Description

The present invention relates to an axial actuation synchronizer for a transmission which can be used aboard a vehicle, in particular a motorcycle, which results to be of the synchronized type, that is acting so that the two portions of the transmission which have to engage for transmitting the torque are brought at the same speed, before the torque is transmitted.

Generally, the synchronizers for known transmissions belong to the family of the truncated-cone ring synchronizers or to the family of the servo-lock synchronizers.

The first ones substantially consist of two interacting truncated-cone surfaces, one integral with a gearwheel and the other one with a sliding sleeve provided with frontal teeth which implements a coupling by moving axially towards the gearwheel.

This type of synchronizer does not guarantee a good operation if the procedure for engaging the speeds is performed very quickly or if there are very different speeds among the elements; moreover, the speed engagement always requires a certain effort, even if the portions of the coupling have the same speed.

The servo-lock synchronizers, instead, are structurally different and obtain only partially from the control lever the force to synchronize the shafts, but they are structurally complex and substantially suitable for high performance transmissions and not within the field of the motorcycles, in particular scooter.

The US patent N. 7,484,605 describes a coupling system with two concentric rings and a system of cams arranged therebetween which is implemented to obtain the mutual engagement thereof.

The US patent N. 7,882,758 describes a system similar to the previous one wherein the cams are actuated by elements sensible to the centrifugal force.

However, this type of couplings suffer from the drawback of having to actuate said cams with a predetermined force, so that they can implement the friction necessary to the coupling.

The technical problem underlying the present invention is to provide an axial actuation synchronizer allowing to obviate the drawback mentioned with reference to the known art.

Such problem is solved by a synchronizer as specified above which characterizes in that it comprises:

• a supporting plate, having a central opening, wherein an actuation end of an axis of the synchronizer (20) is arranged;

• a bell-like spring, substantially shaped like a cone, arranged on said supporting plate so as to cover said central opening;

• a cam connected to said actuation end which rotates around an axis parallel or coincident with the axis of the synchronizer;

• a cam follower, determining an axial shifting of said cam thereto it is associated in axial direction, so as to interfere with said actuation end in opposition to the force exerted by the bell-like spring; e

• means for rotating selectively said rotating cam.

The main advantage of the axial actuation synchronizer according to the present invention lies in the fact of allowing the possibility of selecting each gear in any moment, thanks to a simple and direct mechanical mechanism, which requires an activation force with reduced amount.

The present invention will be described hereinafter according to a preferred embodiment example thereof, provided by way of example and not for limitative purposes with reference to the enclosed drawings wherein:

* figure 1 shows a side view of a scooter incorporating the transmission according to the present invention; and

* figure 2 shows a perspective view of the transmission of figure 1, closed in the container thereof, and of the related engine block.

* figure 3 shows an axonometry view of a synchronized transmission according to the present invention, incorporating a synchronizer according to the invention at the rear wheel of a motorcycle;

* figure 4 shows a diametrical cross section view of an example of axial actuation synchronizer, in a first configuration;

* figure 5 shows another diametrical cross section view of the axial actuation synchronizer of figure 4, in a second enlarged configuration;

* figures 6A and 6B show respective axonometric views of two components of the synchronizer of figure 4;

* figure 7 illustrates the actuation of the axial actuation synchronizer of figure 4, and the relative motion transmission; and

* figures 8A and 8B illustrate two operation steps of the synchronizer of the previous figures.

By referring to figures 1 and 2, a motorcycle, and in particular a scooter, is designated as a whole with 100. The invention relates to the field of the saddle vehicles, or vehicles which are driven astride, in general, having two, three or four wheels, with particular reference to the scooters having a propulsion unit arranged in a position below a saddle 101, inside a chassis 102 which herein is represented laterally, extending from a front wheel 103, driven by a handlebar 104 to a driving rear wheel 105.

The propulsion unit 106 (figure 2) or, in short, the engine is of the type having one or more cylinders arranged in a tilted position approximatively on the median plane of the vehicle which corresponds to the rotation plane of the two wheels during the rectilinear forward motion.

The engine 106 has an engine block 107 in one single piece which receives, in the present embodiment example, a cylinder 108 and a related (not visible) piston.

The piston acting in said cylinder 108 is connected to a crankshaft 2 positioned transversally and perpendicularly to said median plane. On one represented side (figure 1 and 2) of the scooter 100 a transmission device 200 is provided or, more shortly, a transmission of the motion from the crankshaft to the hub of the rear wheel 105.

The transmission 1 has a container 109 which receives inside thereof the transmission elements which will be described in greater detail hereinafter. The container 109 is connected to the engine block 107 by creating a tunnel-like casing including the crankshaft 2 and all transmission elements connected thereto.

