JPH0466146A - Rotation atomizing static coating device - Google Patents

Abstract

PURPOSE:To control run-out amount at the time of rotating an atomizing head by making large a backlash in the radius direction at the time of screwing a first screw section at the end of a rotating shaft with a second screw section formed on the atomizing head, and carrying out securely centering of the rotating shaft and the atomizing head only by means of a tapered section to be fitted on. CONSTITUTION:An atomizing head 25 is mounted on the end of a rotating shaft 22 supported by an air bearing 24, and a coating material feeding tube 23 is disposed on the rotating center of the shaft 22 in a non-contact state. A first screw section 35 is formed at the end of said shaft 22, and first tapered section 36 is formed adjacent to the screw section 35. Also, a second screw section 37 to be able to screw on the screw section 36 is formed on the atomizing head 25, and a second tapered section 38 to be able to fit on the tapered section 36 is provided adjacent to the screw section 37. Further, coaxial degree of the screw 35 and the tapered section 36 is made smaller than a radius direction clearance at the time of screwing the screw section 35 on the screw section 37. The ratio of the length L of the tapered section 36 formed on the rotating shaft 22 and the diameter of 1/2 of the length of the tapered section 36 is set in the given range. As a result, the run-out amount at the time of rotating the atomizing head is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a rotary atomizing electrostatic coating device used for painting automobile bodies, etc., and particularly relates to a structure for suppressing the amount of deflection of a rotary atomizing head.

[Prior art] A rotary atomizing electrostatic coating device atomizes (atomizes) paint using mechanical high-speed rotational force, applies an electric charge to the atomized paint, and uses electrostatic force to spray the paint onto non-coated objects. This is a device that allows it to be adsorbed to. The rotation speed of the atomizing head that atomizes the paint varies depending on the paint, but for solid paint it is 15,000 to 30,000 r.
pm, 30,000 to 5.0 for metallic paints
It rotates at a very high speed of 10,000 rpm. Therefore, if the rotating shaft to which the atomizing head is attached is supported by a normal roller bearing, lubrication will be insufficient, leading to damage to the bearing. Therefore, in order to solve the problems caused by lubrication, a rotary atomizing electrostatic coating device has been proposed in which the rotating shaft to which the atomizing head is attached is supported by an air bearing (Japanese Patent Laid-Open No. 56-14186
Publication No. 4).

FIG. 7 shows the main parts of a conventional air bearing type rotary atomizing electrostatic coating device. In the figure, 1 indicates a rotary atomizing electrostatic coating device, and a rotating shaft 2 is supported by an air bearing 3. An atomizing head 4 for atomizing paint is attached to the tip of the rotating shaft 2. A turbine blade (illustrated path) for rotating the rotating shaft 2 is connected to the opposite end of the rotating shaft 2 to which the atomizing head 4 is attached. The paint is supplied to the atomizing head 4 through the feed tube 5, and is atomized at the edge 6 by the high-speed rotation of the atomizing head 4 to perform painting. A tapered portion 2a is formed at the tip of the rotating shaft 2, and a tapered portion 4a that can fit into the tapered portion 2a of the rotating shaft 2 is formed on the atomizing head 4.

The rotating shaft 2 and the atomizing head 4 are fastened together by screwing and tightening screws (bolts) 7 inserted from the atomizing head 4 side in a fitted state. The atomizer 4 is automatically centered with respect to the rotating shaft 2 by the action of the tapered portion.

By the way, in the rotary atomizing electrostatic coating apparatus 1, the paint supplied from the feed tube 5 on the rear side surface of the atomizing head 4 is discharged from the atomizing head 4. When changing the paint color, the paint of the previous color remaining in the rotary atomizing electrostatic coating device 1 and the piping system 8, as well as thinner and air for cleaning this paint, are also discharged from the atomizing head 4. Therefore, in order to change the color of the paint or wash it, it is necessary to prevent the paint from scattering or adhering to the object to be painted. Conventional rotary atomization electrostatic coating device 1
As shown in FIG. 8, a color change shroud 9 that covers the area around the atomizing head 4 collects paint of the previous color, cleaning thinner, and air.

