FR2807485A1 - Disc brake includes a deformable coupling element linking the disc to the hub while having one face integral in translation with the U-shaped element and the other integral in translation with the disc face - Google Patents

Abstract

A coupling element (6) links the disc (2) to the hub (10) while having one face integral in translation with the U-shaped element (41) and the other integral in translation with the disc face (21). The element is deformable until a limit (K) which is equal to the desired play (J) between disc and brake. Disc (2) is supported by a support (1) integral in rotation with a hub (10) integral with the wheels. The disc has two faces (21,22) in contact with braking surfaces (31,32) when the piston (5) forces the pile (21,2,22) in abutment against the face of the U-shaped element (41). An Independent claim is also included for the method of braking.

Description

The present invention relates, in general, to the technique used for braking a motor vehicle, and in which two friction elements are applied against each other to absorb at least part of the kinetic energy of this vehicle.

More specifically, the present invention relates according to one of its aspects, a disc brake for a motor vehicle comprising at least one suspension element equipped with a wheel, this brake comprising a disc support at least formed by a hub intended to be made integral in rotation of the wheel, a disc integral with rotation of the disc support and having an external face and an internal face, external and internal brake pads kept fixed in rotation relative to the suspension element and respectively turned towards the external faces and internal of the disc, a stirrup straddling the disc and intended to be connected to the suspension element, a jack connected to the stirrup, and wear return and take-up means, the external pad, the disc, and the pad internal being housed in a stack between the jack and a stirrup nose, the jack being selectively controlled to press this stack against the stirrup nose, in a direction transverse to the disc, when the brake is in an actuating state, and to allow pads to disengage from the respective faces of the disc when the brake is in a resting state, the caliper and the outer face of the disc adopting, in the transverse direction, respective transverse positions which vary with respect to each other both according to whether the brake is in its actuation state or in its rest state and according to wear of the external wafer, measured by a loss of thickness, this wafer from a new state, and the wear return and take-up means being able to guarantee less than the external wafer and the external disk face are in the rest state of the brake, spaced from each other by a distance at least equal to a minimum and at most equal to a maximum play, independently of the wear of the external pad.

Brakes of this type, used for several decades, now equip most motor vehicles and include in particular the brakes known under the names of "sliding caliper disc brakes" and "floating disc brakes".

Despite the relatively traditional nature of the technique concerned, disc brakes continue to be the subject of research aimed at increasing performance and reducing production costs.

Among the salient subjects of concern are studies ideally aimed at canceling the residual braking torque, that is to say eliminating the parasitic resistance that the brake can continue to oppose to the rotation of the wheel even when it 'is not requested, the existence of a non-zero residual torque causing an expenditure of energy which inevitably results, for the vehicle, in overconsumption of fuel.

The invention, which is situated in this context, precisely aims to provide a disc brake which, although having a simple structure and inexpensive construction, very satisfactorily solves the problem of reducing or even eliminating the torque residual.

To this end, the disc brake of the invention, which moreover conforms to the generic definition given in the preamble above, is essentially characterized by what it comprises, as at least one return means and wear compensation, a connecting piece having an outer edge and an inner edge distant from each other, one of these edges adopting transverse position linked to that of the stirrup nose and the other edge adopting a transverse position linked to that of the external face of the disc, and in that the connecting piece has, between its external and internal edges in the transverse direction, a limit capacity of elastic deformation of amplitude at least equal minimum clearance and at most equal at maximum play, and plastic deformation capacity of amplitude at least equal to the maximum authorized wear of the outer pad.

In the case where the caliper nose adopts a fixed transverse position relative to that of the disc support hub, and where the disc adopts a variable transverse position relative to that of the disc support hub, the connecting piece may by example connect the hub of the disc support to the disc, the internal edge of the connecting piece being linked to the disc support hub and the external edge of the connecting piece being radially distant from the internal edge and linked to the disc.

In the preferred embodiment of the invention, the connecting piece may essentially consist of an annular web.

In the case where the disc is slidably mounted on the hub of the disc support, the connecting piece can thus be easily interposed between the disc and the hub of the disc support. In the case where the disc support comprises a stamped sheet veil connecting the hub of the disc disc support, the connecting piece can be constituted by this same stamped sheet veil and thus form part of the disc support.

Excellent results can be obtained by using a connecting piece made of a metallic material, this piece also being able to be fixed by its external and internal edges so as to deform at least in part by shearing.

