Patent Publication Number: US-9903270-B2

Title: Cylinder arrangement for opposed piston engine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/031,935, filed on Aug. 1, 2014. The entire disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to an opposed-piston engine and more particularly to an opposed-piston, two-stroke engine including off-set cylinders. 
     BACKGROUND 
     This section provides background information related to the present disclosure and is not necessarily prior art. 
     Opposed-piston, two-stroke engines include two pistons housed within a single cylinder that move in an opposed, reciprocal manner within the cylinder. In this regard, during one stage of operation, the pistons are moving away from one another within the cylinder. During another stage of operation, the pistons are moving towards one another within the cylinder. 
     As the pistons move towards one another within the cylinder, they compress and, thus, cause ignition of a fuel/air mixture disposed within the cylinder. In so doing, the pistons are forced apart from one another, thereby exposing inlet ports and outlet ports formed in the cylinder. Exposing the inlet ports draws air into the cylinder and expels exhaust, thereby allowing the process to begin anew. 
     When the pistons are forced apart from one another, connecting rods respectively associated with each piston transfer the linear motion of the pistons relative to and within the cylinder to one or more crankshafts associated with the connecting rods. The forces imparted on the crankshafts cause rotation of the crankshafts which, in turn, cause rotation of wheels of a vehicle in which the engine is installed. 
     Generally speaking, opposed-piston, two-stroke engines used in a vehicle include a bank of cylinders with each cylinder having a pair of pistons slidably disposed therein. While the engine may include any number of cylinders, the particular number of cylinders included is generally dictated by the type and/or required output of the vehicle. For example, in an automobile, fewer cylinders may be required when compared to a military vehicle such as a tank to properly propel and provide adequate power to the vehicle. Accordingly, an automobile may include an engine having four (4) cylinders and eight (8) pistons while a tank may include six (6) cylinders and twelve (12) pistons. 
     While conventional opposed-piston, two-stroke engines used in vehicles provide adequate power to the particular vehicle, such engines are often difficult to package within an engine compartment of the vehicle. Namely, the cylinders of conventional opposed-piston, two-cylinder engines are typically disposed along a single, longitudinal axis that passes through a center of each cylinder. While this arrangement does not hinder operation of the engine, the overall length of the engine is difficult to package within an engine compartment. Accordingly, the number and size of the cylinders in an opposed-piston, two-stroke engine is often limited by available packaging space within an engine compartment. As a result, use of such engines in vehicle applications is not widespread. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     An opposed-piston, two-stroke engine is provided and includes a first cylinder having a first longitudinal axis and a first pair of pistons slidably disposed within the first cylinder and movable along the first longitudinal axis toward one another in a first mode of operation and away from one another along the first longitudinal axis in a second mode of operation. The engine additionally includes a second cylinder having a second longitudinal axis and a second pair of pistons slidably disposed within the second cylinder and movable along the second longitudinal axis toward one another in the first mode of operation and away from one another along the second longitudinal axis in the second mode of operation. A crankshaft is connected to at least one of the first pair of pistons and at least one of the second pair of pistons and has an axis of rotation. The axis of rotation is disposed between and is substantially perpendicular to the first longitudinal axis and the second longitudinal axis. 
