METHOD AND DEVICE FOR CONTROLLING A MOTOR VEHICLE BRAKE

Description

[0001] The invention relates to a method for controlling a motor vehicle brake and to a device comprising means for implementing such a method. Document US2012 / 193177A1 discloses a method for controlling braking for a vehicle brake, using an abacus establishing a correspondence between a position linked to a position of the clamping member and a clamping force.

[0002] A motor vehicle brake comprising: at least one brake lining intended to cooperate with a friction member of the brake; and a lining clamping member activated by an electric motor and capable of moving against the friction member.

[0003] Furthermore, various methods for determining the clamping force of a brake lining against a brake friction member have already been proposed in the state of the art: either by directly measuring the clamping force by a force sensor; or by determining a value of the travel of the brake clamping member necessary to apply a predetermined clamping force.

[0004] In the second case, the value of the stroke is determined, for example in a laboratory, for the entire duration of use of the brake. This leads to: either to overestimated clamping or release forces, leading to premature wear of the brake components; or, in the event of very pronounced brake wear, to a delay in applying the brake, or even to an inability to park the vehicle effectively in certain vehicle parking configurations.

[0005] The invention aims in particular to optimize the braking process by taking into account the wear of the brake elements, in particular without resorting to a force sensor.

[0006] To this end, the invention relates to a method for controlling a motor vehicle brake, this brake comprising: at least one brake lining intended to cooperate with a friction member of the brake; a member for clamping the lining against the friction member activated by an electric motor; the process being characterized in that during a brake activation or deactivation step, an abacus is created or updated establishing a correspondence between a position linked to a position of the clamping member, called the position of the clamping member, and a clamping or release force of the clamping member, by calculating the position of the clamping member and the clamping force from operating parameters of elements of a kinematic chain connecting a motor shaft to the clamping member, called reference parameters.

[0007] Thus, the invention allows the creation and updating of the abacus in order to adapt the values ​​of the clamping / release force and the position of the clamping member according to the wear of the brake elements. In this way, the positions of the clamping member corresponding to the optimal clamping or release forces are controlled without these forces being overestimated or underestimated. In addition, the estimation of the forces is done without using a force sensor, while obtaining very satisfactory values ​​of the clamping / release force and the position of the clamping member.

[0008] The method according to the present invention may further have one or more of the following characteristics taken alone or in combination.

[0009] Advantageously, the reference parameters include the motor supply voltage, the motor supply current and mechanical parameters of the motor.

[0010] Thus, it is possible to obtain the engine rotation speed and engine torque from these reference parameters.

[0011] Advantageously, the brake comprises movement transmission means connecting the motor shaft to the clamping member, these movement transmission means comprising a screw / nut assembly transforming the rotational movement from the motor shaft into translational movement of the clamping member, the reference parameters further comprising a ratio between the rotation of the screw and the movement of the nut, called the screw pitch ratio, or a ratio between the rotation of the nut and the movement of the screw, called the nut pitch.

[0012] Thus, it is possible to obtain the position of the clamping member as well as the clamping or loosening force of the clamping member from these reference parameters.

[0013] Advantageously, the movement transmission means comprise gear means for reducing the movement between the motor shaft and the screw of the screw / nut assembly, the reference parameters further comprising a reduction ratio associated with the reduction means.

[0014] Thus, it is possible to obtain the screw rotation speed and the screw torque from these reference parameters.

[0015] Advantageously, during a step of activating or deactivating the brake, the value of the clamping or releasing force of the clamping member is estimated as a function of the position of the clamping member and the corresponding value of the clamping or releasing force given by the abacus.

[0016] Thus, the clamping or loosening force corresponding to a position of the clamping member can be estimated precisely using the values ​​of the abacus.

[0017] Advantageously, the chart is created or updated by calculating successive positions of the clamping member and the corresponding clamping or loosening forces from the reference parameters, by recording the successive positions of the clamping member and the corresponding clamping or loosening forces and by comparing the clamping or loosening force with a predetermined threshold, the recording of the successive positions of the clamping member and the corresponding clamping or loosening forces being interrupted when the clamping or loosening force crosses the predetermined threshold.

