WO2021084173A1

WO2021084173A1 - Method for estimating the thermal state of an engine component and method for controlling powertrain commands

Info

Publication number: WO2021084173A1
Application number: PCT/FR2020/051740
Authority: WO
Inventors: Daniel Coulaud; Michel ANGELI; Jean Baptiste OLIVIER
Original assignee: Psa Automobiles Sa
Priority date: 2019-10-29
Filing date: 2020-10-05
Publication date: 2021-05-06
Also published as: FR3102515B1; FR3102515A1; CN114616385A; EP4051897A1

Abstract

The present invention relates to a method for estimating the thermal state of an internal component of a heat engine of a powertrain, allowing thermal management to be improved in the event of engine shut-off. More specifically, the invention proposes, on the one hand, a method involving estimating the internal temperature (Tm) of the engine based on the heat flow generated by the combustion of the working engine and on the action of the cooling fluid and, on the other hand, a method for controlling authorisations for engine shut-offs (CS_auth) and a method for controlling the activation duration of a cooling pump as a function of said temperature (Tm) in order to avoid thermal shocks. The invention is applicable to conventional and hybrid powertrains.

Description

DESCRIPTION

Title: Method for estimating the thermal state of an engine component and method for controlling GMP controls

The present invention claims the priority of French application No. 1912103 filed on October 29, 2019, the content of which (text, drawings and claims) is incorporated here by reference.

The field of the invention relates to a method for estimating the thermal state of a thermal engine component and a method for managing a powertrain for controlling engine shutdowns and a cooling circuit pump.

To reduce the fuel consumption of thermal engine powertrains, energy strategies seek to shut down the thermal engine as soon as an opportunity arises. For this, manufacturers resort to the use of automatic engine stop and restart (STT) systems. In the case of hybrid powertrains, strategies generally include switching off the heat engine in favor of a fully electric driving mode, also known as ZEV ("Zero Vehicle Emission") mode. Conventionally, the authorization of engine shutdowns depends on the torque demand on the wheels, the state of charge of the battery, or even a driving mode parameter which favors or not electric driving.

The repeated cuts of the heat engine cause thermal shocks at the level of the material of the engine components, in particular at the level of the turbocharger, the crankcase, the cylinder head, cylinder head gasket and the coolant pipes. Over time, these thermal shocks, if they are too frequent, are liable to prematurely damage the components of the heat engine.

To avoid this situation, control strategies inhibit the functions of stopping and restarting the thermal engine and / or controlling the cooling loop of the thermal engine according to temperature parameters, measured or estimated, coolant and turbocharger. In particular, in addition to the main mechanical pump of the cooling circuit, strategies also provide for the activation of the electric pump of the turbocharger circuit. For example, patent document DE10347683A1 is known proposing the inhibition of the automatic stop and restart function, when the temperature of the power electronics of an alternator-starter exceeds a threshold value. Also known from the state of the art is the patent document FR3018556A1 filed by the applicant proposing a method for estimating the thermal state of a starter determining the phases of use of the starter and starting of the thermal engine to avoid a heating and premature damage.

However, these strategies are not sufficient to prevent thermal shock to internal engine components. In particular, for hybrid architectures, the engine cuts increase considerably compared to a conventional architecture, in particular when the traction power requested is less than a threshold for triggering the electric driving mode. Repeated thermal shocks increase the risk of boiling the coolant, gasoline, glycol hydrolysis or even overflow.

There is therefore a need to overcome the aforementioned problems. An objective of the invention is to provide efficient thermal regulation of the internal components of the engine. Another objective is to propose a strategy for controlling engine shutdowns to avoid thermal shocks at the level of the internal components of the engine in extreme driving situations of high temperatures, for example at high outside temperature and high and continuous engine torque loads for example. .

More precisely, the invention relates to a method for estimating the temperature of a component of the power train for controlling one or more setpoints during the command to stop the heat engine, in which the temperature estimate consists in estimating the temperature instantaneous material of an internal component of the heat engine, said estimation comprising the following steps:

- The determination of the instantaneous thermal flow of the heat engine and of a temperature variation of the engine resulting from the application of this heat flow,

- The correction of the temperature variation by a heat exchange correction factor resulting from the action of the engine coolant, the correction factor being calculated as a function of the drive speed of a main mechanical circulation pump engine coolant driven by the engine.

