Method for detecting combustion irregularities of an internal combustion engine unit coupled to an electric propulsion unit, of a hybrid motor vehicle

Abstract

A method for detecting combustion irregularities in a combustion engine coupled to an electric engine of a hybrid vehicle having a management unit for determining the respective powers to be supplied by these engines, and for delivering setpoint data dependent on these power distributions, including determining a threshold value corresponding to a percentage of the power supplied by the electric engine, such that values of this percentage less than or equal to the threshold value correspond to operation of the electric engine that is not liable to falsify the results of the combustion irregularity detection diagnostics, and, for the purpose of launching a diagnostic procedure, when the percentage of the power supplied by the electric engine is greater than the threshold value, delivering setpoint data suitable for fixing the value of the power percentage at a setpoint value less than the threshold.

Claims

1. A method for detecting combustion irregularities in an internal combustion engine unit, called a combustion engine, coupled to an electric propulsion unit, called an electric engine, of a hybrid motor vehicle having a management unit designed to determine the respective powers P.sub.Mth and P.sub.Me to be supplied by each of said combustion engine and electric engine, and to deliver to said engines setpoint data dependent on these power distributions, said method comprising: in a preliminary phase, determining using control electronics a threshold value S1 corresponding to a value of the percentage % P.sub.Me=P.sub.Me/(P.sub.Me+P.sub.Mth) of the power supplied by the electric engine, such that values of % PMe less than or equal to S1 correspond to operation of said electric engine that is not liable to falsify the results of the combustion irregularity detection diagnostics, namely leading to a maximum admissible interference, for the purpose of launching, at a time t=T1, a combustion irregularity detection diagnostic procedure, comparing using the control electronics, with the threshold value S1, the value of the percentage % P.sub.Me of the power supplied by the electric engine, determined by the setpoint data, and: when the percentage % P.sub.Me of the power supplied by the electric engine is less than or equal to the threshold value S1: delivering setpoint data suitable for fixing the value of said power percentage at a setpoint value S2, such that 0S2S1+S1, where S1+S1 is the maximum value of the threshold value S1 beyond which the operation of the electric engine falsifies the results of the combustion irregularity detection diagnostics, launching the diagnostic procedure to detect combustion irregularities in the combustion engine, the combustion irregularities including combustion misfires or partial combustions, re-establishing a nominal hybrid operating mode at the end of the diagnostic procedure, when the percentage % P.sub.Me of the power supplied by the electric engine remains greater than the threshold value S1 for a predetermined time interval t=T2T1, where T2>T1, delivering setpoint data suitable for fixing the value of said power percentage at the setpoint value S2, and then launching the diagnostic procedure to detect combustion irregularities in the combustion engine, the combustion irregularities including combustion misfires or partial combustions, and re-establishing the nominal hybrid operating mode at the end of the diagnostic procedure, wherein in each case the re-establishing of the nominal hybrid operating mode at the end the diagnostic procedure comprises, when combustion irregularities are detected, implementation of preventive measures dependent on a nature and severity of said combustion irregularities, including optionally alerting a driver.

2. The detection method as claimed in claim 1, wherein the launches of the irregularity detection diagnostic procedures are commanded periodically with a predetermined period T1.

3. The detection method as claimed in claim 1, wherein a setpoint value S2 is selected so as to be at least substantially equal to the threshold value S1.

4. The detection method as claimed in claim 1, wherein a setpoint value S1 at least substantially equal to 10% is selected.

5. The detection method as claimed in claim 2, wherein a setpoint value S2 is selected so as to be at least substantially equal to the threshold value S1.

6. The detection method as claimed in claim 2, wherein a setpoint value S1 at least substantially equal to 10% is selected.

7. The detection method as claimed in claim 3, wherein a setpoint value S1 at least substantially equal to 10% is selected.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features, aims and advantages of aspects of the invention will emerge from the following detailed description with reference to the appended drawings showing, by way of non-limiting example, one preferred mode of implementation thereof. In these drawings:

(2) FIG. 1 is a schematic plan view of a hybrid vehicle allowing the method according to an aspect of the invention for detecting combustion irregularities in a combustion engine to be implemented,

(3) FIG. 2 shows a flowchart of an example of this detection method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) The method according to an aspect of the invention, the flowchart of which is shown in FIG. 2, is implemented for the purpose of detecting combustion irregularities in a combustion engine Mth mounted in a hybrid vehicle V shown in FIG. 1, comprising an electric engine Me Coupled to said combustion engine by a system Ac for transmitting the engine torque.

