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

Abstract

The invention relates to a method for controlling a controlled-ignition internal combustion engine of a vehicle comprising a heating system configured to recover the thermal energy of the engine in order to heat the passenger compartment of the vehicle, characterised in that it comprises the following steps: - a step of measuring the temperature of a coolant of the engine, - a step of adjusting the engine according to a first mode, which step is implemented if the measured temperature is less than or equal to a first predefined value and as long as the measured temperature remains below a second predefined value that is greater than the first, and - a step of adjusting the engine according to a second adjustment mode if the measured temperature is greater than the first value or if the measured temperature is greater than or equal to the second value; the first adjustment mode being intended to increase the amount of calories from the engine.

Description

[0001] DESCRIPTION

[0002] TITLE: 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

[0003] Technical field

[0004] The present invention relates to vehicles equipped with a spark-ignition engine and relates in particular to a strategy for improving the passenger compartment heating function.

[0005] Previous techniques

[0006] The heat losses from motor vehicle engines are traditionally 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.

[0007] 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.

[0008] 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 emissions, so that the passenger compartment heating function is degraded.

[0009] When starting at low temperatures, especially below zero, the new high-efficiency engines take longer to warm up and therefore not enough calories are transmitted to the heater to heat the passenger compartment properly.

[0010] A classic solution to accelerate engine warm-up during a cold start is to reduce the ignition advance. Indeed, by deviating from the optimal advance that 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. Independently of the increased fuel consumption generated, the ignition advance degradation strategy also has limitations, because it is not possible to reduce the advance very significantly during cold starts due to the risk of combustion instabilities. It is therefore not possible to use ignition advance degradation alone to achieve the expected level of passenger compartment heating performance.

[0011] Statement of the invention

[0012] In view of the above, the invention aims to improve the heating of the passenger compartment of a motor vehicle equipped with a high-efficiency engine.

[0013] The subject of the invention is a method for controlling a spark-ignition internal combustion engine operating according to a four-stroke cycle of a motor vehicle comprising a heating system configured to recover thermal energy from the engine in order to heat the passenger compartment of the vehicle.

[0014] The method comprises the following steps: a step of measuring the temperature (T) of a coolant of the engine, a step of adjusting the engine according to a first adjustment mode carried out if the measured temperature (T) is less than or equal to a first predefined threshold value (T l ) and as long as the measured temperature (T) remains less than a second predefined threshold value (T2) greater than the first (T l ), ​​and a step of adjusting the engine according to a second adjustment mode if the measured temperature (T) is greater than said first threshold value (T l ) or if the measured temperature (T) is greater than or equal to said second threshold value (T2).

[0015] The first adjustment mode aims to increase the amount of calories from the engine that is used by the vehicle's heating system by timing the engine valves with an exhaust opening advance greater than 50°Vil and an exhaust closing advance greater than 35°Vil.

[0016] The second adjustment mode includes the timing of the engine valves with an exhaust valve opening advance of less than 50°Vil, an exhaust valve closing advance of less than 35°Vil.

[0017] According to an advantageous feature, the first adjustment mode uses an intake opening delay greater than 25°Vil. By using such an exhaust closing delay (known by the abbreviation 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.

[0018] For example, the first adjustment mode uses an exhaust opening advance of 70°Vil, an exhaust closing advance of 50°Vil and an intake opening delay of 30°Vil. The first adjustment mode thus increases the engine's thermal energy recovery.

[0019] For example, the timing of the exhaust valves and the timing of the associated intake valves are respectively delayed by an additional value of 40°Vil and advanced by an additional value of 15°Vil in the second adjustment mode compared to the timings of the first adjustment mode. By using these timings, the recirculation of burnt gases is avoided when the engine temperature is sufficiently high.

[0020] Advantageously, the exhaust valve timing and the intake valve timing of the second adjustment mode are mechanically fixed when the engine starts, stops or is stopped.

[0021] According to another aspect, the invention relates to 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.

[0022] Said engine further comprises an engine control system comprising means for controlling 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 control method as described previously.

[0023] Brief description of the drawings

[0024] 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:

[0025] [Fig 1] schematically illustrates the architecture of an internal combustion engine used for implementing the method according to the invention;

[0026] [Fig 2] illustrates an example of a dual variable valve timing system for the engine of Figure 1;

[0027] [Fig 3] illustrates the valve timing diagram and lifts conventionally used in engine tuning in the absence of camshaft offset phases;

[0028] [Fig 4] illustrates a known engine setting including a valve crossover phase; and

[0029] [Fig 5] illustrates the distribution diagram and the valve lifts used according to the method according to the invention;

[0030] [Fig 6] illustrates the evolution of the coefficient of thermal losses Sth as a function of the timing of the exhaust valves of the engine used according to the invention; and

[0031] [Fig 7] is the flowchart of a method according to one embodiment of the invention.

