FR3091243A1 - "Piston / screw-nut assembly for motorized actuator for disc brake" - Google Patents

Abstract

The invention relates to a piston (2) / screw (3) - nut (4) assembly for a motorized actuator (1) for disc brake, comprising: an actuating piston (2) for at least one disc brake pad, said piston (2) having a support housing (22) formed at the rear of the support face (21) of the piston (2), a screw (3)-nut (4) mechanism housed in the housing d support (22) of the piston (2) and intended to apply an axial clamping force on the actuating piston (2) from a rotary drive, the nut (4) being mounted fixed in rotation to the inside of the support housing (22) of the piston (2) and driven in axial translation in said support housing (22), the rotation drive of the screw (3) generating in one direction a stroke of the nut (4) towards and against the rear face (23) of the bearing face (21) of the piston (2) to apply an axial thrust force on said piston (2) and in the opposite direction a stroke to retract the nut (4) and stop its axial thrust on the piston ( 2). The invention consists in that characterized in that the support housing (22) of the piston (2) comprises an axial retaining means (5, 51) formed in radial projection in the support housing (22) and against which, during the withdrawal stroke, the nut (4) is brought into abutment to drive the piston (2) with it back. FIGURE 2

Description

Description

Title of the invention: "Piston / screw-nut assembly for motorized actuator for disc brake"

The invention relates to a piston / screw-nut assembly for a motorized, for example electric actuator, for a disc brake comprising

[0002] - an actuating piston for at least one disc brake pad, said piston having a support housing formed at the rear of the support face of the piston,

- a screw-nut mechanism housed in the piston support housing and intended to apply an axial clamping force on the actuating piston from a rotary drive,

The nut being mounted fixed in rotation inside the support housing of the piston and driven in axial translation in said support housing, the rotary drive of the screw generating in one direction a stroke of support of the nut towards and against the rear face of the support face of the piston to apply an axial thrust force on said piston and in the opposite direction a withdrawal stroke to retract the nut and stop its axial thrust on the piston,

Characterized in that the support housing of the piston comprises an axial retaining means formed in radial projection in the support housing and against which, during the withdrawal stroke, the nut is brought into abutment to drive the piston with him back.

The field of the invention is the automotive field and more particularly the piston / screw-nut assemblies of the electric actuators present in the brake assemblies comprising a piston for actuating at least one disc brake pad. The invention is particularly suitable for cooperating with any type of actuator. This type of assembly can be used in piston brake calipers.

State of the art

In a vehicle, in particular a road vehicle, the parking brake and / or emergency brake function consists in applying and maintaining a tightening of brake pads linked to a part integral with the chassis, on a mobile part in rotation which is linked to one or more wheels, typically a disc or a drum.

In brake assemblies using one or more electric actuators, it is known to use a screw-nut system to exert linear support on the pad, often by means of a piston. Such a configuration is for example described in the document FR2999257. This type of configuration exists for electrical operation alone, or in combination with a hydraulic actuation of this piston or another.

In Figure 1 is illustrated, in the case of a disc brake with hydraulic service braking and electric parking brake, a disc brake caliper 1 currently known, comprising a housing 11 enclosing a disc 19 and its tracks friction between friction linings or pads 17, 18. For example, in this assembly of the sliding caliper type, these elements are clamped against the fingers 101 of the caliper by a piston 13 moving in translation in a direction actuation A2. In service brake mode, this piston 13 is moved into its housing 150 by a hydraulic pressure supplied by a fluid inlet 15. This hydraulic pressure drives the piston in the direction of tightening of the shoe. The piston 13 has a peripheral seal 16 which, upon hydraulic actuation, forms a seal between the piston 13 and the housing of the piston 150.

In parking brake mode, the piston 13 is moved by a nut 122 fixed in rotation in the support housing 131 of the piston 13, cooperating with the rod or threaded shaft of a screw 121 driven in rotation according to the axis A2, the nut 122 and the screw 121 forming a linear parking actuator 12. The screw 121 is driven by an input shaft 129 driven by a geared motor (not shown).

