Patent Publication Number: US-11028800-B1

Title: Engine coolant system and method

Description:
FIELD 
     Embodiments relate to engines. Other embodiments relate to coolant systems for engines. 
     BACKGROUND 
     During engine operation, cylinder combustion generates a large amount of heat. To reduce thermal damage to engine components and improve engine performance efficiency, engine components are cooled via a coolant system. Therein, liquid coolant is pumped and circulated around heat-generating engine components via cooling jackets connected to the coolant system via specialized coolant flow passages. Heated coolant is cooled upon passage through a radiator, where heat is lost to ambient air. Additionally, heated coolant may be circulated through engine components requiring heat, such as a heater core. A thermostat may be included to control coolant flow based on temperature. 
     Due to the relative position of engine components, however, adequate cooling may not be achieved. For example, components closer to the coolant system pump and the thermostat may receive a greater amount of coolant flow as compared to other components further away. As another example, the increased coolant flow may facilitate in improving heat rejection to coolant and cooling required for engine components to achieve improved performance, efficiency, and reliability. In addition, due to the configuration of the coolant system as well as the packaging constraints of the vehicle under-hood area, coolant may flow uni-directionally through components in a specified order. This makes it difficult to direct more coolant flow to some components while reducing coolant flow to other components. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Methods and systems are provided for improving the efficiency of cylinder head cooling and for enabling regulated coolant flow control. In one embodiment, an engine coolant system comprises a plurality of cooling passages coupled to corresponding cylinder heads of an engine block. 
     In one embodiment, a coolant system for a locomotive engine or other vehicle engine or other engine may have a plurality of coolant subunits, each subunit coupled to one cylinder of the engine. Each subunit may include a central cylinder liner jacket that surrounds the cylinder liner of the corresponding cylinder like a sleeve. A central axis of the liner jacket is coaxial with a central axis of the corresponding cylinder. A cylinder head feed line directs coolant from a first opening coupled to an outer surface of the liner jacket to a cylinder head lower coolant jacket. A cylinder liner feedline receives coolant at a second opening coupled to the outer surface of the liner jacket from a first port of a crankcase coolant feed gallery. The crankcase feed gallery is positioned coplanar to a lower surface of the liner jacket, and abuts the liner jacket on one side of the central axis. Coolant is concurrently directed from the crankcase coolant feed gallery to the cylinder head lower coolant jacket which is configured as a ring positioned above and concentric with the cylinder liner jacket. After flowing through the lower coolant jacket, a first portion of coolant is directed to an upper coolant jacket positioned above the lower coolant jacket via a first outlet while a second, remaining portion of coolant is directed to an exhaust port cooling jacket via a second outlet. The upper coolant jacket includes a central cylindrical piece that is concentric with the lower coolant jacket and cylinder liner jacket, the upper coolant jacket further including a projection extending from the central cylindrical piece towards the crankcase feed gallery on the one side of the central axis of the liner jacket. The exhaust port cooling jacket extends outwards from the central axis of the liner jacket and abuts a drilling coupling the upper coolant jacket to the lower coolant jacket. Coolant circulated through the exhaust cooling port is returned to the cylinder head upper coolant jacket. The combined coolant flow then returns via a return feed line extending from the projection on the upper coolant jacket to a crankcase coolant return gallery positioned below the crankcase coolant feed gallery in a crankcase. In this manner, coolant is concurrently circulated to a cylinder liner and a lower portion of a cylinder head of a cylinder to improve cooling efficiency. Coolant from the lower portion is then divided between an exhaust cooling port and an upper portion of the cylinder head to enable regulated cylinder head cooling. Finally, the coolant flow is merged before being returned to a return gallery in the crankcase which is common to all cylinders, thereby allowing for easier packaging of the cooling system components 
     It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTIONS OF FIGURES 
       The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below: 
         FIG. 1  shows a cross sectional view of an example engine block and coolant passages passing there-through. 
         FIG. 2  shows an example embodiment of a coolant system circuit and the circulation of coolant through various locations of an engine block. 
         FIG. 3  shows a block diagram representation of the coolant system circuit of  FIG. 2 . 
         FIG. 4  shows a perspective view of the coolant system of  FIG. 2 . 
         FIG. 5  shows a top view of the coolant system. 
         FIG. 6  shows a bottom view of the coolant system. 
         FIG. 7  shows a front view of the coolant system. 
         FIG. 8  shows a back view of the coolant system. 
         FIG. 9  shows an isometric view of the coolant system when viewed from the left side. 
         FIG. 10  shows an isometric view of the coolant system when viewed from the right side. 
         FIG. 11  shows a high level flow chart of an example method of circulating coolant through a cylinder head and an engine block via the coolant system of  FIGS. 4-10 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a cross sectional view  100  of an example engine block  10  of an engine (e.g., a locomotive engine, or other vehicle engine, or other engine, such as for a stationary generator) and coolant passages passing through the components of the engine block  10 . The engine block  10  may include a plurality of cylinder bores  124  (also referred herein as cylinder  124 ) suitably formed therein. A cylinder head  118  may be positioned atop each cylinder bore  124  and may abut upper surface of the walls around the cylinder bore  124 . Gaskets (including a head gasket) and spacers may be used to position the cylinder head  118  above each cylinder bore  124 . In this example, four cylinder bores  124  along with four corresponding cylinder heads  118  are shown. Each cylinder bore  124  along with the corresponding cylinder head  118  may enclose a combustion chamber  112 . 
     Each combustion chamber  112  may be coupled to an intake port  24  and an exhaust port  26 . During combustion, fuel and air mixture may be introduced from an intake manifold  122  to the combustion chamber  112  via the intake port  24 . An intake valve  28  may open during the intake stroke to admit a desired amount of the air fuel mixture. The cylinder head  118  of each cylinder may include a injector which will provide diesel fuel in to the combustion chamber  112  to initiate combustion. After combustion, residual gas mixture (exhaust) may be routed from the combustion chamber to the exhaust manifold  120  via the exhaust port  26 . During the exhaust stroke, an exhaust valve  30  may open facilitating removal of exhaust gas from the combustion chamber  112  to the exhaust manifold  120 . Each cylinder  124  may include a separate intake port  24  and an exhaust port  26  while sharing a common intake manifold  122  and an exhaust manifold  120 . 
