EP2494161B1 - System and method for controlling the cooling circuit of an internal-combustion engine - Google Patents

Description

The technical field of the invention is the thermal management of an internal combustion engine, and more particularly the management of the cooling system as a function of the temperature of the internal combustion engine.

The invention makes it possible to improve the thermal management of the engine by the use of observers, especially in a context of discontinuity in the flow of the coolant.

The fuel consumption and pollutant production of an internal combustion engine is influenced by its operating temperature. In order to produce vehicles with reduced fuel consumption, it is important to control the temperature of an internal combustion engine so that it is at an optimum level during operation, especially during start-up.

This is the reason why it is customary to position the temperature sensor inside the cooling circuit passing through the cylinder head. If this sensor is additionally positioned inside the cylinder head, it then provides a relevant measurement of the temperature inside the internal combustion engine, including during a phase during which the flow of the liquid of cooling.

If, conversely, the sensor is not positioned inside the cylinder head, during a phase of zero flow of the coolant, the temperature thus measured is then not representative of the temperature inside. of the motor.

Moreover, it is known to use a cooling circuit containing two branches. A cooling branch passes through a radiator for lowering the temperature of the heat transfer fluid contained in the cooling circuit. Branch branch presents only a passive heat exchanger, type heater, limiting the cooling of the liquid.

The French patent application FR 2 908 458 describes several variants of the cooling branch and branch branch. This document notably describes how to limit or cut the circulation of the heat transfer fluid to the cooling branch, in particular to rapidly raise the temperature of an initially cold internal combustion engine. The means for achieving such operation is either a thermostatic valve, an electric valve controlled by control means, or a pump driven on command. However, the control means are not explained.

The French patent application FR 2 912 183 discloses a control device of an internal combustion engine comprising means for determining the temperature of the exhaust gas taking into account the quality of the fuel used.

The US patent application US 2004/0128059 describes a method for correcting the accuracy of the oil temperature measurement according to the operating phases of the internal combustion engine.

International patent application WO 2008/085400 discloses a control means adapted to control the cooling system of an internal combustion engine so that the temperature of said engine is lower than a given value, the control means being further able to trigger an automatic stop,

The French patent application FR 2 869 355 describes a management of the temperature of the coolant to improve the consumption, especially during cold starts. The temperature of the heat transfer fluid at the outlet of the engine does not allow a sufficiently precise characterization of the thermal state of the engine so as to ensure thermal safety of the most fragile parts, such as the inter-cylinder, however, the thermal characterization of these parts is difficult to achieve during operation of the vehicle.

The French patent application FR 2 869 355 proposes a predictive model making it possible to evaluate the specific value or values of the thermal state of the engine. The parameters measured may be the engine rotation speed, the engine load, and the flow rate or temperature of the heat transfer fluid entering the engine. The predictive model is based on the principle that there is a non-zero flow through the main circuit and that we have, at every moment, the temperature at the engine inlet.

The document US 2007/0175415 discloses a method and system for estimating the temperature of an internal combustion engine.

The document US 6394045 discloses a device for controlling the cooling of an internal combustion engine.

The document DE 102006009892 discloses a method and system for controlling the cooling of an internal combustion engine.

During a zero flow of the heat transfer fluid of an initially cold internal combustion engine, the temperature increases rapidly and makes it possible to reach the optimum temperature range more quickly. The quantity of unburned hydrocarbons emitted is then reduced.

However, it is necessary to ensure that the temperature of certain specific areas of the engine remains limited for reasons of reliability. In practice, these specific areas are the water core cylinder in the vicinity of the combustion chamber and the intersoupape bridge.

During a phase of zero flow of the coolant, for an architecture where the temperature sensor is located outside the cylinder head, the measured temperature is not representative of the temperature inside the engine, let alone , that of the specific area of interest of the engine.

In an architecture where the temperature sensor is located inside the cylinder head, it may be desirable to take this measurement into account in order to estimate more precisely the temperature of the specific zone of the engine.

There is therefore a need for a device and a method for controlling the cooling circuit of an internal combustion engine that does not depend on a temperature measurement of the coolant to estimate the thermal state of said engine.

