DEVICE FOR BRAKE SYSTEM AND ASSOCIATED CONTROL METHOD

Abstract

The invention relates in particular to a force measuring device for a brake system comprising a motor (1) for rotating a gear reduction device (3, 4, 5, 8), an input shaft (2), an output shaft (6). The device comprises a first sensor (10), positioned upstream of said gear train so as to measure the angular rotation of said input shaft, a second sensor (20), positioned downstream of said gear train so as to measure the angular rotation of said output shaft, at least one elastically deformable element (7), positioned between said input shaft and said output shaft and a calculation module (30) of a torque (T) transmitted by the reduction device at a given instant, from the angular rotation data transmitted at said given instant by said first and second sensors, said stiffness of the elastically deformable element and the reduction coefficient of said reduction device.Figure for abstract: [Fig.1].

Description

Title of the invention: DEVICE FOR A BRAKE SYSTEM AND ASSOCIATED CONTROL METHOD FIELD OF THE INVENTION

[0001] The present invention relates in particular to a device for controlling operational parameters in a transmission system to optimize a brake system, making it possible to act on the control law of the brake system in real time.

[0002] It also relates to a brake system equipped with such a device and a method of implementing such a device.

[0003] The field of the invention is that of braking systems, in particular for automobiles.

[0004] The invention proposes a solution aimed at improving the performance of braking systems in the event of changes in the behavior of the elements of this system, for example in the event of changes in temperature, climatic conditions or wear.

[0005] STATE OF THE ART

[0006] In a vehicle, particularly a road vehicle, braking systems are increasingly efficient and their development involves highly precise control laws.

[0007] In particular, climatic conditions can have consequences on the precision of the operation of the brakes, and techniques have been developed to take into account these effects of climatic conditions in order to compensate for possible losses of precision in the braking of vehicles.

[0008] All the techniques implemented in vehicles must ensure with greater safety the stopping or deceleration of the vehicle in all scenarios or conditions of use of the braking system (in service, parking, VDC, ABS). Some techniques use a Force / Brake torque distribution profile of each brake: in these conditions, it is relevant to implement a force sensor to meet the profile tracking requirements of the brake system. Torque sensors are generally expensive and it is not easy to implement them in brake systems.

[0009] The invention proposes an alternative solution to known systems which makes it possible to control the brake system in real time when it is actuated in order to act on the control law, to optimize braking performance. Statement of the invention

[0010] According to a first aspect of the invention, at least one of the aforementioned aims is achieved. with a force measuring device for a brake system comprising a motor for rotating a gear reduction device comprising, for applying a braking force to at least one brake pad, at least one gear train of one or more stages of gear pinions (which may be internally or externally toothed) having a reduction coefficient which may range from one to two hundred and fifty, in particular at least twenty and / or at most fifty, said system comprising an input shaft, arranged to be rotated by said motor according to a control law and to drive an output shaft via said gear train.

[0011] According to the invention, said device for a brake system is remarkable in that it comprises: - a first sensor, positioned upstream of said gear train so as to measure the angular rotation of said input shaft between a rest position where the motor does not rotate the input shaft and an actuated position where the motor rotates the input shaft, - a second sensor, positioned downstream of said gear train so as to measure the angular rotation of said output shaft between a rest position where the output shaft is not rotated and an actuated position where the reduction device rotates the output shaft, in that said reduction device comprises at least one elastically deformable element, positioned between said input shaft and said output shaft of the reduction device so as to be elastically deformed by a torque transmitted from the input shaft to the output shaft, said elastically deformable element having a stiffness, and in that it comprises a module for calculating a torque transmitted by the reduction device at a given instant, from the angular rotation data transmitted at said given instant by said first and second sensors, said stiffness of the elastically deformable element and the reduction coefficient of said reduction device.

[0012] Thus produced, the device makes it possible to know the output torque of the transmission system, which makes it possible to act on the control law of the brake system, which acts on the operation of the motor. This makes it possible in particular to overcome certain shortcomings of existing systems which, in order to act on the control law of the brake system, monitor the current: this is not always sufficient to have optimal performance, because the operating conditions of the transmission elements can vary (temperature, humidity, etc.) and the control law does not sufficiently take into account the effects of these conditions on the transmission elements. By taking into consideration the torque actually transmitted from the device, it is possible to act on the law of real-time control which improves braking, because we can act on the actual braking force to be provided by knowing the actual torque.

