JPH0357834B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multi-component coating method,
Specifically, the present invention relates to a method for preventing various problems caused by abnormalities in the paint conveyance path.

[Prior Art] Examples of paints supplied in a multi-liquid form of two or more liquids include urethane resin paints made of polyester resin and isocyanate resin, and epoxy resin paints made of epoxy resin and polyamide resin.
These paints often have a short pot life after mixing, and when painted on a production line, in order to avoid the hassle of frequent mixing, the first tank is filled with the main paint, and the second tank is filled with a hardening agent. Painting was done by using two separate paints and mixing them just before the sprayer or just after they came out of the sprayer. With this method, there was no need to worry about pot life, and only a portion of the coating machine needed to be cleaned, greatly reducing the burden on the operator. Taking advantage of this advantage, it is also used as a three-part solution, with a catalyst or promoter as the third component. In this case, curing and drying properties are greatly improved, contributing to improved work efficiency.

[Problems to be Solved by the Invention] Paints supplied in a multi-liquid form exhibit the best performance when each liquid is accurately blended in predetermined amounts. However, in the conventional multi-component coating method, for example, when an abrasive material such as silica is blended into the base paint, the equipment that supplies the base coat wears out and the flow rate ratio with the hardener side decreases. As a result, the quality of the paint film sometimes differed from the initial quality. Furthermore, when a paint containing a sedimentary material is used, this material settles in the paint transport path, causing a change in the flow rate ratio, or in extreme cases, making it impossible to supply the paint.

To solve these problems, JP-A-Sho
52-2761, a method is provided for measuring the flow rate of each liquid using a flow sensor and controlling the flow rate based on the results. According to this method, if, for example, the flow rate decreases due to deposits accumulating in one paint transport path, the flow rate is automatically increased by increasing the supply amount of the feeder. That is, the flow rate of each liquid and its ratio are always considered to be within a predetermined range.

However, with this method, even if the flow rate decreases due to a paint leak on the primary side of the flow rate sensor, for example at a joint in the paint conveyance path, the flow rate sensor will detect the decrease in flow rate and will supply the amount up to a predetermined flow rate. is increased. Therefore, although the quality of the painted film was maintained, the leakage of paint was left untreated. Further, even when air is mixed into the paint conveyance path and the flow rate is reduced, the amount of paint supplied is simply increased in the same manner as above. This mixed air becomes bubbles and remains on the coating film, and there have been many cases in which the cause of this is not noticed until defects such as pinholes are discovered after the coating film dries, resulting in many coating defects.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to prevent problems caused by abnormalities in the paint conveyance path in a multi-liquid coating method.

[Means for Solving the Problems] The present invention provides a multi-liquid coating method in which the liquids are supplied in the form of multiple liquids, each liquid is conveyed separately, and each liquid is mixed and painted while maintaining a constant flow rate ratio. The flow rate of at least one of the liquids is measured, and when the flow rate deviates from a predetermined setting range, the supply of all liquids is stopped and an alarm is generated.

The term "multi-liquid" as used in the present invention refers to the use of two or more liquids. There are no particular restrictions on the coating material supplied in this form, and a room temperature crosslinking curing type coating material is mainly used, but a solvent evaporation drying type coating material may also be used. For example, when using a urethane resin paint, it is usually a two-component paint, with a main agent made of polyester resin in the first tank and a curing agent made of isocyanate resin in the second tank. In this case, thinner is added to one or both of the base agent and hardening agent in advance to adjust the coating viscosity during mixing. 3 using thinner in the third tank
It is also possible for the liquid to have a coating viscosity upon mixing. Similarly, the paint and thinner can be separated and used as a two-part solution using, for example, nitrified cotton lacquer.

A conventional method can be used as is for the supply device for supplying the multi-liquid paint to the coating machine. For example, a pump such as a plunger pump, a gear pump, or a gravity drop system can be used, but a gear pump that allows fine adjustment of the supply amount is particularly desirable.

Each liquid is supplied from a pump or the like and then conveyed through a resin hose or pipe. Here, the resin hose is preferably made of Teflon, which has excellent solvent resistance, and the pipe is preferably made of stainless steel, which has excellent corrosion resistance. The transported liquids are mixed, for example, just before the coating machine (internal mixing) and then painted, or, for example, after leaving the coating machine, they are mixed (external mixing) and coated. Since each liquid must be mixed as uniformly as possible, internal mixing is preferable, and in particular, it is preferable to use a static mixer because almost complete mixing can be expected.

