Device for absorbing forces of segment ends for a drum brake, drum brake provided with such a device for absorbing forces of segment ends, and method for implementing such a device for absorbing forces of segment ends

Abstract

The invention relates in particular to a drum brake for a road vehicle, in particular a motor vehicle, the drum brake comprising a first and a second segment (1, 2) comprising stop ends (11, 21) bearing against an anchoring element, which is connected to the plate and comprises a force-absorbing device (4). The latter comprises two stops (41, 42) which are positioned on either side of said device between a standby position in which they are spaced apart from one another, under the action of at least one elastically deformable element (61, 62) which bears against the anchoring element, and an active position in which they come into contact with one another. The elastically deformable element has a calibration that is adapted to a predetermined braking force, in order to cause the stops to pass from their standby position into their active position, allowing said drum brake to pass from a first simplex braking function into a second duo-servo braking function.

Description

Device for the recovery of end forces of segments for drum brake, drum brake equipped with such a device for the recovery of end forces of segments and method of implementing such a device for the recovery of end forces of segments. FIELD OF INVENTION

[0001] The invention relates to a drum brake for road vehicles, in particular for a light or heavy motor vehicle. STATE OF THE ART

[0002] In a motor vehicle, the service brake's primary function is to slow the vehicle down and bring it to a stop. In most modern automobiles, the service brake is provided by drum brakes or disc brakes, or disc brakes at the front of the vehicle and drum brakes at the rear.

[0003] The invention relates to a device implemented in a drum brake.

[0004] A drum brake can have several modes of operation: a so-called "simplex" operation and a "duo-servo" operation.

[0005] In "simplex" mode, an actuator separates two movable ends of the segments, while their opposite ends (stop ends) both come to rest against an anchoring element.

[0006] In "duo-servo" mode, the actuator also separates the two moving ends of the segments but, in addition, the ends of the segments opposite the moving ends are pressed against each other so that the movement of one of the two segments is transmitted to the other segment, to increase the braking force.

[0007] In simplex mode, the braking force is therefore less than in duo-servo mode, but has the advantage of being easier to control, particularly with the trajectory control system. Simplex mode also allows for more precise modulation.

[0008] One aim of the invention is to overcome, in whole or in part, the disadvantages of the prior art.

[0009] In particular, one goal is to create a drum brake that allows for better efficiency, or that can be controlled more precisely, or a better compromise between the two.

[0010] The invention relates to a new device to replace the second actuator device. The new device according to the invention aims to provide either a so-called "simplex" operating mode or a so-called "duo-servo" operating mode.

[0011] The invention also relates to a drum brake and vehicle or a vehicle sub-assembly incorporating a drum brake equipped with such a device, as well as a brake control method implementing such a device.

[0012] According to a first aspect of the invention, at least one of the aforementioned goals is achieved with a device for resuming force from the ends of segments for an anchoring element of a drum brake, as defined by claims 1 to 3.

[0013] According to a second aspect of the invention, it also relates to a drum brake for road vehicles as defined by claims 4 to 11.

[0014] According to a third aspect of the invention, it relates to a braking system as defined by claims 12 or 13.

[0015] According to a fourth aspect of the invention, it also relates to a method for designing a braking system as defined by claim 14.

[0016] According to a fifth aspect of the invention, it relates to a method for controlling a braking system as defined by claim 15. The method aims to regulate, in a closed loop, the value of the braking force, to obtain a braking force corresponding to the setpoint braking force.

[0017] The invention also relates to a road vehicle, as defined by claim 16.

[0018] LIST OF FIGURES

[0019] Other features and advantages of the invention will become apparent upon reading the detailed description of implementations and embodiments, which are by no means limiting, and the accompanying drawings where:

[0020] is a top view of a portion of a drum brake according to the invention,

[0021] is a perspective view of a force recovery device housing according to the invention,

[0022] is a schematic and cross-sectional representation of a brake force recovery device according to the invention,

[0023] illustrates the stops and elastically deformable elements that comprise the device, with the stops in their rest position.

[0024] illustrates the stops and elastically deformable elements that comprise the device of the laou de la, the stops being in the active position,

[0025] partially illustrates the force recovery device according to the invention, seen in perspective, comprising a position sensor for a stop, and technical means for retrieving and transmitting, to a remote control unit, information relating to the position of the stop,

[0026] is a perspective view of a brake force recovery device according to the invention, illustrating an embodiment in which the device comprises two stops and two position sensors,

[0027] represents partially and in perspective view of a drum brake and the force-recovery device equipped with a protective cover, the cover being partially illustrated in cross-section, and

[0028] is a schematic representation of a process according to the invention.

