Patent Publication Number: US-6662762-B2

Title: Balanced five cycle engine with shortened axial extent

Description:
This invention relates to internal combustion engines and more particularly to improvements in five cycle engines embodying annularly arranged cylinders having opposed pistons movable by annular cams. 
     BACKGROUND OF THE INVENTION 
     Five cycle engines of the type herein contemplated have been proposed in the patented literature for more than sixty-eight years. The Packard Motor Car Co. was granted U.S. Pat. No. 1,788,140, on Jan. 6, 1931, which discloses the basic five cycle engine herein contemplated. 
     The &#39;140 patent discloses an internal combustion engine comprising a housing, a plurality of annularly arranged cylinders in the housing disposed with their axes parallel with a central longitudinal rotor axis. Each of the cylinders includes an inlet end portion having an inlet port therein, a central working portion, and an outlet end portion having an outlet port therein. An inlet piston is mounted in each cylinder constructed and arranged to be moved in sealing relation to the associated cylinder from an inlet end position wherein the inlet port thereof communicates with the working portion thereof in an axial direction away from the inlet end position into an inlet port cut-off position wherein the inlet piston cuts off communication of the inlet port thereof with the working portion thereof and beyond into the working portion thereof. An outlet piston is mounted in each cylinder constructed and arranged to be moved in sealing relation to the associated cylinder from an outlet end position thereof wherein the outer port thereof is communicated with the working portion thereof in an axial direction away from the outlet end position into an outlet port cut-off position wherein the outlet piston cuts off the communication of the outer port thereof with the working portion thereof and beyond into the working portion thereof. Rotor structure within the housing is constructed and arranged to move with a rotational movement within the housing about the central rotor axis. Each of the inlet pistons includes an inlet cam follower constructed and arranged to follow an annular inlet cam during the rotation of the rotor structure. Each of the outlet pistons includes an outlet cam follower constructed and arranged to follow an annular outlet cam during the rotation of the rotor structure. The inlet and outlet annular cams are configured to move the inlet and outlet pistons within each cylinder through a successive five-cycle repeating movement which includes (1) a power cycle wherein the inlet and outlet pistons are moved axially outwardly from combustion positions disposed in closely spaced relation within the working portion of the associated cylinder into the respective cut-off positions thereof, (2) an exhaust cycle wherein the outlet piston is moved from the outer cut-off position thereof into the outlet end position thereof and the inlet piston is moved through the working portion thereof into close proximity to the outlet piston, (3) a transfer cycle wherein the inlet and outlet pistons are moved together in close proximity to each other through the working portion thereof, (4) an intake cycle wherein the outlet piston is initially moved through the working portion of the associated cylinder while the inlet piston is in a position allowing communication of the inlet port with the working portion with the final movement of the intake cycle resulting in the inlet and outlet pistons being in compression positions spaced from the respective end positions thereof so that the communication of the respective ports are cut off from the working portion of the associated cylinder, and (5) a compression cycle wherein the inlet and outlet pistons are moved from the compression positions thereof toward each other into the combustion positions. 
     The &#39;140 patent disclosure contemplates that the compression positions of the inlet and outlet pistons in the intake cycle constitute the respective cut-off positions thereof, both of which are moved directly therein during the final movements of the intake cycle. In this way, a maximum power is achieved and opposed piston movement balance is achieved during the full movement of the opposed pistons during compression as well as during expansion. 
     It is noted, however, that the transfer cycle introduces an imbalance because both pistons are moved together through a stroke from the outlet to inlet end positions. Similarly, the intake and exhaust cycles involve different movements of the pistons in the same direction. 
     Over the years, there have been various improvements on the basic five cycle engine proposed in the patented literature. The Packard Motor Car Co. was granted improvement U.S. Pat. No. 1,808,083, contemporaneously with the basic &#39;140 patent on June 2, 1931. This Packard improvement was directed toward diminishing the imbalanced movement of the pistons together during the transfer cycle by essentially halving the movement required and doubling the five cycle operation to a ten cycle operation. 
     U.S. Pat. No. 5,289,802 introduced two features of improvement in the basic five-cycle operation. First, an increased compression-expansion ratio beyond one is proposed where the compression positions of the inlet and outlet pistons in the intake cycle constitute the cut-off position of the inlet piston and an intermediate position of the outlet piston disposed inwardly of the outlet cut-off position thereof, both of which are moved directly therein during the final movements of the intake cycle. The intake cycle is essentially accomplished by a movement of the outlet piston within the cylinder which positively displaces a new charge through the open inlet port. Second, the inlet and outlet pistons dwell in the combustion positions thereof longer than the instantaneous dwell provided by simple harmonic motion for a time sufficient to enable a new fueled gas charge within the minimum column to be ignited and to rise to maximum pressure before substantial volume increase toward the maximum volume during the power cycle takes place to thereby eliminate negative work resulting from ignition prior to reaching the minimum volume condition and to obtain optimal work from optimal pressure conditions. 
     While these improvements to some extent have a positive effect on the inherent imbalance of the basic five-cycle movement, it is apparent that the problem of inherent imbalance has gone unsolved since 1931 despite the various improvements which have been proposed over the years. 
