FR3142126A1 - Method for controlling a motor vehicle engine comprising at least one engine adjustment mode aimed at increasing the quantity of calories from the engine used by a vehicle heating system - Google Patents

Abstract

This method of controlling an internal combustion engine with spark ignition of a vehicle comprising a heating system configured to recover thermal energy from the engine in order to heat the passenger compartment of the vehicle, characterized in that it comprises the steps following: a step of measuring the temperature of an engine coolant, a step of adjusting the engine according to a first mode carried out if the measured temperature is less than or equal to a first predefined value and as long as the measured temperature remains less than a second predefined value greater than the first, anda step of adjusting the motor according to a second adjustment mode if the measured temperature is greater than said first value or if the measured temperature is greater than or equal to said second value; said first adjustment mode aimed at increasing the quantity of calories from the engine. Figure for abstract: Figure 7

Description

Method for controlling a motor vehicle engine comprising at least one engine adjustment mode aimed at increasing the quantity of calories from the engine used by a vehicle heating system

The present invention relates to vehicles equipped with a spark-ignition engine and relates in particular to a strategy for improving the heating function of the passenger compartment.

Previous techniques

Thermal losses from motor vehicle engines are conventionally used to heat the passenger compartment by means of a specific heat exchanger called an air heater which is associated with the engine cooling circuit.

In order to comply with increasingly demanding environmental standards, automobile manufacturers are seeking to optimize thermal engines in order to reduce their consumption and consequently to reduce the pollutants emitted.

These developments in thermal engines directly affect air conditioning because optimizing a thermal engine means maximizing its combustion efficiency and therefore minimizing its thermal losses or discharges, so that the heating function of the passenger compartment is degraded.

When leaving at low temperatures, particularly negative ones, the new high effective efficiency engines take longer to heat up and consequently there are not enough calories transmitted to the unit heater to properly heat the passenger compartment.

A classic solution to accelerate the engine temperature rise during a cold start is to reduce the ignition advance. Indeed, by deviating from the optimal advance which maximizes torque and efficiency, more fuel must be burned to obtain the same level of torque. The engine thus heats up more quickly in return for increased fuel consumption. Regardless of the overconsumption generated, the strategy of degrading the ignition advance also has limits, because it is not possible to reduce the advance very significantly during cold starts due to the risk of instability of the ignition. combustion. It is therefore not possible to use only the degradation of the ignition advance to achieve the expected level of passenger compartment heating performance.

In view of the above, the invention aims to improve the heating of the passenger compartment of a motor vehicle equipped with a high effective efficiency engine.

The subject of the invention is a method for controlling an internal combustion engine with spark ignition operating according to a four-stroke cycle of a motor vehicle comprising a heating system configured to recover the thermal energy of the engine in order to heat the vehicle interior.

• une étape de mesure de la température (T) d’un liquide de refroidissement du moteur ,
• une étape de réglage du moteur selon un premier mode de réglage réalisée si la température (T) mesurée est inférieure ou égale à une première valeur de seuil (T1) prédéfinie et tant que la température (T) mesurée reste inférieure à une deuxième valeur de seuil (T2) prédéfinie supérieure à la première (T1), et
• une étape de réglage du moteur selon un deuxième mode de réglage si la température (T) mesurée est supérieure à ladite première valeur de seuil (T1) ou si la température (T) mesurée est supérieure ou égale à ladite deuxième valeur de seuil (T2).

The process includes the following steps:

• a step of measuring the temperature (T) of an engine coolant,
• a step of adjusting the motor according to a first adjustment mode carried out if the measured temperature (T) is less than or equal to a first predefined threshold value (T1) and as long as the measured temperature (T) remains less than a second value of predefined threshold (T2) greater than the first (T1), and
• a step of adjusting the motor according to a second adjustment mode if the measured temperature (T) is greater than said first threshold value (T1) or if the measured temperature (T) is greater than or equal to said second threshold value (T2 ).

