JP3287606B2 - Jam detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jam detecting device for detecting a wrapped jam of a cut sheet.

[0002]

2. Description of the Related Art Conventionally, in a recording apparatus such as a copying machine or a printer, detection of a jam around a fixing roller is performed.

The detection of the wrapping jam is based on the assumption that the wrapping jam did not occur if the sheet discharge sensor provided downstream of the fixing roller detected the leading end of the cut sheet.

[0004]

However, in the conventional detection method, when the cut sheet is wound around the fixing roller after the leading end of the cut sheet once reaches the paper discharge sensor, the wrapped jam or the stagnant jam is detected. There are things you can't do.

[0005] In addition, if the paper discharge sensor detects the cut sheet for a certain period of time, no wrapping jam will occur. However, if the size of the cut sheet is long, it is possible to detect the wrapping jam even if it occurs in the middle. Disappears.

[0006]

Means for Solving the Problems The present invention to solve the above problems, a conveying means for conveying the cut sheet, a pair of rollers provided in the middle of the transport path of the cut sheet, the
Installed upstream of the roller pair to detect the presence of cut sheets
A first sensor, which is provided downstream of the roller pair,
A second sensor for detecting the presence or absence of the cut sheet, the cut
For determining that the sheet has been wound around the roller pair
Timing the cut sheet by the first sensor
Determining means for determining according to the detection timing of the rear end;
After detecting the presence of the cut sheet by the second sensor,
Before the timing determined by the determination means,
If no cut sheet is detected, the cut sheet
Is determined to be wound around the roller pair , control means for stopping the operation of the transport means and the rotation of the roller pair ,
It has.

Further, the present invention provides a sheet feeding means for feeding a cut sheet, a registration roller for temporarily stopping the cut sheet fed by the sheet feeding means, and then conveying the cut sheet at a predetermined timing. A first sensor provided upstream of the registration roller to detect the presence or absence of a cut sheet;
A roller pair provided downstream of the registration roller and transporting the cut sheet, provided downstream of the roller pair,
A second sensor for detecting the presence or absence of a cut sheet; and a first counter for starting a counting operation in synchronization with the start of driving of the registration roller and stopping the counting operation when the first sensor detects the absence of the cut sheet. A second counter which starts a counting operation when the second sensor detects the presence of a cut sheet, and stops a counting operation when the second sensor detects the absence of a cut sheet;
The count value of the second counter is compared with the count value of the second counter. When the count value of the second counter is larger than the count value of the first counter, or when the count value of the first counter is When the count values of the counters are substantially equal to each other, it is determined that the sheet is normal. Otherwise, it is determined that the sheet has been wound around the pair of rollers, and control means for stopping the conveyance of the cut sheet is provided.

[0008]

According to the above construction, the present invention makes it possible to reliably detect a jam wound around a roller pair regardless of the size of a cut sheet.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a drawing which best illustrates the features of the present invention. In FIG. 1, reference numeral 1 denotes a one-chip microcomputer (CPU) having a built-in ROM and RAM; Device, 3
Is a main motor control unit, 4 is a main motor, 5 is a scanner motor control unit, 6 is a scanner motor, 7 is a paper feed roller, 8 is a registration clutch, 9 is a paper size detection unit, 10
Is a registration sensor, 11 is a paper ejection sensor, and 12 is a motor O
N signal, 13 is motor ready signal, 14 is scanner ON
Signal, 15 is a scanner ready signal, 16 is paper feed roller O
N signal, 17 is a registration clutch ON signal, 18 is a paper size signal, 19 is a signal requesting start of printing (hereinafter P
Reference numeral 20 denotes a signal for requesting a vertical synchronization signal (hereinafter, referred to as VSREQ), and reference numeral 21 denotes a vertical synchronization signal (hereinafter, referred to as VSSYNC).

FIG. 2 is a schematic view of an image forming apparatus to which the present invention can be applied. 101 is an apparatus housing, 103 is a registration roller, 104 is a photosensitive drum, 105 is a transfer roller,
6 is a fixing roller, 107 is a pressure roller, 108 is a laser device, 109 is a reflection mirror, 110 is cut paper, 111
Denotes a cassette, 112 denotes a paper discharge tray, 113 denotes an interface cable, and 114 denotes a paper discharge roller.

The general operation of the image recording apparatus will be described with reference to FIGS.

When receiving the PRNT signal 19 from the external device 2, the CPU 1 sends a motor ON signal 12 to the main motor control unit 3. Upon receiving this, the main motor control unit 3 drives the main motor 4. When the main motor 4 reaches a predetermined number of revolutions, the main motor control unit 3 returns a motor ready signal 13 to the CPU 1.

