JPS5889541A - Optically detecting method of sheet in sheet conveyer - Google Patents

Abstract

PURPOSE:To surely detect the presence of a sheet whatever kind of the sheet may be, by using a paper feed cassette different for each kind of the sheet and changing threshold level comparable reference voltage interlocking to the paper feed cassette. CONSTITUTION:A paper feed cassette 9 is provided for every kind of a sheet, and a protrusion 10 is arranged to the cassette as an identifying means in accordance with a kind of the sheet accommodated. Then a switch 11 cooperatively actuated with the protrusion 10 is provided in a copying machine main unit (not shown in the drawing), operated by the protrusion 10 and formed such that threshold level comparable reference voltage of a comparator (not shown in the drawing) is set to an optimum value for a kind of the sheet detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical sheet detection method in a sheet conveying device such as a copying machine that feeds sheets using a sheet feeding cassette.

2. Description of the Related Art As a sheet detection device used for detecting a jam in a copying machine, one having the configuration shown in FIG. 1 using an optical sensor is known. In the figure, / is an optical sensor for sheet detection, and the output voltage increases or decreases depending on the presence or absence of a sheet. The output voltage of the sensor 1 is compared with a threshold voltage obtained from the reference voltage source 3 by a comparator, and the presence or absence of the sheet is determined based on the presence or absence of the comparison output.

In this case, it is sufficient to determine that the sheet is present when the output of the comparator is either high level or low level.

There are two types of optical sensors for sheet detection: transmissive type and reflective type (
Hereinafter, the scattering type will be referred to as the "reflection type." ), and the output current and output voltage of each type changes depending on the presence or absence of a sheet. The transmission type optical sensor is shown in Figure 2A!
As shown in , it is composed of a light emitting part, for example, a light emitting diode j, and a light receiving part, for example, a phototransistor.
When the sheet 7 enters between them and the light that enters the phototransistor from the light emitting diode j is blocked, the output voltage vs of the phototransistor B decreases, thereby sensing the presence of the sheet. Further, as shown in FIG.
When the light from the light-emitting diode S is reflected by the sheet 7 and enters the phototransistor 11-ta, the output voltage s of the phototransistor increases.
Detects the presence of Sheet B.

The sheet detection optical sensor indicated by / in FIG. 1 uses either a transmissive type or a reflective type 1. The output voltage vs obtained from this optical sensor l for sheet detection is determined by a comparator constituted by, for example, an operational amplifier.
The reference voltage (R) from the reference voltage generation source 3 is used as a threshold for comparison, and the presence or absence of a sheet is detected based on a change in the comparison output.

In the conventional optical sheet detection device as described above, the threshold reference voltage R for comparison is fixed.

Figures 3A and 3B show the sheet position and output voltage for each of the transmissive and reflective sheet detection optical sensors.
This shows the relationship between the two. Regardless of whether the sensor is a transmissive type or a reflective type, there is a possibility that the amount of light will decrease and the curve will drop overall due to contamination of the light emitting part, the light receiving part, or both of the sensors that constitute the sensor. Conversely, if the light receiving section is affected by ambient light, the entire curve rises. In order to prevent detection errors due to these fluctuations, it is necessary to set the comparison reference voltage (R) to a level near the midpoint between the levels of the output voltage V3 obtained when the sheet is present and when the sheet is not present. However, as shown in the figure, the level of the output voltage vs. obtained by detecting the sheet differs greatly between an opaque sheet and a transparent sheet, or a highly reflective sheet and a low reflectance sheet, as shown in the figure. It is difficult to set the reference voltage vR. For example, if the comparison reference voltage vR is set so that an opaque sheet or a highly reflective sheet can be safely detected, the sensor output voltage vs and the comparison standard when a transparent sheet or a sheet with a low reflectance is detected are The voltage difference between voltage ■ and becomes smaller,
It may become impossible to detect a transparent sheet or a sheet with low reflectance without error.