[0013] Advantageously, the elastically deformable element is interposed between two coaxial parts of the reducer, one of which drives the other in rotation after taking up an angular play between them, said angular take-up being obtained partially or exclusively by compression of said elastically deformable element between two bearing surfaces carried by said coaxial parts. In the context of such an embodiment, the elastically deformable element is typically deformed in compression only.

[0014] Preferably, the elastically deformable element is interposed between two coaxial gears which belong to two different gear stages within the reducer, and one of which drives the other in rotation after taking up an angular play producing a deformation of said elastically deformable element.

[0015] More preferably, the reduction device comprises one or more stages whose shafts are mounted in the same structure forming a transmission cartridge, and the elastically deformable element and / or the second sensor are / is mounted on a shaft which is driven by said cartridge.

[0016] According to an alternative embodiment, the electric motor is of a vector type integrating an angular position sensor which is also used as a first sensor, in particular a brushless direct current sensor. According to an alternative embodiment, said first sensor and said second sensor are position sensors of the same technology, preferably magnetoresistive sensors and in particular giant magnetoresistance (or GMR for Giant Magneto Resistance in English).

[0017] Advantageously, the brake system device according to the invention comprises at least two elastically deformable elements, said at least two elastically deformable elements having different stiffnesses.

[0018] Preferably, said at least two deformable elements have the same shape and the same dimensions. Thus, produced, the elements are interchangeable with other elastically deformable elements having different stiffnesses.

[0019] More preferably, according to an advantageous embodiment, the motor produces a torque of the order of at least 0.5 Nm and less than 5 Nm, and for example of the order of 1 Nm, and a reduction device having a reduction coefficient of between 20 and 60, and for example between 30 and 50. For a configuration of this type, said at least one elastic element is made of elastomer, for example of the EPDM type. By way of example, such an elastically deformable element may have the shape of an angular sector taken from an annular seal of rectangular section, a sector whose external dimensions are for example at least 3 mm or even 4 mm and by example of at most 10 mm or even at most 7 mm; or a substantially parallelepiped shape of similar dimensions. For example, the material(s) will be chosen with a Shore A hardness of, for example, at least 20 or even at least 30, and for example at most 90 or even at most 70.

[0020] According to another advantageous embodiment, the device according to the invention comprises a temperature sensor, and the calculation module comprises a memory which associates a first panel of stiffnesses of said at least one elastically deformable element with a second panel of temperatures.

[0021] The invention also relates to a brake system comprising a device as defined above.

[0022] The system preferably comprises a disc brake system, preferably with a floating caliper.

[0023] According to an alternative embodiment, the brake system is a hydraulic brake system.

[0024] The invention also relates to a method for controlling a brake system equipped with a device as defined above. The control method according to the invention is remarkable in that it comprises the following steps: - actuation of said motor at a given time, by control of said brake system (by a user), - measuring a first angle of rotation of said input shaft in an actuated position, - measurement of a second angle of rotation of said output shaft in the actuated position, - estimation of a torque at said given instant from the first and second measured angles, said reduction coefficient and the stiffness of said at least one elastically deformable element, by said calculation module, - transmission of said estimated torque, at said given instant, to said brake control system, and - controlling the operation of said motor by said brake control system, taking into consideration, in said control law, said torque estimated at said given instant.

[0025] Advantageously, the calculation module uses the data of the estimated torque value within a closed-loop regulation implemented to adjust the braking force applied, in particular as a function of a received instruction, during a sequence including a braking command.

[0026] According to an advantageous embodiment, where the device comprises at least one elastically deformable element which has a stiffness which depends on the temperature, said method further comprises the following steps: - determination of the temperature at that given time, - identification of a stiffness of said at least one elastically deformable element which corresponds to the stiffness of said element at said determined temperature,

[0027] said step of estimating the torque at said given instant taking into consideration said stiffness identified for said determined temperature.

[0028] Advantageously, the method comprises a step according to which a duration of implementation of said elastically deformable element in said device is monitored and, when said duration reaches a predetermined duration, said system is warned of obsolescence of said elastically deformable element and a predetermined stiffness is applied to carry out the step of estimating the torque.