According to one variant, the instantaneous heat flux is determined from a predetermined map delivering a value of the heat flux as a function of a measurement of the instantaneous engine speed and of an estimate of the instantaneous engine torque. According to one variant, the driving speed of the pump is determined from an instantaneous measurement of the speed of the heat engine.

The invention provides a method for controlling an authorization instruction for a cut-off of a thermal engine of a powertrain, method in which the state of the authorization instruction is controlled by means of a predetermined map receiving a first input parameter which is the instantaneous temperature of the cooling fluid, in which the state of the setpoint is also controlled as a function of a second input parameter of the map which is the instantaneous temperature of the material d an internal component of the heat engine estimated by means of any one of the preceding embodiments of the method for estimating the temperature according to the invention.

The invention also provides a method of controlling an auxiliary electric pump for circulating a thermal engine coolant of a power train comprising the determination of a duration of activation of the pump calculated at the instant of control of a cut-off of the thermal engine by a cut-off instruction and initiated from the moment of command of the cut-off, in which the activation time is determined by means of a map receiving a first input parameter which is a function of the instantaneous temperature of the engine coolant and a second input parameter which is a function of the temperature instantaneous time of the material of an internal component of the heat engine estimated by means of any one of the preceding embodiments of the method for estimating the temperature according to the invention.

According to a variant of the method for controlling the pump, the cut-off instruction is dependent on the authorization instruction determined in accordance with the method according to the invention.

There is also provided according to the invention a motor vehicle comprising a powertrain comprising a heat engine and a cooling circuit of said engine, the cooling circuit comprising a main mechanical pump driven by the motor shaft and an electric auxiliary pump, the group powerplant, in the event of a cut-off of the heat engine, being configured so as to activate the auxiliary pump during an activation period following the command instant of the cut-off, said activation period being determined in accordance with the method according to l 'invention.

The invention also provides a program-computer product comprising instructions which, when the program is executed by a control unit of the powertrain, lead the latter to implement any one of the embodiments of the estimation method. the temperature of an internal component of the engine, the method for controlling the engine cut-off setpoint and the method for controlling the auxiliary pump in accordance with the invention.

Thanks to thermal management based on an estimate of the internal temperature of the thermal engine, the powertrain eliminates thermal shocks resulting from repetitive shutdowns of the thermal engine. Improved cooling thus takes into account the thermal inertia of the material of the internal components and limits its damage.

Other characteristics and advantages of the present invention will emerge more clearly on reading the following detailed description comprising modes embodiment of the invention given by way of non-limiting examples and illustrated by the appended drawings, in which:

[Fig. 1] represents the functional modules of a drive train control unit for estimating the temperature of the internal component material of the engine and controlling an authorization signal for an engine shutdown according to l 'invention.

[Fig.2] more precisely represents the functional module for estimating the temperature of an internal component of the engine according to the invention.

[Fig. 3] represents more precisely the functional module for controlling the authorization signal for an engine shutdown according to the invention.

[Fig. 4] schematically shows an example of a predetermined map for controlling the authorization instruction for an engine shutdown according to the invention.

[Fig. 5] represents an example of an algorithm for executing the method for controlling a cooling circuit pump according to the invention in the non-limiting case of an engine stoppage during the activation of a ZEV driving mode.

The invention applies to motor vehicle powertrains with conventional thermal propulsion or hybrid propulsion and proposes a method for estimating the temperature of the internal components of the thermal engine making it possible to improve the management of engine shutdowns and of the cooling circuit. extreme temperature or heavy load driving situation. The invention aims to improve thermal management during engine cuts of any type, for example STT, or even during ZEV travel.

