FR3057297A1 - METHOD FOR CONTROLLING A VALVE LIFTING OF AN INTERNAL COMBUSTION ENGINE WITH A VARIABLE VALVE LIFTING - Google Patents

Abstract

A method of controlling a valve lift of an engine, provided with at least one variable lift valve, comprising: - in an open loop (44), a step for obtaining a raw valve lift setpoint (L_c), and in a closed loop (45): a step of introducing said raw valve lifting setpoint (L_c) obtained by said open loop (44) to determine a raw filling setpoint (rempl_b), a comparison step; between said filling setpoint (fill_c) and said gross fill setpoint (fill_b) previously obtained, - a step of introducing an error between said two fill instructions (fill_c, fill_b) into a regulator (28) making it possible to make evolving said gross valve lift setpoint (L_c) via said open loop (44), and - a step of controlling said valve lift as a function of said position of said raw valve lift setpoint (L_c) obtained when said error is zero .

Description

Holder (s): PEUGEOT CITROEN AUTOMOBILES SA Société anonyme.

Extension request (s)

Agent (s): PEUGEOT CITROEN AUTOMOBILES SA Public limited company.

METHOD FOR CONTROLLING A VALVE LIFTING OF AN INTERNAL COMBUSTION ENGINE WITH VARIABLE VALVE LIFTING.

FR 3 057 297 - A1 \ 7f) Method for controlling a valve lift of an engine, provided with at least one valve with variable lift, comprising:

- in open loop (44), a step to obtain a gross valve lift instruction (L_c), and

- in closed loop (45):

a step of introducing said gross valve lift instruction (L_c) obtained by said open loop (44) to determine a raw filling instruction (repl_b),

a step of comparison between said filling instruction (repl_c) and said raw filling instruction (repl_b) previously obtained,

a step of introducing an error between said two filling instructions (repl_c, repl_b) in a regulator (28) making it possible to modify said gross valve lift instruction (L_c) via said open loop (44), and

a step of controlling said valve lift as a function of said position of said gross valve lift instruction (L_c) obtained when said error is zero.

The present invention relates to a method for controlling a valve lift of an internal combustion engine with valve lift. variable. The invention finds a particularly advantageous, but not exclusive, application in the field of motor vehicles.

In a manner known per se, the intake valves and the engine exhaust valves are moved by camshafts. In certain engine configurations, the relative position of each camshaft relative to the crankshaft can be changed by means of hydraulically or electrically controlled phase shifters. These phase shifters make it possible, depending on the operating conditions, to advance or delay the opening and / or closing of the intake and exhaust valves, that is to say to vary the phasing of the lifting laws. of these valves compared to a reference operating mode. These phase shifters are known by the acronym WA (Variable Valve Actuation in English) or VVT (Variable Valve Timing in English).

In the case of so-called conventional engines or without variable valve lift, the engine load is managed by using the pressure variation in the intake distributor, engine load is managed by using the pressure variation in the distributor of admission. Such a method is for example described in the document FR2942503. Therefore, to obtain the filling instruction requested by the driver, via the torque instruction and therefore the accelerator pedal, it is necessary to reverse the filling model in order to know the pressure instruction to be obtained in the distributor. of admission.

[0004] Thus, the direct filling model is defined by the following formula:

repl = P ^ dm ^x slope - offset

With:

- fill being the estimated fill: Ma / Mref,

- Ma being the mass of fresh air in the cylinder;

- Mref being the reference air mass under the conditions: 101,300 Pa and 273 K.

- slope being the filling slope, function of the phase shifter at the measured intake;

- offset being the filling offset, a function of the phase shifters at the intake and exhaust measured;

- ^p adm ed ^{as the} pressure measured intake.

And the inverted fill pattern is defined by the following formula:

Padm- ^{c =} (repl_c + offset_c ') / slope_c

With:

- ^{p ADM-c} is the pressure setpoint at the inlet;

- filled being the filling instruction (known via the torque instruction and therefore the position of the pedal);

- slope_c being the filling slope setpoint, a function of the intake phase shifter setpoint;

- offset_c being the filling offset setpoint, a function of the setpoints of the phase shifters at the intake and at the exhaust.

