ITBO20090081A1 - CONTROL DEVICE FOR A MECHANICAL TRANSMISSION STRUCTURE WITH VARIABLE SPEED RATIO. - Google Patents

Description

DEVICE FOR CONTROL OF A MECHANICAL TRANSMISSION STRUCTURE WITH VARIABLE SPEED RATIO.

The present invention relates to the construction of motor vehicles equipped with mechanical motion transmissions which comprise transmission structures operating with a continuously variable speed ratio.

The invention relates in particular to a control device for selectively controlling said transmission structure so as to obtain for the vehicle longer mileage distances with equal consumption with similar vehicles of the known art.

It is known that the current trend in the design and construction technique of most motor vehicles is based primarily on obtaining high functional performance.

In fact, to a generic motor vehicle - such as a car, a motorcycle, an off-road vehicle, etc. - particularly qualified performance standards are currently required in terms of: the vehicle's ability to develop high accelerations, both from a standing start and while running; high ability to climb uphill; and high acceleration speed to quickly get to safety in emergency situations.

In vehicles of the known type, in order to obtain such high performances, one usually operates with engines which operate with rather high crankshaft rotation speeds; however, this condition inevitably leads to proportionately high fuel consumption.

However, such an operating mode - although widely consolidated - is no longer compatible with current trends which require, on the other hand, both for economic and environmental reasons, to reduce fuel consumption and therefore to increase mileage equal to amount of fuel consumed.

The aim of the present invention is therefore to achieve the general objective of reducing consumption without however having to renounce the functional performance standards currently envisaged in the sector.

In accordance with the invention, this purpose is achieved by means of a control device capable of controlling and managing - the transmission structure with variable speed ratio with continuity of the vehicle - selectively and variably according to some actual operating parameters of the vehicle, in such a way as to save fuel consumption in all those operating conditions for which it is not necessary for the vehicle to have the maximum motive power that can be developed by the engine.

The technical characteristics of the invention, according to the aforementioned purposes, are clearly verifiable from the content of the claims reported below, and the advantages thereof will become more evident in the detailed description that follows, made with reference to the attached drawings, which represent a purely embodiment exemplary and not limiting, in which:

- figure 1 is an overall and sectional schematic view of a motion transmission, of known type, which comprises a transmission structure with a continuously variable speed ratio;

Figure 2 is an overall and sectional schematic view of a motion transmission integrating a control device according to the invention, made according to a first embodiment;

- figure 3 is an enlarged scale view of a particular P of figure 2 in a first operative configuration;

Figure 4 is an enlarged view of the detail P of Figure 2 shown in a second operating configuration;

Figures 5 and 6 are views of a second embodiment of detail A of the invention shown in two operating configurations corresponding to those of Figures 3 and 4;

- figure 7 is the representation in a Cartesian plane of a descriptive function of the operation of the transmission structure with variable speed ratio, in which the speed of advancement of the vehicle is shown on the abscissa and the speed of rotation of the engine on the ordinate ;

Figure 8 is a functional block diagram describing the operational interactions between some component parts of the invention.

In accordance with the accompanying drawings, in Figure 1 the number 50 identifies as a whole a conventional motion transmission interposed operatively between an engine 51 and a driving wheel 16 of a generic vehicle; vehicle which is only partially represented in the drawings as it is devoid of interest in the invention and which can be constituted for example by a motorcycle, a scooter, an off-road vehicle or a vehicle similar to them.

The motion transmission 50 essentially comprises a transmission structure 52 with a continuously variable speed ratio and a speed reducer 53 operating instead at a fixed speed ratio. The variable ratio transmission structure 52 and the fixed ratio reducer 53 are arranged in cascade between an input motor shaft 1 to the transmission 50 and an output shaft 15 driven by the same, connected to the driving wheel 16 of the vehicle.

The structure 52 with variable speed ratio with continuity essentially comprises a pair of V-grooved pulleys 54 and 55 and a trapezoidal section belt 5, closed in an endless ring, which wraps together the pulleys 54 and 55 housing inside the relative V-grooves

A pulley 54 - primary of the torque - is mounted on the motor shaft 1 and consists of two conical parts 4 and 6 converging towards each other.

One of the conical parts, the 6, is integrally integral with the motor shaft 1 with which it functions functionally as a single body.

The other conical part, the 4, is integral with the motor shaft 1 exclusively with respect to the rotation, being instead free to translate with respect to it in the two directions of the axis la of rotation of said shaft 1.

