Abstract:
A sealing system of rotary piston machines, the rotor excludes rotor discs which are arranged next to one another, and which are seated on the common rotor axle and are pressed apart from one another by acting spring and/or gas forces in the joints between the discs in such a way that the end sides of the discs which point towards the side walls of the housing bear sealingly against the latter and thus prevent the access of the medium to the axles. Assemblies comprising movable shaped lamellae which adapt to the changing joint widths and prevent an inner flow around the rotor are present in the part joints between the discs.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is directed to a principle and system of sealing rotary pistons against the enclosing casing wall of rotary compression and expansion engines. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the art of rotary piston engines, different solutions for achieving tightness, that is, sealing, of the piston against the enclosing casing wall during the course of movement are known. So-called rotor segment engines achieve an almost good tightness due to the high size accuracy of the components rotor, casing and blades which surround the operating space and yield the smallest possible gap between the components. In certain cases the tightness can even be improved by introducing a suitable fluid into the engine, causing a small fluid film to act as a sealing body between the components. When doing compression work with such engines gap losses must be accounted for. Such losses result in a reduction of the delivery output which can be compensated for by increasing the driving power of the compressor. In expansion engines the gap losses may lead to a loss in operation, especially when a damaging expansion takes place mainly via the gaps which result in providing ineffective rotary power of the rotor. 
         [0003]    On the other hand, expanding media in high temperature conditions such as present in thermal engines can lead to a destruction of the engine as passing hot gases cause material erosion to component parts thereby increasing the gaps. 
         [0004]    F. Wankel found that rotary combustion engines having more than three components moving in relation to each other, such as a rotor, movable piston parts fitted at the rotor, and casing, cannot function, as the sealing elements cannot be arranged such that during the course of motion of the engine, a unified spatial system of sealing lines having the same geometrical shape can be achieved. This defect is clearly visible in rotor segment engines. Though it may be possible to achieve a radial and axial tightness against the casing wall by spring sealing strips along the blade edges, the sealing line is interrupted in the area of the rotor hub by a remaining unsteadiness, which will lead to an untightness of the engine. Resulting from this experience, the rotary piston internal combustion engine developed by F. Wankel was an engine type having only 2 components moving in relation to each other and enclosing the working space: a casing with a trochoidal running way and a rotary piston also derived from a trochoid as internal enclosing body of the casing running way. Sealing strips can be fitted on this piston fulfilling the conditions of an unchanged geometrical shape. This type of engine has become known as Wankel engine. 
         [0005]    In spite of the advantages and the successful development of this type of engine, certain technological targets could not be reached. The geometrically determined change in volume of the trochoid does not allow carrying out a traditional Diesel process. Though less important, the lubrication of the sealing strips and, connected with it, the heat dissipation from the piston to the casing wall are also concerns. 
       SUMMARY OF THE INVENTION 
       [0006]    The aim of the invention is to create a sealing system for rotary piston engines which uses the principle of a similar geometrical shape of the sealing line according to Wankel so that other types of rotary piston engines for expansion and compression processes in higher temperature conditions can be used and which exhibit improved properties concerning change in volume, lubrication and heat dissipation. 
         [0007]    The present invention relates to Wankel-type rotary piston engines in which sealing is improved through structural arrangements that achieve sealing across the rotor resulting in a more economical and environmentally friendly construction than previously possible, while retaining basic engineering principles. 
         [0008]    In one aspect the invention relates to a rotor comprising two or more parallel rotor disc segments, the outer discs of which face the casing wall which disc segments are pressed by spring forces and/or gas pressure to the casing wall in such a way that their planar faces seal against the casing wall preventing circumferential flow, and the invention also relates to a closing of the gaps arising between the spaced rotor segment discs by sealing strips positioned within the gaps. Further the sealing strips are spring actuated to form a sealing in the direction in which the rotor runs in the casing so that the result is a system of thorough, even sealing lines which lack any interruptions. 
