JP3360895B2 - Combination weighing method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used when a large number of objects to be weighed, such as foods, are collected and packed into bags, the contents of the packed products are weighed so as to reach a set value. The present invention relates to a combination weighing method and its device.

[0002]

2. Description of the Related Art Conventionally, when a large number of objects to be weighed are collected and automatically packaged, the objects to be weighed are individually weighed by a plurality of weighing devices, and the weighing signals from these weighing devices are combined and calculated. , Within a certain allowable range, select a combination that is close to the target value obtained by adding a predetermined correction value to the lower limit set value, and discharge the objects to be weighed from the selected weighing machine to the automatic packaging machine. ing.

That is, during automatic packaging, in order to prevent the quantity to be weighed to be packaged from becoming insufficient, as shown in FIG. 3, between the lower limit set value A and the upper limit value B, A target value C obtained by adding a predetermined correction value α to the set value A is set, and combination weighing of the objects to be weighed is performed so as not to fall below the target value C. Then, before the object to be weighed is discharged from the selected weighing device after the combined weighing, the weighing signal from the selected weighing device is fetched and added to recheck the combined weighing value, As a result of the recheck, when the measured value is less than the set value, the weighing object is not discharged from each weighing device to prevent the production of a product with insufficient quantity (see Japanese Patent Publication No. 2-54885).

Here, the correction value α is calculated as follows. That is, the weighing signal from each weighing device is shown in FIG.
As shown in, there is a slight fluctuation due to the vibration of the weighing instrument and the floor vibration due to the falling of the object to be weighed into the weighing hopper. Therefore, if the weighing signal is taken in at timing D in the figure and the combination weighing is performed, and then rechecking is performed at timing E, the signal level difference Δ = (signal level at point E) − (D Point signal level). The level difference Δ may be either a positive value or a negative value. For example, when the level difference Δ is a negative value, the weight at the time of recheck is smaller than the set value A, and as a result, it is considered that the quantity is insufficient. May not discharge from the measuring instrument. Therefore, the correction value α is determined so as to eliminate the influence of the level difference Δ and suppress the decrease in the operating rate due to the occurrence of the insufficient quantity.

That is, assuming that the distribution of the signal level difference Δ is a normal distribution and its standard deviation is σ ₁ , when N weighing instruments are selected by the combination weighing, the weighing of the combined total weight is performed. The difference distribution is also a normal distribution, and its standard deviation σ _N is σ ₁ √N. At this time, since the measurement difference of 99.8% is included within the range of ± 3σ _N that is three times the standard deviation σ _N , if 3σ _N = 3σ ₁ √N is adopted as the correction value α, recheck As a result, it is considered that the case where the quantity becomes insufficient is suppressed to 0.2% or less and the operating rate is sufficiently improved.

However, in combination weighing, it is not preferable to change the target value every time the number N of the selected weighing devices changes, because this leads to an increase in weighing time. Therefore, the average number of measuring instruments N _L is used, and from this, the correction value α = 3σ ₁ √N _L
Is used in search of. For example, when weighing an object to be weighed with a set value (corresponding to the lower limit value) of 100 g with a combination of ten weighing devices, the standard deviation σ ₁ is empirically set to 0.1 g, and the average number of weighing devices N _L 0 when 4 is set to 4.
6 (= 3 × 0.1 × √4) g is adopted as the correction value α. If this correction value α is increased, the occurrence rate of equipment stoppage due to insufficient quantity is reduced and the operating rate is improved, but since the amount of objects to be weighed in one bag is increased on average, the yield is correspondingly increased. descend.

Thus, the correction value α is determined, and the set value A
The target value C is calculated by adding the correction value α to the target value C, and the combination calculation is performed to select a combination that does not fall below the target value C, thereby reducing the frequency of occurrence of insufficient quantity after rechecking and reducing the operating rate. The yield is kept high while increasing the yield.

[0008]

However, in the above-described combination weighing device for objects to be weighed, the correction value is previously set to a constant value based on the average number N _{L of} selected weighing devices and the empirical standard deviation. Since it is set, it becomes difficult to increase both the yield and the operating rate when weighing the objects to be weighed for all the weighing devices having different individual characteristics.

