JPS6336503B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an image forming apparatus that detects a jam in a fed recording material.

[Prior Art] For example, in a copying machine, an electrostatic latent image is formed on a photoreceptor, this latent image is developed with toner, and the toner image is transferred to a fed transfer paper.
Jams may occur at the start of feeding and during feeding.

[Problems to be solved by the invention] In particular, large copying machines have long travel paths.
If a jam occurs deep in the travel path, it will be impossible to find the jammed location, and it will be difficult to remove the jammed paper, and in the case of continuous copying, subsequent sheets of paper may remain even after the jam is removed. Therefore, it may take a long time to restart copying.

[Means for Solving the Problems] The present invention aims to eliminate the above drawbacks and has the following configuration.

That is, means for forming an image on a recording material (FIG. 1);
Means for conveying the recording material along a predetermined conveyance path (Fig. 1 28-1, 28-2, 29-1, 29-
2, 30, 30', 32, etc.), a first recording material detection means (FIG. 1 35) provided on the conveyance path to detect the presence or absence of recording material, and a first recording material detection means downstream from the first recording material detection means. a second recording material detection means (FIG. 1, 40), which is provided in When the first jam detection means (Q12 in FIG. 8), which regards the recording material as a jam and stops the operation of the image forming means, and the second recording material detection means do not detect the recording material at the second timing, the recording material a second jam detection means (Q19 in FIG. 8) which detects a jam and stops the operation of the image forming means; , a display means for determining again whether or not the first recording material detection means and the second recording material detection means have detected a recording material, and displaying the jam position based on the output thereof (see FIG. 2). 64-69,7
6).

[Operation] With the above configuration, the position of the jammed recording material can be accurately known.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a copying apparatus to which the present invention can be applied.

The surface of the drum 11 is made of a three-layer photoreceptor using a CdS photoconductor, is rotatably supported on a shaft 12, and starts rotating in the direction of an arrow 13 in response to a copy command.

When the drum 11 rotates to the normal position, the document placed on the document table glass 14 is illuminated by an illumination lamp 16 that is integrated with the first scanning mirror 15, and the reflected light is used for the first scanning. Mirror 15 and second
It is scanned by a scanning mirror 17. First scanning mirror 1
The second scanning mirror 17 of No. 5 moves at a speed ratio of 1:1/2, so that the document is scanned while the optical path length in front of the lens 18 is always kept constant.

The above reflected light image shows the lens 18 and the third mirror 19.
After passing through the fourth mirror 20, the exposure section 21
Then, an image is formed on the drum 11.

After the drum 11 is charged (for example, +) by a primary charger 22, an image irradiated by an illumination lamp 16 is slit-exposed in the exposure section 21.

At the same time, AC or primary charge removal with a polarity opposite to that of the primary charge (for example, -) is performed by a charge remover 23, and then a high-contrast electrostatic latent image is formed on the drum 11 by full-surface exposure using a full-face exposure lamp 24.
The electrostatic latent image on the photosensitive drum 11 is then transferred to a developing device 25.
It is visualized as a toner image.

The transfer paper 27-1 or 27-2 in the cassette 26-1 or 26-2 is transferred to the paper feed roller 28.
-1 or 28-2, is roughly timed by the first register roller 29-1 or 29-2, and is moved by a signal obtained from the switch 39 that detects a specific passing position of the optical system. The two-register roller 30 takes accurate timing and sends the photosensitive drum 11 toward the photosensitive drum 11 .

Next, while the transfer paper 27 passes between the transfer charger 31 and the drum 11, the toner image on the drum 11 is transferred onto the transfer paper.

After the transfer is completed, the transfer paper is guided to the conveyor belt 32 and further to a pair of fixing rollers 33-1, 33-2, where it is fixed by pressure and heat, and then discharged onto the tray 34.

After the transfer, the surface of the drum 11 is cleaned by a cleaning device 35 composed of an elastic blade, and the process proceeds to the next cycle.

In addition, in order to control the above image forming cycle at each point in time, a drum clock pulse DCK is generated by a sensor 11b that optically detects the clock point of a clock board 11a that rotates with the rotation of the drum 11.

