Internal-combustion engines – Poppet valve operating mechanism – Hydraulic system
Patent
1995-12-04
1996-12-24
Moulis, Thomas N.
Internal-combustion engines
Poppet valve operating mechanism
Hydraulic system
91453, F01L 902
Patent
active
055865267
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a large two-stroke internal combustion engine, in particular a main engine of a ship, having a hydraulically driven cylinder member, such as a fuel pump or an exhaust valve, in which the hydraulic drive of the member comprises a driving piston journalled in a hydraulic cylinder which, through a flow passage, communicates with a spool valve, the spool of which may occupy a position where the flow passage communicates with a high pressure source for hydraulic oil, and another position, where the flow passage communicates with a low pressure port, where during normal engine operation, the spool is positionable by means of an electrically activated positioning means receiving control signals from an engine controlling computer, and where, in case of failure of the normal engine control, the spool is alternatively positionable by means of a camshaft rotating synchronously with the crankshaft of the engine.
Such an internal combustion engine is known from for example international patent publication No. WO89/03939, where the camshaft is of the conventional type whose cam acts directly on a rod connected with the spool or acts on a secondary spool mounted on the spool housing. The publication also indicates that between the cam and the rod connected with the spool, a transversely movable rod may be inserted having an idler contacting the cam, which makes it possible to change the timing of the cam action on the control spool.
In the known engines, the camshaft is positioned immediately below the cylinder members to be activated by the cams. The camshaft extends in the full longitudinal direction of the engine to be able to act on the cylinder members of all the cylinders. In consequence of its length, the camshaft has a large mass and is relatively expensive to manufacture, just as it uses a deal of energy, as it participates in the movements of the crankshaft. To ensure a synchronous movement of the camshaft in relation to the crankshaft, the two shafts are connected by means of a chain drive, which may have a mass of several tonnes in a large internal combustion engine. The bearings and cams of the camshaft further have to be lubricated, which requires designing of oil ducts and lubricating oil pumps, etc., for the camshaft.
The purpose of the invention is to simplify the engine by providing a small camshaft which may be mounted at a distance from the cylinder members activated by the camshaft.
With this in view, the internal combustion engine according to the invention is characterized in that the spool is associated with a first piston on which the pressure in a hydraulic conduit acts, said conduit extending to a second piston which may follow a cam on the rotating camshaft, and that the hydraulically driven cylinder members associated with each of the engine cylinders are mounted at the pertaining cylinder, whereas the camshaft independently of the positioning of the cylinder members is disposed at an appropriate shaft drive, such as the crankshaft.
The spool valve only requires a relatively small force to activate the hydraulically driven cylinder member, which permits the hydraulic hose or conduit interconnecting the first and the second piston to have such a small internal diameter that the amount of hydraulic oil in the conduit will not be very large, even if the conduit is of great length. It is therefore possible to obtain an accurate transmission of the movements of the second piston to the first piston, even though the camshaft is positioned at a large distance from the cylinder members. The hydraulic conduits with the associated pistons act as a rigid push rod, even though there is a vertical and horizontal distance of many meters between the positions of the first and the second piston. The hydraulic force transmission between the two pistons associated with each cylinder member therefore permits the camshaft to be disposed at any suitable shaft drive. It is, for example, possible to position the camshaft at the end of the engine in direct toothed engagement with the cranks
REFERENCES:
patent: 3968735 (1976-07-01), Boisde et al.
patent: 4162614 (1979-07-01), Holleyman
patent: 4664070 (1987-05-01), Meistrick et al.
patent: 4773301 (1994-09-01), Shimamura et al.
patent: 5287829 (1994-02-01), Rose
Derwent's abstract, No. 84-81106/13, week 8413, Abstract of SU, 1023116 15 Jun. 1983.
Man B&W Diesel A/S
Moulis Thomas N.
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