METHOD FOR CONTROLLING THE STARTING OF A HEAT ENGINE IN A VEHICLE EQUIPPED WITH A HYBRID TRANSMISSION

Abstract

The method for controlling the starting of an internal combustion engine (MT) is implemented in an electric hybrid vehicle having a powertrain (eGMP) comprising the internal combustion engine and a hybrid transmission system (eTR), the transmission system having a rotating electric machine (ME) that is coupled to the engine via a clutch device (K0). According to the invention, the method comprises, during a phase for starting the engine with the electric machine while the vehicle is rolling, controlling (M_EB) the clutch by means of a maximum clutch torque setpoint determined according to a predetermined maximum speed gradient (LGR) and a moment of inertia (Jmth) of the engine, and controlling (M_MT) the engine by means of a maximum engine torque setpoint (CM) determined according to a difference (EC) between the maximum clutch torque setpoint and a torque (C0e) transmitted by the clutch.

Claims

1. A method for controlling the starting of an internal combustion engine implemented in an electric hybrid vehicle having a powertrain comprising said internal combustion engine and a hybrid transmission system, said hybrid transmission system having a rotating electric machine that is coupled to said internal combustion engine via a clutch device, wherein it comprises, during a phase for starting said internal combustion engine with said rotating electric machine while said vehicle is rolling, controlling said clutch device by means of a maximum clutch torque setpoint which is determined according to a predetermined maximum engine speed gradient of said internal combustion engine and a moment of inertia of said internal combustion engine, and controlling said internal combustion engine by means of a maximum internal combustion engine torque setpoint which is determined according to a difference between said maximum clutch torque setpoint and a torque transmitted by said clutch device.

2. The method as claimed in claim 1, wherein said torque transmitted by said clutch device is obtained by estimation.

3. A computer comprising a memory storing program instructions for implementing the method as claimed in claim 1.

4. The computer as claimed in claim 3, wherein said computer is an engine control unit.

5. An electric hybrid vehicle having a powertrain comprising an internal combustion engine and a hybrid transmission system, said hybrid transmission system having a rotating electric machine coupled to said internal combustion engine via a clutch device, said powertrain having a phase for starting said internal combustion engine with said rotating electric machine while said vehicle is rolling, wherein it comprises a computer as claimed in claim 3 controlling said starting phase.

6. The electric hybrid vehicle as claimed in claim 5, wherein said hybrid transmission system comprises a dual-clutch transmission.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0019] Further advantages and features will become more clearly apparent from the following detailed description of a number of particular embodiments, with reference to the accompanying drawings, in which:

[0020] FIG. 1 is a block diagram schematically showing an architecture of a powertrain of an electric hybrid vehicle equipped with a dual-clutch hybrid transmission system.

[0021] FIG. 2 is a function block diagram showing one implementation of the method in the powertrain of FIG. 1.

[0022] FIG. 3 shows various curves demonstrating the benefits provided by implementing the method in the powertrain of FIG. 1.

DETAILED DESCRIPTION

[0023] With reference to FIG. 2 and to FIG. 3, one particular embodiment of the method is now described. Here, the method is implemented in a hybrid powertrain, such as the powertrain eGMP of FIG. 1, comprising an internal combustion engine and an eDCT dual-clutch hybrid transmission system, which are labeled MT and eTR, respectively.

[0024] Generally speaking, the method uses the below known relationships (1) and (2) to link the engine speed gradient (expressed in rpm.Math.s.sup.1) to the internal combustion engine torque (expressed in N.Math.m), knowing the moment of inertia (expressed in kg.Math.m.sup.2) of the internal combustion engine, namely: [0025] (1) Co=(J.Math.d/dt), where Co is the torque (in N.Math.m), J is the moment of inertia (in kg.Math.m.sup.2), is the angular velocity (in rd.Math.s.sup.1) and d/dt is the angular acceleration (in rd.Math.s.sup.2); and

[00001]$\begin{array}{cc}1\mathrm{rpm}=120\mathrm{rd}.S^{-1}.& \left(2\right)\end{array}$

[0026] The method comprises a prior test phase on the internal combustion engine MT and a phase of using the method to start the internal combustion engine MT while the vehicle is rolling.

[0027] The purpose of the prior test phase is to determine, using open-loop control, a maximum engine speed gradient LGR, i.e. an engine speed gradient which is close to, but below, an 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 in this instance, for subsequent use in controlling the starting of the internal combustion engine MT while the vehicle is rolling.

[0028] In the phase of using the method to start the internal combustion engine MT, the rotating electric machine ME delivers an electric motor torque Cme the clutch device K0. Typically, the electric motor torque Cme has a constant value throughout the start-up period. The clutch device K0 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, and the internal combustion engine MT is controlled with a maximum engine torque setpoint CM which is dependent on a difference EC between the maximum engine speed gradient LGR and a measured engine speed gradient, and on a clutch torque C0e which is an estimate of the torque C0 actually transmitted by the clutch device K0.

