EP3908768A1

EP3908768A1 - Electromechanical drum brake comprising an actuator that has an elastic reserve with a limited range of travel

Info

Publication number: EP3908768A1
Application number: EP20709651.2A
Authority: EP
Inventors: Alberto MOLINARO; Cédric GUIGNON; Gérard Luu; Cédric Dupas
Original assignee: Hitachi Astemo France SAS
Current assignee: Hitachi Astemo France SAS
Priority date: 2019-02-25
Filing date: 2020-02-11
Publication date: 2021-11-17
Also published as: FR3093151B1; WO2020174149A1; FR3093151A1

Abstract

The invention relates to a device for a drum brake (1) for a road vehicle. The device comprises an actuator (2) designed to urge apart two segments (12, 13) toward a brake drum. The actuator (2) comprises an elastic urging element (35) which is designed to be elastically deformed when the brake (1) is in a first braking position, and to urge the brake (1) toward a second braking position when the actuator (2) has been actuated and the brake (1) is no longer in the first braking position. The elastic urging element (35) is designed to have a range of travel between 2.5 mm and 6 mm with respect to a rest position of said elastic urging element (35).

Description

S64448 ^{AC n}

WO 2020/174149 1 PCT / FR2020 / 050248

ELECTROMECHANICAL DRUM BRAKE INCLUDING AN ACTUATOR INCLUDING AN ELASTIC RESERVE WITH LIMITED STROKE

DESCRIPTION

TECHNICAL AREA

The invention relates to brakes for a road vehicle. More

5 specifically, it relates to a drum brake mechanism, in particular an electromechanical drum brake actuator.

STATE OF THE PRIOR ART

Drum brakes include an actuator which is configured to bias two brake shoes apart, when actuated by a motor.

10 electric. The actuator includes an elastic reserve.

The elastic reserve is configured to be elastically deformed to store mechanical energy when the brake is in the service braking position. The elastic reserve is configured to release this stored mechanical energy and to urge the brake towards a parking brake position

15 and / or an emergency braking position, when the actuator has been actuated and the brake ceases to be in the service braking position.

There is a need to further reduce the power, size and cost of the electric motor of the actuator, while limiting the brake response time and while preserving the reliability of the brake.

20 DISCLOSURE OF THE INVENTION

In this regard, the subject of the invention is a device for a drum brake for a road vehicle. The device comprises an actuator configured to urge two brake shoes apart towards a brake drum.

The actuator comprises an elastic biasing element which is

25 configured to be elastically deformed when the brake is in a first braking position, and to bias the brake to a second braking position when S64448 ^{AC n}

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the actuator has been actuated and the brake ceases to be in the first braking position.

According to the invention, the elastic biasing element is configured to have a stroke between 2.5 mm and 6 mm relative to a rest position of the elastic element, in particular between a preloaded position when the brake is in. the first braking position and that the elastic element is pre-stressed and / or a rest position when the brake is in the second braking position.

Thanks to the invention, the power, size and cost of an actuator motor assembly is limited, while retaining a low response time of the brake and while preserving the reliability of the brake.

The invention may optionally include one or more of the following features combined or not.

According to a particular embodiment, the device comprises a plate, a first brake segment and a second brake segment which are installed on the plate. The actuator comprises a first pusher which bears on the first segment. The actuator comprises a second pusher which bears on the second segment.

According to a particular embodiment, the elastic stressing element has a stiffness strictly between 0 and 500 N / m.

According to a particular embodiment, the stiffness of the elastic element is between 210 and 250 N / mm for a light vehicle whose total rolling weight is less than 3500 kg.

According to a particular embodiment, the elastic biasing element is configured to at least partially surround a housing of the actuator.

According to one particular embodiment, the elastic biasing element is configured to at least partially surround the first pusher.

According to one particular embodiment, the elastic biasing element is configured to at least partially surround the second pusher. S64448 ^{AC n}

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According to one particular embodiment, the elastic biasing element is configured to elastically bias the first segment apart from the second segment, in parallel with a pushing head of the first pusher.

