EP0462924B1 - Scroll type fluid machine - Google Patents

Description

Field of the Invention

The invention relates to a displacer for compressible media, in which a plurality of interlocking, spiral-like displacers are arranged in a fixed manner in a fixed housing, the displacers being held in each case on an eccentrically drivable disk such that during operation each point of a displacer delimits one from the cooperating displacer Performs circular movement, and wherein the curvature of the two spiral displacement bodies is dimensioned such that they almost touch the opposite circumferential walls of the other displacement body on at least one sealing line continuously progressing during operation, and the displacement bodies with their free end faces seal against the opposite disk.

State of the art

• Während des Betriebes eines solchen Kompressors werden bei einer ersten Ausführungsform entlang einer feststehenden Förderkammer zwischen dem spiralförmig ausgebildeten orbitierenden Verdrängerkörper und den beiden Umfangswänden der Förderkammer mehrere, etwa sichelförmige Arbeitsräume eingeschlossen, die sich von dem Einlass durch die Förderkammer hindurch zum Auslass hin bewegen, wobei ihr Volumen ständig verringert und der Druck des Arbeitsmittels dementsprechend erhöht wird. Ein guter volumetrischer Wirkungsgrad setzt bei derartigen Maschinen eine sehr präzise Herstellung voraus. So hat es sich beispielsweise gezeigt, dass sich die zwangsläufig auftretenden Temperaturdifferenzen zwischen feststehenden und orbitierenden Spiralenteilen nachteilig auswirken können.
• Bei einer zweiten, aus der gleichen Schrift bekannten Ausführungsform geschieht die Förderung des Arbeitsmittels auf ähnliche Art, jedoch zeichnet sich diese Ausführung nicht durch eine kreisende Bewegung eines Verdrängerkörpers in einem feststehenden Förderrraum aus, sondern vielmehr durch drehende Bewegung beider involvierter, ineinandergreifender Verdrängerkörper. Dieser rotierende Spirallader besteht im wesentlichen aus einem Gehäuse, in dem zwei symmetrisch aufgebaute Verdrängerscheiben mittels Antriebselementen drehbar angeordnet sind. Eine der beiden Verdrängerscheiben ist auf einem Achsstummel gelagert. Die zweite Scheibe ist drehfest mit einer Antriebswelle verbunden. Anlässlich der Drehung der zweiten Scheibe wird die erste Scheibe im gleichen Drehsinn und mit der gleichen Drehgeschwindigkeit mitgenommen. Beide Scheiben führen dabei eine Relativbewegung in Form einer Kreisverschiebung aus.

Displacement machines of the spiral type are known for example from DE-C-26 03 462. A compressor constructed according to this principle is characterized by an almost pulsation-free conveyance of the gaseous working medium, which consists, for example, of air or an air / fuel mixture, and could therefore also be used advantageously for charging purposes of internal combustion engines, among other things.

• During the operation of such a compressor, in a first embodiment, a number of roughly crescent-shaped working spaces are trapped along a fixed delivery chamber between the spiral-shaped orbiting displacement body and the two peripheral walls of the delivery chamber, which work spaces move from the inlet through the delivery chamber to the outlet, thereby Volume is constantly reduced and the pressure of the working fluid is increased accordingly. With such machines, good volumetric efficiency requires very precise manufacture. For example, it has been shown that the inevitably occurring temperature differences between fixed and orbiting spiral parts can have a disadvantageous effect.
• In a second embodiment known from the same document, the conveying of the working medium takes place in a similar manner, but this embodiment is not characterized by a circular movement of a displacer body in a fixed conveying space, but rather by a rotating movement of the two mutually engaging displacer bodies involved. This rotating spiral charger consists essentially of a housing in which two symmetrically constructed displacement disks are rotatably arranged by means of drive elements. One of the two displacement disks is mounted on an axle stub. The second disc is non-rotatably connected to a drive shaft. On the occasion of the rotation of the second disc, the first disc turns in the same direction and carried along at the same rotational speed. Both disks perform a relative movement in the form of a circular displacement.

