FR3036737A1 - METHOD FOR DISENGAGING CYLINDERS FROM A COMBUSTION ENGINE - Google Patents

Abstract

The invention relates to a method for controlling the combustion of a combustion engine comprising a plurality of combustion cylinders, the method comprising the step of reducing the number of active cylinders (3,6) in the event of a reduction in torque. reference (1), characterized in that it comprises a covering test step (2.5) in which it is evaluated on the one hand whether operation with a less active cylinder has a maximum achievable torque greater than the minimum achievable torque with the current number of active cylinders and it is furthermore evaluated whether the setpoint torque is less than the maximum torque attainable with a less active cylinder, and if this recovery step is successful, reducing the number of active cylinders (3, 6).

Description

The invention relates to motor vehicle combustion engines when such engines are equipped with a combustion cylinder (s) deactivation system.

The invention lies in the technical field of the combustion control system of an engine including spark ignition, and more specifically the strategy to build the selective injection cut cylinder. In particular life situations such as an automatic transmission shift, an anti-slip request or an approval request, for example, the torque setpoint received by the engine can become so low that the engine can no longer respect it. To "follow" this instruction, the motor control uses different levers. On the advance branch, the degradation of the ignition advance decreases the efficiency of the engine and therefore the torque produced. This lever is used for bright transient phases because it has a fast dynamic. On the air branch, the solution is to minimize the engine air supply by closing the butterfly for example. This lever has a rather slow dynamic due to the control of the actuators, the throttle body in this case and because of the dynamics of the air. But these actions, which can be combined, are not always sufficient to monitor the torque setpoint sent to the engine. In other words, to follow a low torque setpoint with a high dynamic range, as for example in the case of a gearshift on automatic gearbox, the lever on the air branch alone can not be used because its potential for degradation of the torque is high but its dynamics is weak. This has the impact of having a poor follow-up of the couple and a quality of change of report degraded, even a bad feeling for the customer. On the other hand, the degradation of ignition advances offers a rather low potential on the torque, but a very high dynamic and here too, torque tracking is not always ensured, with the impacts seen above. The other disadvantage of this lever is that it greatly degrades the efficiency of the engine which generates high thermal stress with an increase in exhaust temperature with risk of breakage. Selective cylinder injection cutoff therefore provides additional leverage in a very dynamic torque reduction application. However, at present, the anti-pollution standards and the wish to limit as much as possible the consumption of the engines lead the car manufacturers to appeal to the "downsizing", English expression 3036737 2 American for "diminution of size" in French, c that is, the production of low-cylinder heat engines with a decreasing number of cylinders. Also, in order to maintain a level of performance equivalent to that of a higher displacement engine, the engine is then very heavily loaded, which creates "dead zones" of torque in the engine field, between operation with all the cylinders. injecting and with a cylinder cut for example. The object of the present invention is to set up a strategy to request the injection cut-off of one or more cylinders with the advantage of improving the torque tracking by a better achievable torque potential and a dynamic equivalent to that of the branch advances. A goal is also to reduce the gas flow output of the engine and thus better contain the exhaust temperature. To achieve this objective, a combustion control method of a combustion engine comprising a plurality of combustion cylinders is provided according to the invention, the method comprising the step of reducing the number of active cylinders in the event of setpoint torque reduction, characterized in that it comprises an overlap test step in which it is evaluated on the one hand whether operation with a less active cylinder has a maximum achievable torque greater than the minimum torque attainable with the number current cylinders active and it is further evaluated if the setpoint torque is less than the maximum torque achievable with a cylinder active less and in the affirmative of this recovery step reduce the number of active cylinders.

The technical effect is to request the cylinder cutoff as soon as the engine can operate with one less cylinder when the engine torque setpoint is in a so-called covering torque zone. In the case of a spark ignition engine this method avoids too much degradation of the ignition advance and therefore the combustion efficiency.

