Abstract:
A rotary internal combustion engine including a housing structure defining a toroidal volume and including first and second housing sections, a rotor structure mounted for rotation in the housing structure and including first and second rotor members respectively that coact with first and second housing sections to define first and second toroidal cylinders. The intake and compression strokes are performed in the first toroidal cylinder and the resultant compressed charge being thereafter transferred by a transfer mechanism through a transfer passage to the second toroidal cylinder where combustion occurs and expansion and exhaust strokes are performed. In the device at least one of the following is true: the transfer mechanism is operative to maintain the volume of the charge substantially constant during the transfer operation; the first and second cylinders have disparate configurations; the second toroidal cylinder has a larger volume that the first toroidal cylinder with the transfer mechanism maintaining the volume of the charge substantially constant during the transfer operation irrespective of the larger volume of the second toroidal cylinder as compared to the first toroidal cylinder.

Description:
BACKGROUND 
       [0001]    The present invention relates to internal combustion engines and in particular to internal combustion engines with coupled cylinders. 
         [0002]    The basic principals of the four stroke-internal combustion engine may be equally applied to conventional reciprocating piston engines as well as rotary engines. In general, all four strokes of the cycle are performed within the same cylinder. That is, a single piston deployed within a cylinder travels through the series of intake compression combustion/expansion and exhaust strokes. Therefore, the power is generated in only one of four strokes, unlike two stroke engines in which power is generated in one of two strokes. 
         [0003]    However, two stroke engines have historically been fuel inefficient due to the overlap of the exhaust and intake processes during a single stroke and the manner in which these processes occur. 
         [0004]    With respect to rotary type engines, toroidal cylinder configurations have emerged in which piston elements travel on a continuous path through a single toroidal chamber. In an attempt to increase power, the number of pistons has been increased. This has been done in the past by increasing the number of pistons traveling through the same toroidal chamber. Alternatively, additional toroidal chambers have been added, which include additional pistons. This alternative is basically linking two or more separate engines. 
         [0005]    In an effort to improve the basic efficiency of a rotary type engine, it has been proposed to configure first and second cylinders utilizing a common rotor deployed within a single toroidal chamber with all four strokes on the four stroke cycle being performed simultaneously with the intake and compression strokes performed in the first cylinder simultaneous to combustion and the expansion and exhaust strokes of a different cycle being performed in the second cylinder. Such a coupled cylinder engine, entitled Internal Combustion Engine with Coupled Cylinders, is disclosed in International Application Number PCT 1IL2005/000855 filed on 9 Aug. 2005 and published on Feb. 16, 2006 as International Publication Number WO 2006/01635882. 
         [0006]    Whereas the coupled cylinder engine disclosed in the identified PCT application offers significant improvements in overall efficiency as compared to prior art rotary engines, applicant has conceived further efficiency improvements in the coupled engine design and these further improvements are the subject of the present application. 
       SUMMARY 
       [0007]    The operations performed over four strokes of an engines operating cycle may be subdivided into stage  1  involving fuel charge preparation and stage  2  involving performance of work. Energy is consumed during the first part of the cycle while work is performed during the second part. The identified coupled cylinder application offers a procedure for performing these two parts of the cycle separately from each other in different toroidal cylinders of the same design. However, different stages of the operating cycle have specific features of their own. Thus, a high efficiency of the entire operating cycle can only be achieved with account being made for the specific operating conditions. 
         [0008]    The present invention is based on the use of two different toroidal cylinder types, taking into account specifics of the first and the second stages of the operating cycle. 
         [0009]    Type 1 cylinders will be adapted to accommodate, the operating sequence, as follows: filling the cylinder with incoming gas charge, charge compression, and bringing it to a ready to use state as per a preset ratio of compression. 
         [0010]    Type 2 cylinders will be designed to allow for a ready to use fuel charge inlet with no changes in charge volume and pressure, charge ignition in this operating state, charge combustion and expansion to be followed by exhaust of combustion products. 
