a switch 23 for detecting the paper discharge state is further provided near a paper discharge roller 19. The detection time of the form P is measured with the output of the switch 22 and the movement of a platen 3 is specified according to the measured time to control the image formation.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Branch of the Invention The present invention relates to an image forming apparatus such as an electronic copying machine.

[Technical Foreword of the Invention] Conventionally, for example, electronic copying machines can be roughly divided into two types: a document table moving type and a document table fixed type. this house,
In the scanner type, the document table supporting the original is moved back and forth parallel to an optical system consisting of a fixed exposure lamp, etc., to optically scan the document on the document table.
The optical image obtained by this scanning is guided to the photoreceptor drum and exposed to light to form an electrostatic latent image on the photoreceptor drum, and this electrostatic latent image is made visible by applying toner with a developing device. This visible image is transferred onto a sheet of paper fed from a paper feeding cassette serving as a paper feeding means.

Recently, in such copying machines, in order to shorten the copying time when continuously copying multiple sheets of paper, the length of the paper being supplied is detected and the length of the detected paper is Some devices control the scanning time of the document (that is, the movement range of the document table) depending on the situation. Conventionally, an apparatus illustrated in FIG. 1 has been used as such a copying machine. In the figure, reference numeral 81 denotes a document table that moves back and forth in the direction of the arrow in the drawing; 82 denotes an exposure lamp that irradiates light onto the document on the document table 81; 83 denotes a light transmission member that guides reflected light from the document to a photosensitive drum 84; and 85 86 is a paper feed cassette that stores the paper P; 87 is the paper P in the paper feed cassette 86;
8B is an aligning roller that conveys the paper P sent out by the paper feed roller 87 to the transfer section, and 89 detects the length of the paper P sent out by the paper feed roller 87. A detector 90 is a detector for detecting whether or not the paper P has reached the aligning roller 88. That is, in this device, the detection distance is longer than the distance 1 from the point A where an image is formed by scanning (hereinafter referred to as the exposure point) to the point B where the image is transferred to the paper P (hereinafter referred to as the transfer point). Conveyance path length 2 from container 89 to transfer point B
is longer, and the image formed at the exposure point A when the trailing edge of the paper P passes the detector 89 is L2-LH.
>0) before the trailing edge of the paper P.

In other words, when the conveyance speed is set to
The document scanning is configured such that scanning of the document is completed after a time period of 12-11/V has passed since the trailing edge has passed.

[Problems in the background art] However, in such conventional devices, two
Therefore, the conveyance path becomes long, which hinders miniaturization of the device.

Furthermore, in addition to the detector 90 that detects whether or not the paper P has reached the aligning row 588, a detector 89 for detecting the length of the paper P is required, leading to a problem of increased costs. . Note that some devices are equipped with a mechanism that can detect the length of paper using a paper feed cassette, but this also has the drawbacks of high cost and a complicated mechanism.

[Purpose of the Invention] The present invention has been made in view of the above-mentioned circumstances, and its purpose is to eliminate the need to lengthen the paper conveyance path, downsize the entire device, and to be able to handle multiple sheets of paper. An object of the present invention is to provide an image forming apparatus that can eliminate wasted document scanning time and significantly shorten image forming time when continuously forming images.

[Summary of the Invention] The image forming apparatus of the present invention is provided with a detection means for detecting the paper fed by the paper feeding means, and measures the detection time of the first sheet of paper supplied by the output of the detection means, The present invention is characterized in that the range of relative movement of the scanning means is regulated from the time of image formation on the second and subsequent sheets of paper in accordance with the measurement time.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows an electronic copying machine of an original table moving type as an example of an image forming apparatus according to the present invention.

That is, reference numeral 1 designates a housing of the copying machine, and a photosensitive drum 25- which rotates in the direction of arrow a in the figure is provided approximately at the center of the housing. Further, in the upper part of the housing 1, a document table 3 for supporting a document is provided so as to be able to reciprocate in the direction indicated by the arrow in the figure. By moving the document table 3 in synchronization with the rotation of the photoreceptor drum 2, the exposure lamp 4
The light irradiated from the original is reflected by the original on the original table 3, and the reflected light forms an image on the photoreceptor drum 2 by the convergent light transmitter 5, and is reflected on the photoreceptor drum 2 as an inverted image of the original.

