WO2017144789A1

WO2017144789A1 - Method for controlling the combustion of a combustion engine by way of an immediate load reduction method

Info

Publication number: WO2017144789A1
Application number: PCT/FR2017/050157
Authority: WO
Inventors: Philippe Quie; Jean Louis CHARRIER; Jonathan DELMACHE
Original assignee: Psa Automobiles S.A.
Priority date: 2016-02-26
Filing date: 2017-01-25
Publication date: 2017-08-31
Also published as: EP3420213A1; FR3048263B1; CN108699986A; CN108699986B; EP3420213B1; FR3048263A1

Abstract

The invention relates mainly to a method for controlling the combustion of a combustion engine, characterized in that said method comprises: - a step of detecting abnormal combustion generating vibrations in a cylinder, known as "knocking", said vibrations having a frequency of between 600 Hz and 1200 Hz, - a step of calculating a load limitation depending notably, in a speed/load map, on an iso-probability curve (C1) of the occurrence of knocking following said detection, and - a step of applying said load limitation so as to cause said combustion engine to operate in the speed/load map at operating points minimizing the risk of knocking occurring.

Description

METHOD FOR CONTROLLING THE COMBUSTION OF A THERMAL ENGINE BY AN IMMEDIATE LOAD DROP METHOD

The present invention relates to a combustion control method of a heat engine by a method of immediate load drop. The invention finds a particularly advantageous, but not exclusive, application in the field of motor vehicles equipped with a gasoline type heat engine.

The anti-pollution standards and the desire to minimize the consumption of heat engines lead car manufacturers to produce low-capacity engines with a reduced number of cylinders (so-called "downsizing" trend in English). Also, to maintain a level of performance equivalent to that of a larger displacement engine, the engine must operate on operating points with high air filling rate in the cylinders.

This is favorable to the occurrence of abnormal combustion for which the air / fuel mixture ignites at a different location from that initiated by the spark plug controlled. The mixture can ignite before the candle spark (it is called "rumble" in English) or after the candle spark (it is called "rumble" late). In addition, this type of abnormal combustion has the faculty of self-maintenance, that is to say that in case of occurrence of "rumble" on a cylinder during a motor cycle, the following cycle also risk seeing the same phenomenon. The "rumble" generates vibrations called "strokes" of rumble in the following description associated with a thump in the combustion chamber constituting an inconvenience for the driver, with a high risk of engine failure. These vibrations have a frequency between 600 Hz and 1200 Hz. These vibrations are transmitted from the combustion chamber to the rods and the crankshaft (unlike the rattling whose vibration in 5000 Hz and 15000 Hz is felt only in the chamber combustion). The "rumble" is caused by an increase in pressure in the combustion chamber, as well as too early ignition or multiple hot spots in the combustion chamber.

[0005] A curative treatment method exists for the purpose of eliminating the phenomenon of "rumble" when it appears. This method consists in detecting abnormal combustions via an accelerometer placed on the engine block, then cutting the injection on the cylinders concerned to remove the "rumble". In the case where the "rumble" persists, the method applies a load limitation on a driving cycle over the entire engine field. The load limitation on a driving cycle, performed during a series of one or more successive rolls without resetting the engine computer (or "driving-cycle" in English), is a load limitation of which the objective is the disappearance of the phenomenon of "rumble" origin of reversible causes, for example in the case of fouling of the combustion chamber, and / or irreversible, for example during a break engine part. The load limitation is based on a "rumble" shot counter with slow dynamics (several minutes or even several rolls) and this load limit is calculated by a map calibrated according to a number of injection cuts made.

However, the load limitation achieved on a driving cycle has several disadvantages. In particular, its action is not immediate since it is based on a counter of "rumble" shots with slow dynamics. In addition, the level of load limitation is a function of the number of injection cuts, which is not always representative of the number of "rumble" strokes suffered. This level of limitation is therefore not adapted to the just necessary. Moreover, by intervening as a second curative action of "rumble", these load restrictions have a reduced efficiency insofar as the first curative action (the injection cut) is effective to remove the "rumble", although that posing a problem of feeling for the driver (jerks, noise).

The invention aims to effectively overcome these disadvantages by providing a combustion control method of a heat engine, characterized in that the method comprises:

a step of detecting abnormal combustions generating vibrations in a cylinder called "shots", the vibrations having a frequency of between 600 Hz and 1200 Hz,

a step of calculating a load limitation as a function in particular, in a regime / load plane, of an iso-probability curve of occurrence of strokes following the detection, calibrated curve so that the probability of appearance of shots is zero or very close to zero, and a step of applying the load limitation so as to operate the heat engine in the speed / load plane at operating points minimizing the risk of blows appearing.

