JPH05271922A - Powder coating device - Google Patents

Abstract

PURPOSE:To form uniform coating layers on individual powder particle surfaces by sputtering by distributing the powder raw materials charged into a rotary drum to the effective sputtering region in the inner bottom of the drum. CONSTITUTION:The raw material powder PW is charged into a drum body 21 of the rotary drum. The raw material powder PW is subjected to coating by the sputtered particles flying from a target plate 38 of a sputtering device 30. The fluidized layer PW1 formed in the inner bottom of the drum body 21 is intermittently agitated by an agitating plate 90 to mingle the powder particles of the upper layer part and the lower layer part. The powder particles sticking to the inside surface of the drum body 21 and the casing 34 of the sputtering device 30 are respectively scraped off by scrapers 95 and 98 and are returned to the fluidized layer PW1. Since the charged raw material powder is equally sputtered, the uniform coating layers are formed on the individual particle surfaces.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder coating apparatus for forming a uniform coating layer on the surface of powder particles while stirring the raw material powder charged in a rotary drum and scraping off the raw material powder adhering to the inner wall of the drum. Regarding

[0002]

2. Description of the Related Art When a metal film, an inorganic film or the like is formed on powder particles of metal, ceramics, plastics or the like, it is possible to give characteristics different from those of the original powder particles. For example, when tungsten particles, diamond particles, etc. are coated with copper, the sinterability is improved and a sintered body having excellent thermal conductivity is obtained. The copper-coated powder is also used as a filler for electromagnetic shielding.

As means for coating the powder particles, there are known a method of performing electroplating or electroless plating with the powder in a suspended state, a method of forming a predetermined film on the powder in a fluidized state by sputtering. ing.
The present inventors have also introduced a sputtering device using a rotary drum as a device for coating powder by sputtering in JP-A-2-153068.

In this powder coating apparatus, as shown in FIG. 1, a reduced pressure heat treatment chamber 1 containing powder particles P before coating is connected to a rotary drum 2 containing a sputtering source 3.

The powder particles P are contained in a container 1b equipped with a heating coil 1a, and are supplied into the rotary drum 2 via a supply conduit 1e by a screw feeder 1d driven by a motor 1c. The supply conduit 1e is supported by a bearing 2f provided on one end surface of the rotary drum 2.
Further, in order to feed the inert gas into the rotary drum 2, a gas introduction pipe 1g is provided concentrically with the supply conduit 1e.

The rotary drum 2 is supported by a driving roll 2a and a driven roll 2b. The drive roll 2a receives power from the motor 2c and rotates the rotary drum 2 around a horizontal axis. The sputtering source 3 includes a rotary drum 2 by an arm 3b which is hermetically supported by a bearing 3a at an end surface (right side in FIG. 2) opposite to the end surface into which the supply conduit 1e is inserted.
A target plate 3c, which is fixedly disposed inside and is slightly shorter than the axial length of the rotary drum 2, is disposed obliquely downward.

The powder particles P supplied from the supply conduit 1e to the axial end of the rotary drum 2 are distributed over the entire length of the drum shaft as the rotary drum 2 rotates, and flow on the inner bottom surface of the rotary drum 2. The coating material is knocked out from the target plate 3c by the impact of plasma such as Ar, and flies in the rotary drum 2 to adhere to the powder particles P in a fluid state. When a predetermined coating layer is formed, the rotary drum 2
And the coated powder particles P are taken out.

Further, as a powder coating apparatus having an increased production capacity, as shown in FIG. 2, a target plate driving unit 5 and a drum driving unit 6 are arranged on both sides of the vacuum chamber 4 so as to be retractable along the guide rails 5a and 5b. The developed device was developed. The target plate drive unit 5 cantilevers a sputtering source 3 similar to that shown in FIG. The drum drive unit 6 includes a drive shaft that meshes with a drive shaft in the vacuum chamber 4 and rotates the rotary drum 2 inside the vacuum chamber 4.

The target plate drive unit 5 and the drum drive unit 6 are connected to the vacuum chamber 4 via airtight joints 5b and 6a at their respective forward positions. Since the guide rail 6a is provided on the upper surface of the moving base 6c, the drum drive unit 6 moves in the X direction retracting from the vacuum chamber 4 and in the Y direction orthogonal thereto.

