CYLINDER HEAD GASKET FOR AN ENGINE

Abstract

Power machine (20) comprising the following: a cylinder block (70) forming a cylinder (22); a cylinder head (72); and a cylinder head gasket (100, 200) positioned between the cylinder block (70) and the cylinder head (72), wherein the cylinder head gasket (100, 200) is first and second outer layers (202, 204) and a spacer layer (206) positioned between them, wherein the first layer (202) defines a first opening having a first diameter surrounding the cylinder (22) and a bead (220) surrounding the opening, wherein the spacer layer (206) defines a second opening having a second diameter larger than the first diameter, such that the second opening is arranged concentrically between the first opening and the bead (220), wherein the cylinder head gasket (100, 200) has a stopper layer (242) extending inwards from the spacer layer (206) to a circular stopper element (252), wherein the stopper element (252) is positioned adjacent to and thus aligned with the first opening, and wherein the stopper element (252) has a first thickness in an axial direction of the cylinder head gasket; wherein the spacer layer (206) and the stopper layer (242) are connected by an overlap between them to provide a second thickness in an axial direction; and where the second thickness is greater than the first thickness.

Description

TECHNICAL FIELD

[0001] Various embodiments relate to a cylinder head gasket (hereinafter also referred to as gasket) for an internal combustion engine, such as a compression ignition engine. STATE OF THE ART

[0002] Internal combustion engines form a combustion chamber using two engine components, such as a cylinder head and a cylinder block. A cylinder block face cooperates with a cylinder head face to enclose the combustion chamber. A sealing element, such as a cylinder head gasket, is positioned between the face of the block and head to seal the combustion chamber during engine operation.

[0003] Multi-layer cylinder-head gaskets for internal combustion engines and their arrangement between the cylinder block and cylinder head are known. DE 195 23 825 A1 also discloses a bead in the top and bottom layers, as well as a spacer or intermediate layer whose opening diameter is larger than the opening diameters of the top and bottom layers.

[0004] DE 197 19 328 C1 discloses overlapping areas consisting of a carrier sheet and a ring. SUMMARY

[0005] Based on this, the object of the present invention is to improve cylinder head gaskets for an engine and an engine therewith, as well as a corresponding method for sealing an engine. According to the invention, an engine according to claim 1, a cylinder head gasket according to claim 4, and a method according to claim 11 are proposed for this purpose. Advantageous embodiments of the invention are specified in the dependent claims and the following description.

[0006] In one embodiment, an engine is provided having a block forming a cylinder, a head, and a gasket positioned between the block and the head. The gasket includes first and second outer layers and a spacer layer positioned therebetween. The first layer defines a first opening having a first diameter surrounding the cylinder and a bead surrounding the opening. The spacer layer defines a second opening having a second diameter greater than the first diameter such that the second opening is concentrically disposed between the first opening and the bead. The gasket includes a stopper layer extending inwardly from the spacer layer to a circular stopper element, the stopper element positioned adjacent to and aligned with the first opening.

[0007] In another embodiment, a cylinder head gasket for an engine is provided with first and second outer layers, each layer having an opening for surrounding a cylinder and a bead surrounding the opening. An intermediate layer is positioned between the first and second layers and has a first axial thickness between the beads, a second axial thickness adjacent the opening, and a third axial thickness between the beads and openings, the second thickness being less than the third thickness.

[0008] In yet another embodiment, a method of sealing an engine is provided and includes compressing a cylinder head gasket between a block and a head to form a primary seal at a first interface between the first and second outer layers and an intermediate layer and to form a secondary seal at a second interface between the first and second outer layers and the intermediate layer, the first interface being positioned between the second interface and a bead surrounding a cylinder. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates an internal combustion engine capable of utilizing various embodiments of the present disclosure; Fig. 2 is a perspective schematic view of a cylinder head gasket for use with the engine Fig. 1 according to one embodiment; Fig. 3 shows a sectional view of the cylinder head gasket Fig. 2 in a prime mover in a non-compressed state; Fig. 4 shows a partial sectional view of the cylinder head gasket Fig. 2 in a power machine in a compressed state; and Fig. 5 shows a partial perspective view of the cylinder head gasket Fig. 3. DETAILED DESCRIPTION

[0009] As required, detailed embodiments of the present disclosure are provided herein; however, it should be understood that the disclosed embodiments are merely exemplary and may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Thus, the specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to variously employ the present disclosure.

