Improved filter pulley

Abstract

A filter pulley (1) for an accessory drive of an internal combustion engine, comprising a hub (2), a crown (3) and a filter unit (4) for transmitting torque, the filter unit (4) being interposed between the hub (2) and the crown (3) and comprising a torsion spring (11), a carrier (12) and a torque limiting joint (20), the torque limiting joint (20) comprising an open loop strip spring (21) and being configured to slide with respect to said surface (3") when the torque transmitted between the crown (3) and the hub (2) reaches a predetermined level (T1, T2).

Description

[0001] Cross-references to related applications

[0002] This patent application claims priority to Italian Patent Application No. 102021000025901, filed on October 8, 2021, the entire disclosure of which is incorporated herein by reference. Technical Field

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

[0004] A preferred application of the invention is as a drive pulley for an alternator in an internal combustion engine, although this is not the only application. This application will be illustrated by examples below, but it should be understood that the pulley of the invention can be used as a drive pulley connected to the engine shaft, or itself as a driven pulley for any other accessory used to drive the engine, such as a reversible electric motor that functions as both a generator and a motor. Background Technology

[0005] In motor vehicles, it is known to use filter pulleys to drive alternators by using accessory drive belts.

[0006] The pulley includes a hub designed to connect to the rotor of an alternator; an annular crown with a profile designed to mate with the belt; and a filter unit inserted between the hub and the crown of the pulley to prevent the belt from being dynamically overloaded when there is torsional vibration of the engine shaft or rapid changes in the speed of the engine itself.

[0007] Filter units typically include springs, such as helical springs or coil springs, or multiple springs or other elastic elements arranged circumferentially between the hub and the crown.

[0008] Because alternators have high equivalent inertia and tend to drive pulleys when the instantaneous speed of the engine shaft decreases, it is known to incorporate a freewheel in the filter unit. The freewheel is designed to transmit the movement of the crown to the hub in one direction (normal operating state), but if the torque is reversed, it will disengage the hub from the crown.

[0009] A start-stop system is introduced, in which a reversible electric motor with drive motor or alternator functions is used depending on the operating state. This makes it impossible to use a filter pulley with a freewheel, as this would disengage the electric motor from the belt drive during operation.

[0010] To address this problem, several solutions have been proposed, in which the filter unit includes a spring attached at its end to corresponding elements connected to the hub and pulley respectively, having a predetermined width of relative rotational freedom.

[0011] An example of a known solution to this problem is shown in WO30 / 2015 / 198277. In any case, this solution is not optimized sufficiently to ensure the desired technical performance. Furthermore, this solution has a large volume in both the radial and axial directions.

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

[0013] Another object of the present invention is to produce a filter pulley that is both compact and low in manufacturing cost. Summary of the Invention

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

[0015] Furthermore, preferred embodiments of the present invention are constructed according to dependent claims or claims related to the above independent claims. Attached Figure Description

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

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

[0018] Figure 2 yes Figure 1 An exploded 3D view of the pulley in the middle;

[0019] Figure 3 and Figure 4 They are Figure 1 The image shows a three-dimensional view of the pulley from different angles, with some parts removed for clarity; and

[0020] Figure 5 and Figure 6 This is a perspective view of a corresponding element that is part of the pulley according to the invention. Detailed Implementation

[0021] Reference Figure 1 and Figure 2 The diagram shows a pulley 1, which essentially comprises a tubular hub 2; a tubular crown 3 externally coaxial with and supported on the hub 2, allowing it to rotate freely on the latter; and a filter unit 4 for transmitting torque, operably inserted between the hub 2 and the crown 3. The hub 2 and the crown 3 are coaxial about a longitudinal axis A.

[0022] The hub 2 is designed to be rigidly fixed to the shaft (not shown) of an accessory component of the internal combustion engine, such as an alternator or a reversible electric motor that functions as both an alternator and a drive motor in a start-stop system.