     A cylinder liner  116  may be concentrically disposed in the cylinder bore  124  encasing the combustion chamber  112 . By reinforcing the cylinder bore  124  with a cylinder liner, the inner wall of the cylinder bore  124  may be protected from wear caused by prolonged sliding contact with a moving piston. The liner typically includes a flange that enables the liner to rest on an engine block. The cylinder liner is then held over the cylinder bore using vertical support via the flange. In one example, the cylinder liner  116  may have a constant diameter around the cylinder bore  124 . In another example (as seen here), diameter of the cylinder liner  116  may change between the cylinder head  118  and the crankcase  142 . The cylinder liner  116  may have a first diameter closer to the cylinder head  118  and a second diameter closer to the crankcase  142 , the first diameter larger than the second diameter. 
     A piston  115  may be positioned within the combustion chamber  112  with a wrist pin coupling the piston  115  to a connecting rod  134  which has its lower end attached to the engine&#39;s crankshaft via a crankpin  136 . The crankshaft may be enclosed in a crankcase  142 . Each cylinder bore  124  may have a corresponding crankcase  142  while each of the crankcases in the engine block  10  may be enclosed in a crankcase housing  140 . 
     The coolant system may include each of a crankcase coolant feed gallery  160  positioned within the crankcase housing  140  and below each of the cylinder bores  124  and a crankcase coolant return galley  162  positioned within the crankcase housing  140  and directly below the crankcase coolant feed gallery  160 . 
     The crankcase coolant feed gallery  160  may be fluidically coupled to a central cylinder liner jacket  42  enclosing a corresponding cylinder liner  116  for each cylinder  124 . The crankcase coolant feed gallery  160  may enclose the central cylinder liner jacket  42  like a sleeve. In this example, there may be four central cylinder liner jackets  42  corresponding to the four cylinders  124 . The cylinder bore  124 , the cylinder liner  116 , and the cylinder liner jacket  42  may be coaxial with a central axis. The cylinder liner jacket  42  may be fluidically coupled to a lower coolant jacket  44  surrounding a lower surface of the cylinder head  118  and placed directly above the cylinder bore  124 . The crankcase coolant feed gallery  160  may also be directly coupled to the lower coolant jacket  44 . The lower coolant jacket may be coupled to an upper coolant jacket  46  surrounding an upper surface of the cylinder head  118 , the lower coolant jacket  44  coaxial with the upper coolant jacket  46 . Further, a coolant line may couple the lower coolant jacket  44  to an exhaust port cooling jacket  48  surrounding the exhaust port  26 . The exhaust port cooling jacket  48  may be coupled between the upper coolant jacket  46  and the lower coolant jacket  44 , and offset to one side of the central axis. The exhaust port cooling jacket  48  may be fluidically coupled to the upper coolant jacket  46  which in turn may be fluidically coupled to crankcase coolant return galley  162 . As discussed in details with relation to  FIG. 2 , coolant may flow from the crankcase coolant feed gallery  160  to the crankcase coolant return galley  162  via each of the central cylinder liner jacket  42 , the lower feed gallery  44 , the upper feed galley  46 , and the exhaust feed gallery  48 , thereby cooling each of engine cylinder liner  116 , the cylinder head  118 , and the exhaust port  26  for each cylinder in the cylinder block  10 . 
       FIG. 2  is a block diagram  200  of an example coolant system  202  showing circulation of coolant through various locations of an engine block. Direction of coolant flow though the plurality of coolant lines in the coolant system  220  is shown by arrows. Components of the coolant system  220  previously introduced in  FIG. 1  are numbered similarly and not reintroduced. In this example, a single combustion chamber  112  (within a cylinder liner in a cylinder bore) is shown along with a corresponding cylinder head  118 . Intake port  24  and exhaust port  26  may be coupled to the combustion chamber  112 . A crankcase housing  140  may encase the crankcases corresponding to each of the cylinders, the crankcase housing  140  enclosing each of the crankcase coolant feed gallery  160  and the crankcase coolant return gallery  162 . 
     The coolant system includes a sump  208  such as reservoir wherein the coolant may be stored prior to being circulated via the engine components. After circulation through the engine components the coolant may return to a radiator  210  which may be in fluidic communication with the atmosphere and heat accumulated by the coolant while flowing through the engine components may be dissipated to the atmosphere (at the radiator). 
     Once the temperature of coolant in the radiator  210  reduces to below a threshold temperature, the coolant may flow from the radiator  210  to the sump  208  via a coolant supply line  205 . As an example, the threshold coolant temperature may correspond to a temperature at which heat may be adsorbed from the metal engine components. The threshold coolant temperature may be pre-calibrated based on the coefficient of specific heat of the coolant and the metal used to form the engine block. In one example, a valve may be positioned in the coolant supply line  205  to facilitate return of the coolant to the sump  208  after cooling. 
     Coolant from the sump  208  may flow to the crankcase coolant feed gallery  160  via a first coolant line  209 . During engine operation, pump  212  may be activated by the controller to flow coolant from the sump  208  to the crankcase coolant feed gallery  160 . Coolant may flow out of the feed gallery  160  via a main coolant feed line  234 . The main coolant feed line  124  may bifurcate into a first coolant feed line  236  supplying a first portion of coolant from the feed galley  160  to a cylinder liner coolant jacket  42  and a second coolant feed line  238  supplying a second portion of coolant from the feed gallery  160  to a lower coolant jacket  44 . In one example, each of the first coolant feed line  236  and the second coolant feed line  238  may originate from the feed gallery  160 . 
     As an example, a pump may be coupled to the coolant feed gallery  160  to pump coolant from the feed gallery  160  to each of the cylinder liner coolant jacket  42  and the lower coolant jacket  44 . A proportioning valve may be coupled to the main coolant feed line  234 , downstream of the feed gallery  160 , for varying a ratio for coolant flow directed to the cylinder liner coolant jacket  42  relative to the lower coolant jacket  44 . The ratio may be based on a temperature of the cylinder liner relative to the temperature of the cylinder head. 
