Speed ratio shift method

The present invention essentially concerns a method for a motor vehicle speed ratio shift. Said method uses a power transmission device (1.1) comprising a traction chain consisting of a heat engine (2), a clutch (3), an electrical machine (4), a gearbox (5), and wheels (6). The invention is characterized in that, upon shifting, the heat engine (2) is started before, during or after the torque (CMEL) observable on the shaft (11) of the electrical machine (4) is canceled, by means of a starter system (7) mechanically independent of the electrical machine (4).

The present invention concerns a method of shifting gear ratios. A purpose of the invention is to carry out a gear ratio shift while at the same time ensuring continuity in the torque applied to a wheel shaft of the vehicle. Another purpose of the invention is to reduce the time during which the torque applied to the wheel shaft is zero during the gear ratio shift. The invention has a particularly useful application in motor vehicles, but it could also be implemented in any kind of hybrid propulsion land vehicle.

In the present text, the term “start” is used to designate the initiation of rotation of the heat engine crankshaft. The term “set in motion” is used to designate the initial movement of the vehicle from a zero speed to a non-zero speed. The term “powered on” is used with the electrical machine when it is turned on.

“Hybrid” vehicles are known that use a combination of heat energy and electrical energy to power their drive. This combining of energy sources is done in such a way as to optimize the fuel efficiency of such vehicles. This optimization of the fuel efficiency makes it possible for the hybrid vehicle to pollute far less and use far less fuel than vehicles operating solely on heat energy and whose efficiency is not optimized. Several types of hybrid vehicle power transmission devices are known.

Firstly, hybrid-type transmission devices are known that have an engine and a pair of electrical machines. The wheel shaft, the engine shaft and the shafts of the two machines are connected to one another through a mechanical assembly. This mechanical assembly is generally made up of at least two planetary gearsets. Such a transmission device is described in the French application FR-A-2832357.

Hybrid-type transmission devices having a heat engine and a single electrical machine connected to one another via a clutch are also known. Such a device is operable in two different modes. In a first mode, known as “electrical mode”, the electrical machine alone powers the vehicle drive. In a second mode, known as “hybrid mode”, the electrical machine and the heat engine together power the vehicle drive.

In hybrid mode, the power supplied by the electrical machine makes it possible to adjust the torque applied to the wheel shaft while also adjusting the torque and speed of the heat engine to an operating point at which its fuel consumption is optimized.

To this end, each member of the transmission device: heat engine, clutch, electrical machine and gearbox, is controlled by a local control device, which is in turn commanded by a specific computer known as a “supervising computer”. This computer can either be independent or integrated into another computer, such as the engine computer. This supervising computer executes programs in particular to synchronize the actions of the various members of the transmission device with one another. This synchronization is carried out in such a way as to best fulfill a driver's request for acceleration.

More precisely, depending on the acceleration desired by the user and vehicle driving conditions, the supervising computer controls the various members of the device, selects the operating mode, coordinates the transitional phases of the various members, and chooses operating points for the engine and the electrical machine. The term “driving conditions” includes vehicle parameters as well as external parameters that can influence the operation of the vehicle. For example, the speed and the acceleration of the vehicle are vehicle parameters, whereas the slope of a hill on which the vehicle is traveling and road surface moisture are external parameters.

FIG. 1shows a schematic representation of a transmission device1according to state of the art. This transmission device1has a heat engine2, a clutch3, an electrical machine4, a gearbox5, and wheels6, which make up a traction drive. As a variant, the gearbox5is replaced by a speed controller.

More precisely, the clutch3has a first clutch plate8and a second clutch plate9. The first clutch plate8is connected to a shaft10of the heat engine2. And the second clutch plate9is connected to a shaft11of the electrical machine4. Additionally, the shaft11of the electrical machine4and a shaft12of the wheels6are respectively connected to an input13and an output14of the gearbox5.

As previously mentioned, the transmission device1is operable in two different modes. In electrical mode, the shaft12of the wheels6is driven by the electrical machine4alone. The clutch3is then released, so that the shaft10of the heat engine2and the shaft11of the electrical machine4are not coupled to one another. In this electrical mode, the electrical machine4generally operates as an engine. In a particular embodiment, then, the machine4draws energy from a storage system18such as a battery, notably through an inverter19. The battery18delivers a DC voltage signal. In electrical mode, the inverter19thus transforms the DC voltage signal detectable between the battery terminals20and21into AC voltage signals, which are applied to phases22-24of the electrical machine4.

