JPS6265777A - Method for coating synthetic resin powder to hollow member - Google Patents

Abstract

PURPOSE:To improve productivity by taking a hollow member out of synthetic resin powder, then executing a heating and holding stage while a masking jig is held attached thereto and removing the masking jig from the member. CONSTITUTION:The masking jig 64 is attached to the hollow member 10 in order to close the aperture thereof. The member 10 is embeddd into the synthetic resin powder P. The member 10 is heated by a coil 34 to the temp. above the m.p. of the powder P to weld the synthetic resin powder to the surface of the hollow member before and/or after the embedment. The member 10 is held at the temp. above the m.p. of the synthetic resin powder and below the thermal decomposition thereof by another heater on the outside of the synthetic resin powder. The masking jig 64 is removed from the hollow member after such heating. The shorter heating time in the heating and holding stage is thus required and the productivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method of coating synthetic resin powder on the surface of a metal hollow member having an opening, and in particular to a method of fusing synthetic resin powder onto the surface of the hollow member using heat. It is about improvement.

BACKGROUND ART Coating a synthetic resin powder on the surface of a metal hollow member having an opening is performed, for example, for the opening and closing of a supercharger, which is a type of Roots-type fluid feeder. This rotor has a plurality of blades, each of which has a weight reduction hole, and is hollow with a rotating shaft insertion hole in the center. In order to reduce the gap between the two rotors and the gap between the rotor and the housing as much as possible and increase volumetric efficiency, a synthetic resin layer is applied to the outer circumferential surface and end surface of the rotor. is being formed. Therefore, the inventors of the present invention attempted to coat a synthetic resin powder by fusion in order to form a synthetic resin layer of a desired thickness in a shorter time. In other words, a masking jig is attached to block both holes to prevent the resin powder from adhering to the opening periphery or inner circumferential surface of the weight reduction hole or rotating shaft insertion hole, and then the rotor material is buried in the synthetic resin powder. Before and/or after burying, the rotor material is heated to a temperature higher than the melting point of the synthetic resin powder, and the synthetic resin powder is fused to the outer peripheral surface of the rotor and the outer peripheral part of the rotor end surface to form a synthetic resin layer. It is.

According to such a resin coating method, efficient
Resin coating can be performed using relatively WIR equipment, but the air present in the resin powder is trapped within the resin layer, creating voids and reducing the adhesive strength between the rotor and the coated resin layer. This may cause peeling of the resin layer during use of the rotor.

Therefore, the inventors of the present invention have
In the application No. 1, after the hollow member with the resin layer formed thereon is taken out of the synthetic resin powder, it is maintained at a temperature above the melting point and below the thermal decomposition point of the synthetic resin powder using a heating furnace, etc., and the resin layer is removed. It was proposed that the adhesive strength of the resin layer be increased by keeping it in a molten state and releasing the air trapped within the resin layer to the outside.

Although it is possible to remove the masking jig from the rotor when performing this heating and holding step, it is necessary to lower the temperature of the rotor.

In other words, if the masking jig is removed while the rotor is at a high temperature, the resin layer formed on the end face of the rotor, especially the resin layer formed on the long distance from the outer periphery to the masking jig, will stick to the masking jig. If the rotor is heated while being suspended by a jig during the heating and holding process, the raised part that has formed on the lower end surface will sag, so this is to the extent that such a situation does not occur. It is necessary to remove the masking jig while lowering the rotor temperature to . For example, if the synthetic resin powder to be coated is Aphron (trade name) powder, which is a copolymer of tetrafluoroethylene and ethylene, the rotor is heated to about 350°C during coating. However, in order to remove the masking jig without causing the resin layer to lift, it is necessary to cool the rotor to at least 180''C.

Problems to be Solved by the Invention However, the rotor heated to 350°C is heated to 180°C.
It takes about 40 minutes to air cool the powder to the desired temperature, which is bad for productivity, and in the heating and holding process, the once cooled rotor must be heated again to a temperature above the melting point and below the thermal decomposition point of the Aphron powder. However, this work also takes time and has the problem of significantly decreasing productivity.

