Fluid reaction surfaces (i.e. – impellers) – Interrelated controls for impeller and drive means – Pitch adjustment and throttle regulation with condition...
Reexamination Certificate
2002-01-14
2003-11-25
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Interrelated controls for impeller and drive means
Pitch adjustment and throttle regulation with condition...
C416S035000, C416S037000
Reexamination Certificate
active
06652233
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control system for an aircraft engine, and more specifically it relates to a control system for a turbo-charged diesel engine used for an aircraft equipped with controllable pitch propeller.
2. Description of the Related Art
In an aircraft equipped with a controllable pitch propeller, usually the engine speed and the engine output power are separately controlled. Namely, the aircraft equipped with a controllable pitch propeller is normally provided with a propeller governor that changes the propeller pitch so that the engine speed becomes a predetermined set speed. Since the power consumption of the propeller changes in accordance with the propeller pitch and the propeller speed, the engine speed (i.e., the propeller speed) changes in accordance with the propeller pitch if the engine output power is kept at constant value. Further, engine output is controlled separately from the engine speed by adjusting the amount of fuel injected into the engine when a diesel engine is used. Therefore, in the conventional control system, the pilot of the aircraft is required to adjust a governor lever for changing the set speed of the propeller governor and a throttle lever for changing the setting value for fuel injection amount (a set amount of fuel) simultaneously in order to obtain desired engine (propeller) speed and engine output.
However, in the above explained conventional control system, since the pilot is required to operate the governor lever and the throttle lever at the same time, complex work is required for controlling the aircraft.
To solve this problem, U.S. Pat. No. 5,810,560 proposes a control system for an aircraft engine in which both the set speed of propeller governor and the set amount of fuel injection is controlled by a single control lever. In U.S. Pat. No. 5,810,560, since a gasoline engine is used, the engine output is controlled by adjusting the degree of opening of a throttle valve disposed on the air intake passage of the engine, and the propeller governor and the throttle valve are connected to a single control lever by means of link and cam mechanism, and the set speed of the propeller governor and the degree of opening of the throttle valve change simultaneously in accordance with the stroke of the control lever. Therefore, when the set speed of the propeller governor becomes low, the degree of opening of the throttle valve is also set at a small value, whereby a low speed and low output power operation of the engine is automatically achieved. Similarly, when the set speed of the propeller governor becomes high, as the degree of opening of the throttle valve also becomes large, a high speed and high output power operation of the engine is automatically achieved.
According to the control system in U.S. Pat. No. 5,810,560, as the engine speed and the engine output power are controlled by a single lever, the complexity of the control of the aircraft is largely reduced. However, when the control system of U.S. Pat. No. 5,810,560 is used for a turbo-charged diesel engine, some problems occur.
In a diesel engine, as intake air amount of the engine is not controlled by a throttle valve, a combustion air-fuel ratio changes in accordance with the fuel injection amount, i.e., the engine load. Therefore, in some operating conditions, if the combustion air-fuel ratio becomes excessively low, exhaust smoke will be formed due to a shortage of the combustion air.
In order to prevent the formation of exhaust smoke, a boost compensator is used in some turbo-charged diesel engines. The boost compensator is an apparatus that restricts the fuel injection amount to a value less than a maximum limit corresponding to an allowable lowest air-fuel ratio. The allowable lowest air-fuel ratio is a lowest air-fuel ratio on which the engine can operate without forming exhaust smoke. Since the amount of air charged into cylinders of the engine increases as the boost pressure increases, the maximum limit of the fuel injection amount is determined by the boost pressure.
When the engine speed and the fuel injection amount are simultaneously controlled by a single control lever, the fuel injection amount changes in accordance with the engine speed. In this case, when the engine speed is determined, the fuel injection amount is simultaneously determined. On the other hand, the boost pressure decreases as the altitude increases even though the engine speed is constant, due to a decrease in the atmospheric pressure. Therefore, if the boost compensator is used in the single control lever system, in some cases, the boost compensator is activated to restrict the fuel injection amount at a high altitude due to a decrease in the boost pressure. In this case, once the boost compensator restricts the fuel injection amount, boost pressure does not increase any more since sufficient engine power for increasing the boost pressure is not available. Therefore, if the boost compensator is used in the single control lever system, the fuel injection amount would likely to be always controlled to the maximum amount determined by the boost pressure once the boost compensator is activated at a high altitude. When the fuel injection amount is controlled by the boost compensator, the fuel injection amount fluctuates in accordance with the fluctuation of the boost pressure. This may cause instability in the engine operation. Therefore, when the single control lever system is used, it is not preferable to use the boost compensator.
SUMMARY OF THE INVENTION
In view of the problems in the related art as set forth above, an objects of the present invention is to provide a control system for a turbo-charged diesel aircraft engine using a single control lever for controlling an engine speed and a fuel injection amount of the engine and capable of preventing the formation of the exhaust gas smoke without using a boost compensator.
The object as set forth above is achieved by a control system for a turbo-charged diesel aircraft engine, according to the present invention, comprising a controllable pitch propeller connected to and driven by the turbo-charged diesel aircraft engine, governor means for controlling the rotational speed of the propeller to a set speed by adjusting the pitch of the propeller, speed setting means for changing the set speed of the propeller governor, throttle means for changing a set amount of fuel supplied to the engine, fuel supply means for supplying fuel to the engine in an amount determined in accordance with the set amount, control means for controlling the speed setting means and the throttle means so that the set speed and the set amount of fuel change simultaneously in accordance with the stroke of a single control lever and, wherein, the control means controls the throttle means according to the stroke of the control lever in such a manner that the set amount of fuel is always smaller than a maximum limit determined in accordance with the set speed of the propeller.
According to the present invention, as the fuel injection amount is always set at a value smaller than a maximum limit determined in accordance with the set speed of the propeller, the fuel injection amount can be restricted to a value in the range where the exhaust smoke is not formed. Further, as the maximum limit of the fuel injection amount is determined in accordance with the set speed of the propeller, the maximum limit of the set amount is not changed even at a high altitude.
According to the present invention, if the maximum limit is determined in such a manner that the air-fuel ratio of the combustion determined by the engine speed and the set amount of fuel is always higher than the lower limit of the air-fuel ratio which allows the engine operation without forming exhaust smoke, the exhaust smoke can be prevented effectively.
Also, if a delay control means such as a mechanical dashpot is provided for restricting the maximum rate of increase in the set amount of fuel, the exhaust smoke can be prevented even during a transient co
Look Edward K.
Toyota Jidosha & Kabushiki Kaisha
White Dwayne J.
LandOfFree
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