Conical Cylinder Bore for Engine Block Thermal Distortion
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Solution Overview
Problem
Cylindrical engine block cylinder bores result in increased piston friction due to geometry changes when the cylinder head is attached or the engine block heats up, particularly because water cooling only cools partial areas, leading to deformation and friction issues.
Innovation Solution
A method for manufacturing an engine block with a cylinder bore that includes an upper widening area and a subsequent enlargement area, allowing for rotational symmetry and compensation of thermal distortions through machining, which reduces piston friction by varying the bore diameter from larger at the top to smaller at the bottom, using an auxiliary structure to simulate a cylinder head for precise machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a cylindrical cylinder bore is used in the engine block, then the manufacturing process is simple, but piston friction increases due to geometry changes when the cylinder head is attached and the engine block heats up
Solution Approach 1:
The patent applies asymmetry by changing the cylinder bore from a cylindrical shape to a conical shape with a larger diameter at the top and a smaller diameter at the bottom. This asymmetric geometry compensates for the thermal expansion and deformation that occurs when the cylinder head is attached and the engine block heats up, thereby reducing piston friction while maintaining manufacturing simplicity through a single machining operation.
2Object-generated harmful factors
If the cylinder bore diameter is reduced to lower piston friction, then piston friction decreases, but the piston clearance becomes insufficient in the lower part of the bore
Solution Approach 1:
The patent applies local quality by creating a conical cylinder bore where the diameter varies along the length of the bore. The upper part has a larger diameter to reduce piston friction in the region most affected by thermal expansion, while the lower part has a smaller diameter to maintain adequate piston clearance. This localized variation in diameter optimizes both friction reduction and clearance requirements in different regions of the cylinder bore.
3Manufacturing precision
If an auxiliary structure is applied to simulate cylinder head for machining, then machining precision improves, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by using an auxiliary structure (such as a dummy cylinder head or blocking element) that is installed in the cylinder bore before the machining operation. This preliminary placement of the auxiliary structure provides the necessary support and reference for the machining tool to achieve the desired rotational symmetry and precision in the conical cylinder bore. After machining, the auxiliary structure is removed, leaving the precisely machined bore.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively reduces piston skirt friction and ring prestressing force, minimizing friction losses by maintaining rotational symmetry and accommodating thermal expansion differences, while simplifying the manufacturing process and maintaining tolerance within specified limits.
Implementation Method 1
The geometry of the cylinder bore typically changes when a cylinder head is fitted and/or the engine block heats up during operation. In particular, differential expansion of the engine block can also result from water cooling only cooling a portion of it.
Data Source
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AI summary
The present invention relates to a method for producing an engine block (1) of an internal combustion engine comprising the steps of: providing an engine block main body (8) comprising head fastening means (17) for fastening a cylinder head and also comprising at least one cylinder bore (4) for a piston of the combustion engine, wherein the cylinder bore (4) extends between an upper end (2) and a lower end (3), applying an auxiliary structure (15) to the engine block main body (8) and fastening the auxiliary structure (15) on the head fastening means (17), wherein the auxiliary structure (15) has a through-opening (16), which exposes the upper end (2) of the cylinder bore (4), establishing a rotational symmetry about a central axis (100) of the cylinder bore (4) by machining the cylinder bore (4), and introducing at least one enlarging region (7) into the volume enclosed by the cylinder bore (4) by machining the cylinder bore (4), wherein the enlarging region (7) has the effect that a diameter of the cylinder bore (4) is smaller at the upper end (2) than at the lower end (3).