JPH0967045A - Sheet detecting mechanism and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a sheet correctly and facilitate the cleaning of a protective cover by providing the transparent protective cover, fitted to an opening part provided at a sheet placing member, in an inclined state to a placing face, and detecting reflected light, reflected by the sheet placed on the placing member, by a light receiving member. SOLUTION: In the case of executing mechanism that can detect the size of a document sheet G set on a document tray 1 as sheet detecting mechanism of an image forming device, an opening part 1a is provided in a specified position of the document tray 1 and a reflecting type photo-sensor 23 composed of a light emitting member 23a and a light receiving member 23b so as to serve as a sheet detecting sensor is provided below the opening part 1a. A dust protective cover 25 is fitted to the opening part 1a. This protective cover 25 is formed of material of high transparency and high transmittance of infrared rays and fitted in an inclined state to a document placing face 1c. Sheet detection without wrong detection can thereby be performed, and the cleaning of the protective cover 25 is facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet detecting mechanism for detecting a sheet such as an original sheet or a recording sheet, and an image forming apparatus using the sheet detecting mechanism.

[0002]

2. Description of the Related Art In many image forming apparatuses such as copying machines, an automatic document feeder is used. However, as shown in FIG. 7 (a), this automatic document feeder is of fixed original type. There are a reading method and an original moving type reading method as shown in FIG.

In the original fixed type reading system shown in FIG. 7A, an operator places an original sheet G on a tray 50 and sets both ends of the sheet G in the width direction to the side regulating members 51. . Then, when the start key is pressed, the rollers 52 rotate to separate and convey the original sheets G one by one, and the front and rear ends of the original sheets G are detected by the sensor 53, and are fed onto the platen glass 55 by the conveying belt 54. In this state, the light source 56 and the scanning mirror 57 are scanned to platen glass.
The document sheet information on 55 is read, and the document sheet G is discharged to the discharge section 58.

On the other hand, in the original moving type reading method shown in FIG. 7B, the operator places the original sheet G on the tray 60 and aligns the widthwise ends of the sheet G with the side regulating members 61. set. When the start key is pressed, the rollers 62 rotate to separate and convey the original sheets G one by one, and the sensor 63 detects the front and rear ends of the original sheets G, and the light source 64 and the mirror fixed during the conveyance. The document sheet information is read by 65 and the document sheet G is discharged to the discharge tray 66.

In the above-mentioned original reading method, when the automatic sheet selection mode for automatically selecting the size of the recording sheet according to the original size is set, the original sheet G
When the document is set, the side regulating members 51 and 61 detect the document width and the conveyed document sheet G is detected by the sensor.
The size of the original is determined by detecting the length of the original based on the time passing through 53 and 63. Then, a cassette of recording sheets suitable for the original size is selected, and the recording sheets are conveyed to record an image. At this time, if there is no recording sheet that matches the original size, and if the automatic scaling mode is set, the image is recorded by automatically scaling the size of the existing recording sheet. .

In the automatic sheet selection mode, the recording sheet cannot be conveyed until the original sheet G passes the positions of the sensors 53 and 63, and the operator presses the start key and then the recording is started. The time until the sheet is conveyed (first copy time) becomes long.

If the original sheet size and the recording sheet size are different, the automatic scaling mode is selected to select whether or not to continue the copy operation. At this time, when the copying operation is stopped, it is necessary to remove the original sheet on the platen glass 55 because it is already fed in the fixed original reading method. Further, in the moving document reading method, it is necessary to return from the discharge tray 66.

Therefore, in the automatic sheet selection mode and the automatic variable magnification mode, the original copy sheet is not required to be removed even if the original sheet size and the recording sheet size are different from each other without increasing the first copy time. There is a device in which the size of the original can be detected when G is set on the trays 50 and 60. For example, when the original sheets G have the same width but different lengths, such as A3 and A4 sizes, A4 size originals are set on the trays 50 and 60 as shown in FIG. 8A. In this case, an opening 70 is provided at a position where an A3 size original is set, and a reflection type photo sensor including a light emitting element 71a and a light receiving element 71b is provided below the opening 70.
71 is provided to detect the A3 size and the A4 size depending on whether or not the document sheet exists at the position of the opening 70.