[0018] Thus, the clamping or loosening forces with which the linings clamp the friction member are kept substantially constant despite wear of the brake elements.

[0019] Advantageously, the abacus is updated periodically after a predetermined number of brake activations or brake deactivations between each abacus update.

[0020] The chart is therefore regularly updated to take into account the wear of brake components. Furthermore, it is possible to monitor the wear of various brake components, including the linings, at regular intervals, based on changes in the chart values.

[0021] The invention also relates to a device for controlling a motor vehicle brake, characterized in that it comprises means implementing a method according to the invention, for example a medium for recording software means.

[0022] The brake that is controlled is, for example, a drum brake or a disc brake, this brake being capable of operating in electromechanical and / or hydraulic mode.

[0023] Thus, the brake control device according to the invention can perform a vehicle braking function while moving (or service braking), a parking brake function, an emergency brake function, or a hill start assistance function. Brief description of the figures

[0024] The invention will be better understood on reading the following description, given solely by way of example and with reference to the appended drawings in which: [ Fig. 1 ] there [ Fig. 1 ] is a front view of a motor vehicle drum brake controlled by a method according to the invention; [ Fig.2 ] there [ Fig.2 ] is a partial perspective view of the brake of the [ Fig. 1 ] ; [ Fig.3 ] there [ Fig.3 ] is a kinematic diagram of motion transmission means connecting a motor shaft to a brake application member illustrated in the figures 1 And 2 ; [ Fig.4 ] there [ Fig.4] is an exploded perspective view of a motor vehicle disc brake controlled by a method according to the invention; [ Fig.5 ] there [ Fig.5 ] is a view of the brake of the [ Fig.4 ] according to arrow V of the [ Fig.4 ] ; [ Fig.6 ] there [ Fig.6 ] is a functional diagram of different components of a motor vehicle brake, in particular the brake of the figures 1 Or 4 , capable of being controlled by the method according to the invention; [ Fig.7 ] there [ Fig.7 ] is a flowchart illustrating the method according to the invention; [ Fig.8 ] there [ Fig.8 ] is an example illustrating the evolution of the position of the clamping member as a function of time during the activation of a brake, in particular the brake of figures 1 Or 4 ; [ Fig.9 ] there [ Fig.9 ] illustrates an example of the evolution of the clamping force when activating a brake, in particular the brake of figures 1 Or 4 ; [ Fig. 10 ] there [ Fig. 10 ] illustrates an example of an abacus obtained from the figures 8 and 9 ; [ Fig. 11 ] there [ Fig. 11 ] illustrates an example of the evolution of the position of the clamping member during a brake clamping and releasing operation, as a function of time; [ Fig. 12 ] there [ Fig. 12 ] illustrates an example of the evolution of the brake application and release force as a function of time deduced from an abacus and the position of the application member of the [ Fig. 11 ]. Detailed description

[0025] It has been represented on the figures 1 to 3 a motor vehicle drum brake controlled by a method according to the invention, designated by the general reference 2.

[0026] This drum brake 2 is described in more detail in document FR 3 031 151 A, the content of which must be considered as part of this application.

[0027] We see in particular by referring to the [ Fig. 1] that the drum brake 2 comprises a drum 4 which is coaxial with a wheel of the vehicle (not shown) with which it is integral. The drum 4 is movable relative to a plate 6 which carries a pair of substantially diametrically opposed segments 8, 10 arranged inside the drum 4. These segments 8, 10 each form a clamping member. Indeed, each segment 8, 10 is coated with a friction lining 12 intended to cooperate by friction with a friction member comprising a friction track 14 formed by an inner surface of the drum 4.

[0028] The wheel is braked by moving the segments 8, 10 apart until they come into contact with the friction track of the drum 4. The segments 8, 10 can be moved apart by hydraulic 16 and / or electromechanical 18 actuating members.