[0032] Detailed description of at least one embodiment In the example illustrated in Figure 1, the internal combustion engine 1 of a motor vehicle is of the spark-ignition type and comprises, in a non-limiting manner, three cylinders 2 in line, a fresh air intake manifold 3, an exhaust manifold 4, a turbocharging system or turbocharger 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 any time its angular position, which corresponds to determined times of opening and closing of the intake valves 7 in the combustion cycle of the engine.The variable timing system 8 of the exhaust valves is also equipped with a sensor 11 which makes it possible to know at any time its angular position, which also corresponds to determined times of opening and closing of the exhaust valves 9 in the combustion cycle of the engine.

[0033] 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 the engine 1.

[0034] 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 providing compression of the air distributed by the air filter 13 or air box, with the aim of increasing the quantity (mass flow rate) of air admitted into the cylinders 2 of the engine 1 for an identical volume flow rate.

[0035] The internal combustion engine 1 comprises an intake circuit Ca and an exhaust circuit Ce.

[0036] The intake circuit Ca includes, from upstream to downstream in the direction of air circulation:

[0037] - the air filter 13;

[0038] - a flow meter 14 arranged in the intake duct 12 downstream of the air filter 13 to measure the actual value of the mass flow of air entering the engine 1; - an air intake valve 15;

[0039] - compressor 5a of turbocharger 5;

[0040] - a 16 throttle body or a gas intake valve in the engine;

[0041] - 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

[0042] - the intake manifold 3.

[0043] The exhaust circuit This includes, from upstream to downstream in the direction of circulation of the burnt gases:

[0044] - the exhaust manifold 4;

[0045] - turbine 5b of turbocharger 5; and

[0046] - an engine combustion gas pollution control system (not shown), including in particular a three-way catalyst.

[0047] As regards the exhaust manifold 16, the latter recovers the exhaust gases from the combustion and evacuates them to the outside, via a gas exhaust duct 18 opening at the inlet of the turbine 5b of the turbocharger 5 and via an exhaust line 19 mounted downstream of the turbine 5b.

[0048] The engine 1 may further comprise a partial recirculation circuit (not shown) of the exhaust gases to the intake, called the “EGR” circuit (“exhaust gas recirculation” in English).

[0049] 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.

[0050] The 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.

[0051] 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 comprises an electronic control unit 21 configured to control the various elements of the internal combustion engine from data collected by sensors at different locations in the engine.

[0052] Figure 2 schematically illustrates the variable timing system 6 of the intake valves 7 of the engine 1 and the variable timing system 8 of the exhaust valves 9 of the engine 1.

[0053] 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.

[0054] In other variants, the engine may be equipped with a single intake valve and a single exhaust valve for each cylinder.

[0055] Other valve configurations are possible, without departing from the scope of the invention.

[0056] The variable timing system 6 of the intake valves 7 of the engine comprises a shifter 23 connected to the intake camshaft 24.

[0057] The variable timing system 8 of the exhaust valves 9 of the engine comprises a shifter 25 connected to the exhaust camshaft 26.

[0058] Each shifter 23, 25 comprises two concentric wheels whose lobes are separated by oil chambers. One wheel is integral with the timing gear called the stator, while the other wheel is integral with the camshaft called the rotor.

[0059] When a solenoid valve 27 transfers pressurized oil into the chambers, the lobes move angularly, rotating the camshaft.

[0060] The electronic control unit 21 of the engine 1 is capable of controlling the solenoid valve 10 to control the angular displacement of the lobes, thus controlling the offset of each camshaft.

[0061] Alternatively, the control of the offsets can be achieved by an electrical control system piloted by the electronic control unit 21 of the engine 1. Variable valve 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.

[0062] 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 crank degrees. The crank degree, noted °Vil, corresponds to the time required 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 four-stroke engine corresponds to two revolutions equivalent to 720 °Vil .

[0063] For example, VVT 30 / 40 denotes a 30°Vil offset on the intake camshaft in the direction of advance of the intake valve openings / closings in the combustion cycle and a 40°Vil offset on the exhaust camshaft in the direction of delay of the exhaust valve openings / closings in the combustion cycle.

