GB2534201A

GB2534201A - Determining an expected lifetime of a valve device

Info

Publication number: GB2534201A
Application number: GB1500759.4A
Authority: GB
Inventors: Kabrich Todd
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2015-01-16
Filing date: 2015-01-16
Publication date: 2016-07-20
Also published as: GB201500759D0

Abstract

Disclosed is a method of determining an expected lifetime of a valve 120a, 120b, 120c, 120d associated with an internal combustion engine 100. The method comprises predicting a time at which a valve timing parameter will equal a threshold value indicative of wear of the valve based on a plurality of measurements of the valve timing parameter. The valve may be a fuel injection valve, an air intake valve or an exhaust valve. The timing parameter may relate to one or more of a valve opening time, a valve opening delay or a valve closing delay. The mathematical method used to predict the valve failure may be based on a regression technique.

Description

DETERMINING AN EXPECTED LIFETIME OF A VALVE DEVICE

Technical field

The present disclosure relates to a method and apparatus for determining an expected lifetime of a valve device of an internal combustion engine.

Background

Over time, valve devices (for example, a fuel injector, or an air intake valve device, or an exhaust valve device) associated with an internal combustion engine, such as a diesel engine, may become worn and require replacing with new valve devices. For example, a fuel injector may get worn over a period of time due to normal 'wear and tear' and/or as a result of debris in the fuel system etc. As a valve device becomes more worn, the valve opening time (VOT) of the valve device may drift and increase. VOT is a measure of the time that a valve in the valve device remains open. For example, for a fuel injection valve in a fuel injector, VOT is a measure of the amount of time that the fuel injection valve is open, injecting fuel into the cylinder.

The opening and closing of a valve in a valve device may be instructed by an engine control unit (ECU). However, the valve may not open the instant that the ECU instructs it to open.

Instead there may be an opening delay between the ECU instructing the valve to open and the valve actually opening. Likewise, there may be a closing delay between the ECU instructing the valve to close and the valve actually closing.

As the valve device becomes more worn, the valve may remain open for longer, for example as a result of increases in the closing delay (e.g., VOT of the fuel injector increases). When VOT of a valve device exceeds a maximum allowable value, the engine cylinder may misfire due to the valve being open for too long. Additionally, or alternatively, the opening delay may increase as the valve device becomes more worn. This may result in the valve opening later, which may affect t engine power (for example, by affecting the amount of fuel injected by a fuel injection valve) and/or causing the engine cylinder to misfire.

Old, worn valve devices may need to be replaced to stop an engine cylinder misfiring. However, replacing a valve device after the VOT and/or opening delay has exceeded the maximum allowable value and the cylinder started to misfire, may be inconvenient and/or costly as the machine in which the engine is operating may need to be taken out of service for a period of time before the valve can be replaced. This may be particularly inconvenient -1 -and/or costly where the machine and/or engine has only recently been serviced, requiring the machine to be returned to the service centre only a short time after the previous service. This inconvenience and cost may be further compounded by the engine having multiple cylinders, and therefore multiple valve devices, each of which may wear at a different rate (for example, due to differences in the valve devices at the time of manufacture and/or due to debris passing through one or more of the valve devices), thereby requiring multiple services to replace each valve as their VOT and/or opening delay exceeds the maximum allowable VOT and/or opening delay.

Whilst all valve devices in the engine could be replaced as soon as a single valve's VOT exceeds the maximum allowable VOT, this may be undesirable as one of the valve devices may have worn substantially more quickly than the other valves (for example. due to a manufacturing defect or damage to the valve device). This may result in the costly replacement of many valve devices that still have a significant useable lifetime remaining.

A valve device may be assigned an expected lifetime at the point of installation in an engine, based on knowledge of the usual lifetime of those sorts of valve device. However, the actual lifetime of a valve device may depend on the operating environment of the engine (for example, usual operating temperatures and/or altitudes etc), the way in which the engine is used (for example, frequency of engine operation and/or workload of the engine and/or work cycles of the engine etc), the type of fuel used for the engine (for example, summer or winter fuel compositions), etc. Therefore, the same type of valve device used on two different engines may have two very different actual lifetimes. Furthermore, the same types of valve device on the same engine may still wear at different rates due to debris passing through the valve and/or manufacturing defects in the valve device etc. Therefore, merely assigning an expected lifetime for a particular type of valve device may result in some valve devices wearing to the point of engine misfire before the expected lifetime is reached, thereby potentially causing unexpected engine failure, or other valves being replaced long before their actual lifetime has expired.

JP4183970A describes a method of checking a fuel injector of an internal combustion engine. In the method, the VOT of a fuel injector is determined and integrated and the fuel flow quantity injected by that fuel injector during valve opening is determined. The injection quantity per hour of the fuel injector is calculated using the integral of the VOT and the integral of the fuel flow quantity. The injection quantity per hour is then compared with a reference valve in order to determine whether the fuel injector is in good condition or in bad condition. -2 -

Therefore, the condition of a fuel injector may be checked and, if found to be bad, may be replaced. However, at the time at which the fuel injector is found to be bad, engine misfiring may already have started to take place. Furthermore, the determined injection quantity per hour may be close to the reference value, but still be found to be good. In this case, the fuel injector may be close to failure during a service, but not be replaced. However, fuel injectors wear with time, so the fuel injector may then wear further shortly after the service and require replacement only a short period of time after the previous engine servicing. This may cause inconvenience and additional cost as the machine in which the engine is operating may need to be taken out of service for a period of time and returned to a servicing centre for fuel injector replacement.

Summary

The present disclosure provides a method for determining an expected lifetime of a valve device associated with an internal combustion engine, the method comprising: predicting a time at which a valve timing parameter of the valve device will equal a valve threshold based on a plurality of measurements of the valve timing parameter.

The present disclosure also provides a computer program for determining an expected lifetime of a valve device associated with an internal combustion engine, the computer program comprising computer readable instructions that, when executed on a computer, cause the computer to: predict a time at which a valve timing parameter of the valve device will equal a valve threshold based on a plurality of measurements of the valve timing parameter.