The conical part 4 is also equipped with masses 3 which are housed on cam tracks 2, radial and oblique of the conical part 4, and which are freely movable along the same. In correspondence with the angular rotation of the motor shaft 1, centrifugal forces are triggered on the masses 3 which, due to the obliquity of the cam tracks 2, generate axial force components for the pulley 54 which determine the approaching or moving away to / from the fixed part 6 of the mobile conical part 4.

As a consequence of this, as the angular speed of rotation of the motor shaft 1 increases, the V-shaped groove of the primary pulley 54 narrows, forcing the belt 5 to move away from the rotation axis 1a of the motor shaft 1, and vice versa as it will be. more evident later in the description.

The secondary pulley 55 of the pair is mounted on an output shaft 10 of the transmission structure 52 with a continuously variable speed ratio; output shaft 10 which extends towards the reducer 53, forming the primary input shaft of the latter.

The secondary pulley 55 also comprises two conical parts, respectively 7 and 8. A first conical part 7 is integrally integral with the shaft 10. The second conical part 8 is instead integral with the shaft 10 limited to rotation only, since it can be moved in the two directions of the axis 10a of the shaft 10 as a function of the instantaneous radial positions assumed by the belt 5 with respect to the axis 10a and consequent to opposite causes determined by the centrifugal forces acting on the driving pulley 54 and by the elastic reaction offered by an elastic element or spring 9 which, associated with the second pulley 55, pushes the constantly translatable conical part 8 towards the fixed conical part 7. Ultimately, as the instantaneous angular speed of the motor shaft 1 varies, in relation to the intensity of the centrifugal forces and in relation to the preload of the reaction spring 9, the belt 5 assumes instantaneous distances from the axes la and 10a of from time to time different which consequently modify the transmission ratio of the structure 52 with variable speed ratio with continuity between a well-defined minimum and maximum.

The reducer 53, located downstream of the transmission structure 52 with continuously variable speed ratio, essentially comprises three shafts with parallel axes: the first, consisting of the aforementioned output shaft 10 of the said structure 52; a second, consisting of the aforementioned shaft 15 connected to the driving wheel 16; the third, being materialized by a tree 56 intermediate to the first two.

Mounted on said shafts 10, 56 and 15 are two pairs 11, 12 and 13, 14 of toothed wheels meshing with each other. The presence of the reducer 53 modifies - in the overall transmission 50 and with a fixed and well determined multiplication factor - the speed ratio of the transmission structure 52 with continuously variable speed ratio

Figure 2 shows the transmission structure 52 with a continuously variable speed ratio which - made in accordance with the present invention - differs from the known technique of Figure 1 essentially in that it presents a device 60 for selectively controlling the transmission structure 52 with continuously variable speed ratio so as to be able to increase the mileage of the vehicle with respect to the known technique - all other conditions being equal.

Said device 60 - visible even more clearly in Figure 3 - essentially comprises a plurality of springs constituted by the spring 9 already present in the solution of Figure 1 and by one or more auxiliary springs 21 associated with the conical, mobile part 8 of the second pulley 55.

The first spring 9 is placed, similarly to the known art: on the one hand, in direct contact with the conical, mobile part 8, of the second pulley 55; and on the opposite side it is opposed by a plate 23, which is blocked on the shaft 10 by a ring nut 36 reacting against a fixed shoulder 37 of the shaft 10 itself.

The preload of this spring 9 is predetermined and invariable: in other words, the minimum and maximum compression heights of the spring 9, once fixed in the design phase, remain invariable during the actual operation of the transmission structure 52.

At least a second spring 21, coaxial with the previous one, also encounters the mobile conical part 8 of the second pulley 55 on one side. which are globally identified with reference 40.

The dynamic recording means 40 essentially comprise: a concave shell-shaped body 24; an annular support 25 with rolling bodies; a hub 26 or stem, threaded; a toothed wheel 27; and a pinion 28 powered by a servomotor 29.

More specifically, the concave shell-shaped body 24 has a seat 38 for containing the end of the second spring 21 farthest from the pulley 55. The hub 26 is placed through a support seat 41 obtained in a structure 42 containment of the transmission structure 52. The hub 26 or stem is helically coupled with the seat 41 and projects towards the pulley 55 with its own ring 43 which, in combination with a complementary ring 44 of the shell-shaped body 24, materializes the annular support 25 with rolling bodies. The hub 26 then also protrudes from the seat 41 (in the direction of the second pulley 55 away) with its own section to which the toothed wheel 27 is integrally fixed.

