EP0545190B1 - Scroll-type fluid displacement machine - Google Patents

Description

Field of the Invention

The invention relates to a displacement machine for compressible media according to the preamble of patent claim 1.

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 conveyance 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, among other things. During the operation of such a compressor, along the displacement chamber between the spiral-shaped displacement body and the two peripheral walls Displacement chamber includes a plurality of roughly crescent-shaped work spaces which move from the inlet through the displacement chamber to the outlet, their volume constantly being reduced and the pressure of the working medium being increased accordingly. With this machine it is assumed that the wrap angle of the spirals leads to a compressor with internal compression. For this purpose, a second spiral part with a significantly smaller radius of curvature is attached to a spiral extending over 360 °.

A machine in which the spirals span a total wrap angle of approx. 450 °, the outlet-side spiral parts also having a significantly larger curvature over an angle of approx. 90 °, a machine which also works with internal compression is known from DE-A-31 38 585. However, the fact of the internal compression alone leads to an increased power requirement precisely in those operating phases in which the full pressure and the full delivery rate are not required by the consumer.

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. These machines, which are used for charging internal combustion engines, show that a geometrically internal compression of approx. 1 represents the optimal value. The above-mentioned second spiral part with a significantly smaller radius of curvature can thus be omitted. This known machine works with a displacer, the spiral walls of which are fastened on both sides to a central wall. This central wall has through-openings in the radially inner region, which make it possible for the air conveyed by the drive-side part of the spirals to get into the air-side part in order to get out of it Machine to be peeled off. Two nested spirals are arranged on each side of the central wall, the outlets of which are offset by 180 ° relative to one another. The conveying spaces arranged in the housing are also configured accordingly. This means that the clear diameter between the inner walls of the delivery chamber at the spiral outlet is decisive for the available space. In this available space, however, not only the working medium displaced by the orbiting spirals has to be conveyed. The drive shaft with the eccentric and the counterweights must also be accommodated in this room.

Presentation of the invention

The invention has for its object to provide a displacement machine of the type mentioned with increased clearance between the fixed spiral ends.

The object is achieved by the characterizing features of the claims.

The advantage of the invention can be seen in the fact that the free cross section of the passage openings in the rotor can be considerably increased by optimizing the spiral outlet. At high throughputs, this measure reduces the pressure losses when passing through the openings. One of the consequences of this is that the axial thrust acting on the air outlet is reduced to the displacer. This in turn relieves the sealing strips on the end faces of the spiral ribs, via which the displacer is supported on the housing in the axial direction. Furthermore, the invention offers the possibility of carrying the eccentric Enlarging the main shaft in diameter and thus making it stiffer, which is very important for the load capacity of the machine.

It is particularly expedient if the spirals at the outlet end are provided with the significantly smaller curvature at an angle of 45 °. With this measure, the greatest possible freedom can be achieved for a spiral machine with a geometric compression ratio of approx. 1.

Brief description of the drawing

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

Fig. 1

einen Querschnitt durch das antriebsseitige Gehäuseteil der Verdrängermaschine nach Linie I-I in Fig. 3;

Fig. 2

eine Vorderansicht des Läufers;

Fig. 3

einen Längsschnitt durch die Verdrängermaschine;

Fig. 4

ein Schaubild Lebensdauer des Hauptexzenterlagers (Nadellager) in Funktion des Verkürzungswinkels;

Fig. 5

ein Schaubild Hubvolumen in Funktion des Verkürzungswinkels;

Fig. 6

Ein Schaubild Drehzahl in Funktion des Verkürzungswinkels;

Fig. 7

Ein Schaubild Masse des Verdrängers in Funktion des Verkürzungswinkels;

Fig. 8

Ein Schaubild Innenraum in Funktion des Verkürzungswinkels;

Fig. 9

Ein Schaubild Durchlassquerschnitt in Funktion des Verkürzungswinkels.

Show it:

Fig. 1

a cross section through the drive-side housing part of the displacement machine 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 diagram of the life of the main eccentric bearing (needle bearing) as a function of the shortening angle;

Fig. 5

a graph of displacement as a function of the shortening angle;

Fig. 6

A graph of speed as a function of the shortening angle;

Fig. 7

A graph of the mass of the displacer as a function of the shortening angle;

Fig. 8

A diagram of the interior as a function of the shortening angle;

Fig. 9

A diagram of the flow cross-section as a function of the shortening angle.

Way of carrying out the invention

In order 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. In the following, only the machine structure and process flow necessary for understanding are briefly described. For the sake of clarity, the runner alone is shown in FIG. 2, and only the conveyor walls and the inserted displacer are shown in FIG. 1. Not shown in Fig. 1 are the other cut elements such as housing, guide shaft, drive shaft, etc.

The rotor of the machine is designated as a whole by 1. On both sides of the disc 2, two spiral-shaped displacers are arranged, which are offset by 180 ° to one another. 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 disk 2 with a roller bearing 22 is seated on an eccentric disk 23 (FIG. 3). This disk is in turn part of the main shaft 24.

5 with a radially outside 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 .

1 shows the housing half 7b shown on the left 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. 9 symbolizes the holder for the main shaft, 10 the holder for the guide shaft. 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 °. The displacers 3a, 3b engage between these cylinder walls, the curvature of which is dimensioned such that the strips almost touch the inner and outer cylinder walls of the housing at a plurality, for example at two points each.

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 work while the rotor disk is being driven through the delivery chambers in the direction of the Outlet to be moved. The volumes of these working spaces decrease and the pressure of the working fluid is increased accordingly.

