FR2812589A1 - Engine and gearbox control system uses variation in clutch operating pressure to maintain constant output speed and torque - Google Patents

Abstract

The thermal engine and automatic gearbox and controlled by units (22 and 24) which regulate the speed and output torque of the engine, by varying the pressure applied to the clutch, with reference to a reference pressure value (CPE). The drive unit comprises a thermal engine (12), a clutch (16) and a controlled transmission (18). Units are provided for controlling both the engine and the clutch of the transmission (22 and 24 respectively). The engine control unit (22) is able to adjust the couple provided by the engine with reference to a reference couple value (CCM). The unit controls the speed of the engine by controlling the pressure with which the clutch (16) is pressed together, transmitting a reference pressure (CPE) to the hydraulic unit (30) which modulates the clutch pressure and controls the selection of a specific gear. The clutch control unit (24) includes a system for modulating the clutch pressure reference (CPE) to adjust the real speed of the engine (12) to maintain the reference speed (CRM).

Description

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"Method for controlling the speed of rotation of an engine by modulating the torque transmitted by a clutch of an automated transmission" The invention relates to a motor vehicle powertrain.

The invention relates more particularly to a motor vehicle powertrain, of the type which comprises, from upstream to downstream, a controlled heat engine, a friction-controlled coupling clutch, and a controlled automated transmission of the type which comprises at least one unit. engine control unit and a clutch and transmission control unit, of the type in which the engine control unit is capable of regulating the engine torque in response to a torque command formulated by a driver of the vehicle and of the type in which the clutch and transmission control unit is capable of controlling the rotation speed of the engine by controlling the clutch tightening pressure by issuing a clutch tightening pressure setpoint at the intention of a hydraulic element for modulating the clutch pressure and establishing at least one reduction ratio of the automated transmission.

The main advantages of such a method are to optimize comfort, consumption and acoustics by positioning the engine at its optimum operating points.

To this end, the invention provides a propulsion unit of the type described above, characterized in that the clutch and transmission control unit includes means for modulating the clutch tightening pressure setpoint. to adjust the actual engine rotation speed to the speed setpoint value.

According to other features of the invention

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 - the clutch and transmission control unit receives parameters including in particular # engine torque information sent by the engine control unit representative of the torque that will actually be delivered by the engine, # information representative of the actual engine rotation speed which is emitted by a first sensor upstream of the clutch, and # information representative of the actual speed of rotation of an input shaft of the automated transmission, downstream of the clutch, according to which it establishes the clutch tightening pressure setpoint and the engine speed setpoint; - the clutch and transmission control unit includes a first calculation and control module which establishes the engine speed setpoint according to the measurement of the engine torque and the actual speed of the input shaft of the transmission, in particular so as to control the variations in the rotation speed of the engine and the slip of the clutch; the clutch and transmission control unit comprises a second calculation module which determines a first torque derivative variable, corresponding to the time derivative of the value of the engine torque information; - the clutch and transmission control unit includes a third calculation module which determines # a second deviation variable, corresponding to the difference between the value of the engine speed information and the value of the engine speed setpoint, and # a third variable derived from deviation, corresponding to the time derivative of the second variable;

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 - the clutch and transmission control unit comprises a fourth calculation and control module which determines the value of the clutch pressure setpoint as a function of the engine torque setpoint, of the first variable derived from torque, the second deviation variable, and the third derived deviation variable; the fourth calculation module comprises # a comparison module, which compares the value of the first variable derived from torque with a determined threshold, to determine a first operating mode if the first variable derived from torque is less than the determined threshold and a second operating mode if the second torque-derived variable is greater than the determined threshold, # a digital regulation module which is capable, in the first operating mode, of operating according to a law with variable coefficients which are a function of the second variable d and the third variable derived from deviation to establish the clutch pressure pressure setpoint and transmit it to the hydraulic element for modulating the clutch pressure, and # a module for learning the behavior of the clutch and the hydraulic element for modulating the clutch pressure which is susceptible, in the second mode of fo operation, to associate a determined value of the clutch pressure setpoint with each value taken by the torque information, using a mathematical model whose parameters are

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 obtained by identification during the first operating mode so as to minimize the difference between the pressure setpoint determined by the mathematical model and the pressure setpoint determined by the digital control module, to establish the pressure pressure setpoint of clutch and transmit it to the hydraulic element for modulating the clutch pressure.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: - Figure 1 is a diagram of a powertrain comprising a unit of control of the engine and a clutch and transmission control unit produced in accordance with the invention, - Figure 2 is a detailed exploded perspective diagram of the different modules of the clutch control unit and the transmission, and - Figure 3 is a detailed diagram of the fourth module for calculating the clutch control unit and the transmission.