However, although most of the previous color paint, cleaning thinner, and air can be collected by providing the shroud 9, the cleaning thinner does not reach the tip 9a of the shroud 9.
There is a problem in that the adhered thinner falls onto the surface to be painted during painting, degrading the quality of the painting. In addition, in the case of the structure of the rotary atomization electrostatic coating device 1 shown in FIG.
Since the chamber 4b of the atomizing head 4 and its surroundings are in a reduced pressure state, an air flow (air pumping phenomenon) 10 is generated around the atomizing head 4, and the atomizing head 4 of the rotary atomizing electrostatic coating device 1 is
There is also the problem that paint adheres to the outer circumferential surface 4C and the shaping air cap 11, and this adhered paint flies onto the object to be painted during painting, resulting in a deterioration in the quality of the painting.

Therefore, in order to solve the above problems, a device is adopted in which a feed tube (paint supply tube) is placed in contact with the center of rotation of the rotating shaft, and paint is discharged from the center of rotation. It has reached this point.

[Problems to be Solved by the Invention] However, in a coating device that discharges paint from the center of rotation, a feed tube is inserted into the center of the rotation shaft, so there is a gap between the rotation shaft and the atomization as shown in Fig. 7. It was not possible to center the atomizing head with respect to the rotating shaft by fastening the head with a screw.

Therefore, a method has been considered in which a tapered part and a threaded part are formed on the rotating shaft and the atomizing head, respectively, and the two are fastened together.
In the case of this fastening structure, there is a problem that the atomizing head cannot be accurately centered with respect to the rotating shaft due to the clearance (radial play) of the screw part when screwed together and the setting method of the taper part. . Therefore, in the case of such a fastening structure, the amount of deflection during rotation of the atomizing head is larger than that of conventional devices, which affects rotational stability, etc., and makes it impossible to perform painting work under desired conditions. There is a problem in that the quality of the coating deteriorates.

The present invention has focused on the above-mentioned problems, and has developed a rotary atomizing electrostatic coating device that discharges paint from the center of rotation of a rotating shaft. The purpose is to provide a fastening structure with the shaft.

[Means for Solving the Problems] The rotary atomization electrostatic coating device according to the present invention that meets this objective has the following features:
The atomizing head is attached to the tip of the rotating shaft supported by an air bearing,
A rotary atomizing electrostatic coating device in which a paint supply pipe is disposed in a non-contact manner at the center of rotation of the rotating shaft, wherein a first threaded portion is formed at the tip of the rotating shaft, and a first threaded portion is formed on the first threaded portion. a first tapered portion is formed adjacent to the atomizing head;
a second threaded part that can be threadedly engaged with the threaded part of the second threaded part, and a second tapered part that can be fitted with the first tapered part adjacent to the second threaded part; The coaxiality between the threaded part and the first tapered part is smaller than the radial clearance when the first threaded part and the second threaded part are screwed together,
The ratio of the length of the first tapered part formed on the rotating shaft to the taper diameter at 1/2 of the length of the first tapered part is set within a predetermined range.

[Function] In the rotary atomizing electrostatic coating device configured as described above, a first threaded portion and a first tapered portion are formed on the rotating shaft,
A second threaded portion and a second tapered portion are formed on the atomizing head.

Then, the first tapered part and the second tapered part are fitted, and the first threaded part and the second threaded part are screwed together. In this case, the coaxiality (eccentricity) between the first threaded part and the first tapered part is smaller than the radial clearance when the first threaded part and the second threaded part are screwed together. Therefore, centering between the atomizing head and the rotating shaft by the tapered portion can be performed reliably. In other words, since the play when the first threaded part and the second threaded part are screwed together is increased, the rotation axis and the atomizing head due to the threaded engagement of the first threaded part and the second threaded part are increased. The centering of the rotating shaft and the atomizing head is not performed, and the centering of the rotating shaft and the atomizing head is performed reliably only by fitting the tapered portions.

