METHOD FOR DETERMINING THE POSITION OF AN INTERNAL COMBUSTION POWER ENGINE

Description

[0001] The invention relates to a method for determining the position of an internal combustion engine and an arrangement for implementing the method. The invention further relates to a computer program and a machine-readable storage medium for implementing the method. State of the art

[0002] For the operation of a modern internal combustion engine, it is necessary to provide the electronic engine control unit (ECU) that controls the internal combustion engine with information about the current engine speed. For example, it is common practice to measure the rotational speed of the engine's crankshaft using an inductive sensor or Hall effect sensor. This sensor registers passing metallic markings and determines the rotational speed based on the time difference between two markings.

[0003] In a conventional internal combustion engine, also referred to as an engine or machine, injection and ignition are controlled by the engine control unit using engine management software. This software needs to know the cylinder position or stroke to trigger injection and ignition. To achieve this, a sensor wheel mounted on the engine's crankshaft, which has a number of teeth and a gap around its circumference, can be used. In some cases, a sensor wheel with several teeth can also be mounted on the camshaft.

[0004] Sensors are then attached to these sensor wheels, which generate electrical signals when the engine is running and the crankshaft is rotating. These sensor wheels have a fixed relationship to the mechanical position of the engine.

[0005] In a single-cylinder four-stroke engine, for example, the crankshaft rotates twice, while the camshaft rotates only once. This means that a gap in the crankshaft's electrical signal can be observed or detected twice. Therefore, while the crankshaft position can be determined from the gap, the power stroke cannot. For example, a top dead center at the end of a compression stroke and a top dead center at the end of the exhaust stroke can be determined, which cannot be distinguished using the tooth gap information.

[0006] A software program must now use an algorithm to detect the gap in the crankshaft signal and distinguish whether this is the gap (GAPO) of the first revolution in the power stroke or the gap (GAP1) of the second revolution in the power stroke. The profile of the camshaft signal can be used for this purpose. Once the software has identified the gap, it is synchronized with the engine position. The software now knows the cylinder position and can time injections and ignitions.

[0007] Systems that have both sensors also support backup modes. For example, if the crankshaft signal is faulty, special crankshaft sensor wheels still allow the software to synchronize with the engine position. However, the accuracy of the information provided by the engine management software may not be very high, and therefore torque is limited in such a mode, which can be referred to as crankshaft backup mode.

[0008] Accordingly, if a camshaft sensor signal is faulty, it is still possible to drive the engine using the crankshaft signal alone in a dual-firing mode. It is also possible to identify the gap, i.e., whether GAPO or GAP1 is present, using software-controlled procedures such as test injections.

[0009] In the low-cost two-wheeler segment, typically only one crankshaft sensor signal is available, even if the engine has more than one cylinder. Software techniques are used to synchronize the software with the engine position. One known technique involves using the intake manifold pressure signal information in combination with the crankshaft sensor signal to detect the engine position.

[0010] DE 10 2014 206 182 A1 discloses a method for determining the crankshaft position of an internal combustion engine. A crankshaft speed curve is recorded over time, and the crankshaft position is determined by comparing the speed curve with a known speed curve of a working cycle of the internal combustion engine. The known speed curve has a section characteristic of the crankshaft position. Another relevant publication is EP 1 507 077 A2. Disclosure of the invention

[0011] Against this background, a method having the features of claim 1 and an arrangement according to claim 10 are presented. Furthermore, a computer program according to claim 11 and a machine-readable storage medium according to claim 12 are presented. Further details emerge from the dependent claims and the description.

[0012] The presented method makes it possible to determine the engine position, i.e., the position of one or more cylinders, and thus the power stroke. At this point, one could also say that the method serves to determine the crankshaft position. Therefore, it is possible to determine the power stroke of the cylinder(s) and, by synchronizing the software, to time injection and ignition accordingly.

[0013] The described method is therefore based on generating or producing a signal that uses the information from the engine speed signal received by the engine control unit. This engine speed typically indicates the engine's rotational speed. The speed information is usually provided either by the crankshaft sensor signal or by the signal from the generator, which in a two-wheeler is attached directly to the crankshaft.

[0014] This generated signal highlights the significant change in engine speed information, or engine speed, in the compression region of the high-pressure loop's top dead center (TDC). Using this signal pattern, it is easy to detect the position of a cylinder in an internal combustion engine. In the case of a single-cylinder engine, there is only one speed change during a combustion cycle due to compression and decompression in the high-pressure loop.

[0015] As previously stated, this method requires only the engine speed signal. No other signals or information are required. It can be used effectively to detect engine position, particularly in all two-wheel systems with a single cylinder, two cylinders, and even multi-cylinder systems.

