WO2001023761A1 - Scroll-type compressor or vacuum pump - Google Patents

Abstract

The invention concerns closed system rotary machines, wherein a base cell of the closed system compresses a gas fluid, comprising a mobile rotor (1), consisting of two scrolls of opposite direction, defined by all kinds of mathematical curves, including arcs, preferably having common tangents at their junction points (B, B1, B2, B3,...), any point of the rotor describing a circle with radius E, and forming the same angle, at the same time, with its starting point, while the cell of the fixed stator (2) is the housing of several successive positions of the rotor (1), the open loop is linked to the suction part (As) and the closed loop to the delivery part (Re). The invention is applicable to self-lubricating or liquid injection air or gas compressor or vacuum pumps.

Description

 COMPRESSOR OR VACUUM SPIRAL PUMP

The present invention relates to a new type of capsulism for a rotary machine conveying a gaseous fluid and which can function as a compressor or as a vacuum pump.

The term capsulism designates the production of a variable closed volume.

The invention relates more precisely to a new family of “dry” vacuum compressors or pumps, in particular a family of particularly compact, light, one, two or three stage air or gas compressors which can discharge under low pressure, medium or high (for example 3, 8 or 20 bars, respectively).

The invention aims to compete with both:

• small oil-injected screw compressors, intended for the transport, industry, public works and building markets, whose simplicity of design of the compressor itself is complicated and weighed down by numerous accessories (regulation, separator tank, pipes and oil filter);

• small piston compressors, which require a tank and generate noise and trepidation.

Consequently, the compressors sought must be compact, therefore having a large ratio of aspirated volume, or cubic capacity, to the total volume of the compression chamber. However, the length of this chamber being constant for a given rotary compressor, it will be clearer to speak about the report: drawn section, on total section (limited by the bores and their common tangents, i.e. including the concave parts) of the chamber compression. This report will hereinafter be referred to as the "aspiration rate".

These sought-after compressors must also be light, and rotors with a large core (screw or toothed compressors) should be avoided.

In this respect, the scroll compressor with orbital movement seems to satisfy the above objectives, but it is not free from defects:

• when it has a central shaft and an outer shaft, it remains limited to low pressures and, moreover, the two shafts are different because the one located in the center must withstand almost all the efforts;

• when it does not have a shaft crossing the spirals, the rotor must be kept in overhang, which implies larger bearings, therefore heavier and bulky;

• moreover, this type of compressor only rises very gradually in pressure and must have several turns to reach only low pressure, or medium pressure for very small flows. It then has long lines of flight, hence the use of segments at the end of the rotor blades (except for very low pressures) rubbing on the stator, and vice versa. This use of dry rubbing segments strongly limits the speed of rotation. The leaks between the curved walls of the fixed (stator) and mobile (rotor) spirals, which can be assumed to be constant whatever the rotation speed, take on more importance compared to a lower flow. In addition, the progressive curvatures generate a low coefficient of upstream-downstream pressure drop, and favor leaks. The friction of the segments added to these leaks and to the fact that the compression is very progressive, causes additional heating during compression, to the detriment of the efficiency of the compressors of this type.

The present invention aims to remedy the aforementioned drawbacks:

• using a new profile allowing much faster or brutal compression, limiting leaks;

• by having one of the highest suction rates of compressors known to date, thus allowing greater compactness, resulting in shorter creepage distances. In addition, this higher suction rate allows the use, for the same displacement, of a radius of eccentricity (each point of the rotor describing the same circular movement, in the plane orthogonal to the drive shafts) ; • if the compressor retains segments at the end of the blades, keeping the product constant: rotation speed x eccentricity, and therefore constant the friction speed of the segments. To compare it to the scroll compressor, the speed is increased in inverse ratio to the decrease in eccentricity, which allows to further increase the compactness, again reducing the displacement, which is practically halved.

