EP0560009A1 - Positive displacement machine on the spiral principle - Google Patents

Abstract

A positive displacement machine for compressible media with a plurality of spiral delivery chambers arranged in a housing functions with a displacement element (1) assigned to the delivery chambers. This element essentially comprises a disc (2) with spiral fillets (3a, 3b) arranged perpendicular on both sides. The disc (2), in the area of the inlet of the spiral fillets (3a, 3b) is extended 2a, 2b beyond the spiral inlet. This disc extension (2a, 2b) is provided radially outwards with an accumulation of material serving as clamping lugs (50a, 50b). The spiral fillets (3a, 3b) on their inlet side ends run out into the disc extension (2a, 2b), the run-out (51a, 51b) opening into the clamping lugs (50a, 50b). <IMAGE>

Description

Field of the Invention

Displacement machine for compressible media with a plurality of spiral conveying spaces arranged in a fixed housing, which lead from a radially outer inlet to a radially inner outlet, and with a displacer assigned to the conveying spaces, essentially consisting of a disk with spiral strips arranged vertically on both sides, the eccentrically driven displacement body executes a circular movement delimited by the circumferential walls of the delivery chamber with each of its points during operation.

State of the art

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 delivery of the gaseous working medium, which consists, for example, of air or an air / fuel mixture and could therefore also be used with advantage for charging purposes of internal combustion engines. During the operation of such a compressor, several, approximately crescent-shaped work spaces are enclosed between the spiral-shaped displacement body and the two peripheral walls of the displacement chamber, which move from the inlet through the displacement chamber to the outlet, their volume constantly decreasing and the pressure of the work equipment is increased accordingly.

A machine of the type mentioned at the outset, in which the spirals span a total wrap angle of approximately 360 °, is known from EP-A-0 321 781. Such a machine has one of the number of nested in the displacer body at the inlet-side ends of the spirals Spirals corresponding number of discontinuities in the radial extension of the center disc. The discontinuity is increased in the axial direction by the spiral strips.

When the working fluid is conveyed from radially outside to radially inward, the temperature of the working fluid increases due to the increasing compression. The consequence of this is that the center disk has a higher temperature in its hub section than in its outer area at the inlet-side end of the spirals. If the displacement body is made of a commercially available material with a coefficient of thermal expansion greater than zero, this temperature distribution creates tensile stresses in the outer area of the disk and compressive stresses in the hub area. The geometric discontinuities mentioned and the temperature profile result in a stress concentration in the inlet area of the pane and thus an increased material stress.

Presentation of the invention

In order to better utilize the construction volume of the machine, the development trend is towards higher pressure ratios and higher speeds. The former causes even steeper temperature gradients in the disk, the latter leads to greater mass forces. The displacement body is therefore preferably made of a light metal alloy, for example magnesium. Such alloys have quite good strength values at room temperature; however, these good values drop rapidly at higher temperatures when it comes to commercially available alloys without costly additives.

Based on the intention to continue to make use of the advantages of the light metal alloys such as weight, cost, friction properties and the like, the object of the invention is to constructively modify a displacement machine of the type mentioned at the beginning in such a way that the stress concentration in the inlet area of the displacement disk is considerably reduced becomes.

• dass die Scheibe im Bereich des Einlasses der spiralförmigen Leisten über den Spiraleneinlass hinaus verlängert ist,
• dass diese Scheibenverlängerung radial aussen mit einer als Aufspannlappen dienenden Materialanhäufung versehen ist,
• und dass spiralförmigen Leisten an ihren eintrittsseitigen Enden in die Scheibenverlängerung auslaufen, wobei der Auslauf in den Aufspannlappen mündet.

The task is solved by

• that the disk in the area of the inlet of the spiral strips is extended beyond the spiral inlet,
• that this disc extension is provided radially on the outside with a material accumulation serving as clamping flaps,
• and that spiral strips run out at their entry-side ends into the pane extension, the run-out opening into the clamping tabs.

The advantage of the invention is to be seen in the fact that a simple structural measure which does not impair the functionality of the machine now limits the application of a material that is advantageous in itself, such as magnesium, are considerably increased.

It is advisable for the outlet of the strip ends to be thinner than the strip itself at the spiral inlet. This makes it easier to machine the outer last contour at the entrance.

If the outlet of the strip ends is curved and ends in the clamping tabs with a very flat transition angle, the tensile stress peaks occurring in the transition region between the strip end and the pane are significantly reduced.

It also makes sense if the clamping flap is dimensioned thinner than the disk or the immediately adjacent disk extension. This allows a further reduction of the tensile stresses in the outlet of the groin ends, since a thin clamping tab is more elastic than a thick-walled version.