At this time, by charging the photoreceptor drum 2 with the charging device 6, an inverted image of the document is formed on the photoreceptor drum 2 as an electrostatic latent image, and this electrostatic latent image is transferred to the developing unit 7. The image is visualized by adhering toner.

On the other hand, a paper feed mechanism 8 is provided below the developing device 7 for supplying the paper P to below the photoreceptor drum 2 (image transfer section 12). This paper feeding mechanism 8 is detachably attached to the side of the housing 1 and can feed a plurality of sheets of paper P.

A paper feed cassette 9 containing ... and a paper feed roller 10 that feeds the paper P one by one from the paper feed cassette 9 are provided. A pair of aligning rollers 11 for positioning and conveying the paper are provided. The paper feed roller 10 is, for example, a half-moon-shaped roller having a contact portion 10a that contacts the paper P in the paper feed cassette 9 and a non-contact portion 10b that does not make contact, and a spring (not shown) for rotating the paper feed roller. By turning on the solenoid of the clutch, the driving force of the motor is transmitted, and the motor is rotated by a predetermined angle (for example, 210 degrees) and then stopped.

Thus, the paper P conveyed by the aligning roller 11 is sent to the image transfer section 12. The paper P sent to the image transfer section 12 comes into close contact with the surface of the photosensitive drum 2 at the transfer charger 13, so that the charger 1
The toner image on the photoreceptor drum 2 is transferred by the charging of the paper P by the photoreceptor drum 3. After the transfer, residual toner on the surface of the photosensitive drum 2 is removed by a cleaner 14.
The configuration is such that the residual image is roughly erased by the static eliminating lamp 15 and the image returns to the initial state. On the other hand, paper P after transfer
After being electrostatically peeled off from the photoreceptor drum 2 by the action of the peeling charger 16, it is guided along the conveyance path 17 and passes through a pair of peelers 18 as a fixing device. The transferred image is heated and fixed. Then, the paper P after fixing is
The paper is configured to be ejected to a tray 20 outside the housing 1 by a pair of ejection rollers 19 . Note that the photosensitive drum 2, document table 3, developing device 7, paper feed roller 101, aligning roller 11, heat roller 18, and paper ejection roller 19
is adapted to operate using a motor 21 as a driving source.

Further, a switch (hereinafter referred to as a paper feed switch) 22 as a detector for detecting the paper feeding state is provided near (in front of) the aligning roller 11, and a paper ejection roller 19
A switch (hereinafter referred to as a paper ejection switch) 23 as a detector for detecting the paper ejection state is provided near (on the front side). Each of these switches is provided primarily to detect paper jams (also referred to as jams).

The housing 1 is divided into two parts, an upper housing 1a and a lower housing 1b, with the transport path 17 as a border, as shown by the two-dot chain line, and both cylinders 1a and 1b are provided at one end. It is pivoted at a fulcrum (not shown), and the upper housing 1a can be opened at a predetermined angle in the direction of arrow C in the figure. Here, the upper housing 1a includes a photosensitive drum 2 and a document table 3.
, an exposure lamp 4, a focusing light transmitter 5, a charger 6, a developer 7, a paper feed row 510, an upper roller of an aligning row 511, a cleaner 14, a static elimination lamp 15, etc., are provided in the lower housing 1b. The paper feed cassette 9, the lower roller of the aligning roller 11, the charger 13.16, the transport path 17, the heat roller 18, the paper ejection roller 19, and the tray 20
, motor 21, etc. are provided respectively.

FIG. 3 shows the document table drive mechanism. That is,
The driving force of the gear 31 directly connected to the motor 21 is transmitted to the electromagnetic clutch 36 via gears 32, 33, 34, 35 for transmitting the driving force. This electromagnetic clutch 36 can be used in three cases according to the control signal: when it does not transmit the driving force to the pulley 37, when it transmits it in the forward direction, and when it transmits it in the reverse direction.
It is designed to perform two switchings. And pulley 3
The driving force transmitted to 7 is transmitted to the document table 3 by a wire 38 whose both ends are fixed to the document table 3, and moves the document table 3. In addition, pulley 3
Reference numeral 9 is for making the path of the wire 38 substantially parallel to the document table 3 so that it does not come into contact with other parts.