         [0009]    In another aspect the invention relates to sealing strips comprising adjustable lamellae units formed of complementary pairs of lamellae which, with each other and together with the rotor disc segments form a labyrinth sealing against the casing. Also, the arrangement of the complementary pairs of lamellae into lamellae units allows the units to adapt by means of spring and/or media, i.e., fluid, forces to the geometric changes in the rotary piston engine caused in the course of movement, or by pressure and temperature. 
         [0010]    In yet another aspect the invention relates to sealing strips, attached to the disc segments in the circumference of the casing running way, comprising lamellae units formed of complementary pairs of lamellae which overlap such that the units form sealing edges which, during the rotor movement, flexibly reach into the corner of the casing, thus sealing same and further, the invention relates to the lamellae units adapting to the radial and axial changes in the casing by means of spring forces. 
         [0011]    In still another aspect the invention relates to the lamellae units having chamfers so that wedge-like compression elements act by spring force on the chamfers such that each of the complementary pairs of lamellae comprising a unit can be shifted with respect to each other in both directions of a plane and thus the lamellae units form sealing elements that can adapt in two directions to the space in which they are arranged. 
         [0012]    In still yet another aspect of the invention, the rotor disc segments comprising the rotor have at the sides facing each other radial grooves into which the lamellae units are inserted so that the gaps between the disc segments are sealed by a flexible labyrinth sealing. Further, the rotor disc segments on the sides facing each other have ring grooves near the opening where the axle is positioned, into which either a closed ring can be inserted to seal the rotor against the axle or a disc segment] having a ring-shaped recess fitting into the opposite ring groove of the opposite disc and sealing the rotor against the axle. 
         [0013]    Yet still further, the invention relates to the piston-forming rotor discs having on the outside recesses between the piston tips so that media forces such as fluid forces can act at these recesses which are contrary to the forces acting in the gaps and thus reduce the resulting compression forces against the casing walls to a size providing tightness (i.e., sealing) but minimising the friction forces. 
         [0014]    Also, the invention relates to compression springs fitted between the rotor segment discs, which press the discs towards the outside during the starting of the engine at which time the media forces forcing the discs apart are not present. 
         [0015]    In still yet another aspect, the invention relates to the disc segments formed so that they are formed lamellae together with other formed lamellae to form a labyrinth sealing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The disclosure of the invention is facilitated by reference to the following figures. 
           [0017]      FIG. 1  is a perspective view of an adaptable sealing line of the present invention, at the rotor disc segment; 
           [0018]      FIG. 2   a  is an exploded view of the rotor segment of the present invention; 
           [0019]      FIG. 2   b  is an exploded view of a blade box of the present invention, and a perspective view of same; 
           [0020]      FIG. 2   c  is a cut away view of a rotor segment, also showing a blade box, of the present invention; 
           [0021]      FIG. 3   a  is an exploded perspective view of a Wankel rotor of the present invention; 
           [0022]      FIG. 3   b  is a perspective view of an internal sealing ring; 
           [0023]      FIG. 3   c  is an exploded view of a sealing arrangement; 
           [0024]      FIG. 3   d  is an exploded view of the rotor segment and sealing arrangement; 
           [0025]      FIGS. 4   a ,  4   b ,  4   c ,  4   d  show the assembly of and assembled Wankel piston; and 
           [0026]      FIGS. 5   a  and  5   b  depict the Wankel piston with fitted sealing strips. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    The principle of sealing is described with reference to  FIG. 1 . The rotor of the engine is divided into the two segment discs  1  and  2  which are pressed with their outer areas/surfaces  6  and  8  against the face sides of the casing  6  and  8  by spring/media forces and thus seal the rotor against the casing. The gap  11  between the segment discs is pressed inward against the rotor shaft by means of a rotating cover  10 . Cover  10  is connected to guiding grooves  5  wherein the blades  3 ,  4  form one blade of the rotor segment. The blades  3 ,  4  are formed by lamellae, depicted as thin plates, which can adapt to geometric changes. 
