JP3135750B2 - Loom weft detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weft detecting device for judging the presence or absence of a weft based on a feeler signal corresponding to the presence or absence of a weft.

[0002]

2. Description of the Related Art In a weft detection device using a photoelectric type weft detector, the fact that the output signal of the detector, that is, the voltage value of a feeler signal differs depending on the presence or absence of a weft, is used.
The voltage value of the feeler signal is compared with a reference value, that is, a threshold value, in a comparison circuit at a so-called weft detection time, which is a time to determine the presence or absence of a weft at the end of weft insertion, thereby determining the presence or absence of a weft.

However, in the photoelectric type weft detecting device, the amount of light incident on the light receiving element of the detector is caused not only by the presence or absence of the weft, but also by other fluctuation factors such as fluctuation of disturbance light, vibration of the reed, and the like. Because of the change, the feeler signal becomes a signal having a vibration waveform including a frequency component caused by another variable element.

In particular, in the case of a reflection type feeler, when the reed oscillates with the beating movement, the light reflecting surface of the reed oscillates, so that the amount of light incident on the light receiving element changes, resulting in a change in the feeler. The amplitude of the signal greatly changes at a frequency corresponding to the vibration frequency of the reed. In the case of a transmissive feeler, if one of the light transmitting element and the light receiving element is provided on the reed, the amplitude of the feeler signal changes greatly at a frequency corresponding to the vibration frequency of the reed. The vibration of the reed increases as the rotation speed of the loom increases, and accordingly, the vibration, that is, the amplitude of the feeler signal increases as the rotation speed of the loom increases.

As described above, when the amplitude of the feeler signal changes due to other fluctuation factors such as the vibration of the reed, the signal change due to the presence or absence of the weft and the signal change due to other fluctuation factors are determined. Since it is not possible to distinguish electrically, for example, when a thin weft, a weft of a color similar to the color of a reed, and the like are used, the weft actually exists (normal weft insertion).
Nevertheless, it may be determined that there is no weft (weft insertion failure), or conversely, it may be determined that there is a weft even though no weft actually exists.

In order to solve the above problem, a maximum value of a feeler signal in a period extending over a plurality of weft insertion cycles is determined, and a threshold value used in the comparison circuit is calculated based on the determined maximum value. An apparatus has been proposed (Japanese Patent Publication No. 1-60570).

However, in this conventional weft detecting device, the maximum value of the feeler signal is obtained by obtaining a feeler signal when the main axis of the loom reaches a specific angle (one point) over a plurality of weft insertion cycles. And does not recognize that the feeler signal is affected by the vibration of the reed.

In such a conventional apparatus, the signal detection point for calculating the maximum value is constant with respect to the weft insertion cycle, but is indefinite with respect to the amplitude of the signal waveform caused by the vibration of the reed. Therefore, it is uncertain which signal level of the amplitude waveform caused by the vibration of the reed is detected for calculating the maximum value.

That is, since the level of the feeler signal at the time of detection differs in each weft insertion cycle due to the vibration of the reed, the maximum value itself becomes inaccurate. Therefore,
The threshold value obtained in this way is also inaccurate, and erroneous detection (erroneous determination) cannot be avoided.

As another one of the other weft detecting devices, a sensing circuit for detecting a minimum value of a feeler signal and a transmission circuit for the feeler signal are provided, and a gain is automatically set based on a detection value of the sensing circuit. (Japanese Patent Publication No. 2-46704).

However, in the other conventional apparatus, the minimum value of the feeler signal is used for the automatic adjustment of the gain. Therefore, when the amplitude of the vibration waveform of the feeler signal caused by the vibration of the reed changes due to the beating state, the automatic gain is automatically adjusted. The adjusted feeler signal may be too large or too small, and erroneous determination may be made even when the gain is automatically adjusted.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to reliably prevent erroneous determinations caused by variable factors other than the weft.

