Improved filter belt wheel

Abstract

A filter pulley (1) for an accessory transmission of an internal combustion engine, comprising a hub (2), a crown (3) and a torque-transmitting filter unit (4) interposed between the hub (2) and the crown (3), and comprising a torsion spring (21), a bracket (22) and a torque-limiting joint (25) comprising a belt spring (26) having an open ring shape, and is configured to slide on the crown (3) or the hub (2) when a given torque is reached.

Description

[0001] Cross-reference to related applications

[0002] This patent application claims priority to Italian Patent Application No. 102023000017880, filed on August 30, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to a filter pulley, and more particularly to a belt drive device for an internal combustion engine in a motor vehicle.

[0004] This invention is preferably, but not exclusively, applied to drive pulleys of internal combustion engine alternators. This application will be mentioned exemplarily below, but it will be apparent that the pulleys of this invention can be used as drive pulleys connected to the crankshaft, or as driven pulleys for driving any other engine accessory (e.g., a reversible motor with generator and electric motor functions). Background Technology

[0005] In motor vehicles, it is known to use a filter pulley to drive an alternator via an accessory drive belt.

[0006] The pulley includes a hub adapted to be connected to the alternator rotor, an annular crown with a profile adapted to cooperate with the belt, and a filter unit disposed between the hub and the crown of the pulley to prevent the belt from being subjected to dynamic overload under the condition of torsional vibration of the crankshaft or rapid changes in engine speed.

[0007] The filter unit generally includes springs, such as helical springs or spiral springs, or multiple springs or other elastic elements, which are arranged circumferentially between the hub and the crown.

[0008] Since alternators have relatively high equivalent inertia and tend to drive pulleys when there is a momentary decrease in crankshaft speed, it is known to introduce a freewheel in the filter unit. This freewheel is adapted to transmit the motion of the crown unidirectionally to the hub (in normal operation), but to separate the hub from the crown when the torque reverses.

[0009] With the introduction of start-stop systems, reversible motors are used as starter motors or alternators depending on operating conditions. Therefore, freewheels cannot be used as filter pulleys because they would separate the motor, which is the drive element, from the belt drive.

[0010] To address this problem, several solutions have been proposed, in which the filter unit includes a spring, with its two ends attached to corresponding elements connected to the hub and pulley, and has a certain degree of relative rotational freedom.

[0011] WO 2015 / 198277A1 illustrates examples of known solutions to the problem. However, these solutions have not been adequately optimized, especially in applications requiring the transmission of high torque (e.g., for heavy-duty vehicles), to guarantee the required technical performance.

[0012] Therefore, there is a need for a filter pulley that can be used in both start-stop systems and conventional drive systems, in order to address the problems associated with the known filter pulleys mentioned above.

[0013] Another object of the present invention is to provide a filter pulley with a compact structure and low production cost. Summary of the Invention

[0014] The above objective is achieved by the pulley claimed in the appended independent claims.

[0015] Other preferred embodiments of the invention are made according to the dependent claims or the claims relating to the above independent claims. Attached Figure Description

[0016] To better understand the present invention, preferred embodiments will be described below by way of non-limiting examples and with reference to the accompanying drawings, wherein:

[0017] Figure 1 This is a longitudinal sectional view of the pulley according to the present invention;

[0018] Figures 2A to 2B yes Figure 1 An exploded perspective view of the pulley; and

[0019] Figure 3 and Figure 4 They are shown from different angles. Figure 1 The pulley is shown in three-dimensional views under two different operating conditions, with components removed for clarity. Detailed Implementation

[0020] refer to Figure 1 As shown in Figure 2, pulley 1 mainly comprises a tubular hub 2, a tubular crown 3 externally coaxial with the hub 2 and rotatably supported on the hub 2, and a torque transmission filter unit 4 operatively inserted between the hub 2 and the crown 3. The hub 2 and the crown 3 are coaxial about the longitudinal axis A.

