ROTATION SPEED OF A CRANKSHAFT

Field of Invention

The invention relates but is not limited to a method, an apparatus, a computer program and/or a computer program product for controlling an operation of an internal combustion engine. The invention relates but is not limited to internal combustion engines comprising a diesel engine and/or a gasoline engine.

Background

Characteristics of an operation of an internal combustion engine of a vehicle may comprise information associated with a characteristic of the fuel fuelling the engine or a characteristic of an exhaust of the engine.

The characteristic of the fuel fuelling the engine may comprise a distillation characteristic and/or a purity of the fuel.

Fuel distillation characteristics must meet given tolerances within regional specifications where the fuel is sold. The distillation characteristic of a fuel is determined by laboratory-based analysis, and there is currently no determination of the fuel distillation characteristic on the vehicle. Additionally, a tank of the vehicle may thus contain a mix of fuels with different individual fuel distillation characteristics creating an unknown resultant mixture distillation characteristic fuelling the engine. The given tolerances and resultant mixture distillation characteristic may vary to such an extent that problems in the engine may occur. The problems in the engine may include e.g. an increase in harmful emissions, in pre-ignition events - such as Low-Speed Pre-Ignition, LSPI, which can cause mega knock and damages to the engine - and in a frequency of maintenance checks and lubricant changes. The problems in the engine may also include e.g. a decrease in efficiency and in driveability.

For modern high efficiency engines operating in their most economic manner, using fuels meeting their relevant regional specifications could still be problematic, especially fuels with higher temperature distillation characteristics. Additionally, vehicle manufacturers are increasingly targeting their vehicles to a global market, so the ability for the engine to be robust to different fuel specifications and wildly varying fuel qualities without additional and costly sensors is desirable.

Furthermore, in some engines (such as in some diesel engines but also in some gasoline engines) an exhaust system comprises a particulate filter to trap particulates generated by a combustion of the fuel fuelling the engine. A high level of particulates may indicate an undesirable distillation characteristic of the fuel fuelling the engine. The characteristic of the exhaust of the engine, such as a loading of the filter with particulates, influences another characteristic of the operation of the internal combustion engine, such as a back pressure in the exhaust of the engine. The back pressure in the exhaust is a factor in the operation of the internal combustion engine which impacts fuel efficiency and emissions.

The loading of the particulate filter can be estimated by determining the pressure drop the filter creates in the exhaust. The pressure drop is usually determined using at least one dedicated pressure sensors in the vehicle exhaust. The dedicated pressure sensor(s) (along with associated diagnostics and evaluation electronics) may be expensive, inaccurate and unreliable. Inaccuracies in the readings of the sensor(s) may lead to mistakes in estimations of the loading of the particulate filter, leading to unnecessary regenerations of the filter and thus an unnecessary increase in fuel consumption. Additionally, algorithms based on driving style, fuel consumed, time and distance may also be used to trigger unnecessary regeneration events, even when the actual loading of the particulate filter may not be requiring of such. Regeneration events use additional fuel compared to normal operation. Summary of Invention

Aspects and embodiments of the invention are set out in the appended claims. These and other aspects and embodiments of the invention are also described herein.

Brief Description of Drawings

Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 schematically represents a flowchart that illustrates an example method in accordance with the present disclosure;

Figure 2 schematically represents an internal combustion engine on which the method of Figure 1 may be at least performed;

Figure 3A schematically represents a first example association between reference data and at least one reference characteristic of an operation of an engine;

Figure 3B schematically represents a second example association between reference data and at least one reference characteristic of an operation of an engine, as well as an example association between operation data and at least one operation characteristic of an operation of an engine;

Figure 4A schematically represents a first example association between characteristics of an operation of an engine;

Figure 4B schematically represents a third example association between reference data and at least one reference characteristic of an operation of an engine; and

Figure 5 schematically represents a flowchart that illustrates another example method in accordance with the present disclosure. In the Figures like reference numerals are used to indicate like elements.