The first adjustment mode aims to increase the quantity of calories from the engine which is used by the vehicle's heating system by timing the engine valves with an exhaust opening advance greater than 50°Vil and a advance from closure to exhaust greater than 35°Vil.

The second adjustment mode includes the timing of the engine valves with an advance from opening to exhaust less than 50°Vil, an advance from closing to exhaust less than 35°Vil.

According to an advantageous characteristic, the first adjustment mode uses an admission opening delay greater than 25°Vil. By using such a close-to-exhaust delay (known as ROA), there is no crossover phase of the intake and exhaust valves. This maximizes the effect of the re-compression phase at the end of exhaust emptying.

For example, the first adjustment mode uses an advance from opening to the exhaust equal to 70°Vil, an advance from closing to the exhaust equal to 50°Vil and a delay from opening to the admission equal to 30°Vil. The first adjustment mode thus makes it possible to increase the thermal energy recovery of the motor.

For example, the timing of the exhaust valves and the timing of the associated intake valves are in the second adjustment mode respectively delayed by an additional value of 40 °Vil and advanced by an additional value of 15 °Vil relative to to the settings of the first adjustment mode. By using these timings we avoid recirculating burnt gases when the engine temperature is sufficiently high.

Advantageously, the timing of the exhaust valves and the timing of the intake valves of the second adjustment mode are mechanically fixed when the engine starts, stops or is stopped.

According to another aspect, the subject of the invention is a motor vehicle comprising a spark-ignition internal combustion engine comprising at least one cylinder comprising at least one exhaust valve and at least one associated intake valve, said engine comprising means for measuring the temperature of a coolant of said engine, said vehicle comprising a heating system configured to recover thermal energy from the engine in order to heat the passenger compartment of the vehicle.

Said engine further comprises an engine control system comprising means for controlling a variable timing system of the intake valves of the engine and means for controlling a system for variable timing of the exhaust valves of the engine, said control system being capable of modifying the timing of said valves according to a control method as described above.

Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

schematically illustrates the architecture of an internal combustion engine used for implementing the method according to the invention;

illustrates an example of a dual variable valve timing system of the engine of the ;

illustrates the timing diagram and valve lifts conventionally used in engine tuning in the absence of camshaft offset phases;

illustrates a known adjustment of the engine comprising a valve crossing phase; And

illustrates the distribution diagram and the valve lifts used according to the method according to the invention;

illustrates the evolution of the thermal loss coefficient ε _th as a function of the timing of the exhaust valves of the engine used according to the invention; And

is the flowchart of a process according to one embodiment of the invention.

Detailed presentation of at least one embodiment

In the example illustrated on the , the internal combustion engine 1 of a motor vehicle is of the spark ignition type and comprises, without limitation, three cylinders 2 in line, a fresh air intake manifold 3, an exhaust manifold 4, a turbo-compression or turbocharger system 5, a variable timing system 6 of the intake valves 7 of the engine and a variable timing system 8 of the exhaust valves 9 of the engine. The variable timing system 6 of the intake valves is equipped with a sensor 10 which makes it possible to know at each instant its angular position, which corresponds to determined instants of opening and closing of the intake valves 7 in the cycle combustion of the engine. The variable timing system 8 of the exhaust valves is also equipped with a sensor 11 which allows its angular position to be known at each instant, which also corresponds to specific opening and closing times of the exhaust valves 9. in the engine combustion cycle.

The cylinders 2 are supplied with air via the intake manifold 3, or distributor, itself supplied by a pipe 12 provided with an air filter 13 and a compressor 5a of the turbocharger 5 of engine 1.

The turbocharger 5 essentially comprises a turbine 5b driven by the exhaust gases and the compressor 5a mounted on the same shaft as the turbine 5b and ensuring compression of the air distributed by the air filter 13 or air box, in the aim of increasing the quantity (mass flow) of air admitted into the cylinders 2 of the engine 1 for an identical volume flow.