At the initial position P ₀ shown in FIG. 2, the rotary drum 2
After cleaning the inside of the chamber and charging the raw material powder to be sputtered, the rotating cradle 2 and the drum driving unit 6 are moved to the standby position P ₁ which coincides with the axis of the vacuum chamber 4 by the traveling of the moving platform 6c. Next, the target plate drive unit 5 and the drum drive unit 6 are advanced to the operating position P ₂ and connected to the vacuum chamber via the airtight joints 5b and 6b.

After the inside of the vacuum chamber 4 is evacuated by the rotary pump 7a and the diffusion pump 7b of the vacuum system 7, the raw material powder is coated by sputtering while rotating the rotary drum 2 inside the vacuum chamber 4. .. Then, it is sent to the initial position P ₀ via the standby position P ₁ and the coated powder is fed to the rotary drum 2.
Take out from. With this method, since the large-diameter rotary drum 2 can be used, the production capacity is improved.

[0012]

The raw material powder charged in the rotary drum 2 adheres to the inner surface of the drum and co-rotates with the rotary drum 2 to form a fluidized bed distributed in a relatively wide range inside the rotary drum 2. Form. Since the sputtered particles fly to this fluidized bed, it is possible to coat individual powder particles. However, when the co-rotating raw material powder has a large adhesion to the inner surface of the drum, the proportion of the raw material powder taken out from the effective sputtering region becomes large. Factors that increase the adhesive force include burning of the powder particles on the inner surface of the drum due to temperature rise during sputtering, and strong mechanical entanglement between the irregularities on the inner surface of the drum and the powder particles.

The seizure of powder particles can be prevented to some extent by cooling the rotary drum 2. Also, by adjusting the surface roughness of the rotary drum 2,
Entanglement between the inner surface of the drum and the powder particles can be weakened. However, it is not possible to eliminate powder particles that adhere to the rotating drum 2 and are lifted from the effective sputtering area.

The powder particles lifted by the co-rotation fall from the inner surface of the drum onto the upper surface of the sputtering device.
It may be accumulated. The powder particles deposited on the upper surface of the sputtering apparatus are not subjected to the sputtering action and are in a state of being uncoated or poorly coated. If the powder particles fall from the upper surface of the sputtering device due to impact, vibration, etc. and mix with the raw material powder in the effective sputtering area at the bottom of the drum, the state of formation of the coating layer will vary greatly.

Further, even in the fluidized bed of the raw material powder formed on the inner bottom of the rotary drum 2, the probability that the sputtered particles adhere to the powdered particles in the upper layer of the fluidized bed is as follows.
It is higher than the probability that sputtered particles adhere to the powder particles in the lower layer. Therefore, a relatively thick coating layer is formed on the powder particles in the upper layer portion, and a relatively thin coating layer is formed on the powder particles in the lower layer portion. When a force that adheres to the inner surface of the drum is generated in the powder particles in the lower layer portion of the fluidized bed, the powder particles in the lower layer portion will not flow to the upper layer portion, and variations in the thickness of the coating layer cannot be avoided.

The present invention has been devised to solve such a problem, and by releasing the adhesion state of the powder particles to the inner surface of the drum and periodically stirring the powder particles in the fluidized bed, The purpose is to form a uniform coating layer on individual powder particles.

[0017]

In order to achieve the object, the powder coating apparatus of the present invention has a rotary drum which is open at both ends and rotates around a horizontal axis, and the rotary drum which is inserted into the rotary drum. An axially long sputtering device, annular drive gears arranged at both ends of the rotary drum, a stirring plate that is extended to the inside of the rotary drum by being passed over the annular drive gears, and the annular ring. And a scraper that is extended to the inside of the rotary drum in the axial direction and is rubbed against the inner surface of the side surface of the rotary drum, wherein the stirring plate and the scraper are powered via the annular drive gear. It is characterized by intermittently reciprocating inside the rotary drum by transmission.

Further, a means for wiping the upper surface of the sputtering apparatus can be incorporated in order to return the raw material powder dropped and deposited on the upper surface of the sputtering apparatus to the inner surface of the bottom portion of the rotary drum. In this case, a sputtering apparatus having a semi-cylindrical casing is used, a wiper is attached to the tip of a support arm extending from the scraper toward the center of the rotary drum, and the wiper is rubbed against the semi-cylindrical outer surface of the casing.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to the large-sized powder coating apparatus shown in FIG. 2 will be described below with reference to the drawings. However, the present invention is not limited to this, and FIG.
Needless to say, the same can be applied to the powder coating apparatus.

