Internal-combustion engines – Particular piston and enclosing cylinder construction – Cylinder detail
Reexamination Certificate
1999-06-18
2001-04-17
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Particular piston and enclosing cylinder construction
Cylinder detail
C123S041740
Reexamination Certificate
active
06216658
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to a cylinder block for an internal combustion engine and more particularly relates to a cylinder block with enhanced structural stiffness.
Deflection of a cylinder block of an engine is generally undesirable. Such deflection contributes to undesirable vibrational modes and noise emission levels when an assembled engine is running. It is known to provide stiffened block components in order to generally reduce the level of noise emitted from a running engine. For example, stiffened cylinder block walls are disclosed in U.S. Pat. Nos. 4,470,376; 4,461,247; and 4,627,394.
Block deflection can also lead to manufacturing complications. A conventional cylinder block substantially deflects between a free condition and an assembled condition due to the loads and stresses from cylinder head bolts and other components. Such distortion leads to an improper fit of components and unwanted tolerance changes. Accordingly, simulated loads are applied to conventional cylinder blocks during machining operations. An example of such a process is known as torque plate honing, whereby a torque plate is bolted to the conventional block to approximate the loads of a bolted-on cylinder head during honing of the cylinder bores. The bores are thus round when the cylinder head is later mounted to the block. Torque plate honing is necessitated by the degree of deflection of a conventional block. Otherwise, if the cylinder bores were machined while the block was in an unloaded condition, the cylinder bores would deflect from a round shape when the block is in its loaded, assembled condition, resulting in imprecise tolerances, undesirable wear patterns and poor oil consumption. Unfortunately, torque plate honing is costly and difficult to control in a production environment.
Conventional cylinder blocks have various openings formed therein to permit the connection of conduits, hoses, and other components. For example, an opening is conventionally formed in the wall of a cylinder block to accommodate the mounting of an oil cooler in fluid communication with the water jacket. A lack of structural material in such an opening leads to undesirable flexibility of the block. Accordingly, a need exists to design such a cavity with improved stiffness.
Another component known to emit noise is a cover plate that is bolted to a side of the cylinder block to cover reciprocating pushrods that extend from the crankcase to the cylinder head. The cover plate is known to transmit substantial levels of noise.
Accordingly, design features are desirable which provide a stiff block structure in order to reduce noise emission levels and to reduce deflection between free and assembly-loaded conditions.
SUMMARY OF THE INVENTION
According to the invention, a cylinder block is provided with enhanced stiffness. The cylinder block has an upper portion with a plurality of cylinder bores and a lower portion which forms a portion of the crankcase. Both the upper and lower portions of the block include sculpted outer wall portions. More specifically, the sculpted outer wall portions include a series of curved, non-planar sections. Each section is shaped generally as a partial cylinder so that the sculpted portion has an undulate shape. It has been found that the curved non-planar sections provide substantially greater stiffness relative to conventional planar wall sections.
An embodiment of the block may include stiffening ribs which extend between the cylinder bore and the outer wall of the block. The ribs are positioned to optimize cylinder bore stiffness. Bolt bosses may be integrally formed in the ribs having bolt holes to accommodate mounting of the cylinder head.
In an embodiment, the cylinder block includes an enclosed closed oil cooler cavity having a wall extending between the cavity and the water jacket. This wall provides structural rigidity to the cavity area, enhancing the stiffness of the block.
The cavity wall has an opening, which permits fluid communication between the cavity and the water jacket. A water pump outlet provides a flow of coolant into the cavity; however, the cavity wall opening is distally located relative to the water pump outlet so that coolant is advantageously guided to flow across the oil cooler with enhanced effectiveness.
In an embodiment, the block includes a closed tappet cavity, further enhancing stiffness of the block. More specifically, the tappet cavity has an upper wall that extends across the deck of the block. Holes are provided in the upper wall to permit pushrods to protrude upwardly to the cylinder head. The upper wall closing the tappet cavity provides additional stiffness to the block.
An advantage of the present invention is to provide a cylinder block with enhanced stiffness.
Another advantage of the present invention is to provide a cylinder block that reduces engine noise.
A further advantage of the present invention is to provide a cylinder block that eliminates a need for a torque plate honing process.
Yet another advantage of the present invention is to provide a cylinder block that reduces oil consumption.
A still further advantage of the present invention is to provide a cylinder block that enhances oil-cooling efficiency.
Additional features and advantages of the invention are described in, and will be apparent from, the Figures, description, and claims herein.
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Chimonides Nikos Jon
Clamp Andrew
Huestegge Hermann-Josef
Korte Craig James
Nydegger Hans-Jurg
Cummins Engine Company Ltd.
Leydig , Voit & Mayer, Ltd.
McMahon Marguerite
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