36 and 37 are sensor groups for detecting misfeeding and skew feeding of paper fed from each upper cassette 26-1 and lower cassette 26-2, and 35 is for detecting a jam near the transfer section. A sensor 40 is a sensor for detecting a jam near the fixing section and a jam near the ejection section, and each sensor detects the amount of light that changes as the paper passes and outputs a signal. The sensor groups 36 and 37 each have three sensors for detecting skew.

FIG. 2 is a plan view of the operating section of FIG. 1. In the figure, 52 is a numerical key for setting the number of repeated copies;
51 is a clear key for clearing the number of sets and the number of completed copies; 72 and 73 are 7-segment displays for displaying the number of sets and the number of completed copies; the former is displayed by the key 52, and erased by the clear key 51. 54
is the copy button to start copying (start exposure), 5
6 is a stop key to interrupt repeated copying, 5
2 and 53 are cassette keys for selecting the upper and lower cassettes to be fed; 61 and 63 are indicators for displaying the selected cassette (upper and lower); 70 and 7
Reference numeral 1 indicates a display device that constantly displays the size of the cassettes stored in each stage.The display device _U1 is of universal size, which is half the size of _U2 . 64 is a display that displays jam trouble; 76 is a display that displays a paper feeding error or skew; 62 is a cassette paper out display; 65 is a display that lights up a line when there is a jam or paper feed is incorrect or skew;
66 is an indicator that displays paper feeding errors and skewed feeding locations;
Reference numeral 7 is an indicator that displays each jam near the transfer section, 68 is an indicator near the fixing section, and 69 is an indicator near the discharge section.
9 lights up and flashes when there is a problem.

FIG. 3 is a time chart of the operations and operation signals of the various parts shown in FIG. 1. In the figure, when the signal is at a high level, the operation is on, indicating signal 1. _S1 is the main motor signal for rotating the drum 11, _S3 is the first registration roller ON signal, _{S5 is the exposure lamp lighting signal, S6 is} the optical system forward command signal, _S7 is the optical system backward command signal, _CL1 ,
CL ₂ is a clutch that moves the optical system forward and backward using the main motor. CPOSA is a paper detection signal output by the paper feed sensor 36 or 37, CPOSB is a paper detection signal output by the transfer port sensor 35, and CPOSC is a paper detection signal output by the discharge port sensor 40. It is a detection signal.

FIG. 4 is a control block diagram for controlling the operation and display of each part in _FIG .
_S16 is an input signal and an operation output signal with timing as shown in FIG. 3, CPB is a signal caused by turning on the copy button 54, and L is a control unit for outputting a control signal based on each input signal. The case where paper is fed from the upper stage will be explained below. When the copy button is turned on, the control unit L outputs the main motor signal S ₁ to rotate the drum, rotates it a predetermined time, and outputs the paper feed signal S ₂
is output, the constantly rotating paper feed roller 28-1 is lowered, and paper is fed from the desired cassette. Predetermined period (S ₃ )
Since the operation of the first register roller 29-1 is once stopped, the fed paper is stopped, and the lamp is turned on by _S5 . Thereafter, _S6 is output at a predetermined time to turn on forward clutch _CL1 . When the optical system leaves its stop position and the signal OHP becomes level H, the signal drives the first registration roller 29-1 again and the second registration roller 29-1 is driven through the constantly rotating roller 30'.
Feeding toward the registration roller 30 begins. During the feeding, the sensor 36 operates to detect the paper and performs skew detection, etc., which will be described later. When the drum rotates approximately twice, the exposure scan ends, and at a predetermined timing, the signal _S6 is turned off, the forward clutch _CL1 is turned off, the forward movement is stopped, and the lamp is turned off. At the same time, a reverse signal _S7 is output to turn on the reverse clutch _CL2 to start moving the optical system in the reverse direction. The signals S ₂ and S ₆ are turned on and off, and the signal S ₇ is turned on by counting clock pulses CL by a control section L.

