JPH0760108B2 - Weighing conveyor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weighing conveyor device that measures the weight of a product while the product is conveyed by a conveyor, and more particularly to a technique for correcting an error in a detected weight value.

(Prior Art) In a weighing conveyor used for sorting products by weight, one product is discharged from the conveyor at the same time as the next product is placed on the conveyor for the purpose of improving the sorting processing speed. The work will proceed.

On the other hand, the weighing conveyor device is configured by placing the conveyor device main body on the weighing mechanism, and because the conveyor device is used as a tare to measure the weight of the product, even mechanical vibration due to the movement of the conveyor is generated. Because it acts on the weighing mechanism,
The signal output from the measuring mechanism contains an extremely large noise component, and a filter for removing a high frequency component and a low frequency component is inserted at the output side of the measuring mechanism for the purpose of removing the noise component.

For this reason, the signal processing system has a large time constant due to the large-capacity capacitor that constitutes the low-frequency component removal filter, and the product is discharged from the conveyor before the output from the filter reaches a steady state. Will be done. On the other hand, after the product is discharged, the residual charge of the filter is gradually discharged based on the large time constant described above, and the output level thereof is lowered.

Therefore, if the loading time interval of the product is incorrect, an error component due to the residual charge is included, which causes a problem that the weighing result includes a large error.

In order to solve such a problem, two kinds of correction coefficients are prepared with the time ΔA until the output of the filter returns to zero as a boundary, and when the load is carried out at an interval longer than the time ΔA and at a short interval. A weighing conveyor is also proposed in which the correction coefficient is selected depending on the time (Japanese Patent Laid-Open No. 62-133321).
Public Law).

(Problems to be Solved) According to such a device, accurate correction can be performed when a product is loaded by clearly distinguishing the loading time of the product based on the reference time interval ΔA. When goods are loaded at intervals shorter than the interval ΔA, the initial potential of the filter varies depending on the loading timing and the variation of the discharge timing due to the size of the goods.

That is, as shown in FIG. 7, when a product having a weight W in a stationary state is loaded in the initial state, there is no initial charge in the filter, and therefore, as shown in FIG. The weight signal rises according to the determined time constant.
Since the product is discharged from the conveyor before this weight signal reaches a steady state, that is, before reaching the level corresponding to the weight W, the signal W'from the filter is normally taken in at the time of discharging the product, and ΔW1 with the true weight. The error amount of is corrected.

On the other hand, when the product is discharged, the electric charge charged in the filter is discharged based on the time constant of the filter (II).

However, in order to increase the efficiency of weighing work, the next product is loaded without waiting for the residual charge on the filter to be completely discharged. The weight signal of the next product will be output from the filter in the form of being superimposed on the determined initial charge (Fig. III). For this reason, the output level at the time of loading the weight signal becomes higher than that at the time of loading the first product, and since loading is performed before reaching the steady value, it is smaller than the initial error ΔW ₁ , but the An error of ΔW ₂ will occur with respect to the weight.

On the other hand, the time required from the complete loading state of the product to the discharge of the leading edge depends on the size of the products A and B, that is, is inversely proportional to the length in the moving direction, when the moving speed of the conveyor is constant. (FIG. 5) Naturally, the timing of loading the weight signal varies depending on the product size, which causes a problem that the reliability of the measurement result further deteriorates.

The present invention has been made in view of such a problem, and an object thereof is to provide a novel weighing conveyor device capable of finely correcting a weighing value in accordance with a loading interval of a product and a size of a product. To do.

(Means for Solving the Problem) In order to solve such a problem, in the present invention, a product detection unit that detects loading of a product on a weighing conveyor,
Interval measuring means for detecting the time interval of loading of goods by a signal from the goods detecting means, external data input means for inputting goods data for specifying the goods whose weight is to be detected, and true weight for each goods And error data representing the difference between the weight when the weighing conveyor is moved at a predetermined speed and measurement, and error data storage means read based on the product data, and a correction factor corresponding to the time interval. Based on the error data and the correction rate data, a means for outputting data, a sampling and holding means for taking a weighing signal at a time point when a time determined by the product data elapses after a signal is output from the product detection means. Correction data calculating means for calculating the correction amount by
A means for correcting the weight signal from the sampling and holding means based on the correction amount is provided.

