Internal-combustion engines – Two-cycle – Rear compression
Reexamination Certificate
1999-04-30
2001-04-17
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Two-cycle
Rear compression
C123S0730CA, C123S298000, C123S1960AB
Reexamination Certificate
active
06216651
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a separate lubricating device for an internal combustion engine, and in particular to a separate lubricating device for supplying a lubricating oil by means of an electronic control to an internal combustion engine, such as a relatively small two-stroke internal combustion engine which is suited for use in a portable working machine, for example, a chain saw, a bush cutter, or the like.
There have been previously known two different systems for supplying lubricating oil to a two-stroke internal combustion engine, namely: a mixture method lubrication system, which is widely employed, wherein lubricating oil is mixed in advance with fuel such that a mixture of fuel and lubricating oil is supplied to the engine intake; and a separate lubricating system, wherein a lubricating oil is supplied mechanically to the engine by a lubricating oil pump. Examples of separate lubricating systems are disclosed in, for example, Japanese Patent Unexamined Publication H1-113510; and Japanese Utility Model Unexamined Publication H2-13111.
The aforementioned mixture method lubrication system is designed to supply a lubricating oil at a predetermined mixing ratio, which is usually established to conform with the quantity of lubricating oil required for a high revolution speed of engine. It is difficult to adjust the quantity of lubricating oil to an optimum degree for low speed operation of the engine, thus causing problems such as the generation of smoke or offensive odor at low engine speeds or at idling of the engine.
On the other hand, with a conventional separate lubricating system, the lubricating oil pump is driven by motive power derived from a crankshaft, thereby to enable an optimum quantity of lubricating oil to be supplied from the discharge port of the pump to the internal combustion engine in conformity with the revolution speed of the engine. However, there is a problem that a fine control of supply of lubricating oil cannot be achieved by only controlling the revolution speed of the pump.
Furthermore, with the previously known apparatus for mechanically supplying lubricating oil, since the lubricating oil pump is driven by making use of the driving force of the engine, the pumping efficiency of the lubricating oil pump is caused to decrease as the revolution speed of the engine becomes higher, thus raising a problem that it becomes impossible to supply a sufficient quantity of lubricating oil which is necessary for a high revolution speed of engine.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made under the aforementioned circumstances, and therefore an object of the present invention is to provide a separate lubricating device for a two-stroke internal combustion engine, which is capable of controlling the quantity or time of lubricating oil to be fed to the engine based on the operating conditions of the engine, thereby always enabling an optimum quantity of lubricating oil to be supplied with fine control.
With a view to attaining the aforementioned object, the present invention provides a separate lubricating device for a two-stroke internal combustion engine having an air intake system and a controlling device. The invention is characterized in that it comprises an injector for injecting lubricating oil into a passage of the air intake system and a lubricating control device associated with the controlling device and in that the lubricating control device controls so either the timing of the supply of lubricating oil from the injector or the quantity of lubricating oil injected into the engine by the injector. Preferably, the lubricating control device controls both the timing of the injections of lubricating oil from the injector and the quantity of lubricating oil injected upon each injection by the injector.
In a preferred embodiment of the separate lubricating device for a two-stroke internal combustion engine according to the present invention, the injector is provided with a heating element for heating the lubricating oil.
The lubricating control device may be provided with an injection mode-controlling means which is capable of transforming DC power into a sequential rectangular pulse wave and of varying the number of outputs of the pulse wave to the injector, thereby to control the time intervals of injection. The injection mode-controlling means provides for selectively switching from an output to the injector of every pulse of the pulse wave to an output to the injector of one pulse out of each consecutive sequence of a selected number of two or more pulses of the pulse wave, such as one out of every two pulses or one out of every three pulses.
In other embodiments of the separate lubricating device according to the present invention, the lubricating control device includes means for controlling the quantity of lubricating oil injected into the engine from the injector upon each injection by the injector. The quantity of lubricating oil injected by the injector may be controlled in response to a signal indicative of the engine load, such as a signal indicative of the revolution speed of the internal combustion engine.
Since lubricating oil is supplied by an electronically controlled injector in the separate lubricating device for a two-stroke internal combustion engine according to the present invention, it is possible to supply the engine with a precisely controlled quantity of lubricating oil, i.e. a larger quantity at high revolution speed of the engine and a smaller quantity at low revolution speed of the engine. Therefore, it becomes possible now to provide a finer control of the supply of lubricating oil as compared with the conventional mechanical pumping system. Further, since the consumption of lubricating oil can be reduced at a low revolution speed, it is possible to produce a two-stroke internal combustion engine which is capable of inhibiting the generation of smoke or offensive odor, thus protecting the environment.
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Ishikawa Takeshi
Kondo Tadashige
Baker & Botts L.L.P.
Huynh Hai
Kioritz & Corporation
Wolfe Willis R.
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