     My U.S. Pat. No. 6,305,334 discloses one way of achieving balance in a five-cycle engine. The manner of achieving balance is to construct a mirror image of the engine. In this way, all movements of the initial engine pistons and cam followers are accompanied by an equal and opposite movement of the mirror image engine pistons and cam followers. While balance is achieved, the resultant construction is a total engine which is elongated in the axial direction by a factor of two. In many installations, the axial length of the engine becomes prohibitive to usage. An example exists in many automobiles. There still exists a need for a solution to the balance problem which does not create the elongation problem of the mirror image solution of the &#39;334 patent. 
     BRIEF SUMMARY OF THE INVENTION 
     An objective of the present invention is to supply the need expressed above. In accordance with the principles of the present invention, this objective is accomplished by providing a five-cycle internal combustion engine having the usual components wherein a plurality of first cylinders and a plurality of second cylinders having axes disposed in annularly spaced relation about the longitudinal axis of the housing assembly and in annularly spaced relation with respect to one another. The inlet and outlet end portions of the first cylinders are arranged in axially opposite relation with respect to the inlet and outlet end portions of the second cylinders respectively. The first and second inlet and outlet cams associated with the first and second cylinders respectively are related to each other so that the transfer cycle movements of the inlet and outlet pistons in the first cylinders are accompanied by a generally equal and axially opposite transfer cycle movement of the inlet and outlet pistons in the second cylinders so that all transfer cycle movements of the first and second inlet and outlet pistons and the associated first and second inlet and outlet cam followers are axially balanced. 
     The present invention also contemplates an improvement capable of varying the compression ratio of the five cycle engine discussed above as well as other five cycle engines. This capability is achieved by providing a compression ratio adjusting system constructed and arranged to effect axial movement between the cooperating inlet and outlet cams so as to vary the spacing between the inlet and outlet pistons in each cylinder at the combustion position thereof so as to vary the minimum volume condition defined thereby in relation to the volume defined by the compression position thereof. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal sectional view of a balanced five-cycle eight cylinder internal combustion engine embodying the principles of the present invention, the background structure not in section being eliminated for purposes of clearer illustration. 
     FIG. 2 is a sectional view taken along the line  2 — 2  of FIG. 1; 
     FIG. 3 is a view similar to FIG. 1 taken along the line  3 — 3  of FIG. 2; 
     FIG. 4 is a view showing the relationship between the cam surfaces of the first and second inlet and outlet cams and one position of the first and second inlet and outlet pistons in the eight first and second cylinders; 
     FIG. 5 is a somewhat schematic view of a pair of inlet and outlet pistons within a cylinder in the combustion position thereof achieved by the inlet and outlet cam configuration shown in FIG. 4; 
     FIG. 6 is a view similar to FIG. 5 showing the inlet and outlet pistons in another combustion position thereof in accordance with the principles of the present invention; 
     FIG. 7 is a view similar to FIG. 5 showing still another combustion position of the inlet and outlet position in accordance with the principles of the present invention; 
     FIG. 8 is a view similar to FIG. 4 showing a modification wherein the engine includes only four cylinders rather than eight; 
     FIG. 9 is a view similar to FIG. 4 showing a modified cam surface configuration wherein only one five cycle movement is undertaken during each revolution; 
     FIG. 10 is a view similar to half of FIG. 2 showing a modified construction suitable to provide for adjustment in the compression ratio of the engine; 
     FIG. 11 is a sectional view taken along the line  11 — 11  of FIG. 10; 
     FIG. 12 is an enlarged fragmentary sectional view taken along the line  12 — 12  of FIG. 11 showing a pair of cam moving members in a teeth interengaging position. 
     FIG. 13 is a view similar to FIG. 12 showing a pair of cam moving members in a teeth meshing position; and 
     FIG. 14 is a fragmentary view partly broken away showing a modification of the structure shown in FIG. 12 enabling each cooperating pair of inlet and outlet cams to be moved toward and away from each other with both an axial and angular movement. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     Referring now more particularly to FIGS. 1-3 of the drawings, there is shown therein a balanced five-cycle combustion engine, generally indicated at  10 , embodying the principles of the present invention. 
     The engine  10  includes a housing assembly  12 , having a longitudinal axis. Within the housing assembly  12 , is a plurality of annularly arranged first cylinders, generally indicated at  14 , having axes which are disposed in an annularly spaced parallel relation with respect to the longitudinal axis. A plurality of second cylinders  14 ′ are arranged in annularly spaced parallel relation with respect to the longitudinal axis and in annularly spaced relation with respect to the plurality of first cylinders  14 . Preferably, the second cylinders  14 ′ are disposed in generally axial coextensive relation with respect to the axes of the first cylinders  14 . As best shown in FIG. 2, the first cylinders  14  have their axes disposed within an outer circle. The second cylinders  14 ′ have their axes interposed therebetween within an inner circle. 
     Each first cylinders  14  has an inlet end portion  16  having one or more inlet ports  18  therein, a central working portion  20 , and an outlet end portion  22  having one or more outlet ports  24  therein. Each of the plurality of second cylinders  14 ′ has an inlet end portion  16 ′ having one or more inlet ports  18 ′ therein, a central working portion  20 ′, and an outlet end portion  22 ′ having one or more outlet ports  24 ′ therein. The inlet end portion  16 , the central working portion  20 , and the outlet end portion  22  of the first cylinders  14  are arranged in axially opposite relation with respect to the inlet end portion  16 ′, the central working portion  20 ′, and the outlet end portion  22 ′ of the plurality of second cylinders  14 ′ respectively. 