[0029] Preferably, when the method implements a device comprising at least two elastically deformable elements, each having a different stiffness, including a low stiffness and a high stiffness, greater than said low stiffness, said method comprising a step according to which the moment at which the elastically deformable element of low stiffness begins to produce an error is determined, and / or the moment at which it no longer produces an error to the benefit of the elastically deformable element of high stiffness, and said determined moment is taken into consideration to modulate the control law, in order to make said determined moment correspond to a moment ("touchpoint") at which the force produced by the motor begins to produce a clamping or braking effect, and for example where the clamping force to be applied is the greatest.

[0030] Thanks to the device and the method according to the invention, it should be noted that the torque is monitored in real time to act on the control law.

[0031] LIST OF FIGURES

[0032] Other features and advantages of the invention will appear on reading the detailed description of implementations and embodiments which are in no way limiting, and the appended drawings where:

[0033] [Fig. 1] is a schematic representation of a device for a brake system according to the invention,

[0034] [Fig.2] is a perspective view of a pinion of a gear of a device in accordance with the invention,

[0035] [Fig.3] is also a perspective view of a pinion of a device according to the invention, which assembles with the pinion shown in [Fig.2],

[0036] [Fig.4] illustrates the pinion of [Fig.3], assembled to the pinion of [Fig.2], and

[0037] [Fig.5] illustrate curves of calculated torque readings, motor angle and error angles for two examples of devices according to the invention, one with a single elastically deformable element, and the other with two elastically deformable elements of different stiffness.

[0038] DESCRIPTION OF EMBODIMENTS

[0039] The embodiments which will now be described are not limiting: it will be possible in particular to produce variants of the invention comprising only a selection of characteristics described subsequently, isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0040] Of course, the invention is not limited to the examples which will be described and numerous adjustments can be made to these examples without departing from the scope of the invention. In addition, the various characteristics, forms, variants and embodiments of the invention can be associated with each other in various combinations to the extent that they are not incompatible or exclusive of each other.

[0041] The invention applies mainly to the braking of motor vehicles.

[0042] [Fig.l] schematically illustrates a device according to the invention, implemented in a brake system.

[0043] The brake system may be a disc brake system, preferably with a floating caliper, or a hydraulic brake system.

[0044] The device comprises a motor-reducer system: it thus comprises a motor 1, associated with a reducer mounted in a pre-assembled cartridge 70 and which comprises different stages of pinions meshed with each other.

[0045] In [Fig.l], in the context of the illustrated example, the geared motor comprises two stages of gear pinions.

[0046] The geared motor has a reduction coefficient that a person skilled in the art knows how to determine based on the pinions used, the number of reduction stages, etc.

[0047] The geared motor comprises an input shaft 2, which is rotated by the motor 1 when a braking command is received by a control unit of the brake system (for example, when the driver presses the brake pedal, when the vehicle control system commands automatic emergency braking, etc.). The force that the motor 1 must deploy or its rotational speed are determined by a control law.

[0048] A first toothed pinion 3 is fixed on the input shaft of the reducer: it is coaxial with the input shaft 2 and it is integral in rotation with this shaft.

[0049] Pinion 3 meshes with pinion 5, by meshing its peripheral teeth with those of pinion 3 whose axis is parallel to that of input shaft 2: in this example, pinion 5 is of a different size from that of pinion 3 and it is considered that it constitutes, with pinion 3, a first stage of the reduction device.

[0050] A second reduction stage is observed comprising a pinion 8 which meshes with a pinion 4. An output shaft 6 of the reduction device is mounted in the axis of the pinion 4 and is rotationally fixed to the pinion 4.

[0051] Between the two stages, pinion 5 drives pinion 8 in rotation.

[0052] According to the invention, the reduction device comprises an elastically deformable element 7 positioned between the two pinions 5 and 8, so that it is elastically deformed when the upstream pinion 5 drives the downstream pinion 8 in rotation, and that it angularly resists this drive by means of its stiffness.

[0053] It is understood here that the rotational drive of the shaft 2 by the motor 1 drives the pinion 3 in rotation, which drives the pinion 5 in rotation, which elastically deforms the elastically deformable element 7, which drives the pinion 8 in rotation, which drives the pinion 4 in rotation, which finally drives the output shaft 6 in rotation.