Description of Example Embodiments

Overview

The disclosure relates to a method for operating an internal combustion engine. The engine comprises a crankshaft, and the method comprises obtaining operation data corresponding to a rotation speed of the crankshaft (such as an instantaneous rotation speed of the crankshaft of the engine, or a variation of the instantaneous rotation speed of the crankshaft of the engine, e.g. the variation including mathematical derivatives of the rotational speed). The method also determines whether or not the operation data is similar to reference data corresponding to at least one reference rotation speed of the crankshaft. The method estimates at least one operation characteristic of the operation of the engine - such as characteristic of the fuel fuelling the engine and/or a characteristic of an exhaust of the engine - , based on the determined similarity, using an association of the reference data with at least one reference characteristic of the operation of the engine.

The method may enable estimating, on the vehicle comprising the internal combustion engine, e.g. a distillation characteristic of the fuel, in some cases including, for example, a final boiling point of the fuel and/or a volatility of the fuel. The estimation may be performed in real-time or near real-time. Alternatively or additionally, the method may enable estimating the loading of the filter with particulates.

In some examples an action associated with the operation of the engine may be triggered, based on the estimation. The method may enable modification of the operation of the engine based on the estimated characteristics of the operation of the engine, and may thus enable robust calibrations of the engine, regardless of the point of sale of the vehicle comprising the engine and/or the driving range of the vehicle comprising the engine.

In some examples the triggered action may cause a modification in an injection of the fuel in the engine, a modification in an ignition of the fuel in the engine, a modification in intake manifold pressure charging in the engine, a regeneration of a particulate filter of an exhaust of the engine. The method may enable potential improved fuel economy through reduced regenerations of the particulate filter. The triggered action may cause a modification in fuel additives or a maintenance operation of the engine (such as planning a lubricant change and/or any other manufacturer-specific on board diagnostics (OBD) measurements or interventions). The method may enable a decrease in harmful emissions, in pre-ignition events - such as Low-Speed Pre-Ignition, LSPI - and in a frequency of maintenance checks and lubricant changes. The method may enable an increase in efficiency and in driveability. The method may improve cold starting refinements in the fuel additives, and enable an indication to a user, such as a service light indication, e.g. in case of off-specification fuel.

The operation data may be obtained from a crankshaft sensor. The method may enable avoiding using any expensive, inaccurate and unreliable pressure sensors in the vehicle exhaust (along with associated diagnostics and evaluation electronics).

Detailed Description

Fig. 1 schematically illustrates a method for controlling an operation of an internal combustion engine 10 schematically illustrated in Fig. 2. Data 13 and 15 and characteristics 14 and 16 are schematically illustrated with reference to Figures 3A, 3B, 4A and 4B and are disclosed in more detail below.

As illustrated in Fig. 2, the engine 10 comprises a crankshaft 11. The internal combustion engine 10 may comprise a diesel engine and/or a gasoline engine. The engine 10 may be controlled by an engine control unit 17, ECU. The method of Fig. 1 comprises:

obtaining, at S 1 , reference data 13 corresponding to at least one reference rotation speed of the crankshaft 11 ; and

obtaining, at S2, operation data 15 corresponding to a rotation speed of the crankshaft 11. In some examples, the data 13 and/or the data 15 comprise data associated with an instantaneous rotation speed of the crankshaft 11 of the engine 10, e.g. as a function of a rotation angle of the crankshaft.

In some examples, and as illustrated in Fig. 2, obtaining at S2 the operation data 15 may comprise receiving the operation data 15 from a crankshaft sensor 12. In some examples the sensor 12 may be configured to sense the crankshaft angular position. The crankshaft sensors commercially available are simple and reliable, and are configured to sense the crankshaft angular position with a high resolution, for rotation speeds of about 600 rotations/min to about 9000 rotations/min. Other rotation speeds ranges are also envisaged. Knowledge of the crankshaft position to a high level of precision is required by the ECU 17, e.g. for existing engine functions based on crank angle, such as fuel injection and spark timing. An instantaneous rotation speed of the crankshaft 11 maybe calculated e.g. by the ECU 17 based on the crankshaft angular position received from the crankshaft sensor 12. Similarly, a variation of the instantaneous rotation speed of the crankshaft maybe calculated e.g. by the ECU 17 based on the crankshaft angular position received from the crankshaft sensor 12. In some cases, the crankshaft instantaneous speed and/or acceleration is already available e.g. to the ECU 17, because the crankshaft instantaneous speed and/or acceleration may be already used for other engine functions.