According to a particular embodiment, the elastic biasing element 5 is compressible. The elastic member is configured to be compressed when the brake is in the first braking position.

According to one particular embodiment, the elastic biasing element comprises at least one Belleville washer, a block of elastic material and / or a spring.

According to one particular embodiment, the elastic biasing element 10 comprises a helical spring and / or a square section spring.

According to a particular embodiment, the first braking position is a service braking position of the brake.

According to a particular embodiment, the second braking position is an emergency braking position of the brake and / or a parking braking position of the brake.

According to a particular embodiment, the actuator is a second actuator, the device comprises a first actuator which is configured to urge the segments apart when the brake is in the first braking position.

According to a particular embodiment, the first actuator is a hydraulic actuator which is configured to move the segments apart under the effect of an increase in hydraulic pressure in the first actuator.

According to a particular embodiment, the second actuator is an electromechanical actuator.

According to a particular embodiment, the second actuator comprises

25 a screw-nut system, the second pusher comprises the screw and / or the nut of the screw-nut system.

According to a particular embodiment, the device comprises a motorization assembly which is connected to the second actuator.

The invention also relates to a drum brake which comprises a device

30 as defined above. S64448 ^{AC n}

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According to a particular embodiment, a light vehicle whose total rolling weight is less than 3500 kg comprises a drum brake as defined above for each of the wheels of the rear axle, the elastic biasing element of each of the drum brakes having a stiffness of 229.8 N / mm. Each of these resilient biasing elements makes it possible in particular to reduce the power of the motor to 60 W for a 12 V supply while ensuring the safety of the parking brake and a rapid application and release time.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood on reading the description of exemplary embodiments, with reference to the accompanying drawings in which:

Figure 1 is a schematic representation partially cut away from the side of a drum brake which is installed on a vehicle;

Figure 2 is a schematic perspective view of a dual-mode drum brake mechanism according to a first embodiment of the invention;

FIG. 3 is a partial schematic front view of the drum brake according to the first embodiment, when the brake is applied and when the vehicle is stationary;

FIG. 4 is a partial schematic front view of the drum brake according to the first embodiment, once the brake is applied and with a holding torque exerted in a first direction of rotation on the segments;

FIG. 5 is a schematic front view of the drum brake according to the first embodiment, once the brake has been applied and with a holding torque exerted on the segments in a second direction of rotation opposite to the first direction of rotation;

Figure 6 is an isometry and partial cutaway of the brake actuator according to the first embodiment;

Fig. 7 is an isometry of a dual-mode drum brake mechanism according to a second embodiment of the invention; S64448 ^{AC n}

WO 2020/174149 ₅ PCT / FR2020 / 050248

FIG. 8 is a representation of an operating diagram of an elastic element for stressing a brake according to the first or the second embodiment.

5 DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

Identical, similar or equivalent parts of the different figures bear the same numerical references so as to facilitate the passage from one figure to another.

Fig. 1 shows a drum brake 1 which is installed on a road vehicle 10, such as an automobile. The drum brake 1 comprises a drum 15, a plate 10, two brake segments 12, 13, a wheel cylinder 11 (figure 2) which forms a first actuator, and a second actuator 2 (figure 2) of the electromechanical type which forms a retractor or fulcrum. The drum brake 1 also comprises a motor assembly 5 which is connected to the second actuator 2.

The drum 15 is crossed by a hub 6 of the wheel to be braked, to which it is attached and to which it is integral in rotation. The plate 10 serves as a support for the brake, being fixed to the frame 7.

Referring to Figures 1 and 2, the drum brake 1 is configured to cause a braking torque between the drum 15 and the plate 10 which are movable in rotation with respect to each other about an axis of rotation Al.

Dual-mode brake mechanism

FIG. 2 represents a "dual-mode" drum brake mechanism according to the first embodiment of the invention. The drum brake 1 can be used as a service brake and / or as a parking brake.