[0010] Fig. 1 illustrates a schematic representation of an internal combustion engine (hereinafter also referred to as engine) 20. The engine 20 includes a plurality of cylinders 22, and one cylinder is illustrated. The engine 20 may include a number of cylinders, and the cylinders may be arranged in various configurations. The engine 20 includes a combustion chamber 24, each associated with a cylinder 22. The cylinder 22 is formed by cylinder walls 32 and a piston 34. The piston 34 is connected to a crankshaft 36. The combustion chamber 24 is in fluid communication with the intake manifold 38 and the exhaust manifold 40. An intake valve 42 controls flow from the intake manifold 38 into the combustion chamber 24. An exhaust valve 44 controls flow from the combustion chamber 24 to the exhaust system(s) 40 or exhaust manifold.The intake and exhaust valves 42, 44 may be operated to control engine operation in various ways known in the art.

[0011] A fuel injector 46 delivers fuel from a fuel system directly into the combustion chamber 24, making the engine a direct-injection engine. In other examples, the fuel is delivered indirectly, such as into a pre-combustion chamber in the head. The engine 20 may be configured as a compression-ignition engine using, for example, diesel fuel. The fuel is injected into the combustion chamber at a specific time and with swirl or other flow characteristics so that the fuel-air mixture self-ignites during the compression stroke. In various examples, a spark plug or other device may be provided to assist engine start-up.In other examples of the engine, the engine may be a spark ignition engine or may be used with other fuels, such as gasoline, other fossil fuel-based fuels, or renewable biofuels such as biodiesel, bioethanol, and the like.

[0012] The engine 20 includes a controller and various sensors configured to provide signals to the controller for use in controlling air and fuel delivery to the engine, ignition timing, power and torque output from the engine, the exhaust system, and the like. Engine sensors may include an oxygen sensor in the exhaust system 40, an engine coolant temperature sensor, an accelerator pedal position sensor, an engine manifold pressure (MAP) sensor or charge air sensor, an engine crankshaft position sensor, a mass air flow sensor in the intake manifold 38, a fuel pump speed sensor, a fuel rail position sensor, a fuel pressure sensor, an exhaust gas temperature sensor in the exhaust system 40, and the like.

[0013] In some embodiments, the engine 20 is used as the sole power source in a vehicle, such as a conventional vehicle or a stop-start vehicle. In further embodiments, the engine may be used in a hybrid vehicle, where an additional power source, such as an electric machine, is available to provide additional power to propel the vehicle.

[0014] Each cylinder 22 may operate in a four-stroke cycle including an intake stroke, a compression stroke, an ignition stroke, and an exhaust stroke. In other embodiments, the engine may operate in a two-stroke cycle. During the intake stroke, the intake valve 42 opens and the exhaust valve 44 closes while the piston 34 moves from the top of the cylinder 22 to the bottom of the cylinder 22 to draw air from the intake manifold into the combustion chamber. A position of the piston 34 at the top of the cylinder 22 is generally known as top dead center (TDC). A position of the piston 34 at the bottom of the cylinder is generally known as bottom dead center (BDC).