[0029] DESCRIPTION OF IMPLEMENTATION METHODS

[0030] The embodiments that will now be described are not limiting: variants of the invention may include only a selection of features described below, isolated from the other features described, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

[0031] Of course, the invention is not limited to the examples that will be described, and many modifications can be made to these examples without departing from the scope of the invention. Furthermore, the various features, forms, variants, and embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive.

[0032] The invention applies mainly to drum brakes, intended to equip vehicles, particularly motor vehicles (but not exclusively).

[0033] Typically, the drum brake consists of two segments 1 and 2 arranged inside a cylinder 3.

[0034] Lamontre part of cylinder 3 and part of segments 1 and 2.

[0035] The two segments carry brake linings 10 and 20, respectively, which come to rub against the cylinder when the segments are pressed against the inner surface of the cylinder 3.

[0036] To induce braking, the segments are moved away from their rest position: each of them therefore has, for this purpose, a first movable end (not illustrated in the figures).

[0037] The moving ends of the segments are opposite each other and are driven into movement by an actuator device which, in response to an applied braking force, controls the separation of the two moving ends of said segments from each other, thus ensuring a first braking function in a first simplex operating mode which brings the brake into a first braking position.

[0038] The other ends of segments 1 and 2 are called stop ends 11 and 21: they are opposite the movable ends and are illustrated in figures 1 and 3 to 6.

[0039] According to the invention, the drum brake includes a force recovery device, which is positioned between the two ends of the stop 11 and 21.

[0040] The force transfer device has the function of transmitting a force from one end of the stop to another, so that segment 1 transmits a movement to segment 2.

[0041] To achieve this, the effort recovery mechanism 4 includes the following elements:

[0042] It comprises two movable elements forming stops 41 and 42, which are positioned opposite the ends of the stops 11 and 21 of segments 1 and 2, respectively.

[0043] The stops are received in a housing 5, of substantially cylindrical shape and open at both ends: the housing 5 thus forms a sleeve, placed between the two stops of segments 1 and 2.

[0044] Figures 3 to 5 show how the movable elements 41 and 42 are positioned and how they are made.

[0045] Each stop includes a rod 40, the axis of which is positioned in the axis of the housing 5, and each rod has, at its end, a flat head 30 against which the stop ends 41 and 42 of segments 1 and 2 can come to rest.

[0046] We note on laque the free ends forming contact faces 34 (of the stop rods 41 and 42) do not touch in the rest position of the force recovery device 4.

[0047] In the example shown, the housing 5 of the transmission device 4 has two cylindrical chambers 51 and 52, coaxial and adjacent, forming receiving and guiding means: chamber 51 receives the stop 41 and chamber 52 receives the stop 42.

[0048] In figures 2 and 4, we observe that an internal radial annular wall 53 separates the two sub-chambers 51 and 52 and forms a means of force retrieval, a communication opening being present between the two sub-chambers, to allow the contact face 34 of the rod 40 of the element 41, to pass through the wall 53, to come into contact with the contact face 34 of the rod 40 of the stop 42 ().

[0049] The transmission device also includes two springs 61 and 62, each positioned in a sub-chamber 51 and 52 around the stop rods 41 and 42.

[0050] The two springs bear against the rear face of a flat head 30 of a stop and against the internal radial annular wall 53 of the housing 5.

[0051] As they move, under the action of the thrust of the end of the stop 11 or 21 of the segments 1 and 2 on the heads 30 of the stops 41 and 42, the stops compress the springs 61 and 62 until their contact faces 34 come into contact.

[0052] In the example described, the transmission device includes two springs 61 and 62. However, it should be understood that the brake force recovery device according to the invention could include only one elastically deformable element, or different elastically deformable elements (such as Belleville washers, for example), without departing from the scope of the invention.

[0053] Thus constructed, the brake force recovery device according to the invention comprises two stops 41 and 42, positioned on either side of said device 4, which face the stop ends 11 and 21 of segments 1 and 2. The stop ends 11 and 21 are able to each come into contact with a stop of the force recovery device 4, the two stops 41 and 42 being movable in displacement between: - a rest position (see), according to which the two stops 41 and 42 are separated from each other, under the action of at least one elastically deformable element (in the example, these are the springs 61 and 62), and - an active position, according to which the two stops come into contact with each other (see).

[0054] According to the invention, the springs each have a setting adapted to a predetermined braking force, beyond which they deform under the action of a push from one of said stops 41 and 42 caused by an end of stop 11 and 21 of segment 1 and 2 in the first braking position.

