JP2621051B2 - Document size detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document size detection device of an image forming apparatus having a document table having a document cover that can be opened and closed, and a scanning unit that optically scans a document. .

[Conventional technology]

2. Description of the Related Art In an image forming apparatus such as a copying machine, means for detecting a size of a document set on a document table is provided in order to realize a function of automatically selecting a sheet feeding cassette according to a document size. In general, a sensor for detecting a document size is provided below a document table and includes a light emitting element and a light receiving element which are arranged adjacent to each other. Then, light is emitted in the direction of the document table by the light emitting element, and reflected light from the document set on the document table is received by the light receiving element to detect the presence or absence of the document and its size.

As an image forming apparatus using such a document size detecting means, there are apparatuses disclosed in JP-A-61-122640 and JP-A-62-200344. In these apparatuses, a light-emitting element and a light-receiving element are provided as sensors on scanning means for scanning a document, and before scanning the document optically, the scanning means is moved to detect the size of the document, and the document is scanned from the document as described above. The reflected light is received by a light receiving element, and the size is detected from the relationship between the output of the light receiving element and the moving distance of the scanning means.

[Problems to be solved by the invention]

The document size detection method in the image forming apparatus described in the above publication is to detect the document size by moving a scanning unit while the document cover is being closed. That is, the start of the closing operation of the document cover is detected by the limit switch,
From this detection point, the scanning means is moved toward the rear end of the document. By the time the document cover is closed on the document table, the rear end of the document is detected by the sensor, and the document size is detected.

However, in such a detection method, it is necessary to stop the movement of the scanning means from the start to the end of the closing operation of the document cover and detect the size. Therefore, when the size of the apparatus is increased and the document size is increased, the document cover may be closed before the scanning unit detects the trailing edge of the document. In order to prevent this, the moving speed of the scanning means needs to be extremely high. If the document cover is closed before the scanning unit detects the trailing edge of the document, it is difficult to distinguish between the white portion on the back surface of the document cover and the white portion of the document. It will be difficult.
Although it is possible to distinguish between the back of the document cover and the document, it is necessary to manage the threshold value of the sensor output with very high precision.

Also, in the case of a normal-size document, if the closing operation of the document cover is performed quickly, the document cover may be closed before the trailing edge of the document is detected. turn into.

Therefore, it is conceivable that the scanning unit is moved toward the rear end of the original when the original cover is open, and the size of the original is detected by detecting the rear end of the original. However, when the document cover is open, the document is often not set in the correct position.If the document size is detected by detecting the trailing edge of the document in this state, the document size may be incorrectly recognized. In some cases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a document size detecting device capable of accurately and easily detecting the rear end of a document and accurately detecting the document size.

[Means for solving the problem]

A document size detecting apparatus according to the present invention is provided in an image forming apparatus having a document table having a document cover that can be opened and closed, and a scanning unit that moves along the document table and optically scans a document. is there.

The apparatus is provided movably in a scanning direction of a scanning unit, and an opening / closing state detecting unit that detects an opening / closing state of a document cover, a document detecting unit that detects that a document is placed on a document table, A document trailing edge detection sensor for detecting the trailing edge of the document placed on the platen, and from the output of the document trailing edge detecting sensor, that the document trailing edge detection sensor is located at the document trailing edge. And a movement control means for moving the sensor for detecting the trailing edge of the document. The movement control means, when the open / closed state detection means and the document detection means detect that the document cover is open and the document is placed on the document table, the identification result of the document rear end identification means. Then, the sensor for detecting the trailing edge of the document is moved to follow the trailing edge of the document.

The document trailing edge detection sensor is composed of a pair of sensors, for example, which are arranged side by side in the scanning direction of the scanning unit and detect the presence or absence of a document. In the case where the sensor for detecting the trailing edge of the document is composed of such a pair of sensors, the trailing edge identification means of the document detects an output signal indicating the presence of the document from one of the pair of sensors. When an output signal indicating that there is no original is detected from the other sensor, the original trailing edge detection sensor recognizes that the original trailing edge detection sensor is at the rear end position of the original.

[Action]

In the present invention, when a document is placed on the platen,
With the document cover opened, the document trailing edge detection sensor is moved toward the document trailing edge to detect the document trailing edge. At this time, if the original cover is open, the original may not be set at the proper position and may be moved. The document is moved following the trailing edge of the document. The moving position of the sensor for detecting the trailing edge of the document is measured by the document size detecting means, and thereby the size of the document is detected.