[0015] During the compression stroke, the intake and exhaust valves 42, 44 are closed. The piston 34 moves from the bottom to the top of the cylinder 22 to compress the air in the combustion chamber 24. In a gasoline engine, fuel may be introduced into the combustion chamber 24 during the compression stroke. As the pressure in the combustion chamber 24 increases during the compression stroke, the fuel-air mixture in the chamber self-ignites and combusts. The timing of the fuel injection can be controlled mechanically or electronically with respect to the crankshaft angle before TDC, e.g., using a governor. If the timing is incorrect, the engine may experience increased noise or incomplete combustion.

[0016] During the power stroke, the ignited fuel-air mixture expands in the combustion chamber 24, causing the piston 34 to move from the top of the cylinder 22 to the bottom of the cylinder 22. The movement of the piston 34 causes a corresponding movement in the crankshaft 36 and provides a mechanical torque output from the engine 20.

[0017] During the exhaust stroke, intake valve 42 remains closed and exhaust valve 44 opens. Piston 34 moves from the bottom of the cylinder to the top of cylinder 22 to remove exhaust gases and combustion products from combustion chamber 24 by reducing the volume of chamber 24. The exhaust gases flow from combustion cylinder 22 to exhaust system 40 and to an aftertreatment system, such as a catalyst converter or diesel particulate filter. Engine 20 may additionally include various components, such as a boost device including a turbocharger or supercharger, heat exchangers such as an intercooler, exhaust gas recirculation (EGR) systems, and the like.

[0018] The positions and timing of the intake and exhaust valves 42, 44 as well as the fuel injection timing are controlled for the various engine cycles and to control engine operation and are variable in some examples.

[0019] The engine 20 includes a cylinder block (hereinafter also referred to as a block) 70 and a cylinder head 72, which cooperate to form the combustion chambers 24. A cylinder head gasket 74 may be positioned between the block 70 and the head 72 to seal the chamber 24. The cylinder block 70 has a block surface that seals the combustion chamber with a head surface of the cylinder head 72 using the cylinder head gasket 74.

[0020] The cylinder head may have a "flat head" design, with the ports for the intake and exhaust valves and the roof area of ​​the cylinder being coplanar with the top surface of the head.

[0021] The engine 20 includes at least one fluid system (not shown). The fluid system may include a cooling system for removing heat from the engine 20 and a lubrication system for lubricating moving engine components.

[0022] Fig. 2 illustrates a perspective schematic view of a cylinder head gasket (hereinafter also referred to as gasket) 100 according to an embodiment. The cylinder head gasket 100 may be used as the cylinder head gasket 74 in the engine 20, as shown in Fig. 1. The cylinder head gasket 100 is illustrated for use with a 4-cylinder engine; however, it may be redesigned for use with an engine having more or fewer than four cylinders, and for use with engines in various configurations, including in-line, V-configuration, and the like.

[0023] The gasket 100 has a first side 102 that engages a top surface of a cylinder head and a second, opposite side that engages a top surface of a cylinder block of the engine. The cylinder head gasket defines openings 104 and sealing beads 106 that surround each cylinder in the engine to seal the cylinder. The head gasket may also have various openings 108 therethrough that allow the flow of intake gases, exhaust gases, coolant, and / or lubricant from the block to the head and vice versa and through the gasket. The gasket also defines various openings 110, such as bolt openings, that allow a head bolt to pass through the gasket when connecting a cylinder head to the cylinder block.

[0024] In one example, the seal 100 is constructed from multiple layers, and each layer may be made of steel or another suitable material. For example, the seal 100 may be a multi-layer steel (MLS) seal. In various examples, all layers may be formed from the same material or may be formed from different materials or alloys. Each layer may be stamped or otherwise processed to provide features associated with the layer, such as the openings 108, 110, sealing beads 106, and the like.

[0025] In one example, the gasket 100 is configured for use with a diesel engine. A diesel engine requires a robust gasket seal due to the high combustion pressures and high thermal loads encountered during engine operation. In one example, the diesel engine may be a light- or medium-duty engine and experience compression ratios above 14:1, with compression ratios up to or above 23:1. The internal cylinder peak operating pressure in the engine may be 170 bar or more for a naturally aspirated engine and higher peak pressures for a turbocharged engine.

