ITBO20130446A1 - METHOD OF CONTROL OF A HYBRID VEHICLE - Google Patents

Description

DESCRIPTION

of the patent for industrial invention entitled:

"METHOD OF CONTROL OF A HYBRID VEHICLE"

TECHNIQUE SECTOR

The present invention relates to a control method of a hybrid vehicle.

ANTERIOR ART

Hybrid vehicles including an internal combustion engine, which transmits torque to the drive wheels by means of a servo-assisted transmission equipped with a mechanical servo-assisted gearbox, and at least one electric machine that is electrically connected to an electrical storage system and connected mechanically to the drive wheels.

Typically the electric machine is of the reversible type, i.e. it can work both as a motor absorbing electric energy and generating mechanical work, and as a generator absorbing mechanical work and generating electric energy and is driven by an electric drive connected to the electric storage system designed to store energy. electric. Typically, the electric machine is keyed to a secondary shaft of the mechanical servo-assisted gearbox and is piloted so as to replace the internal combustion engine, for example when the servo-assisted clutch remains open; in other words, when the power assisted clutch is open, the electric machine absorbs energy from the storage system to generate a drive torque equivalent to the drive torque generated by the internal combustion engine. However, in this configuration the electric motor cannot perform some functions (typically it cannot operate as a starter motor for the internal combustion engine), while it is in an unfavorable condition to perform other functions.

For this reason, a servo-assisted transmission has been proposed comprising a connection device which is suitable for connecting a shaft of the reversible electric machine to a primary shaft of the mechanical servo-assisted gearbox, or for connecting the shaft of the reversible electric machine to the secondary shaft of the gearbox. mechanical power assisted, or to keep the shaft of the reversible electric machine idle (i.e. not connected to either the primary shaft or the secondary shaft).

In this configuration, when the shaft of the reversible electric machine is connected to the primary shaft of the power-assisted mechanical gearbox, the reversible electric machine can be used as a starter motor to start the internal combustion engine.

However, both the configurations described up to now present some criticalities. In particular, during normal operation of the hybrid vehicle, when a sudden increase in the drive torque to be supplied to the drive wheels occurs through a request from the driver who intervenes on the accelerator pedal, the internal combustion engine to transmit the additional torque necessary to the drive wheels it is forced to a very fast transient in which a succession of non-stabilized engine points is explored, which do not allow to optimize fuel consumption and lead to a significant increase in polluting emissions.

In particular, to transmit the additional torque necessary to the drive wheels it is necessary to enrich the air / fuel mixture and it is often not possible to avoid the formation of humidity due to fuel deposits on the walls of the ducts of the internal combustion engine itself (known phenomenon such as "wall wetting").

DESCRIPTION OF THE INVENTION

The purpose of the present invention is to provide a control method for a hybrid vehicle that is free from the drawbacks of the state of the art and is easy and economical to implement.

According to the present invention there is provided a control method of a hybrid vehicle according to what is claimed in the attached claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to the attached drawings, which illustrate a non-limiting example of embodiment, in which:

Figure 1 is a schematic view of a power assisted transmission for a hybrid vehicle which implements the control method implemented in accordance with the present invention; And

Figure 2 illustrates different trends over time of the driving torque supplied to the driving wheels of the hybrid vehicle of Figure 1.

PREFERRED FORMS OF IMPLEMENTATION OF THE INVENTION

In the attached figure, the number 1 indicates as a whole a servo-assisted transmission for a hybrid vehicle driven by an internal combustion engine 2, which is provided with a drive shaft 3 which rotates at a ωmangular speed. In particular, it is a vehicle with hybrid powertrain and parallel architecture.

The servo-assisted transmission 1 comprises a mechanical servo-assisted gearbox 4, which is provided with a primary shaft 5 which rotates at an angle speed ω1 and can be connected to the motor shaft 3 by means of a servo-assisted clutch 6 and a secondary shaft 7 which rotates at a single speed. ω2 angle and is connected to a differential 8 which transmits motion to the driving wheels by means of two half-shafts 9.

