EP1216358B1 - 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

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

One designates by capsulism the realization of a variable closed volume.

The invention relates more precisely to a new family of compressors or vacuum pumps "Dry", including a family of air compressors or particularly compact, light, one, two gases or three stages, capable of delivering at low pressure, medium or high (for example 3, 8 or 20 bars, respectively).

• les petits compresseurs à vis à injection d'huile, destinés aux marchés des transports, de l'industrie, des travaux publics et du bâtiment, dont la simplicité de conception du compresseur proprement dit est compliquée et alourdie par de nombreux accessoires (régulation, réservoir-séparateur, tuyauteries et filtre d'huile) ;
• les petits compresseurs à pistons, qui nécessitent un réservoir et engendrent bruit et trépidations.

The invention aims to compete at the same time:

• 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, tank -separator, pipes and oil filter);
• small reciprocating compressors, which require a reservoir and generate noise and trepidation.

Therefore, the compressors sought must be compact, so have a great ratio sucked volume, or displacement, on total volume of the compression chamber. However, the length of this chamber being constant for a rotary compressor given, it will be clearer to talk about the report: suction section, on total section (limited by bores and their common tangents, that is to say in including the concave parts) of the compression. This report will be referred to below as "rate of suction ”.

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

• lorsqu'il possède un arbre central et un arbre extérieur, il reste limité aux basses pressions et, de plus, les deux arbres sont différents car celui situé au centre doit supporter presque tous les efforts ;
• lorsqu'il ne possède pas d'arbre traversant les spirales, le rotor doit être maintenu en porte-à-faux, ce qui implique des paliers plus importants, donc plus lourds et encombrants ;
• par ailleurs, ce type de compresseur ne monte que très progressivement en pression et doit avoir plusieurs spires pour atteindre seulement une pression basse, ou une pression moyenne pour les très petits débits. Il comporte alors de longues lignes de fuite, d'où l'utilisation de segments en bout des aubes du rotor (sauf pour les très basses pressions) frottant sur le stator, et réciproquement. Cet emploi de segments frottant à sec limite fortement la vitesse de rotation. Les fuites non étanches entre les parois courbes des spirales fixes (stator) et mobiles (rotor), que l'on peut supposer constantes quel que soit le régime de rotation, prennent davantage d'importance par rapport à un débit plus faible. De plus, les courbures progressives engendrent un faible coefficient de perte de charge amont-aval, et favorisent les fuites. Le frottement des segments ajouté à ces fuites et au fait que la compression est très progressive, provoque un supplément d'échauffement en cours de compression, au détriment du rendement des compresseurs de ce type.

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 rises only very gradually in pressure and must have several turns to reach only a low pressure, or an average pressure for very small flow rates. It then has long vanishing lines, 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. 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 compressors of this type.

• en utilisant un nouveau profil permettant une compression beaucoup plus rapide, ou brutale, limitant les fuites ;
• en ayant un taux d'aspiration parmi les plus élevés des compresseurs connus à ce jour, permettant ainsi une compacité plus grande, d'où des lignes de fuite plus courtes. En outre, ce taux d'aspiration plus élevé permet l'emploi, pour une même cylindrée, d'un rayon d'excentration (chaque point du rotor décrivant un même mouvement circulaire, dans le plan orthogonal aux arbres d'entraínement) plus petit ;
• si le compresseur conserve des segments en bout de pales, en gardant constant le produit : régime de rotation x excentricité, et donc constante la vitesse de frottement des segments. Pour le comparer au compresseur à spirales, le régime est augmenté en raison inverse de la diminution d'excentricité, ce qui permet d'augmenter encore la compacité, en réduisant de nouveau la cylindrée, qui est pratiquement divisée par deux.

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, hence 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) smaller ;
• if the compressor keeps 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 makes it possible to further increase the compactness, again reducing the displacement, which is practically halved.

Another possibility is opened by the removal of segments at the tip of blades, increase strongly the rotation regime, resulting in a very clear decrease in displacement, in length of lines leakage, bulk and weight of compressors thus produced. These are less noisy, the air pulsations being weaker and more numerous.