     A first inlet piston  26  is mounted in each of the first cylinders  14 . Each first inlet piston  26  is constructed and arranged to be moved in sealing relation to the associated first cylinder  14  from an inlet end position wherein the inlet port  18  thereof communicates with the working portion  20  thereof. Each first inlet piston  26  moves in an axial direction away from the inlet end position thereof into an inlet port cut-off position wherein the first inlet piston  26  cuts off communication of the inlet port  18  of the first cylinder  14  with the working portion  20  thereof and beyond into the working portion  20  thereof. 
     A second inlet piston  26 ′ is mounted in each second cylinders  14 ′. Each second inlet piston  26 ′ is constructed and arranged to be moved in sealing relation to the associated second cylinder  14 ′ from an inlet end position wherein the inlet port  18 ′ thereof communicates with the working portion  20 ′ thereof. Each second inlet piston  26 ′ moves in an axial direction away from the inlet end position thereof into an inlet port cut-off position wherein the second inlet piston  26 ′ cuts off communication of the inlet port  18 ′ of the associated second cylinder  14 ′ with the working portion  20 ′ thereof and beyond into the working portion  20 ′ thereof. 
     A first outlet piston  28  is mounted in each first cylinder  14  and is constructed and arranged to be moved in sealing relation thereto from an outlet end position wherein the outlet port  24  thereof communicates with the working portion  20  thereof. Each first outlet piston  28  moves in an axial direction away from the outlet end position thereof into an outlet port cut-off position wherein the first outlet piston  28  cuts off the communication of the outlet port  24  of the associated first cylinder  14  with the working portion  20  thereof and beyond into the working portion  20  thereof. 
     A second outlet piston  28 ′ is mounted in each second cylinder  14 ′ and is constructed and arranged to be moved in sealing relation thereto from an outlet end position wherein the outlet ports  24 ′ thereof communicate with the working portion  20 ′ thereof Each second outlet piston  28 ′ moves in an axial direction away from the outlet end position thereof into an outlet port cut-off position wherein the outlet piston  28 ′ cuts off the communication of the outlet port  24 ′ of the associated second cylinder  14 ′ with the working portion  20 ′ thereof and beyond into the working portion  20 ′ thereof. 
     A rotor structure, generally indicated at  30 , is mounted within the housing assembly  12  and is constructed and arranged for rotational movement therein about the longitudinal axis. 
     Each of the first inlet pistons  26  has connected thereto a first inlet cam follower, generally indicated at  32 , which preferably is in the form of a fixed piston rod  34  having a pair of axially spaced rollers  36  on the free end thereof constructed and arranged to follow a first annular outlet cam  38 , disposed annularly about the longitudinal axis axially outwardly of the inlet end portions  16  of the first cylinders  14 . 
     Each of the second inlet pistons  26 ′ has connected thereto a second inlet cam follower, generally illustrated at  32 ′, which preferably is in the form of a fixed piston rod  34 ′ having a pair of axially spaced rollers  36 ′ constructed and arranged to follow a second annular inlet cam  38 ′, disposed annularly about the longitudinal axis axially outwardly of the inlet end portions  16 ′ of the second cylinders  14 ′ during the rotation of rotor structure  30  so as to effect axial movements thereof in opposite directions. 
     The first and second inlet cam followers  32  and  32 ′ are guided for longitudinal rectilinear movement by guide blocks  40  and  40 ′ respectively which, as shown, are fixed to the free ends of the piston rods  34  and  34 ′ of the first and second inlet cam followers  32  and  32 ′ respectively. Each guide block  40  is slidably mounted on a pair of longitudinally extending guide rods  42  suitably fixed to the housing assembly  12 . Each guide block  40 ′ is slidably mounted on a pair of longitudinally extending guide rods  42 ′ suitably fixed to the housing assembly  12 . 
     Each of the first outlet pistons  28  has connected thereto a first outlet cam follower, generally indicated at  44 , which preferably is in the form of a fixed piston rod  46  having a pair of axially spaced rollers  48  on the free end thereof constructed and arranged to follow a first annular outlet cam  50 , disposed annularly about the longitudinal axis axially outwardly of the outlet end portion  22  of the first cylinders  14  during the rotation of rotor structure  30  so as to effect axial movements thereof in opposite directions. 
     Each of the second outlet pistons  28 ′ has connected thereto a second outlet cam follower, generally indicated at  44 ′, which preferably is in the form of a fixed piston rod  46  having a pair of axially spaced rollers on the free end thereof constructed and arranged to follow a second annular outlet cam  50 ′, disposed annularly about the longitudinal axis axially outwardly of the outlet end portions  22 ′ of the second cylinders  14 ′ during the rotation of rotor structure  30  so as to effect axial movements thereof in opposite directions. 
     The first and second outlet cam followers  44  and  44 ′ are guided for longitudinal rectilinear movement by guide blocks  52  and  52 ′ respectively which, as shown, are fixed to the free ends of the piston rods  46  and  46 ′ of the first and second outlet cam followers  44  and  44 ′ respectively. Each guide block  52  is slidably mounted on a pair of longitudinally extending guide rods  54  suitably fixed to the housing assembly  12 . Each guide block  52 ′ is slidably mounted on a pair of longitudinally extending guide rods  54 ′ suitably fixed to the housing assembly  12 . 
