JP2010036063A - Paint feeding control method using pneumatic control valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize the coating quality by eliminating affect by a hysteresis phenomenon of a used device like an adjusting valve when controlling a flow rate, and by attaining stable flow rate regulation. <P>SOLUTION: In the paint feed control by an air-operated flow control device discharging a regulated flow, being operated by receiving control air from a control valve via the open/close control valve feeding the compressed air pressure set by remote control for paint feed to a spray gun, the pressure is set lower than a target value, then set to the target value. In changing the set value, the value is once returned to a low value (zero) and then set to the target value. This operation is incorporated in a recording device as a program control. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a paint supply control method for stably and accurately supplying a predetermined amount of paint to a spray device in an automatic painting line using a painting robot or the like.

Accurate supply of paint to a spray gun or the like, which is a spraying device, is indispensable because it greatly affects the quality of the final coating. In particular, the spray gun performs painting under the optimum conditions according to the application site of the object to be coated by the automation of painting by a painting robot, etc., so that the amount of paint sprayed, according to the movement of the spray gun in one painting program, Increasingly, various coatings are continuously performed by changing the size of the spray pattern, the spray air pressure, and the like.

As a result, even if the object has a complicated shape, it can be applied to a narrow coating area in an unnecessarily large range and amount without losing productivity, and waste of paint or adverse effects on the environment. It is possible to perform effective painting without any problems. In addition, the variation in the amount of paint supplied causes unevenness of the paint sprayed from the spray gun, and causes a defective finish as a disturbance of the coating surface. It is important to accurately supply a predetermined amount of paint according to instructions.

Control of the paint supply amount differs depending on the supply pump or pumping device to be used, and there is a method of determining the supply amount by controlling the rotation speed like a gear pump. The discharge amount from the gun is controlled. And this pressure is adjusted using a pressure regulating valve, especially in the case of control such as remote control or using an automatic program, an air operated pressure regulating valve that adjusts the valve opening by the control pressure due to air pressure is used as a flow control valve used.

FIG. 5 is a simple block diagram showing an example of a general supply apparatus in a conventional coating apparatus. As shown here, the paint in the paint container 1 is sent to the flow rate adjusting valve 3 through the paint passage 8 by the pressure feeding device 2. The flow control valve 3 uses an air-operated flow control valve in which the operation of the on-off valve is adjusted by the control air pressure and discharged at a constant discharge pressure, that is, a flow rate. The pressure air for control is supplied at a set pressure by the electropneumatic regulator 5 that receives an output signal of the electronic control unit 4 and can adjust the compressed air pressure by the output signal. . The paint adjusted to the flow rate set by the flow control valve 3 is sent to the spray gun 9 and sprayed. The control valve 7 is one of the basic components provided for receiving the signal from the control device and sending the operating air of the spray gun, the atomizing air, the pattern adjusting air, and the like. However, these are usually adopted configurations, and detailed description thereof is omitted here.

Such a method in the paint supply is a technique that is conveniently and widely used when managing paint by automatic control because the flow rate can be controlled by an electrical signal output by a program or operation signal stored in advance. . However, in coating, the properties of the paint, the coating conditions, and the environmental conditions of the coating, as well as many other conditions in the related equipment used, are complicated, and the accuracy of the ejection amount is not always sufficient. For this reason, there are problems such as variations in the final painted surface and poor coating. To solve this problem, many techniques for stabilizing the amount of paint supplied have been proposed. .

As an example, the actual paint supply amount is measured by the flow meter 6 shown in FIG. 5, the measured value is fed back and compared, and a new control signal is output for correction. This feedback control has several control methods conceived depending on the complicated conditions, and details thereof are omitted here. However, for example, Japanese Patent Application Laid-Open No. H8 (1994) -8 does not deal with the problem of responsiveness caused by viscosity changes due to differences in paint and temperature. -117655 or the like, or for precipitating paints, see JP-A-2006-272211.

In any case, according to these methods, not only the control and the device are complicated, but also an expensive and accurate flow meter is used. Accurate and stable paint supply is desired by simple control using a control valve.

As described above, many of the flow control valves use an electropneumatic regulator to convert the output signal from the electronic control device to control air pressure and control the operation by the pressure. It has the effect of minimizing the influence of the paint supply pipe line and the change of the water head pressure due to the height of the sprayer. The painting robot is optimally adapted to the painting surface by adjusting the ejection amount within one painting program. It is especially effective when performing various coatings.

