JP3512095B2 - Defective paper detection device in image forming apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defective paper detection device used in an image forming apparatus such as a copying machine or a printer, and more particularly to a device for detecting paper wrinkles that occur during fixing processing.

[0002]

2. Description of the Related Art For example, in an electrophotographic copying machine, a toner image is transferred onto a sheet, and the sheet carrying the toner image is passed between a heating roll and a pressure roll to form a toner image. Is fixed on the paper.

During this fixing process, heat and pressure are applied to the paper, but the paper is curled due to uneven heat distribution and uneven water distribution on the paper. May cause wrinkles. If the paper curls,
In the subsequent paper transport path, inconvenience such as paper jam occurs. Further, when the paper is wrinkled, the paper loses its commercial value.

For this reason, there have been conventionally proposed some techniques for preventing curling and wrinkling of the paper. For example, in Japanese Unexamined Patent Publication No. 63-188177, the posture of a peeling claw for peeling a sheet from a heating roll is made variable, and a sheet discharging roll provided on the downstream side of a fixing device is related to a sheet conveying direction. Provided so that it can move in the intersecting direction,
It is described that the curl of the paper is detected and the posture of the peeling claw and the position of the paper discharge roll are controlled according to the curl state. Further, in Japanese Laid-Open Patent Publication No. 64-72186, the temperature of a portion of a pair of fixing rolls where narrow paper does not pass is detected, and this detected temperature is compared with a reference fixing temperature, and the detected temperature is higher than the reference fixing temperature. It is described that when fixing a wide paper, the fixing pressure is controlled to prevent paper wrinkles and the like.

[0005]

However, the prior arts described in the above publications are intended to reduce or prevent the occurrence of paper wrinkles, and for papers in which paper wrinkles have actually occurred. Does not take any measures.

Although efforts have been made to prevent paper wrinkles in the paper as in the prior art described in the above publication, it is actually difficult to completely prevent paper wrinkles.
Occurrence of paper wrinkles is inevitable, though it is slight. However, like materials for reports and presentations,
When creating a document that emphasizes not only the content of the document but also the appearance and appearance, the value of the document itself will be significantly reduced if the document contains even one wrinkled sheet. Resulting in. Therefore, conventionally, when outputting this type of document from the image forming apparatus, it is necessary to visually inspect the sheet discharged from the image forming apparatus and remove the wrinkled sheet, which is very complicated. However, there was a problem that it was easy to overlook.

Therefore, an object of the present invention is to reliably detect a wrinkled sheet.

[0008]

A defective sheet detection device in an image forming apparatus of the present invention includes a sensor for scanning the surface of the sheet in a predetermined direction to detect a sudden change in height of the surface of the sheet, and the sensor. means for outputting a signal indicating that when an output outputs of the sensor is compared with a predetermined reference value is greater than a predetermined reference value is wrinkled paper, said sensor
Mechanism for moving the paper in the direction intersecting with the paper conveyance
Characterized by comprising and.

Further, the sensor is arranged on the downstream side of the fixing device.

[0010]

Further, the sensor comprises an actuator that comes into contact with the surface of the paper and a sensor body that detects the amount of displacement of the actuator, and means for outputting a signal indicating that the paper has wrinkles, It is characterized in that the displacement amount of the actuator is compared with a predetermined reference value.

Further, the sensor is composed of an actuator that comes into contact with the surface of the paper and a sensor body that detects the acceleration of displacement of the actuator, and means for outputting a signal indicating that the paper has wrinkles. , The acceleration of displacement of the actuator is compared with a predetermined reference value.

Further, it is characterized in that means for changing the number of times of scanning by the scanning mechanism is provided.

Further, it is characterized in that means for varying the scanning speed of the scanning mechanism is provided.

[0015]

1 is a schematic cross-sectional view of a defective sheet detecting device in an image forming apparatus of the present invention. Figure 2
FIG. 3 is a schematic plan view of a defective sheet detection device in the image forming apparatus of the present invention.