Thereafter, the CPU 1 issues a scanner ON signal 14
To the scanner motor control unit 5, which drives the scanner motor 6. When the scanner motor 6 reaches a predetermined number of rotations, the scanner motor control unit 5 returns a scanner ready signal 15 to the CPU 1. Thereafter, the CPU 1 drives the paper feed roller 9 to convey the cut sheet 110 in the cassette 111 to the position of the registration roller 103.

Thereafter, the CPU 1 sends V to the external device 2.
Sends the SREQ signal 20 and outputs the VSYNC from the external device 2.
Wait for signal 21. When the VSYNC signal 21 is sent, the CPU 1 turns on the registration clutch ON signal to turn on the registration clutch 8. When the registration clutch 8 is turned on, the registration roller 103 connected thereto is driven.

CPU 1 applies VIDEO from external device 2 to cut paper 110 conveyed by registration rollers 103.
A signal (not shown) is caused to emit laser light by the laser device 108, and the laser light emitted by the laser device 108 is transmitted to the photosensitive drum 10 by the scanner motor 6 and the reflection mirror 109.
The image is transferred onto the photosensitive drum 4 and the image is transferred by the photosensitive drum 104 and the transfer roller 105.

Thereafter, the cut sheet 110 is fixed to the fixing roller 106.
Is fixed by the pressure roller 107 and discharged onto the discharge tray 112 by the discharge roller 114.

The registration sensor 10 and the paper ejection sensor 11 monitor the conveyance of the cut sheet 110, and
Is ON when each sensor is present and OFF when there is no sensor, and this information is sequentially read by the CPU 1.

On the other hand, the CPU 1 reads the set paper size from the paper size detection unit 9 mounted adjacent to the cassette 111.

FIG. 3 shows the details of the paper size detecting section.

Projection 4 attached to cassette 111
By turning on / off the switches 401, 402, and 403 attached on the paper size detection unit 9, the set paper size can be detected.

By changing the position of the protrusion 404 or using a plurality of protrusions, various paper sizes can be set. FIG. 4 shows an example of the relationship between the ON / OFF state of the switches 401, 402, and 403 and the paper size determined by the ON / OFF state. In the example of FIG. 3, the switch 403 is on and the switch 4
01 and the switch 402 are off, and the paper size is A4.

This embodiment will be described in detail with reference to the flowcharts shown in FIGS. Counters 1 to 6 are CPU1
A down-counter using a RAM inside the counter is used as a timer by decrementing the counter by one every predetermined time in an interrupt process. In step 501, the PRNT from the external device 2
Monitor the transmission of the signal 19. CPU1 is PRN
Upon receiving the T signal 19, the main motor 4 is driven in step 502. In step 503, motor ready is monitored, and if the motor becomes ready, the scanner motor is driven in step 504.

When the feed roller ON signal is turned on in step 505, the counter 1 is started in step 506. The counter 1 has a cut sheet 11 at the sheet feeding position.
A value having a predetermined margin with respect to a value obtained by dividing the distance from the leading end of the register 0 to the registration sensor by the transport speed of the paper feed roller 7 is used for detecting a paper feed delay jam.

At step 507, the registration sensor is turned on.
Watch as they become. If the registration sensor is off, the end of the counter 1 is monitored in step 508 (whether it is 0 or not). If the registration sensor does not turn on even after the counter 1 ends, an error is detected as a jam. As soon as it is determined that a jam has occurred, the transport operation is stopped.

When the registration sensor 10 is turned on, in step 509, a time that is obtained by adding a time for forming a predetermined loop amount to a value obtained by dividing the distance from the registration sensor to the registration roller by the conveyance speed of the paper feed roller has elapsed. Then, the paper feed roller ON signal 16 is turned off to terminate the paper feed.

Thereafter, scanner ready is monitored in step 510, and when it becomes ready, the VSREQ signal 20 is sent to the external device 2 in step 511. Step 512
Waits for the VSYNC signal 21 returned from the external device 2, and when the VSYNC signal 21 is returned, step 513.
Drives the registration clutch 8.

When the registration clutch 8 is driven,
In step 514, the counter 2, the counter 3, and the counter 4 are started. Counter 2 has a registration roller of O
By being N, the cut sheet 110, which is formed in a loop and is pressed against the registration roller, is pulled, whereby the registration sensor chatters, and although the cut sheet is actually at the registration sensor position, This is for preventing an erroneous detection that there is no paper and that there is no paper. The value of the counter 2 is the time from the driving of the registration roller to the elimination of chattering. In this embodiment, the minimum size of the cut sheet is determined by the process speed (transport speed).
(For example, 3 seconds).

The value of the counter 3 is the time required for the cut sheet to pass through the registration sensor, and is a predetermined value for a value obtained by dividing the paper size− (the distance from the registration sensor 10 to the registration roller 103) by the process speed. And is used for detection of a stay jam at the registration sensor position.