Moreover, the container 109 is closed, on the exposed side of the motorcycle 100, by a cover 110 of the transmission 1, which extends substantially from the engine 106 to the hub shaft of the driving wheel 105. The cover 110 is fastened to the container 109 by means of suitable bolts 111. Openings, slots, air intakes could be provided to access and/or cool down the transmission elements through said cover 110. The cover 110 is rested upon a fixing edge 112 of the container 109, provided with fixing seats 113 for said bolts 111 and with additional front connection seat 114, with a hinge connection of axis A to allow the engine block 107 and the transmission 200 to swing, and rear connection seat 115, connected to a rear suspension 116, to connect the casing 109 and the whole transmission 1 to the frame of the vehicle 100.

Such transmission 200 is of multiple gear type and of synchronous type, and it is arranged for connecting the crankshaft 202, which receives the motion from moving one or more pistons, to the hub shaft 205, by considering that these two shafts are parallel therebetween and placed at a prefixed distance. The hub shaft, at a distal end thereof, is provided with a pinion 5 for connecting to the rear wheel 105.

They are both perpendicular to the median plane of the vehicle, defined by the rotation plane of the front and rear wheels. It is further meant that the use of this type of transmission is not limited to the herein represented two- wheel scooter, but it can be extended to a scooter with a pair of front wheels or to four-wheel scooters.

By referring instead to figure 3, a multiple transmission without the casing 109 and the cover 110, in particular a transmission with four-speed transmission, is designated as a whole with 200. It is of the type suitable to be assembled on a motorcycle as transmission element which actuates a driving wheel of the motorcycle, in particular a scooter, that is the rear wheel thereof 105.

On this regard, it comprises a crankshaft 202, which is made to rotate by the engine, thereof the piston rod 230 is represented, and a first driven shaft, that is the primary shaft 53, and a secondary shaft, which can be connected directly to the wheel or which transmits the rotation, as in the present embodiment example, to a hub shaft 205 which is connected to the driving wheel 105 of the vehicle.

It is to be noted that the arrangement of the shafts is so that the crankshaft 202 assumes a position which is substantially parallel to the rotation axis of the driving wheel, that is to the hub shaft 205. Therefore, this transmission element has the purpose of transferring the motion from an engine, having a crankshaft transversal to the motorcycle, to a wheel having an axis transversal to the vehicle, too.

The passage from secondary shaft to hub shaft 5 takes place through a pair of gearwheels 206, 207 which have the function of inverting the rotation direction transmitted to the driving wheel, which in this case is concurrent to the rotation direction of the crankshaft 202, and they introduce a fixed reduction ratio on the hub.

It is to be meant that the hub shaft 205 could be constituted by the same secondary shaft, provided that one renounces to the above mentioned reduction ratio on the hub and providing to invert the rotation direction of the crankshaft 202.

In the light of what above, in each case the secondary shaft is directly or indirectly connected, from the mechanical point of view, to the driving wheel 105 thereto the gearbox refers .

The crankshaft 2 and the primary shaft 3 are substantially parallel and they are connected by transmission elements which allow the motion transmission according to different speed ratios. Such transmission elements include a first group of toothed pulleys assembled on the crankshaft 202, a second group of toothed pulleys assembled at the primary shaft 53, and a pair of transmission belts extending from the first to the second group of pulleys.

Under transmission belt any flexible annular element is meant apt to transmit the motion between two pulleys offset therebetween, in particular with axes parallel therebetween. The transmission belts then include any kind of belts or chains, the pulleys in case could be toothed to implement a synchronous connection.

Generally, the herein described transmission is of the synchronous or almost synchronous type, and it uses a pair of pulleys connected kinematically by a belt, preferably a toothed belt on toothed pulleys or a high performance belt, for example of the Stretch Fit ^® type or the like.

It is to be meant that what described hereinafter can be wholly or partially applied even to an equivalent synchronous transmission of other type, for example a pinion - chain - toothed wheel transmission.

In the present embodiment example, the transmission belts advantageously are synchronous transmission belts; under synchronous belt a belt is meant, usually a toothed belt or a roller chain, which transmits the motion from a wheel or toothed pulley to another wheel or toothed pulley with a transmission ratio which is determined by the ratio between the wheels' diameters, without this being subjected to friction or sliding losses. The absence of sliding portions and/or portions dragged by friction, typical instead of the gearboxes of CVT (Continuously variable transmission) type, even known as continuous gearboxes or continuous variators, makes the herein described transmission of synchronous type.

Therefore, in the present embodiment example as well as in the subsequent ones, the above-mentioned pulleys are toothed pulleys, connected by toothed belts, preferably of the type made of rubber.