The setpoints of the intake and exhaust phase shifters are controlled from maps dependent on the engine speed and the fill set ref_c.

With the pressure setpoint found P _ADM _c and the filling setpoint ref_c emanating from the driver's wishes (pedal position), it is possible to control the butterfly valve, by means of a valve surface setpoint butterfly, using the Barré Saint Venant equation linking mass flow q across a surface S:

SP P q = - == ^ Cfe \ -fp If

P „l _s / + iy

V->

subsonic regime => Cfe \ p Si

P „[/ +1 y

V->

2 · / 1 7 + 1 'ΡΛ ⁷ Pus) r (7-l) _λ Γ 7 + 1 f ² Y J V U + d

With:

- Pds being the pressure setpoint downstream of the butterfly valve in the inlet distributor: P _AD mC

- P _us being the pressure measured or estimated upstream of the butterfly valve;

- q being the flow setpoint of the butterfly valve, obtained from the filling setpoint: q = repl_c x k (k = f (speed));

- T _us being the temperature upstream of the butterfly valve;

- S being the cross section setpoint of the butterfly valve.

In the case of engines incorporating a variable valve lifting device, the engine load is managed using the variation of valve lifting. The purpose of the butterfly valve is to maintain a pressure delta P _atmo - P _ADM of x millibar in the intake distributor.

Therefore, to obtain the filling instruction requested by the driver, via the torque instruction and therefore the accelerator pedal, it is necessary to reverse the filling model in order to know the valve lift instruction to obtain.

[0009] Thus, the direct filling model is defined by the following formula:

repl = Padm ^x slope '- offset

With:

- fill being the estimated fill: Ma / Mref,

- Ma being the mass of fresh air in the cylinder;

- Mref being the reference air mass under the conditions: 101,300 Pa and 273 K.

- slope 'being the filling slope, function of the phase shifter at the measured intake, and of the valve lift measured;

- offset being the filling offset, a function of the phase shifters at the intake and exhaust measured, and the valve lift measured;

- ^p adm ed ^{as the} pressure measured intake.

And the inverted fill pattern is defined by the following formula:

L_c = f (repl_c; offset_c; slope_c ’; Padm_c)

With:

- Padm_c being the inlet pressure setpoint;

- repl_c being the filling instruction (known via the torque instruction and therefore the position of the pedal);

- slope_c 'being the filling slope setpoint, a function of the intake phase shifter setpoint and the valve lift setpoint;

- offset_c being the filling offset setpoint, a function of the intake and exhaust phase-shifter setpoints, and of the valve lift setpoint;

- L_c being the valve lift instruction.

The setpoints of the intake and exhaust phase shifters are controlled from maps dependent on the engine speed and the filling set-up ref_c.

[0011] However, the exact and explicit reversal of the filling model for a variable valve lift engine is complex. One solution could consist in using a simple mapping as a function of the engine speed and of the filling instruction repl_c, making it possible to obtain the valve lifting instruction L_c. However, the first problem of the solution emitted, is that the simple mapping making it possible to link the filled filling instruction to the valve lifting instruction L_c, is dependent on the position of the intake camshaft phase shifters and exhaust. As a result, if these positions of the phase shifters change, for example as a function of different combustion modes (cold atmosphere, performance, etc.), the simple mapping makes it possible to link the filling instruction repl_c to the valve lifting instruction L_c is no longer accurate. Consequently, to be precise whatever the combustion modes, it is necessary as much as maps as of combustion mode, which can be penalizing for the size of the memory of the computer having to contain these maps.

The second problem of the solution issued is that the simple mapping making it possible to link the filling instruction repl_c to the valve lifting instruction L_c does not allow, in stabilized load (or filling), robust management of the load with respect to variations in parameters such as water temperature, air temperature, exhaust pressure by altitude or by adduction of a particulate filter in the exhaust.

The third problem of the solution issued is that the simple mapping making it possible to link the filled filling instruction with the valve lifting instruction L_c does not allow in load transient optimal, coordinated and simultaneous management of the lifting actuators valves, intake phase shifter, exhaust phase shifter, and butterfly valve. The dynamics of these four actuators being different. As a result, the management of the transient motor load is not optimal.