The internal combustion engine 1 includes an intake circuit Ca and an exhaust circuit Ce.

The intake circuit Ca includes, from upstream to downstream in the direction of air circulation:

- the air filter 13;

- a flow meter 14 placed in the intake pipe 12 downstream of the air filter 13 to measure the real value of the mass flow of air entering the engine 1;

- an air intake valve 15;

- compressor 5a of turbocharger 5;

- a throttle body 16 or a gas admission valve into the engine;

- a heat exchanger 17 configured to cool the intake gases corresponding to a mixture of fresh air and recirculated gases after their compression in the compressor 5a; And

- the intake manifold 3.

The exhaust circuit includes, from upstream to downstream in the direction of circulation of the burned gases:

- the exhaust manifold 4;

- turbine 5b of turbocharger 5; And

- a system for depolluting engine combustion gases (not shown), including in particular a three-way catalyst.

Concerning the exhaust collector 16, it recovers the exhaust gases resulting from combustion and evacuates the latter to the outside, via a gas exhaust conduit 18 opening into the the inlet of the turbine 5b of the turbocharger 5 and by an exhaust line 19 mounted downstream of the turbine 5b.

The engine 1 may also include a partial recirculation circuit (not shown) of the exhaust gases at the intake, called the “EGR” circuit (“exhaust gas recirculation” in English).

The engine 1 is associated with a fuel circuit comprising, for example, fuel injectors (not referenced) injecting fuel directly into each cylinder from a fuel tank (not shown). The fuel may in particular be gasoline, alcohol or liquefied petroleum gas.

Engine 1 is equipped with a cooling circuit (not shown) which is associated with a heat exchanger or air heater (not shown) used to heat the passenger compartment of the vehicle.

The engine 1 is provided with a sensor 20 for the temperature of the engine coolant, representative of the temperature of the engine 1.

Furthermore, the engine includes an electronic control unit 21 configured to control the different elements of the internal combustion engine from data collected by sensors at different locations of the engine.

There schematically illustrates the variable timing system 6 of the intake valves 7 of engine 1 and the variable timing system 8 of the exhaust valves 9 of engine 1.

In the example illustrated, the engine 1 comprises three cylinders 2 each comprising a piston 22, two intake valves 7 and two exhaust valves 9.

In other variants, the engine may have a single intake valve and a single exhaust valve for each cylinder.

Other valve configurations are possible, without departing from the scope of the invention.

The variable timing system 6 of the intake valves 7 of the engine includes a shifter 23 connected to the intake camshaft 24.

The variable timing system 8 of the exhaust valves 9 of the engine comprises a shifter 25 connected to the exhaust camshaft 26.

Each shifter 23, 25 comprises two concentric wheels whose lobes are separated by oil chambers. One wheel is attached to the distribution pinion called the stator, while the other wheel is attached to the camshaft called the rotor.

When a solenoid valve 27 transfers the oil under pressure into the chambers, the lobes move angularly causing the camshaft to rotate.

The electronic control unit 21 of the engine 1 is able to control the solenoid valve 10 to control the angular movement of the lobes, thus controlling the offset of each camshaft.

Alternatively, the offsets can be controlled by an electrical control system controlled by the electronic control unit 21 of the motor 1.

Variable timing systems or VVT for “Variable Valve Timing” in English, are a technology almost generalized to all spark ignition engines and which allow the camshafts to be angularly offset.

The timing diagram is defined by angular positions of the crankshaft corresponding to the opening and closing of the valves. The angular position of the crankshaft is measured in crankshaft degrees. The crankshaft degree, noted °Vil, corresponds to the time necessary for the crankshaft to rotate through an angle of 1 degree. One engine revolution represents 360°Vil. In particular, a complete combustion cycle for a 1 four-stroke engine corresponds to two revolutions equivalent to 720 °Vil.

For example, we note VVT 30/40 an offset of 30 °Vil on the intake camshaft in the direction of advance of the openings/closings of the intake valves in the combustion cycle and an offset of 40 °Vil on the exhaust camshaft in the direction of the delay of the exhaust valve openings/closings in the combustion cycle.

