JPH0394868A - Method for controlling discharge quantity of paint - Google Patents

Abstract

PURPOSE:To decrease the wastefully blown quantity of fresh paint arising from a color change and to suppress the fluctuation in discharge quantity by specifying the initial command value of the paint discharge quantity after the color change to the value obtd. by specific equation, then executing feedback control in accordance with specific equation. CONSTITUTION:The paint discharge quantity of a spray nozzle 1 is computed in a microcomputer 7 by the detection electric signal from a flow meter 9 and is converted to an air pressure by an electro-pneumatic converter 8. The paint flow rate is then regulated by an air operation regulator 4. The initial command value X2 after the color change is instructed by X2=(Q2/Q1)X(X1+b/ a)-b/a and thereafter, the feedback to make addition correction by kX(Q'Q2) is continuously executed. In the equation, Q2 denotes the target discharge quantity, Q1 denotes the final discharge quantity to be wastefully blown; X1 denotes the target command value; (a) and (b) denote the constant values determined from the relation Q aX+b of the command value X and the discharge quantity Q. Q' denotes the average value of the present discharge quantity and Q'-Q2 denotes the deviation of the discharge quantity; (k) denotes the correction factor of 0 to 1 to be changed in accordance with a time chart.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a feedback control method for eliminating fluctuations in discharge amount that occur immediately after a color change (replacement of paint in a coating machine due to a change in paint color). <Prior art> In paint machines used for spray painting automobile bodies and bumpers, paint is supplied to the spray nozzle by -
This is done by pressure in M-style. During painting, the paint is uniformly discharged from the spray nozzle by maintaining the paint supply pressure constant, so if the paint viscosity changes due to changes in the external environment, the feedback from the spray nozzle will increase. ki《varies. Fluctuations in the discharge amount cause a loss of slippage, which has become a highly demanded quality in recent years. Therefore, Japanese Patent Application Publication No. 56-139162 and Utility Model Application No. 1988-1
Attempts have been made to use a paint discharge control device such as that disclosed in Publication No. 32066. In such equipment, a flow meter is installed in the paint supply passage for supplying paint from the paint supply source to the nozzle of the paint sprayer, and a flow regulating device (
An air operated regulator) is provided, and this flow regulating device is connected to a microphone u. : Command controlled by one monitor, and paint is sprayed from the nozzle. We are trying to keep the output constant. Furthermore, a device for precisely controlling the discharge force in pulsed discharge in which paint is repeatedly turned ON and OFF periodically during painting is disclosed in Japanese Patent Laid-Open Nos. 63-54969 and 63-5497O. There is. Problems to be Solved by the Invention Generally, in the spray paint line for top coating and intermediate coating of automobile bodies and bumpers, color changes are applied over time. When changing colors, first replace the previously used paint (hereinafter referred to as "old paint") remaining in the paint sprayer with the different color paint (hereinafter referred to as "old paint") that will be used in the future.
(hereinafter referred to as new paint). This replacement is carried out by alternately sending a cleaning pump and compressed air to the paint flow path from the paint inlet valve to the spray nozzle to clean the paint flow path. v
This is done by introducing paint to fill the channels. And in the early days of introducing new paints, a certain amount,
It is necessary to blow it away (dispose of it by discharging it from the nozzle). The reason for this is that a small amount of thinner adhering to the paint distribution channel after cleaning the old paint mixes with the new paint in the early stages of introduction and lowers its viscosity. If the new paint in the early stages of introduction is used as is, it may cause an uneven coating film. This is because large fluctuations in the amount of yelling occur.

In other words, as shown in Figure 4 (a), a large amount of paint is ejected at the beginning of painting with the new paint (1+ = about 30 seconds), and then it rapidly decreases without a pause (if the color is not changed, The initial change is as shown in Figure 4 (mouth). This reduction is particularly significant for high viscosity body paint solids and clear paints.

