Variable valve actuation control for operation at altitude
a valve actuation and altitude technology, applied in the direction of electric control, machines/engines, instruments, etc., can solve the problems of reducing the air-fuel ratio of the engine, affecting the performance of the internal combustion engine, and affecting the efficiency of the engine,
Inactive Publication Date: 2005-12-22
CATERPILLAR INC
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Problems solved by technology
The performance of an internal combustion engine, such as, for example, a diesel, gasoline, or natural gas engine may be impacted by the conditions under which the engine is operated.
In particular, the operation of the engine at higher altitudes may cause a decrease in fuel efficiency and / or an increase in the generation of undesirable emissions.
The decrease in air density and air pressure at higher altitudes causes a reduction in the air-fuel ratio provided to the engine, a reduction in the efficiency of an associated turbocharger system, and a reduction in the combustion efficiency within the engine.
The reduction in each of these parameters may result in a decreased fuel efficiency and / or increased emission generation.
A reduction in the air-to-fuel ratio typically translates to a reduction in the efficiency of combustion.
However, under standard operating conditions, a typical turbocharger system is approximately 60-65% effective, which means that only 60-65% of the recovered energy is applied to the intake air flow.
The lower density of the air at high altitudes further reduces the efficiency of the turbocharger.
Accordingly, the turbocharger will not compensate for all losses associated with operating at higher altitudes.
Method used
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[0017] Reference will now be made in detail to exemplary embodiments of the invention, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
[0018] An exemplary embodiment of an engine system 10 is illustrated in FIG. 1. Engine system 10 includes an intake air passageway 13 that leads to an engine 20. One skilled in the art will recognize that engine system 10 may include various components, such as, for example, a turbocharger 12 and an aftercooler 14. An exhaust air passageway 15 may lead from engine 20 to turbocharger 12.
[0019] Engine 20 may be an internal combustion engine as illustrated in FIG. 2. For the purposes of the present disclosure, engine 20 is depicted and described as a four stroke diesel engine. One skilled in the art will recognize, however, that engine 20 may be any other type of internal combustion engine, such as, for example, a gasoline or natur...
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A method of controlling a variable valve actuation system for an engine is provided. A cam assembly is operated to move an intake valve between a first position and a second position. A parameter indicative of an altitude at which the engine is operating is sensed. A first lookup map is accessed to determine a desired air-to-fuel ratio when the sensed parameter indicates that the engine is operating at an altitude below a first predetermined value. A second lookup map is accessed to determine a desired air-to-fuel ratio when the sensed parameter indicates that the engine is operating at an altitude above the first predetermined value. A desired valve actuation period is determined based on the determined air-to-fuel ratio. The intake valve is prevented from returning to the first position until the end of the determined valve actuation period.
Description
TECHNICAL FIELD [0001] The present invention is directed to a system and method for controlling a variable valve actuation system and, more particularly, to a system and method for controlling a variable valve actuation system to account for altitude operating conditions. BACKGROUND [0002] The performance of an internal combustion engine, such as, for example, a diesel, gasoline, or natural gas engine may be impacted by the conditions under which the engine is operated. For example, the performance of an internal combustion engine may change as the altitude at which the engine is operated increases. In particular, the operation of the engine at higher altitudes may cause a decrease in fuel efficiency and / or an increase in the generation of undesirable emissions. [0003] The impact of altitude on engine performance results from the decrease in air density and air pressure at higher altitudes. The decrease in air density and air pressure at higher altitudes causes a reduction in the ai...
Claims
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IPC IPC(8): F01L13/00F01L1/34F02B29/04F02B75/02F02D13/02F02D41/00F02D41/02F02D41/24F02D43/00F02D45/00F02M51/00G06F19/00G06G7/70
CPCF02B29/0406F02D13/0203F02D13/0226F02D13/0269F02D41/0002Y02T10/42F02D41/2422F02D2041/001F02D2200/703Y02T10/142F02D41/021Y02T10/12Y02T10/40
Inventor PIERPONT, DAVID A.CROWELL, THOMAS J.
Owner CATERPILLAR INC