The invention also relates to a method usable in a brake comprising at least two friction elements, in particular to compensate for wear of at least one of these two friction elements and to maintain between these friction elements, in a state of rest of the brake, a spacing between lower and upper limits, these friction elements being applied against each other in a brake actuation state, and the brake having first and second members undergoing a relative movement, related amplitude at said spacing, when the brake switches from one of its states to the other, this process being essentially characterized in that it comprises the operation consisting in storing a minimum amount of energy in a deformable part by applying to this deformable part, through the first and second members, an elastic deformation of amplitude at least equal to a minimum amplitude each ue once the friction elements are brought towards each other over a stroke between the lower and upper limits, when the brake passes from its rest state to its actuation state; an operation consisting in limiting the energy stored in the deformable part by applying this deformable part, via the first and second members, a plastic deformation as soon as the stroke on which the friction elements are brought together. 'other, when the brake passes from its rest state to its actuation state, exceeds the upper limit; and an operation consisting in using the energy stored in the deformable part to separate the friction elements from one another when the brake passes from its actuation state to its rest state.

Other characteristics and advantages of the invention will emerge clearly from the description which is given below, by way of indication and in no way limiting, with reference to the appended drawings, in which - Figure 1 is a schematic view in partial section a example of a floating disc brake of the prior art, to which the invention can be applied; - Figures 2 to 8 are schematic views in partial section of a floating disc brake according to a first possible embodiment of the invention illustrated in different configurations and different operating states; - Figure 9 is a schematic view in partial section of a floating disc brake according to the second possible embodiment of the invention; and - Figure 10 is a diagram showing the evolution of the amplitude of the plastic elastic deformations undergone by a connecting piece used in the invention, as a function of the amplitude of the force applied to this connecting piece. The brake of the invention is intended, in a conventional manner, to be mounted on each half-axle of a front axle and a rear axle of a motor vehicle, this brake therefore being associated (FIG. 1) with a pivot suspension S and a corresponding wheel R of the vehicle, made integral with a hub 10.

More specifically, this brake comprises for example a disc support 1, possibly constituted by the hub 10, a disc 2 integral in rotation with the disc support 1, external 31 and internal 32 brake pads, a caliper 4, and a cylinder 5.

The internal external 31 brake pads 32 are kept fixed in rotation relative to the chassis of the vehicle and to its suspension pivot S, and are respectively turned towards the external and internal faces, 21 and 22, of the disc 2.

The stirrup 4 is made integral with the suspension pivot S and overlaps the disc 2.

Finally, the jack 5, generally constituted by a hydraulic jack supplied with a pressurized braking fluid, installed inside 1 caliper 4 so as to define, in combination with the nose 41 of the caliper, space of variable width in which are housed, in a stack, the external plate 31, the disk 2, and the internal plate 32.

Under these conditions, the brake can be actuated by controlling the jack 5 so that the latter presses the stack formed by the external plate 31, the disc 1, and the internal plate 32, against the nose 41 of the caliper which induced between the pads, fixed in rotation, the rotating disc, friction forces whose work reduces the kinetic energy of the vehicle accordingly. When the brake is not applied, and is therefore in its rest state, it is however important that the pads 31 and 32 are kept away from the corresponding faces 21 and 22 of the disc, so that the vehicle can roll without having to overcome any friction between the pads and the disc.

To this end, the disc brakes comprise, in known manner, means capable of ensuring the recoil of the pads away from the disc, that is to say the return of these pads to their rest position, after the end of each brake actuation phase.

However, the function of these means must essentially satisfy two additional constraints.

on the one hand, it is advisable to ensure that the recoil of the pads does not have too great an amplitude, failing which the next brake stroke would require an increased stroke of the brake pedal, resulting in a delay in braking and an efficiency reduced insofar as a significant part of this race would only aim to make up for too much play that would have been introduced between the brake pads and the disc.

on the other hand, it is also necessary to take into account, in the adjustment of the position of the pads relative to the disc, the state of wear of these pads, failing which the defined clearance at rest between disc and the pads would not that increase depending on the wear of the latter.

The aforementioned means therefore do not only have the function of recalling the pads at a distance from the disc when the brake returns to its rest state, but also of catching up on the wear of these pads. The object of the invention is precisely to propose a simple and effective solution to the problem posed by the design of these means, in particular in disc brakes in which the caliper nose 41 and the external face 21 of the disc 2 adopt, in the direction T transverse to the disc 2, respective transverse positions which vary with respect to each other both according to whether the brake is in its actuation state or in its rest state, and according to the wear of the external plate 31, in other words as a function of the difference U between the thickness of this plate in the new state and its thickness at the instant considered.

