GB2568089A

GB2568089A - Fuel pump with accelerometer

Info

Publication number: GB2568089A
Application number: GB1718311.2A
Authority: GB
Inventors: J Lane David; Male Andrew; Logue Samuel; O'connell Charlotte
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2017-11-06
Filing date: 2017-11-06
Publication date: 2019-05-08
Also published as: GB201718311D0

Abstract

A high pressure fuel pump, having a cam driven plunger to pressurize fuel within a pressurization chamber of the pump, includes at least one accelerometer, eg a knock sensor, associated with the pump to provide data to the ECU. The accelerometer(s) may be mounted on the pump cambox or the inlet metering valve (IMV) or the outlet metering valve (OMV). The output signal of the accelerometer(s) may be analysed to detect and determine operating parameters or conditions of the pump or fuel delivery system, eg IMV/OMV opening/closing, or faults and anomalies, eg cavitation collapse in the plunger chamber or fuel aeration. For example, a non-return valve (NRV) closing time can be ascertained from the cam angle 4 at which a vibration pulse 2 occurs when the NRV closes. The closed-loop control (on board diagnostics, OBD) can compensate for valve wear. The accelerometer(s) may detect impact/vibration from other components in the engine or vehicle outside the pump.

Description

(57) A high pressure fuel pump, having a cam driven plunger to pressurize fuel within a pressurization chamber of the pump, includes at least one accelerometer, eg a knock sensor, associated with the pump to provide data to the ECU. The accelerometer(s) may be mounted on the pump cambox or the inlet metering valve (IMV) or the outlet metering valve (OMV). The output signal of the accelerometer(s) may be analysed to detect and determine operating parameters or conditions of the pump or fuel delivery system, eg IMV/OMV opening/closing, or faults and anomalies, eg cavitation collapse in the plunger chamber or fuel aeration. For example, a non-return valve (NRV) closing time can be ascertained from the cam angle 4 at which a vibration pulse 2 occurs when the NRV closes. The closed-loop control (on board diagnostics, OBD) can compensate for valve wear. The accelerometer(s) may detect impact/vibration from other components in the engine or vehicle outside the pump.

1/2

Cam angle

Current (IMV solenoid)

time/cam angle

2/2

A 5

-20 0 20 40 60 80 100 120

Cam angle⁰

Fig. 5A

Cam angle⁰

Fig.4B

A

2-1 -

Cam angle⁰

Fig.5B

FUEL PUMP WITH ACCELEROMETER

TECHNICAL FIELD

This invention relates to fuel pumps which include a plunger type arrangement adapted to pressurize fuel. Fuel output may be to fuel injectors via e.g. a common rail system. The invention relates to apparatus and methods of determining operating parameters of a high pressure pumping system and components thereof.

BACKGROUND OF THE INVENTION

Fuel flow into a pressurizing chamber of a piston type pump is typically controlled by an inlet metering valve (IMV). The fuel is subsequently pressurized by such a plunger or piston, (typically cam driven) before the pressurized fuel is outlet, e.g. via a common rail, to fuel injection equipment. The outlet of fuel from the chamber may take place under control of an Outlet Metering Valve (OMV).

In the case of a high pressure fuel pump controlled electronically by an ECU, a current is applied to either an IMV or OMV stator with the aim of regulating fuel delivery from the pump. There is no electronic communication from the high pressure pump to the ECU in such a setup. Because there is no communication from the high pressure fuel pump to the ECU, limited opportunity exists for adjusting ECU outputs based upon on events within the high pressure pump such as valve motion or impact events. This lack of feedback from the high pressure pump also limits opportunity for diagnosing faults within the high pressure pump.

It is an object of the invention to provide feedback from the pump in order for diagnostics and improved control of both the pump and/or other component of a fuel injection system which includes such a pump.

SUMMARY OF THE INVENTION

In one aspect is provided a high pressure fuel pump including a cam driven plunger adapted to pressurize fuel within a pressurization chamber of said pump, and including at least on accelerometer associated with said pump.

Said accelerometer(s) may be mounted onto or integrated with said pump or a pump component.

In a further aspect is provided a high pressure fuel delivery system including a pump as above and an Inlet Metering Valve (IMV) or Outlet Metering Valve (OMV), located upstream of an inlet to said chamber and/or a Non Return Valve (NRV) located downstream of an outlet form said chamber.

Said accelerometer may be is mounted to or adjacent the Inlet / Outlet Metering Valve or the Non Return Valve

The pump or system as claimed in claim 3 including connection means to an Engine Control Unit and adapted to send raw or processed data from the accelerometer to the ECU.