Another possibility is open by eliminating the segments at the end of the blades, greatly increasing the speed of rotation, hence a very marked reduction in the cubic capacity, the length of the creepage distances, the bulk and the weight. compressors thus produced. These are less noisy, the air pulses being weaker and more numerous.

Regarding medium pressure compressors, they are designed with low pressure cells, delivering to an air or gas refrigerant, and medium pressure, sucking in this same refrigerant, which improves compression efficiency and avoids temperatures and deformations profiles, due to the heat given off by the compressed air, prohibitive.

As for high pressure compressors, they obviously have a refrigerant at the outlet of the first two stages, for the same reasons.

More precisely, if the simplest elementary cell is called “basic cell”, it will be seen that, in the context of the invention, it is possible to have, in the same compression chamber, several basic cells, for example two or more identical cells (simple or juxtaposed) for low pressure, and similarly for medium pressure. The fact that the low pressure part and the medium pressure part are in the same chamber brings obviously a great simplification of design and a gain in weight, compactness, in cost price. The conclusions are the same if there is also a high pressure part.

The invention relates, in its most general sense, to a capsulism for a rotary machine conveying a gaseous fluid and capable of operating as a compressor or as a vacuum pump, characterized in that the blade of the movable rotor (1) of a base cell consists of two spirals in opposite directions, the first communicating with the suction As and the second with the discharge Re, these two spirals giving the rotor the shape of the letter "C" with a total angle AT greater than 360 °, where AT denotes the total angle formed between the normal of a first end of the median curved line of the rotor, and the normal of the opposite end.

The fact that the total angle is greater than 360 ° results in a form of "C" coiling on itself.

Preferably, the radius of curvature of the midline increases from each of the ends, up to a maximum radius for the middle zone of the capsulism.

For the purposes of this patent, the term “compression ratio” will be understood to mean the ratio between the volume of the compression chamber when the compression orifice is closed, and the volume of this compression chamber when the compression is opened. delivery port. The concepts of "compression" and "compressor" within the meaning of this patent will relate to this definition.

The essential technical characteristic of the capsulism according to the invention relates to the angle formed between the extreme rays, which is greater than 360 °.

This characteristic is contrary to what could be observed in known capsulisms.

In particular, French patent FR825643 describes a device comprising closed chambers having a total angle less than 360 °. The patent US1967957 also describes a device having a traditional capsulism, not making it possible to produce a compressor within the meaning of the present patent, nor a vacuum pump.

It is the same for Japanese patents 59147892 or 59141786, American US1378065 or US4606711 or German DE19614477

The invention will be better understood by referring to the description below, made with reference to the accompanying drawings.

First, we will define the basic cell, which includes two compression cells. The rotor, as in scroll compressors, is driven by two parallel shafts by means of two eccentrics of the same eccentricity E. Each point of the rotor therefore describes, in its movement, a circle, or an "orbit", of radius E. Referring to FIG. 1, we consider three parallel curves, more precisely two envelope curves C2, C3 of circles T of the same radius E, the center of which moves on a given curve Cl.

Through the center of each circle T, there is a straight line with direction Δ. Only one of these lines cuts T and C2 simultaneously in E2, T and C3 in E3, at the points for which Δ is perpendicular to the tangents to C2, C3, T, therefore to Cl.

Referring to Figure 2, if we move the curve Cl from E in the direction Δ, it comes to Cl and meets C2 in E2, and only in E2, the radius of curvature of Cl in E2 being less than E to that of C2.

We would also show that if we move Cl from

-E according to Δ, it meets C3 in E3, and only in E3.

The simplest possible basic cell has the shape of the letter C. In the following, a theoretical cell is described, in which the blade or the rotor blade, in the section orthogonal to the axes of the drive shafts, has no thickness, which simplifies the description.

Referring to FIG. 3, a rotor 1 being assumed to have zero eccentricity, compared to a fixed stator 2, will be said to be “in the middle position” - which it never occupies in practice, its eccentricity being always equal to E -. Its dawn has the shape of a C. The fixed stator is the envelope of circles of radius E centered on the rotor in the middle position.

