JPH08155347A - Rotary atomizing electrostatic coating device - Google Patents

Abstract

PURPOSE: To reduce an equipment cost and a running cost by supplying exhaust of driving air for air turbine of an electrostatic coating machine as shaping air and also to control a coating pattern at an optional size without, varying a feed flow rate of the shaping air, even though the pressure of the driving air or the flow rate is varied. CONSTITUTION: This device is provided with a control means 16 by which exhaust air of the air turbine 3 and auxiliary air force-fed from a high pressure air feed source 8 are supplied into an air feed flow path 7 for feeding the air becoming the shaping air and the flow rate of the auxiliary air or the pressure is controlled variably corresponding to the flow rate or the pressure of the exhaust air calculated based on the number of revolution of the air turbine 3 and the coating material supply quantity, and the shaping air is maintained at the preliminarily set flow rate or pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary atomizing type electrostatic coating apparatus for performing coating in a predetermined pattern while ejecting shaping air from the rear of a rotary atomizing head toward the periphery thereof.

[0002]

2. Description of the Related Art A rotary atomizing type electrostatic coating apparatus is equipped with an air turbine so that when the flow rate of the coating material is increased or decreased, the rotation speed of the rotary atomizing head does not change due to the resistance and the coating pattern does not change. The rotation speed of the rotary atomizing head is maintained constant by increasing or decreasing the pressure and flow rate of the driving air supplied. On the other hand, the coating pattern of the coating machine is set so that the patterns will exactly overlap each other according to the size of the object to be coated, the number of coating machines installed, and the installation interval, and in order to control the coating pattern to the set size. , The pressure of shaping air ejected from the rear of the rotary atomizing head toward its surroundings is variably controlled.

In the past, air for driving an air turbine and shaping air were separately supplied, but air having a pressure of 1 to 5 kg / cm ² is used to drive 100 to 3 per minute.
00 liters, shaping air pressure 1-3 kg /
Since the air of cm ² is used at about 300 to 500 liters per minute, a large-capacity compressor is required to supply these to each coating machine, resulting in high equipment cost and running cost.

Therefore, the applicant of the present invention has proposed an electrostatic coating device for ejecting exhaust air discharged from an air turbine as shaping air (see Japanese Patent Laid-Open No. 3-114557). According to this, the exhaust flow path of the air turbine is connected to the air supply flow path of the shaping air, and the shaping air is directed from the rear of the rotary atomizing head toward the surroundings without separately supplying the high-pressure air serving as the shaping air. Since the exhaust air of the air turbine is ejected, a small compressor is sufficient, and the equipment cost and running cost are reduced.

[0005]

However, the air for driving the air turbine is rotated at a rotation speed capable of atomizing the coating material to an optimum state so that the rotary atomizing head can be rotated. The supply flow rate / pressure is variably controlled. For example, when the paint supply amount is increased / decreased, the flow rate / pressure of the driving air has to be changed, and naturally, the flow rate / pressure of the exhaust air to be shaping air changes. There was a new problem that the coating pattern could not be controlled arbitrarily.

That is, if another high-pressure air is supplied as the shaping air without using the exhaust air of the air turbine, the coating pattern can be maintained constant, but the equipment cost and running cost are increased, and the exhaust air of the air turbine is used as the shaping air. When using, the equipment cost can be reduced, but the coating pattern cannot be controlled arbitrarily. Therefore, the present invention aims to reduce the equipment cost and running cost by supplying the exhaust air of the driving air of the air turbine as the shaping air, and to supply the shaping air even if the pressure or the flow rate of the driving air fluctuates. It is a technical issue to be able to control the coating pattern to an arbitrary size without changing.

[0007]

In order to solve this problem, according to the present invention, an air turbine provided in a housing is supplied with driving air having a predetermined pressure according to a paint supply amount, and its rotating shaft is rotated. A paint having a predetermined size is sprayed while rotating the attached rotary atomizing head at a preset number of revolutions and ejecting shaping air from the rear of the rotary atomizing head toward its periphery. In the rotary atomization type electrostatic coating device for coating with the above, in the air supply passage for supplying air to be shaping air, exhaust air of the air turbine and auxiliary air pressure-fed from a high pressure air supply source are supplied, The shaping air is preset by variably controlling the flow rate or pressure of the auxiliary air according to the flow rate or pressure of the exhaust air detected based on the number of revolutions of the air turbine and the amount of paint supplied. Characterized by comprising a control means for maintaining the flow rate or pressure.