         [0028]    The implementation of the sealing principle is further described with reference to  FIGS. 2   a ,  2   b  and  2   c ,  3   a ,  3   b ,  3   c  and  3   d ,  4   a ,  4   b  and  4   c.    
         [0029]    With reference to  FIG. 2   a , the rotor of the rotor segment comprises discs  12  and  13  which are pressed apart from each other, that is, biased apart from each other, by springs  14  and thereby providing a press-seal against the face sides of the casing. The springs are located in the bores  15  in both segment discs, which bores do not extend all the way through the discs. Dividing groove  15  is located between the segment discs. The hub  17  of segment disc  12  fits into the reception portion  16  of segment disc  13  and closes the dividing gap  19  according to the cover  10  in  FIG. 1 . The slots  18  in the segment discs  12  and  13  correspond to the guiding grooves  5  in  FIG. 1 . 
         [0030]    With reference to  FIG. 2   b , the blade boxes  20  are situated in the slots  18  of the rotor, and because of internal spring forces caused by the springs  25  in the blade boxes, the blade boxes adapt in the radial direction onto the face side of the casing and also in the axial direction onto the face side of the casing and, at the same time, reach into the corners between both of axial and radial direction in which the rotor runs in the casing and thus forming a seal along the casing walls. 
         [0031]    A blade box contains the two similar half wings  21  and  22  which are assembled with each other such that they are displaced against each other and thereby are pressed against the face side of the casing to form a sealing element. In this arrangement, together with the disc segments  12  and  13 , the blade box forms sealing surfaces against the passing of the medium. The pressing force of the half blades  21  and  22  is obtained for this unit by the inside chamfers  23  and the compression wedge  24  sitting on the compression spring  25 . The compression wedge  24  is situated in the inner space formed by the half blades  21  and  22 . The compression spring  25  sits on the bottom of box hull  27 . The radially sealing movement of the half blades  21  and  22  in the course of rotation of the rotor is additionally facilitated by biasing action provided by the springs  26 . 
         [0032]      FIG. 2   c  shows the interlocking disc segments  12  and  13  with a blade box  20  in slot  18  in the rotor. 
         [0033]      FIGS. 3   a ,  3   b ,  3   c  and  3   d  show another version of the sealing principle of a rotating piston of the rotor of a Wankel engine. 
         [0034]      FIG. 3   a  shows the rotor for a Wankel engine comprising rotor segments  28  and  29  having a similar construction. In the rotor segments three radial grooves  30  are located, extending from the central bore  34  into the three tips of the rotor. The radial grooves  30  extend in the rotor tips into the axial rotor grooves  31 . The grooves  30  and  31  receive the flexible sealing elements. Ring  35  is placed into the central bore  34 . 
         [0035]      FIG. 3   b  shows the ring  35 , which is inserted into the bore  34  so that the rectangular gudgeons  36 , in other words, fins, attached to the ring sit in the grooves  30  of the rotor segments  28  and  29 . Ring  35  serves to seal the gap between the rotor segments against the rotor axle. The gudgeons  36  also seal the groove and at the same time provide support for sealing boxes  39 . 
         [0036]      FIG. 3   c  shows the construction of a lamellae unit from a pair of members of complementary lamellae members  37 , which pair members are placed on top of each other so that their side sealing strips extend away from each other, forming a joint sealing strip with an overlapping gap. In the space between the lamellae  37  a compression wedge  39  is placed. A compression spring  40  presses the compression wedge against the chamfers of the complementary lamellae pairs  37 , thus pushing the unit radially to the casing wall and at the same time forcing the members of the lamellae pairs apart so that, during the course of movement of the piston, the lamellae pair edges are pressed into the edges of the casing where the casing walls meet forming a seal. The compression springs  40  are supported on the gudgeons  36 . The lamellae  37  cover the gudgeons  36  in such a way that the sealing unit formed can be inserted in the rotor grooves  30  and  31 . 