In the first embodiment, the dual-mode drum brake mechanism 1 is here shown in an example with a service brake actuator 11 operating by hydraulic energy, and a parking and emergency brake actuator 2 operating by energy. electric. S64448 L cn

WO 2020/174149 PCT / FR2020 / 050248

Service brake mode

In service brake mode, the braking torque is created by absorbing energy under the effect of friction between: on the one hand, the friction track carried by

5 an inner surface of the drum 15, and on the other hand of the friction linings 123, 133 which are carried respectively by the first and by the second segment 12, 13. This friction is obtained by spacing the segments outwards, under the effect of the first actuator 11.

From the rest position or from the braking position of

10 parking, this first actuator 11 brings the brake 1 to the service braking position, and the return to the rest position is achieved for example by return springs which interconnect the two segments 12, 13, as illustrated in FIG. figure 2.

In this example, the drum brake 1 is arranged to operate in simplex mode when it is actuated as a service brake.

The first actuator 11, which is conventionally referred to as a wheel cylinder, takes the form of a hydraulic cylinder which is configured to move apart segments 12, 13 under the effect of an increase in hydraulic pressure. The first actuator 11 comprises two opposed pistons 111, 112, which each actuate one of the segments 12, 13 by separating their two ends 121, 131 which are opposite and to each other from one another.

20 proximity of the actuator 11. These two ends 121, 131 are here called "movable ends" and they are represented at the top of FIG. 2.

At its opposite end 122, 132, called the stop end, each segment 12, 13 rests on the plate 10 by means of an anchoring element which is integral with the plate 10. The anchoring element forms a stop for this segment 12, 13.

In this example, the fulcrum of the two segments is formed by a housing 21 of the second actuator 2 by which the latter is rigidly secured to the plate 10. This attachment of the housing 21 to the plate 10 is symbolically illustrated in FIG. figure 5 by the symbol of the earth, at the bottom and in the middle of the figures. The second actuator 2 thus forms a fulcrum, as well as with each anchoring element a

30 pivot region for segments 12, 13. S64448 L cn

WO 2020/174149 PCT / FR2020 / 050248

Parking or emergency brake mode

Referring to Figure 3, the second actuator 2 comprises a linear actuator assembly 3 which, in parking or emergency brake mode,

5 presses on the stopper ends 122, 132 of the segments 12, 13 to move them apart, and thus put the segments 12, 13 in abutment against the friction track of the drum 15. The second actuator 2 serves then retractor.

From the rest position, or from the service braking position, this second actuator 2 brings the brake 1 to the parking braking position, and the

Return to the rest position is achieved, for example, by the return springs.

In the present example, the linear actuator assembly 3 includes a first pusher 33 and a second pusher 32 which are moved relative to each other in a linear movement, in an actuation direction D2 which is a linear motion. direction substantially tangential to the plate 10 and orthogonal to the axis of rotation Al of the drum.

As indicated by the two arrows in FIG. 3, this movement presses the two pushers 32, 33 respectively on the two stop ends 122, 132 of the first segment 12 and of the second segment 13.

As illustrated in Figure 4 and Figure 5, as soon as a torque, in one direction C4 or in the other C5, is applied to the segments by the drum 15 relative to the

20 plate 10, for example due to the fact that the vehicle is parked on a slope or that the emergency brake is actuated when the vehicle is in motion, the drum 15 tends to drive the segments 12, 13 in rotation in the direction of this torque due to the frictional contact between segments 12, 13 and drum 15.

FIG. 5 illustrates more particularly the case of a couple C5 in the direction

25 schedule. By friction, the first segment 12 thus receives a torque C52 this from the drum 15.

By its opposite end, that is to say its "mobile" end 121, the first segment 12 bears on an intermediate element 14 by an articulation 142, called the first articulation, for example a pivot or by any other form of cooperation.