The value of the counter 4 is the time required for the cut sheet to reach the discharge sensor from the registration roller, and is a predetermined value relative to a value obtained by dividing the distance from the registration roller 103 to the discharge sensor 11 by the process speed. Is used to detect a paper discharge delay jam.

Thereafter, at step 515, the registration sensor is monitored for OFF, and if it is ON, the end of the counter 3 is monitored at step 516. If the registration sensor 10 is ON even after the counter 3 ends, an error is generated as a registration stagnant jam. When the registration sensor 10 is turned off, the end of the counter 2 is monitored in step 517. If the counter 2 has not ended, step 515
And the above processing is repeatedly executed.

If the counter 2 has been completed, step 51
At 8, after waiting for a time required for the rear end of the cut sheet 110 to pass from the position of the registration sensor 10 to the registration roller 103, the registration clutch 8 is turned off and the driving of the registration roller 103 is stopped. In step 519, it is monitored that the paper discharge sensor 11 is turned on. The paper ejection sensor 11 is O
In the case of the FF, the end of the counter 4 is monitored in step 520. Even if the counter 4 ends, the sheet discharge sensor 11
In the case of F, an error is determined as a paper ejection delay jam. If the paper discharge sensor 11 is turned on, the counter 5 and the counter 6 are started in step 521.

The value of the counter 5 is the time required for the cut sheet 110 to pass through the position of the discharge sensor 11, and is set to a value having a predetermined margin with respect to the value obtained by dividing the paper size by the process speed. Used to detect paper jams.

The value of the counter 6 indicates that the cut sheet 110 has reached the discharge sensor 11 once.
Is for detecting that the paper is likely to be wound around the pressure roller 107 or the fixing roller 106 during the conveyance, and is defined as a value obtained by dividing {paper size-predetermined length (for example, 3 cm)} by the process speed.

At step 522, the control unit monitors whether the paper discharge sensor is OFF. Step 523 if the paper discharge sensor 11 is ON.
Monitor the end of timer 5. If the discharge sensor 11 is not turned off even after the counter 5 ends, an error is determined as a paper jam in the discharge section. Discharge sensor 11 is off
, The counter 6 is monitored in step 524.
If the cut sheet 110 is normally conveyed, the counter 6 should have finished counting when the sheet discharge sensor is turned off. Make an error and stop conveyance. This can prevent the cut sheet from being wound around the fixing roller 106 and the pressure roller 107. If counter 6 is completed to stop the main motor driving at step 525.

In the above-described embodiment, the case where the transport path (the distance from the registration roller 103 to the paper ejection sensor 11) is longer than the paper size is described. In the second embodiment, the operation when the paper size does not depend on the paper size is described. explain.

FIGS. 7 and 8 are flow charts for explaining the second embodiment. Steps 501 to 514 are the same as those in the above-described embodiment, and the description of the operation is omitted here. The same applies to the configurations of the counters 1 to 6.

At step 615, it is monitored that the registration sensor 10 is turned off. Registration sensor 10 is O
If N, the end of the counter 3 is monitored in step 616. Even if the counter 3 ends, the registration sensor 10
In the case of N, an error is made as a resist stay jam. If the counter 3 has not ended, the process proceeds to step 620. When the registration sensor 10 is turned off, if the counter 2 has been completed in step 617, the registration clutch 8 is turned off after a predetermined time has elapsed in step 618.
Change to F. In step 619, a value obtained by subtracting a predetermined delay from a value obtained by dividing the distance from the registration roller 103 to the sheet discharge sensor 11 by the process speed is set in the counter 6, and the counter operation is started. Step 620
Monitor that the paper discharge sensor 11 is turned on. If the paper discharge sensor 11 is OFF, the end of the counter 4 is monitored in step 621. If the paper discharge sensor 11 is OFF even after the counter 4 ends, an error is generated as a paper discharge delay jam. If the counter 4 has not ended, the process proceeds to step 615.

When the paper discharge sensor 11 is turned on, the counters 5 and 6 are started in step 622. The value set in the counter 6 is the same as or larger than that in the first embodiment. However, if the counter 6 has already been set in step 619, that is, if the leading end of the cut sheet has reached the sheet discharge sensor 11 after the trailing end of the cut sheet has passed the registration sensor 10, the setting is performed here. do not do. When the leading end of the cut sheet reaches the sheet discharge sensor before the trailing end of the cut sheet passes through the registration sensor 10, the timer 6 is set and started. Step 6
At 23, it is monitored that the paper discharge sensor 11 is turned off.
If the paper discharge sensor 11 is ON, the counter 5 is monitored in step 624, and if the paper discharge sensor 11 is ON even after the counter 5 ends, an error is generated as a paper discharge jam.
If the counter 5 has not ended, the process proceeds to step 615.

