JP3026394B2 - Dry screw compressor 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 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 solid lubricant (hereinafter, referred to as molybdenum) has conventionally been used.
MoS ₂ ) or polytetrafluoroethylene (hereinafter referred to as PTFE) was fixed on the surface to form a coating film.

Conventionally, a screw rotor is machined to a predetermined size in a process as shown in FIG. 4 and then the rotor tooth surface is cleaned and degreased, followed by manganese phosphate treatment (soaked).
After drying, a coating agent containing MoS ₂ 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 MoS ₂ 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 time, and the moisture in the air is reduced. As a result, 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 disclosed in, for example, Japanese Patent Application Laid-Open No. 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 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 when 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
OSS ₂ is baked and coated on the lobe of the screw rotor to prevent rusting of the rotor.However, the rotor locks up when operated for a long time at a high discharge temperature or when used under conditions where moisture condenses easily. Sometimes. 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 operate without load, 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]

According to the present invention, in order to achieve this object, primer coating is performed on a screw rotor lobe formed into a predetermined tooth shape by machining, and after drying and firing, tetrafluoroethylene powder is obtained. 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.

[0009]

In the process of forming a coating film of PFA coating, first, a solution in which PFA molecules, a binder, a pigment, and water are dispersed and mixed is applied to a rotor base material, dried, and baked, and then an aqueous solution of PFA molecules is applied and dried. By firing, the PFA molecules on the rotor substrate melt to form a continuous film.

[0010] 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 a 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, 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, rusting of the rotor is prevented, and adhesion of the rotor by the rust in the minute clearance between the rotors or between the rotor and the casing is prevented. Rust lock can be prevented.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 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.
Is applied and dried, and a PFA coating agent 6 is applied thereon and baked.

As shown in FIG. 3, the screw rotor lobe 3 (see FIG. 1) of the dry screw compressor is machined into a predetermined shape 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, PFA coating 13 was performed, and it was confirmed that PFA was dried 14.
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 a 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 work flow of the PTFE coating film formation process is the same as that of PFA, but 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 a work flow of the conventional MoS ₂ coating and a process of forming a coating film.

In the MoS ₂ coating, the rotor substrate 3
A manganese phosphate film 40 is formed on the substrate 0, and the MoS ₂ molecules on the dead leaves are laminated thereon, and are bonded with a binder.
Further, although a structure filled with a binder therebetween and folded is MoS ₂ molecules, binder and manganese phosphate film 40, because is the corrosion resistance exposed to a high temperature exceeding 200 ° C. decreased, MoS _bimolecular Pinholes are easily formed in In the case of a dry screw compressor, the air temperature in the compression chamber may exceed 200 ° C. due to adiabatic compression, and MoS ₂ coating cannot always be expected to have a sufficient rust prevention effect.

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 hardly formed and a thin film thickness (50 μm) is formed. The following) provides a great rust prevention effect. 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, rusting of the rotor is prevented, and adhesion of the rotor due to rust at a small clearance between the rotors or between the rotor and the casing is prevented. Rust lock can be prevented.

FIG. 5 shows that a dry screw compressor having a rotor lobe coated with MoS ₂ and a dry screw compressor having a PFA coating are sprayed with salt water periodically and left to forcibly generate rotor rust lock. FIG. 5 is a diagram comparing rotor fixing force measured by rotational torque and comparing the effects. Compared to the conventional MoS ₂ coating, the PFA coating has a greater rotor rust-preventing effect, and it can be seen that the rotor rust lock is less likely to occur.

As described above, according to the present 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 even if rust occurs in the casing, the fluoroplastic does not stick to the casing to prevent the casing from sticking to the rust. The rotor rust lock in the gas compressor chamber can be solved.

[0025]

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 conventional MoS ₂ coating.

[Fig. 5] A screw rotator coated with MoS ₂ coating and a PFA coated one are incorporated into a screw compressor, respectively, and a reproduction test of a rust lock with a rotor is performed. FIG. 4 is a diagram for comparing and explaining the attached lock prevention effects.

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 illustrating a process of forming a coating film of a conventional MoS ₂ coating.

[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: MoS ₂ and binder, PFA: tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, PTFE: polytetrafluoroethylene, MoS ₂ : molybdenum disulfide, Mn: manganese.

Continuation of the front page (56) References JP-A-3-290086 (JP, A) JP-A-56-75992 (JP, A) JP-A-62-165067 (JP, A) JP-A-63-212547 (JP, A) JP-A-1-223174 (JP, A) JP-A-3-261552 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F04C 18/16 F04C 29/00 C09D 127/14 C09D 129/10

Claims (3)

(57) [Claims] A male rotor having a helical convex tooth profile and a female rotor having a helical concave tooth profile housed inside a casing are provided on the casing so as to rotate while meshing with each other in a non-contact manner by a synchronous gear. In a dry screw compressor supported by a bearing, a tetrafluoroethylene / perfluoroalkylvinyl ether copolymer (PFA) formed on the surfaces of the male rotor and the female rotor
After baking after applying a primer coating film containing a binder and a binder, baking after applying a film containing PFA on the surface of the baking film
A dry screw compressor characterized by melting a PFA molecule to form a continuous film . 2. The dry screw compressor according to claim 1, wherein the thickness of the film containing PFA is set to 50 μm or less. 3. A dry disk having a male rotor and a female rotor.
A method for processing a Lew compressor, comprising: (a) adding tetrafluoroethylene to the surface of a rotor forming a compression chamber;
Tylene / perfluoroalkyl vinyl ether copolymer
Primer coating film containing (PFA) and binder
A step of applying, scan for drying and firing (b) the primer coating film
And (c) applying PFA to the surface of the primer coating film.
(D) baking the rotor after step (c); and (e) applying the above (c) until the thickness of the PFA film reaches a predetermined thickness.
And (d) repeating the step of melting the PFA molecules to form a continuous film.
And a method of processing a dry screw compressor.