FR3068420A1 - ROTARY DEVICE EQUIPPED WITH A TARGET - Google Patents

Abstract

The invention relates to a device (1) for a motor vehicle transmission chain comprising: - a rotary element (3) intended to be mounted in rotation about an axis of rotation X, the rotary element (3) comprising a cylindrical skirt (8) of axial orientation; a target (2) intended to be arranged facing a sensor capable of delivering a signal representative of the angular position and / or the speed of the target (2), the target (2) being fixed on the element rotary device (3) and having an annular ring (17) which extends axially and is arranged circumferentially around the cylindrical skirt (8) of the rotary member (3), the annular ring (17) having fingers (18) which extend parallel to the X axis and separate from each other windows (19, 21) distributed about the X axis, each finger (18) having a distal end (20); and - a protection ring (22) which is fixed to the rotary element (3), said protective ring (22) comprising an internal bearing portion (23) positioned radially between the distal end (20) of the fingers (18) and the cylindrical skirt (8) so that the distal end (20) of each finger (20) is able to bear radially inwards on said internal bearing portion in order to limit the deformation of the annular ring (17).

Description

Rotary device equipped with a target

Technical area

The invention relates to the field of motor vehicle transmission chains and relates more particularly to a device of a motor vehicle transmission chain which is equipped with a target intended to be placed opposite a sensor.

Technological background

Document DE102008023869 discloses a primary flywheel of a double shock-absorbing flywheel equipped with a target. The target comprises a flange of radial orientation which is fixed against the cover of the primary flywheel and a plurality of fingers which extend axially from the external periphery of the flange, all around a cylindrical skirt of the primary flywheel. Thus, when the double damping flywheel is rotated, the fingers generate variations in the magnetic field capable of being detected by a sensor positioned opposite the target. Such a sensor is thus able to deliver a signal representative of the angular position and / or the speed of the target. The distal end of each of the fingers bears against an annular boss which projects radially outward from the cylindrical skirt of the primary flywheel. This prevents the fingers from deforming radially inward, for example when transporting the primary flywheel. However, such an arrangement is not entirely satisfactory. In particular, the formation of the annular boss on the cylindrical skirt of the primary flywheel requires a machining operation of the primary flywheel which is expensive, and all the more so if one wishes to obtain a radially external rib of the boss which is precise so to guarantee a suitable arrangement of the boss relative to the end of the fingers.

summary

One idea underlying the invention is to propose a device for a motor vehicle transmission chain, equipped with a target intended to be placed opposite a sensor which is simple to manufacture and in which the risks of deformation of the target are limited.

According to one embodiment, the invention provides a device for a motor vehicle transmission chain comprising:

- A rotary element intended to be mounted in rotation about an axis of rotation X, the rotary element comprising a cylindrical skirt of axial orientation;

a target intended to be placed opposite a sensor capable of delivering a signal representative of the angular position and / or of the speed of the target, the target being fixed on the rotary element and comprising an annular ring which extends axially and is arranged circumferentially around the cylindrical skirt of the rotary element, the annular ring having fingers which extend parallel to the X axis and separate from each other windows distributed around the X axis, each finger having a distal end; and

- a protective ring which is fixed to the rotary element, said protective ring comprising an internal support portion positioned radially between the distal end of the fingers and the cylindrical skirt so that the distal end of each finger is able to bear radially inwards on said internal support portion in order to limit the deformation of the annular ring.

Thus, the protection of the target's fingers is ensured by a protection ring which is separate from the rotary element, which facilitates the manufacture of the device.

According to other advantageous embodiments, such a device can have one or more of the following characteristics.

According to one embodiment, the distal ends of the fingers are in contact against the internal bearing portion of the protective ring.

According to another alternative embodiment, the distal ends of the fingers are radially separated from the internal support portion by a functional clearance less than a radial distance capable of causing plastic deformation of the fingers. This makes it easier to mount the target and / or the protective ring on the rotary element while limiting irreversible deformations of the annular ring. For example, the functional clearance is less than 1 mm, for example of the order of 0.5 mm.

