JP2556903B2 - Sewing object detection device - Google Patents

Description

The present invention relates to a sensor circuit using a CdS (photoconductive cell) for detecting the presence or absence of a sewn item and the end of the sewn item in an automatic sewing machine.

[Conventional technology]

Conventionally, sewn product presence / absence detection devices and sewn product end control devices that use CdS have been known. That is, by utilizing the feature that the resistance value changes due to the change in illuminance of CdS, the output without sewing is obtained by comparing the level change between with sewing and without sewing with the set reference voltage. It is used for control. Moreover, in order to obtain the stability of sensitivity, it is devised to irradiate bias light from the outside to reduce the influence of ambient light and to work in the stable region of CdS.

[Problems to be Solved by the Invention]

However, the conventional device mainly focuses on the simplicity of the circuit and the cost reduction. (A) Since the reference voltage is set semi-fixed, a situation such as a power failure or a filament wire breakage of the bias light source may occur. If there is insufficient illuminance, it may be determined that there is a sewn item and the device may malfunction, and (b) there is a sewn item due to a sensor disconnection or a bad contact such as a connector. Therefore, the device may malfunction. Further, (c) in the conventional device, the level without sewing material and the reference voltage level cannot be brought close to each other in order to prevent malfunction due to slight changes in illuminance. For this reason, stable operation is achieved by adjusting the reference voltage level by changing the illuminance around the CdS (including artificial ones), daytime work and nighttime work, or changes in the detection level due to fabric material, color, etc. It needs to be done.

The present invention is to improve this point, the device does not malfunction due to power failure, the ball of the bias light source, sensor disconnection, connector disconnection, etc., and further the sensitivity of the device according to changes in illuminance, fabric material, color, etc. An object of the present invention is to provide a sewn product detection device that does not require adjustment.

[Means for solving problems]

The present invention separately provides a sewn product detection sensor and an ambient light illuminance detection sensor configured of CdS having the same characteristics, and means for applying a predetermined bias voltage to the output of the illuminance detection sensor, and means for adding the bias voltage. Is provided and means for comparing the output of the sewn product detection sensor is provided.

Further, the present invention is characterized by including means for invalidating the output of the sewn product detection sensor when a disconnection of the sensor or a defect of the connector or the like is detected.

[Action]

Therefore, the influence of the illuminance change of the external light is removed from the sewn product detection sensor and the comparison reference voltage. Further, the bias voltage for setting the reference voltage can be reduced. Further, malfunction due to sensor disconnection or defective contact of the connector or the like is prevented.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of the essential parts of an embodiment of the present invention. In FIG. 1, 1 is a sewn product detection sensor for detecting the presence or absence of a sewn product made of CdS, and 2 is an illuminance detection sensor made of CdS having the same characteristics as the sensor 1. Here, the sensor 2 is arranged at a position where it is not covered with the sewing material.

The output of the sensor 1 is connected to the photoelectric conversion circuit 3, and the output of the sensor 2 is connected to the photoelectric conversion and bias circuit 5. The output of the opto-electrical conversion and bias circuit 5 is connected to the + terminal of the comparison circuit 6 as a reference voltage, and the outputs of the opto-electrical conversion circuit 3 and the input clamp circuit 7 are compared-voltages of the comparison circuit 6. It is connected to the terminal. The output of the comparison circuit 6 is connected to the output control circuit 8. The output of the photoelectric conversion circuit 3 is connected to the sensor disconnection detection circuit 9, and the output of the sensor disconnection detection circuit 9 is connected to the output control circuit 8.

Further, A, B, and C in FIG. 1 indicate output signals at points indicated by X marks, respectively.

FIG. 2 shows a detailed circuit configuration diagram of an example of the present invention.
In FIG. 2, the same reference numerals as those in FIG. 1 denote the same parts as those in FIG. In FIG. 2, R1 to R17 are resistors and C1 to C3.
Are capacitors and D1 to D6 are diodes, which are connected as shown in the figure.

That is, the resistor R1, the resistors R2 to R4, the sensor 1, and the resistor
A bridge circuit 10 is constituted by R6 to R7, the sensor 2 and the resistor R5 as shown in the figure, and the output of the connection point of the resistors R1 and R2 is connected to the negative terminal of the comparator circuit 6 as the voltage to be compared, and the resistor R5 The output of the connection point of the resistor R6 and the resistor R6 is connected to the + terminal of the comparison circuit 6 as a reference voltage. A Zener diode ZD for input clamp is connected to the-terminal of the comparison circuit 6. The output of the comparison circuit 6 is connected to the output control circuit 8 composed of an AND circuit.

Further, the sensor 1 of the bridge circuit 10 and the resistor R4
The output of the connection point is connected to the amplifier 11 in the sensor disconnection detection circuit 9, and the output of the amplifier 11 is connected to the comparison circuit 12 and the compared terminal. The reference voltage terminal of the comparison circuit 12 is connected to the reference voltage divided and set by the resistors R12 and R13. The output of this comparison circuit 12 is NOT circuit 1
It is connected to the output control circuit 8 via 3.

FIG. 3 shows an operation explanatory diagram of one embodiment of the present invention. In FIG. 3, the curve A indicates the potential at the point A when the sensor 1 is not covered with the sewing material, the curve A ′ indicates the potential at the point A when the sensor 1 is covered by the sewing material, and the curve B indicates the potential at the point B. The potentials (that is, the reference voltage of the comparison circuit 6) are shown.