(Function) The loading time of the weighing signal and the size of the product are determined because the loading time of the weighing signal is determined for each product, and error data is provided for each product, which is further corrected by the loading time interval of the product to obtain the correction amount. Accurate weight data can be obtained regardless of.

(Examples) Therefore, the details of the present invention will be described below based on illustrated examples.

FIG. 1 is a block diagram of an apparatus showing an embodiment of the present invention, in which reference numeral 1 is a weighing conveyor apparatus main body, and a conveyor belt 2 connected to a drive mechanism (not shown) is loaded on the weighing mechanism 3. A product detector 6 that outputs a signal from the detection mechanism 3 to a sample hold circuit 5 described later via a filter circuit 4 and that detects that the product has moved to the belt 2 is provided on the carry-in side. . Reference numeral 7 is a weight signal taking-in timer, which is set to output a signal when a predetermined time ΔT has elapsed from the time when the signal from the object detector 6 was inputted. The sample-and-hold circuit 5 is configured to sample and hold the weight signal from the filter circuit 4 when the signal from the weight signal acquisition timer 7 is input. Reference numeral 8 denotes an interval measuring circuit, which is configured to output the input interval of the signal from the product detector 6, that is, the loading time interval Δt of the product.

Reference numeral 9 is an error data storage circuit, and the product codes A, B, C from the product name input key 10 to be weighed as shown in FIG.
... as an address, and the reference weight difference ΔW between the weight W at rest and the uncorrected value from the conveyor weighing device 1 when moved at the reference speed, that is, the output W ′ of the sample hold circuit 5.
= W−W ′, and signal acquisition timing Δ for each product
T ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ ... are stored as data, and a reference error is stored in a correction data calculation circuit 14 which will be described later based on the product code from the product name input key 10 and a loading timing is a weight signal. It is configured to output to the acquisition timer 7.

Reference numeral 12 denotes a correction rate storage circuit, which is a relationship between the time interval Δt at which a product is loaded on the belt and the correction rate α as shown in FIG. 3, that is, a value which becomes smaller as the time interval Δt becomes smaller, The intervals are the addresses Δt1, Δt2, Δt3 ... (Δ
When t1 <Δt2 <Δt3 <... Δtn), the correction rate α (t) is set to the data α1, α2, α3, ... (α1 <α2 <α3 <... <α
(n = 1) is stored as data, and the correction rate α (t) is output to the correction data operation circuit 14 described later by the signal from the interval measuring circuit 8.

Reference numeral 14 is the above-mentioned correction data operation circuit, which is an error amount Δ produced when a signal is acquired by multiplying the reference error ΔW from the error data storage circuit 9 and the correction rate α (t) from the correction rate storage circuit 13.
The correction amount ΔG = ΔW × α (t) corresponding to W ′ is calculated and output to the adder circuit 15. Reference numeral 15 is an addition circuit, which is a correction data calculation circuit for the weight signal of the sample hold circuit
The true weight, that is, the weight signal W that has been subjected to the dynamic correction, is output by adding the correction amounts ΔG of 14 to each other.

Next, the operation of the apparatus thus configured will be described with reference to FIG.

First, before using the device, the true weight of each product, that is, the weight W ₁ , W ₂ , W ₃ , W ₄ in the stationary state is measured, and then the correction function of the conveyor weighing device is stopped to set the reference speed. Weight W ′ ₁ for the same product when transferred by
_{W '2, W' 3,} W '4 ... was measured, and these differences ΔW _{1
= W 1 -W '1, ΔW} 2 = W 2 -W' 2, ΔW 3 = W 3 -W '3,
Stored in the error data storage circuit 9 by _{ΔW 4 = W 4 -W '4} ... numeric keys 16 such as a data input means. Further, in accordance with this, the time ΔT from the detection of each product by the product detector 6 to the loading of the weight signal is inversely proportional to the size of the product, that is, the loading time is shortened for long products. Store the data.