4 to 7 show the document table position detection mechanism. That is, as shown in FIG. 4, -
Three magnets 41, 42. placed at predetermined intervals on a straight line.
43 is attached, and two magnets 44 and 45 are attached to both ends thereof with a phase shift. Also,
As shown in FIG. 5, the housing 1 includes the magnets 41 to
Reed switches 46 and 47 for detecting 45 are attached. This reed switch 46 has magnets 41 to 43
Similarly to the magnets, the reed switch 47 is arranged out of phase so as to detect that the reed switch 44 and the magnet 44 and 45 are placed above it.

In FIGS. 5 to 7, the position of the magnet detected by the reed switch 46 is set to P41. P42°10-p43, and the position of the magnet detected by the reed switch 47 is p44. It shall be P45. FIG. 5 is a diagram when the document table 3 is located at the home position. The home position is the position where the document table 3 is stopped at the end of the copying operation, and as shown in FIG. When the document platen is at a movement stop position (hereinafter referred to as the document platen limit position), which can be detected by This is detected when the reed switch 46 is turned on by the magnet 43. Further, FIG. 6 is a diagram when the document table 3 is located at the backward movement stop position (hereinafter referred to as the document table start position).

The original platen start position is detected by simultaneously turning on reed switches 46 and 47 by magnets 41 and 44. Furthermore, the reed switch 46 is turned on for the first time after the document table 3 starts moving forward from the document table start position and is no longer at the document table start position, that is, the reed switch 46 is turned on by the magnet 42.
The aligning roller start position is detected by turning on.

As mentioned above, since the photosensitive drum 2 and document table 3 are driven in synchronization, the aligning roller 11 is rotated so that the leading edge of the image on the photosensitive drum 2 and the leading edge of the paper P are aligned. The timing to start is when photoconductor drum 2
It can be removed from the document table 3 without removing it from the original plate. The position at which the aligning roller 11 starts rotating is the aligning roller start position.

FIG. 8 schematically shows the overall control circuit.

That is, 51 is a microprocessor as a main control section, which controls the entire copying machine.

Signals from the paper feed switch 22, paper ejection switch 23, reed switch 46, 47 (hereinafter referred to as document table switch), etc. are input to the microprocessor 51 via an input interface circuit 52. . Then, the microprocessor 51 judges and processes the input signal, and sends it to the display 54 via the display interface circuit 53 according to a pre-stored program.
It also outputs various control signals to each control device via the output interface circuit 55. Each control device includes the exposure lamp 4, the motor 21, an electromagnetic clutch (hereinafter referred to as a document platen clutch) 36, and a paper feed roller 10.
a paper feed roller solenoid 56 for transmitting driving force to the
A high voltage power supply 57 for supplying power to the charging charger 6, an aligning roller solenoid 58 for transmitting driving force to the aligning roller 11, a power supply for supplying power to the transfer charger 13 and the peeling charger 16. High voltage electric ll59,
There is a blade solenoid 60 for pressing the blade of the cleaner 14 against the photoreceptor drum 2, and each is operated by a control signal. The display 54 is a number and symbol display that displays the number of copies and the like.

The microprocessor 51 is configured as shown in FIG. 9, for example. That is, the microprocessor 51 is a one-chip microprocessor having an architecture 13- as shown in FIG.

In the figure, 61 is an arithmetic unit (ALU) having an arithmetic judgment function;
62 is a read-only memory (ROM) for storing processing programs, 63 is a random access memory (RAM) for storing data, and 64 is an input/output port and input/output for transmitting and receiving signals with external devices. Control unit (IOC)
, 65 is a program counter (PC), 66 is a flag (FLAG), 67 is an accumulator (ACC), 68
69 is a stack register (STACK), and 69 is an interrupt control unit (INC).

Here, to briefly explain the operation of the microprocessor 51, the address of the processing program stored in the ROM 62 is designated by the PCO2, and the ROM 62
The instruction read from is decoded and executed. FLAG66 stores the carry/borrow status of the result of the calculation. The calculation result is A
RAM via CC67 or ACC67 by instruction
63.

The STACK 68 specifies the depth of the subroutine, stores the return address of the main routine, and is also used to save the contents of the PC 65 at the time of an interrupt. INT
When an internal interrupt or an interrupt from an external terminal (INT) is requested, the C69 terminates the instruction currently being executed and enters interrupt processing. When entering interrupt processing, the contents of the PC 65 are saved in the STACK 68, a jump is made to a specific address for interrupt processing, the interrupt processing program is executed, and then the main program is returned.