[0055] The deformation of the springs ensures the passage of the stops from their rest position to their active position.

[0056] In other words, depending on the spring rate(s), the thrust exerted by the end of the stop 11 or 21 on the stop 41 or 42 is not strong enough to overcome the resistance of the spring 61 or 62: in this case, the brake operates in simplex mode.

[0057] But if the thrust exerted by the end of the stop 11 or 21 on the stop 41 or 42 is strong enough to overcome the resistance of the spring 61 or 62, and compress them, then the contact faces 34 of the stops 41 and 42 touch and the brake changes from its simplex operating mode to duo-servo mode: in this case, one of the segments 1 and 2 pushes the other segment which moves further apart and increases the braking.

[0058] The active position of the stops 41 and 42 of the force recovery device 4 thus ensures a transmission of movement from one segment to another by contact of the stops 41 and 42 with the ends of the stops 11 and 21 of the segments, said transmission of movement allowing the transition from the first braking function to a second braking function in a second duo-servo operating mode.

[0059] The calibration of the spring(s) thus determines the switch from simplex mode to duo-servo mode.

[0060] In other words, the spring rate is adapted to a predetermined braking force beyond which the elastically deformable element (the spring or springs) deforms sufficiently, under the action of a push from one of said stops caused by a stop end of segment in the first braking position, to cause the stops to move from their rest position to their active position, the active position allowing a transfer of forces from one segment to another by contact of the stops with each other and with the stop ends of the segments, said transfer of forces allowing the transition from the first braking function to a second braking function in a second operating mode of the duo-servo type.

[0061] As an example, for drum brakes with the following dimensions, the spring resistance was determined to switch from simplex mode to duo-servo mode:

[0062] a) For a drum brake with a diameter of 9 inches (22.86 cm), the spring has a resistance of at least 9000 N to switch from simplex mode to duo-servo mode,

[0063] b) for a drum brake with a diameter of 10 inches (25.4 cm), the spring has a resistance of at least 10,000 N to switch from simplex mode to duo-servo mode, and

[0064] c) for a drum brake with a diameter of 11 inches (27.94 cm), the spring has a resistance of at least 12,500 N to switch from simplex mode to duo-servo mode.

[0065] In simplex mode, if we consider a brake as illustrated in, the left segment 1 is in compressed mode and the right segment is in tensioned mode.

[0066] If heavy braking is required, a change in braking mode is also necessary, switching from simplex mode to duo-servo mode. In the latter case, the left-hand segment 1 (in the figures) is compressed, and the right-hand segment (segment 2) also becomes a compressed segment.

[0067] During the design of the brake, and in particular the force-recovery device, a braking force is predetermined to be applied for the drum brake to operate according to the second dual-servo operating mode. The calibration of the deformable elastic element is established based on this predetermined braking force.

[0068] To facilitate assembly, in particular, it is provided that the springs 61 and 62 are pre-stressed in the rest position of the stops 41 and 42. For example, the springs 61 and 62 can be pre-stressed by enclosing them in cages 71 and 72, respectively, as can be seen in.

[0069] The cages also facilitate the positioning of the springs during assembly.

[0070] Indeed, during the assembly of the force recovery device, the cages 71 and 72 comprising the prestressed springs are inserted into the sub-chambers 51 and 52, then the stops 41 and 42 are positioned.

[0071] Reference will now be made to figures 6 to 8.

[0072] In the illustrated embodiment, it is planned to equip the force recovery device 4 comprising two position sensors 43 and 44, each precisely determining the position of a stop (respectively 41 and 42), in order to determine a displacement information I1 (respectively I2) of the stop (respectively 41 and 42), for example between the rest position of the stop concerned and its active position.

[0073] In this example implementation, the position sensors 43 and 44 are Hall effect stroke sensors. It should be understood that the invention is not limited to the choice of this type of sensor and extends to the implementation of any equivalent means.

[0074] This displacement information is taken into account in a control law, for example, of the brake, to increase its operating accuracy.

[0075] To do this, the force recovery device is also equipped (or associated with) a module 45 for receiving this displacement information detected by the sensor, the module 45 also ensuring the transmission of this displacement information to an external control unit.

[0076] To achieve this, as illustrated for example, the module 45 is supported by an electronic circuit 46 fixed to the outer wall of the housing 5 of the force-recovery device. It is connected by cables 47 to a connector 48 fixed to the brake plate, the connector 48 itself being connected to the appropriate electronic system external to the brake.

