Abstract:
The invention concerns an internal-combustion engine, the engine comprising a first combustion chamber, a first piston displaceably guided in the first combustion chamber, the first piston facing the first combustion chamber with a first piston surface in a first direction, a second combustion chamber, a second piston displaceably guided in the second combustion chamber, the second piston facing the second combustion chamber with a second piston surface in a second direction, the first direction and the second direction being opposed to each other, the first piston and the second piston being coupled to each other so that they move simultaneously.

Description:
[0001]     This application is a continuation of U.S. application Ser. No. 11/260,372 filed on Oct. 28, 2005 the entire disclosure of which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The invention concerns an internal-combustion engine with a first combustion chamber, a first piston displaceably guided in said first combustion chamber, this first piston facing said first combustion chamber with a first piston surface in a first direction, a second combustion chamber, a second piston displaceably guided in said combustion chamber, this second piston facing said second combustion chamber with a second piston surface in a second direction, said first direction and said second direction being opposed to each other.  
         [0003]     Engines of this type are known as engines of the “boxer type”. They can be used as stationary drives as well as for vehicles.  
         [0004]     Despite substantial progress having been achieved in making internal-combustion engines more efficient, there is still a great need for further improvement of the efficiency of such engines, may it be two-cycle or four-cycle, otto- or diesel-engines. It is the underlying purpose of the invention to provide a combustion engine having higher efficiency.  
       SUMMARY OF THE INVENTION  
       [0005]     This object is achieved in accordance with the invention with a combustion engine of the above-mentioned type, wherein said first piston and said second piston are  
         [0006]     coupled to each other so that they move simultaneously. In contrast to a combustion engine of the “boxer type”, the pistons of the inventive combustion engine do not travel independently of each other. Thereby, the upstroke of the first piston corresponds to the downstroke of the second piston and vice versa. Applying the two cycle principle to the inventive engine, one obtains an engine, that will be very efficient, since every stroke of the two pistons coupled to each other will involve one power stroke. The power strokes are alternately allocated to one of the two combustion chambers.  
         [0007]     It is understood, that the principle underlying the invention can also be applied to engines using the four-cycle principle. This will also lead to an engine with higher efficiency, since the two pistons do not have to be guided separately as known from common engines.  
         [0008]     It is also understood, that the principle underlying the invention can be applied to engines having more than two combustion chambers.  
         [0009]     In one embodiment, the directions, in which the piston surfaces face are directed away from each other. This means, that the pistons are disposed between the combustion chambers.  
         [0010]     In another embodiment, the mentioned directions are directed towards each other. This means that the two combustion chambers are disposed between the two pistons.  
         [0011]     In a particularly preferred embodiment, the two pistons travel along a common axis. This will further increase the efficiency of the engine, since the shear forces, that act perpendicular to the axis, along which the pistons travel, can be eliminated.  
         [0012]     Each piston can drive separate crankshafts, which can be arranged such that the pistons are disposed between the crankshafts. This arrangement leads to a comparatively flat engine, wherein the energy of the power strokes can be transmitted to the crankshafts in an efficient manner.  
         [0013]     A particularly preferred embodiment of the invention comprises pistons which are rotatably disposed within the combustion chambers. This further minimizes shear forces and friction between the pistons and the walls of the combustion chambers.  
         [0014]     In a particularly preferred embodiment, the engine comprises drive means to rotate said pistons. This means, that the pistons are not only rotatably disposed within the combustion chambers, but that they are actively driven to rotate within the combustion chambers. Rotating the pistons will minimize friction between the pistons and the walls of the combustion chambers. The rotation can be continuous, so that the pistons rotate independently of their position along their axis of travel. However, the pistons may be driven in a way that they do not rotate along its entire stroke length.  
         [0015]     It is understood, that the mentioned drive means can be provided by a separate drive. However, it is preferred, that the drive means comprise gear means that are coupled with at least one of the crankshafts. This eliminates the need for a separate drive and has the advantage, that the rotation speed of the pistons is coupled to the rotation speed of the crankshafts. By choosing an appropriate gear ratio, the rotation speed of the pistons can be adjusted.  
         [0016]     In a preferred embodiment the gear means comprise a gear wheel that drives at least one of the pistons. In some embodiments it will be appreciated that the two pistons are driven to avoid torque loads. It is preferred, that said gear wheel interacts with at least one of the pistons which comprises a surface comprising teeth extending parallel to the axis along which the piston travels, wherein the teeth have a length that is at least as great as the stroke length of the piston. This gear arrangement allows for rotating the piston along its entire stroke length, which has the above-mentioned advantages for minimizing friction.  
