METHOD FOR CONTROLLING THE START OF AN INTERNAL COMBUSTION ENGINE IN A VEHICLE WITH A HYBRID TRANSMISSION

Description

[0001] The present invention relates generally to the field of hybrid thermal-electric powertrains for motor vehicles. More particularly, the invention relates to a method for controlling the starting of a thermal engine in a vehicle equipped with a hybrid transmission system.

[0002] In hybrid vehicles, dual-clutch hybrid transmission systems, known as "eDCT" (electric Dual Clutch Transmission), contribute to optimized energy efficiency, resulting in reduced fuel consumption and emissions. eDCT systems offer numerous advantages, particularly in terms of weight, compactness, energy management flexibility, and more. They are applicable to various known powertrain architectures, such as mild-hybrid (MHEV) architecture, full-hybrid ((F)HEV) architecture, and plug-in hybrid (PHEV) architecture.

[0003] There Fig.1 This schematically illustrates a hybrid powertrain (eGMP) of an electric hybrid vehicle. The vehicle considered here is a PHEV, for example, and incorporates three drive modes: a thermal drive mode, an electric drive mode, and a hybrid drive mode.

[0004] The eGMP group comprises an MT internal combustion engine and an "eDCT" type transmission system designated eTR. The eTR transmission system is equipped with a DCT dual-clutch automated gearbox, a rotating electric machine ME, and a clutch device KO.

[0005] The DCT transmission typically includes a K12 dual-clutch unit and GE gear trains, as well as actuators and synchronizers (not shown) for automated gear shifting. The DCT transmission receives mechanical traction torque via its input shaft AE to drive the vehicle's WH wheels, which are coupled to its output shaft AS.

[0006] The rotating electric machine ME is mechanically geared to the input shaft AE of the DCT gearbox in a so-called "P2" configuration. The ME is connected to the vehicle's traction energy storage system (not shown) via a reversible power converter (also not shown). The ME operates in electric motor mode for electric traction of the vehicle and starting the internal combustion engine MT, and in generator mode for generating electrical power via drive from the internal combustion engine MT and for regenerative braking.

[0007] The KO clutch performs a coupling / decoupling function in the transmission of mechanical torque between the MT internal combustion engine and the eTR transmission system. With the KO clutch open, the MT internal combustion engine is disconnected from the drive train. This eliminates friction losses from the MT internal combustion engine in both electric traction mode (ME) and regenerative braking mode, resulting in improved energy efficiency. With the K12 dual clutch open and the KO clutch closed, the ME is disconnected from the drive to the WH wheels and is only engaged with the MT internal combustion engine. This allows the MT internal combustion engine to start with the ME in motor mode and generates electrical power by driving the ME in generator mode.

[0008] The various operating modes and life phases of the eGMP hybrid powertrain are managed by a supervisory control unit (ECU_S), an engine control unit (ECU_E), and a transmission control unit (ECU_T), all connected via a BCD data communication bus, typically of the CAN type. The supervisory control unit (ECU_S) is responsible for the overall management of the eGMP, while the ECU_E and ECU_T are responsible for the detailed management of the internal combustion engine (ME) and the eTR transmission system, respectively. The ECU_S, ECU_E, and ECU_T work together to implement different control strategies based on driver actions and driving conditions.

[0009] Through the BCD data communication bus, the ECU_S supervisor computer receives commands from the driver, notably through an LC control lever manipulated by the driver, information from the vehicle's computers and / or information from various sensors, and transmits information and commands to the ECU_E and ECU_T computers for the control of the eGMP powertrain.

[0010] In this eGMP powertrain architecture, starting or restarting the internal combustion engine (ICE) while the vehicle is in motion is achieved using the rotating electric machine (ME), which is mechanically coupled to the ICE via the clutch device K0. It is desirable that this start-up occur very quickly, typically within a few hundred milliseconds, to ensure rapid availability of ICE torque, a smooth transition between drive modes, and the comfort of vehicle occupants. To achieve this, the electric machine ME in motor mode and the clutch device K0 must apply significant starting torque to the ICE, resulting in a very high engine speed gradient that can exceed 18,000 rpm (revolutions per minute). During the ICE start-up, the engine's lubrication system is not fully operational.An excessively high engine speed gradient creates a risk of damage to the internal combustion engine. Currently, this operating condition for starting the internal combustion engine while the vehicle is in motion is not optimized. The designer has two choices: either limit the applied starting torque by incorporating a safety margin, at the expense of starting time, or exceed the engine speed limits, with negative consequences for engine lifespan.