According to one embodiment, the protective ring further comprises an external support portion, the internal and external support portions being respectively arranged radially on either side of the distal end of the fingers. This makes it possible to limit the radial deformations of the fingers in both directions.

According to one embodiment, the protective ring has a plurality of openings each receiving the distal end of one of the fingers, the external support portion and the internal support portion being respectively constituted by the external edges and the internal edges of the openings.

According to one embodiment, the openings are formed in a portion of radial orientation of the protective ring.

According to one embodiment, the protective ring has an axial orientation portion which extends in a direction opposite to the annular ring from a radially outer edge of the openings. This makes it possible to limit the radial size of the protection ring.

According to one embodiment, the protection ring further comprises an axial protection portion, which projects radially outward relative to the internal bearing portion and is arranged axially opposite the distal end of the fingers . Advantageously, the axial protective portion projects radially beyond the fingers.

According to one embodiment, the external support portion and the internal support portion are connected to each other by the axial protection portion.

According to one embodiment, the axial protection portion has a toothing intended for the rotary drive of the rotary element. In other words, the protective ring also performs a function of toothed ring intended for driving the rotary element in rotation, which makes it possible to limit the number of components of the device.

According to one embodiment, the protective ring is force-fitted into a shoulder formed in an edge of the cylindrical skirt.

According to another embodiment, the protective ring is fixed by welding or riveting on the rotary element.

According to one embodiment, the protective ring is obtained by bending a steel bar, welding its ends end-to-end and optionally by machining said bar.

According to another embodiment, the protective ring is a piece of stamped sheet metal.

According to one embodiment, the rotary element is a flywheel, such as a primary flywheel of a torsion damper.

According to one embodiment, the distal end of the fingers is welded to the protection ring. This makes it possible to limit the radial and circumferential deformations of the fingers.

According to one embodiment, the rotary element comprises a radial portion having an external periphery and the cylindrical skirt extends axially from the external periphery of the radial portion.

According to one embodiment, the target or the protective ring has a portion forming a cover which extends radially and is disposed against one end of the cylindrical skirt which is opposite to the radial portion of the rotary element, the portion forming cover defining, with the cylindrical skirt and the radial portion of the rotary element, an annular chamber.

Such an annular chamber can in particular be intended for housing elastic members when the device is a torsional damper. The elastic members can in particular be helical springs or elastic blades. Such elastic blades are fixed to one of the primary and secondary elements of the torsion damper and have a cam surface which cooperates with a cam follower associated with the other element. Such torsional dampers are described in particular in the documents FR3027986, FR3026801 and FR3032248.

According to a particular embodiment, the device further comprises:

- A web which is movable in rotation relative to the rotary element and which is axially interposed between the cover portion and the radial portion of the rotary element; and

- elastic members, such as helical springs, which are housed in the annular chamber and which are each interposed circumferentially between a support tab integral in rotation with the web and a support seat integral in rotation with the rotary element.

According to one embodiment, each support seat integral in rotation with the rotary element has two facing bosses, respectively formed in the radial portion of the rotary element and in the cover portion of the target or of the ring. protection.

According to one embodiment, the target is made of a metal sheet. Thus, the annular crown generates variations in magnetic fields capable of being detected. The metal sheet is for example steel.

According to one embodiment, the target comprises a flange which has a radial orientation, the annular ring extending axially from an external periphery of the flange, the distal end of the fingers being opposite to the flange.

According to one embodiment, the flange is fixed, for example by welding, against one end of the cylindrical skirt of the rotary element which is opposite to the radial portion of the rotary element. The flange thus forms a cover defining with the radial portion and the cylindrical skirt of the rotary element, an annular chamber.

According to one embodiment, the protection ring is made in one piece.

According to one embodiment, the protection ring is made in several segments. The realization of the protective ring in several segments makes it possible to reduce the quantity of sheet metal necessary for the manufacture of the protective ring.

According to another embodiment, the flange is fixed against the radial portion of the rotary element.

Brief description of the figures

The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely by way of illustration and without limitation. , with reference to the accompanying drawings.