     After flowing through the cylinder liner coolant jacket  42 , the coolant may flow to the lower coolant jacket  44  via a third coolant feed line  239 . In this way, coolant may flow to the lower coolant jacket  44  via two inlets, a first one from the cylinder liner coolant jacket  42  while a second one directly from the feed gallery  160 . The lower coolant jacket  44  may also have two outlets, a first outlet  240  directing a first portion of coolant from the lower coolant jacket  44  to an exhaust port cooling jacket while a second outlet  241  directing a second portion of coolant from the lower coolant jacket  44  to an upper coolant jacket  46 . 
     After flowing through the exhaust port cooling jacket  48 , the coolant may be routed to the upper coolant jacket  46  via a fourth coolant feed line  242 . In this way, the entire volume of coolant flowing through each of the cylinder liner coolant jacket  42 , the lower coolant jacket, and the exhaust port cooling jacket  48  may be routed to the upper coolant jacket  46 . From the upper coolant jacket  46 , the entire volume of coolant may return to the crankcase coolant return gallery  162  gallery via main coolant return line  244 . Since the coolant returns to the crankcase coolant return gallery  162  after absorbing thermal energy from the aforementioned engine components, the temperature of coolant at the crankcase coolant return gallery  162  may be higher than the temperature of coolant at the crankcase coolant feed gallery  160 . In order to cool the coolant prior to recirculating the coolant to the sump  208 , the coolant may be routed from the crankcase coolant return gallery  162  to the radiator  210 . As described previously, at the radiator  210 , in contact with ambient air, heat from the coolant may dissipate to the atmosphere. 
       FIG. 3  shows a block diagram  300  representation of a circuit  301  of the coolant system circuit of  FIG. 2 . Components of the coolant system previously introduced in previous figures are numbered similarly and not reintroduced. 
     In this example, engine block  302  may include six individual cylinder blocks  312 ,  314 ,  316 ,  318 ,  320 , and  322  with each cylinder block including a cylinder bore, a cylinder liner outlining the bore and a cylinder liner coolant jacket. Each cylinder block may be coupled to a corresponding cylinder head. In this example, six cylinder heads  313 ,  315 ,  317 ,  319 ,  321 , and  323  are shown with each cylinder head including a lower cooling jacket, an upper cooling jacket, and an exhaust port cooling jacket. 
     The coolant system circuit  301  may include a coolant reservoir  304  wherein coolant may be stored prior to circulation through the engine block  302 . In one example, coolant reservoir  304  may be the sump  208  in  FIG. 2 . During engine operation, coolant from the reservoir  304  may flow to a feed gallery  160 , positioned in a crankcase housing, via a coolant line  209 . From the feed gallery  160 , coolant may simultaneously flow to each of the cylinder blocks  312 ,  314 ,  316 ,  318 ,  320 , and  322  via respective distinct first coolant feed lines  322 ,  324 ,  326 ,  328 ,  330 , and  332 . 
     In one example, a single pump downstream of the feed gallery may direct coolant from the feed gallery  160  to each of the cylinder blocks  312 ,  314 ,  316 ,  318 ,  320 , and  322  via each of the first coolant feed lines  322 ,  324 ,  326 ,  328 ,  330 , and  332 . A proportioning valve may be coupled downstream of the pump for varying a ratio for coolant flow directed to each of the first coolant feed lines  322 ,  324 ,  326 ,  328 ,  330 , and  332 . Alternatively, each of the first coolant feed lines  322 ,  324 ,  326 ,  328 ,  330 , and  332  may include valves which may be individually actuated based on the cooling needs of the corresponding cylinder block and cylinder head to vary an amount of coolant flowing through each of the first coolant feed lines  322 ,  324 ,  326 ,  328 ,  330 , and  332 . As an example, a higher amount of coolant may be directed to the cylinder with the highest temperature. Also, during conditions when a cylinder is deactivated, coolant may not be routed to that cylinder. 
     In another example, each of the coolant feed lines  322 ,  324 ,  326 ,  328 ,  330 , and  332  may include separate pumps facilitating concurrent flow of coolant from the feed gallery  160  to each of the cylinder blocks  312 ,  314 ,  316 ,  318 ,  320 , and  322 . From each of the cylinder blocks  312 ,  314 ,  316 ,  318 ,  320 , and  322 , the coolant may flow to their corresponding cylinder heads  313 ,  315 ,  317 ,  319 ,  321 , and  323  via respective distinct second coolant feed lines  333 ,  334 ,  336 ,  338 ,  340 , and  342 . After flowing through a lower cooling jacket, an upper cooling jacket, and an exhaust port cooling jacket housed in each of the cylinder heads  313 ,  315 ,  317 ,  319 ,  321 , and  323 , the coolant may return to a return galley  162  from each of the cylinder heads  313 ,  315 ,  317 ,  319 ,  321 , and  323  via a common coolant return line  344 . From the return galley  162 , the coolant may be routed back to the coolant reservoir  304  via a radiator and a second coolant line  346 . 
     In this way, a coolant system for an engine, may comprise: a coolant feed gallery  160  coupled inside an engine crankcase; a coolant return gallery  162  coupled inside the engine crankcase; a first cooling unit including a cylinder liner jacket surrounding a first cylinder, an upper coolant jacket and a lower coolant jacket surrounding a head of the first cylinder, and an exhaust port cooling jacket coupled to an exhaust port of the first cylinder; and a second cooling unit including another cylinder liner jacket surrounding a second cylinder, another upper coolant jacket and another lower coolant jacket surrounding a head of the second cylinder, and another exhaust port cooling jacket coupled to an exhaust port of the second cylinder, wherein each of the first and the second cooling unit is coupled to the coolant feed gallery and the coolant return gallery. 
       FIG. 4  shows a perspective view  400  of a portion  402  of the coolant system of  FIG. 2  coupled to a single cylinder in an engine block. In this example, the cylinder is not shown but the central axis of the cylinder system is marked by the axis A-A′. The cylinder may be radially symmetric around the A-A′ axis. Components of the coolant system previously introduced in are numbered similarly and not reintroduced. 
     A coolant feed gallery  160  may be positioned within a crankcase housing below the cylinder. A main coolant feed line may fluidically couple the feed gallery  160  to a sump (coolant reservoir) and coolant may flow to the feed gallery  160  via the main coolant feed line prior to being circulated through the engine components. The main coolant feed line may be coupled to side surface of the feed gallery  160 , the main coolant feed line parallel to the radius of the cylinder (in the direction perpendicular to the A-A′ axis). Components  432 ,  434 ,  437 ,  439 , and  433  provide core support and are added for casting manufacturability. 