In this way, the rear edge of the original is detected while the original cover is open, and the sensor for detecting the rear end of the original is moved to follow the rear end of the original until the original is set at the proper position. The size of the document can be detected by detecting the trailing edge of the document.

In addition, when the document trailing edge detection sensor is constituted by a pair of sensors, and when the trailing edge of the document is detected based on the output of the pair of sensors, the output level of each sensor may be the presence or absence of the document. It only needs to be able to identify the level of no manuscript,
Adjustment of the threshold value of the sensor is facilitated, and detection accuracy is also improved.

〔Example〕

FIG. 1 shows a copying machine having a document size detecting device according to an embodiment of the present invention.

In FIG. 1, a document table 12 is fixed on an upper surface of a copying machine main body 11, and a document cover 13 is mounted on the document table 12 so as to be openable and closable. On the right side of the copier body 11,
Paper cassettes 14 and 15 are removably mounted, and a paper discharge tray 18 for discharging copied paper is mounted on the left side.

Inside the copier body 11, an exposure device 19 for reading a document is provided above the copier body. The exposure device 19 includes an illumination unit 10 as a scanning unit having a light source and a first mirror, a mirror unit 16 including second and third mirrors, and further includes a lens, a reflection mirror, and the like. The illumination unit 10 is equipped with a sensor that also performs document detection and document trailing edge detection, as described later. The lower part of the illumination unit 10 along the document table 12 is indicated by a solid line in FIG. , Reciprocating between the maximum scan position indicated by the two-dot chain line. At each position, sensors 31 and 32 for detecting that the lighting unit 10 is located at those positions are provided.
The mirror unit 16 also reciprocates partly below the document table 12. Note that the home position of the illumination unit 10 must be set to a position where "document presence" can be detected when a document is set on the document table 12.

A photosensitive drum 20 on which an electrostatic latent image is formed is arranged at the center of the copying machine main body 11. Around the photosensitive drum 20, a charging device 21 for charging the photosensitive drum 20 to a predetermined charge, a developing device 22 for developing an electrostatic latent image, a transfer device 23 for transferring a toner image to paper, a photosensitive member Paper separating device 24 for separating paper from drum 20, and photosensitive drum 20
A cleaning device 25 for removing the upper residual toner is provided. A paper feed transport path 27 is provided between the paper feed cassettes 14 and 15 and an image forming unit including the photosensitive drum 20 and the like, and a paper discharge transport path 28 is provided downstream of the image forming unit. Have been. A fixing device 30 for fixing an image on the conveyed paper is provided between the paper discharge conveyance path 28 and the paper discharge tray 18.
Is arranged.

FIG. 3 shows the upper surface of the copying machine with the original cover 13 opened. The document cover 13 has hinge portions 2a and 2b.
The limit switch 4 is provided near the hinge 2b on the right side of the figure. The limit switch 4 is turned on and off by the hinge 2b, and detects the open / closed state of the document cover 13. In this embodiment, the limit switch 4 is turned on when the document cover 13 is lifted from the document surface of the document table 12 by about 80 mm, and depends on the sensitivity of the document detection sensor. Is to be detected.
As shown in FIG. 3, the original 1 is placed with its left end (hereinafter, the end in this direction is referred to as the front end) approaching the left end of the original table 12. I have.

FIG. 4 shows details of attachment of the document detection sensor. In this example, the case where the maximum document size is A3 is shown.

At the right end of the lighting unit 10 in the figure, a support member 9 is mounted in the width direction (vertical direction in FIG. 4). The document detection sensor 6 is arranged on the support member 9 at a position where the A4 horizontal size and the A5 vertical size can be distinguished in the width direction. Further, a projecting portion 8 projecting rightward in the figure is formed at the center of the support member 9, and a document detection sensor 7 is disposed at the tip of the projecting portion 8. Document detection sensor 7
Is composed of a pair of sensors 7a, 7b and 7c, 7d arranged in the scanning direction, and moves in the scanning direction to function as a sensor for detecting the trailing edge of the document. Each of the sensors 6 and 7 includes a light emitting element 6a, 7a, 7c and a light receiving element 6b,
This is a reflection type photo interrupter composed of 7b and 7d.