In hybrid mode, the shaft12of the wheels6is driven by the heat engine2and the electrical machine4. The clutch3is then engaged, so that the shaft10of the heat engine2and the shaft12of the wheels6are coupled to one another. The electrical machine4acts as an engine or as a generator and transmits power to the shaft12of the wheels6in order to adjust the detectable torque on the shaft12of the wheels6to the setpoint torque. In the same manner as that explained previously, the electrical machine4transfers energy with the battery18.

In hybrid mode and electrical mode, during battery recharge phases that coincide with a deceleration of the vehicle, the electrical machine4acts as a generator. During these recharge phases, the electrical machine4supplies energy to the battery18. The inverter19then transforms the AC voltage signals detectable on phases22-24of the electrical machine4into a DC voltage signal that is applied to the terminals20and21of the battery18.

In practice, the electrical machine4is a three-phase synchronous machine. Machines of this type feature a compact design and good output.

In a particular embodiment, the transmission device1has a flywheel25. This flywheel25performs a function of filtering out cyclical variations in order to ensure a continuous transmission of torque from the heat engine2to the shaft12of the wheels6.

In addition, the transmission device1has a control unit consisting of the supervising computer26in this case. This supervising computer26has a microprocessor26.1, a program memory26.2, a data memory26.3, and an input-output interface26.4, which are connected to one another via a communication bus31.

The data memory26.3contains data D1-DN, which correspond in particular to the characteristics of the various members of the transmission device1, namely, the heat engine2, the clutch3, the electrical machine4and the gearbox5. Some of the data D1-DN, for example, correspond to the response times of these members2-5. Other data D1-DN, for example, correspond to maximum and minimum torques that can be applied to shafts associated with the members2-5.

The input-output interface26.4receives signals M1-MN detectable at sensor outputs (not shown). These sensors make it possible to detect the vehicle driving conditions. For example, acceleration and speed sensors make it possible to know the acceleration and the speed of the vehicle, respectively, at any given moment. A slope sensor can detect whether the vehicle is on a slope or not. In addition, the interface26.4receives a MACC signal corresponding to a torque on the wheel as requested by a driver. This MACC signal is a function of how far down a pedal29is pushed by a driver's foot.

According to the data D1-DN, the driving conditions, and the acceleration requested by the driver, the microprocessor26.1executes one of the programs P1-PN that initiates the operation of the transmission device1in a particular mode, and adjusts the detectable torque on the shaft12of the wheels6. That is, when one of the programs P1-PN is executed, the microprocessor26.1commands the interface26.4in such a way that signals OMTH, OEMB, OMEL and OBV are sent to the heat engine2, the clutch3, the electrical machine4and the gearbox5, respectively, in order to control them in a particular mode.

When there is a change in operating mode, some of the programs P1-PN generate signals OMTH, OEMB, OMEL and OBV that direct the transition from one mode to another.

In addition, the members2-5of the transmission device1each have an internal control system that is not shown. These control systems make it possible to regulate the detectable torque values on shafts associated with these members2-5.

In one example, a request for strong acceleration is made by the driver while the vehicle is changing gear ratios. The computer26then commands the members2-5in such a way that the detectable torque on the shaft12of the wheels6is as great as possible. That is, the computer26commands the members2-5so as to start the engine2and couple its shaft10with the shaft11of the electrical machine4as quickly as possible, not waiting for the gear ratio shift.

When the heat engine2is made to start at the same time a gear ratio shift is occurring, this is known as a synchronized start of the heat engine2. This synchronized start initiates a special transitional regime in which both the gear ratio shift and the change in vehicle mode must be managed. During this transitional regime, in fact, the vehicle changes from electrical mode to hybrid mode while changing gear ratios. To manage the transitional regime, the computer26uses a specific control sequence of the members2-5.

This transitional regime is particularly critical, since it can occur up to 50 times per driving hour, regardless of the vehicle speed or the gear ratio shift under way. To make the transitional regime as pleasant as possible for the driver, the time it takes to change the gear ratio and make the heat engine2available must be kept to a minimum. In addition, the level of acceleration requested by the driver must be maintained throughout the transitional regime. The torque applied to the wheel shaft must also be as continuous as possible throughout the transitional regime, and acoustic comfort must be maximized. Over-revving of the heat engine2must be avoided, then, and the startup noises of this heat engine2must not be heard.

FIG. 2shows some timing diagrams of detectable signals on the various members2-5of the state of the art transmission device1. These signals are detectable during a synchronized start, that is, when the heat engine2starts at the same time a gear ratio shift is occurring.

More precisely,FIG. 2shows the torque signals CEMB, CMEL and CMTH, which correspond to the detectable torque on the clutch3, on the shaft11of the electrical machine4, and on the shaft10of the heat engine2, respectively.