As explained in greater detail below, in some examples, the reference data 13 may be associated with at least one reference characteristic 14 of an operation of the engine 10.

The method of Fig. 1 also comprises:

determining, at S3, a measure of a similarity between the reference data 13 and the operation data 15; and

estimating, at S4, at least one operation characteristic 16 of the operation of the engine 10, based on the determining performed at S3.

As schematically illustrated with reference to Figures 3A, 3B, 4A and 4B, at least one of the characteristic 14 or the characteristic 16 may comprise information associated with at least one of: a characteristic of the fuel fuelling the engine (see e.g. in Figures 3A, 4A and 4B), and/or a characteristic of an exhaust of the engine (see e.g. in Figures 3B and 4B), and/or a characteristic of a combustion chamber of the engine (see e.g. in Figure 4A). In some examples the characteristic of the fuel fuelling the engine comprises at least one of a purity of the fuel, and/or a distillation characteristic of the fuel, including e.g. a volatility of the fuel and/or a final boiling point of the fuel. In some examples, the characteristic of the exhaust of the engine comprises at least one of a back pressure in the exhaust of the engine, and/or a loading of a particulate filter of the exhaust of the engine. In some examples, the characteristic of the combustion chamber of the engine comprises a number of pre- ignition events in the combustion chamber.

As illustrated in more detail in Figures 3 A to 4B, obtaining at SI the reference data 13 may comprise storing the reference data 13 in a lookup table 200 and/or in a plot 200, e.g. in a memory of the ECU 17. The lookup table 200 and/or the plot 200 may reference at least one association between the reference data 13 and at least one reference characteristic 14 of the operation of the engine 10. As illustrated in Figure 3 A, the reference data 13 (referred to as A1 to A6 in Fig. 3A) respectively correspond to the variation of the instantaneous rotation speed of the crankshaft 11. The reference data 13 are also associated with at least one reference characteristic 14 of the operation of the engine 10, the at least one reference characteristic 14 comprising information (referred to as T1 to T6 in Fig. 3 A) associated with a characteristic of the fuel fuelling the engine, such as the final boiling point of the fuel.

As illustrated in Figure 3B, the reference data 13 (see curve 13 in Fig. 3B) correspond to the instantaneous rotation speed of the crankshaft 11. The reference data 13 are also associated with at least one reference characteristic 14 of the operation of the engine 10, the at least one reference characteristic 14 comprising information (see curve 14 in Fig. 3B) associated with a characteristic of the exhaust of the engine, such as the back pressure in the exhaust of the engine.

As illustrated in Figure 4A, the final boiling point 14 of the fuel (see X-axis in Fig. 4A) may be associated with at least one reference characteristic 14 of the operation of the engine 10, the at least one reference characteristic 14 comprising information (see Y-axis in Fig. 4A) associated with a characteristic of a combustion chamber of the engine, such as a number of pre-ignition events in the combustion chamber.

As illustrated in Figure 4B, the reference data 13 (referred to as R1 to R6 in Fig. 4B) respectively correspond to the instantaneous rotation speed of the crankshaft 11. The reference data 13 are also associated with at least one reference characteristic 14 of the operation of the engine 10, the at least one reference characteristic 14 comprising:

information (referred to as PI to P6 in Fig. 4B) associated with a characteristic of the exhaust of the engine, such as the back pressure in the exhaust of the engine; and/or

information (referred to as FI to F6 in Fig. 4B) associated with a characteristic of the exhaust of the engine, such as the loading of a particulate filter of the exhaust of the engine; and/or

information (referred to as G1 to G6 in Fig. 4B) associated with a characteristic of the fuel fuelling the engine, such as the purity and/or a distillation characteristic of the fuel fuelling the engine. The method of Fig. 1 also comprises triggering, at S5, an action associated with the operation of the engine 10, based on the estimating performed at S4.

In some examples, the action may be configured to cause at least one of: a modification in an injection of the fuel in the engine and/or a modification in an ignition of the fuel in the engine and/or an intake manifold pressure charging in the engine and/or a regeneration of a particulate filter of an exhaust of the engine and/or a modification in fuel additives and/or an indication to a user and/or a maintenance operation of the engine. Other actions are envisaged.

