FR3031155A1 - SYSTEM FOR ACTIVE RETRACTING OF BRAKE LININGS, AND CORRESPONDING TRIM. - Google Patents

Abstract

The invention relates to a system for active retraction of friction linings in a brake. According to the invention, this system comprises an electric actuator producing a momentary spacing of at least two elements of said support chain. Preferably, the actuator provides a mechanical action produced directly in translation, without continuously rotated element. Such an actuator and mounted for example in a brake piston, electric or hydraulic, or on the sliding supports of a floating disk brake disc, or in solidarity with the back of one or more pads. It operates for example by resistive heating of a variant element in shape memory material, or a variant element expanding in a confined enclosure, or by feeding a solenoid. The invention further relates to a brake lining thus equipped.

Description

The invention relates to a system for active retraction of friction linings in a brake. According to the invention, this system comprises an electric actuator producing a momentary spacing of at least two elements of said support chain. Preferably, the actuator provides a mechanical action produced directly in translation, without continuously rotated element. Such an actuator is mounted, for example, in an electric or hydraulic brake piston, or on the sliding supports of a floating-mount disc brake, or integrally on the back of one or more gaskets. It functions, for example, by resistive heating of a variant element of shape memory material, or of a variant element expanding in a confined enclosure, or by feeding a solenoid. The invention further relates to a brake lining thus equipped. State of the art 20 In the field of road vehicle brakes, especially four-wheel vehicles and in particular light or heavy motor vehicles or commercial vehicles, the dissipation of kinetic energy is most often obtained by friction created under the effect of a clamping between friction linings and a friction track integral in rotation with the wheel. This clamping is most often obtained by moving one or more pistons under the effect of a hydraulic pressure for the service brake, and by pulling a cable or electromechanical actuator for the parking and emergency brake. . Once a braking phase is completed, during taxiing or at the end of parking, the linings tend to remain in contact with the friction track even if they no longer undergo clamping force. There is thus a permanent friction constituting a "residual" braking, 3031155 - 2 - which represents additional wear and fuel consumption, with all the disadvantages that entails. This problem arises for all hydraulically actuated brakes, and a large number of those with electric actuators.

It has been proposed to insert a spacer spring, but the operation remains insufficiently effective and / or reliable. An object of the invention is to overcome the disadvantages of the state of the art, and to reduce this residual braking. This goal is sought in conjunction with advantages in terms of simplicity, cost and reliability, manufacturing and maintenance. SUMMARY OF THE INVENTION For this purpose, the invention proposes a system for active retraction of the friction linings in a brake operating by clamping friction linings against a rotating friction track within a set of tight elements between them to form a chain of support. According to the invention, this retraction system comprises at least one electric actuator producing a momentary spacing of at least two elements of said support chain.

Preferably, the actuator provides a mechanical action produced directly in translation, without continuously rotated element. Examples of Operating Architectures Different mechanical operating architectures are provided, for example the following. In a first exemplary embodiment, the actuator is installed in a brake mechanism acting by moving at least one brake piston out of its housing to press against at least one friction lining. The actuator then acts by retracting said brake piston inside its housing. In a second exemplary embodiment, the actuator is attached to the liner and acts by moving a biasing member so as to protrude it from the friction surface of said liner on the friction track side. . This thrust element thus relies on the friction surface to actively create a game, or "air gap" in English, between the friction track and the lining.

In a third exemplary embodiment, the retraction system is applied to a floating-mount disk brake in which a so-called floating element (typically the yoke or its yoke) which immobilizes the rotating liner is movable in translation. on at least one sliding guide parallel to the axis of the wheel. The actuator then acts by pressing on said element to move it on its sliding guide and thus introduce a game in the support chain. Examples of modes of operation For these different architectures, different modes of operation are provided according to different physical principles, for example the following. According to a particular feature, the actuator comprises a heating element activated by the passage of an electric current and whose temperature increase causes a modification of the geometry of a so-called variant element made of a shape memory material and which connects mechanically at least two parts, said geometry modification thus producing a reconciliation or a spacing of said parts. According to another feature, the actuator comprises a heating element activated by the passage of an electric current and whose temperature increase causes an expansion of a variant element formed by a material filling a confined enclosure (especially a filled volume). paraffin) closed by a movable thrust member in translation, said expansion thus producing a displacement in translation of said thrust piece.