A paper chute 2 including an upper chute 2a and a lower chute 2b is disposed downstream of the fixing device 1 including the heating roll 1a and the pressure roll 1b, and the downstream end of the paper chute 2 is disposed. A pair of transport rolls 3 is arranged in the section. A long groove 4 is formed in the upper chute 2a in a direction (indicated by an arrow B) orthogonal to the conveyance direction of the sheet P (indicated by an arrow A). The long groove 4 is used for the paper P.
Has a length corresponding to the maximum width of the. A guide shaft 5 is provided above the paper chute 2 along the long groove 4. The guide shaft 5 is supported by a pair of frames 6 arranged so as to face each other. In FIG. 2, only one frame is shown. A pickup sensor 7 is slidably attached to the guide shaft 5, and an actuator 8 of the pickup sensor 7 is
It projects downward through a long groove 4 formed in the upper chute 2a. As the pickup sensor 7, a displacement detection type sensor that detects the displacement of the actuator 8 or an acceleration detection type sensor that detects the acceleration of the movement of the actuator 8 can be used. The pickup sensor 7 is attached to the belt 10 via an attachment member 9. The belt 10 is wound around a pair of pulleys 11 (only one of which is shown in FIG. 2), and the one pulley 11 is rotationally driven by, for example, a pulse motor 12. The belt 10 is rotated by the rotation of the belt 10.
Rotates, and the pickup sensor 7 moves in the direction of arrow B. At a position corresponding to the movement limit of the pickup sensor 7, a pair of position sensors 13 (only one of which is shown in FIG. 2) for optically detecting the position of the pickup sensor 7 are provided. On the upstream side of the long groove 4, an elastic piece 14 made of Mylar or the like extending downward is attached to the inner surface of the upper chute 2a. The elastic piece 14 has a function of elastically pressing the upper surface of the paper P passing through the paper chute 2 from above so as to press the paper P against the lower chute 2b.

FIG. 3 is a block diagram showing a principle control system of the defective sheet detecting device in the above-mentioned image forming apparatus. The microprocessor 15 that controls the entire image forming apparatus inputs various instructions to the image forming apparatus and also displays an operation panel 16 for displaying the setting state and operating state of the image forming apparatus, and each part of the image forming apparatus. Various sensors 17 for detecting the operating state of the, various driving mechanisms 18 controlled by the microprocessor 15 based on signals from the operation panel 16 and signals from the various sensors 17,
At least the ROM 19 in which a program for controlling the operation of the defective sheet detection device is written, the RAM 20 in which at least the set scanning speed and the set number of reciprocations of the pickup sensor 7 are written, and the like are connected. Further, in this embodiment, a motor drive circuit 21 for driving the sensor drive motor 12 and the sensor position sensor 13 are connected to the microprocessor 15. It should be noted that, in FIG. 3, the details are not shown for the parts that are not directly related to the gist of the present invention.

Next, the operation of the defective sheet detecting device in the above-mentioned image forming apparatus will be described. FIG. 4 is a flowchart for explaining the operation of the defective sheet detection device.

First, the set scanning speed and the set number of reciprocations are input from the operation panel 16, and these data are written in the RAM 20 built in the microprocessor 15. It should be noted that these data may be stored in the RAM 20 at the time of shipping from the factory, with a standard value corresponding to the model being configured from a non-volatile memory.

When the image forming apparatus is powered on, RA
The data of the set scanning speed and the set number of reciprocations is read from M20 and set in the motor drive circuit 21 (steps 101 to 104). Next, when image formation is started by an instruction from the operation panel 16 (step 105), the sensor drive motor 12 starts rotating, the belt 10 rotates, and the pickup sensor 7 starts moving in the direction of arrow B1. When the sensor position sensor 13 detects that one of the movement limits is reached, the rotation of the sensor drive motor 12 is reversed, and the pickup sensor 7 moves in the opposite direction (arrow B).
Then, the movement is started (shown by 2) (step 106).

On the other hand, the sheet P after the image formation is fixed on the fixing device 1.
After passing through the sheet to undergo the fixing process, the sheet passes through the sheet chute 2 and is further conveyed by the pair of conveying rolls 3. At this time,
Since the upper surface of the paper P is elastically pressed from the upper side by the tip of the elastic piece 14, the paper P is conveyed in a state where the paper P is in close contact with the lower chute 2b, that is, in a state where the height of the paper is kept constant. It The pickup sensor 7 moves in the direction of arrow B and moves while the tip of the actuator 8 contacts the surface of the paper P, that is, the surface of the paper P is scanned, but the paper P moves in the direction of arrow A. Therefore, the actual scanning locus on the paper P has a triangular wave shape, as indicated by reference numeral S1 in FIG.

