Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B77/00—Component parts, details or accessories, not otherwise provided for
  • F02B77/08—Safety, indicating, or supervising devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B37/00—Engines characterised by provision of pumps driven at least for part of the time by exhaust
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2200/00—Input parameters for engine control
  • F02D2200/70—Input parameters for engine control said parameters being related to the vehicle exterior
  • F02D2200/703—Atmospheric pressure
  • F02D2200/704—Estimation of atmospheric pressure

Definitions

• the present invention relates to the measurement of ambient pressure in a turbocharged engine.
• An atmospheric or turbocharged engine is sensitive to ambient atmospheric pressure. Indeed, depending on this, the filling of the engine cylinders is not done in the same way.
• the pressure at the intake manifold is little different from atmospheric pressure and variations in the pressure in the manifold relative to atmospheric pressure are fairly well known, depending in particular on the engine load and its diet. In such an engine, knowing the pressure in the intake manifold therefore makes it possible to know the ambient pressure by taking into account a few parameters.
• a butterfly regulating the air flow supplying the engine. Upstream of this butterfly is a heat exchange chamber called an intercooler supplied by a compressor of the turbocharger and downstream of the butterfly is the intake manifold.
• the pressure in the engine is therefore strongly influenced by the turbocharger's compressor. It is therefore usual, in order to be able in particular to estimate the overpressure provided by the turbocharger, to provide a turbocharged engine with an external pressure sensor. For engine regulation, there is also a pressure sensor at the heat exchange chamber and also another at the intake manifold.
• the turbocharger boost pressure, upstream of these chambers, is highly variable and a priori prevents any measurement of the ambient pressure in the heat exchange chamber or in the intake manifold except in special cases where this boost pressure is negligible (or known).
• the present invention aims to provide, for a turbocharged engine, a method for determining the ambient pressure without however using a specific sensor. To this end, it proposes a method for determining the ambient pressure in a turbocharged engine having a throttle valve placed between a heat exchange chamber and an intake manifold, a compressor being provided for compressing the air in the chamber. heat exchange and the engine being equipped with means for indicating the pressure prevailing in the heat exchange chamber. According to the invention, this method comprises the following steps: - detection of a throttle opening,
• This process for determining the ambient pressure is based on the observation that when the butterfly valve opens, the pressure in the heat exchange chamber decreases first, passes through a minimum value and then increases beyond its initial value . It has been noted that this pressure then drops below the ambient pressure value and then rises above it. Thus the pressure in the heat exchange chamber, during an opening of the butterfly valve, takes at two separate instants the value of the ambient pressure. It is therefore sufficient to read the pressure in the heat exchange chamber when it is equal to the ambient pressure to know the latter. As the variation of the pressure in the heat exchange chamber during such an opening is always of the same type, this determination for a given engine is possible from calibration measurements carried out once and for all during the development of the engine.
• a preferred embodiment of the present invention chooses as a remarkable point the point of the curve corresponding to the minimum value of the pressure measured just after opening of the butterfly.
• the ambient pressure is then determined, in this preferred embodiment, by measuring the pressure in the heat exchange chamber after a predefined period of time after detection of this minimum value.
• the time period is here advantageously defined as a function of the engine speed.
• the method according to the invention as described above provides for the determination of the ambient pressure during the opening of the butterfly. This normally happens quite frequently when traveling by car. For example, the determination of the ambient pressure can be done at each gear change.
• the invention further proposes to also determine the ambient pressure under other conditions in order to be able to give information about this pressure more often to the device for managing and controlling the corresponding engine. It is thus possible to also determine the ambient pressure before starting the engine, this ambient pressure then being equal to the pressure prevailing in the heat exchange chamber.
• the ambient pressure can also be measured when the throttle valve is closed, the pressure difference between the pressure measured in the heat exchange chamber and the ambient pressure then being known as a function of the engine speed.
• This pressure difference varies from one engine to another, but it is possible to calibrate it for one engine.
• the ambient pressure can for example be calculated in open loop in being decreased by a value given by time interval. It is therefore assumed that the corresponding vehicle is climbing a hill and therefore the ambient pressure decreases as the vehicle gains altitude.
• FIG. 1 schematically represents an air supply system for a turbocharged engine
• FIGS. 2 to 4 are diagrams representing on the same graph, in different situations, the positions of the throttle valve of FIG. 1 and the pressures in the heat exchange chamber 16 and in the intake manifold of this FIG. 1.