In a further aspect is provided a method of detecting operating parameters or conditions of said pump or system or components thereof, comprising analyzing the output signal of said accelerometer, and determining said operating parameter from said signal.

Said parameter may be the opening or closing of an Inlet / Outlet metering valve or and outlet valve such as a Non Return Valve.

In a further aspect is provided a method of detecting faults or anomalies of said pump or system or components thereof, comprising analyzing the output signal of said accelerometer, and determining said faults or anomalies from said signal

Said faults or anomalies may be cavitation collapse within plunger chamber or other parts of the pump.

In a further aspect is provided a method of determining the Inlet / Outlet Metering Valve closing duration in a pump or system; comprising the steps of: a) sending a activation pulse to the solenoid of the OMV actuator to close said valve, b) determining the time of initialization of said activation of said OMV actuator to close said valve, c) the monitoring the signal output of the accelerometer to detecting a pulse therein signal subsequent to activating said OMV to the closed positon, d) determining the time between the initialization of activation and said pulse, as said closing time.

In step b) said time of initialization of said activation may be determined form monitoring the current through the solenoid of said actuator.

The method may include of determining the extent of aeration in said pump, pumping system or components thereof comprising determining the NRV closing duration and determining said extent from said duration.

The method may comprise determining the point of cavitation collapse within the pressurization chamber from said accelerometer signal.

In a further aspect is provided a method of determining the viscosity of fuel entering the pressurization chamber of a pump or system comprising: i) determining the time point of cavitation collapse within the pressurization chamber from said accelerometer signal;

ii) determining an expected time point of cavitation collapse within the pressurization chamber iii) determining a measure of deviation between the results of steps i) and ii); and, iv) determining the viscosity from said deviation.

The method may comprise determining an expected flow rate for a fuel of nominal viscosity entering the pressurisation chamber dependent on a determined fuel feed pressure, pump speed, and the expected time of cavity collapse from step i); determining an actual flow rate entering the pressurisation chamber dependent on a determined fuel feed pressure, pump speed and the actual time of cavity and step iii) comprises determining the viscosity from the difference between actual and expected flow rates and the nominal viscosity

Said parameter may be NRV or OMV closing or opening durations or wear.

The method may including monitoring NRV wear comprising monitoring the magnitude of an output pulse from the accelerometer at a time when the NRV is expected to open.

The method may comprise determining if the output pulse is higher than expected or monitoring any increase in said magnitude over time.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which:

- Figure 1 shows a plot of an accelerometer signal valve with corresponding plot of current through a solenoid of a solenoid operated valve of a pumping system;

- Figure 2 shows a plot of an accelerometer signal valve with corresponding plot of “once per rev” reference signal;

- Figure 3a shows a plot of the camshaft profile, a reverence signal (1/rev) over time during a pumping cycle, as well as the output from an accelerometer signal, and figure 3b shows the region in the left of figure 3a in more detail; Figure 4a and 4b shows figures similar/corresponding to figures 4a and 4b for a pump with a worn OMV; and

- Figures 5a and b shows figures similar/corresponding to figure 4a and 4b where the OMV solenoid control pulse has been varied to compensate for OMV wear.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a general aspect the invention includes incorporating an accelerometer (knock sensor) onto a (high pressure) fuel pump, so as to provide information (i.e. feedback), e.g. to an ECU. The information may relate to operating or other parameters of a high pressure pump system including the high pressure pump, inlet and outlet valves.

The accelerometer may have associated circuitry such as an integrated circuit and digital communication capability co-located on the high pressure pump to allow feedback or processing of data to and for the ECU, e.g. via appropriate wiring, such that the output of the accelerometer can be transmitted to the ECU for processing or processed by an integrated circuit integral with or co-located with the accelerometer, so important parameters associated with the pump can be determined.

The accelerometer can be provided anywhere on the high pressure pumping system, including anywhere on the pump such as on the cambox or on individual pumping elements, or on the inlet or outlet metering valves.

Events or operating parameters that can be detected by detecting the output signal from such an accelerometer include but are not limited to the following data :Inlet valve (e.g. IMV) motion and events (e.g. opening and/or closing); Outlet Metering valve (e.g. OMV) and Non-retum valve (e.g NRV) motion and events (e.g. opening and/or closing); cavitation collapse within plunger chamber or other parts of the pump.

Using the accelerometer to detect the aforementioned events within the high pressure pump, various parameters can be determined and supplied to the ECU. In the following various refined examples are given of the use of such an accelerometer but are not limited.

