WO2019081182A1 - Method for monitoring the start time of a heat engine - Google Patents

Abstract

Method for monitoring the start time of a powertrain heat engine (GMP) of a hybrid vehicle during the transition from a current electrical drive train state, wherein an electrical machine alone provides traction to the vehicle, to a target hybrid drive chain state, wherein the traction of the vehicle is ensured simultaneously by at least one heat engine and one electrical machine, characterised in that: - the force to be achieved by the GMP (FORC_PWT_REQ) is determined, - the force gain (FORC_TRAC_DIF) that the electrical machine is not able to develop in order to achieve the entire force (FORC_PWT_REQ) of the GMP on the current ratio is determined, - the force deviation (FORC_TRAC_DIF) is compared to a reference force gain (FORC_DIF_ALLOW).

Description

 METHOD FOR MONITORING THE STARTING TIME OF AN ENGINE

 THERMAL

The present invention relates to controlling the starting of a heat engine in a hybrid vehicle.

 More specifically, it relates to a method for controlling the start-up time of a hybrid vehicle powertrain engine during the passage of a current electrical kinematic state, in which an electric machine alone ensures the traction of the vehicle on a target hybrid drivetrain state, wherein the traction of the vehicle is provided simultaneously by at least one engine and one electric machine.

 On most hybrid vehicles, equipped with at least one electric machine and a heat engine, there is an all-electric driving mode, where the heat engine is off, and where only the electric machine (s) produce the torque necessary to the traction of the vehicle on one or more ratios of possible reduction, according to the architecture of the powertrain of the vehicle.

 The principle of a hybrid vehicle being to combine the powers of the engine and electric machines, a hybrid mode is generally a more capacity mode in terms of torque level, an all-electric mode.

 The transition from an electric mode to a hybrid mode, is a recurring event on a hybrid vehicle, which can happen in the case of a strong demand for acceleration of the driver involving a start of the engine if it was off. It involves a torque request that is both important and fast to reach, in response to the driver's demand for acceleration.

A transition from an electric mode to a hybrid mode can also occur without demand for performance, which implies that the electrical power is sufficient to tow the vehicle, and that the engine is started only for ancillary reasons (conservation of an instantaneous power reserve for example). In such a case, it is not necessary that the required torque to the engine is large or fast to reach, because its start is not a necessity to meet the demand for acceleration of the driver.

 Publication US 8 204 659 teaches a method of controlling the starting of an engine, which involves the choice of the gear ratio to be engaged according to the acceleration request. This method determines whether the engine should be started or not, but not how quickly it should be started.

 US Pat. No. 7,578,364 discloses modulating the ignition parameters of the engine according to the position of the pedal: the method described thus determines whether the type of starting must be fast or slow.

 The start-up phases are critical for the emission level of pollutants. Knowing that a large and rapid torque demand emits more pollutant than a low and slow torque demand, it is desirable to optimize the torque required for the combustion engine when starting according to the need which has get started.

 The present invention aims in particular to determine whether the starting of the heat engine of a hybrid GMP is imposed to satisfy a request for acceleration of the driver (performance requirement), or for other reasons.

 For this purpose, it provides:

 to determine the force to be achieved by the GMP, - to determine the gain in force that the electric machine is not able to develop to achieve the full force of the GMP on the current ratio, and

 to compare the gain of force with a gain of reference force.

This strategy is based on the construction of a Boolean that allows the couple's management strategies to know the reason for the type of startup, in order to optimize the level of pollutant emitted during the start of the engine.

 It can be used on all hybrid vehicles equipped with an automatic gearbox having at least one electric motor and a heat engine, making it possible to establish at least one electrical traction drive train condition and at least one drive state. Hybrid / thermal traction power train.

 The present invention will be better understood on reading the following description of an embodiment of the invention, with reference to the appended drawings, in which:

 FIG. 1 is a logic diagram of the strategy developed, and

 - Figure 2 is a timing diagram thereof.

 A kinematic chain state is defined as a combination of coupler (s) and gearbox (s) specific to a given vehicle architecture. The progress of the strategy is shown in FIG. 1. It is a method for controlling the start-up time of a hybrid vehicle powertrain engine (GMP) during the passage of a kinematic chain state. electrical current, in which an electric machine alone ensures the traction of the vehicle, a target hybrid kinematic chain state, wherein the traction of the vehicle is ensured simultaneously by at least one engine and an electric machine.