In Fig. 4, UP is a signal from the upper cassette designation key 52, LOW is a signal from the lower cassette designation key 53, and CEP is a signal from the micro switches 42 and 43 (Fig. 1) when the cassette is not properly inserted into the main body.
The signal PEP obtained by PEP is a signal obtained by the photoelectric switches 44 and 45 (FIG. 1) when there is no paper in the cassette, and indicates the state when it is level 1. The control section L performs logical discrimination and arithmetic processing on these detection signals and outputs operation control signals and display control signals as shown in FIG.

The skew detection in the present invention will be explained with reference to FIG. If the paper runs diagonally after being fed, it will be in a state as shown in the figure in the direction of travel indicated by the arrow. If the paper continues to be fed toward the second register roller 30 in this state, it will jam in the middle of the path. When a full-size paper (27F) is skewed to the same extent as a half-size paper (27H), the rear edge of the former paper shifts more. In other words, for the same degree of displacement d at the rear end, the oblique angle at the tip is smaller for the full size than α° for the half size (1/
2α゜). Therefore, full-size paper is more likely to jam, and even a slight skew can cause jams.

The present invention is intended to prevent jamming even when the sizes are different, and to accurately detect skew according to the size.

That is, as shown in the figure, three types of paper sensors 36-1 to 36-3 are arranged in order as the paper feed section sensor 36, and are referred to as a reference sensor, a half-size sensor, and a full-size sensor.
Outputs CPOS3 signal. The distances l ₁ and l ₂ can be approximately determined by the permissible oblique width d, the length of the paper in the traveling direction, and the speed of the paper.

Fig. 6 is a circuit diagram for detecting paper troubles such as skew feeding in the present invention. In the figure, the input signal symbols correspond to Figs. 3 and 4, SIZ is the cassette size signal, and Q ₁ , Q ₂
is an AND gate that inputs signals from the half sensor and full sensor, _Q7 is the reference sensor and timer T4
Q ₁₁ is a flip-flop, Cl is a clutch that drives the first registration roller, PL ₁ is a lamp that indicates line 65 of the jam display (Figure 1), and PL ₂ to _{PL 5} are its displays. line 66 or discharge section 69 of the cassette section
The timer T4 operates as a timer for the time required for the leading edge of the paper tilted by the width d to pass through the sensor 36-1 and then the half sensor 36-2 or the full sensor 36-3.

When the transfer paper is conveyed normally, each sensor 36-
1 to 36-3 simultaneously detect paper. Therefore CPOS
1 to 3 are all 1. The size of the upper cassette you just specified with key 52 is half size (A4, B5,
When U2), the signal SIZ becomes 1, gate _Q1 is selected, and its output becomes 1. Therefore, exclusive OR gate _Q7 outputs 1 when the inputs are at different levels, so there is no output and timer T4 does not start. Signal SIZ for full size (A3, B4, U1)
Since is 0, gate Q ₂ is selected and its output becomes 1. Therefore, similarly, timer T4 does not start during normal operation. Unless the timer starts, the flip-flop will not be set, so the lamps PL ₁ to _{PL 5} will not light up.

When half-size paper is skewed, the reference sensor output CPOS1 is 1, the half-sensor output CPOS2 is 0,
Or sometimes the opposite is true. Therefore exclusive or gate
Since the inputs of Q ₇ are different from each other, gate Q ₇ outputs 1 during different levels. This output starts timer T4, which produces an output of 1 after a preset timer period has elapsed. If CPOS1 and CPOS2 become the same level within the timer time, the timer operation is canceled and the timer does not produce an output. In other words, since the degree of skew is within the allowable width d (FIG. 5), it is not determined that skew is occurring. However, if the outputs of each sensor do not reach the same level and the timer operation is completed, this state is regarded as skew, and the flip-flop is output through gate _Q5 .
Set _Q11 and output level 1 from Q port. Since the gate Q ₁₅ -1 receives a repeated pulse from the oscillator Q ₁₄ on one side, it combines with the level 1 from the Q port to activate the transistor Q ₁₇ and blink the lamp PL ₂ in accordance with the pulse. By this blinking, the upper part of the mark 66 is clearly blinked.
If the lower cassette is specified, the lower side of the mark 66 is clearly displayed by blinking. Also, the set output of flip-flop _Q11 activates transistor _Q16 to turn on the lamp.
Turn on PL ₁ . This lighting makes the mark 65 clearly visible.