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

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

More specifically, if we call "cell of base »the simplest elementary cell, we will see that one can, in the context of the invention, have, in the same compression chamber, several basic cells, for example two or more identical cells (single or juxtaposed) for the low pressure, and the same for medium pressure. The the low pressure part and the middle part pressure are in the same room brings obviously a great simplification of design and a gain in weight, compactness, cost price. The conclusions are the same if there is also a part high pressure.

The invention is as described in claim 1.

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 line median increases from each end, up to a maximum radius for the middle area of capsulism.

By "compression ratio" will be understood in the sense of this patent the ratio between the volume of the compression chamber when closing the compression orifice, and the volume of this chamber compression when opening the orifice of discharge.

The concepts of "compression" and "Compressor" within the meaning of this patent is relate to this definition.

The essential technical characteristic of 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 to be observed in known capsulisms.

In particular, French patent FR825643 describes a device comprising closed chambers with a total angle less than 360 °. The patent US1967957 also describes a device having a traditional capsulism, not allowing to realize a compressor within the meaning of this patent, nor a pump empty.

The same is true for Japanese patents 59147892 or 59141786, American US1378065 or US4606711 or German DE19614477

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

First, we will define the cell of base, which includes two compression cells. The rotor, as in scroll compressors, is driven by two parallel shafts by means of two eccentrics with the same eccentricity E. Each point of the rotor therefore describes, in its movement, a circle, or an "orbit", of radius E.

Referring to Figure 1, we consider three parallel curves, more precisely two curves envelopes C2, C3 of circles Γ with the same radius E, the center moves on a given curve C1.

Through the center of each circle Γ, we conduct a right direction Δ. Only one of these lines cuts simultaneously Γ and C2 in E2, Γ and C3 in E3, at the points for which Δ is perpendicular to the tangents to C2, C3, Γ, therefore to C1.

Referring to Figure 2, if we move the curve C1 of E in the direction Δ, it comes in C'1 and meets C2 in E2, and only in E2, the radius curvature of C'1 in E2 being less than E than that from C2.

We would also show that if we move C1 from -E according to Δ, it meets C3 in E3, and only in E3.

The simplest basic cell possible presents the form of the letter C. In the following, we describes a theoretical cell, in which dawn or the rotor blade, in the section orthogonal to the axes drive trees, has no thickness, which simplifies the description.

Referring to Figure 3, a rotor 1 being assumed to have zero eccentricity, compared to a stator fixed 2, will be said "in medium position" - that never occupies in practice its eccentricity being always equal to E -. Its dawn is shaped like a vs.

The fixed stator is the envelope of the circles of radius E centered on the rotor in the middle position.

Curve C can consist of two spirals in opposite directions, one in direction -, going from As aspiration towards B, and one of sense +, going from repression Re towards B.

It can also be defined by all kinds mathematical curves, provided that the tangent at B either common to the two curves (a break in the curve generator causes a leak at the curve stator) or, rather, that the tangents of the successive curves are common to their points of encounter B, B1, B2, B3, ...

Curve C should form, at the discharge Re, a loop all the more closed as one wishes a higher discharge pressure. It will suffice stops horizontally, or roughly, on 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 they a total angle exceeding 360 °, in the example described in figure 3, this total angle approaches 500 °.

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

The progression of the radius of curvature is not symmetrical with respect to this middle zone.

Referring to Figure 4, this shows the successive phases of compression in a basic cell. The shaded areas show the alveoli communicating with the suction, up to the closing of this one, and those hatched the alveoli expelling compressed air into the discharge port. Suction and discharge are uninterrupted, and there results that the compression principle itself decreases pulsations of air and noise at the upstream ports and downstream.

The dials show the common angle of rotation of the two eccentric drives.

We can see that an upper cell and a lower cell fill once turn, and push back 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 Figure 5, the scroll compressor consists of casings successive of the same basic spiral, generated by circles Γ1, Γ2, Γ3 ... of the same radius E, located on the same normal N to the base spiral, in Re, of which the centers describe, by turning, the rotor (supposed thickness) in the middle position, and whose intersections with N describe the stator.

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

Instead of being formed in two spirals of reverse direction, the rotor curve can be, in the framework of the invention, described by several arcs of successive circles.

