Patent Publication Number: US-9422886-B2

Title: Cylinder head assembly having cooled valve insert

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a cylinder head assembly, and more particularly, to a cylinder head assembly having a cooled valve insert. 
     BACKGROUND 
     An internal combustion engine generally includes one or more combustion chambers that house a combustion process to produce mechanical work and a flow of exhaust. Each combustion chamber is defined by a cylinder, a top surface of a piston, and a bottom surface of a cylinder head. Air or an air/fuel mixture is directed into the combustion chamber by way of intake ports in the cylinder head, and a resulting exhaust flow is discharged from the combustion chamber by way of exhaust ports also in the cylinder head. Valves are located within bores associated with the intake and exhaust ports and sealed against valve seat inserts to selectively allow and block the flows of air and exhaust through the intake and exhaust ports. 
     Traditional valve seat inserts are pressed into their respective bores and then, machined to specific tolerances, allowing the valves to seat properly. While successful, this machining process may not be cost effective. In particular, machining the valve seat inserts after installation into their respective bores can require additional tooling and be difficult to perform in the field. 
     During engine operation, cylinder heads, valves, and valve seat inserts are exposed to high stresses and temperatures. And, over time, these high stresses and temperatures can cause excessive wear of the cylinder head, the valves, and the valve seat inserts. 
     One solution to the high stresses and temperatures described above is disclosed in U.S. Pat. No. 5,745,993 (“the &#39;993 patent”) issued to Adachi et al. on May 5, 1998. The &#39;993 patent describes a reciprocating machine having a cylinder head including intake and exhaust flow passages that are controlled by intake and exhaust poppet-type valves. Each valve has a head portion that cooperates with a respective valve seat formed at lower ends of the intake and exhaust flow passages. The cylinder head utilizes a valve insert ring to form the valve seat that is press-fit within each flow passage. One or more water jackets are formed within the cylinder head and provide cooling for the cylinder head, the valves, and/or the valve insert rings. 
     Although the water jackets of the &#39;993 patent help to provide some cooling for the valves and the valve insert rings, it may still be less than optimal. Specifically, the water jackets of the &#39;993 patent are located a distance from the valve insert rings, and this distance may limit the amount of heat that can transfer from the valve insert rings and their respective valves to coolant in the water jacket. Additionally, the valve insert rings of the &#39;993 patent are first inserted into their respective positions and then, machined into place. This machining process may be expensive and limit remanufacturing options. 
     The cylinder head assembly of the present disclosure solves one or more of the problems set forth above and/or other problems with existing technologies. 
     SUMMARY OF THE DISCLOSURE 
     in one aspect, the present disclosure is directed to a cylinder head assembly. The cylinder head assembly may include a cylinder head having a stepped bore associated with a valve opening. The cylinder head assembly may also include an insert configured to engage the stepped bore, and a cooling passage at least partially formed by the insert and the stepped bore. 
     In another aspect, the present disclosure is directed to a method of cooling a cylinder head assembly. The method may include directing coolant into a cylinder head, and circulating coolant from the cylinder head through a cooling passage at least partially surrounding and formed by a valve insert. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a pictorial illustration of an exemplary disclosed engine; 
         FIG. 2  is a pictorial illustration of an exemplary disclosed cylinder head assembly that may be utilized in conjunction with the engine of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view illustration taken along line  3 - 3  of the cylinder head assembly of  FIG. 2 ; and 
         FIG. 4  is a cross-sectional view illustration taken along line  4 - 4  of the cylinder head assembly of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an exemplary engine  12 . For the purposes of this disclosure, engine  12  is depicted and described as a four-stroke diesel engine. One skilled in the art will recognize, however, that engine  12  may be any other type of combustion engine such as, for example, a two- or four-stroke gasoline or gaseous fuel-powered engine. 
     Engine  12  may include an engine block  14  that at least partially defines a plurality of cylinders  16 . A piston  18  may be slidably disposed within each cylinder  16  to reciprocate between a top-dead-center position and a bottom-dead-center position, and a cylinder head  20  may be associated with each cylinder  16 . Each cylinder  16 , piston  18 , and cylinder head  20  may together at least partially define a combustion chamber  28 . A fuel injector  34  may be at least partially disposed within each cylinder head  20  and configured to inject fuel into each respective combustion chamber  28  to support fuel combustion within engine  12 . Engine  12  may also include a crankshaft  24  that is rotatably supported within engine block  14  by way of a plurality of journal bearings  25 . A connecting rod  26  may connect each piston  18  to crankshaft  24  so that a sliding motion of piston  18  within each respective cylinder  16  results in a rotation of crankshaft  24 . 