[0008]

According to the present invention, the exhaust air of the air turbine is supplied to the air supply passage for supplying the air serving as the shaping air, and the auxiliary air having a predetermined pressure is supplied separately from the exhaust air. Both of the auxiliary air are jetted as shaping air from around the rotary atomizing head. At this time, the flow rate / pressure of the exhaust air of the air turbine depends on the flow rate / pressure of the driving air, and the flow rate / pressure of the driving air is determined by the paint supply amount and the rotation speed of the rotary atomizing head. Fluctuates, the flow rate / pressure of exhaust air fluctuates, and the coating pattern expands and contracts.

Therefore, the flow rate of the entire shaping air is controlled by adjusting the flow rate / pressure of the auxiliary air supplied to the air supply passage. The auxiliary air flow rate / pressure is set so that the shaping air is maintained at a preset flow rate / pressure based on the exhaust air flow rate / pressure calculated from the paint supply amount and the rotation speed of the rotary atomizing head. Therefore, the coating pattern does not expand or contract even if the pressure / flow rate of the driving air changes. Further, the auxiliary air need only be supplied in an amount that is insufficient when only the exhaust air of the air turbine is used as the shaping air, and therefore it is not necessary to use a compressor having a large capacity.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments shown in the drawings. FIG. 1 is a flow sheet showing a rotary atomization type electrostatic coating device according to the present invention, and FIGS. 2 and 3 are flow sheets showing another rotary atomization type electrostatic coating device according to the present invention.

In FIG. 1, reference numeral 1 denotes an electrostatic coating machine in which a cup-shaped rotary atomizing head 5 is attached to the tip of a rotary shaft 4 driven by an air turbine 3 provided in a housing 2. An air supply passage 7 is formed in the housing 2 and communicates with the shaping air ejection ports 6, 6 ... For ejecting shaping air from behind the rotary atomizing head 5.

A drive air supply pipe 9 for supplying drive air from a compressor (high pressure air supply source) 8 is connected to the air turbine 3, and the rotation of the rotary atomizing head 5 is connected to the drive air supply pipe 9. A throttle valve Va that adjusts the opening according to the number is provided. In addition, the shaping air jet 6,
An exhaust passage 11 for discharging exhaust air from the air turbine 3 and a compressor 8 are provided in the air supply passage 7 communicated with 6 ...
Auxiliary air supply pipe 12 for directly feeding high pressure auxiliary air from the
Is connected, and the auxiliary air supply pipe 12 is provided with a pressure adjusting valve Vb for variably controlling the supply flow rate by adjusting the pressure of the auxiliary air supply pipe 12.

Reference numeral 13 is a rotation control device for maintaining the rotary atomizing head 5 at a predetermined rotation speed when the paint supply amount is changed, and is a rotation for optically detecting the rotation speed of the air turbine 3 on the input side. The rotation speed detection sensor 14 is connected with the number detection sensor 14 and the throttle valve Va is connected to the output side thereof.
The rotation speed detected by the above is compared with a preset rotation speed, and the throttle valve Va is opened when the detected rotation speed is low, and the throttle valve Va is closed when the detected rotation speed is high. Perform feedback control to maintain the number at the set value.

Reference numeral 15 is a flow rate control device for maintaining the shaping air at a preset flow rate. The rotation control device 13 and the paint supply amount control device 16 are connected to the input side, and at the output side. Is connected to the pressure regulating valve Vb. Then, the flow rate control device 15 flows through the rotation speed-flow rate conversion table 17 in which the relationship between the rotation speed of the rotary atomizing head 5 and the flow rate of the driving air according to the paint supply amount is stored in advance, and the auxiliary air supply pipe 12. A flow rate-pressure conversion table 18 in which the relationship between the pressure and flow rate of the auxiliary air is stored in advance is provided.

When controlling the flow rate of the shaping air, first, the rotation speed of the rotary atomizing head 5 detected by the rotation speed detection sensor 14 is input from the rotation control device 13 and the paint supply at that time is supplied. The amount is input from the paint supply amount control device 16. Next, the current flow rate of the drive air and thus the flow rate of the exhaust air are calculated by referring to the rotation speed-flow rate conversion table 17 according to the input paint supply amount. Then, the flow rate of auxiliary air to be supplied from the auxiliary air supply pipe 12 is calculated by comparing this with a preset flow rate of shaping air. Next, based on the calculated flow rate of the auxiliary air, by referring to the flow rate-pressure conversion table 18, the flow rate of the auxiliary air is increased or decreased by adjusting the set pressure of the pressure control valve Vb, and the exhaust air and the auxiliary air are combined. Open loop control is performed so that the flow rate matches the preset flow rate of shaping air.