A machine of the type mentioned at the outset, in which, in deviation from the two above-mentioned machine types, several, here two, interlocking, spiral-shaped displacers are arranged in a fixed housing in a fixed housing is known from German Patent No. 174 074, which was issued in 1906. In this machine, which has not been developed since then, the discs on a central drive crankshaft, which are each equipped with a displacer, are guided in a circular manner by means of a plurality of radially external crankshafts which are positively connected to one another and are carried by a rotatable frame.

Presentation of the invention

The invention is therefore based on the object of providing a displacement machine of the type mentioned at the outset, which combines the advantages of the two machine types discussed and which, moreover, has a smaller overall volume with the same delivery rate.

The object is achieved in that each disc carries at least on one of its two sides two symmetrically arranged displacement bodies which are offset by 180 ° relative to one another, the cooperating spiral displacement bodies of both discs having a different wrap angle, in such a way that that displacement body, which acts as the delivery chamber acts, both the radially outermost and the radially innermost spiral section in the system and thus has the larger wrap angle.

The advantages of the invention can be seen on the one hand in the fact that the interlocking displacement bodies on the occasion of the Operation are exposed to the same thermal and mechanical conditions, whereby thermal differences are largely avoided within the active system. On the other hand, the solution with a circulating displacement body compared to the solution customary today, in which only one displacement body circles in a fixed delivery space, results in a doubling of the stroke and thus the delivery rate with constant eccentricity. In addition, the symmetrically designed displacers offset on each disc by 180 ° result in a smooth running of the machine, since the discs together with the displacer, if their center of gravity is in the center, are statically and dynamically balanced.

It is particularly advantageous if two positively connected eccentric arrangements are provided for driving and guiding the disks, the shafts of which are arranged at a distance from one another and are supported in the housing, and if these shafts are double eccentric shafts on which the disks to be driven are not in their displacement bodies occupied outer peripheral zones are stored. The loads occurring during operation are evenly distributed over the two eccentric arrangements and their bearings. The latter do not need to be sealed since they are not exposed to the hot compressed work equipment. The fact that two eccentric arrangements arranged at a distance from one another are provided, one of which, for example, can be driven via a drive shaft, results in a statically determined mounting which, apart from the top and bottom dead centers of the disk position, also ensures that the rotor is guided. In order to achieve clear guidance in the dead center positions of the disks, the double eccentric shafts mounted in the housing are positively connected via a toothed belt drive.

Brief description of the drawing

Fig. 1

einen Querschnitt durch die Verdrängermaschine in der Ebene der Förderräume;

Fig. 2

einen Längsschnitt durch die Verdrängermaschine nach Schnittlinie A-A in Fig. 1

Fig. 3

einen Längsschnitt durch die Verdrängermaschine nach Schnittlinie B-B in Fig. 1

In the drawing, an embodiment of the invention is shown schematically.
It shows:

Fig. 1

a cross section through the displacement machine in the plane of the delivery rooms;

Fig. 2

2 shows a longitudinal section through the displacement machine according to section line AA in FIG. 1

Fig. 3

2 shows a longitudinal section through the displacement machine according to section line BB in FIG. 1

Way of carrying out the invention

To explain the operation of the compressor, which is not the subject of the invention, reference is made to the already mentioned DE-C3-2 603 462 and DE-PS 174 074. Only the machine structure and process flow necessary for understanding the invention are briefly described below.

It can be seen from FIG. 2 and in particular from FIG. 3 that the example shown is a machine with two parallel floods. This has the advantage that a disk common to both floods is provided with the working elements of the left as well as the right flood (according to FIG. 3). With this configuration, not only one disc but also support bearings can be saved, as will be explained later.

