WO2015136171A1

WO2015136171A1 - Motor vehicle combustion engine with cylinder deactivation

Info

Publication number: WO2015136171A1
Application number: PCT/FR2015/050374
Authority: WO
Inventors: Jean Louis CHARRIER; Romain SOUQUET; Gregory SCHEEN-VASSEUR
Original assignee: Peugeot Citroen Automobiles Sa
Priority date: 2014-03-11
Filing date: 2015-02-16
Publication date: 2015-09-17
Also published as: CN106103949A; FR3018549B1; FR3018549A1; EP3117085A1; CN106103949B

Abstract

The invention relates to a method for controlling combustion in a motor vehicle internal combustion engine, the method comprising an overlap-test step (2, 5), which overlap-test step consists in evaluating, on the one hand, whether operating with one fewer cylinder active offers a maximum attainable torque that is above the minimum torque attainable with the current number of cylinders active and, on the other hand, in evaluating whether the reference torque is lower than the minimum torque attainable with the current number of cylinders.

Description

COMBUSTION ENGINE OF A MOTOR VEHICLE

CYLINDER DEACTIVATION

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 a gearshift on an automatic gearbox, an anti-slip request or a request for approval 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 set point with a strong dynamic, 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.

The cylinder selective injection cutoff therefore provides additional leverage during a very dynamic torque reduction request. However, at the present time, anti-pollution standards and the wish to limit the consumption of engines as far as possible lead car manufacturers to resort to "downsizing", the English expression American for "decrease in size" in French, that is to say, the production of low-capacity engines with a decreasing number of cylinders. In order to maintain a level of performance equivalent to that of a larger displacement engine, the engine is then very 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 of one or more cylinders with the advantage of improving torque monitoring by a better torque potential achievable and dynamic equivalent to that of the advance branch. A goal is also to reduce the gas flow output of the engine and thus better contain the exhaust temperature.

This object is achieved according to the invention by a combustion control method of a motor vehicle combustion engine comprising a plurality of combustion cylinders, the method comprising the step of reducing the number of active cylinders. in the event of a decrease in target torque, characterized in that it comprises a recovery test step which recovery test step consists in evaluating firstly whether an operation with a less active cylinder has a maximum attainable maximum torque. the minimum torque achievable with the current number of active cylinders and secondly to evaluate if the setpoint torque is lower than the minimum torque achievable with the current number of cylinders and if this recovery step reduce the number of cylinders assets.

Advantageously, the method comprises, in the negative of the recovery test step, the additional step of evaluating whether the setpoint torque is less than the maximum torque achievable with a less active cylinder and reducing the number of active cylinders in the affirmative of this assessment.

Advantageously, the method comprises a recovery test step which recovery test step consists in evaluating firstly whether an operation with an active cylinder in addition has a minimum attainable torque lower than the maximum torque achievable with the number of current active cylinders and secondly to evaluate whether the setpoint torque is greater than the maximum torque achievable with the number of active cylinders current and if so this recovery test step increase the number of active cylinders.

Advantageously, the method comprising, in the negative of the recovery test step, the additional step of evaluating whether the target torque is greater than the maximum achievable torque with the current number of cylinders and increase the number of active cylinders in the affirmative of this evaluation.

The invention also relates to a motor vehicle combustion engine comprising a plurality of combustion cylinders and a combustion control module configured to reduce the number of active cylinders in the event of a decrease in target torque, characterized in that the control module is configured to carry out an overlap test, which recovery test consists of evaluating whether operation with a less active cylinder has a maximum achievable torque greater than the minimum achievable torque with the number of active cylinders present and to further evaluate if the setpoint torque is lower than the minimum achievable torque with the current active cylinder number and the module is configured to reduce the number of active cylinders in the affirmative of this recovery test step.

[001 1] Advantageously, the control module is configured such that, in the negative of the recovery test step, the module evaluates whether the setpoint torque is lower than the maximum achievable torque with a less active cylinder and reduces the number of active cylinders in the affirmative of this evaluation.