In order to form a uniform coating film, it is best to blow off as much new paint as possible at the initial stage of installation, but doing so will result in a huge loss in paint cost and also increase the loss in coating cycle time. If such drastic discharge fluctuations are extremely large, the above-mentioned Utility Model Application No. 61-1 32066 and Japanese Patent Application Publication No. 63-5
With only the devices and methods disclosed in No. 4969 and No. 63-54970, it is necessary to increase the measurement accuracy by increasing the zumbling time of the flowmeter due to the influence of pulsation of the reciprocal bomb on the paint supply side. ,．． This is where it becomes difficult to control the discharge amount precisely, without having to sacrifice responsiveness. Note that if you use a fixed-volume bomb such as a gas bomb to supply paint to the spray nozzle, the above-mentioned fluctuation in the discharge position will not occur, but this type of bomb has durability problems such as gear wear. Furthermore, since each sprayer requires one bomb, the coating line becomes complicated, and it is difficult to secure space for its installation, so it is not a good idea to use fixed-volume bombs. The present invention was made for the purpose of solving the above-mentioned problems, and the problem to be solved is a method of sharply controlling paint discharge that can reduce the amount of new paint thrown away due to color change and suppress fluctuations in discharge amount. 41? It is to provide. <Means for Solving the Problems> The feedback control method of the present invention that can solve the above problems controls feedback with a your-over-the-air regulator operated by a command from a microcomputer based on the paint flow rate detected by a paint flow meter. In the coating machine, the initial command value Xo after color change is set to [in the formula, Q. is the target value discharge amount, Q is the final blow-off discharge amount, X is the target value command value, and a and b are the relational expressions between the 5 command value X and the discharge amount Q. represents the constant value obtained from QdonaX+t)], and then k (Q'
-Q*) [In the formula, Q' is the average value of current discharge measurements, Q'-
Q2 represents the measured average value of the current discharge amount, and Q'-Q2 represents a correction coefficient of 0 to 1 that is changed based on the time chart].Feedback control is performed to continuously add correction. 〈Operation〉 When controlling the feedback, sequence control such as ``initial command value'' allows the air operated regulator that uses an air operated diaphragm, which has been considered to have poor followability, to function continuously and satisfactorily. Become. In this way, if the discharge amount is tightly controlled to the target value, the fluctuations in the discharge amount of residual thinner will not be affected and the influence will be reduced. This results in a reduction in the amount of new paint required to form a uniform coating film. This is a system that measures and feedback controls the paint flow rate for each spray nozzle in the paint sprayer, and by controlling it as shown below, it is possible to stably maintain the accuracy of the 6 discharge amount after cleaning the paint sprayer with thinner during a color change. The first diagram is a diagram showing the configuration of a paint sprayer equipped with such a control device.The rotary bell-shaped paint spray nozzle 1 is connected to an air oven 17, a regulator 4,
A flow meter 3 and a paint ON-OFF valve 2 are provided, and a paint hose 6 is passed through the pipe. Then, paint is supplied from the color change valve set 5. The manifold part 12 of the color change valve set 5 includes paint valves 1.3, 14, 15. 16, a compressed air valve 17, and a cleaning thinner valve 18 are connected, and a paint regulator 20 is connected to the paint circulation piping 19 to the paint valves 13 to 16 for introducing paints of different colors. Paint is supplied through hose 21. The amount of paint discharged from the spray nozzle 1 is controlled by a Coriolis flowmeter 9 that detects the flow rate of paint and converts it into an electrical signal, a microcomputer 7 that performs calculations from this detected electrical signal and outputs a command electrical signal, and the command electrical signal. It is controlled by a control device consisting of an electro-pneumatic converter 8 which converts the air pressure into air pressure, and an air operated regulator 4 which adjusts the paint flow rate using the air pressure from the electro-pneumatic converter 8. In addition, in the figure, 9 and 1
0 is a compensation line, and 11 is an air hose.

Next, I will explain one feedback control method.
After finishing painting the vehicle body or bumper etc. with Coating A, open the compressed air valve 17 and the cleaning thinner valve 18 of the color change valve set 5 alternately (the last is the ``condensed air valve''), Push out the paint 8 that has been used so far and clean the paint flow path from the manifold 5 to the air operator 1 note regulator 4, the Coriolis flow vane 4, the paint ON-OFF valve 2, the paint spray nozzle 1, and the paint hose 6.