In the structure in which the size of the original is detected by the photo sensor 71 set in the tray, a transparent protective cover 72 is attached to the opening 70 and the photo sensor 71 is attached.
We are trying to protect it from dust.

[0010]

As described above, when the size of the original document on the tray is detected by the photo sensor 71,
When the original sheet G has a high light reflectance such as white, and when the original sheet G has a low light reflectance such as black, the light emission amount of the light emitting element 71a is increased and the light receiving element is used to detect the original reflected light. It is necessary to increase the light receiving sensitivity of 71b. At this time, as shown by the alternate long and short dash line in FIG. 8A, the light receiving element 71b may detect the light specularly reflected by the transparent protective cover 72, and a document having a light reflectance lower than that of the transparent protective cover 72 may be detected. Difficult to detect on the tray.

Therefore, as shown in FIG. 8 (b), the transparent protective cover 72 is lowered below the surface of the trays 50 and 60 so that the light specularly reflected by the transparent protective cover 72 does not enter the light receiving element 71b. However, if this is done, it is necessary to make a deep step h between the surfaces of the trays 50 and 60 and the surface of the transparent protective cover 72, and it becomes difficult to clean the transparent protective cover 72 when removing dirt. . Further, when the transparent protective cover 72 is not attached to the opening 70 and is integrally configured with the photo sensor 71,
The transparent protective cover 72 can be easily cleaned by removing the photosensor 71, but foreign matter may enter through the opening 70.

The present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to detect a sheet accurately and to easily clean the transparent protective cover from dirt. A sheet detection mechanism and an image forming apparatus using the sheet detection mechanism are provided.

[0013]

A typical structure according to the present invention for achieving the above object is a sheet placing member for placing a sheet, and an opening provided in the sheet placing member. A light emitting member that emits light through the opening, a light receiving member that detects reflected light that is emitted from the light emitting member and reflected by a sheet placed on the sheet placing member, and transparency attached to the opening And a protective cover, and the protective cover is inclined with respect to the sheet mounting surface of the sheet mounting member to configure the sheet detection mechanism.

In the above structure, when the light from the light emitting member irradiates the sheet through the protective cover, since the protective cover is inclined with respect to the sheet surface, the light regularly reflected by the protective cover. Is not detected by the light receiving member,
Even if the sensitivity of the sensor is increased, the sheet will not be erroneously detected.

Since the protective cover can be provided near the sheet mounting surface, the surface can be easily cleaned.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of an image forming apparatus using a sheet detecting mechanism according to the present invention will be specifically described with reference to the drawings.

[First Embodiment] FIG. 1 is an explanatory view of the entire structure of an image forming apparatus, FIG. 2 is an explanatory view of a top surface of a document sheet placing member, FIG. 3 is an explanatory view of a sheet detecting structure, and FIG. FIG. 4 is an explanatory diagram of a photo sensor.

Here, as the order of description, the overall structure of the image forming apparatus will be described first, and then the structure of the sheet detecting mechanism will be described.

{Overall Structure of Image Forming Apparatus} This image forming apparatus is an original moving type automatic reading type electrophotographic copying machine, and original information read by an original reading apparatus A arranged above the apparatus is arranged below the apparatus. The recording is performed by the recording device B.

