JPH03168382A - Screw rotating machine - Google Patents

Abstract

PURPOSE:To keep performance to its maximum level for a long period by giving the whole surface of one rotor, self-lubrication coating of soft material and the whole surface of the other, moderate-thickness surface treatment of hard material. CONSTITUTION:The surface of one rotor (e.g. a mail rotor 1) is given self- lubrication coating and the surface of the other rotor (e.g. a femail rotor 2) is given hard plating at a moderate thickness, then a gap between the rotors 1, 2 is made logically zero at B point and an ideal situation with no interference is brought about between the rotors. In fact, however, interference occurs because of misalignment affected by working precision of respective parts. As soft self-lubrication coating is given only to one rotor, cutoff to an optimum condition is made by the other hard plated rotor to allow a machine to be driven in high performance for a long period while maintaining a small gap and burning the rust due to rotor contact to be effectively prevented.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a rotor surface treatment structure for an oil-free screw compressor and a vacuum pump, and in particular, the present invention relates to a rotor surface treatment structure for an oil-free screw compressor and a vacuum pump. , tooth profile, roots-shaped tooth profile, etc.).

[Conventional technology]

In the conventional technology, as described in Japanese Utility Model Application Publication No. 51-62110, a film is formed only on the non-contact surface of one rotor, and a film is formed on the surface of both rotors in consideration of wear of the rotor contact part. There are examples where a coating is applied over the entire rotor, but there is no clear decision on how to ensure the anti-corrosion ability of the coating and performance that takes into account machining errors (misalignment) of the constituent parts. There were contact problems and a decrease in performance due to an increase in the gap between the rotors.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, a self-lubricating coating is not applied over the entire surface of one rotor, and only the non-contact surface is affected, so the thrust of the bearing, the positional displacement in the axial direction, the casing surrounding the rotor, etc. Machining errors, machining accuracy of the rotor tooth profile, and miniaturization of the gap between the rotors are not taken into consideration.If the gap between the rotors is made large, there will be problems with performance deterioration, and if the gap between the rotors is made small, There was a problem of burnout due to metal contact between the rotors. In addition, no consideration was given to optimization of the coating, which caused rotor-to-rotor contact problems due to rotor corrosion.

The purpose of the present invention is to prevent misalignment of component parts. The object of the present invention is to provide a screw rotating machine that maintains maximum performance over a long period of time while minimizing the gap between rotors and having anti-corrosion capabilities.

[Means to solve the problem]

In order to achieve the above object, the present invention applies a self-lubricating coating of about 30 to 40 μm over the entire surface of one rotor and 20 μm over the entire surface of the other rotor.
It has been given a hardness of about m.

[Effect]

One rotor surface is plated with a relatively high hardness of about 20 μm, so the plating thickness error is 1 to 2 μm.
It has good accuracy and the necessary rust prevention ability. One rotor surface has a soft self-lubricating 30~40μ
Since the coated surface is coated with a thickness of approximately 1.5 m, even if the coated surface and the plated surface come into contact due to accumulation of misalignment of the parts, one rotor has self-lubricating properties, so metal contact between the rotors will cause burnout, etc. That's not true. In addition, the interference film thickness between the coating layer and the mating surface is usually about 10 ILm, and even if this interference is scraped off, a coating layer of about 20 to 30 μm remains, so this anti-corrosion ability makes the rotor No problems caused by corrosion.

As a result, the rotor can maintain a minimum gap over a long period of time, ensuring maximum compression or vacuum performance without compromising machine reliability.

〔Example〕

Figure 1 shows the basic profiles of both male and female rotors.

Here, the female rotor is AIB: An arc centered on point S and with a radius of R7 B-C: A curve created by the male rotor arc tooth profile G-H C-D: Centered on point P on the pitch circle arc D-E
: Parabola with point U as focal point and D-U as focal length E-A2: Circular arc Am centered on point R and radius R5 At: Circular arc centered on female rotor center 4 Male rotor is FtG: Female rotor Curve G-H created by the circular arc tooth profile At -B: Arc H-I centered on point T and radius R6: Arc I-J centered on point P on the pitch circle: Parabolic tooth profile of female rotor Curve J-Fz created by D-E: Curve F2 created by the circular tooth profile E-Az of the female rotor.F1: An arc centered on the center 3 of the male rotor.