[0026] Fig. 3 to 5 show various partial views of a cylinder head gasket 200 for an engine, e.g., engine 20. Fig. Figure 3 shows the cylinder head gasket 200 in an uncompressed or free state before the head 72 is attached to the cylinder block 70 and the head bolts 201 connecting the head to the block are tightened. Fig. 4 shows the cylinder head gasket 200 in a compressed state after the head bolts 201 connecting the head 72 to the block 70 are tightened to a specified torque value. Fig. 5 shows a partial perspective view of the gasket 200. The cylinder head gasket 200 may be a cylinder head gasket 100 or 74. The cylinder head gasket 200 prevents internal cylinder gases from flowing behind a bead surrounding the cylinder to prevent or reduce engine ventilation failures. During operation, the air-fuel mixture within the cylinder ignites, causing an increase in in-cylinder pressure and may cause deformation or bending movement of the cylinder head into the bore wall. This movement may result in fatigue or fracture of the layers of the one or more layers of the gasket behind the bore wall. The disclosed gasket 200 provides compliance of the gasket 200 to the bore wall and prevents or reduces problems with gasket fatigue or failure while maintaining the seal of cylinder 22.

[0027] The engine is generally provided by block 70 and head 72 and may be a spark-ignition engine, such as a diesel engine. Head 72 may be configured as a "flat head" with a flat top surface and a roof defining the intake and exhaust ports for the cylinder, or in other examples, the head may define concave areas for the cylinder roofs.

[0028] The disclosed seal 200 seals one or more cylinders 22 in diesel or other engine applications to prevent the flow of gases out of the cylinder and to prevent the flow of fluids, such as coolant or lubricant, into the cylinder. The seal 200 is configured as a multi-layer seal, e.g., an MLS seal with a dual stopper feature that provides primary and secondary sealing functions, and the combustion bead provides a third seal, thus providing three levels of cylinder or combustion sealing.

[0029] With reference to Fig. 3 and Fig. 5, the gasket includes a first outer layer 202, a second outer layer 204, and an intermediate spacer layer (hereinafter also referred to as a spacer layer) 206. The first outer layer 202 has an outer surface 208 that engages the top surface 210 of the cylinder head 72 and an inner surface 212 that engages a first surface 214 of the spacer layer 206. The outer layer 202 has a rim 216 that forms a circular opening through the layer that is aligned with the bore wall 218 of the cylinder 22 and at least partially defines the opening of the gasket, such as opening 104.

[0030] The first outer layer 202 forms a bead 220. The bead 220 may be formed by a concave surface on the outer surface 208 and a corresponding convex surface on the inner surface 212. The bead 220 may also be formed in an opposite manner, with the outer surface 208 forming the convex surface and the inner surface 212 forming the concave surface. The bead 220 is illustrated as a single bead; however, it is contemplated that the bead 220 may have a double bead or a differently shaped bead. The bead 220 may be provided in the outer layer 202 via a stamping process or the like.

[0031] The second outer layer 204 has an outer surface 222 that engages the top surface 211 of the cylinder block 70 and an inner surface 224 that engages a second surface 226 of the spacer layer 206. The outer layer 204 has an edge 228 that forms a circular opening through the layer that is aligned with the bore wall 218 of the cylinder 22 and at least partially defines the opening of the seal, such as the opening 104. The edge 228 or opening of the outer layer may be aligned with the edge 216 or opening of the other outer layer 202 along an axial direction 230. It should be noted that the axial direction 230 and a transverse direction 232 are shown, and that the axial direction 230 may be aligned with the longitudinal axis of the cylinder 22.

