Abstract:
A trochoidal design rotary piston engine design has a rotary piston housing with a double curve inner contour and triangular type rotary pistons. Sliding bearings distribute lubricating oil from a pressure cycle into a high pressure circuit and a low pressure bypass circuit branches to the side parts and axial cooling channels of the rotary piston housing to supply the cooling oil.

Description:
BACKGROUND OF THE INVENTION 
     This application claims the priority of German application 100 26 449.2, filed May 27, 2000, the disclosure of which is expressly incorporated by reference herein. 
     This invention refers to a trochoidal design rotary piston engine with a rotary piston housing, two side disks, one of the eccentric shafts bearing-mounted in the side disks, a rotary piston, and an eccentric cam bearing-mounted eccentric shaft with a pressure oil supply unit for supplying oil to the side disk, the bearings and the rotary piston bearing of the eccentric shaft. 
     Many models of the above-noted rotary piston engine designs are known, for example, from the German Pat. Document No. DE-C 40 03 663 (corresponding U.S. Pat. No. 5,199,863) and are also being serially produced. These types of engines are generally equipped with a fluid cooling system necessary for the peripheral heat exchangers and lines. This supplemental equipment and the cooling fluid will nearly double the total weight of the unit compared to a net engine weight. With the known weight optimizing construction with a performance range of up to approximately 100 kW, the system specific weight is approximately 1 kg/kW or better. A reduction in the system specific weight would be desirable for the use of such engines in aviation operations. Additionally, a demand on the modern engines, in addition to a high specific performance is also a highest possible efficiency. Furthermore, the possibility of supercharging the engine for multi-fuel operations should be available, especially in the shift charging process. This supercharging leads to increased combustion chamber pressures and is linked to high local temperature loading. A weight favorable air-cooling by itself could not meet these demands. 
     An object of this invention is to accomplish the task of producing an above-described rotary piston engine with lowest possible specific system weight ratio. 
     This object has been achieved according to preferred embodiments of the invention in that the pressure oil supply system splits the low pressure line leading to the side disks and rotary piston housing cooling channels which are connected to the re-circulation of the pressure oil supply system. 
     According to certain preferred embodiments of this invention, the bearing lubrication and the pressure oil needed for the cooling of the piston is also used to cool the rotary piston housing and the side disks. That saves on the need for a coolant cooling separator with attendant lines so that the system weight can be reduced accordingly. 
     It has been foreseen in certain preferred embodiments of the invention design that the low-pressure line would be connected to both side disks whose cooling channels are linked to the axial cooling channels of the rotary piston housing. Thus it has been advantageously anticipated that the side disks cooling channels will be designed in such a way that the oil supplied to one side disk will be delivered, after flowing through the cooling channels of the rotary piston housing, to the other side disk. That provides for a very effective cooling of the side disks and the rotary piston housing. 
     In a further design feature of certain preferred embodiments of the invention, it is intended that the rotary piston housing will have an angle range of about 90 degrees in the direction of the motion toward the exhaust pipe and is equipped with axial cooling channels. In the practice, it will mostly suffice to cool only this area with oil, since it is subjected to the highest heat load. 
     For practical purposes, it is provided in certain preferred embodiments of the invention that the pressure oil supply system will include an oil pump with at least twice the capacity requirements of the oil quantity required for lubrication of the bearings. That ensures that a sufficiently large quantity of cooling oil will be supplied by the low-pressure branch of the oil cycle. 
     In order to further reduce the engine load, it has been additionally established according to certain preferred embodiments of the invention that the rotary piston housing would be equipped with cooling ribs over an angular range of about 90 degrees in the direction of the motion toward the exhaust pipe. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an axial section of a rotary piston engine with a schematic representation of the combined lubrication and cooling oil cycle, constructed according to a preferred embodiment of the present invention; 
     FIG. 2 shows a perspective view of a rotary piston housing of the rotary piston engine according to FIG. 1; 
     FIG. 3 shows a perspective view of the output side associated side disk. 
     FIG. 4 shows three cogwheels forming a paired pump. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The rotary piston engine represented in FIGS. 1 through 3 is also the subject of parallel patent applications filed in Germany on May 27, 2000, with respective German patent application numbers 100 26 447.6 and 100 26 448.4. The contents of corresponding U.S. application Ser. Nos. 09/866,467 and 09/866,466, filed May 29, 2001, are incorporated herein by reference thereto to aid in an understanding of the present invention. 