     As shown in  FIG. 2 , cylinder head  20  may include a bottom deck, or firedeck surface  30 , a plurality of side surfaces  32 , and a top surface  33 . Firedeck surface  30  of cylinder head  20  may include a fuel injector opening  35  associated with fuel injector  34  and two or more valve openings. In the embodiment shown, the valve openings include a pair of intake valve openings  38  and a pair of exhaust valve openings  40 . It is contemplated, however, that, in some embodiments, firedeck surface  30  may have only one intake valve opening  38  and/or one exhaust valve opening  40 . Valve openings  38 ,  40  may be evenly spaced about fuel injector opening  35 . A passage (not shown) may be defined within cylinder head  20  extending from each valve opening  38 ,  40  to a respective one of an intake port  46  and an exhaust port  48 . Intake and exhaust ports  46 ,  48  may be disposed in side surfaces  32  of cylinder head  20  to allow air and exhaust to enter and exit cylinder head  20 . 
     Also shown in  FIG. 2 , cylinder head  20  may have a stepped bore  60  associated with each valve opening  38 ,  40 . A generally circular or ring-shaped valve seat insert  42  may be configured to engage each stepped bore  60  and provide a seating surface for a respective one of an intake valve or an exhaust valve (not shown). During engine operation, valve seat inserts  42  may serve to protect cylinder head  20  from excessive wear and/or corrosion resulting from contact with the intake and exhaust valves. Valve seat inserts  42  may also provide a tight seal with the intake and exhaust valves to selectively block unintended leakage of air and exhaust into or out of combustion chamber  28  (referring to  FIG. 1 ). 
     In the disclosed embodiment, valve seat inserts  42  are preferably manufactured from a durable, wear-resistant, and heat-resistant material, such as a high nickel steel. Cylinder head  20 , on the other hand, may be made of cheaper materials, such as a ductile iron. Valve seat inserts  42  may be pre-machined prior to installation into their respective stepped bores  60 . This pre-machining process may include machining precise diameters, curvatures, angles, and/or any other geometrical aspects of both inner and outer surfaces of valve seat insert  42 . By completely pre-machining valve seat inserts  42  prior to installation, this may allow manufacturers to cut down on labor time and cost. Also, having pre-machined valve seat inserts  42  may facilitate field replacement of valve seat inserts  42  and/or maintenance of cylinder head  20 . It is contemplated that stepped bores  60  may also be pre-machined to precise diameters, curvatures, angles, and/or any other geometrical aspects prior to installment of each respective valve seat insert  42 . By having both pre-machined stepped bores  60  and pre-machined valve seat inserts  42 , this may allow for proper alignment of stepped bores  60  and valve seat inserts  42  without a need for additional machining. 
       FIG. 3  illustrates a cross sectional view illustration taken along line  3 - 3  of cylinder head  20  shown in  FIG. 2 . Internally, cylinder head  20  may include a plurality of cooling passages  50  configured to facilitate the transfer of thermal energy away from cylinder head  20 , intake and exhaust valves, and/or valve seat inserts  42 . Cooling passages  50  may include, for example, water jackets that utilize a coolant, such as glycol, water, a water/glycol mixture, or another coolant known in the art. The coolant may enter cooling passages  50  through one or more inlet passages  56 , and exit cooling passages  50  through one or more outlet passages  58 . In the embodiment shown, there are a plurality of inlet passages  56  and a plurality of outlet passages  58 . Inlet passages  56  and outlet passages  58  may be in fluid communication with cooling passages  50  and one or more additional cooling components of engine  12 . Also shown in  FIG. 3 , one or more mounting holes  72  may be disposed within cylinder head  20  and be configured to attach cylinder head  20  to engine block  14  (referring to  FIG. 1 ) using a plurality of bolts, or by any other form of attachment known in the art. 
