CLUTCH ASSEMBLY, IN PARTICULAR FOR MOTORCYCLES, AND TRANSMISSION SYSTEM EQUIPPED WITH SAID CLUTCH ASSEMBLY

Abstract

A clutch comprises a bell alternatively engaged and disengaged by a rotating transmission component, wherein mutual engagement of the bell and the rotating transmission component by first engagement elements results in the bell being dragged in rotation by the transmission component in a first rotation direction, wherein the bell defines an engagement profile formed so as to be alternatively engaged and disengaged by second engagement elements dragged in rotation by the transmission component, and wherein mutual engagement of the second engagement elements and the engagement profile is a result of both the rotation of the transmission component in a second rotation direction, opposite to the first rotation direction, and the rotation of the bell in the first rotation direction. Mutual disengagement of the second engagement elements and the engagement profile is a result of both the rotation of the transmission component in the first rotation direction opposite to the second rotation direction, and the rotation of the bell in the second rotation direction.

Claims

1. A clutch said clutch comprising a bell adapted to be engaged and disengaged alternatively by a rotating transmission component, wherein mutual engagement of said bell and said rotating transmission component by at least one first engagement element results in said bell being dragged in rotation by said transmission component in a first rotation direction (A), wherein said bell defines an engagement profile formed so as to be engaged and disengaged alternatively by at least one second engagement element dragged in rotation by said transmission component, and wherein the mutual engagement of said at least one second engagement element and said engagement profile is a result of both the rotation of said transmission component in a second rotation direction, opposite to said first rotation direction (A), and the rotation of said bell in said first rotation direction (A), whereas mutual disengagement of said at least one second engagement element and said engagement profile is a result of both the rotation of said transmission component in said first rotation direction (A) opposite to said second rotation direction, and the rotation of said bell in said second rotation direction.

2. The clutch of claim 1, wherein said bell comprises a cylindrical portion and said engagement profile is defined by at least one portion of an outer surface of said cylindrical portion.

3. The clutch of claim 2, wherein said cylindrical portion of said bell comprises at least one depression with respect to a cylindrical reference surface, said depression being subtended by a predefined angular sector () centred on a longitudinal axis of said cylindrical portion.

4. The clutch of claim 3, wherein the outer surface of said at least one depression is the locus of generatrix half-lines parallel to the longitudinal axis of said cylindrical portion.

5. The clutch of claim 4, wherein the distance of said generatrix half-lines from said longitudinal axis of said cylindrical portion varies within said angular sector ().

6. The clutch of claim 5, wherein the distance of said generatrix half-lines from said longitudinal axis of said cylindrical portion varies continuously within said angular sector ().

7. The clutch of claim 5, wherein said angular sector () comprises a first subsector (1) and a second subsector (2), and wherein in the first subsector (1) a curve defined by an intersection between a plane perpendicular to the longitudinal axis of said cylindrical portion and the outer surface of said at least one depression comprises at least one concavity faced towards said cylindrical reference surface.

8. The clutch of claim 7, wherein in said second subsector (2) the curve defined by the intersection between a plane perpendicular to the longitudinal axis of said cylindrical portion and said outer surface of said at least one depression comprises at least one convexity faced towards said cylindrical reference surface.

9. The clutch of claim 8, wherein said at least one concavity and said at least one convexity are connected in a continuous manner.

10. A transmission system comprising a rotating transmission component, at least one first engagement element and at least one second engagement element and a bell adapted to be engaged and disengaged alternatively by said rotating transmission component, wherein mutual engagement of said bell and said rotating transmission component by said at least one first engagement element results in said bell being dragged in rotation by said transmission component in a first rotation direction, and wherein mutual engagement of said at least one second engagement element and said engagement profile is a result of both the rotation of said transmission component in a second rotation direction opposite to the said first rotation direction (A), and the rotation of said bell in said first rotation direction (A), whereas mutual disengagement of said second at least one engagement element and said engagement profile is a result of both the rotation of said transmission component in said first rotation direction (A), opposite to said second rotation direction, and the rotation of the bell in said second rotation direction.

11. The transmission system of claim 10, wherein said transmission component comprises a first pulley positioned outside of said bell, wherein said at least one second engagement element comprises at least one pawl fixed to said first pulley and adapted to be switched between a first engagement position wherein it engages said at least one depression and a second disengagement position in which it is disengaged from said at least one depression, and wherein switching of said at least one pawl from said first engagement position to said second disengagement position is a result of both the rotation of said first pulley in said first rotation direction (A), and the rotation of said bell in said second rotation direction.

12. The transmission system of claim 11, wherein said at least one pawl is constrained to said first pulley so that it can be switched by rotation, and wherein both the rotation of said first pulley in said first rotation direction (A), and the rotation of said bell in said second rotation direction, result in said at least one pawl being rotated in a first own rotation direction and being switched from said first engagement position to said second disengagement position.

