FR2661374A1 - DEVICE FOR ACTUATING A FRICTION CLUTCH FOR A MOTOR VEHICLE. - Google Patents

Abstract

It is proposed, to ensure the automatic actuation of a friction clutch (5) disposed between a motor (1) and a gearbox (7), a control (19) which decreases the power of the motor (1), during the gearbox change (7), during the shift of the gearbox to neutral. During the re-engagement following the gear change, the engine speed is automatically adapted to the input speed of the gearbox, in order to avoid jolts. When the speeds of the gearbox (7) are lowered, an "intermediate acceleration" (double declutching) is produced in order to stress as little as possible the forced synchronization devices of the gearbox (7).

Description

Device for actuating a friction clutch for a vehicle

  automobile The invention relates to a device for actuating a friction clutch, disposed between an engine and a gearbox of a motor vehicle, comprising a servomotor coupling and uncoupling the clutch, a motor rotation speed sensor. measuring the speed of rotation of the engine, a device determining the speed of rotation of the gearbox input, a pedal position sensor, measuring the position of an accelerator pedal, a power servomotor, actuating a device for motor power adjustment, as a function of the pedal position sensor, a gearshift intention identification device, picking up the introduction of a gearbox shift, for which, starting from a speed already passed previously, we pass to a new speed, passing through a neutral position and a control, which reacts to the engine speed sensor, to the d termination of the gearbox rotation speed, the pedal position sensor and the gear change intention identification device, which controls both the clutch actuator and also the power servomotor, a control which uncouples and couples the clutch, for gear change, by means of the clutch servomotor and which controls the power adjustment device, when the clutch is coupled, so that the engine rotation speed is substantially equal to the

  gearbox input rotation speed.

  DE-A-30 04 930 discloses a device for automatically actuating a friction clutch of a motor vehicle, for which the clutch is uncoupled, respectively coupled, by means of a clutch servomotor, both during start-up and also when changing the gearbox A gearshift intention identification device presenting itself as a control lever contact or the like triggers the uncoupling process, after which the previously established gear position , the gearbox is switched to shift to the new speed position, passing through a neutral position In the new speed position, the clutch is then coupled, for example with a predetermined setting speed To prevent

  can change, depending on the driving situation, to

  more or less important strokes, using rotational speed sensors, the engine rotational speed and the input speed of the gearbox are measured and a command produces equality between the rotational speed of engine and gearbox input rotation speed, before coupling The engine power adjustment device, for example its check valve or throttle valve or its injection pump, is the object , on the part of a power servomotor, of an adjustment action whose magnitude allows the speed of rotation of the motor to satisfy the above condition Once equality of rotation speeds has been obtained, l clutch can be coupled without

  let this jerk to the clutch.

  In the device known from DE-A-30 04 930, the driver must assist the coupling process by

  to an appropriate actuation of the accelerator pedal.

  Depending on the driving situation, this requires some habit, if comfort is not to be compromised If, for example, the driver actuates the gear lever while he is still pressing the accelerator pedal, the engine is accelerated inadvertently during the gear change, when you are in neutral If on the other hand the driver actuates the accelerator pedal too early when he has shifted to the new speed, the increased speed of rotation of the engine which resulting must be reduced by the slipping of the clutch This is cause of wear of the clutch If on the other hand, once passed the speed, the driver lets pass too much time before actuating the pedal

  accelerator, it loses acceleration.

  Patent 4,281,751 discloses another device for automatically actuating a friction clutch in connection with an automatic gearbox of a motor vehicle, a device for which, to effect the gear change, one begins first with at least partially close the throttle valve by means of a throttle valve drive, before uncoupling the clutch to make the gear change Once the gear change is made, the clutch is coupled and the throttle throttle is also reopened with some delay In this device, the throttle valve is controlled from the accelerator pedal, via a mechanical linkage, and the throttle valve servomotor only allows to close it for the process of

gear switch.

  The object of the invention is to improve a device of the type indicated at the start, so that the speeds of the gearbox can be changed, while notably protecting the friction clutch and without compromising comfort. This problem is solved, according to the invention, by the fact that the control ensures the control of the power servomotor during the gear change, independently of the position, measured by the pedal position sensor, of the accelerator pedal and returns it to the position determined by the accelerator pedal

  immediately after coupling the clutch.

