WO2009128107A1

WO2009128107A1 - Speed variator device

Info

Publication number: WO2009128107A1
Application number: PCT/IT2008/000603
Authority: WO
Inventors: Claudio Luzi; Pasqualina Mercolini
Original assignee: C.S.M. Di Luzi Claudio & C.S.A.S.
Priority date: 2008-04-14
Filing date: 2008-09-19
Publication date: 2009-10-22
Also published as: CN101561032A; ITAN20080017A1

Abstract

A variator device (1) for the mechanical transmission of motion between two shafts (2, 3), respectively a driving shaft and a driven shaft, with a continuously variable ratio, comprises a belt (4) closed to form a loop and having a trapezoidal cross-section, and a pair of pulleys (5, 6) around which the belt (4) is wound. At least a first pulley (5) of the pair has two conical shells (5a, 5b) mounted on the driving shaft (2) with the vertices opposite each other, delimiting a groove (7) in which the belt (4) is housed at a variable distance from the axis (2a, 3a) of rotation of the shafts (2, 3). Both of the conical shells (5a, 5b) of the first pulley (5) can move longitudinally relative to the axis (2a) of rotation of the driving shaft (2). Actuator means (8; 12) are connected to each of the shells (5a, 5b) to control their movement relative to each other and to vary the distance between them so as to correspondingly vary the diameter of the belt (4) wound around the first pulley (5).

Description

Speed variator device

Technical Field

The present invention relates to a speed variator device.

The device is intended for the mechanical transmission of motion between two shafts, respectively driving and driven, with a continuously variable speed ratio, and in particular it can be used to equip a motorcycle.

For the transmission of mechanical power between a driving shaft and a driven shaft which are respectively connected: the former, to an internal combustion engine which drives a vehicle, for example a motorcycle, and the latter to the vehicle's driving wheel, a possible method is the use of continuous speed variators.

Background Art

As is known, such variators comprise a driving belt, closed to form a loop, and a pair of pulleys, one mounted on the driving shaft and the other on the driven shaft, with the driving belt fitting around both pulleys. One of the pulleys, in particular the pulley mounted on the driving shaft, comprises two conical shells whose vertices are positioned opposite each other and which between them define a groove with a trapezoidal cross-section in which the driving belt is housed.

One of the shells of one of the pulleys is integral with the driving shaft, operating in conjunction with the latter as a single body, hi contrast, the other shell of the same pulley can be made integral with the shaft relative to the rotation about its axis, but is still able to move longitudinally to the axis and in both directions in which the shaft extends, so that it can move towards or away from the fixed shell corresponding to it. Varying the distance between the two shells makes the groove wider or narrower. As a result of this, the belt moves towards or, vice versa, away from the axis of rotation of the driving shaft, thus causing a continuous corresponding variation in the transmission ratio between the two shafts.

The distance between the two shells can be varied for example using two types of known actuators: a first, inertial type operates automatically; the other type is motor-driven and can be controlled either at the user's discretion, or by an automatic control managed by a control logic implemented in a control unit.

As regards inertial actuators, in the prior art solutions the movable shell has radial races extending according to oblique surfaces in an axial direction, forming ramps in which rolling bodies are housed. Said rolling bodies, depending on the speed of rotation of the driving shaft, under the effect of centrifugal force, move by rotating and translating along the ramps and, depending on the instantaneous position reached, apply a thrust against the shell directed parallel with the axis of rotation of the driving shaft, a thrust which brings the movable shell towards the fixed shell. The thrust from the rolling bodies is opposed by a spring (usually connected to the other pulley of the transmission) so that for each instantaneous value of the number of revolutions of the driving shaft a dynamic equilibrium is established between the thrust from the rolling bodies and the reaction of the opposing spring. As a result of this equilibrium, the groove adopts a certain instantaneous width which forces the belt to be wound around at a distance from the axis of rotation of the driving shaft correlated with it. Although widely used, such a solution has several significant limits and some disadvantages.

A first disadvantage derives from the fact that the variator operates correctly when the engine is able to develop high revolving speeds and when it operates mostly in acceleration and with masses kept in position away from the axis of rotation of the driving shaft.

Consequently, the system cannot operate in the best possible way in all of the conditions which may effectively arise in practice. This is the case, for example, when the vehicle travels along a long road downhill, with the engine operating at a low revolving speed, or when the engine operates at a relatively low speed because the vehicle is moving at a constant speed on a flat surface after being suitably started.

To overcome such disadvantages attempts are made to reduce the masses, using smaller centrifugal masses, which can accelerate more easily in most of the effective running situations. However, in this case, the smaller masses are subject to greater stresses by the contact forces and the rolling bodies of which they consist are susceptible to more intense deformations and more accentuated wear.