13. The transmission system of claim 12, wherein said system comprises at least one first elastic element interposed between said pulley and said at least one pawl, and wherein said at least one pawl is switched by rotation from said first engagement position to said second disengagement position against the elastic resistance exerted by said at least one first elastic element, whereas said at least one pawl is switched by rotation from said second disengagement position to said first engagement position due to the thrusting action exerted by said at least one first elastic element.

14. The transmission system (100) of claim 10, wherein said rotating transmission component comprises a second pulley or cap equipped with said at least one first engagement element, said at least one first engagement element comprising a plurality of back-pushing and/or engaging shoes at least partially housed inside said bell, wherein each of said plurality of shoes is adapted to be translated along a radial direction, and wherein rotation of said rotating component in said first rotation direction (A) results in said plurality of shoes being radially translated, in the mutual engagement of said second pulley or distributor cap and said bell, and in said bell being dragged in rotation by said rotating transmission component.

15. The transmission system of claim 10, wherein said system comprises a continuously variable transmission (CVT), and wherein said rotating transmission component belongs to a driven rotating component of said continuously variable transmission.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a diagrammatic view of a transmission-clutch system according to the prior art;

[0037] FIG. 2 shows a perspective view of part of a transmission-clutch system according to an embodiment of the present disclosure;

[0038] FIG. 3 shows a side view of a rotating part of a transmission-clutch system according to an embodiment of the present disclosure;

[0039] FIG. 4 shows a perspective view of part of a system according to an embodiment of the present disclosure;

[0040] FIG. 5 shows a perspective view of a system according to an embodiment of the present disclosure; and

[0041] FIG. 6 shows a diagrammatic view of constructional details of a system to an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0042] The present invention is advantageously applied in case of transmission ratio automatic variation and/or continuous transmission systems, in particular in the case of CVTs. For this reason, hereinafter, the present disclosure will be explained with reference to its applications to continuously variable transmissions (CVTs). It is further worth noting that possible applications of the present disclosure are not limited to continuously variable transmissions (CVTs), but include transmission systems of any kind.

[0043] In FIG. 2, reference numeral 100 identifies a transmission-clutch system according to an embodiment of the present disclosure, where, for clarity reasons, only the parts essential for describing the system are shown. Reference numeral 101 identifies a clutch, said clutch 101 comprising a bell 102, which comprises a cylindrical portion 103 extending from a flange 104 to which a wheel hub can be connected by means of a gear final reduction, according to substantially known methods (see the description of FIG. 1). Moreover, in FIG. 2, reference numeral 105 identifies a driven pulley, in turn comprising a movable half-pulley 106 (again according to the methods described above) and a fixed half-pulley 107.

[0044] According to substantially known methods, a cap integral in rotation with the half-pulley 107 is housed in the inner space defined by the cylindrical portion 103 of the bell 102 positioned facing the half-pulley 107, said cap (not shown in the figure) being equipped with back-pushing and/or engagement shoes (first engagement element) radially translatable (expandable) as a consequence of the centrifugal force generated by the rotation of the fixed half-pulley 107 and of the cap housed in the cylindrical portion 103 of the bell 102.

[0045] Assuming, for clarity purposes, that the half-pulley 107 is put into rotation by the vehicle engine in the rotation direction indicated by the arrow A, and that the rotation direction indicated by the arrow A corresponds to the forward direction of the vehicle, the rotation of the half-pulley 107 in the direction of the arrow A, and therefore of the cap housed in the bell, with sufficient rotation speed, results in the engagement of the bell 102 by the expandable shoes, and thus in the rotation of the bell 102 in the same rotation direction A, and finally in rotation of the wheel hub and of the wheel itself in the same rotation direction A.

[0046] Furthermore, the bell 102 has innovative features, as described below in detail with reference to FIGS. 2 and 6.

[0047] As shown in the figures, with respect to a substantially cylindrical reference surface 110, the outer surface 111 of the cylindrical portion 103 comprises mutually contiguous recesses 112, each subtended by an angular sector a centred on the longitudinal symmetry axis X of the cylindrical portion 103. The surface of each depression 112 may be defined as the locus of the generatrix half-lines parallel to the X axis, where the distance of said generating lines from the X axis varies as a function of the angular position, in particular from a maximum corresponding to the radius of the reference surface 110 at the opposite ends of the angular sector u, to a minimum in intermediate position between the two extremes, where the minimum distance of the directrix of the X axis naturally corresponds to the maximum depth of the depression 112. Furthermore, the curvature of the outer surface 111 of each depression 112 is such that the curve defined by the intersection of the surface 111 with a reference plane perpendicular to the X axis (and therefore parallel to the plane of FIG. 6) is such as to comprise a concavity C1 facing towards the reference surface 110 on a first sub-sector al, and a convexity C2 facing towards the reference surface 110 in a second sub-sector u2 of the angular sector u, where also the convexity C2 and the concavity C1 are joined continuously.