The mechanical power assisted gearbox 4 illustrated in Figure 1 comprises six forward gears indicated with Roman numerals (first gear I, second gear II, third gear III, fourth gear IV, fifth gear V and sixth gear VI). The primary shaft 5 and the secondary shaft 7 are mechanically coupled to each other by means of a plurality of gear pairs, each of which defines a respective gear and comprises a primary gear 10 mounted on the primary shaft 5 and a secondary gear 11 mounted on the 7 'secondary shaft.

Each primary gear 10 is mounted idle on the primary shaft 5 and always meshes with the respective secondary gear 11; instead each secondary gear 11 is keyed to the secondary shaft 7 to rotate integrally with the secondary shaft 7 itself. Furthermore, the servo-assisted mechanical gearbox 4 comprises three synchronizers 12, each of which is mounted coaxially to the primary shaft 5, is arranged between two primary gears 10, and is adapted to be actuated to alternately engage the two primary gears 10 to the shaft 5 primary (i.e. to alternatively make the two primary gears 10 angularly integral with the primary shaft 5). In other words, each synchronizer 12 can be moved in one direction to engage a primary gear 10 to the primary shaft 5, or it can be moved in the other direction to engage the other primary gear 10 to the primary shaft 5.

The servo-assisted mechanical gearbox 4 is operated by a hydraulic servo control to drive the synchronizers 12 so as to engage and disengage the gears; also the servo-assisted clutch 6 is operated by a hydraulic servo control to connect and disconnect the motor shaft 3 to the primary shaft 5. The servo-assisted transmission 1 comprises a control unit 13 (shown schematically), which drives the hydraulic servo controls of the mechanical servo-assisted gearbox 4 and of the servo-assisted clutch 6.

According to a different embodiment not shown and perfectly equivalent to the embodiment described above, the primary gears 10 are keyed to the primary shaft 5, the secondary gears 11 are idle mounted on the secondary shaft 7, and the synchronizers 12 are mounted on the secondary shaft 7 for engaging secondary gears 11 to the secondary shaft 7 itself.

Furthermore, the servo-assisted transmission 1 comprises a reversible electric machine 14 (i.e. which can operate both as a motor by absorbing electrical energy and generating mechanical work, and as a generator by absorbing mechanical work and generating electrical energy) driven by an electric drive 15 connected to at least one battery. 16 suitable for storing electrical energy.

The reversible electric machine 14 comprises a shaft 17, which is integral with a rotor of the reversible electric machine 14, is normally idle (i.e. it is not mechanically permanently connected to either the primary shaft 5 or the secondary shaft 7), and it is mechanically connectable to the primary shaft 5.

The servo-assisted transmission 1 comprises a connection device 18 adapted to connect the shaft 17 of the reversible electric machine 14 to the primary shaft 5 of the mechanical servo-assisted gearbox 4, or to connect the shaft 17 of the reversible electric machine 14 to the secondary shaft 7 of the mechanical servo-assisted gearbox 4, or to keep the shaft 17 of the reversible electric machine 14 idle (i.e. not connected to either the primary shaft 5 or the secondary shaft 7).

According to the preferred embodiment illustrated in the attached figures, the connection device 18 comprises a gear transmission 19 interposed between the shaft 17 of the reversible electric machine 14 and the secondary shaft 7 of the mechanical servo-assisted gearbox 4, a socket transmission 20 direct interposed between the shaft 17 of the reversible electric machine 14 and the primary shaft 5, and a synchronizer 21 adapted to alternately engage the gear transmission 19 or the direct drive transmission 20.

The gear transmission 19 preferably has a non-unitary transmission ratio and comprises a gear 22 mounted idle on the shaft 17 of the reversible electric machine 14 and a gear 23 which is keyed on the secondary shaft 7 and permanently meshes with the gear 22; the synchronizer 21 is adapted to engage the gear 22 to the shaft 17 of the reversible electric machine 14 to connect the shaft 17 of the reversible electric machine 14 to the secondary shaft 7. The value of the non-unitary transmission ratio of the gear transmission 19 is such as to optimize the rotation speed and torque values of the reversible electric machine 14 with respect to the rotation speed and the torque transmitted by the secondary shaft 7; normally the gear transmission 19 provides for a reduction in the number of revolutions, that is, the reversible electric machine 14 turns more slowly than the secondary shaft 7.

