Engine with noise reducing exhaust valve arrangement

#This invention relates to internal combustion engines and more particularly to exhaust valve arrangements for engines having multiple exhaust valves per cylinder, particularly two-cycle diesel engines.

#It is known in the art that one substantial cause of exhaust noise in internal combustion engines is the pulsed gas flow in the exhaust system caused by the periodic opening and closing of the exhaust valves. A significant portion of this noise is believed attributable to the initial surges of gas called blowdown pulses which issue from the cylinder upon the opening of the exhaust valve or valves at a time when the cylinder pressure is still relatively high. This blowdown pulse phenomenon occurs in nearly all internal combustion engines, since they are not usually arranged or operated in a manner that permits expansion of the cylinder gases to atmospheric pressure before opening of the exhaust valves. The phenomenon is generally more noticeable in diesel engines which are usually unthrottled and is especially severe in two-cycle engines of the type in which the exhaust valves are opened relatively early in the expansion stroke to permit exhaust blowdown to occur before the intake ports are opened.

#The present invention provides an arrangement for reducing the severity of exhaust blowdown pulses in engines that are provided with more than one exhaust valve per cylinder and means for separately actuating those valves. Although usable with both two and four-stroke engines of the gasoline and diesel type, it is thought the benefits of the invention will be most pronounced when applied to two-stroke cycle diesel engines of the well known uniflow scavenged, ported intake design having multiple exhaust valves in each cylinder.

#These and other features of the invention will be more fully understood from the following description of a preferred embodiment of the invention illustrated in the accompanying drawing in which:

#FIG. 1 is a fragmentary cross-sectional view of a two-stroke cycle uniflow scavenged diesel engine having an exhaust valve arrangement according to the present invention;

#FIG. 2 is a fragmentary cross-sectional view from the plane indicated by the line 2--2 of FIG. 1 and illustrating portions of the novel exhaust valve arrangement;

#Referring now in detail to the drawing, numeral 10 generally indicates an internal combustion engine of the two-stroke cycle, uniflow scavenged diesel type well known in the art and of which FIG. 1 illustrates only a pertinent fragmentary portion of one cylinder bank. Engine 10 includes the usual cylinder block 11 providing a plurality of cylinders defined by removable liners 12 having ports, not shown, for the admission of air in known fashion.

#The ends of the cylinders in each bank are closed by a cylinder head 14 which includes for each cylinder a pair of exhaust ports 15, 16 connecting with the cylinder and with a common lateral exhaust passage 18 that opens through the side of the head and connects with an exhaust manifold 19. The manifold in turn may connect with atmosphere through the usual exhaust pipe, not shown.

#The cylinder head also carries for each cylinder a pair of exhaust valves 20, 22 of the poppet type which include heads adapted to seat against valve seats in the exhaust ports 15, 16, respectively. Valves 20, 22 are movable in known fashion to open or close the irrespective exhaust ports to the passage of exhaust gases therethrough. Intermediate the valves, the cylinder head carries a fuel injector 23 at each cylinder location.