[0029] With particular reference to FIG. 2, an embedded engine control software system SWEN is typically hosted in the engine control unit ECU_E dedicated to management of the engine MT.

[0030] The embedded engine control software system SWEN is implemented in a memory MEM of the control unit ECU_E. The software system SWEN comprises a number of software modules dedicated to the implementation of various control strategies for the engine MT, which are activated according to vehicle situations. The software system SWEN comprises in particular a software module M_CD responsible for managing the starting of the internal combustion engine MT.

[0031] The software module M_CD allows the method to be implemented through the execution of program code instructions by a processor (not shown) of the control unit ECU_E. The control unit ECU_E, under the supervision of the software module M_CD, cooperates in particular with the supervisory control unit ECU_S and the transmission control computer ECU_T to implement the method.

[0032] As can be seen in FIG. 2, the software module M_CD comprises two functional blocks in particular, M_EB and M_MT.

[0033] The functional block M_EB is responsible for determining the maximum clutch torque setpoint C0c for controlling the clutch device K0 and essentially comprises a function CE. The function CE is a calculation function which determines the maximum clutch torque setpoint C0c to be delivered to clutch device K0 based on the above-mentioned maximum engine speed gradient LGR and the moment of inertia Jmth of the internal combustion engine. In particular, the function CE uses the above-mentioned general relationships (1) and (2) to determine the maximum clutch torque setpoint C0c.

[0034] The maximum clutch torque setpoint C0c is delivered to the transmission control unit ECU_T to control the clutch device K0. The control unit ECU_T hosts a functional block M_K0 in memory which is responsible for controlling the clutch device K0, and comprises in particular a control function M_CC0 and an estimation function M_C0e. The function M_CC0 receives as input the maximum clutch torque setpoint C0c and a torque estimate C0e delivered by the estimation function M_C0e. The torque C0e is an estimate of the actual clutch torque C0 delivered to the internal combustion engine MT by the clutch device K0. The function M_CC0 delivers as output a closed-loop command C_C0. The closed-loop command C_C0 controls the clutch device K0 to deliver the required torque C0.

[0035] The functional block M_MT of the software module M_CD is responsible for determining the maximum engine torque setpoint CM for controlling the internal combustion engine MT. In particular, the functional block M_MT comprises functions S1 and CT.

[0036] The function S1 is a subtraction operator which provides a difference EC between the maximum clutch torque setpoint C0c and the actual clutch torque C0 delivered by the clutch device K0, the torque C0 being represented here by its estimate C0e. The torque difference EC is delivered as input to the function CT.

[0037] The function CT is a control function which determines the maximum engine torque setpoint CM according to the torque difference EC, applying gain adjustment and phase correction processing if necessary.

[0038] The contribution of the method over the prior art when starting the internal combustion engine MT while it is rolling is illustrated by the curves in FIG. 3.

[0039] Start-up comprises different phases for the internal combustion engine MT and for the clutch device K0, which are designated M1 to M3 and E1 and E2. Phases M1, M2 and M3 correspond to a start-up launch phase, a ramp-up phase and a torque transfer phase, respectively. Phases E1 and E2 correspond to a clutch slipping phase and a clutch closing phase, respectively.

[0040] Curves C1, C2 and C3 show changes in torque (C) during start-up, i.e. the constant torque Cme delivered by the rotating electric machine ME and the torque C0 transmitted via the clutch device K0. Curves C2 and C3 show the torques C0 for a start-up according to the prior art and a start-up, respectively. Curves C4 and C5 show changes in rotational speed (VR) during start-up, i.e. the rotational speed of the rotating electric machine ME and the rotational speed of the primary drive shaft, respectively. Curves C6 and C7 show changes in the speeds RM of the internal combustion engine for a start-up according to the prior art and for a start-up, respectively. Curves C8 and C9 show changes in engine speed gradient (GRD) during start-up, i.e. engine speed gradients for a start-up according to the prior art and for a start-up, respectively. The straight line C10 represents the limit corresponding to the maximum engine speed gradient LGR.

[0041] The effect of the method on the engine speed gradient and on the change C7 in the engine speed RM is represented schematically by the arrows F1 and F2. With the method, the corresponding gradient curve C9 remains below the set maximum engine speed gradient limit LGR. Compared with the prior art (curve C6), which accepts an engine speed gradient well in excess of LGR to achieve a short start-up time DD, the method (curve C7) achieves a substantially equivalent start-up time while observing the limit LGR.

[0042] Described herein is a low-cost, software-based solution for optimizing the rolling start-up of the internal combustion engine in a hybrid vehicle. The proposed solution is particularly suitable for MHEVs.

[0043] The foregoing methods and devices are not limited to the particular embodiments described here by way of example. Depending on the application, the skilled person will be able to make various modifications and variants falling within the scope of protection.