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EP-4374089-B1 - IMPROVED FILTERING PULLEY

EP4374089B1EP 4374089 B1EP4374089 B1EP 4374089B1EP-4374089-B1

Inventors

  • CARICCIA, GIANLUCA
  • GUALA, ANDREA
  • DELLE ROSE, Gilberto

Dates

Publication Date
20260506
Application Date
20220721

Claims (14)

  1. Filtering pulley (1) for an accessory transmission of an internal combustion engine, comprising a hub (2), an annular crown (3) provided with a profile configured to cooperate with a transmission belt (5), externally coaxial around an axis (A) to said hub (2) and supported in rotationally free motion on the hub (2) itself, and a filtering unit (4) for transmitting the torque interposed between said hub (2) and said crown (3) and comprising a torsion spring (11), a carrier (12) and a torque limiting joint (20), said torsion spring (11), said carrier (12) and said torque limiting joint (20) cooperating with each other to transmit a torque between said hub (2) and said crown (3), said pulley (1) comprising damping means (30) carried by a member integral with one of said hub (2) and said crown (3), said damping means (30) being configured to provide variable damping according to said torque,, comprising a sliding bearing (8) radially interposed between said hub (2) and said crown (3), characterized in that said damping means (30) being carried by said sliding bearing (8).
  2. Pulley according to Claim 1, in which said sliding bearing (8) is integrally carried by said hub (2).
  3. Pulley according to claim 1 or 2, wherein said hub (2) defines a flanged portion (2b) extending radially outward around part of said torsion spring (11), said sliding bearing (8) being carried by said flanged portion (2b).
  4. Pulley according to Claim 3, wherein said flanged portion (2b) defines a seat (32) passing through said flanged portion (2b), said damping means (30) comprising a projection (31) housed in said seat (32) and extending radially towards said torsion spring (11).
  5. Pulley according to Claim 4, wherein said projection (31) is radially spaced from said torsion spring (11) by a distance (H), said distance (H) being predetermined as a function of the torque from which said damping has to be applied.
  6. Pulley according to claim 4 or 5, in which said seat (32) and said projection (31) extend by an angle (γ) in a circumferential direction around said axis, said angle (γ) being predetermined as a function of damping to be imparted between said hub (2) and said crown (3).
  7. Pulley according to one of the preceding claims, in which said sliding bearing (8) is made of polymeric material and damping means (30) are made of one piece with said sliding bearing (8).
  8. Pulley according to any one of the preceding claims, wherein said carrier (12) cooperates by sliding with respect to a portion (7) integral with one between said hub (2) and said crown (3), said carrier (12) defining a spring holder (15) and a projection (17) extending along said axis (A) and configured to cooperate with said torque limiting joint (20), said torsion spring (11) being operatively interposed between said carrier (12) and said one between said hub (2) and said crown (3) and being provided with two ends cooperating in contact with respective spring holders (15) integral with said carrier (12) and said one between said hub (2) and said crown (3), said torque limiting joint (20) being torqued to interference on one surface (3") of the other between said crown (3) and said hub (2) said torque limiting joint (20) comprising an open loop ribbon spring (21) and being configured to slide with respect to said surface (3") when the torque transmitted between said crown (3) and said hub (2) reaches a predetermined level (T1, T2).
  9. Pulley according to claim 8, wherein said surface (3") is made on said crown (3), said carrier (12) slides with respect to said hub (2) and said spring (11) is operatively interposed between said carrier (12) and said hub (2).
  10. Pulley according to Claim 8 or 9, wherein said ribbon spring (21) defines a pair of axial projections (26) configured to cooperate selectively circumferentially in contact with respective axial projections (18) integral with said hub (2).
  11. Pulley according to Claim 10, wherein a free angle between said crown (3) is defined between said projections (26) or said seat of said ribbon spring (21) and said projections (18) of said crown (3) and said hub (2).
  12. Pulley according to one of claims 8 to 11, wherein said ribbon spring (21) defines an axial projection (25) extending on the opposite side to said pair of projections (26), said projection (25) being configured to cooperate in circumferential contact with said projection (17) of said carrier (12).
  13. Pulley according to one of claims 10 to 12, wherein said torque limiting joint (20) comprises an actuator member (28) housed in a space (22) circumferentially delimited between two ends (21', 21") of said ribbon spring (21), said actuator member (28) being axially dimensioned to cooperate in contact, on the one hand, with said projection (17) of said carrier (12) and, on the other, one of said projections (18) of said hub (2).
  14. Pulley according to one of claims 10 to 13, wherein said projections (18) are formed on said flanged portion (2b).

