Method for controlling a motor vehicle engine with at least one engine regulation mode for increasing the amount of thermal energy used in a vehicle heating system - Patents.com

Abstract

The present invention relates to a method for controlling a controlled ignition internal combustion engine of a vehicle equipped with a heating system configured to recover thermal energy of the engine for heating the passenger compartment of the vehicle, comprising the following steps: measuring the temperature of the coolant of the engine; adjusting the engine according to a first mode, which is executed if the measured temperature is less than or equal to a first predetermined value and as long as the measured temperature remains less than a second predetermined value higher than the first predetermined value; and adjusting the engine according to a second adjustment mode if the measured temperature is higher than the first value or if the measured temperature is greater than or equal to the second value, the first adjustment mode being aimed at increasing the amount of heat emitted from the engine.

Description

[Technical Field]

[0001] The present invention relates to vehicles equipped with spark ignition engines, and in particular to strategies for improving passenger compartment heating functions. [Background technology]

[0002] Heat losses from the motor vehicle engine are conventionally used to heat the passenger compartment by means of a special heat exchanger, known as an air heater, associated with the engine cooling circuit.

[0003] To comply with increasingly stringent environmental standards, vehicle manufacturers seek to optimize internal combustion engines to reduce fuel economy and consequently pollutant emissions.

[0004] These developments in internal combustion engines have a direct impact on air conditioning, since optimizing an internal combustion engine means maximizing its combustion efficiency and consequently minimizing its heat loss or rejection, which means a reduction in the passenger compartment heating function.

[0005] When started in low temperatures, especially below zero, newer, more efficient engines take longer to warm up and therefore do not produce enough heat to adequately heat the passenger compartment.

[0006] The classic solution to accelerating engine warm-up during a cold start is to reduce the ignition timing.

[0007] In fact, by deviating from the optimum spark advance that maximizes torque and efficiency, more fuel must be burned to achieve the same level of torque. As a result, the engine heats up more quickly and consumes more fuel. Despite the extra fuel consumption involved, the strategy of reducing spark advance also has its limitations: the advance cannot be reduced very sharply during a cold start due to the risk of combustion instability. Therefore, the desired level of cabin heating performance cannot be achieved using spark advance reduction alone. Summary of the Invention

[0008] In view of the above, it is an object of the present invention to improve passenger compartment heating in motor vehicles equipped with high efficiency engines.

[0009] The subject of the present invention is a method for controlling a spark-ignition internal combustion engine operating according to a four-stroke cycle in a motor vehicle equipped with a heating system configured to recover thermal energy from the engine in order to heat the passenger compartment of the vehicle.

[0010] The process involves the following steps: measuring the temperature (T) of the engine coolant; adjusting the motor according to a first adjustment mode, which is performed when the measured temperature (T) is equal to or less than a first predetermined threshold (T1) and as long as the measured temperature (T) remains below a second predetermined threshold (T2) higher than the first predetermined threshold (T1); adjusting the motor in a second adjustment mode when the measured temperature (T) is higher than the first threshold (T1) or when the measured temperature (T) is equal to or higher than the second threshold (T2); Equipped with.

[0011] The first adjustment mode aims to increase the amount of engine heat used by the vehicle's heating system by adjusting the engine valve timing to an exhaust opening advance of more than 50° Vil and an exhaust closing advance of more than 35° Vil.

[0012] The second adjustment mode consists of timing the engine valves to an exhaust opening advance of less than 50° Vil and an exhaust closing advance of less than 35° Vil.

[0013] According to an advantageous feature, the first adjustment mode uses an intake opening retard of greater than 25° Vil. By using such an exhaust closing retard (known as ROA for short), there is no overlap between the intake and exhaust valves, which maximizes the effect of the recompression phase at the end of the exhaust removal.

[0014] For example, the first adjustment mode uses an exhaust opening advance angle equal to 70° Vil, an exhaust closing advance angle equal to 50° Vil, and an intake opening retard angle equal to 30° Vil. Thus, the first setting mode increases the thermal energy recovery of the engine.

[0015] For example, in the second setting mode, the exhaust valve timing and associated intake timing are retarded by an additional 40° Vil and advanced by an additional 15° Vil, respectively, compared to the timing in the first setting mode. Using these settings, exhaust gas recirculation is avoided when the engine temperature is high enough.

[0016] Advantageously, in the second adjustment mode the exhaust valve timing and intake timing are mechanically fixed when the engine is started, stopped or shut down.