• FIG. 1 very schematically represents an air supply system for a turbocharged engine.
• a piston 2 which can move in a cylinder
• a valve 6 controls the admission of air into the cylinder 4.
• a valve 8 is provided for the exhaust of burnt gases from the cylinder 4.
• the engine corresponding comprises for example several cylinders.
• the feed system is common to all cylinders or to a series of cylinders.
• the air supply system shown in Figure 1 comprises, from upstream to downstream, an air inlet 10, a mass air flow meter 12, a compressor 14 of a turbocharger, a heat exchange chamber 16 called an intercooler 16, a butterfly valve 18 acting on the air flow section and an intake manifold also called a manifold 20.
• the intake valves 6 are in direct connection with the intake manifold 20.
• the ambient pressure AMP is used by a motor control and management device.
• this ambient pressure value influences the air intake on one side and the exhaust of the burnt gases on the other.
• the external pressure On the air intake side, when the external pressure is lower, for example at altitude, the filling of the cylinders is less good.
• the exhaust side On the exhaust side, the external pressure also influences the back pressure prevailing at the exhaust valves 8.
• this value of the ambient pressure is important for perfectly knowing the air flow flowing in the system engine air supply.
• the heat exchange chamber 16 collects the air leaving the compressor 14 of the turbocharger. As indicated above, this heat exchange chamber 16 is placed upstream of the butterfly valve. Conventionally, for controlling the engine, a pressure sensor is used which measures the pressure prevailing in the heat exchange chamber 16. This pressure is sometimes also called BOP for Boost Over Pressure.
• a first strategy already known from the prior art, consists in measuring the pressure in the heat exchange chamber 16 when the engine is stopped, or possibly during starting. Under these conditions, it is clear that the pressure in the entire air supply system of the engine is equal to the ambient pressure AMP prevailing outside the engine. It is therefore easy to start the vehicle to know the ambient pressure AMP. Depending on this pressure, the quantity of fuel to be injected into the engine is then determined for the starting phase.
• the driver generally wants to leave and therefore presses the accelerator. This causes an opening of the butterfly 18.
• This situation is shown diagrammatically in FIG. 2.
• the first curve 22 in this figure represents the opening angle of the butterfly. It is assumed here that this butterfly passes from the closed position to the open position . It is assumed in Figure 2 that before the opening of the butterfly 18, a steady state was established in the air supply system.
• a curve 24 represents the MAP pressure JP in the heat exchange chamber 16 while a curve 26 symbolizes the MAP pressure in the intake manifold 20.
• the butterfly valve 18 is closed, the value of the pressure prevailing in the chamber heat exchange 16 is slightly higher than the ambient pressure AMP.
• the throttle valve 18 is closed, the engine is substantially idle and the overpressure created by the turbocharger is relatively low.
• the MAP pressure is lower. Indeed on one side the air from the intake manifold 20 is sucked in by the movement of the pistons 2 in the cylinders 4 and on the other side the inlet of the intake manifold 20 is closed by the butterfly valve. vacuum is therefore established in the intake manifold 20.
• the throttle valve 18 opens, the pressure in the intake manifold 20 increases immediately following a call for air at the heat exchange chamber 16 due to depression.
• the pressure MAPJJP prevailing in the heat exchange chamber 16 decreases during the opening of the butterfly valve 18 because in fact the heat exchange chamber 16 is connected to the intake manifold 20 in depression, thus inducing a pressure drop.
• This pressure then increases again and in steady state the value of the pressure prevailing in the heat exchange chamber 16 equals that of the pressure in the intake manifold 20 since the corresponding chambers are in free communication, the butterfly 18 being open and not obstructing the free circulation of air from the heat exchange chamber 16 to the intake manifold 20.
• the opening of the butterfly valve 18 creates a greater flow of air in the engine and therefore also a greater flow of burnt gases at the exhaust.
• the turbocharger is driven and the compressor 14 compresses the air entering through the air inlet 10.
• the pressures prevailing in the intake manifold 20 and in the heat exchange chamber 16 become greater than the ambient pressure AMP.
• the invention proposes in one embodiment to determine the instant at which the value of the pressure prevailing in the heat exchange chamber 16 is minimum.
• the pressure prevailing in the heat exchange chamber 16 then takes the value of the ambient pressure AMP after a certain time interval ⁇ t.
• the value of ⁇ t depends essentially on the engine speed N.