         [0011]    To insure optimal operation of the Type 1 toroidal cylinder, and with the cylinders repeatedly filled by one charge portion after another and the charges being compressed along this propagation, a specific interior cylinder geometry will be applied, i.e., geometry intended to provide the least possible fuel charge flow resistance along the propagation path from the cylinder inlet to the place of ready to use charge collection to ready to ignite collection location and its size and geometry inside the cylinder will basically depend on the preset engines specific charge compression value and on conditions of the charge transfer for ignition. In transfer of the ready to ignite fuel charge mix, the charge volume shall remain unchanged. 
         [0012]    The condition of maintaining, a constant fuel charge volume during the process of cylinder to cylinder transfer requires that upon volume reduction in the first cylinder, the volume will be increased by the same amount in the second cylinder. Provided the cylinders maintain similar geometry, this premise means that both the toroidal cylinders in question will feature equal charge inlet/outlet cross-section. In the present case when various purpose cylinders feature use various geometries, the condition of constant volume maintenance will be confined to satisfying the requirement when the charge inlet/outlet cross-section values are in inverse proportion to their respective lengths, i.e. to toroidal cylinder diameter values:
       s/S=d/D where s/S are cross-sections of charge inlet/outlet and d/D are diameters of respective toroidal cylinders.       
 
         [0014]    The cylinder to cylinder charge transfer shall be capable of providing for charge transfer with the least possible losses. The charge inlet/outlet shall only be open for as long as the actual charge is being transferred, remaining shut throughout the rest of the cycle. Such charge transfer path shall demonstrate low hydraulic resistance, low intrinsic volume and total isolation of gaseous combustion products from the consecutive incoming fuel charge. 
         [0015]    The geometry of Type 2 toroidal cylinders will be determined based on requirements for the best possible use of the fuel charge energy. The efficiency of the heat to work transformation process will be expressed using the ratio of:
       J=1−t/T where T is the process commencement temperature and t is the process termination temperature.       
 
         [0017]    In this case the higher the combustion gas temperature at the initial stage of piston displacement and the lower the combustion gas temperature at the point of the piston displacement process termination the higher is the value of J. 
         [0018]    The more homogeneous is the burning fuel mixture and the lower is the charge combustion volume the higher is the burning charge temperature. Both of these conditions will be fulfilled if initially this stirred charge mixture is injected at high velocity into the confined combustion space. 
         [0019]    Meeting the other high efficiency condition, i.e., the achievement of the lowest temperature possible at the termination point involves the highest possible combustion gases expansion volume, i.e., the greatest possible increase in the actual displacement volume of the Type 2 cylinders. 
         [0020]    Such an increase in the Type 2 cylinder volume can be attained either by increasing the toroidal cylinder length or by increasing the cylinder cross-section. 
         [0021]    The cylinder length can be achieved through incrementing the rotor diameter which in combination with the cylinder housing forms a toroidal cylinder while the increase in the cylinder cross-section can be achieved by increasing either the width of the height of a cylinder starting from the end of the charge accumulation section. 
         [0022]    The previously identified coupled cylinder engine features a simple engine design with two equal volume and size cylinders thus allowing the ready to ignite fuel charge to transfer sideways from one cylinder to another, i.e., from one parallel path to another. 
         [0023]    In engines with different diameter cylinders, such sideways charge propagation path bias is augmented with the radial path deviation. Reduction of the total transfer channel length is another prerequisite for a device design optimization. 