In order to lower the temperature of the rotor, it is possible to rapidly cool it with air blow or water, but this is not appropriate because the resin layer will float.

The above problem also occurs when the synthetic resin powder to be coated is a synthetic resin powder other than AFLON powder, and furthermore, the hollow member coated with the synthetic resin powder is other than a supercharger rotor. In this case, the same problem occurs when the masking jig is removed after coating with synthetic resin powder and before heating and holding.

Means for Solving the Problems The present invention has been made to solve the above problems, and after taking out the hollow member from the synthetic resin powder, a heating and holding process is carried out with the masking jig attached. This method is characterized in that the masking jig is removed after the masking jig is carried out.

Effects of the Invention With this method, after the hollow member is taken out from the synthetic resin powder, there is no need for time to cool the hollow member in order to remove the masking jig before performing the heating and holding step.
Since the hollow member is continuously heated while being maintained at a temperature close to the temperature at which it is coated with synthetic resin, the heating time during the heating and holding process is shortened, resulting in a significant increase in productivity. .

EXAMPLES Hereinafter, taking a cocoon-shaped rotor of a supercharger as an example, an example in which the present invention is applied to resin powder coating on the rotor material will be described in detail with reference to the drawings.

Figure 9 shows the rotor material (hereinafter referred to as rotor) before being coated with the synthetic resin powder of the cocoon-shaped rotor.
It is a figure showing 10. In this embodiment, the rotor 10 is made of an aluminum alloy, particularly an Af-3i alloy, with a high silicon content of about 12% (for example, JIS A
4047, etc.), and a rotary shaft insertion hole 12 is formed in the center thereof, while blades on both sides of the rotary shaft insertion hole 12 have holes 1 (IM
Weight reduction holes 14 each having a diameter of I are formed and are hollow. The rotor 10, which is a hollow member, is scheduled to be coated with a synthetic resin over the entire outer peripheral surface and the outer peripheral portions of both end surfaces 16. . As the synthetic resin powder to be coated, for example, powder of Aflon (trade name, hereinafter referred to as Aflon), which is a copolymer of tetrafluoroethylene (tetrafluoroethylene) and ethylene, is used.

FIG. 1 shows an example of an apparatus for coating the rotor 10 with Aflon. In the figure, reference numeral 20 denotes a fluidized tank, in which Aphron powder P is placed, and during coating, the rotor 10 is raised and lowered with its end surfaces 16 and 18 positioned above and below. The rotor 10 is heated in advance and then immersed in the Aphron powder P. In order to make it easy to immerse the rotor 10 into the Aphron powder P and take it out from there, the Aphron powder P in the fluidized bath 20 is heated. Vibrator 2 fixed to the bottom of fluidized tank 20
2 and the compressed air supplied from the air supply port 24 make it fluid. Reference numeral 26 denotes an air filter, which is made of multiple layers of tracing paper (parchment paper), a porous plate made of polyethylene, ceramics, or metal. Provided with air supply U:!
The function is to uniformly supply an appropriate amount of air supplied from 24 to the Aflon powder P.

An upper coil 28 for inductively heating the rotor 10 is provided at a fixed position in the upper part of the fluidized tank 20. The upper coil 28 is of the same type as a coil used for induction hardening, has a similar shape that is larger than the rotor 10, is arranged to surround the rotor 10 at a predetermined distance from the outside, and is connected to the coil power source 30. The rotor 10 is heated by electromagnetic induction when the current is applied.

Below the upper coil 28, a lower coil 34 is placed in a fixed position while being buried in the Aflon powder P. This lower coil 34 has the same structure as the upper coil 28, and is used to reheat the rotor 10 immersed in the Aphron powder P by induction heating by electricity supplied from the coil power supply 36.

Above the coating equipment configured as above,
A hydraulic cylinder 38 for raising and lowering the rotor 10 is provided. The hydraulic cylinder 38 is attached to a fixed member 39, and a holder 4 is attached to the lower end of the piston rod 40.
2 is installed. The holder 42 is attached to the piston rod 40 via a plate 44, and a guide rod 46 erected at the other end of the plate 44 passes through the fixing member 39 to prevent the piston rod 40 from rotating. It is designed to guide movement.

