Patent Application
20200347790
The present document relates to a method for injecting a non-combustible fluid into an internal combustion engine, a corresponding control unit of an internal combustion engine, and a computer program product for carrying out the method by means of a computer. It is a particular technical advantage of the claimed subject-matter that the injected amount of water can be more precisely matched to the real state of the combustion within the internal combustion engine.
Water injection is an effective measure for the prevention of knocking in state of the art vehicle-internal combustion engines. In addition, the injection of water into the internal combustion engine can reduce the fuel consumption of the internal combustion engine. So far, the water injection control and especially the determination of the water amount to be injected is based on feed forward control, such as described by patent literature 1.
PTL 1: JP 2012-112326 A.
Patent literature 1 describes a diesel engine as an internal combustion engine of a vehicle and an amount of water to be injected is calculated by the loss of exhaust energy within a feed forward control system. The water injection is performed during the combustion phase of the diesel engine.
A downside of water injection methods and devices known so far is that the water tank has to be rather large and/or that the water has to be refilled in relatively short time intervals because the injected amount of water is not accurately determined.
The claimed subjected matter according to the appended claims overcomes the above technical problem and provides a method for controlling the amount of noncombustible fluid injected into an internal combustion engine more precisely. Further, a corresponding control device and a software program product are entailed, too.
According to an aspect, the claimed subject matter comprises a method for controlling the injection of a non-combustible fluid into an internal combustion engine. Preferably the non-combustible fluid is not/not fully combusted (i.e. at least partially inert) during the combustion within a cylinder of an internal combustion engine. More preferably, the non-combustible fluid is a gas or liquid with a high latent heat, wherein the latent heat of the fluid is at least 1/10 of the evaporation enthalpy of water. Most preferably, the non-combustible fluid is water.
The internal combustion engine may include at least one (combustion) cylinder, at least one non-combustible fluid injector, at least one combustion phase determining means, and at least one control unit.
Preferably, the at least one non-combustible fluid injector is a water injector and preferably it is disposed so that the non-combustible fluid/water is injected into the cylinder. In this case, it is preferable to provide at least one water injector per cylinder of the internal combustion engine. Alternatively or in addition, the at least one noncombustible fluid injector can be arranged at an air intake port of the internal combustion engine so that the non-combustible fluid is injectable into the air intake port/duct. It may be preferably to have at least one intake port per cylinder.
The at least one control unit may be integrated into the internal combustion engine or, alternatively, the control unit may be disposed at a position within a vehicle remote to the internal combustion engine and the control unit and the internal combustion engine may be connected via one or more signal lines.
Preferably, the non-combustible fluid (or shortly fluid) is not injected during the combustion phase of the combustion cycle. In other words, the fluid is preferably injected when the combustion is not taking place. The even more preferred timing for injecting the water is during the time of the intake of air.
The method may in particular comprise a step of determining a combustion phase by the combustion phase determining means, and a step of determining the amount of non-combustible fluid to be injected depending on the (determined) combustion phase. The term “determining” may preferably include the meanings of “calculating” as well as “estimating”. Preferably, determining the combustion phase may include that the timing of the combustion phase within the combustion cycle may be determined, and preferably the injected amount is determined based on said determined timing. In this regard it shall further be understood, that the “determining” of the amount of fluid to be injected may also include the meaning that an amount of fluid to be injected (which was somehow known before) is corrected or adjusted.
The determined combustion phase is the “real” combustion phase, wherein “real” shall be understood as being distinguished from a target or target combustion phase. In other words, in known systems, a target combustion phase for injecting, e.g., water into the internal combustion engine is predefined and the injection is carried out based on a feedforward control without having the possibility to check whether the actual or real combustion phase is deviated or shifted; e.g., the combustion phase may be shifted such as to be delayed. To the contrary, the claimed method which is described herein enables to get to know the actual/real combustion phase (or its timing) and thus can adapt the injection amount of non-combustible fluid accordingly. The method including the above described steps hence allows injecting an amount of noncombustible fluid into the internal combustion engine which is highly accurate and precisely matched to the real combustion phase/conditions. This allows, i.a., to save non-combustible fluid, such as water, which has to be carried within the vehicle and which has to be refilled repeatedly. In other words, it may either be beneficially possible to reduce the size of the tank for the non-combustible fluid and/or to expand the refill intervals.
Further, the combustion phase determining means may determine (or calculate or estimate) a pressure in the at least one cylinder. If there is more than one cylinder, the means may either determine the pressure in the plurality of cylinders or there may be at least one combustion phase determining means per cylinder. The control unit may determine the (real) combustion phase by comparing said determined (real) pressure with a target pressure, e.g., for the combustion phase. In other words, by determining the pressure and comparing it with a target pressure (e.g. at a preset time or position of the combustion cycle or phase), it is possible to detect the timing of the combustion phase which means that the real combustion phase is determined and whether it is, e.g., delayed.
