FR2837432A1 - Motor vehicle gearchange control method involves controlling clutch actuator dependent on vehicle acceleration and drive slip - Google Patents

Abstract

The motor vehicle gearbox control method involves allowing clutch release by determining the clutch (E) engagement state at a set acceleration value and determining the engine (M) torque at a slip speed between the engine output shaft and a gearbox input shaft. The method involves comparing the actual to a preset acceleration value and controlling the clutch actuator (A) dependent on the difference. Claims include a control using the method.

Description

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Method and control device for a gear change in a robotic gearbox for a motor vehicle
The invention relates to a method and a control device for a change of transmission ratio in a robotic gearbox for a motor vehicle.

 In a well known manner, a change of transmission ratio requires controlling the opening of the clutch to interrupt the transmission of an engine torque by the clutch in order to change the transmission ratio in the gearbox and then , after changing the gear, order the clutch to close to reapply engine torque to the input shaft of the gearbox.

 In other words, to change the transmission ratio, you must first decrease and cancel the engine torque in the transmission, then after changing the ratio, increase the engine torque to a value desired by the driver of the transmission. vehicle.

 In the conventional technique where the gearbox is manually controlled, the opening and closing of the clutch are controlled by the driver of the vehicle by means of a clutch pedal and a mechanical, electrical or hydraulic connection which connects the pedal to clutch release means, the adjustment of the engine torque being controlled mainly by the driver's action on the accelerator pedal and possibly corrected by torque requests controlled by an engine control system.

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 In the case of a robotic gearbox, which is a gearbox in which the transmission ratio changes are controlled by a computer system, the clutch is controlled by an actuator which is controlled by this computer system taking into account orders which are given by the driver via control elements, such as in particular the accelerator pedal (the so-called "computerized" system which may be of the digital or analog type).

 To optimize in this case the transfer of the engine torque to the drive wheels and to obtain a smooth acceleration of the vehicle, it is proposed: - to quickly open the clutch avoiding a sudden increase in the engine rotation speed and a decrease in the rotation speed in the transmission, - to synchronize the rotation speed of the engine to a value corresponding to the speed of the vehicle multiplied by the transmission ratio to be engaged, - and to avoid variations in the rotation speed of the engine during l commitment of the report, so as not to produce oscillations.

 In the known technique, the clutch control means associated with a robotic gearbox and the torque control means are generally controlled by the computer system from the engine speed, in view of the obtaining a result which is the behavior of the vehicle desired by the driver. To improve the speed and comfort of the transmission ratio changes, it would be advantageous to control the clutch control means from the engine torque.

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 However, this poses problems because we do not know how to measure the torque in the transmission and because it is necessary to act on several parameters to vary the engine torque (air and fuel flow and ignition advance or injection point for self-ignition engines).

 Furthermore, the various actuators to be controlled do not have the same characteristics and the same response times, which further increases the difficulties.

 The present invention aims in particular to provide a simple, effective and inexpensive solution to this problem.

 To this end, it proposes a control method for a change of transmission ratio in a robotized gearbox for a motor vehicle, this gearbox being connected by a clutch controlled by an actuator to the output shaft of a motor with internal combustion, this process consisting in controlling the actuator to open the clutch, then in changing the transmission ratio and in controlling the actuator to close the clutch, characterized in that it consists, for the opening of the '' clutch, to control the clutch condition to a vehicle acceleration instruction and to control the torque supplied by the engine to a slip speed instruction between the engine output shaft and an input shaft of the gearbox.

 The method according to the invention is therefore characterized by a double servo, the opening of the clutch being controlled from the acceleration of the vehicle and the torque supplied by the engine being

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 controlled from a slip setpoint between the engine and the gearbox.

 As a result, in general, greater speed and smoothness of the clutch openings for changes in transmission ratio.

 According to other characteristics of the invention, this method also consists in: determining the acceleration of the vehicle, comparing it to an acceleration reference signal and controlling the clutch actuator from their difference; - And generating said acceleration setpoint signal from the difference between a predetermined acceleration profile and an acceleration order given by the driver of the vehicle.

 This makes it possible in particular to adapt the behavior of the vehicle during changes in transmission ratio controlled by a computer system to the behavior of the vehicle desired by the driver.

 According to another characteristic of the invention, this method also consists, during a first phase of the opening of the clutch, in reducing the torque supplied by the engine in accordance with a predetermined profile of torque variation, before controlling this torque at said sliding speed setpoint.

 This simplifies the start of the clutch opening and makes it possible to implement the servo-control of the engine torque to the slip speed setpoint after a significant reduction in this engine torque.