[0054] The elastically deformable element 7 can be of different natures, and it can also have different shapes and be assembled, with the pinions 5 and 8, in several ways, depending on the nature of the element 7, depending on its shape or that of the pinions 5 and 8 facing each other, for example.

[0055] Several elastically deformable parts 7 can also be provided between the pinions 5 and 8, in parallel or in series.

[0056] Concretely, the elastically deformable element 7 can be produced in several parts and comprise, for example, an element 7A and an element 7B, as illustrated in [Fig.3].

[0057] This or these deformable elements are for example made of a material that is elastically deformable in compression, for example EPDM type rubber.

[0058] As soon as the downstream pinion 8 opposes a reaction torque when braking begins, the rotation of the downstream pinion 8 begins to take an angular delay relative to the pinion 5, due to the elastic deformation of the elastically deformable part or parts 7 between them.

[0059] According to the invention, the device comprises a first sensor 10, which makes it possible to measure the angular rotation of the input shaft 2 (i.e. its angular position at a time t relative to its starting position at a time t-1) when the motor 1 commands its rotation.

[0060] The device also comprises a second sensor 20, which makes it possible to measure the angular rotation of the output shaft 6 when the pinion 4 is rotated.

[0061] The sensors 10 and 20 are preferably position sensors. For example, sensors of the same technology may be provided, preferably magnetoresistive sensors which give precise measurements, and in particular of the giant magnetoresistance type, or GMR for "Giant Magneto Resistance" in English vocabulary.

[0062] It should however be understood that the invention is not limited to the presence of sensors of the same nature: the sensors could be of different natures, without going beyond of the scope of the invention, provided that they are capable of transmitting data relating to the angle of rotation made by the input shaft 2 and the output shaft 6 of the motor-reducer group, or their difference.

[0063] The position in which the input shaft is located when the motor 1 is not rotating the input shaft 2 will be called the "rest position of the input shaft", and the angular position taken by the input shaft under the action of the motor 1 which is rotating the input shaft will be called the "actuated position of the input shaft".

[0064] Similarly, the position in which the output shaft is not driven in rotation will be called the "rest position of the output shaft" and the angular position taken by the output shaft 6 when it is driven in rotation by the pinion 4, after actuation of all the pinions of the reduction device as explained above, will be called the "actuated position of the output shaft".

[0065] The objective of this device according to the invention is to determine the output torque of the geared motor device, which will actuate the elements ensuring braking, the torque of the geared motor group being related to the force of the geared motor and the load that it can set in motion.

[0066] The first sensor 10 accurately detects the rotation angle 0M of the input shaft 2 in the actuated position.

[0067] The second sensor 20 accurately detects the rotation angle 06 of the output shaft in the actuated position.

[0068] Without elastic transmission in the reducing device, the angle Ogre corresponds to the following equation:

[0069] 06 = 0M / R6M

[0070] where R6 M is the reduction coefficient of the reducing device.

[0071] In the case of an elastic transmission, as is the case in the device according to the invention, the rotation angle θ6 corresponds to the following equation:

[0072] 06= 0M / R6 M- 07,

[0073] where 07 corresponds to the “error” introduced by the elastically deformable element 7 under stress.

[0074] And:

[0075] 07= T / K,

[0076] where K is the stiffness of the elastically deformable element,

[0077] and where T corresponds to the desired torque.

[0078] By integrating the previous equations, we can determine the desired torque using the following equation:

[0079] T = (0M / R6.M-06).K

[0080] The device comprises a calculation module 30, with which the two sensors 10 and 20 communicate, and which communicates with a control unit U of the system of brake, so that the torque T is taken into consideration to act on the control law of motor 2.

[0081] [Fig.2] illustrates an exemplary embodiment of a pinion 8 carrying projecting rigid fingers 81 which protrude from an axial face 80 of the pinion 8, distributed equidistantly from the center of the pinion and between them.

[0082] The rigid projecting fingers 81 are of such a shape and dimensions that they are capable of being received in housings 9 of the pinion 5 produced, for example, in accordance with the representation given in [Fig.3].