The invention thus allows a rapid elimination of abnormal combustion in the engine without damaging the driving pleasure, insofar as the invention is implemented from the first shots of "rumble" and applies a level of load limitation corresponding to just necessary to remove the phenomenon of "rumble" without requiring injection cuts. In addition, the invention has the advantage of being inexpensive, since it can be integrated by software development in the engine computer without adding additional component.

[001 1] According to one implementation:

the step of calculating the load limitation is carried out when a first shot appears, and

the step of applying the load limitation is performed after N hits detected as a function of a translation of the iso-probability curve at a point regime / load corresponding to the first detected shot.

According to one implementation, the step of calculating the load limitation comprises:

a step of calculating a base load limitation from an isomorphic curve of appearance of shots translated at a point of regime / load of appearance of the first shot,

a step of calculating a feasible minimum load reduction,

a step of calculating a maximum achievable load reduction,

a step of calculating a minimum permissible load, and

an arbitration step between the minimum permissible load and the minimum and maximum load decreases previously calculated.

According to one embodiment, the step of calculating the achievable minimum load drop requires the load limit to be less than a load made during a request for application of the load limit.

According to one implementation, the step of calculating the maximum achievable reduction in load consists in determining a maximum variation in load drop that can not be exceeded during a request to apply the load limit for reasons for approval. According to one implementation, the step of calculating the minimum allowable load is to introduce a torque threshold below which it is not possible to go down. This is to avoid operating the heat engine in an insufficient load area, for example, to ensure a takeoff of the vehicle. According to one implementation, the arbitration step for determining the load limitation is carried out according to the following formula:

Lim_ChC = MAX (S_min; MIN (Del_max; MAX (Del_min; C2)))

Or:

C2 is the load limitation based on the first shot,

Del_min is the minimum allowable load drop delta,

Del_max is the maximum allowable load drop delta,

S_min is the minimum allowable load threshold.

MIN is the function that selects the minimum of two values,

MAX is the function that selects the maximum from two values. The invention also relates to an engine computer having a memory storing software instructions for the implementation of the combustion control method of a heat engine as previously defined.

The invention also relates to a heat engine comprising such a motor calculator. The invention also relates to a vehicle equipped with such a motor.

The invention will be better understood on reading the description which follows and the examination of the figures that accompany it. These figures are given for illustrative but not limiting of the invention.

FIG. 1 is a functional diagrammatic representation of a system according to the present invention implementing different types of actions to remedy abnormal "rumble" type combustion;

FIG. 2 is a schematic representation of the steps of the control method according to the present invention making it possible to obtain an immediate load drop of the heat engine following the detection of "rumble"shots; Figure 3 is a schematic representation of an improved implementation of the immediate load limiting method of the heat engine according to the present invention;

FIG. 4 represents curves in a speed / load plane illustrating a basic implementation of the immediate load limiting method according to the present invention;

Figures 5 to 8 show curves in a plan / load plan illustrating life situations in which the basic implementation of the immediate load limiting method according to the invention has drawbacks; Figures 9 to 16 show curves in a plan / load plane illustrating life situations in which the improved implementation of the load limiting method according to the present invention overcomes the disadvantages of Figures 5 to 8.

FIG. 1 is a functional illustration of a system 10 implementing a thermal engine combustion control method that can equip a vehicle, this method making it possible to treat a so-called "rumble" phenomenon in which the air / fuel mixture is used. ignites at a different location from that initiated by the spark plug ordered. The mixture may ignite before the spark at the candle or after the candle spark (it is called "rumble" late). The "rumble" generates vibrations, called "rumble" 101 in the following description, associated with a thud in the combustion chamber constituting an inconvenience for the driver, with a high risk of engine failure. These vibrations have a frequency between 600 and 1200 Hz. These vibrations are transmitted from the combustion chamber to the rods and the crankshaft (unlike the rattling whose vibration in 5000Hz and 15000Hz is felt only in the combustion chamber) .

The phenomenon of "rumble" generally appears in a zone of engine speed of between 1000 and 3000 rev / min and with high air filling, for example following the actuation of a turbocharger. The rumble 101 is detected by means of a sensor 100 mounted on the engine block. This sensor 100 is also used to detect engine rattling. Among actions that can be implemented, there is a preventive action 104 consisting of avoiding the appearance of "rumble" and actions 102, 103 of the curative type to treat the "rumble" following his appearance.

