JP3279995B2 - Screw rotor and processing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor for a dry screw compressor, and more particularly, to a coating for a screw rotor.

[0002]

2. Description of the Related Art As a method for improving the corrosion resistance of a rotor, a conventional solid lubricant such as molybdenum disulfide (hereinafter referred to as "molybdenum disulfide") has been used.
MoS 2) or polytetrafluoroethylene (hereinafter referred to as PTFE) was fixed on the surface to form a coating.

Conventionally, after the screw rotor is machined to a predetermined size in a process as shown in FIG. 4, the rotor tooth surface is cleaned and degreased, and treated with manganese phosphate (soaked).
After drying, a coating agent containing MoS2 as a main component was applied and baked. If necessary, 24 to 28 in FIG. 4 were repeatedly coated to a required film thickness.
The corrosion resistance of the rotor has been improved to prevent the rust lock of the rotor. However, since the heat resistance of the binder and the manganese phosphate film used in the MoS2 coating agent is about 200 ° C., the corrosion resistance is reduced when the compressor is operated at a compressor discharge air temperature exceeding 200 ° C. for a long period of time. There is a problem that the rotor rusts and the rust lock of the rotor easily occurs.

A conventional example of coating a screw rotor is described in, for example, JP-A-61-190184.

[0005]

In a dry screw compressor, a male rotor and a female rotor mesh with each other in a non-contact manner while maintaining a small clearance by a synchronous gear, and compress air in a compression chamber inside a casing. . As described above, the dry screw compressor has a very small clearance between the rotors and between the rotor and the casing, and does not contain oil in the compression chamber.Therefore, rust is generated on the rotor while the compressor is stopped due to condensation of moisture contained in the air. If this occurs, there is a problem that rusting and fixing occurs between the rotor tooth surface and the female rotor tooth surface or between the rotor and the inner wall of the compression chamber, causing a rotor lock phenomenon in which the rotor does not rotate.

In order to prevent this rotor lock, for example, M
oS2 is baked and coated on the lobe of the screw rotor to prevent rusting of the rotor.However, if the rotor is operated for a long time at a high discharge temperature or used in a condition where moisture condenses easily, the rotor should be locked. There is. Because of this,
By operating the long-term stop switch provided in the operation panel on the machine side, the suction valve of the screw compressor is closed for 20 minutes to perform no-load operation, and after the water in the compression chamber evaporates, an operation system for automatically stopping is added. And other measures were necessary.

It is an object of the present invention to suppress the occurrence of rust on a screw rotor and to prevent rusting of the rotor in the gas compressor chamber due to rust.

[0008]

[0009]

According to the present invention, in order to achieve the above-mentioned object, a lobe of a screw rotor formed into a predetermined tooth shape by machining is coated with a primer, dried, fired, and then dried. By uniformly applying a coating agent of -fluoroalkyl vinyl ether copolymer (PFA), and drying and firing,
A PFA coating is formed on the rotor lobe surface to prevent rusting of the rotor.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the process of forming a coating film of a PFA coating, a PFA molecule and a binder are first placed on a rotor substrate.
After applying, drying and firing a solution in which pigment and water are dispersed and mixed, an aqueous solution of PFA molecules is applied, dried and fired, whereby the PFA molecules on the rotor base material are melted to form a continuous film.

When PFA is coated, the surface of the rotor substrate is covered with a continuous and uniform coating of the melted PFA molecules, so that pinholes are hardly formed, and a small thickness (50 μm or less) and large rust prevention are obtained. The effect is obtained. Further, since the PFA molecules are melted and integrated, the coating does not deteriorate due to desorption from the granular powder.

Further, since PFA has non-adhesiveness, it is also possible to easily remove foreign matter such as dust in the air from entering into the minute gap between the male rotor and the female rotor or between the rotor and the casing. Therefore, there is no trouble such as sticking of the rotor due to accumulation of these foreign substances.

[0013] By applying the PFA coating to the rotor of the dry screw compressor as described above, the rust of the rotor is prevented, and in order to prevent the rust from being fixed in the small clearance between the rotors or between the rotor and the casing, the rotor is fixed. Rust lock can be prevented.

A specific embodiment of the present invention will be described below with reference to the drawings. First, the lobes 3 of the male rotor 1 and the female rotor 2 shown in FIG. 1 are heated and degreased at the same temperature as the firing temperature of the PFA coating agent. Thereafter, as shown in the partial view of the rotor base material shown in FIG. 2, the rotor surface is roughened 4 and a primer coating 5 is applied and dried, and then a PFA coating agent 6 is applied and fired.

As shown in FIG. 3, the screw rotor lobe 3 (see FIG. 1) of the dry screw compressor is machined into a predetermined size and shape, and then heated and degreased 7 at the same temperature as the PFA coating firing temperature. In order to cool to the working room temperature and roughen the coating surface 8, after shot blasting with alumina, cleaning 9, primer coating 1 composed of PFA molecules, binder pigment, etc.
Perform 0. After the primer has dried 11
After calcination 12 at 0 ° C., cooling was performed, and PFA coating 13 was performed.
Baking 15 at ~ 420 ° C. After cooling 16, the film thickness is measured. If the film thickness is less than the predetermined value, steps 13 to 16 in FIG. 3 are repeated until the required film thickness is obtained.

FIG. 6 shows the process of forming a PFA coating film. In this process, first, the PFA is
After applying, drying and calcining a solution 32 in which the molecules 31 are dispersed and mixed with a binder, a pigment, and water, the aqueous solution 34 of the PFA molecules 31 is applied, dried and calcined, so that the PFA molecules 31 on the rotor substrate 30 are Melted and continuous coating 35
To form

On the other hand, as shown in FIG. 7, the process of forming the coating film of the PTFE coating is the same as that of PFA, except that the PTFE molecules 3
No. 6 is laminated in a molecular state without melting to form a film.

