Control Unit for Controlling an Internal Combustion Engine

Abstract

The present subject matter relates to a control unit for controlling an internal combustion engine, wherein the internal combustion engine includes at least one cylinder 100, at least one combustion chamber 90 within which a fuel is burned, at least one fuel injector 40, 50, at least one ignition device 60, and an oxygen determination unit 20 configured to determine the content of oxygen in the fuel, wherein the control unit 10 is configured to control the internal combustion engine based on the content of oxygen in the fuel detected by the oxygen determination unit 20.

Claims

1. Control unit for controlling an internal combustion engine, wherein the internal combustion engine includes at least one cylinder, at least one combustion chamber within which a fuel is burned, at least one fuel injector, at least one ignition device, and an oxygen determination unit configured to determine the content of oxygen in the fuel, wherein the control unit is configured to control the internal combustion engine based on the content of oxygen in the fuel detected by the oxygen determination unit.

2. Control unit according to claim 1, wherein, if the content of oxygen in the fuel is below a first threshold, the control unit is configured to control the internal combustion engine such that an homogenous combustion mode is carried out, and, if the content of oxygen in the fuel is equal to or higher than said first threshold, to control the internal combustion engine such that a stratified combustion mode is carried out.

3. Control unit according to claim 2, wherein the control unit is configured to set, when a stratified combustion mode is carried out, an amount of fuel injected during a compression stroke of a combustion cycle of the internal combustion engine based on the content of oxygen in the fuel.

4. Control unit according to claim 2, wherein, if the content of oxygen in the fuel is equal to or higher than the first threshold and lower than or equal to a second threshold, the amount of fuel injected during a compression stroke of one combustion cycle of the internal combustion engine is set higher the higher the content of oxygen in the fuel.

5. Control unit according to claim 4, wherein, in addition to the amount of fuel injected during a compression stroke of a combustion cycle of the internal combustion engine, the control unit is configured to control at least a further engine control parameter depending on an operational condition of the internal combustion engine during a stratified combustion mode.

6. Control unit according to claim 5, wherein, if the operational condition of the internal combustion engine is a middle rotational speed and a middle to high load, the control unit is configured to set a higher global lambda value the higher the content of oxygen in the fuel.

7. Control unit according to claim 5, wherein, if the operational condition of the internal combustion engine is a low rotational speed and a high load, the control unit is configured to set a lower degree of spark retardation the higher the content of oxygen in the fuel.

8. Control unit according to claim 5, wherein, if the operational condition of the internal combustion engine is a low rotational speed and a low load, the control unit is configured to set a higher degree of spark retardation the higher the content of oxygen in the fuel.

9. Control unit according to claim 1, wherein the control unit is configured to apply an engine operation map with a larger area in which the stratified combustion mode is used the higher the content of oxygen in the fuel.

10. Control unit according to claim 1, wherein the control unit is configured to control a measurement of the content of oxygen in the fuel at least once after a refueling of fuel.

11. Control unit according to claim 1, wherein the control unit is configured to obtain a measurement of the content of oxygen in the fuel by means of the oxygen determination unit, which comprises an oxygen detector and/or a unit determining the oxygen content in the fuel from operational parameters of the internal combustion engine.

12. System including a control unit according to claim 1 and an internal combustion engine which includes at least one cylinder, at least one combustion chamber within which a fuel is burned, at least one fuel injector, at least one ignition device, and an oxygen determination unit configured to determine the content of oxygen in the fuel.

13. A control method for the system according to claim 12, performing control of the internal combustion engine based on the content of oxygen in the fuel detected by the oxygen determination unit.

14. Computer program product storable in a memory comprising instructions which, when carried out by a computer, cause the computer to perform the control method according to claim 13.

Description

[0016] FIG. 1 depicts a schematic view of a cylinder of an internal combustion engine;

[0017] FIGS. 2A-2B depict a schematic view of a combustion chamber of the cylinder during different combustion control modes;

[0018] FIG. 3 shows a control method;

[0019] FIG. 4 shows a basic principle of the claimed subject matter compared to conventional combustion control schemes;

[0020] FIGS. 5A-5C show a use case 1;

[0021] FIGS. 6A-6C show a use case 2;

[0022] FIGS. 7A-7C show a use case 3.

[0023] FIG. 1 schematically shows a cylinder 100 of an otherwise unspecified internal combustion engine (not shown) which may have one or more than one cylinder 100. The engine may, for example, have two, three, four, six, eight or less/more cylinders. The engine comprises at least one piston 110 driven via a connecting rod 120 by a crankshaft (not depicted) for repeated reciprocal movement in the cylinder 100 to define the combustion chamber 90 therein.