[0029] Each segment 8, 10 forms a lever of which a first end 20, 22 rests on an element 24 secured to the plate 6 called the anchoring element and of which a second end 26, 28 is movable.

[0030] To ensure braking of the wheel when the vehicle is moving (operation of the brake in service brake mode), the drum brake 2 comprises a hydraulic actuating member 16 formed by a hydraulic cylinder, provided with pistons, called a “wheel cylinder” (see [ Fig. 1 ]). The movable end 26, 28 of each segment 8, 10 cooperates in this case with the wheel cylinder 16.

[0031] To ensure wheel braking in other vehicle operating modes, in particular when parking the vehicle (brake operation in parking brake mode), the drum brake also includes (see Figures 2 and 3), an electromechanical actuating member 18 comprising a screw / nut assembly 30 extending between the movable ends 26, 28 of the segments.

[0032] The electromechanical actuating member 18 is activated by an electric motor 32, located on an opposite side of the plate 6 relative to the segments 8, 10 (see [ Fig.2 ]). A shaft 34 of the motor 32 is kinematically connected to the electromechanical actuating member 18 by movement transmission means 36.

[0033] These movement transmission means 36 are of the conventional type and comprise gear means for reducing the movement between the shaft 34 of the motor and the nut 38 or the screw 40 of the screw / nut assembly 30.

[0034] It will be noted that the screw / nut assembly 30 transforms the rotational movement from the shaft 34 of the motor into translational movement of the clamping member, namely into translational movement of the movable ends 26, 28 of the segments 8, 10.

[0035] It is therefore understood that the drum brake 2 comprises movement transmission means 36 connecting the shaft 34 of the motor to the clamping member (each segment 8, 10), the screw / nut assembly 30 of these movement transmission means 36 transforming the rotational movement from the shaft 34 of the motor into movement comprising at least one translation component of the clamping member (each free end 26, 28 of a segment 8, 10).

[0036] More particularly, the gear means 36 comprise (see [ Fig.3 ]) : a first epicyclic gear train 42 driven at input 44 by the shaft 34 of the electric motor 32; a first intermediate cascade 46 driven at input 48 by the first epicyclic gear train 42; a second epicyclic gear train 50 driven at input 52 by the first intermediate cascade 46; and a second intermediate cascade 54 driven at input 56 by the second epicyclic gear train 50.

[0037] The second intermediate cascade 54 is coupled to the external toothing 39 of the nut 38 of the screw / nut assembly 30.

[0038] The relative movement between the nut 38 and the screw 40 of the screw / nut assembly 30 by screwing or unscrewing causes the free ends 26, 28 of the segments 8, 10 between which the screw / nut assembly 30 extends to move apart or towards each other.

[0039] It has been represented on the figures 4 to 5 a motor vehicle disc brake controlled by a method according to the invention, designated by the general reference 60.

[0040] This disc brake 60 is described in more detail in document FR 2 999 509 A, the content of which must be considered as part of this application.

[0041] On the [ Fig.4 ], the disc brake 60 comprises a caliper 62 having an axial cavity 64 in which a piston 66 is mounted to slide axially in a sealed manner in two opposite directions. The piston 66 of the brake has a generally circular cylindrical shape open at one end and closed at another end by an external transverse face 68. The piston 66 is capable of cooperating by its external transverse face 68 with one of the linings (not shown) of the brake.

[0042] During braking, the piston 66 forces one of the brake linings against the disc (not shown) forming a friction member. The piston 66 thus forms a clamping member for the disc brake 60.

[0043] The disc brake 60 also includes hydraulic and electromechanical actuating members 70 as in the case of the drum brake 2.

[0044] The hydraulic actuating member comprises the piston 66 sliding in the axial cavity 64 which forms a hydraulic chamber. In operation, the hydraulic pressure in the axial cavity 64 causes the piston 66 to thrust axially towards one of the linings.

