JPH0413934A - Weight detector of weight control type packing machine - Google Patents

Abstract

PURPOSE:To obtain a high precision in measurement at an aimed weight by a method wherein the weight of a vessel holding mechanism element being unnecessary for control of a packing machine is canceled out of the total weight of the weight of a substance to be measured and the weight of a vessel holding mechanism and a weight signal only of the substance to be measured is computed. CONSTITUTION:In regard to the total weight of the weight of a substance to be measured and the weight of a vessel holding mechanism, an arithmetic unit 9 reads a timing signal 11 and an aimed weight 13 from a packing control device 50 through a bus line 16 in accordance with a state of operation, gives an instruction to deliver an output signal of a D/A converter 8, outputs to a switching circuit 5 a select signal for determining an output signal of this circuit, reads an output signal of an A/D converter 6, and outputs a measured weight 14 to the packing control device 50 through the bus line 16. Then, a weight signal only of the substance to be measured is computed and thus measurement is made by a measuring range showing the most excellent precision of the aimed weight.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a weight detection device for a single weight control type filling machine.

To explain the weight detection device of a conventional weight-controlled filling machine using Fig. 4, (1) is a load converter;
In 1), the weight W is the sum of the weight of the object to be measured (filling liquid and container) (the weight to be determined) and the weight M of the holding mechanism for holding the object to be measured (initial weight). Add as value. This weight signal is converted into an electrical signal by the load converter (1), amplified by the preamplifier (2), and then
It is input to the D converter (6). On the other hand, the calculation unit (9
) has a signal proportional to the output signal from the A/D converter (6) as input (Xi)), and the filling control device (50)
When the timing signal (11) manually inputted from the input interface (12) is 1, the timing signal (11) is stored as an initial value (referred to as Xinit) in the memory (10), and when the timing signal (11) is 0. At this time, calculation is performed using the formula 0 to obtain a weight value (referred to as Wi), which is sent to the filling control device (referred to as Wi) via the output interface (15).
50) as the measured weight (14).

Wi=K ・(Xi −Xinit)・・・・・・・
...■Here, X1nit is an initial value stored in the memory (10), and is a conversion coefficient to weight.

By setting the timing signal (11) to 1 at an appropriate timing when there is no object to be measured, the subsequent measured weight (14) can be obtained as the weight of only the object to be measured.

The detection weight range of the weight detection device of the weight-controlled filling machine shown in Fig. 4 above can be up to the maximum weight of the object to be measured plus the maximum value as the initial weight. (1), preamplifier (2), and A/D converter (
6), and the number of conversion bits of the A/D converter (6) is required to be sufficient to obtain the resolution necessary for measurement.

(Problem to be solved by the invention) In a weight-controlled filling machine, the 1" standard weight of the objects to be measured (filling liquid and container) controlled by one machine varies depending on the product type, and a wide range of about 10 times is possible. requested. Also, while controlling the object to be measured, the weight (
The initial weight) often differs because the structure of the holding mechanism changes depending on the target weight or the shape of the container, but in general.

It will weigh between 1 kg and 1.5 kg. However, the initial weight is unnecessary for filling control.

In addition, the accuracy required for filling control is determined by the ratio to the target weight, but the accuracy is strict and recently, 0.5%
It has become a degree. There are two possible factors that affect accuracy, but in digitally controlled weight detectors that use an arithmetic unit (generally an MPU), detection resolution is a major factor, and in order to obtain high accuracy, A resolution of about 11,000 (01%) is required for the target weight.

In order to satisfy the above-mentioned accuracy, the weight detection device of the weight-controlled filling machine shown in FIG. The maximum value of the detected weight range from weight detection to digital conversion must be determined to be greater than or equal to the total weight of the maximum target weight plus the maximum initial value. Also A/D converter (6)
The resolution guarantees the resolution at the minimum target weight, and
It is necessary to set it so that it can cover up to the maximum detection range.

For example, minimum target weight -200g, maximum target weight -2kg
, maximum initial weight], , 5 kg, degree of decomposition 0.
If it is 1%.

Maximum detected weight ・2000 +1500=3500 (g
) Resolution of A/D converter (6)・200X0.001/
3500・1/17500 is required.

As described above, in the weight detection device of the conventional weight-controlled filling machine, the resolution is set to an unnecessary range of signals (initial mold amount). In addition, since all target weights are processed centrally, the target decomposition rate (in the example, 1/100
(1/175 in the example)
00), and it is necessary to use a high-precision A/D converter (6). (1) It is necessary to use a device with a large number of bits, which makes the weight detection device expensive. Also, the higher the resolution, the more stable the circuit up to the A/D converter (6) needs to be.
There was a problem that the circuit configuration and mounting work were troublesome.