When the preparation is completed, the product name is input from the product name input key 10 to specify the product A to be weighed, and the reference error ΔW ₁ = about this product is input from the error data storage circuit 9.
W ₁ -W ′ ₁ is set in the correction data operation circuit 14, and the signal acquisition timing ΔT _{1 of the} product A is set in the weight signal acquisition timer 7.

First product A is conveyed by belt 17 and product detector 6
Is activated, the weight signal acquisition timer 7 and the interval measuring circuit 8 start operating in response to the signal from this. When the product passes through the product detection 6 and transfers to the belt 2, the weight detection mechanism 3 outputs a signal corresponding to the weight of the product and a signal in which noise due to vibration of the belt drive system is superimposed. This signal is input to the filter circuit 4 to remove noise caused by vibrations and the like, while the filter circuit 4
The output level of the weight signal rises with time with a constant time constant due to the capacitance component constituting (I in FIG. 4).

In this way, the signal from the filter 4 is held by the sampling and holding circuit 5 when the time ΔT ₁ set in the weight signal acquisition timer 7 has elapsed. In this case, since the measurement is for the first product, the data reading circuit 13 outputs the correction rate α = 1, and therefore the correction data operation circuit 14 performs the correction due to the initial charge of the filter 4. The reference error ΔW ₁ read from the error data storage circuit 9 is output as the correction amount ΔG ₁ .

As a result, ΔW ′ ₁ + obtained by adding the correction amount ΔG ₁ to the measurement data W ′ held in the sample hold circuit 5 is added.
ΔG ₁ is output, and it is possible to obtain measurement data with the error eliminated as much as possible.

In this way, the product is discharged from the belt 2 before the output level of the filter 4 reaches the steady state, whereby the output level of the filter circuit 4 gradually decreases the signal level based on the time constant. Go (II).

When the next product A of the same type conveyed reaches the product detector 6, the interval measuring circuit 8 measures the time interval Δt ₁ between the product A and the previous product, and the time interval Δt from the correction rate storage circuit 12 is measured.
correction factor corresponding to t ₁ alpha read out (t) = α _1. The correction data calculation circuit 14 determines the error ΔW _{1 of} this product read from the error data storage circuit 9 and the correction rate α just read.
The correction amount ΔG = ΔW ₁ × α ₁ is calculated by multiplying (t) =.

When time ΔT1 elapses from the loading of the second product (II
I), a signal is output from the weight signal receiving circuit 7, the weight signal W'from the filter circuit 4 is taken in by the sampling and holding circuit 5, and the correction amount ΔG ' ₁ =
ΔW ₁ × α ₁ is added and W ′ + ΔG ′ ₁ = W ′ + ΔW ₁ ×
α ₁ is output as weight data. As a result, a weight signal that is as accurate as possible is output regardless of the initial charge amount of the filter circuit 4 caused by the time interval for loading the product on the belt 2.

When continuously measuring the same product in this way,
The time interval Δt from the immediately preceding product removal, that is, the correction rate α is changed according to the interval, and the correction amount ΔG = ΔW ₁ ×
Calculate α (t). As a result, the weight can be accurately measured regardless of the loading interval of the products.

If the time from the last product discharge to the next product loading is sufficiently long, that is, if the residual charge of the filter circuit 4 is longer than the time required to discharge, the correction factor storage circuit 12
Since the correction rate α = 1 is read from, the error data ΔW ₁ of the error data storage circuit 9 is added to the sample hold value W ′ ₁ as it is.

On the other hand, when the product to be weighed is replaced by the next product B, the product code is input from the product name input key 10, and the reference error ΔW ₂ = W ₂ −W ′ ₂ is calculated from the error data storage circuit 9 as the correction data calculation. The signal is read by the circuit 14, and the weight signal acquisition timer 7 is set with the signal acquisition time ΔT ₂ for this product.

At this stage, when another type of product is loaded on the conveyor 17, it undergoes dynamic correction through the same process as described above.