On the crankshaft 202 a main starting clutch 208 is assembled which, in the present example, is of centrifugal type, well known in the art. In this example, this kind of clutch allows the motion transmission from the crankshaft 202 to the cascaded transmission elements, and it engages automatically at a rotation regime comprised in a prefixed range, for example between 1000 and 2000 revolutions per minute. At a lower rotation regime, the clutch 208 is not engaged and the engine is idle, whereas the driving wheel is not stressed.

However, it is meant that, in particular applications, this type of clutch can be replaced by a manual coupling clutch which is perfectly equivalent, or by a clutch actuated by a servo-mechanism.

On the crankshaft 202 a first pulley 209 and a second pulley 210 are keyed in cascade to said clutch 8. They are respectively connected, by means of a first synchronous belt 211, to a third pulley 212 and, by means of a second synchronous belt 213, to a fourth pulley 214.

At the front of the crankshaft 202, there is a first synchronizer 216 for synchronizing the second belt 213, that is the connection between second and fourth pulley 210, 214, whereas at the front of the primary shaft 53 there is a second synchronizer 20 which synchronizes the toothed wheels keyed on such primary shaft 53.

In fact, a first and a second toothed wheel are keyed on the primary shaft 53 which are engaged, respectively, with a third toothed wheel and with a fourth toothed wheel, both keyed on the secondary shaft. The third toothed wheel, in this embodiment example, is assembled on a second free wheel.

When the clutch 208 is activated so that it transmits the motion through the crankshaft 202, the two synchronizers 216, 20 are not active and the first speed is transmitted through the first and the third pulley 209, 212 and the first belt 211. At a particular moment, which can be decided by the driver or autonomously set by the system, according to a well precise implemented logic, the system is requested to pass from the first to the second speed and, even in this case, the transmission uses the first synchronous belt 211.

In this case, however, the second actuated synchronizer 20, arranged on the primary shaft, is activated, and so it intervenes by synchronizing a pair of toothed wheels assigned to the transmission of the second and of the fourth speed. At a particular moment, which can be decided by the driver or autonomously set by the system, according to a well precise implemented logic, the system is requested to pass from the second to the third speed and, in this case, the transmission has to use the second synchronous belt 213.

The first synchronizer 216 placed onto the crankshaft 202 is activated, by implementing the synchronization of the second pulley 210 of the third and of fourth speed. In the latter case, the second synchronous belt 213, now placed in motion, transmits the motion to the primary shaft of the gearbox. As the two belts 211, 213 are moving contemporarily, the primary shaft 53 would have two different speeds set by the transmission, however this is avoided by the presence of a free wheel which allows to disengage the third pulley 213 related to the first and second speed.

However, in the same moment, on the driven shaft, the second synchronizer 20 on the primary shaft 3 has to be deactivated, so as to cease the synchronization of the ratio of toothed wheels of second and fourth speed. Therefore, the motion reaches the primary shaft through the pair of pulleys related to the third and fourth speed, and the primary shaft rotates with the speed set by the third speed.

It is to be noted that the synchronizer has to be deactivated independently from the rotation speed reached by the respective primary shaft, and this makes that it has to be of actuated type, that is of the type which is actuated or deactivated after an actuation determined by a system decision and not by simply reaching a rotation regime.

As last case the insertion of the fourth speed remains: as to the first synchronizer 216 on the crankshaft nothing changes with respect to the case of the third speed. In fact, the second belt 213 between the second and the fourth pulley 210, 214 continues to be active.

However, for the fourth speed, even the second synchronizer 20 has to intervene which is actuated on the primary shaft 53, by synchronizing again a pair of toothed wheels belonging to the second and fourth speed.

By referring to figures 4 to 7, an axial actuation synchronizer according to the invention is designated as a whole with 20, as in the previous figures wherein it is shown as second synchronizer of a transmission 200. However, it is to be meant that what described can be applied to any synchronizer acting on a driven shaft.

It comprises a supporting plate 1 which, together with a disc-pushing element 40 shaped like a cup, defines a space included therein. The plate 1 covers a wide central opening of the disc-pushing element 40 and it has a central hole. Between plate 1 and disc-pushing element 40 there are clutch discs 41, 42.

The synchronizer 20 comprises an actuation axis, constituted by a shaft 53 which, in the transmission described previously, is a primary driven shaft, having a proximal actuation end 2 inserted internally in the central hole of the plate 1. The shaft is included in a tubular element 52 the proximal end thereof is faced towards said central hole of the supporting plate 1 of the synchronizer 20. The tubular element 52 is connected to the disc-pushing element 40.

The rotating shaft 53 extends from the supporting plate 1 and it crosses the remaining portion of the transmission elements which will be now described.