  Within the framework of the invention, the control ensures, when changing speed, not only the control of the clutch servomotor, but also of a motor power servomotor The control ensures the control of the rotation speed of the engine during the gear change, which can be done either manually or automatically, in the case of an automatic gearbox, independently of the momentary setting of the accelerator pedal, which controls, for its part, in normal operation, that is to say before and after the gear change, the power adjusting device, by means of the power servomotor During the gear change, that is to say before a new shift position has completely passed speed on the gearbox, the control adjusts the speed of rotation of the motor by means of the power adjustment device, to the value of the speed of rotation of the gearbox input, which results from the new speed position se, following the driving speed Following which, or if necessary with a time overlap, the command couples the clutch by means of its servomotor Suddenly coupling is avoided, thanks to the adaptation of the engine speed to the gearbox input speed Immediately after coupling the clutch complete, that is to say without additional delay or even, if necessary, a certain anticipation, the control device ensures the control of the power servomotor to return to the position fixed by the accelerator pedal The driver certainly has, during the automatic coupling process, no possibility of modifying the rotation speed of the engine by the intermediate of the accelerator pedal, but the control can be adjusted to an optimum, on the one hand, as regards the interruption of the propulsive force during the gear change and, on the other hand, at the same time ps, for the skating capacity which manifests itself Because the control of the speed of reversion returns, without delay, to the subjugation of the accelerator pedal, once the gear change

  any "inert" behavior of the engine is avoided.

  To be able to equalize the engine rotation speed and the gearbox input rotation speed, on the gearbox input shaft, which results from the running speed once the speed has passed, you must know the speed gearbox input speed In the device known from DE-A-30 04 930, the gearbox input speed is measured using a speed sensor The information concerning the speed of measured rotation is however available once the new gear has been fully engaged In practice, this results in a delay in the coupling process and thus in an impairment of comfort when changing gear. a preferred embodiment, that the gearshift intention identification device produces a gearshift intention signal which represents the new gear, before the gearbox completely says t shifted to the new gear and the command balances the gearbox input rotation speed resulting from the new gear, according to the gear change intention signal, i.e. also before the gearbox speed has not completely shifted to the new speed The control then adjusts the power adjusting device so that the engine speed is substantially equal to the calculated input speed of the gearbox calculated In this way, we anticipates the time interval required to adapt the engine rotation speed to that of the gearbox input and the time interval necessary for

gear change.

  The gear change intention signal which represents the new speed, before it has shifted, is in any case available in the case of an automatic gearbox But, even in the case of a manual gearbox , it can be deduced from the direction in which the gear lever is manually actuated, passing through neutral. For this purpose, it is possible to provide sensors which monitor the movement, guided in a gear change slide, from gear lever, or part of the gearbox

being connected to it.

  When lowering the speeds of a gearbox with forced synchronization, going from a higher speed to a lower speed, comparatively high operating forces must be applied, in particular in the case of high output rotation speeds of the gearbox, which leads, on the one hand, to comparatively long shift times, in the case of a manual control gearbox and to too high drive power during switching, in the case of automatic gearbox Resistance to shifting, which depends on the speed of rotation, makes it difficult to control the automated clutch and can lead to a jerk of the vehicle in the event of a speed downshift. gear change solicits, on the other hand,

  the gearbox synchronization devices.

  To eliminate these drawbacks, according to an advantageous embodiment of the invention, it is provided that in the event of a speed change increasing, for the new speed, the speed of rotation of the gearbox input, relative to what it was for the previous speed, the speed change intention identification device produces a speed change intention signal indicating, before the change of the new speed, the increase in the speed of gearbox input rotation and that the control, when changing gear, while the gearbox is in neutral, in the presence of the gear change intention signal which indicates the increase in speed of the gearbox input rotation, produces the clutch coupling, increases the engine rotation speed and then produces the clutch decoupling, for the change from neutral to the new speed Thanks to the "intermediate clutch", or "double clutch", while the gearbox is in neutral, the gearbox input rotation speed is increased, when the clutch is coupled, to the value expected once shifted to new gear Once the clutch is disconnected, the new gear can then be shifted quickly without any problems and without requiring the

  synchronization of the forced synchronization box.