As indicated above, these wear return and take-up means 6 must therefore guarantee at least that the external pad 31 and the external face 21 of the disc are, in the rest state of the brake, spaced apart from each other a distance D at least equal to a minimum clearance J (Figures 1, 2 and 4) to avoid the appearance of a residual torque, and at most equal to a maximum clearance L (Figure 5) to avoid too great dead travel of the brake pedal, regardless of the wear U of the external pad 31.

To perform this complex function, the invention provides a connecting piece 6, visible in FIGS. 2 to 9, this piece 6 having an outer edge 61 and an inner edge 62, distant from each other, the one adopts, in the transverse direction T, position linked to that of the stirrup nose 41 while its other edge adopts a transverse position linked to that of the external face 21 of the disc 2.

Furthermore, this connecting piece 6 chosen and dimensioned so as to present between external and internal edges 61 and 62, and in the transverse direction T, a limit capacity for elastic deformation of amplitude K at least equal to the minimum clearance J at most equal to the maximum clearance L, and a plastic deformation capacity of amplitude at least equal to the maximum authorized wear Umax of the external plate 31, that is to say at least equal to the maximum authorized difference between the thickness of the insert in new condition and its thickness at the time of its replacement by another new insert.

The invention is in particular usable on so-called "floating disc" brakes, in which the caliper nose 41 adopts a fixed transverse position relative to that of the hub 10 of the disc support 1, while the disc 2 adopts a variable transverse position relative to that of the hub 10 of the disc support 1.

In this case, as shown in FIGS. 2 to 9, the connecting piece 6 connects for example the hub 10 of the disc support 1 to the disc 2, the internal edge 62 of this piece 6 being linked to the hub 10 of the disc support 1 while its outer edge 61, which is radially distant from the inner edge 62, is linked to the disc 2.

The connecting piece 6 thus advantageously takes the form of an annular veil, and preferably a metallic veil.

In the case, illustrated in FIGS. 28, where the disc 2 is slidably mounted on the hub 10 of the disc support 1, the connecting piece 6 can be interposed between the disc 2 and the hub 10 of the disc support 1.

But in the case, illustrated in FIG. 9, where the disc support 1 comprises a sheet of stamped sheet metal connecting the hub 10 of the disc support 1 to the disc 2, the connecting piece 6 may simply be constituted by this sheet of stamped sheet metal, and therefore be an integral part of the disc support 1.

However, to allow local deformation of the connecting piece 6, the latter can then advantageously have a privileged deformation zone 60 where the stresses applied to this piece 6 are concentrated.

In all cases, it is preferable to fix the connecting piece 6 by its external and internal edges and 62 in such a way that it deforms at least partially by shearing.

Several operating states of the brake of the invention are illustrated in FIGS. 10 and 2 to 8.

Figure 2 shows the brake at rest and equipped with new pads.

In this state, the external plate 31 and the external face 21 of the disc 2 are separated from each other by a clearance J just sufficient to avoid the appearance of a residual braking torque.

When the brake is applied (FIG. 3), the external plate 31 is applied to the external face 21 of the disc 2.

The disappearance of the clearance J which this state generates results in an elastic deformation of the connecting piece 6, that is to say a spontaneously reversible deformation which disappears as soon as the brake ceases to be actuated, as shown in the figure 4.

The change of state constituted by the transition from the state illustrated in FIG. 2 to the state illustrated in FIG. 3 is represented, in the diagram in FIG. 10, by a displacement of the state coordinates E2 towards the coordinates state E3, these coordinates representing the deformation dX of the connecting piece 6 in the transverse direction T as a function of the force applied to this piece.

transition from the state illustrated in FIG. 3 to the state illustrated in FIG. 4 is represented, on the diagram of FIG. 10, by a displacement of state coordinates E3 towards the state coordinates E4, the latter being able, first approximation, to be confused with the state coordinates E2 insofar as the wear of the pads in a single brake application is infinitesimal, and therefore quite negligible.

After several hundred or thousands of brakes, the pads, and in particular the outer pad 31, show some wear U (FIG. 10), that is to say difference in thickness compared to its original thickness.