The preventive action 104 consists in particular in limiting the load Lim ChE motor according to a level of fouling of the combustion chamber.

Among the actions of curative type 102, 103, there is a set of curative actions 102, so-called immediate, and a set of curative actions 103 performed on a corresponding driving cycle ("driving-cycle" in English). to a series of one or more successive rollings without reinitialization of a motor ECU. For immediate curative actions 102, the time scales, in particular the duration of monitoring before activation of the curative action 102, are very short, of the order of a few Top Dead Center (or TDC) or even a few seconds. For the curative actions 103 carried out on a driving cycle, the time scales, in particular the duration of monitoring before activation of the curative action 103, are longer than for the immediate curative actions 102, of the order of several minutes.

The curative actions 102, 103 may consist of a load limitation to bring the engine back to an operating point unfavorable filling the "rumble" (a few filling points at full atmospheric load). The feeling for the driver varies from a feeling almost zero to a notable loss of performance. In the case of curative actions 103 carried out on a driving cycle, the load limitation Lim ChR is applied temporarily when the causes of the "rumble" are reversible, for example in case of fouling of the combustion chamber, or permanently Lim Chl when the causes of the "rumble" are irreversible, for example when the engine part breaks. In the case of immediate curative actions 102, a Lim ChC current load limitation having a fast effect is set with a limitation level exactly as necessary to eliminate the "rumble". For this purpose, the load drop Lim ChC is determined from the use of iso-probability curve of appearance of the "rumble".

Activating a specific fuel enrichment R_Spe can cool the air / fuel mixture. Indeed, according to a new enrichment instruction, fuel is added to the air / fuel mixture so as to cool the mixture. This has the effect of improving the thermal conditions in the combustion chamber to reduce the risk of occurrence of "rumble". This action R_Spe, quick to implement, has no feeling for the driver, except for a very small increase in fuel consumption.

The modification of injection patterns RJnj associated with specific advance settings allows to inject enough fuel into the cylinder to allow mixing with the air without the risk of causing self-ignition. Thus, a portion of a quantity of fuel to be injected is injected during an engine cycle during an intake phase and the remaining portion of the quantity of fuel during a combustion phase. This RJnj action has no impact for the driver.

Injection cut CJnj can cut the fuel supply inside the combustion chamber of a cylinder in which the "rumble" appears. The combustion is not done anymore and the "rumble" stops. This CJnj action has the effect of causing a sensation of jerk for the driver and is therefore generally used as a last resort.

A method 106 limits the engine load as a function of a maximum ignition advance efficiency or a maximum ignition advance variation, referenced in both cases Lim Low, minimizing the risk of occurrence of rattling and the phenomenon of "rumble" while taking into account an octane fuel. The method 106 also makes it possible to limit cliquetis Lim Cli.

The invention presents a method of immediate current load drop Lim ChC implemented by the system 10 and to protect the engine from the phenomenon of "rumble". The immediate current load drop Lim ChC intervenes among the first curative actions before the CJnj injection cutoff.

This method of immediate current load drop Lim ChC is based on the notion of iso-probability curve C1 of appearance of "rumble" 101 in the plan / load plan (with R for the regime and Ch for charge - see figure 4). By locating a point of regime / load P exploited during a first "rumble" 101, a load limitation consistent with this iso-probability curve C1 of "rumble" is applied. Its action is immediate and the level of load limitation is just necessary to remove the "rumble". Below the C1 curve, the probability of appearance of the "rumble" is zero, or very close to zero (less than 5%). It depends on how to calibrate this curve C1, and therefore the acceptability of seeing "rumble". More precisely, as illustrated in FIG. 2, the probability curve C1 of appearance of the "rumble" is calculated Cal_C1 by a mapping function of the engine speed R. When a first shot of "rumble "101 is counted by the sensor 100, a" rumble "manager, integrated for example in the engine ECU, sends a registration order Enr P of the point regime / load P. The applicable load limit Lim ChC is then calculated via the module Cal_C2 by translation of the probability curve C1 of appearance of the "rumble" at the regimen point / load P recorded. We then obtain a load limitation curve C2 (see Figure 4). A parametric safety margin is applied and the calculation of this margin is achieved by a map based on engine R.

[0042] When N ^th shot "rumble" 101 appears, the manager of "rumble" issues an order of application of the Lim ChCs load limiting. A delay is applicable between the issuing of the order of application and the execution of the action. This timer is configurable, and can be null. When the "rumble" manager issues a load limit cancellation command Lim ChC, the maximum charge level returns to its nominal level in a progressive manner, for example following a linear slope. A delay is applicable between the issue of the cancellation order and the completion of the cancellation, and this parameterizable time delay may be zero.