[0017] According to another aspect, the present invention relates to a motor vehicle including a spark ignition internal combustion engine, the spark ignition internal combustion engine having at least one cylinder, the cylinder including at least one exhaust valve and at least one associated intake valve, the engine including means for measuring a temperature of a coolant of the engine, and the vehicle including a heating system configured to recover thermal energy from the engine for heating a passenger compartment of the vehicle.

[0018] The engine further comprises an engine control system comprising means for controlling a variable intake valve timing system of the engine and means for controlling a variable exhaust valve timing system of the engine, the control system being adapted to modify the timing of the valves in accordance with the control method described above.

[0019] Further objects, features and advantages of the present invention will become apparent from the following description, given by way of non-limiting example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0020] [Figure 1] 1 shows a schematic representation of the architecture of an internal combustion engine used to implement the process according to the invention; [Figure 2] An example of a dual variable valve timing system for the engine shown in Figure 1 is shown. [Figure 3] 1 shows valve timing diagrams and valve lift conventionally used in engine tuning without camshaft offset phasing. [Figure 4] 1 shows a known engine setup with valve overlap phasing. [Figure 5] 1 shows a valve timing diagram and valve lift used in the process according to the present invention; [Figure 6] 1 shows the progression of the heat loss coefficient ε th as a function of exhaust valve timing for an engine used according to the invention. [Figure 7] 1 is a flowchart of a process according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] In the example shown in FIG. 1 , the motor vehicle internal combustion engine 1 is of the spark ignition type and illustratively includes a line of three cylinders 2, a fresh air intake manifold 3, an exhaust manifold 4, a turbo compression system or turbo compressor 5, a variable valve timing system 6 for the engine intake valves 7, and a variable valve timing system 8 for the engine exhaust valves 9. The variable intake valve timing system 6 is equipped with a sensor 10 which makes it possible to constantly know the angular position of the intake valve 7 corresponding to a particular opening and closing moment in the engine's combustion cycle. The variable exhaust valve timing system 8 is also equipped with a sensor 11 which also makes it possible to determine at any time the angular position of the exhaust valve 9 corresponding to a particular opening or closing moment in the engine's combustion cycle.

[0022] The cylinders 2 are supplied with air via an intake manifold 3 or distributor, which itself is supplied by a line 12 to which an air filter 13 and a compressor 5a of a turbocharger 5 of the engine 1 are attached.

[0023] The turbocharger 5 basically comprises a turbine 5b driven by the exhaust gases and a compressor 5a mounted on the same shaft as the turbine 5b, which compresses the air distributed by the air filter 13 or wind box in order to increase the amount of air (mass flow) drawn into the cylinders 2 of the engine 1 for the same volumetric flow rate.

[0024] The internal combustion engine 1 comprises an intake circuit Ca and an exhaust circuit Ce.

[0025] The intake circuit Ca is arranged from upstream to downstream in the direction of air flow: -Air filter 13, a flow meter 14 located in the intake pipe 12 downstream of the air filter 13, for measuring the actual value of the mass flow of air entering the engine 1; -Air intake valve 15, - turbocharger 5 compressor 5a, - throttle valve 16, i.e. engine intake valve, a heat exchanger 17 configured to cool the intake gas corresponding to the mixture of fresh air and recirculated gas after their compression in the compressor 5a, and -Intake manifold 3 Equipped with.

[0026] The exhaust circuit Ce is arranged from upstream to downstream in the direction of combustion gas flow: -Exhaust manifold 4, - the turbine 5b of the turbocharger 5, and - Engine exhaust pollution control systems such as three-way catalytic converters (not shown) Equipped with.

[0027] The exhaust manifold 4 collects the exhaust gases produced by the combustion and discharges them to the outside via an exhaust gas duct 18 opening at the inlet to the turbine 5b of the turbocharger 5 and via an exhaust line 19 attached downstream of the turbine 5b.

[0028] Engine 1 may include a partial exhaust gas recirculation (EGR) circuit (not shown).

[0029] The engine 1 is associated with a fuel circuit comprising, for example, fuel injectors (not numbered) that inject fuel directly into each cylinder from a fuel tank (not shown). The fuel may be gasoline, alcohol or liquefied petroleum gas.

[0030] The engine 1 is equipped with a cooling circuit (not shown) associated with a heat exchanger or unit heater (not shown) used to heat the passenger compartment of the vehicle.

[0031] The engine 1 is equipped with a sensor 20 for the temperature of the engine coolant, which is indicative of the temperature of the engine 1 .