[0013]

A weft detecting device according to the present invention comprises: sensing means for outputting a feeler signal having a vibration waveform, which is a feeler signal corresponding to the amount of light incident on a light receiving element; and output from the sensing means. Determining means for comparing the feeler signal with a threshold value to determine the presence or absence of a weft; and a feeler signal during a predetermined time within a non-weft detection period and including at least one cycle of the vibration waveform of the feeler signal. Calculating a value, and supplying a predetermined value to the determination means as the threshold based on the calculated value, wherein the feeler signal value obtained by the calculation means is a maximum value, a minimum value of the feeler signal. , At least one selected from an average value and an integral value.

The calculation of the feeler signal value by the calculating means is performed during a non-weft detection period (a period during which the weft does not reach the front surface of the light receiving element and the presence or absence of the weft, in one or more weft insertion cycles). Is performed for a predetermined period of time during the period in which the determination is made.

Accordingly, even if the feeler signal value such as the maximum value, the minimum value, the average value, and the integral value is vibrated due to the vibration of the reed, the correct value corresponding to the vibration is obtained. Become. Therefore, the threshold value set based on the feeler signal value obtained in this manner is also a correct value according to the feeler signal that vibrates due to the vibration of the reed.

As described above, according to the weft detecting device of the present invention, the feeler signal value is calculated for a predetermined time within the non-weft detection period, and the predetermined value is determined based on the calculated value. Since the threshold value is set as the threshold value, it is possible to reliably prevent an erroneous determination caused by a variable element other than the weft.

According to another weft detecting device of the present invention, there is provided a sensing means for outputting a feeler signal corresponding to the amount of light incident on a light receiving element, a maximum value or a minimum value of a feeler signal during a predetermined time within a non-weft detection period. A calculating means for calculating a value, and subtracting a predetermined value from the feeler signal output from the sensing means based on the calculated value; and comparing the value output from the calculating means with a threshold to determine the presence or absence of a weft. Determining means for determining.

In other weft detecting devices, the calculation of the maximum value or the minimum value by the calculating means is performed in a non-weft detecting period in one weft insertion cycle in one or more weft insertion cycles during a predetermined time. Done.

Accordingly, even if the feeler signal vibrates due to the vibration of the reed or the like, the maximum value or the minimum value becomes a correct value corresponding to the vibration. Accordingly, the calculated value itself and a predetermined value such as a value obtained by correcting the calculated value by a predetermined coefficient, which is obtained based on the maximum value or the minimum value obtained in this manner, are also caused by vibration of the reed. The value is correct according to the feeler signal that vibrates. As a result, the signal supplied from the calculation means to the determination means also has a correct value corresponding to the feeler signal that vibrates due to the vibration of the reed.

As described above, according to another weft detecting device of the present invention, the maximum value or the minimum value of the feeler signal during a predetermined time within the non-weft detection period is calculated, and based on the calculated value. Then, the predetermined value is subtracted from the feeler signal output from the sensing means, so that an erroneous determination caused by a variable element other than the weft can be reliably prevented.

The arithmetic means includes a calculating circuit for calculating an average value of the feeler signal, and the sensing means outputs an electric signal corresponding to an amount of light incident on the light receiving element, and an output signal from the sensing circuit. A signal processing circuit that receives the electric signal and outputs the electric signal as the feeler signal, the signal processing circuit performing automatic gain adjustment based on the average value obtained by the calculation circuit.

With this configuration, the automatic gain adjustment is performed based on the average value of the feeler signal. Therefore, even if the amplitude of the vibration waveform of the feeler signal vibrates due to the vibration of the reed, etc.,
The feeler signal that has been subjected to the automatic gain adjustment is always maintained at a predetermined level. As a result, when the amplitude is large unlike the conventional apparatus, the amplitude does not become excessive, and the determination of the presence or absence of the weft becomes more accurate.