     The housing shown in the FIG. 1 of the represented rotary piston engine has a side part or side disk  1 , a rotary piston housing  2  with a double arched trochoid design track casing  3 , and an output side mounted side disk  4  or a side section. An eccentric shaft  5  is seated in the side disks  1  and  4  by means of sliding bearings  6  and  7 . On the eccentric cam  8  of the eccentric shaft  5  is a triangular design rotary piston  9  seated on one of the eccentric sliding bearings  10 . The piston is linked by a synchronization drive, as the principle is known from the German Pat. Document No. DE-C 40 03 663, with the eccentric shaft ( 5 ). 
     An external cogwheel  11  of an external cogwheel oil pump  12 , which is not shown in greater detail, meshes with a pump cogwheel  11   a  of a significantly greater diameter than the drive cogwheel  11 , and is mounted on the eccentric shaft  5 . The external cogwheel oil pump supplies oil under pressure through a pressure line  13  and then through an oil heat exchanger  14  and an oil filter  15 . From the oil filter  15 , a pressure line  16  leads to the lubricating oil supply of the sliding bearing  6  and  7  and the eccentric shaft  5 , and to the sliding bearing  10  of the oil cooled rotary piston  9 . Alternatively, as described in the incorporated German and U.S. patent applications and shown in FIG. 4, three cogwheels  11 ,  11   a ,  11   b  may be provided. The three cogwheels  11 ,  11   a ,  11   b  provide a paired pump  12 ,  12   a . The first pair of cogwheels  11 ,  11   a  forms a first part  12  of the paired pump, and the second pair of cogwheels  11   a ,  11   b  forms a second part  12   a  of the pair pump. The paired pump  12 ,  12   a  is used to supply oil under pressure through the pressure line  13 . 
     A bypass pressure line  18  branches from the pressure line  16  to the exhaust turbo loader  17 . Another line from the exhaust turbo loader  17  leads to an oil collection container  27  to which the oil moving through the slide bearing  6 ,  7 , and  10  is also re-circulated. 
     A low-pressure line with an installed pressure control valve  19  branches off from the pressure line  16  after the oil filter  15 . The control pressure valve  19  ensures that the oil pressure in the pressure line  16  is limited to a maximum value which, as an example, is at 4 Bars, although, the external cogwheel oil pump  12  supplies twice as much or greater quantity of oil then is necessary for lubricating the sliding bearings  6 ,  7 , and  10 . The excess oil pressure is then lowered at the pressure control valve  19  and re-circulated over the low pressure line  20  to the rotary piston engine housing. 
     The low-pressure line  20  is separated by the splitter  21 ,  22  and supplied at the highest point to the side disks  1 ,  4 . The oil supplied through the splitter line  21  to the side disk  1  is bypassed from there in the axial bores  23  from whence it flows to the side disk  4  on the opposite side. Within the side disk  4 , it flows through several cooling channels  24 ,  38  to the ring chamber  25  surrounding the glide bearing  7  and then to an oil re-circulation line  26  leading to the oil container  27 . The side part  4  is made of two parts and consists of a basic element, which preferably has been made as a cast, and a radial inner walling, inclined toward the rotary piston  9  and is provided on the outside with ribs which run around the ring chamber to the oil re-circulation line  26 . The oil supplied to the area of the exhaust pipe  34  flows through channel  38  to the ring chamber  25  and thence to the oil re-circulation  26 . The channel  38  is installed in the area of the exhaust pipe exit and provided with inner lead ribs  39 . 
     Correspondingly, cooling oil is supplied to the side disk  4  through the branch line  22 , thence, over the axial cooling channels  37  of the rotary piston housing  2  through corresponding channels  29  to a ring-form cavity  30  and to the oil re-circulation  31 . 
     FIG. 2 shows a perspective view of the rotary piston housing  2  with the trochoidal design casing track and also shows the installation of the intake opening  33  and the outflow opening  34 . The turning direction of the rotary piston  9 , not shown in FIG. 2, is indicated by an arrow n. Extending from the dip  35  to the outflow opening  34  is the so-called warm curve of about 90 degrees of the rotary piston housing  2 . In this area, the oil cooling takes place and is then supplied over the low pressure line  20  to the branch line point  21 ,  22 . Furthermore, located in the area of the warm curve is the rotary piston housing of the axially arranged outer side cooling ribs  36  to provide for additional air cooling. 
     FIG. 3 is a perspective view of the output side arranged side disk  4 , that is, the basic element of this side disk  4  without the cover disk. The outflow openings  37  are part of the axial cooling bores or cooling channels  23  of the rotary piston housing  2  and lead to the essentially concentrically arranged cooling channels  24  around the ring-form cavity  25 . The direction of the flow of the cooling oil is here in opposite direction of the rotary piston  9  rotation. The additional cooling channel  38 , in which the oil flows through in the direction of the rotary piston  9  occurs, is provided with leading ribs  39 . The cooling channel  39  as well as the cooling channels  24  leads to the oil re-circulation  26 . 
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.