Curve C can be made up of two spirals in opposite directions, one of direction -, going from the suction As towards B, and one of direction +, going from the discharge Re towards B.

It can also be defined by all kinds of mathematical curves, provided that the tangent at B is common to the two curves (a break in the generating curve causes a leak at the lower curve of the stator) or, rather, that the tangents of the successive curves are common to their meeting points B, Bl, B2, B3, ...

Curve C should form, on the discharge Re, a loop which is all the more closed as the higher discharge pressure is desired. It will suffice that it stops horizontally, or almost, at the suction

As.

The center line of the rotor (1) has two ends (110, 111). The normals respectively (100) and (101) at the ends (110, 111) form between them a total angle exceeding 360 °, in the example described in FIG. 3, this total angle approaches 500 °.

The radius of curvature of the center line of the rotor gradually increases from each of the ends, to an intermediate zone.

The progression of the radius of curvature is not symmetrical with respect to this central zone. Referring to Figure 4, this shows the successive phases of compression in a basic cell. The shaded parts show the alveoli communicating with the suction, until the latter is closed, and those hatched the alveoli expelling the compressed air in the discharge port. Suction and discharge are uninterrupted, and the result is that the compression principle itself reduces the pulsations of air and noise at the upstream and downstream ports.

The dials show the common angle of rotation of the two drive eccentrics.

It can be seen that an upper cell and a lower cell fill up once per turn, and discharge before half a turn.

The theoretical cubic capacity of the cell is equal to the sum of the areas SA and SB multiplied by the length of the compression chamber, or of the rotor, parallel to the axes of the drive shafts.

Referring now to FIG. 5, the scroll compressor consists of successive envelopes of the same basic spiral, generated by circles Tl, T2, T3 ... of the same radius E, located on the same normal N to the basic spiral, in Re, whose centers describe, by turning, the rotor (assumed to have no thickness) in the middle position, and whose intersections with N describe the stator.

On the contrary, the basic cell of the C-shaped compressor has its stator defined directly by the envelope of the circles sliding on the rotor serving as generator.

Instead of being formed in two spirals in opposite directions, the rotor curve can be, in the context of the invention, described by several arcs of successive circles.

We notice :

• on the one hand with reference to FIG. 6, that the fact of using arcs of circles simplifies the equations of the stator and the rotor: the latter being in the middle position, let Cl be one of its arcs of circles center Ωl, with radius RI and arc αl. The arcs of circles Cl and C »1 of the stator have the same center Ωl, same angle αl, and for radii R'1 = R1 + E and R» 1 = R1-E. The center Ω2 of the arcs of circles C2, C'2, C »2 is located on the line Δ12, passing through Ωl and limiting the arcs Cl, Cl and C» 1 on this line. Likewise, the center Ω0 of the arcs to the left of Δ01 is on Δ01, and the center Ω3 of the arcs to the right of Δ23 is on Δ23, and so on.

• on the other hand, with reference to FIG. 7, that if the center Ω of the largest radius R of two opposite cells is common, the external shape of the chamber is a circle of this same radius R, limited by the tangents T common to both cells.

The above form is simple, and gives the same maximum speed of movement for the two cells.

It may be preferable to a more flattened shape, such as that shown in FIG. 8, in the aim of obtaining a higher air movement speed, for a given eccentricity, and therefore a better suction rate.

The maximum speed of the air in the cell is indeed ω.R, and the orbital speed of any point of the rotor is ω.E, which makes it possible to multiply the speed in the R / E ratio, and therefore of obtain a high flow rate in a small footprint, the R / E ratio can exceed 10.

Referring now to Figure 9, this shows a compression chamber in which the drive shafts do not pass through the rotor, which is cantilevered.

On the contrary, with reference to FIG. 10, this represents a version in which the two shafts provided with eccentrics cross the rotor, on a low pressure compressor with cells juxtaposed two by two.