As illustrated in Fig. 2, the method of Fig. 1 may be performed, at least partly, by the ECU 17 of a vehicle comprising the internal combustion engine 10. The ECU 17 comprises a memory and a processor, and is configured to process data in order to perform, at least partly, the method of Fig. 1. In some examples, obtaining at SI the reference data 13 may comprise receiving the reference data 13 from a calibration device, during a calibration of the engine 10. Alternatively or additionally, obtaining at S 1 the reference data may comprise determining the reference data 13 based on data received from the crankshaft sensor. In some examples, determining the reference data 13 may comprise using machine learning.

In some examples, determining at S3 the measure of the similarity between the reference data 13 and the operation data 15 comprises comparing the operation data 15 with the reference data 13.

In some examples, comparing the data 13 and 15 may comprise determining a correlation between the reference data 13 and the operation data 15. Alternatively or additionally, comparing the data 13 and 15 may comprise determining a difference between the reference data 13 and the operation data 15. In some examples, determining may comprise extrapolating data and/or interpolating data.

As illustrated in Figure 3A, determining at S3 the measure of the similarity between the reference data 13 and the operation data 15 comprises comparing the operation data 15 with the reference data 13 in the lookup table 200. In the example of Fig. 3 A, the operation data 15 corresponds to the reference data 13 referred to as A3.

As illustrated in Figure 3B, determining at S3 the measure of the similarity between the reference data 13 and the operation data 15 comprises comparing the operation data 15 with the reference data 13 in the lower plot 200. In the example of Fig. 3B, the operation data 15 corresponds to a curve located below the curve of the instantaneous rotation speed of the reference data 13 in Fig. 3B. As illustrated in Figure 4B, determining at S3 the measure of the similarity between the reference data 13 and the operation data 15 comprises comparing the operation data 15 with the reference data 13 in the lookup table 200. In the example of Fig. 4B, the operation data 15 corresponds to a value located between the reference data 13 referred to as R3 and R4 in Figure 4B.

As illustrated in Figures 3A to 4B, estimating at S4 the at least one operation characteristic 16 of the operation of the engine 10 comprises determining the at least one operation characteristic 16 from the lookup table 200 and/or the plot 200 referencing at least one association between the reference data 13 and at least one reference characteristic 14. In some examples, estimating the at least one operation characteristic 16 may comprise using an extrapolation and/or an interpolation from the lookup table 200 and/or the plot 200.

As illustrated in Figure 3 A, estimating at S4 the operation characteristic 16 comprises determining the operation characteristic 16, such as the final boiling point referred to as T3, corresponding to the reference data 13 referred to as A3.

As illustrated in Figure 3B, estimating at S4 the operation characteristic 16 comprises determining the operation characteristic 16 referred to as the upper plot 16, such as the back pressure in the exhaust, by extrapolation from the reference characteristic 14 corresponding to the reference data 13.

As illustrated in Figure 4B, estimating at S4 the at least one operation characteristic 16 of the operation of the engine 10 comprises determining the characteristics 16 as follows:

the back pressure 16 in the exhaust from a value located between the characteristics 14 referred to as P3 and P4 in Figure 4B, by interpolation; and/or

the loading 16 of the particulate filter in the exhaust from a value located between the characteristics 14 referred to as F3 and F4 in Figure 4B, by interpolation; and/or

the purity and/or a resultant distillation characteristic 16 of the fuel from a value located between the characteristics 14 referred to as G3 and G4 in Figure 4B, by interpolation. It should be understood that alternatively or additionally, determining the operation characteristic may be based on machine learning.

In some examples, the method may further comprise optionally correlating the determined at least one operation characteristic with data received from at least one of an exhaust back pressure sensor and/or a combustion pressure sensor. It should be understood that not all the vehicles comprise a back pressure sensor and/or a combustion pressure sensor. In more detail with reference to Figure 3B, the lower part of the plot 200 schematically illustrates the instantaneous rotation speed of the crankshaft, as a function of the crank angle, for an engine operating at idle. Data for one cylinder only are shown in Figure 3B, although it is understood that an engine generally comprises more than one cylinders, e.g. four cylinders or more. The curves 13 and 14 of Fig. 3B correspond to an engine having a clean (e.g. treated or regenerated) particulate filter.