This process is broken down into several steps leading to the development of a boolean to know if the start of the engine is related to a performance query or not. The first step F1 consists in defining a time window during which it is possible to detect whether the start of the heat engine is linked to a performance request or not. The energetic type of traction of the state of the kinematic chain is called "kinematic state typing": this state can be purely electric (EV), purely thermal (TH) or hybrid (HYB). In this step, the time window for detecting a start for performance reasons is activated:

 if the typing of the kinematic state preceding the change of target (DLS TGT PREV) is of purely electric type (DLS_TGT_TYP_PREV = EV),

 - if the engine is off (ENG_STT_STOP) at the time of changing the target kinematic state, and

 - if the start of the engine is required for the realization of a new state of target kinematic chain of thermal or hybrid type (DLS_ENG_STA_REQ and DLS_TGT_TYP = EV).

 In summary, it is necessary that the change of state is a transition from an electrical current state to a hybrid target state, that the heat engine is off during this change of state, and that its start is required to achieve the target state.

 When all three conditions are met, the detection time window (ENG_STA_PERF_WIN) is activated. It is considered that the heat engine is started to provide a power instead / in addition of / electrical machines currently connected to the wheel previously used (s) in the state of previous kinematic chain (DLS_TGT_PREV).

 A shorter start time is imposed on the heat engine during the activation of the window

(ENG_STA_PERF_WIN). It remains active for a period, called period or activation window, defined by an adjustable parameter named (WIN DURA), after which it is deactivated.

The purpose of the F2 function is to define the maximum force (FORC_MAX_DLS_TGT_PREV) of the previous target driveline state (DLS TGT PREV), in order to be able to compare it with the force request to which the powertrain must respond (FORC_PWT_REQ). The maximum force of the previous target state (DLS TGT PREV), is calculated from a vector (FORC MAX DLS) (developed independently of this strategy), representing the set of maximum forces achievable on the possible kinematic chain states of the power train. The force (FORC_MAX_DLS_TGT_PREV) is the maximum force achievable by the electrical machine (s) on the previous EV type power train condition (current state).

 The function F3 consists of comparing the force (FORC_MAX_DLS_TGT_PREV) with the force that the powertrain must realize (FORC PWT REQ). The strength of the power train (FORC PWT REQ) is determined by the driver's demand for power, or and / or strategies that affect the power the power train must provide: cruise control, speed limiter, etc. This comparison makes it possible to determine the difference of force (FORC TRAC DIF), which the powertrain can not realize on the previous kinematic chain state of type EV.

 The function F4 makes it possible to define whether turning on the engine on the new power train condition will, by a force input, achieve the required power for the powertrain, and if this input is sufficient to justify starting the engine. which involves higher pollutant emissions.

 In this step, another parameter (FORC DIF ALLOW) intervenes, representing the gain of force from which it is justified to require a start typed performance. The force gain (FORC TRAC DIF) is determined by comparing the maximum force achievable by the electric machine (FORC_MAX_DLS_TGT_PREV) on the current electrical state, and the force (FORC PWT REQ) to be realized by the GMP.

(FORC_DIF_ALLOW) is subtracted from FORC TRAC DIF. If the difference is positive, the starting of the heat engine provides the necessary force to achieve the force required to the powertrain (FORC PWT REQ) that can not provide the / the electrical machines on the previous kinematic chain state (current state ) DLS TGT PREV. If the difference is negative, the electrical machines respond to the realization of the force required to the power train without intervention of the engine.

 In summary, one determines the force that must realize the GMP (FORC_PWT_REQ), one determines the gain of force (FORC TRAC DIF) that the electric machine is not able to develop to realize the whole force (FORC PWT REQ) of the GMP on the current ratio, and the force difference (FORC TRAC DIF) is compared with a reference force gain (FORC_DIF_ALLOW).

 The F5 function is used to define whether the required startup is typed "performance". The fact that without the engine, the electric machine (s) are, or are not, capable of providing the required power to the power train (FORC PWT REQ) and that the contribution of the engine is negligible is represented in a boolean ( FORC_PWT_NOT_RES). This Boolean is TRUE when both of the following conditions are met:

 the electric machine is not capable of providing the required force to the FORC_PWT_REQ power train, and

 the input of the engine is not negligible.

 If (FORC_PWT_NOT_RES) is TRUE while the detection window (ENG_STA_PERF_WIN) is active, the start type is typed "performance" by a variable (ENG STA PERF ENA). The "performance" typing is retained until the next thermal engine shutdown

 If (FORC_PWT_NOT_RES) is FALSE, while the detection window is active, the start of the engine is not typed "performance".

During the detection time window, the start time is shorter, according to the "performance typing", when the difference between the force gain to be developed and the reference force gain, (FORC_TRAC_DIF) - (FORC_DIF_ALLOW), is positive . According to the policy, it is shorter if the Boolean (FORC_PWT_NOT_RES) is TRUE while the window detection (ENG_STA_PERF_WIN) is active, only in other cases.