     The first inlet and outlet annular cams,  34 ,  34 ′ and  38 ,  38 ′, are configured to move the first and second inlet and outlet pistons,  26 ,  26 ′ and  28 ,  28 ′ within each first and second cylinder  14 ,  14 ′ through a successive five-cycle repeating movement set forth below. 
     (1) a power cycle wherein the first and second inlet and outlet pistons,  26 ,  26 ′ and  28 ,  28 ′, are moved axially outwardly from combustion positions disposed in closely spaced relation within the working portion  20 ,  20 ′ of the associated cylinder  14 ,  14 ′ defining a minimum volume condition into the respective cut-off positions thereof defining a maximum volume condition; 
     (2) an exhaust cycle wherein the first and second outlet pistons  28 ,  28 ′ are moved from the outlet cut-off position thereof into the outlet end positions thereof and the first and second inlet pistons  26 ,  26 ′ are moved through the working portion  20 ,  20 ′ thereof into close proximity to the first and second outlet pistons  28 ,  28 ′; 
     (3) a transfer cycle wherein the first and second inlet and outlet pistons,  26 ,  26 ′ and  28 ,  28 ′, are moved together in close proximity to each other through the working portion  20 ,  20 ′ of the associated first and second cylinders  14 ,  14 ′. 
     ( 4 ) an intake cycle wherein the first and second outlet pistons  28 ,  28 ′ are initially moved through the working portions  20 ,  20 ′ of the associated first and second cylinders  14 ,  14 ′ while the first and second inlet pistons  26 ,  26 ′ respectively are in positions allowing communication of the first and second inlet ports  18 ,  18 ′ respectively with the associated working portions  20 ,  20 ′ with the final movement of the intake cycle resulting in the first and second inlet and outlet pistons,  26 ,  26 ′, and  28 ,  28 ′ being in compression positions spaced from the respective end positions thereof so that the communication of the respective inlet and outlet ports  18 ,  18 ′, and  24 ,  24 ′ are cut off from the working portions  20 ,  20 ′ of the associated first and second cylinders  14 ,  14 ′; 
     and (5) a compression cycle wherein the first and second inlet and outlet pistons,  26 ,  26 ′ and  28 ,  28 ′ are moved from the compression positions thereof toward each other into the combustion positions thereof. 
     In the configuration shown in FIG. 4, the compression position of each outlet piston  28  and  28 ′ is as shown in FIG. 5 inwardly of the cut-off position thereof. In reaching this compression position, each outlet piston  28  and  28 ′ is moved directly into the compression position shown during the final movement of the intake cycle. In addition, the cam configuration is such as to accomplish a piston dwell in the combustion position. 
     The preferred engine  10  shown in FIGS. 1-4 is an eight cylinder engine. As previously indicated, four first cylinders  14  have axes disposed in equal annularly spaced relation about the longitudinal axis of the housing assembly  12  within an outer circle. Four second cylinders  14 ′ have axes disposed in equal annularly spaced relation about the longitudinal axis of the housing assembly  12  between the axes of the first cylinders  14  and within an inner circle. The surfaces of the first inlet and outlet annular cams  34 ,  34 ′ and  38 ,  38 ′ are formed so that each pair of inlet and outlet pistons  26 ,  26 ′ and  28 ,  28 ′ undergo two complete cyclical movements during a single revolution of the rotor structure  30 . 
     As best shown in FIG. 4, with the dual cyclical movement cam surface configuration the first inlet and outlet pistons  26  and  28  in any two diametrically opposed first cylinders  14  will undergo transfer cycle movements at the same time. The cam surfaces of the second inlet and outlet annular cams  34 ′ and  38 ′ are of similar dual cyclical movement configuration so that the second inlet and outlet pistons  26 ′ and  28 ′ in an adjacent two diametrically opposed second cylinders  14 ′ will undergo transfer cycle moments at the same time. The cam surfaces of the second inlet and outlet cams  34  and  38  and are timed with respect to the cam surfaces of the first inlet and outlet annular cams  34  and  38  in a 45° displaced phase relationship, so that the two transfer cycles per revolution of the second inlet and outlet pistons  26 ′ and  28 ′ will take place simultaneously with the two transfer cycle movements per revolution of the first inlet and outlet pistons  26  and  28 . Since the second inlet and outlet ports  18 ′ and  24 ′ are axially opposite the first inlet and outlet ports  18  and  24 ,′ the transfer cycle movements of the diametrically opposed second inlet and outlet pistons  26 ′ and  28 ′ move in an axially opposite direction with respect to the direction of movement of the diametrically opposed first inlet and outlet pistons  26  and  28 . In this way, all of the transfer cycle movements are balanced axially so long as the relative masses are made to be equal. 
     In this regard, it will be noted that the added mass length of the first inlet and outlet cam followers  32  and  44  can be counterbalanced (1) by making the second inlet and outlet pistons  26 ′ and  28 ′ solid while the first inlet and outlet pistons  26  and  28  are hollow and (2) by making the guide blocks  40 ′ and  52 ′ appropriately larger than the guide block  40  and  52 . 
     Similarly, it can be seen that the individually imbalanced intake and exhaust cycle movements also are performed simultaneously so as to achieve axial balance. This relationship also establishes that the moment between the forces created in any two adjacent cylinders will be balanced by the moment created in the diametrically opposed adjacent cylinders. In this way, full dynamic balance is obtained by insuring that the masses of the individual pistons and cam followers are the same, as aforesaid. 
