FR2823574A1 - Method of calibrating equilibrium position of motor vehicle clutch actuator balance spring involves detecting rear position while applying high amplitude position signal - Google Patents

Abstract

The method of calculating the equilibrium position of a motor vehicle clutch actuator compensating spring which balances an electric motor. The method involves applying a high amplitude position signal varying at a high frequency, to power the electric motor. The position signals corresponds to the positions of the actuator which cove the equilibrium position, and detecting the actual position of the actuator using a sensor.

Description

what it is a Cassegrain space telescope.

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  The present invention relates to electrically controlled actuators and, in particular, an electrically controlled actuator for a clutch of a vehicle with

  motor or for a gear selector mechanism.

  Actuators electrically controlled in accordance with the present invention, for example such as those disclosed in the documents GB 2 325 036, GB 2 313 885 or GB 2 309 761 include an electric motor for controlling the actuation of a hydraulic master cylinder and, via a slave cylinder, a clutch or a gear selector mechanism of a vehicle. In such actuators, the electric motor can be connected, via a suitable gearbox and via, for example, a worm and a worm gear mechanism, to a control rod which is connected to the worm gear by means of a crank, so that the rotation of the worm gear is transformed into linear movement of the control rod. The free end of the control rod is fixed to a piston which is sealed by sliding in a master cylinder. The engine, the gear mechanism and the master cylinder are,

  preferably all provided in a common housing.

  The master cylinder of the electric actuator described above is typically connected to a clutch slave cylinder, so that the application of pressure to the clutch slave cylinder operates a clutch fork which acts on a thrust bearing. clutch, to apply a load to disengage the clutch. The clutch release bearing typically acts on a diaphragm spring which normally keeps the clutch plates frictionally coupled, the spring sinking

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  diaphragm causing the clutch discs to spread apart, so that the clutch is uncoupled. The load generated by the electric motor must therefore be capable of driving the diaphragm spring to an extent sufficient to disengage the clutch. The load generated by the electric motor to disengage the clutch must typically be of the order of 450 N. In order to reduce the dimensions of the electric motor necessary for such actuators, it has been proposed to include a spring. compensation in the electric actuator, said compensation spring opposing the load applied by the diaphragm spring. The compensating spring can, for example, be arranged to be fully compressed when the clutch is fully coupled, exerting a load, say of 250 N. which acts on the electric motor in the direction of movement of the actuator, to uncouple the clutch. When the clutch is uncoupled, the initial load to drive the diaphragm spring is then provided by the compensation spring, and while this load has been reduced by the time during which the compensation spring and the diaphragm spring are in balance, the electric motor only needs to provide a charge of

  around 200 N to completely disengage the clutch.

  The load on the electric motor can therefore be lowered, from 450 N or 500 N. which would be necessary without the compensating spring, to 250 N or 300 N using the

compensation spring.

  With electric actuators of the disclosed type, very static friction in the worm gear provides a self-sustaining effect. However, if the internal static friction of the actuator is insufficient, which may be desirable in order to optimize the performance of the actuator, it is possible, when the actuator is at

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  rest, that the load applied by the diaphragm spring, when the clutch is uncoupled, forces the actuator to go back, or that the load applied by the compensating spring, when the clutch is coupled, forces

  the actuator to move forward.

  If the resulting difference between the actual position and the requested position of the actuator is greater than a predetermined tolerance, the

  command will trigger the actuator again.

  In order to compensate for the force applied by the diaphragm spring, which can allow the clutch to unintentionally re-couple, it has been proposed, in German patent application N DE 10 062 456.1, when the actuator is at rest , to apply to an electric motor, typically, a voltage equal to 7 percent of the maximum of the pulse width modulation voltage (PWM), in a direction supporting the. compensation spring and opposing the diaphragm spring. This voltage applies a load to the actuator, which load prevents the actuator from moving backwards under

  the effect of the load applied by the diaphragm spring.

  However, to prevent the actuator from moving forward when the clutch is coupled, the tension of 7 percent is only applied when the load applied by the compensating spring is less than that

  applied by the diaphragm spring.

