FR3070343B1 - TORQUE CONTROL TRANSMITTED BY AN AUTOMATIC TRANSMISSION OF A VEHICLE DURING A REPORT CHANGE - Google Patents

Abstract

A control device (DC) equips a vehicle (V) comprising a gearbox (BV) of automatic type with planetary gear trains (TE1-TE3) each associated with a clutch (EM1-EM3) comprising a piston (P1-P3) exerting pressure on disks (DE1-DE3), and a prime mover (MT) providing a driving torque. This device (DC) determines, during a change between outgoing and incoming reports, an optimum pressure to be exerted by the piston (P1) associated with the inboard ratio to transmit the engine torque when the oil temperature is less than one. first threshold and the number of uses of the clutch (EM1) containing this piston (P1) is less than a second threshold, ie a reduced pressure to be exerted by this piston (P1) to transmit a reduced torque, equal to the torque engine supplied minus a chosen value, when the oil temperature is above the first threshold or the number of uses is greater than the second threshold.

Description

The invention relates to vehicles which comprise an automatic gearbox with epicyclic gear trains and coupled to a prime mover (thermal or non-thermal). , and more precisely the control of the engine torque which is transmitted by such a gearbox.

As known to those skilled in the art, an automatic gearbox, of the type mentioned in the preceding paragraph, comprises epicyclic gear trains whose different parts (crowns, satellites, planetary and planet carriers) are driven by hydraulic elements (clutches and brakes) associated to create the different gear ratios. Each clutch, just like every brake, comprises a piston charged to exert a chosen pressure on disks (clutch).

The transmission of the engine torque, which is provided by the prime mover, is guaranteed by the pressure exerted by the clutch and brake pistons.

The gear changes (from a so-called outgoing ratio to a so-called incoming ratio), or gear changes, are performed by "crossing" (or reversing) the pressures which are exerted respectively by the pistons of the hydraulic elements associated with the planetary gear trains of the outgoing and incoming reports. To do this, the hydraulic element (clutch or brake) associated with the outgoing ratio is emptied and the pressure in the hydraulic element associated with the inward ratio is increased. It will be noted that during a crossing, the pressures in the two hydraulic elements concerned are piloted in order to continue transmitting engine torque to the wheels and thus not to disturb the longitudinal acceleration of the vehicle.

Currently, the design of the automatic transmission takes into account the maximum engine torque that must be transmitted when a gear is engaged with the locked clutch, but not the maximum engine torque that must be transmitted during a gear change. (outgoing ratio to inbound ratio) with sliding clutch. The transmission capacity of the engine torque during the sliding phase of a clutch depends in particular on the friction surface of its disks, the number of its disks, the average diameter of its disks and the pressure exerted on its disks.

The number of disks used and the level of pressure exerted on these disks during a change of ratio causes energy dissipation which induces not only losses but also wear of the parts (function of the number of passages of the associated report).

In order to reduce the losses, which increase the energy consumption and therefore the production of pollutants, it is possible to undersize the gearbox and implement a strategy for limiting the maximum engine torque received by this gearbox during certain phases. driving the vehicle. However, currently this type of strategy usually consists of reducing the engine torque supplied by the prime mover in the phases in which the gearbox can not transmit all the engine torque normally expected. In fact, the engine torque supplied is reduced only when the transmission chain is closed (closed clutches), but not during the gear change phases during which the pressure crossings occur in the hydraulic elements concerned. This results in a limitation of the performance of the transmission chain since the couples transmitted when a report is engaged and during a gear change are different. In addition, this limitation can vary depending on the temperature of the oil in the gearbox, since this oil temperature influences the ability of the clutches to transmit the engine torque. The invention is therefore particularly intended to improve the situation.

It proposes for this purpose a control device intended to equip a vehicle comprising a gearbox of the automatic type with planetary gear trains defining ratios and each associated with a clutch comprising a piston exerting pressure on disks, and a driving machine providing a torque engine to the gearbox.

This control device is characterized in that it comprises control means which, when a change of an outgoing ratio to an incoming ratio has been decided, determine: - either an optimum pressure to be exerted by the piston which is associated with the incoming gear for transmitting integrally the engine torque supplied (by the prime mover) when an oil temperature in the gearbox is lower than a first chosen threshold and a number of uses of the clutch containing this piston is less than a second chosen threshold, or a reduced pressure to be exerted by the piston which is associated with the incoming ratio to transmit a reduced torque, equal to the engine torque supplied (by the prime mover) minus a chosen value, when this oil temperature is higher than this first threshold chosen or that this number of uses is greater than this second threshold chosen.

Thanks to the invention, the life of the gearbox is guaranteed without its torque transmission capacity is limited when it is new or recent and in the presence of an optimum oil temperature.

