JP2607556B2 - Seat abnormality detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet handling apparatus, and more particularly to a sheet abnormality detection apparatus that detects a plurality of sheets being fed.

[Conventional technology]

A conventional sheet abnormality detection device will be described with reference to FIG. The detection device shown in FIG. 7 includes a fixed roller 31, a displacement roller 32 in opposition to the fixed roller 31,
The lever 33 has a function of pressing the displacement roller 32 against the fixed roller 31 by the spring member 35 while transmitting the displacement by the rotational movement, the magnetic sensors 36 and 37 for detecting the displacement, and the detection circuit. It consisted of 38 and. At this time, when the sheet 39 passes between the fixed roller 31 and the displacement roller 32, the displacement roller 32 is displaced,
The lever 33 moves as shown in the figure. At this time, the magnetic sensor 36 attached to the tip of the lever,
The amount of displacement is detected by the magnetic sensor 37 opposed thereto, and the detection circuit 38 detects the feeding of a plurality of sheets and the sheet to which the tape is attached.

[Problems to be solved by the invention]

In the prior art, since the voltage level and output sensitivity of the sensor are determined by the distance between the magnet and the magnetic sensor at the tip of the lever, the distance between the magnet and the magnetic sensor is required to characterize the calibration curve. It was necessary to adjust and set and maintain high accuracy. In addition, a spring member is required to press the displacement roller against a lever or a fixed roller for transmitting the displacement, and the detection device is large and complicated. Furthermore, since the rigidity of the spring member for pressing the displacement roller against the fixed roller is high, there is a problem that a large conveyance resistance force is generated when the sheet passes through the sheet depending on the thickness and folding conditions of the sheet, and there is a high possibility that a jam occurs.
Further, there is a problem that, when two sheets of paper are shifted and overlapped with each other and sent, it may not be possible to detect that the sheets are overlapped and sent.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet abnormality detection device capable of detecting a double feed with high accuracy, and reducing the size and cost.

[Means for solving the problem]

The object of the present invention is to set a detection level in a detection unit of a detection device for detecting a sheet abnormality such as an overlapped feed of a plurality of sheets when the number of output pulses of an abnormality detection pickup exceeds 2 when an output of a passage sensor is on. Even when the level is lower than the level, an abnormal signal indicating that the number of transport sheets is two or more is generated.

[Action]

In the present invention, a piezoelectric element is used as a displacement detection pickup. The piezoelectric element generates a voltage corresponding to only dynamic strain as its characteristic. Therefore, it is not necessary to set the voltage and make detailed adjustments. Also,
If a bimorph type piezoelectric element is used, it itself becomes a spring member, so that a spring member for pressing the displacement roller against the fixed roller is not particularly required, and a lever or the like for transmitting the displacement is not required. Further, since the piezoelectric element generates a relatively large voltage (several tens of volts) with a slight displacement, a power supply and an amplifier for pickup are not required, and the detection circuit can be simplified and the output voltage is large. Therefore, the rigidity of the spring member for pressing the displacement roller against the fixed roller can be reduced, and the possibility of occurrence of a jam can be reduced.

〔Example〕

One embodiment of the sheet abnormality detecting device of the present invention will be described below. FIG. 1 shows the structure and operation of the sheet abnormality detecting device.

The sheet abnormality detection device includes a fixed roller 1 provided in the conveyance path, a displacement roller 2 which is disposed in contact with and fixed to the fixed roller 1 and is movable vertically, a shaft 3 of the displacement roller 2 and a fixture 5. A bimorph-type piezoelectric element 4 that is fixed and held in a cantilever manner, a detection circuit 6 that detects whether the sheet is normal, based on a signal from the bimorph-type piezoelectric element 4 and a signal from the sheet passage sensor 8, and And an optical sheet passage sensor 8 provided in the vicinity of the fixed roller 1 and the displacement roller 2 for confirming the existence of the sheet. At this time, the displacement roller 2 is pressed against the fixed roller by a spring effect of the bimorph type piezoelectric element 4.

Since the piezoelectric element has a characteristic that the output voltage increases in proportion to the displacement, the spring stiffness of the piezoelectric element is required only as a pressing force at the time of passing the sheet and after the sheet has passed, and has no relation to the output characteristic.

Next, the operation of the present apparatus will be described. When the sheet 7 conveyed in the conveyance path passes between the fixed roller 1 and the displacement roller 2, the displacement roller 2 is displaced downward. At this time, the displacement is transmitted to the bimorph-type piezoelectric element through the shaft 3 of the displacement roller and the fixture 5, and the bimorph-type piezoelectric element is deformed, and a voltage is generated at this time. This voltage is transmitted to the detection circuit 6 as a signal. Further, when the sheet passes between the fixed roller 1 and the displacement roller 2, a sheet passage signal is detected by an optical sheet passage sensor 8 provided in the vicinity of both rollers, and is transmitted to the detection circuit 6. The detection circuit 6 detects whether the sheet is normal based on the signal of the bimorph type piezoelectric element 4 and the signal of the optical sheet passage sensor 8. Next, an example of a method for detecting an abnormal sheet will be described.

FIG. 2 and FIG. 3 show an example of a method for detecting a plurality of sheets.