     In accordance with the principles of the present invention, it is the mounting of the first and second cylinders  14  and  14 ′ in annular spaced relation with respect to one another together with the reversal of the port orientation of the first and second cylinders  14  and  14 ′ and the timing of the five cycle movements which enable full dynamic balance to be achieved. A minimum axial dimension of the engine  10  would be achieved by mounting the first and second cylinders  14  and  14 ′ axially within the housing assembly  12  in total axial coextensive relation. In the preferred embodiment described above, the first and second cylinders  14  and  14 ′ are axially displaced somewhat from a full axial coextensive relationship so as to accommodate the provision of inlet and outlet chambers for the first and second cylinders  14  and  14 ′. In its broadest aspects, the invention contemplates the full coextensive relationship as well as a greater amount of axial displacement as between the first and second cylinders  14  and  14 ′ limited only by the desire to limit the growth of the axial extent of the housing assembly  12 . 
     While it is contemplated in the broadest aspects of the present invention that the first and second cylinders  14  and  14 ′ could be rotated with the rotor structure  30  and the first and second inlet and outlet annular cams,  38 ,  38 ′ and  50  and  50 ′ fixed with respect to the housing assembly  12 , it is preferable in accordance with the principles of the present invention to fix the first and second inlet and outlet annular cams  38 ,  38 ′ and  50 ,  50 ′ to the rotor structure  30  so that they rotate therewith and to fix the first and second cylinders  14  and  14 ′ with respect to the housing assembly  12 . 
     It will be understood that the housing assembly  12  may assume different constructions. In the exemplary embodiment shown in FIGS. 1-3 of the drawings, the housing assembly  12  includes a pair of cup-shaped end housing members  56  and  56 ′ which are disposed in spaced relation opening toward one another. 
     Fixed to the open ends of the end housing members  56  and  56 ′ is a pair of outer housing members  58  and  58 ′ which, in turn, are fixed to a pair of intermediate housing members  60  and  60 ′ which, in turn, are fixed to a pair of inner housing members  62  and  62 ′ fixed to one another. A first one of the outer housing members  58  includes four cylinder portions  64  and four openings  66  recessed to axially receive therein marginal edges of the inlet end portions  16  of the four first cylinders  14  and marginal edges of the outlet end portions  22 ′ of the four second cylinders  14 ′ respectively. The second outer housing member  58 ′ includes four cylinder portions  64 ′ and four openings  66 ′ recessed to receive therein marginal edges of the inlet end portions of  16 ′ of the four second cylinders  14 ′ and the marginal edges of the outlet end portions  22  of the four first cylinders  14  respectively. 
     The intermediate housing members  60  and  60 ′ have first and second exhaust openings  68  and  68 ′ respectively formed in the peripheries thereof and are apertured to receive the first and second cylindrical portions  64 ,  64 ′ and the first and second cylinders  14 ,  14 ′ respectively therethrough. The intermediate housing members  60  and  60 ′ are configured to form with the adjacent outer housing members  58 ,  58 ′ first and second intake chambers  70 ′ and  70  respectively, which communicate with outlet ports  24  and  24 ′ respectively. 
     The inner housing members  62  and  62 ′ are formed with intake openings  72  and  72 ′ respectively in the peripheries thereof and are apertured to receive the first and second cylinders  14  and  14 ′ therethrough. The inner housing members  62 ′ and  62 ′ are configured to cooperate with the intermediate housing members  60  and  60 ′ to form intake chambers  74  and  74 ′ respectively which communicate with the first and second outlet ports  24  and  24 ′, respectively. 
     The periphery of a first one of the inner housing members  62  is also apertured to have mounted therein four suitable fuel injector mechanisms illustrated schematically at  76  in FIG. 1 which also extends into communicating relation with the central working portions  20  of the first cylinders  14 . Similarly, the periphery of the second inner housing member  62  is apertured to have mounted therein four annularly spaced fuel injector mechanisms illustrated schematically at  76 ′ in FIG. 3 which also extend into communicating relation with the central working portions  20 ′ of the second cylinders  14 ′. While the preferred engine shown is a diesel type engine it will be understood that other known types of ignitions, are contemplated as, for example, spark ignition. 
     As shown, the rotor structure  30  is in the form of a main output shaft  78  suitably journaled in the housing assembly  12  for rotational movement about the longitudinal axis of the housing assembly  12 . The first and second inlet and outlet cams  38 ,  38 ′ and  50 ,  50 ′ are suitably splined to or otherwise fixed to the shaft  78 . It will be understood that first inlet cam  38  could be made integral with second outlet cam  50 ′ and second inlet cam  38 ′ could be made integral with first outlet cam  50 . 
     Operation of the Engine of FIGS.  1 - 4   
     Referring to FIG. 2, it can be seen that for purposes of further identification the four first cylinders  14  have been numbered clockwise with the numbers  14 A,  14 B,  14 C and  14 D respectively. Likewise, the four second cylinders have been numbered  14 ′ A,  14 ′ B,  14 °C, and  14 ′ D respectively. These distinctive numbers are used to distinguish the operational movements taking place in each cylinder assuming a clockwise rotation of the rotor structure  30  as viewed in FIG.  2 . 