The subject of the invention is a method for controlling a cooling circuit of an internal combustion engine according to claim 1.

The temperature inside the internal combustion engine can be determined by measurement, and a temperature characteristic of the thermal state of the specific zone of the internal combustion engine can be determined by applying a first model as a function of the temperature. inside the internal combustion engine.

The characteristic temperature of the specific zone thermal state of the internal combustion engine can be determined by application of a second model.

The second model is an autoregressive moving average model.

In an example not forming part of the invention, the specific zone whose characteristic temperature is determined may be the coolant at the cylinder head or in the vicinity of the combustion chamber.

In the present invention, the specific zone whose characteristic temperature is determined is the intersoupape bridge.

A control system for a heat transfer fluid cooling circuit of an internal combustion engine equipping a motor vehicle is defined, the control system comprising an electronic control unit able to switch a means for shutting down the flow of said cooling circuit. located downstream of the internal combustion engine.

The electronic control unit is able to determine a temperature characteristic of the thermal state of a specific zone of the internal combustion engine by application of a model, able to compare at a temperature characteristic of the thermal state of the specific zone. of the internal combustion engine at a limit temperature and adapted to switch the means for shutting off the flow rate in a passing position as a function of the characteristic temperature of the specific zone of the thermal state of the internal combustion engine and the limit temperature.

The electronic control unit may comprise comparison means able to compare the temperature characteristic of the thermal state of the specific zone of the internal combustion engine with the limit temperature, the electronic control imity being able to emit a signal of controlling the flow cut-off means according to the comparison result.

The control system may include a determining means adapted to apply a first model to determine the temperature characteristic of the thermal state of the specific zone of the internal combustion engine as a function of the temperature of the internal combustion engine.

The control system may comprise a temperature sensor located inside the internal combustion engine capable of determining the temperature of the internal combustion engine.

The temperature sensor can be located in the cylinder head.

The control system may comprise a determination means able to determine the temperature characteristic of the thermal state of the internal combustion engine by applying a second model.

The flow cutoff means may be a drive means of the pump adapted to drive said pump on command.

The flow cut-off means may be a valve placed at the output of the engine.

The specific area is the intersoupape bridge.

• la figure 1 illustre les principaux éléments compris dans un premier mode de réalisation d'un système de commande du circuit de refroidissement d'un moteur à combustion interne ;
• la figure 2 illustre les principales étapes d'un premier mode de réalisation d'un procédé de commande du circuit de refroidissement ;
• la figure 3 illustre plus en détail une des étapes comprises dans le premier mode de réalisation d'un procédé de commande du circuit de refroidissement ;
• la figure 4 illustre les principaux éléments compris dans un deuxième mode de réalisation d'un système de commande du circuit de refroidissement d'un moteur à combustion interne ;
• la figure 5 illustre les principales étapes d'un deuxième mode de réalisation d'un procédé de commande du circuit de refroidissement ; et
• la figure 6 illustre plus en détail une des étapes comprises dans le deuxième mode de réalisation d'un procédé de commande du circuit de refroidissement.

Other objects, features and advantages will appear on reading the following description given solely as a non-limitative example and with reference to the appended drawings in which:

• the figure 1 illustrates the main elements included in a first embodiment of a control system of the cooling circuit of an internal combustion engine;
• the figure 2 illustrates the main steps of a first embodiment of a control method of the cooling circuit;
• the figure 3 illustrates in greater detail one of the steps included in the first embodiment of a control method of the cooling circuit;
• the figure 4 illustrates the main elements included in a second embodiment of a control system of the cooling circuit of an internal combustion engine;
• the figure 5 illustrates the main steps of a second embodiment of a control method of the cooling circuit; and
• the figure 6 illustrates in more detail one of the steps included in the second embodiment of a control method of the cooling circuit.

The figure 1 illustrates a first embodiment of a control system of the cooling circuit of an internal combustion engine. An internal combustion engine 1 can be seen provided with a cooling circuit comprising a main circuit 2 and a secondary circuit 3.