The present disclosure also provides a valve device lifetime determination module for determining an expected lifetime of a valve device associated with an internal combustion engine, the valve device lifetime determination module being configured to: predict a time at which a valve opening parameter of the valve device will equal a valve threshold based on a plurality of measurements of the valve opening parameter.

Drawings Aspects of the present disclosure are described below, by way of example only, with reference to the following drawings, in which: Figure 1 shows a schematic representation of an internal combustion engine; Figure 2 shows an example method for determining the expected lifetime of a fuel injector of the internal combustion engine of Figure 1; -3 -Figure 3 shows an example plot of valve opening times measured as part of the method represented in Figure 2; Figure 4 shows a further example plot of valve opening times measured as part of the method represented in Figure 2; Figure 5 shows a further example method for determining the expected lifetime of a fuel injector of the internal combustion engine of Figure 1; Figure 6 shows an example plot of valve opening times measured as part of the method represented in Figure 5; Figure 7 shows a further example plot of valve opening times measured as part of the method represented in Figures 5; and Figure 8 shows an example vehicle in which the internal combustion engine of Figure 1 may be used.

Detailed description

The present disclosure relates to determining an expected lifetime of a valve device (for example, a fuel injector) associated with an internal combustion engine. Two or more measurements of a valve timing parameter (such as valve opening time, or valve opening delay, or valve closing delay etc) of the valve device are used to predict when the valve timing parameter of the valve device might equal a valve threshold, thereby determining the expected lifetime of the valve device.

Figure 1 shows a highly schematic representation of an internal combustion engine 100. The internal combustion engine 100 may be, for example, a petrol or gasoline engine, or a diesel engine. The internal combustion engine 100 comprises fuel injectors 120a-120d, combustion cylinders 130a-130d and an engine controller 140. The fuel injectors 120a-120d may be configured to be supplied with fuel, for example petrol, gasoline, diesel, etc, by a fuel rail 110.

Each of the fuel injectors 120a-120d are configured to inject fuel into respective combustion cylinders 130a-130d for operation of the internal combustion engine 100. The operation of the fuel injectors 120a-120d may be controlled, at least in part, by the engine controller 140 using respective control signal lines 142a-142d.

For example, each of the fuel injectors 120a-120d may be electromagnetic devices that are installed in the engine. Each fuel injector 120a-120d may comprise a fuel injector body, a solenoid and a plunger that is moveable to control opening and closing of a fuel injection valve. For a normally closed type of fuel injector, the plunger may be biased (for example, -4 -by a spring) such that when no current is applied to the solenoid, and the solenoid is therefore not energised, the fuel injection valve is closed such that fuel cannot pass from the fuel rail 110, through the fuel injector120a-120d into the combustion cylinder 130a-130d. The engine controller 140 may open, for example, fuel injector120b by applying a current to control signal line 142b. The current on control signal line 142b may energise the solenoid, which may cause the plunger to move such that the fuel injector valve opens. When the valve opens, fuel may pass from the fuel rail 110, through the fuel injector 120b and into the combustion cylinder 130b such that fuel is injected into the combustion cylinder 130b.

There may be an opening delay between the engine controller 140 instructing the fuel injector 120b to open and the valve actually opening. For example, the opening delay may comprise the time it takes to energise the solenoid and/or the time it takes for the plunger to begin moving and then move sufficiently far for the valve to open.

To close the fuel injector 120b to stop fuel being injected into the combustion cylinder 130b, the engine controller 140 may turn off the current applied to the control signal line 142b. The solenoid of the fuel injector 120b may thereby de-energise and the biasing of the fuel injector 120b then cause the valve to close.

There may be a closing delay between the engine controller 140 instructing the fuel injector 120b to close and the valve actually closing. For example, the closing delay may comprise the time it takes for the solenoid to de-energise and/or the time it takes for the plunger to begin moving and then move sufficiently far for the valve to close.

For a normally open type of fuel injector, the plunger may be biased (for example, by a spring) such that when no current is applied to the solenoid, and the solenoid is therefore not energised, the fuel injector valve is open such that fuel can pass from the fuel rail 110, through the fuel injector 120a-120d and into the combustion cylinder 130a-130d. The engine controller 140 may close, for example, fuel injector 120c by applying a current to control signal line 142c. The current on control signal line 142c may energise the solenoid, which may cause the plunger to move such that the valve closes. When the valve closes, fuel may not pass from the fuel rail 110, through the fuel injector 120c and into the combustion cylinder 130c. Therefore, fuel injection into the combustion cylinder 130c ceases.

There may be a closing delay between the engine controller 140 instructing the fuel injector 120b to close and the valve 120b actually closing. For example, the closing delay may -5 -comprise the time it takes to energise the solenoid and/or the time it takes for the plunger to begin moving and then move sufficiently far for the valve to close.

To open the fuel injector 120c to allow fuel to be injected into the combustion cylinder 130c, the engine controller 140 may turn off the current applied to the control signal line 142c. The solenoid of the fuel injection valve 120c may thereby de-energise and the biasing of the plunger then cause the valve to open.

There may be an opening delay between the engine controller 140 instructing the fuel injector 120b to open and the valve actually opening. For example, the opening delay may comprise the time it takes for the solenoid to de-energise and/or the time it takes for the plunger to begin moving and then move sufficiently far for the valve to open.

The fuel injector 120a-120d may be of the normally open or normally closed type.

The valve opening time (VOT) of the fuel injectors 120a-120d may be the time for which the fuel injector valves of the fuel injectors 120a-120d are open. For example, it may be the time between the valve actually opening (at the expiry of the opening delay) and the valve actually closing (at the expiry of the closing delay).

As explained earlier, the valve opening time (VOT) of the fuel injectors 120a-120d may increase over time as the fuel injectors 120a-120d wear, for example, as a result of increases in the closing delay. There may be a maximum allowable VOT, above which misfiring may occur in the respective combustion cylinders 130a-130d. Therefore, as a fuel injector 120a-120d gets older and wears, the actual time its fuel injector valve remains open may exceed the maximum allowable VOT. Consequently, each of the fuel injectors 120a-120d may have a finite lifetime, for example between 3000-10000 operating hours, such as 7000 hours, at the expiry of which they may need to be replaced.