Various additional features may be provided, alone or in combination: the method comprises, in the negative of the overlap test step, an additional step of evaluating whether the setpoint torque is less than a threshold of deactivation threshold included between the minimum achievable torque with the current number of active cylinders and the maximum achievable torque with one less active cylinder and reduce the number of active cylinders in the affirmative of these evaluations. the deactivation threshold torque is half between the minimum attainable torque with the current active number of cylinders and the maximum achievable torque with one less active cylinder. the method comprises another recovery step in which it is evaluated on the one hand whether operation with a further active cylinder has a minimum attainable torque that is lower than the maximum torque achievable with the current number of cylinders and, on the other hand, to be evaluated if the setpoint torque is greater than the maximum achievable torque with the current number of active cylinders and if this other recovery step is successful, increase the number of active cylinders. The method comprises, in the negative of the other recovery step, an additional step in which it is evaluated whether the target torque is greater than an activation threshold torque between the maximum attainable torque with the current active number of cylinders. and the minimum achievable torque with an active cylinder in addition and increase the number of active cylinders in the affirmative of these evaluations. - The activation threshold torque is half between the maximum torque achievable with the current number of active cylinders and the minimum torque achievable with an additional active cylinder.

The invention also relates to an electronic control module characterized in that it comprises the acquisition means, processing by software instructions stored in a memory and the control means required to implement a method according to the invention. any of the previously described variants.

The invention also relates to a combustion engine comprising a plurality of combustion cylinders, characterized in that it is equipped with such an electronic control module for the implementation of a method according to any one of the variants. previously described.

In a variant, the combustion engine is a spark ignition engine.

The invention also relates to a motor vehicle, characterized in that it comprises a combustion engine of the invention.

Other features and advantages will appear on reading the following description of a particular embodiment, not limiting of the invention, with reference to the figures in which: FIG. 1 represents a strategy of selective disconnection in the case of a four-cylinder engine with motor torque recovery monitoring. - Figure 2 is a schematic representation of a strategy of selective shutdown without recovery of the engine torque.

The control of a spark-ignition combustion engine will now be described with reference to the diagram of FIG. 1. When the torque setpoint becomes too low, it may become impossible for the engine to follow it because of the limitation by the engine. minimum advance. It is then necessary to resort to selective injection cutting of cylinder (s). Selective shutdown involves cutting the injection on a number of cylinders to reduce the optimum torque. The target efficiency is then automatically increased in the same proportion: rIcons -Cons Copti When the torque on n cylinders, n being the number of cylinders injecting at the given moment, covers that on n-1 cylinder in the case of a cut or respectively n + 1 cylinders in the case of an injection reactivation, it is called "covering area". In this case, the torque set point exceeds the maximum torque achievable with n-1 cylinders, then the strategy immediately requires the injection cut of a cylinder.

If thereafter the torque setpoint still decreases, another cylinder can be cut until the cylinder limit is reached which is allowed to be cut off. Conversely, when the torque increases sufficiently to exceed the maximum attainable torque with n + 1 cylinders, where n is the number of cylinders injecting at the given instant, the strategy requires the injection of a new injection. cylinder.

Conversely, when the torque on n cylinders does not cover that on n-1 cylinders in the case of a cut, respectively n + 1 cylinders in the case of an injection reactivation, it is called " non-covering area "or dead zone. In this case, when the torque setpoint becomes lower than the maximum achievable torque with a cylinder of 5 less, then the strategy requires the injection cut of a cylinder. If thereafter the torque setpoint still decreases, another cylinder can be cut, until reaching the limit of cylinders allowed to be cut. On the other hand, when the torque setpoint becomes greater than the minimum achievable torque with one more cylinder, then the strategy requires the injection reset of a cylinder. In a first step, the system requests the selective injection cut on one or more cylinders when the torque setpoint requested from the motor on the advance branch can no longer be followed.

Thus, in step 1, the motor control provides a torque setpoint Ccons. In step 2, the motor control performs a test to examine whether the minimum achievable torque with four cylinders is less than the maximum achievable torque with three cylinders, to determine if there is a "blanket area", and whether the Torque setpoint, Ccons, is lower than the maximum torque achievable with three cylinders. If these two conditions are met, then in step 3 the motor control module controls the breaking of a cylinder. The cut cylinder may be a fixed cylinder or the cutoff may be a rotary cut, i.e. the cut cylinder may be different at each combustion cycle of the engine. On the contrary, in the case where one of the two conditions tested is not achieved, it means that it is in the case of a "non-covering area", then the motor control 30 performs, in step 4 , a test consisting in examining whether the setpoint torque is less than a threshold torque Cswitching threshold, which is calibrated, between the minimum torque attainable with the four active cylinders and the maximum torque achievable with three cylinders. If this is the case, then step 3 consists in reducing the number of active cylinders.

