JPH0687550A - Sheet material detecting device - Google Patents

Abstract

PURPOSE:To enable the detection of various sorts of sheet materials such as common paper and an OHP sheet, and eliminate wrong detection caused by the influence of paper powder or the like. CONSTITUTION:A housing 1 has wall parts 1a, 1b provided opposedly in the passing positions of sheet material 5. The wall parts 1a, 1b are provided with light transmission apertures 4a, 4b in the positions shifted from a vertical line to the sheet material carrier face, and elements 2, 3 are disposed in line with an optical axis passing these light transmission apertures 4a, 4b. The element on the lower side of the passing sheet material is provided avoiding an area 6 directly below the light transmission aperture 4b. At the time of the sheet material passing a sensor part, dust 7 such as paper powder falls into the housing 1 through the light transmission aperture, but this dust 7 does not fall on the element but is discharged inside of the housing 1 or outside of the housing 1 from an opening part opened at the part, positioned directly below the light transmission aperture, of the housing 1. Since transmittance is decreased by reducing the angle of incidence theta to the sheet face, the angle of incidence theta is set to an angle smaller than the angle where the transmittance becomes the threshold of the light receiving element or less so as to enable the detection of an OHP sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet material detecting device for determining the presence or absence of a sheet material and the type of the sheet material according to the amount of light incident on a light receiving portion.

[0002]

2. Description of the Related Art Image forming apparatuses such as copiers and facsimiles have been highly functionalized and processed at high speed. Due to diversified usage patterns, various sheet materials such as plain paper and OHP have been used. . An actuator type sensor, a transmission type sensor, and a reflection type sensor are used to detect these sheet materials. In the actuator type, as shown in FIG. 3, a detection lever 11 is provided on a chute 10 that guides the conveyance of the sheet material 5, and the tip of the chute material abuts against this detection lever, and the switch 12 is turned on by falling in the conveyance direction. The sheet material is detected by turning it off.

In the transmissive sensor, as shown in FIG. 5, a light emitting element 2 and a light receiving element 3 are arranged in a direction perpendicular to a conveying surface of a sheet material 5, and the sheet material blocks light emitted from the light emitting element 2. The sheet material is detected from the change in the amount of light incident on the light receiving element 3 due to the above. As shown in FIG. 6, the reflection type sensors are arranged at a predetermined angle with respect to the conveying surface of the sheet material 5, and are reflected by the light emitted from the light emitting element 2 on the surface of the sheet material on which the image 9 is formed. The sheet material is detected from the change in the amount of light incident on the light receiving element. This type of sheet detecting device is disclosed in, for example, Japanese Patent Laid-Open Nos. 60-216359, 61-235337 and 61-290434.
Has been proposed in the issue.

[0004]

By the way, in a digital copying machine which does not require an optical system carriage, the gap between the sheets is made as narrow as possible in order to improve the productivity of copying. It could not be mechanically reduced to below a certain level. If the gap between the sheets becomes narrow, the actuator cannot be turned on and off, and the gap cannot be detected. Further, as shown in FIG. 3, the detection lever 11 becomes a load and causes damage to the leading edge of the sheet 5a and skew 5b.

On the other hand, in the case of the optical sensor, the transmissive sensor is O
It is impossible to detect the HP sheet, and when the light receiving element and the light emitting element are arranged at the upper and lower positions, paper dust or the like is accumulated in the lower element, which causes a malfunction. Further, since the reflection type sensor is affected by the color of the paper to be detected, it may not be possible to detect if an image is present during double-sided copying, resulting in a false detection. An object of the present invention is to provide a sheet material detection device capable of detecting various sheet materials such as plain paper and OHP sheets and eliminating erroneous detection due to the influence of paper dust and the like.

[0006]

In order to achieve the above object, the present invention has a wall portion facing the sheet material conveying surface, and the light passage window provided on each wall portion is aligned with the optical axis. In a sheet material detecting device in which an optical sensor including a light emitting element and a light receiving element is disposed, one element of the optical sensor disposed below the passing sheet material is defined as the light passage window of the lower side wall and the sheet. The material is arranged at a position avoiding the outer region of the lower side wall portion which faces the material in the vertical direction. In another invention, in the above invention, the angle formed by the optical axis of the light beam incident from the light emitting element to the light receiving element and the sheet material conveying surface is set so that the transmittance of the sheet material is equal to or less than the threshold value of the light receiving element. In the configuration. Still another invention is provided with a housing having a wall portion provided with a light passage window as a part, wherein an optical sensor is arranged in the housing, and an opening is provided in a housing portion located directly below the light passage window. The dust is discharged from the sheet material that falls through the light passage window from the opening.

