Improvements in or relating to internal combustion engines and pistons therefor

摘要

762,074. Driving-gear; charge pumps. BRITISH INTERNAL COMBUSTION ENGINE RESEARCH ASSOCIATION. June 3, 1953 [June 10, 1952; Aug. 12, 1952; Nov. 11, 1952], Nos. 14602/52, 20267/52 and 28402/ 52. Class 7 (2). [Also in Group XXVI] To give a compression ratio varying inversely with engine load, an I.C. engine piston has two relatively axially movable parts 1, 6, defining chambers 7, 8, of reciprocably variable volume fed with oil or other liquid from a common passage 9, 10 via respective one-way valves 11, 12, and passages (not shown) and having discharge passages and, in the case of the chamber 7, a discharge valve but not being in effective mutual communication. As shown the chambers 7, 8 discharge via oneway piston valves 13 and an adjustable orifice 29 respectively but the valves 13 may be replaced by a single annular spring plate valve and the orifice 29 by leakage along the piston surface. The passage 9, 10 also supplies a cooling chamber 28, via passages 26, with oil discharged via passages 27. The valve 12 may be in the gudgeon pin 2. In operation, due to the small size of the orifice 29, with decreasing load the piston gradually increases the compression ratio accordingly over a number of engine cycles but, due to the large size of the valves 13, with increasing load the piston quickly decreases the compression ratio accordingly. The invention is applicable to two-stroke or four-stroke engines with an effective expansion stroke greater than the effective compression stroke and an exhaust driven charge compressor. The Specification discusses in detail the working conditions obtainable when the invention is used in conjunction with an air or combustible mixture charge compressor, particularly the variabledelivery compressor of Specification 665,484 [Group XXVI] especially when driven by an exhaust gas turbine which may have a variable nozzle area, and/or when charge cooling is used. Compounding by using an exhaust gas turbine to drive the engine shaft or another shaft, when the engine may be merely a gas generator driving a charge compressor, is also discussed. Specification 762,110 also is referred to.