     Directly below the coolant feed gallery  160 , a coolant return gallery  162  may be positioned within the crankcase housing. A main coolant return line (not shown) may fluidically couple the coolant return galley  162  to a radiator and warm coolant accumulated in the return gallery (after flowing through the engine components) may flow to the radiator. Each of the coolant feed gallery  160  and the coolant return gallery  162  may be aligned to a first side of the central A-A′ axis and the cylinder. The coolant system may include a single coolant feed gallery  160  coupled to coolant lines feeding coolant to different coolant system components corresponding to each cylinder. Similarly, coolant from each of the coolant system components coupled to each cylinder may return to a single coolant return gallery  162 . 
     In one example, each of the coolant feed gallery  160  and the coolant return gallery  162  may be shaped as elongated cuboids with the edges of the coolant feed gallery  160  being coplanar with the edges of the coolant return gallery  162 . 
     A cylinder liner jacket  42  may enclose the cylinder liner of the cylinder like a sleeve. The cylinder liner jacket  42  may include an outer cylindrical surface, an inner cylindrical surface, and a space defined between the inner and outer surface for circulating coolant, each of the inner and outer surface surrounding the cylinder. The cylinder liner jacket  42  may be fluidically coupled to the feed gallery  160  via a first coolant feed line (not shown) positioned between the feed galley  160  and a side of the cylinder liner jacket  42  facing the feed gallery  160  (on the first side of the cylinder). Also, the cylinder liner jacket  42  may be fluidically coupled to a lower coolant jacket  44  via a first coolant passage  412 . The first coolant passage  412  may originate from a conical protrusion  411  in the wall of the cylinder liner jacket  42 . 
     The coolant system may include each of a lower coolant jacket  44  surrounding a lower surface of a cylinder head placed over the cylinder and an upper coolant jacket  46  surrounding an upper surface of the cylinder head. The lower coolant jacket  44  may be positioned directly above the cylinder liner jacket  42  while the upper coolant jacket  46  may be positioned directly above the lower coolant jacket  44 , each of the cylinder liner jacket  42 , the lower coolant jacket  44 , and the upper coolant jacket  46  may be coaxial with the central axis A-A′. The lower coolant jacket  44  may be a circularly formed hollow pipe with coolant flowing there through. A plurality of plurality of cylindrical structures  442  adding core support may radially protrude from the lower coolant jacket  44 . Each cylindrical structure  442  may include a circular cap at the end (away from the lower coolant jacket  44 ). 
     The lower coolant jacket  44  may be fluidically coupled to each of the coolant feed gallery  160 , the upper coolant jacket  46 , and an exhaust port cooling jacket  48 . A first inlet of the lower coolant jacket may be coupled to the cylinder liner jacket  42  via the first coolant passage  412  positioned on a second side of the central axis (and the cylinder) while a second inlet of the lower coolant jacket may be coupled to the coolant feed gallery  160  via a second coolant passage  416  positioned on the first side of the central axis, opposite the second side. A first outlet of the lower coolant jacket may be coupled to the upper jacket  46  via a third coolant passage positioned on the first side of the central axis while a second outlet of the lower coolant jacket may be coupled to the exhaust port cooling jacket  48  via a fourth coolant passage positioned on the second side of the central axis. 
     The upper coolant jacket  46  includes a central circular structure with a plurality of cylindrical structures  446  radially protruding from the central circular structure. The upper cooling jacket may include a first projection  447  extending down and outwards from a top surface of the central circular structure towards a top surface of the lower coolant jacket on the first side of the central axis. The first projection  447  may extend into a coolant return passage  424  coupling the upper coolant jacket  46  with the coolant return gallery  162 . The coolant return passage  424  may be parallel to the second coolant passage  416  and the central axis. The upper coolant jacket  46  may further include a second projection  448  extending outwards from the top surface of the central circular structure towards a top surface of an exhaust cooling port cooling jacket  48  on the second side of the central axis. In this example, the first projection  447  may extend in a direction opposite to the second projection  448 , each of the first and second projections extending along a projection axis that is perpendicular to the central axis. 
     The cylinder head exhaust port cooling jacket  48  may be coupled between the upper and lower coolant jacket, and offset to the second side of the central axis. The exhaust port cooling jacket may be an elongated hollow structure through which coolant may flow. An inlet of the exhaust port cooling jacket  48  may be in fluidic communication with the second outlet of the lower coolant jacket  44  via the fourth coolant passage. The inlet of the exhaust port cooling jacket  48  may be positioned on a lower surface  488  of the exhaust port cooling jacket  48 , the lower surface  488  coplanar with the lower coolant jacket  44 . A cylinder venting hole  414  may be mounted atop of the coolant jacket in cylinder head. 
     In one example, coolant from the feed gallery  160  may simultaneously flow to the cylinder liner coolant jacket  42  and the lower cooling jacket  44  via a first coolant feed line (not shown) and the second coolant passage  416 , respectively. From the cylinder liner coolant jacket  42 , the coolant may flow to the lower coolant jacket  44  via the first coolant passage  412 . Then the coolant may be simultaneously routed from the lower coolant jacket  44  to the upper coolant jacket  46  and the exhaust port cooling jacket  48  via the third coolant passage and the fourth coolant passage respectively. From the exhaust port cooling jacket  48 , the coolant may also be routed to the upper coolant jacket  46  via the fifth coolant passage  436 . Finally, the coolant may flow from the upper coolant jacket  46  to the coolant return galley  162  via the coolant return passage  424 . In this way, the components of  FIGS. 1-4  enable a coolant system for a cylinder of an engine, comprises: a cylinder liner jacket encircling the cylinder and configures to circulate coolant around a liner of the cylinder, a central axis of the liner jacket coaxial with a central axis of the encircled cylinder, a coolant feed gallery positioned within a crankcase below the cylinder, a coolant return gallery positioned within the crankcase, below the coolant feed gallery, a cylinder head lower coolant jacket surrounding a lower surface of a cylinder head positioned over the cylinder, the lower coolant jacket positioned above and coaxial with the liner jacket and, a cylinder head upper coolant jacket surrounding an upper surface of the cylinder head, the upper coolant jacket positioned above the lower coolant jacket, the upper coolant jacket including a central piece that is coaxial with the liner jacket, and a cylinder head exhaust port cooling jacket coupled between the upper coolant jacket and the lower coolant jacket, and offset to one side of the central axis, wherein the lower coolant jacket is fluidically coupled to each of the coolant feed gallery, the upper coolant jacket, the cylinder liner jacket, and the exhaust port cooling jacket. 