As is clear from FIG. 2, the holder 42 includes a base end 50 attached to the piston rod 40 and a base end 5
0, and a plate-like part 54 extending horizontally from the lower end of the plate-like part 52 in a direction facing the base end part 50. A positioning protrusion 56 is provided at the vertically intermediate portion of the plate-like portion 52, while a U-shaped notch 60 is formed in the plate-like portion 54 and opens on the side opposite to the border with the plate-like portion 52. , the hydraulic cylinder 38 has these notches 60 and the positioning projections 56 connected to the coil 28.
．． It is attached to the fixing member 39 so as to be positioned along the longitudinal direction of the cross-sectional shape of 34. In addition, the base end portion 50
An engaging member 62 is embedded in a portion facing the notch 60, and this engaging member 62 is urged by a spring (not shown) in a direction to protrude a certain amount from the base end portion 50.

A masking jig 64 is attached to the rotor 10 in order to prevent the Aflon powder P from being fused to the inner peripheral surfaces of the rotating shaft insertion hole 12 and the weight reduction hole 14 and around their openings. The masking jig 64 includes an upper mask member 66 and a lower mask member 68 that are respectively attached to both sides of the rotor IO. These mask members 66.
Seal members 70.68 are in close contact with the openings at both ends of the rotating shaft insertion hole 12 and the weight reduction hole 14, respectively, and close the openings to the upper and lower end surfaces 16.18 of the guard holes 12, 14, respectively.
72 and a heat insulating material 7.4 fixed to the sealing member 70.72.
It consists of 76. These seal members 70 and 72 are made of a metal that is less susceptible to induction heating than the aluminum alloy forming the rotor 10, such as brass, copper, or stainless steel, and their thickness is greater than the thickness of the resin layer formed on the rotor 10. It is somewhat thick, and has a thickness sufficient to make the surface of the resin layer that contacts the sealing member 70, 72 a straight end surface. The seal members 70 and 72 are large enough to close the rotating shaft insertion hole 12 and the weight reduction hole 14, but are smaller than the end surface of the rotor 10, and the shape of the outer periphery is As shown in FIGS. 3 and 4, the portions that close both holes 12 and 14, that is, the central portion and both ends in the longitudinal direction, are convex in a direction perpendicular to the longitudinal direction, while the portion between these convex portions is The part is said to be recessed towards the axis.

Positioning protrusions 78 are formed at both ends in the longitudinal direction of each end surface of the seal members 70, 72 on the side that comes into close contact with the rotor 10. These positioning protrusions 78 are shaped like annular protrusions whose outer diameter is equal to the diameter of the weight reduction hole 14, with the portions of the protrusions near each other cut out. Seal member 70
．． 72 with respect to the rotor 10. Furthermore, as is clear from FIGS. 5 and 6, the central portion of the end surface of the sealing member 70 that comes into close contact with the rotor 10 is shallowly recessed to minimize the contact area with the rotor 10. As shown in FIG. 3, the sealing member 72 has an elongated hole 82 formed therein.

On the other hand, the heat insulating material 74.76 has a lower heat transfer rate than the sealing material 70.72, such as asbestos plus Shichimen I (trade name: Azhes 1-Hemisoto), ceramics, heat-resistant resin, etc. made of material. The heat insulating material 74 fixed to the sealing member 7o is shown in FIGS.
As shown in the figure, the sealing member 70 is shaped like an oval plate.
It is fixed to the sealing member 70 by a bolt 84 made of the same material as any of the heat insulating materials 74. Further, the heat insulating material 76 fixed to the seal member 72 has a stepped shape as shown in FIGS. 2 and 7, and is secured by bolts 86 similar to the bolts 84 at the flange portions extending on both sides in the longitudinal direction. It is fixed to the seal member 72. This insulation material 76
The elongated hole 8 is formed on the end surface of the side that comes into close contact with the sealing member 72.
A bottomed elongated hole 88 that is continuous with the second elongated hole 88 and a bottomed hole 90 with a circular cross section that opens at the bottom of the elongated hole 88 are formed. Chodai 8
A plate 92 that closes the bottomed hole 90 is fixed to the bottom of the hole 8, and an elongated hole 94 having a length equal to the diameter of the bottomed hole 90 is formed along the longitudinal direction of the elongated hole 88. has been done.