At the end of cleaning, compressed air is used to push out the cleaning thinner.
It is unavoidable that a small amount of cleaning thinner remains in the paint distribution path. Next, a different color paint B to be used in the future is introduced from the paint circulation pipe 19 through the hose 2l where the regulator 20 is located, and into the path from the color correction valve 13 to the spray nozzle 1, and at the same time, a predetermined amount of paint B is sprayed from the nozzle 1 at the initial stage of introduction. dispose of.
At this time, the discharge amount changes as shown in Figure 2.
The command value X at the time of blow-off (time T1 in Figure 2) can be determined as appropriate. If you try to do blowing away in a short time,
All you have to do is step over the X. The discharge amount at this time is about as much as the amount at the start of blow-off compared to the final target discharge flIQ2 because the paint B at the initial stage of introduction mixes with the paint A cleaning thinner that still remains in the path and the paint viscosity decreases. With a large discharge volume and a blow-off time of about 5 seconds, the discharge volume at the final stage of spray painting (time T2 in Figure 2) is also larger than the target value Q2, and the discharge volume at the initial stage of spray painting is shown by the broken line. It becomes large (~Q.).
So, discharge 11Q? Command from microcomputer 7 to electro-pneumatic converter 8? As shown in FIG. 3, the relationship of tflX is approximated by Q. Since there is a relationship of = a After that, the discharge amount value of flow meter 3 is set to 0.0.
1 to 1 seconds, preferably averaged for about 0.1 seconds, o
．． The control is performed at intervals of oi to 1 second, preferably at intervals of about 01 seconds. Compare the magnitude relationship between Q' and Q2, and find that Q2 <
If Q', then 0. k (Q'-Q2) continuously at the corner for l seconds
If Q2>Ω', then subtract k (Q' - Q.) from Q' for correction. Q'-Q. : Deviation, Q' : Measured average value of current discharge amount, Q2 : Target value Discharge amount variable and can be set arbitrarily up to k=o=1 By the way, the command value X' and discharge amount Q' at a certain point, and the value at the next point. The following relationship holds between the command value X" and the discharge amount Q-. Q - Q * = Q" QZ, b b x" = - (x + -) - -Q"
aa With this control method, as shown by the solid line in Fig. 2, the discharge amount is stabilized early, and during spray painting (T. to T4
) The discharge amount remains almost constant. Here, controllability can be further improved by increasing k for several seconds from T3 and then decreasing the k value in stages based on the time schedule. In addition, X. , b, and a may be measured in advance and set as fixed values. Moreover, when the b value is small, Q2 X2 = -X. , Q, can be substituted. If color change cleaning is not to be performed in the above manner, the initial command value and 17 are used to specify the target value 0, and thereafter feedback control is performed while the target value Q2 is specified in the same manner. <Effects of the Invention> According to the present invention, it is possible to control the discharge amount of new paint with high precision even after cleaning the paint machine accompanying a color change, and it is possible to paint a highly smooth paint film.

Furthermore, even if the blow-off time is shortened, the discharge amount can be controlled within the allowable range, so the amount of paint thrown away can be reduced and paint loss can be significantly reduced. Furthermore, since the configuration of the control device is simple, almost no cost is required for microcomputer hardware and software.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the structure of a coating machine used in an embodiment of the present invention, Fig. 2 is a diagram showing changes in paint discharge over time in an embodiment, and Fig. 3 is a control command. Figure 4 is a diagram showing the relationship between values and feedback, and is an explanatory diagram of the problems with conventional color change painting. Figure 1 in the figure 1... Spray nozzle, 3... Frioli flowmeter 4
...Air operated regulator 5...Color change λ valve set 7...Microphone. Computer, 1.3, 14, 15. 16...Paint valve 8.
...Electro-pneumatic converter Fig. 2

Claims (1)

[Scope of Claims] A coating machine that controls the amount of paint discharged by an air-operated regulator operated by a command from a microcomputer based on the paint flow rate detected by a paint flow meter,
The initial command value X_2 after color change is calculated as X_2=(Q_2)/(Q_1){X_1+(b)/(
a)}-b/a [In the formula, Q_2 is the target value discharge amount, Q_1
represents the final discharge amount, X_1 represents the target value command value,
Then, a and b are specified by the relational expression between the command value Paint discharge characterized by performing feedback control that continuously adds and corrects the measured average value, Q'-Q_2 represents the discharge amount deviation, and k represents a correction coefficient of 0 to 1 that is changed based on the time chart. Volume control method.