JP2779014B2 - Oil-free screw fluid machine - Google Patents

Description

The present invention relates to an oil-free screw fluid machine, for example,
It relates to an oil-free screw compressor (including a square screw compressor) or an oil-free screw vacuum pump (including a square screw vacuum pump).

[Prior Art] An oil-free screw fluid machine engages a screw-shaped male and female rotor in a casing with a small gap so as not to contact with each other, drives both rotors via a timing gear outside the casing, and connects between the rotors. No oil is used in the casing. The rotor surface is coated for rust prevention or the like.

[Problems to be Solved by the Invention] In the conventional technology, it is not clear how to determine the film thickness of the coating. No decision has been made. For this reason, if the coating is too thick,
Unnecessary noise and vibration are generated, and depending on the coating material, peeling from the rotor ground surface occurs. On the other hand, if the coating is too thin, there is a problem that the rust prevention ability of the coating is reduced and the performance is reduced due to the spread of the cap between rotors.

A coating of a brittle material is applied to the surface of the rotor at a certain thickness, and when the rotor contacts during operation, the coating is rubbed off by the amount of interference. The gap between the rotors widens, and gas leaks or flows backward from this gap, so that the performance is reduced. Conversely, if the coating film thickness is too thick, the phases of the male and female rotors cannot be taken correctly at the time of assembly, and the grounds of both rotors will come into contact with each other, generating abnormal noise and vibration, and eventually, the rotors will burn out. Sometimes.

[Means for Solving the Problems] The present invention is intended to solve the problems described above,
The oil-free screw fluid machine according to the present invention is an oil-free screw fluid machine in which a rust prevention coating film is applied to a female rotor and a male rotor, wherein the coating film is formed by applying a coating material of a brittle material to the surface of the rotor. The thickness reduction of each of the male rotor and female rotor without gaps theoretically obtained based on at least the thickness of the coating film, the backlash of the timing gear, and the thermal expansion of each rotor. To set the ground surface of each rotor,
At room temperature on the ground surface, each rotor is formed by applying a substantially uniform coating film thickness within a range where the male and female rotors can take a correct relative position, and the male and female rotors are maintained in a correct relative phase. By rotating, when both rotors come into contact during operation, the coating is rubbed by the amount of interference, so that both rotors with the coating film are kept in a non-contact state while maintaining the minimum necessary gap in the operating state. It is characterized by having made it.

[Operation] By increasing the coating film thickness in a range where both the male and female rotors can be kept in a correct phase relationship, the performance can be maintained and the rotor skin contact can be prevented.

[Embodiment] Fig. 1 shows basic profiles of both male and female rotors of a screw fluid machine. Each section shown in the profile of the female rotor has the following curve.

A ₁ -B: An arc centered on the point S and having a radius of R7 B -C: A curve created by the arc tooth profile GH of the male rotor C -D: An arc D centered on the point P on the pitch circle -E: parabola E -A ₂ the point U to the D-U and the focal length at the focal: around the point R, the arc a ₂ -A ₁ where the radius is R5 (tooth next to): the female rotor center 4 Each section shown in the profile of the male rotor profile with the center is the following curve.

F ₁ -G: A curve created by the arc tooth profile A ₁ -B of the female rotor G -H: An arc centered on the point T and having a radius of R6 H -I: An arc centered on the point P on the pitch circle I -J: curves are created in the female rotor parabolic tooth profile D-E J -F _2: curve F ₂ -F ₁ is created by an arc tooth profile E-a ₂ of the female rotor (tooth next): male rotor By the way, in the oil-free screw machine, contact between the rotors is not allowed, and if contact occurs, an abnormal noise is generated and, consequently, seizure occurs. However, even if the gap between the rotors is made large, the backflow of the compressed air and the leakage occur, and the performance is deteriorated. The profile in FIG.
These are theoretically determined gap-free profiles created by each other. Therefore, in practice, the rotor surface (the machined surface of the rotor metal itself) must be machined by adding corrections such as thermal expansion and coating film thickness to the basic profile.

During operation of the single-stage oilless screw compressor rotor, the discharge-side end surface temperature is about 200 ° C higher than the revenue-side end surface temperature. Considering the thermal expansion during operation due to such temperature, the minimum coating film thickness required for rust prevention during operation is appropriately assumed, and further, the backlash and clearance of timing gears and bearings are assumed, and FIG. 2 shows the distribution of the tooth perpendicularity gap at room temperature between the skins of the male and female rotors cut at room temperature at 20 ° C. at room temperature, taking into account these facts. In FIG. 2, the phase relationship between the two rotors is the same as that of the basic profile shown in FIG.