Conventionally, powertrains comprising a thermal engine are equipped with a cooling circuit dedicated to thermal management of engine components. The cooling circuit comprises a high temperature circuit, operating in temperature ranges up to a hundred degrees, and a bypass branch dedicated to cooling a turbocharger. The high temperature circuit comprises a main mechanical pump driven by the shaft of the heat engine ensuring the circulation of the cooling fluid in the high temperature circuit. The bypass has an electric auxiliary pump capable of circulating the liquid cooling in part or in the whole of the cooling circuit when the heat engine is stopped. The auxiliary pump can be controlled by controls, for example of the all-or-nothing type according to an activation setpoint, either when stopped or in constant rotating speed, or in speed regulation. The cooling circuit may include means for regulating the flow of the cooling fluid, for example valves or flaps, controlled by commands determined by the control unit of the heat engine depending on operating parameters of the powertrain, in particular the temperature. of the coolant, estimation of the temperature of the turbocharger, the engine speed, and in the context of the invention, estimates of the temperature of the material of the internal components of the heat engine.

The main mechanical pump is driven by the motor shaft, thus preventing the thermal regulating action resulting from the flow of coolant in the cooling circuit in an engine shutdown situation. The invention firstly aims to authorize or not the engine cuts depending on the thermal situation of the engine to prevent thermal shocks in extreme thermal situations, and judiciously activate the electric auxiliary pump to circulate the cooling fluid in engine outage situation.

For this purpose, FIG. 1 represents a drive unit control unit comprising functional modules according to the invention, a first module 10 is dedicated to the function of estimating the instantaneous temperature Tm of the material of one or more components. internal combustion engine and a second module 11 is dedicated to the control function of the reference signal CS_auth authorizing an engine shutdown.

The first module 10 receives at each instant values of input parameters P_gmp of operation of the powertrain, among which there may be mentioned the temperature of the coolant measured by a sensor of the cooling circuit in degrees Celsius, the speed of rotation of the engine. heat engine in rpm, the engine torque in Nm, and possibly the instantaneous engine power. The estimated temperature Tm is then used for evaluate the operating conditions of internal engine components and manage engine shutdowns.

More specifically, FIG. 2 represents the functional module 10 for estimating the temperature of the material of an internal component of the engine. The temperature of the material Tm is an estimate of the temperature of engine components such as the crankcase, cylinder head, cylinder head gasket, or even the surface temperature of the engine's water core. The actual temperature at the level of the internal components differs significantly upwards from the temperature conventionally measured at the cylinder head outlet which corresponds to the temperature of the coolant and not of the internal components. The objective of module 11 is therefore to estimate the actual temperature in order to improve the management of thermal regulation and in particular to take into account the effects of thermal inertia of the material which can cause boiling, gas and overflow during an engine shutdown. The objective is therefore to set up a regulation process based on a temperature threshold specifically controlling the value of this estimate in addition to the temperature threshold controlling the value of the temperature of the coolant.

More precisely, the module 10 comprises a first block 101 for estimating the instantaneous heat flow 105 of the engine. This value 105 can be determined on the basis of an operating parameter of the powertrain which is representative of the instantaneous power. In a variant, the instantaneous heat flux 105 is determined by a predetermined map, stored in the memory of the powertrain control unit, which delivers the value of the instantaneous heat flux 105 from the instantaneous engine torque and the engine speed. engine. The value 105 is a value expressed in Joule per second or Watts. From the value of this instantaneous heat flux, the block 101 determines an internal temperature variation resulting from the heat flux. The more the engine power increases, the more the temperature resulting from the heat flow increases. In a manner known per se, the heat fluxes are known and calculated empirically by means of maps based on the engine operating points in terms of speed and torque during its design. We can cite for example document EP1916404A1 filed by the applicant describing a technique for estimating heat flows.