         [0017]     To further increase the efficiency of the inventive engine, it is proposed, that the piston surfaces facing the combustion chambers have inclined sections to create a vortex flow within the combustion chambers when rotating the pistons. This vortex flow has several advantages. On the one hand the gas contained in the combustion chambers can be put into a whirling movement so that the gases in the combustion chambers are mixed homogenously, thus achieving uniform combustion and cleaner exhaust gas. The vortex flow is also very beneficial for exchanging the gas mixture in the combustion chambers. The vortex flow can be used to suction fresh air into the combustion chamber as well as to push exhaust gas out of the combustion chamber. This is particularly helpful for engines using the two-cycle principle.  
         [0018]     In one embodiment of the invention the combustion chambers can be constituted by a single cylinder. This means that the walls of the two combustion chambers are in flush configuration with each other, so that the two combustion chambers can be manufactured very easily without misalignment of the two combustion chambers. In this case it is proposed to integrate the two pistons into one unit, so that they are built integrally with each other. This unit does not necessarily need to be one-pieced; it can comprise more pieces that are assembled with each other.  
         [0019]     In another embodiment the combustion chambers are constituted by separate cylinders. For coupling the two pistons it is proposed to connect these pistons by means of a connecting shaft. This connecting shaft allows for the arrangement of the above-mentioned surface comprising teeth to be driven by a gear wheel to rotate the two pistons.  
         [0020]     The pistons can each comprise a piston extension, wherein the piston extensions each extend through one of the combustion chambers, wherein the piston extensions are each coupled with a connection rod and wherein each connection rod is coupled with one of the crankshafts. This arrangement allows for a reliable transmission of forces induced by the power strokes onto the crankshafts. When in this configuration the piston extensions and the connection rods are coupled to each other by means of a ball and socket bearing, the pistons can be rotated as described above.  
         [0021]     The surface comprising teeth which are driven by a gear wheel can also be disposed on at least one of the piston extensions.  
         [0022]     Further advantages, features and details of the invention can be extracted from the dependent claims and the following description which describes in detail a particularly preferred embodiment with reference to the drawing. The features shown in the drawing and mentioned in the claims and in the description may be essential to the invention either individually or in arbitrary combination. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  shows a section through a preferred embodiment of the inventive combustion engine;  
         [0024]      FIG. 2  shows an enlarged view of the region  11  in accordance with  FIG. 1 ;  
         [0025]      FIG. 3  shows a schematic view of gear elements of the engine;  
         [0026]      FIG. 4  shows a top view of a piston surface in accordance with  FIG. 1 ;  
         [0027]      FIG. 5  shows an enlarged view of the region V in accordance with  FIG. 1 ;  
         [0028]      FIG. 6  shows an alternative embodiment of pistons being built integrally with each other; and  
         [0029]      FIG. 7  shows a section through a second embodiment of the inventive combustion engine.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0030]      FIG. 1  shows a side section of an engine which is designated with reference numeral  2 . The engine  2  comprises a housing  4  with two opposite crank houses  6  and  8 , in which crankshafts  10  and  12  are located, respectively.  
         [0031]     Between the crankshafts  10  and  12  two combustion chambers  14  and  16  are arranged. A first piston  18  is allocated to the first combustion chamber  14 . A second piston  20  is allocated to the second combustion chamber  16 . The pistons  16  and  20  are disposed between the two combustion chambers  14  and  16 . The latter are disposed between the two crankshafts  10  and  12 .  
         [0032]     The piston  18  comprises a piston surface  22  which faces the first combustion chamber  14 . The second piston  20  has a second piston surface  24  which faces the second combustion chamber  16 . The two piston surfaces  22  and  24  face away from each other.  
         [0033]     The pistons  18  and  20  are integrated to one unit which can travel along a single cylinder  26 . The pistons  18  and  20  comprise a centrally arranged piston ring  28 , which seals the pistons  18  and  20  with respect to the walls of the cylinder  26 . The piston ring  28  may be of elastic or non-elastic material. If the piston ring  28  is made of non-elastic material (e.g. ceramics), the pistons  18  and  20  may be constituted by two separate parts, as it is indicated by a dashed section-line  30 .  
