Cross-Reference to Related Applications

This Patent Application claims priority from Italian Patent Application No . 102022000015076 filed on July 18 , 2022 , the entire disclosure of which is incorporated herein by reference .

Technical Field

The present invention relates to a filtering pulley .

The present invention finds its preferred, although not exclusive , application in a pulley for a crankshaft in an accessory transmission of an internal combustion engine . This application will be referred to hereinafter by way of example .

State of the Prior Art

As is well known, the drive shaft in internal combustion engines is subj ect to torsional vibrations due to periodic stresses caused by combustion in the cylinders . These vibrations are particularly intense at start-up and at low engine speeds , as well as in the presence of particular construction solutions such as , for example , the use of dualclutch gearboxes or start-stop systems .

Torsional vibrations result in unevenness in the rotation of the drive pulley of the accessory transmission, which is transmitted to the accessories via the transmission belt , which is therefore subj ect to periodic tension variations .

In order to " filter" the torsional oscillations transmitted from the crankshaft to the belt , a filtering pulley provided with a hub integral with the drive shaft is generally used as the drive pulley, as well as a crown cooperating with the belt , and one or more elastic elements through which the drive torque is transmitted from the hub to the crown .

An example of construction of a known type of filtering pulley is illustrated in W02022053097 Al where the filtering pulley is provided with a vibration damper coupled to a filtering pulley actuator .

This construction is particularly expensive and, above all , af fects the ef fectiveness of the damping of the vibrations acting on the hub .

In addition, this construction is particularly complex, thereby increasing the cost of fitting and therefore of manufacturing the filtering pulley .

The purpose of the present invention is to provide a filtering pulley which solves the above technical problems in a simple and inexpensive way .

Summary of the Invention

The above purpose is achieved by means of a filtering pulley as claimed by the attached claims . Brief Description of the Drawings

For a better understanding of the present invention, a preferred embodiment is described below by way of nonlimiting example and with reference to the accompanying drawings , wherein :

• Figure 1 is a longitudinal sectional view of a filtering pulley according to the invention; and

• Figure 2 is an enlarged view of a portion of Figure 1 at a stage of its manufacture ; and

• Figure 3 is an enlarged view of the portion of Figure 1 .

Detailed Description of the Invention

The attached figures show a filtering pulley 1 comprising a hub 2 with an axis A, adapted to be connected to a shaft (not shown) , for example a crankshaft of an internal combustion engine , and an annular crown 3 externally coaxial with the hub 2 and supported in a rotationally free way on the hub 2 by support means 4 .

In particular, the crown 3 comprises an external annular portion 5 defining an internal radial surface , and an external surface defining at least one profile 5 ' adapted to cooperate with a mechanical transmission element , such as , for example , a poly-V belt (not shown) .

The hub 2 essentially comprises a tubular portion 7 and a flanged portion 6. The tubular portion 7 is configured to allow connection to the rotating shaft while the flanged portion 6 is rigidly carried by the tubular portion 7 and configured to support the crown 4 through the support means 3 .

In detail , the flanged portion 6 comprises an inner cylindrical portion 6a and an outer cylindrical portion 6b radially spaced apart and connected by a radial portion 6c . The flanged portion 6 also comprises a lower end portion 6d and an upper end portion 6e extending radially from respective ends o f the inner and outer cylindrical portions 6a, 6b on the side opposite the radial portion 6c .

The tubular portion 7 essentially comprises a cylindrical main portion 7 ' cooperating in contact with the inner cylindrical portion 6a and an end portion 7 ' ' described in detail below .

The pulley 1 further comprises a filtering group 8 which is operatively interposed in the radial direction between the crown 3 and the hub 2 .

In particular, according to the invention, the filtering group 8 comprises a housing 9 integral with the crown 3 and cooperating in contact with the inner radial surface and defining a space 11 , f iltering means 12 movably housed inside the space 11 , and actuator means 13 configured to cooperate in contact with the filtering means 12 inside the space 11 to selectively transmit torque between the hub 2 and the crown 3 .