[0016] The presented method has, at least in some of its embodiments, the following advantages:The engine position information can be reliably acquired in all possible operating conditions with little information when a starter motor drives the engine. The presented algorithm can be used to acquire the phase or power stroke during a kickstart. The generator signal, which provides the engine speed information, can also be used to acquire the engine position. This saves costs for a pickup wheel, a sensor, and signal conditioning circuits. The algorithm can acquire the engine position more quickly than other approaches, thus enabling faster engine starting. There is no need to operate the engine in dual-ignition mode during startup, as the power stroke can be acquired more quickly. Spark plug life is increased. The method can be used to acquire the power stroke during startup.The method can also be used for resynchronization at higher machine speeds. This broadens the application range of the method compared to other methods. The use of additional methods is not required, thus reducing software complexity, and algorithm calibration is also faster than with other power cycle acquisition methods.

[0017] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0018] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0019] Short description of the drawings Figure 1shows curves of a crankshaft and camshaft signal. Figure 2 shows in a graph the speed behavior of an engine when started using an electromechanical starter. Figure 3 shows a waveform of a signal that represents a relationship. Figure 4 shows the processes of the presented procedure using a state machine. Figures 5 to 10 show curves of a crankshaft signal. Figure 11 shows in a graph a speed characteristic of a start with kickstarter. Embodiments of the invention

[0020] The invention is illustrated schematically in the drawings using embodiments and is described in detail below with reference to the drawings.

[0021] Figure 1 shows the curves of a crankshaft signal 10 and a camshaft signal 12. Top dead centers (TDC) are marked in the crankshaft signal, namely TDC 20, TDC 1 22, TDC 3 24 and TDC 4 26.

[0022] Figure 2 shows the curve of an engine speed signal 50 for a single-cylinder two-wheeler during start-up. The crankshaft angle [°CA] is plotted on the abscissa 52, and the engine speed [rpm] is plotted on the ordinate 54. The diagram shows that the engine speed drops during the compression stroke and increases significantly during the decompression phase.

[0023] It is now planned to use the Figure 2 The signal shown, which carries information about the engine speed, is used to generate a special signal to utilize this speed information. In this way, the effect of compression and decompression on the engine speed signal can be detected particularly appropriately. This special signal is hereinafter referred to as the generated signal.

[0024] Figure 3shows the curve or behavior of this generated signal 100. Time is plotted along the abscissa 102 and 104 along the ordinate. Furthermore, a calibrated threshold value 106 is entered in the diagram. A particular pattern 108 can be seen in the curve shown, which repeats in the generated signal 100. This pattern 108 appears once around a compression stroke at top dead center of the high-pressure phase. In a two-wheel system with one cylinder, exactly one such pattern can be seen per working cycle.

[0025] This special pattern 108 has a fixed relationship to the mechanical motor position. Thus, the software can be synchronized with the motor position based on the special pattern once this pattern 108 has been identified in the signal 100.

[0026] If synchronized operation is not present at a higher speed, the engine speed drops because no combustion occurs. Even in such a scenario, it is possible to generate such a pattern 108 or signal pattern from the engine speed signal 100. This allows the software to be easily resynchronized, preventing an engine shutdown. It is particularly important to note that the application range of the method is broader than that of other approaches, such as intake manifold pressure phase detection.

[0027] For example, the signal pattern 100 shown is constructed or generated from the speed signal, as expressed by the following equation: ∑ i = a b t i / ∑ j = c d t j , where t[i], t[j] represent the edge time from the machine speed signal. This edge time on the machine speed signal can be measured between two rising signal edges, between two falling signal edges, or between all signal edges (rising to falling or vice versa). Alternatively, the machine speed can also be used directly instead of the edge times to generate the signal pattern.

[0028] The sums shown are calculated for two different sets of measured edge times. To obtain a suitable ratio of the times t[i] or t[j], these do not have to be consecutive, but can be. Likewise, the number of summed times can be one or more. Depending on the selected times for the numerator and denominator, different ratio properties can be achieved. An example is shown in Figure 3The selection of the quantities for the numerator and denominator can be chosen in such a way that the resulting ratio of the sums clearly highlights the specific pattern for synchronizing the motor position, thus making it particularly detectable.

[0029] To evaluate these curves, the amplitude of the resulting pattern can be checked against a calibratable threshold. If the amplitude is greater than the calibratable threshold, or smaller if the characteristic point is a maximum or minimum, respectively, this means that the software has found the motor position. This threshold depends on environmental conditions, such as motor temperature, motor speed, altitude, etc., and can be easily adjusted through calibration or during runtime. Instead of using a calibratable threshold, the ratio pattern can be evaluated using various other signal processing techniques, such as cross-correlation, to find specific characteristic points.

