WO2016059312A1

WO2016059312A1 - Internal combustion engine for a motor vehicle provided with cylinder deactivation

Info

Publication number: WO2016059312A1
Application number: PCT/FR2015/052450
Authority: WO
Inventors: Jean Louis CHARRIER; Julien PARODI; Efstratios KRETZAS
Original assignee: Peugeot Citroen Automobiles Sa
Priority date: 2014-10-13
Filing date: 2015-09-14
Publication date: 2016-04-21
Also published as: FR3027063A1; EP3207237A1; CN106795822A; FR3027063B1; CN106795822B

Abstract

The invention relates to a method of controlling a motor vehicle internal combustion engine comprising a step for evaluating whether the torque setting (1) is less than a threshold torque (Ts) different from the minimum torque which can be achieved with the current number of active cylinders (3) and different from the maximum torque which can be reached with one active cylinder (5) less.

Description

INTERNAL COMBUSTION ENGINE OF A MOTOR VEHICLE WITH CYLINDER DEACTIVATION

The invention lies in the technical field of controlling the combustion of a motor vehicle engine, including spark ignition, and more specifically the strategy to build the selective injection cut cylinder. This strategy firstly monitors the torque attainable by the heat engine and requests the cut-off, respectively 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. case of delivery of a cylinder.

In particular life situations such as a shift gearbox automatic transmission, an ESP request (for "Electronic Stability Program" in English or Electro-Stabilizer Scheduled) or a request for approval, for example, the torque setpoint received by the engine can become so low that the engine can no longer meet it. To follow this guideline, 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. Thus, to follow a low torque setpoint with a high dynamic range, the lever on the air branch alone can only be used with difficulty, especially during an action such as a gearshift on automatic gearbox, because its potential to torque degradation is high, but its momentum 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 stresses such as an increase in the temperature at the exhaust, with risk of breakage.

These actions, which can be combined, are not always sufficient to monitor the torque setpoint sent to the engine. Selective cylinder injection cut-off thus provides additional leverage in a request for very dynamic torque reduction. However, at the present time, anti-pollution standards and the wish to limit the consumption of engines as much as possible lead automobile manufacturers to resort to "downsizing" or reduction of dimension in French, that is to say the production of thermal engines with low engine capacity, with a decreasing number of cylinders. 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 injecting cylinders and with a cylinder cut for example. The engine control must therefore have a torque monitoring system that can be reached in the event of a cutoff or delivery of the injection.

[0004] With regard to these levers to ensure torque tracking, the cylinder injection cutoff thus offers a high potential. But before establishing the cylinder injection cutoff or cylinder injection reset setpoint, the engine control must ideally ensure in advance that the torque setpoint requested by the torque structure will be reached by engine. Therefore, the challenge is to put in place a strategy to request the injection cut of one or more cylinders with the advantage of improving the torque tracking by a better torque potential achievable and a dynamic equivalent to that branch advance. Also this strategy has the effect of reducing the gas flow output of the engine and thus to control the temperature at the exhaust.

The object of the present invention is to provide an engine in which the deactivations and reactivations of cylinders are effected effectively on torque reference tracking.

This object is achieved according to the invention by a control method of a motor vehicle combustion engine having a plurality of combustion cylinders, the method comprising the step of reducing the number of active cylinders in case torque setpoint reduction method, comprising a step of evaluating whether the torque setpoint is lower than a threshold torque distinct from the minimum torque attainable with the number of active cylinders present and distinct from the maximum torque achievable with an active cylinder minus , the threshold torque being between these two pairs respectively minimum and maximum and the step of reducing the number of active cylinders in the affirmative of this evaluation.

Which, in the context of the present invention, should be understood as "minimum torque" and "maximum torque": For an operating point iso-flow, that is to say when the air flow at the engine inlet is fixed (steady speed and filling), the ignition advance is a lever allowing to vary the realized torque:

- If the ignition advance is undershoot, that is to say that the advance is applied late, the achieved torque can become so low that the air / fuel mixture does not burn, we speak of minimum advance;

- If the ignition advance is over-set, that is to say that the advance applied is too anticipated, in this case, the thermodynamic conditions (pressure / temperature) are such that there is a risk for the components of the combustion chamber and the exhaust line (premature wear of parts, even breakage), here we speak of maximum advance.

In the invention: - the minimum torque is the torque achieved by the motor with a given air flow, if the minimum advance is applied; - and the maximum torque is the torque achieved by the motor with a given air flow, if the maximum advance is applied.