[0024] An (air) intake port 70 with an intake valve 71 as well as an exhaust port 80 with an exhaust valve 81 are connected to the combustion chamber 90. Ambient air is drawn into the combustion chamber 90 through the intake port 70. Exhaust gases are discharged from the combustion chamber 90 via the exhaust port 80. An ignition device 60 comprising a spark plug is provided; optionally a prechamber fuel injector and a prechamber (both not shown) may be optionally attached to the internal combustion engine.

[0025] Furthermore, a direct fuel injector 50, or at least parts thereof, is joined to the inside of the combustion chamber 90 which allows to inject fuel therein. The direct fuel injector 50 may preferably be an electrohydraulic fuel injector or a piezoelectric fuel injector. Additionally, a port fuel 40 injector may be connected to the intake port 70 of the cylinder 100. The high-pressure fuel supply of the direct fuel injector 50 and the high- or low-pressure fuel supply of the port fuel injector 40 are not depicted. The fuel injection may be either performed by the direct main fuel injector 50 or the port main fuel injector 40 or may be divided between both injectors.

[0026] A control unit 10 which may in particular control the ignition device(s) is further shown in FIG. 1. The control unit 10 is electrically connected to the ignition device 60, the direct fuel injector 50 and/or the port fuel injector 40 and may be configured to control the multiple units/injectors/actuators. The control unit 10 may be, for example, the engine control unit (ECU) or may be a part thereof. The control unit 10 may be any other control unit, and signal line connections between the control unit 10 and the controlled units may differ from the example of FIG. 1. For example, there may be a plurality of control units 10 which may control subgroups of the controlled units, e.g. one control unit 10 may control only the ignition device 60, another control unit 10 may control only fuel injectors and so on. Even further, if there is a plurality of control units 10, these control units 10 may be interconnected with each other hierarchically or in another way. Alternatively, there may be one single control unit 10 which includes all the control functions of the multiple actuators of the internal combustion engine.

[0027] FIG. 1 further shows electrical connections between parts of the internal combustion engine and some signals input/output to the each unit. Specifically, in the example of FIG. 1, an oxygen detector or oxygen determination unit 20 is shown that is fluidic connected with a fuel tank 35 and the injectors 40, 50. A low pressure pump 31 connects the oxygen determination unit 20 with the port fuel injector 40 and a high pressure pump 32 connections the oxygen determination unit 20 with the direct fuel injector 50 in the example of FIG. 1. Preferably, as shown, the oxygen determination unit 20 is provided downstream of the tank 35 and upstream of the before described pumps 31, 32. The fuel, before it is supplied to the injectors 40, 50, is analyzed by the oxygen determination unit 20 with regard to the absolute or relative amount of oxygen contained in the fuel. For example, the determination may return the result that a certain percentage between 0% and 100% of e-fuel is contained in the fuel. The determination of the amount of e-fuel in the fuel mixture can be performed by using the known oxygen contents of the fuels included in the mixture. However, it is also sufficient for the herein described control to determine the oxygen content of the fuel mixture only, i.e. without determining the ratio of fossil fuel and e-fuel in the mixture.

[0028] Furthermore, FIG. 1 shows signal connection lines. There is one signal connection line between the oxygen determination unit 20 and the control unit 10 for providing information to the control unit 10 about the determined amount/ratio of oxygen in the fuel. Furthermore, examples of further signals input to the control 10 and used for controlling the internal combustion engine/the combustion are depicted, such as crank angle signal, intake air mass flow and intake air temperature, coolant water temperature, and the like. The control unit 10 may output, inter alia, control signals to the fuel injectors 40, 50.

[0029] In the depicted example of FIG. 1 the control unit 10 is enabled to receive information about the amount of oxygen in the fuel or the ratio of e-fuel to fossil fuel which is to be burned in the combustion chamber 90. The measurement/determination of oxygen does not necessarily has to be carried out each time fuel is pumped to the injectors 40, 50, however, it is one option. Another preferred option may include that a sensor (not shown) connected to the tank 35 detects a process of refueling so that only immediately after a refill operation the oxygen amount is determined. Further, said sensor may not be needed and the control unit 10 may receive a signal instead which indicated a refill operation, e.g., based on the level of fuel in the tank or the like. Further options may include that the oxygen amount/ratio is determined each time after the engine was newly started.