 FIG. 2 illustrates this strategy, in a phase of activation and then deactivation of the start request of the heat engine for a reason of performance. At the date T1, the target kinematic state is EV. Engine is off (ENG_STT_STOP). Its start is required to go to the next state (DLS ENG STA REQ). All the conditions are met to activate the detection phase of a start of the engine for reasons of performance (or not).

 On the date T2, the force required to the powertrain (FORC PWT REQ) becomes greater than that which can provide the previous target kinematic state (current state) (FORC_MAX_DLS_TGT_PREV) but the difference to be provided is still acceptable with regard to the gap (FORC_DIF_ALLOW).

 At the T3 date, the difference in forces remains in the same direction, but is no longer acceptable. It involves starting the engine and the need to quickly establish a high torque, so that the powertrain can meet the force demand (FORC PWT REQ) as soon as possible. The Boolean (FORC_PWT_NOT_RES) changes to TRUE, while the detection time window (ENG_STA_PERF_WIN) is active. Startup request boolean for performance reasons

(ENG_STA_PERF_ENA) also changes to TRUE to allow the torque management strategy to tailor its queries accordingly.

On the date T4, the maximum detection time comes to an end (WIN DURA). The activation time window is disabled. If the Boolean (FORC_PWT_NOT_RES) had not yet passed TRUE before T4, the start query for performance reasons (ENG STA PERF ENA) would not be TRUE and could not be TRUE. Disabling the start request of the heat engine for a performance reason, starts on the T5 date, where the target kinematic state changes from typing hybrid (DLS_TGT_TYP_PREV = HYB) to an EV typing

(DLS_TGT_TYP = EV). The start request of the heat engine to realize the state of kinematic chain (DLS_ENG_STA_REQ) goes to FALSE.

 On the date T6, the engine is considered off (ENG STT STOP). Startup request for performance reasons (ENG_STA_PERF_ENA) changed to FALSE. No detection of the type of start is performed until the conditions of activation of the detection window are again met.

 The advantages of the invention are important. Among these, it should be emphasized that it requires little development, and that it is transversal, because it can be adopted on any hybrid vehicle having at least one electrical kinematic state, and at least one hybrid state or thermal.

Claims

A method for controlling the starting time of a hybrid vehicle powertrain engine (GMP) during the passage of a current electrical drive train state, in which an electric machine alone provides the traction of the vehicle, on a target hybrid kinematic system state, in which the traction of the vehicle is ensured simultaneously by at least one heat engine and an electric machine, characterized in that:

 we determine the force that the GMP must perform (FORC_PWT_REQ),

 the force gain (FORC TRAC DIF) is determined that the electric machine is not able to develop to achieve the full force (FORC_PWT_REQ) of the GMP on the current ratio,

 comparing the force difference (FORC_TRAC_DIF) with a reference force gain (FORC DIF ALLOW), and

 the starting time of the heat engine is shorter when the difference between the force gain to be developed and the reference force gain, (FORC_TRAC_DIF) - (FORC_DIF_ALLOW), is positive.

 2. Control method according to claim 1, characterized in that the force to be achieved by the powertrain (FORC PWT REQ) is determined from the driver's force demand.

 3. Control method according to claim 1 or 2, characterized in that the force to be achieved by the powertrain (FORC PWT REQ) is determined from strategies having an impact on the force that the powertrain must provide.

4. Control method according to claim 1, 2 or 3, characterized in that the force gain (FORC TRAC DIF) is determined by comparing the maximum force achievable by the electric machine (FORC_MAX_DLS_TGT_PREV) on the current electrical state, and force (FORC PWT REQ) to be performed by the GMP.

5. Control method according to claim 4, characterized in that the shortest startup time is imposed on the engine, only during the activation of a detection time window (ENG_STA_PERF_WIN) determined.

 6. Control method according to claim 5, characterized in that the detection period is activated when the following three conditions are met:

 the change of state is a transition from an electric current state to a hybrid target state,

 the engine is off when this change, and

 its startup is required to achieve the target state.

 7. Control method according to one of the preceding claims, characterized in that the start time is determined by a boolean (FORC_PWT_NOT_RES) which is in the TRUE state when the two following conditions are met:

 the electric machine is not capable of providing the required force to the FORC_PWT_REQ power train, and

 the input of the engine is not negligible.

 8. Control method according to claim 5, 6 or 7, characterized in that the start time is shorter if the boolean (FORC_PWT_NOT_RES) is in the TRUE state while the detection window (ENG_STA_PERF_WIN) is active.