FIG. 2also shows the change over time in torque signals CCONS and CREEL, corresponding respectively to the setpoint torque to apply to the shaft12of the wheels6and the actual torque detectable on this shaft12. The torque setpoint signal CCONS is established from the acceleration signal MACC and the signals M1-MN coming from the sensors.

The signals OEMB and OBV are sent from the supervising computer26to the clutch3and the gearbox5to command them. For greater simplicity, the signals OMTH and OMEL, which control the heat engine2and the electrical machine4, respectively, are not shown.

Lastly,FIG. 2shows on the same timing diagram the change over time in the rotation speed WMEL of the electrical machine4and the rotation speed WMTH of the heat engine2.

On the graph showing the torque signals CREEL, CMEL and CMTH, the torque setpoint signal CCONS is represented as a dashed line.

At instant t0, the vehicle has already been set in motion. That is, this vehicle is moving and operating in electrical mode. The electrical machine4thus has a non-zero rotation speed and torque, whereas the heat engine2is off. At instant t0, the driver makes a request for acceleration that requires a gear shift and the startup of the heat engine2.

Between instants t0and t1, the transmission device1enters a first transitional phase. In this first phase, the setpoint torque CCONS has a value V1that corresponds in particular to the acceleration requested by the driver. The computer26commands the electrical machine4so that its torque signal CMEL decreases linearly and is zero at instant t1. Since the heat engine2is not coupled to the shaft of the machine, the detectable torque signal CREEL on the shaft12of the wheels6parallels the change in the torque signal CMEL. This canceling of the detectable torque signal CREEL on the wheels6will make it possible to disengage the current gear ratio, as will be seen. Furthermore, the rotation speed WMEL of the electrical machine4tends to increase. The heat engine2is off. The heat engine2thus has a zero torque CMTH and a zero rotation speed WMTH. There is no detectable torque on the clutch3.

Between instants t1and t2, the transmission device1enters a second transitional phase. In this second phase, the heat engine2is started and the torque of this heat engine2is made available. But first, as soon as the torque signal CREEL reaches zero at instant t1, the computer26sends a signal31to the gearbox5. This signal31commands the current gear ratio to disengage. The torque setpoint signal CCONS still has the value V1. In addition, a signal32is sent from the supervising computer26to the clutch3. This signal32commands this clutch3in such a way that this clutch3transmits a breakaway torque CARR to the heat engine2to set it in rotation.

The electrical machine4is then in speed control mode and thus indirectly offsets the torque withdrawn by the clutch3. So in this second transitional phase, the clutch torque signal CEMB decreases linearly and at instant t2reaches a negative value equal to the breakaway torque value CARR. A heat engine2torque signal CMTH is then detectable, corresponding to the starting torque of this heat engine2. The heat engine2then has a rotation speed WMTH that is increasing, but remains lower than the rotation speed WMEL of the electrical machine4. The purpose of this second acceleration phase is to run the heat engine2through its first compression strokes. After having completed its first compression strokes, the heat engine2is operating at a high enough speed WMTH to be autonomous.

Between instants t2and t3, the transmission device1enters a third transitional phase. During this third phase, the setpoint torque CCONS still has the value V1, whereas the detectable torque CREEL on the shaft12of the wheels6is still zero. At instant t2, when the rotation speeds WMEL and WMTH of the electrical machine4and of the heat engine2are roughly equal, a signal34is sent by the computer26to the clutch3. This signal34commands the clutch3to engage. From the moment the clutch3is engaged, the rotation speeds WMTH and WMEL of the heat engine2and the electrical machine4merge. In this third phase, the speeds WMEL and WMTH of the electrical machine4and the heat engine2converge toward a target value WF. That is, the speeds WMEL and WMTH of the electrical machine4increase linearly and reach the target speed WF at instant t3.

Between instants t3and t4, the transmission device1enters a fourth transitional phase. In this fourth phase, a withdrawal of torque occurs. The torque setpoint signal CCONS increases in a calibrated manner, stepwise, for example, and reaches a value V2at instant t3. In addition, at instant t3, as soon as the speeds of the heat engine2and the electrical machine4have reached the target speed WF, a signal35is sent by the supervising computer26to the gearbox5. This signal35commands the gearbox5so as to engage a new gear ratio. As soon as the new gear ratio is engaged, the computer26commands the heat engine2so as to make the detectable torque signal CREEL on the shaft12of the wheels6gradually approach the torque setpoint signal CCONS. Thus, the torque signal CREEL increases linearly and reaches the torque setpoint signal CCONS at instant t4. The torque signal CMEL of the electrical machine4is still zero. The rotation speeds of the heat engine WMTH and the electrical machine WMEL are both increasing linearly.