By the way, when the product to be calculated is changed and the product size is changed, the time from loading to discharge as described above.
Although L ₁ and L ₂ also change, the signal acquisition timing also changes in FIG. 5 (I, II), but the initial data ΔW ₁ = W ₁ −W to the error data storage circuit 9 is changed. ′ ₁ , ΔW ₂ = W _{2
-W '2, ΔW 3 = W} 3 -W' 3, because it is taken into account as a reference error ΔW at the time of _{ΔW 4 = W 4 -W '4} ... setting, accompanied the change of size under the trade designation of the stage The correction is also performed at the same time, so that there is no error caused by the change in the weight signal acquisition timing ΔT, and high-accuracy measurement is possible.

In this embodiment, the correction factor is stored in the dictionary format, but the same effect can be obtained even if the analog or digital function generating circuit is used to calculate the correction factor with the time data as an independent variable. It is clear that it will play.

Furthermore, in this embodiment, the correction amount ΔG is calculated and added to the sample-held value. However, the final correction amount is calculated as a ratio, and this ratio is multiplied by the sample-hold value or divided by It is obvious that the same effect can be obtained even if added.

Further, in this embodiment, the signal acquisition timing ΔT of each product is stored in the error data storage circuit, but it is clear that the same operation can be achieved even if it is stored in the weight signal acquisition timer 7. .

Further, in the above-described embodiment, the correction rate α is changed according to the interval Δt for loading the goods on the belt and the correction is performed based on this, but as shown in FIG. The signal acquisition timing of is the acquisition timing Δ stored in the error data storage circuit 9.
The signal from the signal acquisition timing determination circuit 20 that determines the acquisition signal in consideration of T and the loading time interval Δt, that is, the acquisition timing is shifted to a time that is inversely proportional to the product loading interval. By adding the reference error ΔW of the error data storage circuit 9, the variation due to the residual charge of the filter circuit 4 can be canceled without the multiplication process of the correction factor α, and the device can be simplified. Can be realized.

(Effect) As described above, in the present invention, the product detection means for detecting the loading of the product on the weighing conveyor, the interval measuring means for detecting the time interval of the product loading by the signal from the product detection means, and the weight External data input means for inputting product data for specifying the product to be detected, and error data representing the difference between the true weight of each product and the weight when measured by moving the weighing conveyor at a predetermined speed. Error data storage means for storing and reading based on the product data, means for outputting correction rate data corresponding to the time interval, and after a signal is output from the product detection means,
Sampling and holding means for taking in a weighing signal when a time determined by the product data has passed, correction data calculating means for calculating a correction amount based on error data and correction rate data, and a correction amount for a weight signal from the sampling and holding means. Since it is equipped with a means for correcting the initial charge amount of the filter, that is, proper correction can be performed regardless of the loading timing and the size of the product, the product can be sent while improving the measurement accuracy. The speed can be improved to improve the efficiency of weighing work.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus showing an embodiment of the present invention, FIGS. 2 and 3 are diagrams schematically showing data of an error data storage circuit and a correction rate storage circuit in the same apparatus, respectively, and FIG. FIG. 5 is an explanatory view showing the operation of the apparatus, FIGS. 5 (I) and (II) are views showing changes in signal acquisition timing when a product is changed, and FIG. 6 is a block showing a second embodiment of the present invention. FIG. 7 and FIG. 7 are explanatory diagrams showing the output characteristics of the weighing conveyor. 1 ... weighing belt main body, 2 ... belt 3 ... weighing mechanism, 6 ... product detector

Claims (1)

[Claims] 1. A product detecting means for detecting a load of a product on a weighing conveyor, an interval measuring means for detecting a time interval of the load of the product by a signal from the product detecting means, and a product for which a weight is to be detected is specified. External data input means for inputting product data for storing, and error data representing the difference between the true weight of each product and the weight when measured by moving the weighing conveyor at a predetermined speed and storing the product. Error data storage means read based on the data,
Means for outputting correction rate data corresponding to the time interval; sampling and holding means for taking in a weighing signal when a time determined by the product data has elapsed since the signal was output from the product detection means; and the error A weighing conveyor device comprising: a correction data calculating means for calculating a correction amount based on data and the correction rate data; and a means for correcting a weight signal from the sampling and holding means based on the correction amount.