[0032] Additionally, the engine includes an electronic control unit 21 configured to control various elements of the internal combustion engine based on data collected by sensors at various locations in the engine.

[0033] FIG. 2 shows a schematic representation of a variable timing system 6 for intake valves 7 of engine 1 and a variable timing system 8 for exhaust valves 9 of engine 1 .

[0034] In the example shown, the engine 1 comprises three cylinders 2, each having a piston 22, two inlet valves 7 and two exhaust valves 9.

[0035] In another variation, the engine is fitted with a single intake valve and a single exhaust valve for each cylinder.

[0036] Other valve configurations are possible without departing from the scope of the present invention.

[0037] The variable timing system 6 for the intake valves 7 of the engine includes a shifter 23 connected to an intake camshaft 24 .

[0038] A variable timing system 8 for the exhaust valves 9 of the engine includes a shifter 25 connected to an exhaust camshaft 26 .

[0039] Each shifter 23, 25 has two concentric wheels whose lobes are separated by an oil chamber. One wheel, called the stator, is integral with the timing gear, and the other wheel, called the rotor, is integral with the camshaft.

[0040] When the solenoid valve 27 moves pressurized oil into the oil chamber, the lobe moves angularly, driving the camshaft in rotation.

[0041] An electronic control unit 21 of the engine 1 can drive the solenoid valves 10 to control the angular displacement of the lobes and thereby the offset of each camshaft.

[0042] Alternatively, the offset control can be performed by an electrical control system controlled by the electronic control unit 21 of the engine 1 .

[0043] Variable valve timing (VVT) is a technology used in virtually all spark ignition engines that allows the camshafts to be angularly offset.

[0044] The timing diagram is defined by the angular position of the crankshaft corresponding to the valve opening and closing. The angular position of the crankshaft is measured in crankshaft degrees. A crankshaft degree, denoted as "°Vil", corresponds to the time it takes for the crankshaft to rotate through one degree of angle. One engine revolution is 360°Vil. In particular, a complete combustion cycle for a four-stroke engine corresponds to two revolutions, which is equivalent to 720°Vil.

[0045] For example, VVT30 / 40 is an offset of 30° Vil relative to the intake camshaft in the direction of advancing intake valve opening / closing in the combustion cycle, and an offset of 40° Vil relative to the exhaust camshaft in the direction of retarding exhaust valve opening / closing in the combustion cycle.

[0046] FIG. 3 shows the valve timing diagram and valve lift conventionally used in engine tuning without camshaft offset phasing. By convention, the threshold required for valve opening / closing corresponds to 0.7 mm in the example shown. Any lift below 0.7 mm therefore corresponds to a closed valve. Conversely, for a lift of 0.7 mm or more, the valve is considered open. Naturally, the value of this valve open / close threshold may vary and take other values ​​without affecting the generality of the invention.

[0047] FIG. 3 shows the complete combustion cycle in four successive stages: compression, expansion, exhaust and intake.

[0048] More specifically, it comprises four successive phases: an intake phase, a compression-ignition phase, a combustion-expansion phase, and an exhaust phase.

[0049] During the intake phase, the piston descends from overlap TDC to intake TDC, creating a vacuum in the cylinder and drawing air in. The intake pressure shown in Figure 3 is well above atmospheric pressure due to the supercharging provided by the compressor 5a.

[0050] During the compression-ignition phase of the air / fuel mixture recently injected into the combustion chamber, the mixture is compressed with the valve closed as the piston rises from intake bottom dead center (BDC) to combustion top dead center (TDC). Spark plug controlled ignition usually occurs a short time before the combustion TDC, usually 10-20°Vil before said TDC, to allow for the time required for combustion to progress.

[0051] In the combustion-expansion phase, combustion progresses, the pressure rises rapidly to a maximum, the gases become very hot, and heat transfer to the cylinder wall is strong. The piston then drops towards the exhaust PMB, reducing the pressure and temperature of the gases as work is transferred to the piston.

[0052] In the exhaust phase, the gases are expelled first under their own pressure and then under the thrust of the piston as it rises to TDC.

[0053] Curve 28 shows the pressure variations in the combustion chamber of the cylinder of engine 1 during the engine cycle described above.

[0054] Curves 29 and 30 show the lift of the exhaust valve 9 and the intake valve 7 respectively.

[0055] The distribution characteristics shown are exhaust opening advance (AOE), exhaust closing advance (AFE), and intake opening retard (ROA). AOE is measured relative to exhaust TDC. The AFE and ROA are measured relative to the crossover TDC.