The invention aims to effectively remedy these drawbacks by proposing a method for controlling a valve lift of an internal combustion engine, in particular of a motor vehicle, provided with at least one valve with variable lift, characterized in that the method comprises:

following an open-loop command, a step of using a map dependent on an engine speed and a filling instruction coming from the driver's will to obtain a gross valve lift instruction, and

- following a closed loop command:

- a step of introducing said gross valve lift instruction obtained by the open loop at the input of a filling model to determine a gross filling instruction,

a step of comparison between the filling instruction coming from the driver's will and the raw filling instruction previously obtained,

a step of introducing an error between the two filling instructions in a regulator making it possible to change the gross valve lifting instruction via the open loop, and

a step for controlling the valve lift as a function of the position of the gross valve lift instruction obtained when the error between the two filling instructions is zero.

The invention thus makes it possible to obtain a robust valve lift instruction in all life situations. The invention makes it possible to obtain the engine load requested by the driver and better control of the pressure in the intake distributor during the variable valve lift transients. In addition, the invention allows better control of fuel consumption and therefore of pollutant emissions.

According to one implementation, the mapping is determined for a specific combustion mode of the internal combustion engine.

According to one implementation, the filling model is based on the following relationship:

repl_b = Padm_c x slope'_c - offset_c

With:

- repl_b being the gross filling instruction: Ma_b / Mref,

- Ma_b being the gross fresh air mass setpoint in the cylinder;

- Mref being the reference air mass under the conditions: 101,300 Pa and 273K.

- slope'_c being the filling slope setpoint, a function of the intake phase shift setpoint, and of the valve lift setpoint;

- offset_c being the filling offset setpoint, a function of the setpoints of the intake and exhaust phase shifters from the module implementing corresponding maps, and of the valve lift setpoint;

- Padm_c being the inlet pressure setpoint.

According to one implementation, there are:

a first piloting zone in which the final valve lift comes from the open loop alone, and

- a second zone in which the final valve lift comes from the open loop and the closed loop.

According to one implementation, a border between the first zone and the second zone is determined by lifting the valves giving maximum filling for an engine speed and a combustion mode used, or by closing a valve d 'admission.

According to one implementation, in the second zone, the filling behavior is strictly monotonous vis-à-vis the lifting of valves.

The invention also relates to a motor vehicle engine computer comprising a memory storing software instructions for the implementation of the method of controlling a lifting of internal combustion engine valves as defined above.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given only by way of illustration but in no way limit the invention.

Figure 1 shows a partial schematic sectional view of an internal combustion engine capable of implementing the method of controlling a valve lift of the internal combustion engine according to the present invention;

Figure 2 is a schematic representation of the functional blocks allowing the implementation of the method of controlling the lifting of valves of the internal combustion engine according to the invention;

Figure 3 is a detailed schematic representation of the functional block of Figure 2 ensuring the inversion of the filling model;

Figure 4 is a graphical representation showing the filling of fresh air into the combustion chamber as a function of the valve lift and highlighting two control zones of the valve lift.

Figure 1 shows a partial schematic sectional view of a gasoline internal combustion engine 1 having a plurality of cylinders 2, for example three or four in number.

Each cylinder 2 has a piston 3, a combustion chamber 5, a fuel injector 6, a spark plug 8 associated with a system 9 for adjusting the ignition advance angle, at least one inlet valve 11, at least one exhaust valve 12. The combustion chamber 5 is thus defined in the cylinder 2 between the lower face of a cylinder head 13 and the upper face of the piston 3.

The spark plug 8 is linked to the cylinder head 13 and provided with electrodes which produce a spark in the combustion chamber 5 when the piston 3 is in the vicinity of its top dead center. The intake 11 and exhaust 12 valves are mounted mobile in the cylinder head 13 and are arranged on either side of a median axial plane P of the cylinder 2 so as to define an intake side and an exhaust side.