     In the disclosed embodiment, cooling passages  50  extend from outer edges of cylinder head  20  towards a center of cylinder head  20 . Cooling passages  50  may function as distribution passages, and connect to multiple smaller cooling passages  52  that substantially surround one or more valve seat inserts  42 . As shown in  FIG. 3 , each cooling passage  52  may entirely surround a periphery of each respective valve seat insert  42  associated with one of intake or exhaust valve opening  38 ,  40 . In addition, cooling passages  52  may be in fluid communication with each other. For example, in the embodiment shown, each cooling passage  52  is connected to two adjacent cooling passages  52  associated with adjacent valve openings  38 ,  40 . It is contemplated that, in other embodiments, cooling passages  52  may be fluidly connected at the center of cylinder head  20 , such that all cooling passages  52  may be fluidly connected with one another. 
       FIG. 4  illustrates a cross sectional view illustration taken along line  4 - 4  of cylinder head  20  shown in  FIG. 2 . As shown in  FIG. 4 , each valve seat insert  42  may have an upper radial surface  62  and a lower radial surface  64 . It should be noted that upper and lower radial surfaces  62 ,  64  may have substantially different outer diameters. Upper and lower radial surfaces  62 ,  64  may engage separate contacting surfaces of stepped bore  60  to at least partially form cooling passage  52 . For example, cooling passage  52  may be formed at an intersection of upper and lower radial surfaces  62 ,  64 . More specifically, a recess of valve seat insert  42  may form one side of cooling passage  52 , while a recess of stepped bore  60  may form the other side of cooling passage  52 . It is contemplated that both the recess of valve seat insert  42  and the recess of stepped bore  60  may be pre-machined prior to installation of valve seat inserts  42 . In addition, each valve seat insert  42  may have an annular and generally flat top surface  66  configured to engage a shoulder of stepped bore  60  to help prevent leakage from either intake port  46  or exhaust port  48 . Top surface  66  may also control an axial position of valve seat insert  42  within cylinder head  20 . It should be noted that top surface  66  may be substantially orthogonal to upper radial surface  62 . 
     The engagement between stepped bore  60  and upper and lower radial surfaces  62 ,  64  may be a tight interference fit (i.e. press-fit) that provides sealing above and below cooling passage  52  to prevent coolant leakage into combustion chamber  28  (referring to  FIG. 1 ) and into either intake port  46  or exhaust port  48 . This engagement may secure valve seat insert  42  within stepped bore  60  as well as adapt to receive and engage the intake or exhaust valves, thereby allowing the valves to selectively seal intake and exhaust passages. Each valve seat insert  42  may be fitted into their respective stepped bores  60  in substantially the same manner. 
     INDUSTRIAL APPLICABILITY 
     The disclosed cylinder head assembly may be implemented into any engine application where engine cooling is utilized. Cooling passages  52  may be formed between valve seat inserts  42  and cylinder head  20 , thereby allowing increased cooling to valve seat inserts  42  and/or their respective valves. The disclosed valve seat inserts  42  may have radial surfaces  62 ,  64  and top surfaces  66  that provide sealing both above and below cooling passages  52 , thus providing increased protection from leakage into combustion chambers  28  and into either intake port  46  or exhaust port  48 . In addition, valve seat inserts  42  may be fully pre-machined prior to installation into their respective stepped bore  60 , thereby reducing upfront labor times and costs, as well as facilitating maintenance and/or replacement of valve seat inserts  42 . The method for directing cooling through the disclosed cylinder head assembly will now be described below. 
     Referring to  FIGS. 3 and 4 , coolant may be directed into cylinder head  20  from one or more additional cooling components of engine  12 . Within cylinder head  20 , the coolant may be directed into cooling passages  50  via inlet passages  56 . The coolant may circulate from cooling passages  50  through cylinder head  20  and be directed into one or more cooling passages  52  surrounding valve seat inserts  42 . Coolant may flow between adjacent cooling passages  52  associated with other valve seat inserts  42 . Coolant may also be divided into two or more flow streams prior to entering cooling passages  52 . For example, coolant may be divided into two substantially equal flow streams prior to entering adjacent cooling passages  52  associated with one of intake or exhaust valve openings  38 ,  40 . The coolant flowing through cooling passages  50 ,  52  may absorb thermal energy from cylinder head  20 , the intake and exhaust valves, and/or valve seat inserts  42 . The coolant may then exit cooling passages  50 ,  52  through one or more outlet passages  58  and continue to additional cooling components of engine  12 . 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed cylinder head assembly. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed cylinder head assembly. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.