Figure 2 shows an example method for determining the expected lifetime of the fuel injectors 120a-120d. In step 210, the VOT of one of the fuel injectors 120a-120d, for example fuel injector 120a, is measured by the engine controller 140. This measurement may be called the first measured VOT, and may be said to take place at a first time. The engine controller 140 may measure the VOT using any suitable technique, which may depend on the type and design of the fuel injector120a-120d. For example, movement of the plunger of the fuel injector 120a may be detected (for example, by monitoring the current on the control signal line 142c, which may vary when the plunger is moving as a result of electromagnetic -6 -induction in the solenoid). As soon as the plunger starts to move from a closed towards an open position, it may be assumed that the fuel injector valve is open. As soon as the plunger stops moving from an open position to a closed position, it may be assumed that the fuel injector valve is closed. Therefore, the time difference between the point at which the plunger starts moving from a closed position to an open position and the point at which the plunger stops moving from an open position to a closed position, may be the VOT.

It will be appreciated that any other suitable technique for monitoring the position and/or movement of the plunger of the fuel injector 120a may be used for determining VOT.

Alternatively, any other suitable technique for determining VOT may be used. By way of example, the fuel flow through the fuel injector may be monitored and the VOT may be the time for which fuel is flowing through the fuel injector120a.

In step 220, the VOT of the same fuel injector, in this example fuel injector120a, is measured again at a later time. This measurement may be called the second measured VOT and may be said to take place at a second time. The second time may be any time after the first time. For example, the period of time between the first and second times may be anything between 1 second of engine operating time (often termed "engine operating second") to 3000 engine operating hours, for example 1200 engine operating hours. In one aspect, it may be a period of time between 10-1000 engine operating hours, for example 80 engine operating hours. In another aspect, it may be a period of time between 100-800 engine operating hours, for example 500 engine operating hours. Engine operating time (for example, engine operating seconds or engine operating hours) is the amount of time for which the engine is on, or operating.

In step 230, the second measured VOT may be compared with the first measured VOT. As explained earlier, over time the measured VOT is expected to increase. Therefore, if the measured VOT decreases, there may be an error. For example, the fuel injector120a may have been replaced between the first and second VOT measurements without the engine controller 140 being notified (in which case the second measured VOT may be significantly less than the first measured VOT), or there may be an error in the first and/or second VOT measurement. Therefore, step 230 may check to see if the second VOT measurement is greater than the first VOT measurement.

If it is determined in step 230 that the second VOT measurement is greater than the first VOT measurement, the method may proceed to step 240 (the 'Yes' path shown in Figure 2). If it is determined in step 230 that the second VOT measurement is not greater than the first -7 -VOT measurement (for example, the second VOT measurement is less than the first VOT measurement), the method may proceed to step 250 (the 'No' path shown in Figure 2).

In step 240, the first and second VOT measurements are used to predict the time at which the VOT of the fuel injector120a will equal a valve threshold. Any form of predictive modelling may be used, for example, any form of mathematical modelling and/or linear or nonlinear regression, etc, such that the first and second VOT measurements are used to predict an expected fuel injector120a operation time at which the valve threshold is reached.

Figure 3 shows an example plot representing how in step 240 the first and second VOT measurements may be used to predict the time at which the VOT of the fuel injector120a will equal the valve threshold. In Figure 3, the operational time of the fuel injector (which may be the same as the engine operating time) is indicated on the x-axis by reference t, the VOT is represented on the y-axis by the reference 'VOT', the first VOT measurement is indicated by reference numeral 310 and the second VOT measurement is indicated by reference numeral 320. A trend 330 may be determined using the first and second VOT measurements 410, 430 using any form of predictive, mathematical modelling. As can be seen, the trend 330 is a function of the VOT and time, t.

The valve threshold is indicated by reference 'a' in Figure 3. As can be seen, the operational time (represented by reference (3') at which the VOT of the fuel injector120a is expected to equal the valve threshold a may be determined using the trend 330. Therefore, the expected lifetime of the fuel injector120a may be determined as operational time p. Thus, the remaining operating time expected to elapse before the fuel injector120a reaches the end of its lifetime may be determined.

The valve threshold a may be set to any suitable value, for example the maximum allowable VOT of the fuel injector120a before misfiring may be expected to occur and/or engine power reduction. This may be dependent on the design of the fuel injector120a and/or any other parts or design of the internal combustion engine 100. For example, the maximum allowable VOT of the fuel injector120a may be any value between 10ms to 1 second, such as 300ms, or 350ms, or 370ms etc. As a result, the valve threshold may be set to a valve at which a function (for example, combustion in the combustion cylinder 130a and/or output power) of the internal combustion engine 100 is expected to deteriorate.

If the valve threshold a is set to the maximum allowable VOT of the fuel injector120a, the expected lifetime j3 of the fuel injector120a may represent the expected total operating time -8 -of the fuel injector120a at which misfiring in the combustion cylinder 130a may occur, thereby causing a deterioration in a function of the internal combustion engine 100 as a result of the operation of the fuel injector 120a. Therefore, it may be arranged that the fuel injector120a is replaced before the fuel injector reaches its expected lifetime p (for example, replaced within a 200 hour period before the expected lifetime (3). By way of example, the expected lifetime 13 may be determined to be determined to be a value between 100-40000 hours, such as 600 hours, or 1800 hours, or 25000 hours, or 38000 hours, or more particularly determined to be a value between 2000-12000 hours, such as 2500 hours, or 6000 hours, or 8500 hours, or 11200 hours.

Alternatively, the valve threshold a may be set to a value different to the maximum allowable VOT. For example, it may be set to a value less than the maximum allowable VOT. By doing so, a 'safer' expected lifetime p of the fuel injector120a may be determined, since the actual maximum VOT that the internal combustion engine 100 may tolerate may be lower than the theoretical maximum VOT, owing to wear and tear of other engine components and/or manufacturing inaccuracies etc. Thus, if the valve threshold a is set to a value that is less than the maximum allowable VOT, it may be less likely that misfiring in the combustion cylinder 130a and/or engine power reduction will take place before the fuel injector120a has reached the expected lifetime p. Therefore, it may be arranged that the fuel injector120a is replaced at, or soon after, the fuel injector reaches its expected lifetime p (for example, replaced within a 150 hour period after expiry of the expected lifetime (3).