[0083] [Fig. 3] also shows that the pinion 5 comprises two types of elastically deformable elements 7A and 7B, having different stiffnesses and positioned in series: elastically deformable elements 7A with a first stiffness K1, and elastically deformable elements 7B with a second stiffness K2, the second stiffness K2 being greater than the stiffness KL

[0084] The elastically deformable elements 7A and 7B have, for example, the same shape and the same size, but are made of different materials to have different stiffnesses.

[0085] The same shape and the same dimensions of elastically deformable elements make it possible to easily replace one elastically deformable element with another, depending on the stiffness that one wishes to use for the implementation of the method according to the invention and which will now be described.

[0086] It is, in fact, interesting, for the implementation of the invention, to be able to have two levels of compression of elastically deformable elements to also act on the control law of the brake system: this makes it possible in particular, as will be seen later, to modulate the moment when the greatest clamping force must be applied by the braking system.

[0087] [Fig.4] illustrates the assembly of the pinions 5 and 8, the projecting fingers 80 being inserted into the housings 9 of the pinion 5.

[0088] The pinion 8 has external peripheral teeth 82 which mesh with those of the pinion 4 (teeth not illustrated, the pinion 4 being shown schematically in [Fig.l]) and the pinion 5 has peripheral teeth which mesh with those of the pinion 3 (not illustrated, the pinion 3 being shown schematically in [Fig.l]).

[0089] It should be noted that the elastically deformable element(s) may exhibit, voluntarily or not, a variation in stiffness depending on the climatic conditions, and in particular depending on the temperature to which it is subjected.

[0090] The invention provides for taking this temperature variation into consideration, so as to allow a precise calculation of the torque T.

[0091] For example, if the temperature to which the device is subjected is rather low (below 5°C for example), the stiffness of the elastically deformable element will be greater than if the temperature is around 20°C.

[0092] Also, for a known elastically deformable element, we can know its stiffness as a function of a temperature panel.

[0093] The torque T calculation module 30 may comprise a memory 31, which is capable of associating a temperature with a stiffness of an elastically deformable element, and in particular that which corresponds to the elastically deformable element implemented, which will have been previously entered.

[0094] The memory 31 thus comprises a panel of stiffnesses K associated with a panel of temperatures.

[0095] To enable the temperature to be identified in real time, the device comprises a temperature sensor 32, which communicates with the calculation module 30 ([Fig.l]) to transmit the temperature in real time, so that the calculation module identifies the stiffness to be taken into consideration in the calculation of the torque T.

[0096] Thus, to determine the torque, according to the method according to the invention, the temperature is determined at the given instant when the brake system is implemented, a stiffness K of the elastically deformable element is identified which corresponds to the stiffness of said element at said determined temperature, then the torque is calculated as indicated previously at the given instant, taking into consideration the stiffness identified for the determined temperature.

[0097] In the context of an exemplary implementation, the motor produces a torque of at least 0.5 Nm and less than 5 Nm, and for example of the order of 1 Nm; and, for a reduction device having a reduction coefficient of between 20 and 60, and for example between 30 and 50.

[0098] For a configuration of this type, said at least one elastic element is here made of elastomer, for example of the EPDM type. By way of example, such an elastically deformable element may have the shape of an angular sector taken from a circular seal of rectangular section, the external dimensions of which are for example at least 3 mm or even 4 mm and for example at most 10 mm or even at most 7 mm; or a substantially parallelepiped shape of similar dimensions.

[0099] By way of example, the material(s) will be chosen with a Shore A hardness of, for example, at least 20 or even at least 30, and for example at most 90 or even at most 70.

[0100] The lower the stiffness of the elastically deformable element, the more precise the torque calculation will be.

[0101] On the other hand, the longer it takes for the elastically deformable element to deform, the longer it takes for the system to calculate the torque and transmit the information to the brake control system U to act on the control law.

[0102] In addition, the more deformable the element, the more absorption there is at the engine level. and therefore an error to correct.

[0103] Thus, the choice of a stiffness of elastically deformable element is to be taken into consideration in relation to the reduction coefficient and the power of the motor, so that the device allows an efficient torque calculation without prejudice to the reaction time of the brake system which will control the force to be applied by taking into consideration the torque transmitted in its control law.

