GB2574044A

GB2574044A - Method of determining vibration events in engines using a plurality of injectors having accelerometers

Info

Publication number: GB2574044A
Application number: GB1808548.0A
Authority: GB
Inventors: T Williams Edward
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2018-05-24
Filing date: 2018-05-24
Publication date: 2019-11-27
Also published as: GB201808548D0

Abstract

A signal of a vibrational event occurring in the engine 1 is formulated from signals of a plurality of accelerometers 4, where each accelerometer is associated with a fuel injector 3. Each of the signals from the accelerometers is shifted time-wise by an amount dependent on the location of the accelerometer and all the time-shifted signals are combined to formulate a summed signal. The summed signal can be used to determine the time of a vibrational event, such as combustion in a particular cylinder, and the sensors may be knock sensors. The time shift applied is dependent on the speed of sound and the distance between the vibrational event to be detected and the respective accelerometer. Processing of the signals may use beamforming and be performed by an electronic control unit to provide a precise time of an event such as combustion.

Description

TECHNICAL FIELD

This invention relates to a method of precisely detecting and characterizing the nature (such as the timing) of a vibrational event in an internal combustion engine by collating and processing signals from a plurality of accelerometers, each accelerometer associated with a fuel injector. It has particular but non-exclusive application to determining the timing of combustion events.

BACKGROUND OF THE INVENTION

It is useful to know when combustion occurs in the cylinders of an internal combustion engine because this allows the engine’s electronic control unit (ECU) to make adjustments to improve emissions and fuel economy. It is also useful to detect vibrations in different parts of an engine in order to know if it is working correctly.

Combustion is usually detected by one of three methods. In one method this is done with a cylinder pressure sensor, which is very precise but is also expensive and not very robust. In another method this is done by monitoring vibrations of the crankshaft; this isn’t expensive but it isn’t very precise. Another method is by monitoring vibrations using an accelerometer attached to the engine block. It is less effective on modern engines where the block is designed to emit less noise. It requires at least two sensors and their wires to connect them to the electronic control unit.

It is known for fuel injectors to have accelerometers (sensors) associated with them (i.e. located on, integral or adjacent to the injector) to provide feedback on fuel injector events for that fuel injector they are located on.

It is an object of the invention to detect and characterize the nature (e.g. timing) of combustion events or other events of engine components without having to add sensors specifically for this purpose.

SUMMARY OF THE INVENTION

In one aspect is provided, in an internal combustion engine having a plurality of fuel injectors, each injector having an accelerometer associated therewith, a method of formulating a signal in respect of a vibrational event occurring in the engine comprising:

a) receiving the signals from a plurality of said accelerometers;

b) for each of said received signals, shifting the signal time-wise by an amount dependent on the location of the accelerometer;

c) combining all the time-shifted signals from step c) to formulate a summed signal.

The method may include determining the time of the vibrational event from the summed signal formulated from step c).

In step b) the time shift applied in step b) in each case may be dependent on the distance between the vibrational event to be detected and the respective accelerometer.

The vibrational event may be combustion in a particular cylinder.

The time shift for each signal may be determined dependent on the distance between the location of vibrational event and the accelerometer, and the speed of sound through steel.

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 representation of an engine having six cylinders and fuel injectors for each cylinder, each fuel injector having an accelerometer located therewith;

- Figure 2 shows schematically the delay of the vibration from a combustion event from cylinder reaching the various accelerometer sensors;

Figure 3 illustrates a simple processing methodology according to one aspect, applied to the above example;

- Figure 4 shows the various signals and signal processing results at various stages.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is known to utilize knock sensors (accelerometers) on fuel injectors for the purpose of detecting vibrations due to events in the operational cycle of the fuel injector, such as injector valves opening and closing. In methodology of the invention these sensors are also used to determine other events in the operation of the engine such as combustion.

In the methodology according to aspects of the invention, the signals from a plurality of such injectors, are combined after suitable processing (such as timeshifting to take into account the variation of distances of travel of the vibrations from the vibrational event to the respective accelerometer), to produce a combined signal of the vibrational event. This processed and combined signal is a clean more accurate signal and can be used to precisely obtain the exact time of the vibrational event.

The processing / combining methodology with regard to the various signals can be regarded as a kind of “beamforming” and may be performed by the electronic control unit so as to provide a precise time of the event e.g. a particular combustion.

Thus the methodology can be used in cases where each injector has a accelerometer (vibration/knock sensor) located on or adjacent to a fuel injector, enabling it to detect noises/vibrational events not just from the injector it is associated with, but from any part of the engine..

Each of the accelerometers is connected to the engine ECU enabling signals from them to be transmitted to or from the ECU. So the injectors are able to transmit signals (i.e. raw data) or processed data in respect of the accelerometer associated with them to the electronic control unit that controls the injectors. Thus the accelerometer signals may be received by the ECU or alternatively, where the injector includes processing ability e.g. a chip associated with the injector, the injector may process the accelerometer signals to extract information from the signals and send refined data to the ECU.

By processing and combining a plurality of signals from corresponding plurality of accelerometer located at spatially diverse locations i.e.. on the various fuel injectors (for example signals from six accelerometers of corresponding six injectors in a six cylinder engine) it is possible to determine more accurately the precise timing of vibrational events (i.e. focus on a particular part of the engine), for example, combustion in cylinder number 2. If a single sensor was used for this purpose it would be very difficult to determine which noises came from which part of the engine.