There illustrates the timing diagram and valve lifts conventionally used in engine tuning in the absence of camshaft offset phases. By convention, the threshold necessary for opening/closing the valves corresponds in the example illustrated to 0.7mm. Thus, any lift of a value less than 0.7mm corresponds to a closed valve. Conversely, from a lift of 0.7mm we consider that the valve is open. Of course, the value of this valve opening/closing threshold can vary and take other values without harming the generality of the invention.

There illustrates a complete combustion cycle over the four successive strokes: compression, expansion, exhaust and admission.

More precisely, the combustion cycle carried out comprises four successive phases, namely an admission phase, a compression-ignition phase, a combustion-expansion phase and an exhaust phase.

In the intake phase, the piston descends from the crossover TDC to the intake BDC, thus creating a vacuum in the cylinder and suction of air. The manifold pressure shown on the is much higher than the atmosphere thanks to supercharging by compressor 5a.

In the compression-ignition phase of the air/fuel mixture previously admitted/injected into the combustion chamber, the compression of the mixture is carried out with the valves closed by the rise of the piston from the intake bottom dead center (BDC) towards the top dead center (TDC) of combustion. Ignition controlled by a candle conventionally occurs a few moments before the TDC of combustion, typically 10 to 20 °Vil before said TDC, in order to take into account the time necessary for the development of combustion.

In the combustion-expansion phase, combustion develops and the pressure increases rapidly to a maximum where the gases are very hot and heat transfers to the cylinder walls are intense. The piston then descends towards the exhaust BDC, the pressure and temperature of the gases decrease at the same time as work is supplied to the piston.

In the exhaust phase, the gases are evacuated initially under the effect of their own pressure, then under the thrust of the piston which rises towards the crossing TDC.

Curve 28 illustrates the variation in pressure in the combustion chamber of a cylinder of engine 1 during the engine cycle described above.

Curves 29 and 30 respectively illustrate the lifts of the exhaust valves 9 and the intake valves 7.

The characteristic distribution quantities represented are the advance of opening at the exhaust (well known by the abbreviation AOE), the advance of closing at the exhaust (or AFE) and the delay of opening at admission (or ROA). AOE is measured relative to exhaust PMB. AFE and ROA are measured relative to crossover TDC.

By convention, advances are counted positively when the valves concerned open or close before the reference dead center. By convention, delays are counted positively when the valves concerned open or close after the reference dead center.

In the example illustrated on the , the AOE is equal to 30°Vil, the AFE is equal to 10°Vil and the ROA is equal to 15°Vil. This motor adjustment constitutes a reference or “rest” position noted VVT 0/0.

On current engines, the angular timing of the camshafts in this VVT 0/0 position is characterized by the absence of a crossover phase of the exhaust valves and the intake valves at crossover TDC. The absence of a crossover phase makes it possible to avoid the transfer of burnt gases to the intake, which is undesirable during the starting and stopping phases of the engine due to insufficient control of the richness.

A crossing phase of the exhaust valves and the intake valves is, however, sought at the other operating points of the engine where the inlet pressure is lower than the exhaust pressure in order to recirculate burnt gases. towards the intake to thus reduce fuel consumption by reducing pumping losses thanks to a larger opening of the throttle body.

There illustrates an example of engine adjustment, denoted VVT 30/30, which generates a crossover phase 31 of the valves. In this setting, compared to the VVT 0/0 setting, the exhaust valve lifts are delayed by 30°Vil and the intake valve lifts are advanced by 30°Vil. The following distribution values are thus obtained for the VVT 30/30 setting: the AOE is equal to 0°Vil, the AOA is equal to 15°Vil and the RFE is equal to 20°Vil.

There illustrates the distribution diagram and the valve lifts used according to the method of the invention. In the figures, the same elements bear the same references.

