GB2582605A

GB2582605A - Method of detecting a leak in a fuel injector

Info

Publication number: GB2582605A
Application number: GB1904251.4A
Authority: GB
Inventors: T Williams Edward; Singh Divjot
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2019-03-27
Filing date: 2019-03-27
Publication date: 2020-09-30
Also published as: GB201904251D0

Abstract

A method of detecting a leak in a fuel injector(s) 3 having a noise, knock, vibration, accelerometer or acoustic sensor 2 comprises the steps of analysing the signal 5, 6 from the sensor(s) or a derived signal(s) or characteristic(s) thereof and determining whether there is a leak in the corresponding injector. Determination may comprise comparing a value derived from the signal indicative of the level of noise, with a threshold value. The method may include a prior step of determining periods of operation of the fuel injector and / or the periods of operation are determined from analysis of the noise signal. The signal may be from the sensors associated with at least two corresponding injectors and comparing the signals to determine a measure of the level of noise in the signals, in respect of time periods between operation, and determining leakage based on the comparison. The derived signals or characteristics are preferably derived by applying a filter 4, or Fourier transform, to the signal(s). Components of the noise signal may have frequencies above 20KHz that are analysed.

Description

METHOD OF DETECTING A LEAK IN A FUEL INJECTOR

TECHNICAL FIELD

This disclosure relates to fuel injectors and specifically to a method of detecting leaks in fuel injectors and fuel injectors systems. It is applicable to fuel injectors having an acoustic sensor located with, on, or adjacent to, the fuel injector. The sensor may be an accelerometer, vibration or knock sensor

BACKGROUND OF THE INVENTION

It is possible, although very rare, for an injector to develop a fuel leak. A leak could occur from the high pressure fuel supply or the low pressure drain/feed path. An injector contains many components that are designed to fit together to be fuel-tight and it is possible that these interfaces could leak. Previously the only way to detect leaks of the high pressure fuel was to observe the rail pressure, so this was only effective for large leaks at rail pressure. Detecting small leaks was very difficult or impossible.

It is an object of the invention to provide a method of detecting leaks including small leaks.

SUMMARY OF THE INVENTION

In one aspect is provided a method of detecting a leak in one or more fuel injectors, each of said fuel injectors having a noise sensor located therewith, comprising the steps of a) analyzing the signal from at least one said noise sensor(s) or a derived signal(s) or characteristic(s) thereof, b) determining whether there is a leak in the corresponding injector of said noise signal from step a).

Step a) may comprise determining the level of noise of said signal or derived signal or characteristics in respect to time periods between periods of operation of said injector.

Step b) may comprise comparing a value derived from said signal indicative of the level of noise, with a threshold value.

The method may include the prior step of determining periods of operation of said fuel injector.

In step i) said periods of operation may be determined from analysis of said noise signal.

Step a) may comprises: i) obtaining a signal from the noise sensors associated with at least two corresponding injectors, or signals or characteristics derived from said signals; ii) comparing said signals or signals or characteristics derived from each signal, to determine a measure of the level of noise in said signals, in respect of time periods between operation, and where step b) comprises determining leakage based on the comparison of step Said derived signals or derived characteristics may be derived by applying a filter or Fourier transform to said signal(s).

In step a) components of the noise signal(s) may have frequencies above 20 or 25 KHz are analysed.

In step ii) the components of said signals which have frequencies above 20 or 25 KHz.

Step a) may comprise determining a parameter indicative of noise levels in said signals or derived signals with respect of signal portions between adjacent operational cycles for two or more successive operation cycles and determining a measure of the increase of said parameters<lo be inserted once claims finalized>

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 system according to one aspect of the invention; Figure 2 shows the relative quietness of six injectors during a 500 hour test; Figure 3 shows a Fourier transform of the sensor signal resulting from operation of the injector which has been modified to leak; Figure 4 shows a Fourier transform of the sensor signal resulting from operation of a normal injector.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The problem of detecting fuel leaks in an injector is solved by listening for the leaks using a vibration or any appropriate acoustic sensor located on or adjacent to a injector. In the same way that it is possible to hear the leaking of air from a car tyre or the leaking of water from a burst pipe, it is also possible to hear leaking of fuel from or within an injector.

Figure 1 shows a system according to one aspect of the invention. An ECU 1 is adapted to receive a signal indicative of the noise or vibration from a vibration (knock) sensor /accelerometer/acoustic sensor 2 located on, integral with or adjacent to a fuel injector 3. The ECU analyses the signal In one example the analysis differentiates leak sounds and normal operational injection sounds to determine the degree of leaking.

The injector may in examples, include a microprocessor 4 associated with it which may also include (software) filters to apply filtering to the sensor signal to discriminate between the sounds of leaking and those of injection. Alternative this functionality may be embodied in the ECU.

In the figure is shown an injector 2 and sensor 3. Included is a microprocessor which includes a processing and filtering functionality 4 which determines and separates the signal into a portion 5 indicative of any leak and a portion 6 indicative of the operational injection. These are fed to the ECU which processes the signals 5 and 6 to determine leak loudness at 7 and injection loudness at 8. The ECU has functionality 9 to compare the leak and injection loudness e.g to each other or to reference values in order to determine the degree of leakage. As a result, a leak is detected, shown by the step/functionality 10 in the figure. Of course processing and filtering functionality 4 which determines and separates the signal into a portion 5 indicative of any leak and a portion 6indicative of the operational injection may occur in the ECU.