To immobilize the nut 122 in rotation inside the piston 13, the nut 122 comprises a radial flange 123 of polygonal outline and the support housing 131 of the piston is delimited by a complementary polygonal wall. The nut 122 with its flange 123 is thus able to slide axially with clearance in the housing 131 of the piston 13 while being fixed in rotation in said housing 131.

When the threaded rod 121 is rotated by the gearmotor, the nut 122 therefore remains stationary in rotation in the support housing 131 of the piston and moves in translation along the threaded rod 121 in the direction of the rear support face of the piston, in a so-called support stroke so as to act on at least one brake shoe 17 by means of the piston 13 and apply to said shoe an axial tightening along the axis A2.

When the parking brake is released, the drive in rotation in the opposite direction of the screw 121 causes the axial drive of the nut 122 in the opposite direction in the housing 131 of the piston 13 according to a so-called withdrawal stroke . During the withdrawal stroke, the nut 122 ceases the axial tightening applied to the shoe 17 and moves away from said piston 13. However, even if the piston 13 is no longer tightened on the shoe 17, the seal 16 which has been compressed then plays a role of elastic return of the piston in return but with a lesser action than in the case of hydraulic pressure. As a result, the piston 13 ceases its axial force on the shoe 17 but is not driven by the travel of the nut 122 and therefore does not always return to a correct position, in particular with respect to the nut 122.

The object of the present invention is to overcome all or part of the drawbacks of the state of the art, and in particular to propose a piston / screw-nut assembly which makes it possible to limit the residual braking and allows correct relative positioning piston and nut when releasing the brake, for example parking.

Statement of the invention

To this end, the invention relates to a piston / screw-nut assembly for a motorized actuator, for example electric, for disc brake comprising

An actuating piston for at least one disc brake pad, said piston having a support housing provided at the rear of the support face of the piston,

- A screw-nut mechanism housed in the piston support housing and intended to apply an axial clamping force on the actuating piston from a rotary drive, the nut being mounted fixed in rotation at the interior of the piston support housing and can be driven in axial translation in said housing, the screw driving in rotation generating in one direction a support stroke of the nut towards and against the rear face of the face d support of the piston to apply an axial thrust force on said piston and in the opposite direction a withdrawal stroke to retract the nut and stop its axial thrust on the piston, characterized in that the support for the piston comprises a axial retaining means arranged in radial projection in the support housing and against which, during the withdrawal stroke, the nut is brought into abutment to drive the piston with it back.

Thus advantageously, when the nut abuts on the retaining means, this abutment causes a pushing effect of the nut against the retaining means, which drives the piston in translation in the direction of the nut withdrawal stroke and, therefore, in the direction of the disc brake pad piston spacing.

Thus, the abutment of the nut against the retaining means makes it possible to obtain the driving of the recessed piston and its repositioning in the housing under the effect of the nut.

The abutment of the nut against the retaining means provides a rearward repositioning of the piston in the housing under the effect of the nut.

More particularly, during a brake release command, the actuator is controlled in the direction of withdrawal over a stroke long enough for the nut to cause withdrawal of the piston.

If the friction pad is attached to the piston, the withdrawal of the piston actively takes off the pad from the friction track. Otherwise, the withdrawal of the piston gives the friction pad an additional clearance, which facilitates its removal and detachment from the friction track.

In all cases, the duration and / or the intensity of the residual friction between the pad and its track is reduced once braking is no longer required.

Advantageously, the retaining means against which the nut abuts allows to limit the withdrawal stroke of the nut in the housing and therefore, to position the nut in said support housing to a desired position defined by the axial retaining means from which the nut also drives the piston back.

According to one embodiment of the invention, the axial retaining means comprises at least one portion of annular ring protruding into the bearing housing of the piston and delimiting the position of the nut in said housing support from which the nut drives the piston back.

According to another embodiment, the retaining means consists of an annular ring integral with the wall of the support housing so as to project radially from said wall over its entire periphery.

Thus, preferably, the rod is a metal rod, preferably elastically deformable, fixed on the wall of the support housing so as to project radially from said wall.