With 1 the "middle" rotor of the machine resulting due to the double flow design is designated as a whole. On both sides of its disc 2 there are two spiral-shaped displacers offset by 180 ° to one another. These consist of strips 3a, 3b which are held vertically on the pane 2. In the example shown, the spirals themselves are composed of a plurality of adjoining ones according to FIG Arcs are formed and loop around an angle of 360 °. These are the spiral strips which are shown in black in FIG. 1 and which are arranged on the only partially recognizable middle pane 2. Only partially recognizable because, for better clarity and better understanding because of FIG. 1, the contours of the disks 6 and 7 (which cannot be seen in the sectional view) of the two "lateral" runners 4 and 5 cooperating with the "middle" runner are shown . As can be seen, the spirals offset by 180 ° to one another are not nested, as in the known machines, in order to form two-course systems. Rather, the spirals are arranged centrally symmetrical to each other. They are therefore independent single-start spirals, which have the advantage over the nested spirals that, with the same eccentricity, they have twice the stroke and thus twice the conveying capacity. From the smoothness, it is useful if the displacement of the two spirals and their arrangement on the disc is such that the connecting axis of the centers of the spirals coincides with the connecting axis of the centers of the drive or drive described below. Cross leadership eccentric in runner 1's center of gravity.

A double eccentric system is provided for driving and guiding rotor 1. With 8 a first hub is designated with which the disc 2 is mounted on a rolling bearing, not shown. This bearing sits on an eccentric 9, which in turn is part of a first double eccentric shaft 10. With 11 a second hub is designated with which the disc 2 is mounted on a rolling bearing, not shown. This bearing sits on an eccentric 12, which in turn is part of a second double eccentric shaft 13. The two hubs 8 and 11 are arranged on the periphery of the disk 2, specifically in those zones which are not occupied by the spirals.

In contrast to the "central" rotor 1, the respective disks 6 and 7 are provided on the two "lateral" rotors 4 and 5 on only one of their sides, each with two, displaced by 180 °, spiral-shaped displacer bodies. These consist of strips 14a, 14b, which are held vertically on the disks 6 and 7. In the example shown in FIG. 1, the spirals themselves are likewise formed from a plurality of circular arcs connected to one another (shown by hatching); Of course, they must have the same geometry as the strips 3a and 3b in order to be able to cooperate with them. As with the middle rotor 1, the condition must of course also be met here that the displacement of the two spirals and their arrangement on the disk is such that the connecting axis of the centers of the spirals coincides with the connecting axis of the centers of the associated drive or. Leading eccentric in the focus of the respective disc 6 or Cross 7. Due to the distance chosen in the example of the spirals 14a and 14b, which are offset by 180 °, they touch over their circumference for a certain distance, specifically at the geometrical point in which the center of gravity of the disk 6, respectively. 7 lies.

Unlike the spirals 3a and 3b, however, the spirals 14a and 14b loop around an angle of 720 °. From a purely static perspective, it can thus be seen in FIG. 1 that the hatched spiral 14 actually forms a conveying space for the black spiral 3. For this reason, the spiral 14 must represent the radially outermost part at the entry of the spiral system and, accordingly, also represent the radially innermost part at the exit of the spiral system. Only in this way can the spiral 14 completely encompass the inner spiral 3 on the occasion of the orbital movement, which explains the different wrap angles . Both the adjoining inner parts of the two spirals 14a and 14b and their adjoining outer parts thus have an S shape. This arrangement prevents vibrations of the air column when entering the spirals.

The same, already mentioned double eccentric system is of course provided for driving and guiding the runners 4 and 5. 15 denotes the hubs with which the disks 6 and 7 are seated on an eccentric 16 of the first double eccentric shaft 10 via roller bearings (not shown). 17 also denotes the hubs via which the disks are mounted on eccentrics 18 of the second double eccentric shaft 13. Here, too, the two hubs 15 and 17 are arranged on the periphery of the disks 6 and 7 in those zones which are not occupied by the spirals. The two eccentrics 16 and 18 are offset from the two eccentrics 9 and 12 by 180 °.

With the drive concept selected in this way, the load is evenly distributed over the two double eccentric shafts. The bearing arrangement outside of the spirals has the extraordinary advantages that on the one hand the dimensioning of the bearings is not affected by any space restrictions, and on the other hand that bearings with permanent lubrication can be used due to the arrangement on the cold side (sucked in ambient air). This also eliminates the need for costly bearing seals. Even if oil-lubricated slide bearings are used, in which oil would escape from the side and reach the area of the spiral inlets 25a, 25b to be described later, this does not impair the oil-free conveying of the working medium. In contrast to the known machines with a fixed delivery chamber and displacer body orbiting therein, in which the orbiting displacer sucks an oil mist present at the inlet into the spiral, in the present embodiment any oil is thrown off the orbiting displacers.