Optionally, the system further comprises a cooling device activated by the passage of an electric current (for example a Peltier effect module), which is arranged to cool the heating element 3031155 - 4 - or the variable element on which it acts, thus achieving a controlled interruption of the retraction action. According to yet another particularity, the actuator comprises a solenoid displacing in translation a movable element under the effect of an electrical current. Optionally and generally in all the embodiments and modes of operation, the actuator is electrically powered. , in whole or in part, by a generator formed between an electromagnetic device fixed in rotation and a permanent magnet fixed in rotation with the wheel. This is for example the permanent magnet detection wheel speed sensor used for ABS or ESP. According to another aspect of the invention, there is provided a vehicle or subassembly of vehicle comprising at least one brake provided with an active retraction system as set forth herein. According to yet another aspect of the invention, there is provided a disc brake friction lining comprising at least one actuator arranged to be used in a system as set forth herein, in its embodiments where the liner carries it. -even an actuator. According to another aspect of the invention, there is provided a method of controlling a brake or a braking system comprising a communication between at least one electronic computer and the retraction actuator of a system such as exposed here. This method then comprises at least one step of controlling said actuator to produce active retraction within at least one brake in one or more of the following situations: detection of a user-controlled brake control end, detection of loosening or release control of the parking brake, receiving a release command generated by an automated braking system, for example in an ABS or traction control or trajectory stabilization system.

This direct-acting technology and few moving parts in particular provide good efficiency in retraction in comparison with packings and / or a normal brake. It makes it possible to generate a loosening force in a very robust manner and with a better efficiency in reducing the residual braking. It is particularly well suited to a wired or wireless electrical control system. It enables good environmental and fuel efficiency improvements, including with hydraulic or even fully hydraulic service brake brakes. Various embodiments of the invention are provided, incorporating, according to all of their possible combinations, the various optional features set forth herein. List of Figures Further features and advantages of the invention will become apparent from the detailed description of a non-limiting embodiment, and the accompanying drawings in which: FIGURE 1 is a flowchart illustrating the functional architecture of FIG. an exemplary embodiment of the invention; FIG. 2 schematically illustrates a first exemplary embodiment of the invention operating by an actuator incorporated in a disk brake cylinder: FIG. 2a, in section along the axis of the piston, FIG. 2b, in perspective transparent view of the back of the trim; FIGURE 3 schematically illustrates a second exemplary embodiment of the actuator-actuated embodi- ment incorporated in a bellows protection bellows bearing the caliper of a floating-mount disk brake, FIG. 3a. FIG. , in section along the axis of the column seen in perspective, o in FIGURE 3b, in perspective only showing the conductive wires, 5 o in FIGURE 3c, in perspective in partial view of the branch portion of the actuator; FIG. 4 schematically illustrates a third exemplary embodiment of the invention operating by an actuator incorporated in a brake caliper lining, seen in longitudinal section along the axis of the actuator, in an alloy-to-brake operation. shape memory FIGURE 5 illustrates the third exemplary embodiment in a variant with confined enclosure heating; FIGURE 6 illustrates the third exemplary embodiment in a solenoid variant; FIGURE 7 is a schematic, transparent perspective view illustrating a liner according to the third exemplary embodiment; FIGURE 8 is a schematic perspective transparent view illustrating the bearing leg of a floating-mount disk brake caliper according to the third exemplary embodiment. DESCRIPTION OF EXAMPLE EMBODIMENT FIGURE 1 generally illustrates an example of a functional architecture that can be applied to a system according to the invention, in particular to the exemplary embodiments described in the following figures. Embodiment 1 FIGURE 2 illustrates a first exemplary embodiment of the invention operating by actuator incorporated in a disk brake cylinder.

In this example, the brake piston encloses a variant element formed by a shape memory alloy wire or spring. At one of its ends, this variant element is fixed one to the wall of the bearing end of the piston. At its other end, it is attached to the caliper housing at the bottom of the piston housing. This variant element is electrically connected at both ends to an electrical circuit and has a resistance ohmic determined for its power supply to heat it up. Under the effect of this rise in temperature, the alloy returns to its original shape, which has been chosen so that its geometry is shortened between the attachment points of its two ends. It then seeks to retract and drives the piston back towards the inside of its housing, creating a game in the support chain that releases the seal and decreases or eliminates the residual braking.

Embodiment 2 FIGURE 3 illustrates a second exemplary embodiment of the actuator-actuated embodiment embodied in a protective gusset which surrounds the sliding columns which carry the yoke or clevis of a disk brake to floating assembly.

This bellows is made by a rubber or elastomer wall which surrounds the column. In the thickness of this wall is embedded a conductive wire, which runs approximately in one or more propellers. The end portions are traversed by a conventional elastic thread, for example steel, which holds and seals. Part of the turns in the center of the bellows is traversed by a shape memory alloy wire forming a variant element. This variant element is electrically connected at both ends to an electrical circuit and has an ohmic resistance determined so that its power supply causes it to heat up. Under the effect of this rise in temperature, the alloy returns to its original shape, which has been chosen so that its geometry is elongated or shortened between the ends of the bellows, according to the arrangement of the bellows inside the brake. It then seeks to lengthen or retract the bellows, thus displacing the floating element of the assembly, which creates a clearance in the support chain which releases the seal and reduces or eliminates the residual braking. Embodiment 3 FIGURE 4 to FIGURE 8 illustrates a third exemplary embodiment of the invention operating as an actuator incorporated in a caliper lining of a disk brake.

