This invention relates generally to cylinder head gaskets from internal combustion engines.
Multilayer steel (MLS) cylinder head gaskets are known to be used between the head and the block on an engine to effect a fluid-tight seal of the combustion cylinders. More demand is placed on such MLS gaskets with rising engine temperatures and pressures calling for stronger gaskets that can withstand the conditions. A common approach for increasing the strength of a gasket is to add one or more additional layers to the gasket, but each gasket layer poses a risk for leakage as each layer introduces two more interfaces that may be prone to leakage.
A cylinder head gasket for an internal combustion engine includes a plurality of metallic gasket layers defining a plurality of combustion openings and including a sealing areas of the gasket encircling each cylinder opening and a body area of the gasket away from the sealing areas. The plurality of metallic gasket layers include a pair of outermost layers, a pair of inner layers and at least one distance layer. The inner layers include ring-shaped sealing portions surrounding each of the cylinder openings having full bead embossments that project away from one another toward the outermost layers. The sealing portions have a material thickness of at least 0.3 mm and the combined material thickness of all layers of material in the sealing areas is greater than a combined material thickness of all layers of material in the body of the gasket adjacent the sealing areas.
According to another aspect, a multilayer steel cylinder head gasket for an internal combustion engine includes a pair of outermost layers fabricated of a first steel material having a first hardness and a first thickness. The pair of first layers includes a plurality of combustion cylinder openings. An intermediate layer is provided and is fabricated of a second steel material having a second hardness and second thickness. The intermediate layer includes an inner edge that surrounds each or all of the plurality of combustion cylinder openings of the outermost layers in radially outwardly spaced relation thereto. Also provided is a pair of opposing elastic sealing rings associated with each of the plurality of combustion cylinder openings. The sealing rings are each fabricated of a third steel material having a third hardness and each are formed with a full bead embossment the encircles the associated combustion cylinder openings, and with the full bead embossments of each pair of sealing rings projecting away from one another toward the outermost layers. The sealing rings are radially inset in relation to the inner edge of the intermediate layer. The outermost layers and sealing rings are made of the same stainless steel material and also have the same hardness. The material of the intermediate layer is different than that of the outermost layers and sealing rings and has a relatively lower hardness. The sealing rings each have a thickness of at least 0.3 mm which is relatively greater than the thickness of each of the outermost layers. The intermediate layer has a thickness that is greater than the thickness of each of the sealing rings and outermost layers. The thickness of the intermediate layer is less than twice the material thickness of each of the sealing rings.
These and other features and advantages will be better understood when considered in connection with the following detailed description and drawings representing non-limiting embodiments, in which:
A gasket for an internal combustion engine is generally shown at 10 in
The cylinder head gasket 10 includes a plurality of metallic gasket layers to be described in greater detail below. The gasket 10 includes sealing areas 14 that immediately surround the combustion cylinder openings 12. A body area 16 of the gasket 10 borders the sealing areas 14. As will also be explained in more detail below, the layers that make up the gasket have predetermined material thicknesses and the stack-up dimension of the layers in the sealing area 14 is greater than the stack-up dimension of the layers outside the sealing areas 14, namely in the body area 16 of the gasket 10.
Further details of a first embodiment of the gasket 10 are illustrated in
The outermost layers are fabricated of a stainless steel material and are of a predetermined material thickness t1 and material hardness. The material composition and properties of the outer layers 18, 20 are preferably the same, that is, they are made of the same steel alloy composition, have the same hardness and the same thickness. The preferred material for the outermost layers 18, 20 is full hard SS301 having an uncoated material thickness t1 of 0.25 mm+/−0.012.
The gasket 10 includes a distance layer 24 arranged between the outermost layers 18, 20. The distance layer 24 includes necessary openings and passages, as needed, to enable the gasket to allow the sealed passage of gases and fluids through the gasket 10. At least one opening 26 is defined by an inner edge of the distance layer and communicates with the cylinder openings 12 of the gasket. However, unlike the fully closed cylinder openings provided by the outermost layers 18, 20, the material of the distance layer 24 does not extend fully between adjacent cylinder openings 12, giving the opening 26 an undulating shape across the cylinder openings 12, including scalloped portions 26a that project inwardly toward one another from opposite sides between adjacent cylinder openings 12 but are spaced apart across intervening gaps 26b in the narrowing part of adjacent cylinders 12 where there is no distance layer material present, but where there are the web portions 22 of the overlying outermost layer material 18, 20.