[0030] In Figure 4A state machine 130 is shown illustrating the phase detection algorithm for each edge of the speed signal. The diagram shows different states, namely: Initializing the work cycle search 132 Work cycle search deactivated 134 Work cycle search successful 136 Work cycle search activated 138 Work cycle search unsuccessful 140

[0031] Arrows indicate prerequisites for state transitions, namely: Activation conditions are met 150 Activation conditions are not met 152 Resynchronization 154 Resynchronization 156 Resynchronization 158 Work cycle search successful 160 Work cycle search failed 162

[0032] Note that other implementations are possible to perform the described synchronization algorithm.

[0033] In addition to a single-cylinder system, the method can be used to detect the engine position in the following systems: Case 1

[0034] In the case of an asymmetrically mounted two-cylinder system with crankshaft sensor: Such a pattern is recorded twice during the engine cycle. Because the top dead centers are asymmetrically distributed, the position of the pattern differs from the gap in the crankshaft sensor signal. This allows the software to easily synchronize with the mechanical engine position using the gap information from the crankshaft sensor and the pattern in the generated signal.

[0035] A crankshaft signal 200 of an engine with an asymmetrically mounted two-cylinder system with crankshaft sensor is in Figure 5The diagram also shows TDC 1 202 and TDC 204. A first arrow 206 indicates the distance between the speed signal gap and a first TDC, and a second arrow 208 indicates the distance between the speed signal gap and a second TDC. The different lengths of the arrows illustrate the asymmetric positioning of the cylinders relative to the crankshaft and the associated speed signal. Case 2

[0036] In the case of a symmetrically mounted two-cylinder system with crankshaft sensor: Such a pattern is recorded twice during the combustion cycle. Since the top dead centers are symmetrically distributed, another signal must be evaluated to distinguish between the two gaps. One possibility is to initially perform an injection into both cylinders, but only an ignition in one of them. Once the combustion cylinder is detected, synchronization is complete.

[0037] A crankshaft signal 250 of an engine with a symmetrically mounted two-cylinder system with crankshaft sensor is in Figure 6 The diagram also shows TDC 1 252 and TDC 204. A first arrow 206 indicates the distance between the speed signal gap and a first TDC, and a second arrow 208 indicates the distance between the speed signal gap and a second TDC. The equal length of the arrows illustrates the symmetrical distance between the cylinders relative to the crankshaft and the associated speed signal. Case 3

[0038] In the case of an asymmetrically mounted two-cylinder system without crankshaft sensor: No gapped crankshaft sensor signal is available. However, engine speed signal information is available via the generator signal. The signal is generated using the engine speed signal, i.e., the generator signal. A pattern is captured twice per cycle in the generated signal. Since the top dead centers are asymmetrically distributed, the spacing between patterns is different. This spacing information can be used to detect the mechanical engine position.

[0039] A crankshaft signal 300 of an engine with an asymmetrically mounted two-cylinder system without a crankshaft sensor is in Figure 7 The illustration also shows OT1 302 and OT2 304. Case 4

[0040] In the case of a symmetrically mounted two-cylinder system without crankshaft sensor: No gapped crankshaft sensor signal is available. However, engine speed signal information is available via the generator signal. The signal is generated using the engine speed signal, i.e., the generator signal. A pattern is detected in the generated signal twice during the combustion cycle. Since the top dead centers are symmetrically distributed, another signal must be evaluated to distinguish between the two top dead centers. One possibility is to initially inject into the assumed cylinder, but with dual ignition. Once the combustion cylinder is detected, synchronization is complete.

[0041] A crankshaft signal 350 of an engine with a symmetrically mounted two-cylinder system without a crankshaft sensor is in Figure 8 The illustration also shows OT1 352 and OT2 354. Case 5

[0042] In the case of a three-cylinder system with crankshaft sensor: Such a pattern is recorded three times per engine cycle. Taking into account the gap in the crankshaft signal, the top dead center position can exhibit a unique pattern. Two top dead centers can be observed in one crankshaft revolution, and only one top dead center can be observed in another crankshaft revolution. Since the pattern in the generated signals in the top dead center region is monitored, it is easy to determine the mechanical engine position in combination with the gap information in the crankshaft signal.