The present invention has been made in view of the above problems, and an object thereof is to provide a combination weighing method and apparatus capable of improving the yield and operation rate of objects to be weighed. .

[0010]

In order to achieve the above object, a combination weighing method according to the present invention comprises a plurality of weighing instruments.
Each of the past sets obtained by detecting the weighing difference between the combination weighing value at the time of combination calculation and the combination weighing value at the time of recheck by using
It is characterized in that the correction value is set so that the desired operation rate and the yield are the optimum values based on the measurement difference between the combined measurement values .

Further, the combination weighing device according to the present invention includes a weighing difference detecting means for detecting a weighing difference between the combination weighing value at the time of combination calculation and the combination weighing value at the time of recheck , using a plurality of weighing devices , The past obtained by the detection means
A correction value calculating means for calculating a correction value so as to obtain an optimum value for obtaining a desired operating rate and a yield based on the difference in measurement of the combination measurement values, and a combination calculating means for calculating the correction value calculated by the calculating means. And a correction value setting means for inputting to the.

[0012]

According to the weighing method of the present invention, a weighing difference between the combination weighing value at the time of combination calculation and the combination weighing value at the time of recheck is detected, and a new correction value is obtained based on this weighing difference and the past weighing difference. Is set. Therefore, by adding this correction value to the set value as a target value and performing the combined weighing of the objects to be weighed based on this target value, a high yield and a high operating rate can be obtained.

According to the weighing apparatus of the present invention, the weighing difference detecting means detects a weighing difference between the combination weighing value by the combination calculating means and the combination weighing value at the time of rechecking by the rechecking means, and the obtained past difference is obtained. A correction value is calculated by the correction value calculation means based on the measurement difference. Then, the correction value is input to the combination calculation means by the correction value setting means, the correction value is added to the set value to obtain the target value, and the combination weighing of the objects to be weighed is performed based on the target value, which is high. Yield and availability can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the combination weighing method and apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 schematically shows the overall structure of a combination weighing device. In this weighing device, a conical dispersion feeder 2 is arranged below a conveyor 1 located above. The conveyor 1 receives an object M to be weighed, such as food, sent from the manufacturing line, conveys it to above the dispersion feeder 2, and drops it in the center thereof. A plurality of vibrating feeders 3 are radially arranged around the outer periphery of the dispersion feeder 2.
Each of these feeders 3 sends the object M to be measured outward in the radial direction while vibrating, and drops it from the pool hopper 4 arranged below it into a plurality of measuring devices 5.

The scales 5 are the pool hoppers 4
It comprises a weighing hopper 51 for receiving the object M to be weighed from and a load cell 52. This load cell 52
Has one end fixed to the base 50 and the other end to which the weighing hopper 51 is attached. The weight of the object to be weighed M supplied to the weighing hopper 51 is detected, and the CPU 1 described later
The weighing signal is output to 0. A collective discharge chute 6 is provided below the weighing hopper 51, and an automatic packaging machine 7 is arranged below the chute 6.

FIG. 2 shows a block diagram of the combination weighing device. An amplifier 11 and a filter 12 are separately connected to each load cell 52 in order to input the weighing signal from each load cell 52 to the CPU 10. At the same time, a multiplexer 13 is connected to the output side of these filters 12, and the respective weighing signals are inputted from the multiplexer 13 to the CPU 10. In the figure,
Reference numeral 14 is an analog / digital converter.

Further, the reading means 15 is connected to the input side of the CPU 10, and by selecting the item selection key 16, various data is read from the memory 17 and input to the CPU 10. Further, the hopper opening / closing control circuit 18 for selectively opening / closing the weighing hoppers 51 is connected to the output side of the CPU 10.

The CPU 10 has a combination calculation means 19, a recheck means 20, a weighing difference detection means 21,
A correction value calculation means 22, a correction value setting means 23, a set value holding means 24 and an upper limit value setting means 25 are provided.

