NON-COMBUSTIBLE FLUID INJECTION METHOD FOR AN INTERNAL COMBUSTION ENGINE

Abstract

Method for controlling injection of a non-combustible fluid into an internal combustion engine. The internal combustion engine may include at least one cylinder, at least one non-combustible fluid injector, at least one combustion phase determining means, and at least one control unit. The method may comprise the steps of determining the combustion phase by the combustion phase determining means, determining the amount of non-combustible fluid to be injected depending on the combustion phase.

Claims

1. A method for controlling injection of a non-combustible fluid into an internal combustion engine, the internal combustion engine includes at least one cylinder at least one non-combustible fluid injector, at least one combustion phase determining means, and at least one control unit; the method comprising the steps of: determining the combustion phase by the combustion phase determining means, determining the amount of non-combustible fluid to be injected depending on the combustion phase.

2. The method according to claim 1, wherein the combustion phase determining means determines a pressure in the cylinder, and the control unit determines the combustion phase by comparing said determined pressure with a target pressure.

3. The method according to claim 1, wherein the control unit determines an amount of the non-combustible fluid to be injected by feedforward control and corrects the amount of the non-combustible fluid to be injected based on the determined combustion phase by feedback control.

4. The method according to claim 1, wherein the control unit: determines the amount of non-combustible fluid to be injected based on an internal combustion engine state, determines a pressure within the cylinder by the combustion phase determining means being a pressure determining means, compares said determined pressure with the target pressure for determining the combustion phase, and corrects the amount of non-combustible fluid to be injected based on the comparison result.

5. The method according to claim 1, wherein the control unit repeatedly performs at least the steps of determining the pressure within the cylinder, comparing the determining pressure with a target pressure and correcting the amount of non-combustible fluid to be injected, wherein the corrected amount of non-combustible fluid to be injected is stored for using it in a subsequent combustion cycle.

6. The method according to claim 1, wherein the control unit reduces the amount of non-combustible fluid to be injected compared to the amount determined by feedforward control when the determined combustion phase is delayed compared to a target combustion phase.

7. The method according to claim 1, wherein the combustion phase determining means is a pressure sensor installed within the cylinder and/or a crank angle sensor obtaining a crank angle based on which the control unit calculates the combustion pressure.

8. The method according to claim 1, the internal combustion engine is a gasoline engine.

9. A control unit of an internal combustion engine configured to carry out the method according to claim 1.

10. An internal combustion engine including the control unit according to claim 9.

11. A computer program product storable in a memory comprising instructions which, when carried out by a computer, cause the computer to perform the method according to claim 1.

12. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0031] FIG. 1 depicts a cross-sectional view of a parts of an internal combustion engine;

[0032] FIG. 2 depicts a water injection device;

[0033] FIG. 3 depicts a control system of the claimed control method;

[0034] FIG. 4 depicts a flow chart of the claimed control method;

[0035] FIG. 5 depicts an example of a curve which shows the amount of water to be injected compared to the timing of the combustion phase;

[0036] FIG. 6A shows cross sections of a cylinder 100 with a crank angle sensor;

[0037] FIG. 6B shows a flow chart of a claimed method for determining the combustion pressure based on the crank angle sensor signals.

DESCRIPTION OF EMBODIMENTS

[0038] FIG. 1 depicts an exemplary cylinder 100 of an otherwise unspecified internal combustion engine, which may have more than one cylinder 100. The engine may, for example, have two, three, four, six, eight or less/more cylinders 100. The cylinder 100 comprises a combustion chamber 1 in which a piston 2 with a connecting rod 3 is disposed allowing it to travel. The connecting rod 3 is connected to a crankshaft 25 that is described later in connection with an aspect of determining the pressure within the combustion chamber 1 of the claimed subject-matter.

[0039] 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.

[0040] 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 FIG. 1. The intake valve phasing actuator 10 is preferably used for realizing early intake valve closing. The exhaust valve phasing actuator 11 is preferably used for adjusting residual gas and/or for varying an exhaust valve opening timing. The valve phasing actuators 10, 11 are preferably hydraulic actuators or electric actuators. Other means for controlling the intake and exhaust valve opening/closing timings may be applied in addition or alternatively. Even further, if not otherwise indicated in the aspects described below, the herein claimed subject-matter may also entail an internal combustion engine which does not have an intake/exhaust valve opening/closing timing means.

[0041] 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 FIG. 1), or in addition thereto, one or more water injectors 9 may be connected to the cylinder wall 14 of one cylinder 100 to inject water directly into the combustion chamber 1.

[0042] Further, FIG. 1 shows a controller 13 which is electrically connected to the spark ignition unit 12, the valve phasing actuators 10, 11, the direct fuel injector 8 and the water injector 9. As an example, input signals, such as a crank angle signal, an intake air amount, a water temperature and a combustion pressure, are shown in FIG. 1. However, other input signals or more or less input signals may be input into the controller 13. The controller 13 controls the multiple units/injectors/actuators. The controller 13 may, for example, be the engine control unit (ECU). The controller 13 may also be any other control unit, and signal line connections between the controller 13 and the controlled units may differ from the example of FIG. 1. For example, there may be a plurality of controllers 13 which can control subgroups of the controlled units, e.g. one controller 13-1 may control only fuel injectors, another controller 13-2 may control only water injectors 9 and so on. Even further, if there is a plurality of controllers 13, these controllers 13 can be interconnected with each other hierarchically or in another way.