[0023] Specifically, the hub 2 includes a tubular cylindrical portion 2a, which defines a connection portion 2c with the aforementioned shaft between a first end 2a' and a second end 2a”. Furthermore, the hub 2 includes a flange portion 2b extending radially from one of the end portions 2a” toward the crown portion 3, and having a longitudinal portion 2b” and a radial portion 2b' extending perpendicularly to the axis A. The longitudinal portion 2b” extends such that it extends parallel to the axis A toward the other end 2a' of the hub 2.

[0024] The crown 3 basically includes an annular portion 3a, which has a multi-grooved profile 3b, designed to be consistent with the multi-V-shaped band 5 (whose cross-section is in...). Figure 1 (Illustrated schematically) The contour 3b is obtained on the outer surface 3' of the crown 3, which is opposite to the inner surface 3” that mates with the filter unit 4.

[0025] The crown 3 is supported on the hub 2 using a rolling / sliding support device. Specifically, the pulley 1 includes a rolling bearing 6 (e.g., a ball bearing) that is radially inserted between the crown 3 and the first end 2a' of the hub 2. In particular, due to the assembly requirements of the pulley 1, the rolling bearing 6 is supported on the hub 2 via a head element 7 attached to the first end 2a'.

[0026] On the other hand, the pulley 1 includes a sliding bearing 8 (e.g., a ring made of a low-friction material) which is radially inserted between the crown 3 and the second end 2a” of the hub 2, that is, between the longitudinal portion 2b” and the inner surface 3” of the crown 3.

[0027] Thus, there is a space 9 between the crown 3 and the hub 2. The space 9 is radially defined between the inner surface 3” of the crown 3 and the outer surface of the cylindrical portion 2a of the hub 2, and axially defined between the aforementioned rolling / sliding support devices.

[0028] Furthermore, the pulley 1 includes a cover 10 configured to axially define one end of the pulley 1 and advantageously configured to be received within the crown 3, i.e., to contact the crown 3 for radial engagement.

[0029] The filter unit 4 is housed in the space 9 and essentially includes a torsion spring 11, a spring retaining element 12 (a carrier as described below) that engages with one end of the spring 11, and a damping ring 13 that is axially inserted between the carrier and the head element 7.

[0030] The carrier 12 engages with the head element 7 through sliding contact; that is, it slides axially to contact the head element 7. (Refer to...) Figure 1 and Figure 5 The support member 12 is annular and defines an annular wall 12' coaxial with axis A and a radial wall 12 extending radially toward axis A from the axial edge of the annular portion 12'.

[0031] The radial wall 12” is configured to engage with the head 7 on a first side by sliding, while on a second side opposite the first side, it defines an internal radial protrusion 14 configured to receive the spring stop element 15. In particular, the spring stop element 15 includes an axial protrusion 16 that extends axially along axis A from the internal radial protrusion 14 and is configured to engage with one end of the spring 11.

[0032] The annular wall 12' also defines an axial protrusion 17, which extends axially along axis A from the axial edge of the annular portion 12' opposite to the radial wall 12', and its function will be described below. In particular, the axial protrusion 17 extends circumferentially around axis A, leaving a seat 17' at an angle α ranging from 35° to 45°, preferably 40°.

[0033] like Figures 3 to 6 As can be seen, the longitudinal portion 2b” of the hub 2 defines a protrusion 18 that extends axially toward the carrier 11 along the axis A relative to the longitudinal portion 2b”. In particular, the axial protrusion 18 extends circumferentially around the axis A, leaving a seat 18' at an angle β between 130° and 150°, preferably 140°.

[0034] Spring 11 is preferably a helical spring having a wire with a rectangular cross-section and comprising a plurality of coils wound around axis A between the carrier 12 and the flange portion 2b of the hub 2. As described above, the end portion of spring 11 contacts and engages with spring retainer 15, while the opposite end contacts and engages with a corresponding spring retainer (not visible) formed in flange portion 2b. Thus, flange portion 2b is configured to partially surround spring 11 on the outside.