Brief description of the drawing

Fig. 1

einen Querschnitt durch das luftseitige Gehäuseteil der Verdrängermaschine mit eingelegtem Läufer nach Linie I-I in Fig. 3;

Fig. 2

eine Vorderansicht des Läufers;

Fig. 3

einen Längsschnitt durch die Verdrängermaschine;

Fig. 4

einen Teilschnitt im Bereich des Spiraleneintritts gemäss Linie 4-4 in Fig. 2;

Fig. 5

eine Ansicht einer auslaufenden Leiste im Eintrittsbereich gemäss Ansichtspfeil D in Fig. 2

In the drawing, an embodiment of the invention is shown schematically.
Show it:

Fig. 1

a cross section through the air-side housing part of the displacement machine with an inserted rotor according to line II in Fig. 3;

Fig. 2

a front view of the runner;

Fig. 3

a longitudinal section through the displacement machine;

Fig. 4

a partial section in the area of the spiral entry according to line 4-4 in Fig. 2;

Fig. 5

2 shows a view of a sloping strip in the entry area according to view arrow D in FIG. 2

Way of carrying out the invention

For an explanation of 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. In the following, only the machine structure and process flow necessary for understanding are briefly described. For the sake of clarity, the rotor alone is shown in FIG. 2, and the housing with the delivery spaces and the inserted displacer are shown in FIG. 1. For a better overview, the housing walls are not hatched, while the cut strips of the runner are black.

The rotor of the machine as a whole is designated by 1 in FIG. 2. Arranged on both sides of the disk 2 are two, displaced, mutually offset by 180 °, spirally extending bodies. These are strips 3a, 3b which are held vertically on the pane 2. In the example shown, the spirals themselves are formed from a plurality of circular arcs adjoining one another. 4 with the hub is designated, via which the disc 2 with a roller bearing 22 is seated on an eccentric disc 23 (FIG. 3). This disk is in turn part of the main shaft 24.

5 with a radially outside of the strips 3a, 3b arranged eye is designated for receiving a guide bearing 25 which is mounted on an eccentric bolt 26. This in turn is part of a guide shaft 27. At the spiral end, four passage windows 6, 6 'are provided in the disk so that the medium can get from one disk side to the other in order to be drawn off in a central outlet 13 (FIG. 3) which is only arranged on one side .

The guide eye 5 of the guide eccentric arrangement is connected to the runner via a bow-shaped 21 rib. The eye lies in the tangential extension of the inlet side End of the spiral bar 3a. With this arrangement, high rigidity in the tangential direction and high elasticity in the radial direction are achieved. In addition, this concept serves to accommodate any length changes occurring between the two points of attack guide eye 5 and hub 4 and causes an automatic compensation.

1 shows the housing half 7b shown on the right in FIG. 3 of the machine housing which is composed of two halves 7a, 7b and is connected via fastening eyes 8 (FIG. 3) for receiving screw connections. 11a and 11b denote the two delivery spaces, each offset by 180 °, which are worked into the two housing halves in the manner of a spiral slot. They each run from an inlet 12a, 12b arranged on the outer circumference of the spiral in the housing to an outlet 13 provided in the interior of the housing and common to both delivery spaces. They have essentially parallel cylinder walls 14a, 14b, 15a, 15b arranged at a constant distance from one another. which, like the displacement bodies of the disk 2, comprise a spiral of 360 °. Between these cylinder walls, the displacement bodies 3a, 3b engage, the curvature of which is dimensioned such that the strips almost touch the inner and outer cylinder walls of the housing at several, for example at two points each. On the free end faces of the strips 3a, 3b and the webs 45, 46, seals 49 are inserted in corresponding grooves. With them, the working rooms against the side walls of the housing respectively. sealed against the displacement disc.

With this type of machine, in which two spirals offset by 180 ° are nested one inside the other, a further seal is required; namely, the inlet-side conveying spaces of the one spiral must be separated from each other against the further radially inner conveying spaces of the other spiral. From Fig. 1 it can be seen that in the region of the inlet 12b, the web 45a with the outer Cylinder wall 14a continues in web 46b with inner cylinder wall 15b. This measure also applies in the area of the inlet 12a. The transition here is from web 45b to web 46a.

FIG. 1 also shows that the disc 2 - apart from the radially protruding eye 5 - closes radially with the strips 3a, 3b. This means that the disk has to penetrate at least one half of the housing in the radial direction in the area of the inlets 12a, 12b. In the present case, this is done on the housing half 7 shown on the left in FIG. This measure has the advantage that, in this housing half, sealing strips are only to be arranged on the inner webs 46a, 46b, which seal the delivery spaces 11a, 11b against one another via the disk 2 up to the outlet.