The gain adjustment time in the signal processing circuit is a predetermined time before the calculation means starts calculating the feeler signal value in the weft insertion cycle after the weft insertion cycle in which the average value is calculated by the calculation circuit. Is preferred. With this configuration, since the gain of the signal processing circuit is kept constant at least during the feeler signal value calculation period and the subsequent weft detection period, the feeler signal value is accurately calculated, and the determination of the presence or absence of the weft is performed. Be more accurate.

Still another weft detecting device of the present invention is a detecting means for outputting a feeler signal corresponding to the amount of light incident on a light receiving element, and comparing the feeler signal output from the detecting means with a threshold value to determine whether or not a weft exists. Determining means, and calculating means for calculating an average value of the feeler signal during a predetermined time within the non-weft detection period, wherein the sensing means comprises an electric signal corresponding to the amount of light incident on the light receiving element. And a signal processing circuit that receives the electrical signal output from the sensing circuit, processes the signal, and outputs the signal as the feeler signal. The signal processing circuit automatically performs the processing based on the average value obtained by the arithmetic unit. And a signal processing circuit for adjusting the gain.

Thus, automatic gain adjustment is performed based on the average value of the feeler signal. Therefore, even if the amplitude of the vibration waveform of the feeler signal oscillates due to the vibration of the reed, the automatic gain adjustment is performed. The feeler signal is always maintained at a predetermined level. As a result, when the amplitude is large unlike the conventional apparatus, the amplitude does not become excessive, and the determination of the presence or absence of the weft becomes more accurate.

It is preferable that the gain adjustment timing in the signal processing circuit is a predetermined timing after the calculation of the average value by the arithmetic means and before the weft detection period arrives. With this configuration, the gain of the signal processing circuit is kept constant at least during the weft detection period, so that the determination of the presence or absence of the weft becomes more accurate.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a weft detecting device 10 includes a light receiving element 12 incorporated in a reflective or transmission type photoelectric feeler, and an amplifier 14 for amplifying an output signal from the light receiving element. . The light receiving element 12 is disposed on the loom so as to detect reflected light from the weft and transmitted light on the weft flight path. In the illustrated example, the light receiving element 12 and the amplifier 14 constitute a sensing circuit that generates an electric signal having a voltage value proportional to the amount of light incident on the light receiving element 12. The output signal of the amplifier 14 is supplied to a signal processing circuit 16 having a function of automatically adjusting gain such as amplification and sensitivity, as indicated by "AGC" in the figure.

The signal processing circuit 16 amplifies the output signal of the amplifier 14, and uses the amplified signal as a feeler signal.
The comparators 18 and 20 function as determination circuits for generating a weft signal indicating the presence or absence of a weft, and a calculation circuit for calculating a feeler signal value such as a maximum value, a minimum value, and an average value of the feeler signal, that is, an arithmetic unit 22. I do. FIG. 2D shows an example of the signal waveform of the feeler signal.

The comparators 18 and 20 receive the timing signal A generated by the timing signal generator 24.
On the other hand, arithmetic unit 22 receives timing signal B generated by timing signal generator 24. The timing signal B is stored in the signal processing circuit 16 and the storage unit 2 that stores the maximum value, the minimum value, and the average value of the feeler signal.
6, 28 and 30.

In the illustrated example, like a multicolor weaving loom,
For a loom using a weft that changes to the positive side and a weft that changes to the negative side with respect to the level when the level of the feeler signal when "weft is present" is "no weft", two comparators 18, 20 is used, but in the case of a monochromatic loom,
Either one of the comparators may be used depending on the weft used, or the comparator used may be switched according to the weft used.

As shown in FIG. 2A, the crank angle is 0
If the time is a beating, for example, as shown in FIG. 2B, the timing signal A is a signal that becomes high during 200 to 290 degrees (a so-called weft detection period for determining the presence or absence of a weft). And the timing signal B
As shown in FIG. 2C, the signal can be a high level signal for 100 to 200 degrees (a so-called non-weft detection period in which the presence or absence of a weft is not determined). FIG. 2D shows an example of a feeler signal having a different voltage level depending on the color of the weft in the case of multicolor weaving.