The upper mask member 66 is attached to a hollow rond 100 so as to be relatively movable in the axial direction, and a large-diameter trenched portion 102 and a held portion 104 are provided at the upper end of the four-rotted portion 100.
is formed. The operated portion 102 is constructed by welding disks 108 and 110 to openings at both ends of a cylinder 106, respectively, and the disks 108 and 110 are fixed to the rod 100 by welding. The held part 104 is composed of a large diameter part 112 and a small diameter part 114, and the upper end of the rod 100 is fitted into a bottomed hole 116 that passes through the small diameter part 114 in the axial direction and reaches the large diameter part 112. Fixed by welding. Positioning holes 118 with bottoms are formed at positions separated in the diametrical direction in the axially intermediate portion of the large diameter portion 102, and the positioning holes 118 are located above the positioning holes 118 and are 90 mm apart from each other. Engagement holes 120 are formed at positions having different degrees of phase. The large-diameter portion 112 further has an inverted conical recess 122 that opens at its upper surface, and both the upper and lower surfaces thereof are tapered surfaces.

A cylindrical member 124 is fixed to the lower part of the operated portion 102 of the rod 100 by welding.
A cylindrical portion 128 of a spring retainer 126 is fitted to the outside of the spring retainer 126 so as to be slidable in the axial direction. The rod 100 and the cylindrical member 124 are each formed with an elongated portion 130 extending axially through the rod 100 and the cylindrical member 124 at positions separated from each other in the diametrical direction.
6, both ends of the bottle 132 inserted through the elongated hole 130 are supported by the cylindrical portion 128, so that although relative rotation is not possible, relative movement is possible for a certain distance in the axial direction. Note that the bottle 132 is prevented from being extracted by a ring-shaped cover 134 fitted into the outer peripheral surface of the cylindrical portion 128.

As is clear from FIG. 4, in the lower part of the cylindrical portion 128, the two positioning holes 118 of the held portion 104 are formed in the same direction and from positions separated in the diametrical direction. Two lug pieces 136 are formed that extend outward, and the upper mask member 66 is fixed to the lug pieces 136 with a sandwiched operating member 138 in between. The upper mask member 66 is fixed in such a manner that its longitudinal direction extends in the direction in which the two ear pieces 136 are formed, and the ear pieces 136
It is biased downward by a compression coil spring 142 disposed between the disk 110 of the operated portion 102 and the disk 110 of the operated portion 102 . The upper mask member 66 is movable relative to the rod 100 within the range in which the bottle 132 moves through the elongated hole 130, and the upper mask member 66 is attached to the operating member 138, as shown in FIG. Two tails 140 each extending outward in a direction perpendicular to the longitudinal direction of the
is formed.

Furthermore, an engaging member 14 is provided at the lower end of the rod 100.
4 is fixed. The engagement member 144 is fitted to the lower end of the rod 100 in a bottomed cylindrical fitting part 146 and fixed by welding.
As shown in FIG. 8, a small-diameter leg portion 148 and a plate-shaped projection 150 are formed. The protrusion 150 is shorter than the length in the longitudinal direction of the elongated hole 94 formed in the plate 92;
The engaging member 144 has a size that can be inserted into the elongated hole 82 and the bottomed hole 90, and the engaging member 144 is arranged so that the protrusion 150 extends in a direction perpendicular to the longitudinal direction of the upper mask member 66. It is fixed to the rod 100.

Note that the rod 100. spring retainer 126,
Operation member 138. The spring 142 etc. are the seal member 70
．． Like 72, it is made of materials that are difficult to be heated by induction, such as brass, copper, and stainless steel.
2. Insulation material 74, 76° Bolt 84.8 that fixes both
6 and other components of the masking jig 64, such as Ron 1100, are coated with polytetrafluoroethylene (tetrafluoroethylene + 1 fat), known by the trade name of Lafron, to prevent the Aflon powder P from fusing. It has been b'.