Between instants t4and t5, the transmission device1enters a fifth acceleration phase. In this fifth phase, the engine members2and4of the device1converge toward their torque setpoint signal. The rotation speeds WMEL and WMTH increase with the speed of the vehicle.

Thus, at the time of this synchronized start, the time gap TC1during which the gearbox5is in neutral is used to start the heat engine2. This time gap TC1occurs between instants t1and t3. Since the gearbox5is in neutral and the detectable torque on the shaft12of the wheels6is zero, the heat engine2startup generates no disturbance in the detectable torque CREEL on the shaft12of the wheels6.

However, this gear ratio shifting method creates two major problems in particular. Firstly, the time gap TC1is lengthened by the time it takes the heat engine2to start. That is, once the gear ratio is disengaged at the end of the first phase, the new gear ratio cannot be engaged until after the heat engine2has been started and synchronized during the second and third phases. Furthermore, this time gap TC1varies widely according to the quality of the torque signal CMTH monitoring. This quality issue in the monitoring of the torque signal CMTH depends largely on the vehicle driving conditions. For example, the time gap TC1is shorter when the heat engine2is warm than when it is cold.

Furthermore, in order to correctly engage a gear ratio, the speeds WMTH and WMEL of the heat engine2and the electrical machine4must attain the target speed WF with great precision. And the detectable torque CREEL on the shaft12of the wheels6must be exactly zero. But it is very difficult to arrive at a precise speed of the electrical machine4and the heat engine2when a quick coupling is occurring between the shaft10of the heat engine2and the shaft11of the electrical machine4. In practice, it is difficult to perform synchronized starts during gear ratio downshifts. Moreover, at the moment this quick coupling is taking place, the shaft11of the electrical machine4has so much inertia that it is very difficult, even impossible, to control the torques applied to the shafts associated with the various members2-5of the device1. This lack of torque control causes a premature wearing of the dogs in the gearbox5. “Quick coupling” is defined as a coupling accomplished in 0 to 200 ms.

Consequently, the state of the art starting method does not make it possible to meet the required criteria for synchronized starts. Indeed, with such a method, gear ratio shift times are long and fragmented. Moreover, problems occur in engaging gear ratios due to wear and tear of the gearbox5.

The invention thus proposes in particular to reduce the time gap and the mechanical constraints imposed on the various members of the transmission device during a synchronized start.

To this end, in the invention, the known architecture of the transmission device is supplemented with a starting system that is mechanically independent of the electrical machine. This starting system drives the heat engine without changing the torque applied to the wheel shaft. In the invention, thus, it is no longer the clutch, but the starting system that transmits the breakaway torque to the heat engine in order to make it start. In this way, this starting system makes it possible to dissociate the problems of starting the engine from those of the vehicle traction drive and gear ratio shifting.

In accordance with the invention, to change from electrical mode to hybrid mode during a gear ratio shift, the speed of the electrical machine is approaching the target speed while the engine is starting and preparing to come into synchronization via the clutch. This means that the gear ratio shift can occur before the heat engine has started. Thus, with the invention it is no longer necessary to wait for the heat engine to be coupled to the shaft of the electrical machine in order to engage a new gear ratio.

In such a method, the time gap is much shorter than the time gap in the state of the art method. The synchronization time, during which the speed of the electrical machine is approaching the target speed, is thus much shorter in the invention than in the state of the art method. This synchronization time is actually identical to the synchronization time detectable during a gear ratio shift in electrical mode. In addition, the inertia of the wheel shaft is much lower than in the state of the art method. This low inertia facilitates gear ratio disengagement and engagement, thereby reducing gearbox wear and tear and noise.

In implementing the method according to the invention, at the time the heat engine is started, a check is performed to see whether there is enough time between this startup and the next gear ratio shift for the heat engine shaft to finish coupling with the electrical machine shaft. If there is enough time, then the coupling is authorized. Conversely, if there is not enough time, then the engine is authorized to start, but the coupling is delayed while the vehicle gear ratio shift is authorized.

Furthermore, introducing the starting system simplifies the control of the clutch and of the electrical machine during a synchronized start. The new architecture, then, makes it possible to bypass synchronizing the actions of the clutch with those of the electrical machine.