In addition, since the ratio of the length of the first tapered part formed on the rotating shaft and the taper diameter at 1/2 of the length of this first tapered part is set within a predetermined range, the rotating shaft It is possible to have a sufficient mating length for the shaft diameter of
It becomes possible to maintain centering accuracy over a long period of time.

[Embodiments] Below, preferred embodiments of the rotary atomization electrostatic coating apparatus according to the present invention will be described with reference to the drawings.

First Embodiment FIGS. 1 to 5 show a first embodiment of the present invention. In FIG. 2, numeral 21 indicates a rotary atomizing electrostatic coating device. The rotary atomizing electrostatic coating device 21 has a substantially cylindrical rotating shaft 22 , and the rotating shaft 22 is supported by an air bearing 24 . An atomizing head 25 for atomizing paint is attached to the tip of the rotating shaft 22. Rotating axis 2
A turbine blade 26 for rotating the rotary shaft 22 is connected to the tip portion on the opposite side of the rotary shaft 2 . At the center of rotation of the rotating shaft 22, a feed tube 23 serving as a paint supply pipe is arranged in a non-contact state with the rotating shaft 22.

The feed tube 23 is composed of a double tube consisting of an inner tube 23a and an outer tube 23b. One end of the inner tube 23a is connected to a color change valve via a paint hose (not shown). At the other end of the inner tube 23a,
A valve 28 is provided that contacts a valve seat 27 located at the tip of the outer tube 23b. The opposite end of the inner tube 23a is connected to an air cylinder 29, and during painting, the air cylinder 29 is operated with pilot air 30 to open the valve 28 and valve seat 27 and atomize the paint. It is designed to supply the head 25. During painting, the paint is atomized by the atomizing head 25 rotating at high speed, and an electrostatic voltage of -90 KV to -110 KV is applied to the atomized paint.
By applying KV, the paint is more efficiently adhered to the object to be coated.

During color change cleaning, the air cylinder 29 is operated by pilot air 30, and the valve 28 and valve seat 27 are
is closed. As a result, the paint of the previous color supplied from the color change valve (path shown) and remaining in the inner pipe 23a is cleaned with thinner and discharged to the outside of the system via the outer pipe 23b with compressed air. ing. Further, when the inner pipe 23a (not shown) is cleaned, the air cylinder 29 is operated with pilot air 30 to open the valve 28 and the valve seat 27, and thinner and air are supplied to the atomization head 25 and atomized. The head 25 is washed.

Through this series of color change cleaning operations, only a very small amount of paint, thinner, and air are discharged from the atomizing head 25, which prevents these discharged substances from scattering or adhering to the object to be painted, thereby suppressing the paint. The quality of the object to be painted is ensured during color change cleaning.

The chamber 25a of the atomizing head 25 is different from the atomizing head chamber shown in the prior art in that it does not come into direct contact with the surrounding air. Therefore, the air around the atomization head 25 is
5 is not generated, and deterioration in the quality of the object to be coated due to scattering of the paint adhering to the outer circumferential surface 25b of the atomizing head 25 and the shaping air cap 31 is prevented. .

FIG. 1 shows the fastening structure between the rotating shaft and the atomizing head.

As shown in FIG. 1, a first threaded portion 35 is formed at the tip of the rotating shaft 22. As shown in FIG. The first threaded portion 35 is composed of a male thread. A first tapered portion 36 is formed at the tip of the rotating shaft 22 adjacent to the first threaded portion 35 . When machining the first threaded part 35 and the first tapered part 36, the processing equipment for the threaded part and the tapered part are different, so the reproducibility of the machining center for both becomes a problem. Based on basic analysis of center coaxiality (eccentricity) and rotational stability, coaxiality is 0.05rII! n or less, and the centers of both are made to coincide with the center of the rotation axis.