• This calculation method can be integrated into an algorithm and programmed into the engine management and control device. It is here provided to store the result of each determination of the ambient pressure AMP carried out. We do not necessarily keep in memory all the measurements made, but at least the last of them. This value of the ambient pressure AMP is then called AMP n-1 .
• the engine management and control device detects an opening of the throttle valve 18, the pressure MAPJJP prevailing in the heat exchange chamber 16 is monitored. It is then verified in particular that this value becomes less than the stored value AMP n- ⁇ . The instant at which the value of the pressure MAPJJP prevailing in the heat exchange chamber 16 becomes minimum is then determined.
• the value of the newly measured ambient pressure, AMP n is the value of the pressure prevailing in the heat exchange chamber 16 at time t 0 + ⁇ t, where t 0 is the time at which the value of the pressure prevailing in the heat exchange chamber 16 is minimum.
• the value of ⁇ t is supplied by the control and management device according to the engine speed. This value is of the order of a few milliseconds to a few tens of milliseconds.
• ⁇ P ⁇ P ⁇ -4 mbar at idle and ⁇ P ⁇ -14 mbar at around 6000 rpm.
• a curve 22 ' illustrates the opening angle of the butterfly valve 18 and the curves 24' and 26 'respectively represent the values of the pressure MAPJJP prevailing in the heat exchange chamber 16 and of the MAP pressure in the intake manifold 20. It is noted that the MAPJJP pressure prevailing in the heat exchange chamber 16 passes through a maximum value just after the butterfly valve is closed 18. This is explained in particular by the fact that when the butterfly 18 is closed, the air which previously circulated freely from the heat exchange chamber 16 to the intake manifold 20, is suddenly blocked by the butterfly 18. This air therefore accumulates in the chamber heat exchange 16 creating an overpressure therein. The value of the MAP pressure in the intake manifold 20 logically decreases since the air supply to the intake manifold 20 and the movement of the pistons 2 in the cylinders 4 continues to draw air out of this intake manifold 20.
• a final strategy can be implemented to supply a value of the ambient pressure AMP to the engine control and management device.
• This fourth strategy is implemented when the previous three cannot be, that is to say in the case where the butterfly 18 remains constantly in an intermediate position and the driver does not move his foot from the accelerator .
• This case typically corresponds to the ascent of a regular hill. This very rarely happens. In fact, in the mountains the slope is not always regular and this causes gear changes. Even if this case is not frequent, it can be foreseen here.
• the regulation is then done in open loop. It is estimated here that the vehicle climbs a substantially constant gradient. It is then possible to estimate the variation in altitude of the vehicle as a function for example of its speed.
• a variation in the ambient pressure of the order of 1 mbar per minute can be provided. This corresponds to an altitude change of 10 meters every minute. This is the case when climbing a hill at 10% at a speed of 60 km / h. This open loop measurement is then carried out until the butterfly 18 opens or closes again.
• the method according to the invention can then be used to control the sensors giving the ambient air pressure and the pressure inside the heat exchange chamber 16.
• the present invention is particularly advantageous in an engine equipped with an electrically controlled throttle valve. Indeed, in such an engine, it is necessary to have a sensor making it possible to measure the pressure in the heat exchange chamber 16.
• the present invention is not limited to the embodiment described above by way of nonlimiting example. On the contrary, it relates to all the variant embodiments within the reach of those skilled in the art. Thus for example other strategies could be implemented to determine the pressure of the ambient value.
• the present invention relates to essentially the determination of this ambient pressure during an opening of the throttle valve. In the strategy described in relation to such an opening, the determination of the ambient pressure can be carried out differently.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Supercharger (AREA)
• Output Control And Ontrol Of Special Type Engine (AREA)
• Combined Controls Of Internal Combustion Engines (AREA)
• Control Of Throttle Valves Provided In The Intake System Or In The Exhaust System (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2003
  • 2003-03-26 FR FR0303702A patent/FR2853012B1/fr not_active Expired - Lifetime
• 2004
  • 2004-03-19 KR KR1020057017956A patent/KR101135228B1/ko active IP Right Grant
  • 2004-03-19 EP EP04721829A patent/EP1606501A1/fr not_active Withdrawn
  • 2004-03-19 JP JP2006504747A patent/JP4490416B2/ja not_active Expired - Fee Related
  • 2004-03-19 US US10/550,686 patent/US7293452B2/en not_active Expired - Fee Related
  • 2004-03-19 WO PCT/EP2004/002887 patent/WO2004085811A1/fr active Application Filing

Non-Patent Citations (1)

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