The invention thus concerns a method of shifting a gear ratio of a vehicle utilizing a power transmission device having a heat engine that is off and an electrical machine, this electrical machine being connected firstly to the heat engine through a disengaged clutch and secondly to a wheel shaft through a gearbox,

characterized in that, in order to start the heat engine during a gear ratio shift,

the heat engine is started by a starting system that is mechanically independent of the electrical machine.

FIG. 3shows a schematic representation of a transmission device1.1according to the invention. Like the state of the art transmission device1, this transmission device1.1has a heat engine2, a clutch3, an electrical machine4, a gearbox5and wheels6. The four members2-5and the wheels6of the vehicle make up a traction drive, and are arranged in the same manner as in the state of the art transmission device1. In addition, in accordance with the invention, the transmission device1.1has a starting system7connected to the heat engine2.

The starting system7therefore never contributes power to the drive.

For this reason it is appropriately sized to generate just enough power to start the heat engine2, which is significantly less power than that of the electrical machine4, and which does not require high input voltage.

This starting system7is connected to the heat engine2and sets it in rotation in order to start it. The starting system7is mechanically independent of the electrical machine4. So the starting system7starts the heat engine2without drawing any power from this traction drive. Consequently, starting the heat engine2no longer has any impact on the continuity of the torque applied to the shaft12of the wheels6.

In a particular embodiment, the heat engine2has a first pulley15attached to one end of its shaft10. And the starting system7has a second pulley16attached to one end of its shaft31. A belt17runs through the grooves in these two pulleys15and16so as to connect the starting system7to the heat engine2.

In the invention, the electrical machine4is always connected to a storage device18, such as a battery. As a variant, the storage system18is an inertia machine or a supercondenser.

In a particular embodiment, the transmission device1.1can also have a flywheel25. This flywheel25is connected to the shaft10of the heat engine2, between this heat engine2and the clutch3.

Additionally, the transmission device1.1according to the invention has the supervising computer26. When one of the programs P1-PN is executed, the microprocessor26.1commands the interface26.4so that, in addition to the signals OMTH, OEMB, OMEL, OBV, a signal ODEM is sent to the starting system7to control it. The signals OMTH and OMEL control the heat engine2and the electrical machine4, respectively, in such a way that this heat engine2always runs at its optimal operating point, where, for a given power level, it consumes a minimum of fuel.

When there is a change in operating mode, some of the programs P1-PN generate signals OMTH, OEMB, OMEL, OBV and ODEM that enable the transition from one mode to another.

The starting system7also has an internal control system that is not shown. This control system makes it possible to regulate the value of the breakaway torque that this starting system7must apply to the shaft10of the heat engine2. This breakaway torque is generally constant.

In the invention, the clutch3is a wet or dry plate clutch.

FIG. 4shows some timing diagrams of detectable signals on the various members2-5of the transmission device1.1according to the invention. As inFIG. 2, these signals can be detected during a synchronized start of the heat engine2. The torque setpoint signal CCONS is represented as a dashed line on the timing diagrams of the torque signals CREEL, CEMB, CMEL and CMTH.

For greater simplicity, only the signals OBV, OEMB and ODEM that play a leading role during the synchronized start are represented.

At instant t0′, the vehicle has already been set in motion. That is, this vehicle is moving and operating in electrical mode, in which the electrical machine4has already been powered on. The electrical machine4then has a non-zero rotation speed WMEL and a non-zero torque CMEL, whereas the heat engine2is off. At instant t0′, driving conditions require a gear ratio shift at the same time as, or before, the starting of the heat engine2.

Between instants t0′ and t1′, the transmission device1.1enters a first transitional phase. In this first phase, the setpoint torque CCONS has a value V1corresponding in particular to the acceleration request of the driver. The torque signal CMEL of the electrical machine4, which is equal to V1at instant t0′, decreases in a linear and calibratable manner so that at instant t1′, this signal CMEL is zero. Since the shaft10of the heat engine2is not coupled with the shaft11of the electrical machine4, the torque signal CREEL follows exactly the same path as the torque signal CMEL of the electrical machine4. In addition, during this first phase, a signal41is sent by the computer26to the starting system7. This signal41commands the starting system7so as to make this starting system7transmit the breakaway torque or starting torque to the heat engine2and set it in rotation. Once the heat engine2has run through its first compression strokes, from 3 to 5 in one example, a signal is sent by the computer26to the starting system7to cut off this starting system7, in other words, to stop it. The rotation speed WMTH of the heat engine2then tends to increase, but remains lower than the rotation speed WMEL of the electrical machine4. The engine torque CMTH is zero. There is no detectable torque on the clutch3, since it no longer participates in starting the heat engine2.