[0043] FIG. 2 shows a water injection device 101 of an aspect in which the non-combustible fluid is water. The water injection device 101 has a water tank 15, a water pump 16 which can supply water from the water tank 15 to the water injector 9 via a water pipe/tube 17. The water injector 9 and the water pump 16 are electrically connected with the controller 13 via signal lines 18. The controller 13 may, inter alia, control the injection pulse width/time, the injection pressure and/or the injection timing. For example, the controller 13 may be adapted to vary the injection pulse width/time so that the amount of water being injected into the engine may be varied. As described above, the water injector 9 may be arranged so that water may be injected directly into the combustion chamber 1. Alternatively or additionally, the water injector 9 may be connected to the intake port 4 so that water may be injected into the stream of air sucked into the combustion chamber 1. The water may further be injected so as to form a (homogenous) mixture of air and water.

[0044] The water injection device 101 according to FIG. 2 is a schematic example which may include further non-shown and/or optional members, such as a fluid rail for connecting multiple water injectors 9, such as sensors for temperature, pressure and the like, such as further signal lines, such as further water lines/tubes for recirculation of water or the like, such as valves, and/or such as further actuators, pumps and the like.

[0045] FIG. 3 shows an aspect of the control method which is used particularly for varying the amount of non-combustible fluid, e.g. water, which is injected into the internal combustion engine. A feedforward control section 21 is used to set an amount of water to be injected, preferably by way of setting a fluid injection control pulse width/time duration. The feedforward control section 21 (and the other sections shown in FIG. 3) can be realized as part of the controller, as a subunit thereof, as stand-alone computing units or the like. The feedforward control section 21 may set the water injection amount or the corresponding control pulse based on (predefined) states or conditions of the engine. For example, this may be done based on predefined internal combustion engine state parameters, such as the number of revolutions, load and the like. In FIG. 3 there is shown an example in which the feedforward control section 21 uses a map which includes the parameters of the number of revolutions (Ne) and the engine load for setting the amount of water to be injected (via setting the control pulse). The feedforward control section 21 may include a plurality of such maps which may also include other parameters. Further, the feedforward control section 21 may, additionally or alternatively, include tables which may be read for setting the water amount/control pulse. In addition or instead, the feedforward control section 21 may also use other means for setting the amount of water/control pulse to be injected at a predefined driving situation and an internal combustion engine state, respectively.

[0046] 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, FIG. 3 shows that the output from the feedback control section 22 is subtracted from the output of the feedforward control section 21. This will be described in more detail below.

[0047] 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 FIG. 3. It shows that it at least receives input (signal) indicating a target pressure and a real/determined pressure. With the input received at the feedback control section 22, the combustion phase may be determined. With the input received at the feedback control section 22, e.g., it may be checked whether the combustion phase of the combustion cycle is present at the moment of the checking, and, preferably, with the received input at the feedback control section 22 it may be determined whether the combustion phase deviates from the regular timing, i.e. whether the combustion phase is ahead of the timing or delayed/retarded. This may be carried out, as a preferred example, by comparing the target pressure with the determined/real pressure. For example, it may be defined that the pressure at a specified time of the combustion cycle and/or at a specified crank angle, shall have a given value or shall be within a given range of values which is then the target pressure. The target pressure may be read from a table, a map or the like which may be stored in the controller's memory. Further in the above example, the target pressure may indicate a predefined state of the combustion cycle so that it is possible to find out whether the combustion phase is delayed or ahead of the timing when it is measured whether the real pressure at a predefined state matches with target pressure or not. In other words, the target pressure may be any pressure during the combustion cycle based on which it may be find out whether the combustion cycle or the combustion phase thereof is ahead, on time or delayed/retarded. A specifically preferred target pressure may be the pressure which is expected at a burn rate of 50% of the total burn rate (MFB50) or which is expected at a crank angle in a range of 6 to 10 or at a specific value, such as 6 or 8, after the top dead center during the combustion phase of the combustion cycle.

[0048] 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 FIG. 1) which determines or measures the pressure within the combustion chamber 1. A further preferred option for a configuration/aspect of the pressure determining means 19 will be described later. The pressure determined by the pressure determining means 19 may be directly submitted by way of a signal to the feedback control section 22 or it may be sent via a/the controller 13.

[0049] 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 FIG. 3, a look-up map is shown as an example. If the varying section 22c is not included in the feedback control section 22, the determining/calculating/estimating of the correction amount may be carried out outside of the feedback control section 22, e.g. within one of the controller(s) 13. A further preferable sub-section of the feedback control section 22 may include a gain 22b which may be preferably set between the comparison section 22a and the varying section 22c.

[0050] 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.