- Figure 1 is a rear perspective view of a torsion damper equipped with a target and a protective ring according to a first embodiment.

- Figure 2 is a half sectional view of the torsional damper of Figure 1.

- Figure 3 is a perspective view of the target of the torsional damper of Figure 1.

- Figure 4 is a perspective view of the protection ring of the torsion damper of Figure 1.

- Figure 5 is a partial sectional view of a torsion damper equipped with a target and a protective ring according to a second embodiment.

- Figure 6 is a partial sectional view of a torsion damper equipped with a target and a protective ring according to a third embodiment.

- Figure 7 is a partial rear view in perspective of a torsion damper equipped with a target and a protective ring according to a fourth embodiment.

- Figure 8 is a sectional view of the torsion damper of Figure 7.

- Figure 9 is a partial rear view of a torsion damper equipped with a target and a protective ring according to a fifth embodiment.

-Figure 10 is a partial sectional view of the torsion damper of Figure 9.

- Figure 11 is a partial rear view of the torsion damper protection ring of Figures 9 and 10.

- Figure 12 is a partial sectional view of a torsion damper equipped with a target and a protective ring according to a sixth embodiment.

- Figure 13 is a partial sectional view of a torsion damper equipped with a target and a protective ring according to a seventh embodiment.

- Figure 14 is a partial sectional view of a torsion damper equipped with a target and a protective ring according to an eighth embodiment.

- Figure 15 is a partial sectional view of a torsion damper equipped with a target and a protective ring according to a ninth embodiment.

- Figure 16 is a partial sectional view of a torsion damper equipped with a target and a protective ring according to a tenth embodiment.

- Figure 17 is a partial sectional view of a torsion damper equipped with a target and a protective ring according to an eleventh embodiment.

- Figure 18 is a rear perspective view of a torsion damper equipped with a target and a protective ring according to a twelfth embodiment.

- Figure 19 is a front perspective view of the target of the torsion damper of Figure 18.

- Figure 20 is a half-sectional view of a torsion damper equipped with a target and a protective ring according to a twelfth embodiment.

- Figure 21 is a rear view of the torsion damper protection ring of Figure 20.

- Figure 22 is a partial sectional view of a torsion damper according to a fourteenth embodiment.

Detailed description of embodiments

In the description and the claims, the terms external and internal as well as the axial and radial orientations will be used to designate, according to the definitions given in the description, elements of the device. By convention, the radial orientation is directed orthogonally to the axis X of rotation of the device determining the axial orientation and, from the inside towards the outside while moving away from said axis, the circumferential orientation is directed orthogonally to the axis of the device and orthogonal to the radial direction. The terms external and internal are used to define the relative position of one element with respect to another, with reference to the axis X of rotation of the device, an element close to the axis is thus qualified as internal as opposed to an external element located radially on the periphery. Furthermore, the terms rear AR and front AV are used to define the relative position of one element with respect to another in the axial direction, an element intended to be placed close to the heat engine being designated by rear and an element intended to be placed close to the gearbox being designated by front.

In connection with FIGS. 1 and 2, there is a device 1 of a transmission chain which is equipped with a target 2 intended to be placed facing a sensor, not shown. The sensor makes it possible to deliver a signal representative of the angular position and / or of the speed of the target 2. Such a sensor is in particular capable of informing the vehicle computer of the crankshaft position, which allows the vehicle computer to control correctly injecting fuel and, for petrol engines, igniting the spark plugs.

In Figures 1 and 2, the device 1 is a torsional damper. This comprises a primary element 3 and a secondary element 4 which are mounted so as to be able to rotate relative to each other about the axis X. The torsion damper also comprises elastic members 5, illustrated in the Figure 2, which are arranged to transmit a torque and dampen the acyclisms of rotation between the primary element 2 and the secondary element 3.

The primary element 3 here is a primary flywheel intended to be fixed to the end of a crankshaft of an engine. As illustrated in FIG. 2, it comprises a hub 6, a radial portion 7 which extends radially outward from the hub 6 and a cylindrical skirt 8 of axial orientation which extends forward from the periphery external of the radial portion. The primary element 3 is provided with holes, illustrated in FIG. 1, allowing the passage of fixing screws, not illustrated, intended for fixing the primary element 3 on the crankshaft of the engine.

