CONTINUOUS SPEED VARIATOR WITH EXPANDING PULLEYS

Abstract: A continuous speed variator including two sets of hydraulically-controlled expandable driving-driven pulleys (6, 7, 8, 9) with respective driving belts (4, 5) arranged in parallel.

Description: The present invention relates generally to continuous speed variators with expandable pulleys. More particularly, the invention concerns a continuous speed variator of the type defined in the pre-characterising part of claim 1, and generally known from DE-A-3000572. The use of a double driving belt enables the field of use of the continuous speed variator with expandable pulleys to be extended to applications for which conventional single-belt variators are inadequate, and particularly for the transmission of high powers such as those of the power units installed in sport cars. The continuous speed variator of the invention is characterised by the feature set forth in the characterising part of Claim 1. The conformation of the unit formed by the two driving pulleys, and more particularly the arrangement of the two movable half-pulleys of these driving pulleys in a unit which floats axially on the driving shaft, ensures correct transmission of the drive from the driving shaft to the driven shaft by the two belts in parallel, ensuring self-adjustment of the transmission ratio regardless of the dimensional tolerances of the components of the variator and, in particular, of any slight differences in the length of the two driving belts. Moreover, due to the claimed arrangement, the variator according to the invention has a compact and symmetrical structure which reduces its bulk, facilitating its installation in restricted spaces. Further characteristics and advantages of the invention will become clear in the course of the detailed description which follows with reference to the appended drawings, provided purely by way of non-limiting example, in which: Figure 1 is a schematic partially-sectioned elevational view of a continuous speed variator with expandable pulleys according to the invention, in a first operative configuration, and Figure 2 is a view similar to Figure 1, with the variator in a second operative condition. With reference to the drawings, a continuous speed variator with expandable pulleys is generally indicated 1 and is intended to be used for the transmission of drive from the power unit to the driving wheels of a motor vehicle. The variator 1 comprises a driving shaft 2 intended to be rotated by the shaft of the engine, through conventional means not illustrated, and a driven shaft 3 parallel to the driving shaft 2 and intended to be connected, also through conventional means not illustrated, to the drive-shafts of the driving wheels of the vehicle. The transmission of drive from the driving shaft 2 to the driven shaft 3 is effected, according to the invention, by means of a pair of endless driving belts 4 and 5, also of conventional type, arranged in parallel and passing around two pairs of expandable driving and driven pulleys 6, 7 and 8, 9 carried by the driving shaft 2 and the driven shaft 3, respectively. The two driving pulleys 6, 7 each comprise a fixed half-pulley 6a, 7a fixed rigidly to the driving shaft 2 and a movable half-pulley 6b, 7b which can be moved towards or away from the fixed half pulley 6a, 7a along the axis A of the driving shaft 2. The two movable half-pulleys 6b, 7b are arranged between the fixed half-pulleys 6a, 7a and form parts of a single expandable and contractible body 18 supported by the driving shaft 2 so as to be able to slide freely in an axial direction. In the embodiment shown in the drawings, the movable half-pulleys 6b, 7b are coupled to each other telescopically and define, within the body 18, an intermediate thrust chamber 19 which is hydraulically sealed and connected, by means of a passage 10 formed within the driving shaft 2, to a hydraulic control circuit of conventional type which effects the expansion and contraction of the body 18 and hence, through the movement of the movable half-pulleys 6b, 7b towards or away from the fixed half-pulleys 6a, 7a, the continuous variation of the transmission ratio of the variator 1. A radial stop carried by the driving shaft 2 in a position intermediate the two fixed half-pulleys 6a, 7a is indicated 11 and has the function of limiting the amount of axial sliding of the body 18 in one direction or in the opposite direction. The two driven pulleys 8, 9 also comprise a fixed half-pulley 8a, 9a rigidly fixed to the driven shaft 3 and a movable half-pulley 8b, 9b which can be moved towards or away from the respective fixed half-pulley 8a, 9a along the axis B of the driven shaft 3. The movable half-pulleys 8b, 9b are situated outwardly of the fixed half-pulleys 8a, 9a and are associated with respective thrust chambers 8c, 9c connected in a conventional manner to the hydraulic circuit for controlling the variator. The two fixed half-pulleys 8a, 9a define a central axial portion 3a of the driven shaft 3 which is aligned with the expandable and contractible body 18 in a direction parallel to the two driving belts 4,5 and carries a toothed output member 12 of the variator. Figure 1 shows the configuration of the variator 1 which corresponds to the lowest transmission ratio, with the two driving pulleys 6, 7 in their configuration of maximum expansion and the drive pulleys 8, 9 in their condition of maximum contraction, whilst Figure 2 shows the configuration of the highest transmission ratio, with the driving pulleys 6, 7 in their condition of maximum contraction and the driven pulleys 8, 9 in their condition of maximum expansion. The use of said double driving belts 4, 5 enables the variator 1 according to the invention to be used for motor vehicles provided with very powerful power units, such as, for example, sport and racing cars. The conformation of the movable half-pulleys 6b, 7b of the two driving pulleys 6, 7 on the axially floating body 18 ensures automatic adaptation and self-adjustment of the transmission ratio of the variator 1, any slight dimensional differences of its components and, in particular, of the length of the two driving belts 4 and 5 being taken up. Furthermore, the generally compact and symmetrical configuration of the variator 1 enables its bulk to be reduced, so that it can be used even where the available space is restricted.

Claims: 1. A continuous speed variator with expandable pulleys, including a driving shaft (2) and a driven shaft (3) carrying first and second expandable driving pulleys (6, 7) and first and second expandable driven pulleys (8, 9) respectively, each formed by a fixed half-pulley (6a, 7a; 8a, 9a) and a half-pulley (6b, 7b; 8b, 9b) which is axially movable relative to the fixed half-pulley, first and second parallel driving belts (4, 5) which pass around the first and second expandable (6, 8; 7, 9) driving and driven pulleys respectively, and hydraulic means for causing displacement of the movable half-pulleys (6b, 7b) of the driving pulleys (6, 7) for continuous variation of the speed ratio, wherein the movable half-pulleys (6b, 7b) of the two driving pulleys (6, 7) are situated between their fixed half-pulleys (6a, 7a) and form parts of a single expandable and contractible body (18) freely slidably supported by the driving shaft (2) in an axial direction (A) and provided with a single thrust chamber (19) which is connected to the hydraulic control means (10), characterised in that the fixed half-pulleys (8a, 9a) of the two driven pulleys (8, 9) are situated between their movable half-pulleys (8b, 9b) and define between these driven pulleys (8, 9) an intermediate axial portion (3a) of the driven shaft (3) which is aligned with the expandable and contractible body (18) in a direction parallel to the driving belts (4, 5) and carries a toothed output member (12) of the variator (1), and in that hydraulic means (8c, 9c) are also provided for causing displacement of the movable half-pulleys (8b, 9b)of the said driven pulleys (8, 9).

Inventors: GIACOSA, DANTE
Applicants: FIAT AUTO S.P.A.
Application year: 1988
Main classification: F16H9
IPC codes: F16H9