In addition, the module 10 comprises a second block 102 whose function is to deliver a correction value 106 for the temperature variation generated by the heat flows of the engine. The correction value 106 is representative of the cooling action of the engine cooling system. This correction value depends on the instantaneous rotation speed of the heat engine. Indeed, the flow rate of the cooling fluid is dependent on the rotational speed of the main mechanical pump and therefore of the heat engine. The more the engine speed increases, the more heat energy is drawn from inside the engine. The second block 102 is for example a predetermined map, stored in the memory of the powertrain control unit, delivering the correction value according to the measurement of the engine speed of rotation. A third block 103 has the function of estimating a temperature value 108 of the internal components from the heat flow 105, the correction factor 106 representative of the cooling action, and a value 107 of the instantaneous temperature of the cooling fluid. engine cooling. One or more other correction factors may be taken into account by block 103 to work out the value 108. The temperature value 108 is preferably processed by fourth final processing block 104, for example a low filter which depends on the value. engine speed, before delivering the temperature Tm to the module 11 for controlling the authorization setpoint for engine shutdown.

Figure 3 now shows the module 11 for controlling the setpoint CS_auth authorizing cut-off of the heat engine. The module estimates from a predetermined map, recorded in the memory of the powertrain control unit, taking as input parameter the value of the temperature Tm, delivered by the module 10, and the value of the temperature Te of the coolant of the thermal regulation circuit of the engine. The value of the setpoint CS_auth is controlled according to said input values

Tm and Te. The CS_auth instruction is in this example a type instruction Boolean signal that can take the value TRUE (1) to authorize an engine shutdown or FALSE (0) to prohibit an engine shutdown.

FIG. 4 schematically represents a non-limiting example of a two-dimensional map for controlling the signal CS_auth. On the x-axis is shown the value of the temperature of the coolant Te, and on the y-axis is shown the values of the temperature Tm of the material of the internal components of the engine determining the value of the signal CS_auth. The boxes of the map represent the values of the signal 1, 0 as a function of the temperatures Tm, Te. More precisely, the thermal engine cut-off authorization setpoint CS_auth is used by the control unit to authorize a cut-out to activate a ZEV driving mode in the case of a hybrid architecture, or a momentary cut-out of the "Stop" type. and Start ”, whatever the engine architecture (hybrid or conventional). In addition, the control unit includes a module for estimating a duration of activation of the auxiliary pump following the instant of detection of an engine failure. The function of this module is to activate the auxiliary pump for a period D_pp depending on the value of the temperature Tm and the value of the temperature of the coolant, in a manner similar to the map shown in figure 4. The determination map of the duration D_pp is configured to determine the value of the duration of actuation of the auxiliary pump as a function of the temperature values Tm, Te when the engine is cut off.

The powertrain (or heat engine) control unit is fitted with an integrated circuit computer and electronic memories, the computer and the memories being configured to execute the temperature estimation process, the control process of the authorization signal and finally the method for controlling the auxiliary pump. But it is not compulsory. Indeed, the computer could be external to the control unit, while being coupled to the latter. In the latter case, it can itself be arranged in the form of a dedicated computer comprising a possible dedicated program, for example. Therefore, the control unit, according to the invention, can be produced in the form of software modules (or computer (or “software”)), or electronic circuits (or “hardware”), or a combination of electronic circuits and software modules.

In FIG. 5, a powertrain control algorithm has now been shown in which the temperature T m is estimated at each instant for the control of the authorization signal CS_auth and the control of the auxiliary pump in the event of an engine shutdown. Likewise, the activation time D_pp of the pump is calculated at each moment.

In a first step 50, the assumption is made that the heat engine is operating at rotating speed, during travel during which an engine torque is transmitted to the wheels to move the vehicle. To represent this situation, for example a powertrain state parameter ET_mth is driven to a value TRUE = 1. Estimates of the temperature Tm and the duration D_pp are also calculated. In a step 51, the control unit determines the value of the authorization setpoint CS_auth according to the predetermined map taking as input parameter the temperature value Tm and the value of the cooling fluid Te.

If the CS_auth setpoint is detected in the FALSE (0) state, the control unit prohibits, in step 52, engine shutdowns to prevent damage to the engine as well as the boiling phenomena explained above. This exceptional situation corresponds for example to very high outside temperatures, 40 ° C or more and / or to engine operating points with high load in torque and speed (for example, uphill mountain road, high vehicle mass) and with high temperatures. high coolant levels.

