JP2006272211A - Paint flow rate feedback controlling system in painting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve and stabilize painting quality by appropriately measuring a flow rate checked by a flowmeter, accurately managing feedback control and dissolving the problem attendant upon precipitation of paint even when precipitable paint is used in flow rate control of spray paint in automatic painting. <P>SOLUTION: The flowmeter is provided in a paint feeding pathway where a flow rate control valve is arranged, measuring result of the flowmeter is fed back to an arithmetic unit and the flow rate control valve is operated. In this feed back control, measurement by the flowmeter is linked with spraying action of a spray gun and a value only at the time of spraying is used for arithmetic control. When a return valve is added and a circulation path is provided for the precipitable paint, the return valve is opened at the time of spray off, the measured value by the flowmeter at this time is input in the arithmetic unit so as not to be fed back and feedback control is performed by measured value only at the time of spray on. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a system for improving the coating quality by controlling and stabilizing the flow rate of a paint sprayed from a spray gun particularly during automatic painting. It also relates to a technology that enables rational automatic painting in conjunction with the control of the painting robot.

In the field of automatic painting such as a painting robot, it is not possible to expect stable quality painting unless the spraying of the paint from the spray gun is performed under the set conditions. Therefore, although various coating conditions and finish in the spray coating are monitored, it is necessary to automatically control these as long as automation is a prerequisite. In many conditions, the amount of spray from the spray gun directly and greatly affects the finish of the paint, so a stable supply of paint is important.

The paint is usually supplied to the spray gun in a state where a flow rate required by a flow rate adjusting valve or the like is set using a pump. However, the amount of spray is constantly changing during use due to changes in paint viscosity, changes in environmental temperature, or changes in devices such as spray guns. In addition, there is a need to control spraying with different spray amounts as required.

The amount of paint supplied to the spray gun is often different from the actual spray gun spray amount even if the flow rate adjustment valve is used, and the operator regularly measures the amount and checks the finished state. It is indispensable to check and work. However, in the mass production and continuous painting sites, the interruption of work leads to a decrease in productivity. Therefore, there is an increasing need for a device that can automatically check and adjust to the correct conditions automatically.

As shown in FIG. 3, in addition to controlling the flow rate by the flow rate control valve 4, the spray amount from the spray gun 3 is measured, and if there is a difference from the set flow rate, the flow rate control valve 4 is operated to The method of making the required amount is known as feedback control. In this case, a flow meter 7 is installed in the supply circuit, the actual flow rate measured by the flow meter 7 is taken out as a signal, and the output value is confirmed by comparing it with a preset flow rate. If necessary, for adjustment An output signal for operating the flow control valve 4 can be output and stabilized at a set value.

These feedback controls require a highly accurate and responsive flow meter, and further require an arithmetic device incorporating a specific program for confirming and adjusting the measured values, which is relatively expensive. In addition, a technology that enables stable feedback control regardless of responsiveness has been proposed. (Japanese Patent Laid-Open No. 7-232113)

On the other hand, the painting by the painting robot, which is at the forefront of automatic painting, consists of a robot body that holds a spray gun on the arm and is controlled by free movement and a control device that controls it. Various programs are incorporated in the control device. In addition to the robot body, it has come to have a function capable of controlling other peripheral equipment such as a peripheral paint supply device and an object conveying device.
JP-A-7-232113 JP 2000-37650 A

However, even if the actual flow rate is accurately measured using a flow meter, it is meaningless if the measured value is not properly used. In this respect, effective and appropriate feedback control has not been achieved in the past. There are problems such as oversight of defects, and insufficient paint management.

As can be seen from the prior art examples, the flow rate control is usually provided in the supply path to the spray gun. However, there are a wide variety of paints in the coating field. For example, in the case of a paint having a precipitating property such as a paint containing fine powders of metals such as metallic paints, the flow is stopped while the spray gun is stopped. Inevitably, the fluidity of the paint path is gradually affected, and the components of the paint may vary during spraying, resulting in coating surface defects.

For this reason, it is possible to improve by providing a paint circuit that circulates in front of the flow regulating valve, but the tip of the flow regulating valve still has a possibility of precipitation and is not sufficient. Immediately before the spray gun, it is desirable to form a circulation passage inside the spray gun to solve the problem of stagnant sedimentation. However, when the spray gun is stopped, the flow rate of the circulating paint does not necessarily match the spray amount. It depends on the paint valve and other structures. Therefore, it is impossible to perform feedback control with this, and there is a problem in management of the actual spray amount.