An object of the present invention is to provide an optical sheet detection method in a sheet conveying device that automatically changes the comparison reference voltage according to the type of sheet, in order to solve the drawbacks of conventional devices such as sheet conveyance devices. The method uses an optical sensor to detect sheets fed from a paper cassette loaded in the paper feed section, and compares this 1□ detected value with a predetermined threshold to detect the presence or absence of a sheet. In an optical sheet detection method for a sheet conveying device, different paper feed cassettes are used for each sheet feed cassette, and each paper feed cassette is provided with a sheet identification means according to the type of sheets stored, and these paper feed cassettes are When the paper cassette is loaded in the paper feed section, the threshold value is determined according to the output of a responsive means provided in the paper feed section so as to cooperate with the sheet identification means of the paper feed cassette. This method is characterized by setting a threshold value suitable for detecting the type of sheet stored in a paper cassette.

The present invention will be explained below based on examples.

Fig. 3 shows the positional relationship between the two when a protrusion is used as an example of the sheet identification means of the paper feed cassette in the present invention, and a switch is used as the corresponding response means provided in the paper feed section. This is what is shown.

There are several types of paper cassettes available for different types of sheets, but
In order to simplify the explanation, this embodiment will be described on the assumption that two types of paper, opaque white paper and highly transparent tracing paper, are detected. 1" For example, as shown in the figure, a protrusion 10 is provided behind the cassette 9 as a sheet type identification means on the paper feed cassette 9 for blank paper. In addition, a protrusion 10 is provided on the paper feed cassette for tracing paper (not shown). The two are distinguished by the presence or absence of this protrusion.
□The copying machine body (not shown) has the blank paper force sensor.

When the sheet 9 is loaded into the paper feed section, the switch l is set to the operating position by the protrusion lθ provided only on the blank paper power center.
/ is fixed. The switch 11 is connected in series with the resistor R2 which is connected in parallel with the reference voltage setting resistor R of the comparator/2 in the optical sheet detection circuit shown in FIG. When actuated by the protrusion /η of the paper feed cassette 9, the resistors R and R2 are connected in parallel.

The other input of the comparator is a light emitting diode provided at a position in the sheet conveyance path where the sheet is to be detected! The output voltage s of the well-known transmission type optical sensor sensor illustrated in FIG. λA is applied to the phototransistor 6.゛□Before starting copying, select a sheet type, store it in a paper feed cassette having a sheet type identification means corresponding to the sheet type, and load this into the paper feed section of the sheet conveyance device of the main body of the copying machine. In that case, if the sheet is tracing paper, the paper feed cassette does not have a protrusion, so the I switch/
1 does not operate and remains OFF, and the comparison reference voltage for the threshold value of the comparator at this time is determined by the resistor R0 and the resistor R.

In that case, the comparison reference voltage is set to the tracing paper detection k[・appropriate value ■R] as shown in FIG.

Next, when the paper feed cassette 9 containing one blank sheet of paper as shown in the figure is loaded into the paper feed section, the protrusion /θ provided on the cassette 9 is switch l
/ to close this switch //. When switch l/ is closed, R and R2 are connected in parallel as shown in Figure 5, so the comparison reference voltage of comparator/2 becomes a low value as shown by R2 in Figure 5. . Therefore, in that case, if the resistance 1 value of R2 is set in advance so that vR2 is the optimal value for detecting blank paper, the threshold voltage of comparator/2 can be set to the optimal value depending on the sheet type. It will take a value. Thereby, it is possible to reduce the risk of detection errors due to ambient light or dirt on the sensor portion when detecting sheets, and moreover, it is possible to detect both blank sheets and highly transparent sheets without error.

Note that the threshold voltage does not necessarily have to be set between the presence of paper and the absence of paper, but the optimum value can be determined experimentally, for example, taking into consideration the dirt on the sensor tag and the state of ambient light based on the environment. May be set. In addition, in the above embodiment, a transmission type optical sensor tag is used for the sheet detection optical sensor tag, but when a reflection type optical sensor is used, the N of the switch //
The threshold voltage of comparator/2 may be changed by 1" using the o (normally open) contact. The threshold voltage in that case is shown in FIG. 7. In that case, the switch l
When / is not operating, that is, when a paper feed cassette containing tracing paper is loaded into the paper feed section, switch // remains in the closed state. The respective resistors are connected in parallel. Therefore, the threshold value vR□ in comparator/2 for detecting tracing paper is the threshold value vR□ for detecting blank paper.
It becomes lower than R2, and the threshold value is automatically changed to an appropriate value depending on the sheet type.