[0104] The curve shown in [Fig.5] illustrates the rotation angle 07 (also called "error") introduced by the elastically deformable elements 7A and 7B as a function of time and the rotation angle 0M of the input shaft of the geared motor group, in the actuated position and the torque T of the assembly which has been calculated, as a function of time, in such a double stiffness system.

[0105] It is noted that the couple T begins to produce effective effects once the elastically deformable element 7A of low stiffness has finished acting on the system, and that the other elastically deformable element 7B of greater stiffness takes over from the first element 7A.

[0106] In other words, in the device, and after the motor has imposed a minimum rotation angle 0Mi on the input shaft, it is noted that the elastic element of low stiffness 7A is compressed quickly, which makes it possible to have a large error angle quickly (see in 07i and 072): the resulting torque T is relatively low (see between Tl and T2 on the curve).

[0107] Even when the elastically deformable element 7A has been completely compressed, the other elastically deformable element 7B, of greater stiffness, still exhibits elastic deformation and thus characterizes the effective force for braking, until reaching the maximum force desired for the device produced (see torque curve T from T2 and error curve 07 from 072).

[0108] With such a device comprising two elastically deformable elements of different stiffnesses (one low and the other high), it is possible to detect several moments in the braking which correspond to several technical effects produced, which have consequences on the braking itself.

[0109] For example, we can determine the moment when the pads touch the disc (called "touchpoint" in English vocabulary) for a drum brake: this makes it possible to detect that there is no unwanted braking, and this makes it possible to use this point as a "zero point" to apply the force necessary for braking.

[0110] The second point may correspond to the determination of the effort to be made in the system to brake: concretely, when the pads touch the disc, the braking of the vehicle begins and, from that moment, we know how to calculate the necessary force if we manage to determine the torque to be applied precisely.

[0111] As the device according to the invention makes it possible to calculate precisely this torque, taking into account the angle measurements, knowing the stiffness and the ratio of the geared motor, the device according to the invention can be used to further improve the control law, for example by modulating the moment when the greatest force must be applied, from the determination of the point of contact of the pad with the disc ("touchpoint") for example by starting to exert the necessary force as soon as possible (for example in the event of emergency braking).

[0112] Furthermore, the method according to the invention may have other characteristics aimed at ensuring that the calculation of the torque remains as precise as possible as a function of the time of use of the system:

[0113] For example, it is provided that a duration of implementation of said elastically deformable element is monitored in said device: for example, the calculation module 30 could comprise a clock making it possible to warn the brake control system U (which can warn the user of the vehicle, via a visual or audible alarm) of an obsolescence of said elastically deformable element (or elastically deformable elements), when a predetermined duration of use is reached, and to apply a predetermined stiffness to carry out the step of estimating the torque while waiting for the change of the elastically deformable element(s).

[0114] It is understood from the preceding description how the invention makes it possible to achieve its objectives of precisely calculating the torque of a geared motor device in order to act on the control law of a brake system, and this, by taking into consideration the effects of climatic conditions, and in particular temperature, on the elements of the reduction device.

[0115] It should be understood that the invention is not limited to the embodiments presented above, and that it extends to the implementation of any equivalent means.

[0116] In particular, the elastically deformable element(s) may be mounted between a pinion and a coaxial shaft, or between two coaxial shafts even if they do not carry a pinion.

[0117] For example, it should be understood that the stages of the reduction device could include further rotational drive elements or that the reduction device could include more than two stages, without departing from the scope of the invention.

[0118] Finally, the device for a brake system according to the invention can be mounted on one of the wheels of a vehicle, or on the two drive wheels, or on all four wheels, without departing from the scope of application of the invention.

[0119] The invention advantageously applies to a brake operating entirely electrically, including for service braking.

[0120] NOMENCLATURE

[0121] 1: engine

[0122] 2: input shaft

[0123] 3: pinion

[0124] 4: pinion

[0125] 5: pinion

[0126] 6: output shaft

[0127] 7: elastically deformable element

[0128] 7A: elastically deformable element of low stiffness Kl

[0129] 7B: elastically deformable element of high stiffness K2

[0130] 8: pinion

[0131] 9: housing for receiving an elastically deformable element

[0132] 10: first angular position sensor

[0133] 20: second angular position sensor

[0134] 30: torque calculation module T

[0135] 31: memory of the calculation module

[0136] 32: temperature sensor

[0137] 51: peripheral teeth of pinion 5

[0138] 70: reducer cartridge

[0139] 80: face of the gable 8

[0140] 81: fingers protruding from the face 80

[0141] 82: peripheral teeth of pinion 8

[0142] U: Brake control system

[0143] Kl: low stiffness

[0144] K2: high stiffness

[0145] 07: error introduced by the elastically deformable element(s)