The housing 9 comprises a cup element 15 comprising an annular wall 16 configured to cooperate in contact with the inner surface of the annular portion 5 of the crown 3 , and a radial wall 17 extending cantilevered from one end of the annular portion 16 . Advantageously, these walls of the cup element 15 are made in one piece .

The crown 3 further comprises a radial wall 18 extending from the outer annular wall 5 on the side opposite the cup element 5 , and an inner annular wall 19 extending radially from the inner radial end of the radial wall 18 .

The support means 4 mentioned above are advantageously interposed between the inner annular wall 19 of the crown 3 and the outer cyl indrical portion 6b of the flanged portion 6 . Advantageously, these support means are made as a bushing, preferably a cylindrical bushing .

The cup element 15 and/or the crown 3 finally comprise two diametrically opposite proj ections 20 extending axially inside the space 11 ; in the case described, the proj ections 20 extend along the axis A from the walls 17 of the cup element 18 and of the crown 3 . The proj ections 20 divide the space 11 into two portions circumferentially delimited by the proj ections 20 and radially delimited by the walls 17 , 18 .

The proj ections 20 are fixedly carried by the respective walls or, alternatively, made in one piece therewith .

As shown, the filtering means 12 comprise at least one elastic group 21 arranged circumferentially free in the respective above-mentioned portions of the space 11 .

Each elastic group 21 , in the embodiment shown, comprises a spring, advantageously a helical spring, configured to slide in the space 11 . In particular, springcarrying elements can be provided to assist this movement , not further described herein for the sake of brevity .

Advantageously, the actuator means 13 comprise a disc actuator 23 , comprising, in the case illustrated, two spokes 24 free to move circumferentially in the space 11 and adapted to interact with the filtering means 12 .

Preferably, the stroke of the elastic groups 21 in the respective portions of the space 11 can be given by an angular clearance between each of the elastic groups 21 arranged in contact with one and the other of the proj ections 20 .

Similarly, the spokes 24 can be spaced by an angular clearance in relation to the elastic groups 21 , which adds to the above-mentioned angular clearance during the operation of the pulley 1 as described for example in EP3271616 Al and not further reported for the sake of brevity .

The pulley 1 comprises an inertial damper 25 essentially comprising a support element 26 and an inertia ring 27 connected by a damping ring 28, as known per se.

In particular, the support element 26 comprises an outer annular portion 26a configured to support, on one side, the damping ring 27, a radial portion 26b extending from one end of the outer annular portion 26a on the side opposite the crown 3, an inner annular portion 26c extending axially on the side opposite the outer annular portion 26a from the radial portion 26b, and an end portion 26d extending radially from one end of the outer annular portion 26a on the side opposite the radial portion 26b.

As better visible in Figure 2, the end portion 7' ' exclusively cooperates in radial contact with the disc 23 and the end wall 26d of the damper 25.

In particular, the end portion defines a first radial surface 7a'' and a second radial surface 7b' ' , which are configured to cooperate radially in contact with the actuator means 13, i.e., the disc 23, and the damper 25, i.e., the end wall 26d, respectively.

In particular, the first radial surface 7a'' is located radially farther from the axis A than the second radial surface 7b' ' . In greater detail, both radial surfaces are substantially cylindrical and therefore the first radial surface 7a'' has a greater radius than the radial surface 7b' ' . Advantageously, both radial surfaces have a smaller radius than the tubular portion 7' of the hub 2.

The actuator means 13 and the damper 25 are rigidly carried by the tubular portion 7' through a mechanical coupling 30. In particular, the mechanical coupling 30 comprises a pivot element 32, such as a pin, or a threaded element configured to fit into openings 31' , 31' ' , 31' ' ' made in the tubular portion 7', in the disc 23 of the actuator means 13, and in the portion 26d of the damper 25.

Advantageously, the end portion 3' ' comprises an appendage portion 3’ ’ ’ which, during machining (Figure 2) , extends axially along the axis A beyond the end portion 7' ’ . The appendage portion 3’ ’ ’ is sized to be reshaped within a seat 26e defined in an inner radial portion of the end portion 26d.

In particular, the appendage portion 3’ ’ ’ , once reshaped (Figure 3) , extends within the seat 26e in order to further axially keep the support element 26 in contact with the end portion 7' ' without protruding from the plane defined by the axial surface of the end portion 26d of the support element 26.