[0035] The damper 13 essentially comprises an annular element 19 made of polymer, the annular element 19 having an "L"-shaped cross-section, thereby providing a longitudinal portion 19' and an axial portion 19" wherein the longitudinal portion 19' is radially inserted between the carrier 12 and the inner surface 3" of the crown 3, and the axial portion 19" is axially inserted between the carrier 12 and the head 7. The annular element 19 is connected to the carrier 12 by friction or by form-fitting, and is thus not integral around axis A.

[0036] Pulley 1 also includes a torque limiting joint 20, which essentially comprises a bar spring 21. Figures 3 to 6 The bar spring 21 is housed in the space 9 and configured to simultaneously function as a freewheel in both directions of relative rotation between the crown 3 and the hub 2. Advantageously, this freewheel effect is provided to enable the transmission of different levels of torque in one direction between the hub 2 and the crown 3 compared to the other direction.

[0037] Specifically, the torque limiting joint 20 is sized to engage with the hub 2 and the carrier 12 to disengage the crown 3. Specifically, the limiting joint 21 is accommodated in a space 9 that contacts the inner surface 3” of the crown 3.

[0038] More specifically, the bar spring 21 has a substantially open-loop shape, with two ends 21', 21" defining a space 22 between them. The bar spring 21 is mounted radially interference-fit inside the inner radial surface 3" of the crown 3, particularly in the machined area 23. Specifically, the area 23 is machined to define an eccentric type groove / wave surface, sized to achieve a predetermined friction between the bar spring 21 and the crown 3.

[0039] The bar spring 21 has a substantially constant axial dimension over its entire circumferential extension and preferably has a rectangular cross-section.

[0040] In any case, one of the two end portions 21”, 21’ defines at least one protrusion 24, 25, 26. In particular, according to the described embodiment,

[0041] - The first protrusion 24 extends in the circumferential direction from the end portion 21' toward the end portion 21” opposite to the interior of the space 22;

[0042] - The second protrusion 25 extends axially along axis A from the axial edge of the bar spring 21 toward the carrier 12; and

[0043] - The third protrusion 26 extends axially along axis A from the axial edge of the bar spring 21 toward the flange portion 2b of the hub 2.

[0044] Specifically, the first protrusion 24 extends near the third protrusion 26.

[0045] The axial dimension of the second protrusion 25 is set to contact and engage with the protrusion 17 defined by the carrier 12 in the circumferential direction, while the axial dimension of the third protrusion 26 is set to contact and engage with the protrusion 18 defined by the hub 2 in the circumferential direction.

[0046] The torque limiting joint 20 also includes an actuator element 27, which is housed in the space 22 and configured to engage with the protrusions 17, 18 to increase or decrease the opening of the bar spring 21 when the actuator element works with them.

[0047] Advantageously, the actuator element 27 includes a metal rod 28, which is received in the space 22 and circumferentially inserted between the end portions 21', 21" of the bar spring 21, configured to engage with the protrusion 24 and the end portion 21" in the circumferential direction, and extend in the axial direction to engage with the protrusion 17 of the carrier members 12 and 18 of the hub 2 in the circumferential direction.

[0048] In particular, the rod 28 has a trapezoidal shape, wherein the plane of the trapezoidal shape is circumferential and the thickness is radial relative to the axis A. Thus, in particular, the rod 28 includes a central portion 28' having a substantially rectangular shape and a pair of tapered lateral portions 28'", the lateral portions 28' being advantageously equal to each other.

[0049] The tilt angle of the lateral portion 28” relative to the central portion 28' is preferably in the range of 20° to 40°, and advantageously 30°.

[0050] The operation of the pulley 1 according to the above invention is as follows.

[0051] Under normal circumstances, that is, when the hub 2 is driven by the crown 3 driven by the belt 4, and thus tends to overtake it ("drive mode"), the spring 21 rotates integrally with the crown 3, and the hub 2 is subject to resistance.

