Rotary piston engine and method for operating a rotary piston engine

Abstract

A rotary piston engine comprises a housing (10), which forms an interior space (11), and at least two rotary pistons (20, 30), which are arranged in the interior space (11). Formed on the interior space (11) are an inlet opening (13) and an outlet opening (15) to guide a fluid through the interior space (11). The rotary pistons (20, 30) are thereby driven by fluid flowing through. Each rotary piston (20, 30) has on its outer circumference at least two sealing strips (21, 31). According to the invention each rotary piston (20, 30) comprises at least two cavities (27, 37), in each of which a tube (38B) or an elastic solid rod is arranged. The sealing strips (21, 31) project into the cavities and against the tube (38B) received therein or the elastic solid rod. Through the tube (38B) or the rod, the sealing strips (21, 31) are pushed radially outwards.

Claims

1. A rotary piston engine, comprising: a housing which forms an interior space, and at least two rotary pistons which are arranged in the interior space, wherein on the interior space an inlet opening and an outlet opening are formed to guide a fluid through the interior space along the pistons, wherein each rotary piston has on its outer circumference at least two sealing strips, wherein: each rotary piston has at least two cavities, in each of which an elastic elongated deformation body is arranged, which comprises a tube or an elastic solid rod, wherein the sealing strips project into the cavities and against the elastic elongated deformation body received therein, and are pushed radially outwards by said elastic elongated deformation body.

2. The rotary piston engine according to claim 1, wherein: each tube or each elastic solid rod is formed by a plurality of tube or rod components, which are arranged one over the other in the respective cavity.

3. The rotary piston engine according to claim 2, wherein: each cavity has a cylindrical shape with a longitudinal axis which extends parallel to a longitudinal axis of the rotary pistons, and each tube extends over an entire length of the associated cavity, wherein the respective tube is in contact over the whole length with the associated sealing strip and pushes it outwards.

4. The rotary piston engine according to claim 1, wherein: each elastic elongated deformation body is cylindrical and has a longitudinal axis parallel to an axis of rotation of the associated rotary piston.

5. The rotary piston engine according to claim 1, wherein: the tube or the elastic solid rod consists of a non-metallic material.

6. The rotary piston engine according to claim 1, wherein: the tube or the elastic solid rod has a round or circular shaped cross-section.

7. The rotary piston engine according to claim 1, wherein: each tube has an external radius which is about equal to a radius of the associated cavity, in which the respective tube is received.

8. The rotary piston engine according to claim 1, wherein: each cavity has a dimension in a circumferential direction of the associated rotary piston which is greater than a dimension of the cavity in a radial direction of the associated rotary piston.

9. The rotary piston engine according to claim 1, wherein: each sealing strip has in cross-section a widened central region, which engages in a corresponding retaining groove in the respective rotary piston, whereby a movement space of the sealing strip is limited in a radial direction of the associated rotary piston.

10. The rotary piston engine according to claim 1, wherein: each rotary piston has on its outer circumference a toothed wheel which is interrupted by: at least two bulge portions which protrude over the toothed wheel, each comprising a slot to receive one of the sealing strips, and at least two depressions, in which the bulge portions of the respective other rotary piston engage during a rotation of the rotary pistons, wherein the bulge portions and the depressions are formed so that, upon engagement of one of the bulge portions in one of the depressions, a sealing contact is produced between the toothed wheels directly in front of the depression, and a first contact between this bulge portion and this depression is realised between a rear face of the bulge portion and a rear portion of the depression, so that a gas inclusion and a gas compression take place in the depression, whereby, through a further gas compression upon further rotation of the rotary pistons, a friction-reducing gas film forms between the rotary pistons.

11. The rotary piston engine according to claim 10, wherein: the shape of each bulge portion forms on both sides of the slot a respective plateau region, over which a rotary piston radius, which is defined to the mid-point of the rotary piston, does not decrease, so that, upon engagement of one of the bulge portions in one of the depressions, the first contact is realised between the depression and a rearmost of the plateau regions defined based on a direction of rotation of the associated rotary piston, or between the depression and a curved portion of the bulge portion which follows behind the plateau region.