As a coating machine, a conventional coating machine can be used as is, for example, an air spray, an airless spray, an electrostatic coating machine, etc. can be used.

The most distinctive feature of the present invention is that the flow rate of at least one of the liquids is measured, and if the flow rate deviates from a predetermined setting range, the supply of all liquids is stopped. Here, as a method for measuring the flow rate, first there is a method of using a flow rate sensor, and as the flow rate sensor, a general volumetric sensor, a turbine type sensor, etc. can be used.
Also, as seen in the above-mentioned Japanese Patent Application Laid-Open No. 52-2761,
A thermal impulse is applied to the liquid being transported, and the impulse is detected by a downstream thermal sensor located a certain distance away.
There is a method of measuring the flow rate based on the time difference, an ultrasonic flow rate sensor, etc., and either method is preferable because it does not interfere with the flow of each liquid. In addition, when a gear pump is used to supply each liquid, the flow rate can be calculated from a sensor that detects the rotation speed of the gear.
When a plunger pump is used, the flow rate can be calculated using a sensor or the like that detects the number of reciprocations of the piston per unit time. It is particularly desirable to use these flow rate sensor measurements in combination with pump operating status measurements.

Detection by the above sensor must be performed periodically, and it is desirable that the time interval be as short as possible.

The signals of the sensors are sent to the control device. This control device consists of a signal analysis section that analyzes sensor signals and calculates the flow rate of each liquid, and a command section that sends signals to control the supply device from the calculation results, and preferably uses a microcomputer. .

The first condition that determines the flow rate setting range is the paint composition ratio. For example, the ratio of the base agent to the curing agent in the paint is determined to be 2:1, 4:1, or the like.
Furthermore, in order to keep the coating viscosity constant, it is necessary to change the amount of thinner, etc. added depending on the temperature, and this must be taken into consideration when separately supplying thinner, etc. Also, the amount of coating determined from the area of the object to be coated, conveyor speed, desired film pressure, etc. is also an important condition.

The optimum flow rate of each liquid is determined from these conditions. Furthermore, the range from the optimum flow rate is determined based on voltage fluctuations, pump performance, etc., and the flow rate range of each liquid is set. It should be noted that in spray painting, etc., paint is often ejected intermittently in order to save paint.
Since the flow rate of each liquid becomes almost zero when the paint discharge is cut off, it is desirable to include this case in the setting range.

If the flow rate deviates from the range set above, the supply of each liquid is immediately stopped. At this time, an alarm device is activated at the same time to notify the operator of the abnormality. This warning device includes a red lamp, a buzzer, etc., and it is desirable to make it visible both visually and perceptually to the worker. It is also preferable to immediately know which sensor has detected the abnormality at this time.

[Function] The function of the multi-component coating method of the present invention will be explained below with reference to the block diagram shown in FIG.

First, the signal analysis unit 21 of the control device 2 analyzes the signal from the sensor 1 to calculate the flow rate of the liquid.
As a result, if the flow rate of the liquid deviates from the predetermined setting range, the command section 22 sends a signal to the supply device 3 and the alarm device 4 to stop the supply of each liquid and issue an alarm. If the result is within the set range, the command unit 22 sends a signal to the supply device 3, and the supply device 3 is controlled so that the flow rate of the liquid approaches the optimum flow rate. Nothing is done when the flow rates of each liquid are all zero, but it is preferable that the alarm device 4 is activated if this state continues for a certain period of time.

[Example] A more detailed explanation will be given below based on a specific example.

FIG. 2 shows a conceptual diagram of a coating apparatus according to a specific embodiment of the multi-liquid coating method of the present invention.

The main ingredient of the urethane resin paint is put into the paint tank 01, and the curing agent for the paint is put into the paint tank 02. These paints are pumped into a mixing chamber 61 by a gear pump 42 driven by a motor 41.
transported to. The paint that has been mixed to some extent in the mixing chamber 61 is further thoroughly mixed in a static mixer 62, and then painted by a spray gun 70.
During this paint conveyance, the flow rate sensor 1
1 and 12 detect the flow rate of each conveyance system, and rotation speed sensors 13 and 14 detect the rotation speed of the primary side gear of the gear pump 42 and transmit the signal to the control device 30.
I am sending it to Normally, the control device 30 calculates the flow rate of each conveyance system from the signal and controls the motor 41 that drives the gear pump 42 to achieve the optimum flow rate, thereby controlling the rotation speed of the gear pump 42. However, if there is an abnormality in the signal, If this is detected, the motor 41 is stopped and the alarm device 50 is activated. Here, the method disclosed in Japanese Patent Application Laid-open No. 52-2761 is used for the flow rate sensors 11 and 12, and frequency type digital counting sensors are used for the rotational speed sensors 13 and 14. Further, the control device 30 uses a microcomputer and a digital comparator.