The powder coating apparatus of this embodiment is shown in FIG.
As shown in FIG.
0s are arranged concentrically, and a sputtering device 30 is set at the center of the rotary drum 20. The inside of the vacuum chamber 10 is vacuum-sucked through an exhaust pipe 11 connected to a vacuum system. A lid 12 for inspecting the inside is airtightly connected to the upper portion of the vacuum chamber 10,
A halogen lamp 13 is provided on the back surface of 2 or in the vicinity thereof.

Both ends of the vacuum chamber 10 are open. At the open end of the vacuum chamber 10, flanges 14 _R and 14 _L are provided, respectively, as shown in FIG. The flanges 14 _R and 14 _L are hermetically connected to a flange plate 41 and a flange plate 51 provided on the end faces of the target drive unit 40 and the drum drive unit 50, respectively, as shown in FIG.

The target drive unit 40 supports the sputtering device 30 in a cantilever manner, so that the bearings 42a to rotatably support the arm 33 protruding from one side of the sputtering device main body 31 via the coupling 32.
42c is provided. The bearing 42a is fixed to the flange plate 41, and projects from the opening formed at the center of the flange plate 41 toward the sputtering apparatus body 31 side. A
The gas supply conduit (not shown) for r, nitrogen, etc.
Is connected to the sputtering apparatus main body 31 via the through hole.

As shown in FIG. 3, the sputtering apparatus main body 31 has a housing 35 attached to a semi-cylindrical casing 34. The inside of the casing 34 is divided into two by the reinforcing plate 36, and becomes a space exhibiting a heat insulating / insulating action. A target plate 38 is attached to the front side of a backing plate 37 fitted in the housing 35, and a water cooling jacket 39 having a cooling water passage on the rear side.
Is attached. As the backing plate 37, a copper plate having good thermal conductivity is used to cool the target plate 38.

Flange plate 51 of drum drive unit 50
In order to observe the vicinity of the target plate 38 of the sputtering apparatus main body 31, a viewing window 52 is provided.
Are formed. Further, below the viewing window 52, a hole portion is formed in the flange plate 51 so as to pass through the drive shaft 61 of the rotary power transmission mechanism 60 that applies rotary power to the rotary drum 20 arranged in the vacuum chamber 10.

The rotary drum 20 has a cylindrical drum body 21 whose both ends are open. Annular external gears 22 _L and 22 _R are attached to the left and right ends of the drum body 21. External gears 23 _L and 23 _R (see FIG. 5) are arranged at both open ends of the rotary drum 20, further axially outside the external gears 22 _L and 22 _R.

On the drive shaft 61 of the rotary power transmission mechanism 60,
The power from the motor 62 is transmitted via the transmission 63. The drive shaft 61 projects into the vacuum chamber 10 via an airtight joint 64 such as a magnetic seal, and is connected to an in-chamber drive shaft 66 via a coupling 65. The drive shaft 66 in the chamber is the bearing 6 attached to the inner surface of the vacuum chamber 10 by the bracket 15 (see FIG. 3).
It is rotatably supported by 7 _L and 67 _R. The drive gears 68 _L and 68 _R mounted on the drive shaft 66 in the chamber are
It meshes with the external gears 22 _L and 22 _R on the rotary drum 20 side, respectively.

As shown in FIG. 5, the maintenance power transmission mechanism 70 reduces the power output from the motor 71 by the transmission 72 and transmits it to the drive shaft 74 via the clutch 73. The drive shaft 74 is connected to the vacuum chamber 1 via an airtight joint 75.
0, and is connected to the in-chamber drive shaft 77 via the coupling 76. The drive shaft 77 in the chamber is
It is rotatably supported by bearings 78 _L and 78 _R mounted on the inner surface of the vacuum chamber 10 by a bracket 15 (see FIG. 3). The drive gears 79 _L and 79 _R mounted on the drive shaft 77 in the chamber mesh with the external gears 22 _L and 22 _R on the rotary drum 20 side, respectively. The annular external gears 22 _L and 22 _R intermittently rotate at a predetermined rotation angle by the switching operation of the clutch 73, then rotate in the opposite direction and return to the initial position.