  Consequently, in this system, it is necessary to know the equilibrium position between the compensating spring and the diaphragm spring. For clutches with self-adjusting devices which regulate the position of the pressure disc to adapt the wear of the

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  friction surfaces, the equilibrium position remains

  practically fixed over the life of the clutch.

  With such clutches, the equilibrium position can be precalibrated. However, when the clutch is not equipped with self-adjusting devices, the equilibrium position varies significantly as the components of the clutch wear out. With such clutches, the 7 percent voltage strategy described above cannot be used, a suitable and much more complex DC supply strategy having to be implemented. The present invention provides a method for calibrating the position of equilibrium of the force between the clutch and the compensating spring, once the system has been installed on a vehicle, so that the equilibrium position can be calibrated in an end-of-line procedure and recalibrated at regular intervals, for example such as those spacing out control checks

  vehicle routine, during the life of the vehicle.

  This allows the 7 percent pulse width modulation (PWM) voltage strategy to be used on vehicles with clutches that do not have auto-tuners. According to one aspect of the present invention, a 2s method for calibrating the equilibrium position at which a compensating spring of an actuator controlled by an electric motor balances a resilient load in the mechanism which is controlled by the actuator, comprises the steps consisting in applying a position signal varying at a high frequency and having a high amplitude, to energize the electric motor, said position signal corresponding to positions of the actuator which cover the equilibrium position, and to measure position

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  of the actuator by means of a position sensor

associated with the actuator.

  Due to the characteristic of the force of the compensating spring and the resilient load applied by the mechanism, at the time of initial tensioning in one direction, when, for example, the movement of the actuator is assisted by the spring compensation, the actuator moves quickly to the equilibrium position, the movement speed is then reduced significantly, as the motor opposes the load applied by the resilient load of the mechanism . Similarly, when the motor is reverse energized, the actuator quickly returns to the equilibrium position and then slowly exceeds the equilibrium position as the compensating spring is compressed. Consequently, the actual position of the actuator is centered on the equilibrium position. The higher the frequency of the variable signal, the shorter the distance traveled beyond the equilibrium point in each direction, and therefore the better the resolution of the equilibrium position. According to a preferred embodiment, the frequency of the variable position signal is equal to 25 Hz or more, a position signal of approximately 50 Hz being used

more preferably.

  The closer the midpoint of the position signal is to the equilibrium position, the more precisely the equilibrium position is determined. Consequently, an iterative technique can be used, by making successive determinations of the equilibrium position, by positioning the midpoint of the variable position signal on the equilibrium position determined previously, until the position of equilibrium coincides with the midpoint of the variable position signal. Initially, the midpoint of the variable position signal may be arranged to coincide with

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  a theoretical equilibrium position calculated from the design characteristics of the actuator / mechanism or from at least the last known equilibrium position

  o the actuator / mechanism have been recalibrated.

  S An embodiment will now be described, only by way of an example, with reference to the following drawings in which: FIG. 1 schematically illustrates a vehicle provided with a clutch actuator controlled by an electric motor; Figure 2 illustrates in more detail the clutch / clutch actuator controlled by an electric motor of the vehicle illustrated in Figure 1; FIG. 3 shows characteristic graphs relating to the stroke of the actuator opposing the load, for the diaphragm spring of the clutch and for the compensating spring of the actuator illustrated in FIG. 2; FIG. 4 shows a graph of the desired output position of the actuator when variable position signals having a high amplitude are applied to the actuator, according to variable frequencies; FIG. 5 is a graph of an actual output position of the actuator when a variable position signal, at high frequency, is applied to the actuator, according to 2s variable amplitudes; and Figure 6 is a graph of an actual output position of the actuator when the midpoint of a high frequency and high amplitude position signal is applied to the actuator, the midpoint of the position signal being variable with respect to the equilibrium position of the bond

actuator / clutch.

  As illustrated in FIG. 1, a vehicle 10 has an internal combustion engine 12 which is connected to a gearbox 14, via a clutch 16. The gearbox 14 is

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  connected by a drive shaft 18 and a rear axle

  , to drive the rear wheels 22 of the vehicle 10.