The actuation of the servomotor 29 allows - by means of the transmission of the motion actuated by the pinion 28 and the wheel 27 meshing with each other - to actuate the roto-translation of the hub 26 on the seat 41, with respect to the axis 10a.

The axial translation of the hub 26 is then transmitted, through the support 25, to the shell-shaped body 24 and from it to the second spring 21.

The hub 26, the support 25 and the shell-shaped body 24 thus materialize thrusting means suitable for allowing the progressive and continuous adjustment of the height of the second spring 21.

The servomotor 29, the pinion 28 and the wheel 27 instead materialize actuator means which, suitably controlled, can allow the dynamic management of the adjustment of the preload of the second spring 21.

Figures 3 and 4 clearly show the configurations of the device 60 in correspondence with which, respectively: the second spring 21 is compressed up to the minimum height, to the maximum of the preload; and vice versa it is compressed to the maximum height which corresponds to the minimum intensity of the preload.

Figures 5 and 6 show a different embodiment of the thrusting means in which the hub 26 is coupled with the seat 41 so as to be translatable as a guide with respect to the axis 10a.

The means for actuating the thrust of the hub 26 in adjustment of the second spring 21 comprise in this case an inter-pivoted lever 31, of the first kind, which carries a first arm 45 associated with the hub 26 and a second arm 46 associated with a rotating cam 32 carried integrally by a toothed wheel 33 which meshes with a pinion 34 moved by the servomotor 29.

Depending on the position assumed by the cam 32, the device 60 is arranged in the maximum and minimum height configurations of the second spring 21 which are shown respectively in Figures 5 and 6 of the accompanying drawings.

In figure 8 it can be seen that the device 60 comprises sensor means adapted to detect significant parameters for the instant representation of the operation of the vehicle; for this purpose the sensor means comprise a sensor 47 of the instantaneous speed of travel of the vehicle and an acceleration sensor 48 with which the supply of the air-fuel mixture to the engine 51 is opened or closed.

The device 60 further comprises driving means 49 which are interfaced with the sensors 47 and 48 and with the servomotor 29 so as to control the latter selectively according to the signals coming from the sensors 47 and 48, conveniently processed.

Figure 7 shows a diagram which describes the operation of the transmission structure 52 with variable speed ratio with continuity in relation to: the vehicle travel speed (km / h) reported on the abscissa and detected by the sensor 47; and the speed of rotation of the motor shaft (rpm) shown on the ordinate axis.

In the section A - B of this diagram it can be seen that the speed of advancement of the vehicle increases proportionally with the speed of rotation of the motor shaft 1, while the speed ratio of the transmission structure 52 remains fixed on a well-determined value since the centrifugal force which is temporarily exerted on the masses 3 has insufficient intensity to overcome the reaction exerted by the springs 9 and 21 which oppose the translation of the movable part 8 of the driven pulley 55.

Once the motor rotation speed equal to B has been reached, the centrifugal force begins to move the masses 3 of the primary pulley 54 over an arc of circumference with a greater radius (the V-belt 5 moves away from the axis la of rotation of the motor shaft 1 ), at the same time on the driven pulley 55 the V-shaped belt 5 moves on a winding arc with a smaller radius than the previous one (the V-shaped belt 5 approaches the rotation axis 10a).

In the transition of the initial configuration towards a new final condition (of equilibrium between the opposite actions of the centrifugal force and of opposition exerted by the springs 9 and 21) the speed ratio of the transmission structure 52 varies continuously: an increase in the speed of vehicle running with constant speed of rotation of the motor shaft 1 (section B - C).

Beyond point C (vehicle speed equal to G and crankshaft rotation speed equal to B) the vehicle travel speed resumes increasing in direct proportion to the engine rotation speed 51.

The speed of rotation B at which the variable speed ratio transmission structure 52 works (in the sense that it varies the speed ratio continuously) is determined by the overall elastic reaction of the springs 9 and 21 on the secondary pulley 55.

That is, the speed of rotation B of the motor shaft 1 is much higher the higher is the intensity of the overall elastic reaction of the springs 9 and 21, and vice versa.

Well, a transmission structure 52 which is made in accordance with the present invention - due to the possibility of varying the preload of one of the springs, 21, is able to operate selectively according to two different operating laws represented in the diagram with a solid line. and with a discontinuous line in dash and dot.