The control method thus allows a speed of intervention because Lim ChC load limitation occurs from the first shots of "rumble" 101. Its effect is immediate or almost immediate in the case of a short delay. The level of load limitation being based on the first rumble 101 detected, it corresponds to the reality of the engine and is not parameterized in an excessively safe manner.

The mode of implementation of the method according to Figures 2 and 4 works correctly when the "rumble" appears in a situation of average acceleration of the engine. However, in the case of a situation of little or no acceleration, a decreasing load situation during the R climb (for example, descent of the pass), or in the case of a very strong situation. acceleration, the method described above has drawbacks. Thus, when the variation of the load Ch over the range of regime R considered is less than the variation of the iso-probability curve C1 of appearance of the "rumble" over the same range of regime R, the curve C2 limitation of load obtained does not allow to prohibit the driver to return to the area of "rumble" potential. Indeed, as this is shown in Figure 5, the 3 ^rd and 4 ^th shots "rumble", represented by stars, are in an area that the load limit does not prohibit exploitation.

[0046] As shown in FIG 6, when the load Ch decreases during the rise in speed R, N ^th shot "rumble" 101 is located in an area less loaded than ¹ shot representing the basis for calculating Cal_C2 of the load limiting curve C2. Thus, the Lim ChC load limit is systematically above these operating points where the "rumble" has appeared, and does not prohibit the engine from exploiting a potential "rumble" zone.

As is shown in FIG. 7, when the load Ch increases very strongly during the ramp-up R, the N ^th rumble 101 is located in a zone very far from the load-limiting curve C2. . When the Lim ChC load limiting request is issued by the rumble manager, the load drop is too great (felt by the driver).

As shown in FIG. 8, when the load Ch is very low at the time of the load drop request, the N ^th rumble 101 may be in an area very close to the minimum load. eligible. The resulting Lim ChC load limit would bring the load below the minimum allowable level. This minimum load makes it possible for example to ensure the take-off of the vehicle when it is at a standstill. [0049] For this purpose, the calculation of the limit load Lim ChCs is not based only on the point of speed / load P during the ^1st shot "rumble" 101 but is also based on a current point in Lim ChC load reduction application by the rumble manager.

The introduction of new features in the immediate current load drop process Lim ChC allows a consistent calculation of the applicable load limit Lim ChC so as to protect the engine in all phases of life of the engine. For the cases mentioned above, the current Lim ChC current load-lowering method implemented by an improved control method further comprising a series of functionalities whose set ensures the management of load limitations in all phases of life. thermal motor. For this purpose, the determination of the applicable load limit Lim ChC, based on the diagram of Figure 3, comprises: a step of calculating the basic load limit Cal_C2 based on the curve of iso-likelihood curve C1 translated at the point of regime / charge P of appearance of the first shot,

a step of calculating a feasible minimum load drop Cal_min,

a step of calculating a maximum achievable reduction in load Cal_max,

a step of calculating a minimum permissible load Cal_S_min, and

In the case of calculating the minimum achievable load drop Cal_min, a minimum delta load delta Del_min is introduced which the method must perform when the Lim ChC load limiting application is requested by the load handler. "rumble". The presence of this minimum Del_min delta forces the load limit to be lower than that achieved during the application request. This is useful in case of increasing load so low or zero, or decreasing during the rise in speed R. In these cases, as described above, load limiting based on ¹ hit "Rumble" would exceed 101 the load achieved during the application request. The delta of load drop Del_min would then be negative (because in the direction of the rise of load). While taking into account a maximum between the load drop delta Del_Pre towards limiting load C2 based on ¹ hit "rumble" 101 and the delta of minimum load down Del_min, which in this case is the Delta minimum load drop Del_min, as is well represented in FIG. 9.

[0052] In the nominal case of a moderate load growth during the rise in speed R, the maximum load is always the Del_Pre drop delta to C2 load limiting based on ¹ hit "rumble" as illustrated in Figure 10. This part of the process can be inhibited by calibration. The delta minimum delta is calculated by an indexed cartography under engine R mode.

In the case of calculating the maximum achievable reduction in load Cal_max, a maximum delta of achievable load drop Del_max is introduced that can be realized by the process when the request for application of the load limitation Lim ChC by the manager of "rumble". Indeed, for reasons of approval, it is not permissible to lower the load too much. This is useful in the case of a strongly increasing load during engine R rise. A maximum is taken into account between the Del_Pre pressure drop delta towards the C2 load limit. based on the first "rumble" 101 and the delta of maximum load Del_max, which in this case is the delta of maximum load drop Del_max, as is well represented in Figure 1 1.