In the case of full-size skew, select the full sensor, so the signal CPOS from the reference sensor and full sensor
1 and CPOS3 are at different levels, the gate _Q7 outputs 1 and starts the timer T4. If both sensors are turned on within the same timer time as for half size, it will not be skewed, but once that time has elapsed it will be considered skewed.

Therefore, using the same timer, it is possible to detect skew according to the size. For example, to detect the skew of another size whose length in the traveling direction is 1/4 of the full size, a sensor is further provided between the sensors 36-1 and 36-2, and the circuit shown in FIG. 6 is used. It can be achieved.

The output of the flip-flop _Q11 that detects the skew passes through the inverter _Q12 and blocks the output of the gate _Q13 to which the first registration roller actuation signal S3 is input, so that the registration clutch Cl is energized and the roller drive is stopped. Thereby, paper feeding is stopped after the skew is detected. At this time, the trailing edge of the paper remains in the cassette as indicated by the lamp _PL2 , or is stopped near the cassette, making it extremely easy to remove the paper.

It is also possible to open the paper path near the sensor with the output of the flip-flop _Q11 and automatically discharge the skewed paper out of the machine.

Next, the method of detecting failure to feed paper from the cassette using the sensor 36-1 for detecting skew will be explained with reference to FIG. As is clear from the time chart in FIG. 3, a signal S5 is output from the control section to turn on the halogen lamp at the time when the paper normally passes through this sensor. That is, when the signal CPOS1 is input to one side of the NAND gate _Q5 , if the ramp signal S5 becomes 1, the gate _Q5 remains at 0. Therefore, gate _Q19 also does not output and flip-flop _Q11 is not set. However, if a paper feed error occurs after the paper feed roller operates and the paper does not reach the sensor 36 no matter how long it takes, the CPOS1 remains at level 0, so the ramp signal S5 is output first and the output of the gate _Q5 becomes level H. Become. Since the level H is input to the AND gate _Q19 and the differential signal of the ramp signal S5 is input to the other gate, _Q19 produces an output according to the differential signal. Therefore, the flip-flop _Q11 is set by the output, the lamps _PL1 and _PL2 are turned on, and the rotation of the first registration roller is stopped as in the case of skew detection. Note that skew feeding and paper feeding errors are the same level of paper trouble in the paper feeding section, so the indicators 65, 66,
76 is used. When this trouble occurs, the other drive systems do not stop operating, and the normal paper in the machine is ejected, and the optical system is also stopped when the double movement is completed, and then the drum rotation is stopped to speed up the operation. Allows replication to be restarted. lamp signal S5
Since a paper feeding error is checked at , it is possible to prevent the optical system from moving forward after the lamp is turned on in the event of a paper feeding error.

The flip-flop Q, which is set by detecting skew or feeding error, is set by attaching and detaching the cassette, contributing to quick restart. When the cassette (in this case, the upper cassette) is removed from the main body in order to remove misfed or skewed paper, the switch 42 is turned off and the signal CEP is output, which is sent to one side of the gate _Q10 . input. In case of skew
Since one of CPOS 1 to 3 detects paper, Noah gate Q ₉ outputs 0, and therefore gate Q ₁₀ outputs 1.
does not output. However, when the skewed paper is removed, all of its inputs become 0, so NOR gate _Q9 outputs 1, gate _Q10 also outputs 1, and its output is input to the reset port of flip-flop _Q11 .
This resets the flip-flop, turns off the lamps PL ₁ and PL ₂ , and enables the first registration roller to be driven. In other words, unless the skewed paper is removed, the cassette will not be reset even if the cassette is removed, thereby preventing further troubles due to errors in paper removal. Furthermore, since the printer is automatically reset when the paper is removed, it is possible to eliminate the complicated process of pressing the reset button to restart copying after removing the jam. In the case of a paper feeding error, it is likely that the paper is not being fed from the cassette, so by removing the cassette, resetting it, checking the paper feeding status, and putting the cassette back on, re-driving can be carried out extremely smoothly. It is also possible to configure the flip-flop to be reset when the cassette is put on.