The main cooling circuit 2 comprises a means 5 for shutting off the flow connected by its inlet to the internal combustion engine 1 via a pipe 4 and its outlet to a main radiator 7 via a pipe 6. The main radiator 7 is connected to the the inlet of a pump 10 via a pipe 8, the outlet of said pump 10 being connected to the internal combustion engine 1 by a pipe 11.

The secondary circuit 3 essentially comprises a heater 18. An inlet pipe 17 is stitched between the flow cutoff means 5 and the internal combustion engine 1, and is connected to the heater 18. An outlet pipe 19 is stitched between the main radiator 7 and the pump 10, and is connected to the heater 18.

A temperature sensor 9 is located in the internal combustion engine, upstream of the flow cut-off means 5. The temperature sensor 9 is able to determine the temperature prevailing in the internal combustion engine. According to a preferred embodiment, the temperature sensor 9 is located inside the water core of the cylinder head. The location of this sensor makes it possible to characterize the gradual rise in the temperature of the heat transfer fluid when the vehicle is started.

The control system comprises an electronic control unit 26 comprising a means 21 for determining the thermal state of the motor connected by a connection 22 to a comparison means 23. The temperature sensor 9 situated at the water core of the the yoke is connected by the connection 20 to the determining means 21.

The water core of the cylinder head is the set of chambers in the cylinder head and designed to allow the circulation of coolant.

Similarly, a control means 27 of the motor is connected by the connection 28 to the determining means 21.

At the output, the comparison means 23 is connected by the connection 25 to the breaking means 5 of the flow.

The operation is described below in the case of a zero flow of the heat transfer fluid. The flow of the coolant can be zero especially during a first heating or during a second heating.

A first heater is defined as the rise in temperature following a first start, when the engine is at a temperature equal to or substantially equal to the ambient temperature.

A second heater is defined as the rise in temperature following a moderate drop in the temperature of the internal combustion engine, for example, following a brief stop of the internal combustion engine.

A discontinuity of the cooling liquid appears during sudden changes in the flow rate and results in the appearance of abrupt thermal transitions. In other words, the flow rate can suddenly change from a large flow rate to a zero flow rate and vice versa.

Such discontinuity can be ordered, or fortuitous. Controlled discontinuity means the cases of the first heating and the second heating. However, the ordered discontinuities also include the case of an alternation of circulations and heat transfer fluid circulation stop for regulating the temperature of the heat transfer fluid.

In contrast, fortuitous discontinuities include failures of an organ involved in the operation of the cooling circuit of the internal combustion engine. The temperature can then be determined in spite of the absence of circulation of the heat transfer fluid, and provide more precise information on the state of possible damage to the internal combustion engine.

The purpose of the control system is to determine a characteristic temperature of a specific area of the engine and then compare it to a limiting temperature to determine whether the flow cut-off means is to be switched to the driving position. For this, the thermal state of the engine is determined, that is to say the distribution of heat inside the engine and more particularly in at least one specific area corresponding to critical locations for the reliability of said engine. We will focus more particularly on the temperature of the intersopeve bridge which represents one of the most sensitive points to the temperature of the internal combustion engine. The intersopepope bridge represents areas of low resistance in the cylinder head. More particularly, it is called jumper intersoupapes the material areas of the cylinder head between two adjacent openings. The openings of the cylinder head are the openings made in particular for the valves, but also for the injector, and the spark plug.

The control of the internal combustion engine 1 is achieved through the cooperation of the determination means 21 and the comparison means 23. These means apply a first statistical model to data received from a control means 27 of the engine.

The control means 27 supplies the electronic control unit 26 with data including, in particular, the rotational speed of the internal combustion engine, the load of the internal combustion engine, the quantity of fuel injected, and / or the flow rate of the fuel. air.

The electronic control unit 26 also receives data relating to the temperature of the coolant determined at the cylinder head from the temperature sensor 9.

A zero flow of the coolant implies that the flow cut-off means is in a non-conducting position. The heat transfer fluid included in the main circuit 2 does not circulate in the internal combustion engine I.