The control device according to the invention may comprise other characteristics that can be taken separately or in combination, and in particular: its control means can choose the value to be subtracted from the engine torque as a function of at least one parameter which is selected from a current vehicle speed, the outgoing ratio, and an ongoing maneuver of the vehicle; its control means can use a first threshold chosen which is between 90 ° C and 110 ° C; its control means may use a second threshold chosen which is between 25,000 and 35,000. The invention also proposes a computer comprising a control device of the type of that described above. The invention also proposes a vehicle, possibly of automotive type, and comprising a) an automatic gearbox with epicyclic gear sets defining ratios and each associated with a clutch comprising a piston exerting pressure on disks, b) a machine motor providing engine torque to the gearbox, and c) a control device of the type shown above or a calculator of the type shown above. The invention also proposes a control method, intended to be implemented in a vehicle comprising an automatic gearbox with epicyclic gear sets defining ratios and each associated with a clutch comprising a piston exerting pressure on disks, and a prime mover providing engine torque to the gearbox.

This method is characterized in that it comprises a step in which, when a change of an outgoing ratio to an incoming ratio has been decided, it is determined: - either an optimum pressure to be exerted by the piston which is associated to the incoming gear for transmitting integrally the engine torque supplied when an oil temperature in the gearbox is lower than a first selected threshold and a number of uses of the clutch containing the piston is less than a second threshold chosen, - either a reduced pressure to be exerted by the piston which is associated with the incoming gear to transmit a reduced torque, equal to the engine torque supplied minus a chosen value, when this oil temperature is above this first threshold chosen or this number of uses is greater than this second threshold chosen.

For example, in the process step it is possible to choose the value to be subtracted from the engine torque as a function of at least one parameter which is chosen from a current speed of the vehicle, the outgoing ratio, and a current maneuver of the vehicle. Other features and advantages of the invention will appear on examining the detailed description below, and the attached drawing, in which the single figure schematically and functionally illustrates a vehicle comprising a transmission chain and a supervision computer. equipped with a control device according to the invention. The object of the invention is in particular to propose a DC control device intended to equip a vehicle V comprising a transmission chain comprising at least one driving machine (thermal or non-thermal) MT providing engine torque cm to a gearbox BV of automatic type with epicyclic gear trains.

In what follows, it is considered, by way of non-limiting example, that the vehicle V is automotive type. This is for example a car. But the invention is not limited to this type of vehicle. It relates in fact to any type of vehicle comprising at least one driving machine (thermal or non-thermal) coupled to an automatic gearbox type epicyclic gear and providing engine torque for at least one train (or the like). Therefore, the invention relates at least to land vehicles.

Here, the term "non-thermal driving machine" means a machine arranged to provide or recover torque to move a vehicle, either alone or in addition to a heat engine. It may for example be an electric machine (or motor), a hydraulic machine, a pneumatic machine (or compressed air), or a flywheel.

Furthermore, the term "heat engine" is understood to mean a machine or engine that consumes fuel to produce torque to move a vehicle.

FIG. 1 shows schematically a vehicle V comprising a transmission chain, a supervision computer CS capable of supervising (or managing) the operation of the transmission chain, and a DC control device according to the invention.

The transmission chain here comprises, in particular, a motor machine MT, an engine shaft AM, a gearbox BV and a transmission shaft AT.

It is important to note that the transmission chain is here of conventional type (that is to say that its MT motor is thermal, and therefore it is devoid of non-thermal driving machine). But it could be hybrid type. In this case it comprises, in addition to its thermal driving machine, at least one non-thermal driving machine responsible for producing torque, from the energy stored in an energy storage means, for at least one train ( possibly different from that which is coupled to the thermal engine), in addition to or instead of the engine torque produced by the thermal engine. Each non-thermal driving machine may, for example, be an electric machine (or motor), a hydraulic machine, or a pneumatic (or compressed air) machine, or a flywheel.

The driving machine MT (here a heat engine) comprises a crankshaft (not shown) which is fixedly attached to the drive shaft AM to drive the latter (AM) in rotation. It is intended to provide motor torque cm for at least a first train T1 (here wheels), via (here) the gearbox BV. But in a hybrid embodiment it could provide torque for at least one train via a clutch, a non-thermal engine and the BV gearbox.

For example, the first train T1 is located at the front of the vehicle V, and coupled to the transmission shaft AT, preferably, and as illustrated, via a differential (here before) D1. But in a variant, this first train T1 could be located at the rear of the vehicle V. In another variant, the heat engine MT could provide engine torque cm for first T1 and second T2 trains.

