Two-Stroke Engine Scavenging Block Design
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Solution Overview
Problem
Existing two-stroke cycle combustion engines of the air scavenging type face challenges in removing casting burrs from cylinder blocks and adjusting the air intake amount due to complex and costly structures, particularly when air is introduced through recesses in the reciprocating piston.
Innovation Solution
The design incorporates scavenging blocks and covering members that expose the scavenging ports for easy burr removal and simplify the structure by introducing air into scavenging passages through radially outward passages, allowing for adjustable air intake amounts and efficient scavenging without varying scavenging timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air is introduced into the second scavenging passage through a recess in the outer periphery of the reciprocating piston, then the air can be supplied to suppress blow-off of the air/fuel mixture, but the structure becomes complicated and manufacturing cost increases
Solution Approach 1:
The invention extracts the air introduction function from the reciprocating piston and relocates it to the cylinder block. The recess is removed from the piston and the air introduction passage is formed directly in the cylinder block, separating the scavenging function from the piston's reciprocating motion function. This simplifies the piston structure while maintaining the air introduction capability for blow-off suppression.
Solution Approach 2:
The invention segments the scavenging system into distinct components: the cylinder block with integrated air introduction passage, the piston with simplified structure, and the scavenging passages. This segmentation allows each component to be optimized independently, reducing overall system complexity while maintaining functional effectiveness.
2Reliability
If air is introduced through a recess in the reciprocating piston, then the scavenging function is achieved, but the manufacturing cost becomes high due to structural complication
Solution Approach 1:
The invention merges the air introduction passage with the cylinder block structure, combining two previously separate functions (cylinder block containment and air introduction) into a single integrated component. This eliminates the need for separate piston recesses and reduces the number of parts requiring precision manufacturing, thereby lowering manufacturing costs.
Solution Approach 2:
The air introduction function is extracted from the expensive-to-manufacture reciprocating piston and relocated to the cylinder block, which is already being manufactured with complex internal passages. This redistribution of functions to the more cost-effective component reduces overall manufacturing cost.
3Ease of manufacture
If the air introduction passage is formed between a recess in the cylinder block and a plate-shaped lid, then the structure can be assembled, but the removal of casting burrs becomes complicated and time-consuming
Solution Approach 1:
The invention performs preliminary action by forming the air introduction passage as an integral part of the cylinder block's casting structure, with the passage opening facing the combustion chamber. This preliminary design consideration allows casting burrs to be accessed and removed easily from the combustion chamber side before final assembly, eliminating the need for complex post-casting burr removal operations.
Solution Approach 2:
Instead of forming the air introduction passage opening on the external surface of the cylinder block (where burrs would be difficult to reach), the invention inverts the approach by opening the passage toward the combustion chamber interior. This allows easy access to the passage entrance for burr removal from within the combustion chamber space.
4Ease of manufacture
If the introducing passage is formed in the cylinder block with opening towards the combustion chamber, then burr removal is facilitated, but the structure becomes more complex
Solution Approach 1:
The cylinder block is designed with multi-functionality, serving both as the containment structure for the combustion chamber and as the housing for the air introduction passage. The passage wall serves dual purposes: structurally supporting the combustion chamber and defining the air introduction pathway. This multi-functionality reduces the need for separate components, offsetting the apparent structural complexity with functional integration.
Data Source
AI summary
A two-stroke cycle combustion engine of an air scavenging type includes one or more scavenging passages (13, 14) for communicating a crank chamber (2a) and a combustion chamber (1a) with each other, an air passage (10) for supplying an air (A), an introducing passages (16) for introducing the air (A) from the air passage (10) into an upper portion of each scavenging passage (13, 14) from a direction radially outwardly of a cylinder block (1), and a covering member (21) for covering the introducing passage (16) from an outer side. The covering member (21), the upper portion of each scavenging passage (13, 14) and a part of the introducing passage (16) are formed integrally with each other by a scavenging block (20).