Advantageously, the maximum achievable torque with a less active cylinder is less than the minimum torque achievable with the current number of active cylinders.

[001 1] The principle of the invention is to request the cylinder cut / reset differently depending on the life situations:

> If there is overlap of the minimum and maximum torque, the strategy requires the cutoff (respectively the reset) when the setpoint torque is lower (respectively greater) than the minimum (respectively maximum) torque.

> If there is no overlap of the minimum and maximum torques, the strategy according to the invention makes it possible to make different types of cutoff / reset: - either cut off as soon as the target torque is lower than the minimum torque, and in this case case achieve a torque lower than the requested torque; - Or cut as soon as the setpoint torque is lower than the maximum torque (that would realize the engine if a cylinder was cut) and in this case, achieve a higher torque, before respecting the target torque; - Or cut as soon as the target torque is less than a "virtual" torque, which is a calibrated intermediate between the minimum torque and the maximum torque with one cylinder less.

Advantageously, the method comprises the step of evaluating whether the torque setpoint is lower than the minimum torque achievable with the current number of active cylinders and performing the step of evaluating whether the torque setpoint is lower than the torque threshold in the case where the torque setpoint is lower than the minimum achievable torque with the current number of active cylinders. Advantageously, the method comprises the step of calculating different torque paths, including a path consisting in deactivating a cylinder when crossing said threshold torque and opting for one of these different paths as a function of a preset parameter of torque tracking.

Advantageously, one of the different calculated paths comprises a section preceding a cylinder deactivation in which section the torque remains greater than the torque setpoint.

Advantageously, one of the different calculated paths is to deactivate a cylinder when the torque setpoint becomes lower than the maximum torque achievable with a cylinder active less.

Advantageously, one of the different calculated paths comprises a section following a cylinder deactivation in which the torque section is less than the torque setpoint.

Advantageously, one of the different paths is to deactivate a cylinder as soon as the torque setpoint becomes lower than the minimum torque achievable with the current number of active cylinders.

The invention also relates to a motor vehicle combustion engine control module comprising a plurality of combustion cylinders, the control module being configured to reduce the number of active cylinders in case of torque setback, characterized in that it is configured to evaluate whether the torque setpoint is lower than a threshold torque that is distinct from the minimum torque attainable with the number of active cylinders present and distinct from the maximum torque attainable with one less active cylinder, the threshold torque being included between these two pairs respectively minimum and maximum and the control module is configured to reduce the number of active cylinders in the affirmative of this evaluation.

The invention also relates to a motor vehicle comprising a combustion engine and such a control module of the combustion 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 is a representative diagram of a cylinder deactivation according to a mode. embodiment of the invention.

An example embodiment of the invention will now be described in which a torque setpoint of the motor becomes too low for the number of active rolls. When the torque setpoint becomes too low, it may become impossible for the motor to follow it because of the limitation by the minimum advance. It is then necessary to use selective injection cutting of one or more cylinders. 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: η _∞η3 = C _con s / C _opt i

One can implement a succession of requests selective injection cutoff, followed by the reactivation of these cylinders, for example on a four-cylinder engine. When the torque on n cylinders overlaps that on n-1 cylinders, in the case of a cut, or n + 1 cylinders in the case of a delivery of injection, we speak of "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. The strategy then requires the injection cut of a cylinder. If thereafter the torque setpoint always decreases, another cylinder can be cut, until reaching the limit of number of cylinders allowed to be cut. Conversely, when the torque increases sufficiently to exceed the minimum torque achievable with 1 + n cylinders, not being the number of cylinders injecting at the instant considered, the strategy requires the surrender injection of a cylinder.

Conversely, when the torque on n cylinders does not cover that on n-1 cylinders in the case of an injection cut, respectively on n + 1 cylinders in the case of a delivery of injection , 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 subsequently, the torque setpoint still decreases, another cylinder can be cut, until reaching the limit of cylinders that is allowed to cut. Conversely, when the torque setpoint becomes greater than the minimum achievable torque with one more cylinder, then the strategy requires the injection refilling of a cylinder.

We will now describe a cylinder deactivation according to one embodiment of the invention in the case of a non-covering area. In the attached figure, there is shown under reference 1 the evolution of a set torque. Zone 2 represents a zone of achievable torque values with a number of four cylinders, this zone 2 having a low limit 3 corresponding to the minimum torque value accessible with four active cylinders.