The gearbox BV is of the automatic type with at least two epicyclic gear trains TE] defining ratios (at least two). In the nonlimiting example illustrated in the single figure, the gearbox BV comprises three epicyclic gear trains TE1 to TE3 (j = 1 to 3). But it could have only two planetary gear trains or more than three (this depends on the number of reports envisaged).

Each planetary gear train TEj comprises, for example, crowns, satellites, planetary gears and planet carriers which are controlled by (and therefore associated with), in particular, a clutch EMj which comprises a piston Pj responsible for exerting a chosen pressure on a set discs (clutch) DEj.

The input of this gearbox BV is coupled to the motor shaft AM to receive the engine torque cm supplied by the heat engine MT. The output of this gearbox BV is coupled to the transmission shaft AT to provide a transmitted torque and.

The transmission chain also comprises a starter or an alternator-starter AD coupled to the heat engine MT and responsible for launching the latter (MT) to allow it to start. This launch is done through electrical energy which is stored in a rechargeable battery BR, which also feeds the vehicle's on-board network V to which are connected the electrical equipment of the latter (V). This rechargeable battery BR is at very low voltage (for example 12 V, 24 V or 48 V).

The operations of the thermal engine MT and the gearbox BV are controlled by the supervision computer CS.

As indicated above, the invention proposes a DC control device intended to equip the vehicle V in order to control the engine torque which is transmitted by the gearbox BV during the gear changes (of an outgoing gear, hitherto engaged , to an incoming report, to engage).

In the nonlimiting example illustrated in the single figure, the DC control device is part of the supervision computer CS. But this is not obligatory. This DC control device could indeed be a device coupled to the supervision computer CS, directly or indirectly. Therefore, the DC control device can be realized in the form of software modules (or computer or "software"), or a combination of electronic circuits (or "hardware") and software modules.

A DC control device, according to the invention, comprises MC control means which intervene whenever a change of ratio (outgoing to incoming) has been decided, for example by the supervision computer CS, while the engine MT is providing a motor torque cm, here to rotate the drive wheels of the first train T1.

These control means MC are arranged in such a way as to determine: either an optimum pressure po which must be exerted by the piston Pj which is associated with the incoming ratio in order to transmit in full the engine torque cm, supplied by the thermal engine MT, when the temperature of oil th in the gearbox BV is less than a first threshold s1 chosen and that the number of uses nj of the clutch EMj containing this piston Pj is less than a second threshold s2 chosen, - or a reduced pressure pr which must be exerted by the piston Pj which is associated with the incoming ratio to transmit a reduced torque cr, equal to the engine torque cm, supplied by the heat engine MT, minus a value vc chosen (ie cr = cm - vc), when this oil temperature th is greater than the first threshold chosen s1 or that this number of uses nj is greater than the second threshold chosen s2.

In other words, either simultaneously th <s1 and nj <s2 and in this case the piston Pj associated with the incoming ratio exerts on the disks DE] associated an optimal pressure po function of the engine torque provided cm, that is It is th> s1 or nj> s2 and in this case the piston Pj associated with the incoming ratio exerts on the associated disks DEj a reduced pressure pr function of a reduced torque cr equal to cm - vc.

It will be understood that the invention requires a vehicle equipment V, such as for example the supervision computer CS or the control device DC, to record the number of uses nj of each clutch EMj of the gearbox BV, when each change of report concerning him. The invention makes it possible to guarantee the service life of the gearbox BV without limiting its torque transmission capacity when it is new or recent (nj low) and in the presence of an optimum oil temperature th. In addition, the performance degradation during a gear change is limited and is effective only in special conditions that do not disturb the driver of the vehicle V.

For example, the control means MC may be arranged so as to choose the value vc, which must be subtracted from the engine torque supplied cm, as a function of at least one parameter which is chosen from the current speed of the vehicle V, the outgoing report, and a current maneuver of the vehicle V.

The higher the speed of the vehicle V, the less torque reduction vc will be important. It is indeed known to those skilled in the art that the higher the speed is less we need a significant engine torque to evolve.

The higher the inboard ratio, the lower the vc torque reduction will be. It is indeed known to those skilled in the art that the higher the ratio is less the need for a significant engine torque to evolve.

In the case of a current maneuver of the vehicle V, such as during a slot or an exit of a parking space, the power is calculated in order to guarantee the possibility of maneuvering the vehicle V.

For example, the control means MC can start from a base torque value equal to the engine torque supplied cm reduced by approximately 10%, and then modulate this base torque value as a function of at least one of the aforementioned parameters. (speed, inward ratio, maneuver) to obtain the chosen value vc.

Also for example, the control means MC may use a first selected threshold s1 which is between 90 ° C and 110 ° C. For example, they may use a first selected threshold s1 equal to 100 ° C. In general, this first threshold chosen s1 corresponds to the maximum value beyond which the wear of the gearbox BV (and in particular the gaskets) begins to increase significantly.