FIG. 10 is a general flowchart of a general copying machine. The initial check is a routine for checking whether or not the copying state is possible. For example, it is checked whether the heat roller 18 is at a temperature that allows heat fixing. After this initial check is completed, if copying is possible, the process moves to a copying standby routine. Here, the routine sets the number of copies and waits until the copying switch is turned on and the copying operation is started. When the copying operation is started, the above-described copying process including charging, exposure, transfer, neutralization, fixing, etc. is sequentially executed to make a copy, and the copying operation is repeated until the set number of copies is completed. Also, during copying operations, checks are made for abnormalities such as paper jams.

In addition, in controlling the copying machine of the present invention, the microprocessor 5
1 internal interrupt is used. This interrupt processing is set to be repeated at a constant period. To explain this using FIG. 11, when the power is turned on, the RO
The main program among the programs stored in M62 is being executed. However, for example, by setting INTC69 so that an internal interrupt is generated every 12a+sec from the start of the copying operation, the main program can be temporarily interrupted and the interrupt program executed when 12m5ec has elapsed from the start of the copying operation. , and the main program is executed again after the interrupt program ends. Furthermore, the flow of the program is such that the interrupt program is executed after 12111 seconds have elapsed, that is, 24111 seconds have elapsed from the start of the copying operation.

Next, the copying operation will be explained in detail using the flowcharts shown in FIGS. 12 and 13 and the timing chart shown in FIG. 14. Note that the flowchart in FIG. 14 initially shows a case where the document table 3 is at the home position. First, the copying operation for the first sheet will be explained. In step A1, the flag FMUL is cleared. This flag FMUL is used to determine the first and second sheets and subsequent sheets when multiple sheets are continuously copied.The first sheet is FMUL=O.
It is now judged by Next, in step A2, the blade solenoid 60 is turned on to press the blade against the photosensitive drum 2. Next, in step A3, the motor 21
is rotated, the static elimination lamp 15 is turned on in step A4, the transfer charger 13 is turned on in step A5, and the stripping charger 16 is turned on in step 80. Next, in steps A7 and A8, it is determined whether the document table 3 is at the document table start position. As mentioned above, the original platen start position is determined by turning on both the original platen switches 46 and 47, so step A7゜A
If YES in both 8, the original platen is at the starting position 17-. If the original platen is at the start position, the original platen 3
Since there is no need to move backward the document table 3 in step 80 is not performed. On the other hand, if the original platen 3 is not at the starting position, a control signal is sent to the original platen clutch 36 in step 80 to move the original platen 3 backward. This is tl on the timing chart in FIG. 14, and steps AIO, A1
In step 1, it is again determined whether the document table is at the start position.

Here, backward movement is continued until the document table 3 reaches its starting position. When the document table moves backward from the home position, the document table switch 46 is turned on at the aligning roller start position at t2. Then, at time t3, step A10. When the original platen start position is determined by A11, the original platen clutch 3
6 to stop the backward movement of the document table 3, and in step A12, the paper feed roller solenoid 56 is activated.
is turned on, and the paper feed roller 10 starts feeding the paper. The fed paper P reaches the paper feed switch 22 at t6. Next, in step 18-A13, the exposure lamp 4 is turned on. The document table 3 has now reached its starting position, that is, the backward limit, so at t4, which is slightly longer than t3, a control signal is sent to the document table clutch 36 in step A14 to move the document table 3 forward. let This is because it takes time to switch the document platen clutch. next,
In step A15, the one-charging charger 6 is turned on to charge the surface of the photosensitive drum 2, and the process moves to the exposure step. Next, in steps A16 and A17, the document table switches 46 and 47 are turned off at timing t5, and it is determined when the document table switches 46 and 47 are no longer in the document table star position. In reality, the timings at which the document table switches 46 and 47 are turned off do not coincide with each other like t5, but are slightly shifted. In this case, step A16゜A1
In step 7, even if either one is turned off first, the aligning roller start position is reliably detected by the original platen switch 46 without assuming that the original platen is no longer at the original platen start position. At time t5 when the document platen is no longer at the start position, it is determined in step A18 whether or not it is the second or subsequent copy of continuous copying, and if it is the first copy, the process moves to step A20, and if it is the second or subsequent copy, the process moves to step A19. . Here, since the operation is still for the first sheet, the flag FMUL is rOJ. In step A20, timer B, which will be described later, is cleared. Next, in step A21, a flag FATM for starting timer A, which will be described later, is set to "1". Next, in step A22, it is determined that the document table switch 46 is turned on at timing t7, that is, at the aligning roller start position, and in step A23, the aligning roller solenoid 58 is turned on, and the aligning roller 11 is rotated. Next, step A24
, flag FB for starting timer B
Set TM to "1".