       FIG. 5  shows a top view (from above a cylinder head)  500  of the coolant system of  FIG. 2  coupled to a single cylinder in an engine block. Components of the coolant system previously introduced in previous figures are numbered similarly and not reintroduced. 
     The upper coolant jacket  46  may include a central solid disc  548  and four circular cavities  546  arranged on a top surface of the upper coolant jacket  46 . The four circular cavities  546  may be symmetrically distributed around the central disc  548 . A plurality of cylindrical structures  446  structures  446  may radially protrude outward from the top surface of the upper coolant jacket  46 . Each of the cylindrical structures  446  may include a rod-like component with an end cap. 
     A first projection  447  may extend outwards from the top surface of the upper coolant jacket  46  to a coolant return passage  424  coupling the upper coolant jacket  46  with the coolant return gallery. A second projection  448  may extend outwards from the top surface of the upper coolant jacket  46  and may couple the upper coolant jacket  46  to outlet core support component  435  via a coolant passage  436 . A cylinder venting hole  414  may be positioned on the exhaust port cooling jacket  48 . 
     The upper coolant jacket  46  may be co-axial with the lower coolant jacket  44  and the cylinder liner coolant jacket  42 . The lower coolant jacket  44  may also include a plurality of cylindrical structures  442  radially protruding outward from the center of the lower coolant jacket  44 . The cylindrical structures  446  corresponding to the upper coolant jacket  46  may not overlap with the cylindrical structures  442  corresponding to the lower coolant jacket  44 . 
     The coolant feed galley  160  may be positioned on a first side of each of the upper coolant jacket  46 , the lower coolant jacket  44 , and the cylinder liner coolant jacket  42  while the exhaust port cooling jacket may be positioned on a second side of each of the upper coolant jacket  46 , the lower coolant jacket  44 , and the cylinder liner coolant jacket  42 , the second side diametrically opposite to the first side. The first coolant feed line  552  is shown coupling the feed gallery  160  to the cylinder liner coolant jacket  42  while the first coolant passage  412  is shown coupling the cylinder liner jacket  42  to the lower coolant jacket  44 . A main coolant feed line may supply coolant to the feed gallery  160 . Since the coolant return galley is housed directly under the feed gallery  160  and the shape and size of the coolant return galley and the coolant feed galley  160  are substantially equal, view of the return the coolant return gallery is obstructed. 
       FIG. 6  shows a bottom view (from below the cylinder)  600  of the coolant system of  FIG. 2  coupled to a single cylinder in an engine block. Components of the coolant system previously introduced in previous figures are numbered similarly and not reintroduced. 
     The co-axial components including the cylinder liner coolant jacket  42 , the lower coolant jacket  44 , and the upper coolant jacket are stacked over one another (in this order). Each of the cylinder liner coolant jacket  42 , the lower coolant jacket  44 , and the upper coolant jacket may be of a similar diameter. Since the cylinder liner coolant jacket  42  is completely hollow (enclosing a cylinder, not shown here), the lower coolant jacket  44  is visible though the cylinder liner coolant jacket  42 . The lower coolant jacket  44  may include a central disc  618  which may be directly under the central solid disc of the upper coolant jacket  46 . Four spokes  614  may connect the central disc  618  to a curved, circular boundary of the lower coolant jacket  44 . Two adjacent spokes  614  form a right angle. The spokes  614  do not overlap with the circular cavities  546  of the upper coolant jacket  46  and each circular cavity  546  is visible between two adjacent spokes  614 . Coolant flow through the spokes  614  intend to cool valve seats. 
     The coolant return galley  162  may be positioned on a first side of each of the upper coolant jacket  46 , the lower coolant jacket  44 , and the cylinder liner coolant jacket  42  while the exhaust port cooling jacket  48  may be positioned on a second side of each of the upper coolant jacket  46 , the lower coolant jacket  44 , and the cylinder liner coolant jacket  42 , the second side diametrically opposite to the first side. Since the coolant return galley  162  is housed directly below the feed gallery, view of the feed gallery is obstructed. The first coolant feed line  552  is shown coupling the feed gallery to the cylinder liner coolant jacket  42  and the first coolant passage  412  is shown coupling the cylinder liner jacket  42  to the lower coolant jacket  44 . The first coolant feed line  552  may be positioned diametrically opposite to the first coolant passage  412  with the first coolant feed line  552  being proximal to the return gallery  162  and the first coolant feed line  552  being proximal to the exhaust port cooling jacket  48 . 
       FIG. 7  shows a front side view  700  of the coolant system of  FIG. 2  coupled to a single cylinder in an engine block. Components of the coolant system previously introduced in previous figures are numbered similarly and not reintroduced. 
     A first surface (distal from the cylinder) of the feed galley  160  may be coplanar with a first surface of the return gallery  162  (distal from the cylinder) with the feed galley  160  positioned directly above the return gallery  162 . A main coolant return line may flow warm coolant accumulated in the return gallery (after flowing through the engine components) to the radiator. A main coolant feed line may be coupled to a second (side) surface of the feed galley  160  to flow coolant from the sump to the feed gallery  160  prior to being circulated through the engine components 
     The feed galley  160  may be positioned next to the cylinder liner jacket  42  on a first side of the cylinder liner jacket  42 . The lower coolant jacket  44  is placed immediately above the cylinder liner jacket  42  and the upper coolant jacket  46  may be positioned immediately above the lower coolant jacket  44 . The coolant passage  416  coupling the lower coolant jacket  44  to the coolant feed gallery  160  is seen to project out of a third surface of the feed galley  160  (proximal to the cylinder liner coolant jacket  42 ). Also, a coolant passage  412  is seen coupling the cylinder liner jacket  42  to the lower coolant jacket  44 . 