In the event of detection that the setpoint CS_auth is in the TRUE state (1), the control unit authorizes, in a step 53, the engine cuts. This situation generally covers all cases of the life of the vehicle, apart from the exceptional ones mentioned in the previous paragraph. In this situation, the heat engine is still running (ET_mth = 1) because the control unit controls a rotating state to provide torque to the wheels for example. The pump activation time is always calculated.

In the event of detection, at a step 54, of an engine shutdown request (RQ_mth = 0) and of a request for a ZEV driving mode (RQ_zev = 1), then at a step 55, the unit The control switch triggers the procedure for stopping the heat engine, until reaching zero rotating speed and cutting off the fuel injection. At this stage of the process, the control unit detects the instant of stopping the heat engine and from this instant controls the activation of the auxiliary pump of the cooling circuit by an activation command ET_pp in the state TRUE = 1 during the duration D_pp which is calculated at each moment as a function of the temperature of the material Tm and of the temperature of the cooling fluid until the engine is cut off. The D_pp activation time is frozen until the next start of the heat engine. After the D_pp time has elapsed after the moment the engine is stopped, the pump is turned off. The flow of coolant during this period cools internal engine components and eliminates thermal shock.

Steps 54, 55 also apply to vehicle stop situations and to STT-type momentary shutdown situations. The electric pump has been described for one embodiment of a turbocharger bypass branch. This case is nevertheless in no way limiting and the invention applies to the control of any electric pump which can be activated in a situation of engine cut-off.

Claims

1. A method of estimating the temperature of a component of the powertrain for controlling one or more setpoints during the control of a stopping of a heat engine of the powertrain, characterized in that the estimate of temperature consists in estimating the instantaneous temperature (T m) of the material of an internal component of the heat engine, said estimate comprising the following steps:

- The determination of the instantaneous heat flow (105) of the heat engine and of a temperature variation of the engine resulting from the application of this heat flow,

- The correction of the temperature variation by a correction factor (106) of heat exchange resulting from the action of the engine coolant, the correction factor (106) being calculated as a function of the driving speed of a main mechanical pump for circulating the engine coolant driven by the engine.

2. Method according to claim 1, characterized in that the instantaneous heat flux (105) is determined from a predetermined map (101) delivering a value of the heat flux as a function of a measurement of the instantaneous engine speed and of an estimate of the instantaneous engine torque.

3. Method according to claim 1 or 2, characterized in that the pump drive speed is determined from an instantaneous measurement of the heat engine speed (102).

4. Method for controlling an authorization instruction (CS_auth) of a thermal engine shutdown of a power train, process in which the state of the authorization instruction (CS_auth) is controlled by means of a predetermined map receiving a first input parameter which is the instantaneous temperature (Te) of the cooling fluid, characterized in that the state of the setpoint is further controlled as a function of a second input parameter (TM) of the mapping which is the estimated instantaneous temperature (Tm) of the material of an internal component of the heat engine by means of the method according to any one of claims 1 to 3.

5. Method for controlling an electric auxiliary pump for circulating a thermal engine coolant of a powertrain comprising the determination of an activation time (D_pp) of the pump calculated at the command instant. a cut-off of the heat engine by a cut-off setpoint (RQ_mth) and initiated from the cut-off command instant, characterized in that the activation time (D_pp) is determined by means of a map receiving a first input parameter (Te) which is a function of the instantaneous temperature of the engine coolant and a second input parameter which is a function of the instantaneous temperature (Tm) of the material of an internal component of the heat engine estimated by means of the method according to any one of claims 1 to 3.

6. Method according to claim 5, characterized in that the cutoff setpoint (RQ_mth) is dependent on the authorization setpoint (CS_auth) determined in accordance with the method according to claim 4.

7. Motor vehicle comprising a powertrain comprising a heat engine and a cooling circuit of said engine, the cooling circuit comprising a main mechanical pump driven by the motor shaft and an electric auxiliary pump, characterized in that in the event of a cut-off of the heat engine, the power train is configured so as to activate the auxiliary pump during an activation period (D_pp) following the command instant of the cut-out, said activation period being determined in accordance with the method according to any of claims 5 to 6.