  An exemplary embodiment of the invention is explained below in more detail and shown in the drawing, in which: FIG. 1 represents a block diagram of a device according to the invention, for actuating a friction clutch of a motor vehicle, and FIG. 2 represents a time diagram of the mode of

operation of the device.

  FIG. 1 schematically represents an engine 1 of a motor vehicle, which is connected to a gearbox 7, acting, for its part, on the driving wheels of the motor vehicle, by means of a friction clutch 5 capable to be positioned, thanks to a servomotor 3, between a coupling position EK and an uncoupling position AK The motor comprises a power adjustment device 9, for example a check valve or throttle valve, or a pump injection, which can be controlled by a power booster 11, as a function of the position of an accelerator pedal 13 actuable by the driver of the motor vehicle The accelerator pedal 13 is coupled to a sensor position 15, which controls the power servomotor 11, via a stage 17, an electronic control, generally designated by 19 Concerning the gearbox 7, in the example of sheave shown, of an automatic gearbox, which is capable of making gear changes, by a servomotor 21, depending on the driving situation, to shift to one, among several gears, with reduction ratios different from each other To carry out the choice of speeds, or groups of speeds, there is provided a speed control stage 23, with a selection lever 25, which controls the servomotor 21, via a stage 27 of the control 19 The servomotor 21 (or the gearbox 7) also sends speed position signals, which represent the instantaneous position of the speed, including its neutral position, in which the shaft gearbox input is uncoupled from its output shaft Concerning the gearbox 7, it can also be, as indicated in FIG. 1 by a gearshift lever 29, a gearbox with manual command e, which sends, via a control line 31, to stage 27 of the control 19, speed change intention signals which designate, when changing speed, the new speed to be shifted before the new gear is shifted using the gear shift lever 29 Signals of intent to shift gear of this nature can, for example, be obtained from the direction in which the shift lever gear 29, guided in a gear change slide or the like of gearbox 7, again leaves the

  neutral during a gear change.

  The control 19 further comprises a stage 33, which controls the servomotor 3 of the clutch 5 and which reacts to the rotation speed of the engine nm, measured by a rotation speed sensor 35, as well as to the running speed of the motor vehicle, measured by means of a speed sensor 37 The stage 33 controls the coupling and uncoupling operation of the clutch 5 and can, for this purpose, react to other driving parameters , measured by sensors not shown, as is known per se To reduce the slip of the clutch and avoid coupling jolts when changing the gearbox 7, the control 19 does not provide only the control of the servomotor 3 of the clutch 5, but also that of the

  servomotor 11 of the power adjustment device 9.

  During the gear change, the control of the servomotor 11 passes from the exclusive subjugation to the accelerator pedal 13 to that of the control 19, which ensures the control of the servomotor 11 in a time synchronism fixed with respect to the servomotor 3 of l clutch 5, namely depending on whether the gears are going up or down In the two cases of gear change, the control 19 calculates, from the speed signals of the speed sensor 37, which represent the taxiing speed and gear change intention signals, which designate the new speed to pass, the gearbox input rotation speed ng, which results on the input shaft of the gearbox 7 , once the clutch is uncoupled, after the new gear has been changed, due to the vehicle's running speed The control 19 adjusts the servomotor 11 of the power adjustment device 9 so that the speed motor rotation speed nm is substantially equal to the calculated gearbox input speed ng Once the speeds have become equal, the clutch 5 can be coupled comparatively quickly, via the servomotor 3, without does not occur suddenly with the clutch Temporarily, immediately after the coupling of the clutch 5, the control of the servomotor 11 returns to the accelerator pedal 13, that is to say that the device for power adjustment 9 is adjusted to the position determined by the accelerator pedal 13 without time delay The motor 1 thus very quickly follows the instant command

  from the accelerator pedal.

