Rocking Beam Stirling Drive for Low-Side-Load Piston Motion
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Solution Overview
Problem
Existing Stirling cycle machines face challenges with friction and side loads due to piston misalignment and lateral forces, leading to increased noise, reduced efficiency, and shorter engine life, with previous improvements resulting in heavier and bulkier machines.
Innovation Solution
A rocking beam drive mechanism that converts linear piston motion to rotary motion, using a rocking beam with a rocker pivot, coupling assemblies, and a crankshaft, minimizing side loads through the use of flexible joints and seals like rolling diaphragms to maintain linear piston motion and reduce friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional piston and crankshaft linkage is used, then rotary motion is achieved, but side loads and friction increase due to piston misalignment
Solution Approach 1:
A rocking beam is introduced as an intermediary component between the piston and crankshaft. The piston connects to the rocking beam, which then connects to the crankshaft, serving as a mediator that transforms the force transmission path and reduces direct side loads on the piston-crankshaft interface
Solution Approach 2:
The rocking beam provides dynamic motion conversion, allowing the piston to maintain more linear motion while the beam itself rocks to accommodate the rotational motion requirement, adapting the rigid linkage into a more flexible dynamic system
2Object-affected harmful factors
If drive mechanisms are improved to reduce side loads, then friction decreases, but the machine becomes heavier and bulkier
Solution Approach 1:
The rocking beam serves multiple functions simultaneously: it converts piston linear motion to crankshaft rotary motion, reduces side loads on the piston, and maintains a compact structure. This multi-functionality avoids the need for additional separate components that would increase weight
Solution Approach 2:
The motion conversion function and the side load reduction function are merged into a single rocking beam component, rather than requiring separate mechanisms for each function, thereby avoiding increased weight and bulk
3Device complexity
If piston misalignment is allowed, then simpler drive mechanisms can be used, but noise and piston wear increase
Solution Approach 1:
The rocking beam acts as an intermediary that absorbs and accommodates motion variations, allowing the piston to maintain better alignment while still achieving the required rotary motion output, thereby reducing noise and wear without significantly increasing complexity
Data Source
AI summary
A Stirling cycle machine. The machine includes at least one rocking drive mechanism which includes: a rocking beam having a rocker pivot, at least one cylinder and at least one piston. The piston is housed within a respective cylinder and is capable of substantially linearly reciprocating within the respective cylinder. Also, the drive mechanism includes at least one coupling assembly having a proximal end and a distal end. The linear motion of the piston is converted to rotary motion of the rocking beam. Also, a crankcase housing the rocking beam and housing a first portion of the coupling assembly is included. The machine also includes a working space housing the at least one cylinder, the at least one piston and a second portion of the coupling assembly. An airlock is included between the workspace and the crankcase and a seal is included for sealing the workspace from the airlock and crankcase. A burner and burner control system is also included for heating the machine and controlling ignition and combustion in the burner.