[0146] 07i: error at start of compression of element 7A

[0147] 072: error at the end of compression of element 7A

[0148] 0M: rotation angle of the input shaft imposed by the motor

[0149] 0M1: rotation angle of the input shaft at the start of compression of element 7A

[0150] 0M2: rotation angle of the input shaft at the end of compression of element 7A

[0151] T: torque

[0152] Tl: torque calculated at the start of compression of element 7A

[0153] T2: torque calculated at the end of compression of element 7A

Claims

Claims

1. Force measuring device for a brake system comprising a motor (1) for rotating a gear reduction device (3, 4, 5, 8) comprising, for applying a braking force to at least one brake pad, at least one gear train of one or more stages of gear pinions having a reduction coefficient which can range from one to two hundred and fifty, in particular at least twenty and / or at most fifty, said system comprising an input shaft (2), arranged to be rotated by said motor (1) according to a control law and to drive an output shaft (6) via said gear train, said device for a brake system being characterized in that it comprises: - a first sensor (10), positioned upstream of said gear train so as to measure the angular rotation (0M) of said input shaft (2) between a rest position where the motor (1) does not rotate the input shaft (2) and an actuated position where the motor (1) rotates the input shaft (2), - a second sensor (20), positioned downstream of said gear train so as to measure the angular rotation (06) of said output shaft (6) between a rest position where the output shaft (6) is not rotated and an actuated position where the reduction device rotates the output shaft (6), in that said reduction device comprises at least one elastically deformable element (7, 7A, 7B), positioned between said input shaft (2) and said output shaft (3) of the reduction device so as to be elastically deformed by a torque transmitted from the input shaft (2) to the output shaft (6), said elastically deformable element (7, 7A, 7B), having a stiffness (K1, K2), and in that it comprises a calculation module (30) of a torque (T) transmitted by the reduction device at a given instant, from the angular rotation data (0M, 06) transmitted at said instant given by said first and second sensors (10, 20), of said stiffness (Kl,K2) of the elastically deformable element (7, 7A, 7B) and the reduction coefficient of said reducing device.,

2. Device according to claim 1, characterized in that the element de- elastically formable element (7, 7A, 7B) is interposed between two coaxial parts (5, 8) of the reducer, one of which drives the other in rotation after taking up an angular play between them, said angular take-up being obtained partially or exclusively by compression of said elastically deformable element between two bearing surfaces carried by said coaxial parts.

3. Device according to any one of the preceding claims, characterized in that the elastically deformable element (7, 7A, 7B) is interposed between two coaxial gears which belong to two different gear stages within the reducer, and one of which (5) drives the other (8) in rotation after taking up an angular play producing a deformation of said elastically deformable element.

4. Device according to any one of the preceding claims, characterized in that the reduction device comprises one or more stages whose shafts are mounted in the same structure forming a transmission cartridge, and in that the elastically deformable element and / or the second sensor (20) is mounted on a shaft which is driven by said cartridge.

5. Device according to any one of the preceding claims, characterized in that the electric motor (1) is of a vector type integrating an angular position sensor which is used as a first sensor (10), in particular direct current and brushless.

6. Brake system device according to any one of the preceding claims, characterized in that said first sensor (10) and said second sensor (20) are position sensors of the same technology, preferably magnetoresistive sensors, in particular with giant magnetoresistance.

7. Brake system device according to any one of the preceding claims, characterized in that it comprises at least two elastically deformable elements (7A, 7B), said at least two elastically deformable elements (7A, 7B) having different stiffnesses (K1, K2).

8. Device according to claim 7 characterized in that said at least two deformable elements (7A, 7B) have the same shape and the same dimensions.

9. Device according to any one of the preceding claims, characterized in that it comprises a temperature sensor (32) and in that the calculation module (30) comprises a memory (31) which associates a

10.

11.

12.