If the transition from the web 45a to the web 46b were now sharp-edged and radial, and consequently the disc 2 was also closed radially at the corresponding inlet parts, a leakage would occur between the delivery chambers 11a and 11b. In order to avoid this, this transition is now designed as a circular shoulder 47a, 47b with the radius R1. The counter surface on the disk 2 is provided with a corresponding circular arc-shaped recess 48a, 48b, the radius R2 of this recess corresponding to the eccentricity e + radius R1. These shoulders 47a, 47b cooperate with the machine operation to form a sealing line with the arcuate recesses 48a, 48b.

The radially inner parts of the recesses 48a, 48b are now the geometric location for the discontinuities that cannot be avoided. According to the invention, the discontinuity in the radial extent of the center disk 2 is locally displaced and that is brought forward. This means that the disc in the The area of the inlet 12a, 12b of the spiral strips 3a, 3b is extended beyond the spiral inlet. The dimension A of the extension 2a, 2b corresponds at least to the simple inside width B between two adjacent, nested spirals in the inlet area. As a result, the transition of the center disk from the inlet-side end of the one spiral to the second spiral rotated by 180 ° and nested inside one another has moved away in the radial direction against the direction of flow of the working medium. The discontinuity is therefore no longer in the endangered zone in the spiral inlet area. The disk 2 is extended with the same outer radius R _A that it has in the inlet area of the spirals.

In the example shown, the dimension A of the disk extension 2a, 2b is significantly larger than the clear width B between two adjacent, nested spirals - which clear width also corresponds to that of the associated conveying spaces - for the following reason:

In the embodiment shown in FIGS. 1 and 2, the spirals span a wrap angle of a total of 360 °, the majority of which are formed with a first curvature and have a significantly smaller radius of curvature on the outlet side over an angular range of approximately 45 °. This shortening of the spiral enables the passage windows 6 ′ to be arranged in the pane 2. These windows are now located approximately in the radial plane of the inlet area of the pane which is at risk from the stress concentration.

In this case, the minimum dimension by which the pane protrudes beyond the inlet area is not measured from the inlet edge of the spiral, but from the plane which marks the narrowest cross section between the passage window 6 'and discontinuity in the pane transition. In the present case, this is the radial plane C. Using this design rule there is in any case a minimum dimension A for the extension 2a, 2b, which is greater than the clear width B of the associated delivery area.

As a further measure for reducing the stress concentration, the disk extensions 2a, 2b are provided radially on the outside with a material accumulation, which form clamping tabs 50a, 50b for the mechanical processing of the rotor. These clamping tabs are thinner than the disc 2 (Fig. 4 and 5). As a result, they are not touched by the milling tool, which is usually used on both sides of the wheel. The pore-free cast skin thus remains unprocessed and does not form a starting point for possible crack formation.

The spiral strips 3a, 3b run into the pane extension 2a, 2b at their ends on the entry side, the outlet 51a, 51b opening into the clamping tabs 50a, 50b (FIG. 5). This outlet 51a, 51b of the strip ends is dimensioned thinner than the strips 3a, 3b. The fact that the end edges of the strips do not run perpendicular to the pane, but rather at an angle to them, gives the free-standing ends of the strips greater stability.

The said slope has a curvature and opens into the clamping tabs 50a, 50b with a very flat transition angle α. This extension of the foot area of the strips in the circumferential direction thus ends in an unprocessed area. This has a favorable effect on the reduction of the tensile stresses which arise due to the temperature gradient present in the radial direction during operation.

The clamping tab 50a is located radially inside the rib 21, which defines the limits of its geometric extension. It has a smaller mass than the opposing clamping tab 50b. This is achieved in that the latter is dimensioned larger in the tangential direction with the same thickness. With this measure you have a simple means in hand to make a mass balance for the rib 21 based on the dimensioning of the flap 50b. This is advantageous for the sake of relieving the guiding intervention provided in eye 5.

The drive and the guide of the rotor 1 are provided by the two spaced-apart eccentric arrangements 23, 24 and. 26, 27. The main shaft 24 is supported in a roller bearing 17 and a slide bearing 18. At its end protruding from the housing half 7b, the shaft is provided with a V-belt pulley 19 for the drive. Counterweights 20 are arranged on the shaft in order to compensate for the inertial forces arising when the rotor is eccentrically driven. The guide shaft 27 is inserted in a sliding bearing 28 within the housing half 7b.