The at least one portion of the rod or the rod forms an insert which is glued or welded or force-fitted on the internal wall of the support housing. For example, the rod is glued to the inner wall of the support housing.

According to an even more preferred embodiment, this axial retaining means is arranged to be able to be erased from the travel of the nut in the support housing under the effect of a thrust exerted by the nut which is greater than a threshold value, and this during its translational drive in the support housing. This erasure of the retaining means allows the passage of said nut, if necessary, for example in the event of disassembly for maintenance, also for assembly and the recalibration phases.

To this end, the annular ring is made of a metallic material, preferably elastic, is open and is housed in a groove formed in the wall of the support housing so as to protrude inward and encroach on the stroke of the nut, the groove having a housing for receiving the rod when the latter is moved aside and pushed back into said groove by the nut.

Preferably, the nut is in the form of a sleeve provided with a tapped internal bore in which the threaded rod or shaft of the screw is engaged.

The end of the nut intended to bear against the piston has a frustoconical shape, or has a chamfer, in order to bear on the rear face of the bearing face of the brake piston having a complementary shape .

The invention also relates to a vehicle brake comprising at least one piston / screw-nut assembly according to one or more of the preceding aspects, or including at least one actuator comprising a piston / screw-nut assembly according to the one or more of the foregoing.

According to another aspect of the invention, in accordance with one or more of the preceding aspects, there is provided a method for assembling a brake or a brake actuator comprising a piston / screw-nut assembly according to the invention, comprising the following steps:

- Providing a support nut, having a determined internal geometry;

- supply of a brake piston comprising a support housing arranged to receive a clamping force on the part of said support nut and having an anti-rotation shape of a determined geometry;

- Provision of a screw to drive in translation the support nut in the support housing

- Provision of an axial retaining means intended to be mounted in the support housing of the piston so as to be radially projecting in said housing and

- assembly of said retaining means, the piston, the support sleeve and the screw to form said assembly, the stroke of the nut being defined between the bearing end of the piston and the retaining means.

Description of the figures and embodiments

Other characteristics and advantages of the invention will appear on reading the detailed description of non-limiting embodiments, with reference to the appended figures in which:

[Fig.l] is a longitudinal sectional view along the axis of the piston, which illustrates a hydraulic disc brake caliper carrying a motorized parking brake actuator comprising a screw-nut mechanism, according to the prior art ;

[Fig.2] is a sectional view of a piston / screw-nut assembly of an actuator according to the invention in the active actuation position when tightening;

[Fig.3] is a sectional view of an assembly according to Figure 2 in the intermediate actuation position during removal;

[Fig.4] is a sectional view of an assembly according to Figure 2 in the inactive actuation position at the end of withdrawal;

[Fig.5A] is a sectional view of another embodiment of an assembly according to the invention with erasable retaining means upon withdrawal;

[Fig.5B] shows a sectional view according to Figure 5A, the retaining means being deleted; and

[Fig.6] shows a diagram representing the force developed as a function of the stroke of the nut of the piston / screw-nut assembly of the invention.

Description of the embodiments

The embodiments which will be described are in no way limiting; it will be possible in particular to implement variants of the invention comprising only a selection of characteristics described subsequently isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention from in the state of the prior art. This selection comprises at least one preferably functional characteristic without structural details, or with only a part of the structural details if this part only is sufficient to confer a technical advantage or to differentiate the invention from the state of the prior art.

In particular, all the variants and all the embodiments described can be combined with one another if nothing is opposed to this combination on the technical level.

In Figure 2 is illustrated a brake piston 2 for the brake caliper, the brake piston 2 being arranged and configured to be driven in translation by a screw-nut mechanism, from left to right (in the figure), or conversely, from a rotary drive, not shown. The brake piston 2 has a bearing face 21 designed to exert an axial force on a shoe which is intended to apply a brake disc (not shown), for example similar to that shown in FIG. 1 while at the 'rear of this support face 21 is provided a support housing 22. The brake piston 2 is immobilized in rotation relative to the brake housing surrounding said piston 2. The brake piston 2 thus comprises a support housing 22 arranged to receive axial support from the nut 4 and having an anti-rotation shape of a determined geometry comprising at least one rib formed in axial projection in the housing 22.