 According to other features of the invention, this method also consists, in controlling the torque supplied by the motor to the sliding speed setpoint, in determining the rotation speeds

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 the input shaft of the gearbox and the output shaft of the engine, to make their difference, to develop a control signal from this difference and the slip speed setpoint and to apply this control signal to torque control means supplied by the engine.

 In addition, the method also consists in determining the torque supplied by the motor, in comparing it with the aforementioned control signal and in applying their difference to the aforementioned torque control means.

 Then, the method according to the invention consists, after opening the clutch, in varying the speed of rotation of the engine to adapt it to the transmission ratio to be engaged, by calculation from the speed of the vehicle and the gear reduction of the transmission report to be engaged.

 Finally, for closing the clutch after changing the transmission ratio, the method according to the invention consists in controlling the state of the clutch to a vehicle acceleration instruction and in controlling the torque supplied by the engine to a slip speed setpoint between the engine output shaft and the gearbox input shaft.

 Closing the clutch after a change in transmission ratio is thus controlled substantially in the same way as opening the clutch, with the same advantages.

 The invention also provides a control device for a change of transmission ratio in a robotic gearbox for a motor vehicle, comprising an actuator for controlling a clutch connecting the output shaft of an internal combustion engine to a input tree

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 of the gearbox, characterized in that it also comprises: - first means for generating control signals of the clutch actuator, receiving as input a signal representing an acceleration or an engine torque requested by the driver of the vehicle, a signal representing a predetermined profile of vehicle acceleration and a signal representing the actual acceleration of the vehicle, these first means developing from these signals an actuator control signal corresponding to the opening or the closing the clutch, - and second means for generating control signals applied to means for controlling the torque supplied by the engine, these second means receiving signals representing the speeds of rotation of the output shaft from the input motor and gearbox input shaft, a slip speed reference signal between the engine output shaft and the input shaft of the gearbox and a signal representing the torque supplied by the engine, these second means developing a control signal applied to the means for controlling the torque supplied by the engine.

 According to other characteristics of the invention: the first means comprise means receiving the signal representing the acceleration or the engine torque requested by the driver and the signal representing the predetermined vehicle acceleration profile and generating a setpoint signal acceleration or torque, and means receiving this setpoint signal and the actual vehicle acceleration signal and applying their difference to the clutch actuator,

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 the second means comprise means receiving the slip speed setpoint signal and a signal representing the actual slip speed and applying the difference of these signals to means generating a torque setpoint signal supplied by the motor and means receiving this setpoint signal and a signal representing the torque supplied by the motor and applying their difference to the aforementioned means for controlling the torque supplied by the motor.

 The invention will be better understood and other characteristics, details and advantages thereof will appear more clearly on reading the description which follows, given by way of example with reference to the appended drawings in which: - Figure 1 shows schematically a motor vehicle powertrain with robotic gearbox; - Figure 2 shows, in the form of block diagrams, a clutch control device according to the invention; - Figure 3 shows the variation of the torque supplied by the engine as a function of time during a gear change; - Figure 4 shows the variation of the engine speed as a function of time during this gear change.

 In the schematic representation of FIG. 1, the output shaft 10 of an internal combustion engine M is connected by a clutch E to the input shaft 12 of a gearbox BV whose shaft outlet 14 rotates the

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 driving wheels 16 of the vehicle by means of a differential 18.

 The clutch E is controlled by an actuator A itself controlled by a computer system 20 which also controls the engine M and the gearbox BV.

 To change the transmission ratio in the gearbox BV, the actuator A of the clutch E is controlled by the system 20 to control the opening of the clutch, simultaneously the engine M is controlled by the system 20 to reduce the torque supplied on the output shaft 10 and to adjust the engine rotation speed to a value determined by the vehicle speed and by the reduction of the gear ratio to be engaged, the gearbox BV is controlled by the system 20 to change the transmission ratio, then the clutch and the engine M are again controlled by the system 20 to close the clutch and to provide an engine torque adapted to the behavior of the vehicle requested by the driver.

 The clutch control device according to the invention, which is part of the system 20 and an embodiment of which is shown by way of example in FIG. 2, comprises first means 22 for controlling the clutch E and second means 24 for controlling the torque supplied by the motor M, the means 22, 24 being of the closed loop type, as will be seen in more detail below.

 In the description which follows, it will be said that the means 22 for controlling the clutch E are controlled from the acceleration of the vehicle and that the means 24 for controlling the torque supplied by the engine M are controlled from a sliding speed between the motor output shaft 10 and the shaft 12

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 gearbox input. It is clear to a person skilled in the art that the acceleration of the vehicle can be determined in several ways, for example by derivation of the speed of the vehicle, and that the acceleration of the vehicle reflects the behavior of the vehicle and also corresponds to the applied torque. to the drive wheels 16. It is also clear to a person skilled in the art that the aforementioned sliding speed can be obtained from the speed of rotation of the input shaft 12 of the gearbox, as described above. but also from the speed of rotation of the output shaft 14 of the gearbox or from the speed of the vehicle as a function of the sensors with which the vehicle is equipped.