 FIG. 4 shows an operation explanatory view of the conventional device.

4, the same symbols as those in FIG. 3 denote the same components as those in FIG. 3, respectively.

〔motion〕

The characteristic operation of the embodiment of the present invention thus constructed will be described. Now, at the illuminance at the point a shown in FIG. 3, the resistance R1 and the resistance of the bridge circuit 10 are biased so that the potential at the point B is biased higher than the potential at the point A by ΔV in the absence of the sewing material.
R5 (see Figure 2) is adjusted. In this state, when the external light changes, the internal resistance of the sensor 1 and the sensor 2 also changes in proportion to the change in illuminance, but since the sensors 1 and 2 are composed of CdS having the same characteristics, the internal resistance of the sensors 1 and 2 is changed. Is the same, and as shown in FIG. 3, the potentials at points A and B change in response to changes in illuminance while maintaining the bias voltage ΔV.

Now, when the sensor 1 is covered with a sewn product and external light is blocked at the sensor 1, the internal resistance of the sensor 1 increases and the potential at point A rises. As a result, the potential at the point A exceeds the reference voltage at the point B, and the comparison circuit 6 outputs an output signal indicating the presence of the sewn product. At this time, the sensor disconnection detection circuit 9
If there is no detection output from, the output control circuit 8 outputs that there is a sewn product.

Further, CdS has a characteristic that it has a relatively high resistance in a dark place to make the circuit unstable and a hysteresis phenomenon becomes remarkable. Therefore, it is preferable to fix the CdS level at a practical illuminance (50 LX or less). Therefore, the present invention connects the Zener diode ZD for input clamp to the compared input terminal of the comparison circuit 6 and clamps the input level to the comparison circuit 6 at low illuminance to stabilize the device.

Next, the operation of the sensor disconnection detection circuit 9 for detecting the disconnection of the sensor, the disconnection of the connector and the like to prevent the malfunction of the device will be described. This is done by monitoring the voltage at point C shown in FIG. That is, at the point C, a divided voltage obtained by dividing the resistance R4, the resistances R1 to R3 and the combined resistance of the sensor 1 appears. The voltage at the point C is amplified by the amplifier 11, and is resistance by the comparison circuit 12.
It is compared with the reference voltage set by R12 and 13, and the comparison output is sent to the output control circuit 8 via the NOT circuit 13 to open the gate of the circuit 8. However, when the sensor 1 is disconnected or the connector connecting the sensors is disconnected, the voltage at the point C is grounded, and the comparison output from the comparison circuit 11 is not output. As a result, the gate of the output control circuit 8 is closed, and the erroneous sensor output from the sensor 1 due to the malfunction is invalidated.

Here, in the conventional device shown in FIG. 4, the reference voltage must be fixedly set, and the usable illuminance region is limited to the narrow range between α and β. Further, in the conventional device, it is necessary to make the bias voltage ΔV large in order to widen the usable illuminance range and stabilize the detection. Depending on the thin cloth or the cloth color, the sewing detection sensor in the usable illuminance range may be detected. May not be able to sufficiently detect the presence of the sewn item.

On the other hand, as described with reference to FIG. 3, according to the present invention, the reference voltage level based on the illuminance detection sensor and the level of the sewn product detection sensor change corresponding to the illuminance change of external light, so that the usable illuminance range is widened. The bias voltage ΔV can be reduced.

〔effect〕

As described above, according to the present invention, a sewn product detection sensor composed of CdS having the same characteristics and an ambient light illuminance detection sensor are separately provided, and a predetermined bias voltage is applied to the output of the illuminance detection sensor. Means and means for comparing the output of the adding means with the output of the sewn product detection sensor are also provided.

Therefore, it is possible to eliminate the influence of the illuminance change of the outside light. Further, since the bias voltage can be reduced, it is not necessary to adjust the reference voltage level according to the work during the day and the work at night, the material and color of the sewn product.

Furthermore, since the output of the sewn product detection sensor is disabled when a sensor disconnection or a defect such as a connector is detected, it is possible to prevent malfunction due to a sensor disconnection or a defective contact such as a connector. it can.

[Brief description of drawings]

 FIG. 1 is a block diagram of a main part of an embodiment of the present invention. FIG. 2 is a circuit configuration diagram of an embodiment of the present invention. FIG. 3 is an operation explanatory diagram of the embodiment of the present invention. FIG. 4 is a diagram for explaining the operation of the conventional device. 1, 2 ... Sensor 3 ... Optical / electrical conversion circuit 5 ... Optical / electrical conversion and bias circuit 6 ... Comparison circuit 7 ... Input clamp circuit 8 ... Output control circuit 9 ... Sensor disconnection detection circuit

Claims (3)

(57) [Claims] 1. A first sensor for detecting the presence / absence of a sewn product, and an element having the same characteristics as those of the first sensor arranged near the first sensor so as not to be covered by the sewn product. A second sensor for detecting the illuminance of light, a first means for applying a predetermined bias voltage to the output of the second sensor, an output of the first sensor and an output of the first means. A sewn object detection device comprising: a second means for comparing and detecting the presence or absence of a sewn object. 2. A means for detecting a defect of the first sensor, and a means for invalidating the output of the second means when there is a detection output from the means for detecting. The sewn object detection device according to claim 1, which is characterized in that. 3. The sewn object detection device according to claim 1, wherein the sensor is made of CdS.