[0011] Document DE102012009481A1 describes a restart command for an internal combustion engine in a hybrid powertrain. The restart command comprises several phases, with a gradual, stepped increase in torque. The different phases of the command take into account the lubrication of the internal combustion engine.

[0012] In addition, the prior art is known from document WO2018162812 A1.

[0013] It is desirable to provide an optimized control solution for starting the internal combustion engine while driving a hybrid vehicle, allowing to minimize the start-up time and to respect the constraint of limiting the engine speed gradient.

[0014] According to a first aspect, the invention relates to a method for controlling the starting of a heat engine implemented in a hybrid electric vehicle having a powertrain comprising the heat engine and a hybrid transmission system, the hybrid transmission system having a rotating electric machine coupled to the heat engine via a clutch device. The method comprises, during a starting phase by the rotating electric machine of the heat engine while the vehicle is in motion, controlling the clutch device by means of a maximum clutch torque setpoint which is determined as a function of a predetermined maximum engine speed gradient of the heat engine and a moment of inertia of the heat engine.According to the invention, the method includes a control of the heat engine by means of a maximum heat engine torque setpoint which is determined as a function of a difference between the predetermined maximum engine speed gradient and a measured engine speed gradient and as a function of a torque transmitted by the clutch device.

[0015] According to a particular characteristic, the torque transmitted by the clutch device is obtained by estimation.

[0016] The invention also relates to a computer comprising a memory storing program instructions for implementing the method briefly described above. This computer is, for example, an engine control unit for the vehicle.

[0017] The invention also relates to a hybrid electric vehicle having a powertrain comprising an internal combustion engine and a hybrid transmission system, the hybrid transmission system having a rotating electric machine coupled to the internal combustion engine via a clutch device, the powertrain having a starting phase by the rotating electric machine of the internal combustion engine while the vehicle is in motion. According to the invention, the method includes a computer as described above ensuring the control of the starting phase.

[0018] According to one particular embodiment, the hybrid transmission system of the electric hybrid vehicle includes a dual-clutch gearbox.

[0019] Other advantages and features of the present invention will become more apparent upon reading the detailed description below of several particular embodiments of the invention, with reference to the accompanying drawings, in which: [ Fig.1 ] There Fig.1 is a block diagram schematically showing the architecture of a powertrain for a hybrid electric vehicle equipped with a dual-clutch hybrid transmission system. Fig.2 ] There Fig.2 is a functional block diagram showing an implementation of the method of the invention in the powertrain of the Fig.1 . [ Fig.3 ] There Fig.3 represents different curves showing the benefit brought about by the implementation of the process of the invention in the powertrain of the Fig.1 .

[0020] With reference to the Fig.2 and to the Fig.3 A particular embodiment of the method according to the invention is now described. The method is implemented here in a hybrid powertrain, such as the eGMP of the Fig.1 , comprising a combustion engine and a dual-clutch hybrid transmission system of the "eDCT" type, designated respectively by their MT and eTR designations.

[0021] In general, the method according to the invention exploits the relationships known below (1) and (2) to link the engine speed gradient (expressed in rpm.s⁻¹) to the internal combustion engine torque (expressed in Nm), knowing the moment of inertia (expressed in kg.m²) of the internal combustion engine, namely: (1) Co=(J.dω / dt), where Co is the torque (in Nm), J is the moment of inertia (in kg.m 2< ), ω is the angular velocity (in rad.s -1< ) ​​and dω / dt is the angular acceleration (in rad.s -2)< ; and (2) 1 rpm = 120π rad.s -1< .

[0022] The method according to the invention includes a preliminary test phase on the MT thermal engine and an operation phase of the method for starting the MT thermal engine while the vehicle is in motion.