A case will be described in which the paper stops on the paper feed section sensor 36 without skew or paper feeding errors. In this case, since the paper does not reach the transfer section sensor 35, the optical system backward movement signal _S7
The sensor 35 checks the presence or absence of paper and indicates the presence of paper. That is, since the signal of the sensor 35 is 0, the signal S7 causes the gates Q ₂₂ and Q ₂₃ to output 1, similar to the relationship between the gates Q ₅ and Q ₁₉ , and the flip-flop Q ₂₁
is set, the lamp PL ₁ is lit, the line 65 is made clear, the jam indicator 64 is made clear, and the lamp PL ₃ is blinking. Then, a jam relay (not shown) is activated to quickly interrupt copying (immediately stop the operation of the motor, optical system, and paper conveyance roller). After clearing the jam, reset flip-flop _Q21 with reset switch RS. A lamp irradiates a mark 67 when the paper stays on the transfer section sensor 35, a mark 68 when a jam occurs between the transfer section and the discharge section, and a mark 69 when the paper stays on the discharge section sensor 40. In either case, the light flashes and the line 65 is lit statically.

The above display marks 65 to 69 are printed in advance on the Mylar surface layer of the display section, and normally a blue smoke material is provided between the Mylar and the lamp that irradiates the Mylar with light so that the marks are not observed from the outside. By doing so, the warning effect of the jam and its location can be made more noticeable.

In the present invention, as an example of skew feeding, paper detection sensors 36-1 and 36-2 are used, and a timer T4 is used.
That is, the leading edge of the paper is 36 mm with the allowable width d shorter than the time limit of
Timer T of the time required to go from -1 to 36-2
There is a method to do this by providing 3. That is, the circuit before X in FIG. 6 is made as shown in FIG.
When it is half size, timer T4 is operated by satisfying the input condition of exclusive OR gate Q _{32 through} gate 30 in the same way as _Q7 , and when it is full size, timer T3 is activated by exclusive OR gate Q ₃₃ through gate 31. is activated, and a skew detection signal is output when the timer completes.

As described above, the present invention detects skew feeding according to the size, and also because the blocking state of the machine due to troubles caused by paper feeding errors and skew feeding is released by attaching and detaching the cassette. Since skew detection is performed using the same sensor, jams can be prevented with high precision, and the machine can be restarted smoothly after paper processing.

FIG. 8 is a circuit diagram for confirming and displaying the location where a paper problem has occurred. In this example, the trouble detection method is the feeding section check as described above, the transfer section delay check that detects whether or not the transfer section has been normally reached after feeding, and the ejection section that detects whether or not the transfer section has been reached after that. This includes a delay check and a discharge section retention check that detects whether the object has passed through the discharge section, and is intended to monitor a large number of locations with a small number of detectors.
67, 68, and 67, 68 of the display in FIG.
69 is displayed blinking, and after a jam is detected and the main motor is stopped, it is checked to see if there is paper in the paper feed section sensor. The system determines whether the problem has occurred on the path to the section and changes the display. That is, for example, when there is a stagnation, the transfer section display is turned off and the paper feed section display is turned on.

In the figure, _Q8 is a flip-flop that is set by the second registration roller signal _S4 and reset by the paper detection signal CPOSC from the transfer section sensor 35, and _Q16 is a forward signal.
Q21 _is a flip-flop that is set at the falling edge of _S6 and reset by the discharge section sensor 40; _Q21 is a flip-flop that is set at the rising edge of signal CPOSC _and reset at the falling edge of _signal CPOSC _; Flip-flops T ₂ , T ₃ , and T ₅ for lighting the display lamps PL1 to PL7 are jam detection timers.