One combustion (power) cycle may include several strokes. The pressure may be mapped to the crank angle, to a time or another variable. If, e.g., the pressure is mapped to the crank angle, the target pressure may be set so that it is possible to determine a shift of the combustion phase by comparing the target pressure at a preset crank angle with the real pressure at said crank angle. If the real pressure and the target pressure deviate from each other at the preset crank angle, the combustion phase is determined to be shifted, i.e. advanced or delayed. Alternatively, the real pressure may be compared with the target pressure to extract the crank angle at the point where the real pressure and the target pressure match with each other. Then, a shift of the combustion phase is determined, e.g., when the crank angle at which the two pressures match with each other deviates from a predefined crank angle. Further, instead of the crank angle in the above examples, it may also be used a certain time after a predefined event or any other variable which allows setting a point during the combustion cycle at which the (combustion) pressures can be compared with each other.
For example, preferably, the target pressure may be set to coincide with 50% of the total burn rate (MFB50) of the combustion within the cylinder. More specifically, it may be defined that the target pressure is a certain numerical value which is expected (e.g. by experiments, analysis, simulation or the like) at MFB50 which is set to be at e.g. a crank angle of 6° or 8° or the like after the top dead center (TDC) during the combustion phase. Then, in this example, if the preset pressure should be detected at another crank angle, e.g., 10°, it would be detected that the combustion phase is shifted. Alternatively, in this example, if, at the preset crank angle of, e.g., 8°, the determined (real) pressure deviates from the target pressure, it can be determined that the (real) combustion phase is shifted compared to the (target) combustion phase.
Comparing the determined/real pressure with the target pressure may show that, e.g., the combustion phase is advanced or delayed compared to the target and, thus, if the injection would be carried out according to the predefined amount which is set based on the target, too much or not enough fluid would be injected. Especially, the first case would mean that too much fluid is injected and that the reservoir/tank would be emptied quickly. Having determined the real/actual combustion phase by determining the real/actual pressure, the amount of injected fluid can be reduced which leads to the technical advantages discussed above.
Further, the control unit may determine an amount of the non-combustible fluid to be injected by feedforward control. This may, e.g., take place during a first combustion cycle after starting the engine, after starting the fluid injection control or after/at any other predefined point in time. The feedforward control may in particular include that the water injection amount is determined, e.g., based on using a lookup table, a map, a predefined equation or the like. For this part of the control process determination parameters are used which allow determining the engine's condition/state and correlating/determining an amount of fluid to be injected thereto. For example, a map may be used which includes an axis on which the engine revolutions are plotted and an axis on which the engine load is plotted. Depending on the actual condition of the engine, e.g., indicated by values for the above exemplarily mentioned parameters (revolutions and load), the map may return a value for an injection amount. The amount of injected non-combustible fluid (or simply fluid) may be expressed in different ways, however, preferably the amount is expressed in terms of a pulse width for driving the fluid/water injector.
After having determined/subsequent to the above described determining of the injection amount, the amount may be corrected. The correction preferably happens at the subsequent combustion cycle, however, this may be varied. The amount of fluid to be injected may be corrected based on the determined combustion phase by feedback control. Here, feedback control shall in particular entail the use of a comparison between the target (predefined) pressure and the pressure that was determined, i.e. the real/actual pressure. The comparison between the two pressure values delivers information about the real combustion phase or the real state of the combustion, i.e. whether the combustion phase is advanced or delayed. Especially and preferably, in case of a delayed combustion phase, the correction is carried out to reduce the amount of fluid to be injected. In other words, the result of the feedforward control in view of the amount of fluid to be injected is adapted to the real/actual combustion conditions/phase based on the result of the feedback control which includes the determining of the real combustion phase by comparing the target pressure and the real/actual determined pressure.
Further, the method, which may be preferably carried out by one or more control units, e.g. the engine control unit (ECU), may preferably include to determine the amount of non-combustible fluid to be injected based on a predefined engine state/condition, such as the load of the engine or a multi-parameter-defined state using, e.g., the load and the number of revolutions. The method may further determine the above discussed real pressure within the cylinder which may preferably be done by the combustion phase determining means itself or by the control unit based on values determined/measured by the combustion phase determining means. Said means may be a pressure determining means. Even further, the method may include the step of comparing said determined pressure with the target pressure in order to determine the (real) combustion phase thereby or therewith. Depending on the comparison result, the amount of non-combustible fluid to be injected may then be corrected based on the comparison result. The method may be carried out with little additional hardware parts and computing effort compared to the known methods, however, it increases the accuracy of the fluid injection amount strongly which leads to the technical benefits that a non-complex system may improve the efficiency of using the non-combustible fluid so that refill intervals or tank sizes may be increased and reduced, respectively.