[0023] The preliminary testing phase aims to determine, using open-loop control, a maximum engine speed gradient (LGR), that is, an engine speed gradient close to, but below, the organic limit of the internal combustion engine (MT). The determined maximum engine speed gradient (LGR) is stored in memory, for example in the engine control unit (ECU_E), to be used subsequently for controlling the starting of the internal combustion engine (MT) while the vehicle is in motion.

[0024] During the process operation phase, for starting the internal combustion engine MT, the rotating electric machine ME supplies the clutch device KO with an electric motor torque Cme. Typically, the electric motor torque Cme has a constant value during the starting period. According to the invention, the clutch device KO is controlled with a maximum clutch torque setpoint C0c, which is determined by the maximum engine speed gradient LGR and the moment of inertia of the internal combustion engine. The internal combustion engine MT is controlled with a maximum engine torque setpoint CM, which is a function of the difference EC between the maximum engine speed gradient LGR and a measured engine speed gradient, and a clutch torque C0e, which is an estimate of the torque C0 actually transmitted by the clutch device K0.

[0025] With particular reference to the Fig.2 , an embedded software system for controlling the internal combustion engine SWEN is typically hosted in the engine control computer ECU_E dedicated to the management of the internal combustion engine MT.

[0026] The SWEN embedded software system for controlling the internal combustion engine is implemented in the ECU_E's MEM memory. The SWEN software system comprises several software modules dedicated to implementing different control strategies for the internal combustion engine (MT), which are activated according to the vehicle's operating conditions. In particular, the SWEN software system includes an M_CD software module responsible for managing the starting of the internal combustion engine (MT) in accordance with the invention.

[0027] The M_CD software module enables the implementation of the method according to the invention by the execution of program code instructions by a processor (not shown) of the ECU_E computer. The ECU_E computer, under the supervision of the M_CD software module, cooperates in particular with the supervisor computer ECU_S and the transmission control computer ECU_T for the implementation of the method according to the invention.

[0028] As seen at the Fig.2 The M_CD software module includes, in particular, two functional blocks: M_EB and M_MT.

[0029] The M_EB function block is responsible for determining the maximum clutch torque setpoint C0c for controlling the KO clutch device and essentially comprises a CE function. The CE function is a calculation function that determines the maximum clutch torque setpoint C0c to be supplied to the KO clutch device based on the aforementioned maximum engine speed gradient LGR and the moment of inertia Jmth of the internal combustion engine. The CE function specifically utilizes the general relationships (1) and (2) mentioned above to determine the maximum clutch torque setpoint C0c.

[0030] The maximum clutch torque setpoint C0c is provided to the transmission control unit ECU_T for controlling the clutch device K0. The ECU_T contains in its memory a function block M_KO responsible for controlling the clutch device KO and including, in particular, a control function M_CCO and an estimation function M_C0e. The M_CCO function receives as input the maximum clutch torque setpoint C0c and a torque estimate C0e provided by the estimation function M_C0e. The torque C0e is an estimate of the actual clutch torque C0 supplied to the internal combustion engine MT by the clutch device K0. The M_CCO function outputs a control signal C_C0. The control signal C_CO drives the clutch device KO to provide the desired torque C0.

[0031] The M_MT function block of the M_CD software module is responsible for determining the maximum internal combustion engine torque setpoint CM for controlling the internal combustion engine MT. The M_MT function block includes, in particular, the SO, CT, and S1 functions.

[0032] The S0 function is a subtraction operator that provides a difference EC between the maximum engine speed gradient LGR and a measured engine speed gradient GR. The measured engine speed gradient GR is typically obtained by differentiating the current engine speed. The difference EC gradient is provided as input to the CT function.

[0033] The CT function is a control function that determines a pre-setpoint for the internal combustion engine torque CP based on the gradient deviation EC. The CT control function determines the pre-setpoint CP by exploiting, in particular, the general relationships (1) and (2) mentioned above, taking into account the moment of inertia Jmth of the internal combustion engine, and applying gain adjustment and phase correction treatments if necessary. The S1 function is a subtraction operator that produces the maximum internal combustion engine torque setpoint CM = CP - COe, by subtracting the estimated clutch torque C0e from the pre-setpoint for the internal combustion engine torque CP.