[0032] The second outer layer 204 forms a bead 234. The bead 234 may be formed by a concave surface on the outer surface 222 and a corresponding convex surface on the inner surface 224. The bead 234 may also be formed in an opposite manner, with the outer surface 222 forming the convex surface and the inner surface 224 forming the concave surface. The bead 234 is illustrated as a single bead; however, it is contemplated that the bead 234 may have a double bead or a differently shaped bead. The bead 234 may be provided in the second outer layer 204 via a stamping process or the like.

[0033] The beads 220, 234 may be aligned with each other or overlap, and in one example, they are arranged directly opposite each other, and in another example, they are transversely offset from each other while maintaining the overlap. The beads 220, 234 may have the same size and shape or different sizes and shapes. In other examples, only one of the outer layers 202, 204 may be provided with a bead, and the other layer is a flat member.

[0034] In other examples, the seal 200 has more than three layers 202, 204, 206, e.g., with two or more spacer layers 206 positioned between the outer layers 202, 204.

[0035] An intermediate or spacer layer 206 is used as a spacing layer between the outer layers 202, 204 and can assist in determining the gasket thickness. The spacer layer 206 can also assist in sealing the cylinders 22 of the engine by cooperating with the outer layers 202, 204, as described below. The spacer layer 206 and the first and second outer layers 202, 204 may have the same thickness or may have different thicknesses. In one example, the first and second outer layers 202, 204 have a common thickness, and the spacer layer 206 has a greater thickness than an outer layer.

[0036] The spacer layer 206 has first and second opposing surfaces 214, 226 with a circular opening 240 formed therethrough such that the surfaces 214, 226 are separated by a rim 240. The opening or rim 240 is positioned between the beads 220, 234 and the openings or rims 216, 228 of the outer layers 202, 204 that define the seal opening surrounding the cylinder. The opening or rim 240 is spaced from the beads 220, 234 and spaced from the openings or rims 216, 228 in the transverse direction 232. In one example, the opening 240 has a diameter that is larger than a diameter of the openings 216, 228 and smaller than a diameter of the beads 220, 234.

[0037] The spacer layer 206 is positioned between the first and second outer layers 202, 204 such that the first surface 214 contacts the outer layer 202 and the second surface 226 contacts the outer layer 204 when the seal 200 is compressed, e.g., as shown in Fig. 4 shown.

[0038] A stopper layer 242 is positioned between the first and second outer layers 202, 204 and is connected to the spacer layer 206. The stopper layer 242 has one end 244 or end region and another end 248 or end region. The end 244 is connected to the spacer layer 206 adjacent the edge 240 of the spacer layer 206. The edge 240 of the opening of the spacer layer may be positioned between the two ends 244, 248 of the stopper layer 242, as shown. The stopper layer 242 has a surface 246 that is connected to one of the surfaces 214, 226 of the spacer layer. In the example shown, the surface 246 of the stopper layer is connected to the surface 226 of the spacer layer so that the end 244 of the stopper layer is positioned between the spacer layer 206 and the outer layer 204.In other examples, the end 244 of the stopper layer 242 is positioned between the spacer layer 206 and the outer layer 202. The stopper layer 242 may have a generally cylindrical shape.

[0039] The end 244 or end region of the stopper layer 242 overlaps the edge 240 of the spacer layer 206 in an overlap region 250. The overlap region 250 has a thickness A in the axial direction, or the combined thicknesses of the spacer and stopper layers 206, 242 have a thickness A. The stopper layer 242 may be joined to the spacer layer 206 via a welding process or other fastening method. In another example, the stopper layer 242 may be integrally formed with the spacer layer 206. The stopper layer 242 may be formed from the same material or alloy as the spacer layer 206 or may be formed from a different material or alloy.