The screw-nut mechanism of the assembly of the invention is housed in the support housing 22 of the piston 2.

A rotary drive (not shown) is provided to rotate the screw 3 of the screw-nut mechanism, while the nut 4 of the screw-nut mechanism is immobilized in rotation in the support housing 22 of the piston 2 .

This nut 4 is therefore arranged and configured to move in translation in the support housing 22 of the piston 2 when the screw 3 is rotated.

According to a first direction of rotation of the screw 3, the nut 4 is driven in translation towards a rear support face 23 of the piston 3 to apply an axial thrust force in the direction of the axis Al, along a so-called support race. In the opposite direction of rotation, the nut 4 is driven in translation in the opposite direction and ceases to apply an axial force and moves away from the bearing face 23 according to a so-called withdrawal stroke.

The nut 4 is in the form of a cylindrical sleeve 41 having the form of a cylindrical tube whose internal threaded bore cooperates with the threaded shaft or rod 31 of the screw 3. The sleeve support 41 comprises a head having an axial support face 42 arranged and configured to bear against the rear support face 23 of the brake piston.

The bearing face of the sleeve 41 has the shape of a chamfer 42, preferably of revolution around the axis and for example conical or ovoid or spherical. The sleeve 41 is provided with an attached flange 43, for example by forced axial fitting, which protrudes radially and has on its periphery at least one notch 44 engaged in a rib protruding from the wall of the support housing 22, and in shape, for example, longitudinal.

When the threaded shaft 31 is rotated in order to apply the brake disc, the nut 4 is driven in translation towards the rear bearing face 23 of the brake piston 2 according to the arrow a. Once the bearing end 42 of the nut 4 in contact with the rear bearing face 23 of the brake piston 2 as can be seen in FIG. 2, the nut 4 exerts an axial thrust force against said face 23.

The bearing face 21 of the piston 2 then exerts an axial thrust force on a shoe (not shown) according to the arrow A.

To release the parking brake, the threaded shaft 31 of the screw 3 is rotated in the opposite direction so that the nut 4 is driven in translation in the opposite direction (arrow b) and ceases to exercise an axial thrust force on the piston 2. During this stroke back from the nut 4, the piston 2 also ceases its axial thrust force against the brake shoe.

The support housing 22 of the piston 2 further comprises an axial retaining means 5 protruding into said housing 22 and limiting the translational travel of withdrawal of the nut 4 in the housing 22.

Thus, during this race back from the nut 4, the radial flange 43 thereof abuts against the axial retaining means 5. This abutment then causes a thrust of the flange 43 according to the arrow b against the axial retaining means 5 and causes the retraction of the piston 2 with the nut 4, from the position shown in Figure 4 by the dotted line.

In this example, this retaining means consists of an annular ring 5 (ring) fixed on the internal wall of the support housing 22 of the piston 2 so as to project radially into said housing 22 and thus form an axial stop ring. This ring has a circular or oval section in this example, but could also have other shapes.

According to an alternative embodiment, shown in Figure 5A, the retaining means 51 is further configured to be mounted projecting in the support housing 22 of the piston 2 thus forming a stop for the nut 4 while being erasable from said support housing 22, to allow the passage of said nut 4 beyond the axial retaining means 51.

Indeed, it is advantageous for example during maintenance to be able to disassemble the screw-nut assembly out of the support housing 22.

To this end, the rod 51 constituting the retaining means is open and made of a deformable material, preferably elastically. It is housed in a groove 52 formed in the internal wall of the support housing 22. The rod 51 is housed in said groove 52 so as to project inward and encroach on the travel of the nut 4, the groove 52 having a receiving housing for the rod 51 when the latter is moved aside and pushed back into said groove 52 by the nut 4 (FIG. 5B).