The synchronizer 20 comprises a bell-like spring 3 which is substantially shaped like a cone, implemented by a metal sheaf wherein through slots are made allowing to deform the spring according to an axial direction.

It has then the shape of a conical disc and the periphery thereof is rested upon the outer edge of the supporting plate 1, so as to cover wholly the central opening of the disc ^¬ pushing element 40; the conical end of the bell-like spring 3 has a central opening with a circular edge thereon a ball bearing 5 is fastened which acts as platform for assembling a cam 6, fastened outside the spring 3, the function thereof is to translate axially opposed to the elastic resistance offered by the spring 3, so as to interfere with the edge 43 of the central hole of the supporting plate 1 and with the actuation end of the shaft 53, as well as on the spring 3 which pushes the supporting plate by determining the closure of the clutch discs 41, 42. On this regard, between the plate 1 and the actuation end 2 of the shaft 53 there is a leaf spring 44 which guarantees the elastic return of the plate 1 in the starting position thereof when it is no more stressed (figure 5) .

The cam 6 is substantially shaped like a disc and it has an actuation face 7, faced towards the opposite direction with respect to the spring 3, having a first cam profile 8 defined on a peripheral circumference arc of the cam 6, formed by a raised rib, as well as a second cam profile determined by the flat surface of the face 7, the two profiles are connected to the respective ends by tilted surfaces.

The disc of the cam 6 forms a plane, corresponding to said exposed face 7, perpendicular to the axis of the synchronizer 20, and the first cam profile 8 projects perpendicularly from said plane, in axial direction.

The cam 6 has a centering hole 13 wherein an actuation spindle 10 with a plug connection is inserted, allowing the rotation of the cam 6 by rotating said spindle 10.

A corresponding cam follower 9, assembled on said spindle 10 the axis thereof coincides with the axis of the actuation shaft 53, is associated to the above-mentioned cam 6.

The cam follower 9 comprises a ring 11 apt to couple with said cam 6, on the exposed face thereof a second cam profile 12 is formed which projects axially and which is intended to couple with said first cam profile 8 of the cam 6. On this regard it will comprise a raised cam surface, a lowered cam surface and related tilted connections.

At the opposite distal end, the actuation spindle 10 comprises a control wheel 16 which is useful to rotate the cam 6 with respect to the cam follower 9, thus determining the translation of the cam 6 and, consequently, of the actuation end 2 and of the shaft 53.

The control wheel 16 in turn is controlled in rotation by a clutch pulley 21, arranged at the first synchronizer 216, at the crankshaft 202. The control wheel 16 and the clutch pulley have a clutch annular belt 22 connecting them.

The clutch pulley 21 is controlled in rotation by a speed- selecting device 23 which includes an electric motor 24 suitably controlled by a control unit or in case through a manual control.

Therefore, a half-rotation of the cam 6 determines its own translation, in one direction or in the other one, with respect to the cam follower 6, of the bearing 5 and of the bell-like spring 3, and then of the actuation end 2.

On this regard, the synchronizer 20 comprises means for rotating selectively said rotating cam, represented in figure 3 and implemented, in the present example, by the control wheel 16, the clutch pulley 21, the clutch belt 22 and the selecting device 23.

The primary shaft 53 receives the motion from a third toothed pulley 212, connected to a corresponding first toothed belt 213, dragged by a crankshaft 202, and from a fourth pulley 214 analogous to the previous one, however assembled on a first free wheel 60, dragged by a corresponding first toothed belt 211.

Also a pair formed by a first toothed wheel 61, in turn assembled on a second free wheel 62, and by a second toothed wheel 63, which transmits the motion only if synchronized, is keyed on the primary shaft 53, as it will become clear hereinafter .

It is to be noted that the toothed wheels 61, 63 will be intended to transmit the motion to respective driven wheels 64, 65 with different transmission ratios.

Since the cam 6 does not exert a pressure towards the actuation end 2 with respect to the cam follower 9 (figure 8A) , the motion path provides the direct passage from the first pulley 212 to the first toothed wheel 61 through the tubular element 52 which rotates on the primary shaft 53.

On the contrary, when the cam 9 is activated (figures 7 and 8B) and pushes, by operating the clutch constituted by the clutch discs 41, 42, the disc-pushing element 40 drags in rotation the tubular element 52 which synchronizes the second toothed wheel 63. Due to the effect of the higher number of revolutions the second free wheel 62 excludes the first toothed wheel 61 and the motion is transmitted through the second toothed wheel 63.

An additional half-rotation of the actuation shaft 10 brings back the gearbox in the preceding situation.

To the above-described actuation synchronizer a person skilled in the art, with the purpose of satisfying additional and contingent needs, could introduce several additional modifications and variants, however all comprised within the protective scope of the present invention, as defined by the enclosed claims.