In other words, the transmission structure 52 can work selectively both at the rotation speed B of the motor, and at a lower rotation speed,

D, in correspondence with which, with respect to the previous one, the engine 51 consumes less fuel. By exploiting this possibility, when high performance capabilities are required of the vehicle, for example in: - acceleration from standstill or while running;

- or high climbing abilities; - or emergency accelerations,

the control device 60 manages the preload of the adjustable spring 21 so as to place it towards higher values, which corresponds to a higher rotation speed B of the motor 51 (as shown in Figures 4 and 6).

When, on the other hand, the vehicle is required to perform not so heavy as for example in running at constant speed, or in slow acceleration or deceleration on a flat road, then the preload of the spring 21 can be decreased as shown in figures 3 and 5 so that the structure 52 transmission comes to work at lower engine rotation speed D (piecewise curve).

Some of the operating modes of the device 60 for varying the preload of the spring 21 as a function of signals from the sensor means 47 and 48 can be described with reference to some examples referring to typical operating situations of the operation of the vehicle described below.

A first typical condition occurs when starting and accelerating from a standstill until cruising speed is reached. In this case the vehicle speed sensor 47 and the sensor 48 of the opening acceleration of the air-fuel mixture feed signal to the piloting means 49 an increasing variation of the forward speed and a high speed of opening of the feed. Faced with these input signals, the control means 49 output signals on the basis of which the servomotor 29 configures the device 60 in the standard working configuration of the transmission structure 52 with a continuously variable speed ratio, a condition which corresponds to the representations of Figures 3 or 5.

A second typical condition occurs when driving at a constant speed above a minimum threshold, for example above 30 km / h. In this case, the vehicle speed sensor 47 and the power supply opening sensor 48 send to the control means 49 corresponding signals of absence of variation of the respective detected quantities. On the basis of these signals, the control means 49 consequently control the servomotor 29 so as to make the transmission structure 52 operate with a variable speed ratio at the economic running condition corresponding to the configurations of Figures 4 and 6 (preload of the spring 21 at the minimum intensity), that is to the speed of rotation D of the motor 51 of figure 7. This speed is evidently achieved by a reduction in consumption compared to the standard operating condition with shaft rotation speed 1 motor at B revolutions per minute .

A third typical condition occurs when the vehicle is running with low acceleration. In this case the vehicle speed sensor 47 and the power supply opening sensor 48 sense modest variations in the relative monitored quantities. The control means 49 therefore also in this case control the adjustment device 60 in such a way as to operate at the economic condition.

A fourth typical condition occurs in the event that the vehicle moves with a travel speed exceeding 30 km / h and decelerates slowly as a consequence of a slow throttling of the power supply to the engine 51. In this case, the control means 49 drive once again the adjustment device 60 in the economic operating condition.

A fifth typical condition occurs in the event that the vehicle is moving at a travel speed of less than 30 km / h and the power supply to the engine 51 is closed quickly. The corresponding signals received by the sensor means 47 and 48 are then processed by the control means 49 so as to command the adjustment device 60 back to standard operation.

A sixth typical condition occurs in the case in which the vehicle has to accelerate rapidly, to escape a situation of danger or emergency. In this case, the signal for rapid opening of the power supply of the motor 51 received by the control means 48 is processed in such a way as to determine a control of the adjustment device 60 adapted to predispose the transmission structure 50 with variable ratio in the standard working conditions. .

In summary, in the transmission 52 of the motion with a continuously variable speed ratio, according to the present invention, the variation of the speed ratio is determined in the presence of an imbalance condition between two concomitant and opposite actions that one exerts on the pulley 54 driving, the other on the driven pulley 55. These actions consist: on the driving pulley 54 in an axial thrust in the direction of the narrowing of the V-shaped groove of the pulley 54, determined by the centrifugal forces acting on the movable masses 3 of said pulley 54, and vice versa; and on the pulley 55 driven by the axial reaction to the pulley 55 determined by a double system of elastic elements 9 and 21 which oppose the widening of the V-shaped groove, and vice versa.

When the vehicle requires high acceleration capacity at starting and running, high climbing capacity and high emergency acceleration, the preload of one of the springs 21 is increased so as to determine the operation of the transmission structure 52 at variable speed. 51 higher engine rotation speed.

If, on the other hand, the vehicle is not required to have such a great force as it runs at a constant speed or gradually accelerates or decelerates on a flat road, the preload of the adjustable spring 21 is reduced so that the transmission structure 52 operates in ratio. of variable speed at a lower rotation speed thus achieving lower consumption and therefore a greater mileage of the vehicle for the same fuel consumed.