According to the invention, the timing of the exhaust camshaft is characterized by very early opening and closing of the exhaust valves.

According to the method of the invention, an anticipated opening relative to the exhaust bottom dead center of at least one exhaust valve of the cylinder is started with an advance of the opening to the exhaust AOE having a value greater than 50°Vil.

In the example shown, the AOE is equal to 70°Vil.

According to the method of the invention, the anticipated closing of said exhaust valve with respect to the crossover top dead center is completed with an advance of the closing at the exhaust AFE having a value greater than 35°Vil.

In the example shown, the AFE is equal to 50°Vil.

Early opening of the exhaust valves interrupts the gas expansion phase, thus degrading engine efficiency and causing a higher exhaust gas temperature.

The early closing of the exhaust valves generates a phase of re-compression 32 of the gases at the end of emptying of the combustion chamber. The re-compression phase 32 of the gases has the effect of increasing both the temperature of the gases and the degradation of efficiency by the resistant work of the piston. For this effect to be significant, it is necessary to provide an exhaust closure advance greater than 35°Vil.

According to the method of the invention, the opening of the intake valves is advantageously delayed by using an ROA greater than 25°Vil, in order not to put the intake and exhaust into communication, that is to say so as to avoid any crossover phase between the exhaust valves and the intake valves.

The process of the invention makes it possible to increase thermal losses through two combined effects.

The first effect is linked to the degradation of efficiency caused by the reduction in the energy recovered from the piston during the expansion phase and by the re-compression phase at the end of exhaust emptying. As with ignition underadvance, more fuel must be injected and burned to ensure the same level of torque. This additional thermal energy will be found partly in thermal losses.

The second effect is linked to the increase in thermal exchanges between the gases in the cylinder and certain engine parts such as the barrels, the cylinder head or the pistons. This second effect is localized on the re-compression phases at the end of the exhaust emptying and on the admission phase because part of the burnt and very hot gases resulting from the re-compression of the phase d is recirculated. 'exhaust. This second effect is all the more important at low engine loads because the rate of gases burned and recirculated at the intake is the highest. However, it is precisely at these operating points that the need for calories is felt for heating the passenger compartment, because the quantities of fuel there are relatively low.

There illustrates the evolution of the thermal loss coefficient ε _th as a function of the timing of the exhaust valves of the engine used according to the invention. The thermal loss coefficient ε _th is the ratio between the power of thermal losses and the chemical power introduced by the injected fuel. There highlights that the share of thermal losses increases when there is a re-compression of the burnt gases at the end of the exhaust emptying. Furthermore, it should be noted that the thermal loss coefficient hardly varies with the ignition underadvance.

The two effects described above can be coupled if necessary to a greater ignition under-advance by taking advantage of the fact that the hot gases recirculated at the intake make it possible to tolerate lower advances when cold thanks to the heating of the chamber combustion.

There is the flowchart of a process according to one embodiment of the invention.

The method begins with a step 33 of measuring the temperature T of a coolant of the engine 1. At this step, the electronic control unit 21 measures the temperature T using the sensor 20 installed on the engine 1 .

Depending on the measured temperature T, the process continues with a step of adjusting the motor according to a first or a second adjustment mode.

If the measured temperature T is less than or equal to a first predefined threshold value T1 and as long as the measured temperature T remains less than a second predefined threshold value T2 greater than the first T1, the motor is adjusted according to the first mode adjustment (step 34). According to the first adjustment mode, the timing of the valves of the engine 1 is controlled by the electronic control unit 21 with an advance from opening to exhaust AOE greater than 50 °Vil, an advance from closing to exhaust exhaust AFE greater than 35°Vil and a delay from opening to admission ROA greater than 25°Vil. The first adjustment mode aims to increase the quantity of calories from engine 1 used by the vehicle's heating system to heat the passenger compartment.

On the contrary, if the measured temperature T is greater than said first predefined threshold value T1 or if the measured temperature T is greater than or equal to said second predefined threshold value T2, the adjustment of the motor is carried out according to the second adjustment mode ( step 35).