All other conditions being equal, the reduction of the masses also results in lower dragging forces by the driving belt. This limits the field of use of the variator to relatively light vehicles, that is to say, to vehicles which are preferably moved by engines able to develop particularly intense revolving speeds, as is the case for example in many types of motorcycles.

Finally, the reduced masses are able to more frequently reach the centrifugal limit positions of the ramp on which they rotate and translate. This constitutes reaching the limit of variator performance, since when said condition is reached the variator is no longer able to further adjust its transmission ratio relative to any further engine capability for further increasing the number of revolutions correspondingly reached.

The above-mentioned limits are even more critical in a competitive situation, or in any case when somewhat extreme performance is required of the variator. In such cases, such variators have to be set up in a way that is quite difficult, since there are many parameters which can significantly modify the dynamics of the variator with changes in engine performance.

Often, if the variator (and in particular its centrifugal masses) is sized to allow strong motorcycle accelerations above all during a standing start, this variator cannot then suitably respond to the motorcycle needs when it must develop maximum racing speeds.

If, vice versa, the variator is sized to develop its best performance at top speeds, then the vehicle can only accelerate very slowly at the start or, at worst, it is unable to start. An acceptable compromise between these two opposite conditions is quite difficult to find and the best set-up can be obtained laboriously, only by trial and error, and after much practical experimentation carried out after mounting on the variator centrifugal masses which are different each time.

On the other hand, it must also be emphasised that inertial mass variators also have advantages which people are unlikely to give up.

The main advantage is their intrinsic ability to allow optimum use of the engine which can operate with continuous feeding of the air - fuel mixture, so without the vehicle having to be subjected to interruptions in the generation of driving power by the engine. This is a significant factor particularly at competition level.

Another advantage of inertial variators can be traced back to their intrinsic capability — in the various conditions in which the vehicle is used - for automatically adjusting the supply of the torque generated by the engine to the driving wheel.

In motor-driven control variators, the variation of the width of the driving pulley groove which determines the consequent variation of the transmission ratio is, in contrast, achieved by activating the movement of the movable shell relative to the fixed shell using a motor which in some cases may be the motorcycle starter motor.

Even variators made in that way have disadvantages.

A first disadvantage is the fact that managing a variator of this type requires continuous work by the actuator motor which adjusts the width of the pulley grooves.

Such operation therefore means intensive use of the actuator motor, with the risk of a consequent loss of vehicle reliability. Such a loss may even be critical if the actuator motor is also the motorcycle starter motor. Another critical aspect is the fact that, since the control signals are electric

(and unlike what happens in inertial variators) the mechanical response of the variator to a generic external stress is not as prompt as would be necessary to suitably assist the engine at the various operating speeds. Another critical aspect is also a reduced variator capacity for automatic adjustment. Since the variator has no inertial masses, it is susceptible to a certain operating instability.

Another disadvantage is the fact that variator performance depends, to a non- negligible extent, on the skill and sensitivity of the motorcycle rider, or in any case on the sophistication of the software and the hardware implemented in the control unit, if present.

Disclosure of the Invention The present invention has for an aim to overcome the various and many disadvantages of the prior art. Accordingly, the invention achieves said aim with a device whose technical features are clear from the content of the claims herein, in particular claim 1, and from any of the claims directly or indirectly dependent on claim 1.

Brief Description of the Drawings

The advantages of the present invention are more apparent in the detailed description which follows, with reference to the accompanying drawings which illustrate preferred, non-limiting embodiments of the invention, in which: Figure 1 is a perspective assembly view of a first embodiment of the variator device in accordance with the present invention;

Figure 2 is a view of some parts of the variator device with some components cut away to better illustrate others;

Figure 3 is a perspective assembly view of a second embodiment of the variator device in accordance with the invention;

Figure 4 is a schematic perspective exploded view of some components of the variator device.

Detailed Description of the Preferred Embodiments of the Invention With reference to the accompanying drawings, the numeral 1 denotes as a whole a variator device for the mechanical transmission of motion between two shafts, of which one is a driving shaft 2 and one is a driven shaft 3, said transmission occurring with a continuously variable ratio.

According to a first embodiment illustrated in Figure 1, the device 1 basically comprises a belt 4, closed to form a loop and having a trapezoidal cross-section, and a pair of pulleys around which the belt 4 is wound, the pulleys labelled 5 and 6 respectively.

The first pulley 5 of the pair has two conical shells 5a and 5b mounted on the driving shaft 2 with their vertices opposite each other, together delimiting an intermediate groove 7 between them.

The second pulley 6 of the pair in turn has a similar structure consisting of two shells, labelled 6a and 6b, which are mounted on the driven shaft 3 with the vertices opposite each other so that they also form a groove 7 matching the cross-section of the belt 4. The two shells 6a and 6b of the second pulley 6 are pushed against each other by elastic reaction means - not illustrated in the accompanying drawings - whose structure and operation are completely known.