The intake valves 11 are moved by a first camshaft 171 so as to put the combustion chamber 5, at a selected time before compression, in communication with an intake duct 18. A valve 20, in the form of a butterfly, manages the air flow introduced into cylinder 2.

Similarly, the exhaust valves 12 are moved by a second camshaft 172 so as to put the combustion chamber 5 at a selected time after combustion, in communication with an exhaust duct 23.

The relative position of each camshaft 171, 172 relative to the crankshaft of the engine 1 (not shown) can be modified respectively by means of a first phase shifter 211 said intake and a second phase shifter 212 said d 'exhaust. Each phase shifter 211, 212 can be controlled hydraulically or electrically. The phase shifters 211, 212 make it possible, depending on the operating conditions, to advance or delay the opening and / or closing of the intake 11 and exhaust 12 valves relative to a reference operating mode.

An engine computer 33 controls the various elements of the architecture of the engine 1 as a function in particular of data from different sensors (not shown) installed in the system. This computer 33 includes for this purpose a memory 331 storing software instructions for implementing the method for controlling the lifting of valves of the internal combustion engine.

As illustrated in FIG. 2, this process aims to obtain the valve lift instruction L_c to be applied to the variable valve lift engine by inversion of the filling model produced by block 42. This lift instruction of L_c valves provides the engine load (or filling) requested by the driver, using an optimal inversion of the filling model.

The exact and explicit inversion of the filling model is carried out via an inversion of the implicit filling model, that is to say step by step, with rapid convergence. To this end, the objective is to use the performance of the direct filling model to determine the valve lift setpoint L_c to apply.

As illustrated in FIG. 3, the inversion block of the filling 42 is broken down into two parts: an open loop part 44, and a closed loop part 45.

Regarding the open loop 44, the principle is to use a first set of valve lift instruction information L_c using the inversion solution of the simplified filling model. This first information is used to pre-position the valve lift actuator. Thus, the open loop 44 is a simple mapping as a function of the engine speed Rmot and of the filling instruction repl_c from block 27, making it possible to obtain a gross valve lift instruction L_c. This mapping is determined for a specific combustion mode, for example an optimal heating mode.

The closed loop 45 aims to solidify the valve lift instruction L_c previously obtained in the open loop 44, in particular with regard to the various problems raised by the use of the open loop 44 alone (simple mapping).

Thus, the principle of the invention allowing optimal control of the valve lift by an implicit inversion of the filling model consists firstly, in the introduction of the gross valve lift instruction L_c obtained by the open loop 44 , at the input of the filling model 29. This makes it possible to determine the raw filling instruction repl_b, with the specific parameters below.

The direct filling model 29 is represented by the following formula:

repl_b = Padm_c x slope'_c - off set _c

With:

- repl_b being the gross filling instruction: Ma_b / Mref,

- Ma_b being the gross fresh air mass setpoint in the cylinder;

- Mref being the reference air mass under the conditions: 101,300 Pa and 273K.

- slope'_c being the filling slope setpoint, a function of the setpoint of the intake phase shifters, and of the valve lift setpoint;

- offset_c being the filling offset setpoint, a function of the setpoints of the intake and exhaust phase shifters from module 40 using corresponding maps, and of the valve lift setpoint;

- Padm_c being the inlet pressure setpoint.

Second, a comparison is made between the filling instruction repl_c coming from the will of the driver and the raw filling instruction repl_b previously obtained. It is specified that the driver's will is determined by the torque setpoint from module 26, and by the position of pedal 25. The error between the two filling setpoints fill_c and fill_b is introduced into a regulator 28 which allows, not step by step, to change the gross valve lift setpoint L_c via the open loop 44. Thus, when the error between the two filling setpoints repl_c, repl_b is substantially zero, this means that the setpoint of raw valve lift L_c to obtain the filling refill set_c coming from the driver's will.

The inversion of the implicit filling model 29, that is to say step by step, is therefore carried out. The gross valve lift instruction L_c is therefore sent to the actuator to control the engine.

