Method of testing fuel injection equipment

Abstract

A method of testing a fuel injection system or components thereof includes running a high pressure fuel pump to provide fluid under pressure to the fuel injection system or components. The pump flow is controlled via an inlet metering valve by controlling current or voltage supplied to the inlet metering valve dependent on the power to the fuel pump.

Claims

1. A method of testing a fuel injection system or components thereof, the method comprising: running a high pressure fuel pump to provide fluid under pressure to the fuel injection system or the components; controlling pump flow of the high pressure fuel pump with an inlet metering valve; and controlling current or voltage supplied to the inlet metering valve based on power to the high pressure fuel pump.

2. The method as claimed in claim 1, where the high pressure fuel pump is driven by an electrical motor and the power is determined from the voltage across and/or current through the electrical motor.

3. The method as claimed in claim 1, wherein the current or the voltage is controlled solely to be dependent on the power.

4. The method as claimed in claim 1, wherein the components are one or more fuel injectors.

5. The method as claimed in claim 4, wherein the one or more fuel injectors are supplied via a common rail fluidly located between the high pressure fuel pump and the one or more fuel injectors.

6. The method as claimed in claim 5, wherein the common rail includes a pressure control valve.

7. The method as claimed in claim 1, wherein the power to the high pressure fuel pump is kept above a minimum threshold level or below a maximum threshold level.

8. The method as claimed in claim 1, wherein said controlling current or voltage supplied to the inlet metering valve based on power to the high pressure fuel pump is performed while said high-pressure fuel pump is running.

9. The method as claimed in claim 2, where the high pressure fuel pump is driven by an electrical motor and the power is determined from the voltage across and/or current through the electrical motor while the electric motor is running.

10. A method of testing a fuel injection system or components thereof, the method comprising: running a high pressure fuel pump to provide fluid under pressure to the fuel injection system or the components; controlling pump flow of the high pressure fuel pump with an inlet metering valve; and controlling current or voltage supplied to the inlet metering valve based on power to the high pressure fuel pump; wherein controlling the current or the voltage supplied to the inlet metering valve comprises incrementing the current or the voltage based on whether the current or the voltage or power is below or above a minimum threshold or a maximum threshold respectively.

11. The method as claimed in claim 10 wherein, the incrementing is variable and based on a rail pressure.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention will now be described by way of example and with reference to the following figure of which:

(2) FIG. 1 shows apparatus used to test a fuel injection system or components thereof.

(3) FIGS. 2a, b, c shows flow charts of one example of implementation of the invention.

DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows apparatus or system used to test a fuel injection system or components thereof. The system is controlled by a controller 1. The controller may comprise an ECU connected to an auxiliary processor or circuitry.

(5) A motor 2 which may be an electrically or electronically controlled/operated motor is used to power a high pressure (e.g. fuel) pump 3. This may be part of or separate to the fuel injection system or components under test. The pump flow is controlled by an Inlet Metering Valve (IMV) 4 associated therewith. The IMV may be integral with the pump. Flow of fuel may be to fuel injection component under test such as one or more fuel injectors 5. The fuel injectors may be provided with flow from the pump via a common rail 6. The common rail may include a pressure control valve (PCV) and/or pressure sensor 7.

(6) In one aspect the IMV is controlled based on the power supplied to the high pressure e.g. common rail pump. The IMV can be controlled by varying the current through it. Thus IMV current is made a function of pump power.

(7) The power to the pump may be determined by measuring or otherwise determining the voltage and/or current across the motor used to drive the pump.

(8) In a preferred aspect the IMV is controlled solely based on the pump power. Thus in one aspect there may be drive power monitoring means and the drive power optimizes the IMV drive current accordingly.

(9) Preferably the motor power is also controlled or limited to a particular power band, i.e. the test equipment system/method can ensure that the power to the pump is not above or below a maximum or minimum level depending on application. This prevents either too high pressure/power, and also prevents to little pressure/power such that there may not be sufficient flow/pressure to test (e.g. faulty) injectors. It is to be understood that the skilled person could readily ascertain power bands parameters.

EXAMPLE

(10) FIG. 2 shows flow charts of one example of implementation of the invention. FIG. 2a is the main flow chart. The process starts with step S1. At step S2 it is decided whether “auto-flow” mode is selected. If so the process proceed to step S3 where it is determined if the common rail pump motor is running. If so the process proceeds to step S4. In this optional step the VCV current step (increment) which may be applied in later steps is determined based on the rail pressure set-point/actual rail pressure. If the rail pressure is very high any increment of the IMV current i.e. change to the IMV current made is preferably small, and vice versa.

(11) In steps S5 and S7 it is determined if the motor current (which is equivalent to power for a fixed voltage electric motor) drives the (common rail pump) is within a certain band. In step S5 it is determined if the motor current is less than a particular level i.e. lower threshold of the band. If so the process proceeds to step S6 where the flow is nudged up by varying the current thought the IMV. This may be performed by an incremental change to the current, the incremental change being dependent on the results of step S4. In order to increase flow the current to the IMV may be increased or decreased depending on the IMV design and logic. Positive logic is defined as where the flow is increased by the IMV if the current is increased. Negative logic is the converse. In steps S7 it is determined if the motor current is more than a particular level i.e. higher threshold of the band. If so the flow is nudged down by making an incremental change to the IMV current appropriately. Again this incremental change may be dependent on the results of step S4.

(12) Regarding steps S4, typically in one example, an IMV control range is between 550-750 mA. For other pumps the range may be from 0 to 2 amps. The “nudge” can be an increment (up or down) of say 2-19 mA dependent on the rail pressure (set-point).

(13) The advantages are that the system automatically compensates for unknown injector characteristics, too much IMV flow, too little IMV flow, excess power to drive the Common Rail pump, manufacturing tolerances and components wear. Map/lookup table generation, storage and reading are not required.

(14) FIGS. 2b and c show flow charts of how the flow can be nudged down or up separately.

(15) In FIG. 2b the process shows the control of how the flow is nudged down. In step S11 it is determined if the IMV valve logic is positive or negative. As mentioned positive is where increase in current provides higher flow. In steps S12 and S13 dependent on the logic the IMV current is incremented up or down. Steps S14 and S15 determine if the IMV current is as a result below or above minimum or maximum set-point respectively. If this is the case the IMV current is set to the minimum or maximum (set-point value) respectively in steps S16 and S17.

(16) FIG. 2c shows the equivalent and corresponding process for nudging the flow up.