When the timing signal A is supplied, the comparator 18 compares the feeler signal with a threshold value for the maximum value, and when the former is equal to or greater than the latter, the truth value "means that weft is present".
On the other hand, when the timing signal A is supplied, the comparator 20 compares the feeler signal with the threshold value for the minimum value, and when the former is equal to or less than the latter, it means "there is a weft". A signal having a truth value "1" is generated.

The arithmetic unit 22 calculates a feeler signal value such as a maximum value, a minimum value and an average value of the feeler signal while the timing signal B is at a high level. For example, the feeler signal value is extracted and stored a plurality of times during the period in which the timing signal B is supplied,
By finally calculating based on those stored values,
Obtainable.

The calculated maximum value, minimum value and average value are written to the storage units 26, 28 and 30, respectively. The calculation time of the feeler signal value and the writing time of the calculated feeler signal value can be the falling time of the timing signal B.

The maximum and minimum values stored in the storages 26 and 28 are supplied to comparators 18 and 20 as thresholds, respectively. On the other hand, the average value stored in the storage device 30 is supplied to the signal processing circuit 16 as a signal for adjusting the gain of the signal processing circuit 16.

The signal processing circuit 16 automatically adjusts the gain each time it receives the timing signal B while receiving a loom operation signal indicating that the loom is operating from a main control circuit (not shown). The first gain adjustment at the start of the operation of the loom is performed based on the feeler signal itself, which is the output of the signal processing circuit 16. Subsequent gain adjustment is performed based on the average value stored in the storage device 30.
In any case, the timing of the gain adjustment is determined by the timing signal B
At the time of rising.

The automatic gain adjustment in the signal processing circuit 16 is performed as shown in FIG.
This is performed in such a manner that a becomes the target value F0. Therefore, even if the amplitude of the vibration waveform of the feeler signal vibrates greatly, the feeler signal that has been subjected to the automatic gain adjustment is always maintained within a predetermined level.

On the other hand, as shown in FIG. 3B, when the gain is adjusted so that the minimum value Fmin of the feeler signal becomes its target value Fmin0, for example, the minimum value of a small amplitude feeler signal indicated by a solid line is obtained. Even if there is no problem when Fmin1 is adjusted to its target value Fmin0, the minimum value Fmin2 of the large amplitude feeler signal shown by the dashed line is set to its target value Fmin0.
, The amplitude becomes larger due to the gain adjustment, and the level of the feeler signal becomes excessive.

In the illustrated example, the calculation of the feeler signal value such as the maximum value, the minimum value, and the average value of the feeler signal, and the adjustment of the gain in the signal processing circuit 16 are performed in each weft insertion cycle. However, these may be performed for each of a plurality of weft insertion cycles.

When the loom is operating, the signal processing circuit 16
, The calculation of the feeler signal value, and the storage of the calculated feeler signal value are performed in that order. Thereby, the thresholds used in the comparators 18 and 20 are stored in the storages 26 and 28, respectively, and the value for the gain adjustment in the signal processing circuit 16 is stored in the storage 30.

Thereafter, whether or not a weft is present is determined by the comparators 18 and 20, and the OR signal of the result of the determination is output from the OR gate 32 as a weft signal meaning "with or without weft". Is done.

According to the weft detecting device 10, the maximum value and the minimum value of the feeler signal over a predetermined time in the non-weft detecting period in each weft insertion cycle are calculated.
Each calculated value is a correct value according to the vibration even if the feeler signal vibrates due to the vibration of the reed. Accordingly, the threshold value set based on the maximum value and the minimum value obtained in this manner is also a correct value corresponding to the feeler signal vibrating due to the vibration of the reed, etc., and an error caused by a variable element other than the weft. The determination can be reliably prevented.

According to the weft detecting device 10, since the gain is adjusted based on the average value of the feeler signal in the signal processing circuit 16, when the amplitude is large as in the conventional device, the feeler signal level becomes excessively large or small. Without becoming
The determination of the presence or absence of a weft becomes more accurate.

