JPS61230767A - Apparatus for controlling coating amount - Google Patents

Abstract

PURPOSE:To enhance the control response of a paint amount and to reduce a time or material at the time of the alteration of the paint amount, by detecting the consumption amount of a paint on the basis of the change in the wt. of a paint tank. CONSTITUTION:The wt. of a paint tank 4 or paint tank 2 is always measured through a load cell 5 and a control apparatus 6 opens a valve V when said wt. reaches a lower limit value or less to replenish a new paint solution to the paint tank 4 and closes the valve V when the wt. reached an upper limit value to stop the replenishment of the paint solution. From wt. data obtained by sampling the wt. of the paint tank 4 or 2 during a time when the new paint solution is not replenished at an appropriate time interval, the consumption amount of the paint per hr at the present point of time is calculated by an averaging technique and this calculated value is compared with a preliminarily inputted objective value and a roll coater 1 is controlled so as to bring the difference between both values to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a coating amount control device in an apparatus for continuously coating a sheet-like continuous body such as paper with paint.

BACKGROUND OF THE INVENTION The conventional coating amount control method is explained in the first embodiment, which shows an embodiment of the present invention.
This will be explained using Figure a. In this figure, 1 is a roll coater, and S is a sheet-like continuous body to be coated. In the roll coater, a pickup roll 3 is partially immersed in the paint liquid in the paint tank 2 and rotates. The paint liquid is returned to the paint tank 4. tank 4
The amount of paint liquid that returns to is smaller than the amount of paint liquid that is supplied to the paint tank 2 by the amount that adheres to the sheet S and is carried away (therefore, the amount of paint liquid in the paint tank 4 gradually decreases, and The amount of decrease becomes the amount of paint applied to the sheet S.The above points are the same in both the present invention and the conventional example.In the conventional example, in order to detect the amount applied to the sheet S, the paint tank 4
The supply of fresh paint liquid to the tank 4 is stopped for 2 to 3 minutes, and the drop in the paint liquid level in the tank 4 during that time is measured to determine the amount of paint liquid consumed, and the feeding speed of the sheet S at that time is determined. The coating amount was calculated from the sheet width.

C.2 Problems to be Solved by the Invention The conventional method described above has the following problems. The paint liquid level in the paint tank 4 is undulating due to the operation of the pump P, the inflow of paint liquid returning from the coater 1, etc., and the liquid level height cannot be measured accurately. Therefore, in order to increase the accuracy of the amount of paint liquid consumed per hour, it is necessary to lengthen the time interval between measuring the liquid level height (increase the difference in liquid level height), and it takes time to determine the amount of paint applied. Gaka\ru. For this reason, the responsiveness when detecting the amount of application and controlling the amount of application is poor, and when changing the amount of application, it takes time to adjust the amount of application and find out the result. It takes a considerable amount of time to settle down to the desired value, and during that time there is a large loss of sheet material and paint.

In short, the conventional method has the problem that it takes time to determine the amount to be applied, and as a result, the responsiveness of controlling the amount of application is low, and the loss of time and materials increases when changing the amount of application.
The present invention seeks to solve these problems.

21 Means for Solving Problems The present invention, as shown in Figures 1a and 1b, constantly measures the weight of the paint tank 4 or paint tank 2, and replenishes fresh paint liquid when the weight falls below the lower limit. When the upper limit is reached, the replenishment of the paint liquid is stopped, and the weight of the paint tank 4 or the paint tank 2 is averaged from the weight data sampled at appropriate time intervals while the fresh paint liquid is not being replenished. The current amount of paint consumed per hour is calculated using the method, and is fed back to the application amount adjusting means.

To detect the amount of paint consumed, use the paint tank or paint tank 2.
Because it uses the weight change of
Since weight can be measured almost continuously, by averaging or calculating the measured data, the weight measurement value can be changed with less statistical fluctuation without the need for long sampling intervals as in conventional methods, and feedback control of application amount is possible. Coupled with the reduction of the delay time, it is possible to control the coating amount with fast response and good stability.
becomes.

To, Example FIG. 1a shows an overview of an embodiment of the present invention.