[0040] The stopper layer 242 extends from the opening or edge 240 of the spacer layer 206 to a stopper element 252 that is connected to the second end 248 of the stopper layer. In one example, the stopper element 252 is connected to the end 248 of the stopper layer 242, e.g., via a welding process or the like. In another example, the stopper element 252 may be integrally formed with the stopper layer 242. The stopper element 252 is positioned adjacent the opening of the seal 200 and within the bore wall 218 of the cylinder. The stopper element 252 has a thickness B in the axial direction. The thickness B of the stopper element 252 is greater than the thickness A of the stopper and spacer layers in the overlap region 250. The stopper element 252 may have a generally cylindrical shape. The spacer layer has a thickness C between the beads 220, 234 and the thickness C is less than the thicknesses A and B, so that C < B < A.

[0041] The stopper element 252 has a first sidewall 254 and a second sidewall 256. The first sidewall 254 cooperates with the edges 216, 228 to define the opening of the seal. The second sidewall 256 is connected to the end 248 of the stopper layer 242, e.g., via a butt joint, as shown, or via a lap joint. The stopper element 252 is therefore spaced from the spacer layer 206 in the transverse direction 232.

[0042] The spacer layer 206, the stopper layer 242, and the stopper element 252 cooperate to provide an intermediate layer for the seal. In one example, the spacer layer 206, the stopper layer 242, and the stopper element 252 may comprise multiple components bonded together to provide internal layers of the seal. In another example, the spacer layer 206, the stopper layer 242, and the stopper element 252 are formed from a single piece of material, e.g., in a stamping or other machining process. For example, a sheet of material may be stamped or otherwise formed into the shape of the layer, and the material may be filled into any cavity formed during the stamping process to provide the stopper element 252 and the overlap region of the layers 206, 242.

[0043] The stopper element 252 has a surface 258 that engages the surface 212 of the outer layer 202 and an opposite surface 260 that engages a surface 224 of the outer layer 204.

[0044] The spacer layer 206, the stopper layer 242, and the stopper element 252 are illustrated as having a stepped structure, with some discontinuities along the upper surfaces and discontinuities along the lower surfaces of the layers and element. In other examples, the upper and lower surfaces may each be smooth, continuous surfaces that still provide the desired thicknesses in the appropriate ranges to form the sealing structure of the gasket.

[0045] The seal 200 may be used with an engine having cylinders arranged in various configurations, such as with coolant passages between adjacent cylinders or with joined or siamesed cylinders. In one example, for any engine configuration, the stopper layer and stopper element surrounding each cylinder may have the same dimensions. For engines having cylinders arranged in close proximity to an adjacent cylinder, such as in an engine with siamesed cylinders or in engines with a narrow bore bridge or bore abutment area, the stopper element may be narrower than in the interbore area.In another example of an engine having a narrow interbore region, the stopper layer may be integral with the interbore region such that the stopper elements of adjacent cylinders are connected to opposite ends of a single stopper layer extending outwardly from both sides of the spacer layer in the interbore region, with the seal 200 having the structure as described above for the remaining circumference of the cylinder facing away from the interbore region.

[0046] With reference to Fig. 4, the gasket 200 is shown in a compressed state, e.g., when the engine is assembled and ready for operation, with the head bolts tightened and the gasket compressed between the engine cover surfaces. The gasket 200 forms a first seal around the cylinder at a first interface between the lap region, the outer layers of the gasket, and the cover surfaces. The gasket forms a second seal around the cylinder at a second interface between the stopper element, the outer layers of the gasket, and the cover surfaces. The gasket also forms a third seal around the cylinder at an interface between the spacer layer, the beads of the gasket, and the cover surfaces. The three seals provide an improved seal for the cylinder to prevent exhaust gases from leaving the cylinder, even at peak pressures and thermal loads.

[0047] To compress the seal 200 to the installed state, as shown in Fig. 4, the cap screws 201 are tightened to a specific torque value that provides a corresponding tension in the cap screws 201. Since the thickness A of the overlap region 250 between the spacer and stopper layers 206, 242 is greater than a thickness B of the stopper element 252, a first clamping load is provided on the first seal 270 by the cover surfaces 210, 211 that is greater than a second clamping load provided on the second seal 272 by the cover surfaces 210, 211. It should be noted that the clamping load is in the axial direction.