  The operating mode of the control 19 is explained below in more detail using the time diagram in FIG. 2 FIG. 2 a represents, as a function of the time parameter t, the position, measured by the sensor 15, of the accelerator pedal 13, which can fluctuate between a rest position and a

full throttle.

  FIG. 2 b represents, as a function of time t, examples of the speed position of the gearbox 7, on which the speeds are mounted, increasing, for example, in the time space going from tl to t 4, the first speed at the second speed and going down, in the space of time going from tî 'to t 4', from the second to the first speed We consider first, below, the rise of the speeds At the instant tl, the control stage il 23 begins to produce a speed change intention signal 512, which represents the intention to change speed

  speed to go from first to second speed.

  In the case of a manual gearbox, the gearshift intention signal can be triggered when contacting the gearshift lever 29 With the start of the gearshift intention signal 512, the control 19 controls the servomotor 3 of the clutch 5, to pass from the coupled position EK to the uncoupled position AK Simultaneously, the power adjusting device 9 is adjusted, by means of the servomotor 11, passing from the position fixed by the accelerator pedal 13 at a position in which the speed of rotation of the motor nm (FIG. 2 a) is approximately equal to the speed of rotation of the gearbox input ng expected for the new speed position, due to the instantaneous driving speed (figure 2 f) Figure 2 c represents the time relationship existing for the fuel flow, which can fluctuate, in normal case, between a full throttle flow and an idling flow The position of em clutch which is fixed by the servomotor 3 is shown in Figure 2 d In conjunction with the reduction of the fuel flow and the uncoupling of the clutch 5, the rotation speed nm decreases, from the value of the rotation speed nml (figure 2 e) associated with the accelerator pedal position at time tl (Figure 2 a) When the clutch is uncoupled, the gearbox undergoes a gear increase, passing through neutral, o, in l time interval from t 2 to t 3, in which the gearbox 5 is in neutral, the input speed of the gearbox ng changes from the value ngl = nml to, for example, the value zero (FIG. 2 f), while the control 19 increases the supply of fuel, by means of the servomotor 11 of the power adjusting device 9, until the speed of rotation of the engine nm reaches the value nm 2 = ng 2, therefore the gearbox input rotation speed calculated for a e second speed fully passed At time t 3, the second speed is passed over the gearbox, whereby the effective speed of rotation of the gearbox input shaft

  also increases to ng 2.

  By temporally overlapping with the increase in the speed of rotation of the motor, the servomotor 3 of the clutch 5 is controlled in the direction of coupling, namely, so that the clutch 5 is then coupled once filled the speed of rotation condition nm 2 equals ng 2 At time t 4, the speed change intention signal 512 ends, whereby the speed change is indicated to be terminated Following this, the control 19 releases, immediately after, the control of the servomotor 11, to return to the subjection to the accelerator pedal 13 which had been switched off during the speed change process, thanks to which the fuel flow (figure 2 c), as well as the motor rotation speed nm (figure 2 e) and the gearbox input rotation speed ng (figure 2 f) vary to pass to values fixed by the position of the pedal

accelerator (Figure 2 a).

  During a speed descent, for example while passing from the second to the first speed, is produced, in a similar way, a signal of intention to change speed 521, which begins at the instant tl 'and which gives rise when actuating the servomotor 3 in the uncoupled position AK of the clutch 5 At time t 2 ', the

  gearbox 7 has shifted from second gear to neutral.

  At neutral there is a decrease in the gearbox input rotation speed ng The motor rotation speed nm is increased by the value nm 2 manifested before the gear change, at a speed nml, which is equal to the value calculated ngl of the rotation speed

  gearbox entry, after shifting from first gear.

