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The Mini-Ecoboy has a Rhombic mechanism as a piston drive mechanism. It consists of two gears, two yokes and four connecting rods as shown in a belows photograph. When length of the connecting rod, length of crank arm, and location of the gears were set to a suitable ratio, phase angle between a displacer and a power piston was set to 90 degrees. In this mechanism, both pistons move in a straight line completely, if it is assembled ideally. 
However, when it has not sufficiently high assembling accuracy, the side thrust force and friction loss of the both pistons increase. In order to make the friction loss low enough even if the assembling accuracy was not good, a lot of free joints were added to the power piston and to the displacer rod of the prototype engine as shown in the figure to the right.
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[ Mini-Ecoboy ] [ Stirling Engine Dictionary ] |
All Right Reserved, Copyright(C), 1999, 2000, 2001 Koichi Hirata (khirata@nmri.go.jp) |
Piston Drive Mechanism