In the document reading device A, the side regulating members 2 are slidably brought into contact with the widthwise ends of the document sheet G placed on the document tray 1 which is a sheet placing member to set the document, and the operator makes a copy. When the start key is pressed, the feeding roller 3a is rotated to send out the original sheet G and the separating roller 3a.
The sheets are separated and fed one by one by b, and discharged onto the discharge tray 4 by the pair of conveying rollers 3c and the pair of discharging rollers 3d.
Then, while the original sheet G is conveyed between the conveying roller pair 3c and the discharging roller 3d, the light source 5 irradiates the light, and the reflected light is radiated through a plurality of mirrors 6 and a lens 7 to CC.
The light is condensed on the photoelectric conversion element 8 such as D and converted into an electric signal.

On the other hand, in the recording apparatus B, among the recording sheets P stacked and housed in the plurality of cassettes 9, the recording sheet P that matches the size of the original read by the reading apparatus A is sent by the pickup roller 10 and a pair of conveying rollers.
The sheet 11 is conveyed to the registration roller pair 13 by the conveyance guide 12. Then, the registration roller pair 13 is driven at the image forming timing to convey the recording sheet P, and an image is formed by the image forming means. This image forming means is an electrophotographic image forming system, and uniformly charges the surface of the photosensitive drum 14 which rotates in accordance with the image operation,
A laser beam is applied to the optical system 15 from the optical system 15 according to an image signal to form an electrostatic latent image, and the latent image is developed with a toner by a developing device 16 to be visualized. The toner image is transferred onto the recording sheet P by the transfer device 17 to form an image.
Incidentally, the toner remaining on the photosensitive drum 14 after the toner transfer is removed by the cleaning device 18.

The recording sheet P on which the toner image is transferred as described above is conveyed to the fixing means 20 by the conveying belt 19,
In the fixing means 20, heat and pressure are applied to fix the toner image, and the toner image is discharged to the discharge tray 21.

When images are recorded on both sides of the recording sheet P, the recording sheet P passing through the fixing means 20 is not discharged to the discharge tray 21, but is sent to the reverse resending path 22 and the pair of registration rollers 13 is again used. It is configured to be conveyed to and to record an image on the back surface.

{Sheet Detecting Mechanism} The image forming apparatus has, as a sheet detecting mechanism, a mechanism capable of detecting the size of the document sheet G set on the document tray 1. Next, the configuration will be described by taking a configuration for detecting A3 size and A4 size as an example.

As shown in the top view of the document tray 1 shown in FIG. 2, an opening 1a is provided at a predetermined position of the document tray 1. The position where the opening 1a is provided is such that when the leading edge of the original sheet G is abutted against the abutting shutter 1b provided on the original tray 1, the original sheet G of A4 size is set.
In the case of 1, it does not take place, and in the case of the A3 size original sheet G2, it is provided at such a position.

Below the opening 1a, as shown in FIG.
As shown in FIG. 2 (an explanatory view around the opening viewed from the direction of arrow a in FIG. 2), a reflective photosensor 23 including a light emitting member 23a and a light receiving member 23b as a sheet detecting sensor is provided.
The photo sensor 23 emits a light beam in an infrared region and receives a reflected light thereof in order to prevent erroneous detection of a sheet due to external light such as an interior light. Further, in order to enhance the directivity of the light emitting member 23a, the light emitting member 23a is surrounded by a slit cover 24 made of a material having a low reflectance. This slit cover
24 is a top view of the photo sensor 24 in FIG. 4 (a), and (b) is
(a) is a cross-sectional view taken along the line bb, and (c) is a cross-sectional view taken along the line cc of (a).) The light-emitting member 23a and the light-receiving member 23b are partitioned to prevent detection of direct light rays. Has a shielding plate 24a and slits 24b for giving directivity to each of the light emitting member 23a and the light receiving member 23b, and infrared light emitted from the light emitting member 23a passes through the slit 24b and is emitted upward. When the original sheet G is present on the opening 1a after passing through the opening 1a provided in the original tray 1, the light reflected by the original sheet G enters the light receiving member 23b. On the other hand, when the document sheet G is not present on the opening 1a, the infrared light emitted from the light emitting member 23a is not reflected, and therefore the infrared light is not incident on the light receiving member 23b. This makes it possible to detect the presence or absence of the original sheet G on the opening 1a.