The direct drive transmission 20 has a unitary transmission ratio and includes a connection element 24 keyed onto the primary shaft 5; the synchronizer 21 is adapted to engage the connecting element 24 to the shaft 17 of the reversible electric machine 14 to connect the shaft 17 of the reversible electric machine 14 to the primary shaft 5.

According to a different embodiment not shown, the direct drive transmission 20 is replaced by a further gear transmission, which is interposed between the shaft 17 of the reversible electric machine 14 and the primary shaft 5, has a transmission ratio not unitary and is completely analogous to the gear transmission 19. Also in this case, the value of the non-unitary transmission ratio of the further gear transmission is such as to optimize the rotation speed and torque values of the reversible electric machine 14 with respect to the rotation speed and the torque transmitted by the primary shaft 5. ; normally the further gear transmission provides for a reduction in the number of revolutions, that is, the reversible electric machine 14 turns more slowly than the primary shaft 5.

In use, when a gear change is not taking place and the vehicle is in gear (i.e. the internal combustion engine 2 is on and the servo-assisted clutch 6 is closed), the shaft 17 of the reversible electric machine 14 is normally connected to the primary shaft 5 and the reversible electric machine 14 functions as an electric power generator to supply the electric energy required by the electric users of the vehicle. If the vehicle slows down, the reversible electric machine 14 can maximize (compatibly with the state of charge of the battery 16 and with the vehicle dynamics) the absorption of mechanical energy to achieve regenerative braking of the vehicle.

In use, when the drive torque C necessary for the drive wheels is generated by the internal combustion engine 2 and at the same time there is a request for an increase in the drive torque C to be supplied to the drive wheels by the driver, the reversible electric machine 14 is set up for operate as an electric motor by absorbing electrical energy from the battery 16 to provide additional drive torque (“electric boost”). That is, the reversible electric machine 14 is designed to function as an electricity generator to provide the electricity necessary to meet the demand for increasing the drive torque C to be supplied to the drive wheels by the driver.

The control mode implemented by the control unit 13 in the event of a request for an increase in the driving torque C to be supplied to the driving wheels by the driver is described below.

The control unit 13 is designed to recognize a request to increase the driving torque C to be supplied to the driving wheels typically by means of a decisive intervention of the driver who intervenes on the accelerator pedal.

In particular, the control unit 13 is designed to determine an objective Cm_objmotrice torque which is such as to ensure that it satisfies the request of the driver who intervenes on the accelerator pedal.

Subsequently, the control unit 13 is adapted to determine the additional torque ΔC to be supplied to the driving wheels starting from the instant in which a request for an increase in the driving torque C is recognized by the driver who intervenes on the accelerator pedal to satisfy the request itself using the following formula:

∆Cm = Cm_obj -Cm [1]

In which:

∆Cm: additional drive torque to be supplied to the drive wheels starting from the instant in which a request for an increase in drive torque C is recognized by the driver who intervenes on the accelerator pedal;

Cm_obj: objective drive torque such as to ensure that the request of the driver who intervenes on the accelerator pedal is met; And

Cm: drive torque supplied by internal combustion engine 2 at the instant in which the request for an increase in drive torque C by the driver who intervenes on the accelerator pedal is recognized by the control unit 13.

The additional ∆Cmmotrice torque to be supplied to meet the request of the driver who intervenes on the accelerator pedal calculated through [1] and is supplied by the reversible electric machine 14 to the drive wheels.

The control unit 13 is therefore arranged to control the reversible electric machine 14 so that it absorbs electrical energy to supply the necessary mechanical torque according to the following formula:

Etot = ∆E (Cm) + Ei [2]

In which:

Ei: electricity supplied by the reversible electric machine 14 for the operation of the electric utilities of the hybrid vehicle at the instant in which a request for an increase in the drive torque C is recognized by the driver who intervenes on the accelerator pedal;

∆E (∆Cm): additional electrical energy supplied by the reversible electric machine 14 to guarantee the additional ∆C drive torque to the drive wheels at the instant in which a request to increase the drive torque C is recognized by the driver who intervenes on the pedal of the 'accelerator; And

Etot: total electricity required to the reversible electric machine 14 at the instant in which a request for an increase in the drive torque C is recognized by the driver who intervenes on the accelerator pedal.