Then, the masking jig 64 is attached to the rotor 10 whose surface has been made suitable for resin coach ink by surface treatment in the following manner.

That is, while holding the operated part 102 and moving the upper mask member 66 toward the operated part 102 while compressing the compression coil spring 142 by applying a measure to the collar 140 of the operating member 138, the rod 100 is moved toward the rotation axis in this state. The seal member 70 is inserted into the insertion hole 12 and the positioning protrusion 78 of the seal member 70 is fitted into the weight reduction hole 14, and the seal member 70 is inserted into the end face 16.
bring it into contact with. In this state, the engaging member 144 fixed to the lower end of the rod 100 protrudes from the lower surface of the rotor 10. Next, hold the lower mask member 68,
The protrusion 15 is inserted into the bottomed hole 90 by aligning the elongated hole 94 formed in the plate 92 with the protrusion 150 of the retaining member i44.
Insert 0. At this time, the protrusion 150 is connected to the upper mask member 66.
Since the protrusion 150 is provided at right angles to the longitudinal direction of the bottom mask member 68, the long hole 94 is formed along the longitudinal direction of the lower mask member 68 when the protrusion 150 is inserted into the bottom growing hole 90.
is in a posture with a phase difference of 90 degrees with respect to the upper mask member 66. From this state, the lower mask part F
By rotating the shaft 68 by 90 degrees, the positioning protrusion 78 can be fitted into the opening of the rotating shaft insertion hole 14, and
The protrusion 150 and the elongated hole 94 are out of phase by 90 degrees.
0 is in a position that can be held on the plate 92, and the collar 140
When you release your finger, the compression coil spring 142
expands, and the urging force causes the seal member 70 to come into close contact with the end face 6 of the rotor 0, and the rod 100
As the projection 150 rises, the projection 150 engages with the plate 92. Due to this engagement, the biasing force of the spring 142 is also transmitted to the seal member 72, and the seal member 72 engages with the plate 92.
8 is fitted into the M strain reduction hole 14 and the end surface 18
It will be brought into close contact with.

The rotor 10 with the masking jig 64 attached as described above is transported to the coating device by a transport device (not shown). The conveyance device is a masking jig 64
The rotor 10 is conveyed while holding the held part 1.
A claw of a holding jig provided on the conveyance device is engaged with the engagement hole 120 formed in 04.

The masking jig 64 held by the conveying device is conveyed to a position where the held part 104 faces the holding tool 42, and then the large diameter part 112 of the held part 104 is moved to the holding part #42.
A small diameter portion 104 is fitted into a notch 60 between the base end portion 50 and the plate-like portion 54 . At this time, the large diameter portion 10
2 is fitted into the proximal end portion 50 by pushing the engaging member 62 into the base end portion 50 against the biasing force of the spring by its tapered surface, and when the engaging member 62 is just fitted into the recess 122, the positioning protrusion 56 is inserted. Positioning hole 11
8 , and the held portion 104 is held non-rotatably by the holding tool 42 .

When held in this manner, the upper mask member 66 has a length of 21 [! The spring retainer 12 is aligned in the same direction as the positioning hole 118 of it.
6, and the positioning protrusion 56 provided on the holder 42 is also formed in the same direction as the longitudinal direction of the cross-sectional shape of the coil 28.34, which is similar in shape to the rotor 10. is positioned on the flow lff20 in a state where it matches the phase of the coils 28 and 34.

Then, before the rotor 10 is immersed into the Aphron powder P housed in the fluidized bath 20, it is first positioned in the upper coil 28, and then induction heated by the upper coil 28 to a temperature higher than the melting point of the Teflon powder P. Ru. Since the Teflon powder P has a melting point of 26 Q'C and a thermal decomposition point of 360°C, the heating temperature of the rotor 10 by the upper coil 28 is at least 260°C, but the coating quality of the Teflon powder P and From the point of view of coating efficiency, it is desirable that the coating efficiency be higher than the thermal decomposition point; for example, 300
The temperature is preferably about 340°C, particularly about 340°C. However, since a certain amount of heat escapes when the rotor 10 is immersed in the Aflon powder P, it may be heated to about 360°C.