The expected lifetime p of the fuel injector120a, and/or an indication that the expected lifetime p of the fuel injector120a has been reached and/or an indication that the expected lifetime 13 of the fuel injector120a will soon be reached (for example, the valve operating time is within a threshold period of the expected lifetime p, for example within 180 hours of the expected lifetime (3) and/or the operating time remaining until the expected lifetime p will be reached, may be output for communication to an operator of the internal combustion engine 100 and/or engine servicing personnel. It may be communicated in any suitable way, for example, during a standard servicing procedure, such as during electronic fuel diagnostic tests or at the time of replacing one or more of the other fuel injectors 120b-120d. Additionally or alternatively, it may be communicated during normal operation of the internal combustion engine 100, for example using an audio and/or visual indictor on an audio and/or visual device, for example via a warning light or alpha-numeric display on the dashboard of a vehicle and/or via a computer, such as a laptop, attached to the internal combustion engine 100. Additionally, or alternatively, it may be communicated to servicing personnel at any time, for example using wireless data networks such as WiFi, Bluetooth, or mobile cellular -9 -networks, such as a Long Term Evolution (LTE) network, or 3rd Generation Partnership Project (3GPP) network, or EDGE network, or GPRS network etc. Returning to Figure 2, in step 250, a valve error flag may be set. The valve error flag may indicate, for example, that the fuel injector120a may have been replaced between the first and second VOT measurements without notifying the engine controller 140. Additionally, or alternatively, it may indicate that there is an error in the expected lifetime determination process and that the expected lifetime 13 should not be trusted and/or that an expected lifetime will not be given. When the valve error flag is set, a valve error alert may be output.

In this way, service personal and/or an operator may be alerted to notify the engine controller 140 of a replacement valve, for example by updating the relevant records files or any files and/or information relevant to the injector performance (such as the injector performance files) that are used by the engine controller 140, and/or to investigate what the problem may be.

After completion of step 240 or 250, the method may proceed to step 260. In step 260, the first, earliest, VOT measurement is discarded and the second VOT measurement becomes the earliest VOT measurement. In this way, the second VOT measurement effectively becomes the first VOT measurement. The method may then return to step 220 where a 'new' second VOT measurement is taken.

If the method has proceeded from step 250 to step 260, the first VOT measurement may not be trustworthy, for example because it was taken before the fuel injector120a was replaced. Therefore, it may be desirable no longer to use the first VOT measurement in determining the expected lifetime p of the fuel injection valve 120a, since it may result in an inaccurate determination.

By way of example, Figure 4 shows an example plot representing an instance where a second VOT measurement is less than a first VOT measurement (which may result in the method proceeding from step 230 to step 250 then to step 260). In this example, the first VOT measurement is represented with reference numeral 410 and the second VOT measurement is represented with reference numeral 420. As may be appreciated, in this circumstance, a trend line generated using the first and second VOT measurements may have a negative gradient, thereby predicting a reduction in VOT as the operational time of the fuel injector120a increases. This may not result in an accurate determination of the expected lifetime of the fuel injector120a.

Before proceeding from step 250 to step 260, the method may optionally pause at step 250 and only proceed to step 260 after the valve error has been investigated and corrected. For example, the engine controller 140 may wait until its records files are updated to indicate that a new fuel injector120a has been fitted.

If the method has proceeded from step 240 to step 260, by discarding the oldest VOT measurement (the first VOT measurement) and making the previous second VOT measurement the 'new' first VOT measurement in step 260 and then returning to step 220 to take a 'new' second VOT measurement, the predictive model may update itself with more up-to-date VOT measurements. In this way, changes in the rate of wear of the fuel injector 120a may be incorporated into the predictive modelling (for example, a reduction in rate of wear due to reduced loading and/or lower fuel consumption, or an increase in the rate of wear due to debris passing through the fuel injector120a), thereby modifying the expected lifetime j3 accordingly.

It will be appreciated that in an alternative, in step 260 the first and second VOT measurements may both be discarded and the method return to step 210.

The method shown in Figure 2 may be applied separately to each of the fuel injectors 120a- 120d such that an expected lifetime p for each of the fuel injectors 120a-120d may be determined. Thus, four different expected lifetimes p may be determined, one for each fuel injector120a-120d. Alternatively, the method shown in Figure 2 may be applied to a single one of the fuel injectors 120a-120d and the determined expected lifetime p used for all of the fuel injectors 120a-120d. Alternatively, the method shown in Figure 2 may be applied to two or more of the fuel injectors 120a-120d so that a corresponding two or more expected lifetimes p are determined.

Figure 5 shows a further example method for determining the expected lifetime p of the fuel injectors 120a-120d. The steps 210, 220, 230, 250 and 260 are the same as those described earlier.

If in step 230 it is determined that the second VOT measurement is greater than the first VOT measurement ('Yes' in Figure 5), the method may proceed to step 510. In step 510, the VOT of the fuel injector120a is measured again. This measurement may be called the third measured VOT, and may be said to take place at a third time. The third time may be any period of time after the second time, for example any period of time between 1 engine operating second to 3000 engine operating hours, for example 1600 engine operating hours.

In a particular aspect, the period of time may be between 10-1000 engine operating hours, for example 80 engine operating hours. In a further particular aspect, the period of time may be between 100-8000 engine operating hours, for example 550 engine operating hours.

The period of time between the second VOT measurement and the third VOT measurement may be the same as, or different to, the period of time between the first VOT measurement and the second VOT measurement.

In step 520, the third measured VOT is compared with the second measured VOT to see if the third measured VOT is greater than the second measured VOT. As explained earlier, over time the measured VOT should increase. Therefore, if the measured VOT decreases, there may be an error. Step 520 is analogous to step 230 where the second measured VOT is compared with the first measured VOT and the explanations set out earlier for performing step 230 may also apply to step 520.