Since the amplitude of the feeler signal caused by the vibration of the reed becomes maximum during beating and then gradually decreases and becomes smaller, the period for calculating the feeler signal value such as the maximum value, the minimum value and the average value of the feeler signal is reduced. Is preferably a period immediately before the weft detection period.

The timing for adjusting the gain is after the elapse of the weft detection period of the weft insertion cycle in which the average value is calculated by the arithmetic unit 22, and the non-weft detection period for the average value calculation by the arithmetic unit 22 in the subsequent weft insertion cycle. , That is, any time from the falling point of the timing signal A of the weft insertion cycle for which the average value is calculated to the rising point of the timing signal B of the subsequent weft insertion cycle, It is preferable to set the time immediately before the start between the non-weft detectors, that is, the rising point of the timing signal.

In this manner, the gain of the signal processing circuit 16 is maintained constant at least during the period of calculating the feeler signal value and the subsequent weft detection period, so that the calculation of the feeler signal value is performed accurately. The determination of the presence or absence of the weft based on the information becomes more accurate.

When the values stored in the storages 26 and 28 are not used as thresholds in the comparators 18 and 20, the timing of adjusting the gain in the signal processing circuit 16 is determined by calculating the average value in the arithmetic unit 22 and then arranging the weft. It is preferable that the predetermined time before the detection period arrives. In this way, the gain of the signal processing circuit 16 is kept constant at least during the weft detection period, so that the determination of the presence or absence of the weft becomes more accurate.

The maximum value and the minimum value respectively written in the storages 26 and 28 may be the actual values of the maximum value and the minimum value calculated by the arithmetic unit 22, but the calculated actual values correspond to the safe values. The value may be a value obtained by adding or subtracting a coefficient to be calculated, or a value obtained by multiplying or dividing the calculated actual value itself by a coefficient corresponding to the safety factor. Such addition, subtraction, multiplication, and division of the coefficients may be performed by the arithmetic unit 22 or by a dedicated circuit.

As described above, since the vibration waveform of the feeler signal attenuates gradually after the beating, there is no particular problem even if the actual values of the calculated maximum value and minimum value are used as the threshold, but when the degree of the attenuation is small. By adding, subtracting, multiplying and dividing these safety factors, the determination of the presence or absence of the weft becomes more accurate.

For the same reason as above, the comparators 18 and 2
The threshold value used at 0 may be the value itself stored in the storage devices 26 and 28, a value obtained by adding or subtracting a coefficient corresponding to a safe value to the stored value, or a value stored in the stored value. It may be a value obtained by multiplying or dividing a coefficient corresponding to the safety factor.

In any of the above cases, the comparators 18, 20
Since the threshold value used in (1) is corrected by the safety coefficient, the presence or absence of the weft can be more accurately determined.

Referring to FIG. 4, the weft detecting device 40 comprises:
The value stored in the storage unit 26 is a coefficient α1 corresponding to a safe value.
Is added to the comparator 18 and supplied to the comparator 18 as a threshold, and an addition circuit 44 which subtracts a coefficient α2 corresponding to a safe value from the value stored in the storage 28 and supplies the result to the comparator 20 as a threshold. Is different from the weft detecting device 10 shown in FIG.

In the weft detecting device 40, the adding circuit 42
And the subtractor 44 instead of the storage 26
A multiplication circuit for multiplying the value stored in the memory by a coefficient α1 corresponding to a safe value, and a division circuit for dividing the value stored in the storage unit 28 by a coefficient α2 corresponding to a safe value may be used.

According to the weft detecting device 40, in addition to the advantages obtained by the weft detecting device 10, the thresholds used in the comparators 18 and 20 are corrected by the safety coefficient in the circuits 42 and 44, and the presence or absence of the weft is more accurately determined. This has the advantage that it can be determined.

Referring to FIG. 5, the weft detecting device 50 comprises:
The difference from the weft detecting device 10 shown in FIG. 1 is that the threshold value used in the comparator 52 is determined based on the average value of the feeler signal over a predetermined time in the non-weft detecting period.