In this embodiment, the first threaded portion 3 formed on the rotating shaft 22
Standard 5 is M2S (metric thread) according to the JIS standard.
The pitch of the first threaded portion 35 is the same value as the JIS standard, and the distance from the thread to the thread root ((outer diameter - root diameter)/2) is the same as the JIS standard. It is larger by 0.2m+ in the thread root direction. That is, the first threaded portion 35 has a diameter of 0.2a in the thread root direction with respect to the JIS standard.
iThere is an extra cut. As a result, the second
The play in the radial direction when screwed together with the threaded portion 37 is large. The first tapered portion 36 formed on the rotating shaft 22 has a length L of 20M, which is 1/1 of the length L of the first tapered portion 36.
The diameter of the taper portion in No. 2 is 20 m. The ratio of the taper diameter at 1/2 length of the first taper part to the length of the first taper part is 0.5 to 1.2 (preferably 0.5 to 1.2).
7-1. O). This relationship, as shown in FIG. 4, was determined through experiments.

A second threaded portion 37 is formed in the atomizing head 25 .

The atomizing head 25 [ has a second tapered portion 38 formed adjacent to the second threaded portion 37 . The second threaded portion 37 is J
It is an M2S (metric thread) according to the IS standard, and the pitch and distance from the thread thread to the thread root are also the same as the JIS standard. The second tapered portion 38 is machined to have the same dimensions as the rotating shaft 22.

Since the processing of the second threaded part 37 and the second tapered part 38 of the atomizing head 25 can be performed with the same equipment, it is assumed that there is no misalignment between the two, and Relationships such as tapered portions are not particularly defined.

A relief groove 39 extending in the circumferential direction is formed between the first threaded portion 37 and the second tapered portion 38 of the rotating shaft 22 . The escape groove 39 prevents the first tapered part 36 of the rotating shaft 22 from coming into contact with the second threaded part 37 of the atomizing head 25 when the rotating shaft 22 and the atomizing head 25 are fastened together, and It has a function of preventing the taper portion 36 from being damaged.

Note that the first threaded portion 35 and the second threaded portion formed on the rotating shaft 22
The coaxiality (eccentricity) of the center of the tapered portion 36 of the atomizing head 2
The weight of 5 is 1809 or less (preferably 20 to 150 g)
And, the effective diameter of the first threaded portion 35 is set to 0.05 mm (preferably 0.01 to 0.03 m) in a region of 10 to 20 m. The radial clearance (play) when the first threaded portion 35 of the rotating shaft 22 and the second threaded portion 37 of the atomizing head 25 are screwed together is such that the weight of the atomizing head 25 is 180 g or less (preferably 20 g). ~150g> and the effective diameter of the first threaded part 35 is 10 to 20InI11, the first threaded part 35 and the first tapered part 36
The coaxiality is set to be larger than 0.05J1111 (preferably 0.2 to 0°35m).

Next, the operation in the first embodiment will be explained.

The rotating shaft 22 shown by the two-dot chain line in FIG. 1 shows the state in which the rotating shaft 22 and the atomizing head 25 are connected. In this example,
The coaxiality (eccentricity) between the first threaded part 35 and the first tapered part 36 is smaller than the radial clearance between the first threaded part 35 and the second threaded part 37 when they are screwed together. Since this is set, centering of the rotating shaft 22 and the atomizing head 25 is reliably performed only by fitting the tapered portions 36 and 38.

FIG. 3 shows the relationship between the clearance of the first threaded portion 36 and the deflection amount of the atomizing head 25 with respect to the coaxiality of the rotating shaft 22 and the atomizing head 25. Here, the effective diameter of the first threaded portion 35 of the rotating shaft 22 is 10 to 20 m, and the ratio of the taper diameter at 1/2 length of the first tapered portion to the length of the first tapered portion is 1. It is 0. Further, the weight of the atomizing head 25 in this case was 1809. As shown in FIG.
The runout amount is the target value of 0°04M! When suppressing the clearance to 11 or less, the upper limit of the clearance when the first threaded portion 35 and the second threaded portion 37 are screwed together was 0.351111. Note that the above clearance is set to 0°1 #tl11, and the coaxiality of the center between the rotating shaft 22 and the atomizing head 25 is set to 0.1.
When set to an, the amount of deflection of the atomizing head 25 is 0, 65JE.
It was I+1.