Figure 1 shows a representation of an engine 1 having six cylinders 2 and fuel injectors 3 for each cylinder, each fuel injector having an accelerometer 4 located therewith. Cylinder number 2 (second from the left) is indicated at the time showing combustion. The vibration from this travels along pathways to the respective accelerometers; the paths that the vibrations travel from the combustion, to the six accelerometers, are shown/represented by arrows 5. The distances of these varying pathways can be determined from engine geometry and may comprise the shortest route through solid engine component e.g. metal to the accelerometer sensors from cylinder number 2 .

Figure 2 shows schematically the delay of the vibration from a combustion event from cylinder 2 reaching the various accelerometer sensors. The arrows 6 represent distances and thus also time delay between vibrations from the combustion event/vibration reaching the respective accelerometers. The time delays can be determined from the distances (such as the shortest route through the metal of the engine) between cylinder number 2 and the respective accelerometers, as well as the speed of sound through steel. So the arrows 6 represent the delay (proportional to distance, due to speed of sound through metal) between the combustion on cylinder2 and the accelerometer sensor detecting it. Note that sensor on cylinder number 2 experiences the shortest delay and the sensor on cylinder number 6 (at the bottom) experiences the longest.

Figure 3 illustrates a simple processing methodology according to one aspect, applied to the above example. The arrows 6 again represent the inherent time delays which represent the delay in time for the combustion vibration (e.g. of cylinder number 2) to reach the accelerometers as described above.. Arrows 7 are time delays/shifts that are added in the methodology such that all the signals are effectively brought into synchronizations regarding the same vibrational event/pulse i.e. all the signal are brought into line in a timewise fashion. Thus effectively here signals are time shifted by an amount 7 (said amount being dependent on the time delay 6). When applying the respective time shifts , all resultant signals should show the vibration at the same time i.e. brought into synchrony.

Then the signals are added together i.e. combined or superimposed at 8. When this is done the resultant processed signal 9 is sharper and less ambiguous, then if they have been combined without the aforementioned processing. Further the resultant combined signal is derived from all accelerometers so provides a more accurate signal/ This can then be used to more accurately determine the timing of the event (e.g. combustion), by determining more accurately the position (in time ) of the maximum (peak value) of the signal.

Thus this superposition of the various signals effectively “averages out” any noises that were not heard on all the sensors or were heard on all the sensors but do not align when the delays have been applied, i.e. noises that do not come from the direction of cylinder 2.

Figure 4 shows the various signals and signal processing results at various stages. Top plot a) shows the original vibrational pulse 10 from the event e.g. the combustion signal at source. Plot b) shows the event (combustion) signal 11 on each of the accelerometers in real time. Plot c) shows the 12 sum of all the signal of plots which gives a noisy signal result. Plot d) shows the results 13 of the processing of the signals according to one aspect so that they are synchronized for the combustion event i.e. synchronized in respect of the combustion in cylinder number 2. In other words they show the measured signals realigned (time shifted) to take into account/compensate for the travel time of the vibrational pulses through steel to the appropriate accelerometer from the cylinder of combustion.

Plot e) shows the combination i.e.. sum of the realigned signals 14 from plot d). As can be seen the resultant signal is sharp and clean and can be used to more precisely determine the time of the combustion e.g. by determining the time of the peak of the maximum amplitude.

So the signals in plot c) are noisy and misshapen result and by realigning (shifting timewise) the six accelerometer signals according to the position of the sensors in relation to the combustion in cylinder number , and then either combining or averaging the signals the shape of the original source is preserved and the noise is reduced. The example of figure 4 is for a simulation example of a 6kHz signal showing how it might appear at the six injector accelerometer sensors. This simulation assumes 25cm pitch of cylinders in a straight- 6 configuration and 6000m/s wave travel speed.

Example 1

In a first step it is decided which engine event is to be detected. So for example it is decided to detect the start of combustion for cylinder number 2. The ECU may send a message to all 6 injectors instructing them to record the signals from their respective accelerometers, when they are given the trigger pulse (a very short voltage pulse on the injector wires sent from the ECU to the injector). The ECU sends the trigger pulse just before it expects combustion to happen. After the recording has finished, each injector sends its recording to the ECU. The ECU combines the recordings using beamforming and filtering to determine exactly when combustion occurred.

The skilled person would be aware of various ways in which the signals from the injectors are processed and combined.

The example above was using the methodology to detect combustion on cylinder 2, but methods can equally be applied to the other cylinders or indeed for other events from other engine components e.g. crankshaft main bearings, valves opening/closing.

Claims

1. In an internal combustion engine having a plurality of fuel injectors, each injector having an accelerometer associated therewith, a method of formulating a signal in respect of a vibrational event occurring in the engine comprising:

a) receiving the signals from a plurality of said accelerometers;

2. A method as claimed in claim 1 including determining the time of the vibrational event from the summed signal formulated from step c).

3. A method as claimed in claims 1 or 2 where in step b) the time shift applied in step b) in each case is dependent on the distance between the vibrational event to be detected and the respective accelerometer.

4. A method as claimed in claims 1 to 3 where the vibrational event is combustion in a particular cylinder.

5. A method as claimed in claim 3 where the time shift for each signal is determined dependent on the distance between the location of vibrational event and the accelerometer, and the speed of sound through steel.