The weft detecting device 50 includes a calculator 54 for calculating an average value of the feeler signal using the timing signal B,
A storage unit 56 for storing the calculated average value, and processing the average value stored in the storage unit by adding, subtracting, multiplying, or dividing the safety value α, and comparing the processed value with a comparator 52 And a threshold processing circuit 58 for supplying a threshold value to the threshold value.

Since the weft detecting device 50 calculates the average value of the feeler signal over a predetermined time during the non-weft detection period in the weft insertion cycle, the amplitude of the feeler signal due to the vibration of the reed and the like is averaged. Even if the feeler signal vibrates due to the vibration of the reed, etc., the average value calculated as a result will be a correct value according to the vibration. Therefore, the same advantages as those of the weft detecting device 10 are also obtained by the weft detecting device 50.

Referring to FIG. 6, the weft detecting device 60 comprises:
It differs from the weft detecting device 50 shown in FIG. Weft detecting device 60
Further includes an arithmetic unit 64 for calculating an average value of the feeler signal using the timing signal A, and a storage unit 66 for storing the calculated average value. The determination of the presence or absence of the weft in the comparator 62 is performed when the timing signal A falls.

According to the weft detecting device 60, in addition to the advantages obtained by the weft detecting device 50, the average value of the feeler signal over the weft detecting period is used as a signal to be compared with the threshold value in the comparator 62. There is an advantage that the presence / absence can be determined more accurately.

Referring to FIG. 7, the weft detecting device 70 comprises:
Based on the point that the integrated value of the feeler signal over a predetermined time of the weft detection period is used as a signal to be compared with the threshold value in the comparator 72, and on the basis of the integrated value of the feeler signal over a predetermined time within the non-weft detection period. The difference from the weft detecting device 60 shown in FIG. 6 is that the threshold value used in the comparator 52 is determined.

The weft detecting device 70 calculates an integrated value of the feeler signal using the timing signal A to calculate an integrated value of the feeler signal, and supplies the calculated integrated value to a signal input terminal of the comparator 72; A computing unit 76 for calculating an integral value of the feeler signal using the timing signal B is processed by adding, subtracting, multiplying, or dividing the calculated integrated value by a safety coefficient α, and comparing the processed values. And a threshold processing circuit 78 for supplying a threshold value to the device 72. The computing units 74 and 76 are actually formed of integrators.
The predetermined times during which the arithmetic units 74 and 76 perform integration are set to be the same. Note that the computing unit 74 may not be provided.

According to the weft detecting device 70, the integrated value of the feeler signal over the weft detection period is used as a signal to be compared with the threshold value in the comparator 72, and the integrated value of the feeler signal over the non-weft detection period is used as the comparator. Since it is used as a threshold value at 72, the same advantage as that of the weft detecting device 60 is obtained.

Referring to FIG. 8, the weft detecting device 80 includes:
The predetermined reference value set in the reference value setting device 86 is compared with the comparator 1
8 and 20, which are used as threshold values. Instead, subtracters 84 and 86, which subtract the value stored in the storages 26 and 28 from the feeler signal and supply the same to the comparators 18 and 20, respectively. It differs from the weft detecting device 10 shown in FIG. 1 in that it is arranged on the input side of the feeler signal.

The weft detecting device 80 determines the presence or absence of the weft in the comparators 18 and 20 based on the signal after the subtraction processing between the feeler signal and the maximum value and the minimum value thereof. For example, it can be determined as "weft".

Also in the case of the weft detecting device 80, since the maximum value and the minimum value of the feeler signal used for the subtraction process are correct values following the vibration of the reed, the same advantages as those of the weft detecting device 10 shown in FIG. Have.

In each of the above embodiments, the signal processing circuit 16 for automatic gain adjustment of the feeler signal is provided, but this may be omitted if necessary.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electric circuit showing a first embodiment of a weft detecting device according to the present invention.