13. first panel of stiffnesses (Kl, K2) of said at least one elastically deformable element (7, 7A, 7B) at a second panel of temperatures. Brake system comprising a device according to any one of the preceding claims. Brake system according to claim 10, characterized in that it comprises a disc brake system, preferably with a floating caliper. Brake system according to claim 10, characterized in that it comprises a hydraulic brake system. Method for controlling a brake system equipped with a device according to any one of claims 1 to 9, comprising a motor (1) for rotating a gear reduction device (3, 4, 5, 8) comprising, for applying a braking force to at least one brake pad, at least one gear train of one or more stages of gear pinions having a reduction coefficient which can range from one to two hundred and fifty, in particular at least 20 and / or at most 50, said system comprising: • an input shaft (2) arranged to be driven in rotation by said motor (1) according to a control law and to drive an output shaft (6) via said gear train, • a first sensor (10), positioned upstream of said gear train so as to measure the angular rotation (0M) of said input shaft (2) between a rest position where the motor (1) does not rotate the input shaft (2) and an actuated position where the motor (2) rotates the input shaft (2), and • a second sensor (20), positioned downstream of said gear train so as to measure the angular rotation (06) of said output shaft (6) between a rest position where the output shaft (6) is not rotated and an actuated position where the reduction device rotates the output shaft (6), said reduction device comprising at least one elastically deformable element (7, 7A, 7B), positioned between said input shaft (2) and said output shaft (3) of the reduction device so as to be deformed elastically by a torque transmitted from the input shaft (2) to the output shaft (6), said elastically deformable element (7, 7A, 7B), having a stiffness (Kl, K2), and a calculation module (30) of a torque (T) transmitted by the reduction device at a given instant, from the angular rotation data (0M, 06) transmitted at said given instant by said first and second sensors (10, 20), of said stiffness (Kl, K2) of the elastically deformable element (7, 7A, 7B) and of the reduction coefficient of said reduction device, said control method being characterized in that it comprises the following steps: - actuation of said motor (1) at a given instant, by control of said brake system, - measurement of a first rotation angle (0M) of said input shaft (2) in the actuated position, - measurement of a second rotation angle (06) of said output shaft (6) in the actuated position, - estimation of a torque (T) at said given instant from the first and second measured angles (0M>06), said reduction coefficient and the stiffness (Kl, K2) of said at least one elastic element (7, 7A, 7B), by said calculation module (30), - transmission of said torque (T) estimated at said given instant, to said brake control system (U), and - controlling the operation of said motor (2) by said brake control system, taking into consideration, in said control law, said torque (T) estimated at said given instant.

14. Method according to claim 13, characterized in that the calculation module (30) uses the data of the estimated torque value (T) within a closed-loop regulation implemented to adjust the braking force applied during a sequence including a braking command.

15. A method according to claim 13 or 14 wherein said at least one elastically deformable element (7, 7A, 7B) has a stiffness (K1, K2) which depends on the temperature, said method further comprising the following steps: - determination of the temperature at that given time, - identification of a stiffness (Kl, K2) of said at least one elastically deformable element (7, 7A, 7B) which corresponds to the stiffness of said elastically deformable element at said determined temperature, and in that said step of estimating the torque (T) at said given instant takes into consideration said stiffness identified for said determined temperature.

16. Control method according to any one of claims 13 to 15, characterized in that a duration of implementation of said elastically deformable element (7, 7A, 7B) is monitored in said device and in that, when said duration reaches a predetermined duration, said brake system is warned of obsolescence or degradation of said elastically deformable element (7, 7A, 7B) and a predetermined stiffness is applied to carry out the torque estimation step.

17. Control method according to any one of claims 13 to 15, implementing the device comprising at least two elastically deformable elements (7A, 7B), each having a different stiffness (K1, K2) among which a low stiffness (K1) and a high stiffness (K2), greater than said low stiffness (K1), said method comprising a step according to which the moment at which the elastically deformable element (7A) of low stiffness (K1) begins to produce an error is determined, and / or the moment at which it no longer produces an error to the benefit of the elastically deformable element (7B) of high stiffness (K2), and in that said determined moment is taken into consideration to modulate the control law, in order to make said determined moment correspond to a moment at which the force produced by the motor begins to produce a clamping or braking effect, and for example where the clamping force to be applied is the greatest.

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