METHOD AND CONTROL DEVICE FOR DETECTING A COMBUSTION PROCESS OF AN INTERNAL COMBUSTION ENGINE OF A HYBRID VEHICLE

Abstract

A method for detecting a combustion process of an internal combustion engine of a hybrid vehicle includes the steps of acquiring a rotational speed signal representing a rotational speed of the crankshaft, acquiring a crankshaft angle signal representing a crankshaft angle of the crankshaft, and determining, based on the rotational speed signal and the crankshaft angle signal, whether a combustion occurs in the internal combustion engine. A control device for detecting a combustion process of an internal combustion engine of a hybrid vehicle is also provided.

Claims

1. A method for detecting a combustion process of an internal combustion engine of a hybrid vehicle wherein the internal combustion engine includes a crankshaft, the method comprising: acquiring a rotational speed signal representing a rotational speed of the crankshaft; acquiring a crankshaft angle signal representing a crankshaft angle of the crankshaft; and determining, based on the rotational speed signal and the crankshaft angle signal, whether a combustion occurs in the internal combustion engine, wherein the step of determining includes detecting a rotational speed curve shape based on the rotational speed signal, wherein the rotational speed curve shape includes a dead center rotational speed and a rotational speed maximum, wherein the dead center rotational speed is reached when a cylinder piston of the internal combustion engine is at a top dead center in a power stroke, and wherein the step of determining further includes ascertaining a maximum increase of the rotational speed, starting from the dead center rotational speed up to the rotational speed maximum, wherein the step of determining further includes ascertaining a reference rotational speed, at which a given percentage of the maximum increase is reached, and ascertaining a reference crankshaft angle associated with the reference rotational speed, wherein the step of determining whether a combustion occurs is based on a threshold angle and includes comparing the reference crankshaft angle to the threshold angle and detecting that a combustion occurs when the reference crankshaft angle exceeds the threshold angle.

2. The method according to claim 1, wherein the step of determining includes ascertaining one of a rotational speed and a rotational speed range and ascertaining one of a crankshaft angle and a crankshaft angle range based on one of the rotational speed and the rotational speed range.

3. The method according to claim 1, wherein the step of determining includes ascertaining one of a crankshaft angle and a crankshaft angle range and ascertaining one of a rotational speed and a rotational speed range based on one of the crankshaft angle and the crankshaft angle range.

4. The method according to claim 1, wherein the step of determining includes detecting, based on the rotational speed signal, at least one rotational speed characteristic selected from the group consisting of a rotational speed minimum, a rotational speed maximum, a rotational speed inflection point and a rotational speed value range.

5. The method according to claim 1, which comprises detecting that no combustion occurs when the reference crankshaft angle is smaller than the threshold angle.

6. The method according to claim 5, which comprises notifying a driver of the hybrid vehicle.

7. The method according to claim 5, which comprises uncoupling the internal combustion engine.

8. The method according to claim 5, which comprises continue moving the hybrid vehicle with an additional drive device as an independent drive.

9. The method according to claim 1, wherein the given percentage is any percentage between 20% and 40% of the maximum increase.

10. A data memory containing a computer program with instructions for executing a method of: acquiring a rotational speed signal representing a rotational speed of a crankshaft of an internal combustion engine of a hybrid vehicle; acquiring a crankshaft angle signal representing a crankshaft angle of the crankshaft; and determining, based on the rotational speed signal and the crankshaft angle signal, whether a combustion occurs in the internal combustion engine, wherein the step of determining includes detecting a rotational speed curve shape based on the rotational speed signal, wherein the rotational speed curve shape includes a dead center rotational speed and a rotational speed maximum, wherein the dead center rotational speed is reached when a cylinder piston of the internal combustion engine is at a top dead center in a power stroke, and wherein the step of determining further includes ascertaining a maximum increase of the rotational speed, starting from the dead center rotational speed up to the rotational speed maximum, wherein the step of determining further includes ascertaining a reference rotational speed, at which a given percentage of the maximum increase is reached, and ascertaining a reference crankshaft angle associated with the reference rotational speed, wherein the step of determining whether a combustion occurs is based on a threshold angle and includes comparing the reference crankshaft angle to the threshold angle and detecting that a combustion occurs when the reference crankshaft angle exceeds the threshold angle.

