WO2002103205A1

WO2002103205A1 - Profiled contour of the spindle rotors of a spindle pump

Info

Publication number: WO2002103205A1
Application number: PCT/EP2002/005775
Authority: WO
Inventors: Ralf Steffens
Original assignee: Ralf Steffens
Priority date: 2001-06-19
Filing date: 2002-05-25
Publication date: 2002-12-27
Also published as: DE10129341A1

Abstract

The invention relates to a profiled contour a pair of rotors associated with a dry-compressing spindle pump in the form of a two-shaft positive displacement machine for conveying and compacting gases. In order to reduce compression power with the aid of a modifiable rotor spindle pitch, enabling sufficiently high inner compression without using bypass valves and achieving a more uniform distribution of compression power along the rotor axis, the profiled contour is provided with an increasing profile relief in each front section in relation the specific toothing law as the spindle pitch decreases. Preferably, said profile relief occurs in the head profile area above the pitch circle for the spindle rotor pair. No profile relief is provided in the inlet area of the spindle rotor for low z-values.

Description

PROFILE CONTOUR OF THE SPINDLE ROTORS OF A SPINDLE PUMP

The invention relates to a dry-compressing spindle pump, in particular a vacuum pump, which is designed as a two-shaft displacement machine for conveying and compressing gases with a pair of oppositely identical spindle rotors with internal compression via variable spindle pitch along the spindle rotor axis, the spindle rotors being designed in mirror-image matching.

Dry-compressing pumps are becoming increasingly important, particularly in vacuum pumps, because due to increasing obligations regarding environmental protection regulations and increasing operating and disposal costs as well as increased requirements regarding the purity of the pumped medium, the well-known wet-running vacuum systems, such as liquid ring machines and rotary vane pumps, are increasingly being replaced by dry-compressing pumps , These dry compacting machines include screw pumps, claw pumps, diaphragm pumps, piston pumps, scroll machines and Roots pumps. What these machines have in common, however, is that they still do not meet today's requirements in terms of reliability and robustness, as well as size and weight, and at the same time a low price level. At the moment, the market is still clearly dominated by the wet-running vacuum pumps of the liquid ring machines and the oil-lubricated rotary vane pumps.

Compared to these wet-running machines, dry-compressing vacuum pumps have the basic advantage that their rotor speed is not restricted as much as the positive displacement machines with an operating fluid in the working cavities. In addition to improving the volumetric efficiency, this can primarily achieve a significant reduction in the cost of the machine. At the same time, it is desirable to reduce the drive power required, which is known to be achieved with dry-compression spindle pumps as 2-shaft displacement machines by internal compression. The working chamber volume enclosed on the inlet side is reduced by a certain factor during transport along the rotor axis in the direction of the fluid outlet, for example by reducing the rotor spindle increase and / or the profile tooth height. The higher the ratio of the working chamber volume on the inlet to the outlet side, the lower the power consumption in the thermally particularly critical final pressure operation, ie in the so-called “zero delivery”, if there is no mass flow of the pumped medium, but the full pressure difference is present very high internal compression ratio (from factor 2 to 3, for example) a critical over-compression for higher intake pressures because the working chamber volume is geometrically reduced along the rotor axis, so that working chamber pressures in the direction of the gas outlet then develop significantly above atmospheric pressure depending on the level of internal compression As a known remedy, bypass valves are provided which open automatically at higher pressures along the rotor axis, for example via spring-loaded valve balls, and so on Release the excess pressure in the outlet direction. However, the bypass valves in dry rotors often have problems with sticking and material deposition, so that the function is impaired.

Furthermore, with the known dry-compressing spindle pumps, the power conversion along the rotor axis is Favorably distributed that the largest part of the compression performance is only implemented in the last rotor end area on the output side, so that correspondingly high temperatures occur during compression.

The object of the present invention is to find a solution for a dry-compressing spindle pump that is as simple and robust as possible and particularly inexpensive, which on the one hand dispenses with bypass valves and on the other hand nevertheless enables a high internal compression ratio with a more favorable distribution of the compression performance along the rotor axis.

The basis of the following invention is the German patent application 101 02 341.3 with a profile contour profile determined by the processing tool for the rotor pair of a screw pump.

According to the invention, this object is achieved in that the profile contour of the spindle rotors is designed with an increasing flank relief in each face cut compared to the profile contour specific to the gearing law.