[0021] The hub 2 is adapted to be rigidly fixed to the shaft (not shown) of an accessory component of the internal combustion engine (e.g., an alternator in a start-stop system or a reversible motor that functions as both an alternator and a starter motor).

[0022] Specifically, the hub 2 includes a first part 2' and a second part 2'' that are rigidly connected to each other.

[0023] Specifically, the first portion 2' is configured to be coupled to the aforementioned shaft and includes a cylindrical portion 4 coaxial with axis A and a radial portion 5 extending radially from one end of the cylindrical portion relative to axis A and connected to the second portion 2''. The radial portion 5 advantageously defines an annular seat 6 configured to allow reception of a portion of the second portion 2'', thereby allowing it to be secured to the first portion 2', as described below.

[0024] The second part 2'' has a "mushroom-shaped" shape, including a cylindrical part 7 sized to fit into the seat 6 of the aforementioned radial part 5, and is engaged with the seat 6 by a mechanical connection, such as a key connection or a friction connection, thereby fixing the first part 2' and the second part 2'' together.

[0025] The second part 2'' also includes a flange portion 8 that extends from the cylindrical portion 7 and defines a "mushroom-shaped" profile that defines the annular seat 9 as described below.

[0026] Specifically, the flange portion 8 is provided with a first radial wall 8a, which extends radially from one end opposite to the first portion 2' relative to the axis A; a cylindrical wall 8b, which originates from the first radial wall 8a and extends parallel to the axis A away from the first radial wall 8a; a second radial wall 8c, which originates from the cylindrical wall 8b and extends on the opposite side of the first radial wall 8a; and a second cylindrical wall 8e, which originates from the second radial wall 8c and extends toward and parallel to the first radial wall 8b.

[0027] According to the above-described shape of flange 8, the annular seat 9 is radially defined on one side along the direction of axis A by a first cylindrical wall 8b and a second cylindrical wall 8d, and axially defined by a second radial wall 8c, while the other side is open.

[0028] The crown 3 mainly comprises a first annular portion 3a and a second annular portion 3b. Preferably, the diameter of the first annular portion 3a is smaller than that of the second annular portion 3b, and it is connected to the second annular portion 3b via a radial portion 3c.

[0029] Preferably, the first annular portion 3a radially surrounds the first portion 2' of the hub 2, while the second annular portion 3b radially surrounds the second portion 2'' of the hub 2.

[0030] Specifically, the first annular portion 3a defines a profile 3' having multiple grooves adapted to mate with a poly-V belt (the cross-section of which is schematically shown in...). Figure 1 (As shown in the image).

[0031] The wheel crown 3 is supported on the wheel hub 2 by a support device that is configured to allow free rotation between the wheel hub 2 and the wheel crown 3.

[0032] Specifically, pulley 1 includes rolling bearings 11, such as a pair of ball bearings, which are radially inserted between the first portion of the crown 3 and the first portion 2' of the hub 2. On the other hand, pulley 1 also includes sliding bearings 12, such as rings made of low-friction material, which are radially inserted between the second portion 3'' of the crown 3 and the second portion 2'' of the hub 2.

[0033] Specifically, the second part 3'' mainly includes a cylindrical wall that is connected to the first part 3a by a radial portion 3c and defines a space 13 that is radially defined by the aforementioned cylindrical wall and the second part 2'' of the hub 2, and is axially closed on one side by the flange portion 5 of the first part 2' of the hub 2 and on the opposite side by a cover 14, which is accommodated in an opening defined by the second part 3b of the crown 3.

[0034] The filter unit 4 is housed in the space 13 and mainly includes a torsion spring 21, a spring retainer element 22 (hereinafter referred to as the bracket) that cooperates with one end of the torsion spring 21, and a damping ring 23 that is axially inserted between the bracket 21, the hub 2 and the pulley 3.

[0035] Specifically, the bracket 22 slides in contact with the radial portions 5 and 3c of the hub 2 in the axial direction, and slides in contact with the inner surface of the cylindrical wall 3b.