11. A control device for detecting a combustion process of an internal combustion engine of a hybrid vehicle, the internal combustion engine having a crankshaft and a cylinder piston, the control device comprising: a signal input configured to acquire a rotational speed signal representing a rotational speed of the crankshaft and a crankshaft angle signal representing a crankshaft angle of the crankshaft; and a processor configured to determine, based on the rotational speed signal and the crankshaft angle signal, whether a combustion occurs in the internal combustion engine, wherein said processor detects a rotational speed curve shape based on the rotational speed signal, wherein the rotational speed curve shape includes a dead center rotational speed and a rotational speed maximum, wherein the dead center rotational speed is reached when the cylinder piston of the internal combustion engine is at a top dead center in a power stroke, and said processor ascertains a maximum increase of the rotational speed, starting from the dead center rotational speed up to the rotational speed maximum, said processor ascertains a reference rotational speed at which a given percentage of the maximum increase is reached, said processor ascertains a reference crankshaft angle associated with the reference rotational speed, and said processor determines whether a combustion occurs based on a threshold angle and compares the reference crankshaft angle to the threshold angle and detects that a combustion occurs when the reference crankshaft angle exceeds the threshold angle.

12. A hybrid vehicle comprising: a plurality of drive systems, a first one of said drive systems being configured as an internal combustion engine with a crankshaft and a cylinder piston, a second one of said drive systems being configured as an electric drive; a control device for detecting a combustion process of the internal combustion engine, said control device acquiring a rotational speed signal representing a rotational speed of said crankshaft and acquiring a crankshaft angle signal representing a crankshaft angle of said crankshaft; and said control device determining, based on the rotational speed signal and the crankshaft angle signal, whether a combustion occurs in said internal combustion engine, wherein said control device detects a rotational speed curve shape based on the rotational speed signal, wherein the rotational speed curve shape includes a dead center rotational speed and a rotational speed maximum, wherein the dead center rotational speed is reached when said cylinder piston of said internal combustion engine is at a top dead center in a power stroke, and said control device ascertains a maximum increase of the rotational speed, starting from the dead center rotational speed up to the rotational speed maximum, said control device ascertains a reference rotational speed at which a given percentage of the maximum increase is reached, said control device ascertains a reference crankshaft angle associated with the reference rotational speed, and said control device determines whether a combustion occurs based on a threshold angle and compares the reference crankshaft angle to the threshold angle and detects that a combustion occurs when the reference crankshaft angle exceeds the threshold angle.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0083] FIG. 1 is a schematic view of an exemplary embodiment of a drive train of a hybrid vehicle according to the invention;

[0084] FIGS. 2A and 2B are graphs illustrating rotational speed signals of an internal combustion engine of a hybrid vehicle in accordance with the invention;

[0085] FIG. 3 is a flow chart of a method according to the invention for detecting a combustion process in an internal combustion engine;

[0086] FIG. 4 is a schematic view of an exemplary embodiment of a control device for detecting a combustion process in accordance with the invention; and

[0087] FIGS. 5A and 5B are graphs illustrating rotational speed signals and the determination whether a combustion occurs in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0088] Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown an exemplary embodiment of a drive train 1 of a hybrid vehicle. The drive train 1 of the hybrid vehicle contains an internal combustion engine 10 with a crankshaft 11, an electric drive 12 and a decoupling clutch 13 via which the electric drive 12 is coupled to the crankshaft 11 of the internal combustion engine 10.

[0089] The drive train 1 also contains a rotational speed sensor which has an encoder wheel 14 with 58 teeth 140 and a Hall sensor 15. The encoder wheel 14 is attached to the crankshaft 11 between the internal combustion engine 10 and the decoupling clutch 13. The Hall sensor 15 senses the encoder wheel 14 during a rotation of the crankshaft 11 and generates a high-resolution oscillating rotational speed signal 30, 31, as is shown by way of example in FIGS. 2A and 2B. The rotational speed signal 30, 31 of the Hall sensor 15 is fed to a control device 2 via a databus 16.

