GB717856A - Improvements in or relating to four-stroke cycle internal combustion engines - Google Patents

Abstract

717,856. Cycles; regulating; direct-injection engines. BRODERSON, N. O. Feb. 8, 1952, No. 3389/52. Classes 7(2), 7(3) and 7(6) A four-stroke engine is operated by admitting at each cycle to the or each cylinder a substantially constant air charge and a fuel charge variable with engine load, a portion only of the fuel charge being, over a substantial load range, injected during the compression stroke into an auxiliary combustion chamber 17, Fig. 4, in which ignition occurs and which has a volume not substantially exceeding that of a main combustion space 14 with which it communicates via a restricted passage 18 and which forms with the remainder of the cylinder working space a main chamber in which the piston 12 operates, and the portion being so varied in amount as always to provide a mixture distribution such that an ignitable mixture exists in the chamber 17 at the time of ignition. As shown, air or weak combustible mixture aspired via a valve 21 auxiliary to and in parallel with the main inlet valve 15 passes over an injection nozzle 20 and igniter 19. At low engine loads liquid or rich mixture injection from the nozzle 20 starts only at the beginning of the compression stroke so that the injected fuel is largely confined to the chamber 17 to give an ignitable mixture therein despite the low amount of total fuel charge. At higher engine loads injection commences during the induction stroke so that part of the injected fluid enters the main chamber to give a more uniform overall mixture strength, the injection period being divided equally between the intake and compression strokes but extending farther into each with increasing engine load. The chamber 17 has a volume one-fifth of that of the total combustion space and may be formed in a supplementary head 16 fitting into a conventional cylinder head ignition plug opening. The exhaust valve (not shown), is in the offset portion of the space 14. At high loads the mixture in the space 14 is too weak, and that in the chamber 17 too rich, to detonate. In Fig. 2, the single inlet valve 7 opens into an auxiliary combustion chamber 5 shaped to form with the main combustion space 6, which may be of equal volume thereto, a figures-ofeight in plan. An igniter 9 and exhaust valve 8 are provided. The injection nozzle 10 may be situated in the main space 6, or at the restriction between the chamber 5 and space 6, so long as it directs its jet into the chamber. With this design. at low engine loads injection may not commence until after the start of compression, and, with increasing loads, the mean point of the injection period is advanced progressively, as by advancing the start of injection and keeping its finishing point constant. In both embodiments, numerical examples are given of mixture strength distribution at differing loads. Preferably, injection always occurs to some degree on the compression stroke, though with suitable engine designs it may occur wholly on the intake stroke at some loads. Engines according to the invention may have all the air charge admitted directly into the main chamber together with all the fuel charge other than the portion injected during the compression stroke into the auxiliary combustion chamber, and may be so controlled that the amount of fuel injected per cycle is variable at will and the mean period of injection varies with engine load.