Claims:We claim:
1. A method of limiting maximum power of an engine (13) of a vehicle, said method comprising :
- detecting if a percentage of an accelerator pedal pressed is more than a first threshold for a first predefined time;
- comparing a boost pressure and an engine speed with a second threshold and a third threshold respectively;
- detecting a load on said vehicle depending on said comparison result; and
- limiting said maximum power of said engine (13) when said detected load is lesser than a predefined load value.
2. The method as claimed in claim 1, wherein said boost pressure is more than said second threshold and said engine speed is less than said third threshold when said detected load is more than said predefined load value.
3. The method as claimed in claim 1, wherein said boost pressure is less than said second threshold and said engine speed is more than said third threshold, when said detected load is less than said predefined load value.
4. The method as claimed in claim 1, wherein the maximum power of said engine (13) is limited by limiting a fuel injection quantity.
5. An electronic control unit (10) to limit maximum power of an engine (13) of a vehicle,
said electronic control unit (10)
- detects if a percentage of an accelerator pedal pressed is more than a first threshold for a first predefined time;
- compares a boost pressure and an engine speed with a second threshold and a third threshold respectively;
- detects a load on said vehicle based on said comparison result; and
- limits said maximum power of said engine (13) when said detected load is lesser than a predefined load value.
6. The electronic control unit as claimed in claim 5, wherein said electronic control unit (10) determines that said detected load is more than said predefined load value when said boost pressure is more than said second threshold and said engine speed is less than said third threshold.
7. The electronic control unit as claimed in claim 5, wherein, when said boost pressure is less than said second threshold and said engine speed is more than said third threshold, said electronic control unit (10) detects a partial load or no-load condition. , Description:Field of the invention
[0001] This disclosure relates to a method of limiting maximum power of an engine of a vehicle depending on the vehicle driving conditions.

Background of the invention:
[0002] Engine control systems for controlling the fueling in combustion engines often utilize fuel maps, which define the amount of fuel to be supplied for an engine operating condition. Full load operating conditions such as heavy acceleration, high payload or traversing in steep grades require high power. However, partial load operating conditions such as less-cargo, low cruising in flat or downhill road grades do not require high engine power. Under these conditions, if the driver operates the vehicle at the full power, fuel is wasted unnecessarily.
[0003] A German patent 4321413 discloses a method for controlling the drive power of a vehicle, in no-load and near-idle operation region, with at least one setting element for influencing the drive power and a means for adjusting an element on the basis of at least one of operating variable.

Brief description of the accompanying drawings:
[0004] An embodiment of the disclosure is described with reference to the following accompanying drawings;
[0005] Figure 1 illustrates a block diagram of an electronic control unit to limit maximum power of an engine of a vehicle in accordance with this invention; and
[0006] Figures 2 illustrates a flowchart of a method of limiting maximum power of an engine of a vehicle in accordance with this invention.

Detailed description of the embodiments:
[0007] Figure 1 illustrates a block diagram of an electronic control unit 10 to limit maximum power of an engine 13 of a vehicle in accordance with this invention. The electronic control unit 10 detects if a percentage of an accelerator pedal pressed is more than a first threshold for a first predefined time. Then, a boost pressure and an engine speed are compared with a second threshold and a third threshold respectively. The electronic control unit 10 detects a load on the vehicle based on the comparison result. The electronic control unit 10 limits the maximum power of the engine 13 when the detected load is lesser than a predefined load value.

[0008] Further construction and operation of the electronic control unit 10 are explained as follows. An accelerator pedal sensor 12 is connected to the electronic control unit 10 transmits a voltage signal to the electronic control unit 10. The ECU converts the received voltage signal into percentage of accelerator pedal pressed. Also, the electronic control unit 10 receives a boost pressure signal from a boost pressure sensor 14 present in an intake manifold and the engine speed from the engine speed sensor 16. The first threshold, second and third threshold values are stored in a memory of the ECU 10 during a calibration process. The electronic control unit 10 is further connected to an injector 20 to control the amount of the fuel injected into the engine.

[0009] Figure 2 illustrates a flowchart of a method of limiting maximum power of a vehicle according to one embodiment of the invention. At step S1, the ECU 10 detects if a percentage of an accelerator pedal pressed is more than a first threshold for a first predefined time. At step S2, the boost pressure received from the boost pressure sensor present at the intake manifold and the engine speed received from the engine speed sensor 16 of the engine are compared with the second threshold and the third threshold respectively. Based on the comparison result, the electronic control unit 10 detects a load on the vehicle at step S3. The ECU 10 limits the maximum power of the engine when the detected load is lesser than a predefined load value at step S4.

[00010] The steps are explained in detail as follows. The ECU 10 determines that the driver demand at step S1. By comparing the boost pressure and the engine speed with the second and third thresholds respectively, the ECU 10 detects the load condition of the vehicle. That is, the ECU 10 determines whether the vehicle is “fully-loaded”, or “partly-loaded”.
[00011] When the boost pressure is more than the second threshold and the engine speed is less than the third threshold, the ECU 10 determines that the detected load is more than the predefined load value. That is, the ECU 10 determines the full-load (for example, in the range of 85%-100%) condition of the vehicle, when the above conditions are met., i.e. At full-load condition, the engine 13 can be operated up to its maximum power based on the driver demand.

[00012] Similarly, when the boost pressure is less than the second threshold and the engine speed is more than the third threshold, the ECU detects a partial load or no-load condition. Upon detecting the partial-load or no-load condition, the ECU limits/reduces the maximum power to a predefined power value by controlling the injector 20. The maximum power of the engine is limited by reducing the fuel injection quantity. During the part-load condition, even when the user presses the accelerator pedal completely (to maximum percentage), the maximum power of the engine will not be more than the predefined power value.

[00013] In an example, the maximum power of the engine is 150HP. During full-load condition, the ECU 10 allows the engine 13 to operate at 150 HP when the accelerator pedal is pressed to 100%. However, when the ECU 10 detects a part-load or no-load condition, the maximum power of the engine is limited to 75HP. During part-load condition, even when the user presses the accelerator pedal completely (i.e. 100%), the maximum power of the engine is limited not to exceed a predefined value, for example, 75HP by controlling the fuel injection quantity. For example, during full-load condition, consider that the amount of fuel required to be injected into the engine is 15mg to obtain the maximum power. During part-load condition, the maximum power of the engine is limited to a predefined power value, by reducing the amount of fuel injected to 7mg.

[00014] With the above method disclosed, the load estimation can be achieved without any additional sensors. Fuel economy is improved remarkably by due to the limiting the maximum power during the partial or no-load condition.

[00015] 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.