[0077] In order to protect the whole from dust, in particular, the circuit 46 equipped with the receiving module 45 and the sensors 43 and 44 is planned to be enclosed under a protective cover 50 which may, possibly, be removable.

[0078] Reference will now be made to the diagram, which schematically illustrates a control method for a drum brake system that has just been presented.

[0079] The braking system is schematically represented by reference 6. It may be a hydraulic braking system 6, or an electromechanical braking system 6, notably without hydraulics.

[0080] Each of the 6 brake systems includes at least one drum brake as described in Figures 1 to 8.

[0081] The control unit is schematically illustrated by reference 7.

[0082] Steering unit 7 carries out the following steps:

[0083] It receives a braking command C, for example when a driver activates the vehicle's brake pedal.

[0084] The control unit 7 then determines a setpoint braking force F(C).

[0085] In parallel, the control unit 7 receives information I1 and I2 concerning the respective movements of the stops 41 and 42 of the force recovery device, from the receiving and transmission module 45 of the drum brake.

[0086] The control unit 7 determines, from the information I1 and I2, the actual braking force FR, and compares this actual braking force FR to the said setpoint braking force F(C).

[0087] If the actual braking force FR is less than the said setpoint braking force F(C), then the actual braking force FR until the actual braking force is at least equal to the said setpoint braking force.

[0088] Conversely, if the actual braking force FR is greater than the said setpoint braking force F(C), then the actual braking force is decreased until the actual braking force is equal to the setpoint braking force.

[0089] From the preceding description, we understand how the invention achieves its objectives.

[0090] NOMENCLATURE

[0091] 1: first segment

[0092] 2: second segment

[0093] 3: cylinder

[0094] 4: Device for transferring end-segment forces

[0095] 5: crankcase

[0096] 6: Drum brake system

[0097] 7: piloting unit

[0098] 10: garnish

[0099] 11: end of stop

[0100] 20: garnish

[0101] 21: end of stop

[0102] 30: flat head of stops 41 and 42

[0103] 34: contact face

[0104] 40: stem of each of the stops

[0105] 41: stop

[0106] 42: stop

[0107] 43: Position sensor

[0108] 44: Position sensor

[0109] 45: Reception and transmission module

[0110] 46: electronic circuit

[0111] 47: Connection cables

[0112] 48: connector

[0113] 50: protective cover

[0114] 51: Reception and guidance means (under chamber)

[0115] 52: Reception and guidance means (under chamber)

[0116] 53: means of resuming effort (internal wall separating the sub-chambers)