Between instants t1′ and t2′, the transmission device1.1enters a second transitional phase. In this second phase, the torque setpoint signal CCONS still has the value V1. At instant t1′, as soon as the torque signal CREEL is zero, a signal42is sent by the computer26to the gearbox5. This signal42commands the gearbox5so as to disengage the current gear ratio. It is preferable to have the gear ratio disengaged when the torque signal CREEL is zero, as it is here. As a variant, for a gear ratio disengagement under torque, the gear ratio can be disengaged when the torque signal CREEL is not zero by controlling the members2-5in a particular way. The torque signal CMEL of the electrical machine4begins a negative oscillation. A heat engine2torque signal CMTH is detectable, corresponding to the starting torque of this heat engine2. The electrical machine4is controlled so as to make its rotation speed WMEL converge toward the target speed WF. The rotation speed WMTH of the heat engine2increases so that at instant t2′, it is higher than the rotation speed WMEL of the electrical machine4. At the end of this second phase, the heat engine2is operating at a high enough speed WMTH to be autonomous.

Between instants t2′ and t3′, the transmission device1.1enters a third transitional phase, which is a torque pick-up phase. That is, in this third phase the setpoint torque CCONS increases while the shaft10of the heat engine2and the shaft11of the electrical machine begin coupling.

More precisely, during this third phase, the torque setpoint signal CCONS increases in a calibratable, stepwise manner and reaches a value V2at instant t2′. At instant t2′, as soon as the rotation speed WMEL of the electrical machine4reaches the target speed WF, a signal43is sent by the computer26to the gearbox5. This signal43commands the gearbox5so as to engage a new gear ratio. The clutch3is then commanded so that its plates8and9begin to slide relative to one another. The detectable torque signal CEMB on the clutch3then increases linearly. And the torque signal CMTH of the heat engine2, which was not zero, also increases in a roughly linear fashion. Thus, as soon as the next gear ratio is engaged, a torque reengagement occurs. The torque signal CREEL then increases to reach the torque setpoint signal CCONS at instant t3′. The rotation speed WMTH of the heat engine2approaches the rotation speed WMEL of the electrical machine4. When these two rotation speeds WMEL and WMTH are equal, a signal44is sent to the clutch. This signal44commands the clutch3to engage. From the instant the clutch3is engaged, the rotation speeds WMTH and WMEL of the heat engine2and the electrical machine4merge.

Between instants t3′ and t4′, the transmission device1.1enters a fourth transitional phase. In this fourth phase, the engine members2and4of the device1.1each converge toward an optimal torque setpoint value in terms of the heat engine2fuel consumption, if they have not already reached it. These setpoint signals are established by the computer26so as to make the heat engine2run at its optimal operating point. More precisely, the torque signal CCONS still has the value V2. The torque signal CMTH of the heat engine2then increases slightly, while the torque signal CMEL of the machine4decreases symmetrically relative to the torque signal CMTH. This way, the torque signal CREEL is always equal to the setpoint signal CCONS. The rotation speeds of the heat engine WMTH and the electrical machine WMEL increase, due to the application of CMTH.

Thus, when the new gear ratio engages, the clutch3is disengaged and remains so for a pre-determined time period extending from t0′ to t2′. This time period can be a function of the time needed to change gears and/or the time needed for the heat engine2to become autonomous. As a variant, the clutch3could be engaged when the heat engine2starts, in which case the members2-5are controlled in a particular way.

In this case, the heat engine2is started while the detectable torque CREEL on the shaft12of the wheels6is being canceled. As a variant, the heat engine2is started before or after torque CREEL cancellation. The signal41can in fact be sent before, during or even after the torque signal CREEL begins to decrease.

A time gap TC2during which a zero torque is detectable on the shaft12of the wheels6is shorter than the time gap TC1detectable in the state of the art method, represented by a dashed line. Consequently, the gear ratio shift in the method according to the invention is more reliable for the driver than in the state of the art method. That is, the time during which the setpoint torque CCONS is not achieved is much shorter in the method according to the invention than in the state of the art method.

Furthermore, although the two electrical machines4have the same dimensions, the rotation speed of the electrical machine4of the device1.1according to the invention is greater than the rotation speed of the electrical machine4of the state of the art device1for the same setpoint torque CCONS. The device1.1according to the invention thus enables greater acceleration during synchronized starting than the state of the art device1. This gain in acceleration is represented on the timing diagram of rotation speeds as a shaded area45.

Additionally, in the invention, when the breakaway torque is transmitted by the starting system7, the actions applied to the clutch3by the heat engine2and the electrical machine4are applied independently of one another. One action applied by the electrical machine4is to power the vehicle. One action applied by the heat engine2is an action by the starting system7, namely, starting the heat engine2.