The gasket 10 also includes a pair of intermediate functional layers 28, 30 associated with each cylinder opening 12. The intermediate layers 28, 30 are disposed between the outermost layers 18, 20 and comprise sealing rings or ring portions 32, 34 that encircle each opening 12. The sealing rings 32, 34 are each formed with a full bead embossment 36, 38 that are circumferentially continuous and project out of the plane of each sealing ring. The sealing rings 32, 34 for each cylinder opening 12 are arranged in stacked pairs and are oriented with the beads 36, 38 opposed, aligned and projecting away from one another toward the outermost layers 18, 20. There are preferably no other bends, folds or deformations in the sealing rings 32, 34 according to this embodiment and they are essentially annular in construction but may and preferably do include radial tabs 40, 42 which project radially outwardly of the seal rings 32, 34. The tabs 40, 42 are captured between the outermost layers 18, 20 and serve as a poka-yoke alignment aid during assembly of the gasket 10. When the sealing rings 32,34 of each set are properly oriented with their full beads 32, 34 aligned and projecting away from one another, the tabs 40, 42 are able to nest within associated cut-outs or slots 44 provided along the edge of the opening 26 of the distance layer 24. The shape and location of the tabs 40, 42 and gaps 44 assure that the sealing rings 32, 34 can be installed only in the proper orientation or else the tabs 40, 42 will not register with the slots 44 to assure optimum function and performance of the gasket 10 in use.
In the first embodiment, the distance layer 24 is generally planar and is adjacent to but does not directly engage the sealing rings 32, 34, apart from receiving the tabs 40, 42 in the slots 44. The sealing rings 32, 34 are radially inset from the inner edge 26 opening of the distance layer 24, apart from the nesting of the alignment tabs 40, 42. The beads 36, 38 of the sealing rings 32, 34 extend above opposite upper and lower surfaces of the distance layer 24, preferably by an equal amount in either side. The centerline plane of the distance layer 24 extends between the two sealing rings 32, 34 such that they are opposed on opposite sides of the plane.
The outermost layers 18, 20 are fabricated of a first steel material. The distance layer 24 is fabricated of a second steel material. The sealing rings 32, 34 are fabricated of a third steel material.
The outermost layers 18, 20 and sealing rings 32, 3 are made of the same stainless steel material and have the same material hardness. The material of the distance layer 24 is different than the material of the outermost layers 18, 20 and rings 32, 34, and the material of the distance layer 24 has a relatively lower hardness.
The sealing rings 32, 34 each have a material thickness t2 that is greater than the material thickness t1 of each of the outermost layers 18, 20. The material thickness t2 of the sealing rings 32, 34 is equal to or greater than 0.3 mm, and more preferably 0.35+/−0.015 mm. The thickness t3 of the distance layer 24 is greater than the thickness of each of the sealing rings 32, 34 and outermost layers 18, 20, but is less than twice the thickness of each of the sealing rings 32, 34.
The preferred material for the outermost layers 18, 20 and sealing rings 32, 34 is full hard SS301. The preferred material for the distance layer 24 is half hard SS430 stainless steel. The outermost layers 18, 20 have a thickness of about 0.25 mm. The thickness of the distance layer is preferably about 0.55 mm+/−0.05. The thickness of the sealing rings 32, 34 enables the beads 36, 38 to exert great sealing force under conditions of high engine compression and temperature. The beads 36, 38 in the sealing area 14 are to be limited to those provided by the sealing rings 32, 34 and are in the form of a pair of opposed sealing beads that face away from one another. As such, the bead portion 36, 38 of the sealing areas 14 made up of just two opposing beads 36, 38 of the sealing rings 32, 34 that surround each cylinder opening 12. The beads 36, 38 have a preferred width of about 2.6 mm+/−0.3 and a height of 0.5 mm+/−0.3. It is further preferred that the beads 36, 38 are pre-set. The beads 36, 38 are initially formed with an as-embossed height that it greater than the pre-set height. For example, the beads 36, 38 may have an as-embossed height of 0.15 mm+/−05 but then during manufacture are compressed flat under heavy load to impart controlled plastic deformation to the beads 36, 38 to achieve the resultant pre-set height of 0.05 mm+/=0.3 mm. The pre-set condition of the beads 36, 38 serves to toughen the beads and make them less prone to cracking in use under conditions of heavy compression load and temperature cycling. The combined thickness of the pre-set beads is greater than the thickness of the distance layer 24.
Common to all embodiments is that the functional layers (or ring portions) are at least 0.3 mm in thickness, they contain full beads surrounding the cylinder openings that face away from one another, the functional layers are made of the same material and have the same hardness as the outermost layers but the material of the functional layers is relatively thicker than the outermost layers, that at least one distance layer is provided between the outermost layers and is of a relatively softer steel material, and that the thickness of the gasket in the sealing area surrounding each cylinder opening is greater than the thickness of the gasket in the body area adjacent the sealing areas such that the sealing beads are compressed fully flat in use when clamped between a cylinder head and block of an engine. The various embodiments represent different constructions for achieving these objectives.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that the invention may be practiced otherwise than as specifically described while still being within the scope of the invention.