30 as notches engaged between them. S64448 ^{AC n}

WO 2020/174149 _g PCT / FR2020 / 050248

The intermediate element 14, for example a rod, is movable or "floating" relative to the plate 10, and is articulated in the same way with the "movable" end 131 of the other segment 13, so as to keep apart one of the other their two movable ends 121, 131. In the present embodiment, this intermediate element 5 is a rod for taking up play resulting from the wear of the linings 123, 133.

Under the support of the first segment 12, the intermediate element 14 thus transmits a support C23 to the mobile end 131 of the second segment 13, substantially tangentially to the plate 10 to an articulation 143 of the second segment 13 and

10 of the intermediate element 14. This second articulation 143 is for example a pivot.

Under the support of the intermediate element 14, the second segment 13 bears on the track of the drum 15, and also receives by friction a torque C53 from the drum 15. By its opposite end, that is to say ie the “stop” end 132, this second segment 13 transmits to the pusher 32 the set C30 of the torques received.

With respect to the housing 21 of the actuator 2, the actuator assembly 3 is mounted free in tangential translation around the axis of rotation A1, over a stroke limited by a stop on each side of its central position. In the direction of rotation of FIG. 5, under the effect of the torques C52 and C53 transmitted by the drum 15, the segments 12, 13 thus have the effect of moving the actuator assembly 3 in the direction of these

20 torques, either in the actuation direction D2 in the direction D22 according to the white arrow to the left and up to the stop position illustrated in Figure 5.

Thus, in the parking or emergency brake mode, the stop end 132 of the second segment 13 bears on the housing 21 of the spacer to transmit to the plate 10 the braking or holding torque created by the support. of

25 segments 12, 13 on drum 15.

In the present example, the stop end 132 of the second segment 13 and the housing 21 of the second actuator 2 bear on each other by means of the second pusher 32, for example by a shape accident, here a shoulder 329 carried by the pusher facing the outer surface of the housing 21 at the

30 level of the vertical line in phantom in the figure. S64448 ^{AC n}

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In this direction of rotation of FIG. 5, the segment 12, the spaced end 122 of which first receives the movement of the drum 15 is the segment 12 on the left in the figure, which pivots and is arched on the articulation 142 of its opposite end and thus forms a "compressed" segment. Closely, thus receiving a tangential force 5 by its end 131 receiving the movement, the second segment 13 also behaves as a “compressed” segment by arching on its stop end 132.

Thus, in parking or emergency brake mode, the activation of the second actuator 2 causes this same brake assembly 1 to operate in "servo duo" mode, which provides a bearing force against the drum 15 much greater than the service brake simplex mode, for the same piston ring actuation force.

In the direction of rotation of Figure 4 which is reversed with respect to that of Figure 5, a couple C4 in the other direction drives the segments 12, 13 and the spacer 14 in the other direction, which moves the actuation assembly 3 in the direction of actuation D2 in a direction D23 opposite to the direction D22, according to the white arrow 15 to the right and up to the stop position illustrated in the figure.

The braking torque is then transmitted by the stop end 122 of the left-hand segment 12 on the housing 21 of the spacer, via the shoulder 339 of the first pusher 33, at the level of the vertical line in dashed line. mixed in the figure.

20 Construction and operation of the second actuator

The structure and operation of the second actuator 2, here also called a spacer, will now be described in more detail with reference to FIGS. 2 to FIG. 7.

In the embodiment of Figure 2 and with reference to Figure 6, the linear actuator assembly 3 of the second actuator 2 comprises a first threaded member and a second threaded member interacting with each other to form a screw-nut system. 31, 32. This screw-nut system 31, 32 produces a linear movement in the direction of actuation D2 under the effect of a rotation of this first element relative to this second element. It transforms the couple received by one of its elements into

30 two opposing axial forces on each of its elements 31, 32 respectively. S64448 ^{AC n}

WO 2020/174149 _1Q PCT / FR2020 / 050248

In this embodiment, the thread angle of this vi-nut system 31, 32 is chosen so that the force transmission obtained is irreversible, by choosing a thread angle which is less than the friction angle of the torque. of materials used to achieve these two elements.