 The first clutch control means 22 E comprise input means 26 to which are applied an order 28 of torque or acceleration given by the driver of the vehicle, in particular by action on the accelerator pedal, and a profile predetermined vehicle acceleration 30, this profile 30 being established to satisfy the condition that the torque supplied by the engine is always greater than or equal to the torque transmitted by the clutch E. In practice, different acceleration profiles are stored in memory, for example three low, medium and high acceleration profiles respectively, and one of these profiles is automatically selected according to the order 28 given by the driver and determined by the position of the accelerator pedal .

 From inputs 28 and 30, the means 26 generate an acceleration setpoint signal 32, which is compared by means 34 to a signal 36 representing the actual acceleration of the vehicle, this

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 signal being picked up at any point at the output of the clutch E. The difference of the signals 32 and 36 is applied to the actuator A which controls the clutch E first in opening, then in closing after changing the transmission ratio in the BV gearbox.

 The means 24 for controlling the torque supplied by the motor M comprise means 38 receiving as input a setpoint 40 of sliding speed between the output shaft 10 of the motor M and the input shaft 12 of the gearbox BV , as well as a signal 42 representing the real value of this sliding speed. The signal 42 is the output signal from comparator means 44 which receive as input a signal 46 representing the speed of rotation of the output shaft 10 of the motor M and a signal 48 representing for example the speed of rotation of the shaft d input 12 of the gearbox BV, this signal being taken at the output of the clutch E.

 The aforementioned means 38 generate a signal 50 which is applied to means 52 generating a signal 54 for setting the torque supplied by the motor M.

 This signal 54 is compared by means 56 to a signal 58 representing the torque supplied by the motor M and their difference is applied to means 60 for controlling the torque supplied by the motor M, these means 60 comprising for example control means ignition advance for a spark-ignition engine and means for controlling the air and fuel flow supplying the engine M.

 As shown diagrammatically in FIG. 2, the signal 36 representing the acceleration at the output of the clutch can also be applied to the engine M, as indicated in 62. This makes it possible to control the engine M, for example to avoid the runaway of the

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 motor in the event of loss of grip of a driving wheel, more quickly than by the loop comprising the means 44, 38, 52, 56 and 60 above, of which the response time is greater. This command 62 performs an arbitration between the different actuators of the engine torque in cases where rapid reaction is necessary.

 The operation of this device will now be described with reference to FIGS. 3 and 4, for controlling the clutch E with a view to changing the transmission ratio.

 In a first phase, after a clutch control command has been given by the system 20 to effect a change of transmission ratio, the torque C supplied by the engine M is reduced as shown in Cl in accordance with a predetermined profile , during a first phase starting at time tl and ending at time t2, the clutch control command being given by the system 20 at time tO.

 The opening of the clutch, which started during the first phase tl-t2, continues during a second phase t2-t3, during which the torque supplied by the motor M varies as shown in C2 until a value zero at time t3.

 During this second phase, the variation C2 of the torque supplied by the motor is controlled by a slip speed setpoint between the rotation of the output shaft 10 of the motor M and that of the input shaft 12 of the gearbox. BV gears.

 In FIG. 4, the curve V1 represents the speed of rotation of the output shaft 10 of the motor M, while the dotted curve V2 represents the speed of rotation of the input shaft 12 of the

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 gearbox, during the aforementioned second phase of the opening of the clutch E.

 It can be seen that, before the first phase and during the first phase, the speeds of rotation V1 and V2 are equal and that from the start of the second phase, the speed of rotation V2 of the input shaft of the gearbox of speeds becomes lower than the speed of rotation V1 of the output shaft of the motor M, the difference V1-V2 being constant and predetermined or variable according to a predefined law.

 The difference between the actual speeds V1 and V2 corresponds to the signal 42 applied at the input of the means 38 of the device in FIG. 2, while the signal 40 corresponds to the predefined value that this sliding speed must have. For example, the preset value of the sliding speed is such that the speed of rotation of the motor is 5.10 or 15% greater than the speed of rotation of the input shaft of the gearbox.

 The change of transmission ratio takes place after the instant t3 and includes a phase t3-t4 of declutching the engaged transmission ratio, synchronization and interconnection of the new transmission ratio, the speed V1 of rotation of the engine being, during this change, set to a value equal to the vehicle speed multiplied by the new transmission ratio.

 Then, in a phase t4-t5, the device represented in FIG. 2 controls the tightening of the clutch E, advantageously in the same way as that described for the control of the opening, that is to say from '' a sliding speed setpoint in a first phase then from a predetermined acceleration or increase profile

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 torque during the next phase t5-t6, up to the torque value requested by the driver.