12. The rotary piston engine according to claim 10, wherein: each sealing strip has in cross-section a length and a width, wherein the length is defined in a radial direction of the associated rotary piston, and wherein the length is at least three times greater than the width.

13. A method for operating a rotary piston engine, the method comprising: introducing a fluid through an inlet opening on a housing, which forms an interior space, wherein at least two rotary pistons are arranged in the interior space, wherein, as the fluid flows through the interior space to an outlet opening, it drives the rotary pistons, wherein each rotary piston has on its outer circumference at least two sealing strips, wherein: each rotary piston has at least two cavities, in each of which an elastic elongated deformation body is arranged, which comprises a tube or an elastic solid rod, wherein the sealing strips project into the cavities and against the elastic elongated deformation body received therein and are pushed radially outwards by said deformation body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and features of the invention are described below with reference to the accompanying schematic drawings, in which:

(2) FIG. 1 shows a cross-section of a rotary piston engine according to an embodiment of the invention;

(3) FIG. 2 shows a further cross-sectional representation of a rotary piston engine according to an embodiment of the invention;

(4) FIG. 3 shows an enlarged cut-out of the rotary piston engine of FIG. 2;

(5) FIGS. 4A, 4B, 4C show cross-sectional views of the rotary piston engine of FIG. 2 in different rotation positions.

(6) Identical and identically acting components are generally identified in the drawings by the same reference numerals.

DETAILED DESCRIPTION OF THE INVENTION

(7) Embodiments according to the invention of a rotary piston engine 100 will be described initially by reference to FIGS. 1 and 2. The rotary piston engine 100 comprises two rotary pistons 20, 30 which rotate together and can be driven by a fluid flowing through. The axes of rotation of the two rotary pistons 20, 30 extend through the respective midpoints of the rotary pistons 20, 30. The cross-sectional representations of FIGS. 1 and 2 are sectional views perpendicular to these axes of rotation.

(8) The rotary piston engine 100 comprises a housing 10, for example a metal housing, which forms inside it an interior space 11. The interior space 11 can be formed fluid-tight apart from an inlet opening 13 and an outlet opening 15. In the interior space 11, the two rotary pistons 20, 30 are arranged so that they each form a sealing contact with the wall of the interior space 11 and also sealingly contact each other, independently of their momentary rotation position. If a fluid is guided through the inlet opening 13 into the interior space 11, it can consequently only reach the outlet opening 15 if it flows along the rotary pistons 20, 30 and sets these in rotation. The rotation energy of the rotary pistons 20, 30 can be used in a way that is known in principle for applications that are arbitrary in themselves, for example as a mechanical drive or to generate electrical energy by means of a generator.

(9) The two rotary pistons 20, 30 have the same diameter and each of them has on its outer circumference a toothed wheel 22, 32. The two toothed wheels 22, 32 mesh with each other. A seal is hereby achieved between the two rotary pistons 20, 30 and a fluid passage is prevented in this position. In addition, the two rotary pistons 20, 30 rotate through the toothed wheels 22, 32 synchronously (one clockwise and the other anti-clockwise).

(10) In addition each rotary piston 20, 30 has two bulge portions 25, 35 which protrude radially outwards over the respective toothed wheel 22, 32. Besides being interrupted by the bulge portions 25, 35, the two toothed wheels 22, 32 are also interrupted by two depressions 24, 34. In the regions of the depressions 24, 34, the respective rotary piston 20, 30 therefore has a smaller radius. When the rotary pistons 20, 30 rotate together, the bulge portion 35 of one of the rotary pistons 30 engages in the depression 24 of the other rotary piston 20, and vice versa.

(11) Each bulge portion 25, 35 has a slot which can extend in the radial direction. Disposed in each slot is a sealing strip 21, 31 which projects outwardly out of the slot. The sealing strips 21, 31 can, in dependence on the rotation position of the rotary pistons 20, 30, sealingly contact the wall of the interior space.

(12) The design of the sealing strip and its fixture and resilience means are of great importance for friction and sealing properties of the engine, through which the efficiency of the engine is largely determined. Frequently, sealing strips and their resilience means are also the components that are subject to the greatest wear, so that the design of the sealing strips and their resilience means is also of great importance for maintenance intervals and the service life of the engine.