[0007]

In the case of a light-impermeable sheet material, it is detected by a large change in the electric signal emitted from the light receiving element. Further, in the case of a light-transmissive sheet material such as OHP, the transmittance decreases as the incident angle to the sheet surface is reduced. Therefore, by setting the angle smaller than the angle at which the transmittance is equal to or less than the threshold value of the light receiving element, the OHP The film can be detected. Dust such as paper dust that comes out of the sheet material falls into the housing through the light transmission window, but since the element of the optical sensor is not arranged in this area, it is not affected by the dust. In particular, in the case where an opening is provided in the housing directly below the light transmission window, the dust that has fallen is discharged to the outside from the opening without accumulating in the housing.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the sheet material detection device of the present invention. The housing 1 of the sheet material detection device has wall portions 1a and 1b provided to face a position where the sheet material 5 passes.
And the elements 2 and 3 of the photosensor are arranged inside this wall. Further, light transmission windows 4a and 4b are provided on the wall portion at positions displaced from the vertical line with respect to the sheet material conveying surface. The elements 2 and 3 have two light transmission windows 4
They are arranged so as to coincide with each other on the optical axis passing through a and 4b. That is, the optical axis of the element is tilted at an angle θ with respect to the sheet material conveying surface. In this example, the light emitting element 2 is arranged on the upper side of the sheet material 5, and the light receiving element 3 is arranged on the lower side.

The light receiving element 2 arranged below the sheet material passing therethrough has a region 6 directly below the light passage window 4b of the lower side wall 1b.
That is, the sheet material 5 is arranged at a position avoiding the outer region of the lower side wall portion passing through the light transmitting window in the vertical direction. When the sheet material 5 passes through the sensor portion of the housing 1, dust 7 such as paper dust falls into the housing through the lower light transmission window 4b. This dust 7 is, as shown in FIG.
It is stored inside the housing 1. Alternatively, as shown in FIG. 2, the particles are discharged to the outside through an opening 8 formed in the housing 1 located directly below the light transmission window 4b.

The sheet detecting operation of the above embodiment will be described. When the sheet material 5 passes through the housing 1, the optical axis of the sensor is blocked, so that the amount of light incident on the light receiving element 3 changes. The sheet material is detected by processing the electric signal from the light receiving element 3 at this time. Films such as OHP sheets have an incident angle θ with respect to the sheet surface of 90.
If you tilt it from 0 ° to 0 °, the transmittance will decrease.
When the OHP sheet is provided, the incident angle θ is arranged in a positional relationship where the light receiving element cannot detect it. Here, the incident angle θ is set to an angle smaller than the angle at which the transmittance is equal to or less than the threshold value of the light receiving element.

[0011]

As described above, according to the present invention, since the element of the optical sensor is arranged so as not to be directly below the light transmitting window on the lower side of the sheet material, paper dust falling from the light transmitting window, etc. It is possible to eliminate malfunctions due to erroneous detection caused by the accumulation of dust in the element. In addition, by setting the angle between the optical axis of the light beam incident on the light receiving part and the sheet material conveying surface to be less than the threshold value of the light receiving element, the sheet material that transmits light can transmit the light transmitted by the reflected light. Can be detected from the decrease of Further, since the housing is provided with an opening that faces the light transmitting window in the vertical direction, dust falling from the light transmitting window is directly discharged from the opening, which facilitates maintenance of the optical sensor.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a sheet material detecting device of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the sheet material detecting device of the present invention.

FIG. 3 is a cross-sectional view of a conventional actuator type sheet material detection device.

FIG. 4 is a diagram illustrating an operation of an actuator type.

FIG. 5 is a cross-sectional view of a conventional transmission type sheet material detection device.

FIG. 6 is a cross-sectional view of a conventional reflection type sheet material detection device.

[Explanation of symbols]

1 housing, 2 light emitting element, 3 light receiving element, 4a,
4b light transmitting window, 5 sheet material, 6 dust falling area, 7
Dust (paper dust), 8 openings

Claims (3)

[Claims] 1. A wall portion facing a sheet material conveying surface,
In a sheet material detection device in which an optical sensor composed of a light emitting element and a light receiving element is arranged by aligning a light passage window provided on each wall portion with an optical axis, an optical sensor arranged below a passing sheet material. The sheet material detection device, wherein one of the elements is arranged at a position avoiding an outer region of the lower wall portion where the light passage window of the lower wall portion and the sheet material face each other in the vertical direction. 2. The angle formed by the optical axis of the light beam incident on the light receiving element from the light emitting element and the sheet material conveying surface is set so that the transmittance of the sheet material is equal to or less than the threshold value of the light receiving element. The sheet material detection device according to claim 1. 3. A housing including a wall portion provided with a light passage window as a part, wherein an optical sensor is disposed in the housing, and an opening is provided in a housing portion located directly below the light passage window. 2. The sheet material detecting device according to claim 1, wherein dust emitted from the sheet material falling through the light passage window from the opening is discharged.