     In another configuration, an opposed-piston, two-stroke engine is provided and includes a first cylinder having a first longitudinal axis and a first pair of pistons slidably disposed within the first cylinder and movable along the first longitudinal axis toward one another in a first mode of operation and away from one another along the first longitudinal axis in a second mode of operation. The engine additionally includes a second cylinder having a second longitudinal axis and a second pair of pistons slidably disposed within the second cylinder and movable along the second longitudinal axis toward one another in the first mode of operation and away from one another along the second longitudinal axis in the second mode of operation. The engine also includes a third cylinder having a third longitudinal axis and a third pair of pistons slidably disposed within the third cylinder and movable along the third longitudinal axis toward one another in the first mode of operation and away from one another along the third longitudinal axis in the second mode of operation. A crankshaft is connected to at least one of the first pair of pistons, at least one of the second pair of pistons, and at least one of the third pair of pistons and has an axis of rotation. The first longitudinal axis, the second longitudinal axis, and the third longitudinal axis extend substantially perpendicular to the axis of rotation with the first longitudinal axis and the third longitudinal axis being disposed on an opposite side of the axis of rotation than the second longitudinal axis. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a perspective view of an opposed-piston, two-stroke engine in accordance with the principles of the present disclosure; 
         FIG. 2  is a side view of the opposed-piston, two-stroke engine of  FIG. 1  showing an arrangement of cylinders of the engine; 
         FIG. 3  is a partial exploded view of the opposed-piston, two-stroke engine of  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of the opposed-piston, two-stroke engine of  FIG. 1  taken along line  4 - 4  of  FIG. 2 ; 
         FIG. 5  is a cross-sectional view of the opposed-piston, two-stroke engine of  FIG. 1  taken along line  5 - 5  of  FIG. 2 ; 
         FIG. 6  is a schematic representation of a cylinder layout of the opposed-piston, two-stroke engine of  FIG. 1 ; and 
         FIG. 7  is a schematic representation of another cylinder layout of the opposed-piston, two-stroke engine of  FIG. 1 . 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     With reference to the figures, an opposed-piston, two-stroke engine  10  is provided and includes an engine block  12  having a series of cylinders  14 . Each cylinder  14  includes a pair of pistons  16  slidably disposed therein and selectively movable toward one another ( FIG. 4 ) and away from one another ( FIG. 5 ). Movement of the pistons  16  relative to and within the cylinders  14  drives a pair of crankshafts  18  which, in turn, drive a gear train  20 . The gear train  20  may be connected to driven wheels of a vehicle (neither shown), for example, whereby the crankshafts  18  and the gear train  20  cooperate to transform the linear motion of the pistons  16  relative to and within the cylinders  14  into rotational motion to allow the motion of the pistons  16  to rotate the driven wheels and propel the vehicle. 
     The cylinders  14  are housed within the block  12  and each includes a longitudinal axis  22  ( FIGS. 4-7 ) that extends substantially perpendicular to a rotational axis  24  of each crankshaft  18 . As shown in  FIGS. 2 and 6 , the cylinders  14  are offset from one another such that some of the cylinders  14  are disposed between a pair of adjacent cylinders but are offset from one another. Namely, the cylinders  14  include six cylinders  14   a ,  14   b ,  14   c ,  14   d ,  14   e ,  14   f  in the example provided. The cylinders  14   a ,  14   b ,  14   c  are all disposed on an opposite side of the rotational axis  24  of the crankshafts  18  than the cylinders  14   d ,  14   e ,  14   f . Further, the cylinder  14   d  is disposed between the cylinders  14   a ,  14   b  and the cylinder  14   e  is disposed between the cylinders  14   b ,  14   c  in a direction (L 0 ) extending substantially parallel to the rotational axis  24  of the crankshafts  18 . Accordingly, the configuration of the cylinders  14   a - 14   f  shown in  FIG. 6  creates a so-called “nested” arrangement of the cylinders  14   a - 14   f , which allows the cylinders  14   a - 14   f  to be packaged in a smaller engine block  12  than if each of the centers of the cylinders  14   a - 14   c —coaxially aligned with the longitudinal axes  22  of each cylinder  14 —were aligned with one another in the direction (L 0 ). 
     As shown in  FIG. 6 , the longitudinal axes  22  of the cylinders  14   a ,  14   b ,  14   c  are aligned with one another such that a plane  26  extending through each axes  22  is substantially parallel to each axes  22  and is substantially parallel to the rotational axes  24  of the crankshafts  18 . Similarly, a plane  28  intersecting the longitudinal axes  22  of the cylinders  14   d ,  14   e ,  14   f  is substantially parallel to the longitudinal axes  22  of the cylinders  14   d ,  14   e ,  14   f  and is substantially parallel to the rotational axes  24  of the crankshafts  18 . As shown in  FIG. 6 , the plane  26  is substantially parallel to and is offset from the plane  28 , as the plane  26  is disposed on an opposite side of the rotational axes  24  of the crankshafts  18  than the plane  28 . 