[0052] Imagine the initial state of one of the lateral portions 28" of the actuator 28 contacting the protrusion 18, driven by the crown 3, causing the bar spring 21 to tend to move clockwise relative to axis A. The actuator 28 moves within the seat 18'. Figure 5 ),until( Figure 6 The protrusion 26 of spring 21 contacts protrusion 18. From this state, the rod 28 is arranged at an angle due to the thrust between the protrusion 17 and the opposite lateral portion 28”, which pushes tangentially between portions 21', 21”. In this way, its opening is increased, thereby increasing the adhesion between the latter and the inner surface of the crown 3. During movement, protrusion 25 contacts and acts in contact with protrusion 17 of head element 7. In this way, spring 11 is loaded with torque and transmits the torque to hub 2, which is being attached to the opposite flange portion 2b. If the torque transmitted by crown 3 continues to increase, at some point, the bar spring 21 slides relative to the inner surface 3” of crown 3, thus lacking the necessary adhesion, thereby causing crown 3 to detach from hub 2.

[0053] Conversely, if the hub 2 tends to overrun the crown 3, the spring 21 rotates integrally with the crown 3 and resists the hub 2.

[0054] Imagine it in the aforementioned disengaged state; the crown 3 tends to rotate counterclockwise relative to the hub 2, thereby disengaging the rod 28 from the protrusion 18. In this case, the spring 11 tends to release, and the bar spring 21 supported by the crown 3 will continue to rotate counterclockwise driven by the protrusion 17, which contacts the protrusion 25 inside the seat 17'. This state continues until the lateral portion 28” of the rod 28 contacts the protrusion 17 on the other side of the seat 17 and tends to close the sliding spring 21.

[0055] Without lever 28, the operation is similar, and under driving torque conditions, the connection occurs directly between protrusions 17, 18 and protrusions 25, 26.

[0056] From the above, the advantages of the pulley 1 according to the present invention are clear.

[0057] Regarding known solutions involving the use of freewheels, the present invention, equipped with a torque limiting joint 20, enables bidirectional connection between the hub and the pulley to be obtained at least within a predetermined torque range, allowing the pulley to be used in a start-stop system.

[0058] Regarding the described scheme, the angle limiting function is directly performed by a torque limiting joint 20 of appropriate size. In particular, due to the different angle intervals α and β between them, these values ​​can be optimized between the drive torque and the overrun.

[0059] In particular, the angle β is specifically reduced to ensure the spring slips once an overrun is detected, thereby avoiding collisions that would cause noise and reduce the lifespan of pulley 1.

[0060] In addition, the trapezoidal shape of rod 28 has been specially optimized to ensure the opening of spring 21 while ensuring sufficient structural resistance.

[0061] Generally, the filter pulleys shown here have small radial and axial dimensions and a limited number of components. As a result, they are inexpensive to manufacture and easier to assemble.

[0062] Finally, according to the present invention, it is clear that changes and modifications can be made to the pulley 1 as long as they do not depart from the scope of protection defined by the claims.

[0063] Specifically, spring 21 can be connected to hub 2, rather than to crown 3.

[0064] If, in “drive mode,” the adhesive force between the spring 21 and the surface 3” of the crown 3 (or hub 2) is sufficient to transmit the required torque, the rod 28 can be omitted.

[0065] Obviously, the angle values ​​of seats 17' and 18' can be varied according to the needs of the vehicle's transmission.

[0066] The pulley can be used as a drive pulley on the engine shaft, instead of a drive pulley on the alternator, and can also be used on a conventional alternator or any other accessory.