Therefore, the document size is detected by the document sheet G.
The leading end of the sheet is abutted against the abutting shutter 1b on the tray 1, and the side regulating member 2 is slid in the direction of arrow d in FIG. At this point, the recording sheet size that matches the position of the regulating member 2 can be detected. That is, when the document width size is single, the recording sheet size suitable for the document size can be determined at that time.

On the other hand, when the document widths are the same and the lengths are different, such as A3 size and A4 size, the regulating member 2
Even if the position of is detected and the document width is detected, the size of the recording sheet cannot be determined by itself. Therefore, in that case, if the sensor 23 detects the original sheet G, the A3 size is determined by the signal from the photo sensor 23, and if the sensor 23 does not detect the original sheet G, the A4 size is determined. Determine the recording sheet size according to the result.

In this way, the original sheet size can be detected when the original sheet G is set on the original tray 1, and the recording sheet size suitable for this can be determined.

Now, in the above structure, a dustproof protection cover 25 is attached to the opening 1a provided in the document tray 1 as shown in FIG. 3 so as to prevent dust and the like from entering through the opening 1a. The protective cover 25 is made of a material having high transparency and a high infrared light transmittance. And
The protective cover 25 is attached so as to be inclined with respect to the document stacking surface 1c of the document tray 1 (in the present embodiment, inclined downward to the left in the document sheet feeding direction). The protective cover 25 is provided in the vicinity of the document placing surface 1c.

As described above, the protective cover 25 is attached to the document placing surface 1
Even if it is provided in the vicinity of c, by providing the protective cover 25 at an inclination, as shown by the one-dot chain line in FIG.
Even if infrared light is specularly reflected by the protective cover 25 upon irradiation from a, the light does not enter the light receiving member 23b, and the protective cover 25 is not erroneously detected as a document sheet.

Further, since the protective cover 25 is located in the vicinity of the upper surface of the tray 1, it is easy to remove dust and the like accumulated on the upper surface of the protective cover 25. Therefore, erroneous detection due to dirt on the protective cover 25 can be prevented.

[Other Embodiments] In the above-described first embodiment, an example in which the inclined surface of the protective cover 25 is a single surface is shown. However, as shown in FIG. You may make it have an inclined surface. With this configuration,
Similar to the first embodiment, even if the light emitted from the light emitting member 23a is specularly reflected by the inclined surface, it does not enter the light receiving member 23b, and the cleaning of the upper surface of the protective cover 25 is easier. .

Further, in the above-described first embodiment, an example in which the inclination of the protective cover 25 is inclined downward and leftward in the document sheet feeding direction is shown, but the inclination direction is not particularly limited. For example, as shown in FIG. 6 (an explanatory view around the opening viewed from the direction of arrow e in FIG. 2), the same effect as that of the first embodiment can be obtained even if it is configured to incline downward in the document sheet feeding direction. You can get it.

In the first embodiment described above, the moving original reading system is exemplified, but the fixed original reading system can be similarly applied.

Further, in the above-described first embodiment, an example in which the sheet detecting mechanism is used for detecting the size of the original sheet G is shown, but the sheet detecting mechanism is also used for detecting other sheets. It can be preferably used. For example, in the above-described image forming apparatus shown in FIG. 1, the recorded recording sheet P is discharged to the discharge tray 21, but when a discharge processing device such as a sorter or a finisher is installed in this discharge section, the operator Before performing a sheet discharge operation such as stapling or sorting, it must be detected that the recording sheet P by the previous operation is not left on the sheet discharge processing device. At this time, similarly to the above-described first embodiment, an opening is provided at a predetermined position of the discharge tray 21, a photo sensor 23 is provided below the opening, and a protective cover is provided in the opening at an inclination. This makes it possible to detect whether or not the recording sheet P is discharged onto the discharge tray 21.