Clearly, the control unit 13 is set up to check that the state of charge of the battery 16 is such as to guarantee the supply of the additional electric energy ∆E (∆Cm) to guarantee the additional torque ∆Cmdrive to the drive wheels at the instant in which a request to increase the drive torque C is recognized by the driver who intervenes on the accelerator pedal.

In other words, the control unit 13 is arranged to verify that the state of charge of the battery 16 is sufficient to supply the total E-telelectric energy required to the reversible electric machine 14 at the instant in which a request for increasing the torque C is recognized. drive by the driver who intervenes on the accelerator pedal, i.e. both such as to guarantee both the supply of additional electrical energy ∆E (∆Cm) to guarantee the additional torque ∆Cmdrive to the drive wheels and to be able to satisfy the requests from electric users of the hybrid vehicle.

In the event that this check gives a negative result (i.e. in the case in which the state of charge of the battery 16 is not sufficient to supply the total E-telelectric energy required by the reversible electric machine 14 at the instant in which a request to increase the drive torque C by the driver, i.e. to ensure both the supply of the additional electrical energy ∆E (∆Cm) necessary for the additional drive torque ∆Cm to the drive wheels and the supply to be able to meet the requests from the electric users of the hybrid vehicle), then the control unit 13 is arranged to control the reversible electric machine 14 so that it functions as an electric energy generator to supply only the electric energy necessary to satisfy the requests from the electric users of the hybrid vehicle.

In other words, in the event that the check gives a negative result (i.e. in the case in which the state of charge of the battery 16 is not sufficient to supply the total E-telelectric energy required by the reversible electric machine 14 and such as to guarantee both the supply of the additional electrical energy ∆E (∆Cm) to guarantee the additional ∆Cdrive torque to the drive wheels and to meet the demands of the electric utilities of the hybrid vehicle), the additional ∆Cmdrive torque to the drive wheels is supplied by the internal combustion engine 2.

In the event that the check gives a positive result (i.e. if the state of charge of the battery 16 is sufficient to supply the total E-telelectric energy required to the reversible electric machine 14 at the instant in which a request to increase the drive torque C by the driver or to ensure both the supply of the additional electrical energy ∆E (∆Cm) necessary for the additional drive torque ∆C to the drive wheels and the supply to be able to meet the requests from the electric utilities of the hybrid vehicle), then the control unit 13 is arranged to control the reversible electric machine 14 so that it functions as a generator of electric energy to supply the total E-telelectric energy.

In other words again, in the event that the verification gives a positive result (i.e. in the case in which the state of charge of the battery 16 is sufficient to supply the total E-telelectric energy required by the reversible electric machine 14 and such as to guarantee both the supply of the additional electrical energy ∆E (∆Cm) to guarantee the additional ∆Cdrive torque to the drive wheels and to meet the demands of the electric utilities of the hybrid vehicle), the additional ∆Cmdrive torque to the drive wheels is supplied by the reversible electric machine 14 which intervenes from booster.

It is important to point out that the operation of the reversible electric machine 14 is almost immediate and it is possible to provide the additional ∆Cdrive torque necessary to meet the demands of the driver who intervenes on the accelerator pedal with a substantially negligible transient.

As illustrated in Figure 2, in the transition interval between the instants t1 and t2 (in which t1 represents the instant in which a request for an increase in the driving torque C is recognized by the driver who intervenes on the accelerator pedal and t2 represents the 'instant in which the transition period ends, as will be better explained in the rest of the discussion) the target torque Cm_objmotrice such as to guarantee to satisfy the request of the driver who intervenes on the accelerator pedal is given by the sum of two contributions according to the equation following:

Cm_obj = Cm_iCme_i [3]

t1 <i <t2

In which:

Cm_obj: objective drive torque such as to ensure that the request of the driver who intervenes on the accelerator pedal is met;

Cm_i: engine torque supplied by the internal combustion engine 2 at the i-th instant; And

Cme_i: drive torque provided by the reversible electric machine 14 at the i-th instant.