If it is determined in step 520 that the third VOT measurement is greater than the second VOT measurement, the method may proceed to step 530 (the 'Yes' path shown in Figure 5). If it is determined in step 520 that the third VOT measurement is not greater than the first VOT measurement (for example, the third VOT measurement is less than the second VOT measurement, etc), the method may proceed to step 550 (the No' path shown in Figure 5).

In step 530, the first, second and third VOT measurements are used to predict the time at which the VOT of the fuel injector120a will equal a valve threshold. Again, any form of predictive modelling may be used, for example, any form of linear or nonlinear regression, etc, such that the first, second and third VOT measurements may be used to predict an expected fuel injector operation time at which the valve threshold is reached.

Figure 6 shows an example plot representing how in step 530 the first, second and third VOT measurements may be used to predict the time at which the VOT of the fuel injector 120a will equal the valve threshold. In Figure 6, the operational time of the fuel injector is indicated on the x-axis by reference t, the VOT is represented on the y-axis by the reference 'VOT', the first VOT measurement is indicated by reference numeral 610, the second VOT measurement is indicated by reference numeral 620 and the third VOT measurement is indicated by reference numeral 630. A trend line 640 may be determined using the first, second and third VOT measurements 610, 620 and 630 with any form of predictive modelling.

As with Figure 3, the valve threshold is indicated by reference 'a' and the expected lifetime of the fuel injector120a is indicated by reference 43'. The valve threshold a may be set as described earlier in respect of Figure 3. The determined expected lifetime j3 of the fuel injector120a, and/or an indication that the determined expected lifetime p of the fuel injector120a has expired and/or an indication that the expected lifetime p of the fuel injector120a will soon be reached (for example, the operating time is within a threshold period of the expected lifetime p, for example within 160 hours of the expected lifetime (3), and/or the operating time remaining until the expected lifetime p will be reached, may be communicated to an operator of the internal combustion engine 100 and/or engine serving personnel as described earlier in respect of Figure 3.

After determining the expected lifetime p of the fuel injector 120a, the method may proceed to step 540. Step 540 is similar to step 250 described earlier. In step 540, the first, earliest, VOT measurement may be discarded and the second VOT measurement may become the earliest VOT measurement. In this way, the second VOT measurement that had previously been taken in step 220 effectively becomes the first VOT measurement and the third VOT measurement that had previously been taken in step 510 effectively becomes the second VOT measurement. The method may then return to step 510 where anew' third VOT measurement is taken. By discarding the oldest VOT measurement (the previous first VOT measurement) and taking anew' third VOT measurement, the predictive model may update itself with more up-to-date VOT measurements. In this way, changes in the rate of wear of the fuel injector120a may be incorporated into the predictive modelling (for example a reduction in rate of wear due to reduced loading and/or lower fuel consumption, or an increase in the rate of wear due to debris passing through the fuel injector120a), thereby modifying the expected lifetime j3 accordingly.

In step 550, the valve error flag described earlier in respect of step 250 of Figure 2 may be set. The method may then proceed to step 560. However, before proceeding from step 550 to step 560, the method may optionally pause at step 550 and only proceed to step 560 after the valve error has been investigated and corrected. For example, the engine controller 140 may wait until its records files are updated to indicate that a new fuel injector120a has been fitted.

In step 560, the first and second VOT measurements may be discarded. The third VOT measurement may then be the earliest VOT measurement. The method may then return to step 220 where a 'new' second VOT measurement is taken. Alternatively, in step 560, all of the first, second and third VOT measurements may be discarded and the method may return to step 210, where a 'new' first VOT measurement is taken.

Where step 520 has determined that the VOT measurement (the most recent VOT measurement) is not greater than the second VOT measurement (the preceding VOT measurement), the first and second VOT measurements (the measurements taken prior to the most recent VOT measurement) may not be trustworthy, for example because they were taken before the fuel injector120a was replaced. Therefore, by discarding at least the measurements taken prior to the most recent VOT measurement in step 560 and returning to step 220 or step 210, the untrustworthy measurements may be excluded from the determination of the expected fuel injector lifetime.

By way of example, Figure 7 shows an example plot representing an instance where a third VOT measurement is less than a second VOT measurement. In this example, the first VOT measurement is represented with reference numeral 710, the second VOT measurement is represented with reference numeral 720 and the third VOT measurement is represented with reference numeral 730. As may be appreciated, in this circumstance, a trend line generated using the first, second and third VOT measurements may be inaccurate, and potentially have a negative gradient thereby predicting a reduction in VOT as the operational time of the fuel injector120a increases. This may result in an accurate determination of the expected lifetime p of the fuel injector120a.

At any time during the methods shown in either Figure 2 or 5, the engine controller 140 may be notified that the fuel injector120a has been replaced, for example by updating the relevant records files held by, or accessible to, the engine controller 140. The engine controller 140 may then clear all previous VOT measurements and return to step 210.

The engine controller 140 may be configured to perform the methods described above and shown in the Figures. The engine controller 140 may be any type of controller device, for example it may be an engine control unit (ECU) configured to perform the method, or a standalone control unit that is separate from, but optionally in communication with, the ECU etc. Figure 8 depicts an example vehicle in which the internal combustion engine 100 may be used. It will be appreciated that Figure 8 represents only one type of machine in which the internal combustion engine 100 may be used. Alternatively, the internal combustion engine 100 may be used in any suitable type of machine, for example in a generator, or in process machinery, or in a vehicle such as an excavator, a bulldozer, a back-hoe loader, a lorry, a truck, a car etc. The skilled person may readily appreciate that a number of alterations and/or alternatives to the aspects described above may be implemented and still fall within the scope of the

present disclosure.

For example, the internal combustion engine 100 may have any number of combustion cylinders 130a-130d and corresponding fuel injectors 120a-120d. For example, it may have only one combustion cylinder and corresponding fuel injector, or two or more combustion cylinders and corresponding fuel injectors, such as eight combustion cylinders and corresponding fuel injectors.

In the above, methods for determining the expected lifetime of fuel injectors are described.