FIG. 2 illustrates more precisely this case and shows the evolution of a set torque 20. An area 21 represents a zone of torque values that can be reached with a number of four cylinders, this zone 21 having a low limit 22. corresponding to the minimum torque value accessible with four active cylinders. Area 23 represents the accessible torque zone with three active cylinders 5, zone 23 having a constant upper limit 24 in the maximum value achievable with three active cylinders. The horizontal band 25 located between the zones 21 and 23 consists of a band of torque values that are not accessible with four cylinders, or with three cylinders, this band consisting of a dead zone as defined above.

Thus, with reference to FIG. 2, the injection cut-off is requested when the motor torque setpoint 20 reaches the threshold torque C.sub.out threshold, comprised between the minimum attainable torque 22 with the four active cylinders and the maximum attainable torque 24. with three cylinders. In this situation, after the effective torque has followed the minimum torque value according to the arrow 26, when the target torque reaches the threshold torque Cseuil during its progression, then a cylinder is deactivated according to the arrow 27 and then the Effective torque follows according to the arrow 28, the maximum torque value 24 with three cylinders until reaching the value of the set torque 20 when it reaches the zone 23. In this case the torque setpoint is followed optimally. The calibrated torque threshold from which deactivation is requested is a percentage of the dead zone. The best compromise is obtained for a percentage around 50%, to a few percent, in other words when the threshold torque, Cseuil, is half between the minimum achievable torque with the number of active cylinders present and the maximum torque achievable with a cylinder active less.

The tests consisting in examining, respectively, whether the setpoint torque Ccons is lower than the maximum torque on two rolls and examining whether the setpoint torque is greater than the maximum torque attainable with three rolls, are then performed in parallel and in a repetitive manner.

If the setpoint torque still decreases, in step 5, it is examined whether the setpoint torque, Ccons, is less than the maximum torque achievable with two rolls and that the minimum torque achievable with three rolls is less than the maximum torque achievable with two cylinders, to determine if there is a "blanket area", then in step 6 a cylinder is disabled. If one of the two conditions tested is not realized, it means that it is in the case of a "non-covering area", then the motor control carries out, in step 7, a test consisting in examining if the setpoint torque is less than a deactivation threshold, which is calibrated, between the minimum achievable torque with the three active cylinders and the maximum torque achievable with two cylinders. If this is the case, then step 6 consists in reducing the number of active cylinders.

If, on the other hand, the setpoint torque rises, in step 8, it is examined whether the setpoint torque, Ccons, is greater than the maximum torque attainable with three cylinders and whether the minimum torque attainable with four cylinders is less than the maximum attainable torque. with three cylinders, to determine if there is a "blanket area".

If both of these conditions are met, then in step 9 an additional roll is made active. If one of the conditions is not satisfied, it means that it is in the case of a "non-covering area", then the motor control carries out, in step 10, a test consisting of examining whether the setpoint torque is greater than an activation threshold torque, which is calibrated, between the maximum torque achievable with the three active cylinders and the minimum torque achievable with four cylinders. If this is the case, then step 9 consisting of making an additional cylinder active is performed.