The corrosion resistance of the PTFE molecule 36 is equivalent to that of the PFA molecule 31, but since the coating is formed as an aggregate of molecules, a pinhole is easily formed at the junction between the molecules, and the corrosion resistance of the coating is high. In order to obtain a film, a film thicker than PFA is required.

FIGS. 4 and 8 show the work flow of the conventional MoS2 coating and the process of forming the coating film.

In the MoS2 coating, the rotor substrate 3
A manganese phosphate film 40 is formed on the substrate 0, and the MoS2 molecules on the dead leaves are laminated thereon, and adhered with a binder.
Further, although the structure in which the MoS2 molecules are folded and filled between them is filled with a binder, the anticorrosive property of the binder and the manganese phosphate film 40 is reduced when exposed to a high temperature exceeding 200 ° C. Easy to form holes. In the case of a dry screw compressor, the air temperature in the compression chamber may exceed 200 ° C. due to adiabatic compression, and a sufficient rust prevention effect cannot always be expected with MoS2 coating.

On the other hand, when PFA is coated, the surface of the rotor substrate 30 is covered with a continuous and uniform film of the melted PFA molecules 31, so that pinholes are not easily formed and a thin film thickness (50 μm) is formed. Below), a large rust prevention effect can be obtained. In addition, since the PFA molecules 31 are melted and integrated, the coating does not deteriorate due to desorption from the granular powder.

Further, since PFA has non-adhesiveness, foreign matter such as dust in the air can be easily eliminated even if a small gap between the male rotor and the female rotor or between the rotor and the casing is mixed. Therefore, there is no trouble such as sticking of the rotor due to accumulation of these foreign substances.

By applying the PFA coating to the rotor of the dry screw compressor as described above, the rust of the rotor is prevented, and the rust of the rotor or the small gap between the rotor and the casing is prevented from being fixed by rust. Rust lock can be prevented.

FIG. 5 shows that a dry screw compressor having a rotor lobe coated with MoS2 and a dry screw compressor having a PFA coating are sprayed with salt water at regular intervals and left forcibly to generate rotor rust locks. FIG. 9 is a diagram in which a rotor sticking force is measured by a rotation torque and effects thereof are compared. Compared with the conventional MoS2 coating, the PFA coating has a greater rotor rust-preventing effect, and it is found that the rotor rust lock is less likely to occur.

As described above, according to this embodiment, the PF
The A coating is used for the lobe of the screw rotor to suppress the rust of the screw rotor lobe and prevent the rust from sticking to the casing due to the non-adhesiveness of the fluorine resin even if rust occurs in the casing. The rotor rust lock in the gas compressor chamber can be solved.

[0026]

[0027]

According to the present invention, by coating the rotor lobe of the dry screw compressor with PFA, it is possible to prevent rusting and fixation and to avoid rotor lock of the compressor.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating engagement between a male rotor and a female rotor of a screw compressor.

FIG. 2 is an enlarged view of a coating layer in an embodiment of the present invention, and is an enlarged sectional view of a main part showing a relationship between a screw rotor substrate and a coating layer.

FIG. 3 is a diagram showing a work flow when performing PFA coating in the present invention.

FIG. 4 is a diagram showing a work flow when performing a conventional MoS2 coating.

[Fig. 5] A screw rotator coated with MoS2 coating and a PFA coated one are each incorporated into a screw compressor, and a reproduction test of a rusted rotor lock is performed. It is a diagram which compares and explains a lock prevention effect.

FIG. 6 is a diagram illustrating a process of forming a coating film of a PFA coating.

FIG. 7 is a diagram illustrating a process of forming a coating film of a conventional PTFE coating.

FIG. 8 is a view for explaining a conventional process of forming a MoS2 coating film.

[Explanation of symbols]

1 ... male rotor, 2 ... male rotor, 3 ... rotor lobe, 4 ... part of rotor substrate roughened, 5 ... primer coating, 6 ... PFA coating, 30 ... rotor substrate, 31 ... P
FA molecules, 32: binder, pigment, and moisture, 33: binder and pigment, 34 PFA: aqueous solution, 35: coating film in which PFA is melt-bonded, 36: PTFE molecule, 37: PTFE molecule, 32: binder, pigment, and moisture, 38 ... Binders and pigments, 39 ... P
TFE aqueous solution, 40: manganese phosphate film, 41: MoS2 and binder, PFA: tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, PTFE: polytetrafluoroethylene, MoS2: molybdenum disulfide, Mn: manganese.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-290086 (JP, A) JP-A-1-223174 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F04C 18/16 F04C 29/00

Claims (5)

(57) [Claims] 1. A male rotor having a helical convex tooth profile.
At least one of female rotors having a spiral concave tooth profile
The tetrafluoroethylene formed on the surface
・ Perfluoroalkyl vinyl ether copolymer (PF
After applying a primer coating film containing A) and a binder
And apply a film containing PFA on the surface of the fired film.
Formed and melted PFA molecules to form a continuous film
Screw low for dry screw compressor
Ta. 2. The method according to claim 1, wherein the thickness of the film containing PFA is 50 μm or less.
The screw according to claim 1, wherein the screw is provided below.
Rotor. 3. The rotor has a plurality of screw teeth.
The screw rotor according to claim 1, wherein: 4. The rotor according to claim 1, wherein the rotor has a plurality of teeth having a concave shape in a section perpendicular to the axis.
2. The female rotor according to claim 1, wherein
Screw rotor. 5. The rotor according to claim 1, wherein the rotor has a plurality of teeth having a convex shape perpendicular to the axis.
2. A male rotor having a plurality of male rotors.
Screw rotor.