Internal-combustion engines – Two-cycle – Rear compression
Patent
1998-09-29
2000-05-16
Solis, Erick R.
Internal-combustion engines
Two-cycle
Rear compression
123317, 1231974, F02B 3304
Patent
active
06062180&
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a device for increasing crankcase compression in an internal combustion engine, said engine comprising a crankshaft having main bearings and at least one crank portion including a counterweight, and filling bodies forming an annular unit together with said crank portion.
It is previously known that the performance of a two-cycle engine can be improved by increasing the crankcase compression, which can be achieved by reducing the volume of the crankcase. To this end it has been proposed to use various types of lightweight filling bodies attached to the crank portion of the crankshaft. Such a filling body is preferably shaped so as to form an annular unit together with the crank portion. The disadvantage of such known devices is that the manufacture and mounting thereof are relatively complicated and costly and they have therefore not been used to any great extent.
Although the device according to the invention is primarily intended to be used in two-cycle engines, it may also be applicable in four-cycle engines, namely such engines of the type using crankcase scavenging for the purpose of lubrication by fuel mixed with lubricating oil. Such four-cycle engines may be used for example in tools having greatly varying angular working positions preventing the use of a normal pressurized lubrication system. The invention is therefore not restricted to two-cycle engines.
SUMMARY OF THE INVENTION
According to the invention, a device for increasing the crankcase compression has been provided which is uncomplicated in manufacture and can thus be produced at low cost. Another advantage is that the device can be easily mounted in the engine and is consequently well adapted to rational series production. A further advantage is that no alteration of the crankshaft is required, and neither is any costly modification of other parts of the engine.
The above advantages have been achieved by means of a device of the kind mentioned in the introduction which according to the invention is generally characterized in that the filling bodies are provided in a holder comprising an annular, peripheral wall adapted to surround said crank portion.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in more detail in the following with reference to the accompanying drawings, in which
FIG. 1 is a perspective view of a preferred embodiment of the device according to the invention,
FIG. 2 is a front plan view on a larger scale of the device shown in FIG. 1,
FIG. 3 is a rear plan view on a larger scale of the same device,
FIG. 4 is a sectional view along line IV--IV in FIG. 3, and
FIG. 5 is a perspective view of a crankshaft provided with the device according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiment of the device shown in the drawings comprises a cup-shaped, cylindrical holder 10, preferably made of metal, such as sheet steel or light metal, or reinforced plastic, such as glass fiber reinforced polyamide. The holder 10 comprises a peripheral, cylindrical wall 10a, and a plane end wall 10b, said last mentioned wall having a central opening 10c for receiving a crankshaft 11. As is best seen in FIGS. 2 and 3, the end wall 10b has recesses 10d for providing gas communication as will be described below. The cylindrical wall 10a has a diameter adapted to surrounding the crank portion 12 of the crankshaft with a suitable fit, and the crank portion has a counterweight 13, as is conventional. The holder is furthermore provided with filling bodies 14, 15 having a shape corresponding to the space between the crank portion 12 and the peripheral wall 10a. In order to minimize the influence of the filling bodies on the balance of the crankshaft the filling bodies are made of a lightweight material such as glass fiber reinforced plastic, or a light metal such as aluminium or magnesium. The filling bodies can be made as hollow shells, or as homogeneous bodies of lightweight material.
For attaching the filling bodies to th
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patent: 1038541 (1912-09-01), Ducker
patent: 1081480 (1913-12-01), Aslakson
patent: 1396045 (1921-11-01), Mellen
patent: 3280805 (1966-10-01), Muller
patent: 3859968 (1975-01-01), Stinebaugh
patent: 5529027 (1996-06-01), Okubo
patent: 5782217 (1998-07-01), Ito et al.
AB Electrolux
Hairston Brian
Solis Erick R.
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