The trend of the Cme_imotrice torque supplied by the reversible electric machine 14 at the i-th instant is indicated with A in figure 2. The Cme_imotrice torque supplied by the reversible electric machine 14 has a maximum value in the instant (indicated with t1) in which it is recognized a request for an increase in the driving torque C by the driver who intervenes on the accelerator pedal; at this instant, the reversible electric machine 14 supplies the drive wheels entirely with the additional torque ∆Cmmotrice calculated through [1].

The trend of the Cme_imotrice torque supplied by the reversible electric machine 14 has a progressively decreasing trend and a minimum value at the instant indicated with t2 in which the reversible electric machine 14 works again only for the supply of electricity necessary for the electric utilities of the hybrid vehicle.

In the transition interval between the instants t1 and t2, the torque Cme_imotrice supplied by the reversible electric machine 14 is equal to a fraction (gradually decreasing) of the target torque Cm_objmotrice such as to guarantee to satisfy the request of the driver who intervenes on the accelerator pedal .

The trend of the Cm_imotrice torque provided by the internal combustion engine 2 at the i-th instant is indicated with B in Figure 2.

This Cm_imotrice torque supplied by the internal combustion engine 2 has a minimum value in the instant (indicated with t1) in which a request for an increase in the driving torque C is recognized by the driver who intervenes on the accelerator pedal. The trend of the Cm_imotrice torque supplied by the internal combustion engine 2 is gradually increasing and assumes a maximum value at the instant indicated with t2 in which it is equal to the target Cm_objmotrice torque such as to guarantee to satisfy the request of the driver who intervenes on the accelerator pedal .

In the transition interval between the instants t1 and t2, the torque Cm_imotrice supplied by the internal combustion engine 2 is equal to a fraction (gradually increasing) of the target torque Cm_objmotrice such as to guarantee to satisfy the request of the driver who intervenes on the pedal of the accelerator.

With C in figure 2, on the other hand, the trend of the total Cm_totmotrice torque to the driving wheels is indicated; in particular, the value is constant until the instant (indicated with t1) in which a request for an increase in the driving torque C is recognized by the driver who intervenes on the accelerator pedal and is constant again starting from the instant t1 and even to the target torque Cm_objmotrice such as to guarantee to satisfy the request of the driver who intervenes on the accelerator pedal.

The control unit 13 is arranged so that the progressively increasing trend of the Cm_imotrice torque supplied by the internal combustion engine 2 (until the target Cm_objmotrice torque is reached such as to guarantee to satisfy the request of the driver who intervenes on the accelerator pedal) allows to explore a succession of stabilized engine points which in turn guarantee to optimize the performance of the internal combustion engine 2.

In other words, the control unit 13 is predisposed to control the internal combustion engine 2 so that in the transition interval between the instants t1 and t2 the internal combustion engine 2 itself operates in stabilized engine points (i.e. which allow to optimize the performance of the internal combustion engine 2 itself) until the target torque Cm_objmotrice is reached such as to ensure that the request of the driver who intervenes on the accelerator pedal is satisfied.

In the transition interval between the instants t1 and t2, the additional torque ∆Cmmotrice to be supplied to the driving wheels calculated through [1] is therefore given by the sum of two contributions: a first contribution of increasing amplitude due to the torque Cm_imotrice supplied by the internal combustion engine 2 and a second contribution of gradually decreasing amplitude due to the Ce_imotrice torque supplied by the reversible electric machine 14.

It is important to highlight that the increasing trend indicated with B in Figure 2 of the Cm_imotrice torque provided by the internal combustion engine 2 allows to optimize the performance of the internal combustion engine 2 itself. In fact, the internal combustion engine 2 explores a succession of stabilized engine points which make it possible to optimize fuel consumption and reduce polluting emissions.

According to a different embodiment not shown, the connection device 18 comprises a pair of clutches, which replace the synchronizer 21 and are interposed between the shaft 17 of the reversible electric machine 14 and respectively the primary shaft 5 and the shaft 7 secondary.

The above discussion can also find advantageous application in a hybrid vehicle with series architecture or in a hybrid vehicle with mixed series / parallel architecture.

The control method of a hybrid vehicle described up to now has the advantage of allowing the reversible electric machine 14 to perform the function of booster to obtain the additional drive torque to the drive wheels with a substantially negligible transient and always in the most favorable conditions, that is in order to optimize fuel consumption and reduce polluting emissions.