The above is an example of the configuration of the present invention.
The operation will be described. When coating is performed, first, the rotary atomizing head 5 is rotated at a rotation speed preset by the rotation control device 13. The rotation speed control at this time is performed by adjusting the flow rate of the drive air supplied to the air turbine 3 with the throttle valve Va provided in the drive air supply pipe 9. Specifically, the rotation speed detected by the rotation speed detection sensor 14 is compared with a set value, and when the detected rotation speed and the set value are different, the throttle valve Va is opened and closed.
Keep the rotation speed at the set value.

For example, if the type and amount of paint supplied to the rotary atomizing head 5 are changed by changing the color, and the rotational speed of the rotary atomizing head 5 is changed, the rotational speed is maintained constant. Therefore, the flow rate of the driving air changes. Then, when the flow rate of the driving air changes, the flow rate of the exhaust air also changes accordingly, and therefore the flow rate of the shaping air also changes.

Therefore, the flow rate control device 15 adjusts the flow rate of the shaping air ejected from the shaping air ejection ports 6, 6 ... To a preset flow rate according to the size of the coating pattern. At this time, the exhaust air discharged from the air turbine 3 through the exhaust flow path 11 and the auxiliary air sent from the compressor 8 through the high pressure air supply pipe 12 are supplied to the air supply flow path 7 of the shaping air. The flow rate of the exhaust air of the air turbine 3 is equal to the flow rate of the drive air, and the flow rate of the drive air is determined by the paint supply amount and the rotation speed of the rotary atomizing head 5, and the flow rate of the exhaust air is Since it cannot be freely adjusted, the flow rate of the shaping air is controlled by adjusting the flow rate of the auxiliary air supplied to the air supply passage 7.

Specifically, the rotation speed of the rotary atomizing head 5 detected by the rotation speed detection sensor 14 is input through the rotation control device 13, and the paint supply amount is controlled by the paint supply control device 16.
The flow rate of driving air, that is, the flow rate of exhaust air is calculated by referring to the rotation speed-flow rate conversion table 17 corresponding to the paint supply amount, and this is compared with the preset flow rate of shaping air. , The flow rate of the auxiliary air to be supplied from the auxiliary air supply pipe 12 is calculated.

Then, based on the calculated flow rate of the auxiliary air, by referring to the flow rate-pressure conversion table 18, the set pressure of the pressure control valve Vb is adjusted to predetermine the total flow rate of the exhaust air and the auxiliary air. Match the set shaping air flow rate. Thereby, even if the flow rate of the exhaust air changes by changing the rotation speed of the rotary atomizing head 5,
It is possible to maintain the coating pattern constant by maintaining the flow rate of the shearing air at a preset flow rate.

FIG. 2 is a flow sheet showing another electrostatic coating apparatus according to the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals and detailed description thereof will be omitted. In this example, the pressure sensor 20 for detecting the pressure of the shaping air in the air supply passage 7 is connected to the input side of the flow rate control device 16 for maintaining the shaping air at a preset flow rate, and the pressure sensor 20 is connected to the output side thereof. The regulating valve Vb is connected, the pressure detected by the pressure sensor 20 is compared with a preset pressure, and when the detected pressure is low, the set pressure of the pressure control valve Vb for adjusting the pressure of the auxiliary air is set. When the detected pressure is low and the detected pressure is low, the set pressure of the pressure control valve Vb is increased to perform feedback control for maintaining the pressure of the entire shaping air at the set value.

According to this, since the pressure of the shaping air is constantly monitored by the pressure sensor 20, when the pressures of the driving air and the exhaust air fluctuate, the pressure of the auxiliary air fluctuates accordingly. The pressure of the shaping air is maintained at a preset pressure, so that the coating pattern can be maintained at a preset size regardless of the paint supply amount and the rotation speed of the rotary atomizing head 5.

Further, FIG. 3 is a flow sheet showing another electrostatic coating apparatus according to the present invention, and in this example, a flow rate control apparatus 1 for maintaining shaping air at a preset flow rate.
A flow rate sensor 21 for detecting the flow rate of the driving air flowing through the driving air supply pipe 9 is connected to the input side of 6, and a pressure adjusting valve Vb is connected to the output side thereof. And
When controlling the flow rate of shaping air, the flow rate detected by the flow rate sensor 21 is compared with the preset flow rate of shaping air to calculate the flow rate of auxiliary air to be supplied. Next, based on the calculated flow rate of the auxiliary air, by referring to the flow rate-pressure conversion table 18, the setting pressure of the pressure control valve Vb is adjusted to set the total flow rate of the exhaust air and the auxiliary air in advance. Performs open loop control to match the air flow rate.

