JPH0329791A - Method and apparatus for weighing and controlling in liquid filling machine - Google Patents

Abstract

PURPOSE:To permit even the liquid changeable in temperature with time to be filled with a good yield rate and a high degree of accuracy by a method wherein the proportional constants for computing difference amount correction are automatically switched between rise and normal times and the difference amount correction is made at each liquid filling at the rise time and, at the normal time, such correction is made based on an average of the values obtained from the filling made several times. CONSTITUTION:When the weighed value obtained from a weigher 5 and the liquid temperature from a temperature detector 13 are arithmetically processed through an input interface 69 by a processing unit 6f, the proportional constants for computing difference amount correction are automatically switched between rise and normal times, whereby the difference amount correction is made at each liquid filling at the rise time and, at the normal time, such correction is made based on an average of the values obtained from the filling made several times. The instructions for opening and closing a liquid supply valve 2 and a filling valve 9 to the respective valves are outputted and controlled through an output interface 6h. This permits the liquid filling to be made with high degree of accuracy, even when the temperature of the liquid to be treated changes with time.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a measurement control method and device for a liquid filling device applied to filling beverage containers in a food machine, and is applicable to pharmaceuticals other than beverages, cosmetics, vI4 It can also be applied to filling devices for flavorings and other liquids.

[Conventional technology]

FIG. 4 shows an outline of a liquid measuring and filling device for which a patent application has been filed as Japanese Patent Application No. 1-57903.

In the figure, l is a supply port for the liquid to be filled, which is fed under pressure from a supply device (not shown). 2 is a liquid sending valve to the crushing container 4, and 9 is a filling valve to the container 11. The container 11 is held in a holder 12, and can be moved up and down as well as horizontally by a drive device (not shown). Liquid sending valve 2
By opening the container, the liquid introduced into the container 4 is automatically detected by the weighing scale 5 for barycrystals. The container l1 is filled by closing the liquid feeding valve 2 and opening the filling valve 9.

The liquid is guided from the inside of the gauge container 4 through the piping 7 and the filling nozzle 10 into the container 11 by the effect of the siphon. 13
6 is a temperature detector that detects the temperature of the liquid, and 6 is a control device that performs metering control.

FIG. 5 schematically shows one cycle of the process of filling the container 11. When the liquid feeding valve 2 is opened at point a,
The liquid is led to the measuring container 4Vc. The measuring scale 5 indicates the liquid feeding set value (
When point b) is detected, a command to close the liquid sending valve 2 is issued, but due to a delay in the control system, it is finally completely closed at point C. The difference between the measured values at point C and point b is the head difference 31 (R
ab).

Then, at point d, when the filling valve 9 is opened, the liquid in the metering container 4 is introduced into the container 1l. When the weighing scale 5 detects the filling set value (point e), it issues a command to close the filling valve 9.
Due to the delay in the control system, it finally closes completely at the Kf point. f
The difference between the measured values at point and d is the amount of head (Ref) during filling.

In the illustrated system, since we do not want the amount of head during liquid transfer to have a particularly negative effect on the filling yn1 degree of the container 11, we will focus on the head i during filling (I will focus on the explanation below, but we will also discuss the amount of head during liquid transfer). The same is true.

When filling with liquid, the flow velocity V can be expressed as v=f (H, v). Here, H is the head difference H shown in FIG. 4, and ■ is the viscosity coefficient of the liquid in the pipe 7. On the other hand, since the viscosity coefficient V varies depending on the liquid temperature TK, if the head difference H is almost constant. The flow rate V depends on the temperature TK. Also, head amount (Ref): = flow velocity (v) x response delay time (fe
)/2, so as a result, the amount of head changes depending on the liquid temperature [T. In the practical permissible temperature range, a correlation as shown in Figure 6 can be obtained between temperature and head. When filling with cooled (or heated) liquid, the temperature of the piping 7 is not sufficiently cooled (or warmed) at K during the initial filling stage (startup), so as the filling cycle is repeated, the liquid temperature may change over time. After changing to , it approaches a stable temperature.

FIG. 7 shows the state of temperature change when filling with cooled liquid.

FIG. 9 is a flowchart showing a conventional method of controlling head correction. Preset filling number (
The average deviation value is calculated every time n), and the head amount is automatically corrected as (new head amount)=(current head*>+<proportionality constant)×(deviation average value). The constant of proportionality is usually 1.0 to 0
．． It is a constant value in the range of 5.

When the cooled liquid is filled in this way, the results shown in Figure 8 are obtained, and it is difficult to control the temperature so that it falls within the control limits immediately after the start-up. This may result in products with defective filling quantities. Also, an offset (steady deviation) occurs between the average filling amount and the predetermined amount. [Invention tries to solve it! lI! Problem: In a liquid measuring system using a pestle. Even if a predetermined amount is detected and a close signal is sent to the valve, the response time of the control system will be delayed for several to several tens of meters.
The valve closes after a delay of sec. The outflow amount during this period is generally referred to as the head amount and becomes an error during measurement. In order to reduce this measurement error, the amount of head is usually corrected as the average value of the measurement command value = predetermined amount - amount of head.

However, with this head correction method, if the liquid temperature T changes over time. (1) Due to poor response during transient periods (start-up), several defective products may be produced before the product falls within the allowable range. (2) Offset (steady deviation) between the measured value and the specified amount
remains.

There is a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a measurement control method and apparatus that can perform filling with high yield and accuracy even when filling with a fluid that is subject to temperature changes over time.

[Means to solve the problem]

(11 When correcting the head amount, use the actual filling amount (metered value)
The correction is made based on the result of adding a proportional fraction obtained by multiplying the deviation, which is the difference between .