Further, especially the steps of determining the pressure within the cylinder, comparing the determined pressure with a target pressure and correcting the amount of non-combustible fluid to be injected may be carried out in a preferably repeated fashion or a loop. More preferably, this “control loop” may be repeated at least once during one combustion cycle. The amount to be corrected may preferably be the first amount determined by the feedforward control. Alternatively, the amount to be corrected may be the amount which is the amount of the directly preceding combustion cycle or control loop. For the correction, preferably, the (corrected) amount of noncombustible fluid to be injected is stored for using it during a subsequent combustion cycle. The storage means may be, e.g., a member of the control unit. However, the storage means may also be located elsewhere.
The method steps and especially the “control loop” steps may be carried out within the control unit, e.g., by using a computing unit, a processor, or any other processing unit of the control unit.
Repeating the control ensures that the amount of injected non-combustible fluid stays precise even if the combustion phase should shift more than one time.
Further, as noted before, the control unit may reduce the amount of non-combustible fluid to be injected compared to the amount determined by feedforward control when the determined (real) combustion phase is retarded compared to the target combustion phase. The variation/correction of the injection amount may be carried out by a separate unit, a sub-unit of the control unit or the control unit which using a correction means, such as a correction map, a correction lookup table, an equation or the like. The computing efforts may be reduced by the latter means.
Further, the combustion phase determining means may be a pressure sensor installed at least partially within the cylinder. Alternatively or in addition, a crank angle sensor obtaining a crank angle may be used. Based on signals/values submitted/measured by the sensor(s), the control unit or any other processing means may calculate/determine the combustion pressure. In case that a pressure sensor is used, the computing effort for determining the pressure is lower for the control unit, however, installing the pressure sensor in the cylinder may increase the system complexity. Using the crank angle sensor, the computing effort is slightly higher, however, the system complexity of the hardware, i.e. within the internal combustion engine, is lower compared to the pressure sensor installed in the cylinder. Nevertheless, determining the real pressure can be efficiently performed and thus the real combustion phase can be determined at low computing costs, reliably and quickly.
Further, the internal combustion engine is preferably a gasoline engine and further preferably the injected fluid is injected outside of the combustion phase of the engine improving the fuel efficiency.
Further, the claimed subject matter may include a control unit of an internal combustion engine, preferably the ECU, which may be configured to carry out the method according to the above described method/aspects of the method, as well as an internal combustion engine which may include the control unit. “Include” may mean that the control unit is physically integrated with the engine or that it is remotely arranged, however, connected thereto by signal lines and the like.
Further, the claimed subject matter may include a computer program product storable in a memory comprising instructions which, when carried out by a computer or a computing unit, cause the computer to perform the above described method or aspects thereof, as well as a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out said method or aspects thereof.
Summarizing, the claimed subject-matter allows reducing the amount of water being used in a water-injection internal combustion engine, in particular when the combustion phase of the internal combustion engine is delayed.
In the following the claimed subject-matter will be further explained based on at least one preferential example of the invention with reference to the attached exemplary drawings, wherein:
An (air) intake port 4 with an intake valve 6 as well as an exhaust port 5 with an exhaust valve 7 are connected to the combustion chamber 1. Ambient air is drawn into the combustion chamber 1 through the intake port 4. Exhaust gases are discharged from the combustion chamber 1 via the exhaust port 5. A spark ignition unit 12 comprising a spark plug 12a and an ignition coil 12b is attached to the internal combustion engine. The spark ignition unit 12 preferably offers a variable spark duration or multi-spark ignition. The internal combustion engine (or briefly: “combustion engine” or “engine”) may have one or more spark ignition units 12. Preferably, it has at least one spark ignition unit(s) 12 per cylinder 100. The spark plug 12a as well as a fuel injector 8, or at least parts thereof, are connected to the inside of the combustion chamber 1 so that a spark and fuel can be introduced/injected into the combustion chamber 1. The high-pressure fuel supply of the fuel injector 8 is not depicted. The fuel injector 8 may preferably be a direct fuel injector 8. Further, the fuel injector 8 may preferably be an electrohydraulic fuel injector or a piezoelectric fuel injector.