     In one configuration, the crankshafts  18  are arranged on a plane  30  ( FIG. 6 ) that is centered between the planes  26 ,  28 . Accordingly, the crankshafts  18  extend between the cylinders  14   a ,  14   b ,  14   c  and the cylinders  14   d ,  14   e ,  14   f . In the example shown in  FIG. 6 , the opposed-piston, two-stroke engine  10  includes six (6) cylinders  14  and, thus, twelve (12) pistons  16 . Because the cylinders  14   a - 14   f  are arranged in a nested configuration, half of the cylinders  14   a ,  14   b ,  14   c  are disposed on an opposite side of the plane  30  and, thus, the rotational axes  24  of the crankshafts  18  from the other half of the cylinders  14   d ,  14   e ,  14   f.    
     The nested arrangement of the cylinders  14   a - 14   f  allows some of the cylinders  14   a - 14   f  to be disposed between adjacent cylinders  14   a - 14   f  in the direction (L 0 ) extending substantially parallel to the rotational axis  24  of the crankshafts  18 . For example, the cylinder  14   d  associated with the plane  28  is disposed between the cylinders  14   a ,  14   b  associated with the plane  26  in a direction extending substantially parallel to the planes  26 ,  28 . Accordingly, a plane  32  extending through the axis  22  of each cylinder  14   a - 14   f  and in a direction substantially perpendicular to the planes  26 ,  28  of each cylinder  14   a - 14   f  does not intersect another cylinder  14   a - 14   f . For example, the cylinder  14   d  disposed between the cylinders  14   a ,  14   b , described above, includes a plane  32  extending through the longitudinal axis  22  of the cylinder  14   d  and in a direction substantially perpendicular to the planes  26 ,  28 ,  30 , but does not intersect either of the cylinders  14   a ,  14   b . Rather, and as shown in  FIG. 6 , the plane  32  of the cylinder  14   d  extends between the planes  32  of the cylinders  14   a ,  14   b . In one configuration, the plane  32  extends between the cylinders  14   a ,  14   b  such that the plane  32  is equidistant from the longitudinal axes  22  of each cylinder  14   a ,  14   b.    
     While the opposed-piston, two-stroke engine  10  is described and shown as including cylinders  14  that have a nested configuration, as shown in  FIG. 6 , such that the planes  32  of each cylinder  14   a - 14   f  are offset in a direction (L 0 ) substantially parallel to the rotation axis  24  of the crankshafts  18 , the cylinders  14  could alternatively be positioned such that some of the planes  32  of adjacent cylinders  14  are aligned. 
     As shown in  FIG. 7 , the plane  32  that extends through the longitudinal axis  22  of the cylinders  14  and substantially perpendicular to the planes  26 ,  28  intersects an adjacent cylinder  14 . For example, the plane  32  of the cylinder  14   d  intersects the cylinder  14   a  at the plane  32  of the cylinder  14   a . Accordingly, the cylinders  14   a ,  14   d  are aligned with one another, as the planes  32  of the cylinders  14   a ,  14   d  are parallel to one another and intersect one another. The remaining cylinders  14   b ,  14   c ,  14   e ,  14   f  are likewise aligned with one another, whereby the planes  32  of the cylinders  14   b ,  14   e  are aligned and the planes  32  of the cylinders  14   c ,  14   f  are aligned. While the opposed-piston, two-stroke engine  10  can have the cylinder arrangement shown in  FIG. 6  or the cylinder arrangement shown in  FIG. 7 , the engine  10  will be described and shown as including the cylinder arrangement shown in  FIG. 6 . 
     The cylinders  14  each include a series of inlet ports  34  extending radially around and through an outer wall of the cylinders  14  and a series of outlet or exhaust ports  36  that similarly extend radially around and through the outer wall of each cylinder  14 . The inlet ports  34  and the exhaust ports  36  are formed through the outer wall of the cylinders  14  to permit fluid communication through the wall of the cylinders  14  and into an interior of each cylinder  14 . 