(5) This hybrid vehicle V has a first DC voltage source 1 integrated into a primary circuit comprising a DC-to-AC converter 2 for supplying power to the electric engine Me.

(6) This hybrid vehicle V also has a secondary circuit connected to the primary circuit by way of a DC-to-DC voltage converter 4 supplied by a second DC voltage source 3.

(7) As is conventional, the first voltage source 1 consists of a high-voltage battery or group of high-voltage batteries, for example a lithium-ion battery or Ni-MH battery, delivering for example a nominal voltage of 48 volts, and the second voltage source 3 consists of a low-voltage battery, such as for example a lead battery delivering a nominal voltage substantially equal to 12 volts.

(8) This hybrid vehicle V lastly has control electronics or a management unit (not shown) having in particular a supervisor designed in particular to: determine, at all times, the power or the torque to be supplied by the combustion engine Mth and the electric engine Me, and to deliver to said engines setpoint data dependent on these distributions, manage the implementation of the method according to an aspect of the invention for detecting potential combustion irregularities in the combustion engine Mth.

(9) According to the flowchart shown in FIG. 2, the method according to an aspect of the invention starts with a step 11, t=0, of triggering a digital clock that is initiated (step 12) during an operating regime in hybrid mode.

(10) Following this time initialization, after a time interval T1, for example of the order of 15 minutes, has elapsed, materialized by step 13, the following step (step 14) comprises comparing the value of the percentage % P.sub.Me=P.sub.Me/(P.sub.Me+P.sub.Mth) of the power supplied by the electric engine Me, determined by the setpoint values, with a calibrated threshold value S1, for example of the order of 10%; this threshold value S1 corresponding to a value of the percentage % Pme=Pme/(PMe+PMth) of the power supplied by the electric engine Me such that values of % PmeS1 correspond to operation of the electric engine that is not liable to falsify the results of the combustion irregularity detection diagnostics.

(11) When the percentage % P.sub.Me, representative of the power determined by the setpoint data, is less than or equal to the threshold S1, the following step, step 16, comprises assigning the value of a set setpoint value S2 to this percentage % P.sub.Me, and then launching a conventional diagnostic procedure for detecting combustion irregularities in the combustion engine Mth (step 17).

(12) This setpoint value S2, which makes it possible to determine the power effectively supplied by the electric engine Me while the diagnostic procedures are taking place, is selected in a range of values [0S1+S1], S1+S1 consisting of the maximum value of the threshold value S1 beyond which the operation of the electric engine Me falsifies the results of the combustion irregularity detection diagnostics.

(13) In this range of values, the setpoint value S2 may in particular be selected so as to have the value of the threshold S1.

(14) When, in step 14, the percentage % P.sub.Me proves to be greater than the threshold value S1, this step 14 is repeated until a time interval T2, for example equal to 30 minutes, has elapsed (step 15), at the end of which step 16 and step 17 of launching a diagnostic procedure are performed in succession.

(15) The diagnostic procedure initiated after step 16 is conventionally intended to detect combustion irregularities in the combustion engine Mth, in particular combustion misfires or partial combustions, using any known method, and, at the end of this procedure, the analysis of the results performed in step 18 leads: in the presence of anomalies, to the implementation of preventive measures (step 19) dependent on the nature and the severity of said anomalies: storing the anomalies in memory, commanding operation of the combustion engine Mth in downgraded mode, etc., and in all cases, possible triggering of means for alerting the driver, in the absence of an anomaly, simultaneously to the establishment of an operating regime in hybrid mode (step 12) and to the initialization of the triggering of the clock (step 11).

(16) The method according to an aspect of the invention therefore makes it possible to diagnose combustion misfires representative of a malfunction of the combustion engine, which in particular generate pollution, and which are masked when conventional detection strategies are implemented due to the operation of the electric engine.