From the above background, when controlling the flow rate of spray paint in automatic coating, measure the flow rate to be checked with a flow meter as an appropriate flow rate that is required, and set the required value as the value to be fed back to ensure accurate flow rate management. It is required to be possible. Furthermore, even when a precipitating paint is used, it is a problem to solve some problems associated with the precipitation of the paint and to enable feedback of an appropriate spray flow rate, and as a result, to improve and stabilize the coating quality. It is also intended to improve the accuracy of paint management comprehensively by making effective use of the flow meter measurement results.

In the feedback control that provides a flow meter in the paint supply path with the flow control valve, feeds back the measurement result of the flow meter to the arithmetic unit, and operates the flow control valve, the measurement by the flow meter is the spray operation of the spray gun The value only at the time of spraying is used for calculation control. As a result, only a substantial spray amount that is reliably sprayed is used as confirmation data for the flow control, and unnecessary data is not entered, so that highly reliable feedback control is possible.

When the spray circuit is provided with a branch circuit on the spray gun side of the paint circuit and a circulation path returning to the paint supply pump via the return valve, the aforementioned return valve is opened when the spray is turned off. The measured value of the meter is incorporated in the arithmetic unit so as not to be fed back, and feedback control is performed based on the measured value only when the spray is ON. Further, the flow rate is controlled by providing a timer means for setting the return valve to open after a predetermined time has elapsed after the spray is turned off, simultaneously with the ON / OFF of the spray.

Furthermore, the amount of paint used can be grasped by integrating and outputting the flow rate only when the spray is ON.

As described above, according to the present invention, by synchronizing the feedback control only during spraying, the actual spray amount can be managed as set, and stable coating can be continued without bothering the operator in automatic coating. it can. Furthermore, it is possible to improve the problem of precipitation that occurs when coating is interrupted with a paint that tends to settle, and to accurately supply a stable spray amount by feedback control based on the flow rate during substantial spraying, thereby maintaining the coating quality.
Also, since the amount of paint used during the painting process can be grasped by integrating the flow rate only during spraying, the management of the flow rate during spraying and the management of the amount of paint used throughout the painting are combined to provide even more accurate paint management. Is possible.

FIG. 1 shows a block diagram of a paint supply circuit of the present invention. The paint supply pump 1 sucks the paint in the paint container 2 and supplies it to the spray gun 3. Generally, a plunger type or a diaphragm type is used. If it is a supply apparatus suitable for continuous supply, it will not be limited to this. In the supply circuit A, a flow control valve 4 and a flow meter 7 are arranged in series. In this example, the flow control valve 4 has an air operator type paint pressure reducing valve structure, and the paint pressure supplied from the inlet side is set by adjusting the opening of the valve by the operation of the diaphragm by the control air pressure. The paint pressure is discharged. Control air is sent to the flow rate control valve 4 through an electropneumatic valve 6 which receives an output signal from the arithmetic unit 5 and is converted and output.

As the flow meter 7, a vibration type flow meter using Coriolis force is used because of responsiveness, but it is not necessarily limited to this. In the case of the flowmeter 7 according to the embodiment, the measured value of the paint flow rate is output as a pulse signal, and is input to the arithmetic unit 5 and recognized as a measured value. The input value recognized as a measured value from the normal flow meter 7 is compared with a preset program information of the calculation device 5 and used as a reference for an output necessary for operating the flow control valve 4.

The spray gun 3 is an automatic gun whose operation is controlled by compressed air, and various types of specifications are used according to the painting. Here, a circulation type automatic gun is used in which the coating material supplied from the coating material inlet is sprayed by opening the tip needle valve and the passage is circulated to the outside. The circulation path B returns from the spray gun 3 to the suction side of the paint pump 1 or the paint container 2 and is again fed into the supply circuit by the paint pump. If a normal non-circulating spray gun is used, a similar circulation can be made possible by connecting a joint with a branch path to the circulation path just before the spray gun.

In the configuration of the above apparatus, the spray gun 3 is operated by compressed air by a control device such as a painting robot, but the circuit of the operating air is omitted in FIG. Although the flow meter 7 is provided in front of the flow control valve 4, it may be installed downstream of the flow control valve. Furthermore, the function of the flow control valve may be incorporated in the paint pump, and the structure of each device is not limited unless otherwise specified.

The circulation passage B is provided with a return valve 8 which functions to open and return to the circulation passage B when the spray of paint from the spray gun 3 stops. The return valve 8 is controlled to open and close by a command signal from the arithmetic unit 5. The open / close control is preferably an air operated type from the viewpoint of safety.
FIG. 2 is a graph showing the opening / closing of the return valve 8 and the operation of the flow meter 7 in accordance with the operation of the spray gun 3 with the above configuration.