If there is a wrinkle W1 extending on the sheet P in the sheet conveying direction (shown by the arrow A), the actuator 8 of the pickup sensor 7 suddenly changes its position in the height direction. Therefore, the presence or absence of wrinkles can be detected by comparing the output of the pickup sensor 7 with a predetermined reference value. In particular, the pickup sensor 7
When an acceleration type sensor is used as the above, an output is generated for a sudden change in position such as a wrinkle, but no output is generated for a gentle change in position such as a curl. Therefore, it is possible to reliably detect only wrinkles. Further, as described above, since the paper P itself is also moving in the direction of arrow A, the actuator 8 of the pickup sensor 7 extends the wrinkle W2 extending in the direction orthogonal to the paper transport direction (shown by arrow A). Therefore, the presence or absence of wrinkles can be detected regardless of the direction of wrinkles. The scanning locus S1 indicated by the broken line reciprocates once for one sheet of paper P, but the scanning velocity of the pickup sensor 7 is doubled and the scanning locus S indicated by the one-dot chain line is shown.
If the sheet P is reciprocated twice with respect to one sheet P as shown in 2, it is possible to detect a short wrinkle as indicated by the symbol W3 and improve the detection accuracy. When a wrinkle is detected (step 107), the wrinkle flag is turned on (step 108). When the pickup sensor 7 reciprocates the set number of times (step 109), the scanning of the pickup sensor 7 is stopped (step 11).
0). If the wrinkle flag is turned on (step 110), the apparatus is stopped, the paper in which the wrinkle is detected is discharged to a specific tray, or a message indicating that wrinkle has occurred is displayed. Operation panel 16
An abnormal process such as displaying on the screen is performed (step 112).

[0023]

According to the present invention, it is possible to detect whether or not wrinkles actually occur by scanning the surface of the paper and detecting the unevenness of the surface. As a result, the wrinkled sheet can be reliably found and removed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a defective sheet detection device in an image forming apparatus of the present invention.

FIG. 2 is a schematic plan view of a defective sheet detection device in the image forming apparatus of the present invention.

FIG. 3 is a block diagram showing a principle control system of a defective sheet detection device in the image forming apparatus.

FIG. 4 is a flowchart for explaining the operation of the defective sheet detection device.

FIG. 5 is an explanatory diagram showing a scanning locus on a sheet.

[Explanation of symbols]

1 ... Fixing device, 1a ... Heating roll, 1b ... Pressure roll,
2 ... Paper chute, 2a ... Upper chute, 2b ... Lower chute, 3 ... Conveying roll pair, 4 ... Long groove, 5 ... Guide shaft, 6
... frame, 7 ... pickup sensor, 8 ... actuator, 9 ... mounting member, 10 ... belt, 11 ... pulley,
12 ... Pulse motor, 13 ... Position sensor, 14 ... Elastic piece, 15 ... Microprocessor, 16 ... Operation panel, 1
7 ... Various sensors, 18 ... Various driving mechanisms, 19 ... ROM,
20 ... RAM, 21 ... Motor drive circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Harada 2274 Hongo, Ebina-shi, Kanagawa Fuji Zerox Co., Ltd. (56) References JP-A-58-148136 (JP, A) JP-A-59-200387 ( JP, A) JP 4-140250 (JP, A) JP 4-182233 (JP, A) JP 6-32497 (JP, A) Actual development Sho 63-150964 (JP, U) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) B65H 43/04 B41J 11/42 B65H 7/02 G03G 15/00 526 G03G 15/20 102

Claims (6)

(57) [Claims] 1. A sensor for scanning a surface of a paper in a predetermined direction to detect a sudden change in height of the surface of the paper, and comparing the output of the sensor with a predetermined reference value so that the output of the sensor is predetermined. If the value is larger than the reference value of, the means for outputting a signal indicating that the paper has wrinkles and the sensor are moved in a direction intersecting with the paper conveyance.
A defective sheet detection device in an image forming apparatus, which is provided with a scanning mechanism . 2. The defective sheet detecting device in an image forming apparatus according to claim 1, wherein the sensor is arranged on a downstream side of the fixing device. 3. The sensor for contacting the surface of a sheet with the sensor.
Detect displacement of actuator and actuator
A means for outputting a signal indicating that the paper has wrinkles , which is composed of a sensor body
Compares the displacement of the actuator with a predetermined reference value
The defective sheet detection device in an image forming apparatus according to claim 1, wherein the defective sheet detection device is a defective sheet detection device. 4. The sensor for contacting the surface of a sheet with the sensor.
The acceleration of displacement of the actuator and the actuator is detected.
And a means for outputting a signal indicating that the paper has wrinkles
Is the acceleration of the actuator displacement compared to a predetermined reference value.
The defective sheet detection device in an image forming apparatus according to claim 1, wherein the defective sheet detection device is a comparison device. 5. The number of scans by the scanning mechanism is changed.
The defective sheet detecting device in the image forming apparatus according to claim 1, further comprising means. 6. A scanning speed of the scanning mechanism is changed.
The defective sheet detecting device in the image forming apparatus according to claim 1, further comprising means.