The primary element 3 also includes a cover 9, in particular illustrated in FIG. 2, fixed on the front end of the cylindrical skirt 8. The cover 9 defines, with the radial portion 7 and the cylindrical skirt 3, an annular chamber 10 in which are housed the elastic members 5. The elastic members 5 are, for example, curved coil springs which are circumferentially distributed around the axis X. Each of the elastic members 5 extends circumferentially between two support legs of a web 11 integral in rotation with the secondary element 4 and two support seats carried by the primary element 3.

Each support seat carried by the primary element 3 is, for example, constituted by two bosses 12, 13 which are respectively formed in the radial portion 7 of the primary element 3 and in the cover 9. The bosses 12 formed in the radial portion 7 of the primary element 3 are shown in FIG. 1 while the bosses 13 formed in the cover 9 are shown in FIG. 3.

Thus, in operation, each of the elastic members 5 is supported, at a first end, against a support seat carried by the primary element 3 and, at a second end, against a support lug, not shown, carried by the web 11, so as to ensure the transmission of the torque between the primary element 3 and the secondary element 4.

According to a variant embodiment not shown, the web 11 is not directly fixed to the secondary element 4 but is movable in rotation about the axis X relative to said secondary element 4. In this case, the torque is transmitted between the web 11 and the secondary element 4 by one or more additional stages of elastic members.

The secondary element 4 is here a secondary flywheel intended to form the reaction plate of a clutch, not shown, connected to the input shaft of a gearbox. The secondary element 4 is centered and guided on the primary element 3 by means of a bearing 14, such as a ball bearing, as shown in FIG. 2.

Furthermore, the primary element 3 is equipped with a ring gear 15 for the rotational drive of the primary element 3, using a starter. The ring gear 15 is here attached by welding against the front face of the cover

9.

The torsion damper is further equipped with a target 2 as shown in detail in Figure 3. The target 2 has a flange 16 which has a radial orientation. In the embodiment shown in Figure 2, the flange 16 is fixed against the front end of the cylindrical skirt 8 and forms the cover 9 of the primary element 3. The flange 16 thus comprises the bosses 13 which are each suitable to form, with a facing boss 12 formed in the radial portion 7 of the primary element 3, a support seat for the elastic members 5.

Furthermore, the target 2 comprises an annular ring 17 which extends axially towards the rear from the external periphery of the flange 16. The annular ring 17 comprises a plurality of fingers 18 which extend in the axial direction, parallel to the axis X and which are separated from each other by windows 19. In the embodiment shown, the distal ends 20 of the fingers 18 are free, that is to say are not connected to each other. However, in other embodiments, not shown, the annular ring 17 has a distal edge, opposite the flange 16, which has an annular shape and provides a connection between the distal ends 20 of the fingers 18.

Such a structure formed by alternating fingers 18 and windows 19 allows a sensor, which is fixed to the chassis of the vehicle and is positioned radially opposite the annular ring 17, to detect the position and / or the speed of target 17.

In an advantageous embodiment, the target 2 is made of a magnetic material. Target 2 is for example made of a metal sheet, preferably steel. In addition, the sensor is able to detect variations in magnetic fields. Such a sensor is for example an active hall effect sensor or a passive sensor. Thus, the alternation of fingers 18 and windows 19 of the annular ring 17 is capable of generating, when the target is rotated, a variation of the magnetic field which is detected by the sensor.

In another embodiment, the sensor is an optical sensor which detects the passage of a window 19 or a finger 18 in its optical field.

Advantageously, at least one of the windows, referenced 21 in FIGS. 1 and 3, has a circumferential dimension different from that of the other windows 19. Such a window 21 constitutes a mark making it possible to determine the angular position of the target 2 Alternatively, such a reference may also be formed by a finger 18 having a dimension in the circumferential direction greater than that of the others.