The horizontal axis in FIG. 2 is the point at which the male and female rotors face each other, that is, the meshing point when the rotors shown in FIG. 1 are subjected to the above-described treatment and rotated in a correct phase relationship while maintaining a small gap. And the vertical axis indicates the perpendicular angle gap between the rotor skins between the meshing points at that time. For example, the notation "G, B" on the horizontal axis in FIG. 2 indicates that the point G and point B in FIG. 1 are meshing points, and the point G when these two points G and B come closest. The vertical axis of the graph shows the tooth perpendicularity gap between the rotor surfaces in B of FIG. Other _{"F 1, A 1], [} H, C "
And so on. The right side of the mesh points I and D indicates the flank of the forward surface, that is, the points I, J and F _{0 of} the male rotor 1 and the points D, E and A ₀ of the female rotor 2 shown in FIG. Are the reverse plane, that is, points I, G, F _{0 of} the female rotor 1 shown in FIG.
Shows D, C, a point meshing in the flank of A ₀ points.

Of the three curves shown in FIG. 2, curve 5 is the perpendicular gap between rotor skin teeth at a position 5 mm in the axial direction from the discharge-side end face, and curves 6 and 7 are the central and suction-side end faces, respectively. These are shown at a position 5 mm axially from.

As can be seen in FIG. 2, the minimum value of the gap between the rotor ground teeth at right angles is at point b on the reversing surface. Larger than.

FIG. 2 shows a state where the phases of the male and female rotors are in the basic profile shown in FIG. At this time, when the coating of the male and female rotors is applied to the surfaces of the male and female rotors almost uniformly on the surfaces of the rotor at the point b in FIG. The perpendicularity gap between the coating surfaces is shown in FIG. As shown in FIG. 3, when the coating having such a thickness is applied to both the male and female rotors, the tooth perpendicular gap between the rotor coating surfaces becomes zero at the point b, and the interference between the rotors (interference) ), The phases of the male and female rotors can be brought to the state of the basic profile shown in FIG. If the coating film thickness is further increased more than necessary, the male and female rotors abut each other up to the point b, and the phase of both rotors will be tightly packed on the forward side, so that the forward side interferes during operation. Will be. Therefore, it can be seen that no more coating can be applied to the male and female rotors.

Next, FIG. 4 shows the rotor coating surface when both the male and female rotors are coated with a thickness of half the gap at point b in FIG. 2 during operation, that is, when the rotor thermally expands. 4 shows a tooth perpendicularity gap. FIG. 5 shows the perpendicular gap between the rotor skin teeth in this case.

In FIG. 4, when both rotors are rotated in the correct phase relationship, the hatched portion has a gap between the coating surfaces, and the portion other than the hatched portion, that is, the right angle gap between the rotor coating surfaces. Is less than 0, which means that the coatings on both the male and female rotor surfaces wear and rub off each other. For this reason, if the coating is ideally scraped to the minimum necessary, the gap between the male and female rotor coating surfaces is zero in portions other than the hatched portions in FIG. Only the hatched portion shown in curve 7 has a gap. On the other hand, as shown in FIG. 5, it can be seen that the minimum coating required for rust prevention and the like remains on both the male and female rotors at least with the coating film thickness.

[Effects of the Invention] In the present invention, both the rotors coated with the coating film are kept in the non-contact state while maintaining the minimum necessary gap in the operating state, so that the rust prevention effect of the rotor and the peeling prevention effect of the coating film are obtained. At the same time.

That is, according to the present invention, the minimum coating thickness required for rust prevention is ensured, and the rust prevention capability of the rotor is improved. Minimum wear of the coating ensures performance by filling the rotor gap. By properly allocating the gap between the forward and reverse surfaces between the male and female rotors, a contact accident between the rotors during operation can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic profile of both male and female rotors,
FIG. 2 is a diagram showing a rotor surface tooth perpendicularity gap at the time of assembly, FIG. 3 is a diagram showing a rotor coating surface tooth perpendicularity gap at the time of assembly, and FIG. FIG. 5 is a diagram showing a gap between right angles between teeth of the rotor during operation. 1 ... male rotor 2 ... female rotor 3 ... center of male rotor 4 ... center of female rotor

Claims (1)

(57) [Claims] 1. An oil-free screw fluid machine in which a rust prevention coating film is applied to a male rotor and a female rotor, wherein the coating film is formed by applying a brittle coating material to the surface of the rotor. The thickness of the coating film, the backlash of the timing gear and the thermal expansion of each rotor are corrected to reduce the thickness of the respective profiles of the male rotor and the female rotor without gaps theoretically obtained. Set the ground surface of the rotor, and at room temperature,
Each rotor is formed by applying a substantially uniform coating film thickness within a range in which the female and female rotors can take the correct relative phase.
By rotating both female rotors while maintaining the correct relative phase, when the two rotors come into contact during operation, the coating is rubbed off by the amount of interference, and both rotors coated with a coating film in the operating state have the minimum necessary An oil-free screw fluid machine characterized in that the gap is maintained in a non-contact state.