HUB FOR A SERVO CLUTCH WITH SLIPPER FUNCTION OF A HANDLEBAR VEHICLE

Abstract

A hub unit for a clutch of a vehicle with a handlebar has both a servo function when closing and a slipper function via the sliding motion of at least one pin along respective inclined and facing tracks. The hub unit includes a hub connected to an output shaft of a vehicle engine and having an axis of rotation, a plurality of guides rigidly connected to the hub, an axial stop rigidly connected to the hub, a disc pressure flange movable in a direction parallel to the guides, and at least one spring. The hub defines at least a first track and a second track facing in an axial direction and arranged in a direction not parallel to the axis of rotation. The disc pressure flange includes at least one pin projecting in a substantially radial direction and arranged in contact with the first track and the second track.

Claims

1. A servo hub unit with slipper function for a clutch of a handlebar vehicle comprising: a hub adapted to be connected to an output shaft of a vehicle engine and having an axis of rotation; a plurality of guides configured to provide translation of a plurality of friction discs and to block rotation of the friction discs, wherein the guides are rigidly connected to the hub; an axial stop for the friction discs, wherein the axial stop is rigidly connected to the hub; a disc pressure flange movable in a direction parallel to the guides to press the friction discs against the axial stop or release the friction discs from the axial stop; at least one spring to press the disc pressure flange towards the axial stop and arranged against a stop rigidly connected to the hub; wherein: the hub defines at least a first track and a second track facing in an axial direction and arranged in a direction not parallel to the axis of rotation; the disc pressure flange comprises at least one pin projecting in a substantially radial direction and arranged in contact with the first track and the second track; the first track has a first inclination configured to convert a first torque applied to the disc pressure flange by the friction discs into a first axial load applied by the disc pressure flange to press the friction discs against the axial stop and have a servo assisting effect when closing the clutch; the second track has a second inclination configured to convert a second torque applied by the hub into a second axial load applied to distance the disc pressure flange from the axial stop to disengage the friction discs and allow a slipper function.

2. The servo hub unit according to claim 1, wherein the pin has a substantially circular cross section.

3. The servo hub unit according to claim 1, wherein the first track and the second track are radially internal to the guides.

4. The servo hub unit according to claim 1, wherein the spring is a washer spring.

5. The servo hub unit according to claim 1, wherein the disc pressure flange comprises a plurality of teeth facing the axial stop and engaging on at least one disc so that the at least one disc applies the first torque.

6. The servo hub unit according to claim 1, wherein the pin is rotatable about a radial axis of the pin.

7. The servo hub unit according to claim 6, wherein the pin is rotatable by means of a rolling bearing.

8. The servo hub unit according to claim 1, wherein the disc pressure flange defines an outer arched surface and an inner arc surface, the inner arched surface and the outer arched surface cooperate in contact and in a relative manner during movement of the pin along the first track or the second track.

9. The servo hub unit according to claim 8, wherein at least one of the inner arched surface and the outer arched surface defines an inclined recess with respect to the axis of rotation to promote distribution of lubricating oil between the inner arched surface and the outer arched surface.

10. The servo hub unit according to claim 1, comprising a lever adapted to be mounted on a handlebar of a vehicle and functionally connected to the spring to release an action of the pressure disc by opposing the spring when the lever is pulled by a hand of a driver and open the clutch.

11. The servo hub unit according to claim 1, further comprising a bell and a plurality of friction discs rigidly connected to rotation to the bell.

12. A handlebar vehicle comprising the servo hub unit according to claim 1, wherein the hub is connected to a traction wheel of the handlebar vehicle, and the traction wheel is disconnected from a traction motor of the handlebar vehicle when the clutch is open.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The invention is described below on the basis of non-limiting examples illustrated by way of example in the following figures, which refer respectively to:

[0024] FIG. 1: an exploded perspective view of a hub unit according to the present invention;

[0025] FIG. 2: a partially sectioned perspective view of some components illustrated in FIG. 1;

[0026] FIG. 3: a section of the hub unit on a plane comprising an axis of rotation of the hub itself;

[0027] FIGS. 4 and 5: sections in two different operating conditions i.e. assisted closing and slipper opening respectively.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In FIG. 1, number 1 shows as a whole a hub unit for a clutch further comprising a bell (not shown) connected in use to one or more rear traction wheels of a vehicle with a handlebar. The hub unit 1 can be supplied both with friction discs (not shown) and in a configuration without discs. The latter cooperate selectively with a plurality of friction discs carried by the bell to connect in torque transmission or disconnect the motor and the traction wheel from rotation.