[0043] A crankshaft signal 400 of an engine with a three-cylinder system with crankshaft sensor is in Figure 9 The illustration also shows OT1 402, OT2 404, and OT3 406. Case 6

[0044] In the case of a three-cylinder system without a crankshaft sensor: No crankshaft signal with a gap is available. However, the engine speed signal is available via the generator signal; such a pattern is recorded three times during the combustion cycle. Since the top dead centers are symmetrically distributed, another signal must be evaluated to differentiate between the three top dead centers of the respective cylinder high-pressure phase. One possibility is to initially inject into a cylinder and then, in the following two revolutions of the crankshaft, to carry out ignition at the corresponding position, relative to the gap in the speed signal. Since successful combustion can only take place for one of the two ignitions, the associated significant speed increase can be detected, thus distinguishing between the two revolutions of the combustion cycle. As soon as the speed increase resulting from combustion in this cylinder is recorded, synchronization is complete.

[0045] A crankshaft signal 450 of an engine with three-cylinder system with crankshaft sensor is in Figure 10 The illustration also shows OT1 452, OT2 454, and OT3 456. Case 7

[0046] It should be noted that during a kickstart it is also possible to observe the unique pattern in the generated signal that was generated based on the engine speed signal.

[0047] Figure 11 shows the behavior of the engine speed signal 500 during a kickstart for a single-cylinder engine. The crankshaft angle [°CA] is plotted on the abscissa 502, and the engine speed [rpm] is plotted on the ordinate 504.

[0048] A unique pattern can also be generated around the compression at top dead center during kickstart in a single-cylinder engine. This signal pattern can be used to detect engine position during kickstart. However, additional intelligence is required to detect the pattern in the generated signal. This is because engine speeds increase significantly during kickstart. This impacts the quality of the generated signal. However, once engine speeds begin to decrease after reaching a maximum value, it must be possible to easily detect the pattern in the generated signal.

[0049] There is therefore a need to differentiate between a kickstart and a starter-driven start. This can also be achieved, for example, based on the battery voltage curve during the start. The electric starter requires a significant amount of energy from the battery. This leads to a measurable drop in battery voltage. In comparison, the kickstart requires no electrical energy.

[0050] The procedures presented for synchronizing systems with one or more cylinders can also be used for kickstarter starting.

[0051] The more cylinders the engine has, the smaller the differences between the speed during the compression phase and the speed during the decompression phase. Therefore, the presented method can be used with any number of cylinders, as long as the speed difference is sufficiently significant. For more than three cylinders, the methods presented for fewer cylinders can be adapted to meet the needs of the number of cylinders.

Claims

1. Method for determining a position of an internal combustion engine comprising at least one cylinder, wherein a response of a speed signal (50) that represents a speed of the internal combustion engine is detected, wherein the speed signal is an engine speed signal (50) and the engine speed drops during the compression cycle and increases greatly during the decompression phase, and the response of the engine speed signal (50) is taken as a basis for generating a generated signal (100) by performing at least one summation, characterized in that a signal pattern (108) in the response of the generated signal (100) is recognized that is taken as a basis for determining the position, and wherein the generated signal (100) is generated from the speed signal (50) by way of ∑ i = a b t i / ∑ j = c d t j , where t[i], t[j] represent individual time intervals between signal edges from the speed signal (50), and wherein at least one time interval or multiple time intervals are summed for each of the sums, the sums being able to comprise different amounts of time intervals from one another.

2. Method according to Claim 1, wherein a signal of an electrical machine coupled to the crankshaft is used as the speed signal (50) that is detected.

3. Method according to Claim 1, wherein the speed signal (50) that is detected represents a rotational speed of the crankshaft.

4. Method according to one of Claims 1 to 3, wherein, after the crankshaft position has been determined, this determined crankshaft position is taken into account for performing a synchronization of the internal combustion engine with a control software.

5. Method according to one of Claims 1 to 4, wherein the response of the generated signal (100) is compared with a response of a reference signal in order to recognize the signal pattern (108).

6. Method according to one of Claims 1 to 5, wherein the amplitude of the signal pattern (108) is tested against a calibratable threshold value (106).

7. Method according to Claim 6, wherein the threshold value (106) is adapted according to different environmental conditions.

8. Method according to one of Claims 1 to 7, wherein the signal pattern (108) appears once around a compression in the upper dead centre of the highpressure phase.

9. Method according to one of Claims 1 to 8, which is used for the start type E-start, kickstart or push.

10. Arrangement for determining a position of an internal combustion engine, which comprises a computing unit and is configured to carry out a method according to one of Claims 1 to 9.

11. Computer program comprising program code means, which is configured to carry out a method according to one of Claims 1 to 9 when the computer program is executed on a computing unit in an arrangement according to Claim 10.

12. Machine-readable storage medium with a computer program according to Claim 11 stored thereon.