Referring to FIG. 11, this represents the diagram of a medium pressure compressor: the two large cells discharge the compressed air into an Rfl refrigerant then until the final pressure in the two small cells. A final refrigerant Rf2 completes this achievement.

In the preceding figures, the cells are grouped head to tail, to reduce the reactions of the bearings. The trees which appear there, subjected to the same efforts on average, for reason of symmetry, can be identical as well as their seals, bearings and counterweights.

However, an asymmetrical construction remains possible, within the framework of the invention, by referring for example to FIG. 12, which shows a three-stage compressor with through shafts.

Except for very low pressure compressors, there is always an interest in opposing two rotors, with the same transverse profile, back to back, as shown in Figure 13 (or it may be a single rotor dug on its right and on its left), or at a distance, as shown in Figure 14, so as to suppress any axial thrust.

This provided that the two halves of the stator and their orifices have the same cross section to properly balance the axial forces.

Of course, the rotors must be balanced radially, especially if the rotational speed is high, but this is easy to achieve, because said rotors have a low mass due to their compact and hollow shape, and a low eccentricity with regard to their displacement.

Referring to Figure 15, it shows a possible embodiment of the sealing at medium speed, where one of the two identical shafts shown is notched to achieve all or part of the balancing. The shaft 3 drives the rotor 4 by means of needle bearings 5, attached to seals 6, retaining the oil, the circulation under low pressure is indicated by arrows.

Referring to FIG. 16, this shows another design, for compressors rotating at high speed, where the bearing 7 is force fitted into the rotor 8. The sealing of the oil leaks is ensured by a barrier of air, taken from the discharge (in the rotor), at the two ends of the offset pin 9 of one of the two identical drive shafts. The action of the compressed air is completed by two threads in opposite directions bringing the oil back to the center of the crankpin. The lubricating oil, circulating according to the arrows, arrives at the center of the crankpin and is collected on either side of the central bearing. The crankpin is of a slightly smaller diameter in the parts comprising threads and grooves, so that the bearing does not rub in these parts little or not lubricated.

This design for fast compressors with through shafts is obviously very compact and light. The bearings of the bearings of each drive shaft are sealed by conventional seals or labyrinths, depending on the speed of rotation, and the remaining (or total) part of the balancing is ensured by masses located outside the bearings .

Referring to Figure 17, this shows an overview of a low pressure compressor, in which the eccentrics, in the center of the rotor, are at the end of the shafts. The tree 10 shown rotates in the stator 11 by means of the bearings 12 and 13. The eccentric drives the rotor 22 by means of the bearing 14. The seals 15, 16 and 17 isolate the compression chamber from the lubricating oil. The oil inlet, in the stator 11, is located between the bearing 12 and the seal 17. The pinion 18 meshes with the wheel 19 which also drives the other shaft. Counterweights 20 and 21 balance the rotor in the radial direction.

The axial stops are not shown in the figures of the present application, so as not to complicate them excessively.

It should be noted that, in the foregoing, no account has been taken of the central flange of the rotor (shown only in FIGS. 13 and 14). The role of this flange is to close off the external part of the cells of the stator, for the entire duration of the rotation of the eccentrics.

Furthermore, the capsulism according to the invention has been designed in particular (but not exclusively) to allow the production of compressors with lower flow rates than screw compressors. The border of a given family of compressors, when the dimensions decrease, comes from the relative increase in clearances, limited by the achievable tolerances, the arrows of the parts, the settlement of the bearings, the relative expansions of the neighboring members, all values that 'One cannot reduce beyond certain limits. In this regard, the family of “dry” air or gas capsulisms according to the invention will also have its own lower flow limit. This can be greatly reduced (in a ratio of 10 or more) by using liquid injection (oil - water - refrigerant), before or during compression, or with lubrication of the compression chamber, this technique employing the classic whole: tank with filter-separator, refrigerant, and regulation, obviously falls within the scope of one invention.