If, for whatever reason, the external plate 31 was then separated from the external face 21 of the disc 2 (FIG. 5) by a distance L substantially greater than the limit capacity for elastic deformation K of the connecting piece 6, the subsequent actuation of the brake would firstly cause elastic deformation of the connecting piece 6 up to its limit K, this situation being illustrated by FIG. 6 and by the state coordinates E6 in FIG. 10.

Then, the continuation of the relative approximation movement of the external plate 31 and the external face 21 of the disc 2 would cause plastic, that is to say permanent, deformation of the connecting piece 6 until the spacing L - K is filled, this situation being illustrated by FIG. 7 and by the state coordinates E7 of FIG. 10. Finally, after the release of the brake, the return of the latter to its rest state would be accompanied by an elastic relaxation of the connecting piece 6 which would thus travel, in the opposite direction, the stroke K traveled during its elastic deformation, this final situation being illustrated by FIG. 8 and by the state coordinates E8 of FIG. 10.

Under these conditions, it is clear that if one neglects the influence of possible parasitic phenomena such as in particular the elastic deformations of the stirrup nose 41, any wear of the external plate 31, even minimal, which leads to discard this plate of the external face 21 of the disc 2 by a distance greater than the limit capacity K of elastic deformation of the connecting piece 6, is gradually caught up by plastic deformation of this piece 6.

This is the reason why, in particular, the connecting piece 6 shown in FIG. 5 appears in this figure as having already undergone, with respect to the connecting piece illustrated in FIG. 2, a plastic deformation having made it possible to catch up the wear U (FIG. 10) of the plate 31.

As just described, the invention can also be seen as a method, usable in a brake comprising at least two friction elements 31, 21, in particular to compensate for wear U of one at least 31 of these two friction elements, and to maintain between these friction elements, in a state of rest of the brake, a spacing D between the lower and upper limits J, K.

The friction elements 31, 21, in this case constituted by the external pad and by the external disc face, are applied one against the other when the brake is placed in its actuated state.

moreover, this brake has mutually movable members, in this case constituted by the disc support 1 and by the disc 2, which, when the brake passes from one of its states to the other, undergo relative movement of amplitude. linked to the spacing D existing at rest between the friction elements 31, and in this case even of amplitude equal to spacing.

The method of the invention essentially comprises three operations.

The first operation consists in storing minimum quantity of energy in a deformable part, the occurrence consisting of the connecting part 6, by applying to this part, by means of the mutually movable members 1, 2, an elastic deformation of amplitude at least equal to a minimum amplitude, in this case equal to the lower limit J, each time that the friction elements 31, 21 are brought close to each other over a stroke comprised between the lower and upper limits J , L, when the brake changes from its rest state to its actuation state.

The second consists in limiting the energy stored in the deformable part 6 by applying to it, via the mutually movable members 1, 2, a plastic deformation as soon as the stroke on which the friction elements 31, 21 are brought together. one on the other, when the brake changes from its rest state to its actuation state, exceeds the upper limit L.

And the third operation consists in using the energy stored in the deformable part 6 to move one of the other friction elements 31, 21 during the passage of the brake from its actuation state to its rest state, the relaxation of the part 6 thus causing a mutual separation of friction elements 31, 21 between the lower and upper limits J and L.

As will be understood by one skilled in the art on reading the description above, the method of the invention does not require that the deformable part 6 be a homogeneous part, or even that it be constituted by a single piece.

In particular, this deformable part can have several elements chosen and arranged in such a way that at least one first of these elements has an essentially elastic behavior, and that at least one second of these elements has an essentially plastic behavior, elements being arranged in series vis-à-vis the force exerted on them by the movable members of the brake including the movement related to the spacing of the friction elements at rest.

When such a composite part is stressed by the movable members of the brake, the essentially elastic element is the first to undergo a significant deformation, the essentially plastic element being able, if necessary, to undergo only an elastic deformation of very slight amplitude.

The maximum value of the elastic deformation of the essentially elastic element is provided to fulfill the return function of the pads.

if, as a result of wear of the pads, the amplitude of movement of the movable members of the brake continues, the deformation of the elastic element reaches a value which corresponds to a force which the essentially plastic element can no longer resist, so that the latter element in turn undergoes deformation, in this case an essentially plastic deformation, which fulfills the function of compensating for wear of the pads and, incidentally, of the disc.