Next, the main parts of the coating apparatus according to the above embodiment will be explained using a block diagram shown in FIG.

The sensor unit 10 includes flow rate sensors 11 and 12 and rotational speed sensors 13 and 14, and performs predetermined processing on signals from these sensors to control the control device 30.
and a signal processing circuit 15 for outputting to.

The control device 30 includes an input interface 31 that transfers electrical signals from the sensor section 10 and the keyboard 20 to a signal analysis section 32, and processes the electrical signals input through the input interface, calculates the flow rate, and outputs an output signal. A signal analysis section 32 that issues signals, and a flow rate command section 33 and an alarm command section 34 that issue control signals to the supply device 40 or the supply device 40 and the alarm device 50 according to a predetermined program based on electrical signals from the signal analysis section 32. A command department consisting of;
This is an electric circuit consisting of an output interface 35 that delivers an electric signal from a command unit to a supply device 40 and an alarm device 50.

The supply device 40 is composed of a motor 41 that is controlled by an electric signal from the control device 30 and a gear pump 42 that is interlocked with the motor 41 through a gear. It consists of a lamp 51 and a buzzer 52 which is turned on at the same time as the red lamp lights up.

Next, the operation of the coating apparatus according to the embodiment of the present invention will be described with reference to flowcharts of the processing contents of the control device shown in FIGS. 4, 5, and 6.

When the base agent put into the paint tank 01 and the curing agent put into the paint tank 02 in Fig. 2 are mixed at a ratio of 4:1, the coating viscosity becomes optimal.
and is tuned for maximum performance. In addition, in this example, the amount of paint calculated from the coating area of the object to be coated, conveyor speed, coating efficiency, desired film pressure, etc. is 300 ml/min, that is, 240 ml/min of the base agent and 60 ml of the hardening agent. It is best to convey the amount per minute. And the rotation speed of the gear on the primary side of the gear pump to obtain this flow rate is
It is known that they are 120rpm and 30rpm. Taking into consideration voltage fluctuations and errors from these optimal flow rates and rotational speeds, the flow rate setting range is set to 240 ± 10
ml/min, the rotation speed of the primary gear is 240 ± 5 rpm, and the curing agent is 60 ± 5 ml/min, the rotation speed of the primary gear is 30
It was set as ±3 rpm.

The flow rate range set above is entered in advance from the keyboard in step 100 and written in the memory within the control device. Here, to simplify the explanation, the optimum flow rate is F, and the optimum rotation speed is R.
Let f be the width of the flow rate in the setting range, and r be the width of the rotation speed.
shall be. That is, the setting ranges are expressed as F±f and R±r.

With the above steps, preparations are completed and operation begins. First, in step 200, an electrical signal from a flow rate sensor provided in the transport path of the base paint is processed and input, and in step 201, the flow rate L is calculated. At step 202, the flow rate L is compared with the optimal flow rate F input and stored at step 100, and three types of processing are performed depending on the magnitude.

First, if the flow rate L is larger than the optimum flow rate F, the variable M is set to 1 in step 203, and the flow rate L is compared with the upper limit F+f of the setting range in step 204.

If the flow rate L is larger than the upper limit F+f, it is determined that there is an abnormality, and the pump is stopped at step 500 in FIG. Waiting for inspection.

If flow rate L is smaller than optimal flow rate F, step
In step 205, the variable M is set to -1, and in step 206, the flow rate L is
is compared with the lower limit F-f of the setting range. Here, if the flow rate L is smaller than the lower limit F-f, it is checked in step 207 whether the flow rate L is zero, and if the flow rate L is not zero, it is determined that there is an abnormality, and steps 500 to 503 are performed.
The abnormality will be dealt with.