In the above-described first embodiment, the copying machine is exemplified as the image forming apparatus. However, such as a facsimile apparatus, an apparatus for receiving and discharging the recording sheet when the operator is not near the apparatus. In this case, the sheet detection mechanism described above may be used to detect that the recording sheet has been ejected to the ejection portion, and to notify the receipt by sound or a lamp.

[0038]

Since the present invention is configured as described above, when the light from the light emitting member irradiates the sheet through the protective cover, the protective cover is inclined with respect to the sheet surface, and therefore the protective cover is inclined. The light reflected by the cover is not detected by the light receiving member, and the sheet will not be erroneously detected even if the sensitivity of the sensor is increased.

Further, since the protective cover can be provided near the sheet mounting surface, the surface can be easily cleaned.

[Brief description of drawings]

FIG. 1 is an overall configuration explanatory diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a top view illustrating a document sheet mounting member.

FIG. 3 is an explanatory diagram of the periphery of an opening as viewed in the direction of arrow a in FIG.

4A and 4B are explanatory views of the photosensor, where FIG. 4A is a top view of the photosensor 24, FIG. 4B is a sectional view taken along the line bb of FIG. 4A, and FIG.
FIG. 7A is a sectional view taken along the line cc of (a).

FIG. 5 is an explanatory diagram of a protective cover having two inclined surfaces.

FIG. 6 is an explanatory diagram of a protective cover having a different inclination direction from that of the first embodiment.

7A and 7B are explanatory diagrams of an automatic document feeder, FIG. 7A is a document fixed type device, and FIG. 7B is a document movable type device.

FIG. 8 is a diagram illustrating a relationship between a sheet detection sensor and a protective cover according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Original document tray, 1a ... Opening portion, 1b ... Impact shutter,
1c ... Original mounting surface, 2 ... Side regulating member, 3a ... Feed roller, 3b ... Separation roller, 3c ... Conveying roller pair, 3d ...
Ejection rollers, 4 ... Ejection tray, 5 ... Light source, 6 ... Mirror,
7 ... Lens, 8 ... Photoelectric conversion element, 9 ... Cassette, 10 ... Pickup roller, 11 ... Conveying roller pair, 12 ... Conveying guide, 13 ... Registration roller pair, 14 ... Photosensitive drum, 15 ... Optical system, 16 ... Development Container, 17 ... transfer device, 18 ... cleaning device,
19 ... Conveyor belt, 20 ... Fixing means, 21 ... Discharge tray, 22 ...
Inversion retransmission path, 23 ... Photo sensor, 23a ... Light emitting member, 23
b ... light receiving member, 24 ... slit cover, 24a ... shielding plate, 24
b ... slit, 25 ... protective cover

Claims (6)

[Claims] 1. A sheet mounting member for mounting a sheet, an opening provided in the sheet mounting member, a light emitting member which irradiates light through the opening, and a sheet which is irradiated from the light emitting member. A light receiving member that detects reflected light reflected by the sheet placed on the placing member, and a transparent protective cover attached to the opening, and the protective cover is mounted on the sheet placing member. A sheet detection mechanism, which is provided so as to be inclined with respect to a placement surface. 2. The sheet detecting mechanism according to claim 1, wherein the protective cover is provided in the vicinity of the sheet mounting surface. 3. An image forming apparatus for conveying an original sheet to form an image on a recording sheet, an original reading unit, an image forming unit for forming an image on the recording sheet, and the image forming apparatus according to claim 1 or 2. An image forming apparatus comprising: the sheet detection mechanism described above. 4. The image forming apparatus according to claim 3, wherein the sheet detection mechanism detects a document sheet read by the document reading unit. 5. The image forming apparatus according to claim 3, wherein the sheet detecting mechanism detects a recording sheet on which an image is formed by the image forming unit. 6. The image forming apparatus according to claim 4, wherein the image forming apparatus has a regulating member for regulating both widthwise ends of the original sheet or the recording sheet.