[0030] The oxygen determination unit 20 may, for example, use a sensor enabled to detect/measure/determine the content of oxygen, preferably intra-molecular oxygen, in the fuel. One technique is to use THz-electromagnetic waves and respective transducers, such as described by Patent Literature 1. Furthermore, besides using sensors for detecting the oxygen content, it may also be possible to detect the combustion conditions and to determine the oxygen content and/or the fuel mixture therefrom, e.g. the fuel properties of fossil fuel and e-fuel are distinctively different so that the combustion conditions change if the mixture changes. This can be detected and, e.g., a map stored in the control unit 10 or elsewhere in the vehicle can be used to determine the oxygen content. Furthermore, gas stations may deliver the information about the fuel refilled at ach refill to the vehicle by way of mobile communication of the like between the vehicle/control unit 10 and the gas station which may allow to determine the oxygen content based on keeping a refill history.

[0031] FIG. 2 shows in FIG. 2A a typical example of a combustion pattern within the combustion chamber 90 when a homogenous combustion is carried out. The fuel is distributed rather homogenously after its injection into the combustion chamber 90 (see zone A in FIG. 2A). FIG. 2B shows a typical example of a combustion pattern within the combustion chamber 90 when a stratified combustion is carried out. The fuel is distributed in a stratified manner after the injections (see exemplary zones A and B within the combustion chamber 90 in FIG. 2B). The stratification may be achieved, e.g., by splitting injections into multiple injections and/or using the direct and port injector 40, 50 in a combined manner. One possibility which is preferably used in the present case includes splitting the total amount of fuel for one combustion cycle into at least two injections, wherein one injection is carried out during the compression stroke, especially preferably closer to the top dead center (TDC) than to the bottom dead center (BDC). More specific application scenarios and examples will be described in the connection with the following Figures.

[0032] FIG. 3 shows a preferred example of the herein described control method and the control for which the control unit is adapted to carry it out, respectfully. In a first step S100 the oxygen content in the fuel is determined. The determination may be used, in an optional further step, determining a ratio of e-fuel compared to fossil fuel.

[0033] If the determined content of oxygen is found to be below a first threshold (S101), which may be set in a range of 10% to 45% oxygen in the fuel, preferably set in a range of 20 to 45% and especially preferably set to be between 35% and 40%, the homogenous combustion mode(s) is/are carried out by the control unit 10. Otherwise, in a Step 102, it is checked whether the oxygen content is below or above a second threshold which is preferably set above 45% and especially preferably above 50%. Preferably the second threshold is set lower than 60% and especially preferably in a range from 50% to 55%. Most preferably, the 2.sup.nd threshold is set around (within few percent points) the value which is expected for pure e-fuel in the tank. If the determined content of oxygen is above the second threshold, the stratified combustion mode is carried out (S103), wherein the amount of fuel injected during the compression mode is not dependent on the content of oxygen in the fuel. Otherwise, if it is found that the oxygen content is below the second threshold (S102), the stratified combustion mode is carried out (S104), wherein the amount of fuel injected during the compression mode depends on the content of oxygen in the fuel. Preferably, in the latter case, the amount of fuel injected during the compression stroke has a linearly increasing relation to an increasing level of content of oxygen. If step S101 returns that the oxygen content is below the first threshold, a homogenous combustion mode is carried out (S105).

[0034] FIGS. 4 to 7 show specific examples/use cases for control modes which are however not limiting for the herein described subject matter and further examples shall be considered encompassed by the herein described subject matter. FIG. 4 shows a basic principle underlying the subject matter. Conventional/fossil fuel, such as gasoline, can be combusted by a single injection of fuel during the intake stroke. If an e-fuel, which shall especially be construed as a high oxygen content fuel as discussed above, is to be burned, the injection amount is increased due to the reduced energy density of e-fuels. The herein described subject matter and the above described examples in particular apply a control concept during which a stratified operation is applied if the amount of e-fuel, determined via the oxygen content of the fuel, is relatively high. FIGS. 5 to 7 then show specific examples of application scenarios/use cases and they show especially examples for the control of the internal combustion engine according to which not only the oxygen content in the fuel is used for selecting a control mode of the engine but an engine condition, too.