[0090] FIGS. 2A and 2B each show on the left a diagram 32, 33 in which a rotational speed n of the internal combustion engine 10 is plotted against an index H which depends on the configuration of the encoder wheel 14 of the rotational speed sensor, as the rotational speed signal 30, 31. On the right, FIGS. 2A and 2B each show an enlarged portion 34, 35 of the rotational speed signal 30, 31, in which there are additionally positions of the dead centers 36 at which one of the cylinder pistons of the internal combustion engine is at the top dead center in the power stroke. The rotational speed signal 30 which is shown in FIG. 2A is a typical rotational speed signal of the internal combustion engine 10 while the latter is being entrained by the electric drive 12, which is apparent from the fact that the coordinates of the dead centers 36 are located at the minimum values of the rotational speed signal 30. The rotational speed signal 31 which is shown in FIG. 2B is a typical rotational speed signal of the internal combustion engine 10 while the latter is running independently, which is apparent from the fact that the positions of the dead centers 36 are shifted from the minimum values of the rotational speed signal 31. The rotational speed signals 30, 31 quickly rise strongly after the start at H≈700 for rotational speed signal 30 and at H≈100 for rotational speed 31 and subsequently settle at a requested rotational speed at H≈1400 for rotational speed signal 30 and at H≈700 for rotational speed 31, in FIGS. 2A and 2B an idling rotational speed in the region of 800 rpm.

[0091] The control device 2 is configured to carry out a method 4 for detecting a combustion process in the internal combustion engine 10 as is shown in the flowchart in FIG. 3. A rotational speed signal 30, 31 which represents a rotational speed n of the crankshaft 11 is acquired at 40. A crankshaft angle signal which represents a crankshaft angle φ of the crankshaft 11 is acquired at 41. At 42, it is determined, on the basis of the rotational speed signal 30, 31 and the crankshaft angle signal, whether combustion is taking place in the internal combustion engine 10.

[0092] In order to carry out the method 4 for detecting a combustion process in the internal combustion engine, the control device 2 contains, as is shown in FIG. 4, a signal input 20 which can be connected to the databus 16 and via which the control device 2 receives the rotational speed signal 30, 31. The control device 2 also contains a processor 21 which is connected to the signal input 20, a memory device 22 which is connected to the processor 21, and a signal output 23 which is connected to the processor 21.

[0093] The rotational speed signal 30, 31 is received at the signal input 20 and passed on to the processor 21. In addition, information about the encoder wheel 14 of the rotational speed sensor is received as a crankshaft angle signal at the signal output 20, the information indicating a relation or ratio of the index H to the crankshaft angle. The rotational speed signal 30, 31 and the crankshaft angle signal are fed to the processor 21. The processor 21 converts the rotational speed signal 30, 31 on the basis of the crankshaft angle signal into a rotational speed signal 50, 51 as a function of the crankshaft angle, as shown in FIGS. 5A and 5B, and analyses the signal.

[0094] During the analysis of the rotational speed signal 50, 51, positions 52 of the dead centers are determined by determining a rotational speed n.sub.τ which is associated with a dead center crankshaft angle φτ, wherein the dead center crankshaft angle φτis defined as 0° in the present exemplary embodiment. For the rotational speed signal 50, the rotational speed n.sub.τ50 is approximately 763 rpm, and for the rotational speed signal 51 the rotational speed n.sub.τ51 is approximately 772 rpm. Furthermore, a rotational speed maximum 53, 54 which follow the positions 52 of the dead centers is determined, and the associated rotational speed n.sub.max is determined. For the rotational speed signal 50, the rotational speed n.sub.max50 is approximately 832 rpm, and for the rotational speed signal 51, the rotational speed n.sub.max51 is approximately 825 rpm.

[0095] For the rotational speed signal 50 a maximum increase in rotational speed is determined on the basis of the rotational speed n.sub.τ50 and the rotational speed n.sub.max50 by calculating the difference 55 between the rotational speeds n.sub.max50 and n.sub.τ50 (n.sub.max50−n.sub.τ50). Subsequently, a portion 56 of the difference 55 is calculated which corresponds to 27% of the difference 55, and is added to the rotational speed n.sub.τ50 in order to acquire a reference rotational speed n.sub.B50. An associated reference crankshaft angle φ.sub.B50 is determined for the reference rotational speed n.sub.B50. In order to detect whether combustion is taking place in the internal combustion engine 10, the reference crankshaft angle φ.sub.B50 is compared with a threshold angle φ.sub.S. Since the reference crankshaft angle φ.sub.B50 is smaller than the threshold angle φ.sub.S, it is determined that no combustion is taking place and the internal combustion engine 10 is being entrained by the electric drive 12.