         [0024]    Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
           [0026]      FIG. 1  is a schematic view of an engine according to a first embodiment of the invention; 
           [0027]      FIG. 2  is a schematic representation featuring engine cylinder cross-sectional views with an interconnecting charge transfer path; 
           [0028]      FIG. 3  is a schematic representation of the transfer path opening sequence; 
           [0029]      FIG. 4  is a transverse cross-sectional view of the engine; 
           [0030]      FIG. 5  is a longitudinal cross-sectional view showing a spacer ring including an arciform groove; 
           [0031]      FIGS. 6A and 6B  are schematic cross-sectional views showing a Type 1 cylinder and Type 2 cylinder respectively of a second embodiment of the invention; 
           [0032]      FIG. 7  is a schematic cross-sectional view of the second embodiment of the invention; 
           [0033]      FIG. 8  is a cross-sectional view of the second embodiment of the invention with the engine in a work performance position; 
           [0034]      FIG. 9  is a cross-sectional view of the second embodiment of the invention showing the interconnecting charge transfer path ready to ignite fuel charge transfer position; 
           [0035]      FIG. 10  is a schematic cross-sectional view of a third embodiment of the invention; 
           [0036]      FIG. 11  is a cross-sectional view of the third embodiment of the invention showing the interconnecting charge transfer passage; 
           [0037]      FIG. 12  is a schematic cross-sectional view showing a fourth embodiment of the invention; and 
           [0038]      FIG. 13  is a cross-sectional view of the fourth embodiment of the invention showing the interconnecting transfer passage. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    The first embodiment of the invention seen in  FIGS. 1-6  includes a housing structure  10  defining a toroidal volume including first and second housing sections  12  and  14  and a rotor structure  16  mounted for rotation in the housing structure and including first and second rotor members  18  and  20  respectively coacting with the first and second housing sections to define first and second toroidal cylinders  22  and  24 . 
         [0040]    Rotor  18  has a generally cylindrical configuration and includes a pair of diametrically opposed lobe portions  26 . 
         [0041]    The engine further includes a pair of diametrically opposed reciprocally moveable partitions or walls  28  which are mounted in radially outwardly projecting portions  12   a  of housing section  12  and are spring biased radially inwardly into engagement with rotor member  18  by compression springs  30 . 
         [0042]    Each lobe portion  26  includes, in circumferential sequence, a entry portion  26   a , a dwell portion  26   b  and a terminal portion  26   c  in sealing engagement with the inner periphery  12   b  of housing section  12 . 
         [0043]    Rotor member  20  has a generally cylindrical configuration. A pair of diametrically opposed reciprocally moveable partitions or walls  32  are mounted in rotor member  20  and are spring biased radially outwardly into engagement with the inner periphery  14   a  of housing section  14  by compression springs  34 . 
         [0044]    A pair of diametrically opposed lobe portions  36  is provided on the inner periphery  14   a  of housing  14 . Each lobe portion  36  includes, in circumferential sequence, an entry portion  36   a , a dwell portion  36   b , and a terminal portion  36   c . The engine further includes intake manifolds  40 , inlet ports  42  in the cylinder  22 , ignition devices  44  communicating with the cylinder  24 , exhaust ports  46  exiting cylinder  24 , exhaust manifolds  48  and transfer passages  50 . 
         [0045]    Each transfer passage  50  is a compound passage establishing communication between cylinder  22  and cylinder  24  only for the period of fuel charge passage. Each passage  50  includes a passage  52  opening in the radially inner end  28   a  of wall  28  in exposure to cylinder  22 ; a passage  54  in housing section  12 ; an arcuate slot or groove  56  in a partition  58  positioned between cylinder housing sections  12  and  14 ; a transfer passage  60  in rotor member  20 ; and a passage  62  in wall  32  opening in cylinder  24 . It will be seen when these passages are in alignment, as seen in  FIG. 2 , the passage is completed between cylinder  22  and cylinder  24 . It will be seen that a passage  50  is provided at two diametrically opposed locations within the engine for selective communication between cylinder  22  and  24  at diametrically opposed locations. 
         [0046]    As will be apparent, the engine seen in  FIGS. 1-6  is arranged with diametrically opposed operating components so that two intake/compression strokes are performed in cylinder  22  and two expansion/exhaust strokes are performed in cylinder  24  for each rotation of the rotor. 