The two double eccentric shafts 10 and 13 are supported in a conventional manner, not shown, in the two side housing halves 19a and 19b. The two lateral housing halves are connected to one another at their periphery by a housing jacket 20 via fastening means, not shown.

Since this jacket is not exposed to any significant stress due to its bilateral (inside and outside) exposure to only atmospheric pressure, it must be dimensioned as a bare outer skin.

The drive and the guide of the rotor 1, 4 and 5 accordingly provide the two spaced eccentric arrangements 9, 10, 16 and. 12, 13, 18. For this purpose, the two shafts 10 and 13 penetrate one of the side housing halves; they are each provided with a toothed belt pulley 21, 22 at their projecting ends. The two toothed belt pulleys are in the same vertical plane. It goes without saying that only one of the two shafts has to be connected to a drive, not shown. The two eccentric arrangements are synchronized with precise angles so that the runners can be clearly guided on the occasion of the orbital movement in the dead center positions. This is done here by merging the actual drive with a toothed belt 23. The toothed belt drive can also be designed as a belt tensioner.

If the above-mentioned definition of the conveying space is taken as a basis for better understanding, the two "conveying spaces", which are each offset by 180 °, can be designated in FIG. 1 by 24a and 24b. They each run from an inlet 25a, 25b formed on the outer circumference of the spiral 14a, 14b to an outlet 26a, 26b provided in the spiral interior. The displacement bodies 3a, 3b engage in these conveying spaces, the curvature of which is dimensioned such that the strips almost touch the inner and outer boundary walls of the respective conveying space at several, for example at two points.

On the occasion of the operation, the double eccentric drive ensures that all points of the runners and thus also all points of the bars perform a circular displacement movement. As a result of the multiple alternating approaches of the strips of the middle runner and that of the lateral runner crescent-shaped work spaces enclosing the working medium between the interlocking strips, which are displaced during the drive of the rotor disks through the conveying chambers formed by the strips in the direction of the outlet. The volumes of these working spaces are reduced and the pressure of the working fluid is increased accordingly.

1 that the "outer" part Aa (hatched vertically) of the left-hand delivery chamber 24a opening against the inlet 25a has a larger area than the "inner" part Ab opening against the inlet 25b in the spiral position shown the right delivery room 24b. Likewise, it can be seen that the “outer” part Ca (also hatched vertically) of the left delivery chamber 24a opening against the outlet 26a has a larger area than the “inner” part Cb of the right delivery chamber 24b opening against the outlet 26b. On the other hand, the enclosed crescent-shaped "inner" part Ba (hatched horizontally) of the left conveying space 24b has a clearly smaller area than the enclosed crescent-shaped "outer" part Bb of the right conveying space 24b. However, the sum of the areas Aa + Ba + Ca is equal to the sum of the areas Ab + Bb + Cb. Since the same volume is thus conveyed at all times regardless of the spiral position in the left and in the right conveying space 24a or 24b, this leads to the aforementioned freedom from vibration during operation.

A breakthrough 27 is provided in each of the two inner spiral ends in the middle disk 2 so that the medium can get from one disk side to the other, ie in the case shown from the right tide to the left tide, in a central outflow 28 arranged only on one side (Fig.3) to be subtracted. For this purpose, the disk 6 of the left runner must of course also be provided with a central opening 29. This opening 29, however, requires sealing measures of the disk 6 against the adjacent lateral one Housing part 19a in order to avoid that the spiral outlet is short-circuited with the spiral inlet.

The sealing problem is of paramount importance in this type of machine. It goes without saying that not only the radial sealing of the strips 3a, 3b against the strips 14a, 14b, i.e. the closure of the conveying spaces 24a, 24b in the circumferential direction is important. The axial tightness of the delivery rooms is also important. For this purpose, the ledges of one runner must lie with their end faces against the disks of the opposite, cooperating runner. Sealing takes place on the basis of actual sliding layers 30 (FIGS. 2 + 3) made of, for example, PTFE, which are applied at the required points on the pane sides and only there by suitable means. Since the increasing pressure against the interior of the spiral tends to push the cooperating runners apart, countermeasures must be taken.