Calculation of closure of NRV and pump camshaft TDC point

It is common to include a non-return valve (NRV) downstream of the outlet of the high pressure pump to ensure there is no flow back of fuel from the high pressure outlet to the chamber. In one aspect the event of closing of such a valve is important to know. Figure 1 illustrates methodology to detection of NRV closing event using accelerometer signal lfrom a fuel pump having an accelerometer, incorporated with it. The bottom trace 1 shows the accelerometer signal against cam angle. When the NRV closes there is a vibration pulse as shown by reference numeral 2, and the cam angle this occurs at is shown by vertical line 4. Thus an outlet valve such as a NRV closing time can be ascertained.

The top plot 5 shows the corresponding “Once per rev” reference signal, from a sensor measuring a fixed position on the pump camshaft, namely top dead centre (TDC) of cylinder 2. The voltage on the ‘once per rev’ trace passes through 0 Volts at the Top Dead Centre position of the piston/cam and so from this trace the point or relative position of the TDC can be determined. The TDC of the pump cam is indicated by the vertical line 3 at 90 degrees. By detecting a fixed point on each rev, interpolation can be used to find the camshaft angle at any given time.

As mentioned, the NRV closing event is calculated from the accelerometer signal.. The relationship in terms of cam angle interval between the TDC and NRV closing can be characterized for a pump module design so that given that the NRV closing event is known from the knock signal trace, the time point when the cam is at TDC can be determined.

Valve travel time during inlet valve closing

This parameter can be calculated from time between application of current to the stator coil of the OMV and the outlet metering valve closing event detected by the accelerometer; this is illustrated in figure 2. The top trace 7 shows the current applied or flowing through the solenoid coil of the Outlet Metering Valve actuator. The bottom trace 1 shows the accelerometer signal against time with pulse 8 detected. When the OMV closes there is a vibration pulse as shown by reference numeral 6. The top plot shows the current through an electrically (e.g. solenoid) operated OMV. The current can be determined by known techniques such as simply having means to measure the current. Vertical line 9 indicates the time-point when the OMV is actuated (by applying a voltage/current through the OMV actuator 7; so the start of actuation. The time span between this point and the start of the vibration pulse (indicated by the arrow A) is thus the valve travel time or time between actuation initiation and closing.

Measurement of any cavitation collapse event within the plunger chamber using an accelerometer to determine the earliest outlet metering valve closure time.

By using an accelerometer, shockwaves produced from a cavity collapsing can be detected. The cavity is formed when the pressure of the fuel in the plunger chamber drops below that of the vapor pressure, which is typically caused by a localized pressure drop at the tip of the plunger at the start of the expansion/filling stroke. When the fuel has had sufficient time to increase the pressure in the plunger chamber, by compression of the cavity or filling, the formed cavities will implode producing a shockwave. Typically the cavity collapse shockwave is greater at higher engine speeds due to the correlation between a larger plunger velocity producing a larger cavity size. Once the cavity collapse event has been detected, it is possible to calculate the optimal outlet metering valve closure time to ensure the plunger chamber is void of any cavities, and the pump is yet to begin spilling fuel back into the inlet system.

The optimal point to close the outlet metering valve for maximum fuel delivery will be after the point of the cavitation collapse. The cavity collapse event can be detected using the knock signal as described in the previous section. Using the calculated cavity collapse event removes the dependence on pump speed or fuel supply pressure for calculation. It is important to base the calculation of the outlet metering valve closure around the point of cavity collapse as if it is prescribed too early, the cavity must be compressed using only the fuel within the plunger chamber before fueling can begin. Similarly if the cavity collapse event is before the outlet metering valve closure, fuel will be spilled from the system back into the inlet system. Both conditions result in maximum fuel delivery not being achieved.

Calculation of viscosity of the fuel

The flow rate at which fuel passes through the inlet system drillings in the pump body and into the plunger chamber can be modelled using Poiseuille’s Law, assuming laminar flow, as described below:

877Δ

Where Q is flow rate, Δρ is pressure drop, r is radius of fuel inlet drilling, η is viscosity and L is the length of the inlet drilling. Since the radius and length of the inlet drillings are fixed for a given pump design and pressure drop can be assumed to be equal to the fuel supply pressure, flow rate can be said to be directly proportional to viscosity.

As described in a previous section, an accelerometer can accurately measure the point of cavity collapse within the plunger chamber and therefore fuel flow rate into the plunger chamber can be calculated. The fuel flow rate into the plunger chamber for a given fuel feed pressure and pump speed can be measured for a known fuel viscosity and therefore an expected time of cavity collapse can be prescribed. Should the cavity collapse event occur before or after the expected time, the deviation from this expected time can be used to calculate the deviation in fuel flow rate into the plunger chamber from the nominal value and therefore fuel viscosity can also be calculated.