Advantageously, the module is configured to carry out an overlap test which consists in evaluating firstly whether an operation with an active cylinder in addition has a minimum achievable torque lower than the maximum achievable torque with the number of active cylinders present and to evaluate on the other hand if the target torque is greater than the maximum torque achievable with the current number of active cylinders and the module is configured to increase the number of active cylinders in the affirmative of this recovery test.

Advantageously, the control module is configured such that, in the negative of the recovery test step, it evaluates whether the setpoint torque is greater than the maximum achievable torque with the number of active cylinders present and the module increases the number of active cylinders in the affirmative of this evaluation.

Advantageously, the control module is configured to perform a phase advance change ignition before a reduction or an increase in the number of active cylinders.

[0015] Advantageously, the engine is a spark ignition engine.

Other features, objects and advantages of the invention will appear on reading the detailed description which follows, with reference to the single appended figure, which represents a selective shutdown strategy in the case of a four-cylinder engine with engine torque overlap monitoring.

We will now describe the control of a spark ignition combustion engine with reference to the diagram of the attached figure.

When the torque setpoint becomes too low, it may become impossible for the engine to follow the limitation by the minimum advance. It is then necessary to resort to selective injection cutting 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: Hcons C _C ons / C ₀ pti

When the torque on n rolls covers the one 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 setpoint becomes very low to the point of being less than the minimum torque achievable with four cylinders, so the strategy requires the injection cut of a cylinder. If subsequently, the torque setpoint still decreases, another cylinder can be cut, until reaching the limit of cylinders allowed to be cut.

Conversely, when the torque increases sufficiently to exceed the minimum torque achievable with 1 + n, n being the number of cylinders injecting at the given time, the strategy requires the injection of a 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, we speak of "Non-covering area" or dead zone. In this case, when the torque setpoint becomes lower than the maximum achievable torque with one less cylinder, then the strategy requires the injection cutoff 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.

Conversely, when the torque setpoint becomes greater than the minimum torque achievable with a cylinder more, then the strategy requires the injection 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 cutting instruction Ccons. In step 2, the motor control performs a test to test if the torque setpoint Ccons is less than the minimum torque achievable with four cylinders and to test whether the minimum torque achievable with four cylinders and less than the maximum torque achievable with three cylinders.

If these two conditions are met, then in step 3 the engine control module controls the cutting of a cylinder. The cut cylinder can be a fixed cylinder or the cut can be a rotating cut, that is to say that the cut cylinder can be different at each combustion cycle of the engine. On the other hand, in the case where one of the two conditions tested is not achieved, then the motor control performs, in step 4, a test consisting of examining whether the target torque is less than the maximum torque with three cylinders. If this is the case, then step 3 consisting of reducing the number of active cylinders is carried out.

The tests are then carried out in parallel and in a repetitive manner consisting respectively in examining whether the setpoint torque is greater than the maximum torque with three cylinders and whether, on the contrary, the setpoint torque is lower than the minimum torque on three cylinders.

In step 5, if the setpoint torque Ccons is lower than the minimum torque achievable with three cylinders and the minimum torque achievable with three cylinders is less than the maximum torque achievable with two cylinders, then in step 6 a cylinder is disabled. If one of these two conditions is not fulfilled, then in step 7 the motor control examines whether the setpoint torque is lower than the maximum torque on two cylinders. If this is the case, then the step referenced 6 of cutting a cylinder is carried out.

If it turns out in step 8 that the target torque is greater than the maximum torque achievable with three cylinders and that the maximum torque achievable with three cylinders is greater than the minimum torque achievable with four cylinders, then in step 9 an additional cylinder is made active. If one of these two conditions is not fulfilled, then in step 10 it is examined whether the setpoint torque Ccons is greater than the maximum torque achievable with three cylinders. If this is the case, then step 9 of reactivating a cylinder is performed.

In the case of operation with two cylinders, the tests described above and referenced globally under the references 20 and 30 consisting of examining, respectively, whether it is expedient to switch to a single mode, are carried out in the same way. only cylinder active or to be ironed in active three-cylinder mode.