In the nominal case of a moderate load growth during the ramp-up R, the minimum will always be the Del_Pre load drop delta towards the C2 load limitation based on the first "rumble" stroke, as illustrated in FIG. 12. Moreover, this part of the process can be inhibited by calibration and the maximum delta Del_max is calculated by an indexed cartography under engine R mode.

In the case of calculating the minimum allowable load Cal_S_min, a threshold S_min is introduced below which it is not possible to go down in order to avoid entering a zone of insufficient load (for takeoff for example). ). This threshold S_min is calculated by a map indexed in engine R mode.

The arbitration between the load limit curve C2, the maximum load drop delta Del_max, the minimum load drop delta Del_min, and the minimum allowable load Cal_S_min previously described makes it possible to determine the load limit Lim ChC to apply to the engine. Thus, the determination of the load limit Lim ChC is carried out according to the following formula:

Lim_ChC = MAX (S_min; MIN (Del_max; MAX (Del_min; C2)))

Or:

C2 is the load limit based on the first "rumble" stroke,

Del_min is the minimum allowable load drop delta,

Del_max is the maximum allowable load drop delta,

S_min is the minimum allowable load threshold,

MIN is the function that selects the minimum of two values,

MAX is the function that selects the maximum from two values.

This arbitration ensures the protection of the engine in all phases of life. Thus, in a nominal case, the curve C2 based on ¹ hit "rumble" 101 is applied, as is well shown in Figure 13, and in case of increasing load weakly / zero or decreasing, the curve delta minimum delta is applied, as is clearly visible in Figures 14 and 15. In addition, in the case of a strongly increasing load, the maximum delta curve Del_max is applied, as is clearly visible in Figure 16.

Claims

Claims:

1. A combustion control method of a heat engine, characterized in that said method comprises:

a step of detecting abnormal combustions generating vibrations in a cylinder called "shots" (101), said vibrations having a frequency of between 600 Hz and 1200 Hz,

a step of calculating a load limitation (Lim ChC) as a function in particular, in a speed / load plane, of an iso-probability curve (C1) of appearance of hits following said detection, calibrated curve so that the probability of occurrence of shots is zero or very close to zero, and

- A step of applying said load limitation (Lim ChC) so as to operate said engine in the speed / load plane at operating points minimizing the risk of appearing blows.

2. Method according to claim 1, characterized in that:

the step of calculating the load limitation is carried out when a first shot (101) appears, and

the step of applying said load limitation (Lim ChC) is carried out after N hits detected as a function of a translation of the iso-probability curve (C1) at a point regime / load (P ) corresponding to the first detected shot.

3. Method according to claim 1, characterized in that the step of calculating the load limitation (Lim ChC) comprises:

a step of calculating (Cal_C2) a base load limitation from an iso-probability curve (C1) of occurrence of moves translated at a point regime / load (P) of first appearance,

a calculation step (Cal_min) of a feasible minimum load reduction,

a calculation step (Cal_max) of a maximum achievable load reduction,

a calculation step (Cal_S_min) of a minimum permissible load, and

4. Method according to claim 3, characterized in that the calculation step (Cal_min) of the achievable minimum load drop forces the load limitation (Lim ChC) to to be less than a load performed during a request to apply said load limit (Lim ChC).

5. Method according to claim 3 or 4, characterized in that the calculation step (Cal_max) of the maximum achievable load reduction consists in determining a maximum variation of load drop that can not be exceeded during a request for application of the load limit (Lim ChC) for approval reasons.

6. Method according to any one of claims 3 to 5, characterized in that the calculation step (Cal_S_min) of the minimum allowable load is to introduce a threshold (S_min) of torque below which it is not possible to go down.

7. Method according to any one of claims 3 to 6, characterized in that the arbitration step for determining said load limitation (Lim ChC) is carried out according to the following formula:

Lim_ChC = MAX (S_min; MIN (Del_max; MAX (Del_min; C2))) Where:

C2 is the load limitation based on the first shot,

Del_min is the minimum allowable load drop delta,

Del_max is the maximum allowable load drop delta,

S_min is the minimum allowable load threshold,

MIN is the function that selects the minimum of two values,

MAX is the function that selects the maximum from two values.

8. Engine calculator comprising a memory storing software instructions for the implementation of the combustion control method of a heat engine as defined in any one of claims 1 to 7.

9. A thermal engine comprising an engine computer according to claim 8.

10. Vehicle equipped with a heat engine according to claim 9.