     FIG. 4 illustrates the layout of a preferred configuration of the first inlet and outlet cams  38  and  50  outermost and of the second inlet and outlet cams  38 ′ and  50 ′ innermost. In addition, FIG. 4 illustrates one position of the pistons with respect to each of the eight cylinders. It will be noted that in FIG. 4, the first pistons  26  and  28  in first cylinder  14 A are just beginning the power cycle and that the first pistons  26  and  28  in the next first cylinder  14 B are in the middle of the transfer cycle movement. The first pistons  26  and  28  in the next two first cylinders  14 C and  14 D are in these same two cyclical movements respectively. Thus, it can be seen that the first pistons  26  and  28  in each pair of diametrically opposed first cylinders  14 A and  14 C or  14 B and  14 D are undergoing simultaneously the same cyclical movements. 
     It will also be seen that the second pistons  26 ′ and  28 ′ are also undergoing similar cyclical movements so that in second cylinders  14 ′ A and  14 ′ C, the second pistons therein are in the middle of the transfer cycle of movement and in second cylinders  14 ′ B and  14 ′ D, the second pistons therein are at the beginning of the power cycle. 
     In the positions shown in FIG. 4, it can be seen that the transfer piston movements in first cylinders  14 B and  14 D are axially counterbalanced by the transfer piston movements in second cylinders  14 ′ A and  14 ′ C since the first piston transfer movement takes place in an opposite axial direction with respect to the second piston transfer movement. In the positions shown in FIG. 4, the pistons in four cylinders are undergoing the same transfer cycle movements and the pistons in the other four cylinders are beginning to undergo power cycle movements which are exactly balanced by equal and opposite movements of each pair of inlet and outlet pistons. Thus, it can be seen that the moments created between each pair of first pistons undergoing transfer cycle movements with respect to the adjacent pair of second pistons undergoing transfer cycle movements are equal and opposite. 
     It can be seen as the pistons in each cylinder continues to move successively through each of the five cycles of movement, this same condition of balance occurs. However, since there are five cycles performed during each half revolution of the rotors structure  30 , the timing of the cycles will be different. 
     With the cyclical movement shown in FIG. 4, the following timing is utilized, it being understood that axial balance occurs even though modified timing and movements may be provided. In the embodiment shown, the transfer cycles takes place in 30° of rotational movement of the rotor structure. The intake cycle takes place in the 40° of rotational movement of the rotor structure  30 . The compression and power cycle movements consume 20° and 30° respectively with a dwell period of 10° therebetween. Finally, the 5 cycles of movement are completed by an exhaust cycle movement during 50° of rotational movement of the rotor structure  30 . 
     Again it will be noted that the individually axially imbalanced movements of each pair of pistons during the intake and exhaust cycles of movement are axially balanced in the same manner as the individually axially imbalanced movements of each pair of pistons during the transfer cycle movements. 
     The movement of the inlet and outlet pistons in each cylinder in the transition between the end of the intake cycle of movement and the start of the compression cycle of movement can be accomplished in any of the three ways, as disclosed in my aforesaid &#39;334 patent. The preferred transitional movement illustrated by the cam curves in FIG. 4 is exemplified by the compression positions shown in FIG.  5 . It will be noted that the inlet piston  26  has just reached the cut-off position thereof while the outlet piston  28  has moved through the cylinder to a position inwardly of the cut-off position thereof. This compression position enables the engine to operate with a greater expansion volume than compression volume which is desirable from an efficiency standpoint. 
     FIG. 6 illustrates another compression position of the pistons  26 ,  26 ′ and  28 ,  28 ′ in which each is at its cut-off position. In this mode of operation, a maximum compression volume is provided for maximum power. 
     FIG. 7 illustrates still another compression position of the pistons  26 ,  26 ′ and  28 ,  28 ′ wherein the inlet piston  26 ,  26 ′ has been moved into the cylinder beyond its cut-off position and the outlet piston  28 ,  28 ′ is at the cut-off position thereof. It will be understood that during the movement of the inlet piston  26 ,  26 ′ into the cylinder  14 ,  14 ′ past the cut-off position thereof, the outlet piston  28 ,  28 ′ is in an open position allowing the inlet piston  26 ,  26 ′ during its movement into the cylinder  14 ,  14 ′ to displace a volume of air through the outlet port  24 ,  24 ′. This mode of operation dilutes the percentage of unwanted products of combustion contained in the exhaust gases and also provides for greater expansion than compression. 
     FIG. 8 illustrates a modification of the engine  10  constructed in accordance with the principles of the present invention. As shown, the modification consists in providing an engine  110  which is constructed exactly like the engine  10  except that there are provided only four cylinders instead of eight. Thus, there are two diametrically opposed first cylinders  114  and  114 B similar to the four first cylinders  14  A-D and two equally annularly spaced diametrically opposed second cylinders  114 ′ A and  114 ′ B similar to the four second cylinders  14 ′ A-D. Instead of the axes of the first cylinders  114  being disposed within a circle outside of a circle within which the axes of the second cylinders  114 ′ are located, all four first and second cylinders  114  and  114 ′ can have their axes disposed within the same circle. 
     FIG. 8 illustrates that, as before, the first inlet and outlet ports  118  and  124  of the two first cylinders  114  are axially reversed in relation to the second inlet and outlet ports  118 ′ and  124 ′. 