Thus, when a thrust is exerted by the nut 4 on the rod 51 and exceeds a threshold value, for example during disassembly, a recalibration or assembly phase, the rod 51 open s 'clears in the empty space of the groove 52 to free the passage of the nut 4 and return to its original projecting position under the effect of its elasticity. Of course, the rod 51 can be erased in the other direction of travel of the nut 4.

The thick vertical line in Figure 6 represents the phase where the brake remains applied, for example the time of parking.

The left part of the curve represents strokes going in the direction of brake application (or forward), while the right part represents strokes going in the direction of brake release (or backwards) ).

When the parking brake is actuated using a piston / screw-nut assembly according to the invention, the drive in translation of the nut 4 is controlled from its inactive position shown in FIG. 2 by the rotary drive of the screw 3. This support stroke is thus represented by the portions a (approach stroke) and b (tightening stroke) of the curve shown in FIG. 6. As can be seen , the start of the stroke is made without exerting a push and corresponds to the approach stroke of the nut 4 towards the rear support face 23 of the piston 2. Once the support end 42 of the nut 4 in abutment against this face 23, as can be seen in FIG. 2, the continuation of the bearing stroke of the nut 4 generates the axial thrust against the piston 2 which then in turn exerts an axial thrust against a pad Clamping. This portion of the nut's stroke is represented by the portion b of the curve in FIG. 6, and can be qualified as a tightening stroke.

Once, the release of the controlled parking brake, the nut 4 is driven in translation in the opposite direction according to a withdrawal stroke by which the thrust exerted on the piston 2 decreases (portion c of the curve of the Figure 6, or loosening stroke) to a spacing of the support end 42 of the nut 4 of the rear support surface 23. Once the contact of the nut 4 and the rear face d support 23 of the broken piston, the recessed stroke of the nut 4 alone is represented by the portion d of the curve in FIG. 6.

This withdrawal stroke continues until the radial flange 43 of the nut 4 abuts against the retaining means 5 which generates a thrust force on the retaining means 5 as illustrated in portion e of the curve of FIG. 6, forming a retraction stroke of the piston 2. This effort ceases at the same time with the stopping of the drive in rear translation of the nut 4 (stopping the rotation of the screw 3 ) and the drive back of the piston 2 relative to the tightening of the shoe, which correctly reposition the nut 4 and the piston 2 relative to each other as well as the piston 2 relative to its position in the housing as shown the portion f of the curve in FIG. 6. The portion f of the curve represents an optional actuation in the direction of tightening, which is determined to reposition the nut 4, and preferably the piston 2, in a position where it is ready to re-tighten for new braking.

The assembly of the piston / screw-nut assembly will now be described. This assembly includes the following steps:

- Supply of a support nut, having a determined internal geometry;

- supply of a brake piston comprising a support housing arranged to receive a clamping force on the part of said support nut and having an anti-rotation shape of a determined geometry;

- provision of a screw to drive the support nut in translation in the support housing,

- Provision of an axial retaining means intended to be mounted in the support housing of the piston so as to be radially projecting in said housing and

- assembly of said retaining means, the piston, the nut and the screw to form an assembly according to the invention.

Of course, the invention is not limited to the examples which have just been described and numerous modifications can be made to these examples without departing from the scope of the invention.

Nomenclature

1 disc brake caliper

101 stirrup fingers

11 caliper housing

12 linear parking actuator

121 actuator screw

122 actuator nut

123 radial flange of the nut

129 input shaft of the actuator screw

13 brake piston

130 bearing face of the brake piston

131 brake piston support housing

15 hydraulic inlet

150 piston housing - hydraulic chamber

16 peripheral seal

17, 18 friction linings

19 brake disc - friction tracks

2 brake piston

21 support face of the piston

22 piston support housing

23 rear face of the support face

3 screws of the actuator

31 threaded shaft of the screw

[0102] 4 actuator nut

41 sleeve of the nut

42 support face of the nut

43 radial flange of the nut

44 notch in the collar

5 retaining means

51 rod

52 antlers

Al direction of actuation - axis of the brake piston and the nut device

A2 actuation direction - axis of the brake piston (prior art)