The pulley 1 further comprises sealing means 40 configured to be operatively interposed between the crown 3 and the hub 2, in particular between the radial wall 18 and the end wall 6e of the flanged portion 6, to prevent the passage of foreign elements towards the support means 4. In particular, these sealing means 40 comprise a preferably labyrinthine dust protection lip clamped in the axial direction along the axis A between the aforementioned walls .

On the other side , the pulley 1 comprises sealing and damping means 50 configured to isolate the space 11 and provide an axial force to provide a damping between the hub 2 and the crown 3 .

In particular, these sealing and damping means 50 essentially comprise an advantageously labyrinthine dust protection lip 51 cooperating in contact with the lower radial end of the radial wall 17 of the housing 15 , and a cup spring 52 interposed between the damper 25 and the dust protection lip 51 in order to keep it in contact with the housing 15 .

In particular, the sealing and damping means 50 comprise a support element 53 , for example a ring, fitted on the wall 26c of the damper 25 and configured to provide support to one end of the cup spring 52 oppos ite the end cooperating with the dust protection lip 51 .

The operation of the pulley 1 according to the invention is described below .

In a first phase of operation, called "driving mode" and constituting the normal operation of the pulley 1 , when the drive shaft drags the accessories , the speed of the hub 2 tends to exceed the speed of the crown 3 . For this reason, the spokes 24 transmit torque to the proj ections 20 with the interposition of the respective elastic groups 21 .

The above occurs symmetrically in the "overrunning" condition, i . e . , when the speed of the crown 3 tends to exceed the speed of the hub 2 .

In both operating conditions , the sealing means 40 and 50 damp down the free rotation ensured by the support means 4 between the hub 2 and the crown 3 and prevent dirt from entering the space 11 .

This damping is also provided by the passage of oil contained in the space 11 and passing through the elastic groups 21 .

I f the free angles a, p are present , there will be a free rotation angle between the hub 2 and the crown 3 , so no torque is transmitted despite the relative rotation between these two elements . This free rotation angle is the sum of the free angles a, p .

In fact , at first the spoke 31 begins to idle until the elastic groups 21 meet the respective proj ection 20 so that they begin to compress , transmitting torque .

Therefore , the advantages of a pulley 1 according to the invention are clear .

The end portion 7 ' of the hub 2 allows easy centering of the actuator means 13 and damper 25 , making the assembly easier .

Furthermore , the speci fic assembly via the mechanical connection 30 , in addition to further ensuring correct centering, is particularly compact and robust .

The use of a flanged portion allows the tipping loads acting on the hub to be further reduced as well as it reduces the volume of the space 11 , thus allowing the definition of a chamber that keeps the elastic means 21 in motion, preventing them from developing bumps or noises .

Additionally, the appendage portion 7 ’ ’ ’ reshaped in a seat 26e further allows the support element 26 and the actuator 23 to be kept in a package .

Moreover, the use of sealing means 40 , 50 allows the contamination of the space 11 to be reduced while providing a damping between the hub and the crown .

In addition, a variable-amplitude angular clearance may be present between the spoke and/or proj ections and the elastic groups , the angular clearance being configured to provide a dead angle between the hub and the crown of variable amplitude according to the di f ferent filtering requirements .

Lastly, it is clear that modifications and variations may be made to the pulley described herein without departing from the scope of protection defined by the claims .

First of all , the pulley could be used not only on the crankshaft of an internal combustion engine but for one of its accessories.

With reference to the elastic group 21, it may be made in different shapes without however changing its function. For example, it may include springs of different nature or multiple springs, either in series or in parallel. Furthermore, the elastic groups could be four, like the spokes of the actuator.

Furthermore, the angular values a, p could be absent or have different amplitudes depending on the dynamic torsional behaviour of the drive shaft in the specific application.

Furthermore, the mechanical connection 30 could be made differently, just as the relative distance between the radial surfaces 7a'' , 7b' ' of the end portion of the hub could be different.

Furthermore, the damper could be of any type, such as a viscous damper.