(13) Each sealing strip 21, 31 is received in a slot in one of the bulge portions 25, 35 on the rotary pistons. The slots each open into a cavity 27, 37. In conventional rotary piston engines there is disposed at the end of such slots a spring, for example a coil spring or leaf spring. However, these cause an uneven pressure: in the axial direction (from the drawing plane) a leaf spring has only in its centre a high pressure, which decreases sharply towards the edge. Coil springs also act selectively, i.e. area-wise. Furthermore, there is the risk—if such a metal spring breaks—of small metal particles penetrating into other parts of the engine and causing serious damage. These disadvantages are overcome by the provision in each cavity 27, 37 of one or a plurality of cylindrical deformation bodies 28, 38 which consist of an elastic material such as silicone or rubber. The deformation bodies 28, 38 each consist of a tube, in particular a silicone tube, or a solid elastic rod. The sealing strip 21, 31 projects as far as, or projects into, the cavity 27, 37 and against the silicone tube. The silicone tube is thereby compressed and exerts a radially outwardly orientated pressure on the sealing strip 21, 31. In the axial direction this cylindrical deformation body can have an equal cross-section so that a uniform pressure is exerted over the axial length. Furthermore, no metal parts are used so that, in the event of a break in the tube/deformation body, there is no risk of resulting damage to the engine.

(14) FIG. 2 shows for illustration purposes on the rotary piston 30 only a single sealing strip with the associated tube, while the second cavity 37 and the slot adjacent thereto are shown empty. During use, of course, also disposed here are a tube as a resilience means in the cavity 37 and a sealing strip in the slot. The circumferential direction 47 (dashed line) and radial direction 57 (solid line) in which the cavity 37 extends are also illustrated in FIG. 2.

(15) Each rotary piston can be symmetrically constructed, i.e. the shapes of the bulge portions, sealing strips and depressions to the fluid-inflow side being independent of the direction of rotation of the rotary piston. The rotary piston engine can thus be operated equally in both rotation directions 23 and 33 of rotary pistons 20 and 30, respectively. For a change of direction, the introduction of the fluid is merely reversed, thus being introduced through the outlet opening 15 into the interior space 11 and out through the inlet opening 13.

(16) An enlarged cut-out of the rotary piston 30 is shown in FIG. 3. The sealing strip 31 projects radially outwards over the bulge portion 35 and projects inwards into the cavity 37, in which, here, a hollow tube 38B is used as a deformation body 38. A length (L) and width (W) of the sealing strip 31 are indicated in FIG. 3. The sealing strip 31 has in a central region a thickened area 31A. The gap or slot for the sealing strip has at a corresponding position a recess (retaining groove), into which the thickened area 31A projects. The sealing strip 31 thus has a cross-shaped cross-section. The sealing strip 31 is hereby held in the slot and cannot exit the slot either radially outwards or radially inwards. The cross-section dimensions of the sealing strip 31 and the position of the recess on the slot are selected so that the sealing strip 31 projects into the cavity 37 and (when the engine is stationary) compresses the tube 38B. The tube 38B is therefore pre-tensioned and causes, in the stationary state or upon start-up of the engine, a sealing contact of the sealing strip 31 with the inner wall of the housing. The tube 38B has a round cross-section, which can be circular shaped without pre-tension and, through the pre-tension against the sealing strip 31, can have an arched or oval shape. At higher speeds of the engine the centrifugal forces also push the sealing strip outwards and thus provide a sealing effect. In order to ensure that the pressure/pushing of the sealing strips outwards does not become unnecessarily large and produce unnecessary friction, through the thickened area 31A a movement space of the sealing strip 31 is outwardly limited. If at higher centrifugal forces the sealing strip 31 is pushed outwards through its own weight, the silicone tube 38B is hereby unburdened, which has a positive effect on the service life of the silicone tube 38B.

(17) The thickened area 31A on the sealing strip 31 can in principle also be formed at its inner end, thus directly against the deformation body 38. A possible compression distance of the deformation body 38 is greater, however, if the contact area with the sealing strip is not too large, so that it can be advantageous if the thickened area 31A is formed in a central region. In addition, the thickened area 31A also limits the movement possibility of the sealing strip 31 inwards, thereby facilitating an exchange of the deformation body 38 for maintenance purposes.