FIG. 2 is a diagram showing a waveform of an electric signal in the weft detecting device of FIG.

FIG. 3 is a diagram showing a waveform of a feeler signal for comparison between the device of the present invention and a conventional device.

FIG. 4 is a block diagram of an electric circuit showing a second embodiment of the weft detecting device according to the present invention.

FIG. 5 is a block diagram of an electric circuit showing a third embodiment of the weft detecting device according to the present invention.

FIG. 6 is a block diagram of an electric circuit showing a fourth embodiment of the weft detecting device according to the present invention.

FIG. 7 is a block diagram of an electric circuit showing a fifth embodiment of the weft detecting device according to the present invention.

FIG. 8 is a block diagram of an electric circuit showing a sixth embodiment of the weft detecting device according to the present invention.

[Explanation of symbols]

 10, 40, 50, 60, 70, 80 weft detection device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-247796 (JP, A) JP-A 63-154687 (JP, U) JP-A 63-145874 (JP, U) JP-B 64-64 1574 (JP, B2) JP 1-60570 (JP, B2) JP 2-46704 (JP, B2) Japanese Patent Application No. 1-1116683 (Japanese Utility Model Application No. 3-55883) Microfilm photographing the contents of documents and drawings (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) D03D 51/34

Claims (7)

(57) [Claims] 1. A sensing means for outputting a feeler signal having a vibration waveform, which is a feeler signal corresponding to the amount of light incident on a light receiving element, and comparing the feeler signal output from the sensing means with a threshold value to determine whether a weft exists. Determining means for calculating a feeler signal value during a predetermined time within a non-weft detection period and including at least one cycle of the vibration waveform of the feeler signal, based on the calculated value. Computing means for supplying a predetermined value to the determination means as the threshold value, wherein the feeler signal value obtained by the computing means is at least one selected from a maximum value, a minimum value, an average value, and an integral value of the feeler signal. One is a weft detection device for a loom. 2. A sensor for outputting a feeler signal corresponding to the amount of light incident on a light receiving element, and calculating a maximum value or a minimum value of the feeler signal during a predetermined time within a non-weft detection period, and calculating the calculated value. Calculating means for subtracting a predetermined value from the feeler signal output from the sensing means based on the reference value, and determining means for determining the presence or absence of a weft by comparing the value output from the calculating means with a threshold value, Weft detection device for loom. 3. The apparatus according to claim 1, wherein the predetermined value is the calculated value itself or a value obtained by correcting the calculated value by a predetermined coefficient. 4. The arithmetic unit includes a calculating circuit for calculating an average value of the feeler signal, the sensing unit outputs an electric signal corresponding to an amount of light incident on the light receiving element, and Receiving the output electric signal,
4. The apparatus according to claim 1, further comprising: a signal processing circuit that outputs the signal as the feeler signal; and a signal processing circuit that performs automatic gain adjustment based on the average value obtained by the calculation circuit. 5. The gain adjustment timing in the signal processing circuit is a predetermined timing before the start of calculation of the feeler signal value by the calculating means in the weft insertion cycle after the weft insertion cycle in which the average value is calculated by the calculation circuit. 5. The device of claim 4, wherein the device is provided. 6. A sensing means for outputting a feeler signal corresponding to the amount of incident light, a determining means for comparing the feeler signal output from the sensing means with a threshold to determine the presence or absence of a weft;
A calculating means for calculating an average value of the feeler signal during a predetermined time within the non-weft detecting period, wherein the sensing means outputs an electric signal corresponding to the amount of incident light, and an output from the sensing circuit. A signal processing circuit that receives the electrical signal received, processes the signal, and outputs the signal as the feeler signal, the signal processing circuit performing automatic gain adjustment based on the average value obtained by the arithmetic unit. Weft detection device. 7. The adjustment time of the gain in the signal processing circuit is calculated by calculating the average value by the calculating means.
The apparatus according to claim 6, wherein the predetermined time is before the weft detection period reaches.