GB1368721A - Piston for internal combustion engines - Google Patents

Abstract

1368721 Pistons; connecting rods; ratchet mechanisms MAHLE GmbH 2 Jan 1973 [12 Jan 1972] 233/73 Headings F2T and F2Q A piston having a skirt 2 rotatably mounted on a gudgeon pin seat 1 is progressively rotated in its cylinder 15 during operation by means comprising an internally toothed ratchet ring 3 secured to the inner surface of the skirt, a bowed leaf spring 11 having one end engaging the ratchet teeth 4 and secured at its other end to the seat 1, and a control member which during engine operation deflects the spring in a manner to increase the distance between its ends and thus cause stepwise rotation of the skirt. In the embodiment shown in Fig. 1, the control member 14 is secured to the engine cylinder 15 and as the piston approaches bottom dead centre, extends into the open end of the skirt to engage and extend the spring thus rotating the ring 3. In other embodiments, Figs. 3 and 4 (not shown), the control member is a cam (16, 17) on the connecting-rod (9) which cam engages the spring as the connecting-rod approaches maximum angle of swing. In another embodiment, Fig. 5, for a variable compression ratio piston in which the seat 1 and skirt 2 are relatively axially displaceable and closed chambers 18 and 19 above and below the seat are supplied with pressure oil from a passage in the connecting rod via conduits 20, 21 and non-return valves 22, 23, the spring 11 is actuated by the stem of a spring- loaded relief valve 28 operated when excess oil pressure occurs in the chamber 18 during the engine cycle. The chamber 19 communicates through a throttle aperture (not shown) with the engine crank chamber.