In order to achieve clear guidance of the rotor in the dead center positions, the two eccentric arrangements are synchronized with precise angles. This is done via a toothed belt drive 16. On the occasion of operation, the double eccentric drive ensures that all points of the rotor disk and thus also all points of the two strips 3a, 3b perform a circular displacement movement. As a result of the multiple alternating approaches of the strips 3a, 3b to the inner and outer cylinder walls of the associated delivery chambers, crescent-shaped workrooms enclosing the working medium result on both sides of the strips, which are displaced by the delivery chambers during the drive of the rotor disk in the direction of the outlet. The volumes of these working spaces are reduced and the pressure of the working fluid is increased accordingly.

Of course, the invention is not limited to the exemplary embodiment shown and described. The new measure can be used just as advantageously for positive-displacement runners whose disc does not end on the outside with the strips, but where the center disc forms a sealing surface projects beyond the strips in diameter, as is the case, for example, in the aforementioned DE-C-26 03 462.

LIST OF DESIGNATIONS

1

runner

2nd

disc

2a, 2b

Window extension

3a, 3b

strip

4th

hub

5

eye

6, 6 '

Passage window

7a, 7b

Half of the housing

8th

Mounting eye

9

Recording for 24

10th

Recording for 27

11a, 11b

Funding room

12a, 12b

inlet

13

Outlet

14a, 14b

Cylinder wall

15a, 15b

Cylinder wall

16

Timing belt drive

17th

Rolling bearings for 24

18th

Slide bearing for 24

19th

V-belt pulley

20th

Counterweight on 24

21

bow-shaped rib

22

Rolling bearings for 23

23

Eccentric disc

24th

Main shaft

25th

Guide bearings

26

Eccentric bolt

27

Guide shaft

28

Slide bearing for 27

45a, 45b

Bridge with outer cylinder wall

46a, 46b

Bridge with inner cylinder wall

47a, 47b

paragraph

48a, 48b

Recess

49

poetry

50a, 50b

Clamping rags

51a, 51b

Outlet of 3a, 3b

R1

Radius of 47a, 47b

R2

Radius of 48a, 48b

e

Eccentricity (Fig. 1 + 3)

R _A

outer radius of the disc 2

B

clear width of the funding rooms

C.

Radial plane

α

Transition angle from 51 to 50

Claims (7)

Displacement machine for compressible media with a plurality of spiral conveying spaces (11a, 11b) arranged in a fixed housing (7a, 7b), which lead from a radially outer inlet (12a, 12b) to a radially inner outlet (13), and with one of the conveying spaces assigned displacement body, essentially consisting of a disk (2) with spiral strips (3a, 3b) arranged vertically on both sides, the eccentrically driven displacement body executing a circular movement with each of its points during operation, limited by the peripheral walls of the delivery chamber,
characterized, - that the disc (2) in the area of the inlet (12a, 12b) of the spiral strips (3a, 3b) is extended beyond the spiral inlet, that this disk extension (2a, 2b) is provided radially on the outside with a material accumulation serving as clamping flaps (50a, 50b), - And that the spiral strips (3a, 3b) end at their entry ends in the disc extension (2a, 2b), the outlet (51a, 51b) opening into the clamping tabs (50a, 50b). Displacement machine according to claim 1, characterized in that the disc is extended with approximately the same outer radius (R _A ) that it has in the inlet region of the spirals. Displacement machine according to claim 1, characterized in that the outlet (51a, 51b) of the strip ends is dimensioned thinner than the strips (3a, 3b). Displacement machine according to claim 1, characterized in that the outlet (51a, 51b) of the strip ends is curved and opens into the clamping tabs (50a, 50b) with a very flat transition angle (α). Displacement machine according to claim 1, characterized in that the clamping tab (50a, 50b) is dimensioned thinner than the disc (2). Displacement machine according to Claim 1, in which a second eccentric arrangement (26, 27) which is arranged at a distance from a first eccentric arrangement (23, 24) is provided for guiding the displacer body relative to the housing, and wherein the guide eye (5) of the second guide eccentric arrangement with the disk (2) is connected via a rib (21) such that the guide eye lies at least approximately in the tangential extension of the inlet-side end of the associated spiral bar (3a),
characterized in that the clamping tab (50a) is located radially inside the rib (21). Displacement machine according to claims 5 and 6, characterized in that the disc (2) is provided with two diametrically opposite clamping tabs (50a, 50b), the clamping tab (50a) located radially inside the rib (21) having a smaller mass than the opposite clamping tab (50b).

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