The present strategy therefore calculates in real time the achievable torque once a cylinder cut or respectively a cylinder more, and prohibits the cut-off instruction, respectively of reactivation of a cylinder, when the engine torque setpoint is in a so-called "dead" engine torque zone. This strategy therefore monitors beforehand the torque achievable by the heat engine and requires the cut-off, or the delivery, of injection of one or more cylinders when the engine is no longer able to follow a torque setpoint that has become too low, respectively too high. in case of delivery of a cylinder. The engine control therefore has a torque monitoring system that can be reached in the event of a cutoff or delivery of the injection. This strategy therefore makes it possible to monitor in real time the achievable torque during a cutoff or selective injection delivery. The monitoring of the achievable torque makes it possible in particular to avoid situations of sloshing of the injection cut-off setpoint because the system is in a dead zone of torque.

The proposed strategy improves the torque monitoring by the engine during life situations with very high dynamics that can be critical for the engine itself and consumer systems such as the gearbox or 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 exhaust gas temperature. These gains are obtained without requiring additional cost, because this strategy can be implemented by the motor control alone, without the need for sensor and / or additional actuator.

Claims

A method for controlling the combustion of a motor vehicle 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 the torque of setpoint (1), characterized in that it comprises a covering test step (2.5) which recovery test step consists of evaluating firstly whether an operation with a less active cylinder has a maximum attainable torque greater than the minimum torque achievable with the number of active cylinders present and secondly to evaluate if the setpoint torque is lower than the minimum achievable torque with the current number of cylinders and if yes to this recovery step reduce the number of active cylinders (3,6).

2. Method according to claim 1, characterized in that the method comprises, in the negative of the recovery test step, the additional step of evaluating whether the target torque is less than the maximum torque achievable with an active cylinder. less (4.7) and reduce the number of active cylinders (3.6) in the affirmative of this assessment.

3. Method according to claim 1 or claim 2, characterized in that it comprises a recovery test step (8) which recovery test step consists of evaluating firstly whether an operation with an active cylinder in addition has a minimum achievable torque lower than the maximum torque achievable with the current number of active cylinders and secondly to evaluate if the setpoint torque is greater than the maximum torque achievable with the current number of active cylinders and if yes this step recovery test increase the number of active cylinders (9).

4. Method according to the preceding claim, the method comprising, in the negative of the recovery test step, the additional step of evaluating whether the target torque is greater than the maximum torque achievable with the current number of cylinders (10). ) and increase the number of active cylinders (9) in the affirmative of this evaluation.

5. Motor vehicle combustion engine comprising a plurality of combustion cylinders and a combustion control module configured to reduce the number of active cylinders (3.6) in the event of a decrease in the target torque (1), characterized in that that the control module is configured to perform a recovery test (2,5) which recovery test consists of evaluating on the one hand whether operation with a less active cylinder has a maximum attainable torque greater than the minimum torque achievable with the current number of active cylinders and evaluate on the other hand if the setpoint torque is lower than the minimum achievable torque with the current number of active cylinders and the module is configured to reduce (3,6) the number of active cylinders in the affirmative of this recovery test step (2,5).

6. Combustion engine according to the preceding claim, characterized in that the control module is configured such that, in the negative of the recovery test step (2.5), the module evaluates whether the set torque is less than the maximum achievable torque with a less active cylinder (4.7) and reduces the number of active cylinders (3.6) in the affirmative of this evaluation.

7. Combustion engine according to claim 5 or claim 6, characterized in that the module is configured to perform a recovery test (8) which consists of evaluating firstly whether an operation with an active cylinder in addition has a minimum achievable torque lower than the maximum torque achievable with the current number of active cylinders and also evaluate whether the target torque is greater than the maximum achievable torque with the current active number of cylinders and the module is configured to increase (9) the number of active cylinders in the affirmative of this recovery test (8).

8. Combustion engine according to the preceding claim, characterized in that the control module is configured such that, in the negative of the recovery test step (8), it evaluates whether the target torque is greater than the maximum torque achievable with the current number of active cylinders (10) and the module increases the number of active cylinders (9) in the affirmative of this evaluation.

9. Combustion engine according to any one of claims 5 to 8, characterized in that the control module is configured to carry out a change of phase advance ignition before a reduction or an increase in the number of cylinders assets.

10. Combustion engine according to any one of claims 5 to 9, characterized in that the engine is a spark ignition engine.