Normally, automatic painting, especially painting robots, is often performed efficiently by incorporating the painting process under several painting conditions into one program. Or in the local painting, the amount of paint sprayed is different, and the flow rate of the supplied paint needs to be changed. In such a case, in the conventional control, the signal output from the control device is changed directly from the previous value to the next value in order to change from the previous flow rate to the next required flow rate.

In this case, the relationship between the voltage input from the control device to the electropneumatic regulator and the output air pressure shows a proportional trend, but when the set value is gradually increased as shown in FIG. 2 as an example (A). When the actual discharge pressure is gradually decreased from the high set value, the actual discharge pressure in (B) is different. This is affected by individual differences in equipment as hysteresis, and it is difficult to quantitatively correct this.

Furthermore, there is a similar phenomenon in the flow control valve. Even if air with the same control pressure is supplied from the electropneumatic regulator, the pressure supplied from the flow control valve receives both fluctuation factors and maintains the same paint supply amount. It is difficult to do. For this reason, the operator makes mechanical corrections such as changing the opening of the valve. However, the hysteresis is canceled by operating several times, and this time the corrected amount is distorted. The magnitude of this error varies from device to device, and workers are forced to perform corrective operations after understanding their properties.

When the paint supply amount is automatically and repeatedly changed by the painting program as described above, the command control signal including the electropneumatic regulator is changed when the paint supply amount is changed using the flow control valve. The output values by may not always match. In other words, when the control value before the change is lower and higher than the control value after the change, the so-called hysteresis phenomenon, in which the reached value differs due to the influence of the previous state due to various resistances etc. accompanying the operation of the valve, As a result, the output value is different and the supply amount is different.

This phenomenon occurs depending on the electropneumatic regulator and flow control valve used, and the values differ and are difficult to correct. Although it is expensive, it relies on the feedback control and PID control using the flow meter described above. It was. The present invention eliminates the hysteresis phenomenon that causes instability in the supply control by the flow control valve, enables accurate and stable supply control, and improves the durability of the electropneumatic regulator and flow control valve to be used. The issue is to produce an effect.

An electro-pneumatic regulator that receives electrical output signals by remote control and discharges compressed air at a set pressure, and a flow control that operates by receiving control air supplied via the electro-pneumatic regulator and discharges adjusted paint flow In paint supply control for supplying paint to the spray gun by a valve, after setting at least one of the set pressure of the electropneumatic regulator and the discharge flow rate of the flow rate control valve below the target value when changing the set value The program is controlled so as to be set to the target value.

The electropneumatic regulator whose valve opening / closing degree is controlled by an electric signal and the flow rate adjusting valve whose valve opening / closing degree is also controlled by an air pressure signal are moved downward when moving to a target set value determined by each control value. The target set value varies depending on whether the value is set from the lower value or the lower value, but the target value always fluctuates according to the above method. Since the control valve is adjusted, the fluctuation factor due to the operation error of the device is eliminated and the stability is improved.

As a result, it is possible to ensure the stability of the paint supply using the flow rate control valve, and to improve the finish of the coating and the quality of the coating surface. Therefore, it is not necessary to control the flow rate using an expensive flow meter for the paint supply stability in robot painting, etc., and it can be managed sufficiently simply by using a flow control valve, reducing not only the equipment cost but also maintenance. I can plan.

In addition, the load on the device can be reduced by setting the start point to a lower value, and by setting it to always return to zero with no load at the end of the program, unnecessary load conditions can be eliminated and the durability of the device can be improved. it can.

The overall configuration of the paint supply apparatus for carrying out the present invention will be described with reference to the block diagram shown in FIG. Devices having the same configuration as in FIG. 5 shown as a conventional example are indicated by the same symbols, and are simplified to only the configuration necessary for the description. In many cases, the electronic control unit is usually integrated with a drive control unit such as a painting robot or incorporated in a program of the robot control unit and controlled in synchronization with the operation of the painting robot. Therefore, operation of sprayer mounted on the painting robot, spraying pressure, pattern opening and control of paint supply amount are performed, and various conditions are programmed so that optimum painting according to the object to be painted and its painted surface is performed. ing.

As described above, the signal from the control device 4 is generally sent as a voltage signal to the electropneumatic regulator 5, adjusted to a preset opening degree by the voltage, and connected to the electropneumatic regulator 5. Compressed air from the air source 10 is sent to the flow control valve 3 at a predetermined pressure. The supplied paint is supplied from the paint container 1 to the flow rate adjusting valve 3 by the supplying device 2, adjusted by the flow rate adjusting valve 3, and sent to the spray gun 9. The spray gun 9 opens and closes the paint valve via the control valve in response to a signal from the control device 4, and spraying is performed and stopped. Although the operation control of the spray gun by the control valve is omitted in FIG. 1, it is configured in the same manner as FIG. 5 shown as a conventional example.