However, the methods may be applied to the determination of the expected lifetime of any type of valve device of an internal combustion engine. For example, it may additionally or alternatively be applied to determining the expected lifetime of one or more exhaust valve devices in the internal combustion engine 100 by using a plurality of measured VOTs of the exhaust valve(s), and/or one or more air intake valve devices in the internal combustion engine 100 by using a plurality of measured VOTs of the air intake valve(s).

In the above described aspects, the fuel injectors 120a-120d are of an electromagnetic type that are controlled by the engine controller 140. However, the fuel injectors 120a-120d may be of any type and may, or may not, be controlled by the engine controller 140. Regardless of how the opening and closing of the fuel injectors 120a-120d is controlled, the engine controller 140 may be configured to measure the VOT of at least one of the fuel injectors 120a-120d.

In the method represented in Figure 2 and described in the corresponding description, two measurements of VOT are used in the determination of the expected lifetime p of a fuel injector. In the method represented in Figure 5 and described in the corresponding description, three measurements of VOT are used in the determination of the expected lifetime p of a fuel injector. However, it will be appreciated that more than three measurements of VOT may be used in the determination of the expected lifetime of a fuel injector (or any type of valve device). For example, four, or five, or six, or ten, or one hundred, etc., measurements of VOT may be used. In this way, the expected lifetime of a valve device may be determined using a plurality of measurements of VOT (for example, two or more measurements of VOT), wherein each of the plurality of VOT measurements is taken at a different time (i.e. a period of time elapses between the taking of each of the plurality of VOT measurements).

In the above methods, measurements of VOT are used in order to determine the expected lifetime 13 of a fuel injector. However, any suitable valve timing parameter may be used to determine the expected lifetime p of a valve device and all instances of 'VOT measurement(s)' in the present disclosure may be replaced with 'measurement(s) of a valve timing parameter'. For example, the opening delay and/or closing delay of the valve may be expected to change as the valve gets older and more worn. Therefore, two or more measurements of the valve opening delay and/or two or more measurements of the valve closing delay and/or two or more measurements of the VOT may be used to determine the expected lifetime p of the valve device. Thus, an expected lifetime p of a valve device may be determined by predicting a time at which a valve timing parameter (for example, VOT, valve opening delay, valve closing delay, etc) of the valve device will equal a valve threshold a (which may, for example, comprise at least one of a valve opening delay threshold, a valve closing delay threshold and/or a VOT threshold) using a plurality of measurements of the valve timing parameter.

The valve timing parameter may be measured using any suitable techniques. For example, if it comprises the valve opening delay, the valve opening delay may be determined by measuring the time difference between the valve opening being instructed and the valve actually opening. If it comprises the valve closing delay, the valve closing delay may be determined by measuring the time difference between the valve closing being instructed and the valve actually closing. The valve actually opening or closing may be identified using any suitable technique, such as monitoring the current in the control signal line controlling opening and closing of the valve device and/or the displacement of the plunger in the valve device and/or the fuel flow rate through a fuel injector 120a-120d, etc. The method represented in Figures 2 and 5 and the corresponding description show example method steps that may be used to determine the expected lifetime of a valve device. It will be appreciated that the order of these steps is an example only and that they may be undertaken in any suitable alternative order. For example, in the method shown in Figure 5, the first, second and third VOT measurements may be taken (i.e., steps 210, 220 and 510 may take place first) before the first, second and third VOT measurements are checked in steps 230 and 520. In this case, the 'Yes' branch from step 230 may proceed directly to step 520.

In step 230 described above, it is determined whether or not the second VOT measurement is greater than the first VOT measurement. In an alternative, step 230 may instead determine if the second VOT measurement is greater than the first VOT measurement by more than a difference threshold. If the VOT measurement has not increased between the first and second measurement by more than the difference threshold, it may be assumed that there is some sort of valve error. Therefore, if the second VOT measurement is greater than the first VOT measurement by more than the difference threshold, the method may proceed to step 240. If it is not, the method may proceed to step 250.

The difference threshold may be set to any suitable value. For example, it may be set in consideration of normal VOTs of the valve devices and/or the degree of accuracy of VOT measurements and/or the time period between VOT measurements being compared (since a larger time difference between the VOT measurements might be expected to result in a larger change in VOT).

The difference threshold may be set to an amount of time, for example an amount of time between 1ps and 20ms, such as 1 ms. Alternatively, the difference threshold may be set to a percentage of the first VOT measurement, for example a percentage between 0.01% -20%, such as 1.5%. In this way, the second VOT measurement must be greater than the first VOT measurement by at least the difference threshold percentage of the first VOT measurement (for example, by more than 1.5% of the first VOT measurement) for the method still proceed to step 240. If the second VOT measurement is not greater than the first VOT measurement by more than the difference threshold valve percentage of the first VOT measurement (for example, by more than 1.5% of the first VOT measurement, such as only 0.5% greater than the first VOT measurement), the method may proceed to step 250.

Likewise, in an alternative, step 520 may determine if the third VOT measurement is greater than the second VOT measurement by more than a difference threshold. If the third VOT measurement is greater than the second VOT measurement by more than the difference threshold, the method may proceed to step 530. If it is not, the method may proceed to step 550.

In a further alternative, in step 230, rather than checking to see if the second VOT measurement is greater than the first VOT measurement, it may instead check that the second VOT measurement is greater than or equal to the first VOT measurement.

Additionally, or alternatively, step 520 may check that the third VOT measurement is greater than or equal to the second VOT measurement.

Furthermore, one or more of the steps shown in Figures 2 and/or 5 and the corresponding description may be omitted from the method. For example, step 250 and/or 550 may be omitted such that a valve error flag may not be set. Alternatively, step 230 and/or step 520 may be omitted such that the first, second and/or third VOT measurements are not checked. In this instance, it may be assumed that the first, second and/or third VOT measurements are reliable, such that steps 230 and 250 may be omitted from Figure 2 and steps 230, 250, 260, 520, 550 and 560 may be omitted from Figure 5.