• d'une part en se référant à la figure 6, que le fait d'utiliser des arcs de cercles simplifie les équations du stator et du rotor : ce dernier étant en position moyenne, soit C1 l'un des ses arcs de cercles de centre Ω1, de rayon R1 et d'arc α1. Les arcs de cercles C'1 et C »1 du stator ont même centre Ω1, même angle α1, et pour rayons R'1=R1+E et R »1=R1-E. Le centre Ω2 des arcs de cercles C2, C'2, C »2 est situé sur la droite Δ12, passant par Ω1 et limitant les arcs C1, C'1 et C »1 sur cette droite. De même, le centre Ω0 des arcs à gauche de Δ01 est sur Δ01, et le centre Ω3 des arcs à droite de Δ23 est sur Δ23, et ainsi de suite.
• d'autre part, en se référant à la figure 7, que si le centre Ω du plus grand rayon R de deux cellules opposées est commun, la forme extérieure de la chambre est un cercle de ce même rayon R, limité par les tangentes T communes aux deux cellules.

We notice :

• on the one hand by referring to FIG. 6, that the fact of using arcs of circles simplifies the equations of the stator and the rotor: the latter being in medium position, let C1 be one of its arcs of circles of center Ω1, with radius R1 and arc α1. The arcs of circles C'1 and C »1 of the stator have the same center Ω1, same angle α1, 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 Ω1 and limiting the arcs C1, C'1 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 a same maximum travel speed for both cells.

We can prefer a more flat shape, such as that shown in Figure 8, in the goal of getting faster movement speed of air, for a given eccentricity, and therefore a better suction rate.

The maximum air speed in the cell is indeed ω.R, and the orbital speed of any point of the rotor is ω.E, which allows to multiply the speed in the R / E ratio, and therefore to obtain a high throughput 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 Figure 10, this represents a version in which both shafts with eccentrics cross the rotor, on a low pressure compressor with juxtaposed cells two by two.

Referring to Figure 11, this represents the diagram of a medium pressure compressor: the two large cells discharge into a cooler Rf1 the compressed air then until the final pressure in the two small cells. A final refrigerant Rf2 completes this achievement.

In the preceding figures, the alveoli are grouped head to tail, to reduce reactions bearings. The trees listed there, subject to same efforts on average, for reasons of symmetry, can be identical as well as their seals, bearings and counterweight.

However, an asymmetrical construction remains possible, in the context of the invention, by referring for example in figure 12, which shows a compressor with three floors with through trees.

Except for very low compressors pressure, there is always an interest in opposing two rotors, of 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 well away, as shown in Figure 14, from so as to eliminate 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 radially balanced, especially if the rotation is high, but this is easy to achieve, because said rotors have a low mass due to their compact and hollowed out shape, and a low eccentricity with regard to their displacement.

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

Referring to Figure 16, this shows another design, for compressors rotating at high speed, where the bearing 7 is force-fitted in rotor 8. Oil leakage tightness is ensured by an air barrier, taken from the discharge (in the rotor), at both ends of the crankpin offset 9 from one of the two drive shafts identical. The compressed air action is completed by two threads in opposite directions bringing back the oil toward the center of the crankpin. Lubricating oil, circulating according to the arrows, arrives at the center of the crankpin and is recovered from either side of the central pad. The crankpin is of a diameter slightly lower in parts with threads and grooves, so that the pad does not rub not in these parts little or not lubricated.

This design for fast compressors through trees is obviously very compact and lightly. The bearings of the bearings of each tree are sealed by seals or classic labyrinths, depending on the speed of rotation, and the remaining (or total) part of balancing, is ensured by masses located in outside the landings.

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 trees. The tree 10 shown rotates in the stator 11 by means of bearings 12 and 13. The eccentric drives the rotor 22 by means of the bearing 14. Seals 15, 16 and 17 isolate the compression chamber of the lubricating oil. The oil inlet, in 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 on the figures of this application, so as not to overcomplicate these.

It should be noted that, in the above, the central flange of the rotor (shown only in Figures 13 and 14). The role of this collar is to close off the part outside of the stator sockets, throughout the duration of the rotation of the eccentrics.

Furthermore, the capsulism according to the invention has designed in particular (but not exclusively) to allow the production of more compressors lower flow rates than screw compressors. The border of a given family of compressors, when the dimensions decrease, comes from the increase relative clearances, bounded by tolerances achievable, the arrows of the parts, the settlements of bearing, relative expansions of organs neighbors, all values that cannot be reduced beyond certain limits.