[0034] The contribution of the invention's process, compared to the prior art, for starting the MT internal combustion engine while in motion is illustrated by the curves of the Fig.3 .

[0035] The starting process comprises several phases for both the MT internal combustion engine and the K0 clutch assembly, designated M1 to M3 and E1 and E2. Phases M1, M2, and M3 correspond respectively to a starting phase, a speed increase phase, and a torque transfer phase. Phases E1 and E2 correspond respectively to a clutch slippage phase and a clutch engagement phase.

[0036] Curves C1, C2, and C3 show the evolution of torques (C) during starting, namely, the constant torque Cme supplied by the rotating electrical machine ME and the torque C0 transmitted via the clutch device K0. Curves C2 and C3 show the torques C0 for a start according to the prior art and a start according to the invention, respectively. Curves C4 and C5 show the evolution of rotational speeds (VR) during starting, namely, the rotational speed of the rotating electrical machine ME and the rotational speed of the primary transmission shaft, respectively. Curves C6 and C7 show the evolution of the engine speeds RM for a start according to the prior art and for a start according to the invention, respectively.Curves C8 and C9 show engine speed gradient (GRD) evolutions during starting, namely, engine speed gradients for a start according to the prior art and for a start according to the invention, respectively. Line C10 represents the limit corresponding to the maximum engine speed gradient LGR.

[0037] The effect of the method of the invention on the engine speed gradient and on the evolution C7 of the engine speed RM is schematically represented by arrows F1 and F2. With the method of the invention, the corresponding gradient curve C9 remains below the fixed limit of the maximum engine speed gradient LGR. Compared to the prior art (curve C6), which accepts an engine speed gradient much higher than LGR to obtain a short starting time DD, the method according to the invention (curve C7) makes it possible to obtain a substantially equivalent starting time while respecting the limit LGR.

[0038] The present invention provides a low-cost, software-based solution for optimizing the starting of the internal combustion engine in a hybrid vehicle while driving. The proposed solution is suitable for various types of hybrid electric vehicles.

[0039] The invention is not limited to the particular embodiments described herein by way of example. A person skilled in the art may, depending on the applications of the invention, make various modifications and variations that fall within the scope of the invention's protection.

Claims

1. Method for controlling the starting of a heat engine (MT) implemented in a hybrid electric vehicle having a power train comprising (eGMP) said heat engine (MT) and a hybrid transmission system (eTR), said hybrid transmission (eTR) system having a rotary (ME) electric machine (ME)coupled to said heat engine (MT) via a clutch device (K0), the method comprising, during a start-up phase by said rotary electric machine (ME), a order(M_EB) of said clutch device (K0) by means of a maximum clutch torque setpoint (C0c) that is determined as a function of a predetermined maximum engine speed gradient (LGR) of said heat engine (MT) and a moment of inertia(Jmth) of said heat engine (MT), said method comprising: it comprises a order of said heat engine (M_MT) by means of a maximum engine torque setpoint (CM) which is determined as a function of a variance between said predetermined maximum engine speed gradient and a measured engine speed gradient and as a function of a torque (C0e) transmitted by said clutch device (K0).

2. Method according to claim 1, wherein said torque transmitted by said clutch device (K0) is obtained by estimation (C0e).

3. Computer comprising a memory (MEM) storing program instructions (M_CD) for implementing the method according to claim 1 or 2.

4. Computer as claimed in claim 3, wherein said computer is an engine control computer (ECU_E).

5. Hybrid electric vehicle having a powertrain (eGMP) comprising a heat engine (MT) and a hybrid transmission system (eTR), said hybrid transmission system (eTR) having a rotary electric machine (ME) coupled to said heat engine (MT) via a clutch device (K0), said powertrain (eGMP) having a start-up phase by said rotary electric machine (ME) of said in progress heat engine (MT) running said vehicle, wherein it comprises a computer (ECU_E) according to claim 3 or 4 ensuring the control of said start-up phase.

6. Hybrid electric vehicle according to claim 5, wherein said hybrid transmission system (eTR), comprises a dual-clutch transmission (DCT).