[0045] The electromechanical actuating member 70 comprises a housing 72 fixed on a rear transverse face of the caliper 62. The housing 72 has an open transverse face 74 aligned with respect to the axial cavity 64 of the caliper 62. The housing 72 contains a reduction mechanism with epicyclic gears 76 (see [ Fig.5 ]), arranged in a first housing 78 of the housing, and an electric motor (not shown) arranged in a second housing 80 of the housing.

[0046] On the [ Fig.5], we see in more detail the two housings 78, 80 of the housing. The first housing 78 is closed axially by an annular bottom wall 81. The annular bottom wall 81 has a central orifice 82 for the passage of an output element of the epicyclic gear train 76, said element forming the movement output element of the electromechanical actuating member 70.

[0047] The housing 72 comprises the second housing 80 open axially towards the rear and arranged to house the electric motor (not shown).

[0048] The shaft of the electric motor is connected by conventional gear means not shown to the epicyclic gear train 76 housed in the first housing 78.

[0049] The electromechanical actuating member 70 comprises an assembly 84 comprising a drive screw 86 cooperating by screwing with an axial thrust nut 88. The nut 88 is housed in the piston 66 while being integral with this piston 66.

[0050] The conventional gear means and the epicyclic gear train 76 form motion transmission means comprising gear means for reducing the motion between the motor shaft and the screw 86 of the screw / nut assembly 84.

[0051] It will be noted that the screw / nut assembly 84 transforms the rotational movement from the motor shaft into translational movement of the clamping member, namely into translational movement of the piston 66.

[0052] Thus the rotation of the screw 86 causes the nut 88 to slide integrally with the piston 66 inside the axial cavity 64. The screw 86 comprises a drive head 90 intended to be driven in rotation in two opposite directions by the output element of the epicyclic gear train 76, through the open transverse face 74 of the housing 72.

[0053] It is therefore understood that the disc brake 60 comprises movement transmission means (gear means and epicyclic gear train 76) connecting the motor shaft to the clamping member (piston 66), the screw / nut assembly 84 of these movement transmission means transforming the rotational movement from the motor shaft into translational movement of the clamping member (piston 66).

[0054] It has been represented on the [ Fig.6 ] a functional diagram illustrating functional blocks, common to the drum brakes 2 and disc brakes 60 described above, activated during the electromechanical actuation of a motor vehicle brake.

[0055] This figure also shows the parameters from the functional blocks during electromechanical actuation.

[0056] From left to right, the first block 92 diagrams the electric motor 32 of the drum brake 2 or the disc brake 60, equipped with the motor shaft 34. This motor is supplied by a voltage Umot and a current Imot intended to be measured. From the current and the voltage applied to the electric motor, the torque T1 of the motor and the angular speed Ω1 of the motor shaft are obtained.

[0057] The second block 94 schematizes the transmission means of the drum brake 2 or the disc brake 60, comprising epicyclic gear trains. These transmission means form gear means for reducing the movement between the shaft 34 of the motor and the screw or nut of the screw / nut assembly. This block 94 receives as input the angular speed Ω1 and the torque T1 of the motor and reduces these parameters by a reduction ratio associated with the gear means to obtain the angular speed Ω2 and the torque T2 of the screw or nut.

[0058] The third block 96 schematizes the screw / nut assembly of the drum brake 2 or the disc brake 60, this screw / nut assembly receiving as input the angular speed Ω2 and the torque T2. Here, it is considered that the position of the screw-nut assembly is substantially identical to that of the clamping member. Of course, the clamping member moves at the same speed as the screw or the nut of the screw / nut assembly.

[0059] The fourth block 98 schematizes the usual elastic forces of elements of the drum brake 2 or of the disc brake 60 appearing under the effect of the position x of the clamping member and the clamping force F.

[0060] A method according to the invention for controlling a motor vehicle brake, for example a drum brake 2 or a disc brake 60 as described above, will be described below.