Description

Technical Field The present invention is related to a filtering pulley, in particular for a belt drive of an internal combustion engine for a motor vehicle. The present invention finds its preferred, although not exclusive, application in the drive pulley of an internal combustion engine alternator. Reference will be made to this application hereinafter by way of example, it being clear that the pulley of the invention can be used either as a driving pulley connected to the crankshaft or as a driven pulley for dragging any other accessory of the engine itself, e.g., a reversible electric machine with generator and motor function. State of Known Art In motor vehicles, the use a filtering pulley for dragging the alternator through the accessory transmission belt is known. This pulley comprises a hub adapted to be connected to the alternator rotor, an annular crown provided with a profile adapted to cooperate with the belt and a filtering unit interposed between the hub and the pulley crown to avoid exposing the belt to dynamic overloads in the presence of torsional vibrations of the crankshaft or rapid changes in the speed of the engine itself. The filtering unit generally comprises a spring, e.g., a helical or spiral spring, or a plurality of springs or other resilient members arranged circumferentially between the hub and the crown. Since the alternator has a relatively high equivalent inertia and tends to drag the pulley in the presence of immediate reductions in the crankshaft speed, it is known to incorporate in the filtering unit a free wheel adapted to transmit unidirectionally the motion of the crown to the hub (normal operating condition) but to decouple the hub from the crown in case of torque inversion. The introduction of start-stop systems in which a reversible electric machine is used having the function of starting motor or alternator depending on the operating conditions makes it impossible to use a filtering pulley with free wheel because this would decouple the electric machine from the belt transmission when it is a driving electric machine. To solve this problem, solutions in which the filtering unit comprises a spring constrained at ends thereof to respective members coupled respectively to the hub and to the pulley with a relative freedom of rotation of predetermined amplitude have been proposed. Examples of known solutions to this problem are illustrated in WO 2015/198277 A1, WO2012/061936 A1, DE102019112738 A1 or US2018/106355 A1. However, this solution is not yet sufficiently optimized to guarantee the desired technical performance. Also, this solution is radially and axially bulky. Therefore, the need to supply a filtering pulley usable both in a start-stop system and in a conventional transmission system is felt, which allows to solve the above-described problems of the known filtering pulleys. Another object of the present invention is to provide a filtering pulley which is compact and economical to produce. Summary of the Invention The above object is achieved by a pulley as claimed in the appended independent claims. Further preferred embodiments of the invention are implemented according to the dependent claims or connected to the aforementioned independent claims. Brief Description of the Drawings For a better understanding of the present invention, a preferred embodiment is described below, by way of non- limiting example, and with reference to the attached drawings in which: Fig. 1 is a longitudinal sectional view of a pulley according to the invention;Fig. 2 is an exploded perspective view of the pulley of Fig. 1;Figs. 3 and 4 are perspective views, respectively from different angles, of the pulley of Fig. 1 with parts removed for clarity;Figs. 5 and 6 are perspective views of respective members forming part of the pulley according to the invention;Fig. 7 is a graph representing the transmitted torque as a function of the relative rotation angle between two members of the pulley according to the invention. Detailed Description of the Invention With reference to Figs. 1 and 2, a pulley 1 essentially comprising a tubular hub 2, a tubular crown 3 externally coaxial to the hub 2 and supported in a rotationally free manner on the latter and a filtering unit 4 for transmitting the torque operationally interposed between the hub 2 and the crown 3 is illustrated. The hub 2 and the crown 3 are coaxial around a longitudinal axis A. The hub 2 is adapted to be rigidly fixed to a shaft, not shown, of an accessory member of an internal combustion engine, e.g., an alternator or a reversible electric machine with the function of alternator and starting motor in a start-stop system. In particular, the hub 2 comprises a tubular cylindrical portion 2a internally defining a coupling portion 2c with the aforementioned shaft between a first end 2a' and a second end 2a'' of the cylindrical portion 2a. The hub 2 also comprises a flanged portion 2b extending radially from one 2a'' of the end portion