Claims:CLAIMS

We Claim

1. An algorithm (10) for planned opening of a pressure limiting valve of a high pressure common rail to overcome the aging effects of stagnant fuel within the pressure limiting valve by an engine control unit, the method comprising:
determining (12) a status of an engine to be in an on condition or in an off condition;
determining (14) if fuel leakage from the high pressure common rail is existent as sensed by a rail pressure sensor;
determining (16) if pressurized fuel is flushed out of the pressure limiting valve from the high pressure common rail at a time interval that is greater than a threshold value as pre-determined by a user; and
determining (18) a number of times at which the pressure limiting valve is opened and a duration of time for which the pressure limiting valve is opened for a life span of the high pressure common rail.

2. The algorithm (10) for planned opening of the pressure limiting valve of the high pressure common rail to overcome the aging effects of stagnant fuel within the pressure limiting valve by the engine control unit in accordance with Claim 1, wherein the pressure limiting valve is triggered (20) to force open by supplying excess pressurized fuel into the high pressure common rail, wherein the pressure of the excess pressurized fuel that is supplied into the high pressure common rail is greater than an opening pressure of the pressure limiting valve when:
a status of the engine is in an off condition;
fuel leakage from the high pressure common rail is non-existent as is sensed by the rail pressure sensor;
pressurized fuel is flushed out of the pressure limiting valve from the high pressure common rail at a time interval that is greater than the threshold value as determined by the user; and
the number of times at which the pressure limiting valve is opened is lesser than a threshold value as determined by the user.

3. The algorithm (10) for planned opening of the pressure limiting valve of the high pressure common rail to overcome the aging effects of stagnant fuel within the pressure limiting valve by the engine control unit in accordance with Claim 2, wherein excess pressurized fuel is not supplied into the high pressure common rail thereby not triggering the pressure limiting valve to force open when at least one of:
the status of the engine is in an on condition;
fuel leakage from the high pressure common rail is existent as sensed by the rail pressure sensor by a reduction in pressure within the high pressure common rail;
pressurized fuel is flushed out of the pressure limiting valve from the high pressure common rail at a time interval that is lesser than the threshold value as determined by the user; and
the number of times in which the pressure limiting valve is opened is greater than a threshold value as determined by the user.

4. The algorithm (10) for planned opening of the pressure limiting valve of the high pressure common rail to overcome the aging effects of stagnant fuel by the engine control unit in accordance with Claim 1, wherein excess pressurized fuel within the pressure limiting valve is supplied into the high pressure common rail, thereby triggering the pressure limiting valve to force open for a calibrated number of counts and for a predetermined duration of time in each count.

5. The algorithm (10) for planned opening of the pressure limiting valve of the high pressure common rail to overcome the aging effects of stagnant fuel by the engine control unit in accordance with Claim 4, wherein the engine control unit determines if the pressure limiting valve has been opened for a calibrated number of counts and for a predetermined duration of time, and wherein the algorithm is ended if it is determined by the engine control unit that the pressure limiting valve has been opened for the calibrated number of counts and for the predetermined duration of time.
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention relates to an algorithm for opening a pressure limiting valve, and more specifically to a method of planned opening of a pressure limiting valve by forcefully injecting fuel into a high pressure common rail to overcome the aging effects of fuel.

Background of the invention
[0002] IN 202141033899 describes a fuel flow system that is positioned between leak ports of a high pressure fuel pump / fuel injectors and a pressure limiting valve of a high pressure rail and a fuel tank. The fuel flow system comprises a first fuel flow path positioned between the leak ports of the high pressure fuel pump / fuel injectors, and a second fuel flow path. The second fuel flow path is adapted to house a solenoid valve therein. The solenoid valve is adapted to be electrically actuated to facilitate channeling fuel from the leak ports of the high pressure fuel pump / fuel injectors. A third fuel flow path is positioned between the second fuel flow path and an outlet of the pressure limiting valve of the high pressure rail. The third fuel flow path is adapted to deliver pressurized fuel that flows through the first fuel flow path to the outlet of the pressure limiting valve. A fourth fuel flow path is positioned between the third fuel flow path and the fuel tank of a vehicle. The fourth fuel flow path is adapted to deliver pressurized fuel from the outlet of the pressure limiting valve to the fuel tank of the vehicle via the third fuel flow path.