The present invention has been proposed in view of the above-mentioned problems, and its purpose is to provide high measurement accuracy for a wide range of target weights even if an A/D converter with the minimum number of bits is used. The object of the present invention is to provide a weight detection device for a weight-controlled filling machine that can achieve accuracy, reduce costs, and simplify work in terms of implementation.

(Means for Solving the Problems) In order to achieve the above objects, the weight detection device of the weight control type filling machine of the present invention holds the weight of the filling liquid and the container as the objects to be measured, and A load converter (1) that measures the combined weight of the holding mechanism and converts the result into an electrical signal and outputs it, and a preamplifier (1) that inputs the output signal of the load converter (1). 2) and the same preamplifier (2)
A subtracter (3) that calculates the difference between the output signal from the D/A converter (8) and the output signal from the D/A converter (8) described later and outputs the result, and each output from the subtracter (3) with a different gain. A plurality of amplifiers (4a) (4b) to which signals are input, and an output signal from the preamplifier (2) and each amplifier (4a)
) (4b) A switching circuit (5) that inputs the output signal from... and the selection signal from the arithmetic unit (9) described later.
, an A/D converter (6) that inputs the output signal of the switching circuit (5), detects whether or not there is an object to be measured in the holding mechanism, and uses the resulting detection signal as a timing signal. signal(
11) to the bus line (16), and the measured weight (14) of the object to be measured is output to the bus line (16).
6), a memory (10) that stores signals via the bus line (16), and an electrical signal in accordance with a command signal from the arithmetic unit (9) described later to the subtracter. (3) a D/A converter (8) that outputs to the
and a calculation unit (9), which receives a timing signal (11) and a target weight (13) from the filling control device (50) via the bus line (16) depending on the operating state. and the above D/A converter (8)
outputs a select signal that determines the output signal of the switching circuit (5) to the switching circuit (5), reads the output signal of the A/D converter (6), The measured weight (14) is configured to be output to the filling control device (50) via the filling control device (50).

(Function) The weight detecting device of the weight-controlled filling machine of the present invention is configured as described above, and is based on the combined weight of the object to be measured detected by the load converter and the weight of the container holding mechanism.
The weight of the container holding mechanism that is unnecessary for controlling the filling machine is canceled, the weight signal of only the object to be measured is calculated, and this is measured using the measurement range that provides the highest accuracy for the target weight that changes depending on the product type. In order to obtain a weight measurement accuracy of - with respect to the target weight, the minimum number of bits required is Δ/
Even when using a D converter, high measurement accuracy can be obtained for a wide range of target weights, reducing costs.

This simplifies the work in terms of implementation.

(Example) Next, the weight detection device of the weight control type filling machine of the present invention was
To explain with one embodiment shown in the figure, (1) is a load converter, (2) is a preamplifier, and (3) is a subtracter.

(4a) (4b) (4c) ... are amplifiers, (5) are switching circuits, (6) are A/D converters, (7) are latch, (
8) is a D/A converter, (9) is an arithmetic unit, (10
) is the memory, (11) is the timing signal, (12) is the input interface, (13) is the target weight, (1
4) is the measured weight, (15) is the output interface,
(16) is a bus line, and (50) is a filling control device.

Next, the operation of the weight detection device of the weight control type filling machine shown in FIG. 1 will be explained in detail. In a weight-controlled filling machine, when the product type (manufactured product type) to be filled is determined, the target weight determined by the product type and the weight of the container holding mechanism whose structure matches the container shape are added to the load converter (1). It will be done. In addition, a product code for specifying the manufactured product type is input to the filling control device (50) (at this point, the load converter (1
) is only the weight (initial weight) due to container holding and mechanism). When one product code is input, the filling control device (50) selects target weight data specified by nine product codes from pre-stored operation data and outputs it to the target weight (13).

At the same time, it outputs 1 to the timing signal (11) for a certain period of time. The arithmetic unit (9) has a timing signal (11) of 1
When a change is detected, the fifth-order processing is sequentially executed.

(1) Perform initial weight detection processing. That is, the switching circuit (5)
A gain selection code (assumed to be CodeO) whose input (5A) becomes the input of the A/D converter (6) is output to the latch (7). As a result, the input signal of the A/D converter (6) is a signal corresponding to the initial weight output by the preamplifier (2) (
E o,). A/D converter (6) is EO4
A digital signal corresponding to is outputted to the arithmetic unit (9) (denoted as E OAD ).

(11) Next, initial weight cancellation processing is performed. That is,
Arithmetic units i to (9) output +E OAD to A/I) converter (6). As a result, the human power (3
The same signal as the other inputs (38) is input to B), and the output of the subtracter (3) becomes O (the output of the initial type quantity is canceled). From this point on until the next product is selected, the input of the D/A converter (8) is set to E by the latch function. It is held at A. In FIG. 2, the discontinuous input to the D/D converter (6) indicates this operation.