  A gear selector lever 24 is mechanically connected to the gearbox 14, in a conventional manner, for manual selection of the transmission ratio. The coupling and uncoupling of the clutch 16 are controlled by a clutch actuator controlled by an electric motor, a sensor 32 placed on the gear selector lever 24 providing a command signal to a control unit 34 which triggers the clutch actuator 30 for uncoupling and re-coupling the clutch 16 as appropriate, when a change in the transmission ratio is triggered by the movement of the

gear selector lever 24.

  IS As illustrated in FIG. 2, the clutch actuator 30 comprises a direct current electric motor 40, mounted on the casing 42. The motor 40 is connected directly or via a gear mechanism with fixed ratio, via a screw worm 44 and via a worm gear 46, to a control rod 48, the control rod 48 being connected to a crank 50 associated with the worm gear 46, so that the rotation of the worm gear 46 is transformed into a linear movement of the control rod 48. Instead of the worm gear 44, 46, other forms of connection can be used to transmit , to the rod

  control 48, the rotary movement of the electric motor 40.

  For example, you can alternatively use a planetary gear, a pinion gear with straight teeth, a

  bevel pulley gear or a threaded pin gear.

  The control rod 48 is connected, at its free end, to a piston 54 of a hydraulic master cylinder 52, the hydraulic master cylinder 52 being formed integrally with the casing 42 of the electric motor. The rod

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  control 48 is connected to the piston 54, by means of a formation of balls 56 which is a snap-in mounting in a spherical cavity 58 of a part, formed axially with respect to the piston 54. A compression spring 60, of helical type acts between the casing 42 and a sleeve 62 mounted on the control rod 48, to push the control rod 48 towards the closed end 64 of the master cylinder 52. An orifice 66 opens on the master cylinder 52 at sound level

end 64.

  A position sensor 68, in the form of a linear potentiometer, is mounted to move with the control rod 48 and provide a signal indicating the

position of the control rod 48.

  The orifice 66 of the master cylinder 52 is connected to a slave cylinder 70 of the clutch, by a hydraulic line 72. The slave cylinder 70 acts on a declutching fork 74 which operates on a declutching stop 76, to control , conventionally,

  clutch coupling and uncoupling 16.

  The clutch 16 comprises a friction disc 80 which is connected diagonally to the input shaft 82 of the gearbox 14. The friction disc 80 is mounted coaxially and between a flywheel 84, which is connected to the engine by a drive control, and a pressure disc 86 which is connected, via a clutch housing 88, to the flywheel 84, to be in rotation with it, the pressure disc 86 being axially movable relative to the flywheel 84 The pressure disc 86 is pushed towards the flywheel 84, so that the friction disc 80 is clamped between these elements, in order to transmit, by means of a diaphragm spring 90, the torque existing between the engine 12 and the gearbox 14. The clutch 16 is uncoupled by the application of a load to the flywheel 84, on the internal diameter of the disphragm spring 90, by means of the declutching fork 74 and the declutching stop 76. Instead of having a hydraulic connection eu between the clutch actuator 30 and the clutch release fork 74, a clutch actuator 30 can be connected to this fork

  S declutching by pneumatic or mechanical connection.

  For example, the control rod 48 can act directly on the declutching fork 74 or can be connected to this declutching fork by means of a mechanical connection or

a cable.

  IO When the clutch 16 is fully coupled, the clutch actuator 30 is in the position illustrated in FIG. 2, the control rod 48 is shifted widely to the left, so that the piston 59 of the master cylinder 52 is like its distance limit from end 64 of

  lS master cylinder, spring 60 being fully compressed.

  When the electric motor 40 is energized to disengage the clutch 16, the control rod 48 is moved to the right, so that the piston 54 moves towards the end 64 of the master cylinder 52. The fluid is thus moved, from the master cylinder 52 to the receiving cylinder 70. The receiving cylinder 70 thus applies a load to the declutching fork 74 which moves the declutching stop 76 towards the flywheel 84 and applies the load to the inner periphery of the spring diaphragm 90, to limit the load thus applied to the pressure disc 86, reducing the clamping load on the disc by

friction 80.

  As illustrated in FIG. 3, initially, the load applied by the spring comes out completely compensated 6 0 beyond the reaction load of the diaphragm spring 90 and, consequently, the control rod 48 and the piston 54 move under the effect of the load applied by the spring 60. The electric motor 40 consequently undergoes a very low load acting only to allow the

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  displacement of the control rod 48 under the action of the

spring 60.