The paint is fed into the supply circuit A in a pressurized state by the operation of the paint pump 1. The flow rate control valve 4 is controlled in a state where it is supplied at a preset pressure, and is fed to the spray gun 3 side with a paint pressure at a predetermined spray amount. The spray amount is almost determined by the paint pressure in relation to the paint nozzle diameter of the spray gun 3, and the relation of the actual spray quantity according to conditions such as the paint viscosity is tested in advance and used as data. Therefore, the spray amount corresponding to each condition can be controlled by the supply pressure of the paint.

In FIG. 2, at the same time the spray gun is turned on in C, the flow meter 7 starts measurement and sends the result to the arithmetic unit 5. The arithmetic unit 5 controls the flow rate control valve 4 according to this measured value, and outputs as necessary. That is, feedback control is performed, and if the measured value is within the range of a preset spray amount, that is, the flow rate and the set allowable value, it is left as it is, and if it exceeds the allowable value, a correction signal is output.

Next, when the spray is turned off at D, the feedback control is stopped, and the return valve 8 is opened after a short time T1. This is because the spraying is usually performed intermittently in a short time in the painting work, and when the return valve 8 is operated in synchronism with the spray, the operation of the return valve 8 is not affected by frequent operations. Thus, this time is usually set from several seconds to several tens of seconds, and can be set long as long as there is no problem in the precipitation of the paint.

While the spraying is stopped and the return valve 8 is open, the supply continues through the circulation passage B with the paint pressure when the spraying is stopped. At this time, the flow meter 7 does not count with the arithmetic unit 5. It is set. Further, when the spray is turned on again at E, the return valve 8 is closed at the time T2 immediately before the spray is turned on. Normally, this time T2 is several hundred milliseconds, and simultaneously with the spray ON, the feedback control is also started. Therefore, the spraying of the spray gun 3 and the feedback control by the flow meter 7 are performed at the same time, and reliable feedback control can be performed. Although T2 at the timing of closing the return valve 8 is set immediately before the spray is turned on, it may be after the spray is turned on depending on the spray characteristics of the spray gun and the piping conditions.

If the feedback control is performed when the spray is other than ON, even if the discharge pressure of the flow control valve 4 is the same, a difference occurs in the actual flow, and the flow at the next spray ON changes.

Moreover, the measured value of the flow meter 7 at the time of feedback control is integrated and memorize | stored in the calculating apparatus 5, and it can know the whole coating-material usage of the limited painting process by displaying as needed. As a result, in addition to the spray amount management at the time of spraying, it is possible to determine whether or not the coating is performed with an appropriate amount of paint used as a whole, thereby enabling more accurate coating management.

Furthermore, when it is incorporated in the control of the painting robot, even if there are different processes in the painting location and painting conditions of the object to be coated, if the flow rate during spraying required in each painting process is set, In accordance with the operation of the painting robot, the spray amount corresponding to the situation and the feedback control at that time can be performed for each process.

1 is a block diagram of a flow rate feedback control system showing an embodiment of the present invention. It is a graph explaining opening and closing of a return valve and operation of a flow meter accompanying operation of a spray gun. The block diagram of the conventional flow volume feedback control system is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paint pump 2 Paint container 3 Spray gun 4 Flow control valve 5 Arithmetic device 6 Electropneumatic valve 7 Flow meter 8 Return valve 9 Electromagnetic valve A Supply circuit B Circulation passage

Claims (4)

In the circuit that supplies paint from the paint supply pump to the spray gun, a flow control valve that receives command signals and adjusts the opening and a flow meter that measures the actual flow and outputs the measurement result are connected in series. In the paint supply flow rate feedback control system that feeds back the measured results to the arithmetic unit for comparison and outputs and controls the necessary output signal to the flow rate control valve, the measurement by the flow meter is linked with the spray operation of the spray gun. Paint flow rate feedback control system that uses only the time value for calculation control. A branch circuit is provided on the spray gun side of the circuit, a circulation path is provided to return to the paint supply pump via the return valve, the return valve is opened at the time of spray OFF, and at this time it is incorporated in the arithmetic unit so as not to feed back from the flow meter, 2. The flow rate feedback control system according to claim 1, wherein the flow rate feedback control system is performed by a measured value only when the spray is ON. 3. The flow rate feedback control system according to claim 2, further comprising timer means for interlocking the measurement of the flow meter simultaneously with the ON / OFF of the spray and setting the return valve to open after a predetermined time has elapsed after the spray is turned OFF. 2. The flow rate feedback control system according to claim 1, wherein the flow rate only when the spray is ON is integrated and output.

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