The coolant contained in the portion of the cooling circuit passing through the internal combustion engine 1 can flow through the secondary circuit 3 under the action of the pump 10. A major part of the heat generated by the operation of the internal combustion engine is communicated to the heat transfer fluid. However, because the heat transfer fluid passes through the heater 18, a minimum amount of the heat stored in the heat transfer fluid is dispersed. The temperature of the heat transfer fluid then increases rapidly.

It is also possible to place a complementary valve between the pump 10 and the internal combustion engine 1 on the branch 11, to prevent any circulation of the coolant in the internal combustion engine. The temperature of the internal combustion engine then increases more rapidly than in the previous embodiment.

An alternative for cutting the circulation of the heat transfer fluid may be to stop the operation of the pump 10. For this it can either disengage the pump 10, or directly control the stop of its operation.

The electronic control unit 26 then controls the cutoff means 5 of the flow so that the increase in the temperature of the internal combustion engine is slowed down and stopped in the vicinity of a temperature threshold. The electronic control unit 26 may optionally control the pump 10.

Indeed, the opening of the flow cutoff means 5 has the effect of circulating the coolant contained in the main circuit 2 and being at a temperature below the temperature of the internal combustion engine. In addition, a portion of the heat transfer fluid from the output of the cooling circuit included in the internal combustion engine is directed into the main circuit 2 where it is cooled in the main radiator 7. From this moment, the cooling circuit is controlled in a conventional manner to maintain the internal combustion engine at the desired temperature.

The figure 2 illustrates the control method of the cooling circuit. This control method is applied when starting the internal combustion engine. The temperature of the engine is close to the ambient temperature and the flow cutoff means 5 is in a non-conducting position.

The control method begins with step 29 in which the operating conditions of the internal combustion engine are determined. In particular, the rotational speed, the engine torque and the injected fuel flow rate are determined. Furthermore, in step 30, the temperature of the coolant inside the internal combustion engine is determined, more particularly at the level of the cylinder head.

The method is continued in step 31 during which a temperature characterizing the thermal state of a specific zone of the engine is determined by application of a first model. During step 32, it is determined whether the temperature characterizing the thermal state of the specific zone of the motor is greater than a stored threshold temperature. If the result is true, the process is continued at step 34 during which the flow cutoff means 5 is switched. Otherwise, the process is continued in step 35 during which the flow-off means 5 is held in the non-conducting position. The process then recommences with steps 29 and 30.

The figure 3 illustrates in more detail step 31 illustrated on the figure 2 . During step 36, several occurrences of the operating conditions of the internal combustion engine determined during step 29 described above are memorized. These occurrences are determined in succession, each being spaced from the next of a given duration. The time between two occurrences is related to the acquisition speed of the sensor and the processing capabilities of the system. Generally speaking, a time between two occurrences will be considered small compared to the total duration of the temperature rise phenomenon of the internal combustion engine. For example, a measurement speed of between one measurement every two hundred milliseconds and one measurement per second will be considered.

The number of stored occurrences is between five and three hundred occurrences, preferably between five and thirty occurrences.

We can also define an acquisition time. The number of occurrences and the duration of acquisition are related by the speed of acquisition of the sensor. The duration of acquisition of the occurrences must be short compared to the duration characterizing the evolution of the temperature of the internal combustion engine to avoid masking said revolution by an effect of average. The acquisition time is thus between one second and one minute, preferably between one second and thirty seconds.

Similarly, during step 37, several occurrences of the temperature measurement performed in step 30 are stored. The acquisition speed, the number of occurrences or the acquisition duration characterizing these measurements are the same as those characterizing the acquisition made during step 36.

In step 38, the characteristic temperature of the thermal state of the specific zone of the internal combustion engine is determined as a function of the occurrences stored in steps 37 and 38. The method then proceeds to step 32 as illustrated. on the figure 2 and as described previously.

The temperature characterizing the thermal state of the specific area of the engine T _{ss_biais} is determined by a statistical model according to the variables provided by the control means 27 of the engine and by the temperature sensor 9 located in the internal combustion engine. A model is used autoregressive moving average (ARMA).

