Integrated pulley-torsional damper assembly

An integrated pulley-torsional damper assembly (1) comprises a hub (2) designed for being rigidly connected to a drive member (3), a pulley (4) connected to the hub (2) by means of a first ring (5) made of elastomeric material having the function of filter for the torsional oscillations, and an inertia ring (6), connected to the hub (2) by means of a second ring (7) made of elastomeric material, which defines with the inertia ring (6) a damping system. The first elastomeric ring is connected to the hub by mans of a coupling flange (25), which can be pack-tightened between an internal annular flange (10) of the hub and the drive member (3), the hub (2) comprising a first cylindrical wall (11) and a second cylindrical wall (12), which are coaxial with respect to one another and define between them an annular cavity (9) housing the first elastomeric ring (5), the external cylindrical wall (12) defining a support for the second elastomeric ring (7).

CROSS-REFERENCE TO OTHER APPLICATIONS

This is a National Phase of International Application No. PCT/IT2003/000432, filed on Jul. 10, 2003, which claims priority from Italian Patent Application No. T02002A000622, filed on Jul. 16, 2002.

TECHNICAL FIELD

The present invention relates to an integrated pulley-torsional damper assembly.

BACKGROUND ART

Integrated pulley-torsional damper assemblies are known, which comprise a hub designed for being rigidly connected to a drive member, for example the drive shaft of an internal-combustion engine, a pulley connected to the hub by means of a first ring made of elastomeric material having the function of filter for torsional oscillations, and a inertia ring, connected to the hub by means of a second ring made of elastomeric material, which defines with the inertia ring a damping system.

Integrated assemblies of the type described briefly above are used, for instance, in the automotive sector and are connected, at one end of the drive shaft of an internal-combustion engine, to enable driving, by means of a belt transmission, of auxiliary members of the engine, for example, an alternator, a fan and/or a compressor, and enable, at the same time, damping of the torsional oscillations of the drive shaft.

U.S. Pat. No. 5,637,041 discloses an integrated pulley-torsional damper assembly having the features of the preamble of claim1.

DISCLOSURE OF INVENTION

The purpose of the present invention is to provide an integrated pulley-damper assembly of an improved type, which has a particularly small number of components and presents contained axial dimensions.

The aforesaid purpose is achieved by an integrated pulley-torsional damper assembly as claimed in claim1.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to the figure, the number1designates, as a whole, a pulley-torsional damper assembly according to the present invention.

The assembly1comprises a hub2designed for being rigidly connected to a drive member3, for example, the drive shaft or a gear of the distribution rigidly constrained thereto, a pulley4angularly connected to the hub2by means of a first ring5made of elastomeric material (hereinafter referred to simply as “first elastomeric ring5”) having the function of filter for torsional oscillations, and a inertia ring6connected to the hub2by means of a second annular element7made of elastomeric material (hereinafter referred to simply as “second elastomeric ring7”), which defines with the inertia ring6a damping system.

In greater detail, the hub2is made of stamped sheet metal and comprises integrally an internal annular flange10designed for connection to the drive member3, an internal tubular wall11extending axially on the side opposite to the drive member3and co-operating radially with the second elastomeric ring7, an external tubular wall12, which is coaxial with respect to the internal tubular wall11, and an end wall13, which is plane, and connects integrally the tubular walls11and12together. The walls11,12and13form, as a whole, an annular coupling portion14of the hub2, which presents a substantially C-shaped cross section open on the side where the flange10is located and defines an annular cavity9.

The inertia ring6is mounted on the outer tubular wall12, with interposition in a forced way of the second elastomeric ring7, and is withheld on the aforesaid wall exclusively as a result of the friction generated by the radial compression of the second elastomeric ring7.

The pulley4, which is conveniently of the type having multiple grooves (poly-V type), is conveniently made of sheet metal by means of successive pressing and rolling operations and comprises integrally a substantially cylindrical peripheral crown15, which defines, on one of its outer surfaces, a plurality of V-shaped grooves16, which are symmetrical with respect to a median plane II, and an annular flange17, which extends integrally inwards from an axial end18of the crown15, which faces the drive member3.