[0064] Figure 3 illustrates the valve timing diagram and valve lifts conventionally used in engine settings in the absence of camshaft offset phases. By convention, the threshold required for valve opening / closing corresponds to 0.7mm in the example illustrated. Thus, any lift of a value less than 0.7mm corresponds to a closed valve. Conversely, from a lift of 0.7mm the valve is considered to be open. Of course, the value of this valve opening / closing threshold can vary and take other values ​​without detracting from the generality of the invention.

[0065] Figure 3 illustrates a complete combustion cycle over the four successive strokes: compression, expansion, exhaust and intake.

[0066] More precisely, the combustion cycle carried out comprises four successive phases, namely an intake phase, a compression-ignition phase, a combustion-expansion phase and an exhaust phase.

[0067] In the intake phase, the piston descends from the crossover TDC to the intake BDC, thus creating a vacuum in the cylinder and sucking in air. The intake pressure illustrated in Figure 3 is significantly higher than atmospheric pressure thanks to the supercharging by the compressor 5a.

[0068] 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 bottom dead center (BDC) of admission to the top dead center (TDC) of combustion. The ignition controlled by a spark plug 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.

[0069] In the combustion-expansion phase, combustion develops and the pressure increases rapidly up 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 provided to the piston.

[0070] In the exhaust phase, the gases are initially evacuated under the effect of their own pressure, then under the thrust of the piston which rises towards the TDC crossing.

[0071] Curve 28 illustrates the variation of the pressure in the combustion chamber of a cylinder of engine 1 during the engine cycle described previously.

[0072] Curves 29 and 30 illustrate the lifts of the exhaust valves 9 and the intake valves 7 respectively.

[0073] The characteristic timing quantities represented are the exhaust opening advance (well known by the abbreviation AOE), the exhaust closing advance (or AFE) and the intake opening delay (or ROA). The AOE is measured relative to the exhaust BDC. The AFE and ROA are measured relative to the crossover TDC.

[0074] By convention, advances are counted positively when the relevant valves open or close before the reference dead center. By convention, lags are counted positively when the relevant valves open or close after the reference dead center.

[0075] In the example shown in Figure 3, the AOE is equal to 30°Vil, the AFE is equal to 10°Vil and the ROA is equal to 15°Vil. This engine setting constitutes a reference or “rest” position noted VVT 0 / 0.

[0076] 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 the 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 engine start and stop phases due to insufficient control of the richness.

[0077] A crossover phase of the exhaust valves and the intake valves is, on the other hand, sought at the other operating points of the engine where the intake pressure is lower than the exhaust pressure in order to recirculate burnt gases towards the intake and thus reduce fuel consumption by reducing pumping losses thanks to a larger opening of the throttle body.

[0078] Figure 4 illustrates an example of engine adjustment, denoted VVT 30 / 30, which generates a 3 1 valve crossover phase. In this adjustment, the exhaust valve lifts are delayed by 30°Vil compared to the VVT ​​0 / 0 adjustment and the intake valve lifts are advanced by 30°Vil. The following valve timing values ​​are thus obtained for the VVT ​​30 / 30 adjustment: the AOE is equal to 0°Vil, the AOA is equal to 15°Vil and the RFE is equal to 20°Vil. Figure 5 illustrates the valve timing diagram and valve timings used according to the method of the invention. In the figures, the same elements have the same references.

[0079] According to the invention, the timing of the exhaust camshaft is characterized by very early opening and closing of the exhaust valves.

[0080] According to the method of the invention, an early opening relative to the bottom dead center of the exhaust of at least one exhaust valve of the cylinder is started with an advance of the opening at the exhaust AOE having a value greater than 50°Vil.

[0081] In the example shown, the AOE is equal to 70°Vil.

[0082] According to the method of the invention, the early closing of said exhaust valve is completed relative to the top dead center of the crossover with an advance of the exhaust closure AFE having a value greater than 35°Vil.

[0083] In the example shown, the AFE is equal to 50°Vil.

[0084] Opening the exhaust valves early interrupts the gas expansion phase, thus degrading engine efficiency and causing higher exhaust gas temperatures.

[0085] The early closing of the exhaust valves causes a gas re-compression phase 32 at the end of the combustion chamber emptying. The gas re-compression phase 32 has the effect of increasing both the gas temperature and the degradation of the efficiency by the resistive work of the piston. For this effect to be significant, it is necessary to provide an exhaust closing advance greater than 35 °Vil.

[0086] 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 in communication, that is to say in such a way as to avoid any crossover phase between the exhaust valves and the intake valves. The method of the invention makes it possible to increase thermal losses by two combined effects.