       Operation 
       [0047]    The operation of the engine of  FIGS. 1-6  will be described with respect to one set of operating components of the engine and it will be understood that similar operations are simultaneously occurring at the diametrically opposed set of operating components as the engine undergoes two intake/compression and two ignition/exhaust strokes for each rotation of the rotor. 
         [0048]    The operation of the engine will be described beginning with the component positions seen in  FIG. 1 . In  FIG. 1  the wall  28  has been moved radially outwardly by the entry portion  26   a  of the lobe  26  to a position in which the passage  52  is in alignment with the passage  54  in housing section  10  and in communication with arcuate groove  56  and the wall  32  is positioned on the dwell portion  36   b  of the lobe  36  on the inner periphery of housing section  14  with passage  62  in communication with the opposite end of groove  56  whereby to establish communication between cylinders  22  and  24  to begin the charge transfer process from cylinder  22  to  24 . It will be understood that prior to arrival at the positions seen in  FIG. 1  the rotor  16  would have moved within the housing  10  in a manner such that each lobe portion  26 , acting as a piston, would have moved past a respective intake port  42  and coacted with a respective moveable wall  28  to develop a compressed fuel charge and, upon arrival in the positions seen in  FIG. 1 , will coact with the respective moveable wall  28  to establish a transfer passage between the cylinders  20  and  24  and begin the transfer process. 
         [0049]    The transfer process continues for the period of time that walls  28  move along dwell portions  26   b  and walls  32  move along dwell portions  36   b . During this time, the passages  62  in the walls  32  are in communication with and move arcuately along arcuate slots  56  whereafter, upon arrival of the walls  28  at the end of dwell portions  26   b  and arrival of walls  32  at the end of dwell portions  36   b , the passages between the cylinders are interrupted by the radially outward movement of walls  28 , the radially outer movement of walls  32 , and the movement of the port  62  beyond the arcuate groove  56 . 
         [0050]    After the compressed charges are moved to the cylinder  24 , the charges are ignited using ignition devices  44  and the expanding gasses act upon the walls  32  to provide power strokes which terminate in the discharge of the dissipated gasses through the respective exhaust ports  46  for discharge through the respective exhaust manifolds  48 . During these power and exhaust strokes in the second cylinder, the first cylinder is undergoing a new intake and compression cycle so that when the rotors again assume the position seen in  FIG. 1 , new compressed charges are ready for transfer to the cylinder  24  to initiate new power and exhaust strokes in the cylinder  24 . 
         [0051]    According to an important feature of the invention the cross-sectional area of the void  64  between the lobe portion  26   b  and the inner housing periphery  12   b  in the  FIG. 1  position is identical to the cross-sectional area of the void  66  between the outer periphery  20   a  of rotor  20  and lobe dwell portion  36   b  with the components in the  FIG. 1  position. As a result, the charge volume in the second toroidal cylinder during the transfer operation is progressively increased by an amount corresponding to the progressive decrease in the charge volume in the toroidal cylinder  22 . Note that in order to maintain an equal cross-sectional volume in the void  66  as compared to the void  64 , given the increased diameter of the cylinder  24 , the radial height of the void  66  is compensatingly less than the radial height of the void  64 . 
         [0052]    As an example, the dimensions of the various components of the engine may be chosen such that the volume of the second cylinder  24  is twice that of the volume of the first cylinder  22  with the result that, upon performing the work cycle, the volume of combustion gasses will be twice that of the fuel charge initially filling up the internal space of cylinder  22 . This makes it possible to significantly reduce the final temperature t of the combustion gasses which, in accordance with the previously described formula J=1−t/T, will result in enhanced efficiency. 
         [0053]    The engine efficiency is further improved, again by reference to the formula J=1−t/T, by maximizing the process commencement temperature t which is accomplished according to an important feature of the invention by maintaining a constant charge volume as the charge is transferred from cylinder  22  to cylinder  24 . 
