JPH04259690A - Screw type rotary machine - Google Patents

Abstract

PURPOSE:To enhance the efficiency by forming the tooth part of a screw from a material with low thermal expansion, and consolidating this tooth part tightly with the shank which is made of usual steel. CONSTITUTION:Plating of Ni-P, etc., is applied to the exterior surface of a shank 3 made of usual steel, and a similar plating is applied to the inner surface (boss) of the tooth part 1 of a screw for a rotary machine according to the invention. This is heated, and the shank 3 is fitted on the boss of the tooth part 1, and the resultant is kept at a high temp. Thereby the two platings are dispersed to each other, which should achieve a tightly consolidated structure.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention relates to a composite screw rotor for a compressor, and more particularly to an oil-free screw type rotary machine which supplies compressed gas without oil, such as an oil-free screw rotor.
Related to screw compressors and screw vacuum pumps.

0002

[Prior Art] Conventional screw rotors for oil-free screw compressors and screw type compressors are
An integrated male and female screw-shaped rotor is used, and by rotating these rotors at high speed, gas such as air is compressed and discharged or evacuated. This rotor consists of a toothed portion, a shaft portion, and a nucleation boundary. A compressor will be described below as an example.

In this compressor, since gas such as air is compressed and exhausted without containing oil, oil is not supplied into the compression chamber for lubrication or cooling. For this reason, the pair of male and female rotors mesh with each other with a constant gap, rotate in a non-contact state, and compress gas such as air. The screw rotor is heated by the heat generated when gas such as air is compressed, and during steady operation, the temperature is 100°C to 250°C.
It is heated to about ℃. As a result, the screw rotor thermally expands, the gap between the rotors decreases, and the male and female rotors eventually come into contact, resulting in a seizure and locking accident. Therefore, in order to maintain an appropriate gap between the rotors during compression during steady operation, it is necessary to set the gap between the rotors as wide as the thermal expansion when assembling at room temperature. However, the actual internal temperature distribution of the rotor during steady operation is not uniform and is not accurately understood.

Carbon steel, chromium molybdenum steel, etc. are used as conventional screw rotor materials, and the coefficient of thermal expansion of these materials is approximately 12×10￣6/ at 20°C to 250°C.
℃, it is necessary to have a large gap between the rotors during assembly at room temperature, and because the temperature distribution is not clear, even more gaps between the rotors are considered. However, setting such a large gap has the disadvantage that the compression efficiency during operation is greatly reduced. On the other hand, if the gap is made small, there is a risk of seizure and locking accidents.

[0005] To solve this problem, there is a conventional example in which the compression efficiency is improved by using a composite screw rotor in which the rotor teeth are made of low thermal expansion, high Ni ductile cast iron and the shaft part is made of steel.

In this conventional example, the tooth profile material is, for example, Fe-39%Ni-2.4%C-2%Si-1%M.
A composite screw rotor is manufactured by using n-ductile cast iron, inserting a consumable electrode made of S45C steel forming a shaft into the internal cavity of the cylindrical ingot, and filling it by electroslag remelting.

Furthermore, Japanese Patent Laid-Open No. 63-272986 discloses a composite screw rotor in which the teeth are made of a material with low thermal expansion of 6×10° C. or less and the shaft portion is made of a material with high strength. This is made by making a toothed part with a hole made of a low thermal expansion material, and melting a welding rod mainly made of high-strength ordinary steel into the hole using the electroslag method and integrating it with the shaft part. . Although these examples are excellent methods, they are a type of casting method, and the conditions must be strictly controlled to ensure sufficient welding, which may result in insufficient welding in some areas.

[0008]

[Problems to be Solved by the Invention] The object of the present invention is to provide a screw-type rotating machine (compressor, vacuum The aim is to improve the efficiency and reduce the efficiency of pumps (pumps), and in this case, the issue is the close adhesion between the low thermal expansion material and the shaft material.

[0009]

[Means for solving the problem] The tooth profile of the screw rotor is made of a low thermal expansion material, a through hole is provided therein, the shaft is made of another metal material, and the outer diameter of the shaft is plated with metal, such as Ni, Apply Ni-P, Cr, etc.

Next, this toothed portion is heated to a high temperature to enlarge the through hole, and the plated shaft is inserted into the through hole. Next, the integrally assembled rotor is placed in a heating furnace and held for a long period of time to diffuse and penetrate the components in the plating layer into the tooth profile and the shaft, thereby obtaining a screw rotor that is in close contact with the rotor.

[0011]

[Operation] As shown in FIG. 1 and FIG. 2, which is a longitudinal cross-sectional view of the same, metal plating 3a is applied to the inner diameter portion of the rotor tooth profile 1. Further, a similar plating 1a is applied to the outer peripheral portion of the metal shaft, especially the portion that contacts the toothed portion. At this time, the shaft diameter should be made larger than the hole diameter at the same temperature.

Next, the toothed portion is heated to a predetermined temperature to enlarge the through hole, and in this state, the shaft 3 coated with plating 1a is inserted to assemble the screw rotor.

By placing this integrally assembled rotor in a heating furnace and holding it for a predetermined period of time, the components in the plating layers are diffused and infiltrated in relation to each other, the plating and the shaft, and the plating and the tooth profile. Obtain a tightly fitted screw rotor.