The internal combustion engine may be equipped with one or more intake valve phasing actuator(s) 10 and/or one or more exhaust valve phasing actuator(s) 11 as shown in
Further, a non-combustible liquid injector 9 is connected to the intake port 4 of the cylinder 100. Since most preferably the liquid to be injected is water, even though other liquids having a high evaporation enthalpy may be used as well, the term “water injector” will be used as one specific example for a non-combustible liquid injector 9. The water injector 9 may be a low-pressure injector with an injection pressure of up to 4 bar or a high-pressure injector with an injection pressure of more than 4 bar. As an alternative to the water injector 9 connected to the intake port 4 (as shown in
Further,
The water injection device 101 according to
The feedforward control section 21 outputs a control signal indicating at least a value for the amount of water to be injected. Preferably, the amount of water to be injected is expressed by way of a pulse width/time duration. The signal output by the feedforward control section 21 is input into a merging unit 23 which further receives at least an output (signal) from a feedback control section 22. The merging unit 23 may combine the two signals which are input thereto. For example,
The feedback control section 22 may include various optional sub-sections. One example of a preferred configuration of the feedback control section 22 is schematically depicted by
The real or determined pressure is a pressure which was measured by a pressure determining means 19. This may, for example, be a pressure sensor 20 being arranged (at least partially) within the combustion chamber 1 (as schematically shown in
The feedback control section 22 has at least one comparison section 22a which is adapted to compare the two input pressure values described above. The comparison section 22a may be a CPU or the like or it may be a specifically designed electrical circuit for comparing two values with each other and to output a comparison result. In the present example, the output of the comparison section 22a may preferably be a pressure difference value (delta p) indicating a difference between the two input pressure values. If the pressure difference delta p is unequal zero, the combustion cycle timing is either ahead or delayed in timing. If the timing is ahead or delayed, the feedback control section 22 will output a correction amount (signal) which is input into the merging unit 23. For example, if the timing/combustion phase is found to be delayed, the feedback control section 22 will output a correction amount signal for reducing the amount of water to be injected which was set by the feedforward control section 21. Further, preferably, the feedback control section 22 may include a varying section 22c which may include computing means for determining/calculating/estimating the correction amount to be output by the feedback control section 22. The varying section 22c may use tables, maps or other options, such as equations and the like, for finding the correction amount. In
As already described above, the merging unit 23 combines the at least two input values, the feedforward-control-set water injection amount (preferably expressed as a control pulse width/duration time) and the correction amount input from the feedback control section 22. After the combination, carried out by CPUs or specific electrical circuitry of the merging unit 23, the merging unit 23 outputs a corrected amount, e.g. such as a corrected fluid injection pulse width, to the controller 13 which controls the water injector 9. Alternatively, the output may performed by an optional output unit 24 which passes the control signal to the controller 13 which controls the water injector 9. By the above described combination of feedforward and (closed-loop) feedback control of the water injection amount, a higher accuracy of the precise amount of water to be injected into the internal combustion engine can be achieved. Especially when the combustion cycle is shifted, e.g. delayed, the water amount can be accurately adjusted and water is saved to the benefit of the water use efficiency.
With the correct/corrected water injection amount being set, either by correction (yes-route in
J{dot over (ω)}=τ
combustion+τfriction+τinner+τinner+τload [Math. 1]
With the value for the torque T, combustion pressure p can be calculated based on the following equation (2):
A is the effective square of the piston, R is the conrod radius, φ is the crank angle and θ is the angle of the rod connected to the piston (see
The pressure determined according to the above described method can be used to determine whether it deviates from a target pressure to find out whether the timing of the combustion phase is shifted. In other words, the above described method for correcting/adjusting the amount of injected non-combustible fluid can either use one or more pressure sensors or the method for determining the combustion pressure as described in connection with
While the above describes a particular order of operations performed by certain aspects and examples, it should be understood that such order is exemplary, as alternatives may perform the operations in a different order, combine certain operations, overlap certain operations, or the like. References in the specification to a given aspect indicate that the aspect described may include a particular feature, structure, or characteristic, but every aspect may not necessarily include the particular feature, structure, or characteristic. The features which are described herein and which are shown by the Figures may be combined. The herein described and claimed subject-matter shall also entail these combinations as long as they fall under scope of the independent claims.
It should again 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.
Furthermore, it should be noted that steps of various above-described methods and components of described systems can be performed by programmed computers. Herein, some embodiments are also intended to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine-executable or computer-executable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods. The program storage devices may be, e.g., digital memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. The embodiments are also intended to cover computers programmed to perform said steps of the above-described methods.
In addition, it should be noted that the functions of the various elements described herein may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional and/or custom, may also be included.
Finally, it should be noted that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the claimed subject-matter. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable storage medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2018 201 152.4 | Jan 2018 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/002371 | 1/24/2019 | WO | 00 |
