Patent Application
20110030626
Embodiments described herein relate to engines of vehicles. More specifically, embodiments described herein relate to firing decks of engines for vehicles.
A cylinder block and a crankcase form the main structural component of an engine, and are often cast integral with each other. The crankcase forms the housing of a crankshaft, and the cylinder block defines at least one cylinder bore, within which combustion takes place to drive the crankshaft. The cylinder bore acts as a guide and as a sealing surface for a sliding piston and rings, and as such, the cylinder bore should be accurately machined to minimize out-of-roundness.
The cylinder block includes a firing deck at a top surface of the cylinder block. Head bolts, typically four for each cylinder bore, are introduced into bosses disposed through the firing deck to attach the cylinder block to a cylinder head.
Due to the uneven distributions of both cylinder block stiffness and clamping forces developed from the placement of the head bolts through the firing deck, the cylinder bores can undergo distortion. Mathematically, the bore distortion can be decomposed into many orders, and it is known that fourth order distortion of the cylinder bores can result in increased engine oil consumption. Additionally, the gasket sealing pressures are decreased at locations between the head bolts due to the structural weakness (less stiffness) there. The decreased gasket sealing pressures can in turn lead to combustion leaks and can also lead to engine failure.
To address the distortion in conventional crankcases, the firing deck has conventionally been reinforced by filling in shake-out holes that are located on the intake side only of the firing deck, or modifying the tooling for the casting to eliminate the shake-out holes. Further, the filled-in shake-out holes have been provided with arch-formations on a bottom or coolant side surface of the firing deck at the intake side only.
The firing deck of a conventional cylinder block typically has a uniform thickness, however to address distortion and to reinforce the firing deck, areas of increased thickness have sometimes been added to an exhaust side only of the firing deck. Further, the thickness of the firing deck between the cylinder bores (generally on a line connecting the centers of adjacent cylinder bores) has sometimes been increased up to fifty percent. However, bore distortions can continue to occur in the conventional cylinder block.
A firing deck for an engine crankcase includes a firing side surface and a coolant side surface. A plurality of cylinder bores are disposed through the firing deck from the firing side surface to the coolant side surface. The cylinder bores form a centerline defining an intake side of the firing deck and an exhaust side of the firing deck. A plurality of bosses through the deck from the firing side surface to the coolant side surface are disposed around each cylinder bore. A plurality of anti-distortion projections are disposed on a coolant side surface of the firing deck and provide the firing deck with a varied thickness. The anti-distortion projections are disposed on both the intake side and the exhaust side of the firing deck.
Referring now to
Referring to
The firing deck 16 also includes a plurality of bosses 30 disposed at generally 90-degree increments around each cylinder bore 18. With respect to the centers of the cylinders 20 in
To reduce the weight and for casting purposes, the firing deck 16 may have a plurality of shake-out holes 32 and/or other formations. The firing deck 16 may additionally have transfer ducts that are provided in a coolant side surface 34 of the firing deck to permit the circulation of coolant to the cylinder head. A firing side surface 35 (
The firing deck 16 has a plurality of anti-distortion projections 36 disposed between the plurality of bosses 30. Referring to
Specifically, at least one gusset formation 36 is disposed between two adjacent bosses 30. With respect to the centerline of the cylinders 20, the gusset formations 36 are located at 0-degrees, 90-degrees, 180-degrees, and 270-degrees. The gusset formations 36 are disposed on both the intake side 26 of the firing deck 16 and the exhaust side 28 of the firing deck.
Between the raised cylinder lip 22 and the raised exterior lip 24, and aside from the bosses 30 and the shake-out holes 32, the coolant side surface 34 of the deck portion 14 of the firing deck 16 is generally planar. The firing deck 16 generally has a uniform thickness at locations between the between the raised cylinder lip 22 and the raised exterior lip 24, except at the gusset formations 36, which provide locations of increased thickness of the firing deck. The gusset formations 36 are cast directly into the firing deck 16 and project from the coolant side surface 34 of the firing deck, the height H of the gusset formations providing the firing deck with a varied thickness.
The dimensions of each of the gusset formations 36 are generally the same, although it is possible that the gusset formations can differ from each other. The height H of the gusset formation 36 is generally uniform across the length L of the gusset formation, and is generally equal to the thickness of the firing deck 16, therefore generally providing the firing deck with twice the thickness in the y-axis at the location of the gusset formation. The width W of the gusset formation 36 is generally equal to the thickness of the firing deck 16 plus 1 mm. The length L of the gusset formations 36 on the intake side 26 and the exhaust side 28 generally extend from the raised cylinder lip 22 to the raised exterior lip 24. The gusset formations 36 located generally on the centerline of the cylinders 20 and at the interior of the firing deck generally extend from one raised cylinder lip 22 to the adjacent raised cylinder lip, and the gusset formations located on the centerline of the cylinders 20 and at the exterior generally extend from the raised cylinder lip to the raised exterior lip 24.
Referring now to FIGS. 2 and 5-7, a second embodiment of anti-distortion projection is a trapezoid formation 136 having varying thickness T across the width W2 of the trapezoid formation. Specifically, at least one trapezoid formation 136 is disposed between two adjacent bosses 30. With respect to the center of the cylinders 20, the trapezoid formations 136 are located at 0-degrees, 90-degrees, 180-degrees, and 270-degrees. The trapezoid formations 136 are disposed on both the intake side 26 of the firing deck 16 and the exhaust side 28 of the firing deck.
While a conventional firing deck 16 generally has a uniform thickness at locations between the cylinder bores 18, the bosses 30, and the shake-out holes 32, the trapezoid formations 136 provide locations of increased and varying thickness of the firing deck. The trapezoid formations 136 are cast directly into the firing deck 16 and project from the coolant side surface 34 of the firing deck.
The trapezoid formation 136 has a top width W1 that is generally equal to the thickness of the firing deck 16 minus 1 mm, and a bottom width W2 that is generally equal to three-times the W1. The height H of the trapezoid formation 136 is generally equal to the thickness T of the firing deck 16. With respect to the y-axis, the trapezoid formation 136 provides the firing deck 16 with twice the thickness 2T over the top width W1 of the trapezoid formation, and decreasing from twice the thickness 2T to no additional thickness T over the width W2 minus W1.
Other shapes and dimensions of anti-distortion projections 136 that have varying thickness across the length L or across the width W2 are possible. The firing deck 16 with anti-distortion projections 36, 136 may be formed of cast iron or aluminum alloy, however other materials are contemplated.
With the anti-distortion projections 36, 136, the improvements in fourth order distortion of the cylinder bore 18 over conventional uniform firing decks 16 can range from about a 20% improvement to about a 45% improvement, depending on the cylinder bores. Specifically, testing has shown that the improvement in fourth order distortions are improved by about 24% for the middle bores and about 43% for the end bores. Improvement of second order and third order distortion may also be realized with the anti-distortion projections 36, 136. Additionally, with the anti-distortion projections 36, 136, the minimum gasket sealing pressure between cylinders 20 is increased from about 131 MPa to about 140 MPa.