Reference numeral 1 denotes a roll coater in which a pickup roll 3 is partially immersed in a paint tank 2 and rotates, and is a sheet-like continuous body to be coated with S. Paint liquid is supplied to the paint tank 2 from a paint tank 4 by a pump P, and the paint liquid overflowing from the paint tank 2 returns to the paint tank 4. The paint tank 4 is supported by a load cell 5, and a signal corresponding to the weight of the paint tank 4 is output from the load cell 5. Reference numeral 6 denotes a control device that performs data processing and coating amount control, which samples the output of the load cell 5 at regular time intervals, executes averaging calculations to be described later, and detects the weight of the paint tank 4 almost in real time. When the weight falls below the lower limit value YL, open the valve V to replenish the paint tank 4 with fresh paint liquid, keep the valve V open until the weight of the paint tank reaches the upper limit value Yh, and close the valve V when it reaches Yh. . In this way, paint liquid is replenished into the paint tank 4 until the weight reaches Yh, and then the tank weight gradually decreases without replenishment until YL.
When the weight reaches Yh, the operation of replenishing the paint liquid until the tank weight reaches Yh is repeated.

FIG. 1 shows another embodiment of the present invention, in which a paint tank 2 in which a pickup roll 3 is immersed in a coating device is supported by a load cell 5 to detect the weight of the paint tank 2. The replenishment of liquid is controlled in the same manner as in the embodiment of FIG. 1a.

Figure 2 shows changes in the weight of the paint tank 4 or paint tank 2, which decreases while fluctuating vertically due to various error factors.By averaging these small fluctuations, the weight of the paint tank 4 can be determined accurately. Alternatively, in order to detect the weight of the paint tank 2, the control device 6 performs the following averaging operation on the data sampled from the load cell 5.This averaging method is an intermediate method between a simple interval average and a simple moving average. It is characterized by the fact that it includes another parameter that can be appropriately selected in addition to the interval in which the average is averaged using the average method. The amount of liquid consumed is determined, and the amount of application is calculated from the feed speed F and sheet width W of the sheet S, which have been input in advance to the control device 6. The control device 6 calculates the amount of application calculated in this way. The roll coater 1 is compared with a target value that has been input in advance, and the roll coater 1 is controlled so that the difference between the two becomes O.The control points in the roll coater 1 are adjustment of the rotation speed of the pickup roll 3, and adjustment of the coating liquid adhering to the pickup roll 3. Pressing the scraping lever is used to adjust the pressure, etc.

The averaging method in the present invention described above will be described. Third
In figure a, the horizontal line is the time axis, and the points on the line indicate data sampling points. As shown in Figure 3, the simple interval average is the average of each data in interval B that includes n sampling points, and the next average value is found in interval B° that includes n sampling points next to interval B. It will be done. In this method, if the number of sampling data in one section is increased, the stability of the average value increases, but the time interval in which the average is determined becomes longer, and the responsiveness of the control operation decreases. In simple moving average, as shown in Figure 3C, the interval B in which the average is taken is shifted by -sampling interval.The average value is calculated at the same interval as the sampling interval, but the average value is For example, if we consider the difference between the averages of sections B and B in Figure 3C, this is the difference between the sampling data at sampling time and r, and k
.

rSince the data at each time point are raw data that have not been averaged, the variation in the difference is the same as the variation in the sampling data itself, and when using a simple moving average, even if the interval width is widened. The stability of the average value does not improve.

In contrast, in the present invention, as shown in FIG. 3d, the sections for which the average is to be calculated are shifted by X sampling points and overlapped. In 2\, X is a parameter that can be selected appropriately, and when x=n, it becomes a simple interval average, and when X=1, it becomes a simple moving average.

In order to evaluate the suitability of these averaging methods, we did the following. Y (i)-0,02 as a random function that approximates the sampling data of the weight of paint tank 4 or paint tank 2
774i +60 + 0.2924 (RN low 0.5
) is set (RND is a random number between 0 and 1, i is the sampling number), and the stability of the average value is evaluated by the size of the standard difference of the fluctuation of the average value obtained by each averaging method with a sampling interval of 1 second. Then, I drew a graph of the relationship between this standard deviation and the time between adjacent average values (number of sampling points). For example, in the case of a simple interval average, this graph shows that stability improves (standard deviation decreases) by increasing the interval (sampling number) for which the average is calculated, and the time between adjacent average values is the interval itself for calculating the average. , shows a tendency as shown in Figure 4.