FIG. 4 shows the relationship between the taper diameter/taper length and the deflection amount of the atomizing head 25 at 1/2 length of the first tapered portion of the rotating shaft 22. Here, the effective diameter of the first threaded portion 35 of the rotating shaft 22 is 10 to 2071111, and the coaxiality of the first threaded portion 35 and the first tapered portion 36 is 0°05m.
is set to . Further, the radial clearance when the first threaded portion 35 and the second threaded portion 38 are screwed together is set to 0.2#l. The weight of the atomizing head 25 is 18
It was set to 0g. As shown in FIG. 4, in order to suppress the deflection amount of the atomizing head 25 to below the target value of 0.047M, the ratio of the taper diameter at 1/2 of the taper length is preferably 0.5 to 1.2. It is sufficient to set it to 0.7 to 1.0.

In this manner, in the rotary atomizing electrostatic coating device 21, by setting the fastening conditions between the rotating shaft 22 and the atomizing head 25 as described above, the vibration during rotation of the atomizing head 25 is reduced. This enables stable high-speed rotation and improves coating quality and equipment durability.

Second example FIG. 5 shows a second embodiment of the invention.

The difference between the second embodiment and the first embodiment is that the rotating shaft 22
Since only the structure of the tip is the same as in the first embodiment, other parts are the same as those in the first embodiment, so by assigning the same numbers as in the first embodiment to the corresponding parts, explanation of the corresponding parts will be omitted, and only the different parts will be explained. do.

The same applies to other embodiments to be described later.

In FIG. 5, a hard layer 41 is formed on the surface of the first tapered portion 36 of the rotating shaft 22. As shown in FIG. In this example,
The rotating shaft 22 is made of stainless steel (SUS), and the hard layer 41 is made of hard chrome plating. Furthermore, when the rotating shaft 22 is made of hardenable steel, the hard layer 41 may be formed by heat treatment or the like.

In this embodiment, the width W of the relief groove 39 located between the first threaded portion 35 and the first tapered portion 36 is 0.5 to 2.01111 mm from the end surface of the first tapered portion 36. The depth D is set within a range of 0.5 from the end of the first tapered portion 36.
It is set in the range of ~2.0 at.

In the second embodiment configured in this way, the rotating shaft 2
Since the hard layer 41 is formed on the surface of the first tapered part 36 of the second embodiment, the first tapered part 36 is not damaged by contact with the atomizing head 25 when the rotating shaft 22 and the atomizing head 25 are fastened together. This will prevent you from doing so. This prevents misalignment between the rotating shaft 22 and the atomizing head 25 due to damage to the first tapered portion 36, and makes it possible to maintain the deflection amount of the atomizing head 25 at a desired value.

Third embodiment FIG. 6 shows a third embodiment of the invention.

In this embodiment, the first threaded portion 36 is Mlo according to the JIS standard.
-M2O, the distance T from the bottom of the relief groove 39 to the inner circumferential wall surface of the rotating shaft 22 is set to, for example, 1.0 m. Note that, if it is possible to sufficiently satisfy the mechanical strength of the tip of the rotating shaft 22, it is desirable that the above-mentioned distance T be 1.06 or more.

In the third embodiment configured in this way, the rotating shaft 2
2 and the atomizing head 25, the end of the first threaded portion 36 can be reliably released by the escape groove 39. Therefore, the first screw portion 35 is prevented from collapsing,
The coaxiality (eccentricity) between the threaded center of the first threaded part 35 and the second threaded part 37 and the fitted center of both tapered parts 36.38 is in the radial direction when both threaded parts 35.37 are threaded together. This will prevent the clearance from becoming larger than the clearance. Therefore, the amount of deflection of the atomizing head 25 is maintained within a predetermined value.