[0036] like Figure 2A and Figure 2B As shown, preferably, the bracket 22 is annular and defines an annular wall 22' coaxial with axis A and a radial wall 22'' extending radially toward axis A from the axial edge of the annular portion 22'.

[0037] Similarly, the damping element 23 includes an annular wall 23' coaxial with axis A and a radial wall 23'' extending radially toward axis A from the axial edge of the annular wall 23', so as to engage with the annular wall 22' and the radial wall 22''. Specifically, the damping element 23 is coupled to the support 22 by friction or form coupling, and thus is integrally formed with the support 22 around axis A. Preferably, it is made of a polymer material.

[0038] As previously described, the radial wall 22'' on the first side slides into the wall and flange 4 of the crown 3, and defines an axial protrusion 22''' on the second side opposite to the first side. The axial protrusion 22''' is configured to engage with the spring 25.

[0039] In addition, the annular wall 22' also defines a pair of inner radial protrusions 24, which are preferably arranged opposite each other circumferentially along axis A and configured to cooperate with protrusion 5', which extends axially from the radial portion 5 of the hub 2 and is arranged opposite each other circumferentially around axis A.

[0040] The inner radial protrusion 24 is configured to engage with the protrusion 5' so as to selectively contact the bracket 22 according to its rotation about axis A, thereby restricting free rotation relative to the hub 2.

[0041] Spring 21 is preferably a helical spring having a circular cross-section steel wire and comprising multiple coils wound around axis A between the flange portion 8 of the second part 2'' of the bracket 22 and the hub 2. As described above, the end of spring 21 contacts and engages with the axial protrusion 22''' which serves as a spring retainer, while the opposite end contacts and engages with a corresponding spring retainer (not shown), which is preferably housed within an annular seat 9.

[0042] In detail, the size of the spring 21 is at least equal to the diameter of the multi-V profile 3', and in particular corresponds to the diameter of the first part 3a of the crown 3.

[0043] like Figure 2B , Figure 3 and Figure 4 As shown, the filter unit also includes a torque limiting connector 25, which mainly comprises a band spring 26 housed within the space 13 and is configured to simultaneously perform a freewheel function in two relative rotational directions between the crown 3 and the hub 2. Preferably, the freewheel effect is provided at different torque levels transmitted between the hub 2 and the crown 3 in one direction relative to the other.

[0044] Specifically, the torque limiting joint 25 is sized to engage with the hub 2 and bracket 22 to decouple from the crown 3. Specifically, the limiting joint 25 is received within space 13 and contacts the inner surface of the crown 3. Advantageously, in the contact portion, the inner surface of the crown 3 includes a machined area to increase friction between the band spring 26 and the crown 3. Specifically, this area is machined to define a "rib-like" groove / wavy surface, sized to allow a given frictional force between the band spring 26 and the crown 3.

[0045] More specifically, the band spring 26 has the shape of a generally open loop, with its two ends 26' and 26'' defining a space 27 between them. The band spring 21 has a substantially constant axial dimension over its entire circumferential extension and has a preferably rectangular cross-section.

[0046] However, one of the two ends 26'' defines at least one protrusion 31, 32. Specifically, according to the described embodiment,

[0047] - The first protrusion 31 extends circumferentially from end 26' toward the opposite end 26'' within space 27; and

[0048] - The second protrusion 32 extends axially along axis A from the axial edge of the strip spring 26 toward the bracket 22.

[0049] The axial dimension of the second protrusion 31 allows it to contact and engage with the bracket 12 in the circumferential direction, particularly axially on the inner side of the axial seat 33, which is obtained on the edge of the annular wall 22'. The axial seat extends axially and circumferentially around axis A at a given angle, preferably less than 90°, and particularly less than 45°.

[0050] Therefore, the axial seat 33 is defined by a pair of circumferential edges / walls.

[0051] In addition, the torque limiting joint 20 also includes an actuator element 34, which is housed in the space 28 and configured to engage with the bracket 22 in the axial seat 33 to increase or decrease the opening of the strip spring 25 when the actuator element contacts the aforementioned circumferential edge / wall, which serves as a stop.