Claims (8)

CLAIMS. 1. Disc brake for a motor vehicle comprising at least one suspension element (S) fitted with a wheel (R), this brake comprising a disc support at least formed by a hub (10) intended to be made integral in rotation with the wheel (R), a disc (2) integral in rotation with the disc support (1) and having an external face (21) and an internal face (22), external (31) and internal brake pads kept fixed in rotation relative to the suspension element (S) and respectively turned towards the external and internal faces (21, 22) of the disc, a stirrup overlapping the disc (2) and intended to be connected to 1 suspension element (S), a jack connected to 1 stirrup (4), and wear return and take-up means (6), the external plate (31), the disc (2), and the internal plate (32) being housed in a stack between the cylinder (5) and a nose (41) of the stirrup, the cylinder (5) being selectively controlled to press this stack 31, 2, 32) against the caliper nose (41), in a direction (T) transverse to the disc, when the brake is in an actuated state, and to allow the pads (31, 32) to disengage respective faces 22) of the disc (2) when the brake is in a rest state, the caliper nose (41) and the external face (21) of the disc (2) adopting, in the transverse direction (T), respective transverse positions which vary one from the other both according to the brake in its actuation state or in rest state and as a function of wear of the external pad (31), measured by a loss of thickness of this plate (31) from a new state, and the wear take-up return means (6) being able to guarantee less that the external plate (31) and external face (21) of the disc (2) are , in the brake rest state, spaced from each other by a distance (D) at least equal to a minimum clearance (J) and at most equal to a 'maximum (L), independently of the wear of the external pad (31), characterized in that it comprises, as at least one of the wear return and take-up means (6), a connecting piece having an outer edge (61) and an inner edge distant from each other, one of these edges (61, 62) adopting a transverse position linked to that of the stirrup nose (41) and the other edge adopting a transverse position linked to that of the external face (21) of the disc (2), and in that the connecting piece has, between its external and internal edges (61, 62) in transverse direction (T ), a capacity limit elastic deformation of amplitude (K) at least minimum equal (J) and at most equal to the maximum clearance (L), and a capacity of plastic deformation of amplitude at least equal to a maximum authorized wear (Umax ) of the external plate (31). 2. Disc brake according to claim 1, characterized in that the caliper nose (41) adopts a fixed transverse position relative to that of the hub (10) of the disc support (1), in that the disc adopts a variable transverse position relative to that of the hub (10) of the disc support (1), and in that the connecting piece (6) connects the hub (10) disc support (1) to the disc (2), the internal edge of the connecting piece (6) being linked to the hub (10) of the disc support (1) and the external edge (61) of the connecting piece (6) being radially distant from the internal edge (62) and linked to the disc (2). 3. Disc brake according to any one of the preceding claims, characterized in that the connecting piece (6) essentially consists of an annular web. 4. Disc brake according to any one of the preceding claims, characterized in that the disc (2) is slidably mounted on the hub (10) of the disc support (1) and in that the connecting piece (6) is interposed between the disc (2) and the disc support hub (10) (1). 5. Disc brake according to any one of the preceding claims, characterized in that the connecting piece (6) is constituted by a sheet of pressed sheet metal which is part of the disc support (1). 6. Disc brake according to any one of the preceding claims, characterized in that the connecting piece (6) is metallic. 7. Disc brake according to any one of the preceding claims, characterized in that the connecting piece (6) is fixed by its internal external edges (61, 62) so as to deform at least partly by shearing. 8. A method usable in a brake comprising at least two friction elements (31, 21), in particular for compensating for wear (U) of at least one (31) of these two friction elements and maintaining between these friction elements, in a state of rest of the brake, a spacing between lower and upper limits K), these friction elements (31, 21) being applied one against the other in a state of actuation of the brake, the brake having first and second members (1, undergoing a relative movement, of amplitude linked to said spacing (D), when the brake passes from one of the states to the other, characterized in that it comprises operation consisting in storing a minimum quantity of energy in a deformable part (6) by applying to this deformable part (6), by means of the first and second members (1, 2), an elastic deformation of amplitude at least equal to a minimum amplitude (J ) whenever friction LEMENTS (31, 21) are moved towards one another over a stroke between the upper and lower limits K), during passage of the brake its rest state to its actuating state; an operation consisting in limiting the energy stored in the deformable part by applying to this deformable part, 'intermediate of the first and second members (1, 2), plastic deformation as soon as the stroke on which the friction elements are brought together one of the other, when the brake changes from its rest state to its actuation state, exceeds the upper limit (K); and an operation consisting in using the energy stored in the deformable part (6) to separate the friction elements (31, 21) from one another when the brake passes from its actuation state to its state of rest.