     The inlet ports  34  are in fluid communication with an intake manifold  38 . The intake manifold  38  includes a pair of intake ports  40  that draw air into a body  42  of the intake manifold  38  which, in turn, communicates the air drawn into the intake ports  40  into each cylinder  14  via the inlet ports  34 . 
     In one configuration, the body  42  includes a series of apertures  44  that are in fluid communication with the inlet ports  34  of the respective cylinders  14 . The apertures  44  surround the cylinders  14  and are positioned along the longitudinal axis  22  of each cylinder  14  such that the apertures  44  oppose the inlet ports  34 . In this way, air received by the body  42  from the intake ports  40  may be communicated to the cylinders  14  via the interface of the apertures  44  and the inlet ports  34  of each cylinder  14 . As shown in  FIGS. 1 and 3 , the body  42  extends in a direction substantially perpendicular to the longitudinal axis  22  of each cylinder  14  and is in fluid communication with each of the cylinders  14  at the inlet ports  34 . Accordingly, the intake manifold  38  provides air to each of the cylinders  14  without requiring an individual intake manifold for each cylinder  14 . 
     In one configuration, the intake ports  40  receive a pressurized or charged stream of air from a supercharger (not shown). The supercharger directs pressurized air to the intake ports  40  of the intake manifold  38  to provide pressurized air to the cylinders  14  during operation of the opposed-piston, two-stroke engine  10 , as will be described in greater detail below. 
     The pistons  16  are slidably disposed within the cylinders  14  and each includes a piston head  46  and a connecting rod  48 . Once assembled, the piston heads  46  are slidably received within the cylinders  14  and are connected to a respective crankshaft  18  via a connecting rod  48 . For example, and as shown in  FIGS. 4 and 5 , each cylinder  14  includes a pair of piston heads  46  and a pair of connecting rods  48 . The piston heads  46  are slidably disposed within the cylinders  14  such that a distal end  50  of each piston head  46  opposes one another within the cylinder  14 . The connecting rods  48  extend between the piston heads  46  and a respective crankshaft  18  and are rotatably attached to the piston heads  46  at a first end and are rotatably attached to the crankshafts  18  at a second end. 
     As described above, the crankshafts  18  may be disposed between the cylinders  14 . For example, the crankshafts  18  may be disposed between a first bank of cylinders  14   a ,  14   b ,  14   c  and a second bank of cylinders  14   d ,  14   e ,  14   f , as shown in  FIG. 6 . If the opposed-piston, two-stroke engine  10  includes the cylinder arrangement shown in  FIG. 6 , a single crankshaft  18  may be located at each end of the cylinders  14 . As shown in  FIG. 5 , for example, the crankshafts  18  are shown as being connected to each piston head  46  via individual connecting rods  48  along the length of the crankshafts  18 . 
     The crankshafts  18  may be coupled to each piston head  46  by positioning the crankshaft  18  at a location between the first bank of cylinders  14   a ,  14   b ,  14   c  and the second bank of cylinders  14   d ,  14   e ,  14   f  and, further, by providing each connecting rod  48  with a clearance or recess  52 . The clearance or recess  52  allows the connecting rod  48  to extend past a distal end  54  of the cylinders  14  ( FIG. 5 ) without causing contact between the cylinders  14  and the connecting rods  48 . This allows the pivotable connection between the connecting rod  48  and the crankshaft  18  to be made at a location above or below the longitudinal axis  22  of each cylinder  14 . This, in turn, allows the crankshafts  18  to be positioned above or below the longitudinal axis  22  of each cylinder  14 , thereby allowing the crankshafts  18  to be attached to each piston head  46  along a length of one side of the engine  10 , as shown in  FIG. 2 . In short, the rotational axis  24  of the crankshafts  18  is offset from the effective center of each cylinder  14  (i.e., is offset from the central, longitudinal axis  22  of each cylinder  14 ). 