         [0034]     The pistons  18  and  20  travel along a common axis  32 . In  FIG. 1 , the pistons  18  and  20  are in the middle position between the two top dead center positions. In top dead center position, the piston  18  and the wall of the housing  4  opposing the piston surface  22  have a spherical shape. This is because of the piston surface  22  having a spherical shape and the opposing surface of the housing  4  also having a spherical shape  34 . The combustion chamber  16  is symmetrical to the combustion chamber  14 , thus also having a spherical wall  36  opposing the spherical piston surface  24 .  
         [0035]     The piston  18  comprises a piston extension  38 , which is integrally built with piston  18  or connected to piston  18 . The piston extension  38  extends through the combustion chamber  14 . The piston  20  comprises a piston extension  40 , extending through combustion chamber  16 . Both piston extensions  38  and  40  extend through walls of the crankcases  6  and  8 , respectively, passing a bearing  42  and  44 , respectively. The piston extensions  38  and  40  carry at their free ends, which are facing away from the pistons  18  and  20 , sockets  46  and  48 , respectively. These sockets  46  and  48  interact with corresponding balls  50  and  52  which are provided on connection rods  54  and  56 . Each connection rod  54  and  56 , respectively, is coupled to one of the crankshafts  10  and  12 , respectively. When the pistons  16  and  18  move in a simultaneous manner, each upstroke of one piston corresponds to a downstroke of the other piston. The arrangement of the connection rods  54  and  56  and the crankshafts  10  and  12  is such that the crankshafts  10  and  12  turn in the same rotation directions  58  and  60 .  
         [0036]     The combustion chambers  14  and  16  are supplied with fuel by fuel injection units  62  and  64  (multi port in one chamber). These fuel injection units  62  are disposed within the spherical walls  34  and  36 , respectively. In these regions two pairs of spark plugs  66 ,  68  and  70 ,  72  are provided.  
         [0037]     The engine  2 , that is their combustion chambers  14  and  16 , is provided with fresh air by an intake  74 , which separates into two branches. In each branch a one-way valve  76  is arranged, so that air from the intake  74  into the combustion chambers  14  and  16  can only flow in this direction. On the opposite side of the intake  74  an exhaust  78  is provided.  
         [0038]     The transport of air into the combustion chambers  14  and  16  is supported by an air cooling and pressure system. Fresh air is forced through an inter-cooler into a pressure tank via a compressor that is driven by the engine  2 . The intake system also comprises a throttle body to regulate the air pressure and volume, an air pressure sending unit and a mass-air-flow sensor.  
         [0039]     The intake of air is also facilitated by the particular shape of the piston surfaces  22  and  24  which will be further described in accordance with  FIG. 4 . The pistons  16  and  18  are rotatably disposed within the cylinder  26 . The piston extensions  38  and  40  and thereby the pistons  18  and  20  are driven by drive means acting on the piston extensions  38  and  40 . These drive means act on the piston extensions in regions  11  indicated in  FIG. 1 . The piston extensions  38  and  40  each comprise a surface  80  having teeth. This ridged surface  80  is meshing with a gear wheel  82 , which at one end comprises an angle portion  34 . This angle portion  34  is meshing with a gear wheel  86 .  
         [0040]      FIG. 3  shows, how the gear wheel  86  is driven. The two crankshafts  10  and  12  drive intermediate transfer gears  88 , which are coupled to the gears  86 . Each gear  86  drives a gear wheel  82 , which in turn drives one of the piston extensions  38  and  40 . Since the teeth provided on the surface  80  are at least as long as the stroke length of each piston  16  and  18 , the pistons  16  and  18  can be rotationally driven along its entire stroke length.  
         [0041]      FIG. 3  also shows, that the transfer gears  88  are coupled with a common fly wheel  90 . This fly wheel helps to eliminate unwanted vibrations of the engine  2 .  
         [0042]      FIG. 4  shows that the piston surfaces  22  and  24 , which on a macro scale have a spherical shape, are provided with inclined sections  92  and  94  on a smaller scale. These inclined sections  92  and  94  form a propeller shape, which helps to create a vortex flow within the combustion chambers  14  and  16 , when the pistons  16  and  18  are rotationally driven, such as described above. The particular shape of the piston surfaces  22  and  24  also helps to suction fresh air through intake  74  and to push exhaust gas out through exhaust  78 .  