It is appreciated that for a cycle of the crankshaft (e.g. between 0 and 360 degrees), the speed of the crankshaft varies significantly as a function of the crank angle. The rotation speed accelerates during phases 13-1 and 13-3, corresponding to a combustion (or expansion) stroke in the engine (occurring at 0 and 180 degrees). The rotation speed decelerates during phases 13.2 and 13-4, corresponding to an exhaust stroke in the engine.

The rates of the deceleration between the phases 13-1 and 13-2 and between the phases 13-3 and 13-4 correspond to the reference data.

The curve 14 in the upper part of the plot 200 schematically illustrates that the pressure in the cylinder can be considered to be approximately the same as the pre-turbine pressure. The curve 14 corresponds to the reference characteristic.

The curves 15 and 16 of Fig. 3B correspond to an engine having a saturated particulate filter, increasing the back pressure in the exhaust of the engine. It is appreciated from the upper part of the plot 200 that increased backpressure 16 provides extra resistance to the piston during phases 15-2 and 15-4 (corresponding to an exhaust stroke in the engine). The speed deceleration during the phases 15-2 and 15-4 is greater than the speed deceleration during the phases 13-2 and 13-4, because of the increased pre-turbine pressure. As the crankshaft decelerates, the increased pre-turbine pressure causes the crankshaft to decelerate faster. It is also appreciated from the lower part of the plot 200 that the rotation speed also varies more during phases 15-1 and 15-3 (corresponding to an combustion stroke in the engine) compared to the phases 13-1 and 13-3. In order to overcome the increased resistance to exhaust the burnt gas, while maintaining a certain idle speed, more fuel is injected in the engine. The injection of more fuel in the engine results in the greater variation in the instantaneous speed during the phases 15-1 and 15-3.

It is thus appreciated that the back pressure in the exhaust and/or the loading of the particulate filter may be estimated by determining the instantaneous variations of the rotation speed during the rotation of the crankshaft.

Alternatively or additionally, the method may comprise monitoring the instantaneous rotation speed of the crankshaft, for at least one cycle of the crankshaft, under known and stable conditions, such as for an engine operating at idle.

Variations of the rotation speed may be detected (such as angular accelerations and/or engine speed oscillations) and compared, as shown in Figure 3 A to reference variations for fuels of known distillation characteristics. The distillation characteristic of the fuel may thus be estimated, on the vehicle, in real-time or near real time.

In some examples, the detection of the variation of the engine speed may be enhanced by introducing a (e.g. momentary, e.g. small) change of injection and/or spark timing on at least one cycle of the engine. This change of injection and/or spark timing can help accentuate the impact of the e.g. actual distillation characteristic of the fuel mixture presented to the combustion chamber on the combustion. For example, by slightly delaying the end of overall injection under fixed condition (e.g. a hot and stable idle condition) for at least one cycle, a fuel mixture with a higher final boiling point may vaporise more slowly and combust less efficiently at the end of its combustion cycle, and this can be measured by resolving the angular acceleration of the crankshaft speed compared to a reference fuel of a known distillation characteristic at that point in the cycle. The change in injection can be volume as well as timing.

The method illustrated in Figure 5 comprises:

obtaining, at S10, data associated with a crankshaft speed sensor signal associated with an internal combustion engine comprising a crankshaft;

determining, at S20, real time fuel distillation and/or exhaust back pressure characteristics associated with the internal combustion engine, based on the obtained data; and

using, at S30, the determined characteristics in order to optimise an efficiency associated with the internal combustion engine.

In some examples, using at S30 the determined characteristics may comprise triggering an action associated with an operation of the engine, based on the determining. The action may be configured to cause at least one of: a modification in an injection of a fuel in the engine and/or a modification in an ignition of the fuel in the engine and/or intake manifold pressure charging in the engine and/or a regeneration of a particulate filter of an exhaust of the engine and/or a modification in fuel additives and/or an indication to a user and/or a maintenance operation of the engine. The method of Fig. 5 may be performed, at least partly, by the ECU 17 of the vehicle comprising the internal combustion engine 10.