Claims (1)

Claims [Claim 1] Piston (2) / screw (3) - nut (4) assembly for motorized actuator (1) for disc brake comprising: an actuating piston (2) for at least one disc brake pad, said piston (2) having a support housing (22) formed at the rear of the support face (21) of the piston ( 2), - a screw (3) - nut (4) mechanism housed in the support housing (22) of the piston (2) and intended to apply an axial clamping force on the actuating piston (2) from a rotary drive, the nut (4) being mounted fixed in rotation inside the support housing (22) of the piston (2) and driven in axial translation in said support housing (22), the drive in rotation of the screw (3) generating in one direction a bearing stroke of the nut (4) towards and against the rear face (23) of the bearing face (21) of the piston (2) to apply an axial thrust force on said piston (2) and in the opposite direction a withdrawal stroke to retract the nut (4) and stop its axial thrust on the piston (2), characterized in that the bearing housing (22) of the piston ( 2) comprises an axial retaining means (5, 51) formed in radial projection in the support housing (22) and against which, during the withdrawal stroke, the nut (4) is brought into abutment to drive the piston (2) with him back. [Claim 2] Assembly according to claim 1, characterized in that the axial retaining means (5) comprises at least one portion of annular ring mounted in the bearing housing (22) of the piston (2) and delimiting the position of the nut ( 4) in said support housing (22) from which the nut (4) drives the piston (2) back. [Claim 3] Assembly according to either of Claims 1 and 2, characterized in that the axial retaining means (5) is an annular ring integral with the wall of the support housing (22) so as to project radially from said wall on all its periphery. [Claim 4] Assembly according to either of Claims 2 and 3, characterized in that the at least one portion of the rod or the rod forms an insert which is glued or welded or force-fitted on the internal wall of the support housing (22) . [Claim 5] An assembly according to claim 1, characterized in that the axial retaining means (5) is arranged to be able to be erased from the travel of the nut (4) in the support housing (22), under the effect of a thrust exerted by the nut (4) greater than a threshold value, during the drive in translation of the nut (4) in the support housing (22). [Claim 6] Assembly according to claim 5, characterized in that the annular ring (51) is made of a metallic material, preferably elastic, is open and is housed in a groove (52) formed in the wall of the support housing (22) so as to protrude inwards and encroach on the travel of the nut (4), the groove (52) having a receiving housing for the rod (51) when this is moved apart and pushed back into said groove (52) by the nut (4). [Claim 7] Assembly according to one of claims 1 to 6, characterized in that the brake piston (2) comprises a support housing (22) arranged to receive an axial support from the nut (4) and having a anti-rotation shape of a determined geometry comprising at least one rib formed in axial projection in the housing (22). [Claim 8] Assembly according to one of claims 1 to 6, characterized in that the nut (4) comprises a cylindrical sleeve (41) with a tapped internal bore in which is engaged the threaded shaft (31) of the screw, the sleeve (41) comprising an attached flange (43) projecting radially having on its periphery a notch (44) arranged to cooperate with the axial rib of the support housing (22), said flange (43) providing the stop means of the 'nut (4) against the axial retaining means (5) of the support housing (22) of the piston (2). [Claim 9] Vehicle brake, characterized in that it comprises at least one motorized actuator comprising a piston / screw-nut assembly according to one of the preceding claims. [Claim 10] Method for assembling a brake or a brake actuator comprising a piston / screw-nut assembly (10) according to any one of claims 1 to 9, characterized in that it comprises the following stages: - supply a support nut (4), having a determined internal geometry; -provision of a brake piston (2) comprising a support housing (22) arranged to receive a tightening force on the part of said support nut (4) and having an anti-rotation shape of a determined geometry ; - supply of a screw (3) to drive the support nut in translation (4) in the support housing (22), - Provision of an axial retaining means (5, 51) intended to be mounted in the support housing (22) of the piston (2) so as to be radially projecting in said housing (22) and - assembly of said retaining means (5, 51), of the piston (2), of the nut (4) and of the screw (3) to form said assembly.