FIGS. 3 and 4 show the coefficient of thermal expansion of Fe--Ni alloy. Ni with a thermal expansion coefficient of 8×10￣6/℃ or less
The amount added is from 32 wt% to 46 wt%. Figure 3 shows C2.4wt%, Si20wt% and Mn1w.
Figure 2 shows the coefficient of thermal expansion of high Ni ductile cast iron with addition of t%. The amount of Ni that gives a thermal expansion coefficient of 6×10￣6/°C or less is 37
It is from wt% to 41wt%. In this way, C, Si,
The coefficient of thermal expansion tends to increase due to Mn and the like. Therefore, it is desirable that the addition of C, Si, Mn, etc. be as small as possible. However, the Fe-Ni alloy has poor machinability, and it may be added in an amount necessary to improve the machinability, deoxidize the molten metal, strengthen the matrix, etc. However, as far as C is concerned, if C is 0.5 wt% or less, the effect of improving machinability is small;
Above this, floating of hypereutectic graphite occurs. Therefore, C is 0
．． It should be limited to 5wt% to 3.5wt%. On the other hand, since Co also has almost the same effect as Ni, the amount of Ni added in FIGS. 3 and 4 may be set as the amount of Ni+Co added.

[0015]

[Example] <Example 1> Figures 5 and 6 show the tooth profile of a screw rotor made of a low thermal expansion material containing 44% Ni and provided with through holes. The inner diameter portion of this rotor is plated with 25 μm Ni.

Separately, a shaft 6 made of common steel and having a 20 μm Ni plating layer 5 on its surface is prepared.

The rotor tooth profile 4 is heated to 650° C. for two hours, thereby increasing its inner diameter.

[0018] The steel shaft was heated to 500°C, and the assembled rotor was inserted into the through hole of the tooth profile and held at 650°C for 4 hours, thereby allowing the plating components to interdiffuse and become integrated. A rotor, that is, a screw rotor made of a low thermal expansion material only in the tooth profile was obtained. In this rotor, at the operating environment temperature (RT - 350 DEG C.), physical adhesion forces act on the toothed portions in addition to chemical bonding, so the shaft and the toothed portions are solidly bonded so that they will never come apart.

<Embodiment 2> In this example, the steel shaft is not circumferential, but
It has a shape with unevenness.

[0020] As shown in FIG. 8, a steel shaft 9 is provided with unevenness.
20 μm of Ni-P is placed on the outer periphery of the
Apply plating 5.

[0021] Separately, it is made of ordinary steel and has a 20 μm Ni-
A shaft 6 plated with P is prepared.

[0022] The rotor tooth profile 4 is heated to 650°C for two hours, thereby enlarging its inner diameter.

[0023] The steel shaft 6 is heated to 500°C, and the assembled rotor is inserted into the through hole of the tooth profile and held at 650°C for 4 hours to allow the plating components to interdiffuse and become integrated. A rotor, that is, a screw rotor whose only tooth profile is made of a low thermal expansion material was obtained. In this rotor, at the operating environment temperature (RT - 350 DEG C.), physical adhesion forces act on the toothed portions in addition to chemical bonding, so the shaft and the toothed portions are solidly bonded so that they will never come apart.

<Embodiment 3> In Embodiment 1, the steel solid shaft 6
A taper is applied to the tooth profile 4, and a similar taper is applied to the through hole of the tooth profile 4 in accordance with the taper of the bridge.

After heating these in accordance with Example 1, the shaft 6 is set in the through hole, and heated again under pressure to form the toothed portion 4 and the shaft 6 into a tightly integrated product.

[0026]

According to the present invention, the gap between the male and female rotors can be strictly controlled, thereby improving the performance of the screw type rotating machine.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the principle of the present invention.

FIG. 2 is a longitudinal sectional view showing the principle of the present invention.

FIG. 3 is an expansion characteristic diagram of a low thermal expansion material.

FIG. 4 is an expansion characteristic diagram of a low thermal expansion material.

FIG. 5 is a sectional view showing an embodiment of the present invention.

FIG. 6 is a sectional view showing an embodiment of the present invention.

FIG. 7 is a sectional view showing an embodiment of the present invention.

FIG. 8 is a sectional view showing an embodiment of the present invention.

FIG. 9 is a sectional view showing an embodiment of the present invention.

[Explanation of symbols]

1, 4, 7... Screw rotor tooth profile, 3, 6, 9... Metal shaft, 1a, 3a, 5, 8... Plating layer.

Claims (6)

[Claims] Claim 1: The tooth profile is mainly composed of Fe and Ni and is 8×10￣
1. A screw-type rotary machine, characterized in that the boundary between a low thermal expansion material having a coefficient of thermal expansion of 6/°C or less and a shaft portion is plated with metal, and is provided with at least a pair of screw rotors. 2. The screw compressor according to claim 1, wherein the low thermal expansion material is mainly composed of 32 to 46% Ni by weight, and the remainder is Fe and irreversible impurities. 3. At least a pair of tooth profile parts and shaft parts made of a low thermal expansion material mainly composed of Fe, Ni and/or Co and having a coefficient of thermal expansion of 8×10￣6/°C or less and integrated by diffusion bonding. A screw-type rotating machine with a screw rotor. 4. A screw-type rotating machine according to claim 2, comprising at least a pair of screw rotors in which the toothed portion and the shaft portion are integrated by diffusion bonding. 5. In the screw rotor, the surface of the steel shaft is plated with Ni, and a hole with a slightly smaller diameter is drilled therein.
Fe, Ni and/or Co as main components 8×10￣6/
The shaft is inserted into the hole of the tooth profile having a coefficient of thermal expansion of 0.degree. A screw-type rotating machine that is also characterized by being made by hand. 6. In claim 2, the surface of the shaft portion made of steel is plated with Ni, and the shaft portion is inserted into the hole of the tooth-shaped member having a hole with a slightly smaller diameter than the surface of the shaft portion. A screw-type rotating machine that is manufactured by heating the material at a predetermined temperature to diffuse plating components into the material forming the shaft portion and the tooth profile portion, and then integrally joining the material.