[0056] By convention, advance is considered positive when the valve concerned opens or closes before reference dead center. By convention, retard is considered positive when the valve concerned opens or closes after reference dead center.

[0057] In the example shown in Figure 3, AOE is equal to 30° Vil, AFE is equal to 10° Vil and ROA is equal to 15° Vil. This motor setting constitutes the reference or "rest" position VVT0 / 0.

[0058] In current engines, the camshaft angle timing at this VVT 0 / 0 position is characterized by no overlap phase between the exhaust and intake valves at overlap TDC. The absence of overlap phases avoids undesirable combustion gas transfer to the intake during engine start and shut-down phases due to insufficient richness control.

[0059] On the other hand, overlap phasing between the exhaust and intake valves is required at other engine operating points where the intake pressure is lower than the exhaust pressure in order to recirculate the burnt gases back to the intake, thereby reducing fuel consumption by reducing pumping losses due to the larger throttle body opening.

[0060] FIG. 4 shows an example of an engine setting VVT30 / 30 that produces a valve overlap phase 31. In this setting, the exhaust valve lift is retarded by 30°Vil compared to the VVT0 / 0 setting, and the intake valve lift is advanced by 30°Vil. This gives the following valve timing values ​​for a VVT30 / 30 setting: AOE equals 0°Vil, AOA equals 15°Vil, and RFE equals 20°Vil.

[0061] Figure 5 shows the timing diagram and valve lift used in the present invention, in which like elements are numbered likewise.

[0062] In accordance with the present invention, exhaust camshaft timing is characterized by very early opening and closing of the exhaust valves.

[0063] According to the process of the present invention, early opening of at least one cylinder exhaust relative to exhaust bottom dead center is initiated with the exhaust opening advance AOE having a value greater than 50° Vil.

[0064] In the example shown, the AOE is equal to 70° Vil.

[0065] According to the method of the present invention, the early closing of the exhaust relative to top dead center is completed with the AFE exhaust closing advance having a value greater than 35° Vil.

[0066] In the example shown, AFE is equal to 50° Vil.

[0067] Premature opening of the exhaust port interrupts the gas expansion phase, reducing engine efficiency and producing higher exhaust gas temperatures.

[0068] The early closing of the exhaust port creates a gas recompression phase 32 at the end of the combustion chamber emptying. The gas recompression phase 32 has the effect of increasing both gas temperature and reducing efficiency through piston drag effects. To make this effect significant, an exhaust closure advance of more than 35° Vil is required.

[0069] According to the process of the present invention, the intake valve opening is advantageously retarded with an ROA greater than 25° Vil to prevent communication between the intake and exhaust ports, i.e., to avoid overlapping phases between the exhaust and intake ports.

[0070] The treatment of the present invention increases heat loss through two combined effects.

[0071] The first effect is related to the loss of efficiency caused by the reduction in energy recovered from the piston during the expansion phase and the recompression phase at the end of the exhaust discharge. As in the case of under-ignition, more fuel must be injected and burned to ensure the same level of torque, and some of this additional heat energy is lost.

[0072] The second effect is related to the increased heat exchange between the gases in the cylinder and certain engine parts such as the barrel, cylinder head and piston. This second effect is localized during the recompression phase at the end of the exhaust discharge and during the intake phase, due to the recirculation of some of the very hot burned gases from the recompression exhaust phase. This second effect is most important at low engine loads, where the ratio of burned gases to recirculated gases is highest. It is at these operating points that the need for heat to heat the passenger compartment becomes critical due to the relatively low amount of fuel.

[0073] FIG. 6 shows the heat loss coefficient ε as a function of exhaust valve timing in an engine used in accordance with the present invention. th The transition of the heat loss coefficient ε th is the ratio of the thermal power lost to the chemical power introduced by the injected fuel. Figure 6 shows that the rate of heat loss increases when the exhaust gases are recompressed at the end of the exhaust discharge. It should also be noted that the heat loss coefficient varies little with under-advance ignition.

[0074] Taking advantage of the fact that hot gases recirculated at the intake can tolerate a smaller cold advance due to heating of the combustion chamber, the two effects described above may be combined with a larger under-advance spark, if desired.

[0075] FIG. 7 shows a flowchart of a process according to one embodiment of the present invention.

[0076] The process begins with step 33, in which the temperature T of the coolant in the engine 1 is measured. In this step, the electronic control unit 21 measures the temperature T using the sensor 20 installed in the engine 1.