Furthermore, the torsion damper comprises a protective ring 22 which is fitted on the cylindrical skirt 8 of the primary element 3 and which aims to protect the annular ring 17, and more particularly its fingers 18 against deformations which would risk degrade the accuracy of the signal delivered by the sensor.

As shown in FIG. 2, the cylindrical skirt 8 has a shoulder, formed in the rear edge of said cylindrical skirt 8, and in which the protective ring 22 is mounted.

The protective ring 22 has an internal support portion 23 which is located radially inside the fingers 18, and more particularly between the distal end 20 of said fingers 18 and the cylindrical skirt 8.

According to one embodiment, the distal end 20 of each of the fingers 18 is in contact against the internal bearing portion 23 of the protective ring 22. This makes it possible to limit the deformation of the annular crown 17, and more particularly fingers 18, radially inward in the event of impact. However, such a structure requires a force assembly of the target 2 relative to the protective ring 22.

According to another alternative embodiment, each of the distal ends 20 of the fingers 18 is separated from the internal bearing portion 23 by a functional clearance less than a radial distance capable of causing plastic deformation of the fingers 18. The functional clearance is typically less than 1 mm, for example of the order of 0.5 mm.

Furthermore, the protective ring 22 also includes an axial protection portion 24. The axial protection portion 24 is here constituted by an annular bead which projects radially outward relative to the internal support portion 23 and which is located axially opposite the distal end 20 of the fingers 18. Thus, this axial protection portion 24 makes it possible to protect the fingers 18 against impacts in the axial direction. Advantageously, the external end of the axial protective portion 24 is located at a radial distance from the axis X equal to or greater than that of the external surface of the fingers 18.

According to one embodiment, the protective ring 22 is obtained by bending a steel bar so that its two ends can be welded end to end and then machining the steel bar thus bent.

According to one embodiment, the protective ring 22 is secured to the primary element 3 by tight fitting, for example by hot fitting, in the shoulder, formed in the rear edge of the cylindrical skirt 8.

In another embodiment shown in Figure 13, the protective ring 22 is welded to the primary element 3, for example, between the inner periphery of the protective ring 22 and the axial orientation surface of the 'shoulder formed in the cylindrical skirt 8 of the primary element 3.

Furthermore, according to another embodiment shown in FIG. 14, the distal end 20 of the fingers 18 is welded against the protective ring 22. Such a weld 26 thus makes it possible to limit the radial or circumferential deformations of the fingers 18. The weld 26 can be produced between the distal end 20 of the fingers 18 and the axial protective portion 24, as shown in FIG. 14, or between the distal end 20 of the fingers 18 and the internal support portion

23.

The embodiment of Figure 15, which does not represent the invention, is a degraded version of the embodiment of Figures 1 to 4. In this embodiment, the protective ring 22 does not include a portion of internal support 23 capable of protecting the fingers 18 against inward radial deformation and has only an axial orientation portion 24 which is located axially opposite the distal end 20 of the fingers 18 and which thus makes it possible to protect fingers 18 against impacts in the axial direction.

The embodiment of Figure 16 differs from the embodiment of Figures 1 to 4 in that the protective ring 22 has only an internal support portion 23 and no axial protection portion 24. If such protection ring 22 is simpler to manufacture, it does not ensure protection of the fingers 18 against impacts in the axial direction.

The embodiment of FIG. 22 differs from the embodiment of FIGS. 1 to 4 in that the protective ring 22 also performs the function of a toothed ring intended for driving in rotation the primary element 3 to the using a starter. In this case, the toothing 36 is formed in the axial protective portion 24 which projects radially outward relative to the internal bearing portion 12 and is thus located axially opposite the distal end 20 of the fingers 18 .

The embodiment shown in FIG. 5 differs from that described above in relation to FIGS. 1 to 4 in that the protective ring 22 also comprises an external support portion 25. The external support portion 25 is disposed radially outside the distal ends 20 of the fingers 18 so that said distal ends 20 of the fingers 18 are arranged radially between the external support portion 25 and the internal support portion 23. Thus, such a ring protection 22 makes it possible to limit the radial deformations of the fingers 18 in both directions, that is to say radially outward and radially inward. In the embodiment shown, the external support portion 25 projects radially forward from the axial protection portion 24. Such an external support portion 25 can, for example, be obtained by folding the radially external edge of the axial protection portion 24 or by machining the protection ring 22 so as to provide an annular housing, intended to receive the distal end 20 of the fingers 18, the housing being defined by the internal support portion 23, the axial protection portion 24 and the external support portion 25. The external support portion 25 makes it possible in particular to limit the deformation of the fingers 18 towards the outside under the effect of centrifugal forces during the rotation of the shock absorber .