The copying machine has a control unit 35 as shown in FIG. The control unit 35 includes a CPU, a ROM, a RAM, an I / O port, and the like. The control unit 35 includes a home position detecting means 31 (switch 31 in FIG. 1), a maximum scan position detecting means 32 (switch 32 in FIG. 1), and a document cover open / close detecting means 4 (limit switch 4 in FIG. 3). ) Are connected to each other, and the light emitting elements 6 forming the sensors 6 and 7
a, 7a, 7c, light receiving elements 6b, 7b, 7d and other input sections 38 are connected. Similarly, the control unit 35 includes a scan motor control circuit 36 for driving a moving unit such as the illumination unit 10 and a copy operation unit 4 for performing a normal copy operation.
0 and other output units 39 are connected. Further, a scan motor 37 is connected to the scan motor control circuit 36. The control unit 35 and the scan motor control circuit 36 constitute a unit for detecting the movement position of the illumination unit 10, that is, the document detection sensor (document trailing edge detection sensor), and a unit for controlling the movement of the illumination unit 10. The control unit 35 constitutes means for detecting the size of the document.

Next, the operation will be described with reference to the flowcharts of FIGS. 5A and 5B. It is assumed that the main switch has already been turned on.

In step S1, it is detected from the signal from the limit switch 4 whether or not the document cover 13 is open. If the document cover 13 is closed, the process proceeds to step S2, and the lighting unit (hereinafter, referred to as scan) is operated by the switch 31.
It is determined whether or not 10 is at the home position (HP).
If the scan 10 is at the home position, the process proceeds to step S4 without moving the scan 10 (step S3), and the open / closed state of the document cover 13 is detected again. If the document cover 13 is closed, the process directly proceeds to step S6. If the document cover 13 is opened, the state of "no document" is set in the RAM of the control unit 35 in step S5, and the process proceeds to step S6. In step S6, it is determined whether the scan 10 is moving. When the original is not set on the original platen 12 first, the scan 10 does not move, and the process proceeds to step S7. In step S7, it is determined whether or not the copy key has been turned on. However, since no original has been set, the coby key has not been turned on, and the process returns to step S1.

Next, when the document cover 13 is opened and the limit switch 4 is turned on, YES is determined in step S1 and step S8 is performed.
Move to In step S8, it is determined whether or not the document detection sensor (first sensor) 7b detects "document presence". Until the document is placed on the document table 12, the determination is NO and the process proceeds to step S2, where steps S3 to S7 are processed in the same manner as described above, and the process returns to step S8.

If the original is placed on the platen 12, YES in step S8
And the process moves to step S10. In step S10, it is determined whether or not the document detection sensor (second sensor) 7d detects "document presence". In a state immediately after the document is placed on the document table 12, since the scan 10 is located at the home position, both the first sensor 7b and the second sensor 7d detect "document present". Therefore, the process proceeds to step S11. In step S11, it is determined whether or not the scan 10 is at the maximum scan position. Whether or not this is the maximum scan position is determined by whether or not the switch 32 is turned on. If the maximum scan position has not been reached, the scan 10 is moved to the rear end side of the document in step S12. The movement of the scan 10 is performed by the control unit.
A control signal is output from 35 to the scan motor control circuit 36,
This is performed by rotating the scan motor 37 in a predetermined direction. In this example, the scan 10 moves rightward in FIG. Thereafter, in step S6, it is determined whether the scan 10 is moving. In this case, since the scan 10 is moving, the process returns to the step S1, and the steps S8 → S10 → S11 → S12 → S6 → S1
→ Execute S8 → S10 repeatedly.

While the scan 10 is moving toward the rear end of the document, the second sensor
When 7d comes off the rear end of the document, the second sensor 7d detects "no document". As a result, NO is determined in step S10. The control unit 35 determines that the first sensor 7b
Since the sensor 7d indicates "no document", it is recognized that the document detection (document rear end detection sensor) sensor 7 is positioned at the rear end of the document. Accordingly, the process shifts to step S13, in which the control signal is output from the scan motor control circuit 36 to stop the rotation of the scan motor 37, thereby stopping the movement of the scan 10. Next, in step S14, the document size is detected. That is, the distance from the home position of the scan 10 to the stop position where the rear end is detected is the scan motor.
The control unit 35 calculates the rotation direction and the rotation angle of the 37, and the size of the document is detected based on the calculation result. Then, this detection result is stored in the RAM of the control unit 35.