This screw-nut system 31, 32 produces an irreversibility which provides a locking function in the parking brake position. In other words, a force received by the pushers 32, 33 from the segments 13, 12 is blocked by the non-slip between the threads of the two elements of the screw-nut system 31, 32. It is thus not transmitted to motorization, thus making it unnecessary to block the motor or keep it charged.

As can be seen for example in FIG. 2 to FIG. 6, this screw-nut system comprises the second pusher 32. This takes the form of a pusher screw comprising a threaded male part 323 in the form of a rod, and a pusher head 322 which comes to bear on the second segment 13. This push screw 32 interacts with the other part of the screw-nut system, formed by a nut 31 provided with an internal thread. In the present embodiment, it is the nut 31 which receives the actuation torque by the drive assembly 5.

The drive assembly 5 of the nut 31 of the second actuator 2 is shown in Figures 2 and 6. The drive assembly 5 comprises an outer casing

20 51, an electric motor 52, a reduction gear 55 and a transmission sub-assembly 56.

The outer casing 51 defines an internal housing for the electric motor 52, the reduction gear 55 and the transmission sub-assembly 56.

The electric motor 52 is electrically supplied by an electric power supply cable 529. The electric motor 52 is configured to move the nut 25 31 of the second actuator 2 in the direction of actuation D2, via the reduction gear 55 and the transmission sub-assembly 56.

Reducer 55 is, for example, an epicyclic reducer. It is located between the engine 52 and the transmission sub-assembly 56, being substantially in the extension of the engine 52, for example in a direction substantially parallel to the

30 actuation direction D2. S64448 ^{AC n}

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The transmission sub-assembly 56 is located between the reduction gear 55 and the nut 31 which it drives. It extends substantially orthogonally to the actuation direction D2. It comprises a gear train, one of the toothed wheels of which engages mechanically by complementarity of the external shape of the nut 31, to drive it in translation in the direction of actuation D2.

With reference to each of the embodiments shown, the first pusher 33 comprises a pusher head 332 and a pusher body 333. The pusher head 33 has a skirt rearwardly within which the body can slide. pusher 333. The pusher body 333 and the nut 31 are in mutual axial bearing according to the

10 actuation direction D2 with the possibility of relative rotation between them by mutual sliding of their bearing surfaces, so that the first pusher 33 is non-rotating and immobilized in rotation by the first segment 12 which mechanically engages the head 332 of the first pusher.

15 Elastic stress element

The drum brake 1 comprises a mechanism ensuring a function of locking the brake 1 in the parking braking position, and also a function of stabilizing the forces in the mechanical chain which carries out the support of the segments 12, 13 on the drum 15 in case of dimensional variations of the constituent elements of the brake

20 drum 1.

In each of the embodiments shown, to provide the function of stabilizing the forces in the mechanical chain of the drum brake 1, the second actuator 2 elastically urges the stop ends 122, 132 of the two segments apart by means of an elastic biasing element 331, 35

25 in the direction D2 of the actuating movement. The elastic stress element

331, 35 is elastically deformable in the direction D2 of actuation. This elastic stressing element 331, 35, called an elastic element, is also called a “spring package” in English.

The elastic biasing element 331, 35 forms an elastic reserve

30 which makes it possible to fill the races which are necessary for the passage of a first position S64448 ^{AC n}

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braking to a second braking position of the brake 1, while ensuring a sufficient load to meet the needs of the immobilization of the vehicle.

In particular, the resilient biasing element 331, 35 is capable of storing, by compression in the actuation assembly 3 during actuation of the second actuator 2 while the drum brake 1 is in a first position. braking, a quantity of mechanical energy sufficient to maintain or bring the drum brake 1 into a second braking position, if the pressing of the first actuator 11 is interrupted and when the second actuator 2 is not actuated again.

10 Such a situation of compression of the elastic biasing element

331, 35 occurs, for example, when the driver stops the vehicle and keeping it stopped with the service brake, then engages the parking brake before releasing the service brake control, for example when stopping for parking on a slope.