Moreover, in the method according to the invention, the heat engine2startup is more robust than in the state of the art method. That is, the starting system7starts the heat engine2with a generally constant torque, regardless of the vehicle driving conditions.

FIG. 5shows stages of an alternative gear shifting method according to the invention. These stages are implemented according to the time between the heat engine2startup and a gear ratio shift.

More precisely, in a first stage48, a check is performed to see whether a request has been made to start the heat engine2. This startup request is dependent on the vehicle driving conditions. That is, this startup request depends in particular on the signals M1-MN and MACC that the computer26receives. If no startup request is made, then there is a return to stage48. Conversely, if a startup request is made, a second stage49is initiated.

In this second stage49, the computer26commands the starting system7to turn on, which provides the breakaway torque to the heat engine2in order to start it. After the heat engine2has been started, a third stage50is initiated.

In this third stage50, a check is performed to see whether there is enough time between the heat engine2startup and a gear ratio shift to authorize a coupling between the heat engine2shaft10and the electrical machine4shaft11. That is, the computer26manages two different processes in particular, which are executed concurrently: a first process of starting the heat engine2and a second process of changing the vehicle operating mode. This third stage50makes it possible to time the coupling of the engine2with the machine4as a function of when the gear shift occurs.

More precisely, a check is performed to see whether the time period CdR between a prior order to start the heat engine2and a subsequent order to shift gear ratios is less than a threshold time period TS. The threshold time period TS is adjustable and corresponds approximately to the time needed for the heat engine2to start and for its shaft10to couple with the shaft11of the electrical machine4. In one example, this threshold time TS is equal to 350 ms and is slightly longer than the average time needed for the shafts of the heat engine2and the electrical machine4to finish coupling.

If the time CdR between a heat engine2startup and a gear shift is greater than the threshold time TS, then a stage51is initiated. In this stage51, the coupling of the engine2shaft with the machine4shaft is authorized.

However, if the time between the engine2startup and the gear shift is less than the threshold time TS, then a time delay stage52is initiated. In this time delay stage52, the coupling of the heat engine2and the machine4shafts is delayed for a time delay period T1. During this time delay period T1, the clutch plates8and9are not even authorized to begin sliding relative to one another. During the time delay period T1, the gear shift takes place. The time delay period T1is therefore calculated in such a way that there is time to complete the gear ratio shift. In one example, the time delay period T1is 450 ms. The time delay period is adjustable as well, and is generally greater than the threshold time TS. After the time delay stage52, a new stage53is initiated.

In this stage53, a check is performed to see whether the time between the end of the time delay stage and an upcoming gear ratio shift is greater or less than the threshold time TS. If the time between the time delay stage and the upcoming gear ratio shift is less than the threshold time TS, then stage52is repeated. Otherwise, stage51is initiated. Stage53can be used in a transmission device1.1in which very closely spaced gear ratio shifts are authorized.

As a variant, stage51is initiated directly after stage52.

In the method according to the invention, the heat engine2is thus started as soon as it is needed. However, its coupling with the shaft11of the electrical machine4is delayed if the time between its startup and a gear ratio shift is less than the threshold time TS. The method according to the invention thus makes it possible to avoid interrupted coupling attempts due to gear ratio shifts that are too close in time to the starting of the heat engine2.

FIG. 6shows timing diagrams of detectable signals on the various members2-5of the transmission device1.1according to the invention when the time between a heat engine2startup and a gear ratio shift is less than the threshold time period TS. The setpoint signal CCONS is again represented here as a dashed line on the diagrams of the torque signals CREEL, CEMB, CMEL and CMTH.

For greater simplicity, only the signals OEMB, OBV and ODEM that play a leading role are shown.

At instant t0″, the vehicle is in motion and operating in electrical mode. The electrical machine4then has a non-zero rotation speed WMEL and a non-zero torque CMEL, while the heat engine2is off. At instant t0″, the computer26detects the need to start the heat engine2.

Between instants t0″ and tl″, the transmission device1.1enters a first transitional phase. During this first phase, the torque setpoint signal CCONS has a value V1corresponding in particular to the acceleration request of the driver. A little before instant t1″, a signal59is sent from the computer26to the starting system7. This signal59commands the starting system7in such a way that the starting system7provides the breakaway torque to the heat engine2in order to start it. The rotation speed WMTH of the heat engine2then trends upward, but remains lower than the rotation speed WMEL of the electrical machine4. The torque signal CMEL of the electrical machine4is equal to the torque setpoint signal CCONS. The torque signal CREEL thus merges with the torque setpoint signal CCONS expected on the shaft12of the wheels6. There is no detectable torque on the clutch3, since it is not involved in starting the heat engine2.