Claims (1)

CLAIMS 1.- Control method of a hybrid vehicle equipped with an internal combustion engine (2), a power-assisted transmission (1) and a reversible electric machine (14) designed to generate a drive torque (C) to be transmitted to the wheels motor vehicles; the method involves the steps of: recognize a request for an increase in the driving torque (C) by the driver who intervenes on the accelerator pedal; learn the driving torque (Cm) supplied to the drive wheels by the internal combustion engine (2) at the instant (t1) in which a request for an increase in the driving torque (C) is recognized by the driver who intervenes on the accelerator pedal ; calculate an objective driving torque (Cm_obj) to be supplied to the driving wheels such as to satisfy the request for an increase in driving torque (C) by the driver who intervenes on the accelerator pedal; And determine an additional driving torque (∆Cm) to be supplied to the driving wheels to satisfy the request for an increase in driving torque (C) by the driver who intervenes on the accelerator pedal by means of the difference between the objective driving torque (Cm_obj) such as to satisfy the request to increase the driving torque by the driver who intervenes on the accelerator pedal and the driving torque (Cm) supplied to the drive wheels by the internal combustion engine (2) at the instant (t1) in which a request is recognized increase of the driving torque (C) by the driver who intervenes on the accelerator pedal; and control the reversible electric machine (14) to provide the drive wheels with the additional drive torque (∆Cm) to meet the request for an increase in drive torque (C) by the driver who intervenes on the accelerator pedal. 2.- Control method according to Claim 1, wherein the reversible electric machine (14) is connected to an accumulation system (16) suitable for storing electric energy; the method involves the further steps of: learning the state of charge of the storage system (16); And control the reversible electric machine (14) to supply the drive wheels with the additional drive torque (∆Cm) only if the state of charge of the storage system (16) is sufficient to supply the additional drive torque (∆Cm) for satisfy the request for an increase in the driving torque (C) by the driver who intervenes on the accelerator pedal. 3.- Control method according to Claim 2 and comprising the further step of controlling the internal combustion engine (2) to supply the drive wheels with the additional drive torque (∆Cm) in the event that the state of charge of the system ( 16) of accumulation is not sufficient to supply the additional driving torque (∆Cm) to satisfy the request for an increase in the driving torque (C) by the driver who intervenes on the accelerator pedal. 4.- Control method according to one of the preceding claims, in which the objective driving torque (Cm_obj) to ensure that the request of the driver who intervenes on the accelerator pedal is met is given by the following equation: Cm_obj = Cm_iCme_i [3] t1 <i <t2 In which: Cm_obj: objective drive torque such as to ensure that the request of the driver who intervenes on the accelerator pedal is met; Cm_i: engine torque provided by the internal combustion engine (2) at the i-th instant; Cme_i: drive torque provided by the reversible electric machine (14) at the i-th instant; And t1: initial instant of a transition period in which that corresponds to the instant in which a request to increase the driving torque (C) is recognized by the driver who intervenes on the accelerator pedal; And t2: final instant of the transition period. 5.- Control method according to Claim 4, and comprising the further step of controlling, in the transition interval, the internal combustion engine (2) to operate in stabilized engine points, or to explore a succession of points which allow to optimize the performance of the internal combustion engine (2) itself. 6.- Control method according to claim 4 or 5, in which the driving torque (Cm_i) supplied by the internal combustion engine (2) has an increasing trend during the transition interval. 7.- Control method according to Claim 6, in which the driving torque (Cm_i) supplied by the internal combustion engine (2) assumes a maximum value at the final instant (t2) of the transition period in which it is equal to the torque (Cm_obj ) objective driving force to be supplied to the driving wheels such as to satisfy the request for an increase in driving torque (C) by the driver who intervenes on the accelerator pedal. 8.- Control method according to one of claims 4 to 7, in which the driving torque (Cme_i) provided by the reversible electric machine (14) has a decreasing trend during the transition interval. 9.- Control method according to claim 8, in which the driving torque (Cme_i) supplied by the reversible electric machine (14) assumes a maximum value at the initial instant (t1) of the transition period.