Such induction heating is performed by heating the upper coil 28 with, for example, 3 k.
This is carried out by passing a high frequency current of about 120° to about 120 degrees, and this high frequency current of about 3 kllz heats not only the surface layer of the rotor 10 but also the inside to some extent almost uniformly.

The mouth heated by the upper coil 28 in this way
is then lowered by the operation of the hydraulic cylinder 38 and immersed into the Aflon powder P contained in the fluidization tank 20. In this immersion process, 'the vibration exciter 22
The Aphron powder P is vibrated through the fluidized tank 20 by the operation of the Aphron powder P, and compressed air is supplied from the air supply port 24 and is caused to rise inside the Aphron powder P through the air filter 26. It is considered to be in a fluid state. In addition, the coil power supply 36 of the lower coil 34 is turned off.
The rotor IO is immersed in the Aphron powder P which is maintained in the F state and is in a fluid state as described above.

During this immersion process, the undersurface of the rotor 10 and the fluidized tank 2, which have already been heated to a temperature higher than the melting point of the aphron,
The Aphron powder P in the 0 is relatively moved and comes into contact with the Aphron powder P.

Therefore, the Aflon powder P is instantaneously fused to the underlying surface, and in this first step, a thin resin film is formed on the surface of the rotor 10 without high speed.

When the rotor 10 and the Aflon powder P are fused together in a stationary state, once a void is created, the void remains at a fixed position on the surface of the rotor material, so the air in the void is directly absorbed into the resin layer. On the other hand, when the two are moving relative to each other, the gap moves on the rotor surface, so the fusion of the Aflon powder P to a specific part is not hindered. .

For example, the rotor 10 is
It is completely embedded in the powder P in about 0 to 30 seconds, and is placed in the lower coil 34. In this state, the vibration caused by the excitation ta22 and the air supply port 24
The supply of compressed air is stopped, and the Aflon powder P becomes non-fluid.

The reason for this is that after the rotor 10 is immersed, the fusion of the Aphron powder P further progresses, but if the Aphron powder P is kept in a fluid state, the boundary between the rotor 10 and the Aphron powder P is This is because a portion that becomes a passage for air is created, and the Aflon powder P tends to be fused to that portion.

In this way, after the rotor 10 is completely immersed and the Aphron powder P is brought into a non-flowing state, the rotor 10 is held as it is within the Aphron powder P for a certain period of time, for example, about 60 seconds, and during this holding process, the rotor 10 More Aphron powder P is fused to the surface of 10, and the thickness of the resin layer gradually increases. In this process, the heat of the rotor 10 escapes to the Afroon powder P side, so as is clear from FIG. 10, the rotor 10
temperature gradually decreases. Therefore, when the temperature of the rotor 10 drops to a certain temperature, for example, about 300° C., the coil power supply 36 is turned on, and a high frequency current of about 3 kHz, for example, is passed through the lower coil 34 to reheat the rotor 10.

This reheating is continued for about 40 seconds, for example, and the rotor 10
After the temperature is raised to, for example, about 320° C., the power supply to the lower coil 34 is stopped. After such reheating, the rotor 10 is further kept in the Aphron powder P for a certain period of time, for example, around 60 seconds. During the above-mentioned reheating process and this holding process, the resin layer due to the fusion of the Aflon powder P to the rotor 10 becomes even thicker. In this example, a resin layer thickness of about 1.2 mm can be obtained in about 2 to 3 minutes, including the reheating time and the holding time before and after the reheating, but in general, the desired resin The holding time and reheating time will be set to obtain the desired layer thickness.

The reason why the afron powder is retained for a certain period of time after reheating is to use the heat given to the rotor 10 as effectively as possible for coating. In some cases, it is also possible to take out the rotor 10 immediately after the reheating is finished.

In this embodiment, the seal members 70 of the upper mask member 66 and the lower mask member 68 of the masking jig 64 are
．． The rod 72 is made as thin as possible, has a small heat capacity, and has a contact area with the rotor 10 as small as possible.
00, there is less heat transfer from the rotor 10 to both mask members 66, 68, and the resin layer becomes thinner due to insufficient amount of fused Aphron powder P near the masking jig 64. is avoided.