The first braking position corresponds to the service braking position, that is to say a braking position in which the first actuator 11 is actuated and acts as a separator for the segments 12, 13. In the first braking position, the second actuator 2 is a fulcrum for segments 12, 13.

The second braking position corresponds to the braking position of

20 parking and / or emergency braking, that is to say a braking position in which the second actuator 2 is actuated and acts as a separator for the segments 12, 13. In the second braking position, the first actuator 11 and / or the intermediate element 14 form a fulcrum.

The passage from the first braking position corresponds to the passage of

25 simplex mode to servo duo mode of drum brake 1.

The stroke of the elastic biasing element 33, 331 also allows, during a variation in dimensions of elements 12, 13 of the drum brake 1, and without activation of the second actuator 2:

- to maintain the support force of segments 12, 13 against the track of

30 friction in the event of dimensional variations in a first direction, for example in the event of S64448 ^{AC n}

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thermal shrinkage of segments 12, 13 or pushers 32, 33, or in the event of thermal expansion of drum 15; and

- to limit the increase in the forces in the mechanism of the drum brake 1 in the event of dimensional variations in a second direction opposite to the first direction, which may be caused for example by a thermal retraction of the drum 15 when the latter cools down to stopping after being warmed up as a service brake during a journey.

The elastic biasing element 331, 35 thus makes it possible to limit and / or avoid any need for automatic reactivation of the second actuator 2 during parking, also called "re-clamping", which can be energy consuming and subject to dysfunctions that can have serious consequences.

First embodiment

With reference more specifically to the first embodiment shown in Figures 2 and 6, the elastic biasing element 331 is formed by a compressible elastic structure which comprises a stack of conical steel washers, called "Belleville" washers. The compressible stack 331 is here maintained by crimping the end of the skirt around the rear of the body 333 of the first pusher 33.

20

Second embodiment

FIG. 7 represents a drum brake 1 according to a second embodiment. The drum brake 1 according to the second embodiment differs from the drum brake 1 according to the first embodiment by the structure of the second actuator 2, in particular by the structure of the elastic biasing element and by the structure of the first. pusher 33.

The elastic biasing element 35 comprises a helical spring which is configured to elastically bias the first segment 12 of the second segment 13 apart, in parallel with the push head 332 of the first pusher 33. This S64448 ^{AC n}

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helical spring 35 surrounds the housing 21 of the second actuator. It partially surrounds the first pusher 33 and the second pusher 32.

The first pusher 33 lacks a compressible structure, such as the stack of Belleville washers of the first embodiment, between the pusher head 332 and the pusher body 333.

Ranges of values of stiffness and stroke of the elastic element

FIG. 8 shows a deformation of the elastic biasing element 331, 35 along the axial direction of movement D2, in relation to the load 10 exerted on the elastic biasing element 331, 35.

With reference more specifically to the first embodiment shown, the deformation of the elastic element 331 along the direction of movement D2 corresponds in particular to the distance traveled by the end of the head 332 of the first pusher in the direction of movement D2 between a rest position of the head 332 and a compression position in which the elastic biasing element 331 is compressed when the brake 1 is in the first braking position.

With reference more specifically to the second embodiment shown, the deformation of the elastic element 35 along the direction of movement D2 corresponds in particular to the distance traveled by the longitudinal ends of the spring 20 35 between a rest position of the spring 35 and a position compression in which the spring 35 is compressed when the brake 1 is in the first braking position.

In general, the load which is exerted on the elastic biasing element 331, 35 is in particular the compressive force which is exerted on the elastic biasing element 331, 35 by the stop end 122, 132 of at least one of

25 segments 12, 13, when the first actuator 11 is actuated and the brake 1 is in the first braking position.

The representation of FIG. 8 makes it possible in particular to determine an acceptable range of values for the stiffness of the elastic biasing element 331, 35, as well as an acceptable range of values for the maximum stroke of the elastic element.