[0077] Depending on the measured temperature T, the process continues with the motor regulation step in either the first or second regulation mode.

[0078] If the measured temperature T is less than or equal to a first predetermined threshold T1 and as long as the measured temperature T remains below a second predetermined threshold T2 that is higher than the first T1, the engine is regulated in a first regulation mode (step 34). In the first adjustment mode, the valve timing of the engine 1 is controlled by the electronic control unit 21 with an exhaust open advance AOE greater than 50°Vil, an exhaust close advance AFE greater than 35°Vil, and an intake open retard ROA greater than 25°Vil. The first regulation mode increases the amount of heat from the engine 1 that is used by the vehicle's heating system to heat the passenger compartment.

[0079] On the other hand, if the measured temperature T is higher than the first predetermined threshold T1 or if the measured temperature T is equal to or greater than the second predetermined threshold T2, the motor is regulated in the second regulation mode (step 35).

[0080] According to the second adjustment mode, the valve timing of the engine 1 is controlled by the electronic control unit 21 with an exhaust opening advance AOE equal to a value less than 50° Vil and an exhaust closing advance AFE equal to a value less than 35° Vil.

[0081] For example, the second adjustment mode may include valve timing that allows overlapping phasing between the exhaust and intake valves to improve fuel consumption.

[0082] For example, the second adjustment mode may include valve timing that prevents recirculation of burnt intake gases, which is of particular interest during the start, stop and shut-down phases of the engine. For example, the exhaust valve timing and associated intake valve timing in the second adjustment mode may be retarded by an additional 40°Vil and advanced by an additional 15°Vil, respectively, compared to the timing in the first adjustment mode, 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 is started, stopped, or shut down in order to progressively control camshaft timing when the minimum oil pressure level required for shifter control is not available. This reference position can be achieved, for example, by using a mechanical indexing pin to prevent rotation of one lobe of each shifter.

Claims

1. A method for controlling a spark ignition internal combustion engine (1) operating according to a four-stroke cycle of a motor vehicle, comprising: The motor vehicle includes a heating system configured to recover thermal energy from the engine (1) for heating a passenger compartment of the vehicle. Equipped with The control method is as follows: measuring the temperature (T) of the engine coolant; adjusting the motor according to a first adjustment mode, which is performed when the measured temperature (T) is equal to or less than a first predetermined threshold (T1) and as long as the measured temperature (T) remains below a second predetermined threshold (T2), which is higher than the first predetermined threshold (T1); adjusting the motor in a second adjustment mode when the measured temperature (T) is higher than the first threshold (T1) or when the measured temperature (T) is equal to or greater than the second threshold (T2); Including, the first adjustment mode is intended to increase the amount of heat from the engine (1) used by the vehicle's heating system by adjusting the timing of the engine valves to an exhaust opening advance (AOE) equal to a value greater than 50° Vil and an exhaust closing advance (AFE) equal to a value greater than 35° Vil; the second adjustment mode consists in timing the engine valves to an exhaust opening advance (AOE) less than 50° Vil and an exhaust closing advance (AFE) equal to a value less than 35° Vil; Control method.

2. The first adjustment mode uses a retarded intake opening angle (ROA) equal to a value greater than 25° Vil. The control method according to claim 1 .

3. The first adjustment mode uses an exhaust opening advance (AOE) equal to 70° Vil, an exhaust closing advance (AFE) equal to 50° Vil, and an intake opening retard (ROA) equal to 30° Vil. The control method according to claim 2 .

4. the exhaust valve timing and associated intake valve timing in the second adjustment mode are retarded by an additional 40° Vil and advanced by an additional 15° Vil, respectively, compared to the timing in the first adjustment mode; The control method according to any one of claims 1 to 3.

5. the exhaust valve timing and the intake valve timing in the second adjustment mode are mechanically fixed when the engine is started, stopped, or turned off; The control method according to claim 4.

6. A motor vehicle equipped with a spark ignition internal combustion engine (1), the engine comprises at least one cylinder; The cylinder is at least one exhaust valve; At least one associated intake valve and the engine includes means for measuring the temperature of the engine's coolant; the vehicle including a heating system configured to recover thermal energy from the engine to heat a passenger compartment of the vehicle; the engine further comprising an engine control system comprising means for controlling an intake variable valve timing system of the engine and means for controlling an exhaust variable valve timing system of the engine; The control system is adapted to modify the timing of the valve by a control method according to any one of claims 1 to 5. Motor vehicle.

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