Further, in order to cool the rotary drum 20, a cooling mechanism 80 shown in FIG. 6 is additionally provided. Cooling mechanism 80
Has a water supply pipe 81 connected to a water source. The water absorption pipe 81 faces the inside of the vacuum chamber 10 via a cock 82 and an airtight joint 83, and is connected to water cooling rolls 85 a and 85 b by a rotary joint 84. Water cooling roll 85
The insides of a and 85b are hollow, and the peripheral wall thereof contacts the outer peripheral surface of the drum body 21. This water cooling roll 85a,
85b also has a bearing 86 mounted by the bracket 15.
It is rotatably supported by _L and 86 _R , and is driven to rotate by friction with the drum body 21.

The drive shafts 66 and 77 in the chamber and the water cooling rolls 85a and 85b are arranged at the bottom of the vacuum chamber 10 in the positional relationship shown in FIG. As a result, the drum main body 21 is rotatably supported, and the annular external gears 23 _L and 23 _R can be intermittently rotated independently of the rotary drum 21. In addition, water-cooled rolls 85a, 85
Since the drum main body 21 is cooled by b, the adhesion of the powder particles to the inner surface of the drum is suppressed.

A stirring plate 90 is passed through the inside of the drum body 21 to the external gears 23 _L and 23 _R arranged at both ends of the drum body 21. As shown in FIGS. 7 and 8, the stirring plate 90 has a support plate 9 at both ends of a flat plate body 91.
2 _L and 92 _R are fixed. On the lower surface of the plate body 91 facing the inner surface side of the drum body 21, a plurality of ridges 93 _L , 9
3 _R is formed in the width direction. Ridges 93 _L and 93 _R
Are inclined in opposite directions with the center of the plate body 91, that is, the axial center of the drum body 21 as a boundary. Fulcrum 92
_{L 1} and 92 _R are formed in such a shape that the plate member 91 is located near the inner surface of the drum body 21 when the base ends are attached to the external gears 23 _L and 23 _R.

Scrapers 95 are attached to the external gears 23 _L and 23 _R by similar supporting legs (not shown). As shown in FIG. 3, the scraper 95 is provided with a positional relationship of a central angle of 120 to 240 degrees with respect to the stirring plate 90 with the rotation axis of the drum body 21 as the center. As shown in FIG. 9, the scraper 95 has a rubbing member 96 made of elastic synthetic resin or the like attached to the base end 97. The rubbing member 96 rubs the inner surface of the drum main body 21 to separate the adhered powder particles from the inner surface of the drum.

A wiper 98 may be attached to the scraper 95. That is, the plurality of support arms 9 extending from the scraper 95 toward the center of the drum body 21.
8a is attached to the base end portion 97, and the base 98b is attached to the supporting leg 98a.
Hand over. Then, the rubbing member 98c made of synthetic resin or the like having a high elasticity is erected on the substrate 98b. The length of the support arm 98a is set so that the rubbing member 98c is pressed against the outer surface of the casing 34 of the sputtering apparatus 30.

Charge the raw material powder PW to the rotary drum 20,
When the sputtering is performed by the sputtering device 30 while rotating the drum body 21 in the rotation direction D, the raw material powder PW is distributed to the inner bottom portion of the drum body 21 as shown in FIG. 7. Most of the raw material powder PW is the fluidized bed PW ₁ formed at the inner bottom portion of the drum body 21, and is exposed to the sputtering by the sputtered particles flying from the target plate 38 to be coated.

However, the powder particles attached to the inner surface of the drum body 21 or mechanically entangled with each other may be carried out from the fluidized bed PW ₁ along with the drum body 21. When the adhesion and the entanglement are strong, the powder particles are present at the same position on the inner surface of the drum, and the probability that the sputter particles are attached is reduced. Depending on the degree of adhesion or entanglement, the drum body 2
Some of the powder particles are detached from the inner surface of the drum during the rotation of No. 1 and fall / deposit on the casing 34 of the sputtering apparatus main body 30. Further, in the fluidized bed PW ₁ itself, the upper layer portion and the lower layer portion may not be sufficiently mixed, and the powder particles in the upper layer portion may be exclusively coated.