FIG. 2 shows signals when a plurality of sheets pass between the fixed roller 1 and the displacement roller 2 at the same time. The upper part shows the voltage signal from the piezoelectric element, and the lower part shows the signal from the passage sensor. It is. In this case, since the displacement of the displacement roller 2 is large, the voltage signal generated by the piezoelectric element 4 is a voltage signal when one sheet passes (shown by a dotted line in the figure).
Greater than. Therefore, the detection level of a plurality of sheets is set at a level slightly higher than the voltage signal when one sheet passes, and the voltage signal from the piezoelectric element exceeds this level, and the signal from the sheet passage sensor is If ON, it is assumed that there are a plurality of sheets.

FIG. 3 shows signals when a plurality of sheets are conveyed in a shifted form. The upper part is a voltage signal from the piezoelectric element 4 and the lower part is a signal from the optical sheet passage sensor 8. is there. In this case, since the displacement of the displacement roller 2 is equivalent to one sheet, the signal from the piezoelectric element 4 does not reach the detection level of a plurality of sheets. However, if the number of pulses of the voltage signal from the piezoelectric element 4 is counted and the number of pulses is 2 or more and the signal from the sheet passage sensor is ON, it is assumed that there are a plurality of sheets.

At the time of sheet abnormality detection, the piezoelectric element shown in FIG.
In some cases, it takes time to attenuate the generated voltage as shown in FIG. 13. In this case, as shown in FIG. 5, connecting the resistor 11 in parallel with the piezoelectric element 12 can speed up the attenuation of the generated voltage. it can. The generated voltage at this time is indicated by a dotted line in FIG.
It looks like 14. Further, since the voltage generated by the piezoelectric element depends on the temperature, it is necessary to compensate for this. For this reason, if a bridge circuit is formed as shown in FIG. 6, for example, the influence of temperature can be compensated. Where 11,1
Reference numeral 2 denotes the above-described resistor and piezoelectric element, and reference numerals 15 and 16 also denote resistors. In this case, 17 is used as active and 18 is used as dummy.

The sheet conveyed by skew can be detected by arranging the detecting device in a direction perpendicular to the sheet conveying direction.

According to the present embodiment, this is necessary for the conventional sheet abnormality detection device. This eliminates the need for voltage setting of the displacement sensor requiring complicated adjustments and a displacement transmitting mechanism such as a lever or a spring member for transmitting the displacement to the displacement sensor, thereby making it possible to reduce the size and cost of the device. In addition, since the voltage generated by the piezoelectric element is relatively high, an amplifier is not required, and no power supply is required. This makes it possible to simplify the detection circuit and the electric circuit.

〔The invention's effect〕

As described above, according to the present invention, a special mechanism such as a displacement sensor or a lever for transmitting displacement, which has been relatively expensive, is not required, thereby realizing a low-cost and small-sized sheet abnormality detection device. it can. Also, since troublesome adjustment of the displacement sensor is not particularly required, the cost can be reduced in this respect as well. Furthermore, a detection circuit without a displacement sensor or an amplifier can be realized, and the overall size and cost of the sheet abnormality detection device can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a sheet abnormality detecting device according to an embodiment of the present invention, FIGS. 2 and 3 are diagrams illustrating an example of a method for detecting a plurality of sheets in the present invention, and FIG. FIG. 5 is a diagram comparing output voltages when a resistor is connected to a piezoelectric element according to the present invention and FIG. 5 is a diagram illustrating a resistor connected in parallel to a piezoelectric element according to the present invention, and FIG. FIG. 7 is a diagram showing an example of a circuit, and FIG. 7 is a diagram showing the structure of a conventional sheet abnormality detection device. DESCRIPTION OF SYMBOLS 1 ... Fixed roller, 2 ... Displacement roller, 4 ... Bimorph type piezoelectric element, 6 ... Detection circuit, 7 ... Sheet, 8 ...
Sheet passage sensor, 11: resistance, 12: piezoelectric element (circuit), 15, 16: resistance.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshifumi Onoe 502 Kandate-cho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratory, Hitachi, Ltd. In the laboratory (56) References JP-A-60-122646 (JP, A)

Claims (2)

(57) [Claims] 1. A piezoelectric element as a pickup for detecting an abnormality of a sheet on a sheet conveying path, and a pulse voltage as a sheet detection signal from the piezoelectric element are input, and the pulse voltage is set to a predetermined level. In a sheet abnormality detection device provided with a sheet abnormality detection unit that detects overlap feed when the sheet exceeds, a passage sensor that detects passage of a sheet near an upstream side of the abnormality detection pickup is provided, and the sheet abnormality detection unit includes: The output of the pass sensor is provided, and counting means for counting the number of pulse-like signals, which are output signals of the piezoelectric element for detecting the abnormality, while the ON signal of the pass sensor is being input, includes the pulse-like voltage. Even when the count value is equal to or less than the predetermined level, when the counting means counts more than 2, an abnormal signal indicating that there are two or more conveyed sheets is generated. Sheet abnormality detection apparatus which is characterized in that raw. 2. The sheet abnormality detecting device according to claim 1, further comprising a temperature compensation circuit for compensating temperature characteristics of said piezoelectric element.