In this respect, the family of air capsulisms or gas "dry" according to the invention, will also have its own lower flow limit. This could be greatly reduced (in a ratio of 10 or more) in using liquid injection (oil - water - fluid refrigerant), before or during compression, or with lubrication of the compression chamber, this technique using the classic together: tank with filter-separator, refrigerant, and regulation, obviously falls within the scope of the invention.

In all the solutions represented in this above as an 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 °.

Claims (15)

1. Internal combustion for rotating machines conveying a gaseous fluid and which can operate as a compressor or a vacuum pump, the vane of the movable rotor (1) of a base cell being constituted of two spirals in reverse direction, the first linking with the suction As and the second with the discharge Re, characterised in that these two spirals give the rotor the general shape of the letter "C" with a complete angle AT greater than 360°, where AT designates the total angle between the normal at the first end of the curved median line of the rotor, and the normal at the opposite end, and in that the curve C creates, at the discharge Re, a loop tighter than that at the suction.
2. Internal combustion according to claim 1, characterised in that the curve C is defined by the two spirals, or by any type of mathematical curve preferably having common tangents at their points of connection (B, B1, B2, B3...).
3. Internal combustion according to claim 1, characterised in that the curve C creates, at discharge Re, a loop all the tighter as the compression ratio (or ratio of absolute pressure at discharge to that at suction) is higher and stops almost horizontally, on the suction As side.
4. Internal combustion according to any one of claims 1 to 3, characterised in that the rotor (1) follows an orbital movement, each of its points following a same circle of eccentricity E, and bearing the same angle at the same moment with its starting point, the said rotor being driven by two identical shafts, with parallel axes, synchronised in rotation, by means of eccentrics with the same radius E.
5. Internal combustion according to any one of claims 1 to 4, characterised in that the cell of the fixed stator (2) is the envelope of the successive positions of the rotor (1) in its movement, i.e. the envelope of the circles whose radius is equal to the eccentricity E increased by half the thickness of the vane of the rotor, and whose centres slide along the median axis of this vane.
6. Internal combustion according to any one of claims 1 to 5, characterised in that the two spirals of the rotor (1) can be made of arcs of circles (C0, C1, C2, C3...) so as to simplify the dimensioning calculations and the manufacturing checks, the inside of the cell of the stator (2) then being defined by arcs of circles (C'0, C'1, C'2, C'3... and C"0, C"1, C"2, C"3...) that are concentric to those of the rotor, all of these circles preferably having common tangents at their points of connection.
7. Internal combustion according to any one of claims 1 to 6, characterised in that several simple or juxtaposed base cells, with one, two or three pressure stages, are grouped in the same compression chamber (low-, mid- or high-pressure compressors) or vacuum compressor, with intermediary coolants separating the different compression stages so as to avoid extreme temperatures and heat distortions.
8. Internal combustion according to any one of claims 1 to 7, characterised in that the cells can be grouped head to tail to reduce the reactions at the plateaux.
9. Internal combustion according to any one of claims 1 to 8, characterised in that the ratio of the radius R of the side wall of the stator furthest from the centre Ω to the eccentricity E is equal to the ratio of the maximum speed of the air in the cell to the orbital speed of any point of the rotor, and can exceed 10.
10. Internal combustion according to any one of claims 1 to 9, characterised in that the drive shaft(s) pass(es) entirely or partially through the compression chamber.
11. Internal combustion according to any one of claims 1 to 10, characterised in that two rotors, with the same transverse profile, back-to-back or at a distance, are set against each other, so as to eliminate any axial thrust.
12. Internal combustion according to any one of claims 1 to 11, characterised in that the rotors are radially balanced, via counterweights placed on the outside of the compression chamber.
13. Internal combustion according to any one of claims 1 to 12, characterised in that the compressors or vacuum pumps only compress air or dry gases.
14. Internal combustion according to any one of claims 1 to 12, characterised in that the compressors or vacuum pumps operate with the injection of liquid before or during the compression or with lubrication of the compression chamber.
15. Internal combustion according to any one of claims 1 to 14, characterised in that the radius of curvature of the median line of the rotor progressively increases at each end, until it reaches an intermediary zone.

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