In normal operation, the paper that has passed the sensor 36 is
The roller 30, which had been stopped until then, reaches the registration roller 30 and stops, and the signal _S16 from the second registration sensor 39 generated while the optical system is moving forward causes the roller 30 to stop.
starts rotating (S ₄ ) and is sent to the transfer section. Then, the paper passes through the sensor 35 and is transferred at the transfer section so that the leading edge of the toner image on the drum and the leading edge of the paper coincide.
It passes through the fixing rollers 33-1 and 33-2 and is fixed, passes through the sensor 40, and is stored in the tray 34. The paper passage timing of each sensor is shown in FIG.

Paper feed section sensor 3 after paper is fed from the upper cassette
6, the delay jam is detected as a paper feeding error using the lamp lighting signal S5 and the paper detection signal CPOSA from the sensor 36, as described above. That is, when a paper feeding error occurs, the flip-flop _Q5 is set by the gate operation described above, the PL1 and PL2 are turned on and blinking, and the display 76 of the operation section is turned on by RL6.

The delay jam to the transfer section sensor 35 is caused by the second registration roller signal _S4 and the paper detection signal of the sensor 35.
This is done by CPOSB.

That is, the flip-flop _Q8 is set by the signal _S4 , and the Q output of the flip-flop _Q8 operates the timer _T5 . When the timer _T5 expires, the transistor _Q7 is turned on and the level 1 is output from the inverter _Q6 . Thereby, flip-flop _Q12 is set to blink lamp PL3 in response to repeated pulses from oscillator _Q26 , causing transfer mark 67 to blink.
However, if the sensor 35 detects paper within the time limit of the timer _T5 , the flip-flop _Q8 is reset by the signal CPOSB and the timer operation of the timer _T5 is canceled.
Therefore, _Q12 is not set and does not blink as described above. The time limit of the timer T ₅ is set so as to add some margin to the time required for the leading edge of the paper to reach the transfer section sensor 35 after the signal S ₄ , that is, the signal S ₁₆ from the registration sensor 39 is generated.

The delay jam check for the discharge section sensor 40 is as follows:
Optical system reversal signal and paper detection signal by sensor 40
This is done by CPOSC. That is, when the advance signal _S6 is turned off (optical system inversion), the flip-flop _Q16 is set via the inverter _Q15 , and the timer _T2 is activated by the set signal. When the time limit of the timer _T2 expires, the flip-flop _Q19 is set in the same manner as described above, the lamp PL4 is blinked, and the fixing section mark 68 is blinked. However, within the time limit of timer _T2 , sensor 40
When paper is detected, the signal CPOSC resets the flip-flop _Q16 and releases the time limit of the timer _T2 . Therefore, the lamp PL4 does not blink. timer
The time T ₂ is the time required for the leading edge of the trailing paper to reach the sensor 40 after the signal S ₆ is turned off, with some leeway.

To check the retention jam at the discharge sensor, set the flip-flop _Q21 with the paper detection signal CPOSC.
This is done by resetting with the paper ejection signal (inversion of CPOSC). In other words, flip-flop
The Q output of _Q21 activates the timer _T3 , and when the paper is ejected from the sensor 40 within the timer time, _Q21 is reset and the operation of the timer _T3 is canceled. When the timer _T3 expires without the sensor 40 detecting the trailing edge of the paper, the flip-flop _Q25 is set as described above and the lamp PL5 flashes in response to repeated pulses. Therefore, the jam line 65 is lit and the discharge mark 69 is blinked to warn of the accumulation on the sensor 40. Further, when a jam occurs from transfer to ejection, the lamp PL7 is turned on and the jam indicator 64 is displayed. In addition, the output of gate _Q38 that lights up lamp PL7 is input to the control section shown in Fig. 4, and the main motor
Control signals are turned off to stop operation of process loads such as clutches. At the same time, the jam relay is activated and the relay is mechanically held. still
Instead of stopping the motor immediately with the output of Q ₃₈ , it is also possible to stop the motor after removing static electricity and cleaning the drum surface. Therefore, copying cannot be restarted simply by opening the case door and removing the jam paper (although the configuration shown in FIG. 1 can be observed). Furthermore, when the enclosure door is opened, the power to the process load is turned off regardless of the main switch, but the power (DC) to the display and control section L is maintained.