[0052] Preferably, the actuator element 34 includes a metal rod received within the space 28 and circumferentially inserted between the ends 26', 26'' of the strip spring 26, configured to circumferentially contact and engage with the protrusion 31 and the ends 26'', and extending in the axial direction to circumferentially contact and engage within the axial seat 33.

[0053] Specifically, the rod of actuator element 34 has a trapezoidal shape, wherein the base of the trapezoidal shape is in the circumferential direction and the thickness is in the radial direction relative to axis A. Therefore, in particular, the rod includes a central portion having a generally rectangular shape and a pair of tapered sides that are preferably equal to each other.

[0054] Preferably, the inclination angle of the side portion relative to the center portion is between 20° and 40°, and more preferably 30°.

[0055] The operation of the pulley 1 according to the above embodiment of the present invention is as follows.

[0056] In the normal state, that is, when the wheel crown 3 driven by the belt 4 drives the wheel hub 2 and tends to overtake the wheel hub 2 ("drive mode"), the belt spring 26 rotates together with the wheel crown 3 and the wheel hub 2 is subjected to resistance.

[0057] Assuming that in the initial state, one side of the actuator 34 is in contact with the stop wall of the axial seat 33, then driven by the crown 3, the band spring 26 tends to move clockwise relative to axis A. The actuator 34 moves within the seat 18' until ( Figure 3 The protrusion 32 of spring 26 contacts the protrusion of the opposing stop of axial seat 33. From this state, actuator 34 will tilt ( Figure 4 Because it is pushed tangentially between portions 26' and 26'' by the thrust between protrusion 31 and the aforementioned stop, the opening increases, thereby increasing the adhesion between the latter and the inner surface of the crown 3. Thus, spring 21 is subjected to torsional load and transmits torque to the hub 2 attached to the opposing flange portion 8. If the torque transmitted by the crown 3 continues to increase, at some point, the strip spring 26 slides relative to the inner surface of the crown 3, losing the necessary adhesion, thereby decoupling the crown 3 from the hub 2.

[0058] Conversely, when the hub 2 tends to overtake the crown 3 ("overspeed"), the spring 26 will rotate with the crown 3 and generate resistance to the hub 2.

[0059] Assuming the decoupling condition described above, the crown 3 will rotate counterclockwise relative to the hub 2, thereby decoupling the actuator rod 34 from the stop defined by the seat 33. In this condition, the spring 11 will tend to unload, while the band spring 26 carried by the crown 3 will continue to rotate counterclockwise until the protrusion 32 contacts the opposing stop of the seat 33, thereby tending to close the band spring 26, which will then easily slide relative to the inner surface of the crown 3, thus decoupling the crown 3 from the hub 2.

[0060] If actuator 34 is not provided, the operation is similar, and under driving torque conditions, coupling occurs directly between the stop of protrusion 32 and seat 33.

[0061] In summary, the advantages of the pulley 1 according to the present invention are obvious.

[0062] Compared to known solutions that use freewheels, the present invention provides a torque limiting joint 20 that allows bidirectional coupling between the hub and the pulley, at least within a given torque range, thereby enabling the pulley to be used in a start-stop system.

[0063] Furthermore, compared to the described solution, the housing of the torsion spring 21 enables high torque transmission, allowing the pulley to function properly even in heavy-duty applications.

[0064] In particular, the dedicated housing is located in a space larger than the belt connection profile, which allows the use of torsion springs with larger diameters and smaller axial dimensions, thereby achieving high torque transmission in a significantly reduced space.

[0065] In addition, the trapezoidal shape of the actuator rod 34 has been specially optimized to ensure the opening of the spring 26 while ensuring sufficient structural strength.

[0066] Finally, it is obvious that modifications and substitutions can be made to the pulley 1 according to the present invention without exceeding the scope of protection defined by the claims.

[0067] Specifically, spring 26 can be connected to hub 2 instead of crown 3.