Timer B will now be explained using steps B10-B13 of the interrupt processing flowchart in FIG.

When FBTM=1 is determined in step B10, "1" is added to timer B in step B12 while it is determined in step B11 that the paper feed switch 22 is on. Here, timer B is the RA
Several addresses in M63 are considered as one, and since this has been cleared in step A20, the flag FBTM is set to "1", and when the first interrupt occurs, it becomes "1", and the next interrupt is set to "1". Then it becomes "2".

Since the period at which interrupts occur is a fixed period of time, timer B
The value corresponds to the time since the flag FBTM was set to "1". Then, when the paper feed switch 22 is turned off, that is, at timing t10, step B
11 proceeds to step [313, where the flag FBTM is
is cleared, and therefore "1" is no longer added to timer B. That is, the value of timer B corresponds to time T1.

When the flag FBTM is set to "1" in step A24, the timing t8 when the aligning roller is no longer at the start position is detected in step A25, and the document table home position at timing t9, which is performed using the same document table switch 46, is detected. Ensure step A26. Next, in step A27, a time T4 is set in a timer C to be described later, and in step A28, a flag FCTM for starting timer C is set to "1".

Here, timer C will be explained in steps 81 to B4 of the interrupt processing flowchart in FIG. 13.

Interrupt processing is performed at regular intervals as described above. Let this period be t. Using some addresses in the RAM 63, set the integer part of T4/l + 1, subtract "1" for each interrupt, and set the address to "O".
It almost corresponds to the time T4 after the start of subtraction. Note that the reason for the delay is that there is a slight shift in the timing at which the interrupt occurs. This timer C
It is said that That is, when it is determined in step B1 that FCTM=1, RA is determined in step B2.
"1" is subtracted from timer C set in M63. It is determined in step B3 that the value of this timer C has become "0", and the flag FCTM is set to rO in step B4.
Almost T4 has elapsed since the flag FCTM was cleared to J and the flag FCTM was set.

When the flag FCTM is set to "1" in step A22, then when it is detected in step A29 that time T4 has elapsed, that is, that the flag FCTM has been cleared to rOJ, step A30. Go to A31, judgment of document table backward timing. In other words, the document table 3 is always moved forward for about 14 hours after the document table home position is detected. Step A3
0 is a judgment to proceed to step A32 if the flag FATM for starting timer A set in step A21 has been cleared, but the first one is the process of clearing the flag FATM (performed in step B9). Since the document table switch 47 is always turned on when the document table limit position is reached, t11 is step A.
The process does not proceed to step A32 until the determination is made in step A31. When proceeding to step A32, the document platen clutch 36
A control signal is sent to stop the forward movement of the document table 3, and then the charging device 6 is turned off in step A33, and at t12, which is slightly longer than timing t11,
In step A34, a control signal is sent to the document table clutch 36 to move the document table 3 backward. This is because it takes time to switch the document table clutch 36. Here, the time from the time when the original platen is no longer at the original platen start position until the original platen limit position is detected is defined as T3.

Next, in step A35, the exposure lamp 4 is turned off.