     A first projection  447  is seen originating from the central portion of the upper coolant jacket  46  and extending down and outwards to the coolant return passage  424  coupling the upper coolant jacket  46  with the coolant return gallery  162 . A second projection  448  is seen originating from the central portion of the upper coolant jacket  46  and extending outwards from the central portion of the upper coolant jacket  46 . The first projection  447  and the second projection  448  may be diametrically opposite to one another. The second projection  448  may be fluidically coupled, via a coolant passage  436 , to an outlet of the exhaust port cooling jacket  48  and the upper coolant jacket may receive coolant form the exhaust port cooling jacket  48  via the second projection  448 . A first set of cylindrical structures  446  may protrude from the upper coolant jacket  46  and a second set of cylindrical structures  442  may protrude from the lower coolant jacket  44 . 
     The exhaust port cooling jacket  48  may be positioned next to the upper coolant jacket  46  on a second side of the upper coolant jacket  46 . The feed galley  160  and the return galley  162  may be positioned on opposite sides of the cylinder. 
       FIG. 8  shows a back view  800  of the coolant system of  FIG. 2  coupled to a single cylinder in an engine block. Components of the coolant system previously introduced in previous figures are numbered similarly and not reintroduced. 
     A third surface (proximal to the cylinder) of the feed galley  160  may be coplanar with a third surface of the return gallery  162  (proximal to the cylinder) with the feed galley  160  positioned directly above the return gallery  162 . A coolant return passage  424  may be coupled to the third side of the return gallery  162  via which coolant may return to the return galley  162  after flowing through each of the cylinder liner coolant jacket  42 , the lower coolant gallery  44 , the upper coolant galley  46 , and the exhaust port cooling jacket  48 . 
     The cylinder liner coolant jacket  42  may partly obstruct the third surface of the feed galley  160 . A coolant passage  412  coupling the cylinder liner coolant jacket  42  to the lower coolant jacket  44  may originate from a conical protrusion  411  on the wall of the cylinder liner jacket  42  facing away from the feed gallery  160 . The lower coolant jacket  44  is placed immediately above the cylinder liner jacket  42  and the upper coolant jacket  46  may be positioned immediately above the lower coolant jacket  44 . A first set of cylindrical structures  446  is seen protruding from the upper coolant jacket  46  while a second set of cylindrical structures  442  is seen protruding from the lower coolant jacket  44 . The coolant passage  416  coupling the lower coolant jacket  44  to the coolant feed gallery  160  is seen behind the cylinder liner jacket  42 . 
     The exhaust port cooling jacket  48  may be shaped as a chair including a seat  48   a  and a back  48   b . The exhaust port may pass through the region between the seat  48   a  and the back  48   b . A rod-shaped drilling  472  is seen couple the upper coolant jacket  46  to the seat portion  48   a  of the exhaust port cooling jacket  48 . 
       FIG. 9  shows a right side view  900  and  FIG. 10  shows a left side view  1000  of the coolant system of  FIG. 2  coupled to a single cylinder in an engine block. Components of the coolant system previously introduced in previous figures are numbered similarly and not reintroduced. The central axis of the cylinder is shown by dashed line A-A′. 
     In each of the views, the coolant feed galley  160  is seen to be positioned immediately atop the coolant return gallery  162 . In the right side view, the right end faces of each of the coolant feed galley  160  and the coolant return gallery  162  are seen while in the left side view, the left end faces of each of the coolant feed galley  160  and the coolant return gallery  162  are visible. In the right side view, view of the return passage  424  is partially obstructed via a coolant passage  416  coupling the coolant feed gallery  160  to the lower coolant jacket  44  while in the left side view, view of the coolant passage  416  is obstructed by the return passage  424 . The return passage  424  and the coolant passage  416  may be parallel to each other and to the central axis A-A′. 
     While the coolant feed galley  160  and the return gallery  162  are positioned on a first side of the central axis A-A′, each of the cylinder liner coolant jacket  42 , the lower coolant jacket  44 , and the upper coolant jacket  46  may be symmetric around the central axis A-A′. The exhaust port cooling jacket  48  may be positioned on a second side of the central axis A-A′, opposite to the first side. 
     A coolant passage  412  coupling the cylinder liner coolant jacket  42  to the lower coolant jacket  44  is seen originating from a conical protrusion  411  on the wall of the cylinder liner jacket  42 . A first set of cylindrical structures  446  is seen radially protruding from the upper coolant jacket  46  while a second set of cylindrical structures  442  is seen radially protruding from the lower coolant jacket  44 . A first projection  447  of the upper coolant jacket  46  is seen extending in a direction opposite to a second projection  448 , each of the first and second projections extending along a projection axis that is perpendicular to the central axis. 
     A front face of the exhaust port cooling jacket  48  is visible in the right side view while a back face of the exhaust port cooling jacket  48  is seen in the left side view. A rod-shaped drilling  472  is visible across the front face of the exhaust port cooling jacket  48 , the drilling  472  coupling the upper coolant jacket  46  to the exhaust port cooling jacket  48 . The rod-shape may correspond to an elongated cylindrical shape with a high aspect ratio (ratio between length and diameter). 
     Turning now to  FIG. 11 , an example method  1000  is described for circulating coolant through a cylinder head and an engine block via the coolant system of  FIGS. 4-10 . Instructions for carrying out method  1100  may be executed by a controller based on instructions stored on a memory of the controller and in conjunction with signals received from sensors of the vehicle system. The controller may employ actuators of the vehicle system to adjust coolant flow through engine components, according to the methods described below. 
     At  1102 , the routine includes determining if coolant flow is required. Coolant flow may be required if the engine is operational such as combusting fuel and air. Combustion creates heat which causes engine components to warm up. Excessive heating of the engine components may increase engine wear and fuel consumption. Coolant flow through (or around) engine components including the cylinder heads and the cylinder liners may cause thermal energy from the engine components to be transferred to the coolant, thereby cooling the engine components. Coolant flow may not be required when the engine is in a non-combusting condition such as during a vehicle off condition or when the vehicle is being propelled via machine torque. 
     If it is determined that coolant flow is not required, at  1104 , a coolant pump (such as pump  212  in  FIG. 2 ) coupled to a first coolant line (such as coolant line  209  in  FIG. 2 ) connecting a coolant sump (such as sump  208  in  FIG. 2 ) to a coolant feed galley (such as feed gallery  160  in  FIG. 2 ) may be maintained in an off state. While in the off state, coolant may not be routed from the sump to the feed gallery. 