  Because the ngl value is greater than the ng 2 value of the gearbox input shaft, before the gear change is effective, there is an automatic "double clutch" operation, in order to discharge the synchronization device from the forced synchronization gearbox 7 The clutch 5 is, for this purpose, coupled and, shortly: afterwards, again uncoupled, by means of the servomotor 3 (FIG. 2 b) The speed of rotation of the gearbox input shaft is thus raised to a value which is the expected value after switching from the first speed, due to the instantaneous speed of travel At the instant t 3 ', the first can be passed speed without requesting the gearbox synchronization device Since the engine rotation speed nml and the gearbox input rotation speed ngl are kept substantially equal during the double clutch release process, the clutch 5 can then be fast mated coupled, without causing a clutch jerk At time t 4 ', the gear change intention signal 521 signals the end of the gear change, and the command 19 again releases the subjugation command of the accelerator pedal and stops controlling the servomotor 11 of the power adjustment device 9 The fuel flow rate (figure 2 c) and the engine rotation speed nm (figure 2 e) thus vary according to the value set by the accelerator pedal 13. In the device explained above, the gearbox input rotation speed, which must be calculated before a gear change by control 19, is based on the signal intention to change speed and a signal which represents the speed of taxiing, for example a signal which represents the speed of rotation of the gearbox output As a variant, as shown in FIG. 1, one can also use, for the calculation of the rotation speed of e Box input expected at the new speed, the box input rotation speed measured by a rotation speed sensor 39 We use, at the same time, the fact that the driving speed will change little or not at all during the change of speed, so that the speed of rotation established during operation with the old speed, multiplied by the transmission ratio between old and new speed, gives a measure of the input speed of gearbox expected for the new speed Command 19 must, if necessary, store this speed value of

rotation.

  The devices explained above make it possible to control the clutch operation automatically and comfortably, while protecting the clutch 7 and the

  gearbox synchronization device 7.

Claims (4)

RESELL ICAT IONS   1 Device for actuating a friction clutch (5), arranged between a motor (1) and a gearbox (7) of a motor vehicle, comprising a servomotor (3) coupling and uncoupling the clutch (5 ), an engine speed sensor (35) measuring the engine speed, a device (37; 39) determining the gearbox input speed, a pedal position sensor (15) , measuring the position of an accelerator pedal (13), a power servomotor (11), actuating a power adjustment device (9) of the engine (1) as a function of the pedal position sensor (15), a gearshift intention identification device (23,31), picking up the introduction of a gearbox shift (7), for which, starting from a speed already passed previously, one passes at a new speed, passing through a neutral position, and a control (19), which reacts to the engine rotation speed sensor (35), to the gearbox rotation speed determining device (37; 39), the pedal position sensor (15) and the gearshift intention identification device (23,31) and which controls both the clutch servomotor (3) and also the power servomotor ( 11), control (19) which uncouples and couples the clutch (5), for the gear change, by means of the clutch servomotor (3), and which controls the power adjustment device (11), when the clutch coupling, so that the speed of rotation of the motor is substantially equal to the speed of rotation of the gearbox input, characterized in that the control (19) controls the power servomotor (11 ) during the gear change, regardless of the position, measured by the pedal position sensor (12), of the accelerator pedal (13) and immediately returns it to the position determined by the accelerator pedal (13) after coupling the clutch (5). 2 Device according to claim 1, characterized in that the speed change intention identification device (23,31) produces a speed change intention signal which represents the new speed, before the gearbox (7) is completely shifted to the new speed, and the control (19) calculates the gearbox input rotation speed which results from the new speed, as a function of the gear change intention signal, before the gearbox (7) is not completely shifted to the new speed and controls the power adjustment device (11) so that the engine rotation speed is substantially equal to the input rotation speed of calculated gearbox.   3 Device according to claim 1 or 2, characterized in that in the event of a speed change (lowering speed) increasing, for the new speed, the speed of rotation of the gearbox input, relative to this as it was for the previous speed, the speed change intention identification device (23,31) produces a speed change intention signal (521) indicating, before the change of the new speed, the increase in speed of input of the gearbox and the control (19), during the gear change, while the gearbox (7) is in neutral, in the presence of the signal of intention to gear change (521) which indicates the increase in the input speed of the gearbox, producing the coupling of the clutch (5) and increasing the speed of the engine and then producing the uncoupling of the '' clutch (5), for changing from neutral to new speed.   4 Device according to any one of   Claims 1 to 3, characterized in that the box   gear (7) has a servomotor (21) which performs the gear change and the gear change intention identification device (23) being connected to a gearbox control (27) which controls the   servomotor (21) of the gearbox (7).