30 for biasing 331, 35 between the compression position and the rest position. S64448 ^{AC n}

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In each of the embodiments shown, the elastic biasing element 331, 35 has a stiffness which is strictly between 0 and 500 N / m. The elastic biasing element 331, 35 is configured to have a stroke between 2.5mm and 6mm relative to a rest position of the elastic biasing element 331, 35 in which the drum brake 1 is is not actuated.

Due to these ranges of stiffness and stroke values of the resilient biasing element 331, 35, the power, size and cost of the motor assembly 5 of the second actuator are limited, while retaining time. low response of the second actuator 2 and while preserving the reliability of the brake 1.

In particular, these ranges of stiffness and stroke values of the elastic biasing element 331, 35 make it possible to use an electric motor 52 that is less bulky and less powerful, to actuate the spacer 2 with response time and at reliability equivalents.

Of course, various modifications can be made by

15 those skilled in the art to the invention which has just been described without departing from the scope of the description of the invention.

As a variant, the vehicle comprises at least a disc brake, to brake one of the wheels. For example, the drum brake 1 is partially integrated in the central bell of a brake disc, which then forms the drum 15 of the drum brake. Such a

20 architecture is sometimes called "Drum in Hat".

As a variant, the drum brake 1 has no wheel cylinder and the first actuator 11 is not connected to a hydraulic braking circuit. In this case, the first actuator 11 is in particular an electromechanical actuator which is connected to a motor assembly.

25 The drum brake 1 may be without a first actuator 11 when the drum brake 1 is a parking and emergency brake, for example when it is intended to operate only in duo servo mode or when the brake 1 is of type "Drum in Hat".

The intermediate element 14 can take other forms than a connecting rod

30 for taking up play, for example by an intermediate plate resting between the two S64448 ^{AC n}

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segments 12, 13. It can also be produced by the wheel cylinder 11 if it is mounted floating, through its housing or its pistons 111, 112.

The reduction gear 55 and the transmission sub-assembly 56 of the power unit 5 may include other types of motion transmission elements, for example bevel gears.

As a variant, the screw-nut system 31, 32 is reversible. In this case, the motor 52 and / or the reduction gear is for example blocked in rotation, to prevent the release of the brake 1.

In addition or as a variant, the drive assembly 5 is configured to drive the screw 32 in translation in the actuation direction D2, instead of the nut 31. In other words, the male and female elements of the screw system. nut 31, 32 are reversed.

The vehicle may also include a pawl retaining the "handbrake" operating member or lever and a resilient control cable which is connected to segments 12, 13 of the drum brake.

Alternatively, the resilient biasing element 331, 35 may be resiliently biased in traction when the brake 1 while the drum brake 1 is in a first braking position, to store a sufficient amount of mechanical energy to maintain or bring the drum brake 1 in the second braking position, if the pressing of the first actuator 11 is interrupted and the second actuator 2 is not actuated.

In general, the elastic biasing element 331, 35 can take different forms such as a stack of Bellevilles washers, a spring or a block of elastic material, in particular an elastomer block. It can be located at different locations of the second actuator 2, for example by surrounding or not the first pusher 33 and / or the second pusher 32, or by elastically or not biasing the head 322 of the second pusher and / or the head 332 of the pusher. first pusher.

The first pusher 33 of the drum brake 1 according to the second embodiment may comprise an elastic biasing element between the pusher head. S64448 ^{AC n}

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332 and the pusher body 333, for example a compressible structure such as a block of elastomeric material, a spring or a stack of Belleville washers.

As a variant of the second embodiment, the elastic biasing element 35 comprises a spring with a square section, in particular to form the shoulder.

5 339 which serves as a stop for the first pusher 33 in the direction of actuation D2.