Note that timing t13 is when the aligning roller solenoid 58 is turned off in order to stop the aligning roller 11, and this is done at a certain time after the paper feed switch 22 is turned off. Then, at timing t14, the document table 3 reaches its home position. If this is determined in step A36, step A37.
The end of copying A3B is determined. In this case, in step A37 it is determined whether the set number of copies have been completed, and in step A38 it is determined whether the copy stop switch has been turned on. If either is judged here,
The process goes to the copy end routine of steps A40 to A46, and when it is detected that the document platen clutch 36 is turned off and the sheet ejection switch 23 is turned off, the transfer charger 13
, the stripping charger 16, and the static elimination lamp 15 are turned off, and the motor 21 is turned off, and the blade tumbles.
To explain the copying operation for the th sheet, in this case, the process returns from step A39 to step A10, and step A10. All
From then on, the copying operation is performed in the same way as for the first copy. Below, only the differences from the first image will be explained. Step A16. At the time t1'8 when the document platen is no longer at the start position due to A17, the process moves from step A18 to step A19, where 1
The value of timer B counted for the first sheet (corresponding to TI), plus the maximum time count from the start position of the document platen to the point at which the leading edge of the document is exposed, plus a certain margin ( The timer B+α) is moved to the timer A using some addresses in the RAM 63. Here, timer A will be explained in steps 85 to B9 of the interrupt processing flowchart in FIG. 13. In the first copy, the value of timer B has not been determined yet, so FMUL = 0.
If so, the process moves from Step 25-B5 to Step 810. For the second and subsequent sheets, the 7-lag FATM is set to "1" in step A21, and when this is determined in step B6, it begins to be subtracted by "1" in step B7. In this case, since the value corresponding to T1 is subtracted from +α, after time T2, which is longer than T1 by +α, timer A starts rOJ.
When this is determined in step B8, the 7-lag FATM is cleared to rOJ in step B9. This is timing t23. At this point, at least the length of the paper P has been exposed from the leading edge of the document, so there is no need for the document table 3 to move forward, and when FATM=O is determined in step A30, steps A32 to A34 The document table 3 is moved backward. However, as mentioned above, t18+T2 <t
In the case of 22+T4, the fact that this flag FATM is cleared is ignored. This is to prevent the temperature from rising too much due to continuous copying with too short paper P.

Further, if t18+T2 >t18+T3, that is, the document table 26-limit position is faster, the next step is performed in step A31.

In addition, in FIG. 14, t17 is t4, and t19 is t6.
, t20 is t7, t21 is t8, t22 is t9
, t25 is tlo, t26 is t14, t15. t28 corresponds to t2, respectively.

In this way, during the copying operation of the (n+1)th sheet, the document table 3 is moved according to the length of the nth sheet P. By controlling the document table 3 in this manner, the document table 3 is not moved unnecessarily, and the time required to move the document table 3 is accordingly shortened, and the time required for copying can be significantly shortened. In other words, it is possible to eliminate wasted document scanning time and to significantly shorten copying time without creating obstacles to miniaturizing the entire apparatus and without increasing costs. Furthermore, since the length of the paper P is counted in terms of time, the document can be moved to the exposure point by the length of the paper P even if the speed of the drive source decreases or increases due to power supply conditions or the like.

In the embodiments of the present invention, abnormalities in circuit elements such as microprocessors and printed circuit boards in which they are incorporated can be easily detected by the inspection method described below.

FIG. 15 is a hardware block diagram for performing the test. In the figure, the area within the broken line 71 indicates one printed circuit board. That is, the microprocessor 51, input interface circuit 52, display interface circuit 53, and output interface circuit 55
constitutes one printed circuit board. Input signals are input from the input ports 13, 14, 15, 16, and 17 of the microprocessor 51 through the input interface circuit 52, and output signals are output from the output ports 8, 9, 10, 11, and 12 of the microprocessor 51. and is outputted via the output interface circuit 55. Reference numeral 72 denotes a harness for returning the output signal to the input side during inspection, so that the output and input are one-to-one, that is, the output port and input port of the microprocessor 51 are 8, 13.9, 14, 10, and 15. .11 and 16.12 and 17.

FIG. 16 is a flowchart of a program for performing this test. First, in step C1, the device waits until a predetermined time (for example, 0.24 seconds) has elapsed since the power was turned on, and during this time, a signal of a certain pattern is output from the output port 12.

Next, in step C2, the signal output from the output port 12 is transferred to the output interface circuit 55 and the harness 7.
2. Input port 1 via input interface circuit 52
7, it is determined whether the input is correct.