[0061] According to this method, during a brake activation or deactivation step, a chart is created or updated. The chart establishes a correspondence between a position linked to a position of the clamping member, called the position of the clamping member, and a clamping or release force of the clamping member. To do this, the position of the clamping member and the clamping force are calculated from operating parameters of elements of a kinematic chain connecting the motor shaft to the clamping member, called reference parameters.

[0062] In the case of the drum brake 2, the clamping member is formed by the segments 8, 10. In the case of the disc brake 60, the clamping member is formed by the piston 66. It will be recalled that the shaft and the motor are shown in the figures only in the case of the drum brake (see [ Fig.3 ]: shaft 34 of motor 32).

[0063] The reference parameters include motor supply voltage, motor supply current, and motor mechanical parameters.

[0064] The reference parameters further include a ratio between the rotation of the screw 86 and the displacement of the nut 88, called the screw pitch ratio, or the ratio between the rotation of the nut 38 and the displacement of the screw 40, called the nut pitch ratio.

[0065] The reference parameters also include a gear ratio associated with the gearing means.

[0066] In the case of the drum brake 2, the movement reduction means are formed by the gear means 36 comprising epicyclic gear trains 42, 46, 50, 54.

[0067] In the case of the disc brake 60, the means for reducing the movement are formed by the conventional gear means and the epicyclic gear train 76.

[0068] The clamping or loosening force, denoted Fs, is established by the following relation (1), from the reference parameters mentioned above: [Math.1] F s = k mot I − I i − 2 π * J r dω dt * η * ratio ssp

[0069] The definitions of the reference parameters used in this relationship are as follows.

[0070] kmot corresponds to a constant of the electric motor allowing to determine or estimate the torque at the output of the electric motor. This constant is described in more detail in document US 2016 103 430 A1, the content of which must be considered as part of the present application.

[0071] I corresponds to the current supplying the motor and Ii corresponds to the current when the motor is stopped.

[0072] Jr corresponds to the moment of inertia of the motor shaft.

[0073] ω corresponds to the angular velocity of the motor shaft. dω / dt therefore corresponds to the angular acceleration of the motor shaft.

[0074] η corresponds to the gear ratio associated with the gearing means.

[0075] ratio corresponds to a constant.

[0076] ssp stands for screw pitch ratio or nut pitch ratio.

[0077] It has been represented on the [ Fig.7 ] a flowchart illustrating in a non-limiting manner the method according to the invention.

[0078] First, we check whether the braking is active or inactive (step 100).

[0079] Next, we check whether an abacus has already been created (step 200).

[0080] If no chart has been created, a chart establishing a correspondence between a position linked to a position of the clamping member and a clamping or release force is created. To do this, the speed and positions of the clamping member are first recorded (step 302) until the brake clamping member reaches the end of its travel (step 400).

[0081] For example, on the [ Fig.8 ] illustrating a case where the clamping member approaches a friction member, called the clamping case, the position of the stroke of the clamping member is reached after 0.5 seconds.

[0082] Then, the position of the stroke of the clamping member is continued to be recorded (step 304) and, from this moment, with reference to the [ Fig.9 ], the value of the clamping or loosening force Fs of the clamping member is estimated as a function of the position of the clamping member from reference parameters, using relation (1) above (step 600).

[0083] The successive positions of the clamping member and the corresponding clamping or loosening forces are recorded (step 700) by comparing the clamping or loosening force with a predetermined force threshold (step 802). When the loosening clamping force exceeds the predetermined threshold, the recording of the clamping or loosening force is interrupted.

[0084] Indeed, on the [ Fig.9 ] illustrating the evolution of the clamping force as a function of time, we see that, after about 0.8 seconds, the clamping force reaches its maximum value (about 12 kN). Thus, the abacus was created (step 900, see [ Fig. 10 ]) and the recording of the successive positions of the clamping member and the corresponding clamping or loosening forces in the chart is interrupted.