An example of actual calculation is shown in FIG. The horizontal axis is shown in seconds;
Since the sampling interval is one second, the horizontal axis also represents the number of samples. In the calculation, the number of samples used for the average was set in six stages from 10 to 120. In a simple moving average, the time between adjacent average values is 1 second, and the standard deviations when the number of samples is changed are arranged vertically on a line of 1 second. When the number of samples is 120, the time width between adjacent average values in simple interval averaging is 120 seconds, and the standard deviation in this case is 2.
．． It is 6×10 and is indicated by the point marked 120 on the top of FIG. Similarly, for each other number of samples, the standard deviation of the simple interval average and the time interval between adjacent average values are shown by the points marked with the numbers of each sample, and the curve U connecting these points is 5 is a graph showing the relationship between the standard deviation and the interval between adjacent average values in the case of the simple interval average schematically shown in FIG. 4. FIG.

For example, when the number of samples is 60, the parameter X in the present invention can be selected from 1 to 60, and in the calculation example of FIG. 5, five types are shown: 1, 20.40°, 60.80°. Stability and quick response are required for the measured value in feedback control, and quick response increases as the time interval between adjacent average values becomes narrower. Therefore, in Figure 5, the points closer to the lower left corner are more desirable, but the tendency is for the calculation points to fall toward the lower right corner. If only a simple interval average is used, the only option is to select an appropriate point on the curve U in FIG. With simple moving average, you can only select a fixed interval on the 1 second line. In the present invention, a selection range of width below the curve U is formed, so that the practical range of selection is expanded.

In the present invention, it is also important to improve the stability of the raw measurement data of the weight of the paint tank 4 or the paint tank 2. In the embodiment shown in FIG. The open end of the return pipe 7 is positioned below the lowest liquid level of the tank 4 to reduce the reaction of the drop, and the flow of the paint liquid returned to the side does not directly hit the bottom or side wall of the tank. Make the return pipe 7 as thick as possible to make the return of the paint liquid as fast as possible, and move the support position of the load cell 5 closer to the center of gravity of the tank 4 to prevent shaking of the tank 4 due to vibrations of the pump P, etc. It is desirable to detect the weight at the smallest point.Also, in the embodiment shown in Figure 1, it is preferable that the paint tank 2 is supported by a load cell near the center of gravity.In this embodiment, the paint liquid level is Since the paint liquid is not replenished while it is within the predetermined level range, the vibration of the pump P does not have a negative effect on weight detection. However, on the other hand, since the pickup roll 3 is rotating at high speed, This causes noise in weight detection.To prevent this, it is recommended to use a baffle plate that is fixed to the frame of the coating equipment and inserted into the paint liquid in the paint tank 2 to prevent the liquid from shaking. .

According to the present invention, the amount of paint consumed per hour is detected almost in real time, so the responsiveness of the coating amount control system is ironic. Since we use the average value obtained by shifting the simple interval average by an appropriate number of samples on the raw sampling data, the stability of the measured values is good (and the time interval between measured values can be compressed). Therefore, the good response of the feedback system due to constant detection of the controlled variable can be more effectively utilized.

[Brief explanation of the drawing]

Figure 2 is a graph of the measurement results of the weight of the paint tank over time in the same example, Figure 3 is a graph explaining the averaging method,
Figure 4 is a graph showing the tendency of the relationship between the stability of the average value and the average interval in the simple interval averaging method, and Figure 5 is the graph showing the stability of the average value and the relationship between adjacent average values in each averaging method. This is a graph of a calculation example. Agent Hiroshi Agata, Patent Attorney Figure 3 Spacing between 6 flats next to the eye Figure 5

Claims (1)

[Claims] A paint tank that continuously supplies paint to the coating device or a paint tank in the coating device is intermittently supplied with fresh paint liquid, and a means is provided to constantly detect the weight of the paint tank or paint tank. , while the above paint liquid is not being replenished,
The output of the weight detection means of the paint tank or paint tank is sampled, and the simple interval average is calculated for an appropriate number of samples of this sampling data, and the process is repeated by shifting the sample number by an appropriate number of samples less than or equal to the sample number. A coating amount control device characterized in that the coating amount is controlled based on an average value of the coating amount.