[0096] Correspondingly, for the rotational speed signal 51 a maximum increase in the rotational speed is determined on the basis of the rotational speed n.sub.τ51 and the rotational speed n.sub.max51 by calculating the difference 57 between the rotational speeds n.sub.max51 and n.sub.τ51 (n.sub.max51n.sub.τ51). Subsequently, a portion 58 of the difference 57 is calculated which corresponds to 27% of the difference 57 and is added to the rotational speed n.sub.τ51 in order to acquire a reference rotational speed n.sub.B51. An associated reference crankshaft angle φ.sub.B51 is determined for the reference rotational speed n.sub.B51. This reference crankshaft angle φ.sub.B51 is compared with the threshold angle φ.sub.S. Since the reference crankshaft angle φ.sub.B51 is larger than the threshold angle φ.sub.S it is determined that combustion is taking place and the internal combustion engine 10 is running independently.

[0097] In a further exemplary embodiment of a control device, the control device is embodied similarly to the control device 2 in FIG. 4. In addition, the control device is configured to detect a start of the internal combustion engine 10 and to start the process of determining whether combustion is taking place. After the detection of the start of the internal combustion engine, the control device 2 carries out a quality analysis of the received rotational speed signal 30, 31 and uses the result of the quality analysis as the basis for determining whether combustion is taking place. The control device carries out a diagnosis on the basis of the results of the quality analysis and the determination whether combustion is taking place, and generates a diagnostic signal in order to indicate to the driver that the driver should look for a repair shop if the internal combustion engine has failed, and in order, if appropriate, to prevent restarting of the internal combustion engine.

[0098] By using the method and device in accordance with the invention for detecting a combustion process in an internal combustion engine of a hybrid vehicle it is possible to reliably detect entraining of the internal combustion engine by the electric drive both in the stationary state and during travel. It thereby becomes possible to take precautions to avoid the vehicle becoming immobilized and/or damage to the internal combustion engine. In this context, it is not necessary to install additional hardware but rather it is possible to have recourse to the signal of a rotational speed sensor which is already present.

LIST OF REFERENCE CHARACTERS

[0099] 1 Drive train [0100] 10 Internal combustion engine [0101] 11 Crankshaft [0102] 12 Electric drive [0103] 13 Decoupling clutch [0104] 14 Encoder wheel [0105] 140 Teeth of the encoder wheel [0106] 15 Hall sensor [0107] 16 Databus [0108] 2 Control device [0109] 20 Signal input [0110] 21 Processor [0111] 22 Memory device [0112] 23 Signal output [0113] 30, 31 Rotational speed signal [0114] 32, 33 Diagram [0115] 34, 35 Enlarged portion [0116] 36 Position of the dead centers [0117] 4 Method for detecting a combustion process [0118] 40 Acquiring a rotational speed signal [0119] 41 Acquiring a crankshaft angle signal [0120] 42 Determining whether a combustion occurs [0121] 50, 51 Rotational speed signal [0122] 52 Position of the dead centers [0123] 53, 54 Rotational speed maximum [0124] 5, 57 Difference [0125] 56, 58 Portion of the difference [0126] H Index [0127] n Rotational speed [0128] n.sub.max50, n.sub.max51 Rotational speed at maximum of rotational speed signal 50, 51 [0129] n.sub.B50, n.sub.B51 Reference rotational speed of rotational speed signal 50, 51 [0130] n.sub.τ50, n.sub.τ51 Dead center rotational speed of rotational speed signal 50, 51 [0131] φ Crankshaft angle [0132] φτ Dead center crankshaft angle [0133] φ.sub.B50, φ.sub.B51 Reference point crankshaft angle of rotational speed signal 50, 51 [0134] φ.sub.S Threshold angle