[0035] FIGS. 5A, 6A and 7A each show an engine map with the engine load on the vertical axis and the engine speed on the horizontal axis as well as three regions for three exemplary use cases 1 to 3 which are further depicted in the FIGS. 5B,c; 6B,c and 7B,c. FIGS. 5B and 5C show the use case in which the engine operates in a region of the engine map which allow a control with regard to achieving the best/high efficiency. The region of high/best efficiency control is located in a mid-range of engine load and engine speed. The mid-range preferably is located in between 20% and 80%, more preferably between 30% and 70%, more preferably between 40% and 60% and very preferably between 45% and 55%. As soon as the oxygen content in the fuel is found to be higher than the 1.sup.st threshold, which is shown in FIG. 5C between 35% and 40% of oxygen content in the fuel, the stratified operation with at least one fuel injection during the compression stroke (see FIG. 5B) is started. The compression-stroke fuel injection is preferably smaller with regard to the amount of fuel injected than the injection during the intake stroke. Very preferably, the compression-stroke injection is carried out briefly before TDC, e.g. after 300° of the crank angle.

[0036] Controlled parameters and the specific control thereof being carried out for the use case 1, which is based on the oxygen content in the fuel, are depicted by FIG. 5C. The Figure shows that below the first threshold, the indicated parameters are kept constant irrespective of the exact value of the content of oxygen in the fuel. The parameters of specific interest in use case 1 are the compression-stroke injection amount (indicated in [mg] in the FIG. 5C), the lambda value and the fuel consumption (LHV normalized). In the region of oxygen content values below the first threshold homogenous combustion is carried out and the amount of fuel injected during the compression stroke is kept constantly at zero, while lambda is kept constantly at 1.0. If the oxygen content in the fuel is however found to fall in a range between the 1.sup.st threshold and the 2.sup.nd threshold, the compression-stroke injection amount is increased as well as the lambda value with increasing oxygen content values in the fuel. FIG. 5C shows approximately a linear relation, however, other correlations may be applied as well. Starting with the 2.sup.nd threshold, which is located in between 50% to 55%, as an example, in FIG. 5C, the compression-stroke injection amount and the lambda values are both maximized and are kept constant over further increasing oxygen content values. The exemplary values shown in the FIG. 5C are between 5 to 10 mg fuel injection during the compression-stroke and 2.0 lambda. The fuel consumption can be optimized by the above discussed control which is also shown by the decreasing trend in the lowest graph of FIG. 5C.

[0037] Use case 2, which is shown in FIG. 6, shows knocking condition or knock zone cooling operations. The engine speed, as shown by FIG. 6A, is relatively low, e.g. below 40% or lower and the engine load is near to the maximum, e.g. above 80% or higher. Parameters of especial interest for the control of use case 2 are again the compression-stroke injection amount in FIG. 6C and the MFB50 value. One can see from FIG. 6C that the stratified operation, see FIG. 6B, is applied for e-fuel amounts of above the 1.sup.st threshold (which is shown to be the same as in FIG. 5C). The compression-stroke injection amount is again increased with increasing content of oxygen in the fuel until the 2.sup.nd threshold. However, the ignition is shifted from the retarded side to the optimum, as the middle graph of FIG. 6C indicates. The fuel consumption can be improved again with increasing amounts of e-fuel in the fuel.

[0038] Further, use case 3, which relates to a catalyst heating scenario in which the engine speed is very low, e.g. below 20% or 30%, and the engine load is very low, e.g., below 20% or 30%, too. In this case the same parameters are used and shown in FIG. 7C, however, the ignition is shifted to the more retarded side for increasing values of oxygen in the fuel until the 2.sup.nd threshold.

[0039] A control unit, a control method and a related computer program product are described which allow using e-fuels in internal combustion engines wherein the control is such optimized that low fuel consumption is achieved and low PN emissions.

[0040] In general, all features of the different embodiments, aspects and examples, which are described herein, and which are shown by the Figures, may be combined either in part or in whole. The herein described subject-matter shall also entail these combinations as far as it is apparent to the person skilled in the art without applying inventive activity.

[0041] It should also be noted that the description and drawings merely illustrate the principles of the proposed methods, devices and systems. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the claimed subject matter and are included within its spirit and scope.

[0042] Although the citation of other claims in dependent claims is a single claim citation for the sake of clarity in the dependent claims, the invention includes the form in which multiple claims are cited in dependent claims (multi-claim dependent claims) and the form in which multiple multi-claim dependent claims are cited in dependent claims.

REFERENCE SIGN LIST

[0043] 10 Control Unit [0044] 20 Oxygen Determination Unit [0045] 31, 32 Pump [0046] 35 tank [0047] 40 port fuel injector [0048] 50 direct fuel injector [0049] 60 ignition device [0050] 70 intake port [0051] 71 intake valve [0052] 80 exhaust port [0053] 81 exhaust valve [0054] 90 combustion chamber [0055] 100 cylinder [0056] 110 piston [0057] 120 connecting rod