[0048] The first seal 270 therefore has a first clamping load that is greater than a second clamping load of the second seal 272 due to the greater thickness A of the overlap region 250 and the seal 200 at the first seal 270 compared to the thickness B at the second seal 272. Since the first clamping load is greater than the second clamping load due to a thickness difference in the axial direction 230, the first clamping load is greater than the second clamping load regardless of the operating conditions, e.g., operating temperature and pressure of the cylinder 22. Since the first seal 270 has a greater clamping load than the second seal 272, the first seal 270 is the primary seal for the seal 200, and the second seal 272 is a secondary seal.The third seal 274 is a tertiary seal because it is formed due to the flexion of the sealing beads 220, 234, and has a third clamping load related to the thickness C and the conformity of the beads 220, 234, the third clamping load being smaller than the first and second clamping loads.

[0049] The second clamping load for the second seal 272 varies based on the operating conditions or condition of the cylinder 22 and the engine. For example, the second clamping load increases with increasing operating temperature and pressure of the cylinder 22 due to thermal expansion of the stopper element 252.

[0050] The seal 200 is configured such that the secondary seal 272, provided by the stopper element 252, is positioned adjacent the cylinder bore wall 218 and the cylinder's internal gases, and the secondary seal 272 is positioned between the cylinder 22 and the primary seal 270, provided by the overlap region 250 of the spacer and stopper layers. Both the primary and secondary seals 270, 272 are provided and positioned between the cylinder bore wall 218 and the third seal 274, provided by the sealing beads.By spacing the first seal 270 from the bore wall 218 and positioning the second seal 272 between the first seal 270 and the bore wall 218, the seal 200 has an improved functional seal to prevent in-cylinder gases from leaking into or through the bead and preventing engine ventilation. The second seal 272 prevents overpressurization of the seal 200 against the bore wall 218 to protect the third seal 274 formed with the sealing beads. The remote position of the first seal 270 from the bore wall 218 allows for some conformity of the seal 200 to the bore wall 218 when the head flexes into the bore wall at peak cylinder pressures and loads during engine operation and the second clamp load is less than the first clamp load.This additional conformation of the seal 200 to the bore wall 218, with the three seals 270, 272, 274 provided in the seal, provides improved sealing of the cylinder 22 as well as a reduction in fatigue or fracture of the layers of the seal 200 that would otherwise occur with a primary seal adjacent the bore wall.

[0051] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms of the invention. Instead, the terms used in the description are for the purpose of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. Furthermore, the features of the various implementation embodiments may be combined to form further embodiments of the disclosure.