If the input has been correct in the processing up to this point, it is considered that the harness 72 is connected. Furthermore, if the input is not correct, the harness 72 is not connected. That is, it means that no inspection is performed, or that an abnormality already exists in the path from the output port 12 to the input port 17. Therefore, if the input information is not correct, a normal program, for example, a control program for a copying machine, is executed in step C3. If the input is correct, proceed to steps 04-C.
29- Execute the 11 inspection program. First, step C4
In step C5, it is determined whether all the input ports 13-v16 are at low level. If the level is not low, that is, if there is an abnormality such as a short circuit to the high level line between the output interface circuit 55, input interface circuit 52, and input ports 13 to 16, proceed to step C6. and its input port, for example 1
If it is 4, then number is assigned such as No., boat 2, etc., and if that number and steps 04 to C6 are to be the first inspection, for example, the number is written as "12" and stored in the RAM 63. Remember. Next, in steps 07 to C10, in step C7, the output port 8
.about.11 are set at high level and the others at low level, and it is determined in step C8 whether or not the same signal as the signal at the output port is input to the input port, as in steps C4 to C6.

If the signals are not the same, this is also stored as "23" in R30-AM63, similarly to steps 04-C6. This is done for all boats, such as when only output boat 9 is set to high level, when only output boat 10 is set to high level, and so on. When it is determined in step C10 that all the tests have been completed, step C11 indicates that there is an abnormality and the RAM 6
For example, the data stored in 3 is sequentially stored in ``12'' every second.
"," and "23" are displayed on the display 54. If such an inspection is performed, it is possible to easily find out the location of the abnormality, and depending on the output pattern, it is also possible to narrow down to a certain extent which location has the type of abnormality.

In the above embodiment, the case where the present invention is applied to an electronic copying machine with a moving document table type has been described, but the present invention is not limited to this, and can be similarly applied to an electronic copying machine with a fixed document table type. . Further, the present invention can be applied not only to electronic copying machines but also to other image forming apparatuses.

[Effects of the Invention] As detailed above, according to the present invention, there is no need to lengthen the paper conveyance path, the entire device can be downsized and costs can be reduced, and multiple sheets of paper can be processed continuously. When forming an image, it is possible to provide an image forming apparatus that eliminates wasted document scanning time and can significantly shorten the image forming time.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram for explaining a conventional electronic copying machine, Figs. 2 to 16 are for explaining an embodiment of the present invention, and Fig. 2 is a schematic diagram of an electronic copying machine. 3 is a side view showing the document table drive mechanism, FIGS. 4 to 7 are diagrams for explaining the document table position detection mechanism, and FIG. 8 is a schematic diagram of the overall control circuit. 9 is a block diagram of a microprocessor, FIG. 10 is a general flowchart of a general copying machine, FIG. 11 is a flowchart of a program including microprocessor interrupts, and FIG.
Figure 2 is a flowchart of copying operations, Figure 13 is a flowchart of interrupt processing, Figure 14 is a timing chart of copying operations, Figure 15 is a hardware block diagram for abnormality testing, and Figure 16 is a flowchart for abnormality testing. It is a flowchart of the program to be executed. 2... Photosensitive drum, 3... Document table, 4... Exposure lamp, 7... Developing device, 8... Paper feeding mechanism, 9...
Paper feed cassette, P... paper, 10... paper feed roller,
11... Aligning roller, 12... Image transfer section,
13... Transfer charger, 22... Paper feed switch, 2
3... Paper discharge switch, 51... Microprocessor (main control unit). Applicant's agent Patent attorney Takehiko Suzue 33- Figure 1 1 Ku Guimi Tentj) ts- Takashi Yabu Tokukaisho Go-73641 (13) Figure 13 (a) Figure 13 (b)

Claims (2)

[Claims] (1) A scanning means that moves relative to the original and optically scans the original; an image forming means that forms an image corresponding to the optical image obtained by scanning the scanning means; and an image formed by the image forming means. a transfer means for transferring the image to the supplied paper;
A paper feeding means that supplies paper to this transfer means, a detection means that detects the paper fed by this paper feeding means, and a detection time of the first sheet of paper supplied by the output of this detection means. An image forming apparatus comprising: a control means for regulating the range of relative movement of the scanning means from the time of image formation on the second and subsequent sheets of paper according to the measurement time. (2) When the range of relative movement of the scanning means exceeds a predetermined range, the relative movement of the scanning means for optical scanning is interrupted even before the measurement time by the control means has elapsed. An image forming apparatus according to claim 1.