(18) The sealing action of the sealing strips 21, 31 is desired for the contact with the housing inner wall. On the other hand a seal between the two rotary pistons 20, 30 is already brought about through the intermeshing toothed wheels 22, 32 and also by the bulge portions 25, 35 engaging in the depressions 24, 34. Contact between the sealing strips 21, 31 and the depressions 34, 24 is not therefore required and on the contrary can even be undesirable, as the sealing strips 21, 31 are hereby ground down and would need to be replaced sooner.

(19) In order to overcome these disadvantages, a special form of the rotary pistons and the sealing strips is used, leading to particularly low friction between the rotary pistons. This will be described in more detail by reference to FIGS. 4A to 4C. These drawings show the contact area between the two rotary pistons 20, 30, wherein the drawings differ in the momentary rotation positions of the rotary pistons 20, 30. In FIG. 4A the bulge portion 25 (with rear face 25A) is still outside of the depression 34 (with rear portion 34A, whereas in FIG. 4B the bulge portion 25 is just dipping into the depression 34, and in FIG. 4C it has been almost completely received in the depression 34.

(20) A sealing contact between the rotary pistons 20, 30 is already achieved in FIG. 4A through the intermeshing toothed wheels 22, 32 before the bulge portion 25 contacts a wall of the depression 34. The depression 34 is thus filled by the fluid in the interior space 11, wherein the toothed wheels 22, 32 prevent the fluid from leaving the depression 34 in the direction of rotation of the two rotary pistons. If the bulge portion 25 (having a rearmost portion 25B of a plateau portion) is driven into the depression 34 (FIG. 4B), the fluid in the depression 34 is compressed. The high pressure in the depression 34 pushes the sealing strip 21 into its slot. The sealing strip 21 does not hereby come into contact, or hardly comes into contact, with the wall of the depression 34, so that there is hardly any wear or friction on the sealing strip 21. If the rotary pistons 20, 30 are rotated further, the compressed air/the compressed fluid escapes from the depression 34 and indeed counter to the direction of rotation of the pistons 20, 30 (because in the direction of rotation of the pistons, through the toothed wheels, wherein constantly at least two teeth of each piston engage in two grooves of the other piston, no fluid can escape). Through this escape of the air, an air film or an air lubrication is produced on the sealing strip 21 and the bulge portion 25, thereby reducing the contact and thus avoiding unnecessary friction (FIG. 4C). This advantageous effect can be clearly demonstrated experimentally through the noise evolution of the air compression and can be distinguished from conventional structures, wherein, although bulge portions engage in depressions, an adequate seal is not produced that leads to the air compression and the friction-reducing air film.

(21) For example, in GB 2486787A there is no tooth system that produces sufficient sealing in the direction of rotation, which would be necessary to make high air compression possible. In addition, the form of the bulge portion is important, as described in more detail below. As shown in FIG. 3, a bulge portion has a central straight region 35B which goes via curved lateral areas 35A and 35C to the toothed wheel 32. In order to protect the accommodated sealing strip 31 from abrasion against the wall of the depression 24, it is advantageous if an air compression arises in the depression 24 before the sealing strip comes into contact with the depression wall. For this, when the bulge portion 35 dips into the depression 24, a first contact (or alternatively a very small distance) can arise between the bulge portion 35 and the depression 24 at a position of the bulge portion 35 behind (i.e. behind as viewed in the direction of rotation) the sealing strip 31. This is either the arched region 35C (curved portion 35C) in FIG. 3 or the central plateau region 35B between the sealing strip 31 and the arched region 35C. In order to achieve this, the bulge portion 35 must be sufficiently wide. This can be the case in particular if the plateau region between the sealing strip 31 and the arched region 35C corresponds to at least 40% of the sealing strip width.

(22) Preferably, this friction-reducing utilisation of an air film is used together with the sealing strip resilience means through a silicone tube or a similar cylindrical deformation body.

(23) The various aspects of the invention thus offer a rotary piston engine having an excellent level of efficiency at the same time as low wear.