The invention therefore provides that the profile contour profile for the pair of spindle rotors is changed in the end section along the rotor axis in such a way that the profile contour in the longitudinal direction of the rotor toward the outlet side in the sense of gas backflow with increasingly larger flank gap openings is carried out as partial flank recesses in the profile contour rolling of the rotor pair. For this purpose, in the head profile area above the pitch circle, the actually produced flank contour is theoretically compared to that determined according to the gearing law TARGET profile profile in the respective face cut is withdrawn so that this partial flank reduction in the longitudinal direction of the rotor towards the outlet leads to an increasing gap between the rolling profile flanks of the pair of rotor spindles in the face cut. This results in different end cut profiles along the rotor axis. This targeted flank relief can advantageously be achieved very easily with very little effort by the approach of the tool-specific profile contour described in German patent application 101 02 341.3.

In principle, the rotor profile rolling in the face cut is assessed using the toothing law. Based on the pitch circle, a distinction is made between a base profile area below the pitch circle and a head profile area above the pitch circle. In the face cut, the tooth area of the one spindle rotor is subject to the head area of the counter rotor and vice versa. Compared to the prior art, however, this profile contour is not kept constant in the frontal section over the entire longitudinal axis of the rotor, but in the axial direction towards the outlet, the flank profile is preferably increasingly withdrawn in the head profile area, so that a pressure reduction can take place between the individual working chambers via the gas backflow. This creates a certain internal bypass function so that the known external bypass valves can be omitted. The amount of internal compression, on the other hand, can be increased in the sense of the desired performance saving. Furthermore, by eliminating the bypass valves, the pump housing is simplified in such a way that the manufacture of the pump housing can be easily converted to a simple extruded profile.

Furthermore, this increased internal leakage The compressor output along the spindle rotor axis is better distributed in the desired sense by not only converting the main part of the compressor output at the rotor end on the outlet side, but by distributing the compressor output better over a longer rotor area, so that heat dissipation is cheaper and the well-known extreme ones Temperature peaks can be avoided better. To ensure the desired compression capacity of the spindle pump, the increased internal leakage is compensated for by a higher number of stages. This increases the number of closed working chambers between the inlet and outlet of the spindle pump, and the rotor length generally increases.

An embodiment of the invention is described below with reference to the drawing. It shows in a partly very schematic representation:

1 shows a spindle rotor which, in a dry-compressing spindle pump, not shown in detail, interacts with a counter-spindle rotor which corresponds in mirror image, and

2 shows, by way of example, various end cuts for individual z positions of the spindle rotor with the increasing flank relief according to the invention.

In the exemplary embodiment described below, a spindle rotor 1 is shown in FIG. 1, which in the actual spindle pump rolls in opposite directions with a counter-spindle rotor, the pitch of which is exactly inversely oriented, but otherwise has exactly the same dimensions and profile flanks for reasons of simple manufacture (= known prior art). The Spindle rotor 1 has the length l, the outer diameter 0D and the profile tooth depth h. On the inlet side the rotor has the spindle pitch m _E i _N and on the outlet side the pitch m _AUS with the respective angle of increase ß _E iN _{/ AUS} ^{un (} ä an intermediate range in which the pitch m _E ι _{N is} reduced to the pitch m _AU s (= more known State of the art) .

The rotor-fixed coordinate system defines the face cut in the xy plane, whereas the z-axis runs along the rotor axis, with the inlet-side rotor face and z = (.) The outlet-side rotor face being clearly defined at z = 0. Based on German patent application 101 02 341.3 shows an example of the tool WZ for manufacturing the profile flanks, with which the profile design according to the invention can be implemented in a particularly favorable manner in the face cut according to FIG. 2.

Various end cuts for individual z positions are shown by way of example in FIG. 2, only one individual profile flank side being shown in a simplified manner. The complete forehead incision is made by simple symmetrical mirroring according to the number of teeth. In this FIG. 2, the invention is made very clear by the fact that the profile end cut flanks of the various z positions are all rotated in such a way that they all pass through the profile point C on the pitch circle 3 in this illustration. The foot profile flank 5 runs between the profile point A on the base circle 2 and the point C on the pitch circle 3, whereas the head profile contour 6 associated according to the toothing law runs between the point C and the profile point E on the tip circle 4 with diameter 0D. The invention is shown by way of example for the modification on the profile of the head profile. On the rotor spindle input side at z = 0, the face cut of the profile flank via foot contour 5 and head profile 6 still corresponds exactly to the course according to the toothing law, so there is no flank relief yet, so that the head profile flank of one spindle rotor rolls exactly with the foot course of the counter rotor according to the toothing law.