In the above aspects, the engine controller 140 performs all of the steps of the disclosed methods. However, the engine controller 140 may alternatively perform only some of the steps with any remaining steps performed by a different entity, for example, a valve device lifetime determination module. For example, the engine controller 140 may take the VOT measurements and the valve device lifetime determination module may use the measurements of VOT to determine the expected lifetime(s) p of the valve device(s) (i.e. perform step 240 or 540). The VOT measurements may be communicated by the engine controller 140 to the valve device lifetime determination module, via either a wired or wireless interface. Alternatively, the valve device lifetime determination apparatus may retrieve the VOT measurements, for example from a database in which they have been stored by the engine controller 140. In this example, the database may be part of the engine controller 140, or may be separate from the engine controller 140 and located in/on the internal combustion engine 100, or located in/on the machine in which the internal combustion engine 100 is used, or located in some other location remote from the internal combustion engine 100 and machine (for example, at a servicing centre). The valve device lifetime determination module may be co-located with the engine controller 140 in the internal combustion engine 100, or located in/on the machine in which the internal combustion engine 100 is used, or located in some other location remote from the internal combustion engine 100 and machine (for example, at a servicing centre).

Where the engine controller 140 itself determines the expected lifetime(s) p of the valve device(s) (i.e. perform step 240 or 540), it may comprise the functionality of the valve device lifetime determination module. Therefore, the engine controller 140 may be considered to comprise the valve lifetime determination module.

Determination of the expected lifetime p of a valve device may be implemented by one or more computer programs (for example, one or more computer-readable media) comprising computer readable instructions. In this way, a computer executing the computer readable instructions may determine the expected lifetime of a valve device by predicting a time at which a valve timing parameter of the valve device will equal a valve threshold based on a plurality of measurements of the valve timing parameter. The computer may be any suitable type of electronic device that may comprise one or more of at least one processor, at least one memory, at least one storage medium, such as a hard-disk drive and/or solid-state drive, at least one storage reading drive, such as a diskette drive and/or CD-ROM drive and/or DVD drive and/or Blu-ray drive and/or USB port etc. The computer may be a mobile device, such as a laptop or tablet, or an immobile device, such as a desktop computer. The computer may alternatively be an electronic chip, such as an engine control unit (ECU), that is suitable for executing the computer program, wherein the computer program is stored on the chip, or elsewhere (for example, on a separate memory device).

The computer program may also comprise computer readable instructions that cause the computer, when executing the computer program, to carry out any or all of the other method steps described above. For example, it may cause the computer to determine a plurality of measurements of a valve timing parameter (either by measuring the valve timing parameter, or by retrieving the measurements of the valve timing parameter, for example from a database in which they are stored), comparing a measurement of a valve timing parameter with an earlier measurement of the valve timing parameter, etc, etc. Rather than discarding the oldest VOT measurement in order to update the VOT measurements (steps 260 and 540), the expected lifetime of a valve may instead be determined using the most recent plurality of VOT measurements. For example, each VOT measurement may be stored in a database and the most recent two, or three, or four etc VOT measurements used to predict the time at which the VOT of the valve device will equal the valve threshold a. Thus, VOT measurements may periodically be taken and added to the database and the oldest VOT measurements of the database optionally omitted from determining the expected lifetime of the valve device. Therefore, determination of the expected lifetime p may update itself with more up-to-date VOT measurements. In this way, changes in the rate of wear of the valve device (for example a reduction in rate of wear due to reduced loading and/or lower fuel consumption, or an increase in the rate of wear due to debris passing through the valve device) may modify the expected lifetime R. In the above described measurements, the most recent valve timing parameter measurement is compared with the previous valve timing parameter measurement in steps 230 and/or 520. However, it will be appreciated that any of the plurality of valve timing parameter measurements may be compared with the previous valve timing parameter measurement. For example, five valve timing parameter measurements may be taken (each at a different time) and the third measurement compared with the second measurement to see if the third measurement is greater than the second measurement. Thus, any valve timing parameter measurement, which may be labelled as 'measurement mzi, may be compared with the preceding valve timing parameter measurement, which may be labelled as 'measurement my' to see if measurement rriz is greater than measurement my.

If measurement mz (for example, the second or third VOT measurement in the above described methods) is not greater than measurement my (for example, as determined in step 230 and/or 520), rather than assume that there is a valve error and proceed to step 250 or 550, one or more further VOT measurements may be taken. One or more of these further measurements may then be compared with measurement my.

If one or more of the further measurements is greater than measurement my, it may be assumed that measurement m, is erroneous. In this case, measurement mz may be discarded from the plurality of VOT measurements and the method proceed to step 240 or 530 for determination of the expected lifetime p of the fuel injection valve 120a-120d, or to step 210, 220 or 510 for the taking of new VOT measurements. Optionally, the one or more further VOT measurements may be added to the plurality of VOT measurements, thereby effectively replacing measurement mz. Optionally, a measurement error flag may be set such that the measurement error may be investigated.

If one or more of the further measurements is not greater than measurement my, it may be assumed that there is a valve error. In this case, the one or more further measurements may be discarded and the method may proceed to step 250 or 550.

Industrial applicability

In the present disclosure, an expected lifetime of a valve device (for example, a fuel injection valve) associated with an internal combustion engine is determined by predicting a time at which a valve timing parameter of the valve device will equal a valve threshold using a plurality of measurements of the valve timing parameter. Each of the plurality of measurements of the valve timing parameter is taken at a different time. By determining the expected lifetime of a valve device, the valve device may be replaced before engine misfiring and/or engine power reduction occurs and at a convenient time that minimises inconvenience and cost for the owner and/or operator of the internal combustion engine.

For example, based on the expected lifetime of the valve device, it may be determined that the valve device may need replacing between scheduled machine services. In this case, the valve device may be replaced during the earlier scheduled service so that the machine will not need to be taken out of operation for a valve device replacement between scheduled services.

