JPS5889542A - Paper sheet detector - Google Patents

Abstract

PURPOSE:To limit influence of diffused light when a sheet is not present, by deflecting light irradiated from a light emitting means to a direction except a light receiving means. CONSTITUTION:A sensor 26 comprising a light emitting diode 28 and phototransistor 29 and a reflecting plate 27 are provided by interposing a conveying path 14. Then the reflecting plate 27 is diagonally placed by an angle theta with respect to the conveying direction of a sheet P. When the sheet P is placed in a detected position, light from the light emitting diode 28 is reflected by the sheet P to travel as shown by a broken line in the drawing and received by the phototransistor 29. While when the sheet P is not present, the light travels as shown by a one-dot chain line and is reflected by the reflecting plate 27 then guided to a direction dislocated from the direction toward the phototransistor 29. In this way, an influence of scattered light can be eliminated to surely detect the presence of the sheet of paper in no relation to its kind.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a paper sheet detection device that optically detects paper sheets, and particularly to a paper sheet detection device that irradiates light onto paper sheets and receives reflected light from the paper sheets. The system is designed to detect the presence of paper sheets.

Technical Background of the Invention In a copying machine, when a filter paper sheet (hereinafter simply referred to as a sheet) on which a copied image is formed is conveyed along a conveyance path, the sheet is placed at a predetermined position for the purpose of monitoring the conveyance state of the sheet. We are trying to detect whether or not it exists. Conventionally, sheet detection means for this purpose includes a light-emitting means for irradiating light onto the sheet and a light-receiving means for receiving reflected light from the sheet, which are disposed near the conveyance path. A sensor was used that detects changes in the amount of light received when the light is present and when it is not.

Problems with the Background Art The above-mentioned conventional technology has the following problems. In other words, when the sheet is not present at the detection position,
The light emitted from the light emitting means reaches various mechanical parts within the copying machine and is diffused by the mechanical parts. This diffused light is then received by the light receiving means.

Therefore, the light-M received by the light-receiving means is always present in some fabrics regardless of the presence or absence of a sheet. Moreover, the above-mentioned diffused light fluctuates depending on the displacement and movement of the mechanical parts of the copying machine.

Therefore, the amount of light received by the light receiving means when the sheet is not present fluctuates, making it difficult to determine the reference level when the sheet is not present, making it impossible to reliably detect the sheet.

Furthermore, since the difference in the amount of light received by the light receiving means when the sheet is present and when the sheet is not present is not large, the 8N ratio is small and there is a risk of erroneous detection.

OBJECTS OF THE INVENTION The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to provide a paper sheet detection device that can reliably detect sheets.

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention guides the light emitted from the light emitting means in a direction other than the light receiving means by means of a deflecting means such as a reflector when no sheet is present, and diffuses the light. This system suppresses the influence of light as much as possible to ensure sheet detection.

Embodiment of the Invention FIG. 1 is a front view of a copying machine embodying the invention. 1st
First, a brief explanation will be given of the copying machine shown in the figure.

This copying machine is composed of an upper frame 1 and a lower frame 2, and each frame 1, 2 is pivoted at a pivot point 3 so as to be openable and closable. The upper frame 1 is provided with an exposure section 4, a photosensitive drum 5, a charging section 6, a developing section 7, and a cleaning section 8.

The exposure unit 4 includes a table 9 on which a document is placed and moves back and forth, and a lamp 1 that illuminates the document placed on the table 9.
0, it has a lens 11 that forms an image of the original onto the photosensitive drum 5. The photosensitive drum 5 is designed to cure a photoconductive material such as selenium and rotate in the direction of the arrow shown in the figure. The charging unit 6 is a well-known corona charger that charges the photosensitive drum 5. The developing section 7 causes the toner stored therein to adhere to the photosensitive drum 5 by means of a developing roller 12 . The cleaning section 8 includes a rotating fur brush 13
This removes residual toner adhering to the photosensitive drum 5.

On the other hand, a sheet conveyance path 14 is provided in the lower frame 2 along a dividing line (shown by a two-dot chain line) between the two frames 1.2.