         [0054]    In considering the operation of the invention it will be understood that in the first cylinder  22  each reciprocal wall acts as a barrier Wall for coaction with a piston constituted by a respective lobe portion  26   c  and in the second cylinder  24  each reciprocal wall acts as a piston receiving the expanding energy of the charge in the power stroke and sweeping the exhaust gasses from a previous cycle out of the respective exhaust port. 
         [0055]    The second embodiment of the engine seen in  FIGS. 7 ,  8 , and  9  is generally similar to the embodiment of  FIGS. 1-6  with the exception that in this case the moveable walls associated with the first cylinder as well as the moveable walls associated with the second cylinder are both mounted in their respective housing sections and are biased radially inwardly against the respective rotor members. 
         [0056]    Specifically, the engine of  FIGS. 7-9  includes a housing having a first section  70  and a second section  72 , a rotor  74  coacting with the first housing  70  to form a first cylinder  76  and including a lobe  78 , a second rotor member  80 , coacting with the second housing section  72  to define the second cylinder  82  and including a lobe  84 , a reciprocal wall  86  mounted in the first housing section and a reciprocal wall  88  mounted in the second housing section. 
         [0057]    In this case the transfer passage  90  interconnecting cylinders  76  and  82  during the charge transfer process includes an inclined passage  92  connecting the two cylinders passing through mutually fixed parts of both the cylinder housing sections and through a coupling ring  94 , a passage  96  in wall  86  opening in the first cylinder, and a passage  98  in the wall  88  opening in the second cylinder. As seen by a comparison of  FIG. 8  showing a work performance position of the engine, and  FIG. 9 , showing a charge transfer position of the engine, the passages  96 ,  92  and  98  are normally disconnected to preclude interchange of charge between the cylinders. 
         [0058]    When the walls  88  and  86  are moved to the dwell portions  84   a  and  78   a  of the respective coacting rotor lobes, as seen in  FIG. 9 , the passages  96 ,  92  and  98  interconnect to form the passage  90  and allow the transfer of the fuel charge from cylinder  76  to cylinder  82  for so long as the walls  86  and  88  are engaging the respective dwell portions of the respective dwell portions of the respective rotor lobes whereafter the passage is interrupted by subsequent movements of the reciprocating walls to the main body portions of the respective rotors as seen in  FIG. 8 . 
         [0059]    The transfer passage arrangement of the  FIG. 7-9  embodiment eliminates the arcuate groove  56  in the  FIGS. 1-6  embodiment, reduces the transfer path length and volume, decreases the number of intermediate contacts, and enhances the reliability of the transfer operation. 
         [0060]    The engine of the  FIGS. 10- and   11  embodiment is generally similar to the engine of the  FIGS. 1-6  embodiment with exception that transfer passage between the first cylinder and the second cylinder opens in the second cylinder in the cylinder housing rather than in the reciprocal wall of that cylinder. 
         [0061]    Specifically, the engine of  FIGS. 10 and 11  includes a housing including a first section  100 , a second section  102  and a rotor structure including a first rotor member  104  coacting with the first housing section  100  to define the first cylinder  106  and a second rotor member  108  coacting with the second housing section to define the second cylinder  110 . 
         [0062]    Reciprocal walls  112  are mounted in housing section  100  for coaction with lobes  114  on rotor  104  and reciprocal walls  116  are mounted on housing section  108  for coaction with lobes  118  on the inner periphery  102   a  of housing section  102 . 
         [0063]    The transfer passage  120  in this case includes a passage  122  in reciprocating wall  112  opening in the cylinder  106 , a passage  124  in a central housing partition  126  and a passage  127  opening in a lobe  118  on the inner periphery of hosing section  102  through a series of windows  128 . 