The combination calculation means 19 performs combination calculation of the weighing signals from the load cells 52, and as shown in FIG. 3, within a certain allowable range AB, the correction value is set to the lower limit set value A. A combination close to the target value C obtained by adding α is selected.

The recheck means 20 is selected from the combination calculation means 19 after the combination calculation by the combination calculation means 19 and before the object M to be weighed is discharged from each selected weighing hopper 51. The signal indicative of the weighing instrument is received, and the weighing signal from each of the selected load cells 52 is fetched and added to recheck the combined weighing value. Then, this recheck value is the above-mentioned allowable range A.
When it is within -B, the signal indicating the selected weighing device from the combination calculation means 19 is directly output to the hopper opening / closing control circuit 18 to open each of the selected weighing hoppers 51. on the other hand,
When the recheck value is less than or equal to the set value A, no signal is output from the recheck means 20 to the hopper opening / closing control circuit 18, and the weighing hoppers 51 are not opened.

The weighing difference detecting means 21 detects the weighing difference Δ between the combination weighing value at the time of the combination calculation by the combination calculating means 19 and the combination weighing value at the time of the recheck by the recheck means 20.

Further, the correction value calculating means 22 is based on the past measurement difference obtained by the measurement difference detecting means 21 so that the desired operation rate and the yield can be the optimum values. Calculate α.

As the correction value α, for example, the absolute value of the maximum value of all the measurement differences Δ from the past to the present is adopted. In this case, there is a possibility that the correction value α becomes large and the yield slightly deteriorates, but the operating rate can be made almost 100%, and it is particularly suitable when the distribution of the measurement difference is a uniform distribution. .

Further, when the above-described metering difference Δ is a normal distribution as shown in FIG. 3, as the correction value alpha, weighed difference
The standard deviation σ 1 of the distribution can be calculated each time, this can be multiplied by the square root √NL of the average number of measuring instruments, and the value obtained by further multiplying it by 3 can be adopted. In this case, as described above, 99.8% of the measurement difference Δ is included, so that the operating rate is increased. Moreover, since the correction value α can be made as small as possible, the yield is also improved.

Further, as the correction value α, an average value of absolute values of the measurement difference Δ may be adopted. In this case,
Since the correction value α can be made even smaller, the yield can be increased, although there is a risk of a slight decrease in the operating rate.

Further, the correction value setting means 23 comprises a correction value updating means 23a and a correction value holding means 23b, and the correction value α calculated by the correction value calculating means 22 is inputted to the correction value updating means 23a. The correction value α is held in the correction value holding means 23b and the combination calculation means 1 is updated.
9 is input.

Next, a combination weighing method of the object M to be weighed using the above combination weighing device will be described. First, Fig. 1
The objects to be weighed M supplied to the dispersion feeder 2 from the transport conveyor 1 of FIG. 1 are dropped into the pool hoppers 4 through the plurality of vibrating feeders 3, and the weighing devices 5 arranged below the pool hoppers 4 are provided. Is fed into the weighing hopper 51, and the objects to be weighed M in the weighing hopper 51 are individually weighed by the load cell 52.

Then, the weighing signal from each of the load cells 52 is sent to the combination calculating means 19 in the CPU 10, and by selecting the item selection key 16, the correction value of the object to be weighed M selected from the memory 17 is selected. The α, the initial value setting value (lower limit value) A, and the upper limit value B are read by the reading means 15, and the correction value holding means 23 of the CPU 10 is read.
b, the setting value holding means 24 and the upper limit value setting means 25 once hold the data, and the holding means 23b, 24, 25 input the data to the combination calculating means 19.

Further, in the combination calculating means 19,
Based on the input values α, A and B from the correction value holding means 23b, the set value holding means 24 and the upper limit value setting means 25,
The weighing signals from each of the load cells 52 are combined and calculated, and as described above, a combination close to the target value C obtained by adding the correction value α to the set value A is selected within the certain allowable range AB.