The rotor lO coated with a desired thickness of resin in the Aphron powder P as described above is raised by the operation of the hydraulic cylinder 38 shown in FIG. 1 and taken out from the Aphron powder P. In the process, as in the case of immersion, the Aphron powder P is brought into a fluid state by the vibration of the vibrator 22 and the supply of compressed air, and the rotor '10 can be easily taken out.

As mentioned above, a gap is created between the resin layer coated as described above and the rotor surface, and a product with high adhesive strength and fairly high quality can be obtained. A heating and holding step is carried out to further improve quality.

That is, the removed rotor coated with resin is placed in a heating furnace using an electric heater, a combustion gas heater, or the like as a heat source, with the masking jig 64 still attached, and heated and maintained. The temperature of this heating furnace is approximately 300°
The temperature of the rotor 10 taken out from the Afron powder P decreases as it comes into contact with the atmosphere, but the temperature decreases because it is immediately put into the heating furnace without removing the masking jig e4 after being taken out. is small,
Heating can be maintained efficiently. That is, when heating the rotor 10 after removing the masking jig 64, the temperature of the rotor 10 is lowered to at least around 180°C to prevent the resin layer formed by coating from sticking to the masking jig 64. In addition, as shown by the dashed line in FIG. If the coater 10 is put into the heating furnace without removing the coater 10, the cooling time of the rotor 10 as described above is not required, and the rotor 10 is kept almost warm before being put into the heating furnace. Since the temperature is about 250°C, it takes about 9 minutes to reach the set temperature, as shown by the solid line in the figure. In addition, since the temperature drop of the rotor 10 is small in this way and the time required to reach the set temperature of the heating furnace is short, the rotor 10 in the heating furnace
The masking jig 64 is used in order to fully obtain the effect of the heating and holding process by requiring a short heating and holding time.
When it is removed, it is necessary to heat and hold for about 25 minutes, whereas when it is not removed, it only takes about 20 minutes, which can improve productivity.

Note that the masking jig 64 has both upper and lower mask members 66.6.
8 are made as thin as possible, and the rod 100 is also made hollow, so less heat is absorbed by the masking jig 64 when it is roofed in the heating furnace. It has the advantage of high thermal efficiency.

Since the resin layer is kept in a molten state during the heating and holding process as described above, the air existing in the resin layer is released to the outside, improving the adhesive strength between the resin layer and the rotor 10. At the same time, the porosity of the entire resin layer is reduced and a resin layer of good quality is obtained. After this heating and holding step, the masking jig 64 is removed from the rotor 10.

In addition, during the heating and holding process, the air inside the resin layer is removed from the outside g((
When a heat-resistant tape is attached to a part of the surface of the resin layer and the heat is maintained as described above, the air released from the resin layer accumulates between the surface of the resin layer and the heat-resistant tape.
This is confirmed by the fact that it produces a large number of depressions on the surface of the resin layer.

Furthermore, the rotor 10 is preheated to a temperature equal to or higher than the melting point of the Aphron powder P and then immersed in the Aphron powder P, and the resin layer formed on the foot is heated and held for a relatively long time outside the Aphron powder P. The effect was confirmed by comparison with an experiment in which the rotor was immersed in Aflon powder P without preheating, and then a resin layer was formed only by induction heating.

That is, after cooling the obtained resin layer to room temperature, a peeling tool with chamfered edges of about 0.2 mm is pressed against the end face of the resin layer, and the peeling tool is moved along the surface of the rotor material. The resin layer is attached to the rotor 10 by
The adhesive strength of the resin layer can be measured from the magnitude of the peel resistance at this time, and the adhesive strength is 20 kg in the comparative example, but it is as large as 50 kg in the present example. And also,
When the surface of the peeled resin layer that was in close contact with the rotor 10 is observed under a microscope, many voids are observed in the comparative example G, but almost none are observed in the present example. Note that if the rotor 10 is preheated to a temperature equal to or higher than the melting point of the Aflon powder P in step C, but the heating and holding step is not carried out, the adhesive strength will be approximately 30 kg. It can be seen that this greatly contributes to the improvement of