According to the second adjustment mode, the timing of the valves of the engine 1 is controlled by the electronic control unit 21 with an advance of the opening at the exhaust AOE equal to a value less than 50 °Vil, an advance of the AFE exhaust closure equal to a value less than 35°Vil.

For example, the second adjustment mode may include valve timings allowing a crossover phase of the exhaust valves and the intake valves in order to improve fuel consumption.

For example, the second adjustment mode can include valve timings which avoid the recirculation of gases burned at the intake, and which are particularly interesting during the starting, switching off and stopping phases of the engine. For example, the timing of the exhaust valves and the timing of the associated intake valves can be in the second adjustment mode respectively delayed by an additional value of 40 °Vil and advanced by an additional value of 15 °Vil by compared to the settings of the first adjustment mode in order to correspond to an AOE equal to 30°Vil, an AFE equal to 10°Vil and an ROA equal to 15°Vil. This engine adjustment constitutes a reference or “rest” position which is mechanically fixed when the engine starts, stops or is stopped, in order to control the timing of the camshafts in phases where an oil pressure level minimum necessary for controlling the shifters is not available. This reference position can for example be obtained with a mechanical indexing finger capable of blocking the rotation of a lobe of each shifter.

Claims (6)

Method for controlling an internal combustion engine (1) with spark ignition operating according to a four-stroke cycle of a motor vehicle comprising a heating system configured to recover the thermal energy of the engine (1) in order to heat the vehicle passenger compartment, characterized in that it comprises the following steps:

• a step of measuring the temperature (T) of an engine coolant,
• a step of adjusting the motor according to a first adjustment mode carried out if the measured temperature (T) is less than or equal to a first predefined threshold value (T1) and as long as the measured temperature (T) remains less than a second value of predefined threshold (T2) greater than the first (T1), and
• a step of adjusting the motor according to a second adjustment mode if the measured temperature (T) is greater than said first threshold value (T1) or if the measured temperature (T) is greater than or equal to said second threshold value (T2 );

said first adjustment mode aimed at increasing the quantity of calories from the engine (1) used by the vehicle heating system by timing the engine valves with an advance of the exhaust opening (AOE) equal to one value greater than 50 °Vil and an advance from closing to exhaust (AFE) equal to a value greater than 35 °Vil, said second adjustment mode comprising the timing of the engine valves with an advance from opening to l exhaust (AOE) less than 50 °Vil, an advance from closure to exhaust (AFE) equal to a value less than 35 °Vil. Method according to claim 1 in which the first adjustment mode uses an inlet opening delay (ROA) equal to a value greater than 25 °Vil. Method according to claim 2, in which the first adjustment mode uses an advance of the opening at the exhaust (AOE) equal to 70 °Vil, an advance of the closing at the exhaust (AFE) equal to 50 °Vil and a delay from opening to admission (ROA) equal to 30 °Vil. Method according to any one of the preceding claims, in which the timing of the exhaust valves and the timing of the associated intake valves are in the second adjustment mode respectively delayed by an additional value of 40 °Vil and advanced by an additional value of 15°Vil compared to the settings of the first adjustment mode. A method according to claim 4, wherein the timing of the exhaust valves and the timing of the intake valves of the second adjustment mode are mechanically fixed when the engine starts, stops or is stopped. Motor vehicle comprising a spark-ignition internal combustion engine (1) comprising at least one cylinder comprising at least one exhaust valve and at least one associated intake valve, said engine comprising means for measuring the temperature of a coolant of said engine, said vehicle comprising a heating system configured to recover thermal energy from the engine in order to heat the passenger compartment of the vehicle, characterized in that said engine further comprises an engine control system comprising means for control of a variable timing system for the intake valves of the engine and means for controlling a variable timing system for the exhaust valves of the engine, said control system being capable of modifying the timing of said valves according to a method control according to any one of claims 1 to 5.