FIELD OF THE INVENTION:

The invention relates to adapting the engine operation to different ambient air pressures.

BACKGROUND OF THE INVENTION:

In the gasoline engines it is important to run the engine at optimal operation condition. which depends on maintaining a stoichiometric ratio or the air fuel ratio which is the exact quantity of air required to completely burn all of the fuel. In a vehicle fitted with engine management system (EMS), the amount of fuel injected depends upon the available or the measured air inside the combustion chamber to maintain
the stoichiometric ratio.

The air inside the combustion chamber for every operating cycle is calculated using flow over the throttle
valve, ambient pressure and temperature. Sensors are provided to measure the throttle position and temperature. But to measure the ambient pressure and the intake manifold pressure two different sensors are required on each side of the throttle valve. The ambient pressure defines density of air which is used to calculate the accurate quiantity of air entering the combustion chamber. Based on this quantity of air the fuel quantity for injection is determined to achieve the stoichiometric ratio.

The present system for pressure adaptation requires two pressure sensors which result in additional costs. Further if any one of the pressure sensor fails adapting the engine operation to maintain the stoichiometric ratio'operation fails as the quantity of air entering the combustion chamber cannot be determined correctly.

ADVANTAGES OF THE INVENTION:

The present invention reduces the number of sensors required for the air intake system and makes it simple in operation and reliable, even after the elimination of a discrete ambient pressure sensor, where the ambient pressure adaption is done using a manifold pressure sensor.

The pressure adaptation for the engine can be carried out at any engine operating conditions and there is no need to wait for suitable conditions for pressure adaptation. The pressure is continuously monitored and adaptation is carried out when required. Thus, pressure adaptation can be achieved even at Jow throttle and engine speeds.

The invention helps to maintain the engine operation at the stoichiometric ratio during entire duration of operation of the engine.

DESCRIPTION OF THE INVENTION:

The present invention discloses a device and method for adapting the engine operation to ambient pressure. The device includes an air path to the intake manifold of the vehicle. The air path is provided with a throttle valve and a bypass path across the throttle valve. The bypass path has a bypass valve operated by a controller. The throttle valve is mechanically actuated by the user/ driver of the vehicle. The device uses the pressure sensor in the intake manifold to measure the ambient pressure. The pressure in the intake manifold is allowed to recover to the ambient pressure and become stable by completely opening the bypass valve for the duration of one engine cycle. The bypass valve is opened completely after a predetermined time period repeatedly. Thus, the ambient pressure can be determined which is same as the pressure in the intake manifold. Thus, the engine operation is adapted to achieve the ideal stoichiometric ratio.

BRIEF DESCRIPTION OF THE DRAWINGS:

The invention is now described in reference to the accompanying drawings

Fig. 1 shows a schematic diagram of a device on a vehicle for adapting the engine operation to ambient air pressure;

Fig. 2 shows a flowchart illustrating the method for adapting the engine operation to ambient air pressure; and

Fig. 3 illustrates a graph indicating the status of different parameters determining operation of the device in accordance with the invention.

DETAILED DESCRIPTION OF THE DRAWINGS:

Fig. 1 illustrates a diagram showing a device for adapting engine operation to ambient pressure in accordance with this invention. The device in accordance with this invention comprises an air path (10) connecting an air inlet to the engine and a throttle valve (12) positioned in the air path (10). A pressure sensor (14) is positioned in the air path (10) after the throttle valve (12). A bypass path (16) connects one side of the throttle valve (12) to the other side of the throttle valve (12). A bypass valve (18) is provided in the bypass path (16). A controller (20) is provided to control the bypass valve (18). The throttle valve (12) is mechanically actuated based on the user input. For one cycle when the throttle valve (12) is partially open, the controller (20) opens the bypass valve (18) completely, receives the pressure measured by said pressure sensor and achieves optimum engine operation parameters at said measured pressure.

Fig. 2 illustrates a method for adapting the engine operation to the ambient air pressure. The method comprises the steps of detecting (SO) of throttle open condition. On detection of .throttle open condition the bypass valve is opened completely (SI) for one engine operation cycle. Opening of the bypass valve results in faster pressure recovery in the intake manifold. The intake manifold pressure reaches a value equal to the ambient pressure and becomes stable. The pressure sensor detects the pressure in the intake manifold which is equal to the ambient pressure. The engine operation is adapted (S2) to the detected ambient pressure to achieve optimum engine efficiency. The bypass valve is opened completely after every predetermined time interval (t) for the duration of one engine cycle. This is repeated continuously throughout the engine operation duration. Based on the detected ambient pressure the engine is adapted to operate at stoichiometric ratio.