     If it is determined that coolant flow is required, at  1106 , the controller may send a signal to an actuator coupled to the pump to enable the coolant pump. Upon operation of the pump, at  1108 , coolant may flow from the coolant sump to the crankcase coolant feed gallery via the first coolant line. Prior to circulation through the coolant system, the coolant may be stored at the sump. 
     At  1110 , from the crankcase coolant feed gallery, coolant flow may be split to simultaneously flow to a cylinder liner coolant jacket (such as cylinder liner coolant jacket  42  in  FIG. 2 ) and to a cylinder head lower coolant jacket (such as lower coolant jacket  44  in  FIG. 2 ). Coolant may flow out of the feed gallery via a main coolant feed line. The main coolant feed line may bifurcate into a first coolant feed line supplying a first portion of coolant from the feed galley to the cylinder liner coolant jacket and a second coolant feed line supplying a second portion of coolant from the feed gallery to a lower coolant jacket. In one example, each of the first coolant feed line and second coolant feed line may originate from the feed gallery. 
     In one example, coolant from the feed galley may be simultaneously directed to a plurality of cooling units encasing distinct cylinders such as a first cooling unit encasing a first cylinder block and an associated cylinder head and a second cooling unit encasing a second cylinder block and an associated cylinder head. The first and second cylinder blocks may be positioned adjacent to each other, each of the first and second cylinder block coupled to a crankcase. As an example, a first ratio of coolant flowing through the first cooling unit relative to the second cooling unit may be varied based on individual cylinder operating conditions. The first ratio may be varied by adjusting a proportioning valve coupled to the main coolant feed line, the valve adjusted to increase the first ratio relative to the second ratio if the as a cylinder head temperature of the first cylinder block exceeds the cylinder head temperature of the second cylinder block. 
     At  1112 , coolant from the cylinder liner coolant jacket may be routed to the cylinder head lower cooling jacket. In this way, the lower coolant jacket may receive coolant from each of the cylinder liner coolant jacket and the feed gallery. At  1114 , coolant from the cylinder head lower coolant jacket may be split to flow to each of a cylinder head upper coolant jacket (such as upper coolant jacket  44  in  FIG. 2 ) and an exhaust port cooling jacket (such as exhaust port cooling jacket  48  in  FIG. 2 ). The lower coolant jacket  44  may have two outlets, a first outlet directing a first portion of coolant from the lower coolant jacket to the exhaust port cooling jacket while a second outlet directing a second portion of coolant from the lower coolant jacket to the upper coolant jacket. 
     At  1116 , coolant from the cylinder head upper coolant jacket and the exhaust port cooling jacket may be routed to crankcase coolant return gallery (such as return gallery  162  in  FIG. 2 ). From the exhaust port cooling jacket, the coolant may flow to the upper coolant jacket via a fourth coolant feed line. From the upper coolant jacket, the entire volume of coolant may return to the crankcase coolant return gallery via a main coolant return line. As heat from the engine is transferred to the coolant circulating there through, coolant temperature increases. Therefore, the temperature of coolant in the coolant return gallery may be higher than the temperature of coolant in the coolant feed gallery. 
     At  1118 , the coolant from the main coolant gallery may be returned to the sump via a radiator. At the radiator, the coolant may dissipate the heat adsorbed from the engine components and the coolant may return to the sump. The temperature of coolant entering the radiator may be higher than that of coolant exiting the radiator. 
     A method for cooling an engine may comprise: flowing coolant, drawn from a feed gallery coupled to a crankcase, through a first cooling unit encasing a first cylinder block and an associated cylinder head, concurrently flowing coolant, drawn from the feed gallery coupled to the crankcase, through a second cooling unit encasing a second cylinder block and an associated cylinder head, wherein the first and second cylinder block are positioned adjacent to each other, each of the first and second cylinder block coupled to the crankcase, and varying a first ratio of coolant flowing through the first cooling unit relative to the second cooling unit based on individual cylinder operating conditions. 
     An example coolant system for a cylinder of an engine comprises: a cylinder liner jacket encircling the cylinder and configures to circulate coolant around a liner of the cylinder, a central axis of the liner jacket coaxial with a central axis of the encircled cylinder, a coolant feed gallery positioned within a crankcase below the cylinder, a coolant return gallery positioned within the crankcase, below the coolant feed gallery, a cylinder head lower coolant jacket surrounding a lower surface of a cylinder head placed over the cylinder, the lower coolant jacket positioned above and coaxial with the liner jacket and, a cylinder head upper coolant jacket surrounding an upper surface of the cylinder head, the upper coolant jacket positioned above the lower coolant jacket, the upper coolant jacket including a central piece that is coaxial with the liner jacket, and a cylinder head exhaust port cooling jacket coupled between the upper and lower coolant jacket, and offset to one side of the central axis, wherein the lower coolant jacket is fluidically coupled to each of the coolant feed gallery, the upper coolant jacket, the cylinder liner jacket, and the exhaust port cooling jacket. In any preceding example, additionally or optionally, the lower coolant jacket being fluidically coupled to each of the coolant feed gallery, the upper coolant jacket, and the exhaust port cooling jacket includes the lower coolant jacket configured to receive coolant flow concurrently from each of the coolant feed gallery and the cylinder liner jacket, and to flow coolant concurrently from the lower coolant jacket to each of the upper coolant jacket and the exhaust port cooling jacket. In any or all of the preceding examples, additionally or optionally, the lower coolant jacket is configured to receive coolant from the cylinder liner jacket at a first inlet via a first coolant passage positioned on the one side of the central axis and wherein the lower coolant jacket is configured to receive coolant from the coolant feed gallery at a second inlet positioned diametrically opposite the first inlet, and via a second coolant passage positioned on another side of the central axis, opposite the one side. In any or all of the preceding examples, additionally or optionally, an inlet of the exhaust port cooling jacket for receiving coolant from the lower coolant jacket is positioned on a lower surface of the exhaust port cooling jacket, the lower surface coplanar with the lower coolant jacket, and wherein an outlet of the exhaust port cooling jacket for directing coolant to the upper coolant jacket is positioned on an upper surface of the exhaust port cooling jacket and coplanar with an upper surface of the upper coolant jacket. In any or all of the preceding examples, additionally or optionally, the upper coolant jacket further includes a first projection extending down and outwards from a top surface of the central piece towards a top surface of the lower coolant jacket on the one side of the central axis, the first projection further extending into a return coolant passage, parallel to the central axis, coupling the upper coolant jacket to the return feed gallery. In any or all of the preceding examples, additionally or optionally, the upper coolant jacket further includes a second projection extending outwards from the top surface of the central piece towards a top surface of the exhaust cooling port cooling jacket on the other side of the central axis, opposite the one side, the second projection abutting and receiving coolant from an outlet of the exhaust cooling port. In any or all of the preceding examples, additionally or optionally, the first projection extends in a direction opposite to the second projection, each of the first and second projections extending along a projection axis that is perpendicular to the central axis. In any or all of the preceding examples, additionally or optionally, the coolant system is selectively coupled to only the cylinder of engine. In any or all of the preceding examples, additionally or optionally, the cylinder liner jacket includes an outer cylindrical surface, an inner cylindrical surface, and a space defined between the inner and outer surface for circulating coolant, each of the inner and outer surface surrounding the cylinder. In any or all of the preceding examples, the system further comprising, additionally or optionally, a rod-shaped drilling coupling the second projection of the upper coolant jacket to the exhaust port cooling jacket on the one side of the central axis, the drilling substantially coaxial to the central axis and abutting the exhaust port cooling jacket. 