FIG. r shows another embodiment of the sheet type identification means provided in the paper feed cassette.

In this embodiment, as a sheet type identification means, the six/6
3 is provided, and the paper feed cassette containing blank paper is not provided with a hole, so that the two can be distinguished.

When the paper feed cassette 9 containing tracing paper is loaded into the paper feed section, the switch// fixed to the paper feed section of the copying machine body opens the hole 1 provided in the paper feed cassette 9.
The operating rod /l of switch // is inserted into position 3 and the switch // is not activated, but the position is set such that switch l/ is activated when the blank paper feed cassette is loaded.

In other words, since the paper feed cassette containing blank paper does not have a hole □, when this paper feed cassette is loaded into the paper feed section, the paper feed cassette comes into contact with the switch //, thereby causing the above-mentioned embodiment Similarly, the threshold value of the comparator is switched to a value suitable for detecting each sheet type. The sheet detection circuit in this embodiment may be the same as that shown in FIG. Further, similarly to the embodiment of the rabbit, if the NO contact of the switch // is used, the present invention can be applied to the case where a reflective type optical sensor sensor for sheet detection is used as shown in FIG.

FIG. 9 shows another embodiment of the sheet type identification means in the present invention, in which a reflective member 15 is used as the sheet type identification means provided in the paper feed cassette 9, and light is irradiated onto it to determine whether or not it is reflected. Accordingly, the threshold value of the comparator in the sheet detection circuit is changed.

A reflective optical sensor /l is fixed to the main body of the copying machine at a position that illuminates a reflective member /j provided on the paper feed cassette 9 when the paper feed cassette 9 is loaded in the paper feed section.

The output of the reflective optical sensor No. 2 for determining the sheet type is inputted to the gate of field effect transistor (FET) /7 in the sheet detection circuit shown in Fig. 1θ, for example. Resistance R due to switching operation
By opening and closing 2, R□.

The comparison reference voltage of comparator/2 determined by R2 and R8 is changed to a value suitable for detecting the sheets stored in the paper feed cassette 9. 1. Now, to explain the case where a transmission type optical sensor l shown by l in Fig. 1θ is used as an optical sensor for sheet detection, a reflective member /S is attached only to the paper feed cassette 9 for blank paper, and tracing Do not attach the reflective member /3 to the paper feed cassette.

In Fig. 1θ, when the blank paper feed cassette is loaded into the paper feed section of the copying machine main body, the □゛□ reflective optical sensor/ The output voltage v8o of B increases, and FET /7
becomes conductive. Therefore, R2 is connected in parallel to R, and the reference voltage for comparison in comparator/2 drops, becoming the optimal threshold voltage R2 for detecting a blank page, as shown in FIG. ``On the other hand, when the paper feed cassette for tracing paper is loaded into the paper feed section, since the reflective member /j is not attached to this paper feed cassette, the output voltage of the reflective optical sensor /l for determining the sheet type is Vso decreases and FET /7 becomes disconnected. Therefore, R2''□ is disconnected and the comparison reference voltage of comparator /2 increases, and the tracing paper is removed as shown in the VR work in Figure 6. The optimal threshold voltage for detection is R.

In addition, if a transmissive sensor is used for the sheet detection sensor instead of the transmissive optical sensor tag shown in Figure 1O, the reflective member 15 is installed only in the tracing paper feed cassette.
, and the reflective member IS may not be attached to the blank paper cassette.

Fig. 1 shows another embodiment of the sheet type identification means in the present invention. This is provided on the outer surface of the paper feed cassette 9 and serves as a sheet type identification means.In other words, /l is a holding frame provided on the outer surface of the paper feed cassette 9 to hold some of the same type of sheets as the stored sheets. The sheet sample 19 held by this holding frame can be changed depending on the type of sheet stored in the paper feed cassette 9./
Reference numeral 6 indicates that when the paper feed cassette 9 configured in this way is loaded into the paper feed section of the main body of the copying machine, the paper feed cassette 9 is protected.
Holding frame/sheet sample held in l/position facing q 1
A reflective optical sensor for determining sheet type is fixed to the sheet feeding section, and is capable of measuring the reflectance of the sheet sample 19.