Claims

1. A filter pulley (1) for an accessory drive of an internal combustion engine, comprising a hub (2), an annular crown (3), and a filter unit (4) for transmitting torque, the crown (3) having a profile configured to engage with a drive belt (5), being coaxial with the hub (2) externally about an axis (A), and being supported on the hub by free rotational movement, the filter unit (4) being inserted between the hub (2) and the crown (3) and comprising a torsion spring (11), a support member (12), and a torque limiting joint (20). The carrier (12) engages with a portion (7) integral with one of the hub (2) and the crown (3) by sliding. The carrier (12) defines a spring retainer (15) and a protrusion (17) extending along the axis (A) and configured to engage with the torque limiting joint (20). The torsion spring (11) is operably inserted between the support member (12) and one of the hub (2) and crown (3), and has two ends that engage with corresponding spring retainers (15), which are integral with the support member (12) and the hub (2) and crown (3). The torque limiting joint (20) is interferentially connected to one surface (3”) of the other between the crown (3) and the hub (2). The torque limiting joint (20) includes an open-loop bar spring (21) and is configured to slide relative to the surface (3”) when the torque transmitted between the crown (3) and the hub (2) reaches a predetermined level (T1, T2). in, The bar spring (21) defines a pair of axial protrusions (26, 25), which are configured to selectively engage in the circumferential direction with at least one axial protrusion (18) integral with the hub (2) and at least one axial protrusion (17) integral with the carrier (12), respectively.

2. The pulley according to claim 1, wherein, The axial protrusion (18) carried by the hub (2) defines a seat, the axial protrusion (26) being circumferentially movable within the seat, the seat extending annularly at an angle (β) between 130° and 150°.

3. The pulley according to claim 1, wherein, The axial protrusion (17) carried by the carrier (12) defines a seat, the axial protrusion (25) being circumferentially movable within the seat, the seat extending in annular shape at an angle (α) between 35° and 45°.

4. The pulley according to claim 1, wherein, The torque limiting joint (20) includes an actuator element (28) housed in a space (22) circumferentially defined between the two ends (21', 21") of the bar spring (21), the axial dimension of which is configured to engage with the protrusion (17) of the carrier (12) on one hand and with the protrusion (18) of the hub (2) on the other hand.

5. The pulley according to claim 4, wherein, The actuator element (28) is a metal rod that can deploy the spring (21) under the thrust of the protrusion (17) of the support member (12).

6. The pulley according to claim 4, wherein, One of the ends (20', 20") defines a circumferential protrusion (24) that extends into the space (22) and is configured to engage with the actuator element (28). The protrusion (24) extends near the axial protrusion (26) to engage with the protrusion (18) which is integral with the hub (2).

7. The pulley according to claim 4, wherein, The actuator element (28) has a trapezoidal cross section, wherein the plane of the cross section is circumferential and the thickness of the actuator element (28) is radial.

8. The pulley according to claim 7, wherein, The trapezoidal cross section defines a pair of equal inclined lateral portions.

9. The pulley according to claim 8, wherein, The inclination of the tilted lateral portion is between 20° and 40°.

10. The pulley according to claim 1, wherein, The portion (7) integral with the hub (2) includes an annular head, on which a bearing (6) is mounted to support the crown (3).

11. The pulley according to claim 1, wherein, The protrusion (18) is formed on a flange portion (2b) integral with the hub (2), the flange portion (2b) being sized to partially surround the torsion spring (11) on the outside.

12. The pulley according to claim 11, wherein, The pulley (1) includes a sliding bearing (8) which is operably inserted between the flange portion (2b) and the crown portion (3).

13. The pulley according to claim 1, wherein, The carrier (12) defines a radial protrusion (14), which defines a spring retainer (15) for one end of the end of the spring (11).

14. The pulley according to claim 1, wherein, The pulley (1) includes a damping ring (13) operably inserted between the carrier (12) and the portion (7) integral with the hub (2), the damping ring (13) being configured to allow the carrier (12) to slide relative to the portion (7).

15. The pulley according to claim 14, wherein, The damping ring (13) includes a portion (19') radially inserted between the crown (3) and the carrier (12) and a portion (19”) inserted between the carrier (12) and the portion (7) integral with the hub (2).

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