     Another example coolant system for an engine comprises: a coolant feed gallery coupled inside an engine crankcase, a coolant return gallery coupled inside the engine crankcase, a first cooling unit including a cylinder liner jacket surrounding a first cylinder, an upper coolant jacket and a lower coolant jacket surrounding a head of the first cylinder, and an exhaust port cooling jacket coupled to an exhaust port of the first cylinder, and a second cooling unit including another cylinder liner jacket surrounding a second cylinder, another upper coolant jacket and another lower coolant jacket surrounding the head of the second cylinder, and another exhaust port cooling jacket coupled to an exhaust port of the second cylinder, wherein each of the first and the second cooling unit is coupled to the coolant feed gallery and the coolant return gallery. In any preceding example, the system further comprising, additionally or optionally, a pump coupled to the coolant feed gallery for pumping coolant from the coolant feed gallery into each of the first cooling unit and the second cooling unit, and a proportioning valve coupled downstream of the pump for varying a ratio for coolant flow directed to the first cooling unit relative to the second cooling unit. In any or all of the preceding examples, additionally or optionally, each of the first cooling unit and the second cooling unit further includes a first feed passage flowing coolant from the coolant feed gallery to a corresponding cylinder liner jacket, and a second feed passage flowing coolant from the coolant feed gallery to a corresponding lower coolant jacket, the first feed passage positioned perpendicular to the second feed passage, the first feed passage and second feed passage further positioned on diametrically opposite ends of the first or second cooling unit. In any or all of the preceding examples, additionally or optionally, each of the first cooling unit and the second cooling unit further includes a third feed passage flowing coolant from the corresponding lower coolant jacket to a corresponding exhaust port cooling jacket, and a fourth feed passage flowing coolant from the corresponding lower coolant jacket to the corresponding upper coolant jacket, the third feed passage positioned parallel to the fourth feed passage. In any or all of the preceding examples, the system further comprising, additionally or optionally, a common coolant return passage receiving coolant from the exhaust port cooling jacket of each of the first and second cooling unit, the common coolant return passage returning coolant to the coolant return gallery. In any or all of the preceding examples, additionally or optionally, a central axis of the first cooling unit is coaxial with a central axis of the first cylinder and a central axis of the second cooling unit is coaxial with a central axis of the second cylinder, the first cylinder and the second cylinder positioned adjacent to one another along an engine block. 
     In yet another example, a method for cooling an engine comprises: flowing coolant, drawn from a feed gallery coupled to a crankcase, through a first cooling unit encasing a first cylinder block and an associated cylinder head, concurrently flowing coolant, drawn from the feed gallery coupled to the crankcase, through a second cooling unit encasing a second cylinder block and an associated cylinder head, wherein the first and second cylinder block are positioned adjacent to each other, each of the first and second cylinder block coupled to the crankcase, and varying a first ratio of coolant flowing through the first cooling unit relative to the second cooling unit based on individual cylinder operating conditions. In any preceding example, additionally or optionally, flowing coolant through the first cooling unit includes: flowing the coolant, drawn from the feed gallery, concurrently to each of a liner coolant jacket and a cylinder head lower coolant jacket of the first cylinder block, flowing coolant from the liner coolant jacket to the cylinder head lower coolant jacket, flowing coolant, drawn from the cylinder head lower coolant jacket, concurrently to each of a cylinder head upper coolant jacket and a cylinder head exhaust port coolant jacket, flowing coolant from the cylinder head exhaust port coolant jacket to the cylinder head upper coolant jacket, and returning coolant drawn from the cylinder head upper coolant jacket to a return gallery positioned below the feed gallery in the crankcase. In any or all of the preceding examples, the method further comprising, additionally or optionally, varying a second ratio of coolant flowing to the liner coolant jacket relative to the cylinder head lower coolant jacket of the first cooling unit based on cylinder head temperature, and varying a third ratio of coolant flowing to the cylinder head upper coolant jacket relative to the exhaust port cooling jacket of the first cooling unit based on exhaust temperature. In any or all of the preceding examples, additionally or optionally, varying the first ratio includes increasing the first ratio of coolant flowing through the first cooling unit relative to the second cooling unit, via a proportioning valve, as a cylinder head temperature of the first cylinder block exceeds the cylinder head temperature of the second cylinder block. 
     In an embodiment, an engine system includes a crankcase, a feed gallery coupled to the crankcase, a first cooling unit encasing a first cylinder block and an associated cylinder head, a second cooling unit encasing a second cylinder block and an associated cylinder head, and a controller. The first and second cylinder blocks are positioned adjacent to each other, and are coupled to the crankcase. The first cooling unit is configured to receive a first coolant flow from the feed gallery. The second cooling unit is configured to receive a second coolant flow from the feed gallery concurrent with the first coolant flow. The controller is configured to vary a ratio of the first coolant flow relative to the second coolant flow based on individual cylinder operating conditions. 
     This written description uses examples to disclose the invention, and to enable one of ordinary skill in the relevant art to practice embodiments of the invention, including making and using the devices or systems and performing the methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to one of ordinary skill in the relevant art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the language of the claims.