In all the solutions shown in the above by way of example, it is important to note that the total angle formed between the normal of a first end of the median curved line of the rotor, and the normal at the opposite end is greater than 360 °.

In addition, it is understood that the present invention has only been described and shown for explanatory but not limiting purposes and that any useful modification may be made to it, in particular in the field of technical equivalences, without going beyond its ambit. .

Claims

1- Capsulism for a rotating machine conveying a gaseous fluid and capable of operating as a compressor or as a vacuum pump, characterized in that the blade of the movable rotor (1) of a base cell consists of two spirals in opposite directions, the first communicating with the suction As and the second with the discharge Re, these two spirals giving the rotor the general shape of the letter "C" with a total angle AT greater than 360 °, where AT designates the total angle formed between the normal of the first end of the median curved line of the rotor, and the normal of the opposite end. 2- Capsulism according to claim 1, characterized in that the curve C is defined by the two spirals, or by all kinds of mathematical curves preferably having tangents common to their junction points (B, Bl, B2, B3. ..). 3- Capsulism according to claim 1, characterized in that the curve C forms, at the delivery Re, a loop all the more closed as the compression ratio (or ratio of absolute pressures delivery on suction) is high and stops about horizontal, suction side As. 4- Capsulism according to any one of claims 1 to 3, characterized in that the rotor (1) is driven by an orbital movement, each of its points describing the same circle of eccentricity E, and having the same angle at the same instant with its starting point, said rotor being driven by two identical shafts, of parallel axes, synchronized in rotation, by means of eccentrics of the same radius E. 5- Capsulism according to any one of claims 1 to 4, characterized in that the cell of the fixed stator (2) is the envelope of the successive positions of the rotor (1) in its movement, that is to say the envelope of the circles of radius equal to the eccentricity E increased by the half thickness of the blade of the rotor, the centers of which slide on the median axis of this blade. 6- Capsulism according to any one of claims 1 to 5, characterized in that the two rotor spirals (1) can be constituted by arcs of circles (C0, Cl, C2, C3, ...) so to simplify the dimensioning calculations and the manufacturing controls, the interior of the cell of the stator (2) then being defined by arcs of circles (C'O, Cl, C'2, C'3, ... and C »0, C» 1, C »2, C» 3, ...) concentric with those of the rotor, all these circles preferably having tangents common to their connection points. 7- Capsulism according to any one of Claims 1 to 6, characterized in that several simple or juxtaposed basic cells, with one, two or three pressure stages, are grouped in the same compression chamber (low compressors, medium or high pressure) or vacuum, intermediate refrigerants separating the different compressor stages so as to avoid excessive temperatures and thermal deformations. 8- Capsulism according to any one of claims 1 to 7, characterized in that the alveoli can be grouped head to tail to reduce the reactions on the bearings. 9- Capsulism according to any one of claims 1 to 8, characterized in that the ratio of the radius R of the wall of the stator furthest from the center Ω to the eccentricity E is equal to the ratio of the maximum speed of l air in the cell at the orbital speed of any point on the rotor, and may exceed 10. 10- Capsulism according to any one of claims 1 to 9, characterized in that the drive shaft or shafts completely or partially pass through the compression chamber. 11- Capsulism according to any one of claims 1 to 10, characterized in that one opposes two rotors, of the same transverse profile, back to back or at a distance, so as to suppress any axial thrust. 12- Capsulism according to any one of claims 1 to 11, characterized in that the rotors are balanced radially, by counterweights placed outside the compression chamber. 13- Capsulism according to any one of claims 1 to 12, characterized in that the compressors or vacuum pumps compress only air or dry gases. 14- Capsulism according to any one of claims 1 to 12, characterized in that the compressors or vacuum pumps operate with injection of liquid before or during compression or with lubrication of the compression chamber. 15- Capsulism according to any one of claims 1 to 14, characterized in that the radius of curvature of the center line of the rotor gradually increases from each of the ends, to an intermediate zone.