Expendable Salt Cores for High Pressure Die Cast Engine Blocks
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Solution Overview
Problem
High pressure die casting methods struggle to produce closed deck engine blocks with optimal water jacket cooling passage geometry and structural rigidity due to the fragility of existing core materials and the need for additional steps in manufacturing, leading to structural weaknesses and increased scrap rates.
Innovation Solution
The use of multiple small expendable cores in conjunction with a metallic slide to form metal bridges between the water jacket and cylinder bores, allowing for improved bore stiffness and structural support during high pressure die casting, with the cores being made of materials like salt, bonded sand, or semi-permanent metal inserts that can be easily removed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional sand cores or salt cores are used in high pressure die casting, then water jacket passages can be formed, but the cores are too fragile to withstand the influx of pressurized molten metal while retaining their necessary shape
Solution Approach 1:
The core is divided into multiple segments: a fragile salt core for defining the water jacket passage geometry and multiple rigid support arms that extend from the salt core to the cylinder bore. The support arms are structured with varying thicknesses - thicker at the ends for strength and thinner in the middle to allow salt dissolution - creating a segmented structure that simultaneously provides geometric definition and mechanical strength.
Solution Approach 2:
The core assembly combines two different materials with complementary properties: salt (sodium chloride) which is chemically reactive and dissolvable for creating clean passages, and a rigid material (such as metal or strong polymer) for the support arms that provide structural strength to withstand high pressure die casting forces. This composite core structure leverages the advantages of both materials.
2Strength
If a closed deck design is implemented to enhance cylinder bore stability, then structural rigidity is improved, but the complexity of casting increases due to tight tolerances and the need for core support
Solution Approach 1:
The support arms are pre-formed as integral parts of the core assembly before casting. The rigid support structures are manufactured in advance with the correct geometry and strength characteristics, then positioned within the mold cavity. This preliminary preparation ensures that the complex structural requirements for closed deck stability are met without adding complexity to the actual high pressure die casting process.
Solution Approach 2:
The support arms act as intermediary structures between the fragile salt core and the cylinder bore. They transfer and distribute the mechanical loads, providing the necessary support to maintain tight tolerances and ensure cylinder bore stability during casting. The support arms mediate between the conflicting requirements of core fragility and structural strength.
3Manufacturing precision
If a large amount of salt is used for the salt core to define water jacket passages, then passage geometry can be achieved, but difficulty arises in removing the large amount of salt after casting
Solution Approach 1:
The support arms are designed with varying thicknesses along their length, with thinner sections strategically positioned where salt removal is most critical. These thinner regions allow for more efficient salt extraction and dissolution after casting. The support arm structure is optimized to facilitate the removal of salt material while maintaining the necessary structural support during the casting process.
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
This approach enables the production of closed deck engine blocks with enhanced structural rigidity and reduced manufacturing complexity, improving the integrity of the water jacket and cylinder bore support, while minimizing scrap rates and ensuring unitary casting without leaks.
Implementation Method 1
The salt portion of the composite core is dissolved
Data Source
AI summary
A slide for the high pressure die casting of at least one closed deck engine block having at least one cylinder is disclosed. The slide includes a tool steel portion with reliefs for forming a water jacket surrounding each cylinder. At least one expendable core is located in each relief, the expendable core having an inner surface and an outer surface with an aperture extending therethrough. The outer surface and inner surface of the expendable core is coextensive with an inner surface and outer surface of the tool steel portion. A method for high pressure die casting a closed deck engine block using the disclosed slide and expendable cores is also disclosed. The expendable cores are separable from the reliefs in the slide, and form bridges or supports across a water jacket to add stiffness and rigidity to the cast engine cylinders.