If the paper discharge sensor 11 is turned off, the end of the counter 6 is monitored in step 625. If the counter 6 is not completed, an error is generated as a fixing wrap jam and the conveyance is stopped. If the counter 6 has ended, the driving of the main motor is stopped in step 626.

Depending on the paper size, there are cases where the leading edge of the paper arrives at the paper ejection sensor 11 earlier than when the trailing edge of the paper passes through the registration sensor 10 and vice versa. According to the above-described processing, if the trailing edge of the paper passes the registration sensor 10 early, the counter 6 is set in step 619, and the setting in 622 is not performed. In the opposite case, the value set in step 622 is
It is reset at 9.

In the second embodiment, the cut paper 110
Has detected the wrapping jam by starting the counter 6 at the timing of turning off the registration sensor 10 and the timing of turning on the paper ejection sensor 11. However, in the third embodiment, the up counters 7 and 8 are newly added. In addition to the above, the fixing wrap jam can be monitored regardless of the paper size.

FIGS. 9 and 10 are flow charts for explaining the operation of the third embodiment. Steps 501 to 514, 515, 516, 518 to 520, 5
Steps 22 to 525 are the same as in the first embodiment, and a description thereof will be omitted.

Step 701 is executed between steps 514 and 515. That is, the registration clutch 10 is turned on.
After that, the counter 7 is started. Thereafter, when the registration sensor 10 is turned off, the counter 7 is stopped in step 702. When the discharge sensor 11 is turned on, the counters 5 and 8 are started in step 703, and when the discharge sensor 11 is turned off, the counter 8 is stopped in step 704. Step 70
If the value of the counter 8 is substantially equal to the value of the counter 7 at 5 (if the value of the counter 8 is larger than the value of the counter 7 even if they are not substantially equal), the process proceeds to step 525. On the other hand, if NO in step 705, an error is determined as a fixing wrap jam and the conveyance is stopped.

That is, the counter 7 counts up to a count value corresponding to a length slightly shorter than the paper size (shorter by the distance between the registration sensor and the registration roller), and the value of the counter 8 becomes almost equal to the value of the counter 7. If it is equal to or larger than this, it can be determined that the cut sheet has been normally conveyed.

[0045]

As described above, according to the present invention, the wrapping jam on the roller pair is performed in accordance with the value of the counter when the sensor provided downstream of the roller pair detects the presence or absence of the cut sheet. Is detected, regardless of the sheet size, the winding jam can be reliably detected, and the cut sheet can be prevented from completely winding around the roller.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an image recording apparatus to which the present invention can be applied;

2 is a cross-sectional view of an image recording apparatus that can be applied to the present invention,

FIG. 3 is a diagram for explaining paper size detection;

FIG. 4 is a diagram showing the relationship between the state of switches 401 to 403 and the paper size.

FIG. 5 is a flowchart for explaining the operation of the first embodiment;

FIG. 6 is a flowchart for explaining the operation of the first embodiment,

FIG. 7 is a flowchart for explaining the operation of the second embodiment;

FIG. 8 is a flowchart for explaining the operation of the second embodiment;

FIG. 9 is a flowchart for explaining the operation of the third embodiment;

FIG. 10 is a flowchart for explaining the operation of the third embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CPU 2 External device 3 Main motor control part 4 Main motor 5 Scanner motor control part 6 Scanner motor 7 Paper feed roller 8 Registration clutch 9 Paper size detection part 10 Registration sensor 11 Paper supply sensor 12 Motor ON signal 13 Motor ready signal 14 Scanner ON signal 15 Scanner ready signal 16 Paper feed roller ON signal 17 Registration clutch ON signal 18 Paper size signal 19 PRNT signal 20 VSREQ signal 21 VSYNC signal

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Hashimoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Soya Endo 3-30-2 Shimomaruko, Ota-ku, Tokyo (56) References JP-A-4-110880 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B65H ^7/ 00-7/20

Claims (1)

(57) [Claims] 1. A conveying means for conveying a cut sheet, a roller pair provided in the middle of a cut sheet conveying path, and a roller provided upstream of the roller pair for detecting the presence or absence of a cut sheet.
Determining a first sensor for detecting, provided downstream of the roller pair, and a second sensor for detecting the presence or absence of the cut sheet, that cut sheets with wound the roller pair
Timing for the cutoff by the first sensor.
Deciding means for deciding according to the detection timing of the rear end of the port
And the presence of a cut sheet is detected by the second sensor.
Later, before the timing determined by the determining means
If no cut sheet is detected, the cut sheet
A jam detecting device for judging that the sheet has been wound around the pair of rollers , and control means for stopping the operation of the conveying means and the rotation of the pair of rollers.