Next, the process proceeds to step S6, where it is determined whether the scan 10 is moving. Since the scan 10 has been stopped in step S13, it is determined to be NO. And step
Move to S7 and wait for the copy key to be turned on. If the copy key is turned on, a paper cassette (paper size) is selected and an automatic magnification is set in step S15 based on the detection result of the document size, and a copy operation is performed in step S16. Will be Note that the automatic magnification is to calculate the magnification of a document and copy the selected paper when the paper of a predetermined size is selected in advance, and to set the magnification.

If it is determined in step S11 that the scan 10 has reached the maximum scan position, the process proceeds to step S17, where the scan 10 is stopped.In step S18, the document size is set to the maximum size in the RAM of the control unit 35. Remember.

If the original is set on the original platen 12 once the original cover 13 is opened and the original is removed after the scan 10 starts moving, if the original is removed at step S8 during the trailing edge detection operation of the original, "No" is determined, and the routine goes to Step S2. In step S2, it is determined whether the scan 10 is at the home position as described above. In this example, since scan 10 is once moved, it is determined that
The process moves to S9 and moves the scan 10 to the home position. Then, step until the scan 10 is at the home position, that is, until the switch 31 is turned on.
S6 → S1 → S8 → S2 → S9 are repeatedly executed, and when the switch 31 is turned on, the scan 10 is stopped in step S3. Thereafter, steps S4 to S7, steps S1 and S8, and S2 and S3 are executed, and the process waits for setting of a document.

Further, when a document is placed on the document table 12 with the document cover 13 opened, the document may not be set at a proper position. In this case, the original is moved on the original platen 12. In this case, the scan 10 is moved in the scanning direction by the above-described steps S8, S10 to S12, and by steps S8, S2, S9, and the trailing edge of the original is moved. When step S1 is detected
3 and step S14 are executed. In this way, when the document size is detected a plurality of times before the copy key is turned on, the document size data in the RAM of the control unit 35 is updated each time, and the latest data is stored.

As described above, the document size is detected by detecting the trailing edge of the document, and the movement of the scan 10 is controlled. If the originals have the same size in the scanning direction, the size in the width direction is detected by the sensor 6 and distinguished. That is, the fourth
In the illustrated example, the rear ends of the A4 horizontal size and the A5 vertical size are at the same position. Therefore, as described above, the sensor 6 is disposed at an intermediate position in the width direction between the A4 horizontal size and the A5 vertical size, and when the sensor 6 is on, the A4 horizontal size is used, and when the sensor 6 is off, the A5 vertical size is used. Judge. In addition, since the sensor 7 and the sensor 6 are displaced from each other in the scanning direction, if the document size is such that the sensor 6 is turned on, the sensor 7
Is turned on, the sensor 6 is always turned on, so that the sensor output can be prevented from being ambiguous.

In this embodiment, since the document size is detected with the document cover 13 opened, the document size can be reliably detected. Further, since it is not necessary to distinguish between the document and the back of the document cover as the sensor output, and a pair of sensors arranged side by side in the scanning direction detects the trailing edge of the document, each of the sensors has “document presence”. Any sensor capable of reading the two levels of "" and "no document" can be used, and the threshold adjustment of the sensor can be made rough. Also, the accuracy of document detection is improved.

If the document size detection result is displayed on the operation panel, the document size can be displayed with the document cover open in this embodiment, so that the operator can check the actual document and the size detection result. Can be checked to determine whether the detection result is correct, and copy errors can be eliminated.

[Other embodiments]

(A) FIG. 6 shows a document size detecting device according to another embodiment of the present invention. In this example, a support member 9 for supporting sensors 6 and 7 provided in a scan 10 is different from that of the above-described embodiment. That is, the support member 9 according to this embodiment
Is formed such that a protruding portion 8a at the center in the width direction extends to the vicinity of the rear end of the original of the minimum size in the scanning direction. A pair of sensors 7 is provided at the tip of the protruding portion 8a.

In such an embodiment, the time until the trailing edge of the document is detected can be reduced.

(B) FIG. 7 shows a document size detecting apparatus according to still another embodiment of the present invention. In this example, scan 10
Is located near the rear end of the smallest original in the scanning direction. According to this embodiment, similarly to the embodiment of FIG. 6, the time until the trailing edge of the document is detected can be reduced. Further, in this embodiment, after the detection of the document size is completed, the home position returns to the home position (the left end in the figure) similar to that of the conventional apparatus. However, during this movement, the image density detection for performing the automatic exposure is performed. And a pre-scan for automatic exposure can be omitted.