As seen in FIGURE 4, this embodiment includes an actuator attached to the back of the liner. This actuator is of a type causing displacement of a push rod in translation. This push rod is directed towards the friction track of the disc, and is movable in a hole through the entire thickness of the liner. In position at rest, the remote end 10 of the push rod is substantially at the friction surface of the liner. Typically, it is made of a soft material that can wear together with the trim without noise or damage to the disc, for example copper or bronze. When activated, the actuator moves the push rod towards the disc and presses it on its surface. By reaction, the actuator then drives the liner in the opposite direction, thereby creating a clearance or gap between the liner and the disk. This results in a reliable and effective decrease in residual braking. Optionally, the push rod is electrically connected with the wear detection system, and can perform the wear sensor function. The same wiring can then be used, with additional drivers or with the same drivers. FIGURE 4 illustrates this embodiment with an actuator operating by a shape memory alloy variant element, which changes geometry as it heats up under the effect of a power supply. This variant element is here a propeller surrounding the push rod and fixed on one side to the pad and on the other side to a cup. When it retracts this propeller pulls on the washer that presses the push rod and pushes it into the hole of the seal.

FIG. 5 illustrates this embodiment with an actuator operating by heating an enclosure confined by a resistor, forming a thermo-actuator. This enclosure is filled with a material that expands strongly with heat, for example paraffin similar to that used in thermostatic valves. Its expansion displaces a piston that presses on the push rod. FIGURE 6 illustrates this embodiment with a solenoid operated actuator, the core of which is attached to or presses on the push rod. The power supply of the turns then moves the push rod towards the disc. FIGURE 7 illustrates a packing thus equipped when mounted in a brake caliper on the piston side. FIGURE 8 illustrates a packing thus fitted when mounted in a floating mounting brake caliper on the caliper fingers side. Of course, the invention is not limited to the examples that have just been described and many adjustments can be made to these examples without departing from the scope of the invention. 15

Claims (13)

REVENDICATIONS1. Active retraction system of the friction linings in a friction brake by clamping friction linings against a rotating friction track within a set of elements clamped together to form a chain of support, characterized in that it comprises at least one electric actuator producing a momentary spacing of at least two elements of said support chain. 2. System according to the preceding claim, characterized in that the actuator is installed in a brake mechanism acting by displacement of at least one brake piston out of its housing to press against at least one friction lining, and in that the actuator acts by retracting said brake piston inside its housing. 3. System according to any one of the preceding claims, characterized in that the actuator is fixed to the lining and acts by displacing a thrust element so as to make it protrude from the friction surface of said lining on the side of the liner. the friction track. 4. System according to any one of the preceding claims applied to a floating mounting disc brake in which a so-called floating element which immobilizes the rotating seal is movable in translation on at least one sliding guide parallel to the axis. of the wheel, characterized in that the actuator acts by pressing on said element to move it on its sliding guide and thus introduce a game in the support chain 30. 5. System according to any one of the preceding claims, characterized in that the actuator provides a mechanical action produced directly in translation, without a member driven in rotation so 3031155 continuous. 6. System according to the preceding claim, characterized in that the actuator comprises a heating element activated by the passage of an electric current and whose temperature increase causes a change in geometry of a so-called variant element made of a material shape memory and which mechanically connects at least two parts, said geometry modification thus producing a reconciliation or a spacing of said parts. 10 7. System according to any one of claims 5 to 6, characterized in that the actuator comprises a heating element activated by the passage of an electric current and whose temperature increase causes expansion of a variant element formed by a material filling a confined enclosure closed by a push member movable in translation, said expansion thus producing a translation displacement of said thrust piece. 8. System according to any one of claims 6 to 7, characterized in that it further comprises a cooling device activated by the passage of an electric current, which is arranged to cool the heating element or the heating element. variant element on which it acts, thus achieving a controlled interruption of the retraction action. 25 9. System according to any one of claims 5 to 7, characterized in that the actuator comprises a solenoid moving in translation a movable member under the effect of an electric current. 10. System according to any one of the preceding claims, characterized in that the actuator is electrically powered, in whole or in part, by a generator formed between an electromagnetic device fixed in rotation and a permanent magnet fixed in rotation with the wheel. 11. Vehicle or sub-assembly of a vehicle comprising at least one brake 3031155 - 12 - provided with an active retraction system according to any one of the preceding claims. A disc brake friction lining comprising an actuator arranged for use in a system according to any one of the preceding claims in combination with claim 3. 13. A method of controlling a brake or a braking system comprising a communication between at least one electronic computer 10 and the retraction actuator of a system according to any one of claims 1 to 10, and comprising at least one least one step of controlling said actuator to produce active retraction within at least one brake upon detection of a user-initiated brake control end, or detection of loosening or a release command 15 of the parking brake, or upon receipt of a release command generated by an automated braking system.