The embodiment of Figure 6 differs in particular from that described above in connection with Figures 1 to 4 in that the protective ring 122 is here produced by stamping a metal sheet. The protective ring 122 comprises a first cylindrical portion 126 of axial orientation intended to be mounted on the axial orientation portion of the shoulder formed in the rear edge of the cylindrical skirt 8. The protection ring 122 also comprises a first radial orientation portion 127 which extends radially outward from the front end of the first cylindrical portion 126 and which abuts against the radial orientation surface of the shoulder formed in the edge rear of the cylindrical skirt 8. The protective ring 122 further comprises a second cylindrical portion of axial orientation. This second axial orientation portion 123 extends axially rearward from the outer edge of the first radial orientation portion 127. The second axial orientation portion 123 forms an internal support portion which is located radially at inside the fingers 18 and which makes it possible to limit the deformation of the fingers 18 radially inwards. Finally, the protective ring 122 comprises a second radial orientation portion 124 which projects radially outward from the rear end of the second axial orientation portion 123. This second radial orientation portion 124 forms the axial protection portion for protecting the fingers 18 against impacts in the axial direction. The protective ring 122 can be made in one piece or in several segments. The production of the protective ring 122 in several segments makes it possible to reduce the quantity of sheet metal necessary for the manufacture of the protective ring 122. The segments of the protective ring 122 can be fixed on the portion of axial orientation of the shoulder formed in the rear edge of the cylindrical skirt 8 by means of a weld.

Figures 7 and 8 show a torsional damper according to another embodiment. In this embodiment, the elements of the protective ring 222 identical or fulfilling the same function as those of FIG. 6 are referenced with the same number increased by 100. As in the embodiment of FIG. 6, the protection ring 222 is made of a metal sheet. In this embodiment, the protective ring 222 comprises a cylindrical portion of axial orientation 226 and a portion of radial orientation 227. The cylindrical portion of axial orientation 226 is intended to be mounted against the portion of axial orientation of the shoulder formed in the edge of the cylindrical skirt 8. The radial orientation portion 227 projects radially outward from the front end of the cylindrical portion of axial orientation 226 and abuts against the surface d 'radial orientation of the shoulder formed in the cylindrical skirt 8. The radial orientation portion 227 has a plurality of openings 229 each receiving the distal end 20 of a respective finger 18. Thus, as in the embodiment of FIG. 5, the distal ends 20 of the fingers 18 are arranged between an internal support portion 223 and an external support portion 225 which are respectively constituted by the internal edges of the openings 229 and by their external edges, which makes it possible to limit the radial deformations of the fingers in both directions. In addition, the circumferentially opposite edges of the openings make it possible to maintain an orientation of the fingers 18 parallel to the axis X.

In such an embodiment, the protective ring 222 can in particular be fixed to the primary element 3 by force fitting or by welding.

Figures 9, 10 and 11 show a torsional damper according to yet another embodiment. In this embodiment, the elements of the protective ring 322 identical or fulfilling the same function as those of FIGS. 7 and 8 are referenced with the same number increased by 100. In the embodiment of FIGS. 7 and 8, l the protective ring 322 comprises a radial orientation portion 327 having openings 329 in which the distal ends 20 of the fingers 18 are housed. However, in this embodiment, the radial orientation portion 327 is extended axially towards the rear by an axial orientation portion 332 from the radially external edge of the openings 329. Thus, such an arrangement allows this embodiment to have a more limited radial size than the previous embodiment of FIGS. 7 and 8.