  At the equilibrium position, when the load applied by the spring 60 balances the reaction load of the diaphragm spring 90, the load required to continue uncoupling the clutch 16 is then supplied by the electric motor 40. As indicated in FIG. 3, the load applied to the diaphragm spring 90, in order to completely uncouple the clutch 16, is typically 10O of the order of 430 N. The compensation spring 60 is designed to provide a nominal load of l order of 250 N when the clutch is fully coupled and the reaction load of the diaphragm spring is practically zero, the load applied by the compensating spring 60 falling to about 210 N at the equilibrium position. The electric motor 40 must therefore be capable of applying a sufficient load to drive the diaphragm spring 90 from the equilibrium position to the fully uncoupled position of the clutch, that is to say going from 210 N to 430 N. and fully compress the spring 60 from the equilibrium position to the fully coupled position of the clutch. An electric motor 40 designed to provide a nominal load between 220 N and 250 N will therefore be appropriate, rather than needing a motor capable of producing charges greater than 430 N. As illustrated in Figure 3, in due to the hysteresis of the diaphragm spring 90, the equilibrium position when the clutch 16 is uncoupled (BPdiscoupled1) is different from the equilibrium position when the clutch 16 is coupled (BPaccoupled) , these equilibrium positions being respectively 4.5 mm and .7 mm.

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  With electric actuators of the type disclosed above, unless there is a significant friction in the mechanism, the loads applied by the compensating spring 60, when the clutch is fully coupled or by the diaphragm spring 90 when the clutch is completely uncoupled, have the effect of causing the electric motor 40 to be rewound when it is not energized, thus allowing the actuator 30 to move relative to the required position. If, during a gear change, the actual position of the actuator 30 varies with respect to the required position, by a magnitude greater than a predetermined magnitude, the electric motor is again energized to return the actuator 30 in the desired position. In order to avoid the above, when the actuator 30 is at rest, it has been proposed to apply to the electric motor 40, an intensity sufficient to keep the motor 40 in position, but not

  sufficient to cause the actuator 30 to move.

  Typically, a voltage of 7% of the normal pulse width modulation (PWM) voltage is. to this end, applied to the electric motor 40. This strategy of modulation of the pulse width at 7% is however only used when the actuator 30 is at rest during a gear change, the actuator 30 being placed between the equilibrium position and the completely uncoupled position of the clutch 16. It is therefore necessary, using this strategy, to know precisely the equilibrium position of the actuator assembly

/ clutch.

  As the equilibrium position of the actuator / clutch assembly varies with the wear of the friction surfaces of the clutch 16, it is necessary to calibrate the actuator / clutch assembly over the entire duration

vehicle life.

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  FIG. 4 illustrates the effect of applying a position signal varying at frequencies of 5 Hz, 10 Hz, 25 Hz and Hz, to the electric motor 40 of the actuator 30. The position signal is of a amplitude of 6 mm, the midpoint (MP) of the oscillation being around the expected equilibrium point of

  the assembly composed of the actuator 30 / of the clutch 16.

  When the position signal is applied from the fully coupled position of the clutch 16, the electric motor 40 aided by the compensating spring 60 moves

  the actuator 30 rapidly to the equilibrium position.

  The actuator 30 then moves more slowly, as the motor 40 acts itself to overcome the reaction force of the disphragm spring 90. Consequently, even at a frequency of 5 Hz, the actuator does not not reach the IS position required by the position signal, before the position signal is inverted. When the position signal is inverted, the electric motor 40, aided by the diaphragm spring 90, quickly returns the actuator 30 to the equilibrium position, the actuator then moving more slowly when the motor 40 compresses the spring 60. The higher the frequency of the position signal, the less the actuator exceeds the equilibrium position and, at frequencies of 25 Hz and 50 Hz, the actuator 30 attaches to the

  equilibrium position, as illustrated in figure 4.

  As illustrated in FIG. 5, a position signal varying at a frequency of 50 Hz and having a variable amplitude is applied to the actuator 30. As shown in FIG. 5, at lower amplitudes, the actuator 30 is fixed at the midpoint of the variable position signal. The greater the amplitude, the closer the actuator is fixed to a position corresponding to the position

actuator balance 30.