[0085] Referring again to the [ Fig.8], we see that a discontinuity is observed at 0.8 seconds, or approximately 1.1 mm into the stroke of the clamping member. The part of the curve between 1.1 mm and 1.5 mm corresponds to a play take-up and not to a movement of the clamping member, the linings 12 being pressed against the friction member.

[0086] Advantageously, the values ​​between 1.1 mm and 1.5 mm (after 0.8 seconds) are not taken into account in the abacus that has just been created. Of course, all elastic forces were compensated for when estimating the clamping force, especially for the 60 disc brake.

[0087] If a chart has already been created, the speed and positions of the clamping member are recorded (step 306) in order to deduce the corresponding value of the clamping or loosening force from the chart (step 500) until the clamping or loosening force crosses a predetermined force threshold (step 804).

[0088] It has been represented on the [ Fig. 11 ] an example of the evolution of the position of the clamping member during a brake clamping and releasing operation, as a function of time.

[0089] On the [ Fig. 11 ], tightening is shown from 0 to 1 second and holding the tightening position from 1 to 3.5 seconds, then loosening is shown from 3.5 seconds to 4.5 seconds. In this figure, discontinuities are visible and present at approximately 0.8 seconds during tightening and at 3.7 seconds during loosening. These discontinuities mark the crossing of predetermined force thresholds as observed above in the [ Fig.8 ].

[0090] On the [ Fig. 12 ], the clamping force is deduced from 0.5 seconds using the abacus already created and from the position of the clamping member of the [ Fig. 11 ]. The curve of the tightening and loosening force thus obtained is smoothed by using the abacus.

[0091] Thus, the discontinuities are no longer visible on the [ Fig. 12 ] and the clamping force is presented between 0.5 seconds and 0.8 seconds, and the loosening force is presented between approximately 3.7 and 4.5 seconds. For the time interval during which the clamping force is not recorded (between approximately 0.8 and approximately 3.7 seconds), the value of the position of the clamping member at the clamping stop position (at approximately 1.1 mm) is taken into account for the calculation of the clamping holding force.

[0092] Preferably, provision is made to update the abacus periodically after a predetermined number of brake activations or brake deactivations between each abacus update.

[0093] Of course, the control method described above may be implemented by a device for controlling a motor vehicle brake comprising, for example, a medium for recording software means such as a computer program intended to carry out the steps of the method.

[0094] The invention is not limited to the embodiments presented and other embodiments will become apparent to those skilled in the art.

[0095] The method according to the invention can also be implemented by an emergency braking device, for example electromechanical, activated automatically or manually via a conventional actuator. List of references

[0096] 2: drum brake 4: drum 6: plate 8, 10: segments 12: lining 14: friction track 16: hydraulic actuating member of the drum brake 18: electromechanical actuating member of the drum brake 20, 22: first end (fixed) of each segment 24: element secured to the plate 26, 28: second end (movable) of each segment 30: screw-nut assembly of the drum brake 32: electric motor 34: shaft of the electric motor 36: means for transmitting movement of the drum brake 38: nut of the drum brake 39: external teeth of the nut of the drum brake 40: screw of the drum brake 42: first epicyclic gear train 44: input of the first epicyclic gear train 46: first intermediate cascade 48: input of the first intermediate cascade 50: second epicyclic gear train 52: input of the second gear train epicyclic 54: second intermediate cascade 56: input of the second intermediate cascade 60: disc brake 62: caliper 64: cavityaxial 66: piston 68: external transverse face of the piston 70: electromechanical actuating member of the disc brake 72: housing 74: open transverse face of the housing 76: epicyclic gears 78: first housing housing 80: second housing housing 81: annular bottom wall of the first housing 82: central orifice of the first housing 84: screw / nut assembly of the disc brake 86: drive screw of the disc brake 88: thrust nut of the disc brake 90: drive head 92: first block diagramming the electric motor of the brake 94: second block diagramming the transmission means of the brake 96: third block diagramming the screw / nut assembly of the brake 98: fourth block diagramming the usual elastic forces of elements of the brake 100: Step of checking the activation or deactivation of the brake 200: Step of checking the creation of an abacus 302, 304; 306: Stage of recording speed and positionof the clamping member 400: Step of checking the end of travel of the clamping member 500: Step of estimating the clamping or loosening force from the chart 600: Step of estimating the clamping or loosening force as a function of the clamping position of the clamping member from reference parameters 700: Step of recording the successive positions of the clamping member and the corresponding clamping or loosening forces 802; 804: Step of comparing the clamping or loosening force with respect to a predetermined force threshold 900: Step of creating a chart comprising the position values ​​of the clamping member and the clamping or loosening force values.