Figure 2 shows the relative quietness of six injectors during a 500 hour test. It shows plots 11 of values for each injector which is the amount (magnitude) of sound from each injector in between injections. i.e. the sound is measured for an injector between one injection and the next and the quietest sound level during that short time is recorded on the graph.

The principle is that leaking is something that is continuous so if an injector were to be completely silent at any point then it would have no leaks. In figure 2, for injector number #4 the plot is shown by reference numeral 12 and this value gets progressively louder until at point (marked by a circle A). This indicates that the injector has a leak. Thus in one method the loudness of the noise, in between injections of with respect to one or more fuel injectors is determined and if this exceeds a threshold value, then a leak is determined. Preferably the loudness (magnitude) of noise is determined when the injector is not operational, i.e. between cycles.

The skilled person would readily be aware of how to determine the time periods /slots when the particular injector is not operational. For example, the ECU knows when the injectors are non-operational as e.g. it sends activation commands to the injector when it is operational. Alternatively the operational and/or nonoperational times can be detected by the sensor itself e.g. by looking at the signal from the sensor and optionally applying filtering. Noise from operation will e.g. have a regularity.

Any detected leak may be flagged by the ECU and subsequently visually by display means.

The term threshold value should be understood to a preset or predetermined threshold or also a threshold based on the noise previously recorded in one or more previous operational cycles; particularly between the cycles. So the method may look at the noise levels between a number of previous adjacent cycles to see the degree or extent of any increase in noise. The noise may get progressively louder.

Alternatively, where there are a plurality of injectors each with a noise sensor, the method may entail obtaining signals from the plurality (at least two) sensors and compare noise levels thereof preferably in the times when the injectors are non-operational, and determining leakage based on this comparison.

In preferred embodiments as will be explained below, for leak detections the component of the signal or signals used in the methods which is above 20 KhZ or 25 KHz is used to determine leakage. Thus a filter may be applied to the signal, and the level (preferably between operating) of filtered signal is compared with a threshold or with results from other injectors. Again this is done preferably on the signal portion(s) between injector operation.

Alternatively, a characteristic based on the signal such as a Fourier transform of the signal may be analyzed to determine leak, Where at least two signals are compared the components of the signals above a frequency of 20Khz or 25KHz are analyzed compared to determine a leak.

Returning to figure 2, after point A the leaking injectors it was replaced with another injector which was a lot quieter as can be seen. The original injector in cylinder 4 was found to have a broken (leaking) header.

In practical embodiments the Engine Control Unit or injector processor would periodically measure the vibrations on the injector (preferably in between injections), filter the measured signal so as to highlight the frequencies that are typical of a leaking injector.

If the ECU noticed over time that the amplitude was getting much higher then it could infer that the injector was leaking. This is an improvement on existing solutions that monitor the rail pressure because it can detect leaks anywhere in the injector and this facility to measure vibrations is built in to an injector.

With reference to the control chamber of a Diesel injector; which includes a control valve assembly, on actuation of the nozzle control valve, the control valve pin lifts to drain the volume of pressurized fluid from back of the nozzle needle, through the control valve assembly, past its pin and out of a drain hole. This should create a pressure difference across the needle resulting in enough force to lift the needle to cause injection. In an experiment a modified nozzle needle was used which resulted in excessive leakage past the nozzle needle at rail pressure. When the control valve pin lifts up to drain the volume not enough force is generated to lift the nozzle needle. As a result, there was constant leakage past the pin which can be noisy.

Figure 3 below shows a Fourier transform of the sensor signal resulting from operation of the injector which has been modified to leak as above, and not inject Note that the frequencies are mostly above 25kHz.

Figure 4 shows a Fourier transform of the sensor signal resulting from operation of a normal injector; which has a lot of signal content below 25kHz. From this we can conclude that leaking is a higher frequency signal than we would find in a non-leaking injector.

Claims

CLAIMS1. A method of detecting a leak in one or more fuel injectors, each of said fuel injectors having a noise sensor located therewith, comprising the steps of a) analyzing the signal from at least one said noise sensor(s) or a derived signal(s) or characteristic(s) thereof; b) determining whether there is a leak in the corresponding injector of said noise signal from step a).
2. A method as claimed in claim 1 where step a) comprises determining the level of noise of said signal or derived signal or characteristics in respect to time periods between periods of operation of said injector.
3. A method as claimed in claim 1 or 2 wherein step b) comprises comparing a value derived from said signal indicative of the level of noise, with a threshold value.
4. A method as claimed in claim as claimed in claim 2 or 3 including the prior step of determining periods of operation of said fuel injector.
5. A method as claimed in claim as claimed in claim 4 wherein step said periods of operation are determined from analysis of said noise signal.
6. A method as claimed in claim 1 where step a) comprises: i) obtaining a signal from the noise sensors associated with at least two corresponding injectors, or signals or characteristics derived from said signals; ii) comparing said signals or signals or characteristics derived from each signal, to determine a measure of the level of noise in said signals, in respect of time periods between operation, and where step b) comprises determining leakage based on the comparison of step ii).
7. A method as claimed in claims 1 to 6 where said derived signals or derived characteristics are derived by applying a filter or Fourier transform to said signal(s).
8. A method as claimed in claim 1 wherein in step a) components of the noise signal(s) which have frequencies above 20 or 25 KT-lz are analysed.
9. A method as claimed in claim 6 wherein in step ii) comprises comparing components of said signals which have frequencies above 20 or 25 KHz.
10. A method as claimed in claims 1 to 5 wherein step a) comprises determining a parameter indicative of noise levels in said signals or derived signals with respect of signal portions between adjacent operational cycles for two or more successive operation cycles and determining a measure of the increase of said parameters.