Furthermore, in this embodiment, the protective ring 322 comprises a radial orientation fixing portion 330 which is pressed against the radial orientation portion 7 of the primary element 3 and which is fixed thereto. , for example by a weld 31. The radial orientation portion 327 and the radial orientation fixing portion 330 are here connected to each other by a substantially frustoconical portion 333.

The torsional damper of FIG. 12 differs from that described above in relation to FIGS. 9, 10 and 11 only in that the fixing portion 430 of the protective ring 422 is not secured to the primary element 3 by welding but by riveting. In this embodiment, the elements of the protective ring 422 identical or fulfilling the same function as those of FIGS. 7 and 8 are referenced with the same number increased by 100. The protective ring 422 is fixed on the element primary by means of rivets 34 which are formed in the mass of the primary element 3 and which pass through orifices formed in the fixing portion 430 of the protective ring 422. In another embodiment not shown, the rivets 34 are not formed in the mass of the primary element 3 and pass both through openings formed in the radial portion 7 of the primary element 3 and in the fixing portion 430 of the ring protection 422.

As in the embodiment of FIG. 6, the protective rings 222, 322 and 422 of the embodiments of FIGS. 7 and 8, 9 to 11, and 12 can be produced in several segments

Figures 17 to 19 illustrate a torsional damper according to another embodiment. In this embodiment, the axial positions of the target 2 and of the protective ring 522 are reversed with respect to their positioning of the embodiments described above. Thus, the protective ring 522 has a radial orientation portion 537 which forms the cover 9 of the primary element

3. The radial orientation portion 537 is fixed against the front edge of the cylindrical skirt 8. In addition, in such an embodiment, the internal radial orientation portion 537 has bosses, not shown, which are each suitable to form, with a facing boss 12 formed in the radial portion 7 of the primary element 3, a support seat for the elastic members 5.

The flange 16 of the target 2 is fixed against the radial orientation portion 7 of the primary element 3 and the annular ring 17 extends axially forward from the outer periphery of the flange 16. The flange 16 is fixed by riveting against the radial orientation portion 7 of the primary element 3. As shown in Figures 17 to 19, the flange 16 has holes 40 allowing the passage of rivets 39 through said flange However, the flange 16 can also be fixed to the primary element 3 by any other means. As in the previous embodiments, the annular ring 17 has a plurality of fingers 18 separated from each other by windows 19.

The protective ring 522 comprises an axial orientation portion 538 which extends rearwards from the outer periphery of the radial orientation portion 537. The axial orientation portion 538 is disposed around the cylindrical skirt 8 of the primary element 3. The rear end of the axial orientation portion 538 extends radially between the distal end 20 of each of the fingers 18 and the cylindrical skirt 8 of the primary element 3. The portion of axial orientation 538 thus forms an internal support portion 523 intended to limit the deformation of the fingers 18, radially inwards in the event of impacts.

Figures 20 and 21 illustrate a torsional damper according to another embodiment. In this embodiment, the elements of the protective ring 622 identical or fulfilling the same function as those of FIGS. 17 to 19 are referenced with the same number increased by 100. This embodiment differs from the embodiment of FIGS. 17 to 19 in that the protective ring 622 comprises at the rear end of the axial orientation portion 538 a radial orientation portion 641 which is equipped with openings 629 housing the distal ends 20 of the fingers 18 in a similar manner in the embodiment of Figure 8. Figure 21 illustrates in particular the bosses 613 which are formed in the radial orientation portion 637 of the protective ring 622 forming the cover 9 and which are each capable of forming, with a boss 12 facing arranged in the radial portion 7 of the primary element 3, a support seat for the elastic members 5.

As for the embodiment represented in FIG. 14, the protective ring 222, 322, 422 and 622 of the embodiments of FIGS. 7 and 8, 9 and 11, 12 and that of FIGS. 20 and 21, makes it possible to limit circumferential deformations of the fingers 18.

Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

In particular, if the invention has been described above in relation to a device of the torsion damper type, a target as described above can also be associated with other types of device, such as a flywheel , rigid or flexible, a torque converter or others.

The use of the verb "behave", "understand" or "include" and its conjugate forms do not exclude the presence of other elements or steps than those set out in a claim.