The advantage of this strategy, linked to the use of the filling model 29, thus makes it possible to obtain a robust L_c valve lift instruction in all life situations. In fact, to estimate the gross refill setpoint ref_b, the fill model 29 uses the exhaust and intake phase shifters 211, 212, the water temperature, as well as the pressure at the exhaust. Thus, if one of these parameters varies, in stabilized and load or load transient, the filling varies and the closed-loop structure 45 modifies the gross valve lift setpoint L_c accordingly to maintain equality between the setpoint of filling repl_c coming from the driver's desire via the torque setpoint 26 and the position of the pedal 25 and the gross filling setpoint repl_b.

The open loop 44 is used over the entire range of engine speed-load. On the other hand, the closed loop 45 is used when the valve lift is considered as an actuator capable of controlling the engine load. Indeed, at a valve lift close to the high lift, the valve lift cannot be considered as a load actuator because, in this zone, the variation of valve lift has very little influence on filling.

Therefore, as shown in Figure 4, we can distinguish two zones Z1, Z2 for controlling the valve lift. A first zone Z1 is thus observed in which the final valve lift L_c sent to the engine comes from the open loop 44 alone. This corresponds to the area in which the lifting of valves L_c has little influence on the filling filled.

There is also a second zone Z2 in which the final valve lift L_c comes from the open loop 44 and the closed loop 45. This corresponds to the zone where the valve lift L_c has an influence on the filling ref.

The border between the first zone Z1 and the second zone Z2, located for example at 5 mm in the example shown, is determined by lifting the valves L_c giving the maximum filling replmax, on the engine speed Rmot and the mode used, or when the intake valve is closed. Thus, in the second zone Z2, the behavior of the filled filling is strictly monotonic with respect to the lifting of valves L_c.

Claims (7)

Claims: 1. Method for controlling a valve lift of an internal combustion engine, provided with at least one valve with variable lift, characterized in that said method comprises: - following an open-loop command (44), a step of using a map depending on an engine speed (Rmot) and a filling instruction (repl_c) coming from a driver's desire to obtain an instruction gross valve lift (L_c), and - following a closed loop command (45): - a step of introducing said gross valve lift instruction (L_c) obtained by said open loop (44) at the input of a filling model (29) to determine a gross filling instruction (repl_b), a step of comparison between said filling instruction (repl_c) coming from the will of the driver and said raw filling instruction (repl_b) previously obtained, a step of introducing an error between said two filling instructions (repl_c, repl_b) in a regulator (28) making it possible to modify said gross valve lift instruction (L_c) via said open loop (44), and a step of controlling said valve lift as a function of said position of said gross valve lift setpoint (L_c) obtained when said error between said two filling setpoints (repl_c, repl_b) is zero. 2. Method according to claim 1, characterized in that said mapping is determined for a specific combustion mode of said internal combustion engine. 3. Method according to claim 1 or 2, characterized in that said filling model (29) is based on the following relation: repl_b = Padm_c x slope'_c - offset_c With: - repl_b being the gross filling instruction: Ma_b / Mref, - Ma_b being the gross fresh air mass setpoint in the cylinder; - Mref being the reference air mass under the conditions: 101,300 Pa and 273K. - slope'_c being the filling slope setpoint, a function of the intake phase shift setpoint, and of the valve lift setpoint; - offset_c being the filling offset setpoint, a function of the setpoints of the intake and exhaust phase shifters from the module (40) implementing corresponding maps, and of the valve lift setpoint; - Padm_c being the inlet pressure setpoint. 4. Method according to any one of claims 1 to 3, characterized in that a distinction is made: a first piloting zone (Z1) in which said final valve lift comes from said open loop (44) alone, and - A second zone (Z2) in which said final valve lift comes from said open loop (44) and said closed loop (45). 5. Method according to claim 4, characterized in that a border between said first zone (Z1) and said second zone (Z2) is determined by lifting the valves giving a maximum filling (replmax) for an engine speed (Rmot) and a combustion mode used, or to a closing of an intake valve. 6. Method according to claim 4 or 5, characterized in that, in said second zone (Z2), a filling behavior (repl) is strictly monotonous with respect to said valve lift. 7. Motor vehicle engine computer comprising a memory storing software instructions for implementing the method for controlling a lifting of internal combustion engine valves as defined in any one of the preceding claims. 1/2