In this embodiment, an example of a sheet detection circuit when a transmission type optical sensor is used for sheet detection is shown in the first example.
Shown in Figure 2.

Reflective optical sensor for sheet type discrimination/≦ output voltage.

The voltage vso is input to a differential amplifier. The non-inverting input of the differential amplifier is connected to each resistor Ill of R3 and R4.
A constant voltage ■o obtained by dividing the power supply voltage ■cc is applied. Therefore, at the output of the differential amplifier, a voltage of an appropriate level is generated as a threshold corresponding to the difference between vo and ■so (vo-"So), that is, the reflectance of the sheet sample 19. 1 is led to the comparator/2 as the comparison reference voltage VR<〇On the other hand, the comparator 12
The output voltage s from the transmission optical sensor 1 for sheet detection provided in the sheet conveying system is led to the other input of the , and is compared with the comparison reference voltage s from the differential amplifier. The presence or absence of one sheet passing through the transmissive optical sensor for detecting the previous sheet is determined.

Now, let's consider the case of using white paper, which has high light reflectance and low light transmittance. As shown in Figure 1, a sheet sample /9 of the same quality as the blank paper □ is held by a holding frame /r on the side of the paper feed cassette containing the blank paper. Therefore, the reflective optical sensor l≦ for sheet type discrimination measures the reflectance of white paper with high reflectance, and its output voltage VSO
will rise. Therefore ■. The difference between and vso (V○ - VSO
) becomes smaller, and the comparison reference voltage VR of comparator/2 also decreases in proportion to it. Comparison reference voltage V at this time
The resistance value of each part may be determined so that R becomes the optimal threshold level for detecting a blank sheet shown in the aFIZJ, ①R2.

On the other hand, when using tracing paper with low light reflectance and high transmittance, place a sheet of the same quality on the sheet sample holding frame/g of the paper feed cassette 9 containing the tracing paper. Hold the sheet sample. When this tracing paper is loaded into the paper feed section, the reflectance of the tracing paper is small, so the output voltage of the reflective optical sensor 1/4 for determining the sheet type decreases, and the output voltage of the differential amplifier is obtained. The voltage of (■o−■so) increases.

Therefore, the comparison reference voltage ■R applied to the comparator increases, and the sixth
As shown by the VR technique in the figure, this is the reference voltage for comparison at the optimal threshold level for detecting tracing paper.

In the embodiment shown in Fig. 12, a circuit example is shown in which a transmissive type is used as the optical sensor for sheet detection, but a 1.1 reflective type is used as the optical sensor for sheet detection L4S. In this case, the configuration shown in FIG. 13 may be used. That is, the output voltage v8o of the reflective optical sensor/l for determining the sheet type is converted into a threshold voltage vR of an appropriate level by a non-inverting coefficient converter, and is sent to the comparator/2 as a comparison reference voltage vB. Enter. As the other input, the output voltage of the reflective optical sensor t for sheet detection is derived as in the previous embodiment shown in FIG. 72, and is compared with the comparison reference voltage vR.

Now, when using white paper with a high reflectance of light - Mi □ A sheet sample of the same quality as blank paper 1 is held in the paper cassette containing the blank paper, as in the previous embodiment. Therefore, when this paper feed cassette is loaded into the paper feed section of a copying machine, the output voltage of the reflective optical sensor for sheet type identification shown at 16 in Fig. 13 increases, and the output voltage increases proportionally. The output of the non-inverting coefficient unit J, that is, the comparator/
The comparison reference voltage VR of No. 2 also increases. This corresponds to the fact that the threshold voltage has become ■R2 in FIG. On the other hand, when using tracing paper, a paper feed cassette holding the tracing paper in a holding frame as a sheet sample is loaded into the paper feed section, so the reflectance of the sheet sample is measured. The output voltage of the reflective optical sensor/4 for determining the sheet type, which is set as described above, decreases. Therefore, the comparison standard □ voltage of the comparator/λ also decreases,
It is possible to obtain the optimum threshold voltage vR for detecting tracing paper.