Incidentally, in the event of a trouble (above), it is also possible to blink the corresponding mark among the marks 65 to 69 and to statically light the other marks.

Therefore, since PL1 to PL7 are lit during jam processing, the processing is facilitated. When the reset button provided inside the processing case is turned on, the jam relay is released and the signal RS by the reset button is turned on.
Then, the flip-flops Q ₁₂ , Q ₁₄ , and Q ₂₅ shown in FIG. 8 are reset, and the lamps PL1 to PL5 and PL7 are turned off.

Next, the display switching of the jam location will be explained in detail.
Lamp PL3 is blinking due to transfer jam detection.
When the main motor signal _S1 is turned off as described above, the signal inverted by the inverter _Q14 is input to the gates _Q4 and _Q13 . At this time, if paper is retained in the paper feed section sensor 36 and CPOSA is output, the flip-flop is output via the OR gate _Q11 by the output of the gate _Q4.
Q12 is reset to turn off lamp PL3, and flip-flop _Q5 is set via OR gate _Q3 to turn on lamps PL2 and PL6. Therefore, the blinking is switched from the transfer section display mark 67 to the upper cassette section of the paper feed section display mark 66. Furthermore, when the main motor signal S ₁ is turned off and the paper feed section sensor 36 does not detect paper, it is assumed that paper is staying on the path between the paper feed section sensor 36 and the transfer section sensor 35. , the lamp PL3 continues to blink.
In addition, when a jam is detected in the fixing unit and the main motor is stopped while the lamp PL4 is blinking and paper is stuck in the transfer unit sensor 35 and the CPOSB is output, the flip-flop is output via the gate Q ₂₀ by the output of the gate 13.
Reset _Q19 , turn off lamp PL4, and turn off gate
Flip-flop _Q12 is set via _Q10 to turn on lamp PL3. Therefore, the blinking is switched from the fixing section display mark 68 to the transfer section mark 67. Furthermore, when the main motor signal _S1 is turned off and the transfer section sensor 35 does not detect paper, it is assumed that paper is staying on the path between the transfer section sensor 35 and the paper discharge section sensor 40, Lamp PL
Let 4 continue blinking.

[Effect] As explained above, according to the present invention, when the second jam detection means detects a jam, after the operation of the image forming means is stopped, the first recording material detection means and the second recording material detection means are activated again. By determining whether or not the means detects the recording material and displaying the jammed position, the jammed position can be accurately known.
In addition, in the case of continuous copying, it is also possible to detect subsequent recording materials.
It becomes easier to resume operation.

[Brief explanation of the drawing]

1 is a sectional view of the image forming apparatus according to the present invention, FIG. 2 is a plan view of the operating section of FIG. 1, FIG. 3 is an operation time chart of each part of FIG. 1, and FIG. 5 is an explanatory diagram of the skew detection section in FIG. 1, FIG. 6 is a trouble detection circuit in FIG. 1, and FIGS. 7 and 8 are other trouble detection circuits in FIG. 1. In the figure, 26-1 and 26-2 are cassettes, 36 and 37 are paper feed section sensors, 35 are transfer section sensors, 40 are discharge section sensors, 42 and 43 are micro switches for detecting cassette attachment/detachment, and 65 is a trouble indicator. , 66 to 69 are trouble location indicators.

Claims (1)

[Scope of Claims] 1: means for forming an image on a recording material; means for transporting the recording material along a predetermined transport path; and a first recording device provided on the transport path to detect the presence or absence of the recording material. a second recording material detection means that is provided downstream of the first recording material detection means and detects the presence or absence of a recording material; and the first recording material detection means records at a first timing. When the recording material is not detected, the first jam detection means considers the recording material to be jammed and stops the operation of the image forming means; and when the second recording material detection means does not detect the recording material at a second timing. , a second jam detecting means that regards the jam as a jam of the recording material and stops the operation of the image forming means; The apparatus further comprises a display means for determining whether or not the first recording material detection means and the second recording material detection means detect a recording material, and for displaying the jam position based on the output thereof. image forming device.