The temperature characterizing the thermal state of the specific area of the engine T _{ss bias is determined} according to the speed of rotation, the load, the amount of fuel injected, and the speed of the vehicle. The temperature of the coolant determined at the level of the cylinder head is considered as one of these variables. Other parameters can also be integrated.

dans laquelle

• α(k) est un régresseur;
• x(n-k) correspond aux différentes variables de l'unité de commande électronique ; et
• K₀ est le nombre d'occurrences sur lequel on réalise la moyenne.

In the context of a moving average model, the temperature of the specific area of the engine is estimated by the following equation: $${\mathrm{T}}_{\mathrm{ss\_biais}}={\displaystyle \underset{\mathrm{k}=\mathrm{0}}{\overset{{\mathrm{K}}_0}{\Sigma }}}\mathrm{\alpha }\left(\mathrm{k}\right)\times \left(\mathrm{not}-\mathrm{k}\right)$$

in which

• α (k) is a regressor;
• x (nk) corresponds to the different variables of the electronic control unit; and
• K ₀ is the number of occurrences on which the average is made.

The variables of the electronic control unit include the rotation speed of the internal combustion engine, the speed of the vehicle and the load of the engine. The regressor corresponding to each of these variables is determined in the form of a cartography resulting from a test campaign.

The control system and method is for controlling the cooling of an internal combustion engine when the coolant flow rate is zero. Under such conditions, Equation 1 shows that it is possible to determine the temperature characteristic of the thermal state of the specific area of the engine _ T _{ss bias} directly at the end of an acquisition period.

A second embodiment is illustrated by the figure 4 . Similar elements of the figure 1 and some figure 4 , have the same references. The temperature sensor 9 is either absent or placed in a non-optimal way not making it possible to account for the gradual temperature rise of the coolant in the internal combustion engine. In both cases, the data provided by the temperature sensor 9 are not reliable and are therefore not used to model the thermal state of the specific area of the engine. The temperature sensor 9 is therefore not represented on the figure 4 .

In the second embodiment, it is therefore desired to determine the temperature characterizing the thermal state of the specific area of the motor without using a temperature sensor.

For this, the temperature characteristic of the thermal state of the specific zone of the engine is calculated by applying a second model. The second model is a statistical model to characterize the phenomenon of gradual rise in engine temperature,

In a first step, the evolution of the temperature of the material of the engine block around the combustion chamber is determined. The material forming the engine block is in thermal equilibrium between the gaseous environment and the engine specific zone corresponding to the thermal state that is to be modeled. By material is meant all non-gaseous material capable of transmitting heat.

dans laquelle

• k représente le coefficient de pertes thermiques de la matière,
• T_Mat représente la température de la matière, et
• T_out représente la température de l'environnement.

Two main terms govern this thermal equilibrium. The first term is a term of convective heat exchange that characterizes the heat exchange between the material and the gaseous environment, typically the atmosphere present under the hood of the engine. $$\mathrm{Ech\_Convection}=-\mathrm{\kappa }\cdot \left({\mathrm{T}}_{\mathrm{Mast}}-{\mathrm{T}}_{\mathrm{out}}\right)$$

in which

• k represents the coefficient of thermal losses of the material,
• T _Mat represents the temperature of the material, and
• T _out represents the temperature of the environment.

dans laquelle

• α représente le coefficient de conduction thermique de la matière ; et
• T_{ss_biais} représente la température caractérisant l'état thermique de la zone spécifique du moteur.

The second term is a term of thermal exchange by conduction which makes it possible to characterize the thermal exchanges between the specific engine area corresponding to the thermal state T _{ss_biais} that one seeks to model and the material, typically the engine block surrounding the specific area. $$\mathrm{Ech\_Conduction}=-\mathrm{\alpha }\cdot \left({\mathrm{T}}_{\mathrm{Mast}}-{\mathrm{T}}_{\mathrm{ss\_biais}}\right)$$

in which

• α represents the coefficient of thermal conduction of the material; and
• T _{ss_biais} represents the temperature characterizing the thermal state of the specific zone of the motor.

dans laquelle C_{p_mat} représente la capacité calorifique de la matière.The evolution of the temperature of matter is governed by the following equation. $${\mathrm{VS}}_{\mathrm{p\_mat}}\cdot \frac{{\mathrm{dT}}_{\mathrm{mast}}}{\mathrm{dt}}=\mathrm{Ech\_Convection}+\mathrm{Ech\_Conduction}$$

where C _{p_mat} represents the heat capacity of the material.