Therefore, the maintenance power transmission mechanism 70 is intermittently driven to reciprocate the stirring plate 90 and the scraper 95 within the range of the angle α shown in FIG. By the stirring blade 90, the powder particles in the upper layer portion and the powder particles in the lower layer portion forming the fluidized bed PW ₁ are mixed with each other, and the individual powder particles are equally exposed to the sputtering. The plurality of ridges 93 _L and 93 _R formed on the lower surface of the plate 91 move the powder particles in the fluidized bed PW ₁ in the axial direction of the drum, and uniformize the sputtering conditions in the axial direction as well.

Further, the scraper 95 scrapes off the powder particles that adhere to the inner surface of the drum and try to rotate together with the drum body 21, and return them to the fluidized bed PW ₁ . In the case where the wiper 98 is provided, the powder particles dropped and accumulated on the upper surface of the casing 34 are also returned to the fluidized bed PW ₁ . In this way, by returning the powder particles that are not subjected to sputtering to the fluidized bed PW ₁ , the charged raw material powder is equally sputtered.

The angle α at which the stirring plate 90 and the scraper 95 reciprocate is determined according to the positional relationship between the two with respect to the rotation axis of the drum body 21. For example, in the case where the stirring plate 90 and the scraper 95 are separated from each other at the central angle of 120 degrees, the stirring plate 90 and the scraper 95 are reciprocated over the range of 60 to 120 degrees. Further, the stirring blade 90 and the scraper 95 can be activated during either forward movement or backward movement. For example, when the stirring plate 90 is moved in the rotation direction D of the drum body 21, the scraper 95 is moved away from the inner surface of the drum at the standby position, and when the stirring plate 90 is moved in the direction opposite to the rotation direction D, The scraper 95 is moved while being pressed against the inner surface. As a result, the powder particles adhering to the inner surface of the drum move in the fluidized bed PW _{1 in the} rotation direction D.
Returned to the downstream side of.

In this way, when the fluidized bed PW ₁ is sputtered while stirring and separating the powder particles attached to the inner surface of the drum, a uniform coating layer is formed on the treated powder particles and the coating is performed. There were no powder particles. On the other hand, in the case of performing the sputtering without using the stirring plate 90 and the scraper 95, the coating layer was not formed on about 30% of the raw material powder charged. The formed coating layer also had a thickness with large variations.

[0039]

As described above, in the present invention, when the raw material powder is coated by sputtering inside the rotary drum, the fluidized bed is agitated so that the charged raw material powder is equally exposed to the sputtering. At the same time, powder particles adhering to the inner surface of the drum and co-rotating with the rotating drum are scraped off and returned to the fluidized bed. As a result, a uniform coating layer is formed on each powder particle, and a high-quality coating powder is obtained with a high yield.

[Brief description of drawings]

FIG. 1 Small-scale powder coating apparatus previously proposed by the present inventors

FIG. 2 Large-scale powder coating device developed by the present inventors

FIG. 3 shows a state in which a sputtering device is incorporated in a rotating drum.

FIG. 4 is a sectional view taken along the line IV-IV in FIG.

5 is a sectional view taken along the arrow V in FIG.

6 is a cross-sectional view taken along line VI of FIG.

FIG. 7 is a perspective view of the inside of the rotating drum.

FIG. 8 Stir plate

[Figure 9] Scraper

[Explanation of symbols]

20 rotating drum 23 _L , 23 _R external gear (annular drive gear) 30 sputtering device 90 stirring plate 95 scraper 98 wiper

Claims (2)

[Claims] 1. A rotary drum whose both ends are opened and rotates about a horizontal axis, a sputtering device which is inserted inside the rotary drum and is long in the axial direction of the rotary drum, and which is arranged at both ends of the rotary drum. An annular drive gear, an agitator plate that is inserted into the annular drive gear and extends axially inside the rotary drum, and an agitator plate that is inserted into the annular drive gear and extends axially inside the rotary drum, A scraper that slides on the inner surface of the side surface of the rotary drum, and the stirring plate and the scraper intermittently reciprocate inside the rotary drum by power transmission via the annular drive gear. Powder coating equipment. 2. The sputtering apparatus according to claim 1, wherein the sputtering apparatus has a semi-cylindrical target casing, a wiper is attached to a tip of a support arm extending from the scraper toward the center of the rotary drum, and the semi-cylindrical outer surface of the casing has the wiper. The powder coating device is characterized in that it is rubbed against.