 This gives a quick and comfortable change of transmission ratio, avoiding negative accelerations at the end of declutching and sudden variations in acceleration at the clutch.

Claims (12)

1 - Control method for a change of transmission ratio in a robotic gearbox for a motor vehicle, this gearbox being connected by a clutch (E) controlled by an actuator (A) to the output shaft (10) of an internal combustion engine, this method consisting in controlling the actuator (A) to open the clutch (E), in changing the transmission ratio and in controlling the actuator (A) to close the clutch (E ), characterized in that it consists, for the opening of the clutch, in controlling the state of the clutch to a vehicle acceleration instruction and in controlling the torque supplied by the engine (M) to a slip speed setpoint between the motor output shaft (10) and a gearbox input shaft (12).  2- A method according to claim 1, characterized in that it consists in determining the acceleration of the vehicle, in comparing it with an acceleration reference signal (32) and in controlling the actuator (A) of the clutch. from their difference.  3- Method according to claim 2, characterized in that it consists in generating the acceleration setpoint signal (32) from the difference between a predetermined acceleration profile (30) and an acceleration order (28 ) given by the driver of the vehicle.  4- Method according to one of the preceding claims, characterized in that, during a <Desc / CRUD Page number 15>  first phase of the clutch opening, it consists in reducing the torque supplied by the engine (M) in accordance with a predetermined profile of torque variation, before slaving this torque to said slip speed setpoint.  5- Method according to one of the preceding claims, characterized in that, to control the torque supplied by the motor (M) to the sliding speed setpoint, it consists in determining the rotational speeds of the shaft (10) motor output and gearbox input shaft (12), to make their difference, to develop from this difference and the slip speed setpoint (40) a control signal and to apply this signal to means (60) for controlling the torque supplied by the motor (M).  6- A method according to claim 5, characterized in that it also consists in determining the torque supplied by the motor (M), in comparing it with the aforementioned control signal and in applying their difference to said means (60) for controlling the torque .  7- Method according to one of the preceding claims, characterized in that, after opening the clutch (E), it consists in varying the rotation speed of the engine to adapt it to the transmission ratio to be engaged, by calculation from the vehicle speed and the gear ratio to be engaged.  8- Method according to one of the preceding claims, characterized in that, for closing <Desc / Clms Page number 16>  of the clutch after changing the transmission ratio, it consists in slaving the state of the clutch to a vehicle acceleration instruction and to controlling the torque supplied by the engine (M) to a slip speed instruction between the engine output shaft (10) and the gearbox input shaft (12).  9 - Control device for a change of transmission ratio in a robotic gearbox for a motor vehicle, this device comprising an actuator (A) for controlling a clutch (E) connecting the output shaft (10) of an internal combustion engine with an input shaft (12) of the gearbox, characterized in that it also comprises: - first means (22) for generating actuator control signals (A) of the clutch, receiving as input a signal (28) representing an acceleration or engine torque requested by the driver of the vehicle, a signal (30) representing a predetermined profile of acceleration of the vehicle and a signal (36) representing the acceleration vehicle, and developing from these signals an actuator control signal (A) for opening or closing the clutch, - and second means (24) for generating control signals applied to communication means (60) control of the torque supplied by the engine, these second means (24) receiving at the input signals representing the rotational speeds of the output shaft of the engine and of the input shaft of the gearbox, a signal (40 ) slip speed setpoint and a signal (58) representing the torque <Desc / Clms Page number 17>  supplied by the motor (M), these second means developing a control signal applied to the means (60) for controlling the torque supplied by the motor.  10- Device according to claim 9, characterized in that the first means (22) comprise means (26) receiving the signal representing the acceleration or the torque requested by the driver and the signal (30) representing the predetermined profile of acceleration of the vehicle and generating an acceleration or torque setpoint signal (32), and means (34) receiving this setpoint signal and the signal (36) of actual acceleration of the vehicle and applying their difference to the actuator (A) of the clutch.  11 - Device according to claim 9 or 10, characterized in that the second means (24) comprise means (38) receiving the signal (40) sliding speed setpoint and a signal (42) representing the actual sliding speed and applying the difference of these signals to means (52) generating an engine torque setpoint signal, and means (56) receiving the engine torque setpoint signal and a signal (58) representing the torque supplied by the engine and applying their difference to said torque control means (60).  12 - Device according to claim 10 or 11, characterized in that it comprises means (44) receiving the signal (46) of rotation speed of the motor output shaft (M) and the signal (48) of speed of rotation of the input shaft of the gearbox <Desc / Clms Page number 18>  speed and generating said slip speed signal (42).