In a second step, the evolution of the temperature characterizing the thermal state of the specific zone of the engine is calculated. The specific area of the engine corresponding to the thermal state that is to be modeled is in thermal equilibrium between the heat conveyed by matter and the heat generated by the combustion. It is called that one is in a situation of zero flow of the heat transfer fluid. The equilibrium between the specific zone of the engine corresponding to the thermal state that one seeks to model and the material is governed here also by the term of Conduction Ech_Conduction previously defined.

The heat generated by combustion _combustion is determined by a statistical model as a function of the variables provided by the motor control means 27. Different models can be used such as linear, quadratic, kriging, lolimot, AR, MA or ARMA models.

In particular, a moving average model can be used to determine the heat generated by combustion _combustion as a function, for example, of the speed, rotation, the load, the amount of fuel injected, and the air flow. Other parameters can also be integrated.

dans laquelle

• α(k) représente un régresseur ;
• x(n-k) représente les différentes variables disponibles dans l'unité de commande électronique ; et
• K₀ représente le nombre d'occurrences sur lequel on réalise la moyenne.

Under this formalism, the heat generated by combustion is governed by the following equation: $${\mathrm{h}}_{\mathrm{combustion}}={\displaystyle \underset{\mathrm{k}=0}{\overset{{\mathrm{K}}_0}{\Sigma }}}\mathrm{\alpha }\left(\mathrm{k}\right)\times \left(\mathrm{not}-\mathrm{k}\right)$$

in which

• α (k) represents a regressor;
• x (nk) represents the different variables available in the electronic control unit; and
• K ₀ represents the number of occurrences on which the average is made.

Here again, the variables of the electronic control unit include the rotation speed of the internal combustion engine, the speed of the vehicle and the load of the engine. The regressor corresponding to each of these variables is determined in the form of a cartography resulting from a test campaign.

dans laquelle C_{p_ponter} représente la capacité calorifique de la zone spécifique du moteur correspondant à l'état thermique que l'on cherche à modéliser.The temperature characterizing the thermal state of the engine is then defined by the following equation. $${\mathrm{VS}}_{\mathrm{p\_pantet}}\cdot \frac{{\mathrm{dT}}_{\mathrm{ss\_biais}}}{\mathrm{dt}}={\mathrm{h}}_{\mathrm{combustion}}-\mathrm{Ech\_Conduction}$$

in which C _{p_ponter} represents the heat capacity of the specific zone of the engine corresponding to the thermal state that is to be modeled.

As can be seen, the thermal state of the system is governed by a system of coupled differential equations. The resolution of this type of equation goes through an iterative resolution.

The iterative resolution of the system of equations formed by equations Eq. 4 and Eq. 6 involves the initialization of the system.

In the case of a zero flow of the coolant in a first heated situation, the equation system will be initialized using the instantaneous value of the ambient temperature as the temperature value T of the _mat material and the temperature T _{ss_biais} characterizing the thermal state of the specific area of the engine.

Indeed, the system and the control method are intended to control the thermal evolution of an internal combustion engine 1 and the cooling system of such an engine, when the coolant flow rate is zero. Under such conditions, it is considered that the internal combustion engine and the environment are at the same temperature during the first moments of startup. So there is no convection, the atmosphere and the engine being at the same temperature. There is also no conduction, the thermal energy generated by combustion has not begun to spread.

In the case of a zero flow of coolant in a second heating situation, the equation system will be initialized using the instantaneous value of the temperature measured by a temperature sensor located in the internal combustion engine as a value of the temperature of the material T _mat and the temperature T _{ss_biais} characterizing the thermal state of the specific area of the engine.

The internal combustion engine has a residual temperature from the previous operating period. Due to the thermal inertia of the various elements of the internal combustion engine, it can be estimated that all the elements of the internal combustion engine are at the same temperature, which temperature can be measured by a sensor located in the internal combustion engine.