The flange17basically comprises a plane outer annular portion19, an intermediate tubular wall20, which is coaxial with respect to the crown15and is internal thereto, and an inner annular flange21, which extends from an axial end of the tubular wall20opposite to the outer annular portion19. Conveniently, the flange21has a conical profile converging in the direction of the plane outer annular portion19towards the drive member3. The flange21is fitted to the first elastomeric ring5, with which it forms a single body. Conveniently, the first elastomeric ring5has an outer lip22, which adheres to the inner face of the tubular wall20of the flange17of the pulley4.

According to a preferred embodiment of the invention, the assembly1comprises a coupling flange25having the function of connecting the first elastomeric ring5to the hub2.

In greater detail, the coupling flange25comprises an inner annular wall26set so that it bears axially upon the flange10and of the hub2, and a conical annular edge27radiused to the inner annular wall26by means of a step-shaped portion28. The conical annular edge27is set facing the flange21of the pulley4, diverges outwards with respect to the latter, and is fitted to the first elastomeric ring5on the axially opposite side.

On account of the conicity of the flange21and of the annular edge27of the coupling flange25, the first elastomeric ring5has a substantially trapezoidal cross section, which diverges outwards. Connection of the pulley4and the coupling flange25to the first elastomeric ring5is obtained in a vulcanization mould (not illustrated). After vulcanization, the coupling flange25, the first elastomeric ring5, and the pulley4define a transmission member30in the form of a single body.

The first elastomeric ring5is made of a relatively “soft” elastomeric material, i.e., one with a sufficiently low modulus of elasticity. The resulting high torsional deformability enables “filtration” of the pulse-like variations of torque and resistant torque, thus providing a sort of “flexible coupling” between the drive member3and the pulley4.

The transmission member30is mounted on the coupling portion14of the hub2with interposition of a bushing34having the function of a radial and axial bearing for supporting the pulley4with respect to the hub2with a minimum friction between the two. In particular, the bushing34comprises integrally a tubular portion35, which is set radially between the outer tubular wall12of the hub2and the intermediate tubular wall20of the pulley4, and a flange36, which is set axially between the plane outer annular portion19of the flange17of the pulley4and a free edge of the outer tubular wall12of the hub2.

The bushing34is conveniently made of a plastic material having a low coefficient of friction, such as, for example, a fluoropolymer.

Once assembly is completed, the first elastomeric ring5is housed inside the cavity9of the coupling portion14of the hub2. In an altogether similar way, the second elastomeric ring7and the inertia ring6are housed inside the crown16of the pulley4. The assembly1is therefore particularly compact in the axial direction.

Installation of the assembly1on the drive member3is obtained by means of a single axial tap screw37, which pack-tightens the flange10of the hub2and the annular wall26of the coupling flange25, and is axially screwed into the drive member3.

In use, the pulley4is fitted rotationally to the hub2and to the drive member3by means of the first elastomeric ring5, which filters any lack of uniformity in the angular velocity of the drive shaft and filters any instantaneous variations of resistant torque. The inertia ring6and the second elastomeric ring7are sized, in terms of moment of inertia of the former and torsional elasticity of the latter, to obtain pre-set damping characteristics.

From an examination of the characteristics of the assembly1built according to the present invention, the advantages that the said invention enables emerge evidently.

In the first place, the arrangement of the hub2, of the pulley4and of the bushing34enables a reduction in the total number of components (seven in the example illustrated), as well as a simultaneous reduction of the axial dimensions.

Furthermore, the axial position of the pulley4is defined accurately and does not require the need for any subsequent machining operations once assembly is complete, since it depends upon a small combination of tolerances, which can be easily controlled during production. In particular, there are only four parameters subject to tolerance which condition the axial position of the grooves of the pulley, namely, the distance between the median plane M of the grooves16of the pulley4and the inner face of the plane outer annular portion19of the flange17of the pulley4, the thickness of the flange36of the bushing34, the distance between the free edge of the outer tubular wall12and the plane of the outer face of the flange10of the hub2, and the thickness of the coupling flange25.

Finally, the noise of the device is attenuated since the pulley4is “shielded” by the inertia ring6, which is not in rigid connection with the drive shaft and, hence, is isolated from any causes of forced oscillation.

A further advantage is represented by the fact that the bushing34, thanks to its arrangement, is protected from external agents (water, dirt).

Finally, it is clear that modifications and variations can be made to the integrated assembly1described herein, without thereby departing from the sphere of protection of the ensuing claims.