[0068] As mentioned earlier, if the adhesion between the spring 26 and the surface of the crown 3 (or hub 2) is sufficient to transmit the required torque in the "drive mode", the actuator element 34 can be omitted.

[0069] Obviously, the angle value of seat 34 can be varied according to the vehicle's transmission requirements.

[0070] The pulley can be used as a drive pulley on the crankshaft instead of a drive pulley on an alternator, or it can be used in a conventional alternator or any other accessory.

Claims

1. A filter pulley (1) for an accessory drive of an internal combustion engine, the filter pulley (1) comprising a hub (2), an annular crown (3) and a torque transmission filter unit (4), the annular crown (3) having a profile (3') configured to engage with a drive belt (V), the annular crown (3) being externally coaxial with the hub (2) about an axis (A) and supported on the hub itself in a freely rotatable manner, the torque transmission filter unit (4) being inserted between the hub (2) and the crown (3) and comprising a torsion spring (21), a bracket (22) and a torque limiting joint (25). The wheel crown (3) includes a first annular portion (3a) and a second annular portion (3b), the first annular portion (3a) defining the profile (3'), and the second annular portion (3b) defining a space (13) with the wheel hub (2), the space (13) being configured to accommodate the filter unit (4), the second annular portion (3b) having a larger diameter than the first annular portion (3a), such that the torsion spring (21) has a larger diameter than the connecting profile (3'). in, The hub includes a first portion (2') and a second portion (2''), the first portion (2'') being configured to be connected to the rotating shaft, and the second portion (2'') defining the space (13) together with the second annular portion (2b). The second part (2'') defines an annular seat (9) configured to support a first end of the spring (21), and the bracket (22) configured to support a second end of the spring (21), the bracket (22) engaging with a portion (5) integral with one of the first part (2') and the second part (2'').

2. The pulley according to claim 1, wherein the first annular portion (3a) is supported on the first portion (2') by a rolling support device (11).

3. The pulley according to claim 1 or 2, wherein the second annular portion (3b) is supported on the second portion (2'') by a sliding support device (12).

4. The pulley according to any one of the preceding claims, wherein the bracket (22) includes a radial wall (22'') that engages with the portion (5) by sliding, the radial wall (22'') defining at least one protrusion (24) extending radially inside the radial wall (22''), and the at least one protrusion being configured to engage with at least one projection (5') extending axially from the portion (5).

5. The pulley according to claim 4, comprising a pair of protrusions (24) and a pair of projections (5') that are angled relative to each other with respect to the axis (A).

6. The pulley according to any one of the preceding claims, wherein the bracket (22) includes an annular wall (22') defining an axial seat (33), and the torque limiting joint (25) includes a strip spring (26) having a first end (26') and a second end (26''), at least one of the first end (26') and the second end (26'') having a protrusion (32) configured to selectively engage with one of the circumferential edges of the axial seat (33).

7. The pulley according to claim 6, wherein the torque limiting joint (25) includes an actuator element (34) received within a circumferentially defined space (27) between the first end (26') and the second end (26'') of the strip spring (26), the actuator element (34) being axially sized to engage with one of the circumferential edges of the axial seat (33).

8. The pulley according to claim 7, wherein the actuator element (34) is a metal rod adapted to expand the spring (26) under the thrust of the circumferential edge of the axial seat (33).

9. The pulley according to claim 7 or 8, wherein one of the ends (26', 26'') defines a circumferential protrusion (31) that extends into the space (22) and is configured to engage with the actuator element (34).

10. The pulley according to any one of claims 8 to 9, wherein the actuator element (34) has a trapezoidal cross section, the base of the trapezoidal cross section being in the circumferential direction, and the thickness of the actuator element (34) being in the radial direction.

11. The pulley according to any one of the preceding claims further includes a damping ring (23) operatively inserted between the bracket (22) and the portion (5) integral with the hub (2), the damping ring (23) being configured to facilitate sliding of the bracket (22) relative to the portion (5).

12. The pulley according to any one of the preceding claims, including a cover (14) supported by the wheel crown (3) and configured to isolate the space (13) from the external environment.

Images