The figure 5 illustrates the control method according to the second embodiment. The control method starts with step 39 during which the operating conditions of the internal combustion engine 1 are determined. In particular, the rotational speed, the engine torque and the injected fuel flow rate are determined. The method is continued in step 40 during which a temperature characterizing the thermal state of the specific zone of the engine is determined. In step 40, the temperature of the environment is taken into account. In step 41, it is determined whether the temperature characterizing the thermal state of the engine specific zone is greater than a stored threshold temperature. If the result is true, the process proceeds to step 42 in which the flow rate cutoff means is switched to the driving position. Otherwise, the method is continued in step 43 during which the flow-off means 5 is held in the non-conducting position. The process starts again at step 39.

The figure 6 illustrates in more detail step 40 illustrated on the figure 5 Step 40 makes it possible to determine the temperature characteristic of the thermal state of the specific zone of the motor at iteration n.

In step 44, the convective heat exchange is determined at iteration n as a function of the material temperature at the iteration n-1 and the temperature of the environment at the iteration n-1. For this, the equation (Eq.2) is applied.

In step 45, the material temperature is determined at the iteration n as a function of the convective heat exchange at the iteration n and the heat exchange by conduction at the iteration n. For this, the equation (Eq.4) is applied.

In step 46, the conductive heat exchange is determined at time n as a function of the material temperature at time n-1 and as a function of the temperature characteristic of the thermal state of the specific zone of the engine at the moment n-1. For this, the equation (Eq.3) is applied.

During step 47, several occurrences of the operating conditions of the internal combustion engine determined during step 39 described above are memorized. These occurrences are determined in succession, each being spaced from the next of a given duration. The values characterizing these measurements are the same as those defined in the description of step 36 of the first embodiment.

During step 47, the heat generated by the combustion is also determined. The heat generated by the combustion is determined according to the stored occurrences. Two Determinations of the energy released during combustion are spaced in time by a duration at least equal to the acquisition duration, the acquisition duration being equal to the number of occurrences multiplied by the duration between two measurements. Thus the energy released during combustion is determined with a period at least equal to the acquisition time,

The heat generated by the combustion is determined by applying the equation (Eq.5).

In step 48, the temperature characterizing the thermal state of the engine specific zone at time n is determined as a function of the heat generated by the combustion at time n and as a function of the conductive heat exchange. at iteration n. For this, the equation (Eq.6) is applied,

Here again, during the first iterations of the control method, a value equal to the temperature of the environment or a value equal to the last known value of the temperature characteristic of the thermal state of the zone will be considered as initialization value. specific to the editor.

Moreover, it appears that the calculation of the temperature characterizing the thermal state of the specific zone of the engine at time n requires knowledge of different variables at time n-1 and previous. It thus appears that the device and the control method incorporating a memory effect capable of restoring the different variables measured at different times on a simple request.

The system and the control method of the cooling system of an internal combustion engine make it possible to accurately determine the temperature of the specific zone of the engine corresponding to the thermal state that is to be modeled. Depending on this temperature, the cooling system can be controlled so that the temperature of the internal combustion engine increases rapidly during a first start without compromising the safety of said engine. Such a control advantageously makes it possible to quickly bring the internal combustion engine to a temperature at which its fuel consumption is reduced. and pollutant emissions from unburned hydrocarbons are reduced.

Claims (1)

1. Method for controlling, during cold-starting, a circuit for cooling, by means of a heat-transfer fluid, an internal-combustion engine (1) mounted in an automobile, the cooling circuit being provided, downstream of the internal-combustion engine (1), with a means (5) for interrupting the flow able to create a discontinuity in the flow of the heat-transfer fluid through the internal-combustion engine initially in a no through-flow position, characterized in that it comprises the following steps:

   determining a characteristic temperature for the thermal condition of a specific zone in the internal-combustion engine, the valve bridge, by applying an autoregressive moving-average model depending on the temperature inside the internal-combustion engine, the speed of rotation, the load and the quantity of fuel injected into the internal-combustion engine and the speed of the vehicle and

   switching the flow interruption means (5) into a through-flow position if the characteristic temperature for the thermal condition of the valve bridge in the internal-combustion engine is higher than a maximum temperature.

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