According to the invention, the spirals of the conveying spaces 11a, 11b and the displacement bodies 1-4, which all span a wrap angle of 360 ° in total, extend in their predominant extent with a first curvature. In the present example, this first section of curvature extends from the entry-side end of the spirals over an angle of 315 °. This first section consists of two arcs A and B, with its initial part A running over 180 and the end part over 135 °. The pole of the beginning portion A is designated for the Verdrängerspirale in Fig. 2 with P _A, that of the end portion P with _B. The associated radii of curvature are designated R _A and R _B.

At the exit end, the curvature of the second section C extends over the remaining angle of 45 ° with a significantly smaller radius of curvature. This second section is also a circular arc, the pole of which is denoted by P _C and the radius of curvature by R _C.

The cylinder walls of the delivery rooms are adapted to this displacement form. In the example chosen, the second section C _{ZA of} the outer cylinder wall can be clearly seen in FIG. 1. On the other hand, the second section C _{Zi of} the inner cylinder wall is not so clearly recognizable. This is the usual rounding of the wall at the end of the spiral, the radius of the rounding corresponding to half the wall thickness. From the point of view of production technology, the configuration selected is therefore advantageous, since no special work processes have to be carried out for the inner cylinder wall.

The effects of the new measure are explained below using the diagrams in FIGS. 4-9. The shortening angle ϕ is plotted on the abscissa of these graphs. This is the angular range in which the second sections of the spirals with the substantially smaller radius of curvature are to be formed. The effects were examined in a range between 0 ° and 180 °. The latter value would mean that the spirals would only consist of an arc in their first section. The second part would have the much smaller radius R _C and would extend over 180 °.

The ordinate of FIG. 4 shows the service life L of the main eccentric bearing 17 in [%]. This assumes that it is a needle bearing and that the machine is designed for a constant maximum volume flow. By shortening the spiral by the shortening angle, the orbiting mass of the rotor 1 becomes smaller and thus loads the bearing less at a constant speed. According to the diagram it can be seen that compared to the initial case, i.e. a 360 ° spiral without the inventive measure, any shortening in the range between 0 ° and 100 ° causes an increase in the service life. The subsequent drop is due to the speed increase that becomes necessary if the speed is reduced further.

Because the shortening of the spiral naturally results in a decrease in the maximum suction volume that can be enclosed in the delivery rooms. This fact can be seen in FIG. 5, in which the displacement V is shown on the ordinate. It can be seen that if the spiral is shortened by 90 °, only approx. 95 ° of the original volume is conveyed. If, however, one wishes to maintain this original volume, this must be compensated for by increasing the circular speed of the rotor.

The required increase in the speed of the main shaft 24 is shown in FIG. 6, in which the speed n is plotted on the ordinate.

7 shows the displacer mass m on the ordinate. Here, a cross-comparison with FIGS. 6 and 4 shows that from a ten percent increase in speed, despite a considerable decrease in mass, the speed begins to have a dominant influence on the service life of the rolling bearing.

The available interior space D (FIG. 1) between the spiral ends is plotted in [%] on the ordinate of FIG. 8. It can be seen that, compared to the initial case, a significant gain in space can be achieved by shortening over a wide angular range.

9 finally shows the dependence of the cross section A of the passage windows in the rotor. The discontinuity in the angular range of 90 ° is due to the structurally and structurally necessary arrangement of spokes between the windows. It can be seen that the shortening angle of 45 °, for example, makes it possible to arrange passage windows 6 'in the rotor in addition to the previously usual passage windows 6 (FIG. 2) and thus to almost double the area through which flow passes.

It follows from all of this that a shortening angle in the range from 30 ° to 90 ° leads to the desired result, and that the shortening angle of 45 ° shown and described for example is particularly advantageous.

LIST OF DESIGNATIONS

1

runner

2nd

disc

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 area

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

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

ϕ

Shortening angle of the spiral

L

Lifetime of the rolling bearing

V

Stroke volume

n

Main shaft speed

m

Displacement mass

D

available interior

A

Cross section of the passage window

A

Beginning part of the first section

B

End part of the first section

C.

second part

P _A

Pole of the beginning of the first section

P _B

Pole of the end part of the first section

P _C

Pole of the second section

R _A

Radius of the beginning of the first section

R _B

Radius of the end part of the first section

R _C

Radius of the second section

C _ZA

Second section of the outer cylinder wall

C _room

Second section of the inner cylinder wall

Claims (2)

1. Displacement machine for compressible media, having at least two helical delivery chambers (11a, 11b), which are mutually offset by 180° and are disposed in a fixed housing (7a, 7b) and which span an angle of wrap of 360°, and having a helical displacement body (1-4) assigned to each delivery chamber, which helical displacement body spans an angle of wrap of 360° and is held in such a way on a disc-shaped rotor (1) which can be eccentrically driven relative to the housing that, during operation, each of its points performs a circular motion limited by the peripheral walls of the delivery chamber, and the curvature of which displacement body is dimensioned relative to that of the delivery chamber such that it almost touches the inner and outer peripheral walls of the delivery chamber at at least one sealing line in each case, which sealing line continually advances during operation, characterized in that the spirals of the delivery chamber (11a, 11b) and of the displacement body (1-4) display from their inlet, in their predominant extent, a first curvature section comprising at least one circular arc, and in that the outlet-side end of the spirals displays, over an angular range (ψ) ranging from about 30° to about 90°, a second curvature section having a markedly greater curvature.
2. Displacement machine according to Claim 1, characterized in that the second curvature section having the markedly greater curvature extends over an angle (ψ) of 45° at the outlet-side end of the spirals.

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