Also for example, the control means MC may use a second selected threshold s2 which is between 25000 and 35000. For example, a second chosen threshold s2 may be used equal to 30000. This threshold s2 corresponds to a number of activations of hydraulic elements (brake and clutch EMj). It corresponds to what is commonly called a "mission profile", which consists in quantifying the number of gear changes that the BV gearbox will experience in its complete use. The number of stresses of the hydraulic elements is thus determined.

It is important to note that the invention can also be considered in terms of a control method, which can be implemented in particular by means of a DC control device of the type presented above. The functionalities offered by the implementation of the method according to the invention being identical to those offered by the DC control device presented above, only the combination of main features offered by the method is presented below.

This control method comprises a step in which, when a change of an outgoing ratio to an incoming ratio has been decided (for example by the supervision computer CS), (the DC control device of the vehicle V) determines: - An optimum pressure po to be exerted by the piston Pj which is associated with the incoming gear to transmit fully the motor torque cm supplied (by the thermal engine MT) when the oil th temperature in the gearbox BV is lower than first threshold chosen s1 and that the number of uses nj of the clutch EMj containing this piston Pj is less than the second selected threshold s2, - is a reduced pressure to be exerted by the piston Pj which is associated with the incoming ratio to transmit a reduced torque cr, equal to the motor torque cm supplied (by the heat engine MT) minus a value vc chosen, when this oil temperature th is greater than the first threshold choi if s1 or this number of uses nj is greater than the second threshold chosen s2.

Claims (9)

1. Control device (DC) for a vehicle (V) comprising i) a gearbox (BV) of automatic type with epicyclic gear trains (TE)) defining ratios and each associated with a clutch (EMj) comprising a piston ( Pj) exerting pressure on disks (DEj), and ii) a prime mover (MT) providing a driving torque to said gearbox (BV), characterized in that it comprises control means (MC) which, when a change of an outgoing ratio to an incoming ratio has been decided, determine either an optimum pressure to be exerted by the piston (Pj) associated with said incoming ratio to transmit integrally said engine torque supplied when an oil temperature in said gearbox (BV) is smaller than a first selected threshold and that a number of uses of said clutch (EMj) containing said piston (Pj) is less than a second chosen threshold, ie a reduced pressure to be exerted by the piston (Pj) associated with said incoming gear for transmitting a reduced torque, equal to said supplied engine torque minus a selected value, when said oil temperature is greater than said first selected threshold or said number of uses is greater than said second threshold selected. 2. Device according to claim 1, characterized in that said control means (MC) choose said value to be subtracted from said engine torque as a function of at least one parameter selected from a running speed of said vehicle (V), said outgoing ratio , and a current maneuver of said vehicle (V). 3. Device according to claim 1 or 2, characterized in that said control means (MC) use a first threshold selected between 90 ° C and 110 ° C. 4. Device according to one of claims 1 to 3, characterized in that said control means (MC) use a second threshold selected between 25000 and 35000. 5. Computer (CA), characterized in that it comprises a control device (DC) according to one of the preceding claims. 6. Vehicle (V) comprising i) a gearbox (BV) of the automatic type with planetary gear trains defining ratios and each associated with a clutch (EM)) having a piston (Pj) exerting pressure on disks (DEj) and ii) a prime mover (MT) providing a driving torque to said gearbox (BV), characterized in that it further comprises a control device (DC) according to one of claims 1 to 4 or a computer (CA) according to claim 5. 7. Vehicle according to claim 6, characterized in that it is automotive type. 8. Control method for a vehicle (V) comprising i) a gearbox (BV) of the automatic type with planetary gear trains defining ratios and each associated with a clutch (EMj) comprising a piston (Pj) exerting pressure on discs (DEj), and ii) a prime mover (MT) providing a driving torque to said gearbox (BV), characterized in that it comprises a step in which, when a change from an outgoing gear to a gear Incoming ratio has been decided, it is determined either an optimum pressure to be exerted by the piston (Pj) associated with said incoming report to transmit integrally said engine torque provided when an oil temperature in said gearbox (BV) is less than a first threshold chosen and a number of uses of said clutch (EMj) containing this piston (Pj) is less than a second chosen threshold, ie a reduced pressure to be exerted by the piston (Pj) associated with said incoming report for transmitting a reduced torque, equal to said supplied engine torque minus a selected value, when said oil temperature is greater than said first selected threshold or said number of uses is greater than said second chosen threshold. 9. Method according to claim 8, characterized in that in said step said value is chosen to subtract said engine torque as a function of at least one parameter selected from a current speed of said vehicle (V), said outgoing ratio, and a running maneuver of said vehicle (V).