In the example describing the invention, reference has been made to a servomotor 29 as a preferable embodiment of an actuator for controlling the adjustment of the elastic element 21.

It is quite clear that it must be understood only as an indication, but not limiting of a possible embodiment of an electric actuator that can be driven by the control means 49, an actuator that can also be made in different forms such as for example in the form of electromagnetic switch.

The invention fully achieves the intended purposes by achieving longer distances with lower consumption with functional performances corresponding to the performance standards currently allowed by the solutions of the known art.

The invention thus conceived is susceptible of evident industrial application; it can also be subject to numerous modifications and variations, all of which are within the scope of the inventive concept; all the details can also be replaced by technically equivalent elements.

Claims (14)

CLAIMS 1. Control device of a transmission structure (52) with continuously variable speed ratio of a motor vehicle (51), wherein said transmission structure (52) is arranged between a motor shaft (1) of the vehicle and at least one driving wheel (16) thereof and comprises a secondary pulley (55) which is connected to the driving wheel (16) and is driven in motion by means of a belt (5) by a primary pulley (54) connected to the motor ( 51), said secondary pulley (55) being provided with a fixed part (7) and a mobile part (8) between which the belt (5) is interposed and being provided with elastic reaction means (9) suitable for pressing said movable part (8) against the belt (5) and abutting the latter against the fixed part (7), the control device (60) being characterized in that said elastic means include at least one selectively elastic element (21) adjustable, associated with said movable part (8) of the pulley (55) and by the fact that it comprises adjusting means (40) for selectively varying the preload of at least said elastic element (21) in relation to the instantaneous operating state of the vehicle, so as to allow said transmission structure (52) to vary the speed ratio in correspondence of different values (B, D) of the motor rotation speed (51). 2. Control device according to claim 1, characterized in that it comprises sensor means (47, 48) suitable for detecting parameters suitable for representing the instantaneous and effective operating state of the motor (51); and control means (49), which are interconnected with the sensor means (47, 48) and with the recording means (40) so as to drive the latter according to the signals received from the sensor means (47, 48). 3. Control device according to claim 2, characterized in that the sensor means comprise at least one sensor (47) suitable for detecting the speed of travel of the vehicle; and at least one sensor (48) adapted to detect the opening or closing acceleration of a throttling of the motor supply (51). Control device according to claim 2 0 3, characterized in that said control means (49) include electric actuators (29) for driving the recording means (40). 5. Control device according to claim 4, characterized in that said electric actuators include a servomotor (29) or an electromagnetic switch. 6. Control device according to claim 1, characterized by the fact that said recording means (40) comprise a body (24) and a hub (26) or stem, said body (24) integrating an abutment surface (38) of said one or each elastic element (21), said hub (26) being placed in thrust association with said body (24) and being mounted in guide (41) so as to be translatable along a direction parallel to the axis (10a) of said one or each elastic element (21); pusher means (27, 28, 29; 31, 32, 33, 34, 29) being operatively connected to the hub (26), so as to impart to said hub (26) suitable at least translational displacements in opposition to the elastic reaction exerted by said element (21) elastic on said body (24). 7. Control device according to claim 6, characterized in that said body (24) and said hub (26) are made in distinct parts, the recording means (40) comprising rolling supports (25) interposed between said body (24 ) and said hub (26) so as to make them independently rotatable with respect to each other around the axis (10a) of said elastic element (21). Control device according to claim 6 or 7, characterized in that said body (24) has the shape of a shell, said abutment surface (38) being implemented by a circular base ring of said shell. 9. Control device according to claim 6, characterized in that said guide (41) is rectilinear and is adapted to allow the mobility of said hub (26) in translation with respect to the axis (10a) of said element (21 ) rubber band. 10. Control device according to claims 6 and 7, characterized in that said pushing means include a lever (31) carrying a first arm (45) associated with the hub (26) or stem and a second arm (46) associated with means cam (32) moved by said control means (49; 29). 11. Control device according to claim 9, characterized in that said lever (31) is pivoted in an intermediate position to said arms (45, 12. Control device according to claim 6, characterized in that said guide (41) is helical and is adapted to allow the movement of said hub (26) or stem in roto-translation with respect to the axis (10a) of the 'element (21) elastic. 13. Control device according to claim 10, characterized in that said thrusting means include a toothed wheel (27) integral with said hub (26) or rod and a pinion (28) powered by said control means (29) which engages with said toothed wheel (27). Control device according to one of the preceding claims, characterized in that said elastic means (9, 21) include at least two mutually coaxial cylindrical springs.