     In the operation of the engine  110  it can be seen that the 5 cyclic movements of the pistons  126  and  128  in the cylinders  114  move essentially in unison in essentially the same manner as previously described. Thus, as the inlet and outlet pistons  126  and  128  in the two diametrically opposed first cylinders  114  move through a transfer cycle of movement in one axial direction, the inlet and outlet pistons  126 ′ and  128 ′ in the two 90° displaced diametrically opposed second cylinders  114 ′ also undertake a transfer movement but in the axially opposite direction. This simultaneous opposed axial movement, as before, not only achieves axial balance but a balance of the moments about the longitudinal axis created by the piston movements in adjacent cylinders. A similar full balance can be achieved by providing six cylinders with the cams modified to provide three five cycle movements per revolution. 
     FIG. 9 illustrates still another modification of the engine  10  constructed in accordance with the principles of the present invention. As shown, this modification consists in providing an engine  210  having first and second inlet cams  238  and  238 ′ and corresponding first and second outlet cams  250  and  250 ′ configured to move the inlet and outlet pistons  226 ,  226 ′ and  228 ,  228 ′ through only one five cycle movement during each revolution rather that two as before. 
     With this cam configuration, the first inlet and outlet pistons  226  and  228  in only one of the four first cylinders  214  will undergo a transfer cycle movement at only one time during each revolution. However, for each such transfer cycle movement there will be an equal axially opposite transfer cycle movement by the second inlet and outlet pistons  226 ′ and  228 ′ within an adjacent one of the second cylinders  214 ′. In this way, axial balance is achieved. However, there remains in imbalance about the longitudinal axis because the movements created by first and second inlet and outlet pistons  226 ,  226 ′ and  228 ,  228 ′ in adjacent first and second cylinders  214  and  214 ′ are not balanced about the longitudinal axis because the piston movements occurring in any two adjacent cylinders  214  and  214 ′ are different from the piston movements taking place on the diametrically opposed two adjacent cylinders  214  and  214 ′. However, since the lever arms between adjacent cylinders are relatively short, the piston movements remain axially balanced and substantially balanced overall but without the moment balance of the engine  10  and  110  previously described. 
     FIGS. 10-13 illustrate still another modification of the engine  10  constructed in accordance with the principles of the present invention. The modification consists in providing an engine  310  having the capability of selectively varying the operating compression ratio thereof. FIG. 10 illustrates only one half of the engine  310 , it being understood that the other half is an image thereof just like the engine  10 . Consequently, a description of the half shown should suffice to give an understanding of both halves. 
     The engine  310  is like the engine  10  in many respects and corresponding parts are indicated by preceding the reference numbers of the engine  10  with the number  3 . Thus, unless hereinafter described as differing from the engine  10 , the engine  310  is like the engine  10 . The basic difference between engine  310  and engine  10  is in the manner in which the inlet and outlet cams  338 ,  338 ′ and  350 ,  350 ′ are mounted within the engine  310 . Whereas the first inlet and outlet cams  38  and  50  and the second inlet and outlet cams  38  and  50 ′ of the engine  10  are fixed in axially spaced relation on the output shaft  78 , as shown in FIG. 10, the first inlet and outlet cams  338  (not shown in FIG. 10) and  350  are splined to the output shaft  378  for rotational movement therewith and for limited axial movement with respect to the shaft  378 . It will be understood that the inlet and outlet cams  338  and  350 ′ (not shown in FIG. 10) are similarly mounted on the output shaft  378  on the opposite side of the central housing members  358 ,  360  and  362  from the inlet and outlet cams  338 ′ and  350  shown in FIG.  10 . It will be understood that the description of the mounting of second inlet cam  338 ′ and first outlet cam  350  set forth below applies equally to the first inlet cam  338  and second outlet cam  350 ′. 
     As best shown in FIG. 10, the separate inlet and outlet cams  338 ′ and  350  are splined to the output shaft  378  on opposite sides of a central thrust ring  380  capable of being moved axially with respect to the output shaft  378 . An inner thrust ring  382  is mounted on the output shaft  378  in abutting relation to an inner flange  384  formed on the output shaft  378 . 
     Mounted on the output shaft  378  between the inner thrust ring  382  and the second inlet cam  338 ′ is a power operated inner cam moving assembly, generally indicated at  386 . A similar outer cam moving assembly, generally indicated at  388 , is mounted on the output shaft  378  between the first outlet cam  350  and an outer thrust ring  390 . The outer thrust ring  390  is retained on the output shaft  378  by a pair of threaded rings  392  threadedly engaged on the adjacent end portion of the output shaft  378 . 
     The power operated inner and outer cam moving assemblies  386  and  388  are of similar mirror image construction so that a description of the power operated outer cam moving assembly  388  should be sufficient to provide an understanding of the power operated inner cam moving assembly  386  as well. 
     As best shown in FIGS. 10-13, the power operated outer cam moving assembly  388  includes a pair of cooperating annular cam moving members  394  and  396 . As best shown in FIGS. 11-13, the pair of cooperating cam moving members  394  and  396  have opposite faces formed with intermeshing flat shallow teeth  398  configured to have one sloping side and one straight side. Cam moving member  394  is rotatably mounted on the output shaft  378  as by sleeve bearing  400  and includes an arm  402  extending radially outwardly therefrom. 
     As best shown in FIG. 11, the extremity of the arm  402  has formed thereon an arcuate series of gear teeth  404 . Gear teeth  404  mesh with a driving worm gear  406  which is mounted on the output shaft of an electric motor and reduction gear unit  408  suitably mounted in fixed relation to the housing assembly  12 , as by a bracket  410 . 