In the following description, identical reference numerals designate identical parts or having similar functions.

There is shown in Figure 1 the whole of a motor vehicle powertrain 10.

In known manner, the powertrain 10 comprises, from upstream to downstream, a thermal engine 12 controlled, which is coupled to a set 14 of torque controlled transmission which includes in particular a controlled clutch 16

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 friction, and a controlled automated transmission 18 which is capable of transmitting engine torque to a wheel 20 of the vehicle. The controlled clutch 16 may, by way of example and without limitation of the invention, be a multi-plate clutch in oil bath which comprises a plurality of discs which are driven by an output shaft 34 of the heat engine 12 and which can be tightened by means of a hydraulic cylinder controlled against a plurality of plates driving the automated transmission 18 by means of an input shaft 35 of the transmission 18.

The powertrain 10 comprises at least one unit 22 for controlling the engine and a unit 24 for controlling the clutch 16 and the transmission 18. The unit 22 for controlling the engine controls the engine 12 for example by means of one or more piloted intake members 26.

In particular, the unit 22 is capable of regulating the torque of the engine 12 in response to a setpoint of engine torque CCM which is formulated by a driver of the vehicle, for example by means of an accelerator pedal 28.L the clutch and transmission control unit 24 is capable of controlling the tightening of the clutch 16 by issuing a CPE clutch tightening pressure instruction intended for a hydraulic element 30 for modulating the pressure of the clutch 16 and to establish at least one reduction ratio of the automated transmission 18.

In accordance with the invention, the unit 24 for controlling the clutch 16 and the transmission 18 includes means for modulating the CPE setting of the clutch tightening pressure 16 to adjust the real speed of rotation of the engine 12 to the value of the engine speed CRM setpoint.

This setpoint can for example be determined so as to ensure the filtering of the acyclisms generated by the

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 engine 12, while minimizing the power dissipated by sliding in the coupling clutch 16.

To this end, the clutch and transmission control unit 24 receives different parameters from the entire powertrain 10, as a function of which it establishes the clutch clamping pressure CPE setpoint and the setpoint Engine speed CRM. These parameters include in particular - the engine torque information CCM which is sent by the engine control unit 22, - RM information representative of the actual engine rotation speed which is sent by a first sensor 32 which is arranged on a input shaft 34 upstream of the clutch 16, and - RT information representative of the actual speed of rotation of the input shaft 35 of the automated transmission, which is emitted by a sensor 36 arranged downstream of the 'clutch 16 on the input shaft 35 of the transmission.

The operating detail of the clutch and transmission control unit 24 is now described with reference to FIG. 2.

The unit 24 comprises a first calculation and control module 38 which establishes the engine speed setpoint CRM as a function of the information CCM of engine torque and of the real speed RT of the input shaft 35 of the transmission, in particular so as to control the variations in the speed RM of rotation of the engine 12 and the slip of the clutch 16, that is to say the difference between the engine speed and the speed RT of the input shaft 35 of the transmission .

The clutch and transmission control unit 24 comprises a second calculation module 40 which determines a first torque-derived OCCM variable,

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 corresponding to the time derivative of the value of the information CCM of engine torque OCCM = d (CCM) / dt The clutch and transmission control unit 24 comprises a third calculation module 42 which determines - a second ERM deviation variable, corresponding to the difference between the value of the RM information of the engine speed and the CRM engine speed setpoint value: ERM = RM-CRM - and a third variable derived from oERM deviation corresponding to the time derivative of the second variable: oERM = d (ERM) / dt = d (RM-CRM) / dt These variables and information are sent to a fourth module 44 for calculation and control which determines the value of the clutch pressure setpoint CPE and transmits it to the hydraulic element 30 for modulating the clutch pressure 16. The fourth calculation and control module 44 therefore receives directly from the control unit 22 CCM engine torque information , from the second module 42, the first OCCM variable derived from torque, and from the third module 42, the second deviation ERM variable and the third variable AERM derived from deviation.