Claims

1. Method for controlling a motor vehicle brake (2; 60), this brake (2; 60) comprising: - at least one brake lining (12) intended to cooperate with a brake friction member (14); - a clamping member (8, 10; 66) for clamping the lining (12) against the friction member (14) activated by an electric motor (32); wherein, during a step of activating or deactivating the brake (2; 60), a chart establishing a mapping between a position linked to a position of the clamping member, called position of the clamping member (8, 10; 66), and a clamping or unclamping force of the clamping member (8, 10; 66) is created or updated, by calculating (600) the position of the clamping member (8, 10; 66) and the clamping force using operating parameters of elements of a kinematic chain connecting a shaft (34) of the motor (32) to the clamping member (8, 10; 66), called reference parameters, characterised in that the chart is updated periodically after a predetermined number of activations of the brake (2; 60) or of deactivations of the brake (2; 60) between each update of the chart.

2. Method for controlling according to claim 1, wherein the reference parameters comprise the power supply voltage of the motor (32), the power supply current of the motor (32) and mechanical parameters of the motor (32).

3. Method for controlling according to any one of the preceding claims, wherein the brake (2; 60) comprises movement transmission means (36) connecting the shaft (34) of the motor (32) to the clamping member (8, 10; 66), these movement transmission means (36) comprising a screw / nut assembly (30; 84) transforming the rotational movement from the shaft (34) of the motor (32) into translational movement of the clamping member (8, 10; 66), the reference parameters also comprising a ratio between the rotation of the screw (40; 86) and the displacement of the nut (38; 88), called screw pitch ratio or a ratio between the rotation of the nut (38; 88) and the dis placement of the screw (40; 86), called nut pitch ratio.

4. Method for controlling according to claim 3, wherein the movement transmission means (36) comprise gear means (42, 46, 50, 54; 76) for reducing the movement between the shaft (34) of the motor (32) and the screw (40; 86) or the nut (38; 88) of the screw / nut assembly (30; 84), the reference parameters also comprising a reduction ratio associated with the reduction means (42, 46, 50, 54; 76).

5. Method for controlling according to any one of the preceding claims, wherein during a step of activating or deactivating the brake (2; 60), the value of the clamping or unclamping force of the clamping member (8; 10, 66) is estimated (500) according to the position of the clamping member (8; 10, 66) and the corresponding value of the clamping or unclamping force given by the chart.

6. Method for controlling according to any one of the preceding claims, wherein the chart is created or updated by calculating (600) successive positions of the clamping member (8; 10, 66) and corresponding clamping or unclamping forces using reference parameters, by recording (700) the successive positions of the clamping member (8; 10, 66) and the corresponding clamping or unclamping forces and by comparing (802, 804) the clamping or unclamping force with a predetermined threshold, the recording of the successive positions of the clamping member and of the corresponding clamping or unclamping forces being interrupted when the clamping or unclamping force crosses the predetermined threshold.

7. Device for controlling a motor vehicle brake (2; 60), characterised in that it comprises means implementing a method according to any one of the preceding claims, for example a medium for recording software means.

8. Device for controlling according to claim 7, wherein the brake (2; 60) is a drum brake (2) or a disc brake (60), this brake (2; 60) being capable of operating in electromechanical and / or hydraulic mode.