         [0037]      FIG. 3   d  shows the sealing unit including the pair of lamellae members  37  forming a unit, the compression wedge  39  and the compression spring  40 , which is mounted on to the gudgeon  36  of the sealing ring  35 . The sealing ring  35  with the sealing units sits in the grooves  30 ,  31  of the rotor segments  28 ,  29 . These components form the sealing system of the rotor. The compression springs  41  press the rotor segments  28 ,  29  on to the face-side areas of the casing. The spring force is required for the rotor segments during the starting phase. When the engine is running, the media pressure (fluid pressure) takes over the pressing function. To reduce the friction on the face-side areas the rotor segments, recesses  33  are provided on the outer faces of the rotor segments, which lessens the pressure exerted on the rotor segments. 
         [0038]      FIG. 4   a  shows a rotor of a Wankel engine comprising a central rotor segment  42  and the two side rings  43 . Both side rings  43  interlock with the recesses  46  and the gudgeons  47  in the side ring grooves  44  and the radial grooves  45  of the piston central part  42 . In the piston central part, the through bores  49  house compression springs  50  which are configured to abut the recesses  46  of the side rings  43  and press them against the side walls of the engine, to seal the rotor against a circumferential flow.
       The side rings  43  have no function in the transmission of the torque.         
         [0040]      FIG. 4   d  shows a complimentary pair of lamellae  51 , in which its full thickness is shown at side  51   a . At  51   b  the lamella possesses only half its thickness. Two similar lamellae are placed on top of each other, overlapping each other so that they form a lamellae unit which is placed into the cross groove  48  and the radial grooves  45  of the rotor in such a way that both sides  51   a  are facing the rotor side, and the gudgeons  47  of the side rings  43  are positioned in the slots  51   e  to form a closed seal at the side planes of the rotor. 
         [0041]    As shown in  FIG. 4   b , two lamellae pair  51 , together with cover  51   c , form a space inside the lamella unit in which compression wedge  52  is located, and when the compression wedge is pressed outward by compression spring  53  it forces the chamfers  51   d  outward. The compression springs  53  are supported by wedges  47 , so that the spring force acts in the radial and axial directions on the lamella pair  51 , creating a sealing force. In addition, the spring forces applied by the compression springs  53 , press the side rings  43  a providing a spring-actuated sealing system, thereby sealing the rotor against the casing wall. 
         [0042]      FIG. 4   c  shows the complete rotor, fitted with a plurality of lamellae units comprising lamellae pairs  51 .  FIG. 4   c  also shows the side rings  43  assembled in the rotor. 
         [0043]      FIG. 5   a  shows the rotor of a rotary piston engine comprising the rotor segments  54  and  55  provided with a seal against the central shaft as a result of the ring-shaped recess  57 , which is inserted into ring groove  56 . In the same way, the sealing lips  58 , which are tightly connected to the rotor segments and comprise the same material, or another tightly inserted material, are inserted. For this purpose, the sealing lips  58  have notches  59  allowing their interlocking. In addition to the sealing lips, the rotor segments  54  and  55  are fitted with mould  60  in a suitable geometric shape having the function of tension release when friction and pressure forces act on the sealing lip  58  in the circumferential direction of the rotor and require an opposite spring action of the sealing lips  58 . 
         [0044]      FIG. 5   b  shows the rotor segments  54  and  55  in axle alignment and facing each other in such a way that recess  57  is facing ring groove  56 . When inserting rotor segment  55  into rotor segment  54  the sealing lips  58  with their notches  59  are interlocking in such a way that in radial and axial direction of the rotor a dynamic sealing is achieved acting in the direction of rotation of the rotor. 
         [0045]    Sealing of the rotor segments  54  and  55  against the face-sides of the casing is achieved by the spring force of springs  62 . The recesses  63  at the outer sides of the piston segments  54  and  55  cause an almost complete compensation of the media forces acting in the dividing grooves of the rotor segments  54  and  55  as friction forces directed against the face side of the rotor by media forces acting from outside.