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 The details of the operation of the fourth calculation and control module 44 are now described with reference to FIG. 3.

According to the invention, the fourth calculation module comprises firstly a comparison module 46, which compares the absolute value of the first torque-derived OCCM variable with a determined threshold S, to determine a first operating mode M1 if the first torque-derived OCCM variable is less than the determined threshold S and a second operating mode M2 if the first torque-derived OCCM variable is greater than the determined threshold S.

In this way, the comparison module 46 behaves like a two-position switch which determines the operation of the fourth module 44 according to the operating mode M1 or M2.

The fourth calculation and control module 44 also includes a digital regulation module 48 which is capable, in the first operating mode M1, of operating according to a law with variable coefficients which are a function of the second difference variable ERM and of the third variable DERM derived from deviation for establishing the CPE clutch pressure setpoint and transmitting it to the hydraulic element 30 for modulating the clutch pressure. Since such a digital regulation module is known from the state of the art, it will not be described more explicitly in the present description. It is for example of the non-linear PID type, a structure adapted to the non-linear properties of the friction of the coupling clutch 16.

Due to its construction, the digital regulation module 48 ensures optimal positioning of the engine RM speed at the CRM setpoint as long as the first

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 OCCM variable derived from torque is less than threshold S, i.e. as long as the engine torque varies slowly.

The fourth calculation and control module 44 finally comprises a module 50 for learning the behavior of the clutch 16 and of the hydraulic element 30 for modulating the pressure of the clutch which is capable, in the second mode M2 of operation, to associate a determined value of the clutch pressure setpoint with each value taken by the torque CCM information, using a mathematical model M whose parameters are obtained by identification during the first mode M1 operating so as to minimize the difference between the CPE pressure setpoint which is determined by the mathematical model and the CPE pressure setpoint determined by the digital regulation module 48, to establish the CPE clutch pressure pressure setpoint and transmit it to the hydraulic element 30 for modulating the pressure of the clutch 16.

In fact, if the first ACCM variable derived from torque is greater than the threshold S, this means that the torque delivered by the motor varies rapidly, and the digital regulation module 48 is unsuitable for satisfactorily guaranteeing the positioning of the speed RM to the value CRM deposit. In this case, only the calculation of the CPE pressure command by the mathematical model M is able to guarantee an adequate positioning of the engine speed RM at the setpoint CRM, thus ensuring a dynamic of the clutch tightening pressure 16 correlated with that of the torque delivered by the engine.

This correlation is only possible if the CCM information delivered by the engine control unit is in time ahead of the torque actually delivered by the engine.

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 To allow learning of the module 50, a link 52 allows for example the learning module 50 to receive information from the digital regulation module 48 during the first operating mode M1, so as to establish an appropriate correlation of the sound coefficients mathematical model M so as to minimize the difference between the prediction of the model and the pressure setpoint.

It will be understood that different types of mathematical models M can be used, whether they are of the discrete or continuous type, without modifying the characteristics and advantages of the invention. .

It will also be understood that the process of identifying the mathematical model M is made necessary because of the manufacturing dispersions, in particular of the engine 12, of the coupling clutch 16 and of the hydraulic control unit 30.

The invention therefore makes it possible to optimally adjust the actual engine rotation speed RM of the engine 12 to the value of the engine speed setpoint CRM, generally close to the input rotation speed of the automatic transmission, whatever variations in the torque delivered by the engine.