(C) In the above-described embodiment, the detection of the document and the detection of the trailing edge of the document are performed by the sensor 7. However, the detection of the document and the detection of the trailing edge of the document may be performed by different sensors. Good.

When the document detection sensor and the document rear end detection sensor are provided separately, the document rear end detection sensor may be moved from the rear end side of the document.

(D) In the above-described embodiment, the case where the maximum original size is A3 has been described. However, the present invention can be applied to a copying machine capable of copying a larger size, and the same effect as that of the above-described embodiment can be obtained. Play.

(E) In the above embodiment, the case where the support member 9 is fixed to the scan 10 and the document detection sensor 7 is attached to the support member 9 has been described. The supporting member may be provided with a document detection sensor and a document trailing edge detection sensor.

(F) In the above embodiment, a pair of sensors are provided in parallel in the original scanning direction as sensors for detecting the trailing edge of the original, but one sensor (7c, 7d in the above embodiment) The detection of the document and the detection of the trailing edge of the document may be performed by using this method. In this case, the output level from the light receiving element 7d is observed by the control unit 35, and when the output level reaches an intermediate level between "document present" and "document not present", this is recognized as the trailing edge of the document. Thus, the trailing edge of the document is detected.

(G) In the above embodiment, in the flowchart of FIG. 5A, if it is determined in step S1 that the document cover 13 is closed, it is detected in step S2 whether the scan 10 is in the home position. If it is not at the home position, the scan 10 is returned to the home position at step S9, but the scan 10 does not need to be particularly returned to the home position.

That is, the scan 10 only needs to be at the home position when the document cover 13 is opened. Therefore, in the flowchart of FIG.
If it is determined that the document cover 13 is closed in
It is also possible to skip step S2 and proceed directly to step S3 to stop the scan 10. Then, when the document cover 13 is opened, the scan 10 may be positioned at the home position, and scanning for document size detection may be started.

〔The invention's effect〕

According to the present invention, the size of the document is detected with the document cover opened, and the sensor for detecting the trailing edge of the document follows the trailing edge of the document until the document is set at a proper position on the platen. The document size is calculated based on the result.Therefore, unlike the conventional apparatus, the document size detection operation is not hindered by the closing operation of the document cover, and the document is moved on the document table. In this case, the size of the original can be reliably detected.

[Brief description of the drawings]

FIG. 1 is a sectional view of a copying machine having a document size detecting device according to an embodiment of the present invention, FIG. 2 is a block diagram of the copying machine, FIG. 3 is a top perspective view of the copying machine, and FIG. 5A and 5B are flow charts for explaining the operation of the document size detecting apparatus, and FIGS. 6 and 7 are views showing another embodiment of the present invention. 4 Limit switch, 6, 7 Original detection sensor and original trailing edge detection sensor, 9 Support member, 10 Illumination unit (scan), 12 Original platen, 13 Original cover, 35 …… Control unit, 36 …… Scan motor control circuit, 37
…… Scan motor.

Claims (2)

(57) [Claims] A document table having a document cover that can be freely opened and closed;
A scanning unit that optically scans a document placed on the document table by moving along the document table, wherein the document size detection device detects an open / closed state of the document cover. Opening / closing state detecting means, a document detecting means for detecting that a document is placed on the document table, and a movable means for moving in the scanning direction of the scanning means. A document trailing edge detection sensor for detecting the edge, and a document trailing edge identification for identifying from the output of the document trailing edge detecting sensor that the document trailing edge detecting sensor is positioned at the document trailing edge. Means, when the open / closed state detection means and the document detection means detect that the document cover is open and the document is placed on the document table, based on the identification result of the document rear end identification means. The document trailing edge detection And movement control means for moving so as to follow a difference in the trailing edge of the document, the document size detection means for detecting the document size by moving the position of the trailing edge detection sensor, document size detection device provided with a. 2. The document trailing edge detection sensor includes a pair of sensors arranged side by side in the scanning direction of the scanning unit and respectively detecting presence / absence of a document. When one of the sensors detects an output signal indicating presence of a document from one of the sensors, and the other sensor detects an output signal indicating absence of a document, the sensor for detecting the trailing edge of the document is recognized as being at the trailing edge of the document. The document size detecting device according to claim 1, wherein