         [0064]    The ready to ignite fuel charge transfer is initiated at the instant when the entry portion  114   a  of lobe  114  lifts the reciprocal wall  112  up onto the lobe dwell portion  114   b . Simultaneously the reciprocal wall  116  moves onto the dwell portion  118   a  of lobe  118  whereupon the ready to ignite fuel charge, its constant volume being maintained, begins to flow into the cylinder  110  through the windows  128 . During this transfer, the charge is ignited and the combustion process begins. The transfer of the ready to ignite fuel charge is completed when the reciprocal wall  112  travels beyond the dwell portion  114   b  of the lobe  114  and is shifted outwardly by the lobe portion  114   c , thus interrupting the transfer passage between the first and second cylinders. 
         [0065]    As compared to the engines of the  FIGS. 1-6  and  7 - 9  embodiments, the engine of the  FIGS. 10 and 11  embodiment has the lowest number of contact-points between the elements of the ready to ignite charge transfer passage and the shortest transfer passage length. 
         [0066]    The engine of the  FIGS. 12 and 13  embodiment is similar to the engine of the  FIGS. 1-6 ,  7 - 9  and  11 - 12  embodiments with the exception that the moveable walls in this embodiment are mounted for pivotal rather than reciprocal movement. 
         [0067]    A reciprocal wall or partition has to be open to the outside atmosphere to avoid pumping of the charge into the compartment. This requires a tight sealing of the wall within the compartment. Further, pressure differences generated between the two faces of wall will force it toward the compartment wall and impede its slide. Further the spring that forces the wall toward the rotor is elongated during the work phase when the partition is outside its compartment and seals the cylinder. Force applied by the spring on the wall at this time is smaller than at the idle phase when the wall is shifted into the compartment to allow the pistons passage. Further the wall has to be light and durable. All of these disadvantages are overcome by replacing the reciprocal wall of the previous embodiments with the pivotally mounted wall seen in the  FIGS. 12 and 13  embodiment. 
         [0068]    The first cylinder as seen in  FIG. 12  includes a housing section  130  and a rotor  132  coacting with the housing section to define a first cylinder  134  and having a lobe  136 . The engine further includes pivotal wall  138  mounted on the inner periphery of housing section  130  by a pin  140  for pivotal movement about an axis  142 . A bias pin  144  is mounted in housing  130  and includes a roll  146  on its inboard end received in a cavity  138   a  in the wall  138 . Pin  144  is biased radially inwardly by a compression spring  148  whereby to bias the wall  138  pivotally inwardly to press the free end  138   b  of the wall against the periphery  132   a  of the rotor. A groove  150  is machined into the inner periphery of housing  130  to accommodate wall  138  in its outwardly pivoted position. The back face  138   c  of the wall has a special profile designed to reduce the relative change in the length of the spring  148  (and therefore changes in the force that the spring applies) between the fully open and fully closed positions. Specifically, the partition is thick in the open state and thin in the closed state. 
         [0069]    The charge transfer passage  152  passes along the pivotal axis  142  of the wall  138 . The passage  152  has the form of a pipe with intake apertures  154  opening in the first cylinder and outlet apertures  156  opening in the second cylinder. The rotating wall rotates about the charge transfer passage and includes apertures  158  that align with apertures  154  during the charge transfer time only and seal with respect to the apertures  154  during the rest of the cycle. 
         [0070]    The invention engine will be seen to provide many important advantages for a coupled cylinder rotary type engine. 
         [0071]    Specifically, by providing a different configuration for the first and second cylinders the overall efficiency of the engine is improved. Yet more specifically, the process commencement temperature T is maximized by maintaining a constant charge volume during the transfer process and the process termination temperature t is minimized by providing a larger volume for the second cylinder as compared to the first cylinder. Further, the efficiency of the charge transfer process between the first and second cylinders is optimized by keeping the transfer path open only for so long as the actual charge is being transferred and by providing total isolation of gaseous combustion products from the consecutive incoming charges. Overall, by providing different design and dimensional characteristics for the first and second cylinders, the operational aspects of each cylinder may be optimized to provide an optimized overall engine efficiency. 
         [0072]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.