JP2001162148A - Control method for mixing multiple liquids - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method for mixing multiple liquids, which is used for mixing multiple fluids in a mixing room while weighing them alternately and supplying the mixture to a spray gun, by which the error of the mixing ratio is reduced and kept within tolerance even when the mixture is intermittently supplied or the flow rate is extremely changed. SOLUTION: Each amount of a-liquid and b-liquid to be supplied this time is controlled to be a target amount corrected by subtracting the previous excess amount while considering the last mixing ratio of the actual discharged amount of the a-liquid to that of the b-liquid when the multiple fluids are mixed in a mixing room while weighing them alternately and the mixture is supplied to the spray gun.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-liquid mixing control method for precisely metering and mixing a main agent and a curing agent, such as those used in two-component polyurethane coating, and supplying the same.

[0002]

2. Description of the Related Art In recent years, various fields have been required to deal with environmental pollution problems, and urgent improvements are required in paints and coating methods. One of the measures is the growing paint and coating method. In two-pack polyurethane coating and two-pack epoxy coating, by mixing and spraying a curing agent, which is a catalyst, on a base material with a small solvent component, the coating is formed by reaction and curing, so that the solvent can be reduced and This is a painting method that eliminates the need for a drying oven and lowers the temperature, and is effective in reducing energy. Further, since the coating performance such as weather resistance, chemical resistance, and water resistance is excellent, the production amount is increasing.

[0003] However, in a two-pack paint such as a two-pack polyurethane paint or a two-pack epoxy paint, when a hardener is mixed with a main component, there is a limitation on a usable time called a pot life. After the pot life, the paint is hardened in the coating apparatus, so it is necessary to perform the coating work within the pot life. In addition, since the resin hardens and adheres to the inner wall of the flow path of the apparatus, there is a problem that a change in the flow rate occurs, and frequent maintenance is required. For this reason, it has been demanded that the hardener be mixed with the main agent at a position as close as possible to the spray gun as soon as possible, immediately before coating, with respect to the main agent.

As a countermeasure, there is a method in which two kinds of liquids are alternately sent to a mixing section while intermittently measuring each of them by a pneumatically operated opening / closing valve, and the mixed two liquids are immediately sent to a spray gun by a paint hose. However, it is difficult to accurately mix the sprayed amounts of the two liquids in a sequential flow, which has a problem. In particular, since a pneumatically driven on-off valve must be used for safety, there is a problem that a mixing ratio error occurs due to a delay in closing the on-off valve, and Japanese Patent Laid-Open Nos. 6-294674 and 11-165118. Has been made by the control method and the like disclosed in US Pat.

However, in the conventional control method, the control target amount of the first liquid is set to (actual discharge amount of other liquid × mixing ratio × fixed correction value), and when the control target amount is measured by the flow meter, the on-off valve is closed. Therefore, the control is performed so as to approach the reference discharge amount of the first liquid, but since the correction amount is a fixed correction value, the actual discharge amount tends to be larger or smaller than the reference discharge amount. Tended to fall off. In another control method, the control target amount of each of the first liquid and the other liquid is set to (actual discharge amount-excess amount of the previous cycle), and control is performed so that each liquid approaches the reference discharge amount. When the mixing ratio increases, the reference discharge amount of the small amount side liquid tends to decrease and the error tends to increase. As a result, in these conventional control methods, the mixing ratio error is maintained within an allowable range at a constant flow rate, but a plurality of spray guns are connected to an automatic coating or one multi-liquid supply device, When each spray gun is used individually, the intermittent supply and the change in the flow rate are severe, and it has been difficult to maintain the mixing ratio error within an allowable range.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for controlling the mixing of multiple liquids to be supplied to a spray gun while mixing and supplying a plurality of fluids alternately in a mixing chamber. It is an object of the present invention to provide a mixing control method capable of maintaining an allowable range with a small mixing ratio error even when the change is severe.

[0007]

According to the present invention, at least two
A multi-liquid system that controls each on-off valve so that each liquid is supplied to the mixing chamber while measuring the flow rate with each flow meter in each individual flow path so as to mix the liquids at a constant mixing ratio. In the mixing control method, a method of calculating a reference amount of the first liquid and a reference amount of the other liquid according to a preset mixing ratio, and a closing signal to the on-off valve for each of the first liquid and the other liquid. A method of measuring each excess flow until each liquid flow of the first liquid and the other liquid is stopped after the output, and a method of measuring in the previous cycle of the first liquid from the reference amount of the first liquid A method of outputting a closing signal to the on-off valve of the first liquid when the flow rate meter of the first liquid measures the control target amount of the first liquid calculated by subtracting the excess flow rate; From the amount obtained by multiplying the actual flow rate of the last cycle of one solution by the mixing ratio, A method of outputting a closing signal to the on-off valve of the other liquid when the flow rate meter of the other liquid measures the control target amount of the other liquid calculated by subtracting the excess flow rate. With the multi-liquid mixing control method to be executed, multi-liquid mixing control with high mixing accuracy is performed.