In order to obtain such an effect, the rotor 1 must be
Taking into consideration the time required for the temperature of 0 to reach the set temperature of the heating furnace, it is desirable to carry out the heating and holding step for 10 minutes or more, and it is particularly preferable to carry out the heating and holding step for 15 minutes or more. In addition, from the viewpoint of reducing voids, the longer the heating and holding time, the better; however, if the heating and holding time is held at 340°C for more than 40 minutes, the resin layer will sag and the quality of the shape and dimensions will deteriorate. The heating holding time is limited, and even if the heating holding time is increased in this way, if the time required for the rotor 10 to reach the set temperature of the heating furnace is shortened,
Of course, the heating holding time becomes shorter accordingly.

Further, the present invention is not limited to the rotor 10 made of aluminum alloy as described above, but is also applicable to rotors made of steel or other metals. In the case of an aluminum rotor, the heat capacity is small, Because it gets cold easily in Aphron powder,
Although it is desirable to perform reheating as described above, in the case of materials such as steel, they have a large heat capacity and are difficult to cool, so reheating is not necessarily necessary in that case. The same applies when the thickness of the resin layer to be coated is relatively thin.

Furthermore, as a means for heating and maintaining the rotor 10 after being coated with AFLON powder, various heating methods such as induction heating can be employed in addition to the above-mentioned heating furnace.

Furthermore, in the above explanation, so-called Aphron powder was taken as an example, but the present invention is not limited to Aphron powder, and can be applied to coating various other synthetic resin powders, as well as hollow holes to be coated. As a component,
The present invention is applicable not only to the above-mentioned cocoon-shaped rotor but also to other roots-shaped rotors, and even to hollow members having openings other than roots-shaped rotors.

Although not described in detail, it goes without saying that the present invention can be practiced with various improvements and changes made to the structure of the masking jig based on the knowledge of those skilled in the art.

[Brief explanation of drawings]

FIG. 1 shows an apparatus suitable for carrying out the method of the present invention,
FIG. 3 is a cross-sectional view showing a heating process thereof. FIG. 2 is a front sectional view showing a state in which a masking jig is attached to a rotor on which a resin layer is formed in the coating process. FIG. 3 is a plan view showing the lower mask member of the masking jig in relation to the rotor, and FIG. 4 is a plan view showing the upper mask member fixed to the spring retainer together with the operating member of the jig. FIG. 5 is a bottom view of the seal member constituting the upper mask member, and FIG. 6 is a side sectional view thereof. FIG. 7 is a bottom view of the lower mask member. FIG. 8 is a front cross-sectional view showing a state in which the protrusion formed on the rod of the jig and the plate fixed to the lower mask member are engaged. FIG. 9 is a perspective view of the rotor. FIG. 10 is a graph showing the coating process as a function of time and temperature. FIG. 11 shows the relationship between the temperature of the rotor and the heating holding time when the rotor after resin coating is heated and held in a heating furnace.
It is a graph which shows the case where the masking jig is removed and heated and held, and the case where the masking jig is heated and held without being removed. 10: Rotor (hollow member)

Claims (3)

[Claims] (1) A method of coating a surface of a hollow member having an opening with synthetic resin powder, the method comprising: attaching a masking jig to close the opening of the hollow member; and placing the hollow member within the synthetic resin powder. A coating process in which the hollow member is buried and before and/or after the burial is heated to a temperature higher than the melting point of the synthetic resin powder to fuse the synthetic resin powder to the surface of the hollow member, and the hollow member after the coating is synthesized. A heating and holding step in which the temperature of the synthetic resin powder is maintained at a temperature higher than the melting point and lower than the thermal decomposition point by a heating device different from the heating device used in the coating step outside the resin powder, and a masking jig from the hollow member after heating. 1. A synthetic resin powder coating method for a hollow member, the method comprising: removing the hollow member. (2) The coating method according to claim 1, wherein the heating and holding step is performed in a heating furnace. (3) Claim 1, wherein the hollow member is a rotor material of a roots-type fluid feeder, and the synthetic resin powder is a synthetic resin powder that is a copolymer of tetrafluoroethylene and ethylene. Or the coating method according to item 2.