[0048] Further aspects of the present disclosure may be appreciated with reference to FIGS. 2 and 3, showing two second engagement elements 120 applied on the driven half-pulley 107, and in particular on its inner face facing towards the bell 102. The number of the engagement elements may vary from a minimum of one to a maximum corresponding to the number of depressions 112, according to requirements and/or circumstances. Each element 120 comprises a plate 123 parallel to the half-pulley 107 and interposed between the pulley 107 and the bell 102, the plate 123 being positioned outside the bell 102. The plate 123 is rotatably constrained to the half-pulley 107 by a constraint or pin 121, the plate 123 being switchable by rotation about the pin 121 in the two opposite rotation directions indicated by the double arrow in FIG. 3. A cylindrical pawl 122 extends from the plate 123, in a direction transversal to the plate 123 and parallel to the axis X of the cylindrical portion 103 of the bell 102, said pawl 122 extending from the plate 123 so as to be positioned above the outer surface 111 of said cylindrical portion 103. Elastic back-pulling means, e.g. a spring, are interposed between the plate 123 and the half-pulley 107. The switch by rotation of the element 120 in a first rotation direction towards the outside and thus with the pawl 122 away from the surface 111 occurs against the elastic bias applied by the spring, while the switch for rotation of the element 120 in a second rotation direction opposite to the first one, in particular towards the inside and thus with the pawl 122 approaching towards the surface 111 is promoted by the elastic reaction of the spring itself.

[0049] The operation of the system according to the embodiment of the present disclosure described above can be summarized as follows.

[0050] FIG. 2 shows a first configuration in which each one of the pawls 122, by virtue of the action of the respective spring, is pushed against the surface 111 and engages a corresponding depression 112, being housed in the concavity C1 of the depression itself. In this configuration, a possible rotation of the bell 102 in the rotation direction A shown in FIG. 2 results into dragging into rotation the driven pulley 105. Assuming a situation in which the engine is off, the pads inside the bell 102 are in the retracted position and the bell 102 is released from the cap, so that any rotation of the bell 102 would not result in rotation of the driven pulley 105, by virtue of the engagement of the elements 120 on the surface 111 of the bell 102, the rotation of the bell 102 results in the rotation respectively of the pulley 105, of the driving pulley, and thus of the drive shaft, allowing starting the engine itself, if, for example, the rotation of the bell 102 is caused by pushing the vehicle. The configuration in FIG. 2 does not hinder the normal operation of the vehicle, in particular of the transmission of the vehicle itself, in any manner. Indeed, assuming that the pulley 105 is put into rotation in rotation direction A by starting the engine and then through the transmission (drive pulley, belt etc.), the rotation of the half-pulley 107 in the rotation direction A results in putting into rotation the bell 102 in an entirely normal manner, rather than by action of the engagement elements 120 on the bell, during coupling between the bell 102 and the half-pulley 107 deriving from the expansion of the shoes housed inside the bell 102 and by virtue of the dragging action applied by the shoes on the inner surface of the cylindrical portion 103 of the bell 102. The pawls 122 are instead switched to the disengagement configuration (FIGS. 4 and 5) as a result of both the thrust action applied on each pawl 122 of the assembly C2 of the respective depression 122 and of the centrifugal force, where the pawls 122 are rotated away from the outer surface 111 and disengaged from the respective depressions 122.

[0051] A further use of the system according to the present invention can finally be summarized as follows.

[0052] Assuming the driven pulley 105 is put into rotation in the rotation direction opposite to the rotation direction A shown in FIG. 2, that is, when the engine is off or running at a very slow speed, either close to or lower than idling speed (and thus in disengagement condition between the bell 102 and the pads inside it, the pads being in retracted position), and, for example, the drive force generated by the alternator to the drive shaft is applied, by virtue of the engagement of the pawls 122 in the respective depressions 112, the bell 102 is also dragged into rotation in the rotation direction opposite to the rotation direction A, where the hub applied to the bell 102 and the wheel are put into rotation in the rotation direction contrary to the forward travel rotation direction, thus allowing to reverse the vehicle, for instance, by exploiting the contrary rotation on the drive shaft.

[0053] The present disclosure provides a solution which allows both reversing the vehicle with engine off or running at a very slow rpm, close to idling, and/or push-starting the engine, that is, in case of flat battery and/or of fault in the electrical system.

[0054] Moreover, the aforesaid objects are achieved by using a limited number of component parts of simple construction which can be manufactured at a low cost.

[0055] The present disclosure is not limited to the embodiments described above and shown in the drawings. Embodiments and constructional details may be modified with respect to those described herein by way of non-limiting examples, without thereby departing from the scope of protection as described and claimed herein.