In each of the above embodiments, the threshold value for determining the presence or absence of a sheet is changed by changing the comparison reference voltage of the comparator depending on the sheet to be detected. Of course, the threshold value may be changed by changing the load resistance of the optical sensor or the amount of light from the light emitting element.

In addition, the sheet types are not limited to these types, but are
Regarding the detection of more than one sheet type, it is possible to set the optimal threshold level for each sheet type using the same method as shown in each of the above embodiments.

As is clear from the description of each of the embodiments above, according to the present invention, in a sheet detection method in a sheet conveying device such as a copying machine, it is possible to change the sheet type by simply replacing the paper feed cassette. Since the optimal threshold level for detecting sheets stored in a paper cassette can be automatically set, it is possible to not only reliably detect sheets regardless of the type of sheet, but also to configure the sheet detection circuit. This method has the effect of sufficiently reducing the risk of detection errors due to contamination of the sheet detection optical sensor or disturbance light, compared to conventional methods.

Simple fx and explanation of the French drawings. Figure 1 shows the circuit W of a conventional optical sheet detection device. Figures A and B show the circuit configurations for explaining the respective functions of the transmission type sensor and the reflection type sensor. Figures 3A and 3B are curve diagrams showing the relationship between the sheet position and output voltage in a transmission type sensor and a reflection type sensor, respectively, and Figure 7 is an example of the sheet identification means of the frame F in the present invention. A diagram for explaining the positional relationship between the two when a switch is used as a response means that responds by that means, and FIG. FIGS. 6 and 7 are curve diagrams showing the relationship between the output of the optical sheet sensor and the threshold voltage in the comparator, and FIGS. / Figures are diagrams showing other different embodiments of the sheet type identification means of the present invention, and Figure 1θ is a block diagram showing an example of an optical sheet detection circuit when the sheet type identification means of Figure 9 is used. , Fig. 12 uses the sheet type identification means shown in Fig. 1/Fig.
FIG. 13 is a configuration diagram showing an example of one optical sheet detection circuit when detecting a sheet. FIG. 13 is a configuration diagram in which the transmissive optical semi-sensor for sheet detection in the circuit configuration of FIG. 12 is replaced with a reflective sensor sensor. FIG. 3 is a configuration diagram showing an example of a sheet detection circuit when

/... Optical sensor for sheet detection, 2, 12... Comparator, 3... Reference voltage source, V... Transmissive optical sensor for sheet detection, j... Light emitting diode, t・・・
・Phototransistor, 7...Sheet, Su...Reflective optical sensor for sheet detection, Ri...Paper feed cassette,
/θ...protrusion 1z//...switch, /3...hole, lug...operating rod, /S...reflector, /&...
Reflective optical sensor for determining sheet type, /7... Field effect transistor, /I... Sheet sample holding frame, /9.
...Sheet sample,〃...Differential amplifier, 21...Non-inverting coefficient unit.

Figure 1 Figure 2 A B 3rd Do I The fourth is I Figure 6 Figure 7

Claims (1)

[Claims] 1. A sheet in which the presence or absence of a sheet is detected by using an optical sensor to detect a sheet fed from a paper cassette loaded in a paper feeding unit, and by comparing this detected value with a predetermined threshold value. In the optical sheet detection method of the conveyance device, 14 paper feed cassettes are used for each sheet type, and each paper feed cassette is provided with a sheet type identification means according to the sheet type to be accommodated, and these paper feed cassettes are The threshold value is applied to the paper feed unit in accordance with the output of a responsive means provided in the paper feed unit so as to cooperate with the sheet identification unit of the paper feed cassette when loaded into the paper feed unit. 1. An optical sheet detection method in a sheet conveying device, characterized by setting a threshold value suitable for detecting the type of sheet contained in a loaded paper feed cassette.