An area 4 represents the accessible torque zone with three active cylinders, the zone 4 having an upper limit 5 consisting of the maximum torque value achievable with three active cylinders. The horizontal band 6 situated between zones 2 and 4 consists of a band of torque values which are not accessible with four cylinders or with three cylinders, this band consisting of a dead zone as defined above.

In this part of the motor field, in case of too low torque setpoint, the present strategy proposes different paths for the effective torque, among which the motor control will choose according to the type of desired torque tracking.

In a first path, the injection cutoff is requested when the motor can no longer follow the torque setpoint with the current roll number. The deactivation of the cylinder is represented in the form of a vertical arrow 10 which originates at the point where the torque setpoint reaches the lower limit 3 of zone 2 achievable with four cylinders. In this case, the torque setpoint 1 is underestimated as illustrated by the horizontal arrow 1 1 as the torque setpoint has not reached the torque zone 4 achievable with one cylinder less.

According to a second path, the injection cutoff is requested when the torque setpoint 1 reaches the maximum achievable torque 5 with one less cylinder. In this case, the torque setpoint is overestimated according to the horizontal arrow 20 during the time interval when the torque setpoint 1 is in the dead zone 6, that is to say during the time interval where the Torque reference 1 has not yet reached the torque zone 4 achievable with one less cylinder, here with three cylinders. Once the torque setpoint 1 has reached the torque zone 4, then the deactivation of a cylinder is controlled and the cylinder is deactivated according to the vertical arrow 21.

According to a third path, the injection cutoff is requested when the engine torque setpoint 1 reaches a torque Ts which is calibrated between the minimum torque 3 achievable with the number of active cylinders current and the maximum torque 5 achievable with the number of active cylinders decreased by one cylinder, here with three active cylinders. Thus, after the effective torque has followed the minimum torque value 3 according to the horizontal arrow 30, when the torque setpoint reaches a progression established between the minimum torque value 3 and the lower maximum torque value 5, this progression being by example established at a value of 60 percent, then a cylinder is deactivated according to the arrow 31 and then the effective torque follows, according to the horizontal arrow 32, the maximum value 5 with three active cylinders until reaching the set point 1 when the It joins zone 4. In this case, the torque setpoint is optimally monitored. In the case of this torque path, the strategy measures the difference between the minimum torque with the number of cylinders running and the maximum torque with the current cylinder number decreased by one cylinder. The calibrated torque threshold from which the deactivation of a cylinder is requested is a percentage of the dead zone. A percentage at 100% is equivalent to the first path described above, a percentage at 0% is equivalent to the second path described above.

In the same way, for the delivery of injection of a cylinder cut, when the torque setpoint increases, the present strategy proposes different paths depending on the type of desired torque tracking. According to a first path, the injection delivery is requested when the engine can no longer follow the torque setpoint with the number of cylinders running. In this case, the torque setpoint is overestimated until it reaches the achievable torque zone with one more cylinder. According to a second path, the injection delivery is requested when the torque setpoint reaches the achievable torque with one more cylinder. In this case, the torque setpoint is underestimated until it reaches the achievable torque zone with one more cylinder.

According to a third path, the injection reset is requested when the engine torque setpoint reaches a calibrated torque between the minimum torque with the number of active cylinders added with a cylinder and the maximum torque achievable with the number of cylinders. active cylinders current. In this case, the torque setpoint is optimally monitored. In the case of this third path, the strategy measures the difference between the minimum achievable torque with one more active cylinder and the maximum achievable torque with the number of active cylinders running. The calibratable threshold is a percentage of the dead zone. A percentage of 0% is equivalent to the first path described above, a percentage of 100% is equivalent to the second path described above.

The present device therefore requires the selective deactivation of injection on one or more cylinders when the torque setpoint requested to the motor on the branch advance or the air branch can not be followed, respectively, in the case of a reactivation when the torque setpoint requested from the motor can be realized with one more cylinder. For this it calculates in real time the achievable torque once a deactivated cylinder or once a reactivated cylinder to request the deactivation or activation according to several "paths" calibrated according to the type of desired torque tracking. The desired type of torque tracking, which generates the implementation of one or the other of the elaborated paths, is for example a choice of driving comfort level, chosen by the driver at the dashboard or chosen at the factory . The type of monitoring can alternatively be conditioned by the fact that the vehicle is driven in the city or highway, on the basis of a detection of more or less high variations of the speed of the vehicle.

Although we have described an embodiment where different torque control paths are developed, alternatively engine control develops a single path such as the third calibrated trigger path of the deactivation and / or reactivation of cylinder, thereby allowing improved control of the deactivation and / or reactivation. The device described here is particularly advantageous when the motor torque setpoint is in a so-called "dead" motor torque zone, that is to say where the desired torque evolution can not be achieved.