[0087] The first effect is linked to the degradation of efficiency caused by the reduction in energy recovered from the piston during the expansion phase and by the re-compression phase at the end of exhaust emptying. As with under-advanced ignition, more fuel must be injected and burned to ensure the same level of torque. This additional thermal energy will be partly reflected in thermal losses.

[0088] The second effect is linked to the increase in heat exchange 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 drain and on the intake phase because part of the burnt and very hot gases from the re-compression of the exhaust phase are recirculated. This second effect is all the more important at low engine loads because the rate of burnt and recirculated gases at the intake is the highest there. 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.

[0089] Figure 6 illustrates the evolution of the thermal loss coefficient sth as a function of the valve timing at the exhaust of the engine used according to the invention. The thermal loss coefficient Sth is the ratio between the power of the thermal losses and the chemical power introduced by the injected fuel. Figure 6 highlights that the share of thermal losses increases when there is a recompression of the burnt gases at the end of the exhaust drain. Furthermore, it will be noted that the thermal loss coefficient hardly varies with the ignition under-advance.

[0090] The two effects described above can be coupled if necessary with a greater under-advance on ignition by taking advantage of the fact that the hot gases recirculated to the intake make it possible to tolerate lower advances when cold thanks to the heating of the combustion chamber. Figure 7 is the flowchart of a method according to an embodiment of the invention.

[0091] 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.

[0092] Depending on the measured temperature T, the process continues with a step of adjusting the engine according to a first or second adjustment mode.

[0093] 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 engine is adjusted according to the first adjustment mode (step 34). According to the first adjustment mode, the valve timing of the engine 1 is controlled by the electronic control unit 21 with an exhaust opening advance AOE greater than 50°V11, an exhaust closing advance AFE greater than 35°V11 and an intake opening delay ROA greater than 25°V11. The first adjustment mode aims to increase the quantity of calories from the engine 1 used by the vehicle's heating system to heat the passenger compartment.

[0094] 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 engine is carried out according to the second adjustment mode (step 35).

[0095] According to the second adjustment mode, the valve timing of the engine 1 is controlled by the electronic control unit 21 with an advance of the exhaust opening AOE equal to a value less than 50°Vil, an advance of the exhaust closing AFE equal to a value less than 35°Vil.

[0096] For example, the second tuning mode may include valve timings that allow for crossover phasing of the exhaust valves and intake valves to improve fuel consumption.

[0097] For example, the second adjustment mode may include valve timings that prevent the recirculation of burnt gases at the intake, and which are particularly advantageous during the engine start, shutdown and stop phases. For example, the exhaust valve timing and the associated intake valve timing may be, 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 the timings 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 setting constitutes a reference or “rest” position that is mechanically fixed when the engine starts, stops or is stopped, in order to control the camshaft timing in the phases where a minimum oil pressure level 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

CLAIMS 1. Method for controlling a spark-ignition internal combustion engine (1) operating according to a four-stroke cycle of a motor vehicle comprising a heating system configured to recover thermal energy from the engine (1) in order to heat the passenger compartment of the vehicle, characterized in that it comprises the following steps: a step of measuring the temperature (T) of a coolant of the engine, a step of adjusting the engine according to a first adjustment mode carried out if the measured temperature (T) is less than or equal to a first predefined threshold value (Tl) and as long as the measured temperature (T) remains less than a second predefined threshold value (T2) greater than the first (Tl), and a step of adjusting the engine according to a second adjustment mode if the measured temperature (T) is greater than said first threshold value (Tl) or if the measured temperature (T) is greater than or equal to said second threshold value (T2);said first adjustment mode aiming to increase the quantity of calories from the engine (1) used by the vehicle heating system by the timing of the engine valves with an advance of the exhaust opening (AOE) equal to a value greater than 50°Vil and an advance of the exhaust closing (AFE) equal to a value greater than 35°Vil, said second adjustment mode comprising the timing of the engine valves with an advance of the exhaust opening (AOE) less than 50°Vil, an advance of the exhaust closing (AFE) equal to a value less than 35°Vil.; 2. Method according to claim 1 in which the first adjustment mode uses an intake opening delay (ROA) equal to a value greater than 25°Vil.

3. Method according to claim 2, in which the first adjustment mode uses an advance of the exhaust opening (AOE) equal to 70°Vil, an advance of the exhaust closing (AFE) equal to 50°Vil and a delay of the opening at the admission (ROA) equal to 30°Vil.

4. 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 timings of the first adjustment mode.

5. The method of claim 4, wherein the exhaust valve timing and the intake valve timing of the second adjustment mode are mechanically fixed when the engine starts, stops or is stopped.

6. 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 controlling 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 control method according to any one of claims 1 to 5.

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