Brief description of the accompanying drawing
[0003] Figure 1 depicts a flow chart illustrating an algorithm for a method of planned opening of a pressure limiting valve of a high pressure common rail to overcome aging effects of fuel in one embodiment of the invention.

Detailed description of the embodiments
[0004] An algorithm 10 for planned opening of a pressure limiting valve of a high pressure common rail to overcome the aging effects of stagnant fuel within the pressure limiting valve by an engine control unit is described. The method comprises determining 12 a status of an engine to be in an on condition or in an off condition, and determining 14 if fuel leakage from the high pressure common rail is existent as sensed by a rail pressure sensor. The method further comprises determining 16 if pressurized fuel is flushed out of the pressure limiting valve from the high pressure common rail at a time interval that is greater than a threshold value as pre-determined by a user, and determining 18 a number of times at which the pressure limiting valve is opened and a duration of time for which the pressure limiting valve is opened for a life span of the high pressure common rail.

[0005] In an exemplary embodiment, an algorithm 10 for planned opening of a pressure limiting valve of a high pressure common rail to overcome the aging effects of stagnant fuel within the pressure limiting valve by the engine control unit is described. The method comprises determining 12 a status of an engine to be in an on condition or in an off condition. More specifically, if the ignition is turned off, the engine is considered to be in an off condition. In the event that the ignition is turned on, the engine is considered to be in an on condition. Therein, the engine control unit determines 14 if fuel leakage from the high pressure common rail is existent as sensed by a rail pressure sensor. More specifically, if fuel leaks from the high pressure common rail via the fuel flow path that supplies pressurized fuel from the high pressure fuel pump to the high pressure common rail, then the pressure in the high pressure common rail as sensed by the rail pressure sensor will be lower than the maximum pressure within the high pressure common rail that is required to open the pressure limiting valve. The engine control unit therein determines 16 if pressurized fuel is flushed out of the pressure limiting valve from the high pressure common rail at a time interval that is greater than a threshold value as determined by a user. If the pressurized fuel is flushed out of the pressure limiting valve of the high pressure common rail at a time interval that is lesser than the threshold value as determined by the user, it may be inferred that the fuel within the high pressure common rail is still fresh and has not yet decomposed, thereby producing particulate deposits in the interfaces of the pressure limiting valve. If the pressurized fuel is flushed out of the pressure limiting valve of the high pressure common rail at a time interval that is greater than the threshold value as determined by the user, it may be inferred that the fuel within the high pressure common rail has decomposed, thereby producing particulate deposits at the interfaces of the pressure limiting valve. The engine control unit therein determines 18 a number of times at which the pressure limiting valve is opened. If the pressure limiting valve has been opened lesser than a threshold number of times, the physical significance is that the wear that occurs in the pressure limiting valve due to the opening and closure of the pressure limiting valve is lower. However, if the pressure limiting valve has been opened more than a threshold number of times, the physical significance is that the wear that occurs in the pressure limiting valve due to the opening and closure of the pressure limiting valve is higher. Finally, the engine control unit determines 18 a duration of time for which the pressure limiting valve has been opened for a life span of the high pressure common rail.

[0006] In an exemplary embodiment, the engine control unit triggers 20 pressure limiting valve to force open by supplying excess pressurized fuel into the high pressure common rail. More specifically, when excess pressurized fuel is supplied into the high pressure common rail, the pressure of the fuel supplied exceeds the opening pressure of the pressure limiting valve. Therein, the pressure limiting valve is triggered 20 to force open, thereby channeling the pressurized fuel from the high pressure common rail back to the fuel tank via the pressure limiting valve. The flow of pressurized fuel from the high pressure common rail back to the fuel tank via the pressure limiting valve facilitates flushing the pressure limiting valve of particulate matter that settles in the pressure limiting valve into the fuel tank. The flushing action of the pressure limiting valve facilitates cleaning the pressure limiting valve with excess pressurized fuel that flows from the high pressure common rail to the fuel tank via the pressure limiting valve.