[0008]

FIG. 1 is a block diagram showing a multi-liquid mixing control method according to the present invention, wherein a liquid a is supplied from a supply device 1a to a flow meter 2a.
To the mixer 4 via the opening and closing valve 3a. On the other hand, the liquid b is sent from the supply device 1b to the mixer 4 via the flow meter 2b and the on-off valve 3b. The liquid a and the liquid b are mixed by the mixer 4 and become a mixed liquid 7 which is discharged via a discharge opening / closing valve 5 such as a spray gun. A plurality of discharge opening / closing valves 5 may be connected to the mixer 4. In this case, the supply of the mixed liquid 7 is stopped at random, and the discharge amount of the mixed liquid 7 changes greatly. .

When the discharge on-off valve 5 is opened, the control device 6 alternately opens and closes the on-off valve 3a and the on-off valve 3b so that the mixing ratio α is inputted in advance. Control is performed to supply the reference amount Vb to the mixer 4. However, since the air-driven opening / closing valves 3a and 3b have an operation delay with respect to the control signal from the control device 6, an excess amount Wa and an excess amount Wb are generated, and a large mixing ratio error occurs. Resulting in. Further, when the flow rate changes, the excess amount Wa and the excess amount Wb with respect to the operation delay of the on-off valve 3a and the on-off valve 3b also change, so that a larger mixing ratio error occurs. The reference amount and excess amount of each liquid are sent to the control device 6 as the number of pulses measured by the flow meter 2a and the flow meter 2b.

In order to reduce these mixing ratio errors and maintain them within an allowable range, the present invention has invented the following control method. FIG. 2 is an explanatory diagram of the multi-liquid mixing control of the present invention.
The configuration of the calculation amount and the actual amount is shown. First, the control device 6 opens and closes the on-off valve 3a, and closes the on-off valve 3a when the discharge amount of the a-liquid reaches the target amount VA of the a-liquid calculated by calculation = (reference amount Va-previous excess amount Wa '). And then open / close valve 3a
The actual discharge amount of the liquid a approaches the reference amount Va of the liquid a due to the excess amount Wa generated by the closing delay of the liquid. Next, on-off valve 3
b is opened and the on-off valve 3b is closed when the discharge amount of the liquid b reaches the target amount VB of the liquid b calculated by calculation = {actual discharge amount of liquid a (VA + Wa) × mixing ratio α−previous excess amount Wb ′}. Control, and the excess amount W caused by the delay in closing the on-off valve 3b at that time.
By b, the actual discharge amount of the liquid b approaches the reference amount Vb of the liquid b. As a result, the supply of the mixed liquid 7 is stopped by controlling the opening / closing valve with the target amount calculated by correcting the previous excess amount of each liquid while considering the mixing ratio of the immediately preceding liquid a to the actual discharge amount. When the mixing is performed at random or when the discharge amount of the mixed liquid 7 changes greatly, the mixing ratio error can be kept small, and the mixing ratio can be maintained without being larger or smaller than the set mixing ratio.

[0011]

Since the present invention is configured as described above, it has the following effects. (1) Even if the mixing ratio increases, the mixing ratio error can be maintained within a certain range without increasing. (2) It is possible to maintain a mixture ratio that is not biased to be larger or smaller than a set mixture ratio.

[Brief description of the drawings]

FIG. 1 shows a block diagram of a multi-liquid mixing control method of the present invention.

FIG. 2 is an explanatory diagram of the multi-liquid mixing control of the present invention, showing the configuration of a calculation amount and an actual amount.

[Explanation of symbols]

 1a ・ 1b Supply device 2a ・ 2b Flow meter 3a ・ 3b On-off valve 4 Mixer 5 Discharge on-off valve 6 Control device 7 Mixed liquid

Claims (1)

[Claims] 1. Each of the liquids is supplied to a mixing chamber so that at least two types of liquids are mixed at a constant mixing ratio and the liquids are supplied to the mixing chamber while measuring the flow rate with each flow meter in an individual flow path. In a multi-liquid mixing control method for controlling an on-off valve, a method of calculating a reference amount of a first liquid and a reference amount of another liquid according to a preset mixing ratio; and a method of calculating a reference amount of each of the first liquid and the other liquid. A method of measuring each excess flow until the flow of each of the first liquid and the other liquid stops after the output of the closing signal to the on-off valve, and a method of measuring the first flow from the reference amount of the first liquid. A method of outputting a closing signal to the on-off valve of the first liquid when the flow meter of the first liquid measures a control target amount of the first liquid calculated by subtracting an excess flow rate measured in a previous cycle of the liquid; ,
The control target amount of the other liquid is calculated by subtracting the excess flow of the other liquid measured in the previous cycle from the amount obtained by multiplying the actual flow of the previous liquid by the mixing ratio of the other liquid, and the control target amount of the other liquid. And a method of outputting a close signal to the on-off valve of the other liquid when the flow meter measures, wherein each method is executed by a control device.