[0024]

As described above, according to the present invention, the exhaust of the air for driving the air turbine is used as the shaping air, and the amount of high pressure air used can be saved, so that a large capacity compressor can be used. Need not use
The equipment cost and running cost can be reduced. Furthermore, the exhaust air of the air turbine is used as the shaping air, and the auxiliary air supplied in a system different from the exhaust air is used as the shaping air, and the flow rate of the auxiliary air or Since the pressure is variably controlled based on the flow rate or pressure of the exhaust air, even if the flow rate or pressure of the exhaust air fluctuates due to changes in the rotational speed of the rotary atomizing head, the flow rate or pressure of the shaping air fluctuates. It has a very excellent effect that the coating pattern can be maintained at a constant size without doing so.

[Brief description of drawings]

FIG. 1 is a flow sheet showing a rotary atomization type electrostatic coating device according to the present invention.

FIG. 2 is a flow sheet showing another rotary atomization type electrostatic coating device according to the present invention.

FIG. 3 is a flow sheet showing still another rotary atomization type electrostatic coating device according to the present invention.

[Explanation of symbols]

 1 ... Electrostatic coating machine 2 ... Housing 3 ... Air turbine 4 ... Rotating shaft 5 ... Rotating atomizing head 6 ... Shaping air jet 7 ... Air supply passage 8. ..Compressor (high pressure air supply source) 11 ... Exhaust flow passage 12 ... Auxiliary air supply pipe Va ... Throttle valve Vb ... Pressure adjusting valve 13 ... Rotation control device 14 ... Rotation speed Detection sensor 16 ... Flow rate control device (adjusting means) 20 ... Pressure sensor 21 ... Flow rate sensor

Claims (3)

[Claims] 1. A rotary atomizing head mounted on a rotating shaft (4) of the air turbine (3) provided in a housing (2), which is supplied with driving air having a predetermined pressure according to the amount of coating material supplied. The paint is atomized while rotating (5) at a preset number of revolutions, and at the same time, the shaping air is ejected from the rear of the rotary atomizing head (5) toward the periphery thereof in a pattern of a predetermined size. In a rotary atomization type electrostatic coating device for coating, exhaust air from the air turbine (3) and a high pressure air supply source (8) are pressure-fed to an air supply passage (7) for supplying air serving as shaping air. Auxiliary air is supplied, and the flow rate or pressure of the auxiliary air is variably controlled in accordance with the flow rate or pressure of the exhaust air calculated based on the number of revolutions of the air turbine (3) and the amount of coating material supplied. Set in advance A rotary atomization type electrostatic coating device comprising a control means (16) for maintaining a fixed flow rate or pressure. 2. Driving air is supplied to an air turbine (3) provided in a housing (2), and a rotary atomizing head (5) attached to a rotating shaft (4) thereof is rotated in advance. A rotary atomizing electrostatic that atomizes the paint while rotating it by a number and sprays shaping air from the rear of the rotary atomizing head (5) toward its surroundings to apply a pattern of a predetermined size. In the coating apparatus, exhaust air of the air turbine (3) and auxiliary air pressure-fed from a high-pressure air supply source (8) are supplied to an air supply passage (7) that supplies air that serves as shaping air, and the supply air is supplied. Air flow path (7)
A control means for variably controlling the flow rate or pressure of the auxiliary air based on the pressure of the shaping air detected inside to maintain the shaping air at a preset flow rate or pressure (1
6) A rotary atomizing type electrostatic coating device characterized by being provided with. 3. A drive air is supplied to an air turbine (3) provided in a housing (2), and a rotary atomizing head (5) attached to a rotary shaft (4) of the drive air is preset to rotate. A rotary atomization type electrostatic sprayer that atomizes the paint while rotating it by a number and sprays shaping air from the rear of the rotary atomization head (5) toward the periphery thereof to form a pattern of a predetermined size. In the coating apparatus, exhaust air of the air turbine (3) and auxiliary air pressure-fed from a high-pressure air supply source (8) are supplied to an air supply passage (7) for supplying shaping air, and the driving is performed. Control means for variably controlling the flow rate or pressure of the auxiliary air according to the flow rate or pressure of the exhaust air detected based on the flow rate or pressure of the working air to maintain the shaping air at a preset flow rate or pressure (16 ) Rotary atomizing electrostatic coating apparatus characterized by comprising.