The amount of paint sprayed from the spray gun is determined by the specifications of the spray gun and the supply pressure from the flow control valve 3, and when the flow control valve and spray gun installed in the painting robot operate under almost constant conditions, There is no influence of other factors, and the amount of paint sprayed is determined by the discharge pressure of the flow control valve. Therefore, if the flow control valve is sufficiently accurate, the amount of spray from the spray gun can be accurately controlled.

The flow control valve 3 is an on-off valve that operates in accordance with the compressed air pressure from the electropneumatic regulator 5 and can control the flow in equilibrium with the discharged paint pressure and supply it at a constant pressure. As a result, the flow rate is constant under almost constant conditions. For this reason, the control air pressure discharged from the electropneumatic regulator 5 needs to be supplied accurately. FIG. 3 shows an example of the amount of paint discharged with respect to the air pressure of the flow control valve.

When painting with a paint robot as an example with the above configuration, the spray gun is operated on the object to be coated, the spray gun is turned ON / OFF, and the spraying air pressure is supplied by the program built into the painting robot controller. A spray pattern adjustment signal is sent, and an electric signal (set voltage) set in the electropneumatic regulator is sent as a paint supply.

There are cases where the change in the amount of paint spraying due to the painting process is increased and when it is decreased. As shown schematically in FIG. In some cases, the paint is applied again, and then moved to a narrow paint surface again and applied with a small ejection amount (A). Therefore, in such a case, the output signal from the control device is programmed not to change from the previous set value to the next set value as it is, but to set the lower value once and then change to the new set value. Yes.

Therefore, even when changing from a large ejection amount to a small ejection amount, since it is always changed from below, the operating characteristics of the valve are set in the same state, and the variation with respect to the set value is eliminated. The lower value to be set is not particularly limited, but setting it to zero is simple and easy to understand. In addition, when the output of the set value is stopped and when one cycle of the painting program is completed, the output value is memorized so as to return to zero, thereby eliminating the load on each device and extending the life of the device accordingly. .

Even with the same target set value due to the hysteresis phenomenon, the result is different, and a difference in the amount of paint jetting occurs, resulting in instability of coating film quality and coating film failure. However, in the present invention, when changing the ejection amount, that is, the paint supply amount, after setting it to a value lower than the target set value, the opening of the electropneumatic regulator by the output voltage is always adjusted from below by setting it again to the target set value. Outputs a stable air pressure. The lower value at this time is not particularly limited as long as it is lower than the target value. However, it is desirable that the lower value be zero, which is a constant operation from a stable value with no load.

When the pressure is set lower than the set pressure, the output pressure on the output side is preferably removed before the next pressure is output. For example, even if the pressure on the output side is not excluded during the painting process, the next discharge is performed. In the initial stage, the pressure instantaneously returned to the lower value (zero) and then adjusted to the set pressure, so that the coating could be performed without affecting the substantial spraying. Especially in the spraying operation of spray coating, the position of the start of spraying is hardly directed directly at the object to be coated, and starts from the outside of the paint position (not spraying the object to be coated from the beginning of spraying, but throwing it outside. It is possible to stabilize to a normal value during this period.

1 is a configuration block diagram of a coating apparatus for carrying out the present invention. It is a graph which shows the hysteresis phenomenon in which the difference of setting pressure and measured pressure produced. It is a graph which shows the change of the paint supply pressure with respect to the control air pressure of a flow control valve. It is a schematic diagram which shows the change of the setting pressure of supply amount control in a painting process. It is a block diagram which shows an example of a structure of the conventional coating apparatus.

Explanation of symbols

1, paint container
2, pumping device
3, flow control valve
4, electronic control device
5, electro-pneumatic regulator
6.Flow meter
7, control valve
8, paint passage
9, spray gun
10, air source

Claims (2)

An electro-pneumatic regulator that receives electrical output signals by remote control and discharges compressed air at a set pressure, and a flow control that operates by receiving control air supplied via the electro-pneumatic regulator and discharges adjusted paint flow In paint supply control for supplying paint to the spray gun by a valve, after setting at least one of the set pressure of the electropneumatic regulator and the discharge flow rate of the flow rate control valve below the target value when changing the set value A paint supply control method using an air pressure control valve, wherein program control is performed such that the target value is set. 2. The paint supply control method according to claim 1, wherein the lower portion of the target value is zero.

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