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Claims (7)

1. Powertrain (10) of a motor vehicle, of the type which comprises, from upstream to downstream, a heat engine (12) controlled, a clutch (16) friction controlled, and a controlled automatic transmission (18), of the type which comprises at least one engine control unit (22) and a clutch and transmission control unit (24), of the type in which the engine control unit (22) is capable of regulating the torque of the engine (12) in response to a torque setpoint (CCM) formulated by a driver of the vehicle and of the type in which the clutch and transmission control unit (24) is capable of controlling the rotation speed of the engine by controlling the clutch tightening pressure (16) by issuing a clutch tightening pressure instruction (CPE) for a hydraulic element (30) for modulating the clutch pressure (16) and to establish at least one transmission reduction ratio ( 16) automated, characterized in that the clutch and transmission control unit (24) comprises means for modulating the clutch tightening pressure setpoint (CPE) to adjust the actual rotation speed of the engine (12) at the speed setpoint value (CRM). 2. Powertrain (10) according to the preceding claim, characterized in that the clutch and transmission control unit (24) receives parameters comprising in particular - information (CCM) of engine torque emitted by the engine control unit (22), and representative of the torque that will actually be delivered by the engine. <Desc / Clms Page number 12>  - information (RM) representative of the actual engine rotation speed which is emitted by a first sensor (32) upstream of the clutch (16), and - information (RT) representative of the actual speed of rotation of an input shaft (35) of the automated transmission, downstream of the clutch (16), as a function of which it establishes the setpoint (CPE) of clutch tightening pressure and the setpoint (CRM) of engine speed. 3. Powertrain (10) according to the preceding claim, characterized in that the unit (24) for controlling the clutch and the transmission comprises a first module (38) for calculation and control which establishes the setpoint (CRM ) of engine speed as a function of the information (CCM) of engine torque and of the real speed (RT) of the input shaft (35) of the transmission, in particular so as to control the variations of the speed (RM) rotation of the motor (12) and the sliding of the clutch (16). 4. Powertrain (10) according to the preceding claim, characterized in that the unit (24) for controlling the clutch and the transmission includes a second calculation module (40) which determines a first derived variable (4CCM) of torque, corresponding to the time derivative of the engine torque information (CCM). 5. Powertrain (10) according to one of claims 3 or 4, characterized in that the unit (24) for controlling the clutch and the transmission comprises a third calculation module (42) which determines - a second deviation variable (ERM), corresponding to the difference between the value of the engine speed information (RM) and the engine speed setpoint value (CRM), and <Desc / Clms Page number 13>  - a third variable derived from deviation (AERM), corresponding to the time derivative of the second variable (ERM). 6. Powertrain (10) according to claims 3 to 5, characterized in that the unit (24) for controlling the clutch and the transmission comprises a fourth module (44) for calculation and control which determines the value of the clutch pressure setpoint (CPE) as a function of the engine torque information (CCM), of the first torque-derived variable (ACCM), of the second deviation variable (ERM), and of the third deviation derived variable (DERM). 7. Powertrain (10) according to the preceding claim, characterized in that the fourth calculation module (44) comprises - a comparison module (46), which compares the value of the first torque derived variable (ACCM) to a threshold (S) determined, to determine a first mode (M1) of operation if the first variable derived from torque (ACCM) is less than the threshold (S) determined and a second mode of operation if the first variable derived from torque (ACCM) is greater than the determined threshold (S), - a digital regulation module (48) which is capable, in the first operating mode (M1), of operating according to a law with variable coefficients which are a function of the second deviation variable (ERM) and the third derivative variable of deviation (oERM) to establish the clutch pressure pressure setpoint (CPE) and transmit it to the hydraulic element (30) for modulating the clutch pressure ( 16), and - a learning module (50) of the behavior of the clutch (16) and of the hydraulic element (30) for modulating the pressure of the clutch (16) which is capable, in the <Desc / Clms Page number 14>  second operating mode (M2), associating a determined value of the clutch pressure setpoint (CPE) with each value taken by the torque information (CCM), using a mathematical model (M ) whose parameters are obtained by identification during the first operating mode (M1) so as to minimize the difference between the pressure setpoint (CPE) determined by the mathematical model (M) and the pressure setpoint (CPE) determined by the digital regulation module (48), to establish the clutch pressure pressure setpoint (CPE) and transmit it to the hydraulic element (30) for modulating the clutch pressure (16).