JPS60142081A - Compressor - Google Patents

Abstract

PURPOSE:To reduce the thermal expansion coefficient of screw rotors and the gap therebetween and as well to aim at greatly enhancing the efficiency of compression, by forming the screw rotors from alloy in a specific composition consisting of 32-42wt% Ni as a main component and the remainder of Fe together with unavoidable impurities. CONSTITUTION:Each screw rotor is formed of Fe-Ni group alloy consisting of 32-42wt% as a main component and the remainder of Fe together with unavoidable impurities, Fe-Ni-Co group alloy consisting of 32-46wt% Ni+Co as a main component and the remainder of Fe together with unavoidable impurities or Fe-Ni group cast iron consisting of less than 2.4wt% C, less than 2wt% Si, less than 1wt% Mn, 35-42wt% Ni and the remainder of Fe together with unavoidable impurities. With this arrangement, the thermal expansion coefficient of the rotor becomes about 6X10<-6> less than one-half of that of conventional rotors and therefore, the gap between the rotors upon assembly at a room temperature may be reduced to about one-half of conventional rotors, and therefore, the efficiency of compression may be greatly improved.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a compressor that compresses air using a screw rotor, and in particular uses a rotor material with low thermal expansion in order to perform efficient compression. Moreover, the present invention relates to a compressor in which the gap between the rotors is made smaller by the amount of smaller thermal expansion.

[Background of the invention]

The screw type compression section has a structure that compresses and exhausts air using a rotor consisting of a pair of male and female screws.

FIGS. 1(A) and 1(B) are front side and sectional views showing an example of a screw rotor structure of a screw compressor,
Male 1. Air supplied from the suction side is compressed in the gap between the rotors by rotation of a pair of screw rotors of the female 2, and is discharged to the discharge side.

In consideration of the fact that in conventional screw compressors, the compression efficiency decreases due to rotor wear, etc., the male and female 20 rotors are driven one rotation without contact.

Generally, in a screw compressor, air is compressed and heat is generated by the rotation of the screw rotor, and the screw rotor is accordingly heated to about 200 C during steady operation.

Therefore, the screw rotor thermally expands as the temperature rises, the gap between the rotors decreases, and eventually the male and female rotors come into contact. Therefore, the rotor is worn out by one drive rotation of the screw rotor, and the compression efficiency is reduced. Therefore, in order to maintain an appropriate gap between the rotors during compression during steady operation, it is necessary to widen the gap between the rotors by the amount of thermal expansion when assembling at room temperature.

Conventional screw rotor materials are 330C to 545
Structural carbon steel up to C or ductile cast iron is generally used, but this persimmon material has a high thermal expansion coefficient of 12 x 10-', so it is difficult to make a large gap between the rotors during assembly at room temperature. need to take it. For example, if a pair of male and female screw rotors are made at 840C (thermal expansion coefficient 112X10-') and the steady operation temperature is 200C, the gap between the rotors when assembled at room temperature (2OC) will be about 400 μm.

Therefore, because the gap between the screw rotors from room temperature to the temperature of steady operation is large, conventional compressors made of materials with a large coefficient of thermal expansion have a problem in that the air compression efficiency is low by the difference in thermal expansion. . As described above, conventional screw rotors made of structural carbon steel and ductile cast iron inherently have a large coefficient of thermal expansion, making it difficult to reduce the size of the gear fittings between the rotors during assembly at room temperature.

Therefore, the conventional compressor has the problem that even if the design of the screw rotor is changed, there is a limit to improving the compression efficiency from room temperature to steady operation to 1].

[Purpose of the invention]

An object of the present invention is to provide a compressor that can obtain compression efficiency that is the same as that during steady operation even at the initial stage of operation of the compressor.
It is in.

[Summary of the invention]

The gist of the present invention is a compressor that compresses air using a pair of male and female screw rotors, in which the screw rotor has Ni: 32 to 42 as its main component and the balance is Fe.
Fe-Ni alloy consisting of N and inevitable impurities, N
i0Co: Fe-Ni-'Co alloy consisting of 32 to 46H as the main component and the remainder Fe and inevitable impurities, or C: 2.4H or less, 8i: 2% or less, Mn
: 1% or less, Ni: 35 to 42%, the balance being Fe--Ni cast iron containing pe and inevitable impurities.

The material that makes up the screw rotor has a thermal expansion coefficient of 6XIO4 or less, which is half smaller than conventional structural carbon steel or ductile cast iron (thermal expansion coefficient of 12x10~6). There is.

During steady operation of the compressor (male in 20(1)).

Assuming that the gap between the female screw rotors is zero, the screw rotor of the compressor according to the present invention can reduce the gap between the rotors by about half that of the conventional screw rotor when assembled at room temperature.

Therefore, it is possible to greatly improve compression efficiency from room temperature to steady operation.

FIG. 2 is a diagram showing the relationship between thermal expansion and temperature of the conventional 845C and the Fe-Ni alloy (Ni: 31 to 47 inches) of the present invention.

The thermal expansion of 545C increases linearly with increasing temperature. On the other hand, Fe- containing 35% and 39% nickel
For Ni-based alloys, the thermal expansion at 200C is about 10 at 545C.
It has become 1/1.

Therefore, if this type of material is applied to the screw rotor, the gap between the rotors at room temperature can be reduced by the difference in the amount of thermal expansion at temperatures during steady operation (<2000). Therefore, the compression efficiency during transition from room temperature to steady operation can be greatly improved.