In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims (13)

1. Device (1) for a motor vehicle transmission chain comprising: - a rotary element (3) intended to be mounted in rotation about an axis of rotation X, the rotary element (3) comprising a cylindrical skirt (8) of axial orientation; - a target (2) intended to be placed opposite a sensor capable of delivering a signal representative of the angular position and / or of the speed of the target (2), the target (2) being fixed on the element rotary (3) and comprising an annular ring (17) which extends axially and is arranged circumferentially around the cylindrical skirt (8) of the rotary element (3), the annular ring (17) comprising fingers (18) which extend parallel to the X axis and separate from each other windows (19, 21) distributed around the X axis, each finger (18) having a distal end (20); and - a protection ring (22, 122, 222, 322, 422, 522, 622) which is fixed to the rotary element (3), said protection ring (22, 122, 222, 322, 422, 522, 622 ) comprising an internal support portion (23, 123, 223, 323, 423, 523, 623) positioned radially between the distal end (20) of the fingers (18) and the cylindrical skirt (8) so that the distal end (20) of each finger (20) is able to bear radially inwards on said internal support portion in order to limit the deformation of the annular crown (17). 2. Device according to claim 1, in which the distal ends (20) of the fingers (18) are in contact against the internal bearing portion (23, 123, 223, 323, 423, 523, 623) of the ring protective (22, 122, 222, 322, 422, 522, 622) or radially separated from the internal support portion by a functional clearance less than a radial distance capable of causing plastic deformation of the fingers (18). 3. Device according to claim 1 or 2, wherein the protective ring (22, 222, 322, 422, 622) further comprises an external support portion (25, 225, 325, 425, 625) the portions internal and external support being respectively arranged radially on either side of the distal end (20) of the fingers (18). 4. Device according to claim 3, wherein the protective ring (22, 222, 322, 422, 622) has a plurality of openings (229, 329, 429, 629) each receiving the distal end (20) of one of the fingers (18), the external support portion (225, 325, 425, 625) and the internal support portion (223, 323, 423, 623) being respectively constituted by the external edges and the internal edges of the openings (229, 329, 429, 629). 5. Device according to any one of claims 1 to 3, wherein the protective ring (22) further comprises an axial protective portion (24), which projects radially outward relative to the portion d internal support (23) and is disposed axially opposite the distal end (20) of the fingers (18). 6. Device according to claim 5 taken in combination with claim 3, wherein the external support portion (25) and the internal support portion (23) are connected to each other by the protective portion axial (24). 7. Device according to claim 5 or 6, wherein the axial protective portion (24) has a toothing (36) intended for driving in rotation the rotary element (3). 8. Device according to any one of claims 1 to 7, wherein the protective ring (22, 122, 222, 322, 422) is force fitted into a shoulder formed in an edge of the cylindrical skirt (8) . 9. Device according to any one of claims 1 to 8, wherein the protective ring (22, 322, 422) is fixed by welding or riveting on the rotary element (3). 10. Device according to any one of claims 1 to 9, in which the distal end (20) of the fingers (18) is welded to the protective ring (22). 11. Device according to any one of claims 1 to 10, in which the rotary element (3) comprises a radial portion (7) having an external periphery and in which the cylindrical skirt (8) extends axially from the periphery external of the radial portion (7). 12. Device according to claim 11, wherein the target (2) or the protective ring (522, 622) has a cover portion (16, 537, 637) which extends radially and is arranged against one end of the cylindrical skirt (8) which is opposite to the radial portion (7) of the rotary element (3), the cover portion (16, 537, 637) defining with the cylindrical skirt (8) and the radial portion (7 ) of the rotary element (3) an annular chamber (10). 13. Device according to claim 11, further comprising: - a web (11) which is rotatable with respect to the rotary element (3) and which is axially interposed between the cover portion (16, 537, 637) and the radial portion (7) of the element rotary (3); and - elastic members (15) which are housed in the annular chamber (5) and which are each interposed circumferentially between a support lug secured in rotation of the web (11) and a support seat secured in rotation of the element rotary (3).