The required pressure pattern for ambient pressure adaptation occurs infrequently, especially at lower throttle openings and low engine speeds. The present invention proposes a device and method for learning the ambient pressure using a pressure sensor provided in the intake manifold. The pressure adaptation is carried out continually after predetermined time intervals.

Fig. 3 illustrates a graph indicating the status of different parameters determining operation of the device in accordance with the invention. In accordance with the present invention the throttle valve is controlled by the driver by mechanical means. The position of the throttle valve determines the quantity of air supplied for the combustion. This position is indicated by the graph 'V in Fig. 3. Thus, the quantity of air supplied is directly controlled by the driver. The quantity of the air supplied to the engine manifold also depends on the ambient air pressure (Pa). If the air ambient pressure is low, then density of air is lesser and hence the quantity of air actually entering the combustion chamber through the intake manifold is also low. The variations in the pressure of the air in the intake manifold are shown by the graph Pm. Generally the vehicle is adapted to operate with stoichiometric ratio at a set ambient pressure. In case there is a drop in ambient pressure and the fuel injection and the engine operation are not adapted to the ambient pressure, then the fuel injected would be in excess of the quantity that can be completely combusted by the air entering the combustion chamber. This results in incomplete combustion and wastage of fuel and also increases exhaust emission. Thus, the fuel injection should be adjusted accordingly to be suitable for the quantity being supplied to the combustion chamber and achieve operation at stoichiometric ratio.

The device according to this invention uses an existing idle speed actuator (ISA) or a bypass valve positioned across the throttle valve to aid the pressure recovery during lower throttle openings and lower engine speeds. The ISA or the bypass valve is opened for one engine operating cycle (tl) based on a time delay and controlled by.a controller which creates the required pressure characteristics for ambient pressure adaptation. When the ISA or the bypass valve is opened at low throttle openings then the pressure recovery in the intake path is faster. Thus, the pressure in the intake manifold reaches equal to the value of ambient pressure and becomes stable. Once the pressure in manifold becomes stable it can be assumed to be equal to the ambient pressure. The ambient pressure is measured in the intake manifold by a pressure sensor.

It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.

WE CLAIM:

1. A device on a vehicle for adapting the engine operation to ambient air pressure, said device comprising

an air path (10) connecting an air inlet to the engine; a throttle valve (12) positioned in said air path (10);

a pressure sensor (14) positioned in the air path (10) after said throttle valve (12);

a bypass path (16) connecting one side of the throttle valve (12) to the other side of the throttle valve (12), said bypass path (16) provided with a bypass valve (18);

said device characterized by a controller (20) adapted to open the bypass valve (18) completely for one cycle when said throttle valve (12) is marginally open, receive the pressure measured by said pressure sensor and achieve optimum engine operation. parameters at said measured pressure.

2. A device as claimed in claim (1) wherein the throttle valve (12) is mechanically actuated based on the user input.

3. A device as claimed in claim (1) wherein the bypass valve (18) is electronically actuated.

4. A method for adapting the engine operation to the ambient air pressure, said method comprising the following steps

detecting (SO) of throttle open condition;

opening (SI) the bypass valve after a periodic time interval (t) for one engine operation cycle to detect the ambient pressure;

adapting (S2) the engine operation to said detected ambient pressure to achieve optimum engine operation.

5. A method as claimed in claim (4) wherein said bypass valve is opened completely after every predetermined time interval for the duration of one engine cycle throughout the engine operation duration.

6. A method as claimed in claim (4) wherein opening of said bypass valve completely causes the pressure in intake manifold to recover and reach a stable value equal to ambient pressure.

7. A method as claimed in claim (4) (5) and (6) wherein, said pressure measured by the pressure sensor during the cycle when the bypass valve is completely open is equal to the ambient pressure.

8. A method as claimed in claim (4) wherein the engine is adapted to operate at stoichiometric ratio at said detected ambient pressure.