Calculation of the optimal point to close the outlet metering valve for maximum fuel delivery irrespective of pump speed or fuel supply pressure

Figure 3a shows a plot similar to that of figure 2 with corresponding reference numerals as well as the camshaft profile 10, and so includes a reference signal (1/rev) over time during a pumping cycle, denoted by reference numeral 5, as well as the output from an accelerometer signal 1. In addition is shown the current profile 7 through the outlet metering valve solenoid in order to close it. The accelerometer plot shows a small pulse 8 on the left on the figure which shows the point at which the outlet metering valve closes and a larger pulse 11 which indicates the reopening of the outlet metering valve. Figure 3b shows the left hand side of the plot in greater detail. The arrow A indicates the valve travel time during closing and is from initial activation as indicated form the current/voltage pulse across the solenoid actuator of the outlet metering valve, to the point of the smaller pulse.

Figure 4a and b shows corresponding plots where the outlet metering valve travel time during opening increases as a result of e.g. valve wear.

Presently, when injectors and pumps are manufactured, they undergo pass-off tests which characterize the performance of the unit. This will include different parameters such as valve travel time, nozzle opening delay etc. These performance indicators are sent to the customer as a map and are configured with the ECU for engine control. This means that valve travel time, for example, is defined at start of life and does not change throughout the course of the parts’ life.

By having an integrated accelerometer on the pumping element, this allows the pump to use closed loop control ensuring optimum performance of the pump at all times throughout life. The example above shows how the closed loop control can compensate for valve wear; if over time the outlet metering valve wears and travel time increases, this would normally result in a delay to valve closure resulting in less than the full pumping stroke being used, creating inefficiencies. By knowing the outlet metering valve travel time the start of current can be shifted, ensuring the valve still shuts at the point for optimum efficiency. Figure 5a and 5b illustrates how the start of the current can be shifted to ensure this.

Examples of using the accelerometer are equally applicable to determine the valve time where IMV are biased in the closed position and include solenoid actuated mean activated to close the valve.

Fuel aeration

Fuel aeration can be detected in aspects of the invention.. If the outlet metering valve travel time in either the closing or opening phase is significantly shorter than expected, this indicates that the valve damping is too low and there is likely to be a lack of fuel around the armature to damp the valve, which would indicate fuel aeration. Thus, comparing actual valve travel time with expected travel times can be used to determine fuel aeration. Expected travel times may be dependent on various parameters, and these may be stored in the ECU e.g. as a map, and used for subsequent comparison. If the difference between the expected travel time and actual travel time (as measured using the accelerometer) exceeds a threshold, then aeration is indicated.

Detection of Non-Return Valve (NRV) seat wear

If NRV seat wear occurs, the ball or other sealing component can create a wider sealing band in the sealing cone, which in turn creates a difference between the area exposed to rail pressure above the sealing band and the area exposed to pressure in the plunger chamber below the sealing band. This change requires a greater pressure differential between the plunger chamber and fuel rail to open the NRV. This pressure differential is equalized rapidly during the NRV opening and leads to a pressure pulse that can be detected using an accelerometer.

Thus during periods when the NRV is expected to open, the output of the accelerometer is monitored. If the pulse is greater than a threshold , NRV valve wear is indicated. The threshold may also comprise historic data. In other words the wear may be monitored by determining the magnitude of any pulse during NRV opening times to see if it increases with time.

In general accelerometers mounted with or integral with pumps or pump elements can provide valuable diagnostics such as On Board Diagnostic (OBD) failure mode feedback to ECU. It can determine which pump element has experienced an issue for systems that include more than one pumping element; fuel aeration;

premature ageing of pump elements or cambox assembly and such like. Also , such accelerometers can provide detection and processing of impact / vibration event from other components within the engine or vehicle truck assembly outside of the high pressure pump within which the accelerometer is integrated

Claims

1. A high pressure fuel pump including a cam driven plunger adapted to pressurize fuel within a pressurization chamber of said pump, and including at least on accelerometer associated with said pump.

2. A pump as claimed in claim 1 where said accelerometer(s) is mounted onto or integrated with said pump or a pump component.

3. A high pressure fuel delivery system including a pump as claimed in claims 1 or 2 and an Inlet Metering Valve (IMV) or Outlet Metering Valve (OMV), located upstream of an inlet to said chamber and/or a Non Return Valve (NRV) located downstream of an outlet form said chamber.