Furthermore, by determining the expected lifetime of a valve device in this way, the operating conditions/environment of the internal combustion engine may be taken into account. That is to say, an internal combustion engine operating in a harsh environment and/or that is worked very hard, may experience faster valve device wear than an internal combustion engine that is not subjected to such harsh environment and/or working conditions. By predicting a time at which a valve timing parameter of the valve device will equal a valve threshold using a plurality of measurements of the valve timing parameter, it may be identified that the valve device needs to be replaced more quickly than the average replacement time. This may enable it to be replaced before engine misfiring and/or a reduction in engine power occurs. Likewise, an internal combustion engine operating in a gentle environment and/or that is worked very lightly, may experience slower valve wear than an internal combustion engine that is not subjected to such light environment and/or working conditions. By predicting a time at which a valve timing parameter of the valve device will equal a valve threshold using a plurality of measurements of the valve timing parameter, it may be identified that the valve device does not need to be replaced as quickly as the average replacement time. It may therefore be left in place for longer, thereby enabling money to be saved by not replacing good valve devices.

Separate expected lifetimes for two or more valve devices of an internal combustion engine may be determined, such that each valve device may have its own expected lifetime. In this way, valve devices that are wearing more quickly may be replaced before engine misfiring and/or a reduction in engine power occurs, whilst valve devices that are wearing more slowly may be replaced later, thereby saving costs. Furthermore, at the time of replacing one valve device, it may be determined if any other valve devices should be replaced, or if they may be expected to last until at least the next scheduled service.

Additionally, or alternatively, valve timing parameter measurement, measurement mz, may be compared with the valve timing parameter measurement preceding measurement m, (i.e. -21 the valve timing parameter measurement that was taken immediately before measurement mz) -measurement my. If measurement mz is not greater than measurement my, there may be an error in at least one of the measurements and/or the valve device may have been replaced between the measurements. In this instance, all valve timing parameter measurements taken prior to measurement m, may be discarded, thereby eliminating measurements that were taken in relation to an old, now replaced, valve device and/or eliminating erroneous measurements. In this way, the accuracy of the expected lifetime of the valve device may be improved.

In an alternative, rather than discarding measurements taken prior to measurement m, when a valve error is identified, one or more further valve timing parameter measurements may be taken. One or more of these further valve timing parameter measurements may then be compared with measurement my. If the one or more further valve timing parameter measurements is greater than measurement my, it may be determined that there is an error in measurement mz. In this case, measurement m, may be discarded from the plurality of measurements and optionally the one or more further valve timing parameter measurements added to the plurality of measurements. The expected lifetime p of the valve device may then be determined based on the plurality of measurements.

If, however, the one or more further valve timing parameter measurements is not greater than measurement my, it may be assumed that there is a valve error and the plurality of measurements preceding measurement mz may be discarded from the plurality of valve timing parameter measurements, as described above.

By taking one or more further valve timing parameter measurements, a valve device replacement may be identified more confidently and corrective action taken.

Periodically, a new valve timing parameter measurement may be taken and added to the plurality of valve timing parameters. This may improve the accuracy of the expected lifetime of the valve device by taking into account any changes (for example, increases or decreases) in the rate of wear of the valve device. Optionally, one or more of the oldest valve timing parameter measurements may be discarded from the plurality of valve timing parameters, thereby removing potentially less relevant measurements from the determination of the expected lifetime of the valve device.

Claims

Claims 1. A method for determining an expected lifetime of a valve device associated with an internal combustion engine, the method comprising: predicting a time at which a valve timing parameter of the valve device will equal a valve threshold based on a plurality of measurements of the valve timing parameter.
2. The method of claim 1, wherein the valve threshold is set to a value at which a function of the internal combustion engine is expected to deteriorate as a result of the operation of the valve device.
3. The method of any preceding claim, wherein predicting the time at which the valve timing parameter of the valve device will equal a valve threshold is based on a mathematical model that uses the plurality of measurements of the valve timing parameter to determine a trend, wherein the trend is a function of the valve timing parameter and time.
4. The method of claim 3, wherein the predicted time at which the valve timing parameter of the valve device will equal a valve threshold is the time at which the trend indicates the valve timing parameter of the valve device will equal the valve threshold.
5. The method of any preceding claim, wherein predicting the time at which the valve timing parameter will equal the valve threshold comprises using a regression technique based on the plurality of measurements of the valve timing parameter.
6. The method of any preceding claim, wherein the valve timing parameter comprises at least one of a valve opening time, a valve opening delay and/or a valve closing delay.
7. The method of any preceding claim, further comprising: comparing a valve timing parameter measurement, measurement mz, of the plurality of measurements of the valve timing parameter, with the valve timing parameter measurement, measurement my, which precedes measurement mz; and if measurement rn, is not greater than measurement my, discarding from the plurality of measurements of the valve timing parameter all valve timing parameter measurements taken prior to measurement mz.
8. The method of any of claims 1 to 6, further comprising: comparing a valve timing parameter measurement, measurement m7, of the plurality of measurements of the valve timing parameter, with the valve timing parameter measurement, measurement my, which precedes measurement mz; and if measurement rn, is not greater than measurement my, making a further measurement of the valve timing parameter and comparing the further valve timing parameter measurement with measurement my; and if the further valve timing parameter measurement is greater than measurement my, discarding measurement m from the plurality of measurements of the valve timing parameter.
9. The method of any preceding claim, wherein a plurality of valve devices are associated with the internal combustion engine, and wherein the method comprises: for each of the plurality of valve devices, predicting the time at which the valve timing parameter of the valve device will equal the valve threshold using a plurality of valve timing parameter measurements of the respective valve device.
10. The method of any preceding claim, wherein the valve device is a fuel injector, or an air intake valve device, or an exhaust valve device.
11. A computer program for determining an expected lifetime of a valve device associated with an internal combustion engine, the computer program comprising computer readable instructions that, when executed on a computer, cause the computer to perform the method of any preceding claim.
12. A valve device lifetime determination module for determining an expected lifetime of a valve device associated with an internal combustion engine, the valve device lifetime determination module being configured to perform the method of any of claims 1-10.
13. An engine controller comprising the valve device lifetime determination module of claim 12.
14. An internal combustion engine comprising: at least one valve device; and the valve lifetime determination module of claim 12 configured to determine the expected lifetime of at least one of the at least one valve device.
15. A machine comprising the internal combustion engine of claim 14. -24