Claims

[1] Power machine (20) comprising: a cylinder block (70) forming a cylinder (22); a cylinder head (72); and a cylinder head gasket (100, 200) positioned between the cylinder block (70) and the cylinder head (72), the cylinder head gasket (100, 200) having first and second outer layers (202, 204) and a spacer layer (206) positioned therebetween, the first layer (202) defining a first opening having a first diameter surrounding the cylinder (22) and a bead (220) surrounding the opening, the spacer layer (206) defining a second opening having a second diameter greater than the first diameter such that the second opening is concentrically disposed between the first opening and the bead (220), the cylinder head gasket (100, 200) comprising a stopper layer (242) extending inwardly from the spacer layer (206) to a circular stopper element (252), the stopper element (252) positioned adjacent to and aligned with the first opening, the stopper element (252) having a first thickness in an axial direction of the cylinder head gasket; wherein the spacer layer (206) and the stopper layer (242) are connected by an overlap therebetween to provide a second thickness in an axial direction; and wherein the second thickness is greater than the first thickness. [2] The engine of claim 1, wherein the spacer layer (206) has a third thickness, the third thickness being less than the first thickness. [3] The engine of claim 1, wherein the engine (20) is a compression ignition engine and the cylinder head (72) has a flat top surface defining intake and exhaust ports for the cylinder (22). [4] Cylinder head gasket (100, 200) for an engine (20), comprising: first and second outer layers (202, 204), each layer (202, 204) having an opening for surrounding a cylinder (22) and a bead (220, 234) surrounding the opening; and an intermediate layer positioned between the first and second layers (202, 204), the intermediate layer having a first axial thickness between the beads (220, 234), a second axial thickness adjacent the opening, and a third axial thickness between the beads (220, 234) and the openings, the second thickness being less than the third thickness. [5] Cylinder head gasket (100, 200) for an engine according to claim 4, wherein the intermediate layer further comprises: a spacer layer (206) positioned between the outer layers (202, 204) and having first and second opposing surfaces defining an opening therethrough, an edge of the opening being positioned between the beads (220, 234) and the openings of the first and second layers (202, 204) for surrounding a cylinder (22), the spacer layer (206) having the first axial thickness; a stopper layer (242) having a first end connected to the first surface adjacent the edge to provide the third axial thickness and a second opposite end; and a stopper element (252) connected to the second end of the stopper layer (242) and adjacent the opening, the stopper element (252) having the second axial thickness. [6] Cylinder head gasket (100, 200) according to claim 5, wherein the edge is positioned between the first and second ends of the stopper layer (242). [7] Cylinder head gasket (100, 200) according to claim 5, wherein the stopper element (252) has a first side wall partially defining the opening and a second, opposite side wall connected to the second end of the stopper layer (242). [8] Cylinder head gasket (100, 200) according to claim 5, wherein the stopper element (252) is spaced from the spacer layer (206). [9] Cylinder head gasket (100, 200) according to claim 5, wherein the spacer layer (206) is positioned between the first and second outer layers (202, 204) such that the first surface contacts the first layer and the second surface contacts the second layer when the cylinder head gasket (100, 200) is compressed. [10] The cylinder head gasket (100, 200) of claim 5, wherein the first outer layer (202) has an outer surface (208) and an opposite inner surface (212), the inner surface (212) positioned adjacent the intermediate layer, the outer surface (208) defining the bead (220) as a concave surface, the inner surface defining the bead (234) as a convex surface. [11] A method of sealing a power machine, comprising: Compressing a cylinder head gasket (100, 200) between a cylinder block and a cylinder head, thereby forming a primary seal at a first interface between the first and second outer layers (202, 204) and an intermediate layer, and forming a secondary seal at a second interface between the first and second outer layers (202, 204) and the intermediate layer, wherein the first interface is positioned between the second interface and a bead surrounding a cylinder (22), wherein compression of the cylinder head gasket (100, 200) requires a first clamping load to provide the primary seal and a second clamping load to provide the secondary seal, the second load being greater than the first load. [12] The method of claim 11, wherein the intermediate layer further comprises a stopper layer (242) and a spacer layer (206) at the first interface, such that the first interface is provided between the first and second outer layers (202, 204), the stopper layer (242) and the spacer layer (206) of the cylinder head gasket (100, 200); and wherein the intermediate layer further comprises a stopper element (252) such that the second interface is formed between the first and second outer layers (202, 204) and the stopper element (252), the stopper layer (242) connecting the stopper element (252) to the spacer layer (206). [13] The method of claim 11, wherein the first clamping load is greater than the second clamping load regardless of the operating temperature and operating pressure of the engine (20). [14] The method of claim 11, wherein the second clamping load increases with increasing operating temperature of a cylinder (22). [15] The method of claim 11, wherein the cylinder head gasket (100, 200) is compressed to form a tertiary seal at an interface between a bead formed by the first outer layer (202) and the intermediate layer. [16] The method of claim 11, wherein a thickness of the intermediate layer at the first interface in an axial direction is greater than a thickness of the intermediate layer at the second interface in the axial direction.

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