Further, a cassette 15 for storing sheets P, a roller 16 for supplying sheets P from this cassette 15, and a roller 16
(a registration roller 17 that aligns and feeds the sheet P supplied by the transfer unit 18, a transfer unit 18, a peeling unit 19, an adsorption conveyance bell)
20, a fixing section 21, and a paper discharge roller 22 are sequentially arranged along the conveyance path 14. The cassette 15 is a box that stores stacked sheets P, and is removably attached to the lower frame 2. The row 216 is a rubber roller, for example, and rotates at a predetermined timing to feed the sheet P from the cassette 15. The transfer section 18 is, for example, a corona charger, and transfers the toner image formed on the photosensitive drum 5 onto the sheet P.

The peeling section 19 peels off the photosensitive drum 5 (P). The belt 20 conveys the sheet P on which an unfixed toner image is formed while adsorbing it to the belt 20. The fixing section 21 heats and presses the sheet P in order to fix the toner image on the sheet P. The sheet) P that has been fixed by the fixing unit 21 is discharged onto a paper discharge tray 23 by a paper discharge roller 22. This paper output tray 2
3 is attached to the lower frame 2.

Note that the fan 24 provided in the upper frame 1 is used to cool the inside of the machine.

To briefly explain the operation of the copying machine configured as described above, first, a copying process is started by setting a document on the table 9 and operating a copy button (not shown). As the photosensitive drum 5 rotates, the table 9 also begins to move forward. The photosensitive drum 5 is uniformly charged in advance by the charging section 6. Next, the original is illuminated by the lamp 1o, and the reflected light from the original is guided to the photosensitive drum 5 by the lens 11.

In this way, the original is exposed to light, thereby forming a latent image on the photosensitive drum 5 in accordance with the image of the original. The photosensitive drum 5 further rotates, the latent image is developed by the developing section 7, and a toner image is formed.

On the other hand, the sheet P is fed from the cassette 15 to the conveyance path 14 by rollers 16, and further aligned by registration rollers 17, and then fed toward the photosensitive drum 5.

Then, the toner image formed on the photosensitive drum 5 is transferred onto the sheet P by the transfer section 18. The photosensitive drum 5 continues to rotate, and the untransferred remaining toner on the photosensitive drum 5 is removed by the cleaning section 8 and prepared for the next copying process. On the other hand, the sheet P after the transfer is peeled off from the photosensitive drum 19 by the peeling section 19 and sent to the belt 20. The belt 20 conveys the transferred image on the sheet P without disturbing it and sends it to the fixing section 21 . However, C)
The transferred image f of P is fixed by the fixing unit 21, and
P is discharged from the paper discharge roller 22 to the paper discharge tray 23 .

Now, in the conveyance path 14 of a copying machine having such a configuration, there is a sea)
A detection device 25 for detecting P is provided. In the example shown in FIG. 1, the detection device 25 is provided facing the belt 20 to ensure that the sheet P is transferred to the photosensitive drum 5 after transfer.
It is designed to detect that the sheet has been peeled off from the sheet and has been conveyed to the position of the belt 20.

The detection device 25 has a sensor 26 and a reflection plate 27. As shown in FIG. 2, the sensor 26 includes a light emitting diode 28 as a light emitting means and a phototransistor 29 as a light receiving means. Further, as shown in FIG. 2, the above-mentioned reflecting plate 27 as a deflection means is provided on the opposite side of the sensor 26 across the conveyance path 14.

This reflecting plate 27 is provided so as to be inclined by a certain angle 0 with respect to the conveying direction of the sheet P by the conveying path 14.

The light emitting diode 28 has its anode side connected to the power supply Vcc via a current limiting resistor 30, and its cathode side grounded. Further, the collector of the phototransistor 29 is connected to a power supply, and the emitter is grounded via a load resistor 31. Then, the output voltage is taken out from point A. This point A is the comparator 3
Connected to 2. The comparator 32 includes a resistor 33
．． A reference voltage divided by 34 is also input.

Resistor 33 is connected to power supply Vcc. The comparator 32 compares the reference voltage with the output voltage at point A, and outputs a detection signal when the output voltage at point A is equal to or higher than the reference voltage.

As shown in FIG.
When in the detection position facing the light emitting diode 28
The light from the phototransistor 29 travels as shown by the broken line, is reflected by the sheet P, and is received by the phototransistor 29.

