Lubricating System for a Two-Stroke Engine

Abstract

A lubricating system for a two-stroke engine is provided in which oil is more reliably pumped into the two-stroke engine. The oil travels through passages that are integrally cast into the cylinder and / or crankcase. The oil may be injected directly into the crankcase chamber or intake passage. The oil pump may be a rotary pump mounted on the crankcase concentric to the crankshaft. It is also possible to not use an oil pump, and have the oil drawn into the engine by vacuum created in the crankcase.

Description

[0001]This patent application claims the benefit of and priority of U.S. Provisional Patent Application Ser. No. 61 / 326,662, entitled “Lubricating. System for a Two Stroke Engine” by Nagesh Mavinahally, David Kostka, and Bernardo Herzer, filed on Apr. 22, 2010.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates to an internal combustion engine. In particular it pertains to a lubricating system for two stroke or two cycle engines.[0004]2. Description of the Related Art[0005]Conventional low cost two stroke engines, particularly the ones used in lawn and garden applications typically mix lubricating oil with the fuel to lubricate the internal parts of the engine. The disadvantage with pre-mixing is that the ratio of fuel to oil is very much dependent on the manufacturer, duty cycle of the engine, and model of the equipment. Having to use different ratios for different engines / models can confuse the user as to how much oil has to be mixed with the fue...

AI Technical Summary

Benefits of technology

[0007]The design described here eliminates the disadvantages of the current systems by not having external hoses, fewer parts, and therefore lowers the cost and increases the robustness of the lubrication system. In one of the embodiments, the oil passages from the oil tank to the oil pump and from pump to the engine (into intake passage or crankcase) are integrally cast into the cylinder and crankcase, thus eliminating the external oil pipes / hoses. In another embodiment, the oil pump is a rotary pump mounted on the crankcase concentric to the crankshaft. In yet another embodiment, there is no oil pump, the oil is drawn into the engine by vacuum created in the crankcase during the engine operating cycle.

[0009]The present invention reduces the number of parts and reduces the potential for oil leaks between the joints, particularly in the oil supply line, where the pressure is higher than atmospheric. The additional improvement to the oil pump design simplifies the construction and operation of the pump by driving the oil pump directly without the need for intermediate gears between the drive shaft (crankshaft) and the driven shaft (in the oil pump), or in the last embodiment, the elimination of the pump entirely.

Problems solved by technology

The disadvantage with pre-mixing is that the ratio of fuel to oil is very much dependent on the manufacturer, duty cycle of the engine, and model of the equipment.

Having to use different ratios for different engines / models can confuse the user as to how much oil has to be mixed with the fuel.

Secondly, if the ratio of fuel to oil is not correct the engine will either be overly lubricated or under lubricated, both of which are detrimental.

The disadvantage with current systems are that external fittings and hoses are used to inject oil into the intake manifold, which can leak oil at the hose or fitting junctions and add cost to the equipment because of additional parts.

Also, in existing designs, the oil pump is driven by gears and the pump has a reciprocating plunger, which adds additional components and cost.

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