For the following frontal cut at z = zi, according to the invention, the flank relief is clearly recognizable for the head profile course 7 between the profile points C and Ei, which is already clear with the next frontal cut at z = z for the head profile course 8 between the profile points C and E ₂ is increased to at the smallest spindle pitch m _AUS in the last forehead section at z = £ for the head profile profile 9 between the

Points C and E ^ have reached the maximum value.

This withdrawal of the head profile flank can be described and recorded, for example, in the forehead section using the central angle y. This retraction of the profile flank depending on the z position in the face section via the value for the central angle y comprises several angular degrees in the x-y plane and is preferably in an angular range between 5 ° and 25 °.

Of course, the flank relief can also be applied to the foot profile area: separately or in combination with the head profile area. In any case, it is crucial according to the invention that this form of flank relief increases as a function of the z position with decreasing spindle increase along the spindle rotor axis. On the one hand, the bypass function is specifically shifted into the spindle profile, so that higher values for the internal compression ratio can be achieved, and at the same time a new type of power distribution tion along the spindle rotor axis by no longer converting most of the compaction performance on one side at the rotor end as before.

This profile contour according to the invention is preferably produced in accordance with German patent application 101 02 341.3 using a particularly simple tool for profile processing.

The invention relates to the profile contour for the rotor pair of a dry-compressing spindle pump as a 2-shaft displacement machine for conveying and compressing gases. In order to enable a sufficiently high internal compression to reduce the compressor output via a variable rotor spindle pitch without the use of bypass valves and at the same time to achieve a more uniform distribution of the compressor output along the rotor axis, it is proposed that the profile contour in each face cut compared to the specific toothing law Profile contour with an increasing flank retraction with decreasing spindle increase. This flank relief is preferably carried out in the head profile area above the pitch circle for the spindle rotor pair, with no flank relief being provided in the inlet region of the spindle rotor when the z values are low.

/ claims LIST OF REFERENCE NUMBERS

1. Spindle rotor with different pitch falling from m _ON to m _OFF

Rotor length l

Outer diameter 0D profile tooth depth h

2. Foot circle of the spindle rotor

3rd pitch circle of the pair of spindle rotors

4. Head circle of the spindle rotor

5. Foot profile flank from profile point A to profile point C

6. Head profile flank at z = 0 without flank relief in accordance with the toothing law from profile point C to profile point E

7. Head profile flank at z = zi with a small flank relief from profile point C to profile point E-i

8. Head profile flank at z = z ₂ with higher flank relief from profile point C to profile point E ₂

9. Head profile flank at z - with the highest flank relief

from profile point C to profile point E ^

Claims

claims

1. Dry-compressing spindle pump, in particular a vacuum pump, which is designed as a two-shaft displacement machine for conveying and compressing gases with a pair of oppositely identical spindle rotors (1) with internal compression via variable spindle pitch along the spindle rotor axis, the spindle rotors being designed in mirror image are characterized in that the profile contour of the spindle rotors (1) is designed with an increasing flank relief in each face cut compared to the profile contour specific to the gearing law.

2. Dry-compressing spindle pump according to claim 1, characterized in that the spindle rotors (1) have no flank relief in the inlet area of the spindle pump with low z values.

3. Dry-compressing spindle pump according to claim 1, characterized in that the flank relief in the head profile area (7, 8, 9) above the pitch circle (3) is provided for the spindle rotor pair.

4. Dry-compressing spindle pump according to one of the preceding claims, characterized in that the central angle (y) as a measure of the extent of the flank relief in the end cut is in the angular range between 5 ° and 25 °.

5. Dry-compressing spindle pump according to one of the preceding claims, characterized in that the function for the flank relief over the longitudinal axis of the rotor up to the central angle (γ) from the tool for profile machining is determined.

Dry-compressing spindle pump according to one of the preceding claims, characterized in that the number of stages and rotor length are increased for the spindle rotor (1).