In cases other than the above, that is, when the flow rate L is the same as the optimal flow rate F in step 202 (step 209
If the flow rate L is within the set range F±f in steps 204 and 206, and if the flow rate L is zero in step 207, no abnormality processing is performed and the process proceeds to the next step. In addition, step
If the flow rate L is zero in step 207 and the flow rate L' of the same paint detected and calculated one time before in step 208 is B, nothing is done, but in other cases, abnormality processing is performed.

Next, in step 300, the electrical signal from the rotation speed sensor installed on the primary gear of the gear pump that supplies the base paint is processed and input.
In step 301, the rotation speed N is calculated. In step 302, the rotational speed N is compared with a pre-stored optimum rotational speed R, and three types of processing are performed depending on the magnitude.

First, if the rotation speed N is larger than the optimum rotation speed R, in step 304 the rotation speed N is set to the upper limit R+ of the setting range.
compared with r. Here, if the rotation speed N is larger than the upper limit R+r, it is determined that there is an abnormality, and steps 500~
Abnormality processing in step 503 is performed.

If the rotational speed N is smaller than the optimum rotational speed R, then in step 305 the rotational speed N is compared with the lower limit R-r of the set range. Here, if the rotational speed N is smaller than the lower limit R-r, it is determined that there is an abnormality, and steps 500 to 503 are performed to handle the abnormality.

When the rotational speed N is the same as the optimum rotational speed R, the detection of the flow rate of the main paint is completed and the process moves on to the detection of the flow rate of the curing agent paint.

In a case other than the above, that is, if the rotational speed N is within the set range R±r in steps 304 and 305, the value of the variable M mentioned above is checked in step 400,
When M=1, that is, when the flow rate L is larger than the optimum flow rate F, the rotation speed of the gear pump motor is lowered in step 401, the gear pump supply amount is reduced, and the flow rate of the base paint is reduced. If M=-1, that is, the flow rate L is smaller than the optimal flow rate F, step 402
The rotation speed of the gear pump motor is increased, the supply amount of the gear pump is increased, and the flow rate of the base paint is increased. If M=0, that is, the flow rate L and the optimal flow rate F are the same value, nothing is done.

As described above, the detection of the flow rate of the main paint is completed, and then the detection of the hardener paint is started. Detection of the hardener paint is carried out in exactly the same manner as described above from step 200, and once the hardener paint has been detected, the main paint is detected again, and this process is repeated during the painting process.

Coating work was carried out continuously for 8 hours using a coating apparatus according to a specific embodiment of the multi-component coating method of the present invention, and the discharge amount was almost constant during that time, and the quality of the resulting coating film was excellent. Ta. Also, air got into the paint conveyance system during the process, but the alarm was activated before the air was discharged from the spray gun, and the problem was resolved. Furthermore, when we intentionally applied finger pressure on the paint hose to change the flow rate, the alarm system immediately activated, confirming that it was functioning normally.

[Effects of the Invention] According to the multi-component coating method of the present invention, there are no problems such as paint leakage that occurs in the paint conveyance path up to the installation position of the flow sensor, clogging of the conveyance path, air intrusion, failure of the paint supply pump, and spraying. Abnormalities such as gun malfunctions are immediately detected, the equipment automatically stops, and a buzzer etc. immediately alerts the operator to the abnormality, allowing prompt treatment. As a result, paint defects can be prevented from occurring over a long period of time, and problems such as pump wear and port clogging can be quickly corrected, extending the life of the equipment and improving the working environment. The effects of the present invention are extremely large.

[Brief explanation of drawings]

FIG. 1 is a conceptual block diagram of the operation of the multi-component coating method of the present invention, and FIGS. 2, 3, 4, 5, and 6 are implementations of the multi-component coating method of the present invention. It represents the device according to the example, and the second
3 is a block diagram thereof, and FIGS. 4, 5, and 6 are flowcharts thereof. 11, 12...Flow rate sensor, 13, 14...
Rotation speed sensor, 2, 30...control device.

Claims (1)

[Scope of Claims] 1. A multi-liquid coating method in which the liquids are supplied in the form of multiple liquids, each liquid is conveyed separately, and the liquids are mixed and painted while keeping the flow rate ratio of each liquid constant. A multi-liquid coating method characterized in that the flow rate of the liquid is measured, and when the flow rate deviates from a predetermined setting range, the supply of all liquids is stopped and an alarm is generated. 2. The multi-liquid coating method according to claim 1, wherein the flow rate measurement is always performed and the flow rate of each liquid is usually kept constant based on the measurement results.