[0029] According to the embodiment of FIG. 1, hub unit 1 comprises an axial stop flange 2, a hub 3 for rotating connection with a crankshaft of the engine and a plurality of guides 4, for example a ring gear cooperating with the friction discs to provide a rigid coupling to rotation and sliding coupling along the guides. In particular, flange 2 is a piece different from hub 3 and guides 4 form a single body with hub 3 but other configurations are possible. For example, flange 2, hub 3 and guides 4 can be a single piece, e.g. made by casting and co-molding.

[0030] The hub unit 1 also comprises a disc pressure flange 5 movable parallel to an axis of rotation of hub 3, a spring 6 preferably a washer spring loaded to bring the disc pressure flange 5 closer to stop flange 2, an abutment 7 having an axial fixed position with respect to hub 3 and defining a constraint for axially loading spring 6. In particular, abutment 7 is rigidly connected to hub 3 by means of a spacer structure 8 preferably comprising a plurality of columns 9 extending axially between hub 3 and abutment 7. Disc pressure flange 5, as will be described in greater detail below, rotates with respect to hub 3 in addition to translating and for this purpose it is supported radially to guide the roto-translational movement on an internal surface of sliding bearing 10. The latter has, as shown in the figure, a cylindrical internal surface or a plurality of coaxial arc surfaces so as to define an adequate radial support. However, a dual configuration is possible wherein the bearing has external arc surfaces on which internal arc surfaces carried by flange 5 move. As shown in the figures, the arc surfaces can identify, in their complex, cylindrical surfaces. The sliding bearing 10 is rigidly connected to hub 3 as an insert according to the illustrated embodiment or it can be made in a single body with hub 3 and / or optionally with guides 4 and / or with stop flange 2. The sliding bearing 10 is surrounded by guides 4 and is therefore radially internal to the latter.

[0031] According to an important aspect of the present invention, tracks are formed fixed to hub 3 inclined with respect to the axis of rotation and the disc pressure flange 5 comprises at least one pin 11, preferably a plurality of angularly equispaced pins, movable along the tracks to guide the approach by roto-translation of flange 5 to flange 2 in order to close the clutch in a servo manner by applying an additional axial force to that of spring 6 (FIG. 4) when a lever on the handlebar is released and to open by roto-translation of flange 5 the clutch when an inertial torque comprising that of the rear wheel exceeds the torque of the driving shaft, for example after a sudden deceleration of the engine at the end of a straight path at high speed.

[0032] Preferably, the tracks are made on bearing 10 and in the embodiment in the figure they are inclined to generate a clockwise rotation for the opening (track 12) and anticlockwise for the closing (track 13) of the clutch. Tracks 12, 13 cooperating with a single pin 11 are preferably facing and spaced so that a maximum play with the pin does not exceed 2 millimeters in the angular position between pins 11 and tracks 12, 13 when the clutch is closed. Pin 11 may have a cross section with radii of curvature designed to decrease the contact pressure with tracks 12, 13 and, consequently, the wear. According to a preferred embodiment, pin 11, which extends radially cantilevered, is rotatable around its own axis by means of a rolling bearing 14 (FIG. 2) in order to minimize friction during movement on the tracks 12, 13 In this way, it is possible to use hub unit 1 also dry and not only wet in lubricating oil. In order to improve the lubrication between bearing 10 and flange 5, at least one of the internal or external arc / circumferential surfaces has a continuous recess 15 to house a predefined quantity of lubricating oil.

[0033] According to the embodiment in the figure, the axial closing force additional to that of the spring 6 (FIG. 4) is generated by converting the torque of at least one friction disc rigidly connected to rotation to the pressure flange 5 by means of a connection rigid to rotation and, preferably, also free to translation parallel to the rotation axis. For example, this connection is implemented by means of a toothing 16.

[0034] The unit is mounted in accordance to general practice on the handlebar vehicle, e.g. a motorcycle, so that the bell is permanently connected e.g. via gear wheels to the motor e.g. via a gearbox and the hub is permanently connected to the drive wheel, e.g. rear wheel, preferably via a chain so that both the wheel and the hub are disconnected from the engine when the clutch is open. The handlebar lever is connected e.g. through a push rod to the hub so that, when the lever is pulled, the rod counteracts the action of the spring 6 and opens the clutch.

[0035] According to an embodiment which is not shown, tracks 12, 13 converge or have different patterns to achieve particular servo and slipper laws.

[0036] The washer spring can be replaced by a plurality of helical springs.