Oil-free screw machines do not allow rotors to contact each other, and if contact occurs, it may produce abnormal noises or even cause
This will cause burn-in. However, if the gap between the rotors is too large, compressed air may backflow or leak, resulting in decreased performance, so it is necessary to keep the gap to the minimum necessary. 1st
The profiles in the figure are theoretically determined profiles with no gaps created by each other. Therefore, in practice, for example, thermal expansion,
It must be machined with modifications to the coating thickness, etc.

Figure 2 shows the normal gap distribution between the male and female rotor surfaces at room temperature. The discharge end surface temperature of the rotor of a single-stage oil-free screw compressor during operation is about 20° higher than the suction end surface temperature.
0℃ higher. This rotor was created by considering the minimum coating and surface treatment film thickness necessary for rust prevention during rotation, and also taking into consideration timing gears, bearing backlash and gaps, and a multi-lead design. was introduced and cut into gears at room temperature of 20°C.

The horizontal axis of FIG. 2 shows the result when the rotor shown in FIG. 1 is treated as described above and rotated while maintaining a small gap. , indicates the opposing point of the female rotor, that is, the meshing point,
The vertical axis shows the rotor skin-to-tooth normal gap at that time.

The right side of the meshing points H and C is the forward movement plane, that is, the points I, J and Fo of the male rotor 1 and the points D and E of the female rotor 2 shown in FIG.
, shows the flank of Ao, and the left side of points H and C is the backward plane,
That is, points I, G, and Fo of the male rotor 1 shown in FIG. 1, and points D, C, and Ao of the female rotor shown in FIG.

Among the three curves shown in Fig. 2, curve 5 represents the inter-rotor tooth normal gap at a position 5nII+ in the axial direction from the discharge end face, and curves 6 and 7 represent the gap at the center and from the suction end face, respectively. It is shown at a position 5IIn in the axial direction.

A self-lubricating coating is applied to the surface of one rotor (for example, male rotor 1) and a hard plating is applied to the surface of the other rotor (for example, female rotor 2) in the inter-rotor gap at point B in Figure 2. FIG. 3 shows the gap between the surfaces of the rotor after the corresponding surface treatment.

If a suitable thickness of surface treatment (coating and plating) is applied to both the male and female rotors, the gap between the rotors after the rotor surface treatment will theoretically be O at point B, and interference (jumping) between the rotors will occur. This is the ideal state. However, in reality, misalignment occurs due to the influence of the machining accuracy of each part, so there is interference, but according to this example,
Since only one rotor is coated with a soft self-lubricating coating, the hardness of the other rotor is ground to the optimum condition, allowing the machine to maintain high performance over a long period of time with a small gap. It can be operated while maintaining the rotor, and has the effect of preventing burnout due to contact between rotor metal surfaces and rust prevention due to rotor surface treatment. [Effects of the Invention] Since the present invention is configured as described above, it produces the effects described below.

One rotor surface has a soft self-lubricating coating, and the other rotor surface has a hard plating, so even if they interfere with each other, the softer coating can be easily scraped off to the optimum condition, so there is no possibility of peeling of the coating. There are no problems such as this, the optimum gap can be maintained, high efficiency can be achieved, and the noise can be reduced because operation can be performed while maintaining a small gap.

Furthermore, both rotors are surface-treated to a certain thickness, so the rotors will not corrode. In addition, the surface treatment of one of the rotors is plating, and the plating accuracy is usually 1 to 2 μm, which is higher precision than coating, so maintenance and management of the minimum required coating thickness is possible for both of them. The quality is superior to that of treated products.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a basic profile of an embodiment of the present invention,
FIG. 2 is an explanatory diagram of the right angle gap between the rotor surfaces, and FIG. 3 is an explanatory diagram of the right angle gap between the surfaces after the rotor surface treatment. l...male rotor, 2...female rotor, 3...male rotor middle 4...female rotor center.

Claims (1)

[Claims] 1. Two rotors that rotate in synch with each other and mesh with each other. One surface of the rotor is coated with a soft self-lubricating material, and the other surface is coated with a hard material with an appropriate thickness. A screw rotating machine characterized by: