JPS59208077A - Production of tapered screw rotor - Google Patents

Abstract

PURPOSE:To form the taper meeting the axial temp. distribution to a screw rotor in an oil-free screw compressor, etc. with high productivity by treating said rotor by an etching method in the stage of forming the rotor into a tapered shape by taking the axial temp. gradient into consideration. CONSTITUTION:A screw rotor to be used in a single stage oil-free screw compressor, etc. is formed with the taper meeting a temp. distribution in order to maintain the clearance between the rotors at a required min. value according to the expanding rate thereof from the change in the longitudinal temp. distribution during operation and to improve operating efficiency. The formation of said taper is accomplished by suspending the rotor 1 by means of a wire 100 with the suction side end face 51 faced upward and the discharge side end face faced downward, dipping the rotor into an etching soln. 140 of a nitric acid soln., etc. down to a certain position and neutralizing away the etching soln. sticking thereon right after pulling the rotor from the etching soln. The time when the rotor is dipped in the soln. 140 is longer on the end face 50 than 51 to increase the etching rate from the end face 51 toward 50. The tapered rotor is thus easily manufactured without using mechanical grinding.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to screw fluid machines in general, and in particular to high pressure ratio oil-free screw compressors and screw fluid machines with a large temperature difference between discharge air temperature and intake air temperature. The present invention relates to a method of manufacturing a screw rotor having a tooth shape suitable for an expander.

[Background of the invention]

Japanese Patent Publication No. 38-15286 discloses that the rotor at room temperature is formed into a tapered shape in consideration of the axial temperature gradient of the rotor. However, the method shown in this patent publication attempts to obtain the final shape by cutting, and with such cutting, only a linear taper can be formed, and the rotor axis It is not easy to form a taper from an intermediate position in the direction, or to form a taper that matches the temperature gradient in the axial direction of the rotor.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing a tapered rotor that is more productive than the above-described machining method and that can quickly respond to the temperature distribution in the longitudinal direction of the rotor.

[Summary of the invention]

An explanation will be given by taking a single stage oil-free screw pressure Mm with a high pressure ratio as an example. This compressor has severe operating conditions, and in order to achieve high performance, the clearance between the rotors must be kept to the minimum necessary and it must be operated at high speed. Since the discharge air temperature exceeds 300 tl, the temperature gradient in the axial direction of the rotor teeth must be quite large.In order to achieve one minute during operation and the minimum necessary clearance, the following crest shape is required. There is a need to. That is, the rotor is tapered so that the clearance on the suction side is small at room temperature, and the clearance increases continuously toward the discharge side. The ratio of this taper and its shape may be determined depending on the temperature gradient during operation.

As mentioned above, the method of machining is already known and results in a rotor that is both cumbersome and expensive.

The present invention aims to obtain a tapered rotor by corrosion, and it is possible to provide a rotor that is considerably cheaper than a mechanical processing method. The rotor can be machined into any shape.

[Embodiments of the invention]

The present invention is applicable to rotors of screw fluid machines in general, but is it applicable to oil-free screw compressors? By way of example, the following embodiments will be described.

The overall structure of an oil-free screw compressor will be explained with reference to FIG. 1. The male rotor 1 and the female rotor 2 are housed in the gaging in a meshed state.

The gauging consists of a suction casing 4, a discharge gauging 3, and an end cover 5. Both rotors are housed in the discharge gauging 3, and the suction casing 4 is attached to the suction side end.
Rotor axes ls, 2s and ld.

2d is inserted into a shaft seal material 8 disposed in the shaft penetrating part of the gauging, and this shaft seal 8 seals the sole of the compressed air and the oil sent to the bearing. Furthermore, the radial load of both rotors is supported by a bearing 6, and the thrust load is supported by a bearing 7, respectively.

A pair of timing gears 9 are provided at the discharge side shaft ends of the male rotor and female rotor. The rotors are arranged in mesh with each other, and both rotors are arranged to rotate without contacting each other. A pinion 11 is attached to the ISO shaft end of the male rotor on the suction side, and is driven by a pull gear (not shown). When rotational force is transmitted to the pinion 11 from the drive source, the pair of male and female rotors rotate synchronously while maintaining a small gap by the timing gears 9 and 10. As a result, the intake air is drawn into the intake space formed by the tooth profiles of both rotors through the intake passage (not shown), and as both rotors rotate, the tooth profile space gradually decreases, and the sealed air is discharged and compressed. The air becomes air, is discharged from a discharge boat (not shown), and is used for various purposes.

However, as mentioned above, since the discharge air temperature is 300C or more, the temperature gradient in the axial direction of the rotor is quite large, and with a straight rotor, the amount of thermal expansion on the discharge side is small.
There is a risk of burnout due to contact between the rotors. In order to prevent this burnout, if the design is designed to have a uniform and large clearance in the axial direction, the thermal expansion will be large on the discharge side during operation, resulting in a small clearance, but as it approaches the suction side, the thermal expansion will increase. The smaller the size, the greater the clearance. Therefore, a high-performance compressor cannot be provided.

If processing is performed so that the clearance on the suction side is small at room temperature and increases continuously toward the discharge side as in the present invention, the axial clearance distribution can be made uniform during operation. Moreover, since the two rotors do not come into contact with each other on the discharge side, the clearance can be reduced, and a compressor with high performance and high reliability can be provided.

Next, an embodiment of the working force method for a tapered rotor according to the present invention will be described with reference to FIG. This method involves corroding the rotor to form a tapered rotor. In the figure, motor 12 mounted on column 130
0 is equipped with a drum 110, and one rotor is supported by a wire 100 wound around the drum 110. The tank is filled with a corrosive liquid 140 (for example, 18% diluted nitric acid), and is equipped with an agitator 150 and an electric heater 160 via a transformer 170.

The corrosive liquid 140 is stirred by a stirrer, and the electric heater 1
60, the temperature is controlled to be uniform and constant.

Temperature control is performed by adjusting the voltage of transformer 170.

The rotor I is a straight rotor machined by a general-purpose hobbing machine, and corrosion-proofing treatment is applied to unnecessary parts of the rotor. When the motor 120 is rotated counterclockwise in the state shown in FIG. 2, the rotor 1 is lowered and immersed in a corrosive liquid bath to be corroded. The rotor 1 is lowered to a certain position, and then the rotor 120 is reversely rotated to raise the rotor. Immediately thereafter, rotor 1 (i
=Remove it and neutralize it with a neutralizing solution (not shown) to prevent further corrosion than necessary. The mounting direction of the rotor 1 in FIG. 2 is such that the upper side is the suction side and the lower side is the discharge side. The time period during which the rotor teeth are immersed in the corrosive liquid is longest at the discharge end face 50 and gradually becomes shorter as it approaches the suction end face 51. Therefore, a tapered rotor with the greatest amount of corrosion on the discharge end face 50 can be obtained.

The rotational speed of the motor 120, that is, the time during which the rotor teeth are immersed in the corrosive liquid, and the temperature of the corrosive liquid are closely related to the amount of corrosion, so the rate of progress of corrosion must be fully understood and determined through preliminary experiments. .

According to the results of preliminary experiments, 30 μm of corrosion occurs in 3 minutes, and the rate of corrosion progress within this time, that is, the relationship between the amount of corrosion and time is shown in FIG. 3, and is approximately in direct proportion.

In Figure 4, the amount of corrosion δ and the distance from the discharge end surface
The relationship between .delta. and .delta. is determined in advance by the critical gradient of the rotor during operation, but if .delta. is a continuously decreasing function of X, it can be obtained by controlling the rotational speed of the motor 120.

As described above, according to the present invention, the amount of corrosion of the rotor tooth shape can be continuously changed in the axial direction, and as a result, a tapered rotor can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, since a tapered rotor is obtained through corrosion, a high-performance compressor is provided by minimizing the axial clearance of the rotor uniformly and to the necessary minimum during operation. can. Furthermore, even if the clearance during operation is reduced, there is no risk of contact between the rotors, contributing to improved reliability.

Furthermore, compared to the method of modifying a general-purpose hobbing machine and machining it into a tapered shape by cutting, it is possible to provide a considerably cheaper rotor.

Under the most severe operating conditions of a single-stage oil-free screw compressor, the suction temperature is 40C and the discharge temperature is 35CI.
It will be 8 degrees. In stone-shaped rotors as in the prior art, the rotors come into contact with each other under this condition, causing considerable damage. Therefore, the performance under the standard condition of suction temperature of 20C is significantly reduced due to the increase in clearance due to the damage.

According to the present invention, the rotors can be prevented from contacting each other even at a suction temperature of 40C, so the above-mentioned significant performance deterioration does not occur.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a screw compressor, FIG. 2 is an explanatory diagram of the method of manufacturing a tapered rotor according to the present invention, and FIG. 3 is a diagram showing the rate of corrosion progress. FIG. 4 is a diagram showing the relationship between the axial length of the rotor teeth and the amount of corrosion. 1...male rotor, 2...female rotor, 120...
・Motor, 140... Corrosive liquid, 150... Stirrer,
160...Electric heater. Fig. 2-426- ■ Fig. 3 Fig. 4

Claims (1)

[Claims] 1. In a screw rotor in which a male rotor and a female rotor mesh with each other and rotate in contact or non-contact, a tapered rotor can be obtained by continuously changing the amount of corrosion of the rotor tooth shape in the axial direction. The manufacturing method of the characteristic Keskri rotor.