         [0043]      FIG. 5  shows an enlarged view of the region V, indicated in  FIG. 1 . The piston extension  40  carries at its free end the said socket  46 . This socket  46  is constituted by an upper part  96  and a bottom part  98 . The two parts  96  and  98  are secured to each other by means of screws  100 . The upper part  96  can be detached from the bottom part  98  to place the said ball  50  of the connection rod  56  within the socket part belonging to the bottom part  98 . Fixing the upper part  96  to the bottom part  98  will attach the ball  50  securely within the socket  46 .  
         [0044]     The connection rod  56  has central lubrication or oil channels  102 , through which lubrication fluid or oil can be driven into the ball and socket region, thereby cooling the connection between the piston extension  40  and the connection rod  56 . This cooling will enable thermal stability of the engine  2 , when the piston extension  40  is driven at high rotational speeds. To further improve cooling, the piston extension  40  may comprise lubrication or oil channels  104 , too.  
         [0045]      FIG. 6  shows an alternative embodiment of pistons  16  and  18 , which are connected to each other by means not shown in further detail. Between  16  and  18  a spring  106  is arranged, which allows for thermal expansion, when the pistons  16  and  18  and the piston extensions  38  and  40  expand, because of the engine  2  warming up to operating temperature.  
         [0046]     In  FIG. 6  pistons  16  and  18  are shown in an “x-ray”illustration. Within the piston extensions  38  and  40  and the pistons  16  and  18  lubrication or oil channels  104  are provided, to cool the pistons  16  and  18 . Arrows  108  indicate how lubrication fluid or oil can flow through one piston extension  40 , through lubrication or oil channels  104  within piston  18  to lubrication or oil channels  104  within piston  16  to a lubrication or oil channel  104  within piston extension  38 .  
         [0047]      FIG. 7  shows a second embodiment of the inventive engine. The engine shown in  FIG. 7  is designated with reference numeral  200 . Parts of engine  200  that have the same function as parts of engine  2  according to FIGS.  1  to  6 , are designated with the same reference numerals. For all parts, which are not mentioned in the following specification, reference is made to the above specification corresponding to FIGS.  1  to  6 .  
         [0048]     In the embodiment shown in  FIG. 7  the two pistons  18  and  20  are not integrally built with each other, but separate and connected to each other by means of a connecting shaft  110 . This connecting shaft  110  has a surface with teeth parallel to the axis of travel  32  of the pistons  18  and  20 . This connecting shaft  110  is driven by a gear wheel  82  which in turn is driven by another gear wheel  86 . Gear wheel  86  is driven by at least one of the crankshafts  10  and  12 . This can be achieved by a gear drive, for example by a gear drive as shown in  FIG. 2 .  
         [0049]     The pistons  18  and  20  are facing combustion chambers  14  and  16 , respectively. These combustion chambers have the same shape as already described with respect to the first embodiment in accordance with FIGS.  1  to  6 . However, in the embodiment shown in  FIG. 7 , the pistons  18  and  20  delimit with their bottom surfaces, facing towards each other and arranged around the connecting shaft  110 , air chambers  112  and  114 , respectively. The air chambers are also delimited by walls of the crankcases  6  and  8  as well as walls of cylinders  26 , in which the pistons  18  and  20  are displaceably guided.  
         [0050]     The air chambers  112  and  114  are provided with fresh air by intakes  74 , in which one way valves  76  are arranged. When the piston  18  travels from its shown bottom dead center position to its top dead center position, the air chamber  112  increases in volume and suctions air through the intake  74  into the air chamber  112 . When piston  18  travels from its top dead center position back to the bottom dead center position as shown in  FIG. 7 , the air contained in air chamber  112  is pushed through an air channel  116  into the combustion chamber  14 . The air being forced into the combustion chamber  14  passes another one-way valve  120 . The air providing system of combustion chamber  16  functions in the same way. Air suctioned into the air chamber  114  can flow through an air channel  118 , pass a one-way valve  122  and is forced into the combustion chamber  16 .  
         [0051]     It is understood, that the piston surfaces  22  and  24  can have the same shape as shown in  FIG. 4 . This will support the intake of fresh air and will also facilitate pushing the exhaust gas through exhausts  78 .  
         [0052]     The embodiment shown in  FIG. 7  has the advantage that its overall width as defined between the two crankshafts  10  and  12  can be comparatively small.