[Effects of the Invention] As explained above, when using the rotary atomization electrostatic coating device according to the present invention, the first threaded portion is formed at the tip of the rotating shaft, and the first threaded portion is formed adjacent to the first threaded portion. a second threaded part that can be screwed into the first threaded part on the atomizing head, and a second threaded part that can be fitted with the first tapered part adjacent to the second threaded part; A second tapered part is formed, and the coaxiality between the first threaded part and the first tapered part is adjusted between the first threaded part and the second tapered part.
The length of the first tapered part formed on the rotating shaft and the taper diameter at 1/2 of the length of the first tapered part are smaller than the radial clearance when screwed together with the threaded part of the rotating shaft. Since the ratio is set within a predetermined range, the following effects can be obtained.

(a) Since the radial clearance (play) when the first threaded part and the second threaded part are screwed together is increased, the first
Avoid centering the rotating shaft and atomizing head due to the threaded engagement of the second threaded part with the second threaded part, and ensure centering of the rotating shaft and atomizing head only by fitting the tapered part. I can do it. Therefore, it is possible to suppress the amount of deflection during rotation of the atomizing head, and rotational stability is improved. As a result, it is possible to improve the coating quality and the durability of the device compared to the conventional method.

In addition, since the ratio of the length of the first tapered part formed on the rotating shaft and the taper diameter at 1/2 of the length of this first tapered part is set within a predetermined range, the rotating shaft A sufficient fitting length can be provided for the shaft diameter, and centering accuracy can be maintained over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the assembled state of the rotating shaft and the atomizing head in the rotary atomizing electrostatic coating device according to the first embodiment of the present invention, and FIG. 2 is the rotary atomizing electrostatic coating device shown in FIG. 3 is a characteristic diagram showing the relationship between the clearance of the first screw part and the amount of deflection of the atomizing head in the device shown in FIG. 1, and FIG. 4 is a sectional view of the main parts of the coating device A characteristic diagram showing the relationship between the amount of deflection of the atomizing head and the ratio of the length and diameter of the first tapered part. FIG. FIG. 6 is a sectional view showing the assembled state of the rotating shaft and the atomizing head in a rotary atomizing electrostatic coating device according to the third embodiment of the present invention; Figure 7 is a cross-sectional view of the vicinity of the atomizing head of a conventional rotary atomizing electrostatic coating device, and Figure 8 is a cross-sectional view of a conventional rotary atomizing electrostatic coating device equipped with a shroud to prevent paint from scattering. be. 21...Rotary atomization electrostatic coating device 22...
- Rotating shaft 23... Feed tube 24 as a paint supply pipe... Air bearing 25... Atomization head 35... First threaded portion 36. ...First tapered part 37... Second threaded part 38... Second tapered part 39... Escape groove 41... hard layer

Claims (1)

[Claims] 1. A rotary atomizing electrostatic coating device in which an atomizing head is attached to the tip of a rotating shaft supported by an air bearing, and a paint supply pipe is arranged in a non-contact manner at the center of rotation of the rotating shaft, the rotating shaft being supported by an air bearing. a first threaded part is formed at the tip of the atomizing head, a first tapered part is formed adjacent to the first threaded part, and a second threaded part that is threadably engageable with the first threaded part is formed on the atomizing head. a threaded portion is formed, and a second tapered portion that can be fitted with the first tapered portion is formed adjacent to the second threaded portion, and the first threaded portion and the first
The coaxiality of the first tapered part formed on the rotating shaft is made smaller than the radial clearance when the first threaded part and the second threaded part are screwed together. A rotary atomizing electrostatic coating device characterized in that a ratio between the length and the taper diameter at 1/2 of the length of the first tapered portion is set within a predetermined range.