4. A system as claimed in claim 3 where said accelerometer is mounted to or adjacent the Inlet / Outlet Metering Valve or the Non Return Valve

5. A pump or system as claimed in claim 3 including connection means to an Engine Control Unit and adapted to send raw or processed data from the accelerometer to the ECU.

6. A method of detecting operating parameters or conditions of said pump or system of claims 1 to 5 or components thereof, comprising analyzing the output signal of said accelerometer, and determining said operating parameter from said signal.

7. A method as claimed in claim 6 where said parameter is the opening or closing of an Inlet / Outlet metering valve or and outlet valve such as a Non Return Valve.

8. A method of detecting faults or anomalies of said pump or system of claims 1 to 5 or components thereof, comprising analyzing the output signal of said accelerometer, and determining said faults or anomalies from said signal

9. A method as claimed in claim 8 where said faults or anomalies are cavitation collapse within plunger chamber or other parts of the pump.

10. A method of determining the Inlet / Outlet Metering Valve closing duration in a pump or system of claims 1 to 5; comprising the steps of:

a) sending a activation pulse to the solenoid of the OMV actuator to close said valve,

b) determining the time of initialization of said activation of said OMV actuator to close said valve,

c) the monitoring the signal output of the accelerometer to detecting a pulse therein signal subsequent to activating said OMV to the closed positon,

d) determining the time between the initialization of activation and said pulse, as said closing time.

11. A method as claimed in claim 10 where in step b) said time of initialization of said activation is determined form monitoring the current through the solenoid of said actuator.

12. A method as claimed in claims 10 to 11 including of determining the extent of aeration in said pump, pumping system or components thereof comprising determining the NRV closing duration and determining said extent from said duration.

13. A method as claimed in claim 6 comprising determining the point of cavitation collapse within the pressurization chamber from said accelerometer signal.

14. A method of determining the viscosity of fuel entering the pressurization chamber of a pump or system as claimed in claims 1 to 5 comprising:

i) determining the time point of cavitation collapse within the pressurization chamber from said accelerometer signal;

15. A method as claimed in claim 14 comprising:

determining an expected flow rate for a fuel of nominal viscosity entering the pressurisation chamber dependent on a determined fuel feed pressure, pump speed, and the expected time of cavity collapse from step i) determining an actual flow rate entering the pressurisation chamber dependent on a determined fuel feed pressure, pump speed and the actual time of cavity and step iii) comprises determining the viscosity from the difference between actual and expected flow rates and the nominal viscosity

16. A method as claimed in claim 6 as claimed in wherein said parameter is NRV or OMV closing or opening durations or wear.

17. A method as claimed on claim 16 including monitoring NRV wear comprising monitoring the magnitude of an output pulse from the accelerometer at a time when the NRV is expected to open.

18. A method as claimed in claim 17 comprising determining if the output pulse is higher than expected or monitoring any increase in said magnitude over time.

Intellectual Property Office

Application No: GB1718311.2

Claims searched: 1 to 18

Examiner: John Twin

Date of search: 20 March 2018

Patents Act 1977: Search Report under Section 17

Documents considered to be relevant:

Category Relevant to claims Identity of document and passage or figure of particular relevance X 1,2,6,8 at least WO 2017/001090 Al (Robert Bosch) - see eg the EPODOC & WPI abstracts; fig. 1; note acceleration sensor 18 in body of HP pump 1 X 1-6 at least KR 10-2017-0076120 A (Hyundai Kefico) - note vibration sensor 130 on flow control valve 120 of HP pump 110 X 1-6 at least CN 105402115 B (North China Inst. Aerospace Eng.) - note vibration sensor 3 associated with fuel pump 2 X 1-3 at least JP 57020553 A (Hitachi Shipbuilding) - see eg the EPODOC abstract; fig. 1; a vibration detector is installed eg on a HP fuel pump X 1-5 at least US 5533477 Al (Siemens) - a diesel injection piston pump P includes a structure-bornesound (piezo) transducer PZ X 1,3,5,6 at least JP 04109072 A (Zexel) - see eg the EPODOC abstract; fig.l; a shock wave sensor 44 is associated with a HP fuel pump P X 1,3-6 at least JP 60026164 A (Hitachi Construction) - an accelerometer 3 is secured on the case of a fuel injection pump 1

Categories:

X Document indicating lack of novelty or inventive step A Document indicating technological background and/or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of before the filing date of this invention. same category. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.

Field of Search:

Search of GB, EP, WO & US patent documents classified in the following areas of the UKCX :

Worldwide search of patent documents classified in the following areas of the IPC____________

F02D; F02M_________________________________________________

The following online and other databases have been used in the preparation of this search report