Both of the conical shells 5a and 5b of the first pulley 5 can move longitudinally relative to the axis 2a of rotation of the driving shaft 2. Actuator means - generically labelled 8 - are connected to each of the shells

5a and 5b of the driving shaft 2. These are provided to control the movement of the shells 5a and 5b relative to each other according to the direction of the axis 2a and to vary the distance between them so as to correspondingly vary the diameter of the belt 4 wound around the first pulley 5, doing this according to the instantaneous revolving speed of the driving shaft 2.

More specifically, and according to the embodiment of the variator device 1 shown in Figure 1, the actuator means 8 comprise inertial masses 9 connected to both of the conical shells 5a and 5b of the first pulley 5.

Figure 2 shows how the actuator means 8 equipped with the inertial masses 9 comprise inside the respective shells 5a and 5b, and according to a known solution - ramps 10 extending radially and axially relative to the shells 5a and 5b, and which guide the inertial masses 9 in their movement towards the outside of the shell 5a or 5b, or, vice versa, towards the axis 2a of rotation of the shaft 2, a movement induced by the greater or lesser instantaneous revolving speed of the driving shaft 2. Figure 2 also shows how the actuator means 8 also comprise a cover 13 which can be connected to a corresponding shell 5b of the two shells 5a and 5b with which the driving pulley 5 is equipped. The cover 13 is such that together with the ramps 10 it defines a path for the masses 9 whose transit cross-section decreases from the centre to the outside of the shells 5a and 5b. Consequently, when the masses 9 rotate and translate towards the outside of the respective shell 5a or 5b, the masses 9 apply against the shell 5a or 5b a thrust directed parallel with the axis 2a which moves the latter shell 5a or 5b towards the other shell 5b or 5a of the driving pulley 5, and which, reducing the cross-section of the groove 7, forces the belt 4 to move towards the outside of the shell 5a or 5b and so to move away from the axis 2a of rotation of the driving shaft 2. Vice versa, when the masses 9 move towards the axis 2a of rotation, due to the lower revolving speed of the driving shaft 2, the consequent widening of the groove 7 causes the belt 4 to move towards the axis 2a of the driving shaft 2, whilst the variation in the length of the belt 4 loop is obviously recovered by the elastic adjusting means which, as already indicated, are positioned on the pulley 6 of the driven shaft 3 a.

The inertial masses 9 connected to the shells 5 a and 5b preferably have identical configurations and dimensions for both of the shells 5a and 5b.

The driving shaft 2 should be considered to be preferably connected, but without thereby limiting the scope of the invention, to an internal combustion engine of a vehicle which can operate at high revolving speeds, for example as is the case in the engines of some types of motorcycles.

It should be noticed that the embodiment of the variator device 1 in Figure 1 is particularly advantageous both for vehicle use at competition level and for its use for tourism. Indeed, the shells 5a and 5b having the same mechanical configuration, the masses 9 being the same and the geometry and length of the ramps 10 being the same, the range of operation of the variator device 1 is such that in practice the masses 9 cannot reach the end of stroke positions on the ramps 10, at which the device 1 would have exhausted its capacity for kinematic adjustment. Consequently, the variator device 1 disclosed can operate just as well if the vehicle is moving off from a standing start or if it is racing and must operate at the top speeds allowed by the engine.

The possibility in practice of having a wide operating range for rotation and translation of the masses 9 also makes vehicle set-up much easier and more immediate. This means that it is quite rapid and hardly affected even by any rough errors in selection of the most suitable size of the masses 9 to be mounted on the

, ramps 10 each time.

Another advantage derives from the fact that the centrifugal masses — in their interaction with the ramps - are subjected to contact forces which are not particularly high, guaranteeing long life and regular rolling of the masses even after long periods of use.

Since both shells 5a and 5b of the driving pulley 5 can move longitudinally relative to the axis 2a of rotation of the driving shaft 2, compared with conventional variators which have one of the two shells fixed, the driving belt 4 operates with greater alignment between the driving pulley 5 and the driven pulley 6, meaning that the belt 4 operates more regularly, with less heating, less wear and, finally, can last longer.

Figure 3 shows an alternative embodiment of the variator device 1 in which the actuator means 8 also comprise at least one electronically controlled actuator 12, connected to one 5b or to both of the conical shells 5a and 5b equipped with inertial masses 9, and with its movement driven by a motor 14.

Such a type of actuator 12 may be made as illustrated in Figure 4, where it is shown connected to one of the shells 5a or 5b of the driving pulley 5 (in particular the shell 5a adjacent to the engine) which may be made with or without inertial masses 9, whilst the outermost shell 5b is always equipped with inertial masses 9. The actuator 12 is an electronic actuator which allows the imparting to the shell 5a to which it is connected of a controlled movement in both directions of the axis 2a of the driving shaft 2.