When the phototransistor 29 receives light, an emitter current flows, causing a voltage drop due to the load resistor 31, and a voltage corresponding to the current flowing to the point A is generated.In addition, if the sheet P does not exist, the light emitting diode 28 The light from the phototransistor 29 travels as shown by the dashed line in the figure, is reflected by the reflecting plate 27, and is guided in a direction away from the phototransistor 29.

Such a relationship will be explained in more detail with reference to FIGS. 3 and 4.

In FIG. 3, the light emitted from the center of the light emitting diode 28 is reflected by the C12 reflection plate 27.
If the path reflected by C2v is the path reflected by the light emitting diode 28 (see), the path reflected by P is a1 and the path reflected by the reflector 27 is b, then both the center light and the leakage light from the light emitting diode 28 are It can be seen that the light is guided in a direction away from the phototransistor 29 by the reflection plate 27.

In addition, in FIG. 3, the distance between the sensor 26 and the conveyance path 14 is d.
When the distance between the ie sensor 26 and the reflection &27 is d2, the output voltage at the point A mentioned above is plotted as shown in Figure @4.

In FIG. 4, the horizontal axis represents the above-mentioned distances dl and d2, and the vertical axis represents the output voltage at point A. Furthermore, in Figure 4,
Data is plotted for various sheets; for example, output voltages are shown for 90% reflectance white paper, straw paper, 0HP (Over Rad Projector) paper, and black paper.

As can be seen from Figure 4, the distance dl for each sheet is
The output voltage is maximum when . This is uniquely determined from the arrangement state of the sensor 26. FIG. 4 shows that when the distance between the reflector 27 is d2 and the angle θ of the reflector 270 is θ-0° and θ-20°, the output voltage based on the reflected light from the reflector 27 is , Y.

As is clear from FIG. 4, the reflection plate 27 is tilted so that θ
The output voltage V6 due to the reflected light from the reflection plate 27 when the angle is −20° is much smaller than the output voltage V4 when there is black paper at the distance d1, and there is a certain level difference between the two. Therefore, a sufficient signal-to-noise ratio can be secured. If this is the case,
Assuming that the angle of the reflection plate 27 is θ=00, the output voltage 5 at this time is not much different from the voltage v4, and there is almost no difference in level between the two. Therefore, the SN ratio is small and there is a risk of erroneous detection.

Furthermore, the output voltage 6 at point Y in Figure 4 is much smaller than the output voltage V 1 y V2 y 3 when various sheets are present, and there is a sufficient level difference between them. .

Therefore, the reference voltage of the comparator 32 is set to the output voltage Vs at point Y (When the reflecting plate 27 is tilted by θ=20°, the light emitted from the light emitting diode 28 is reflected by the reflecting plate 27, and this reflected light By setting the level slightly higher than the voltage at point A when the light is received by the phototransistor 29, the presence of various sheets can be reliably detected.

In the above example, the reflective plate 27 was provided separately, but the inclined surface of the bottom plate of the cleaning section 8 may be used instead.

As described in detail, according to the present invention, the influence of scattered light can be eliminated and the presence of paper sheets can be reliably detected regardless of the type of paper sheet.

[Brief explanation of the drawing]

Fig. 1 is a front view of one embodiment of the present invention, Fig. 2 is a circuit diagram showing the configuration of the main part of the detection device of the same embodiment, Fig. 3 is an explanatory diagram of the operation of the same embodiment, and Fig. 4 is the same example. FIG. 3 is an explanatory diagram for explaining the characteristics of the detection device of FIG. P...Sheet, 27...Reflector. 28...Light emitting diode, 29...Phototransistor. Agent: Patent attorney Noriyuki Chika (and 1 other person) Figure 3? r? 4 4th Figure 1 d-z Blood Dragon 237-

Claims (1)

[Claims] A light emitting means for irradiating light onto paper sheets, a light receiving element for receiving light irradiated by the light emitting means and reflected from the paper sheets, and a light receiving element for receiving light irradiated from the light emitting means toward the paper sheets. A paper sheet detection device comprising: deflection means for directing the light receiving element in a direction other than the light receiving element when the paper sheet is not present.