NOMENCLATURE WITH REFERENCE TO FIGURES

1: drum brake

10: support plate

10 11: first actuator - wheel cylinder - service brake

111, 112: wheel cylinder pistons

12, 13: segments

121. 131: movable ends of segments

122. 132: stop ends of segments

15 123, 133: friction linings

14: spacer element - play take-up link

142, 143: intermediate element joints

15: drum

2: second actuator - fulcrum

20 21: main spreader housing

3: linear actuator assembly

31: screw-nut system nut

32: screw-nut system screw, second plunger

322: head of the second pusher

25 323: threaded male part

329: thrust screw bearing shoulder - braking torque transmission

33: first pusher

331: elastic element - stack of Belleville washers

332: elastic pusher head, S64448 ^{AC n}

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333: elastic pusher body

339: bearing shoulder of the elastic plunger - transmission of the braking torque 35: linear elastic element - "spring package"

5: motorization assembly

5 51: motor unit

52: electric motor

529: motor power supply

55: reducer

6: hub of the wheel to be braked

10 7: vehicle chassis

Claims

19 PCT / FR2020 / 050248 CLAIMS

1. Device for a drum brake (1) for a road vehicle, comprising an actuator (2) configured to bias two segments (12,

5 13) brake to a brake drum (15),

the actuator (2) comprising an elastic biasing element (331, 35) which is configured to be elastically deformed when the brake (1) is in a first braking position, and to bias the brake (1) to a second position brake when the actuator (2) has been actuated and the brake (1) ceases to be in the first

10 braking position,

characterized in that the elastic biasing element (331, 35) is configured to have a stroke between 2.5mm and 6mm relative to a rest position of the elastic biasing element (331, 35).

2. Device according to the preceding claim, comprising a plate (10), a first brake segment (12) and a second brake segment (13) which are installed on the plate (10),

the actuator (2) comprising a first pusher (33) which bears on the first segment (12), the actuator (2) comprising a second pusher (32) which is in

20 press on the second segment (13).

3. Device according to any one of the preceding claims, wherein the elastic biasing element (331, 35) has a stiffness strictly between 0 and 500 N / m.

25

4. Device according to any one of the preceding claims, wherein the resilient biasing element (331, 35) is configured to at least partially surround a housing (21) of the actuator (2), the first pusher (33). ) and / or the second pusher (32).

30 S64448 ^{AC n}

WO 2020/174149 _2Q PCT / FR2020 / 050248

5. Device according to any one of the preceding claims combined with claim 2, wherein the elastic biasing element (331, 35) is configured to elastically bias the first segment (12) away from the second segment (13), in parallel with a push head (332) of the first pusher (33).

5

Device according to any one of the preceding claims, in which the elastic biasing element (331, 35) is compressible, the elastic biasing element (331, 35) being configured to be compressed when the brake (1). is in the first braking position.

10

7. Device according to any one of the preceding claims, wherein the resilient biasing element (331, 35) comprises at least one Belleville washer (331), a block of elastic material and / or a spring (35).

Device according to the preceding claim, in which the elastic biasing element (331, 35) comprises a helical spring (35) and / or a spring with a square section.

9. Device according to any one of the preceding claims, in which the first braking position is a brake service braking position.

(1), the second braking position being an emergency braking position of the brake (1) and / or a parking braking position of the brake (1).

10. Device according to any one of claims

25 preceding, in which the actuator (2) is a second actuator, the device comprising a first actuator (11) which is configured to urge the segments (12, 13) apart when the brake (1) is in the first position braking.

11. Device according to the preceding claim, wherein the

The first actuator (11) is a hydraulic actuator which is configured to spread the 21 PCT / FR2020 / 050248

segments (12, 13) under the effect of an increase in hydraulic pressure in the first actuator (11).

12. Device according to any one of claims

5 above, in which the second actuator (2) is an electromechanical actuator.

13. Device according to any one of the preceding claims, wherein the second actuator (2) comprises a screw-nut system, the second pusher (32) comprising the screw (32) and / or the nut (31) of the system. screw nut.

10

14. Device according to any one of claims 12 to 13, comprising a motor assembly (5) which is connected to the second actuator (2).

15. Drum brake (1) comprising a device according to one of

15 preceding claims.