Such a device does not improve the intrinsic performance of the engine, the torque areas covering or not are defined by the physics of the engine such as the displacement and the combustion technologies used and the choice of calibrations. However, once these parameters have been defined, such a device, and in particular the path with deactivation and / or reactivation calibration, makes it possible to offer a significant gain in the torque control by artificially varying the torque zones that can be reached by the motor.

The strategy makes it possible to follow as closely as possible the torque setpoint in delicate life situations such as automatic gearbox ratio changes or ESP activations using to the maximum the potential of the selective disconnection of the gearbox. cylinder. The proposed strategy makes it possible to improve torque monitoring by the engine during very dynamic life situations that may be critical for the engine itself and the consumer systems such as the automatic gearbox or the ESP actuators, with for impact a bad feeling by the customer, even a risk for 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. The monitoring of the achievable torque also makes it possible to avoid situations of sloshing of the injection cut-off set point because the system is found in a dead zone of torque.

Such a strategy can be implemented without additional high cost because it can be implemented in the motor control alone, without the need for sensor and / or additional actuator.

This type of strategy is particularly advantageous on heavily loaded small displacement engines and sometimes with little cylinders because their torque reduction potential is quite low by the only degradation of the ignition advance compared to a thermal engine with a lot of cylinders and a high cylinder capacity.

Claims

1. A method of controlling a motor vehicle combustion engine having a plurality of combustion cylinders, the method comprising the step of decreasing the number of active cylinders (10,21,31) in the event of a torque setpoint decrease ( 1), characterized in that it comprises a step of evaluating whether the torque setpoint (1) is lower than a threshold torque (T _s ) distinct from the minimum torque attainable with the number of active cylinders present (3) and distinct maximum torque achievable with an active cylinder minus (5), the threshold torque (Ts) being between these two pairs respectively minimum (3) and maximum (5) and the step of reducing the number of active cylinders (10). , 21, 31) in the affirmative of this evaluation.

2. Method according to claim 1, characterized in that the maximum torque achievable with a cylinder active less (5) is less than the minimum torque achievable with the number of active cylinders current (3).

3. Method according to claim 1 or claim 2, characterized in that it comprises the step of evaluating whether the torque setpoint (1) is lower than the minimum torque achievable with the number of active cylinders present (3) and performing the step of evaluating whether the torque setpoint (1) is lower than the threshold torque (T _s ) in the case where the torque setpoint (1) is lower than the minimum torque achievable with the current number of active cylinders ( 3).

4. Method according to any one of the preceding claims, characterized in that it comprises the step of calculating different torque paths (10,20,30) among which a path (30) consisting of deactivating a cylinder (31). ) during a crossing of said threshold torque (Ts) and to opt for one of these different paths (10, 20, 30) as a function of a predetermined parameter of torque tracking.

5. Method according to the preceding claim, characterized in that one of the different calculated paths (10,20,30) comprises a section (30) preceding a deactivation of cylinder (31) in which section (30) the torque remains higher to the torque setpoint (1).

6. Method according to the preceding claim, characterized in that one of the different calculated paths (10,20,30) is to deactivate a cylinder (21) when the torque setpoint (1) becomes lower than the maximum torque achievable with a active cylinder less (5).

7. Method according to any one of claims 4 to 6, characterized in that one of the different calculated paths (10,20,30) comprises a section (1 1) consecutive to a cylinder deactivation (10) in which section (1 1) the torque is less than the torque setpoint (1).

8. Method according to the preceding claim, characterized in that one of the different paths (10,20,30) is to deactivate a cylinder (10) as soon as the torque setpoint (1) becomes less than the minimum torque achievable with the number of active cylinders present (3).

Motor vehicle combustion engine control module comprising a plurality of combustion cylinders, the control module being configured to reduce the number of active cylinders (10, 21, 31) in the event of a decrease in the torque set point (1). ), characterized in that it is configured to evaluate whether the torque setpoint (1) is lower than a threshold torque (T _s ) distinct from the minimum torque attainable with the current active number of cylinders (3) and distinct from the maximum torque achievable with an active cylinder minus (5), the threshold torque (Ts) being between these two pairs respectively minimum (3) and maximum (5) and the control module is configured to reduce the number of active cylinders (10, 21, 31) in the affirmative of this evaluation.

10. Motor vehicle comprising a combustion engine and a control module of the combustion engine according to the preceding claim.