[0051] FIG. 4 further describes an example for a series of steps to be carried out when performing the control method as claimed. In a first step, the combustion pressure phase is determined. This particular includes the measurement/determination/calculation of the real pressure by means of the pressure determining means 19, which may comprise, in an aspect of the claimed subject-matter, one or more pressure sensors included in the cylinder 100 or the combustion chamber 1 thereof. With this step completed, the determined pressure is compared with the pressure of the target. The target may be the pressure at the point of 50% total burn rate (MFB50) or at a crank angle of 6, 8 or 10 or the like after the top dead center during the combustion phase. If the two pressure values match with each other, the combustion phase is determined and, more specifically, it is determined that the combustion phase is on time. If the two pressure values do not match, it is checked in this step or in a sub-step whether the combustion phase is delayed/retarded. If this is found, the further steps of a feedback control are carried out by which the water amount to be injected is reduced. FIG. 4 only shows a reduction of the water amount when a delay of the combustion phase is found. According to an aspect, there may be only a step of reducing the injected water amount when a delay of the combustion phase is found. In another aspect, however, the correction may also be carried out when the combustion phase is earlier, i.e. ahead of the timing.

[0052] With the correct/corrected water injection amount being set, either by correction (yes-route in FIG. 4) or by feedforward control only (no-route in FIG. 4), the water injector 9 is controlled to inject the set amount. Preferably, the injection takes place outside of the combustion phase, and, most preferably, it takes places during the intake of air before the combustion phase. The reduction amount of the present loop is stored so that it can be used as a starting point for the next loop of the above described steps.

[0053] FIG. 5 shows the example of a curve which relates the amount of water in the air, as a water air ratio, to the deviation from MFB50 expressed as difference degree of the crank angle. The curve previously determined schematically indicates a trend which corroborates that the accuracy of the determination of the combustion phase has a considerably effect on the injected water amount. In other words, if it is determined that the combustion phase is delayed by 1, the injected water amount can be reduced by up to approx. 6%. The claimed subject-matter therefore allows saving a considerable amount of water due to the above-described method of correcting the water injection amount based on real/determined pressure values.

[0054] FIGS. 6A and 6B further show an aspect for determining the pressure within the combustion chamber 1 based on the crank angle of the crankshaft 25 which preferably has teeth 26b in this aspect. The steps may be performed in a different order. For performing this determination method, the pressure determining means 19 has at least one detector 26a for detecting the teeth 26b, as schematically shown in FIG. 6A. The detector 26a may preferably count the teeth 26b by way of optical means or by way of magnetic fields or the like, as an example. The detector 26a may be disposed in a space close to the crank shaft 25. As shown in FIG. 6B, the one or more controller(s) 13 may obtain the sensor signals from the detector 26a in a first step. Subsequently, the sensor signals, such as pulse signals, are used to calculate the rotational speed of the crankshaft 25 and after this step, the sample, i.e. the crankshaft 25, may be held or stopped (it is also possible to measure the rotational speed difference in a different way without stopping the sample). Then a difference between the rotational speeds is obtained and it is divided by the time step/period between the two rotational speed values with which the difference was build, and the resulting value (the first derivative of w) is multiplied by the inertia, which will have the sign J in the following. By these steps as shown in FIG. 6B, the torque of the crankshaft 25 is determined/calculated based on the following equation (1):

J{dot over ()}=.sub.combustion+.sub.friction+.sub.inner+.sub.inner+.sub.load[Math. 1]

[0055] With the value for the torque T, combustion pressure p can be calculated based on the following equation (2):

[00001]$\begin{array}{cc}p=\frac{\cos .Math..Math.}{A_{\mathrm{cylinder}}.Math.R.Math..Math.\sin \left(+\right)}& \left[\mathrm{Math}..Math.2\right]\end{array}$

[0056] A is the effective square of the piston, R is the conrod radius, is the crank angle and is the angle of the rod connected to the piston (see FIG. 6A).

[0057] 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 FIGS. 6A and 6B or a combination thereof.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

REFERENCE SIGNS LIST

[0063] 1 combustion chamber [0064] 2 piston [0065] 3 connecting rod [0066] 4 intake port [0067] 5 exhaust port [0068] 6 intake valve [0069] 7 exhaust valve [0070] 8 fuel injector [0071] 9 non-combustible fluid/water injector [0072] 10 intake valve phasing actuator [0073] 11 exhaust valve phasing actuator [0074] 12 spark ignition unit, 12a spark plug, 12b ignition coil [0075] 13 controller [0076] 14 cylinder wall [0077] 15 (water) tank [0078] 16 (water) pump [0079] 17 (water) pipe [0080] 18 signal line [0081] 19 pressure determining means [0082] 20 pressure sensor [0083] 21 feedforward control section [0084] 22 feedback control section [0085] 22a comparison section [0086] 22b gain [0087] 22c varying section [0088] 23 merging unit [0089] 24 output unit [0090] 25 crank shaft [0091] 26a crank angle sensor (detector for crank shaft teeth) [0092] 26b tooth/teeth of crank shaft [0093] 100 cylinder [0094] 101 (water) injection device