     The crankshafts  18  are positioned on opposite sides of the opposed-piston, two-stroke engine  10 . Each crankshaft  18  is rotatably attached to and is driven by the piston heads  46  during operation of the engine  10 . As shown in  FIG. 2 , each crankshaft  18  includes a series of attachment locations  56  that attach the connecting rods  48  to the crankshafts  18  along a length of the crankshafts  18 . As shown in  FIG. 2 , the attachment locations  56  may be aligned with the rotational axis  24  or, alternatively, may be offset from the rotational axis  24  of the crankshafts  18 . Offsetting some of the attachment locations  56  of the crankshafts  18  from the rotational axis  24  of the crankshafts  18  allows the piston heads  46  to be in different locations within each cylinder  14  at any given time. For example, the piston heads  46  shown in  FIG. 4  are positioned within their respective cylinder  14  such that the distal ends  50  of the opposed piston heads  46  are virtually in contact with one another while the distal ends  50  of the piston heads  46  shown in  FIG. 5  are spaced apart from one another within their respective cylinder  14  at the same time. The piston heads  46  are permitted to be in the position shown in  FIGS. 4 and 5  at the same time due to the offset of the attachment locations  56  of the connecting rods  48  to the crankshafts  18 . 
     With particular reference to  FIGS. 1, 4, and 5 , operation of the opposed-piston, two-stroke engine  10  will be described in detail. During operation, the piston heads  46  may move toward one another ( FIG. 4 ) and away from one another ( FIG. 5 ) within each cylinder  14 . When the piston heads  46  are sufficiently moved away from one another, the distal ends  50  of the piston heads  46  expose the inlet ports  34  and the exhaust ports  36  of the cylinder  14 . 
     When the inlet ports  34  are exposed, pressurized air is received by the cylinders  14  via the inlet ports  34  due to the pressurized air supplied to the intake manifold  38  by the supercharger. The pressurized air flows into the cylinder  14  at the inlet ports  34  and, in so doing, forces exhaust gas disposed within the cylinder  14  out of the cylinders  14  via the exhaust ports  36 . The exhaust gas exits the exhaust ports  36  and enters an exhaust manifold  58 . As with the intake manifold  38 , the exhaust manifold  58  surrounds each cylinder  14  and is in fluid communication with the cylinders  14  via the exhaust ports  36 . Therefore, when the pressurized air enters the cylinders  14  at the inlet ports  34 , the pressurized air causes the exhaust gas disposed within the cylinders  14  to exit the cylinders  14  and enter the exhaust manifold  58  via the exhaust ports  36 . 
     When one of the cylinders  14  is in a position such that the inlet ports  34  and the exhaust ports  36  are exposed, one or more of the other piston heads  46  are in a position whereby the distal ends  50  are in close proximity to one another. Air disposed within these cylinders  14  is compressed due to movement of the piston heads  46  towards one another. 
     One or more fuel injectors  60  may be located along a length of each cylinder  14  at an area between each piston head  46  when the piston heads  46  are moved toward one another. Fuel may be injected into the cylinders  14  by the fuel injectors  60  at a location proximate to the distal end  50  of each piston head  46  such that when the air disposed within the cylinder  14  is compressed between the distal ends  50  of each piston head  46 , fuel is mixed with the compressed air, thereby causing combustion. 
     When the fuel/air mixture combusts, a force is generated, thereby causing the piston heads  46  to move away from one another along the longitudinal axis  22  of the cylinder  14 . In so doing, an axial force is applied to the respective connecting rods  48  of the piston heads  46  which, in turn, causes the particular crankshaft  18  to rotate. Rotation of the crankshaft  18  likewise causes movement of the other piston heads  46  attached to the crankshaft  18  due to the offset position of the attachment locations  56  of each connecting rod  48  to the crankshaft  18 . Further, rotation of the crankshaft  18  likewise causes a rotational force to be applied to the gear train  20  which, in turn, causes a rotational force to be applied to driven wheels of a vehicle, for example. 
     When the distal ends  50  of each piston head  46  move apart from one another and the piston heads  46  sufficiently move along the longitudinal axis  22  in a direction away from one another, the inlet ports  34  and the exhaust ports  36  of the cylinder  14  are once again exposed and the cycle begins anew. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.