FIELD OF INVENTION:

The invention relates to a monitoring device to detect clogging of a fuel filter.

BACKGROUND OF THE INVENTION:

Detecting clogging of a fuel filter used in vehicles is known in prior arts. The US patent 6672147 discloses a method to detect the clogging of a filter. The method disclosed in the said prior art comprises: determining the fuel pressure at the filter intake; determining the fuel pressure at the filter outlet; determining the pressure drop of the filter from the difference between the filter input and output pressure levels, and by comparing the pressure drop with a reference value to deduce information concerning the clogging condition of the filter.

OBJECT OF THE INVENTION:

The object of this invention is to provide a device and a method to determine the clogging level of the filter used for filtering the fuel in a vehicle.

ADVANTAGES OF THE INVENTION:

The proposed invention provides a simple solution to detect the clogging of the filter through monitoring the pump current and comparing the pump current with reference values. As the clogging level of the filter increases, it offers more and more resistance to the pump. The pump has to work more to overcome the resistance offered by the filter thereby drawing more current from the power supply. The amount of current drawn by the pump is an indicative of the clogging of the filter.

BRIEF DESCRIPTION OF THE DRAWINGS:-

FIG. 1 shows a schematic of the invention

DETAILED DESCRITPION OF THE INVENTION:

The present invention is described in the preferred embodiment as follows:-

FIG. 1 shows a schematic of a fuel supply system for a vehicle which is not shown, involving the invention. In fig. 1 only the components which are relevant to describe the invention are shown, whereas all the other components which form essential parts of any fuel supply system for a vehicle, are not shown.

The fuel supply system shown in FIG. 1 comprises a fuel tank 10, a fuel pump 12, a filter 14 and a high pressure pump 16. The fuel pump 12 acts as a feed pump feeding the fuel at an intermediate pressure to the high pressure pump 16. The fuel pump 12 is an electric pump of any appropriate type which are already known, with a pumping stage driven by an electric motor which is not shown in figure. The fuel pump 12 may be submerged in the fuel tank. An electronic control unit (ECU) 18 controls the fuel pump and also monitors the current drawn by the electric motor.

The electric motor has a provision to indicate a measure of the current drawn by the electric motor from the battery of the vehicle. This information is monitored by the ECU 18. Alternatively the ECU may have suitable circuitry to monitor current drawn by the motor through the power supply line to the electric motor.

The power to the electric motor of the pump is supplied from the battery of the vehicle. The power to the electric motor is controlled by the ECU 18. The ECU 18 controls the operation of the fuel pump 12 by controlling the power to the electric motor. The ECU 18 continuously monitors the current drawn by the electric motor.

The pump 1 draws the fuel from the fuel tank 10 through a supply path and delivers the fuel through the filter 14 to the high pressure pump 16. The high pressure pump 16 further pressurizes the fuel and delivers the fuel to the next stages of the fuel supply system which is not shown. A pressure regulator returns the excess fuel to the fuel tank through the return path 22. The further stages of the fuel supply system may be a common rail, injectors etc. The pressure regulators used in the combustion engines are already known.

Some of the components explained above may be combined and may exist in common physical units. The ECU 18 may be an existing ECU in the vehicle which is responsible to control the engine.

The ECU 18 controls the operation of the fuel pump 12 by means of the electric supply to the electric motor of the pump 12 and continuously monitors the current drawn by the electric motor. The instantaneous values of the current are accumulated and an average value of the current is computed considering a predefined number of instantaneous values of the current.

Assume the case when the filter is new. The pressure at the inlet of the pump is PI and the pressure at the outlet of the pump be P2. The load seen by the pump because of the filter is LI. Because of the load LI, the electric motor draws a current II. The value of II may be an average value derived from a plurality of instantaneous values recorded.

The ECU 18 contains a table containing reference values for II under different conditions and/or for different types of fuel filters. This table is filled with reference values of II applicable for the fuel filter installed in the vehicle by the vehicle manufacturer for the first time when the engine is being tested. Also it is possible to change or fine tune the values in the table when a new filter is installed, based on the specifications of the fuel filter 12. The table is stored in non-volatile memory.

Assume that the filter is clogged by x% now. As the filter is partially blocking the flow of the fuel through it, the load as seen by the pump because of the clogged filter is more. Because of the increase in load, the current drawn by the electric motor will increase accordingly. Let the current drawn by the electric motor be |2 for this case, |2 being an average value derived from a plurality of instantaneous values recorded.

As the ECU is monitoring the fuel pump continuously, it detects a difference in the currents drawn by the fuel when the filter starts getting clogged.

The ECU 18 computes the difference between the|1 and |2 after picking the associated |1 from the table based on the fuel filter type. The difference between |1 and |2 is an indicative of the level of clogging of the filter. By comparing the difference in |1 and |2 the ECU determines the percentage of clogging in the filter.

By comparing the percentage of clogging to a threshold value, the ECU determines when to replace the filter. The ECU may generate an advance warning to the user to inform that the filter is getting clogged when the percentage of clogging crosses a first threshold. The advance warning may be in the form of an audio output 20 in the form of a beep or a blinking lamp 20. When the clogging crosses a second threshold a malfunction indicator may generated for the user to inform him to replace the filter. The malfunction indicator may be in the form of a continuous audio output and/or glowing of a lamp. When the malfunction indicator is generated, the user needs to replace the filter 12. The malfunction indicator may be reset temporarily for the current driving cycle. But during the next driving cycle, the malfunction indicator is generated again to attract the user's attention.

Alternatively, the level of clogging may be informed to the user by using a set of lamps, for example, one lamp glowing for 10% clogging, two lamps glowing for 20% and so on.
Also the level of clogging may be displayed directly as percentage on the instrumentation cluster of the vehicle.

Also, depending on the clogging of the filter, engine torque reduction feature may be enabled to safe guard the fuel injection system in the vehicle.

To pick up the associated |1 for comparing with the |2, the ECU may check for type of filter and then pick up the corresponding |1 from the table.

The invention provides a simple method to determine clogging of a fuel filter in a vehicle. The components used are already available in most of the vehicles thereby eliminating need of any additional components. Also the invention eliminates need of some pressure sensors used in the prior arts to determine the clogging of the fuel filter.

WE CLAIM:

1. A method to determine clogging level of a filter (14), the said method comprising the steps:

monitoring actual current drawn by an electric motor of a fuel pump (12) supplying fuel to the said filter (14)

- comparing the said actual current with a reference current

- generating a warning if the said actual current exceeds the said reference current by a threshold

2. A method according to claim 1 involves displaying the level of clogging of the filter (14) by using lamps.

3. A method according to claim 1 involves displaying the level of clogging of the filter (14) on an instrumentation cluster of a vehicle.

4. An electronic control unit ECU (18) to detect clogging of a filter (14) the said ECU (18) adapted to:

- monitor actual current drawn by an electric motor of a fuel pump (12) supplying fuel to the said fuel filter

- compare said actual current with a reference current

- generate a warning if the said actual current exceeds the said reference current by a threshold

5. An ECU (18) according to claim 4 where in the reference current is stored in a table in a memory

6. An ECU (18) according to claim 4 and 5 where in the said table contains different reference currents for different types of filters

7. An ECU (18) according to claim 4 displays percentage of clogging of the filter (12) through at least one lamp.

8. An ECU (18) according to claim 4 indicates percentage of clogging of the filter through (12) an audio output.