  Finally, as illustrated in FIG. 6, in which a variable position signal at a frequency of 50 Hz and having

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  an amplitude of 6 mm is applied to the actuator 30, the midpoint of the oscillation of the position signal being variable, it is shown that the accuracy of the determination of the equilibrium position improves progressively the midpoint of the position signal is approaching the

equilibrium position.

  According to an embodiment of the invention, to calibrate the equilibrium position of an actuator 30, a variable position signal at a frequency of 50 Hz and having an amplitude of 6 mm is applied to the actuator 30, the actual position of the actuator 30 being determined, as indicated by the position sensor 68. Initially, the midpoint of the variable position signal is fixed to coincide with a calculated equilibrium position or

previously determined.

  The calibration procedure is then repeated, the midpoint of the position signal being repositioned to coincide with the equilibrium position determined during the previous calibration procedure, until the determination of the equilibrium position coincides with the

midpoint of the position signal.

  Various modifications can be made without departing from the invention. For example, while a 50 Hz variable position signal is used in the preferred embodiment described above, variable position signals at 25 Hz or more can be used. In addition, while an amplitude of 6 mm is used in the embodiment described above, it is appreciated that the actual amplitude used depends on the extent of movement of the actuator, from the fully coupled position to the completely uncoupled position of the clutch, and that it depends on the location of the equilibrium position in relation to these extreme trajectories

of displacement.

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  While the invention has been described with reference to a clutch actuator, it is also applicable to other electronic motor actuators which include a compensating spring and are used to control the movement of a mechanism which produces a resilient reaction force, for example actuators used in speed selector mechanisms. Actuators according to the present invention can also be used in completely transmission systems

automatisce or semi-automated.

  The claims provided with the application are

  formulations proposed without prejudging the obtaining of extended protection conferred by the patent. The applicant reserves the right to submit claims for other combinations of features disclosed

  previously only in the description and / or in the

drawings.

  References used in subclaims make

  reference to the further development of the subject-matter of the main claim, by the features of the respective sub-claim i these references should not be understood as being a renunciation of obtaining protection independent of the subject-matter for the combination of

  features contained in the subclaims

concerned.

  Since the subject-matter of the sub-claims may

  constitute separate and independent inventions with reference to the technique prior to the priority date, the applicant reserves the right to be the subject of it

  independent claims or make declarations

  of division. In addition, they may also contain independent inventions which show a design which is

  independent of any of the objects of the subclaims

preceding.

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  The embodiments must not be considered as a limitation of the invention. What is more, a wide range of changes and modifications is possible within the scope of this disclosure, in particular variations, elements, combinations and / or materials such as, for example, those of skill in the art. art can explain by combining features or

  individual elements described in the description

  general, and embodiments in addition to the characteristics and / or elements or steps of processes

  described in the claims and contained in the drawings

  with the aim of solving a task, thus leading to a new object or to new process steps or to new sequences, by characteristics which can be combined, even where they relate to manufacturing, control and work processes.

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Claims (6)

R E V E N D I C A T I O N S   l. A method of calibrating the equilibrium position at which a compensating spring of an actuator controlled by an electric motor balances a resilient load in the mechanism which is controlled by the actuator, comprising the steps of applying a position signal high amplitude, varying at a high frequency, for energizing the electric motor, said position signal corresponding to positions of the actuator which cover the equilibrium position, and to measuring the actual position of the actuator by means of '' a position sensor associated with the actuator. 2. Method according to claim l, wherein the variable position signal varies at a frequency equal to Hz or higher.   3. Method according to claim 1 or 2, wherein the variable position signal varies at a frequency of around 50 Hz.   4. Method according to any of claims l   to 3, in which the variable position signal has a amplitude of the order of 6 mm.   5. Method according to any one of claims l   to 4, in which the midpoint of the variable position signal is positioned to coincide with a position of estimated balance.   6. Method according to any one of the claims   previous, in which successive calibrations are 17 2823574   performed during each calibration following the initial calibrate, the midpoint (MP) of the variable position signal being repositioned to coincide with the equilibrium position determined by the previous calibration, until the determined equilibrium position coincides with point