Further, after the combination calculation by the combination calculation means 19, the weighing signal from each of the selected load cells 52 is taken into the recheck means 20, and the recheck means 20 performs the combination weighing by the combination calculation means 19. The value is rechecked. When the recheck value is within the allowable range AB, the weighing hoppers 51 selected via the hopper opening / closing control circuit 18 are opened, and the objects M to be weighed are shown in FIG. It is discharged to the collective discharge chute 6 and is packaged by the automatic packaging machine 7. On the other hand, when the recheck value is equal to or less than the set value B, the object M to be weighed is not discharged, and the occurrence of insufficient quantity is prevented.

Further, at the time of weighing the object M to be weighed as described above, the weighing difference detecting means 21 in the CPU 10 in FIG.
A measurement difference Δ between the combination measurement value by the combination calculation means 19 and the recheck value by the recheck means 20 is detected.

Further, the measurement difference Δ is the correction value calculation means 2
2 is input to the correction value calculating means 22 based on the past measurement difference Δ including the present measurement difference Δ, and the optimum correction value α for increasing the yield and the operating rate as described above.
Is calculated.

Then, the correction value α is calculated by the correction value updating means 2
3a is updated and input to the correction value holding means 23b, the correction value α from the correction value holding means 23b, the set value A from the set value holding means 24, and the upper limit value B from the upper limit value holding means 25. Are input to the combination calculation means 19 and are used as a reference for selecting combinations of the weighing hoppers 51 close to the target value C. In this way, by adding the correction value α to the set value A to obtain the target value C and performing the combined weighing of the objects M to be weighed based on the target value C, a high yield and an operating rate can be obtained.

[0034]

As described above, according to the combination weighing method and the combination weighing device of the present invention, the weighing difference between the combination weighing value at the time of combination calculation and the combination weighing value at the time of recheck is detected and obtained. The correction value is set based on the past measurement difference, this correction value is added to the set value as the target value, and the combined weighing of the objects to be weighed is performed based on this target value. Both rates can be increased.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration of a combination weighing device according to the present invention.

FIG. 2 is a block diagram showing a main part of the combination weighing device.

FIG. 3 is an explanatory diagram when setting a target value.

FIG. 4 is a signal waveform diagram showing a weighing signal sent from the weighing machine.

[Explanation of symbols]

5 ... Measuring instrument, 19 ... Combination computing means, 20 ... Rechecking means, 21 ... Metering difference detecting means, 22 ... Correction value computing means,
23 ... Correction value setting means.

Claims (2)

(57) [Claims] 1. A weighing signal from a plurality of weighing devices for weighing an object to be weighed is combined and calculated, and a combination close to a target value obtained by adding a correction value to a lower limit set value is selected within a certain allowable range. To discharge the object to be weighed from the selected weighing instrument, and to acquire and add the weighing signal from the selected weighing instrument before the object to be weighed from the selected weighing instrument after combination calculation. In the combination weighing method in which the combination weighing value is rechecked by, the weighing difference between the combination weighing value at the time of combination calculation and the combination weighing value at the time of recheck is detected by using the above-mentioned multiple weighing devices, and the obtained past A combination weighing method, wherein the correction value is set so that a desired operating rate and a yield are obtained on the basis of a difference in measurement of the respective combination weighing values . 2. A plurality of weighing devices that weigh an object and output a weighing signal, and these weighing signals are combined and calculated, and a correction value is added to a lower limit set value within a certain allowable range. A combination calculation means for selecting a combination close to the target value to discharge the object to be weighed from the selected weighing device, and a selected combination before the object to be weighed is discharged from the weighing device selected after the combination calculation. In a combination weighing device equipped with recheck means for rechecking a combination weight value by taking in and adding a weighing signal from the weighing machine, a combination weight value and a combination weight value at the time of combination calculation are re-checked by using the plurality of weighing machines. Weighing difference detection means for detecting a weighing difference from the combined weighing value at the time of checking, and a desired operating rate and yield based on the weighing difference of each past combined weighing value obtained by this detecting means. The optimum value that can be obtained A combination weighing device comprising: a correction value calculating means for calculating the correction value as described above; and a correction value setting means for inputting the correction value calculated by the correction value calculating means to the combination calculating means.