First of all, the lateral rotor 5 is sealed against the housing half 19b by means of a fixed sliding seal 31. This seal, designed as a ring, is inserted into a corresponding groove in the housing half 19b and is therefore not subject to the translatory movement. The space 32 within the ring is acted upon by the pressure of the working medium at the outlet, which reaches the rear via a bore 33 in the disk 7. Outside the ring acts on the back of the disc 7 that pressure that prevails in the inlet, ie the atmospheric pressure. It can thus be seen that simply by dimensioning the ring diameter of the seal 31 and thus the active pane surface, one has a simple means in hand to determine the contact pressure of the strips against the corresponding panes on the one hand and the panes against the fixed walls on the other hand . The friction and thus the abrasion can thus be optimized. With this concept it can also be seen that the frontal use of the strips is automatically compensated.

The same applies analogously to the left machine side on which the outflow 28 is located. Now, however, a precaution must be taken so that the axial tightness of the conveying spaces is guaranteed even when depressurized, such as when the machine starts up. Pneumatic sealing is not possible in this state. This provision can be, for example, a spring-supported sliding ring 34, which is additionally configured such that it seals the outlet side against the inlet side. In this case, the spring provides the necessary contact pressure to hold the lateral rotor 4 against the middle rotor 1, the latter against the lateral rotor 5 and the latter against the housing half 19b.

LIST OF DESIGNATIONS

1

"middle" runner

2nd

disc

3a, 3b

Groin, spiral

4th

"lateral" runner

5

"lateral" runner

6

Slice of 4

7

Disc of 5

8th

hub

9

eccentric

10th

Double eccentric shaft

11

hub

12

eccentric

13

Double eccentric shaft

14a, 14b

Groin, spiral

15

hub

16

eccentric

17th

hub

18th

eccentric

19a, 19b

Half of the housing

20th

Housing jacket

21

Timing belt pulley

22

Timing belt pulley

23

Timing belt

24a, 24b

Funding room

25a, 25b

inlet

26a, 26b

Outlet

27

breakthrough

28

Outflow

29

key breakthrough

30th

Sliding layer

31

Sliding seal

32

room

33

drilling

34

Slide ring

Claims (3)

1. Displacement machine for compressible media, in which a plurality of spiral-type displacement bodies which engaged in one another (3a, 3b, 14a, 14b) are arranged in a stationary casing (19a, 20, 19b) so as to circulate, the displacement bodies each being held on an eccentrically driven disc (6, 2, 7) in such a way that, during operation, each point of a displacement body executes a circular motion bounded by the interacting displacement body, and the curvature of the two spiral-type displacement bodies being so dimensioned that they almost touch the opposite peripheral walls of the respective other displacement body at, in each case, at least one sealing line which advances continuously during operation, and the free end faces of the displacement bodies sealing against the opposite disc, characterised in that each disc (6, 2, 7) carries, on at least one of its two sides, two symmetrically arranged displacement bodies (3a, 3b, 14a, 14b) offset by 180° relative to one another, the interacting spiral-type displacement bodies of both discs having a different angle of wrap to be precise in such a way that each displacement body (14a, 14b) which acts as delivery chamber (24a, 24b) has both the radially outermost and the radially innermost spiral part in the system and, therefore, the larger angle of wrap.
2. Displacement machine according to Claim 1, characterised in that, in order to drive and guide the discs (6, 2, 7), two eccentric arrangements are provided which are positively connected together and whose shafts (10, 13), which arranged at a distance from one another, are supported in the casing (19a, 19b).
3. Displacement machine according to Claims 1 and 2, characterised in that the shafts are double-eccentric shafts on which the outer edge zones, not occupied by the displacement bodies (3a, 3b, 14a, 14b), of the discs to be driven (6, 2, 7) are mounted.

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