(iii) Next, search processing for the Kane selection code and weight conversion coefficient is performed. That is, the arithmetic unit (9) reads the target weight (13), determines the optimal measurement range for the target weight (13) by referring to the measurement range data table stored in advance in the memory (10), and determines the optimum measurement range for the target weight (13). The gain selection code and weight conversion coefficient for selecting the amplifier (4) corresponding to the measurement range are determined. An example of the structure of the measurement range data table is shown in the table below.

The optimum measurement range for the maximum value can be easily determined from the target weight (13) and the measurement range maximum value in the measurement range cheetah table. The obtained gain selection code is Code n
l Let Kn be the weight conversion coefficient.

(iv) Next, gain setting and weight conversion coefficient storage processing are performed. That is, the arithmetic unit (9) outputs Code n to the rack (7). As a result, the output of the amplifier (4) having the optimum measurement range for the target weight is selected by the switching circuit (5) as the input to the A/D converter (6). From this point on until the next product type is selected, the output of the latch (7) is held at Code n. Further, the weight conversion coefficient obtained in the above (iii) is stored in the memory (10).

(v) Next, calculation output processing of the measured weight is performed. That is, the arithmetic unit (9) reads the signal output by the A/D converter (6) (set it as EfAll) (E; the magnitude of Ao is the input value E of the load converter (]).1. ). Furthermore, the measurement type quantity K-ErAn is calculated from E iAD and the weight conversion coefficient stored in the memory (10), and this is sent to the filling control device (50) via the output interface (15). 14).

The above is the operation of the calculation unit (9) when it detects that the timing signal (11) changes to 1, but when the timing (11) is other than that, the calculation process of the measured weight (■) only is executed. FIG. 3 shows the processing procedure of the arithmetic unit (9). In this embodiment, the amplifier (4
), a plurality of amplifiers with different gains are used, but it is also possible to use a programmable amplifier whose gain can be changed by an external command.

(Effects of the Invention) The weight detection device of the weight-controlled filling machine of the present invention controls the filling machine based on the combined weight of the object to be measured detected by the load converter and the weight of the container holding mechanism as described above. By canceling the unnecessary weight of the container holding mechanism and calculating the weight signal of only the object to be measured, this is measured using the measurement range that provides the highest accuracy for the target weight, which changes depending on the product type, to reach the target. Since the weight measurement accuracy is similar to that of the weight, even if an A/D converter with the minimum number of bits is used, high measurement accuracy can be obtained for a wide range of target weights, reducing costs. This has the effect of reducing costs and simplifying the work in terms of mounting.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an embodiment of the weight detection device of the weight-controlled filling machine of the present invention, Fig. 2 is an explanatory diagram showing the measurement range of the amplifier and A/D converter, and Fig. 3 is the calculation FIG. 4 is a system diagram showing a weight detection device of a conventional weight-controlled filling machine. (1)...Load transducer, (2)...Preamplifier, (
3)...Subtractor, (4a) (4b) (4c)
(4d) ...Amplifier. (5)...Switching circuit, (6)...A/D converter, (
7)...Latch, (8)...D/A converter, (9)
...Arithmetic unit (10) ...Memory, (11
)...Timing signal, (12)...Human power interface (13)...Target weight, (14
)...Measurement weight, (15)...Output interface, (16)...Bus line, (50
)...Filling control device.

Claims (1)

[Claims] a load converter (1) that measures the combined weight of the filled liquid and container as the object to be measured and the weight of the holding mechanism that holds the object to be measured, and converts the result into an electrical signal and outputs it; , a preamplifier (2) into which the output signal of the load converter (1) is input, and an output signal from the preamplifier (2) and D described below.
A subtracter (3) that calculates the difference with the output signal from the /A converter (8) and outputs the result, and a plurality of amplifiers that input the output signals with different gains from the subtracter (3). (4
a) (4b)..., the output signal from the preamplifier (2), the output signal from each of the amplifiers (4a), (4b)..., and the select signal from the arithmetic unit (9) described later. a switching circuit (5) that inputs the signal, an A/D converter (6) that inputs the output signal of the switching circuit (5), and detects whether or not there is an object to be measured in the holding mechanism and outputs the result. The obtained detection signal is used as a timing signal (11) to connect to the bus line (16).
) and also outputs the measured weight of the object to be measured (14
) from the bus line (16), a memory (10) that stores signals via the bus line (16), and a filling control device (50) that receives signals from the arithmetic unit (9) described later. It has a D/A converter (8) that outputs an electrical signal to the subtracter (3), and an arithmetic unit (9),
The calculation unit (9) reads the timing signal (11) and target weight (13) from the filling control device (50) via the bus line (16) according to the operating state,
It commands the output signal of the D/A converter (8), outputs a select signal determining the output signal of the switching circuit (5) to the switching circuit (5), and A weight detection device for a weight-controlled filling machine, characterized in that it is configured to read an output signal and output a measured weight (14) to the filling control device (50) via the bus line (16). .