Between instants t1″ and t2″, the transmission device1.1enters a second transitional phase. This second phase is a detection and decision-making phase. That is, at instant t1″, the computer26detects that the time period between the heat engine2startup and a gear ratio shift is less than the threshold time TS. The computer26will thus command the members2-5so as to delay the coupling between the shafts of the heat engine2and of the electrical machine4, as will be seen. During the second transitional phase, the torque signal CMEL of the electrical machine4has the same value V1as the torque setpoint signal CCONS. Since the shaft10of the heat engine2is still not coupled with the shaft11of the electrical machine4, the torque signal CREEL merges with the torque setpoint signal CCONS. A torque signal CMTH is detectable on the shaft10of the heat engine2, corresponding to the starting torque of the heat engine2. The rotation speed WMTH of the heat engine2is increasing, but remains lower than the rotation speed WMEL of the electrical machine4.

Between instants t2″ and t3″, the transmission device1.1enters a third transitional phase. In this third phase, the computer26commands the electrical machine4so as to cancel the torque CMEL of this machine4. Thus, the torque signal CMEL of the electrical machine4decreases linearly, so that it is zero at instant t3″. Since the shaft of the heat engine2is still not coupled with the shaft11of the electrical machine4, the torque signal CREEL parallels the torque signal CMEL of the electrical machine4. Canceling the detectable torque signal CREEL on the shaft12of the wheels6will allow the current gear ratio to disengage, as will be seen. At the outset of the third phase, the heat engine2is on and ready for synchronization. The torque setpoint signal CCONS is still equal to V1.

Between instants t3″ and t4″, the transmission device1.1according to the invention enters a fourth transitional phase. In this fourth phase, the value of the torque setpoint signal CCONS is still equal to V1. At instant t3″, as soon as the detectable torque signal CREEL on the shaft12is zero, a signal60is sent to the gearbox to command the current gear ratio to disengage. The torque signal CMEL of the electrical machine4begins a negative oscillation. The rotation speed WMEL of the electrical machine4converges toward a target speed WF in order to authorize a new gear ratio to engage, as will be seen.

Between instants t4″ and t5″, the transmission device1.1enters a fifth transitional phase. In this fifth phase, the torque signal CCONS increases in a stepwise manner to reach a value V2at instant t4″. At instant t4″, as soon as the electrical machine4reaches the target speed WF, a signal61is sent by the computer26to the gearbox5. This signal61commands the gearbox so as to engage a new gear ratio. The coupling delay is over as soon as the new gear ratio is engaged. Thus, at instant t4″, the clutch plates8and9begin sliding with respect to one another. The torque signal CMTH of the heat engine2and the torque signal CEMB of the clutch3both increase at this point. Consequently, the torque signal CREEL also increases to reach the setpoint torque signal CCONS at instant t5″. The rotation speed WMTH of the heat engine2approaches the rotation speed WMEL of the electrical machine4. When these two rotation speeds WMEL and WMTH are equal, a signal62is sent to the clutch3. This signal62commands the clutch3to engage. From the instant the clutch3engages, the rotation speeds WMTH and WMEL of the heat engine2and the electrical machine4merge.

Between instants t5″ and t6″, the transmission device1.1enters a sixth acceleration phase. As already mentioned, in this sixth phase, the engine members2and4of the device1.1converge toward their optimal torque setpoint value, if they have not already reached it. These setpoint signals are established so as to make the heat engine2run at its optimal operating point. More precisely, the torque signal CCONS still has the value V2. The torque signal CMTH of the heat engine2then increases slightly, while the torque signal CMEL of the electrical machine4decreases symmetrically with respect to the torque signal CMTH, in one example. In this way, the torque signal CREEL is always equal to the setpoint signal CCONS. The rotation speeds of the heat engine WMTH and the electrical machine WMEL increase linearly with the vehicle speed.

Thus, whether the heat engine2starts before, during or after a gear ratio shift, the starting system7always makes it possible to reduce the time this gear ratio shift takes. This is because the synchronization of the wheel shaft with the target speed WF is always carried out by the electrical machine4, which is not affected by the clutch3. In the invention, moreover, since the inertia of the shaft11of the electrical machine4is controlled, the time it takes for a gear ratio to engage or disengage is generally constant regardless of the driving conditions.

As a variant, the method according to the invention is used while the electrical machine4is off, to set the vehicle in motion.