Piston Engine Torque Control via Crankpin Offset and Auxiliary Piston
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Solution Overview
Problem
Existing piston engines with crankpin offset compromise output torque while attempting to reduce side force on the cylinder wall, and existing algorithms for auxiliary pistons are not optimized for both side force reduction and torque enhancement.
Innovation Solution
The implementation of an auxiliary piston system with a shorter connecting rod and smaller crankshaft radius, moving at different frequencies than the main piston, to constrain the combustion chamber volume and maintain a constant clearance volume over a wider crank angle range, thereby reducing side force and increasing output torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If crankpin offset is increased to reduce side force on cylinder wall, then side force is reduced, but output torque on crankshaft is compromised
Solution Approach 1:
The invention divides the piston system into two independent pistons: a main piston connected to the crankshaft via a connecting rod with crankpin offset (to reduce side force), and an auxiliary piston connected directly to the crankshaft centerline (to generate torque). This segmentation allows each piston to perform its specialized function without compromising the other, resolving the contradiction between side force reduction and torque generation.
Solution Approach 2:
The invention merges the functions of side force reduction and torque generation into a single engine cycle by combining the main piston (optimized for side force reduction through offset) and the auxiliary piston (optimized for torque generation through centerline connection). The two pistons work simultaneously in the same cylinder, with the auxiliary piston compensating for the torque loss caused by the main piston's offset configuration.
2Use of energy by moving object
If auxiliary piston is added to extend clearance volume and improve fuel efficiency, then fuel efficiency is improved, but existing algorithms are not optimized for both side force reduction and torque enhancement
Solution Approach 1:
The invention optimizes specific parameters of the auxiliary piston system: the connecting rod length ratio (l/L) and crankshaft radius ratio (r/R) are set within specific ranges (0.2-0.4 and 0.3-0.5 respectively) to achieve the dual objectives of side force reduction and torque enhancement. These parameter changes provide a simplified optimization approach compared to complex algorithms, while maintaining fuel efficiency improvements.
3Power
If auxiliary piston connects to crankshaft centerline, then torque is enhanced, but side force reduction is compromised
Solution Approach 1:
The invention segments the torque generation and side force management functions between two pistons: the auxiliary piston connects to the crankshaft centerline to maximize torque generation, while the main piston uses crankpin offset to minimize side force. This segmentation allows each piston to be optimized for its specific function without compromising the other.
Data Source
AI summary
A piston engine is provided; the piston engine has a cylinder, a main piston and an auxiliary piston; a combustion chamber is formed between the main piston and the auxiliary piston within the cylinder; the main piston has an crankpin offset L0, the auxiliary piston and the main piston move in different frequencies, an extended constant V≈Vc of the combustion chamber is formed from θ to >10° CA; when at a=θ=arc sin[L0/(L+R)] the main piston is at its top dead center; at a=arc sin(L0/R) the side force on the main piston is 0; when peak pressure of combustion is located at PPmax by choosing ignition timing, the most effective torque can be obtained; the torque is controlled by the amount of fuel injected; engine knocking can be prevented by retarded ignition at a>θ.