In this situation, where the reactivation of a cylinder is required, after the actual torque has followed the maximum torque value with the three active cylinders, when the target torque reaches, during its upward progression, the threshold torque d activation, then a cylinder is activated and then the actual torque follows the minimum torque value with four cylinders until it reaches the value of the target torque when it reaches the accessible torque zone with four active cylinders. In this case the torque setpoint is followed optimally. The calibrated torque threshold at which activation is requested is a percentage of the dead zone. In this case again, the best compromise is obtained for a percentage around 50%, to a few percent, in other words when the activation threshold torque is halfway between the maximum achievable torque with the current number of active cylinders and the minimal torque achievable with an active cylinder in addition. In the case of operation with two cylinders, if the torque setpoint still decreases, the above tests are carried out in the same manner and referenced overall A 35 of examining whether it is expedient to switch to single cylinder mode. active. If the torque setpoint rises, the above tests and referenced globally B in FIG. 1 are carried out in the same way, consisting of examining whether it is advisable to go back to three active cylinders. This method is suitable for controlling a combustion engine comprising a plurality of combustion cylinders, in particular a motor equipping a motor vehicle. The engine can be a spark ignition engine. An electronic control module comprising the acquisition means, processing by software instructions stored in a memory as well as the control means required to implement the method of the invention described is also provided for controlling the combustion engine. The proposed strategy makes it possible to improve the real-time monitoring of the torque by the engine during very dynamic life situations that may be critical for the engine itself and the consumer systems such as the gearbox or the actuators. anti-skating with the impact of a bad feeling by the customer, or even a risk to his safety. Thus, this strategy provides a gain in torque tracking by allowing high dynamics combined with high torque reduction potential. It also brings a gain in terms of protection of the engine because the degradation of advance ignition is less and as the injection is cut on one or more cylinders, the exhaust gas flow is lower, which decreases the temperature of the exhaust gases. On a spark ignition engine equipped with a particulate filter, this strategy improves its regeneration by an oxygen supply to the exhaust. These gains are obtained without requiring additional cost, because this strategy can be implemented by the motor control alone, without the need for a sensor and / or additional actuator.

Claims (10)

REVENDICATIONS1. A method of controlling the combustion of a combustion engine comprising a plurality of combustion cylinders, the method comprising the step of reducing the number of active cylinders (3,6) in the event of a decrease in the target torque (1), characterized in that it comprises an overlapping test step (2.5) in which it is evaluated on the one hand whether an operation with a less active cylinder has a maximum achievable torque greater than the minimum attainable torque with the number of cylinders current assets and it is further evaluated if the setpoint torque is less than the maximum torque achievable with a cylinder active less and if so this recovery step reduce the number of active cylinders (3,6). 2. Method according to claim 1, characterized in that it comprises in the negative of the recovery test step, an additional step of evaluating whether the target torque is less than a threshold torque (Cseuil) of deactivation included between the minimum achievable torque with the actual number of active cylinders and the maximum achievable torque with one less active cylinder (4.7) and reduce the number of active cylinders in the affirmative of these evaluations. 3. Method according to claim 2, characterized in that the threshold torque (Cseuil) deactivation is half between the minimum torque achievable with the current number of active cylinders and the maximum torque achievable with a cylinder active less. 4. Method according to any one of claims 1 to 3, characterized in that it comprises another recovery step (8) in which it is evaluated on the one hand whether an operation with an active cylinder in addition has a minimum torque achievable less than the maximum torque achievable with the current number of cylinders and secondly to evaluate whether the target torque is greater than the maximum torque achievable with the current number of active cylinders and in the affirmative of this other recovery step increase the number of active cylinders (9). 5. Method according to the preceding claim, characterized in that it comprises in the negative of the other step of recovery (8), an additional step in which it is evaluated whether the target torque is greater than a torque threshold activation between the maximum torque achievable with the number of active cylinders current and the minimum torque achievable with an active cylinder in addition (10) and increase the number of active cylinders in the affirmative of these assessments. 3036737 10 6. Method according to the preceding claim, characterized in that the activation threshold torque is half between the maximum torque achievable with the current number of active cylinders and the minimum torque achievable with an additional active cylinder. 7. Electronic control module characterized in that it comprises the means 5 acquisition, processing by software instructions stored in a memory and the control means required to implement a method according to any one of the Claims 1 to 6. 8. Combustion engine comprising a plurality of combustion cylinders, characterized in that it is equipped with an electronic control module according to claim 7 for the implementation of a method according to any one of claims 1 to 6. 9. Combustion engine according to claim 8, characterized in that it is a spark ignition engine. 10. Motor vehicle, characterized in that it comprises a combustion engine 15 according to claim 8 or claim 9.