[0117] 61: first spring

[0118] 62: second spring

[0119] 71: cage

[0120] 72: cage

[0121] I1: Information concerning the movement of element 41

[0122] I2: Information concerning the movement of element 42

[0123] FR: actual braking force

[0124] F(C): setpoint force

[0125] C: instruction

Claims

A device for absorbing end loads from segments, for an anchoring element of a drum brake, said drum brake comprising a first and a second segment (1, 2) carried by a plate, capable of producing friction braking, said segments (1, 2) having movable ends facing each other and stop ends (11, 21) opposite said movable ends, said stop ends (11, 21) bearing against said anchoring element, said anchoring element being connected to the plate, said force absorption device being characterized in that it comprises: - a first stop (41) comprising a head (30) for absorbing end loads from the segments of said drum brake, a contact face (34) axially opposite said head (30) and, disposed between said head (30) and said contact face (34), means for absorbing loads from a first end of a first element elastically deformable (61),typically a shoulder; - a second stop (42) comprising a head (30) for absorbing forces from the ends of segments of said drum brake, a contact face (34) axially opposite said head (30) and, disposed between said head (30) and said contact face (34), means for absorbing forces from a first end of a second elastically deformable element (62), typically a shoulder; - said first and second elastically deformable elements (61, 62) each having a setting adapted to a predetermined braking force, beyond which said at least one elastically deformable element (61, 62) deforms sufficiently, under the action of a thrust from one of said stops (41, 42) caused by a stop end of segment (11, 21) in a first braking position, to cause the stops (41, 42) to move from a rest position to a active position,the active position allowing a transfer of forces from one segment to the other by contact of the stops (41, 42) with each other and with the ends of the stops of the segments (11, 21), said transfer of forces allowing the transition from the first braking function to a second braking function in a second operating mode of the duo-servo type, - a housing (5) provided with means for securing it to the drum brake plate, means for receiving and guiding (51, 52) the first stop (41) provided with the first elastically deformable element (61), means for receiving and guiding the second stop (42) provided with the second elastically deformable element (62), the first and second stops (41, 42) being arranged head-to-tail, and means (53) for transferring forces from the second ends of the elastically deformable elements (61, 62). Force recovery device according to claim 1, characterized in that said elastically deformable elements are springs. Force recovery device according to claim 1 or 2, characterized in that it comprises means for pre-stressing the elastically deformable elements (61, 62), and in that the receiving and guiding means (51, 52) ensure translational guidance of the first and second stops (41, 42) between a first position in which said first and second stops (41, 42) are not in mutual contact and a second position in which the contact faces (34) of the first and second stops (41, 42) are in mutual contact. Drum brake for road vehicle, in particular motor vehicle, said drum brake comprising: - a first and a second segment (1, 2) carried by a plate, capable of causing braking by friction, said segments (1, 2) having movable ends opposite each other and stop ends (11, 21), opposite said movable ends, bearing on an anchoring element linked to the plate, - an actuator which, in response to a braking force requested, causes the two movable ends of said segments (1, 2) to separate from each other, thus ensuring a first braking function in a first simplex operating mode which brings the brake into a first braking position, said drum brake being characterized in that the anchoring element comprises a force-recovery device (4) according to any one of claims 1 to 3, positioned between the two stop ends (11, 21). Drum brake according to claim 4, characterized in that said at least one elastically deformable element (61, 62) is pre-stressed in the rest position of the stops (41, 42). Drum brake according to claim 5, characterized in that said at least one elastically deformable and prestressed element (61, 62) is enclosed in a cage. Drum brake according to any one of claims 4 to 6, characterized in that said stops (41, 42) are aligned in said casing (5). Drum brake according to any one of claims 4 to 7, characterized in that the force recovery device (4) comprises at least one position sensor (43, 44) of at least one stop (41, 42), for determining at least one displacement information (I1, I2) of said at least one stop (41, 42), in particular from said rest position to said active position or even between the two, as well as a module (45) for receiving and transmitting said at least one displacement information (I1, I2) to an external control unit (7). Drum brake according to claim 8, characterized in that said at least one position sensor (43, 44) is a hall effect stroke sensor. Drum brake according to any one of claims 8 or 9, characterized in that said force recovery device (4) comprises two position sensors (43, 44), each of the position sensors being associated with a stop (41, 42), allowing to determine a displacement information (I1, I2) for each of the stops (41, 42), in particular between their rest position and their active position, or even between the two. Drum brake according to claim 8, 9 or 10, characterized in that it comprises a protective cover (50) of said at least one position sensor (43, 44) and of said receiving and transmitting module (45), said cover (50) being optionally removable. Hydraulic braking system (6), characterized in that it comprises at least one drum brake according to any one of claims 4 to 11. Electromechanical braking system (6), in particular without hydraulics, characterized in that it comprises at least one drum brake according to any one of claims 4 to 11. A method for designing a braking system (6) according to any one of claims 12 or 13, comprising a drum brake according to any one of claims 4 to 11, equipped with a force-recovery device (4), comprising two movable elements (41, 42) moving between: - a rest position, according to which the two stops (41, 42) are separated from each other, under the action of at least one elastically deformable element (61, 62) connected to the anchoring element, and - an active position, according to which the two stops (41, 42) come into contact with each other, said at least one elastically deformable element (61, 62) having a setting adapted to a predetermined braking force (F(C)), said design method comprising the following steps: - determination of a predetermined braking force (F(C)) to be applied for the drum brake to operate according to said second mode dual-servo operationand- calibration of said at least one elastically deformable element (61, 62) as a function of said predetermined braking force (F(C)). A method for controlling a braking system (6) according to claim 12 or 13, comprising a drum brake according to any one of claims 8 to 11 and a control unit (7), characterized in that said control unit (7) performs the following steps: - receiving a braking command (C), in particular by actuation of a brake pedal by a driver, - determining a target braking force (F(C)), - receiving at least one displacement information (I1, I2) from at least one stop (41, 42) of said force-resistance device (4) from the drum brake receiving and transmission module (45), - determining an actual braking force (FR) as a function of said at least one displacement information (I1, I2) received, - comparing said actual braking force (FR) to said target braking force (F(C)), and - if the actual braking force (FR) is less than said target braking force (F(C)),Then we increase the actual braking force (FR) until the actual braking force (FR) is at least equal to the setpoint braking force (F(C)), or if the actual braking force (FR) is greater than the setpoint braking force (F(C)), then we decrease the actual braking force (FR) until the actual braking force (FR) is equal to the setpoint braking force (F(C)). Road vehicle, in particular motor vehicle, comprising a braking system (6) according to claim 12 or 13.

Images