The command to operate may be issued to the electronic actuator 12 voluntarily by the user, or automatically, subject to control by a logic implemented in suitable control means.

It should be noticed that in the case in question the electronic actuator 12 does not operate continuously, since the transmission ratio is continuously adjusted by the inertial masses 9 in particular fitted on the shell 5b furthest from the engine. Instead, more simply it allows the vehicle user to correct according to requirements the width of the groove 7 automatically produced by the inertial masses 9.

This brings many advantages.

The variator device 1 operating range relating to a specific structure in particular of the shells 5a and 5b, relative to a specific shape of the ramps 10 and/or to a specific size of the masses 9 positioned on the ramps 10, may be greatly extended, since for each of the many positions which can be imparted to the shell 5a along the axis 2a of the driving shaft 2, there is available the entire range of transmission ratios which can be obtained for that specific variator thanks to the presence of the inertial masses 9. However, on each occasion, said range may be varied at will by the user according to the nominal width of the groove 7 he presets each time by operating the electronic actuator 12.

Thus the speed variator device 1 has an exceptional capability for making itself perfectly congruent: on one hand, with the engine instantaneous performance, and on the other hand with the actual forward movement conditions encountered by the vehicle as it is travelling. In practice, the vehicle user, although having available a variator device 1 with a rigid and well-defined mechanical structure, can make use of a range of operationally different virtual variators, each corresponding to one of the many positions which can be imparted to one of the shells 5a; and within said range the user can make the choice he considers most appropriate on each occasion depending on the travel conditions encountered, depending on the desired use of the vehicle and/or depending on his own driving style.

Another advantage, directly consequent to said possibility of modulating vehicle performance, is a significant reduction in engine consumption, the engine always being able to operate in optimum use conditions. The resulting benefits are obvious and consist of energy savings and reduced environmental pollution.

Another advantage is increased reliability of the actuator motor 14 which gives the electronic actuator 12 the energy it needs to operate. The reduced number of activations and their shorter duration allow the motor 14 a very long working life. Yet another advantage is the fact that, if despite the high level of reliability of the actuator motor 14 for the electronic actuator 12, the latter should develop a fault, the vehicle does not become faulty, but instead continues to maintain a high level of residual operation because speed variation is still guaranteed by the presence of the inertial masses 19 and their automatic adjustment with changes in the driving shaft 2 revolving speed. The invention described above is susceptible of industrial application and may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all details of the invention may be substituted by technically equivalent elements.

Claims

1. A speed variator device for the mechanical transmission of motion between two shafts, of which one is a driving shaft (2) and one is a driven shaft (3), with a continuously variable ratio, comprising a belt (4) closed to form a loop and having a trapezoidal cross-section and a pair of pulleys (5, 6) around which the belt (4) is wound, at least a first pulley (5) of said pair having two conical shells (5 a, 5b) mounted on the driving shaft (2) with the vertices opposite each other, and delimiting a groove (7) in which the belt (4) is housed at a variable distance from the axis of rotation of the shafts (2, 3); the device being characterised in that both of the conical shells (5a, 5b) of the first pulley (5) can move longitudinally relative to the axis (2a) of rotation of the driving shaft (2); there being actuator means (8; 12) connected to each of the shells (5 a, 5b) to control their movement relative to each other and to vary the distance between them so as to correspondingly vary the diameter of the belt (4) wound around the first pulley (5).

2. The device according to claim 1, characterised in that the actuator means comprise inertial masses (9) connected to at least one of the conical shells (5a, 5b) of the first pulley (5).

3. The device according to claim 2, characterised in that the inertial masses (9) are connected to both of the shells (5a, 5b).

4. The device according to claim 2 or 3, characterised in that the inertial masses (9) have identical configurations for both of the shells (5a, 5b).

5. The device according to claim 2 or 3, characterised in that the actuator means equipped with inertial masses comprise ramps (10) extending radially and axially relative to said shells (5a, 5b), the ramps (10) containing and guiding the inertial masses (9) during the movement induced on them by the driving shaft (2) revolving speed.

6. The device according to the foregoing claims, characterised in that the driving shaft (2) is driven by an internal combustion engine (11).

7. The device according to claim 6, characterised in that the internal combustion engine (11) is a vehicle engine.

8. The device according to claim 7, characterised in that the internal combustion engine (11) is a motorcycle engine.

9. The device according to claim 2 or 3, characterised in that the actuator means comprise at least one electronically controlled actuator (12) connected to one (5b) or to both of the conical shells (5 a, 5b) which are equipped with inertial masses (9).

10. The device according to claim 9, characterised in that said one or each electronically controlled actuator (12) can be activated voluntarily by the user.

11. The device according to claim 9, characterised in that said one or each electronically controlled actuator (12) can be activated automatically subject to a logic implemented in suitable control means.