[0007] In the exemplary embodiment, pressurized fuel, the pressure of which is greater than the opening pressure of the pressure limiting valve is channeled from the high pressure fuel pump to the high pressure common rail. The flow of pressurized fuel into the high pressure common rail facilitates force opening the pressure limiting valve, thereby flushing out all the impure fuel that exists in the high pressure common rail along with particulate matter that is deposited in the clearance between the pressure limiting valve and the housing of the high pressure common rail. Once the pressure limiting valve is held open for a predetermined duration of time until all the impure fuel that exists in the high pressure common rail along with the particulate matter that is deposited in the clearance between the pressure limiting valve and the housing of the high pressure common rail is flushed out, the pressure limiting valve closes completely. More specifically, the pressure limiting valve of the high pressure common rail is forced open by supplying pressurized fuel from the high pressure fuel pump to the high pressure common rail when a status of the engine is in an off condition, and the fuel leakage from the high pressure common rail is non-existent as sensed by the rail pressure sensor. In addition, the pressure limiting valve of the high pressure common rail is forced open by supplying pressurized fuel from the high pressure fuel pump to the high pressure common rail when pressurized fuel is flushed out of the pressure limiting valve from the high pressure common rail at a time interval that is greater than the threshold value as determined by the user, and the number of times at which the pressure limiting valve is opened is lesser than a threshold value as determined by the user.

[0008] Conversely, in the exemplary embodiment, pressurized fuel whose pressure is equal to the normal operating pressure of the high pressure common rail is channeled from the high pressure fuel pump to the high pressure common rail. The flow of pressurized fuel into the high pressure common rail facilitates retaining the pressure limiting valve in the same position. The pressure limiting valve of the high pressure common rail is retained in the same position when a status of the engine is in an on condition, and/or the fuel leakage from the high pressure common rail exists as sensed by the rail pressure sensor. In addition, the pressure limiting valve of the high pressure common rail is retained in the same position when pressurized fuel is flushed out of the pressure limiting valve from the high pressure common rail at a time interval that is lesser than the threshold value as determined by the user, and/or the number of times at which the pressure limiting valve is opened is greater than the threshold value as is determined by the user.

[0009] In the exemplary embodiment, when the conditions for triggering the pressure limiting valve have been successfully met as described above, the engine control unit facilitates channeling 22 excess pressurized fuel into the high pressure common rail from the high pressure fuel pump via a high pressure fuel line. Therein, excess pressurized fuel is supplied into the high pressure common rail from the high pressure fuel pump, thereby triggering the pressure limiting valve to force open for a calibrated number of counts and for a predetermined duration of time as is predetermined by a user. During the time period in which the pressure limiting valve is triggered to force open by supplying excess pressurized fuel into the high pressure common rail from the high pressure fuel pump, the particulate matter that is deposited and the stagnant fuel that is contained within the pressure limiting valve is flushed out by the excess pressurized fuel that is channeled into the high pressure common rail from the high pressure fuel pump and retained therein. Therein, the particulate matter that is deposited and the stagnant fuel that is flushed out of the pressure limiting valve is allowed to flow back into the fuel tank.

[0010] The engine control unit therein determines if the pressure limiting valve open cycles have been completed. More specifically, after the pressure limiting valve has been forced open for a calibrated number of counts and for a predetermined duration of time as is predetermined by the user, the engine control unit performs a validation step in which it is determined if the pressure limiting valve has been forced open for a calibrated number of counts and for the predetermined duration of time. If the pressure limiting valve has not been forced open for the predetermined duration of time as is determined by the user, then the process loops back to the step where the engine control unit determines 12 if the status of the engine is in an on condition or in an off condition, if 14 fuel leakage from the high pressure common rail is existent as is sensed by a rail pressure sensor, if 16 pressurized fuel is flushed out of the pressure limiting valve from the high pressure common rail at a time interval that is greater than a threshold value as is determined by a user, a number of times 18 at which the pressure limiting valve is opened, and a duration of time for which the pressure limiting valve is opened for a life span of the high pressure common rail. However, if the engine control unit determines that the pressure limiting valve has been forced open for the predetermined duration of time as is determined by the user, then the process ends at this step and no further procedures are followed hereinafter.

[0011] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to dimensions of various components are envisaged and form a part of this invention. The scope of the invention is only limited by the scope of the claims.