As an example, screw rotor @ p e -39%Ni
The distance between the rotor axes is 20 mm.
When the temperature during steady operation is 200 C, the total gear gap between the rotors can be reduced to 140 μm when assembled at room temperature, which can be halved compared to the conventional gap between the rotors.

Figure 3 shows the thermal expansion coefficient of N in li”e-Ni alloy.
FIG. 2 is a diagram showing the influence of l content.

For Fe-Ni binary alloys, in order to reduce the gap between the rotors by half during constant temperature assembly and obtain high compression efficiency, it is necessary to suppress the thermal expansion coefficient to 6 x 10-6 or less between 30 and 200C. Therefore, it is preferable to limit the amount of Nl to 32 to 46 inches.

If the Ni content is less than 32mm, the thermal expansion coefficient of the Fe-Ni alloy cannot be reduced to less than 6 If the coefficient becomes 6×10−′ or more, the compression efficiency will be reduced.

Therefore, the basic composition is iron with 32 to 4 nickel added.
The base is an alloy containing 6.

On the other hand, since cobalt has an effect equivalent to that of nickel on the coefficient of thermal expansion, in the present invention, when cobalt is contained, the amount of nickel + cobalt is defined as 32 to 46%.

On the other hand, since the Fe-NlZ base alloy is an austenitic alloy, it has the disadvantage that machinability and strength are slightly inferior. Therefore, in order to improve machinability, it is preferable to add phosphorus or crystallize graphite in the base. In order to further improve the strength, it is necessary to add chromium, which is a carbide-forming element, or to add aluminum, which is a precipitation-strengthening element.
It is preferable to use precipitation hardening by adding titanium or the like.

However, the above elements (P r Crl A t l T
If 1 etc.) are added vertically multiple times, there are problems such as a decrease in intelligence and an increase in the coefficient of thermal expansion, so it should preferably be limited within the range shown below.

C: 3.0% or less, Mn: 5% or less, Si: 5% or less,
Cr: 9% or less, Co: 9% or less, Cu: 3% or less, Ti: 5% or less, At: 3% or less.

Figure 4 shows 2.4% carbon, 2% silicon and 1% manganese.
FIG. 3 is a diagram showing the relationship between the thermal expansion coefficient and the amount of Ni of a Fe-Ni binary alloy when the amount of nickel is changed while keeping the amount constant.

As mentioned above, the Fe-N1 binary alloy containing carbon, silicon and manganese is the pe-Ni 2 alloy shown in Figure 3.
The coefficient of thermal expansion tends to be larger than that of the original alloy.

Here, in the present invention, the composition with a thermal expansion coefficient of 6 x 10''6 has an Ni content of 35 to 42%.

This Fe--Ni binary alloy having the above composition is used for integrally molding a screw rotor by a casting method, or for integrally casting a screw rotor and a shaft by casting.

[Embodiments of the invention]

Low thermal expansion material in the present invention (thermal tensile coefficient 6 x io-
') and conventional structural carbon steel (thermal expansion coefficient 12 x 10''
'. ), male and female rotors were manufactured, and the compression efficiency was compared. Discharge pressure Kq/anl,
Suction flow rate 1. OO0m3/h To L Te pressure 1 m Efficiency was compared.

As a result, it was found that the compression efficiency of the conventional compressor was 65%, but the compression efficiency of the compressor according to the present invention was 68%, which was a significant improvement.

From this, the present invention, in which the screw rotor is made of a Fe-Ni alloy, can reduce the gap between the rotors by half during milling at room temperature, and can greatly improve compression efficiency. I can do that.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the compression efficiency of the compressor, especially the compression efficiency from room temperature to steady operation, can be greatly increased, and a large amount of energy can be saved during operation. This has the remarkable effect that even if the rotor temperature rises abnormally due to overload, the rotors are unlikely to come into contact with each other, improving the reliability of the compressor. Furthermore, since the screw rotor is made of austenitic material, it has excellent corrosion resistance and has the advantage of being able to compress humid air.

[Brief explanation of drawings]

Figure 1 (4) (B) is a plan view and longitudinal sectional view showing an example of the structure of the screw part of a screw compressor, Figure 2 is the thermal expansion curve of 545C and iron-nickel alloy against temperature change, and Figure 3 is a diagram showing the relationship between the Ni content in iron-nickel alloys and the coefficient of thermal expansion, and Figure 4 is a diagram showing the relationship between the Ni content and the coefficient of thermal expansion in high nickel spheroidal graphite cast iron. . 1...Male screw rotor, 2...Female screw rotor representative Patent attorney Tatsuyuki Unuma 1 figure and 'no 1 j 1 - Loaf town funeral 2 figure degree of intensity (°C) rate 3 figure Niri ( LIJ right cut (3o -2oo°c)

Claims (1)

[Claims] 1. In a compressor that compresses air using a pair of male and female screw rotors, the screw rotors mainly contain Ni: 32 to 46% by weight, with the remainder being fil e
and unavoidable impurities. 2. A compressor according to claim 1, wherein the screw rotor is mainly composed of Ni+Co: 32-42% by weight, with the balance being Fe and inevitable impurities. 3. In claim 1, the screw rotor has a weight ratio of C: 2.4% or less, Si: 2% or less, Mn:
1% or less, Ni: 35-42%, balance Fe and unavoidable impurities: cast iron. 4. A compressor according to claims 1, 2, and 3, characterized in that the gap between the pair of male and female screw rotors is reduced by the difference in thermal expansion.