(2) The constant of the proportional component can be set to different values at startup (when the temperature changes are relatively large) and at steady state. Note that good results can be obtained by setting the proportional constant during steady state to a value lower than the proportional constant during startup. During the transient period, 1
Each time the filling is performed, the next head is corrected based on the filling results, and in steady state, it is performed multiple times in a row (usually 4 to 8 times).
The next head correction will be performed based on the average value or moving average value of the filling results. (3) When filling for the first time, use an initial value that matches the filling start temperature. After that, it will be updated sequentially based on the filling results.

[For production]

(1) In addition to proportional control, integral control is also performed, so the offset is small.

(2) During the transient period, it responds quickly to sudden changes in fluid temperature. (3) If the initial value of the head is set appropriately, the filling amount can be controlled to be within the allowable range from the first filling.

The initial value of the head can be determined by detecting the fluid temperature and calculating the head corresponding to the temperature, or by referencing the initial value of the head corresponding to the temperature from the initial head value storage. Even more precise control is possible from the time of filling.

〔Example〕

Fig. 1 shows a second embodiment (flow chart) based on the present invention.
The figure shows a block diagram of the metering control device 6.

The differences from the conventional technique shown in FIG. 9 are as follows.

(1) Receive a start-up command when starting filling or restarting filling after a long stop.

(2) When a start-up command is received, set FLAG to 1...In addition, hold the start-up command, measure the liquid temperature...calculate the amount of head commensurate with the temperature of the liquid. Alternatively, the head amount is selected from the initial value storage section 6a and initialized. If the fluctuation range of liquid temperature is not large,
The initial value of the head does not necessarily need to be determined by measuring the liquid temperature discharge, and may be a fixed value.

In the conventional method, the initial value of the head amount storage value is set to O.

(3) Set different proportional constants during startup (transient time) and during steady state after that...32.34, For example, set the proportional constant to 1.0 during startup and 0.75 during steady state. ~0.
5. These values change depending on the characteristics of the system, and the same value may be set depending on the S combination.

(4) During start-up, the amount of head is corrected according to the measured value each time it is filled, so that it responds promptly to sudden changes in the amount of head.

(5) During steady state, individual variations are smoothed by taking the average value of several filling results.

In the illustrated flow, the average value is simply taken n times, but
You can also take the moving average value...ah.

The accumulated deviation value Ep for proportional control is cleared every n times of measurement...21. In addition, data with abnormally large or small deviations should be excluded and not used as data for head correction.

The deviation here is the difference between the current head and the stored head (past head)...4.

(6) In steady state, integral correction is also performed based on the integrated deviation value Ei...37. The integral constant in the case of the illustrated flow is suitably a value that is one to two orders of magnitude smaller than the proportionality constant. Fill by performing integral correction! (1 value in total) and the predetermined t (target value) (offset) can be made sufficiently small...40.

The accumulated deviation value E1 for correcting the number of small tombs is cleared only when a start-up command is received.

As explained above, in the FC FIG. A liquid sending valve opening/closing command is outputted to the filling valve 9, and a filling valve opening/closing command is outputted to the filling valve 9 through the output interface 6h for control. FIG. 3 shows changes in measured values when filling according to this method. It can be seen that the controllability is improved compared to FIG. 8 (when using the conventional method).

still. In FIG. 2, at least the head initial value storage unit 6a,
If the start-up constant storage section 6c and the steady-state constant storage section 6d are stored in a ROM or nonvolatile RAM, the stored values will not be lost during a power outage.

〔Effect of the invention〕

The weighing control method according to the present invention, in a device for filling liquid into containers using a weighing scale, automatically switches the proportional constant for head correction calculation between startup and steady state, and once at startup. By correcting the amount of head every time it is filled and performing the correction of the amount of head on the basis of the average value of several filling results during steady state, the following effects can be achieved.

(11) High filling accuracy can be maintained even if the temperature of the liquid being handled changes over time.

(2) It has a good response I force even during transient periods of severe temperature changes, so it is possible to perform filling with a high yield and fewer deviations from specifications. (3) It is possible to keep the filling amount within the specifications even at the start of operation or the first filling after a long stop.

[Brief explanation of drawings]

@Figure 1 is a flow diagram of a control method according to an embodiment of the present invention, and Figure 2 is a block diagram of the same control device. Figure 3 is a control chart of the weight distribution as above, Figure 4 is a configuration diagram showing a conventional liquid filling device, Figure 5 is a diagram showing changes in the meter value during one conventional filling cycle, and Figure 6 is a diagram showing the relationship between the conventional head 8 and liquid temperature, t47 is a diagram showing the relationship between the conventional liquid temperature and the number of times of filling, Fig. 8 is a conventional control chart of measured value distribution, and Fig. 9 is a flow diagram of a conventional control method. Ref... Head element (at the time of filling), proportional constant, deviation average value 6a... Head amount initial value storage section 6b... Drop platform storage section 6... Metering control device

Claims (2)

[Claims] (1) In a device for filling liquid into containers using a weighing scale,
The proportional constant for head correction calculation is automatically switched between start-up and steady state, and during start-up, the head is corrected every time it is filled, and during steady state, the head is corrected based on the average value of several filling results. A metering control method in a liquid filling device, characterized by performing head correction. (2) In a metering control device that is equipped with a memory that issues a liquid sending valve opening/closing command or a filling valve opening/closing command to a liquid sending valve or a filling valve, respectively, based on the measured value obtained from a measuring device, the memory contains a head A metering control device for a liquid filling device, comprising an initial volume storage unit and a head storage unit, and is configured to transfer the initial head volume value to a head volume correction value when a start-up command is received. .