     The other cam moving member  396  is fixed to the outlet cam  350  as by a securing ring  412  bolted to the outlet cam  350  by bolts  414  extending through the securing ring  412  and the cam moving member  396  and threaded into the outlet cam  350 . The securing ring  412  also serves to slidably engage the periphery of the movable cam moving member  394 . 
     The pair of cam moving members  394  and  396  of the outer cam moving assembly  388  is normally retained in a teeth interengaging position, as shown in FIGS. 11 and 12, whereas the pair of cam moving members  394  and  396  of the outlet cam moving assembly  386 , is normally retained in a teeth meshing position as shown in FIG.  13 . With inner cam moving assemblies  386 , and outer cam moving assemblies  388  on each side of the engine  310  in these respective positions, the relationship of the surfaces of the first inlet and outlet cams  338  and  350  and the relationship of the surfaces of the second inlet and outlet cams  338 ′ and  350 ′ is as shown in FIG.  4 . Compression ratio adjustment can be obtained by operating the electric motor gear reduction units  408  so as to move the first outlet cam  350  and second inlet cam  338  on one side of the engine together to the left as shown in FIG. 10 while the first inlet cam  338  and second outlet cam  350 ′ on the other side of the engine  310  are moved together to the right. The effect of this movement is to cause the position of each pair of inlet and outlet pistons  326 ,  326 ′ and  328 ,  328 ′ to be spaced apart a greater distance at their combustion position at the end of the compression cycle of movement. Since substantially the same amount of inlet air is trapped in each cylinder  314 ,  314 ′ at the beginning of the compression cycle of movement, the compression ratio is reduced. 
     In the embodiment shown, the operation is such that only two different compression ratios can be obtained. A typical example in the difference between the two different compression ratios is the difference between a compression ratio of 14 and a compression ratio of 23. 
     The increase in the axial spacing between each pair of the inlet and outlet cams does not effect the dynamic balance, but has other effects as well. For example, each pair of inlet and outlet pistons when undertaking the transfer cycle movement are spaced apart more than in the FIG. 4 mode so that there is a slight loss in the positive displacement of the gases at the end of the exhaust cycle movement and at the beginning of the intake cycle movement. In addition, the inlet and outlet end portions of the cylinders can be provided with small extensions to accommodate the axial outward movement of the inlet and outlet pistons. 
     It will be understood that since the inlet cam  338 ′ and outlet cam  350  are moved axially together, they need not be separated as shown. 
     In the embodiment shown in FIGS. 10-12, movement of the power operated cam moving assemblies  386  and  388  to achieve movement from the normal position shown in FIG. 4 into the other reduced compression ratio position is as follows. Basically, the pair of electric motor and gear reduction units  408  operating the cam moving assemblies  386  and  388  on each side of the engine  310  must be sequentially actuated. For this purpose, computer control is contemplated capable of automatically carrying out the sequence in response to an input signal such as a manually operated switch or a switch controlled by the main operating computer of the automobile or engine control unit in response to an operating event where a change in compression ratio is desirable. 
     The sequence required is to first actuate the electric motor and gear reduction unit  402  of the outer cam moving assembly  388  on each side of the engine  310  having the cam moving members  394  and  396  thereof in teeth engaging relation as shown in FIG.  11 . At the point after actuation when the flats of the teeth  398  are moving out of interengagement, the other electric motor and gear reduction unit  408  of the inner cam moving assembly  386  on each side of the engine is actuated so that a short period of simultaneous movement takes place as the sloping sides of the teeth  398  move past one another. At the end of this mutual movement, the teeth  398  that are associated with the outer cam moving assemblies  388  having the initially actuated units  408  are in meshing relation, as shown in FIG. 12, and the initial motor units  408  are switched off. The two other motor units  408  are allowed to continue their movement until the associated teeth  398  move into full abutting relation, as shown in FIG. 11, after which the other motor units  408  are switched off. It will be understood that rather having a short period of mutual movement, the entire movement of the initial motor unit  408  could be completed before the movement of the second motor units begin. 
     While the provision of two sets of inner and outer power operated cam moving assemblies  386  and  388 , one set on each side of the engine, is preferred as described above, it is possible to achieve compression ratio orientation in accordance with the principles of the present invention by utilizing only one set of inner and outer power operated cam moving assemblies  386  and  388 . 
     FIG. 14 shows a variation of the construction shown in FIGS. 10-13 wherein during the axially outward movement of the pairs of first and second inlet and outlet cams sufficient relative angular movement is imparted between each pair to bring each pair of first and second inlet and outlet pistons back together for the transfer cycle movement. The angular movement changes the phase between the two pairs of inlet and outlet cams and introduces some dynamic imbalance but substantial dynamic balance is maintained because the change in angular movement is slight. 
     FIG. 14 illustrates a simple structure change capable of achieving the added angular movement. As shown, the spline connection between the shaft  378  and each of the first and second inlet cams  338  and  338 ′ is changed from a conventional spline connection to one having helical shaft splines  412  engaged within conforming helical cam grooves  414 . 
     To accommodate the added angular movements, the electric motor and reduction gear units  408  are chosen to be variable speed units and the computer control is programmed to angularly move the movable cam members  394  whenever axial and angular movement is taking place with the cam members  394  and  396  in teeth meshing relation. 
     The disclosure of any patent or patent application identified by number heretofore is hereby incorporated by reference into the present specification.